Role of miRNA in the regulation of inflammatory genes in staphylococcal enterotoxin B-induced acute inflammatory lung injury and mortality.

Exposure to Staphylococcal enterotoxin B (SEB) causes food poisoning, acute inflammatory lung injury, toxic shock syndrome, and often death. In this study, we investigated whether microRNA (miRNA) play a role in regulating SEB-driven inflammation in the lungs. Exposure to SEB caused immune cell infiltration, robust cytokine and chemokine production, compromised lung function, and 100% mortality in mice. We assessed miRNA and mRNA expression in lung infiltrating mononuclear cells following exposure to SEB and found 89 miRNA that were dysregulated (>2-fold) compared with vehicle controls. In silico analysis revealed that the miRNA exhibited biological functions pertaining to cell death and survival, cellular proliferation, and cell cycle progression. Through the use of q-RT PCR, we validated 9 specific miRNA (miR-155, miR-132, miR-31, miR-222, miR-20b, miR-34a, miR-192, miR-193*, and let-7e) and observed that they were predicted to bind the 3'-UTR of a number of genes that were either involved in the stringent regulation of inflammation (Smad3, Tgfb, Runx1, and Foxo3) or those that contributed to its exacerbation (Stat3, Ptgs2, Ccnd1, Ccne1, NfκB, and Tbx21). Further, by increasing or decreasing the levels of miR-132 (a miRNA highly induced by SEB), we noted the corresponding decrease or increase in the levels of its predicted target FOXO3. As a result of FOXO3 suppression by miR-132, we saw increase in Ifn-γ, Ccnd, and Ccne1. Taken together, our data support the role for miRNA in actively participating and orchestrating SEB-mediated inflammation in the lungs and provide several therapeutic targets for the treatment of SEB-driven toxicity via the modulation of miRNA.