Christine De Saeger

Role of inflammatory pathways, blood mononuclear cells, and gut-derived bacterial products in alcohol dependence

BACKGROUND Inflammation might play a role in the development of several psychiatric diseases. However, the origins of processes that mediate inflammation are unknown. We previously reported increased intestinal permeability, elevated blood lipopolysaccharide levels, and low-grade systemic inflammation associated with psychological symptoms of alcohol dependence in alcohol-dependent subjects. In this study, we tested inflammatory responses of peripheral blood mononuclear cells (PBMCs) to gut-derived bacterial products during detoxification and the relationship to alcohol craving. METHODS In 63 actively drinking noncirrhotic alcohol-dependent subjects, testing was performed at the beginning (day 2) and end (day 18) of alcohol detoxification and compared with testing in 14 healthy subjects. Activation of various intracellular signaling pathways by gut-derived bacterial products was analyzed by quantitative polymerase chain reaction, Western blotting, and DNA binding assays (for transcription factors). Toll-like receptor activation was assessed by cell cultures. RESULTS In addition to lipopolysaccharides, we showed that peptidoglycans may also cross the gut barrier to reach the systemic circulation. Both activate their respective Toll-like receptors in peripheral blood mononuclear cells. Chronic alcohol consumption inhibited the nuclear factor kappa B proinflammatory cytokine pathway but activated the mitogen-activated protein kinase/activator protein 1 pathway, together with the inflammasome complex. This activity resulted in increased messenger RNA and plasma levels of interleukin (IL)-8, IL-1β, and IL-18. Activated proinflammatory pathways, in particular, IL-8 and IL-1β, were positively correlated with alcohol consumption and alcohol-craving scores. Short-term alcohol withdrawal was associated with the recovery of lipopolysaccharide-dependent receptors but not peptidoglycan-dependent receptors. CONCLUSIONS Lipopolysaccharides and peptidoglycans from the gut microbiota stimulate specific inflammatory pathways in peripheral blood mononuclear cells that are correlated with alcohol craving.

Salirasib inhibits the growth of hepatocarcinoma cell lines in vitro and tumor growth in vivo through ras and mTOR inhibition

BackgroundDysregulation of epidermal growth factor and insulin-like growth factor signaling play important roles in human hepatocellular carcinoma (HCC), leading to frequent activation of their downstream targets, the ras/raf/extracellular signal-regulated kinase (ERK) and the phosphoinositide 3-kinase (PI3K)/Akt/mammalian Target of Rapamycin (mTOR) pathways. Salirasib is an S-prenyl-cysteine analog that has been shown to block ras and/or mTOR activation in several non hepatic tumor cell lines. We investigated in vitro the effect of salirasib on cell growth as well as its mechanism of action in human hepatoma cell lines (HepG2, Huh7, and Hep3B) and its in vivo effect in a subcutaneous xenograft model with HepG2 cells.ResultsSalirasib induced a time and dose dependent growth inhibition in hepatocarcinoma cells through inhibition of proliferation and partially through induction of apoptosis. A 50 percent reduction in cell growth was obtained in all three cell lines at a dose of 150 μM when they were cultured with serum. By contrast, salirasib was more potent at reducing cell growth after stimulation with EGF or IGF2 under serum-free conditions, with an IC50 ranging from 60 μM to 85 μM. The drug-induced anti-proliferative effect was associated with downregulation of cyclin A and to a lesser extent of cyclin D1, and upregulation of p21 and p27. Apoptosis induction was related to a global pro-apoptotic balance with caspase 3 activation, cytochrome c release, death receptor upregulation, and a reduced mRNA expression of the apoptosis inhibitors cFLIP and survivin. These effects were associated with ras downregulation and mTOR inhibition, without reduction of ERK and Akt activation. In vivo, salirasib reduced tumour growth from day 5 onwards. After 12 days of treatment, mean tumor weight was diminished by 56 percent in the treated animals.ConclusionsOur results show for the first time that salirasib inhibits the growth of human hepatoma cell lines through inhibition of proliferation and induction of apoptosis, which is associated with ras and mTOR inhibition. The therapeutic potential of salirasib in human HCC was further confirmed in a subcutaneous xenograft model.

Expression of Presumed Specific Early and Late Factors Associated with Liver Regeneration in Different Rat Surgical Models

Experiments performed on the portal branch ligation (PBL) model indicate that early changes observed after surgery are not related to the regenerative process because they also occur in atrophying lobes. To further confirm the lack of specificity of the early events and to exclude the influence of circulatory factors released by proliferating lobes on their occurrence, we investigated this response after sham operation (SO) and portacaval shunt (PCS), a model characterized by liver atrophy. We also attempted to determine expression of later events associated specifically with regeneration, ie, expression of p53 or c-Ha-ras, or inhibition of proliferation, ie, interleukin-1β (IL-1β) and transforming growth factor-β1 (TGF-β1) after partial (PH) and temporary partial (TPH) hepatectomy, SO and PCS. Nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) DNA binding were assessed by electrophoretic mobility shift assay (EMSA), interleukin-6 (IL-6) mRNA by reverse transcription-polymerase chain reaction (RT-PCR), c-myc and c-jun mRNAs by Northern blot analysis at 0.5 and 2 hours, p53 and c-Ha-ras mRNAs by Northern blot analysis at 8 and 24 hours, and IL-1β and TGF-β1 by RT-PCR at 24 hours. The early response including an increase of NF-κB, STAT3, IL-6, and immediate-early genes expression was present after PH, PCS, and SO. In SO, slight differences were observed in comparison with PH: no NF-κB p65/p50 DNA binding was observed, only three of six SO rats were positive for IL-6, and immediate-early genes induction showed differences in the intensity of the response. At later times, p53 mRNA increased at 8 hours after PH and TPH, c-Ha-ras mRNA at 24 hours after PH, and IL-1β mRNA at 24 hours after PCS. Early events are not specifically associated with the reduction of liver mass or with the regenerative process, are not predictive of future cell fate, and are most likely related to surgical stress. p53 and c-Ha-ras induction is closely associated with cell cycle progression whereas IL-1β, but not TGF-β1, appears to be one of the negative growth regulators that might play an important role in atrophy.

Role of signal transducer and activator of transcription 3 in liver fibrosis progression in chronic hepatitis C-infected patients.

In vitro and animal data suggest that hepatitis C virus (HCV) proteins might interfere with signal transducer and activator of transcription 3 (Stat3) signaling. It remains unknown whether Stat3 influences the apoptotic–proliferation balance and how this may relate to liver fibrosis progression in HCV-infected patients. We assessed Stat3 expression and DNA-binding as well as expression of its regulators protein inhibitor of activated Stat 3 (Pias3) and suppressor of cytokine signaling 3 (Socs3) in 65 HCV-infected livers at various stages of fibrosis progression. We then determined the level of expression of the proliferation markers cyclin D1 and proliferating cell nuclear antigen (PCNA) in conjunction with pro- and antiapoptotic markers Bax and Bcl-2 in the same liver samples. With the onset of fibrosis, Stat3 DNA-binding decreased and became almost undetectable in livers with bridging fibrosis or cirrhosis. Stat3 DNA-binding inversely correlated with Pias3 expression and Stat3-Pias3 interaction increased with the progression of fibrosis. Cyclin D1 and PCNA in hepatocytes decreased dramatically during fibrosis progression and levels highly correlated with Stat3 expression. In addition, an antiapoptotic profile due to upregulation of Bcl-2 principally in infiltrating inflammatory cells was observed with progressing fibrosis. In conclusion, fibrosis progression is characterized by a continuous decline in Stat3 DNA-binding activity related to overexpression and progressive interaction of Pias3–Stat3. The decrease in Stat3 activity correlated with reduced hepatocytes proliferation and a positive antiapoptotic balance in infiltrating inflammatory cells that are known mediators of cell damage in HCV.

Blunted DNA synthesis and delayed S-phase entry following inhibition of Cdk2 activity in the regenerating rat liver

Activation of the cyclin E/Cdk2 complex may play an important role in mid-G1/S-phase progression in proliferating mammalian cells. We evaluated the effect of targeted inhibition of Cdk2 activity by CYC202 (R-roscovitine) on hepatocytes proliferation in vivo after 70% partial hepatectomy (PH) in rats. In controls, Cdk2 activity and DNA synthesis peaked 24 h after PH. CYC202 abrogated Cdk2 activity, prevented BrdU incorporation and PCNA expression and increased mortality 24 h after PH. Cyclin E and Cdk2 protein expression and complex formation was not affected by CYC202 nor was cyclin D1, Cdk4 and c-ras mRNA expression. Two consecutive injections 8 and 20 h after PH were required to elicit the inhibitory effect of CYC202, which was lost when either the injection at 8 h or at 20 h was withheld. Cdk2 activity and cell progression resumed 48 h after PH in surviving animals suggesting that CYC202 induced a reversible inhibition of the cell cycle. Our results confirm an important role for Cdk2 in hepatocytes proliferation in the regenerating liver. We demonstrate that molecular events, including Cdk2 activation, occurring within the 8th and 24th hour after PH (G1/S-phase transition) are crucial in determining whether or not DNA synthesis and hepatocytes proliferation proceed normally after PH.

Ras inhibition in hepatocarcinoma by S-trans-trans-farnesylthiosalicyclic acid: Association of its tumor preventive effect with cell proliferation, cell cycle events, and angiogenesis

Activation of Ras and its downstream signaling pathways, likely contribute to the development of hepatocarcinoma. We have previously shown that intraperitoneal injections of the Ras inhibitor S‐trans, trans‐farnesylthiosalicyclic acid (FTS) blocks Ras activation and prevents heptocarcinoma development in rats receiving weekly injections of the carcinogene diethylnitrosamine (DEN) for 16 wk. Using this in vivo model, we evaluated the relationship between the tumor preventive effect of Ras inhibition and activation of downstream signaling pathways, cell proliferation, cell cycle events, and angiogenesis. Western blotting, quantitative PCR, immunohistochemistry, and transcription factor activity assays were used. DEN‐induced activation of NFkB and Stat3 was abrogated by FTS treatment. FTS treatment showed no effect on DEN‐induced elevation of TNFα, interleukin 6 and TLR4, known activators of these transcription factors. FTS significantly reduced phosphorylation of the MAPkinase p38 and of the p70S6 kinase, a surrogate marker for mTor activation, without affecting ERK and AKT phosphorylation. These events were associated with reduced c‐myc and cyclin D expression as well as reduced cell proliferation in transformed, GSTp‐positive hepatocytes. Moreover, FTS treatment shifted cell proliferation from transformed hepatocytes to apparently normal, GSTp negative hepatocytes. FTS treatment did not down‐regulate expression of angiogenesis markers HIFα, VEGF, VEGF receptor1, and placenta growth factor. FTS treatment inhibits important signaling pathways involved in cellular proliferation leading to strongly reduced proliferation of transformed hepatocytes without affecting normal hepatocytes. This re‐adjustment of the proliferation balance likely contributes to the tumor preventive of FTS in the context of Ras inhibition in hepatocarcinogenesis.

Tetrahydro Iso-Alpha Acids and Hexahydro Iso-Alpha Acids from Hops Inhibit Proliferation of Human Hepatocarcinoma Cell Lines and Reduce Diethylnitrosamine Induced Liver Tumor Formation in Rats

Chronic inflammation plays important role in the pathogenesis of hepatocellular carcinoma (HCC). To date, no antiinflammatory approach has shown its efficacy in preventing HCC occurrence in humans. Because tetra- and hexahydro isoalpha acids (THIAA and HHIAA) from hops elicit antiinflammatory properties, we evaluated these compounds for antitumor effects in vitro in human HCC cell lines (HepG2, Hep3B, Huh7) and in vivo in diethylnitrosamine (DEN)-induced animal model of HCC. In human HCC cell lines, THIAA and HHIAA reduced cell proliferation and viability which was associated with the inhibition of the NF-κB-DNA binding and tumor necrosis factor α mRNA expression. Both compounds also inhibited phosphorylation of the mTOR effector p70S6 kinase without affecting ERK, AKT, JNK, and GSK3β phosphorylation or activator protein-1 activation. In DEN-treated rats, administration of THIAA and HHIAA in food reduced the tumor numbers and the expression of the cellular transformation marker glutathione-S-transferase in the liver. In conclusion, THIAA and HHIAA show antitumor properties in vitro in human HCC cell lines as well as in vivo in a chemically induced animal model of HCC.

Linalool induces cell cycle arrest and apoptosis in HepG2 cells through oxidative stress generation and modulation of Ras/MAPK and Akt/mTOR pathways

Aims: Linalool is a plant‐derived monoterpene with anticancer activity, however its mechanisms of action remain poorly understood. The aim of this work was to elucidate the anticancer mechanisms of action of linalool in hepatocellular carcinoma (HCC) HepG2 cells. Main methods: Cell viability and proliferation were determined by WST‐1 assay and BrdU incorporation, respectively. Cell cycle analysis was assessed through flow cytometry (FC) and western blot (WB). Apoptosis was determined by caspase‐3 activity, TUNEL assay and WB. Reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were analyzed by FC and fluorescence microscopy. Expression of Ras, MAPKs (ERK, JNK and p38) and Akt/mTOR pathways were evaluated by WB. Key findings: Linalool (0–2.5 mM) dose‐dependently inhibited cell proliferation by inducing G0/G1 cell cycle arrest, through Cdk4 and cyclin A downregulation, p21 and p27 upregulation, and apoptosis, characterized by MMP loss, caspase‐3 activation, PARP cleavage and DNA fragmentation. Low concentrations of linalool (1.0 mM) reduced membrane‐bound Ras and Akt activity whereas higher amounts (2.0 mM) triggered mTOR inhibition and ROS generation, in correlation with MAPKs activation and Akt phosphorylation. ROS scavenger N‐acetyl‐L‐cysteine partially rescued HepG2 cell growth and prevented MPP depolarization, ERK and JNK activation. Moreover, specific ERK and Akt phosphorylation inhibitors potentiated linalool anti‐cancer activity, pointing Akt and ERK activation as pro‐survival mechanisms in response to higher concentrations of linalool. Significance: This report reveals that linalool induces G0/G1 arrest and apoptosis in HepG2 cells involving Ras, MAPKs and Akt/mTOR pathways and suggests that linalool is a promising anticancer agent for HCC therapy. Graphical abstract: Figure. No caption available.