Autophagy is a regulator of TGF-β1-induced fibrogenesis in primary human atrial myofibroblasts

Functional variants of the ATG7 gene promoter in acute myocardial infarction

BACKGROUND

Coronary artery disease including acute myocardial infarction (AMI) is mainly caused by atherosclerosis, an inflammatory and metabolic disease. Autophagy has been demonstrated to play critical roles in lipid metabolism and inflammation. Altered autophagic activity has been reported in AMI patients. However, molecular basis for dysfunctional autophagy in AMI remains unexplained.

METHODS

In this study, the promoter of the ATG7 gene, encoding a core protein for autophagy, was genetically and functionally analyzed in large cohorts of AMI patients (n = 355) and ethnic-matched healthy controls (n = 363). Related molecular mechanisms were also explored.

RESULTS

A total of 19 DNA sequence variants (DSVs) including single-nucleotide polymorphisms (SNPs) were found in the ATG7 gene promoter. Two novel DSVs and five SNPs were only identified in AMI patients group. These DSVs and SNPs, except one SNP, significantly altered the transcriptional activity of the ATG7 gene promoter in both HEK-293 and H9c2 cells (p < 0.05). Further electrophoretic mobility shift assay revealed that the DSVs and SNPs evidently affected the binding of transcription factors.

CONCLUSIONS

ATG7 gene DSVs and SNPs identified in AMI patients may alter the transcriptional activity of the ATG7 gene promoter and change ATG7 level, contributing to the AMI development as a rare risk factor.

Single-Stranded DNA-Binding Protein 1 Abrogates Cardiac Fibroblast Proliferation and Collagen Expression Induced by Angiotensin II

Angiotensin II (Ang II), an effective component of renin-angiotensin system, plays a pivotal role in cardiac fibrosis, which may further contribute to heart failure. Single-stranded DNA-binding protein 1 (SSBP1), a DNA damage response protein, regulates both mitochondrial function and extracellular matrix remodeling. In this study, we aim to investigate the role of SSBP1 in cardiac fibrosis that is induced by Ang II. We infused C57BL/6J mice with vehicle or Ang II and valsartan using implanted osmotic mini-pumps. Moreover, heart function was examined by echocardiography and cardiac fibrosis was analyzed via picrosirus red staining. The expression of COL1A1, COL3A1, SSBP1, p53, Nox1, and Nox4 was analyzed via qRT-PCR and/or immunoblots. The SSBP1 expression was manipulated via SSBP1 shRNA and pcDNA3.1/SSBP1 plasmids, while the p53 expression was enhanced via AdCMV-p53 infection. The exposure to Ang II increased the mouse heart weight, systolic blood pressure, interventricular septal thickness diastolic (IVSTD) and left ventricular end posterior wall dimension diastolic (LVPWD), which were counteracted by valsartan. While cardiac fibrosis was induced with Ang II treatment, it was relieved using valsartan. Furthermore, Ang II treatment caused mitochondrial dysfunction, oxidative stress, and down-regulated SSBP1 expression. The knockdown of SSBP1 increased cardiac fibroblast proliferation, collagen expression, and decreased p53 expression, which was impeded via SSBP1 overexpression. Moreover, the forced expression of p53 abated the fibroblast proliferation and collagen expression that was induced by Ang II. To summarize, SSBP1 was down-regulated by Ang II and implicated in cardiac fibroblast proliferation and collagen expression partly via the p53 protein.

Toll-like receptor 4 contributes to a myofibroblast phenotype in cardiac fibroblasts and is associated with autophagy after myocardial infarction in a mouse model

BACKGROUND AND AIMS

Cardiac fibrosis after myocardial infarction (MI) is involved in fibroblast transforming and differentiating into myofibroblast phenoconversion, however, the underlying mechanisms are poorly understood. Toll-like receptor 4 (TLR4)-mediated pathogen-associated molecular patterns are key factors that deteriorate cardiac remodelling after MI. Moreover, autophagy has dual roles in cell survival in myocardial tissues after MI. We evaluated the relationship between TLR4 signalling and cardiac myofibroblast transformation-differentiation after MI in vivo and in vitro and analysed the role of autophagy.

METHODS

We reproduced a model of MI by the permanent ligation of the left anterior descending coronary artery of Tlr4-knockout (Tlr4^-/-) and wild-type (WT) male mice. We evaluated scar formation, myofibroblast phenoconversion, LC3 dot formation, autophagy related proteins and α-smooth muscle actin (SMA) in cardiac tissues, 7, 14, and 28 days after myocardial infarction. Cardiac fibroblasts were cultured from Tlr4^-/- or WT mice. Vimentin, α-SMA, bilayer membrane vesicle structures of autophagosomes, and autophagy related proteins were observed after treatment with lipopolysaccharide (LPS) or 3-methyladenine (3-MA) at 24 h.

RESULTS

After MI on 7, 14, and 28 days, Tlr4^-/- mice showed that heart tissue fibrosis and expression of α-SMA, a marker of myofibroblasts, were decreased compared to WT mice. Additionally, levels of LC3II, Atg5, Atg7, and Beclin-1, which are involved in autophagy, were lower than those in WT mice. Further, p62 expression, which is negatively correlated with autophagy levels, was higher in Tlr4^-/- mice. Moreover, LC3-labelled autophagosomes in cardiac tissues were reduced in these animals. In vitro, LPS, a ligand of TLR4, stimulated α-SMA expression in cardiac fibroblasts, enhanced autophagic flux, and increased autophagosome numbers. In contrast, these effects were not obvious in Tlr4^-/- cardiac fibroblasts. LC3II, Atg5, Atg7, and Beclin-1 were upregulated, and p62 was downregulated in cardiac fibroblasts of WT mice stimulated with LPS. However, these effects were blocked by 3-methyladenine, an inhibitor of autophagy.

CONCLUSIONS

These results suggest that TLR4 signalling executes the development of a myofibroblast phenotype after MI via autophagy and could be therapeutically exploited to improve outcome after myocardial injury.

Endocrine Regulation of Energy Balance by Drosophila TGF-β/Activins

The Transforming growth factor beta (TGF-β) family of secreted proteins regulates a variety of key events in normal development and physiology. In mammals, this family, represented by 33 ligands, including TGF-β, activins, nodal, bone morphogenetic proteins (BMPs), and growth and differentiation factors (GDFs), regulate biological processes as diverse as cell proliferation, differentiation, apoptosis, metabolism, homeostasis, immune response, wound repair, and endocrine functions. In Drosophila, only 7 members of this family are present, with 4 TGF-β/BMP and 3 TGF-β/activin ligands. Studies in the fly have illustrated the role of TGF-β/BMP ligands during embryogenesis and organ patterning, while the TGF-β/activin ligands have been implicated in the control of wing growth and neuronal functions. In this review, we focus on the emerging roles of Drosophila TGF-β/activins in inter-organ communication via long-distance regulation, especially in systemic lipid and carbohydrate homeostasis, and discuss findings relevant to metabolic diseases in humans.

MicroRNA-101a suppresses fibrotic programming in isolated cardiac fibroblasts and in vivo fibrosis following trans-aortic constriction

AIMS

MiR-101a is reported to reduce post-infarction myocardial fibrosis through targeting c-FOS and TGFbr1. However the actions of miR-101a within the TGF-β signaling pathway are largely unknown. We demonstrate the mechanisms underlying mutual inhibition between miR-101a and TGF-β signaling and explore the therapeutic potential of miR-101a in suppressing pressure overload-induced cardiac fibrosis.

METHODS AND RESULTS

The effects of miR-101a on fibroblast proliferation, myofibroblast transdifferentiation, collagen synthesis, apoptosis, and autophagy were assessed in isolated rat cardiac fibroblasts (cFB). MiR-101a effects upon cFB TGF-β signaling were assessed by qPCR, Western blotting, 3'UTR luciferase reporter assay and promoter activity assessments. Rats subjected to transverse aortic constriction (TAC) were treated with PBS or 1 mg/kg of a miR-101a mimic i.v. at 1, 3, and 7-day post-surgery. Left ventricular (LV) function (echocardiography; LV catheterization) and LV fibrosis (picro-sirius red staining, qPCR and WB) were assessed at 2-day and 2 & 10-week post-surgery. MiR-101a inhibited cFB proliferation by inducing cell apoptosis rather than through cell cycle inhibition; and reduced collagen synthesis by downregulation of collagen gene expression and increased autophagy. MiR-101a inhibited TGF-β signaling pathways by directly targeting TGFbr1, reducing Smad3 phosphorylation and inhibiting Tab3 promoter activity. Conversely TGF-β inhibited promoter activity for both miR-101a and b. In vivo endogenous miR-101a expression was downregulated 2-day post-TAC returning to baseline by 14-day. MiR-101a mimic treatment inhibited myocardial TGF-β signaling and collagen gene up-regulation at 2-day post-TAC. MiR-101a reduced fibrosis, improved +dP/dt and lowered end diastolic pressure (EDP) at 2-week post-TAC. Treatment also attenuated adverse LV remodeling and preserved cardiac ejection fraction at 10-week post-TAC.

CONCLUSIONS

MiR-101a and TGF-β are mutually inhibitory and co-direct the activation, proliferation, and collagen synthesis of cFBs. The predominance of TGF-β signaling over reduced miR-101a expression early post-TAC is associated with cardiac fibrosis and dysfunction. Treatment with miR-101a, introduced early after imposition of abnormal pressure loading, inhibits TGF-β signaling, reduces cardiac fibrosis and preserves LV function.

Thrombin induces protease-activated receptor 1 signaling and activation of human atrial fibroblasts and dabigatran prevents these effects

BACKGROUND

Data with animal cells and models suggest that thrombin activates cardiac fibroblasts (Fib) to myofibroblasts (myoFib) via protease-activated receptor 1 (PAR1) cleavage, and in this way promotes adverse atrial remodeling and, thereby, atrial fibrillation (AF).

OBJECTIVE

Here, we explored the effects of thrombin on human atrial Fib and whether they are antagonized by the clinically available direct thrombin inhibitor, dabigatran.

METHODS

Fib isolated from atrial appendages of patients without AF undergoing elective cardiac surgery were evaluated for PAR expression and treated with thrombin with or without dabigatran. PAR1 cleavage, downstream signaling and myoFib markers were investigated by immunofluorescence and Western blot. Collagen synthesis, activity of matrix metalloprotease (MMP)-2 and proliferation were assessed by Picro-Sirius red staining, gelatinolytic zymography and BrdU incorporation, respectively. Fib function was studied as capability to contract a collagen gel and stimulate the chemotaxis of peripheral blood monocytes from healthy volunteers.

RESULTS

Primary human atrial Fib expressed PAR1, while levels of the other PARs were very low. Thrombin triggered PAR1 cleavage and phosphorylation of ERK1/2, p38 and Akt, elicited a switch to myoFib enriched for αSMA, fibronectin and type I collagen, and induced paracrine/autocrine transforming growth factor beta-1, cyclooxygenase-2, endothelin-1 and chemokine (C-C motif) ligand 2 (CCL2); conversely, MMP-2 activity decreased. Thrombin-primed cells displayed enhanced proliferation, formed discrete collagen-containing cellular nodules, and stimulated the contraction of a collagen gel. Furthermore, their conditioned medium caused monocytes to migrate. All these effects were prevented by dabigatran.

CONCLUSION

These results with human cells complete the knowledge about thrombin actions on cardiac Fib and strengthen the translational potential of the emerging paradigm that pharmacological blockade of thrombin may counteract molecular and cellular events underlying AF.

Reduced Autophagy by a microRNA-mediated Signaling Cascade in Diabetes-induced Renal Glomerular Hypertrophy

Autophagy plays a key role in the pathogenesis of kidney diseases, however its role in diabetic nephropathy (DN), and particularly in kidney glomerular mesangial cells (MCs) is not very clear. Transforming Growth Factor- β1 (TGF-β), a key player in the pathogenesis of DN, regulates expression of various microRNAs (miRNAs), some of which are known to regulate the expression of autophagy genes. Here we demonstrate that miR-192, induced by TGF-β signaling, plays an important role in regulating autophagy in DN. The expression of key autophagy genes was decreased in kidneys of streptozotocin-injected type-1 and type-2 (db/db) diabetic mice and this was reversed by treatment with Locked Nucleic Acid (LNA) modified miR-192 inhibitors. Changes in autophagy gene expression were also attenuated in kidneys of diabetic miR-192-KO mice. In vitro studies using mouse glomerular mesangial cells (MMCs) also showed a decrease in autophagy gene expression with TGF-β treatment. miR-192 mimic oligonucleotides also decreased the expression of certain autophagy genes. These results demonstrate that TGF-β and miR-192 decrease autophagy in MMCs under diabetic conditions and this can be reversed by inhibition or deletion of miR-192, further supporting miR-192 as a useful therapeutic target for DN.

Lactone Component From Ligusticum chuanxiong Alleviates Myocardial Ischemia Injury Through Inhibiting Autophagy

The dysregulation of autophagy is associated with a series of cardiovascular diseases, such as myocardial ischemia injury. Lactone component from Ligusticum chuanxiong (LLC) is the major constituent of the traditional Chinese herb L. chuanxiong Hort., which has been reported to hold potential cardioprotective effects. In this study, to determine whether LLC protects the heart through regulation of autophagy, we explored the effects of LLC on cardioprotection and autophagy in myocardial ischemia injured rats and H9c2 cardiomyocytes. Our results showed that LLC significantly reduced infarct size and serum levels of lactate dehydrogenase, creatine kinase, and cardiac troponin and ameliorated histological features in a dose-dependent manner. Similar protections were observed in cardiomyocytes subjected to oxygen-glucose deprivation (OGD). Meanwhile, LLC inhibited autophagy induced by myocardial ischemia injury, characterized by increased autophagic vacuoles, LC3-II/LC3-I ratio and the expression of Beclin 1, whereas decreased the expression of p62. Additionally, LLC combined with a lysosomal inhibitor chloroquine (CQ) reduced LC3-II/LC3-I ratio in cardiomyocytes compared with CQ alone. Furthermore, LLC-afforded cardioprotection was abolished by a specific PI3K inhibitor LY294002. Collectively, these findings demonstrated that cardioprotective effects of LLC were related to restoration of autophagic flux through the activation of PI3K/Akt/mTOR signaling pathway.

Myocardin regulates mitochondrial calcium homeostasis and prevents permeability transition

Myocardin is a transcriptional co-activator required for cardiovascular development, but also promotes cardiomyocyte survival through an unclear molecular mechanism. Mitochondrial permeability transition is implicated in necrosis, while pore closure is required for mitochondrial maturation during cardiac development. We show that loss of myocardin function leads to subendocardial necrosis at E9.5, concurrent with elevated expression of the death gene Nix. Mechanistically, we demonstrate that myocardin knockdown reduces microRNA-133a levels to allow Nix accumulation, leading to mitochondrial permeability transition, reduced mitochondrial respiration, and necrosis. Myocardin knockdown elicits calcium release from the endo/sarcoplasmic reticulum with mitochondrial calcium accumulation, while restoration of microRNA-133a function, or knockdown of Nix rescues calcium perturbations. We observed reduced myocardin and elevated Nix expression within the infarct border-zone following coronary ligation. These findings identify a myocardin-regulated pathway that maintains calcium homeostasis and mitochondrial function during development, and is attenuated during ischemic heart disease. Given the diverse role of Nix and microRNA-133a, these findings may have broader implications to metabolic disease and cancer.

Autophagy modulates transforming growth factor beta 1 induced epithelial to mesenchymal transition in non-small cell lung cancer cells

Lung cancer is considered one of the most frequent causes of cancer-related death worldwide and Non-Small Cell Lung Cancer (NSCLC) accounts for 80% of all lung cancer cases. Autophagy is a cellular process responsible for the recycling of damaged organelles and protein aggregates. Transforming growth factor beta-1 (TGFβ₁) is involved in Epithelial to Mesenchymal Transition (EMT) and autophagy induction in different cancer models and plays an important role in the pathogenesis of NSCLC. It is not clear how autophagy can regulate EMT in NSCLC cells. In the present study, we have investigated the regulatory role of autophagy in EMT induction in NSCLC and show that TGFβ₁ can simultaneously induce both autophagy and EMT in the NSCL lines A549 and H1975. Upon chemical inhibition of autophagy using Bafilomycin-A1, the expression of the mesenchymal marker vimentin and N-cadherin was reduced. Immunoblotting and immunocytochemistry (ICC) showed that the mesenchymal marker vimentin was significantly downregulated upon TGFβ₁ treatment in ATG7 knockdown cells when compared to corresponding cells treated with scramble shRNA (negative control), while E-cadherin was unchanged. Furthermore, autophagy inhibition (Bafilomycin A1 and ATG7 knockdown) decreased two important mesenchymal functions, migration and contraction, of NSCLC cells upon TGFβ₁ treatment. This study identified a crucial role of autophagy as a potential positive regulator of TGFβ₁-induced EMT in NSCLC cells and identifies inhibitors of autophagy as promising new drugs in antagonizing the role of EMT inducers, like TGFβ₁, in the clinical progression of NSCLC.

Inhibition of autophagy inhibits the conversion of cardiac fibroblasts to cardiac myofibroblasts

The incidence of heart failure with concomitant cardiac fibrosis is very high in developed countries. Fibroblast activation in heart is causal to cardiac fibrosis as they convert to hypersynthetic cardiac myofibroblasts. There is no known treatment for cardiac fibrosis. Myofibroblasts contribute to the inappropriate remodeling of the myocardial interstitium, which leads to reduced cardiac function and ultimately heart failure. Elevated levels of autophagy have been linked to stress-induced ventricular remodeling and other cardiac diseases. Previously, we had shown that TGF-β₁ treatment of human atrial fibroblasts both induced autophagy and enhanced the fibrogenic response supporting a linkage between the myofibroblast phenotype and autophagy. We now demonstrate that with in vitro culture of primary rat cardiac fibroblasts, inhibition of autophagy represses fibroblast to myofibroblast phenoconversion. Culturing unpassaged cardiac fibroblasts for 72 hours on plastic tissue culture plates is associated with elevated α-smooth muscle actin (α-SMA) expression. This activation parallels increased microtubule-associated protein 1A/1B-light chain 3 (LC-3β II) protein expression. Inhibition of autophagy with bafilomycin-A1 (Baf-A1) and chloroquine (CQ) in cardiac fibroblasts significantly reduces α-SMA and extracellular domain A fibronectin (ED-A FN) protein vs untreated controls. Myofibroblast cell migration and contractility were significantly reduced following inhibition of autophagy. These data support the possibility of a causal link between cardiac fibroblast-to-myofibroblast phenoconversion and autophagy.

Antagonism of Interleukin-17A ameliorates experimental hepatic fibrosis by restoring the IL-10/STAT3-suppressed autophagy in hepatocytes

Interleukin-17A has been identified as a driver of hepatic stellate cell activation and plays a critical role in the pathogenesis of hepatic fibrosis. However, the underlining fibrosis-promoting mechanism of IL-17A is far from understood. Here we aimed to define whether hepatocytes directly respond to IL-17A stimulation and are associated with the development of hepatic fibrosis. The functional significance of IL-17A was evaluated in bile duct ligation (BDL) or thioacetamide (TAA) injection-induced mouse models of hepatic fibrosis. Human cirrhosis and control tissues were obtained from the patients with cirrhosis who received an open surgical repair process. Neutralizing IL-17A promoted the resolution of BDL or TAA-induced acute or chronic inflammation and fibrosis, resulted in a shift of the suppressive immune response in fibrotic liver toward a Th1-type immune response, and restored autophagy activity in both cholestatic and hepatotoxic liver injury induced fibrotic liver tissues, which was accompanied by a significant inhibition of STAT3 phosphorylation. Moreover, we found that IL-17A stimulated the concentration-and time-dependent phosphorylation of STAT3 in AML-12 liver cells. Blocking STAT3 with a specific inhibitor STATTIC or STAT3 siRNA protected from the IL-17A-induced autophagy suppression in AML-12 cells, indicating that STAT3 mediates IL-17A-suppressed autophagy. Administration of IL-10, which activated STAT3 and inhibited autophagy, reversed the therapeutic effect of IL-17A antagonism in vivo. Our study suggests that the IL-17A/STAT3 signaling pathway plays a crucial role in the pathogenesis of hepatic fibrosis through suppressing hepatocellular autophagy and that blocking this pathway may provide therapeutic benefits for the treatment of hepatic fibrosis.

Deregulation of microRNA-193b affects the proliferation of liver cancer via myeloid cell leukemia-1

Deregulation of microRNA (miR)-193b has been revealed to be associated with the proliferation of liver cells. However, the interaction between miR-193b and their targets inducing liver cancer remains largely unknown. The aim of the present study was to investigate the hypothesis that miR-193b affects the proliferation of liver cancer cells. In the present study, the overall survival of patients with liver cancer and low fold change of miR-193b was higher compared with that of patients with liver cancer patients and high fold change of miR-193b. The expression level of myeloid cell leukemia-1 (Mcl-1) in patients with liver cancer was lower compared with in the control group. The results of the present study demonstrated that downregulation of miR-193b suppressed the proliferation and induced apoptosis of liver cancer cells, and inhibited the Mcl-1 protein expression level in liver cancer cells. Upregulation of miR-193b increased cell proliferation and decreased apoptosis of liver cancer cells and promoted the expression level of Mcl-1 protein. The results of the present study demonstrated that the expression of miR-193b as a novel tumor suppressor serves an important role in the proliferation of liver cancer cells by mediating Mcl-1 expression.

Activation of calcium-sensing receptor-mediated autophagy in angiotensinII-induced cardiac fibrosis in vitro

Cardiac fibrosis is one of the primary mechanisms of ventricular remodeling, and there is no effective method for reversal. Activation of calcium sensing receptor (CaSR) has been reported to be involved in the development of myocardial fibrosis, but the molecular mechanism for CaSR activation has not yet been clarified and needs to be further explored. Here, we found that AngII induces cardiac fibroblast proliferation and phenotypic transformation in a dose-dependent manner with increased CaSR and autophagy related protein (Beclin1, LC3B) expression. CaSR activation results in intracellular calcium release, MEK1/2 pathway phosphorylation, autophagy activation and collagen formation induced by AngII in cardiac fibroblasts. However, pretreating the cells with Calhex₂₃₁, PD98059 or 3-MA partially blocked AngII-induced cardiac fibrosis. Our data indicate that the activation of CaSR-mediated MEK/ERK and autophagic pathways is involved in AngII-induced cardiac fibrosis in vitro.

The hypoxic tumour microenvironment

Cancer progression often benefits from the selective conditions present in the tumour microenvironment, such as the presence of cancer-associated fibroblasts (CAFs), deregulated ECM deposition, expanded vascularisation and repression of the immune response. Generation of a hypoxic environment and activation of its main effector, hypoxia-inducible factor-1 (HIF-1), are common features of advanced cancers. In addition to the impact on tumour cell biology, the influence that hypoxia exerts on the surrounding cells represents a critical step in the tumorigenic process. Hypoxia indeed enables a number of events in the tumour microenvironment that lead to the expansion of aggressive clones from heterogeneous tumour cells and promote a lethal phenotype. In this article, we review the most relevant findings describing the influence of hypoxia and the contribution of HIF activation on the major components of the tumour microenvironment, and we summarise their role in cancer development and progression.

ASPP2 Inhibits the Profibrotic Effects of Transforming Growth Factor-β1 in Hepatic Stellate Cells by Reducing Autophagy

BACKGROUND

Apoptosis-stimulating protein of p53-2 (ASPP2) is a damage-inducible P53-binding protein that enhances damage-induced apoptosis. Fibrosis is a wound-healing response, and hepatic stellate cells (HSCs) are key players in liver fibrogenesis. However, little is known about the relationship between ASPP2 and hepatic fibrosis.

AIMS

We investigated the effects of ASPP2 overexpression in HSCs and the role of ASPP2 in mouse liver fibrogenesis.

METHODS

Human HSCs (LX-2 cells) were pre-incubated with GFP adenovirus (Ad) or ASPP2 adenovirus (AdASPP2) for 24 h and then treated with or without TGF-β1. ASPP2^+/- and ASPP2+/+ Balb/c mice were used to examine the effects of ASPP2 on liver fibrosis in vivo. ASPP2+/+ Balb/c mice were generated by injecting AdASPP2 into the tail vein of ASPP2 WT Balb/c mice; all mice received intraperitoneal injections of carbon tetrachloride.

RESULTS

In this study, ASPP2 was found to markedly inhibit TGF-β1-induced fibrogenic activation of LX-2 cells. Further experiments using an autophagic flux assay confirmed that ASPP2 reduced the fibrogenic activation of LX-2 cells by inhibiting autophagy. Moreover, we found that ASPP2 overexpression attenuated the anti-apoptotic effects of TGF-β1 in LX-2 cells. The extent of liver fibrosis was markedly reduced in ASPP2+/+ mouse liver tissue compared with control mice; however, in ASPP2^+/- mice, hepatic collagen deposition was significantly increased.

CONCLUSION

These results suggest that TGF-β1-induced autophagy is required for the fibrogenic response in LX-2 cells and that ASPP2 may both inhibit TGF-β1-induced autophagy and decrease liver fibrosis.

Autophagy regulates TGF-β2-induced epithelial-mesenchymal transition in human retinal pigment epithelium cells

Transforming growth factor (TGF)-β2-induced epithelial-mesenchymal transition (EMT) in human retinal pigment epithelium (RPE) cells has an important role in the pathophysiology of intraocular fibrotic disorders, which may cause vision impairment and blindness. Autophagy, an intracellular homeostatic pathway, contributes to the physiological and pathological processes of RPE. Furthermore, autophagy has previously been reported to function in the EMT process in numerous tissue and cell types. However, the association between autophagy and the EMT process in RPE cells has not yet been fully determined. The present study demonstrated that TGF-β2-treated human RPE cells (ARPE-19 cell line) exhibited a significantly increased autophagic flux compared with control cells, as determined by western blot analysis of the protein levels of microtubule-associated protein 1 light chain 3-II and p62 (also termed sequestosome 1). Furthermore, it was demonstrated that autophagy activation enhanced the TGF-β2-induced EMT process in ARPE-19 cells, and inhibition of autophagy by chloroquine administration attenuated TGF-β2-induced EMT, which was determined by analyzing the expression of mesenchymal and epithelial markers by reverse transcription-quantitative polymerase chain reaction and/or western blotting. A transwell migration and invasion assays was also performed that demonstrated that autophagy activation by rapamycin enhanced TGF-β2-stimulated RPE cell migration and invasion, and inhibition of autophagy reduced TGF-β2-stimulated RPE cell migration and invasion. These results also demonstrated that autophagy activation enhanced the TGF-β2-induced EMT process in ARPE-19 cells, and inhibition of autophagy attenuated TGF-β2-induced EMT. Overall, the results of the present study demonstrated that TGF-β2-induced EMT may be regulated by autophagy, thus indicating that autophagy may serve as a potential therapeutic target for the attenuation of EMT in intraocular fibrotic disorders.

Autophagy promotes fibrosis and apoptosis in the peritoneum during long-term peritoneal dialysis

Long-term peritoneal dialysis is accompanied by functional and histopathological alterations in the peritoneal membrane. In the long process of peritoneal dialysis, high-glucose peritoneal dialysis solution (HGPDS) will aggravate the peritoneal fibrosis, leading to decreased effectiveness of peritoneal dialysis and ultrafiltration failure. In this study, we found that the coincidence of elevated TGF-β1 expression, autophagy, apoptosis and fibrosis in peritoneal membrane from patients with peritoneal dialysis. The peritoneal membranes from patients were performed with immunocytochemistry and transmission electron microscopy. Human peritoneal mesothelial cells were treated with 1.5%, 2.5% and 4.25% HGPDS for 24 hrs; Human peritoneal mesothelial cells pre-treated with TGF-β1 (10 ng/ml) or transfected with siRNA Beclin1 were treated with 4.25% HGPDS or vehicle for 24 hrs. We further detected the production of TGF-β1, activation of TGF-β1/Smad2/3 signalling, induction of autophagy, EMT, fibrosis and apoptosis. We also explored whether autophagy inhibition by siRNA targeting Beclin 1 reduces EMT, fibrosis and apoptosis in human peritoneal mesothelial cells. HGPDS increased TGF-β1 production, activated TGF-β1/Smad2/3 signalling and induced autophagy, fibrosis and apoptosis hallmarks in human peritoneal mesothelial cells; HGPDS-induced Beclin 1-dependent autophagy in human peritoneal mesothelial cells; Autophagy inhibition by siRNA Beclin 1 reduced EMT, fibrosis and apoptosis in human peritoneal mesothelial cells. Taken all together, these studies are expected to open a new avenue in the understanding of peritoneal fibrosis, which may guide us to explore the compounds targeting autophagy and achieve the therapeutic improvement of PD.

Autophagy and the unfolded protein response promote profibrotic effects of TGF-β1 in human lung fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a lethal fibrotic lung disease in adults with limited treatment options. Autophagy and the unfolded protein response (UPR), fundamental processes induced by cell stress, are dysregulated in lung fibroblasts and epithelial cells from humans with IPF. Human primary cultured lung parenchymal and airway fibroblasts from non-IPF and IPF donors were stimulated with transforming growth factor-β₁ (TGF-β₁) with or without inhibitors of autophagy or UPR (IRE1 inhibitor). Using immunoblotting, we monitored temporal changes in abundance of protein markers of autophagy (LC3βII and Atg5-12), UPR (BIP, IRE1α, and cleaved XBP1), and fibrosis (collagen 1α2 and fibronectin). Using fluorescent immunohistochemistry, we profiled autophagy (LC3βII) and UPR (BIP and XBP1) markers in human non-IPF and IPF lung tissue. TGF-β₁-induced collagen 1α2 and fibronectin protein production was significantly higher in IPF lung fibroblasts compared with lung and airway fibroblasts from non-IPF donors. TGF-β₁ induced the accumulation of LC3βII in parallel with collagen 1α2 and fibronectin, but autophagy marker content was significantly lower in lung fibroblasts from IPF subjects. TGF-β₁-induced collagen and fibronectin biosynthesis was significantly reduced by inhibiting autophagy flux in fibroblasts from the lungs of non-IPF and IPF donors. Conversely, only in lung fibroblasts from IPF donors did TGF-β₁ induce UPR markers. Treatment with an IRE1 inhibitor decreased TGF-β1-induced collagen 1α2 and fibronectin biosynthesis in IPF lung fibroblasts but not those from non-IPF donors. The IRE1 arm of the UPR response is uniquely induced by TGF-β₁ in lung fibroblasts from human IPF donors and is required for excessive biosynthesis of collagen and fibronectin in these cells.

Endoplasmic Reticulum Stress Is Associated With Autophagy and Cardiomyocyte Remodeling in Experimental and Human Atrial Fibrillation

BACKGROUND

Derailment of proteostasis, the homeostasis of production, function, and breakdown of proteins, contributes importantly to the self-perpetuating nature of atrial fibrillation (AF), the most common heart rhythm disorder in humans. Autophagy plays an important role in proteostasis by degrading aberrant proteins and organelles. Herein, we investigated the role of autophagy and its activation pathway in experimental and clinical AF.

METHODS AND RESULTS

Tachypacing of HL-1 atrial cardiomyocytes causes a gradual and significant activation of autophagy, as evidenced by enhanced LC3B-II expression, autophagic flux and autophagosome formation, and degradation of p62, resulting in reduction of Ca2+ amplitude. Autophagy is activated downstream of endoplasmic reticulum (ER) stress: blocking ER stress by the chemical chaperone 4-phenyl butyrate, overexpression of the ER chaperone-protein heat shock protein A5, or overexpression of a phosphorylation-blocked mutant of eukaryotic initiation factor 2α (eIF2α) prevents autophagy activation and Ca2+-transient loss in tachypaced HL-1 cardiomyocytes. Moreover, pharmacological inhibition of ER stress in tachypaced Drosophila confirms its role in derailing cardiomyocyte function. In vivo treatment with sodium salt of phenyl butyrate protected atrial-tachypaced dog cardiomyocytes from electrical remodeling (action potential duration shortening, L-type Ca2+-current reduction), cellular Ca2+-handling/contractile dysfunction, and ER stress and autophagy; it also attenuated AF progression. Finally, atrial tissue from patients with persistent AF reveals activation of autophagy and induction of ER stress, which correlates with markers of cardiomyocyte damage.

CONCLUSIONS

These results identify ER stress-associated autophagy as an important pathway in AF progression and demonstrate the potential therapeutic action of the ER-stress inhibitor 4-phenyl butyrate.

Relaxin alleviates TGFβ1-induced cardiac fibrosis via inhibition of Stat3-dependent autophagy

Cardiac fibrosis is a pathological feature common to a variety of heart diseases such as myocardial infarction, arrhythmias, cardiomyopathies and heart failure. Emerging data has indicted that autophagy is involved in fibrotic synthesis. Relaxin as a pleiotropic hormone can attenuate cardiac fibrosis and hypertrophy, however the exact molecular mechanism remains largely unknown. In this work, we evaluated whether the antifibrotic effect of relaxin relies on regulating autophagy in primary cardiac fibroblasts (CFs). Our results showed that relaxin significantly attenuated TGFβ1-induced autophagy in parallel with the reduction of fibrosis. Moreover, relaxin inhibited the phosphorylation of Stat3/Smad3 signaling. Then we observed that knockdown of Stat3 synchronously suppressed the fibrogenesis and autophagic flux which was stimulated by TGFβ1 in CFs. More importantly, we simultaneously administrated relaxin and Stat3 knockdown into CFs, which did not cause further downregulation of autophagy process and collagen protein compared with only Stat3 knockdown or relaxin treatment. These data suggested that relaxin ameliorates TGFβ-induced fibrosis dependent on Stat3 signaling-mediated autophagy. This study uncovered a previously unrecognized antifibrotic role of relaxin in cardiac fibrosis, which is achieved through the inhibition of Stat3-dependent autophagy, implying a potential therapeutic target in fibrotic diseases.

Autophagy and Mitophagy in Cardiovascular Disease

Autophagy contributes to the maintenance of intracellular homeostasis in most cells of cardiovascular origin, including cardiomyocytes, endothelial cells, and arterial smooth muscle cells. Mitophagy is an autophagic response that specifically targets damaged, and hence potentially cytotoxic, mitochondria. As these organelles occupy a critical position in the bioenergetics of the cardiovascular system, mitophagy is particularly important for cardiovascular homeostasis in health and disease. Consistent with this notion, genetic defects in autophagy or mitophagy have been shown to exacerbate the propensity of laboratory animals to spontaneously develop cardiodegenerative disorders. Moreover, pharmacological or genetic maneuvers that alter the autophagic or mitophagic flux have been shown to influence disease outcome in rodent models of several cardiovascular conditions, such as myocardial infarction, various types of cardiomyopathy, and atherosclerosis. In this review, we discuss the intimate connection between autophagy, mitophagy, and cardiovascular disorders.

A microfluidic chip for screening individual cancer cells via eavesdropping on autophagy-inducing crosstalk in the stroma niche

Autophagy is a cellular homeostatic mechanism where proteins and organelles are digested and recycled to provide an alternative source of building blocks and energy to cells. The role of autophagy in cancer microenvironment is still poorly understood. Here, we present a microfluidic system allowing monitoring of the crosstalk between single cells. We used this system to study how tumor cells induced autophagy in the stromal niche. Firstly, we could confirm that transforming growth factor β1 (TGFβ1) secreted from breast tumor cells is a paracrine mediator of tumor-stroma interaction leading to the activation of autophagy in the stroma component fibroblasts. Through proof of concept experiments using TGFβ1 as a model factor, we could demonstrate real time monitoring of autophagy induction in fibroblasts by single tumor cells. Retrieval of individual tumor cells from the microfluidic system and their subsequent genomic analysis was possible, allowing us to determine the nature of the factor mediating tumor-stroma interactions. Therefore, our microfluidic platform might be used as a promising tool for quantitative investigation of tumor–stroma interactions, especially for and high-throughput screening of paracrine factors that are secreted from heterogeneous tumor cell populations.

[Autophagy in chronic liver diseases: a friend rather than a foe?]

Within recycling damaged cell components, autophagy maintains cell homeostasis. Thus, it has been anticipated that autophagy would play an essential role in the pathogenesis of chronic liver diseases. Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are the most prevalent chronic liver diseases in Western countries, sharing common histopathologic features and a common disease progression. In this review, we discuss the role of autophagy at different stages of NAFLD and ALD as well as in liver regeneration and hepatocarcinogenesis.

Autophagy and airway fibrosis: Is there a link?

In the past decade, an emerging process named “autophagy” has generated intense interest in many chronic lung diseases. Tissue remodeling and fibrosis is a common feature of many airway diseases, and current therapies do not prevent or reverse these structural changes. Autophagy has evolved as a conserved process for bulk degradation and recycling of cytoplasmic components to maintain basal cellular homeostasis and healthy organelle populations in the cell. Furthermore, autophagy serves as a cell survival mechanism and can also be induced by chemical and physical stress to the cell. Accumulating evidence demonstrates that autophagy plays an essential role in vital cellular processes, including tissue remodeling. This review will discuss some of the recent advancements made in understanding the role of this fundamental process in airway fibrosis with emphasis on airway remodeling, and how autophagy can be exploited as a target for airway remodeling in asthma and chronic obstructive pulmonary disease.

Autophagy and airway fibrosis: Is there a link?

In the past decade, an emerging process named "autophagy" has generated intense interest in many chronic lung diseases. Tissue remodeling and fibrosis is a common feature of many airway diseases, and current therapies do not prevent or reverse these structural changes. Autophagy has evolved as a conserved process for bulk degradation and recycling of cytoplasmic components to maintain basal cellular homeostasis and healthy organelle populations in the cell. Furthermore, autophagy serves as a cell survival mechanism and can also be induced by chemical and physical stress to the cell. Accumulating evidence demonstrates that autophagy plays an essential role in vital cellular processes, including tissue remodeling. This review will discuss some of the recent advancements made in understanding the role of this fundamental process in airway fibrosis with emphasis on airway remodeling, and how autophagy can be exploited as a target for airway remodeling in asthma and chronic obstructive pulmonary disease.

Aspirin alleviates cardiac fibrosis in mice by inhibiting autophagy

Aspirin (ASA) is a cardioprotective drug with anti-cardiac fibrosis action in vivo. This study was aimed to clarify the anti-cardiac fibrosis action of ASA and the underlying mechanisms. Two heart injury models (injection of isoproterenol and ligation of the left anterior descending branch) were used in mice to induce cardiac fibrosis. The animals were treated with ASA (10 mg·kg^-1·d^-1, ig) for 21 and 14 d, respectively. ASA administration significantly improved cardiac function, and ameliorated heart damage and fibrosis in the mice. The mechanisms underlying ASA's anti-fibrotic effect were further analyzed in neonatal cardiac fibroblasts (CFs) exposed to hypoxia in vitro. ASA (0.5-5 mmol/L) dose-dependently inhibited the proliferation and Akt phosphorylation in the CFs. In addition, ASA significantly inhibited CF apoptosis, and decreased the levels of apoptosis markers (cleaved caspase 3 and Parp1), which might serve as a side effect of anti-fibrotic effect of ASA. Furthermore, ASA dose-dependently inhibited the autophagy in the CFs, as evidenced by the reduced levels of autophagy marker LC3-II. The autophagy inhibitor Pepstatin A (PepA) promoted the inhibitory effect of ASA on CF proliferation, whereas the autophagy inducer rapamycin rescued ASA-caused inhibition of CF proliferation, suggesting an autophagy-dependent anti-proliferative effect of ASA. Both p38 inhibitor SB203580 and ROS scavenger N-acetyl-cysteine (NAC) significantly decreased Akt phosphorylation in CFs in the basal and hypoxic situations, but they both significantly increased LC3-II levels in the CFs. Our results suggest that an autophagy- and p38/ROS-dependent pathway mediates the anti-cardiac fibrosis effect of ASA in CFs. As PepA and SB203580 did not affect ASA-caused inhibition of CF apoptosis, the drug combination will enhance ASA's therapeutic effects.

Increased Autophagy-Related 5 Gene Expression Is Associated with Collagen Expression in the Airways of Refractory Asthmatics

BACKGROUND

Fibrosis, particularly excessive collagen deposition, presents a challenge for treating asthmatic individuals. At present, no drugs can remove or reduce excessive collagen in asthmatic airways. Hence, the identification of pathways involved in collagen deposition would help to generate therapeutic targets to interfere with the airway remodeling process. Autophagy, a cellular degradation process, has been shown to be dysregulated in various fibrotic diseases, and genetic association studies in independent human populations have identified autophagy-related 5 (ATG5) to be associated with asthma pathogenesis. Hence, the dysregulation of autophagy may contribute to fibrosis in asthmatic airways.

OBJECTIVE

This study aimed to determine if (1) collagen deposition in asthmatic airways is associated with ATG5 expression and (2) ATG5 protein expression is associated with asthma per se and severity.

METHODS

Gene expression of transforming growth factor beta 1, various asthma-related collagen types [collagen, type I, alpha 1; collagen, type II, alpha 1; collagen, type III, alpha 1; collagen, type V, alpha 1 (COL5A1) and collagen, type V, alpha 2], and ATG5 were measured using mRNA isolated from bronchial biopsies of refractory asthmatic subjects and assessed for pairwise associations. Protein expression of ATG5 in the airways was measured and associations were assessed for asthma per se, severity, and lung function.

MAIN RESULTS

In refractory asthmatic individuals, gene expression of ATG5 was positively associated with COL5A1 in the airways. No association was detected between ATG5 protein expression and asthma per se, severity, and lung function.

CONCLUSION AND CLINICAL RELEVANCE

Positive correlation between the gene expression patterns of ATG5 and COL5A1 suggests that dysregulated autophagy may contribute to subepithelial fibrosis in the airways of refractory asthmatic individuals. This finding highlights the therapeutic potential of ATG5 in ameliorating airway remodeling in the difficult-to-treat refractory asthmatic individuals.

Oxidant-induced autophagy and ferritin degradation contribute to epithelial-mesenchymal transition through lysosomal iron

Purpose

Transforming growth factor (TGF)-β1 triggers epithelial–mesenchymal transition (EMT) through autophagy, which is partly driven by reactive oxygen species (ROS). The aim of this study was to determine whether leaking lysosomes and enhanced degradation of H-ferritin could be involved in EMT and whether it could be possible to prevent EMT by iron chelation targeting of the lysosome.

Materials and methods

EMT, H-ferritin, and autophagy were evaluated in TGF-β1-stimulated A549 human lung epithelial cells cultured in vitro using Western blotting, with the additional morphological assessment of EMT. By using immunofluorescence and flow cytometry, lysosomes and ROS were assessed by acridine orange and 6-carboxy-2′,7′-dichlorodihydrofluorescein acetate assays, respectively.

Results

TGF-β1-stimulated cells demonstrated a loss of H-ferritin, which was prevented by the antioxidant N-acetyl-L-cysteine (NAC) and inhibitors of lysosomal degradation. TGF-β1 stimulation generated ROS and autophagosome formation and led to EMT, which was further promoted by the additional ROS-generating cytokine, tumor necrosis factor-α. Lysosomes of TGF-β1-stimulated cells were sensitized to oxidants but also completely protected by lysosomal loading with dextran-bound deferoxamine (DFO). Autophagy and EMT were prevented by NAC, DFO, and inhibitors of autophagy and lysosomal degradation.

Conclusion

The findings of this study support the role of enhanced autophagic degradation of H-ferritin as a mechanism for increasing the vulnerability of lysosomes to iron-driven oxidant injury that triggers further autophagy during EMT. This study proposes that lysosomal leakage is a novel pathway of TGF-β1-induced EMT that may be prevented by iron-chelating drugs that target the lysosome.

Autophagy in chronic liver diseases: the two faces of Janus

Alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) are the leading causes of cirrhosis and increase the risk of hepatocellular carcinoma and liver-related death. ALD and NAFLD share common pathogenic features extending from isolated steatosis to steatohepatitis and steatofibrosis, which can progress to cirrhosis and hepatocellular carcinoma. The pathophysiological mechanisms of the progression of NAFLD and ALD are complex and still unclear. Important links between the regulation of autophagy (macroautophagy and chaperone-mediated autophagy) and chronic liver diseases have been reported. Autophagy may protect against steatosis and progression to steatohepatitis by limiting hepatocyte injury and reducing M1 polarization, as well as promoting liver regeneration. Its role in fibrosis and hepatocarcinogenesis is more complex. It has pro- and antifibrogenic properties depending on the hepatic cell type concerned, and beneficial and deleterious effects on hepatocarcinogenesis at initiating and late phases, respectively. This review summarizes the latest advances on the role of autophagy in different stages of fatty liver disease progression and describes its divergent and cell-specific effects during chronic liver injury.

Perturbation of redox balance after thioredoxin reductase deficiency interrupts autophagy-lysosomal degradation pathway and enhances cell death in nutritionally stressed SH-SY5Y cells

Oxidative damage and aggregation of cellular proteins is a hallmark of neuronal cell death after neurotrauma and chronic neurodegenerative conditions. Autophagy and ubiquitin protease system are involved in degradation of protein aggregates, and interruption of their function is linked to apoptotic cell death in these diseases. Oxidative modification of cysteine groups in key molecular proteins has been linked to modification of cellular systems and cell death in these conditions. Glutathione and thioredoxin systems provide reducing protons that can effectively reverse protein modifications and promote cell survival. The central role of Thioredoxin in inhibition of apoptosis is well identified. Additionally, its involvement in initiation of autophagy has been suggested recently. We therefore aimed to investigate the involvement of Thioredoxin system in autophagy-apoptosis processes. A model of serum deprivation in SH-SY5Y was used that is associated with autophagy and apoptosis. Using pharmacological and RNA-editing technology we show that Thioredoxin reductase deficiency in this model enhances oxidative stress and interrupts the early protective autophagy and promotes apoptosis. This was associated with decreased protein-degradation in lysosomes due to altered lysosomal acidification and accumulation of autophagosomes as well as impairment in proteasome pathway. We further confirmed that the extent of oxidative stress is a determining factor in autophagy- apoptosis interplay, as upregulation of cellular reducing capacity by N-acetylcysteine prevented impairment in autophagy and proteasome systems thus promoted cell viability. Our study provides evidence that excessive oxidative stress inhibits protein degradation systems and affects the final stages of autophagy by inhibiting autolysosome maturation: a novel mechanistic link between protein aggregation and conversion of autophagy to apoptosis that can be applicable to neurodegenerative diseases.

Selective Reversible Inhibition of Autophagy in Hypoxic Breast Cancer Cells Promotes Pulmonary Metastasis

Autophagy influences how cancer cells respond to nutrient deprivation and hypoxic stress, two hallmarks of the tumor microenvironment (TME). In this study, we explored the impact of autophagy on the pathophysiology of breast cancer cells using a novel hypoxia-dependent, reversible dominant-negative strategy to regulate autophagy at the cellular level within the TME. Suppression of autophagy via hypoxia-induced expression of the kinase-dead unc-51-like autophagy-activating kinase (ULK1) mutant K46N increased lung metastases in MDA-MB-231 xenograft mouse models. Consistent with this effect, expressing a dominant-negative mutant of ULK1 or ATG4b or a ULK1-targeting shRNA facilitated cell migration in vitro Functional proteomic and transcriptome analysis revealed that loss of hypoxia-regulated autophagy promotes metastasis via induction of the fibronectin integrin signaling axis. Indeed, loss of ULK1 function increased fibronectin deposition in the hypoxic TME. Together, our results indicated that hypoxia-regulated autophagy suppresses metastasis in breast cancer by preventing tumor fibrosis. These results also suggest cautions in the development of autophagy-based strategies for cancer treatment. Cancer Res; 77(3); 646-57. ©2016 AACR.

Autophagy is involved in TGF-β1-induced protective mechanisms and formation of cancer-associated fibroblasts phenotype in tumor microenvironment

Transforming growth factor-β1 (TGF-β1) present in tumor microenvironment acts in a coordinated fashion to either suppress or promote tumor development. However, the molecular mechanisms underlying the effects of TGF-β1 on tumor microenvironment are not well understood. Our clinical data showed a positive association between TGF-β1 expression and cancer-associated fibroblasts (CAFs) in tumor microenvironment of breast cancer patients. Thus we employed starved NIH3T3 fibroblasts in vitro and 4T1 cells mixed with NIH3T3 fibroblasts xenograft model in vivo to simulate nutritional deprivation of tumor microenvironment to explore the effects of TGF-β1. We demonstrated that TGF-β1 protected NIH3T3 fibroblasts from Star-induced growth inhibition, mitochondrial damage and cell apoptosis. Interestingly, TGF-β1 induced the formation of CAFs phenotype in starvation (Star)-treated NIH3T3 fibroblasts and xenografted Balb/c mice, which promoted breast cancer tumor growth. In both models, autophagy agonist rapamycin increased TGF-β1-induced protective effects and formation of CAFs phenotypes, while autophagy inhibitor 3-methyladenine, Atg5 knockdown or TGF-β type I receptor kinase inhibitor LY-2157299 blocked TGF-β1 induced these effects. Taken together, our results indicated that TGF-β/Smad autophagy was involved in TGF-β1-induced protective effects and formation of CAFs phenotype in tumor microenvironment, which may be used as therapy targets in breast cancer.

Oxymatrine inhibits aldosterone-induced rat cardiac fibroblast proliferation and differentiation by attenuating smad-2,-3 and-4 expression: an in vitro study

BACKGROUND

We previously demonstrated oxymatrine, an alkaloid from the Chinese medicine radix Sophorae flavescentis, ameliorates hemodynamic disturbances and cardiac fibrosis; however, the underlying mechanisms are unclear. Here, we investigated the effect and mechanism of action of oxymatrine on aldosterone-induced cardiac fibroblast to myofibroblast differentiation in vitro.

METHODS

Cardiac fibroblasts were isolated purified from neonatal Sprague Dawley rats. The optimal concentration of aldosterone to stimulate cardiac fibroblast proliferation was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cardiac fibroblasts were pretreated with 7.57 × 10(-4) mol/L or 3.78 × 10(-4) mol/L oxymatrine or without oxymatrine for 2 h, and then coincubated with 1 × 10(-8) mol/L aldosterone for 48 h. The MTT assay and Masson staining were used to detect the cardiac fibroblast proliferation and myofibroblast differentiation. The secretion of type I and III collagen was measured by commercial ELISA kits, and the hydroxyproline content was determined by the colorimetric assay. Western blotting assayed the Smad-2, Smad-3, and Smad-4 protein expression in cardiac fibroblasts.

RESULTS

The present results confirmed that aldosterone induced cardiac fibroblast to myofibroblast proliferation and differentiation. The MTT assay and Masson staining indicated oxymatrine significantly inhibited aldosterone-induced cardiac fibroblast proliferation and myofibroblast differentiation. Oxymatrine significantly inhibited aldosterone-induced secretion of type I and III collagen, as indicated by commercial ELISA kits, and aldosterone-induced increase in hydroxyproline content, as indicated by a colorimetric assay. Western blotting revealed oxymatrine attenuated aldosterone-induced Smad-2, Smad-3, and Smad-4 expression in cardiac fibroblasts.

CONCLUSION

Oxymatrine can inhibit cardiac fibroblast proliferation and differentiation into myofibroblasts via a mechanism linked to attenuation of the Smad signaling pathway.

Autophagy Improves the Immunosuppression of CD4+ T Cells by Mesenchymal Stem Cells Through Transforming Growth Factor-β1

: Mesenchymal stem cells (MSCs) have been extensively investigated as a promising approach to treat many autoimmune and inflammatory diseases. The stress condition would affect the therapeutic efficacy and induce autophagy of MSCs. However, whether autophagy would affect the immunosuppressive capacity of MSCs is largely unknown. The present study aimed to assess whether autophagy plays an important role in regulating the immunomodulation of MSCs and the undermechanisms. We successfully inhibited and induced autophagy of MSCs using 3-methyladenine (3-MA) and rapamycin, respectively. Our results demonstrated that rapamycin strengthened the capacity of MSCs to inhibit CD4⁺ T-cell proliferation, whereas 3-MA weakened the inhibitory ability of MSCs. Mechanistically, 3-MA-pretreated MSCs secreted less, whereas rapamycin-pretreated MSCs secreted more transforming growth factor-β1 (TGF-β1) compared with the control cells. Furthermore, exogenous TGF-β1 addition recovered the immunosuppressive capacity of 3-MA-pretreated MSCs, whereas exogenous anti-TGF-β1 antibody addition reduced the immunosuppressive capacity of rapamycin-pretreated MSCs. These results indicated that the autophagy level regulates the immunosuppression of CD4⁺ T cells by MSCs through affecting TGF-β1 secretion and provides a novel method for improving the therapeutic efficacy of MSCs by activating autophagy.

SIGNIFICANCE

Mesenchymal stem cell (MSC)-based therapy is a promising tool to treat many diseases. Autophagy occurred in MSCs during their application, especially in those exposed to stress conditions. However, whether autophagy will affect the therapeutic efficacy of MSCs is largely unknown. This study makes a significant contribution to demonstrate that autophagy could improve the immunosuppression of CD4⁺ T cells by mesenchymal stem cells through transforming growth factor-β1. Therefore, regulation of autophagy in MSCs would provide a promising strategy to improve the therapeutic efficacy of these cells.

MiR-449a regulates autophagy to inhibit silica-induced pulmonary fibrosis through targeting Bcl2

Silicosis is a fatal pulmonary fibrotic disorder characterized by accumulation of fibroblasts and myofibroblasts and deposition of extracellular matrix proteins. MiR-449a is a potential mediator of many cellular processes, including cell proliferation, differentiation, and apoptosis. We hypothesized that miR-449a may play a crucial role in the progression of pulmonary fibrogenesis. Here, we described miR-449a as a new autophagy-regulated miRNA. Importantly, miR-449a expression was significantly decreased in lung tissues of mice with silica treatment, and it was similarly expressed in NIH-3T3 and MRC-5 cells stimulated with TGF-β1. The activity of autophagy was inhibited in fibrotic lung tissues and TGF-β1-treated fibroblasts. To investigate the potential effect of miR-449a, we overexpressed miR-449a in mouse models and found that miR-449a significantly reduced both the distribution and severity of lung lesions induced by silica. In addition, miR-449a was observed to induce the activity of autophagy in vivo and in vitro. Notably, Bcl2 was identified as a target of miR-449a. Bcl2 levels were decreased in NIH-3T3 cells upon miR-449a overexpression. Indeed, the Bcl2 3' UTR contained functional miR-449a responsive sequences. Furthermore, TGF-β1 was observed to increase the expression of Bcl2 via the MAPK/ERK pathway. These results suggest that miR-449a is an important regulator of autophagy, as well as a novel endogenous suppressor of pulmonary fibrosis.

KEY MESSAGE

MiR-449a expression was decreased in fibrotic lungs and activated fibroblasts. Autophagy was inhibited in fibrotic lung tissues and TGF-β1-treated fibroblasts. MiR-449a had an antifibrotic effect in silica-induced lung fibrosis. MiR-449a upregulated autophagic activity in vitro. Bcl2 is the autophagy-related target of miR-449a.

Therapeutic targeting of autophagy in myocardial infarction and heart failure

INTRODUCTION

Myocardial infarction (MI) is the leading cause of death. When MI is not lethal, heart failure (HF) is a major consequence with high prevalence and poor prognosis. The targeting of autophagy represents a potentially therapeutic approach for the treatment of both pathologies.

AREAS COVERED

PubMed searches were performed to discuss the current state of the art regarding the role of autophagy in MI and HF. We review available and potential approaches to modulate autophagy from a pharmacological and genetic perspective. We also discuss the targeting of autophagy in myocardial regeneration. Expert commentary: The targeting of autophagy has potential for the treatment of MI and HF. Autophagy is a process that takes place in virtually all cells of the body and thus, in order to evaluate this therapeutic approach in clinical trials, strategies that specifically target this process in the myocardium is required to avoid unwanted effects in other organs.

Interactions between Autophagy and Inhibitory Cytokines

Autophagy is a degradative pathway that plays an essential role in maintaining cellular homeostasis. Most early studies of autophagy focused on its involvement in age-associated degeneration and nutrient deprivation. However, the immunological functions of autophagy have become more widely studied in recent years. Autophagy has been shown to be an intrinsic cellular defense mechanism in the innate and adaptive immune responses. Cytokines belong to a broad and loose category of proteins and are crucial for innate and adaptive immunity. Inhibitory cytokines have evolved to permit tolerance to self while also contributing to the eradication of invading pathogens. Interactions between inhibitory cytokines and autophagy have recently been reported, revealing a novel mechanism by which autophagy controls the immune response. In this review, we discuss interactions between autophagy and the regulatory cytokines IL-10, transforming growth factor-β, and IL-27. We also mention possible interactions between two newly discovered cytokines, IL-35 and IL-37, and autophagy.

1,4-Butanediol diglycidyl ether-cross-linked hyaluronan inhibits fibrosis in rat primary tenocytes by down-regulating autophagy modulation

Epidural fibrosis, an inevitable part of the postoperative healing process, is one of the important causes of failed back surgery syndrome after spinal surgery. The aim of this study was to examine the inhibitory effect of a novel material 1,4-butanediol diglycidyl ether-cross-linked hyaluronan (cHA) on fibrosis in primary tenocytes. cHA inhibited migration, cell proliferation, and suppressed the expression of fibronectin, but not transforming growth factor-β, in primary tenocytes. cHA significantly increased matrix metalloproteinase-3 but decreased collagen-1 and microtubule-associated protein light chain 3-II expression in a dose-dependent manner compared with control groups. We therefore concluded that suppressing autophagy activity may be involved in the anti-fibrotic effect of cHA in primary tenocytes. Further, cHA may have the potential for preventing epidural fibrosis and subsequent failed back syndrome in patients with laminectomy in the future.

Persistent activation of autophagy in kidney tubular cells promotes renal interstitial fibrosis during unilateral ureteral obstruction

Renal fibrosis is the final, common pathway of end-stage renal disease. Whether and how autophagy contributes to renal fibrosis remains unclear. Here we first detected persistent autophagy in kidney proximal tubules in the renal fibrosis model of unilateral ureteral obstruction (UUO) in mice. UUO-associated fibrosis was suppressed by pharmacological inhibitors of autophagy and also by kidney proximal tubule-specific knockout of autophagy-related 7 (PT-Atg7 KO). Consistently, proliferation and activation of fibroblasts, as indicated by the expression of ACTA2/α-smooth muscle actin and VIM (vimentin), was inhibited in PT-Atg7 KO mice, so was the accumulation of extracellular matrix components including FN1 (fibronectin 1) and collagen fibrils. Tubular atrophy, apoptosis, nephron loss, and interstitial macrophage infiltration were all inhibited in these mice. Moreover, these mice showed a specific suppression of the expression of a profibrotic factor FGF2 (fibroblast growth factor 2). In vitro, TGFB1 (transforming growth factor β 1) induced autophagy, apoptosis, and FN1 accumulation in primary proximal tubular cells. Inhibition of autophagy suppressed FN1 accumulation and apoptosis, while enhancement of autophagy increased TGFB1-induced-cell death. These results suggest that persistent activation of autophagy in kidney proximal tubules promotes renal interstitial fibrosis during UUO. The profibrotic function of autophagy is related to the regulation on tubular cell death, interstitial inflammation, and the production of profibrotic factors.

Autophagy inhibition of hsa-miR-19a-3p/19b-3p by targeting TGF-β R II during TGF-β1-induced fibrogenesis in human cardiac fibroblasts

Transforming growth factor-β1 (TGF-β1) plays an important role on fibrogenesis in heart disease. MicroRNAs have exhibited as crucial regulators of cardiac homeostasis and remodeling in various heart diseases. MiR-19a-3p/19b-3p expresses with low levels in the plasma of heart failure patients. The purpose of our study is to determine the role of MiR-19a-3p/19b-3p in regulating autophagy-mediated fibrosis of human cardiac fibroblasts. We elucidate our hypothesis in clinical samples and human cardiac fibroblasts (HCF) to provide valuable basic information. TGF-β1 promotes collagen I α2 and fibronectin synthesis in HCF and that is paralleled by autophagic activation in these cells. Pharmacological inhibition of autophagy by 3-methyladenine decreases the fibrotic response, while autophagy induction of rapamycin increases the response. BECN1 knockdown and Atg5 over-expression either inhibits or enhances the fibrotic effect of TGF-β1 in experimental HCF. Furthermore, miR-19a-3p/19b-3p mimics inhibit epithelial mesenchymal transition (EMT) and extracellular matrix (ECM) prodution and invasion of HCF. Functional studies suggest that miR-19a-3p/19b-3p inhibits autophagy of HCF through targeting TGF-β R II mRNA. Moreover, enhancement of autophagy rescues inhibition effect of miR-19a-3p/19b-3p on Smad 2 and Akt phosphorylation through TGF-β R II signaling. Our study uncovers a novel mechanism that miR-19a-3p/19b-3p inhibits autophagy-mediated fibrogenesis by targeting TGF-β R II.

Macrophage Akt1 Kinase-Mediated Mitophagy Modulates Apoptosis Resistance and Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disorder with increasing incidence. Mitochondrial oxidative stress in alveolar macrophages is directly linked to pulmonary fibrosis. Mitophagy, the selective engulfment of dysfunctional mitochondria by autophagasomes, is important for cellular homeostasis and can be induced by mitochondrial oxidative stress. Here, we show Akt1 induced macrophage mitochondrial reactive oxygen species (ROS) and mitophagy. Mice harboring a conditional deletion of Akt1 in macrophages (Akt1(-/-)Lyz2-cre) and Park2(-/-) mice had impaired mitophagy and reduced active transforming growth factor-β1 (TGF-β1). Although Akt1 increased TGF-β1 expression, mitophagy inhibition in Akt1-overexpressing macrophages abrogated TGF-β1 expression and fibroblast differentiation. Importantly, conditional Akt1(-/-)Lyz2-cre mice and Park2(-/-) mice had increased macrophage apoptosis and were protected from pulmonary fibrosis. Moreover, IPF alveolar macrophages had evidence of increased mitophagy and displayed apoptosis resistance. These observations suggest that Akt1-mediated mitophagy contributes to alveolar macrophage apoptosis resistance and is required for pulmonary fibrosis development.

Protective effect of fucoidan from Fucus vesiculosus on liver fibrosis via the TGF-β1/Smad pathway-mediated inhibition of extracellular matrix and autophagy

Liver fibrosis is a dynamic reversible pathological process in the development of chronic liver disease to cirrhosis. However, the current treatments are not administered for a long term due to their various side effects. Autophagy is initiated to decompose damaged or excess organelles, which had been found to alter the progression of liver fibrosis. In this article, we hypothesized that fucoidan from Fucus vesiculosus may attenuate liver fibrosis in mice by inhibition of the extracellular matrix and autophagy in carbon tetrachloride- and bile duct ligation-induced animal models of liver fibrosis. The results were determined using enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, Western blotting, and immunohistochemical staining. Fucoidan from F. vesiculosus could inhibit the activation of hepatic stellate cells and the formation of extracellular matrix and autophagosomes, and its effect may be associated with the downregulation of transforming growth factor beta 1/Smads pathways. Fucoidan, as an autophagy and transforming growth factor beta 1 inhibitor, could be a promising potential therapeutic agent for liver fibrosis.

Autophagy in airway diseases: a new frontier in human asthma?

The study of autophagy ('self-eating'), a fundamental cell fate pathway involved in physiological and pathological subcellular processes, opens a new frontier in the continuous search for novel therapies for human asthma. Asthma is a complex syndrome with different disease phenotypes. Autophagy plays a central role in cell physiology, energy and metabolism, and cell survival. Autophagy's hallmark is the formation of double-membrane autophagic autophagosomes, and this process is operational in airway epithelial and mesenchymal cells in asthma. Genetic associations between autophagy genes and asthma have been observed including single nucleotide polymorphisms in Atg5 which correlate with reduced lung function. Immune mechanisms important in asthma such as Th2 cells and eosinophils also manifest autophagy. Lastly, we address the role of autophagy in extracellular matrix deposition and fibrosis in asthmatic airways remodeling, a pathologic process still without effective therapy, and discuss potential pharmacologic inhibitors. We end by offering two opposing but plausible hypotheses as to how autophagy may be directly involved in airway fibrosis.