MRP8 drives production of the chemokine MCP-1 from human skeletal muscle. (A) Expression of TLR4 mRNA (upper panel) by RT-PCR in human skeletal myoblasts (LHCNM2) and muscle tissue from JDM and controls. HPRT mRNA was amplified as a house keeping gene (lower panel). (B) MCP-1 and IL-6 production by LHCNM2 cells stimulated for 24 hours with 5 μg/ml MRP8, MRP14, MRP8/14 or 100 ng/ml LPS or cultured in medium alone (NS, non stimulated); MCP-1 and IL-6 were measured in cell culture supernatants by ELISA and multiplex immunoassay, respectively; n = 6, bars and lines represent mean and SEM, respectively. Paired t -test was used for comparisons. (C) Quantitative PCR analysis of MCP-1 expression (relative units) in quadriceps tissue from JDM patients (n = 6) compared to age matched controls (n = 4) normalised to HPRT expression. (D) MCP-1 protein concentration in serum from 14 JDM patients compared to 16 aged matched controls, measured by multiplex immunoassay. (E) Serum IL-6 in JDM patients (n = 27) and controls (n = 16), measured by multiplex immunoassay. Lines represent medians. Mann Whitney test was used for unpaired comparisons, *P <0.05, **P <0.001. JDM, juvenile dermatomyositis; LPS, lipopolysaccharide; MCP-1, monocyte chemoattractant protein-1; SEM, standard error of the mean; TLR4, Toll-like receptor 4.
Nistala et al. Arthritis Research & Therapy 2013 15:R131 doi:10.1186/ar4311