In vitro anion transport alterations and apoptosis induced by phenylbutazone in the right dorsal colon of ponies

Colonic Health in Hospitalized Horses Treated with Non-Steroidal Anti-Inflammatory Drugs - A Preliminary Study

Non-steroidal anti-inflammatory drugs (NSAIDs) can cause right dorsal colitis, but longitudinal clinical studies are lacking. This study investigates whether NSAID treated horses develop right dorsal colonic pathology in a clinical setting. Non-gastrointestinal hospitalized horses treated with NSAIDs >4 days, and untreated hospital-owned teaching horses and non-gastrointestinal client-owned hospitalized horses were included. All horses were monitored over time with clinical examinations (focusing on presence of colic, depression, reduced appetite, unstructured feces), ultrasonographic intestinal wall measurements, fecal occult blood tests (semi-quantitative results), and blood analysis (total protein and albumin concentrations, white blood cell and neutrophil counts). Outcomes were recorded as "ultrasonographically thickened right dorsal colon (RDC) walls", "colitis" and "right dorsal colitis". Findings over time were compared to baseline values and to control horses. Seventeen NSAID treated horses and 5 controls were included. NSAID treated horses developed thickened RDC walls (4/9), and subclinical and mild colitis (9/11) and right dorsal colitis (4/10), whereas all control horses remained healthy. The first changes were identified on treatment day 2. RDC walls of treated horses were significantly thicker compared to their own baseline values and compared to control horses. In conclusion, presumptive colon pathology was identified with a high incidence, starting early in the course of treatment, but with low severity. Appropriate monitoring should be advised throughout NSAID treatment. Additional research for noninvasive diagnostic tests for colon pathology is required.

Expression of cyclooxygenase-1 and -2 in the left dorsal colon after different durations of ischemia and reperfusion in horses

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.

Effects of flunixin meglumine on recovery of colonic mucosa from ischemia in horses

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.

Effects of phenylbutazone, indomethacin, prostaglandin E2, butyrate, and glutamine on restitution of oxidant-injured right dorsal colon of horses in vitro

OBJECTIVE

To study the effects of phenylbutazone, indomethacin, prostaglandin E2 (PGE2), glutamine, and butyrate on restitution of oxidant-injured right dorsal colon of horses in vitro.

SAMPLE POPULATION

Right dorsal colon from 9 adult horses euthanatized for reasons other than gastrointestinal tract disease.

PROCEDURES

Mucosal segments from the right dorsal colon were injured via exposure to HOCl and incubated in Ussing chambers in solutions containing phenylbutazone, indomethacin, indomethacin and PGE2, glutamine, and butyrate. Transepithelial resistance and mucosal permeability to mannitol were measured, and all mucosal segments were examined histologically.

RESULTS

The HOCl-injured mucosa had lower resistance and higher permeability to mannitol, compared with control tissue. Histologic changes were also evident. Resistance of HOCl-injured mucosa recovered partially during the incubation period, and glutamine improved recovery. Phenylbutazone and indomethacin increased resistance, but these increases were not significant. Butyrate and PGE2 had no effects, compared with nontreated HOCl-injured tissues. Mucosal permeability to mannitol was lower in glutamine-treated tissue, compared with nontreated tissue. Histologic changes reflected the resistance and permeability changes.

CONCLUSIONS AND CLINICAL RELEVANCE

According to our findings, phenylbutazone and indomethacin do not seem to interfere with restitution of oxidant-injured mucosa of equine colon in vitro, and glutamine could facilitate mucosal restitution.

Assessment of apoptosis in epidermal lamellar cells in clinically normal horses and those with laminitis

OBJECTIVE

To determine and compare the number, type, location, and distribution of apoptotic epidermal cells in the laminae of clinically normal horses and horses with laminitis.

SAMPLE POPULATION

Formalin-fixed samples of digital lamellar tissue from 47 horses (including clinically normal horses [controls; n = 7], horses with acute [4] and chronic [7] naturally acquired laminitis, and horses with black walnut extract-induced [11] or carbohydrate overload-induced [18] laminitis).

PROCEDURE

Blocks of paraffin-embedded lamellar tissues were stained for DNA fragmentation with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) technique. Differential immunohistochemical staining for caspases 3 and 14 were used to confirm apoptosis.

RESULTS

The number of TUNEL-positive epidermal cells per 0.1 mm of primary laminae was significantly greater in the acute laminitis group than in the other groups. In the acute laminitis group, there were 17 and 1,025 times as many TUNEL-positive basal layer cells and keratinocytes, respectively, compared with the control group. Apoptosis of TUNEL-positive basal layer cells was confirmed by results of caspase 3 immunohistochemical staining. The TUNEL-positive keratinocytes did not stain for caspases 3 or 14.

CONCLUSIONS AND CLINICAL RELEVANCE

The large number of apoptotic basal layer cells detected in the lamellar tissue of horses with acute naturally acquired laminitis suggests that apoptosis may be important in the development of acute laminitis. The role of the large number of TUNEL-positive keratinocytes detected in the interface of primary and secondary epidermal laminae of horses with acute laminitis remains to be elucidated.

Detection of apoptotic cells in intestines from horses with and without gastrointestinal tract disease

OBJECTIVE

To identify apoptosis in equine intestines and determine whether apoptosis is associated with gastrointestinal tract disease or a specific tissue layer of intestine.

ANIMALS

38 horses that underwent surgery or were euthanatized for small or large intestine obstruction, strangulation, or distension and 9 control horses euthanatized for reasons other than gastrointestinal tract disease or systemic disease.

PROCEDURE

Specimens were collected at surgery from intestine involved in the primary lesion and distant to the primary lesion site or at necropsy from several sites including the primary lesion site. Histologic tissue sections were stained with H&E, and apoptosis was detected by use of the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling technique. The number of apoptotic cells per hpf was counted in the mucosa, circular muscle, longitudinal muscle, and serosa.

RESULTS

Apoptotic nuclei were seen in all layers of intestine. An increased number of apoptotic cells was found in the circular muscle of the intestine from horses with simple obstruction, compared with strangulating obstruction or healthy intestine. Intestine distant from a primary strangulating lesion had higher numbers of apoptotic cells than did intestine distant from a simple obstructive lesion or intestine taken at the site of a strangulating or simple obstructive lesion.

CONCLUSIONS AND CLINICAL RELEVANCE

Intestine from horses with obstructing or strangulating lesions in the small intestine and large colon had high numbers of apoptotic cells possibly because of ischemic cell injury and subsequent inflammation. Whether substantial apoptosis affects intestinal function is not yet known.