There is growing evidence that endogenous nitric oxide (NO) regulates mucosal barrier integrity under physiological conditions and counters the increase in mucosal permeability associated with acute pathophysiological states. The potential mechanisms of action for the protective effects of NO are discussed. These include maintenance of blood flow, inhibition of platelet and leukocyte adhesion and/or aggregation within the vasculature, modulation of mast cell reactivity, and scavenging of reactive oxygen metabolites such as superoxide. On the basis of the data presented, we conclude that both constitutive nitric oxide synthase (cNOS)-derived endogenous NO and exogenous NO (from NO donors) appear to reduce the sequelae of acute inflammation. The second section of this review summarizes the data germane to prolonged (chronic) inflammatory conditions associated with the overproduction of NO from the inducible form of NOS (iNOS). Some emphasis is placed on the role of NO in sepsis and inflammatory bowel disease (IBD), and data to suggest that NO, or more specifically a NO-derived mediator, is involved in these disorders are summarized. These studies are compared with recent publications suggesting that inhibition of NO synthesis with nonspecific inhibitors of NOS or selective iNOS inhibitors may not protect in models of sepsis or IBD. Overall, the review highlights the potential importance of the type of NOS enzyme involved in the particular inflammatory process being studied.

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Chronic renal failure (CRF) is associated with oxidative stress that promotes production of reactive oxygen species. L-Carnitine is a cofactor required for transport of long-chain fatty acids into the mitochondrial matrix. Recent research has shown that some clinical conditions (i.e., anorexia, chronic fatigue, coronary heart disease, diphtheria, hypoglycemia, and male infertility) benefit from exogenous supplementation of L-carnitine. The aim of this study was to examine the role of L-carnitine in protecting the aorta, heart, corpus cavernosum, and kidney tissues against oxidative damage in a rat model of CRF. Male Wistar albino rats were randomly assigned to either the CRF group or the sham-operated control group, which had received saline or L-carnitine (500 mg/kg, i.p.) for 4 weeks. CRF was evaluated by BUN and serum creatinine measurements. Aorta and corporeal tissues were used for contractility studies or stored along with heart and kidney tissues for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels. Plasma MDA, GSH levels and erythrocyte superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities were also studied. In the CRF group, the contraction and the relaxation of aorta and corpus cavernosum samples decreased significantly compared with controls and were partially reversed by L-carnitine treatment. In the CRF group, there were significant increases in tissue MDA with marked reductions in GSH levels in all tissues and plasma compared with controls. In the plasma SOD, CAT and GSH-Px activities were also reduced. All these effects were reversed by L-carnitine as well. The increase in MDA level and the concomitant decrease in GSH level of tissues and plasma and also suppression of the antioxidant enzyme activities in plasma demonstrate that oxidative mechanisms are involved in CRF-induced tissue damage. L-carnitine, possibly via its free radical scavenging and antioxidant properties, ameliorates oxidative organ injury and CRF-induced dysfunction of the aorta and corpus cavernosum. These results suggest that L-carnitine supplementation may have some benefit in CRF patients.

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ALA is beneficial in TNBS-induced gut inflammation in rats via suppression of neutrophil accumulation, preservation of endogenous glutathione and inhibition of reactive oxidant generation.