Hormetic Effects of 7-Ketocholesterol in Preventing Ferroptosis in Hepatocytes

Ferroptosis, a form of cell death marked by iron dysregulation and lipid peroxidation, has been implicated in liver and neurodegenerative diseases. 7-ketocholesterol (7KC), a cholesterol oxidation product, induces oxidative stress and inflammation at high concentrations. However, the effects of low, subtoxic levels of 7KC are unclear. This study investigates the potential hormetic effects of low concentrations of 7KC on hepatocytes and neuronal cells during ferroptosis.

Ferroptosis was induced in AML12 hepatocytes using 20 µM Erastin, with cells co-treated with varying concentrations of 7KC. Cell death was assessed, and gene expression was analyzed via RNA sequencing (RNA-seq) and real-time PCR. HT4 hippocampal neuronal cells were treated with glutamate to induce ferroptosis, both with and without 7KC.

Low, nontoxic concentrations of 7KC protected both hepatocytes and neuronal cells from ferroptosis induced by Erastin and glutamate, respectively. In contrast, higher concentrations of 7KC increased cell death. 7KC's protective effects in hepatocytes were linked to lower malondialdehyde (MDA) levels and reduced peroxidation of polyunsaturated fatty acids (PUFAs). The cholesterol synthesis pathway, as well as lipid accumulation, was suppressed by 7KC. Conversely, these processes were upregulated by Erastin. Notably, 7KC showed a stronger anti-ferroptotic effect than 7-dehydrocholesterol (7DHC) at low concentrations, possibly through Nrf2-independent upregulation of the gamma-glutamylcysteine ligase catalytic (GCLC) unit.

This study reveals that 7KC can have a hormetic effect on ferroptosis at low concentrations, suggesting a potential advantage. Further research is needed to clarify the underlying mechanisms, particularly regarding GCLC upregulation.