Antiviral Effect Of Polydatin In Vivo And In Vitro On Viral Myocarditis

[Objective] To study the antiviral and protective effect of Polydatin (PD) on the cultured rat neonatal cardiomyocytes and murine model of viral myocarditis (VMC) induced by Coxsackievirus B₃ (CVB₃). It will have great importance in basic research, clinical therapy and drug screening.[ Methods ] Primary cultures of Sprague-Dawley (SD) rat neonatal cardiac myocytes were prepared and inoculated with 100 TCID50 CVB3 as experimental model of viral myocarditis. Different concentration of PD was added into cardiomyocytes infected by CVB₃. The cardiomyocyte viability was detected by MTT assay for calculating the survival rate and the inhibitory rate of the virus. Myocardial F-actin and VEGF were analyzed by immunofluorescent staining with confocal microscopy. Mean fluorescent intensity of F-actin and VEGF was determined by flow cytometry.One hundred and twenty male BALB/c mice, 2 to 4 weeks old, were divided into 4 groups randomly, included normal control group, PD control group, viral control group and PD treatment group. The latter two groups were inoculated intraperitoneally of 10⁶TCID₅₀ CVB₃ at a dose of 0.1ml per mouse. Five mice of each group were sacrificed on 3, 7, 10, 14, 21 and 30 days post-inoculation. The general condition was observed. The histological changes of heart, virus titer in heart by plaque-forming assay, expression of VEGF protein and microvessel density in heart with immunohistochemistry and serum VEGF level with Enzyme-linked immunosorbent assay (ELISA) were measured.[Results] There is no toxicity on cardiomyocytes when PD is at concentration of 0.02 mmol/L and 0.2 mmol/L while there is toxicity at concentration of 2 mmol/L. CVB₃ could reduce the viability of cardiomyocytes, depolymerize F-actincytoskeleton and reorganize VEGF protein. Different concentration of PD could effectively lessen the occurrence of cytopathic effect and increase the survival rate of CVB3 infected cardiomyocytes significantly. PD could also inhibit the replication of CVB3 and attenuate the CVB3-induced changes of myocardial cytoskeleton and VEGF organization, especially at dose of 0. 2 mmol/L. The results of flow cytometry showed the expression of F-actin and VEGF were significantly increased in PD treated group compared with viral control group and the level of VEGF was increased in dose-dependent manner.No myocardial lesions were noted in both normal control group and PD control group. In viral control group on day 3 after infection, cardiac lesions appeared and became more extensive reaching a peak on day 14, and then recovered after day 21. The similar process to myocardial VEGF and serum VEGF was observed. Compared with viral control, the myocardial lesions were significantly less severe and the duration of disease was shortened after PD treatment. It could also maintain expression of VEGF and serum VEGF to increase the microvessel density and improve the ischemic state of myocardium. [ Conclusions ]1. C VB3 could cause damage of rat neonatal cardiomyocytes directly, induce F-actin cytoskeleton depolymerization and VEGF protein reorganization and then decline the contractility of cardiac myocytes.2. PD could effectively lessen the occurrence of cytopathic effect induced by CVB3 and maintain normal morphology and function of cardiomyocytes, especially at a dose of 0. 2 mmol/L.3. PD could increase the expression of VEGF in CVB3 infected cardiomyocytes in dose-dependent pattern.4. PD could protect cardiac myocytes from being damaged by CVB3, increase the survival rate of CVB3 infected mice by inhibiting CVB3 replication and maintaining expression of VEGF and serum VEGF which could increase the microvessel density and improve the ischemic state of myocardium.