Effect of curcumin on the proliferation and apoptosis of hepatic stellate cells

Curcumin downregulates Smad pathways and reduces hepatic stellate cells activation in experimental fibrosis

INTRODUCTION AND OBJECTIVES

Curcumin, a polyphenol, is a natural compound that has been widely studied as a hepatoprotector; however, only a few studies have examined its ability to reduce fibrosis in previously established cirrhosis. The objective of this study was to investigate whether curcumin could reduce carbon tetrachloride (CCl₄)-induced fibrosis and if so, to determine the action mechanisms involved in the reduction process.

MATERIALS AND METHODS

CCl₄ was administered to male Wistar rats (400 mg/kg, three times a week, i. p.) for 12 weeks; curcumin (100 mg/kg body weight twice per day, p. o.) was administered from week 9-12 of CCl₄ treatment. Biochemical markers of hepatic injury and oxidative stress were evaluated. Hematoxylin and eosin, Masson's trichrome stains, transmission electron microscopy; immunohistochemistry, and zymography assays were carried out. Moreover, Smad3 and α-SMA mRNA and protein levels were studied. Western blotting by TGF-β, CTGF, Col-I, MMP-13, NF-κB, IL-1, IL-10, Smad7, pSmad3, and pJNK proteins was developed.

RESULTS AND CONCLUSIONS

Curcumin reduced liver damage, oxidative stress, fibrosis, and restored normal activity of MMP-9 and MMP-2. Besides, curcumin restored NF-κB, IL-1, IL-10, TGF-β, CTGF, Col-I, MMP-13, and Smad7 protein levels. On the other hand, curcumin decreased JNK and Smad3 phosphorylation. Furthermore, curcumin treatment decreased α-SMA and Smad3 protein and mRNA levels. Curcumin normalized GSH, and NF-κB, JNK-Smad3, and TGF-β-Smad3 pathways, leading to a decrement in activated hepatic stellate cells, thereby producing its antifibrotic effects.

Danshensu, a novel indoleamine 2,3-dioxygenase1 inhibitor, exerts anti-hepatic fibrosis effects via inhibition of JAK2-STAT3 signaling

BACKGROUND

Indoleamine 2,3-dioxygenase 1 (IDO1), an important intracellular rate-limiting enzyme in the development of Hepatic fibrosis (HF), and has been proposed as a hallmark of HF. Danshensu (DSS) is a major bioactive component that isolated from a edible traditional Chinese medicinal herb Salviae Miltiorrhizae Radix et Rhizoma (Danshen), while, the anti-HF mode and mechanism of action of DSS have not been fully elucidated.

METHODS

Carbon tetrachloride (CCl4)-induced rat HF model and TGF-β1-induced hepatic stellate cell (HSC) model were employed to assess the in vivo and in vitro anti-HF effects of DSS. HSC-T6 cells stably expressing IDO1, a constitutively active IDO1 mutant, was used to determine the role of JAK2-STAT3 signaling in the DSS's anti-HF effects.

RESULTS

We found that intragastric administration of DSS potently reduced fibrosis, inhibited IDO1 expression and STAT3 activity both in vitro and in vivo. Using molecular docking and molecular dynamics analysis, DSS was identified as a novel IDO1 inhibitor. Mechanistic studies indicated that DSS inhibited JAK2-STAT3 signaling, it reduced IDO1 expression, STAT3 phosphorylation and STAT3 nuclear localization. More importantly, overexpression of IDO1 diminished DSS's anti-HF effects.

CONCLUSION

Our findings provide a pharmacological justification for the clinical use of DSS in treating HF, and suggest that DSS has the potential to be developed as a modern alternative and/or complimentary agent for HF treatment and prevention.

Gypsophila elegans isoorientin-2″-O-α-l-arabinopyranosyl ameliorates porcine serum-induced immune liver fibrosis by inhibiting NF-κB signaling pathway and suppressing HSC activation

The present study was to investigate the inhibitory effect of Gypsophila elegans isoorientin-2″-O-α-l-arabinopyranosyl (GEI) on hepatic stellate cells (HSCs), to reveal the underlying mechanism of GEI against hepatic fibrosis. Our study showed that GEI significantly alleviated liver injury induced by porcine serum (PS) in rats; it notably alleviated collagen accumulation as evidenced by a significant decrease in the levels of collagen biomarkers including hyaluronic acid, laminin, hydroxyproline and procollagen III N-terminal peptide. Moreover, GEI treatment markedly decreased the secretion of inflammatory cytokines by inhibiting the NF-κB pathway and significantly inhibited the generation of excessive extracellular matrix (ECM) components by restoring the balance between matrix metalloproteinases (MMPs) and tissue inhibitor of matrix metalloproteinases (TIMPs). Additionally, the cell experiments in vitro showed that GEI strongly inhibited HSC proliferation, migration and clonogenicity and markedly induced HSC apoptosis. Moreover, GEI caused cell cycle arrest at G2 phase. In conclusion, our study demonstrates that GEI significantly alleviates PS-induced hepatic fibrosis by inhibiting the NF-κB pathway, restoring the balance between MMPs and TIMPs, and suppressing HSC activation.

Highly Selective Targeting of Hepatic Stellate Cells for Liver Fibrosis Treatment Using a d-Enantiomeric Peptide Ligand of Fn14 Identified by Mirror-Image mRNA Display

Although liver fibrosis is a major public health issue, there is still no effective drug therapy in the clinic. Fibroblast growth factor-inducible 14 (Fn14), a membrane receptor highly specifically expressed in activated hepatic stellate cells (HSCs), is the key driver of liver fibrosis, and thus, it has a great potential as a novel target for the development of effective treatment. Here, we identified a d-enantiomeric peptide ligand of Fn14 through mirror-image mRNA display. This included the chemical synthesis of a d-enantiomer of the target protein (extracellular domain of Fn14), identification of an l-peptide ligand of d-Fn14 using a constructed mRNA peptide library, and identification of a d-enantiomer of the l-peptide, which is a ligand of the natural Fn14 for reasons of symmetry. The obtained d-peptide ligand showed strong binding to Fn14 while maintaining high proteolytic resistance. As a targeting moiety, this d-peptide successfully mediated high selectivity of activated HSCs for liposomal vehicles compared to that of other major cell types in the liver and significantly enhanced the accumulation of liposomes in the liver fibrosis region of a carbon tetrachloride-induced mouse model. Moreover, in combination with curcumin as an encapsulated load, a liposomal formulation conjugated with this d-peptide showed powerful inhibition of the proliferation of activated HSCs and reduced the liver fibrosis to a significant extent in vivo. This Fn14-targeting strategy may represent a promising approach to targeted drug delivery for liver fibrosis treatment. Meanwhile, the mirror-image mRNA display can provide a new arsenal for the development of d-peptide-based therapeutics against a variety of human diseases.

Curcumin, the main active constituent of turmeric (Curcuma longa L.), induces apoptosis in hepatic stellate cells by modulating the abundance of apoptosis-related growth factors

In order to elucidate the mechanism of action of curcumin against hepatic fibrosis, cultured rat hepatic stellate cells (HSC) (HSC-T6) were incubated with curcumin for 24 h, after which apoptosis was measured by flow-cytometry. The protein levels of the pro-apoptotic factors Fas and p53b as well as of the anti-apoptotic factor Bcl-2 were monitored by immunocytochemical ABC staining after incubation with curcumin for 24 h. In the case of 20 μM curcumin, not only was the respective apoptosis index increased, but also the abundance of the pro-apoptotic factors Fas and p53 were amplified, whereas that of the anti-apoptotic factor Bcl-2 decreased. All these effects were highly reproducible (P<0.05). Consequently, curcumin has an up-regulating effect on pro-apoptotic factors like Fas and p53 as well as a down-regulating effect of the anti-apoptotic factor Bcl-2, thus inducing apoptosis in HSC.

Curcuminoid binding to embryonal carcinoma cells: reductive metabolism, induction of apoptosis, senescence, and inhibition of cell proliferation

Curcumin preparations typically contain a mixture of polyphenols, collectively referred to as curcuminoids. In addition to the primary component curcumin, they also contain smaller amounts of the co-extracted derivatives demethoxycurcumin and bisdemethoxycurcumin. Curcuminoids can be differentially solubilized in serum, which allows for the systematic analysis of concentration-dependent cellular binding, biological effects, and metabolism. Technical grade curcumin was solubilized in fetal calf serum by two alternative methods yielding saturated preparations containing either predominantly curcumin (60%) or bisdemethoxycurcumin (55%). Continual exposure of NT2/D1 cells for 4–6 days to either preparation in cell culture media reduced cell division (1–5 µM), induced senescence (6–7 µM) or comprehensive cell death (8–10 µM) in a concentration-dependent manner. Some of these effects could also be elicited in cells transiently exposed to higher concentrations of curcuminoids (47 µM) for 0.5–4 h. Curcuminoids induced apoptosis by generalized activation of caspases but without nucleosomal fragmentation. The equilibrium binding of serum-solubilized curcuminoids to NT2/D1 cells incubated with increasing amounts of curcuminoid-saturated serum occurred with apparent overall dissociation constants in the 6–10 µM range. However, the presence of excess free serum decreased cellular binding in a hyperbolic manner. Cellular binding was overwhelmingly associated with membrane fractions and bound curcuminoids were metabolized in NT2/D1 cells via a previously unidentified reduction pathway. Both the binding affinities for curcuminoids and their reductive metabolic pathways varied in other cell lines. These results suggest that curcuminoids interact with cellular binding sites, thereby activating signal transduction pathways that initiate a variety of biological responses. The dose-dependent effects of these responses further imply that distinct cellular pathways are sequentially activated and that this activation is dependent on the affinity of curcuminoids for the respective binding sites. Defined serum-solubilized curcuminoids used in cell culture media are thus suitable for further investigating the differential activation of signal transduction pathways.

Expression of survivin in activated hepatic stellate cells and effect of transfection of antisense oligonucleotide targeting the survivin gene on apoptosis of HSC-T6 cells

AIM: To investigate the expression of survivin in activated hepatic stellate cell (HSC) and the effect of transfection of antisense oligonucleotide (ASODN) targeting the survivin gene on apoptosis of HSC-T6 cells.

METHODS: The experiment set the control group which not added liposome and oligonucleotide (ODN), liposome group which only added liposome, sense oligonucleotide (SODN) group (1 000 nmol/L) and 400, 800, 1 000 nmol/L ASODN group. The expression of survivin protein in activated HSC, hepatic carcinoma cells, and normal liver cells was detected by immunofluorescence. ASODN targeting the survivin gene was transfected into HSC-T6 cells with LipofectamineTM 2000, and transfection efficiency was detected by fluorescence microscopy. Forty-eight hours after transfection, the changes in survivin mRNA and protein expression were assessed by RT-PCR and Western blot, respectively, and cell apoptosis was measured by PI staining and flow cytometry.

RESULTS: The positive rate of survivin expression in activated HSC was significantly higher than that in normal liver cells (66.07% ± 8.55% vs 9.74% ± 2.68%, P < 0.05). The positive rate of survivin expression was highest in hepatic carcinoma cells among the three groups of cells (69.41% ± 9.10%). Strong green fluorescence was observed by fluorescence microscopy in cells transfected with different concentrations of ASODN, and the transfection efficiency reached 80%. Compared with blank control cells and cells transfected with empty lipofectamineTM 2000 or control oligonucleotide, the expression levels of survivin mRNA (0.94 ± 0.03, 0.95 ± 0.04 and 0.92 ± 0.04 vs 0.64 ± 0.02, 0.54 ± 0.02 and 0.26 ± 0.01) and protein (0.84 ± 0.02, 0.82 ± 0.03 and 0.81 ± 0.02 vs 0.53 ± 0.02, 0.38 ± 0.01 and 0.20 ± 0.01) were significantly decreased (all P < 0.01), and the apoptosis rate (19.00% ± 0.53%, 29.80% ± 1.54% and 48.70% ± 2.00%, respectively) significantly increased (all P < 0.01) in cells transfected with different concentrations of ASODN.

CONCLUSION: Survivin is highly expressed in activated HSC-T6 cells. Down-regulation of survivin expression by transfection of ASODN targeting the survivin gene can induce apoptosis of HSC-T6 cells.