Quantitative determination of lysophosphatidic acids (LPAs) in human saliva and gingival crevicular fluid (GCF) by LC-MS/MS.

Lysophosphatidic acid (LPA) is a phospholipid mediator that plays multiple cellular functions by acting through G protein-coupled LPA receptors. LPAs are known to be key mediators in inflammation, and several lines of evidence suggest a role for LPAs in inflammatory periodontal diseases. A simple and sensitive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method has been developed and validated to quantify LPA species (LPA 18:0, LPA 16:0, LPA 18:1 and LPA 20:4) in human saliva and gingival crevicular fluid (GCF). LPA 17:0 was used as an internal standard and the LPA species were extracted from saliva by liquid-liquid extraction using butanol. Chromatography was performed using a Macherey-Nagel NUCLEODUR® C8 Gravity Column (125 mm × 2.0 mm ID) with a mixture of methanol/water: 75/25 (v/v) containing 0.5% formic acid and 5 mM ammonium formate (mobile phase A) and methanol/water: 99/0.5 (v/v) containing 0.5% formic acid and 5mM ammonium formate (mobile phase B) at a flow rate of 0.5 mL/min. LPAs were detected by a linear ion trap-triple quadrupole mass spectrometer with a total run time of 8.5 min. The limit of quantification (LOQ) in saliva was 1 ng/mL for all LPA species and the method was validated over the range of 1-200 ng/mL. The method was validated in GCF over the ranges of 10-500 ng/mL for LPA 18:0 and LPA 16:0, and 5-500 ng/mL for LPA 18:1 and LPA 20:4. This sensitive LC-MS/MS assay was successfully applied to obtain quantitative data of individual LPA levels from control subjects and patients with various periodontal diseases. All four LPA species were consistently elevated in samples obtained from periodontal diseases, which supports a role of LPAs in the pathogenesis of periodontal diseases.

Kinetic analysis of bile acid sulfation by stably expressed human sulfotransferase 2A1 (SULT2A1).

Human sulfotransferase 2A1 (SULT2A1) is a member of the hydroxysteroid sulfotransferase (SULT2) family that mediates sulfo-conjugation of a variety of endogenous molecules including dehydroepiandrosterone (DHEA) and bile acids. In this study, we have constructed a stable cell line expressing SULT2A1 by transfection into HEK293 cells. The expression system was used to characterize and compare the sulfation kinetics of DHEA and 15 human bile acids by SULT2A1. Formation of DHEA sulfate demonstrated Michaelis-Menten kinetics with apparent K(m) and V(max) values of 3.8 muM and 130.8 pmol min(-1) mg(-1) protein, respectively. Sulfation kinetics of bile acids also demonstrated Michaelis-Menten kinetics with a marked variation in apparent K(m) and V(max) values between individual bile acids. Sulfation affinity was inversely proportional to the number of hydroxyl groups of bile acids. The monohydroxy- and most toxic bile acid (lithocholic acid) had the highest affinity, whereas the trihydroxy- and least toxic bile acid (cholic acid) had the lowest affinity to sulfation by SULT2A1. Intrinsic clearance (CL(int)) of ursodeoxycholic acid (UDCA) was approximately 1.5- and 9.0-fold higher than that of deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA), respectively, despite the fact that all three are dihydroxy bile acids.