Hands racked by rheumatoid arthritis, excessive growth of synovial cells in rheumatoid arthritis, and the plant of the Thunder God vine.
A chemical extracted from the Thunder God vine, a plant used in traditional Chinese medicine for hundreds of years, is being investigated by Hong Kong researchers as a potential treatment for rheumatoid arthritis. Test tube studies so far have shown that the vine chemical, triptolide, suppresses the abnormal growth of immune cells that cause the painful disease in human joints. Rheumatoid arthritis develops from the knock-on effect of the overactive immune cells, resulting in the inflammation and overgrowth of synovial cells which line the joints. Particularly susceptible are joints in the hands, feet, wrists, elbows, ankles and knees, but almost all joints can be affected. The Thunder God vine, Trypterygium Wilfordii hook F, which grows in the southern part of China, has been used as a herbal treatment to combat rheumatoid arthritis for centuries. Its effectiveness, however, is offset by toxicity side effects which include hair loss, diarrhoea, bone marrow suppression and infertility. Triptolide, extracted from the vine, accounts for most of the therapeutic actions of the herbal treatment. Using special chemical assays, researchers at The University of Hong Kong under Prof C S Lau and Dr Dan Yang have dissected the structure of triptolide to evaluate how it produces its various biochemical and cytotoxic effects. When tested in an in vitro system, triptolide was found to suppress the overactive immune cells leading rheumatoid arthritis, and inhibit the growth and proliferation of damaging T-cells, a kind of lymphocyte which circulates in the blood. Triptolide was also found to inhibit active T-lymphocytes which are capable of secreting chemicals known as cytokines that can activate other immune cells as well as the synovial cells. Prof Lau said: "The action of tripolide does not appear to be related to the direct killing of the damaging cells but rather to induce their apoptosis, a kind of natural programmed cell death." The normal function of the joint lining, or synovium, is to secrete small amounts of fluid which act as a lubricant as well as providing essential nutrients. A healthy synovium is very thin, composed of only one or two layers of cells. In rheumatoid arthritis sufferers, however, inflamed synovial cells become aggressive and invade surrounding tissues leading to joint damage. More than 60 different triptolide-based compounds have been tested by Prof Lau's team so far. Clinical tests have yet to take place. The underlying cause of rheumatoid arthritis is not fully understood and there is no cure for the disease. Middle aged people are the most common victims with the peak age of onset between 35 and 55. Females appear to be more susceptible to the disease than males by a ratio of about three to one. In Western countries, about 1 per cent of populations have the disease. In Hong Kong, an estimated 0.4 per cent of the population is affected.
Principal Investigators Prof C S Lau > Email > cslau@hkucc.hku.hk Dr Dan Yang > Email > yangdan@hkusua.hku.hk