Thiol regulation of endotoxin-induced release of tumour necrosis factor α from isolated rat Kupffer cells

Abstract

Proinflammatory cytokines released by hepatic macrophages (Kupffer cells) have a central role in the pathogenesis of liver injury and the cardiovascular abnormalities of sepsis. Because cytokine release is controlled primarily at the level of gene expression, intracellular signalling mechanisms that control the transcription of cytokine genes are critical links to organ injury. Oxidant stress up-regulates and antioxidants down-regulate the pleiotropic transcription factor NF-kappa B, a DNA-binding protein that induces the expression of cytokines and vascular adhesion molecules. Thiol-bearing molecules are also important inhibitors of NF-kappa B activation, but whether this inhibition represents an antioxidant effect is unknown. This study was undertaken to determine whether important endogenous and pharmacological thiols modulate the activation of NF-kappa B and the release of tumour necrosis factor alpha (TNF-alpha) from Kupffer cells and to ascertain whether these effects are mediated through glutathione. Exposure of rat Kupffer cells to a physiologically relevant concentration of lipopolysaccharide (10 ng/ml) activated NF-kappa B within 1 h and induced the release of TNF-alpha over 5 h. Cellular glutathione content remained unchanged after lipopolysaccharide exposure, but both glutathione monoethyl ester and N-acetyl-L-cysteine increased cellular glutathione levels, blocked NF-kappa B activation and inhibited the release of TNF-alpha. Inhibition of glutathione synthesis prevented the NAC-induced increase in Kupffer cell glutathione, yet it did not prevent the inhibition of TNF-alpha release by NAC. Thus the inhibition of NF-kappa B activation by pharmacological thiols such as NAC might reflect a more general role of the intracellular thiol redox status in NF-kappa B regulation rather than the antioxidant properties of these agents.

Evidence That Glutathione Depletion Is a Mechanism Responsible for the Anti-Inflammatory Effects of Ethyl Pyruvate in Cultured Lipopolysaccharide-Stimulated RAW 264.7 Cells

“…Since EP and NAC were similarly effective with respect to amelioration of LPS-induced TBARS formation but exhibited differential pharmacological effects with respect to inhibition of LPS-induced NF-B activation and mediator secretion, we investigated the effects of these two agents on cellular levels of the reduced and oxidized forms of glutathione (GSH and GSSG, respectively). Consistent with previously reported findings from other laboratories (Neuschwander-Tetri et al, 1996;Parmentier et al, 2000), we showed that treatment with NAC increased intracellular levels of GSH but had only a minimal effect on the levels of GSSG. The effect of EP was qualitatively different.…”

Thiol regulation of the production of TNF-α, IL-6 and IL-8 by human alveolar macrophages

“…Treatment by NAC enhances the intracellular concentration of GSH in AMs exposed to oxidant stress [17]; however, the capacity of intracellular GSH to modulate the production of cytokines by macrophages has not been demonstrated. In rat Kupffer cells, inhibition of GSH synthesis does not prevent the inhibition of TNF-a release by NAC [18]. For these reasons, this study measured the effect of variation in intracellular GSH and of exogenous thiols on the production of TNF-a, IL-6 and IL-8 by human AMs.…”

Metallothionein modulates lipopolysaccharide-stimulated tumour necrosis factor expression in mouse peritoneal macrophages

“…Macrophages stimulated by LPS secrete large quantities of TNF [18,19], and this process is influenced by the redox state of cells [25,26]. PEMs obtained from MT +/+ or MT −/− mice were used to investigate whether or not these proteins are involved in TNF production.…”

“…NF-κB was found to have an important role in the regulation of TNF-α gene transcription [23,24]. The functions of LPS-activated macrophages are regulated by cellular redox states [25,26]. MT has many thiol groups, and all of them are bound to metals.…”