MiR-26a Reduces Inflammatory Responses via Inhibition of PGE2 Production by Targeting COX-2

MicroRNAs are small non-coding RNA regulatory molecules that play an important role in the development and function of immune cells. MicroRNA-26a (miR-26a) exhibits anti-inflammatory immune effects on immune cells. However, the exact mechanism by which miR-26a plays an anti-inflammatory role remains unclear. Here, we report that miR-26a reduces inflammatory response via inhibition of prostaglandin E2 (PGE2) production by targeting cyclooxygenase-2 (COX-2). We found that miR-26a was downregulated in vitro and in vivo. The miR-26a mimic significantly decreased COX-2 protein levels, further inhibiting pro-inflammatory cytokine production in LPS-stimulated macrophages. We predicted that miR-26a could potentially target COX-2 in LPS-stimulated macrophages. Computational algorithms showed that the 3'-UTR of COX-2 mRNA contains a binding site for miR-26a. This putative targeting relationship between miR-26a and COX-2 was further confirmed by a dual-reporter gene assay. The anti-inflammatory effects of the miR-26a mimic were diminished by PGE2 supplementation. Importantly, miR-26a mimics protected mice from lethal endotoxic shock and attenuated pro-inflammatory cytokine production. Collectively, these results suggest that miR-26a may function as a novel feedback negative regulator of the hyperinflammatory response and as a drug target for the progression of inflammation.