Copper impact on heat shock protein 70 expression and apoptosis in rainbow trout hepatocytes

• Published in: Comparative biochemistry and physiology. Toxicology & pharmacology Vol. 135; no. 3; pp. 345 - 355
• Main Authors: Feng, Qiang, Boone, Adrienne N., Vijayan, Mathilakath M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.07.2003
• Subjects: Animals; Apoptosis - drug effects; Apoptosis - physiology; Ascorbic Acid - pharmacology; Copper Sulfate - toxicity; Dose-Response Relationship, Drug; Fish; Gene Expression Regulation - drug effects; Gene Expression Regulation - physiology; Heat shock protein 70; Heavy metal; Hepatocytes - drug effects; Hepatocytes - metabolism; HSP70 Heat-Shock Proteins - biosynthesis; HSP70 Heat-Shock Proteins - genetics; Oncorhynchus mykiss; Oncorhynchus mykiss - metabolism; Reactive oxygen species; Stress; Toxicology; Vitamin C; Reactive oxygen species; LDH, lactate dehydrogenase; BCIP, 5-bromo-4-chloro-3-indolyl phosphate; Oncorhynchus mykiss; NBT, nitro blue tetrazolium; Stress; Cu or CuSO 4, copper (II) sulfate; hsp, heat shock protein; Heavy metal; Toxicology; NADPH, nicotinamide adenine dinucleotide phosphate; NADH, nicotinamide adenine dinucleotide; Vitamin C; Fish; Heat shock protein 70; Vc or Vit. C, vitamin C; ROS, reactive oxygen species; DNA, deoxyribonucleic acid
• ISSN: 1532-0456; 1878-1659
• DOI: 10.1016/S1532-0456(03)00137-6

The mechanism underlying copper hepatotoxicity was investigated in primary cultures of rainbow trout hepatocytes maintained in Leibovitz-15 media. CuSO 4 treatment (0, 25, 50, 100 and 200 μM) resulted in a dose-dependent elevation in heat shock protein 70 (hsp70) expression at 24 and 48 h post-exposure. There was no effect of copper (200 μM CuSO 4) on hepatotoxicity at 24 h, whereas longer exposures (48 h) resulted in increased lactate dehydrogenase (LDH) leakage and apoptosis, demonstrated by fluorescence nuclear staining and DNA fragmentation. Vitamin C (1 mM), a free radical scavenger, inhibited this copper-induced apoptosis implying a role for reactive oxygen species in copper toxicity. However, no parallel inhibition of either LDH leakage or hsp70 protein expression was observed with vitamin C suggesting that at least two independent mechanisms are involved in the cellular response to copper. Also, copper exposed (24 h) cells were unable to mount an hsp70 response to a standardized heat shock (+15 °C for 1 h), even in the presence of vitamin C. Together, these results suggest that hepatotoxicity of copper includes impairment of hsp70 response to subsequent stressors and/or signals, which is crucial for protecting cells from proteotoxicity.