Nitric Oxide as a Unique Bioactive Signaling Messenger in Physiology and Pathophysiology

Abstract

Nitric oxide (NO) is an intra- and extracellular messenger that mediates diverse signaling pathways in target cells and is known to play an important role in many physiological processes including neuronal signaling, immune response, inflammatory response, modulation of ion channels, phagocytic defense mechanism, penile erection, and cardiovascular homeostasis and its decompensation in atherogenesis. Recent studies have also revealed a role for NO as signaling molecule in plant, as it activates various defense genes and acts as developmental regulator. In plants, NO can also be produced by nitrate reductase. NO can operate through posttranslational modification of proteins (nitrosylation). NO is also a causative agent in various pathophysiological abnormalities. One of the very important systems, the cardiovascular system, is affected by NO production, as this bioactive molecule is involved in the regulation of cardiovascular motor tone, modulation of myocardial contractivity, control of cell proliferation, and inhibition of platelet activation, aggregation, and adhesion. The prime source of NO in the cardiovascular system is endothelial NO synthase, which is tightly regulated with respect to activity and localization. The inhibition of chronic NO synthesis leads to neurogenic and arterial hypertensions, which later contribute to development of myocardial fibrosis. Overall, the modulation of NO synthesis is associated with hypertension. This review briefly describes the physiology of NO, its synthesis, catabolism, and targeting, the mechanism of NO action, and the pharmacological role of NO with special reference to its essential role in hypertension.

Cardiac Depression Produced by L-Arginine and Phosphodiestrase Inhibitor on Isolated Mammalian Rabbit Heart: Function of Cyclic Guanosine Monophosphate (cGMP)

“…It is now well established that when the production of ROS exceeds the capacity of antioxidant defenses, oxidative stress will produce a harmful effect on the functional and structural integrity of biological tissues..The biological effects of ROS-mediated reactions are due to their direct interaction with cellular lipids, proteins and DNA (e.g., nicking, base-pair mutations, rearrangements, deletions, insertions and sequence amplification), causing cell damage and death. ROS also causes lipid peroxidation, which results in damage to the cell membrane and the membranes of cellular organelles (Tuteja et al, 2004).…”

Effect of Nitric Oxide on the Antifungal Activity of Oxidative Stress and Azoles Against Candida albicans

“…We found that NO production in C. albicans could be inhibited by the specific NOS inhibitor L-NAME, indicating that C. albicans may produce NO by a classic NOS mechanism [14,23]. We have carried out bioinformatic analysis on the C. albicans genome but failed to identify sequences that are homologous to known NOS (data not shown).…”

“…In mammals, NO acts as a critical regulator in nervous, immune and cardiovascular systems [12], and an important mediator in certain pathophysiologic conditions [13]. NO in animals is synthesized by a family of enzymes, known as nitric oxide synthases (NOS), which catalyze the conversion of the amino acid L-arginine to NO and L-citrulline [14]. In plants, algae, and fungi, no true NOS homologs has yet been identified.…”

Nitric oxide is an upstream signal involved in the multisignalling network during the Russian wheat aphid resistance response and its application enhances resistance

“…During the defence responses, NO may very rapidly react with O 2 -, provided there is sufficient NO to form peroxynitrite in the absence of enzymatic catalysis (Tuteja et al 2004;Saito et al 2006). An increase in peroxynitrite formation (9 h.p.i) in the resistant, with a transient peak induction (12 h.p.i; Fig.…”