Contribution of Necroptosis to Myofiber Death in Idiopathic Inflammatory Myopathies.

OBJECTIVE: Myofiber necrosis is a significant pathologic characteristic of idiopathic inflammatory myopathies (IIMs), and its molecular mechanism is largely unknown. Necroptosis is a recently identified form of regulated necrotic cell death, and its activation might have crucial biologic consequences. The aim of the present study was to investigate the role of necroptosis in IIM muscle damage. METHODS: Western blot and immunohistochemistry analyses were performed to examine the expression of receptor-interacting protein 3 (RIP-3) and mixed-lineage kinase domain-like (MLKL) proteins in 26 IIM patients and 4 healthy controls, as well as necroptosis-related damage-associated molecular pattern molecules. Tumor necrosis factor (TNF) was used to stimulate cultured C2C12 myoblasts, and the involvement of necroptosis in cell death of C2C12 cells was studied in vitro. RESULTS: The expression of RIP-3 and MLKL proteins and their phosphorylated forms was significantly increased in the muscle tissue of IIM patients compared to that of healthy controls. The expression levels of RIP-3 and MLKL proteins were associated with the severity of muscle damage in patients with IIM. Significant colocalization of MLKL with high mobility group box chromosomal protein 1 in necrotizing myofibers was observed in muscle biopsy tissue from patients with IIM. Stimulation of C2C12 myoblasts with TNF and a pan-caspase inhibitor, Z-VAD, resulted in the overactivation of necroptosis and significantly increased necrotic cell death. Strategies involving either inhibition of necroptosis with necrostatin-1 or knockdown of MLKL expression successfully prevented necroptosis-induced cell death of C2C12 cells. CONCLUSION: These findings demonstrate that overactivated necroptosis contributes to muscle damage in IIMs and suggest that necroptosis inhibitors could represent a new therapeutic target in the treatment of IIMs.

Expression of tumor necrosis factor-like weak inducer of apoptosis and fibroblast growth factor-inducible 14 in patients with polymyositis and dermatomyositis.

INTRODUCTION: The aim of this study was to investigate the expression of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor fibroblast growth factor-inducible 14 (Fn14) in patients with polymyositis (PM) and dermatomyositis (DM), and their relation to clinical manifestations. METHODS: Serum levels of TWEAK were detected in 98 PM/DM patients and 37 healthy controls by using the ELISA method. Total RNA isolated from fresh-frozen muscle tissue samples of 36 PM/DM patients and 10 healthy controls were used for analyzing the mRNA levels of TWEAK and Fn14 by quantitative reverse transcription polymerase chain reaction (RT-PCR). Immunofluorescence staining of TWEAK and Fn14 was conducted on muscle biopsy specimens from 23 PM/DM patients and seven healthy controls. RESULTS: Serum levels of TWEAK were significantly decreased in the PM/DM patients compared to those in the healthy controls (P < 0.001), and serum TWEAK levels negatively correlated with serum CD163 levels in PM/DM patients (r = -0.49, P < 0.001). The expression of Fn14 mRNA was significantly increased in the muscle tissue of PM/DM patients than in the muscle tissue of healthy controls (P < 0.01), whereas the expression of TWEAK mRNA in PM/DM patients was not statistically different from that of the healthy controls (P > 0.05). Fn14 mRNA levels in muscle tissue positively correlated with muscle disease activity (r = 0.512, P < 0.01). Patients with oropharyngeal dysphagia had significantly higher Fn14 mRNA levels than patients without oropharyngeal dysphagia (P < 0.05). The results of immunofluorescence staining showed that 19 out of 23 PM/DM patients were TWEAK-positive, and 20 out of 23 PM/DM patients were Fn14-positive. No detectable expressions of TWEAK or Fn14 were observed in the healthy controls. CONCLUSIONS: TWEAK-Fn14 axis may be involved in the pathogenesis of PM/DM. Further understanding of TWEAK-Fn14 function in PM/DM may help to define therapeutic targets for PM/DM.

Intravenous immunoglobulin therapy in adult patients with polymyositis/dermatomyositis: a systematic literature review.

The objectives of this study are to review and summarize published information on the use, effectiveness, and adverse effects of intravenous immunoglobulin (IVIG) in patients with polymyositis (PM) or dermatomyositis (DM) and to search MEDLINE and CNKI (Chinese) databases from 1985 to 2011 to retrieve clinical research articles concerning IVIG in adult patients with PM/DM. Of the 14 articles selected, two were randomized controlled trials, nine prospective open studies, and three retrospective studies with a total of 308 adult patients. IVIG has been used successfully in the treatment of PM/DM. The standard dose is 2 g/kg, given in two to five individual daily doses. The course of IVIG treatment is usually 3~6 months. IVIG therapy seemed rarely employed as first-line therapy in PM/DM. In a double-blind study conducted in patients with refractory DM, IVIG combined with corticosteroid significantly improved muscle strength and decreased serum creatine kinase level, compared with placebo. The beneficial effect of IVIG in refractory, flare-up, rapidly progressive, or severe PM/DM has been documented in many open-label trials. IVIG was shown to be effective in most of PM/DM patients with lung involvement and esophageal involvement. In some patients, IVIG can lower the corticosteroid dose required for maintenance, demonstrating the most effective steroid-sparing effect. Adverse effects were generally tolerable. IVIG is effective in the treatment of adult patients with PM/DM and appears to be relatively well tolerated and safe. IVIG may be a good choice especially in patients with refractory, flare-up, rapidly progressive, or severe PM/DM, and can be tried in patients with a contraindication for corticosteroid.