The Cross-Border Biotech Blog

Biotechnology, Health and Business in Canada, the United States and Worldwide

Friday Science Review: June 17, 2011

New Players in Interleukin-17 Response to Bacterial Pathogens

University of Toronto ♦ St. Michael’s Hospital ♦ Published in Nature Medicine, June 12, 2011

Interleukin-17 (IL-17) is a well established chemical messenger that modulates antimicrobial immune response in the stomach and intestine in the presence of various bacterial pathogens, including Pseudomonas, HelicobacterCitrobacter, and Salmonella; this has been known for some time, but the mechanism stimulating IL-17 release was until now a mystery. Researchers recently discovered that in the presence of such pathogens, CD4+ T helper cells interact with TGF-β and IL-6 to differentiate into T helper type 17 (Th17) cells that are characterized by the secretion of IL-17 and IL-22. Furthermore, they found that Th17 cells are regulated by the Nod-like receptors, Nod-1 and Nod-2. Researchers termed the cells “innate” T helper type 17 cells due to their early induction and regulation by Nod receptors, unlike adaptive-phase Th17 cells that arise at late stages of exposure. As a result of their involvement in regulating inflammation and antimicrobial response, it is believed that the Nod receptors may play a role in inflammatory bowel disease.

Treating Atherosclerosis: Shipping the Cholesterol Out of Foam Cells

University of Ottawa Heart Institute ♦ Published in Cell Metabolism, June 8, 2011

Macrophage foam cells contain large quantities of cholesterol inside an organelle known as a lipid droplet. Macrophages rich in cholesterol are problematic, as they tend to build up in atherosclerotic lesions causing plaque build-up in the arteries. An interesting paradigm for the treatment of atherosclerosis has been reverse cholesterol transport; the process wherein cholesterol hidden away within lipid droplets is hydrolyzed and removed from the peripheral tissues to the liver, where it can be excreted via bile. Over the years researchers have been investigating how cholesterol hydrolysis actually occurs to assess whether it can be leveraged to treat atherosclerosis. The dominant theory has been that all hydrolysis is driven by neutral cholesterol hydrolases, but new findings show that another mechanism also contributes to the process. Researchers found that lipid droplets in the cytoplasm of foam cells are transported to another organelle, known as a lysosome, where they are absorbed and broken down by lysosomal acid lipase. Lipid droplets are delivered to lysosomes while additional cholesterol is being loaded into the cytoplasm of macrophages from the blood, suggesting that lysosomal degradation serves as a reverse cholesterol transport mechanism.

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