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Nitric
Oxide:
Nitric oxide (NO) is synthesized in inflammation by
the enzyme "inducible nitric oxide synthase" (iNOS).
NO is synthesized from L-arginine and oxygen using NADPH oxidase as well
as iNOS.
NO is normally a mediator of vascular tone and is a
potent vasodilator. It is normally secreted by endothelial cells at a
low concentration at regular intervals to maintain the level of vascular
tone.
In the context of inflammation, NO has other important
functions as well as its effects on blood vessels.
Macrophages secrete large amounts of NO in the context
of inflammation using iNOS. This enables macrophages to have a wider array
of targets for killing compared to neutrophils. NO is inhibitory or destructive
to many pathogens, for example:
Bacteria such as Mycobacterium spp. and Staphylococcus
aureus.
Fungi such as Cryptococcus neoformans.
Protozoa such as Leishmania major, Trypanosoma brucei
and T. cruzi, and Plasmodium spp.
Metazoa such as Schistosoma mansoni.
This effect of NO is mediated by the production of a
very reactive intermediate molecule, peroxynitrite by the reaction of
NO with the superoxide anion.
 
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