The hypothesis tying these three aims together is that the hundreds of molecules released by astrocytes, i.e. the astrocyte secretome affect the genotype, and therefore, the functional phenotype of various cells within the CNS, such as vascular endothelium responds to the astrocyte secretome by inducing new blood vessel formation. Furthermore, we find that exposure of the cerebral vasculature changes the phenotype in a manner which regulates cerebral blood flow (CBF) autoregulation (i.e. as blood pressure raises the capacity to regulate pressure-dependent myogenic tone such that blood flow is constant) is regulated in a circadian manner. Thus, blood flow autoregulation is at its lowest early in the morning and highest late at night when rat metabolic activity is within four hr of its highest level. It is interesting that stroke in most animals is at its greatest occurrence between 4 and 8 AM. Experiments are designed to determine if astrocytes act as a cellular pacemaker to modify myogenic activity and arterial pressure. Thus far, nearly all studies on astrocytes have been done in neonatal astrocytes. We provide data that astrocytes isolated and cultured from adults exhibit altered physiologic and phenotypic activity compared to those harvested from neonatal pups. To define differences in astrocyte secretome and the ability to change the genotype of neighboring cells in the CNS we will compare the astrocyte proteome from neonatal vs. adult to define the ability to alter the genotype of endothelial the cerebral circulation and vascular endothelium. Finally we will define the ability of neonatal and adult astrocyte proteome to affect the genome and function of invading tumor cells using a variety of techniques including: DNA microarray, intravital microscopy, continuous blood pressure recording of awake rats via 24 hr. telemetry as well as comparing changes in specific cellular signaling function. DNA analysis will be done using commercially available microchip arrays commercially available Arraystar microchips containing ~ 30,000 genes. The astrocyte proteome will be done using the Institutions Proteomic facility. Insight gained from such molecular/genetic data will provide novel clues in defining the function of neonatal and adult astrocytes, which exist together in the adult brain. We realize that, as written, each Specific Aim can stand alone. The common thread in the proposed approach is the specific ability to define the action of proteome from glial lineage aimed at matching blood flow to cerebral metabolic demand and dealing with cells which invade the brain. We have added two key personal to this grant to assist who have the prerequisite expertise to help ensure the completion of the Aims as outlined.
The main goal of this competing renewal application is to a) Identify the makeup of factors released by astrocytes, a major component of cells in the brain b) To define the differences in the number of and identity of these cellular components in astrocytes between those of a newly borne rat pup and compare it to that of mature astrocytes found in adult rats and, c) Define and compare the action of cellular components from astrocytes from newly borne rat pups vs. those from animals 6-8 weeks of age on the genetic profile and function imposed on vascular endothelial cells, and invading tumor cells from a distant site, on the ability of astrocytes from rat pups vs. adult cells which line the blood vesse wall, on changes of the vascular response to increasing arterial pressure at different times of day and compare and contrast the effects of those components from pups to those with different functions due to the properties of substances released from mature astrocytes of 6-8 week old adult rats, the physiologic responses between pups and adult animals will affect the pathologic actions of stroke, high blood pressure and a variety of physiological events including Alzheimer's and Parkinson's Disease along with a variety of other maladies directly affecting the quality of life.
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