Up-regulation of RACK1 by TGF-β1 promotes hepatic fibrosis in mice. PLoS One. 2013;8:e60115. [PMID: 23555900 DOI: 10.1371/journal.pone.0060115]

Abnormal metabolism in hepatic stellate cells: Pandora's box of MAFLD related hepatocellular carcinoma

Metabolic associated fatty liver disease (MAFLD) is a significant risk factor for the development of hepatocellular carcinoma (HCC). Hepatic stellate cells (HSCs), as key mediators in liver injury response, are believed to play a crucial role in the repair process of liver injury. However, in MAFLD patients, the normal metabolic and immunoregulatory mechanisms of HSCs become disrupted, leading to disturbances in the local microenvironment. Abnormally activated HSCs are heavily involved in the initiation and progression of HCC. The metabolic disorders and abnormal activation of HSCs not only initiate liver fibrosis but also contribute to carcinogenesis. In this review, we provide an overview of recent research progress on the relationship between the abnormal metabolism of HSCs and the local immune system in the liver, elucidating the mechanisms of immune imbalance caused by abnormally activated HSCs in MAFLD patients. Based on this understanding, we discuss the potential and challenges of metabolic-based and immunology-based mechanisms in the treatment of MAFLD-related HCC, with a specific focus on the role of HSCs in HCC progression and their potential as targets for anti-cancer therapy. This review aims to enhance researchers' understanding of the importance of HSCs in maintaining normal liver function and highlights the significance of HSCs in the progression of MAFLD-related HCC.

Indirubin alleviates CCl4-induced liver fibrosis by regulation of TGF-β-mediated signaling pathways

Objectives

Liver fibrosis is a common liver disease caused by chronic liver damage. However, there are currently no approved drugs available to treat it. Therefore, the therapeutic effect of indirubin on liver fibrosis was evaluated. This study investigated the protective effect and related molecular mechanism of indirubin against CCl4-induced liver fibrosis in mice.

Materials and Methods

We first detected the effect of indirubin on liver fibrosis in mice (n=8 per group, 32 mice total) by ELISA, HE, and Masson staining. Subsequently, the proliferation of activated HSCs was detected by MTT and EdU. Finally, the changes of related proteins and signaling pathways in mice treated with indirubin were investigated by qRT-PCR and Western blot. One-way ANOVA or two-tailed student's t-test was used for comparison between groups.

Results

Firstly, we found that indirubin (25 mg/kg) therapy could attenuate liver injury and significantly down-regulate α-SMA (P=0.0038) and collagen 1 (P=0.0057) in the liver using CCl4-induced liver fibrosis in mice. Secondly, we showed that indirubin (25 μM) could significantly inhibit hepatic stellate cell (HSC) trans-differentiation into myofibroblasts and proliferation (P=0.0063) in HSC-T6 cells treated by TGF-β. Finally, we showed that indirubin could greatly reduce the protein levels of p-Smad2/3, p38, p-ERK, and p-JNK in vivo and in vitro.

Conclusion

Our results suggested that indirubin alleviated liver fibrosis and HSC activation mainly through TGF-β-mediated signaling pathways in vivo and in vitro. In conclusion, our data showed that indirubin could be a promising clinical therapeutic drug for the prevention and treatment of liver fibrosis.

Rosmarinic acid ameliorates acetaminophen-induced acute liver injury in mice via RACK1/TNF-α mediated antioxidant effect

CONTEXT

Rosmarinic acid (RA) dose-dependently ameliorates acetaminophen (APAP) induced hepatotoxicity in rats. However, whether RA hepatoprotective effect is by regulating RACK1 and its downstream signals is still unclear.

OBJECTIVE

This study explores the RA protective effect on APAP-induced ALI and its mechanism.

MATERIALS AND METHODS

Sixty Kunming mice 6-8 weeks old were randomly separated into six groups (n = 10) and pre-treated with normal saline, ammonium glycyrrhetate (AG) or RA (10, 20 or 40 mg/kg i.p./day) for two consecutive weeks. Then, APAP (300 mg/kg, i.g.) was administrated to induce ALI, except for the control. Serum alanine/aspartate aminotransferases (ALT and AST), malondialdehyde (MDA), superoxide dismutase (SOD) and histopathology were used to authenticate RA effect. The liver RACK1 and TNF-α were measured by western blot.

RESULTS

Compared with the APAP group, different dosages RA significantly decreased ALT (52.09 ± 7.98, 55.13 ± 10.19, 65.08 ± 27.61 U/L, p < 0.05), AST (114.78 ± 19.87, 115.29 ± 31.91, 101.78 ± 21.85 U/L, p < 0.05), MDA (2.37 ± 0.87, 2.13 ± 0.87, 1.86 ± 0.39 nmol/mg, p < 0.01) and increased SOD (306.178 ± 90.80, 459.21 ± 58.54, 444.01 ± 78.09 U/mg, p < 0.05). With increasing doses of RA, RACK1 and TNF-α expression decreased. Moreover, the RACK1 and TNF-α levels were positively correlated with MDA (r = 0.8453 and r = 0.9391, p < 0.01).

DISCUSSION AND CONCLUSIONS

Our findings support RA as a hepatoprotective agent to improve APAP-induced ALI and the antioxidant effect mediated through RACK1/TNF-α pathway.

Insulin/IGF-1 signaling promotes immunosuppression via the STAT3 pathway: impact on the aging process and age-related diseases

BACKGROUND

The insulin/IGF-1 signaling pathway has a major role in the regulation of longevity both in Caenorhabditis elegans and mammalian species, i.e., reduced activity of this pathway extends lifespan, whereas increased activity accelerates the aging process. The insulin/IGF-1 pathway controls protein and energy metabolism as well as the proliferation and differentiation of insulin/IGF-1-responsive cells. Insulin/IGF-1 signaling also regulates the functions of the innate and adaptive immune systems. The purpose of this review was to elucidate whether insulin/IGF-1 signaling is linked to immunosuppressive STAT3 signaling which is known to promote the aging process.

METHODS

Original and review articles encompassing the connections between insulin/IGF-1 and STAT3 signaling were examined from major databases including Pubmed, Scopus, and Google Scholar.

RESULTS

The activation of insulin/IGF-1 receptors stimulates STAT3 signaling through the JAK and AKT-driven signaling pathways. STAT3 signaling is a major activator of immunosuppressive cells which are able to counteract the chronic low-grade inflammation associated with the aging process. However, the activation of STAT3 signaling stimulates a negative feedback response through the induction of SOCS factors which not only inhibit the activity of insulin/IGF-1 receptors but also that of many cytokine receptors. The inhibition of insulin/IGF-1 signaling evokes insulin resistance, a condition known to be increased with aging. STAT3 signaling also triggers the senescence of both non-immune and immune cells, especially through the activation of p53 signaling.

CONCLUSIONS

Given that cellular senescence, inflammaging, and counteracting immune suppression increase with aging, this might explain why excessive insulin/IGF-1 signaling promotes the aging process.

Perturbation of Specific Signaling Pathways Is Involved in Initiation of Mouse Liver Fibrosis

BACKGROUND AND AIMS

To identify the regulatory role of protein phosphatase 2A (PP2A) in the development of liver disease, we generated a mouse model with hepatocyte-specific deletion of Ppp2r1a gene (encoding PP2A Aα subunit).

APPROACH AND RESULTS

Homozygote (HO) mice and matched wild-type littermates were investigated at 3, 6, 9, 12, 15, and 18 months of age. Pathological examination showed that PP2A Aα deficiency in hepatocytes resulted in progressive liver fibrosis phenotype from 9 months of age. No hepatocyte death was observed in HO mice. However, perturbation of pathways including epidermal growth factor receptor 1 (EGFR1), amino acid metabolism, and translation factors as well as leptin and adiponectin led to pronounced hepatic fibrosis. In vitro studies demonstrated the involvement of specific B subunit complexes in the regulation of EGFR1 signaling pathway and cross talk between defected hepatocytes and stimulation of interstitial hyperplasia. It is noteworthy that HO mice failed to develop hepatocellular carcinoma for as long as 22 months of age. We further demonstrate that PP2A Aβ-containing holoenzymes played a critical role in preventing hepatocyte apoptosis and antagonizing tumorigenesis through specific pathways on Aα loss. Furthermore, PP2A Aα and Aβ were functionally distinct, and the Aβ isoform failed to substitute for Aα in the development of inflammation and liver fibrosis.

CONCLUSIONS

These observations identify pathways that contribute to the pathogenesis of liver fibrosis and provide putative therapeutic targets for its treatment.

Up-regulation of FUT8 inhibits TGF-β1-induced activation of hepatic stellate cells during liver fibrogenesis

Liver fibrosis is a continuous wound healing response caused by chronic liver injury, and the activation of hepatic stellate cells (HSCs) is considered as the main event for it. Core fucosylation catalyzed by FUT8 refers to adding the fucosyl moiety to the innermost GlcNAc residue of N-linked oligosaccharides and is involved in many biological processes such as cell differentiation, migration, and signaling transduction. Aberrant core fucosylation is associated with a variety of diseases including cardiovascular disease, tumors and neuroinflammation, but much less is understood in liver fibrosis. Herein, we reported FUT8 mRNA level was increased in patients with liver fibrosis from GEO database and positively correlated with fibrosis progression. FUT8 expression and the core fucosylation were also elevated in TAA-induced mouse liver fibrosis model, and were mainly distributed in the fibrous septum of mouse liver. TGF-β1, as the most pro-fibrogenic cytokine, could promote the expression of FUT8 and total core fucosylation levels in HSCs in vitro. However, up-regulation of FUT8 in turn inhibited TGF-β1-induced trans-differentiation, migration and pro-fibrogenic signaling pathways in HSCs. In conclusion, our results suggest that the up-regulation of FUT8 inhibits TGF-β1-induced HSC activation in a negative feedback loop, and provide potential new therapeutic strategy for liver fibrosis by targeting FUT8.

HMGB1 Inhibits HNF1A to Modulate Liver Fibrogenesis via p65/miR-146b Signaling

High mobility group box 1 (HMGB1) is essential for the pathogenesis of liver injury and liver fibrosis. We previously revealed that miR-146b promotes hepatic stellate cells (HSCs) activation and proliferation. Nevertheless, the potential mechanisms are still unknown. Herein, HMGB1 increased HSCs proliferation and COL1A1 and α-SMA protein levels. However, the knockdown of miR-146b inhibited HSCs proliferation and COL1A1 and α-SMA protein levels induced via HMGB1 treatment. miR-146b was upregulated by HMGB1 and miR-146b targeted hepatocyte nuclear factor 1A (HNF1A) 3'-untranslated region (3'UTR) to modulate its expression negatively. Further, we confirmed that HMGB1 might elicit miR-146b expression via p65 within HSCs. Knockdown or block of HMGB1 relieved the CCl₄-induced liver fibrosis. In fibrotic liver tissues, miR-146b expression was positively correlated with p65 mRNA, but HNF1A mRNA was inversely correlated with p65, and miR-146b expression. In summary, our findings suggest that HMGB1/p65/miR-146b/HNF1A signaling exerts a crucial effect on liver fibrogenesis via the regulation of HSC function.

Dual role of RACK1 in airway epithelial mesenchymal transition and apoptosis

Airway epithelial apoptosis and epithelial mesenchymal transition (EMT) are two crucial components of asthma pathogenesis, concomitantly mediated by TGF‐β1. RACK1 is the downstream target gene of TGF‐β1 shown to enhancement in asthma mice in our previous study. Balb/c mice were sensitized twice and challenged with OVA every day for 7 days. Transformed human bronchial epithelial cells, BEAS‐2B cells were cultured and exposed to recombinant soluble human TGF‐β1 to induced apoptosis (30 ng/mL, 72 hours) and EMT (10 ng/mL, 48 hours) in vitro, respectively. siRNA and pharmacological inhibitors were used to evaluate the regulation of RACK1 protein in apoptosis and EMT. Western blotting analysis and immunostaining were used to detect the protein expressions in vivo and in vitro. Our data showed that RACK1 protein levels were significantly increased in OVA‐challenged mice, as well as TGF‐β1‐induced apoptosis and EMT of BEAS‐2B cells. Knockdown of RACK1 (siRACK1) significantly inhibited apoptosis and decreased TGF‐β1 up‐regulated EMT related protein levels (N‐cadherin and Snail) in vitro via suppression of JNK and Smad3 activation. Moreover, siSmad3 or siJNK impaired TGF‐β1‐induced N‐cadherin and Snail up‐regulation in vitro. Importantly, JNK gene silencing (siERK) also impaired the regulatory effect of TGF‐β1 on Smad3 activation. Our present data demonstrate that RACK1 is a concomitant regulator of TGF‐β1 induces airway apoptosis and EMT via JNK/Smad/Snail signalling axis. Our findings may provide a new insight into understanding the regulation mechanism of RACK1 in asthma pathogenesis.

Transforming Growth Factor-β-Induced Cell Plasticity in Liver Fibrosis and Hepatocarcinogenesis

The Transforming Growth Factor-beta (TGF-β) family plays relevant roles in the regulation of different cellular processes that are essential for tissue and organ homeostasis. In the case of the liver, TGF-β signaling participates in different stages of disease progression, from initial liver injury toward fibrosis, cirrhosis and cancer. When a chronic injury takes place, mobilization of lymphocytes and other inflammatory cells occur, thus setting the stage for persistence of an inflammatory response. Macrophages produce profibrotic mediators, among them, TGF-β, which is responsible for activation -transdifferentiation- of quiescent hepatic stellate cells (HSC) to a myofibroblast (MFB) phenotype. MFBs are the principal source of extracellular matrix protein (ECM) accumulation and prominent mediators of fibrogenesis. TGF-β also mediates an epithelial-mesenchymal transition (EMT) process in hepatocytes that may contribute, directly or indirectly, to increase the MFB population. In hepatocarcinogenesis, TGF-β plays a dual role, behaving as a suppressor factor at early stages, but contributing to later tumor progression, once cells escape from its cytostatic effects. As part of its potential pro-tumorigenic actions, TGF-β induces EMT in liver tumor cells, which increases its pro-migratory and invasive potential. In parallel, TGF-β also induces changes in tumor cell plasticity, conferring properties of a migratory tumor initiating cell (TIC). The main aim of this review is to shed light about the pleiotropic actions of TGF-β that explain its effects on the different liver cell populations. The cross-talk with other signaling pathways that contribute to TGF-β effects, in particular the Epidermal Growth Factor Receptor (EGFR), will be presented. Finally, we will discuss the rationale for targeting the TGF-β pathway in liver pathologies.

RACK1 is indispensable for porcine reproductive and respiratory syndrome virus replication and NF-κB activation in Marc-145 cells

Porcine reproductive and respiratory syndrome virus (PRRSV) causes porcine reproductive and respiratory syndrome (PRRS), which is currently insufficiently controlled. RACK1 (receptor of activated protein C kinase 1) was first identified as a receptor for protein kinase C, with increasing evidence showing that the functionally conserved RACK1 plays important roles in cancer development, NF-κB activation and various virus infections. However, the roles of RACK1 during PRRSV infection in Marc-145 cells have not been described yet. Here we demonstrated that infection of Marc-145 cells with the highly pathogenic PRRSV strain YN-1 from our lab led to activation of NF-κB and upregulation of RACK1 expression. The siRNA knockdown of RACK1 inhibited PRRSV replication in Marc-145 cells, abrogated NF-κB activation induced by PRRSV infection and reduced the viral titer. Furthermore, knockdown of RACK1 could inhibit an ongoing PRRSV infection. We found that RACK1 is highly conserved across different species based on the phylogenetic analysis of mRNA and deduced amino acid sequences. Taken together, RACK1 plays an indispensable role for PRRSV replication in Marc-145 cells and NF-κB activation. The results would advance our further understanding of the molecular mechanisms underlying PRRSV infection in swine and indicate RACK1 as a promising potential therapeutic target.

RACK1 silencing attenuates renal fibrosis by inhibiting TGF-β signaling

The receptor for activated C-kinase 1 (RACK1) is a member of the WD40-repeat family of proteins and has been reported to be implicated in the development of liver fibrosis. However, the role of RACK1 in renal fibrosis remains unclear. Therefore, in this study, we investigated the effects of RACK1 on transforming growth factor-β1 (TGF-β1)-treated human proximal tubular epithelial cells and aimed to elucidate the possible mechanisms responsible for its anti-fibrotic effects. Our results revealed that RACK1 was highly expressed in the renal fibrotic tissues and TGF-β1-treated HK-2 cells. RACK1 silencing inhibited TGF-β1‑induced α-smooth muscle actin and connective tissue growth factor expression in the HK-2 cells. Furthermore, RACK1 silencing inhibited the expression of phosphorylated Smad3 in the TGF-β1-treated HK-2 cells. To the best of our knowledge, these data demonstrate for the first time the role of RACK1 in renal fibrosis. The present findings indicate that RACK1 silencing attenuates renal fibrosis by suppressing the activation of TGF-β1/Smad3 signaling pathway in HK-2 cells. Thus, RACK1 may serve as a novel regulator of renal fibrosis.

BNIP3L promotes cardiac fibrosis in cardiac fibroblasts through [Ca2+]i-TGF-β-Smad2/3 pathway

Fibrosis is an important, structurally damaging event that occurs in pathological cardiac remodeling, leading to cardiac dysfunction. BNIP3L is up-regulated in pressure overload-induced heart failure and has been reported to play an important role in cardiomyocyte apoptosis; however, its involvement in cardiac fibroblasts (CFs) remains unknown. We prove for the first time that the expression of BNIP3L is significantly increased in the CFs of rats undergoing pressure overload-induced heart failure. Furthermore, this increased BNIP3L expression was confirmed in cultured neonatal rat CFs undergoing proliferation and extracellular matrix (ECM) protein over-expression that was induced by norepinephrine (NE). The overexpression or suppression of BNIP3L promoted or inhibited NE-induced proliferation and ECM expression in CFs, respectively. In addition, [Ca²⁺]_i, transforming growth factor beta (TGF-β) and the nuclear accumulation of Smad2/3 were successively increased when BNIP3L was overexpressed and reduced when BNIP3L was inhibited. Furthermore, the down-regulation of TGF-β by TGF-β-siRNA attenuated the increase of BNIP3L-induced fibronectin expression. We also demonstrated that the increase of BNIP3L in CFs was regulated by NE-AR-PKC pathway in vitro and in vivo. These results reveal that BNIP3L is a novel mediator of pressure overload-induced cardiac fibrosis through the [Ca²⁺]_i-TGF-β-Smad2/3 pathway in CFs.

Histone deacetylases 3 deletion restrains PM2.5-induced mice lung injury by regulating NF-κB and TGF-β/Smad2/3 signaling pathways

Acute lung injury (ALI) as a serious disease with high mortality has been emphasized as a threat to human health and life. Accumulating studies demonstrated that PM2.5 plays a significant role in metabolic and lung diseases. Histone deacetylases 3 (HDAC3) is an important regulator in control of gene transcription, required in up-regulation of inflammation-related signaling, and has been known as a key hotpot in treating a lot of chronic inflammatory diseases. TGF-β/Smad signaling pathway has been proven to be of significance in fibrosis development. Our results found that PM2.5 induced lung function injury in WT mice with a inflammatory responses through the activation of TGF-β/Smad signaling pathways, resulting in lung injury. Of note, HDAC3-deficient mice after PM2.5 administration further promoted TGF-β/Smad signaling pathways activation. In addition, TLR4, p-NF-κB and p-IκBα indicated that HDAC3 knockout mice have a higher inflammation-related signals expression in lung tissue than WT mice after PM2.5 administration, resulting in pro-inflammatory cytokines releasing. Moreover, in vitro experiment of lung epithelial cells challenged with PM2.5, further indicated that TGF-β/Smad2/3 was involved in fibrosis development, leading to inflammation response. Also, the activation of TLR4/NF-κB could be observed in PM2.5-induced lung epithelial cells, leading to inflammation infiltration. These results indicate a new therapeutic target to protect against lung injury caused by PM2.5.

Oxidative stress and dysfunctional NRF2 underlie pachyonychia congenita phenotypes

Palmoplantar keratoderma (PPK) are debilitating lesions that arise in individuals with pachyonychia congenita (PC) and feature upregulation of danger-associated molecular patterns and skin barrier regulators. The defining features of PC-associated PPK are reproduced in mice null for keratin 16 (Krt16), which is commonly mutated in PC patients. Here, we have shown that PPK onset is preceded by oxidative stress in footpad skin of Krt16-/- mice and correlates with an inability of keratinocytes to sustain nuclear factor erythroid-derived 2 related factor 2-dependent (NRF2-dependent) synthesis of the cellular antioxidant glutathione (GSH). Additionally, examination of plantar skin biopsies from individuals with PC confirmed the presence of high levels of hypophosphorylated NRF2 in lesional tissue. In Krt16-/- mice, genetic ablation of Nrf2 worsened spontaneous skin lesions and accelerated PPK development in footpad skin. Hypoactivity of NRF2 in Krt16-/- footpad skin correlated with decreased levels or activity of upstream NRF2 activators, including PKCδ, receptor for activated C kinase 1 (RACK1), and p21. Topical application of the NRF2 activator sulforaphane to the footpad of Krt16-/- mice prevented the development of PPK and normalized redox balance via regeneration of GSH from existing cellular pools. Together, these findings point to oxidative stress and dysfunctional NRF2 as contributors to PPK pathogenesis, identify K16 as a regulator of NRF2 activation, and suggest that pharmacological activation of NRF2 should be further explored for PC treatment.

Carnosic acid nanoparticles suppress liver ischemia/reperfusion injury by inhibition of ROS, Caspases and NF-κB signaling pathway in mice

Living donor liver transplantation (LDLT) requires ischemia/reperfusion (I/R), which can lead to early graft injury. However, the detailed molecular mechanism of I/R injury remains unclear. Carnosic acid, as a phenolic diterpene with function of anti-inflammation, anti-cancer, anti-bacterial, anti-diabetic, as well as neuroprotective properties, is produced by many species from Lamiaceae family. Nanoparticulate drug delivery systems have been known to better the bioavailability of drugs on intranasal administration compared with only drug solutions. Administration of carnosic acid nanoparticles was thought to be sufficient to lead to considerable inhibition of liver injury progression induced by ischemia/reperfusion. In our study, liver ischemia/reperfusion injury was established successfully with C57BL/6 animal model. 10 and 20mg/kg carnosic acid nanoparticles were injected to mice for five days prior to ischemia. After liver ischemia/reperfusion, the levels of serum AST, ALT and APL were increased, which was attenuated by pre-treatment with carnosic acid nanoparticles. In addition, carnosic acid nanoparticles inhibited ROS production via its related signals regulation. And carnosic acid nanoparticles also suppressed the ischemia/reperfusion-induced up-regulation in the pro-apoptotic protein and mRNA levels of Bax, Cyto-c, Apaf-1 and Caspase-9/3 while increased ischemia/reperfusion-induced decrease of anti-apoptotic factor of Bcl-2. Further, ischemia/reperfusion-induced inflammation was also inhibited for carnosic acid nanoparticles administration via inactivating NF-κB signaling pathway, leading to down-regulation of pro-inflammatory cytokines releasing. In conclusion, our study suggested that carnosic acid nanoparticles protected against liver ischemia/reperfusion injury via its role of anti-oxidative, anti-apoptotic and anti-inflammatory bioactivity.

Inhibition of MAPK and NF-κB signaling pathways alleviate carbon tetrachloride (CCl4)-induced liver fibrosis in Toll-like receptor 5 (TLR5) deficiency mice

Current researches showed that TLR family plays an important role in liver fibrosis, yet the molecular mechanism by which this occurs is not fully explained. In this study, we investigated the role of TLR5 in carbon tetrachloride-induced liver fibrosis, and further examined wether TLR5 knockout attenuated tetrachloride-induced liver fibrosis by inhibiting hepatic stellate cells activation via modulating NF-κB and MAPK signaling pathways. Our results found that carbon tetrachloride induced liver function injury in WT mice with a inflammatory responses through the activation of NF-κB and MAPK signaling pathways, resulting in hepatic stellate cells activation. In contrast, TLR5 deficiency mice after carbon tetrachloride administration reduced NF-κB and MAPK signaling pathways activation, which down regulated hepatic stellate cells activation. In addition, alpha smooth muscle-actin as marker of hepatic stellate cells further indicated that TLR5 knockout mice have a lower collagen accumulation in liver tissue than WT mice after carbon tetrachloride administration, resulting in inhibition of NF-κB and MAPK signaling pathways activation. Moreover, in vitro experiment of hepatic stellate cells challenged with LPS or TGF-β, further indicated that NF-κB and MAPK were involved in liver fibrosis development, leading to α-SMA expression and inflammation infiltration. However, cells from TLR5(-)(/-) may weaken phosphorylation levels of signal pathways, finally suppress progress of collagen accumulation and inflammatory responses. These results suggest a new therapeutic approach or target to protect against fibrosis caused by chronic liver diseases.

Overexpression of RACK1 inhibits collagen synthesis in keloid fibroblasts via inhibition of transforming growth factor-β1/Smad signaling pathway

Keloids are benign skin tumors characterized by collagen accumulation and hyperproliferation of fibroblasts. The receptor for activated C-kinase 1 (RACK1) was involved in liver fibrosis. However, the role of RACK1 in dermal fibrosis keloids is still unclear. Therefore, in this study, we investigated the effects of RACK1 on keloid fibroblasts (KFs) and transforming growth factor-β1 (TGF-β1)-induced collagen expression and explored the underlying mechanism. We found that RACK1 was decreased in KFs, overexpression of RACK1 significantly inhibited TGF-β1-induced KFs proliferation. RACK1 also obviously inhibited the expression of TGF-β1-induced TGF-β receptor I, II, type I collagen and α-smooth muscle actin (α-SMA) in human KFs. In addition, RACK1 suppressed the expression of TGF-β1-induced Smad2 and Smad3 phosphorylation in human KFs. Taken together, our study suggested that RACK1 inhibits collagen synthesis in KFs via inhibition the TGF-β1/Smad signaling pathway, and RACK1 is a potential target for treatment of the keloid disease.

Genome-wide RNAi screen for nuclear actin reveals a network of cofilin regulators

Nuclear actin plays an important role in many processes that regulate gene expression. Cytoplasmic actin dynamics are tightly controlled by numerous actin-binding proteins, but regulation of nuclear actin has remained unclear. Here, we performed a genome-wide RNA interference (RNAi) screen in Drosophila cells to identify proteins that influence either nuclear polymerization or import of actin. We validate 19 factors as specific hits, and show that Chinmo (known as Bach2 in mammals), SNF4Aγ (Prkag1 in mammals) and Rab18 play a role in nuclear localization of actin in both fly and mammalian cells. We identify several new regulators of cofilin activity, and characterize modulators of both cofilin kinases and phosphatase. For example, Chinmo/Bach2, which regulates nuclear actin levels also in vivo, maintains active cofilin by repressing the expression of the kinase Cdi (Tesk in mammals). Finally, we show that Nup98 and lamin are candidates for regulating nuclear actin polymerization. Our screen therefore reveals new aspects of actin regulation and links nuclear actin to many cellular processes.

RACK1-mediated translation control promotes liver fibrogenesis

Activation of quiescent hepatic stellate cells (HSCs) is the central event of liver fibrosis. The translational machinery is an optimized molecular network that affects cellular homoeostasis and diseases, whereas the role of protein translation in HSCs activation and liver fibrosis is little defined. Our previous report suggests that up-regulation of receptor for activated C-kinase 1(RACK1) in HSCs is critical for liver fibrogenesis. In this study, we found that RACK1 promoted macrophage conditioned medium (MCM)-induced assembly of eIF4F and phosphorylation of eIF4E in primary HSCs. RACK1 enhanced the translation and expression of pro-fibrogenic factors collagen 1α1, snail and cyclin E1 induced by MCM. Administration of PP242 or knock-down of eIF4E suppressed RACK1-stimulated collagen 1α1 production, proliferation and migration in primary HSCs. In addition, depletion of eIF4E attenuated thioacetamide (TAA)-induced liver fibrosis in vivo. Our data suggest that RACK1-mediated stimulation of cap-dependent translation plays crucial roles in HSCs activation and liver fibrogenesis, and targeting translation initiation could be a promising strategy for the treatment of liver fibrosis.

RACK1 expression contributes to JNK activity, but JNK activity does not enhance RACK1 expression in hepatocellular carcinoma SMMC-7721 cells

Receptor for activated C kinase 1 (RACK1) is up-regulated in hepatocellular carcinoma (HCC) and has been reported to augment c-Jun N-terminal protein kinase (JNK) activity in HCC SMMC-7721 cells. By contrast, activator protein-1, a downstream JNK transcription factor, has been revealed to mediate the overexpression of RACK1 in melanoma cells. Therefore, the association between RACK1 and JNK activity in HCC cells has yet to be completely elucidated. The present study analyzed the effects of RACK1 or JNK loss of function on the levels of RACK1 protein, JNK activity, cell proliferation and apoptosis induced by tumor necrosis factor-related apoptosis inducing ligand in HCC SMMC-7721 cells. It was found that JNK loss of function exhibited no effect on RACK1 expression, whereas a loss of RACK1 function led to reduced JNK activity in SMMC-7721 cells. RACK1 and JNK loss of function resulted in the impaired oncogenic growth of SMMC-7721 cells. The present data further support a pivotal role of RACK1 in mediating enhanced JNK activity in HCC cells and also indicate that a novel mechanism exists for RACK1 overexpression in HCC SMMC-7721 cells.

Pyrroloquinoline-quinone suppresses liver fibrogenesis in mice

Liver fibrosis represents the consequences of a sustained wound healing response to chronic liver injuries, and its progression toward cirrhosis is the major cause of liver-related morbidity and mortality worldwide. However, anti-fibrotic treatment remains an unconquered area for drug development. Accumulating evidence indicate that oxidative stress plays a critical role in liver fibrogenesis. In this study, we found that PQQ, a natural anti-oxidant present in a wide variety of human foods, exerted potent anti-fibrotic and ROS-scavenging activity in Balb/C mouse models of liver fibrosis. The antioxidant activity of PQQ was involved in the modulation of multiple steps during liver fibrogenesis, including chronic liver injury, hepatic inflammation, as well as activation of hepatic stellate cells and production of extracellular matrix. PQQ also suppressed the up-regulation of RACK1 in activated HSCs in vivo and in vitro. Our data suggest that PQQ suppresses oxidative stress and liver fibrogenesis in mice, and provide rationale for the clinical application of PQQ in the prevention and treatment of liver fibrosis.

Age and ethnicity in cirrhosis

BACKGROUND

Cirrhosis is diagnosed in patients of all ages and is the end result of many different diseases. The aim of this study was to characterize clinical and ethnic features of adult patients who were admitted to the hospital at different (young/old) ages and examine associations between age and ethnicity within these groups.

METHODS

In this retrospective analysis of a diverse cohort of 2017 patients with a clinical diagnosis of cirrhosis between January 2001 and December 2011, we focused on age, ethnicity, and outcome of patients with cirrhosis.

RESULTS

We identified 219 patients younger than the age of 40 years, including 87 (11%) of 802 white, 31 (6%) of 550 African American, and 89 (16%) of 550 Hispanic patients (P < 0.001). Ethnicity and causes of cirrhosis were found to have a significant correlation with age. Overall, Hispanic and white patients together were more than twice as likely to be diagnosed with cirrhosis at an age younger than 40 years compared with African American patients (P < 0.001). Autoimmune hepatitis caused cirrhosis at a younger age regardless of ethnicity (P < 0.001), whereas cryptogenic/nonalcoholic fatty liver disease/nonalcoholic steatohepatitis was more likely identified at an older age (P = 0.008). African American patients with cirrhosis due to either alcohol or hepatitis C virus were older than Hispanic (P < 0.001 and P = 0.003, respectively) and white patients (P < 0.001 and P < 0.001, respectively) at presentation. Finally, younger patients admitted with cirrhosis had a higher in-hospital mortality rate (P < 0.001).

CONCLUSIONS

The data suggest an association between ethnicity and age of cirrhosis diagnosis, both overall and in patients with certain cirrhosis etiologies. This work raises the possibility of an ethnic and/or genetic basis for cirrhosis.

Insulin-like growth factor binding protein-related protein 1 (IGFBPrP1) contributes to liver inflammation and fibrosis via activation of the ERK1/2 pathway

BACKGROUND AND AIM

Previously, we suggested that IGFBPrP1 played a major role in hepatic stellate cell (HSC) activation, yet the molecular mechanism of IGFBPrP1 in hepatic fibrosis is unclear. The ERK pathway is involved in activation of HSCs. This study investigated the involvement of the ERK1/2 pathway in IGFBPrP1-induced liver inflammation and fibrosis.

METHODS

An adenoviral vector encoding IGFBPrP1 (AdIGFBPrP1) was constructed. Rats received AdIGFBPrP1 or CAd (vector control) via their tail vein injection. One hour prior to adenoviral injections, rats were intraperitoneally administrated with 10 mg/kg U0126 (a specific MEK/ERK1/2 inhibitor) or DMSO (vehicle control). At weeks 2 or 4 post-gene transduction, serum samples were obtained and the levels of liver enzymes and hydroxyproline were determined. Liver tissue were histologically evaluated for inflammation and fibrosis. The expression of α-SMA and ECM were evaluated by qRT-PCR and western blotting.

RESULTS

After transduction, IGFBPrP1 expression significantly increased in livers and transduced cells. MEK/ERK1/2 inhibition administration of AdIGFBPrP1-treated rats and cells significantly blocked AdIGFBPrP1-induced activation of ERK1/2. U0126 significantly down-regulated the number of F4/80-positive cells and CD3-positive cells (markers of liver inflammation), the expression of α-SMA and the concentration of ECM components in vivo. In addition, α-SMA and TGF-β1 levels in AdIGFBPrP1 HSCs were markedly inhibited by a MEK/ERK1/2 inhibitor, indicating that HSC activation was inhibited.

CONCLUSION

These findings suggest that IGFBPrP1 acts as an initiator of liver fibrosis by inducing inflammation, HSC activation and ECM deposition through the ERK1/2 pathway.

Toll like receptor 2 knock-out attenuates carbon tetrachloride (CCl4)-induced liver fibrosis by downregulating MAPK and NF-κB signaling pathways

Innate immune signaling associated with Toll-like receptors (TLRs) is a key pathway involved in the progression of liver fibrosis. In this study, we reported that TLR2 is required for hepatic fibrogenesis induced by carbon tetrachloride (CCl4). After CCl4 treatment, TLR2(-/-) mice had reduced liver enzyme levels, diminished collagen deposition, decreased inflammatory infiltration and impaired activation of hepatic stellate cells (HSCs) than wild type (WT) mice. Furthermore, after CCl4 treatment, TLR2(-/-) mice demonstrated downregulated expression of profibrotic and proinflammatory genes and impaired mitogen-activated protein kinases (MAPK) and nuclear factor kappa B (NF-κB) activation than WT mice. Collectively, our data indicate that TLR2 deficiency protects against CCl4-induced liver fibrosis.

Th17 cells are associated with the Th1/Th2‑cell balance during Echinococcus multilocularis infection

The present study investigated the immunopathological effect of Echinococcus multilocularis (Em) using cytokine detection. Expression of the T‑helper (Th) 17‑cytokine, interleukin 17 (IL‑17), was observed using immunohistochemical staining, and levels of cytokines, including IL‑17, transforming growth factor β1 (TGF‑β1), IL‑6, interferon γ (IFN‑γ) and IL‑4, were assessed using ELISA at different stages of infection. IL‑17 expression occurred in hepatic cells at 1 month post‑infection, reached a maximum at 3 months post‑infection and then decreased gradually. Compared with the uninfected control, levels of the cytokines IL‑17, TGF‑β1, IL‑6, IFN‑γ and IL‑4 exhibited different dynamic patterns when infected with Em. In the immune response during the whole infection period, Th17 cells play an important role by secreting IL‑17, which may be involved in the Th1/Th2‑cell balance during the immune response. Th17 cells are associated with immunopathology in Em infection.

Valsartan improves portal hypertensive gastropathy in rats possibly via TGF-β1/Smad signaling pathway

AIM: To investigate the efficacy and mechanisms of action of valsartan on portal hypertensive gastropathy in rats with gastric mucosa lesions.

METHODS: Forty-eight SD rats were randomly divided into a sham-operated group, a portal hypertension gastropathy group, a valsartan prevention group, a normal dose valsartan group and a high dose valsartan group. Portal hypertensive gastropathy was induced by the partial portal vein ligation method. Gastric mucosa TGF-beta1 expression and microvessel density (MVD) were detected by immunohistochemical staining method. Gastric mucosa Smad2 and Smad7 protein expression was detected by Western blot. Plasma levels of rennin activity (PRA), angiotensin II (Ang II), alanine aminotransferase (ALT), and albumin (ALB) were determined by ELISA.

RESULTS: Compared with the model group, gastric mucosa TGF-β1 (11.58 ± 2.27, 13.29 ± 2.82, 13.15 ± 3.36 vs 24.25 ± 3.48, all P <0.05) and Smad2 (0.86 ± 0.59, 0.82±0.36, 0.83 ± 0.49 vs 1.60 ± 0.77, P < 0.05) protein expression was significantly decreased in the valsartan prevention group, normal dose valsartan group and high dose valsartan group. Smad7 protein expression in the valsartan prevention group, normal dose valsartan group and high dose valsartan group was significantly higher than that in the model group (1.59 ± 0.72, 1.65 ± 0.80, 1.69 ± 0.85 vs 0.58 ± 0.35, all P < 0.05). Plasma PRA (16.49 ng/mL ± 2.77 ng/mL, 15.92 ng/mL ± 4.30 ng/mL, 16.72 ng/mL ± 5.48 ng/mL vs 11.49 ng/mL ± 2.12 ng/mL, all P <0.05) and Ang II (1664.44 pg/mL ± 285.47 pg/mL, 1686.82 pg/mL ± 499.16 pg/mL, 1734.07 pg/mL ± 326.66 pg/mL vs 1110.38 pg/mL ± 193.85 pg/mL, all P <0.01) were also significantly higher in the valsartan prevention group, normal dose valsartan group and high dose valsartan group than in the model group.

CONCLUSION: Valsartan can improve portal hypertensive gastropathy probably by down-regulating TGF-β1 and Smad2 expression and up-regulating Smad7 expression.

Treatment with valsartan reduces TGF-β1 expression and collagen fiber content in the portal vein of rats with portal hypertensive gastropathy

AIM: To investigate the effect of treatment with valsartan on portal vein lesions in rats with portal hypertensive gastropathy (PHG).

METHODS: Forty-eight SD rats were randomly divided into a sham operation group, a PHG model group, a valsartan prevention group, a normal dose valsartan group, and a double dose valsartan group. Partial portal vein ligation was used to induce PHG. Portal venous pressure (PVP) and heart rate (HR) were measured. Immunohistochemistry was used to detect TGF-β1 protein expression in the portal vein, and Masson's trichrome technique was used to determine the content of collagen fibers.

RESULTS: The PVP decreased significantly in the normal dose valsartan group, double dose valsartan group and prevention group compared with the model group (13.32 cmH₂O ± 0.96 cmH₂O vs 9.54 cmH₂O ± 0.80 cmH₂O, 9.04 cmH₂O ± 0.96 cmH₂O, 8.30 cmH₂O ± 0.41 cmH₂O, all P < 0.01). TGF-β1 expression and collagen fiber content were significantly higher in the model group than in the sham operation group (8.51 ± 1.42 vs 5.73 ± 0.87, 2.01 ± 1.25 vs 0.82 ± 0.54); however, TGF-β1 expression and collagen fiber content were significantly lower in the valsartan normal dose group, double dose group and prevention group than in the model group (6.54 ± 1.09, 6.45 ± 1.37, 6.42 ± 1.98 vs 8.51 ± 1.42; 0.92 ± 0.53, 1.09 ± 0.40, 1.03 ± 0.36 vs 2.01 ± 1.25, all P < 0.05).

CONCLUSION: TGF-β1 expression and collagen fiber content in the portal vein increase in rats with PHG. Treatment with valsartan can not only reduce portal pressure and TGF-β1 expression in the portal vein but also decrease collagen synthesis.