Activation of peroxisome proliferator-activated receptor-gamma by curcumin blocks the signaling pathways for PDGF and EGF in hepatic stellate cells

Defining the mechanisms behind the hepatoprotective properties of curcumin

As a critical cause of human dysfunctionality, hepatic failure leads to approximately two million deaths per year and is on the rise. Considering multiple inflammatory, oxidative, and apoptotic mechanisms behind hepatotoxicity, it urges the need for finding novel multi-targeting agents. Curcumin is a phenolic compound with anti-inflammatory, antioxidant, and anti-apoptotic roles. Curcumin possesses auspicious health benefits and protects against several diseases with exceptional safety and tolerability. This review focused on the hepatoprotective mechanisms of curcumin. The need to develop novel delivery systems of curcumin (e.g., nanoparticles, self-micro emulsifying, lipid-based colloids, solid lipid nanoparticles, cyclodextrin inclusion, phospholipid complexes, and nanoemulsions) is also considered.

Evaluating the Therapeutic Potential of Curcumin and Synthetic Derivatives: A Computational Approach to Anti-Obesity Treatments

Natural compounds such as curcumin, a polyphenolic compound derived from the rhizome of turmeric, have gathered remarkable scientific interest due to their diverse metabolic benefits including anti-obesity potential. However, curcumin faces challenges stemming from its unfavorable pharmacokinetic profile. To address this issue, synthetic curcumin derivatives aimed at enhancing the biological efficacy of curcumin have previously been developed. In silico modelling techniques have gained significant recognition in screening synthetic compounds as drug candidates. Therefore, the primary objective of this study was to assess the pharmacokinetic and pharmacodynamic characteristics of three synthetic derivatives of curcumin. This evaluation was conducted in comparison to curcumin, with a specific emphasis on examining their impact on adipogenesis, inflammation, and lipid metabolism as potential therapeutic targets of obesity mechanisms. In this study, predictive toxicity screening confirmed the safety of curcumin, with the curcumin derivatives demonstrating a safe profile based on their LD50 values. The synthetic curcumin derivative 1A8 exhibited inactivity across all selected toxicity endpoints. Furthermore, these compounds were deemed viable candidate drugs as they adhered to Lipinski's rules and exhibited favorable metabolic profiles. Molecular docking studies revealed that both curcumin and its synthetic derivatives exhibited favorable binding scores, whilst molecular dynamic simulations showed stable binding with peroxisome proliferator-activated receptor gamma (PPARγ), csyclooxygenase-2 (COX2), and fatty acid synthase (FAS) proteins. The binding free energy calculations indicated that curcumin displayed potential as a strong regulator of PPARγ (-60.2 ± 0.4 kcal/mol) and FAS (-37.9 ± 0.3 kcal/mol), whereas 1A8 demonstrated robust binding affinity with COX2 (-64.9 ± 0.2 kcal/mol). In conclusion, the results from this study suggest that the three synthetic curcumin derivatives have similar molecular interactions to curcumin with selected biological targets. However, in vitro and in vivo experimental studies are recommended to validate these findings.

Molecular Mechanisms of Curcumin in the Pathogenesis of Metabolic Dysfunction Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a multifactorial condition characterized by insulin resistance, oxidative stress, chronic low-grade inflammation, and sometimes fibrosis. To date, no effective pharmacological therapy has been approved for the treatment of metabolic-associated steatohepatitis (MASH), the progressive form of MASLD. Recently, numerous in vitro and in vivo studies have described the efficacy of nutraceutical compounds in the diet has been tested. Among them, curcumin is the most widely used polyphenol in the diet showing potent anti-inflammatory and antifibrotic activities. This review aims to summarize the most important basic studies (in vitro and animal models studies), describing the molecular mechanisms by which curcumin acts in the context of MASLD, providing the rationale for its effective translational use in humans.

The role of curcumin in the liver-gut system diseases: from mechanisms to clinical therapeutic perspective

Natural products have provided abundant sources of lead compounds for new drug discovery and development over the past centuries. Curcumin is a lipophilic polyphenol isolated from turmeric, a plant used in traditional Asian medicine for centuries. Despite the low oral bioavailability, curcumin exhibits profound medicinal value in various diseases, especially liver and gut diseases, bringing an interest in the paradox of its low bioavailability but high bioactivity. Several latest studies suggest that curcumin's health benefits may rely on its positive gastrointestinal effects rather than its poor bioavailability solely. Microbial antigens, metabolites, and bile acids regulate metabolism and immune responses in the intestine and liver, suggesting the possibility that the liver-gut axis bidirectional crosstalk controls gastrointestinal health and diseases. Accordingly, these pieces of evidence have evoked great interest in the curcumin-mediated crosstalk among liver-gut system diseases. The present study discussed the beneficial effects of curcumin against common liver and gut diseases and explored the underlying molecular targets, as well as collected evidence from human clinical studies. Moreover, this study summarized the roles of curcumin in complex metabolic interactions in liver and intestine diseases supporting the application of curcumin in the liver-gut system as a potential therapeutic option, which opens an avenue for clinical use in the future.

Regulatory Effects of Curcumin on Platelets: An Update and Future Directions

The rhizomatous plant turmeric, which is frequently used as a spice and coloring ingredient, yields curcumin, a bioactive compound. Curcumin inhibits platelet activation and aggregation and improves platelet count. Platelets dysfunction results in several disorders, including inflammation, atherothrombosis, and thromboembolism. Several studies have proved the beneficial role of curcumin on platelets and hence proved it is an important candidate for the treatment of the aforementioned diseases. Moreover, curcumin is also frequently employed as an anti-inflammatory agent in conventional medicine. In arthritic patients, it has been shown to reduce the generation of pro-inflammatory eicosanoids and to reduce edema, morning stiffness, and other symptoms. Curcumin taken orally also reduced rats' acute inflammation brought on by carrageenan. Curcumin has also been proven to prevent atherosclerosis and platelet aggregation, as well as to reduce angiogenesis in adipose tissue. In the cerebral microcirculation, curcumin significantly lowered platelet and leukocyte adhesion. It largely modulated the endothelium to reduce platelet adhesion. Additionally, P-selectin expression and mice survival after cecal ligation and puncture were improved by curcumin, which also altered platelet and leukocyte adhesion and blood-brain barrier dysfunction. Through regulating many processes involved in platelet aggregation, curcuminoids collectively demonstrated detectable antiplatelet activity. Curcuminoids may therefore be able to prevent disorders linked to platelet activation as possible therapeutic agents. This review article proposes to highlight and discuss the regulatory effects of curcumin on platelets.

Cynarin inhibits PDGF-BB-induced proliferation and activation in hepatic stellate cells through PPARγ

Cynarin, a caffeoylquinic acid compound that was mainly extracted from Cynara scolymus L., displays various activities such as antioxidant, antibacterial, choleretic, and hepatoprotective functions. However, the target of cynarin and the mechanism of its hepatoprotective effect are still unclear. To find cynarin’s target, we performed molecular docking analysis, fluorescence-based ligand-binding assay, and reporter gene system assay. Our results indicated that cynarin was a partial agonist of peroxisome proliferator-activated receptor gamma (PPARγ). Further studies showed that cynarin significantly inhibited platelet-derived growth factor (PDGF)-BB-induced proliferation and activation of rat CFSC-8G hepatic stellate cells (HSCs). Our results also revealed that cynarin inhibited PDGF-BB-induced extracellular regulated protein kinase (ERK) and v-akt murine thymoma viral oncogene homolog (AKT) phosphorylation in HSCs. In addition, this inhibition effect was PPARγ dependent since the knockdown of PPARγ significantly attenuated the effects of cynarin on PDGF-BB-induced p-ERK, p-AKT, and α-smooth muscle actin (α-SMA) expressions. Therefore, this study suggests that cynarin is a promising antifibrotic lead compound that inhibits the activation of HSCs, and it works by targeting PPARγ.

Relationship between Hepatitis B virus infection and platelet production and dysfunction

Hepatitis B virus (HBV) is a kind of hepatotropic DNA virus. The main target organ is liver, except for liver, HBV has been found in a variety of extrahepatic tissues, such as kidney, thyroid, pancreas, bone marrow, etc. HBV can cause severe complications by invading these tissues. Among them, pancytopenia is one of the common complications, especially thrombocytopenia that causes life-threatening bleeding. However, the mechanism of thrombocytopenia is unclear and the treatment is extremely difficult. It has been confirmed that HBV has a close relationship with platelets. HBV can directly infect bone marrow, inhibit platelet production, and accelerate platelet destruction by activating monocyte-macrophage system and immune system. While platelets act as a double-edged sword to HBV. On one hand, the activated platelets can degranulate and release inflammatory mediators to help clear the viruses. Furthermore, platelets can provide anti-fibrotic molecules to improve liver functions and reduce hepatic fibrosis. On the other hand, platelets can also cause negative effects. The infected platelets collect HBV-specific CD8⁺ T cells and nonspecific inflammatory cells into liver parenchyma, inducing chronic inflammation, liver fibrosis and hepatic carcinoma. This article explores the interaction between HBV infection and platelets, providing a theoretical basis for clinical treatment of thrombocytopenia and severe hemorrhage caused by HBV infection.

Epiregulin (EREG) and Myocardin Related Transcription Factor A (MRTF-A) Form a Feedforward Loop to Drive Hepatic Stellate Cell Activation

Trans-differentiation of quiescent hepatic stellate cells (HSC) into myofibroblast cells is considered the linchpin of liver fibrosis. A myriad of signaling pathways contribute to HSC activation and consequently liver fibrosis. Epidermal growth factor (EGF) family of cytokines signal through the cognate receptor EGFR to promote HSC activation. In the present study we investigated the transcription regulation of epiregulin (EREG), an EGFR ligand, during HSC activation. We report that EREG expression was significantly up-regulated in activated HSCs compared to quiescent HSCs isolated from mice. In addition, there was an elevation of EREG expression in HSCs undergoing activation in vitro. Of interest, deficiency of myocardin-related transcription factor A (MRTF-A), a well-documented regulator of HSC trans-differentiation, attenuated up-regulation of EREG expression both in vivo and in vitro. Further analysis revealed that MRTF-A interacted with serum response factor (SRF) to bind directly to the EREG promoter and activate EREG transcription. EREG treatment promoted HSC activation in vitro, which was blocked by MRTF-A depletion or inhibition. Mechanistically, EREG stimulated nuclear trans-location of MRTF-A in HSCs. Together, our data portray an EREG-MRTF-A feedforward loop that contributes to HSC activation and suggest that targeting the EREG-MRTF-A axis may yield therapeutic solutions against liver fibrosis.

SPOCK1 overexpression induced by platelet-derived growth factor-BB promotes hepatic stellate cell activation and liver fibrosis through the integrin α5β1/PI3K/Akt signaling pathway

Sparc/osteonectin, cwcv, and kazal-like domain proteoglycan 1 (SPOCK1) is a matricellular protein which regulates cell proliferation, invasion, and survival but the function of SPOCK1 in liver fibrosis is obscure. In this study, we found that SPOCK1 expression increased significantly in fibrotic liver tissues and activated primary rat hepatic stellate cells (R-HSCs). SPOCK1 co-localized with α-smooth muscle actin (α-SMA) in the cytoplasm. Mechanistically, we found platelet-derived growth factor-BB (PDGF-BB) induced SPOCK1 expression by activating the PI3K/Akt/forkhead box M1 (FoxM1) signaling pathway. Intracellular SPOCK1 downregulation decreased the HSC activation, proliferation, and migration induced by PDGF-BB. Furthermore, intracellular SPOCK1 overexpression or recombinant SPOCK1 treatment promoted HSC activation, proliferation, and migration by activating the PI3K/Akt signaling pathway. Co-immunoprecipitation, double immunofluorescence staining indicated that SPOCK1 interacted with integrin α5β1, and neutralization of integrin α5β1 significantly reduced the role of recombinant SPOCK1 in HSCs. In vivo HSC-specific SPOCK1 knockdown following lentivirus administration dramatically ameliorated thioacetamide (TAA)-induced collagen deposition in rat livers. Collectively, our study indicates that SPOCK1 is crucial for hepatic fibrosis and it might be a promising therapeutic target.

Liquiritigenin suppresses the activation of hepatic stellate cells via targeting miR-181b/PTEN axis

BACKGROUND

Liquiritigenin (LQ), an aglycone of liquiritin in licorice, has demonstrated antioxidant, anti-inflammatory and anti-tumor activities. Previously, LQ was found to inhibit liver fibrosis progression.

PURPOSE

Phosphatase and tensin homolog (PTEN) has been reported to act as a negative regulator of hepatic stellate cell (HSC) activation. However, the roles of PTEN in the effects of LQ on liver fibrosis have not been identified to date.

METHODS

The effects of LQ on liver fibrosis in carbon tetrachloride (CCl₄) mice as well as primary HSCs were examined. Moreover, the roles of PTEN and microRNA-181b (miR-181b) in the effects of LQ on liver fibrosis were examined.

RESULTS

LQ markedly ameliorated CCl₄-induced liver fibrosis, with a reduction in collagen deposition as well as α-SMA level. Moreover, LQ induced an increase in PTEN and effectively inhibited HSC activation including cell proliferation, α-SMA and collagen expression, which was similar with curcumin (a positive control). Notably, loss of PTEN blocked down the effects of LQ on HSC activation. PTEN was confirmed as a target of miR-181b and miR-181b-mediated PTEN was involved in the effects of LQ on liver fibrosis. LQ led to a significant reduction in miR-181b expression. LQ-inhibited HSC activation could be restored by over-expression of miR-181b. Further studies demonstrated that LQ down-regulated miR-181b level via Sp1. Collectively, we demonstrate that LQ inhibits liver fibrosis, at least in part, via regulation of miR-181b and PTEN.

CONCLUSION

LQ down-regulates miR-181b level, leading to the restoration of PTEN expression, which contributes to the suppression of HSC activation. LQ may be a potential candidate drug against liver fibrosis.

Early intervention with ABA prevents neuroinflammation and memory impairment in a triple transgenic mice model of Alzheimer´s disease

Neuroinflammation and insulin resistance in the brain are intimately linked to neurodegenerative disorders, including Alzheimer's disease. Even though traditionally Alzheimer´s disease has been associated to Aβ deposits and hyperphosphorylated Tau intracellular tangles, several studies show that neuroinflammation may be the initial cause that triggers degeneration. Accordingly, a number of natural supplements that improves brain insulin sensitivity and reduce neuroinflammation have been proposed as good choices in the therapeutic prevention of cognitive decline. Further supporting this evidence, we show that phytohormone Abscisic Acid, can prevent memory impairment and neuroinflammation markers in a triple transgenic mouse model, where no peripheral inflammatory changes have occurred. Moreover, our data strongly suggests that early intervention is critical for good prognosis, and that cognitive improvement requires longer treatment than recovering neuroinflammation markers.

Effect of SEPT6 on the biological behavior of hepatic stellate cells and liver fibrosis in rats and its mechanism

Hepatic stellate cells (HSCs) are key effectors during the development of liver fibrosis. Septin 6 (SEPT6) is a highly evolutionarily conserved GTP-binding protein that regulates various cell biological behaviors. The expression and function of SEPT6 in HSCs remain unknown. Here we demonstrate that SEPT6 expression is significantly elevated following the activation of primary rat HSCs, the human hepatic stellate cell line LX-2 and the rat hepatic stellate cell line HSC-T6, as well as in both human and rat fibrotic liver tissue. In vitro, the overexpression of SEPT6 promoted HSCs activation, proliferation, cell cycle progression and migration and inhibited HSCs apoptosis. In contrast, knockdown of SEPT6 exerted the opposite effects on HSCs. Mechanistically, SEPT6 exerted its pro-fibrogenic effect by promoting the expression of TGF-β1 and the phosphorylation of Smad2, Smad3, extracellular-signal-regulated kinase, c-Jun NH2-terminal kinase, stress-activated protein kinase-2, and protein kinase B. However, in HSC-T6 cells, blockade of the TGF-β1/Smad signaling pathway by SB431542 significantly decreased the expression of α-smooth muscle actin, cyclin D1, BCL2, and matrix metalloproteinase-2 and -9, which had been enhanced by SEPT6 overexpression. In vivo, adenovirus-mediated SEPT6 inhibition attenuated thioacetamide (TAA)-induced liver fibrosis in rats by decreasing the deposition of the extracellular matrix (ECM). SEPT6 inhibition decreased the proliferation capacity of HSCs and induced apoptosis of HSCs. Collectively, our results reveal that SEPT6 regulates various biological behaviors in HSCs through TGF-β1/Smad, mitogen-activated protein kinases and phosphatidylinositol-3-kinase/protein kinase B signaling pathways, thus promoting liver fibrosis.

Modulators of inflammation in Bronchopulmonary Dysplasia

Over 50 years after its first description, Bronchopulmonary Dysplasia (BPD) remains a devastating pulmonary complication in preterm infants with respiratory failure and develops in 30-50% of infants less than 1000-gram birth weight. It is thought to involve ventilator- and oxygen-induced damage to an immature lung that results in an inflammatory response and ends in aberrant lung development with dysregulated angiogenesis and alveolarization. Significant morbidity and mortality are associated with this most common chronic lung disease of childhood. Thus, any therapies that decrease the incidence or severity of this condition would have significant impact on morbidity, mortality, human costs, and healthcare expenditure. It is clear that an inflammatory response and the elaboration of growth factors and cytokines are associated with the development of BPD. Numerous approaches to control the inflammatory process leading to the development of BPD have been attempted. This review will examine the anti-inflammatory approaches that are established or hold promise for the prevention or treatment of BPD.

The regulatory role of curcumin on platelet functions

Curcumin, the main ingredient of Curcuma longa L., has been used as a spice and as a herbal medicine with different therapeutic characteristics for centuries in Asian countries. This phytochemical has been shown to possess beneficial antiplatelet activity that has introduced it as a promising candidate for the treatment of thromboembolism, atherothrombosis, and inflammatory diseases. Platelet dysfunction under different circumstances may lead to cardiovascular disease, and curcumin has been shown to have beneficial effects on platelet dysfunction in several studies. Therefore, this narrative review is aimed to summarize available evidence on the antiplatelet activity of curcumin and related molecular mechanisms for this activity.

Abscisic Acid Supplementation Rescues High Fat Diet-Induced Alterations in Hippocampal Inflammation and IRSs Expression

Accumulated evidence indicates that neuroinflammation induces insulin resistance in the brain. Moreover, both processes are intimately linked to neurodegenerative disorders, including Alzheimer's disease. Potential mechanisms underlying insulin resistance include serine phosphorylation of the insulin receptor substrate (IRS) or insulin receptor (IR) misallocation. However, only a few studies have focused on IRS expression in the brain and its modulation in neuroinflammatory processes. This study used the high-fat diet (HFD) model of neuroinflammation to study the alterations of IR, an insulin-like growth factor receptor (IGF1R) and IRS expressions in the hippocampus. We observed that HFD effectively reduced mRNA and protein IRS2 expression. In contrast, a HFD induced the upregulation of the IRS1 mRNA levels, but did not alter an IR and IGF1R expression. As expected, we observed that a HFD increased hippocampal tumor necrosis factor alpha (TNFα) and amyloid precursor protein (APP) levels while reducing brain-derived neurotrophic factor (BDNF) expression and neurogenesis. Interestingly, we found that TNFα correlated positively with IRS1 and negatively with IRS2, whereas APP levels correlated positively only with IRS1 but not IRS2. These results indicate that IRS1 and IRS2 hippocampal expression can be affected differently by HFD-induced neuroinflammation. In addition, we aimed to establish whether abscisic acid (ABA) can rescue hippocampal IRS1 and IRS2 expression, as we had previously shown that ABA supplementation prevents memory impairments and improves neuroinflammation induced by a HFD. In this study, ABA restored HFD-induced hippocampal alterations, including IRS1 and IRS2 expression, TNFα, APP, and BDNF levels and neurogenesis. In conclusion, this study highlights different regulations of hippocampal IRS1 and IRS2 expression using a HFD, indicating the important differences of these scaffolding proteins, and strongly supports ABA therapeutic effects.

Exploring the Mechanism of Dangguiliuhuang Decoction Against Hepatic Fibrosis by Network Pharmacology and Experimental Validation

Dangguiliuhuang decoction (DGLHD) has been demonstrated to be effective in treating inflammatory, hepatic steatosis, and insulin resistance. In the study, we tried to elucidate the pharmacological efficacy and mechanism of DGLHD against liver fibrosis and predicate potential active ingredients and targets via network analysis and experimental validation. In the formula, we totally discovered 76 potential active ingredients like baicalein, berberine, and wogonin, and 286 corresponding targets including PTGS (prostaglandin-endoperoxide synthase) 2, PPAR (peroxisome proliferator-activated receptors) -γ, and NF-κB (nuclear factor-κB). Pathway and functional enrichment analysis of these putative targets indicated that DGLHD obviously influenced NF-κB and PPAR signaling pathway. Consistently, DGLHD downregulated levels of ALT (alanine transaminase) and AST (aspartate transaminase), reduced production of proinflammatory cytokines-TNF (tumor necrosis factor) -α and IL (Interleukin) -1β in serum and liver from mice with hepatic fibrosis, and inhibited hepatic stellate cell (HSC)-T6 cells proliferation. DGLHD decreased TGF (transforming growth factor) -β1 and α-SMA (smooth muscle actin) expression as well, maintained MMP (matrix metalloprotein) 13-TIMP (tissue inhibitor of metalloproteinases) 1 balance, leading to mitigated ECM (extracellular matrix) deposition in vivo and in vitro. Moreover, our experimental data confirmed that the alleviated inflammation and ECM accumulation were pertinent to NF-κB inhibition and PPAR-γ activation. Overall, our results suggest that DGLHD aims at multiply targets and impedes the progression of hepatic fibrosis by ameliorating abnormal inflammation and ECM deposition, thereby serving as a novel regimen for treating hepatic fibrosis in clinic.

Docosahexaenoic acid attenuates carbon tetrachloride-induced hepatic fibrosis in rats

Fish oil containing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) has been reported to exert beneficial health effects, including hepatoprotection. However, the effect of DHA alone has not been well studied, and the mechanism is not fully understood. In the present study, we reported the protective effect of DHA on carbon tetrachloride (CCl₄) induced hepatic fibrosis. Compared with the control group, the CCl₄ group showed hepatic damage as evidenced by histological changes and elevation in serum transaminase activity, fibrosis, inflammation and oxidative stress levels. These pathophysiological changes were attenuated by chronic DHA supplementation. The anti-fibrotic effect of DHA was accompanied by reductions in gene and protein expression of α-smooth muscle actin (α-SMA), fibronectin, and collagen in the liver tissue. DHA also attenuated CCl₄-induced elevation of lipid peroxidation (LPO) and decrease of glutathione (GSH)/oxidized GSH (GSSG) ratio. The upregulated inflammatory cytokines tumor necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-6 by CCl₄ were also ameliorated by DHA. Peroxisome proliferator-activated receptor (PPAR)-γ upregulation and type I and II receptors for transforming growth factor (TGF)-β (Tβ-RI and Tβ-RII) and platelet-derived growth factor (PDGF)-β receptor (PDGF-βR) downregulation on both mRNA and protein levels were observed by DHA treatment compared to CCl₄ group. Moreover, in vitro study showed that DHA inhibited HSC activation, being associated with elevating PPARγ level and reducing the phosphorylation levels of Smad2/3 and ERKs, which are downstream intermediates of TGFβ and PDGF receptors, respectively. Taken together, the hepatoprotective, anti-inflammatory and anti-fibrotic effects of DHA appeared to be multifactorial. Further, one of the mechanisms of the anti-fibrotic effect of chronic DHA supplementation is probably through PPARγ signaling to interrupt TGFβ/Smad and PDGF/ERK pathways in HSCs.

Paired related homeobox protein 1 regulates PDGF-induced chemotaxis of hepatic stellate cells in liver fibrosis

Activation of the platelet-derived growth factor (PDGF)/PDGF beta receptor (PDGFβR) axis has a critical role in liver fibrosis. However, the mechanisms that regulate the PDGF signaling are yet to be elucidated. The present study demonstrates that paired related homeobox protein 1 (Prrx1) is involved in PDGF-dependent hepatic stellate cell (HSCs) migration via modulation of the expression of metalloproteinases MMP2 and MMP9. PDGF elevated the level of Prrx1 through the activation of ERK/Sp1 and PI3K/Akt/Ets1 pathways. In vivo, an adenoviral-mediated Prrx1 shRNA administration attenuated liver fibrosis in thioacetamide-induced fibrotic models. These studies reveal a role of Prrx1 as a modulator of PDGF-dependent signaling in HSCs, and inhibiting its expression may offer a therapeutic approach for hepatic fibrosis.

Regulation of cell signaling pathways by dietary agents for cancer prevention and treatment

Although it is widely accepted that better food habits do play important role in cancer prevention and treatment, how dietary agents mediate their effects remains poorly understood. More than thousand different polyphenols have been identified from dietary plants. In this review, we discuss the underlying mechanism by which dietary agents can modulate a variety of cell-signaling pathways linked to cancer, including transcription factors, nuclear factor κB (NF-κB), signal transducer and activator of transcription 3 (STAT3), activator protein-1 (AP-1), β-catenin/Wnt, peroxisome proliferator activator receptor- gamma (PPAR-γ), Sonic Hedgehog, and nuclear factor erythroid 2 (Nrf2); growth factors receptors (EGFR, VEGFR, IGF1-R); protein Kinases (Ras/Raf, mTOR, PI3K, Bcr-abl and AMPK); and pro-inflammatory mediators (TNF-α, interleukins, COX-2, 5-LOX). In addition, modulation of proteasome and epigenetic changes by the dietary agents also play a major role in their ability to control cancer. Both in vitro and animal based studies support the role of dietary agents in cancer. The efficacy of dietary agents by clinical trials has also been reported. Importantly, natural agents are already in clinical trials against different kinds of cancer. Overall both in vitro and in vivo studies performed with dietary agents strongly support their role in cancer prevention. Thus, the famous quote "Let food be thy medicine and medicine be thy food" made by Hippocrates 25 centuries ago still holds good.

Silencing of α-complex protein-2 reverses alcohol- and cytokine-induced fibrogenesis in hepatic stellate cells

BACKGROUND AND AIM

α-complex protein-2 (αCP2) encoded by the poly (rC) binding protein 2(PCBP2) gene is responsible for the accumulation of type I collagen in fibrotic livers. In this study, we silenced the PCBP2 gene using a small interfering RNA (siRNA) to reverse alcohol-and cytokine-induced profibrogenic effects on hepatic stellate cells (HSCs).

METHODS

Primary rat HSCs and the HSC-T6 cell line were used as fibrogenic models to mimic the initiation and perpetuation stages of fibrogenesis, respectively. We previously found that a PCBP2 siRNA, which efficiently silences expression of αCP2, reduces the stability of type I collagen mRNA. We investigated the effects of the PCBP2 siRNA on cell proliferation and migration. Expression of type I collagen in HSCs was analyzed by quantitative real-time PCR and western blotting. In addition, we evaluated the effects of the PCBP2 siRNA on apoptosis and the cell cycle.

RESULTS

PCBP2 siRNA reversed multiple alcohol- and cytokine-induced profibrogenic effects on primary rat HSCs and HSC-T6 cells. The PCBP2 siRNA also reversed alcohol- and cytokine-induced accumulation of type I collagen as well as cell proliferation and migration. Moreover, the combination of LY2109761, a transforming growth factor-β1 inhibitor, and the PCBP2 siRNA exerted a synergistic inhibitive effect on the accumulation of type I collagen in HSCs.

CONCLUSIONS

Silencing of PCBP2 using siRNA could be a potential therapeutic strategy for alcoholic liver fibrosis.

The stellate cell system (vitamin A-storing cell system)

Past, present, and future research into hepatic stellate cells (HSCs, also called vitamin A-storing cells, lipocytes, interstitial cells, fat-storing cells, or Ito cells) are summarized and discussed in this review. Kupffer discovered black-stained cells in the liver using the gold chloride method and named them stellate cells (Sternzellen in German) in 1876. Wake rediscovered the cells in 1971 using the same gold chloride method and various modern histological techniques including electron microscopy. Between their discovery and rediscovery, HSCs disappeared from the research history. Their identification, the establishment of cell isolation and culture methods, and the development of cellular and molecular biological techniques promoted HSC research after their rediscovery. In mammals, HSCs exist in the space between liver parenchymal cells (PCs) or hepatocytes and liver sinusoidal endothelial cells (LSECs) of the hepatic lobule, and store 50-80% of all vitamin A in the body as retinyl ester in lipid droplets in the cytoplasm. SCs also exist in extrahepatic organs such as pancreas, lung, and kidney. Hepatic (HSCs) and extrahepatic stellate cells (EHSCs) form the stellate cell (SC) system or SC family; the main storage site of vitamin A in the body is HSCs in the liver. In pathological conditions such as liver fibrosis, HSCs lose vitamin A, and synthesize a large amount of extracellular matrix (ECM) components including collagen, proteoglycan, glycosaminoglycan, and adhesive glycoproteins. The morphology of these cells also changes from the star-shaped HSCs to that of fibroblasts or myofibroblasts.

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.

Ameliorative Effect of Curcumin-Encapsulated Hyaluronic Acid-PLA Nanoparticles on Thioacetamide-Induced Murine Hepatic Fibrosis

In this study, we developed curcumin-encapsulated hyaluronic acid–polylactide nanoparticles (CEHPNPs) to be used for liver fibrosis amelioration. CD44, the hyaluronic acid (HA) receptor, is upregulated on the surface of cancer cells and on activated hepatic stellate cells (aHSCs) rather than normal cells. CEHPNPs could bind to CD44 and be internalized effectively through endocytosis to release curcumin, a poor water-soluble liver protective agent. Thus, CEHPNPs were potentially not only improving drug efficiency, but also targeting aHSCs. HA and polylactide (PLA) were crosslinked by adipic acid dihydrazide (ADH). The synthesis of HA–PLA was monitored by Fourier-transform infrared (FTIR) and Nuclear Magnetic Resonance (NMR). The average particle size was approximately 60–70 nm as determined by dynamic light scattering (DLS) and scanning electron microscope (SEM). Zeta potential was around −30 mV, which suggested a good stability of the particles. This drug delivery system induced significant aHSC cell death without affecting quiescent HSCs, hepatic epithelial, and parenchymal cells. This system reduced drug dosage without sacrificing therapeutic efficacy. The cytotoxicity IC₅₀ (inhibitory concentration at 50%) value of CEHPNPs was approximately 1/30 to that of the free drug treated group in vitro. Additionally, the therapeutic effects of CEHPNPs were as effective as the group treated with the same curcumin dose intensity in vivo. CEHPNPs significantly reduced serum aspartate transaminase/alanine transaminase (ALT/AST) significantly, and attenuated tissue collagen production and cell proliferation as revealed by liver biopsy. Conclusively, the advantages of superior biosafety and satisfactory therapeutic effect mean that CEHPNPs hold great potential for treating hepatic fibrosis.

Novel protective role of curcumin and taurine combination against experimental hepatocarcinogenesis

Hepatocarcinogenesis is a prerequisite to hepatocellular carcinoma (HCC), which is one of the most common cancers among humans. Therefore, it is important to search for agents that protect against hepatocarcinogenesis. The present study aimed to investigate the protective effects of a combination of taurine and curcumin against experimental hepatocarcinogenesis induced by diethyl nitrosamine (DENA) in a rat model. A total of 100 rats were divided into eight groups. Eight weeks following DENA injection and treatment with curcumin and taurine, the rats were sacrificed to obtain blood and hepatic tissue samples for the evaluation of various markers and histopathological observations. Serum levels of interleukin-2 (IL-2), interferon-γ (IFN-γ), α-fetoprotein (AFP) and α-L-fucosidase (AFU) were determined. Rats injected with DENA for eight weeks showed a high percentage of malignant changes in hepatic tissues, as well as a significant increases in the serum levels of AFP and AFU and significant reductions in the serum levels of IL-2 and IFN-γ. Treatment with curcumin and taurine markedly reduced the extent of malignant changes in the rat liver tissues, with their liver tissues showing patterns similar to that of the normal control rats. In addition, this combination resulted in normal serum levels of IL-2, IFN-γ, AFP and AFU. The results of the present study suggested that a combination of curcumin and taurine may be a novel prophylactic agent against hepatocarcinogenesis in high-risk groups exposed to chemical hepatocarcinogens.

Curcumin Inhibits Transforming Growth Factor β Induced Differentiation of Mouse Lung Fibroblasts to Myofibroblasts

Transforming growth factor β (TGF-β) induced differentiation of lung fibroblasts to myofibroblasts is a key event in the pathogenesis of pulmonary fibrosis. This study aimed to evaluate the effect of curcumin on TGF-β induced differentiation of lung fibroblasts to myofibroblasts and explore the underlying mechanism. Mouse lung fibroblasts were cultured and treated with TGF-β2 and curcumin or rosiglitazone. Cell vitality was examined by MTT assay. The secretion of collagen-1 was assessed by ELISA. α smooth muscle actin (α-SMA) was visualized by immunofluorescence technique. The expression of peroxisome proliferator activated receptor γ (PPAR-γ) and platelet derived growth factor R β (PDGFR-β) was detected by PCR and Western blot analysis. We found that curcumin and rosiglitazone inhibited the proliferation and TGF-β induced differentiation of mouse lung fibroblasts. In addition, curcumin and rosiglitazone inhibited collagen-1 secretion and α-SMA expression in mouse lung fibroblasts. Furthermore, curcumin and rosiglitazone upregulated PPAR-γ and downregulated PDGFR-β expression in mouse lung fibroblasts. In conclusion, our study reveals novel mechanism by which curcumin inhibits TGF-β2 driven differentiation of lung fibroblasts to myofibroblasts. Curcumin could potentially be used for effective treatment of pulmonary fibrosis.

MicroRNA-17-5p-activated Wnt/β-catenin pathway contributes to the progression of liver fibrosis

Aberrant Wnt/β-catenin pathway contributes to the development of liver fibrosis. MicroRNAs (MiRNAs) are found to act as regulators of the activation of hepatic stellate cell (HSC) in liver fibrosis. However, whether miRNAs activate Wnt/β-catenin pathway in activated HSCs during liver fibrosis is largely unknown. In this study, we found that Salvianolic acid B (Sal B) treatment significantly inhibited liver fibrosis in CCl₄-treated rats, HSC-T6 cells and rat primary HSCs, resulting in the suppression of type I collagen and alpha-smooth muscle actin. Also, Sal B suppressed HSC activation and cell proliferation in vitro. Interestingly, Sal B treatment induced the inactivation of Wnt/β-catenin pathway, with an increase in P-β-catenin and Wnt inhibitory factor 1 (WIF1). We demonstrated that the anti-fibrotic effects caused by Sal B were, at least in part, via WIF1. Moreover, our study revealed that miR-17-5p was reduced in vivo and in vitro after Sal B treatment. As confirmed by luciferase activity assays, WIF1 was a direct target of miR-17-5p. Notably, the suppression of HSCs induced by Sal B was almost inhibited by miR-17-5p mimics. Collectively, we demonstrated that miR-17-5p activates Wnt/β-catenin pathway to result in HSC activation through inhibiting WIF1 expression.

Identification of a Novel lincRNA-p21-miR-181b-PTEN Signaling Cascade in Liver Fibrosis

Previously, we found that long intergenic noncoding RNA-p21 (lincRNA-p21) inhibits hepatic stellate cell (HSC) activation and liver fibrosis via p21. However, the underlying mechanism of the antifibrotic role of lincRNA-p21 in liver fibrosis remains largely unknown. Here, we found that lincRNA-p21 expression was significantly downregulated during liver fibrosis. In LX-2 cells, the reduction of lincRNA-p21 induced by TGF-β1 was in a dose- and time-dependent manner. lincRNA-p21 expression was reduced in liver tissues from patients with liver cirrhosis when compared with that of healthy controls. Notably, lincRNA-p21 overexpression contributed to the suppression of HSC activation. lincRNA-p21 suppressed HSC proliferation and induced a significant reduction in α-SMA and type I collagen. All these effects induced by lincRNA-p21 were blocked down by the loss of PTEN, suggesting that lincRNA-p21 suppressed HSC activation via PTEN. Further study demonstrated that microRNA-181b (miR-181b) was involved in the effects of lincRNA-p21 on HSC activation. The effects of lincRNA-p21 on PTEN expression and HSC activation were inhibited by miR-181b mimics. We demonstrated that lincRNA-p21 enhanced PTEN expression by competitively binding miR-181b. In conclusion, our results disclose a novel lincRNA-p21-miR-181b-PTEN signaling cascade in liver fibrosis and suggest lincRNA-p21 as a promising molecular target for antifibrosis therapy.

Demethyleneberberine Protects against Hepatic Fibrosis in Mice by Modulating NF-κB Signaling

Demethyleneberberine (DMB) is an essential metabolite of Berberine (BBR) in vivo. Recent reports have revealed multiple novel therapeutic applications of BBR. However, the pharmacological activities of DMB remain to be elucidated. This study aimed to demonstrate the hepatoprotective and anti-fibrotic effects of DMB both in vitro and in vivo. Here we showed that DMB protects against thioacetamide (TAA)-induced hepatic fibrosis in mice and exhibits a higher safety profile as compared to BBR. Flow cytometry and Western blotting analysis showed that DMB is able to suppress the activation of hepatic stellate cells (HSCs) and induce cell apoptosis through the nuclear factor-κB (NF-κB) cascade. Immunohistochemical (IHC) and quantitative polymerase chain reaction (qPCR) analysis indicated that DMB also has inhibitory effects on collagen synthesis and is able to increase collagen degradation by blocking the transforming growth factor β 1 (TGF-β1)-Smad signaling and reducing the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of MMP (TIMPs). These findings indicate that DMB has the potential to attenuate hepatic fibrosis via suppressing HSC activation.

MicroRNA-17-5p activates hepatic stellate cells through targeting of Smad7

A considerable amount of research has focused on the roles of microRNAs (miRNA) in the pathophysiology of liver fibrosis in view of their regulatory effects on hepatic stellate cell (HSC) functions, including proliferation, differentiation, and apoptosis. Recently, miR-17-5p was shown to promote cell proliferation and migration in liver. Transforming growth factor-β1 (TGF-β1) has been characterized as the master fibrogenic cytokine that stimulates HSC activation and promotes progression of liver fibrosis. The issue of whether miR-17-5p plays a role in TGF-β1-induced hepatic fibrogenesis remains to be established. In this study, we demonstrated a dose-/time-dependent increase in miR-17-5p expression in TGF-β1-treated HSCs. Enhanced miR-17-5p expression was additionally observed in CCl4-induced rat liver fibrosis. Inhibition of miR-17-5p led to suppression of HSC proliferation induced by TGF-β1 without affecting cellular apoptosis. Notably, miR-17-5p was significantly associated with TGF-β1-induced expression of type I collagen and α-SMA in HSC. Furthermore, Smad7, a negative regulator of the TGF-β/Smad pathway, was confirmed as a direct target of miR-17-5p. Serum miR-17-5p levels were significantly higher in patients with cirrhosis, compared to healthy controls. Our results collectively indicate that miR-17-5p promotes HSC proliferation and activation, at least in part, via reduction of Smad7, supporting its potential utility as a novel therapeutic target for liver fibrosis.

Curcumin ameliorates renal fibrosis by inhibiting local fibroblast proliferation and extracellular matrix deposition

Renal fibrosis is mainly characterized by activation and proliferation of interstitial fibroblasts and by excessive synthesis and accumulation of extracellular matrix (ECM) components, including fibronectin (FN) and collagen. This study investigated the effects of curcumin on proliferation of renal interstitial fibroblasts and their underlying mechanisms in vivo and in vitro. ECM components were visualized by Sirius red and immunohistochemistry staining and quantified by western blot analysis in mice with unilateral ureteral obstruction (UUO). Duplex staining for proliferating cell nuclear antigen and α-smooth muscle actin (α-SMA), as well as MTT and flow cytometry assays, were performed to measure fibroblast proliferation. Protein expression of phosphorylated Smad2/3 (p-Smad2/3) and peroxisome proliferator-activated receptor-γ (PPAR-γ) were assessed by western blotting. Curcumin treatment decreased the accumulation of type I collagen and FN in the kidney of animals with UUO. Activation of rat renal interstitial fibroblasts (NRK-49F) was induced by TGF-β1. Curcumin treatment inhibited fibroblast proliferation and the cell cycle was arrested in the G1 phase. Curcumin treatment upregulated the expression of PPAR-γ and downregulated the expression of p-Smad2/3. These results suggest that curcumin treatment ameliorates renal fibrosis by reducing fibroblast proliferation and ECM accumulation mediated by PPAR-γ and Smad-dependent TGF-β1 signaling.

Influence of Biejiajian pill on PDGF and Ras signaling pathways in hepatic fibrosis in rats

AIM: To explore the anti-fibrotic mechanism of Biejiajian pill, a traditional Chinese medicine for activating blood circulation and eliminating stasis, in rats with hepatic fibrosis.

METHODS: Hepatic fibrosis was induced in rats by subcutaneous injection of CCl₄. SD rats were randomly divided into five groups: a control group, a model group, low-, medium- and high-dose Biejiajian pill treatment groups. The three treatment groups were given Biejiajian pill 0.55, 1.10, and 2.20 g/(kg•d), respectively, while the normal control group and model group were treated with equal volume of normal saline by gavage. At the 11^th week, hepatic pathological changes were observed. The immunohistochemical technique was applied to analyze the expression of extracellular signal regulated kinase 1 (ERK1) in hepatic tissue. RT-PCR was applied to analyze the expression of platelet derivative growth factor (PDGF) and Ras mRNAs in hepatic tissue.

RESULTS: Compared with the control group, the expression levels of ERK1 protein and PDGF and Ras mRNAs increased significantly in the model group (0.19 ± 0.001 vs 0.71 ± 0.018, 0.12 ± 0.000 vs 0.42 ± 0.006, 0.12 ± 0.000 vs 0.44 ± 0.017, P < 0.05). Compared with the model group, Biejiajian pill significantly improved hepatic pathological changes and decreased the expression of ERK1 protein and PDGF and Ras mRNAs, and the efficacy of high-dose Biejiajian pill was the best.

CONCLUSION: Biejiajian pill can improve hepatic pathological changes in rats with hepatic fibrosis possibly via mechanisms associated with activating the Ras/ERK signaling pathway.

Hepatic stellate cell is activated by microRNA-181b via PTEN/Akt pathway

Activation of hepatic stellate cells (HSCs) is an essential event in the initiation and progression of liver fibrosis. MicroRNAs have been shown to play a pivotal role in regulating HSC functions such as cell proliferation, differentiation, and apoptosis. Recently, miR-181b has been reported to promote HSCs proliferation by targeting p27. But whether alpha-smooth muscle actin (α-SMA) or collagens could be promoted by miR-181b in activated HSCs is still not clear. Therefore, the understanding of the role of miR-181b in liver fibrosis remains limited. Our results showed that miR-181b expression was increased much higher than miR-181a expression in vitro in transforming growth factor-β1-induced HSC activation as well as in vivo in carbon tetrachloride-induced rat liver fibrosis. Of note, overexpression of miR-181b significantly increased the expressions level of α-SMA and type I collagen, and further promoted HSCs proliferation. Furthermore, phosphatase and tensin homologs deleted on chromosome 10 (PTEN), a negative regulator of PI3K/Akt pathway, were confirmed as a direct target of miR-181b. We demonstrated that miR-181b could suppress PTEN expression and increase Akt phosphorylation in HSCs. Interestingly, the effects of miR-181b on the activation of HSCs were blocked down by Akt inhibitor LY294002. Our results revealed a profibrotic role of miR-181b in HSC activation and demonstrated that miR-181b could activate HSCs, at least in part, via PTEN/Akt pathway.

Curcumin attenuates angiogenesis in liver fibrosis and inhibits angiogenic properties of hepatic stellate cells

Hepatic fibrosis is concomitant with sinusoidal pathological angiogenesis, which has been highlighted as novel therapeutic targets for the treatment of chronic liver disease. Our prior studies have demonstrated that curcumin has potent antifibrotic activity, but the mechanisms remain to be elucidated. The current work demonstrated that curcumin ameliorated fibrotic injury and sinusoidal angiogenesis in rat liver with fibrosis caused by carbon tetrachloride. Curcumin reduced the expression of a number of angiogenic markers in fibrotic liver. Experiments in vitro showed that the viability and vascularization of rat liver sinusoidal endothelial cells and rat aortic ring angiogenesis were not impaired by curcumin. These results indicated that hepatic stellate cells (HSCs) that are characterized as liver-specific pericytes could be potential target cells for curcumin. Further investigations showed that curcumin inhibited VEGF expression in HSCs associated with disrupting platelet-derived growth factor-β receptor (PDGF-βR)/ERK and mTOR pathways. HSC motility and vascularization were also suppressed by curcumin associated with blocking PDGF-βR/focal adhesion kinase/RhoA cascade. Gain- or loss-of-function analyses revealed that activation of peroxisome proliferator-activated receptor-γ (PPAR-γ) was required for curcumin to inhibit angiogenic properties of HSCs. We concluded that curcumin attenuated sinusoidal angiogenesis in liver fibrosis possibly by targeting HSCs via a PPAR-γ activation-dependent mechanism. PPAR-γ could be a target molecule for reducing pathological angiogenesis during liver fibrosis.

Protective effect of curcumin against heavy metals-induced liver damage

Occupational or environmental exposures to heavy metals produce several adverse health effects. The common mechanism determining their toxicity and carcinogenicity is the generation of oxidative stress that leads to hepatic damage. In addition, oxidative stress induced by metal exposure leads to the activation of the nuclear factor (erythroid-derived 2)-like 2/Kelch-like ECH-associated protein 1/antioxidant response elements (Nrf2/Keap1/ARE) pathway. Since antioxidant and chelating agents are generally used for the treatment of heavy metals poisoning, this review is focused on the protective role of curcumin against liver injury induced by heavy metals. Curcumin has shown, in clinical and preclinical studies, numerous biological activities including therapeutic efficacy against various human diseases and anti-hepatotoxic effects against environmental or occupational toxins. Curcumin reduces the hepatotoxicity induced by arsenic, cadmium, chromium, copper, lead and mercury, prevents histological injury, lipid peroxidation and glutathione (GSH) depletion, maintains the liver antioxidant enzyme status and protects against mitochondrial dysfunction. The preventive effect of curcumin on the noxious effects induced by heavy metals has been attributed to its scavenging and chelating properties, and/or to the ability to induce the Nrf2/Keap1/ARE pathway. However, additional research is needed in order to propose curcumin as a potential protective agent against liver damage induced by heavy metals.

Cross-species analysis of nicotine-induced proteomic alterations in pancreatic cells

Toxic compounds in tobacco, such as nicotine, may adversely affect pancreatic function. We aim to determine nicotine-induced protein alterations in pancreatic cells, thereby revealing links between nicotine exposure and pancreatic disease. We compared the proteomic alterations induced by nicotine treatment in cultured pancreatic cells (mouse, rat, and human stellate cells and human duct cells) using MS-based techniques, specifically SDS-PAGE (gel) coupled with LC-MS/MS and spectral counting. We identified thousands of proteins in pancreatic cells, hundreds of which were identified exclusively or in higher abundance in either nicotine-treated or untreated cells. Interspecies comparisons of stellate cell proteins revealed several differentially abundant proteins (in nicotine treated versus untreated cells) common among the three species. Proteins appearing in all nicotine-treated stellate cells include amyloid beta (A4), procollagen type VI alpha 1, integral membrane protein 2B, and toll-interacting protein. Proteins that were differentially expressed upon nicotine treatment across cell lines were enriched in certain pathways, including nicotinic acetylcholine receptor, cytokine, and integrin signaling. At this analytical depth, we conclude that similar pathways are affected by nicotine, but alterations at the protein level among stellate cells of different species vary. Further interrogation of such pathways will lead to insights into the potential effect of nicotine on pancreatic cells at the biomolecular level and the extension of this concept to the effect of nicotine on pancreatic disease.

Nuclear erythroid 2-related factor 2: a novel potential therapeutic target for liver fibrosis

Hepatic stellate cells (HSC) are the key fibrogenic cells of the liver. HSC activation is a process of cellular transdifferentiation that occurs upon liver injury, but the mechanisms underlying liver fibrosis are unknown. Nuclear erythroid 2-related factor 2 (Nrf2) is an oxidative stress-mediated transcription factor with a variety of downstream targets aimed at cytoprotection. However, Nrf2 has recently been implicated as a new therapeutic target for the treatment of liver fibrosis. This review focuses on the transcriptional repressors that either control liver injury or regulate specific fibrogenic functions of liver fibrosis. We also show that Nrf2 may reveal significant gene expression changes, suggesting that Nrf2 activation may ameliorate liver fibrosis.

Global microRNA expression profiling: curcumin (diferuloylmethane) alters oxidative stress-responsive microRNAs in human ARPE-19 cells

PURPOSE

In recent years, microRNAs (miRNAs) have been reported to play important roles in a broad range of biologic processes, including oxidative stress-mediated ocular diseases. In addition, the polyphenolic compound curcumin has been shown to possess anti-inflammatory, antioxidant, anticancer, antiproliferative, and proapoptotic activities. The aim of this study was to investigate the impact of curcumin on the expression profiles of miRNAs in ARPE-19 cells exposed to oxidative stress.

METHODS

MiRNA expression profiles were measured in ARPE-19 cells treated with 20 μΜ curcumin and 200 μΜ H₂O₂. PCR array analysis was performed using web-based software from SABiosciences. The cytotoxicity of ARPE-19 cells was determined with the CellTiter-Blue cell viability assay. The effects of curcumin on potential miRNA targets were analyzed with quantitative real-time PCR and western blotting.

RESULTS

Curcumin treatment alone for 6 h had no effect on ARPE-19 cell viability. Incubation with H₂O₂ (200 µM) alone for 18 h decreased cell viability by 12.5%. Curcumin alone downregulated 20 miRNAs and upregulated nine miRNAs compared with controls. H₂O₂ downregulated 18 miRNAs and upregulated 29 miRNAs. Furthermore, curcumin pretreatment in cells exposed to H₂O₂ significantly reduced the H₂O₂-induced expression of 17 miRNAs. As determined with quantitative real-time PCR and western blotting, curcumin increased the expression of antioxidant genes and reduced angiotensin II type 1 receptor, nuclear factor-kappa B, and vascular endothelial growth factor expression at the messenger RNA and protein levels.

CONCLUSIONS

The results demonstrated that curcumin alters the expression of H₂O₂-modulated miRNAs that are putative regulators of antioxidant defense and renin-angiotensin systems, which have been reported to be linked to ocular diseases.

A novel mechanism of PPAR gamma induction via EGFR signalling constitutes rational for combination therapy in bladder cancer

Background

Two signalling molecules that are attractive for targeted therapy are the epidermal growth factor receptor (EGFR) and the peroxisome proliferator-activated receptor gamma (PPARγ). We investigated possible crosstalk between these 2 pathways, particularly in light of the recent evidence implicating PPARγ for anticancer therapy.

Principal Findings

As evaluated by MTT assays, gefitinib (EGFR inhibitor) and DIM-C (PPARγ agonist) inhibited growth of 9 bladder cancer cell lines in a dose-dependent manner but with variable sensitivity. In addition, combination of gefitinib and DIM-C demonstrated maximal inhibition of cell proliferation compared to each drug alone. These findings were confirmed in vivo, where combination therapy maximally inhibited tumor growth in contrast to each treatment alone when compared to control (p<0.04). Induction of PPARγ expression along with nuclear accumulation was observed in response to increasing concentrations of gefitinib via activation of the transcription factor CCAT/enhancer-binding protein-β (CEBP-β). In these cell lines, DIM-C significantly sensitized bladder cancer cell lines that were resistant to EGFR inhibition in a schedule-specific manner.

Conclusion

These results suggest that PPARγ agonist DIM-C can be an excellent alternative to bladder tumors resistant to EGFR inhibition and combination efficacy might be achieved in a schedule-specific manner.

Curcumin and liver disease

Liver diseases pose a major medical problem worldwide and a wide variety of herbs have been studied for the management of liver-related diseases. In this respect, curcumin has long been used in traditional medicine, and in recent years it has been the object of increasing research interest. In combating liver diseases, it seems clear that curcumin exerts a hypolipidic effect, which prevents the fatty acid accumulation in the hepatocytes that may result from metabolic imbalances, and which may cause nonalcoholic steatohepatitis. Another crucial protective activity of curcumin, not only in the context of chronic liver diseases but also regarding carcinogenesis and other age-related processes, is its potent antioxidant activity, which affects multiple processes and signaling pathways. The effects of curcumin on NF-κβ are crucial to our understanding of the potent hepatoprotective role of this herb-derived micronutrient. Because curcumin is a micronutrient that is closely related to cellular redox balance, its properties and activity give rise to a series of molecular reactions that in every case and biological situation affect the mitochondria.

Curcumin inhibits gene expression of receptor for advanced glycation end-products (RAGE) in hepatic stellate cells in vitro by elevating PPARγ activity and attenuating oxidative stress

BACKGROUND AND PURPOSE

Diabetes is characterized by hyperglycaemia, which facilitates the formation of advanced glycation end-products (AGEs). Type 2 diabetes mellitus is commonly accompanied by non-alcoholic steatohepatitis, which could lead to hepatic fibrosis. Receptor for AGEs (RAGE) mediates effects of AGEs and is associated with increased oxidative stress, cell growth and inflammation. The phytochemical curcumin inhibits the activation of hepatic stellate cells (HSCs), the major effectors during hepatic fibrogenesis. The aim of this study was to explore the underlying mechanisms of curcumin in the elimination of the stimulating effects of AGEs on the activation of HSCs. We hypothesize that curcumin eliminates the effects of AGEs by suppressing gene expression of RAGE.

EXPERIMENTAL APPROACH

Gene promoter activities were evaluated by transient transfection assays. The expression of rage was silenced by short hairpin RNA. Gene expression was analysed by real-time PCR and Western blots. Oxidative stress was evaluated.

KEY RESULTS

AGEs induced rage expression in cultured HSCs, which played a critical role in the AGEs-induced activation of HSCs. Curcumin at 20 µM eliminated the AGE effects, which required the activation of PPARγ. In addition, curcumin attenuated AGEs-induced oxidative stress in HSCs by elevating the activity of glutamate-cysteine ligase and by stimulating de novo synthesis of glutathione, leading to the suppression of gene expression of RAGE.

CONCLUSION AND IMPLICATIONS

Curcumin suppressed gene expression of RAGE by elevating the activity of PPARγ and attenuating oxidative stress, leading to the elimination of the AGE effects on the activation of HSCs.

LINKED ARTICLE

This article is commented on by Stefanska, pp. 2209-2211 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2012.01959.x.

DNMT1-mediated PTEN hypermethylation confers hepatic stellate cell activation and liver fibrogenesis in rats

Hepatic stellate cell (HSC) activation is an essential event during liver fibrogenesis. Phosphatase and tension homolog deleted on chromosome 10 (PTEN), a tumor suppressor, is a negative regulator of this process. PTEN promoter hypermethylation is a major epigenetic silencing mechanism in tumors. The present study aimed to investigate whether PTEN promoter methylation was involved in HSC activation and liver fibrosis. Treatment of activated HSCs with the DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-azadC) decreased aberrant hypermethylation of the PTEN gene promoter and prevented the loss of PTEN expression that occurred during HSC activation. Silencing DNA methyltransferase 1 (DNMT1) gene also decreased the PTEN gene promoter methylation and upregulated the PTEN gene expression in activated HSC-T6 cells. In addition, knockdown of DNMT1 inhibited the activation of both ERK and AKT pathways in HSC-T6 cells. These results suggest that DNMT1-mediated PTEN hypermethylation caused the loss of PTEN expression, followed by the activation of the PI3K/AKT and ERK pathways, resulting in HSC activation.

Preventive action of curcumin in experimental acute pancreatitis in mouse

BACKGROUND & OBJECTIVES

Curcuma longa (turmeric) has a long history of use in Ayurvedic medicine as a treatment for inflammatory conditions. The purpose of the present study was to investigate the preventive effects of curcumin against acute pancreatitis (AP) induced by caerulein in mouse and to elucidate possible mechanism of curcumin action.

METHODS

Curcumin (50 mg/kg/day) was intraperitoneally injected to Kun Ming male mice for 6 days, followed by injection of caerulein to induce AP. GW9662 (0.3 mg/kg), a specific peroxisome proliferator-activated receptor gamma (PPARγ) antagonist, was intravenously injected along with curcumin. Murine macrophage RAW264.7 cells were treated with 100 μmol/l curcumin for 2 h, and then stimulated with 0.1 μ g/ml lipopolysaccharide (LPS). Serum amylase and transaminase levels were measured at 10 h after AP. TNF-α level in mouse serum and cell culture medium were detected by ELISA. Expression of PPARγ and NF-κB were analyzed by RT-PCR and Western blot.

RESULTS

Curcumin significantly decreased the pancreas injury and reversed the elevation of serum amylase, ALT and AST activities and TNF-α level in mice with AP. Curcumin treatment inhibited the elevation of NF-κB-p65 in the nucleus of mouse pancreas AP group and RAW264.7 cells, but significantly increased the expression of PPARγ. GW9662 could abolish the effects of curcumin on serum levels of amylase, ALT, AST, TNF-α, and NF-κB level.

INTERPRETATION & CONCLUSIONS

Our results suggest that curcumin could attenuate pancreas tissue and other organ injury by inhibiting the release of inflammatory cytokine TNF-α. These effects may involve upregulation of PPARγ and subsequent downregulation of NF-κB.

Protective effects of kaerophyllin against liver fibrogenesis in rats

BACKGROUND

We previously demonstrated that kaerophyllin, a lignan, isolated from a widely used traditional Chinese herb, Bupleurum scorzonerifolium, leading to the inhibition of hepatic stellate cells (HSCs) activation in vitro. This current study evaluated the in vivo role of kaerophyllin in protecting the liver against injury and fibrogenesis caused by thioacetamide (TAA) in rats and further explored the underlying mechanisms.

MATERIALS AND METHODS

Liver fibrosis in Sprague-Dawley rats was induced by intraperitoneal injection of TAA (200 mg/kg) twice per week for 6 weeks. Animals were divided into five groups: vehicle control, TAA control, TAA + low dose kaerophyllin, TAA + high dose kaerophyllin and TAA + curcumin groups. Kaerophyllin (10 or 30 mg/kg) or curcumin (150 mg/mL) was given by gavage twice per day consecutively for 4 weeks starting 2 weeks after TAA injection. Rat HSCs were used to investigate the anti-inflammatory role of kaerophyllin against tumour necrosis factor α (TNF-α) in vitro. Peroxisome proliferator-activated receptor-γ (PPAR-γ) expression was knocked down in rat HSCs using PPAR-γ small interfering RNAs.

RESULTS

Kaerophyllin significantly protected liver from injury by reducing serum aspartate transaminase and alanine transaminase levels and by improving the histological architecture and fibrosis score. In addition, kaerophyllin suppressed inflammation by reducing the mRNA of TNF-α, interleukin-1β (IL-1β) and monocyte chemoattractant protein-1 (MCP-1) genes. In HSCs, kaerophyllin elevated PPAR-γ activity and reduced TNF-α-stimulated mRNA levels of intracellular adhesion molecule-1 (ICAM-1), MCP-1 and IL-1β genes, which were reversed by small interfering RNA knockdown of PPAR-γ gene.

CONCLUSIONS

Our results demonstrated that kaerophyllin protected the rat liver from TAA-caused injury and fibrogenesis by suppressing hepatic inflammation and inhibiting HSC activation, possibly through upregulation of PPAR-γ expression.

Curcumin eliminates the inhibitory effect of advanced glycation end-products (AGEs) on gene expression of AGE receptor-1 in hepatic stellate cells in vitro

Diabetes is featured by hyperglycemia, which facilitates the formation of advanced glycation end-products (AGEs). AGEs are a causal factor in development of diabetic complications. AGE receptor-1 (AGE-R1) is responsible for detoxification and clearance of AGEs. Type 2 diabetes mellitus is commonly accompanied by non-alcoholic steatohepatitis, which could cause hepatic fibrosis. Little attention has been paid to effects of AGEs on hepatic fibrogenesis. Curcumin, a phytochemical from turmeric, has been reported to inhibit the activation of hepatic stellate cells (HSCs), the major effectors during hepatic fibrogenesis, and to protect against hepatic fibrogenesis in vitro and in vivo. The current study was designed to evaluate the effects of AGEs on inducing HSC activation, to assess the role of curcumin in diminishing the AGE effects, and to explore the underlying mechanisms. Our results showed that AGEs stimulated HSC activation by inducing cell proliferation and expression of genes relevant to HSC activation, which were abrogated by curcumin. Curcumin induced gene expression of AGE-R1 in passaged HSCs, which might facilitate the attenuation of the stimulatory effects of AGEs on the activation of HSCs. Further experiments revealed that curcumin inhibited the activity of extracellular signal-regulated kinase (ERK), and induced gene expression and the activity of peroxisome proliferator-activated receptor-gamma (PPARγ), leading to the induction of the AGE-R1 gene expression. In summary, AGEs stimulated HSC activation. Curcumin eliminated the AGE effects at least partially by inducing the AGE-R1 gene expression. The process was mediated by inhibiting ERK activity, inducing gene expression of PPARγ and stimulating its transactivity.

Heme oxygenase-1 prevents liver fibrosis in rats by regulating the expression of PPARγ and NF-κB

AIM: To investigate the effects of heme oxygenase (HO)-1 on liver fibrosis and the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and nuclear factor-kappa B (NF-κB) in rats.

METHODS: Sixty Wistar rats were used to construct liver fibrosis models and were randomly divided into 5 groups: group A (normal, untreated), group B (model for 4 wk, untreated), group C (model for 6 wk, untreated), group D [model for 6 wk, treated with zinc protoporphyrin IX (ZnPP-IX) from week 4 to week 6], group E (model for 6 wk, treated with hemin from week 4 to week 6). Next, liver injury was assessed by measuring serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and albumin levels. The degree of hepatic fibrosis was evaluated by measuring serum hyaluronate acid (HA), type IV collagen (IV-C) and by histological examination. Hydroxyproline (Hyp) content in the liver homogenate was determined. The expression levels of alpha-smooth muscle actin (α-SMA) in liver tissue were measured by real-time quantitative polymerase chain reaction (RT-PCR). The expression levels of PPARγ and NF-κB were determined by RT-PCR and Western blotting.

RESULTS: The expression of HO-1 increased with the development of fibrosis. Induction of HO-1 by hemin significantly attenuated the severity of liver injury and the levels of liver fibrosis as compared with inhibition of HO-1 by ZnPP-IX. The concentrations of serum ALT, AST, HA and IV-C in group E decreased compared with group C and group D (P < 0.01). Amount of Hyp and α-SMA in the liver tissues in group E decreased compared with group C (0.62 ± 0.14 vs 0.84 ± 0.07, 1.42 ± 0.17 vs 1.84 ± 0.17, respectively, P < 0.01) and group D (0.62 ± 0.14 vs 1.11 ± 0.16, 1.42 ± 0.17 vs 2.56 ± 0.37, respectively, P < 0.01). The expression of PPARγ at levels of transcription and translation decreased with the development of fibrosis especially in group D; and it increased in group E compared with groups C and D (0.88 ± 0.15 vs 0.56 ± 0.19, 0.88 ± 0.15 vs 0.41 ± 0.11, respectively, P < 0.01). The expression of NF-κB increased with the development of fibrosis especially in group D; and it decreased in group E compared with groups C and D (1.43 ± 0.31 vs 1.89 ± 0.29, 1.43 ± 0.31 vs 2.53 ± 0.54, respectively, P < 0.01).

CONCLUSION: Our data demonstrate a potential mechanism that HO-1 can prevent liver fibrosis by enhancing the expression of PPARγ and decreasing the expression of NF-κB in liver tissues.