[Regulation of rat airway smooth muscle cell proliferation by mitochondrial ATP-sensitive K(+) channel in asthmic rats.].

The objective of this paper was to investigate the effect and mechanism of mitochondrial ATP-sensitive K(+) (MitoK(ATP)) channel on the proliferation of airway smooth muscle cells (ASMCs) in asthmic rats. Thirty-six Sprague-Dawley (SD) rats were randomly assigned into 2 groups (18 in each): (1) Asthma group: the asthmic rat model was established by ovalbumin (OVA) sensitization and excitation; (2) Normal group: rats were subjected to inhalation of equal amount of normal saline. The rat ASMCs were isolated from fresh lung tissues and cultured respectively as follows: (1) CONTROL GROUP: normal ASMCs were cultured under normoxia for 24 h; (2) Diazoxide group: normal ASMCs were cultured under normoxia for 24 h with diazoxide (an opener of MitoK(ATP) channel); (3) 5-HD group: normal ASMCs were cultured under normoxia for 24 h with 5-hydroxydecanoate (5-HD) (an antagonist of MitoK(ATP) channel); (4) Asthma group: Asthmic ASMCs were cultured under normoxia for 24 h; (5) Asthma + diazoxide group: Asthmic ASMCs were cultured under normoxia with diazoxide for 24 h; (6) Asthma + 5-HD group: Asthmic ASMCs were cultured under normoxia with 5-HD for 24 h. The mitochondrial membrane potential (ΔΨm) was detected using Rhodamine 123 (R-123). The level of reactive oxygen species (ROS) was detected by DCF fluorescence. The expression of nuclear factor-kappa B (NF-κB) mRNA was examined by RT-PCR. The proliferation and apoptosis of rat ASMCs were examined respectively by MTT colorimetric assay and cell cycle analysis. The results were as follows. (1) After exposure to diazoxide for 24 h, the R-123 fluorescence intensity, the ROS level, NF-κB mRNA expression and the MTT absorbance value (A value) in normal ASMCs were significantly increased, and the apoptosis of rat ASMCs was significantly decreased compared to the control group (P<0.05). However, there was no significant changes in those indices after the normal ASMCs had been exposed to 5-HD for 24 h. (2) In Asthma and Asthma + diazoxide groups, the R-123 fluorescence intensity, ROS level and the MTT A value were markedly increased, and the apoptosis was markedly decreased compared to control group (P<0.05). These changes were more obvious in Asthma + diazoxide group than those in Asthma group (P<0.05). 5-HD partly weakened the effect of asthma on the R-123 fluorescence intensity, ROS level and the MTT A value and the apoptosis of rat ASMCs (P<0.05). R-123 fluorescence intensity and NF-κB mRNA expression were positively correlated with ROS level. NF-κB mRNA expression was positively correlated with the MTT A value and negatively correlated with the apoptosis of rat ASMCs. All the results suggest that the opening of MitoK(ATP) channel followed by a depolarization of ΔΨm contributes to the increase in ROS level and NF-κB mRNA expression in rat ASMCs and to the unbalance between cell proliferation and apoptosis of ASMCs induced by asthma. This might be a mechanism of the development of airway remodeling in asthma.