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Published on: May 24, 2019
Inactivation of glutathione S-transferase alpha 4 blocks Enterococcus faecalis-induced bystander effect by promoting
Yuanyuan Ju1,2, Chunhua Ma1,2, Lin Huang3
1Nantong Institute of Genetics and Reproductive Medicine, Affiliated Maternity and Child Healthcare Hospital of Nantong University, Nantong, Jiangsu, China.
Abstract:
Enterococcus faecalis-infected macrophages produce 4-hydroxynonenal (4-HNE) that mediates microbiota-induced bystander effect (MIBE) leading to colorectal cancer (CRC). Glutathione S-transferase alpha 4 (Gsta4), a specific detoxifying enzyme for 4-HNE, is overexpressed in human CRC and E. faecalis-induced murine CRC. However, the roles of Gsta4 in E. faecalis-induced colitis and CRC remain unclear. Herein, we demonstrate that Gsta4 is essential for MIBE by protecting macrophages from E. faecalis-induced ferroptosis. E. faecalis OG1RFSS was used to induce colitis in Gsta4-/- and Il10-/-/Gsta4-/- mice by orogastric gavage. Ferroptosis was assessed in Gsta4-deficient murine macrophages. We found that, unlike Il10-/- mice, Gsta4-/- and Il10-/-/Gsta4-/- mice colonized with E. faecalis failed to develop colitis or CRC. Immunofluorescent staining showed a reduction of macrophages in the lamina propria of E. faecalis-colonized Il10-/-/Gsta4-/- mice, as well as decreased Gpx4 expression, indicating the occurrence of ferroptosis. Ferroptosis was further confirmed in Gsta4-deficient murine macrophages infected with E. faecalis. 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 E. faecalis-infected Gsta4-deficient macrophages. These results suggest that Gsta4 inactivation blocks MIBE by eliminating macrophages, thereby attenuates E. faecalis-induced colitis and CRC.
Insights
Glutathione S-transferase alpha 4 (Gsta4) protects macrophages from ferroptosis during Enterococcus faecalis infection. Gsta4 inactivation prevents microbiota-induced bystander effect, blocking colitis and colorectal cancer development.
Area of Science:
- Immunology
- Gastroenterology
- Oncology
Background:
- Enterococcus faecalis infection induces 4-hydroxynonenal (4-HNE) production in macrophages, mediating the microbiota-induced bystander effect (MIBE) and leading to colorectal cancer (CRC).
- Glutathione S-transferase alpha 4 (Gsta4) detoxifies 4-HNE and is overexpressed in human CRC and E. faecalis-induced murine CRC, but its role in colitis and CRC remains unclear.
Purpose of the Study:
- To investigate the role of Gsta4 in Enterococcus faecalis-induced colitis and colorectal cancer.
- To determine if Gsta4 is essential for the microbiota-induced bystander effect (MIBE) by protecting macrophages from ferroptosis.
Main Methods:
- Enterococcus faecalis OG1RFSS was used to induce colitis in Gsta4-deficient and Il10-/-/Gsta4-/- mice.
- Ferroptosis was assessed in Gsta4-deficient murine macrophages infected with E. faecalis.
- Immunofluorescence staining and molecular analyses (Hmox1, p-c-Jun, Nos2, Mapk8, Gpx4) were performed.
Main Results:
- Gsta4-deficient and Il10-/-/Gsta4-/- mice colonized with E. faecalis did not develop colitis or CRC, unlike Il10-/- mice.
- Gsta4 deficiency led to reduced macrophages in the lamina propria and decreased Gpx4 expression, indicating ferroptosis.
- Gsta4 inactivation in macrophages induced ferroptosis by upregulating Hmox1 and p-c-Jun, downregulating Nos2, and increasing Mapk8, a ferroptosis driver.
Conclusions:
- Gsta4 is essential for the microbiota-induced bystander effect (MIBE) by protecting macrophages from Enterococcus faecalis-induced ferroptosis.
- Gsta4 inactivation blocks MIBE by eliminating macrophages, thereby attenuating E. faecalis-induced colitis and colorectal cancer.
