Ligustrazine attenuates oxidative stress-induced activation of hepatic stellate cells by interrupting platelet-derived growth factor-β receptor-mediated ERK and p38 pathways. Toxicol Appl Pharmacol. 2012;265:51-60. [PMID: 23022513 DOI: 10.1016/j.taap.2012.09.016]

Research progress of prodrugs for the treatment of cerebral ischemia

It is well-known that pharmacotherapy plays a pivotal role in the treatment and prevention of cerebral ischemia. Nevertheless, existing drugs, including numerous natural products, encounter various challenges when applied in cerebral ischemia treatment. These challenges comprise poor brain absorption due to low blood-brain barrier (BBB) permeability, limited water solubility, inadequate bioavailability, poor stability, and rapid metabolism. To address these issues, researchers have turned to prodrug strategies, aiming to mitigate or eliminate the adverse properties of parent drug molecules. In vivo metabolism or enzymatic reactions convert prodrugs into active parent drugs, thereby augmenting BBB permeability, improving bioavailability and stability, and reducing toxicity to normal tissues, ultimately aiming to enhance treatment efficacy and safety. This comprehensive review delves into multiple effective prodrug strategies, providing a detailed description of representative prodrugs developed over the past two decades. It underscores the potential of prodrug approaches to improve the therapeutic outcomes of currently available drugs for cerebral ischemia. The publication of this review serves to enrich current research progress on prodrug strategies for the treatment and prevention of cerebral ischemia. Furthermore, it seeks to offer valuable insights for pharmaceutical chemists in this field, offer guidance for the development of drugs for cerebral ischemia, and provide patients with safer and more effective drug treatment options.

Traditional Chinese medicine inspired dual-drugs loaded inhalable nano-therapeutics alleviated idiopathic pulmonary fibrosis by targeting early inflammation and late fibrosis

Idiopathic pulmonary fibrosis (IPF) is a highly debilitating and fatal chronic lung disease that is difficult to cure clinically. IPF is characterized by a gradual decline in lung function, which leads to respiratory failure and severely affects patient quality of life and survival. Oxidative stress and chronic inflammation are believed to be important pathological mechanisms underlying the onset and progression of IPF, and the vicious cycle of NOX4-derived ROS, NLRP3 inflammasome activation, and p38 MAPK in pulmonary fibrogenesis explains the ineffectiveness of single-target or single-drug interventions. In this study, we combined astragaloside IV (AS-IV) and ligustrazine (LIG) based on the fundamental theory of traditional Chinese medicine (TCM) of "tonifying qi and activating blood" and loaded these drugs onto nanoparticles (AS_LIG@PPGC NPs) that were inhalable and could penetrate the mucosal barrier. Our results suggested that inhalation of AS_LIG@PPGC NPs significantly improved bleomycin-induced lung injury and fibrosis by regulating the NOX4-ROS-p38 MAPK and NOX4-NLRP3 pathways to treat and prevent IPF. This study not only demonstrated the superiority, feasibility, and safety of inhalation therapy for IPF intervention but also confirmed that breaking the vicious cycle of ROS and the NLRP3 inflammasome is a promising strategy for the successful treatment of IPF. Moreover, this successful nanoplatform is a good example of the integration of TCM and modern medicine.

Blueberry and cranberry extracts mitigate CCL4-induced liver damage, suppressing liver fibrosis, inflammation and oxidative stress

The current study aims to evaluate potential hepatoprotective effect of lingonberry, cranberry and blueberry polyphenols on carbon tetrachloride (CCL-4)-induced acute and subacute liver injury in rats. A total of 55 male Wistar rats, divided into six experimental and control groups. With the exception of the negative control group, all groups received an intraperitoneal injection of CCl-4, twice a week for 14 days. An extract of lingonberry, cranberry, blueberry polyphenols and the positive control, silymarin were administered daily via intragastric route, for 14 consecutive days. The untreated control group showed characteristic of classical oxidative stress-mediated liver damage with vacuolization of the hepatocyte cytoplasm, infiltration by immune cells and proliferation of collagen fibers, decrease in body weight and increase in liver weight; increased levels of AST and ALT in serum, an increased lipid peroxidation in the liver. However, the use of cranberry and blueberry polyphenols significantly suppressed liver damage, exerting an effect comparable to the hepatoprotective effect of the positive control. The extracts prevented and reduced inflammatory liver damage by reducing IL-6, TNF-α and IFN-γ levels. In conclusion, blueberry and cranberry extracts have a protective effect against acute and subacute CCl4-induced hepatotoxicity in rats.

Anti-liver fibrosis activity of curcumin/chitosan-coated green silver nanoparticles

Liver fibrosis results from the hepatic accumulation of the extracellular matrix accompanied by a failure of the mechanisms responsible for matrix dissolution. Pathogenesis of liver fibrosis is associated with many proteins from different cell types. In the present study, in silico molecular docking analysis revealed that curcumin may inhibit the fibrosis-mediating proteins PDGF, PDGFRB, TIMP-1, and TLR-9 by direct binding. Nano-formulation can overcome curcumin problems, increasing the efficacy of curcumin as a drug by maximizing its solubility and bioavailability, enhancing its membrane permeability, and improving its pharmacokinetics, pharmacodynamics and biodistribution. Therefore, green silver nanoparticles (AgNPs) were synthesized in the presence of sunlight by means of the metabolite of Streptomyces malachiticus, and coated with curcumin-chitosan mixture to serve as a drug delivery tool for curcumin to target CCl4-induced liver fibrosis mouse model. Fibrosis induction significantly increased hepatic gene expression of COL1A1, α-SMA, PDGFRB, and TIMP1, elevated hepatic enzymes, increased histopathological findings, and increased collagen deposition as determined by Mason's trichrome staining. Treatment with naked AgNPs tended to increase these inflammatory effects, while their coating with chitosan, similar to treatment with curcumin only, did not prevent the fibrogenic effect of CCl4. The induction of liver fibrosis was reversed by concurrent treatment with curcumin/chitosan-coated AgNPs. In this nano form, curcumin was found to be efficient as anti-liver fibrosis drug, maintaining the hepatic architecture and function during fibrosis development. This efficacy can be attributed to its inhibitory role through a direct binding to fibrosis-mediating proteins such as PDGFRB, TIMP-1, TLR-9 and TGF-β.

Pathogenesis of Liver Fibrosis and Its TCM Therapeutic Perspectives

Liver fibrosis is a pathological process of abnormal tissue proliferation in the liver caused by various pathogenic factors, which will further develop into cirrhosis or even hepatocellular carcinoma if liver injury is not intervened in time. As a diffuse progressive liver disease, its clinical manifestations are mostly excessive deposition of collagen-rich extracellular matrix resulting in scar formation due to liver injury. Hepatic fibrosis can be caused by hepatitis B and C, fatty liver, alcohol, and rare diseases such as hemochromatosis. As the metabolic center of the body, the liver regulates various vital activities. During the development of fibrosis, it is influenced by many other factors in addition to the central event of hepatic stellate cell activation. Currently, with the increasing understanding of TCM, the advantages of TCM with multiple components, pathways, and targets have been demonstrated. In this review, we will describe the factors influencing liver fibrosis, focusing on the effects of cells, intestinal flora, iron death, signaling pathways, autophagy and angiogenesis on liver fibrosis, and the therapeutic effects of herbal medicine on liver fibrosis.

In situ synthesis and unidirectional insertion of membrane proteins in liposome-immobilized silica stationary phase for rapid preparation of microaffinity chromatography

Cell membrane affinity chromatography has been widely applied in membrane protein (MP)-targeted drug screening and interaction analysis. However, in current methods, the MP sources are derived from cell lines or recombinant protein expression, which are time-consuming for cell culture or purification, and also difficult to ensure the purity and consistent orientation of MPs in the chromatographic stationary phase. In this study, a novel in situ synthesis membrane protein affinity chromatography (iSMAC) method was developed utilizing cell-free protein expression (CFE) and covalent immobilized affinity chromatography, which achieved efficient in situ synthesis and unidirectional insertion of MPs into liposomes in the stationary phase. The advantages of iSMAC are: 1) There is no need to culture cells or prepare recombinant proteins; 2) Specific and purified MPs with stable and controllable content can be obtained within 2 h; 3) MPs maintain the transmembrane structure and a consistent orientation in the chromatographic stationary phase; 4) The flexible and personalized construction of cDNAs makes it possible to analyze drug binding sites. iSMAC was successfully applied to screen PDGFRβ inhibitors from Salvia miltiorrhiza and Schisandra chinensis. Micro columns prepared by in-situ synthesis maintain satisfactory analysis activity within 72 h. Two new PDGFRβ inhibitors, salvianolic acid B and gomisin D, were screened out with K_D values of 13.44 and 7.39 μmol/L, respectively. In vitro experiments confirmed that the two compounds decreased α-SMA and collagen Ӏ mRNA levels raised by TGF-β in HSC-T6 cells through regulating the phosphorylation of p38, AKT and ERK. In vivo, Sal B could also attenuate CCl₄-induced liver fibrosis by downregulating PDGFRβ downstream related protein levels. The iSMAC method can be applied to other general MPs, and provides a practical approach for the rapid preparation of MP-immobilized or other biological solid-phase materials.

Activation of spinal PDGFRβ in microglia promotes neuronal autophagy via p38 MAPK pathway in morphine-tolerant rats

The adverse side effects of opioids, especially antinociceptive tolerance, limit their clinical application. A recent study reported that platelet-derived growth factor receptor β (PDGFRβ) blockage selectively inhibited morphine tolerance. Autophagy has been reported to contribute to the cellular and behavioral responses to morphine. However, little is known about the relationship between PDGFRβ and autophagy in the mechanisms of morphine tolerance. In this study, rats were intrathecally administered with morphine twice daily for 7 days to induce antinociceptive tolerance, which was evaluated using a tail-flick latency test. By administration autophagy inhibitor 3-Methyladenine, PDGFRβ inhibitor imatinib, p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 hydrochloride and minocycline hydrochloride, western blot, immunofluorescence, and transmission electron microscopy techniques were used to elucidate the roles of PDGFRβ, autophagy, and related signaling pathways in morphine tolerance. This study demonstrated for the first time that spinal PDGFRβ in microglia promotes autophagy in gamma-aminobutyric acid (GABA) interneurons through activating p38 MAPK pathway during the development of morphine tolerance, which suggest a potential strategy for preventing the development of morphine tolerance clinically, thereby improving the use of opioids in pain management.

A Newly-Synthesized Chalcone Derivative of Ligustrazine Induces Caspase-Dependent and Apoptosis-Inducing Factor-Dependent Apoptosis in Cochlear Hair Cells

Objective: A newly synthesized derivative of ligustrazine chalcone, named as Z11, has shown a variety of promising biological activities. Here we aim to explore the effects of Z11 on the cochlear hair cells (HCs). Methods: Immunostaining and transmission electron microscopy (TEM) were used to examine the survival of HCs and their morphological changes. Furthermore, apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and the mRNA expression of apoptosis related genes including Caspase-9, Caspase-3, Bcl-2, Bax and Apaf1 were measured by RT-PCR. In addition, the protein expression of cleaved-Caspas-3 and cleaved-Caspase-9 were analyzed by Western blot respectively, and the protein expressionof AIF and cleaved-Caspase-3 were assessed by immunofluorescence as well. Results: Immunostaining showed that Z11 was ototoxic to mouse cochlear hair cells and significantly triggered cell death in a concentration-, time- and location-dependent manner. TUNEL assays evidenced that Z11 exerts its cytotoxicity through induction of apoptosis of cochlear hair cells in vitro. Immunofluorescence and western blot assay showed that Z11 activated the translation of apoptosis-inducing factor (AIF) and Caspase-9/Caspase-3 dependent apoptotic pathway in cochlear hair cells (HCs). Conclusion:These findings suggest that Z11 exhibits its ototoxicity through inducing apoptosis of HCs via both Caspase-dependent and AIF translocation pathways in mouse cochlear cultures.

A comprehensive review of natural products to fight liver fibrosis: Alkaloids, terpenoids, glycosides, coumarins and other compounds

The discovery of drugs to treat liver fibrosis has long been a challenge over the past decades due to its complicated pathogenesis. As a primary approach for drug development, natural products account for 30% of clinical drugs used for disease treatment. Therefore, natural products are increasingly important for their medicinal value in liver fibrosis therapy. In this part of the review, special focus is placed on the effect and mechanism of natural compounds, including alkaloids, terpenoids, glycosides, coumarins and others. A total of 36 kinds of natural compounds demonstrate significant antifibrotic effects in various liver fibrosis models in vivo and in hepatic stellate cells (HSCs) in vitro. Revealing the mechanism will provide further basis for clinical conversion, as well as accelerate drug discovery. The mechanism was further summarized with the finding of network regulation by several natural products, such as oxymatrine, paeoniflorin, ginsenoside Rg1 and taurine. Moreover, there are still improvements needed in investigating clinical efficacy, determining mechanisms, and combining applications, as well as semisynthesis and modification. Therefore, natural products area promising resource for agents that protect against liver fibrosis.

Oxidative Stress in Chronic Liver Disease and Portal Hypertension: Potential of DHA as Nutraceutical

Chronic liver disease constitutes a growing public health issue worldwide, with no safe and effective enough treatment clinical scenarios. The present review provides an overview of the current knowledge regarding advanced chronic liver disease (ACLD), focusing on the major contributors of its pathophysiology: inflammation, oxidative stress, fibrosis and portal hypertension. We present the benefits of supplementation with docosahexaenoic acid triglycerides (TG-DHA) in other health areas as demonstrated experimentally, and explore its potential as a novel nutraceutical approach for the treatment of ACLD and portal hypertension based on published pre-clinical data.

Study on the relationship between hepatic fibrosis and epithelial-mesenchymal transition in intrahepatic cells

Hepatic fibrosis is a pathophysiological process, which causes excessive extracellular matrix (ECM) deposition resulting from persistent liver damage. Myofibroblasts are the core cells that produce ECM. It is known that epithelial-mesenchymal transition (EMT) is not a simple transition of cells from the epithelial to mesenchymal state. Instead, it is a process, in which epithelial cells temporarily lose cell polarity, transform into interstitial cell-like morphology, and acquire migration ability. Hepatocytes, hepatic stellate cells, and bile duct cells are the types of intrahepatic cells found in the liver. They can be transformed into myofibroblasts via EMT and play important roles in the development of hepatic fibrosis through a maze of regulations involving various pathways. The aim of the present study is to explore the relationship between the relevant regulatory factors and the EMT signaling pathways in the various intrahepatic cells.

Prevention of neointimal formation after angioplasty using tetramethylpyrazine-coated balloon catheters in a rabbit iliac artery model

Background

Restenosis remains a clinical problem; drug-coated balloons (DCBs) have demonstrated high efficiency in this situation. DCBs prevent neointimal hyperplasia by inhibiting cell proliferation and migration. Tetramethylpyrazine (TMP) is a traditional Chinese medicine originally isolated from the rhizome of Ligusticum Walliichii, which can inhibit platelet aggregation and smooth muscle cell proliferation. We hypothesized that TMP-coated balloons (TCB) could reduce neointimal hyperplasia through the NF-κB signalling pathway.

Methods

Twenty-one New-Zealand White rabbits (2.5-3.0 kg, male) were fed high-fat diets; 36 bilateral iliac artery stenosis models were successfully established by balloon straining. Rabbits were randomly treated with TCB (n=20) or plain balloons (PBA, n=16) (3 died during model construction). Angiographies were recorded at baseline, the immediate period, and 4 weeks later. Animals were euthanized and arteries collected for histological analysis and immunohistochemical staining. Protein expression of proliferating cell nuclear antigen (PCNA) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 of the vessel samples were analyzed using Western blotting.

Results

No difference existed in the baseline lesion characteristics or procedural results. Angiographic follow-up was successfully performed on 18 rabbits (TCB: n=20, PBA: n=16), except for 3 deaths related to the operation. Treatment with TCB was superior to that with PBA, with lower late lumen loss (0.45±0.23 vs. 0.84±0.17 mm, P<0.01). Pathological analysis confirmed the efficiency of TCB through decreasing the area stenosis rate compared with PBA (46.48%±8.22% vs. 75.24%±6.10%, P<0.01). As determined by Western blotting, significant reductions occurred in PCNA and NF-κB p65 protein intensity in the TCB group versus the PBA group (all P<0.01). TCB efficiently mitigated restenosis in the rabbit iliac artery model.

Conclusions

This study elucidated that TCB could restrain intimal hyperplasia of vessels by inhibiting the activation of the NF-κB pathway to reduce inflammatory response and decrease the rate of cell proliferation through suppressing PCNA expression.

Rosmarinic Acid Ameliorates H2O2-Induced Oxidative Stress in L02 Cells Through MAPK and Nrf2 Pathways

Liver cells are easily damaged by oxidative stress during progression both in liver development and throughout adult life, resulting in tissue pathology that ranges from simple hepatitis to nonalcoholic fatty liver disease. In this study, we determined the attenuation of oxidative stress in liver cells with pretreatment of rosmarinic acid (RA), which is an antioxidant agent from Rosmarinus officinalis. The human liver cell line L02 was damaged by hydrogen peroxide (H2O2). In the RA treatment group, the viability of L02 cells increased and the intracellular reactive oxygen species levels decreased compared with the H2O2-induced damage group. Analysis of flow cytometry revealed that the percentage of G2/M cell cycle arrest and cell apoptosis decreased in the RA treatment group. This alteration was associated with activation of a G2/M DNA damage and oxidative stress apoptotic signal. Furthermore, we determined the redox-sensitive protein expression of mitogen-activated protein kinases (MAPKs), quinone acceptor oxidoreductase 1 (NQO1), and nuclear factor E2-related factor 2 (Nrf2), and the expression of both MAPKs and Nrf2 was activated in the RA group. Results showed that the relevant protein expression of MAPKs and Nrf2 was activated in the RA group. Thus, RA protected L02 cells from oxidative damage through suppressing cell cycle arrest and cell apoptosis with the activation of MAPK and Nrf2 signaling pathways.

p66Shc Contributes to Liver Fibrosis through the Regulation of Mitochondrial Reactive Oxygen Species

Background: p66Shc is a redox enzyme that mediates mitochondrial reactive oxygen species (ROS) generation. p66Shc inhibition confers protection against liver injury, however, its functional contribution to liver fibrosis remains unclear. The aim of this study is to explore the involvement of p66Shc in liver fibrosis and underlying mechanism of p66Shc by focusing on mitochondrial ROS. Methods: p66Shc-silenced mice were injected with carbon tetrachloride (CCl₄). Primary hepatic stellate cells (HSCs) were performed with p66Shc silencing or overexpression prior to TGF-β1 stimulation. Results: p66Shc expression was progressively elevated in mice with CCl₄-induced liver fibrosis, and p66Shc silencing in vivo significantly attenuated fibrosis development, reducing liver damage, oxidative stress and HSC activation, indicated by the decreased α-SMA, CTGF and TIMP1 levels. Furthermore, in primary HSCs, p66Shc-mediated mitochondrial ROS production played a vital role in mitochondrial morphology and cellular metabolism. Knockdown of p66Shc significantly inhibited mitochondrial ROS production and NOD-like receptor protein 3 (NLRP3) inflammasome activation, which were closely associated with HSC activation, indicated by the decreased α-SMA, CTGF and TIMP1 levels. However, p66Shc overexpression exerted the opposite effects, which were suppressed by a specific mitochondrial ROS scavenger (mito-TEMPO). More importantly, p66Shc expression was significantly increased in human with liver fibrosis, accompanied by NLRP3 inflammasome activation. Conclusions: p66Shc is a key regulator of liver fibrosis by mediating mitochondrial ROS production, which triggers NLRP3 inflammasome activation.

Signaling pathways involved in p38-ERK and inflammatory factors mediated the anti-fibrosis effect of AD-2 on thioacetamide-induced liver injury in mice

Ginseng is a type of medicinal and edible homologous plant that is very common in medicine, food and even cosmetics.

Ligustrazine inhibits platelet activation via suppression of the Akt pathway

Aberrant activation of platelets has a critical role in thrombotic vascular events, including atherosclerosis, arterial thrombosis and myocardial infarction. The process of platelet activation is associated with multiple intracellular signaling pathways, including the phosphoinositide 3‑kinase/AKT serine/threonine kinase (Akt) pathway. The well‑known medicinal herb Rhizoma Ligusticum Wallichii (RLW) has long been used in China to clinically treat various cardiovascular disorders. As the most pharmacologically active component of RLW, ligustrazine has been demonstrated to possess a potent antiplatelet activity. However, the precise mechanisms mediating the bioactivities of ligustrazine have not been thoroughly elucidated. The present study evaluated the effects of ligustrazine hydrochloride (LH; the clinical‑grade form of ligustrazine) on platelet activation and investigated the underlying molecular mechanisms. In vitro and ex vivo platelet activation models were used, established by stimulating rat platelet‑rich plasma either with the platelet activator adenosine diphosphate (ADP) or with the specific Akt pathway activator insulin‑like growth factor‑1 (IGF‑1). The results demonstrated that treatment with LH significantly and dose‑dependently inhibited ADP‑induced platelet aggregation, in addition to thromboxane A2 (TXA2) secretion and intracellular Ca2+ mobilization in platelets, in vitro and ex vivo. In addition, LH markedly suppressed ADP‑induced Akt phosphorylation in vitro and ex vivo. Furthermore, LH markedly inhibited IGF‑1‑induced Akt phosphorylation, platelet aggregation, TXA2 formation and Ca2+ mobilization in vitro. Finally, LH was able to reverse adrenaline‑induced shortening of bleeding time. Taken together, these results suggested that ligustrazine possesses a broad range of antiplatelet activities without apparent hemorrhagic side-effects, and suppression of Akt signaling may be one of the mechanisms by which ligustrazine exerts its antiplatelet activities.

Recent progress in the structural modification and pharmacological activities of ligustrazine derivatives

Ligustrazine is a main active fraction of the traditional medicine known as Ligusticum chuanxiong hort, which has been used as clinical medication for cerebral thrombosis, coronary heart disease and stenocardia recently. The rapid metabolism and short half-life of ligustrazine seriously limits its application in clinical practice. Therefore, derivatives of ligustrazine are designed and synthesized in our and other labs, including piperazine, cinnamic acid, styrene, acylguanidine, amides, curcumin and triterpenes derivatives of ligustrazine. Most of these compounds present better pharmacodynamics activities and more favorable pharmacokinetic properties compared to the parent compound. Besides, some new biological activities of these compounds are discovered. Hence, this review continues the previous review of our group as well as aims to highlight recent prominent advances in this field in the past ten years.

Magnesium isoglycyrrhizinate promotes the activated hepatic stellate cells apoptosis via endoplasmic reticulum stress and ameliorates fibrogenesis in vitro and in vivo

Varied pathogenetic elements have been touched upon the liver fibrosis, including inflammatory, stress, apoptosis and unfolded proteins aggregation. Magnesium Isoglycyrrhizinate (MgIG) has been accepted to be a neuroprotective effect, hepatoprotective and anti-inflammatory molecule. In our vitro researches, MgIG was considered to activate hepatic stellate cells (HSCs) apoptosis by promoting endoplasmic reticulum stress (ERS) detrimental response to a certain extent. Consequently, MgIG showed its potential therapeutic capacity in fibrogenesis and counteracted the pathogenetic aspects, which were involved in integrating current treatments correcting liver fibrosis. In addition, we further verificated the behavior and pathogenic mechanisms in the CCl₄ -induced liver fibrosis in male mice. What surprised us was that with the treatment of MgIG caused the activation of ERS and resisted the activated HSCs in the protective effects on liver damage. We found MgIG significantly promoted the apoptosis of activated HSCs and protected the CCl₄ -induced liver fibrosis. Main molecules came down to the unfolded protein response signaling pathway. Furthermore, MgIG inhibited the levels of the downstream inflammatory cytokines, which were triggered by CCl₄ -induced liver fibrosis. Here, we reported that MgIG improved behavioral impairments induced by intraperitoneal injection of CCl₄ and decreased the expression of proinflammatory factor, which indicated the preserving effects on liver fibrosis. © 2017 BioFactors, 43(6):836-846, 2017.

Oroxylin A prevents angiogenesis of LSECs in liver fibrosis via inhibition of YAP/HIF-1α signaling

Angiogenesis of liver sinusoidal endothelial cells (LSECs) accompanies with hypoxia in liver fibrosis and they are of mutual promotion, which has raised wide concern. Here we established murine model of liver fibrosis and found that oroxylin A (40 mg/kg) could ameliorate angiogenesis in liver fibrosis may related to hypoxia inducible factor 1α (HIF-1α). The underlying mechanism was further investigated by isolating and culturing murine primary LSECs. Hypoxia induced vascular endothelial growth factor A (VEGF-A), angiopoietin 2 (Ang-2), and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) elevated in LSECs were reduced by oroxylin A or acriflavine (ACF, an HIF-1α inhibitor), indicating HIF-1α involved the angiogenesis of LSECs. Additionally, interference with Yes-associated protein (YAP) significant downregulated the protein expression of HIF-1α and VEGF-A, while YAP plasmid exhibited an opposite effect. We next found that oroxylin A inhibited hypoxia-induced nuclear translocation of YAP, which may influence the accumulation of HIF-1α and subsequently decrease transcription of downstream target gene including VEGF-A and Ang-2, thereby exerting an anti-angiogenic activity.

Schisandrin B attenuates CCl4-induced liver fibrosis in rats by regulation of Nrf2-ARE and TGF-β/Smad signaling pathways

Liver fibrosis is a major pathological feature of chronic liver diseases and there is no effective therapy program at present. Schisandrin B (Sch B) is the major bioactive ingredient of Schisandra chinensis, with antioxidative, anti-inflammatory, antitumor, and hepatoprotective properties. This study aimed to investigate the protective effect and related molecular mechanism of Sch B against carbon tetrachloride (CCl₄)-induced liver fibrosis in rats. The in vivo therapeutic effect of Sch B on liver fibrosis induced by CCl₄ was examined in rats. In vitro, rat hepatic stellate cells (HSC-T6) were used to assess the effect of Sch B on the activation of HSCs. Sch B effectively attenuated liver damage and progression of liver fibrosis in rats, as evidenced by improved liver function and decreased collagen deposition. The effects of Sch B were associated with attenuating oxidative stress by activating nuclear factor-erythroid 2-related factor 2 (Nrf2)-mediated antioxidant signaling and suppressing HSC activation by inhibiting the transforming growth factor-β (TGF-β)/Smad signaling pathway. In an in vitro study, it was shown that Sch B inhibited TGF-β-induced HSC activation. Finally, Sch B significantly inhibited TGF-β1-stimulated phosphorylation of Smad and signaling of mitogen-activated protein kinases. This study demonstrates that Sch B prevents the progression of liver fibrosis by the regulation of Nrf2-ARE and TGF-β/Smad signaling pathways, and indicates that Sch B can be used for the treatment of liver fibrosis.

Platelet-Derived Growth Factor Receptor α Contributes to Human Hepatic Stellate Cell Proliferation and Migration

Platelet-derived growth factor receptor α (PDGFRα), a tyrosine kinase receptor, is up-regulated in hepatic stellate cells (HSCs) during chronic liver injury. HSCs mediate hepatic fibrosis through their activation from a quiescent state partially in response to profibrotic growth factors. HSC activation entails enhanced expression of profibrotic genes, increase in proliferation, and increase in motility, which facilitates migration within the hepatic lobule. We show colocalization of PDGFRα in murine carbon tetrachloride, bile duct ligation, and 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine models of chronic liver injury, and investigate the role of PDGFRα on proliferation, profibrotic gene expression, and migration in primary human HSCs (HHSteCs) using the PDGFRα-specific inhibitory monoclonal antibody olaratumab. Although lacking any effects on HHSteC transdifferentiation assessed by gene expression of ACTA2, TGFB1, COL1A1, SYP1, and FN1, olaratumab specifically reduced HHSteC proliferation (AlamarBlue assay) and cell migration (transwell migration assays). Using phospho-specific antibodies, we show that olaratumab attenuates PDGFRα activation in response to PDGF-BB, and reduced phosphorylation of extracellular signal-regulated kinase 1 and 2, Elk-1, p38, Akt, focal adhesion kinase, mechanistic target of rapamycin, C10 regulator of kinase II, and C10 regulator of kinase-like, suggesting that PDGFRα contributes to mitogenesis and actin reorganization through diverse downstream effectors. Our findings support a distinct contribution of PDGFRα signaling to HSC proliferation and migration and provide evidence that inhibition of PDGFRα signaling could alter the pathogenesis of hepatic fibrosis.

肝星状细胞衰老与增殖、凋亡的关系

肝星状细胞(hepatic stellate cells, HSCs)活化、细胞外基质大量形成是肝纤维化发生发展的关键环节. 许多研究发现, 抑制HSCs增殖、促进HSCs凋亡可阻断肝纤维化进程; 同时研究发现, 促进活化HSCs衰老也可为肝纤维化的防治提供新的策略. 本文就HSCs衰老与增殖、凋亡的关系以及在肝纤维化中的作用相关研究进展予以综述.

Stachydrine ameliorates isoproterenol-induced cardiac hypertrophy and fibrosis by suppressing inflammation and oxidative stress through inhibiting NF-κB and JAK/STAT signaling pathways in rats

Cardiac hypertrophy (CH), as one of the major causes of morbidity and mortality in the world, has become an independent and predictive risk factor for adverse cardiovascular events. However, progress in treatment remains sluggish in recent years. Therefore, compounds derived from non-toxic nature plants are urgently needed. Stachydrine (STA), which is isolated from Leonurus, has various activities, including resistance to cardiovascular disease, but little is known about its effect on CH or the mechanisms. We herein investigated the effect of STA on isoproterenol-induced CH and the underlying mechanisms. Treatment with STA significantly increased the ratios of heart weight/body weight, left ventricle weight/body weight and the cross-sectional areas of cardiomyocytes. In addition, STA significantly decreased the mRNA levels of atrial natriuretic peptide, B-type natriuretic peptide and β-myosin heavy chain. Furthermore, isoproterenol-induced fibrosis in rats receiving STA was significant attenuated, as evidenced by decreased ratio of fibrotic area/total area and decreased mRNA levels of collagens I and III. Given down-regulation of interleukin-6, tumor necrosis factor-α, interferon-γ (IFN-γ) and IFN-1β, treatment with STA significantly reversed the expressions of pro-inflammatory induced by isoproterenol. Moreover, STA attenuated the oxidative stress level in serum of isoproterenol-induced CH rats, as shown by increased activity of superoxide dismutase and decreased malondialdehyde level. STA inhibited the expressions of phosphorylated IκBα, NF-κB p65, JAK2 and STAT3 in vivo. Thus, both NF-κB and JAK/STAT signalings played essential roles in mediating the anti-CH effect of STA. Collectively, STA has a potent protective effect on isoproterenol-induced CH, with therapeutic implication for CH.

Aucubin and its hydrolytic derivative attenuate activation of hepatic stellate cells via modulation of TGF-β stimulation

Eucommia ulmoides is an important traditional Chinese medicine and has been used as a tonic with a long history. Aucubin is an active component extracted from Eucommia ulmoides, which has liver-protection effects. However the mechanisms are still unclear. To investigate the inhibitory effects and the underlying mechanisms of aucubin on TGF-β1-induced activation of hepatic stellate cells and ECM deposition, Human hepatic stellate cells (LX-2 cells) were incubated with TGF-β1 to evaluate the anti-fibrotic effect of aucubin. Western blot was used to investigate the expression of α-SMA, Col I, Col III, MMP-2 and TIMP-1. ROS production was monitored using DCFH-DA probe, and NOX4 expression was detected by Real-time PCR. Results indicated that TGF-β1 stimulated the activation and ECM deposition of LX-2 cells. Compared with the control group, aucubin and aucubigenin both reduced the protein expression of α-SMA, Col I, Col III and MMP-2 in LX-2 cells. Aucubin and aucubigenin also suppressed the generation of ROS and down-regulated the NOX4 mRNA expression. Taken together, aucubin and aucubigenin both inhibit the activation and ECM deposition of LX-2 cells activated by TGF-β1. Aucubin and aucubigenin are potential therapeutic candidate drugs for liver fibrosis.

Diallyl Trisulfide Suppresses Oxidative Stress-Induced Activation of Hepatic Stellate Cells through Production of Hydrogen Sulfide

Accumulating data reveal that garlic has beneficial effects against chronic liver disease. We previously reported that diallyl trisulfide (DATS), the primary organosulfur compound in garlic, reduced fibrosis and attenuated oxidative stress in rat fibrotic liver. The present study was aimed at elucidating the underlying mechanisms. The primary rat hepatic stellate cells (HSCs) were cultured and stimulated with hydrogen peroxide (H₂O₂) for inducing HSC activation under oxidative stress. We examined the effects of DATS on the profibrogenic properties and oxidative stress in H₂O₂-treated HSCs. The results showed that DATS suppressed and reduced fibrotic marker expression in HSCs. DATS arrested cell cycle at G2/M checkpoint associated with downregulating cyclin B1 and cyclin-dependent kinase 1, induced caspase-dependent apoptosis, and reduced migration in HSCs. Moreover, intracellular levels of reactive oxygen species and lipid peroxide were decreased by DATS, but intracellular levels of glutathione were increased in HSCs. Furthermore, DATS significantly elevated hydrogen sulfide (H₂S) levels within HSCs, but iodoacetamide (IAM) reduced H₂S levels and significantly abrogated DATS production of H₂S within HSCs. IAM also abolished all the inhibitory effects of DATS on the profibrogenic properties and oxidative stress in HSCs. Altogether, we demonstrated an H₂S-associated mechanism underlying DATS inhibition of profibrogenic properties and alleviation of oxidative stress in HSCs. Modulation of H₂S production may represent a therapeutic remedy for liver fibrosis.

Hepatic stellate cell interferes with NK cell regulation of fibrogenesis via curcumin induced senescence of hepatic stellate cell

Hepatic fibrosis, a common scarring response to various forms of chronic liver injury, is a precursor to cirrhosis and liver cancer. During liver fibrosis, hepatic stellate cells (HSCs) initially activate and proliferate, which are responsible for the secretion of extracellular matrix components. However, these cells eventually senesce and are cleared by natural killer (NK) cells. Our previous researches have shown that the natural product curcumin could promote the senescence of activated HSC. In this study, we investigated how NK cells target senescent HSC and assessed the effect of this process on liver fibrosis. We found that senescent HSC induced by curcumin are susceptible to NK cells killing, due to the increased expression of NK cell activating ligand major histocompatibility complex class I chain-related genes A (MICA) and UL16-binding proteins 2 (ULBP2), but not Poliovirus Receptor (PVR). Further studies displayed that the interaction between NK cells and senescent LX2 cells stimulated granule exocytosis. Moreover, the inhibition of granule exocytosis weakened the cytotoxicity of NK cells and promoted the accumulation of senescent LX2 cells. Therefore, these aggregated data indicated that NK cells mediated clearance of senescent LX2 cells and granule exocytosis could play a protective role in the improvement of liver fibrosis.

Canonical hedgehog signalling regulates hepatic stellate cell-mediated angiogenesis in liver fibrosis

BACKGROUND AND PURPOSE

Hepatic stellate cells (HSCs) are liver-specific pericytes regulating angiogenesis during liver fibrosis. We aimed to elucidate the mechanisms by which hedgehog signalling regulated HSC angiogenic properties and to validate the therapeutic implications.

EXPERIMENTAL APPROACH

Rats and mice were treated with carbon tetrachloride for in vivo evaluation of hepatic angiogenesis and fibrotic injury. Diversified molecular approaches including real-time PCR, Western blot, luciferase reporter assay, chromatin immunoprecipitation, electrophoretic mobility shift assay and co-immunoprecipitation were used to investigate the underlying mechanisms in vitro.

KEY RESULTS

Angiogenesis was concomitant with up-regulation of Smoothened (SMO) and hypoxia inducible factor-1α (HIF-1α) in rat fibrotic liver. The SMO inhibitor cyclopamine and Gli1 inhibitor GANT-58 reduced expression of VEGF and angiopoietin 1 in HSCs and suppressed HSC tubulogenesis capacity. HIF-1α inhibitor PX-478 suppressed HSC angiogenic behaviour, and inhibition of hedgehog decreased HIF-1α expression. Furthermore, heat shock protein 90 (HSP90) was characterized as a direct target gene of canonical hedgehog signalling in HSCs. HSP90 inhibitor 17-AAG reduced HSP90 binding to HIF-1α, down-regulated HIF-1α protein abundance and decreased HIF-1α binding to DNA. 17-AAG also abolished 1-stearoyl-2-arachidonoyl-sn-glycerol (SAG) (a SMO agonist)-enhanced HSC angiogenic properties. Finally, the natural compound ligustrazine was found to inhibit canonical hedgehog signalling leading to suppressed angiogenic properties of HSCs in vitro and ameliorated liver fibrosis and sinusoidal angiogenesis in mice.

CONCLUSION AND IMPLICATIONS

We have provided evidence that the canonical hedgehog pathway controlled HSC-mediated liver angiogenesis. Selective inhibition of HSC hedgehog signalling could be a promising therapeutic approach for hepatic fibrosis.

Dihydroartemisinin alleviates bile duct ligation-induced liver fibrosis and hepatic stellate cell activation by interfering with the PDGF-βR/ERK signaling pathway

Liver fibrosis represents a frequent event following chronic insult to trigger wound healing responses in the liver. Activation of hepatic stellate cells (HSCs), which is a pivotal event during liver fibrogenesis, is accompanied by enhanced expressions of a series of marker proteins and pro-fibrogenic signaling molecules. Artemisinin, a powerful antimalarial medicine, is extracted from the Chinese herb Artemisia annua L., and can inhibit the proliferation of cancer cells. Dihydroartemisinin (DHA), the major active metabolite of artemisinin, is able to attenuate lung injury and fibrosis. However, the effect of DHA on liver fibrosis remains unclear. The aim of this study was to investigate the effect of DHA on bile duct ligation-induced injury and fibrosis in rats. DHA improved the liver histological architecture and attenuated collagen deposition in the fibrotic rat liver. Experiments in vitro showed that DHA inhibited the proliferation of HSCs and arrested the cell cycle at the S checkpoint by altering several cell-cycle regulatory proteins. Moreover, DHA reduced the protein expressions of a-SMA, α1 (I) collagen and fibronectin, being associated with interference of the platelet-derived growth factor β receptor (PDGF-βR)-mediated ERK pathway. These data collectively revealed that DHA relieved liver fibrosis possibly by targeting HSCs via the PDGF-βR/ERK pathway. DHA may be a therapeutic antifibrotic agent for the treatment of hepatic fibrosis.

Inhibition of YAP signaling contributes to senescence of hepatic stellate cells induced by tetramethylpyrazine

Accumulating evidence indicates that hepatic stellate cells (HSCs) are the central mediators and major effectors in the development of hepatic fibrosis. It is well-known that regulation of cell proliferation and apoptosis are potential strategies to block the activation of HSCs. Recently, several studies have revealed that induction of HSC senescence could prevent and cure the liver fibrosis. In our previous work, we have demonstrated that the natural product tetramethylpyrazine (TMP) could inhibit the activation of HSCs and ameliorate hepatic fibrosis. The aim of this study was to identify a new role of TMP in the regulation of activated HSC senescence and to elucidate the underlying mechanisms. In this study, our data showed that TMP could promote HSC senescence in vivo and in vitro. Moreover, TMP affected the cell cycle and telomerase activity. We further demonstrated that P53 siRNA or P53 pharmacological inhibitor PFT-α abrogated the TMP-induced HSC senescence in vitro. Meanwhile, similar results were obtained in vivo. Further studies indicated that TMP promoted the expression of P53 through a YAP inhibition-dependent mechanism. Moreover, silencing YAP enhanced TMP induction of activated HSC senescence. Collectively, our results suggested that TMP inhibited the activation of HSCs by inducing senescence and had therapeutic implication for the treatment of liver fibrosis.

Activation of PPARγ/P53 signaling is required for curcumin to induce hepatic stellate cell senescence

Activation of quiescent hepatic stellate cells (HSCs) is the major event in hepatic fibrogenesis, along with enhancement of cell proliferation and overproduction of extracellular matrix. Although inhibition of cell proliferation and induction of apoptosis are potential strategies to block the activation of HSCs, a better understanding of the senescence of activated HSCs can provide a new therapeutic strategy for prevention and treatment of liver fibrosis. The antioxidant curcumin, a phytochemical from turmeric, has been shown to suppress HSC activation in vitro and in vivo. The current work was aimed to evaluate the effect of curcumin on senescence of activated HSCs and to elucidate the underlying mechanisms. In this study, curcumin promoted the expression of senescence marker Hmga1 in rat fibrotic liver. In addition, curcumin increased the number of senescence-associated β-galactosidase-positive HSCs in vitro. At the same time, curcumin induced HSC senescence by elevating the expression of senescence markers P16, P21 and Hmga1, concomitant with reduced abundance of HSC activation markers α-smooth muscle actin and α1(I)-procollagen in cultured HSCs. Moreover, curcumin affected the cell cycle and telomerase activity. We further demonstrated that P53 pharmacological inhibitor pifithrin-α (PFT-α) or transfection with P53 siRNA abrogated the curcumin-induced HSC senescence in vitro. Meanwhile, curcumin disruption of P53 leading to increased senescence of activated HSCs was further verified in vivo. Further studies indicated that curcumin promoted the expression of P53 through a PPARγ activation-dependent mechanism. Moreover, promoting PPARγ transactivating activity by a PPARγ agonist 15d-PGJ2 markedly enhanced curcumin induction of senescence of activated HSCs. However, the PPARγ antagonist PD68235 eliminated curcumin induction of HSC senescence. Taken together, our results provided a novel insight into the mechanisms underlying curcumin inhibition of HSC activation through inducing senescence.

Effect of Ligustrazine on rat peritoneal mesothelial cells treated with lipopolysaccharide

The apoptosis of peritoneal mesothelial cells (PMCs) and peritoneal fibrosis may induce failure of peritoneal membrane function. The study explored the changes of apoptosis and fibrosis in PMCs under lipopolysaccharides (LPS) culture and investigated whether Ligustrazine can affect LPS-induced apoptosis and fibrosis. We found that exposure of rat PMCs to 5 mg·L(-1) LPS for 24 h resulted in a significant induction of apoptosis and increased levels in Reactive oxygen species, and caspase-3 activity. Fibronectin, Collagen I, p-p38, and matrix metalloprotein-9 (MMP-9) levels were also significantly increased by LPS. But superoxide dismutase levels were remarkably decreased. Ligustrazine can restore the changes induced by LPS. The protective effect of Ligustrazine on LPS-induced apoptosis and fibrosis may act through inhibition of oxidative stress and p38/MAPKS, ROS/MMP-9 activation in PMCs.

Effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus)

Nitrite (NO2(-)) is commonly present as contaminant in aquatic environment and toxic to aquatic organisms. In the present study, we investigated the effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus). Fish were exposed to various concentrations of nitrite (0, 0.02, 0.08, 0.4 and 0.8mM) for 96 h. Fish blood and gills were collected to assay haematological parameters, oxidative stress and expression of genes after 0, 24, 48 and 96 h of exposure. In blood, the data showed that the levels of methemoglobin (MetHb), triglyceride (TG), potassium (K(+)), cortisol, heat shock protein 70 (HSP70) and glucose significantly increased in treatments with higher concentrations of nitrite (0.4 and/or 0.8mM) after 48 and 96 h, while the levels of haemoglobin (Hb) and sodium (Na(+)) significantly decreased in these treatments. In gills, nitrite (0.4 and/or 0.8mM) apparently reduced the levels of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione (GSH), increased the formation of malondialdehyde (MDA), up-regulated the mRNA levels of c-jun amino-terminal kinase (JUK1), p53, caspase-3, caspase-7 and caspase-9 after 48 and 96 h of exposure. The results suggested caspase-dependent and JUK signaling pathways played important roles in nitrite-induced apoptosis in fish. Further, this study provides new insights into how nitrite affects the physiological responses and apoptosis in a marine fish.

M1 Muscarinic Receptor Deficiency Attenuates Azoxymethane-Induced Chronic Liver Injury in Mice

Cholinergic nervous system regulates liver injury. However, the role of M1 muscarinic receptors (M1R) in modulating chronic liver injury is uncertain. To address this gap in knowledge we treated M1R-deficient and WT mice with azoxymethane (AOM) for six weeks and assessed liver injury responses 14 weeks after the last dose of AOM. Compared to AOM-treated WT mice, M1R-deficient mice had attenuated liver nodularity, fibrosis and ductular proliferation, α-SMA staining, and expression of α1 collagen, Tgfβ-R, Pdgf-R, Mmp-2, Timp-1 and Timp-2. In hepatocytes, these findings were associated with reductions of cleaved caspase-3 staining and Tnf-α expression. In response to AOM treatment, M1R-deficient mice mounted a vigorous anti-oxidant response by upregulating Gclc and Nqo1 expression, and attenuating peroxynitrite generation. M1R-deficient mouse livers had increased expression of Trail-R2, a promotor of stellate cell apoptosis; dual staining for TUNNEL and α-SMA revealed increased stellate cells apoptosis in livers from M1R-deficient mice compared to those from WT. Finally, pharmacological inhibition of M1R reduced H₂O₂-induced hepatocyte apoptosis in vitro. These results indicate that following liver injury, anti-oxidant response in M1R-deficient mice attenuates hepatocyte apoptosis and reduces stellate cell activation, thereby diminishing fibrosis. Therefore, targeting M1R expression and activation in chronic liver injury may provide therapeutic benefit.

Effects of Tetramethylpyrazine on Functional Recovery and Neuronal Dendritic Plasticity after Experimental Stroke

The 2,3,5,6-tetramethylpyrazine (TMP) has been widely used in the treatment of ischemic stroke by Chinese doctors. Here, we report the effects of TMP on functional recovery and dendritic plasticity after ischemic stroke. A classical model of middle cerebral artery occlusion (MCAO) was established in this study. The rats were assigned into 3 groups: sham group (sham operated rats treated with saline), model group (MCAO rats treated with saline) and TMP group (MCAO rats treated with 20 mg/kg/d TMP). The neurological function test of animals was evaluated using the modified neurological severity score (mNSS) at 3 d, 7 d, and 14 d after MCAO. Animals were euthanized for immunohistochemical labeling to measure MAP-2 levels in the peri-infarct area. Golgi-Cox staining was performed to test effect of TMP on dendritic plasticity at 14 d after MCAO. TMP significantly improved neurological function at 7 d and 14 d after ischemia, increased MAP-2 level at 14 d after ischemia, and enhanced spine density of basilar dendrites. TMP failed to affect the spine density of apical dendrites and the total dendritic length. Data analyses indicate that there was significant negative correlation between mNSS and plasticity measured at 14 d after MCAO. Thus, enhanced dendritic plasticity contributes to TMP-elicited functional recovery after ischemic stroke.

Tetramethylpyrazine Inhibits Activation of Hepatic Stellate Cells through Hedgehog Signaling Pathways In Vitro

Background and Aim. Tetramethylpyrazine (TMP), a major alkaloid isolated from Ligusticum chuanxiong, has been reported in hepatic fibrosis models. However, the action mechanism remains unclear. In the present study, effects of tetramethylpyrazine (TMP) against hepatic stellate cell (HSC) activation as well as the possible mechanisms were evaluated. Methods. Western blot assay was used to detect TMP effects on protein expression of Smo, Patched, Hhip, and Gli and to investigate the effects of TMP on Cyclin D1, Cyclin E1, CDK2, Bcl-2, Bax, and caspase expression with cyclopamine supplementation. Results. Our results showed that TMP significantly inhibits the expression of Cyclin D1, Cyclin E1, and Cyclin-dependent kinase CDK2 and changes the HSC cycle by inhibiting the proliferation of HSC. Moreover, TMP has also been shown to decrease the expression of Bcl-2 and increase the expression of Bax in HSC-T6 cells. Furthermore, TMP can inhibit the expression of connective tissue growth factor (CTGF), and the inhibitory effect was intensified after the application of joint treatment with TMP and cyclopamine. Conclusion. TMP may be an effective Hh signaling pathway inhibitor for hepatic fibrosis treatment.

Curcumin regulates cell fate and metabolism by inhibiting hedgehog signaling in hepatic stellate cells

Accumulating evidence indicates that Hedgehog (Hh) signaling becomes activated in chronic liver injury and plays a role in the pathogenesis of hepatic fibrosis. Hepatic stellate cells (HSCs) are Hh-responsive cells and activation of the Hh pathway promotes transdifferentiation of HSCs into myofibroblasts. Targeting Hh signaling may be a novel therapeutic strategy for treatment of liver fibrosis. We previously reported that curcumin has potent antifibrotic effects in vivo and in vitro, but the underlying mechanisms are not fully elucidated. This study shows that curcumin downregulated Patched and Smoothened, two key elements in Hh signaling, but restored Hhip expression in rat liver with carbon tetrachloride-induced fibrosis and in cultured HSCs. Curcumin also halted the nuclear translocation, DNA binding, and transcription activity of Gli1. Moreover, the Hh signaling inhibitor cyclopamine, like curcumin, arrested the cell cycle, induced mitochondrial apoptosis, reduced fibrotic gene expression, restored lipid accumulation, and inhibited invasion and migration in HSCs. However, curcumin's effects on cell fate and fibrogenic properties of HSCs were abolished by the Hh pathway agonist SAG. Furthermore, curcumin and cyclopamine decreased intracellular levels of adenosine triphosphate and lactate, and inhibited the expression and/or function of several key molecules controlling glycolysis. However, SAG abrogated the curcumin effects on these parameters of glycolysis. Animal data also showed that curcumin downregulated glycolysis-regulatory proteins in rat fibrotic liver. These aggregated data therefore indicate that curcumin modulated cell fate and metabolism by disrupting the Hh pathway in HSCs, providing novel molecular insights into curcumin reduction of HSC activation.

Delivery and targeting of miRNAs for treating liver fibrosis

Liver fibrosis is a pathological condition originating from liver damage that leads to excess accumulation of extracellular matrix (ECM) proteins in the liver. Viral infection, chronic injury, local inflammatory responses and oxidative stress are the major factors contributing to the onset and progression of liver fibrosis. Multiple cell types and various growth factors and inflammatory cytokines are involved in the induction and progression of this disease. Various strategies currently being tried to attenuate liver fibrosis include the inhibition of HSC activation or induction of their apoptosis, reduction of collagen production and deposition, decrease in inflammation, and liver transplantation. Liver fibrosis treatment approaches are mainly based on small drug molecules, antibodies, oligonucleotides (ODNs), siRNA and miRNAs. MicroRNAs (miRNA or miR) are endogenous noncoding RNA of ~22 nucleotides that regulate gene expression at post transcription level. There are several miRNAs having aberrant expressions and play a key role in the pathogenesis of liver fibrosis. Single miRNA can target multiple mRNAs, and we can predict its targets based on seed region pairing, thermodynamic stability of pairing and species conservation. For in vivo delivery, we need some additional chemical modification in their structure, and suitable delivery systems like micelles, liposomes and conjugation with targeting or stabilizing the moiety. Here, we discuss the role of miRNAs in fibrogenesis and current approaches of utilizing these miRNAs for treating liver fibrosis.

Nrf2 pathway activation contributes to anti-fibrosis effects of ginsenoside Rg1 in a rat model of alcohol- and CCl4-induced hepatic fibrosis

AIM

To investigate the anti-fibrosis effects of ginsenoside Rg1 on alcohol- and CCl4-induced hepatic fibrosis in rats and to explore the mechanisms of the effects.

METHODS

Rats were given 6% alcohol in water and injected with CCl4 (2 mL/kg, sc) twice a week for 8 weeks. Rg1 (10, 20 and 40 mg/kg per day, po) was administered in the last 2 weeks. Hepatic fibrosis was determined by measuring serum biochemical parameters, HE staining, Masson's trichromic staining, and hydroxyproline and α-SMA immunohistochemical staining of liver tissues. The activities of antioxidant enzymes, lipid peroxidation, and Nrf2 signaling pathway-related proteins (Nrf2, Ho-1 and Nqo1) in liver tissues were analyzed. Cultured hepatic stellate cells (HSCs) of rats were prepared for in vitro studies.

RESULTS

In the alcohol- and CCl4-treated rats, Rg1 administration dose-dependently suppressed the marked increases of serum ALT, AST, LDH and ALP levels, inhibited liver inflammation and HSC activation and reduced liver fibrosis scores. Rg1 significantly increased the activities of antioxidant enzymes (SOD, GSH-Px and CAT) and reduced MDA levels in liver tissues. Furthermore, Rg1 significantly increased the expression and nuclear translocation of Nrf2 that regulated the expression of many antioxidant enzymes. Treatment of the cultured HSCs with Rg1 (1 μmol/L) induced Nrf2 translocation, and suppressed CCl4-induced cell proliferation, reversed CCl4- induced changes in MDA, GPX, PCIII and HA contents in the supernatant fluid and α-SMA expression in the cells. Knockdown of Nrf2 gene diminished these actions of Rg1 in CCl4-treated HSCs in vitro.

CONCLUSION

Rg1 exerts protective effects in a rat model of alcohol- and CCl4-induced hepatic fibrosis via promoting the nuclear translocation of Nrf2 and expression of antioxidant enzymes.

Cellular and molecular mechanisms in the pathogenesis of liver fibrosis: An update

There have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying liver fibrogenesis. Recent data indicate that the termination of fibrogenic processes and the restoration of deficient fibrolytic pathways may allow the reversal of advanced fibrosis and even cirrhosis. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in liver fibrosis. Activation of hepatic stellate cells (HSCs) remains a central event in fibrosis, complemented by other sources of matrix-producing cells, including portal fibroblasts, fibrocytes and bone marrow-derived myofibroblasts. These cells converge in a complex interaction with neighboring cells to provoke scarring in response to persistent injury. Defining the interaction of different cell types, revealing the effects of cytokines on these cells and characterizing the regulatory mechanisms that control gene expression in activated HSCs will enable the discovery of new therapeutic targets. Moreover, the characterization of different pathways associated with different etiologies aid in the development of disease-specific therapies. This article outlines recent advances regarding the cellular and molecular mechanisms involved in liver fibrosis that may be translated into future therapies. The pathogenesis of liver fibrosis associated with alcoholic liver disease, non-alcoholic fatty liver disease and viral hepatitis are also discussed to emphasize the various mechanisms involved in liver fibrosis.

Tetramethylpyrazine inhibits angiotensin II-induced activation of hepatic stellate cells associated with interference of platelet-derived growth factor β receptor pathways

Liver fibrosis represents a frequent event following chronic insult to trigger wound healing responses in the liver. Activation of hepatic stellate cells (HSCs) is a pivotal event during liver fibrogenesis. Compelling evidence indicates that the renin-angiotensin system (RAS) takes part in the pathogenesis of liver fibrosis. Angiotensin II (Ang II), the primary effector peptide of the RAS, has been demonstrated to be a potent pro-fibrogenic molecule for HSC activation. In this study we investigated the effects of tetramethylpyrazine (TMP) on HSC activation induced by Ang II in order to elucidate the underlying mechanisms. Our results demonstrated that Ang II significantly promoted cell growth, upregulated the expression of the fibrotic markers α-smooth muscle actin (α-SMA) and α1(I) procollagen, and enhanced the invasion capacity in HSCs. TMP inhibited proliferation and arrested the cell cycle at the G2/M checkpoint associated with altering several cell cycle regulatory proteins in Ang II-treated HSCs. TMP also modulated Bcl-2 family proteins and activated the caspase cascade leading to apoptosis in Ang II-treated HSCs. Moreover, TMP reduced the expression of α-SMA and α1(I) procollagen at mRNA and protein levels, and these effects were associated with interference of the platelet-derived growth factor β receptor (PDGF-βR) mediated PI3K/AKT/mTOR pathway in HSCs exposed to Ang II. Furthermore, Ang II-enhanced HSC invasion capacity was diminished by TMP, which was associated with interference of PDGF-βR/FAK signaling. These data collectively indicated that interference of PDGF-βR-mediated fibrotic pathways was involved in TMP inhibition of HSC activation caused by Ang II, providing novel mechanistic insights into TMP as a potential therapeutic remedy for hepatic fibrosis.

Peroxisome proliferator-activated receptor-γ interrupts angiogenic signal transduction by transrepression of platelet-derived growth factor-β receptor in hepatic stellate cells

Hepatic stellate cells (HSCs) are liver-specific pericytes that are recruited to vessels and secret pro-angiogenic cytokines, and thus actively involved in pathological vascularization during liver fibrosis. Peroxisome proliferator-activated receptor-γ (PPARγ) is a switch molecule controlling HSC activation. We investigated PPARγ regulation of angiogenic signal transduction and the molecular mechanisms involved in HSCs. Primary rat HSCs and liver sinusoidal endothelial cells (LSECs) were isolated and used in this study. Boyden chamber and tubulogenesis assays, identified that focal adhesion kinase (FAK)-RhoA signaling activated by platelet-derived growth factor (PDGF) was required for HSC motility and the associated vascularization. PDGF also stimulated vascular endothelial growth factor (VEGF) expression and HSC-driven vascularization through signals mediated by extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin (mTOR). Gain- and loss-of-function analyses demonstrated that activation of PPARγ interrupted FAK-RhoA, ERK and mTOR cascades and inhibited HSC-based vascularization. Molecular evidence further revealed that PPARγ attenuation of HSC angiogenic properties was dependent on inhibition of PDGF-β receptor expression. We concluded that PPARγ inhibited angiogenic signal transduction through transrepression of PDGF-β receptor leading to reduced HSC motility, reduced VEGF expression, and thereby attenuated HSC-driven angiogenesis. PPARγ could be a molecular target for preventing vascular remolding in hepatic fibrosis.