Pharmacological inhibition of Hippo pathway, with the novel kinase inhibitor XMU-MP-1, protects the heart against adverse effects during pressure overload

Dysfunctional cardiomyocyte signalling and heart disease

Cardiomyocyte signalling pathways are central to maintaining the structural and functional integrity of the heart. Dysregulation of these pathways contributes to the onset and progression of heart diseases, including heart failure, arrhythmias and cardiomyopathies. This review focuses on very recent work on dysfunctional cardiomyocyte signalling and its role in the pathophysiology of heart disease. We discuss key pathways, including immune signalling within cardiomyocytes, signalling associated with microtubule dysfunction, Hippo-yes-associated protein signalling and adenosine monophosphate-activated protein kinase signalling, highlighting how aberrations in their regulation lead to impaired cardiomyocyte functions and pinpointing the potential therapeutic opportunities in these pathways. This review underscores the complexity of cardiomyocyte signalling networks and emphasises the need for further dissecting signalling pathways to prevent cardiomyocyte dysfunction.

Pharmacological regulators of Hippo pathway: Advances and challenges of drug development

The Hippo signaling pathway is crucial in regulating organ size, tumor progression, tissue regeneration, and bone homeostasis. Inactivation of the Hippo pathway results in the nuclear translocation and activation of YAP/TAZ. This activation not only promotes tumor progression but also enhances tissue regeneration, wound healing, and maintenance of bone stability Although its discovery occurred over two decades ago, developing effective inhibitors or activators for the Hippo pathway remains challenging. Recently, however, the pace of advancements in developing Hippo signaling-related agonists and antagonists has accelerated, with some drugs that target TEAD advancing to clinical trials and showing promise for treating related diseases. This review summarizes the progress in research on Hippo signaling-related agonists and inhibitors, offering an in-depth analysis of their regulatory mechanisms, pharmacological properties, and potential in vivo applications.

Mixed exposure to PFOA and PFOS induces oocyte apoptosis and subfertility in mice by activating the Hippo signaling pathway

Per- and polyfluoroalkyl substances (PFAS) are synthetic perfluorinated compounds known for their persistence in the environment and reproduction toxicity. PFAS, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), have been identified in the follicular fluid of infertile women. However, the specific of PFOA and PFOS mixture on oocyte quality and female fertility remain unclear. In this study, we exposed female mice to combination of PFOA and PFOS to investigate the underlying mechanisms impairing fertility and oocyte maturation. Our results showed that exposure to the mixture induced epigenetic alterations and DNA damage in oocytes, impairing meiosis. Additionally, mitochondrial dysfunction caused by the exposure to the mixture led to oxidative stress and apoptosis in the oocytes. The reduction in oocyte quality resulted in a decrease in blastocyst quality and litter size. Furthermore, single-cell transcriptome analysis indicated that exposure to the mixture disrupted energy metabolism and triggered apoptosis, possibly through the activation of the Hippo signaling pathway. Overall, our results suggest that exposure to PFOA and PFOS mixture impairs the fertility in mice through the activation of the Hippo signaling pathway-induced oocytes apoptosis.

Expression of foetal gene Pontin is essential in protecting heart against pathological remodelling and cardiomyopathy

Cardiac remodelling is a key process in the development of heart failure. Reactivation of foetal cardiac genes is often associated with cardiac remodelling. Here we study the role of Pontin (Ruvbl1), which is highly expressed in embryonic hearts, in mediating adverse remodelling in adult mouse hearts. We observe that Pontin deficiency in cardiomyocytes leads to induced apoptosis, increased hypertrophy and fibrosis, whereas Pontin overexpression improves survival, increases proliferation and reduces the hypertrophic response. Moreover, RNAseq analysis show that genes involved in cell cycle regulation, cell proliferation and cell survival/apoptosis are differentially expressed in Pontin knockout. Specifically, we detect changes in the expression of Hippo pathway components in the Pontin knockout mice. Using a cellular model we show that Pontin induces YAP activity, YAP nuclear translocation, and transcriptional activity. Our findings identify Pontin as a modulator of adverse cardiac remodelling, possibly via regulation of the Hippo pathway. This study may lead to the development of a new approach to control cardiac remodelling by targeting Pontin.

Inhibition of MST1/2 Kinases of the Hippo Signaling Pathway Enhances Antitumor Chemotherapy in Hematological Cancers

Primary drug resistance of tumor cells or resistance acquired during treatment is among the main factors that significantly limit the efficacy of antitumor chemotherapy, along with severe side effects depending on the drug dose. To increase the efficacy, chemotherapeutics can be used in combination with substances that modulate the functions of cell signaling pathways. In this work, the substance XMU-MP-1, an inhibitor of key MST1/2 kinases of the Hippo signaling pathway, was shown to enhance the antitumor activity of two genotoxic chemotherapeutics, etoposide and cisplatin, against Namalwa Burkitt's B-cell lymphoma cells. XMU-MP-1 increased the cytotoxicity of the agents and significantly reduced their CTD50. The drug efficacy is therefore possible to increase significantly, and a therapeutic effect might be achieved at a lower drug concentration to reduce the likelihood of life-threatening side effects.

A CD26+ tendon stem progenitor cell population contributes to tendon repair and heterotopic ossification

Inadequate tendon healing and heterotopic bone formation result in substantial pain and disability, yet the specific cells responsible for tendon healing remain uncertain. Here we identify a CD26+ tendon stem/progenitor cells residing in peritendon, which constitutes a primitive stem cell population with self-renewal and multipotent differentiation potentials. CD26+ tendon stem/progenitor cells migrate into the tendon midsubstance and differentiation into tenocytes during tendon healing, while ablation of these cells led to insufficient tendon healing. Additionally, CD26+ tendon stem/progenitor cells contribute to heterotopic ossification and Tenascin-C-Hippo signaling is involved in this process. Targeting Tenascin-C significantly suppresses chondrogenesis of CD26+ tendon stem/progenitor cells and subsequent heterotopic ossification. Our findings provide insights into the identification of tendon stem/progenitor cells and illustrate the essential role of CD26+ tendon stem/progenitor cells in tendon healing and heterotopic bone formation.

Decoding the Impact of the Hippo Pathway on Different Cell Types in Heart Failure

The evolutionarily conserved Hippo pathway plays a pivotal role in governing a variety of biological processes. Heart failure (HF) is a major global health problem with a significant risk of mortality. This review provides a contemporary understanding of the Hippo pathway in regulating different cell types during HF. Through a systematic analysis of each component's regulatory mechanisms within the Hippo pathway, we elucidate their specific effects on cardiomyocytes, fibroblasts, endothelial cells, and macrophages in response to various cardiac injuries. Insights gleaned from both in vitro and in vivo studies highlight the therapeutic promise of targeting the Hippo pathway to address cardiovascular diseases, particularly HF.

YAP/TAZ as mechanobiological signaling pathway in cardiovascular physiological regulation and pathogenesis

Cardiovascular diseases (CVDs) persistently rank as a leading cause of premature death and illness worldwide. The Hippo signaling pathway, known for its highly conserved nature and integral role in regulating organ size, tissue homeostasis, and stem cell function, has been identified as a critical factor in the pathogenesis of CVDs. Recent findings underscore the significance of the Yes-associated protein (YAP) and the Transcriptional Coactivator with PDZ-binding motif (TAZ), collectively referred to as YAP/TAZ. These proteins play pivotal roles as downstream components of the Hippo pathway, in the regulation of cardiovascular development and homeostasis. YAP/TAZ can regulate various cellular processes such as cell proliferation, migration, differentiation, and apoptosis through their interactions with transcription factors, particularly those within the transcriptional enhancer associate domain (TEAD) family. The aim of this review is to provide a comprehensive overview of the current understanding of YAP/TAZ signaling in cardiovascular physiology and pathogenesis. We analyze the regulatory mechanisms of YAP/TAZ activation, explore their downstream effectors, and examine their association across numerous cardiovascular disorders, including myocardial hypertrophy, myocardial infarction, pulmonary hypertension, myocardial ischemia-reperfusion injury, atherosclerosis, angiogenesis, restenosis, and cardiac fibrosis. Furthermore, we investigate the potential therapeutic implications of targeting the YAP/TAZ pathway for the treatment of CVDs. Through this comprehensive review, our aim is to elucidate the current understanding of YAP/TAZ signaling in cardiovascular biology and underscore its potential implications for the diagnosis and therapeutic intervention of CVDs.

The Hippo Signaling Pathway, Reactive Oxygen Species Production, and Oxidative Stress: A Two-Way Traffic Regulation

The Hippo signaling pathway is recognized for its significant role in cell differentiation, proliferation, survival, and tissue regeneration. Recently, the Hippo signaling pathway was also found to be associated with oxidative stress and reactive oxygen species (ROS) regulation, which are important in the regulation of cell survival. Studies indicate a correlation between components of the Hippo signaling pathway, including MST1, YAP, and TAZ, and the generation of ROS. On the other hand, ROS and oxidative stress can activate key components of the Hippo signaling pathway. For example, ROS production activates MST1, which subsequently phosphorylates FOXO3, leading to apoptotic cell death. ROS was also found to regulate YAP, in addition to MST1/2. Oxidative stress and ROS formation can impair lipids, proteins, and DNA, leading to many disorders, including aging, neurodegeneration, atherosclerosis, and diabetes. Consequently, understanding the interplay between the Hippo signaling pathway, ROS, and oxidative stress is crucial for developing future disease management strategies. This paper aimed to review the association between the Hippo signaling pathway, regulation of ROS production, and oxidative stress to provide beneficial information in understanding cell function and pathological processes.

Mammalian Ste-20-like Kinase 1/2 (MST1/2) Inhibitor XMU-MP-1: A Potential Compound to Improve Spermatogenesis in Mouse Model of Diabetes Mellitus

Background/Objectives: Spermatogenesis is a key process in male reproduction that, if it does not happen correctly, can lead to infertility, with diabetes being one of the most prevalent causes of spermatogenesis disruption. Currently, there is a lack of research examining the potential benefits of targeting cell proliferation to enhance spermatogenesis in this condition. XMU-MP1 has been identified as an inhibitor of MST1, a core component of the Hippo pathway, which is anticipated to promote proliferation and regeneration. This study aims to evaluate the effects of XMU-MP1 treatment on sperm and testicular characteristics in mice. Methods: We used the STZ-induced diabetic mouse model to investigate the impact of administering XMU-MP1 on testicular tissue and sperm parameters. This study compared the seminiferous tubules, specifically focusing on the diameter of the seminiferous tubule, the thickness of the seminiferous tubule epithelium, the ratio of the thickness of the seminiferous tubule epithelium to the diameter of the seminiferous tubules, and the lumen diameter of the seminiferous tubules. We also conducted a comparison of sperm parameters, including sperm concentration, progressive motility, total motility, total motility, and morphology. Results: XMU-MP1-treated mice had a larger spermatogenesis area and better sperm motility than control mice. Diabetic mice treated with XMU-MP1 also showed a trend toward improvements in the spermatogenesis area, sperm concentration, sperm motility, and sperm morphology, although these improvements were not statistically significant. Conclusions: XMU-MP1 serves as a potential compound to improve spermatogenesis in mice.

SON-dependent nuclear speckle rejuvenation alleviates proteinopathies

Current treatments targeting individual protein quality control have limited efficacy in alleviating proteinopathies, highlighting the prerequisite for a common upstream druggable target capable of global proteostasis modulation. Building on our prior research establishing nuclear speckles as a pivotal membrane-less organelle responsible for global proteostasis transcriptional control, we aim to alleviate proteinopathies through nuclear speckle rejuvenation. We identified pyrvinium pamoate as a small-molecule nuclear speckle rejuvenator that enhances protein quality control while suppressing YAP1 signaling via decreasing the surface/interfacial tension of nuclear speckle condensates through interaction with the intrinsically disordered region of nuclear speckle scaffold protein SON. In pre-clinical models, nanomolar pyrvinium pamoate alleviated retina degeneration and reduced tauopathy by promoting autophagy and ubiquitin-proteasome system in a SON-dependent manner without causing cellular stress. Aberrant nuclear speckle morphology, reduced protein quality control and increased YAP1 activity were also observed in human tauopathies. Our study uncovers novel therapeutic targets for tackling protein misfolding disorders within an expanded proteostasis framework encompassing nuclear speckles and YAP1.

Targeting the Hippo pathway in Schwann cells ameliorates peripheral nerve degeneration via a polypharmacological mechanism

Peripheral neuropathies (PNs) are common diseases in elderly individuals characterized by Schwann cell (SC) dysfunction and irreversible Wallerian degeneration (WD). Although the molecular mechanisms of PN onset and progression have been widely studied, therapeutic opportunities remain limited. In this study, we investigated the pharmacological inhibition of Mammalian Ste20-like kinase 1/2 (MST1/2) by using its chemical inhibitor, XMU-MP-1 (XMU), against WD. XMU treatment suppressed the proliferation, dedifferentiation, and demyelination of SCs in models of WD in vitro, in vivo, and ex vivo. As a downstream mediator of canonical and noncanonical Hippo/MST1 pathway activation, the mature microRNA (miRNA) let-7b and its binding partners quaking homolog (QKI)/nucleolin (NCL) modulated miRNA-mediated silencing of genes involved in protein transport. Hence, direct phosphorylation of QKI and NCL by MST1 might be critical for WD onset and pathogenesis. Moreover, p38α/mitogen-activated protein kinase 14 (p38α) showed a strong affinity for XMU, and therefore, it may be an alternative XMU target for controlling WD in SCs. Taken together, our findings provide new insights into the Hippo/MST pathway function in PNs and suggest that XMU is a novel multitargeted therapeutic for elderly individuals with PNs.

MST1 selective inhibitor Xmu-mp-1 ameliorates neuropathological changes in a rat model of sporadic Alzheimer's Disease by modulating Hippo-Wnt signaling crosstalk

Alzheimer's disease (AD), the most prevalent form of dementia, is characterized by progressive cognitive impairment accompanied by aberrant neuronal apoptosis. Reports suggest that the pro-apoptotic mammalian set20-like kinase 1/2 (MST1/2) instigates neuronal apoptosis via activating the Hippo signaling pathway under various stress conditions, including AD. However, whether inhibiting MST1/2 has any therapeutic benefits in AD remains unknown. Thus, we tested the therapeutic effects of intervening MST1/2 activation via the pharmacological inhibitor Xmu-mp-1 in a sporadic AD rat model. Sporadic AD was established in adult rats by intracerebroventricular streptozotocin (ICV-STZ) injection (3 mg/kg body weight). Xmu-mp-1 (0.5 mg/kg/body weight) was administered once every 48 h for two weeks, and Donepezil (5 mg/kg body weight) was used as a reference standard drug. The therapeutic effects of Xmu-mp-1 on ICV-STZ rats were determined through various behavioral, biochemical, histopathological, and molecular tests. At the behavioral level, Xmu-mp-1 improved cognitive deficits in sporadic AD rats. Further, Xmu-mp-1 treatment reduced STZ-associated tau phosphorylation, amyloid-beta deposition, oxidative stress, neurotoxicity, neuroinflammation, synaptic dysfunction, neuronal apoptosis, and neurodegeneration. Mechanistically, Xmu-mp-1 exerted these neuroprotective actions by inactivating the Hippo signaling while potentiating the Wnt/β-Catenin signaling in the AD rats. Together, the results of the present study provide compelling support that Xmu-mp-1 negated the neuronal dysregulation in the rat model of sporadic AD. Therefore, inhibiting MST/Hippo signaling and modulating its crosstalk with the Wnt/β-Catenin pathway can be a promising alternative treatment strategy against AD pathology. This is the first study providing novel mechanistic insights into the therapeutic use of Xmu-mp-1 in sporadic AD.

Inhibiting endothelial cell Mst1 attenuates acute lung injury in mice

Lung endothelium plays a pivotal role in the orchestration of inflammatory responses to acute pulmonary insults. Mammalian sterile 20-like kinase 1 (Mst1) is a serine/threonine kinase that has been shown to play an important role in the regulation of apoptosis, stress responses, and organ growth. This study investigated the role of Mst1 in lung endothelial activation and acute lung injury (ALI). We found that Mst1 was significantly activated in inflamed lung endothelial cells (ECs) and mouse lung tissues. Overexpression of Mst1 promoted nuclear factor κ-B (NF-κB) activation through promoting JNK and p38 activation in lung ECs. Inhibition of Mst1 by either its dominant negative form (DN-Mst1) or its pharmacological inhibitor markedly attenuated cytokine-induced expression of cytokines, chemokines, and adhesion molecules in lung ECs. Importantly, in a mouse model of lipopolysaccharide-induced (LPS-induced) ALI, both deletion of Mst1 in lung endothelium and treatment of WT mice with a pharmacological Mst1 inhibitor significantly protected mice from LPS-induced ALI. Together, our findings identified Mst1 kinase as a key regulator in controlling lung EC activation and suggest that therapeutic strategies aimed at inhibiting Mst1 activation might be effective in the prevention and treatment of inflammatory lung diseases.

Polyunsaturated fatty acids promote M2-like TAM deposition via dampening RhoA-YAP1 signaling in the ovarian cancer microenvironment

BACKGROUND

Peritoneal metastases frequently occur in epithelial ovarian cancer (EOC), resulting in poor prognosis and survival rates. Tumor-associated-macrophages (TAMs) massively infiltrate into ascites spheroids and are multi-polarized as protumoral M2-like phenotype, orchestrating the immunosuppression and promoting tumor progression. However, the impact of omental conditioned medium/ascites (OCM/AS) on TAM polarization and its function in tumor progression remains elusive.

METHODS

The distribution and polarization of TAMs in primary and omental metastatic EOC patients' tumors and ascites were examined by m-IHC, FACS analysis, and immunofluorescence. QPCR, immunofluorescence, FACS analysis, lipid staining assay, ROS assay, and Seahorse real-time cell metabolic assay characterized TAMs as being polarized in the ascites microenvironment. The oncogenic role of TAMs in tumor cells was demonstrated by co-cultured migration/invasion, proliferation, and spheroid formation assays. Mechanistic studies of the regulations of TAM polarization were performed by using RNA-Seq, GTPase pull-down, G-LISA activation assays, and other biochemical assays. A Yap1 macrophages (MФs) conditional knockout (cKO) mouse model demonstrated the roles of YAP1 in TAM polarization status and its pro-metastatic function. Finally, the anti-metastatic potential of targeting TAMs through restoring YAP1 by pharmacological agonist XMU MP1 was demonstrated in vitro and in vivo.

RESULTS

Abundant polyunsaturated fatty acids (PUFAs) in OCM/AS suppressed RhoA-GTPase activities, which, in turn, downregulated nuclear YAP1 in MФs, leading to increased protumoral TAM polarization accompanied by elevated OXPHOS metabolism. Abolishment of YAP1 in MФs further confirmed that a higher M2/M1 ratio of TAM polarization could alleviate CD8+ T cell infiltration and cytotoxicity in vivo. Consistently, the loss of YAP1 has been observed in EOC metastatic tissues, suggesting its clinical relevance. On the contrary, restoration of YAP1 expression by pharmaceutical inhibition of MST1/2 induced conversion of M2-to-M1-like polarized MФs, elevating the infiltration of CD8+ T cells and attenuating tumor growth.

CONCLUSION

This study revealed that PUFAs-enriched OCM/AS of EOC promotes M2-like TAM polarization through RhoA-YAP1 inhibition, where YAP1 downregulation is required for accelerating protumoral M2-like TAM polarization, thereby causing immunosuppression and enhancing tumor progression. Conversion of M2-to-M1-like polarized MФs through Yap1 activation inhibits tumor progression and contributes to developing potential TAMs-targeted immunotherapies in combating EOC peritoneal metastases.

Non-coding RNAs as regulators of the Hippo pathway in cardiac development and cardiovascular disease

Cardiovascular diseases pose a serious threat to human health. The onset of cardiovascular diseases involves the comprehensive effects of multiple genes and environmental factors, and multiple signaling pathways are involved in regulating the occurrence and development of cardiovascular diseases. The Hippo pathway is a highly conserved signaling pathway involved in the regulation of cell proliferation, apoptosis, and differentiation. Recently, it has been widely studied in the fields of cardiovascular disease, cancer, and cell regeneration. Non-coding RNA (ncRNAs), which are important small molecules for the regulation of gene expression in cells, can directly target genes and have diverse regulatory functions. Recent studies have found that ncRNAs interact with Hippo pathway components to regulate myocardial fibrosis, cardiomyocyte proliferation, apoptosis, and hypertrophy and play an important role in cardiovascular disease. In this review, we describe the mode of action of ncRNAs in regulating the Hippo pathway, provide new ideas for further research, and identify molecules involved in the mechanism of action of ncRNAs and the Hippo pathway as potential therapeutic targets, with the aim of finding new modes of action for the treatment and prevention of cardiovascular diseases.

Role of MST2/YAP1 signaling pathway in retinal cells apoptosis and diabetic retinopathy

Diabetic retinopathy (DR) is a main factor affecting vision of patients, and its pathogenesis is not completely clear. The purpose of our study was to investigate correlations between MST2 and DR progression, and to study the possible mechanism of MST2 and its down pathway in high glucose (HG)-mediated RGC-5 apoptosis. The diabetic rat model was established by intraperitoneal injection of streptozotocin (STZ) 60 mg/kg. HE and TUNEL staining were used to evaluate the pathological changes and apoptosis of retinal cells in rats. Western blot, qRT-PCR and immunohistochemistry showed that levels of MST2 were increased in diabetic group (DM) than control. In addition, the differential expression of MST2 is related to HG-induced apoptosis of RGC-5 cells. CCK-8 and Hoechst 33,342 apoptosis experiments showed that MST2 was required in HG-induced apoptosis of RGC-5 cells. Further research revealed that MST2 regulated the protein expression of YAP1 at the level of phosphorylation in HG-induced apoptosis. Simultaneously, we found that Xmu-mp-1 acts as a MST2 inhibitor to alleviate HG-induced apoptosis. In summary, our study indicates that the MST2/YAP1 signaling pathway plays an important role in DR pathogenesis and RGC-5 apoptosis. This discovery provides new opportunities for future drug development targeting this pathway to prevent DR.

Activation of TAZ by XMU-MP-1 inhibits osteoclastogenesis and attenuates ovariectomy-induced cancellous bone loss

Osteoporosis is a metabolic bone loss disorder usually accompanied by overactivated osteoclast formation and increased bone resorption. Transcriptional co-activator with PDZ-binding motif (TAZ) is an emerging potential target for the treatment of osteoporosis. Our previous research showed that TAZ overexpression inhibited osteoclast formation while TAZ silencing had the opposite effect. In addition, TAZ knockout in mouse osteoclasts induced osteoporosis in animal experiments. XMU-MP-1 (XMU) is a selective MST1/2 inhibitor that can theoretically activate TAZ; however, its effect on osteoporosis remains unknown. In this study, we found that XMU treatment significantly increased TAZ expression in osteoclasts and inhibited osteoclast formation in vitro; however, this inhibitory effect was eliminated after the deletion of TAZ. Furthermore, XMU treatment upregulated TAZ expression in osteoclasts and alleviated ovariectomy (OVX)-induced osteoporosis in bilateral OVX mouse models. These findings suggest that XMU can effectively activate TAZ and that pharmacological activation of TAZ may be a promising option for the treatment of osteoporosis.

An updated review of YAP: A promising therapeutic target against cardiac aging?

The transcriptional co-activator Yes-associated protein (YAP) functions as a downstream effector of the Hippo signaling pathway and plays a crucial role in cardiomyocyte survival. In its non-phosphorylated activated state, YAP binds to transcription factors, activating the transcription of downstream target genes. It also regulates cell proliferation and survival by selectively binding to enhancers and activating target genes. However, the upregulation of the Hippo pathway in human heart failure inhibits cardiac regeneration and disrupts astrogenesis, thus preventing the nuclear translocation of YAP. Existing literature indicates that the Hippo/YAP axis contributes to inflammation and fibrosis, potentially playing a role in the development of cardiac, vascular and renal injuries. Moreover, it is a key mediator of myofibroblast differentiation and fibrosis in the infarcted heart. Given these insights, can we harness YAP's regenerative potential in a targeted manner? In this review, we provide a detailed discussion of the Hippo signaling pathway and consolidate concepts for the development and intervention of cardiac anti-aging drugs to leverage YAP signaling as a pivotal target.

Hyperglycemia-Induced Overexpression of PH Domain Leucine-Rich Repeat Protein Phosphatase 1 (PHLPP1) Compromises the Cardioprotective Effect of Ischemic Postconditioning Via Modulation of the Akt/Mst1 Pathway Signaling

PURPOSE

Ischemic postconditioning (IPostC) alleviates myocardial ischemia/reperfusion (IR) injury, but the protective effect is lost during diabetes. PH domain leucine-rich repeat protein phosphatase 1 (PHLPP1) is able to inactivate Akt. Our previous study found that PHLPP1 expression was upregulated in diabetic hearts. We presumed that the attenuation of myocardial injury by IPostC might be hindered by PHLPP1 overexpression in diabetic animals.

METHODS AND RESULTS

Nondiabetic and diabetic mice were subjected to 45 min of ischemia followed by 2 h of reperfusion with or without IPostC. H9c2 cells were exposed to normal or high glucose and were subjected to 4 h of hypoxia followed by 4 h of reoxygenation with or without hypoxic postconditioning (HPostC). IPostC attenuated postischemic infarction, apoptosis, creatine kinase-MB, and oxidative stress, which were accompanied by increased p-Akt and decreased PHLPP1 expression and p-Mst1 in nondiabetic but not in diabetic mice. PHLPP1 knockdown or an Mst1 inhibitor reduced hypoxia/reoxygenation (HR)-induced cardiomyocyte damage in H9c2 cells exposed to normal glucose, but the effect was abolished by a PI3K/Akt inhibitor. HPostC attenuated HR-induced cardiomyocyte injury and oxidative stress accompanied by increased p-Akt as well as decreased PHLPP1 expression and p-Mst1 in H9c2 cells exposed to normal glucose but not high glucose. In addition, HPostC in combination with PHLPP1 knockdown or PHLPP1 knockdown alone reduced cell death and oxidative stress in H9c2 cells exposed to high glucose, which was hindered by PI3K/Akt inhibitor.

CONCLUSION

IPostC prevented myocardial IR injury partly through PHLPP1/Akt/Mst1 signaling, and abnormalities in this pathway may be responsible for the loss of IPostC cardioprotection in diabetes.

Hepatic HDAC3 Regulates Systemic Iron Homeostasis and Ferroptosis via the Hippo Signaling Pathway

Histone deacetylases (HDACs) are epigenetic regulators that play an important role in determining cell fate and maintaining cellular homeostasis. However, whether and how HDACs regulate iron metabolism and ferroptosis (an iron-dependent form of cell death) remain unclear. Here, the putative role of hepatic HDACs in regulating iron metabolism and ferroptosis was investigated using genetic mouse models. Mice lacking Hdac3 expression in the liver (Hdac3-LKO mice) have significantly reduced hepatic Hamp mRNA (encoding the peptide hormone hepcidin) and altered iron homeostasis. Transcription profiling of Hdac3-LKO mice suggests that the Hippo signaling pathway may be downstream of Hdac3. Moreover, using a Hippo pathway inhibitor and overexpressing the transcriptional regulator Yap (Yes-associated protein) significantly reduced Hamp mRNA levels. Using a promoter reporter assay, we then identified 2 Yap-binding repressor sites within the human HAMP promoter region. We also found that inhibiting Hdac3 led to increased translocation of Yap to the nucleus, suggesting activation of Yap. Notably, knock-in mice expressing a constitutively active form of Yap (Yap K342M) phenocopied the altered hepcidin levels observed in Hdac3-LKO mice. Mechanistically, we show that iron-overload-induced ferroptosis underlies the liver injury that develops in Hdac3-LKO mice, and knocking down Yap expression in Hdac3-LKO mice reduces both iron-overload- and ferroptosis-induced liver injury. These results provide compelling evidence supporting the notion that HDAC3 regulates iron homeostasis via the Hippo/Yap pathway and may serve as a target for reducing ferroptosis in iron-overload-related diseases.

Radioprotective effect of Ginkgolide B on brain: the mediating role of DCC/MST1 signaling

PURPOSE

The risk of brain exposure to ionizing radiation increases gradually due to the extensive application of nuclear technology in medical, industrial, and aerospace fields. Radiation-induced brain injury (RBI) is highly likely to cause a wide range of neurological complications, including schizophrenia, Alzheimer's disease (AD), depression. Ginkgolide B (GB) is one of the effective active components extracted from ginkgo biloba leaves, exerts protective effects on CNS, which is involved in the regulation of the Hippo signaling pathway. MST1, as one of the core kinases of the Hippo pathway, participated in regulating cell proliferation, differentiation, and apoptosis. However, it remains unclear whether GB attenuates radiation brain injury (RBI) and whether the radioprotective effect of GB refers to MST1 signaling. Hence, our study aimed to explore the radiation protection effect and the potential mechanism of GB.

MATERIALS AND METHODS

C57BL/6 mice were stimulated with an X-ray (20 Gy) to establish an RBI model. Then, morris water maze test (MWM) and step-down passive avoidance test (SDPAT) were used to assess the learning and memory function of mice. The open field test (OFT), tail suspension test (TST), and forced swimming test (FST) were used to assess changes in locomotor activity and hopelessness. Besides, X-ray-stimulated SH-SY5Y cells were used to verify the radioprotective effect of GB. Immunofluorescence double staining, Dihydroethidium (DHE), western blot, and flow cytometry were used to explore the role of DCC/MST1 signaling in RBI.

RESULTS

In this study, X-ray-treated mice exhibited cognitive impairment and depression-like behavior, which was ameliorated by GB treatment. GB also reduced the ROS production and the number of TUNEL-positive cells in the hippocampus. Moreover, GB increased the protein levels of p-AKT and Bcl2, while decreased the protein levels of MST1, p-p38, p-JNK, cleaved-caspase-3 and Bax both in vivo and in vitro. Additionally, exogenous Netrin-1 alleviated X-ray-induced ROS production and apoptosis, whereas knockout of Netrin-1 receptor DCC abolished the protective effect of GB.

CONCLUSION

Oxidative stress and MST1-mediated neuronal apoptosis participated in radiation-induced cognitive impairment and depression-like behaviors, and modulation of DCC by GB was an effective intervention against RBI.

Targeting Hippo signaling in cancer: novel perspectives and therapeutic potential

As highly conserved among diverse species, Hippo signaling pathway regulates various biological processes, including development, cell proliferation, stem cell function, tissue regeneration, homeostasis, and organ size. Studies in the last two decades have provided a good framework for how these fundamental functions of Hippo signaling are tightly regulated by a network with numerous intracellular and extracellular factors. The Hippo signaling pathway, when dysregulated, may lead to a wide variety of diseases, especially cancer. There is growing evidence demonstrating that dysregulated Hippo signaling is closely associated with tumorigenesis, cancer cell invasion, and migration, as well as drug resistance. Therefore, the Hippo pathway is considered an appealing therapeutic target for the treatment of cancer. Promising novel agents targeting the Hippo signaling pathway for cancers have recently emerged. These novel agents have shown antitumor activity in multiple cancer models and demonstrated therapeutic potential for cancer treatment. However, the detailed molecular basis of the Hippo signaling-driven tumor biology remains undefined. Our review summarizes current advances in understanding the mechanisms by which Hippo signaling drives tumorigenesis and confers drug resistance. We also propose strategies for future preclinical and clinical development to target this pathway.

Inhibiting endothelial cell Mst1 attenuates acute lung injury in mice

Background

Lung endothelium plays a pivotal role in the orchestration of inflammatory and injury responses to acute pulmonary insults. Mammalian sterile 20-like kinase 1 (Mst1), a mammalian homolog of Hippo, is a serine/threonine kinase that is ubiquitously expressed in many tissues and has been shown to play an important role in the regulation of apoptosis, inflammation, stress responses, and organ growth. While Mst1 exhibits high expression in the lung, its involvement in the endothelial response to pulmonary insults remains largely unexplored.

Methods

Mst1 activity was assessed in lung endothelium by western blot. Mst1 endothelial specific knockout mice and a pharmacological inhibitor were employed to assess the effects of Mst1 on homeostatic and lipopolysaccharide (LPS)-induced endothelial responses. Readouts for these studies included various assays, including NF-κB activation and levels of various inflammatory cytokines and adhesion molecules. The role of Mst1 in lung injury was evaluated in a LPS-induced murine model of acute lung injury (ALI).

Results

Mst1 phosphorylation was significantly increased in lung endothelial cells after exposure to tumor necrosis factor (TNF)-alpha (TNF-α) and mouse lung tissues after LPS exposure. Overexpression of full length Mst1 or its kinase domain promoted nuclear factor kappaB (NF-κB) activation through promoting JNK and p38 activation, whereas dominant negative forms of Mst1 (DN-Mst1) attenuated endothelial responses to TNF-α and interleukin-1β. Consistent with this, targeted deletion of Mst1 in lung endothelium reduced lung injury to LPS in mice. Similarly, wild-type mice were protected from LPS-induced lung injury following treatment with a pharmacological inhibitor of Mst1/2.

Conclusions

Our findings identified Mst1 kinase as a key regulator in the control of lung EC activation and suggest that therapeutic strategies aimed at inhibiting Mst1 activation might be effective in the prevention and treatment of lung injury to inflammatory insults.

Genetic and Pharmacological YAP Activation Induces Proliferation and Improves Survival in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Cardiomyocyte loss following myocardial infarction cannot be addressed with current clinical therapies. Cell therapy with induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) is a potential approach to replace cardiomyocyte loss. However, engraftment rates in pre-clinical studies have been low, highlighting a need to refine current iPSC-CM technology. In this study, we demonstrated that inducing Yes-associated protein (YAP) by genetic and pharmacological approaches resulted in increased iPSC-CM proliferation and reduced apoptosis in response to oxidative stress. Interestingly, iPSC-CM maturation was differently affected by each strategy, with genetic activation of YAP resulting in a more immature cardiomyocyte-like phenotype not witnessed upon pharmacological YAP activation. Overall, we conclude that YAP activation in iPSC-CMs enhances cell survival and proliferative capacity. Therefore, strategies targeting YAP, or its upstream regulator the Hippo signalling pathway, could potentially be used to improve the efficacy of iPSC-CM technology for use as a future regenerative therapy in myocardial infarction.

MST1 mediates doxorubicin-induced cardiomyopathy by SIRT3 downregulation

Heart failure is a major side effect of doxorubicin (DOX) treatment in patients with cancer. However, the mechanisms underlying the development of DOX-induced heart failure need to be addressed. This study aims to test whether the serine/threonine kinase MST1, a major Hippo pathway component, contributes to the development of DOX-induced myocardial injury. C57BL/6J WT mice and mice with cardiomyocyte-specific dominant-negative MST1 (kinase-dead) overexpression received three weekly injections of DOX, reaching a final cumulative dose of 18 mg/kg. Echocardiographic, histological and biochemical analyses were performed six weeks after the first DOX administration. The effects of MST1 inhibition on DOX-induced cardiomyocyte injury were also tested in vitro. MST1 signaling was significantly activated in cardiomyocytes in response to DOX treatment in vitro and in vivo. Wild-type (WT) mice treated with DOX developed cardiac dysfunction and mitochondrial abnormalities. However, these detrimental effects were abolished in mice with cardiomyocyte-specific overexpression of dominant-negative MST1 (DN-MST1) or treated with XMU-MP-1, a specific MST1 inhibitor, indicating that MST1 inhibition attenuates DOX-induced cardiac dysfunction. DOX treatment led to a significant downregulation of cardiac levels of SIRT3, a deacetylase involved in mitochondrial protection, in WT mice, which was rescued by MST1 inhibition. Pharmacological inhibition of SIRT3 blunted the protective effects of MST1 inhibition, indicating that SIRT3 downregulation mediates the cytotoxic effects of MST1 activation in response to DOX treatment. Finally, we found a significant upregulation of MST1 and downregulation of SIRT3 levels in human myocardial tissue of cancer patients treated with DOX. In summary, MST1 contributes to DOX-induced cardiomyopathy through SIRT3 downregulation.

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.

Targeting the Divergent Roles of STK3 Inhibits Breast Cancer Cell Growth and Opposes Doxorubicin-Induced Cardiotoxicity In Vitro

Breast cancer (BCa) is the most prevalent type of cancer in women. Several therapies used in the treatment of breast cancer are associated with clinically important rates of cardiovascular toxicity during or after treatment exposure, including anthracyclines. There is a need for new BCa therapeutics and treatments that mitigate chemotherapy-induced cardiotoxicity in BCa. In this study, we examine the effects of Serine/Threonine Kinase 3 (STK3) inhibition in the context of BCa therapy and cardioprotection from doxorubicin. STK3 (also known as MST2) is a key member of the Hippo Tumor-Suppressor Pathway, which regulates cell growth and proliferation by inhibiting YAP/TAZ co-transcription factors. Canonically, STK3 should restrict BCa growth; however, we observed that STK3 is amplified in BCa and associated with worse patient outcomes, suggesting a noncanonical pro-tumorigenic role. We found BCa cell lines have varying dependence on STK3. SUM52PE cells had the highest expression and dependence on STK3 in genetic and pharmacological assays. MCF-7 and MDA-MB-231 were less sensitive to STK3 targeting in standard proliferation assays, but were STK3 dependent in colony formation and matrigel invasion assays. In contrast, STK3 inhibition mitigated the toxic effects of doxorubicin in H9C2 rat cardiomyocytes by increasing YAP expression. Importantly, STK3 inhibition in BCa cells did not interfere with the therapeutic effects of doxorubicin. Our studies highlight STK3 is a potential molecular target for BCa with dual therapeutic effects: suppression of BCa growth and progression, and chemoprotection in cardiomyocytes.

MST1 DOWNREGULATES TAZ TUMOUR SUPPRESSOR PROTEIN IN MULTIPLE MYELOMA AND IS A POTENTIAL THERAPEUTIC TARGET

We have previously reported that TAZ functions as a tumor suppressor in multiple myeloma. MST1 is a serine-threonine kinase upstream of the Hippo-signaling pathway that functions as a tumor suppressor in many non-haematological malignancies. However, its role in hematological malignancies, including MM is still poorly understood. In this paper, we provide evidence that MST1 expression is higher in MM, and negatively correlates with TAZ expression in both cell lines and patient samples. High MST1 expression was associated with poor clinical outcomes. Genetic or pharmacological inhibition of MST1 leads to increased TAZ expression and cell death. Importantly, MST1 inhibitors sensitizes myeloma cells to frontline antimyeloma agent-lenalidomide and dexamethasone. Taken together, our data reveals a key role for MST1 in MM pathogenesis and provide evidence to explore the therapeutic potential of using MST inhibitors to upregulate TAZ expression in MM to promote response to anticancer agents.

The hippo kinases MST1/2 in cardiovascular and metabolic diseases: A promising therapeutic target option for pharmacotherapy

Cardiovascular diseases (CVDs) and metabolic disorders are major components of noncommunicable diseases, causing an enormous health and economic burden worldwide. There are common risk factors and developmental mechanisms among them, indicating the far-reaching significance in exploring the corresponding therapeutic targets. MST1/2 kinases are well-established proapoptotic effectors that also bidirectionally regulate autophagic activity. Recent studies have demonstrated that MST1/2 influence the outcome of cardiovascular and metabolic diseases by regulating immune inflammation. In addition, drug development against them is in full swing. In this review, we mainly describe the roles and mechanisms of MST1/2 in apoptosis and autophagy in cardiovascular and metabolic events as well as emphasis on the existing evidence for their involvement in immune inflammation. Moreover, we summarize the latest progress of pharmacotherapy targeting MST1/2 and propose a new mode of drug combination therapy, which may be beneficial to seek more effective strategies to prevent and treat CVDs and metabolic disorders.

Yes-associated protein regulates glutamate homeostasis through promoting the expression of excitatory amino acid transporter-2 in astrocytes via β-catenin signaling

The homeostasis of glutamate is mainly regulated by the excitatory amino acid transporters (EAATs), especially by EAAT2 in astrocytes. Excessive glutamate in the synaptic cleft caused by dysfunction or dysregulation of EAAT2 can lead to excitotoxicity, neuronal death and cognitive dysfunction. However, it remains unclear about the detailed regulation mechanism of expression and function of astrocytic EAAT2. In this study, first, we found increased neuronal death and impairment of cognitive function in YAP^GFAP -CKO mice (conditionally knock out Yes-associated protein [YAP] in astrocytes), and identified EAAT2 as a downstream target of YAP through RNA sequencing. Second, the expression of EAAT2 was decreased in cultured YAP^-/- astrocytes and the hippocampus of YAP^GFAP -CKO mice, and glutamate uptake was reduced in YAP^-/- astrocytes, but increased in YAP-upregulated astrocytes. Third, further investigation of the mechanism showed that the mRNA and protein levels of β-catenin were decreased in YAP^-/- astrocytes and increased in YAP-upregulated astrocytes. Wnt3a activated YAP signaling and up-regulated EAAT2 through β-catenin. Furthermore, over-expression or activation of β-catenin partially restored the downregulation of EAAT2, the impairment of glutamate uptake, neuronal death and cognitive decline that caused by YAP deletion. Finally, activation of EAAT2 also rescued neuronal death and cognitive decline in YAP^GFAP -CKO mice. Taken together, our study identifies an unrecognized role of YAP signaling in the regulation of glutamate homeostasis through the β-catenin/EAAT2 pathway in astrocytes, which may provide novel insights into the pathogenesis of brain diseases that closely related to the dysfunction or dysregulation of EAAT2, and promote the development of clinical strategy.

The ovarian-related effects of polystyrene nanoplastics on human ovarian granulosa cells and female mice

Nanoplastics (NPs) have recently emerged in the context of global plastic pollution. They may be more toxic than macroplastics litter and microplastic fragments due to its abundances, tiny sizes, and cellular accessibility. The female reproductive toxicity of NPs has been widely documented for aquatic animals, but their effects and underlying mechanisms remain poorly understood in mammals. This study aimed to explore the effects of NPs on female reproduction using human ovarian granulosa cells (GCs) and female mice. The accumulation of polystyrene NPs (PS-NPs) in human granulosa-like tumor cells (KGN cells) and the ovaries of female Balb/c mice were evaluated by exposure to fluorescent PS-NPs. Proliferation and apoptosis, reactive oxygen species (ROS), and Hippo signaling pathway-related factors were analyzed in KGN cells. In addition, fertility rate, litter size, ovarian weight and microstructure, follicle development, serum level of anti-Mullerian hormone, and apoptosis in ovaries were examined in female mice. Here, the PS-NPs can penetrate the KGN cells and accumulate in the ovaries. In vitro, 100 μg/ml PS-NPs inhibited proliferation, induced apoptosis, accumulated ROS, activated three key regulators of the Hippo signaling pathway (MST1, LATS1, and YAP1), and downregulated the mRNA levels of CTGF and Cyr61 in KGN cells. Furthermore, salidroside, an antioxidative compound extracted from Rhodiola rosea, alleviated the damage of PS-NPs to KGN and inhibited the activation of the Hippo signal pathway. In vivo, exposure to 1 mg/day PS-NPs resulted in decreased fertility, abnormal ovarian function, and increased ovarian apoptosis in female mice. Overall, our data suggest that PS-NPs cause granulosa cell apoptosis and affect ovarian functions, leading to reduced fertility in female mice, by inducing oxidative stress and dysregulating the Hippo pathway.

Discovery of IHMT-MST1-39 as a novel MST1 kinase inhibitor and AMPK activator for the treatment of diabetes mellitus

Insulin-producing pancreatic β cell death is the fundamental cause of type 1 diabetes (T1D) and a contributing factor to type 2 diabetes (T2D). Moreover, metabolic disorder is another hallmark of T2D. Mammalian sterile 20-like kinase 1 (MST1) contributes to the progression of diabetes mellitus through apoptosis induction and acceleration of pancreatic β cell dysfunction. AMP-activated protein kinase (AMPK) is an energy sensing kinase and its activation has been suggested as a treatment option for metabolic diseases. Thus, pharmacological inhibition of MST1 and activation of AMPK simultaneously represents a promising approach for diabetes therapy. Here, we discovered a novel selective MST1 kinase inhibitor IHMT-MST1-39, which exhibits anti-apoptosis efficacy and improves the survival of pancreatic β cells under diabetogenic conditions, as well as primary pancreatic islets in an ex vivo disease model. Mechanistically, IHMT-MST1-39 activated AMPK signaling pathway in hepatocytes in vitro, combination of IHMT-MST1-39 and metformin synergistically prevented hyperglycemia and significantly ameliorated glucose tolerance and insulin resistance in diabetic mice. Taken together, IHMT-MST1-39 is a promising anti-diabetic candidate as a single agent or in combination therapy for both T1D and T2D.

MST1: A future novel target for cardiac diseases

Major heart diseases pose a serious threat to human health. Finding early diagnostic markers and key therapeutic targets is an urgent scientific problem in this field. Mammalian sterile 20-like kinase 1 (MST1) is a protein kinase, and the occurrence of many heart diseases is related to the continuous activation of the MST1 gene. With the deepening of the research, the potential role of MST1 in promoting the development of heart disease has become more apparent. Therefore, to better understand the role of MST1 in the pathogenesis of heart disease, this work systematically summarizes the role of MST1 in the pathogenesis of heart disease, gives a comprehensive overview of its possible strategies in the diagnosis and treatment of heart disease, and analyzes its potential significance as a marker for the diagnosis and treatment of heart disease.

The role of the Hippo pathway in autophagy in the heart

The Hippo pathway, an evolutionarily conserved signalling mechanism, controls organ size and tumourigenesis. Increasing lines of evidence suggest that autophagy, an important mechanism of lysosome-mediated cellular degradation, is regulated by the Hippo pathway, which thereby profoundly affects cell growth and death responses in various cell types. In the heart, Mst1, an upstream component of the Hippo pathway, not only induces apoptosis but also inhibits autophagy through phosphorylation of Beclin 1. YAP/TAZ, transcription factor co-factors and the terminal effectors of the Hippo pathway, affect autophagy through transcriptional activation of TFEB, a master regulator of autophagy and lysosomal biogenesis. The cellular abundance of YAP is negatively regulated by autophagy and suppression of autophagy induces accumulation of YAP, which, in turn, acts as a feedback mechanism to induce autophagosome formation. Thus, the Hippo pathway and autophagy regulate each other, thereby profoundly affecting cardiomyocyte survival and death. This review discusses the interaction between the Hippo pathway and autophagy and its functional significance during stress conditions in the heart and the cardiomyocytes therein.

Inhibition of YAP by lenvatinib in endothelial cells increases blood pressure through ferroptosis

Lenvatinib, a multitarget tyrosine kinase inhibitor (TKI), increases the incidence of severe hypertension and thus the incidence of cardiovascular complications. Inhibition of ferroptosis, a newly recognized type of cell death, alleviates endothelial dysfunction. Here, we report that lenvatinib-induced hypertension is associated with ferroptosis of endothelial cells. RNA sequencing (RNA-seq) showed that lenvatinib led to ferroptosis of endothelial cells and that administration of mouse with ferrostatin-1 (Fer-1), a specific ferroptosis inhibitor, dramatically ameliorated lenvatinib-induced hypertension and reversed lenvatinib-induced impairment of endothelium-dependent relaxation (EDR). Furthermore, lenvatinib significantly reduced glutathione peroxidase 4 (GPX4) expressions in the mouse aorta and human umbilical vein endothelial cells (HUVECs) and increased lipid peroxidation, lactate dehydrogenase (LDH) release, and malondialdehyde (MDA) levels in HUVECs. Immunofluorescence and Western blotting showed that lenvatinib significantly reduced Yes-associated protein (YAP) nuclear translocation but not cytoplasmic YAP expression in HUVECs. The data, generated from both in vivo and in vitro, showed that lenvatinib reduced total YAP (t-YAP) expression and increased the phosphorylation of YAP at both Ser127 and Ser397, without affecting YAP mRNA levels in HUVECs. XMU-MP-1 mediated YAP activation or YAP overexpression effectively attenuated the lenvatinib-induced decrease in GPX4 expression and increases in LDH release and MDA levels. In addition, overexpression of YAP in HUVECs ameliorated lenvatinib-induced decrease in the mRNA and protein levels of spermidine/spermine N (1)-acetyltransferase-1 (SAT1), heme oxygenase-1 (HO-1), and ferritin heavy chain 1 (FTH1). Taken together, our data suggest that lenvatinib-induced inhibition of YAP led to ferroptosis of endothelial cells and subsequently resulted in vascular dysfunction and hypertension.

Signaling Pathways in Inflammation and Cardiovascular Diseases: An Update of Therapeutic Strategies

Inflammatory processes represent a pivotal element in the development and complications of cardiovascular diseases (CVDs). Targeting these processes can lead to the alleviation of cardiomyocyte (CM) injury and the increase of reparative mechanisms. Loss of CMs from inflammation-associated cardiac diseases often results in heart failure (HF). Evidence of the crosstalk between nuclear factor-kappa B (NF-κB), Hippo, and mechanistic/mammalian target of rapamycin (mTOR) has been reported in manifold immune responses and cardiac pathologies. Since these signaling cascades regulate a broad array of biological tasks in diverse cell types, their misregulation is responsible for the pathogenesis of many cardiac and vascular disorders, including cardiomyopathies and atherosclerosis. In response to a myriad of proinflammatory cytokines, which induce reactive oxygen species (ROS) production, several molecular mechanisms are activated within the heart to inaugurate the structural remodeling of the organ. This review provides a global landscape of intricate protein–protein interaction (PPI) networks between key constituents of NF-κB, Hippo, and mTOR signaling pathways as quintessential targetable candidates for the therapy of cardiovascular and inflammation-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.

Hippo signaling pathway activation during SARS-CoV-2 infection contributes to host antiviral response

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), responsible for the Coronavirus Disease 2019 (COVID-19) pandemic, causes respiratory failure and damage to multiple organ systems. The emergence of viral variants poses a risk of vaccine failures and prolongation of the pandemic. However, our understanding of the molecular basis of SARS-CoV-2 infection and subsequent COVID-19 pathophysiology is limited. In this study, we have uncovered a critical role for the evolutionarily conserved Hippo signaling pathway in COVID-19 pathogenesis. Given the complexity of COVID-19-associated cell injury and immunopathogenesis processes, we investigated Hippo pathway dynamics in SARS-CoV-2 infection by utilizing COVID-19 lung samples and human cell models based on pluripotent stem cell-derived cardiomyocytes (PSC-CMs) and human primary lung air-liquid interface (ALI) cultures. SARS-CoV-2 infection caused activation of the Hippo signaling pathway in COVID-19 lung and in vitro cultures. Both parental and Delta variant of concern (VOC) strains induced Hippo pathway. The chemical inhibition and gene knockdown of upstream kinases MST1/2 and LATS1 resulted in significantly enhanced SARS-CoV-2 replication, indicating antiviral roles. Verteporfin, a pharmacological inhibitor of the Hippo pathway downstream transactivator, YAP, significantly reduced virus replication. These results delineate a direct antiviral role for Hippo signaling in SARS-CoV-2 infection and the potential for this pathway to be pharmacologically targeted to treat COVID-19.

Melatonin activates the Mst1-Nrf2 signaling to alleviate cardiac hypertrophy in pulmonary arterial hypertension

Among pulmonary arterial hypertension (PAH) patients, right ventricular (RV) functioning has been considered a major determining factor for cardiac capacity and survival. However, despite the recognition of the clinical importance for preserving RV functioning, no effective treatments are currently available for RV failure. This study aims to suggest one such possible treatment, through investigating the cardio-protective capabilities of the anti-oxidant, melatonin (Mel), for treating adverse RV remodeling in PAH, along with its underlying mechanisms. Arginine vasopressin induced neonatal rat cardiomyocyte hypertrophy in vitro; in vivo, PAH was induced in rats through intraperitoneal monocrotaline (MCT) injections, and Mel was administered intraperitoneally 24 h prior to MCT. Mel reduced rat cardiomyocyte hypertrophy and mitochondrial oxidative stress in vitro by activating the Mst1-Nrf2 pathway, which were all reversed upon siRNA knockdown of Mst1. Likewise, in vivo, Mel pre-treatment significantly ameliorated MCT-induced deterioration in cardiac function, RV hypertrophy, fibrosis and dilation. These beneficial effects were also associated with Mst1-Nrf2 pathway up regulation and its associated reduction in oxidative stress, as evidenced by the decrease in RV malondialdehyde content. Notably, results from Mel treatment were similar, or even superior, to those obtained from N-acetyl cysteine (NAC), which has already been-confirmed as an anti-oxidative treatment for PAH. By contrast, co-treatment with the Mst1 inhibitor XMU-MP-1 reversed all of those Mel-associated beneficial effects. Our findings thus identified Mel as a potent cardio-protective agent against the onset of maladaptive RV remodeling, through enhancement of the anti-oxidative response via Mst1-Nrf2 pathway activation.

Exploration of fetal growth restriction induced by vitamin D deficiency in rats via Hippo-YAP signaling pathway

INTRODUCTION

Maternal vitamin D deficiency (VDD) is associated with intrauterine growth restriction (IUGR), but the exact mechanism remains unclear. Here we explored the mechanism through which VDD induced IUGR.

METHODS

Female SD rats were fed a control normal diet (VD > 800 IU/Kg) or VDD diet (VD: 0 IU/Kg) for 8 weeks. Then, females were mated with 12-week-old male SD rats, and fetal and placental tissue were collected on the gestational day 13 (GD13) or 18 (GD18) to analyze the effects of VDD on pregnancy outcome and embryonic development. In vitro, the VDR gene of HTR-8/SVneo cells was knocked down to establish VDD model. Then, HTR-8/SVneo cells were treated with the MST1/2 inhibitor XMU-MP-1 or 0.1 μM/L calcitriol for 24 h (h). The mechanism of Hippo-YAP signaling pathway in VDD-induced placental dysplasia was further investigated by western blot, invasion assay, wound healing assay and Hoechst/PI staining.

RESULTS

The IUGR of the pregnant rats in the VDD group was significant, the placental structure and function were damaged, and there was an obvious inflammatory response, accompanied by a significant increase in the level of the transcription co-activator YAP phosphorylation. In vitro, VDD significantly inhibited the migratory and invasive abilities of HTR-8/SVneo cells, accompanied by decreased EMT capacity and increased apoptosis. When intervening with XMU-MP-1 in advance, we found that the effects of VDD were neutralized by Hippo-YAP signaling blocker.

DISCUSSION

Maternal VDD causes placental dysplasia and IUGR, and these abnormal changes may be associated with the activation of Hippo-YAP signaling pathway.

The Hippo-YAP pathway in various cardiovascular diseases: Focusing on the inflammatory response

The Hippo pathway was initially discovered in Drosophila melanogaster and mammals as a key regulator of tissue growth both in physiological and pathological states. Numerous studies depict the vital role of the Hippo pathway in cardiovascular development, heart regeneration, organ size and vascular remodeling through the regulation of YAP (yes-associated protein) translocation. Recently, an increasing number of studies have focused on the Hippo-YAP pathway in inflammation and immunology. Although the Hippo-YAP pathway has been revealed to play controversial roles in different contexts and cell types in the cardiovascular system, the mechanisms regulating tissue inflammation and the immune response remain to be clarified. In this review, we summarize findings from the past decade on the function and mechanism of the Hippo-YAP pathway in CVDs (cardiovascular diseases) such as myocardial infarction, cardiomyopathy and atherosclerosis. In particular, we emphasize the role of the Hippo-YAP pathway in regulating inflammatory cell infiltration and inflammatory cytokine activation.

Micro RNA-411 Expression Improves Cardiac Phenotype Following Myocardial Infarction in Mice

Induction of endogenous regenerative capacity has emerged as one promising approach to repair damaged hearts following myocardial infarction (MI). Re-expression of factors that are exclusively expressed during embryonic development may reactivate the ability of adult cardiomyocytes to regenerate. Here, we identified miR-411 as a potent inducer of cardiomyocyte proliferation. Overexpression of miR-411 in the heart significantly increased cardiomyocyte proliferation and survival in a model MI. We found that miR-411 enhances the activity of YAP, the main downstream effector of the Hippo pathway, in cardiomyocytes. In conclusion, miR-411 induces cardiomyocyte regeneration and improves cardiac function post-MI likely by modulating the Hippo/YAP pathway.

New Insights into Hippo/YAP Signaling in Fibrotic Diseases

Fibrosis results from defective wound healing processes often seen after chronic injury and/or inflammation in a range of organs. Progressive fibrotic events may lead to permanent organ damage/failure. The hallmark of fibrosis is the excessive accumulation of extracellular matrix (ECM), mostly produced by pathological myofibroblasts and myofibroblast-like cells. The Hippo signaling pathway is an evolutionarily conserved kinase cascade, which has been described well for its crucial role in cell proliferation, apoptosis, cell fate decisions, and stem cell self-renewal during development, homeostasis, and tissue regeneration. Recent investigations in clinical and pre-clinical models has shown that the Hippo signaling pathway is linked to the pathophysiology of fibrotic diseases in many organs including the lung, heart, liver, kidney, and skin. In this review, we have summarized recent evidences related to the contribution of the Hippo signaling pathway in the development of organ fibrosis. A better understanding of this pathway will guide us to dissect the pathophysiology of fibrotic disorders and develop effective tissue repair therapies.

A conserved YAP/Notch/REST network controls the neuroendocrine cell fate in the lungs

The Notch pathway is a conserved cell-cell communication pathway that controls cell fate decisions. Here we sought to determine how Notch pathway activation inhibits the neuroendocrine cell fate in the lungs, an archetypal process for cell fate decisions orchestrated by Notch signaling that has remained poorly understood at the molecular level. Using intratumoral heterogeneity in small-cell lung cancer as a tractable model system, we uncovered a role for the transcriptional regulators REST and YAP as promoters of the neuroendocrine to non-neuroendocrine transition. We further identified the specific neuroendocrine gene programs repressed by REST downstream of Notch in this process. Importantly, we validated the importance of REST and YAP in neuroendocrine to non-neuroendocrine cell fate switches in both developmental and tissue repair processes in the lungs. Altogether, these experiments identify conserved roles for REST and YAP in Notch-driven inhibition of the neuroendocrine cell fate in embryonic lungs, adult lungs, and lung cancer.

The development of shape. Modular control of growth in the lepidopteran forewing

The mechanisms by which tissues and organs achieve their final size and shape during development are largely unknown. Although we have learned much about the mechanisms that control growth, little is known about how those play out to achieve a structure's specific final size and shape. The wings of insects are attractive systems for the study of the control of morphogenesis, because they are perfectly flat and two-dimensional, composed of two closely appressed cellular monolayers in which morphogenetic processes can be easily visualized. The wings of Lepidoptera arise from imaginal disks whose structure is always perfectly congruent with that of the adult wing, so that it is possible to fate-map corresponding positions on the larval disk to those of the adult wing. Here we show that the forewing imaginal disks of Junonia coenia are subdivided into four domains, with characteristic patterns of expression of known patterning genes Spalt (Sal), Engrailed (En), and Cubitus interruptus (Ci). We show that DNA and protein synthesis, as well as mitoses, are spatially patterned in a domain-specific way. Knockdown of Sal and En using produced domain-specific reductions in the shape of the forewing. Knockdown of signaling pathways involved in the regulation of growth likewise altered the shape of the forewing in a domain-specific way. Our results reveal a multi-level regulation of forewing shape involving hormones and growth-regulating genes.

New Progress in the Molecular Regulations and Therapeutic Applications in Cardiac Oxidative Damage Caused by Pressure Overload

Chronic pressure overload is a key risk factor for mortality due to its subsequent development of heart failure, in which the underlying molecular mechanisms remain vastly undetermined. In this review, we updated the latest advancements for investigating the role and relevant mechanisms of oxidative stress involved in the pathogenesis of pressure-overload-induced cardiomyopathy and cardiac dysfunction, focusing on significant biological sources of reactive oxygen species (free radical) production, antioxidant defenses, and their association with the cardiac metabolic remodeling in the stressed heart. We also summarize the newly developed preclinical therapeutic approaches in animal models for pressure-overload-induced myocardial damage. This review aims to enhance the current understanding of the mechanisms of chronic hypertensive heart failure and potentially improve the development of better therapeutic strategies for the associated diseases.

High MST2 expression regulates lens epithelial cell apoptosis in age-related cataracts through YAP1 targeting GLUT1

Age-related cataract (ARC) is a severe visual impairment disease and its pathogenesis remains unclear. This study investigated the relevance of MST2/YAP1/GLUT1 in ARC development in vivo and in vitro, and explored the role and possible mechanisms of this pathway in oxidative damage-mediated apoptosis of lens epithelial cells (LECs). Western blot analysis and immunohistochemistry showed that MST2 and phosphorylated (p)-YAP (Ser127) protein levels were increased, and YAP1 and GLUT1 protein levels were decreased in LECs of ARC patients and aged mice. Additionally, differential expression of MST2 and YAP1 was associated with H₂O₂-induced apoptosis of human lens epithelial B3 (HLE-B3) cells. CCK-8 and Hoechst 33,342 apoptosis assays showed that MST2 and YAP1 were involved in H₂O₂-induced apoptosis of LECs. Subsequent experiments showed that, during MST2-mediated H₂O₂-induced apoptosis, p-YAP (Ser127) levels were elevated and immunofluorescence revealed nucleoplasmic translocation and inhibition of YAP1 protein expression. Furthermore, GLUT1 was in turn synergistically transcriptionally regulated by YAP1-TEAD1 in dual luciferase reporter assays. In conclusion, our study indicates that the MST2/YAP1/GLUT1 pathway plays a major role in the pathogenesis of ARC and LECs apoptosis, providing a new direction for future development of targeted inhibitors that block this signaling pathway to prevent, delay, or even cure ARC.

Hippo Signaling Pathway Activation during SARS-CoV-2 Infection Contributes to Host Antiviral Response

SARS-CoV-2, responsible for the COVID-19 pandemic, causes respiratory failure and damage to multiple organ systems. The emergence of viral variants poses a risk of vaccine failures and prolongation of the pandemic. However, our understanding of the molecular basis of SARS-CoV-2 infection and subsequent COVID-19 pathophysiology is limited. In this study, we have uncovered a critical role for the evolutionarily conserved Hippo signaling pathway in COVID-19 pathogenesis. Given the complexity of COVID-19 associated cell injury and immunopathogenesis processes, we investigated Hippo pathway dynamics in SARS-CoV-2 infection by utilizing COVID-19 lung samples, and human cell models based on pluripotent stem cell-derived cardiomyocytes (PSC-CMs) and human primary lung air-liquid interface (ALI) cultures. SARS-CoV-2 infection caused activation of the Hippo signaling pathway in COVID-19 lung and in vitro cultures. Both parental and Delta variant of concern (VOC) strains induced Hippo pathway. The chemical inhibition and gene knockdown of upstream kinases MST1/2 and LATS1 resulted in significantly enhanced SARS-CoV-2 replication, indicating antiviral roles. Verteporfin a pharmacological inhibitor of the Hippo pathway downstream transactivator, YAP, significantly reduced virus replication. These results delineate a direct antiviral role for Hippo signaling in SARS-CoV-2 infection and the potential for this pathway to be pharmacologically targeted to treat COVID-19.

Integrated Analysis of lncRNA and mRNA Expression Profiles Indicates Age-Related Changes in Meniscus

Little has been known about the role of long non-coding RNA (lncRNA) involves in change of aged meniscus. Microarray analyses were performed to identify lncRNAs and mRNAs expression profiles of meniscus in young and aging adults and apple bioinformatics methods to analyse their potential roles. The differentially expressed (DE) lncRNAs and mRNAs were confirmed by qRT-PCR. A total of 1608 DE lncRNAs and 1809 DE mRNAs were identified. Functional and pathway enrichment analyses of all DE mRNAs showed that DE mRNAs were mainly involved in the TGF-beta, Wnt, Hippo, PI3K-Akt signaling pathway. The expressions of TNFRSF11B and BMP2 were significantly upregulated in aging group. LASSO logistic regression analysis of the DE lncRNAs revealed four lncRNAs (AC124312.5, HCG11, POC1B-AS1, and AP001011.1) that were associated with meniscus degradation. CNC analysis demonstrated that AP001011 inhibited the expression of TNFRSF11B and AC1243125 upregulated the expression of TNFRSF11B. CeRNA analysis suggested that POC1B-AS1 regulates the expression of BMP2 by sponging miR 130a-3p, miR136-5p, miR 18a-3p, and miR 608. Furthermore, subcellular localization and m⁶A modification sites prediction analysis of these four lncRNAs was performed. These data lay a foundation for extensive studies on the role of lncRNAs in change of aged meniscus.