Identification of N-acetyl Proline–Glycine–Proline (acPGP) in human serum of adults and newborns by liquid chromatography–tandem mass spectrometry

BackgroundN-acetyl Proline–Glycine–Proline (acPGP) is a novel neutrophil chemoattractant. However, no studies have been reported to identify the presence of acPGP in human serum. The purpose of our study was to establish a method for measuring acPGP, and to determine whether acPGP is present in human serum.MethodsSerum samples were obtained from 22 healthy adults and 26 term and preterm newborns. For the sensitive analysis of acPGP, we utilized liquid chromatography–tandem mass spectrometry (LC–MS/MS) with a multiple reaction monitoring (MRM) positive ion mode.ResultsThe major product ions of acPGP ([M + H]+ ion, m/z 312) appeared at 112 and 140. The MRM (transition: m/z 312/112) chromatogram in human serum showed a single peak with the same retention time as that of authentic acPGP. The calibration curve of authentic acPGP was linear, and our quantitative results indicated high precision. The mean serum acPGP levels in adults and newborns were 6.3 and 18.7 pg/ml, respectively. In newborns, lower birth weight infants had significantly higher serum acPGP levels.ConclusionsWe established a method for the quantification of serum acPGP using LC–MS/MS, and this paper provides the first evidence for the presence of acPGP in human serum of adults and newborns.