Nitric-oxide synthases cytokine effects

The other broad category of MSP actions on macrophages relates to mediator production. Endotoxin, or combinations of proinflammatory cytokines, causes expression of murine macrophage-inducible nitric oxide synthase, an effect that can be detected by Northern blots for the mRNA or by measurement of nitrate in the culture fluid. MSP prevents induction of NO-synthase by any of the above stimuli (Wang et al., 1994d). The inhibitory action of MSP is confined to this specific mediator. MSP did not inhibit endotoxin-induced expression of mRNA for monocyte chemoattractant protein-1. Furthermore, MSP caused secretion of IL-6 (but not IL-1 or TNFa) within 6 hr, and did not inhibit endotoxin-induced secretion of IL-1, IL-6, or TNFa (A. Skeel and E. J. Leonard, unpublished data). The in vitro modulation by MSP of endotoxin-induced NO production now has an in vivo counterpart. Concentrations of nitrate in serum of Stk / mice that received endotoxin intravenously were higher than in serum of comparably treated normal mice and at a critical endotoxin dose, only 20% of the Stk / mice survived, compared to 80% survival for normal mice (Correll et al., 1997). If MSP plays a role in the host response to endotoxemia, pro-MSP must be cleaved to biologically active MSP. Within 4 hr after i.v. administration of... 

Exposure to trichothecenes at levels that partially inhibit translation upregulates expression of many inflammatory and immune-related genes including macrophage, Thl and Th2 cytokines as well as chemokines, cyclooxygenase 2 and inducible nitric oxide synthase.1518 Contrastingly, suppressive effects of trichothecenes on leukocyte function are intimately linked with the induction of apoptosis as has been demonstrated in macrophages, T cells and B cells both in vivo and in vitro.19-20... 

In addition to direct effects on genes regulating inflammation, glucocorticoids also inhibit the transcription factors that initiate synthesis of pro-inflammatory cytokines (e.g., interleukin-1, tumor necrosis factor), enzymes (e.g., COX-2, nitric oxide synthase), and receptor proteins (e.g., natural killer receptors).17,87,89 Glucocorticoids may also exert some of their effects via a membrane-bound receptor that regulates activity of macrophages, eosinophils, T lymphocytes, and several other types of cells involved in the inflammatory response.89 Consequently, glucocorticoids affect many aspects of inflammation, and their powerful anti-inflammatory effects in rheumatoid arthritis result from their ability to blunt various cellular and chemical components of the inflammatory response. 

Ulisse, S., Gionchetti, P, D Alo, S. et al. 2001. Expression of cytokines, inducible nitric oxide synthase, and matrix metalloproteinases in pouchitis Effects of probiotic treatment. Am J Gastroenterol 96 2691-2699. 

Bisphosphonates (particularly clodronate) have been shown to have anti-inflammatory effects in animal models of rheumatoid arthritis (RA), as well as in arthritis in humans. In adjuvant- and antigen-induced arthritis in rats, clodronate suppresses the inflammatory articular lesions in the inflamed joints [29], whilst in human RA, clodronate decreases the levels of interleukin (ILJ-1, tumor necrosis factor-alpha (TNFaand /1-microglobulin in the circulation [30]. In vitro, clodronate inhibits cytokine and nitric oxide (NO) release and inducible nitric oxide synthase (iNOS) expression in macrophage-like cells. 

Tanacetum parthenium (Asteraceae), commonly known as feverfew, is a popular herbal remedy used a prophylactic in the treatment of migraine [88]. Studies have revealed that the action of feverfew is probably mediated by the sesquiterpene lactone parthenolide. Indeed, feverfew and parthenolide produce anti-inflammatory and antinociceptive effects in experimental animals [89]. Parthenolide is a potent inhibitor of the transcription factor NF-kB activation, a key regulator of pro-inflammatory protein production, such as cytokines, COX-2 and inducible nitric oxide synthase [90]. However, a clinical study revealed that feverfew did not provide any benefit in the treatment of rheumatoid arthritis [91]. Additional clinical studies must be carried out to explore the feverfew efficacy as an analgesic. 

In A549-cells, stimulation with a combination of interferon y, tumour necrosis factor a, interleukin-ip, and LPS for 12, 24 and 48 h induced inducible nitric oxide synthase (Watkins et al. 1997). TNF-a alone does not induce NO production directly however, it does have a stimulatory effect on IL-ip-induced NO production (Kwon and George 1999). IL-lp and interferon y both NO production alone, yet at different concentration thresholds, and act synergis-tically when present together. In the presence of all three cytokines, the net effect of NO production exceeded the predicted additive effect of each individual cytokine and the two-way interactions. 

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