Impact of cellular ATP levels on cell viability in response to fluorouracil through lysophosphatidic acid (LPA) receptor-4 (LPA4) and LPA6 in colon cancer cells.

Lysophosphatidic acid (LPA) signaling via LPA receptors (LPA1 to LPA6) mediates various aspects of cancer cell behaviors. This study aimed to investigate the variation in intracellular ATP levels and its impact on cell viability in response to fluorouracil (5-FU) through LPA4 and LPA6 in colon cancer DLD-1 cells. LPA4 and LPA6 are linked to Gs and Gi proteins. Gs protein stimulates the activity of adenylyl cyclase, which catalyzes the conversion of ATP to cAMP, whereas Gi protein inhibits this activity. In cell survival assay, cells were treated with 5-FU every 24 h for 3 days. The viability in response to 5-FU in DLD-1 cells was enhanced by LPA4 and LPA6 knockdowns. Furthermore, LPA4 and LPA6 knockdowns reduced the expression of cleaved-PARP1 protein when cells were treated with 5-FU. Since ethidium bromide (EtBr) reduces mitochondrial DNA level in cultured cells, EtBr-treated (DLD-EtBr) cells were generated from DLD-1 cells. The viability to 5-FU in DLD-EtBr cells was higher than that of DLD-1 cells. Additionally, culturing DLD-1 cells in a low glucose-containing medium led to increased viability to 5-FU. LPAR4 and LPAR6 expressions were reduced in both DLD-EtBr and low glucose-treated cells. The cellular ATP levels were significantly decreased in DLD-1 cells following EtBr treatment and exposure to low glucose conditions. Conversely, in the presence of LPA, LPA4 and LPA6 knockdowns resulted in a marked elevation of ATP levels. These results suggest that cell viability to 5-FU is negatively regulated via the activation of LPA4-and LPA6-Gs protein pathways in DLD-1 cells rather than Gi protein.

A Reliable System for Quantitative G-Protein Activation Imaging in Cancer Cells.

Fluorescence resonance energy transfer (FRET) biosensors have proven to be an indispensable tool in cell biology and, more specifically, in the study of G-protein signalling. The best method of measuring the activation status or FRET state of a biosensor is often fluorescence lifetime imaging microscopy (FLIM), as it does away with many disadvantages inherent to fluorescence intensity-based methods and is easily quantitated. Despite the significant potential, there is a lack of reliable FLIM-FRET biosensors, and the data processing and analysis workflows reported previously face reproducibility challenges. Here, we established a system in live primary mouse pancreatic ductal adenocarcinoma cells, where we can detect the activation of an mNeonGreen-Gαi3-mCherry-Gγ2 biosensor through the lysophosphatidic acid receptor (LPAR) with 2-photon time-correlated single-photon counting (TCSPC) FLIM. This combination gave a superior signal to the commonly used mTurquoise2-mVenus G-protein biosensor. This system has potential as a platform for drug screening, or to answer basic cell biology questions in the field of G-protein signalling.

Hypoxia Promotes Invadosome Formation by Lung Fibroblasts.

Lung parenchymal hypoxia has emerged as a cardinal feature of idiopathic pulmonary fibrosis (IPF). Hypoxia promotes cancer cell invasion and metastasis through signaling that is dependent upon the lysophosphatidic acid (LPA) receptor, LPA1 (LPAR1). Abundant data indicate that LPA1-dependent signaling also enhances lung fibrogenesis in IPF. We recently reported that fibroblasts isolated from the lungs of individuals with IPF have an increased capacity to form subcellular matrix-degradative structures known as invadosomes, an event that correlates with the degree of lung fibrosis. We therefore hypothesized that hypoxia promotes invadosome formation in lung fibroblasts through LPA1-dependent signaling. Here, it is demonstrated that invadosome formation by fibroblasts from the lungs of individuals with advanced IPF is inhibited by both the tyrosine receptor kinase inhibitor nintedanib and inhibition of LPA1. In addition, exposure of normal human lung fibroblasts to either hypoxia or LPA increased their ability to form invadosomes. Mechanistically, the hypoxia-induced invadosome formation by lung fibroblasts was found to involve LPA1 and PDGFR-Akt signaling. We concluded that hypoxia increases the formation of invadosomes in lung fibroblasts through the LPA1 and PDGFR-Akt signaling axis, which represents a potential target for suppressing lung fibrosis.

Autotaxin-Lysophosphatidate Axis: Promoter of Cancer Development and Possible Therapeutic Implications.

Autotaxin (ATX) is a member of the ectonucleotide pyrophosphate/phosphodiesterase (ENPP) family; it is encoded by the ENPP2 gene. ATX is a secreted glycoprotein and catalyzes the hydrolysis of lysophosphatidylcholine to lysophosphatidic acid (LPA). LPA is responsible for the transduction of various signal pathways through the interaction with at least six G protein-coupled receptors, LPA Receptors 1 to 6 (LPAR1-6). The ATX-LPA axis is involved in various physiological and pathological processes, such as angiogenesis, embryonic development, inflammation, fibrosis, and obesity. However, significant research also reported its connection to carcinogenesis, immune escape, metastasis, tumor microenvironment, cancer stem cells, and therapeutic resistance. Moreover, several studies suggested ATX and LPA as relevant biomarkers and/or therapeutic targets. In this review of the literature, we aimed to deepen knowledge about the role of the ATX-LPA axis as a promoter of cancer development, progression and invasion, and therapeutic resistance. Finally, we explored its potential application as a prognostic/predictive biomarker and therapeutic target for tumor treatment.

Lysophosphatidic acid receptor 1 inhibition: a potential treatment target for pulmonary fibrosis.

Lysophosphatidic acid (LPA)-mediated activation of LPA receptor 1 (LPAR1) contributes to the pathophysiology of fibrotic diseases such as idiopathic pulmonary fibrosis (IPF) and systemic sclerosis (SSc). These diseases are associated with high morbidity and mortality despite current treatment options. The LPA-producing enzyme autotaxin (ATX) and LPAR1 activation contribute to inflammation and mechanisms underlying fibrosis in preclinical fibrotic models. Additionally, elevated levels of LPA have been detected in bronchoalveolar lavage fluid from patients with IPF and in serum from patients with SSc. Thus, ATX and LPAR1 have gained considerable interest as pharmaceutical targets to combat fibrotic disease and inhibitors of these targets have been investigated in clinical trials for IPF and SSc. The goals of this review are to summarise the current literature on ATX and LPAR1 signalling in pulmonary fibrosis and to help differentiate the novel inhibitors in development. The mechanisms of action of ATX and LPAR1 inhibitors are described and preclinical studies and clinical trials of these agents are outlined. Because of their contribution to numerous physiologic events underlying fibrotic disease, ATX and LPAR1 inhibition presents a promising therapeutic strategy for IPF, SSc and other fibrotic diseases that may fulfil unmet needs of the current standard of care.

Roles of lysophosphatidic acid (LPA) receptor-mediated signaling in cancer cell biology.

Lysophosphatidic acid (LPA) is a simple lipid which is endogenously synthesized from lysophosphatidylcholine (LPC) by autotaxin (ATX). LPA mediates a variety of cellular responses through the binding of G protein-coupled LPA receptors (LPA1 to LPA6). It is considered that LPA receptor-mediated signaling plays an important role in the pathogenesis of human malignancy. Genetic alterations and epigenetic changes of LPA receptors have been detected in some cancer cells as well as LPA per se. Moreover, LPA receptors contribute to the promotion of tumor progression, including cell proliferation, invasion, metastasis, tumorigenicity, and angiogenesis. In recent studies, the activation of LPA receptor-mediated signaling regulates chemoresistance and radiosensitivity in cancer cells. This review provides an updated overview on the roles of LPA receptor-mediated signaling in the regulation of cancer cell functions and its potential utility as a molecular target for novel therapies in clinical cancer approaches.

Involvement of lysophosphatidic acid (LPA) receptor-mediated signaling in breast cancer cell functions by long-term tamoxifen treatment under hypoxic and estrogen-deprived conditions.

BACKGROUND: Tamoxifen (TAM) is a selective estrogen receptor modulator and has anti-estrogenic activity. Breast cancer cells acquire drug resistance to TAM as a consequence of long-term treatment. Lysophosphatidic acid (LPA) receptor-mediated signaling contributes to the promotion of tumor progression. This study aimed to evaluate the role of LPA receptors in the modulation of biological functions by long-term TAM treatment in breast cancer MCF-7 cells under hypoxic and estrogen-deprived conditions. METHODS: Long-term TAM treated (MCF-TAM) cells were generated from MCF-7 cells. Cells were cultured in estrogen-free medium at 1 % O2. LPA receptor expressions were measured by quantitative real-time RT-PCR analysis. Cell motile activity was investigated using Cell Culture Inserts. The CCK-8 kit was used to determine the cell proliferation rate. RESULTS: LPAR1 and LPAR3 expressions were elevated in MCF-TAM cells. MCF-TAM cell motility was enhanced by culturing at 1 % O2, compared with MCF-7 cells. When cells were cultured in estrogen-deprived medium at 1 % O2, the cell proliferation rate of MCF-TAM cells was significantly higher than that of MCF-7 cells. CONCLUSION: These results suggest that LPA receptor-mediated signaling plays an important role in the acquisition of malignant properties in long-term TAM treated MCF-7 cells under hypoxic and estrogen-deprived conditions.

Integrating transformers and many-objective optimization for drug design.

BACKGROUND: Drug design is a challenging and important task that requires the generation of novel and effective molecules that can bind to specific protein targets. Artificial intelligence algorithms have recently showed promising potential to expedite the drug design process. However, existing methods adopt multi-objective approaches which limits the number of objectives. RESULTS: In this paper, we expand this thread of research from the many-objective perspective, by proposing a novel framework that integrates a latent Transformer-based model for molecular generation, with a drug design system that incorporates absorption, distribution, metabolism, excretion, and toxicity prediction, molecular docking, and many-objective metaheuristics. We compared the performance of two latent Transformer models (ReLSO and FragNet) on a molecular generation task and show that ReLSO outperforms FragNet in terms of reconstruction and latent space organization. We then explored six different many-objective metaheuristics based on evolutionary algorithms and particle swarm optimization on a drug design task involving potential drug candidates to human lysophosphatidic acid receptor 1, a cancer-related protein target. CONCLUSION: We show that multi-objective evolutionary algorithm based on dominance and decomposition performs the best in terms of finding molecules that satisfy many objectives, such as high binding affinity and low toxicity, and high drug-likeness. Our framework demonstrates the potential of combining Transformers and many-objective computational intelligence for drug design.

Unveiling the therapeutic promise: exploring Lysophosphatidic Acid (LPA) signaling in malignant bone tumors for novel cancer treatments.

Malignant bone tumors, including primary bone cancer and metastatic bone tumors, are a significant clinical challenge due to their high frequency of presentation, poor prognosis and lack of effective treatments and therapies. Bone tumors are often accompanied by skeletal complications such as bone destruction and cancer-induced bone pain. However, the mechanisms involved in bone cancer progression, bone metastasis and skeletal complications remain unclear. Lysophosphatidic acid (LPA), an intercellular lipid signaling molecule that exerts a wide range of biological effects mainly through specifically binding to LPA receptors (LPARs), has been found to be present at high levels in the ascites of bone tumor patients. Numerous studies have suggested that LPA plays a role in primary malignant bone tumors, bone metastasis, and skeletal complications. In this review, we summarize the role of LPA signaling in primary bone cancer, bone metastasis and skeletal complications. Modulating LPA signaling may represent a novel avenue for future therapeutic treatments for bone cancer, potentially improving patient prognosis and quality of life.

Transcriptome and metabolome sequencing identifies glutamate and LPAR1 as potential factors of anlotinib resistance in thyroid cancer.

OBJECTIVE: To explore the mechanism of anlotinib resistance in thyroid carcinoma. METHODS: We constructed an anlotinib-resistant thyroid carcinoma cell line and observed the effect of drug resistance on the functional activity of these cell lines. Transcriptome sequencing and metabolomic sequencing combined with biosynthesis analysis were used to explore and screen possible drug resistance regulatory pathways. RESULTS: Through transcriptomic sequencing analysis of drug-resistant cell lines, it was found that the differentially expressed genes of drug-resistant strains were enriched mainly in the interleukin 17, transforming growth factor-ß, calcium, peroxisome proliferator activated receptor, and other key signaling pathways. A total of 354 differentially expressed metabolic ions were screened using liquid chromatography-mass spectrometry/mass spectrometry to determine the number of metabolic ions in the drug-resistant strains. The results of the Venn diagram correlation analysis showed that glutamate is closely related to multiple pathways and may be an important regulatory factor of anlotinib resistance in thyroid carcinoma. In addition, eight common differentially expressed genes were screened by comparing the gene expression profiling interactive analysis database and sequencing results. Further quantitative real time polymerase chain reaction verification, combined with reports in the literature, showed that LPAR1 may be an important potential target. CONCLUSION: This is the first study in which the drug resistance of thyroid cancer to anlotinib was preliminarily discussed. We confirmed that anlotinib resistance in thyroid cancer promotes the progression of malignant biological behavior. We conclude that glutamate may be a potential factor for anlotinib resistance in thyroid cancer and that LPAR1 is also a potentially important target.

CYRI-B-mediated macropinocytosis drives metastasis via lysophosphatidic acid receptor uptake.

Pancreatic ductal adenocarcinoma carries a dismal prognosis, with high rates of metastasis and few treatment options. Hyperactivation of KRAS in almost all tumours drives RAC1 activation, conferring enhanced migratory and proliferative capacity as well as macropinocytosis. Macropinocytosis is well understood as a nutrient scavenging mechanism, but little is known about its functions in trafficking of signalling receptors. We find that CYRI-B is highly expressed in pancreatic tumours in a mouse model of KRAS and p53-driven pancreatic cancer. Deletion of Cyrib (the gene encoding CYRI-B protein) accelerates tumourigenesis, leading to enhanced ERK and JNK-induced proliferation in precancerous lesions, indicating a potential role as a buffer of RAC1 hyperactivation in early stages. However, as disease progresses, loss of CYRI-B inhibits metastasis. CYRI-B depleted tumour cells show reduced chemotactic responses to lysophosphatidic acid, a major driver of tumour spread, due to impaired macropinocytic uptake of the lysophosphatidic acid receptor 1. Overall, we implicate CYRI-B as a mediator of growth and signalling in pancreatic cancer, providing new insights into pathways controlling metastasis.

Pancreatic cancer is an aggressive disease with limited treatment options. It is also associated with high rates of metastasis ­ meaning it spreads to other areas of the body. Environmental pressures, such as a lack of the nutrients metastatic cancer cells need to grow and divide, can change how the cells behave. Understanding the changes that allow cancer cells to respond to these pressures could reveal new treatment options for pancreatic cancer. When nutrients are scarce, metastatic cancer cells can gather molecules and nutrients by capturing large amounts of the fluid that surrounds them using a mechanism called macropinocytosis. They can also migrate to areas of the body with higher nutrient levels, through a process called chemotaxis. This involves cells moving towards areas with higher levels of certain molecules. For example, cancer cells migrate towards high levels of a lipid called lysophosphatidic acid, which promotes their growth and survival. A newly discovered protein known as CYRI-B has recently been shown to regulate how cells migrate and take up nutrients. It also interacts with proteins known to be involved in pancreatic cancer progression. Therefore, Nikolaou et al. set out to investigate whether CYRI-B also plays a role in metastatic pancreatic cancer. Experiments in a mouse model of pancreatic cancer showed that CYRI-B levels were high in pancreatic tumour cells. And when the gene for CYRI-B was removed from the tumour cells, they did not metastasise. Further analysis revealed that CYRI-B controls uptake and processing of nutrients and other signalling molecules through macropinocytosis. In particular, it ensures uptake of the receptor for lysophosphatidic acid, allowing the metastatic cancer cells to migrate. The findings of Nikolaou et al. reveal that CYRI-B is involved in metastasis of cancer cells in a mouse model of pancreatic cancer. This new insight into how metastasis is controlled could help to identify future targets for treatments that aim to prevent pancreatic cancer cells spreading to distant sites.

Lysophosphatidic Acid Receptor 1 (LPA1) Antagonists as Potential Migrastatics for Triple Negative Breast Cancer.

Metastasis is responsible for about 90 % of cancer deaths. Anti-metastatic drugs, termed as migrastatics, offer a distinctive therapeutic approach to address cancer migration and invasion. However, therapeutic exploitation of metastasis-specific targets remains limited, and the effective prevention and suppression of metastatic cancer continue to be elusive. Lysophosphatidic acid receptor 1 (LPA1) is activated by an endogenous lipid molecule LPA, leading to a diverse array of cellular activities. Previous studies have shown that the LPA/LPA1 axis supports the progression of metastasis for many types of cancer. In this study, we report the synthesis and biological evaluation of fluorine-containing triazole derivatives as potent LPA1 antagonists, offering potential as migrastatic drugs for triple negative breast cancer (TNBC). In particular, compound 12 f, the most potent and highly selective in this series with an IC50 value of 16.0 nM in the cAMP assay and 18.4 nM in the calcium mobilization assay, inhibited cell survival, migration, and invasion in the TNBC cell line. Interestingly, the compound did not induce apoptosis in TNBC cells and demonstrated no cytotoxic effects. These results highlight the potential of LPA1 as a migrastatic target. Consequently, the LPA1 antagonists developed in this study hold promise as potential migrastatic candidates for TNBC.

Loss of LPAR6 and CAB39L dysregulates the basal-to-luminal urothelial differentiation program, contributing to bladder carcinogenesis.

We describe a strategy that combines histologic and molecular mapping that permits interrogation of the chronology of changes associated with cancer development on a whole-organ scale. Using this approach, we present the sequence of alterations around RB1 in the development of bladder cancer. We show that RB1 is not involved in initial expansion of the preneoplastic clone. Instead, we found a set of contiguous genes that we term "forerunner" genes whose silencing is associated with the development of plaque-like field effects initiating carcinogenesis. Specifically, we identified five candidate forerunner genes (ITM2B, LPAR6, MLNR, CAB39L, and ARL11) mapping near RB1. Two of these genes, LPAR6 and CAB39L, are preferentially downregulated in the luminal and basal subtypes of bladder cancer, respectively. Their loss of function dysregulates urothelial differentiation, sensitizing the urothelium to N-butyl-N-(4-hydroxybutyl)nitrosamine-induced cancers, which recapitulate the luminal and basal subtypes of human bladder cancer.

Lysophosphatidic acid (LPA) receptor-mediated signaling regulates hypoxia-induced biological functions of lymphatic endothelial cells.

The tumor microenvironment is an extremely complex composed of cancer cells and various non-cancer cells, including lymphatic endothelial cells. Lysophosphatidic acid (LPA) receptors (LPA1 to LPA6) activate a variety of malignant properties in human malignancies. In the present study, we examined the roles of LPA receptor-mediated signaling in biological responses of lymphatic endothelial SVEC4-10 cells induced by hypoxia. Lpar1, Lpar2 and Lpar3 expressions were decreased in SVEC4-10 cells cultured at hypoxic conditions (1 % O2). LPA had no impact on the cell growth activity of SVEC4-10 cells in 21 % O2 culture conditions. Conversely, the cell growth activity of SVEC4-10 cells in 1 % O2 culture conditions was reduced by LPA. The cell motile activity of SVEC4-10 cells was elevated by 1 % O2 culture conditions. GRI-977143 (LPA2 agonist) and (2S)-OMPT (LPA3 agonist) stimulated SVEC4-10 cell motility as well as AM966 (LPA1 antagonist). In tube formation assay, the tube formation of SVEC4-10 cells in 1 % O2 culture conditions was markedly increased, in comparison with 21 % O2. GRI-977143 and (2S)-OMPT elevated the tube formation of SVEC4-10 cells. Furthermore, the tube formation of SVEC4-10 cells was increased by AM966. These results suggest that LPA receptor-mediated signaling contributes to the modulation of hypoxic-induced biological functions of lymphatic endothelial cells.

Deciphering a GPCR-lncrna-miRNA nexus: Identification of an aberrant therapeutic target in ovarian cancer.

Ovarian cancer ranks as a leading cause of mortality among gynecological malignancies, primarily due to the lack of early diagnostic tools, effective targeted therapy, and clear understanding of disease etiology. Previous studies have identified the pivotal role of Lysophosphatidic acid (LPA)-signaling in ovarian cancer pathobiology. Our earlier transcriptomic analysis identified Urothelial Carcinoma Associated-1 (UCA1) as an LPA-stimulated long non-coding RNA (lncRNA). In this study, we elucidate the tripartite interaction between LPA-signaling, UCA1, and let-7 miRNAs in ovarian cancer progression. Results show that the elevated expression of UCA1 enhances cell proliferation, invasive migration, and therapy resistance in high-grade serous ovarian carcinoma cells, whereas silencing UCA1 reverses these oncogenic phenotypes. UCA1 expression inversely correlates with survival outcomes and therapy response in ovarian cancer clinical samples, underscoring its prognostic significance. Mechanistically, UCA1 sequesters let-7 miRNAs, effectively neutralizing their tumor-suppressive functions involving key oncogenes such as Ras and c-Myc. More significantly, intratumoral delivery of UCA1-specific siRNAs inhibits the growth of cisplatin-refractory ovarian cancer xenografts, demonstrating the therapeutic potential of targeting LPAR-UCA1-let-7 axis in ovarian cancer. Thus, our results identify LPAR-UCA1-let-7 axis as a novel avenue for targeted treatment strategies.

Design, synthesis and evaluation of new thiazolidin-4-ones as LPA1 receptor antagonists for breast cancer therapy.

Aim: Breast cancer has been a leading cause of mortality among women worldwide in recent years. Targeting the lysophosphatidic acid (LPA)-LPA1 pathway using small molecules could improve breast cancer therapy. Materials & methods: Thiazolidin-4-ones were developed and tested on MCF-7 cancer cells, and active compounds were analyzed for their effects on apoptosis, migration angiogenesis and LPA1 protein and gene expression. Results & conclusion: Compounds TZ-4 and TZ-6 effectively reduced the migration of MCF-7 cells, and induced apoptosis. TZ-4, TZ-6, TZ-8 and TZ-14 significantly reduced the LPA1 protein, LPA1 and angiogenesis gene expression in treated MCF-7 cells. Molecular docking and molecular dynamic simulation studies reveal the ligand interactions and stability of the LPA1-ligand complex. Developed thiazolidin-4-ones showed great potential as an LPA1-targeted approach to combating breast cancer.

Breast cancer is a major cause of death for women worldwide. Using small molecules to target the lysophosphatidic acid (LPA)­LPA₁ pathway could improve breast cancer treatment. We tested a type of molecule called thiazolidin-4-ones on breast cancer cells in the lab. We looked at how these molecules affected cell death, movement, blood vessel growth and the activity of the LPA₁ gene and protein. Some of these molecules, such as TZ-4 and TZ-6, reduced the movement of cancer cells and caused them to die. They also decreased the levels of LPA₁ protein and gene activity in the cells. We used computer simulations to see how these molecules interacted with the LPA₁ protein. Our findings suggest that thiazolidin-4-ones could be a promising treatment for breast cancer by targeting LPA₁.

Targeting AQP9 enhanced the anti-TNF therapy response in Crohn's disease by inhibiting LPA-hippo pathway.

Although anti-TNF antibodies are extensively used to treat Crohn's disease (CD), a significant proportion of patients, up to 40%, exhibit an inadequate response to this therapy. Our objective was to identify potential targets that could improve the effectiveness of anti-TNF therapy in CD. Through the integration and analysis of transcriptomic data from various CD databases, we found that the expression of AQP9 was significantly increased in anti-TNF therapy-resistant specimens. The response to anti-TNF therapy in the CD mouse model was significantly enhanced by specifically inhibiting AQP9. Further experiments found that the blockade of AQP9, which is dominantly expressed in macrophages, decreased inflamed macrophage functions and cytokine expression. Mechanistic studies revealed that AQP9 transported glycerol into macrophages, where it was metabolized to LPA, which was further metabolized to LPA, resulting in the activation of the LPAR2 receptor and downstream hippo pathway, finally promoting the expression of cytokines, especially IL23 and IL1ß⊡ Taken together, the expansion of AQP9+ macrophages is associated with resistance to anti-TNF therapy in Crohn's disease. These findings indicated that AQP9 could be a potential target for enhancing anti-TNF therapy in Crohn's disease.

Regulation of cellular responses to X-ray irradiation through the activation of lysophosphatidic acid (LPA) receptor-3 (LPA3) and LPA2 in osteosarcoma cells.

Lysophosphatidic acid (LPA) binds to its specific G protein-coupled LPA receptors (LPA1 to LPA6), resulting in the activation of various cellular functions. LPA receptor-mediated signaling facilitates tumor progression in human malignancies. In the present study, we investigated whether LPA receptor-mediated signaling contributes to cellular responses to X-ray irradiation in osteosarcoma MG-63 cells. After X-ray irradiation (2, 4 and 8 Gy), LPAR2 and LPAR3 expression levels in MG-63 cells were significantly elevated in a dose-dependent manner, but no change of LPAR1 expression level was observed. The cell growth activities of MG-63 cells irradiated with X-rays (2, 4 and 8 Gy) were reduced by LPA. Conversely, LPA3 agonist (2 S)-OMPT enhanced the cell growth activities of X-ray irradiated MG-63 cells. The cell movement of MG-63 cells exposed to X-ray irradiation (8 Gy) was inhibited by (2 S)OMPT. In cell survival assay, (2 S)-OMPT suppressed the cell survival to cisplatin (CDDP) of MG-63 cells irradiated with X-rays (8 Gy). The cell survival to CDDP of X-ray irradiated cells was elevated by LPA3 knockdown. Moreover, we evaluated the effects of LPA2 on the cell survival to CDDP of MG-63 cells exposed to X-ray irradiation (8 Gy). The cell survival to CDDP of X-ray irradiated cells was increased by LPA2 agonist GRI-977143 and reduced by LPA2 knockdown. These results suggest that LPA receptor-signaling participates in the modulation of cellular functions induced by X-ray irradiation in osteosarcoma cells.

Discovery of the Novel, Orally Active, and Selective LPA1 Receptor Antagonist ACT-1016-0707 as a Preclinical Candidate for the Treatment of Fibrotic Diseases.

Piperidine 3 is a potent and selective lysophosphatidic acid receptor subtype 1 receptor (LPAR1) antagonist that has shown efficacy in a skin vascular leakage target engagement model in mice. However, compound 3 has very high human plasma protein binding and high clearance in rats, which could significantly hamper its clinical development. Continued lead optimization led to the potent, less protein bound, metabolically stable, and orally active azetidine 17. Rat pharmacokinetics (PK) studies revealed that 17 accumulated in the liver. In vitro studies indicated that 17 is an organic anion co-transporting polypeptide 1B1 (OATP1B1) substrate. Although analogue 24 was no longer a substrate of OATP1B1, PK studies suggested that the compound undergoes enterohepatic recirculation. Replacing the carboxylic acidic side chain by a non-acidic sulfamide moiety and further fine-tuning of the scaffold yielded the potent, orally active LPAR1 antagonist 49, which was selected for preclinical development for the treatment of fibrotic diseases.

Lysophosphatidic Acid Receptor 3 Activation Is Involved in the Regulation of Ferroptosis.

Ferroptosis, a unique form of programmed cell death trigged by lipid peroxidation and iron accumulation, has been implicated in embryonic erythropoiesis and aging. Our previous research demonstrated that lysophosphatidic acid receptor 3 (LPA3) activation mitigated oxidative stress in progeria cells and accelerated the recovery of acute anemia in mice. Given that both processes involve iron metabolism, we hypothesized that LPA3 activation might mediate cellular ferroptosis. In this study, we used an LPA3 agonist, 1-Oleoyl-2-O-methyl-rac-glycerophosphothionate (OMPT), to activate LPA3 and examine its effects on the ferroptosis process. OMPT treatment elevated anti-ferroptosis gene protein expression, including solute carrier family 7 member 11 (SLC7A11), glutathione peroxidase 4 (GPX4), heme oxygenase-1 (HO-1), and ferritin heavy chain (FTH1), in erastin-induced cells. Furthermore, OMPT reduced lipid peroxidation and intracellular ferrous iron accumulation, as evidenced by C11 BODIPY™ 581/591 Lipid Peroxidation Sensor and FerroOrange staining. These observations were validated by applying LPAR3 siRNA in the experiments mentioned above. In addition, the protein expression level of nuclear factor erythroid 2-related factor (NRF2), a key regulator of oxidative stress, was also enhanced in OMPT-treated cells. Lastly, we verified that LPA3 plays a critical role in erastin-induced ferroptotic human erythroleukemia K562 cells. OMPT rescued the erythropoiesis defect caused by erastin in K562 cells based on a Gly A promoter luciferase assay. Taken together, our findings suggest that LPA3 activation inhibits cell ferroptosis by suppressing lipid oxidation and iron accumulation, indicating that ferroptosis could potentially serve as a link among LPA3, erythropoiesis, and aging.