Lead increases lipopolysaccharide-induced liver-injury through tumor necrosis factor-a overexpression by monocytes/macrophages: role of protein kinase C and p42/44 mitogen-activated protein kinase.

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Title:	Lead increases lipopolysaccharide-induced liver-injury through tumor necrosis factor-a overexpression by monocytes/macrophages: role of protein kinase C and p42/44 mitogen-activated protein kinase.
Authors:	鄭宇容(Cheng, Yu-Jung);楊倍昌(Yang BC)*;劉明毅(Liu MY)
Contributors:	健康照護學院物理治療學系
Keywords:	lead;lipopolysaccharide;liver injury;monocytes/macrophage;p42/44 mitogen-activated protein kinase;protein kinase C;tumor necrosis factor-α
Date:	2006-04
Issue Date:	2010-09-23 19:54:57 (UTC+8)
Abstract:	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.
Appears in Collections:	[Department of Physical Therapy, Graduate Institute of Rehabilitation Science] Journal articles

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