Lysophosphatidic acid in vascular development and disease

Artificial intelligence in therapeutic management of hyperlipidemic ocular pathology

Hyperlipidemia has many ocular manifestations, the most prevalent being retinal vascular occlusion. Hyperlipidemic lesions and occlusions to the vessels supplying the retina result in permanent blindness, necessitating prompt detection and treatment. Retinal vascular occlusion is diagnosed using different imaging modalities, including optical coherence tomography angiography. These diagnostic techniques obtain images representing the blood flow through the retinal vessels, providing an opportunity for AI to utilize image recognition to detect blockages and abnormalities before patients present with symptoms. AI is already being used as a non-invasive method to detect retinal vascular occlusions and other vascular pathology, as well as predict treatment outcomes. As providers see an increase in patients presenting with new retinal vascular occlusions, the use of AI to detect and treat these conditions has the potential to improve patient outcomes and reduce the financial burden on the healthcare system. This article comprehends the implications of AI in the current management strategies of retinal vascular occlusion (RVO) in hyperlipidemia and the recent developments of AI technology in the management of ocular diseases.

Effects of Regulating Hippo and Wnt on the Development and Fate Differentiation of Bovine Embryo

The improvement of in vitro embryo development is a gateway to enhance the output of assisted reproductive technologies. The Wnt and Hippo signaling pathways are crucial for the early development of bovine embryos. This study investigated the development of bovine embryos under the influence of a Hippo signaling agonist (LPA) and a Wnt signaling inhibitor (DKK1). In this current study, embryos produced in vitro were cultured in media supplemented with LPA and DKK1. We comprehensively analyzed the impact of LPA and DKK1 on various developmental parameters of the bovine embryo, such as blastocyst formation, differential cell counts, YAP fluorescence intensity and apoptosis rate. Furthermore, single-cell RNA sequencing (scRNA-seq) was employed to elucidate the in vitro embryonic development. Our results revealed that LPA and DKK1 improved the blastocyst developmental potential, total cells, trophectoderm (TE) cells and YAP fluorescence intensity and decreased the apoptosis rate of bovine embryos. A total of 1203 genes exhibited differential expression between the control and LPA/DKK1-treated (LD) groups, with 577 genes upregulated and 626 genes downregulated. KEGG pathway analysis revealed significant enrichment of differentially expressed genes (DEGs) associated with TGF-beta signaling, Wnt signaling, apoptosis, Hippo signaling and other critical developmental pathways. Our study shows the role of LPA and DKK1 in embryonic differentiation and embryo establishment of pregnancy. These findings should be helpful for further unraveling the precise contributions of the Hippo and Wnt pathways in bovine trophoblast formation, thus advancing our comprehension of early bovine embryo development.

LPA2 Alleviates Septic Acute Lung Injury via Protective Endothelial Barrier Function Through Activation of PLC-PKC-FAK

Background

Increased endothelial permeability of pulmonary vessels is a primary pathological characteristic of septic acute lung injury (ALI). Previously, elevated lysophosphatidic acid (LPA) levels and LPA2 (an LPA receptor) expression have been found in the peripheral blood and lungs of septic mice, respectively. However, the specific role of LPA2 in septic ALI remains unclear.

Methods

A lipopolysaccharide (LPS)-induced model of sepsis was established in wild-type (WT) and global LPA2 knockout (Lpar2-/-) mice. We examined mortality, lung injury, assessed endothelial permeability through Evans blue dye (EBD) assay in vivo, and transendothelial electrical resistance (TEER) of mouse lung microvascular endothelial cells (MLMECs) in vitro. Enzyme-linked immunosorbent assay (ELISA), histopathological, immunofluorescence, immunohistochemistry, and Western blot were employed to investigate the role of LPA2 in septic ALI.

Results

Lpar2 deficiency increased vascular endothelial permeability, impaired lung injury, and increased mortality. Histological examination revealed aggravated inflammation, edema, hemorrhage and alveolar septal thickening in the lungs of septic Lpar2-/- mice. In vitro, loss of Lpar2 resulted in increased permeability of MLMECs. Pharmacological activation of LPA2 by the agonist DBIBB led to significantly reduced inflammation, edema and hemorrhage, as well as increased expression of the vascular endothelial tight junction (TJ) protein zonula occludens-1 (ZO-1) and claudin-5, as well as the adheren junction (AJ) protein VE-cadherin. Moreover, DBIBB treatment was found to alleviate mortality by protecting against vascular endothelial permeability. Mechanistically, we demonstrated that vascular endothelial permeability was alleviated through LPA-LPA2 signaling via the PLC-PKC-FAK pathway.

Conclusion

These data provide a novel mechanism of endothelial barrier protection via PLC-PKC-FAK pathway and suggest that LPA2 may contribute to the therapeutic effects of septic ALI.

A type IV Autotaxin inhibitor ameliorates acute liver injury and nonalcoholic steatohepatitis

The lysophosphatidic acid (LPA) signaling axis is an important but rather underexplored pathway in liver disease. LPA is predominantly produced by Autotaxin (ATX) that has gained significant attention with an impressive number of ATX inhibitors (type I-IV) reported. Here, we evaluated the therapeutic potential of a (yet unexplored) type IV inhibitor, Cpd17, in liver injury. We first confirmed the involvement of the ATX-LPA signaling axis in human and murine diseased livers. Then, we evaluated the effects of Cpd17, in comparison with the classic type I inhibitor PF8380, in vitro, where Cpd17 showed higher efficacy. Thereafter, we characterized the mechanism-of-action of both inhibitors and found that Cpd17 was more potent in inhibiting RhoA-mediated cytoskeletal remodeling, and phosphorylation of MAPK/ERK and AKT/PKB. Finally, the therapeutic potential of Cpd17 was investigated in CCl₄ -induced acute liver injury and diet-induced nonalcoholic steatohepatitis, demonstrating an excellent potential of Cpd17 in reducing liver injury in both disease models in vivo. We conclude that ATX inhibition, by type IV inhibitor in particular, has an excellent potential for clinical application in liver diseases.

Lysophosphatidic acid receptor1/3 antagonist inhibits the activation of satellite glial cells and reduces acute nociceptive responses

Lysophosphatidic acid (LPA) exerts various biological activities through six characterized G protein-coupled receptors (LPA_1-6 ). While LPA-LPA₁  signaling contributes toward the demyelination and retraction of C-fiber and induces neuropathic pain, the effects of LPA-LPA₁  signaling on acute nociceptive pain is uncertain. This study investigated the role of LPA-LPA₁  signaling in acute nociceptive pain using the formalin test. The pharmacological inhibition of the LPA-LPA₁ axis significantly attenuated formalin-induced nociceptive behavior. The LPA₁  mRNA was expressed in satellite glial cells (SGCs) in dorsal root ganglion (DRG) and was particularly abundant in SGCs surrounding large DRG neurons, which express neurofilament 200. Treatment with LPA_1/3 receptor (LPA_1/3 ) antagonist inhibited the upregulation of glial markers and inflammatory cytokines in DRG following formalin injection. The LPA_1/3 antagonist also attenuated phosphorylation of extracellular signal-regulated kinase, especially in SGCs and cyclic AMP response element-binding protein in the dorsal horn following formalin injection. LPA amounts after formalin injection to the footpad were quantified by liquid chromatography/tandem mass spectrometry, and LPA levels were found to be increased in the innervated DRGs. Our results indicate that LPA produced in the innervated DRGs promotes the activation of SGCs through LPA₁ , increases the sensitivity of primary neurons, and modulates pain behavior. These results facilitate our understanding of the pathology of acute nociceptive pain and demonstrate the possibility of the LPA₁ on SGCs as a novel target for acute pain control.

Effect of Lysophosphatidic Acid on the Vascular Endothelial Growth Factor Expression in Autotransplanted Mouse Ovaries Encapsulated in Sodium Alginate

Objective: The aim of this study was to evaluate the effect of lysophosphatidic acid (LPA) supplementation during in vitro culture and transplantation of mouse ovaries on the follicular development and expression of vascular endothelial growth factor (VEGF) as an angiogenesis factor at the mRNA and protein levels. Materials and methods: Three weeks old mice ovaries were cultured in the presence and absence of LPA for 24 hours, then they were capsulated in sodium alginate in the presence and absence of LPA as four experimental groups. After transplantation the vaginal smears were performed daily to evaluate the initiation of the estrous cycle. The morphology and follicular distribution were analyzed at the first and fourth estrous cycles using hematoxylin and eosin staining. Then in the groups that showed higher and lower follicular development the immunohistochemistry assay was conducted to identify VEGF protein expression, and the real time RT-PCR was done to analyze the expression of Vegf gene at the first estrus cycle. Results: The large size follicles and also the corpus luteum were prominent in all transplanted groups at fourth estrus cycle in comparison with intact control groups. The statistically lowest percentage of small size follicles and the highest percentages of large size follicles were seen in LPA⁺/LPA^- group (p<0.05). The expression ratio of Vegf to β-actin was significantly higher in this group in comparison with non-LPA treated and intact control groups (p <0.05). Conclusion: LPA as an angiogenesis factor increases the follicular development in transplanted ovaries but it causes early discharge of ovarian reserve.

Generation of an Lpar1-EGFP Fusion Knock-in Transgenic Mouse Line

Lysophosphatidic acid (LPA) is a lysophospholipid that acts as an extracellular signal through the activation of cognate G protein-coupled receptors (GPCRs). There are six known LPA receptors (LPA1-6). The first such receptor, LPA1, was identified in the embryonic brain and has been studied extensively for gene expression throughout the body, including through studies of receptor-null mice. However, identifying receptor protein expression in situ and in vivo within living cells and tissues has been difficult because of biologically low receptor expression and variable antibody specificity. To visualize native LPA1 receptor expression in situ, we generated a knock-in mouse produced by homologous recombination in murine embryonic stem (ES) cells to replace a wildtype Lpar1 allele with a mutant allele created by in-frame fusion of EGFP to the 4th exon of Lpar1 (Lpar1-EGFP knock-in allele). Homozygous knock-in mice appeared normal and the expected mendelian ratios of knock-in allele transmission were present in females and males. Histological assessments of the fetal and adult central nervous system (CNS) demonstrated expression patterns that were consistent with prior in situ hybridization studies. This new mouse line will be useful for studies of LPA1 in the developing and adult CNS, as well as other tissues, and for receptor assessments in living tissues and disease models.

Lysophosphatidic Acid Accelerates Bovine In Vitro-Produced Blastocyst Formation through the Hippo/YAP Pathway

The segregation of trophectoderm (TE) and inner cell mass in early embryos is driven primarily by the transcription factor CDX2. The signals that trigger CDX2 activation are, however, less clear. In mouse embryos, the Hippo-YAP signaling pathway is important for the activation of CDX2 expression; it is less clear whether this relationship is conserved in other mammals. Lysophosphatidic acid (LPA) has been reported to increase YAP levels by inhibiting its degradation. In this study, we cultured bovine embryos in the presence of LPA and examined changes in gene and protein expression. LPA was found to accelerate the onset of blastocyst formation on days 5 and 6, without changing the TE/inner cell mass ratio. We further observed that the expression of TAZ and TEAD4 was up-regulated, and YAP was overexpressed, in LPA-treated day 6 embryos. However, LPA-induced up-regulation of CDX2 expression was only evident in day 8 embryos. Overall, our data suggest that the Hippo signaling pathway is involved in the initiation of bovine blastocyst formation, but does not affect the cell lineage constitution of blastocysts.

The lysophosphatidic acid axis in fibrosis: Implications for glaucoma

Glaucoma is a common progressive optic neuropathy that results in visual field defects and can lead to irreversible blindness. The pathophysiology of glaucoma involves dysregulated extracellular matrix remodelling in both the trabecular meshwork in the anterior chamber and in the lamina cribrosa of the optic nerve head. Fibrosis in these regions leads to raised intraocular pressure and retinal ganglion cell degeneration, respectively. Lysophosphatidic acid (LPA) is a bioactive lipid mediator which acts via six G-protein coupled receptors on the cell surface to activate intracellular pathways that promote cell proliferation, transcription and survival. LPA signalling has been implicated in both normal wound healing and pathological fibrosis. LPA enhances fibroblast proliferation, migration and contraction, and induces expression of pro-fibrotic mediators such as connective tissue growth factor. The LPA axis plays a major role in diseases such as idiopathic pulmonary fibrosis, where it has been identified as an important pharmacological target. In glaucoma, LPA is present in high levels in the aqueous humour, and its signalling has been found to increase resistance to aqueous humour outflow through altered trabecular meshwork cellular contraction and extracellular matrix deposition. LPA signalling may, therefore, also represent an attractive target for treatment of glaucoma. In this review we wish to describe the role of LPA and its related proteins in tissue fibrosis and glaucoma.

Prostaglandin E2 Receptor 4 (EP4) as a Therapeutic Target to Impede Breast Cancer-Associated Angiogenesis and Lymphangiogenesis

The formation of new blood (angiogenesis) and lymphatic (lymphangiogenesis) vessels are major events associated with most epithelial malignancies, including breast cancer. Angiogenesis is essential for cancer cell survival. Lymphangiogenesis is critical in maintaining tumoral interstitial fluid balance and importing tumor-facilitatory immune cells. Both vascular routes also serve as conduits for cancer metastasis. Intratumoral hypoxia promotes both events by stimulating multiple angiogenic/lymphangiogenic growth factors. Studies on tumor-associated lymphangiogenesis and its exploitation for therapy have received less attention from the research community than those on angiogenesis. Inflammation is a key mediator of both processes, hijacked by many cancers by the aberrant expression of the inflammation-associated enzyme cyclo-oxygenase (COX)-2. In this review, we focus on breast cancer and showed that COX-2 is a major promoter of both events, primarily resulting from the activation of prostaglandin (PG) E receptor EP4 on tumor cells, tumor-infiltrating immune cells, and endothelial cells; and the induction of oncogenic microRNAs. The COX-2/EP4 pathway also promotes additional events in breast cancer progression, such as cancer cell migration, invasion, and the stimulation of stem-like cells. Based on a combination of studies using multiple breast cancer models, we show that EP4 antagonists hold a major promise in breast cancer therapy in combination with other modalities including immune check-point inhibitors.

Therapeutic Potential of Porcine Liver Decomposition Product: New Insights and Perspectives for Microglia-Mediated Neuroinflammation in Neurodegenerative Diseases

It is widely accepted that microglia-mediated inflammation contributes to the progression of neurodegenerative diseases; however, the precise mechanisms through which these cells contribute remain to be elucidated. Microglia, as the primary immune effector cells of the brain, play key roles in maintaining central nervous system (CNS) homeostasis. Microglia are located throughout the brain and spinal cord and may account for up to 15% of all cells in the brain. Activated microglia express pro-inflammatory cytokines that act on the surrounding brain and spinal cord. Microglia may also play a detrimental effect on nerve cells when they gain a chronic inflammatory function and promote neuropathologies. A key feature of microglia is its rapid morphological change upon activation, characterized by the retraction of numerous fine processes and the gradual acquisition of amoeba-like shapes. These morphological changes are also accompanied by the expression and secretion of inflammatory molecules, including cytokines, chemokines, and lipid mediators that promote systemic inflammation during neurodegeneration. This may be considered a protective response intended to limit further injury and initiate repair processes. We previously reported that porcine liver decomposition product (PLDP) induces a significant increase in the Hasegawa’s Dementia Scale-Revised (HDS-R) score and the Wechsler Memory Scale (WMS) in a randomized, double-blind, placebo-controlled study in healthy humans. In addition, the oral administration of porcine liver decomposition product enhanced visual memory and delayed recall in healthy adults. We believe that PLDP is a functional food that aids cognitive function. In this review, we provide a critical assessment of recent reports of lysophospholipids derived from PLDP, a rich source of phospholipids. We also highlight some recent findings regarding bidirectional interactions between lysophospholipids and microglia and age-related neurodegenerative diseases such as dementia and Alzheimer’s disease.

Safety Assessment of Lecithin and Other Phosphoglycerides as Used in Cosmetics

The phosphoglycerides considered in this safety assessment are reported to function primarily as skin and hair conditioning agents, emulsifying agents, and surfactants in cosmetic products and are used up to a maximum reported concentration of 50%. Although phospholipids exert physiologic effects, these are not reproduced by application of phospholipid ingredients to the skin. Given the possibility that Lecithin may be derived from animal sources, it should be noted that the Food and Drug Administration does not permit the use of ingredients made from bovine specified risk materials in cosmetic products. The Expert Panel for Cosmetic Ingredient Safety concluded that the 17 phosphoglycerides are safe in the present practices of use and concentration in cosmetics, as described in this safety assessment.

The Role of Lysophosphatidic Acid in Adult Stem Cells

Stem cells are undifferentiated multipotent precursor cells that are capable both of perpetuating themselves as stem cells (self-renewal) and of undergoing differentiation into one or more specialized types of cells. And these stem cells have been reported to reside within distinct anatomic locations termed “niches”. The long-term goals of stem cell biology range from an understanding of cell-lineage determination and tissue organization to cellular therapeutics for degenerative diseases. Stem cells maintain tissue function throughout an organism’s lifespan by replacing differentiated cells. To perform this function, stem cells provide a unique combination of multilineage developmental potential and the capacity to undergo self-renewing divisions. The loss of self-renewal capacity in stem cells underlies certain degenerative diseases and the aging process. This self-renewal regulation must balance the regenerative needs of tissues that persist throughout life. Recent evidence suggests lysophosphatidic acid (LPA) signaling pathway plays an important role in the regulation of a variety of stem cells. In this review, we summarize the evidence linking between LPA and stem cell regulation. The LPA-induced signaling pathway regulates the proliferation and survival of stem cells and progenitors, and thus are likely to play a role in the maintenance of stem cell population in the body. This lipid mediator regulatory system can be a novel potential therapeutics for stem cell maintenance.

Lipid Signaling in Ocular Neovascularization

Vasculogenesis and angiogenesis play a crucial role in embryonic development. Pathological neovascularization in ocular tissues can lead to vision-threatening vascular diseases, including proliferative diabetic retinopathy, retinal vein occlusion, retinopathy of prematurity, choroidal neovascularization, and corneal neovascularization. Neovascularization involves various cellular processes and signaling pathways and is regulated by angiogenic factors such as vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF). Modulating these circuits may represent a promising strategy to treat ocular neovascular diseases. Lipid mediators derived from membrane lipids are abundantly present in most tissues and exert a wide range of biological functions by regulating various signaling pathways. In particular, glycerophospholipids, sphingolipids, and polyunsaturated fatty acids exert potent pro-angiogenic or anti-angiogenic effects, according to the findings of numerous preclinical and clinical studies. In this review, we summarize the current knowledge regarding the regulation of ocular neovascularization by lipid mediators and their metabolites. A better understanding of the effects of lipid signaling in neovascularization may provide novel therapeutic strategies to treat ocular neovascular diseases and other human disorders.

Advancements in understanding the role of lysophospholipids and their receptors in lung disorders including bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a devastating chronic neonatal lung disease leading to serious adverse consequences. Nearly 15 million babies are born preterm accounting for >1 in 10 births globally. The aetiology of BPD is multifactorial and the survivors suffer lifelong respiratory morbidity. Lysophospholipids (LPL), which include sphingosine-1-phosphate (S1P), and lysophosphatidic acid (LPA) are both naturally occurring bioactive lipids involved in a variety of physiological and pathological processes such as cell survival, death, proliferation, migration, immune responses and vascular development. Altered LPL levels have been observed in a number of lung diseases including BPD, which underscores the importance of these signalling lipids under normal and pathophysiological situations. Due to the paucity of information related to LPLs in BPD, most of the ideas related to BPD and LPL are speculative. This article is intended to promote discussion and generate hypotheses, in addition to the limited review of information related to BPD already established in the literature.

Bioactive Lipid Signaling in Cardiovascular Disease, Development, and Regeneration

Cardiovascular disease (CVD) remains a leading cause of death globally. Understanding and characterizing the biochemical context of the cardiovascular system in health and disease is a necessary preliminary step for developing novel therapeutic strategies aimed at restoring cardiovascular function. Bioactive lipids are a class of dietary-dependent, chemically heterogeneous lipids with potent biological signaling functions. They have been intensively studied for their roles in immunity, inflammation, and reproduction, among others. Recent advances in liquid chromatography-mass spectrometry techniques have revealed a staggering number of novel bioactive lipids, most of them unknown or very poorly characterized in a biological context. Some of these new bioactive lipids play important roles in cardiovascular biology, including development, inflammation, regeneration, stem cell differentiation, and regulation of cell proliferation. Identifying the lipid signaling pathways underlying these effects and uncovering their novel biological functions could pave the way for new therapeutic strategies aimed at CVD and cardiovascular regeneration.

Porcine liver decomposition product-derived lysophospholipids promote microglial activation in vitro

Cognitive impairments such as dementia are common in later life, and have been suggested to occur via a range of mechanisms, including oxidative stress, age-related changes to cellular metabolism, and a loss of phospholipids (PLs) from neuronal membranes. PLs are a class of amphipathic lipids that form plasma membrane lipid bilayers, and that occur at high concentrations in neuronal membranes. Our previous study suggested that a porcine liver decomposition product (PLDP) produced via protease treatment may improve cognitive function at older ages, by acting as a rich source of PLs and lysophospholipids (LPLs); however, its specific composition remains unclear. Thus, the present study used a novel liquid chromatography electrospray ionization tandem mass spectrometric (LC-MS/MS) protocol to identify the major PLs and LPLs in PLDP. Furthermore, it assessed the effect of identified LPLs on microglial activation in vitro, including cell shape, proliferation, and cell morphology. The results of the conducted analyses showed that PLDP and PLDP-derived LPLs concentration-dependently modulate microglial activation in vitro. In particular, lysophosphatidylcholine (LPC) concentration-dependently promotes cell morphology, likely via effects mediated by the enzyme autotaxin (ATX), since inhibiting ATX also promoted cell morphology, while conversely, increasing ATX production (via treatment with high levels of LPC) abolished this effect. These findings suggest that LPC is likely neuroprotective, and thus, support the importance of further research to assess its use as a therapeutic target to treat age-related cognitive impairments, including dementia.

Dynamic actin remodeling in response to lysophosphatidic acid

Lysophosphatidic acid (LPA) is a multifunctional regulator of actin cytoskeleton that exerts a dramatic impact on the actin cytoskeleton to build a platform for diverse cellular processes including growth cone guidance, neurite retraction and cell motility. It has been implicated in the formation and dissociation of complexes between actin and actin binding proteins, supporting its role in actin remodeling. Several studies point towards its ability to facilitate formation of special cellular structures including focal adhesions and actin stress fibres by phosphoregulation of several actin associated proteins and their multiple regulatory kinases and phosphatases. In addition, multiple levels of crosstalk among the signaling cascades activated by LPA, affect actin cytoskeleton-mediated cell migration and chemotaxis which in turn play a crucial role in cancer metastasis. In the current review, we have attempted to highlight the role of LPA as an actin modulator which functions by controlling activities of specific cellular proteins that underlie mechanisms employed in cytoskeletal and pathophysiological events within the cell. Further studies on the actin affecting/remodeling activity of LPA in different cell types will no doubt throw up many surprises essential to gain a full understanding of its contribution in physiological processes as well as in diseases.Communicated by Ramaswamy H. Sarma.

Lysophosphatidic Acid Upregulates Recepteur D'origine Nantais Expression and Cell Invasion via Egr-1, AP-1, and NF-κB Signaling in Bladder Carcinoma Cells

Muscle invasive bladder carcinoma is a highly malignant cancer with a high mortality rate, due to its tendency to metastasize. The tyrosine kinase recepteur d’origine nantais (RON) promotes bladder carcinoma metastasis. Lysophosphatidic acid (LPA) is a phospholipid derivative, which acts as a signaling molecule to activate three high affinity G-protein coupled receptors, LPA1, LPA2, and LPA3. This in turn leads to cell proliferation and contributes to oncogenesis. However, little is known about the effects of LPA on invasive bladder cancer (IBC). In this study, we discovered that LPA upregulated RON expression, which in turn promoted cell invasion in bladder cancer T24 cells. As expected, we found that the LPA receptor was essential for the LPA induced increase in RON expression. More interestingly, we discovered that LPA induced RON expression via the MAPK (ERK1/2, JNK1/2), Egr-1, AP-1, and NF-κB signaling axes. These results provide experimental evidence and novel insights regarding bladder malignancy metastasis, which could be helpful for developing new therapeutic strategies for IBC treatment.

Monocytes as Endothelial Progenitor Cells (EPCs), Another Brick in the Wall to Disentangle Tumor Angiogenesis

Bone marrow contains endothelial progenitor cells (EPCs) that, upon pro-angiogenic stimuli, migrate and differentiate into endothelial cells (ECs) and contribute to re-endothelialization and neo-vascularization. There are currently no reliable markers to characterize EPCs, leading to their inaccurate identification. In the past, we showed that, in a panel of tumors, some cells on the vessel wall co-expressed CD14 (monocytic marker) and CD31 (EC marker), indicating a putative differentiation route of monocytes into ECs. Herein, we disclosed monocytes as potential EPCs, using in vitro and in vivo models, and also addressed the cancer context. Monocytes acquired the capacity to express ECs markers and were able to be incorporated into blood vessels, contributing to cancer progression, by being incorporated in tumor neo-vasculature. Reactive oxygen species (ROS) push monocytes to EC differentiation, and this phenotype is reverted by cysteine (a scavenger and precursor of glutathione), which indicates that angiogenesis is controlled by the interplay between the oxidative stress and the scavenging capacity of the tumor microenvironment.

Endocervical trophoblast for interrogating the fetal genome and assessing pregnancy health at five weeks

Prenatal testing for fetal genetic traits and risk of obstetrical complications is essential for maternal-fetal healthcare. The migration of extravillous trophoblast (EVT) cells from the placenta into the reproductive tract and accumulation in the cervix offers an exciting avenue for prenatal testing and monitoring placental function. These cells are obtained with a cervical cytobrush, a routine relatively safe clinical procedure during pregnancy, according to published studies and our own observations. Trophoblast retrieval and isolation from the cervix (TRIC) obtains hundreds of fetal cells with >90% purity as early as five weeks of gestation. TRIC can provide DNA for fetal genotyping by targeted next-generation sequencing with single-nucleotide resolution. Previously, we found that known protein biomarkers are dysregulated in EVT cells obtained by TRIC in the first trimester from women who miscarry or later develop intrauterine growth restriction or preeclampsia. We have now optimized methods to stabilize RNA during TRIC for subsequent isolation and analysis of trophoblast gene expression. Here, we report transcriptomics analysis demonstrating that the expression profile of TRIC-isolated trophoblast cells was distinct from that of maternal cervical cells and included genes associated with the EVT phenotype and invasion. Because EVT cells are responsible for remodeling the maternal arteries and their failure is associated with pregnancy disorders, their molecular profiles could reflect maternal risk, as well as mechanisms underlying these disorders. The use of TRIC to analyze EVT genomes, transcriptomes and proteomes during ongoing pregnancies could provide new tools for anticipating and managing both fetal genetic and maternal obstetric disorders.

Lysophosphatidic acid: Its role in bone cell biology and potential for use in bone regeneration

Lysophosphatidic acid (LPA) is a simple phospholipid that exerts pleiotropic effects on numerous cell types by activating its family of cognate G protein-coupled receptors (GPCRs) and participates in many biological processes, including organismal development, wound healing, and carcinogenesis. Bone cells, such as bone marrow mesenchymal stromal (stem) cells (BMSCs), osteoblasts, osteocytes and osteoclasts play essential roles in bone homeostasis and repair. Previous studies have identified the presence of specific LPA receptors in these bone cells. In recent years, an increasing number of cellular effects of LPA, such as the induction of cell proliferation, survival, migration, differentiation and cytokine secretion, have been found in different bone cells. Moreover, some biomaterials containing LPA have shown the ability to enhance osteogenesis. This review will focus on findings associated with LPA functions in these bone cells and present current studies related to the application of LPA in bone regenerative medicine. Further understanding this information will help us develop better strategies for bone healing.

Lysophosphatidic Acid Is Associated With Cardiac Dysfunction and Hypertrophy by Suppressing Autophagy via the LPA3/AKT/mTOR Pathway

Background: Lysophosphatidic acid (LPA), as a phospholipid signal molecule, participates in the regulation of various biological functions. Our previous study demonstrated that LPA induces cardiomyocyte hypertrophy in vitro; however, the functional role of LPA in the post-infarct heart remains unknown. Growing evidence has demonstrated that autophagy is involved in regulation of cardiac hypertrophy. The aim of the current work was to investigate the effects of LPA on cardiac function and hypertrophy during myocardial infarction (MI) and determine the regulatory role of autophagy in LPA-induced cardiomyocyte hypertrophy.

Methods:In vivo experiments were conducted in Sprague-Dawley rats subjected to MI surgery or a sham operation, and rats with MI were assigned to receive an intraperitoneal injection of LPA (1 mg/kg) or vehicle for 5 weeks. The in vitro experiments were conducted in H9C2 cardiomyoblasts.

Results: LPA treatment aggravated cardiac dysfunction, increased cardiac hypertrophy, and reduced autophagy after MI in vivo. LPA suppressed autophagy activation, as indicated by a decreased LC3II-to-LC3I ratio, increased p62 expression, and reduced autophagosome formation in vitro. Rapamycin, an autophagy enhancer, attenuated LPA-induced autophagy inhibition and H9C2 cardiomyoblast hypertrophy, while autophagy inhibition with Beclin1 siRNA did not further enhance the hypertrophic response in LPA-treated cardiomyocytes. Moreover, we demonstrated that LPA suppressed autophagy through the AKT/mTOR signaling pathway because mTOR and PI3K inhibitors significantly prevented LPA-induced mTOR phosphorylation and autophagy inhibition. In addition, we found that knockdown of LPA3 alleviated LPA-mediated autophagy suppression in H9C2 cardiomyoblasts, suggesting that LPA suppresses autophagy through activation of the LPA3 and AKT/mTOR pathways.

Conclusion: These findings suggest that LPA plays an important role in mediating cardiac dysfunction and hypertrophy after a MI, and that LPA suppresses autophagy through activation of the LPA3 and AKT/mTOR pathways to induce cardiomyocyte hypertrophy.

Autotaxin⁻Lysophosphatidic Acid Signaling in Alzheimer's Disease

The brain contains various forms of lipids that are important for maintaining its structural integrity and regulating various signaling cascades. Autotaxin (ATX) is an ecto-nucleotide pyrophosphatase/phosphodiesterase-2 enzyme that hydrolyzes extracellular lysophospholipids into the lipid mediator lysophosphatidic acid (LPA). LPA is a major bioactive lipid which acts through G protein-coupled receptors (GPCRs) and plays an important role in mediating cellular signaling processes. The majority of synthesized LPA is derived from membrane phospholipids through the action of the secreted enzyme ATX. Both ATX and LPA are highly expressed in the central nervous system. Dysfunctional expression and activity of ATX with associated changes in LPA signaling have recently been implicated in the pathogenesis of Alzheimer’s disease (AD). This review focuses on the current understanding of LPA signaling, with emphasis on the importance of the autotaxin–lysophosphatidic acid (ATX–LPA) pathway and its alterations in AD and a brief note on future therapeutic applications based on ATX–LPA signaling.

Lysophosphatidic acid enhances neointimal hyperplasia following vascular injury through modulating proliferation, autophagy, inflammation and oxidative stress

Lysophosphatidic acid (LPA), which is one of the intermediate products of membrane phospholipid metabolism, is a bioactive phospholipid that possesses diverse activities. In the present study, the effects of LPA on neointimal formation following vascular injury were investigated. A carotid artery balloon injury model was employed in the present study, and following vascular injury, rats received an intraperitoneal injection of 1 mg/kg LPA. Subsequently, histopathological alterations were assessed by hematoxylin and eosin staining, the expression levels of proliferating cell nuclear antigen (PCNA) were detected by immunohistochemistry, apoptosis was assessed via a terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, and the expression levels of apoptosis-associated and autophagy-associated proteins were detected by western blotting. In addition, inflammatory and oxidative stress-associated factors were assessed by reverse transcription-quantitative polymerase chain reaction or corresponding kits. The results of the present study demonstrated that LPA enhanced vascular injury-induced neointimal hyperplasia. LPA further elevated the expression levels of PCNA in the injured carotid artery tissues. LPA exhibited no effect on apoptosis in carotid artery tissues, whereas it modulated autophagy in the injured carotid artery tissues. Furthermore, LPA enhanced vascular injury-induced inflammation and oxidative stress. The present study demonstrated that LPA may enhance neointimal hyperplasia following vascular injury by modulating proliferation, autophagy, inflammation and oxidative stress, but not apoptosis. Furthermore LPA may contribute to the pathology of atherosclerosis and may be considered a promising therapeutic target for the treatment of atherosclerosis.

Blood-based metabolic signatures in Alzheimer's disease

Introduction

Identification of blood-based metabolic changes might provide early and easy-to-obtain biomarkers.

Methods

We included 127 Alzheimer's disease (AD) patients and 121 control subjects with cerebrospinal fluid biomarker-confirmed diagnosis (cutoff tau/amyloid β peptide 42: 0.52). Mass spectrometry platforms determined the concentrations of 53 amine compounds, 22 organic acid compounds, 120 lipid compounds, and 40 oxidative stress compounds. Multiple signatures were assessed: differential expression (nested linear models), classification (logistic regression), and regulatory (network extraction).

Results

Twenty-six metabolites were differentially expressed. Metabolites improved the classification performance of clinical variables from 74% to 79%. Network models identified five hubs of metabolic dysregulation: tyrosine, glycylglycine, glutamine, lysophosphatic acid C18:2, and platelet-activating factor C16:0. The metabolite network for apolipoprotein E (APOE) ε4 negative AD patients was less cohesive compared with the network for APOE ε4 positive AD patients.

Discussion

Multiple signatures point to various promising peripheral markers for further validation. The network differences in AD patients according to APOE genotype may reflect different pathways to AD.

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Multiple metabolic signatures point to peripheral AD markers for future validation.

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AD may be described by changes in the metabolism of amines and oxidative stressors.

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APOE ε4-driven AD and non- APOE ε4-driven AD represent different biochemical pathways.

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Network analyses of metabolomics data enable the study of metabolic changes in AD.

Lysophosphatidic acid plasma concentrations in healthy subjects: circadian rhythm and associations with demographic, anthropometric and biochemical parameters

Background

Lysophosphatidic acid (LPA) is a bioactive lipid with a wide biological activity. Previous studies have shown its potential usefulness as a diagnostic marker for ovarian cancer. The aim of the study was to investigate which factors may influence plasma LPA concentrations in healthy subjects and to propose reference values.

Methods

The study group consisted of 100 healthy subjects. From all of them the blood samples were taken at 7 a.m. (fasting state). From 40 volunteers additional blood samples were taken at 2 p.m., at 8 p.m. and at 2 a.m. next morning. Concentrations of LPA were measured in plasma samples using enzyme-linked immunosorbent assay.

Results

Analysis of samples from 100 healthy volunteers showed significant influence of sex and age on plasma LPA. The reference range for the plasma LPA concentration corrected for age and sex, determined at 2.5–97.5 percentile interval is 0.14–1.64 μM. LPA correlates positively with BMI, serum total cholesterol, triacylglycerols, uric acid and negatively with estimated glomerular filtration rate and serum albumin. Concentration of LPA at 2 a.m. was lower than at 2 p.m. There were not any significant differences between plasma LPA at 7 a.m. and any other time of the day.

Conclusions

Plasma LPA is associated with demographic, anthropometric and biochemical parameters. It seems that LPA concentrations have no specific circadian rhythm and the time of donation and fasting state have marginal effect on plasma LPA. These findings may be helpful in future incorporation of LPA as a diagnostic marker.

Discovery of Novel Gq-Biased LPA1 Negative Allosteric Modulators

Lysophosphatidic acid (LPA) activates the G-protein-coupled receptor LPA1, which regulates various cellular processes, including cell proliferation and migration. Although LPA1 transduces cellular responses via Gq, Gi, and G12/13, associations between these signaling molecules and cellular phenotypes remain poorly characterized due to the lack of signal-specific pharmacological tools. Here, we characterized novel signal-biased modulators using multiple assays, including label-free impedance assays. LPA caused dramatic changes in cellular impedance in LPA1-expressing recombinant cells, which were susceptible to G-protein and protein kinase inhibitors. Subsequently, Gq-biased LPA1 negative allosteric modulators (NAMs) were identified using high-throughput screening, and a nonbiased antagonist differently affected the LPA-induced cellular impedance. These NAMs provide pharmacological tools for further investigations of the biology of LPA1.

Different origins of lysophospholipid mediators between coronary and peripheral arteries in acute coronary syndrome

Lysophosphatidic acids (LysoPAs) and lysophosphatidylserine (LysoPS) are emerging lipid mediators proposed to be involved in the pathogenesis of acute coronary syndrome (ACS). In this study, we attempted to elucidate how LysoPA and LysoPS become elevated in ACS using human blood samples collected simultaneously from culprit coronary arteries and peripheral arteries in ACS subjects. We found that: 1) the plasma LysoPA, LysoPS, and lysophosphatidylglycerol levels were not different, while the lysophosphatidylcholine (LysoPC), lysophosphatidylinositol, and lysophosphatidylethanolamine (LysoPE) levels were significantly lower in the culprit coronary arteries; 2) the serum autotaxin (ATX) level was lower and the serum phosphatidylserine-specific phospholipase A₁ (PS-PLA₁) level was higher in the culprit coronary arteries; 3) the LysoPE and ATX levels were significant explanatory factors for the mainly elevated species of LysoPA, except for 22:6 LysoPA, in the peripheral arteries, while the LysoPC and LysoPE levels, but not the ATX level, were explanatory factors in the culprit coronary arteries; and 4) 18:0 and 18:1 LysoPS were significantly correlated with PS-PLA₁ only in the culprit coronary arteries. In conclusion, the origins of LysoPA and LysoPS might differ between culprit coronary arteries and peripheral arteries, and substrates for ATX, such as LysoPC and LysoPE, might be important for the generation of LysoPA in ACS.

G-Protein-Coupled Lysophosphatidic Acid Receptors and Their Regulation of AKT Signaling

A hallmark of G-protein-coupled receptors (GPCRs) is their ability to recognize and respond to chemically diverse ligands. Lysophospholipids constitute a relatively recent addition to these ligands and carry out their biological functions by activating G-proteins coupled to a large family of cell-surface receptors. This review aims to highlight salient features of cell signaling by one class of these receptors, known as lysophosphatidic acid (LPA) receptors, in the context of phosphatidylinositol 3-kinase (PI3K)-AKT pathway activation. LPA moieties efficiently activate AKT phosphorylation and activation in a multitude of cell types. The interplay between LPA, its receptors, the associated Gαi/o subunits, PI3K and AKT contributes to the regulation of cell survival, migration, proliferation and confers chemotherapy-resistance in certain cancers. However, detailed information on the regulation of PI3K-AKT signals induced by LPA receptors is missing from the literature. Here, some urgent issues for investigation are highlighted.

Expression of autotaxin and lysophosphatidic acid receptors 1 and 3 in the developing rat lung and in response to hyperoxia

We sought to evaluate lysophosphatidic acid (LPA) signaling improvement in lung development by assessing the expression of autotaxin and LPA receptor 1 and 3 (LPAR1 and LPAR3) in the neonatal rat lung during normal perinatal development and in response to hyperoxia. In the developmental study, rats were sacrificed on days 17, 19, and 21 of gestation; on postnatal days 1, 4, and 7; and at adulthood (postnatal 9 weeks). In the hyperoxia study, 42 postnatal 4-day-old rat pups were divided into seven groups and exposed to either 85% O2 for 24, 72, or 120 h or room air for 0, 24, 72, or 120 h. The rats were then euthanized after 0, 24, 72, and 120 h of exposure. Immunofluorescence demonstrated that autotaxin, LPAR1, and LPAR3 proteins were broadly colocalized in airway epithelial cells, but mainly distributed in vascular endothelial and mesenchymal cells during the first postnatal week. The expression of autotaxin, LPAR1, and LPAR3 were increased during late gestation and then decreased after birth. Autotaxin expression and enzymatic activity were significantly increased at 72 and 120 h after exposure to hyperoxia. LPAR1 and LPAR3 expression was also increased after 120 h of hyperoxic exposure. These findings suggest that LPA-associated molecules were upregulated at birth and induced by hyperoxia in the developing rat lung. Therefore, the LPA pathway may be involved in normal lung development, including vascular development, as well as wound-healing processes of injured neonatal lung tissue, which is at risk of neonatal hyperoxic acute lung injury.

Lysophosphatidic acid signalling in development

Lysophosphatidic acid (LPA) is a bioactive phospholipid that is present in all tissues examined to date. LPA signals extracellularly via cognate G protein-coupled receptors to mediate cellular processes such as survival, proliferation, differentiation, migration, adhesion and morphology. These LPA-influenced processes impact many aspects of organismal development. In particular, LPA signalling has been shown to affect fertility and reproduction, formation of the nervous system, and development of the vasculature. Here and in the accompanying poster, we review the developmentally related features of LPA signalling.

Lysophosphatidic Acid signaling in the nervous system

The brain is composed of many lipids with varied forms that serve not only as structural components but also as essential signaling molecules. Lysophosphatidic acid (LPA) is an important bioactive lipid species that is part of the lysophospholipid (LP) family. LPA is primarily derived from membrane phospholipids and signals through six cognate G protein-coupled receptors (GPCRs), LPA1-6. These receptors are expressed on most cell types within central and peripheral nervous tissues and have been functionally linked to many neural processes and pathways. This Review covers a current understanding of LPA signaling in the nervous system, with particular focus on the relevance of LPA to both physiological and diseased states.

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.

LPA receptor signaling: pharmacology, physiology, and pathophysiology

Lysophosphatidic acid (LPA) is a small ubiquitous lipid found in vertebrate and nonvertebrate organisms that mediates diverse biological actions and demonstrates medicinal relevance. LPA's functional roles are driven by extracellular signaling through at least six 7-transmembrane G protein-coupled receptors. These receptors are named LPA1-6 and signal through numerous effector pathways activated by heterotrimeric G proteins, including Gi/o, G12/13, Gq, and Gs LPA receptor-mediated effects have been described in numerous cell types and model systems, both in vitro and in vivo, through gain- and loss-of-function studies. These studies have revealed physiological and pathophysiological influences on virtually every organ system and developmental stage of an organism. These include the nervous, cardiovascular, reproductive, and pulmonary systems. Disturbances in normal LPA signaling may contribute to a range of diseases, including neurodevelopmental and neuropsychiatric disorders, pain, cardiovascular disease, bone disorders, fibrosis, cancer, infertility, and obesity. These studies underscore the potential of LPA receptor subtypes and related signaling mechanisms to provide novel therapeutic targets.

Methods for quantifying lysophosphatidic acid in body fluids: a review

Lysophosphatidic acid (LPA) is a bioactive lipid involved in cellular signal transduction. LPA plays a role in both physiological and pathological processes. Elevated levels of LPA are observed in the plasma of patients with epithelial ovarian cancer, indicating its potential as a diagnostic marker. Quantification of total LPA can be performed by radioenzymatic, fluorometric, colorimetric, or immunoezymatic assay. Determination of individual LPA molecular species requires the use of capillary electrophoresis, gas chromatography, thin layer chromatography, liquid chromatography, or a matrix-assisted laser desorption/ionization time-of-flight method connected to an appropriate detection system.

Lysophosphatidic acid protects human mesenchymal stromal cells from differentiation-dependent vulnerability to apoptosis

The survival of transplanted cells and their resulting efficacy in cell-based therapies is markedly impaired due to serum deprivation and hypoxia (SD/H) resulting from poor vascularization within tissue defects. Lysophosphatidic acid (LPA) is a platelet-derived growth factor with pleiotropic effects on many cell types. Mesenchymal stromal cells (MSC) exhibit unique secretory and stimulatory characteristics depending on their differentiation state. In light of the potential of MSC in cell-based therapies, we examined the ability of LPA to abrogate SD/H-induced apoptosis in human MSC at increasing stages of osteogenic differentiation in vitro and assessed MSC survival in vivo. Undifferentiated MSC were rescued from SD/H-induced apoptosis by treatment with both 25 and 100 μM LPA. However, MSC conditioned with osteogenic supplements responded to 25 μM LPA, and cells conditioned with dexamethasone-containing osteogenic media required 100 μM LPA. This rescue was mediated through LPA1 in all cases. The addition of 25 μM LPA enhanced vascular endothelial growth factor (VEGF) secretion by MSC in all conditions, but VEGF availability was not responsible for protection against apoptosis. We also showed that codelivery of 25 μM LPA with MSC in alginate hydrogels significantly improved the persistence of undifferentiated MSC in vivo over 4 weeks as measured by bioluminescence imaging. Osteogenic differentiation alone was protective of SD/H-induced apoptosis in vitro, and the synergistic delivery of LPA did not enhance persistence of osteogenically induced MSC in vivo. These data demonstrate that the capacity of LPA to inhibit SD/H-induced apoptosis in MSC is dependent on both the differentiation state and dosage. This information will be valuable for optimizing osteogenic conditioning regimens for MSC before in vivo implementation.

Simple enrichment and analysis of plasma lysophosphatidic acids

A simple and highly efficient technique for the analysis of lysophosphatidic acid (LPA) subspecies in human plasma is described. The streamlined sample preparation protocol furnishes the five major LPA subspecies with excellent recoveries. Extensive analysis of the enriched sample reveals only trace levels of other phospholipids. This level of purity not only improves MS analyses, but enables HPLC post-column detection in the visible region with a commercially available fluorescent phospholipids probe. Human plasma samples from different donors were analyzed using the above method and validated by LC-ESI/MS/MS.

Compartmentalizing the embryo: lipids and septate junction mediated barrier function

Lipid phosphate phosphatases (LPPs) are a class of enzymes that can dephosphorylate a number of lysophopholipids in vitro. Analysis of knockouts of LPP family members has demonstrated striking but diverse developmental roles for these enzymes. LPP3 is required for mouse vascular development while the Drosophila LPPs Wunen (Wun) and Wunen2 (Wun2) are required during embryogenesis for germ cell migration and survival. In a recent publication we examined if these fly LPPs have further developmental roles and found that Wun is required for proper tracheal formation. In particular we highlight a role for Wun in septate junction mediated barrier function in the tracheal system. In this paper we discuss further the possible mechanisms by which LPPs may influence barrier activity.

Primary human endothelial cells secrete agents that reduce responsiveness to lysophosphatidic acid (LPA)

The plasma level of LPA (lysophosphatidic acid) (200–600 nM) is well within the range that promotes proliferation and migration of vascular ECs (endothelial cells), yet vessels are quiescent and stable. In this report, we considered one explanation for this paradox: that ECs secrete agents that attenuate responsiveness to LPA. Indeed, we observed that CM (conditioned medium) from confluent, quiescent cultures of primary HUVECs (human umbilical vein ECs) contained an agent that inhibited LPA-mediated signalling events and cellular responses. The putative inhibitor, which we tentatively call ILMR (inhibitor of LPA-mediated responsiveness) seemed to act on cells (instead of at the level of LPA) by suppressing the ability of LPA receptor 1 to signal. The amount and/or activity of ILMR was regulated by growth factors; exposing HUVECs to VEGF-A (vascular endothelial growth factor A), but not bFGF (basic fibroblast growth factor), reduced the amount and/or activity of ILMR in CM. We conclude that in addition to promoting angiogenesis directly, VEGF-A can also act indirectly by modulating the bioactivity of angiomodulators such as LPA.

Galectin-3 contributes to melanoma growth and metastasis via regulation of NFAT1 and autotaxin

Melanoma is the deadliest form of skin cancer in which patients with metastatic disease have a 5-year survival rate of less than 10%. Recently, the overexpression of a β-galactoside binding protein, galectin-3 (LGALS3), has been correlated with metastatic melanoma in patients. We have previously shown that silencing galectin-3 in metastatic melanoma cells reduces tumor growth and metastasis. Gene expression profiling identified the protumorigenic gene autotaxin (ENPP2) to be downregulated after silencing galectin-3. Here we report that galectin-3 regulates autotaxin expression at the transcriptional level by modulating the expression of the transcription factor NFAT1 (NFATC2). Silencing galectin-3 reduced NFAT1 protein expression, which resulted in decreased autotaxin expression and activity. Reexpression of autotaxin in galectin-3 silenced melanoma cells rescues angiogenesis, tumor growth, and metastasis in vivo. Silencing NFAT1 expression in metastatic melanoma cells inhibited tumor growth and metastatic capabilities in vivo. Our data elucidate a previously unidentified mechanism by which galectin-3 regulates autotaxin and assign a novel role for NFAT1 during melanoma progression.

Lysophosphatidic acid causes endothelial dysfunction in porcine coronary arteries and human coronary artery endothelial cells

AIM

The objective of this study was to determine the effects of lysophosphatidic acid (LPA) on endothelial functions and molecular alternations in both porcine coronary arteries and human coronary artery endothelial cells (HCAECs).

METHODS AND RESULTS

The vessel rings and HCAECs were treated with clinically relevant concentrations of LPA for different times. Vasomotor reactivity was studied with a myograph tension system. LPA (10 and 50 μM) treatment for the vessel rings significantly reduced endothelium-dependent vasorelaxation in response to bradykinin (×10(-5)M) by 32% and 49%, respectively, compared with the control (P<0.05). LPA decreased endothelial nitric oxide synthase (eNOS) mRNA and immunoreactivity levels in the vessel rings. In HCAECs, LPA reduced eNOS mRNA, phospho-eNOS and total eNOS protein levels. In addition, superoxide anion levels in LPA-treated vessel rings and HCAECs were significantly increased by lucegenin-enhanced chemiluminescence assay and dihydroethidium staining, respectively. Mitochondrial membrane potential and ATP content in LPA-treated HCAECs were substantially decreased. The mRNA levels of reactive oxygen species generating enzymes NOX4 and p40(phox) were increased, while endogenous antioxidant enzyme superoxide dismutase 1 was decreased in response to LPA treatment in HCAECs. Furthermore, exogenous antioxidant molecule selenomethionine (SeMet) effectively reversed these LPA-induced effects in both porcine coronary arteries and HCAECs.

CONCLUSIONS

LPA causes endothelial dysfunction by a mechanism associated with decreased eNOS expression and increased oxidative stress in porcine coronary arteries and HCAECs.

Lysophosphatidic acid-induced p21Waf1 expression mediates the cytostatic response of breast and ovarian cancer cells to TGFβ

Lysophosphatidic acid (LPA) is a multifunctional intercellular phospholipid mediator present in blood and other biological fluids. In cancer cells, LPA stimulates expression or activity of inflammatory cytokines, angiogenic factors, matrix metalloproteinases, and other oncogenic proteins. In this study, we showed that LPA upregulated expression of the cyclin-dependent kinase inhibitor p21(Waf1) in TGFβ-sensitive breast and ovarian cancer cells, but not in TGFβ-resistant ones. We examined the possibility that LPA-induced p21 might contribute to the cytostatic response to TGFβ. In serum-free conditions, TGFβ alone induced p21 expression weakly in TGFβ-sensitive cells. Serum or serum-borne LPA cooperated with TGFβ to elicit the maximal p21 induction. LPA stimulated p21 via LPA(1) and LPA(2) receptors and Erk-dependent activation of the CCAAT/enhancer binding protein beta transcription factor independent of p53. Loss or gain of p21 expression led to a shift between TGFβ-sensitive and -resistant phenotypes in breast and ovarian cancer cells, indicating that p21 is a key determinant of the growth inhibitory activity of TGFβ. Our results reveal a novel cross-talk between LPA and TGFβ that underlies TGFβ-sensitive and -resistant phenotypes of breast and ovarian cancer cells.

International Union of Basic and Clinical Pharmacology. LXXVIII. Lysophospholipid receptor nomenclature

Lysophospholipids are cell membrane-derived lipids that include both glycerophospholipids such as lysophosphatidic acid (LPA) and sphingoid lipids such as sphingosine 1-phosphate (S1P). These and related molecules can function in vertebrates as extracellular signals by binding and activating G protein-coupled receptors. There are currently five LPA receptors, along with a proposed sixth (LPA₁-LPA₆), and five S1P receptors (S1P₁-S1P₅). A remarkably diverse biology and pathophysiology has emerged since the last review, driven by cloned receptors and targeted gene deletion ("knockout") studies in mice, which implicate receptor-mediated lysophospholipid signaling in most organ systems and multiple disease processes. The entry of various lysophospholipid receptor modulatory compounds into humans through clinical trials is ongoing and may lead to new medicines that are based on this signaling system. This review incorporates IUPHAR Nomenclature Committee guidelines in updating the nomenclature for lysophospholipid receptors ( http://www.iuphar-db.org/DATABASE/FamilyMenuForward?familyId=36).

Apoptosis-induced changes in mitochondrial lipids

Apoptosis is an active and tightly regulated form of cell death, which can also be considered a stress-induced process of cellular communication. Recent studies reveal that the lipid network within cells is involved in the regulation and propagation of death signalling. Despite the vast growth of our current knowledge on apoptosis, little is known of the specific role played by lipid molecules in the central event of apoptosis-the piercing of mitochondrial membranes. Here we review the information regarding changes in mitochondrial lipids that are associated with apoptosis and discuss whether they may be involved in the permeabilization of mitochondria to release their apoptogenic factors, or just lie downstream of this permeabilization leading to the amplification of caspase activation. We focus on the earliest changes that physiological apoptosis induces in mitochondrial membranes, which may derive from an upstream alteration of phospholipid metabolism that reverberates on the mitochondrial re-modelling of their characteristic lipid, cardiolipin. Hopefully, this review will lead to an increased understanding of the role of mitochondrial lipids in apoptosis and also help revealing new stress sensing mechanisms in cells. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.

Group VIA phospholipase A2 in both host and tumor cells is involved in ovarian cancer development

Host-tumor cell interactions are recognized to be critical in tumor development. We have shown that group VIA phospholipase A(2) [calcium-independent phospholipase A(2)β (iPLA(2)β)] is important in regulating extracellular lysophosphatidic acid (LPA) levels around human epithelial ovarian cancer (EOC) cells. To explore the role of iPLA(2)β in host-tumor cell interactions, we have used immunocompetent iPLA(2)β knockout (iPLA(2)β(-/-)) mice and the mouse EOC cell line ID8. Tumorigenesis and ascites formation were reduced in iPLA(2)β(-/-) mice compared with wild-type (WT) mice by more >50% and were reduced further when ID8 cell iPLA(2)β levels were lowered (by>95%) with shRNA. LPA and lysophosphatidylcholine (LPC) levels in the tumor microenvironment were reduced to ∼80% of WT levels in iPLA(2)β(-/-) mice. LPA, but not LPC, stimulated ID8 cell migration and invasion with cells in which iPLA(2)β expression had been down-regulated in vitro. LPA, but not LPC, also enhanced in vivo ascites formation (by ∼5-fold) and tumorigenesis in iPLA(2)β(-/-) mice. This is the first demonstration of a role for host cell iPLA(2)β in cancer, and these findings suggest that iPLA(2)β is a potential target for developing novel antineoplastic therapeutic strategies.

Deficiency of autotaxin/lysophospholipase D results in head cavity formation in mouse embryos through the LPA receptor-Rho-ROCK pathway

Autotaxin, encoded by the Enpp2 gene, generates lysophosphatidic acid (LPA) extracellularly, eliciting various cellular responses through specific LPA receptors. Previous studies have revealed that Enpp2(-/-) mice die at E9.5 owing to angiogenic defects in the yolk sac. Moreover, Enpp2(-/-) embryos show growth retardation, allantois malformation, no axial turning, and head cavity formation. We have also demonstrated that lysosome biogenesis is impaired in yolk sac visceral endoderm cells of Enpp2(-/-) embryos as a result of the downregulation of the Rho-ROCK (Rho-associated coiled-coil containing protein kinase)-LIM kinase pathway. In this study, we examine what signaling defect(s) is responsible for head cavity formation and yolk sac angiogenic defects. By using a whole embryo culture system, we show that 10 μM Ki16425, an antagonist for the LPA receptors, induces head cavity formation and yolk sac angiogenic defects in wild-type embryos. Moreover, 1 μM Ki16425 induces both phenotypes in Enpp2 heterozygous embryos at significantly higher incidence than in wild-type embryos, suggesting an interaction between autotaxin and LPA receptor signaling. Furthermore, we show that inhibition of the Rho-ROCK pathway induces head cavity formation, whereas multiple pathways are involved in yolk sac angiogenic defects. These results reveal the signal transduction defects that underlie the abnormalities in Enpp2(-/-) embryos.

Protection by D609 through cell-cycle regulation after stroke

Expressions of cell-cycle regulating proteins are altered after stroke. Cell-cycle inhibition has shown dramatic reduction in infarction after stroke. Ceramide can induce cell-cycle arrest by up-regulation of cyclin-dependent kinase (Cdk) inhibitors p21 and p27 through activation of protein phosphatase 2A (PP2A). Tricyclodecan-9-yl-xanthogenate (D609)-increased ceramide levels after transient middle cerebral artery occlusion (tMCAO) in spontaneously hypertensive rat (SHR) probably by inhibiting sphingomyelin synthase (SMS). D609 significantly reduced cerebral infarction and up-regulated Cdk inhibitor p21 and down-regulated phospho-retinoblastoma (pRb) expression after tMCAO in rat. Others have suggested bFGF-induced astrocyte proliferation is attenuated by D609 due to an increase in ceramide by SMS inhibition. D609 also reduced the formation of oxidized phosphatidylcholine (OxPC) protein adducts. D609 may attenuate generation of reactive oxygen species and formation of OxPC by inhibiting microglia/macrophage proliferation after tMCAO (please also see note added in proof: D609 may prevent mature neurons from entering the cell cycle at the early reperfusion, however may not interfere with later proliferation of microglia/ macrophages that are the source of brain derived neurotrophic factor (BDNF) and insulin-like growth factor (IGF-1) in offering protection). It has been proposed that D609 provides benefit after tMCAO by attenuating hypoxia-inducible factor-1alpha and Bcl2/adenovirus E1B 19 kDa interacting protein 3 expressions. Our data suggest that D609 provides benefit after stoke through inhibition of SMS, increased ceramide levels, and induction of cell-cycle arrest by up-regulating p21 and causing hypophosphorylation of Rb (through increased protein phosphatase activity and/or Cdk inhibition).