miR-511-3p, embedded in the macrophage mannose receptor gene, contributes to intestinal inflammation.

MiR-511-3p is embedded in intron 5 of the CD206/MRC1 gene Mrc1, expressed by macrophage and dendritic cell populations. CD206 and miR-511-3p expression are co-regulated, and their contribution to intestinal inflammation is unclear. We investigated their roles in intestinal inflammation in both mouse and human systems. Colons of CD206-deficient mice displayed normal numbers of monocytes, macrophage, and dendritic cells. In experimental colitis, CD206-deficient mice had attenuated inflammation compared with wild-type (WT) mice. However, neither a CD206 antagonist nor a blocking antibody reproduced this phenotype, suggesting that CD206 was not involved in this response. Macrophages isolated from CD206-deficient mice had reduced levels of miR-511-3p and Tlr4 compared with WT, which was associated with reduced pro-inflammatory cytokine production upon lipopolysaccharides (LPS) and fecal supernatant stimulation. Macrophages overexpressing miR-511-3p showed 50% increase of Tlr4 mRNA, whereas knockdown of miR-511-3p reduced Tlr4 mRNA levels by 60%, compared with scrambled microRNA (miRNA)-transduced cells. Response to anti-tumor necrosis factor (TNF) treatment has been associated with elevated macrophage CD206 expression in the mucosa. However, in colon biopsies no statistically significant change in miR-511-3p was detected. Taken together, our data show that miR-511-3p controls macrophage-mediated microbial responses and is involved in the regulation of intestinal inflammation.

Susceptibility to Coccidioides species in C57BL/6 mice is associated with expression of a truncated splice variant of Dectin-1 (Clec7a).

Coccidioides posadasii spherules stimulate macrophages to make cytokines via TLR-2 and Dectin-1. We used formalin-killed spherules and 1,3-beta-glucan purified from spherules to stimulate elicited peritoneal macrophages and myeloid dendritic cells (mDCs) from susceptible (C57BL/6) and resistant (DBA/2) mouse strains. DBA/2 macrophages produced more TNF-alpha and IL-6 than macrophages from C57BL/6 mice, and the amount of TNF-alpha made was dependent on both TLR2 and Dectin-1. DCs from C57BL/6 mice made more IL-10 and less IL-23p19 and IL-12p70 than did DBA/2 DC. These responses were inhibited by a monoclonal antibody to Dectin-1. DBA/2 mice expressed full-length Dectin-1, whereas C57BL/6 mice spliced out exon 3, which encodes most of the stalk. RAW cells transduced to express the full-length Dectin-1 responded better to FKS than cells expressing truncated Dectin-1. We compared the isoform of Dectin-1 expressed by 34 C57BL/6 X DBA/2 recombinant inbred (BXD RI) lines with their susceptibility to Coccidioides immitis. In 25 of 34 RI lines susceptibility or resistance corresponded to short or full-length isoforms, respectively. These results suggest that alternative splicing of the Dectin-1 gene contributes to susceptibility of C57BL/6 mice to coccidioidomycosis, and affects the cytokine responses of macrophages and mDCs to spherules.