Low level bacterial endotoxin activates two distinct signaling pathways in human peripheral blood mononuclear cells

Abstract

BackgroundBacterial endotoxin, long recognized as a potent pro-inflammatory mediator in acute infectious processes, has more recently been identified as a risk factor for atherosclerosis and other cardiovascular diseases. When endotoxin enters the bloodstream, one of the first cells activated is the circulating monocyte, which exhibits a wide range of pro-inflammatory responses.MethodsWe studied the effect of low doses of E. coli LPS on IL-8 release and superoxide formation by freshly isolated human peripheral blood mononuclear cells (PBMC).ResultsIL-8 release was consistently detectable at 10 pg/ml of endotoxin, reaching a maximum at 1 ng/ml, and was exclusively produced by monocytes; the lymphocytes neither produced IL-8, nor affected monocyte IL-8 release. Superoxide production was detectable at 30 pg/ml of endotoxin, reaching a maximum at 3 ng/ml. Peak respiratory burst activity was seen at 15-20 min, and superoxide levels returned to baseline by 1 h. IL-8 release was dependent on both membrane-associated CD14 (mCD14) and Toll-like receptor 4 (TLR4. Superoxide production was dependent on the presence of LBP, but was not significantly affected by a blocking antibody to TLR4. Moreover, treatment with lovastatin inhibited LPS-dependent IL-8 release and superoxide production.ConclusionsThese findings suggest that IL-8 release and the respiratory burst are regulated by distinct endotoxin-dependent signaling pathways in PBMC in low level of endotoxin exposure. Selectively modulating these pathways could lead to new approaches to treat chronic inflammatory diseases, such as atherosclerosis, while preserving the capacity of monocytes to respond to acute bacterial infections.

Activation of innate immune system in response to lipopolysaccharide in chicken Sertoli cells

“…Furthermore, the expression of defensins and proinflammatory cytokines has been reported to be dependent on breed or cell, affected by the dose of LPS, and depended on the time of stimulation (Ebers et al 2009, Blomkalns et al 2011, Sorensen et al 2011). Therefore, we developed an in vitro model to investigate the timing of response to LPS on patterns of gene expression in rooster SCs.…”

Immunomodulatory effects of testosterone evaluated in all-trans retinoic acid differentiated HL-60 cells, granulocytes, and monocytes

“…This has been illustrated in human endothelial cells treated with dihydrotestosterone for 4 hours [56] and murine macrophages exposed to testosterone for 12-24 hours [57]. However, a recent study has shown that ROS generation is independent of TLR4 activation in monocytes [35]. Another explanation could be that bacteria and zymosan particles are recognized through several pathways, such as TLR2, dectin-1, and complement receptor 3 [58][59][60], which may lead to compensation for inhibitory effects, compared to LPS recognition [61].…”

“…In innate immunity, IL-8 is reported to be produced mainly by monocytes [35][36][37][38], whereas granulocytes only secrete a limited amount of the cytokine [45][46][47]. It is therefore interesting that differentiated HL-60 cells secrete a considerable amount of IL-8 ( Fig.…”

“…Granulocytes and monocytes were obtained from five healthy male volunteers (age: [25][26][27][28][29][30][31][32][33][34][35]. Venous blood was collected in a sodium heparinised vacutainer.…”

“…Results on IL-8 secretion by HL-60 cells are confirmed in peripheral blood mononuclear cells (PBMC). Preparations of PBMC contain monocytes and lymphocytes but only the monocytes secrete IL-8 [35][36][37][38] and consequently the PBMC in this context are described as monocytes.…”