Are gastric mucosal macrophages responsible for gastric injury in acute pancreatitis?

AIM: To investigate the protective effect of clodronate-containing liposomes against severe acute pancreatitis (SAP)-triggered acute gastric mucosal injury (AGMI) in rats. METHODS: Clodronate- and phosphate-buffered saline (PBS)-containing liposomes were prepared by reverse-phase evaporation. The SAP rat model was established by injecting sodium taurocholate into the pancreatic subcapsular space. Sprague-Dawley rats were randomly divided into three groups: control (C), SAP plus PBS-containing liposome (P) and SAP plus clodronate-containing liposome (T). Serum tumor necrosis factor (TNF)-alpha levels were estimated by ELISA. Pathological changes in the gastric mucosa and pancreas were observed by hematoxylin and eosin (HE) staining. Apoptotic cells were detected by terminal deoxynucleotidyl transferase dUTP nick end labeling staining. The numbers of macrophages in the gastric mucosa were analyzed by CD68 immunohistochemical staining. RESULTS: The liposomes had a mean diameter of 150 +/- 30 nm. The TNF-alpha levels were significantly higher in the P group than that in the C group (2 h, 145.13 +/- 11.50 vs 23.2 +/- 2.03; 6 h, 245.06 +/- 12.11 vs 30.28 +/- 6.07, P < 0.05), and they were significantly lower in the T group than that in the P group (2 h, 93.24 +/- 23.11 vs 145.13 +/- 11.50; 6 h, 135.18 +/- 13.10 vs 245.06 +/- 12.11, P < 0.05). The pathological scores of the pancreas were lower in the T group than in the P group (2 h, 1.88 +/- 0.83 vs 4.13 +/- 0.83; 6 h, 2.87 +/- 0.64 vs 6.25 +/- 0.88, P < 0.01). The pathological scores of the gastric mucosa were also lower in the T group than in the P group (2 h, 1.12 +/- 0.64 vs 2 +/- 0.75; 6 h, 1.58 +/- 0.53 vs 3 +/- 1.31, P < 0.05). In addition, increased CD68 levels were observed in the gastric mucosa of the P group compared with the C group. Clodronate-containing liposomes decreased the CD68 levels in the mucosa of the T group. The apoptotic indexes of the gastric mucosa were higher in the T group than in the P group (2 h, 15.7 +/- 0.92 vs 11.5 +/- 1.64; 6 h, 21.12 +/- 1.06 vs 12.6 +/- 2.44, P < 0.01). CONCLUSION: Gastric macrophages contribute to the pathogenesis of gastric injury in SAP. Clodronate-containing liposomes have protective effects against AGMI in rats with SAP.