ABSTRACT
OBJECTIVE: To assess the effects of ischemia and reperfusion on indicators of oxidative stress, activation of eosinophils, and apoptosis in the large colonic mucosa of horses. ANIMALS: 40 horses. PROCEDURES: In 1 or two 20-cm-long segments of the pelvic flexure, ischemia was induced for 1 or 2 hours followed by no reperfusion or 30 minutes and 18 hours of reperfusion in anesthetized horses. Mucosal specimens were collected before (controls; n = 20 horses) and after each period of ischemia, and full-thickness tissue samples were collected after each period of reperfusion. Sections of colonic tissues were stained for histomorphometric analysis or assessment of eosinophil accumulation. Nitrotyrosine was identified immunohistochemically, and severity of apoptosis was determined via the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method. RESULTS: Numbers of mucosal eosinophils were similar before induction of ischemia, after ischemia, and after ischemia-reperfusion. Eosinophil nitrotyrosine production increased significantly during ischemia and continued through 30 minutes of reperfusion; production was decreased at 18 hours of reperfusion but remained greater than that of the controls. In other leukocytes, nitrotyrosine generation peaked at 1 hour of ischemia and again at 18 hours of reperfusion. Compared with control findings, epithelial apoptosis increased gradually at 1 through 2 hours of ischemia with no further progression after reperfusion. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that resident eosinophils in the large colon of horses react to mucosal injury from ischemia and reperfusion and may undergo oxidative stress under those conditions. Epithelial apoptosis could contribute to tissue damage.
Subject(s)
Colon/pathology , Colonic Diseases/veterinary , Horse Diseases/physiopathology , Horses , Intestinal Mucosa/pathology , Ischemia/veterinary , Reperfusion Injury/veterinary , Animals , Apoptosis , Colon/cytology , Colon/immunology , Colon/metabolism , Colonic Diseases/immunology , Colonic Diseases/metabolism , Colonic Diseases/physiopathology , Eosinophils/cytology , Female , Horse Diseases/immunology , Horse Diseases/metabolism , In Situ Nick-End Labeling/veterinary , Intestinal Mucosa/immunology , Intestinal Mucosa/injuries , Intestinal Mucosa/metabolism , Ischemia/metabolism , Ischemia/physiopathology , Male , Microscopy, Electron, Scanning/veterinary , Oxidative Stress , Random Allocation , Reperfusion Injury/metabolism , Reperfusion Injury/physiopathology , Tyrosine/analogs & derivatives , Tyrosine/metabolismABSTRACT
OBJECTIVE-To identify expression and localization of cyclooxygenase (COX)-1 and COX-2 in healthy and ischemic-injured left dorsal colon of horses. SAMPLE POPULATION-Left dorsal colon tissue samples from 40 horses. PROCEDURES-Tissue samples that were used in several related studies on ischemia and reperfusion were evaluated. Samples were collected during anesthesia, before induction of ischemia, and following 1 hour of ischemia, 1 hour of ischemia and 30 minutes of reperfusion, 2 hours of ischemia, 2 hours of ischemia and 30 minutes of reperfusion, and 2 hours of ischemia and 18 hours of reperfusion. Histomorphometric analyses were performed to characterize morphological injury. Immunohistochemical analyses were performed to characterize expression and localization of COX-1 and COX-2. RESULTS-COX-1 and COX-2 were expressed in control tissues before ischemia was induced, predominantly in cells in the lamina propria. Ischemic injury significantly increased expression of COX-2 in epithelial cells on the colonic surface and in crypts. A similar significant increase of COX-1 expression was seen in the epithelial cells. CONCLUSIONS AND CLINICAL RELEVANCE-On the basis of information on the role of COX-2, upregulation of COX-2 in surface epithelium and crypt cells following ischemic injury in equine colon may represent an early step in the repair process.
Subject(s)
Colitis, Ischemic/veterinary , Cyclooxygenase 1/metabolism , Cyclooxygenase 2/metabolism , Horse Diseases/pathology , Reperfusion Injury/veterinary , Animals , Colon/blood supply , Colon/metabolism , Colon/pathology , Cyclooxygenase 1/genetics , Cyclooxygenase 2/genetics , Gene Expression Regulation, Enzymologic , Horse Diseases/metabolism , Horses , Reperfusion Injury/metabolism , Time FactorsABSTRACT
OBJECTIVE: To examine the effects of flunixin meglumine (FM) on recovery of colonic mucosa from experimentally induced ischemia in horses. ANIMALS: 14 research horses. PROCEDURES: Ischemia was induced in the colons of anesthetized horses for 2 hours. Afterward, horses received saline (0.9% NaCl) solution (12 mL, IV, q 12 h; n = 7) or FM (1.1 mg/kg, IV, q 12 h; 7) and were allowed to recover for 18 hours after termination of the ischemic event. Postoperative pain scores were recorded every 4 hours throughout the recovery period. At the end of the recovery period, horses were anesthetized, and ischemic and nonischemic segments of colonic mucosa were harvested for histologic evaluation, western blot analysis, and in vitro assessment of transepithelial electric resistance (TER) and transmucosal flux of tritium-labeled (3H-) mannitol. Horses were then euthanatized. RESULTS: Flunixin meglumine significantly lowered pain scores at the first postoperative recording. There were no significant differences between treatment with saline solution and FM in any of the measurements for TER, 3H-mannitol flux, histomorphometric variables, neutrophil infiltration (detected via calprotectin immunostaining), and expressions of cyclooxygenase-1 and -2. After both treatments, TER declined significantly in nonischemic tissues in vitro, whereas it increased significantly in ischemic-injured tissues. CONCLUSIONS AND CLINICAL RELEVANCE: Flunixin meglumine did not affect recovery of equine colonic mucosa from ischemic injury, and continued use in horses with colonic ischemia is therefore justified.
