Chronic intermittent hypoxia impaired collagen synthesis in mouse genioglossus via ROS accumulation: A transcriptomic analysis.

Obstructive sleep apnea (OSA) is a sleep-related breathing disorder characterized by intermittent and recurrent upper airway collapse during sleep that leads to chronic intermittent hypoxia (CIH). The genioglossus (GG) is the largest dilator muscle, which controls the upper airway and plays an important role in OSA pathology. Elucidating its genetic alterations may help identify potential targets for OSA. However, the genetic aspects of the GG in CIH mice remain unclear. Here, we have conducted an RNA sequencing (RNA-Seq) analysis to assess the differentially expressed genes (DEGs) in the GG between CIH mice and normoxia (NOR) mice. A total of 637 DEGs were identified to be dysregulated in CIH mice compared with control mice. Bioinformatics analysis showed that the DEGs were related to various physiological processes, such as the endogenous stimulus responses, cellular component organization and metabolic processes. Extracellular matrix (ECM)-receptor interaction was the top KEGG pathway in the environmental information processing category with high significance and large fold changes. From the gene weight distributions of collagen (Col)-related biological processes (BPs), we found several significant DEGs, such as Col1a1, Col1a2, Mmp2, Col3a1, Col5a1, Fmod, and Col5a2. A PPI network showed that Col1a1 was linked to ECM-receptor interactions, responses to reactive oxygen species (ROS) and Col-related BPs. It was verified in vivo and in vitro that hypoxia can induce excess ROS and reduce Col expression levels. Moreover, we found NAC can effectively scavenge ROS and restore collagen synthesis. These findings contribute to a better understanding of the mechanisms linking OSA and upper airway muscle injury and may help identify potential therapeutic targets.

[Salidroside inhibits phenotypic transformation of rat pulmonary artery smooth muscle cells induced by hypoxia].

This study investigated the effect of salidroside on phenotypic transformation of rat pulmonary artery smooth muscle cells(PASMCs) induced by hypoxia. Rat pulmonary arteries were isolated by tissue digestion and PASMCs were cultured. The OD values of cells treated with salidroside at different concentrations for 48 hours were measured by cell counting kit-8(CCK-8) to determine the appropriate concentration range of salidroside. The cells were divided into a normal(normoxia) group, a model(hypoxia) group, and three hypoxia + salidroside groups(40, 60, and 80 µg·mL~(-1)). Quantitative real-time PCR(qRT-PCR) was used to detect the mRNA expression of cell contractile markers in each group, such as α-smooth muscle actin(α-SMA), smooth muscle 22(SM22), and calcium-binding protein(calponin), and synthetic marker vimentin. The expression levels of cell phenotypic markers and proliferating cell nuclear antigen(PCNA) were detected by Western blot. The proliferation of cells in each group was detected by the 5-ethynyl-2'-deoxyuridine(EdU) assay. Cell migration was measured by Transwell assay. As revealed by results, compared with the normal group, the model group showed decreased mRNA and protein expression of contractile phenotypic markers of PASMCs and increased mRNA and protein expression of synthetic markers. Compared with the conditions in the model group, salidroside could down-regulate the mRNA and protein expression of synthetic markers in PASMCs and up-regulated the mRNA and protein expression of contractile phenotypic markers. Compared with the normal group, the model group showed potentiated proliferation and migration. Compared with the model group, the hypoxia + salidroside groups showed blunted proliferation and migration of cells after phenotypic transformation. The results suggest that salidroside can inhibit the expression of synthetic markers in PASMCs and promote the expression of contractile markers to inhibit the hypoxia-induced phenotypic transformation of PASMCs. The mechanism of salidroside in inhibiting the proliferation and migration of PASMCs is related to the inhibition of the phenotypic transformation of PASMCs.

Hypoxia-Induced ROS Contribute to Myoblast Pyroptosis during Obstructive Sleep Apnea via the NF-κB/HIF-1α Signaling Pathway.

Tissue hypoxia caused by upper airway collapse is a main cause of excessive oxidative stress and systemic inflammation in obstructive sleep apnea (OSA) patients. Increased reactive oxygen species (ROS) and inflammatory responses affect cell survival and ultimately contribute to tissue injury. In the present study, we proposed that the induction of ROS by hypoxia, as an intrinsic stress, activates myoblast pyroptosis in OSA. We found increased cell death and abnormal expression of pyroptosis markers in the skeletal muscle of OSA mice. In vitro studies showed hypoxia-induced pyroptotic death of C2C12 myoblasts, as evidenced by the activation of caspase-1 and gasdermin D (GSDMD). Hypoxia induced ROS overproduction and accumulation in myoblasts. More importantly, applying N-acetylcysteine (NAC), an ROS scavenger, rescued cell swelling, downregulated the inflammatory response, and prevented pyroptotic death in hypoxia-cultured myoblasts. Hypoxia stimulation promoted NF-κB P65 phosphorylation and HIF-1α nuclear translocation. Moreover, hypoxia increased the nuclear level of cleaved caspase-1 and GSDMD. NAC inhibited hypoxia-induced variations in the HIF-1α and NF-κB signaling pathway. Taken together, our results determined that hypoxia-induced ROS contribute to myoblast pyroptosis. Therefore, our findings suggest that ROS may be a potential therapeutic target for ameliorating hypoxia-induced cell death and tissue injury, especially in OSA and hypoxia-related diseases.