| Part 1 Expression of macrophage migration inhibitory factor in murine hearts with viral myocarditisObjective: Macrophage migration inhibitory factor (MIF) don't belong to any cytokine family that is finded now. As a important pro-inflammatory cytokine, MIF participates in the genesis and development of a variety of inflammatory diseases. The purpose of this study was to investigate the kinetic features of MIF expression in mice with viral myocarditis (VMC), and its significance in the pathogenesis of VMC.Methods: Eighty Balb/c mice were divided into two groups: the infected group (VMC group) and a control group. Mice in the infected group (n=70) were inoculated intraperitoneally with o.1 mL of 1×102 TCID50 CVB3 diluted in Eagle's minimal essential medium (EMEM) solution. Control mice were treated with 0.1 mL of EMEM. Ten infected mice were sacrificed on days 3,7,15 and 30 after inoculation, and the control mice were killed on day 30 postinoculation. The expression levels of MIF mRNA and protein in VMC mice were examined by RT-PCR and immunohistochemistry respectively. The correlation analysis between the expression of MIF protein and myocardial histopathologic scores was investigated.Results: The expression levels of myocardial MIF mRNA and protein were elevated on day 3 after virus inoculation, and reached the peack on day 7, then slowly decreased from day 15 to 30, but still sustained a high level on day 30. There were significant differences in the expression of MIF mRNA and protein between on days 3, 7,15, 30 and control group. Furthermore, the MIF protein expression levels showed significantly positive correlation with the myocardial histopathologic scores.Conclusion: It is presumed that MIF may play an important role in the pathogenic mechanisms of VMC with CVB3.Part 2 Influence of astragaloside on myocardial macrophage migration inhibitory factor expression in viral myocarditic miceObjective: Astragaloside is a simple substance of saponin, which is the active constituent of astragali.It were reported that the astragaloside had therapeutic effect to viral myocarditis (VMC) and dilated cardiomyopathy (DCM). The purpose of this study was to investigate the new therapeutical mechanism of astragaloside intervention on myocardial macrophage migration inhibitory factor (MIF) expression in VMC.Methods: 100 Balb/c mice were randomly divided into 6 groups: normal control group (group A,n=10), high-dose control group (group B,n=10), myocarditic control group (group C,n=20), low-dose intervention group (group D,n=20), middle-dose intervention group (group E,n=20) and high-dose intervention group (group D,n=20). Mice in group A and group B were inoculated intraperitoneally with 0.1 mL of 1×102 TCID50 CVB3 diluted in EMEM solution, and mice in group C, D, E and F 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 1 week, respectively. At the same time, mice in group C, D, E and F were treated with carboxymethycellulose solution and 1%,3%,9% astragaloside in carboxymethycellulose solution (0.07, 0.2 and 0.6g/kg.d,respectively) 0.1mL, ig, for 1 week, respectively. The mice were killed and their hearts were removed after 14 day. The expression levels of MIF mRNA and protein in the myocardium were examined by RT-PCR and immunohistochemistry, respectively.The pathologic morphologic change was observed by using the method of HE staining.Results: (1) Mice in normal control group and high-dose control group had no death and no any pathological lesions in myocardium. The mortality in myocarditic control group, low-dose intervention group, middle-dose intervention group and high-dose intervention group was 45% (9/20), 30% (6/20), 25% (5/20) and 10% (2/20). The mortality and myocardial histopathologic scores were significantly decreased in high-dose intervention group compared with in myocarditic control group (P<0.05), but no significant difference in low-dose, middle-dose intervention group and myocarditic control group (P>0.05). (2) There were no significant difference MIF mRNA and protein expression between normal control group and high-dose control group (P>0.05). The expression levels of MIF mRNA and protein in myocarditic normal group were markedly higher than those in normal control group (P<0.01). After intervention of various-dose astragaloside, the expression levels of MIF mRNA and protein were significantly lower in high-dose intervention group than those in myocarditic control group (P<0.01), however, no significant difference in low-dose and middle-dose intervention group compared with myocarditic normal group, respectively (P>0.05).Conclusion: Astragaloside could markedly cut down the mortality of mice with VMC, attenuate inflammatory reaction, and show better therapeutical effect on VMC. Our results supported that astragaloside may play a pivotal role in protecting the heart injure in VMC by suppressing excessive expression of MIF.
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