title: Hemozoin increases IFN-gamma-inducible macrophage nitric oxide generation through extracellular signal-regulated kinase- and NF-kappa B-dependent pathways.
abstract: NO overproduction has been suggested to contribute to the immunopathology related to malaria infection. Even though a role for some parasite molecules (e.g., GPI) in NO induction has been proposed, the direct contribution of hemozoin (HZ), another parasite metabolite, remains to be established. Therefore, we were interested to determine whether Plasmodium falciparum (Pf) HZ and synthetic HZ, beta-hematin, alone or in combination with IFN-gamma, were able to induce macrophage (Mphi) NO synthesis. We observed that neither Pf HZ nor synthetic HZ led to NO generation in B10R murine Mphi; however, they significantly increased IFN-gamma-mediated inducible NO synthase (iNOS) mRNA and protein expression, and NO production. Next, by investigating the transductional mechanisms involved in this cellular regulation, we established that HZ induces extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinase phosphorylation as well as NF-kappaB binding to the iNOS promoter, and enhances the IFN-gamma-dependent activation of both second messengers. Of interest, cell pretreatment with specific inhibitors against either NF-kappaB or the ERK1/2 pathway blocked the HZ + IFN-gamma-inducible NF-kappaB activity and significantly reduced the HZ-dependent increase on IFN-gamma-mediated iNOS and NO induction. Even though selective inhibition of the Janus kinase 2/STAT1alpha pathway suppressed NO synthesis in response to HZ + IFN-gamma, HZ alone did not activate this signaling pathway and did not have an up-regulating effect on the IFN-gamma-induced Janus kinase 2/STAT1alpha phosphorylation and STAT1alpha binding to the iNOS promoter. In conclusion, our results suggest that HZ exerts a potent synergistic effect on the IFN-gamma-inducible NO generation in Mphi via ERK- and NF-kappaB-dependent pathways.
authors.affiliation: Centre de Recherche en Infectiologie, Département de Biologie médicale, Faculté de Médecine, Université Laval, Ste-Foy, Québec, Canada.
authors.forename: Maritza
authors.initials: M
authors.lastname: Jaramillo
authors.forename: D Channe
authors.initials: DC
authors.lastname: Gowda
authors.forename: Danuta
authors.initials: D
authors.lastname: Radzioch
authors.forename: Martin
authors.initials: M
authors.lastname: Olivier
mesh_terms: D000818:Animals; D002460:Cell Line; D004340:Drug Contamination; D004357:Drug Synergism; D004789:Enzyme Activation / Q000276:immunology; D006420:Hemeproteins / Q000494:pharmacology / Q000502:physiology*; D050832:Interferon-Stimulated Gene Factor 3; D007371:Interferon-gamma / Q000502:physiology*; D007502:Iron Chelating Agents / Q000494:pharmacology; D053614:Janus Kinase 2; D008070:Lipopolysaccharides / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000276:immunology*; D008264:Macrophages / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism* / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D010963:Plasmodium falciparum / Q000276:immunology; D011401:Promoter Regions, Genetic / Q000276:immunology; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins; D015800:Protozoan Proteins / Q000494:pharmacology / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D014157:Transcription Factors / Q000502:physiology; D015854:Up-Regulation / Q000276:immunology*
chemical_list: D006420:Hemeproteins; D050832:Interferon-Stimulated Gene Factor 3; D007502:Iron Chelating Agents; D008070:Lipopolysaccharides; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C079868:gamma interferon activation factor; D009569:Nitric Oxide; C020753:hemozoin; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases