TGF-β/Smad-signaling in liver cells: Target genes and inhibitors of two parallel pathways

Protocatechuic acid inhibits TGF-β1-induced proliferation and migration of human airway smooth muscle cells

Protocatechuic acid (3, 4-dihydroxybenzoic acid, PCA) is a major metabolite of anthocyanins and was reported to possess anti-allergic response. However, the effects of PCA on airway smooth muscle cells (ASMCs) proliferation and migration remain unclear. Therefore, this study aims to investigate the effects of PCA on proliferation and migration of ASMCs. ASMCs were pre-incubated with various concentrations of PCA for 30 min before stimulation with transforming growth factor-β1 (TGF-β1) for different times. Cell proliferation was determined using the colony formation assay. Cell migration was detected using the Transwell chamber assay. The levels of type I collagen, fibronectin, phosphorylated Smad2, Smad2, phosphorylated Smad3 and Smad3 were detected by western blot analysis. Our results demonstrated that PCA inhibited the proliferation and migration of ASMCs, as well as suppressed the expression levels of type I collagen and fibronectin in ASMCs induced by TGF-β1. Furthermore, PCA obviously down-regulated the phosphorylation levels of Smad2/3 in ASMCs exposed to TGF-β1. Taken together, the present results have revealed that PCA inhibits asthma airway remodeling by suppressing proliferation and extracellular matrix (ECM) protein deposition in TGF-β1-mediated ASMCs via the inactivation of Smad2/3 signaling pathway. Therefore, PCA may be useful for the prevention or treatment of asthma airway remodeling.

Analysis of the expression of mir-34a, mir-199a, mir-30c and mir-19a in peripheral blood CD4+T lymphocytes of relapsing-remitting multiple sclerosis patients

BACKGROUND

Multiple sclerosis is an immune-mediated inflammatory disease of central nervous system. MicroRNAs play important roles in autoimmune diseases such as MS.

OBJECTIVES

The aim was to evaluate the expression pattern of miR-34a, miR-199a, miR-30c and miR-19a in peripheral blood derived CD4+ T lymphocytes of both relapsing and remitting phases of MS.

METHODS

Blood samples from 40 RRMS patients (20 in relapsing and 20 in remitting phase) and 20 healthy volunteers were taken. CD4+ T cells were isolated. The expression level of miR-34a, miR-199a, miR-30c and miR-19a, and the percentage of Th17 and Treg cells were measured. Expression of master transcription factors of Th17 and Treg cells and several targets of these miRNAs were also evaluated.

RESULTS

Data indicated an increased expression of miR-34a, miR-30c and miR-19a in relapsing phase and decreased expression of miR-199a in remitting phase. ROC curve data add other prestigious information of miR-34a, miR-199a, miR-30c and miR-19a by defining relapsing and remitting phase and also healthy cases with high specificity and sensitivity at a proposed optimum cut-off point.

CONCLUSION

Collectively, we showed a correlation between the four miRNAs with different phases of MS and their possible involvement in differentiation pathways of Th17 cells, as the most important players in MS.

Knockdown of Fstl1 attenuates hepatic stellate cell activation through the TGF‑β1/Smad3 signaling pathway

Follistatin‑like 1 (Fstl1) is a secreted glycoprotein that belongs to the follistatin and SPARC (secreted protein, acidic and rich in cysteine) families and was identified to serve a critical role in lung fibrosis. However, the role of Fstl1 in liver fibrosis remains undefined. Therefore, the aim of the present study was to investigate the role of Fstl1 in liver fibrosis. The results indicated that Fstl1 was highly expressed in human hepatic fibrosis tissues and activated hepatic stellate cells (HSCs). Furthermore, knockdown of Fstl1effectively suppressed HSC proliferation and the protein expression levels of α‑SMA and collagen I in transforming growth factor (TGF)‑β1‑treated HSCs. Mechanistically, knockdown of Fstl1 remarkably decreased the phosphorylation level of Smad3 in TGF‑β1‑induced HSCs. Taken together, the present study demonstrated that Fstl1serves an important role in liver fibrosis and target deletion of Fstl1 attenuated HSCs activation through suppressing TGF‑β1/Smad3 signaling pathway. Therefore, Fstl1 may be a potential therapeutic target for the treatment of liver fibrosis.

Knockout of krüppel-like factor 10 suppresses hepatic cell proliferation in a partially hepatectomized mouse model

The liver has marked regenerative capabilities, and numerous signaling pathways are involved in liver regeneration. The transforming growth factor-β (TGF-β)/Smad pathway, which is also involved in liver regeneration, regulates numerous biological processes. Krüppel-like factor 10 (KLF10) has been reported to activate the TGF-β/Smad signaling pathway; however, the exact functions of KLF10 under various pathophysiological conditions remain unclear. In the present study, the role of KLF10 in liver regeneration following partial hepatectomy (PH) was investigated using KLF10-knockout (KO) mice. KLF10-KO mice exhibited lower liver/body weight ratios and 5-bromo-2-deoxy-uridine labeling indices compared with wild-type (WT) mice, and significant differences (P=0.028) were obtained at 72 h after PH. To understand the causes of the gross and histopathological findings, the expression levels of the components of the TGF-β/Smad pathway were examined using reverse transcription-quantitative polymerase chain reaction and western blot analysis. The mRNA and protein levels of Smad3, p15, TGF-β1 and TGF-β receptor 1 were significantly increased, while those of cMyc and cyclin D1 (proliferation-associated genes) were significantly lower in the liver tissues of the KLF10-KO mice compared with those of the WT mice at 72 h post-PH. These results indicated that KLF10-KO may exhibit antiproliferative effects on liver regeneration following PH, through strengthening the TGF-β/Smad signaling pathway in a delayed manner.

Relaxin decreases the severity of established hepatic fibrosis in mice

BACKGROUND & AIMS

Hepatic fibrosis is characterized by excess collagen deposition, decreased extracellular matrix degradation and activation of the hepatic stellate cells. The hormone relaxin has shown promise in the treatment of fibrosis in a number of tissues, but the effect of relaxin on established hepatic fibrosis is unknown. The aim of this study was to determine the effect of relaxin on an in vivo model after establishing hepatic fibrosis

METHODS

Male mice were made fibrotic by carbon tetrachloride treatment for 4 weeks, followed by treatment with two doses of relaxin (25 or 75 μg/kg/day) or vehicle for 4 weeks, with continued administration of carbon tetrachloride.

RESULTS

Relaxin significantly decreased total hepatic collagen and smooth muscle actin content at both doses, and suppressed collagen I expression at the higher dose. Relaxin increased the expression of the matrix metalloproteinases MMP13 and MMP3, decreased the expression of MMP2 and tissue inhibitor of metalloproteinase 2 (TIMP2) and increased the overall level of collagen-degrading activity. Relaxin decreased TGFβ-induced Smad2 nuclear localization in mouse hepatic stellate cells.

CONCLUSIONS

The results suggest that relaxin reduced collagen deposition and HSC activation in established hepatic fibrosis despite the presence of continued hepatic insult. This reduced fibrosis was associated with increased expression of the fibrillar collagen-degrading enzyme MMP13, decreased expression of TIMP2, and enhanced collagen-degrading activity, and impaired TGFβ signalling, consistent with relaxin's effects on activated fibroblastic cells. The results suggest that relaxin may be an effective treatment for the treatment of established hepatic fibrosis.

Tumour necrosis factor alpha downregulates human hemojuvelin expression via a novel response element within its promoter

Background

Iron homeostasis is chiefly regulated by hepcidin whose expression is tightly controlled by inflammation, iron stores, and hypoxia. Hemojuvelin (HJV) is a bone morphogenetic protein co-receptor that has been identified as a main upstream regulator of hepcidin expression; HJV mutations are associated with a severe form of iron overload (Juvenile haemochromatosis). Currently however, there is no information on how HJV is regulated by inflammation.

Methods

To study the regulation of Hjv expression by inflammation and whether Hfe has a role in that regulation, control and LPS-injected wild type and Hfe KO mice were used. Moreover, human hepatoma cells (HuH7) were used to study the effect of IL-6 and TNF-α on HJV mRNA expression.

Results

Here we show that LPS repressed hepatic Hjv and BMPs, while it induced hepcidin 1 expression in wild-type and Hfe KO mice with no effect on hepatic pSMAD 1, 5, 8 protein levels. In addition, exogenous TNF-α (20 ng/mL) decreased HJV mRNA and protein expression to 40% of control with no effect on hepcidin mRNA expression in 24 hours. On the other hand, IL-6 induced hepcidin mRNA and protein expression with no effect on HJV mRNA expression levels. Moreover, using the HJV promoter-luciferase reporter fusion construct (HJVP1.2-luc), we showed that the basal luciferase activity of HJVP1.2-luc was inhibited by 33% following TNF-α treatment of HuH7 transfected cells suggesting that the TNF-α down-regulation is exerted at the transcriptional level. Additionally, mutation of a canonical TNF- alpha responsive element (TNFRE) within HJVP1.2-luc abolished TNF-α response suggesting that this TNFRE is functional.

Conclusions

From these results, we conclude that TNF-α suppresses HJV transcription possibly via a novel TNFRE within the HJV promoter. In addition, the results suggest that the proposed link between inflammation and BMP-SMAD signalling is independent of HJV and BMP ligands.