Role of tryptase in intestinal ischemia-reperfusion injury in rats: the relationship with inflammatory responses, lipid peroxidation and cell apoptosis

Objective To evaluate the role of tryptase in intestinal ischemia-reperfusion (I/R) injury in rats and the relationship with inflammatory responses, lipid peroxidation and cell apoptosis. Methods Thirty clean-grade healthy male Sprague-Dawley rats, aged 2-3 months, weighing 150-270 g, were divided into 3 groups (n=10 each) using a random number table method: sham operation group (Sham group), intestinal I/R group (II/R group) and tryptase inhibitor group (PRTM group). Intestinal I/R was produced by occlusion of the superior mesenteric artery for 75 min followed by 4-h reperfusion in II/R and PRTM groups.The superior mesenteric artery was only exposed but not occluded in Sham group.Protamine 2.5 mg/kg was injected via the caudal vein at 5 min of before reperfusion in PRTM group.The rats were sacrificed at the end of reperfusion, and the small intestinal tissues 1 cm in length 5 cm away from the terminal ileum were removed for examination of the pathological changes (with a light microscope) and for determination of intestinal mucosal mast cell (IMMC) count and expression of tryptase in mast cells (by immunohistochemical SP staining), malondialdehyde (MDA) content (using thiobarbituric acid assay), superoxide dismutase (SOD) activity (by xanthine oxidase method), expression of caspase-3 (by Western blot) and contents of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) (by enzyme-linked immunosorbent assay). The degree of intestinal tissue damage was graded using Chiu′s scoring system. Results Compared with Sham group, the pathological changes were significantly accentuated, Chiu′s score was increased, the expression of tryptase was up-regulated, the IMMC count and contents of TNF-α, IL-6 and MDA were increased, the activity of SOD was decreased, and the expression of caspase-3 was up-regulated in II/R and PRTM groups (P<0.05). Compared with II/R group, the pathological changes were significantly attenuated, Chiu′s score was decreased, the expression of tryptase was down-regulated, the IMMC count and contents of TNF-α, IL-6 and MDA were decreased, the activity of SOD was increased, and the expression of caspase-3 was down-regulated in PRTM group (P<0.05). Conclusion Tryptase is involved in the process of intestinal I/R injury though promoting inflammatory responses, lipid peroxidation and cell apoptosis in rats. Key words: Tryptases; Intestine; Reperfusion injury; Inflammation; Lipid peroxidation; Apoptosis