Sonic Hedgehog Acts Via A Smoothened‐Dependent Pathway As A Macrophage Chemoattractant

Abstract

Helicobacter pylori (H. pylori) infection elicits recruitment of macrophages (Mø) to the stomach. In mice expressing a deletion of the Sonic Hedgehog (Shh) signaling protein Smoothened (Smo) within the myeloid lineage, Mø are not recruited to the stomach in response to H. pylori infection. Therefore, we hypothesize that Shh acts as a Mø chemoattractant via a Smo‐dependent mechanism. Bone marrow‐derived macrophages (BM‐Mø) were collected from control mice and transgenic mice lacking the Hedgehog signaling protein Smo (LysMCre/SmoKO) in cells of myeloid lineage. Migration of BM‐Mø was performed using ibidi μ‐Slide Chemotaxis chambers following addition of Shh or chemokine ligand CCL2. A stable chemotaxis gradient was confirmed by diffusion of lucifer yellow. Forward migration index, a measure of directed movement, was significantly elevated in control Mø migrating towards Shh compared to media. In contrast, Smo‐deficient Mø did not migrate towards Shh. Control, but not Smo‐deficient, Mø migrated toward chemokine CCL2 indicating involvement of Smo in macrophage migration. In conclusion, Shh acts as a Mø chemoattractant via a Smo‐dependent mechanism. Such findings are consistent with in vivo studies showing that Smo is required in macrophages for their recruitment to the stomach following H. pylori infection. Funding: NIH 1R01DK083402–01 (Y Zavros), Albert J. Ryan Foundation Fellowship (MA Schumacher)