bims-mikwok 2024-03-31 papers

bims-mikwok

Biomed News

on Mitochondrial quality control

Issue of 2024–03–31
27 papers selected by
Gavin McStay, Liverpool John Moores University

Mitophagy mediated by BNIP3 and NIX protects against ferroptosis by downregulating mitochondrial reactive oxygen species.
Mapping Stress-Responsive Signaling Pathways Induced by Mitochondrial Proteostasis Perturbations.
DELE1 promotes translation-associated homeostasis, growth, and survival in mitochondrial myopathy.
Diterpenoid honatisine overcomes temozolomide resistance in glioblastoma by inducing mitonuclear protein imbalance through disruption of TFAM-mediated mtDNA transcription.
Cloflucarban Illuminates Specificity and Context-Dependent Activation of the PINK1-Parkin Pathway by Mitochondrial Complex Inhibition.
Nickel induces mitochondrial damage in renal cells in vitro and in vivo through its effects on mitochondrial biogenesis, fusion, and fission.
Quantitative imaging and semiotic phenotyping of mitochondrial network morphology in live human cells.
Rab4A-directed endosome traffic shapes pro-inflammatory mitochondrial metabolism in T cells via mitophagy, CD98 expression, and kynurenine-sensitive mTOR activation.
Distinct types of intramitochondrial protein aggregates protect mitochondria against proteotoxic stress.
OMA1 protease eliminates arrested protein import intermediates upon mitochondrial depolarization.
Involvement of DJ-1 in the pathogenesis of intervertebral disc degeneration via hexokinase 2-mediated mitophagy.
Norcantharidin Sensitizes Colorectal Cancer Cells to Radiotherapy via Reactive Oxygen Species-DRP1-Mediated Mitochondrial Damage.
Force-induced tail-autotomy mitochondrial fission and biogenesis of matrix-excluded mitochondrial-derived vesicles for quality control.
How Mitochondrial Signaling Games May Shape and Stabilize the Nuclear-Mitochondrial Symbiosis.
Insulin induces bioenergetic changes and alters mitochondrial dynamics in podocytes.
CgPHB2 involved in the haemocyte mitophagy in response to Vibrio splendidus stimulation in Pacific oyster Crassostrea gigas.
Mitophagy modulation for the treatment of cardiovascular diseases.
Bioinformatics integration reveals key genes associated with mitophagy in myocardial ischemia-reperfusion injury.
Mdivi-1 alleviates sepsis-induced liver injury by inhibiting STING signaling activation.
Mitofusin 2 plays a critical role in maintaining the functional integrity of the neuromuscular-skeletal axis.
Real-time analysis of osteoclast resorption and fusion dynamics in response to bone resorption inhibitors.
A pH-response-based fluorescent probe for detecting the mitophagy process by tracing changes in colocalization coefficients.
Humanin inhibits lymphatic endothelial cells dysfunction to alleviate myocardial infarction-reperfusion injury via BNIP3-mediated mitophagy.
The Mitochondrial Connection: The Nek Kinases' New Functional Axis in Mitochondrial Homeostasis.
L-arginine alleviates heat stress-induced mammary gland injury through modulating CASTOR1-mTORC1 axis mediated mitochondrial homeostasis.
Ion channel-mediated mitochondrial volume regulation and its relationship with mitochondrial dynamics.
Vascular Endothelial Cell-Derived Exosomal Sphingosylphosphorylcholine Attenuates Myocardial Ischemia-Reperfusion Injury through NR4A2-Mediated Mitophagy.

Cell Death Differ. 2024 Mar 22.

Mitophagy mediated by BNIP3 and NIX protects against ferroptosis by downregulating mitochondrial reactive oxygen species.

Shun-Ichi Yamashita, Yuki Sugiura, Yuta Matsuoka, Rae Maeda, Keiichi Inoue, Kentaro Furukawa, Tomoyuki Fukuda, David C Chan, Tomotake Kanki.

Mitophagy plays an important role in the maintenance of mitochondrial homeostasis and can be categorized into two types: ubiquitin-mediated and receptor-mediated pathways. During receptor-mediated mitophagy, mitophagy receptors facilitate mitophagy by tethering the isolation membrane to mitochondria. Although at least five outer mitochondrial membrane proteins have been identified as mitophagy receptors, their individual contribution and interrelationship remain unclear. Here, we show that HeLa cells lacking BNIP3 and NIX, two of the five receptors, exhibit a complete loss of mitophagy in various conditions. Conversely, cells deficient in the other three receptors show normal mitophagy. Using BNIP3/NIX double knockout (DKO) cells as a model, we reveal that mitophagy deficiency elevates mitochondrial reactive oxygen species (mtROS), which leads to activation of the Nrf2 antioxidant pathway. Notably, BNIP3/NIX DKO cells are highly sensitive to ferroptosis when Nrf2-driven antioxidant enzymes are compromised. Moreover, the sensitivity of BNIP3/NIX DKO cells is fully rescued upon the introduction of wild-type BNIP3 and NIX, but not the mutant forms incapable of facilitating mitophagy. Consequently, our results demonstrate that BNIP3 and NIX-mediated mitophagy plays a role in regulating mtROS levels and protects cells from ferroptosis.

DOI: https://doi.org/10.1038/s41418-024-01280-y
Mol Biol Cell. 2024 Mar 27. mbcE24010041

Mapping Stress-Responsive Signaling Pathways Induced by Mitochondrial Proteostasis Perturbations.

Nicole Madrazo, Zinia Khattar, Evan T Powers, Jessica D Rosarda, R Luke Wiseman.

Imbalances in mitochondrial proteostasis are associated with pathologic mitochondrial dysfunction implicated in etiologically-diverse diseases. This has led to considerable interest in defining the mechanisms responsible for regulating mitochondria in response to mitochondrial stress. Numerous stress-responsive signaling pathways have been suggested to regulate mitochondria in response to proteotoxic stress. These include the integrated stress response (ISR), the heat shock response (HSR), and the oxidative stress response (OSR). Here, we define the stress signaling pathways activated in response to chronic mitochondrial proteostasis perturbations by monitoring the expression of sets of genes regulated downstream of each of these signaling pathways in published Perturb-seq datasets from K562 cells CRISPRi-depleted of mitochondrial proteostasis factors. Interestingly, we find that the ISR is preferentially activated in response to chronic, genetically-induced mitochondrial proteostasis stress, with no other pathway showing significant activation. Further, we demonstrate that CRISPRi depletion of other mitochondria-localized proteins similarly shows preferential activation of the ISR relative to other stress-responsive signaling pathways. These results both establish our gene set profiling approach as a viable strategy to probe stress responsive signaling pathways induced by perturbations to specific organelles and identify the ISR as the predominant stress-responsive signaling pathway activated in response to chronically disrupted of mitochondrial proteostasis.

DOI: https://doi.org/10.1091/mbc.E24-01-0041
bioRxiv. 2024 Feb 29. pii: 2024.02.29.582673. [Epub ahead of print]

DELE1 promotes translation-associated homeostasis, growth, and survival in mitochondrial myopathy.

Hsin-Pin Lin, Jennifer D Petersen, Alexandra J Gilsrud, Angelo Madruga, Theresa M D'Silva, Xiaoping Huang, Mario K Shammas, Nicholas P Randolph, Yan Li, Drew R Jones, Michael E Pacold, Derek P Narendra.

Mitochondrial dysfunction causes devastating disorders, including mitochondrial myopathy. Here, we identified that diverse mitochondrial myopathy models elicit a protective mitochondrial integrated stress response (mt-ISR), mediated by OMA1-DELE1 signaling. The response was similar following disruptions in mtDNA maintenance, from knockout of Tfam , and mitochondrial protein unfolding, from disease-causing mutations in CHCHD10 (G58R and S59L). The preponderance of the response was directed at upregulating pathways for aminoacyl-tRNA biosynthesis, the intermediates for protein synthesis, and was similar in heart and skeletal muscle but more limited in brown adipose challenged with cold stress. Strikingly, models with early DELE1 mt-ISR activation failed to grow and survive to adulthood in the absence of Dele1 , accounting for some but not all of OMA1's protection. Notably, the DELE1 mt-ISR did not slow net protein synthesis in stressed striated muscle, but instead prevented loss of translation-associated proteostasis in muscle fibers. Together our findings identify that the DELE1 mt-ISR mediates a stereotyped response to diverse forms of mitochondrial stress and is particularly critical for maintaining growth and survival in early-onset mitochondrial myopathy.

DOI: https://doi.org/10.1101/2024.02.29.582673
Phytomedicine. 2023 Dec 29. pii: S0944-7113(23)00686-4. [Epub ahead of print]128 155328

Diterpenoid honatisine overcomes temozolomide resistance in glioblastoma by inducing mitonuclear protein imbalance through disruption of TFAM-mediated mtDNA transcription.

Zongyang Li, Ke Sai, Guoxu Ma, Fanfan Chen, Xudong Xu, Lei Chen, Sicen Wang, Weiping Li, Guodong Huang, Ping Cui.

   BACKGROUND: Glioblastoma (GBM) represents as the most formidable intracranial malignancy. The systematic exploration of natural compounds for their potential applications in GBM therapy has emerged as a pivotal and fruitful avenue of research.
PURPOSE: In the present study, a panel of 96 diterpenoids was systematically evaluated as a repository of potential antitumour agents. The primary objective was to discern their potency in overcoming resistance to temozolomide (TMZ). Through an extensive screening process, honatisine, a heptacyclic diterpenoid alkaloid, emerged as the most robust candidate. Notably, honatisine exhibited remarkable efficacy in patient-derived primary and recurrent GBM strains. Subsequently, we subjected this compound to comprehensive scrutiny, encompassing GBM cultured spheres, GBM organoids (GBOs), TMZ-resistant GBM cell lines, and orthotopic xenograft mouse models of GBM cells.
RESULTS: Our investigative efforts delved into the mechanistic underpinnings of honatisine's impact. It was discerned that honatisine prompted mitonuclear protein imbalance and elicited the mitochondrial unfolded protein response (UPRmt). This effect was mediated through the selective depletion of mitochondrial DNA (mtDNA)-encoded subunits, with a particular emphasis on the diminution of mitochondrial transcription factor A (TFAM). The ultimate outcome was the instigation of deleterious mitochondrial dysfunction, culminating in apoptosis. Molecular docking and surface plasmon resonance (SPR) experiments validated honatisine's binding affinity to TFAM within its HMG-box B domain. This binding may promote phosphorylation of TFAM and obstruct the interaction of TFAM bound to heavy strand promoter 1 (HSP1), thereby enhancing Lon-mediated TFAM degradation. Finally, in vivo experiments confirmed honatisine's antiglioma properties. Our comprehensive toxicological assessments underscored its mild toxicity profile, emphasizing the necessity for a thorough evaluation of honatisine as a novel antiglioma agent.
CONCLUSION: In summary, our data provide new insights into the therapeutic mechanisms underlying honatisine's selective inducetion of apoptosis and its ability to overcome chemotherapy resistance in GBM. These actions are mediated through the disruption of mitochondrial proteostasis and function, achieved by the inhibition of TFAM-mediated mtDNA transcription. This study highlights honatisine's potential as a promising agent for glioblastoma therapy, underscoring the need for further exploration and investigation.

Keywords:  Chemotherapy resistance; Glioblastoma; Honatisine; Mitonuclear protein imbalance; TFAM

DOI:  https://doi.org/10.1016/j.phymed.2023.155328
Biomolecules. 2024 Feb 20. pii: 248. [Epub ahead of print]14(3):

Cloflucarban Illuminates Specificity and Context-Dependent Activation of the PINK1-Parkin Pathway by Mitochondrial Complex Inhibition.

Adrian T Ramirez, Zeyu Liu, Quanbin Xu, Sarah Nowosadtko, Xuedong Liu.

  The PTEN-induced kinase 1 (PINK1)-Parkin pathway plays a vital role in maintaining a healthy pool of mitochondria in higher eukaryotic cells. While the downstream components of this pathway are well understood, the upstream triggers remain less explored. In this study, we conducted an extensive analysis of inhibitors targeting various mitochondrial electron transport chain (ETC) complexes to investigate their potential as activators of the PINK1-Parkin pathway. We identified cloflucarban, an antibacterial compound, as a novel pathway activator that simultaneously inhibits mitochondrial complexes III and V, and V. RNA interference (RNAi) confirmed that the dual inhibition of these complexes activates the PINK1-Parkin pathway. Intriguingly, we discovered that albumin, specifically bovine serum albumin (BSA) and human serum albumin (HSA) commonly present in culture media, can hinder carbonyl cyanide m-chlorophenyl hydrazone (CCCP)-induced pathway activation. However, cloflucarban's efficacy remains unaffected by albumin, highlighting its reliability for studying the PINK1-Parkin pathway. This study provides insights into the activation of the upstream PINK1-Parkin pathway and underscores the influence of culture conditions on research outcomes. Cloflucarban emerges as a promising tool for investigating mitochondrial quality control and neurodegenerative diseases.

Keywords:  CCCP; PINK1; Parkin; bovine serum albumin; cloflucarban; complex V; electron transport complex III; human serum albumin; mitochondrial quality control; mitophagy

DOI:  https://doi.org/10.3390/biom14030248
Chem Biol Interact. 2024 Mar 27. pii: S0009-2797(24)00121-2. [Epub ahead of print] 110975

Nickel induces mitochondrial damage in renal cells in vitro and in vivo through its effects on mitochondrial biogenesis, fusion, and fission.

Heng Yin, Xinglai Li, Chengbi Wang, Xiaocong Li, Jingbo Liu.

  Nickel (Ni) and its compounds are common, widely distributed components of hazardous waste in the chemical industry. Excessive exposure to Ni can cause kidney damage in humans and animals. We investigated the impact of Ni on renal mitochondria using in vivo and in vitro models of Ni nephrotoxicity, and explored the Ni nephrotoxic mechanism. We showed that nickel chloride (NiCl2) damaged the renal mitochondria, causing mitochondrial swelling, breakage of the mitochondrial cristae, increased levels of mitochondrial reactive oxygen species (mt-ROS), and depolarization of the mitochondrial membrane potential (MMP). The levels of the mitochondrial respiratory chain complexes I-IV were reduced in the kidneys of mice treated with NiCl2. In addition, NiCl2 treatment inhibited mitochondrial biogenesis in renal cells by down-regulating mRNA and the protein expression of TFAM, PGC-1α, and NRF1. Moreover, NiCl2 reduced the levels of the proteins involved in mitochondrial fusion, including Mfn1 and Mfn2, while significantly augmenting the levels of the proteins Fis1 and Drip1 involved in mitochondrial fission in renal cells. Taken together, these results suggested that NiCl2 inhibited mitochondrial biogenesis, suppressed mitochondrial fusion, and promoted mitochondrial fission, resulting in mitochondrial dysfunction in renal cells, ultimately causing renal injury. This study provided novel insights into the mechanisms of nephrotoxicity of Ni and new ideas for the development of targeted treatments for Ni-induced kidney injury.

Keywords:  Kidney; Mitochondria; Mitochondrial biogenesis; Mitochondrial division; Mitochondrial fusion; Nickel

DOI:  https://doi.org/10.1016/j.cbi.2024.110975
PLoS One. 2024 ;19(3): e0301372

Quantitative imaging and semiotic phenotyping of mitochondrial network morphology in live human cells.

Sophie Charrasse, Victor Racine, Charlotte Saint-Omer, Titouan Poquillon, Loïc Lionnard, Marine Ledru, Christophe Gonindard, Sandrine Delaunois, Karima Kissa, Richard E Frye, Manuela Pastore, Christelle Reynes, Mathilde Frechet, Hanane Chajra, Abdel Aouacheria.

The importance of mitochondria in tissue homeostasis, stress responses and human diseases, combined to their ability to transition between various structural and functional states, makes them excellent organelles for monitoring cell health. There is therefore a need for technologies to accurately analyze and quantify changes in mitochondrial organization in a variety of cells and cellular contexts. Here we present an innovative computerized method that enables accurate, multiscale, fast and cost-effective analysis of mitochondrial shape and network architecture from confocal fluorescence images by providing more than thirty features. In order to facilitate interpretation of the quantitative results, we introduced two innovations: the use of Kiviat-graphs (herein named MitoSpider plots) to present highly multidimensional data and visualization of the various mito-cellular configurations in the form of morphospace diagrams (called MitoSigils). We tested our fully automated image analysis tool on rich datasets gathered from live normal human skin cells cultured under basal conditions or exposed to specific stress including UVB irradiation and pesticide exposure. We demonstrated the ability of our proprietary software (named MitoTouch) to sensitively discriminate between control and stressed dermal fibroblasts, and between normal fibroblasts and other cell types (including cancer tissue-derived fibroblasts and primary keratinocytes), showing that our automated analysis captures subtle differences in morphology. Based on this novel algorithm, we report the identification of a protective natural ingredient that mitigates the deleterious impact of hydrogen peroxide (H2O2) on mitochondrial organization. Hence we conceived a novel wet-plus-dry pipeline combining cell cultures, quantitative imaging and semiotic analysis for exhaustive analysis of mitochondrial morphology in living adherent cells. Our tool has potential for broader applications in other research areas such as cell biology and medicine, high-throughput drug screening as well as predictive and environmental toxicology.

DOI: https://doi.org/10.1371/journal.pone.0301372
Nat Commun. 2024 Mar 22. 15(1): 2598

Rab4A-directed endosome traffic shapes pro-inflammatory mitochondrial metabolism in T cells via mitophagy, CD98 expression, and kynurenine-sensitive mTOR activation.

Nick Huang, Thomas Winans, Brandon Wyman, Zachary Oaks, Tamas Faludi, Gourav Choudhary, Zhi-Wei Lai, Joshua Lewis, Miguel Beckford, Manuel Duarte, Daniel Krakko, Akshay Patel, Joy Park, Tiffany Caza, Mahsa Sadeghzadeh, Laurence Morel, Mark Haas, Frank Middleton, Katalin Banki, Andras Perl.

Activation of the mechanistic target of rapamycin (mTOR) is a key metabolic checkpoint of pro-inflammatory T-cell development that contributes to the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE), however, the underlying mechanisms remain poorly understood. Here, we identify a functional role for Rab4A-directed endosome traffic in CD98 receptor recycling, mTOR activation, and accumulation of mitochondria that connect metabolic pathways with immune cell lineage development and lupus pathogenesis. Based on integrated analyses of gene expression, receptor traffic, and stable isotope tracing of metabolic pathways, constitutively active Rab4AQ72L exerts cell type-specific control over metabolic networks, dominantly impacting CD98-dependent kynurenine production, mTOR activation, mitochondrial electron transport and flux through the tricarboxylic acid cycle and thus expands CD4+ and CD3+CD4-CD8- double-negative T cells over CD8+ T cells, enhancing B cell activation, plasma cell development, antinuclear and antiphospholipid autoantibody production, and glomerulonephritis in lupus-prone mice. Rab4A deletion in T cells and pharmacological mTOR blockade restrain CD98 expression, mitochondrial metabolism and lineage skewing and attenuate glomerulonephritis. This study identifies Rab4A-directed endosome traffic as a multilevel regulator of T cell lineage specification during lupus pathogenesis.

DOI: https://doi.org/10.1038/s41467-024-46441-2
Cell Rep. 2024 Mar 28. pii: S2211-1247(24)00346-2. [Epub ahead of print]43(4): 114018

Distinct types of intramitochondrial protein aggregates protect mitochondria against proteotoxic stress.

Lea Bertgen, Jan-Eric Bökenkamp, Tim Schneckmann, Christian Koch, Markus Räschle, Zuzana Storchová, Johannes M Herrmann.

  Mitochondria consist of hundreds of proteins, most of which are inaccessible to the proteasomal quality control system of the cytosol. How cells stabilize the mitochondrial proteome during challenging conditions remains poorly understood. Here, we show that mitochondria form spatially defined protein aggregates as a stress-protecting mechanism. Two different types of intramitochondrial protein aggregates can be distinguished. The mitoribosomal protein Var1 (uS3m) undergoes a stress-induced transition from a soluble, chaperone-stabilized protein that is prevalent under benign conditions to an insoluble, aggregated form upon acute stress. The formation of Var1 bodies stabilizes mitochondrial proteostasis, presumably by sequestration of aggregation-prone proteins. The AAA chaperone Hsp78 is part of a second type of intramitochondrial aggregate that transiently sequesters proteins and promotes their folding or Pim1-mediated degradation. Thus, mitochondrial proteins actively control the formation of distinct types of intramitochondrial protein aggregates, which cooperate to stabilize the mitochondrial proteome during proteotoxic stress conditions.

Keywords:  CP: Cell biology; CP: Molecular biology; Hsp78; MitoStores; Pim1 protease; Var1 bodies; aggregates; chaperones; mitochondria; mitoribosome; protein folding; protein import

DOI:  https://doi.org/10.1016/j.celrep.2024.114018
J Cell Biol. 2024 May 06. pii: e202306051. [Epub ahead of print]223(5):

OMA1 protease eliminates arrested protein import intermediates upon mitochondrial depolarization.

Magda Krakowczyk, Anna M Lenkiewicz, Tomasz Sitarz, Dominika Malinska, Mayra Borrero, Ben Hur Marins Mussulini, Vanessa Linke, Andrzej A Szczepankiewicz, Joanna M Biazik, Agata Wydrych, Hanna Nieznanska, Remigiusz A Serwa, Agnieszka Chacinska, Piotr Bragoszewski.

Most mitochondrial proteins originate from the cytosol and require transport into the organelle. Such precursor proteins must be unfolded to pass through translocation channels in mitochondrial membranes. Misfolding of transported proteins can result in their arrest and translocation failure. Arrested proteins block further import, disturbing mitochondrial functions and cellular proteostasis. Cellular responses to translocation failure have been defined in yeast. We developed the cell line-based translocase clogging model to discover molecular mechanisms that resolve failed import events in humans. The mechanism we uncover differs significantly from these described in fungi, where ATPase-driven extraction of blocked protein is directly coupled with proteasomal processing. We found human cells to rely primarily on mitochondrial factors to clear translocation channel blockage. The mitochondrial membrane depolarization triggered proteolytic cleavage of the stalled protein, which involved mitochondrial protease OMA1. The cleavage allowed releasing the protein fragment that blocked the translocase. The released fragment was further cleared in the cytosol by VCP/p97 and the proteasome.

DOI: https://doi.org/10.1083/jcb.202306051
Exp Mol Med. 2024 Mar 27.

Involvement of DJ-1 in the pathogenesis of intervertebral disc degeneration via hexokinase 2-mediated mitophagy.

Jialiang Lin, Longjie Wang, Yuhao Wu, Qian Xiang, Yongzhao Zhao, Xuanqi Zheng, Shuai Jiang, Zhuoran Sun, Dongwei Fan, Weishi Li.

Intervertebral disc degeneration (IDD) is an important pathological basis for degenerative spinal diseases and is involved in mitophagy dysfunction. However, the molecular mechanisms underlying mitophagy regulation in IDD remain unclear. This study aimed to clarify the role of DJ-1 in regulating mitophagy during IDD pathogenesis. Here, we showed that the mitochondrial localization of DJ-1 in nucleus pulposus cells (NPCs) first increased and then decreased in response to oxidative stress. Subsequently, loss- and gain-of-function experiments revealed that overexpression of DJ-1 in NPCs inhibited oxidative stress-induced mitochondrial dysfunction and mitochondria-dependent apoptosis, whereas knockdown of DJ-1 had the opposite effect. Mechanistically, mitochondrial translocation of DJ-1 promoted the recruitment of hexokinase 2 (HK2) to damaged mitochondria by activating Akt and subsequently Parkin-dependent mitophagy to inhibit oxidative stress-induced apoptosis in NPCs. However, silencing Parkin, reducing mitochondrial recruitment of HK2, or inhibiting Akt activation suppressed DJ-1-mediated mitophagy. Furthermore, overexpression of DJ-1 ameliorated IDD in rats through HK2-mediated mitophagy. Taken together, these findings indicate that DJ-1 promotes HK2-mediated mitophagy under oxidative stress conditions to inhibit mitochondria-dependent apoptosis in NPCs and could be a therapeutic target for IDD.

DOI: https://doi.org/10.1038/s12276-024-01196-0
Antioxidants (Basel). 2024 Mar 14. pii: 347. [Epub ahead of print]13(3):

Norcantharidin Sensitizes Colorectal Cancer Cells to Radiotherapy via Reactive Oxygen Species-DRP1-Mediated Mitochondrial Damage.

Qiong Xu, Heng Zhang, Haoren Qin, Huaqing Wang, Hui Wang.

  Norcantharidin (NCTD), a cantharidin derivative, induces ROS generation and is widely used to treat CRC. In this study, we clarified the role and mechanism of action of norcantharidin in increasing CRC sensitivity to radiotherapy. We treated the CRC cell lines LoVo and DLD-1 with NCTD (10 or 50 μmol/L), ionizing radiation (IR, 6 Gy), and a combination of the two and found that NCTD significantly inhibited the proliferation of CRC cells and enhanced their sensitivity to radiotherapy. NCTD induced ROS generation by decreasing the mitochondrial membrane potential, increasing mitochondrial membrane permeability, and promoting cytochrome C release from mitochondria into the cytoplasm. IR combined with NCTD induced ROS production, which activated the mitochondrial fission protein DRP1, leading to increased mitochondrial fission and CRC sensitivity to radiotherapy. NCTD also reduced CRC cell resistance to radiotherapy by blocking the cell cycle at the G2/M phase and decreasing p-CHK2, cyclin B1, and p-CDC2 expression. NCTD and IR also inhibited radiation resistance by causing DNA damage. Our findings provide evidence for the potential therapeutic use of NCTD and IR against CRC. Moreover, this study elucidates whether NCTD can overcome CRC radiation tolerance and provides insights into the underlying mechanisms.

Keywords:  DRP1; NCTD; ROS; colorectal cancer; mitochondria

DOI:  https://doi.org/10.3390/antiox13030347
Proc Natl Acad Sci U S A. 2024 Apr 02. 121(14): e2217019121

Force-induced tail-autotomy mitochondrial fission and biogenesis of matrix-excluded mitochondrial-derived vesicles for quality control.

Xiaoying Liu, Linyu Xu, Yutong Song, Zhihao Zhao, Xinyu Li, Cheuk-Yiu Wong, Rong Chen, Jianxiong Feng, Yitao Gou, Yajing Qi, Hei-Man Chow, Shuhuai Yao, Yi Wang, Song Gao, Xingguo Liu, Liting Duan.

  Mitochondria constantly fuse and divide for mitochondrial inheritance and functions. Here, we identified a distinct type of naturally occurring fission, tail-autotomy fission, wherein a tail-like thin tubule protrudes from the mitochondrial body and disconnects, resembling autotomy. Next, utilizing an optogenetic mitochondria-specific mechanostimulator, we revealed that mechanical tensile force drives tail-autotomy fission. This force-induced fission involves DRP1/MFF and endoplasmic reticulum tubule wrapping. It redistributes mitochondrial DNA, producing mitochondrial fragments with or without mitochondrial DNA for different fates. Moreover, tensile force can decouple outer and inner mitochondrial membranes, pulling out matrix-excluded tubule segments. Subsequent tail-autotomy fission separates the matrix-excluded tubule segments into matrix-excluded mitochondrial-derived vesicles (MDVs) which recruit Parkin and LC3B, indicating the unique role of tail-autotomy fission in segregating only outer membrane components for mitophagy. Sustained force promotes fission and MDV biogenesis more effectively than transient one. Our results uncover a mechanistically and functionally distinct type of fission and unveil the role of tensile forces in modulating fission and MDV biogenesis for quality control, underscoring the heterogeneity of fission and mechanoregulation of mitochondrial dynamics.

Keywords:  mitochondrial fission; mitochondrial quality control; optogenetics; photoactivatable proteins; tensile force

DOI:  https://doi.org/10.1073/pnas.2217019121
Biology (Basel). 2024 Mar 15. pii: 187. [Epub ahead of print]13(3):

How Mitochondrial Signaling Games May Shape and Stabilize the Nuclear-Mitochondrial Symbiosis.

Will Casey, Thiviya Kumaran, Steven E Massey, Bud Mishra.

  The eukaryotic lineage has enjoyed a long-term "stable" mutualism between nucleus and mitochondrion, since mitochondrial endosymbiosis began about 2 billion years ago. This mostly cooperative interaction has provided the basis for eukaryotic expansion and diversification, which has profoundly altered the forms of life on Earth. While we ignore the exact biochemical details of how the alpha-proteobacterial ancestor of mitochondria entered into endosymbiosis with a proto-eukaryote, in more general terms, we present a signaling games perspective of how the cooperative relationship became established, and has been maintained. While games are used to understand organismal evolution, information-asymmetric games at the molecular level promise novel insights into endosymbiosis. Using a previously devised biomolecular signaling games approach, we model a sender-receiver information asymmetric game, in which the informed mitochondrial sender signals and the uninformed nuclear receiver may take actions (involving for example apoptosis, senescence, regeneration and autophagy/mitophagy). The simulation shows that cellularization is a stabilizing mechanism for Pareto efficient sender/receiver strategic interaction. In stark contrast, the extracellular environment struggles to maintain efficient outcomes, as senders are indifferent to the effects of their signals upon the receiver. Our hypothesis has translational implications, such as in cellular therapy, as mitochondrial medicine matures. It also inspires speculative conjectures about how an analogous human-AI endosymbiosis may be engineered.

Keywords:  endosymbiosis; information asymmetry; mitochondria; signaling game

DOI:  https://doi.org/10.3390/biology13030187
J Endocrinol. 2024 Mar 01. pii: JOE-23-0357. [Epub ahead of print]

Insulin induces bioenergetic changes and alters mitochondrial dynamics in podocytes.

Irena Audzeyenka, Patrycja Rachubik, Dorota Rogacka, Moin A Saleem, Agnieszka Piwkowska.

Diabetic nephropathy (DN) is one of the most frequent complications of diabetes. Early stages of DN are associated with hyperinsulinemia and progressive insulin resistance in insulin-sensitive cells, including podocytes. The diabetic environment induces pathological changes, especially in podocyte bioenergetics, which is tightly linked with mitochondrial dynamics. The regulatory role of insulin in mitochondrial morphology in podocytes has not been fully elucidated. Therefore, the main goal of the present study was to investigate effects of insulin on the regulation of mitochondrial dynamics and bioenergetics in human podocytes. Biochemical analyses were performed to assess oxidative phosphorylation efficiency by measuring the oxygen consumption rate (OCR) and glycolysis by measuring the extracellular acidification rate (ECAR). mRNA and protein expression were determined by real-time polymerase chain reaction and Western blot. The intracellular mitochondrial network was visualized by MitoTracker staining. All calculations were conducted using CellProfiler software. Short-term insulin exposure exerted inhibitory effects on various parameters of oxidative respiration and adenosine triphosphate production, and glycolysis flux was elevated. After a longer time of treating cells with insulin, an increase in mitochondrial size was observed, accompanied by a reduction of expression of the mitochondrial fission markers DRP1 and FIS1 and an increase in mitophagy. Overall, we identified a previously unknown role for insulin in the regulation of oxidative respiration and glycolysis and elucidated mitochondrial dynamics in human podocytes. The present results emphasize the importance of the duration of insulin stimulation for its metabolic and molecular effects, which should be considered in clinical and experimental studies of DN.

DOI: https://doi.org/10.1530/JOE-23-0357
Dev Comp Immunol. 2024 Mar 22. pii: S0145-305X(24)00040-5. [Epub ahead of print]156 105168

CgPHB2 involved in the haemocyte mitophagy in response to Vibrio splendidus stimulation in Pacific oyster Crassostrea gigas.

Shurong Li, Jiejie Sun, Yinan Li, Xiaoqian Lv, Lingling Wang, Linsheng Song.

  Prohibitin2 (PHB2) is recently identified as a novel inner membrane mitophagy receptor to mediate mitophagy. In the present study, the function of CgPHB2 in mediating mitophagy in response to Vibrio splendidus stimulation was investigated in Crassostrea gigas. CgPHB2 protein was mainly distributed in the cytoplasm of three subpopulations of haemocytes. After V. splendidus stimulation, the expressions of CgPHB2 mRNA in haemocytes were up-regulated significantly at 6, 12 and 24 h, and the abundance of CgPHB2 protein was also enhanced at 12-24 h compared to control group. Furthermore, the green signals of CgPHB2 were colocalized respectively with the red signals of mitochondria and CgLC3 in the haemocytes at 12 h after V. splendidus stimulation, and the co-localization value of CgPHB2 and mtphagy Dye was significantly increased. The direct interaction between CgPHB2 and CgLC3 was simulated by molecular docking. In PHB2-inhibitor Fluorizoline-treated oysters, the mRNA expressions of mitophagy-related genes and the ratio of mitophagy were significantly decreased in haemocytes of oysters after V. splendidus stimulation. All the results collectively suggested that CgPHB2 participated in mediating the haemocyte mitophagy in the antibacterial immune response of oysters.

Keywords:  Crassostrea gigas; Innate immunity; Mitophagy; Prohibitin 2

DOI:  https://doi.org/10.1016/j.dci.2024.105168
Eur J Clin Invest. 2024 Mar 26. e14199

Mitophagy modulation for the treatment of cardiovascular diseases.

Italian Society of Cardiology Working Group on Cellular and Molecular Biology of the Heart

   BACKGROUND: Defects of mitophagy, the selective form of autophagy for mitochondria, are commonly observed in several cardiovascular diseases and represent the main cause of mitochondrial dysfunction. For this reason, mitophagy has emerged as a novel and potential therapeutic target.
METHODS: In this review, we discuss current evidence about the biological significance of mitophagy in relevant preclinical models of cardiac and vascular diseases, such as heart failure, ischemia/reperfusion injury, metabolic cardiomyopathy and atherosclerosis.
RESULTS: Multiple studies have shown that cardiac and vascular mitophagy is an adaptive mechanism in response to stress, contributing to cardiovascular homeostasis. Mitophagy defects lead to cell death, ultimately impairing cardiac and vascular function, whereas restoration of mitophagy by specific compounds delays disease progression.
CONCLUSIONS: Despite previous efforts, the molecular mechanisms underlying mitophagy activation in response to stress are not fully characterized. A comprehensive understanding of different forms of mitophagy active in the cardiovascular system is extremely important for the development of new drugs targeting this process. Human studies evaluating mitophagy abnormalities in patients at high cardiovascular risk also represent a future challenge.

Keywords:  autophagy; heart failure; metabolic cardiomyopathy; mitochondrial dysfunction; mitophagy; myocardial ischemia

DOI:  https://doi.org/10.1111/eci.14199
BMC Cardiovasc Disord. 2024 Mar 27. 24(1): 183

Bioinformatics integration reveals key genes associated with mitophagy in myocardial ischemia-reperfusion injury.

Zhian Chen, Tianying Liu, Hao Yuan, Han Sun, Sitong Liu, Shuai Zhang, Li Liu, Shuang Jiang, Yong Tang, Zhi Liu.

   BACKGROUND: Myocardial ischemia is a prevalent cardiovascular disorder associated with significant morbidity and mortality. While prompt restoration of blood flow is essential for improving patient outcomes, the subsequent reperfusion process can result in myocardial ischemia-reperfusion injury (MIRI). Mitophagy, a specialized autophagic mechanism, has consistently been implicated in various cardiovascular disorders. However, the specific connection between ischemia-reperfusion and mitophagy remains elusive. This study aims to elucidate and validate central mitophagy-related genes associated with MIRI through comprehensive bioinformatics analysis.
METHODS: We acquired the microarray expression profile dataset (GSE108940) from the Gene Expression Omnibus (GEO) and identified differentially expressed genes (DEGs) using GEO2R. Subsequently, these DEGs were cross-referenced with the mitophagy database, and differential nucleotide sequence analysis was performed through enrichment analysis. Protein-protein interaction (PPI) network analysis was employed to identify hub genes, followed by clustering of these hub genes using cytoHubba and MCODE within Cytoscape software. Gene set enrichment analysis (GSEA) was conducted on central genes. Additionally, Western blotting, immunofluorescence, and quantitative polymerase chain reaction (qPCR) analyses were conducted to validate the expression patterns of pivotal genes in MIRI rat model and H9C2 cardiomyocytes.
RESULTS: A total of 2719 DEGs and 61 mitophagy-DEGs were identified, followed by enrichment analyses and the construction of a PPI network. HSP90AA1, RPS27A, EEF2, EIF4A1, EIF2S1, HIF-1α, and BNIP3 emerged as the seven hub genes identified by cytoHubba and MCODE of Cytoscape software. Functional clustering analysis of HIF-1α and BNIP3 yielded a score of 9.647, as determined by Cytoscape (MCODE). In our MIRI rat model, Western blot and immunofluorescence analyses confirmed a significant elevation in the expression of HIF-1α and BNIP3, accompanied by a notable increase in the ratio of LC3II to LC3I. Subsequently, qPCR confirmed a significant upregulation of HIF-1α, BNIP3, and LC3 mRNA in the MIRI group. Activation of the HIF-1α/BNIP3 pathway mediates the regulation of the degree of Mitophagy, thereby effectively reducing apoptosis in rat H9C2 cardiomyocytes.
CONCLUSIONS: This study has identified seven central genes among mitophagy-related DEGs that may play a pivotal role in MIRI, suggesting a correlation between the HIF-1α/BNIP3 pathway of mitophagy and the pathogenesis of MIRI. The findings highlight the potential importance of mitophagy in MIRI and provide valuable insights into underlying mechanisms and potential therapeutic targets for further exploration in future studies.

Keywords:  Bioinformatics; Hub genes; Ischemia–reperfusion injury; Mitophagy

DOI:  https://doi.org/10.1186/s12872-024-03834-x
Shock. 2024 Mar 25.

Mdivi-1 alleviates sepsis-induced liver injury by inhibiting STING signaling activation.

Qin Zhang, Zhuanhua Liu, Xiaoxia Huang, Xin Heng, Jie Wu, Zhenfeng Chen, Xiaohua Guo, Jun Fan, Qiaobing Huang.

ABSTRACT: Pro-inflammatory hyperactivation of kupffer cells (KCs) is foremost involved in the pathogenesis of sepsis-induced liver injury. Our previous study found that stimulator of interferon genes (STING) signaling was activated in KCs in response of lipopolysaccharide (LPS) and knocking down dynamin-related protein 1 (DRP1) in KCs effectively inhibited the activation of STING signaling and the subsequent production of pro-inflammatory cytokines. In this study, we demonstrated that in vivo treatment with mitochondrial division inhibitor 1 (Mdivi-1), a selective inhibitor of DRP1, alleviated cecal ligation and puncture (CLP)-induced liver injury with the improvement of liver pathology and function. Moreover, we found that STING in liver was mainly concentrated in KCs and STING signaling was significantly activated in KCs after CLP. STING deficiency effectively ameliorated liver injury and decreased the mortality of septic mice, which were reversely worsened by the enhanced activation of STING with DMXAA. The further study showed that Mdivi-1 markedly attenuated STING signaling activation in KCs and inhibited systemic inflammatory response. Importantly, DMXAA application in CLP mice blunted Mdivi-1's liver protection effect. Taken together, our study confirmed Mdivi-1 effectively alleviated CLP-induced liver injury partially through inhibiting STING signaling activation in KCs, which provides new insights and a novel potential pharmacological therapeutic target for treating septic liver injury.

DOI: https://doi.org/10.1097/SHK.0000000000002349
Bone. 2024 Mar 27. pii: S8756-3282(24)00075-9. [Epub ahead of print] 117086

Mitofusin 2 plays a critical role in maintaining the functional integrity of the neuromuscular-skeletal axis.

Meiling Zhu, Caroline Zeiss, Mark W Hamrick, Robert S Weinstein, Ben-Hua Sun, Marco Brotto, Xinran Liu, Edwin Siu, Anita Huttner, Steven Tommasini, Christine Simpson, Karl Insogna.

PURPOSE: Mitofusin 2 (Mfn2) is one of two mitofusins involved in regulating mitochondrial size, shape and function, including mitophagy, an important cellular mechanism to limit oxidative stress. Reduced expression of Mfn2 has been associated with impaired osteoblast differentiation and function and a reduction in the number of viable osteocytes in bone. We hypothesized that the genetic absence of Mfn2 in these cells would increase their susceptibility to aging-associated metabolic stress, leading to a progressive impairment in skeletal homeostasis over time.
METHODS: Mfn2 was selectively deleted in vivo at three different stages of osteoblast lineage commitment by crossing mice in which the Mfn2 gene was floxed with transgenic mice expressing Cre under the control of the promoter for Osterix (OSX), collagen1a1, or DMP1 (Dentin Matrix Acidic Phosphoprotein 1).
RESULTS: Mice in which Mfn2 was deleted using DMP1-cre demonstrated a progressive and dramatic decline in bone mineral density (BMD) beginning at 10 weeks of age (n = 5 for each sex and each genotype from age 10 to 20 weeks). By 15 weeks, there was evidence for a functional decline in muscle performance as assessed using a rotarod apparatus (n = 3; 2 males/ 1 female for each genotype), accompanied by a decline in lean body mass. A marked reduction in trabecular bone mass was evident on bone histomorphometry, and biomechanical testing at 25 weeks (k/o: 2 male/1 female, control 2 male/2 female) revealed severely impaired femur strength. Extensive regional myofiber atrophy and degeneration was observed on skeletal muscle histology. Electron microscopy showed progressive disruption of cellular architecture, with disorganized sarcomeres and a bloated mitochondrial reticulum. There was also evidence of neurodegeneration within the ventral horn and roots of the lumbar spinal cord, which was accompanied by myelin loss and myofiber atrophy. Deletion of Mfn2 using OSX-cre or Col1a1-cre did not result in a musculoskeletal phenotype. Where possible, male and female animals were analyzed separately, but small numbers of animals in each group limited statistical power. For other outcomes, where sex was not considered, small sample sizes might still limit the strength of the observation.
CONCLUSION: Despite known functional overlap of Mfn1 and Mfn2 in some tissues, and their co-expression in bone, muscle and spinal cord, deletion of Mfn2 using the 8 kB DMP1 promoter uncovered an important non-redundant role for Mfn2 in maintaining the neuromuscular/bone axis.

DOI: https://doi.org/10.1016/j.bone.2024.117086
Sci Rep. 2024 Mar 28. 14(1): 7358

Real-time analysis of osteoclast resorption and fusion dynamics in response to bone resorption inhibitors.

Preety Panwar, Jacob Bastholm Olesen, Galia Blum, Jean-Marie Delaisse, Kent Søe, Dieter Brömme.

  Cathepsin K (CatK), an essential collagenase in osteoclasts (OCs), is a potential therapeutic target for the treatment of osteoporosis. Using live-cell imaging, we monitored the bone resorptive behaviour of OCs during dose-dependent inhibition of CatK by an ectosteric (Tanshinone IIA sulfonate) and an active site inhibitor (odanacatib). CatK inhibition caused drastic reductions in the overall resorption speed of OCs. At IC50 CatK-inhibitor concentration, OCs reduced about 40% of their trench-forming capacity and at fourfold IC50 concentrations, a > 95% reduction was observed. The majority of CatK-inhibited OCs (~ 75%) were involved in resorption-migration-resorption episodes forming adjacent pits, while ~ 25% were stagnating OCs which remained associated with the same excavation. We also observed fusions of OCs during the resorption process both in control and inhibitor-treated conditions, which increased their resorption speeds by 30-50%. Inhibitor IC50-concentrations increased OC-fusion by twofold. Nevertheless, more fusion could not counterweigh the overall loss of resorption activity by inhibitors. Using an activity-based probe, we demonstrated the presence of active CatK at the resorbing front in pits and trenches. In conclusion, our data document how OCs respond to CatK-inhibition with respect to movement, bone resorption activity, and their attempt to compensate for inhibition by activating fusion.

Keywords:  Active-site probe; Bone resorption; Cathepsin K; Cell fusion; Human osteoclast; Live-imaging

DOI:  https://doi.org/10.1038/s41598-024-57526-9
Anal Methods. 2024 Mar 27.

A pH-response-based fluorescent probe for detecting the mitophagy process by tracing changes in colocalization coefficients.

Nongyi Hao, Zekun Jiang, Lina Zhou, Xiaoyu Dai, Xiuqi Kong.

Mitochondria are not only the center of energy metabolism but also involved in regulating cellular activities. Quality and quantity control of mitochondria is therefore essential. Mitophagy is a lysosome-dependent process to clear dysfunctional mitochondria, and abnormal mitophagy can cause metabolic disorders. Therefore, it is necessary to monitor the mitophagy in living cells on a real-time basis. Herein, we developed a pH-responsive fluorescent probe MP for the detection of the mitophagy process using real-time tracing colocalization coefficients. Probe MP showed good pH responses with high selectivity and sensitivity in spectral testing. Probe MP is of positive charge, which is beneficial for accumulating into mitochondrial in living cells. Cells exhibited pH-dependent fluorescence when they were treated with different pH media. Importantly, the changes in the colocalization coefficient between probe MP and Lyso Tracker® Deep Red from 0.4 to 0.8 were achieved in a real-time manner during the mitophagy stimulated by CCCP, starvation and rapamycin. Therefore, combined with the parameter of the colocalization coefficient, probe MP is a potential molecular tool for the real-time tracing of mitophagy to further explore the details of mitophagy.

DOI: https://doi.org/10.1039/d4ay00211c
Free Radic Res. 2024 Mar 27. 1-14

Humanin inhibits lymphatic endothelial cells dysfunction to alleviate myocardial infarction-reperfusion injury via BNIP3-mediated mitophagy.

Lu Chen, Xiaohua Yang, Kai Wang, Lina Guo, Cao Zou.

   OBJECTIVE: Acute myocardial infarction (AMI) ranks among the top contributors to sudden death and disability worldwide. It should be noted that current therapies always cause increased reperfusion damage. Evidence suggests that humanin (HN) reduces mitochondrial dysfunction to have cardio-protective effects against MI-reperfusion injury. In this context, we hypothesized that HN may attenuate MI-reperfusion injury by alleviating lymphatic endothelial cells dysfunction through the regulation of mitophagy.
MATERIALS AND METHODS: In this study, primary lymphatic endothelial cells were selected as the experimental model. Cells were maintained under 1% O2 to induce a hypoxic phenotype. For in vivo experiments, the left coronary arteries of C57/BL6 mice were clamped for 45 min followed by 24 h reperfusion to develop MI-reperfusion injury. The volume of infarcted myocardium in MI-reperfusion injury mouse models were TTC staining. PCR and western blot were used to quantify the expression of autophagy-, mitophagy- and mitochondria-related markers. The fibrosis and apoptosis in the ischemic area were evaluated for Masson staining and TUNEL respectively. We also used western blot to analyze the expression of VE-Cadherin in lymphatic endothelial cells.
RESULTS: We firstly exhibited a specific mechanism by which HN mitigates MI-reperfusion injury. We demonstrated that HN effectively reduces such injury in vivo and also inhibits dysfunction in lymphatic endothelial cells in vitro. Importantly, this inhibitory effect is mediated through BNIP3-associated mitophagy.
CONCLUSIONS: In conclusion, HN alleviates myocardial infarction-reperfusion injury by inhibiting lymphatic endothelial cells dysfunction, primarily through BNIP3-mediated mitophagy.

Keywords:  Myocardial infarction-reperfusion injury; humanin; lymphatic endothelial cells; mitophagy

DOI:  https://doi.org/10.1080/10715762.2024.2333074
Cells. 2024 Mar 07. pii: 473. [Epub ahead of print]13(6):

The Mitochondrial Connection: The Nek Kinases' New Functional Axis in Mitochondrial Homeostasis.

Fernanda L Basei, Ivan Rosa E Silva, Pedro R Firmino Dias, Camila C Ferezin, Andressa Peres de Oliveira, Luidy K Issayama, Livia A R Moura, Fernando Riback da Silva, Jörg Kobarg.

  Mitochondria provide energy for all cellular processes, including reactions associated with cell cycle progression, DNA damage repair, and cilia formation. Moreover, mitochondria participate in cell fate decisions between death and survival. Nek family members have already been implicated in DNA damage response, cilia formation, cell death, and cell cycle control. Here, we discuss the role of several Nek family members, namely Nek1, Nek4, Nek5, Nek6, and Nek10, which are not exclusively dedicated to cell cycle-related functions, in controlling mitochondrial functions. Specifically, we review the function of these Neks in mitochondrial respiration and dynamics, mtDNA maintenance, stress response, and cell death. Finally, we discuss the interplay of other cell cycle kinases in mitochondrial function and vice versa. Nek1, Nek5, and Nek6 are connected to the stress response, including ROS control, mtDNA repair, autophagy, and apoptosis. Nek4, in turn, seems to be related to mitochondrial dynamics, while Nek10 is involved with mitochondrial metabolism. Here, we propose that the participation of Neks in mitochondrial roles is a new functional axis for the Nek family.

Keywords:  Nek kinase family functions; cell cycle; cellular signaling; mitochondrial homeostasis

DOI:  https://doi.org/10.3390/cells13060473
Sci Total Environ. 2024 Mar 27. pii: S0048-9697(24)02160-0. [Epub ahead of print] 172017

L-arginine alleviates heat stress-induced mammary gland injury through modulating CASTOR1-mTORC1 axis mediated mitochondrial homeostasis.

Zhongchao Gai, Songhao Hu, Yujiao He, Sijia Yan, Ranran Wang, Guoli Gong, Jieqiong Zhao.

  As global warming intensifies, extreme heat is becoming increasingly frequent. These extreme heatwaves have decreased the milk production of dairy animals such as cows and goats and have caused significant damage to the entire dairy industry. It is known that heat stress (HS) can induce the apoptosis and autophagy of mammary epithelial cells (MECs), leading to a decrease in lactating MECs. L-arginine can effectively attenuate HS-induced decreases in milk yield, but the exact mechanisms are not fully understood. In this study, we found that HS upregulated the arginine sensor CASTOR1 in mouse MECs. Arginine activated mTORC1 activity through CASTOR1 and promoted mitochondrial biogenesis through the mTORC1/PGC-1α/NRF1 pathway. Moreover, arginine inhibited mitophagy through the CASTOR1/PINK1/Parkin pathway. Mitochondrial homeostasis ensures ATP synthesis and a stable cellular redox state for MECs under HS, further alleviating HS-induced damage and improving the lactation performance of MECs. In conclusion, these findings reveal the molecular mechanisms by which L-arginine relieves HS-induced mammary gland injury, and suggest that the intake of arginine-based feeds or feed additives is a promising method to increase the milk yield of dairy animals in extreme heat conditions.

Keywords:  CASTOR1; Climate change; Heat stress; L-arginine; Mitochondrial homeostasis; mTORC1 signaling

DOI:  https://doi.org/10.1016/j.scitotenv.2024.172017
Channels (Austin). 2024 Dec;18(1): 2335467

Ion channel-mediated mitochondrial volume regulation and its relationship with mitochondrial dynamics.

Yujia Zhuang, Wenting Jiang, Zhe Zhao, Wencui Li, Zhiqin Deng, Jianquan Liu.

  The mitochondrion, one of the important cellular organelles, has the major function of generating adenosine triphosphate and plays an important role in maintaining cellular homeostasis, governing signal transduction, regulating membrane potential, controlling programmed cell death and modulating cell proliferation. The dynamic balance of mitochondrial volume is an important factor required for maintaining the structural integrity of the organelle and exerting corresponding functions. Changes in the mitochondrial volume are closely reflected in a series of biological functions and pathological changes. The mitochondrial volume is controlled by the osmotic balance between the cytoplasm and the mitochondrial matrix. Thus, any disruption in the influx of the main ion, potassium, into the cells can disturb the osmotic balance between the cytoplasm and the matrix, leading to water movement between these compartments and subsequent alterations in mitochondrial volume. Recent studies have shown that mitochondrial volume homeostasis is closely implicated in a variety of diseases. In this review, we provide an overview of the main influencing factors and research progress in the field of mitochondrial volume homeostasis.

Keywords:  Ion channels; cell volume regulation; mitochondrial

DOI:  https://doi.org/10.1080/19336950.2024.2335467
Int J Mol Sci. 2024 Mar 14. pii: 3305. [Epub ahead of print]25(6):

Vascular Endothelial Cell-Derived Exosomal Sphingosylphosphorylcholine Attenuates Myocardial Ischemia-Reperfusion Injury through NR4A2-Mediated Mitophagy.

Yifan Yu, Zhiliang Li, Yuqing Cai, Jiahui Guo, Yushuang Lin, Jing Zhao.

  Cardiomyocyte survival is a critical contributing process of host adaptive responses to cardiovascular diseases (CVD). Cells of the cardiovascular endothelium have recently been reported to promote cardiomyocyte survival through exosome-loading cargos. Sphingosylphosphorylcholine (SPC), an intermediate metabolite of sphingolipids, mediates protection against myocardial infarction (MI). Nevertheless, the mechanism of SPC delivery by vascular endothelial cell (VEC)-derived exosomes (VEC-Exos) remains uncharacterized at the time of this writing. The present study utilized a mice model of ischemia/reperfusion (I/R) to demonstrate that the administration of exosomes via tail vein injection significantly diminished the severity of I/R-induced cardiac damage and prevented apoptosis of cardiomyocytes. Moreover, SPC was here identified as the primary mediator of the observed protective effects of VEC-Exos. In addition, within this investigation, in vitro experiments using cardiomyocytes showed that SPC counteracted myocardial I/R injury by activating the Parkin and nuclear receptor subfamily group A member 2/optineurin (NR4A2/OPTN) pathways, in turn resulting in increased levels of mitophagy within I/R-affected myocardium. The present study highlights the potential therapeutic effects of SPC-rich exosomes secreted by VECs on alleviating I/R-induced apoptosis in cardiomyocytes, thereby providing strong experimental evidence to support the application of SPC as a potential therapeutic target in the prevention and treatment of myocardial infarction.

Keywords:  NR4A2; exosome; mitophagy; optineurin; sphingosylphosphorylcholine

DOI:  https://doi.org/10.3390/ijms25063305