Regulatory effects of lipopolysaccharide in murine macrophage proliferation

AIM:To study the regulatory effects of bacterial lipopolysaccharide (LPS) in murine macrophage proliferation.METHODS:Using murine peritoneal exudate macrophage (PEM) and macrophage cell line J(774) A.1 as targets, LPS effects on M-CSF and granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulated macrophage colony-forming cells (CFU-M) were detected. (125)I-GM-CSF receptor binding assay was used to examine LPS regulation on GM-CSF receptor expres-sion.RT-PCR was employed to test TGF-beta(1) inhibition on IFN-gamma mRNA expression on macrophage induced by LPS.RESULTS:Without direct effect on macrophage proliferation, LPS could inhibit the macrophage proliferation stimulated by GM-CSF.However,with the concomitant existence of GM-CSF and TGF-beta(1), the LPS inhibitory effect was eliminated.RT-PCR analysis indicated that the strongest mac-rophage growth inhibitory factor IFN-gammamRNA expression in macrophage induced by LPS was remarkably suppressed by TGF-beta(1), (125)I-GM-CSF receptor binding assay showed that LPS could enhance GM-CSF receptor expression likewise as TGF-beta(1).CONCLUSION:LPS is involved in the network of macrophage proliferative regulation by multiple cytokines, displaying inhibitory and stimulatory effects based on the coexisting cytokines.