Aneurysm disease burden and pathophysiology

Abdominal aortic aneurysms (AAAs) primarily affect elderly males with a prevalence of 5%. In England, rupture of aortic aneurysms cause 10,000 deaths per year [1]. Many risk factors have been associated with aneurysmal rupture eg., high diastolic blood pressure, smoking, family history of AAA and chronic obstructive pulmonary disease but the principle determinant of rupture is the maximum diameter of the aneurysm, which increases with age [2].Initiation of the lesion is associated with inflammation and modulation of proteolytic enzymes, causing the early loss of elastin and a compensatory increase in the expression of collagen [2,3].Subsequent formation of thrombus, which can cause alterations of blood flow as well as creating ischaemia, is most likely to induce new blood vessel development and changes in the expression of ischemia-induced genes.Angiogenesis further exacerbates the inflammatory process by providing a conduit for infiltration of immune-responsive cells.The combination of conditions which are anti-proliferative and pro-apoptotic result in cellular losses [6,7].Ultimately the aortic wall is thickened, non-compliant, matrix-rich and cell poor.Our recent studies suggest that bursts of subsequent medial neo-angiogenesis may provide the final differential weakening across the structurally compromised lesion, leading to aneurysmal rupture.

As we recently reported that the differentially expressed genes involved in human aneurysm rupture implicate effective treatment may only be possible through drugs with pleiotropic effects [4], we investigated the ability of Rosiglitazone, to ameliorate aneurysm development in an experimental model.We have shown that this drug significantly reduces AA in an experimental model.We hypothesise that the mechanism of action is via an effect on MAPK signalling pathways and propose to examine this hypothesis using western blotting and by measuring MAPK enzyme activity.

Western Blotting with phosphospecific antibodies.Tissue lysates will be used for western blotting (using standard laboratory methods) using phosphospecific antibodies to p38MAPK, pJNK and P44/42 ERK (Cell Technology Inc, USA), according to the manufacturers recommendations.

Measuring the activity of MAPKs — the MAPK activities of p38MAPK, pJNK and p44/42 ERK will be determined in tissue lysates using assay kits commercially available (Cell Technology Inc., USA), according to manufacturers recommendations.

References:

1. Thompson MM.(2003). Infrarenal Abdominal Aortic Aneurysms. Curr Treat Options Cardiovasc Med. 5:137-146.

2. Mortality results for randomised controlled trial of early elective surgery or ultrasonographic surveillance for small abdominal aortic aneurysms. (1998) The UK Small Aneurysm Trial Participants. Lancet .352:1649-1655.

3. Wills A, Thompson MM, Crowther M, Sayers RD, Bell PR.(1996) Pathogenesis of abdominal aortic aneurysms--cellular and biochemical mechanisms. Eur J Vasc Endovasc Surg . 12(4):391-400.

4. Choke E, Torsney E, Nasr H, Jones A, Dawson J, Loftus I, Thompson MM, Cockerill GW. 2006. Gene expression profiling of abdominal aortic aneurysm rupture. NYAS.10^th Symposium The Abdominal Aortic Aneurysm: Genetics, pathophysiology and Molecular Biology. April 3-5.