Beyond somatosensation: Mrgprs in mucosal tissues

Mas-related G coupled receptors (Mrgprs) are a superfamily of receptors expressed in sensory neurons that are known to transmit somatic sensations from the skin to the central nervous system. Interestingly, Mrgprs have recently been implicated in sensory and motor functions of mucosal-associated neuronal circuits. The gastrointestinal and pulmonary tracts are constantly exposed to noxious stimuli. Therefore, it is likely that neuronal Mrgpr signaling pathways in mucosal tissues, akin to their family members expressed in the skin, might relay messages that alert the host when mucosal tissues are affected by damaging signals. Further, Mrgprs have been proposed to mediate the cross-talk between sensory neurons and immune cells that promotes host-protective functions at barrier sites. Although the mechanisms by which Mrgprs are activated in mucosal tissues are not completely understood, these exciting studies implicate Mrgprs as potential therapeutic targets for conditions affecting the intestinal and airway mucosa. This review will highlight the central role of Mrgpr signaling pathways in the regulation of homeostasis at mucosal tissues

Carbonic anhydrase enzymes regulate mast cell–mediated inflammation

Type 2 cytokine responses are necessary for the development of protective immunity to helminth parasites but also cause the inflammation associated with allergies and asthma. Recent studies have found that peripheral hematopoietic progenitor cells contribute to type 2 cytokine–mediated inflammation through their enhanced ability to develop into mast cells. In this study, we show that carbonic anhydrase (Car) enzymes are up-regulated in type 2–associated progenitor cells and demonstrate that Car enzyme inhibition is sufficient to prevent mouse mast cell responses and inflammation after Trichinella spiralis infection or the induction of food allergy–like disease. Further, we used CRISPR/Cas9 technology and illustrate that genetically editing Car1 is sufficient to selectively reduce mast cell development. Finally, we demonstrate that Car enzymes can be targeted to prevent human mast cell development. Collectively, these experiments identify a previously unrecognized role for Car enzymes in regulating mast cell lineage commitment and suggest that Car enzyme inhibitors may possess therapeutic potential that can be used to treat mast cell–mediated inflammation

Tumor suppressor p53 regulates intestinal type 2 immunity

P53 is a well-known tumour suppressor, however its role in intestinal type 2 immunity is currently unclear. Here authors report that during parasitic infections, p53 triggers tuft cell Ca2+ influx and IL-25 release, and shows a regulatory role for p53 in intestinal type 2 immunity via transcriptional regulation of the Lrmp gene

Trichinella spiralis-induced mastocytosis and erythropoiesis are simultaneously supported by a bipotent mast cell/erythrocyte precursor cell.

Anti-helminth responses require robust type 2 cytokine production that simultaneously promotes worm expulsion and initiates the resolution of helminth-induced wounds and hemorrhaging. However, how infection-induced changes in hematopoiesis contribute to these seemingly distinct processes remains unknown. Recent studies have suggested the existence of a hematopoietic progenitor with dual mast cell-erythrocyte potential. Nonetheless, whether and how these progenitors contribute to host protection during an active infection remains to be defined. Here, we employed single cell RNA-sequencing and identified that the metabolic enzyme, carbonic anhydrase (Car) 1 marks a predefined bone marrow-resident hematopoietic progenitor cell (HPC) population. Next, we generated a Car1-reporter mouse model and found that Car1-GFP positive progenitors represent bipotent mast cell/erythrocyte precursors. Finally, we show that Car1-expressing HPCs simultaneously support mast cell and erythrocyte responses during Trichinella spiralis infection. Collectively, these data suggest that mast cell/erythrocyte precursors are mobilized to promote type 2 cytokine responses and alleviate helminth-induced blood loss, developmentally linking these processes. Collectively, these studies reveal unappreciated hematopoietic events initiated by the host to combat helminth parasites and provide insight into the evolutionary pressure that may have shaped the developmental relationship between mast cells and erythrocytes

Intestinal measurements of WT mice following infection with WT- or STAT6 KO-adapted <i>N</i>. <i>brasiliensis</i>.

A. Length of intestine. B-E. RT-qPCR expression relative to GAPDH. Circles are individual infected hosts, bars are mean values, ns p-value > 0.05 by t-test. Data is representative of 1 independent experiment. (TIF)</p

Fig 6 -

STAT6 KO-adapted N. brasiliensis elicit a stronger inflammatory WT host immune response. Mesenteric lymph node data (A-K) A. Experimental design; WT or STAT6 KO (generation 25 or 24, respectively) adapted worms infected WT mice, and flow cytometry was run on cells from mesenteric lymph nodes at day 8 post infection. B. Gating strategy. C. Total number of mesenteric lymph node cells. D-E. Percent and total cell number of IL-13+ Th2 cells. F-G. Percent and total cell number of ST2+ Th2 cells. H-I. Percent and total cell number of IL-17+ γδT cells. J-K. Percent and total cell number of IFNγ+ CD8+ T cells in mesenteric lymph nodes. Data from the peritoneal cavity (L-T). L. Gating strategy to detect myeloid cell populations; cell types outlined by boxes. M-N. Percentage of parent population or total cell number of FcεR positive cells. O-P. Percentage of parent population or total cell number of macrophages. Q-R. Percentage or total cell number of Arg-1 expressing macrophages. S-T. Percentage of parent population of eosinophils or neutrophils. Each point is a replicate mouse, and error bars are SEM. * p < 0.05 ** p < 0.01, *** p < 0.001, by t-test. Data are representative of 3 independent experiments.</p

<i>N</i>. <i>brasiliensis</i> exhibits increased size, hemoglobin, and ATP content, in the absence of STAT6-driven immune responses.

A. 10x magnification images of adult female WT or STAT6 KO-adapted worms (generation 23 and 22) derived from passage hosts at day 7 post-infection (scale bars = 200 μm, arrows indicate edge of worms). Data in B-F are from adult worms isolated at day 8 post-infection from the 21st (WT) or 20th (STAT6 KO) generation. B. Female worm lengths of WT- or STAT6 KO-adapted worms derived from passage hosts. C-D. Hemoglobin concentration or worm length-normalized concentration of worms derived from passage hosts. E-F. ATP concentration or worm length-normalized concentration of worms derived from passage hosts. Unless otherwise indicated, data are individual values (circles) with mean ± SEM indicated (bars), * p < 0.05 ** p < 0.01, *** p < 0.001, by t-test.</p

<i>N</i>. <i>brasiliensis</i> exposed to STAT6 KO hosts for one prior generation do not elicit a stronger inflammatory WT host immune response.

Mesenteric lymph node data (A-J) A. Experimental design; Parental worms infected WT or STAT6 KO mice, and resulting progeny (G1 adapted) infected WT mice. Flow cytometry was run on cells from mesenteric lymph nodes at day 8 post infection. B. Total number of mesenteric lymph node cells. C-D. Percent and total cell number of IL-13+ Th2 cells. E-F. Percent and total cell number of ST2+ Th2 cells. G-H. Percent and total cell number of IL-17+ γδT cells. I-J. Percent and total cell number of IFNγ+ CD8+ T cells in mesenteric lymph nodes. Data from the peritoneal cavity (K-P). K-L. Percentage of parent population or total cell number of macrophages. M-N. Percentage or total cell number of Arg-1 expressing macrophages. O-P. Percentage of parent population of eosinophils and neutrophils. Q. Parasite burden by number of eggs per gram of feces (EPG) for each day post infection. R. Area under the curve. S. Number of worms from host small intestine at day 8 post infection. Each point is a replicate mouse, and error bars are SEM. * p (TIF)</p

Parasitology associated with WT mice infected with WT or STAT6 KO adapted <i>N</i>. <i>brasiliensis</i> (G25/24) Fig 6.

A. Average eggs per gram of feces by days post infection, with SEM error bars. B. Average area under the curve of data plotted in A. C. Number of adult parasites in the small intestine at day 8 post infection. (TIF)</p

Comparison of differentially expressed genes in adapted (G15/14) vs G1 adult female <i>N</i>. <i>brasiliensis</i> from STAT6 vs WT hosts.

A. Venn diagrams of significantly up (Log2FoldChange > 2) versus down (Log2FoldChange B. Scatterplot of all STAT6 KO vs. WT host condition Log2(FoldChange) values, filtered on adjusted p-value N. brasiliensis infection, (G1) (y-axis) versus adapted N. brasiliensis (G15/14) (x-axis). Values represent the number of genes in each quadrant. (TIF)</p