DHCR7 as a novel regulator of ferroptosis in hepatocytes
Recent evidence indicates that ferroptosis is implicated in the pathophysiology of various liver diseases; however, the mechanism of ferroptosis regulation in the liver is poorly understood. Here, using the whole-genome screening approach, we identified 7-dehydrocholesterol reductase (DHCR7), the terminal enzyme of cholesterol biosynthesis, as a novel regulator of ferroptosis in hepatocytes. Genetic and pharmacological inhibition (with AY9944) of DHCR7 suppressed lipid peroxidation and ferroptosis in human hepatocellular carcinoma Huh-7 cells. DHCR7 inhibition increased its substrate, 7-dehydrocholesterol (7-DHC), and extrinsic 7-DHC supplementation in turn suppressed ferroptosis. On the other hand, cholesterol deprivation had no effect on ferroptosis. A 7-DHC-derived oxysterol metabolite, 3{beta},5-dihydroxycholest-7-en-6-one (DHCEO), was increased by a ferroptosis inducer RSL-3 in DHCR7-deficient cells, suggesting that the ferroptosis-suppressive effect of DHCR7 inhibition was driven by intracellular 7-DHC as a radical scavenger. While extrinsic 7-DHC supplementation suppressed ferroptosis in various cancer cells, pharmacological DHCR7 inhibition by AY9944 showed cell-type specific effects, which could be explained by high DHCR7 expression in Huh-7 cells. We further showed that AY9944 suppressed ferroptosis in murine primary hepatocytes in vitro and systemic administration of AY9944 inhibited hepatic ischemia-reperfusion injury in vivo. These findings provide new insights into the regulatory mechanism of liver ferroptosis and suggest that DHCR7 inhibition is a potential therapeutic option for ferroptosis-related liver diseases.