Vanguard (Lagos)
Sola Ogundipe
18 November 2008
TAT2 - a drug extracted from Astragalus membranaceus a plant used in Chinese medicine is helping immune cells fight HIV and is also raising the possibility of slowing the ageing process in other parts of the human body.
A report in The Journal of Immunology says excitement about the plant hinges upon telomeres which are caps of repetitive DNA found at the ends of chromosomes. These get shorter as cells age and are thought to affect the cell's lifespan.
The caps can be rebuilt with an enzyme called telomerase, and some people have suggested it might be possible to extend human life by boosting telomerase production - though this has never been tested.
According to studies by a researcher, Rita Effros, of the University of California, Los Angeles, had previously inserted part of the telomerase gene into so-called killer T-cells - immune cells that fight infections including HIV - and found that the cells had stronger anti-viral activity than normal.
However, such gene therapy is not a practical way of treating the millions of people infected with HIV.
Effros took killer T-cells from HIV-infected people and exposed them to TAT2. She found that TAT2 reduced telomere shortening, increased cells' ability to divide, and enhanced their antiviral activity.
This effect was blocked when a second drug was used to inhibit telomerase, suggesting that TAT2 was indeed working through the enzyme - although the exact mechanism is not understood.
Effros said: "It is beginning to look like telomerase is doing more than just keeping telomeres from getting too short. It seems to be mediating some anti-viral mechanisms as well."
A previous study suggested that people living with HIV who control the infection for many years without developing AIDS, have killer T-cells with high telomerase activity and longer telomeres.
Ultimately, Effros hopes that TAT2 could be used to supplement existing anti-retroviral drugs, by boosting the immune systems of people with HIV.
Astragalus has been used in traditional Chinese medicine for thousands of years, often in combination with other herbs, to strengthen the body against disease. It contains antioxidants, which protect cells against damage caused by free radicals, byproducts of cellular energy. reputed to have antibacterial, anti-inflammatory, and diuretic properties, the plant is sometimes used topically for wounds.
Researchers have investigated astragalus as a possible treatment for people whose immune systems have been compromised by chemotherapy or radiation. In these studies, astragalus supplements have been shown to speed recovery and extend life expectancy.
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