Novel chlorinated phospholipids-possible biomarkers of chlorine gas exposure

Biomarkers are needed to verify suspected exposure to chlorine gas in chemical attacks. Here, we aimed to expand upon the array of known biomarkers of chlorine gas exposure. 1-Palmitoyl- 2-oleoyl-sn-glycero- 3-phosphocholine (POPC), a phospholipid belonging to the phosphatidylcholine (PC) class, was chosen as the study material. The lipids were chlorinated using chlorine gas, followed by analysis for chlorinated PCs using liquid chromatography (LC) coupled with mass spectrometry (MS), using unit- (MS, MS/MS) and high-resolution (HRMS, MS/HRMS). By interpreting accurate masses, isotopic patterns, and fragmentation patterns, PC chlorohydrin, PC dichloride, the chlorinated PC with m/z 794.54611 (here denoted as PC A) and 10 novel chlorinated PCs were identified: four PCs chlorinated at the glycerol backbone and six chlorinated peroxy-diphospholipids. Similar experiments with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) resulted in the formation of the corresponding chlorohydrin and dichloride, as well as five chlorinated phosphatidylethanolamines (PEs) with chlorine in the glycerol backbone. Surprisingly, no chlorinated forms of 1-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholine (PSPC) were observed in similar experiments. In total, 15 novel chlorinated lipids were found. Furthermore, to determine the relevance of the novel lipids as biomarkers, a pig lung tissue sample was chlorinated in vitro. Two monomeric chlorinated PCs and two chlorinated peroxy-diphospholipids were identified from the chlorine-exposed lung sample, showing that the novel lipid compounds are potential biomarkers for chlorine gas exposure.