The use of Chinese herb medicine in experimental radiotherapy

Radioprotection by plant products: present status and future prospects

The development of radioprotective agents has been the subject of intense research in view of their potential for use within a radiation environment, such as space exploration, radiotherapy and even nuclear war. However, no ideal, safe synthetic radioprotectors are available to date, so the search for alternative sources, including plants, has been on going for several decades. In Ayurveda, the traditional Indian system of medicine, several plants have been used to treat free radical-mediated ailments and, therefore, it is logical to expect that such plants may also render some protection against radiation damage. A systematic screening approach can provide leads to identifying potential new candidate drugs from plant sources, for mitigation of radiation injury. This article reviews some of the most promising plants, and their bioactive principles, that are widely used in traditional systems of medicine, and which have rendered significant radioprotection in both in vitro and in vivo model systems. Plants and their constituents with pharmacological activities that may be relevant to amelioration of radiation-mediated damage, including antiemetic, antiinflammatory, antioxidant, cell proliferative, wound healing and haemopoietic stimulatories are also discussed.

Captopril reduces collagen and mast cell accumulation in irradiated rat lung

The angiotensin converting enzyme inhibitor captopril ameliorates radiation-induced pulmonary endothelial dysfunction in rats. The present study determined whether captopril also reduces collagen (hydroxyproline) accumulation in the lungs of rats sacrificed 2 months after a range of single doses (0-30 Gy) of 60Co gamma rays to the right hemithorax. Captopril was administered in the feed at a regimen of 0, 25, or 50 mg/kg/day continuously after irradiation. Mast cell counts also were obtained from lungs of all animals exposed to 30 Gy. In rats receiving no captopril, there was a radiation dose-dependent increase in right lung hydroxyproline (HP) content and in HP concentration per g wet weight. Captopril produced a drug dose-dependent suppression in this radiation-induced HP accumulation. At a dose of 50 mg/kg/d, captopril reduced the slope of the radiation dose response curve for lung HP content by a factor of 1.7, and completely prevented the increase in HP concentration. At an isoeffect level of 550 micrograms HP per right superior lobe, this dose of captopril exhibited a DRF of 1.7 +/- 0.2. In rats exposed to 30 Gy, moreover, the number of mast cells per mm2 of alveolar cross-sectional surface area decreased from 105 +/- 8 to 100 +/- 7 and 59 +/- 5 in the groups given 0, 25 or 50 mg/kg/d of captopril, respectively, (vs none in sham-irradiated rats). These data are the first to demonstrate that the ACE inhibitor captopril might provide a novel intervention in the pathogenesis of radiation fibrosis.