30.9. The Role of Macrophage Scavenger Receptors and Endothelial Lipase in Atherosclerosis: Studies with Lentiviral Vector Mediated Gene Silencing

Public examination of a doctoral dissertation in the field of Molecular Medicine

Doctoral candidate: MScPetri Mäkinen

Date and venue: 30.9.2011 at 12 noon Mediteknia Auditorium, Kuopio Campus

Cardiovascular diseases are the most common cause of death in the Western world. Atherosclerosis is a disease characterized by inflammation and accumulation of lipids in the arteries. Macrophage scavenger receptors mediate the uptake of modified lipoproteins leading to the formation of foam cells which further maintain the inflammatory status of arteries. Endothelial lipase (EL) is one of the main regulators of HDL cholesterol in mouse and humans. Inflammation is involved in EL regulation.

RNA interference (RNAi) is a conserved biological mechanism, which allows silencing of a cognate gene in target cells. Lentiviral vector (LV) is a gene transfer tool which integrates its genome into target cells. Therefore, it is possible to achieve long-term effects with LV mediated gene transfer. The goal of this study was to develop an LV-mediated RNAi system, and use it for studying the pathogenesis of atherosclerosis and related inflammation.

It was found that LV-mediated RNAi silences a marker gene for at least 6 months in cell culture and 9 months in mice in vivo. Furthermore, it was demonstrated that this method is suitable for silencing macrophage scavenger receptors SR-A and CD36 in mouse macrophages. This silencing was able to attenuate the atherogenic process in hyperlipidaemic mice. This study revealed also a novel reciprocal regulation mechanism between these two receptors: when one receptor is silenced the expression of the other is upregulated. Additionally, it was revealed that silencing of these receptors modulates the activity of transcription factor NF-kB, a major mediator for inflammatory responses. Furthermore, it was demonstrated that NF-kB regulates EL expression under inflammatory conditions, and that this activation could be attenuated by sulforaphane.

In conclusion, this study shows that LV-RNAi is a versatile tool for long-term gene silencing, and it can be applied for studying cardiovascular diseases. Furthermore, it demonstrates that scavenger receptors participate not only in foam cell formation but also in regulating inflammatory responses in macrophages.

The doctoral dissertation of Master of Science Petri Mäkinen, entitled The Role of Macrophage Scavenger Receptors and Endothelial Lipase in Atherosclerosis: Studies with Lentiviral Vector Mediated Gene Silencing, will be examinde at the Faculty of Health Sciences. The opponent in the public examination will be Docent Vesa Olkkonen of Minerva Foundation Institute for Medical Research, and the custos will be Professor Seppo Ylä-Herttuala of the University of Eastern Finland.

Photo available for download at http://www.uef.fi/en/vaitoskuvat.

 

Publishing year: 2011

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