Pharmacological inhibition of the vitronectin receptor abrogates PDGF-BB-induced hepatic stellate cell migration and activation in vitro

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.

Delivery technologies for therapeutic targeting of fibronectin in autoimmunity and fibrosis applications

Fibronectin (FN) is a critical component of the extracellular matrix (ECM) contributing to various physiological processes, including tissue repair and immune response regulation. FN regulates various cellular functions such as adhesion, proliferation, migration, differentiation, and cytokine release. Alterations in FN expression, deposition, and molecular structure can profoundly impact its interaction with other ECM proteins, growth factors, cells, and associated signaling pathways, thus influencing the progress of diseases such as fibrosis and autoimmune disorders. Therefore, developing therapeutics that directly target FN or its interaction with cells and other ECM components can be an intriguing approach to address autoimmune and fibrosis pathogenesis.

Salvianolic acid B attenuates liver fibrosis by targeting Ecm1 and inhibiting hepatocyte ferroptosis

Hepatocyte ferroptosis promotes the pathogenesis and progression of liver fibrosis. Salvianolic acid B (Sal B) exerts antifibrotic effects. However, the pharmacological mechanism and target has not yet been fully elucidated. In this study, liver fibrosis was induced by CCl4 in wild-type mice and hepatocyte-specific extracellular matrix protein 1 (Ecm1)-deficient mice, which were separately treated with Sal B, ferrostatin-1, sorafenib or cilengitide. Erastin- or CCl4-induced hepatocyte ferroptosis models with or without Ecm1 gene knockdown were evaluated in vitro. Subsequently, the interaction between Ecm1 and xCT and the binding kinetics of Sal B and Ecm1 were determined. We found that Sal B significantly attenuated liver fibrosis in CCl4-induced mice. Ecm1 deletion in hepatocytes abolished the antifibrotic effect of Sal B. Mechanistically, Sal B protected against hepatocyte ferroptosis by upregulating Ecm1. Further research revealed that Ecm1 as a direct target for treating liver fibrosis with Sal B. Interestingly, Ecm1 interacted with xCT to regulate hepatocyte ferroptosis. Hepatocyte ferroptosis in vitro was significantly attenuated by Sal B treatment, which was abrogated after knockdown of Ecm1 in LO2 cells. Therefore, Sal B alleviates liver fibrosis in mice by targeting up-regulation of Ecm1 and inhibiting hepatocyte ferroptosis. The interaction between Ecm1 and xCT regulates hepatocyte ferroptosis.

Inhibition of TGFβ1 activation prevents radiation-induced lung fibrosis

BACKGROUND

Radiotherapy is the main treatment modality for thoracic tumours, but it may induce pulmonary fibrosis. Currently, the pathogenesis of radiation-induced pulmonary fibrosis (RIPF) is unclear, and effective treatments are lacking. Transforming growth factor beta 1 (TGFβ1) plays a central role in RIPF. We found that activated TGFβ1 had better performance for radiation pneumonitis (RP) risk prediction by detecting activated and total TGFβ1 levels in patient serum. αv integrin plays key roles in TGFβ1 activation, but the role of αv integrin-mediated TGFβ1 activation in RIPF is unclear. Here, we investigated the role of αv integrin-mediated TGFβ1 activation in RIPF and the application of the integrin antagonist cilengitide to prevent RIPF.

METHODS

ItgavloxP/loxP ;Pdgfrb-Cre mice were generated by conditionally knocking out Itgav in myofibroblasts, and wild-type mice were treated with cilengitide or placebo. All mice received 16 Gy of radiation or underwent a sham radiation procedure. Lung fibrosis was measured by a modified Ashcroft score and microcomputed tomography (CT). An enzyme-linked immunosorbent assay (ELISA) was used to measure the serum TGFβ1 concentration, and total Smad2/3 and p-Smad2/3 levels were determined via Western blotting.

RESULTS

Conditional Itgav knockout significantly attenuated RIPF (p < .01). Hounsfield units (HUs) in the lungs were reduced in the knockout mice compared with the control mice (p < .001). Conditional Itgav knockout decreased active TGFβ1 secretion and inhibited fibroblast p-Smad2/3 expression. Exogenous active TGFβ1, but not latent TGFβ1, reversed these reductions. Furthermore, cilengitide treatment elicited similar results and prevented RIPF.

CONCLUSIONS

The present study revealed that conditional Itgav knockout and cilengitide treatment both significantly attenuated RIPF in mice by inhibiting αv integrin-mediated TGFβ1 activation.

HIGHLIGHTS

Activated TGFβ1 has a superior capacity in predicting radiation pneumonitis (RP) risk and plays a vital role in the development of radiation-induced pulmonary fibrosis (RIPF). Conditional knock out Itgav in myofibroblasts prevented mice from developing RIPF. Cilengitide alleviated the development of RIPF by inhibiting αv integrin-mediated TGFβ1 activation and may be used in targeted approaches for preventing RIPF.

CREKA-modified liposomes target activated hepatic stellate cells to alleviate liver fibrosis by inhibiting collagen synthesis and angiogenesis

Activated hepatic stellate cells (HSCs) are considered the key driver of excessive extracellular matrix and abnormal angiogenesis, which are the main pathological manifestations of hepatic fibrosis. However, the absence of specific targeting moieties has rendered the development of HSC-targeted drug delivery systems a significant obstacle in the treatment of liver fibrosis. Here we have identified a notable increase in fibronectin expression on HSCs, which positively correlates with the progression of hepatic fibrosis. Thus, we decorated PEGylated liposomes with CREKA, a peptide with high affinity for fibronectin, to facilitate the targeted delivery of sorafenib to activated HSCs. The CREKA-coupled liposomes exhibited enhanced cellular uptake in the human hepatic stellate cell line LX2 and selective accumulation in CCl4-induced fibrotic liver through the recognition of fibronectin. When loaded with sorafenib, the CREKA-modified liposomes effectively suppressed HSC activation and collagen accumulation in vitro. Furthermore. in vivo results demonstrated that the administration of sorafenib-loaded CREKA-liposomes at a low dose significantly mitigated CCl4-induced hepatic fibrosis, prevented inflammatory infiltration and reduced angiogenesis in mice. These findings suggest that CREKA-coupled liposomes have promising potential as a targeted delivery system for therapeutic agents to activated HSCs, thereby providing an efficient treatment option for hepatic fibrosis. STATEMENT OF SIGNIFICANCE: In liver fibrosis, activated hepatic stellate cells (aHSCs) are the key driver of extracellular matrix and abnormal angiogenesis. Our investigation has revealed a significant elevation in fibronectin expression on aHSCs, which is positively associated with the progression of hepatic fibrosis. Thus, we developed PEGylated liposomes decorated with CREKA, a molecule with a high affinity for fibronectin, to facilitate the targeted delivery of sorafenib to aHSCs. The CREKA-coupled liposomes can specifically target aHSCs both in vitro and in vivo. Loading sorafenib into CREKA-Lip significantly alleviated CCl4-induced liver fibrosis, angiogenesis and inflammation at low doses. These findings suggest that our drug delivery system holds promise as a viable therapeutic option for liver fibrosis with minimal risk of adverse effects.

TGF-beta signal transduction: biology, function and therapy for diseases

The transforming growth factor beta (TGF-β) is a crucial cytokine that get increasing concern in recent years to treat human diseases. This signal controls multiple cellular responses during embryonic development and tissue homeostasis through canonical and/or noncanonical signaling pathways. Dysregulated TGF-β signal plays an essential role in contributing to fibrosis via promoting the extracellular matrix deposition, and tumor progression via inducing the epithelial-to-mesenchymal transition, immunosuppression, and neovascularization at the advanced stage of cancer. Besides, the dysregulation of TGF-beta signal also involves in other human diseases including anemia, inflammatory disease, wound healing and cardiovascular disease et al. Therefore, this signal is proposed to be a promising therapeutic target in these diseases. Recently, multiple strategies targeting TGF-β signals including neutralizing antibodies, ligand traps, small-molecule receptor kinase inhibitors targeting ligand-receptor signaling pathways, antisense oligonucleotides to disrupt the production of TGF-β at the transcriptional level, and vaccine are under evaluation of safety and efficacy for the forementioned diseases in clinical trials. Here, in this review, we firstly summarized the biology and function of TGF-β in physiological and pathological conditions, elaborated TGF-β associated signal transduction. And then, we analyzed the current advances in preclinical studies and clinical strategies targeting TGF-β signal transduction to treat diseases.

Structure-Based Discovery of a Novel Class of Small-Molecule Pure Antagonists of Integrin αVβ3

Inhibitors of integrin αVβ3 have therapeutic promise for a variety of diseases. Most αVβ3-targeting small molecules patterned after the RGD motif are partial agonists because they induce a high-affinity, ligand-binding conformation and prime the receptor to bind the ligand without an activating stimulus, in part via a charge-charge interaction between their aspartic acid carboxyl group and the metal ion in the metal-ion-dependent adhesion site (MIDAS). Building upon our previous studies on the related integrin αIIbβ3, we searched for pure αVβ3 antagonists that lack this typical aspartic acid carboxyl group and instead engage through direct binding to one of the coordinating residues of the MIDAS metal ion, specifically β3 E220. By in silico screening of two large chemical libraries for compounds interacting with β3 E220, we indeed discovered a novel molecule that does not contain an acidic carboxyl group and does not induce the high-affinity, ligand-binding state of the receptor. Functional and structural characterization of a chemically optimized version of this compound led to the discovery of a novel small-molecule pure αVβ3 antagonist that (i) does not prime the receptor to bind the ligand and does not induce hybrid domain swing-out or receptor extension as judged by antibody binding and negative-stain electron microscopy, (ii) binds at the RGD-binding site as predicted by metadynamics rescoring of induced-fit docking poses and confirmed by a cryo-electron microscopy structure of the compound-bound integrin, and (iii) coordinates the MIDAS metal ion via a quinoline moiety instead of an acidic carboxyl group.

Novel Pure αVβ3 Integrin Antagonists That Do Not Induce Receptor Extension, Prime the Receptor, or Enhance Angiogenesis at Low Concentrations

The integrin αVβ3 receptor has been implicated in several important diseases, but no antagonists are approved for human therapy. One possible limitation of current small-molecule antagonists is their ability to induce a major conformational change in the receptor that induces it to adopt a high-affinity ligand-binding state. In response, we used structural inferences from a pure peptide antagonist to design the small-molecule pure antagonists TDI-4161 and TDI-3761. Both compounds inhibit αVβ3-mediated cell adhesion to αVβ3 ligands, but do not induce the conformational change as judged by antibody binding, electron microscopy, X-ray crystallography, and receptor priming studies. Both compounds demonstrated the favorable property of inhibiting bone resorption in vitro, supporting potential value in treating osteoporosis. Neither, however, had the unfavorable property of the αVβ3 antagonist cilengitide of paradoxically enhancing aortic sprout angiogenesis at concentrations below its IC50, which correlates with cilengitide's enhancement of tumor growth in vivo.

Bivalent Ligand UDCA-LPE Inhibits Pro-Fibrogenic Integrin Signalling by Inducing Lipid Raft-Mediated Internalization

Ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE) is a synthetic bile acid-phospholipid conjugate with profound hepatoprotective and anti-fibrogenic functions in vitro and in vivo. Herein, we aimed to demonstrate the inhibitory effects of UDCA-LPE on pro-fibrogenic integrin signalling. UDCA-LPE treatment of human embryonic liver cell line CL48 and primary human hepatic stellate cells induced a non-classical internalization of integrin β1 resulting in dephosphorylation and inhibition of SRC and focal adhesion kinase (FAK). Signalling analyses suggested that UDCA-LPE may act as a heterobivalent ligand for integrins and lysophospholipid receptor1 (LPAR1) and co-immunoprecipitation demonstrated the bridging effect of UDCA-LPE on integrin β1 and LPAR1. The disruption of either the UDCA-moiety binding to integrins by RGD-containing peptide GRGDSP or the LPE-moiety binding to LPAR1 by LPAR1 antagonist Ki16425 reversed inhibitory functions of UDCA-LPE. The lack of inhibitory functions of UDCA-PE and UDCA-LPE derivatives (14:0 and 12:0, LPE-moiety containing shorter fatty acid chain) as well as the consistency of the translocation of UDCA-LPE and integrins, which co-fractionated with LPE but not UDCA, suggested that the observed UDCA-LPE-induced translocation of integrins was mediated by LPE endocytic transport pathway.

The Extracellular Matrix and Pancreatic Cancer: A Complex Relationship

Pancreatic ductal adenocarcinoma (PDAC) has an extraordinarily dense fibrotic stroma that impedes tumor perfusion and delivery of anticancer drugs. Since the extracellular matrix (ECM) comprises the bulk of the stroma, it is primarily responsible for the increased interstitial tissue pressure and stiff mechanical properties of the stroma. Besides its mechanical influence, the ECM provides important biochemical and physical cues that promote survival, proliferation, and metastasis. By serving as a nutritional source, the ECM also enables PDAC cells to survive under the nutrient-poor conditions. While therapeutic strategies using stroma-depleting drugs have yielded disappointing results, an increasing body of research indicates the ECM may offer a variety of potential therapeutic targets. As preclinical studies of ECM-targeted drugs have shown promising effects, a number of clinical trials are currently investigating agents with the potential to advance the future treatment of PDAC. Thus, the present review seeks to give an overview of the complex relationship between the ECM and PDAC.

Overexpression of C‑sis inhibits H2O2‑induced Buffalo rat liver cell apoptosis in vitro and alleviates liver injury in a rat model of fulminant hepatic failure

The present study aimed to investigate the role of the C‑sis gene in the apoptosis of hepatocytes in vitro and in the liver function of a rat model of fulminant hepatic failure (FHF). Buffalo rat liver (BRL) cells were treated with hydrogen peroxide (H2O2) to induce apoptosis and then transfected with a C‑sis overexpression vector. A rat model of FHF was established, and C‑sis was overexpressed. The mRNA and protein expression of C‑sis were examined using reverse transcription‑polymerase chain reaction and western blot analyses, respectively. Cell viability was assessed by CCK8, and a TUNEL assay was used to examine cell apoptosis. Flow cytometry was used for cell cycle detection. Hematoxylin and eosin staining was used for histological examination. The levels of alanine transaminase (ALT) and aspartate transaminase (AST) were also examined in the rats. The results showed that C‑sis was successfully overexpressed in the cells and rat model. Compared with H2O2‑treated BRL cells, the overexpression of C‑sis significantly inhibited cell apoptosis, promoted cell viability, and decreased the expression of cleaved caspase-3. Similar results were observed in the FHF rats treated with the C‑sis overexpression plasmid, compared with those treated with empty plasmids. In addition, in the FHF rats overexpressing C‑sis, histological examination showed that liver injury was alleviated, the levels of ALT and AST were significantly decreased, and mortality rate was significantly decreased, compared with those observed in the rats treated with empty plasmids. In conclusion, the overexpression of C‑sis inhibited the H2O2‑induced apoptosis of BRL cells in vitro, and alleviated liver injury, improved liver function, and decreased mortality rates in rat models of FHF.

Evaluation of hepatic integrin αvβ3 expression in non-alcoholic steatohepatitis (NASH) model mouse by 18F-FPP-RGD2 PET

Background

Activated hepatic stellate cells (HSCs), which express integrin αvβ3, are a major fibrogenic factor in NASH pathophysiology. ¹⁸F-labeled cyclic arginine-glycine-aspartic acid penta-peptide (¹⁸F-FPP-RGD₂) has been used as a PET probe for tumors expressing integrin αvβ3. The aim of this study was to assess the potential of PET with ¹⁸F-FPP-RGD₂ to detect hepatic integrin αvβ3 expression in non-alcoholic steatohepatitis (NASH) model mice.

Results

Thirty-two male C57BL/6 mice aged 6 weeks were fed a choline-deficient, l-amino acid-defined, high-fat diet (CDAHFD) for 3 and 8 weeks. ¹⁸F-FPP-RGD₂ PET imaging of the liver was performed at 3 and 8 weeks after CDAHFD feeding. After PET scanning, levels of hepatic integrin αvβ, 3α-smooth muscle actin (α-SMA), and collagen type 1 alpha 1(col1a1) were measured. Histopathological analysis of hepatic steatosis, inflammation, and fibrosis, as well as blood biochemistry analysis, was also performed. CDAHFD for 3 and 8 weeks produced a moderate-to-severe steatosis and inflammation of the liver in mice. NAFLD activity score (NAS) in mice fed the CDAHFD for 3 and 8 weeks were more than 4 indicating NASH or borderline NASH pathology. Fibrosis was observed only in mice fed the CDAHFD for 8 weeks. PET imaging showed that the hepatic standardized uptake value, SUV_80–90 min, was increased with prolonged CDAHFD feeding compared with the respective controls (CDAHFD 3 weeks 0.32 ± 0.06 vs 0.48 ± 0.05, p < 0.01; CDAHFD 8 weeks 0.35 ± 0.04 vs 0.75 ± 0.07, p < 0.01, respectively). Prolonged CDAHFD feeding increased hepatic mRNA and protein levels of integrin αv and β3 at 3 and 8 weeks. Hepatic ¹⁸F-FPP-RGD₂ uptake and amount of integrin αv and β3 protein were well correlated (r = 0.593, p < 0.05 and r = 0.835, p < 0.001, respectively). Hepatic ¹⁸F-FPP-RGD₂ uptake also showed a positive correlation with Sirius red-positive area.

Conclusions

The hepatic uptake of ¹⁸F-FPP-RGD₂ correlated well with integrin αv and β3 expression and histological fibrosis in a mouse model of NASH, suggesting the predictability of fibrosis in NASH pathology.

CCN1/Cyr61 enhances the function of hepatic stellate cells in promoting the progression of hepatocellular carcinoma

Hepatic stellate cells (HSCs) are the main extracellular matrix (ECM)-producing cells in liver fibrosis. Activated HSCs stimulate the proliferation and migration of hepatocellular carcinoma (HCC) cells. Cysteine-rich 61 (CCN1/Cyr61) is an ECM protein. Our previous studies demonstrated that the expression of CCN1 was significantly higher in benign hepatic cirrhosis tissue and cancer-adjacent hepatic cirrhosis tissues. CCN1 is a target gene of β-catenin in HCC and promotes the proliferation of HCC cells. The present study aimed to examine whether CCN1 can activate HSCs and affect the function of activated HSCs in promoting the progression of HCC. CCN1 expression was determined during the progression of liver fibrosis in a mouse model. LX-2 cells, which were infected with adenoviruses AdCCN1 or AdRFP, and HepG2 cells were co-cultured or subcutaneously co-implanted into in nude mice. MTT assay, Crystal Violet staining, Boyden chamber, matrigel invasion and monolayer scratch assays were used to analyze the proliferation, migration and invasion capability of HepG2 cells. Xenograft sizes were measured and histological analyses were performed by hematoxylin and eosin, immunohistochemical, immunefluorescence and Sirius Red staining. It was demonstrated that the expression of CCN1 was continually increased in liver fibrosis and the that expression may be correlated with the progression of liver fibrosis. CCN1 affected the function of LX-2 and enhanced the effect of LX-2 on promoting the viability, migration and invasion of HepG2 cells in vitro. CCN1 enhanced the effect of LX-2 on promoting the growth of HepG2 xenografts in vivo. CCN1 also affected the function of activated HSCs and regulated the formation of the xenograft microenvironment, including fibrogenesis and angiogenesis, which are beneficial for the progression of HCC. These findings demonstrated that CCN1 may be involved in the progression of the hepatic cirrhosis-HCC axis through regulating HSCs.

Periostin promotes hepatic fibrosis in mice by modulating hepatic stellate cell activation via αv integrin interaction

BACKGROUND

Periostin is a matricellular protein that serves as a ligand for integrins and is required for tissue remodeling and fibrosis. We investigated the role of periostin in hepatic fibrosis and the mechanisms involved.

METHODS

Primary hepatic stellate cells (HSCs) and the HSC-immortalized cell line LX2 were used to study the profibrotic property of periostin and the interaction of periostin with integrins. Wild-type and periostin-deficient (periostin^-/-) mice were subjected to two distinct models of liver fibrosis induced by hepatotoxic (carbon tetrachloride or thioacetamide) or cholestatic (3.5-diethoxycarbonyl-1.4-dihydrocollidine) injury.

RESULTS

Periostin expression in HSCs and LX2 cells increased in association with their activation. Gene silencing of periostin resulted in a significant reduction in the levels of profibrotic markers. In addition to enhanced cell migration in response to periostin, LX2 cells incubated on periostin showed significant induction of α-smooth muscle actin and collagen, indicating a profibrotic property. An antibody targeting α_vβ₅ and α_vβ₃ integrins suppressed cell attachment to periostin by 60 and 30 % respectively, whereas anti-α₅β₁ antibody had no effect. Consistently, α_v integrin-silenced LX2 cells exhibited decreased attachment to periostin, with a significant reduction in the levels of profibrotic markers. Moreover, these profibrotic effects of periostin were observed in the mouse models. In contrast to extensive collagen deposition in wild-type mice, periostin^-/- mice developed less noticeable hepatic fibrosis induced by hepatotoxic and cholestatic liver injury. Accordingly, the profibrotic markers were significantly reduced in periostin^-/- mice.

CONCLUSION

Periostin exerts potent profibrotic activity mediated by α_v integrin, suggesting the periostin-α_v integrin axis as a novel therapeutic target for hepatic fibrosis.

Dendritic cell expression of ADAM23 governs T cell proliferation and cytokine production through the α(v)β(3) integrin receptor

ADAM23 is a member of the brain macrophage-derived chemokine family. Structural homology of ADAM proteins suggests their function as integrin receptors. Previous studies have linked ADAM23 as a dominant contributor to brain development and cancer metastasis. The present studies now show that ADAM23 expression on DCs partially governs antigen-presentation capacities to responder CD4⁺ T cells. With the use of RNAi approaches, knockdown of ADAM23 in murine BMDCs resulted in impaired T cell activation, proliferation, and cytokine production. Knockdown did not alter the maturation profile of DCs (i.e., costimulatory molecule expression or production of proinflammatory cytokines) but markedly impaired cognate T cell responses. There was a significant decrease in antigen-specific clonal expansion coupled with a global decrease in Th cytokine production. Impaired early activation and proliferation did not alter/skew the balance of Th polarization but significantly depressed total levels of IL-2, IFN-γ, IL-4, and IL-17 cytokine production in CD4⁺ T cells primed by ADAM23 knockdown versus control DCs. Finally, neutralizing antibodies targeting the α(v)β(3) integrin receptors resulted in similar phenotypes of impaired CD4⁺ T cell responses. Taken together, these studies show a novel role of ADAM23 in governing DC antigen presentation to cognate CD4⁺ T cells.

Targeting the PDGF-B/PDGFR-β Interface with Destruxin A5 to Selectively Block PDGF-BB/PDGFR-ββ Signaling and Attenuate Liver Fibrosis

PDGF-BB/PDGFR-ββ signaling plays very crucial roles in the process of many diseases such as liver fibrosis. However, drug candidates with selective affinities for PDGF-B/PDGFR-β remain deficient. Here, we identified a natural cyclopeptide termed destruxin A5 that effectively inhibits PDGF-BB-induced PDGFR-β signaling. Interestingly and importantly, the inhibitory mechanism is distinct from the mechanism of tyrosine kinase inhibitors because destruxin A5 does not have the ability to bind to the ATP-binding pocket of PDGFR-β. Using Biacore T200 technology, thermal shift technology, microscale thermophoresis technology and computational analysis, we confirmed that destruxin A5 selectively targets the PDGF-B/PDGFR-β interaction interface to block this signaling. Additionally, the inhibitory effect of destruxin A5 on PDGF-BB/PDGFR-ββ signaling was verified using in vitro, ex vivo and in vivo models, in which the extent of liver fibrosis was effectively alleviated by destruxin A5. In summary, destruxin A5 may represent an efficacious and more selective inhibitor of PDGF-BB/PDGFR-ββ signaling.

Association of serum IFN-λ3 with inflammatory and fibrosis markers in patients with chronic hepatitis C virus infection

BACKGROUND

Hepatitis C virus (HCV) is one of the major causes of liver cancer. The single nucleotide polymorphisms within the IFNL3 gene, which encodes interferon (IFN)-λ(3), are strongly associated with the response to pegylated IFN-α (PEG-IFN-α) plus ribavirin (RBV) therapy in chronic hepatitis C (C-CH) patients. However, the roles of IFN-λ(3) in chronic HCV infection are still elusive. In this study, we aimed to identify clinical and immunological factors influencing IFN-λ(3) and evaluated whether serum IFN-λ(3) levels are involved or not involved in the response to PEG-IFN-α plus RBV therapy.

METHODS

We enrolled 119 C-CH patients with HCV genotype 1 infection who underwent 48 weeks of PEG-IFN-α plus RBV therapy. As controls, 23 healthy subjects and 56 patients with non-HCV viral hepatitis were examined. Serum IFN-λ(3) was quantified by chemiluminescence enzyme immunoassay, and 27 cytokines or chemokines were assayed by the multiplexed BioPlex system.

RESULTS

Serum IFN-λ(3) levels were higher in C-CH patients or acute hepatitis E patients than in healthy volunteers. Such levels did not differ between the IFNL3 genotypes. In C-CH patients, serum IFN-λ(3) was positively correlated with aspartate aminotransferase, alanine aminotransferase, α-fetoprotein, histological activity, fibrosis index, IFN-γ-inducible protein 10, and platelet-derived growth factor. Multivariate analysis showed that IFNL3 single nucleotide polymorphisms, fibrosis score, and macrophage inflammatory protein 1α were involved in the sustained viral clearance in PEG-IFN-α plus RBV therapy; however, serum IFN-λ(3) levels were not involved.

CONCLUSION

Serum IFN-λ(3) levels are increased in C-CH patients regardless of the IFNL3 genotype. IFN-λ(3) is a biomarker reflecting the activity and fibrosis of liver disease, but is not correlated with the responsiveness to PEG-IFN-α plus RBV therapy.

Spike-in SILAC proteomic approach reveals the vitronectin as an early molecular signature of liver fibrosis in hepatitis C infections with hepatic iron overload

Hepatitis C virus (HCV)-induced iron overload has been shown to promote liver fibrosis, steatosis, and hepatocellular carcinoma. The zonal-restricted histological distribution of pathological iron deposits has hampered the attempt to perform large-scale in vivo molecular investigations on the comorbidity between iron and HCV. Diagnostic and prognostic markers are not yet available to assess iron overload-induced liver fibrogenesis and progression in HCV infections. Here, by means of Spike-in SILAC proteomic approach, we first unveiled a specific membrane protein expression signature of HCV cell cultures in the presence of iron overload. Computational analysis of proteomic dataset highlighted the hepatocytic vitronectin expression as the most promising specific biomarker for iron-associated fibrogenesis in HCV infections. Next, the robustness of our in vitro findings was challenged in human liver biopsies by immunohistochemistry and yielded two major results: (i) hepatocytic vitronectin expression is associated to liver fibrogenesis in HCV-infected patients with iron overload; (ii) hepatic vitronectin expression was found to discriminate also the transition between mild to moderate fibrosis in HCV-infected patients without iron overload.

Extrahepatic platelet-derived growth factor-β, delivered by platelets, promotes activation of hepatic stellate cells and biliary fibrosis in mice

BACKGROUND & AIMS

Platelet-derived growth factor-β (PDGFB) is a mitogen for hepatic stellate cells (HSCs). We studied the cellular sources of PDGFB and the effects of a high-affinity monoclonal antibody against PDGFB (MOR8457) in mouse models of biliary fibrosis.

METHODS

Cellular sources of PDGFB were identified using quantitative reverse-transcription polymerase chain reaction, biochemical, and immunohistologic methods. Mice with advanced biliary fibrosis, MDR2(Abcb4)-null mice, and C57Bl/6 (control) mice were placed on 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-supplemented diets and were given weekly intraperitoneal injections of MOR8457. Platelets were depleted from MDR2-null mice by injection of an antibody against CD41, or inhibited with diets containing low-dose aspirin. Liver tissues were collected and analyzed by quantitative reverse-transcription PCR and histologic and biochemical analyses.

RESULTS

Levels of PDGFB protein, but not messenger RNA, were increased in fibrotic livers of MDR2-null mice, compared with control mice. Platelet clusters were detected in the hepatic endothelium, in close proximity to HSCs, and were identified as a source of PDGFB protein in MDR2-null mice. Levels of the PDGFB were increased in serum samples from patients with early stages of liver fibrosis of various etiologies (F1-2, n = 16; P < .05), compared with nonfibrotic liver tissue (F0, n = 12). Depletion of platelets from MDR2-null mice normalized hepatic levels of PDGFB within 48 hours, reducing levels of a marker of HSC activation (α-smooth muscle actin) and expression of genes that promote fibrosis. Diets supplemented with low-dose aspirin reduced circulating serum and hepatic levels of PDGFB and significantly reduced progression of fibrosis in MDR2-null mice over 1 year. MOR8457 produced a dose-dependent decrease in liver fibrosis in MDR2-null mice, reducing collagen deposition by 45% and expression of fibrosis-associated genes by 50%, compared with mice given a control antibody. In vitro, platelets activated freshly isolated HSCs (induction of α-smooth muscle actin and fibrosis-associated genes) via a PDGFB-dependent mechanism. MOR8457 also reduced liver fibrosis in mice placed on DDC-supplemented diets.

CONCLUSIONS

Platelets produce PDGFB to activate HSC and promote fibrosis in MDR2-null mice and mice on DDC-supplemented diets. Antiplatelet therapy or selective inhibition of PDGFB might reduce biliary fibrosis in patients with liver disease.

Assessing activation of hepatic stellate cells by (99m)Tc-3PRGD2 scintigraphy targeting integrin αvβ3: a feasibility study

OBJECTIVE

Hepatic stellate cell (HSC) activation, which is accompanied by increased expression of integrin αvβ3, is an important factor in liver fibrogenesis. Molecular imaging targeting the integrin αvβ3 could provide a non-invasive method for evaluating the expression and the function of the integrin αvβ3 on the activated HSCs (aHSCs) in the injured liver, and then provide important prognostic information. (99m)Tc-3PRGD2 is such a radiotracer specific for integrin αvβ3. In this study, we aimed to compare the differences in liver uptake and retention of the (99m)Tc-3PRGD2 between normal liver and injured liver to evaluate the feasibility of (99m)Tc-3PRGD2 scintigraphy for this purpose.

METHODS

We used planar scintigraphy to assess changes in integrin αvβ3 binding of intravenously-administered (99m)Tc-3PRGD2 in the livers of rats with thioacetamide (TAA)-induced liver fibrosis compared with the controls. We co-injected cold c(RGDyK) with (99m)Tc-3PRGD2 to assess the specific binding of the radiotracer. We performed Sirius red staining to assess liver fibrosis, immunofluorescent colocalization to identify the location of integrin αvβ3 expressed in the fibrotic liver, and we measured protein and messenger RNA expression of integrin αvβ3 and alpha smooth muscle actin (α-SMA) in the control and fibrotic livers.

RESULTS

The fibrotic livers showed enhanced (99m)Tc-3PRGD2 uptake and retention. The radiotracer was demonstrated to bind specifically with the integrin αvβ3 mainly expressed on the aHSCs. The liver-to-heart ratio at 30 min post-injection was higher in the fibrotic livers than in the control livers (TAA, 1.98±0.08 vs. control, 1.50±0.12, p<0.01). The liver t1/2 was longer than in the controls (TAA, 27.07±10.69 min vs. control, 12.67±4.10 min, p<0.01). The difference of heart t1/2 between the two groups was not statistically significant (TAA, 3.13±0.63 min vs. control, 3.41±0.77 min, p=0.94).

CONCLUSIONS

(99m)Tc-3PRGD2 molecular imaging can provide a non-invasive method for assessing activation of HSCs.

Identification and characterization of mesenchymal-epithelial progenitor-like cells in normal and injured rat liver

In normal rat liver, thymocyte antigen 1 (Thy1) is expressed in fibroblasts/myofibroblasts and in some blood progenitor cells. Thy1-expressing cells also accumulate in the liver during impaired liver regeneration. The origin and nature of these cells are not well understood. By using RT-PCR analysis and immunofluorescence microscopy, we describe the presence of rare Thy1(+) cells in the liver lobule of normal animals, occasionally forming small collections of up to 20 cells. These cells constitute a small portion (1.7% to 1.8%) of nonparenchymal cells and reveal a mixed mesenchymal-epithelial phenotype, expressing E-cadherin, cytokeratin 18, and desmin. The most potent mitogens for mesenchymal-epithelial Thy1(+) cells in vitro are the inflammatory cytokines interferon γ, IL-1, and platelet-derived growth factor-BB, which are not produced by Thy1(+) cells. Thy1(+) cells express all typical mesenchymal stem cell and hepatic progenitor cell markers and produce growth factor and cytokine mRNA (Hgf, Il6, Tgfa, and Tweak) for proteins that maintain oval cell growth and differentiation. Under appropriate conditions, mesenchymal-epithelial cells differentiate in vitro into hepatocyte-like cells. In this study, we show that the adult rat liver harbors a small pool of endogenous mesenchymal-epithelial cells not recognized previously. In the quiescent state, these cells express both mesenchymal and epithelial cell markers. They behave like hepatic stem cells/progenitors with dual phenotype, exhibiting high plasticity and long-lasting proliferative activity.

Plasminogen activator-1 overexpression decreases experimental postthrombotic vein wall fibrosis by a non-vitronectin-dependent mechanism

BACKGROUND

Factors associated with postthrombotic syndrome are known clinically, but the underlying cellular processes at the vein wall are not well delineated. Prior work suggests that vein wall damage does not correlate with thrombus resolution but rather with plasminogen activator-1 (PAI-1) and matrix metalloproteinase (MMP) activity.

OBJECTIVE

We hypothesized that PAI-1 would confer post venous thrombosis (VT) vein wall protection via a vitronectin (Vn)-dependent mechanism.

METHODS

A stasis model of VT was used with harvest over 2 weeks, in wild-type, Vn(-/-) , and PAI-1-overexpressing mice (PAI-1 Tg).

RESULTS

PAI-1 Tg mice had larger VT at 6 and 14 days, compared to controls, but Vn(-/-) mice had no alteration of VT resolution. Gene deletion of Vn resulted in an increase in, rather than the expected decrease in, circulating PAI-1 activity. While both Vn(-/-) and PAI-1 Tg had attenuated intimal fibrosis, PAI-1 Tg had significantly less vein wall collagen and a compensatory increase in collagen III gene expression. Both Vn(-/-) and PAI-1 Tg vein wall had less monocyte chemotactic factor-1 and fewer macrophages (F4/80), with significantly less MMP-2 activity and decreased TIMP-1 antigen. Ex vivo assessment of transforming growth factor β-mediated fibrotic response showed that PAI-1 Tg vein walls had increased profibrotic gene expression (collagens I and III, MMP-2, and α-smooth muscle actin) compared with controls, opposite of the in vivo response.

CONCLUSIONS

The absence of Vn increases circulating PAI-1, which positively modulates vein wall fibrosis in a dose-dependent manner. Translationally, PAI-1 elevation may decrease vein wall damage after deep vein thrombosis, perhaps by decreasing macrophage-mediated activities.

Tetramethylpyrazine inhibits angiotensin II-induced activation of hepatic stellate cells associated with interference of platelet-derived growth factor β receptor pathways

Liver fibrosis represents a frequent event following chronic insult to trigger wound healing responses in the liver. Activation of hepatic stellate cells (HSCs) is a pivotal event during liver fibrogenesis. Compelling evidence indicates that the renin-angiotensin system (RAS) takes part in the pathogenesis of liver fibrosis. Angiotensin II (Ang II), the primary effector peptide of the RAS, has been demonstrated to be a potent pro-fibrogenic molecule for HSC activation. In this study we investigated the effects of tetramethylpyrazine (TMP) on HSC activation induced by Ang II in order to elucidate the underlying mechanisms. Our results demonstrated that Ang II significantly promoted cell growth, upregulated the expression of the fibrotic markers α-smooth muscle actin (α-SMA) and α1(I) procollagen, and enhanced the invasion capacity in HSCs. TMP inhibited proliferation and arrested the cell cycle at the G2/M checkpoint associated with altering several cell cycle regulatory proteins in Ang II-treated HSCs. TMP also modulated Bcl-2 family proteins and activated the caspase cascade leading to apoptosis in Ang II-treated HSCs. Moreover, TMP reduced the expression of α-SMA and α1(I) procollagen at mRNA and protein levels, and these effects were associated with interference of the platelet-derived growth factor β receptor (PDGF-βR) mediated PI3K/AKT/mTOR pathway in HSCs exposed to Ang II. Furthermore, Ang II-enhanced HSC invasion capacity was diminished by TMP, which was associated with interference of PDGF-βR/FAK signaling. These data collectively indicated that interference of PDGF-βR-mediated fibrotic pathways was involved in TMP inhibition of HSC activation caused by Ang II, providing novel mechanistic insights into TMP as a potential therapeutic remedy for hepatic fibrosis.

Dipeptidyl peptidase-4 inhibitor attenuates hepatic fibrosis via suppression of activated hepatic stellate cell in rats

BACKGROUND

Dipeptidyl peptidase-4 inhibitor (DPP4-I) is clinically used as a new oral antidiabetic agent. Although DPP4 is reportedly associated with the progression of chronic liver diseases, the effect of DPP4-I on liver fibrosis development is still obscure. This study was designed to elucidate the effect of DPP4-I on liver fibrosis development in conjunction with the activated hepatic stellate cells (Ac-HSCs).

METHODS

The antifibrotic effect of DPP4-I was assessed in vivo and in vitro using porcine serum-induced experimental liver fibrosis model. DPP4-I, sitagliptin, at a clinically comparable low dose was administered by gavage daily.

RESULTS

DPP4-I significantly attenuated liver fibrosis development along with the suppression of hepatic transforming growth factor (TGF)-β1, total collagen, and tissue inhibitor of metalloproteinases-1 in a dose-dependent manner. These suppressive effects occurred almost concurrently with the attenuation of HSCs activation. Our in vitro studies showed that DPP4-I inhibited platelet-derived growth factor-BB-mediated proliferation of the Ac-HSCs as well as upregulation of TGF-β1 and α1(I)-procollagen at magnitudes similar to those of the in vivo studies. The inhibitory effects of DPP4-I against HSCs proliferation and fibrogenic gene expression are mediated through the inhibition of the phosphorylation of ERK1/2, p38 and Smad2/3, respectively.

CONCLUSIONS

DPP4-I markedly inhibits liver fibrosis development in rats via suppression of HSCs proliferation and collagen synthesis. These suppressive effects are associated with dephosphorylation of ERK1/2, p38 and Smad2/3 in the HSCs. Since DPP4-I is widely used in clinical practice, this drug may represent a potential new therapeutic strategy against liver fibrosis in the near future.

Gene expression profiling of early hepatic stellate cell activation reveals a role for Igfbp3 in cell migration

Background

Scarring of the liver is the result of prolonged exposure to exogenous or endogenous stimuli. At the onset of fibrosis, quiescent hepatic stellate cells (HSCs) activate and transdifferentiate into matrix producing, myofibroblast-like cells.

Aim and methods

To identify key players during early HSC activation, gene expression profiling was performed on primary mouse HSCs cultured for 4, 16 and 64 hours. Since valproic acid (VPA) can partly inhibit HSC activation, we included VPA-treated cells in the profiling experiments to facilitate this search.

Results

Gene expression profiling confirmed early changes for known genes related to HSC activation such as alphasmoothmuscleactin (Acta2), lysyloxidase (Lox) and collagen, type I, alpha 1 (Col1a1). In addition we noticed that, although genes which are related to fibrosis change between 4 and 16 hours in culture, most gene expression changes occur between 16 and 64 hours. Insulin-likegrowthfactorbinding protein 3 (Igfbp3) was identified as a gene strongly affected by VPA treatment. During normal HSC activation Igfbp3 is up regulated and this can thus be prevented by VPA treatment invitro and invivo. siRNA-mediated silencing of Igfbp3 in primary mouse HSCs induced matrix metalloproteinase (Mmp) 9 mRNA expression and strongly reduced cell migration. The reduced cell migration after Igfbp3 knock-down could be overcome by tissue inhibitor of metalloproteinase (TIMP) 1 treatment.

Conclusion

Igfbp3 is a marker for culture-activated HSCs and plays a role in HSC migration. VPA treatment prevents Igfbp3 transcription during activation of HSCs invitro and invivo.

Interplay between αvβ3 integrin and nucleolin regulates human endothelial and glioma cell migration

The multifunctional protein nucleolin (NCL) is overexpressed on the surface of activated endothelial and tumor cells and mediates the stimulatory actions of several angiogenic growth factors, such as pleiotrophin (PTN). Because α(v)β(3) integrin is also required for PTN-induced cell migration, the aim of the present work was to study the interplay between NCL and α(v)β(3) by using biochemical, immunofluorescence, and proximity ligation assays in cells with genetically altered expression of the studied molecules. Interestingly, cell surface NCL localization was detected only in cells expressing α(v)β(3) and depended on the phosphorylation of β(3) at Tyr(773) through receptor protein-tyrosine phosphatase β/ζ (RPTPβ/ζ) and c-Src activation. Downstream of α(v)β(3,) PI3K activity mediated this phenomenon and cell surface NCL was found to interact with both α(v)β(3) and RPTPβ/ζ. Positive correlation of cell surface NCL and α(v)β(3) expression was also observed in human glioblastoma tissue arrays, and inhibition of cell migration by cell surface NCL antagonists was observed only in cells expressing α(v)β(3). Collectively, these data suggest that both expression and β(3) integrin phosphorylation at Tyr(773) determine the cell surface localization of NCL downstream of the RPTPβ/ζ/c-Src signaling cascade and can be used as a biomarker for the use of cell surface NCL antagonists as anticancer agents.

Enterolobium contortisiliquum trypsin inhibitor (EcTI), a plant proteinase inhibitor, decreases in vitro cell adhesion and invasion by inhibition of Src protein-focal adhesion kinase (FAK) signaling pathways

Tumor cell invasion is vital for cancer progression and metastasis. Adhesion, migration, and degradation of the extracellular matrix are important events involved in the establishment of cancer cells at a new site, and therefore molecular targets are sought to inhibit such processes. The effect of a plant proteinase inhibitor, Enterolobium contortisiliquum trypsin inhibitor (EcTI), on the adhesion, migration, and invasion of gastric cancer cells was the focus of this study. EcTI showed no effect on the proliferation of gastric cancer cells or fibroblasts but inhibited the adhesion, migration, and cell invasion of gastric cancer cells; however, EcTI had no effect upon the adhesion of fibroblasts. EcTI was shown to decrease the expression and disrupt the cellular organization of molecules involved in the formation and maturation of invadopodia, such as integrin β1, cortactin, neuronal Wiskott-Aldrich syndrome protein, membrane type 1 metalloprotease, and metalloproteinase-2. Moreover, gastric cancer cells treated with EcTI presented a significant decrease in intracellular phosphorylated Src and focal adhesion kinase, integrin-dependent cell signaling components. Together, these results indicate that EcTI inhibits the invasion of gastric cancer cells through alterations in integrin-dependent cell signaling pathways.

Molecular imaging of hepatic stellate cell activity by visualization of hepatic integrin αvβ3 expression with SPECT in rat

The key factors in the pathogenesis of liver fibrosis are the activation and proliferation of hepatic stellate cells (HSCs), which express integrin αvβ3 after activation. This study aimed to explore the potential of (99m)Tc-labeled cyclic arginine-glycine-aspartic acid pentapeptide (cRGD) as a single photon emission computed tomography (SPECT) radiotracer to image hepatic integrin αvβ3 expression to reflect HSC activity in fibrotic livers. Rat models of liver fibrosis caused by thioacetamide or carbon tetrachloride (CCl(4)) treatment were employed to examine the expression and distribution of integrin αvβ3 during fibrotic progression or regression. The binding activity of radiolabeled cRGD to integrin αvβ3 was assessed in liver sections. SPECT was performed to determine hepatic integrin αvβ3 expression in rats with different stages of liver fibrosis. Protein and messenger RNA (mRNA) levels of integrin αv and β3 subunits were increased with the progression of liver fibrosis and reduced with its regression. The cell type that expressed the majority of integrin αvβ3 in fibrotic livers was found to be activated HSCs. The cRGD binding to activated HSCs displayed a high receptor-coupling affinity and an abundant receptor capacity. Iodine-125 ((125)I)-labeled cRGD bound to fibrotic liver sections and the binding activity was the highest in advanced fibrosis. Intravenously administered carboxyfluorescein-labeled cRGD was accumulated in fibrotic liver, and the accumulation amount was increased with the progression and reduced with the regression of fibrosis. A SPECT imaging study with (99m)Tc-labeled cRGD as a tracer demonstrated that the radioactivity ratio of liver to heart increased progressively along with severity of hepatic fibrosis.

CONCLUSION

Hepatic integrin αvβ3 expression in fibrotic liver reflects HSC activity and its imaging using (99m)Tc-labeled cRGD as a SPECT radiotracer may distinguish different stages of liver fibrosis in rats.

The role of dystroglycan in PDGF-BB-dependent migration of activated hepatic stellate cells/myofibroblasts

Hepatic stellate cells are embedded in the loose connective tissue matrix within the space of Disse. This extracellular matrix contains several basement membrane components including laminin, but its composition changes during liver injury because of the production of extracellular matrix components found in scar tissue. These changes in extracellular matrix composition and in cell-extracellular matrix interactions may play a key role in hepatic stellate cell transdifferentiation. In this communication we used early passages of mouse hepatic stellate cells (activated HSC/myofibroblasts) to study the platelet-derived growth factor BB (PDGF-BB)-dependent expression and regulation of β-dystroglycan and its role in activated HSC/myofibroblast migration. We used Northern and Western analysis to study dystroglycan expression and confocal microscopy to investigate changes in subcellular distribution of the protein. Activated HSC migration was investigated using an in vitro wound-healing assay. PDGF-BB induced significant changes in dystroglycan regulation and subcellular distribution of the protein. Whereas steady-state levels of dystroglycan mRNA remained constant, PDGF-BB increased dystroglycan transcription but shortened the t(1/2) by 50%. Moreover, PDGF-BB changed dystroglycan and α5-integrin cellular distribution. Cell migration experiments revealed that PDGF-BB-dependent migration of activated HSC/myofibroblasts was completely blocked by neutralizing antibodies to fibronectin, α5-integrin, laminin, and β-dystroglycan. Overall, these findings suggest that both laminin and fibronectin and their receptors play a key role in PDGF-BB-induced activated HSC migration.

Role of integrins in fibrosing liver diseases

Integrins and other cell adhesion molecules regulate numerous physiological and pathological mechanisms by mediating the interaction between cells and their extracellular environment. Although the significance of integrins in the evolution and progression of certain cancers is well recognized, their involvement in nonmalignant processes, such as organ fibrosis or inflammation, is only beginning to emerge. However, accumulating evidence points to an instrumental role of integrin-mediated signaling in a variety of chronic and acute noncancerous diseases, particularly of the liver.

Cannabinoid receptor type I modulates alcohol-induced liver fibrosis

The cannabinoid system (CS) is implicated in the regulation of hepatic fibrosis, steatosis and inflammation, with cannabinoid receptors 1 and 2 (CB1 and CB2) being involved in regulation of pro- and antifibrogenic effects. Daily cannabis smoking is an independent risk factor for the progression of fibrosis in chronic hepatitis C and a mediator of experimental alcoholic steatosis. However, the role and function of CS in alcoholic liver fibrosis (ALF) is unknown so far. Thus, human liver samples from patients with alcoholic liver disease (ALD) were collected for analysis of CB1 expression. In vitro, hepatic stellate cells (HSC) underwent treatment with acetaldehyde, Δ9-tetrahydrocannabinol H₂O₂, endo- and exocannabinoids (2-arachidonoylglycerol (2-AG) and [THC]), and CB1 antagonist SR141716 (rimonabant). In vivo, CB1 knockout (KO) mice received thioacetamide (TAA)/ethanol (EtOH) to induce fibrosis. As a result, in human ALD, CB1 expression was restricted to areas with advanced fibrosis only. In vitro, acetaldehyde, H₂O₂, as well as 2-AG and THC, alone or in combination with acetaldehyde, induced CB1 mRNA expression, whereas CB1 blockage with SR141716 dose-dependently inhibited HSC proliferation and downregulated mRNA expression of fibrosis-mediated genes PCα1(I), TIMP-1 and MMP-13. This was paralleled by marked cytotoxicity of SR141716 at high doses (5-10 μmol/L). In vivo, CB1 knockout mice showed marked resistance to alcoholic liver fibrosis. In conclusion, CB1 expression is upregulated in human ALF, which is at least in part triggered by acetaldehyde (AA) and oxidative stress. Inhibition of CB1 by SR141716, or via genetic knock-out protects against alcoholic-induced fibrosis in vitro and in vivo.

Anoikis induction and metastasis suppression by a new integrin αvβ3 inhibitor in human melanoma cell line M21

Integrin αvβ3 plays a critical role in the survival and metastasis process of cancer cells. It is therefore desirable to develop new types of small molecule inhibitors of integrin αvβ3. IH1062 (3, 5-dichloro-phenylbiguanide) is a novel small molecule inhibitor of integrin αvβ3 that we have recently discovered. In this study, we investigated the induction effects of anoikis in human melanoma cell line M21 by IH1062, by detecting caspase activity, measuring the expression levels of apoptosis-related proteins, and performing the AnnexinV/PI apoptosis assay. Furthermore, we established a melanoma pulmonary metastasis mouse model in order to evaluate the suppression of metastasis by IH1062 in vivo. Our results demonstrate that IH1062 triggered human melanoma M21 cells to undergo anoikis by interrupting the attachment of M21 cells to extracellular matrix, reducing the phosphorylation of focal adhesion kinase, decreasing survivin and the ratio of Bcl-2/Bax proteins, and activating caspase cascades in vitro. Additionally, IH1062 showed markedly anti-metastatic effects in the pulmonary metastasis model in vivo, which makes it a promising lead to develop new drugs for anti-metastasis therapies.

Specific shRNA targeting of FAK influenced collagen metabolism in rat hepatic stellate cells

AIM

To investigate the effects and mechanism of disruption of focal adhesion kinase (FAK) expression on collagen metabolism in rat hepatic stellate cells (HSC).

METHODS

The plasmids expressing FAK short hairpin RNA (shRNA) were transfected into HSC-T6 cells, and the level of FAK expression was determined by both real-time quantitative polymerase chain reaction (Q-PCR) and Western blotting analysis. The production of type I collagen and type III collagen in FAK-disrupted cells was analyzed by real-time Q-PCR. The level of collagen metabolism proteins, including matrix metalloproteinases-13 (MMP-13) and tissue inhibitors of metalloproteinases-1 (TIMP-1) was also determined by both real-time Q-PCR and Western blotting analysis.

RESULTS

The transfection of FAK shRNA plasmids into HSC resulted in disrupted FAK expression. Compared with the HK group, the levels of type I collagen and type III collagen mRNA transcripts in FAK shRNA plasmid group were significantly decreased (0.69 +/- 0.03 vs 1.96 +/- 0.15, P = 0.000; 0.59 +/- 0.07 vs 1.62 +/- 0.12, P = 0.020). The production of TIMP-1 in this cell type was also significantly reduced at both mRNA and protein levels (0.49 +/- 0.02 vs 1.72 +/- 0.10, P = 0.005; 0.76 +/- 0.08 vs 2.31 +/- 0.24, P = 0.000). However, the expression of MMP-13 mRNA could be significantly up-regulated by the transfection of FAK shRNA plasmids into HSC (1.74 +/- 0.20 vs 1.09 +/- 0.09, P = 0.000).

CONCLUSION

These data support the hypothesis that shRNA-mediated disruption of FAK expression could attenuate extracellular matrix (ECM) synthesis and promote ECM degradation, making FAK a potential target for novel anti-fibrosis therapies.

No contribution of umbilical cord mesenchymal stromal cells to capillarization and venularization of hepatic sinusoids accompanied by hepatic differentiation in carbon tetrachloride-induced mouse liver fibrosis

BACKGROUND AIMS

The acceleration of capillarization and venularization of hepatic sinusoids after cell therapy would not be beneficial to restoration after liver disease. The goal was to observe the effects of umbilical cord (UC)-derived mesenchymal stromal cells (MSC) on liver microcirculation and their therapeutic potential in liver fibrosis.

METHODS

Human UC MSC labeled with or without CM-DIL were transplanted into NOD/SCID mice with carbon tetrachloride (CCl4)-induced chronic liver fibrosis models. Because of the high autofluorescence on the injured liver sections, we used immunohistochemistry, Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR), but not immunofluorescence, in order to avoid false images under a confocal fluorescence microscope.

RESULTS

Human-specific alpha-fetoprotein and albumin mRNA and proteins were detected in CCl4-treated mouse livers receiving human UC MSC transplants. We only observed the gene expression of human-specific endothelial-like cells markers CD31 and KDR by RT-PCR, but not protein expression by immunohistochemistry, in UC MSC-transplanted mouse livers. Vascular endothelial growth factor (VEGF) expression in injured livers 4 weeks after UC MSC transplantation was higher than in normal livers. However, UC MSC injection did not increase significantly the vascular density labeled by CD31 and (vWF) in the injured livers of UC MSC-transplanted mice compared with non-transplanted mice after CCl4 treatment. In addition, liver function was partly improved after UC MSC transplantation.

CONCLUSIONS

Human UC MSC can differentiate into hepatocyte-like cells but do not accelerate the capillarization and venularization of hepatic sinusoids, finally leading to the partial improvement of liver function in mice with CCl4-mediated chronic liver fibrosis.

Vascular factors, angiogenesis and biliary tract disease

PURPOSE OF REVIEW

Recent studies have brought to light that angiogenesis and the expression of pro-angiogenic factors such as vascular endothelial growth factors (VEGFs) participate in the pathogenesis of biliary tract diseases. This review summarizes recent progress that has been accomplished in the field, which expands our understanding of the relationship between vascular growth and the biliary tract, particularly the molecular mechanisms that underlie the pathogenesis of biliary tract diseases.

RECENT FINDINGS

Angiogenesis and the expression of vascular factors play a key role in the pathogenesis of primary biliary cirrhosis, cholangiocarcinoma, liver cysts, and in the progression of biliary fibrosis in animal models. Inhibition of angiogenesis limits fibrosis in animal models, whereas the bile acid, taurocholate, has protective effects in animal models of bile duct and peribiliary vascular plexus damage.

SUMMARY

A widening body of information indicates that the expression of pro-angiogenic factors such as VEGFs and angiogenesis play an important role in a variety of biliary tract diseases. Further characterization of the link between angiogenesis and vascular growth factor expression will help in elucidating the mechanisms regulating the pathogenesis of biliary tract diseases and in devising new treatment approaches for these devastating diseases.

Biochemical characterization of the binding of cyclic RGDyK to hepatic stellate cells

Activated hepatic stellate cells (HSCs) play a crucial role in the development of liver fibrosis. Noninvasive monitoring of the activation of HSCs has been challenging due to the lack of specific receptors or motifs on the cells. The present study provides the evidence that integrin alpha v beta 3 expressed on HSCs is a biomarker reflecting the activation of HSCs. Solid-phase synthesis of cRGDyK (Arg-Gly-Asp-(D)Tyr-Lys) peptide and FAM-conjugated peptide were employed for binding to integrin alpha v beta 3. The increased expression of integrin alpha v and beta 3 at mRNA and protein levels was detected during HSC activation. The affinity of cRGDyK to integrin alpha v beta 3 was examined by both radioligand binding assay and FAM-conjugated peptide binding measurements. Quantitative RT-PCR and Western blotting showed a less dramatic, but significant increase in alpha v and beta 3 integrin mRNA and protein expression following activation of rat HSCs. Radioiodinated cRGDyK binds to both purified and membrane-bound integrin alpha v beta 3 with high affinity in a dissociable manner. FAM-conjugated cRGDyK was coupled to activated HSCs in a time- and dose-dependent, receptor-mediated manner. Activated HSCs express sufficient number of integrin alpha v beta 3 receptor. cRGDyK peptide binds to both purified and membrane-bound integrin alpha v beta 3 with high affinity in a reversible fashion. Thus, the cRGDyK peptide represented a new agent potentially useful for the diagnosis of liver fibrosis.

The alphavbeta6 integrin is a highly specific immunohistochemical marker for cholangiocarcinoma

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC) are common primary hepatic malignancies. Their immunohistological differentiation using specific markers is pivotal for treatment and prognosis. We found alphavbeta6 integrin strongly upregulated in biliary fibrosis, but its expression in primary and secondary liver tumours is unknown. Here, we aimed to evaluate the diagnostic applicability of alphavbeta6 integrin in differentiating primary liver cancers.

METHODS

Expression of alphavbeta6 integrin was evaluated in liver tissues from patients with CC, HCC, fibrolamellar HCC, combined CC/HCC, hepatic metastases of colorectal and pancreatic carcinomas, primary sclerosing cholangitis (PSC), and in human primary and tumour-derived liver cell lines by immunohisto- and cytochemistry, and by TaqMan PCR. Diagnostic performance of the beta6 subunit was compared with CK7, CK20, and HepPar 1.

RESULTS

In CC cells beta6 mRNA levels were induced 125-fold compared to primary cholangiocytes, while it was completely absent in hepatoma cells. In human tissues, beta6 transcripts were more than 100-fold upregulated in CC compared to normal liver. By immunohistochemistry, 88% of CC, 50% of PSC, 13% of colorectal carcinoma metastases, and 80% of pancreatic carcinoma metastases presented alphavbeta6, whereas all HCC, combined CC/HCC and fibrolamellar HCC stained negative. Specificity of beta6 immunohistochemistry for CC (100%) surpassed all other tested markers and sensitivity was equal to CK7 (86% vs. 90%).

CONCLUSION

The alphavbeta6 integrin is strongly expressed in human CC but not in HCC and therefore can be considered as a specific immunohistochemical marker in the differential diagnosis of primary liver tumours.

Role of the receptor for advanced glycation end products in hepatic fibrosis

AIM: To study the role of advanced glycation end products (AGE) and their specific receptor (RAGE) in the pathogenesis of liver fibrogenesis.

METHODS: In vitro RAGE expression and extracellular matrix-related gene expression in both rat and human hepatic stellate cells (HSC) were measured after stimulation with the two RAGE ligands, advanced glycation end product-bovine serum albumin (AGE-BSA) and N^ε-(carboxymethyl) lysine (CML)-BSA, or with tumor necrosis factor-α (TNF-α). In vivo RAGE expression was examined in models of hepatic fibrosis induced by bile duct ligation or thioacetamide. The effects of AGE-BSA and CML-BSA on HSC proliferation, signal transduction and profibrogenic gene expression were studied in vitro.

RESULTS: In hepatic fibrosis, RAGE expression was enhanced in activated HSC, and also in endothelial cells, inflammatory cells and activated bile duct epithelia. HSC expressed RAGE which was upregulated after stimulation with AGE-BSA, CML-BSA, and TNF-α. RAGE stimulation with AGE-BSA and CML-BSA did not alter HSC proliferation, apoptosis, fibrogenic signal transduction and fibrosis- or fibrolysis-related gene expression, except for marginal upregulation of procollagen α1(I) mRNA by AGE-BSA.

CONCLUSION: Despite upregulation of RAGE in activated HSC, RAGE stimulation by AGE does not alter their fibrogenic activation. Therefore, RAGE does not contribute directly to hepatic fibrogenesis.

Pharmacological inhibition of integrin alphavbeta3 aggravates experimental liver fibrosis and suppresses hepatic angiogenesis

The vitronectin receptor integrin alphavbeta3 promotes angiogenesis by mediating migration and proliferation of endothelial cells, but also drives fibrogenic activation of hepatic stellate cells (HSCs) in vitro. Expecting antifibrotic synergism, we studied the effect of alphavbeta3 inhibition in two in vivo models of liver fibrogenesis. Liver fibrosis was induced in rats by way of bile duct ligation (BDL) for 6 weeks or thioacetamide (TAA) injections for 12 weeks. A specific alphavbeta3 (alphavbeta5) inhibitor (Cilengitide) was given intraperitoneally twice daily at 15 mg/kg during BDL or after TAA administration. Liver collagen was determined as hydroxyproline, and gene expression was quantified by way of quantitative polymerase chain reaction. Liver angiogenesis, macrophage infiltration, and hypoxia were assessed by way of CD31, CD68 and hypoxia-inducible factor-1alpha immunostaining. Cilengitide decreased overall vessel formation. This was significant in portal areas of BDL and septal areas of TAA fibrotic rats and was associated with a significant increase of liver collagen by 31% (BDL) and 27% (TAA), and up-regulation of profibrogenic genes and matrix metalloproteinase-13. Treatment increased gamma glutamyl transpeptidase in both models, while other serum markers remained unchanged. alphavbeta3 inhibition resulted in mild liver hypoxia, as evidenced by up-regulation of hypoxia-inducible genes. Liver infiltration by macrophages/Kupffer cells was not affected, although increases in tumor necrosis factor alpha, interleukin-18, and cyclooxygenase-2 messenger RNA indicated modest macrophage activation.

CONCLUSION

Specific inhibition of integrin alphavbeta3 (alphavbeta5) in vivo decreased angiogenesis but worsened biliary (BDL) and septal (TAA) fibrosis, despite its antifibrogenic effect on HSCs in vitro. Angiogenesis inhibitors should be used with caution in patients with hepatic fibrosis.

PTEN expression is down-regulated in liver tissues of rats with hepatic fibrosis induced by biliary stenosis

The gene phosphatase and tensin homolog deleted on chromosome 10 (PTEN) codes for a tumor-suppressor phospholipid phosphatase. Deletion, mutation or abnormal expression of PTEN is commonly found in many kinds of malignant tumors. At the time of this study, though, the role of PTEN expression in the pathology of hepatic fibrosis remains unclear. In this study, we investigate the dynamic expression of PTEN in a rat model of hepatic fibrosis, with special emphasis on the activation and proliferation of hepatic stellate cells (HSC) in vivo. The rat model of hepatic fibrosis used in this study employed common bile duct ligation. At four time points, the expression of PTEN in hepatic tissues and activated HSC in rat liver tissues was measured by immunohistochemical staining, Western blotting, real-time fluorescent quantitative PCR and immunofluorescence confocal laser scanning microscopy, respectively. Further, alpha-smooth muscle actin (alpha-SMA), an activated HSC marker in rat liver tissues, was detected by immunohistochemical staining. This study showed that aggravation of hepatic fibrosis led to gradually decreasing expression of PTEN in the hepatic tissues. Further, as hepatic fibrosis worsens, PTEN-expressing activated HSC accounts for an increasingly smaller percentage of all activated HSC. In contrast, the percentage of alpha-SMA-expressing HSC cells increases significantly. In conclusion, expression of PTEN mRNA and protein is down-regulated in fibrogenic rat liver tissue, and its expression in HSC in vivo also decreases with progression of fibrosis. Thus, these results show that the dynamic expression of PTEN in hepatic tissues negatively correlates with activation and proliferation of HSC.

Integrin alpha(v)beta(3) is a pleiotrophin receptor required for pleiotrophin-induced endothelial cell migration through receptor protein tyrosine phosphatase beta/zeta

We have previously shown that the angiogenic growth factor pleiotrophin (PTN) induces migration of endothelial cells through binding to its receptor protein tyrosine phosphatase beta/zeta (RPTPbeta/zeta). In this study, we show that a monoclonal antibody against alpha(nu)beta(3) but not alpha(5)beta(1) integrin abolished PTN-induced human endothelial cell migration in a concentration-dependent manner. Integrin alpha(nu)beta(3) was found to directly interact with PTN in an RGD-independent manner, whereas a synthetic peptide corresponding to the specificity loop of the beta(3) integrin extracellular domain ((177)CYDMKTTC(184)) inhibited PTN-alpha(nu)beta(3) interaction and totally abolished PTN-induced endothelial cell migration. Interestingly, alpha(nu)beta(3) was also found to directly interact with RPTPbeta/zeta, and PTN-induced Y773 phosphorylation of beta(3) integrin was dependent on both RPTPbeta/zeta and the downstream c-src kinase activation. Midkine was found to interact with RPTPbeta/zeta, but not with alpha(nu)beta(3), and caused a small but statistically significant decrease in cell migration. In the same line, PTN decreased migration of different glioma cell lines that express RPTPbeta/zeta but do not express alpha(nu)beta(3), while it stimulated migration of U87MG cells that express alpha(nu)beta(3) on their cell membrane. Overexpression or down-regulation of beta(3) stimulated or abolished, respectively, the effect of PTN on cell migration. Collectively, these data suggest that alpha(nu)beta(3) is a key molecule that determines the stimulatory or inhibitory effect of PTN on cell migration.

Genistein inhibits proliferation and functions of hypertrophic scar fibroblasts

Hypertrophic scarring is abnormal proliferation of dermal fibroblasts and excessive deposition of extracellular matrix. To date, despite many studies, treatments have not been satisfactory. Genistein, a potent, specific inhibitor of tyrosine protein kinases (TPKs), has been proved to inhibit many kinds of tumour and some fibrotic diseases. The purpose of this study was to investigate the effects of genistein on the proliferation and functions of hypertrophic scar fibroblasts (HSFBs) and the mechanism by which genistein inhibits TPK signal transduction. The first effect was observed by methyl-thiazol-diphenyl-tetrazolium assay and the second by [gamma-(32)p] adenosine triphosphate incorporation assay. The results demonstrated that genistein inhibits the proliferation and function of HSFBs and changes the TPK signal transduction pathway, which can provide an experimental basis for treating HS with genistein.

Inhibition of integrin alphavbeta6 on cholangiocytes blocks transforming growth factor-beta activation and retards biliary fibrosis progression

BACKGROUND & AIMS

Integrin alphavbeta6 is highly expressed on certain activated epithelia, where it mediates attachment to fibronectin and serves as coreceptor for the activation of latent transforming growth factor (TGF)-beta1. Because its role in liver fibrosis is unknown, we studied alphavbeta6 function in vitro and explored the antifibrotic potential of the specific alphavbeta6 antagonist EMD527040.

METHODS

Experimental liver fibrosis was studied in rats after bile duct ligation (BDL) and in Mdr2(abcb4)(-/-) mice. Different doses of EMD527040 were given to rats from week 2 to 6 after BDL and to Mdr2(-/-) mice from week 4 to 8. Liver collagen was quantified, and expression of alphavbeta6 and fibrosis-related transcripts was determined by quantitative reverse-transcription polymerase chain reaction. alphavbeta6-expressing cells, bile duct proliferation, and apoptosis were assessed histologically. The effect of EMD527040 on cholangiocyte adhesion, proliferation, apoptosis, and TGF-beta1 activation was studied in vitro.

RESULTS

alphavbeta6 was highly expressed on proliferating bile duct epithelia in fibrosis, with 100-fold increased transcript levels in advanced fibrosis. EMD527040 attenuated bile ductular proliferation and peribiliary collagen deposition by 40%-50%, induced down-regulation of fibrogenic and up-regulation of fibrolytic genes, and improved liver architecture and function. In vitro alphavbeta6 inhibition reduced activated cholangiocyte proliferation, their adhesion to fibronectin, and endogenous activation of TGF-beta1 by 50% but did not affect bile duct apoptosis.

CONCLUSIONS

Integrin alphavbeta6 is strongly up-regulated in proliferating bile duct epithelia and drives fibrogenesis via adhesion to fibronectin and auto/paracrine TGF-beta1 activation. Pharmacologic inhibition of alphavbeta6 potently inhibits the progression of primary and secondary biliary fibrosis.

Activation of focal adhesion kinase and JNK contributes to the extracellular matrix and cAMP-GEF mediated survival from bile acid induced apoptosis in rat hepatocytes

BACKGROUND/AIMS

Adherence to an extracellular matrix (ECM) rescues hepatocytes from apoptosis, but how hepatocytes adhered to different ECM and respond to apoptotic and cytoprotective stimuli is unknown.

METHODS

Rat hepatocytes were plated on type 1 collagen (CI), laminin (LM) or polylysine (PL) and the amount of apoptosis induced by glycochenodeoxycholate (GCDC), deoxycholate (DCA), Fas ligand or serum withdrawal was determined by Hoechst staining. The response to cytoprotection by cAMP-guanine exchange factor (cAMP-GEF) activation was determined. Kinase activation was determined by immunoblotting with phosphospecific antibodies.

RESULTS

Hepatocytes on LM and PL had more apoptosis in response to all apoptotic stimuli. GCDC increased c-jun-N-terminal kinase (JNK) phosphorylation 2-fold in hepatocytes on CI, but 15- and 30-fold in hepatocytes on PL or LM. SP-600125, a JNK inhibitor, prevented LM and PL potentiation of bile acid apoptosis. GCDC induced dephosphorylation of focal adhesion kinase (FAK) was prevented by cAMP-GEF activation. Cytochalasin B which decreased FAK phosphorylation prevented cAMP-GEF cytoprotection.

CONCLUSIONS

JNK activation augments apoptosis in hepatocytes plated on PL and LM. Decreased FAK phosphorylation as seen in cells treated with bile acids or attached to PL and LM promotes hepatocyte apoptosis.

Integrin alphavbeta6 is a marker of the progression of biliary and portal liver fibrosis and a novel target for antifibrotic therapies

BACKGROUND/AIMS

The integrin alphavbeta6 promotes proliferation of specialized epithelia and acts as a receptor for the activation of latent TGFbeta1. We studied alphavbeta6 expression in experimental and human liver fibrosis and the potential of its pharmacological inhibition for treatment of hepatic fibrosis.

METHODS

alphavbeta6 expression was studied by quantitative PCR and immunohistochemistry in rats with cirrhosis due to bile duct ligation (BDL), administration of thioacetamide (TAA), in Mdr2(Abcb4)(-/-) mice with spontaneous biliary fibrosis, and in livers of patients with chronic hepatitis C (n=79) and end-stage liver disease due to various etiologies (n=18). The effect of a selective alphavbeta6 inhibitor was evaluated in Mdr2(Abcb4)(-/-) mice with ongoing fibrogenesis.

RESULTS

Integrin beta6 mRNA increased with fibrosis stage in hepatitis C and was upregulated between 25- and 100-fold in TAA- and BDL-induced cirrhosis, in Mdr2(Abcb4)(-/-) mice and in human end-stage liver disease. alphavbeta6 protein was absent in normal livers and expressed de novo on (activated) bile duct epithelia and transitional hepatocytes. A single dose of the alphavbeta6 inhibitor injected into Mdr2(Abcb4)(-/-) mice significantly induced profibrolytic matrix metalloproteinases (MMP)-8 and -9 after 3 h, with a corresponding increase in extracellular matrix-degrading activities. In parallel profibrogenic transcripts (procollagen alpha1(I), TGFbeta2, and MMP-2) showed a trend of downregulation.

CONCLUSIONS

(1) Integrin alphavbeta6 is induced de novo in rodent and human liver fibrosis, where it is expressed on activated bile duct epithelia and (transitional) hepatocytes during fibrosis progression. (2) In vivo a single dose of a small molecule alphavbeta6 inhibitor induced antifibrogenic and profibrolytic genes and activities, suggesting alphavbeta6 is a unique target for treatment of liver fibrosis.