Copper toxicity affects proliferation and viability of human hepatoma cells (HepG2 line)

In Wilson's disease and Indian childhood cirrhosis (ICC) copper accumulates in the liver resulting in poor hepatocyte regeneration and fibrosis. An in hibition of hepatocyte proliferation and an increase in cell death could ac count for these outcomes. To establish how the toxicity of this metal ion i mpacts upon the proliferation and viability of the HepG2 cells they were cu ltured in 4-32 mu M copper(II) sulphate (CuSO4). These levels were comparab le to the circulatory and tissue concentrations of copper recorded for thes e two diseases. Specific uptake comparable to levels of copper recorded in the livers of pa tients with Wilson's disease and ICC was measured in the HepG2 cells. After 48 h acid vesicle function increased from 4 to 32 mu M Cu2+ but signi ficantly declined at 64 mu M compared to the controls, Lysosomal acid phosp hatase showed a concentration dependent decline in activity at 72 h. Cells exposed to 64 mu M Cu2+ had a potential doubling time (Tpot) 21 h lon ger than the control cells due to a prolonged DNA synthesis phase. At 64 mu M Cu2+, increases of necrosis up to 18% were seen whereas comparab le levels of apoptotic and necrotic cells (<5%) were seen below this concen tration. Chronic exposure over 8 weeks impaired colony-forming efficiency a t concentrations of 16 mu M Cu2+ and above. This study suggests that when liver cells sequester large amounts of copper , the toxic effects include delayed cell-cycle progression, a gradual loss of replicative capacity, and an increased incidence of cell death.