Overexpression of thioredoxin prevents thioacetamide-induced hepatic fibrosis in mice

Thioredoxin/Glutaredoxin Systems and Gut Microbiota in NAFLD: Interplay, Mechanism, and Therapeutical Potential

Non-alcoholic fatty liver disease (NAFLD) is a common clinical disease, and its pathogenesis is closely linked to oxidative stress and gut microbiota dysbiosis. Recently accumulating evidence indicates that the thioredoxin and glutaredoxin systems, the two thiol-redox dependent antioxidant systems, are the key players in the NAFLD's development and progression. However, the effects of gut microbiota dysbiosis on the liver thiol-redox systems are not well clarified. This review explores the role and mechanisms of oxidative stress induced by bacteria in NAFLD while emphasizing the crucial interplay between gut microbiota dysbiosis and Trx mediated-redox regulation. The paper explores how dysbiosis affects the production of specific gut microbiota metabolites, such as trimethylamine N-oxide (TMAO), lipopolysaccharides (LPS), short-chain fatty acids (SCFAs), amino acids, bile acid, and alcohol. These metabolites, in turn, significantly impact liver inflammation, lipid metabolism, insulin resistance, and cellular damage through thiol-dependent redox signaling. It suggests that comprehensive approaches targeting both gut microbiota dysbiosis and the thiol-redox antioxidant system are essential for effectively preventing and treating NAFLD. Overall, comprehending the intricate relationship between gut microbiota dysbiosis and thiol-redox systems in NAFLD holds significant promise in enhancing patient outcomes and fostering the development of innovative therapeutic interventions.

Comparison of the efficacy of the mouse hepatic and renal antioxidant systems against inflammation-induced oxidative stress

This study was conducted to compare the efficacy of the mouse hepatic and renal antioxidant systems against inflammation-induced oxidative stress. Increased Il-1 and Il-6 expressions, markers of inflammation, were represented by inflammation models in mouse liver and kidney tissues injected intraperitoneally with LPS. After establishing the model, the GSH level and the GSH/GSSG ratio, which are oxidative stress markers, were investigated in both tissues treated with LPS and the control group. The expression of Trx1, TrxR, and Txnip genes increased in the liver tissues of LPS-treated mice. In the kidney tissue, while Trx1 expression decreased, no change was observed in TrxR1 expression, and Txnip expression increased. In the kidneys, TRXR1 and GR activities decreased, whereas GPx activity increased. In both tissues, the TRXR1 protein expression decreased significantly, while TXNIP expression increased. In conclusion, different behaviors of antioxidant system members were observed during acute inflammation in both tissues. Additionally, it can be said that the kidney tissue is more sensitive and takes earlier measures than the liver tissue against cellular damage caused by inflammation and inflammation-induced oxidative stress.

Acute bone damage through liver-bone axis induced by thioacetamide in rats

Background

Thioacetamide (TAA) is used in various fields, such as synthetic drugs, organic chemical synthesis, and materials chemistry. TAA is mainly used to establish animal liver injury models and other organ damage models to explore their mechanisms for helping patients with liver disease. Liver damage can lead to abnormal expression of some enzymes in the serum, so we detected the appropriate enzyme levels in the serum of SD rats to verify the damage of TAA to the liver. More importantly, TAA caused bone damage is barely understood. Therefore, our research aims to establish a rat model reflecting the acute bone damage injury caused by TAA.

Methods

The SD rats were intraperitoneally injected with normal saline (0.9%) or TAA (200 mg/kg, 400 mg/kg) for 1 month (once the other day). After the last intraperitoneal injection, serum samples from rats were used for biochemical tests. Masson staining is used to detect liver damage, and micro-CT is used to detect the changes in bone. Moreover, the three-point bending experiment was used to detect the force range of the hind limbs of SD rats.

Results

Compared with the control group, after the intraperitoneal injection of TAA, the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), uric acid (UA), total bile acid (TBA), alkaline phosphatase (ALP), carbamide (UREA) and creatinine (CREA) rose sharply, while the levels of serum content of total protein (TP), lactate dehydrogenase (LDH), calcium (Ca) and phosphorus (P) were severely reduced. After TAA administration, collagen fibers were deposited and liver fibrosis was obvious. Micro-CT results showed that the bone surface, tissue surface, bone volume, and tissue volume of rats with an intraperitoneal injection of TAA were significantly reduced. In addition, the bones of rats with an intraperitoneal injection of TAA can resist less pressure and are prone to fractures.

Conclusions

TAA can cause liver damage in SD rats, which is explained by the changes in serum biochemical indicators and the deposition of liver collagen. More importantly, TAA can reduce bone mineral density and increase the separation of bone trabeculae in SD rats, and finally lead to bone injury. This suggests that TAA may become an ideal model to investigate abnormal bone metabolism after liver injury.

Nephrotoxicity evaluation and proteomic analysis in kidneys of rats exposed to thioacetamide

Thioacetamide (TAA) was administered orally at 0, 10, and 30 mg/kg body weight (BW) daily to Sprague–Dawley rats aged 6–7 weeks for 28 consecutive days. Nephrotoxicity and proteomics were evaluated in the kidneys of rats exposed to TAA. The BW decreased, however, the relative kidneys weight increased. No significant histopathologic abnormalities were found in the kidneys. The numbers of monocytes and platelets were significantly increased. However, the mean corpuscular volume and hematocrit values were decreased significantly in rats exposed to 30 mg/kg BW TAA. The expression levels of Kim-1 and NGAL were increased 4 to 5-fold in the kidneys, resulting in significant nephrotoxicity. Proteomic analysis was conducted and a total of 5221 proteins spots were resolved. Of these, 3 and 21 protein spots were up- and downregulated, respectively. The validation of seven proteins was performed by Western blot analysis. The expression level of ASAP2 was significantly upregulated, whereas RGS14, MAP7Dl, IL-3Rα, Tmod1, NQO2, and MUP were reduced. Sixteen isoforms of MUP were found by the 2DE immunoblot assay and were significantly downregulated with increasing exposure to TAA. MUP isoforms were compared in the liver, kidneys, and urine of untreated rats and a total of 43 isoforms were found.

Carvacrol hinders the progression of hepatic fibrosis via targeting autotaxin and thioredoxin in thioacetamide-induced liver fibrosis in rat

Fibrosis is a common outcome of nearly all chronic diseases of liver that results in changes of its functions which requires medical attention. The current research aims to investigate the potential anti-fibrotic efficacy of Carvacrol against thioacetamide (TAA)-induced liver fibrosis in male rats using Ursodeoxycholic acid (UDCA) as a reference anti-fibrotic product. Carvacrol (25 and 50 mg/kg) markedly declined TAA-increased serum liver enzymes; alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) as well as total bilirubin (TB) and direct bilirubin (DB) levels as well as increased levels of total protein (TP) and albumin. Carvacrol significantly reduced glutathione depletion (GSH), Nitric oxide (NOX) and malondialdehyde (MDA) accumulation in liver tissue. Additionally, its anti-oxidant effect brightened up via affecting markers of stress found in the cell as nuclear factor erythroid 2-related factor 2 (Nrf-2) where it still had high content and decreased Thioredoxin (Trx) level. The anti-inflammatory effect of Carvacrol was confirmed by decreasing nuclear factor kappa B (NF-κB), interleukin-1beta (IL-1β) and inducible nitric oxide synthase (iNOS) contents. Carvacrol showed anti-fibrotic effect clarified by turning down fibrosis-related markers; TGF-β1, matrix metalloproteinase-3 and 9 (MMP-3 and 9) and Autotaxin (ATX) contents. Furthermore, it decreased alpha smooth muscle actin (α-SMA) and caspase-3 immune-expression. The overall outcome of aforementioned markers results showed that Carvacrol suppresses the progression of liver fibrosis via its anti-oxidant, anti-inflammatory, anti-apoptotic effect and its ability in lowering Thioredoxin and Autotaxin; hence it can be categorized as a hepatoprotective natural substance.

Secreted matrix metalloproteinase-14 is a predictor for antifibrotic effect of IC-2-engineered mesenchymal stem cell sheets on liver fibrosis in mice

Introduction

Transplantation of IC-2-engineered bone marrow-derived mesenchymal stem cell (BM-MSC) sheets (IC-2 sheets) was previously reported to potentially reduce liver fibrosis.

Methods

This study prepared IC-2-engineered cell sheets from multiple lots of BM-MSCs and examined the therapeutic effects of these cell sheets on liver fibrosis induced by carbon tetrachloride in mice. The predictive factors for antifibrotic effect on liver fibrosis were tried to identify in advance.

Results

Secreted matrix metalloproteinase (MMP)-14 was found to be a useful predictive factor to reduce liver fibrosis. Moreover, the cutoff index of MMP-14 for 30% reduction of liver fibrosis was 0.918 fg/cell, judging from univariate analysis and receiver operating curve analysis. In addition, MMP-13 activity and thioredoxin contents in IC-2 sheets were also inversely correlated with hepatic hydroxyproline contents. Finally, IC-2 was also found to promote MMP-14 secretion from BM-MSCs of elderly patients. Surprisingly, the values of secreted MMP-14 from BM-MSCs of elderly patients were much higher than those of young persons.

Conclusion

The results of this study suggest that the IC-2 sheets would be applicable to clinical use in autologous transplantation for patients with cirrhosis regardless of the patient's age.

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IC-2- sheets from multiple lots of BM-MSCs ameliorate liver fibrosis in mice.

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Secreted MMP-14 is a useful predictive marker to reduce liver fibrosis.

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MMP-13 and thioredoxin in IC-2 sheets were also associated with liver fibrosis.

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IC-2 also promotes MMP-14 secretion from BM-MSCs of elderly patients.

Redox Regulation in Aging Lungs and Therapeutic Implications of Antioxidants in COPD

Mammals, including humans, are aerobic organisms with a mature respiratory system to intake oxygen as a vital source of cellular energy. Despite the essentiality of reactive oxygen species (ROS) as byproducts of aerobic metabolism for cellular homeostasis, excessive ROS contribute to the development of a wide spectrum of pathological conditions, including chronic lung diseases such as COPD. In particular, epithelial cells in the respiratory system are directly exposed to and challenged by exogenous ROS, including ozone and cigarette smoke, which results in detrimental oxidative stress in the lungs. In addition, the dysfunction of redox regulation due to cellular aging accelerates COPD pathogenesis, such as inflammation, protease anti-protease imbalance and cellular apoptosis. Therefore, various drugs targeting oxidative stress-associated pathways, such as thioredoxin and N-acetylcysteine, have been developed for COPD treatment to precisely regulate the redox system. In this review, we present the current understanding of the roles of redox regulation in the respiratory system and COPD pathogenesis. We address the insufficiency of current COPD treatment as antioxidants and discuss future directions in COPD therapeutics targeting oxidative stress while avoiding side effects such as tumorigenesis.

Hepatoprotective effect of Saccharomyces Cervisciae Cell Wall Extract against thioacetamide-induced liver fibrosis in rats

Fibrosis represents a common outcome of almost all chronic liver diseases and leads to an impairment of liver function that requires medical intervention. The current study aimed to evaluate the potential anti-fibrotic effect of Saccharomyces cervisciae cell wall extract (SCCWE) against thioacetamide (TAA)-induced liver fibrosis in rats (200mg/kg b.w. i.p. twice weekly for 6 weeks) using Ursodeoxycholic acid (UDCA) as a reference anti-fibrotic product. SCCWE at two doses (50 and 100 mg/kg) significantly ameliorated the rise in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma glutamide transferase (GGT) activities, total bilirubin and direct bilirubin, increased total protein and albumin. SCCWE significantly reduced glutathione depletion (GSH), Nitric oxide (NOx) and malondialdehyde (MDA), thioredoxin (Trx) contents and elevated nuclear factor erythroid 2–related factor 2 (Nrf-2) content. Its anti-inflammatory effects were confirmed by observing a decrease in nuclear factor-κB (NF- κβ), interleukin-1b (IL-1β) and inducible nitric oxide synthase (iNOS) content. The anti-fibrotic effects of SCCWE were explored by assessing fibrosis related markers as it significantly reduced transform growth factor-β (TGF-β) and autotaxin (ATX) contents. Administration of SCCWE significantly decreased matrix metalloproteinase-3 and 9 (MMP-3 and -9). Furthermore, it also decreased alpha smooth muscle actin (α-SMA) and caspase-3 as assessed immunohistochemically those results were similar to that of the standard drug UDCA. This study shows that SCCWE protects against TAA-induced liver fibrosis in rats, through attenuating oxidative stress, and inflammation, ameliorating MMPs, combating apoptosis and thereby fibrotic biomarkers in addition to improving histopathological changes.

Decellularized hepatic extracellular matrix hydrogel attenuates hepatic stellate cell activation and liver fibrosis

Liver fibrosis results from excessive accumulation of extracellular matrix (ECM) proteins that distort the hepatic architecture. Progression of liver fibrosis results in cirrhosis and liver failure, and often, liver transplantation is required. The decellularized liver tissue contains different components that mimic the natural hepatic environment. We hypothesized that a decellularized liver hydrogel can be used to replace the necrotic hepatocytes and damaged ECM. Therefore, our aim in this study is to develop a therapy for treating liver fibrosis. Mice livers were decellularized and processed to form a hepatic hydrogel. We evaluated the biocompatibility and bioactivity of the hydrogel. The ability of the hydrogel to enhance the migration of hepatocytes and endothelial cells was investigated. Human hepatic stellate cell line (LX-2) activated by transforming growth factor-β1 (TGF-β1) was used as in vitro model for fibrogenesis. Then, the hydrogel was injected into the liver parenchyma of mice after the induction of liver fibrosis using thioacetamide. The resulting hydrogel maintained a complex composition, which included glycosaminoglycans, collagen, elastin, and growth factors. Hepatocytes and endothelial cells were shown to migrate toward the hydrogel in vitro. Liver hydrogel improved TGF-β1-induced LX-2 cells activation via blocking the TGF-β1/Smad pathway. The matrix was delivered successfully in vivo and enhanced the reduction of fibrosis and recovery to a nearly normal structure. In conclusion, we have demonstrated that the liver hydrogel can be utilized as an injectable biomaterial for liver tissue engineering in order to reduce the degree of fibrosis.

Concordance between Thioacetamide-Induced Liver Injury in Rat and Human In Vitro Gene Expression Data

The immense resources required and the ethical concerns for animal-based toxicological studies have driven the development of in vitro and in silico approaches. Recently, we validated our approach in which the expression of a set of genes is uniquely associated with an organ-injury phenotype (injury module), by using thioacetamide, a known liver toxicant. Here, we sought to explore whether RNA-seq data obtained from human cells (in vitro) treated with thioacetamide-S-oxide (a toxic intermediate metabolite) would correlate across species with the injury responses found in rat cells (in vitro) after exposure to this metabolite as well as in rats exposed to thioacetamide (in vivo). We treated two human cell types with thioacetamide-S-oxide (primary hepatocytes with 0 (vehicle), 0.125 (low dose), or 0.25 (high dose) mM, and renal tubular epithelial cells with 0 (vehicle), 0.25 (low dose), or 1.00 (high dose) mM) and collected RNA-seq data 9 or 24 h after treatment. We found that the liver-injury modules significantly altered in human hepatocytes 24 h after high-dose treatment involved cellular infiltration and bile duct proliferation, which are linked to fibrosis. For high-dose treatments, our modular approach predicted the rat in vivo and in vitro results from human in vitro RNA-seq data with Pearson correlation coefficients of 0.60 and 0.63, respectively, which was not observed for individual genes or KEGG pathways.

Assessing Chemical-Induced Liver Injury In Vivo From In Vitro Gene Expression Data in the Rat: The Case of Thioacetamide Toxicity

Consumers are exposed to thousands of chemicals with potentially adverse health effects. However, these chemicals will never be tested for toxicity because of the immense resources needed for animal-based (in vivo) toxicological studies. Today, there are no viable in vitro alternatives to these types of animal studies. To develop an in vitro approach, we investigated whether we could predict in vivo organ injuries in rats with the use of RNA-seq data acquired from tissues early in the development of toxicant-induced injury, by comparing gene expression data from RNA isolated from these rat tissues with those obtained from in vitro exposure of primary liver and kidney cells. We collected RNA-seq data from the liver and kidney tissues of Sprague-Dawley rats 8 or 24 h after exposing them to vehicle (control), low (25 mg/kg), or high (100 mg/kg) doses of thioacetamide, a known liver toxicant that promotes fibrosis; we used these doses and exposure times to cause only mild toxicant-induced injury. For the in vitro study, we treated two cell types from Sprague-Dawley rats, primary hepatocytes (vehicle; low, 0.025 mM; or high, 0.125 mM dose), and renal tube epithelial cells (vehicle; low, 0.125 mM; or high, 0.500 mM) dose) with the thioacetamide metabolite, thioacetamide-S-oxide, selecting in vitro doses and exposure times to recreate the early-stage toxicant-induced injury model that we achieved in vivo. RNA-seq data were collected 9 or 24 h after application of vehicle or thioacetamide-S-oxide. We found that our modular approach for the analysis of gene expression data derived from in vivo RNA-seq strongly correlated (R² > 0.6) with the in vitro results at two different dose levels of thioacetamide/thioacetamide-S-oxide after 24 h of exposure. The top-ranked liver injury modules in vitro correctly identified the ensuing development of liver fibrosis.

Reversal of established liver fibrosis by IC-2-engineered mesenchymal stem cell sheets

Chronic hepatitis viral infection, alcoholic intoxication, and obesity cause liver fibrosis, which progresses to decompensated liver cirrhosis, a disease for which medical demands cannot be met. Since there are currently no approved anti-fibrotic therapies for established liver fibrosis, the development of novel modalities is required to improve patient prognosis. In this study, we clarified the anti-fibrotic effects of cell sheets produced from human bone marrow-derived mesenchymal stem cells (MSCs) incubated on a temperature-sensitive culture dish with the chemical compound IC-2. Orthotopic transplantation of IC-2-engineered MSC sheets (IC-2 sheets) remarkably reduced liver fibrosis induced by chronic CCl4 administration. Further, the marked production of fibrolytic enzymes such as matrix metalloproteinase (MMP)-1 and MMP-14, as well as thioredoxin, which suppresses hepatic stellate cell activation, was observed in IC-2 sheets. Moreover, the anti-fibrotic effect of IC-2 sheets was much better than that of MSC sheets. Finally, knockdown experiments revealed that MMP-14 was primarily responsible for the reduction of liver fibrosis. Here, we show that IC-2 sheets could be a promising therapeutic option for established liver fibrosis.

Identification of the Toxicity Pathways Associated With Thioacetamide-Induced Injuries in Rat Liver and Kidney

Ingestion or exposure to chemicals poses a serious health risk. Early detection of cellular changes induced by such events is vital to identify appropriate countermeasures to prevent organ damage. We hypothesize that chemically induced organ injuries are uniquely associated with a set (module) of genes exhibiting significant changes in expression. We have previously identified gene modules specifically associated with organ injuries by analyzing gene expression levels in liver and kidney tissue from rats exposed to diverse chemical insults. Here, we assess and validate our injury-associated gene modules by analyzing gene expression data in liver, kidney, and heart tissues obtained from Sprague-Dawley rats exposed to thioacetamide, a known liver toxicant that promotes fibrosis. The rats were injected intraperitoneally with a low (25 mg/kg) or high (100 mg/kg) dose of thioacetamide for 8 or 24 h, and definite organ injury was diagnosed by histopathology. Injury-associated gene modules indicated organ injury specificity, with the liver being most affected by thioacetamide. The most activated liver gene modules were those associated with inflammatory cell infiltration and fibrosis. Previous studies on thioacetamide toxicity and our histological analyses supported these results, signifying the potential of gene expression data to identify organ injuries.

The molecular and biochemical insight view of lycopene in ameliorating tramadol-induced liver toxicity in a rat model: implication of oxidative stress, apoptosis, and MAPK signaling pathways

The influence of tramadol (TD) on hepatic tissue and the potential efficiency of lycopene to mitigate TD-induced hepatotoxic impacts were determined. Forty male albino rats were allocated into four groups: group I, untreated (placebo); group II, injected with TD (15 mg kg^-1) intraperitoneally (i.p.); group III, gastrogavaged with lycopene (10 mg kg^-1) per os (p.o.); and group IV received TD with lycopene with the same mentioned doses for 15 days. The results demonstrated that TD induced augmentation in tissue lipid peroxidation biomarker and disturbance in the antioxidant homeostasis and elevated the activity of serum liver injury biomarkers and decreased serum protein, globulin, and albumin. Hepatic glutathione S-transferase (GST), superoxide dismutase (SOD), thioredoxin-1 (Txn-1), and catalase (CAT) activities and gene expression were decreased and glutathione content was reduced in the TD-challenged rats, and these effects were alleviated by lycopene. Furthermore, TD induced apoptosis in liver tissues as shown by DNA fragmentation and upregulation of proapoptotic Bax and Casp-3 while lycopene upregulated the antiapoptotic Bcl-2. The results of Western blot showed that lycopene initiated low expression of mitogen activated protein kinase pathway (MAPK) protein expression in liver tissues of TD-challenged rats. In addition, lycopene reduced fatty degeneration and necrosis of the liver in TD-challenged group. Our data demonstrate that lycopene appears to be highly efficient in mitigating the hepatotoxic impacts of TD by preventing lipid peroxidation and initiating modifications in the expression and activity of antioxidant pathways. Surprisingly, lycopene fortified liver tissue by inhibiting DNA fragmentation and apoptosis signaling induced by TD. MAPK activation may be dependent from ROS generation; due to lycopene which possessed antioxidant potential did have a substantial effect on MAPK activity.

Melatonin mitigates thioacetamide-induced hepatic fibrosis via antioxidant activity and modulation of proinflammatory cytokines and fibrogenic genes

AIMS

The potential antifibrotic effects of melatonin against induced hepatic fibrosis were explored.

MAIN METHODS

Rats were allocated into four groups: placebo; thioacetamide (TAA) (200mg/kg bwt, i.p twice weekly for two months); melatonin (5mg/kgbwt, i.p daily for a week before TAA and continued for an additional two months); and melatonin plus TAA. Hepatic fibrotic changes were evaluated biochemically and histopathologically. Hepatic oxidative/antioxidative indices were assessed. The expression of hepatic proinflammatory cytokines (tumor necrosis factor-α, and interleukin-1β), fibrogenic-related genes (transforming growth factor-1β, collagen I, collagen, III, laminin, and autotaxin) and an antioxidant-related gene (thioredoxin-1) were detected by qRT-PCR.

KEY FINDINGS

In fibrotic rats, melatonin lowered serum aspartate aminotransferase, alanine aminotransferase, and autotaxin activities, bilirubin, hepatic hydroxyproline and plasma ammonia levels. Melatonin displayed hepatoprotective and antifibrotic potential as indicated by mild hydropic degeneration of some hepatocytes and mild fibroplasia. In addition, TAA induced the depletion of glutathione, glutathione s-transferase, glutathione peroxidase, superoxide dismutase, catalase, and paraoxonase-1 (PON-1), while inducing the accumulation of malondialdehyde, protein carbonyl (C=O) and nitric oxide (NO), and DNA fragmentation. These effects were restored by melatonin pretreatment. Furthermore, melatonin markedly attenuated the expression of proinflammatory cytokines and fibrogenic genes via the upregulation of thioredoxin-1 mRNA transcripts.

SIGNIFICANCE

Melatonin exhibits potent anti-inflammatory, antioxidant and fibrosuppressive activities against TAA-induced hepatic fibrogenesis via the suppression of oxidative stress, DNA damage, proinflammatory cytokines and fibrogenic gene transcripts. In addition, we demonstrate that the antifibrotic activity of melatonin is mediated by the induction of thioredoxin-1 with attenuation of autotaxin expressions.

Solanum trilobatum L. Ameliorate Thioacetamide-Induced Oxidative Stress and Hepatic Damage in Albino Rats

Solanum trilobatum L. (Solanaceae) has been well known as nightshade, commonly used by diverse populations to heal several disorders. Earlier studies in Solanum trilobatum were focused on different pharmacological activities and a few were concerned with antioxidant and hepatoprotective effects. Thus, the current study was focused to evaluate the antioxidant potential and hepatoprotective effects of S. trilobatum L. on thioacetamide (TAA) intoxication in Wistar albino rats. The rats were kept into four groups and six animals each. Group A was normal control. Group B was the TAA treated control. Groups C and D were pretreated with the aqueous extract from the leaves of S. trilobatum (100 mg, 200 mg/kg bw p.o.) once daily for 10 consecutive days administration followed by a single dose infusion of TAA (100 mg/kg s.c.). After 10 days, blood and livers were collected. The biochemical assay was carried out in the GSH (reduced glutathione), TBARS(thiobarbituric acid reactive substances), Na⁺-K⁺-ATPase, and antioxidant enzymes viz., SOD (superoxide dismutase), CAT (catalase), GPx (glutathione peroxidase), GST (glutathione-S-transferase), and GR (glutathione reductase) were analyzed in samples of blood and liver. Treatment with S. trilobatum reduced blood and liver TBARS, and Na⁺ K⁺ ATPase activity in TAA (thioacetamide)-induced hepatotoxicity rats. Furthermore, the above antioxidant enzymes were increased in the pretreatment of S. trilobatum in TAA intoxicated rats. Finally, we concluded that S. Trilobatum displayed potent antioxidant properties and alleviate oxidative stress induced hepatotoxic effects and possible engross mechanisms related to free radical scavenging properties.

All-trans retinoic acid ameliorates hepatic stellate cell activation via suppression of thioredoxin interacting protein expression

Activation of hepatic stellate cells (HSCs) is the effector factor of hepatic fibrosis and hepatocellular carcinoma (HCC) development. Accumulating evidence suggests that retinoic acids (RAs), derivatives of vitamin A, contribute to prevention of liver fibrosis and carcinogenesis, however, regulatory mechanisms of RAs still remain exclusive. To elucidate RA signaling pathway, we previously performed a genome-wide screening of RA-responsive genes by in silico analysis of RA-response elements, and identified 26 RA-responsive genes. We found that thioredoxin interacting protein (TXNIP), which inhibits antioxidant activity of thioredoxin (TRX), was downregulated by all-trans retinoic acid (ATRA). In the present study, we demonstrate that ATRA ameliorates activation of HSCs through TXNIP suppression. HSC activation was attenuated by TXNIP downregulation, whereas potentiated by TXNIP upregulation, indicating that TXNIP plays a crucial role in activation of HSCs. Notably, we showed that TXNIP-mediated HSC activation was suppressed by antioxidant N-acetylcysteine. In addition, ATRA treatment or downregulation of TXNIP clearly declined oxidative stress levels in activated HSCs. These data suggest that ATRA plays a key role in inhibition of HSC activation via suppressing TXNIP expression, which reduces oxidative stress levels.

Txn1, Ctsd and Cdk4 are key proteins of combination therapy with taurine, epigallocatechin gallate and genistein against liver fibrosis in rats

The anti-fibrotic mechanism of combination therapy with taurine, epigallocatechin gallate and genistein was studied from the perspective of serum proteomics in our previous work. In order to further investigate and systematically analyse other possible therapeutic mechanism of combination therapy against liver fibrosis, isobaric tags for relative and absolute quantification (iTRAQ) proteomic analysis was applied to study the protein profile changes in liver tissue of carbon tetrachloride-induced liver fibrosis rats after combination therapy. A total of 115 differentially expressed proteins containing 84 up-regulated and 31 down-regulated proteins in response to combination therapy were identified. Three differentially expressed proteins (Txn1, Ctsd and Cdk4) involved in antioxidant defense system and the activation and proliferation of hepatic stellate cell were selected for further validation by western blot and real-time PCR analysis. Our study highlight the importance of differentially expressed proteins Txn1, Ctsd and Cdk4 against liver fibrosis, which may provide a more precise and comprehensive perspective for clarifying the roles of combination therapy as a potential agent for treatment of liver fibrosis.

Nature and Implications of Oxidative and Nitrosative Stresses in Autoimmune Hepatitis

Oxidative and nitrosative stresses can damage cellular membranes, disrupt mitochondrial function, alter gene expression, promote the apoptosis and necrosis of hepatocytes, and increase fibrosis in diverse acute and chronic liver diseases, including autoimmune hepatitis. The objectives of this review are to describe the mechanisms of oxidative and nitrosative stresses in inflammatory liver disease, indicate the pathogenic implications of these stresses in autoimmune hepatitis, and suggest investigational opportunities to develop interventions that counter them. The principal antioxidant defenses, including glutathione production, the activities of antioxidant enzymes, and the release of the nuclear factor erythroid 2-related factor 2, may be inadequate or suppressed by transforming growth factor beta. The generation of reactive oxygen species can intensify nitrosative stress, and this stress may not be adequately modulated by the thioredoxin-thioredoxin reductase system and induce post-translational modifications of proteins that further disrupt hepatocyte function. The unfolded protein response and autophagy may be unable to restore redox stability, meet metabolic demands, and maintain hepatocyte survival. Emerging interventions with highly selective site- and organelle-specific actions may improve outcomes, and they include inhibitors of nicotinamide adenine dinucleotide phosphate oxidase, nitric oxide synthase, and transforming growth factor beta. Pharmacological manipulation of nuclear transcription factors may favor expression of antioxidant genes, and stimulation of chaperone proteins within the endoplasmic reticulum and modulation of autophagy may prevent hepatic fibrosis and enhance cell survival. These interventions constitute investigational opportunities to improve the management of autoimmune hepatitis.

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.

Potential Use of Biological Proteins for Liver Failure Therapy

Biological proteins have unlimited potential for use as pharmaceutical products due to their various biological activities, which include non-toxicity, biocompatibility, and biodegradability. Recent scientific advances allow for the development of novel innovative protein-based products that draw on the quality of their innate biological activities. Some of them hold promising potential for novel therapeutic agents/devices for addressing hepatic diseases such as hepatitis, fibrosis, and hepatocarcinomas. This review attempts to provide an overview of the development of protein-based products that take advantage of their biological activity for medication, and discusses possibilities for the therapeutic potential of protein-based products produced through different approaches to specifically target the liver (or hepatic cells: hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells, and Kupffer cells) in the treatment of hepatic diseases.

Increased serum bile acid concentration following low-dose chronic administration of thioacetamide in rats, as evidenced by metabolomic analysis

A liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS)-based metabolomics approach was employed to identify endogenous metabolites as potential biomarkers for thioacetamide (TAA)-induced liver injury. TAA (10 and 30mg/kg), a well-known hepatotoxic agent, was administered daily to male Sprague-Dawley (SD) rats for 28days. We then conducted untargeted analyses of endogenous serum and liver metabolites. Partial least squares discriminant analysis (PLS-DA) was performed on serum and liver samples to evaluate metabolites associated with TAA-induced perturbation. TAA administration resulted in altered levels of bile acids, acyl carnitines, and phospholipids in serum and in the liver. We subsequently demonstrated and confirmed the occurrence of compromised bile acid homeostasis. TAA treatment significantly increased serum levels of conjugated bile acids in a dose-dependent manner, which correlated well with toxicity. However, hepatic levels of these metabolites were not substantially changed. Gene expression profiling showed that the hepatic mRNA levels of Ntcp, Bsep, and Oatp1b2 were significantly suppressed, whereas those of basolateral Mrp3 and Mrp4 were increased. Decreased levels of Ntcp, Oatp1b2, and Ostα proteins in the liver were confirmed by western blot analysis. These results suggest that serum bile acids might be increased due to the inhibition of bile acid enterohepatic circulation rather than increased endogenous bile acid synthesis. Moreover, serum bile acids are a good indicator of TAA-induced hepatotoxicity.

Effects of vitamin D3 stimulation of thioredoxin-interacting protein in hepatocellular carcinoma

AIM

Thioredoxin-interacting protein (TXNIP) promotes oxidative stress by inactivating thioredoxin (TXN). This protein is involved in diverse disease processes, including insulin resistance, atherosclerosis and carcinogenesis. The aim of the present study was to measure the expression and function of TXNIP in in vitro models of liver disease, as well as in primary human hepatocellular carcinoma (HCC) tissue specimens. In addition, we wanted to determine the effects of vitamin D3-induced TXNIP stimulation in HCC-derived cell lines.

METHODS

TXNIP expression was measured by quantitative reverse transcription polymerase chain reaction and western blots. TXNIP expression was stimulated by vitamin D exposure and by transfection. Cell proliferation, apoptosis and reactive oxygen species were determined by standard assays.

RESULTS

TXNIP expression levels were low in HCC cell lines, and vitamin D3 stimulated TXNIP expression in vitro. In HCC cells transfected with a TXNIP expression vector or treated with exogenous vitamin D3, there was a reduction in cell proliferation and an increase in apoptosis. Cells expressing TXNIP were markedly susceptible to oxidative injury induced by cobalt chloride or bacterial lipopolysaccharide. TXNIP expression was reduced or absent in a majority of primary human HCC specimens relative to matching, non-cancerous liver tissue.

CONCLUSION

TXNIP expression is low or absent in human HCC specimens and HCC-derived cell lines. Vitamin D3 stimulates TXNIP expression, resulting in diminished proliferation and enhanced apoptosis. Liver cells expressing TXNIP are primed for oxidative injury. These findings suggest that stimulation of TXNIP expression, by factors such as vitamin D3, may attenuate carcinogenesis in patients with chronic liver disease.

iTRAQ-based proteomic analysis of combination therapy with taurine, epigallocatechin gallate, and genistein on carbon tetrachloride-induced liver fibrosis in rats

Combination therapy with taurine, epigallocatechin gallate, and genistein was effective in alleviating the progression of liver fibrosis in our previous study. To better understand the anti-fibrotic mechanisms of combination therapy, an iTRAQ-based proteomics approach was used to study the expression profiles of proteins in carbon tetrachloride-induced liver fibrosis rats following combination therapy. The anti-fibrotic effects of combination therapy were assessed directly by liver histology, and indirectly by measurement of serum biochemical markers and antioxidant enzymes. The results showed that combination therapy could significantly improve the liver function, as indicated by decreasing levels of alanine aminotransferase (ALT), aspartate transaminase (AST), transforming growth factor-β1 (TGF-β1), and collagen I, increasing levels of total antioxidative capacity (T-AOC), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px), and reducing the pathological tissue damage. A total of 89 differential expressed proteins in response to combination therapy were identified by iTRAQ, which were interacted with each other and involved in different biological processes and pathways. Four differentially expressed proteins (Tpi1, Txn1, Fgb, and F7) involved in antioxidant defense system, glycolysis pathway and coagulation cascade pathway were validated by enzyme-linked immunosorbent assay. Our work provided valuable insights into the molecular mechanism of combination therapy against liver fibrosis, and the identified targets may be useful for treatment of liver fibrosis in future.

Canine mesenchymal stem cells show antioxidant properties against thioacetamide-induced liver injury in vitro and in vivo

AIM

To overcome current limitations of therapy for liver diseases, cell-based therapies using mesenchymal stem cells (MSC) have been attempted through basic and clinical approaches. Oxidative stress is a crucial factor in hepatology, and reactive oxygen species (ROS) are well-established molecules responsible for its deleterious effects. The antioxidant properties of MSC were recently demonstrated, and therefore we examined the antioxidant activity of canine MSC (cMSC), their effects on isolated hepatocytes in vitro and their curative potential against thioacetamide (TAA)-induced liver injury in vivo.

METHODS

To evaluate the ability of cMSC to challenge oxidative stress, cell viability, cytotoxicity and ROS were measured in cultured cMSC treated with TAA. Also, cMSC were co-cultured with hepatocytes in the same injury condition, and the ROS level was measured exclusively in hepatocytes. Finally, to verify the curative potential of cMSC, 2.0 × 10(6) cells or phosphate-buffered saline were injected systemically in non-obese diabetic/severe combined immunodeficiency mice that received TAA injections twice a week for 13 weeks. We then evaluated histological parameters, serum injury markers and redox homeostasis.

RESULTS

cMSC overcame TAA-induced oxidative stress in vitro, as shown by increased viability and lower cytotoxicity and ROS levels. Moreover, hepatocytes co-cultured with cMSC also showed decreased cellular ROS. The in vivo study showed that mice treated with cMSC presented with an ameliorated histological pattern, suppressed fibrosis, lower serum injury marker levels and better oxidative parameters.

CONCLUSION

We concluded that cMSC injection reduce TAA-induced liver injury through antioxidant activities and hepatoprotective effects, showing a curative potential in liver diseases.

Pathogenic role of oxidative and nitrosative stress in primary biliary cirrhosis

Primary biliary cirrhosis is a multifactor autoimmune disease characterized by hepatic and systemic manifestations, with immune system dysregulation and abnormalities in the hepatic metabolism of bile salts, lipids, and nutrients, as well as destruction of membrane lipids and mitochondrial dysfunction. Both oxidative and nitrosative stress are associated with ongoing manifestations of the disease. In particular, abnormalities in nitric oxide metabolism and thiol oxidation already occur at early stages, thus leading to the hypothesis that these biochemical events play a pathogenic role in primary biliary cirrhosis. Moreover, the association of these metabolic abnormalities with the progression of the disease may indicate some biochemical parameters as early diagnostic markers of disease evolution, and may open up the potential for pharmacological intervention to inhibit intra- and extra-cellular stress events for resuming hepatocellular functions. The following paragraphs summarize the current knowledge by outlining molecular mechanisms of the disease related to these stress events.

Experimental liver fibrosis research: update on animal models, legal issues and translational aspects

Liver fibrosis is defined as excessive extracellular matrix deposition and is based on complex interactions between matrix-producing hepatic stellate cells and an abundance of liver-resident and infiltrating cells. Investigation of these processes requires in vitro and in vivo experimental work in animals. However, the use of animals in translational research will be increasingly challenged, at least in countries of the European Union, because of the adoption of new animal welfare rules in 2013. These rules will create an urgent need for optimized standard operating procedures regarding animal experimentation and improved international communication in the liver fibrosis community. This review gives an update on current animal models, techniques and underlying pathomechanisms with the aim of fostering a critical discussion of the limitations and potential of up-to-date animal experimentation. We discuss potential complications in experimental liver fibrosis and provide examples of how the findings of studies in which these models are used can be translated to human disease and therapy. In this review, we want to motivate the international community to design more standardized animal models which might help to address the legally requested replacement, refinement and reduction of animals in fibrosis research.

Metabolism and toxicity of thioacetamide and thioacetamide S-oxide in rat hepatocytes

The hepatotoxicity of thioacetamide (TA) has been known since 1948. In rats, single doses cause centrolobular necrosis accompanied by increases in plasma transaminases and bilirubin. To elicit these effects, TA requires oxidative bioactivation, leading first to its S-oxide (TASO) and then to its chemically reactive S,S-dioxide (TASO(2)), which ultimately modifies amine-lipids and proteins. To generate a suite of liver proteins adducted by TA metabolites for proteomic analysis and to reduce the need for both animals and labeled compounds, we treated isolated hepatocytes directly with TA. Surprisingly, TA was not toxic at concentrations up to 50 mM for 40 h. On the other hand, TASO was highly toxic to isolated hepatocytes as indicated by LDH release, cellular morphology, and vital staining with Hoechst 33342/propidium iodide. TASO toxicity was partially blocked by the CYP2E1 inhibitors diallyl sulfide and 4-methylpyrazole and was strongly inhibited by TA. Significantly, we found that hepatocytes produce TA from TASO relatively efficiently by back-reduction. The covalent binding of [(14)C]-TASO is inhibited by unlabeled TA, which acts as a "cold-trap" for [(14)C]-TA and prevents its reoxidation to [(14)C]-TASO. This in turn increases the net consumption of [(14)C]-TASO despite the fact that its oxidation to TASO(2) is inhibited. The potent inhibition of TASO oxidation by TA, coupled with the back-reduction of TASO and its futile redox cycling with TA, may help explain phenomena previously interpreted as "saturation toxicokinetics" in the in vivo metabolism and toxicity of TA and TASO. The improved understanding of the metabolism and covalent binding of TA and TASO facilitates the use of hepatocytes to prepare protein adducts for target protein identification.

Covalent modification of lipids and proteins in rat hepatocytes and in vitro by thioacetamide metabolites

Thioacetamide (TA) is a well-known hepatotoxin in rats. Acute doses cause centrilobular necrosis and hyperbilirubinemia while chronic administration leads to biliary hyperplasia and cholangiocarcinoma. Its acute toxicity requires its oxidation to a stable S-oxide (TASO) that is oxidized further to a highly reactive S,S-dioxide (TASO(2)). To explore possible parallels among the metabolism, covalent binding, and toxicity of TA and thiobenzamide (TB), we exposed freshly isolated rat hepatocytes to [(14)C]-TASO or [(13)C(2)D(3)]-TASO. TLC analysis of the cellular lipids showed a single major spot of radioactivity that mass spectral analysis showed to consist of N-acetimidoyl PE lipids having the same side chain composition as the PE fraction from untreated cells; no carbons or hydrogens from TASO were incorporated into the fatty acyl chains. Many cellular proteins contained N-acetyl- or N-acetimidoyl lysine residues in a 3:1 ratio (details to be reported separately). We also oxidized TASO with hydrogen peroxide in the presence of dipalmitoyl phosphatidylenthanolamine (DPPE) or lysozyme. Lysozyme was covalently modified at five of its six lysine side chains; only acetamide-type adducts were formed. DPPE in liposomes also gave only amide-type adducts, even when the reaction was carried out in tetrahydrofuran with only 10% water added. The exclusive formation of N-acetimidoyl PE in hepatocytes means that the concentration or activity of water must be extremely low in the region where TASO(2) is formed, whereas at least some of the TASO(2) can hydrolyze to acetylsulfinic acid before it reacts with cellular proteins. The requirement for two sequential oxidations to produce a reactive metabolite is unusual, but it is even more unusual that a reactive metabolite would react with water to form a new compound that retains a high degree of chemical reactivity toward biological nucleophiles. The possible contribution of lipid modification to the hepatotoxicity of TA/TASO remains to be determined.

Ipomoea aquatica extract shows protective action against thioacetamide-induced hepatotoxicity

In the Indian system of traditional medicine (Ayurveda) it is recommended to consume Ipomoea aquatica to mitigate disorders like jaundice. In this study, the protective effects of ethanol extract of I. aquatica against liver damage were evaluated in thioacetamide (TAA)-induced chronic hepatotoxicity in rats. There was no sign of toxicity in the acute toxicity study, in which Sprague-Dawley (SD) rats were orally fed with I. aquatica (250 and 500 mg/kg) for two months along with administration of TAA (i.p injection 200 mg/kg three times a week for two months). The results showed that the treatment of I. aquatica significantly lowered the TAA-induced serum levels of hepatic enzyme markers (ALP, ALT, AST, protein, albumin, bilirubin and prothrombin time). The hepatic content of activities and expressions SOD and CAT that were reduced by TAA were brought back to control levels by the plant extract supplement. Meanwhile, the rise in MDA level in the TAA receiving groups also were significantly reduced by I. aquatica treatment. Histopathology of hepatic tissues by H&E and Masson trichrome stains displayed that I. aquatica has reduced the incidence of liver lesions, including hepatic cells cloudy swelling, infiltration, hepatic necrosis, and fibrous connective tissue proliferation induced by TAA in rats. Therefore, the results of this study show that the protective effect of I. aquatica in TAA-induced liver damage might be contributed to its modulation on detoxification enzymes and its antioxidant and free radical scavenger effects. Moreover, it confirms a scientific basis for the traditional use of I. aquatica for the treatment of liver disorders.

Serum manganese superoxide dismutase and thioredoxin are potential prognostic markers for hepatitis C virus-related hepatocellular carcinoma

AIM: To evaluate the clinical significance of oxidative stress markers in patients with hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC).

METHODS: Sixty-four consecutive patients who were admitted to Kagoshima University Medical and Dental Hospital were enrolled in this retrospective study. All patients had chronic liver disease (CLD) due to infection with HCV. Thirty patients with HCV-related HCC, 34 with HCV-related CLD without HCC (non-HCC), and 20 healthy volunteers (HVs) were enrolled. Possible associations between serum manganese superoxide dismutase (MnSOD) and thioredoxin (TRX) levels and clinical parameters or patient prognosis were analyzed over a mean follow-up period of 31.7 mo.

RESULTS: The serum MnSOD levels were significantly higher in patients with HCV-related HCC than in patients without HCC (P = 0.03) or HVs (P < 0.001). Similarly, serum TRX levels were also significantly higher in patients with HCV-related HCC than in patients without HCC (P = 0.04) or HVs (P < 0.01). However, serum levels of MnSOD and TRX were not correlated in patients with HCC. Among patients with HCC, the overall survival rate (OSR) was lower in patients with MnSOD levels ≥ 110 ng/mL than in patients with levels < 110 ng/mL (P = 0.01), and the OSR tended to be lower in patients with TRX levels < 80 ng/mL (P = 0.05). In addition, patient prognosis with HCC was poorest with serum MnSOD levels ≥ 110 ng/mL and serum TRX levels < 80 ng/mL. Furthermore, a multivariate analysis using a Cox proportional hazard model and serum levels of five factors (MnSOD, prothrombin time, serum albumin, serum α-fetoprotein (AFP), and serum des-γ-carboxy prothrombin) revealed that MnSOD levels ≥ 110 ng/mL (risk ratio: 4.12, 95% confidential interval: 1.22-13.88, P = 0.02) and AFP levels ≥ 40 ng/mL (risk ratio: 6.75; 95% confidential interval: 1.70-26.85, P < 0.01) were independent risk factors associated with a poor patient prognosis.

CONCLUSION: Serum MnSOD and TRX levels are potential clinical biomarkers that predict patient prognosis in HCV-related HCC.

Synthesis of carbon-14, carbon-13 and deuterium labeled forms of thioacetamide and thioacetamide S-oxide

Thioacetamide (TA) is a model hepatotoxin that undergoes metabolic activation via two successive S-oxidations. The ultimate toxic metabolite thioacetamide S,S-dioxide, or its tautomer acetimidoyl sulfinic acid CH₃C(NH)SO₂H, then acylates lysine side chains on cellular proteins leading to cellular dysfunction or death. To identify individual target proteins, quantitate the extent of their modification and elucidate the structural details of their modification we required both radio-labeled and stable-labeled forms of TA and its intermediate metabolite thioacetamide S-oxide (TASO). The latter is stable when purified but can be difficult to isolate. Considering currently available isotopic precursors we devised and report here methods for the synthesis and isolation of TA and TASO labeled with C-14, C-13 and/or deuterium. The methods are straightforward, utilize readily available precursors and are amenable to small scale.

Depletion of cytosolic or mitochondrial thioredoxin increases CYP2E1-induced oxidative stress via an ASK-1-JNK1 pathway in HepG2 cells

Thioredoxin is an important reducing molecule in biological systems. Increasing CYP2E1 activity induces oxidative stress and cell toxicity. However, whether thioredoxin protects cells against CYP2E1-induced oxidative stress and toxicity is unknown. SiRNA were used to knockdown either cytosolic (TRX-1) or mitochondrial thioredoxin (TRX-2) in HepG2 cells expressing CYP2E1 (E47 cells) or without expressing CYP2E1 (C34 cells). Cell viability decreased 40-60% in E47 but not C34 cells with 80-90% knockdown of either TRX-1 or TRX-2. Depletion of either thioredoxin also potentiated the toxicity produced either by a glutathione synthesis inhibitor or by TNFα in E47 cells. Generation of reactive oxygen species and 4-HNE protein adducts increased in E47 but not C34 cells with either thioredoxin knockdown. GSH was decreased and adding GSH completely blocked E47 cell death induced by either thioredoxin knockdown. Lowering TRX-1 or TRX-2 in E47 cells caused an early activation of ASK-1, followed by phosphorylation of JNK1 after 48 h of siRNA treatment. A JNK inhibitor caused a partial recovery of E47 cell viability after thioredoxin knockdown. In conclusion, knockdown of TRX-1 or TRX-2 sensitizes cells to CYP2E1-induced oxidant stress partially via ASK-1 and JNK1 signaling pathways. Both TRX-1 and TRX-2 are important for defense against CYP2E1-induced oxidative stress.

Production of biologically active human thioredoxin 1 protein in lettuce chloroplasts

The production of human therapeutic proteins in plants provides opportunities for low-cost production, and minimizes the risk of contamination from potential human pathogens. Chloroplast genetic engineering is a particularly promising strategy, because plant chloroplasts can produce large amounts of foreign target proteins. Oxidative stress is a key factor in various human diseases. Human thioredoxin 1 (hTrx1) is a stress-induced protein that functions as an antioxidant against oxidative stress, and overexpression of hTrx1 has been shown to suppress various diseases in mice. Therefore, hTrx1 is a prospective candidate as a new human therapeutic protein. We created transplastomic lettuce expressing hTrx1 under the control of the psbA promoter. Transplastomic plants grew normally and were fertile. The hTrx1 protein accumulated to approximately 1% of total soluble protein in mature leaves. The hTrx1 protein purified from lettuce leaves was functionally active, and reduced insulin disulfides. The purified protein protected mouse insulinoma line 6 cells from damage by hydrogen peroxide, as reported previously for a recombinant hTrx1 expressed in Escherichia coli. This is the first report of expression of the biologically active hTrx1 protein in plant chloroplasts. This research opens up possibilities for plant-based production of hTrx1. Considering that this expression host is an edible crop plant, this transplastomic lettuce may be suitable for oral delivery of hTrx1.

Thioredoxin, thioredoxin-interacting protein and digestive diseases

The thioredoxin system is an antioxidative and redox-regulating system that consists of several small proteins, including thioredoxin (TRX), reduced coenzyme II (NADPH) and thioredoxin reductase (TRX-R). It can function to regulate oxidation-reduction state of cells, resist oxidative stress, activate transcription factors NF-κB and AP-1 to promote the growth and proliferation of cells, and interact with ASK-1 to inhibit apoptosis. Thioredoxin-interacting protein (TXNIP) is a member of the thioredoxin-binding protein family and plays a role in mediating oxidative stress, resisting cell proliferation and inducing apoptosis, acting as a negative regulator of the TRX system. Since oxidative stress and apoptosis are often involved in the pathogenesis of digestive diseases, TRX and TXNIP may play roles in the pathogenesis of digestive diseases. This paper gives an overview of the structure and functions of TRX and TXNIP and reviews the recent advances in understanding the relationship between the two proteins and digestive diseases.

Thioredoxin glycation: A novel posttranslational modification that inhibits its antioxidant and organ protective actions

Thioredoxin (Trx) is an antioxidant and antiapoptotic molecule, and its activity is regulated by posttranslational modifications. Trx-1 has recently been reported to exert potent protective action against endotoxic liver injury. However, whether Trx-1 activity is affected by endotoxin has never been previously investigated. The aim of the present study was to determine endotoxic regulation of Trx-1, and the potential mechanism involved. In vitro coincubation of Trx-1 with lipopolysaccharide (LPS) inhibited Trx-1 activity in a dose- and time-dependent fashion. The core (polysaccharide containing) region of LPS had a greater inhibitory effect on Trx-1 activity than its Lipid A fragment, suggesting the involvement of sugar groups. Periodic acid-Schiff staining and fructosamine assay demonstrated that Trx-1 was rapidly glycated by LPS. Aminoguanidine, a competitive glycation-inhibitor, completely blocked the inhibitory effect of LPS on Trx-1. Moreover, Trx-1 activity was also significantly inhibited by in vitro ribose incubation. Finally, in vivo administration of Trx-1, but not glycated Trx-1, reduced LPS-induced hepatic injury. Taken together, these results demonstrated for the first time that Trx-1 is susceptible to glycative inactivation. This novel posttranslational Trx-1 modification contributes to LPS cytotoxicity, suggesting that blockading protein glycation might be a new therapeutic strategy against endotoxic organ injury.

Thiol redox systems and protein kinases in hepatic stellate cell regulatory processes

Hepatic stellate cells (HSC) are the major producers of collagen in the liver and their conversion from resting cells to a proliferating, contractile and fibrogenic phenotype ('activation') is a critical step, leading to liver fibrosis characterized by deposition of excessive extracellular matrix. Cytokines, growth factors, reactive oxygen and nitrogen species (ROS/RNS), lipid peroxides and their products deriving from hepatocytes, Kupffer cells and other cells converge on HSC and influence their activation. This review focuses on glutathione and thioredoxin pathways, with particular emphasis on their role in HSC. These two systems have been shown to act in the metabolism of hydrogen peroxide, control of thiol redox balance and regulation of signalling pathways. Particular attention is paid to mitochondria and NADPH oxidase. Detailed knowledge of specific signalling, redox conditions and apoptotic processes will be of help in devising proper pharmacological treatments for liver fibrosis.

Dynamic expression of hepatic thioredoxin mRNA in rats with non-alcoholic fatty liver disease

OBJECTIVE

To investigate the expression and significance of thioredoxin messenger ribonucleic acid (mRNA) in the development of non-alcoholic fatty liver disease (NAFLD) induced by a high fat diet.

METHODS

A total of 48 male Wistar rats were divided into a normal control group and a model group, which were both divided into three subgroups (at weeks 9, 13 and 18, respectively). The levels of serum tumor necrosis factor-alpha (TNF-alpha), free fatty acid (FFA), total cholesterol (TC) and triglyeride (TG), changes in the serum and hepatic tissue superoxide dismutase (SOD), reduced glutathione hormone (GSH) and malondialdehyde (MDA) were measured. The expression of thioredoxin mRNA in rat livers were detected with reverse transcriptase polymerase chain reaction (RT-PCR). Meanwhile, the pathological changes of liver tissue were observed by hematoxylin-eosin stain.

RESULTS

Simple fatty liver was observed in model group at week 9. From weeks 13 to 18, liver histopathology showed steatohepatitis. Compared with corresponding normal groups, in the model groups the levels of TNF-alpha, FFA, TC, TG in serum, and MDA in serum and liver increased significantly, while the vitality of SOD and GSH content in serum and liver decreased remarkably. Meanwhile, in the model group, the expression of hepatic thioredoxin mRNA was significantly decreased at week 9 compared with the normal group (P < 0.01), then increased gradually, but were lower than the corresponding normal groups at all times (P < 0.01).

CONCLUSION

The expression of thioredoxin mRNA is significantly lower in the liver of rats with NAFLD and might reach the lowest point after developing simple fatty liver. Meanwhile the downregulation of thioredoxin mRNA may cause the inflammatory injury initially in NAFLD.

Thioredoxin binding protein 2 modulates natural killer T cell-dependent innate immunity in the liver: possible link to lipid metabolism

Thioredoxin binding protein 2 (TBP2) plays a regulatory role in lipid metabolism and immune regulation. We previously reported the effect of TBP2 loss-of-function on lipid metabolism using TBP2 knockout (TBP2KO) mice. In this study, we employed TBP2 transgenic (TBP2TG) mice to analyze the in vivo effect of TBP2 gain-of-function. We revealed a decrease in the percentage of hepatic natural killer T (NKT) cells in TBP2KO mice and an increase in the percentage of hepatic NKT cells in TBP2TG mice. The TBP2KO mice were resistant to concanavalin A (ConA)-induced hepatitis, but they were highly susceptible to other types of hepatitis. TBP2 modulates lipid metabolism as well as NKT cell activity. Moreover, TBP2 expression was increased significantly in klotho-deficient mice, which exhibit a syndrome resembling aging human phenotypes. TBP2 may play multiple roles in lipid metabolism, innate immunity, and aging.

Thioredoxin suppresses the contact hypersensitivity response by inhibiting leukocyte recruitment during the elicitation phase

Thioredoxin, a redox-regulating protein that scavenges reactive oxygen species, appears to show an excellent antiinflammatory effect in treating animal models of various human inflammatory diseases. The aim of this study was to clarify whether thioredoxin is useful for treating inflammatory skin diseases, such as contact dermatitis, caused by epicutaneous exposure to environmental and occupational antigens. The allergic contact hypersensitivity response was suppressed in thioredoxin-transgenic mice. This suppressive effect of thioredoxin appeared to be via the inhibition of the efferent limb of contact hypersensitivity because administration of recombinant thioredoxin suppressed the inflammatory response in the elicitation phase but not in the induction phase. Adoptive-transfer studies revealed that the host environment, but not donor leukocytes, is critical in this suppressive effect. In thioredoxin-transgenic mice, the infiltration of neutrophils in the elicitation site was diminished, whereas the migratory function of cutaneous dendritic cells and hapten-specific cell proliferation were not disturbed. Thioredoxin-transgenic mice had also an attenuated inflammatory response to croton oil. These findings suggest that thioredoxin prevents skin inflammatory responses and could be a suitable candidate for the treatment of contact dermatitis.

Thioredoxin 1 delivery as new therapeutics

Thioredoxin 1 (Trx 1) is a redox-active small protein ubiquitously present in human body. It is one of the defensive proteins induced in response to various stress conditions. In addition to its anti-oxidative effect by dithiol-disulfide exchange in its active site, Trx 1 has anti-apoptotic and anti-inflammatory effects. Trx 1 overexpression has been shown to be effective in a wide variety of animal models for oxidative and inflammatory disorders. An administration of recombinant Trx 1 protein is also effective in animal models especially for severe acute lung diseases where Trx 1 is likely to act with its anti-inflammatory properties. Trx 1 in circulation shows anti-chemotactic effects for neutrophils and inhibitory effects against macrophage migration inhibitory factor (MIF). Neovascularization is also suppressed by Trx 1 via inhibition of the complement activation. Here we discuss precise mechanisms of Trx 1 and potential therapeutic approach of this molecule.

Thioredoxin and thioredoxin binding protein 2 in the liver

Thioredoxin (TRX) is a 12-kDa protein with redox-active dithiol in the active site -Cys-Gly-Pro-Cys- and constitutes a major thiol reducing system. TRX protects cells from stress-induced damage through antioxidative, antiapoptotic, and anti-inflammatory effect. In animal models, thioacetamide (TAA)-induced acute hepatitis and TAA-induced liver fibrosis was attenuated in TRX transgenic (TRXTG) mice. Plasma level of TRX is a good marker for hepatitis and nonalcoholic steatohepatitis (NASH) in human patients. Recently, we identified TRX binding protein 2 (TBP2) in a yeast two-hybrid screening. TBP2 regulates both the expression and reducing activity of TRX as well as cell growth. TBP2 knockout (TBP2KO) mice showed disorder in lipid metabolism. TBP2 plays a multiple role on cell growth and lipid and glucose metabolism. Thus, TRX and TBP2 play important roles in the pathophysiology of liver diseases, including NASH, indicating that ratio of TRX and TBP2 expression could be a novel marker of liver diseases like NASH.

Redox mechanisms in hepatic chronic wound healing and fibrogenesis

Reactive oxygen species (ROS) generated within cells or, more generally, in a tissue environment, may easily turn into a source of cell and tissue injury. Aerobic organisms have developed evolutionarily conserved mechanisms and strategies to carefully control the generation of ROS and other oxidative stress-related radical or non-radical reactive intermediates (that is, to maintain redox homeostasis), as well as to 'make use' of these molecules under physiological conditions as tools to modulate signal transduction, gene expression and cellular functional responses (that is, redox signalling). However, a derangement in redox homeostasis, resulting in sustained levels of oxidative stress and related mediators, can play a significant role in the pathogenesis of major human diseases characterized by chronic inflammation, chronic activation of wound healing and tissue fibrogenesis. This review has been designed to first offer a critical introduction to current knowledge in the field of redox research in order to introduce readers to the complexity of redox signalling and redox homeostasis. This will include ready-to-use key information and concepts on ROS, free radicals and oxidative stress-related reactive intermediates and reactions, sources of ROS in mammalian cells and tissues, antioxidant defences, redox sensors and, more generally, the major principles of redox signalling and redox-dependent transcriptional regulation of mammalian cells. This information will serve as a basis of knowledge to introduce the role of ROS and other oxidative stress-related intermediates in contributing to essential events, such as the induction of cell death, the perpetuation of chronic inflammatory responses, fibrogenesis and much more, with a major focus on hepatic chronic wound healing and liver fibrogenesis.