Hypoxia-inducible factor–dependent induction of netrin-1 dampens inflammation caused by hypoxia

Abstract

Hypoxia incites inflammation, particularly at mucosal surfaces. Eltzschig and colleagues show that hypoxia also suppresses inflammation by inducing expression of the neuronal guidance molecule netrin-1, which inhibits the transepithelial migration of neutrophils. The neuronal guidance molecule netrin-1 is linked to the coordination of inflammatory responses. Given that mucosal surfaces are particularly prone to hypoxia-elicited inflammation, we sought to determine the function of netrin-1 in hypoxia-induced inflammation. We detected hypoxia-inducible factor 1α (HIF-1α)-dependent induction of expression of the gene encoding netrin-1 (Ntn1) in hypoxic epithelia. Neutrophil transepithelial migration studies showed that by engaging A2B adenosine receptor (A2BAR) on neutrophils, netrin-1 attenuated neutrophil transmigration. Exogenous netrin-1 suppressed hypoxia-elicited inflammation in wild-type but not in A2BAR-deficient mice, and inflammatory hypoxia was enhanced in Ntn1+/− mice relative to that in Ntn1+/+ mice. Our studies demonstrate that HIF-1α-dependent induction of netrin-1 attenuates hypoxia-elicited inflammation at mucosal surfaces.