Mitochondrial ATP-Sensitive K+ Channel Opening Increased the Airway Smooth Muscle Cell Proliferation by Activating the PI3K/AKT Signaling Pathway in a Rat Model of Asthma

Abnormal proliferation of airway smooth muscle cells (ASMCs) leads to airway remodeling and the development of asthma. This study aimed to assess whether mitochondrial ATP-sensitive K+ (mitoKATP) channels regulated the proliferation of ASMCs by regulating the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway in asthmatic rats. Forty-eight Sprague Dawley rats were immunized with ovalbumin-containing alum to establish the asthma models. The ASMCs were isolated and identified by phase-contrast microscopic images and immunohistochemical staining for α-smooth muscle actin. The ASMCs were treated with a potent activator of mitoKATP, diazoxide, or an inhibitor of mitoKATP, 5-hydroxydecanoate (5-HD). Rhodamine-123 (R-123) was used for detecting the mitochondrial membrane potential (Δψm). The proliferation of ASMCs was examined by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. The protein and mRNA expressions of AKT and p-AKT were detected using western blotting and quantitative real-time PCR. The results showed that diazoxide enhanced the mitoKATP channel opening in ASMCs in the rat model of asthma, while 5-HD impeded it. Diazoxide also increased ASMC proliferation in the rat model of asthma, whereas 5-HD alleviated it. However, LY294002, a PI3K/AKT pathway inhibitor, reversed the functional roles of diazoxide in the proliferation ability of ASMCs in the rat model of asthma. Furthermore, treatment with diazoxide induced the phosphorylation of AKT, and treatment with 5-HD decreased the phosphorylation of AKT in ASMCs in the rat model of asthma. In conclusion, the mitoKATP channel opening increased the proliferation of ASMCs by activating the PI3K/AKT signaling pathway in a rat model of asthma.

Protective effect of uridine on metabolic processes in rat myocardum during its ischemia/reperfusion damage

The experimental study of the cardioprotective effect of uridine, the metabolic precursor of the endogenous activator of mitochondrial ATP-dependent K+-channels (mitoKATP-channels), was performed using the model of myocardial ischemia/reperfusion (I/RP) in rats. Ischemia for 30 min followed by reperfusion for 120 min resulted in a significant decrease in ATP and phosphocreatine (PC) content, intensification of lipid peroxidation (LPO), and inhibition of the antioxidant system (AOS) in cardiomyocytes. Uridine in a dose of 30 mg/kg, administered intravenously prior to reperfusion, had a protective effect on myocardial metabolism in the I/RP zone. It prevented the decrease of ATP and PC, limited the LPO processes, evaluated by the content of lipid hydroperoxides and conjugated dienes, and improved the AOS state by, preventing the decrease of superoxide dismutase (SOD) activity and increasing the content of reduced glutathione (GSH). The mitoKATP-channel blocker 5-hydroxydecanoate (5-HD, 5 mg/kg) eliminated the ability of uridine to maintain the ATP level and to exhibit its positive effect on the intensity of the LPO and activity of AOS. The obtained data allow us to conclude that activation of mitoKATP-channels play an important role in the mechanism of the cardioprotective effect of uridine in I/RP damage of myocardium.