Chemokines have been shown to be involved in brain development, in the maintenance of normal brain homeostasis, and in the migration, differentiation, and proliferation of glial and neuronal cells. Chemokine and chemokine receptor expression can be increased by inflammatory mediators and have been associated with a number of neuroinflammatory and neurological disorders including multiple sclerosis, trauma, stroke, AIDS dementia, tumor progression and Alzheimers Disease (AD). The hallmark pathological feature of AD is the accumulation of b-amyloid (Ab) plaques, the ensuing neurodegeneration and neuroinflammation within the brains of AD patients. There are several forms of Ab, including Ab1-40 and 1-42, each exhibiting differing cellular associations as well as neurotoxic potency. For example, Ab 1-40 is primarily associated with reactive astrocytes, while Ab 1-42 is associated with activated microglia-macrophages and exhibits greater neurotoxic potency than Ab 1-40. The presence of activated glia in both cases results in the production of chemokines and inflammatory cytokines, which we believe may mediate as well as exacerbate Ab-induced neurotoxicity. We and others have recently shown that chemokines may contribute to the neurodegenerative processes within a truamatized CNS or during ongoing disease states. Using cDNA microarray technology, we have analyzed the effect of the two forms of Ab peptide on neuronal and astroglial populations and their ability to induce differential gene expression. A number of proinflammatory (including chemokines and several CCRs), apoptotic, and glutamate receptor-associated genes were found to be upregulated in human astrocytes and neuronal cells. We are currently examining the specific role of these genes in Ab-mediated activation and cell death as well as examining histological sections of control aged and AD brain tissue for the RNA and protein expression of the genes in question. We believe these studies may elucidate the pathways via which glia cells may directly and indirectly mediate neuroinflammation, neurodegeneration and AD pathology. In addition to the work above, we have recently acquired highly defined hippocampal tissue from AD patients along with age-matched counterparts with the hope of building a model defining the inflammatory mechanisms of AD as well as Ab- and chemokine-induced neurotoxicity and astrocyte activation. The goals of this project are to characterize and compare the gene expression profile of CNS tissue obtained from trauma, Parkinson disease, age- and pathology-related dementia and AD patients as well as age-matched control subjects using cDNA microarray analysis. We have now completed the screening of a series of human AD brain samples. RNA were isolated from chunks of fresh frozen inferior parietal lobes (IPL) slices from 6 AD patients and 6 non-AD age-matched controls, reverse-transcribed in the presence of 33P-dCTP and hybridized to our arrays. By sampling across a given slice of tissue, we obtained a genetic composite of up- and down-regulated genes from Alzheimers and control IPL. Spot densities obtained from the scanned filters were subjected to a Z-transformation, and a correlation and linear regression analysis with cut-offs of s = 0.95 for controls and s = 0.90 for AD samples. Interestingly, 3/6 AD samples were control-like in our analysis of spot densities, which could be due to our sampling procedure (e.g., sample did not contain a high amount of pathology). Nevertheless, the genes in the 3/6 AD samples suggest ongoing neuronal degeneration, (Caspase 9 and BCL2), and inflammation (colony stimulating factor 3 receptor and TNF). We have now confirmed the tissue- and subject-related expression of these genes both on an mRNA and protein level. Overall, we believe there are both common and distinct biochemical and molecular mechanisms involved in both acute and chronic neurodegenerative and neuroinflammatory processes. Understanding the commonality between these various pathways may provide valuable information into the diagnosis and control of these disease states.
