Glial Inducible Nitric Oxide Synthase Research Articles

Nitric oxide, hypoxia and brain inflammation

NO (nitric oxide) acutely and potently inhibits mitochondrial cytochrome oxidase in competition with oxygen, thereby raising the apparent K(M) for oxygen of mitochondria and neurons into the physiological or pathological range. We find that NO from an NO donor or glial inducible NOS (nitric oxide synthase) highly sensitizes neurons to hypoxia-induced death, probably via the NO-oxygen competition at cytochrome oxidase. Thus the NO from neuronal NOS during excitotoxicity or the NO from inducible NOS during inflammation may sensitize the brain to hypoxic/ischaemic damage.

Inhibitory Effects of Cigarette Smoke on Glial Inducible Nitric Oxide Synthase and Lack of Protective Properties Against Oxidative Neurotoxins In Vitro

Epidemiological studies consistently report an inverse correlation between cigarette smoking and associated risk for Parkinson's disease (PD). The degeneration of dopaminergic neurons may involve the toxic metabolic products of glial cell monoamine oxidase (MAO) and inducible nitric oxide synthase (iNOS). This study evaluates the direct protective effects of cigarette smoke (CS) against potential neurotoxic products of MAO, such as 1-methyl-4-phenylpyridinium (MPP +), 6-hydroxydopamine (6-OHDA) and hydrogen peroxide (H 2O 2) in brain neuroblastoma. Moreover, the effects of CS were also evaluated on endotoxin/cytokine activated glioma iNOS protein expression and MAO enzyme activity. Cigarette smoke condensates (CSCs) were acquired from Marlboro 20 Class A and Kentucky 2R4F reference research (2R4F) cigarettes. The CSCs did not protect against 6-OHDA or H 2O 2 toxicity in neuroblastoma, and exhibited a very mild protective effect [∼10%] against MPP +. Neither CSC demonstrated antioxidant capability, but conversely contained high concentration of NO 2 − . Paradoxically, in glioma cells, iNOS protein expression and endogenous enzymatic NO 2 − production were significantly blocked by both CSCs. Both CSCs also inhibited glioma MAO-A and MAO-B [1.4.3.4]. Kinetic analysis indicated that 2R4F–CSC displayed competitive inhibition and the Marlboro–CSC exerted potent competitive and non-competitive inhibition. In conclusion, these data suggest that cigarette smoke does not appear to directly protect against the toxicity of the selected neurotoxins. In contrast, CS exerts pronounced effects on glia, whereby its presence can simultaneously attenuate cytokine induction of iNOS and MAO.

Mechanism of glial activation by S100B: involvement of the transcription factor NFkappaB.

Compelling evidence links chronic activation of glia and the subsequent cycle of neuroinflammation and neuronal dysfunction to the progression of neurodegeneration in disorders such as Alzheimer's disease (AD). S100B, a glial-derived cytokine, is significantly elevated in the brains of AD patients and high concentrations of S100B are believed to be detrimental to brain function. As a first step toward elucidating the mechanisms by which S100B might be serving this detrimental role, we examined the mechanisms by which S100B stimulates glial inducible nitric oxide synthase (iNOS), an oxidative stress related enzyme that has been linked to neuropathology through the production of neurotoxic peroxynitrite. We report here that S100B stimulates iNOS in rat primary cortical astrocytes through a signal transduction pathway that involves activation of the transcription factor NFkappaB. NFkappaB activation was demonstrated by nuclear translocation of the p65 NFkappaB subunit, stimulation of NFkappaB-specific DNA binding activity, and stimulation of NFkappaB-dependent transcriptional activity. Furthermore, S100B-induced iNOS promoter activation was inhibited upon mutation of the NFkappaB response element in the promoter, and transfection of cells with an NFkappaB inhibitor blocked S100B-induced iNOS promoter activation and nitric oxide production. These studies define a signal transduction pathway by which S100B activation of glia could participate in the generation of oxidative stress in the brain.

Selective inhibition of human glial inducible nitric oxide synthase by interferon‐β: Implications for multiple sclerosis

Nitric oxide generated from the inducible nitric oxide synthase (iNOS) has been implicated in the pathogenesis of multiple sclerosis. Because significant species- and cell-specific differences exist in the expression of iNOS, we used primary human glial cell cultures to screen for an inhibitor of iNOS expression. Remarkably, among numerous soluble factors tested, interferon-beta (IFN-beta) alone showed a selective and potent inhibition of interleukin-1beta/interferon-gamma (IL-1beta/IFN-gamma)-induced iNOS expression in astrocytes. Inhibition of iNOS may provide a mechanism by which IFN-beta can ameliorate inflammation and cytotoxicity in the central nervous system of patients with multiple sclerosis.

CD 14 mediates endotoxin induction of nitric oxide synthase in cultured brain glial cells

Here we show that lipopolysaccharide (LPS) induction of glial inducible nitric oxide synthase (iNOS) requires membrane (m) and soluble (s) forms of CD14. In glial cell cultures, an anti-rat CD14 monoclonal antibody detected CD14 protein in whole cells and cell lysates, and reduced LPS-dependent iNOS expression. Glial cells and normal brain tissue expressed CD14 mRNA, as revealed by isolation of a rat CD14 clone (rCD14) from an astrocyte cDNA library, and RT-PCR analysis. Finally, serum reduced the ED 50 of LPS required for glial iNOS expression, and antibodies against sCD14 blocked the potentiating effect of serum.