Comparison of Intestinal Cold Preservation Injury on Pituitary Adenylate Cyclase–Activating Polypeptide in Knockout and Wild-Type Mice

Abstract

Tissue injury caused by cold preservation remains a problem in small intestinal transplantation. Pituitary adenylate cyclase-activating polypeptide (PACAP) has a central role in intestinal physiology. The objective of the present study was to compare the effects of cold ischemia injury in PACAP-38 knockout and wild-type mice after cold storage of small bowel. Cold ischemia was produced using small bowel preservation in University of Wisconsin solution at 4°C in 20 PACAP-38 wild-type mice for 1, 3, and 6 hours (groups 1, 2, and 3, respectively) and 20 PACAP-38 knockout mice for 1, 3, and 6 hours (groups 4, 5, and 6, respectively). Biopsy samples of small bowel were obtained after laparotomy (control) and at the end of preservation periods. To determine oxidative stress, malondialdehyde, reduced glutathione, and superoxide dismutase concentrations were measured. Tissue damage was assessed using a quantitative method on sections stained with hematoxylin-eosin. After 6 hours, tissue lipid peroxidation was increased significantly in PACAP-38 knockout mice (mean ± SD, 153.04 ± 7.2 μmol/g) compared with sham-operated mice (110.44 ± 5.5 μmol/g) and wild-type mice (120.0 ± 1.1 μmol/g) ( P < .05). The capacity and activity of the endogenous antioxidant system decreased significantly after 3 and 6 hours of preservation (reduced glutathione, 808.7 ± 5.2 μmol/g and 720.4 ± 8.7 μmol/g; and superoxide dismutase, 125.1 ± 1.4 IU/g and 103.3 ± 1.9 IU/g vs 212.11 ± 5.8 IU/g; P < .05). Quantitative histologic analysis demonstrated destruction of mucosal and submucosal layers and crypts in knockout mice compared with wild-type mice. These processes depended on duration of cold preservation. These findings demonstrate that PACAP-38 has a key role in protection against intestinal cold preservation injury.