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Disturbed Hsp70 and Hsp27 expression and thiol redox status in porcine kidney PK15 cells provoked by individual and combined ochratoxin A and citrinin treatments

The aim of this study was to explore the oxidative properties of ochratoxin A (OTA) and citrinin (CTN) as a possible underlying mechanism of their individual and/or combined cytotoxicity. Metabolic activity of PK15 porcine kidney cells, determined by MTT assay, was significantly reduced at 48 h with single and dual treatments, and even at 12 h with OTA and CTN co-exposures. Most importantly, cytotoxic interactions were synergistic. Next we explored redox status by determining total thiols and glutathione concentrations. Single CTN increased both reduced (GSH) and oxidized (GSSG) glutathione after 24 h. However, GSH was significantly lowered with all combined exposures after 12 and 24 h, with OTA and CTN showing synergistic type of interactions. GSH/GSSG ratio was decreased in most combined and individual treatments, which suggested the presence of oxidative stress. Single or dual OTA and CTN exposures significantly lowered concentrations of total thiols, with mycotoxins interactions being synergistic or antagonistic. In order to explore cellular protective and redox sensing capacity, we detected Hsp70 and Hsp27 expressions by Western blot analysis. The expression levels of Hsps were differentially affected by single and dual mycotoxin(s) applications. Single OTA provoked significant down-regulation of Hsp70 and Hsp27 expressions, while CTN stimulated Hsps expressions. Hsps were also up-regulated by dual treatments, and this induction was much stronger then with single CTN. In conclusion, significant alterations in cellular redox status (glutathione, thiols) and protective mechanisms (Hsps) suggest that those disturbances might be involved in OTA and CTN individual and combined mechanisms of cytotoxicity.

ochratoxin A; citrinin; heat shock proteins; oxidative stress; glutathione; PK15 cells

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