Circ-CIMIRC inhibition alleviates CIH-induced myocardial damage via FbxL4-mediated ubiquitination of PINK1.

Obstructive sleep apnea (OSA) is a common sleep disordered breathing diseases that characterized by chronic intermittent hypoxia (CIH). This work aimed to explore the role of circ-CIMIRC in CIH-induced myocardial injury. CIH aggravated myocardial tissue damage in rats. Circ_CIMIRC overexpression promoted apoptosis and reduced the colocalization of Tom20 and Parkin and mitophagy in CIH-treated H9c2 cells. Additionally, FbxL4 interacted with PINK1, FbxL4 silencing reduced PINK1 ubiquitination in H9c2 cells. Two major ubiquitination sites (K319 and K433) were responsible for ubiquitination of PINK1. Circ_CIMIRC promoted FbxL4-mediated ubiquitination and degradation of PINK1. Furthermore, circ_CIMIRC inhibition alleviated the pathological damage, fibrosis and apoptosis of myocardial tissues, reduced oxidative stress in CIH rats. In conclusion, circ_CIMIRC silencing repressed FbxL4-mediated ubiquitination and degradation of PINK1 and then enhanced PINK1/Parkin-mediated mitophagy, thereby alleviating myocardial damage in CIH rats. Thus, circ_CIMIRC may be a potential strategy to alleviate CIH-induced myocardial damage.

The role of ferroptosis in chronic intermittent hypoxia-induced liver injury in rats.

PURPOSE: Obstructive sleep apnea (OSA) has been related to an increased risk of liver injury. Ferroptosis is a form of programmed cell death implicated in multiple physiological and pathological processes. This study aimed to explore the role of ferroptosis in chronic intermittent hypoxia (CIH)-induced liver injury as well as to uncover the underlying mechanisms using a CIH rat model. METHODS: Fourteen male Sprague-Dawley rats were randomly allocated to either the normal control (NC) (n = 7) or the CIH group (n = 7). Rats were exposed to intermittent hypoxia for 8 weeks in CIH group. Liver function, histological changes, and markers of oxidative stress were evaluated. The protein levels of hypoxia-inducible factor-1α, nuclear factor E2-related factor 2 (Nrf2), Acyl-CoA synthetase long-chain family member 4 (ACSL4), and glutathione peroxidase 4 (GPX4) in liver were examined by Western blot analysis. RESULTS: CIH treatment caused significant increase of serum alanine aminotransferase, aspartate aminotransferase, and malondialdehyde (MDA). Liver MDA was significantly higher in CIH group than that in NC group. Histology showed that CIH treatment induced discernible swelled, disordered hepatocytes, necrosis, and infiltrated inflammatory cells. CIH treatment significantly reduced the expression of GPX4, while markedly up-regulated expression of ACSL4, indicating elevation in hepatic ferroptosis. In addition, the protein expression of Nrf2 in CIH group was significantly lower than that in NC group. CONCLUSIONS: Ferroptosis played a crucial role in CIH-induced liver injury. The hepatic ferroptosis in CIH rat model might be mediated by the dysregulation of Nrf2. This highlights a potential therapeutic target for the treatment of OSA-related liver injury.

Effect of chronic intermittent hypoxia on gene expression profiles of rat liver: a better understanding of OSA-related liver disease.

PURPOSE: Obstructive sleep apnea (OSA) and OSA-associated chronic intermittent hypoxia (CIH) have been suggested to be associated with increased risk of liver disease. Little is known about the biological pathophysiology and underlying molecular mechanisms. Here we use whole-genome expression profiling to explore the transcriptomic changes induced by CIH in rat liver. METHODS: Rats (n = 3) were exposed to CIH for 8 weeks and were compared with rats exposed to normoxia (n = 3). Illumina HiSeq 4000 platform was used to examine differentially expressed genes (DEGs) in the liver between control group and CIH rat model. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to validate DEGs. Biological functions of DEGs were determined by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. RESULTS: Compared with control group, 318 genes were identified to be dysregulated in the liver of CIH rat model, with 211genes upregulated and 107 genes downregulated. Bioinformatics analysis showed that these genes were extensively related to various physiologic processes such as hepatic metabolism, apoptotic process, and oxidative stress. 10 genes with 5 upregulated and 5 downregulated were selected and further verified by qRT-PCR. CONCLUSIONS: CIH resulted in altered gene expression patterns in the liver of rat. The DEGs were related to various physiological and pathological processes in CIH rat liver. These data provide a better understanding of the mechanisms and underlying molecular changes of OSA-related liver disease.

Effect of chronic intermittent hypoxia on theophylline metabolism in mouse liver.

BACKGROUND: Chronic intermittent hypoxia (CIH) has been associated with abnormalities in the liver, which is the most important organ for drug metabolism. This study aimed to investigate the effect of CIH on theophylline metabolism in mouse liver. METHODS: Eight C57BL/6J mice were exposed to CIH for 12 weeks. Eight C57BL/6J mice were exposed to room air as a control group. Serum levels of alanine aminotransferase and aspartate aminotransferase were measured. Liver histology was observed by light and electron microscopy. Total hepatic cytochrome P450 concentration was measured. Hepatocytes were isolated and incubated with 15 mg/ml theophylline for four hours. After incubation, the theophylline concentration in the supernatant was measured and the theophylline metabolism rate was calculated. RESULTS: CIH did not affect the serum transaminase levels. Livers from mice exposed to CIH showed hepatocellular edema, and liver cells had fuzzy rough endoplasmic reticulum under the electron microscope. The theophylline metabolism rate was significantly inhibited by CIH compared with controls; (16.60 ± 2.43)% vs. (21.58 ± 4.52)% (P = 0.02). The total liver cytochrome P450 concentration in the CIH group was significantly lower than in the control group; (0.83 ± 0.08) vs. (1.13 ± 0.21) mol/mg microsomal protein (P = 0.004). CONCLUSION: CIH decreases theophylline metabolism by mouse hepatocytes, which may correlate with the downregulation of cytochrome P450 expression by CIH.

Intermittent hypoxia and isoniazid plus rifampicin affect hepatic ultrastructure in mice.

BACKGROUND: Chronic intermittent hypoxia is the most important pathophysiologic feature of sleep apnea syndrome. The present study aimed to determine whether chronic intermittent hypoxia, which is associated with sleep apnea syndrome, can cause or increase damage to liver cell ultrastructure induced by isoniazid and rifampicin in mice. METHODS: Based on a 2 × 2 full factorial design consisting of two factors of chronic intermittent hypoxia and isoniazid plus rifampicin, 32 male C57B6J mice were randomized into the control group, the chronic intermittent hypoxia group, the isoniazid plus rifampicin group, and the chronic intermittent hypoxia + isoniazid plus rifampicin group. Twelve weeks after treatment, we examined the ultrastructure of liver cells and quantitatively analyzed mitochondrial morphology in C57B6J mice. RESULTS: Chronic intermittent hypoxia did not significantly affect the ultrastructure of liver cells. The main effect of chronic intermittent hypoxia did not lead to an increase of mean profile area or mean perimeter of mitochondria, and a decrease of numerical density on area of mitochondria (all P > 0.05). Isoniazid plus rifampicin significantly affected liver cell ultrastructure. The main effect of isoniazid plus rifampicin resulted in an increase of mean profile area and mean perimeter of mitochondria, and a decrease of numerical density on area of mitochondria (all P < 0.05). Moreover, there was a positive interaction among the chronic intermittent hypoxia and the isoniazid plus rifampicin groups for mean profile area, mean perimeter, and numerical density on area of mitochondria (all P < 0.05). CONCLUSION: Chronic intermittent hypoxia and isoniazid plus rifampicin treatment lead to synergistic liver cell ultrastructural injury.