Nitric Oxide and Cell Stress

Nitric Oxide (NO) is a major signaling molecule in neurons and in the immune system, either acting within the cell in which it is produced or by penetrating cell membranes to affect adjacent cells. Nitric oxide is generated from arginine by the action of nitric oxide synthases (NOS). NO has a half-life of only a few seconds in vivo. However, since it is soluble in both aqueous and lipid media, it readily diffuses through the cytoplasm and plasma membranes. NO has effects on neuronal transmission as well as on synaptic plasticity in the central nervous system. In the vasculature, NO reacts with iron in the active site of the enzyme guanylyl cyclase (GC), stimulating it to produce the intracellular mediator cyclic GMP (cGMP), which in turn enhances the release of neurotransmitters resulting in smooth muscle relaxation and vasodilation.

Nitric oxide via cyclic GMP can also regulate protein kinase G activity, protein phosphorylation and numerous other biological processes. However, some effects of nitric oxide such as its antimicrobial, cytotoxic and inflammatory effects are independent of cyclic GMP and may result from nitric oxide′s interactions with transitional metals, thiol groups and other free radicals such as superoxide anion. These complexes may alter the structure or function of the macromolecule. Some complexes may act as nitric oxide reservoirs or "prodrugs" for nitric oxide release under appropriate conditions.

The participation of nitric oxide and cyclic GMP in cell signaling has been one of the most rapidly developing areas in biology since the first biological effects of nitric oxide were described in 1977. While the field has grown exponentially, many important questions regarding the formation, function, and metabolism of these important messengers and signaling molecules remain to be answered.

Sigma offers a comprehensive product line for all your nitric oxide and cell stress research needs, including numerous compounds that alter NO formation, metabolism and function, as well as highly characterized antibodies, enzymes, and proteins.

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