Down-Regulation of Inducible Nitric-Oxide Synthase (NOS-2) During Parasite-Induced Gut Inflammation: A Path to Identify a Selective NOS-2 Inhibitor

Abstract

Nitric oxide (NO) possesses potent anti-inflammatory properties; however, an over-production of NO will promote inflammation and induce cell and tissue dysfunction. Thus, the ability to precisely regulate NO production could prove beneficial in controlling damage. In this study, advantage was taken of the well characterized inflammatory response caused by an intestinal parasite, Trichinella spiralis, to study the relationship between intestinal inflammation and the regulation of nitric oxide synthase-type 2 (NOS-2) expression. Our study revealed that a specific gut inflammatory reaction results in inhibition of NOS-2 expression. Characteristics of this inhibition are: 1) local jejunal inflammation induced by T. spiralis systemically inhibits NOS-2 gene transcription, protein expression, and enzyme activity; 2) the inhibition blunts endotoxin-stimulated NOS-2 expression; 3) the inhibition does not extend to the expression of other isoforms of NOS, to paxillin, a housekeeper protein, or to cyclooxygenase-2, another protein induced by proinflammatory cytokines; 4) the inhibition is unlikely related to the formation of specific anti-parasite antibodies; and 5) the inhibition may involve substances other than stress-induced corticosteroids. Elucidation of such potent endogenous NOS-2 down-regulatory mechanisms could lead to the development of new strategies for the therapy of inflammatory conditions characterized by the overproduction of NO.

Helminth regulation of host IL-4Rα/Stat6 signaling: Mechanism underlying NOS-2 inhibition byTrichinella spiralis

“…Increasing the concentration of LPS to 100 ng͞ml only partially overcame the inhibition by worm-cultured medium [expression in response to 100 ng͞ml LPS was still Ͻ50% of the expression in response to LPS (50 ng͞ml) in control medium]. Our in vivo study (8) demonstrated that T. spiralis-induced NOS-2 inhibition is highly selective and does not extend to the expression of COX-2. We used the same cell lysates to observe protein expression of COX-2.…”

“…We have previously demonstrated that Trichinella spiralis infection induces down-regulation of NOS-2 expression (8), which has the following characteristics. (i) Local jejunal infection by T. spiralis systemically inhibits NOS-2 gene transcription, protein expression, and enzyme activity in the ileum, jejunum, colon, kidney, lung, and uterus.…”

“…Further elucidation of this pathway could lead to the development of new therapies for inflammatory conditions characterized by overproduction of NO, and also could provide more insight into the hygiene hypothesis that has been very influential in directing strategies to prevent allergic diseases. inoculated orally with 600 T. spiralis larvae obtained by enzymatic digestion of skeletal muscle from infected mice (8). For cytokine measurements, animals were killed 1-10 days after oral inoculation (8).…”

“…inoculated orally with 600 T. spiralis larvae obtained by enzymatic digestion of skeletal muscle from infected mice (8). For cytokine measurements, animals were killed 1-10 days after oral inoculation (8). For the experiments involving tyrosine kinase inhibition, T. spiralis-infected or uninfected mice were divided into herbimycin A-treated and vehicle (DMSO)-treated groups.…”

In vivo inhibition of inducible nitric oxide synthase by aminoguanidine influences free radicals production and macrophage activity in Trichinella spiralis infected low responders (C57BL/6) and high responders (BALB/c) mice

“…Modulation of free radicals production by AG treatment is a good tool for studying the role of these substances during trichinellosis, because only iNOSderived NO can play role in infected host organisms besides potential side-effects of AG administration are negligible (Misko et al, 1993). It is known that iNOS activity is changing during T. spiralis infection (Bian et al, 2001;Bian et al, 2005), so the inhibition of this enzyme by AG affects cytotoxic activity of macrophages, which could play role during infection. Our previous study showed that also macrophages play important role during intestinal phase of infection as well as revealed some new information about the role of free radicals during T. spiralis infection (Kołodziej-Sobocińska et al, 2006a,b) and reinfection (Kołodziej-Sobocińska et al, 2007).…”