Advancing age is associated with a number of geriatric syndromes linked to hypoxic-ischemic injury, such as cerebral microvascular disease, autonomic failure with orthostatic hypotension, stroke, dementia and congestive heart failure. Underlying all of these conditions lies the aging blood vessel, damaged with a dysfunctional endothelium. Potential corrective therapies are unknown. Studies suggest that reduced activation of hypoxia inducible transcription factor-1 (HIF-1) may be involved in age-related vascular dysfunction. HIF-1 is a heterodimeric transcription factor expressed in all tissues in response to hypoxia and ischemia and activates a repertoire of target genes which function to protect oxygen or glucose deprived cells by activating a cassette of cellular, local and systemic responses. In animal studies, pharmacologic augmentation of HIF-1 can reverse age-related decline in HIF-1 activation. However, there have been no prior studies of HIF-1 activation in human aging. There are now two HIF-1 activators available for use in humans-the iron chelator Desferrioxamine (DFO) and a dietary flavonol, quercetin, which can be used to test the effects of acute and chronic HIF-1 activation on the vascular aging process. We have preliminary data to show that the infusion of DFO and the dietary intake of a flavonol-enriched cocoa drink are both associated with a significant cerebral vasodilation and increased cerebral blood flow response in elderly volunteers, as measured by transcranial Doppler ultrasound (TCD). The current proposal will examine the hypothesis that that HIF-1 can be pharmacologically activated in elderly humans and that pharmacologic augmentation of HIF-1 expression can improve age-related changes in cerebrovascular function. Specifically, using a double blind placebo controlled study design, we will compare DFO and quercetin mediated HIF-1 transcriptional activation and cerebrovascular responses in young and elderly healthy volunteers. DFO- and quercetin- mediated HIF-1 activation allows us to examine HIF-1 activation in aging as well as vascular responses to acute and chronic HIF-1 activation in cerebrovascular aging, which have not been previously investigated in humans. The TCD procedures routinely used in our laboratory allow us to assess these hypotheses as they relate to the cerebral arteries of humans, a field in which our knowledge is most deficient. Findings from our study will pave the way for clinical trials of HIF-1 activators in a number of hypoxic-ischemic geritaric disorders, especially cerebrovascular disorders such as ischemia and vascular cognitive impairment, which pose a significant health burden in our aging population.
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