Nitric Oxide

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-ß) alone showed a selective and potent inhibition of InterLeukin-ß/Interferon-gamma (IL-ß/IFN-γ) induced INOS expression in Astrocytes.

Inhibition of INOS may provide a mechanism by which IFN-ß can ameliorate Inflammation and CytoToxicity in the Central Nervous System of patients with MS.

Excessive Nitric Oxide/Peroxynitrite generation has been implicated in the PathoGenesis of Multiple Sclerosis, and the demonstration of increased Astrocytic Nitric Oxide Synthase activity in the postmortem Brain of Multiple Slerosis patients supports this hypothesis.

Interferon-ß is used for the treatment of Multiple Sclerosis, but currently little is known regarding its mode of action.

Exposure of Astrocytes in culture to Interferon-γ plus LipoPolySaccharide results in stimulation of Nitric Oxide release.

Using a co-culture system, we have been able to use Astrocytes as a source of Nitric Oxide/Peroxynitrite in an attempt to "model" the effects of raised Cytokine levels observed in Multiple Sclerosis and to monitor the effect on Neurons.

Our results indicate that stimulation of Astrocytic Nitric Oxide Synthase activity causes significant damage to the Mitochondrial activities of complexes II/III and IV of neighboring Neurons.

This damage was prevented by a Nitric Oxide Synthase inhibitor, suggesting that the damage was Nitric Oxide-mediated. Furthermore, Interferon-/ß also prevented this damage.

In view of these results, we suggest that a possible mechanism of action of IFN-ß in the treatment of Multiple Sclerosis is that it prevents Astrocytic Nitric Oxide production, thereby limiting damage to neighboring cells, such as Neurons.

InterLeukin-6 (IL-6) and Nitric Oxide (NO) are implicated in the pathology of Multiple Sclerosis (MS). We have investigated the levels of these mediators in the CerebroSpinal Fluid (CSF) from 50 patients with MS and 23 control subjects.

Mean CSF IL-6 level was higher in the total MS group in comparison with controls, but not significantly, whilst the difference between patients with stable MS and controls reached the level of statistical significance.

Mean CSF Nitrite/Nitrate level was significantly higher in the total MS group compared with the control group, as well as in active MS patients versus controls.

There was significant difference neither in the mean CSF IL-6 nor in Nitrite/Nitrate levels between active and stable MS patients.

Interestingly, we observed a significant negative correlation between IL-6 and Nitrite/Nitrate levels in the CSF in the total MS group.

Such a trend existed in both subgroups with active and stable MS, but without reaching the level of statistical significance.

Our data further support the involvement of IL-6 and NO in ongoing pathological processes in MS, suggesting their potential interplay within the Central Nervous System in this disease.

Increasing evidence has suggested that inflammation in the Brain is closely associated with the pathogenesis of several Degenerative Neurologic Disorders, including Parkinson's Disease, Alzheimer's Diseases, Multiple Sclerosis, Amyotrophic Lateral Sclerosis, and AIDS Dementia.

The hallmark of Brain inflammation is the activation of Glial Cells, especially that of Microglia that produce a variety of ProInflammatory and NeuroToxic factors, including Cytokines, Fatty Acid Metabolites, Free Radicals - such as Nitric Oxide (NO) and SuperOxide.

Excessive production of NO, as a consequence of Nitric Oxide Synthase induction in activated Glia, has been attributed to participate in NeuroDegeneration.

Using primary mixed Neuron-Glia cultures and Glia-enriched cultures prepared from embryonic rodent Brain tissues, we have systemically studied the relationship between the production of NO and NeuroDegeneration in response to stimulation by the inflammagen LipopolySaccharide.

This review summarizes our recent findings on the kinetics of NO generation:
1. The relative contribution of Microglia and Astrocytes to NO accumulation
2. The relationship between NO production and NeuroDegeneration
3. Points of intervention along the pathways associated with NO generation to achieve NeuroProtection

We also describe our results relating to the effect of several Opioid-related agents on Microglial activation and NeuroProtection.

Among these agents, the Opioid Receptor Antagonist Naloxone, especially its NonOpioid Enantiomer ^+-Naloxone, promises to be of potential therapeutic value for the treatment of Inflammation-Related Diseases.

Objective
To investigate the relationship of CSF and the Serum Nitric Oxide metabolites Nitrite and Nitrate (NOx) to disease activity and progression in patients with Multiple Sclerosis (MS).

Methods
The study was divided into cross-sectional and follow-up. In the cross-sectional study, 20 patients with Relapsing/Remitting (RR), 21 with Secondary/Progressive (SP), and 10 with Primary/Progressive (PP) MS and 14 control subjects were included.

Patients were assessed on clinical (Expanded Disability Status Scale [EDSS], Ambulation Index [AI], 9-Hole Peg Test [9-HPT]) and MRI measurements.

In the follow-up study, 34 MS patients from the cross-sectional study agreed to be assessed again after an average of 3.0 +/- 0.5 years. NOx was measured using a vanadium-based assay.

Results
In the cross-sectional study, CSF NOx was raised in patients with RR-MS (p = 0.001) and PP-MS (p = 0.02) vs controls.

Higher CSF NOx levels were found in patients with mild disability (AI < or = 6.0; EDSS < or = 4.0; Multiple Sclerosis Severity Score [MSSS] < or = 4.8) vs patients with advanced disease (AI > 6.0 [p = 0.002]; EDSS > 4.0 [p = 0.02]; MSSS > 4.8 [p = 0.01]).

In the subgroup of patients having Gd-enhancing MRI lesions (n = 11), correlation between the volume of enhancement and CSF NOx was found (r = 0.74, p = 0.01).

In the follow-up study, patients with disability progression had higher baseline CSF NOx levels than those who were stable on EDSS (p = 0.02) or AI (p = 0.03).

A positive correlation was found between baseline CSF NOx and the change in MR T₂-weighted lesion load (r = 0.4, p = 0.03).

Conclusions
CSF Nitrite and Nitrate levels were increased in mildly disabled patients with MS and found to correlate with the volume of Gd-enhanced lesions on MRI.

Raised baseline CSF NOx was associated with clinical and MRI progression in MS patients over 3-year follow-up.