Effect of CD40 small interfering RNA on the expressions of peripheral blood interleukin-21 and interleukin-35 in rats with autoimmune myocarditis

Abstract

Objective To explore the effect of CD40 small interfering RNA(siRNA) on the expressions of peripheral blood interleukin(IL)-21 and IL-35 in rats with experimental autoimmune myocarditis (EAM) and its significance. Methods Twenty 6-8 week male Lewis rats were divided into normal group, EAM group, CD40siRNA group and siRNA group by using random number table, with 5 rats in each group.The normal rats were induced with phosphate buffer saline in double foot pads on day 0 and day 7, while the rest 3 groups were induced with cardiac myosin protein to establish EAM models.The rats in CD40siRNA group and siRNA group were respectively injected with CD40siRNA and siRNA slow virus expression vector through the tail vein of rats on day 7.The rats were executed on 21 day after echocardiogram examination was made.The histopathologic changes were observed by using light microscope and the myocardial histopathology scores were calculated.Enzyme- linked immunosorbent assay was used to determine the levels of IL-21 and IL-35 in peripheral blood. Results (1)Except the normal group, the total incidence rate of rats of each group was 100%, and there was no rat death.(2)Compared with EAM group, the heart mass/body ratio and myocardial histopathology scores were lower in CD40siRNA group, and the differences were significant (3.13±0.21 vs 3.80±0.29, 2.22±0.43 vs 3.32±0.51, F=0.332, 0.456, all P< 0.05). (3)The echocardiogram showed that there was only 1 rat in EAM group with massive pericardial effusion, and there was no pericardial effusion in CD40siRNA group.EAM group, CD40siRNA group and siRNA group displayed hypertrophy of the ventricular septum and left ventricular wall, narrow heart cavity and weakening of ventricular wall motion.The left ventricular shortening rate in CD40siRNA group was significantly higher than that in the EAM group[(63.34±11.06)% vs (38.56±6.98)%, F=16.080, P<0.05]. (4)The peripheral blood level of IL-21 in CD40siRNA group was lower than that in EAM group [(141.19±17.46) ng/L vs (157.81±17.58) ng/L, F=57.008, P<0.05], while its level of IL-35 was significantly higher than that in the EAM group [(195.96±18.26) ng/L vs (174.78±13.91) ng/L, F=31.727, P<0.05]. (5)The level of IL-21 in peripheral blood was positively correlated with myocardial histopathology scores in EAM group (r= 0.69, P< 0.05), but IL-35 was negatively correlated with myocardial histopathology scores (r=-0.64, P<0.05). Conclusions CD40siRNA might relieve the myocardial inflammation and reduce the myocardial injury of EAM rats.The levels of IL-21 and IL-35 can partly reflect the degree of myocardial injury.The mechanism may be related to down-regulating the expression IL-21 and up-regulating the expression of IL-35. Key words: CD40 small interfering RNA; Autoimmune myocarditis; Rat; Interleukin-21; Interleukin-35