YAP promotes ocular neovascularization by modifying PFKFB3-driven endothelial glycolysis

Metabolic Regulation of Endothelial Cells: A New Era for Treating Wet Age-Related Macular Degeneration

Wet age-related macular degeneration (wet AMD) is a primary contributor to visual impairment and severe vision loss globally, but the prevailing treatments are often unsatisfactory. The development of conventional treatment strategies has largely been based on the understanding that the angiogenic switch of endothelial cells (ECs) is mainly dictated by angiogenic growth factors. Even though treatments targeting vascular endothelial growth factor (VEGF), like ranibizumab, are widely administered, more than half of patients still exhibit inadequate or null responses, suggesting the involvement of other pathogenic mechanisms. With advances in research in recent years, it has become well recognized that EC metabolic regulation plays an active rather than merely passive responsive role in angiogenesis. Disturbances of these metabolic pathways may lead to excessive neovascularization in angiogenic diseases such as wet AMD, therefore targeted modulation of EC metabolism represents a promising therapeutic strategy for wet AMD. In this review, we comprehensively discuss the potential applications of EC metabolic regulation in wet AMD treatment from multiple perspectives, including the involvement of ECs in wet AMD pathogenesis, the major endothelial metabolic pathways, and novel therapeutic approaches targeting metabolism for wet AMD.

The Hippo signalling pathway and its impact on eye diseases

The Hippo signalling pathway, an evolutionarily conserved kinase cascade, has been shown to be crucial for cell fate determination, homeostasis and tissue regeneration. Recent experimental and clinical studies have demonstrated that the Hippo signalling pathway is involved in the pathophysiology of ocular diseases. This article provides the first systematic review of studies on the regulatory and functional roles of mammalian Hippo signalling systems in eye diseases. More comprehensive studies on this pathway are required for a better understanding of the pathophysiology of eye diseases and the development of effective therapies.

PFKFB3 in neovascular eye disease: unraveling mechanisms and exploring therapeutic strategies

BACKGROUND

Neovascular eye disease is characterized by pathological neovascularization, with clinical manifestations such as intraocular exudation, bleeding, and scar formation, ultimately leading to blindness in millions of individuals worldwide. Pathologic ocular angiogenesis often occurs in common fundus diseases including proliferative diabetic retinopathy (PDR), age-related macular degeneration (AMD), and retinopathy of prematurity (ROP). Anti-vascular endothelial growth factor (VEGF) targets the core pathology of ocular angiogenesis.

MAIN BODY

In recent years, therapies targeting metabolism to prevent angiogenesis have also rapidly developed, offering assistance to patients with a poor prognosis while receiving anti-VEGF therapy and reducing the side effects associated with long-term VEGF usage. Phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a key enzyme in targeted metabolism, has been shown to have great potential, with antiangiogenic effects and multiple protective effects in the treatment of neovascular eye disease. In this review, we summarize the mechanisms of common types of neovascular eye diseases; discuss the protective effect and potential mechanism of targeting PFKFB3, including the related inhibitors of PFKFB3; and look forward to the future exploration directions and therapeutic prospects of PFKFB3 in neovascular eye disease.

CONCLUSION

Neovascular eye disease, the most common and severely debilitating retinal disease, is largely incurable, necessitating the exploration of new treatment methods. PFKFB3 has been shown to possess various potential protective mechanisms in treating neovascular eye disease. With the development of several drugs targeting PFKFB3 and their gradual entry into clinical research, targeting PFKFB3-mediated glycolysis has emerged as a promising therapeutic approach for the future of neovascular eye disease.

5-Aza-2'-Deoxycytidine Ameliorates Choroidal Neovascularization by Inhibiting the Wnt/β-Catenin Signaling Pathway

Purpose

Choroidal neovascularization (CNV) can constitute the final pathology of many ocular diseases and result in severe vision loss. Studies have demonstrated that DNA methylation is critical in retinal development, aging, and disorders. The current work investigated the effects and underlying mechanism of 5-Aza-2'-deoxycytidine (5-aza-dC), a suppressor of DNA methylation, in the pathological progression of CNV.

Methods

The DNA methylation profiles of retinal pigment epithelial (RPE)/choroidal complexes in normal and laser-induced CNV mice were assessed by Arraystar Mouse RefSeq Promoter Arrays. The CNV area and blood flow density and intensity were observed by optical coherence tomography angiography, and fluorescence leakage was examined by fundus fluorescein angiography in CNV mice with systemic administration of 5-aza-dC. The effects of 5-aza-dC on the biological functions of bEnd.3 cells were estimated by related assays. Notum gene promoter methylation was measured using bisulfite sequencing PCR. Methyltransferases and Wnt signaling-related genes were detected in animal and cell culture experiments by real-time PCR and immunoblot.

Results

Methyltransferases were upregulated, but Notum (a secretion inhibitor of Wnt signaling) was downregulated in the RPE/choroidal complexes of mice with experimental CNV. Intraperitoneal injection of 5-aza-dC inactivated the Wnt pathway and ameliorated the lesion area and the intensity and density of blood flow, as well as the degree of leakage in CNV. In vitro, vascular endothelial growth factor A (VEGFA) stimulation promoted methyltransferases expression and suppressed Notum expression, consequently activating Wnt signaling, whereas exogenous 5-aza-dC reversed VEGFA-induced hyperpermeability, proliferation, migration, and tube formation in bEnd.3 cells via demethylation of Notum promoter.

Conclusions

We observed that 5-aza-dC attenuates the growth of CNV by inhibiting the Wnt signaling pathway via promoter demethylation of the Wnt antagonist Notum. These findings provide a theoretical basis for methylation-based treatment with the Notum gene as a potential target for CNV treatment.

Hypoxia-induced P4HA1 overexpression promotes post-ischemic angiogenesis by enhancing endothelial glycolysis through downregulating FBP1

BACKGROUND

Angiogenesis is essential for tissue repair in ischemic diseases, relying on glycolysis as its primary energy source. Prolyl 4-hydroxylase subunit alpha 1 (P4HA1), the catalytic subunit of collagen prolyl 4-hydroxylase, is a glycolysis-related gene in cancers. However, its role in glycolysis-induced angiogenesis remains unclear.

METHODS

P4HA1 expression was modulated using adenoviruses. Endothelial angiogenesis was evaluated through 5-ethynyl-2'-deoxyuridine incorporation, transwell migration, and tube formation assays in vitro. In vivo experiments measured blood flow and capillary density in the hindlimb ischemia (HLI) model. Glycolytic stress assays, glucose uptake, lactate production, and quantitative reverse transcription-polymerase chain reaction (RT-PCR) were employed to assess glycolytic capacity. Transcriptome sequencing, validated by western blotting and RT-PCR, was utilized to determine underlying mechanisms.

RESULTS

P4HA1 was upregulated in endothelial cells under hypoxia and in the HLI model. P4HA1 overexpression promoted angiogenesis in vitro and in vivo, while its knockdown had the opposite effect. P4HA1 overexpression reduced cellular α-ketoglutarate (α-KG) levels by consuming α-KG during collagen hydroxylation. Downregulation of α-KG reduced the protein level of a DNA dioxygenase, ten-eleven translocation 2 (TET2), and its recruitment to the fructose-1,6-biphosphatase (FBP1) promoter, resulting in decreased FBP1 expression. The decrease in FBP1 enhanced glycolytic metabolism, thereby promoting endothelial angiogenesis.

CONCLUSIONS

Hypoxia-induced endothelial P4HA1 overexpression enhanced angiogenesis by promoting glycolytic metabolism reprogramming through the P4HA1/α-KG/TET2/FBP1 pathway. The study's findings underscore the significance of P4HA1 in post-ischemic angiogenesis, suggesting its therapeutic potential for post-ischemic tissue repair.

Targeting the SphK1/S1P/PFKFB3 axis suppresses hepatocellular carcinoma progression by disrupting glycolytic energy supply that drives tumor angiogenesis

BACKGROUND

Hepatocellular carcinoma (HCC) remains a leading life-threatening health challenge worldwide, with pressing needs for novel therapeutic strategies. Sphingosine kinase 1 (SphK1), a well-established pro-cancer enzyme, is aberrantly overexpressed in a multitude of malignancies, including HCC. Our previous research has shown that genetic ablation of Sphk1 mitigates HCC progression in mice. Therefore, the development of PF-543, a highly selective SphK1 inhibitor, opens a new avenue for HCC treatment. However, the anti-cancer efficacy of PF-543 has not yet been investigated in primary cancer models in vivo, thereby limiting its further translation.

METHODS

Building upon the identification of the active form of SphK1 as a viable therapeutic target in human HCC specimens, we assessed the capacity of PF-543 in suppressing tumor progression using a diethylnitrosamine-induced mouse model of primary HCC. We further delineated its underlying mechanisms in both HCC and endothelial cells. Key findings were validated in Sphk1 knockout mice and lentiviral-mediated SphK1 knockdown cells.

RESULTS

SphK1 activity was found to be elevated in human HCC tissues. Administration of PF-543 effectively abrogated hepatic SphK1 activity and significantly suppressed HCC progression in diethylnitrosamine-treated mice. The primary mechanism of action was through the inhibition of tumor neovascularization, as PF-543 disrupted endothelial cell angiogenesis even in a pro-angiogenic milieu. Mechanistically, PF-543 induced proteasomal degradation of the critical glycolytic enzyme 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3, thus restricting the energy supply essential for tumor angiogenesis. These effects of PF-543 could be reversed upon S1P supplementation in an S1P receptor-dependent manner.

CONCLUSIONS

This study provides the first in vivo evidence supporting the potential of PF-543 as an effective anti-HCC agent. It also uncovers previously undescribed links between the pro-cancer, pro-angiogenic and pro-glycolytic roles of the SphK1/S1P/S1P receptor axis. Importantly, unlike conventional anti-HCC drugs that target individual pro-angiogenic drivers, PF-543 impairs the PFKFB3-dictated glycolytic energy engine that fuels tumor angiogenesis, representing a novel and potentially safer therapeutic strategy for HCC.

Glycolysis Reprogramming in Idiopathic Pulmonary Fibrosis: Unveiling the Mystery of Lactate in the Lung

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease characterized by excessive deposition of fibrotic connective tissue in the lungs. Emerging evidence suggests that metabolic alterations, particularly glycolysis reprogramming, play a crucial role in the pathogenesis of IPF. Lactate, once considered a metabolic waste product, is now recognized as a signaling molecule involved in various cellular processes. In the context of IPF, lactate has been shown to promote fibroblast activation, myofibroblast differentiation, and extracellular matrix remodeling. Furthermore, lactate can modulate immune responses and contribute to the pro-inflammatory microenvironment observed in IPF. In addition, lactate has been implicated in the crosstalk between different cell types involved in IPF; it can influence cell-cell communication, cytokine production, and the activation of profibrotic signaling pathways. This review aims to summarize the current research progress on the role of glycolytic reprogramming and lactate in IPF and its potential implications to clarify the role of lactate in IPF and to provide a reference and direction for future research. In conclusion, elucidating the intricate interplay between lactate metabolism and fibrotic processes may lead to the development of innovative therapeutic strategies for IPF.

Role of glycolysis in inflammatory bowel disease and its associated colorectal cancer

Inflammatory bowel disease (IBD) has been referred to as the "green cancer," and its progression to colorectal cancer (CRC) poses a significant challenge for the medical community. A common factor in their development is glycolysis, a crucial metabolic mechanism of living organisms, which is also involved in other diseases. In IBD, glycolysis affects gastrointestinal components such as the intestinal microbiota, mucosal barrier function, and the immune system, including macrophages, dendritic cells, T cells, and neutrophils, while in CRC, it is linked to various pathways, such as phosphatidylinositol-3-kinase (PI3K)/AKT, AMP-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and transcription factors such as p53, Hypoxia-inducible factor (HIF), and c-Myc. Thus, a comprehensive study of glycolysis is essential for a better understanding of the pathogenesis and therapeutic targets of both IBD and CRC. This paper reviews the role of glycolysis in diseases, particularly IBD and CRC, via its effects on the intestinal microbiota, immunity, barrier integrity, signaling pathways, transcription factors and some therapeutic strategies targeting glycolytic enzymes.

CircXRN2 suppresses tumor progression driven by histone lactylation through activating the Hippo pathway in human bladder cancer

BACKGROUND

Bladder cancer (BCa) is the fourth most common malignant tumor with a poor prognosis worldwide. Further exploration and research are needed to unmask the underlying roles and molecular mechanisms of circular RNAs. In the current study, our findings showed that circXRN2 suppresses tumor progression driven by histone lactylation by activating the Hippo pathway in human bladder cancer.

METHODS

RNA immunoprecipitation (RIP) followed by circRNA sequencing confirmed circXRN2 as the research object. Overexpression of circXRN2 and knockdown of TAZ/YAP further verified the biological functions in T24 and TCCSUP cells. RIP, immunoprecipitation and coimmunoprecipitation were used to elucidate the interaction between circXRN2 and LATS1. A Seahorse metabolic analyzer was used to determine the glycolytic rate. Cleavage under targets and Tagmentation (CUT&Tag) and chromatin immunoprecipitation (ChIP) were employed to ensure the regulatory roles of H3K18 lactylation in the transcriptional activity of LCN2.

RESULTS

CircXRN2 is aberrantly downregulated in bladder cancer tissues and cell lines. CircXRN2 inhibits the proliferation and migration of tumor cells both in vitro and in vivo. In addition, circXRN2 serves as a negative regulator of glycolysis and lactate production. Mechanistically, circXRN2 prevents LATS1 from SPOP-mediated degradation by binding to the SPOP degron and then activates the Hippo signaling pathway to exert various biological functions. The circXRN2-Hippo pathway regulatory axis further modulates tumor progression by inhibiting H3K18 lactylation and LCN2 expression in human bladder cancer.

CONCLUSIONS

CircXRN2 suppresses tumor progression driven by H3K18 lactylation by activating the Hippo signaling pathway in human bladder cancer. Our results indicated novel therapeutic targets and provided promising strategies for clinical intervention in human bladder cancer.

Dihydroartemisinin inhibited interleukin-18 expression by decreasing YAP1 in hepatocellular carcinoma cells

BACKGROUND

Yes-associated protein 1 (YAP1) is highly expressed in liver cancer and has been used as an independent prognostic marker for hepatocellular carcinoma (HCC), while inhibition of YAP1 slows down the progression of HCC. Interleukin-18 (IL-18) also tends to be highly expressed in liver cancer. Previous research has proved that dihydroartemisinin (DHA) plays an important role in HCC treatment by reducing YAP1 expression. However, the relationship between YAP1 and IL-18 has not been reported in HCC, especially during DHA therapy.

OBJECTIVE

The purpose of this study was to clarify the relationship between YAP1 and IL-18 in HCC cells, and to explicit the role of IL-18 in the treatment of HCC by DHA.

METHODS AND RESULTS

We found that YAP1 and IL-18 were highly expressed in patients with hepatocellular carcinoma by bioinformatics analysis. Moreover, YAP1 was positively correlated with IL18 in liver cancer. YAP1 and IL18 correlated with immune cell infiltration, notably T cell exhaustion. YAP1 knockdown decreased IL-18 expression, while YAP1 overexpression increased the IL-18 expression in HCC cells. DHA reduced IL-18 expression through YAP1 in HCC cells. Further, DHA reduced the growth of Hepa1-6 cells subcutaneous xenograft tumors by inhibiting the expression of YAP1 and IL-18. However, DHA improved IL-18 in serum and adjacent tissues from DEN/TCPOBOP-induced liver tumor model in C57BL/6 mice.

CONCLUSION

YAP1 was positively correlated with IL-18 in HCC. DHA reduced the expression of IL-18 by inhibiting YAP1 and plays a role in the treatment of HCC. Our study suggested that IL-18 is a potential target for the treatment of HCC, and DHA is a promising drug for HCC therapy.

DATA AVAILABILITY

The dataset that supports the findings of this study is available from the corresponding author upon reasonable request.

Glycolysis and de novo fatty acid synthesis cooperatively regulate pathological vascular smooth muscle cell phenotypic switching and neointimal hyperplasia

Switching of vascular smooth muscle cells (VSMCs) from a contractile phenotype to a dedifferentiated (proliferative) phenotype contributes to neointima formation, which has been demonstrated to possess a tumor-like nature. Dysregulated glucose and lipid metabolism is recognized as a hallmark of tumors but has not thoroughly been elucidated in neointima formation. Here, we investigated the cooperative role of glycolysis and fatty acid synthesis in vascular injury-induced VSMC dedifferentiation and neointima formation. We found that the expression of hypoxia-inducible factor-1α (HIF-1α) and its target 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3), a critical glycolytic enzyme, were induced in the neointimal VSMCs of human stenotic carotid arteries and wire-injured mouse carotid arteries. HIF-1α overexpression led to elevated glycolysis and resulted in a decreased contractile phenotype while promoting VSMC proliferation and activation of the mechanistic target of rapamycin complex 1 (mTORC1). Conversely, silencing Pfkfb3 had the opposite effects. Mechanistic studies demonstrated that glycolysis generates acetyl coenzyme A to fuel de novo fatty acid synthesis and mTORC1 activation. Whole-transcriptome sequencing analysis confirmed the increased expression of PFKFB3 and fatty acid synthetase (FASN) in dedifferentiated VSMCs. More importantly, FASN upregulation was observed in neointimal VSMCs of human stenotic carotid arteries. Finally, interfering with PFKFB3 or FASN suppressed vascular injury-induced mTORC1 activation, VSMC dedifferentiation, and neointima formation. Together, this study demonstrated that PFKFB3-mediated glycolytic reprogramming and FASN-mediated lipid metabolic reprogramming are distinctive features of VSMC phenotypic switching and could be potential therapeutic targets for treating vascular diseases with neointima formation. © 2023 The Pathological Society of Great Britain and Ireland.

Andrographolide inhibits murine embryonic neuronal development through PFKFB3-mediated glycolytic pathway

Dysregulation of neuronal development may cause neurodevelopmental disorders. However, how to regulate embryonic neuronal development and whether this regulation can be medical interrupted are largely unknown. This study aimed to investigate whether and how andrographolide (ANP) regulates embryonic neuronal development. The pregnant mice at embryonic day 10.5 (E10.5) were administrated with ANP, and the embryonic brains were harvested at E17.5 or E18.5. Immunofluorescence (IF), Immunohistochemistry (IHC) performed to determine whether ANP is critical in regulating neuronal development. Real-time quantitative PCR, western blotting, cell counting kit-8 assay, Flow Cytometry assay, Boyden Chamber Migration assay carried out to evaluate whether ANP regulates neuronal proliferation and migration. Protein-protein interaction, CO-immunoprecipitation and IF staining carried out to evaluate whether ANP regulates the interaction between PFKFB3, NeuN and TBR1. Knockdown or overexpression of PFKFB3 by adenovirus infection were used to determine whether ANP inhibits neuronal development through PFKFB3 mediated glycolytic pathway. Our data indicated that ANP inhibited the maturation of embryonic neurons characterized by suppressing neuronal proliferation and migration. ANP regulated the interaction between PFKFB3, NeuN, and TBR1. Knockdown of PFKFB3 aggravated ANP mediated inhibition of neuronal proliferation and migration, while overexpression of PFKFB3 attenuated ANP mediated neuronal developmental suppression. In summary, ANP suppressed the expression of PFKFB3, and interrupted the interaction between TRB1 and NeuN, resulting in suppressing neuronal proliferation, migration and maturation and eventually inhibiting murine embryonic neuronal development.

Small extracellular vesicles derived from human adipose-derived stem cells regulate energetic metabolism through the activation of YAP/TAZ pathway facilitating angiogenesis

Recent studies have found small extracellular vesicles (sEVs) that are secreted from human adipose tissue-derived stem cells (hADSCs-sEVs) and contribute to angiogenesis. Glycolysis, the primary energetic pathway of vascular endothelial cells, plays a key role in the process of angiogenesis. However, hADSCs-sEVs' effects on energy metabolism within endothelial cells remain unclear. In our study, we found that hADSCs-sEVs restored glycolytic metabolism suppressed by 3-(pyridinyl)-1-(4-pyridinyl)-2-propen-1-one(3PO), a unique glycolytic inhibitor increasing the extracellular acidification rate (ECAR), oxygen consumption rate (OCR), glycolytic gene expression as well as pyruvate, lactate, and ATP production in HUVEC cells. In contrast, hADSCs-sEVs decreased PDH-E1α expression and acetyl-CoA production. The above results indicate that hADSCs-sEVs promote HUVEC angiogenesis via enhancing glycolysis and suppressing mitochondrial oxidative phosphorylation. Furthermore, we found that the YAP/TAZ pathway may play a key role in the effects hADSCs-sEVs have on HUVECs, thus, providing a promising approach for pro-angiogenesis-related regeneration.

Potential Roles of YAP/TAZ Mechanotransduction in Spaceflight-Induced Liver Dysfunction

Microgravity exposure during spaceflight causes the disordered regulation of liver function, presenting a specialized mechano-biological coupling process. While YAP/TAZ serves as a typical mechanosensitive pathway involved in hepatocyte metabolism, it remains unclear whether and how it is correlated with microgravity-induced liver dysfunction. Here, we discussed liver function alterations induced by spaceflight or simulated effects of microgravity on Earth. The roles of YAP/TAZ serving as a potential bridge in connecting liver metabolism with microgravity were specifically summarized. Existing evidence indicated that YAP/TAZ target gene expressions were affected by mechanotransductive pathways and phase separation, reasonably speculating that microgravity might regulate YAP/TAZ activation by disrupting these pathways via cytoskeletal remodeling or nuclear deformation, or disturbing condensates formation via diffusion limit, and then breaking liver homeostasis.

Yes-Associated Protein and Transcriptional Coactivator with PDZ-Binding Motif in Cardiovascular Diseases

Yes-associated protein (YAP, also known as YAP1) and its paralogue TAZ (with a PDZ-binding motif) are transcriptional coactivators that switch between the cytoplasm and nucleus and regulate the organ size and tissue homeostasis. This review focuses on the research progress on YAP/TAZ signaling proteins in myocardial infarction, cardiac remodeling, hypertension and coronary heart disease, cardiomyopathy, and aortic disease. Based on preclinical studies on YAP/TAZ signaling proteins in cellular/animal models and clinical patients, the potential roles of YAP/TAZ proteins in some cardiovascular diseases (CVDs) are summarized.

MicroRNA-376b-3p Suppresses Choroidal Neovascularization by Regulating Glutaminolysis in Endothelial Cells

Purpose

Choroidal neovascularization (CNV) is a common pathological change of various ocular diseases that causes serious damage to central vision. Accumulated evidence shows that microRNAs (miRNAs) are closely related with the regulation of endothelial metabolism, which plays crucial roles in angiogenesis. Here, we investigate the molecular mechanism underlying the regulation of endothelial glutamine metabolism by miR-376b-3p in the progression of CNV.

Methods

Human retinal microvascular endothelial cells (HRMECs) were transfected with control or miR-376b-3p mimics, and the expression of glutaminase 1 (GLS1), a rate-limiting enzyme in glutaminolysis, was detected by real-time PCR or Western blotting. The biological function and glutamine metabolism of transfected HRMECs were measured by related kits. Luciferase reporter assays were used to validate the CCAAT/enhancer-binding protein beta (CEBPB) was a target of miR-376b-3p. Chromatin immunoprecipitation and RNA immunoprecipitation assays were performed to verify the binding of CEBPB on the promoter region of GLS1. Fundus fluorescein angiography and immunofluorescence detected the effect of miR-376b-3p agomir on rat laser-induced CNV.

Results

The expression of miR-376b-3p was decreased, whereas GLS1 expression was increased in the retinal pigment epithelial-choroidal complexes of rats with CNV. HRMECs transfected with miR-376b-3p mimic showed inhibition of CEBPB, resulting in the inactivation of GLS1 transcription and glutaminolysis. Moreover, the miR-376b-3p mimic inhibited proliferation, migration and tube formation but promoted apoptosis in HRMECs, whereas these effects counteracted by α-ketoglutarate supplementation or transfection with CEBPB overexpression plasmid. Finally, the intravitreal administration of the miR-376b-3p agomir restrained CNV formation.

Conclusions

Collectively, miR-376b-3p is a suppressor of glutamine metabolism in endothelial cells that could be expected to become a therapeutic target for the treatment of CNV-related diseases.

The Hippo signalling pathway and its implications in human health and diseases

As an evolutionarily conserved signalling network, the Hippo pathway plays a crucial role in the regulation of numerous biological processes. Thus, substantial efforts have been made to understand the upstream signals that influence the activity of the Hippo pathway, as well as its physiological functions, such as cell proliferation and differentiation, organ growth, embryogenesis, and tissue regeneration/wound healing. However, dysregulation of the Hippo pathway can cause a variety of diseases, including cancer, eye diseases, cardiac diseases, pulmonary diseases, renal diseases, hepatic diseases, and immune dysfunction. Therefore, therapeutic strategies that target dysregulated Hippo components might be promising approaches for the treatment of a wide spectrum of diseases. Here, we review the key components and upstream signals of the Hippo pathway, as well as the critical physiological functions controlled by the Hippo pathway. Additionally, diseases associated with alterations in the Hippo pathway and potential therapies targeting Hippo components will be discussed.

YAP is critical to inflammation, endothelial-mesenchymal transition and subretinal fibrosis in experimental choroidal neovascularization

Subretinal fibrosis causes local damage to the retina and irreversible vision loss, as the final stage of neovascular age-related macular degeneration (nAMD). More recently, the endothelial-to-mesenchymal transition (EndoMT) has been considered one of the most significant sources of myofibroblasts in subretinal fibrosis, though the underpinning molecular mechanisms remain unclear. In this study, a series of experiments were performed to test the hypothesis that Yes-associated protein (YAP) may be involved in EndoMT and subretinal fibrosis. We demonstrated that transforming growth factor (TGF)-β2 stimulation induces YAP dephosphorylation (activated) and nuclear transcription in human umbilical vein endothelial cells (HUVECs) by increasing reactive oxygen species (ROS) levels. Moreover, TGF-β2-mediated EndoMT and proinflammatory cytokine production in HUVECs were reduced by ROS clearance or YAP knockdown. Furthermore, the severity of subretinal fibrosis was markedly relieved by intravitreal administration of a small interfering RNA targeting YAP in the mouse laser-induced choroidal neovascularization (CNV) model. Our findings provide novel insights into a previously unknown effect of YAP on the EndoMT process and reveal YAP as a potential target for suppressing CNV-related subretinal fibrosis and protect vision.

Silencing of YAP attenuates pericyte-myofibroblast transition and subretinal fibrosis in experimental model of choroidal neovascularization

Age-related macular degeneration (AMD) is the main reason of irreversible vision loss in the elderly. The subretinal fibrosis subsequent to choroidal neovascularization (CNV) is an important feature in the late stage of wet AMD and is considered to be one reason for incomplete response to anti-VEGF drugs. Recent studies have shown that pericyte-myofibroblast transition (PMT) is an important pathological process involving fibrotic diseases of various organs. However, the specific role and mechanism of PMT in the subretinal fibrosis of CNV have not been clarified. It has been clear that the Hippo pathway along with its downstream effector Yes-associated protein (YAP) plays an important role in both epithelial and endothelial myofibroblast development. Therefore, we speculate whether YAP participates in PMT of pericytes and promotes fibrosis of CNV. In this study, experimental CNV was induced by laser photocoagulation in C57BL/6J (B6) mice, and aberrant YAP overexpression was detected in the retinal pigment epithelial/choroid/sclera tissues of the laser-injured eyes. YAP knockdown reduced the proliferation, migration, and differentiation of human retinal microvascular pericytes in vitro. It also reduced subretinal fibrosis of laser-induced CNV in vivo. Moreover, by proteomics-based analysis of pericyte conditioned medium (PC-CM) and bioinformatic analyses, we identified that the crosstalk between Hippo/YAP and MAPK/Erk was involved in expression of filamin A in hypoxic pericytes. These findings suggest that Hippo/YAP and MAPK/Erk are linked together to mediate pericyte proliferation, migration as well as differentiation, which may embody potential implications for treatment in diseases related to CNV.

Glycometabolic reprogramming-mediated proangiogenic phenotype enhancement of cancer-associated fibroblasts in oral squamous cell carcinoma: role of PGC-1α/PFKFB3 axis

BACKGROUND

Angiogenesis is a key rate-limiting step in the process of tumour progression. Cancer-associated fibroblasts (CAFs), the most abundant component OSCC stroma, play important roles in pro-angiogenesis. Recently, the stroma "reverse Warburg effect" was proposed, and PFKFB3 has been brought to the forefront as a metabolic enzyme regulating glycometabolism. However, it remains unclear whether glycometabolism reprogramming is involved in promoting the angiogenesis of CAFs.

METHODS

CAFs and paracancerous fibroblasts (PFs) were isolated from OSCC and adjacent tissues. We detected the pro-angiogenesis and glycometabolism phenotype of three pairs of fibroblasts. Targeted blockage of PFKFB3 or activation of PGC-1α signal was used to investigate the effect of glycolysis on regulating angiogenesis of CAFs in vitro and vivo.

RESULTS

CAFs exhibited metabolic reprogramming and enhanced proangiogenic phenotype compared with PFs. Inhibition of PFKFB3-dependent glycolysis impaired proangiogenic factors (VEGF-A, PDGF-C and MMP9) expression in CAFs. Furthermore, CAFs proangiogenic phenotype was regulated by glycometabolism through the PGC-1α/PFKFB3 axis. Consistently, PGC-1α overexpression or PFKFB3 knockdown in CAFs slowed down tumour development by reducing tumour angiogenesis in the xenograft model.

CONCLUSION

CAFs of OSCC are characterised with glycometabolic reprogramming and enhanced proangiogenic phenotypes. Our findings suggest that activating PGC-1α signalling impairs proangiogenic phenotype of CAFs by blocking PFKFB3-driven glycolysis.

Glucocorticoids Promote Extracellular Matrix Component Remodeling by Activating YAP in Human Retinal Capillary Endothelial Cells

Remodeling of extracellular matrix (ECM) components of endothelial cells is the main cause of retinal vascular basement membrane (BM) thickening, which leads to the initiation and perpetuation of microvasculopathy of diabetic retinopathy (DR). Excessive amounts of glucocorticoids (GCs) are related to the presence and severity of DR, however transcriptional effects of GCs on the biology of human retinal capillary endothelial cells (HRCECs) and its impacts on DR are still unclear. Here, we showed that GC (hydrocortisone) treatment induced ECM component [fibronectin (FN) and type IV collagen (Col IV)] expression and morphological changes in HRCECs via the glucocorticoid receptor (GR), which depended on the nuclear translocation of YAP coactivator. Mechanistically, GCs induced stress fiber formation in HRCECs, while blocking stress fiber formation inhibited GC-induced YAP nuclear translocation. Overexpression of FN, but not Col IV, activated YAP through the promotion of stress fiber formation via ECM-integrin signaling. Thus, a feedforward loop is established to sustain YAP activity. Using mRNA sequencing of HRCECs with overexpressed YAP or GC treatment, we found a similarity in Gene Ontology (GO) terms, differentially expressed genes (DEGs) and transcription factors (TFs) between the two RNA-seq datasets. In vivo, YAP was activated in retina vascular ECs of STZ-induced diabetic mice, and TF prediction analysis of published RNA-seq data of dermal vascular ECs from T2DM patients showed that GR and TEAD (the main transcription factor for YAP) were enriched. Together, GCs activate YAP and promote ECM component (FN and Col IV) remodeling in retinal capillary endothelial cells, and the underlying regulatory mechanism may provide new insights into the vascular BM thickening of the retina in the early pathogenesis of DR.

Canonical and Non-Canonical Roles of PFKFB3 in Brain Tumors

PFKFB3 is a bifunctional enzyme that modulates and maintains the intracellular concentrations of fructose-2,6-bisphosphate (F2,6-P2), essentially controlling the rate of glycolysis. PFKFB3 is a known activator of glycolytic rewiring in neoplastic cells, including central nervous system (CNS) neoplastic cells. The pathologic regulation of PFKFB3 is invoked via various microenvironmental stimuli and oncogenic signals. Hypoxia is a primary inducer of PFKFB3 transcription via HIF-1alpha. In addition, translational modifications of PFKFB3 are driven by various intracellular signaling pathways that allow PFKFB3 to respond to varying stimuli. PFKFB3 synthesizes F2,6P2 through the phosphorylation of F6P with a donated PO4 group from ATP and has the highest kinase activity of all PFKFB isoenzymes. The intracellular concentration of F2,6P2 in cancers is maintained primarily by PFKFB3 allowing cancer cells to evade glycolytic suppression. PFKFB3 is a primary enzyme responsible for glycolytic tumor metabolic reprogramming. PFKFB3 protein levels are significantly higher in high-grade glioma than in non-pathologic brain tissue or lower grade gliomas, but without relative upregulation of transcript levels. High PFKFB3 expression is linked to poor survival in brain tumors. Solitary or concomitant PFKFB3 inhibition has additionally shown great potential in restoring chemosensitivity and radiosensitivity in treatment-resistant brain tumors. An improved understanding of canonical and non-canonical functions of PFKFB3 could allow for the development of effective combinatorial targeted therapies for brain tumors.

Lack of WWC2 Protein Leads to Aberrant Angiogenesis in Postnatal Mice

The WWC protein family is an upstream regulator of the Hippo signalling pathway that is involved in many cellular processes. We examined the effect of an endothelium-specific WWC1 and/or WWC2 knock-out on ocular angiogenesis. Knock-outs were induced in C57BL/6 mice at the age of one day (P1) and evaluated at P6 (postnatal mice) or induced at the age of five weeks and evaluated at three months of age (adult mice). We analysed morphology of retinal vasculature in retinal flat mounts. In addition, in vivo imaging and functional testing by electroretinography were performed in adult mice. Adult WWC1/2 double knock-out mice differed neither functionally nor morphologically from the control group. In contrast, the retinas of the postnatal WWC knock-out mice showed a hyperproliferative phenotype with significantly enlarged areas of sprouting angiogenesis and a higher number of tip cells. The branching and end points in the peripheral plexus were significantly increased compared to the control group. The deletion of the WWC2 gene was decisive for these effects; while knocking out WWC1 showed no significant differences. The results hint strongly that WWC2 is an essential regulator of ocular angiogenesis in mice. As an activator of the Hippo signalling pathway, it prevents excessive proliferation during physiological angiogenesis. In adult animals, WWC proteins do not seem to be important for the maintenance of the mature vascular plexus.

PFKFB3: A Potential Key to Ocular Angiogenesis

The current treatment for ocular pathological angiogenesis mainly focuses on anti-VEGF signals. This treatment has been confirmed as effective despite the unfavorable side effects and unsatisfactory efficiency. Recently, endothelial cell metabolism, especially glycolysis, has been attracting attention as a potential treatment by an increasing number of researchers. Emerging evidence has shown that regulation of endothelial glycolysis can influence vessel sprouting. This new evidence has raised the potential for novel treatment targets that have been overlooked for a long time. In this review, we discuss the process of endothelial glycolysis as a promising target and consider regulation of the enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase as treatment for ocular pathological angiogenesis.