Lysophosphatidic Acid Research Articles

The autotaxin-LPA axis promotes membrane trafficking and secretion in yolk sac visceral endoderm cells.

Autotaxin, encoded by the Enpp2 gene, is an exoenzyme that produces lysophosphatidic acid, thereby regulating many biologic functions. We previously reported that Enpp2 mRNA was abundantly expressed in yolk sac visceral endoderm (VE) cells and that Enpp2-/- mice were lethal at embryonic day 9.5 owing to angiogenic defects in the yolk sac. Enpp2-/- mice showed lysosome fragmentation in VE cells and embryonic abnormalities including allantois malformation, neural tube defects, no axial turning, and head cavity formation. However, whether the defects in endocytic vesicle formation affect membrane trafficking in VE cells remained to be directly examined. In this study, we found that pinocytosis, transcytosis, and secretion of angiogenic factors such as vascular endothelial growth factor and transforming growth factor β1 were impaired in Enpp2-/- VE cells. Moreover, pharmacologic inhibition of membrane trafficking phenocopied the defects of Enpp2-/- mice. These findings demonstrate that Enpp2 spromotes endocytosis and secretion of angiogenic factors in VE cells, thereby regulating angiogenesis/vasculogenesis and embryonic development.

Autotaxin in encephalitogenic CD4 T cells as a therapeutic target for multiple sclerosis.

Multiple sclerosis (MS) is an immune-mediated inflammatory disease of the CNS. A defining characteristic of MS is the ability of autoreactive T lymphocytes to cross the blood-brain barrier and mediate inflammation within the CNS. Previous work from our lab found the gene Enpp2 to be highly upregulated in murine encephalitogenic T cells. Enpp2 encodes for the protein autotaxin, a secreted glycoprotein that catalyzes the production of lysophosphatidic acid and promotes transendothelial migration of T cells from the bloodstream into the lymphatic system. The present study sought to characterize autotaxin expression in T cells during CNS autoimmune disease and determine its potential therapeutic value. Myelin-activated CD4 T cells upregulated expression of autotaxin in vitro, and ex vivo analysis of CNS-infiltrating CD4 T cells showed significantly higher autotaxin expression compared with cells from healthy mice. In addition, inhibiting autotaxin in myelin-specific T cells reduced their encephalitogenicity in adoptive transfer studies and decreased in vitro cell motility. Importantly, using two mouse models of MS, treatment with an autotaxin inhibitor ameliorated EAE severity, decreased the number of CNS infiltrating T and B cells, and suppressed relapses, suggesting autotaxin may be a promising therapeutic target in the treatment of MS.

Plasma Lysophosphatidic Acid Concentrations in Sex Differences and Psychiatric Comorbidity in Patients with Cocaine Use Disorder.

We have recently reported sex differences in the plasma concentrations of lysophosphatidic acid (LPA) and alterations in LPA species in patients with alcohol and cocaine use disorders. Preclinical evidence suggests a main role of lysophosphatidic acid (LPA) signaling in anxiogenic responses and drug addiction. To further explore the potential role of the LPA signaling system in sex differences and psychiatric comorbidity in cocaine use disorder (CUD), we conducted a cross-sectional study with 88 patients diagnosed with CUD in outpatient treatment and 60 healthy controls. Plasma concentrations of total LPA and LPA species (16:0, 18:0, 18:1, 18:2 and 20:4) were quantified and correlated with cortisol and tryptophan metabolites [tryptophan (TRP), serotonin (5-HT), kynurenine (KYN), quinolinic acid (QUIN) and kynurenic acid (KYNA)]. We found sexual dimorphism for the total LPA and most LPA species in the control and CUD groups. The total LPA and LPA species were not altered in CUD patients compared to the controls. There was a significant correlation between 18:2 LPA and age at CUD diagnosis (years) in the total sample, but total LPA, 16:0 LPA and 18:2 LPA correlated with age at onset of CUD in male patients. Women with CUD had more comorbid anxiety and eating disorders, whereas men had more cannabis use disorders. Total LPA, 18:0 LPA and 20:4 LPA were significantly decreased in CUD patients with anxiety disorders. Both 20:4 LPA and total LPA were significantly higher in women without anxiety disorders compared to men with and without anxiety disorders. Total LPA and 16:0 LPA were significantly decreased in CUD patients with childhood ADHD. Both 18:1 LPA and 20:4 LPA were significantly augmented in CUD patients with personality disorders. KYNA significantly correlated with total LPA, 16:0 LPA and 18:2 LPA species, while TRP correlated with the 18:1 LPA species. Our results demonstrate that LPA signaling is affected by sex and psychiatric comorbidity in CUD patients, playing an essential role in mediating their anxiety symptoms.

Changes in serum levels of pain mediators in hemiplegic shoulder pain.

To provide a new insight into the diagnosis and treatment of hemiplegic shoulder pain (HSP) by investigating changes in serum pain mediators. Cross-sectional study. Shoulder pain group (n=34) and control group (n=21). Pain-free shoulder mobility, anxiety status, depression status, and shoulder pain were measured by passive range of motion (PROM), self-rating anxiety scale, self-rating depression scale (SDS), and visual analog scale, respectively. The enzyme-linked immunosorbent assay was used to test the serum pain mediators, including interleukin (IL)-1β, IL-2, IL-6, IL-10, nerve growth factor (NGF), tumor necrosis factor-α (TNF-α), substance P (SP), calcitonin gene-related peptide (CGRP), bradykinin (BK), 5-hydroxytryptamine (5-HT), prostaglandin E2 (PGE2), and lysophosphatidic acid (LPA). Shoulder pain group pain-free PROM significantly lower than control (p<.01), and SDS index score of shoulder pain group was significantly higher than control (p<.05). The rate of spasticity in the flexor elbow muscles is higher in shoulder pain group (p<.01). CGRP, IL-10, and IL-2 were significantly upregulated in shoulder pain group compared with control (p<.01), whereas NGF, TNF-α, IL-6, 5-HT, PGE2, SP, LPA, BK, and IL-1β were significantly decreased (p<.01). Patients with HSP have a higher risk of joint mobility disorders and depression; spasticity may be an important factor in the development of shoulder pain; CGRP is thought to be the major pain mediator in HSP, and HSP may not be inflammatory.

Design and Computational Evaluation of New Carbamate Derivatives for the Inhibition of Monoacylglycerol Lipase Enzyme by using Docking

Different disorders and physiological process have been found to be associated with monoacylglycerol lipase enzyme in humans, like pain, inflammation, and neurodegenerative diseases also. The enzyme is a 33 KDa in weight and a type of serine hydrolase enzyme in nature. The presence of enzyme has been reported in both central and peripheral nervous systems and has show its importance as a key signalling factor in endocannabinoid signalling network system. The enzyme has also reported as source of free fatty acid provider for the cancer cell and tumor growth and their proliferation. In proliferative cancer cells, increased the monoacylglycerol lipase activity is observed. The growth, migration and survival of cancer cells have also found to be associated with phosphatidic acid, lysophosphatidic acid, sphingosine phosphate and prostaglandin E2, which are act as signalling molecules and are found to be derived from free fatty acid. These are also found to be related to the growth, transmission and viability of cancer cells, which increases with the enzyme activity. In the present study we performing computation screening studies of newly designed monoacylglycerol inhibitors which contains carbamate features, these molecules are designed based on previously developed monoacylglycerol carbamate inhibitors

Discovery of Chemical Scaffolds as Lysophosphatidic Acid Receptor 1 Antagonists: Virtual Screening, In Vitro Validation, and Molecular Dynamics Analysis

Discovery of Chemical Scaffolds as Lysophosphatidic Acid Receptor 1 Antagonists: Virtual Screening, <i>In Vitro</i> Validation, and Molecular Dynamics Analysis

Expression pattern of AGPATs isoforms indicate different functions during the triacylglyceride synthesis in Chinese mitten crab, Eriocheir sinensis

The 1-acylglycerol-3-phosphate acyltransferase (AGPAT) acts as a crucial enzyme in the process of triacylglycerol (TAG) synthesis, enabling the acylation of lysophosphatidic acid (LPA) into phosphatidic acid (PA). In order to decode the distinctive roles of AGPAT isoforms in the TAG production pathway, three AGPAT isoforms were detected for the first time in the Chinese mitten crab Eriocheir sinensis (Es-agpat2, Es-agpat3, and Es-agpat4). The mRNA levels of Es-agpat2 and Es-agpat4 demonstrated a conspicuous presence in the hepatopancreas, with subsequent high levels in the heart, muscle, and thoracic ganglion. On the other hand, the thoracic ganglion exhibited abundant levels of Es-agpat3, while other tissues recorded relatively low expression levels. Observing the molting cycle of E. sinensis, the hepatopancreas showed minimum expression levels of Es-agpat2 and Es-agpat4 at stage A/B. A peak at stage C was noted, which was then followed by a gradual drop until stage E. For the ovarian development cycle, stage II witnessed the maximum expression level of Es-agpat2 and Es-agpat4, succeeded by a sharp fall in stage III. After this, there was an increasing trend from stage III up to stage V. Expression of Es-agpat3 in the hepatopancreas was consistently lower than Es-agpat2 and Es-agpat4 during either the molting or ovarian development. However, in terms of ovarian expression, Es-agpat3 outperformed Es-agpat2 and Es-agpat4. It exhibited a steep increase in expression, peaking at stage II and subsequently diminishing. In situ hybridization (ISH) revealed that in stages II and IV hepatopancreas, Es-agpat4-mRNA was primarily located in fibrillar cells (F cell) and resorptive cells (R cell), with no signal from Es-agpat3. During stage II of ovarian development, both Es-agpat3-mRNA and Es-agpat4-mRNA were located in the cytoplasm of previtellogenic oocyte (PRO) and endogenous vitellogenic oocyte (EN), with no expression at stage IV. Additionally, the silencing of Es-agpat2 and Es-agpat4 caused a downward trend in the expression levels of all subsequent genes in the E. sinensis TAG synthesis pathway. To sum up, these findings suggest that the three Es-agpats may have unique functions in TAG synthesis during either the molting process or ovarian maturation of E. sinensis.

Integration of an LPAR1 Antagonist into Liposomes Enhances Their Internalization and Tumor Accumulation in an Animal Model of Human Metastatic Breast Cancer.

Lysophosphatidic acid receptor 1 (LPAR1) is elevated in breast cancer. The deregulation of LPAR1, including the function and level of expression, is linked to cancer initiation, progression, and metastasis. LPAR1 antagonists, AM095 or Ki16425, may be effective therapeutic molecules, yet their limited water solubility hinders in vivo delivery. In this study, we report on the synthesis of two liposomal formulations incorporating AM095 or Ki16425, embedded within the lipid bilayer, as targeted nanocarriers for metastatic breast cancer (MBC). The data show that the Ki16425 liposomal formulation exhibited a 50% increase in internalization by MBC mouse epithelial cells (4T1) and a 100% increase in tumor accumulation in a mouse model of MBC compared with that of a blank liposomal formulation (control). At the same time, normal mouse epithelial cells (EpH-4Ev) internalized the Ki16425 liposomal formulation 25% lesser than the control formulation. Molecular dynamics simulations show that the integration of AM095 or Ki16425 modified the physical and mechanical properties of the lipid bilayer, making it more flexible in these liposomal formulations compared with liposomes without drug. The incorporation of an LPAR1 antagonist within a liposomal drug delivery system represents a viable therapeutic approach for targeting the LPA-LPAR1 axis, which may hinder the progression of MBC.

Upregulation of fibronectin and its integrin receptors - an adaptation to isolation stress that facilitates tumor initiation.

Tumor initiation at either primary or metastatic sites is an inefficient process in which tumor cells must fulfill a series of conditions. One critical condition involves the ability of individual tumor-initiating cells to overcome 'isolation stress', enabling them to survive within harsh isolating microenvironments that can feature nutrient stress, hypoxia, oxidative stress and the absence of a proper extracellular matrix (ECM). In response to isolation stress, tumor cells can exploit various adaptive strategies to develop stress tolerance and gain stemness features. In this Opinion, we discuss how strategies such as the induction of certain cell surface receptors and deposition of ECM proteins enable tumor cells to endure isolation stress, thereby gaining tumor-initiating potential. As examples, we highlight recent findings from our group demonstrating how exposure of tumor cells to isolation stress upregulates the G-protein-coupled receptor lysophosphatidic acid receptor 4 (LPAR4), its downstream target fibronectin and two fibronectin-binding integrins, α5β1 and αvβ3. These responses create a fibronectin-rich niche for tumor cells, ultimately driving stress tolerance, cancer stemness and tumor initiation. We suggest that approaches to prevent cancer cells from adapting to stress by suppressing LPAR4 induction, blocking its downstream signaling or disrupting fibronectin-integrin interactions hold promise as potential strategies for cancer treatment.

A Review of Cyclic Phosphatidic Acid and Other Potential Therapeutic Targets for Treating Osteoarthritis.

Osteoarthritis (OA), a chronic degenerative joint disease, is the most common form of arthritis. OA occurs when the protective cartilage that cushions the ends of bones gradually breaks down. This leads to the rubbing of bones against each other, resulting in pain and stiffness. Cyclic phosphatidic acid (cPA) shows promise as a treatment for OA. In this article, we review the most recent findings regarding the biological functions of cPA signaling in mammalian systems, specifically in relation to OA. cPA is a naturally occurring phospholipid mediator with unique cyclic phosphate rings at the sn-2 and sn-3 positions in the glycerol backbone. cPA promotes various responses, including cell proliferation, migration, and survival. cPA possesses physiological activities that are distinct from those elicited by lysophosphatidic acid; however, its biochemical origin has rarely been studied. Although there is currently no cure for OA, advances in medical research may lead to new therapies or strategies in the future, and cPA has potential therapeutic applications.

Qushi Huayu decoction ameliorates non-alcoholic fatty liver disease in rats by modulating gut microbiota and serum lipids.

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial disease. As a clinical empirical prescription of traditional Chinese medicine, Qushi Huayu decoction (QHD) has attracted considerable attention for its advantages in multi-target treatment of NAFLD. However, the intervention mechanism of QHD on abnormal lipid levels and gut microbiota in NAFLD has not been reported. Therefore, we verified the therapeutic effect of QHD on high-fat diet (HFD)-induced NAFLD in rats by physiological parameters and histopathological examination. In addition, studies on gut microbiota and serum lipidomics based on 16S rRNA sequencing and ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) were conducted to elucidate the therapeutic mechanism of NAFLD in QHD. The changes in gut microbiota in NAFLD rats are mainly reflected in their diversity and composition, while QHD treated rats restored these changes. The genera Blautia, Lactobacillus, Allobaculum, Lachnoclostridium and Bacteroides were predominant in the NAFLD group, whereas, Turicibacter, Blautia, Sporosarcina, Romboutsia, Clostridium_sensu_stricto_1, Allobaculum, and Psychrobacter were predominant in the NAFLD+QHD group. Lipid subclasses, including diacylglycerol (DG), triglycerides (TG), phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidic acid (PA), phosphatidylserine (PS), lysophosphatidylinositol (LPI), and phosphatidylglycerol (PG), were significantly different between the NAFLD and the control groups, while QHD treatment significantly altered the levels of DG, TG, PA, lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), and platelet activating factor (PAF). Finally, Spearman's correlation analysis showed that NAFLD related differential lipid molecules were mainly associated with the genera of Bacteroides, Blautia, Lachnoclostridium, Clostridium_sensu_stricto_1, and Turicibacter, which were also significantly correlated with the biological parameters of NAFLD. Taken together, QHD may exert beneficial effects by regulating the gut microbiota and thus intervening in serum lipids.

A dual role of lysophosphatidic acid type 2 receptor (LPAR2) in nonsteroidal anti-inflammatory drug-induced mouse enteropathy

Lysophosphatidic acid (LPA) is a bioactive phospholipid mediator that has been found to ameliorate nonsteroidal anti-inflammatory drug (NSAID)-induced gastric injury by acting on lysophosphatidic acid type 2 receptor (LPAR2). In this study, we investigated whether LPAR2 signaling was implicated in the development of NSAID-induced small intestinal injury (enteropathy), another major complication of NSAID use. Wild-type (WT) and Lpar2 deficient (Lpar2−/−) mice were treated with a single, large dose (20 or 30 mg/kg, i.g.) of indomethacin (IND). The mice were euthanized at 6 or 24 h after IND treatment. We showed that IND-induced mucosal enteropathy and neutrophil recruitment occurred much earlier (at 6 h after IND treatment) in Lpar2−/− mice compared to WT mice, but the tissue levels of inflammatory mediators (IL-1β, TNF-α, inducible COX-2, CAMP) remained at much lower levels. Administration of a selective LPAR2 agonist DBIBB (1, 10 mg/kg, i.g., twice at 24 h and 30 min before IND treatment) dose-dependently reduced mucosal injury and neutrophil activation in enteropathy, but it also enhanced IND-induced elevation of several proinflammatory chemokines and cytokines. By assessing caspase-3 activation, we found significantly increased intestinal apoptosis in IND-treated Lpar2−/− mice, but it was attenuated after DBIBB administration, especially in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Finally, we showed that IND treatment reduced the plasma activity and expression of autotaxin (ATX), the main LPA-producing enzyme, and also reduced the intestinal expression of Lpar2 mRNA, which preceded the development of mucosal damage. We conclude that LPAR2 has a dual role in NSAID enteropathy, as it contributes to the maintenance of mucosal integrity after NSAID exposure, but also orchestrates the inflammatory responses associated with ulceration. Our study suggests that IND-induced inhibition of the ATX-LPAR2 axis is an early event in the pathogenesis of enteropathy.

Longitudinal metabolomics integrated with machine learning identifies novel biomarkers of gestational diabetes mellitus

BackgroundEvidence from longitudinal studies is crucial to enhance our understanding of the role of metabolites in the progression of gestational diabetes mellitus (GDM). Herein, a longitudinal untargeted metabolomic study was conducted to reveal the metabolomic profiles and biomarkers associated with the progression of GDM, and characterize the changing patterns of metabolites. MethodsWe collected serum samples at three trimesters from 30 patients with GDM and 30 healthy Chinese pregnant women with pre-pregnancy BMI, age, and parity matched, and untargeted metabolomic analysis was performed, followed by machine learning approaches that integrated bootstrap and LASSO. Cluster analysis was conducted to elucidate the patterns of metabolite changes. Pathway analyses were conducted to gain insights into the underlying pathways involved. ResultsA total of 32 metabolites, mainly belonging to amino acid and its derivatives, were significantly associated with GDM across three trimesters, and were clustered into three distinct patterns. Metabolites belonging to phosphatidylcholines, lysophosphatidylcholines, lysophosphatidic acids, and lysophosphatidylethanolamines were consistently upregulated, and 2,3-Dihydroxypropyl dihydrogen phosphate was downregulated in GDM group. Amino acid-related, glycerophospholipid, and vitamin B6 metabolism were enriched in multiple trimesters. The levels of allantoic acid, which was positively correlated with blood glucose, was consistently higher in GDM patients and exhibited good discriminatory ability for GDM in the early and mid-pregnancy. ConclusionWe identified and characterized distinct patterns of metabolites associated with GDM throughout pregnancy, and found that allantoic acid was a potential biomarker for early diagnosis of GDM.

Antibiotic intervention exacerbated oxidative stress and inflammatory responses in SD rats under hypobaric hypoxia exposure

The gut microbiota plays a crucial role in maintaining host nutrition, metabolism, and immune homeostasis, particularly in extreme environmental conditions. However, the regulatory mechanisms of the gut microbiota in animal organisms hypobaric hypoxia exposure require further study. We conducted a research by comparing SD rats treated with an antibiotic (ABX) cocktail and untreated SD rats that were housed in a low-pressure oxygen chamber (simulating low pressure and hypoxic environment at 6000 m altitude) for 30 days. After the experiment, blood, feces, and lung tissues from SD rats were collected for analysis of blood, 16S rRNA amplicon sequencing, and non-targeted metabolomics. The results demonstrated that the antibiotic cocktail-treated SD rats exhibited elevated counts of neutrophil (Neu) and monocyte (Mon) cells, an enrichment of sulfate-reducing bacteria (SBC), reduced levels of glutathione, and accumulated phospholipid compounds. Notably, the accumulation of phospholipid compounds, particularly lysophosphatidic acid (LPA), lipopolysaccharide (LPS), and lysophosphatidylcholine (LPC), along with the aforementioned changes, contributed to heightened oxidative stress and inflammation in the organism. In addition, we explored the resistance mechanisms of SD rats in low-oxygen and low-pressure environments and found that increasing the quantity of the Prevotellaceae and related beneficial bacteria (especially Lactobacillus) could reduce oxidative stress and inflammation. These findings offer valuable insights into enhancing the adaptability of low-altitude animals under hypobaric hypoxia exposure.

Simulated microgravity attenuates skin wound healing by inhibiting dermal fibroblast migration via F-actin/YAP signaling pathway.

Skin and its cell components continuously subject to extrinsic and intrinsic mechanical forces and are mechanical sensitive. Disturbed mechanical homeostasis may lead to changes in skin functions. Gravity is the integral mechanical force on the earth, however, how gravity contributes to the maintenance of skin function and how microgravity in space affects the wound healing are poorly understood. Here, using microgravity analogs, we show that simulated microgravity (SMG) inhibits the healing of cutaneous wound and the accumulation of dermal fibroblasts in the wound bed. In vitro, SMG inhibits the migration of human foreskin fibroblast cells (HFF-1), and decreases the F-actin polymerization and YAP (yes-associated protein) activity. The SMG-inhibited migration can be recovered by activating YAP or F-actin polymerization using lysophosphatidic acid (LPA) or jasplakinolide (Jasp), suggesting the involvement of F-actin/YAP signaling pathway in this process. In SMG rats, LPA treatment improves the cutaneous healing with increased dermal fibroblasts in the wound bed. Together, our results demonstrate that SMG attenuates the cutaneous wound healing by inhibiting dermal fibroblast migration, and propose the crucial role of F-actin/YAP mechano-transduction in the maintenance of skin homeostasis under normal gravity, and YAP as a possible therapeutic target for the skin care of astronauts in space.

GPAT1 Deficiency in Mice Modulates NASH Progression in a Model-Dependent Manner

Nonalcoholic fatty liver disease (NAFLD), and its more severe form, nonalcoholic steatohepatitis (NASH), is the leading cause for liver failure and liver cancer. Although the etiology is likely multifactorial, genes involved in regulating lipid metabolism are enriched in human NAFLD genome-wide association studies (GWAS), pointing to dysregulated lipid metabolism as a major pathogenic factor. Glycerol-3-phosphate acyltransferase 1 (GPAT1), encoded by GPAM, converts acyl-CoAs and glycerol-3-phosphate into lysophosphatidic acid and has been shown to regulate lipid accumulation in the liver. However, its role in mediating the progression from NAFLD to NASH has not been explored. GPAT1-deficient mice were generated and challenged with diets inducing hepatic steatosis and NASH. Effects of GPAT1 deficiency on lipid and systemic metabolic end points were evaluated. Ablating GPAT1 globally or specifically in mouse hepatocytes reduced hepatic steatosis in the context of diet-induced or genetic obesity. Interestingly, blunting of progression from NAFLD to NASH in global GPAT1 knockout (KO) mice was model dependent. GPAT1 KO mice were protected from choline deficient, amino acid defined high-fat diet-induced NASH development, but not from the high fat, high carbohydrate, and high cholesterol diet-induced NASH. Our preclinical data support the notion that lipid metabolism pathways regulated by GPAT1 in hepatocytes play an essential role in NASH progression, albeit in a model-dependent manner.

Autotaxin-lysophosphatidic acid receptor 5 axis evokes endothelial dysfunction via reactive oxygen species signaling.

Lysophosphatidylcholine (LPC) is a bioactive lipid that has been shown to attenuate endothelium-dependent vasorelaxation contributing to endothelial dysfunction; however, the underlying mechanisms are not well understood. In this study, we investigated the molecular mechanisms involved in the development of LPC-evoked impairment of endothelium-dependent vasorelaxation. In aortic rings isolated from wild-type (WT) mice, a 20-min exposure to LPC significantly reduced the acetylcholine chloride (ACh)-induced vasorelaxation indicating the impairment of normal endothelial function. Interestingly, pharmacological inhibition of autotaxin (ATX) by GLPG1690 partially reversed the endothelial dysfunction, suggesting that lysophosphatidic acid (LPA) derived from LPC may be involved in the effect. Therefore, the effect of LPC was also tested in aortic rings isolated from different LPA receptor knock-out (KO) mice. LPC evoked a marked reduction in ACh-dependent vasorelaxation in Lpar1, Lpar2, and Lpar4 KO, but its effect was significantly attenuated in Lpar5 KO vessels. Furthermore, addition of superoxide dismutase reduced the LPC-induced endothelial dysfunction in WT but not in the Lpar5 KO mice. In addition, LPC increased H2O2 release from WT vessels, which was significantly reduced in Lpar5 KO vessels. Our findings indicate that the ATX-LPA-LPA5 receptor axis is involved in the development of LPC-induced impairment of endothelium-dependent vasorelaxation via LPA5 receptor-mediated reactive oxygen species production. Taken together, in this study, we identified a new pathway contributing to the development of LPC-induced endothelial dysfunction.

Biomarkers in the Pathogenesis, Diagnosis, and Treatment of Systemic Sclerosis.

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by vascular damage, vasoinstability, and decreased perfusion with ischemia, inflammation, and exuberant fibrosis of the skin and internal organs. Biomarkers are analytic indicators of the biological and disease processes within an individual that can be accurately and reproducibly measured. The field of biomarkers in SSc is complex as recent studies have implicated at least 240 pathways and dysregulated proteins in SSc pathogenesis. Anti-nuclear antibodies (ANA) are classical biomarkers with well-described clinical classifications and are present in more than 90% of SSc patients and include anti-centromere, anti-Th/To, anti-RNA polymerase III, and anti-topoisomerase I antibodies. Transforming growth factor-β (TGF-β) is central to the fibrotic process of SSc and is intimately intertwined with other biomarkers. Tyrosine kinases, interferon-1 signaling, IL-6 signaling, endogenous thrombin, peroxisome proliferator-activated receptors (PPARs), lysophosphatidic acid receptors, and amino acid metabolites are new biomarkers with the potential for developing new therapeutic agents. Other biomarkers implicated in SSc-ILD include signal transducer and activator of transcription 4 (STAT4), CD226 (DNAX accessory molecule 1), interferon regulatory factor 5 (IRF5), interleukin-1 receptor-associated kinase-1 (IRAK1), connective tissue growth factor (CTGF), pyrin domain containing 1 (NLRP1), T-cell surface glycoprotein zeta chain (CD3ζ) or CD247, the NLR family, SP-D (surfactant protein), KL-6, leucine-rich α2-glycoprotein-1 (LRG1), CCL19, genetic factors including DRB1 alleles, the interleukins (IL-1, IL-4, IL-6, IL-8, IL-10 IL-13, IL-16, IL-17, IL-18, IL-22, IL-32, and IL-35), the chemokines CCL (2,3,5,13,20,21,23), CXC (8,9,10,11,16), CX3CL1 (fractalkine), and GDF15. Adiponectin (an indicator of PPAR activation) and maresin 1 are reduced in SSc patients. A new trend has been the use of biomarker panels with combined complex multifactor analysis, machine learning, and artificial intelligence to determine disease activity and response to therapy. The present review is an update of the various biomarker molecules, pathways, and receptors involved in the pathology of SSc.

PIP5Kγ Mediates PI(4,5)P2/Merlin/LATS1 Signaling Activation and Interplays with Hsc70 in Hippo-YAP Pathway Regulation.

The type I phosphatidylinositol 4-phosphate 5-kinase (PIP5K) family produces the critical lipid regulator phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) in the plasma membrane (PM). Here, we investigated the potential role of PIP5Kγ, a PIP5K isoform, in the Hippo pathway. The ectopic expression of PIP5Kγ87 or PIP5Kγ90, two major PIP5Kγ splice variants, activated large tumor suppressor kinase 1 (LATS1) and inhibited Yes-associated protein (YAP), whereas PIP5Kγ knockdown yielded opposite effects. The regulatory effects of PIP5Kγ were dependent on its catalytic activity and the presence of Merlin and LATS1. PIP5Kγ knockdown weakened the restoration of YAP phosphorylation upon stimulation with epidermal growth factor or lysophosphatidic acid. We further found that PIP5Kγ90 bound to the Merlin's band 4.1/ezrin/radixin/moesin (FERM) domain, forming a complex with PI(4,5)P2 and LATS1 at the PM. Notably, PIP5Kγ90, but not its kinase-deficient mutant, potentiated Merlin-LATS1 interaction and recruited LATS1 to the PM. Consistently, PIP5Kγ knockdown or inhibitor (UNC3230) enhanced colony formation in carcinoma cell lines YAP-dependently. In addition, PIP5Kγ90 interacted with heat shock cognate 71-kDa protein (Hsc70), which also contributed to Hippo pathway activation. Collectively, our results suggest that PIP5Kγ regulates the Hippo-YAP pathway by forming a functional complex with Merlin and LATS1 at the PI(4,5)P2-rich PM and via interplay with Hsc70.

Influence of Aortic Valve Stenosis and Wall Shear Stress on Platelets Function.

Aortic valve stenosis (AS) is a common heart valve disease in the elderly population, and its pathogenesis remains an interesting area of research. The degeneration of the aortic valve leaflets gradually progresses to valve sclerosis. The advanced phase is marked by the presence of extracellular fibrosis and calcification. Turbulent, accelerated blood flow generated by the stenotic valve causes excessive damage to the aortic wall. Elevated shear stress due to AS leads to the degradation of high-molecular weight multimers of von Willebrand factor, which may involve bleeding in the mucosal tissues. Conversely, elevated shear stress has been associated with the release of thrombin and the activation of platelets, even in individuals with acquired von Willebrand syndrome. Moreover, turbulent blood flow in the aorta may activate the endothelium and promote platelet adhesion and activation on the aortic valve surface. Platelets release a wide range of mediators, including lysophosphatidic acid, which have pro-osteogenic effects in AS. All of these interactions result in blood coagulation, fibrinolysis, and the hemostatic process. This review summarizes the current knowledge on high shear stress-induced hemostatic disorders, the influence of AS on platelets and antiplatelet therapy.