Ochratoxin A (OTA) is a mycotoxin currently detected in stored animal and human food supplies as well as in human sera worldwide. OTA has diverse toxicological effects; however, the most prominent one is the nephrotoxicity. The present investigation was conducted to determine the molecular aspects of OTA toxicity in cultured human hepatocellular carcinoma cells. With this aim, we have monitored the effects of OTA on (i) cell viability, (ii) heat shock protein expressions as a parameter of protective and adaptive response, (iii) oxidative damage, and (iv) cell death signaling pathway. Our results clearly showed that OTA treatment inhibits cell proliferation, downregulates Hsp 70 and Hsp 27 protein and mRNA levels, and did not induce a significant reactive oxygen species generation. We have also demonstrated a decrease in mitochondrial membrane potential, a cytochrome c release, and an activation of caspase 9 and caspase 3 in response to OTA exposure. Moreover, OTA activates p53 expression, while some of its transcriptional target genes (Bax, Bak, PUMA, and p21) were found to downregulate. According to these data, we concluded that OTA may exert an inhibitory action on the transcriptional process. Besides, oxidative damage is not a major contributor to OTA toxicity. This mycotoxin induces a mitochondrial and caspase-dependent apoptotic cell death, which seems to be mediated by p53 transcriptional independent activities.
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