Effects of methylprednisolone and glatiramer acetate on nitric oxide formation of cytokine-stimulated cells from the rat oligodendroglial cell line OLN-93.

OBJECTIVES: In multiple sclerosis, an autoimmune inflammatory disease, oligodendroglia are primarily affected and play an important role in the onset and process of the degeneration of neuronal axons. High-dose therapy with glucocorticoids like 6alpha-methylprednisolone (MP) as well as the application of immunomodulatory agents like glatiramer acetate (GA) are commonly used in the treatment of MS. The purpose of our study was to examine, in an adequate cell culture model, the effect of MP and GA on oligodendroglial activation induced by pro-inflammatory stimuli. METHODS: In the present study, we measured the mRNA (real-time RT-PCR) and protein (Western blot) expression of inducible nitric oxide synthase (iNOS) and the release of nitric oxide (NO; Griess reagent) of rat oligodendroglial progenitor cell line OLN-93 after pro-inflammatory stimulation, and searched for influences of MP and GA on these parameters. OLN-93 cells were treated either with a combination of TNF-alpha and IFN-gamma alone, or additionally with MP or GA. Cell viability and cell protein contents were determined in parallel. RESULTS: Our results show that TNF-alpha and IFN-gamma increased iNOS mRNA and protein expression and the NO production in OLN-93 cells. The elevated production of NO and iNOS protein was reduced in the presence of MP, whereas under treatment with GA, the cytokine-induced overproduction of NO did not change significantly. CONCLUSIONS: The presented data suggest an active role of oligodendroglial cells in inflammatory processes like multiple sclerosis and indicate different properties of MP and GA regarding immunosuppression.

Human neuromelanin induces neuroinflammation and neurodegeneration in the rat substantia nigra: implications for Parkinson's disease.

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by a selective loss of dopaminergic neurons in the substantia nigra (SN). It has been suggested that microglial inflammation augments the progression of PD. Neuromelanin (NM), a complex polymer pigment found in catecholaminergic neurons, has sparked interest because of the suggestion that NM is involved in cell death in Parkinson's disease, possibly via microglia activation. To further investigate the possible role of NM in the pathogenesis of PD, we conducted in vivo experiments to find out whether microglial cells become activated after injection of human neuromelanin (NM) into (1) the cerebral cortex or (2) the substantia nigra to monitor in this PD-relevant model both microglial activation and possible neurodegeneration. In this study, adult male Wistar rats received an intracerebral injection of either NM, bacterial lipopolysaccharide (LPS, positive control), phosphate-buffered saline (PBS, negative control) or colloidal gold suspension (negative particular control). After different survival times (1, 8 or 12 weeks), brain slices from the cerebral cortex or substantia nigra (SN, 1 week) were stained with Iba-1 and/or GFAP antibody to monitor microglial and astrocytic reaction, and with tyrosine hydroxylase (TH) to monitor dopaminergic cell survival (SN group only). The injection of LPS induced a strong inflammatory response in the cortex as well in the substantia nigra. Similar results could be obtained after NM injection, while the injection of PBS or gold suspension showed only moderate or no glial activation. However, the inflammatory response declined during the time course. In the SN group, there was, apart from strong microglia activation, a significant dopaminergic cell loss after 1 week of survival time. Our findings clearly indicate that extracellular NM could be one of the key molecules leading to microglial activation and neuronal cell death in the substantia nigra. This may be highly relevant to the elucidation of therapeutic strategies in PD.