A novel HDAC1-Hcy/Glu-ferroptosis axis underlies valproic acid-induced hepatic steatosis

Valproic acid (VPA), a widely used antiepileptic drug, often induces hepatic steatosis during long-term treatment, though the underlying mechanisms remain incompletely understood. In our study, epileptic patients with abnormal liver function exhibited significantly elevated levels of homocysteine (Hcy) and glutamate (Glu) compared to those with normal liver function. Moreover, Hcy and Glu levels were positively correlated with markers of lipid accumulation and oxidative stress. Similar elevations in Hcy and Glu were observed in VPA-treated mice and hepatocyte models (HepG2, AML12), suggesting that disrupted Hcy/Glu homeostasis may be a hallmark of VPA-induced hepatic steatosis. Further in vitro experiments demonstrated that treatment with either Hcy or Glu not only increased lipid accumulation but also triggered ferroptosis, as indicated by Fe²⁺ overload, suppression of the GSH-GPX4 axis, and ACSL4-mediated lipid peroxidation. These effects were attenuated by the ferroptosis inhibitor ferrostatin-1 (Fer-1), confirming the contribution of ferroptosis to Hcy/Glu-induced hepatotoxicity. Additional investigations revealed that VPA promotes Hcy accumulation by downregulating its catabolic enzymes (MTR, CBS, CTH), while enhancing Glu accumulation through upregulation of its synthetic enzymes (ALDH4A1, GLS) and repression of the catabolic enzyme GLUL, both in vivo and in vitro. The alterations in MTR, CBS, ALDH4A1, and GLS levels were shown to depend on HDAC1, as demonstrated using HDAC1 knockdown and overexpression systems in HepG2 cells. In summary, VPA disrupts Hcy/Glu homeostasis via HDAC1, leading to ferroptosis and subsequent hepatic steatosis. These findings highlight the HDAC1-Hcy/Glu-ferroptosis axis as a promising therapeutic target for mitigating VPA-induced hepatotoxicity.