Chem/ChemR23 Signaling Axis Is Involved In The Endothelial Protection By K_atp And NNMR Activation

Endohtelial cells release several vasoactive mediators participating in the regulation of endothelial and cardiovascular function. The equilibrium of the endothelial-derived factors maintaines the balance of vascular tension and the endothelin surface as a anti-thrombotic and anti-aggregation of leukocytes and platelets. In response to impact of physical or chemical stimuli, endothelial-derived vasoactive mediators lose their balance. This arises to the disorder of the regulation of the vascular tension, coagulation and fibrolysis and contributes to the development of cardiovascular diseases. Targeting at endothelial dysfunction is a new therapeutic pathway for cardiovascular disease.Endothelial ATP-sensitive potassium channels (KATP channels) and non-neuronal muscarinic channels (NNMRs) are endothelial protective pharmaceutical targets,which were both firstly demonstrated by our laboratory. KATP channel opening and NNMR activating elevate endothelial nitric oxide (NO) system to improve endothelial function. Iptakalim and natakalim targeting at KATP channels and arecoline targeting at NNMRs are endothelial protectors without completely understood of the detailed mechanisms. Basal and clinical investigations suggest that ChemR23 is of great consequence in the combined application of fish oil and low dose of aspirin reducing secondary cardiovascular events. This study investigates the roles of Chem/ChemR23 axis in endothelial function and KATP opening and NNMR activation in protecting against endothelial dysfunction. The aim of this study was to elucidate the role of the Chem/ChemR23 axis in endothelial cells and in improving endothelial function by activating KATP channels and NNMRs.In primary cultured rat aortic endothelial cells (RAECs), endothelial dysfunction was induced by hyperhomocysteinaemia, hyperuricemia, hyperglycemia and hyperlipidemia, which are independent cardiovascular risk factors. We examined the effect of exogenous chemerin and KATP channel opener (KCO) iptakalim and natakalim and NNMR activatior arecoline on endothelial NO production and the effect of ChemR23 antibody. In dysfunctional endothelial cells injured by homocysteine, uric acid, glucose and oxidized low-density lipoprotein (ox-LDL), chemerin secretion and ChemR23 protein/gene expression was determined by western blot and RT-PCR. The effect of iptakalim, natakalim and arecoline on chemerin secretion and ChemR23 protein/gene expression was observed in homocysteine-stimulated RAECs. KATP channel blocker glibenclamide and M antagonist atropine was used to elucidate the mechanism of KATP channel opening and NNMR activation in modulating the Chem/ChemR23 axis. By way of ChemR23 antibody, the effect of ChemR23 activation has been investigated in the course of iptakalim and arecoline alone or combined on promoting endothelial NO system in uric acid-stimulated endothelial dysfunction.The data demonstrate that ChemR23 antibody blocked the NO production in normal endothelial cells as a function of concentration. Exogenous chemerin reversed the inhibition of NO production in uric acid-stimulated RAECs, which dependent on ChemR23 activation. Homocysteine, uric acid, glucose and ox-LDL reduced the ChemR23 gene expression as a function of concentration and time. Iptakalim, natakalim and arecoline increased the chemerin secretion and ChemR23 protein/gene expression depressed by homocysteine. Glibenclamide and atropine antagonized the effect of iptakalim, natakalim and arecoline on Chem/ChemR23 expression as a function of concentration, respectively. Iptakalim, natakalim and arecoline upregulated endothelial NO production in dysfunctional endothelial cells induced by uric acid as a function of concentration. The combined application of iptakalim and arecoline has no synergistic effect on NO production, and also blocked by ChemR23 antibody.In conclusion, enhancement of endothelial Chem/ChemR23 signaling promotes NO release, while blocking ChemR23 inhibited endothelial NO production. It suggests that the Chem/ChemR23 signaling closely associated with the pathway of endothelial NO production. The Chem/ChemR23 axis is downregulated in dysfunction endothelial cells and upregulated by KATP opening, especially for SUR2B/Kir6.1 subtypes, and NNMR activation in dysfunctional endothelial cells induced by homocysteine, uric acid, glucose and ox-LDL. Upregulation of Chem/ChemR23 axis is involed in the promotion of NO production by KATP opening and NNMR activation.Thus, the expression and activity of Chem/ChemR23 axis is parallel with endothelial function, and the enhancement of Chem/ChemR23 signaling improves NO-related endothelial function and cardiovascular system. Augmentation of the Chem/ChemR23 axis may be a novel therapeutic pathway for endothelial dysfunction. Activation of KATP and NNMR enhances the expression and activity of Chem/ChemR23 axis, which may be an important mechanism of activating KATP and NNMR to protect endothelial and cardiovascular function.