Nonsteroidal anti-inflammatory drug administration alters crypt distribution of the peroxisomal marker acyl-coenzyme A oxidase 1 in the equine right dorsal colon.

NSAID administration induces region-specific increases in ACOX1 at the RDC crypt tip, potentially contributing to right dorsal colitis susceptibility.

This study investigated the distribution of peroxisomal markers in equine colonic tissue to better understand the regional susceptibility of the right dorsal colon (RDC) to NSAID-induced injury. Archived colonic tissues from 10 horses were evaluated, comparing five horses administered phenylbutazone (4.4 mg/kg PO BID for 10 days) to five placebo controls. Immunofluorescence was used to quantify peroxisomal biogenesis factor 14 (PEX14) and acyl-coenzyme A oxidase 1 (ACOX1) distribution across crypt regions (tip, mid, base) in both the RDC and left ventral colon (LVC). In healthy horses, no significant differences in PEX14 or ACOX1 distribution were detected between the RDC and LVC. ACOX1 fluorescence area per cell was greater at the crypt tip than the base in both colonic regions, while PEX14 distribution did not vary along the crypt axis. NSAID administration did not affect PEX14 distribution in either region; however, ACOX1 area per cell at the crypt tip was significantly greater in the RDC compared to the LVC in NSAID-treated horses (mean difference 1.66 μ²/nuclei; 95% CI, 0.35–2.97). These findings suggest a region-specific peroxisomal response to NSAIDs in the RDC, which may partly explain the known susceptibility of this region to NSAID-associated colitis. The authors conclude that peroxisomal pathway differences in the RDC warrant further investigation into underlying injury mechanisms and potential prevention strategies.

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