J. Neurochem. (2010) 113, 1632–1643. Abstract Catechol‐O‐methyltranferase (COMT) has both soluble (S‐COMT) and membrane‐bound (MB‐COMT) isoforms. A specific COMT antibody was used in immunohistochemical and confocal co‐localization studies to explore the distribution of COMT in general in normal mice and MB‐COMT in particular, in an S‐COMT deficient mouse line. In the peripheral tissues, high COMT protein and activity levels were observed in liver and kidney, whereas in the brain, COMT expression and activity were much lower. MB‐COMT was widely distributed throughout all tissues, and overall, the MB‐COMT distribution mimicked the distribution of S‐COMT. MB‐COMT displayed some preference for brain tissue, notably in the hippocampus. MB‐COMT related enzymatic activity was also pronounced in the cerebral cortical areas and hypothalamus. MB‐COMT, like S‐COMT, was found to be an intracellular enzyme but it was not associated with plasma membranes in the brain. Both COMT forms were abundantly found in microglial cells and intestinal macrophages, but also in astroglial cells. COMT was also present in some neuronal cells, like pyramidal neurons, cerebellar Purkinje and granular cells and striatal spiny neurons, but not in major long projection neurons. Finally, it seemed that nuclear COMT is not visible in S‐COMT deficient mice.

Amantadine is commonly given to alleviate L-DOPA-induced dyskinesia of Parkinson’s disease (PD) patients. Animal and human evidence showed that amantadine may also exert neuroprotection in several neurological disorders. Additionally, it is generally believed that this neuroprotection results from the ability of amantadine to inhibit glutamatergic NMDA receptor. However, several lines of evidence questioned the neuroprotection capacity of NMDA receptor antagonists in animal models of PD. Thus the cellular and molecular mechanism of neuroprotection of amantadine remains unclear. Using primary cultures with different composition of neurons, microglia, and astroglia we investigated the direct role of these different glial cell types in the neuroprotective effect of amantadine. First, amantadine protected rat midbrain cultures from either MPP+ or lipopolysaccharide (LPS), two toxins commonly used PD models. Second, our studies revealed that amantadine reduced both LPS- and MPP+ -induced toxicity of dopamine neuron through 1) the inhibition of the release of microglial pro-inflammatory factors, 2) an increase in expression of neurotrophic factor such as GDNF from astroglia. Lastly, differently from the general view on amantadine´s action, we provided evidence suggesting that NMDA receptor inhibition was not crucial for the neuroprotective effect of amantadine. In conclusion, we report that amantadine protected dopamine neurons in two PD models through a novel dual mechanism, namely reducing the release of pro-inflammatory factors from activated microglia and increasing the expression of GNDF in astroglia.

BACKGROUND AND PURPOSE Prevention or disease‐modifying therapies are critical for the treatment of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Huntington's disease. However, no such intervention is currently available. Growing evidence has demonstrated that administration of histone deacetylase (HDAC) inhibitors ameliorates a wide range of neurologic and psychiatric disorders in experimental models. Suberoylanilide hydroxamic acid (SAHA) was the first HDAC inhibitor approved by the Food and Drug Administration for the sole use of cancer therapy. The purpose of this study was to explore the potential new indications of SAHA for therapy of neurodegenerative diseases in in vitro Parkinson's disease models. EXPERIMENTAL APPROACH Mesencephalic neuron–glia cultures and reconstituted cultures were used to investigate neurotrophic and neuroprotective effects of SAHA. We measured toxicity in dopaminergic neurons, using dopamine uptake assay and morphological analysis and expression of neurotrophic substances by enzyme‐linked immunosorbent assay and real‐time RT PCR. KEY RESULTS In mesencephalic neuron–glia cultures, SAHA displayed dose‐ and time‐dependent prolongation of the survival and protection against neurotoxin‐induced neuronal death of dopaminergic neurons. Mechanistic studies revealed that the neuroprotective effects of SAHA were mediated in part by promoting release of neurotrophic factors from astroglia through inhibition of histone deacetylation. CONCLUSION AND IMPLICATIONS The novel neurotrophic and neuroprotective effects of SAHA demonstrated in this study suggest that further study of this HDAC inhibitor could provide a new therapeutic approach to the treatment of neurodegenerative diseases.