History of infection before the onset of juvenile dermatomyositis: results from the National Institute of Arthritis and Musculoskeletal and Skin Diseases Research Registry.

OBJECTIVE: To obtain data concerning a history of infection occurring in the 3 months before recognition of the typical weakness and rash associated with juvenile dermatomyositis (JDM). METHODS: Parents or caretakers of children within 6 months of JDM diagnosis were interviewed by the registry study nurse concerning their child's symptoms, environment, family background, and illness history. Physician medical records were reviewed, confirming the JDM diagnosis. RESULTS: Children for which both a parent interview and physician medical records at diagnosis were available (n = 286) were included. Diagnoses were as follows: definite/probable JDM (n = 234, 82%), possible JDM (n = 43, 15%), or rash only (n = 9, 3%). The group was predominantly white (71%) and had a girl:boy ratio of 2:1. Although the mean age at onset was 6.7 years for girls and 7.3 years for boys, 25% of the children were < or =4 years old at disease onset. In the 3 months before onset, 57% of the children had respiratory complaints, 30% had gastrointestinal symptoms, and 63% of children with these symptoms of infection were given antibiotics. CONCLUSION: This study provides evidence that JDM affects young children. The symptoms of the typical rash and weakness often follow a history of respiratory or gastrointestinal complaints. These data suggest that the response to an infectious process may be implicated in JDM disease pathogenesis.

Retinoblastoma suppression of matrix metalloproteinase 1, but not interleukin-6, through a p38-dependent pathway in rheumatoid arthritis synovial fibroblasts.

OBJECTIVE: Rheumatoid arthritis (RA) is characterized by increased synovial lining cellularity, inflammation, and destruction of cartilage and bone. During the pathogenesis of RA, synovial fibroblasts reenter the cell cycle and multiply in number. RA synovial fibroblasts express high levels of the MAP kinase p38, which may contribute to the production of interleukin-6 (IL-6) and matrix metalloproteinases (MMPs). IL-6 and MMP-1 promote inflammation and joint destruction, respectively. Taken together, these findings indicate that in RA the enhanced cell cycle activity and production of IL-6 and MMP-1 may be linked. Therefore, we sought to determine if the tumor suppressor gene product retinoblastoma (Rb), a negative regulator of cell cycle activity, inhibits IL-6, MMP-1, and p38 in RA synovial fibroblasts. METHODS: RA and non-RA synovial fibroblasts were examined by enzyme-linked immunosorbent assay (ELISA) for the relative expression of inactive hyperphosphorylated Rb (inactive Rb/total Rb). Ectopic Rb expression was mediated by infection with a replication-defective adenovirus that expresses Rb (Ad-Rb). A control replication-defective adenovirus that expresses beta-galactosidase (Ad-beta-gal) was used. Cell cycle activity was determined by flow cytometry. IL-6 and MMP-1 expression was examined by real-time polymerase chain reaction and ELISA. Expression and activation of p38 were determined by kinase assays and ELISA. The activity of p38 was enhanced by infecting RA synovial fibroblasts with a replication-defective adenovirus that expresses a constitutively active form of MAPK kinase 3 (Ad-CA-MKK3), an upstream activator of p38. RESULTS: Quiescent RA, compared with non-RA synovial fibroblasts, displayed a 200% (P < 0.02) increase in the inactive Rb isoform. Proliferating RA synovial fibroblasts exhibited a 60% (P < 0.12) increase in the inactive Rb isoform compared with non-RA synovial fibroblasts. Increased levels of the active Rb isoform inhibited cell cycle progression and suppressed IL-6 and MMP-1 secretion in RA synovial fibroblasts, although the steady-state levels of IL-6 and MMP-1 messenger RNA remained unchanged. However, Rb overexpression had no effect on spontaneous or IL-1beta-induced production of IL-6 or MMP-1 in non-RA synovial fibroblasts. Ectopic Rb expression reduced the activity of p38. Ad-CA-MKK3 infection in RA synovial fibroblasts increased p38 phosphorylation, and MMP-1 but not IL-6 secretion. In contrast, Rb overexpression inhibited Ad-CA-MKK3-mediated phosphorylation of p38 and subsequent increase in MMP-1. CONCLUSION: Rb-mediated suppression of IL-6 and MMP-1 occurs at a posttranscriptional level. However, Ad-Rb reduction of MMP-1 but not IL-6 requires inhibition of the p38 pathway. These results suggest that Rb negatively regulates p38 activation, leading to decreased MMP-1 secretion in RA synovial fibroblasts.

IL-6 and matrix metalloproteinase-1 are regulated by the cyclin-dependent kinase inhibitor p21 in synovial fibroblasts.

During the pathogenesis of rheumatoid arthritis (RA), the synovial fibroblasts increase in number and produce proinflammatory cytokines and matrix metalloproteinases (MMPs) that function to promote inflammation and joint destruction. Recent investigations have suggested that cell cycle activity and inflammation may be linked. However, little is known about the mechanisms responsible for the coordinate regulation of proliferation and the expression of proinflammatory molecules in RA synovial fibroblasts. Here, we demonstrate a 50 +/- 10% decrease in the expression of p21, a cell cycle inhibitor, in the synovial fibroblast population from RA compared with osteoarthritis (OA) synovial tissue. Moreover, p21 positivity in the synovial fibroblasts inversely correlates with medium synovial lining thickness (r = -0.76; p < 0.02). The expression of p21 is also reduced in isolated RA synovial fibroblasts compared with OA synovial fibroblasts. Adenovirus-mediated delivery of p21 (Ad-p21) arrests both RA and OA synovial fibroblasts in the G(0)/G(1) phase of the cell cycle without inducing cytotoxicity. However, the spontaneous production of IL-6 and MMP-1 is suppressed only in the Ad-p21-infected RA synovial fibroblasts, indicating a novel role for p21 in RA. Analyses of p21-deficient mouse synovial fibroblasts reveal a 100-fold increase in IL-6 protein and enhance IL-6 and MMP-3 mRNA. Restoration of p21, but not overexpression of Rb, which also induces G(0)/G(1) cell cycle arrest, decreases IL-6 synthesis in p21-null synovial fibroblasts. Furthermore, in RA synovial fibroblasts the ectopic expression of p21 reduces activation of the AP-1 transcription factor. Additionally, p21-null synovial fibroblasts display enhanced activation of AP-1 compared with wild-type synovial fibroblasts. These data suggest that alterations in p21 expression may activate AP-1 leading to enhanced proinflammatory cytokine and MMP production and development of autoimmune disease.