Phosphatidylinositol 3-kinase/Akt pathway regulates hepatic stellate cell apoptosis

Mitochondrial quality control in liver fibrosis: Epigenetic hallmarks and therapeutic strategies

BACKGROUND AND AIM

Mitochondrial quality control (MQC) plays a significant role in the progression of liver fibrosis, with key processes such as mitochondrial fission, fusion, mitophagy and biogenesis maintaining mitochondrial homeostasis. To understand the molecular mechanisms underlying epigenetic regulation of mitochondrial quality control in liver fibrosis, with the aim of uncovering novel therapeutic targets for treating, mitigating, and potentially reversing liver fibrosis, in light of the most recent advances in this field.

METHODS

We searched PubMed, Web of Science, and Scopus for published manuscripts using terms "mitochondrial quality control" "mitochondrial fission" "mitochondrial fusion" "mitochondrial biogenesis" "mitophagy" "liver fibrosis" "epigenetic regulation" "DNA methylation" "RNA methylation" "histone modification" and "non-coding RNA". Manuscripts were collated, studied and carried forward for discussion where appropriate.

RESULTS

Mitochondrial fission, fusion, biogenesis, and mitophagy regulate the homeostasis of mitochondria, and the imbalance of mitochondrial homeostasis can induce liver fibrosis. Epigenetic regulation, including DNA methylation, RNA methylation, histone modifications, and non-coding RNAs, plays a significant role in regulating the processes of mitochondrial homeostasis.

CONCLUSION

Mitochondrial quality control and epigenetic mechanisms are intricately linked to the pathogenesis of liver fibrosis. Understanding these molecular interactions provides insight into potential therapeutic strategies. Further research is necessary to translate these findings into clinical applications, with a focus on developing epigenetic drugs to ameliorate liver fibrosis by modulating MQC and epigenetic pathways.

Research progress on rodent models and its mechanisms of liver injury

The liver is the most important organ for biological transformation in the body and is crucial for maintaining the body's vital activities. Liver injury is a serious pathological condition that is commonly found in many liver diseases. It has a high incidence rate, is difficult to cure, and is prone to recurrence. Liver injury can cause serious harm to the body, ranging from mild to severe fatty liver disease. If the condition continues to worsen, it can lead to liver fibrosis and cirrhosis, ultimately resulting in liver failure or liver cancer, which can seriously endanger human life and health. Therefore, establishing an rodent model that mimics the pathogenesis and severity of clinical liver injury is of great significance for better understanding the pathogenesis of liver injury patients and developing more effective clinical treatment methods. The author of this article summarizes common chemical liver injury models, immune liver injury models, alcoholic liver injury models, drug-induced liver injury models, and systematically elaborates on the modeling methods, mechanisms of action, pathways of action, and advantages or disadvantages of each type of model. The aim of this study is to establish reliable rodent models for researchers to use in exploring anti-liver injury and hepatoprotective drugs. By creating more accurate theoretical frameworks, we hope to provide new insights into the treatment of clinical liver injury diseases.

Cancer Stem Cell and Hepatic Stellate Cells in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common liver cancer. It is highly lethal and has high recurrence. Death among HCC patients occur mainly due to tumor progression, recurrence, metastasis, and chemoresistance. Cancer stem cells (CSCs) are cell subpopulations within the tumor that promote invasion, recurrence, metastasis, and drug resistance. Hepatic stellate cells (HSCs) are important components of the tumor microenvironment (TME) responsible for primary secretory ECM proteins during liver injury and inflammation. These cells promote fibrogenesis, infiltrate the tumor stroma, and contribute to HCC development. Interactions between HSC and CSC and their microenvironment help promote carcinogenesis through different mechanisms. This review summarizes the roles of CSCs and HSCs in establishing the TME in primary liver tumors and describes their involvement in HCC chemoresistance.

Mitofusin-2 Restrains Hepatic Stellate Cells' Proliferation via PI3K/Akt Signaling Pathway and Inhibits Liver Fibrosis in Rats

The mitochondrial GTPase mitofusin-2 (MFN2) gene can suppress the cell cycle and regulate cell proliferation in a number of cell types. However, its function in hepatic fibrosis remains largely unexplored. We attempted to understand the mechanism of MFN2 in hepatic stellate cell (HSC) proliferation and the development of hepatic fibrosis. Rat HSC-T6 HSC were cultured and transfected by adenovirus- (Ad-) Mfn2 or its negative control (NC) vector (Ad-green fluorescent protein (GFP)); a rat liver cirrhosis model was established via subcutaneous injection with carbon tetrachloride (CCl4). Seventy-two rats were randomly divided into four groups: CCl4, Mfn2, GFP, and NC. Ad-Mfn2 or Ad-GFP was transfected into the circulation via intravenous injection at day 1, 14, 28, 42, or 56 after the first injection of CCl4 in the Mfn2/GFP groups. Biomarkers related to HSC proliferation and the development of hepatic fibrosis were detected using western blotting, hematoxylin-eosin and Masson staining, and immunohistochemistry. In vitro, Mfn2 interfered specifically with platelet-derived growth factor- (PDGF-) induced signaling pathway (phosphatidylinositol 3-kinase- (PI3K-) AKT), inhibiting HSC-T6 cell activation and proliferation. During the process of hepatic fibrosis in vivo, extracellular collagen deposition and the expression of fibrosis-related proteins increased progressively, while Mfn2 expression decreased gradually. Upregulating Mfn2 expression at the early stage of fibrosis impeded the process, triggered the downregulation of type I collagen, and antagonized the formation of factors associated with liver fibrosis. Mfn2 suppresses HSC proliferation and activation and exhibits antifibrotic potential in early-stage hepatic fibrosis. Therefore, it may represent a significant therapeutic target for eradicating hepatic fibrosis.

Targeting Follistatin like 1 ameliorates liver fibrosis induced by carbon tetrachloride through TGF-β1-miR29a in mice

Background

Hepatic fibrosis is a pathological response of the liver to a variety of chronic stimuli. Hepatic stellate cells (HSCs) are the major source of myofibroblasts in the liver. Follistatin like 1 (Fstl1) is a secreted glycoprotein induced by transforming growth factor-β1 (TGF-β1). However, the precise functions and regulation mechanisms of Fstl1 in liver fibrogenesis remains unclear.

Methods

Hepatic stellate cell (HSC) line LX-2 stimulated by TGF-β1, primary culture of mouse HSCs and a model of liver fibrosis induced by CCl4 in mice was used to assess the effect of Fstl1 in vitro and in vivo.

Results

Here, we found that Fstl1 was significantly up regulated in human and mouse fibrotic livers, as well as activated HSCs. Haplodeficiency of Fstl1 or blockage of Fstl1 with a neutralizing antibody 22B6 attenuated CCl₄-induced liver fibrosis in vivo. Fstl1 modulates TGF-β1 classic Samd2 and non-classic JNK signaling pathways. Knockdown of Fstl1 in HSCs significantly ameliorated cell activation, cell migration, chemokines C-C Motif Chemokine Ligand 2 (CCL2) and C-X-C Motif Chemokine Ligand 8 (CXCL8) secretion and extracellular matrix (ECM) production, and also modulated microRNA-29a (miR29a) expression. Furthermore, we identified that Fstl1 was a target gene of miR29a. And TGF-β1 induction of Fstl1 expression was partially through down regulation of miR29a in HSCs.

Conclusions

Our data suggests TGF-β1-miR29a-Fstl1 regulatory circuit plays a key role in regulation the HSC activation and ECM production, and targeting Fstl1 may be a strategy for the treatment of liver fibrosis.

Identification lncRNA LOC102551149/miR-23a-5p pathway in hepatic fibrosis

BACKGROUND

Hepatic fibrosis is a worldwide incurable disease; due to the complex and unclear mechanism, there lack the effective therapeutic targets. However, the mechanism of miR-23a-5p underling this pathological process is largely not clear. The purpose of this study was to investigate the role of miR-23a-5p in hepatic fibrosis and HSC activation.

METHODS

The content of miR-23a-5p in hepatic fibrosis induced by N-nitrosodimethylamine (NDMA) and HSC activation induced by platelet-derived growth factor (PDGF) was detected by qRT-PCR. H&E staining, Masson staining and Shear wave electrography (SWE) were used to detect the degree of hepatic fibrosis. Immunohistochemistry staining, qRT-PCR and Western blot detect the related markers of liver fibrosis or HSC activation, as well as the related pathway genes and proteins. Dual-luciferase reporter system verifies the interaction between miR-23a-5p with PTEN or miR-23a-5p with lncRNA LOC102551149 in HSC-T6. siRNA and miRNA mimic transfer to HSC-T6 to detect the function of lncRNA LOC102551149 and miR-23a-5p on HSC activation.

RESULTS

After hepatic fibrosis and HSC activation happened, the expression of miR-23a-5p was up-regulated, whereas anti-miR-23a-5p can alleviate hepatic fibrosis and HSC activation. Further research shows miR-23a-5p can target PTEN and degrade it, causing activation of PI3K/Akt/mTOR/Snail pathway. lncRNA LOC102551149 can be used as a competition endogenous RNA (ceRNA) targeting miR-23a-5p through base pairing, and siRNA LOC102551149 or exogenous miR-23a-5p can induce HSC activation through PI3K/Akt/mTOR/Snail pathway.

CONCLUSION

We demonstrate mechanism pathway of miR-23a-5p on hepatic fibrosis and HSC activation, which may develop a therapeutic target for hepatic fibrosis.

Silencing of EPCAM suppresses hepatic fibrosis and hepatic stellate cell proliferation in mice with alcoholic hepatitis via the PI3K/Akt/mTOR signaling pathway

Alcoholic hepatitis (AH) is a severe condition developed in patients with underlying alcoholic liver disease. Epithelial cell adhesion molecule (EPCAM) plays a role in hepatitis. Therefore, the current study aimed to explore the effect of EPCAM and its potential mechanism in AH. Bioinformatic analysis was performed to screen differentially expressed genes associated with AH. AH mouse models were established through a Lieber-DeCarli liquid diet containing 4% ethanol, which were co-treated with siRNA against EPCAM or the PI3K/Akt/mTOR signaling pathway inhibitor in order to investigate the effects of EPCAM and the PI3K/Akt/mTOR signaling pathway on hepatic fibrosis, hepatic stellate cell (HSC) proliferation and apoptosis. The relationship between EPCAM and the PI3K/Akt/mTOR signaling pathway was investigated for the purposes of elucidating the potential mechanism of EPCAM in AH. EPCAM was predicted to regulate AH progression through the PI3K/Akt/mTOR signaling pathway. Silencing EPCAM or inhibition of the PI3K/Akt/mTOR signaling pathway inhibited the hepatic fibrosis and HSC proliferation yet induced HSC apoptosis. Moreover, silencing EPCAM was found to repress the PI3K/Akt/mTOR signaling pathway as evidenced by decreased levels of Bcl2 yet increased levels of caspase-3. Collectively, silencing EPCAM could hinder AH progression by inhibiting the PI3K/Akt/mTOR signaling pathway, which might serve as a potential therapeutic target for AH treatment.

lncRNA GAS5 restrains CCl4-induced hepatic fibrosis by targeting miR-23a through the PTEN/PI3K/Akt signaling pathway

Hepatic fibrosis is chronic liver damage with many causes that has a relatively high death rate. The current study showed that long noncoding RNA (lncRNA) growth arrest-specific transcript 5 (GAS5), microRNA-23a (miR-23a), and phosphatase and tensin homolog (PTEN) play important roles in the pathological process of hepatic fibrosis but have a relatively unclear regulatory mechanism. This study aimed to investigate the roles of lncRNA GAS5, miR-23a, and PTEN in the pathological process of hepatic fibrosis and hepatic stellate cell (HSC) activation. We used carbon tetrachloride (CCl₄) intraperitoneal injections to establish a rat hepatic fibrosis model and exogenous transforming growth factor-β1 to establish an HSC activation model. Quantitative RT-PCR, Western blot, dual-luciferase reporter system, and RNA pull-down assays were used to investigate which microRNAs and lncRNAs participate in the process of hepatic fibrosis and HSC activation. miR-23a expression increased significantly in hepatic fibrosis tissues and activated HSCs. miR-23a interaction with and degradation of PTEN further influenced the downstream signaling pathway phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin/Snail (PI3K/Akt/mTOR/Snail), causing E-cadherin expression levels to decrease and α-smooth muscle actin and collagen I expression levels to increase. lncRNA GAS5 can be used as a sponge platform for miR-23a to decrease miR-23a expression levels competitively. We revealed the role of the lncRNA GAS5/miR-23a/PTEN/PI3K/Akt/mTOR/Snail signaling pathway in hepatic fibrosis, providing molecular targets for the treatment of hepatic fibrosis. NEW & NOTEWORTHY This is the first study revealing that microRNA-23a (miR-23a) promotes hepatic fibrosis through the phosphatase and tensin homolog/phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin/Snail signaling pathway, and long noncoding RNA (lncRNA) growth arrest-specific transcript 5 (GAS5) can act as a sponge platform for miR-23a. Therefore, lncRNA GAS5/miR-23a may bring molecular targets for hepatic fibrosis therapy.

Nrf2 protects stellate cells from Smad-dependent cell activation

Hepatic stellate cells (HSC) orchestrate the deposition of extracellular matrix (ECM) and are the primary effector of liver fibrosis. Several factors, including TGF-β1, PDGF and oxidative stress, have been shown to trigger HSC activation. However, the involvement of cellular defence mechanisms, such as the activation of antioxidant response by Nrf2/Keap1 in the modulation of HSC activation is not known. The aim of this work was to elucidate the role of Nrf2 pathway in HSC trans-differentiation involved in the development of fibrosis. To this end, we repressed Nrf2 and Keap1 expression in HSC with specific siRNAs. We then assessed activation markers, as well as proliferation and migration, in both primary and immortalised human HSCs exposed to Smad inhibitors (SB-431542 hydrate and SB-525334), TGF-β1 and/or PDGF. Our results indicate that knocking down Nrf2 induces HSC activation, as shown by an increase in αSMA-positive cells and by gene expression induction of ECM components (collagens and fibronectin). HSC with reduced Nrf2-levels also showed an increase in migration and a decrease in proliferation. We could also demonstrate that the activation of Nrf2-deficient HSC involves the TGF-β1/Smad pathway, as the activation was successfully inhibited with the two tested Smad inhibitors. Moreover, TGF-β1 elicited a stronger induction of HSC activation markers in Nrf2 deficient cells than in wild type cells. Thus, our data suggest that Nrf2 limits HSCs activation, through the inhibition of the TGF-β1/Smad pathway in HSCs.

Isobavachalcone inhibits the proliferation and invasion of tongue squamous cell carcinoma cells

Isobavachalcone (2′,4′,4-trihydroxy-3′-[3′-methylbut-3′-ethyl] chalcone or IBC) exhibits anticancer activities in a number of types of cancer cell. However, its role in tongue squamous cell carcinoma (TSCC) cells remains unclear. The aim of the present study was to investigate the biological effect of IBC in TSCC Tca8113 cells. The function of IBC on Tca8113 cell apoptosis and apoptosis-associated signaling pathways was determined using an MTT assay, morphological staining, annexin V-propidium iodide (PI) staining and Western blot analysis. The effects of IBC on Tca8113 cell migration, invasion and relative protein expression were confirmed using wound healing analysis, Transwell invasion analysis and Western blot analysis, respectively. The results of the MTT assay and annexin V-PI staining indicated that IBC is able to significantly inhibit proliferation and induce apoptosis of Tca8113 cells in vitro. IBC treatment resulted in typical apoptotic morphology of nuclear fragmentation and apoptotic bodies in Tca8113 cells. Western blot analysis further demonstrated that IBC caused downregulation of the expression of B-cell lymphoma 2 (Bcl-2) protein, upregulation of the expression of Bcl-2-associated X protein (Bax), activation of caspases, and dephosphorylation of protein kinase B (Akt) and extracellular-signal-regulated kinase (ERK) proteins in a concentration- and time-dependent manner. The results of the present study suggest that IBC induces apoptosis in Tca8113 cells and that the induction may be associated with the activation of Bcl-2, Bax and caspase-3, and the inactivation of Akt and ERK. Furthermore, IBC inhibited migration and invasion of Tca8113 cells in vitro by downregulating matrix metalloproteinase (MMP)-2 and MMP-9 protein expression. The results of the present study indicate that IBC may be a potential anticancer drug for the treatment of TSCC.

mTOR Overactivation in Mesenchymal cells Aggravates CCl4- Induced liver Fibrosis

Hepatic stellate cells are of mesenchymal cell type located in the space of Disse. Upon liver injury, HSCs transactivate into myofibroblasts with increase in expression of fibrillar collagen, especially collagen I and III, leading to liver fibrosis. Previous studies have shown mTOR signaling is activated during liver fibrosis. However, there is no direct evidence in vivo. The aim of this study is to examine the effects of conditional deletion of TSC1 in mesenchymal on pathogenesis of liver fibrosis. Crossing mice bearing the floxed TSC1 gene with mice harboring Col1α2-Cre-ER(T) successfully generated progeny with a conditional knockout of TSC1 (TSC1 CKO) in collagen I expressing mesenchymal cells. TSC1 CKO and WT mice were subjected to CCl₄, oil or CCl₄+ rapamycin treatment for 8 weeks. TSC1 CKO mice developed pronounced liver fibrosis relative to WT mice, as examined by ALT, hydroxyproline, histopathology, and profibrogenic gene. Absence of TSC1 in mesenchymal cells induced proliferation and prevented apoptosis in activated HSCs. However, there were no significant differences in oil-treated TSC1 CKO and WT mice. Rapamycin, restored these phenotypic changes by preventing myofibroblasts proliferation and enhancing their apoptosis. These findings revealed mTOR overactivation in mesenchymal cells aggravates CCl₄− induced liver fibrosis and the rapamycin prevent its occurance.

Thymosin Beta 4 Is a Potential Regulator of Hepatic Stellate Cells

Liver fibrosis, a major characteristic of chronic liver disease, is inappropriate tissue remodeling caused by prolonged parenchymal cell injury and inflammation. During liver injury, hepatic stellate cells (HSCs) undergo transdifferentiation from quiescent HSCs into activated HSCs, which promote the deposition of extracellular matrix proteins, leading to liver fibrosis. Thymosin beta 4 (Tβ4), a major actin-sequestering protein, is the most abundant member of the highly conserved β-thymosin family and controls cell morphogenesis and motility by regulating the dynamics of the actin cytoskeleton. Tβ4 is known to be involved in various cellular responses, including antiinflammation, wound healing, angiogenesis, and cancer progression. Emerging evidence suggests that Tβ4 is expressed in the liver; however, its biological roles are poorly understood. Herein, we introduce liver fibrogenesis and recent findings regarding the function of Tβ4 in various tissues and discuss the potential role of Tβ4 in liver fibrosis with a special focus on the effects of exogenous and endogenous Tβ4. Recent studies have revealed that activated HSCs express Tβ4 in vivo and in vitro. Treatment with the exogenous Tβ4 peptide inhibits the proliferation and migration of activated HSCs and reduces liver fibrosis, indicating it has an antifibrotic action. Meanwhile, the endogenously expressed Tβ4 in activated HSCs is shown to promote HSCs activation. Although the role of Tβ4 has not been elucidated, it is apparent that Tβ4 is associated with HSC activation. Therefore, understanding the potential roles and regulatory mechanisms of Tβ4 in liver fibrosis may provide a novel treatment for patients.

Potential role of thymosin Beta 4 in liver fibrosis

Liver fibrosis, the main characteristic of chronic liver diseases, is strongly associated with the activation of hepatic stellate cells (HSCs), which are responsible for extracellular matrix production. As such, investigating the effective regulators controlling HSC activation provides important clues for developing therapeutics to inhibit liver fibrosis. Thymosin beta 4 (Tβ4), a major actin-sequestering protein, is known to be involved in various cellular responses. A growing body of evidence suggests that Tβ4 has a potential role in the pathogenesis of liver fibrosis and that it is especially associated with the activation of HSCs. However, it remains unclear whether Tβ4 promotes or suppresses the activation of HSCs. Herein, we review the potential role of Tβ4 in liver fibrosis by describing the effects of exogenous and endogenous Tβ4, and we discuss the possible signaling pathway regulated by Tβ4. Exogenous Tβ4 reduces liver fibrosis by inhibiting the proliferation and migration of HSCs. Tβ4 is expressed endogenously in the activated HSCs, but this endogenous Tβ4 displays opposite effects in HSC activation, either as an activator or an inhibitor. Although the role of Tβ4 has not been established, it is apparent that Tβ4 influences HSC activation, suggesting that Tβ4 is a potential therapeutic target for treating liver diseases.

Antifibrotic effects of luteolin on hepatic stellate cells and liver fibrosis by targeting AKT/mTOR/p70S6K and TGFβ/Smad signalling pathways

BACKGROUND & AIMS

Luteolin has been reported to exert antifibrogenic effects in CCl4 -induced hepatic fibrosis in mice. However, limited information is available on the cellular and molecular events responsible for this effect. This study focused on the action of luteolin on hepatic stellate cells (HSCs) and the relevant signalling molecules and pathways as well as the antifibrotic efficacy in multiple models of fibrosis.

METHODS

The in vitro effect of luteolin on rat HSCs and HSC-T6 cells was assessed using proliferation assays, invasion chamber, quantitative real-time PCR analysis and Western blotting. The in vivo effect of luteolin on progression of fibrosis was assessed in three experimental rat models induced by CCl4 , dimethylnitrosamine (DMN) and bile duct ligation (BDL).

RESULTS

Luteolin inhibited proliferation, migration, collagen synthesis as well as expression of fibrosis-related genes in the activated HSCs and HSC-T6 cells stimulated with or without transforming growth factor-β1(TGFβ1) or platelet-derived growth factor (PDGF). Luteolin induced HSC apoptosis associated with the increased caspase 3 activity and p53 expression, and induced G1 arrest with the decreased expression of bcl-2, Cyclin E and p-Cdk-2. Moreover, luteolin significantly inhibited PDGF and TGFβ1-simulated phosphorylation of AKT and Smad pathway. In vivo study showed that luteolin administration markedly alleviated hepatic fibrosis along with reduced elevations of alanine aminotransferase and aspartate aminotransferase. HSCs were found to undergo apoptosis and decreased expression of p-Smad2 and p-AKT in luteolin-treated animals.

CONCLUSIONS

This study demonstrates that luteolin prevents the progression of liver fibrosis through multiple mechanisms and indicates that luteolin has potential for effective treatment of liver fibrosis.

MicroRNA-21/PTEN/Akt axis in the fibrogenesis of biliary atresia

BACKGROUND

MicroRNAs (miRNAs) are short, noncoding RNA molecules that act as post-transcriptional negative regulators of target mRNAs. Increasing evidence suggests that miRNAs are involved in liver fibrotic processes. Biliary atresia (BA) is characterized by rapid and progressive liver fibrosis. Therefore, we investigated the role of miRNA-21in the pathogenesis of BA.

METHODS

We collected liver samples from patients with BA or liver trauma to examine the role of miRNA-21. We examined RNA expression of miRNA-21, phosphatase and tensin homolog deleted on chromosome ten (PTEN), and α-smooth muscle actin (α-SMA) in liver tissue using real-time fluorescence quantitative PCR. Western blot analyses and immunohistochemical staining were performed to evaluate protein expression of PTEN, α-SMA, and phosphorylated AKT in liver.

RESULTS

We found that miRNA-21was upregulated in liver samples from BA patients, whereas PTEN negatively correlated with suppression of the 3'-untranslated region (3'-UTR). Activation of the downstream AKT pathway provoked liver fibrosis by enhancing α-SMA levels.

CONCLUSIONS

The miRNA-21/PTEN/AKT axis promotes the fibrosis process in BA, which might be a potential therapeutic target to improve the prognosis of patients with BA.

Handan Ganle inhibits PI3K/Akt signaling pathway in liver fibrosis in rats

AIM: To observe the change of the PI3K/Akt signaling pathway in CCl₄ induced liver fibrosis and to explore the effect of Handan Ganle on this signaling pathway in hepatic fibrosis in rats.

METHODS: Thirty SD rats were randomly divided into a normal control group, a liver fibrosis group and a Handan Ganle treated group. The rats of the liver fibrosis group and Handan Ganle treated group were treated by hypodermic injection of 40% CCl₄ at 0.3 mL/100 g body weight to induce hepatic fibrosis. Then, the rats in the Handan Ganle group were treated with 1.0 g/kg Handan Ganle once daily for 8 weeks. The expression of Akt1 and phospho-Akt1 was detected by immunohistochemistry and Western blot, and the apoptosis of HSCs was determined by TUNEL assay.

RESULTS: Compared with the normal control group, the expression of Akt1 (2.73 ± 0.52 vs 9.60 ± 2.28, P < 0.01) and phospho-Akt1 (0.92 ± 0.40 vs 6.51 ± 1.39, P < 0.01) in the liver fibrosis group was increased. Handan Ganle treatment decreased the levels of Akt1 (9.60 ± 2.28 vs 5.36 ± 1.59, P < 0.01) and phospho-Akt1 (6.51 ± 1.39 vs 2.08 ± 0.85, P < 0.01) but increased the apoptosis of HSCs (1.07 ± 0.32 vs 4.24 ± 0.86, P < 0.01).

CONCLUSION: The PI3K/Akt signaling pathway may play an important role in CCl₄ induced liver fibrosis. Handan Ganle can suppress this signaling pathway and increase the apoptosis of HSCs, which might be related with its anti-hepatic fibrosis activity.

Heparin-binding epidermal growth factor-like growth factor: a hepatic stellate cell proliferation inducer via ErbB receptors

BACKGROUND AND AIM

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has a proliferative effect on several types of cells. However, the role of HB-EGF on hepatic stellate cells (HSCs) is not clear. The present study is to investigate the regulatory effects of HB-EGF on HSC proliferation and apoptosis.

METHODS

Activated primary rat HSCs and two HSC cell lines (human LX2 and rat T6) were used in this study. Four inhibitors (CRM197 to HB-EGF, AG1478 to epidermal growth factor receptor [EGFR], PD98059 to mitogen-activated kinase, and LY294002 to phosphatidylinositol 3-kinase) were employed to verify the pathway of HB-EGF on cell proliferation and apoptosis.

RESULTS

HB-EGF expression was significantly increased in activated HSCs. HB-EGF increased the expressions of phospho-EGFR and ErbB4 receptors, the phosphorylation of extracellular signal-regulated kinase (ERK) and Akt. Consequently, HB-EGF stimulated HSC proliferation and suppressed HSC apoptosis. Each individual inhibitor specifically inhibited the correlated receptor or enzyme and inhibited HSC proliferation and induced its apoptosis.

CONCLUSIONS

HB-EGF promotes HSC proliferation via activation of the EGFR and ErbB4 receptors and, subsequently, via activation of ERK and Akt. Any blockage in the chain obstructs the flow from HB-EGF to HSC proliferation. Therefore, HB-EGF is a potential therapeutic target in liver fibrosis.

microRNA-222 modulates liver fibrosis in a murine model of biliary atresia

microRNA-222 (miR-222) has been shown to initiate the activation of hepatic stellate cells, which plays an important role in the pathogenesis of liver fibrosis. The aim of our study was to evaluate the role of miR-22 in a mouse model of biliary atresia (BA) induced by Rhesus Rotavirus (RRV) infection. New-born Balb/c mice were randomized into control and RRV infected groups. The extrahepatic bile ducts were evaluated. The experimental group was divided into BA group and negative group based on histology. The expression of miR-222, protein phosphatase 2 regulatory subunit B alpha (PPP2R2A), proliferating cell nuclear antigen (PCNA) and phospho-Akt were detected. We found that the experimental group showed signs of cholestasis, retardation and extrahepatic biliary atresia. No abnormalities were found in the control group. In the BA group, miR-222, PCNA and Akt were highly expressed, and PPP2R2A expression was significantly inhibited. Our findings suggest that miR-222 profoundly modulated the process of fibrosis in the murine BA model, which might represent a potential target for improving BA prognosis.

Rapamycin ameliorates inflammation and fibrosis in the early phase of cirrhotic portal hypertension in rats through inhibition of mTORC1 but not mTORC2

Objective

Hepatic stellate cells (HSCs) transdifferentiation and subsequent inflammation are important pathological processes involved in the formation of cirrhotic portal hypertension. This study characterizes the pathogenetic mechanisms leading to cholestatic liver fibrosis and portal hypertension, and focuses on mammalian target of rapamycin (mTOR) pathway as a potential modulator in the early phase of cirrhotic portal hypertension.

Methods

Early cirrhotic portal hypertension was induced by bile duct ligation (BDL) for three weeks. One week after operation, sham-operated (SHAM) and BDL rats received rapamycin (2 mg/kg/day) by intraperitoneal injection for fourteen days. Vehicle-treated SHAM and BDL rats served as controls. Fibrosis, inflammation, and portal pressure were evaluated by histology, morphometry, and hemodynamics. Expressions of pro-fibrogenic and pro-inflammatory genes in liver were measured by RT-PCR; alpha smooth muscle actin (α-SMA) and antigen Ki67 were detected by immunohistochemistry; expressions of AKT/mTOR signaling molecules, extracellular-signal-regulated kinase 1/2 (ERK1/2), p-ERK1/2, and interleukin-1 beta (IL-1β) were assessed by western blot.

Results

The AKT/mTOR signaling pathway was markedly activated in the early phase of cirrhotic portal hypertension induced by BDL in rats. mTOR blockade by rapamycin profoundly improved liver function by limiting inflammation, fibrosis and portal pressure. Rapamycin significantly inhibited the expressions of phosphorylated 70KD ribosomal protein S6 kinase (p-P70S6K) and phosphorylated ribosomal protein S6 (p-S6) but not p-AKT Ser473 relative to their total proteins in BDL-Ra rats. Those results suggested that mTOR Complex 1 (mTORC1) rather than mTORC2 was inhibited by rapamycin. Interestingly, we also found that the level of p-ERK1/2 to ERK1/2 was significantly increased in BDL rats, which was little affected by rapamycin.

Conclusions

The AKT/mTOR signaling pathway played an important role in the early phase of cirrhotic portal hypertension in rats, which could be a potential target for therapeutic intervention in the early phase of such pathophysiological progress.

Effects of Ganfukang on expression of connective tissue growth factor and focal adhesion kinase/protein kinase B signal pathway in hepatic fibrosis rats

OBJECTIVE

To investigate the effect of Ganfukang (GFK) on connective tissue growth factor (CTGF) and focal adhesion kinase (FAK)/protein kinase B (PKB or Akt) signal pathway in a hepatic fibrosis rat model and to explore the underlying therapeutic molecular mechanisms of GFK.

METHODS

Fifty SD rats were randomly divided into five groups as follows: the control group, the model group (repeated subcutaneous injection of CCl4), and the three GFK treatment groups (31.25, 312.5, and 3125 mg/kg, intragastric administration). Reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemistry were used to examine the expression of CTGF, integrin α5, integrin β1, FAK/Akt signal pathway, cyclinD1, and collagen in the different-treated rats.

RESULTS

GFK attenuated the up-regulation of CTGF, integrin α5, and integrin β1 in hepatic fibrosis rats and suppressed both the phosphorylation of FAK and the phosphorylation of Akt simultaneously (P<0.01). At the same time, the expression of cyclinD1, collagen I, and collagen III was decreased by GFK significantly (P<0.01).

CONCLUSIONS

CTGF and FAK/Akt signal pathway were activated in the CCl4-induced hepatic fibrosis rats, which contribute to increased expression of cyclinD1 and collagen genes. The mechanisms of the anti-fibrosis activity of GFK may be due to its effects against CTGF and FAk/Akt signal pathway.

Correlation between PDGFs and their receptor and liver fibrosis

Liver fibrosis occurs as a result of various injurious processes and is the common pathologic basis for all chronic hepatic diseases. Platelet-derived growth factors (PDGFs) are homodimers or heterodimers consisting of two polypeptide chains. Previous studies have proved that PDGFs are closely related to the occurrence and development of liver fibrosis. In this article, we review the advances in research on the role of PDGFs and their receptor in pathogenesis and therapy of liver fibrosis.

NOX-mediated MAPK and PI3K/Akt signaling pathways and liver fibrosis

Hepatic satellite cells (HSCs) are the main cell type involved in the development of liver fibrosis and have been recognized as the important cellular source of extracellular matrix (ECM). NADPH oxidase (NOX) catalyzes the generation of reactive oxygen species (ROS), regulates signal transduction in HSCs, and thereby plays a key role in the pathogenesis of hepatic fibrosis. ROS generated by NOX promotes proliferation and inhibits apoptosis of HSCs by activation of mitogen-activated protein kinase and phosphatidylinositol-3 kinase/Akt signaling pathways, thus contributing to the development of liver fibrosis. Inhibition of NOX activation to generate ROS and NOX-mediated signal transduction induces HSC apoptosis. Therefore, drugs that target specific NOX can be expected to be useful in arresting the progression of liver fibrosis.

Pentoxifylline inhibits hepatic stellate cells proliferation via the Raf/ERK pathway

Pentoxifylline (PTX), which is a xanthine derivative, is a well-known suppressor of tumor necrosis factor-alpha (TNF-alpha) production in inflammatory cells and has also been shown to inhibit collagen synthesis in hepatic stellate cells (HSCs) in vitro. The present study aimed to evaluate the effects of PTX on proliferation in HSCs as mediated by the Raf/MEK/extracellular-signal-regulated kinase (ERK) signaling pathway. The rat hepatic stellate cell line T6 and activated primary rat HSCs were used in this study. The proliferation rate of the cells treated with 1 mM PTX significantly decreased compared with that of the control in T6 cells (78.3 ± 6.03% at 12 h, 61.0 ± 7.55% at 24 h, and 44.7 ± 2.08% at 48 h, p < 0.05). PTX (1 mM) also decreased the fraction of the HSC population in the S and G2/M-phases of the cell cycle in primary activated rat HSCs. The Raf-1 inhibitor GW5074 and the ERK inhibitor U0126 had inhibitory effects that were similar to those of PTX on HSC proliferation. In addition, PTX inhibited the phosphorylation of Raf-1 (p-Raf-1) and ERK (p-ERK) in a dose- and time-dependent manner in HSCs. These data provide evidence that PTX suppresses HSC proliferation via the Raf/MEK/ERK pathway.

Indoor air pollution from biomass burning activates Akt in airway cells and peripheral blood lymphocytes: a study among premenopausal women in rural India

Biomass burning is a major source of indoor air pollution in rural India. The authors investigated in this study whether cumulative exposures to biomass smoke cause activation of the serine/threonine kinase Akt in airway cells and peripheral blood lymphocytes (PBL). For this, the authors enrolled 87 premenopausal (median age 34 years), nonsmoking women who used to cook with biomass (wood, dung, crop wastes) and 85 age-matched control women who cooked with cleaner fuel liquefied petroleum gas. Immunocytochemical and immunoblotting assays revealed significantly higher levels of phosphorylated forms of Akt protein (p-Akt(ser473) and p-Akt(thr308)) in PBL, airway epithelial cells, alveolar macrophages, and neutrophils in sputum of biomass-using women than control. Akt activation in biomass users was associated with marked rise in generation of reactive oxygen species and concomitant depletion of superoxide dismutase. Measurement of particulate matter having a diameter of less than 10 and 2.5 µm in indoor air by real-time aerosol monitor showed 2 to 4 times more particulate pollution in biomass-using households, and Akt activation was positively associated with particulate pollution after controlling potential confounders. The findings suggest that chronic exposure to biomass smoke activates Akt, possibly via generation of oxidative stress.

New insights into the antifibrotic effects of sorafenib on hepatic stellate cells and liver fibrosis

BACKGROUND & AIMS

During the process of liver fibrosis, hepatic stellate cells (HSCs) play a critical role in the excessive production of extracellular matrix (ECM). We evaluated the therapeutic effects of sorafenib, a multiple receptor tyrosine kinase inhibitor, targeting platelet-derived growth factor (PDGF) receptor and the Raf/extracellular-signal-regulated kinase (ERK) signaling pathway, on liver fibrosis and HSC proliferation.

METHODS

The in vivo effects of sorafenib were monitored in the livers of rats with liver fibrosis, and simultaneously proliferation assays, apoptosis induction studies, and collagen synthesis measurement were conducted in vitro in rat and human HSCs and primary HSCs.

RESULTS

Sorafenib treatment attenuated liver fibrosis and was associated with a significant decrease in intrahepatic fibrogenesis, hydroxyproline accumulation and collagen deposition. Sorafenib reduced HSC proliferation and resulted in significantly higher levels of apoptosis. Moreover, sorafenib downregulated Cyclin D1 and Cyclin-dependent kinase 4 (Cdk-4), simultaneously increased expression of Fas, Fas-L, and Caspase-3, and decreased the ratio of Bcl-2 to Bax. Sorafenib treatment increased the ratio of matrix metalloproteinases (MMPs) to tissue inhibitor of matrix metalloproteinases (TIMPs) and reduced collagen synthesis in HSCs. Sorafenib inhibited the phosphorylation of ERK, Akt and 70-kDa ribosomal S6 kinase (p70S6K), both in vitro and in vivo.

CONCLUSIONS

Sorafenib induces the suppression of collagen accumulation and HSC growth warranting the use of sorafenib as a potential therapeutic agent in the treatment of liver fibrosis.

Proanthocyanidin derived from the leaves of Vaccinium virgatum suppresses platelet-derived growth factor-induced proliferation of the human hepatic stellate cell line LI90

AIM

Hepatic stellate cell (HSC) proliferation plays a pivotal role in liver fibrogenesis, and agents that suppress HSC activation, including platelet-derived growth factor (PDGF)-induced HSC proliferation, are good candidates for antifibrogenic therapies. In this report, we use the LI90 HSC line to elucidate the antifibrogenic effects of proanthocyanidin derived from the leaves of Vaccinium virgatum.

METHODS

Proanthocyanidin (PAC) was extracted from the leaves of blueberry V. virgatum (BB-PAC), grape seeds (GS-PAC) and Croton lechleri (CL-PAC). These extracts were examined for their effects on PDGF-BB-induced LI90 cell proliferation and DNA synthesis. Extracellular signal-regulated kinase (ERK) and Akt phosphorylation and PDGF receptor-beta (PDGFR-beta) expression were evaluated by western blot analysis.

RESULTS

BB-PAC potently suppressed PDGF-BB-induced proliferation and DNA synthesis of LI90 cells. BB-PAC also suppressed PDGF-BB-induced DNA synthesis in primary cultured rat HSC. Moreover, GS-PAC and CL-PAC suppressed PDGF-BB-induced DNA synthesis in LI90 cells. In contrast, the monomeric PAC catechin and epicatechin and dimeric PAC procyanidin B2 only slightly suppressed PDGF-BB-induced DNA synthesis. Western blot analysis showed that BB-PAC completely or partially inhibited PDGF-BB-induced ERK and Akt phosphorylation, respectively. In addition, BB-PAC partially inhibited the PDGF-BB-induced degradation of PDGFR-beta.

CONCLUSION

Our results suggest that BB-PAC suppresses activated HSC by inhibiting the PDGF signaling pathway. In addition, these results provide novel findings that may facilitate the development of antifibrogenic agents.