The aims of this study were to ascertain whether aurintricarboxylic acid (ATA), an endonuclease inhibitor, known to interfere, with the actions of cytokines such as interferons, is able to antagonize the toxic effects produced by tumor necrosis factor alpha (TNF-alpha) in human healthy peripheral B lymphocytes and try to elucidate the molecular machinery through which this possible antagonism takes place. Results evidenced that the balance of survival signals of human B lymphocytes in the presence of TNF-alpha was altered by the interaction of TNF-alpha with a salicylate compound, ATA. Apoptosis effected by TNF-alpha alone was suppressed in the presence of ATA, and this effect appeared essentially characterized by: (i) phosphorylation of phosphatidylinositol-3 kinase (PI-3K), influencing in turn protein kinase B/Akt (Akt) and Bad phosphorylation; (ii) nuclear translocation of the nuclear factor kappa B (NF-kappaB) and (iii) nuclear translocation of protein kinase C zed (PKCzeta). Reversal of TNF-alpha/ATA effects occurred in the presence of the PI-3K specific inhibitors wortmannin or LY294002 in the culture medium and was coincident with inhibition of the translocation of PKCzeta in the nucleus, while NF-kappaB was less affected. These results indicate, therefore, that PI-3K-mediated activation and nuclear transfer of PKCzeta might be essential steps of ATA antagonism against TNF-alpha, suggesting that possible ATA pharmacological applications might be taken into account for staving off systemic or local toxic effects produced by TNF-alpha.