Abstract
BackgroundObstructive sleep apnoea (OSA) induced chronic kidney disease is mainly caused by chronic intermittent hypoxia (CIH). Our study investigate the mechanism underlying CIH-induced renal damage and whether the cannabinoid receptor 1 (CB1R) antagonist rimonabant (Ri) alleviates CIH-induced renal injury.MethodsMale Sprague-Dawley rats were randomly divided into five groups: one normal control (NC) group, two chronic intermittent hypoxia (CIH) groups, and two CIH + Ri groups. Rats in the NC groups were exposed to room air, while the CIH groups were exposed to a CIH environment for 4 weeks (4w CIH group) and 6 weeks (6w CIH group), respectively. Additionally, rats in the CIH + Ri groups were administered 1.5 mg/kg/day Ri for 4 weeks (4w CIH + Ri group) and 6 weeks (6w CIH + Ri group), respectively. Following this, the rats were euthanized and kidneys were excised for downstream analysis. In the renal tissues, the morphological alterations were examined via haematoxylin eosin (HE) staining and periodic acid schiff (PAS) staining, CB1R, Fis1, Mfn1, and p66Shc expression was assessed through western blot and immunohistochemistry, and the mitochondrial ultrastructural changes in kidney sections were assessed by electron microscopy.ResultsCB1R expression in the 4w and 6w CIH groups was significantly elevated, and further increased with prolonged hypoxia; however, Ri prevented the increase in CIH-induced CB1R expression. Fis1 and p66Shc expression in the CIH groups were increased, but Mfn1 expression decreased. Ri decreased Fis1 and p66Shc expression and increased Mfn1 expression. Renal damage in the 4w or 6w CIH + Ri group was evidently improved compared with that in the 4w or 6w CIH group. CB1R expression was positively correlated with Fis1 and p66Shc and negatively correlated with Mfn1. Meanwhile, electron microscopy showed that the percentage of fragmented mitochondria in the tubular cells in each group was consistent with the trend of CB1R expression.ConclusionCIH causes endocannabinoid disorders and induces abnormal mitochondrial dynamics, resulting in renal injury. Treatment with CB1R antagonists reduces CIH-induced renal damage by inhibiting dysregulated renal mitochondrial dynamics.
Highlights
Obstructive sleep apnoea (OSA) induced chronic kidney disease is mainly caused by chronic intermittent hypoxia (CIH)
Some brush border of the tubules was lost while tubule dilatation, and the renal tubules were slightly damaged compared with those in the normal control (NC) group (p < 0.05)
The tubular epithelial cells in the 6w CIH+ Ri group were less swollen than the 6w CIH group, the loss of brush border and the tubule dilatation were reduced (p < 0.05)
Summary
Obstructive sleep apnoea (OSA) induced chronic kidney disease is mainly caused by chronic intermittent hypoxia (CIH). Obstructive sleep apnoea (OSA) is one of the most common sleep respiratory disorders that may present with or without symptoms. The pathogenesis of OSA is characterised by repeated upper airway obstruction, which causes partial or whole upper airway closure leading to apnoea and arousal. Chronic intermittent hypoxia (CIH) is a central dominant feature of OSA [2], and produces serious damage, which resembles that caused by ischaemia-reperfusion injury [3]. Increasing evidence from the past two decades indicates that patients with untreated OSA have increased risk of advanced chronic kidney disease (CKD) [10]. Recent studies revealed that OSA contributes to CKD via intrarenal hypoxia [11]. Developing a new therapeutic approach for OSA-induced CKD can have significant implications for clinical practice and reduce the population health burden [12]
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