Slowing or preventing age-induced arterial vasomotor dysfunction that is associated with an increased risk for cardiovascular diseases remains a significant clinical challenge. Increasing evidence supports that changes in the extracellular matrix alone are insufficient to fully account for vascular stiffness and loss of arterial contractility in aging, and a new concept has emerged that vascular smooth muscle (VSM) cells are important contributors to age-induced arterial dysfunction. The role of integrin-mediated signaling to the regulation of cytoskeletal contractility in the aged VSM cells remains largely unknown. Therefore, there is a critical need to determine the mechanisms whereby age-induced alterations of integrin signaling contributes to decreased vascular contractility in aged resistance arteries. Our long-term goal is to identify mechanisms responsible for the age-induced decline in arterial contractility. The overall objective for this proposal is to determine the mechanistic contribution of integrin signaling to impaired VSM contractility in aged resistance arteries. Our central hypothesis is that age- induced alteration of integrin function impairs recruitment of key adhesion proteins and stress fiber formation resulting in reduced VSM contractility in resistance arteries. We have formulated this hypothesis on the basis of our strong preliminary data indicating that aging decreases key contractile and adhesion proteins. These age- induced changes contribute to the conversion of VSM cells to a synthetic phenotype, which is characterized by reduced VSM cell contractility and mechanosensing in resistance arteries. The rationale for the proposed research is that a mechanistic understanding of how aging affects integrin function and VSM contractility will enable the identification of novel targets to prevent or reverse age-associated loss of vascular contractility. The hypothesis will be tested by pursuing the following two specific aims: (1) Determine the contribution of integrins to the regulation of cell-matrix adhesion in aged VSM; (2) Determine the contribution of integrin signaling to stress fiber formation in aged VSM. The approach will involve the use of real-time, high-resolution fluorescence and atomic force microscopy in live cells, and ex-vivo functional experiments in resistance arteries from young and old, male and female, Fischer 344 rats. The proposed research is innovative because it represents a novel mechanism in aging by which integrin adhesion regulates ROCK/MRTF-A/SRF activation by controlling actin stress fiber formation and actomyosin activation. The proposed research is significant because understanding the mechanism by which integrin function regulates VSM contractility in aged resistance arteries will fill a gap in knowledge regarding age progression. Ultimately, this work will be critical for future studies underlying age- induced loss of contractile function by giving a new direction for therapeutic intervention - vascular remodeling as opposed to blood pressure reduction.
The proposed research is relevant to public health because its completion will provide a framework for the identification of mechanism-based new targets to prevent or treat age-related decrease in vascular contractility. Thus, the proposed research is relevant to the part of NIH?s mission pertaining to the development of fundamental knowledge about the nature and behavior of living systems that will help reduce illness and disability in the elderly.
