Lysophosphatidic Acid Receptor Antagonist Research Articles

Evidence from recent clinical trials in fibrotic interstitial lung diseases.

Idiopathic pulmonary fibrosis (IPF) is the prototype of fibrosing interstitial lung diseases. It is mirrored by progressive pulmonary fibrosis (PPF), an umbrella term which characterizes disease behavior of various fibrotic interstitial lung diseases with irreversible progression, accounting for loss of lung function, exercise intolerance and respiratory failure leading to early mortality. Pirfenidone and nintedanib halve the decline in lung function but do not halt disease progression. Since the publication in 2014 of pivotal pirfenidone and nintedanib studies, a number of clinical trials were conducted, many of them did not reach their primary endpoints. In IPF, promising phase 2 trials were followed by large phase 3 trials that did not confirm a favorable efficacy to tolerability favorable profile, including those with ziritaxestat, an autotaxin-1 inhibitor, zinpentraxin-alpha (human recombinant pentraxin-2), and the monoclonal antibody pamrevlumab targeting connective tissue growth factor. Nevertheless, newer compounds that hold promise are currently being evaluated in phase 3 or phase 2b randomized controlled trials, including: nerandomilast, a preferential phosphodiesterase 4B inhibitor; admilparant, a lysophosphatidic acid receptor antagonist; inhaled treprostinil, a prostacyclin agonist; and bexotegrast, a dual-selective inhibitor of αvβ6 and αvβ1 integrins. Nerandomilast, admilparant, inhaled treprostinil, and inhaled AP01 (pirfenidone), are currently studied in patients with PPF. Despite recent frustrating negative results, there is a growing portfolio of candidate drugs developed in both IPF and PPF.

In vitro pharmacological characterization of standard and new lysophosphatidic acid receptor antagonists using dynamic mass redistribution assay.

Lysophosphatidic acid (LPA) is a bioactive phospholipid that acts as an agonist of sixG protein-coupled receptors named LPA receptors (LPA1-6). LPA elicits diverse intracellular events and modulates several biological functions, including cell proliferation, migration, and invasion. Overactivation of the LPA-LPA receptor system is reported to be involved in several pathologies, including cancer, neuropathic pain, fibrotic diseases, atherosclerosis, and type 2 diabetes. Thus, LPA receptor modulators may be clinically relevant in numerous diseases, making the identification and pharmacodynamic characterization of new LPA receptor ligands of strong interest. In the present work, label-free dynamic mass redistribution (DMR) assay has been used to evaluate the pharmacological activity of some LPA1 and LPA2 standard antagonists at the recombinant human LPA1 and LPA2 receptors. These results are compared to those obtained in parallel experiments with the calcium mobilization assay. Additionally, the same experimental protocol has been used for the pharmacological characterization of the new compound CHI. KI 16425, RO 6842262, and BMS-986020 behaved as LPA1 inverse agonists in DMR experiments and as LPA1 antagonists in calcium mobilization assays. Amgen compound 35 behaved as an LPA2 antagonist, while Merck compound 20 from WO2012028243 was detected as an LPA2 inverse agonist using the DMR test. Of note, for all the compounds, similar potency values were estimated by DMR and calcium assay. The new compound CHI was found to be an LPA1 inverse agonist, but with potency lower than that of the standard compounds. In conclusion, we have demonstrated that DMR assay can be successfully used to characterize LPA1 and LPA2 ligands. Compared to the classical calcium mobilization assay, DMR offers some advantages, in particular allowing the identification of inverse agonists. Finally, in the frame of this study, a new LPA1 inverse agonist has been identified.

The contribution of lysophosphatidic acid receptors in the response of human lower esophageal sphincter under the electrical field stimulation

BackgroundThis study aims to identify the impact on the reaction while the clasp and sling fibers of the human lower esophageal sphincter are under the electrical field stimulation, by adding lysophosphatidic acid receptor subtypes antagonist.MethodsBetween March 2018 to December 2018, muscle strips were isolated from 28 patients who underwent esophagectomy for mid-third esophageal carcinomas. Muscle tension measurement technique in vitro and electrical field stimulation were used to examine the effects of selective lysophosphatidic acid receptor antagonist on the clasp and sling fibers of human lower esophageal sphincter.ResultsThe optimal frequency of frequency-dependent relaxation in clasp fibers and contraction in sling fibers induced by electrical field stimulation is 64 Hz and 128 Hz respectively. The selective lysophosphatidic acid 1 and 3 receptor antagonist produced no significant difference in the frequency-dependent relaxation in clasp fibers and contraction in sling fibers induced by the electrical field stimulation (P > 0.05).ConclusionThe electrical field stimulation induced a frequency-dependent relaxation in clasp fibers and contraction in sling fibers. The lysophosphatidic acid 1 and 3 receptors are not involved in the response of clasp and sling fibers of the human lower esophageal sphincter induced by the electrical field stimulation.

Effects of lysophosphatidic acid on sling and clasp fibers of the human lower esophageal sphincter

Background This study aims to explore the role of lysophosphatidic acid receptors in the regulation mechanisms of contraction and relaxation of human lower esophageal sphincter. Methods Between July 2015 and March 2016, muscle strips were collected from a total of 30 patients (19 males, 11 females; mean age: 62±9.9 years; range, 52 to 68 years) who underwent an esophagectomy for mid-third esophageal carcinomas. The specimens were maintained in oxygenated Krebs solution. Muscle tension measurement technique in vitro was used to examine the effects of non-selective lysophosphatidic acid receptors agonists and antagonists, as well as selective lysophosphatidic acid receptors agonists on the clasp and sling fibers of human lower esophageal sphincter. Results The non-selective dopamine receptor agonist lysophosphatidic acid induced the contraction of the clasp and sling fibers of the human lower esophageal sphincter. The response induced by nonselective lysophosphatidic acid receptor agonist was inhibited completely by non-selective lysophosphatidic acid receptor antagonist. The selective lysophosphatidic acid 1 and 2 receptor agonist and the selective lysophosphatidic acid 3 receptor agonist induced a concentration-dependent contractile response of the clasp and sling fibers of the human lower esophageal sphincter. There was no significant difference in contraction rates between the clasp and sling fibers (p>0.05). Conclusion This study indicates that lysophosphatidic acid regulates the lower esophageal sphincter is through its receptor; the lysophosphatidic acid receptors may be involved in the contractile response of the human lower esophageal sphincter.

Abstract 5810: LPAR2 depletion suppresses gastric cancer via alteration of mitochondrial energy metabolism

Abstract Introduction: Gastric cancer is the second most common cause of cancer-related death worldwide. Altered metabolism is considered a primary hallmark of tumorigenesis, as it can regulate important processes associated with proliferation, migration, and invasion. Lysophosphatidic acid (LPA), a multifunctional endogenous phospholipid, plays a vital role in cellular homeostasis and malignant behavior of the cancer cells through G-protein coupled receptors. Although several signaling pathways have been reported as a critical mediator of gastric cancer, LPA-LPAR2 axis-mediated alteration of energy metabolism in gastric cancer progression has not been established yet. Therefore, our study focused on the molecular mechanism of LPA-LPAR2 axis-mediated alteration of mitochondrial bioenergetics during gastric cancer progression. Method: TCGA database analysis was carried out to check the mRNA levels of the LPA receptors. Expression of LPA receptors was investigated in human gastric cancer samples by immunoblotting, RT-PCR, and immunohistochemical analysis. We elucidated the functional effects of LPA on gastric cancer by performing ECIS proliferation, migration assay, scratch assay, and transwell invasion assay in gastric cancer cells. To confirm the involvement of the specific LPA receptor on gastric cancer progression, we treated the cells with LPA1-3 receptor blocker (Ki16425) and LPA2 receptor-specific antagonist. Following LPA receptor blockade, we analyzed the glycolytic and mitochondrial functions by measuring extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) using a Seahorse XF24 analyzer. Result: Our TCGA dataset analysis, LPA ELISA, and the Western blotting result showed the presence of LPA receptors in human gastric cancer tissues, specifically LPAR2 was robustly increased (P<0.001) in human gastric cancer tissue samples, and LPA level was significantly higher (P<0.001), suggesting a possible role of LPA in gastric cancer. LPA treatment increased proliferation, migration, and invasion activity in AGS and NCI-N87 gastric cancer cell lines. In contrast, LPA receptor antagonist Ki16425 abrogated the LPA-induced effect. Our seahorse analysis results showed that LPA treatment increased the OCR (P<0.001) and the ECAR (P<0.001), whereas LPAR2 specific receptor antagonists abrogated this effect (P<0.001). Conclusion: Together, our results suggested that the LPA-LPAR2 axis mediates gastric cancer initiation and progression by increasing energy metabolism via oxidative phosphorylation and glycolysis. Thus, targeting the LPAR2 receptor may give us a novel therapeutic approach to treat gastric cancer. Citation Format: Hosne Ara, Susmita Bhattarai, Sudha Sharma, Utsab Subedi, Xiuping Yu, Md. Shenuarin Bhuiyan, Sumitra Miriyala, Manikandan Panchatcharam. LPAR2 depletion suppresses gastric cancer via alteration of mitochondrial energy metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5810.

Roles for CCN proteins in Lysophosphatidic Acid and Sphingosine 1‐Phosphate Signaling in Prostate Cancer Cells

IntroductionCysteine rich angiogenic factor (CCN1/Cyr61) and connective tissue growth factor (CCN2/CTGF) are members of the CCN family of matricellular proteins. These secreted proteins interact with extracellular matrix proteins and integrins to modulate cell signaling. CCN proteins have been implicated in survival and other mitogenic responses in various cancers. CCN1 and CCN2 are the two early inducible genes in this family. Lysophosphatidic acid (LPA) and sphingosine‐1‐phosphate (S1P) are lipid growth factors known to contribute to tumor progression in prostate cancer. In previous work, our group showed that LPA stimulates proliferation and migration in prostate cancer cells via the G protein‐coupled receptor LPAR1. Free fatty acid receptor 4 (FFAR4) agonists, inhibit LPA‐induced responses in prostate cancer cells. We also demonstrated that CCN1 expression is induced by LPA in human prostate cancer cells. However, the roles of CCN1 and CCN2 in cancer cell signaling have not been fully elucidated.HypothesisWe hypothesize that CCN proteins contribute to LPA‐ and S1P‐induced adhesion and mitogenic signaling in prostate cancer cells.Methods and ResultsPC‐3 human prostate cancer cells were used in the current study. For all experiments, cells were serum starved for 24 hours and then treated with and without 10 µM LPA or S1P. Immunoblotting showed that CCN1 and CCN2 were induced by LPA after 2‐5 hours in PC‐3 cells. The response was inhibited by the LPA receptor antagonist Ki1625. TUG‐891, an FFAR4 agonist, inhibited LPA‐induced CCN1 expression in PC‐3 cells. S1P also induced CCN1 expression in PC‐3 cells. In related experiments, whole cell extracts, and extracellular matrix were subjected to immunoblotting for CCN1, and immunofluorescence microscopy was used to localize the induced CCN1. CCN1 protein levels in extracellular matrix were increased 2‐5 hours after LPA treatment, as compared to untreated controls, and CCN1 was detected outside the cells by confocal microscopy. In cell adhesion assays, LPA‐treated PC‐3 cells exhibited an increase in adhesion to fibronectin‐coated 96‐well plates that was detected by 2 hours. Erk MAPK activation in response to LPA was biphasic, with the later phase occurring after CCN1/2 induction.ConclusionThe results of this study suggest that CCN proteins may play roles in LPA‐ and S1P‐induced signaling in prostate cancer cells and are thus potential therapeutic targets.

An Update on Sphingosine-1-Phosphate and Lysophosphatidic Acid Receptor Transcripts in Rodent Olfactory Mucosa.

Olfactory neurons connect the external environment and the brain, allowing the translocation of materials from the nasal cavity into the brain. The olfactory system is involved in SARS-CoV-2 infections; early in the pandemic declared in 2020, a loss of the sense of smell was found in many infected patients. Attention has also been focused on the role that the olfactory epithelium appears to play in the entry of the SARS-CoV-2 virus into the brain. Specifically, SARS-CoV-2 enters cells via the angiotensin-converting enzyme 2 protein (ACE2), which is found on supporting cells in the olfactory epithelium. The intranasal administration of sphingosine has been proposed to prevent the binding of SARS-CoV-2 to ACE2. Further, sphingosine-1-phosphate (S1P) receptors appear to facilitate the entry of SARS-CoV-2 into the brain. The goal of these studies was to characterize S1P receptor expression status in rodent olfactory mucosa. The expression of receptors for a related sphingolipid, lysophosphatidic acid (LPA), was also assessed. The results confirm previous reports of S1P1 and S1P3 receptor expression, as well as LPA receptor 1, in mouse olfactory mucosa; moreover, they extend the previous findings to identify additional S1P and LPA receptor transcripts in rat and mouse olfactory mucosa, as well as in cultured olfactory neurons. These findings may enhance the utility of rodent models in identifying agonists and/or antagonists of S1P and LPA receptors that may block the entry of SARS-CoV-2 and other viruses into nasal epithelial cells, and prevent transmission from the nasal cavity into the brain.

Phospholipase A1 Member A Activates Fibroblast-like Synoviocytes through the Autotaxin-Lysophosphatidic Acid Receptor Axis.

Lysophosphatidylserine (lysoPS) is known to regulate immune cell functions. Phospholipase A1 member A (PLA1A) can generate this bioactive lipid through hydrolysis of sn-1 fatty acids on phosphatidylserine (PS). PLA1A has been associated with cancer metastasis, asthma, as well as acute coronary syndrome. However, the functions of PLA1A in the development of systemic autoimmune rheumatic diseases remain elusive. To investigate the possible implication of PLA1A during rheumatic diseases, we monitored PLA1A in synovial fluids from patients with rheumatoid arthritis and plasma of early-diagnosed arthritis (EA) patients and clinically stable systemic lupus erythematosus (SLE) patients. We used human primary fibroblast-like synoviocytes (FLSs) to evaluate the PLA1A-induced biological responses. Our results highlighted that the plasma concentrations of PLA1A in EA and SLE patients were elevated compared to healthy donors. High concentrations of PLA1A were also detected in synovial fluids from rheumatoid arthritis patients compared to those from osteoarthritis (OA) and gout patients. The origin of PLA1A in FLSs and the arthritic joints remained unknown, as healthy human primary FLSs does not express the PLA1A transcript. Besides, the addition of recombinant PLA1A stimulated cultured human primary FLSs to secrete IL-8. Preincubation with heparin, autotaxin (ATX) inhibitor HA130 or lysophosphatidic acid (LPA) receptor antagonist Ki16425 reduced PLA1A-induced-secretion of IL-8. Our data suggested that FLS-associated PLA1A cleaves membrane-exposed PS into lysoPS, which is subsequently converted to LPA by ATX. Since primary FLSs do not express any lysoPS receptors, the data suggested PLA1A-mediated pro-inflammatory responses through the ATX-LPA receptor signaling axis.

LPA and Autotaxin: Potential Drug Targets in Asthma?

Lysophosphatidic acid (LPA) is a versatile lysolipid, and activates a variety of signaling cascades in many cell types. Extracellular LPA is produced from lysophosphatidylcholine (LPC) by the enzyme autotaxin (ATX), and binds to a family of G-protein coupled receptors on its target cells. Research by many groups continues to support the idea that LPA, and the ATX-LPA axis, have important roles in asthma and allergic airway inflammation. In vitro studies have shown that LPA activates many cell types implicated in airway inflammation, including eosinophils, mast cells, dendritic cells, lymphocytes, airway epithelial cells, and airway smooth muscle cells. In animal models ATX and LPA receptor antagonists have been shown to attenuate allergic airway inflammation and hyperreactivity, cardinal features of asthma in humans. ATX and LPA antagonists are currently under active development to treat lung fibrosis, cancer, and other conditions. If compounds with acceptable safety profiles can be identified, then it seems likely that they will be useful in inflammatory lung diseases like asthma.

Abstract 1987: Lysophosphatidic acid's unknown role in the initiation and progression of gastric cancer through LPAR2 receptor and beta-catenin signaling pathway by altering the energy metabolism

Abstract Introduction: Lysophosphatidic acid (LPA), a multifunctional endogenous phospholipid, plays a vital role in cellular homeostasis and malignant behavior of the cancer cells through G-protein coupled receptors. Although dysregulated beta-catenin signaling pathway has been reported as a critical mediator of gastric cancer, LPA's role in beta-catenin mediated gastric cancer is unknown. Hence, our study aims to determine LPA's functional role and its downstream signaling mechanism in beta-catenin mediated gastric cancer. Method: We used commercially available tissue lysates from the human normal and cancerous stomach to check the LPA level and the expression of LPA receptors by ELISA, western blotting, and Immunohistochemical analysis. To examine LPA's functional effect in gastric cancer, we performed ECIS proliferation, migration assay, scratch assay, and transwell invasion assay in LPA treated gastric cancer cells. Next, to elucidate LPA's molecular mechanism mediated gastric cancer progression, we performed Western blotting, and Real-time PCR of beta-catenin and its downstream target genes in LPA treated cells. To investigate the LPA-induced beta-catenin activity, Luciferase assay, Immunocytochemistry, and nuclear fractionation were done in LPA-treated cells. TCGA database analysis was carried out to check the mRNA level of beta-catenin and its downstream target genes and LPA receptors. Furthermore, superoxide production and Seahorse analysis were performed in the LPA treated cells to determine the oxidative stress and mitochondrial energy metabolism. Result: LPA ELISA and Western blotting of LPA receptors in human gastric cancer tissues showed that the LPA level is significantly higher (P<0.001), and LPAR2 is robustly increased (P<0.001)in human gastric cancer tissue samples suggesting a possible role of LPA in gastric cancer. In cultured gastric cancer cell line, LPA treatment increased proliferation, migration, and invasion activity, whereas LPA receptor antagonist abrogated the LPA induced effect. Similarly, LPA treatment leads to activate the beta-catenin and increased the expression of the downstream target genes of the beta-catenin signaling pathway. LPA-induced activation of beta-catenin signaling pathway was abrogated with the addition of LPA receptor antagonist and knockdown of LPAR2. Besides, LPA treatment increased oxidative stress and increased glucose uptake and ATP production (P<0.001) by both oxidative phosphorylation and glycolysis, whereas LPA antagonist abrogated this effect. Conclusion: Together, all of our results suggested that LPA mediates gastric cancer initiation and progression through the beta-catenin signaling pathway via the LPAR2 receptor by altering energy metabolism. Our findings will provide a novel insight into gastric cancer treatment. Citation Format: Hosne Ara, Susmita Bhattarai, Sudha Sharma, Utsab Subedi, MD.Shenuarin Bhuiyan, Xiuping Yu, Sumitra Miriyala, Manikandan Panchatcharam. Lysophosphatidic acid's unknown role in the initiation and progression of gastric cancer through LPAR2 receptor and beta-catenin signaling pathway by altering the energy metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1987.

Interplay between LPA2 and LPA3 in LPA-mediated phosphatidylserine cell surface exposure and extracellular vesicles release by erythrocytes

Evidence is growing for the role of red blood cells (RBCs) in vascular homeostasis, including thrombogenic events and inflammation. Lysophosphatidic acid (LPA) is known to induce phosphatidylserine (PS) exposure and the release of RBC Extracellular Vesicles (REVs). Using high sensitivity flow cytometry, we examined the effects and the mechanisms by which the LPA species commonly found in human plasma could activate RBCs. We report that LPA 16:0, 18:0 and 18:1, but not LPA 20:4, induced PS exposure and the release of small PS− and large PS+ REVs through LPA3 receptor signalling in RBCs. The release of large PS+ REVs required higher concentrations of LPA. RBCs were not activated by LPA 20:4. Interestingly, blockade of LPA2 enhanced LPA-mediated PS− REV release in RBCs. Furthermore, LPA receptor agonists and antagonists highlighted that LPA 20:4 inhibited LPA3-dependent PS exposure and, through the LPA2 receptor, inhibited PS− REV production. Activation of RBCs with LPA 18:1 in normal plasma stimulated the release of PS− and PS+ REVs. REVs released in response to LPA were similar to those found in the plasma of systemic lupus erythematosus patients. Our results suggest that LPA species exhibit different biological activities in RBCs through targeting LPA2 and/or LPA3 receptors.

Lysophosphatidic Acid Receptor Antagonists and Cancer: The Current Trends, Clinical Implications, and Trials.

Lysophosphatidic acid (LPA) is a bioactive lipid mediator primarily derived from membrane phospholipids. LPA initiates cellular effects upon binding to a family of G protein-coupled receptors, termed LPA receptors (LPAR1 to LPAR6). LPA signaling drives cell migration and proliferation, cytokine production, thrombosis, fibrosis, angiogenesis, and lymphangiogenesis. Since the expression and function of LPA receptors are critical for cellular effects, selective antagonists may represent a potential treatment for a broad range of illnesses, such as cardiovascular diseases, idiopathic pulmonary fibrosis, voiding dysfunctions, and various types of cancers. More new LPA receptor antagonists have shown their therapeutic potentials, although most are still in the preclinical trial stage. This review provided integrative information and summarized preclinical findings and recent clinical trials of different LPA receptor antagonists in cancer progression and resistance. Targeting LPA receptors can have potential applications in clinical patients with various diseases, including cancer.

Cannabinoid CB1 and CB2 receptors differentially regulate TNF-α-induced apoptosis and LPA1-mediated pro-survival signaling in HT22 hippocampal cells

AimsThe aim of the study was to investigate the interaction between cannabinoid CB1/CB2 and lysophosphatidic acid (LPA) receptors in controlling neuronal signaling and fate. MethodsHT22 hippocampal cells were treated with different cannabinoid and LPA receptor agonists and antagonists. Western blot and immunofluorescence microscopy were used to study intracellular signaling and the expression of apoptotic markers. Cell viability was determined by a luminescence assay. Key findingsCannabinoid agonists induced activation of both ERK1/2 and p38 MAP kinases. The effects of the CB1/CB2 receptor agonist HU210 were antagonized by the CB1 antagonist rimonabant, whereas the responses to the CB2 agonist JWH133 were blocked by the CB2 antagonist SR144528. HU210 reduced the apoptotic cell death induced by the pro-inflammatory cytokine TNF-α, whereas JWH133 enhanced the cytokine cytotoxicity. Blockade of ERK1/2 and p38 MAPK activation abrogated the HU210 pro-survival and the JWH133 pro-apoptotic effects, respectively. HU210 and the endocannabinoid anandamide, but not JWH133, potentiated ERK1/2 stimulation by LPA and the tricyclic antidepressant amitriptyline acting through the LPA1 receptor. HU210 enhanced amitriptyline-stimulated CREB phosphorylation and protection against TNF-α-induced apoptosis, whereas JWH133 had no effect. ERK1/2 stimulation by either HU210 or amitriptyline was dependent on fibroblast growth factor receptor (FGF-R) kinase activity and the combination of the two stimulants induced FGF-R phosphorylation. Moreover, the CB1 receptor was found to co-immunoprecipitate with the LPA1 receptor. ConclusionsIn HT22 hippocampal cells CB1 and CB2 receptors differentially regulate TNF-α-induced apoptosis and CB1 receptors positively interact with amitriptyline-stimulated LPA1 in promoting FGF-R-mediated ERK1/2 signaling and neuroprotection.

Increased Levels of Renal Lysophosphatidic Acid in Rodent Models with Renal Disease.

Lysophosphatidic acid (LPA) is a bioactive lipid mediator that has been implicated in the pathophysiology of kidney disease. However, few studies have attempted to measure changes in the levels of various LPA species in the kidney after the development of renal disease. The present study measured the renal LPA levels during the development of kidney disease in rat models of hypertension, diabetes, and obstructive nephropathy using liquid chromatography/mass spectrometry/mass spectrometry. LPA levels (sum of 16:0, 18:0, 18:1, 18:2, and 20:4 LPA) were higher in the renal cortex of hypertensive Dahl salt-sensitive (Dahl S) rats fed a high-salt diet than those in normotensive rats fed a low-salt diet (296.6 ± 22.9 vs. 196.3 ± 8.5 nmol/g protein). LPA levels were elevated in the outer medulla of the kidney of streptozotocin-induced type 1 diabetic Dahl S rats compared with control rats (624.6 ± 129.5 vs. 318.8 ± 17.1 nmol/g protein). LPA levels were also higher in the renal cortex of 18-month-old, type 2 diabetic nephropathy (T2DN) rats with more severe renal injury than in 6-month-old T2DN rats (184.9 ± 20.9 vs. 116.9 ± 6.0 nmol/g protein). LPA levels also paralleled the progression of renal fibrosis in the renal cortex of Sprague-Dawley rats after unilateral ureteral obstruction (UUO). Administration of an LPA receptor antagonist, Ki16425, reduced the degree of renal fibrosis in UUO rats. These results suggest that the production of renal LPA increases during the development of renal injury and contributes to renal fibrosis. SIGNIFICANCE STATEMENT: The present study reveals that the lysophosphatidic acid (LPA) levels increase in the kidney in rat models of hypertension, diabetes, and obstructive nephropathy, and administration of an LPA receptor antagonist attenuates renal fibrosis. Therapeutic approaches that target the formation or actions of renal LPA might be renoprotective and have therapeutic potential.

Involvement of autotaxin in the pathophysiology of elevated intraocular pressure in Posner-Schlossman syndrome

To examine whether autotaxin (ATX) in the aqueous humor causes elevated intraocular pressure (IOP) in patients with Posner-Schlossman syndrome (PSS). ATX and transforming growth factor beta (TGF-β) in the aqueous humor were quantified in PSS patients. The expression of ATX and TGF-β in cytomegalovirus (CMV)-infected-human trabecular meshwork (hTM) cells was examined. Biological changes in hTM cells and monkey Schlemm’s canal endothelial (SCE) cells cultured in the conditioned medium of CMV-infected hTM cells were analyzed. The expression of ATX and TGF-β1 was upregulated in the aqueous humor of CMV-positive PSS patients, and the level of ATX in the aqueous humor was positively correlated with IOP. CMV infection upregulated ATX and TGF-β1 in hTM cells. The conditioned medium induced fibrotic changes in hTM cells and reduced SCE permeability, which was attenuated by an ATX inhibitor, a lysophosphatidic acid receptor antagonist, and a Rho kinase inhibitor. ATX in the aqueous humor induced by CMV infection may trigger elevated IOP. Modulating ATX activity may be a novel treatment modality for PSS.

Inhibition of store-operated calcium channels by N-arachidonoyl glycine (NAGly): no evidence for the involvement of lipid-sensing G protein coupled receptors

N-arachidonoyl glycine (NAGly) is an endogenous lipid deriving from the endocannabinoid anandamide (AEA). Identified as a ligand of several G-protein coupled receptors (GPCRs), it can however exert biological responses independently of GPCRs. NAGly was recently shown to depress store-operated Ca2+ entry (SOCE) but its mechanism of action remains elusive. The major aim of this study was to gain a better knowledge on the NAGly-dependent impairment of SOCE in neurons of the central nervous system (CNS) from mice. First, we examined the expression of genes encoding for putative lipid sensing GPCRs using transcriptomic data publicly available. This analysis showed that the most abundant GPCRs transcripts present in the cerebral cortices of embryonic brains were coding for lysophosphatidic acid (LPA) and sphingosine-1 phosphate (S1P) receptors. Next, the presence of functional receptors was assessed with live-cell calcium imaging experiments. In primary cortical cells S1P and LPA mobilize Ca2+ from internal stores via a mechanism sensitive to the S1P and LPA receptor antagonists Ex26, H2L5186303, or Ki16425. However, none of these compounds prevented or attenuated the NAGly-dependent impairment of SOCE. We found no evidence for the requirement of lipid sensing GPCRs in this inhibitory process, indicating that NAGly is an endogenous modulator interfering with the core machinery of SOCE. Moreover, these data also raise the intriguing possibility that the depression of SOCE could play a role in the central effects of NAGly.

LPA1/3 overactivation induces neonatal posthemorrhagic hydrocephalus through ependymal loss and ciliary dysfunction.

Posthemorrhagic hydrocephalus (PHH) in premature infants is a common neurological disorder treated with invasive neurosurgical interventions. Patients with PHH lack effective therapeutic interventions and suffer chronic comorbidities. Here, we report a murine lysophosphatidic acid (LPA)-induced postnatal PHH model that maps neurodevelopmentally to premature infants, a clinically accessible high-risk population, and demonstrates ventriculomegaly with increased intracranial pressure. Administration of LPA, a blood-borne signaling lipid, acutely disrupted the ependymal cells that generate CSF flow, which was followed by cell death, phagocytosis, and ventricular surface denudation. This mechanism is distinct from a previously reported fetal model that induces PHH through developmental alterations. Analyses of LPA receptor-null mice identified LPA1 and LPA3 as key mediators of PHH. Pharmacological blockade of LPA1 prevented PHH in LPA-injected animals, supporting the medical tractability of LPA receptor antagonists in preventing PHH and negative CNS sequelae in premature infants.

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

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

Lysophosphatidic acid and its receptors: pharmacology and therapeutic potential in atherosclerosis and vascular disease.

Lysophosphatidic acid (LPA) is a collective name for a set of bioactive lipid species. Via six widely distributed G protein-coupled receptors (GPCRs), LPA elicits a plethora of biological responses, contributing to inflammation, thrombosis and atherosclerosis. There have recently been considerable advances in GPCR signaling especially recognition of the extended role for GPCR transactivation of tyrosine and serine/threonine kinase growth factor receptors. This review covers LPA signaling pathways in the light of new information. The use of transgenic and gene knockout animals, gene manipulated cells, pharmacological LPA receptor agonists and antagonists have provided many insights into the biological significance of LPA and individual LPA receptors in the progression of atherosclerosis and vascular diseases. This review provides a comprehensive presentation of LPA with the highlight of the distinct role of its receptors in cell and animal models that relate to atherosclerosis and vascular diseases, and therefore provides new opportunities to reduce the burden of cardiovascular diseases. The recent drug development strategies that target LPA signaling pathways are also included in this review.

Effects of a gintonin-enriched fraction on hair growth: an in vitro and in vivo study

BackgroundGinseng has been widely used as a health-promoting tonic. Gintonin present in ginseng acts as a lysophosphatidic acid (LPA) receptor ligand that activates six LPA receptor subtypes. The LPA6 subtype plays a key role in normal hair growth, and mutations in the LPA6 receptor impair normal human hair growth. Currently, human hair loss and alopecia are concerning issues that affect peoples' social and day-to-day lives. ObjectiveWe investigated the in vitro and in vivo effects of a gintonin-enriched fraction (GEF) on mouse hair growth. MethodsHuman hair follicle dermal papilla cells (HFDPCs) and six-week-old male C57BL/6 mice were used. The mice were divided into the four groups: control, 1% minoxidil, 0.75% GEF, and 1.5% GEF. The dorsal hair was removed to synchronize the telogen phase. Each group was treated topically, once a day, for 15 days. We analyzed hair growth activity and histological changes. ResultsGEF induced transient [Ca2+]i, which stimulated HFDPC proliferation and caused 5-bromo-2′-deoxyuridine (BrdU) incorporation in a concentration-dependent manner. GEF-mediated HFDPC proliferation was blocked by the LPA receptor antagonist and Ca2+ chelator. HFDPC treatment with GEF stimulated vascular endothelial growth factor release. Topical application of GEF and minoxidil promoted hair growth in a dose-dependent manner. Histological analysis showed that GEF and minoxidil increased the number of hair follicles and hair weight. ConclusionTopical application of GEF promotes mouse hair growth through HFDPC proliferation. GEF could be one of the main components of ginseng that promote hair growth and could be used to treat human alopecia.