Dysregulation of antioxidant responses in patients diagnosed with concomitant Primary Sclerosing Cholangitis/Inflammatory Bowel Disease

Loss of β-catenin reveals a role for glutathione in regulating oxidative stress during cholestatic liver disease

BACKGROUND

Cholestasis is an intractable liver disorder that results from impaired bile flow. We have previously shown that the Wnt/β-catenin signaling pathway regulates the progression of cholestatic liver disease through multiple mechanisms, including bile acid metabolism and hepatocyte proliferation. To further explore the impact of these functions during intrahepatic cholestasis, we exposed mice to a xenobiotic that causes selective biliary injury.

METHODS

α-naphthylisothiocyanate (ANIT) was administered to liver-specific knockout (KO) of β-catenin and wild-type mice in the diet. Mice were killed at 6 or 14 days to assess the severity of cholestatic liver disease, measure the expression of target genes, and perform biochemical analyses.

RESULTS

We found that the presence of β-catenin was protective against ANIT, as KO mice had a significantly lower survival rate than wild-type mice. Although serum markers of liver damage and total bile acid levels were similar between KO and wild-type mice, the KO had minor histological abnormalities, such as sinusoidal dilatation, concentric fibrosis around ducts, and decreased inflammation. Notably, both total glutathione levels and expression of glutathione-S-transferases, which catalyze the conjugation of ANIT to glutathione, were significantly decreased in KO after ANIT. Nuclear factor erythroid-derived 2-like 2, a master regulator of the antioxidant response, was activated in KO after ANIT as well as in a subset of patients with primary sclerosing cholangitis lacking activated β-catenin. Despite the activation of nuclear factor erythroid-derived 2-like 2, KO livers had increased lipid peroxidation and cell death, which likely contributed to mortality.

CONCLUSIONS

Loss of β-catenin leads to increased cellular injury and cell death during cholestasis through failure to neutralize oxidative stress, which may contribute to the pathology of this disease.

Therapeutic potential of berberine in attenuating cholestatic liver injury: insights from a PSC mouse model

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is a chronic liver disease characterized by progressive biliary inflammation and bile duct injury. Berberine (BBR) is a bioactive isoquinoline alkaloid found in various herbs and has multiple beneficial effects on metabolic and inflammatory diseases, including liver diseases. This study aimed to examine the therapeutic effect of BBR on cholestatic liver injury in a PSC mouse model (Mdr2-/- mice) and elucidate the underlying mechanisms.

METHODS

Mdr2-/-mice (12-14 weeks old, both sexes) received either BBR (50 mg/kg) or control solution daily for eight weeks via oral gavage. Histological and serum biochemical analyses were used to assess fibrotic liver injury severity. Total RNAseq and pathway analyses were used to identify the potential signaling pathways modulated by BBR in the liver. The expression levels of key genes involved in regulating hepatic fibrosis, bile duct proliferation, inflammation, and bile acid metabolism were validated by qRT-PCR or Western blot analysis. The bile acid composition and levels in the serum, liver, small intestine, and feces and tissue distribution of BBR were measured by LC-MS/MS. Intestinal inflammation and injury were assessed by gene expression profiling and histological analysis. The impact on the gut microbiome was assessed using 16S rRNA gene sequencing.

RESULTS

BBR treatment significantly ameliorated cholestatic liver injury, evidenced by decreased serum levels of AST, ALT, and ALP, and reduced bile duct proliferation and hepatic fibrosis, as shown by H&E, Picro-Sirius Red, and CK19 IHC staining. RNAseq and qRT-PCR analyses indicated a substantial inhibition of fibrotic and inflammatory gene expression. BBR also mitigated ER stress by downregulating Chop, Atf4 and Xbp-1 expression. In addition, BBR modulated bile acid metabolism by altering key gene expressions in the liver and small intestine, resulting in restored bile acid homeostasis characterized by reduced total bile acids in serum, liver, and small intestine and increased fecal excretion. Furthermore, BBR significantly improved intestinal barrier function and reduced bacterial translocation by modulating the gut microbiota.

CONCLUSION

BBR effectively attenuates cholestatic liver injury, suggesting its potential as a therapeutic agent for PSC and other cholestatic liver diseases.

Oxidative Stress and Redox-Dependent Pathways in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a primary liver tumor that accounts for 2% of all cancer-related deaths worldwide yearly. It can arise from cholangiocytes of biliary tracts, peribiliary glands, and possibly from progenitor cells or even hepatocytes. CCA is characterized by high chemoresistance, aggressiveness, and poor prognosis. Potentially curative surgical therapy is restricted to a small number of patients with early-stage disease (up to 35%). Accumulating evidence indicates that CCA is an oxidative stress-driven carcinoma resulting from chronic inflammation. Oxidative stress, due to enhanced reactive oxygen species (ROS) production and/or decreased antioxidants, has been recently suggested as a key factor in cholangiocyte oncogenesis through gene expression alterations and molecular damage. However, due to different experimental models and conditions, contradictory results regarding oxidative stress in cholangiocarcinoma have been reported. The role of ROS and antioxidants in cancer is controversial due to their context-dependent ability to stimulate tumorigenesis and support cancer cell proliferation or promote cell death. On these bases, the present narrative review is focused on illustrating the role of oxidative stress in cholangiocarcinoma and the main ROS-driven intracellular pathways. Heterogeneous data about antioxidant effects on cancer development are also discussed.

Thioredoxin reductase 1 regulates hepatic inflammation and macrophage activation during acute cholestatic liver injury

BACKGROUND AND AIMS

Cholestatic liver diseases, including primary sclerosing cholangitis, are characterized by periportal inflammation with progression to hepatic fibrosis and ultimately cirrhosis. We recently reported that the thioredoxin antioxidant response is dysregulated during primary sclerosing cholangitis. The objective of this study was to examine the impact of genetic and pharmacological targeting of thioredoxin reductase 1 (TrxR1) on hepatic inflammation and liver injury during acute cholestatic injury.

APPROACH AND RESULTS

Primary mouse hepatocytes and intrahepatic macrophages were isolated from 3-day bile duct ligated (BDL) mice and controls. Using wildtype and mice with a liver-specific deletion of TrxR1 (TrxR1LKO), we analyzed the effect of inhibition or ablation of TrxR1 signaling on liver injury and inflammation. Immunohistochemical analysis of livers from BDL mice and human cholestatic patients revealed increased TrxR1 staining in periportal macrophages and hepatocytes surrounding fibrosis. qPCR analysis of primary hepatocytes and intrahepatic macrophages revealed increased TrxR1 mRNA expression following BDL. Compared with sham controls, BDL mice exhibited increased inflammation, necrosis, and increased mRNA expression of pro-inflammatory cytokines, fibrogenesis, the NLRP3 inflammatory complex, and increased activation of NFkB, all of which were ameliorated in TrxR1LKO mice. Importantly, following BDL, TrxR1LKO induced periportal hepatocyte expression of Nrf2-dependent antioxidant proteins and increased mRNA expression of basolateral bile acid transporters with reduced expression of bile acid synthesis genes. In the acute BDL model, the TrxR1 inhibitor auranofin (10 mg/kg/1 d preincubation, 3 d BDL) ameliorated BDL-dependent increases in Nlrp3, GsdmD, Il1β, and TNFα mRNA expression despite increasing serum alanine aminotransferase, aspartate aminotransferase, bile acids, and bilirubin.

CONCLUSIONS

These data implicate TrxR1-signaling as an important regulator of inflammation and bile acid homeostasis in cholestatic liver injury.

The autophagic protein p62 is a target of reactive aldehydes in human and murine cholestatic liver disease

Inflammatory cholestatic liver diseases, including Primary Sclerosing Cholangitis (PSC), are characterized by periportal inflammation with progression to cirrhosis. The objective of this study was to examine interactions between oxidative stress and autophagy in cholestasis. Using hepatic tissue from male acute cholestatic (bile duct ligated) as well as chronic cholestatic (Mdr2KO) mice, localization of oxidative stress, the antioxidant response and induction of autophagy were analyzed and compared to human PSC liver. Concurrently, the ability of reactive aldehydes to post-translationally modify the autophagosome marker p62 was assessed in PSC liver tissue and in cell culture. Expression of autophagy markers was upregulated in human and mouse cholestatic liver. Whereas mRNA expression of Atg12, Lamp1, Sqstm1 and Map1lc3 was increased in acute cholestasis in mice, it was either suppressed or not significantly changed in chronic cholestasis. In human and murine cholestasis, periportal hepatocytes showed increased IHC staining of ubiquitin, 4-HNE, p62, and selected antioxidant proteins. Increased p62 staining colocalized with accumulation of 4-HNE-modified proteins in periportal parenchymal cells as well as with periportal macrophages in both human and mouse liver. Mechanistically, p62 was identified as a direct target of lipid aldehyde adduction in PSC hepatic tissue and in vitro cell culture. In vitro LS-MS/MS analysis of 4-HNE treated recombinant p62 identified carbonylation of His123, Cys128, His174, His181, Lys238, Cys290, His340, Lys341 and His385. These data indicate that dysregulation of autophagy and oxidative stress/protein damage are present in the same periportal hepatocyte compartment of both human and murine cholestasis. Thus, our results suggest that both increased expression as well as ineffective autophagic degradation of oxidatively-modified proteins contributes to injury in periportal parenchymal cells and that direct modification of p62 by reactive aldehydes may contribute to autophagic dysfunction.

Prolonged Administration of Melatonin Ameliorates Liver Phenotypes in Cholestatic Murine Model

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) is characterized by biliary senescence and hepatic fibrosis. Melatonin exerts its effects by interacting with Melatonin receptor 1 and 2 (MT1/MT2) melatonin receptors. Short-term (1 wk) melatonin treatment reduces a ductular reaction and liver fibrosis in bile duct-ligated rats by down-regulation of MT1 and clock genes, and in multidrug resistance gene 2 knockout (Mdr2^-/-) mice by decreased miR200b-dependent angiogenesis. We aimed to evaluate the long-term effects of melatonin on liver phenotype that may be mediated by changes in MT1/clock genes/miR200b/maspin/glutathione-S transferase (GST) signaling.

METHODS

Male wild-type and Mdr2^-/- mice had access to drinking water with/without melatonin for 3 months. Liver damage, biliary proliferation/senescence, liver fibrosis, peribiliary inflammation, and angiogenesis were measured by staining in liver sections, and by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay in liver samples. We confirmed a link between MT1/clock genes/miR200b/maspin/GST/angiogenesis signaling by Ingenuity Pathway Analysis software and measured liver phenotypes and the aforementioned signaling pathway in liver samples from the mouse groups, healthy controls, and PSC patients and immortalized human PSC cholangiocytes.

RESULTS

Chronic administration of melatonin to Mdr2^-/- mice ameliorates liver phenotypes, which were associated with decreased MT1 and clock gene expression.

CONCLUSIONS

Melatonin improves liver histology and restores the circadian rhythm by interaction with MT1 through decreased angiogenesis and increased maspin/GST activity.

NF-κB Regulation of LRH-1 and ABCG5/8 Potentiates Phytosterol Role in the Pathogenesis of Parenteral Nutrition-Associated Cholestasis

BACKGROUND AND AIMS

Chronically administered parenteral nutrition (PN) in patients with intestinal failure carries the risk for developing PN-associated cholestasis (PNAC). We have demonstrated that farnesoid X receptor (FXR) and liver X receptor (LXR), proinflammatory interleukin-1 beta (IL-1β), and infused phytosterols are important in murine PNAC pathogenesis. In this study we examined the role of nuclear receptor liver receptor homolog 1 (LRH-1) and phytosterols in PNAC.

APPROACH AND RESULTS

In a C57BL/6 PNAC mouse model (dextran sulfate sodium [DSS] pretreatment followed by 14 days of PN; DSS-PN), hepatic nuclear receptor subfamily 5, group A, member 2/LRH-1 mRNA, LRH-1 protein expression, and binding of LRH-1 at the Abcg5/8 and Cyp7a1 promoter was reduced. Interleukin-1 receptor-deficient mice (Il-1r^-/- /DSS-PN) were protected from PNAC and had significantly increased hepatic mRNA and protein expression of LRH-1. NF-κB activation and binding to the LRH-1 promoter were increased in DSS-PN PNAC mice and normalized in Il-1r^-/- /DSS-PN mice. Knockdown of NF-κB in IL-1β-exposed HepG2 cells increased expression of LRH-1 and ABCG5. Treatment of HepG2 cells and primary mouse hepatocytes with an LRH-1 inverse agonist, ML179, significantly reduced mRNA expression of FXR targets ATP binding cassette subfamily C member 2/multidrug resistance associated protein 2 (ABCC2/MRP2), nuclear receptor subfamily 0, groupB, member 2/small heterodimer partner (NR0B2/SHP), and ATP binding cassette subfamily B member 11/bile salt export pump (ABCB11/BSEP). Co-incubation with phytosterols further reduced expression of these genes. Similar results were obtained by suppressing the LRH-1 targets ABCG5/8 by treatment with small interfering RNA, IL-1β, or LXR antagonist GSK2033. Liquid chromatography-mass spectrometry and chromatin immunoprecipitation experiments in HepG2 cells showed that ATP binding cassette subfamily G member 5/8 (ABCG5/8) suppression by GSK2033 increased the accumulation of phytosterols and reduced binding of FXR to the SHP promoter. Finally, treatment with LRH-1 agonist, dilauroyl phosphatidylcholine (DLPC) protected DSS-PN mice from PNAC.

CONCLUSIONS

This study suggests that NF-κB regulation of LRH-1 and downstream genes may affect phytosterol-mediated antagonism of FXR signaling in the pathogenesis of PNAC. LRH-1 could be a potential therapeutic target for PNAC.

The Gut-Liver Axis in Chronic Liver Disease: A Macrophage Perspective

Chronic liver disease (CLD) is a growing health concern which accounts for two million deaths per year. Obesity, alcohol overconsumption, and progressive cholestasis are commonly characterized by persistent low-grade inflammation and advancing fibrosis, which form the basis for development of end-stage liver disease complications, including hepatocellular carcinoma. CLD pathophysiology extends to the intestinal tract and is characterized by intestinal dysbiosis, bile acid dysregulation, and gut barrier disruption. In addition, macrophages are key players in CLD progression and intestinal barrier breakdown. Emerging studies are unveiling macrophage heterogeneity and driving factors of their plasticity in health and disease. To date, in-depth investigation of how gut-liver axis disruption impacts the hepatic and intestinal macrophage pool in CLD pathogenesis is scarce. In this review, we give an overview of the role of intestinal and hepatic macrophages in homeostasis and gut-liver axis disruption in progressive stages of CLD.

Cholestatic liver disease results increased production of reactive aldehydes and an atypical periportal hepatic antioxidant response

Cholangiopathies such as primary sclerosing cholangitis (PSC) are chronic liver diseases characterized by increased cholestasis, biliary inflammation and oxidative stress. The objective of this study was to elucidate the impact of cholestatic injury on oxidative stress-related factors. Using hepatic tissue and whole cell liver extracts (LE) isolated from 11-week old C57BL/6J (WT) and Mdr2^KO mice, inflammation and oxidative stress was assessed. Concurrently, specific targets of carbonylation were assessed in LE prepared from murine groups as well as from normal and human patients with end-stage PSC. Identified carbonylated proteins were further evaluated using bioinformatics analyses. Picrosirius red staining revealed extensive fibrosis in Mdr2^KO liver, and fibrosis colocalized with increased periportal inflammatory cells and both acrolein and 4-HNE staining. Western blot analysis revealed elevated periportal expression of antioxidant proteins Cbr3, GSTμ, Prdx5, TrxR1 and HO-1 but not GCLC, GSTπ or catalase in the Mdr2^KO group when compared to WT. From immunohistochemical analysis, increased periportal reactive aldehyde production colocalized with elevated staining of Cbr3, GSTμ and TrxR1 but surprisingly not with Nrf2. Mass spectrometric analysis revealed an increase in carbonylated proteins in the Mdr2^KO and PSC groups compared to respective controls. Gene ontology and KEGG pathway analysis of carbonylated proteins revealed a propensity for increased carbonylation of proteins broadly involved in metabolic processes as well more specifically in Rab-mediated signal transduction, lysosomes and the large ribosomal subunit in human PSC. Western blot analysis of Rab-GTPase expression revealed no significant differences in Mdr2^KO mice when compared to WT livers. In contrast, PSC tissue exhibited decreased levels of Rabs 4, 5 and increased abundance of Rabs 6 and 9a protein. Results herein reveal that cholestasis induces stage-dependent increases in periportal oxidative stress responses and protein carbonylation, potentially contributing to pathogenesis in Mdr2^KO. Furthermore, during early stage cholestasis, there is cell-specific upregulation of some but not all, antioxidant proteins.

Nonenzymatic Serum Antioxidant Capacity in IBD and Its Association with the Severity of Bowel Inflammation and Corticosteroids Treatment

Background and objectives: Oxidative stress signalling plays a monumental role in inflammatory bowel disease (IBD). Reduction of oxidative stress might control inflammation, block tissue damage, and reverse natural history of IBD. We assessed the serum concentrations of free thiols (FT) and uric acid (SUA), together constituting a large part of nonenzymatic serum antioxidant capacity, as well as total antioxidant status (TAS) with reference to IBD phenotype, activity, co-occurrence of anemia, and treatment with azathioprine (AZA) and corticosteroids (CS). Additionally, we appraised the potential of uric acid, thiol stress, and TAS as mucosal healing (MH) markers in ulcerative colitis. Materials and methods: SUA, FT, and TAS were measured colorimetrically using, respectively, uricase, Ellman's and 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) methods. Results: The study group consisted of 175 individuals: 57 controls, 71 ulcerative colitis (UC), and 47 Crohn's disease (CD) patients. When compared to controls, SUA levels were significantly lower in patients with CD, and FT and TAS levels were significantly lower in patients with CD and UC. In UC patients, SUA, FT, and TAS inversely correlated with the severity of bowel inflammation. As MH markers, SUA displayed better overall accuracy and higher specificity than FT. In active CD, FT, and SUA were significantly lower in patients with anemia. FT was significantly lower in patients treated with corticosteroids. Conclusions: IBD patients, regardless the disease phenotype, have systemic thiol stress, depleted total antioxidant capacity, and reduced concentrations of uric acid, reflecting, to various degrees, clinical and local disease activity as well as presence of anaemia, the most common extraintestinal manifestation of IBD. Evaluation of systemic total antioxidant status may be useful in noninvasive assessment of mucosal healing. Our findings on thiol stress provide an additional aspect on adverse effects of corticosteroids therapy.

Nonenzymatic Serum Antioxidant Capacity in IBD and Its Association with the Severity of Bowel Inflammation and Corticosteroids Treatment

Background and objectives: Oxidative stress signalling plays a monumental role in inflammatory bowel disease (IBD). Reduction of oxidative stress might control inflammation, block tissue damage, and reverse natural history of IBD. We assessed the serum concentrations of free thiols (FT) and uric acid (SUA), together constituting a large part of nonenzymatic serum antioxidant capacity, as well as total antioxidant status (TAS) with reference to IBD phenotype, activity, co-occurrence of anemia, and treatment with azathioprine (AZA) and corticosteroids (CS). Additionally, we appraised the potential of uric acid, thiol stress, and TAS as mucosal healing (MH) markers in ulcerative colitis. Materials and methods: SUA, FT, and TAS were measured colorimetrically using, respectively, uricase, Ellman’s and 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) methods. Results: The study group consisted of 175 individuals: 57 controls, 71 ulcerative colitis (UC), and 47 Crohn’s disease (CD) patients. When compared to controls, SUA levels were significantly lower in patients with CD, and FT and TAS levels were significantly lower in patients with CD and UC. In UC patients, SUA, FT, and TAS inversely correlated with the severity of bowel inflammation. As MH markers, SUA displayed better overall accuracy and higher specificity than FT. In active CD, FT, and SUA were significantly lower in patients with anemia. FT was significantly lower in patients treated with corticosteroids. Conclusions: IBD patients, regardless the disease phenotype, have systemic thiol stress, depleted total antioxidant capacity, and reduced concentrations of uric acid, reflecting, to various degrees, clinical and local disease activity as well as presence of anaemia, the most common extraintestinal manifestation of IBD. Evaluation of systemic total antioxidant status may be useful in noninvasive assessment of mucosal healing. Our findings on thiol stress provide an additional aspect on adverse effects of corticosteroids therapy.

Dexamethasone counteracts hepatic inflammation and oxidative stress in cholestatic rats via CAR activation

Glucocorticoids (GCs) are currently used for the therapeutic management of cholestatic diseases, but their use and molecular mechanism remain controversial. The aims of this study were 1) to assess the therapeutic effect of a 2-week treatment with the GC dexamethasone on hepatic damage in bile duct-ligated rats; 2) to investigate its effect on the activation of the nuclear receptors (NRs) pregnane X receptor (PXR), constitutive androstane receptor (CAR) and GC receptor (GR), and NF-kB, as well as on oxidative stress and bile acid (BA) hepatic composition. Cholestasis was induced by ligation of bile duct (BDL animals) in 16 male Wistar-Kyoto rats, and eight of them were daily treated by oral gavage with 0.125 mg/ml/kg DEX for 14 days. Eight Sham-operated rats were used as controls. Severity of cholestasis was assessed histologically and on plasma biochemical parameters. The nuclear expression of NF-kB (p65), GR, PXR and CAR was measured in hepatic tissue by Western Blot. Oxidative stress was evaluated by measuring malondialdehyde, carbonylated proteins, GHS and ROS content in rat livers. LC-MS was used to measure the plasma and liver concentration of 7 BAs. Histological findings and a significant drop in several markers of inflammation (p65 nuclear translocation, mRNA expressions of TNF-α, IL-1β, IL-6) showed that DEX treatment reversed cholestasis-induced inflammation, and similar results have been obtained with oxidative stress markers. The nuclear expression of p65 and CAR were inversely correlated, with the latter increasing significantly after DEX treatment (p<0.01 vs vehicle). Hepatic BA levels tended to drop in the untreated cholestatic rats, whereas they were similar to those of healthy rats in DEX-treated animals. Plasma BAs decreased significantly in DEX-treated animals with respect to untreated cholestatic rats. In conclusion, DEX reduces inflammation and oxidative stress in BDL rats, and probably CAR is responsible for this effect. Therefore, this NR represents a promising pharmacological target for managing cholestatic and inflammatory liver diseases.

Aberrant expression of redox regulatory proteins in patients with concomitant primary Sclerosing cholangitis/inflammatory bowel disease

OBJECTIVE

Primary Sclerosing Cholangitis (PSC) is a severe cholestatic liver disease characterized by progressive peri-biliary tract inflammation, elevated oxidative stress and hepatocellular injury. A hallmark of PSC patients is the concurrent diagnosis of Inflammatory Bowel Disease occurring in approximately 70%-80% of PSC patients (PSC/IBD). We previously reported dysregulation of key anti-oxidant pathways in PSC/IBD. The objective of this study was to expand previous data by examining the abundance of thioredoxins (Trx) in PSC/IBD.

METHODS

Using hepatic tissue and whole cell extracts isolated from age-matched healthy humans and patients diagnosed with end stage PSC/IBD, the protein abundance of thioredoxin, thioredoxin reductase (TrxR1), and their downstream substrates peroxiredoxins was assessed.

RESULTS

Western blot analyses of thioredoxin and peroxiredoxin abundance revealed significant increases in abundance of Trx1 and TrxR1 whereas expression of thioredoxin-interacting protein was significantly decreased in PSC/IBD. Concurrently, abundance of cytosolic peroxiredoxins was not significantly impacted. The abundance of mitochondrial Trx2, along with peroxiredoxins 3, 5 and 6 were significantly decreased by concurrent PSC/IBD. Histological staining of Trx1/TrxR1 revealed elevated nuclear Trx1 and TrxR1 staining within cholangiocytes as well as an overall periportal increase in expression in PSC/IBD. An examination of additional anti-oxidant responses reveal suppression of gamma-glutamylcysteine synthetase and heme oxygenase (HO-1) whereas expression of the protein chaperone glucose regulated protein 78 increased suggesting elevated cellular stress in PSC/IBD.

CONCLUSIONS

Results herein suggest that in addition to severe dysregulation of anti-oxidant responses, cholestasis impacts both cytosolic/nuclear (Trx1) as well as mitochondrial (Trx2) redox signaling and control pathways.