Fish omega-3 fatty acids induce liver fibrosis in the treatment of bile duct-ligated rats

Backstage players of fibrosis: NOX4, mTOR, HDAC, and S1P; companions of TGF-β

The fibrotic process could be easily defined as a pathological excess of extracellular matrix deposition, leading to disruption of tissue architecture and eventually loss of function; however, this process involves a complex network of several signal transduction pathways. Virtually almost all organs could be affected by fibrosis, the most affected are the liver, lung, skin, kidney, heart, and eyes; in all of them, the transforming growth factor-beta (TGF-β) has a central role. The canonical and non-canonical signal pathways of TGF-β impact the fibrotic process at the cellular and molecular levels, inducing the epithelial-mesenchymal transition (EMT) and the induction of profibrotic gene expression with the consequent increase in proteins such as alpha-smooth actin (α-SMA), fibronectin, collagen, and other extracellular matrix proteins. Recently, it has been reported that some molecules that have not been typically associated with the fibrotic process, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4), mammalian target of rapamycin (mTOR), histone deacetylases (HDAC), and sphingosine-1 phosphate (S1P); are critical in its development. In this review, we describe and discuss the role of these new players of fibrosis and the convergence with TGF-β signaling pathways, unveiling new insights into the panorama of fibrosis that could be useful for future therapeutic targets.

N-acetyl cysteine treatment mitigates biomarkers of oxidative stress in different tissues of bile duct ligated rats

Cholestasis is a multifaceted clinical complication. Obstructive jaundice induced by bile duct ligation (BDL) is known as an animal model to investigate cholestasis and its associated complications. N-acetyl cysteine (NAC) is an antioxidant, radical scavenger, and thiol reductant widely investigated for its cytoprotective properties. The current investigation was designed to evaluate the role of NAC treatment on biomarkers of oxidative stress and organ histopathological alterations in a rat model of cholestasis/cirrhosis. BDL animals were supplemented with NAC (100 and 300 mg/kg, i.p, 42 consecutive days). Biomarkers of oxidative stress in the liver, brain, heart, skeletal muscle, lung, serum, and kidney tissue, as well as organ histopathological changes, were monitored. A significant increase in reactive oxygen species, lipid peroxidation, and protein carbonylation were detected in different tissues of BDL rats. Moreover, tissue antioxidant capacity was hampered, glutathione (GSH) reservoirs were depleted, and oxidized glutathione (GSSG) levels were significantly increased in the BDL group. Significant tissue histopathological alterations were evident in cirrhotic animals. It was found that NAC treatment (100 and 300 mg/kg, i.p) significantly mitigated biomarkers of oxidative stress and alleviated tissue histopathological changes in cirrhotic rats. These data represent NAC as a potential protective agent with therapeutic capability in cirrhosis and its associated complications.HIGHLIGHTSCholestasis is a multifaceted clinical complication that affects different organsOxidative stress plays a pivotal role in cholestasis-associated complicationsTissue antioxidant capacity is hampered in different tissues of cholestatic animalsAntioxidant therapy might play a role in the management of cholestasis-induced organ injuryNAC alleviated biomarkers of oxidative stress in cholestatic animalsNAC significantly improved tissues histopathological alterations in cholestatic rats.

Docosahexaenoic acid inhibits hepatic stellate cell activation to attenuate liver fibrosis in a PPARγ-dependent manner

Docosahexaenoic acid (DHA) has been found to have a hepatoprotective effect. In this study, we investigated the role of peroxisome proliferator-activated receptor γ (PPARγ) in DHA regulation of liver fibrosis. DHA was found to inhibit hepatic stellate cell (HSC)-LX2 cell viability and downregulate marker proteins of HSC activation. Furthermore, DHA induced cell cycle arrest at G1 phase in HSCs. Antagonism of PPARγ by GW9662 abrogated the effects of DHA on HSCs. Computer-aided molecular docking predicted that DHA bound to PPARγ via hydrogen bonding with residues Ser289, His323, Tyr473, and His499. We overexpressed Ser289 mutant PPARγ in HSC-LX2 cells and investigated fibrotic marker modulation, and found that DHA effects on HSCs were diminished. Thus, bonding with the Ser289 residue might be indispensable for DHA to activate PPARγ to exert its inhibiting effect on activated HSCs. Last, data from a CCl₄-treated mouse model confirmed that PPARγ activation was required for DHA to attenuate liver fibrosis.

Galectin-1-induced tolerogenic dendritic cells combined with apoptotic lymphocytes prolong liver allograft survival

Donor-derived tolerogenic dendritic cells (DCs) and apoptotic lymphocytes (ALs) are practical tools for controlling rejection after transplantation by targeting direct and indirect allorecognition pathways, respectively. To date, few studies have investigated the combination of donor-derived tolerogenic DCs and ALs infusion in organ transplantation protection. In the present study, we generated galectin-1-induced tolerogenic DCs (DC_gal-1s) and ultraviolet irradiation-induced ALs with stable immune characteristics in vitro and potential immune regulatory activity in vivo. A rat model of acute liver transplant rejection was established, and the intrinsic tolerogenic profiles associated with the short-term alleviation of rejection and the long-term maintenance of tolerance in the absence of immunosuppressive drugs were evaluated. The DC_gal-1-AL treatment prolonged allograft survival more significantly than a transfusion of DC_gal-1s or ALs alone. This benefit was associated with CD4⁺ Treg cell expansion and decreased interferon (IFN)-γ⁺ T cell levels. Moreover, DC_gal-1-AL treatment led to different cytokine/chemokine changes in the allograft and peripheral blood, that indicated an alleviation of local and systemic inflammation on day 7 post-transplantation. TGF-β1 and TGF-β2 were significantly increased in the long-term surviving allografts after DC_gal-1-AL treatment. Our results indicate that the combination of DC_gal-1s with ALs effectively prolongs liver allograft survival and represents a novel therapeutic strategy for liver transplant rejection.

N-3 Polyunsaturated Fatty Acids Stimulate Bile Acid Detoxification in Human Cell Models

Cholestasis is characterized by the accumulation of toxic bile acids (BAs) in liver cells. The present study aimed to evaluate the effects of n-3 polyunsaturated fatty acids (n-3 PUFAs), such as docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, on BA homeostasis and toxicity in human cell models. The effects of EPA and/or DHA on the expression of genes involved in the maintenance of BA homeostasis were analyzed in human hepatoma (HepG2) and colon carcinoma (Caco-2) cells, as well as in primary culture of human intestinal (InEpC) and renal (RPTEC) cells. Extracellular BA species were quantified in culture media using LC-MS/MS. BA-induced toxicity was evaluated using caspase-3 and flow cytometry assays. Gene expression analyses of HepG2 cells reveal that n-3 PUFAs reduce the expression of genes involved in BA synthesis (CYP7A1, CYP27A1) and uptake (NTCP), while activating genes encoding metabolic enzymes (SULT2A1) and excretion transporters (MRP2, MRP3). N-3 PUFAs also generate a less toxic BA pool and prevent the BA-dependent activation of apoptosis in HepG2 cells. Conclusion. The present study reveals that n-3 PUFAs stimulate BA detoxification.

Omega-3 fatty acids and non-alcoholic fatty liver disease: Evidence of efficacy and mechanism of action

For many years it has been known that high doses of long chain omega-3 fatty acids are beneficial in the treatment of hypertriglyceridaemia. Over the last three decades, there has also been a wealth of in vitro and in vivo data that has accumulated to suggest that long chain omega-3 fatty acid treatment might be beneficial to decrease liver triacylglycerol. Several biological mechanisms have been identified that support this hypothesis; notably, it has been shown that long chain omega-3 fatty acids have a beneficial effect: a) on bioactive metabolites involved in inflammatory pathways, and b) on alteration of nuclear transcription factor activities such as peroxisome proliferator-activated receptors (PPARs), sterol regulatory element-binding protein 1c (SREBP-1c) and carbohydrate-responsive element-binding protein (ChREBP), involved in inflammatory pathways and liver lipid metabolism. Since the pathogenesis of non alcoholic fatty liver disease (NAFLD) begins with the accumulation of liver lipid and progresses with inflammation and then several years later with development of fibrosis; it has been thought in patients with NAFLD omega-3 fatty acid treatment would be beneficial in treating liver lipid and possibly also in ameliorating inflammation. Meta-analyses (of predominantly dietary studies and small trials) have tended to support the assertion that omega-3 fatty acids are beneficial in decreasing liver lipid, but recent randomised controlled trials have produced conflicting data. These trials have suggested that omega-3 fatty acid might be beneficial in decreasing liver triglyceride (docosahexanoic acid also possibly being more effective than eicosapentanoic acid) but not in decreasing other features of steatohepatitis (or liver fibrosis). The purpose of this review is to discuss recent evidence regarding biological mechanisms by which long chain omega-3 fatty acids might act to ameliorate liver disease in NAFLD; to consider the recent evidence from randomised trials in both adults and children with NAFLD; and finally to discuss key 'known unknowns' that need to be considered, before planning future studies that are focussed on testing the effects of omega-3 fatty acid treatment in patients with NAFLD.

Chemopreventive and Chemotherapeutic Effects of Fish Oil derived Omega-3 Polyunsaturated Fatty Acids on Colon Carcinogenesis

Colorectal cancer is the third most common cause of cancer related death in the world. Multiple lines of evidence suggest that there is an association between consumption of dietary fat and colon cancer risk. Not only the amount but also the type and the ratio of fatty acids comprising dietary fats consumed have been implicated in the etiology and pathogenesis of colon cancer. Omega-3 (n-3) polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have been known to inhibit development of colon cancer by downregulating the expression of genes involved in colon carcinogenesis and also by altering the membrane lipid composition. Data from laboratory, epidemiological, and clinical studies substantiate the beneficial role of n-3 PUFAs in preventing colitis and subsequent development of colon cancer. In addition, recent studies suggest that some n-3 PUFAs can be effective as an adjuvant with chemotherapeutic agents and other natural anticancer compounds in the management of colon cancer. In this review, we discuss chemopreventive and therapeutic effects of fish oil derived long chain n-3 PUFAs, particularly EPA and DHA, with focus on synergetic effects of which they exert when combined with chemotherapeutic agents and other natural compounds.

An ω-3-enriched diet alone does not attenuate CCl4-induced hepatic fibrosis

Exposure to the halogenated hydrocarbon carbon tetrachloride (CCl₄) leads to hepatic lipid peroxidation, inflammation and fibrosis. Dietary supplementation of ω-3 fatty acids has been increasingly advocated as being generally anti-inflammatory, though its effect in models of liver fibrosis is mixed. This raises the question of whether diets high in ω-3 fatty acids will result in a greater sensitivity or resistance to liver fibrosis as a result of environmental toxicants like CCl₄. In this study, we fed CCl₄-treated mice a high ω-3 diet (using a mix of docosahexaenoic acid and eicosapentaenoic acid ethyl esters). We also co-administered an inhibitor of soluble epoxide hydrolase, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), which has been shown to boost anti-inflammatory epoxy fatty acids that are produced from both ω-3 and ω-6 dietary lipids. We showed that soluble epoxide inhibitors reduced CCl₄-induced liver fibrosis. Three major results were obtained. First, the ω-3-enriched diet did not attenuate CCl₄-induced liver fibrosis as judged by collagen deposition and collagen mRNA expression. Second, the ω-3-enriched diet raised hepatic tissue levels of several inflammatory lipoxygenase metabolites and prostaglandins, including PGE2. Third, treatment with TPPU in drinking water in conjunction with the ω-3-enriched diet resulted in a reduction in liver fibrosis compared to all other groups. Taken together, these results indicate that dietary ω-3 supplementation alone did not attenuate CCl₄-induced liver fibrosis. Additionally, oxylipin signaling molecules may play role in the CCl₄-induced liver fibrosis in the high ω-3 diet groups.

EPA or DHA enhanced oxidative stress and aging protein expression in brain of d-galactose treated mice

BACKGROUND

Effects of eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, 22:6) upon fatty acid composition, oxidative and inflammatory factors and aging proteins in brain of d-galactose (DG) treated aging mice were examined.

METHODS

Each fatty acid at 7 mg/kg BW/week was supplied for 8 weeks. Brain aging was induced by DG treatment (100 mg/kg body weight) via daily subcutaneous injection for 8 weeks.

RESULTS

DG, EPA and DHA treatments changed brain fatty acid composition. DG down-regulated brain Bcl-2 expression and up-regulated Bax expression. Compared with DG groups, EPA and DHA further enhanced Bax expression. DG decreased glutathione content, increased reactive oxygen species (ROS) and oxidized glutathione (GSSG) production, the intake of EPA or DHA caused greater ROS and GSSG formation. DG treatments up-regulated the protein expression of p47(phox) and gp91(phox), and the intake of EPA or DHA led to greater p47(phox) and gp91(phox) expression. DG increased brain prostaglandin E2 (PGE2) levels, and cyclooxygenase (COX)-2 expression and activity, the intake of EPA or DHA reduced brain COX-2 activity and PGE2 formation. DG enhanced brain p53, p16 and p21 expression. EPA and DHA intake led to greater p21 expression, and EPA only caused greater p53 and p16 expression.

CONCLUSION

These findings suggest that these two PUFAs have toxic effects toward aging brain.

Hepatoprotective and Anti-fibrotic Agents: It's Time to Take the Next Step

Hepatic fibrosis and cirrhosis cause strong human suffering and necessitate a monetary burden worldwide. Therefore, there is an urgent need for the development of therapies. Pre-clinical animal models are indispensable in the drug discovery and development of new anti-fibrotic compounds and are immensely valuable for understanding and proofing the mode of their proposed action. In fibrosis research, inbreed mice and rats are by far the most used species for testing drug efficacy. During the last decades, several hundred or even a thousand different drugs that reproducibly evolve beneficial effects on liver health in respective disease models were identified. However, there are only a few compounds (e.g., GR-MD-02, GM-CT-01) that were translated from bench to bedside. In contrast, the large number of drugs successfully tested in animal studies is repeatedly tested over and over engender findings with similar or identical outcome. This circumstance undermines the 3R (Replacement, Refinement, Reduction) principle of Russell and Burch that was introduced to minimize the suffering of laboratory animals. This ethical framework, however, represents the basis of the new animal welfare regulations in the member states of the European Union. Consequently, the legal authorities in the different countries are halted to foreclose testing of drugs in animals that were successfully tested before. This review provides a synopsis on anti-fibrotic compounds that were tested in classical rodent models. Their mode of action, potential sources and the observed beneficial effects on liver health are discussed. This review attempts to provide a reference compilation for all those involved in the testing of drugs or in the design of new clinical trials targeting hepatic fibrosis.

Sunflower Oil but Not Fish Oil Resembles Positive Effects of Virgin Olive Oil on Aged Pancreas after Life-Long Coenzyme Q Addition

An adequate pancreatic structure is necessary for optimal organ function. Structural changes are critical in the development of age-related pancreatic disorders. In this context, it has been reported that different pancreatic compartments from rats were affected according to the fat composition consumed. Since there is a close relationship between mitochondria, oxidative stress and aging, an experimental approach has been developed to gain more insight into this process in the pancreas. A low dosage of coenzyme Q was administered life-long in rats in order to try to prevent pancreatic aging-related alterations associated to some dietary fat sources. According to that, three groups of rats were fed normocaloric diets containing Coenzyme Q (CoQ) for two years, where virgin olive, sunflower, or fish oil was included as unique fat source. Pancreatic samples for microscopy and blood samples were collected at the moment of euthanasia. The main finding is that CoQ supplementation gives different results according to fat used in diet. When sunflower oil was the main fat in the diet, CoQ supplementation seems to improve endocrine pancreas structure and in particular β-cell mass resembling positive effects of virgin olive oil. Conversely, CoQ intake does not seem to improve the structural alterations of exocrine compartment previously observed in fish oil fed rats. Therefore CoQ may improve pancreatic alterations associated to the chronic intake of some dietary fat sources.

Integrin β-8, but not β-5 or -6, protein expression is increased in livers of children with biliary atresia

OBJECTIVES

Our previous work demonstrated altered messenger RNA expression of integrin β-5 and -8, using an in silico analysis of publically available data from patients with biliary atresia (BA); however, we were unable to demonstrate statistically significant differences in protein expression because of sample size. In the present study, we repeated the analysis of liver fibrosis and protein expression of the integrins in a larger cohort of patients with BA and compared them with patients undergoing liver biopsy for other diagnoses, with the hypothesis that ≥ 1 of the integrins would be differentially expressed.

METHODS

Liver specimens were obtained at 2 collaborating institutions. Samples from infants with BA (n = 23) were compared with samples from those who underwent liver biopsy for neonatal hepatitis (n = 9). All of the specimens were analyzed by 2 pathologists (C.R. and R.A.), who were blinded to the diagnoses. Standard Ishak scoring was performed to evaluate fibrosis and inflammation, and immunohistochemical (IHC) positivity was graded from 0 to 4. Comparisons between the IHC positivity and Ishak scoring for the BA and control groups were performed using the Student t test with P < 0.01 considered significant because of the multiple comparisons. Interobserver variability was assessed by intraclass correlation (ICC).

RESULTS

Pooled analysis from specimens from patients with BA showed significantly more fibrosis than controls based on Ishak scores (3.21 ± 1.82 vs 1.17 ± 1.00, P < 0.005). IHC evaluation showed increased integrin ανβ8 protein expression when compared with controls (2.67 ± 0.81 vs 1.72 ± 0.62, P < 0.005); however, there were no significant differences in integrin ανβ5 (1.93 ± 0.84 vs 1.50 ± 0.90, P = 0.23) or integrin ανβ6 (0.85 ± 1.20 vs 0.94 ± 0.85, P = 0.82) expression. These data were confirmed on individual analysis. Interobserver agreement was fair for integrin ανβ5 (ICC 0.52), good for integrin ανβ6 (ICC 0.72), and excellent for integrin ανβ8 (ICC 0.79) and fibrosis (ICC 0.89).

CONCLUSIONS

Our data show that integrin ανβ8, but not integrin ανβ5 or integrin ανβ6, protein expression is increased in liver specimens of patients with BA. These data support the mounting evidence that transforming growth factor-β (TGF-β) activation is responsible for the fibrosis found in BA. Anti-integrin ανβ8 or more global integrin blocking strategies may be therapeutic options in BA, but further work is clearly needed.

Omega-3 Polyunsaturated Fatty Acid for Cholestasis due to Bile Duct Paucity

Omega (ω)-3 polyunsaturated fatty acids appear to be effective in preventing and treating parenteral nutrition-associated liver disease, and several mechanisms were proposed for this observation. An 8-week-old male infant with cholestasis and acholic stool was diagnosed non-syndromic intrahepatic interlobular bile duct paucity by open-wedge liver biopsy. Initially he was treated with usual supportive medical therapy, including ursodeoxycholic acid. However, the clinical status and laboratory tests did not improve. Omega (ω)-3 polyunsaturated fatty acids (initially intravenous administration and oral administration later), were started and his liver function, including aminotransferase level and bilirubin levels normalized, and the ivory stool color turned green. We report the possible effectiveness of ω-3 polyunsaturated fatty acids as a potent choleretic agent for non-syndromic intrahepatic interlobular bile duct paucity, a very rare structural pediatric hepatic disease.