TRAIL regulates collagen production through HSF1-dependent Hsp47 expression in activated hepatic stellate cells

Targeting HSP47 for cancer treatment

Heat shock protein 47 (HSP47) serves as an endoplasmic reticulum residing collagen-specific chaperone and plays an important role in collagen biosynthesis and structural assembly. HSP47 is encoded by the SERPINH1 gene, which is located on chromosome 11q13.5, one of the most frequently amplified regions in human cancers. The expression of HSP47 is regulated by multiple cellular factors, including cytokines, transcription factors, microRNAs, and circular RNAs. HSP47 is frequently upregulated in a variety of cancers and plays an important role in tumor progression. HSP47 promotes tumor stemness, angiogenesis, growth, epithelial-mesenchymal transition, and metastatic capacity. HSP47 also regulates the efficacy of tumor therapies, such as chemotherapy, radiotherapy, and immunotherapy. Inhibition of HSP47 expression has antitumor effects, suggesting that targeting HSP47 is a feasible strategy for cancer treatment. In this review, we highlight the function and expression of regulatory mechanisms of HSP47 in cancer progression and point out the potential development of therapeutic strategies in targeting HSP47 in the future.

Loss of heat shock factor 1 promotes hepatic stellate cell activation and drives liver fibrosis

Liver fibrosis is an aberrant wound healing response that results from chronic injury and is mediated by hepatocellular death and activation of hepatic stellate cells (HSCs). While induction of oxidative stress is well established in fibrotic livers, there is limited information on stress‐mediated mechanisms of HSC activation. Cellular stress triggers an adaptive defense mechanism via master protein homeostasis regulator, heat shock factor 1 (HSF1), which induces heat shock proteins to respond to proteotoxic stress. Although the importance of HSF1 in restoring cellular homeostasis is well‐established, its potential role in liver fibrosis is unknown. Here, we show that HSF1 messenger RNA is induced in human cirrhotic and murine fibrotic livers. Hepatocytes exhibit nuclear HSF1, whereas stellate cells expressing alpha smooth muscle actin do not express nuclear HSF1 in human cirrhosis. Interestingly, despite nuclear HSF1, murine fibrotic livers did not show induction of HSF1 DNA binding activity compared with controls. HSF1‐deficient mice exhibit augmented HSC activation and fibrosis despite limited pro‐inflammatory cytokine response and display delayed fibrosis resolution. Stellate cell and hepatocyte‐specific HSF1 knockout mice exhibit higher induction of profibrogenic response, suggesting an important role for HSF1 in HSC activation and fibrosis. Stable expression of dominant negative HSF1 promotes fibrogenic activation of HSCs. Overactivation of HSF1 decreased phosphorylation of JNK and prevented HSC activation, supporting a protective role for HSF1. Our findings identify an unconventional role for HSF1 in liver fibrosis. Conclusion: Our results show that deficiency of HSF1 is associated with exacerbated HSC activation promoting liver fibrosis, whereas activation of HSF1 prevents profibrogenic HSC activation.

Multifactorial Attenuation of the Murine Heat Shock Response With Age

Age-dependent perturbation of the cellular stress response affects proteostasis and other key functions relevant to cellular action and survival. Central to age-related changes in the stress response is loss of heat shock factor 1 (HSF1)-DNA binding and transactivation properties. This report elucidates how age alters different checkpoints of HSF1 activation related to posttranslational modification and protein interactions. When comparing liver extracts from middle aged (12 M) and old (24 M) mice, significant differences are found in HSF1 phosphorylation and acetylation. HSF1 protein levels and messenger RNA decline with age, but its protein levels are stress-inducible and exempt from age-dependent changes. This surprising adaptive change in the stress response has additional implications for aging and chronic physiological stress that might explain an age-dependent dichotomy of HSF1 protein levels that are low in neurodegeneration and elevated in cancer.

HSP47: a potential target for fibrotic diseases and implications for therapy

Introduction: Chronic fibrotic disorders are challenging clinical problems. The major challenge is the identification of specific targets expressed selectively in fibrotic tissues. Collagen accumulation is the hallmark fibrosis. HSP47 is a collagen-specific chaperon with critical role in collagen folding. This review discusses the anti-fibrotic potential of HSP47. Areas covered: This review compiles data retrieved from the PubMed database with keywords 'HSP47+fibrosis' from 01/2005 to 06/2020. We examined 1) collagen biology and its role in fibrotic diseases, 2) HSP47 role in fibrosis, 3) HSP47 inhibition strategies and 4) clinical investigations. The identification of the HSP47-collagen binding site led to the development of methods to screen HSP47 inhibitors with anti-fibrotic potential. Specific in vivo  delivery systems of HSP47 siRNA to fibrotic tissue reduced collagen production/secretion associated with fibrosis inhibition in preclinical models. This strategy is about to be tested in clinical trials. Expert opinion: As a collagen-specific chaperon, HSP47 is a promising therapeutic target in fibrosis. Preclinical models have shown encouraging anti-fibrotic results. Anti-HSP47 strategies need to be further evaluated in clinical trials. The increase in circulating-HSP47 in lung fibrosis patients highlights the potential of HSP47 as a noninvasive biomarker and may represent an important step toward personalized medicine in fibrotic disorders.

The role of heat shock proteins in the regulation of fibrotic diseases

Heat shock proteins (HSPs) are key players to restore cell homeostasis and act as chaperones by assisting the folding and assembly of newly synthesized proteins and preventing protein aggregation. Recently, evidence has been accumulating that HSPs have been proven to have other functions except for the classical molecular chaperoning in that they play an important role in a wider range of fibrotic diseases via modulating cytokine induction and inflammation response, including lung fibrosis, liver fibrosis, and idiopathic pulmonary fibrosis. The recruitment of inflammatory cells, a large number of secretion of pro-fibrotic cytokines such as transforming growth factor-β1 (TGF-β1) and increased apoptosis, oxidative stress, and proteasomal system degradation are all events occurring during fibrogenesis, which might be associated with HSPs. However, their role on fibrotic process is not yet fully understood. In this review, we discuss new discoveries regarding the involvement of HSPs in the regulation of organ and tissue fibrosis, and note recent findings suggesting that HSPs may be a promising therapeutic target for improving the current frustrating outcome of fibrotic disorders.

Transcription factor YY1 inhibits the expression of THY1 to promote interstitial pulmonary fibrosis by activating the HSF1/miR-214 axis

Interstitial pulmonary fibrosis (IPF) is a progressive disease of diverse etiology manifesting with proliferation of lung fibroblasts and accumulation of extracellular matrix deposition in pulmonary interstitium. Recent studies show aberrant expression of mRNAs and microRNAs (miRNAs) in human embryonic pulmonary fibroblasts (HEPFs). In this study, we investigated effects of the YY1/HSF1/miR-214/THY1 axis on the functions of HEPFs and IPF. Loss- and gain-of-function tests were conducted to identify roles of YY1, HSF1, miR-214, and THY1 in IPF. As determined by RT-qPCR or western blot assay, silencing YY1 down-regulated HSF1 expression and attenuated the expression of pro-proliferative and fibrosis markers in HEPFs. Meanwhile, viability of HEPFs was impeded by YY1 knockdown. The binding relationship between miR-214 and THY1 was verified using dual-luciferase reporter assay. In HEPFs, down-regulation of HSF1 reduced miR-214 expression to repress proliferation and fibrogenic transformation of HEPFs, while inhibition of miR-214 expression could restrain the fibrogenic transformation property of HEPFs by up-regulating THY1. Subsequently, IPF model in mice was induced by bleomycin treatment. These animal experiments validated the protective effects of YY1 knockdown against IPF-induced lung pathological manifestations, which could be reversed by THY1 knockdown. Our study demonstrates the important involvement of YY1/HSF1/miR-214/THY1 axis in the development of IPF.

HSF1Base: A Comprehensive Database of HSF1 (Heat Shock Factor 1) Target Genes

HSF1 (heat shock factor 1) is an evolutionarily conserved master transcriptional regulator of the heat shock response (HSR) in eukaryotic cells. In response to high temperatures, HSF1 upregulates genes encoding molecular chaperones, also called heat shock proteins, which assist the refolding or degradation of damaged intracellular proteins. Accumulating evidence reveals however that HSF1 participates in several other physiological and pathological processes such as differentiation, immune response, and multidrug resistance, as well as in ageing, neurodegenerative demise, and cancer. To address how HSF1 controls these processes one should systematically analyze its target genes. Here we present a novel database called HSF1Base (hsf1base.org) that contains a nearly comprehensive list of HSF1 target genes identified so far. The list was obtained by manually curating publications on individual HSF1 targets and analyzing relevant high throughput transcriptomic and chromatin immunoprecipitation data derived from the literature and the Yeastract database. To support the biological relevance of HSF1 targets identified by high throughput methods, we performed an enrichment analysis of (potential) HSF1 targets across different tissues/cell types and organisms. We found that general HSF1 functions (targets are expressed in all tissues/cell types) are mostly related to cellular proteostasis. Furthermore, HSF1 targets that are conserved across various animal taxa operate mostly in cellular stress pathways (e.g., autophagy), chromatin remodeling, ribosome biogenesis, and ageing. Together, these data highlight diverse roles for HSF1, expanding far beyond the HSR.

miR-455-3p Alleviates Hepatic Stellate Cell Activation and Liver Fibrosis by Suppressing HSF1 Expression

Liver fibrosis is a common pathological process of end-stage liver diseases. However, the role of microRNA (miRNA) in liver fibrosis is poorly understood. The activated hepatic stellate cells (HSCs) are the major source of fibrogenic cells and play a central role in liver fibrosis. In this study, we investigated the differential expression of miRNAs in resting and transforming growth factor β1 (TGF-β1) activated HSCs by microarray analysis and found that miR-455-3p was significantly downregulated during HSCs activation. In addition, the reduction of miR-455-3p was correlated with liver fibrosis in mice with carbon tetrachloride (CCl₄), bile duct ligation (BDL), and high-fat diet (HFD)-induced liver fibrosis. Our functional analyses demonstrated that miR-455-3p inhibited expression of profibrotic markers and cell proliferation in HSCs in vitro. Moreover, miR-455-3p regulated heat shock factor 1 (HSF1) expression by binding to the 3′ UTR of its mRNA directly. Overexpression of HSF1 facilitated HSCs activation and proliferation by promoting heat shock protein 47 (Hsp47) expression, leading to activation of the TGF-β/Smad4 signaling pathway. To explore the clinical potential of miR-455-3p, we injected ago-miR-455-3p into mice with CCl₄-, BDL-, and HFD-induced hepatic fibrosis in vivo. The overexpression of miR-455-3p suppressed HSF1 expression and reduced fibrosis marker expression, which resulted in alleviated liver fibrosis in mice. In conclusion, our present study suggests that miR-455-3p inhibits the activation of HSCs through targeting HSF1 involved in the Hsp47/TGF-β/Smad4 signaling pathway. Therefore, miR-455-3p might be a promising therapeutic target for liver fibrosis.

Receptor-specific TRAIL as a means to achieve targeted elimination of activated hepatic stellate cells

Activated hepatic stellate cells (HSCs) are known to play a central role in liver fibrosis and their elimination is a crucial step toward the resolution and reversion of liver fibrosis. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a molecule that may contribute to the apoptotic removal of activated HSC through binding to its dedicated receptors. In the present study, we investigated the potential application of recombinant receptor-specific TRAIL proteins in the efficient elimination of activated HSCs. Our finding revealed differential contribution of TRAIL receptors among HSCs populations with activated hepatic stellate cells expresses more TRAIL receptors DR5. In vitro treatment of activated HSCs with DR5-specific or wild-type TRAIL variants induced a significant reduction in viability and extracellular matrix production, whereas no significant decrease in viability was associated with the treatment of cells by DR4-specific TRAIL. Our analysis indicate the successful application of the DR5 receptor-specific TRAIL variant in the targeted elimination of activated HSCs via interference with collagen production and simultaneous induction of apoptosis via activation of the caspase pathway. DR5 receptor-specific TRAIL may thus represent a new therapeutic compound for the treatment of liver fibrosis.

A pathogenic role for tumor necrosis factor-related apoptosis-inducing ligand in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a life-threatening inflammatory respiratory disorder, often induced by cigarette smoke (CS) exposure. The development of effective therapies is impaired by a lack of understanding of the underlining mechanisms. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytokine with inflammatory and apoptotic properties. We interrogated a mouse model of CS-induced experimental COPD and human tissues to identify a novel role for TRAIL in COPD pathogenesis. CS exposure of wild-type mice increased TRAIL and its receptor messenger RNA (mRNA) expression and protein levels, as well as the number of TRAIL(+)CD11b(+) monocytes in the lung. TRAIL and its receptor mRNA were also increased in human COPD. CS-exposed TRAIL-deficient mice had decreased pulmonary inflammation, pro-inflammatory mediators, emphysema-like alveolar enlargement, and improved lung function. TRAIL-deficient mice also developed spontaneous small airway changes with increased epithelial cell thickness and collagen deposition, independent of CS exposure. Importantly, therapeutic neutralization of TRAIL, after the establishment of early-stage experimental COPD, reduced pulmonary inflammation, emphysema-like alveolar enlargement, and small airway changes. These data provide further evidence for TRAIL being a pivotal inflammatory factor in respiratory diseases, and the first preclinical evidence to suggest that therapeutic agents that target TRAIL may be effective in COPD therapy.

Toll-like receptor 8 (TLR8) polymorphisms are associated with non-progression of chronic hepatitis C in HIV/HCV coinfected patients

Toll-like receptor 8 (TLR8) polymorphisms have been related to hepatitis C virus (HCV) infection. The aim was to estimate the association of TLR8 polymorphisms with HCV-related outcomes in HIV/HCV coinfected patients. We performed a cross-sectional study of 220 patients who underwent a liver biopsy. TLR8 polymorphisms were genotyped using GoldenGate® assay. The outcome variables were non-fibrosis (F0), mild-inflammation (A0/A1), and non-steatosis [fatty hepatocytes (FH) <10%]. Logistic regression analysis was used to compare the outcome variables according to TLR8 polymorphisms. Four polymorphisms were analyzed (rs1013151, rs5744069, rs17256081 and rs3764880rs1013151). Female patients had higher frequency of TLR8 major alleles at rs17256081 and rs101315, and minor alleles at rs3764880 and rs5744069. Male patients had higher frequency of TLR8 minor alleles except for rs3764880, where major alleles were higher (p<0.01). Two TLR8 polymorphisms (rs1013151 and rs5744069) were significantly associated with non-fibrosis (F0) [adjusted odds ratio (aOR)=4.42 (95% of confidence interval (95%CI)=1.54; 12.68) (p=0.006) and aOR=4.76 (95%CI=1.69; 13.37) (p=0.003); respectively]. When data were stratified by gender, rs1013151 and rs5744069 polymorphisms remained significant for male patients [adjusted odds ratio (aOR)=4.49 (95%CI=1.08; 18.62) (p=0.039) and aOR=6.17 (95%CI=1.45; 26.20) (p=0.014); respectively]. When data were stratified by major HCV genotypes, patients infected with HCV genotype 1 (GT1) had significant values for both rs1013151 and rs5744069 polymorphisms [aOR=5.79 (95%CI=1.44; 23.32) (p=0.013) and aOR=8.01 (95%CI=2.16; 35.65) (p=0.005); respectively]. Finally, none of the TLR8 polymorphisms were significantly associated with mild-inflammation or non-steatosis. In conclusion, TLR8 polymorphisms seem to be related to non-progression of liver fibrosis in HIV/HCV coinfected patients, particularly in males and those patients infected with GT1.

Roles of heat shock factor 1 in isoproterenol‑induced myocardial fibrosis in mice

Although it is well known that isoproterenol (ISO) causes myocardial hypertrophy and myocardial fibrosis in rats, it has remained elusive whether heat shock factor 1 (HSF1) has a role in this process. The present study aimed to investigate the possible roles of HSF1 in ISO-induced fibrosis in mice. It was found that after administration of ISO in Kunming and HSF1-/+ mice, there was a large number of fibers deposited around blood vessels and among cardiocytes, accompanied with an obvious increase in the protein expressions of type I or III collagen and heat shock protein 47 (HSP47), as indicated by western blot analysis. After intervention with insulin-like growth factor 1 (IGF-1), myocardial fibrosis was significantly attenuated, with a paralleled decrease in the expression of collagen and HSP47 in the mice. However, in HSF1-/- mice, fiber hyperplasy was not observed after injection of ISO, and the levels of type I or III collagen and HSP47 were not significantly increased at the protein and mRNA level. Furthermore, it was demonstrated that after subcutaneous injection of ISO into the back of Kunming and HSF1-/+ mice, large amounts of HSF1 protein were localized to the nucleus, and there was an increase in phosphorylated HSF1 as indicated by western blot and immunohistochemical analysis, respectively. Intervention with IGF-1 inhibited HSF1 activation mediated by ISO. These results suggested that HSF1 is required for myocardial fibrosis in ISO-treated mice, and the underlying molecular mechanism may involve the regulation of HSP47.

The interplay between hepatic stellate cells and hepatocytes in an in vitro model of NASH

BACKGROUND & AIM

A complex interplay exists between hepatocytes and hepatic stellate cells (HSC) in hepatic fibrogenesis. The activation of HSCs after liver injury leads to production of extracellular matrix (ECM). Co-culture models could be useful to mimic the liver microenvironment. This study evaluates the effect of free fatty acids (FFA) on HSC cells and the interplay with hepatocytes via both soluble-mediator and cell-cell contact.

METHODS

The human hepatocyte cell line (HuH7) and HSC cells (LX2) were exposed to FFA for 24 h in 3 different experimental set-ups: (A) monoculture of HSC; (B) Transwell® system (effect of soluble mediators); and (C) Simultaneous Co-Culture (SCC) (cell-to-cell connections). Intracellular FFA accumulation was assessed qualitatively (microscopy) and quantitatively (flow cytometry); the activation of HSC (alpha smooth muscle actin, α-SMA) expression of ECM components were quantified by RT-PCR.

RESULTS

FFA exposure induces intracellular fat accumulation in all the experimental set-up but the expression of α-SMA was significantly increased only in SCC. On the contrary, the expression of ECM was substantially decreased in the transwell® system.

CONCLUSIONS

The HSC activation is independent of FFA accumulation but requires cell-to-cell interaction with hepatocyte. On the contrary, the gene regulation of ECM components seems to occur through paracrine mediators.

Strategies to prevent and reverse liver fibrosis in humans and laboratory animals

Liver fibrosis results from chronic damage to the liver in conjunction with various pathways and is mediated by a complex microenvironment. Based on clinical observations, it is now evident that fibrosis is a dynamic, bidirectional process with an inherent capacity for recovery and remodeling. The major mechanisms involved in liver fibrosis include the repetitive injury of hepatocytes, the activation of the inflammatory response after injury stimulation, and the activation and proliferation of hepatic stellate cells (HSCs), which represents the major extracellular matrix (ECM)-producing cells, stimulated by hepatocyte injury and inflammation. The microenvironment in the liver is synergistically regulated abnormal ECM deposition, scar formation, angiogenesis, and fibrogenesis. Moreover, recent studies have clarified novel mechanism in fibrosis such as epigenetic regulation of HSCs, the leptin and PPARγ pathways, the coagulation system, and even autophagy. Uncovering the mechanisms of liver fibrogenesis provides a basis to develop potential therapies to reverse and treat the fibrotic response, thereby improving the outcomes of patients with chronic liver disease. Although both scientific and clinical challenges remain, emerging studies attempt to reveal the ideal anti-fibrotic drug that could be easily delivered to the liver with high specificity and low toxicity. This review highlights the mechanisms, including novel pathways underlying fibrogenesis that may be translated into preventive and treatment strategies, reviews both current and novel agents that target specific pathways or multiple targets, and discusses novel drug delivery systems such as nanotechnology that can be applied in the treatment of liver fibrosis. In addition, we also discuss some current treatment strategies that are being applied in animal models and in clinical trials.