Research

Kupffer cells promote lead nitrate-induced hepatocyte apoptosis via oxidative stress

Patrizia Pagliara , Emanuela C Carlà , Sonia Caforio , Alfonsina Chionna , Silvia Massa , Luigi Abbro and Luciana Dini

Department of Science and Biological and Environmental Technologies, University of Lecce, via per Monteroni, Lecce, Italy

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Comparative Hepatology 2003, 2:8doi:10.1186/1476-5926-2-8

Published:	23 July 2003

Abstract

Background

Apoptosis and its modulation are crucial factors for the maintenance of liver health, allowing hepatocytes to die without provoking a potential harmful inflammatory response through a tightly controlled and regulated process. Since Kupffer cells play a key role in the maintenance of liver function, the aim of this study was to verify whether Kupffer cells are involved in the induction of liver apoptosis after i.v. injection of Pb(NO₃)₂ likely by secretion mechanisms.

Results

The in vivo hepatic apoptosis, induced by Pb(NO₃)₂ was prevented by a pre-treatment with gadolinium chloride (GdCl₃), a Kupffer cells toxicant, that suppresses Kupffer cell activity and reduces to a half the apoptotic rate. In addition, in vivo Pb(NO₃)₂ administration deprives hepatocytes of reduced glutathione, whereas the loss of this important oxidation-preventing agent is considerably mitigated or abolished by pre-treatment with GdCl₃. However, incubation of isolated hepatocytes and Kupffer cells and HepG2 cells with Pb(NO₃)₂ for 24 hours induced necrotic but not apoptotic cells. Apoptosis of hepatocytes and HepG2 cells was observed only after the addition of conditioned medium obtained from Kupffer cells cultured for 24 hours with Pb(NO₃)₂, thus indicating the secretion of soluble mediators of apoptosis by Kupffer cells. Apoptosis in the HepG2 cells was observed upon 24-hours incubation of HepG2 cells with 1 mM buthionine sulfoximine, a glutathione depleting agent, thus showing that there is an oxidative apoptogenic pathway in HepG2 cells.

Conclusion

Pb(NO₃)₂ has, at most, a direct necrotic (but not apoptogenic) effect on hepatocytes and HepG2 cells, giving a clue about the regulatory role of Kupffer cells in the induction of liver apoptosis after a single Pb(NO₃)₂ injection without pre-treatment with GdCl₃, probably via secreting soluble factors that trigger oxidative stress in target cells.