ABSTRACT
This study was aimed to establish an experimental mouse model of combined transgenic inhibition of both multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and inward rectifier potassium current (Ik1), and to observe whether the specific inhibition of both CaMKII and Ik1 can bring about any effects on cardiac remodeling. Mice were divided into 4 groups: wild type (WT), CaMKII inhibited (AC3-I), Ik1 inhibited (Kir2.1-AAA) and combined inhibition of both CaMKII and Ik1 (AC3-I+Kir2.1-AAA). Mice in each group received electrocardiogram (ECG) and echocardiography examination. ECG in the condition of isoproterenol (ISO) injection was also checked. The whole cell patch clamp technique was used to measure Ik1 and the transient outward potassium current (Ito) from enzymatically isolated myocytes of left ventricle. In the condition of basal status, no significant changes of heart rate, PR interval and QRS interval were observed. No mouse showed ventricular arrhythmias in all of the 4 groups. After ISO injection, each group presented no significant ventricular arrhythmias either. The indexes measured by M-mode (motion-mode) and two-dimensional echocardiography had no significant differences among the four groups. Ik1 in AC3-I group was significantly higher than those in other three groups (P < 0.01) because of the results brought about by CaMKII inhibition. Among the latter three groups, both Kir2.1-AAA group and AC3-I+Kir2.1-AAA group had a significant reduced Ik1 compared with that of WT group, which was due to the Ik1 inhibition (P < 0.01). Ito in AC3-I group was higher than that of the other three groups (P < 0.01), but there were no significant differences in Ito among WT, Kir2.1-AAA and AC3-I+Kir2.1-AAA groups. Thus, combined transgenic myocardial CaMKII and Ik1 inhibition eliminated the up-regulation of Ik1 in CaMKII inhibited mice, and had no effects on cardiac remodeling including heart structure and function as well as arrhythmias at the basic and ISO conditions. The results of this study may provide a basis for the further investigation of combined inhibition of CaMKII and Ik1 in pathogenic cardiac remodeling.
Subject(s)
Animals , Mice , Arrhythmias, Cardiac , Brugada Syndrome , Calcium-Calmodulin-Dependent Protein Kinase Type 2 , Physiology , Cardiac Conduction System Disease , Disease Models, Animal , Electrocardiography , Heart , Physiology , Heart Conduction System , Congenital Abnormalities , Heart Ventricles , Isoproterenol , Mice, Transgenic , Patch-Clamp Techniques , Potassium Channels, Inwardly Rectifying , Physiology , Up-Regulation , Ventricular RemodelingABSTRACT
<p><b>OBJECTIVE</b>To investigate effects of supplementation of folate on the expression of monocyte chemoattractant protein-1 (MCP-1) in aortic endothelium and release from peripheral blood mononuclear cells (PBMC) in rats with hyperhomocysteinemia induced by ingestion of excess methionine.</p><p><b>METHODS</b>Thirty male SD rats were randomly divided into 3 groups (n = 10 for each group): control group (Control), high homocysteinemia group (Hhcy), and folate supplementation group (FA). They were fed with nomal diet, normal diet enriched by 1.7% methionine, and normal diet plus 1.7% methionine and 0.006% folate, respectively, for 45 days. The levels of total plasma homocysteine (Thcy) were measured by high performance liquid chromatography and the concentrations of chemokine MCP-1 released from PBMC stimulated by oxidized low density lipoprotein were detected by enzyme immunoassays. The expression of MCP-1 on aortas of rats was detected by immunohistochemistry and Western blot.</p><p><b>RESULTS</b>A high methionine diet for 45 days induced hyperhomocysteinemia. Folate supplementation to high-methionine diet significantly decreased plasma Thcy levels (P < 0.01). The expression of MCP-1 in aortic endothelium and the levels of MCP-1 released from PBMC stimulated by oxidized low density lipoprotein were significantly higher in rats of Hhcy group than in rats of control group (P < 0.05, P < 0.01). During supplementation of folate, normalization of Thcy levels was accompanied by a marked reduction of MCP-1 expression in aortic endothelium and by a significant decrease of MCP-1 released from PBMC stimulated by oxidized low density lipoprotein (P < 0.05, P < 0.01).</p><p><b>CONCLUSION</b>Folate supplementation can prevent an elevation of homocysteine levels in the blood and decrease the expression MCP-1 in aortic endothelium and release of MCP-1 from PBMC in rats with hyperhomocysteinemia.</p>