Regulation of Nitric Oxide Production by Stimulated Rat Kupffer Cells

Abstract

Macrophages have been described to release nitric oxide (NO) as a cytotoxic radical. This highly unstable substance is as well known as endothelium-derived relaxing factor produced by vascular endothelial cells. Because of its cytotoxic activity the synthesis of NO by rat Kupffer cells, the liver macrophages, upon stimulation with endotoxin (lipopolysaccharide; LPS) and tumor necrosis factor-α (TNF-α) in combination with prostaglandin E₂ (PGE₂) and dibutyryl cAMP (dBcAMP) was studied. Kupffer cells were stimulated after 48 h of primary culture. NO was quantified as NO₂ in the cell medium 24 h after stimulation. LPS stimulated NO generation 5- to 10-fold over the basal level. This increase could be further enhanced by PGE₂ and dBcAMP, especially when added 1 h after LPS. NO generation after stimulation with LPS or LPS + PGE₂ depended on the simultaneous production of PGE₂ by the stimulated Kupffer cells. It could be partly inhibited by anti-PGE₂ antibody or acetylsalicylic acid. While murine TNF-α did not stimulate NO synthesis significantly, added PGE₂ raised NO synthesis about 6-fold. The addition of dBcAMP to TNF-α in the same concentration as with LPS, however, had no effect. Thus, stimulation by LPS + PGE₂ equals that of LPS + dBcAMP whereas TNF-α + PGE₂ does not equal TNF-α + dBcAMP, indicating differences in the mode of action of PGE₂ on LPS- or TNF-α-treated Kupffer cells.

Induction of nitric oxide synthase in cultured vascular smooth muscle cells: the role of cyclic AMP

“…Specific inhibition of iNOS activity in vascular tissues requires a better understanding of the factors governing the expression and function of this enzyme. Some progress has been made in elucidating factors regulating iNOS activity in endothelial, macrophage and neuronal cell lines (Nakane et al, 1991;Brune & Lapetina, 1991;Gaillard et al, 1991;Bredt et al, 1992;Severn et al, 1992;Marotta et al, 1992;Hortelano et al, 1992;1993;Feinstein et al, 1993). One factor that appears to play a role in regulating NO production is adenosine 3':5'-cyclic monophosphate (cyclic AMP) but the effect of increasing cyclic AMP levels appears to differ in different tissues such that it is not possible to extrapolate from these studies to VSM cells.…”

Effect of rosuvastatin on cholestasis‐induced hepatic injury in rat livers

“…This is accompanied by the release of inflammatory cytokines [34,35] and the infiltration of circulating monocytes and neutrophils [36]. Inducible NO synthase (iNOS) is an isoform of NOS expressed under the influence of stimulation by cytokines or microbial products.…”

Structural and functional aspects of the liver and liver sinusoidal cells in relation to colon carcinoma metastasis

“…A pivotal role for IFN- in the clearance of various intracellular pathogens has been amply demonstrated [53,54] . It has been described that macrophages release the cytotoxic radical, NO [55,56] . In vitro studies suggested that NO induces mitochondrial dysfunction in tumor cells followed by membrane barrier dysfunction in the liver sinusoid [57,58] .…”