We detected large numbers of HLA-DR-positive reactive microglia (macrophages), along with Lewy bodies and free melanin, in the substantia nigra of all cases studied with Parkinson's disease (5) and parkinsonism with dementia (PD) (5). We found similar, but less extensive, pathology in the substantia nigra of six of nine cases of dementia of the Alzheimer type (DAT) but in only one of 11 age-matched nonneurologic cases. All dementia cases with a premortem diagnosis of DAT or PD showed large numbers of HLA-DR-positive reactive microglia and significant plaque and tangle counts in the hippocampus, as well as reduced cortical choline acetyltransferase activity. One of 11 nondemented controls showed mild evidence of similar cortical pathology. These data indicate that HLA-DR-positive reactive microglia are a sensitive index of neuropathologic activity. They suggest a frequent coexistence of DAT- and Parkinson-type pathology in elderly patients.

No abstract

Alzheimer's disease (AD) lesions are characterized by the presence of numerous inflammatory proteins. This has led to the hypothesis that brain inflammation is a cause of neuronal injury in AD and that anti-inflammatory drugs may act as protective agents. Seventeen epidemiologic studies from nine different countries have now been published in which arthritis, a major indication for the use of anti-inflammatory drugs, or anti-inflammatory drugs themselves have been considered as risk factors for AD. Both factors appear to be associated with a reduced prevalence of AD. The small size of most studies has limited their individual statistical significance, but similarities in design have made it possible to evaluate combined results. We have used established methods of statistical meta-analysis to estimate the overall chance of individuals exposed to arthritis or anti-inflammatory drugs developing AD as compared with the general population. Seven case-control studies with arthritis as the risk factor yielded an overall odds ratio of 0.556 (p < 0.0001), while four case-control studies with steroids yielded odds ratios of 0.656 (p = 0.049) and three case-control studies with nonsteroidal anti-inflammatory drugs (NSAIDs) yielded an odds ratio of 0.496 (p = 0.0002). When NSAIDs and steroids were combined into a single category of anti-inflammatory drugs, the odds ratio was 0.556 (p < 0.0001). Population-based studies were less similar in design than case-control studies, complicating the process of applying statistical meta-analytical techniques. Nevertheless, population-based studies with rheumatoid arthritis and NSAID use as risk factors strongly supported the results of case-control studies. These data suggest anti-inflammatory drugs may have a protective effect against AD. Controlled clinical trials will be necessary to test this possibility.

No abstract

Dopaminergic neurons of the substantia nigra are particularly vulnerable to oxidative and inflammatory attack. Such processes may play a crucial role in the etiology of Parkinson disease (PD). Since glia are the main generators of these processes, the possibility that PD may be caused by glial dysfunction needs to be considered. This review concentrates on glial reactions in PD. Reactive astrocytes and reactive microglia are abundant in the substantia nigra (SN) of PD cases indicating a robust inflammatory state. Glia normally serve neuroprotective roles but, given adverse stimulation, they may contribute to damaging chronic inflammation. Microglia, the phagocytes of brain, may be the main contributors since they can produce large numbers of superoxide anions and other neurotoxins. Their toxicity towards dopaminergic neurons has been demonstrated in tissue culture and various animal models of PD. The MPTP and ␣-synuclein models are of particular interest. Years after exposure to MPTP, inflammation has been observed in the SN. This has established that an acute insult to the SN can result in a sustained local inflammation. The ␣-synuclein model indicates that an endogenous protein can induce inflammation, and, when overexpressed, can lead to autosomal dominant PD. Less is known about the role of astrocytes than microglia, but they are known to secrete both inflammatory and anti-inflammatory molecules and may play a role in modulating microglial activity. Oligodendrocytes do not seem to play a role in promoting inflammation although, like neurons, they may be damaged by inflammatory processes. Further research concerning glial reactions in PD may lead to disease-modifying therapeutic approaches.