Aberrant TGF-β1 signaling contributes to the development of primary biliary cirrhosis in murine model

The role of circular RNAs in autoimmune diseases: Potential diagnostic biomarkers and therapeutic targets

With the emergence of high-quality sequencing technologies, further research on transcriptomes has become possible. Circular RNA (circRNA), a novel type of endogenous RNA molecule with a covalently closed circular structure through "back-splicing," is reported to be widely present in eukaryotic cells and participates mainly in regulating gene and protein expression in various ways. It is becoming a research hotspot in the non-coding RNA field. CircRNA shows close relation to several varieties of autoimmune diseases (AIDs) in both the physiological and pathological level and could potentially be used clinically in terms of diagnosis and treatment. Here, we focus on reviewing the importance of circRNA in various AIDs, with the aim of establishing new biomarkers and providing novel insights into understanding the role and functions of circRNA in AIDs. Specific signaling pathways of how circular RNAs are regulated in AIDs will also be illustrated in this review.

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

Animal models of primary biliary cholangitis: status and challenges

BACKGROUND

Primary biliary cholangitis (PBC) is an autoimmune liver disease. The aetiology of PBC remains unclear, and its pathogenesis is complex. Animal models are essential to clarify the pathogenesis of PBC and explore the occurrence of early events.

MAIN BODY

Herein, we review recent research progress in PBC animal models, including genetically modified, chemically inducible, biologically inducible, and protein-immunised models. Although these animal models exhibit several immunological and pathological features of PBC, they all have limitations that constrain further research and weaken their connection with clinical practice.

CONCLUSION

The review will benefit efforts to understand and optimise animal models in order to further clarify PBC pathogenesis and molecular targets for therapeutic interventions.

Inhibiting NADPH Oxidases to Target Vascular and Other Pathologies: An Update on Recent Experimental and Clinical Studies

Reactive oxygen species (ROS) can be beneficial or harmful in health and disease. While low levels of ROS serve as signaling molecules to regulate vascular tone and the growth and proliferation of endothelial cells, elevated levels of ROS contribute to numerous pathologies, such as endothelial dysfunctions, colon cancer, and fibrosis. ROS and their cellular sources have been extensively studied as potential targets for clinical intervention. Whereas various ROS sources are important for different pathologies, four NADPH oxidases (NOX1, NOX2, NOX4, and NOX5) play a prominent role in homeostasis and disease. NOX1-generated ROS have been implicated in hypertension, suggesting that inhibition of NOX1 may be a promising therapeutic approach. NOX2 and NOX4 oxidases are of specific interest due to their role in producing extra- and intracellular hydrogen peroxide (H₂O₂). NOX4-released hydrogen peroxide activates NOX2, which in turn stimulates the release of mitochondrial ROS resulting in ROS-induced ROS release (RIRR) signaling. Increased ROS production from NOX5 contributes to atherosclerosis. This review aims to summarize recent findings on NOX enzymes and clinical trials inhibiting NADPH oxidases to target pathologies including diabetes, idiopathic pulmonary fibrosis (IPF), and primary biliary cholangitis (PBC).

Biological Effects of Transforming Growth Factor Beta in Human Cholangiocytes

TGF-β is a cytokine implicated in multiple cellular responses, including cell cycle regulation, fibrogenesis, angiogenesis and immune modulation. In response to pro-inflammatory and chemotactic cytokines and growth factors, cholangiocytes prime biliary damage, characteristic of cholangiopathies and pathologies that affect biliary tree. The effects and signaling related to TGF-β in cholangiocyte remains poorly investigated. In this study, the cellular response of human cholangiocytes to TGF-β was examined. Wound-healing assay, proliferation assay and cell cycle analyses were used to monitor the changes in cholangiocyte behavior following 24 and 48 h of TGF-β stimulation. Moreover, proteomic approach was used to identify proteins modulated by TGF-β treatment. Our study highlighted a reduction in cholangiocyte proliferation and a cell cycle arrest in G0/G1 phase following TGF-β treatment. Moreover, proteomic analysis allowed the identification of four downregulated proteins (CaM kinase II subunit delta, caveolin-1, NipSnap1 and calumin) involved in Ca2+ homeostasis. Accordingly, Gene Ontology analysis highlighted that the plasma membrane and endoplasmic reticulum are the cellular compartments most affected by TGF-β. These results suggested that the effects of TGF-β in human cholangiocytes could be related to an imbalance of intracellular calcium homeostasis. In addition, for the first time, we correlated calumin and NipSnap1 to TGF-β signaling.

The contribution of neuropilin-1 in the stability of CD4+ CD25+ regulatory T cells through the TGF-β1/Smads signaling pathway in the presence of lipopolysaccharides

Introduction

This study investigates the synergistic effect of TGF‐β1 and Nrp‐1 on CD4⁺CD25⁺ T_regs' stabilization, and the associated pathways of signal transduction, in vitro models in the presence of LPS.

Materials and Methods

Spleen CD4⁺CD25⁺ T_regs cells of mice models in the presence of LPS, were transfected with an shRNA targeting Nrp‐1, Smad2, or Smad3, may or may not be treated with recombinant TGF‐β1. Followed by subsequent determination of cellular proliferation, rate of apoptosis, observation of the Foxp3, CTLA‐4, and TGF‐β1^m+ expression levels, foxp3‐TSDR methylation, secretion levels of the inhibitory cytokines IL‐10 and TGF‐β1, and Smad2/3 of CD4⁺CD25⁺ T_regs expression.

Results

A remarkable stimulation in CD4⁺CD25⁺ T_regs' stability is noted after administering recombinant TGF‐β1 in the presence of LPS, and promoted cellular viability, increased Foxp3, CTLA‐4, and TGF‐β1^m+ expression, and elevated secretion of IL‐10 and TGF‐β1. This also inhibited the apoptosis and methylation of foxp3‐ TSDR of CD4⁺CD25⁺ T_regs. The shRNA transfection silenced Nrp‐1 and Smad3, but not Smad2, resulting in the suppression of the recombinant TGF‐β1‐mediated effects in the presence of LPS.

Conclusions

According to the results, Nrp‐1 mediates TGF‐β1 to improve the stability of regulatory CD4⁺CD25⁺ T cells and maybe a possible therapeutic target with the ability to improve the CD4⁺CD25⁺ T_regs associated negative immunoregulation that is related to the TGF‐β1/Smads cell signaling during sepsis.

Knockout of the Cannabinoid Receptor 2 Gene Promotes Inflammation and Hepatic Stellate Cell Activation by Promoting A20/Nuclear Factor-κB (NF-κB) Expression in Mice with Carbon Tetrachloride-Induced Liver Fibrosis

Background

This study aimed to investigate the effect of deleting the cannabinoid receptor 2 (CB2) gene on the development of hepatic fibrosis induced by carbon tetrachloride (CCl₄) in mice via regulating inflammation.

Material/Methods

The DNA was extracted from the tails of mice to identify whether the cannabinoid receptor 2 gene was successfully knocked out. A liver fibrosis model was established by an intraperitoneal injection of CCl₄ into mice. Hepatic damage and hepatic fibrosis were evaluated by detecting serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and staining paraffin sections of liver tissue with hematoxylin-eosin (HE). The secretion and distribution of collagen in liver tissue were observed by Masson staining. Western blot analysis was performed to detect the expression of α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), tumor necrosis factor alpha-induced protein 3 (A20), phosphorylated nuclear factor-κB p65 (p-NF-κB p65), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6) in liver tissue. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the expression of IL-6 and TNF-α mRNA in liver tissue.

Results

Compared with the control mice, the mice with CB2 knockout that were exposed to CCl₄ exhibited increased liver damage, liver fibrosis, and upregulated α-SMA, TGF-β1, A20, and p-NF-κB p65 protein levels. IL-6 and TNF-α protein levels and mRNA levels were upregulated.

Conclusions

The deletion of the CB2 gene promoted the activation of hepatic stellate cells in mice with liver fibrosis and aggravated liver fibrosis by up-regulating the protein expression of A20 and p-NF-κB p65 and inducing inflammatory response, potentially providing new insight into the treatment of liver fibrosis.

MicroRNA-34a Promotes EMT and Liver Fibrosis in Primary Biliary Cholangitis by Regulating TGF-β1/smad Pathway

Background and Aims

Primary biliary cholangitis (PBC) is an autoimmune cholestatic liver disease. We found microRNA-34a (miR-34a), as the downstream gene of p53, was overexpressed in some of fibrogenic diseases. In this study, we sought to explore whether miR-34a plays a role in the fibrosis of PBC.

Methods

The peripheral blood of PBC patients and controls was collected to analyze the level of miR-34a. Human intrahepatic biliary epithelial cells (HIBEC) were cultured. The expression of miR-34a was regulated by miR-34a mimics and inhibitor. The biomarkers of epithelium-mesenchymal transition (EMT), fibrogenesis, inflammation, and transforming growth factor- (TGF-) β1/smad pathway were analyzed.

Results

We found that miR-34a was overexpressed in the peripheral blood in PBC patients. In vitro, overexpressed miR-34a increased the EMT and fibrogenesis activity of HIBEC. Transforming growth factor-beta type 1 receptor (TβR1), TGF-β1, and p-smad2/3 were upregulated by miR-34a. Inflammatory factors such as IL-6 and IL-17 were also upregulated. Finally, we showed that miR-34a promoted EMT and liver fibrosis in PBC by targeting the TGF-β1/smad pathway antagonist transforming growth factor-beta-induced factor homeobox 2 (TGIF2).

Conclusions

Our findings show that miR-34a plays an important role in the EMT and fibrosis of PBC through the TGF-β1/smad pathway by targeting TGIF2. This study suggests that miR-34a may be a new marker of fibrogenesis in PBC. Inhibition of miR-34a may be a promising strategy in treating PBC and improving the prognosis of the disease.

Mechanism of TGF-β1 inhibiting Kupffer cell immune responses in cholestatic cirrhosis

Effect of exogenous transforming growth factor-β1 (TGF-β1) on cholestatic mice by inhibiting Kupffer cell immune responses in liver was investigated. To induce cholestasis, BALB/c mice received a sham operation (Mock group), or underwent a bile duct ligation (BDL group) and then were subcutaneously injected with TGF-β1 at multiple sites (TGF group). Liver functions were evaluated according to the levels of alanine aminotransferase (ALT), aspartate aminotransferase AST and γ-glutamyltranspeptidase (γ-GT) in serum samples. Expression of nuclear factor-κB (NF-κB), interleukin-6 (IL-6), IL-1β and tumor necrosis factor-α (TNF-α) was detected. Expression of inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1) in Kupffer cells (KCs) of the liver was detected. The isolated KCs were divided into control group, LPS group, TGF group and Galunisertib group and western blot analysis was used to detect the expression of NF-κB, IL-6, IL-1β, TNF-α, iNOS and Arg-1. The percentage of CD40, CD86, CD204 and CD206 as macrophage cell surface antigens were measured by flow cytometry. The indexes of liver function and liver fibrosis of the mice in the TGF group were significantly lower than those in the BDL group (P<0.05). The levels of IL-1β, IL-6 and TNF-α in the liver were lower than those in the BDL group, while the level of IL-10 was significantly increased (P<0.05). M2-type transformation occurred in liver Kupffer cells of mice in the TGF group. In cell experiments, TGF treatment downregulated the expression of IL-1β, IL-6, TNF-α and NF-κB, increased the expression of IL-10, and induced M2-type transformation in macrophages (P<0.05). In conclusion, TGF-ß1 diminished the progression of cholestasis in mice by inhibiting the inflammatory response of KCs and regulating KC polarization.

Protective effects of Liuweiwuling tablets on carbon tetrachloride-induced hepatic fibrosis in rats

BACKGROUND

Liuweiwuling tablets (LWWL) are an herbal product that exerts remarkable effects on liver protection and aminotransferase levels, and they have been approved by the Chinese State Food and Drug Administration (CFDA). Clinical studies have found that LWWL can inhibit collagen production and reduce the levels of liver fibrosis markers in the serum. Thus, LWWL is expected to have beneficial effects in the treatment of liver fibrosis. The purpose of this study was to evaluate the pharmacological effects of LWWL.

METHODS

Hepatic fibrosis was induced in rats via carbon tetrachloride (CCl₄) treatment. The rats were treated twice weekly for 8 weeks with either 2 mL·kg^- 1 body weight of a 50% solution of CCl₄ in olive oil or olive oil alone by oral gavage. A subset of rats received daily intraperitoneal injections of either colchicine (0.2 mg/kg per day), LWWL (0.4, 1.6, or 6.4 g/kg per day), or vehicle (N = 12 for all groups) during weeks 9-12. The rats were sacrificed after 12 weeks. Pathological changes in hepatic tissue were examined using hematoxylin and eosin (H&E) and Sirius Red staining. Immunohistochemistry was performed to observe α-smooth muscle actin (α-SMA) and collagen type I (collagen I) protein expression. Western blotting was also used to detect α-SMA protein expression. Real-time quantitative reverse-transcription polymerase chain reaction (RT-qPCR) was used to detect transforming growth factor-1 (TGF-β1), platelet-derived growth factor (PDGF), tissue inhibitor of metalloproteinase-1 (TIMP1), and tissue inhibitor of metalloproteinase-2 (TIMP2) mRNA expression.

RESULTS

LWWL significantly reversed histological fibrosis and liver injury, reduced the hydroxyproline content in liver tissue, and decreased α-SMA and collagen I expression. LWWL also suppressed hepatic stellate cell (HSC) activation by reducing the expression of the profibrogenic factors TGF-β1 and PDGF. The expression levels of TIMP1 and TIMP2, which regulate extracellular matrix (ECM) degradation, were decreased after CCl₄ injury in LWWL-treated rats.

CONCLUSIONS

These data suggest that LWWL may serve as a promising therapeutic agent to reduce fibrogenesis.

The interplay between Th17 and T-regulatory responses as well as adipokines in the progression of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a chronic progressive liver disease, coupled with metabolic syndrome, which may progress to non-alcoholic steatohepatitis (NASH). Diabetes, obesity, hypertension, hypercholesterolemia, and hypertriglyceridemia are considered to be the most common causes leading to the incidence of NAFLD. It is assumed that the accumulation of lipid deposits in hepatocytes leads to production of proinflammatory cytokines that triggers the development of liver inflammation. Regulatory T cells (Tregs) play a critical role in regulating inflammatory processes in NASH, while T helper type 17 (Th17) might functionally oppose Treg-mediated responses. In addition, important mediators of hepatic steatosis are fatty hormones known as adipokines. We aimed to describe the significance and interaction between Treg and Th17-related cytokines as well as adipokines in pathogenesis and its potential use as biomarkers of NAFLD, especially with respect to progression to NASH.

HIF-1 α as a Key Factor in Bile Duct Ligation-Induced Liver Fibrosis in Rats

BACKGROUND

Although several studies suggested hypoxia as an important microenvironmental factor contributing to inflammation and fibrosis in chronic liver diseases, the mechanism of this process is not fully understood. We considered hypoxia inducible factor (HIF-1α) as a key transcription factor in liver fibrosis. The aim of the study was to evaluate the mechanisms of signaling pathway during bile duct ligation (BDL)-induced liver fibrosis in rats.

METHODS

BDL animal model of liver fibrosis was used in the study. Male Wistar rats were divided randomly into two experimental groups: sham group (n = 15), BDL group (n = 30). Hydroxyproline (Hyp) content as a marker of collagen accumulation in liver of rats subjected to BDL was evaluated according to the method described by Gerling B et al. Expression of signaling proteins [integrin β₁ receptor, HIF-1α, nuclear factor kappa B (NF-κB), and transforming growth factor (TGF-β)] was evaluated applying Western-immunoblot analysis. In all experiments, the mean values for six assays ± standard deviations (SD) were calculated. The results were submitted to the statistical analysis using the Student's "t" test, accepting p < 0.05 as significant.

RESULTS

Ligation of bile ducts was found to increase Hyp content in rat liver, accompanied by increase of HIF-1α expression during 10 weeks after BDL. The Hyp level was time dependent. There was not such a difference in control group (p < 0.001). Simultaneously expression of NF-κB, TGF-β, β₁-integrin receptor was significantly elevated starting from sixth week after ligation. Activity of metalloproteinases 2 and 9 in the livers were increased 1 week after surgery and remained increased until the end of the experiment.

CONCLUSIONS

The mechanism of development of liver fibrosis involves activation of Matrix metalloproteinase-2 (MMP-2) and Matrix metalloproteinase-9 (MMP-9), upregulation of HIF-1α transcriptional activity and its related factors, NF-κB and TGF-β. It suggests that they may represent targets for the treatment of the disease.

Decreased expression of TIPE2 contributes to the hyperreactivity of monocyte to Toll-like receptor ligands in primary biliary cirrhosis

BACKGROUND AND AIM

Previous studies have shown differential TIPE2 expression in several autoimmune diseases. However, the expression levels of TIPE2 in primary biliary cirrhosis (PBC) remained unclear. The purposes of this study were to evaluate TIPE2 expression levels in patients with PBC and further investigate its role in PBC pathogenesis.

METHODS

A total of 40 PBC patients and 44 healthy controls were included in the present study. Quantitative reverse-transcription polymerase chain reaction and western blotting were used to determine the differences in mRNA and protein expression levels of TIPE2. The correlations of TIPE2 expression levels and clinical characteristics, inflammatory cytokines, and ursodeoxycholic acid treatment were also assessed. Besides, the influence of TIPE2 on the reactivity of monocyte to Toll-like receptor ligands was further analyzed.

RESULTS

The expression levels of TIPE2 were significantly decreased in PBC patients compared with normal controls (P < 0.01). The expression levels of TIPE2 were negatively correlated with alanine aminotransferase (r = -0.40, P = 0.01), alkaline phosphatase (r = -0.36, P = 0.02), gamma glutamyl transpeptidase (r = -0.53, P < 0.01), tumor necrosis factor (TNF)-α (r = -0.332, P = 0.03), interleukin (IL)-1β (r = -0.386, P = 0.01), and IL-8 (r = -0.366, P = 0.02) levels in sera from PBC patients. TIPE2 expression level could be significantly increased after ursodeoxycholic acid treatment (P < 0.01). The production of TNF-α, IL-1β, and IL-8 by monocytes from PBC patients after stimulation with lipopolysaccharide and lipoteichoic acid was significantly increased when TIPE2 was knocked down. Furthermore, TIPE2 knockdown could promote activation of nuclear factor-κB pathways through increasing phosphorylation and degradation of IκB in peripheral blood monocytes from PBC patients.

CONCLUSION

The present study reported that insufficient expression of TIPE2 might be involved in the hyperreactivity of monocyte to Toll-like receptor ligands in PBC.

Recent advances in diagnosis and treatment of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic progressive cholestatic autoimmune liver disease characterized by the destruction of small intrahepatic bile ducts and the presence of highly specific serum antimitochondrial antibodies (AMAs). In this article, we will review the clinical, serological and histopathological features of PBC as well as the advances in the diagnosis and differential diagnosis of PBC. In addition, this article systematically describes the advances in the treatment of PBC, and the treatments include ursodeoxycholic acid (UDCA), budesonide, methotrexate (MTX), farnesoid X receptor (FXR) agonists, cyclosporine A, bezafibrate, rituximab, bone marrow-derived mesenchymal stem cell (BM-MSC) transplantation, and liver transplantation. At present, liver transplantation is the only option with known therapeutic benefit for end-stage PBC patients.