Effects Of Glutamine Induced Heat Shock Protein70Overexpression On Atrial Fibrosis And Connexin43Remodeling In Isoprenaline-treated Rats

Objective：To explor the effects of glutamine induced heat shock protein70overexpression onatrial fibrosis and connexin43remodeling in Isoprenaline-treated rats and relatedmechanisms. Compared the effects of glutamine and valsartan on atrial fibrosis andconnexin43remodeling，evaluate the clinical value of glutamine.Methods：This experiment is divided into two parts, the specific experimental methods asfollows。The first part of the experiment: Forty male SD rats were randomly divided into fivegroups（n=8）： control group, DMSO group, ISO5mg kg^-1 d^-1group （Fibrosis group）,ISO5mg kg^-1 d^-1+Ala-Gln0.75mg kg^-1 d^-1group （Intervention group） and ISO5mg kg^-1 d^-1+QUE100mg kg^-1 d^-1+Ala-Gln0.75mg kg^-1 d^-1+DMSO group（QUEgroup）. rats were killed after7days.The AngⅡ expression in myocardial tissue wasdetected by radioimmunoassay; myocardial fibrosis was observed by H-E staining;Collagen volume fractions were quantified by Masson staining and as the indicators ofatrial fibrosis;The expressions of Hsp70, p-JNK1/2/3,c-Jun and Cx43were determained with immunohistochemical method.The second part of the experiment: Thirty-two male SD rats（160±20g） wererandomly divided into four groups（n=8）： control group（A）,ISO（5mg/[kg d]） group （B）,and ISO[5mg/（kg d）]+Ala-Gln [0.75mg/（kg d）] group （C）, ISO[5mg/（kg d）]+valsartan[30mg/（kg d）] group（D）. Each group was treated with the corresponding reagent once a day，ISO administration for seven days，group C and D continued to be treated withcorresponding drugs for28days，all rats were killed after28days. The AngⅡ content wasmeasured by radioimmunoassay; myocardial fibrosis was analyzed by H-E staining;Collagen volume fractions were quantified by Masson staining and as the indicators ofatrial fibrosis; The expressions of Hsp70, p-JNK1/2/3,c-Jun and Cx43weresemi-quantified with immunohistochemical method.Results：Results of first part of the experiment: AngⅡ content （pg/L） was similar between thecontrol group and DMSO group （P>0.05）, and significantly increased in fibrosis group,intervention groupand QUE group （P<0.01）. Atrial fibrosis was significantly haigher infibrosis group and QUE group， but not in intervention group compared with controlgroup and DMSO group. The expression of Hsp70were Similar in the control group,DMSO group, fibrosis group and QUE group （P>0.05）, but significantly upregulated inintervention group （P<0.01）. The expressions of p-JNK1/2/3and c-Jun were similarbetween control group and DMSO group（P>0.05）,while significantly upregulated infibrosis group and QUE group（P<0.01vs control group）,but in intervention group werenot obvious change（P>0.05vs control grou）. The content of Cx43was similar betweencontrol group and DMSO group （P＞0.05）， and linearly distributed in intercalated discof the cardiac myocyte, however the content of Cx43was obviously reduced（P<0.01）andthe Cx43distribution was disordered in fibrosis group and QUE group, while thesechanges were not found in intervention group.Results of second part of the experiment: Compared with the Agroup, the contents ofAngⅡ in group B、C、and D were significantly increased （P<0.01,respectively）.; Noobvious atrial fibrosis was observed in group A, and there was evident atrial fibrosis in group B， and was much higher than that in group C、group D（P<0.01,respectively）. Theexpressions of p-JNK1/2/3and c-Jun in group B were significantly increased（P<0.01）,while the expressions of p-JNK1/2/3and c-Jun in the group A、C and D werenot obvious change（P>0.05）， The content of Hsp70in group C was significantlyincreased, and the difference was statistically was significant higher than that in othergroups （P <0.01,respectively）. There was no significant difference in contents of Hsp70among the groups ofA、B and D. The content of Cx43in group B was obvious reduced（P＜0.01）with irregular distribution, relatively increased in the side of the myocardial cells.While the content of Cx43in group C and D had no obvious change compared with that inA group（P>0.05）. The Cx43partly linearly distributed in myocardial cell intercalateddisc，and the content of Cx43in group C and D showed no significant difference （P>0.05）.Conclusion：1. Glutamine cound reduce the atrial fibrosis and Cx43remodeling inIsoprenaline-treated rats by up-regulating Hsp70and inhibiting JNK signalingpathway activation through down-regulation p-JNK1/2/3and c-Jun expression.2. Glutamine and valsartan can reduce the atrial fibrosis and connexin43remodelingin rats induced by isoprenaline. The mechanism may be relate to inhibit JNK pathways atdifferent levels.