The study of IL-1β biphasic effect on large conductance calcium sensitive potassium channel activity in rat aortic smooth muscle cells through hydrogen peroxide

AIM To observe the effect of IL-1β on hydrogen peroxide (H₂O₂) concentration and large conductance Ca²⁺-activated K⁺ channel(BKCa) activity in rat aortic smooth muscle cells (ASMCs) at different time points and to explore the mechanism of IL-1β time dependent biphasic modulation of the activity of BKCa channels. METHODS Five groups included:normal saline control group (Group saline), IL-1β treatment 30 min group, catalase (H₂O₂ scavenger)+IL-1β treatment 30 min group, IL-1β treatment 48 h group, and catalase+IL-1β treatment 48 h group. Changes were observed of intracellular H₂O₂ levels in the ASMCs treated with IL-1β at different time points. A patch clamp technique was used to observe the change of BKCa single channel current open probability (NPo) in each experimental group. RESULTS Compared with the results of the saline group (36.7±7.23) μmol/ml, the level of H₂O₂ in the 30 min group co-cultured with IL-1β increased to (79.1±8.93) μmol/ml (P<0.01), and in the 48 h group co-cultured with IL-1β, the H₂O₂ level was up to (116.4±12.77) μmol/ml (P<0.01). H₂O₂ scavenger catalase can completely reverse the influence of IL-1β at either time piont. The IL-1β alone treated group with ASMCs for 30 min increased NPo significantly (P<0.05). When catalase pretreated with cells, no significant changes in NPo was observed when compared with the saline group, but decreased when compared with IL-1β alone treaed with ASMCs for 30 min (P<0.05). IL-1β alone treated with ASMCs for 48 h decreased NPo significantly (P<0.05). When catalase pretreated with cells, NPo increased when compared with saline group (P<0.05), but decreased when compared with IL-1β alone treaed with ASMCs for 48 h (P<0.05). CONCLUSION IL-1β short time treated with ASMCs increased the activity of BKCa channel, while low concentration H₂O₂ mediated the process. Long time treatment reduced the activity of BKCa channel, and its mechanism was partly achieved by high concentration H₂O₂; The BKCa channel may be a promising drug target for the prevention and treatment of coronary spasm.