LXR Proteins- New target for antitubercular activity?

As we are aware that TB, has become a major threat to the world and a recent study also reports an estimated one-third of the world population is latently infected with Mycobacterium tuberculosis. And also I did mention (earlier blog) that the strain has got resistance for drugs Rifampicin and hence comibination of drugs (Rifampicin, Isoniazid, Euthumbutol) is being used. The most worst part of this is for those who are already infected with HIV. Not only these are the facts of concern, the worst part of this bacterium is "M. tuberculosis has the ability to adapt and survive for long periods of time within the host macrophage in a state of clinical dormancy". The researchers attribute the reason for this as the switching to lipids as their main carbon source of the nutrient-deficient macrophage phagosome. A recent report implicated that mycobacterial persistence is critically linked to its ability to acquire and catabolize cholesterol from the host. Cholesterol, besides being used as an energy or carbon source, is also essential for the phagocytosis of the bacterium by the macrophage and for the inhibition of phagosome maturation. Recently, liver X receptors (LXRs), LXRα and LXRβ, have emerged as master regulators of macrophage transcriptional programs involved in cholesterol, fatty acid, and glucose homeostasis. All these facts encouraged Kris Huygen and colleagues of Scientific Institute of Public Health, Belgium to identify the role of LXR proteins in the mouse immune response to airway infection with Mycobacterium tuberculosis.

In the study, when compared with normal mice, mice lacking both forms of LXR (LXR-alpha and LXR-beta) were more susceptible to airway infection with Mycobacterium tuberculosis and developed more severe disease. Further analysis revealed that these mice did not mount an effective immune response in the airways. There was no accumulation of immune cells (neutrophils) in the lungs and little evidence of Th1 and Th17 immune responses. Importantly, the marked protection from infection seen in normal mice treated with molecules that target LXRs was accompanied by increased Th1 and Th17 immune responses.

Congrats Kris for this achievement. More...