Tu1228 Effect of Phosphatidylcholine (PC)-Aspirin on Small Bowel Mucosal Injury

Abstract

Background: Aspirin can induce small bowel injury. There is no proven treatment of aspirin enteropathy other than withdrawal. Recently, a novel aspirin associated with phosphatidylcholine(PC) is designed to be gastric protective due to hydrophobic property of PC. Lysophosphatidic acid (LPA), a metabolite from PC and mucin were found to play roles in integrity of gastrointestinal tract epithelium. This study hypothesized that PC-aspirin would reduce aspirin-induced small bowel injury. Methods: Sprague-Dawley rats were intra-duodenally administrated with either PC-aspirin (100mg, n=12-14), Plain aspirin (100mg, n=12-14) or vehicle (1ml 2%methtcellylulose, n=12), and euthanized after 90 minutes. Small bowel injury was assessed by lesion area, vascular permeability (i.v. 1% Evan's blue solution), intestinal hemoglobin concentration and histological change (H&E stained slides were scored with a scoring system). Apoptotic index was estimated with western blot and TUNEL staining (apoptotic cell in 5 villi would be counted). The expressions of lysophosphatidic acid receptor 2 (LPA2), MUC2 the mainly expressed secretory mucin in intestine, and TLR4, MyD88, NF-κΒp50 were test with Western blot or real-time PCR. Mucins were stained with Periodic Acid Schiff (PAS). Prostaglandin E2 (PGE2) concentration were detect with ELISA. Results: Comparing to plain aspirin-treated rats, PC-aspirin caused fewer injuries in the small bowel as assessed in: lesion area (4.82±1.61mm2 vs 196.00±84.89mm2 P=0.003), vascular permeability (42.81±7.69ug/ml vs 74.73±18.61ug/ml P=0.003), intestinal hemoglobin concentration (66.67±16.81ng/ml vs 91.83±14.80ng/ml P=0.020) and histological change (2.12±0.56 vs 3.06±1.07 P=0.044)(Figure 1). Also a decreased apoptotic index was found in PC-aspirin group (16.43±4.28 vs 38.71±5.59 P<0.001 for TUNEL, 0.49±0.14 vs 1.06±0.33 P=0.007 for cleaved caspase-3, 0.81±0.29 vs 1.40±0.56 P=0.043 for cleaved caspase-7, Figure 1). Immunohistochemical staining and western blot (0.21±0.06 vs 0.14±0.06 P=0.044 for PCaspirin vs Plain aspirin) showed that LPA2-positive cells were strongly expressed in surfacelining of small bowel mucosa in the control and PC-aspirin groups but not in the plain aspirin group (Figure 2). Moreover, PAS staining reveals a thicker mucin layer in PC-aspirin rats, with a higher MUC2 mRNA level than plain aspirin rats (1.70±0.75 vs 0.98±0.45 P= 0.039)(Figure 2). The tissue expressions of TLR4, MyD88, NF-κΒp50 and COX-2 were increased while PGE2was decreased in both plain aspirin and PC-aspirin groups. Conclusion: PC-aspirin significantly decreased aspirin induced small bowel injury, this effect may associated with (1) increased LPA2 expression, which protect mucosa from apoptotic damages, and (2) increased MUC2 mRNA expression and decreased mucin layer consumption caused by aspirin, which help to suppress bacterial invasion.