Expression of arginase I and inducible nitric oxide synthase in the peripheral blood and lymph nodes of HIV-positive patients

ZHANG, NAICHUN; DENG, JIANNING; WU, FENGYAO; LU, XIANGCHAN; HUANG, LEI; ZHAO, MIN

Previous studies have shown that the metabolism of L-arginine is one of the important mechanisms underlying the regulation of immune responses (5, 6) . L-arginine is a substrate of arginase (Arg), including Arg I and II, and nitric oxide synthase (NOS), including NOS1, 2 and 3). Arg I and II hydrolyzes L-arginine into L-ornithine and urea, and L-ornithine is further metabolized into polyamines, which are involved in the proliferation and differentiation of cells (7) . NOS catalyzes the conversion of L-arginine into citrulline and nitric oxide (NO), and NO is an important effector and regulator of the immune system (8, 9) . Arg I is released from immune cells, including polymorphonuclear neutrophils, during inflammation, and is also involved in the inflammatory response (10) . NOS2, or inducible NOS (iNOS) is expressed in a variety of immune cells (11) . Studies have reported that Arg I regulates the bioavailability of L-arginine, which is involved in certain immune-associated pathological processes, including inflammation-triggered immune dysfunction, immune evasion of cancer cells, fibrosis, immunosuppression and immune responses to infectious agents (5, 11, 12) . As a competitor to Arg I, iNOS hydrolyzes L-arginine into NO, which is important in destroying parasites, bacteria, viruses and cancer cells, as well as in vascular dilation (13) (14) (15) .