Development and validation of a simple and rapid HILIC-MS/MS method for the quantification of low-abundant lysoglycerophospholipids in human plasma

Lysoglycerophospholipid metabolism alterations associated with ambient fine particulate matter exposure: Insights into the pro-atherosclerotic effects

The biological pathways connecting ambient fine particulate matter (PM2.5)-induced initial adverse effects to the development of atherosclerotic cardiovascular diseases are not fully understood. We hypothesize that lysoglycerophospholipids (LysoGPLs) are pivotal mediators of atherosclerosis induced by exposure to PM2.5. This study investigated the changes of LysoGPLs in response to PM2.5 exposure and the mediation role of LysoGPLs in the pro-atherosclerotic effects of PM2.5 exposure. In this longitudinal panel study, 110 adults aged 50-65 years from Beijing, China, were followed between 2013 and 2015. Targeted metabolomics analyses were utilized to quantify 18 LysoGPLs from five subclasses in 579 plasma samples. Daily PM2.5 mass concentration was monitored at a station. We used linear mixed-effect models to estimate the responses of LysoGPLs to PM2.5 exposure. Subsequently, mediation analyses were conducted to investigate the mediating role of LysoGPLs in PM2.5-associated changes in non-high density lipoprotein-cholesterol (Non-HDL-C), a biomarker for pro-atherosclerotic apolipoprotein B-containing lipoproteins, and various inflammatory biomarkers, including interleukin (IL)-8, monocyte chemoattractant protein-1 (MCP-1), soluble CD40 ligand, and interferon (IFN)-γ. Short-to medium-term (1-30 days) PM2.5 exposure was associated with significant increases in six lysophosphatidic acids (LPAs), three lysoalkylphosphatidylcholines [LPC(O)s], and three lysophosphatidylglycerols (LPGs), as well as decreases in two LPAs and one lysophosphatidylserine (LysoPS), with maximus changes of 0.5-2.1%, 0.8-2.1%, 1.9-3.0%, -1.4-3.7%, and -8.0%, respectively. Furthermore, the elevated levels of LPA 18:1/18:2, LPC(O) 18:0/18:1, and LPG 16:0/16:1/18:0 significantly mediated the PM2.5-associated increase in Non-HDL-C (18-49%), IL-8 (9-24%), MCP-1 (12-26%), and IFN-γ (4-12%) over 30 days. In conclusion, short-to medium-term PM2.5 exposure was associated with altered metabolism of LysoGPLs, which mediated the PM2.5-associated pro-atherosclerotic response.

Lysophosphatidylserine: A Signaling Lipid with Implications in Human Diseases

Lysophosphatidylserine (lyso-PS) has emerged as yet another important signaling lysophospholipid in mammals, and deregulation in its metabolism has been directly linked to an array of human autoimmune and neurological disorders. It has an indispensable role in several biological processes in humans, and therefore, cellular concentrations of lyso-PS are tightly regulated to ensure optimal signaling and functioning in physiological settings. Given its biological importance, the past two decades have seen an explosion in the available literature toward our understanding of diverse aspects of lyso-PS metabolism and signaling and its association with human diseases. In this Review, we aim to comprehensively summarize different aspects of lyso-PS, such as its structure, biodistribution, chemical synthesis, and SAR studies with some synthetic analogs. From a biochemical perspective, we provide an exhaustive coverage of the diverse biological activities modulated by lyso-PSs, such as its metabolism and the receptors that respond to them in humans. We also briefly discuss the human diseases associated with aberrant lyso-PS metabolism and signaling and posit some future directions that may advance our understanding of lyso-PS-mediated mammalian physiology.

GDE7 produces cyclic phosphatidic acid in the ER lumen functioning as a lysophospholipid mediator

Cyclic phosphatidic acid (cPA) is a lipid mediator, which regulates adipogenic differentiation and glucose homeostasis by suppressing nuclear peroxisome proliferator-activated receptor γ (PPARγ). Glycerophosphodiesterase 7 (GDE7) is a Ca2+-dependent lysophospholipase D that localizes in the endoplasmic reticulum. Although mouse GDE7 catalyzes cPA production in a cell-free system, it is unknown whether GDE7 generates cPA in living cells. Here, we demonstrate that human GDE7 possesses cPA-producing activity in living cells as well as in a cell-free system. Furthermore, the active site of human GDE7 is directed towards the luminal side of the endoplasmic reticulum. Mutagenesis revealed that amino acid residues F227 and Y238 are important for catalytic activity. GDE7 suppresses the PPARγ pathway in human mammary MCF-7 and mouse preadipocyte 3T3-L1 cells, suggesting that cPA functions as an intracellular lipid mediator. These findings lead to a better understanding of the biological role of GDE7 and its product, cPA.