Inactivation of glutathione -transferase alpha 4 blocks -induced bystander effect by promoting macrophage ferroptosis.

-infected macrophages produce 4-hydroxynonenal (4-HNE) that mediates microbiota-induced bystander effect (MIBE) leading to colorectal cancer (CRC). Glutathione -transferase alpha 4 (Gsta4), a specific detoxifying enzyme for 4-HNE, is overexpressed in human CRC and -induced murine CRC. However, the roles of Gsta4 in -induced colitis and CRC remain unclear. Herein, we demonstrate that Gsta4 is essential for MIBE by protecting macrophages from -induced ferroptosis. OG1RFSS was used to induce colitis in and mice by orogastric gavage. Ferroptosis was assessed in Gsta4-deficient murine macrophages. We found that, unlike mice, and / mice colonized with failed to develop colitis or CRC. Immunofluorescent staining showed a reduction of macrophages in the lamina propria of -colonized / mice, as well as decreased Gpx4 expression, indicating the occurrence of ferroptosis. Ferroptosis was further confirmed in -deficient murine macrophages infected with . Moreover, Gsta4 inactivation induced the upregulation of Hmox1 and phosphorylated c-Jun while blocked Nos2 expression, leading to the accumulation of intracellular ferrous iron, lipid peroxidation and, eventually, ferroptosis. Finally, Mapk8, as a ferroptosis driver, was remarkably elevated in -infected -deficient macrophages. These results suggest that Gsta4 inactivation blocks MIBE by eliminating macrophages, thereby attenuates -induced colitis and CRC.