The proteomic differences and expression of fatty acid-binding protein 6 (FABP6) associated with gastrointestinal injury in horses with oral administration of a clinical dose of phenylbutazone.

Background: Phenylbutazone (PBZ) can potentially induce gastrointestinal ulceration, and early detection of PBZ-induced gastroenteropathy will be useful for the diagnosis, treatment, and prevention of PBZ toxicity.

Objectives: To identify putative proteins associated with equine gastric ulcer syndrome after clinical dose (4.4 mg/kg) administration of PBZ by proteomic study.

Study design: In vivo experiments.

Methods: Proteomic analysis using LC-MS/MS compared protein expression in serum and faeces of seven PBZ-treated horses with seven placebo-treated controls, and a novel putative biomarker was validated via enzyme-linked immunosorbent assay.

Results: Differentially expressed proteins (DEPs) analysis on 5298 serum annotated proteins and 3538 faecal annotated proteins using the DESeq2 were performed between the control and treatment of EGUS groups. The results showed a list of 226 and 181 significant proteins in serum and faecal samples, respectively with a p adjust value <0.05. The proteomic serum and faeces samples were integrated into STITCH to illustrate PBZ interaction with bile acid homeostasis. FABP6 was significantly increased in PBZ-treated horses. The serum FABP6 concentration in the treatment group on Day 8 (1.80 ± 0.37 ng/mL) was higher than on Day 0 (1.15 ± 0.33 ng/mL, p = 0.01, 95% CI [-1.07, -0.25]). On Day 8, the serum FABP6 concentration in the treatment group was also higher than the control group (1.20 ± 0.48 ng/mL; p = 0.02, 95% CI [-1.10, -0.11]).

Main limitations: Validation of all expressed proteins is a main limitation.

Conclusions: Administration of PBZ at a clinical dose of 4.4 mg/kg twice daily for 7 days may cause gastric mucosal damage. PBZ treatment increased the expression of SLC10A1 and FABP6, suggesting that early gastric mucosal injury may be linked to the bile acid pathway. Bile acids could potentially exacerbate PBZ-induced EGUS.