Suppression of LPS-induced IFNg and NO in splenocytes by select E2-regulated miRNA: A novel mechanism of immune mod.. Mus musculus

microRNA (miRNA), recently identified, non-coding, small RNA, are emerging as key regulators in homeostasis of the immune system. Therefore, aberrant expression of miRNA may be linked to immune dysfunction, such as in chronic inflammation and autoimmunity. In this study, we investigated the potential role of miRNA in estrogen-mediated regulation of innate immune responses, as indicated by upregulation of LPS-induced IFNg, inducible nitric oxide synthase (iNOS), and nitric oxide in splenic lymphocytes from estrogen-treated mice. We found that miR-146a, a negative regulator of Toll-like receptor (TLR) signaling, was decreased in freshly-isolated splenic lymphocytes from estrogen-treated mice compared to placebo controls. Increasing the activity of miR-146a significantly inhibited LPS-induced IFNg and iNOS expression in mouse splenic lymphocytes. Further, miRNA microarray and Real-time RT-PCR analysis revealed that estrogen selectively upregulates/downregulates the expression of miRNA in mouse splenic lymphocytes. miR-223, which is highly upregulated by estrogen, regulates LPS-induced IFNg, but not iNOS or nitric oxide in splenic lymphocytes. Inhibition of miR-223 activity decreased LPS-induced IFNg in splenic lymphocytes from estrogen-treated mice. Our data are the first demonstrating selective regulation of miRNA expression in immune cells by estrogen and are indicative of an important role of miRNA in estrogen-mediated immune regulation. Keywords: microRNAs, estrogen, splenic lymphocytes, TLR4 signaling, mouse Overall design: Total RNAs were isolated from freshly-isolated splenic lymphocytes from 2 pairs of placebo-and estrogen-treated mice