Effects of rAAV9-mediated siRNA for p65 knockdown on myocardial fibrosis and apoptosis in rats with pressure overload

AIM To investigate the effect of p65 gene knock-down mediated by recombinant adeno-associated virus serotype 9 （rAAV9） on the cardiac function of pressure overload rat and its possible mechanism. METHODS The rat model of left ventricular hypertrophy was established by abdominal aortic coarctation（AAC）. SD rats were randomly divided into sham operation group， AAC group， AAC+rAAV9-eGFP group and AAC+rAAV9-eGFP-P65-siRNA group. The abdominal cavity was closed directly after laparotomy in the rats of sham operation group， the abdominal cavity was closed after ligation of the abdominal aorta in the rats of AAC group， and normal saline， rAAV9-eGFP and rAAV9-eGFP-P65-siRNA were injected into the tail vein 3 d after operation. After 4 weeks， the hemodynamic indexes were measured， the heart mass parameters were calculated， the degree of myocardial fibrosis was detected by Masson staining， the expression level of myocardial P65 was detected by Western blot， the degree of apoptosis was detected by TUNEL staining， and the serum contents of tumor necrosis factor-α （TNF-α） and interleukin-6 （IL-6） of the rats in each group were measured by ELISA. RESULTS The expression of P65 in AAC group and AAC+rAAV9-eGFP group was higher than that in sham operation group， while the expression of P65 in AAC+rAAV9-eGFP-P65-siRNA group was significantly lower than that in AAC group. The levels of systolic blood prossure （SBP）， diastolic blood pressure （DBP）， left ventricular weight/body weight （LVW/BW）， cardiomyocyte apoptotic rate and TNF- α and IL-6 in AAC group and AAC+rAAV9-eGFP group were higher than those in sham operation group， while SBP， DBP， LVW/BW， cardiomyocyte apoptosis rate and TNF-α in AAC+rAAV9-eGFP-P65-siRNA group were significantly lower than those in AAC group. The results of Masson staining showed that the deposition of collagen in cardiac tissue in AAC group and AAC+rAAV9-eGFP group was higher than that in sham operation group， and treatment with rAAV9-eGFP-P65-siRNA alleviated hypertension-induced fibrosis. CONCLUSION Knockdown of p65 gene reduces the degree of left ventricular fibrosis and apoptosis in rats with stress overload， and its mechanism is related to the regulation of NF-κB pathway and the reduction of inflammatory response.