Recent epidemiological studies have made clear that human proximal aortic stiffness increases with age and is an early and independent biomarker of, and probable contributor to, subsequent adverse cardiovascular outcomes including kidney failure, hypertension and Alzheimer's Disease-related dementia. The normal flexibility of the proximal aorta functions as a critical ?shock absorber? to protect small downstream vessels from the high pulses of pressure generated by the heart. We have shown in published studies that the vascular smooth muscle cell (VSMC) regulates up to half of total aortic stiffness and that aging-induced loss of regulation of the VSMC cytoskeleton leads to impairment of the ability of the aorta to perform this shock absorption function. A major advance from our lab has been the demonstration that the cortical nonmuscle actin cytoskeleton and its linkages to focal adhesions and the extracellular matrix are a particularly dynamic and important part of the VSMC cytoskeleton. The broad goal of this program is to test the concept that ultrasound-targeted, cell permeant decoy peptides and small molecule inhibitors can be used both to probe function and to reverse aging-induced malfunction of the VSMC cytoskeleton. We will use cell permeant decoy peptides and recombinant proteins developed by our lab, and for comparison, small molecule inhibitors, to test the hypothesis that ex vivo stiffness of aortas from aged mice can be decreased by mechanisms targeted to the VSMC cytoskeleton. We will mine protein sequence data bases to identify VSMC-specific sequences. Synthetic decoy constructs targeting these sequences will test a proof of concept for the selectivity and efficacy of the peptide approach. We will use biomechanics, magnetic tweezers, proximity ligation analysis, actin polymerization assays and immunoprecipitation to confirm the mechanism of action of decoys. We will test, in collaboration with Tyrone Porter of our Nanoscience Center, the hypothesis that microbubble-packaging of cell-permeant decoys and ultrasound-mediated release will allow localized, tissue-specific targeted delivery of effective decoys. We will test the hypothesis that tissue-targeted decoys can acutely reduce PWV in vivo in mice and that chronic in vivo treatment can prevent 3 negative outcomes associated with aging-induced increased aortic stiffness: brain vascular lesions, hypertension and renal damage. Hence, we propose a highly innovative research strategy to attack aging-induced alterations in the vascular actin cytoskeleton and its linkage to focal adhesions. This approach, no matter the outcome, will answer major questions about aortic stiffness and its relationship to vascular function with age. If successful, this approach has the potential to prevent or reverse a host of aging-associated cardiovascular disorders.
The aorta normally functions as a critical shock absorber to prevent the full force of the heartbeat from reaching the delicate small blood vessels downstream, where it would cause damage in the brain, kidney, and heart that would lead to Alzheimer's disease-related dementia, kidney failure and heart failure. Trauma of the small vessels can also lead to systemic secondary hypertension. With aging, this shock absorption function fails and in this project we plan to develop novel decoy peptides that will be tissue targeted by microbubbles to prevent or reverse the effects of aging and subsequent hypertension, kidney disease and vascular dementia.
