ABSTRACT
BACKGROUND: Palindromic rheumatism (PR) is a rare periodic arthritis characterized by relapsing short episodes of arthritis. Although the pathogenesis of PR is still unclear, the clinical condition is similar to that of autoinflammatory diseases caused by dysregulation of inflammasome-related genes. OBJECTIVE: We analyzed the inflammasome adapter PYD and CARD domain-containing protein/apoptosis-associated speck-like protein containing a CARD (PYCARD/ASC) in Japanese patients with PR. METHODS: Serum interleukin (IL)-1ß concentrations in three Japanese patients with PR were measured. We also cloned PYCARD/ASC cDNA variants and expressed them in THP-1 cells to determine their effects on inflammasome activity following stimulation with phorbol 12-myristate 13-acetate and monosodium urate. Lysates of recombinant THP-1 cells were subjected to co-immunoprecipitation assays. RESULTS: Serum IL-1ß concentrations were significantly elevated in patients with PR, and a splice variant of PYCARD/ ASC mRNA lacking exon 2 (Δexon2) was dominantly expressed compared with that in controls. Moreover, IL-1ß secretion was significantly increased in THP-1 cells expressing Δexon2PYCARD/ASC compared with that in cells expressing the wild-type protein. The amount of NLRP3 bound to Δexon2PYCARD/ASC was increased after stimulation, whereas that bound to the wild-type protein was decreased. There were no differences in caspase-1 binding. CONCLUSIONS: Δexon2 PYCARD/ASC was associated with the pathogenesis of PR.
Subject(s)
CARD Signaling Adaptor Proteins , NLR Family, Pyrin Domain-Containing 3 Protein , Arthritis, Rheumatoid , CARD Signaling Adaptor Proteins/genetics , CARD Signaling Adaptor Proteins/metabolism , Exons , Humans , Interleukin-1beta/genetics , Interleukin-1beta/metabolism , Japan , NLR Family, Pyrin Domain-Containing 3 Protein/genetics , NLR Family, Pyrin Domain-Containing 3 Protein/metabolismABSTRACT
Epithelial-mesenchymal transition (EMT) plays a pivotal event in the development of pulmonary fibrosis. We have previously reported that methotrexate (MTX)-induced alveolar epithelial cell injury followed by pulmonary fibrosis as a result of the recruitment and proliferation of myofibroblasts. However, there is no data concerning whether EMT occurs in MTX-induced pulmonary fibrosis. In the present study, therefore, we investigated the expression of EMT markers such as E-cadherin, α-SMA, and vimentin by immunofluorescence analysis in mouse lung tissues after administration of MTX. We found that vimentin and α-SMA-positive cells of the MTX-induced pulmonary fibrosis were increased; on the other hand, E-cadherin was decreased, indicating that epithelial cells act as the main source of mesenchymal expansion. These results exhibited the down-regulation of E-cadherin expression and the up-regulation of α-smooth muscle actin (α-SMA) in primary mouse alveolar epithelial cells (MAECs) and A549 cell lines. Additionally, MTX-induced A549 cells exhibited an EMT-like phenotype accompanied by the elevation of the expression of interleukin-6 (IL-6) and transforming growth factor (TGF)-ß1, as well as an enhancement of migration. All of these findings suggest that MTX-induced pulmonary fibrosis occurs via EMT.
