Integrin-mediated transforming growth factor-beta activation, a potential therapeutic target in fibrogenic disorders

Dietary nucleic acids promote oral tolerance through innate sensing pathways in mice

Oral tolerance is essential for intestinal homeostasis and systemic immune function. However, our understanding of how oral tolerance is maintained is inadequate. Here we report that food-derived nucleic acids promote oral tolerance through innate sensing pathways. We find that dietary nucleic acids, but not microbiota, expand the natural intraepithelial lymphocyte (IEL) pool, specifically in the small intestine. TGF-β1, produced by natural IELs, then promotes activation of gut CD103+ dendritic cells to support the induction of antigen-specific Treg cells in a mouse model of OVA-induced oral tolerance. Mechanistically, MAVS and STING are redundantly required for sensing dietary RNAs and DNAs to activate downstream TBK1 signalling to induce IL-15 production, which results in the accumulation of natural IELs. Thus, our study demonstrates a key role of food-triggered innate sensing pathways in the maintenance of natural IELs and oral tolerance.

Core Modifications of GSK3335103 toward Orally Bioavailable αvβ6 Inhibitors with Improved Synthetic Tractability

The αvβ6 integrin has been identified as a target for the treatment of fibrotic diseases, based on the role it has in activating TGF-β1, a protein implicated in the pathogenesis of fibrosis. However, the development of orally bioavailable αvβ6 inhibitors has proven challenging due to the zwitterionic pharmacophore required to bind to the RGD binding site. This work describes the design and development of a novel, orally bioavailable series of αvβ6 inhibitors, developing on two previously published αvβ6 inhibitors, GSK3008348 and GSK3335103. Strategies to reduce the basicity of the central ring nitrogen present in GSK3008348 were employed, while avoiding the synthetic complexity of the chiral, fluorine-containing quaternary carbon center contained in GSK3335103. Following initial PK studies, this series was optimized, aided by analysis of the physicochemical and in vitro PK properties, to deliver lead molecules (S)-20 and 28 as potent and orally bioavailable αvβ6 inhibitors with improved synthetic tractability.

Photobiomodulation suppresses allergic contact dermatitis by inhibiting T-cell activation

BACKGROUND

Allergic contact dermatitis (ACD) is a dermal inflammatory disease caused by allergic reactions to substances that contact the skin. The hyperactivation of T cells plays an important role in its pathogenesis. Photobiomodulation (PBM) is an efficacious therapeutic approach for suppressing inflammatory diseases.

OBJECTIVE

This study aimed to evaluate the potentially beneficial role of PBM in ACD models and investigate its possible mechanisms.

METHODS

In this study, the ACD model of C57BL/6 mice was produced and treated with PBM, and the number of T cells was evaluated. In an in vitro study, naïve T cells were isolated and intervened with PBM. The markers of T cell activation were detected by flow cytometer. Transforming growth factor-β (TGF-β) and reactive oxygen species (ROS) were detected to investigate the mechanism.

RESULTS

PBM effectively inhibited the inflammatory response by impeding the number of T cells in the ACD model. And in vitro studies showed that PBM could directly moderate the activation of naïve T cells and possess the capability to impede T cell activation via TGF-beta signaling pathway.

CONCLUSION

Our finding elucidates the potential mechanism underlying the inhibitory effects of PBM in inflammatory diseases and furnishes a theoretical foundation for its clinical application.

The Role of αvβ3 Integrin in Lamina Cribrosa Cell Mechanotransduction in Glaucoma

Purpose: Glaucoma, one of the leading causes of irreversible blindness, is a common progressive optic neuropathy characterised by visual field defects and structural changes to the optic nerve head (ONH). There is extracellular matrix (ECM) accumulation and fibrosis of the lamina cribrosa (LC) in the ONH, and consequently increased tissue stiffness of the LC connective tissue. Integrins are cell surface proteins that provide the key molecular link connecting cells to the ECM and serve as bidirectional sensors transmitting signals between cells and their environment to promote cell adhesion, proliferation, and remodelling of the ECM. Here, we investigated the expression of αVβ3 integrin in glaucoma LC cell, and its effect on stiffness-induced ECM gene transcription and cellular proliferation rate in normal (NLC) and glaucoma (GLC) LC cells, by down-regulating αVβ3 integrin expression using cilengitide (a known potent αVβ3 and αVβ5 inhibitor) and β3 integrin siRNA knockdown. Methods: GLC cells were compared to age-matched controls NLC to determine differential expression levels of αVβ3 integrin, ECM genes (Col1A1, α-SMA, fibronectin, vitronectin), and proliferation rates. The effects of αVβ3 integrin blockade (with cilengitide) and silencing (with a pool of four predesigned αVβ3 integrin siRNAs) on ECM gene expression and proliferation rates were evaluated using both reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blotting in the human NLC cells cultured on soft (4 kPa) and stiff (100 kPa) substrate and in GLC cells grown on standard plastic plates. Results: αVβ3 integrin gene and protein expression were enhanced (p < 0.05) in GLC cells as compared to NLC. Both cilengitide and siRNA significantly reduced αVβ3 expression in GLC. When NLC were grown in the stiff substrate, cilengitide and siRNA also significantly reduced the increased expression in αVβ3, ECM components, and proliferation rate. Conclusions: Here, we provide evidence of cilengitide- and siRNA-mediated silencing of αVβ3 integrin expression, and inhibition of ECM synthesis in LC cells. Therefore, αVβ3 integrin may be a promising target for the development of novel anti-fibrotic therapies for treating the LC cupping of the ONH in glaucoma.

Targeting alternative splicing of fibronectin in human renal proximal tubule epithelial cells with antisense oligonucleotides to reduce EDA+ fibronectin production and block an autocrine loop that drives renal fibrosis

TGFβ1 is a powerful regulator of fibrosis; secreted in a latent form, it becomes active after release from the latent complex. During tissue fibrosis, the EDA + isoform of cellular fibronectin is overexpressed. In pulmonary fibrosis it has been proposed that the fibronectin splice variant including an EDA domain (FN EDA+) activates latent TGFβ. Our work investigates the potential of blocking the 'splicing in' of EDA with antisense oligonucleotides to inhibit TGFβ1-induced EDA + fibronectin and to prevent the cascade of events initiated by TGFβ1 in human renal proximal tubule cells (PTEC). Human primary PTEC were treated with TGFβ1 for 48 h, medium removed and the cells transfected with RNase H-independent antisense oligonucleotides (ASO) designed to block EDA exon inclusion (ASO5). The efficacy of ASO to block EDA exon inclusion was assessed by EDA + fibronectin RNA and protein expression; the expression of TGFβ, αSMA (α smooth muscle actin), MMP2 (matrix metalloproteinse-2), MMP9 (matrix metalloproteinse-9), Collagen I, K Cadherin and connexin 43 was analysed. Targeting antisense oligonucleotides designed to block EDA exon inclusion in fibronectin pre mRNA were effective in reducing the amount of TGFβ1 -induced cellular EDA + fibronectin RNA and secreted EDA + fibronectin protein (assessed by western immunoblotting and immunocytochemistry) in human proximal tubule cells in an in vitro cell culture model. The effect was selective for EDA + exon with no effect on EDB + fibronectin RNA and total fibronectin mRNA. Exogenous TGFβ1 induced endogenous TGFβ, αSMA, MMP2, MMP9 and Col I mRNA. TGFβ1 treatment for 48h reduced the expression of K-Cadherin and increased the expression of connexin-43. These TGFβ1-induced pro-fibrotic changes were attenuated by ASO5 treatment. 48 h after the removal of exogenous TGFβ, further increases in αSMA, MMP2, MMP9 was observed; ASO5 significantly inhibited this subsequent increase. ASO5 treatment also significantly inhibited ability of the cell culture medium harvested at the end of the experiment (96h) to stimulate SMAD3 reporter cells. The role of endogenous TGFβ1 was confirmed by the use of a TGFβ receptor inhibitor. Our results demonstrate a critical role of FN EDA+ in a cycle of TGFβ driven pro-fibrotic responses in human PTEC and blocking its production with ASO technology offers a potential therapy to interrupt this vicious circle and hence limit the progression of renal fibrosis.

Potential of αvβ6 and αvβ1 integrin inhibition for treatment of idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease of unknown cause with a dismal prognosis. Nintedanib and Pirfenidone are approved worldwide for the treatment of IPF, but they only slow the rate of functional decline and disease progression. Therefore, there is an urgent need for more efficacious and better tolerated drugs.

AREAS COVERED

αvβ6 and αvβ1 are two integrins overexpressed in fibrotic tissue, which play a critical role in the development of lung fibrosis. They act by converting transforming growth factor (TGF)-β, one of the most important profibrotic cytokine, in its active form. Here, we summarize and critically discuss the potential of a dual αvβ6/αvβ1 integrin inhibitor for the treatment of IPF.

EXPERT OPINION

Bexotegrast, a dual αvβ6/αvβ1 integrin inhibitor, has the potential to slow or even halt disease progression in IPF. Indeed, the strong pre-clinical rationale and promising early phase clinical trial data have raised expectations.

Transforming growth factor-β receptors: versatile mechanisms of ligand activation

Transforming growth factor-β (TGF-β) signaling is initiated by activation of transmembrane TGF-β receptors (TGFBR), which deploys Smad2/3 transcription factors to control cellular responses. Failure or dysregulation in the TGF-β signaling pathways leads to pathological conditions. TGF-β signaling is regulated at different levels along the pathways and begins with the liberation of TGF-β ligand from its latent form. The mechanisms of TGFBR activation display selectivity to cell types, agonists, and TGF-β isoforms, enabling precise control of TGF-β signals. In addition, the cell surface compartments used to release active TGF-β are surprisingly vibrant, using thrombospondins, integrins, matrix metalloproteinases and reactive oxygen species. The scope of TGFBR activation is further unfolded with the discovery of TGFBR activation initiated by other signaling pathways. The unique combination of mechanisms works in series to trigger TGFBR activation, which can be explored as therapeutic targets. This comprehensive review provides valuable insights into the diverse mechanisms underpinning TGFBR activation, shedding light on potential avenues for therapeutic exploration.

Myosin light chain phosphatase is a downstream target of Rho-kinase in endothelin-1-induced transactivation of the TGF-β receptor

BACKGROUND

Rho-kinase (ROCK) regulates actomyosin contraction, coronary vasospasm, and cytoskeleton dynamics. ROCK and of NADPH oxidase (NOX) play an essential role in cardiovascular disease and proteoglycan synthesis, which promotes atherosclerosis by trapping low density lipoprotein. ROCK is activated by endothelin-1 (ET1) and transactivates the transforming growth factor beta receptor (TGFβR1), intensifying Smad signaling and proteoglycan production. This study aimed to identify the role of myosin light chain phosphatase (MLCP) as a downstream target of ROCK in TβR1 transactivation.

METHODS

Vascular smooth muscle cells were treated with ET1 and inhibitors of ROCK and MLCP were added. The phosphorylation levels of Smad2C, myosin light chain (MLC), and MLCP were monitored by western blot, and the mRNA expression of chondroitin 4-O-sulfotransferase 1 (C4ST1) was assessed by quantitative real-time PCR.

RESULTS

We examined ROCK's role in ET1-induced TGFβR1 activation. ROCK phosphorylated MLCP at the MYPT1 T853 residue, blocked by the ROCK inhibitor Y27632. ROCK also increased MLC phosphorylation and actomyosin contraction in response to ET1, enhanced by the phosphatase inhibitor Calyculin A. Calyculin A also increased C4ST1 expression, GAG-chain synthesizing enzymes.

CONCLUSIONS

This work suggests that ROCK is involved in ET1-mediated TβR1 activation through increased MLCP phosphorylation, which leads to Smad2C phosphorylation and stimulates C4ST1 expression.

Differential regulation of fibronectin expression and fibrillogenesis by autocrine TGF-β1 signaling in malignant and benign mammary epithelial cells

Remodeling of the extracellular matrix (ECM) is a key hallmark of cancer progression. A critical component of ECM remodeling is the assembly of the glycoprotein fibronectin (FN) into insoluble fibrils, which provide a scaffold for invading vascular endothelial cells and escaping cancer cells, as well as a framework for collagen deposition and oncogenic cytokine tethering. FN fibril assembly is induced by Transforming Growth Factor-β1 (TGF-β1), which was originally identified for its role in malignant transformation. Addition of exogenous TGF-β1 drives FN fibril assembly while also upregulating endogenous TGF-β1 expression and autocrine signaling. In the current study, we sought to determine if autocrine TGF-β1 signaling plays a role in FN fibril formation in either MCF10A mammary epithelial cells, which behave similarly to healthy epithelia, or malignant MDA- MB-231 breast cancer cells. Our results show two interesting findings: first, malignant MDA-MB- 231 cells assemble less FN into fibrils, despite expressing and secreting more soluble FN; second, autocrine TGF-β1 signaling is required for FN fibril formation in MCF10A epithelial cells, even in the presence of exogenous, active TGF-β1. This suggests that autocrine TGF-β1 is signaling through distinct pathways from active exogenous TGF-β1. We hypothesized that this signaling was mediated by interactions between the TGF-β1 latency associated peptide (LAP) and αv integrins; indeed, incubating MCF10As with soluble LAP, even in the absence of the active TGF-β1 ligand, partially recovered FN fibril assembly. Taken together, these data suggests that autocrine TGF-β1 plays a critical role in FN fibril assembly, and this interaction is mediated by LAP-integrin signaling.

Obstructive nephropathy and molecular pathophysiology of renal interstitial fibrosis

The kidneys play a key role in maintaining total body homeostasis. The complexity of this task is reflected in the unique architecture of the organ. Ureteral obstruction greatly affects renal physiology by altering hemodynamics, changing glomerular filtration and renal metabolism, and inducing architectural malformations of the kidney parenchyma, most importantly renal fibrosis. Persisting pathological changes lead to chronic kidney disease, which currently affects ∼10% of the global population and is one of the major causes of death worldwide. Studies on the consequences of ureteral obstruction date back to the 1800s. Even today, experimental unilateral ureteral obstruction (UUO) remains the standard model for tubulointerstitial fibrosis. However, the model has certain limitations when it comes to studying tubular injury and repair, as well as a limited potential for human translation. Nevertheless, ureteral obstruction has provided the scientific community with a wealth of knowledge on renal (patho)physiology. With the introduction of advanced omics techniques, the classical UUO model has remained relevant to this day and has been instrumental in understanding renal fibrosis at the molecular, genomic, and cellular levels. This review details key concepts and recent advances in the understanding of obstructive nephropathy, highlighting the pathophysiological hallmarks responsible for the functional and architectural changes induced by ureteral obstruction, with a special emphasis on renal fibrosis.

BRD4 as a Therapeutic Target in Pulmonary Diseases

Bromodomain and extra-terminal domain (BET) proteins are epigenetic modulators that regulate gene transcription through interacting with acetylated lysine residues of histone proteins. BET proteins have multiple roles in regulating key cellular functions such as cell proliferation, differentiation, inflammation, oxidative and redox balance, and immune responses. As a result, BET proteins have been found to be actively involved in a broad range of human lung diseases including acute lung inflammation, asthma, pulmonary arterial hypertension, pulmonary fibrosis, and chronic obstructive pulmonary disease (COPD). Due to the identification of specific small molecular inhibitors of BET proteins, targeting BET in these lung diseases has become an area of increasing interest. Emerging evidence has demonstrated the beneficial effects of BET inhibitors in preclinical models of various human lung diseases. This is, in general, largely related to the ability of BET proteins to bind to promoters of genes that are critical for inflammation, differentiation, and beyond. By modulating these critical genes, BET proteins are integrated into the pathogenesis of disease progression. The intrinsic histone acetyltransferase activity of bromodomain-containing protein 4 (BRD4) is of particular interest, seems to act independently of its bromodomain binding activity, and has implication in some contexts. In this review, we provide a brief overview of the research on BET proteins with a focus on BRD4 in several major human lung diseases, the underlying molecular mechanisms, as well as findings of targeting BET proteins using pharmaceutical inhibitors in different lung diseases preclinically.

A specialized integrin-binding motif enables proTGF-β2 activation by integrin αVβ6 but not αVβ8

Activation of latent transforming growth factor (TGF)-β2 is incompletely understood. Unlike TGF-β1 and β3, the TGF-β2 prodomain lacks a seven-residue RGDLXX (L/I) integrin-recognition motif and is thought not to be activated by integrins. Here, we report the surprising finding that TGF-β2 contains a related but divergent 13-residue integrin-recognition motif (YTSGDQKTIKSTR) that specializes it for activation by integrin αVβ6 but not αVβ8. Both classes of motifs compete for the same binding site in αVβ6. Multiple changes in the longer motif underlie its specificity. ProTGF-β2 structures define interesting differences from proTGF-β1 and the structural context for activation by αVβ6. Some integrin-independent activation is also seen for proTGF-β2 and even more so for proTGF-β3. Our findings have important implications for therapeutics to αVβ6 in clinical trials for fibrosis, in which inhibition of TGF-β2 activation has not been anticipated.

αvβ3 Integrin as a Link between the Development of Fibrosis and Thyroid Hormones in Systemic Sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. Key players mediating fibrosis are myofibroblasts (MF) that, following transforming growth factor β (TGFβ) exposure, produce a collagen-rich extracellular matrix (ECM) that induces myofibroblast differentiation. Myofibroblasts express αvβ3 integrin (a membrane receptor for thyroid hormones) and miRNA-21 that promotes deiodinase-type-3 expression (D3), causing the degradation of triiodothyronine (T3) that attenuates fibrosis. We hypothesized that αvβ3 affects the fibrotic processes through its thyroid hormones (THs) binding site. To test this, dermal fibroblasts (DF) were cultured with/without TGFβ and removed with a base, leaving only normal/fibrotic ECMs in wells. Then, DF were cultured on the ECMs with/without tetrac (αvβ3 ligand, T4 antagonist), and evaluated for pro-fibrotic characteristics, αvβ3, miRNA-21, and D3 levels. Blood free-T3 (fT3), miRNA-21 levels, and the modified Rodnan skin score (MRSS) were evaluated in SSc patients. We found that the "fibrotic-ECM" significantly increased the pro-fibrotic characteristics of DF and the levels of miRNA-21, D3, and αvβ3, compared to the "normal-ECM." Tetrac significantly inhibited the effects of the "fibrotic-ECM" on the cells. In accordance with tetrac's effect on D3/miRNA-21, a negative correlation was found between the patients' fT3 to miRNA-21 levels, and to the development of pulmonary arterial hypertension (PAH). We conclude that occupying the THs binding site of αvβ3 may delay the development of fibrosis.

Mesenchymal cells in the Lung: Evolving concepts and their role in fibrosis

Mesenchymal cells in the lung are crucial during development, but also contribute to the pathogenesis of fibrotic disorders, including idiopathic pulmonary fibrosis (IPF), the most common and deadly form of fibrotic interstitial lung diseases. Originally thought to behave as supporting cells for the lung epithelium and endothelium with a singular function of producing basement membrane, mesenchymal cells encompass a variety of cell types, including resident fibroblasts, lipofibroblasts, myofibroblasts, smooth muscle cells, and pericytes, which all occupy different anatomic locations and exhibit diverse homeostatic functions in the lung. During injury, each of these subtypes demonstrate remarkable plasticity and undergo varying capacity to proliferate and differentiate into activated myofibroblasts. Therefore, these cells secrete high levels of extracellular matrix (ECM) proteins and inflammatory cytokines, which contribute to tissue repair, or in pathologic situations, scarring and fibrosis. Whereas epithelial damage is considered the initial trigger that leads to lung injury, lung mesenchymal cells are recognized as the ultimate effector of fibrosis and attempts to better understand the different functions and actions of each mesenchymal cell subtype will lead to a better understanding of why fibrosis develops and how to better target it for future therapy. This review summarizes current findings related to various lung mesenchymal cells as well as signaling pathways, and their contribution to the pathogenesis of pulmonary fibrosis.

Heart failure in systemic right ventricle: Mechanisms and therapeutic options

d-loop transposition of the great arteries (d-TGA) and congenitally corrected transposition of the great arteries (cc-TGA) feature a right ventricle attempting to sustain the systemic circulation. A systemic right ventricle (sRV) cannot support cardiac output in the long run, eventually decompensating and causing heart failure. The burden of d-TGA patients with previous atrial switch repair and cc-TGA patients with heart failure will only increase in the coming years due to the aging adult congenital heart disease population and improvements in the management of advanced heart failure. Clinical data still lags behind in developing evidence-based guidelines for risk stratification and management of sRV patients, and clinical trials for heart failure in these patients are underrepresented. Recent studies have provided foundational data for the commencement of robust clinical trials in d-TGA and cc-TGA patients. Further insights into the multifactorial nature of sRV failure can only be provided by the results of such studies. This review discusses the mechanisms of heart failure in sRV patients with biventricular circulation and how these mediators may be targeted clinically to alleviate sRV failure.

Transforming Growth Factor-β1 in Cancer Immunology: Opportunities for Immunotherapy

Transforming growth factor-beta1 (TGF-β) regulates a plethora of cell-intrinsic processes that modulate tumor progression in a context-dependent manner. Thus, although TGF-β acts as a tumor suppressor in the early stages of tumorigenesis, in late stages, this factor promotes tumor progression and metastasis. In addition, TGF-β also impinges on the tumor microenvironment by modulating the immune system. In this aspect, TGF-β exhibits a potent immunosuppressive effect, which allows both cancer cells to escape from immune surveillance and confers resistance to immunotherapy. While TGF-β inhibits the activation and antitumoral functions of T-cell lymphocytes, dendritic cells, and natural killer cells, it promotes the generation of T-regulatory cells and myeloid-derived suppressor cells, which hinder antitumoral T-cell activities. Moreover, TGF-β promotes tumor-associated macrophages and neutrophils polarization from M1 into M2 and N1 to N2, respectively. Altogether, these effects contribute to the generation of an immunosuppressive tumor microenvironment and support tumor promotion. This review aims to analyze the relevant evidence on the complex role of TGF-β in cancer immunology, the current outcomes of combined immunotherapies, and the anti-TGF-β therapies that may improve the success of current and new oncotherapies.

Molecular Approaches and Echocardiographic Deformation Imaging in Detecting Myocardial Fibrosis

The pathological remodeling of myocardial tissue is the main cause of heart diseases. Several processes are involved in the onset of heart failure, and the comprehension of the mechanisms underlying the pathological phenotype deserves special attention to find novel procedures to identify the site of injury and develop novel strategies, as well as molecular druggable pathways, to counteract the high degree of morbidity associated with it. Myocardial fibrosis (MF) is recognized as a critical trigger for disruption of heart functionality due to the excessive accumulation of extracellular matrix proteins, in response to an injury. Its diagnosis remains focalized on invasive techniques, such as endomyocardial biopsy (EMB), or may be noninvasively detected by cardiac magnetic resonance imaging (CMRI). The detection of MF by non-canonical markers remains a challenge in clinical practice. During the last two decades, two-dimensional (2D) speckle tracking echocardiography (STE) has emerged as a new non-invasive imaging modality, able to detect myocardial tissue abnormalities without specifying the causes of the underlying histopathological changes. In this review, we highlighted the clinical utility of 2D-STE deformation imaging for tissue characterization, and its main technical limitations and criticisms. Moreover, we focalized on the importance of coupling 2D-STE examination with the molecular approaches in the clinical decision-making processes, in particular when the 2D-STE does not reflect myocardial dysfunction directly. We also attempted to examine the roles of epigenetic markers of MF and hypothesized microRNA-based mechanisms aiming to understand how they match with the clinical utility of echocardiographic deformation imaging for tissue characterization and MF assessment.

CWHM-12, an Antagonist of Integrin-Mediated Transforming Growth Factor-Beta Activation Confers Protection During Early Mycobacterium tuberculosis Infection in Mice

Tuberculosis (TB) caused by the pathogenic bacterium Mycobacterium tuberculosis (Mtb) is one of the most lethal infectious diseases in the world. Presently, Bacillus Calmette-Guerin, the vaccine approved for use against TB, does not offer complete protection against the disease, which necessitates the development of new therapeutics to treat this infection. Overexpression of transforming growth factor beta (TGF-β) is associated with pulmonary profibrotic changes. The inactive TGF-β secreted is activated through its cleavage and release by αv integrins. Integrin-mediated regulation of TGF-β is considered as a master switch in the profibrotic process and a potential therapeutic target. Thus, in this study, we sought to determine if treatment with a broad range antagonist of integrins, CWHM-12, has the potency to inhibit pulmonary fibrosis and enhance Mtb control in a highly susceptible mouse model of Mtb infection, namely the C3Heb/FeJ (FeJ). CWHM-12 treatment at the early stages of Mtb infection was efficacious in reducing disease severity and inflammation associated with decreased iNOS, MIP-2, and IL-10 production without degradation of collagen. This suggests a potential for CWHM-12 targeting of TGF-β to be explored as an adjunct therapeutic for early Mtb infection.

Inhibition of Integrin αvβ6 Activation of TGF-β Attenuates Tendinopathy

Tendinopathy is a common tendon disorder that causes pain and impairs function. It is the most common reason for consultation with musculoskeletal specialists. The available therapies for tendinopathy are limited in number and efficacy and have unclear cellular and molecular mechanisms. Here it is shown that transforming growth factor-beta (TGF-β) activated by integrin αvβ6 promotes tendinopathy in mice. Excessive active TGF-β is found during tendinopathy progression, which led to tenocytes' phenotype transition to chondrocytes. Transgenic expression of active TGF-β in tendons induced spontaneous tendinopathy, whereas systemic injection of a TGF-β neutralizing antibody attenuated tendinopathy. Inducible knockout of the TGF-β type 2 receptor gene (Tgfbr2) in tenocytes inhibited tendinopathy progression in mice. Moreover, it is found that integrin αvβ6 induces TGF-β activation in response to mechanical load in tendons. Conditional knockout of the integrin αv gene in tendons prevented tendinopathy in mice. The study suggests that integrin αvβ6 activation of TGF-β is the mechanism of tendinopathy, and that integrin αvβ6 may be a therapeutic target in tendinopathy.

The functional multipotency of transforming growth factor β signaling at the intersection of senescence and cancer

The transforming growth factor β (TGF-β) family of cytokines comprises a group of proteins, their receptors, and effector molecules that, in a coordinated manner, modulate a plethora of physiological and pathophysiological processes. TGF-β1 is the best known and plausibly most active representative of this group. It acts as an immunosuppressant, contributes to extracellular matrix remodeling, and stimulates tissue fibrosis, differentiation, angiogenesis, and epithelial-mesenchymal transition. In recent years, this cytokine has been established as a vital regulator of organismal aging and cellular senescence. Finally, the role of TGF-β1 in cancer progression is no longer in question. Because this protein is involved in so many, often overlapping phenomena, the question arises whether it can be considered a molecular bridge linking some of these phenomena together and governing their reciprocal interactions. In this study, we reviewed the literature from the perspective of the role of various TGF-β family members as regulators of a complex mutual interplay between senescence and cancer. These aspects are then considered in a broader context of remaining TGF-β-related functions and coexisting processes. The main narrative axis in this work is centered around the interaction between the senescence of normal peritoneal cells and ovarian cancer cells. The discussion also includes examples of TGF-β activity at the interface of other normal and cancer cell types.

Molecular Mechanisms of Tumor Immunomodulation in the Microenvironment of Colorectal Cancer

Colorectal cancer remains one of the most important health challenges in our society. The development of cancer immunotherapies has fostered the need to better understand the anti-tumor immune mechanisms at play in the tumor microenvironment and the strategies by which the tumor escapes them. In this review, we provide an overview of the molecular interactions that regulate tumor inflammation. We particularly discuss immunomodulatory cell-cell interactions, cell-soluble factor interactions, cell-extracellular matrix interactions and cell-microbiome interactions. While doing so, we highlight relevant examples of tumor immunomodulation in colorectal cancer.

Thy-1 (CD90), Integrins and Syndecan 4 are Key Regulators of Skin Wound Healing

Acute skin wound healing is a multistage process consisting of a plethora of tightly regulated signaling events in specialized cells. The Thy-1 (CD90) glycoprotein interacts with integrins and the heparan sulfate proteoglycan syndecan 4, generating a trimolecular complex that triggers bi-directional signaling to regulate diverse aspects of the wound healing process. These proteins can act either as ligands or receptors, and they are critical for the successful progression of wound healing. The expression of Thy-1, integrins, and syndecan 4 is controlled during the healing process, and the lack of expression of any of these proteins results in delayed wound healing. Here, we review and discuss the roles and regulatory events along the stages of wound healing that support the relevance of Thy-1, integrins, and syndecan 4 as crucial regulators of skin wound healing.

Transforming growth factor β latency: A mechanism of cytokine storage and signalling regulation in liver homeostasis and disease

Transforming growth factor-β (TGF-β) is a potent effector in the liver, which is involved in a plethora of processes initiated upon liver injury. TGF-β affects parenchymal, non-parenchymal, and inflammatory cells in a highly context-dependent manner. Its bioavailability is critical for a fast response to various insults. In the liver – and probably in other organs – this is made possible by the deposition of a large portion of TGF-β in the extracellular matrix as an inactivated precursor form termed latent TGF-β (L-TGF-β). Several matrisomal proteins participate in matrix deposition, latent complex stabilisation, and activation of L-TGF-β. Extracellular matrix protein 1 (ECM1) was recently identified as a critical factor in maintaining the latency of deposited L-TGF-β in the healthy liver. Indeed, its depletion causes spontaneous TGF-β signalling activation with deleterious effects on liver architecture and function. This review article presents the current knowledge on intracellular L-TGF-β complex formation, secretion, matrix deposition, and activation and describes the proteins and processes involved. Further, we emphasise the therapeutic potential of toning down L-TGF-β activation in liver fibrosis and liver cancer.

The Effect of TGF-β1 Reduced Functionality on the Expression of Selected Synaptic Proteins and Electrophysiological Parameters: Implications of Changes Observed in Acute Hepatic Encephalopathy

Decreased platelet count represents a feature of acute liver failure (ALF) pathogenesis. Platelets are the reservoir of transforming growth factor 1 (TGF-β1), a multipotent cytokine involved in the maintenance of, i.a., central nervous system homeostasis. Here, we analyzed the effect of a decrease in TGF-β1 active form on synaptic proteins levels, and brain electrophysiology, in mice after intraperitoneal (ip) administration of TGF-β1 antibody (anti-TGF-β1; 1 mg/mL). Next, we correlated it with a thrombocytopenia-induced TGF-β1 decrease, documented in an azoxymethane-induced (AOM; 100 mM ip) model of ALF, and clarified the impact of TGF-β1 decrease on blood–brain barrier functionality. The increase of both synaptophysin and synaptotagmin in the cytosolic fraction, and its reduction in a membrane fraction, were confirmed in the AOM mice brains. Both proteins’ decrease in analyzed fractions occurred in anti-TGF-β1 mice. In turn, an increase in postsynaptic (NR1 subunit of N-methyl-D-aspartate receptor, postsynaptic density protein 95, gephyrin) proteins in the AOM brain cortex, but a selective compensatory increase of NR1 subunit in anti-TGF-β mice, was observed. The alterations of synaptic proteins levels were not translated on electrophysiological parameters in the anti-TGF-β1 model. The results suggest the impairment of synaptic vesicles docking to the postsynaptic membrane in the AOM model. Nevertheless, changes in synaptic protein level in the anti-TGF-β1 mice do not affect neurotransmission and may not contribute to neurologic deficits in AOM mice.

Role of the hippo signaling pathway in the extracellular matrix degradation of chondrocytes induced by fluoride exposure

To identify the role of the Hippo signaling pathway in the extracellular matrix degradation of chondrocytes induced by fluoride exposure. Environmental response genes (ERGs) of bone injury induced by fluoride exposure were obtained from the Comparative Toxicogenomics Database, and annotated by STRING for KEGG pathway enrichment analysis. The CCK-8 kit was used to measure the proliferation of ATDC5 cells. The malondialdehyde (MDA), total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD), and glutathione peroxidase (GSH-PX) levels in ATDC5 cells were measured using oxidative stress detection kit. Western blot analysis was used to measure the p-MST1/2, p-LATS1/2, and p-YAP/YAP1 expression levels in the Hippo pathway and the COL2A1, ACAN and MMP13 expression levels in the cartilage matrix. Localizations of YAP1 and COL2A1 proteins in chondrocytes were performed using cell immunofluorescence. Continuous data from the multiple groups were compared using one-way analysis of variance, and then the differences between groups were tested with Dunnett's t-test, with the test level α = 0.05. The 145 ERGs of bone injury induced by fluoride exposure were identified, and KEGG enrichment analysis revealed Hippo signaling pathways significantly related to bone injury. A CCK-8 assay revealed that the viability of the ATDC5 cells was significantly decreased with increased fluorine concentration. The MDA content in 20 mg/L sodium fluoride (NaF) exposure group was significantly higher than that in the control group, the T-SOD, T-AOC and GSH-PX activities in 15 and 20 mg/L NaF exposure groups were significantly lower than those in the control group (P < 0.05). Western blot results showed the protein levels of p-MST1/2, p-LATS1/2 and p-YAP1 in 15 and 20 mg/L NaF exposure groups were significantly lower than those in the control group, while the YAP1 protein level in 20 mg/L NaF group was significantly higher than that in the control group. The COL2A1 and ACAN proteins in 20 mg/L NaF group were significantly decreased, while the MMP13 protein level in 15 and 20 mg/L NaF groups were significantly increased (P < 0.05). It was observed that the expression of YAP1 protein expression level in the cytoplasm decreased with the increased fluoride exposure, whereas that the expression level of YAP1 protein in the nucleus increased. Fluoride inhibited the proliferation of ATDC5 cells, induced oxidative stress, inhibited the activity of the Hippo pathway, and eventually led to cartilage matrix degradation.

Common and Rare Genetic Variants That Could Contribute to Severe Otitis Media in an Australian Aboriginal Population

BACKGROUND

Our goal was to identify genetic risk factors for severe otitis media (OM) in Aboriginal Australians.

METHODS

Illumina® Omni2.5 BeadChip and imputed data were compared between 21 children with severe OM (multiple episodes chronic suppurative OM and/or perforations or tympanic sclerosis) and 370 individuals without this phenotype, followed by FUnctional Mapping and Annotation (FUMA). Exome data filtered for common (EXaC_all ≥ 0.1) putative deleterious variants influencing protein coding (CADD-scaled scores ≥15] were used to compare 15 severe OM cases with 9 mild cases (single episode of acute OM recorded over ≥3 consecutive years). Rare (ExAC_all ≤ 0.01) such variants were filtered for those present only in severe OM. Enrichr was used to determine enrichment of genes contributing to pathways/processes relevant to OM.

RESULTS

FUMA analysis identified 2 plausible genetic risk loci for severe OM: NR3C1 (Pimputed_1000G = 3.62 × 10-6) encoding the glucocorticoid receptor, and NREP (Pimputed_1000G = 3.67 × 10-6) encoding neuronal regeneration-related protein. Exome analysis showed: (i) association of severe OM with variants influencing protein coding (CADD-scaled ≥ 15) in a gene-set (GRXCR1, CDH23, LRP2, FAT4, ARSA, EYA4) enriched for Mammalian Phenotype Level 4 abnormal hair cell stereociliary bundle morphology and related phenotypes; (ii) rare variants influencing protein coding only seen in severe OM provided gene-sets enriched for "abnormal ear" (LMNA, CDH23, LRP2, MYO7A, FGFR1), integrin interactions, transforming growth factor signaling, and cell projection phenotypes including hair cell stereociliary bundles and cilium assembly.

CONCLUSIONS

This study highlights interacting genes and pathways related to cilium structure and function that may contribute to extreme susceptibility to OM in Aboriginal Australian children.

Integrin β1 Promotes Pancreatic Tumor Growth by Upregulating Kindlin-2 and TGF-β Receptor-2

The tumor microenvironment plays a critical role in defining the growth and malignancy of solid tumors. Extracellular matrix (ECM) proteins such as collagen, vitronectin, and fibronectin are major components of the tumor microenvironment. Tumor growth-promoting reciprocal interaction between ECM and cytoplasmic proteins is regulated by the cell surface receptors called integrins. This study investigated the mechanism by which integrin β1 promotes pancreatic tumor growth. In MIA PaCa-2 pancreatic cancer cell line, the loss of integrin β1 protein reduced the ability of cells to proliferate in a 3D matrix and compromised the ability to form a focal adhesion complex. Decreased expression of integrin α5 was observed in KO cells, which resulted in impaired cell spreading and adhesion on vitronectin and fibronectin. Reduced expression of the integrin-associated protein, kindlin-2 was also recorded. The downregulation of kindlin-2 decreased the phosphorylation of Smad2/3 by reducing the expression of TGF-β receptor 2. These results unravel a new mechanism of integrin β1 in tumor growth by modifying the expression of kindlin-2 and TGF-β receptor 2 signaling.

CG223, a novel BET inhibitor, exerts TGF-β1-mediated antifibrotic effects in a murine model of bleomycin-induced pulmonary fibrosis

Pulmonary fibrosis is a progressive disease with poor prognosis and limited therapeutic options. In this study, we evaluated the potential therapeutic effects of CG223, a novel inhibitor of bromodomain and extra-terminal motif (BET) proteins, on pulmonary fibrosis by focusing on the transforming growth factor-β1 (TGF-β1) pathway. In a murine model of bleomycin-induced pulmonary fibrosis, CG223 attenuated fibrosis while reducing the infiltration of inflammatory cells into the lungs. Fibroblasts expressing BRD4, a member of the BET protein family, were enriched in the tissue regions corresponding to bleomycin-induced fibrotic lesions. Additionally, pulmonary fibroblasts isolated from bleomycin-instilled mice showed a significantly increased association of BRD4 with the promoters of two pro-fibrotic genes linked to the entry into the TGF-β1 autocrine/paracrine loop, thrombospondin 1 (Thbs1) and integrin β3 (Itgb3), as well as with the promoter of a myofibroblast marker gene, actin alpha 2 (Acta2). Subsequent in vitro studies with murine primary lung fibroblasts showed that the mRNA induction of Thbs1, Itgb3, and Acta2 by TGF-β1 can be inhibited by CG223 in a dose-dependent manner. Taken together, CG223-induced BRD4 inhibition suppressed lung fibrogenesis by affecting multiple genes, including those involved in the triggering of the TGF-β1 autocrine/paracrine loop.

Nutrition profile and potency of RGD motif in protein hydrolysate of green peas as an antifibrosis in chronic kidney disease

OBJECTIVES

Fibrosis is the major cause of chronic kidney injury and the primary etiology in diabetic glomerulosclerosis. The initial study of protein hydrolysate of green peas hydrolyzed by bromelain (PHGPB) considered it to improve kidney function parameters and showed no fibrosis in histopathology features in gentamicin-induced nephrotoxicity rats. In the current study, we aimed to assess the nutrition profile and potency of RGD in PHGPB as antifibrosis in chronic kidney disease (CKD).

MATERIALS AND METHODS

Green peas (Pisum sativum) were hydrolyzed by bromelain from pineapple juice to obtain PHGPB. The amino acid content of PHGPB was measured using the UPLC method, while the primary structure used LC-MS/MS. Bioinformatic analysis was conducted using the Protease Specificity Predictive Server (PROSPER). The potency of RGD in PHGPB was characterized by determining the levels of Fibronectin (FN) and TGF-β1 in mesangial SV40 MES 13 cell lines of diabetic glomerulosclerosis.

RESULTS

The level of lysine was 364.85 mg/l. The LC-MS/MS data showed two proteins with 4-15 kDa molecular weight originated from convicilin (P13915 and P13919) which were predicted by PROSPER proteolytic cleavage, resulted in RGD in the LERGDT sequence peptide. PHGPB increased SV40 MES 13 mesangial cell proliferation that died from high-glucose levels (diabetic glomerulosclerosis model). PHGPB and RGD reduced the levels of FN and TGF-β1 in mesangial cell lines of diabetic glomerulosclerosis.

CONCLUSION

The nutrition profile and RGD motif in PHGPB show great potential as antifibrosis in CKD.

A tumor-specific mechanism of Treg enrichment mediated by the integrin αvβ8

Regulatory T cells (T_regs) that promote tumor immune evasion are enriched in certain tumors and correlate with poor prognosis. However, mechanisms for T_reg enrichment remain incompletely understood. We described a mechanism for T_reg enrichment in mouse and human tumors mediated by the αvβ8 integrin. Tumor cell αvβ8 bound to latent transforming growth factor-β (L-TGF-β) presented on the surface of T cells, resulting in TGF-β activation and immunosuppressive T_reg differentiation in vitro. In vivo, tumor cell αvβ8 expression correlated with T_reg enrichment, immunosuppressive T_reg gene expression, and increased tumor growth, which was reduced in mice by αvβ8 inhibition or T_reg depletion. Structural modeling and cell-based studies suggested a highly geometrically constrained complex forming between αvβ8-expressing tumor cells and L-TGF-β-expressing T cells, facilitating TGF-β activation, independent of release and diffusion, and providing limited access to TGF-β inhibitors. These findings suggest a highly localized tumor-specific mechanism for T_reg enrichment.

Targeting cancer metastasis with antibody therapeutics

Cancer metastasis, the spread of disease from a primary to a distal site through the circulatory or lymphatic systems, accounts for over 90% of all cancer related deaths. Despite significant progress in the field of cancer therapy in recent years, mortality rates remain dramatically higher for patients with metastatic disease versus those with local or regional disease. Although there is clearly an urgent need to develop drugs that inhibit cancer spread, the overwhelming majority of anticancer therapies that have been developed to date are designed to inhibit tumor growth but fail to address the key stages of the metastatic process: invasion, intravasation, circulation, extravasation, and colonization. There is growing interest in engineering targeted therapeutics, such as antibody drugs, that inhibit various steps in the metastatic cascade. We present an overview of antibody therapeutic approaches, both in the pipeline and in the clinic, that disrupt the essential mechanisms that underlie cancer metastasis. These therapies include classes of antibodies that indirectly target metastasis, including anti-integrin, anticadherin, and immune checkpoint blocking antibodies, as well as monoclonal and bispecific antibodies that are specifically designed to interrupt disease dissemination. Although few antimetastatic antibodies have achieved clinical success to date, there are many promising candidates in various stages of development, and novel targets and approaches are constantly emerging. Collectively, these efforts will enrich our understanding of the molecular drivers of metastasis, and the new strategies that arise promise to have a profound impact on the future of cancer therapeutic development. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Extracellular Matrix Remodeling in Chronic Liver Disease

PURPOSE OF THE REVIEW

This review aims to summarize the current knowledge of the extracellular matrix remodeling during hepatic fibrosis. We discuss the diverse interactions of the extracellular matrix with hepatic cells and the surrounding matrix in liver fibrosis, with the focus on the molecular pathways and the mechanisms that regulate extracellular matrix remodeling.

RECENT FINDINGS

The extracellular matrix not only provides structure and support for the cells, but also controls cell behavior by providing adhesion signals and by acting as a reservoir of growth factors and cytokines.

SUMMARY

Hepatic fibrosis is characterized by an excessive accumulation of extracellular matrix. During fibrogenesis, the natural remodeling process of the extracellular matrix varies, resulting in the excessive accumulation of its components, mainly collagens. Signals released by the extracellular matrix induce the activation of hepatic stellate cells, which are the major source of extracellular matrix and most abundant myofibroblasts in the liver.

GRAPHICAL ABSTRACT

Atypical structure and function of integrin αV β8

Integrins are heterodimeric transmembrane proteins that play important roles in various biological processes. Most integrins serve as adhesion molecules and transmit bidirectional signaling across the cell membrane through global conformational changes from the bent closed to the extended open conformation. However, integrin β₈ is distinctive in structure and function. Its cytoplasmic domain lacks the conserved protein-binding sequence, which is important in transmitting inside-out signals, suggesting that integrin β₈ may have a different activation mechanism or lack such signaling. In addition, the ligand-binding or activating metal ion Mn²⁺ does not induce a global conformational change in integrin β₈ . It may have only one conformation, that is, an extended, closed conformation, but with high affinity for ligands under physiological conditions, and is, therefore, considered an atypical integrin member. The extended structure and high ligand-binding affinity of integrin α_v β₈ make it ideal for encountering and binding ligands expressed on an opposing cell or in the extracellular matrix. In this review, we summarize the progress in integrin β₈ research with a focus on its distinctive function and structure among integrin members.

Lyme Disease Pathogenesis

Lyme disease Borrelia are obligately parasitic, tick- transmitted, invasive, persistent bacterial pathogens that cause disease in humans and non-reservoir vertebrates primarily through the induction of inflammation. During transmission from the infected tick, the bacteria undergo significant changes in gene expression, resulting in adaptation to the mammalian environment. The organisms multiply and spread locally and induce inflammatory responses that, in humans, result in clinical signs and symptoms. Borrelia virulence involves a multiplicity of mechanisms for dissemination and colonization of multiple tissues and evasion of host immune responses. Most of the tissue damage, which is seen in non-reservoir hosts, appears to result from host inflammatory reactions, despite the low numbers of bacteria in affected sites. This host response to the Lyme disease Borrelia can cause neurologic, cardiovascular, arthritic, and dermatologic manifestations during the disseminated and persistent stages of infection. The mechanisms by which a paucity of organisms (in comparison to many other infectious diseases) can cause varied and in some cases profound inflammation and symptoms remains mysterious but are the subjects of diverse ongoing investigations. In this review, we provide an overview of virulence mechanisms and determinants for which roles have been demonstrated in vivo, primarily in mouse models of infection.

Hiding in Plain Sight: Interleukin-11 Emerges as a Master Regulator of Fibrosis, Tissue Integrity, and Stromal Inflammation

Interleukin (IL)-11 is upregulated in a wide variety of fibro-inflammatory diseases such as systemic sclerosis, rheumatoid arthritis, pulmonary fibrosis, inflammatory bowel disease, kidney disease, drug-induced liver injury, and nonalcoholic steatohepatitis. IL-11 is a member of the IL-6 cytokine family and has several distinct properties that define its unique and nonredundant roles in disease. The IL-11 receptor is highly expressed on stromal, epithelial and polarized cells, where noncanonical IL-11 signaling drives the three pathologies common to all fibro-inflammatory diseases-myofibroblast activation, parenchymal cell dysfunction, and inflammation-while also inhibiting tissue regeneration. This cytokine has been little studied, and publications on IL-11 peaked in the early 1990s, when it was largely misunderstood. Here we describe recent advances in our understanding of IL-11 biology, outline how misconceptions as to its function came about, and highlight the large potential of therapies targeting IL-11 signaling for treating human disease.

Prominin-1-expressing hepatic progenitor cells induce fibrogenesis in murine cholestatic liver injury

Cholestatic liver injury is associated with intrahepatic biliary fibrosis, which can progress to cirrhosis. Resident hepatic progenitor cells (HPCs) expressing Prominin-1 (Prom1 or CD133) become activated and participate in the expansion of cholangiocytes known as the ductular reaction. Previously, we demonstrated that in biliary atresia, Prom1(+) HPCs are present within developing fibrosis and that null mutation of Prom1 significantly abrogates fibrogenesis. Here, we hypothesized that these activated Prom1-expressing HPCs promote fibrogenesis in cholestatic liver injury. Using Prom1CreERT2-nLacZ/+ ;Rosa26Lsl-GFP/+ mice, we traced the fate of Prom1-expressing HPCs in the growth of the neonatal and adult livers and in biliary fibrosis induced by bile duct ligation (BDL). Prom1-expressing cell lineage labeling with Green Fluorescent Protein (GFP) on postnatal day 1 exhibited an expanded population as well as bipotent differentiation potential toward both hepatocytes and cholangiocytes at postnatal day 35. However, in the adult liver, they lost hepatocyte differentiation potential. Upon cholestatic liver injury, adult Prom1-expressing HPCs gave rise to both PROM1(+) and PROM1(-) cholangiocytes contributing to ductular reaction without hepatocyte or myofibroblast differentiation. RNA-sequencing analysis of GFP(+) Prom1-expressing HPC lineage revealed a persistent cholangiocyte phenotype and evidence of Transforming Growth Factor-β pathway activation. When Prom1-expressing cells were ablated with induced Diphtheria toxin in Prom1CreERT-nLacZ/+ ;Rosa26DTA/+ mice, we observed a decrease in ductular reactions and biliary fibrosis typically present in BDL as well as decreased expression of numerous fibrogenic gene markers. Our data indicate that Prom1-expressing HPCs promote biliary fibrosis associated with activation of myofibroblasts in cholestatic liver injury.

Pharmacologic inhibition of RGD-binding integrins ameliorates fibrosis and improves function following kidney injury

Fibrosis is a final common pathway for many causes of progressive chronic kidney disease (CKD). Arginine-glycine-aspartic acid (RGD)-binding integrins are important mediators of the pro-fibrotic response by activating latent TGF-β at sites of injury and by providing myofibroblasts information about the composition and stiffness of the extracellular matrix. Therefore, blockade of RGD-binding integrins may have therapeutic potential for CKD. To test this idea, we used small-molecule peptidomimetics that potently inhibit a subset of RGD-binding integrins in a murine model of kidney fibrosis. Acute kidney injury leading to fibrosis was induced by administration of aristolochic acid. Continuous subcutaneous administration of CWHM-12, an RGD integrin antagonist, for 28 days improved kidney function as measured by serum creatinine. CWHM-12 significantly reduced Collagen 1 (Col1a1) mRNA expression and scar collagen deposition in the kidney. Protein and gene expression markers of activated myofibroblasts, a major source of extracellular matrix deposition in kidney fibrosis, were diminished by treatment. RNA sequencing revealed that inhibition of RGD integrins influenced multiple pathways that determine the outcome of the response to injury and of repair processes. A second RGD integrin antagonist, CWHM-680, administered once daily by oral gavage was also effective in ameliorating fibrosis. We conclude that targeting RGD integrins with such small-molecule antagonists is a promising therapeutic approach in fibrotic kidney disease.

Cryo-EM Reveals Integrin-Mediated TGF-β Activation without Release from Latent TGF-β

Integrin αvβ8 binds with exquisite specificity to latent transforming growth factor-β (L-TGF-β). This binding is essential for activating L-TGF-β presented by a variety of cell types. Inhibiting αvβ8-mediated TGF-β activation blocks immunosuppressive regulatory T cell differentiation, which is a potential therapeutic strategy in cancer. Using cryo-electron microscopy, structure-guided mutagenesis, and cell-based assays, we reveal the binding interactions between the entire αvβ8 ectodomain and its intact natural ligand, L-TGF-β, as well as two different inhibitory antibody fragments to understand the structural underpinnings of αvβ8 binding specificity and TGF-β activation. Our studies reveal a mechanism of TGF-β activation where mature TGF-β signals within the confines of L-TGF-β and the release and diffusion of TGF-β are not required. The structural details of this mechanism provide a rational basis for therapeutic strategies to inhibit αvβ8-mediated L-TGF-β activation.

Multiple Targets of the Canonical WNT/β-Catenin Signaling in Cancers

Canonical WNT/β-catenin signaling is involved in most of the mechanisms that lead to the formation and development of cancer cells. It plays a central role in three cyclic processes, which are the cell division cycle, the immune cycle, and circadian rhythms. When the canonical WNT pathway is upregulated as in cancers, the increase in β-catenin in the nucleus leads to activation of the expression of numerous genes, in particular CYCLIN D1 and cMYC, where the former influences the G1 phase of the cell division cycle, and the latter, the S phase. Every stage of the immune cycle is disrupted by the canonical WNT signaling. In numerous cancers, the dysfunction of the canonical WNT pathway is accompanied by alterations of the circadian genes (CLOCK, BMAL1, PER). Induction of these cyclic phenomena leads to the genesis of thermodynamic mechanisms that operate far from equilibrium, and that have been called “dissipative structures.” Moreover, upregulation of the canonical WNT/β-catenin signaling is important in the myofibroblasts of the cancer stroma. Their differentiation is controlled by the canonical WNT /TGF-β1 signaling. Myofibroblasts present ultraslow contractile properties due to the presence of the non-muscle myosin IIA. Myofibroblats also play a role in the inflammatory processes, often found in cancers and fibrosis processes. Finally, upregulated canonical WNT deviates mitochondrial oxidative phosphorylation toward the Warburg glycolysis metabolism, which is characteristic of cancers. Among all these cancer-generating mechanisms, the upregulated canonical WNT pathway would appear to offer the best hope as a therapeutic target, particularly in the field of immunotherapy.

TGF-β in Hepatic Stellate Cell Activation and Liver Fibrogenesis-Updated 2019

Liver fibrosis is an advanced liver disease condition, which could progress to cirrhosis and hepatocellular carcinoma. To date, there is no direct approved antifibrotic therapy, and current treatment is mainly the removal of the causative factor. Transforming growth factor (TGF)-β is a master profibrogenic cytokine and a promising target to treat fibrosis. However, TGF-β has broad biological functions and its inhibition induces non-desirable side effects, which override therapeutic benefits. Therefore, understanding the pleiotropic effects of TGF-β and its upstream and downstream regulatory mechanisms will help to design better TGF-β based therapeutics. Here, we summarize recent discoveries and milestones on the TGF-β signaling pathway related to liver fibrosis and hepatic stellate cell (HSC) activation, emphasizing research of the last five years. This comprises impact of TGF-β on liver fibrogenesis related biological processes, such as senescence, metabolism, reactive oxygen species generation, epigenetics, circadian rhythm, epithelial mesenchymal transition, and endothelial-mesenchymal transition. We also describe the influence of the microenvironment on the response of HSC to TGF-β. Finally, we discuss new approaches to target the TGF-β pathway, name current clinical trials, and explain promises and drawbacks that deserve to be adequately addressed.

The Role of the TGF-β Superfamily in Myocardial Infarction

The members of the transforming growth factor β (TGF-β) superfamily are essential regulators of cell differentiation, phenotype and function, and have been implicated in the pathogenesis of many diseases. Myocardial infarction is associated with induction of several members of the superfamily, including TGF-β1, TGF-β2, TGF-β3, bone morphogenetic protein (BMP)-2, BMP-4, BMP-10, growth differentiation factor (GDF)-8, GDF-11 and activin A. This manuscript reviews our current knowledge on the patterns and mechanisms of regulation and activation of TGF-β superfamily members in the infarcted heart, and discusses their cellular actions and downstream signaling mechanisms. In the infarcted heart, TGF-β isoforms modulate cardiomyocyte survival and hypertrophic responses, critically regulate immune cell function, activate fibroblasts, and stimulate a matrix-preserving program. BMP subfamily members have been suggested to exert both pro- and anti-inflammatory actions and may regulate fibrosis. Members of the GDF subfamily may also modulate survival and hypertrophy of cardiomyocytes and regulate inflammation. Important actions of TGF-β superfamily members may be mediated through activation of Smad-dependent or non-Smad pathways. The critical role of TGF-β signaling cascades in cardiac repair, remodeling, fibrosis, and regeneration may suggest attractive therapeutic targets for myocardial infarction patients. However, the pleiotropic, cell-specific, and context-dependent actions of TGF-β superfamily members pose major challenges in therapeutic translation.

Emerging strategies to disrupt the central TGF-β axis in kidney fibrosis

Chronic kidney disease (CKD) affects more than 20 million people in the United States and the global burden of this disorder is increasing. Many affected individuals will progress to end stage kidney disease necessitating dialysis or transplantation. CKD is also a major independent contributor to the risk of cardiovascular morbidity and mortality. Tubulointerstitial fibrosis is a final common pathway for most causes of progressive CKD. Currently, there are no clinically available therapies targeting fibrosis that can slow the decline in kidney function. Although it has long been known that TGF-β signaling is a critical mediator of kidney fibrosis, translating this knowledge to the clinic has been challenging. In this review, we highlight some recent insights into the mechanisms of TGF-β signaling that target activation of this cytokine at the site of injury or selectively inhibit pro-fibrotic gene expression. Molecules directed at these targets hold the promise of attaining therapeutic efficacy while limiting toxicity seen with global inhibition of TGF-β. Kidney injury has profound epigenetic effects leading to altered expression of more than a thousand genes. We discuss how drugs targeting epigenetic modifications, some of which are in use for cancer therapy, have the potential to reprogram gene regulatory networks to favor adaptive repair and prevent fibrosis. The lack of reliable biomarkers of kidney fibrosis is a major limitation in designing clinical trials for testing CKD treatments. We conclude by reviewing recent advances in fibrosis biomarker development.

Fibroblasts in the Infarcted, Remodeling, and Failing Heart

Expansion and activation of fibroblasts following cardiac injury is important for repair but may also contribute to fibrosis, remodeling, and dysfunction. The authors discuss the dynamic alterations of fibroblasts in failing and remodeling myocardium. Emerging concepts suggest that fibroblasts are not unidimensional cells that act exclusively by secreting extracellular matrix proteins, thus promoting fibrosis and diastolic dysfunction. In addition to their involvement in extracellular matrix expansion, activated fibroblasts may also exert protective actions, preserving the cardiac extracellular matrix, transducing survival signals to cardiomyocytes, and regulating inflammation and angiogenesis. The functional diversity of cardiac fibroblasts may reflect their phenotypic heterogeneity.

An Inhibitor of Arginine-Glycine-Aspartate-Binding Integrins Reverses Fibrosis in a Mouse Model of Nonalcoholic Steatohepatitis

The presence and stage of liver fibrosis in patients with nonalcoholic steatohepatitis (NASH) is strongly associated with mortality. Thus, both preventing and reversing fibrosis are critically important approaches to prevent death or the need for liver transplantation from NASH. Recently, fibrosis in several mouse models of organ injury was shown to be prevented and reversed with the potent small molecule, arginine-glycine-aspartic acid tripeptide (RGD)-binding, integrin antagonist (3S)-3-(3-bromo-5-(tert-butyl)phenyl)-3-(2-(3-hydroxy-5-((5-hydroxy-1,4,5,6-tetrahydropyrimidin-2-yl)amino)benzamido)acetamido)propanoic acid (Center for World Health and Medicine [CWHM]-12). We hypothesized that RGD-binding integrins may play an important role in fibrosis progression in NASH. We assessed the efficacy of CWHM-12 in a choline deficient, amino-acid defined, high-fat diet (CDAHFD) mouse model of NASH. Mice were kept on the CDAHFD or a control diet for 10 weeks, and CWHM-12 was delivered by continuous infusion for the final 4 weeks. The parameters of NASH and liver fibrosis were evaluated before and after drug treatment. Hepatic steatosis, liver injury, and inflammation were significantly induced by the CDAHFD at week 6 and did not change by week 10. Hepatic profibrogenic gene expression was induced by the CDAHFD at week 6, further increased at week 10, and decreased by CWHM-12. Fibrosis measured by analysis of liver collagen was reduced by CWHM-12 to levels significantly less than found at 6 weeks, demonstrating the possibility of reversing already established fibrosis despite ongoing injury. Demonstrated mechanisms of the antifibrotic effect of CWHM-12 included loss of activated hepatic stellate cells through apoptosis and suppression of hepatic profibrotic signal transduction by transforming growth factor β. Conclusion: RGD-binding integrins may be critical in the development of fibrosis in NASH and may represent potential targets for treating patients with NASH to reverse advanced liver fibrosis.

Systemic Sclerosis Pathogenesis and Emerging Therapies, beyond the Fibroblast

Systemic sclerosis (SSc) is a complex rheumatologic autoimmune disease in which inflammation, fibrosis, and vasculopathy share several pathogenic pathways that lead to skin and internal organ damage. Recent findings regarding the participation and interaction of the innate and acquired immune system have led to a better understanding of the pathogenesis of the disease and to the identification of new therapeutic targets, many of which have been tested in preclinical and clinical trials with varying results. In this manuscript, we review the state of the art of the pathogenesis of this disease and discuss the main therapeutic targets related to each pathogenic mechanism that have been discovered so far.

The effect of mesenchymal stem cell-secreted factors on airway epithelial repair

Aim: This study was aimed to investigate the effect of mesenchymal stem cell (MSC)-secreted factors on airway repair. Materials & methods: An indirect in vitro coculture model of injured airway epithelium explant with MSCs was developed. LC–MS/MS analysis was performed to determine factors secreted by MSCs and their involvement in epithelium repair was evaluated by histopathological assessment. Results: The identification of 54 of MSC proteins of which 44 of them were secretory/extracellular proteins. 43 of the secreted proteins were found to be involved in accelerating airway epithelium repair by stimulating the migratory, proliferative and differentiation abilities of the endogenous repair mechanisms. MSC-secreted proteins also initiated epithelial–mesenchymal transition process during early repair. Conclusion: MSC-secreted factors accelerated airway epithelial repair by stimulating the endogenous reparative and regenerative ability of lung cells.

Integrin αvβ8-expressing tumor cells evade host immunity by regulating TGF-β activation in immune cells

TGF-β is a promising immunotherapeutic target. It is expressed ubiquitously in a latent form that must be activated to function. Determination of where and how latent TGF-β (L-TGF-β) is activated in the tumor microenvironment could facilitate cell- and mechanism-specific approaches to immunotherapeutically target TGF-β. Binding of L-TGF-β to integrin αvβ8 results in activation of TGF-β. We engineered and used αvβ8 antibodies optimized for blocking or detection, which - respectively - inhibit tumor growth in syngeneic tumor models or sensitively and specifically detect β8 in human tumors. Inhibition of αvβ8 potentiates cytotoxic T cell responses and recruitment of immune cells to tumor centers - effects that are independent of PD-1/PD-L1. β8 is expressed on the cell surface at high levels by tumor cells, not immune cells, while the reverse is true of L-TGF-β, suggesting that tumor cell αvβ8 serves as a platform for activating cell-surface L-TGF-β presented by immune cells. Transcriptome analysis of tumor-associated lymphoid cells reveals macrophages as a key cell type responsive to β8 inhibition with major increases in chemokine and tumor-eliminating genes. High β8 expression in tumor cells is seen in 20%-80% of various cancers, which rarely coincides with high PD-L1 expression. These data suggest tumor cell αvβ8 is a PD-1/PD-L1-independent immunotherapeutic target.

Cryo-EM structure of the αvβ8 integrin reveals a mechanism for stabilizing integrin extension

Integrins are conformationally flexible cell surface receptors that survey the extracellular environment for their cognate ligands. Interactions with ligands are thought to be linked to global structural rearrangements involving transitions between bent, extended-closed and -open forms. Thus far, structural details are lacking for integrins in the extended conformation due to extensive flexibility between the headpiece and legs within this conformation. Here we present single-particle electron cryo-microscopy structures of human αvβ8 integrin in the extended-closed conformation, which has been considered to be a low-affinity intermediate. Our structures show the headpiece rotating about a flexible αv-knee, suggesting a ligand surveillance mechanism for integrins in their extended-closed form. Our model predicts that the extended conformation is mainly stabilized by an interface formed between flexible loops in the upper and lower domains of the αv-leg. Confirming these findings with the αvβ3 integrin suggests that our model of stabilizing the extended-closed conformation is generalizable to other integrins.