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Aberrant intestinal inflammation plays a critical role in the development of colitis-associated colorectal cancer (CAC), yet the mechanisms controlling tumor development by the myeloid immune compartment are not fully understood. Although altered microRNA expression is observed in CAC, it is also unclear how myeloid-specific microRNAs impact the inflammatory process that underpins the continuum from ulcerative colitis to tumorigenesis. In this study, we report that miR-223 acts to limit myeloid-driven inflammation in the azoxymethane (AOM)-dextran sodium sulfate (DSS) model of CAC in mice. In this model, miR-223-/y mice present with significantly larger tumors with an enhanced proliferative signature. Immunoprofiling showed that miR-223-/y mice have significantly increased colonic myeloid immune infiltrate (neutrophils, monocytes, and macrophages) following AOM-DSS. This was accompanied by an increased inflammatory chemokine and cytokine signature for monocytes and neutrophils. Bone marrow chimera studies demonstrate that myeloid-expressed miR-223 is responsible for the enhanced tumor proliferation and inflammatory response. RNA sequencing identified several pathways that could be contributing to the development of CAC in miR-223-/y mice, including the IL-6/IL-17a cytokine family and STAT3 signaling. Lastly, neutrophil depletion with an anti-GR1 Ab (Ly6G/Ly6C) during the initial phase of the AOM-DSS model reduced the tumor burden in miR-223-/y mice. Collectively, our data indicate that miR-223 is an important regulator of mucosal inflammation and acts to constrain the progression from ulcerative colitis to CAC by limiting myeloid-associated inflammation., (Copyright © 2024 by The American Association of Immunologists, Inc.)

Proinflammatory consequences have been described for lysophosphatidylcholine, a lipid product of cellular injury, signaling via the G protein-coupled receptor G2A on myeloid and lymphoid inflammatory cells. This prompted the hypothesis that genetic deletion of G2A would limit intestinal inflammation in a mouse model of colitis induced by dextran sodium sulfate. Surprisingly, G2A(-/-) mice exhibited significantly worsened colitis compared with wild-type mice, as demonstrated by disease activity, colon shortening, histology, and elevated IL-6 and IL-5 in colon tissues. Investigation of inflammatory cells recruited to inflamed G2A(-/-) colons showed significantly more TNF-α(+) and Ly6C(hi)MHCII(-) proinflammatory monocytes and eosinophils than in wild-type colons. Both monocytes and eosinophils were pathogenic as their depletion abolished the excess inflammation in G2A(-/-) mice. G2A(-/-) mice also had less IFN-γ in inflamed colon tissues than wild-type mice. Fewer CD4(+) lymphocytes were recruited to inflamed G2A(-/-) colons, and fewer colonic lymphocytes produced IFN-γ upon ex vivo stimulation. Administration of IFN-γ to G2A(-/-) mice during dextran sodium sulfate exposure abolished the excess colitic inflammation and reduced colonic IL-5 and eosinophil numbers to levels seen in wild-type mice. Furthermore, IFN-γ reduced the numbers of TNF-α(+) monocyte and enhanced their maturation from Ly6C(hi)MHCII(-) to Ly6C(int)MHCII(+) Taken together, the data suggest that G2A signaling serves to dampen intestinal inflammation via the production of IFN-γ, which, in turn, enhances monocyte maturation to a less inflammatory program and ultimately reduces eosinophil-induced injury of colonic tissues., (Copyright © 2016 by The American Association of Immunologists, Inc.)

NK cells are innate lymphoid cells important for immune surveillance, identifying and responding to stress, infection, and/or transformation. Whereas conventional NK (cNK) cells circulate systemically, many NK cells reside in tissues where they appear to be poised to locally regulate tissue function. In the present study, we tested the contribution of tissue-resident NK (trNK) cells to tissue homeostasis by studying ischemic injury in the mouse kidney. Parabiosis experiments demonstrate that the kidney contains a significant fraction of trNK cells under homeostatic conditions. Kidney trNK cells developed independent of NFIL3 and T-bet, and they expressed a distinct cell surface phenotype as compared with cNK cells. Among these, trNK cells had reduced asialo-GM1 (AsGM1) expression relative to cNK cells, a phenotype observed in trNK cells across multiple organs and mouse strains. Strikingly, anti-AsGM1 Ab treatment, commonly used as an NK cell-depleting regimen, resulted in a robust and selective depletion of cNKs, leaving trNKs largely intact. Using this differential depletion, we tested the relative contribution of cNK and trNK cells in ischemic kidney injury. Whereas anti-NK1.1 Ab effectively depleted both trNK and cNK cells and protected against ischemic/reperfusion injury, anti-AsGM1 Ab preferentially depleted cNK cells and failed to protect against injury. These data demonstrate unanticipated specificity of anti-AsGM1 Ab depletion on NK cell subsets and reveal a new approach to study the contributions of cNK and trNK cells in vivo. In total, these data demonstrate that trNK cells play a key role in modulating local responses to ischemic tissue injury in the kidney and potentially other organs., (Copyright © 2015 by The American Association of Immunologists, Inc.)