CYP1a1, HSP70, P53, and c-fos expression in human liver carcinoma cells (HepG2) exposed to pentachlorophenol.
Pentachlorophenol (PCP) is a widely used biocidal compound with several industrial, agricultural and domestic applications. Although it has been shown to induce systemic toxicity and carcinogenesis in several experimental studies, the literature is scarce regarding its toxic mechanisms of action. Recent investigations in our laboratory have shown that PCP induces cytotoxicity and transcriptionally activates stress genes in human liver carcinoma (HepG2) cells [1]. We hypothesized that PCP-induced expression of stress proteins may play a role in the molecular events leading to toxicity and tumorigenesis in liver cells. To test this hypothesis, we performed the MTT-assay for cell viability, and the Western Blot and densitometric analyses to assess the expression of cellular protein including CYP1A1, c-fos, HSP70, and p53. Data obtained from the MTT-assay indicated a strong dose-relationship with respect to PCP cytotoxicity. The LD50 was computed to be 23.0 +/- 5.6 micrograms/mL. Western Blot and densitometric analyses also demonstrated a linear dose-response relationship with regard to CYP1A1 expression within the dose range of 0-50 micrograms/mL. However, a biphasic response was obtained with regard to HSP70, c-fos, and p53 expression, showing a peak induction at 25 micrograms/mL, and a drastic reduction in protein expression at 50 micrograms/mL, probably due to cell death at higher level of PCP exposure. At lower level of exposure, PCP was found to be mitogenic.
Molecular Toxicology Research Laboratory, NIH-Center for Environmental Health, School of Science and Technology, Jackson State University, 1400 Lynch Street, P.O. Box 18540, Jackson, Mississippi 39217, USA.
Waneene C
WC
Dorsey
Paul B
PB
Tchounwou
D017209:Apoptosis / Q000187:drug effects; D015197:Carcinogenicity Tests / Q000379:methods; D002455:Cell Division / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007928:Lethal Dose 50; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology* / Q000503:physiopathology; D009363:Neoplasm Proteins / Q000378:metabolism*; D010416:Pentachlorophenol / Q000008:administration & dosage*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D018840:HSP70 Heat-Shock Proteins; D009363:Neoplasm Proteins; D016760:Proto-Oncogene Proteins c-fos; D016159:Tumor Suppressor Protein p53; D010416:Pentachlorophenol; D019363:Cytochrome P-450 CYP1A1