Investigation of novel protein pathways which regulate vascular smooth muscle cell phenotype in neointimal hyperplasia

Cardiovascular disease remains the biggest killer in the developed world. In many cases, deaths from this disease result from a blockage of the arteries, typically in the heart. Surgical intervention of arteries is commonly used to prevent cardiovascular disease developing to a fatal degree, which consists of either balloon angioplasty (insertion of a small balloon into the artery to physically widen the blood vessel opening) or artery bypass (where another artery, commonly from the leg is inserted into the heart artery to bypass the blocked artery). Although these interventions have dramatically improved life expectancy in cardiovascular disease patients, in time the benefits are commonly lost as the blood flow in the arteries is blocked by a thickening blood vessel wall. Prevention of this blood vessel thickening, which occurs via an inappropriate growth of the cells in the artery wall, would dramatically improve the life expectancy of patients following surgical intervention. We now have evidence that a protein found within cells in the artery wall, and previously unknown, can regulate thickening of the artery observed following angioplasty and bypass surgery. This protein is called PEA-15 and our previous results have revealed that it prevents inappropriate growth of cells in the artery wall, i.e. it helps maintain healthy blood vessels. Our preliminary experiments indicate that PEA-15 is decreased in diseased arteries and this may lead to growth in cells from arteries and thickening of the blood vessel wall. In this study we will aim to fully understand the role of PEA-15 in blood vessels and its relation to cardiovascular disease. In addition, we propose that increasing PEA-15 may help prevent blood vessel thickening. In our study we will also focus on one agent which recent evidence suggests can increase PEA-15 in cells, vitamin D. Vitamin D has long been recognised as producing benefits in cardiovascular disease however how this occurs is not clear. Our experiments aim to demonstrate that vitamin D, by increasing PEA-15 in the cells of arteries, can be beneficial in preventing cardiovascular disease. This new information will provide further evidence of the potential therapeutic value of vitamin D in cardiovascular disease patients following angioplasty or bypass surgery.

Despite recent advances in stenting, neointimal hyperplasia from increased vascular smooth muscle (VSM) cell proliferation remains a significant clinical problem, particularly in peripheral arterial disease. Delineation of the mechanisms which change VSM cells from a quiescent to a proliferative cell phenotype during neointimal formation is still urgently required to alleviate this health burden. Our recent study has uncovered a protein, uncharacterised in the cardiovascular system, which we revealed has an important role in regulating VSM cell gene expression. This protein is called phosphoprotein enriched in astrocytes-15 (PEA-15). We have already determined that PEA-15 binds the mitogen-activated protein kinases (ERK1/2) and acts as a cytoplasmic "tether" preventing ERK1/2 activating gene expression in the nucleus. ERK1/2-induced gene expression is directly associated with growth factor-mediated proliferation and, by preventing this, PEA-15 maintains VSM cells in a quiescent state. Our preliminary evidence now indicates that PEA-15 expression is substantially decreased in the VSM cells of arteries from a mouse model of neointimal hyperplasia. In the current proposal we will address the hypothesis that PEA-15 expression is decreased in neointimal hyperplasia and directly contributes to VSM cell proliferation during neointimal development. Both in vivo and in vitro models will be used to fully uncover the effects and mechanisms which modulate PEA-15 expression in neointimal formation. We will further examine the therapeutic potential of increasing PEA-15 expression to reduce ERK1/2-induced gene expression and inhibit neointimal formation. Our pilot data has indicated that vitamin D can increase PEA-15 expression and this will be examined in models of vascular disease. In this project, we will therefore uncover a novel mechanism responsible for the development of neointimal hyperplasia and, in addition, reveal a viable therapeutic approach.

Who will benefit from this research?
The results generated from the studies will be of benefit to academia, industry, government, clinical medicine, and the general public, both nationally and internationally. The output from this grant, although basic science in nature, is aimed at a greater understanding the development of vascular disease, specifically following angioplasty or vein graft bypass. Neointimal hyperplasia following angioplasty or arterial bypass remains a major clinical problem and a costly burden on healthcare. Stenotic lesions occur in 25 to 30% of patients within the first year following surgery. In particular, the potential beneficial role of vitamin D will be investigated. This has implications both for general health and for patients who have an increased likelihood of developing vascular disease. It is anticipated that the main beneficiaries will be to this wider audience. However, the immediate beneficiaries will be health professionals who will take forward findings, such as clinicians and medical dieticians. This work could directly lead to further clinical trials examining further the potential vasculoprotective effect of vitamin D.

Several drug companies manufacture vitamin D analogues and they will also be potential beneficiaries. The knowledge obtained in this grant may lead to an expanded market for such compounds.

It is possible in the longer term that results may also lead to input into nutrition guidelines on vitamin D through national government bodies involved in assessing advice on nutritional supplements.

How will they benefit from this research?
Together with other scientific findings, this project may inform the use of supplements to help prevent the development of vascular disease. This is particularly an issue in northern European countries, and particularly northern Scotland, where low levels of sunlight results in a higher incidence of vitamin D deficiency. It should also be acknowledged that general health, and particularly that related to cytoskeletal physiology, is also profoundly affected by vitamin D deficiency. Scientific evidence from combined studies in multiple areas could therefore have many general health benefits and lead to an enhanced quality of life, at least in more northern parts of the UK. The timescale for this information to filter through, and be qualified by clinical studies, is likely to be in the medium to longer term.

What will be done to ensure that they benefit from this research?
Health professional groups will be engaged as results are forthcoming. This will include NHS clinicians who have interests in vascular function and vascular disease. Such exchange already takes place, and the Aberdeen Royal Infirmary is adjacent to the laboratory where this work will be carried out.

Drug companies with an interest will also be approached. To engage with Industry will first require protection of intellectual assets. This will be achieved with help from the University of Aberdeen Research and Innovation team (http://www.abdn.ac.uk/R&I).