The tumor suppressor RASSF1A modulates inflammation and injury in the reperfused murine myocardium

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.

RASFF1A inhibits the epithelial-mesenchymal transition of lens epithelial cells induced by TGFβ through regulating HDAC6

To explore the role of Ras-association domain family 1 A (RASSF1A) in TGFβ2-induced changes of lens epithelial cells (LECs) behavior. The human LEC line SRA01/04 cells were treated with TGFβ2 in the presence or absence of RASSF1A and histone deacetylase 6 (HDAC6). qRT-PCR and western blot were performed to analysis mRNA and proteins expression. Cell proliferation was evaluated using MTT assay and colony formation assay. Transwell and scratch-wound healing assays were conducted to detected cell migration ability. RASSF1A was downregulated in TGFβ2-induced SRA01/04 cells. RASSF1A overexpression inhibited the cell viability, colony formation and migration abilities of SRA01/04 cells induced by TGFβ2. Overexpression of RASSF1A suppressed TGFβ2-induced EMT of SRA01/04 cells, which was manifested as inhibition of EMT-related proteins α-SMA, Vimentin, Snail and Fn expression. Moreover, RASSF1A down-regulated the expression of HDAC6. Importantly, HDAC6 reversed the effects of RASSF1A on SRA01/04 cells. These findings indicate that RASSF1A prevented TGFβ2-induced proliferation, migration, and EMT of LECs by regulating HDAC6 expression, suggesting that RASSF1A holds promise as a potential target for cataracts treatment.

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.

Suppression of myeloid YAP antagonizes adverse cardiac remodeling during pressure overload stress

Inflammation is an integral component of cardiovascular disease and is thought to contribute to cardiac dysfunction and heart failure. While ischemia-induced inflammation has been extensively studied in the heart, relatively less is known regarding cardiac inflammation during non-ischemic stress. Recent work has implicated a role for Yes-associated protein (YAP) in modulating inflammation in response to ischemic injury; however, whether YAP influences inflammation in the heart during non-ischemic stress is not described. We hypothesized that YAP mediates a pro-inflammatory response during pressure overload (PO)-induced non-ischemic injury, and that targeted YAP inhibition in the myeloid compartment is cardioprotective. In mice, PO elicited myeloid YAP activation, and myeloid-specific YAP knockout mice (YAPF/F;LysMCre) subjected to PO stress had better systolic function, and attenuated pathological remodeling compared to control mice. Inflammatory indicators were also significantly attenuated, while pro-resolving genes including Vegfa were enhanced, in the myocardium, and in isolated macrophages, of myeloid YAP KO mice after PO. Experiments using bone marrow-derived macrophages (BMDMs) from YAP KO and control mice demonstrated that YAP suppression shifted polarization toward a resolving phenotype. We also observed attenuated NLRP3 inflammasome priming and function in YAP deficient BMDMs, as well as in myeloid YAP KO hearts following PO, indicating disruption of inflammasome induction. Finally, we leveraged nanoparticle-mediated delivery of the YAP inhibitor verteporfin and observed attenuated PO-induced pathological remodeling compared to DMSO nanoparticle control treatment. These data implicate myeloid YAP as an important molecular nodal point that facilitates cardiac inflammation and fibrosis during PO stress and suggest that selective inhibition of YAP may prove a novel therapeutic target in non-ischemic heart disease.

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.

Hippo-Yap signaling in cardiac and fibrotic remodeling

Cardiac injury initiates a tissue remodeling process in which aberrant fibrosis plays a significant part, contributing to impaired contractility of the myocardium and the progression to heart failure. Fibrotic remodeling is characterized by the activation, proliferation, and differentiation of quiescent fibroblasts to myofibroblasts, and the resulting effects on the extracellular matrix and inflammatory milieu. Molecular mechanisms underlying fibroblast fate decisions and subsequent cardiac fibrosis are complex and remain incompletely understood. Emerging evidence has implicated the Hippo-Yap signaling pathway, originally discovered as a fundamental regulator of organ size, as an important mechanism that modulates fibroblast activity and adverse remodeling in the heart, while also exerting distinct cell type-specific functions that dictate opposing outcomes on heart failure. This brief review will focus on Hippo-Yap signaling in cardiomyocytes, cardiac fibroblasts, and other non-myocytes, and present mechanisms by which it may influence the course of cardiac fibrosis and dysfunction.

Targeting the Hippo pathway in heart repair

The Hippo pathway is an evolutionarily and functionally conserved signaling pathway that controls organ size by regulating cell proliferation, apoptosis, and differentiation. Emerging evidence has shown that the Hippo pathway plays critical roles in cardiac development, homeostasis, disease, and regeneration. Targeting the Hippo pathway has tremendous potential as a therapeutic strategy for treating intractable cardiovascular diseases such as heart failure. In this review, we summarize the function of the Hippo pathway in the heart. Particularly, we highlight the posttranslational modification of Hippo pathway components, including the core kinases LATS1/2 and their downstream effectors YAP/TAZ, in different contexts, which has provided new insights and avenues in cardiac research.

The role of the Hippo pathway in heart disease

Heart disease, including coronary artery disease, myocardial infarction, heart failure, cardiac hypertrophy, and cardiomyopathies, is the leading causes of death worldwide. The Hippo pathway is a central controller for organ size and tissue growth, which plays a pivotal role in determining cardiomyocytes and nonmyocytes proliferation, regeneration, differentiation, and apoptosis. In this review, we summarize the effects of the Hippo pathway on heart disease and propose potential intervention targets. Especially, we discuss the molecular mechanisms of the Hippo pathway involved in maintaining cardiac homeostasis by regulating cardiomyocytes and nonmyocytes function in the heart. Based on this, we conclude that the Hippo pathway is a promising therapeutic target for cardiovascular therapy, which will bring new perspectives for their treatments.

Microtubule Acetylation Controls MDA-MB-231 Breast Cancer Cell Invasion through the Modulation of Endoplasmic Reticulum Stress

During aggressive cancer progression, cancer cells adapt to unique microenvironments by withstanding various cellular stresses, including endoplasmic reticulum (ER) stress. However, the mechanism whereby cancer cells overcome the ER stress to survive remains to be elucidated. Herein, we demonstrated that microtubule acetylation in cancer cells grown on a stiff matrix promotes cancer progression by preventing excessive ER stress. Downregulation of microtubule acetylation using shRNA or CRSIPR/Cas9 techniques targeting ATAT1, which encodes α-tubulin N-acetyltransferase (αTAT1), resulted in the upregulation of ER stress markers, changes in ER morphology, and enhanced tunicamycin-induced UPR signaling in cancer cells. A set of genes involved in cancer progression, especially focal adhesion genes, were downregulated in both ATAT1-knockout and tunicamycin-treated cells, whereas ATAT1 overexpression restored the gene expression inhibited by tunicamycin. Finally, the expression of ATAT1 and ER stress marker genes were negatively correlated in various breast cancer types. Taken together, our results suggest that disruption of microtubule acetylation is a potent therapeutic tool for preventing breast cancer progression through the upregulation of ER stress. Moreover, ATAT1 and ER stress marker genes may be useful diagnostic markers in various breast cancer types.

AAV-mediated YAP expression in cardiac fibroblasts promotes inflammation and increases fibrosis

Fibrosis is a hallmark of heart disease independent of etiology and is thought to contribute to impaired cardiac dysfunction and development of heart failure. However, the underlying mechanisms that regulate the differentiation of fibroblasts to myofibroblasts and fibrotic responses remain incompletely defined. As a result, effective treatments to mitigate excessive fibrosis are lacking. We recently demonstrated that the Hippo pathway effector Yes-associated protein (YAP) is an important mediator of myofibroblast differentiation and fibrosis in the infarcted heart. Yet, whether YAP activation in cardiac fibroblasts is sufficient to drive fibrosis, and how fibroblast YAP affects myocardial inflammation, a significant component of adverse cardiac remodeling, are largely unknown. In this study, we leveraged adeno-associated virus (AAV) to target cardiac fibroblasts and demonstrate that chronic YAP expression upregulated indices of fibrosis and inflammation in the absence of additional stress. YAP occupied the Ccl2 gene and promoted Ccl2 expression, which was associated with increased macrophage infiltration, pro-inflammatory cytokine expression, collagen deposition, and cardiac dysfunction in mice with cardiac fibroblast-targeted YAP overexpression. These results are consistent with other recent reports and extend our understanding of YAP function in modulating fibrotic and inflammatory responses in the heart.

The Hippo Pathway in Cardiac Regeneration and Homeostasis: New Perspectives for Cell-Free Therapy in the Injured Heart

Intractable cardiovascular diseases are leading causes of mortality around the world. Adult mammalian hearts have poor regenerative capacity and are not capable of self-repair after injury. Recent studies of cell-free therapeutics such as those designed to stimulate endogenous cardiac regeneration have uncovered new feasible therapeutic avenues for cardiac repair. The Hippo pathway, a fundamental pathway with pivotal roles in cell proliferation, survival and differentiation, has tremendous potential for therapeutic manipulation in cardiac regeneration. In this review, we summarize the most recent studies that have revealed the function of the Hippo pathway in heart regeneration and homeostasis. In particular, we discuss the molecular mechanisms of how the Hippo pathway maintains cardiac homeostasis by directing cardiomyocyte chromatin remodeling and regulating the cell-cell communication between cardiomyocytes and non-cardiomyocytes in the heart.