| Summary: | 博士 === 國立臺灣師範大學 === 生命科學研究所 === 96 === Asthma is characterized as a chronic disease which causes an important public health problem worldwide. The symptoms of asthma include wheezing, cough, shortness of breath, airway narrowing and mucus increase cause suffocation and death. In addition, more eosinophils infiltration and airways hyperresponsiveness (AHR) are usually found in the airways of asthmatic patients. The Th2-type cytokines appear to be crucial in the pathogenesis of asthma. Thus, to suppress Th2-induced cytokines secretion might be able to inhibit asthma symptoms. Steroid is commonly used to treat asthma. Although it suppresses the respiratory track inflammation, long-term usage of steroids may cause potential side effects. Therefore, doctors in Western and Chinese medicine desire to have alternative ways to treat asthma. Gynostemma pentaphyllum is a perennial liana plant and widely used as an herbal tea in Japan, southern China and Taiwan. About 90 different gypenosides have been identified from the extract of G. pentaphyllum. Among them, six gypenosides are the same with the ginsenosides from Panax ginseng. Recent studies found that G. pentaphyllum has additional pharmacological effects on the inhibition of blood-sugar, hyperlipidaemia, and the treatment of hepatitis.
Our results indicated that the extract of G. pentaphyllum could promote the expression of Th1 cytokines and IgG2a secretion from splenocytes of mice that were intraperitoneally injected or orally administrated with the extract for 5 consecutive days. Since more Th2-associated cytokines in lung were found in asthmatic patients, we proposed that G. pentaphyllum might be able to module the balance of Th1/Th2 cytokines and to suppress the inflammation in asthma airways. Chicken ovalbumin (OVA) was used as the allergen to induce asthmatic immune responses and symptoms. We tested the efficacy of G. pentaphyllum in 5 experimental models. BALB/c mice were firstly sensitized with intraperitoneal injection and challenged with 3 times of OVA inhalation (IH3 model) or 5 times (IH3 model). G. pentaphyllum was orally administrated for 7 consecutive days before the end of the OVA challenge. Asthmatic symptoms were examined, including AHR, eosinohpilia in lungs, and serum levels of OVA-specific IgG1 and IgE. The cytokine concentrations of the supernatants of OVA-activated splenocytes were also determined. Oral administration of G. pentaphyllum extracts significantly attenuated AHR and inhibited eosinophil infiltration in mice of both IH3 and IH5 models. Significantly decreased serum OVA-specific antibodies and Th2-type cytokines, as well as the increased IFN- production, were detected in the IH5 model. Moreover, whether the long-administration of G. pentaphyllum was able to prevent asthma was examined in T-A model. The mice received the extract for 28 days before the sensitization with OVA. No significant reduction of asthma symptoms was detected. In the other 2 models, mice received the G. pentaphyllum extract before and during the contact with OVA (the T-B model) and 28 days since the first dose of OVA injection (the T-C model). The result showed that G. pentaphyllum extract could significantly attenuate inflammatory responses and Th2-cell activity. Therefore, the results suggested that G. pentaphyllum inhibited airway inflammation and over-active immune responses, but can not prevent the symptoms in asthmatic mice.
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