Lysophosphatidic acid signaling protects pulmonary vasculature from hypoxia-induced remodeling

Glycerophospholipid and Sphingosine- 1-phosphate Metabolism in Cardiovascular Disease: Mechanisms and Therapeutic Potential

Cardiovascular disease remains a leading cause of mortality worldwide, driven by factors such as dysregulated lipid metabolism, oxidative stress, and inflammation. Recent studies highlight the critical roles of both glycerophospholipid and sphingosine- 1-phosphate metabolism in the pathogenesis of cardiovascular disorders. However, the contributions of glycerophospholipid-derived metabolites remain underappreciated. Glycerophospholipid metabolism generates bioactive molecules that contribute to endothelial dysfunction, lipid accumulation, and cardiac cell injury while also modulating inflammatory and oxidative stress responses. Meanwhile, sphingosine- 1-phosphate is a bioactive lipid mediator that regulates vascular integrity, inflammation, and cardiac remodeling through its G-protein-coupled receptors. The convergence of these pathways presents novel therapeutic opportunities, where dietary interventions such as omega- 3 polyunsaturated fatty acids and pharmacological targeting of sphingosine- 1-phosphate receptors could synergistically mitigate cardiovascular risk. This review underscores the need for further investigation into the interplay between glycerophospholipid metabolism and sphingosine- 1-phosphate signaling to advance targeted therapies for the prevention and management of cardiovascular disease.

Evaluation of conical 9 well dish on bovine oocyte maturation and subsequent embryonic development

The Conical 9 well dish (C9 well dish) is characterized by a decreasing cross-sectional area towards the base. This design was hypothesized to enhance embryonic development by emulating the in vivo physical environment through density modulation. Comparative analyses revealed no significant difference in nuclear maturation rates between the C9 well dish and the 5-well dish. Reactive oxygen species (ROS) generation was lower in the C9 well dish compared to the 5-well dish; however, this difference was not statistically significant. On the second day of in vitro culture, the cleavage rate in the C9 well dish was 4.66% higher, although not statistically significant, and the rates of blastocyst development were similar across both dishes. No significant differences were observed in the intracellular levels of glutathione (GSH) and ROS, as well as in the total cell number within the blastocysts between the dish types. The expression of mitogen-related factors, TGFα and IGF-1, in the blastocysts was consistent between the dishes. However, PDGFβ expression was significantly lower in the C9 well dish compared to the 35 mm petri dish. Similarly, the expression of the apoptosis factor Bax/Bcl2l2 showed no significant differences between the two dishes. Despite the marked difference in PDGFβ expression, its impact on blastocyst formation appeared negligible. The study also confirmed the feasibility of culturing a small number of oocytes per donor, collected via Ovum Pick-Up (OPU), with reduced volumes of culture medium and mineral oil, thus offering economic advantages. In conclusion, the present study indicates that the C9 well dish is effective for in vitro development of a small quantity of oocytes and embryos, presenting it as a viable alternative to traditional cell culture dishes.

Stretch regulates alveologenesis and homeostasis via mesenchymal Gαq/11-mediated TGFβ2 activation

Alveolar development and repair require tight spatiotemporal regulation of numerous signalling pathways that are influenced by chemical and mechanical stimuli. Mesenchymal cells play key roles in numerous developmental processes. Transforming growth factor-β (TGFβ) is essential for alveologenesis and lung repair, and the G protein α subunits Gαq and Gα11 (Gαq/11) transmit mechanical and chemical signals to activate TGFβ in epithelial cells. To understand the role of mesenchymal Gαq/11 in lung development, we generated constitutive (Pdgfrb-Cre+/-;Gnaqfl/fl;Gna11-/-) and inducible (Pdgfrb-Cre/ERT2+/-;Gnaqfl/fl;Gna11-/-) mesenchymal Gαq/11 deleted mice. Mice with constitutive Gαq/11 gene deletion exhibited abnormal alveolar development, with suppressed myofibroblast differentiation, altered mesenchymal cell synthetic function, and reduced lung TGFβ2 deposition, as well as kidney abnormalities. Tamoxifen-induced mesenchymal Gαq/11 gene deletion in adult mice resulted in emphysema associated with reduced TGFβ2 and elastin deposition. Cyclical mechanical stretch-induced TGFβ activation required Gαq/11 signalling and serine protease activity, but was independent of integrins, suggesting an isoform-specific role for TGFβ2 in this model. These data highlight a previously undescribed mechanism of cyclical stretch-induced Gαq/11-dependent TGFβ2 signalling in mesenchymal cells, which is imperative for normal alveologenesis and maintenance of lung homeostasis.

Lysophosphatidic acid, a simple phospholipid with myriad functions

Lysophosphatidic acid (LPA) is a simple phospholipid consisting of a phosphate group, glycerol moiety, and only one hydrocarbon chain. Despite its simple chemical structure, LPA plays an important role as an essential bioactive signaling molecule via its specific six G protein-coupled receptors, LPA_1-6. Recent studies, especially those using genetic tools, have revealed diverse physiological and pathological roles of LPA and LPA receptors in almost every organ system. Furthermore, many studies are illuminating detailed mechanisms to orchestrate multiple LPA receptor signaling pathways and to facilitate their coordinated function. Importantly, these extensive "bench" works are now translated into the "bedside" as exemplified by approaches targeting LPA₁ signaling to combat fibrotic diseases. In this review, we discuss the physiological and pathological roles of LPA signaling and their implications for clinical application by focusing on findings revealed by in vivo studies utilizing genetic tools targeting LPA receptors.

Pathophysiological Involvement of Mast Cells and the Lipid Mediators in Pulmonary Vascular Remodeling

Mast cells are responsible for IgE-dependent allergic responses, but they also produce various bioactive mediators and contribute to the pathogenesis of various cardiovascular diseases, including pulmonary hypertension (PH). The importance of lipid mediators in the pathogenesis of PH has become evident in recent years, as exemplified by prostaglandin I2, the most central therapeutic target in pulmonary arterial hypertension. New bioactive lipids other than eicosanoids have also been identified that are associated with the pathogenesis of PH. However, it remains largely unknown how mast cell-derived lipid mediators are involved in pulmonary vascular remodeling. Recently, it has been demonstrated that mast cells produce epoxidized n-3 fatty acid (n-3 epoxides) in a degranulation-independent manner, and that n-3 epoxides produced by mast cells regulate the abnormal activation of pulmonary fibroblasts and suppress the progression of pulmonary vascular remodeling. This review summarizes the role of mast cells and bioactive lipids in the pathogenesis of PH. In addition, we introduce the pathophysiological role and therapeutic potential of n-3 epoxides, a mast cell-derived novel lipid mediator, in the pulmonary vascular remodeling in PH. Further knowledge of mast cells and lipid mediators is expected to lead to the development of innovative therapies targeting pulmonary vascular remodeling.

Bioactive lipids and metabolic syndrome-a symposium report

Recent research has shed light on the cellular and molecular functions of bioactive lipids that go far beyond what was known about their role as dietary lipids. Bioactive lipids regulate inflammation and its resolution as signaling molecules. Genetic studies have identified key factors that can increase the risk of cardiovascular diseases and metabolic syndrome through their effects on lipogenesis. Lipid scientists have explored how these signaling pathways affect lipid metabolism in the liver, adipose tissue, and macrophages by utilizing a variety of techniques in both humans and animal models, including novel lipidomics approaches and molecular dynamics models. Dissecting out these lipid pathways can help identify mechanisms that can be targeted to prevent or treat cardiometabolic conditions. Continued investigation of the multitude of functions mediated by bioactive lipids may reveal additional components of these pathways that can provide a greater understanding of metabolic homeostasis.

Preventing the Increase in Lysophosphatidic Acids: A New Therapeutic Target in Pulmonary Hypertension?

Cardiovascular diseases (CVD) are the leading cause of premature death and disability in humans that are closely related to lipid metabolism and signaling. This study aimed to assess whether circulating lysophospholipids (LPL), lysophosphatidic acids (LPA) and monoacylglycerols (MAG) may be considered as potential therapeutic targets in CVD. For this objective, plasma levels of 22 compounds (13 LPL, 6 LPA and 3 MAG) were monitored by liquid chromatography coupled with tandem mass spectrometry (HPLC/MS²) in different rat models of CVD, i.e., angiotensin-II-induced hypertension (HTN), ischemic chronic heart failure (CHF) and sugen/hypoxia(SuHx)-induced pulmonary hypertension (PH). On one hand, there were modest changes on the monitored compounds in HTN (LPA 16:0, 18:1 and 20:4, LPC 16:1) and CHF (LPA 16:0, LPC 18:1 and LPE 16:0 and 18:0) models compared to control rats but these changes were no longer significant after multiple testing corrections. On the other hand, PH was associated with important changes in plasma LPA with a significant increase in LPA 16:0, 18:1, 18:2, 20:4 and 22:6 species. A deleterious impact of LPA was confirmed on cultured human pulmonary smooth muscle cells (PA-SMCs) with an increase in their proliferation. Finally, plasma level of LPA(16:0) was positively associated with the increase in pulmonary artery systolic pressure in patients with cardiac dysfunction. This study demonstrates that circulating LPA may contribute to the pathophysiology of PH. Additional experiments are needed to assess whether the modulation of LPA signaling in PH may be of interest.

The Ion Channel and GPCR Toolkit of Brain Capillary Pericytes

Brain pericytes reside on the abluminal surface of capillaries, and their processes cover ~90% of the length of the capillary bed. These cells were first described almost 150 years ago (Eberth, 1871; Rouget, 1873) and have been the subject of intense experimental scrutiny in recent years, but their physiological roles remain uncertain and little is known of the complement of signaling elements that they employ to carry out their functions. In this review, we synthesize functional data with single-cell RNAseq screens to explore the ion channel and G protein-coupled receptor (GPCR) toolkit of mesh and thin-strand pericytes of the brain, with the aim of providing a framework for deeper explorations of the molecular mechanisms that govern pericyte physiology. We argue that their complement of channels and receptors ideally positions capillary pericytes to play a central role in adapting blood flow to meet the challenge of satisfying neuronal energy requirements from deep within the capillary bed, by enabling dynamic regulation of their membrane potential to influence the electrical output of the cell. In particular, we outline how genetic and functional evidence suggest an important role for G_s-coupled GPCRs and ATP-sensitive potassium (K_ATP) channels in this context. We put forth a predictive model for long-range hyperpolarizing electrical signaling from pericytes to upstream arterioles, and detail the TRP and Ca²⁺ channels and G_q, G_i/o, and G_12/13 signaling processes that counterbalance this. We underscore critical questions that need to be addressed to further advance our understanding of the signaling topology of capillary pericytes, and how this contributes to their physiological roles and their dysfunction in disease.

ENPP4 overexpression is associated with no recovery from Barrett's esophagus

Early diagnosis and treatment of precancerous conditions of the esophagus is important to improve overall survival. Barrett's esophagus is the most common precancerous condition of the esophagus, and patients with Barrett's esophagus may develop tumor, maintain a precancerous condition, or recover. We analyzed miRNA and mRNA expression profiles from esophageal adenocarcinoma tissue and normal esophageal tissue in GEO database. We identified DEGs and DE_miRNAs from GEO2R online tools and used Venn software were used to detect the common DEGs and DE_miRNAs. We used Enrichr, an online bioinformatic tool, to perform the gene ontology (GO) analysis including BP, MF, and CC. We analyzed Mirdb.tsv, mirtarbase.tsv, and targetscan.tsv files and identified miRNA targeting genes. We analysed the data of RNA sequencing expression retrieved from the GEPIA website on the basis of thousands of samples from the GTEx projects and TCGA. There were three miRNA (has-mir-205, has-mir-203, has-mir-18) and one DEG (ENPP4) that were associated with the recovery from Barrett's esophagus. ENPP4 promotes coagulation, hemostasis, wound healing, and participates in neutrophil degranulation, neutrophil immune activation and its mediated immunity, contributes to the composition of some membrane particles and tertiary particles, and is related to nucleotide diphosphatase activity. ENPP4 overexpression was not conducive to Barrett's esophagus recovery.

Plasma metabolomic profile in chronic thromboembolic pulmonary hypertension

We aimed to characterize the plasma metabolome of chronic thromboembolic pulmonary hypertension patients using a high-throughput unbiased omics approach. We collected fasting plasma from a peripheral vein in 33 operable chronic thromboembolic pulmonary hypertension patients, 31 healthy controls, and 21 idiopathic pulmonary arterial hypertension patients matched for age, gender, and body mass index. Metabolomic analysis was performed using an untargeted approach (Metabolon Inc. Durham, NC). Of the total of 862 metabolites identified, 362 were different in chronic thromboembolic pulmonary hypertension compared to controls: 178 were higher and 184 were lower. Compared to idiopathic pulmonary arterial hypertension, 147 metabolites were different in chronic thromboembolic pulmonary hypertension: 45 were higher and 102 were lower. The plasma metabolome allowed us to distinguish subjects with chronic thromboembolic pulmonary hypertension and healthy controls with a predictive accuracy of 89%, and chronic thromboembolic pulmonary hypertension versus idiopathic pulmonary arterial hypertension with 80% accuracy. Compared to idiopathic pulmonary arterial hypertension and healthy controls, chronic thromboembolic pulmonary hypertension patients had higher fatty acids and glycerol; while acyl cholines and lysophospholipids were lower. Compared to healthy controls, both idiopathic pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension patients had increased acyl carnitines, beta-hydroxybutyrate, amino sugars and modified amino acids and nucleosides. The plasma global metabolomic profile of chronic thromboembolic pulmonary hypertension suggests aberrant lipid metabolism characterized by increased lipolysis, fatty acid oxidation, and ketogenesis, concomitant with reduced acyl choline and phospholipid moieties. Future research should investigate the pathogenetic and therapeutic potential of modulating lipid metabolism in chronic thromboembolic pulmonary hypertension.

Regulation of PLPP3 gene expression by NF-κB family transcription factors

Lipid phosphate phosphatase 3 (LPP3), encoded by the PLPP3 gene, is an integral membrane enzyme that dephosphorylates phosphate esters of glycero- and sphingophospholipids. Cell surface LPP3 can terminate the signaling actions of bioactive lysophosphatidic acid (LPA) and sphingosine 1 phosphate, which likely explains its role in developmental angiogenesis, vascular injury responses, and cell migration. Heritable variants in the final intron PLPP3 associate with interindividual variability in coronary artery disease risk that may result from disruption of enhancer sequences that normally act in cis to increase expression of the gene. However, the mechanisms regulating PLPP3 expression are not well understood. We show that the human PLPP3 promoter contains three functional NF-κB response elements. All of these are required for maximal induction of PLPP3 promoter activity in reporter assays. The identified sequences recruit RelA and RelB components of the NF-κB transcription complex to chromatin, and these transcription factors bind to the identified target sequences in two different cell types. LPA promotes binding of Rel family transcription factors to the PLPP3 promoter and increases PLPP3 gene expression through mechanisms that are attenuated by an NF-κB inhibitor, LPA receptor antagonists, and inhibitors of phosphoinositide 3 kinase. These findings indicate that up-regulation of PLPP3 during inflammation and atherosclerosis results from canonical activation of the NF-κB signaling cascade to increase PLPP3 expression through nuclear import and binding of RelA and RelB transcription factors to the PLPP3 promoter and suggest a mechanism by which the LPP3 substrate, LPA, can regulate PLPP3 expression.

RNA sequencing reveals widespread transcriptome changes in a renal carcinoma cell line

We used RNA sequencing (RNA-Seq) technology to investigate changes in the transcriptome profile in the Caki-1 clear cell renal cell carcinoma (ccRCC) cells, which overexpress monocyte chemoattractant protein-induced protein 1 (MCPIP1). RNA-Seq data showed changes in 11.6% and 41.8% of the global transcriptome of Caki-1 cells overexpressing wild-type MCPIP1 or its D141N mutant, respectively. Gene ontology and KEGG pathway functional analyses showed that these transcripts encoded proteins involved in cell cycle progression, protein folding in the endoplasmic reticulum, hypoxia response and cell signalling. We identified 219 downregulated transcripts in MCPIP1-expressing cells that were either unchanged or upregulated in D141N-expressing cells. We validated downregulation of 15 transcripts belonging to different functional pathways by qRT-PCR. The growth and viability of MCPIP1-expressing cells was reduced because of elevated p21Cip1 levels. MCPIP1-expressing cells also showed reduced levels of DDB1 transcript that encodes component of the E3 ubiquitin ligase that degrades p21Cip1. These results demonstrate that MCPIP1 influences the growth and viability of ccRCC cells by increasing or decreasing the transcript levels for proteins involved in cell cycle progression, protein folding, hypoxia response, and cell signaling.

Lysophosphatidic acid counteracts glucagon-induced hepatocyte glucose production via STAT3

Hepatic glucose production (HGP) is required to maintain normoglycemia during fasting. Glucagon is the primary hormone responsible for increasing HGP; however, there are many additional hormone and metabolic factors that influence glucagon sensitivity. In this study we report that the bioactive lipid lysophosphatidic acid (LPA) regulates hepatocyte glucose production by antagonizing glucagon-induced expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK). Treatment of primary hepatocytes with exogenous LPA blunted glucagon-induced PEPCK expression and glucose production. Similarly, knockout mice lacking the LPA-degrading enzyme phospholipid phosphate phosphatase type 1 (PLPP1) had a 2-fold increase in endogenous LPA levels, reduced PEPCK levels during fasting, and decreased hepatic gluconeogenesis in response to a pyruvate challenge. Mechanistically, LPA antagonized glucagon-mediated inhibition of STAT3, a transcriptional repressor of PEPCK. Importantly, LPA did not blunt glucagon-stimulated glucose production or PEPCK expression in hepatocytes lacking STAT3. These data identify a novel role for PLPP1 activity and hepatocyte LPA levels in glucagon sensitivity via a mechanism involving STAT3.

Role of oxidized lipids in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a multifactorial disease characterized by interplay of many cellular, molecular, and genetic events that lead to excessive proliferation of pulmonary cells, including smooth muscle and endothelial cells; inflammation; and extracellular matrix remodeling. Abnormal vascular changes and structural remodeling associated with PAH culminate in vasoconstriction and obstruction of pulmonary arteries, contributing to increased pulmonary vascular resistance, pulmonary hypertension, and right ventricular failure. The complex molecular mechanisms involved in the pathobiology of PAH are the limiting factors in the development of potential therapeutic interventions for PAH. Over the years, our group and others have demonstrated the critical implication of lipids in the pathogenesis of PAH. This review specifically focuses on the current understanding of the role of oxidized lipids, lipid metabolism, peroxidation, and oxidative stress in the progression of PAH. This review also discusses the relevance of apolipoprotein A-I mimetic peptides and microRNA-193, which are known to regulate the levels of oxidized lipids, as potential therapeutics in PAH.

Effect of lysophosphatidic acid on the immune inflammatory response and the connexin 43 protein in myocardial infarction

Lysophosphatidic acid (LPA) is an intermediate product of membrane phospholipid metabolism. Recently, LPA has gained attention for its involvement in the pathological processes of certain cardiovascular diseases. The aim of the present study was to clarify the association between the effect of LPA and the immune inflammatory response, and to investigate the effects of LPA on the protein expression levels of connexin 43 during myocardial infarction. Surface electrocardiograms of myocardial infarction rats and isolated rat heart tissue samples were obtained in order to determine the effect of LPA on the incidence of arrhythmia in rats that exhibited changes in immune status. The results demonstrated that the incidence of arrhythmia decreased when the rat immune systems were suppressed, and the incidence of arrhythmia increased when the rat immune systems were enhanced. The concentration levels of tumor necrosis factor (TNF)-α were determined by ELISA, and the results demonstrated that LPA induced T lymphocyte synthesis and TNF-α release. Using a patch-clamp technique, LPA was shown to increase the current amplitude of the voltage-dependent potassium channels (K_v) and calcium-activated potassium channels (K_Ca) in Jurkat T cells. The protein expression of connexin 43 (Cx43) was determined by immunohistochemical staining. The results indicated that LPA caused the degradation of Cx43 and decreased the expression of Cx43. This effect was associated with the immune status of the rats. There was a further decrease in Cx43 expression in the rats of the immune-enhanced group. To the best of our knowledge, these results provide the first evidence that LPA causes arrhythmia through the regulation of immune inflammatory cells and the decrease of Cx43 protein expression. The present study provided an experimental basis for the treatment of arrhythmia and may guide clinical care.

Deficiency or inhibition of lysophosphatidic acid receptor 1 protects against hyperoxia-induced lung injury in neonatal rats

AIM

Blocking of lysophosphatidic acid (LPA) receptor (LPAR) 1 may be a novel therapeutic option for bronchopulmonary dysplasia (BPD) by preventing the LPAR1-mediated adverse effects of its ligand (LPA), consisting of lung inflammation, pulmonary arterial hypertension (PAH) and fibrosis.

METHODS

In Wistar rats with experimental BPD, induced by continuous exposure to 100% oxygen for 10 days, we determined the beneficial effects of LPAR1 deficiency in neonatal rats with a missense mutation in cytoplasmic helix 8 of LPAR1 and of LPAR1 and -3 blocking with Ki16425. Parameters investigated included survival, lung and heart histopathology, fibrin and collagen deposition, vascular leakage and differential mRNA expression in the lungs of key genes involved in LPA signalling and BPD pathogenesis.

RESULTS

LPAR1-mutant rats were protected against experimental BPD and mortality with reduced alveolar septal thickness, lung inflammation (reduced influx of macrophages and neutrophils, and CINC1 expression) and collagen III deposition. However, LPAR1-mutant rats were not protected against alveolar enlargement, increased medial wall thickness of small arterioles, fibrin deposition and vascular alveolar leakage. Treatment of experimental BPD with Ki16425 confirmed the data observed in LPAR1-mutant rats, but did not reduce the pulmonary influx of neutrophils, CINC1 expression and mortality in rats with experimental BPD. In addition, Ki16425 treatment protected against PAH and right ventricular hypertrophy.

CONCLUSION

LPAR1 deficiency attenuates pulmonary injury by reducing pulmonary inflammation and fibrosis, thereby reducing mortality, but does not affect alveolar and vascular development and, unlike Ki16425 treatment, does not prevent PAH in neonatal rats with experimental BPD.

Homology modeling and docking studies of ENPP4: a BCG activated tumoricidal macrophage protein

BACKGROUND

The 3D structure and functions of ENPP4, a protein expressed on the surface of Bacillus Calmette-Guerin (BCG)-activated macrophages, are unknown. In this study, we analyzed the 3D structure of ENPP4 and determined its tumoricidal effects on MCA207 cells.

RESULTS

Homology modeling showed that Arg305, Tyr341, Asn291, and Asn295 are important residues in substrate, adenosine triphosphate (ATP), binding. A molecular dynamics study was also carried out to study the stability of ENPP4 (including zinc atoms) as well as its ligand-enzyme complex. BCG increased ENPP4 expression in macrophages, and specific blocking of ENPP4 in BCG-activated macrophages (BAMs) significantly reduced their cytotoxicity against MCA207 cells.

CONCLUSIONS

These results indicate that zinc remains inside the ENPP4 protein, a BCG activated tumoricidal macrophage protein, throughout the simulation. Important information for the design of new inhibitors was obtained.

Recent advances in targeting the autotaxin-lysophosphatidate-lipid phosphate phosphatase axis in vivo

Extracellular lysophosphatidate (LPA) is a potent bioactive lipid that signals through six G-protein-coupled receptors. This signaling is required for embryogenesis, tissue repair and remodeling processes. LPA is produced from circulating lysophosphatidylcholine by autotaxin (ATX), and is degraded outside cells by a family of three enzymes called the lipid phosphate phosphatases (LPPs). In many pathological conditions, particularly in cancers, LPA concentrations are increased due to high ATX expression and low LPP activity. In cancers, LPA signaling drives tumor growth, angiogenesis, metastasis, resistance to chemotherapy and decreased efficacy of radiotherapy. Hence, targeting the ATX-LPA-LPP axis is an attractive strategy for introducing novel adjuvant therapeutic options. In this review, we will summarize current progress in targeting the ATX-LPA-LPP axis with inhibitors of autotaxin activity, LPA receptor antagonists, LPA monoclonal antibodies, and increasing low LPP expression. Some of these agents are already in clinical trials and have applications beyond cancer, including chronic inflammatory diseases.

Genetic and Functional Evidence Supports LPAR1 as a Susceptibility Gene for Hypertension

Essential hypertension is a complex disease affected by genetic and environmental factors and serves as a major risk factor for cardiovascular diseases. Serum lysophosphatidic acid correlates with an elevated blood pressure in rats, and lysophosphatidic acid interacts with 6 subtypes of receptors. In this study, we assessed the genetic association of lysophosphatidic acid receptors with essential hypertension by genotyping 28 single-nucleotide polymorphisms from genes encoding for lysophosphatidic acid receptors, LPAR1, LPAR2, LPAR3, LPAR4, LPAR5, and LPAR6 and their flanking sequences, in 3 Han Chinese cohorts consisting of 2630 patients and 3171 controls in total. We identified a single-nucleotide polymorphism, rs531003 in the 3'-flanking genomic region of LPAR1, associated with hypertension (the Bonferroni corrected P=1.09×10(-5), odds ratio [95% confidence interval]=1.23 [1.13-1.33]). The risk allele C of rs531003 is associated with the increased expression of LPAR1 and the susceptibility of hypertension, particularly in those with a shortage of sleep (P=4.73×10(-5), odds ratio [95% confidence interval]=1.75 [1.34-2.28]). We further demonstrated that blood pressure elevation caused by sleep deprivation and phenylephrine-induced vasoconstriction was both diminished in LPAR1-deficient mice. Together, we show that LPAR1 is a novel susceptibility gene for human essential hypertension and that stress, such as shortage of sleep, increases the susceptibility of patients with risk allele to essential hypertension.

Possible role of lysophosphatidic acid in rat model of hypoxic pulmonary vascular remodeling

Pulmonary hypertension is characterized by cellular and structural changes in the vascular wall of pulmonary arteries. We hypothesized that lysophosphatidic acid (LPA), a bioactive lipid, is implicated in this vascular remodeling in a rat model of hypoxic pulmonary hypertension. Exposure of Wistar rats to 10% O2 for 3 weeks induced an increase in the mean serum levels of LPA, to 40.9 (log-detransformed standard deviations: 23.4-71.7) μM versus 21.6 (11.0-42.3) μM in a matched control animal group (P = 0.037). We also observed perivascular LPA immunohistochemical staining in lungs of hypoxic rats colocalized with the secreted lysophospholipase D autotaxin (ATX). Moreover, ATX colocalized with mast cell tryptase, suggesting implication of these cells in perivascular LPA production. Hypoxic rat lungs expressed more ATX transcripts (2.4-fold) and more transcripts of proteins implicated in cell migration: β2 integrin (1.74-fold), intracellular adhesion molecule 1 (ICAM-1; 1.84-fold), and αM integrin (2.70-fold). Serum from the hypoxic group of animals had significantly higher chemoattractant properties toward rat primary lung fibroblasts, and this increase in cell migration could be prevented by the LPA receptor 1 and 3 antagonists. LPA also increased adhesive properties of human pulmonary artery endothelial cells as well as those of human peripheral blood mononuclear cells, via the activation of LPA receptor 1 or 3 followed by the stimulation of gene expression of ICAM-1, β-1, E-selectin, and vascular cell adhesion molecule integrins. In conclusion, chronic hypoxia increases circulating and tissue levels of LPA, which might induce fibroblast migration and recruitment of mononuclear cells in pulmonary vasculature, both of which contribute to pulmonary vascular remodeling.

Insulin-like growth factor 1 (IGF-1) stabilizes nascent blood vessels

Here we report that VEGF-A and IGF-1 differ in their ability to stabilize newly formed blood vessels and endothelial cell tubes. Although VEGF-A failed to support an enduring vascular response, IGF-1 stabilized neovessels generated from primary endothelial cells derived from various vascular beds and mouse retinal explants. In these experimental systems, destabilization/regression was driven by lysophosphatidic acid (LPA). Because previous studies have established that Erk antagonizes LPA-mediated regression, we considered whether Erk was an essential component of IGF-dependent stabilization. Indeed, IGF-1 lost its ability to stabilize neovessels when the Erk pathway was inhibited pharmacologically. Furthermore, stabilization was associated with prolonged Erk activity. In the presence of IGF-1, Erk activity persisted longer than in the presence of VEGF or LPA alone. These studies reveal that VEGF and IGF-1 can have distinct inputs in the angiogenic process. In contrast to VEGF, IGF-1 stabilizes neovessels, which is dependent on Erk activity and associated with prolonged activation.

DNAH5 is associated with total lung capacity in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by expiratory flow limitation, causing air trapping and lung hyperinflation. Hyperinflation leads to reduced exercise tolerance and poor quality of life in COPD patients. Total lung capacity (TLC) is an indicator of hyperinflation particularly in subjects with moderate-to-severe airflow obstruction. The aim of our study was to identify genetic variants associated with TLC in COPD.

METHODS

We performed genome-wide association studies (GWASs) in white subjects from three cohorts: the COPDGene Study; the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE); and GenKOLS (Bergen, Norway). All subjects were current or ex-smokers with at least moderate airflow obstruction, defined by a ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC) <0.7 and FEV1 < 80% predicted on post-bronchodilator spirometry. TLC was calculated by using volumetric computed tomography scans at full inspiration (TLCCT). Genotyping in each cohort was completed, with statistical imputation of additional markers. To find genetic variants associated with TLCCT, linear regression models were used, with adjustment for age, sex, pack-years of smoking, height, and principal components for genetic ancestry. Results were summarized using fixed-effect meta-analysis.

RESULTS

Analysis of a total of 4,543 COPD subjects identified one genome-wide significant locus on chromosome 5p15.2 (rs114929486, β = 0.42L, P = 4.66 × 10-8).

CONCLUSIONS

In COPD, TLCCT was associated with a SNP in dynein, axonemal, heavy chain 5 (DNAH5), a gene in which genetic variants can cause primary ciliary dyskinesia. DNAH5 could have an effect on hyperinflation in COPD.

Autotaxin in the crosshairs: taking aim at cancer and other inflammatory conditions

Autotaxin is a secreted enzyme that produces most of the extracellular lysophosphatidate from lysophosphatidylcholine, the most abundant phospholipid in blood plasma. Lysophosphatidate mediates many physiological and pathological processes by signaling through at least six G-protein coupled receptors to promote cell survival, proliferation and migration. The autotaxin/lysophosphatidate signaling axis is involved in wound healing and tissue remodeling, and it drives many chronic inflammatory conditions from fibrosis to colitis, asthma and cancer. In cancer, lysophosphatidate signaling promotes resistance to chemotherapy and radiotherapy, and increases both angiogenesis and metastasis. Research into autotaxin inhibitors is accelerating, both as primary and adjuvant therapy. Historically, autotaxin inhibitors had poor bioavailability profiles and thus had limited efficacy in vivo. This situation is now changing, especially since the recent crystal structure of autotaxin is now enabling rational inhibitor design. In this review, we will summarize current knowledge on autotaxin-mediated disease processes including cancer, and discuss recent advancements in the development of autotaxin-targeting strategies. We will also provide new insights into autotaxin as an inflammatory mediator in the tumor microenvironment that promotes cancer progression and therapy resistance.

Autotaxin and lysophosphatidic acid signalling in lung pathophysiology

Autotaxin (ATX or ENPP2) is a secreted glycoprotein widely present in biological fluids. ATX primarily functions as a plasma lysophospholipase D and is largely responsible for the bulk of lysophosphatidic acid (LPA) production in the plasma and at inflamed and/or malignant sites. LPA is a phospholipid mediator produced in various conditions both in cells and in biological fluids, and it evokes growth-factor-like responses, including cell growth, survival, differentiation and motility, in almost all cell types. The large variety of LPA effector functions is attributed to at least six G-protein coupled LPA receptors (LPARs) with overlapping specificities and widespread distribution. Increased ATX/LPA/LPAR levels have been detected in a large variety of cancers and transformed cell lines, as well as in non-malignant inflamed tissues, suggesting a possible involvement of ATX in chronic inflammatory disorders and cancer. In this review, we focus exclusively on the role of the ATX/LPA axis in pulmonary pathophysiology, analysing the effects of ATX/LPA on pulmonary cells and leukocytes in vitro and in the context of pulmonary pathophysiological situations in vivo and in human diseases.

Lysophosphatidic acid in atherosclerotic diseases

Lysophosphatidic acid (LPA) is a potent bioactive phospholipid. As many other biological active lipids, LPA is an autacoid: it is formed locally on demand, and it acts locally near its site of synthesis. LPA has a plethora of biological activities on blood cells (platelets, monocytes) and cells of the vessel wall (endothelial cells, smooth muscle cells, macrophages) that are all key players in atherosclerotic and atherothrombotic processes. The specific cellular actions of LPA are determined by its multifaceted molecular structures, the expression of multiple G-protein coupled LPA receptors at the cell surface and their diverse coupling to intracellular signalling pathways. Numerous studies have now shown that LPA has thrombogenic and atherogenic actions. Here, we aim to provide a comprehensive, yet concise, thoughtful and critical review of this exciting research area and to pinpoint potential pharmacological targets for inhibiting thrombogenic and atherogenic activities of LPA. We hope that the review will serve to accelerate knowledge of basic and clinical science, and to foster drug development in the field of LPA and atherosclerotic/atherothrombotic diseases.

Lysophospholipids and their receptors in the central nervous system

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), two of the best-studied lysophospholipids, are known to influence diverse biological events, including organismal development as well as function and pathogenesis within multiple organ systems. These functional roles are due to a family of at least 11 G protein-coupled receptors (GPCRs), named LPA(1-6) and S1P(1-5), which are widely distributed throughout the body and that activate multiple effector pathways initiated by a range of heterotrimeric G proteins including G(i/o), G(12/13), G(q) and G(s), with actual activation dependent on receptor subtypes. In the central nervous system (CNS), a major locus for these signaling pathways, LPA and S1P have been shown to influence myriad responses in neurons and glial cell types through their cognate receptors. These receptor-mediated activities can contribute to disease pathogenesis and have therapeutic relevance to human CNS disorders as demonstrated for multiple sclerosis (MS) and possibly others that include congenital hydrocephalus, ischemic stroke, neurotrauma, neuropsychiatric disorders, developmental disorders, seizures, hearing loss, and Sandhoff disease, based upon the experimental literature. In particular, FTY720 (fingolimod, Gilenya, Novartis Pharma, AG) that becomes an analog of S1P upon phosphorylation, was approved by the FDA in 2010 as a first oral treatment for MS, validating this class of receptors as medicinal targets. This review will provide an overview and update on the biological functions of LPA and S1P signaling in the CNS, with a focus on results from studies using genetic null mutants for LPA and S1P receptors. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.