Cigarette smoke induces <i>miR-132</i> in Th17 cells that enhance osteoclastogenesis in inflammatory arthritis.

Abstract

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by joint destruction and severe morbidity. Cigarette smoking (CS) can exacerbate the incidence and severity of RA. Although Th17 cells and the Aryl hydrocarbon receptor (AhR) have been implicated, the mechanism by which CS induces RA development remains unclear. Here, using transcriptomic analysis, we show that <i>microRNA-132</i> is specifically induced in Th17 cells in the presence of either AhR agonist or CS-enriched medium. <i>miRNA-132</i> thus induced is packaged into extracellular vesicles produced by Th17 and acts as a proinflammatory mediator increasing osteoclastogenesis through the down-regulation of COX2. In vivo, articular knockdown of <i>miR-132</i> in murine arthritis models reduces the number of osteoclasts in the joints. Clinically, RA patients express higher levels of <i>miR-132</i> than do healthy individuals. This increase is further elevated by cigarette smoking. Together, these results reveal a hitherto unrecognized mechanism by which CS could exacerbate RA and further advance understanding of the impact of environmental factors on the pathogenesis of chronic inflammatory diseases.