Page 166 - Veterinary Immunology, 10th Edition

macrophages is much closer to humans than to mice.) NOS2
VetBooks.ir converts L-arginine and oxygen to citrulline and nitric oxide (NO)

(Fig. 6.7). Nitric oxide alone is not highly toxic, but it can react with
superoxide anion to produce potent RNS such as peroxynitrite and

nitrogen dioxide radical.

FIG. 6.7 The two pathways of arginine metabolism in
macrophages. The production of nitric oxide through the use of nitric
oxide synthase 2 is a major antimicrobial pathway and the key
feature of M1 macrophages. The use of arginase to produce
ornithine, however, reduces the antimicrobial activities of M2 cells.

RNS inactivate iron and sulfur-containing enzymes such as the

heme-containing respiratory enzymes. They nitrosylate proteins,
oxidize lipids, and damage DNA.

Macrophage Polarization

166