Expression Of IGF-1 And Associated Protein In The Viral Myocarditis And Intervention Study Of Astragaloside

Part 1 Expression of IGF-1 and associated proteins in mice with viral myocarditisObjective: To study expression of IGF-1 and associated proteins in mice with viral myocarditis at different phases, explore its potential role in the pathogenesis of viral myocarditis.Methods: 60 Balb/c male mice of four weeks were randomized divided into two groups: the infected group (n=40) and a control group (n=20). Mice in the infected group were inoculated intraperitoneally with 0.1 ml of 1×10² TCID₅₀ CVB₃ diluted in Eagle's minimal essential medium (EMEM) solution .The control mice were treated with 0.1 ml of EMEM. The mice were sacrificed on days 3,7,15 and 30 after inoculation randomized. The concentration of plasma IGF-1 was detected by ELISA , and the expression levels of IGF-1 and associated proteins in the myocardium tissue were examined by RT-PCR and immunohistochemistry, and the histopathological characteristics were evaluated by hematoxylin and eosin staining, respectively.Results: (1) The concentrations of plasma IGF-1 were higher in the infected group (565.75±63.2 pg/ml) than in control group(365.92±37.31 pg/ml), There were significant differences in the concentrations of plasma IGF-1 between the infected group and the control group(t=13.21,p<0.01).(2) The concentrations of plasma IGF-1 were elevated gradually after virus inoculation, and reached the peak on day 15, then decreased on 30, but still sustained a high level. There were significant differences in the expression of plasma IGF-1 between on days 3, 7,15, 30 and control group, respectively(F=19.53,p<0.01). (3) The protein expression levels of IGF-1, IGF-1R and IGFBP₃ were low in normal myocardium tissue by Immunohistochemistry stain, and were elevated gradually after virus inoculation, and reached the peak on day 15, There were significant significance in the protein expression levels of IGF-1, IGF-1R and IGFBP₃ between on days 3, 7,15, 30 and control group, respectively (F_IGF-1=26.72, p<0.01; F_IGF-1R=6.73, p<0.05; FIGFBP₃=21.57, p<0.01). The expression levels of IGF-1 and IGFBP-3 mRNA in myocardium tissue by RT-PCR were higher in infected group than in control group.Conclusion: The results show the GRH━GH━IGF-1━IGFBPs axis may play an important role in the pathogenic mechanisms of viral myocarditis.Part 2 The effect of astragaloside on expression of IGF-1 and associated proteins in viral myocarditisObjective: To observe the effect of astragaloside on expression of IGF-1 and associated proteins in mice with viral myocarditis, and research the therapentic machine of astragaloside on viral myocarditis in Balb/c mice with CVB₃.Methods: 65 Balb/c male mice of 4 weeks were randomized divided into 5 groups: normal control group (group A, n=10), high-dose control group (group B, n=10), high-dose intervention group (group C, n=15), low-dose intervention group (group D, n=15) and viral control group (group E, n=15). Mice in group C,D and E were inoculated intraperitoneally with 0.1 ml of 1×10² TCID₅₀ CVB₃ diluted in EMEM solution, and mice in group A and B were treated with 0.1 ml of EMEM. Then, mice in group A and group B were treated with carboxymethycellulose solution and 9% astragaloside in carboxymethycellulose solution 0.1ml, ig, for 2 week, respectively. At the same time, mice in group C, D and E were treated with carboxymethycellulose solution and 1% and 9% astragaloside in carboxymethycellulose solution (0.07 and 0.6g/kg.d) 0.1ml respectively, ig, for 2 week, respectively. The survival mice were observed . The mice were killed on day 15 post infection. The level of IGF-1 in the peripheral blood was detected respectively by enzyme-labeled immunosorbent assay (ELISA),and the expression levels of IGF-1,IGF-1R, IGFBP₃ mRNA and proteins in myocardium tissue , by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry,respectively.Results:(1) The death rate was significantly lower in group C than in group D and E, none of the rats of group B was dead.(2) The myocardial histopathologic scores of group C was significantly lower than those of group D and E, but there was no significant difference between group D and E.(3) The plasma level of IGF-1 in group A was 365.92pg/ml, group B ,372.23 pg/ml, group C , 472.46 pg/ml, group D , 654.51 pg/ml, and group E, 648.75 pg/ml. Compared with group A, the level of group C was increased ,and those of group D and E were significantly higher(p<0.05 or 0.01),but there was no significant difference between group A and B, neither between group D and E.(4) The expression levels of IGF-1,IGF-1R,IGFBP₃ were low in myocardium tissue by RT-PCR and immunohistochemistry staining in normal group , and were increased in group C, D and E. but there was no significant difference between group A and B, neither between group D and E.Conclusions: The results show that regulating the expression of IGF-1 and associated proteins could be one of the mechanisms of astragaloside on viral myocarditis in Balb/c mice with CVB₃.