Overview

Cardiovascular disease has been identified as one of the leading causes of death worldwide, and particularly in North America. Cardiovascular disease is strongly associated with atherosclerotic plaque: the accumulation of oxidized lipids and foam cells over the inner layer of arteries; atherosclerotic plaque does not only affect the behaviour of factors as blood pressure, but is also a major cause of strokes and cardiovascular events.

Formerly, atherosclerosis was strongly associated with the daily intake of cholesterol in products derived from an animal source; however, it has recently been shown that it is not cholesterol itself, but its oxidized derivatives which cause the development of atherosclerotic plaque. When cholesterol travels through the bloodstream, in the form of lipoproteins, it is susceptible to a variety of chemical reactions, among which oxidation caused by reactive oxygen species (ROS) is quite common. When cholesterol is oxidized, it can no longer undergo a normal metabolic control: it starts accumulating and the cells responsible for its degradation, the macrophages, are unable to metabolize it. This is the ultimate cause of Atherosclerosis.

A variety of oxidized cholesterol species exists, it is the purpose of this project to enhance the macrophage-mediated degradation of a particular molecule, namely 7-ketocholesterol. In order to perform this task, the genes encoding three microbial enzymes will be transformed into human macrophages. The enzymes were firstly isolated from two genres of bacteria which inhabit the soil, where they are exposed to death animal rests; this kind of organisms are then naturally able to metabolize the compounds accumulated in the bodies, as oxidized cholesterol. First, we are testing the functionality of the three recombinant enzymes in E. coli and the degradation rates showed on 7-ketocholesterol, after that we will be able to transform mammalian cells.

By using this approach, it is expected that the ability of macrophages to degrade 7-ketocholesterol will be increased at a genomic and metabolic level. Once suitable results are obtained, a new approach will be taken so that a therapy can be developed.

Our Project

Our project is to design and develop a preventive gene therapy for atherosclerosis, based on the usage of microbial enzymes. This is based on the fact that the human body is incapable to degrade or break down many substances that affect our health, these substances start to accumulate slowly and ultimately reduce our life span. How does it relate to atherosclerosis? The treatment would consist on the degradation of oxidized cholesterol. Three enzymes originally from Chromobacterium sp.6 and Rhodococcus jostii4, are capable of degrading the molecule of 7-ketocholesterol.5 The DNA enconding those three enzymes, will then be transfected into mammalian cells and localized within the lysozome, to ensure their degrading function. This project will potentially be the basis of the development of novel treatments for atherosclerosis, as well as the enzymatic tratment of food in order to remove trace amounts of 7-ketocholesterol they might contain.

References

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4. Mathieu JM, Mohn WW, Eltis LD, LeBlanc JC, Stewart GR, Dresen C, et al. 7-Ketocholesterol catabolism by Rhodococcus jostti RHA1. Appl Environ Microbiol. 2009 Oct 26; 76(1): 352-355.

5. Mathieu JM, Schloendron J, Rittmann BE, Álvarez PJJ. Microbial degradation of 7-ketocholesterol. Biodegradation. 2008; 19: 807-813.

6. Mathieu JM. Strategies for the mitigation of oxysterol-induced cytotoxicity. Texas: Rice University; 2011.
7. Pérez Guerra Y. Oxidación de las LDL (lipoproteínas de baja densidad) y su relación con la patogénesis de la aterosclerosis. Revista CENIC de ciencias biológicas. 2007; 38(1): 3-11.

8. Tubbs RS, Blouir MC, Romeo AK, Mortazavi MM, Choen-Gadol AA. Spinal cord ischemia and atherosclerosis: a review of literature. Br J Neurosurg. 2011 Dec 25; 25(6): 666-670.

Image Sources

1. Heart attack- http://www.pasadenahealthcenter.com/site/wp-content/uploads/2013/02/bigstock-Heart-Attack-4863606.jpg.

2. Atheroma- http://www.brown.edu/Courses/Digital_Path/systemic_path/cardio/51.jpg.

3. LDL- http://www.jlr.org/content/42/4/605/F10.medium.gif.

4. Cholesterol Meds Cartoon- http://www.physiciansweekly.com/wp-content/uploads/2013/06/CholesterolMeds-cartoon.png