Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations in beta-globin, glucose-6-phosphate dehydrogenase, and promoters for tumor necrosis factor-alpha and inducible nitric oxide synthase (iNOS) were examined for associations with the incidence of symptomatic malaria in a cohort of 307 Ugandan children. After adjustment of incidence rates for age, water source, use of preventative measures, and proximity to mosquito breeding sites, glucose-6-phosphate dehydrogenase A- heterozygous females had a significantly higher incidence of malaria (incidence rate ratio [IRR] = 1.63, P = 0.03) and a trend towards higher parasite densities (37,100 versus 26,200 parasites/microL; P = 0.18) compared with wild-type children. Male hemizygotes had trends in the same direction. Heterozygotes for sickle hemoglobin had trends toward a lower incidence of malaria and lower parasite density at presentation. Heterozygotes for the iNOS promoter G954C polymorphism, but not other promoter polymorphisms, had a significantly lower incidence of malaria compared with wild-type children (IRR = 0.69, P = 0.05). Host polymorphisms appear to impact upon the incidence of uncomplicated malaria in Ugandan children.
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PMID:Host polymorphisms and the incidence of malaria in Ugandan children. 1564 65

Chloroquine, a well-known lysosomotropic agent, has long been used for the treatment of malaria and rheumatologic disorders. However, therapeutic doses of chloroquine are known to cause behavioral side effects. In the present study, we investigated whether chloroquine stimulates inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) synthesis in C6 glioma cells. Chloroquine caused dose-dependent increase in iNOS protein expression and NO production in C6 glioma cells. A tyrosine kinase inhibitor (genistein), a protein kinase C (PKC) inhibitor (Ro 31-8220), and a p38 mitogen-activated protein kinase (MAPK) inhibitor (SB 203580) all respectively suppressed chloroquine-induced iNOS expression and NO release from C6 glioma cells. Chloroquine activates p38 MAPK and stimulates PKC-alpha and -delta translocation from the cytosol to the membrane in C6 glioma cells. Chloroquine-stimulated p38 MAPK activation was blocked by genistein (20 microM), Ro 31-8220 (3 microM), and SB 203580 (10 microM). Incubation of lipopolysaccharide (LPS)-stimulated cells with chloroquine at non-toxic concentrations (10-100 microM) for 48 h increased iNOS expression, and led to a significant loss of adherent cells. Induction of DNA fragmentation in floating cells indicated that the C6 glioma cells were undergoing apoptosis. Taken together, our data suggest that chloroquine may activate tyrosine kinase and/or PKC to induce p38 MAPK activation, which in turn induces iNOS expression and NO production.
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PMID:Chloroquine induces the expression of inducible nitric oxide synthase in C6 glioma cells. 1568 46

Nitric oxide (NO) has toxic properties against Plasmodium falciparum. While high blood levels have been associated with protection against severe malarial disease, they may also contribute to the pathophysiology of cerebral malaria and severe anaemia. Promoter variants in the inducible nitric oxide synthase (iNOS) gene have been shown to influence NO concentrations and disease manifestation. However, findings are conflicting. We examined associations of plasma NO metabolites (NOx) with symptoms of severe malaria, particularly malarial anaemia and cerebral malaria, and with iNOS promoter variants. In 210 Ghanaian children with severe malaria, we measured plasma nitrite, nitrate, and S-nitrosothiol, and genotyped the iNOS promoter variants -954G-->C, -1173C-->T, and the -2.5 kb (CCTTT)(n) microsatellite. NOx levels decreased with age. In young children (<24 months), high NOx was associated with reduced parasite density. This was not seen in patients of 24-48 months of age and reversed in older children. Subgroup analysis revealed that in children with severe anaemia but without cerebral involvement (prostration, impaired consciousness, convulsions), high NOx levels correlated with low parasitaemia (P = 0.02). In these children, elevated NOx levels were also associated with the iNOS-954C-->T/(CCTTT)(8) haplotype (P = 0.03). No association between NOx or iNOS genotypes and cerebral malaria was observed. Our findings suggest that in young children with severe malaria NOx reduces parasitaemia. This effect wanes at higher ages and may reflect a predominance of unspecific immune responses to infection in early childhood. This finding may have importance for the understanding of associations between iNOS variants and severe malaria in regions of differing disease manifestation.
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PMID:Age-dependent effect of plasma nitric oxide on parasite density in Ghanaian children with severe malaria. 1596 Jul 6

Cerebral malaria, one of the most serious complications of Plasmodium falciparum infection, is characterized by the sequestration of parasitized red blood cells (PRBCs) in cerebral microvascular beds. The precise mechanisms involved in the onset of neuropathology remain unknown, but parasite sequestration in the brain, metabolic disturbances, and host immune responses all play a role. Sequestration of PRBCs is mediated by different endothelial cell surface receptors, mainly ICAM-1 and CD36. In vitro studies demonstrated that PRBC adhesion to endothelial cells induces over-expression of various adhesion molecules including ICAM-1, expression of iNOS, oxidative stress and finally apoptosis in endothelial cells. In vivo studies, in humans and in mice models of cerebral malaria brought striking evidence of the implication of brain infiltrating cytotoxic effector CD8T lymphocytes in the development of murine cerebral malaria pathogenesis. These cells probably act by direct cytotoxicity against endothelial cells. Cytotoxicity and apoptosis potentially lead blood-brain-barrier disruption and could contribute to the development of cerebral malaria. We propose a key role for endothelial cells in the pathogenesis of cerebral malaria, both by suicide / apoptosis, and / or by murder / cytotoxicity.
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PMID:Blood-brain barrier breakdown during cerebral malaria: suicide or murder? 1611 23

Malaria is one of the most important global health problems, potentially affecting more than one third of the world's population. Cerebral malaria (CM) is a deadly complication of Plasmodium falciparum infection, yet its pathogenesis remains incompletely understood. In this review, we discuss some of the principal pathogenic events that have been described in murine models of the disease and relate them to the human condition. One of the earliest events in CM pathogenesis appears to be a mild increase in the permeability to protein of the blood-brain barrier. Recent studies have shown a role for CD8+T cells in mediating damage to the microvascular endothelium and this damage can result in the leakage of cytokines, malaria antigens and other potentially harmful molecules across the blood-brain barrier into the cerebral parenchyma. We suggest that this, in turn, leads to the activation of microglia and the activation and apoptosis of astrocytes. The role of hypoxia in the pathogenesis of cerebral malaria is also discussed, with particular reference to the local reduction of oxygen consumption in the brain as a consequence of vascular obstruction, to cytokine-driven changes in glucose metabolism, and to cytopathic hypoxia. Interferon-gamma, a cytokine known to be produced in malaria infection, induces increased expression, by microvascular endothelial cells, of the haem enzyme indoleamine 2,3-dioxygenase, the first enzyme in the kynurenine pathway of tryptophan metabolism. Enhanced indoleamine 2,3-dioxygenase expression leads to increased production of a range of biologically active metabolites that may be part of a tissue protective response. Damage to astrocytes may result in reduced production of the neuroprotectant molecule kynurenic acid, leading to a decrease in its ratio relative to the neuroexcitotoxic molecule quinolinic acid, which might contribute to some of the neurological symptoms of cerebral malaria. Lastly, we discuss the role of other haem enzymes, cyclooxygenase-2, inducible nitric oxide synthase and haem oxygenase-1, as potentially being components of mechanisms that protect host tissue against the effects of cytokine- and leukocyte-mediated stress induced by malaria infection.
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PMID:Immunopathogenesis of cerebral malaria. 1667 81

Nitric oxide (NO) has been shown to play a crucial role in various physiological and pathological conditions. NO plays a role in the immunoregulation and it is implicated in the host non-specific defence in a variety of infections. Abundant evidence indicates that NO contributes to the host defence function of macrophages. High levels of NO are mediated by up-regulated expression of the iNOS gene in response to the activating signals, in particular to the secretion of pro-inflammatory cytokines (IFN-gamma, TNF-alpha, IL-1, IL-2) by Thl cells. In this review, the role of NO during a number of parasitic infections has been summarized. Up to now, enhanced levels of NO production and expression of iNOS gene have been described in such infective diseases as malaria, toxoplasmosis, leishmaniosis, trypanosomosis and schistosomosis. During these infections, the preferential production of pro-inflammatory cytokines predisposes to the increased synthesis of NO, which mediates host protection through either direct parasite killing or by limiting parasite growth. The evidence presented in this review supports the conclusion that NO plays an important role in the majority of parasitic infections.
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PMID:[The role of nitric oxide (NO) in parasitic infections]. 1686 1

The most common and deadly form of the malaria parasite, Plasmodium falciparum, is responsible for 1.5-2.7 million deaths and 300-500 million acute illnesses annually [Bremen in J. Trop. Med. Hyg. 64:1-11 (2001); World Health Organization (2002)]. Hemozoin, the biomineral formed to detoxify the free heme produced during parasitic hemoglobin catabolism, has long been suspected of contributing to the pathological immunodeficiencies that occur during malarial infection. While there is a growing consensus in the literature that native hemozoin maintains immunosuppressive activity, there is considerable controversy over the reactivity of the synthetic form, beta-hematin (BH). Given the emerging importance of hemozoin in modulating a host immune response to malarial infection, a careful examination of the effects of the constitutive components of the malaria pigment on macrophage response has been made in order to clarify the understanding of this process. Herein, we present evidence that BH alone is unable to inhibit stimulation of NADPH oxidase and inducible nitric oxide synthase, the key enzymes involved in oxidative burst, and is sensitive to the microbicidal agents of these enzymes both in vitro and in vivo. Further, by systematically examining each of the malaria pigment's components, we were able to dissect their impact on the immune reactivity of a macrophage model cell line. Reactions between BH and red blood cell (RBC) ghosts effectively reconstituted the observed immunomodulatory reactivity of native hemozoin. Together, these results suggest that the interaction between hemozoin and the RBC lipids results in the generation of toxic products and that these products are responsible for disrupting macrophage function in vivo.
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PMID:The basis of the immunomodulatory activity of malaria pigment (hemozoin). 1686 43

The pathogenesis of cerebral malaria, a major complication of Plasmodium falciparum infection, relies on mechanisms such as cytokine production and cytoadherence of parasitized red blood cells (PRBCs) on microvascular endothelial cells. In this way parasites avoid spleen clearance by sequestration in post-capillary venules of various organs including the brain. Infected erythrocytes adhesion has also been shown to have molecular signaling consequences providing insight on how tissue homeostasis could be comprised by endothelium perturbation. Our previous work demonstrated that PRBCs adhesion to human lung endothelial cells (HLEC) induces caspases activation, oxidative stress and apoptosis. Cytoplasmic Cu/Zn superoxide dismutase (SOD1), which provides the first line of defense against oxidative stress within a cell, is now used as a treatment of numerous diseases including traumatic brain injury and ischemic stroke. In this report, we demonstrated that transient supplementation of SOD1 protects endothelial cells against P. falciparum induced oxidative stress and apoptosis. We also showed a significant decrease in PRBCs cytoadherence through a downregulation of ICAM-1 and an induction of iNOS. Protection of endothelium via antioxidant delivery may constitute a relevant strategy in cerebral malaria treatment.
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PMID:Transient supplementation of superoxide dismutase protects endothelial cells against Plasmodium falciparum-induced oxidative stress. 1693 Jul 39

Despite decades of research and multiple initiatives, malaria continues to be one of the world's most debilitating infectious diseases. New insights for malaria control and vaccine development will be essential to thwart the staggering worldwide impact of this disease (A. Bjorkman and A. Bhattarai, Acta Trop. 94:163-169, 2005); ultimately successful vaccine strategies will undoubtedly be multifactorial, incorporating multiple antigens and targeting diverse aspects of the malaria parasites' biology (M. F. Good et al., Immunol. Rev. 201:254-267, 2004). Using a murine model of malaria infection, we show here that exposure to bites from uninfected mosquitoes prior to Plasmodium yoelii infection influences the local and systemic immune responses and limits parasite development within the host. In hosts preexposed to bites from uninfected mosquitoes, reduced parasite burdens in the livers were detected early, and during the blood-stage of the life cycle, these burdens remained lower than those in hosts that received mosquito bites only at the time of infection. Repeated exposure to bites from uninfected mosquitoes skewed the immune response towards a T-helper 1 (Th1) phenotype as indicated by increased levels of interleukin-12, gamma interferon, and inducible nitric oxide synthase. These data suggest that the addition of mosquito salivary components to antimalaria vaccines may be a viable strategy for creating a Th1-biased environment known to be effective against malaria infection. Furthermore, this strategy may be important for the development of vaccines to combat other mosquito-transmitted pathogens.
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PMID:Uninfected mosquito bites confer protection against infection with malaria parasites. 1733 56

The intracellular protozoan parasite Leishmania causes leishmaniasis, which is the second biggest killer worldwide among parasitic diseases, after malaria. As drug therapy for leishmaniasis is toxic and resistance is growing, a vaccine is an important weapon against this disease. Unfortunately, no effective vaccine exists for any human parasitic infection. Worse yet, nearly all effective vaccines whose mechanisms are known work through the induction of protective antibodies. Leishmania mexicana causes primarily chronic cutaneous disease. Not only are antibodies not effective at killing Leishmania, as it hides inside the parasitophorous vacuole of the host cell, but new research indicates that IgG antibodies may be crucial in suppressing the host immune response by generating an immunosuppressive interleukin-10 response. IL-10 is able to decrease the needed Th1-generated IFN-gamma and downregulates production of nitric oxide, a required effector mechanism of parasite killing. We have been studying the pathways that the host uses to partially control L. mexicana infection, which include STAT4, IFN-gamma, and inducible nitric oxide synthase, but found that the IL-12 pathway is suppressed by IL-10. We are now studying the mechanisms by which IgG, bound to parasites, can induce IL-10 through FcgammaR ligation and how this suppresses a healing immune response. We are examining which IgG isotypes bind to which FcgammaRs and whether macrophages are the necessary source of IL-10 for chronic disease. Elucidation of these mechanisms may help us to design vaccines that will not induce antibody-mediated immunosuppressive IL-10 responses.
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PMID:A detrimental role for IgG and FcgammaR in Leishmania mexicana infection. 1900 8


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