Annexin A1 Mediates Hydrogen Sulfide Properties in the Control of Inflammation

Hydrogen sulfide (H2S) is a gaseous mediator synthesized in mammalian tissues by three main enzymes-cystathionine-beta-synthase (CBS), cystathionine-gamma-lyase (CSE), and 3-mercaptopyruvate-sulfurtransferase-and its levels increase under inflammatory conditions or sepsis. Since H2S and H2S-releasing molecules afford inhibitory properties in leukocyte trafficking, we tested whether endogenous annexin A1 (AnxA1), a glucocorticoid-regulated inhibitor of inflammation acting through formylated-peptide receptor 2 (ALX), could display intermediary functions in the anti-inflammatory profile of H2S. We first investigated whether endogenous AnxA1 could modulate H2S biosynthesis. To this end, a marked increase in CBS and/or CSE gene products was quantified by quantitative real-time polymerase chain reaction in aortas, kidneys, and spleens collected from AnxA1(-/-) mice, as compared with wild-type animals. When lipopolysaccharide-stimulated bone marrow-derived macrophages were studied, H2S-donor sodium hydrosulfide (NaHS) counteracted the increased expression of inducible nitric oxide synthase and cyclooxygenase 2 mRNA evoked by the endotoxin, yet it was inactive in macrophages harvested from AnxA1(-/-) mice. Next we studied the effect of in vivo administration of NaHS in a model of interleukin-1 beta (IL-1 beta)-induced mesenteric inflammation. AnxA1(+/+) mice treated with NaHS (100 mu mol/kg) displayed inhibition of IL-1 beta-induced leukocyte adhesion/emigration in the inflamed microcirculation, not observed in AnxA1(-/-) animals. These results were translated by testing human neutrophils, where NaHS (10-100 mu M) prompted an intense mobilization (>50%) of AnxA1 from cytosol to cell surface, an event associated with inhibition of cell/endothelium interaction under flow. Taken together, these data strongly indicate the existence of a positive interlink between AnxA1 and H2S pathway, with nonredundant functions in the control of experimental inflammation.