Lysophosphatidic acid-induced YAP/TAZ activation promotes developmental angiogenesis by repressing Notch ligand Dll4

Optimization of culture conditions to generate vascularized multi-lineage liver organoids with structural complexity and functionality

Hepatic organoids (HOs), primarily composed of hepatobiliary cells, do not represent the pathogenesis of liver diseases due to the lack of non-parenchymal cells. Multi-lineage liver organoids (mLOs) containing various cell types found in the liver offer a promising in vitro disease model. However, their structural complexity remains challenging to achieve due to the difficulty in optimizing culture conditions that meet the growth need of all component cell types. Here, we demonstrate that cystic HOs generated from hPSCs can be expanded long-term and serve as a continuous source for generating complex mLOs. Assembling cystic HOs with hPSC-derived endothelial and hepatic stellate cell-like cells under conventional HO culture conditions failed to support the development of multiple cell types within mLOs, resulting in biased differentiation towards specific cell types. In contrast, modulating the cAMP/Wnt/Hippo signaling pathways with small molecules during assembly and differentiation phases efficiently generate mLOs containing both hepatic parenchymal and non-parenchymal cells. These mLOs exhibited structural complexity and functional maturity, including vascular network formation between parenchymal lobular structures, cell polarity for bile secretion, and the capacity to respond to fibrotic stimuli. Our study underscores the importance of modulating signaling pathways to enhance mLO structural complexity for applications in modeling liver pathologies.

Preconditioning with Ginsenoside Rg3 mitigates cardiac injury induced by high-altitude hypobaric hypoxia exposure in mice by suppressing ferroptosis through inhibition of the RhoA/ROCK signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng has historically been utilized as a conventional herbal remedy and dietary supplement to enhance physical stamina and alleviate fatigue. The primary active component of Ginseng, Ginsenoside Rg3 (GS-Rg3), possesses diverse pharmacological properties including immune modulation and anti-inflammatory effects. Furthermore, GS-Rg3 has demonstrated efficacy in mitigating tissue and organ damage associated with metabolic disorders such as hypertension, hyperglycemia, and hyperlipidemia. Nevertheless, its potential impact on high-altitude cardiac injury (HACI) remains insufficiently explored.

AIM OF THE STUDY

The aim of this study was to examine the potential cardioprotective effects of Ginsenoside Rg3, and to investigate how Ginsenoside Rg3 preconditioning can enhance high-altitude cardiac injury by inhibiting the RhoA/ROCK pathway and ferroptosis in cardiac tissue. The findings of this study may contribute to the development of novel therapeutic strategies using traditional Chinese medicine for high-altitude cardiac injury, based on experimental evidence.

MATERIALS AND METHODS

A hypobaric hypoxia chamber was employed to simulate hypobaric hypoxia conditions equivalent to an altitude of 6000 m. Through a randomization process, groups of six male mice were assigned to receive either saline, Ginsenoside Rg3 at doses of 15 mg/kg or 30 mg/kg, or lysophosphatidic acid (LPA) at 1 mg/kg. The impact of Ginsenoside Rg3 on high altitude-induced arrhythmias was evaluated using electrocardiography. Cardiac pathology sections stained with hematoxylin and eosin were evaluated for damage, with the extent of cardiomyocyte damage observed via transmission electron microscopy. The impact of Ginsenoside Rg3 on high-altitude cardiac injury was investigated through analysis of serum biomarkers for cardiac injury (CK-MB, BNP), inflammatory cytokines (TNF, IL-6, IL-1β), reactive oxygen species (ROS) and glutathione (GSH). The expression levels of hypoxia and hypoxia-related proteins in myocardial tissues from each experimental group were assessed using Western blot analysis. Following a review of the existing literature, the traditional regulatory mechanisms of ferroptosis were examined. Immunofluorescence staining of cardiac tissues and Western blotting techniques were utilized to investigate the impact of Ginsenoside Rg3 on cardiomyocyte ferroptosis through the RhoA/ROCK signaling pathway under conditions of hypobaric hypoxia exposure.

RESULTS

Pre-treatment with Ginsenoside Rg3 improved high altitude-induced arrhythmias, reduced cardiomyocyte damage, decreased cardiac injury biomarkers and inflammatory cytokines, and lowered the expression of hypoxia-related proteins in myocardial tissues. Both Western blotting and immunofluorescence staining of cardiac tissues demonstrated that exposure to high-altitude hypobaric hypoxia results in elevated expression of ferroptosis and proteins related to the RhoA/ROCK pathway. Experimental validation corroborated that the role of the RhoA/ROCK signaling pathway in mediating ferroptosis.

CONCLUSIONS

The findings of our study suggest that preconditioning with Ginsenoside Rg3 may attenuate cardiac injury caused by high-altitude hypobaric hypoxia exposure in mice by inhibiting ferroptosis through the suppression of the RhoA/ROCK signaling pathway. These findings contribute to the current knowledge of Ginsenoside Rg3 and high-altitude cardiac injury, suggesting that Ginsenoside Rg3 shows potential as a therapeutic agent for high-altitude cardiac injury.

Inhibition of lysophosphatidic acid receptor 2 attenuates neonatal chronic lung disease in mice by preserving vascular and alveolar development

AIM

Bronchopulmonary dysplasia (BPD) is a common morbidity in extremely premature infants. Previous studies demonstrated the important role of lysophosphatidic acid (LPA) in inflammation in BPD. However, the role of LPA and its receptors in hyperoxia-induced vascular malformations in BPD remains to be elucidated.

METHODS AND RESULTS

Elevated plasma LPA levels were observed in mice with BPD compared to controls (792 vs. 607 ng/mL, p < 0.05). Inhibition of LPA signaling protected against hyperoxia-induced lung injury in neonatal mice, demonstrated by a 2.8-fold increase in pulmonary vascular density and a 14% reduction in alveolar enlargement. In vitro studies showed that LPA suppressed tube formation in human umbilical vein endothelial cells (HUVECs) by approximately 50%. LPA receptor 2 (LPA2) was identified as a functional LPA receptor in primary endothelial cells from the lungs of hyperoxic mice and in HUVECs under hyperoxic conditions. The LPA2 antagonist H2L5186303 enhanced the tube formation ability of HUVECs exposed to LPA, both under normoxia (4-fold) and hyperoxia (5-fold). Moreover, H2L5186303 significantly protected against hyperoxia-induced vascular malformation (2-fold) and improved alveolarization in neonatal mice (12% decrease in mean linear intercept, MLI). Early growth response 1 (EGR1) was characterized as a downstream target of LPA2, silencing EGR1 restored tube formation in HUVECs exposed to LPA and hyperoxia.

CONCLUSIONS

Our in vitro and in vivo findings demonstrate that the inhibition of LPA/LPA2 signaling mitigates hyperoxia-induced pulmonary vascular malformations, suggesting the LPA/LPA2-dependent signaling pathway has therapeutic potential for extremely premature infants with BPD.

YAP/TAZ drives Notch and angiogenesis mechanoregulation in silico

Endothelial cells are key players in the cardiovascular system. Among other things, they are responsible for sprouting angiogenesis, the process of new blood vessel formation essential for both health and disease. Endothelial cells are strongly regulated by the juxtacrine signaling pathway Notch. Recent studies have shown that both Notch and angiogenesis are influenced by extracellular matrix stiffness; however, the underlying mechanisms are poorly understood. Here, we addressed this challenge by combining computational models of Notch signaling and YAP/TAZ, stiffness- and cytoskeleton-regulated mechanotransducers whose activity inhibits both Dll4 (Notch ligand) and LFng (Notch-Dll4 binding modulator). Our simulations successfully mimicked previous experiments, indicating that this YAP/TAZ-Notch crosstalk elucidates the Notch and angiogenesis mechanoresponse to stiffness. Additional simulations also identified possible strategies to control Notch activity and sprouting angiogenesis via cytoskeletal manipulations or spatial patterns of alternating stiffnesses. Our study thus inspires new experimental avenues and provides a promising modeling framework for further investigations into the role of Notch, YAP/TAZ, and mechanics in determining endothelial cell behavior during angiogenesis and similar processes.

Novel Autotaxin Inhibitor ATX-1d Significantly Enhances Potency of Paclitaxel-An In Silico and In Vitro Study

The development of drug resistance in cancer cells poses a significant challenge for treatment, with nearly 90% of cancer-related deaths attributed to it. Over 50% of ovarian cancer patients and 30-40% of breast cancer patients exhibit resistance to therapies such as Taxol. Previous literature has shown that cytotoxic cancer therapies and ionizing radiation damage tumors, prompting cancer cells to exploit the autotaxin (ATX)-lysophosphatidic acid (LPA)-lysophosphatidic acid receptor (LPAR) signaling axis to enhance survival pathways, thus reducing treatment efficacy. Therefore, targeting this signaling axis has become a crucial strategy to overcome some forms of cancer resistance. Addressing this challenge, we identified and assessed ATX-1d, a novel compound targeting ATX, through computational methods and in vitro assays. ATX-1d exhibited an IC50 of 1.8 ± 0.3 μM for ATX inhibition and demonstrated a significant binding affinity for ATX, as confirmed by MM-GBSA, QM/MM-GBSA, and SAPT in silico methods. ATX-1d significantly amplified the potency of paclitaxel, increasing its effectiveness tenfold in 4T1 murine breast carcinoma cells and fourfold in A375 human melanoma cells without inducing cytotoxic effects as a single agent.

Artificial intelligence in therapeutic management of hyperlipidemic ocular pathology

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

Recent Advances in Graphene Oxide-Based on Organoid Culture as Disease Model and Cell Behavior - A Systematic Literature Review

Due to their ability to replicate the in vivo microenvironment through cell interaction and induce cells to stimulate cell function, three-dimensional cell culture models can overcome the limitations of two-dimensional models. Organoids are 3D models that demonstrate the ability to replicate the natural structure of an organ. In most organoid tissue cultures, matrigel made of a mouse tumor extracellular matrix protein mixture is an essential ingredient. However, its tumor-derived origin, batch-to-batch variation, high cost, and safety concerns have limited the usefulness of organoid drug development and regenerative medicine. Its clinical application has also been hindered by the fact that organoid generation is dependent on the use of poorly defined matrices. Therefore, matrix optimization is a crucial step in developing organoid culture that introduces alternatives as different materials. Recently, a variety of substitute materials has reportedly replaced matrigel. The purpose of this study is to review the significance of the latest advances in materials for cell culture applications and how they enhance build network systems by generating proper cell behavior. Excellence in cell behavior is evaluated from their cell characteristics, cell proliferation, cell differentiation, and even gene expression. As a result, graphene oxide as a matrix optimization demonstrated high potency in developing organoid models. Graphene oxide can promote good cell behavior and is well known for having good biocompatibility. Hence, advances in matrix optimization of graphene oxide provide opportunities for the future development of advanced organoid models.

YAP in development and disease: Navigating the regulatory landscape from retina to brain

The distinctive role of Yes-associated protein (YAP) in the nervous system has attracted widespread attention. This comprehensive review strategically uses the retina as a vantage point, embarking on an extensive exploration of YAP's multifaceted impact from the retina to the brain in development and pathology. Initially, we explore the crucial roles of YAP in embryonic and cerebral development. Our focus then shifts to retinal development, examining in detail YAP's regulatory influence on the development of retinal pigment epithelium (RPE) and retinal progenitor cells (RPCs), and its significant effects on the hierarchical structure and functionality of the retina. We also investigate the essential contributions of YAP in maintaining retinal homeostasis, highlighting its precise regulation of retinal cell proliferation and survival. In terms of retinal-related diseases, we explore the epigenetic connections and pathophysiological regulation of YAP in diabetic retinopathy (DR), glaucoma, and proliferative vitreoretinopathy (PVR). Lastly, we broaden our exploration from the retina to the brain, emphasizing the research paradigm of "retina: a window to the brain." Special focus is given to the emerging studies on YAP in brain disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD), underlining its potential therapeutic value in neurodegenerative disorders and neuroinflammation.

LPA5-Dependent signaling regulates regeneration of the intestinal epithelium following irradiation

Lysophosphatidic acid (LPA) is a bioactive lipid molecule that regulates a wide array of cellular functions, including proliferation, differentiation, and survival, via activation of cognate receptors. The LPA5 receptor is highly expressed in the intestinal epithelium, but its function in restoring intestinal epithelial integrity following injury has not been examined. Here, we use a radiation-induced injury model to study the role of LPA5 in regulating intestinal epithelial regeneration. Control mice (Lpar5f/f) and mice with an inducible, epithelial cell-specific deletion of Lpar5 in the small intestine (Lpar5IECKO) were subjected to 10 Gy total body X-ray irradiation and analyzed during recovery. Repair of the intestinal mucosa was delayed in Lpar5IECKO mice with reduced epithelial proliferation and increased crypt cell apoptosis. These effects were accompanied by reduced numbers of OLFM4+ intestinal stem cells (ISCs). The effects of LPA5 on ISCs were corroborated by studies using organoids derived from Lgr5-lineage tracking reporter mice with deletion of Lpar5 in Lgr5+-stem cells (Lgr5Cont or Lgr5ΔLpar5). Irradiation of organoids resulted in fewer numbers of Lgr5ΔLpar5 organoids retaining Lgr5+-derived progenitor cells compared with Lgr5Cont organoids. Finally, we observed that impaired regeneration in Lpar5IECKO mice was associated with reduced numbers of Paneth cells and decreased expression of Yes-associated protein (YAP), a critical factor for intestinal epithelial repair. Our study highlights a novel role for LPA5 in regeneration of the intestinal epithelium following irradiation and its effect on the maintenance of Paneth cells that support the stem cell niche.NEW & NOTEWORTHY We used mice lacking expression of the lysophosphatidic acid receptor 5 (LPA5) in intestinal epithelial cells and intestinal organoids to show that the LPA5 receptor protects intestinal stem cells and progenitors from radiation-induced injury. We show that LPA5 induces YAP signaling and regulates Paneth cells.

Lysophosphatidic Acid-Mediated Inflammation at the Heart of Heart Failure

PURPOSE OF REVIEW

The primary aim of this review is to provide an in-depth examination of the role bioactive lipids-namely lysophosphatidic acid (LPA) and ceramides-play in inflammation-mediated cardiac remodeling during heart failure. With the global prevalence of heart failure on the rise, it is critical to understand the underlying molecular mechanisms contributing to its pathogenesis. Traditional studies have emphasized factors such as oxidative stress and neurohormonal activation, but emerging research has shed light on bioactive lipids as central mediators in heart failure pathology. By elucidating these intricacies, this review aims to: Bridge the gap between basic research and clinical practice by highlighting clinically relevant pathways contributing to the pathogenesis and prognosis of heart failure. Provide a foundation for the development of targeted therapies that could mitigate the effects of LPA and ceramides on heart failure. Serve as a comprehensive resource for clinicians and researchers interested in the molecular biology of heart failure, aiding in better diagnostic and therapeutic decisions.

RECENT FINDINGS

Recent findings have shed light on the central role of bioactive lipids, specifically lysophosphatidic acid (LPA) and ceramides, in heart failure pathology. Traditional studies have emphasized factors such as hypoxia-mediated cardiomyocyte loss and neurohormonal activation in the development of heart failure. Emerging research has elucidated the intricacies of bioactive lipid-mediated inflammation in cardiac remodeling and the development of heart failure. Studies have shown that LPA and ceramides contribute to the pathogenesis of heart failure by promoting inflammation, fibrosis, and apoptosis in cardiac cells. Additionally, recent studies have identified potential targeted therapies that could mitigate the effects of bioactive lipids on heart failure, including LPA receptor antagonists and ceramide synthase inhibitors. These recent findings provide a promising avenue for the development of targeted therapies that could improve the diagnosis and treatment of heart failure. In this review, we highlight the pivotal role of inflammation induced by bioactive lipid signaling and its influence on the pathogenesis of heart failure. By critically assessing the existing literature, we provide a comprehensive resource for clinicians and researchers interested in the molecular mechanisms of heart failure. Our review aims to bridge the gap between basic research and clinical practice by providing actionable insights and a foundation for the development of targeted therapies that could mitigate the effects of bioactive lipids on heart failure. We hope that this review will aid in better diagnostic and therapeutic decisions, further advancing our collective understanding and management of heart failure.

Autotaxin and Lysophosphatidate Signaling: Prime Targets for Mitigating Therapy Resistance in Breast Cancer

Overcoming and preventing cancer therapy resistance is the most pressing challenge in modern breast cancer management. Consequently, most modern breast cancer research is aimed at understanding and blocking these therapy resistance mechanisms. One increasingly promising therapeutic target is the autotaxin (ATX)-lysophosphatidate (LPA)-lipid phosphate phosphatase (LPP) axis. Extracellular LPA, produced from albumin-bound lysophosphatidylcholine by ATX and degraded by the ecto-activity of the LPPs, is a potent cell-signaling mediator of tumor growth, invasion, angiogenesis, immune evasion, and resistance to cancer treatment modalities. LPA signaling in the post-natal organism has central roles in physiological wound healing, but these mechanisms are subverted to fuel pathogenesis in diseases that arise from chronic inflammatory processes, including cancer. Over the last 10 years, our understanding of the role of LPA signaling in the breast tumor microenvironment has begun to mature. Tumor-promoting inflammation in breast cancer leads to increased ATX production within the tumor microenvironment. This results in increased local concentrations of LPA that are maintained in part by decreased overall cancer cell LPP expression that would otherwise more rapidly break it down. LPA signaling through six G-protein-coupled LPA receptors expressed by cancer cells can then activate virtually every known tumorigenic pathway. Consequently, to target therapy resistance and tumor growth mediated by LPA signaling, multiple inhibitors against the LPA signaling axis are entering clinical trials. In this review, we summarize recent developments in LPA breast cancer biology, and illustrate how these novel therapeutics against the LPA signaling pathway may be excellent adjuncts to extend the efficacy of evolving breast cancer treatments.

Role of cell rearrangement and related signaling pathways in the dynamic process of tip cell selection

Angiogenesis is a complex, highly-coordinated and multi-step process of new blood vessel formation from pre-existing blood vessels. When initiated, the sprouting process is spearheaded by the specialized endothelial cells (ECs) known as tip cells, which guide the organization of accompanying stalk cells and determine the function and morphology of the finally-formed blood vessels. Recent studies indicate that the orchestration and coordination of angiogenesis involve dynamic tip cell selection, which is the competitive selection of cells to lead the angiogenic sprouts. Therefore, this review attempt to summarize the underlying mechanisms involved in tip cell specification in a dynamic manner to enable readers to gain a systemic and overall understanding of tip cell formation, involving cooperative interaction of cell rearrangement with Notch and YAP/TAZ signaling. Various mechanical and chemical signaling cues are integrated to ensure the right number of cells at the right place during angiogenesis, thereby precisely orchestrating morphogenic functions that ensure correct patterning of blood vessels. Video Abstract.

Cooperative Response to Endocardial Notch Reveals Interaction With Hippo Pathway

BACKGROUND

The endocardium is a crucial signaling center for cardiac valve development and maturation. Genetic analysis has identified several human endocardial genes whose inactivation leads to bicuspid aortic valve formation and calcific aortic valve disease, but knowledge is very limited about the role played in valve development and disease by noncoding endocardial regulatory regions and upstream factors.

METHODS

We manipulated Notch signaling in mouse embryonic endocardial cells by short-term and long-term coculture with OP9 stromal cells expressing Notch ligands and inhibition of Notch activity. We examined the transcriptional profile and chromatin accessibility landscape for each condition, integrated transcriptomic, transcription factor occupancy, chromatin accessibility, and proteomic datasets. We generated in vitro and in vivo models with CRISPR-Cas9-edited deletions of various noncoding regulatory elements and validated their regulatory potential.

RESULTS

We identified primary and secondary transcriptional responses to Notch ligands in the mouse embryonic endocardium, and a NOTCH-dependent transcriptional signature in valve development and disease. By defining the changes in the chromatin accessibility landscape and integrating with the landscape in developing mouse endocardium and adult human valves, we identify potential noncoding regulatory elements, validated selected candidates, propose interacting cofactors, and define the timeframe of their regulatory activity. Additionally, we found cooperative transcriptional repression with Hippo pathway by inhibiting nuclear Yap (Yes-associated protein) activity in the endocardium during cardiac valve development.

CONCLUSIONS

Sequential Notch-dependent transcriptional regulation in the embryonic endocardium involves multiple factors. Notch activates certain noncoding elements through these factors and simultaneously suppresses elements that could hinder cardiac valve development and homeostasis. Biorxviv: https://www.biorxiv.org/content/10.1101/2023.03.23.533882v1.full.

Vasculature is getting Hip(po): Hippo signaling in vascular development and disease

The Hippo signaling pathway regulates developmental organ growth, regeneration, and cell fate decisions. Although the role of the Hippo pathway, and its transcriptional effectors YAP and TAZ, has been well documented in many cell types and species, only recently have the roles for this pathway come to light in vascular development and disease. Experiments in mice, zebrafish, and in vitro have uncovered roles for the Hippo pathway, YAP, and TAZ in vasculogenesis, angiogenesis, and lymphangiogenesis. In addition, the Hippo pathway has been implicated in vascular cancers and cardiovascular diseases, thus identifying it as a potential therapeutic target for the treatment of these conditions. However, despite recent advances, Hippo's role in the vasculature is still underappreciated compared with its role in epithelial tissues. In this review, we appraise our current understanding of the Hippo pathway in blood and lymphatic vessel development and highlight the current knowledge gaps and opportunities for further research.

Association between plasma lysophosphatidic acid levels and bronchopulmonary dysplasia in extremely preterm infants: A prospective study

BACKGROUND

Lysophosphatidic acid (LPA) is implicated in bronchopulmonary dysplasia (BPD) pathogenesis, but clinical evidence is lacking. This study aimed to investigate LPA levels in preterm infants with and without BPD and explore LPA as a biomarker for predicting BPD occurrence.

METHODS

Premature infants with a gestational age of <28 weeks or a birth weight of <1000 g were enrolled. Blood samples were collected at postnatal day (PD) 7, 28, and postmenstrual age (PMA) 36 weeks, and plasma LPA levels were measured using a commercial ELISA kit. Receiver operating characteristic curve (ROC) curve analysis determined the PD 28 cutoff for LPA, and multivariable regression analyzed LPA's independent contribution to BPD and exploratory outcomes.

RESULT

Among the 91 infants enrolled in this study, 35 were classified into the non-BPD group and 56 into the BPD group. Infants with BPD had higher plasma LPA levels at PD 28 (6.467 vs. 4.226 μg/mL, p = 0.034) and PMA 36 weeks (2.330 vs. 1.636 μg/mL, p = 0.001). PD 28 LPA level of 6.132 μg/mL was the cutoff for predicting BPD development. Higher PD 28 LPA levels (≥6.132 μg/mL) independently associated with BPD occurrence (OR 3.307, 95% CI 1.032-10.597, p = 0.044). Higher LPA levels correlated with longer oxygen therapy durations [regression coefficients (β) 0.147, 95% CI 0.643-16.133, p = .034].

CONCLUSIONS

Infants with BPD had higher plasma LPA levels at PD 28 and PMA 36 weeks. Higher PD 28 LPA levels independently associated with an increased BPD risk.

LIPH contributes to glycolytic phenotype in pancreatic ductal adenocarcinoma by activating LPA/LPAR axis and maintaining ALDOA stability

BACKGROUND

LIPH, a membrane-associated phosphatidic acid-selective phospholipase A1a, can produce LPA (Lysophosphatidic acid) from PA (Phosphatidic acid) on the outer leaflet of the plasma membrane. It is well known that LIPH dysfunction contributes to lipid metabolism disorder. Previous study shows that LIPH was found to be a potential gene related to poor prognosis with pancreatic ductal adenocarcinoma (PDAC). However, the biological functions of LIPH in PDAC remain unclear.

METHODS

Cell viability assays were used to evaluate whether LIPH affected cell proliferation. RNA sequencing and immunoprecipitation showed that LIPH participates in tumor glycolysis by stimulating LPA/LPAR axis and maintaining aldolase A (ALDOA) stability in the cytosol. Subcutaneous, orthotopic xenograft models and patient-derived xenograft PDAC model were used to evaluate a newly developed Gemcitabine-based therapy.

RESULTS

LIPH was significantly upregulated in PDAC and was related to later pathological stage and poor prognosis. LIPH downregulation in PDAC cells inhibited colony formation and proliferation. Mechanistically, LIPH triggered PI3K/AKT/HIF1A signaling via LPA/LPAR axis. LIPH also promoted glycolysis and de novo synthesis of glycerolipids by maintaining ALDOA stability in the cytosol. Xenograft models show that PDAC with high LIPH expression levels was sensitive to gemcitabine/ki16425/aldometanib therapy without causing discernible side effects.

CONCLUSION

LIPH directly bridges PDAC cells and tumor microenvironment to facilitate aberrant aerobic glycolysis via activating LPA/LPAR axis and maintaining ALDOA stability, which provides an actionable gemcitabine-based combination therapy with limited side effects.

Ultra-Deep Sequencing Reveals the Mutational Landscape of Classical Hodgkin Lymphoma

The malignant Hodgkin and Reed Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL) are scarce in affected lymph nodes, creating a challenge to detect driver somatic mutations. As an alternative to cell purification techniques, we hypothesized that ultra-deep exome sequencing would allow genomic study of HRS cells, thereby streamlining analysis and avoiding technical pitfalls. To test this, 31 cHL tumor/normal pairs were exome sequenced to approximately 1,000× median depth of coverage. An orthogonal error-corrected sequencing approach verified >95% of the discovered mutations. We identified mutations in genes novel to cHL including: CDH5 and PCDH7, novel stop gain mutations in IL4R, and a novel pattern of recurrent mutations in pathways regulating Hippo signaling. As a further application of our exome sequencing, we attempted to identify expressed somatic single-nucleotide variants (SNV) in single-nuclei RNA sequencing (snRNA-seq) data generated from a patient in our cohort. Our snRNA analysis identified a clear cluster of cells containing a somatic SNV identified in our deep exome data. This cluster has differentially expressed genes that are consistent with genes known to be dysregulated in HRS cells (e.g., PIM1 and PIM3). The cluster also contains cells with an expanded B-cell clonotype further supporting a malignant phenotype. This study provides proof-of-principle that ultra-deep exome sequencing can be utilized to identify recurrent mutations in HRS cells and demonstrates the feasibility of snRNA-seq in the context of cHL. These studies provide the foundation for the further analysis of genomic variants in large cohorts of patients with cHL.

SIGNIFICANCE

Our data demonstrate the utility of ultra-deep exome sequencing in uncovering somatic variants in Hodgkin lymphoma, creating new opportunities to define the genes that are recurrently mutated in this disease. We also show for the first time the successful application of snRNA-seq in Hodgkin lymphoma and describe the expression profile of a putative cluster of HRS cells in a single patient.

Hypoxia-induced AFAP1L1 regulates pathological neovascularization via the YAP-DLL4-NOTCH axis

BACKGROUND

Pathological neovascularization plays a pivotal role in the onset and progression of tumors and neovascular eye diseases. Despite notable advancements in the development of anti-angiogenic medications that target vascular endothelial growth factor (VEGF) and its receptors (VEGFRs), the occurrence of adverse reactions and drug resistance has somewhat impeded the widespread application of these drugs. Therefore, additional investigations are warranted to explore alternative therapeutic targets. In recent years, owing to the swift advancement of high-throughput sequencing technology, pan-cancer analysis and single-cell sequencing analysis have emerged as pivotal methodologies and focal areas within the domain of omics research, which is of great significance for us to find potential targets related to the regulation of pathological neovascularization.

METHODS

Pan-cancer analysis and scRNA-seq data analysis were employed to forecast the association between Actin filament-associated protein 1 like 1 (AFAP1L1) and the development of tumors and endothelial cells. Tumor xenograft model and ocular pathological neovascularization model were constructed as well as Isolectin B4 (IsoB4) staining and immunofluorescence staining were used to assess the effects of AFAP1L1 on the progression of neoplasms and neovascular eye diseases in vivo. Transwell assay, wound scratch assay, tube forming assay, three-dimensional germination assay, and rhodamine-phalloidin staining were used to evaluate the impact of AFAP1L1 on human umbilical vein endothelial cells (HUVECs) function in vitro; Dual luciferase reporting, qRT-PCR and western blot were used to investigate the upstream and downstream mechanisms of pathological neovascularization mediated by AFAP1L1.

RESULTS

Our investigation revealed that AFAP1L1 plays a crucial role in promoting the development of various tumors and demonstrates a strong correlation with endothelial cells. Targeted suppression of AFAP1L1 specifically in endothelial cells in vivo proves effective in inhibiting tumor formation and ocular pathological neovascularization. Mechanistically, AFAP1L1 functions as a hypoxia-related regulatory protein that can be activated by HIF-1α. In vitro experiments demonstrated that reducing AFAP1L1 levels can reverse hypoxia-induced excessive angiogenic capacity in HUVECs. The principal mechanism of angiogenesis inhibition entails the regulation of tip cell behavior through the YAP-DLL4-NOTCH axis.

CONCLUSION

In conclusion, AFAP1L1, a newly identified hypoxia-related regulatory protein, can be activated by HIF-1α. Inhibiting AFAP1L1 results in the inhibition of angiogenesis by suppressing the germination of endothelial tip cells through the YAP-DLL4-NOTCH axis. This presents a promising therapeutic target to halt the progression of tumors and neovascular eye disease.

YAP/TAZ: Molecular pathway and disease therapy

The Yes-associated protein and its transcriptional coactivator with PDZ-binding motif (YAP/TAZ) are two homologous transcriptional coactivators that lie at the center of a key regulatory network of Hippo, Wnt, GPCR, estrogen, mechanical, and metabolism signaling. YAP/TAZ influences the expressions of downstream genes and proteins as well as enzyme activity in metabolic cycles, cell proliferation, inflammatory factor expression, and the transdifferentiation of fibroblasts into myofibroblasts. YAP/TAZ can also be regulated through epigenetic regulation and posttranslational modifications. Consequently, the regulatory function of these mechanisms implicates YAP/TAZ in the pathogenesis of metabolism-related diseases, atherosclerosis, fibrosis, and the delicate equilibrium between cancer progression and organ regeneration. As such, there arises a pressing need for thorough investigation of YAP/TAZ in clinical settings. In this paper, we aim to elucidate the signaling pathways that regulate YAP/TAZ and explore the mechanisms of YAP/TAZ-induce diseases and their potential therapeutic interventions. Furthermore, we summarize the current clinical studies investigating treatments targeting YAP/TAZ. We also address the limitations of existing research on YAP/TAZ and propose future directions for research. In conclusion, this review aims to provide fresh insights into the signaling mediated by YAP/TAZ and identify potential therapeutic targets to present innovative solutions to overcome the challenges associated with YAP/TAZ.

The Hippo Pathway Effectors YAP/TAZ-TEAD Oncoproteins as Emerging Therapeutic Targets in the Tumor Microenvironment

Various cancer cell-associated intrinsic and extrinsic inputs act on YAP/TAZ proteins to mediate the hyperactivation of the TEAD transcription factor-based transcriptome. This YAP/TAZ-TEAD activity can override the growth-limiting Hippo tumor-suppressor pathway that maintains normal tissue homeostasis. Herein, we provide an integrated summary of the contrasting roles of YAP/TAZ during normal tissue homeostasis versus tumor initiation and progression. In addition to upstream factors that regulate YAP/TAZ in the TME, critical insights on the emerging functions of YAP/TAZ in immune suppression and abnormal vasculature development during tumorigenesis are illustrated. Lastly, we discuss the current methods that intervene with the YAP/TAZ-TEAD oncogenic signaling pathway and the emerging applications of combination therapies, gut microbiota, and epigenetic plasticity that could potentiate the efficacy of chemo/immunotherapy as improved cancer therapeutic strategies.

Lysophosphatidic Acid Receptor Signaling in the Human Breast Cancer Tumor Microenvironment Elicits Receptor-Dependent Effects on Tumor Progression

Lysophosphatidic acid receptors (LPARs) are six G-protein-coupled receptors that mediate LPA signaling to promote tumorigenesis and therapy resistance in many cancer subtypes, including breast cancer. Individual-receptor-targeted monotherapies are under investigation, but receptor agonism or antagonism effects within the tumor microenvironment following treatment are minimally understood. In this study, we used three large, independent breast cancer patient cohorts (TCGA, METABRIC, and GSE96058) and single-cell RNA-sequencing data to show that increased tumor LPAR1, LPAR4, and LPAR6 expression correlated with a less aggressive phenotype, while high LPAR2 expression was particularly associated with increased tumor grade and mutational burden and decreased survival. Through gene set enrichment analysis, it was determined that cell cycling pathways were enriched in tumors with low LPAR1, LPAR4, and LPAR6 expression and high LPAR2 expression. LPAR levels were lower in tumors over normal breast tissue for LPAR1, LPAR3, LPAR4, and LPAR6, while the opposite was observed for LPAR2 and LPAR5. LPAR1 and LPAR4 were highest in cancer-associated fibroblasts, while LPAR6 was highest in endothelial cells, and LPAR2 was highest in cancer epithelial cells. Tumors high in LPAR5 and LPAR6 had the highest cytolytic activity scores, indicating decreased immune system evasion. Overall, our findings suggest that potential compensatory signaling via competing receptors must be considered in LPAR inhibitor therapy.

The Role of Autotaxin and LPA Signaling in Embryonic Development, Pathophysiology and Cancer

Autotaxin (ATX) or Ectonucleotide Pyrophosphatase/Phosphodiesterase 2 (ENPP2) is a secreted enzyme with lysophospholipase D activity, with its primary function being the extracellular hydrolysis of lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA), a bioactive lipid [...].

The tissue-specific transcriptional landscape underlines the involvement of endothelial cells in health and disease

Endothelial cells (ECs) that line vascular and lymphatic vessels are being increasingly recognized as important to organ function in health and disease. ECs participate not only in the trafficking of gases, metabolites, and cells between the bloodstream and tissues but also in the angiocrine-based induction of heterogeneous parenchymal cells, which are unique to their specific tissue functions. The molecular mechanisms regulating EC heterogeneity between and within different tissues are modeled during embryogenesis and become fully established in adults. Any changes in adult tissue homeostasis induced by aging, stress conditions, and various noxae may reshape EC heterogeneity and induce specific transcriptional features that condition a functional phenotype. Heterogeneity is sustained via specific genetic programs organized through the combinatory effects of a discrete number of transcription factors (TFs) that, at the single tissue-level, constitute dynamic networks that are post-transcriptionally and epigenetically regulated. This review is focused on outlining the TF-based networks involved in EC specialization and physiological and pathological stressors thought to modify their architecture.

Lysophosphatidic acid, a simple phospholipid with myriad functions

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

Endothelial FAT1 inhibits angiogenesis by controlling YAP/TAZ protein degradation via E3 ligase MIB2

Activation of endothelial YAP/TAZ signaling is crucial for physiological and pathological angiogenesis. The mechanisms of endothelial YAP/TAZ regulation are, however, incompletely understood. Here we report that the protocadherin FAT1 acts as a critical upstream regulator of endothelial YAP/TAZ which limits the activity of these transcriptional cofactors during developmental and tumor angiogenesis by promoting their degradation. We show that loss of endothelial FAT1 results in increased endothelial cell proliferation in vitro and in various angiogenesis models in vivo. This effect is due to perturbed YAP/TAZ protein degradation, leading to increased YAP/TAZ protein levels and expression of canonical YAP/TAZ target genes. We identify the E3 ubiquitin ligase Mind Bomb-2 (MIB2) as a FAT1-interacting protein mediating FAT1-induced YAP/TAZ ubiquitination and degradation. Loss of MIB2 expression in endothelial cells in vitro and in vivo recapitulates the effects of FAT1 depletion and causes decreased YAP/TAZ degradation and increased YAP/TAZ signaling. Our data identify a pivotal mechanism of YAP/TAZ regulation involving FAT1 and its associated E3 ligase MIB2, which is essential for YAP/TAZ-dependent angiogenesis.

An Update of G-Protein-Coupled Receptor Signaling and Its Deregulation in Gastric Carcinogenesis

G-protein-coupled receptors (GPCRs) belong to a cell surface receptor superfamily responding to a wide range of external signals. The binding of extracellular ligands to GPCRs activates a heterotrimeric G protein and triggers the production of numerous secondary messengers, which transduce the extracellular signals into cellular responses. GPCR signaling is crucial and imperative for maintaining normal tissue homeostasis. High-throughput sequencing analyses revealed the occurrence of the genetic aberrations of GPCRs and G proteins in multiple malignancies. The altered GPCRs/G proteins serve as valuable biomarkers for early diagnosis, prognostic prediction, and pharmacological targets. Furthermore, the dysregulation of GPCR signaling contributes to tumor initiation and development. In this review, we have summarized the research progress of GPCRs and highlighted their mechanisms in gastric cancer (GC). The aberrant activation of GPCRs promotes GC cell proliferation and metastasis, remodels the tumor microenvironment, and boosts immune escape. Through deep investigation, novel therapeutic strategies for targeting GPCR activation have been developed, and the final aim is to eliminate GPCR-driven gastric carcinogenesis.

Autotaxin facilitates selective LPA receptor signaling

Autotaxin (ATX; ENPP2) produces the lipid mediator lysophosphatidic acid (LPA) that signals through disparate EDG (LPA1-3) and P2Y (LPA4-6) G protein-coupled receptors. ATX/LPA promotes several (patho)physiological processes, including in pulmonary fibrosis, thus serving as an attractive drug target. However, it remains unclear if clinical outcome depends on how different types of ATX inhibitors modulate the ATX/LPA signaling axis. Here, we show that the ATX "tunnel" is crucial for conferring key aspects of ATX/LPA signaling and dictates cellular responses independent of ATX catalytic activity, with a preference for activation of P2Y LPA receptors. The efficacy of the ATX/LPA signaling responses are abrogated more efficiently by tunnel-binding inhibitors, such as ziritaxestat (GLPG1690), compared with inhibitors that exclusively target the active site, as shown in primary lung fibroblasts and a murine model of radiation-induced pulmonary fibrosis. Our results uncover a receptor-selective signaling mechanism for ATX, implying clinical benefit for tunnel-targeting ATX inhibitors.

Matrix stiffness regulates Notch signaling activity in endothelial cells

Notch signaling is critical for many developmental and disease-related processes. It is widely accepted that Notch has a mechanotransduction module that regulates receptor cleavage. However, the role of biomechanical properties of the cellular environment in Notch signaling in general is still poorly understood. During angiogenesis, differentiation of endothelial cells into tip and stalk cells is regulated by Notch signaling, and remodeling of the extracellular matrix occurs. We investigated the influence of substrate stiffness on the Notch signaling pathway in endothelial cells. Using stiffness-tuned polydimethylsiloxane (PDMS) substrates, we show that activity of the Notch signaling pathway inversely correlates with a physiologically relevant range of substrate stiffness (i.e. increased Notch signaling activity on softer substrates). Trans-endocytosis of the Notch extracellular domain, but not the overall endocytosis, is regulated by substrate stiffness, and integrin cell-matrix connections are both stiffness dependent and influenced by Notch signaling. We conclude that mechanotransduction of Notch activation is modulated by substrate stiffness, highlighting the role of substrate rigidity as an important cue for signaling. This might have implications in pathological situations associated with stiffening of the extracellular matrix, such as tumor growth.

Nanoceria-GO-intercalated multicellular spheroids revascularize and salvage critical ischemic limbs through anti-apoptotic and pro-angiogenic functions

Critical limb ischemia (CLI) is a serious form of peripheral arterial disease that involves severe blockage of blood flow in lower extremities, often leading to foot necrosis and limb loss. Lack of blood flow and high pro-inflammation with overproduced reactive oxygen species (ROS) in CLI aggravate the degenerative events. Among other therapies, cell delivery is considered potential for restoring regenerative capacity, and preservation of cell survival under high oxidative stress has been challenging and prerequisite to harness cellular functions. Here, we introduce a multicellular delivery system that is intercalated with nanoceria-decorated graphene oxide (CeGO), which is considered to have high ROS scavenging ability while providing cell-matrix interaction signals. The CeGO nano-microsheets (8-nm-nanoceria/0.9-μm-GO) incorporated in HUVEC/MSC (7/3) could form cell-material hybrid spheroids mediated by cellular contraction. Under in vitro oxidative-stress-challenge with H₂O₂, the CeGO-intercalation enhanced the survival and anti-apoptotic capacity of cellular spheroids. Pro-angiogenic events of cellular spheroids, including cell sprouting and expression of angiogenic markers (HIF1α, VEGF, FGF2, eNOS) were significantly enhanced by the CeGO-intercalation. Proteomics analysis also confirmed substantial up-regulation of a series of angiogenesis-related secretome molecules. Such pro-angiogenic events with CeGO-intercalation were proven to be mediated by the APE/Ref-1 signaling pathway. When delivered to ischemic hindlimb in mice, the CeGO-cell spheroids could inhibit the accumulation of in vivo ROS rapidly, preserving high cell survival rate (cells were more proliferative and less apoptotic vs. those in cell-only spheroids), and up-regulated angiogenic molecular expressions. Monitoring over 28 days revealed significantly enhanced blood reperfusion and tissue recovery, and an ultimate limb salvage with the CeGO-cell delivery (∼60% salvaged vs. ∼29% in cell-only delivery vs. 0% in ischemia control). Together, the CeGO intercalated in HUVEC/MSC delivery is considered a potential nano-microplatform for CLI treatment, by scavenging excessive ROS and enhancing transplanted cell survival, while stimulating angiogenic events, which collectively help revascularization and tissue recovery, salvaging critical ischemic limbs.

Lysophosphatidic acid signaling via LPA6 : A negative modulator of developmental oligodendrocyte maturation

The developmental process of central nervous system (CNS) myelin sheath formation is characterized by well-coordinated cellular activities ultimately ensuring rapid and synchronized neural communication. During this process, myelinating CNS cells, namely oligodendrocytes (OLGs), undergo distinct steps of differentiation, whereby the progression of earlier maturation stages of OLGs represents a critical step toward the timely establishment of myelinated axonal circuits. Given the complexity of functional integration, it is not surprising that OLG maturation is controlled by a yet fully to be defined set of both negative and positive modulators. In this context, we provide here first evidence for a role of lysophosphatidic acid (LPA) signaling via the G protein-coupled receptor LPA6 as a negative modulatory regulator of myelination-associated gene expression in OLGs. More specifically, the cell surface accessibility of LPA6 was found to be restricted to the earlier maturation stages of differentiating OLGs, and OLG maturation was found to occur precociously in Lpar6 knockout mice. To further substantiate these findings, a novel small molecule ligand with selectivity for preferentially LPA6 and LPA6 agonist characteristics was functionally characterized in vitro in primary cultures of rat OLGs and in vivo in the developing zebrafish. Utilizing this approach, a negative modulatory role of LPA6 signaling in OLG maturation could be corroborated. During development, such a functional role of LPA6 signaling likely serves to ensure timely coordination of circuit formation and myelination. Under pathological conditions as seen in the major human demyelinating disease multiple sclerosis (MS), however, persistent LPA6 expression and signaling in OLGs can be seen as an inhibitor of myelin repair. Thus, it is of interest that LPA6 protein levels appear elevated in MS brain samples, thereby suggesting that LPA6 signaling may represent a potential new druggable pathway suitable to promote myelin repair in MS.

TKF, a mexicanolide-type limonoid derivative, suppressed hepatic stellate cells activation and liver fibrosis through inhibition of the YAP/Notch3 pathway

BACKGROUND

Liver fibrosis is a common scarring response and may ultimately lead to liver cancer, unfortunately, there is currently no effective antifibrotic drug approved for human use. Limonoids exhibit a broad spectrum of biological activities; however, the potential role of limonoids against fibrosis is largely unknown.

PURPOSE

This study investigates the antifibrotic activities and potential mechanisms of TKF (3-tigloyl-khasenegasin F), a natural mexicanolide-type limonoid derivative.

STUDY DESIGN/METHODS

Two well-established mouse models (CCl₄ challenge and bile duct ligation) were used to assess anti-fibrotic effects of TKF in vivo. Human hepatic stellate cell (HSC) line LX-2 and mouse primary hepatic stellate cells (pHSCs) also served as in vitro liver fibrosis models.

RESULT

TKF administration significantly attenuated hepatic histopathological injury and collagen accumulation and suppressed fibrogenesis-associated gene expression including Col1a1, Acta2, and Timp1. In LX-2 cells and mouse pHSCs, TKF dose-dependently suppressed HSC activation and the expression levels of fibrogenic markers. Mechanistic studies showed that TKF inhibited Notch3-Hes1 and YAP signalings in vivo and in vitro. Furthermore, YAP inhibition or knockdown downregulated the Notch3 expression; however, Notch3 inhibition or knockdown did not affect the level of YAP in activated HSC. We revealed that TKF inhibited Notch3-Hes1 activation and downregulated hepatic fibrogenic gene expression via inhibiting YAP.

CONCLUSION

The therapeutic benefit of TKF against liver fibrosis results from inhibition of YAP and Notch3-Hes1 pathways, indicating that TKF may be a novel therapeutic candidate for liver fibrosis.

Elucidating the binding mechanism of LPA species and analogs in an LPA4 receptor homology model

Lysophosphatidic acid receptor 4 (LPA₄) has emerged as a potential therapeutic target for the treatment of a variety of diseases, including cancer and obesity-induced diabetes, but its structure remains to be revealed. In the present work, a homology model of LPA₄ was built for studying the binding mechanism of LPA species and analogs. Then five selected LPA species and analogs with structural variations in their phosphate groups, substitutions on the glycerol backbone, and fatty acyl chains were docked into the LPA₄ model, followed by molecular dynamics simulations and energy analyses. The computational results revealed that the aliphatic residues located at the vertical cleft of LPA₄ may form a hydrophobic environment for the fatty acyl moiety of LPA species and their analogs. Meanwhile, the positively charged residues in the central cavity of LPA₄ may form ionic interactions with the negatively charged hydrophilic head group of LPA species and their analogs. In addition, it was noted that a different binding mode of the hydrophilic head group in each species with the central cavity of the LPA₄ might lead to a special rearrangement of the fatty acyl moiety. Taken together, these results may facilitate understanding of the activation mechanism of LPA₄ and help design selective ligands to modulate its function for therapeutic purposes.

Lysophosphatidic Acid Induced Apoptosis, DNA Damage, and Oxidative Stress in Spinal Cord Neurons by Upregulating LPA4/LPA6 Receptors

Lysophosphatidic acid (LPA) has disruptive effects on lumbar spinal stenosis (LSS). Recently, LPA has been reported to be involved in spinal cord neuronal injury and toxicity, promoting the pathogenesis of LSS. However, the exact effects of LPA on spinal cord neurons remain unknown. The purpose of this study is to investigate the effects of LPA (18 : 1) on spinal cord neuronal cytotoxicity, apoptosis, DNA damage, and oxidative stress. After clinical detection of LPA secretion, spinal cord neurons were treated with LPA (18 : 1); cell viability was analyzed by MTT assay, and LDH leakage was detected by LDH kit; cell apoptosis was detected by flow cytometry; ROS production was measured by DCFDA staining and MitoSOX Red Staining; the activation of the Gα12/Gα13 signaling pathway was detected by serum response factor response element (SRF-RE) luciferase reporter gene; the relationship among LPA, LPA4/6, and ROCK was examined by western blotting. In spinal cord neurons treated with LPA (18 : 1), cellular activity decreased and LDH release increased. The Rho kinase inhibitor (Y-27632) can attenuate LPA-induced apoptosis, DNA damage, and oxidative stress in spinal cord neurons. Moreover mechanistic investigation indicated that LPA (18 : 1) activates Gα12/13–Rho–ROCK2-induced apoptosis, DNA damage, and oxidative stress in spinal cord neurons by upregulating LPA4/LPA6 receptors. Further, the Rho kinase inhibitor Y-27632 attenuates the effects of LPA by downregulating LPA4/LPA6 receptors. Taken together, the possible mechanism by which LPA secretion in LSS patients aggravates patient injury was further elucidated using an LPA-induced spinal cord neuronal injury cell model in vitro.

LPA2 Contributes to Vascular Endothelium Homeostasis and Cardiac Remodeling After Myocardial Infarction

RATIONALE

Myocardial infarction (MI) is one of the most dangerous adverse cardiovascular events. Our previous study found that lysophosphatidic acid (LPA) is increased in human peripheral blood after MI, and LPA has a protective effect on the survival and proliferation of various cell types. However, the role of LPA and its receptors in MI is less understood.

OBJECTIVES

To study the unknown role of LPA and its receptors in heart during MI.

METHODS AND RESULTS

In this study, we found that mice also had elevated LPA level in peripheral blood, as well as increased cardiac expression of its receptor LPA₂ in the early stages after MI. With adult and neonate MI models in global Lpar2 knockout (Lpar2-KO) mice, we found Lpar2 deficiency increased vascular leak leading to disruption of its homeostasis, so as to impaired heart function and increased early mortality. Histological examination revealed larger scar size, increased fibrosis, and reduced vascular density in the heart of Lpar2-KO mice. Furthermore, Lpar2-KO also attenuated blood flow recovery after femoral artery ligation with decreased vascular density in gastrocnemius. Our study revealed that Lpar2 was mainly expressed and altered in cardiac endothelial cells during MI, and use of endothelial-specific Lpar2 knockout mice phenocopied the global knockout mice. Additionally, adenovirus-Lpar2 and pharmacologically activated LPA₂ significantly improved heart function, reduced scar size, increased vascular formation, and alleviated early mortality by maintaining vascular homeostasis owing to protecting vessels from leakage. Mechanistic studies demonstrated that LPA-LPA₂ signaling could promote endothelial cell proliferation through PI3K-Akt/PLC-Raf1-Erk pathway and enhanced endothelial cell tube formation via PKD1-CD36 signaling.

CONCLUSIONS

Our results indicate that endothelial LPA-LPA₂ signaling promotes angiogenesis and maintains vascular homeostasis, which is vital for restoring blood flow and repairing tissue function in ischemic injuries. Targeting LPA-LPA₂ signal might have clinical therapeutic potential to protect the heart from ischemic injury.

Autotaxin Activity in Chronic Subdural Hematoma: A Prospective Clinical Study

Autotaxin (ATX) is the ectoenzyme producing the bulk of lysophosphatidic acid (LPA) in circulation. ATX and LPA-mediated signaling (the ATX-LPA axis) play critical roles in the vascular and nervous system development. In adults, this axis contributes to diverse processes, including coagulation, inflammation, fibroproliferation and angiogenesis under physiological and/or pathophysiological conditions. Given evidence implicating several of these processes in chronic subdural hematoma (CSDH) pathogenesis and development, we assessed ATX activity in CSDH patients. Twenty-eight patients were recruited. Blood and hematoma fluid were collected. Enzymatic assays were used to establish serum and hematoma ATX activity. Enzyme-linked immunosorbent assays were used to establish hematoma beta trace (BT) levels, a cerebrospinal fluid (CSF) marker, in a hematoma. ATX activity was nearly three folds higher in hematoma compared to serum (P < 0.001). There was no significant correlation between BT levels and ATX activity in a hematoma. The present results show, for the first time, that ATX is catalytically active in the hematoma fluid of CSDH patients. Moreover, our findings of significantly elevated ATX activity in hematoma compared to serum, implicate the ATX-LPA axis in CSDH pathophysiology. The CSF origin of ATX could not be inferred with the present results. Additional research is warranted to establish the significance of the ATX-LPA axis in CSDH and its potential as a biomarker and/or therapeutic target.

The regulation of yes-associated protein/transcriptional coactivator with PDZ-binding motif and their roles in vascular endothelium

Normal endothelial function plays a pivotal role in maintaining cardiovascular homeostasis, while endothelial dysfunction causes the occurrence and development of cardiovascular diseases. Yes-associated protein (YAP) and its homolog transcriptional co-activator with PDZ-binding motif (TAZ) serve as crucial nuclear effectors in the Hippo signaling pathway, which are regulated by mechanical stress, extracellular matrix stiffness, drugs, and other factors. Increasing evidence supports that YAP/TAZ play an important role in the regulation of endothelial-related functions, including oxidative stress, inflammation, and angiogenesis. Herein, we systematically review the factors affecting YAP/TAZ, downstream target genes regulated by YAP/TAZ and the roles of YAP/TAZ in regulating endothelial functions, in order to provide novel potential targets and effective approaches to prevent and treat cardiovascular diseases.

Compensatory Upregulation of LPA2 and Activation of the PI3K-Akt Pathway Prevent LPA5-Dependent Loss of Intestinal Epithelial Cells in Intestinal Organoids

Renewal of the intestinal epithelium is orchestrated by regenerative epithelial proliferation within crypts. Recent studies have shown that lysophosphatidic acid (LPA) can maintain intestinal epithelial renewal in vitro and conditional deletion of Lpar5 (Lpar5iKO) in mice ablates the intestinal epithelium and increases morbidity. In contrast, constitutive Lpar5 deletion (Lpar5cKO) does not cause a defect in intestinal crypt regeneration. In this study, we investigated whether another LPA receptor (LPAR) compensates for constitutive loss of LPA5 function to allow regeneration of intestinal epithelium. In Lpar5cKO intestinal epithelial cells (IECs), Lpar2 was upregulated and blocking LPA2 function reduced proliferation and increased apoptosis of Lpar5cKO IECs. Similar to Lpar5cKO mice, the absence of Lpar2 (Lpar2-/-) resulted in upregulation of Lpar5 in IECs, indicating that LPA2 and LPA5 reciprocally compensate for the loss of each other. Blocking LPA2 in Lpar5cKO enteroids reduced phosphorylation of Akt, indicating that LPA2 maintains the growth of Lpar5cKO enteroids through activation of the PI3K-Akt pathway. The present study provides evidence that loss of an LPAR can be compensated by another LPAR. This ability to compensate needs to be considered in studies aimed to define receptor functions or test the efficacy of a LPAR-targeting drug using genetically engineered animal models.

YAP1/TAZ activity maintains vascular integrity and organismal survival

Radiation therapy is one of the major treatment modalities for patients with cancers. However, ionizing radiation (IR) damages not only cancer cells but also the surrounding vascular endothelial cells (ECs). Hippo pathway effector genes Yap1 and Taz are the two transcriptional coactivators that have crucial roles in tissue homeostasis and vascular integrity in various organs. However, their function in adult ECs at the steady state and after IR is poorly understood. Here, we report sex- and context-dependent roles of endothelial YAP1/TAZ in maintaining vascular integrity and organismal survival. EC-specific Yap1/Taz deletion compromised systemic vascular integrity, resulting in lethal circulation failure preferentially in male mice. Furthermore, EC-specific Yap1/Taz deletion induced acute lethality upon sublethal IR that was closely associated with exacerbated systemic vascular dysfunction and circulation failure. Consistent with these findings, RNA-seq analysis revealed downregulation of tight junction genes in Yap1/Taz-deleted ECs. Collectively, our findings highlight the importance of endothelial YAP1/TAZ for maintaining adult vascular function, which may provide clinical implications for preventing organ injury after radiation therapy.

Self-Sustained Regulation or Self-Perpetuating Dysregulation: ROS-dependent HIF-YAP-Notch Signaling as a Double-Edged Sword on Stem Cell Physiology and Tumorigenesis

Organ development, homeostasis, and repair often rely on bidirectional, self-organized cell-niche interactions, through which cells select cell fate, such as stem cell self-renewal and differentiation. The niche contains multiplexed chemical and mechanical factors. How cells interpret niche structural information such as the 3D topology of organs and integrate with multiplexed mechano-chemical signals is an open and active research field. Among all the niche factors, reactive oxygen species (ROS) have recently gained growing interest. Once considered harmful, ROS are now recognized as an important niche factor in the regulation of tissue mechanics and topology through, for example, the HIF-YAP-Notch signaling pathways. These pathways are not only involved in the regulation of stem cell physiology but also associated with inflammation, neurological disorder, aging, tumorigenesis, and the regulation of the immune checkpoint molecule PD-L1. Positive feedback circuits have been identified in the interplay of ROS and HIF-YAP-Notch signaling, leading to the possibility that under aberrant conditions, self-organized, ROS-dependent physiological regulations can be switched to self-perpetuating dysregulation, making ROS a double-edged sword at the interface of stem cell physiology and tumorigenesis. In this review, we discuss the recent findings on how ROS and tissue mechanics affect YAP-HIF-Notch-PD-L1 signaling, hoping that the knowledge can be used to design strategies for stem cell-based and ROS-targeting therapy and tissue engineering.

Regulation of Hippo signaling by metabolic pathways in cancer

Hippo signaling is known to maintain balance between cell proliferation and apoptosis via tight regulation of factors, such as metabolic cues, cell-cell contact, and mechanical cues. Cells directly recognize glucose, lipids, and other metabolic cues and integrate multiple signaling pathways, including Hippo signaling, to adjust their proliferation and apoptosis depending on nutrient conditions. Therefore, the dysregulation of the Hippo signaling pathway can promote tumor initiation and progression. Alteration in metabolic cues is considered a major factor affecting the risk of cancer formation and progression. It has recently been shown that the dysregulation of the Hippo signaling pathway, through diverse routes activated by metabolic cues, can lead to cancer with a poor prognosis. In addition, unique crosstalk between metabolic pathways and Hippo signaling pathways can inhibit the effect of anticancer drugs and promote drug resistance. In this review, we describe an integrated perspective of the relationship between the Hippo signaling pathway and metabolic signals in the context of cancer. We also characterize the mechanisms involved in changes in metabolism that are linked to the Hippo signaling pathway in the cancer microenvironment and propose several novel targets for anticancer drug treatment.

Notch signalling in healthy and diseased vasculature

Notch signalling is an evolutionarily highly conserved signalling mechanism governing differentiation and regulating homeostasis in many tissues. In this review, we discuss recent advances in our understanding of the roles that Notch signalling plays in the vasculature. We describe how Notch signalling regulates different steps during the genesis and remodelling of blood vessels (vasculogenesis and angiogenesis), including critical roles in assigning arterial and venous identities to the emerging blood vessels and regulation of their branching. We then proceed to discuss how experimental perturbation of Notch signalling in the vasculature later in development affects vascular homeostasis. In this review, we also describe how dysregulated Notch signalling, as a consequence of direct mutations of genes in the Notch pathway or aberrant Notch signalling output, contributes to various types of vascular disease, including CADASIL, Snedden syndrome and pulmonary arterial hypertension. Finally, we point out some of the current knowledge gaps and identify remaining challenges in understanding the role of Notch in the vasculature, which need to be addressed to pave the way for Notch-based therapies to cure or ameliorate vascular disease.

Gα12 and Gα13: Versatility in Physiology and Pathology

G protein-coupled receptors (GPCRs), as the largest family of receptors in the human body, are involved in the pathological mechanisms of many diseases. Heterotrimeric G proteins represent the main molecular switch and receive cell surface signals from activated GPCRs. Growing evidence suggests that Gα₁₂ subfamily (Gα_12/13)-mediated signaling plays a crucial role in cellular function and various pathological processes. The current research on the physiological and pathological function of Gα_12/13 is constantly expanding, Changes in the expression levels of Gα_12/13 have been found in a wide range of human diseases. However, the mechanistic research on Gα_12/13 is scattered. This review briefly describes the structural sequences of the Gα_12/13 isoforms and introduces the coupling of GPCRs and non-GPCRs to Gα_12/13. The effects of Gα_12/13 on RhoA and other signaling pathways and their roles in cell proliferation, migration, and immune cell function, are discussed. Finally, we focus on the pathological impacts of Gα_12/13 in cancer, inflammation, metabolic diseases, fibrotic diseases, and circulatory disorders are brought to focus.

Mechanoregulation of Vascular Endothelial Growth Factor Receptor 2 in Angiogenesis

The endothelial cells that compose the vascular system in the body display a wide range of mechanotransductive behaviors and responses to biomechanical stimuli, which act in concert to control overall blood vessel structure and function. Such mechanosensitive activities allow blood vessels to constrict, dilate, grow, or remodel as needed during development as well as normal physiological functions, and the same processes can be dysregulated in various disease states. Mechanotransduction represents cellular responses to mechanical forces, translating such factors into chemical or electrical signals which alter the activation of various cell signaling pathways. Understanding how biomechanical forces drive vascular growth in healthy and diseased tissues could create new therapeutic strategies that would either enhance or halt these processes to assist with treatments of different diseases. In the cardiovascular system, new blood vessel formation from preexisting vasculature, in a process known as angiogenesis, is driven by vascular endothelial growth factor (VEGF) binding to VEGF receptor 2 (VEGFR-2) which promotes blood vessel development. However, physical forces such as shear stress, matrix stiffness, and interstitial flow are also major drivers and effectors of angiogenesis, and new research suggests that mechanical forces may regulate VEGFR-2 phosphorylation. In fact, VEGFR-2 activation has been linked to known mechanobiological agents including ERK/MAPK, c-Src, Rho/ROCK, and YAP/TAZ. In vascular disease states, endothelial cells can be subjected to altered mechanical stimuli which affect the pathways that control angiogenesis. Both normalizing and arresting angiogenesis associated with tumor growth have been strategies for anti-cancer treatments. In the field of regenerative medicine, harnessing biomechanical regulation of angiogenesis could enhance vascularization strategies for treating a variety of cardiovascular diseases, including ischemia or permit development of novel tissue engineering scaffolds. This review will focus on the impact of VEGFR-2 mechanosignaling in endothelial cells (ECs) and its interaction with other mechanotransductive pathways, as well as presenting a discussion on the relationship between VEGFR-2 activation and biomechanical forces in the extracellular matrix (ECM) that can help treat diseases with dysfunctional vascular growth.

Arsenic trioxide activates yes-associated protein by lysophosphatidic acid metabolism to selectively induce apoptosis of vascular smooth muscle cells

Inhibition of vascular smooth muscle cells (VSMCs) proliferation without dysregulating endothelial cells (ECs) may provide an ideal therapy for in-stent restenosis. Due to its anti-proliferation effect on VSMCs and pro-endothelium effect, arsenic trioxide (ATO) has been used in a drug-eluting stent in a recent clinical trial. However, the underlying mechanism by which ATO achieves this effect has not been determined. In the present work, we showed that ATO induced apoptosis in VSMCs but not in ECs. Mechanistically, ATO achieved this through modulation of cellular metabolism to increase lysophosphatidic acid (LPA) in VSMCs, while LPA concentration was stable in ECs. The elevated LPA facilitated the nuclear accumulation and initiated the transcriptional function of Yes-associated protein (YAP) in VSMCs. YAP regulated the transcription of N6-Methyladenosine (m⁶A) modulators (Mettl14 and Wtap) to increase the m⁶A methylation levels of apoptosis-related genes to induce their high expression and exacerbate VSMCs apoptosis. On the other hand, YAP nuclear accumulation in ECs was not observed. Collectively, our data exhibited the molecular process involved in selective apoptosis of VSMCs induced by ATO.

Distinctive Roles of YAP and TAZ in Human Endothelial Progenitor Cells Growth and Functions

The hippo signaling pathway plays an essential role in controlling organ size and balancing tissue homeostasis. Its two main effectors, yes-associated protein (YAP) and WW domain-containing transcription regulator 1, WWTR1 or TAZ, have also been shown to regulate endothelial cell functions and angiogenesis. In this study, the functions of YAP and TAZ in human endothelial progenitor cells (EPCs) were investigated by a loss-of-function study using CRISPR/Cas9-mediated gene knockdown (KD). Depletion of either YAP or TAZ reduced EPC survival and impaired many of their critical functions, including migration, invasion, vessel-formation, and expression of pro-angiogenic genes. Notably, TAZ-KD EPCs exhibited more severe phenotypes in comparison to YAP-KD EPCs. Moreover, the conditioned medium derived from TAZ-KD EPCs reduced the survivability of human lung cancer cells and increased their sensitivity to chemotherapeutic agents. The overexpression of either wild-type or constitutively active TAZ rescued the impaired phenotypes of TAZ-KD EPCs and restored the expression of pro-angiogenic genes in those EPCs. In summary, we demonstrate the crucial role of Hippo signaling components, YAP and TAZ, in controlling several aspects of EPC functions that can potentially be used as a drug target to enhance EPC functions in patients.

Electrochemically derived nanographene oxide activates endothelial tip cells and promotes angiogenesis by binding endogenous lysophosphatidic acid

Graphene oxide (GO) exhibits good mechanical and physicochemical characteristics and has extensive application prospects in bone tissue engineering. However, its effect on angiogenesis is unclear, and its potential toxic effects are heavily disputed. Herein, we found that nanographene oxide (NGO) synthesized by one-step water electrolytic oxidation is smaller and shows superior biocompatibility. Moreover, NGO significantly enhanced angiogenesis in calvarial bone defect areas in vivo, providing a good microenvironment for bone regeneration. Endothelial tip cell differentiation is an important step in the initiation of angiogenesis. We verified that NGO activates endothelial tip cells by coupling with lysophosphatidic acid (LPA) in serum via strong hydrogen bonding interactions, which has not been reported. In addition, the mechanism by which NGO promotes angiogenesis was systematically studied. NGO-coupled LPA activates LPAR6 and facilitates the formation of migratory tip cells via Hippo/Yes-associated protein (YAP) independent of reactive oxygen species (ROS) stimulation or additional complex modifications. These results provide an effective strategy for the application of electrochemically derived NGO and more insight into NGO-mediated angiogenesis.

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Electrochemically derived nanographene oxide (NGO) has good cytocompatibility without upregulating reactive oxygen species.

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NGO exhibits better dispersibility and couples with endogenous lysophosphatidic acid (LPA) in body fluid.

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NGO enhances the angiogenesis by recruiting endogenous LPA and promoting endothelial tip cell formation.

An ATX-LPA6-Gα13-ROCK axis shapes and maintains caudal vein plexus in zebrafish

Lysophosphatidic acid (LPA) is a potential regulator of vascular formation derived from blood. In this study, we utilized zebrafish as a model organism to monitor the blood vessel formation in detail. Zebrafish mutant of ATX, an LPA-producing enzyme, had a defect in the caudal vein plexus (CVP). Pharmacological inhibition of ATX resulted in a fusion of the delicate vessels in the CVP to form large sac-like vessels. Mutant embryos of LPA₆ receptor and downstream Gα₁₃ showed the same phenotype. Administration of OMPT, a stable LPA-analog, induced rapid CVP constriction, which was attenuated significantly in the LPA₆ mutant. We also found that blood flow-induced CVP formation was dependent on ATX. The present study demonstrated that the ATX-LPA₆ axis acts cooperatively with blood flow and contributes to the formation and maintenance of the CVP by generating contractive force in endothelial cells.

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Blocking an ATX-LPA₆-Gα₁₃-ROCK axis causes malformation of the caudal vein plexus

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The axis also contributes to maintaining the fine structure of the caudal vein plexus

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Activation of LPA₆ induces vasoconstriction

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Caudal vein plexus formation evoked by blood flow is dependent on an ATX-LPA₆ axis

Substrate stiffness modulates endothelial cell function via the YAP-Dll4-Notch1 pathway

Endothelial cells adapt their functions as a consequence of sensing extracellular substrate stiffness; these alterations allow them to maintain their vascular structure and function. Substrate stiffness-mediated yes-associated protein 1 (YAP) activation plays an important role in mechano-transduction and pro-angiogenic phenotype of endothelial cells, and Delta-like ligand 4 (Dll4)-Notch1 signaling is closely related to angiogenesis; however, the impact of substrate stiffness-mediated interrelation of these pathways on endothelial cell functions remains elusive. We confirmed that endothelial cells on softer substrates not only elongate cellular aspects but also attenuate YAP activation compared to cells on stiffer substrates. Endothelial cells on softer substrates also upregulate the vascular endothelial growth factor receptor 1 (VEGFR1) and VEGFR2 mRNA expression that is enhanced by VEGF stimulation. We determined that endothelial cells on softer substrates increased Dll4 expression, but not Notch1 expression, via YAP signaling. Moreover, endothelial cells on soft substrates induced not only VEGFRs upregulation but also suppression of pro-inflammatory interleukin-6 and plasminogen activator inhibitor-1 mRNA expression and the facilitation of anti-coagulant thrombomodulin and pro-coagulant tissue factor mRNA expression. Our results suggest that endothelial cells activate the YAP-Dll4-Notch signaling pathway in response to substrate stiffness and dictate cellular function.

At the nuclear envelope of bone mechanobiology

The nuclear envelope and nucleoskeleton are emerging as signaling centers that regulate how physical information from the extracellular matrix is biochemically transduced into the nucleus, affecting chromatin and controlling cell function. Bone is a mechanically driven tissue that relies on physical information to maintain its physiological function and structure. Disorder that present with musculoskeletal and cardiac symptoms, such as Emery-Dreifuss muscular dystrophies and progeria, correlate with mutations in nuclear envelope proteins including Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, Lamin A/C, and emerin. However, the role of nuclear envelope mechanobiology on bone function remains underexplored. The mesenchymal stem cell (MSC) model is perhaps the most studied relationship between bone regulation and nuclear envelope function. MSCs maintain the musculoskeletal system by differentiating into multiple cell types including osteocytes and adipocytes, thus supporting the bone's ability to respond to mechanical challenge. In this review, we will focus on how MSC function is regulated by mechanical challenges both in vitro and in vivo within the context of bone function specifically focusing on integrin, β-catenin and YAP/TAZ signaling. The importance of the nuclear envelope will be explored within the context of musculoskeletal diseases related to nuclear envelope protein mutations and nuclear envelope regulation of signaling pathways relevant to bone mechanobiology in vitro and in vivo.