Enhanced inducible nitric oxide synthase expression and nitrotyrosine accumulation in experimental granulomatous hepatitis caused by Toxocara canis in mice (original) (raw)
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The Chinese journal of physiology, 2004
Nitric oxide (NO) is known to be produced by macrophages, endothelial cells and neurons and synthesized by an enzyme called nitric oxide synthase (NOS). Various effector mechanisms and infections can affect the NO production. Excessive amount of NO will lead to biochemical reactions, which cause toxic effects. In this study the role of NO has been evaluated in larval toxocarosis, which is a systemic parasite infection caused by T. canis larvae. Infection was established in the Balb/c mice with or without inducible NOS (iNOS) inhibition and the effects of infection and NOS inhibition were observed according to the results of SOD and LPx measurements in brain tissue and NADPH-diaphorase (NADP-d) histochemistry. Results of NADPH-d histochemistry indicate that iNOS inhibition has protective effect on the brains of infected mice and that larval T. canis infection could be related to oxidative stress, and NO production and iNOS inhibition can protect the tissue from damage in this infection.
International Journal for Parasitology, 2004
Nitric oxide has been extensively studied as an effector molecule of the host immune response against both protozoa and helminths, but parasites can also produce this molecule, through the action of nitric oxide (NO) synthases or NO synthases-like enzymes. The aim of this study was to verify the possible production of NO by Trichinella britovi L 1 larvae and the enzymes involved in this process. The NO synthase immunoreactivity and putative nitric oxide synthase-activity was analysed using antibodies to mammalian NO synthase III and to nitrotyrosine with immunohistochemistry, gold immunocytochemistry and immunoblot analysis and NADPH-diaphorase histochemistry. Our results show that T. britovi L 1 larvae possess an enzymatic activity capable of producing NO. The localisation of this activity, according to the NADPH-diaphorase histochemistry, is both at the cuticular and the internal level. This localisation is confirmed by nitrotyrosine immunohistochemistry both under optical and electron microscopy. Using the NO synthase III antibody, a similar pattern of labelling was found: in particular, electron microscopy showed a localisation of this immunoreactivity in the cuticle and in the stichocytes, where only the a2 granules contained gold particles, mainly concentrated at their periphery. Four polypeptides reacting to the NO synthase III antibody are revealed by Western blotting. Their molecular weight ranged from 38 to 50 kDa. A significant reaction of the anti-nitrotyrosine antibody to polypeptides 95, 60, 48 and 39 kDa from the same sample suggested the presence of different nitrosylated proteins. q
Parasite Immunology, 2002
The direct effect of nitric oxide (NO) on the viability of Toxocara canis larvae was studied. We observed that the nitric oxide donors, SIN-1 and SNOG, exert no cytotoxic effect on the in vitro viability of T. canis larvae. In addition, we developed a model in rats to elucidate the role of NO during T. canis infection. We evaluated different indicators in four experimental groups: morphological parameters, the total number cells and cell types recovered, nitrite and protein concentration, lactate dehydrogenase and alkaline phosphatase enzymatic activity in the bronchoalveolar lavage fluid, lung index and detection of anti-T. canis specific antibodies. We observed significant differences between non-infected and infected groups. The infected animals treated with the inducible nitric oxide synthase (iNOS) inhibitor aminoguanidine were less damaged than infected, non-treated animals. Our results suggest that the in vivo inhibition of the synthesis of NO triggered by iNOS diminishes the deleterious effects of the parasite upon the host, especially the vascular alterations in the lungs. We could show that in vivo production of NO induced by infection with T. canis results in direct host damage. Thus, this induction may constitute an evasion/adaptation mechanism of the parasite.
Cytokines and nitric oxide as effector molecules against parasitic infections
Philosophical Transactions of the Royal Society B: Biological Sciences, 1997
Nitric oxide (NO) derived from L-arginine by the catalytic action of inducible NO synthase (iNOS) plays an important role in killing parasites. Many cell types express high levels of iNOS when activated by a number of immunological stimuli which include interferon-gamma (IFN-), tumour necrosis factor alpha, and lipopolysaccharide. IFN-is typically produced by the Th1 subset of CD4+ T cells, whose di¡erentiation depends on interleukin-12 (IL-12) produced by macrophages. Mice with a disrupted iNOS gene were highly susceptible to Leishmania major infection compared with similarly infected control wild-type mice.The mutant mice developed signi¢cantly higher levels of TH1-cell response compared with the control mice, suggesting that NO is likely to be the e¡ector molecule in the immunological control of this and other intracellular parasitic infections. To ensure their survival, the Leishmania parasites have evolved e¡ective means to inhibit NO synthesis. The highly conserved major surface glycolipids, glycoinositol-phospholipids and lipophosphoglycan (LPG), of Leishmania are potent inhibitors of NO synthesis. Furthermore, LPG can also inhibit IL-12 synthesis, thereby indirectly blocking the induction of iNOS. The evolutionary and therapeutic implications of these ¢ndings are discussed.
Nitric oxide blocks the development of the human parasiteSchistosoma japonicum
Proceedings of the National Academy of Sciences
Human schistosomiasis, caused bySchistosomaspecies, is a major public health problem affecting more than 700 million people in 78 countries, with over 40 mammalian host reservoir species complicating the transmission ecosystem. The primary cause of morbidity is considered to be granulomas induced by fertilized eggs of schistosomes in the liver and intestines. Some host species, like rats (Rattus norvegicus), are naturally intolerant toSchistosoma japonicuminfection, and do not produce granulomas or pose a threat to transmission, while others, like mice and hamsters, are highly susceptible. The reasons behind these differences are still a mystery. Using inducible nitric oxide synthase knockout (iNOS−/−) Sprague–Dawley rats, we found that inherent high expression levels of iNOS in wild-type (WT) rats play an important role in blocking growth, reproductive organ formation, and egg development inS. japonicum, resulting in production of nonfertilized eggs. Granuloma formation, induced by...
Parasitology Research, 2001
Entamoeba histolytica trophozoites were inoculated into the liver of hamsters and serum nitrate/ nitrite levels [expressed as nitric oxide (NO) production] were determined at dierent times during amebic liver abscess (ALA) development. We also tested the eects of NO synthase (NOS) inhibitors such as N G-nitro-L-arginine methyl ester (L-NAME), aminoguanidine, and dexamethasone during ALA production. Since NOS activity has been correlated with expression of reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) in tissues, we performed histochemistry studies to determine the activity of the latter in livers infected with E. histolytica trophozoites. Production of NO in serum was directly proportional to the size of ALAs, and NOS inhibitors caused low levels of NO and smaller ALAs. Our data suggest that NO does not have any lytic eect on E. histolytica trophozoites and is therefore incapable of providing protection against the amebic liver infection. In addition, NADPHd activity was detected histochemically in hepatocytes and in¯ammatory cells associated with focal necrosis containing trophozoites. The positive reactivity observed in these parasites may be attributable to a close biochemical similarity of NADPHd to the NAD-PH:¯avin oxidoreductase described in E. histolytica by other investigators.
A dichotomous role for nitric oxide during acute Toxoplasma gondii infection in mice
Proceedings of the National Academy of Sciences of the United States of America, 1997
Production of nitric oxide by macrophages is believed to be an important microbicidal mechanism for a variety of intracellular pathogens, including Toxoplasma gondii. Mice with a targeted disruption of the inducible nitric oxide synthase gene (iNOS) were infected orally with T. gondii tissue cysts. Time to death was prolonged compared with parental controls. Histologic analysis of tissue from infected mice showed scattered small foci of inflammation with parasites in various tissues of iNOS-/- mice, whereas tissue from the parental C57BL/6 mice had more extensive tissue inflammation with few visible parasites. In particular, extensive ulceration and necrosis of distal small intestine and fatty degeneration of the liver was seen in the parental mice at day 7 postinfection, as compared with the iNOS-/- mice where these tissues appeared normal. Serum interferon γ and tumor necrosis factor α levels postinfection were equally elevated in both mouse strains. Treatment of the parental mice with a NO synthase inhibitor, aminoguanidine, prevented early death in these mice as well as the hepatic degeneration and small bowel necrosis seen in acutely infected control parentals. These findings indicate that NO production during acute infection with T. gondii can kill intracellular parasites but can be detrimental, even lethal, to the host.
Brazilian Journal of Medical and Biological Research, 1999
Nitric oxide (NO) is an extremely important and versatile messenger in biological systems. It has been identified as a cytotoxic factor in the immune system, presenting anti-or pro-inflammatory properties under different circumstances. In murine monocytes and macrophages, stimuli by cytokines or lipopolysaccharide (LPS) are necessary for inducing the immunologic isoform of the enzyme responsible for the high-output production of NO, nitric oxide synthase (iNOS). With respect to human cells, however, LPS seems not to stimulate NO production in the same way. Addressing this issue, we demonstrate here that peripheral blood mononuclear cells (PBMC) obtained from schistosomiasis-infected patients and cultivated with parasite antigens in the in vitro granuloma (IVG) reaction produced more nitrite in the absence of LPS. Thus, LPS-induced nitrite levels are easily detectable, although lower than those detected only with antigenic stimulation. Concomitant addition of LPS and L-N-arginine methyl ester (L-NAME) restored the ability to produce detectable levels of nitrite, which had been lost with L-NAME treatment. In addition, LPS caused a mild decrease of the IVG reaction and its association with L-NAME was responsible for reversal of the L-NAME-exacerbating effect on the IVG reaction. These results show that LPS alone is not as good an NO inducer in human cells as it is in rodent cells or cell lines. Moreover, they provide evidence for interactions between LPS and NO inhibitors that require further investigation. Correspondence A.M. Goes
Journal of Experimental Medicine, 1997
The induction by IFN-γ of reactive nitrogen intermediates has been postulated as a major mechanism of host resistance to intracellular pathogens. To formally test this hypothesis in vivo, the course of Toxoplasma gondii infection was assessed in nitric oxide synthase (iNOS)−/− mice. As expected, macrophages from these animals displayed defective microbicidal activity against the parasite in vitro. Nevertheless, in contrast to IFN-γ−/− or IL-12 p40−/− animals, iNOSdeficient mice survived acute infection and controlled parasite growth at the site of inoculation. This early resistance was ablated by neutralization of IFN-γ or IL-12 in vivo and markedly diminished by depletion of neutrophils, demonstrating the existence of previously unappreciated NO independent mechanisms operating against the parasite during early infection. By 3-4 wk post infection, however, iNOS knockout mice did succumb to T. gondii. At that stage parasite expansion and pathology were evident in the central nervous...
Nitric Oxide Donors with Therapeutic Strategic in Experimental Schistossomiasis Mansoni
American Journal of Immunology, 2014
Schistosomiasis, an immune disease, remains a major public health problem in endemic area. To determine the influence of Nitric Oxide (NO) on this disease, we tested two compounds (Trans-[Ru(bpy) 2 (NO)SO3](PF)-PF 6 and Na 2 [Fe(CN) 5 (NO)]-SNP, which releases NO when activated by biological reducing agents, in BALB/c mice infected subcutaneously by Schistosoma BH strains. The parasitic activity of NO-donors was evaluated in this model by measuring the immune cellular response in liver with: Cytokines levels; histopathological characteristics and the number of the granulomatous lesions; and NO levels. We found that NO-donors treated mice were more resistant to infection, since they exhibited higher survival. Furthermore, we observed in histopathological analysis a decreased influx of inflammatory cells in the hepatic tissue of mice treated with both donors. The parasite counting (estimated as eggs and worms number) was also minor in treated mice. Moreover, decreased levels of IL-10 were detected in the liver of infected mice treated with SNP. The animals treated with PF 6 showed high plasmatic NO levels at 45 days after infection. Altogether, these data suggest that NO is a pivotal factor of resistance during schistossomiasis by controlling parasites proliferation, influencing cytokine production and consequently modulating the development of inflammatory response.