Effect of pentoxifylline on arachidonic acid metabolism, neutral lipid synthesis and accumulation during induction of the lipocyte phenotype by retinol in murine hepatic stellate cell

Geniposide Ameliorates Liver Fibrosis Through Reducing Oxidative Stress and Inflammatory Respose, Inhibiting Apoptosis and Modulating Overall Metabolism

Liver fibrosis is a progressive liver damage condition caused by various factors and may progress toward liver cirrhosis, and even hepatocellular carcinoma. Many studies have found that the disfunction in metabolism could contribute to the development of liver fibrosis. Geniposide, derived from Gardenia jasminoides J. Ellis, has been demonstrated with therapeutic effects on liver fibrosis. However, the exact molecular mechanisms of such liver-protection remain largely unknown. The aim of this study was to explored the effect of geniposide on metabolic regulations in liver fibrosis. We used carbon tetrachloride (CCl₄) to construct a mouse model of liver fibrosis and subsequently administered geniposide treatment. Therapeutic effects of geniposide on liver fibrosis were accessed through measuring the levels of hepatic enzymes in serum and the pathological changes in liver. We also investigated the effects of geniposide on inflammatory response, oxidative stress and apoptosis in liver. Furthermore, serum untargeted metabolomics were used to explore the metabolic regulatory mechanisms behind geniposide on liver fibrosis. Our results demonstrated that geniposide could reduce the levels of hepatic enzymes in serum and ameliorate the pathological changes in liver fibrosis mice. Geniposide enhanced the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreased methane dicarboxylic aldehyde (MDA) levels in liver. Geniposide treatment also decreased the levels of interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha (TNF-a) in liver tissue homogenate. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) staining demonstrated that geniposide could reduce the apoptosis of hepatocytes. Geniposide increased the protein expression of B-cell lymphoma-2 (Bcl-2) and downregulated the protein expression of Bcl-2 Associated X (Bax), cleaved-Caspase 3, and cleaved-Caspase 9. Serum untargeted metabolomics analysis demonstrated that geniposide treatment improved the metabolic disorders including glycerophospholipid metabolism, arginine and proline metabolism, and arachidonic acid (AA) metabolism. In conclusion, our study demonstrated the protective effects of geniposide on liver fibrosis. We found that geniposide could treat liver fibrosis by inhibiting oxidative stress, reducing inflammatory response and apoptosis in the liver, and modulating glycerophospholipid, and arginine, proline, and AA metabolism processes.

Activated hepatic stellate cells promote liver cancer by induction of myeloid-derived suppressor cells through cyclooxygenase-2

Hepatic stellate cells (HSCs) are critical mediators of immunosuppression and the pathogenesis of hepatocellular carcinoma (HCC). Our previous work indicates that HSCs promote HCC progression by enhancing immunosuppressive cell populations including myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). MDSCs are induced by inflammatory cytokines (e.g., prostaglandins) and are important in immune suppression. However, how HSCs mediate expansion of MDSCs is uncertain. Thus, we studied activated HSCs that could induce MDSCs from bone marrow cells and noted that HSC-induced MDSCs up-regulated immunosuppressive activity via iNOS, Arg-1, and IL-4Rα. After treating cells with a COX-2 inhibitor or an EP4 antagonist, we established that HSC-induced MDSC accumulation was mediated by the COX2-PGE₂-EP4 signaling. Furthermore, in vivo animal studies confirmed that inhibition of HSC-derived PGE₂ could inhibit HSC-induced MDSC accumulation and HCC growth. Thus, our data show that HSCs are required for MDSC accumulation mediated by the COX2-PGE₂-EP4 pathway, and these data are the first to link HSC and MDSC subsets in HCC immune microenvironment and provide a rationale for targeting PGE₂ signaling for HCC therapy.

Capsaicin induces de-differentiation of activated hepatic stellate cell

Hepatic stellate cells (HSC) play a key role in liver fibrogenesis. Activation of PPARγ and inhibition of fibrogenic molecules are potential strategies to block HSC activation and differentiation. A number of natural products have been suggested to have antifibrotic effects for the de-activation and de-differentiation of HSCs. The purpose of this study was to investigate the in vitro effects of capsaicin on HSC de-activation and de-differentiation. The results demonstrated that capsaicin induced quiescent phenotype in GRX via PPARγ activation. Significant decrease in COX-2 and type I collagen mRNA expression was observed in the first 24 h of treatment. These events preceded the reduction of TGF-β1 and total collagen secretion. Thus, capsaicin promoted down-regulation of HSC activation by its antifibrotic and anti-inflammatory actions. These findings demonstrate that capsaicin may have potential as a novel therapeutic agent for the treatment of liver fibrosis.

Combined itraconazole-pentoxifylline treatment promptly reduces lung fibrosis induced by chronic pulmonary paracoccidioidomycosis in mice

Fibrosis is a severe and progressive sequel of many pulmonary diseases, has no effective therapy at present and, consequently, represents a serious health problem. In Latin America, chronic pulmonary paracoccidioidomycosis (PCM) is one of the most important, prevalent and systemic fungal diseases that allows the development of lung fibrosis, with the additional disadvantage that this sequel may appear even after an apparently successful course of antifungal therapy. In this study, was propose the pentoxifylline as complementary treatment in the pulmonary PCM due to its immunomodulatory and anti-fibrotic properties demonstrated in vitro and in vivo in liver, skin and lung. Our objective was to investigate the possible beneficial effects that a combined antifungal (Itraconazole) and immunomodulatory (Pentoxifylline) therapy would have in the development of fibrosis in a model of experimental chronic pulmonary PCM in an attempt to simulate the naturally occurring events in human patients. Two different times post-infection (PI) were chosen for starting therapy, an "early time" (4 weeks PI) when fibrosis was still absent and a "late time" (8 weeks PI) when the fibrotic process had started. Infected mice received the treatments via gavage and were sacrificed during or upon termination of treatment; their lungs were then removed and processed for immunological and histopathologic studies in order to assess severity of fibrosis. When pulmonary paracoccidioidomycosis had evolved and reached an advanced stage of disease before treatment began (as normally occurs in many human patients when first diagnosed), the combined therapy (itraconazole plus pentoxifylline) resulted in a significantly more rapid reduction of granulomatous inflammation and pulmonary fibrosis, when compared with the results of classical antifungal therapy using itraconazole alone.

Hepatic stellate cell line modulates lipogenic transcription factors

BACKGROUND/AIMS

Pre-adipocyte differentiation into adipocyte is a terminal differentiation process triggered by a cascade of transcription factors. Conversely, hepatic stellate cells (HSC) can switch between lipid storing and the myofibroblast phenotype in association with liver fibrotic processes. Here, adipogenic/lipogenic-related transcription factors and downstream-regulated genes were evaluated in a murine HSC cell line. GRX-HSC cells are transitional myofibroblasts that differentiate into lipocytes following retinol or indomethacin treatment.

METHODS/RESULTS

Specific mRNAs were quantified by a real-time polymerase chain reaction after 24 h or 7 days of cell culture with indomethacin or retinol. Proliferator-activated receptorgamma and Pex16 transcripts were increased either by retinol or indomethacin. Retinol induced a minor increase in C/enhancer binding proteinalpha transcripts, while only indomethacin increased adipsin transcripts.

CONCLUSIONS

Our results showed that the myofibroblast to lipocyte phenotype switch follows partially different transcriptional pathways, according to the effector. Retinol induces lipid synthesis and storage without affecting characteristic adipocytic genes, while indomethacin treatment restores the lipocytic phenotype with increased adipisin expression.

In vivo transfection of C/EBP-alpha gene could ameliorate CCL(4)-induced hepatic fibrosis in mice

AIM

Hepatic stellate cells (HSCs) play a key role in liver fibrosis. CCAAT/enhancer-binding proteins-alpha (C/EBP-alpha) can inhibit HSCs activation in vitro, as described in our previous study. However, little is known about the in vivo effect of C/EBP-alpha gene in hepatic fibrosis.

METHODS

Male BALB/c mice were injected by hydrodynamic protocol with pIRES2-EGFP-C/EBPalpha expression vector from the first to the fourth week (early intervention) or from the ninth to the 12th week (late intervention) after CCl(4) injection, respectively. Successful transfection of vector and the expression of C/EBP-alpha were confirmed with the appearance of green fluorescence in liver cells, immunohistochemical staining and the western blot.

RESULTS

High expression of C/EBP-alpha gene in liver cells, especially in non-parenchymal cells, could reduce the content of collagens by 82.5% and 72.3% (Sirius red staining + image analysis) and the content of hydroxyproline by 56.3% and 51.6%, respectively, in the early and late intervention experiments.

CONCLUSION

It is evident that exogenous C/EBP-alpha gene has an early and late intervention role in mice liver fibrosis.

Variations of ganglioside biosynthetic pathways in the phenotype conversion from myofibroblasts to lipocytes in murine hepatic stellate cell line

GRX cell line represents hepatic stellate cell and can be transformed from an actively proliferation myofibroblast phenotype into a quiescent fat-storing lipocyte phenotype. Both express the same gangliosides (GM3, GM2, GM1 and GD1a), which are resolved as doublets on HPTLC. Upper/lower band ratio is increased in lipocyte-like cells and the upper band is composed by ceramides with long-chain fatty acids. This study evaluated the contribution of de novo synthesis, sphingosine and Golgi recycling pathways on ganglioside biosynthesis, in both phenotypes. Cells were preincubated with 5 mM beta-chloroalanine (SPT: serine palmitoyltransferase inhibitor) or with 25 muM fumonisin B1 (ceramide synthase inhibitor) and then radiolabeled with [U-(14)C]galactose in the continued presence of inhibitors. Gangliosides were extracted, purified and analyzed by HPTLC. In myofibroblast-like cells, simple gangliosides use the de novo pathway while complex gangliosides are mainly synthesized by recycling pathways. In lipocyte-like cells, de novo pathway has a lesser contribution and this is in agreement with the lower activity of the committed enzyme of sphingolipid synthesis (SPT) detected in this phenotype. SPT mRNA has an identical expression in both phenotypes. It was also observed that gangliosides doublets from myofibroblast-like cells have the same distribution between triton soluble and insoluble fractions (upper band > lower band) while the gangliosides doublets from lipocyte-like cells show an inversion in the insoluble fraction (lower band > upper band) in comparison to soluble fraction. These results indicate that myofibroblast- and lipocyte-like cells have important differences between the glycosphingolipid biosynthetic pathways, which could contribute with the respective glycosphingolipid-enriched membrane microdomain's composition.

Involvement of C/EBP-alpha gene in in vitro activation of rat hepatic stellate cells

Hepatic stellate cells (HSCs) play key roles in hepatic fibrosis. One of the most striking alterations in activated HSCs is loss of cytoplasmic lipid droplets. However, the association of lipid storage with the activation of HSCs remains unclear. CCAAT/enhancer-binding proteins family (C/EBPs), especially C/EBP-alpha, controls differentiation of adipocytes. We suggested that C/EBP-alpha gene may be involved in HSCs activation. The present results showed that the expression levels of C/EBP-alpha and C/EBP-beta genes declined in activated HSCs. Over-expression of C/EBP-alpha gene in activated HSCs: (1) inhibited HSCs proliferation, extracellular matrix-producing, alpha-smooth muscle actin gene expression, and induced rebound of cytoplasmic lipid droplets; (2) reduced retinoic acid receptor-beta, C/EBP-delta and -beta gene expressions, but increased the active form C/EBP-beta PSer(105), and induced retinoid X receptor-alpha gene expression; and (3) did not affect the protein level of p16INK4a, p21Cip1/WAF1 or p27Kip1. In conclusions, C/EBP-alpha gene is involved in in vitro activation of rat HSCs.

Establishment and identification of a novel immortalized rat hepatic stellate cell line HSC-PQ

AIM: To establish and identify a novel immortalized rat hepatic stellate cell (HSC) line.

METHODS: Primary HSCs were isolated from the liver of adult male Sprague-Dawley rats by a combination of pronase-collagenase perfusion and density gradient centrifugation. Then a new HSC line, being HSC-PQ, was established, cultured, and passaged by way of cellular clone. Furthermore, cellular dynamics, light microscopy, transmission electron microscopy, and immunocytochemistry were employed to investigate characteristics of the HSC line.

RESULTS: About 2×10⁷ HSCs could be harvested from a Sprague-Dawley rat with the live rate over 95% and purity over 90%. Afterwards, HSC-PQ line was obtained on the basis of total activation of primary HSCs. The phenotype of HSC-PQ cells resembled that of fibroblasts. Firstly, the existence of a-SMA as well as desmin in these cells exhibited their HSC-derived-myofibroblast identity clearly. Secondly, both the doubling time of about 75 hours, and the stable expression of extracellular matrixs including collagen type I, collagen type III, fibronectin, laminin, etc. showed the fibroblast-like-characteristics of HSC-PQ line. But collagen IV could not be detected in cytoplasm. In addition, maintaining over one year, 32 passages of the cell line might demonstrate its immortalisation.

CONCLUSION: We have established a new immortalized rat HSC line (HSC-PQ), which shares most of the characteristics with primary activated rat HSCs.