Pharmacokinetic model to describe the disposition of lead in the rat

Lead increases lipopolysaccharide-induced liver-injury through tumor necrosis factor-alpha overexpression by monocytes/macrophages: role of protein kinase C and P42/44 mitogen-activated protein kinase

Although lead and lipopolysaccharide (LPS), both important environmental pollutants, activate cells through different receptors and participate in distinct upstream signaling pathways, Pb increases the amount of LPS-induced tumor necrosis factor-alpha (TNF-alpha). We examined the cells responsible for the excess production of Pb-increased LPS-induced TNF-alpha and liver injury, and the roles of protein kinase C (PKC) and p42/44 mitogen-activated protein kinase (MAPK) in the induction of TNF-alpha. Peritoneal injection of Pb alone (100 micromol/kg) or a low dose of LPS (5 mg/kg) did not affect serum TNF-alpha or liver functions in A/J mice. In contrast, coexposure to these noneffective doses of Pb plus LPS (Pb+LPS) strongly induced TNF-alpha expression and resulted in profound liver injury. Direct inhibition of TNF-alpha or functional inactivation of monocytes/macrophages significantly decreased the level of Pb+LPS-induced serum TNF-alpha and concurrently ameliorated liver injury. Pb+LPS coexposure stimulated the phosphorylation of p42/44 MAPK and the expression of TNF-alpha in CD14+ cells of cultured mouse whole blood, peritoneal macrophages, and RAW264.7 cells. Moreover, blocking PKC or MAPK effectively reduced Pb+LPS-induced TNF-alpha expression and liver injury. In summary, monocytes/macrophages were the cells primarily responsible for producing, through the PKC/MAPK pathway, the excess Pb-increased/LPS-induced TNF-alpha that caused liver injury. alpha.

COEXPOSURE OF LEAD- AND LIPOPOLYSACCHARIDE-INDUCED LIVER INJURY IN RATS: INVOLVEMENT OF NITRIC OXIDE-INITIATED OXIDATIVE STRESS AND TNF-??

In this study, we investigated the interaction between lipopolysaccharide (LPS) and lead (Pb) and the involvement of tumor necrosis factor-alpha (TNF-alpha) and oxidative stress in Pb-plus-LPS (Pb/LPS)-induced liver damage in rats. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), TNF-alpha, nitric oxide (NO), and lipid peroxidation (LPO) were determined in rats treated with Pb and/or LPS. Pb ranging from 0 to 15 mg/kg dose dependently increased AST, ALT, NO, or LPO in LPS-treated rats. Pretreatment with iNOS inhibitor 1400W reduced NO, LPO, TNF-alpha, AST, and ALT in Pb/LPS-treated rats. Thus, Pb increased LPS-induced liver damage, which might be associated with increased NO-initiated oxidative stress and TNF-alpha in rats.