Simultaneous analysis of acetylcarnitine, proline, hydroxyproline, citrulline, and arginine as potential plasma biomarkers to evaluate NSAIDs-induced gastric injury by liquid chromatography–tandem mass spectrometry

[Display omitted] •LC–MS/MS analysis for simultaneous determination of 5 amino acids was developed.•The assay was fully validated and applied to in vivo studies in rats and dogs.•Proline, hydroxyproline, and citrulline levels were reduced by aceclofenac doses.•The assay may be useful to monitor changes of the amino acid levels as biomarkers. Although major adverse effects associated with nonsteroidal anti-inflammatory drugs (NSAIDs) are gastric injury, assessment of NSAIDs-induced gastrointestinal adverse effects is mostly dependent on endoscopy due to the lack of plasma biomarkers. Several amino acids associated with collagenase activity and gastric mucosal mass have been suggested as plasma biomarker candidates for gastric injury. Therefore, this study aimed to develop a liquid chromatography-tandem mass spectrometry (LC–MS/MS) method for the plasma biomarker candidates, i.e., acetylcarnitine, proline, hydroxyproline, citrulline, and arginine and evaluate their potential as a biomarker for NSAIDs-induced gastric injury. The method utilized simple protein precipitation with methanol and D4-citrulline as an internal standard (IS). The assay resulted in the lower limit of quantification (LLOQ) of 0.1 μg/mL for acetylcarnitine and 1 μg/mL for proline, hydroxyproline, citrulline, and arginine in the surrogate blank plasma. The intra- and inter-day accuracy ranged 82.5–111.2% for acetylcarnitine, 95.4–103.3% for proline, 98.9–106.4% for hydroxyproline, 99.5–103.5% for citrulline, and 87.4–105.3% for arginine. The precision was within 6.17%, 3.63%, 6.20%, 6.31%, and 6.17% for acetylcarnitine, proline, hydroxyproline, citrulline, and arginine, respectively. The developed assay was successfully applied to monitor the changes of the plasma levels of the five amino acids in rats and Beagle dogs following repeated oral administrations of aceclofenac. In rats, plasma concentrations of proline, hydroxyproline, and citrulline were significantly reduced after 4 days of aceclofenac administration compared to the control group. In dogs, plasma concentrations of proline and citrulline were significantly decreased after 7 days of aceclofenac administration compared to those obtained after the first aceclofenac administration. These data indicate that plasma levels of proline, hydroxyproline, and citrulline may be used as quantitative biomarkers of NSAIDs-induced gastric damage. The present assay could also be utilized to monitor the changes of these amino acids as potential