Atomic Force Microscopic Studies of Dissecting Aneurysm

University Of Texas Med Br Galveston, Galveston TX

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Abstract

DESCRIPTION (provided by applicant): The industrial chemical N-(2-aminoethyl) ethanolamine (AEEA) has enormous worldwide production and use. Human environmental exposures to AEEA occur, and AEEA is found in a variety of common products. Blood vessels are the target of many environmental toxins. Furthermore, it is becoming increasingly recognized that vascular disorders begin in childhood, and may be related to prenatal exposure. This and other laboratories have found that AEEA, given to pregnant rats (dams) during their third trimester, results in a vascular lesion in newborn pups known as dissecting aortic aneurysm, or DAA. DAA is the sudden tearing, or splitting of the layers of the muscular wall of the thoracic aorta. In humans, DAA affects those in the teen years to early adulthood, resulting in occlusion of distal vessels, aortic rupture, and sudden death. DAA is associated with several well-described clinical syndromes, but the vast majority of DAAs occur sporadically, without known genetic defects, and with hypertension as the only clear-cut risk factor. The long-term goal of this proposed research is to better understand the physical weakening of the aortic wall that underlies arterial dissection; by understanding these mechanisms in this in vivo model, in vascular cells, and in spontaneously hypertensive rats, strategies for diagnosis and prevention of human DAA can be devised. The hypothesis to be tested is that AEEA's toxic insult causes damaged, dysfunctional fetal collagen fibrillogenesis by vascular smooth muscle cells (VSMCs) of the aortic wall (or media). Deranged biophysical properties and weakening of the blood vessel wall result. The rationale for the proposed studies is that by understanding the physical and molecular defects that lead to dissection, strategies to prevent or attenuate DAA can be devised. The hypothesis will be addressed by two Specific Aims: First, physical defects in the aorta's major structural proteins (collagen; elastin) will be defined after in vivo or in vitro AEE exposure. This will be accomplished by measuring physical characteristics of aortic matrix and isolated molecules with atomic force microscopy (AFM), a technique that measures piconewton molecular forces. In Specific Aim #2, mechanisms underlying vascular dissection and the role of hypertension (a risk factor in humans) will be revealed by: a) characterizing defects from matrix produced by isolated VSMCs through biochemical and molecular techniques, and b) defining prenatal AEEA effects in control and spontaneously hypertensive rats. These combined in vivo, in vitro, biophysical and molecular approaches will identify the structural/molecular toxic effects of AEEA that weaken the aortic wall to result in DAA.