Expression of inducible nitric oxide synthase (iNOS) protein was studied in the brain after intracerebroventricular injections of interferon (IFN)-γ, and IFN-γ combined with lipopolysaccharide (LPS) or tumor necrosis factor (TNF)-α, compared to ovalbumin as control. Wild-type mice and mice with targeted deletion of the IFN-γ receptor gene were used. Findings based on iNOS immunoreactivity were evaluated at 1, 2, 4 and 7 days post-injection, using also quantitative image analysis and double labeling with glial cell markers. IFN-γ administration induced iNOS immmunostaining in activated microglia and macrophages in the parenchyma surrounding the ventricular system, several cortical fields and fiber tracts. IFN-γ-elicited iNOS immunoreactivity was down-regulated after 1 day. The number of iNOS-immunopositive cells was significantly enhanced by co-administration of LPS or TNF-α; IFN-γ+TNF-α injections also resulted in longer persistence of iNOS immunoreactivity. No immunopositive cells were seen in the brain of IFN-γ receptor knockout mice after IFN-γ administration; very few immunostained macrophages were detected in these cases, mostly around the injection needle track, after co-administration of LPS or TNF-α. Western blot analysis confirmed a marked iNOS induction in the brain of wild-type mice 24 h after IFN-γ+LPS injections. The findings show that inflammatory mediators circulating in the cerebrospinal fluid induce in vivo iNOS in the brain with topographical selectivity and temporal regulation. The data also demonstrate that the signaling cascade activated by IFN-γ binding to its receptor is critical for iNOS induction, and the synergistic action of LPS and TNF-α as iNOS inducers in brain cells is largely mediated by the receptor-regulated action of IFN-γ. (C) 2000 Elsevier Science B.V.
Inducible nitric oxide synthase expression elicited in the mouse brain by inflammatory mediators circulating in the cerebrospinal fluid
Costanzo C.;Bentivoglio M.
2000-01-01
Abstract
Expression of inducible nitric oxide synthase (iNOS) protein was studied in the brain after intracerebroventricular injections of interferon (IFN)-γ, and IFN-γ combined with lipopolysaccharide (LPS) or tumor necrosis factor (TNF)-α, compared to ovalbumin as control. Wild-type mice and mice with targeted deletion of the IFN-γ receptor gene were used. Findings based on iNOS immunoreactivity were evaluated at 1, 2, 4 and 7 days post-injection, using also quantitative image analysis and double labeling with glial cell markers. IFN-γ administration induced iNOS immmunostaining in activated microglia and macrophages in the parenchyma surrounding the ventricular system, several cortical fields and fiber tracts. IFN-γ-elicited iNOS immunoreactivity was down-regulated after 1 day. The number of iNOS-immunopositive cells was significantly enhanced by co-administration of LPS or TNF-α; IFN-γ+TNF-α injections also resulted in longer persistence of iNOS immunoreactivity. No immunopositive cells were seen in the brain of IFN-γ receptor knockout mice after IFN-γ administration; very few immunostained macrophages were detected in these cases, mostly around the injection needle track, after co-administration of LPS or TNF-α. Western blot analysis confirmed a marked iNOS induction in the brain of wild-type mice 24 h after IFN-γ+LPS injections. The findings show that inflammatory mediators circulating in the cerebrospinal fluid induce in vivo iNOS in the brain with topographical selectivity and temporal regulation. The data also demonstrate that the signaling cascade activated by IFN-γ binding to its receptor is critical for iNOS induction, and the synergistic action of LPS and TNF-α as iNOS inducers in brain cells is largely mediated by the receptor-regulated action of IFN-γ. (C) 2000 Elsevier Science B.V.
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