Exploring the Different CaMKII Isoforms in the Vasculature

Abstract

Coronary artery disease continues to be the leading cause of mortality in the world and a major source of disability, particularly for the aged population. The presence of vascular diseases such as atherosclerosis is a predisposition to life threatening events such as acute myocardial infarctions and strokes.

Whilst the current best treatment is the use of statins, they still hold a significant residual cardiovascular risk. 1 in 4 people on statins still die as a result of cardiovascular disease, therefore there is much potential for supplementary treatments. Previous work in the Heather Lab has shown that the inhibition of the enzyme calcium/calmodulin dependent protein kinase 2 (CaMKII) through the administration of KN-93 reduces the atherosclerotic lesion size in ApoE-/- mice. The results of this study show the involvement of CaMKII in atherosclerosis, and thereby a potential target for treatment.

Pathologies occurring in the vasculature such as atherosclerosis are characterised by endothelial dysfunction and increased migration and proliferation of vascular smooth muscle cells (VSMC). Different isoforms of CaMKII has emerged to play a role in the regulation of vascular homeostasis, namely the delta and gamma isoforms. Studies in rats using balloon angioplasty have shown that the CaMKII delta isoform is associated with adverse migration and proliferation of VSMC, whilst CaMKII gamma isoform is associated with decreased VSMC migration and proliferation.

Determining which CaMKII isoforms are present in ApoE-/- mice, and their expression pattern during the development of atherosclerosis remains an active field of research, and will lead to a better understanding of the mechanism of atherosclerosis. It was hypothesised that as atherosclerosis progresses, the CaMKII delta isoform would both increase at the mRNA and protein level, whilst the CaMKII gamma isoform would decrease in the mouse aorta. To test this hypothesis, 13, 16 and 20 week old ApoE-/- mice had their whole aorta extracted and analysed for CaMKII protein and mRNA expression.

The expression of protein and mRNA of both CaMKII delta and CaMKII gamma was also explored in human umbilical vein endothelial cells (HUVEC), human coronary artery endothelial cells (HCAEC) and human coronary artery smooth muscle cells (HCASMC). It was hypothesised that there are differences in CaMKII isoform expression among the different human cell types of HUVEC, HCAEC and HCASMC.