Copper impact on heat shock protein 70 expression and apoptosis in rainbow trout hepatocytes.
The mechanism underlying copper hepatotoxicity was investigated in primary cultures of rainbow trout hepatocytes maintained in Leibovitz-15 media. CuSO4 treatment (0, 25, 50, 100 and 200 microM) 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 microM CuSO4) 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 degrees 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.
Feng
Qiang
Q
Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1.
Boone
Adrienne N
AN
Vijayan
Mathilakath M
MM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001205:Ascorbic Acid / Q000494:pharmacology; D019327:Copper Sulfate / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*
D018840:HSP70 Heat-Shock Proteins; D019327:Copper Sulfate; D001205:Ascorbic Acid