CYTOTOXICITY OF NAPHTHYLISOTHIOCYANATES IN RAT HEPATOCYTE-NEUTROPHIL COCULTURES

1-Naphthylisothiocyanate (ANIT) produces cholangiolitic hepatitis in r ats. This injury is characterized by periportal bile duct and hepatic parenchymal cell necrosis with inflammatory cell involvement. In contr ast, 2-naphthylisothiocyanate (BNIT) does not induce cholangiolitic he patitis. The mechanism(s) involved in ANIT-induced hepatic injury rema in to be elucidated. To investigate this difference in toxicity furthe r, we examined the cytotoxicity of ANIT and BNIT in primary rat hepato cyte cultures. Since neutrophils (PMNs) are required for the developme nt of ANIT-induced cholangiolitic hepatitis in vivo, we also examined the potential for PMNs to modulate ANIT and BNIT cytotoxicity in rat h epatocyte-PMN cocultures. Both ANIT and BNIT injured rat hepatocytes w ithin the range of concentrations examined (0-100 mu M); however, BNIT was more potent. The presence of PMNs did not significantly influence the hepatocellular injury produced by either naphthylisothiocyanate ( NIT). In an attempt to clarify the disparity between these results in vitro and observations reported in vivo, we examined, in hepatocyte-PM N cocultures, the cytotoxic potential of bile collected from NIT-treat ed rats. Bile from BNIT-treated rats was markedly more cytotoxic to he patocytes than was bile from ANIT-treated rats. As was observed in ear lier experiments, the inclusion of PMNs had no effect on the hepatocel lular toxicity of bile from NIT- treated rats. These findings prompted evaluation of the effect of NITs on rat PMNs. ANIT (1 and 10 mu M) ha d no effect on phorbal myristate acetate (PMA)-induced superoxide prod uction by PMNs, whereas BNIT (1 and 10 mu M) markedly inhibited PMA-in duced superoxide production. In contrast, ANIT and BNIT were equally e ffective at inhibiting f-met-leu-phe (fMLP)-induced PMN degranulation (beta-glucuronidase release). Altogether, the relative NIT toxicity ob served in hepatocyte primary cultures is contrary to reports of hepato toxic potential of these NITs in vivo. The PMN-dependence of ANIT hepa totoxicity in vivo was not reproduced in hepatocyte-PMN cocultures exp osed to ANIT, suggesting that the PMN dependence in vivo involves fact ors not present in hepatocyte-PMN cocultures. The greater PMN inhibito ry effect of BNIT may, in part, underlie its inability to elicit the P MN-dependent liver injury in vivo that characterizes ANIT-induced chol angiolitic hepatitis. (C) 1998 Elsevier Science Ireland Ltd. All right s reserved.