Loss of Sprouty2 enhances IL‐33 expression and protects against experimental colitis.

OBJECTIVE Sprouty2 (Spry2) is an intracellular modulator of MAPK signaling. It is present in the intestinal tract, but its function there is unknown. Aberrant MAPK signaling is associated with altered cytokine production in disorders such as inflammatory bowel disease, raising the possibility that Spry2 may affect the response to colitis. In particular, MAPK regulates IL‐33 expression in response to bacterial infection, and IL‐33 has been shown to be protective in some forms of colitis. Furthermore, both MAPK and IL‐33 regulate secretory cell differentiation. Here we tested the hypothesis that Spry2 control of MAPK signaling alters cytokine production and/or secretory cell development, thus altering the intestinal response to injury. METHODS Mice that lack Spry2 in the intestinal epithelium (VillinCre;Spry2flox/flox, hereafter Spry2KOIE) and littermate controls were given 3% dextran sodium sulfate (DSS) in drinking water for 4 days followed by 3 days without DSS, and colitis severity was assessed. Cytokine levels and epithelial marker expression were determined by qPCR in challenged and unchallenged mice. GSK3beta phosphorylation was determined by western blot. In vitro , IEC6 and YAMC intestinal epithelial cells were treated with GSK3beta and MAPK inhibitors and cytokine expression was assessed. RESULTS Colonic Spry2 levels were reduced in DSS colitis by 59% (p<0.05). Spry2KOIE mice subjected to DSS had lower levels of pro‐inflammatory cytokines versus wildtype littermates, and were protected from histological damage (injury score reduced by 30%, p=0.037), weight loss, and colon shortening. Unchallenged Spry2KOIE mice displayed elevated GSK3beta phosphorylation on the inactivating Ser9 site in epithelial cells (88% increase, p<0.01). These mice also had increased IL‐33 expression (80% increase, p<0.05) and more DCLK1+ tuft cells in the colon (2.2‐fold increase, p<0.01). In vitro , inactivation of GSK3beta in both IEC6 and YAMC cells mimicked the increased IL‐33 observed in vivo; this effect was attenuated by ERK or p38 MAPK inhibitors. Expression of the epithelial‐derived cytokine CXCL2 was unaffected by GSK3beta inhibition, suggesting an IL‐33 specific response. CONCLUSION Colonic epithelial Spry2 is downregulated in response to injury and inflammation. This may represent an integration point of environmentally‐driven MAPK signals that leads to altered Wnt signaling, elevated IL‐33 expression, and promotion of intestinal tuft cell development as a protective or regenerative mechanism. Support or Funding Information NIH R01DK095004 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .