Cerebral Amyloid Angiopathy, Vascular Dysfunction & Ischemic Brain Injury

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DESCRIPTION (provided by applicant): The candidate is an academic neurosurgeon specializing in cerebrovascular surgery whose career goal is to investigate the mechanisms underlying ischemic brain injury and intracerebral hemorrhage, with an emphasis on cerebral amyloid angiopathy (CM). The proposed period of mentored scientific training in the laboratory of Dr. David Holtzman at Washington University will allow the candidate to develop the scientific skills to become an independent investigator. CM, which is commonly noted in older patients and is found in the vast majority of patients with Alzheimer's disease, is increasingly implicated as a contributor to cerebral dysfunction, likely through promotion or exacerbation of ischemic brain injury. The central hypotheses that will be tested during the proposed project are as follows: 1) CAA as well as soluble and/or aggregated amyloid beta peptide (A-beta) cause cerebral arteriolar dysfunction. 2) The resulting arteriolar dysfunction is detrimental to cerebral blood flow (CBF), both at baseline and during conditions where autoregulatory mechanisms are required to maintain appropriate cerebral perfusion (i.e. during increased neural activity or systemic hypotension). 3) CAA-induced arteriolar dysfunction and its effects on CBF lead to exacerbation in ischemic brain injury 4) Strategies that block soluble and/or aggregated A-beta will reduce arteriolar dysfunction, abnormal CBF, and ischemic brain injury. The candidate proposes to test these hypotheses using a unique double transgenic mouse model that produces both mutant amyloid precursor protein and apolipoprotein E4, leading to age-dependent development of almost exclusively CAA. In vivo imaging for the measurement of arteriolar function (i.e. vessel diameter response to vasodilatory agents and hypercapnia) will be performed in CAA-affected vessels and appropriate controls. Quantitative cerebral blood flow measurements, both at baseline and during somatosensory activation (whisker stimulation) and elevation/reduction in mean arterial pressure, will be obtained via 14C iodoantipyrine (lAP)-autoradiography and laser-Doppler flowmetry. Ischemic brain injury will be induced by transient middle cerebral artery occlusion. Interventions will include topical and peripheral administration of anti-A-beta antibodies specific to either soluble or aggregated A-beta to determine the effect of A-beta on CAA-induced arteriolar dysfunction, CBF, and ischemic brain injury. This work may lead to new therapeutic options for patients with CAA, Alzheimer's disease, or both disorders. Relevance to Public Health: Cerebral amyloid angiopathy (CAA) is a common blood vessel disorder in older patient populations and is almost always found in patients with Alzheimer's disease. A growing body of evidence suggests that CAA may increase the likelihood that an older individual might suffer a stroke or develop dementia. Results from the proposed research project may lead to new treatment options for those individuals with CAA, Alzheimer's disease, or both disorders.