Dose Effects of Chronically Infused Nitric Oxide Synthase Inhibitor NG-Nitro-L-arginine Methyl Ester on Anabolic Response and Arginine Metabolism in Rats with Subacute Peritonitis

Abstract

Patients with peritonitis develop arginine deficiency due to decreased consumption, impaired absorption, and increased utilization of arginine.1,2) Arginine, a precursor for the synthesis of nitric oxide (NO), urea, creatinine, glutamate, proline, and polyamines, is a conditionally essential amino acid in stressed conditions, especially in inflammation. 1,3,4) Green et al. 5) was the first research group to show that nitrate/nitrite concentrations and the severity of infection are closely correlated. Subsequent studies showed that patients with peritonitis have uncontrolled activation of inducible nitric oxide synthase (NOS), which results in NO overproduction and the following sepsis.6) Therefore, inhibition of NOS might be a useful strategy to treat arginine deficiency and inhibit excess NO production. 6,7) In animal and human studies, the results of NOS inhibition in inflammation have been ambiguous. For example, N G -nitro-L-arginine methyl ester (L-NAME), a nonselective NOS inhibitor which inhibits both constitutive and inducible NOS, effectively ameliorated the inflammatory lesions in the skin of zinc-deficient rats, 8) improved the myocardial function in sepsis, 9) and attenuated the lipopolysaccharide-induced peritoneal permeability and NO release in mice.10) On the contrary, some studies have shown that L-NAME may cause hypertension, augment the expressions of interferon (IFN)-g and interleukin (IL)-2, and result in markedly severe disease in rats with T cell-dependent autoimmune interstitial nephritis.11) The adverse effects of NOS inhibitors have also been observed in subjects with hemodynamic instability and sepsis. [12][13][14] Evidence suggests that the therapeutic effects of NOS inhibitors may depend on the dose, timing, and the severity and category of diseases.In clinical practice, a number of in hospital patients with subacute peritonitis developed chronic malnutrition and inflammation. Administration of total parenteral nutrition solution is an efficient method to supply all daily nutrition requirements; however, it is associated with occurrence of increased complicated infections.15) Zheng et al. 16) indicated that long-term parenteral nutrition-induced liver steatosis may be attenuated by L-NAME administration. Up to now, only few reports have described the long-term application of L-NAME for subacute peritonitis. Additionally, no study has ever addressed the effects of L-NAME on the inflammatory response and amino acid metabolism in subjects administered parenteral nutrition. In our study, we used a rat model with subacute peritonitis induced by cecal puncture and administered total parenteral nutrition solution to provide adequate nutrition, and we investigated the dose effects of parenterally supplemented L-NAME on the anabolism, inflammatory response, and arginine-derived metabolites such as the intermediates of the urea cycle, circulating profile of amino acids, NO, and cytokines. MATERIALS AND METHODS Animals and Experimental DesignMale Wistar rats (8-9 weeks old), initially weighi...

The Dose-Dependent Immunoregulatory Effects of the Nitric Oxide Synthase Inhibitor NG-Nitro-L-Arginine Methyl Ester in Rats with Sub-Acute Peritonitis

“…Although we did not determine the production of anti-inflammatory cytokines in immunocytes, the elevated Th1 response of monocytes and the diminished pro-inflammatory and Th1 responses of T-leukocytes implied that parenteral L-NAME may increase innate immunity and decrease adaptive immunity in sub-acute peritonitis in a dose-dependent manner. According to the results of our previous study, sub-acute peritonitic animals with chronic inhibition of L-NAME (≤ 25 mg·kg −1 ·day −1 ) had significantly increased plasma arginine and ornithine [17], an arginase-catalyzed metabolite and a precursor of polyamines and proline, without affecting systemic NO homeostasis (Table 2). Therefore, we speculated that the elevated circulating arginine and ornithine, two amino acids with immunoregulatory activities, might be associated with the changes in the immunocytic response [35].…”

“…They also had increased liver and spleen weights accompanied by sacs composed of muscular and connective tissue filled with intra-abdominal abscesses [17], [21]. Moreover, the circulating numbers of WBCs were significantly increased.…”

“…In rats with sub-acute peritonitis, an appropriate dose of parenteral arginine, a well-known immunonutrient, may enhance leukocytic and splenocytic responses [6], and continuous infusion of L-NAME (25 mg·kg −1 ·day −1 ) may increase arginine-associated metabolites without altering the circulating NO status or inducing significant adverse responses [17]. In the present study, continuous infusion of 5 and 25 mg·kg −1 ·day −1 of L-NAME significantly decreased TNF-α and IFN-γ production by T-leukocytes and 50 mg·kg −1 ·day −1 of L-NAME significantly increased TNF-α production by splenic macrophages and IFN-γ and IL-2 production by T-splenocytes in rats with sub-acute peritonitis.…”

“…Animals with sub-acute peritonitis were divided into 4 groups (n = 8 per group) to receive conventional parenteral nutrition solutions supplemented with 0, 5, 25, or 50 mg·kg −1 ·day −1 of L-NAME for 7 days [17]. The study design was as follows:…”

“…Using rats with cecal puncture-induced nonlethal peritonitis, we previously found that chronic infusion of L-NAME up to 50 mg·kg −1 ·day −1 may not alter circulating NOx and cytokines and may facilitate the production of arginine-associated amino acids, such as ornithine, glutamate, and proline [17]. Ornithine, a non-protein amino acid forming part of the urea cycle, can be further metabolized to polyamines, i.e., putrescine, spermidine, and spermine, to participate in lymphocyte mitogenesis [18], [19].…”