Nitric oxide synthase mechanism

Wolff, D. J., Datto, G. A., Samatovicz, R. A., and Tempsick, R. A. (1993). Calmodulin-dependent nitric oxide synthase—Mechanism of inhibition by imidazole and phenylimida-zoles.. Biol. Chem. 268, 9425-9429. 

Fleming I, Busse R (2003) Molecular mechanisms involved in the regulation of the endothelial nitric oxide synthase. Am J Physiol 284 R1-12... 

Buisson, A., Margaill, L, Callebert, J., Plotkine, M. and Boulu, R.G. (1993). Mechanism involved in the neuroprotective activity of a nitric oxide synthase inhibitor during focal cerebral ischemia. J. Neurochem. 61, 690-696. 

The interaction of estrogen receptors with signaling systems of the cell membrane that respond to growth factors and mediate nongenomic, fast actions of estrogens will be reviewed as well. These mechanisms have a growing importance in the comprehension of phenomena like the induction of endothelial NOS (nitric oxide synthase) by estrogens (Rubanyi et al. 2002). 

Simoncini T, Genazzani AR, Liao JK (2002a) Nongenomic mechanisms of endothelial nitric oxide synthase activation by the selective estrogen receptor modulator raloxifene. Circulation 105 1368-1373... 

Griffith, O. W., Stuehr, D. J., Nitric oxide synthases properties and catalytic mechanism, Annu. Rev. Physiol. 57 (1995), p. 707-736... 

Besides cholesterol efflux from arterial wall and its role in RCT, additional properties of HDL have been proposed for its protective anti-atherogenic activities. HDL protects vascular function by a number of potential alternative mechanisms, including inhibition of LDL oxidation [8,9], platelet aggregation and coagulation [10], and endothelial monocyte adhesion [11], as well as promotion of endothelial nitric oxide synthase (eNOS) [12], and prostacyclin synthesis [13-15]. The proposed alternate protective mechanisms for HDL are attractive but many of them lack validation under in vivo conditions. 

Although NO does not itself use a G-protein for signalling, the mechanism of NO production in vascular endothelium is initiated by IP3 via a G-protein-linked acetylcholine receptor on the cell surface. The IP3 causes activation of nitric oxide synthase via calcium- calmodulin and the NO generated diffuses from the endothelial cell into the adjacent smooth muscle cell where cGMP is produced. 

Opioids also interact with excitatory amino acid neurotransmitters. At lower micromolar concentrations, p agonists (e.g., DAMGO) enhance NMDA activity in the nucleus accumbens, but inhibit non-NMDA activity (Martin et al. 1997). At higher concentrations (5 pM), NMDA currents are reduced. Conversely, central administration of glutamate can precipitate a withdrawal syndrome in morphine-dependent animals, similar to the opioid antagonist naloxone. NMDA mechanisms also appear to be involved in the development of morphine tolerance. Competitive and noncompetitive NMDA antagonists and inhibitors of nitric oxide synthase reduce or eliminate tolerance to morphine (Elliott et al. 1995 Bilsky et al. 1996). However, this does not occur for tolerance to k opioids. Pharmacokinetics... 

A less common reactive species is the Fe peroxo anion expected from two-electron reduction of O2 at a hemoprotein iron atom (Fig. 14, structure A). Protonation of this intermediate would yield the Fe —OOH precursor (Fig. 14, structure B) of the ferryl species. However, it is now clear that the Fe peroxo anion can directly react as a nucleophile with highly electrophilic substrates such as aldehydes. Addition of the peroxo anion to the aldehyde, followed by homolytic scission of the dioxygen bond, is now accepted as the mechanism for the carbon-carbon bond cleavage reactions catalyzed by several cytochrome P450 enzymes, including aromatase, lanosterol 14-demethylase, and sterol 17-lyase (133). A similar nucleophilic addition of the Fe peroxo anion to a carbon-nitrogen double bond has been invoked in the mechanism of the nitric oxide synthases (133). 

Fig. 3. Mechanisms of vasocontraction and vasorelaxation in endothelial and smooth muscle cells. COX cyclooxygenase, eNOS endothelial nitric oxide synthase, HO-1 heme oxygenase-1, EET epoxyeicosatrienoic acid, EDHF endothelium-derived hyperpolariz-ing factor, PGI2 prostaglandin I2, NO nitric oxide, CO carbon monoxide, PLC phospholipase C, IP3 inositol 1,4,5-trisphosphate, DAG diacylglycerol, ER/SR endo-plasmic/sarcoplasmic reticulum, AC adenylyl cyclase, cAMP cyclic adenosine monophosphate, sGC soluble guanylyl cyclase, cGMP cyclic guanosine monophosphate.

Andrographolide, thus, has different mechanisms of anti-inflammatory activity. It can inhibit the activation of NF-kB, suppress inducible nitric oxide synthase (iNOS) expression, inhibit COX-2 expression in human fibroblast cells and also prevent oxygen radical production by human. The compound is also able to modulate T-cell activation both in vitro as well as in vivo, it is evident that it could prevent initial T-cell priming by interfering with DC maturation and antigen presentation capacity. Therefore, andrographolide may have utility as a therapeutic agent for the treatment of autoimmune diseases, such as multiple sclerosis. " ... 

Chiou WF, Chen CF, Lin JJ. (2000) Mechanism of suppression of inducible nitric oxide synthase (iNOS) expression in RAW 264.7 cells by andrographolide. Br J Pharmacol 129 1553-1560. 

Kramer MS, Cutler NR, Ballenger JC, Patterson WM, Mendels J (1995) A placebo-controlled trial of L-365,260, a CCK antagonist, in panic disorder. Biol Psychiatry 37 462-466 Kramer MS, Cutler N, Feighner J, Shrivastava R, Carman J, Sramek IJ, Reines SA, Snavely D, Wyatt-Knowles E, Hayle EJ (1998) Distinct mechanism for antidepressant activity by blockade of central substance P receptors. Science 281 1640-1645 Kriegsfeld LJ, Dawson TM, Dawson VL, Nelson RJ, Snyder SH (1997) Aggressive behavior in male mice lacking the gene for neuronal nitric oxide synthase requires testosterone. Brain Res 769 66-70... 

Wallerath, T., Poleo, D., Li, H., and Forstermann, U., Red wine increases the expression of human endothelial nitric oxide synthase a mechanism that may contribute to its beneficial cardiovascular effects, J. Am. Coll Cardiol, 41, 471, 2003. 

A further review of the mechanism of action of tetrahydrobiopterin in nitric oxide synthases has appeared with emphasis on studies of the enzyme under high pressures <2006BBA578>. 

VI. SIGNALING MECHANISM OF INTERLEUKIN 1-INDUCED EXPRESSION OF NITRIC OXIDE SYNTHASE... 

---