bims-noxint 2021-08-08 papers

Issue of 2021–08–08
four papers selected by
Laia Caja Puigsubira, Uppsala University

Antioxidants (Basel). 2021 Jul 10. pii: 1103. [Epub ahead of print]10(7):

Nox4 Maintains Blood Pressure during Low Sodium Diet.

Flávia Rezende, Pedro Felipe Malacarne, Niklas Müller, Birgit Rathkolb, Martin Hrabě de Angelis, Katrin Schröder, Ralf P Brandes.

The NADPH oxidase Nox4 is a hydrogen peroxide (H2O2)-producing enzyme, with the highest expression in the kidney. As the kidney is involved in volume and blood pressure control through sodium handling, we set out to determine the impact of a low sodium diet on these parameters in WT and Nox4-/- mice. Nox4 expression in the murine kidney was restricted to the proximal tubule. Nevertheless, low-sodium-induced weight loss and sodium sparing function was similar in WT and Nox4-/- mice, disputing an important function of renal Nox4 in sodium handling. In contrast, a low sodium diet resulted in a reduction in systolic blood pressure in Nox4-/- as compared to WT mice. This was associated with a selectively lower pressure to heart-rate ratio, as well as heart to body weight ratio. In general, a low sodium diet leads to activation of sympathetic tone and the renin angiotensin system, which subsequently increases peripheral resistance. Our observations suggest that the control by this system is attenuated in Nox4-/- mice, resulting in lower blood pressure in response to low sodium.

Keywords: NADPH oxidase 4; proximal tubule cells; reactive oxygen species

DOI: https://doi.org/10.3390/antiox10071103

Vasc Med. 2021 Aug 02. 1358863X211024721

Regulation of reactive oxygen species in the pathogenesis of matrix vesicles induced calcification of recipient vascular smooth muscle cells.

Neal X Chen, Kalisha D O'Neill, James M Dominguez, Sharon M Moe.

INTRODUCTION: Increased oxidative stress is associated with vascular calcification in patients with chronic kidney disease (CKD). We have previously demonstrated that cellular-derived matrix vesicles (MV), but not media-derived MV, are endocytosed in the presence of phosphorus by recipient normal rat vascular smooth muscle cells (VSMC) and induce calcification through ERK1/2 and [Ca2+]i signaling. We hypothesized that these changes were mediated by increased reactive oxygen species (ROS) production.
METHODS: MV were co-cultured with recipient VSMC in the presence of high phosphorus and ROS production and cell signaling assessed.
RESULTS: The results demonstrated MV endocytosis led to increased ROS production in recipient VSMC with no increase in mitochondrial oxygen consumption or oxidative phosphorylation (OXPHOS), indicating the ROS was not from the mitochondria. The use of inhibitors demonstrated that endocytosis of these MV by VSMC led to a signaling cascade in the cytoplasm beginning with ERK1/2 signaling, then increased [Ca2+]i and stimulation of ROS production, mediated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX)1/4. Media-derived MV did not induce this cascade, indicating endocytosis itself was not a factor. Furthermore, inhibition of either ERK1/2 activation or [Ca2+]i reduced vascular calcification.
CONCLUSION: We conclude that endocytosis of pro-mineralizing MV can induce a series of signaling events in normal VSMC that culminate in generation of ROS via activation of NOX1/4. Understanding these pathways will allow the development of future targeted therapeutics.

Keywords: calcification; cell signaling; matrix vesicle; mitochondria; oxidative stress; vascular smooth muscle cells

DOI: https://doi.org/10.1177/1358863X211024721

Redox Biol. 2021 Jul 24. pii: S2213-2317(21)00240-8. [Epub ahead of print]46 102081

H2O2-mediated autophagy during ethanol metabolism.

Cheng Chen, Shijin Wang, Linna Yu, Johannes Mueller, Franco Fortunato, Vanessa Rausch, Sebastian Mueller.

BACKGROUND: Alcoholic liver disease (ALD) is the most common liver disease worldwide and its underlying molecular mechanisms are still poorly understood. Moreover, conflicting data have been reported on potentially protective autophagy, the exact role of ethanol-metabolizing enzymes and ROS.
METHODS: Expression of LC3B, CYP2E1, and NOX4 was studied in a mouse model of acute ethanol exposure by immunoblotting and immunohistochemistry. Autophagy was further studied in primary mouse hepatocytes and huh7 cells in response to ethanol and its major intermediator acetaldehyde. Experiments were carried out in cells overexpressing CYP2E1 and knock down of NOX4 using siRNA. The response to external H2O2 was studied by using the GOX/CAT system. Autophagic flux was monitored using the mRFP-GFP-LC3 plasmid, while rapamycin and chloroquine served as positive and negative controls.
RESULTS: Acute ethanol exposure of mice over 24 h significantly induced autophagy as measured by LC3B expression but also induced the ROS-generating CYP2E1 and NOX4 enzymes. Notably, ethanol but not its downstream metabolite acetaldehyde induced autophagy in primary mouse hepatocytes. In contrast, autophagy could only be induced in huh7 cells in the presence of overexpressed CYP2E1. In addition, overexpression of NOX4 also significantly increased autophagy, which could be blocked by siRNA mediated knock down. The antioxidant N-acetylcysteine (NAC) also efficiently blocked CYP2E1-and NOX4-mediated induction of autophagy. Finally, specific and non-toxic production of H2O2 by the GOX/CAT system as evidenced by elevated peroxiredoxin (Prx-2) also induced LC3B which was efficiently blocked by NAC. H2O2 strongly increased the autophagic flux as measured by mRFP-GFP-LC3 plasmid.
CONCLUSION: We here provide evidence that short-term ethanol exposure induces autophagy in hepatocytes both in vivo and in vitro through the generation of ROS. These data suggest that suppression of autophagy by ethanol is most likely due to longer alcohol exposure during chronic alcohol consumption with the accumulation of e.g. misfolded proteins.

Keywords: Alcohol liver disease (ALD); Cytochrome P450 2E1(CYP2E1); Ethanol metabolism; Hydrogen peroxide (H(2)O(2)); NADPH oxidase (NOX); Reactive oxygen species (ROS)

DOI: https://doi.org/10.1016/j.redox.2021.102081

Bioengineered. 2021 Dec;12(1): 4868-4877

Ramelteon ameliorated 1-methyl-4-phenylpyridinium (MPP+)-induced neurotoxicity in neuronal cells in a mitochondrial-dependent pathway.

Chuo Li, Yusheng Zhang, Rongrong Liu, Yuzhen Mai.

Parkinson's disease (PD) is a common neurodegenerative disease with global health and economic impact. 1-methyl-4-phenylpyridinium (MPP+)-induced mitochondrial dysfunction and oxidative stress are reported to participate in the pathological mechanism of PD. Ramelteon is a novel oral hypnotic agent that has recently been reported to display neuronal protective effects. However, it is unknown whether Ramelteon possesses a beneficial effect in PD. In this study, we aimed to examine the potential function of Ramelteon in MPP+-challenged neurons. We found that Ramelteon rescued the cell viability reduced by MPP+-stimulation. Further, oxidative stress in MPP+-challenged SH-SY5Y cells was mitigated by Ramelteon as verified by the upregulated levels of mitochondrial reactive oxygen species (ROS) and protein carboxyl, and the upregulation of NADPH oxidase 4 (NOX-4). Furthermore, the declined mitochondrial membrane potential (ΔΨm) caused by MPP+ was reversed by Ramelteon. Importantly, Ramelteon attenuated MPP+-induced apoptosis, accompanied by a decreased ratio of Bax/Bcl-2, inhibition of cytochrome C release, and downregulation of cleaved caspase-3. For the first time, we conclude that Ramelteon might ameliorate MPP+-induced neurotoxicity in neuronal cells in a mitochondrial-dependent pathway.

Keywords: Parkinson’s disease; mitochondria; mpp+; ramelteon

DOI: https://doi.org/10.1080/21655979.2021.1960767