The Expression Of Cathepsin B And The Protective Effects Of Its Inhibitor CA-074Me In Polymyositis

Background:Polymyositis (PM) is a chronic inflammatory myopathy, which is charactered by cell-mediated immunological reaction. PM generally causes pain and weakness of muscle, even threatens patient’s lives, but the etiology and pathogenesis of it remains partially understood. Previous studies have proved Cathepsin B (CB) was strongly stained in muscle tissues from PM patients. But the role of CB in PM needs further studies.Objective:To investigate the expression of CB in PM patients and the role of CB in the pathogenesis of PM. Establishing an animal model of CVB1-induced PM to investigate the expression and role of CB in the guinea-pig model of CVB1-induced PM, and observe the protective effects of CA-074Me in the guinea-pig model of CVB1-induced PM, after giving CA-074Me, the inhibitor of CB. To explore the mechanism of CB in PM, and find new therapeutic targets for PM.Methods:(1)20patients with PM and5healthy adults were included in this study. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL assay), western blot, immunohistochemistry analysis and histologic examination (HE) staining were performed to detect the apoptosis, the number of CD8+T cells and CB+cells and inflammation in muscle tissues from human. Both immunohistochemistry and western blot were used to determine the expression of CB protein.(2)32shorthair guinea pigs (154g±18g)4weeks old were obtained from animal center of Zhongshan Hospital of Fudan University and were divided into four groups randomly and averagely with8in each group. Guinea pigs were inoculated with Coxsackie virus B1(CVB1), and the effects of CB inhibitor CA-074Me on CB expression, inflammation and apoptosis were then investigated. Inflammation was assessed by histological examination. Both immunohistochemistry staining and western blot were used to determine the protein expression of CB. The mRNA levels of CB were measured by Real-Time RT-PCR. The apoptosis was determined by TUNEL assay.Results:(1) In patients with PM, the protein levels of CB were significantly up-regulated in muscle tissues compared with healthy controls, which correlated with increases in inflammation score and apoptotic rate in PM patients.(2) Consistently, the protein levels of CB, inflammation score, CD8T cells infiltration and apoptotic rate were significantly increased in the guinea-pig model of CVB1-induced PM. Administration of CA-074Me reduced CB expression, decreased inflammation score and attenuated apoptosis in muscle tissues of the guinea-pig model of CVB1-induced PM. The inhibitory effect of CA-074Me on apoptosis was associated with down-regulation of Bax expression and consequent increase in the ratio of Bcl-2/Bax. However, CA-074Me did not have any effect on CD8+T cells infiltrations in the guinea-pig model of CVB1-induced PM.Conclusions:This study confirms up-regulation of CB in PM patients and in guinea pig models of CVB1-induced PM, and demonstrates that inhibition of CB provides protective effects in a guinea pig model of CVB1-induced PM. Thus, CB will be an important therapeutic target for PM.