The proximal aorta normally functions as a critical shock absorber to protect small downstream vessels from the high pulses of pressure generated by the heart. 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 vascular dementia. 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 linkage to focal adhesions and the extracellular matrix is a particularly dynamic and important part of the VSMC cytoskeleton. The broad goal of this program is to define molecular mechanisms of aging-associated malfunction of the vascular actin cytoskeleton and its connection with focal adhesion (FA) complexes and to furthermore develop a nanoparticle-targeted approach utilizing cell permeant decoy peptides to reverse this malfunction. In the R21 phase, we will use small molecule inhibitors and decoy peptides, together with biomechanics, magnetic tweezers, deconvolution microscopy, proximity ligation analysis (PLA), immunoprecipitation and other biochemical and cellular assays to test, in vitro, the cause-and-effect relationship between changes in the cytoskeleton and aortic tissue stiffness. Based on preliminary data, we will focus specifically on inhibition of cortical actin elongation and branching mechanisms, actin-focal adhesion connections and focal adhesion protein-protein interactions. In the R33 phase we will extend the cell permeant peptide approach to select peptides that are effective in aged mouse tissues in vitro, and implement, with Dr. Porter in the BU Engineering College an application of his nanotechnology approach for tissue-specific targeted release of the decoy peptides. The successful nanoparticle-packaged peptides will be used in young and old mice acutely in vivo to determine the effect of the peptides to decrease pulse wave velocity (PWV) and blood pressure and hence demonstrate a cause-and-effect relationship between cytoskeletal function and aortic stiffness. Additionally, a 6 month chronic trial will test the ability of nanoparticle packaged peptides to reverse changes in blood pressure, PWV, MRI-monitored brain vascular damage and kidney damage to provide the impetus for longer chronic studies. Hence, we propose a highly innovative research strategy to define and attack aging-induced alterations in the vascular actin cytoskeleton and its linkage to FAs. This approach, if successful, 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 of the brain, kidney, and heart, where it would damage them and lead to dementia, kidney failure and heart failure. With aging, the shock absorption function fails. In this project we plan to determie the mechanisms involved and use nanoparticles containing therapeutic peptides to prevent or reverse the effects of aging and subsequent cardiovascular disease.
