bims-mideyd 2026-06-07 papers

Cell Mol Biol Lett. 2026 May 30.

Exendin-4 averts all-trans-retinal-driven damage to photoreceptors and the retina via the GLP-1R/PKA/CREB1 signaling axis.

Beiting He, Yuling Chen, Peixin Cai, Ruitong Xi, Xiaoqing Shen, Shuting Guo, Jingmeng Chen, Shiying Li, Yalin Wu.

BACKGROUND: Atrophic macular degeneration comprises dry age-related macular degeneration (AMD) and autosomal recessive Stargardt disease (STGD1). These disorders lead to irreversible blindness and still lack effective therapies. The rise of all-trans-retinal (atRAL) brought on by visual cycle disruption closely links to retinal atrophy in both conditions, yet the key downstream targets remain obscure. Exendin-4 (EX-4) is a natural glucagon-like peptide-1 receptor (GLP-1R) agonist. Recent clinical retrospective studies indicate that GLP-1R agonists such as exenatide (synthetic EX-4) can markedly lower the 5-year risk of developing dry AMD. Here, we sought to clarify the protective effect of natural EX-4 against retinal degeneration in atrophic macular degeneration linked to impaired clearance of atRAL.
METHODS: Cell and animal paradigms of STGD1 and dry AMD were generated by atRAL-loaded 661W cells and light-exposed Abca4-/-Rdh8-/- mice, respectively. RNA-sequencing, cell viability assays, morphometric analysis, annexin V/propidium-iodide staining using flow cytometry, quantitative polymerase chain reaction (qPCR), western blotting, immunofluorescence, electroretinography (ERG), fundus photography, hematoxylin and eosin (H&E) histology, and TUNEL staining were integrated to delineate the anti-apoptotic actions of EX-4 and to uncover its underlying protective mechanism.
RESULTS: GLP-1R/cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA)/cAMP response element-binding protein 1 (CREB1) signaling was markedly downregulated in atRAL-challenged 661W cells and in neural retina of light-exposed Abca4-/-Rdh8-/- mice. EX-4 reinstated this pathway, suppressed caspase-3 activation and DNA damage, and curtailed apoptosis in both cell and tissue contexts. Silencing of Glp1r or the PKA catalytic subunits by small interfering RNA (siRNA) abrogated EX-4-induced activation of the PKA/CREB1 axis in atRAL-loaded 661W cells. Pharmacologic blockade of CREB1 phosphorylation with the PKA inhibitor H-89 or the CREB1 inhibitor 666-15 largely nullified the DNA-protective and anti-apoptotic benefits conferred by EX-4 in 661W cells following atRAL exposure, suggesting that the GLP-1R/PKA/CREB1 signaling axis contributes to its cytoprotection action. More importantly, intraperitoneal injection of EX-4 significantly preserved retinal structure and function in Abca4-/-Rdh8-/- mice after exposure to light, and mitigated punctate lesions in the fundus.
CONCLUSIONS: EX-4 exerted anti-apoptotic and DNA-protective effects against atRAL-induced photoreceptor loss and retinal degeneration at least partially through activating the GLP-1R/PKA/CREB1 pathway. These findings suggest that GLP-1R agonists could serve as potential preventive therapeutics for atrophic macular degeneration associated with atRAL toxicity, including dry AMD and STGD1.

Keywords: Agonists; Apoptosis; Atrophic macular degeneration; Exendin-4; Glucagon-like peptide-1 receptor (GLP-1R); Retina

DOI: https://doi.org/10.1186/s11658-026-00952-6

Mitochondrion. 2026 Jun 03. pii: S1567-7249(26)00062-0. [Epub ahead of print] 102172

Mitochondrial C3aR and endoplasmic reticulum C5aR orchestrate calcium imbalance during oxidative stress in retinal pigment epithelial cells.

Masaaki Ishii, Bärbel Rohrer.

Although C3a and C5a are classically recognized as extracellular anaphylatoxins, we previously identified mitochondrial C3a receptors (mt-C3aR) in stressed RPE cells, where its activation enhanced Ca2+ uptake and inhibited oxidative phosphorylation (OXPHOS). Here, we demonstrate a second intracellular anaphylatoxin receptor, C5aR, localized to the endoplasmic reticulum (ER) by confocal and immuno-electron microscopy. ER-C5aR activation increased SERCA-dependent Ca2+ uptake and, together with mt-C3aR, facilitated ER-to-mitochondria Ca2+ transfer at mitochondria-endoplasmic reticulum contact sites (MERCS). Moreover, oxidative stress induced Gα16 redistribution, enabling its interaction with ER-C5aR. These findings reveal a novel mechanism by which intracellular anaphylatoxin receptors shape Ca2+ homeostasis and cellular stress responses.

Keywords: Anaphylatoxin; Calcium; Endoplasmic reticulum; Intracellular complement signaling; mitochondria-ER contacts

DOI: https://doi.org/10.1016/j.mito.2026.102172

Eur J Pharm Sci. 2026 Jun 04. pii: S0928-0987(26)00149-1. [Epub ahead of print] 107575

H₂O₂-Induced Oxidative Stress Modulates Methotrexate and Dexamethasone-Dependent Regulation of NLRP3-Associated Transcription and HLA Class I Expression in Primary Human RPE Cells.

Zahra Souri, Mohammad Malekahmadi.

PURPOSE: Oxidative stress-driven inflammation is a central mechanism in retinal diseases. This study investigated how methotrexate (MTX) and dexamethasone (DEX), alone or in combination, modulate NLRP3-related gene expression and HLA class I expression in primary human retinal pigment epithelial (RPE) cells under basal and oxidative stress conditions.
METHODS: Primary human RPE cells were isolated from cadaveric donor eyes and treated with MTX (100 µg/mL), DEX (50 µg/mL), or their combination for 24 hours under normal culture conditions or following H₂O₂-induced oxidative stress (100 µM). mRNA expression of NLRP3, PYCARD, CASPASE-1, HLA-A, and HLA-B was quantified by qPCR. ELISA measured IL-1β and IL-18 secretion.
RESULTS: Under basal conditions, MTX and DEX downregulated NLRP3 and HLA-A/B mRNA expression while increasing PYCARD and CASPASE-1 transcripts. Combination treatment reduced IL-1β secretion, whereas MTX and combination therapy decreased IL-18 levels. In oxidative stress conditions, MTX and combination therapy upregulated NLRP3 and CASPASE-1 mRNA, while HLA-A/B and PYCARD transcripts were primarily increased by combination treatment. IL-1β levels remained unchanged, and IL-18 was reduced only in the combination group.
CONCLUSIONS: MTX and DEX modulate NLRP3-associated and HLA class I transcriptional responses in RPE cells in a redox-dependent manner. Although oxidative stress modulated drug-associated gene expression profiles, these transcriptional changes were not paralleled by corresponding alterations in secreted inflammatory cytokine levels, suggesting that the context-dependent nature of inflammatory signaling and cytokine release in RPE cells should be taken into consideration.

Keywords: HLA class I; NLRP3 inflammasome; Oxidative stress; Retinal pigment epithelium

DOI: https://doi.org/10.1016/j.ejps.2026.107575

J Inflamm Res. 2026 ;19 612984

Dysregulated Polarized Secretion of Small Extracellular Vesicles in the Retinal Pigment Epithelium: Mechanisms and Pathological Roles in Age-Related Macular Degeneration.

Haoxin Guo, Ruiyi Yan, Xiaoxu Han, Weihong Yu.

The pathogenesis of age-related macular degeneration (AMD) is intrinsically driven by retinal pigment epithelium (RPE) dysfunction. Under physiological conditions, the strictly polarized secretion of small extracellular vesicles (sEVs) by the RPE dictates outer retinal homeostasis. In response to oxidative and hypoxic stress, this secretory architecture is profoundly disrupted, transforming sEVs into mediators of drusen formation, inflammation, and neovascularization. This review systematically delineates the molecular machinery governing RPE-sEV trafficking, unveiling the distinct protein and miRNA cargo profiles segregated between the apical and basolateral domains. We highlight the unique secretory features of RPE and elucidate how AMD stressors disrupt this polarity via cytoskeletal collapse, secretory autophagy, and Rab GTPase dysregulation. Consequently, this altered sEV secretion abolishes apical neurotrophic support while deteriorating the basolateral microenvironment. Crucially, this establishes a vicious pathological loop where microenvironmental deterioration and sEV dysregulation are mutually causative. Recognizing dysregulated sEV polarity as a contributing factor to AMD, we propose that repairing RPE intracellular trafficking offers a fundamental strategy to restore secretory homeostasis and impede disease progression.

Keywords: age-related macular degeneration; polarization; retinal pigment epithelium; small extracellular vesicles; vesicular trafficking

DOI: https://doi.org/10.2147/JIR.S612984

Front Cell Dev Biol. 2026 ;14 1832772

From BEST1 mutations to retinal regeneration: integrating stem cell-derived RPE models and gene correction strategies.

Yan Wang, Sihua Cheng, Yu Zhang, Tingting Yang.

Retinal degenerative diseases are among the leading causes of irreversible vision loss worldwide and arise primarily from progressive dysfunction and death of photoreceptors and retinal pigment epithelial (RPE) cells. Because the mammalian retina lacks an intrinsic capacity for regeneration, current treatments remain limited and largely palliative. Recent advances in stem cell technologies and gene-based therapies, however, have opened new avenues for retinal repair and functional restoration. Among monogenic retinal disorders, BEST1-associated retinopathies provide a particularly informative paradigm for linking molecular mechanisms to emerging regenerative strategies.The human BEST1 encodes bestrophin-1 (BEST1), a calcium-activated chloride channel predominantly expressed in the RPE, where it plays essential roles in ionic homeostasis, transepithelial transport, and regulation of the visual cycle. Pathogenic variants in BEST1 give rise to a spectrum of inherited retinal diseases, including Best vitelliform macular dystrophy, autosomal recessive bestrophinopathy, and adult-onset vitelliform dystrophy. Mechanistic studies of BEST1 mutations have revealed diverse functional consequences, ranging from loss-of-function to gain-of-function effects, highlighting the importance of precise molecular diagnosis for therapeutic intervention.Here, we synthesize recent progress in stem cell-derived RPE models and gene correction strategies, using BEST1-associated retinopathies as a conceptual framework. We discuss how human induced pluripotent stem cell-derived RPE systems enable disease modeling and functional analysis of pathogenic variants, and how gene replacement and genome editing approaches are tailored to distinct mutation classes. Finally, we explore how integration of stem cell and gene therapy strategies may advance retinal regeneration and outline future directions for personalized and mechanism-based treatments of retinal degenerative diseases.

Keywords: bestrophin-1(BEST1); bestrophinopathy; calcium-activated chloride channel; gene therapy; hiPSC-derived RPE; retinal pigment epithelium; retinal regeneration; stem cells

DOI: https://doi.org/10.3389/fcell.2026.1832772

Stem Cell Res Ther. 2026 Jun 02.

L-DOPA enhances iRPE differentiation via Wnt signaling and improves cytotherapy for retinal degradation.

Yifeng Ke, Yingxiang Zhao, Qiang Feng, Min Xue, Mingxuan Zhang, Liangzhang Tan, Xinjun Ren.

BACKGROUND: Transplantation of stem cell-derived Retinal Pigment Epithelium (RPE) cells offers significant therapeutic potential for treating retinal degenerative diseases (RDDs). To enhance the efficacy and safety of such cell replacement therapies, it is essential to efficiently generate high-quality RPE donor cells. The crosstalk between dopamine signalling and the Wnt pathway provides an important mechanism underlying RPE cell fate determination during eye development.
METHODS: We present a protocol for RPE differentiation from iPSCs with L-DOPA supplementation. The effect of L-DOPA is attributed to the activation of Wnt signalling, mediated through the dopamine D1 receptor, which triggers the downstream cAMP/PKA signalling cascade. Subsequent phosphorylation of GSK3β and β-catenin by PKA facilitates the stabilization and nuclear translocation of β-catenin.
RESULTS: L-DOPA supplementation significantly enhances the efficiency of RPE induction, as well as the maturity and functionality of iRPE. Moreover, L-DOPA-treated iRPE cells demonstrated robust resistance to oxidative stress and exhibited improved therapeutic effects in RCS rats after transplantation, alleviating retinal degeneration and preserving retinal function.
CONCLUSION: These findings highlight the potential of L-DOPA as a promising adjunct for iRPE differentiation and stem cell-based therapies for RDDs.

Keywords: Dopamine; Induced pluripotent stem cell; L-DOPA; Retinal Pigment Epithelium cells; Retinal degeneration; Wnt signaling

DOI: https://doi.org/10.1186/s13287-026-05074-6