n-(1-3-benzodioxol-5-ylmethyl)-2-6-dichlorobenzamide and Non-alcoholic-Fatty-Liver-Disease

Vinyl chloride (VC), an abundant environmental contaminant causes steatohepatitis at high levels, but is considered safe at lower (i.e., sub-OSHA) levels. However, we have previously shown that even lower VC levels exacerbate experimental nonalcoholic fatty liver disease (NAFLD) caused by high-fat diet (HFD). Mitochondrial oxidative injury and subsequent metabolic dysfunction appeared to play key roles in mediating this interaction. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) serves as a key line of defense against endogenous and exogenous reactive aldehydes. The current study therefore tests the hypothesis that allosteric activation of ALDH2 with Alda-1 will protect against VC-enhanced NAFLD. Mice were exposed to low VC concentrations (<1 ppm), or room air for 6 h/day, 5 days/week for 12 weeks, while on HFD or low-fat control diet (LFD). Some mice received Alda-1 (20 mg/kg i.p., 3 × /week) for the last 3 weeks of diet/VC exposure. Indices of liver injury, oxidative stress, metabolic and mitochondrial (dys)function were measured. As observed previously, low-dose VC did not cause liver injury in control mice; while liver injury caused by HFD was enhanced by VC. VC decreased hepatic ALDH2 activity of mice fed HFD. Alda-1 attenuated oxidative stress, liver injury, and dysmetabolism in mice exposed to HFD+VC under these conditions. Importantly, alterations in mitochondrial function caused by VC and HFD were diminished by Alda-1. Previous studies have indicated that liver injury caused by HFD is mediated, at least in part, by enhanced mitochondrial autophagy (mitophagy). Here, Alda-1 suppressed PINK1/PARKIN-mediated mitophagy. Taken together, these results support the hypothesis that ALDH2 is a critical defense against mitochondrial injury caused by VC in experimental NAFLD. The ALDH2 activator Alda-1 conferred protection against liver damage under these conditions, most likely via increasing clearance of aldehydes and preserving mitochondrial respiratory function.

Topics: Aldehyde Dehydrogenase, Mitochondrial; Animals; Autophagy; Benzamides; Benzodioxoles; Enzyme Activation; Fatty Liver; Male; Mice; Mitochondria; Neutrophil Infiltration; Neutrophils; Non-alcoholic Fatty Liver Disease; Oxidative Stress; Phenotype; Protective Agents; Vinyl Chloride

Mitochondrial dysfunction has been shown to play an important role in the development of atherosclerosis and nonalcoholic fatty liver disease (NAFLD). Mitochondrial aldehyde dehydrogenase (ALDH2), an enzyme responsible for the detoxification of reactive aldehydes, is considered to exert protective function in mitochondria. We investigated the influence of Alda-1, an activator of ALDH2, on atherogenesis and on the liver steatosis in apolipoprotein E knockout (apoE(-/-)) mice.. Alda-1 caused decrease of atherosclerotic lesions approximately 25% as estimated by "en face" and "cross-section" methods without influence on plasma lipid profile, atherosclerosis-related markers of inflammation, and macrophage and smooth muscle content in the plaques. Plaque nitrotyrosine was not changed upon Alda-1 treatment, and there were no changes in aortic mRNA levels of factors involved in antioxidative defense, regulation of apoptosis, mitogenesis, and autophagy. Hematoxylin/eosin staining showed decrease of steatotic changes in liver of Alda-1-treated apoE(-/-) mice. Alda-1 attenuated formation of 4-hydroxy-2-nonenal (4-HNE) protein adducts and decreased triglyceride content in liver tissue. Two-dimensional electrophoresis coupled with mass spectrometry identified 20 differentially expressed mitochondrial proteins upon Alda-1 treatment in liver of apoE(-/-) mice, mostly proteins related to metabolism and oxidative stress. The most up-regulated were the proteins that participated in beta oxidation of fatty acids.. Collectively, Alda-1 inhibited atherosclerosis and attenuated NAFLD in apoE(-/-) mice. The pattern of changes suggests a beneficial effect of Alda-1 in NAFLD; however, the exact liver functional consequences of the revealed alterations as well as the mechanism(s) of antiatherosclerotic Alda-1 action require further investigation.

Topics: Aldehyde Dehydrogenase; Aldehyde Dehydrogenase, Mitochondrial; Animals; Aorta; Aortic Diseases; Apolipoproteins E; Atherosclerosis; Benzamides; Benzodioxoles; Biomarkers; Disease Models, Animal; Enzyme Activation; Enzyme Activators; Female; Gene Expression Regulation; Hep G2 Cells; Humans; Liver; Mice, Inbred C57BL; Mice, Knockout; Mitochondria, Liver; Non-alcoholic Fatty Liver Disease; Signal Transduction