Specific role of NAD+ biosynthesis reduction mediated mitochondrial dysfunction in vascular endothelial injury induced by chronic intermittent hypoxia.

OBJECTIVE: Cardiovascular diseases (CVD) are prevalent among those with obstructive sleep apnea (OSA) and are the leading cause of death in these individuals. However, due to clinical confounders, the mechanism by which OSA induces CVD is still unclear. Previous studies have shown that chronic intermittent hypoxia (CIH) and high cholesterol diet (HCD) induce distinct characteristics of atherosclerotic plaques, highlighting the specific mechanisms involved in CIH-induced vascular endothelial injury. MATERIALS AND METHODS: This study aims to investigate whether nicotinamide adenine dinucleotide (NAD+) biosynthesis reduction-mediated mitochondrial dysfunction is responsible for vascular endothelial injury induced by CIH and to elucidate its specific role in this process. Models were established to stimulate human umbilical vein endothelial cells (HUVECs) with CIH and oxidized low-density lipoprotein (ox-LDL), and the NAD+ biosynthesis-related indicators, such as NAD+ levels and nicotinamide phosphoribosyltransferase (NAMPT) enzyme activity, were measured in this model. Additionally, interventions were performed by supplementing NAD+ levels with nicotinamide mononucleotide (NMN), inhibiting NAD+ synthesis with FK866, and evaluating mitochondrial function, oxidative stress status, vascular constriction and dilation function, and endothelial adhesion function in these models. A comparative study was conducted to assess the effects of these interventions. RESULTS: We found that under CIH conditions, NAMPT enzyme activity was inhibited, leading to a reduction in NAD+ biosynthesis and a decrease in NAD+/NADH ratio. At the same time, CIH caused mitochondrial dysfunction in HUVECs, including a decrease in adenosine triphosphate (ATP) content and mitochondrial membrane potential, as well as the activity of respiratory chain complex I and III, induced an increase in oxidative stress levels in endothelial cells, impaired vascular constriction and dilation function, and significantly increased expression of adhesion factors. The impact of CIH on endothelial cell-related mitochondrial function and endothelial function was restored by supplementing NMN. Although ox-LDL also causes multi-level endothelial injury, it does not involve the NAD+ pathway, as there were no significant changes in the related indicators, and the impaired endothelial function under ox-LDL conditions was not restored by supplementing NMN. CONCLUSIONS: CIH-induced vascular endothelial injury may be associated with NAD+ biosynthesis reduction-mediated mitochondrial dysfunction. Supplementing NAD+ precursors to increase its levels may be a potential intervention to ameliorate CIH-induced vascular endothelial injury, while it does not have a significant effect on endothelial injury caused by ox-LDL.

[Expression of long-chain non-coding RNA LINC00152 in laryngeal squamous cell carcinoma and its clinical significance].

Objective:The aim of this study is to explore the relative expression level of LINC00152 in laryngeal squamous cell carcinoma（LSCC） and its clinical significance. Method:The relative expression levels of LINC00152 in LSCC cell lines and 36 paired LSCC specimens were measured by qRT-PCR method. And the correlations between the expression level of LINC00152 and the clinical features derived from LSCC patients were analyzed and compared through the independent sample t-test. Result:The relative expression level of LINC00152 was over-expressed in LSCC cell lines and cancerous tissues than that in paired adjacent normal tissues, and the difference was statistically significant（P=0.006）. Even the associations between LINC00152 expression level and clinicopathological features（P=0.044 for clinical stage, P=0.032 for pathological differentiation degree） were significantly. Conclusion:LINC00152 is highly expressed in LSCC and it may become a new tumor marker for the diagnosis and prognosis of LSCC.