Study On The Regulation Of SK2 Channels In Myocardium Of Diabetic Rats By Dapagliflozi

Objective:To investigate the regulatory effects of dapagliflozin（Dapa）on small conductance calcium-activated potassium channel 2（SK2 channel）in diabetic cardiomyopathy rats and the possible signaling pathways involved.Methods:In vivo diabetes mellitus model was constructed by high sugar and high fat diet combined with intraperitoneal injection of low dose streptozotocin(35 mg·kg^-1),and dagliflozin(1 mg·kg^-1·d^-1)was administered as therapeutic intervention,and the experiment was divided into control group（control,con）,diabetes mellitus（DM）,and dagliflozin treatment group（DM+Dapa）;HE staining to observe the heart structure;cardiac ultrasound to detect cardiac function;immunofluorescence and immunoblotting to detect NOX4,p38MAPK,p-p38MAPK,SK1,SK2,SK3 protein expression.By stimulating H9C2 cardiomyocytes and primary cardiomyocytes with high glucose to mimic the diabetes mellitus model and administering dagliflozin(10μmol·L^-1)for 48 h,the experiment was divided into con group,（con+Dapa）group,hyperosmolar control group（mannitol）,hyperosmolar control administration group（mannitol+Dapa）,high glucose group（HG）,high glucose administration group（HG+Dapa）;DCFH-DA fluorescent probe was used to detect the level of reactive oxygen species（ROS）;membrane clamp was used to detect SK channel current and action potential related parameters;immunohistochemistry and immunoblotting were used to detect NOX4,p38MAPK,p-p38MAPK,SK1,SK2,SK3 protein expression;real-time fluorescent quantitative PCR method was used to detect the mRNA level of NOX4,p38MAPK,SK2.Results:Dagliflozin ameliorated cardiac structural and functional dysfunction in diabetes;dagliflozin reduced ROS production;dagliflozin inhibited NOX4,activated p38MAPK protein expression and mRNA levels;dagliflozin mediated action potential remodeling and increased SK channel current density;dagliflozin significantly upregulated SK2 expression and partially downregulated SK3 expression,while having no effect on SK1;Dagliflozin promoted SK2 protein expression and mRNA levels;NOX4/p38MAPK signaling pathway was involved in reversing the low expression of SK2 in diabetic rat myocardium.Conclusion:Dagliflozin can promote SK2 expression,and its mechanism of action may be mediated through the NOX4/p38MAPK signaling pathway,thus attenuate oxidative stress and improve cardiac structure and dysfunction in diabetic rats.