Gliosis, as evidenced by increases in GFAP staining of astrocytes and activation of microglia, is a common feature of CNS injury. Studies in animal models reveal that gliosis occurs following damage to neurons or neuronal processes. Indeed, gliosis is a prominent feature of neurodegenerative diseases including Alzheimer's disease (AD). Activated astrocytes and glia elaborate a wide variety of factors, ranging from neurotrophic activities to factors with frank neuronal toxicity. A balance of these molecules is clearly critical to the outcome of neurological injury. Importantly, a number of the factors expressed in gliosis are identical to factors expressed by the immune system in response to inflammation and infection. Among these endogenous brain inflammatory factors, interleukin-1beta (IL- 1beta) appears to play a major role in the response of glia to CNS injury and neuronal death. Astrocytes activated by IL-1beta produce factors which affect neuron survival and process outgrowth. Furthermore, IL-1beta has been shown to be elevated in AD brain. In order to better understand the role of IL-1beta in the normal glial response to neuron loss as well as provide tools for determining the extent to which this process is activated in AD, high-resolution giant two dimensional (2-D) gel electrophoresis has been used to characterize secreted proteins that are induced in rat astrocytes treated with IL-1beta. Initial investigations have revealed eight protein species that are secreted in response to IL- 1beta; the identities of seven of these proteins have not yet been determined. In addition, transient induction of the enzymes responsible for prostaglandin and nitric oxide synthesis occurs in astrocytes treated with IL-1beta. This proposal outlines a plan to: 1) Further characterize the astrocytic proteins that are made in response to IL-1, including their microsequencing and cDNA cloning; 2) Characterize the temporal sequence of induction of these mediators of IL-1 action in models of brain injury; 3) Examine the responses of human fetal astrocytes to recombinant IL-1; and 4) Examine expression of these proteins in normal human aging and Alzheimer's disease. In addition to identifying specific mediators of IL-1 action, these studies will establish the sequence of expression of these mediators following injury. Examination of their expression in AD will thus allow a characterization of the inflammatory response in AD as either acute, chronic, residual, or absent. This information may be useful in designing novel therapeutic approaches, such as the use of anti-inflammatory or IL-1 blocking compounds, for AD and other neurodegenerative diseases. Similarly, these studies of mediators of IL-1 action will identify potential targets for intervention following acute CNS injury (e.g. trauma and stroke), where IL-1 is known to dramatically increase.
