MicroRNA (miRNA)-mediated RNA interference regulates many immune processes, but how miRNA circuits orchestrate aberrant intestinal inflammation during inflammatory bowel disease (IBD) is poorly defined. Here, we report that miR-223 limits intestinal inflammation by constraining the nlrp3 inflammasome. miR-223 was increased in intestinal biopsies from patients with active IBD and in preclinical models of intestinal inflammation. miR-223-/y mice presented with exacerbated myeloid-driven experimental colitis with heightened clinical, histopathological, and cytokine readouts. Mechanistically, enhanced NLRP3 inflammasome expression with elevated IL-1β was a predominant feature during the initiation of colitis with miR-223 deficiency. Depletion of CCR2+ inflammatory monocytes and pharmacologic blockade of IL-1β or NLRP3 abrogated this phenotype. Generation of a novel mouse line, with deletion of the miR-223 binding site in the NLRP3 3′ untranslated region, phenocopied the characteristics of miR-223-/y mice. Finally, nanoparticle-mediated overexpression of miR-223 attenuated experimental colitis, NLRP3 levels, and IL-1β release. Collectively, our data reveal a previously unappreciated role for miR-223 in regulating the innate immune response during intestinal inflammation.

Intercellular transfer of miR-223 from neutrophils to alveolar epithelial cells reduces lung inflammation in a mouse model of ventilator-induced lung injury or pulmonary bacterial infection.

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.

Epithelial barrier dysfunction is a significant factor in many allergic diseases, including eosinophilic esophagitis (EoE). Infiltrating leukocytes and tissue adaptations increase metabolic demands and decrease oxygen availability at barrier surfaces. Understanding of how these processes impact barrier is limited, particularly in allergy. Here, we identified a regulatory axis whereby the oxygen-sensing transcription factor HIF-1α orchestrated epithelial barrier integrity, selectively controlling tight junction CLDN1 (claudin-1). Prolonged experimental hypoxia or HIF1A knockdown suppressed HIF-1α–dependent claudin-1 expression and epithelial barrier function, as documented in 3D organotypic epithelial cultures. L2-IL5^OXA mice with EoE-relevant allergic inflammation displayed localized eosinophil oxygen metabolism, tissue hypoxia, and impaired claudin-1 barrier via repression of HIF-1α/claudin-1 signaling, which was restored by transgenic expression of esophageal epithelial-targeted stabilized HIF-1α. EoE patient biopsy analysis identified a repressed HIF-1α/claudin-1 axis, which was restored via pharmacologic HIF-1α stabilization ex vivo. Collectively, these studies reveal HIF-1α’s critical role in maintaining barrier and highlight the HIF-1α/claudin-1 axis as a potential therapeutic target for EoE.

Eosinophils are implicated in the pathophysiology of a spectrum of eosinophil-associated diseases, including gastrointestinal eosinophilic diseases (EGIDs). Biologics that target the IL-5 pathway and are intended to ablate eosinophils have proved beneficial in severe eosinophilic asthma and may offer promise in treating some endotypes of EGIDs. However, destructive effector functions of eosinophils are only one side of the coin; eosinophils also play important roles in immune and tissue homeostasis. A growing body of data suggest tissue eosinophils represent a plastic and heterogeneous population of functional sub-phenotypes, shaped by environmental (systemic and local) pressures, which may differentially impact disease outcomes. This may be particularly relevant to the GI tract, wherein the highest density of eosinophils reside in the steady state, resident immune cells are exposed to an especially broad range of external and internal environmental pressures, and greater eosinophil longevity may uniquely enrich for co-expression of eosinophil sub-phenotypes. Here we review the growing evidence for functional sub-phenotypes of intestinal tissue eosinophils, with emphasis on the multifactorial pressures that shape and diversify eosinophil identity and potential targets to inform next-generation eosinophil-targeting strategies designed to restrain inflammatory eosinophil functions while sustaining homeostatic roles.

Metabolic imbalance leading to inflammatory hypoxia and stabilization of hypoxia-inducible transcription factors (HIFs) is a hallmark of inflammatory bowel diseases. We hypothesize that HIF could be stabilized in CD4⁺ T cells during intestinal inflammation and alter the functional responses of T cells via regulation of microRNAs. Our assays reveal markedly increased T cell-intrinsic hypoxia and stabilization of HIF protein during experimental colitis. microRNA screen in primary CD4⁺ T cells points us towards miR-29a and our subsequent studies identify a selective role for HIF-2α in CD4-cell-intrinsic induction of miR-29a during hypoxia. Mice with T cell-intrinsic HIF-2α deletion display elevated T-bet (target of miR-29a) levels and exacerbated intestinal inflammation. Mice with miR-29a deficiency in T cells show enhanced intestinal inflammation. T cell-intrinsic overexpression of HIF-2α or delivery of miR-29a mimetic dampen T_H1-driven colitis. In this work, we show a previously unrecognized function for hypoxia-dependent induction of miR-29a in attenuating T_H1-mediated inflammation.