Nitric oxide releasing drugs: from bench to bedside

NO biology has had an enormous boost and several aspects of its role in physiology and pathology has been extensively studied. NO acts as a double edge sword mediator that has beneficial physiological effects as well as detrimental pathological effects making very difficult to develop drugs. Studies on nitric oxide therapeutic approach can be divided into two simple approaches: one directed to increase the NO release and another to inhibit NO release. Gene therapy approach have been also developed and pre-clinical data on iNOS and eNOS have shown promising results in post-angioplasty restenosis. The major limitation to the use of NSAID is represented by their ability to cause ulceration and bleeding in the gastrointestinal tract NO plays an important role in GI integrity. NO releasing NSAID have higher GI tolerability and retain their anti-inflammatory activity as well as the ability to inhibit platelet aggregation. NO-NSAIDs not only represents a new class of drugs but they represent the first "proof of concept" on the key role of NO in the gastrointestinal homeostasis

Nitric oxide synthase activity in molluscan hemocytes

The hemocytes of the freshwater snail Viviparus ater have nitric oxide synthase (NOS) activity, as demonstrated by [H-3]citrulline and nitrite + nitrate formation. The enzyme is NADPH dependent and is competitively inhibited by the mammalian NOS inhibitor N-G-monomethyl-L-arginine (K-i = 4.7 mu M). The K-m for L-arginine is 2.5 mu M. 70% of the total activity is observed at very low free Ca2+ concentration (3 nM). LPS treatment increased total NOS activity 2.4 fold. The activity is partly present in the non-soluble fraction of hemocytes (24% and 8% in non-stimulated and LPS-stimulated snails, respectively). An antiserum to the C-terminal synthetic pentadecapeptide of the rat cerebellar NOS inhibited the enzyme activity in a concentration-dependent manner. This is the first biochemical demonstration of the existance of NOS activity in molluscan hemocytes, the cells responsible for defence mechanisms

Nitric oxide: An ancestral immunocyte effector molecule

The presence and the role of nitric oxide synthase (NOS) were investigated in the molluscan hemocytes by immunocytochemical, biochemical and functional ap preaches. Using an anti-NOS polyclonal antibody, immunoreactivity was observed in the hemocytes, and this reactivity increased after stimulation of the animals with Escherichia coli, indicating that this enzyme is inducible. The NOS inducibility was also histochemically demonstrated by detection of NADPH-diaphorase activity. Biochemical studies show that the enzyme is 70% cytoplasmatic and 30% membrane bound and that the inducible form is mainly cytoplasmatic. The nitrite + nitrate and citrulline formation, the inhibition by N-omega-nitro-L-arginine, the Km value for arginine, the calcium and co-enzyme dependence show that the molluscan NOS shares the same properties as the NOS isoenzymes so far studied. However, it cannot be identified with any of these enzymes. It appears to be in some way similar to an inducible form of human hepatocyte NOS. Also cytokines are able to induce NOS. In vitro studies have shown that hemocytes produce nitric oxide (NO), a bactericide substance, and that there is a relationship between the NO system and phagocytosis. The presence of NO in the invertebrate hemocyte demonstrates that critical molecules have been conserved over the course of evolution