Putting recommendations into practice: Australian rheumatologists’ opinions on leflunomide use in rheumatoid arthritis

Abstract

AIM: Primary Sjögren’s Syndrome (pSS) is an autoimmune inflammatorydisease affecting salivary glandular epithelium. It is characterised by thepresence of immune complexes comprising autoantibodies bound to RNA/protein, which correlate with disease severity and potentially drive inflam-mation. Inflammasomes are a component of the innate immune systemthought to play a role in immune surveillance of mucosal surfaces. Wehypothesise that inflammasome activation by immune complexes may playa key role in salivary gland inflammation in pSS. In immune cells, inflammasomeactivation requires both priming through toll-like receptors (eg LPS-TLR4for NLRP3), followed by specific activation. However, nothing is knownabout inflammasome priming in salivary gland epithelial cells (SGEC).The aim of this study was to examine TLR priming, of both NLRP3 andAIM2 inflammasomes in a human, secondary SGEC line.METHODS: A253 cells were primed with PolyIC (TLR 3), LPS (TLR4),Imiquimod (TLR 7) and CL264 (TLR 7) for 6 hours. Changes in transcript/protein levels were measured by both qPCR, western blotting and immu-nocytochemistry.RESULTS: NLRP3 was lowly expressed, by both qPCR and western blot, andwas not induced by any TLR ligands. However, polyIC upregulated bothAIM2 and IL-1beta as shown by both qPCR (6-fold and 3-fold respectively,p < 0.05) and western blot. Preliminary immunohistochemistry demon-strates AIM2 staining of the epithelium lining the ducts and acini of salivarygland biopsies from both pSS patients and controls.CONCLUSIONS: The AIM2 inflammasome is expressed in SGEC lining theducts and acini, and polyIC, a dsRNA analogue, primes the AIM2inflammasome in the A253 SGEC cell line. These results support a poten-tial role for inflammasome activation in SGEC in pSS, possibly mediated byRNA containing immune complexes which are present in this disease. TheA253 SGEC cell line may be a suitable model to further investigateinflammasome activation by immune complexes in epithelial cells.