An in vitro system for studying potential biological mechanisms of human sex differences in susceptibility to acute liver injury

Women are more susceptible than men to acute liver injury from drugs and other xenobiotics. The biological mechanisms for this sex difference are unknown, but known sex differences in steroid hormone levels and immune response could play a role. A human hepatocyte cell line, HepG2, was cultured for 8 days in either a male hormone, female hormone, or sex hormone-free medium. The cells were then exposed to a mixture of pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, TNFα) for 72 h to simulate acute inflammation. Cell viability (total DNA) and various metabolic functions (reactive oxygen species (ROS), neutral and polar lipid (PL) accumulation, mitochondrial membrane potential, cytochrome P450 (CYP) activities) were measured fluorometrically. Acute phase proteins (albumin, IL-1ra) were measured in the culture medium by ELISA. This model gave both significant hormone only effects (ROS, PL accumulation) and cytokine only effects (total DNA, CYP1A, neutral and PL accumulation, albumin, IL-1ra) consistent with known biological responses. Significant hormone–cytokine interactions were observed for several endpoints (total DNA, ROS, neutral and PL accumulation, albumin). These findings suggest that sex hormones and pro-inflammatory cytokines can interact to alter liver metabolism in ways that may contribute to the marked sex difference in susceptibility to chemical-induced acute liver injury.