Expression And Significance Of Macrophage Inflammatory Protein-1α In Murine Viral Myocarditis

Objective Macrophage inflammatory protein-1α(MIP-1α), a member of CCsubfamily of chemokines, can specifically induce chemotaxis of inflammatory cellsincluding monocytes, lymphocytes and neutrophils, thereby being involved inpathogenesis of a variety of inflammatory diseases. The aim of the present study wasto investigate the kinetic features of MIP-1α expression in mice with viral myocarditis(VM), and its roles in the pathogenesis of VM.Method: Seventy five Balb/c mice were randomly divided into two groups: themyocarditic group and a control group. Mice in the myocarditic group (n=65) wereinoculated intraperitoneally with0.1mL of1×102TCID50coxsackievirus B3(CVB3)diluted in Eagle’s minimal essential medium (EMEM) solution. Control mice weretreated with0.1mL of EMEM. After weighing body weight(BW),10infected micewere sacrificed on days3,7,15and30postinoculation, and the control mice werekilled on day30postinoculation. The hearts were removed and weighed to calculateheart weight(HW)/BW. Blood was centrifugated to obtain serum. Changes ofmyocardial histopathology were examined through HE stain. Expression of MIP-1αmRNA and protein in the myocardium were examined by RT-PCR and westernblotting, respectively. Serum MIP-1α concentrations, myocardial interleukin-1β andtumor necrosis factor-α(TNF-α) contents were detected using enzyme linkedimmunosorbent assay(ELISA). Correlation analyses between the expression of MIFprotein or serum MIP-1α concentration and myocardial histopathologic scores wereinvestigated.Results1. The mortality in myocarditic group was38.46%（25/65）. Mice in control grouphad no death.2. Myocardial morphology was normal in control mice. Myocardial necrosis and inflammatory cells infiltration were found on days3,7,15and30postinoculation. Themost severe histopathologic change was found on day7after inoculation. However,there was no infiltration of inflammatory cells on day3.3. HW/BW in myocarditic group from7d to30d after infection was higher thanthat of control, whereas there was no significantly difference between on day3andcontrol group(P>0.05).4. Serum MIP-1α concentrations on days7,15and30after inoculation weremarkedly increased compared with control group(P<0.01), and peaked on day7.There was no significantly difference between on day3and control group(P>0.05).5. The significant up-regulation of myocardial MIP-1α mRNA expression levels ondays7,15and30after viral infection within myocarditic group in comparison withcontrol group(P<0.01), except for day3(P>0.05).6. MIP-1α protein expression levels in myocardial tissue of control group were low.Those were elevated on days from7to30after inoculation(P<0.01or0.05), andreached the peack on day7. Significant difference did not exist between on day3andcontrol group (P>0.05).7. Correlation analysis between the expression levels of MIP-1α protein and myo-cardial histopathologic scores: MIP-1α protein expression levels showed asignificantly positive correlation with the myocardial histopathologic scores（r=0.82,P<0.05）.8. Correlation analysis between serum MIP-1α concentrations and myocardialhistopathologic scores: Serum MIP-1αconcentrations was significantly correlated withmyocardial histopathologic scores (r=0.89,P<0.05).9. Myocardial IL-1β and TNF-α contents on days7,15and30after infection werehigher than those of control(P<0.01). Nevertheless, there was no significant diffencebetween3days after infection and control group(P>0.05).conclusion1. Over-expression of MIP-1α is involved in the pathogenesis of VM, which mightbe associated with promoting infiltration of inflammatory cells to myocardium and increasing secretion of IL-β and TNF-α.2. Serum MIF concentrations may be used to reflect the severity of myocarditis,and it can be a serumal indicator of pathogenetic condition for VM.