| Objectives:1.The left atrial pressure overload model was established by transverse aortic coarctation(TAC)in rats,and the modeling method was optimized to lay a methodological foundation for further study.2.To detect the effect of TAC on gap junction and interstitial fibrosis protein expression in rat atria,and to study the possible molecular mechanism of atrial fibrillation induced by pressure overload.3.To observe the activation of atrial Rho/ROCK signaling pathway under mechanical stimulation and explore its regulatory role in the process of atrial electrical-structural remodeling induced by pressure overload.Methods:1.Different intensity(18G,20G)of aortic coarctation was performed on rats by TAC method,and the modeling effect was comprehensively evaluated by invasive pressure measurement of carotid artery,cardiac index,HE staining of atrial tissue,Western-blot detection of Caspase3,etc.,so as to screen the optimized modeling method and lay a methodological foundation for further research on mechanical mechanism of atrial fibrillation based on TAC.2.The expression of Cx43,Cx40 and Collagen I was detected by immunofluorescence,immunohistochemistry and Western-blot.The degree of atrial interstitial fibrosis was observed by Masson staining.The effects of TAC on atrial gap junction remodeling and myocardial fibrosis were evaluated.3.Immunohistochemistry and Western-blot were used to detect the expression of Rho A and ROCK,and G-LISA was used to detect the activity of Rho A.The effect of TAC on the activity of Rho/ROCK signaling pathway was evaluated.Fasudil was used to inhibit the Rho/ROCK signaling pathway to observe its regulatory effect on the expression of connexin and myocardial fibrosis induced by pressure overload.Results:1.TAC significantly increased the proximal arterial pressure compared with sham operated rats(P < 0.05),leading to the increase of cardiac index in experimental animals(P < 0.05),the area of myocardial cells increased(P < 0.05),and the expression of apoptosis related marker Caspase3 protein increased(P < 0.05),which indicated that the atrial pressure overload model of SD rats could be successfully established by TAC method.At the same time,compared with TAC-20 G,the survival rate of experimental animals was higher(P < 0.05),which could meet the needs of further research.2.After 12 weeks of TAC treatment,the degree of atrial fibrosis and the expression of Collagen I protein were increased(P < 0.05),and the expression of Cx43 protein was decreased(P < 0.05).There was no significant difference in the expression of Cx40 among the experimental groups(P = 0.81).3.The protein expression of Rho A and ROCK increased significantly(P < 0.05),and Rho A activity increased significantly(P < 0.05).Fasudil could decrease the protein and m RNA expression of Rho A and ROCK(P < 0.05),and inhibit the phosphorylation of MYPT-1(P < 0.05),suggesting that fasudil could inhibit the Rho/ROCK signaling pathway in rat atria.Furthermore,inhibition of Rho/ROCK signaling pathway partially reversed the decrease of Cx43 protein expression(P <0.05)and the increase of Collagen I m RNA and protein expression(P < 0.05)induced by TAC,but had no effect on Cx43 m RNA expression(P = 0.98).Conclusions:1.The model of left atrial pressure overload in SD rats was successfully established by TAC-18 G method,which laid a methodological foundation for further study on the mechanical mechanism of atrial fibrillation.2.TAC can decrease the expression of Cx43 and increase the expression of Collagen I in the atria of SD rats,which may be one of the reasons for the occurrence and persistence of atrial fibrillation caused by mechanical factors.3.Pressure overload can activate the Rho/ROCK signaling pathway in rat atria.The Rho/ROCK signaling pathway may mediate the decrease of Cx43 protein expression and the increase of Collagen I expression caused by pressure overload,suggesting that it may participate in the process of atrial electro-structural remodeling caused by mechanical factors. |
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