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Polycyclic aromatic hydrocarbons (PAHs) such as benzo[ a]yrene (B[ a]P) constitute a widely distributed class of environmental pollutants, responsible for highly toxic effects. Elucidating the intracellular mechanisms of this cytotoxicity thus remains a major challenge. Besides the activation of the p53 apoptotic pathway, we have previously found in F258 hepatic cells that the B[ a]P (50 nM)-induced apoptosis was also dependent upon the transmembrane transporter NHE1, whose activation might result from membrane alterations in our model. We here demonstrate that: (1) B[ a]P induces a membrane fluidization surprisingly linked to NHE1 activation; (2) membrane stabilization by exogenous cholesterol protects cells from B[ a]P-induced apoptosis, via an effect on late acidification and iron uptake. [ABSTRACT FROM AUTHOR]

How pHi changes, more specifically alkalinization, affect the apoptotic cascade has yet to be determined. The aim of the present work was to test the involvement of mitochondria in the apoptotic cascade triggered by benzo(a)pyrene [B(a)P] and to determine the role of pHi changes and p53 relative to mitochondria. Our results indicate that B(a)P-induced apoptosis might rely upon a p53-dependent and a pH-sensitive mitochondrial dysfunction. [ABSTRACT FROM AUTHOR]