Effect Of Water-solubie Polysaccharides Derived From Poria Cocos On Ethylene Glycol Induced Urolithiasis In Rats

Objective:Urolithiasis, one of the most painful ailments of the urinary tract disorder, is one of the most common diseases in the urinary system. The prevalence differs in various parts of the world,1-5%in Asia,5-9%in Europe,13%in North America, and20%in Saudi Arabia, and there are a few geographical areas in which stone disease is rare, e.g. in Greenland and in the coastal areas of Japan. Unlike any other human disease, the occurrence of urinary calculi was documented far back into antiquity. Approximately of80%of the stone are composed of calcium oxalate (CaOx). Urinary calculi may cause obstruction, infection, hemorrhage, hydronephrosis in the urinary tract, and renal function insufficiency. Great improvements have been made in the treatment of urinary calculi thanks to the development of extracorporeal shock wave lithotripsy (ESWL) and the endoscopic surgery. Currently, open renal surgery for nephrolithiasis is unusual and uesd only rarely since the introduction of ESWL and endoscopic lithotripsy. The patients who exposure to ESWL may cause hemorhage, hypertention, tubular necrosis, kidney fibrosis, acute kidney injury (AKI), decrease in renal function, and increase in calculi recurrence. But it is important to point out that urolithiasis is characterized by high recurrence rate. It is reported that the recurrence rate of urolithiasis without preventive treatment is approximately10%at one year, 33%at five year,50%at ten years and75%at15years. There has been no effective measures to prevent the occurrence of urinary calculi. Kidney stone formation is a complex process that results from a succession of several events including supersaturation, nucleation, growth, aggregation, and retention within renal tubules. Renal stone can be broadly classified into two large groups:tissue attached and tissue unattached. Renal cellular exposure to oxalate and/or CaOx crystals leads to the production of reactive oxygen species (ROS), development of oxidative stress (OS) followed by injury and inflammation. At present, it seems clear that renal epithelial cell injuries play a decisive role in renal calculi development. It has been reported that raised OS is often present in urolithiasis in human, animal and in vitro studies. Oxalate promotes oxidative stress, which is retarded by antioxidants. Free radicals, molecules or atoms with unpaired electrons, and their metabolites, collectively called ROS which are high reactive. ROS play a important role in a variety of signaling pathways. Furthermore, they can produce damage to, and modifications of nucleotides, lipids, protein and carbohydrates. Major cellular reactive oxygen species include nitric oxide radical, hydroxyl radical, hydrogen peroxide, and superoxide anion. ROS are produced from many sources. Nitric oxide radical are produced by the endothelial nitric oxide synthase (eNOS) mediated oxidation of L-arginine. Superoxide anions are produced by xanthine oxidase, NADPH oxidase, hemeoxygenase, lipooxigenase, cyclooxygenase, and as a byproduct of the mitochondrial respiratory chain. Lipid radicals can also produce superoxide anions. eNOS can also produce superoxide anions rather than nitric oxide radical. Reactions between nitric oxide and superoxide can produce the highly reactive peroxynitrite ONOO-.Cells are equipped with several scavenging systems to limit ROS, such as superoxide dismutase (SOD) which has the ability to eliminate superoxide anions, catalase and glutathione peroxidase to detoxify hydrogen peroxide. Under normal conditions ROS are generated by tightly controlled enzymes and involved in various regulatory processes and signaling pathways, but an overproduction of ROS and/or a reduction in cellular antioxidant capacities leads to the development of OS. Because most ROS are short-lived and do not travel long distance, the presence of OS is recognized by a lots of byproducts of ROS interaction with carbohydrate, lipids, nucleic acids, amino acids, and protein. Malondialdehyde (MDA), oxidized lipids are the major byproducts of ROS induced OS. OS is injurious to all components of the renal epithelium which can be retard by antioxidants. Herbal medicine has been used for several thousands years and is as ancient as the history of mankind. Actually, natural herbal medicine has been used widely in Asia, and has gained popularity in Europe, and in United Stated as well. Various herbal medicines have been used in treating urolithiasis, but the exact mechanism of herbal medicine in treating urinary calculi has not been revealed. Poria cocos is one of the most popular traditional Chinese medicinal plant and has pharmacological importance in antilithic activities. Water soluble polysaccharides (WSP) is the main active material derived from poria cocos which is very little content in poria cocos, β-(1-3)-D-glucan is the major content of poria cocos, which shows little activity, but its derivatives can show anti-tumor activity.In this study, we want to evaluate the antilithic mechanism of WSP derived from poria cocos on ethylene glycol induced urolithiasis in rats. Methods:The effect of WSP derived from poria cocos on calcium oxalate urolithiasis was studied in male Wistar rats. Urolithiasis rat model were induced by0.8%ethylene glycol [v/v](EG) and1%ammonium chloride [w/v](AC) for eight days. In addition to EG/AC treatment rats were also treated solutions containing WSP derived from poria cocos (150mg/kg). Positive control rats were treated only with EG/AC. Negative control rats were provided with normal drinking water, and were administered normal water by gavage. Each group contained six rats. After eight days, twenty-four hour urine samples were collected for analysis, the left kidney was removed and assessed for crystal deposition using light microscopy, the right kidney was assessed for malondiadehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) levels by elisa method.Result:There was a significant loss weight after inducing crystal deposition in Group Ⅱ while a normal body weight increase in Group Ⅰ,and a less loss weight in Group Ⅲ. The rats treated with EG/AC alone had higher amounts of crystal deposition in the kidneys compared to negative control group of rats. This EG/AC-induced increase in kidney crystal deposition was inhibited by the administration of WSP derived from poria cocos. An increased level of SOD, CAT, magnesium excretion and decreased level of MDA were also found in polysaccharide-treated group, as compared with positive control group.Conclusion:We concluded that administration of WSP derived from poria cocos to rats with EG/AC induced rats, prevented the formation of urolithiasis. The mechanism underlying this effect is related to increased diuresis, urinary magnesium excretion and inhibition of OS activity.Significance:To study the efficacy of WSP derived from poria cocos on ethylene glycol induced urolithiasis in rats, not only understand the exact antilithic mechanism of WSP from poria cocos, but also make a basis of studying the mechanism of derivatives of β-(1-3)-D-glucan isolated poria cocos, making full use of poria cocos and sparing the natural medicinal herb.