https://staff.blog.ui.ac.id/hsuryadi/files/2012/02/ROS_RNS.pdf

Free radicals and antioxidants in normal physiological functions and human disease

At high concentrations, free radicals and radical-derived, nonradical reactive species are hazardous for living organisms and damage all major cellular constituents. At moderate concentrations, how...

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Free Radicals in the Physiological Control of Cell Function

The discovery that mammalian cells generate nitric oxide, a gas previously considered to be merely an atmospheric pollutant, is providing important information about many biologic processes. Nitric oxide is synthesized from the amino acid L-arginine by a family of enzymes, the nitric oxide synthases, through a hitherto unrecognized metabolic route -- namely, the L-arginine-nitric oxide pathway1–8. The synthesis of nitric oxide by vascular endothelium is responsible for the vasodilator tone that is essential for the regulation of blood pressure. In the central nervous system nitric oxide is a neurotransmitter that underpins several functions, including the formation of memory. . . .

The L-Arginine-Nitric Oxide Pathway

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

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Nitric Oxide and Peroxynitrite in Health and Disease

Evolution has resorted to nitric oxide (NO), a tiny, reactive radical gas, to mediate both servoregulatory and cytotoxic functions. This article reviews how different forms of nitric oxide synthase help confer specificity and diversity on the effects of this remarkable signaling molecule.

https://faseb.onlinelibrary.wiley.com/doi/pdf/10.1096/fasebj.6.12.1381691

Nitric oxide as a secretory product of mammalian cells.

Nitric oxide gas (NO) increased guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] activity in soluble and particulate preparations from various tissues. The effect was dose-dependent and was observed with all tissue preparations examined. The extent of activation was variable among different tissue preparations and was greatest (19- to 33-fold) with supernatant fractions of homogenates from liver, lung, tracheal smooth muscle, heart, kidney, cerebral cortex, and cerebellum. Smaller effects (5- to 14-fold) were observed with supernatant fractions from skeletal muscle, spleen, intestinal muscle, adrenal, and epididymal fat. Activation was also observed with partially purified preparations of guanylate cyclase. Activation of rat liver supernatant preparations was augmented slightly with reducing agents, decreased with some oxidizing agents, and greater in a nitrogen than in an oxygen atmosphere. After activation with NO, guanylate cyclase activity decreased with a half-life of 3-4 at 4° but re-exposure to NO resulted in reactivation of preparations. Sodium azide, sodium nitrite, hydroxylamine, and sodium nitroprusside also increased guanylate cyclase activity as reported previously. NO alone and in combination with these agents produced approximately the same degree of maximal activation, suggesting that all of these agents act through a similar mechanism. NO also increased the accumulation of cyclic GMP but not cyclic AMP in incubations of minces from various rat tissues. We propose that various nitro compounds and those capable of forming NO in incubations activate guanylate cyclase through a similar but undefined mechanism. These effects may explain the high activities of guanylate cyclase in certain tissues (e.g., lung and intestinal mucosa) that are exposed to environmental nitro compounds.

https://www.pnas.org/content/pnas/74/8/3203.full.pdf

Nitric oxide activates guanylate cyclase and increases guanosine 3':5'-cyclic monophosphate levels in various tissue preparations.

The particulate enzyme responsible for the synthesis of endothelium-derived relaxing factor has been purified from cultured and native (noncultured) bovine aortic endothelial cells. Purification of the solubilized particulate enzyme preparation by affinity chromatography on adenosine 2',5'-bisphosphate coupled to Sepharose followed by Superose 6 gel filtration chromatography resulted in a single protein band after denaturing polyacrylamide gel electrophoresis that corresponded to approximately 135 kDa. The enzyme activity in the various fractions was assayed by its stimulatory effect on soluble guanylyl cyclase of rat fetal lung fibroblasts (RFL-6 cells), by the formation of L-citrulline from L-arginine, by measuring nitrite/nitrate formation, and by bioassay on endothelium-denuded vascular strips. Endothelium-derived relaxing factor synthase was purified 3419-fold from the crude particulate fraction of cultured bovine aortic endothelial cells with a 12% recovery (RFL-6 assay). Purified endothelium-derived relaxing factor synthase required L-arginine, NADPH, Ca2+, calmodulin, and 5,6,7,8-tetrahydrobiopterin for full activity.

https://www.pnas.org/content/pnas/88/23/10480.full.pdf

Purification and characterization of particulate endothelium-derived relaxing factor synthase from cultured and native bovine aortic endothelial cells.

The present study investigates the hypothesis that endothelium-dependent relaxation of vascular smooth muscle may be mediated through the formation of cGMP. Relaxation of the rat thoracic aorta to acetylcholine, histamine, and Ca++ ionophore A23187 was associated with increased levels of cGMP in a time- and concentration-dependent manner, whereas cAMP levels were unaltered. Removal of the endothelium prevented relaxation to these agents and prevented the increased levels of cGMP. Removal of the endothelium after exposure to acetylcholine only partially decreased the elevated levels of cGMP, suggesting that the changes in cGMP occurred within the smooth muscle cells. Eicosatetraynoic acid, an inhibitor of lipoxygenase and cyclooxygenase, and quinacrine, an inhibitor of phospholipase, prevented and reversed acetylcholine-induced relaxation, respectively, and inhibited acetylcholine-induced increased levels of cGMP. In contrast, sodium nitroprusside-induced relaxation and increased levels of cGMP were independent of the presence of the endothelium, exposure to eicosatetraynoic acid, and quinacrine. The present results support the hypothesis that vascular smooth muscle relaxation induced by some agents is dependent on the presence of the endothelium and is mediated through the formation of an endothelial factor that increases cGMP levels in smooth muscle.

Agonist-induced endothelium-dependent relaxation in rat thoracic aorta may be mediated through cGMP.

Cyclic GMP synthesis and function.

/pdf/cyclic-guanosine-monophosphate-as-a-mediator-of-vasodilation-3trqjbgu70.pdf

Ferid Murad

Papers

Nitric oxide activates guanylate cyclase and increases guanosine 3':5'-cyclic monophosphate levels in various tissue preparations.

Purification and characterization of particulate endothelium-derived relaxing factor synthase from cultured and native bovine aortic endothelial cells.

Agonist-induced endothelium-dependent relaxation in rat thoracic aorta may be mediated through cGMP.

Cyclic GMP synthesis and function.

Cyclic guanosine monophosphate as a mediator of vasodilation.