Protective Effects Of Rheum Tanguticum Polysaccharide On Stress Ulcer In Rats

Background: Stress ulcer is defined as acute gastric mucosal lesions occurring in severely ill patients in the condition such as trauma, infection, shock, severe psychological block and so on. Over the past several years, the vital organs of critically ill patients have got effective treatment, and the mortality has decreased markedly, probably as a result of advance in the intensive care facilities and technologies. At the same time it results in the prolonged critical period and the increasing rate of stress ulcer. All these make the clinical importance of stress ulcer gradually prominent. Stress ulcer usually occurs between the third and seventh days after intensive care unit (ICU) admission. Once the massive hemorrhage is intercurrent, there is lack of effective remedy in clinic. Therefore, much hope is currently placed on prevention. It has been reported that rhubarb had striking therapeutic effectson gastrointestinal disease both in animal experiments and in clinical using, especially on gut failure. In traditional Chinese medicine, rhubarb is one of the necessary drugs used in emergency situation. Rheum tanguticum polysaccharide (RTP), one of the water soluble components extracted from Rheum tanguticum Maxim.ex Regel in our laboratory, have showed significant effects against oxidation injury, traumatic brain injury and ulcerative colitis. In present study, the experiments were designed to investigate the protective effects of RTP on stress ulcer in rats and explore the possible mechanism.Methods: Water immersion and restraint stress (WRS) induced acute gastric injury was used as the experimental model of stress ulcer of rats. All the animals were randomly divided into 6 groups, the control group, the model group, RTP 100, 200, 400mg/kg and sucralfate 500mg/kg group. Rats were orally administrated with RTP or sucralfate for 5 days before stressed. 6 hours after WRS, rats were anaesthetized and the stomachs were removed to examine the ulcer index as the method described by Guth. Morphological observation of the change of pathology and ultrastructure in gastric mucosa was performed by light microscopy and transmission electron microscopy. The activity of total superoxide dismutase (SOD) and malondialdehyde (MDA) level in serum and gastric mucosa were measured by xanthine oxidase method and thibabituric acid (TBA) method respectively. Immunohistochemical staining was used to determine the expression and the distribution of heat shock protein 70 (HSP70). The detection of the change of HSP70 in gastric mucosa was performed by Western blot. The effect of RTP on apoptosis of gastric epithelial cells was assessed by Terminaldeoxynucleotide transferase-mediated dUTP nick end labeling ( TUNEL ) technique.Results: 6h WRS resulted in acute gastric mucosal lesions, characterized by extensive erosion, hemorrhage and ulceration. The administration of RTP or sucralfate could significantly decrease the ulcer index (P<0.01). RTP 200mg/kg exerted the best protective effect and was superior to sucralfate 500mg/kg (P<0.05). RTP could lessen the mucosal damage and alleviate the edema in capillary vessel and interstitial tissue. In RTP 200mg/kg and 400mg/kg group, RTP exhibited the strong ability to rise the activity of SOD both in serum and gastric mucosa (P<0.01) and lower the mucosal MDA concentration (P<0.01). The results of immunohistochemical staining showed that WRS induced more HSP70 positive cells in gastric mucosa, while the number of HSP70 positive cells was increased and there was a wider distribution of HSP70 positive cells covering the whole mucosa in RTP pretreatment group compared with the model group. Similarly, the analysis of Western blot showed that RTP-pretreated rats acquired more HSP70 expression in gastric mucosa than control rats in response to the same stress. The number of apoptotic cells was increased strikingly by 6h WRS, while RTP pretreatment could decrease the number of apoptotic cells significantly. Conclusion: RTP exhibits remarkable protective effects on WRS induced stress ulcer in rats. The protective effects might be related to trigger the intrinsic protective mechanism by enhancing the anti-oxidative effect, increasing the expression of HSP70 in the gastric mucosa and interfering with the stress-induced apoptotic programme. Therefore, the results suggest that RTP may be an effective component of rhubarb on the therapy of stress...