scholarly journals Determination of the Underlying Mechanisms for the Anti-fibrogenic Effect of n-3 Polyunsaturated Fatty Acids in Hepatic Stellate Cells (P08-105-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Siqi Hu ◽  
Minkyung Bae ◽  
Young-Ki Park ◽  
Ji-Young Lee
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Fatty Acid ◽  
Hepatic Stellate Cells ◽  
Stellate Cells ◽  
Inhibitory Effect ◽  
Basal Expression ◽  
Epa And Dha ◽  
Human Hscs ◽  
Underlying Mechanisms

Abstract Objectives We previously reported that n-3 polyunsaturated fatty acids (PUFAs) exhibit potent anti-fibrogenic effects independent of the SMA- and MAD-related protein (SMAD3) pathway in primary human hepatic stellate cells (HSCs), the major cell type responsible for extracellular matrix production for the development of liver fibrosis. The objective of this study was to further elucidate the underlying mechanisms for the anti-fibrogenic effect of n-3 PUFAs in HSCs with a primary focus on peroxisome proliferator-activated receptor γ (PPARγ) as it is known to inhibit HSC activation. Methods n-3 PUFAs, including alpha linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were complexed with bovine serum albumin (BSA) at a BSA to fatty acid molar ratio of 1:2.5. Primary human HSCs were treated either with BSA vehicle control or 50 μM of a fatty acid for 24 h, after which they were activated with transforming growth factor β1 (TGFβ1; 4 ng/ml), a potent fibrogenic cytokine, for additional 24 h. Also, in another experiment, primary human HSCs were pre-treated with 10 μM of GW9662, a PPARγ antagonist, 18 h prior to the fatty acid and TGFβ1 treatments. Results ALA, EPA and DHA significantly decreased TGFβ1-induced mRNA expression of fibrogenic genes such as α-smooth muscle actin and collagen type I alpha 1 chain with EPA and DHA being more potent than ALA. The similar trend was also observed in their protein levels. In the absence of TGFβ1 treatment, EPA and DHA markedly increased PPARγ mRNA abundance. TGFβ1 significantly decreased PPARγ mRNA, which was attenuated by EPA and DHA, but not by ALA. Inhibition of PPARγ by GW9662 did not alter either the basal expression of PPARγ or the basal expression of fibrogenic genes. However, the inhibitory effect of EPA and DHA on the induction of fibrogenic gene expression by TGFβ1 was not diminished by GW9662. Conclusions n-3 PUFAs showed a potent inhibitory effect on TGFβ1-induced fibrogenic gene expression in primary human HSCs. Inhibition of PPARγ activity did not alter the anti-fibrogenic effect of n-3 PUFAs. The results suggest that n-3 PUFAs, particularly EPA and DHA to a similar degree, exert their anti-fibrogenic effect in primary human HSCs independent of the activation of PPARγ pathway. Funding Sources This study was supported by USDA Multistate Hatch and USDA Hatch.

scholarly journals Inhibition of SIRT2 suppresses hepatic fibrosis

2016 ◽  
Vol 310 (11) ◽  
pp. G1155-G1168 ◽  
Author(s):  
Maribel Arteaga ◽  
Na Shang ◽  
Xianzhong Ding ◽  
Sherri Yong ◽  
Scott J. Cotler ◽  
...  
Keyword(s):  
Gene Expression ◽  
Liver Fibrosis ◽  
Hepatic Fibrosis ◽  
Hepatic Stellate Cells ◽  
Histone Deacetylases ◽  
Critical Role ◽  
Stellate Cells ◽  
Novel Strategy ◽  
Underlying Mechanisms

Liver fibrosis can progress to cirrhosis and result in serious complications of liver disease. The pathogenesis of liver fibrosis involves the activation of hepatic stellate cells (HSCs), the underlying mechanisms of which are not fully known. Emerging evidence suggests that the classic histone deacetylases play a role in liver fibrosis, but the role of another subfamily of histone deacetylases, the sirtuins, in the development of hepatic fibrosis remains unknown. In this study, we found that blocking the activity of sirtuin 2 (SIRT2) by using inhibitors or shRNAs significantly suppressed fibrogenic gene expression in HSCs. We further demonstrated that inhibition of SIRT2 results in the degradation of c-MYC, which is important for HSC activation. In addition, we discovered that inhibition of SIRT2 suppresses the phosphorylation of ERK, which is critical for the stabilization of c-MYC. Moreover, we found that Sirt2 deficiency attenuates the hepatic fibrosis induced by carbon tetrachloride (CCl4) and thioacetamide (TAA). Furthermore, we showed that SIRT2, p-ERK, and c-MYC proteins are all overexpressed in human hepatic fibrotic tissues. These data suggest a critical role for the SIRT2/ERK/c-MYC axis in promoting hepatic fibrogenesis. Inhibition of the SIRT2/ERK/c-MYC axis represents a novel strategy to prevent and to potentially treat liver fibrosis and cirrhosis.

scholarly journals Differential Lipotoxic Effects of Palmitate and Oleate in Activated Human Hepatic Stellate Cells and Epithelial Hepatoma Cells

2016 ◽  
Vol 39 (4) ◽  
pp. 1648-1662 ◽  
Author(s):  
Alexandra M. Hetherington ◽  
Cynthia G. Sawyez ◽  
Emma Zilberman ◽  
Alexandra M. Stoianov ◽  
Debra L. Robson ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Er Stress ◽  
Hepatic Stellate Cells ◽  
Hepg2 Cells ◽  
Stellate Cells ◽  
Hepatoma Cells ◽  
Surrounding Tissue ◽  
High Oleate ◽  
Activated Hepatic Stellate Cells

Background/Aims: Nonalcoholic fatty liver disease (NAFLD) progression to fibrosis, cirrhosis and hepatocellular carcinoma, alters the cellular composition of this organ. During late-stage NAFLD, fibrotic and possibly cancerous cells can proliferate and, like normal hepatocytes, are exposed to high concentrations of fatty acids from both surrounding tissue and circulating lipid sources. We hypothesized that primary human activated hepatic stellate cells and epithelial hepatoma (HepG2) cells respond differently to lipotoxic conditions, and investigated the mechanisms involved. Methods: Primary activated hepatic stellate cells and HepG2 cells were exposed to pathophysiological concentrations of fatty acids and comparative studies of lipid metabolic and stress response pathways were performed. Results: Both cell types remained proliferative during exposure to a combination of palmitate plus oleate reflective of the general saturated versus unsaturated fatty acid composition of western diets. However, exposure to either high palmitate or high oleate alone induced cytotoxicity in activated stellate cells, while only palmitate caused cytotoxicity in HepG2 cells. mRNA microarray and biochemical comparisons revealed that stellate cells stored markedly less fatty acids as neutral lipids, and had reduced capacity for beta-oxidation. Similar to previous observations in HepG2 cells, palmitate, but not oleate, induced ER stress and actin stress fiber formation in activated stellate cells. In contrast, oleate, but not palmitate, induced the inflammatory signal TXNIP, decreased cytoskeleton proteins, and decreased cell polarity preceding cell death in activated stellate cells. Conclusions: Palmitate-induced lipotoxicity was associated with ER stress pathways in both primary activated hepatic stellate cells and epithelial hepatoma cells, whereas high oleate caused lipotoxicity only in activated stellate cells, possibly through a distinct mechanism involving disruption of cytoskeleton components. This may have implications for optimal dietary fatty acid compositions during various stages of NAFLD.

scholarly journals Acetaldehyde stimulates the activation of latent transforming growth factor-β1 and induces expression of the type II receptor of the cytokine in rat cultured hepatic stellate cells

2002 ◽  
Vol 368 (3) ◽  
pp. 683-693 ◽  
Author(s):  
Anping CHEN
Keyword(s):  
Gene Expression ◽  
Growth Factor ◽  
Hepatic Stellate Cells ◽  
Transforming Growth Factor ◽  
Stellate Cells ◽  
Transforming Growth Factor Β1 ◽  
Collagen Gene ◽  
Type Ii ◽  
Underlying Mechanisms ◽  
Tgf Β1

Acetaldehyde, the major active metabolite of alcohol, induces the activation of hepatic stellate cells (HSC), leading to over-production of α1(I) collagen and ultimately causing hepatic fibrosis. The underlying mechanisms of this process remain largely unknown. Transforming growth factor-β1 (TGF-β1) is a potent inducer of α1(I) collagen production. Accumulating evidence has shown a potential role for TGF-β1 in alcohol-induced hepatic fibrogenesis. The aims of this study were to determine the effect of acetaldehyde on TGF-β signalling, to elucidate the underlying mechanisms as well as to evaluate its role in expression of α1(I) collagen gene in cultured HSC. It was hypothesized that acetaldehyde activated TGF-β signalling by inducing the expression of elements in the TGF-β signal transduction pathway, which might contribute to α1(I) collagen gene expression in cultured HSC. Initial results revealed that acetaldehyde activated TGF-β signalling in cultured HSC. Additional studies demonstrated that acetaldehyde stimulated the secretion and activation of latent TGF-β1, and induced the expression of the type II TGF-β receptor (Tβ-RII). Further experiments found cis- and trans-activating elements responsible for Tβ-RII gene expression induced by acetaldehyde. Activation of TGF-β signalling by acetaldehyde contributed to α1(I) collagen gene expression in cultured HSC. In summary, this report demonstrated that acetaldehyde stimulated TGF-β signalling by increasing the secretion and activation of latent TGF-β1 as well as by inducing the expression of Tβ-RII in cultured HSC. Results from this report provided a novel insight into mechanisms by which acetaldehyde stimulated the expression of α1(I) collagen in HSC and a better understanding of effects of alcohol (or acetaldehyde) on hepatic fibrogenesis.

scholarly journals Long-chain fatty acids and inflammation

2012 ◽  
Vol 71 (2) ◽  
pp. 284-289 ◽  
Author(s):  
Philip C. Calder
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Arachidonic Acid ◽  
Fatty Acid ◽  
Inflammatory Cell ◽  
Expression Patterns ◽  
Cell Signalling ◽  
Inflammatory Cells ◽  
Membrane Phospholipids ◽  
Epa And Dha

Inflammation plays a key role in many common conditions and diseases. Fatty acids can influence inflammation through a variety of mechanisms acting from the membrane to the nucleus. They act through cell surface and intracellular receptors that control inflammatory cell signalling and gene expression patterns. Modifications of inflammatory cell membrane fatty acid composition can modify membrane fluidity, lipid raft formation and cell signalling leading to altered gene expression and can alter the pattern of lipid and peptide mediator production. Cells involved in the inflammatory response usually contain a relatively high proportion of the n-6 fatty acid arachidonic acid in their membrane phospholipids. Eicosanoids produced from arachidonic acid have well-recognised roles in inflammation. Oral administration of the marine n-3 fatty acids EPA and DHA increases the contents of EPA and DHA in the membranes of cells involved in inflammation. This is accompanied by a decrease in the amount of arachidonic acid present. EPA is a substrate for eicosanoid synthesis and these are often less potent than those produced from arachidonic acid. EPA gives rise to E-series resolvins and DHA gives rise to D-series resolvins and protectins. Resolvins and protectins are anti-inflammatory and inflammation resolving. Thus, the exposure of inflammatory cells to different types of fatty acids can influence their function and so has the potential to modify inflammatory processes.

scholarly journals PNPLA3 downregulation exacerbates the fibrotic response in human hepatic stellate cells

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0260721
Author(s):  
Brian Rady ◽  
Takahiro Nishio ◽  
Debanjan Dhar ◽  
Xiao Liu ◽  
Mark Erion ◽  
...  
Keyword(s):  
Gene Expression ◽  
Hepatic Stellate Cells ◽  
Missense Variant ◽  
Stellate Cells ◽  
Mutant Form ◽  
Wild Type ◽  
Fibrotic Response ◽  
Human Hscs ◽  
Complications And Mortality

Non-alcoholic steatohepatitis (NASH) results, in part, from the interaction of metabolic derangements with predisposing genetic variants, leading to liver-related complications and mortality. The strongest genetic determinant is a highly prevalent missense variant in patatin-like phospholipase domain-containing protein 3 (PNPLA3 p.I148M). In human liver hepatocytes PNPLA3 localizes to the surface of lipid droplets where the mutant form is believed to enhance lipid accumulation and release of pro-inflammatory cytokines. Less is known about the role of PNPLA3 in hepatic stellate cells (HSCs). Here we characterized HSC obtained from patients carrying the wild type (n = 8 C/C) and the heterozygous (n = 6, C/G) or homozygous (n = 6, G/G) PNPLA3 I148M and investigated the effect of genotype and PNPLA3 downregulation on baseline and TGF-β-stimulated fibrotic gene expression. HSCs from all genotypes showed comparable baseline levels of PNPLA3 and expression of the fibrotic genes α-SMA, COL1A1, TIMP1 and SMAD7. Treatment with TGF-β increased PNPLA3 expression in all 3 genotypes (~2-fold) and resulted in similar stimulation of the expression of several fibrogenic genes. In primary human HSCs carrying wild-type (WT) PNPLA3, siRNA treatment reduced PNPLA3 mRNA by 79% resulting in increased expression of α-SMA, Col1a1, TIMP1, and SMAD7 in cells stimulated with TGF-β. Similarly, knock-down of PNPLA3 in HSCs carrying either C/G or G/G genotypes resulted in potentiation of TGF-β induced expression of fibrotic genes. Knockdown of PNPLA3 did not impact fibrotic gene expression in the absence of TGF-β treatment. Together, these data indicate that the presence of the I148M PNPLA3 mutation in HSC has no effect on baseline activation and that downregulation of PNPLA3 exacerbates the fibrotic response irrespective of the genotype.

scholarly journals Polyunsaturated fatty acids inhibit fatty acid synthase and spot-14-protein gene expression in cultured rat hepatocytes by a peroxidative mechanism

1999 ◽  
Vol 341 (2) ◽  
pp. 371-376 ◽  
Author(s):  
Marc FORETZ ◽  
Fabienne FOUFELLE ◽  
Pascal FERRÉ
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Fatty Acid ◽  
Lactate Dehydrogenase ◽  
Polyunsaturated Fatty Acids ◽  
Fatty Acid Synthase ◽  
Rat Hepatocytes ◽  
Inhibitory Effect ◽  
Spot 14

In vivo, polyunsaturated fatty acids (PUFA) inhibit the expression of hepatic genes related to the lipogenic process such as fatty acid synthase and spot-14-protein (S14) genes. In vitro studies have suggested that this was a direct transcriptional effect of PUFA. In hepatocytes, the inhibition of the lipogenic rate by PUFA is not specific, but is linked to a cytotoxic effect due to peroxidative mechanisms. We have investigated whether peroxidation could also explain the inhibitory effect of PUFA on gene expression. Rat hepatocytes were cultured for 24 h with mono-unsaturated or PUFA. PUFA inhibited the expression of fatty acid synthase and S14 genes, and this inhibition was directly related to the number of unsaturations. However, the β-actin and albumin mRNA concentrations were also affected by the most unsaturated fatty acids, suggesting a non-specific effect of PUFA on gene expression. Measurement of lactate dehydrogenase released into the medium indicated a cytotoxicity of PUFA. This was associated with their peroxidation as evaluated by the presence of thiobarbituric acid-reactive substances in the culture medium. The addition of high concentrations of antioxidants abolished lipid peroxidation and lactate dehydrogenase leakage and completely reversed the inhibitory effect of PUFA on gene expression. This suggests (i) that the results obtained previously in cultured hepatocytes in the presence of low concentrations of antioxidants must be interpretated cautiously and (ii) that in vivo, the inhibitory effect of PUFA on lipogenesis-related genes could be indirect through hormonal or metabolic changes or that their effect on gene expression is somehow linked to peroxidative mechanisms.

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