Cystathionine β‐synthase is required for body iron homeostasis

Cystathionine β‐synthase (CBS) catalyzes the transsulfuration pathway and contributes, among other functions, to the generation of hydrogen sulfide. In view of the exceptionally high expression of CBS in the liver and the common interleukin‐6 pathway used in the regulatory systems of hydrogen sulfide and hepcidin, we speculate that CBS is involved in body iron homeostasis. We found that CBS knockout (CBS−/−) mice exhibited anemia and a significant increase in iron content in the serum, liver, spleen, and heart, along with severe damage to the liver, displaying a hemochromatosis‐like phenotype. A high level of hepatic and serum hepcidin was also found. A major cause of the systemic iron overload is the reduced iron usage due to suppressed erythropoiesis, which is consistent with an increase in interleukin‐6 and reduced expression of erythropoietin. Importantly, in the liver, absence of CBS caused both a reduction in the transcriptional factor nuclear factor erythroid 2–related factor‐2 and an up‐regulation of hepcidin that led to a decrease in the iron export protein ferroportin 1. The resulting suppression of iron export exacerbates iron retention, causing damage to hepatocytes. Finally, administration of CBS‐overexpressing adenovirus into CBS mutant mice could partially reverse the iron‐related phenotype. Conclusion: Our findings point to a critical role of CBS in iron homeostasis of the body, and the liver in particular; it is likely that a hemochromatosis‐like phenotype in patients can be induced by aberration not only in the expression of key molecules in the hepcidin pathway but also of those related to CBS. (Hepatology 2018;67:21‐35)