Oxidative and nitrosative stress and fibrogenic response

Association between frailty and hepatic fibrosis in NAFLD among middle-aged and older adults: results from NHANES 2017-2020

Background

Although previous studies found that frailty is prevalent in NAFLD patients with advanced liver fibrosis and cirrhosis, studies examining the relationship are spare.

Aim

Our study aspires to investigate the potential correlation between the Frailty Index (FI) and hepatic fibrosis among middle-aged and older adults with NAFLD.

Methods

Data from the 2017-2020.03 National Health and Nutrition Examination Survey (NHANES) were utilized for this study, with a final of 2,383 participants aged 50 years and older included. The quantification of frailty was executed employing a 49-item frailty index. The recognition of hepatic steatosis and fibrosis was accomplished through the utilization of the controlling attenuation parameter (CAP) and transient elastography (TE). The relationship between the FI and hepatic fibrosis were investigated employing univariable and multivariable-adjusted logistic regression analyses. A subgroup analysis was conducted, dividing the subjects based on gender, Body Mass Index (BMI), and the presence of hyperlipidemia.

Results

The findings demonstrated a positive correlation between the FI and significant hepatic fibrosis in NAFLD, even after using multivariate logistic regression models adjusting for potential confounding factors (OR = 1.022, 95% CI, 1.004-1.041) and in tertiles (Q3vs Q1: OR = 2.004, 95% CI, 1.162-3.455). In the subgroup analysis, the correlation was more statistically significant in male (OR = 1.046, 95% CI, 1.022-1.071), under/normal weight (OR = 1.077, 95% CI, 1.009-1.150), overweight (OR = 1.040, 95% CI, 1.010-1.071), and subjects without hyperlipidemia (OR = 1.054, 95% CI, 1.012-1.097). The area under the Receiver Operating Characteristic (ROC) curve for the FI in assessing the existence of substantial fibrosis in NAFLD was 0.612 (95% CI, 0.596-0.628).

Conclusion

This study demonstrated a positive correlation between significant hepatic fibrosis and frailty, particularly among males aged 50 years and older, who were non-obese and did not have hyperlipidemia with NAFLD. Additional studies are required to further validate these findings.

Cold plasma treatment of tannic acid as a green technology for the fabrication of advanced cross-linkers for bioactive collagen/gelatin hydrogels

Tannic acid (TA) is a natural compound studied as the cross-linker for biopolymers due to its ability to form hydrogen bonds. There are different methods to improve its reactivity and effectiveness to be used as a modifier for biopolymeric materials. This work employed plasma to modify tannic acid TA, which was then used as a cross-linker for fabricating collagen/gelatin scaffolds. Plasma treatment did not cause any significant changes in the structure of TA, and the resulting oxidized TA showed a higher antioxidant activity than that without treatment. Adding TA to collagen/gelatin scaffolds improved their mechanical properties and stability. Moreover, the obtained plasma-treated TA-containing scaffolds showed antibacterial properties and were non-hemolytic, with improved cytocompatibility towards human dermal fibroblasts. These results suggest the suitability of plasma treatment as a green technology for the modification of TA towards the development of advanced TA-crosslinked hydrogels for various biomedical applications.

Protective role of curcumin in disease progression from non-alcoholic fatty liver disease to hepatocellular carcinoma: a meta-analysis

Background: Pathological progression from non-alcoholic fatty liver disease (NAFLD) to liver fibrosis (LF) to hepatocellular carcinoma (HCC) is a common dynamic state in many patients. Curcumin, a dietary supplement derived from the turmeric family, is expected to specifically inhibit the development of this progression. However, there is a lack of convincing evidence. Methods: The studies published until June 2023 were searched in PubMed, Web of Science, Embase, and the Cochrane Library databases. The SYstematic Review Center for Laboratory animal Experimentation (SYRCLE) approach was used to evaluate the certainty of evidence. StataSE (version 15.1) and Origin 2021 software programs were used to analyze the critical indicators. Results: Fifty-two studies involving 792 animals were included, and three disease models were reported. Curcumin demonstrates a significant improvement in key indicators across the stages of NAFLD, liver fibrosis, and HCC. We conducted a detailed analysis of common inflammatory markers IL-1β, IL-6, and TNF-α, which traverse the entire disease process. The research results reveal that curcumin effectively hinders disease progression at each stage by suppressing inflammation. Curcumin exerted hepatoprotective effects in the dose range from 100 to 400 mg/kg and treatment duration from 4 to 10 weeks. The mechanistic analysis reveals that curcumin primarily exerts its hepatoprotective effects by modulating multiple signaling pathways, including TLR4/NF-κB, Keap1/Nrf2, Bax/Bcl-2/Caspase 3, and TGF-β/Smad3. Conclusion: In summary, curcumin has shown promising therapeutic effects during the overall progression of NAFLD-LF-HCC. It inhibited the pathological progression by synergistic mechanisms related to multiple pathways, including anti-inflammatory, antioxidant, and apoptosis regulation.

Potential Therapeutic Implication of Herbal Medicine in Mitochondria-Mediated Oxidative Stress-Related Liver Diseases

Mitochondria are double-membrane organelles that play a role in ATP synthesis, calcium homeostasis, oxidation-reduction status, apoptosis, and inflammation. Several human disorders have been linked to mitochondrial dysfunction. It has been found that traditional therapeutic herbs are effective on alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) which are leading causes of liver cirrhosis and hepatocellular carcinoma. The generation of reactive oxygen species (ROS) in response to oxidative stress is caused by mitochondrial dysfunction and is considered critical for treatment. The role of oxidative stress, lipid toxicity, and inflammation in NAFLD are well known. NAFLD is a chronic liver disease that commonly progresses to cirrhosis and chronic liver disease, and people with obesity, insulin resistance, diabetes, hyperlipidemia, and hypertension are at a higher risk of developing NAFLD. NAFLD is associated with a number of pathological factors, including insulin resistance, lipid metabolic dysfunction, oxidative stress, inflammation, apoptosis, and fibrosis. As a result, the improvement in steatosis and inflammation is enough to entice researchers to look into liver disease treatment. However, antioxidant treatment has not been very effective for liver disease. Additionally, it has been suggested that the beneficial effects of herbal medicines on immunity and inflammation are governed by various mechanisms for lipid metabolism and inflammation control. This review provided a summary of research on herbal medicines for the therapeutic implementation of mitochondria-mediated ROS production in liver disease as well as clinical applications through herbal medicine. In addition, the pathophysiology of common liver disorders such as ALD and NAFLD would be investigated in the role that mitochondria play in the process to open new therapeutic avenues in the management of patients with liver disease.

Alcohol and HIV-Derived Hepatocyte Apoptotic Bodies Induce Hepatic Stellate Cell Activation

Recently, we found that both HIV and acetaldehyde, an alcohol metabolite, induce hepatocyte apoptosis, resulting in the release of large extracellular vesicles called apoptotic bodies (ABs). The engulfment of these hepatocyte ABs by hepatic stellate cells (HSC) leads to their profibrotic activation. This study aims to establish the mechanisms of HSC activation after engulfment of ABs from acetaldehyde and HIV-exposed hepatocytes (ABAGS+HIV). In vitro experiments were performed on Huh7.5-CYP (RLW) cells to generate hepatocyte ABs and LX2 cells were used as HSC. To generate ABs, RLW cells were pretreated for 24 h with acetaldehyde, then exposed overnight to HIV1ADA and to acetaldehyde for 96 h. Thereafter, ABs were isolated from cell suspension by a differential centrifugation method and incubated with LX2 cells (3:1 ratio) for profibrotic genes and protein analyses. We found that HSC internalized ABs via the tyrosine kinase receptor, Axl. While the HIV gag RNA/HIV proteins accumulated in ABs elicited no productive infection in LX2 and immune cells, they triggered ROS and IL6 generation, which, in turn, activated profibrotic genes via the JNK-ERK1/2 and JAK-STAT3 pathways. Similarly, ongoing profibrotic activation was observed in immunodeficient NSG mice fed ethanol and injected with HIV-derived RLW ABs. We conclude that HSC activation by hepatocyte ABAGS+HIV engulfment is mediated by ROS-dependent JNK-ERK1/2 and IL6 triggering of JAK-STAT3 pathways. This can partially explain the mechanisms of liver fibrosis development frequently observed among alcohol abusing PLWH.

Non-alcoholic Fatty Liver Disease and Liver Fibrosis during Aging

Non-alcoholic fatty liver disease (NAFLD) and its progressive form non-alcoholic steatohepatitis (NASH) have emerged as the leading causes of chronic liver disease-related mortality. The prevalence of NAFLD/NASH is expected to increase given the epidemics of obesity and type 2 diabetes mellitus. Older patients are disproportionally affected by NASH and related complications such as progressive fibrosis, cirrhosis and hepatocellular carcinoma; however, they are often ineligible for liver transplantation due to their frailty and comorbidities, and effective medical treatments are still lacking. In this review we focused on pathways that are key to the aging process in the liver and perpetuate NAFLD/NASH, leading to fibrosis. In addition, we highlighted recent findings and cross-talks of normal and/or senescent liver cells, dysregulated nutrient sensing, proteostasis and mitochondrial dysfunction in the framework of changing metabolic milieu. Better understanding these pathways during preclinical and clinical studies will be essential to design novel and specific therapeutic strategies to treat NASH in the elderly.

Association of serum vitamin C with liver fibrosis in adults with nonalcoholic fatty liver disease

OBJECTIVE

This study aimed to investigate the association between serum vitamin C and liver fibrosis in patients with NAFLD in the US adults.

METHODS

We conducted a cross-sectional analysis of data from the 2017 to 2018 cycle of National Health and Nutrition Examination Survey (NHANES). Serum vitamin C and transient elastography (TE)-accessed liver stiffness was taken as independent and dependent variables, respectively. Liver steatosis and fibrosis were detected by controlling attenuation parameter (CAP) and TE. NAFLD was defined by a CAP score of ≥248 dB/m without any indication of other causes of chronic liver disease. The median liver stiffness of ≥8.2 kPa was used to identify significant fibrosis (≥F2) among NAFLD patients. We calculated the adjusted odds ratio (OR) and 95% confidential intervals (CIs) for associations with significant NAFLD fibrosis using multivariable logistic regression models.

RESULTS

Overall, 1926 individuals with NAFLD were included in the analysis and 267 subjects met the definition of significant fibrosis. Serum vitamin C was associated with lower odds of liver fibrosis in NAFLD after adjusting for potential confounders (OR = 0.60, 95% CI, 0.43-0.84), while in the subgroup analysis stratified by gender and body mass index (BMI), this association showed a difference after adjusting for confounders (males: OR = 0.43, 95% CI, 0.26-0.71; females: OR = 0.78, 95% CI, 0.49-1.24). There were no significant associations of serum vitamin C with liver fibrosis in NAFLD with underweight or normal (OR = 1.34, 95% CI, 0.19-9.34).

CONCLUSIONS

This cross-sectional study indicated an association of serum vitamin C with significant fibrosis in men and overweight or obese patients with NAFLD.

Heparanase-1 is upregulated by hepatitis C virus and favors its replication

BACKGROUND & AIMS

Over time, chronic HCV infection can lead to hepatocellular carcinoma (HCC), a process that involves changes to the liver extracellular matrix (ECM). However, the exact mechanisms by which HCV induces HCC remain unclear. Therefore, we sought to investigate the impact of HCV on the liver ECM, with a focus on heparanase-1 (HPSE).

METHODS

HPSE expression was assessed by quantitative reverse-transcription PCR, immunoblotting and immunofluorescence in liver biopsies infected or not with HCV, and in 10-day-infected hepatoma Huh7.5 cells. Cell lines deficient for or overexpressing HPSE were established to study its role during infection.

RESULTS

HCV propagation led to significant HPSE induction, in vivo and in vitro. HPSE enhanced infection when exogenously expressed or supplemented as a recombinant protein. Conversely, when HPSE expression was downregulated or its activity blocked, HCV infection dropped, suggesting a role of HPSE in the HCV life cycle. We further studied the underlying mechanisms of such observations and found that HPSE favored HCV release by enhancing CD63 synthesis and exosome secretion, but not by stimulating HCV entry or genome replication. We also showed that virus-induced oxidative stress was involved in HPSE induction, most likely through NF-κB activation.

CONCLUSIONS

We report for the first time that HCV infection is favored by HPSE, and upregulates HPSE expression and secretion, which may result in pathogenic alterations of the ECM.

LAY SUMMARY

Chronic hepatitis C virus (HCV) infection can lead to hepatocellular carcinoma development in a process that involves derangement of the extracellular matrix (ECM). Herein, we show that heparanase-1, a protein involved in ECM degradation and remodeling, favors HCV infection and is upregulated by HCV infection; this upregulation may result in pathogenic alterations of the ECM.

Metabolic reprogramming of tumor-associated macrophages by collagen turnover promotes fibrosis in pancreatic cancer

A hallmark of pancreatic tumors is their highly desmoplastic stroma composed of fibroblasts, immune cells, and a dense network of collagen fibers. Tumor-associated macrophages are one of the most abundant immune cell populations in the pancreatic tumor stroma. Their protumorigenic function has been attributed predominantly to their capacity to promote immune evasion and metastasis. Tumor-assoc iated macrophages are also well known for their role in the remodeling of the stroma via collagen production and degradation, with the latter being mediated by mannose receptor (MRC1)-dependent endocytosis of collagen. Here we show that MRC1-mediated collagen internalization and subsequent lysosomal degradation by macrophages harboring a tumor-associated phenotype are accompanied by the accumulation of collagen-derived intracellular free amino acids and increased arginine biosynthesis. The resulting increase in intracellular arginine levels leads to the up-regulation of inducible nitric oxide synthase and the production of reactive nitrogen species. Furthermore, reactive nitrogen species derived from internalized and degraded collagen promotes a profibrotic phenotype in pancreatic stellate cells resulting in enhanced intratumoral collagen deposition. Overall, our findings identify a role for extracellular matrix remodeling in the functional modulation of tumor-associated macrophages via metabolic rewiring.

Guizhi Fuling pill attenuates liver fibrosis in vitro and in vivo via inhibiting TGF-β1/Smad2/3 and activating IFN-γ/Smad7 signaling pathways

Liver fibrosis resulting from chronic liver injuries (CLI) is a common health problem globally. Guizhi Fuling pill (GZFL), a modern preparation from traditional Chinese medicine, exhibited anti-dysmenorrhea, anti-inflammatory, and immune-regulative effects. However, the effect of GZFL on liver fibrosis remains unknown. In this research, LX-2 cells were stimulated with acetaldehyde for mimicking liver fibrosis progression in vitro. In addition, carbon tetrachloride (CCl₄)-induced mouse model of liver fibrosis was established as well. The data revealed GZFL obviously suppressed the proliferation and triggered the apoptosis of acetaldehyde-stimulated LX-2 cells. In addition, GZFL prevented acetaldehyde-induced activation of LX-2 cells via downregulation of TGF-β1, p-Smad2, p-Smad3, CUGBP1, and upregulation of p-STAT1 and Smad7. Meanwhile, GZFL significantly alleviated CCl₄‑induced liver fibrosis, as evidenced by the decrease of ALT and AST levels. Moreover, GZFL downregulated the expressions of TGF-β1, p-Smad2, p-Smad3, and CUGBP1 in CCl₄-treated mice. Furthermore, GZFL remarkably elevated the levels of IFN-γ, p-STAT1, and Smad7 in CCl₄-treated mice. To sum up, GZFL was able to inhibit liver fibrosis in vitro and in vivo through suppressing TGF-β1/Smad2/3-CUGBP1 signaling and activating IFN-γ/STAT1/Smad7 signaling. Thus, GZFL might have a potential to act as a therapeutic agent for anti-fibrotic therapy.

Anti-fibrotic activity of natural products, herbal extracts and nutritional components for prevention of liver fibrosis: review

Liver fibrosis is a grave problem worldwide, and the development of this condition is the first step towards cirrhosis. In fact, when lesions of different aetiologies chronically affect the liver, it triggers fibrogenesis, the resulting damage and the progression of fibrosis cause serious clinical influences including severe complications, expensive treatments, and death in end-stage liver disease. Although impressive progress has been reported in understanding the pathogenesis of liver fibrosis, no effective agent has been developed to prevent or reverse the fibrotic process directly. This article reviews natural products, herbal medicines and nutritional components that exhibited an anti-fibrotic activity through different mechanisms of action, including suppressing of cytokine production, inhibition of hepatic stellate cells "HSCs" propagation, modulation of the molecular mechanisms leading to hepatic fibrosis, free radical scavenging and anti-inflammatory properties.

Impact of Dietary Fat on the Progression of Liver Fibrosis: Lessons from Animal and Cell Studies

Previous studies have revealed that a high-fat diet is one of the key contributors to the progression of liver fibrosis, and increasing studies are devoted to analyzing the different influences of diverse fat sources on the progression of non-alcoholic steatohepatitis. When we treated three types of isocaloric diets that are rich in cholesterol, saturated fatty acid (SFA) and trans fatty acid (TFA) with hepatitis C virus core gene transgenic mice that spontaneously developed hepatic steatosis without apparent fibrosis, TFA and cholesterol-rich diet, but not SFA-rich diet, displayed distinct hepatic fibrosis. This review summarizes the recent advances in animal and cell studies regarding the effects of these three types of fat on liver fibrogenesis.

The Power of Plasticity-Metabolic Regulation of Hepatic Stellate Cells

Hepatic stellate cells (HSCs) are resident non-parenchymal liver pericytes whose plasticity enables them to regulate a remarkable range of physiologic and pathologic responses. To support their functions in health and disease, HSCs engage pathways regulating carbohydrate, mitochondrial, lipid, and retinoid homeostasis. In chronic liver injury, HSCs drive hepatic fibrosis and are implicated in inflammation and cancer. To do so, the cells activate, or transdifferentiate, from a quiescent state into proliferative, motile myofibroblasts that secrete extracellular matrix, which demands rapid adaptation to meet a heightened energy need. Adaptations include reprogramming of central carbon metabolism, enhanced mitochondrial number and activity, endoplasmic reticulum stress, and liberation of free fatty acids through autophagy-dependent hydrolysis of retinyl esters that are stored in cytoplasmic droplets. As an archetype for pericytes in other tissues, recognition of the HSC's metabolic drivers and vulnerabilities offer the potential to target these pathways therapeutically to enhance parenchymal growth and modulate repair.

Elucidating Potential Profibrotic Mechanisms of Emerging Biomarkers for Early Prognosis of Hepatic Fibrosis

Hepatic fibrosis has been associated with a series of pathophysiological processes causing excessive accumulation of extracellular matrix proteins. Several cellular processes and molecular mechanisms have been implicated in the diseased liver that augments fibrogenesis, fibrogenic cytokines and associated liver complications. Liver biopsy remains an essential diagnostic tool for histological evaluation of hepatic fibrosis to establish a prognosis. In addition to being invasive, this methodology presents with several limitations including poor cost-effectiveness, prolonged hospitalizations, and risks of peritoneal bleeding, while the clinical use of this method does not reveal underlying pathogenic mechanisms. Several alternate noninvasive diagnostic strategies have been developed, to determine the extent of hepatic fibrosis, including the use of direct and indirect biomarkers. Immediate diagnosis of hepatic fibrosis by noninvasive means would be more palatable than a biopsy and could assist clinicians in taking early interventions timely, avoiding fatal complications, and improving prognosis. Therefore, we sought to review some common biomarkers of liver fibrosis along with some emerging candidates, including the oxidative stress-mediated biomarkers, epigenetic and genetic markers, exosomes, and miRNAs that needs further evaluation and would have better sensitivity and specificity. We also aim to elucidate the potential role of cardiotonic steroids (CTS) and evaluate the pro-inflammatory and profibrotic effects of CTS in exacerbating hepatic fibrosis. By understanding the underlying pathogenic processes, the efficacy of these biomarkers could allow for early diagnosis and treatment of hepatic fibrosis in chronic liver diseases, once validated.

Inhibitory Effect of Sestrin 2 on Hepatic Stellate Cell Activation and Liver Fibrosis

Aims: Hepatic fibrosis results from chronic liver injury and inflammatory responses. Sestrin 2 (Sesn2), an evolutionarily conserved antioxidant enzyme, reduces the severities of acute hepatitis and metabolic liver diseases. However, the role of Sesn2 in the pathogenesis of liver fibrosis remains obscure. Here, we used cultured hepatic stellate cells (HSCs) and chronic carbon tetrachloride (CCl₄) and bile duct ligation (BDL) murine models to investigate the effects of Sesn2 on fibrogenesis. Results: Sesn2 protein and mRNA levels were upregulated in activated primary HSCs, and by increasing transcription, transforming growth factor-β (TGF-β) also increased Sesn2 expression in HSCs. Furthermore, Smad activation was primarily initiated by TGF-β signaling, and Smad3 activation increased Sesn2 luciferase activity. In silico analysis of the 5' upstream region of the Sesn2 gene revealed a putative Smad-binding element (SBE), and its deletion demonstrated that the SBE between -964 and -956 bp within human Sesn2 promoter was critically required for TGF-β-mediated response. Moreover, ectopic expression of Sesn2 reduced gene expressions associated with HSC activation, and this was accompanied by marked decreases in SBE luciferase activity and Smad phosphorylation. Infection of recombinant adenovirus Sesn2 reduced hepatic injury severity, as evidenced by reductions in CCl₄- or BDL-induced alanine aminotransferase and aspartate aminotransferase, and inhibited collagen accumulation. Furthermore, HSC-specific lentiviral delivery of Sesn2 prevented CCl₄-induced liver fibrosis. Finally, Sesn2 expression was downregulated in the livers of patients with liver cirrhosis and in mouse models of hepatic fibrosis. Innovation and Conclusion: Our findings suggest that Sesn2 has the potential to inhibit HSC activation and hepatic fibrosis.

Fibrogenesis in Chronic DSS Colitis is Not Influenced by Neutralisation of Regulatory T Cells, of Major T Helper Cytokines or Absence of IL-13

Mechanisms underlying fibrogenesis in chronic colitis are largely unknown. There is an urgent need for clinical markers and identification of targets to prevent, treat and limit intestinal fibrosis. This study investigated the contribution of major T cell cytokines and T regulatory cells (Tregs) to inflammation and fibrosis induced in a model of experimental colitis by oral intake of dextran sodium sulphate (DSS) in wild type and IL-13 knock-out C57Bl/6 mice. Inflammation and fibrosis were scored by macroscopic and histological examination and fibrosis was quantified by hydroxyproline. Numbers of Tregs and IFN-γ⁺, IL-13⁺ and IL-17A⁺ CD4⁺ T helper (Th) cells in mesenteric lymph nodes increased during chronic DSS administration and mRNA for IFN-γ and IL-17 in the inflamed colon tissue was upregulated. However, antibody-mediated neutralisation of IFN-γ or IL-17A/F in a therapeutic setting had no effect on chronic intestinal inflammation and fibrosis. Antibody-mediated depletion of Tregs did not enhance fibrosis, nor did IL-13 deficiency have an effect on the fibrotic disease. These data argue against an important contribution of Tregs and of the cytokines IFN-γ, IL-13, IL-17A, IL-17F in the induction and/or control of fibrosis in this Crohn's disease like murine model.

Modulation of inducible nitric oxide synthase pathway by eugenol and telmisartan in carbon tetrachloride-induced liver injury in rats

AIMS

Inducible nitric oxide synthase (iNOS) pathway has been in the limelight since its discovery as a key mediator in the process of liver fibrogenesis. Therefore, the objective of the current study was to elucidate the in vivo molecular mechanism underlying the hepatic preventive relevance of eugenol (EUG) and telmisartan (TEL) through iNOS pathway modulation against carbon tetrachloride (CCl4)-induced hepatic injury.

METHODS

Sixty healthy male albino rats were used in this study. Serum aminotransferases activities and NO levels were assessed. Hepatic malondialdehyde (MDA), total nitrite/nitrate content and reduced glutathione (GSH) concentration were estimated. Liver NF-kB, TNF-α, IL-6 and iNOS proteins expressions were investigated by western blot assay. Histopathological examination was done.

KEY FINDINGS

CCl4 resulted in damage to centrilobular regions of the liver, elevation of serum aminotransferases, rise in oxidative parameters level, and up-regulation of NF-kB, TNF-α, IL-6 as well as iNOS proteins expressions. Treatment of fibrotic rats with either EUG or TEL significantly alleviated CCl4-induced biochemical, inflammatory and histopathological changes. Moreover, the combined administration of EUG with TEL has an ameliorative effect which is greater than either of them alone.

SIGNIFICANCE

In conclusion, the combination therapy between EUG and TEL is more effective than either drug alone which is attributed to suppression of NO production and iNOS protein expression. The results support that use of EUG and TEL exerts beneficial effects in the attenuation of CCl4-induced liver fibrosis in rats.

Overexpression of C‑sis inhibits H2O2‑induced Buffalo rat liver cell apoptosis in vitro and alleviates liver injury in a rat model of fulminant hepatic failure

The present study aimed to investigate the role of the C‑sis gene in the apoptosis of hepatocytes in vitro and in the liver function of a rat model of fulminant hepatic failure (FHF). Buffalo rat liver (BRL) cells were treated with hydrogen peroxide (H2O2) to induce apoptosis and then transfected with a C‑sis overexpression vector. A rat model of FHF was established, and C‑sis was overexpressed. The mRNA and protein expression of C‑sis were examined using reverse transcription‑polymerase chain reaction and western blot analyses, respectively. Cell viability was assessed by CCK8, and a TUNEL assay was used to examine cell apoptosis. Flow cytometry was used for cell cycle detection. Hematoxylin and eosin staining was used for histological examination. The levels of alanine transaminase (ALT) and aspartate transaminase (AST) were also examined in the rats. The results showed that C‑sis was successfully overexpressed in the cells and rat model. Compared with H2O2‑treated BRL cells, the overexpression of C‑sis significantly inhibited cell apoptosis, promoted cell viability, and decreased the expression of cleaved caspase-3. Similar results were observed in the FHF rats treated with the C‑sis overexpression plasmid, compared with those treated with empty plasmids. In addition, in the FHF rats overexpressing C‑sis, histological examination showed that liver injury was alleviated, the levels of ALT and AST were significantly decreased, and mortality rate was significantly decreased, compared with those observed in the rats treated with empty plasmids. In conclusion, the overexpression of C‑sis inhibited the H2O2‑induced apoptosis of BRL cells in vitro, and alleviated liver injury, improved liver function, and decreased mortality rates in rat models of FHF.

Pomegranate action in curbing the incidence of liver injury triggered by Diethylnitrosamine by declining oxidative stress via Nrf2 and NFκB regulation

Unearthing and employment of healthy substitutes is now in demand to tackle a number of diseases due to the excessive repercussions of synthetic drugs. In this frame of reference pomegranate juice (PGJ) is a boon comprising of anthocyanins and hydrolysable tannins, known for its anti-oxidant and anti-inflammatory properties. Despite various documented roles of PGJ, there are no studies on antifibrotic potential in NDEA-induced mammalian liver fibrotic model. Hepatic fibrosis in rats was induced by the intra-peritoneal injection of NDEA (10 mlkg-1b.wt. of 1% NDEA) in two weeks. Biochemical, histopathological and ultra-structural studies were carried out on control, fibrotic and treated rats. The liver function indices and LPO were increased significantly by intoxication of NDEA. The antioxidant status was disturbed with the decrease in SOD, GST and catalase in the liver and membrane-ATPases as well. Histopathological observations by H&E, M&T, picro-sirius and ultra-structural scrutiny by SEM and TEM indicated liver damage and increase in COX2 and α-SMA by NDEA which was successfully rectified by the supplementation of PGJ. PGJ abrogates liver fibrosis instigated by NDEA in Wistar rats by declining oxidative stress via regulation of Nrf2 and NFκB. These findings point towards pomegranate as a potential and efficacious therapeutic agent against liver fibrosis.

Cellular and Molecular Mediators of Intestinal Fibrosis

Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.

Cellular and Molecular Mediators of Intestinal Fibrosis

Intestinal fibrosis is a major complication of the inflammatory bowel diseases (IBD) and although inflammation is necessary for its development, it would appear that it plays a minor role in its progression as anti-inflammatory treatments in IBD do not prevent fibrosis once it has started. The processes that regulate fibrosis would thus appear to be distinct from those regulating inflammation and, therefore, a detailed understanding of these pathways is vital to the development of anti-fibrogenic strategies. There have been several recent reviews exploring what is known, and what remains unknown, about the development of intestinal fibrosis. This review is designed to add to this literature but with a focus on the cellular components that are involved in the development of fibrogenesis and the major molecular mediators that impact on these cells. The aim is to heighten the understanding of the factors involved in intestinal fibrogenesis so that detailed research can be encouraged in order to advance the processes that could lead to effective treatments.

Food components with antifibrotic activity and implications in prevention of liver disease

Increasing prevalence of nonalcoholic fatty liver disease (NAFLD) in parallel with the obesity epidemic has been a major public health concern. NAFLD is the most common chronic liver disease in the United States, ranging from fatty liver to steatohepatitis, fibrosis and cirrhosis in the liver. In response to chronic liver injury, fibrogenesis in the liver occurs as a protective response; however, prolonged and dysregulated fibrogenesis can lead to liver fibrosis, which can further progress to cirrhosis and eventually hepatocellular carcinoma. Interplay of hepatocytes, macrophages and hepatic stellate cells (HSCs) in the hepatic inflammatory and oxidative milieu is critical for the development of NAFLD. In particular, HSCs play a major role in the production of extracellular matrix proteins. Studies have demonstrated that bioactive food components and natural products, including astaxanthin, curcumin, blueberry, silymarin, coffee, vitamin C, vitamin E, vitamin D, resveratrol, quercetin and epigallocatechin-3-gallate, have antifibrotic effects in the liver. This review summarizes current knowledge of the mechanistic insight into the antifibrotic actions of the aforementioned bioactive food components.

Coenzyme Q10 inhibits the activation of pancreatic stellate cells through PI3K/AKT/mTOR signaling pathway

Aim

Pancreatic stellate cells (PSCs) have a vital role in pancreatic fibrosis accompanied by pancreatic ductal adenocarcinoma (PDAC) and chronic pancreatitis (CP). Any agents which can affect the activation of PSCs could become potential candidates for treatment strategies in PDAC and CP. Our aim was to explore the effect of Coenzyme Q10 (CoQ10) in the process of PSCs activation.

Methods

Isolated PSCs from C57BL/6 mice were treated with various dosages of CoQ10 (1, 10, and 100μM) and different time (24h, 48h, and 72 h). Effect of CoQ10 on autophagy, apoptosis, senescence and oxidative stress, as well as the activation of PSCs were analyzed by immunocytofluorescent staining, quantitative real time RT-PCR, western blotting, SA-β-galactosidase staining, malondialdehyde and reactive oxygen species (ROS) assay.

Results

Expression of α-smooth muscle actin, LC3II, Beclin1, Cleaved caspases-3 and Bax levels were significantly reduced in CoQ10 treatment groups. Meanwhile, compared with the control group, significant differences for the expression of desmin, P62, Bcl-2, p-PI3K, p-AKT and p-mTOR levels in CoQ10 treatment groups were found. Moreover, CoQ10 affected the secretion of extracellular matrix components for PSCs. Few SA-β-gal positive cells were found in CoQ10 treated groups. A significant decrease in ROS positive cells and malondialdehyde levels were observed after 72 h exposure to CoQ10.

Conclusions

Our finding suggests that CoQ10 inhibits the activation of PSCs by suppressing autophagy through activating the PI3K/AKT/mTOR signaling pathway. CoQ10 may act as a therapeutic agent in PSC-relating pathologies and/or anti-fibrotic approaches.

Apocynin prevented inflammation and oxidative stress in carbon tetra chloride induced hepatic dysfunction in rats

BACKGROUND

Liver fibrosis is a leading pathway to cirrhosis and a global clinical issue. Oxidative stress mediated tissue damage is one of the prime causes of hepatic dysfunction and fibrosis. Apocynin is one of many strong antioxidants.

OBJECTIVE

To evaluate the effect of apocynin in the CCl₄ administered hepatic dysfunction in rats.

METHODS

Female Long Evans rats were administered with CCl₄ orally (1mL/kg) twice a week for 2 weeks and were treated with apocynin (100mg/kg). Both plasma and liver tissues were analyzed for alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase activities. Oxidative stress parameters were also measured by determining malondialdehyde (MDA), nitric oxide (NO), myeloperoxidase (MPO), advanced protein oxidation product (APOP). In addition, antioxidant enzyme activities such as superoxide dismutase (SOD) and catalase activities in plasma and liver tissues were analyzed. Moreover, inflammation and tissue fibrosis were confirmed by histological staining of liver tissue sections.

RESULTS

Apocynin significantly reduced serum AST, ALT, and ALP activities in carbon tetrachloride treated rats. It also exhibited a considerable reduction of the oxidative stress markers (MDA, MPO, NO, and APOP level) which was elevated due to CCl₄ administration in rats. Apocynin treatment also restored the catalase and superoxide dismutase activity in CCl₄ treated rats. Histological analysis of liver sections revealed that apocynin prevented inflammatory cells infiltration and fibrosis in CCl₄ administered rats.

CONCLUSION

These results suggest that apocynin protects liver damage induced by CCl₄ by inhibiting lipid peroxidation and stimulating the cellular antioxidant system.

Ammonia produces pathological changes in human hepatic stellate cells and is a target for therapy of portal hypertension

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are vital to hepatocellular function and the liver response to injury. They share a phenotypic homology with astrocytes that are central in the pathogenesis of hepatic encephalopathy, a condition in which hyperammonemia plays a pathogenic role. This study tested the hypothesis that ammonia modulates human HSC activation in vitro and in vivo, and evaluated whether ammonia lowering, by using l-ornithine phenylacetate (OP), modifies HSC activation in vivo and reduces portal pressure in a bile duct ligation (BDL) model.

METHODS

Primary human HSCs were isolated and cultured. Proliferation (BrdU), metabolic activity (MTS), morphology (transmission electron, light and immunofluorescence microscopy), HSC activation markers, ability to contract, changes in oxidative status (ROS) and endoplasmic reticulum (ER) were evaluated to identify effects of ammonia challenge (50 μM, 100 μM, 300 μM) over 24-72 h. Changes in plasma ammonia levels, markers of HSC activation, portal pressure and hepatic eNOS activity were quantified in hyperammonemic BDL animals, and after OP treatment.

RESULTS

Pathophysiological ammonia concentrations caused significant and reversible changes in cell proliferation, metabolic activity and activation markers of hHSC in vitro. Ammonia also induced significant alterations in cellular morphology, characterised by cytoplasmic vacuolisation, ER enlargement, ROS production, hHSC contraction and changes in pro-inflammatory gene expression together with HSC-related activation markers such as α-SMA, myosin IIa, IIb, and PDGF-Rβ. Treatment with OP significantly reduced plasma ammonia (BDL 199.1 μmol/L±43.65 vs. BDL+OP 149.27 μmol/L±51.1, p<0.05) and portal pressure (BDL 14±0.6 vs. BDL+OP 11±0.3 mmHg, p<0.01), which was associated with increased eNOS activity and abrogation of HSC activation markers.

CONCLUSIONS

The results show for the first time that ammonia produces deleterious morphological and functional effects on HSCs in vitro. Targeting ammonia with the ammonia lowering drug OP reduces portal pressure and deactivates hHSC in vivo, highlighting the opportunity for evaluating ammonia lowering as a potential therapy in cirrhotic patients with portal hypertension.

Curcumin upregulates Nrf2 nuclear translocation and protects rat hepatic stellate cells against oxidative stress

The present study aimed to investigate the protective role of curcumin against oxidative stress in rat hepatic stellate cells (HSCs)-T6, and to determine the possible underlying mechanisms. HSC-T6 cells were divided into three groups: Negative control group, oxidant-treated group and curcumin-treated group. Flow cytometry and spectrophotometry were used to measure the production of reactive oxygen species (ROS), and the levels of malondialdehyde (MDA) and glutathione (GSH). Immunocytochemistry and a radioimmunoassay were used to determine the expression of smooth muscle α-actin (α-SMA) and the secretion of extracellular matrix (ECM) molecules. In addition, western blotting and immunocytochemistry were used to determine the expression levels of nuclear factor-erythroid 2-related factor (Nrf2). Treatment with glucose oxidase (GO) significantly stimulated the formation of ROS and increased the production of MDA, as compared with the control cells; however, the production of GSH was only slightly increased. In addition, treatment with GO significantly promoted the expression of α-SMA and the secretion of ECM molecules. Conversely, treatment with curcumin significantly decreased the levels of ROS and MDA, and significantly increased the levels of GSH. Curcumin significantly inhibited the expression of α-SMA and decreased the secretion of ECM molecules. Furthermore, treatment with curcumin significantly increased the nuclear expression levels of Nrf2. These results indicated that curcumin may protect rat HSCs against oxidative stress and inhibit the GO-induced activation and secretion of ECM molecules in vitro. These effects were mediated by the upregulation of Nrf2 nuclear translocation.

Simple sugar intake and hepatocellular carcinoma: epidemiological and mechanistic insight

Sugar intake has dramatically increased during the last few decades. Specifically, there has been a clear trend towards higher consumption of fructose and high fructose corn syrup, which are the most common added sugars in processed food, soft drinks and other sweetened beverages. Although still controversial, this rising trend in simple sugar consumption has been positively associated with weight gain and obesity, insulin resistance and type 2 diabetes mellitus and non-alcoholic fatty liver disease. Interestingly, all of these metabolic alterations have also been related to the development of hepatocellular carcinoma. The purpose of this review is to discuss the evidence coming from epidemiological studies and data from animal models relating the consumption of simple sugars, and specifically fructose, with an increased risk of hepatocellular carcinoma and to gain insight into the putative molecular mechanisms involved.

Transplantation and inflammation: implications for the modification of chemokine function

Oxidative stress is a major and recurring cause of damage during inflammation, especially following organ transplantation. Initial ischaemia–reperfusion injury causes the production of many reactive oxygen and nitrogen species, and subsequent recruitment and activation of inflammatory cells can lead to further oxidative stress. This stress is well known to cause damage at the cellular level, for example by induction of senescence leading to the production of a characteristic senescence-associated secretory phenotype. Chemokines are an important component of the senescence-associated secretory phenotype, recruiting further leucocytes and reinforcing the stress and senescence responses. As well as inducing the production of proteins, including chemokines, oxidative stress can alter proteins themselves, both directly and by induction of enzymes capable of modification. These alterations can lead to important modifications to their biological activity and also alter detection by some antibodies, potentially limiting the biological relevance of some immunochemical and proteomic biomarkers. Peroxynitrite, a reactive nitrogen species generated during inflammation and ischaemia, can cause such modifications by nitrating chemokines. Matrix metalloproteinases, released by many stressed cells, can cleave chemokines, altering function, while peptidylarginine deiminases can inactivate certain chemokines by citrullination. This review discusses the relationship between inflammation and post-translational modification, focusing on the functional modulation of transplant-relevant pro-inflammatory chemokines.

Helium generated cold plasma finely regulates activation of human fibroblast-like primary cells

Non-thermal atmospheric pressure plasmas are being developed for a wide range of health care applications, including wound healing. However in order to exploit the potential of plasma for clinical applications, the understanding of the mechanisms involved in plasma-induced activation of fibroblasts, the cells active in the healing process, is mandatory. In this study, the role of helium generated plasma in the tissue repairing process was investigated in cultured human fibroblast-like primary cells, and specifically in hepatic stellate cells and intestinal subepithelial myofibroblasts. Five minutes after treatment, plasma induced formation of reactive oxygen species (ROS) in cultured cells, as assessed by flow cytometric analysis of fluorescence-activated 2′,7′-dichlorofluorescein diacetate probe. Plasma-induced intracellular ROS were characterized by lower concentrations and shorter half-lives with respect to hydrogen peroxide-induced ROS. Moreover ROS generated by plasma treatment increased the expression of peroxisome proliferator activated receptor (PPAR)-γ, nuclear receptor that modulates the inflammatory responses. Plasma exposure promoted wound healing in an in vitro model and induced fibroblast migration and proliferation, as demonstrated, respectively, by trans-well assay and partitioning between daughter cells of carboxyfluorescein diacetate succinimidyl ester fluorescent dye. Plasma-induced fibroblast migration and proliferation were found to be ROS-dependent as cellular incubation with antioxidant agents (e.g. N-acetyl L-cysteine) cancelled the biological effects. This study provides evidence that helium generated plasma promotes proliferation and migration in liver and intestinal fibroblast-like primary cells mainly by increasing intracellular ROS levels. Since plasma-evoked ROS are time-restricted and elicit the PPAR-γ anti-inflammatory molecular pathway, this strategy ensures precise regulation of human fibroblast activation and can be considered a valid therapeutic approach for liver and gut lesions.

Oxidative stress as a crucial factor in liver diseases

Redox state constitutes an important background of numerous liver disorders. The redox state participates in the course of inflammatory, metabolic and proliferative liver diseases. Reactive oxygen species (ROS) are primarily produced in the mitochondria and in the endoplasmic reticulum of hepatocytes via the cytochrome P450 enzymes. Under the proper conditions, cells are equipped with special molecular strategies that control the level of oxidative stress and maintain a balance between oxidant and antioxidant particles. Oxidative stress represents an imbalance between oxidant and antioxidant agents. Hepatocytic proteins, lipids and DNA are among the cellular structures that are primarily affected by ROS and reactive nitrogen species. The process results in structural and functional abnormalities in the liver. Thus, the phenomenon of oxidative stress should be investigated for several reasons. First, it may explain the pathogenesis of various liver disorders. Moreover, monitoring oxidative markers among hepatocytes offers the potential to diagnose the degree of liver damage and ultimately to observe the response to pharmacological therapies. The present report focuses on the role of oxidative stress in selected liver diseases.

Liver fibrosis: Role of oxidative stress and therapeutic countermeasures

A variety of factors can lead to chronic inflammation of the liver and thus the occurrence of liver fibrosis. The activation of hepatic stellate cell (HSC) plays a key role in the pathogenesis of liver fibrosis. Activated HSC exhibit characteristic changes in the morphology and function and promote the development of liver fibrosis. Intrahepatic oxidative stress injury is an important mechanism involved in HSC activation and hepatic collagen deposition. There is a close relationship between liver fibrosis and oxidative stress levels. Reducing the levels of oxidative stress has gradually become an aim of anti-fibrotic therapy. In this paper we review recent progress in research of oxidative stress, liver fibrosis and its therapeutic strategies.

Amelioration of systemic fibrosis in mice by angiotensin II receptor blockade

OBJECTIVE

Systemic sclerosis (SSc) is characterized by microvascular damage, fibrosis of skin and visceral organs, and autoimmunity. Previous studies have shown that angiotensin II is involved in the synthesis of type I collagen. We investigated whether the blockade of angiotensin II receptor type I (AT1 ) by irbesartan reduces skin and lung fibrosis in 2 murine models of SSc.

METHODS

SSc was induced by daily intradermal injection of HOCl into the backs of BALB/c mice (HOCl-induced SSc). Mice were treated daily with irbesartan by oral gavage.

RESULTS

Irbesartan reduced dermal thickness, collagen concentration, Smad2/3, and α-smooth muscle actin expression, as well as fibroblast proliferation and H-Ras expression in the skin of mice with HOCl-induced SSc. Mice treated with irbesartan also displayed less lung fibrosis, less inflammation, and a lower concentration of collagen in the lungs than untreated mice. Exhaled nitric oxide, inducible nitric oxide synthase, and 3-nitrotyrosine expression in the lungs were decreased following irbesartan treatment. Moreover, irbesartan reduced the number and the proliferation of splenic B and T cells and the serum levels of anti-DNA topoisomerase I autoantibodies.

CONCLUSION

Irbesartan, an AT1 antagonist, prevents fibrosis and inflammation and inhibits nitric oxide production in HOCl-induced models of systemic fibrosis. Our findings extend the indication of an AT1 antagonist to SSc patients with diffuse fibrosis, especially those with lung involvement.

A novel transcription mechanism activated by ethanol: induction of Slc7a11 gene expression via inhibition of the DNA-binding activity of transcriptional repressor octamer-binding transcription factor 1 (OCT-1)

Solute carrier family 7, member 11 (Slc7a11) is a plasma membrane cystine/glutamate exchanger that provides intracellular cystine to produce glutathione, a major cellular antioxidant. Oxidative and endoplasmic reticulum stresses up-regulate Slc7a11 expression by activation of nuclear factor erythroid 2-related factor 2 and transcription factor 4. This study examined the effect of ethanol on Slc7a11 expression and the underlying mechanism involved. Treatment of mouse hepatic stellate cells with ethanol significantly increased Slc7a11 mRNA and protein levels. Deletion of a 20-bp DNA sequence between -2044 to -2024 upstream of the transcription start site significantly increased basal activity and completely abolished the ethanol-induced activity of the Slc7a11 promoter. This deletion did not affect Slc7a11 promoter activity induced by oxidative or endoplasmic reticulum stress. DNA sequence analysis revealed a binding motif for octamer-binding transcription factor 1 (OCT-1) in the deleted fragment. Mutation of this OCT-1 binding motif resulted in a similar effect as the deletion experiment, i.e. it increased the basal promoter activity and abolished the response to ethanol. Ethanol exposure significantly inhibited OCT-1 binding to the Slc7a11 promoter region, although it did not alter OCT-1 mRNA and protein levels. OCT-1 reportedly functions as either a transcriptional enhancer or repressor, depending on the target genes. Results from this study suggest that OCT-1 functions as a repressor on the Slc7a11 promoter and that ethanol inhibits OCT-1 binding to the Slc7a11 promoter, thereby increasing Slc7a11 expression. Taken together, inhibition of the DNA binding activity of transcriptional repressor OCT-1 is a mechanism by which ethanol up-regulates Slc711 expression.

Heme oxygenase/carbon monoxide pathway inhibition plays a role in ameliorating fibrosis following splenectomy

Splenectomy is a recognized therapy for liver cirrhosis with splenomegaly, since it decreases free iron concentration that accompanies the destruction of red blood cells. Heme oxygenase (HO)-1 and its by-products, iron and carbon monoxide (CO), play crucial roles in hepatic fibrosis. The aim of the present study was to determine whether splenectomy in cirrhotic rats induced by bile duct ligation (BDL), through the HO/CO pathway, could slow down the development of liver fibrosis. Male Sprague-Dawley rats were divided randomly into the sham, BDL, splenectomy, Fe, zinc protoporphyrin (Znpp) and cobalt protoporphyrin (Copp) treatment groups, for inhibiting and inducing HO-1 expression. The level of HO-1 was detected by western blot analysis and reverse transcription-polymerase chain reaction. Serum carboxyhemoglobin (COHb), iron and portal vein pressure (PVP) were also quantified. Liver iron was measured by atomic absorption spectrometry with acetylene-air flame atomization. HO-1 and α-smooth muscle actin (α-SMA) were localized by immunohistochemistry. Liver and spleen iron were visualized by Perls' Prussian blue staining. Hepatic fibrosis was assessed using hematoxylin and eosin (H&E) staining. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum transforming growth factor-β1 (TGF-β1). The results showed that liver, spleen and serum levels of HO-1, COHb and iron were greatly enhanced in the BDL group compared with the sham group; they were reduced following splenectomy and Znpp treatment, but were elevated in the Copp and Fe groups. Hydroxyproline, TGF-β1, α-SMA, PVP and malonaldehyde levels were lower in the splenectomy and Znpp groups compared to BDL, while higher levels were observed in the Copp and Fe-treated groups. Our study shows that splenectomy reduces iron and CO levels in part by reducing HO-1 expression, and it decreases portal pressure and slightly decreases hepatic fibroproliferation.

Reactive oxygen species-mediated killing of activated fibroblasts by arsenic trioxide ameliorates fibrosis in a murine model of systemic sclerosis

OBJECTIVE

In patients with systemic sclerosis (SSc), activated fibroblasts produce reactive oxygen species (ROS) that stimulate their proliferation and collagen synthesis. By analogy with tumor cells that undergo apoptosis upon cytotoxic treatment that increases ROS levels beyond a lethal threshold, we tested whether activated fibroblasts could be selectively killed by the cytotoxic molecule arsenic trioxide (As(2) O(3) ) in a murine model of SSc.

METHODS

SSc was induced in BALB/c mice by daily intradermal injections of HOCl. Mice were simultaneously treated with daily intraperitoneal injections of As(2) O(3) .

RESULTS

As(2) O(3) limited dermal thickness and inhibited collagen deposition, as assessed by histologic examination and measurement of mouse skin and lung collagen contents. As(2) O(3) abrogated vascular damage, as shown by serum vascular cell adhesion molecule 1 level, and inhibited the production of autoantibodies, interleukin-4 (IL-4), and IL-13 by activated T cells. These beneficial effects were mediated through ROS generation that selectively killed activated fibroblasts containing low levels of glutathione.

CONCLUSION

Our findings indicate that treatment with As(2) O(3) dramatically improves skin and lung fibrosis in a mouse model of SSc, providing a rationale for the evaluation of As(2) O(3) treatment in patients with SSc.

Peroxisome proliferator-activated receptor-γ as a therapeutic target for hepatic fibrosis: from bench to bedside

Hepatic fibrosis is a dynamic chronic liver disease occurring as a consequence of wound-healing responses to various hepatic injuries. This disorder is one of primary predictors for liver-associated morbidity and mortality worldwide. To date, no pharmacological agent has been approved for hepatic fibrosis or could be recommended for routine use in clinical context. Cellular and molecular understanding of hepatic fibrosis has revealed that peroxisome proliferator-activated receptor-γ (PPARγ), the functioning receptor for antidiabetic thiazolidinediones, plays a pivotal role in the pathobiology of hepatic stellate cells (HSCs), whose activation is the central event in the pathogenesis of hepatic fibrosis. Activation of PPARγ inhibits HSC collagen production and modulates HSC adipogenic phenotype at transcriptional and epigenetic levels. These molecular insights indicate PPARγ as a promising drug target for antifibrotic chemotherapy. Intensive animal studies have demonstrated that stimulation of PPARγ regulatory system through gene therapy approaches and PPARγ ligands has therapeutic promise for hepatic fibrosis induced by a variety of etiologies. At the same time, thiazolidinedione agents have been investigated for their clinical benefits primarily in patients with nonalcoholic steatohepatitis, a common metabolic liver disorder with high potential to progress to fibrosis and liver-related death. Although some studies have shown initial promise, none has established long-term efficacy in well-controlled randomized clinical trials. This comprehensive review covers the 10-year discoveries of the molecular basis for PPARγ regulation of HSC pathophysiology and then focuses on the animal investigations and clinical trials of various therapeutic modalities targeting PPARγ for hepatic fibrosis.

Anti-fibrotic effects of L-2-oxothiazolidine-4-carboxylic acid via modulation of nuclear factor erythroid 2-related factor 2 in rats

L-2-Oxothiazolidine-4-carboxylic acid (OTC) is a cysteine prodrug that maintains glutathione in tissues. The present study was designed to investigate anti-fibrotic and anti-oxidative effects of OTC via modulation of nuclear factor erythroid 2-related factor 2 (Nrf2) in an in vivo thioacetamide (TAA)-induced hepatic fibrosis model. Treatment with OTC (80 or 160 mg/kg) improved serum liver function parameters and significantly ameliorated liver fibrosis. The OTC treatment groups exhibited significantly lower expression of α-smooth muscle actin, transforming growth factor-β 1, and collagen α 1 mRNA than that in the TAA model group. Furthermore, the OTC treatment groups showed a significant decrease in hepatic malondialdehyde level compared to that in the TAA model group. Nrf2 and heme oxygenase-1 expression increased significantly in the OTC treatment groups compared with that in the TAA model group. Taken together, these results suggest that OTC restores the anti- oxidative system by upregulating Nrf2; thus, ameliorating liver injury and a fibrotic reaction.

Cellular and molecular mechanisms of intestinal fibrosis

Fibrosis is a chronic and progressive process characterized by an excessive accumulation of extracellular matrix (ECM) leading to stiffening and/or scarring of the involved tissue. Intestinal fibrosis may develop in several different enteropathies, including inflammatory bowel disease. It develops through complex cell, extracellular matrix, cytokine and growth factor interactions. Distinct cell types are involved in intestinal fibrosis, such as resident mesenchymal cells (fibroblasts, myofibroblasts and smooth muscle cells) but also ECM-producing cells derived from epithelial and endothelial cells (through a process termed epithelial- and endothelial-mesenchymal transition), stellate cells, pericytes, local or bone marrow-derived stem cells. The most important soluble factors that regulate the activation of these cells include cytokines, chemokines, growth factors, components of the renin-angiotensin system, angiogenic factors, peroxisome proliferator-activated receptors, mammalian target of rapamycin, and products of oxidative stress. It soon becomes clear that although inflammation is responsible for triggering the onset of the fibrotic process, it only plays a minor role in the progression of this condition, as fibrosis may advance in a self-perpetuating fashion. Definition of the cellular and molecular mechanisms involved in intestinal fibrosis may provide the key to developing new therapeutic approaches.

Liver fibrosis and hepatocyte apoptosis are attenuated by GKT137831, a novel NOX4/NOX1 inhibitor in vivo

Reactive oxygen species (ROS) play a key role in chronic liver injury and fibrosis. Homologs of NADPH oxidases (NOXs) are major sources of ROS, but the exact role of the individual homologs in liver disease is unknown. Our goal was to determine the role of NOX4 in liver fibrosis induced by bile duct ligation (BDL) with the aid of the pharmacological inhibitor GKT137831, and genetic deletion of NOX4 in mice. GKT137831 was either applied for the full term of BDL (preventive arm) or started at 10 day postoperatively (therapeutic arm). Primary hepatic stellate cells (HSC) from control mice with and without BDL were analyzed and the effect of NOX4 inhibition on HSC activation was also studied. FasL or TNFα/actinomycin D-induced apoptosis was studied in wild-type and NOX4(-/-) hepatocytes. NOX4 was upregulated by a TGF-β/Smad3-dependent mechanism in HSC. Downregulation of NOX4 decreased ROS production and the activation of NOX4(-/-) HSC was attenuated. NOX4(-/-) hepatocytes were more resistant to FasL or TNFα/actinomycin D-induced apoptosis. Similarly, after pharmacological NOX4 inhibition, ROS production, the expression of fibrogenic markers, and hepatocyte apoptosis were reduced. NOX4 was expressed in human livers with stage 2-3 autoimmune hepatitis. Fibrosis was attenuated by the genetic deletion of NOX4. BDL mice gavaged with GKT137831 in the preventive or the therapeutic arm displayed less ROS production, significantly attenuated fibrosis, and decreased hepatocyte apoptosis. In conclusion, NOX4 plays a key role in liver fibrosis. GKT137831 is a potent inhibitor of fibrosis and hepatocyte apoptosis; therefore, it is a promising therapeutic agent for future translational studies.

Liver fibrogenesis in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is emerging as one of the most common chronic liver diseases in developed western countries. Non-alcoholic steatohepatitis (NASH) is the most severe form of NAFLD, and can progress to more severe forms of liver disease, including fibrosis, cirrhosis, and even hepatocellular carcinoma. The activation of hepatic stellate cells plays a critical role in NASH-related fibrogenesis. Multiple factors, such as insulin resistance, oxidative stress, pro-inflammatory cytokines and adipokines, and innate immune responses, are known to contribute to the development of NASH-related fibrogenesis. Furthermore, these factors may share synergistic interactions, which could contribute to the process of liver fibrosis. Given the complex etiology of NASH, combined treatment regimes that target these different factors provide potential treatment strategies for NASH-related liver fibrosis.

Oxidative stress: a pathogenic mechanism for Niemann-Pick type C disease

Niemann-Pick type C (NPC) disease is a neurovisceral atypical lipid storage disorder involving the accumulation of cholesterol and other lipids in the late endocytic pathway. The pathogenic mechanism that links the accumulation of intracellular cholesterol with cell death in NPC disease in both the CNS and the liver is currently unknown. Oxidative stress has been observed in the livers and brains of NPC mice and in different NPC cellular models. Moreover, there is evidence of an elevation of oxidative stress markers in the serumof NPC patients. Recent evidence strongly suggests that mitochondrial dysfunction plays an important role in NPC pathogenesis and that mitochondria could be a significant source of oxidative stress in this disease. In this context, the accumulation of vitamin E in the late endosomal/lysosomal compartments in NPC could lead to a potential decrease of its bioavailability and could be another possible cause of oxidative damage. Another possible source of reactive species in NPC is the diminished activity of different antioxidant enzymes. Moreover, because NPC is mainly caused by the accumulation of free cholesterol, oxidized cholesterol derivatives produced by oxidative stress may contribute to the pathogenesis of the disease.

Age related changes of the extracellular matrix and stem cell maintenance

Aging is characterized by reduced tissue and organ function, regenerative capacity, and accompanied by a decrease in tissue resident stem cell numbers and a loss of potency. The impact of aging on stem cell populations differs between tissues and depends on a number of non cell-intrinsic factors, including systemic changes associated with immune system alterations, as well as senescence related changes of the local cytoarchitecture. The latter has been studied in the context of environmental niche properties required for stem cell maintenance. Here, we will discuss the impact of the extracellular matrix (ECM) on stem cell maintenance, its changes during aging and its significance for stem cell therapy. We provide an overview on ECM components and examples of age associated remodeling of the cytoarchitecture. The interaction of stem cells with the ECM will be described and the importance of an intact and hospitable ECM for stem cell maintenance, differentiation and stem cell initiated tissue repair outlined. It is concluded that a remodeled ECM due to age related inflammation, fibrosis or oxidative stress provides an inadequate environment for endogenous regeneration or stem cell therapies. Means to provide adequate ECM for stem cell therapies and endogenous regeneration and the potential of antioxidants to prevent ECM damage and promote its repair and subsequently support regeneration are discussed.

A systems biology approach for understanding the collagen regulatory network in alcoholic liver disease

Among the pathogenesis and risk factors of alcoholic liver disease (ALD) are the source of dietary fat, obesity, insulin resistance, adipokines and acetaldehyde. Translocation of Gram-negative bacteria from the gut, the subsequent effects mediated by endotoxin, and the increased production of matricellular proteins, cytokines, chemokines and growth factors, actively participate in the progression of liver injury. In addition, generation of reactive oxygen and nitrogen species and the activation of non-parenchymal cells also contribute to the pathophysiology of ALD. A key event leading to liver damage is the transition of quiescent hepatic stellate cells into activated myofibroblasts, with the consequent deposition of fibrillar collagen I resulting in significant scarring. Thus, it is becoming clearer that matricellular proteins are critical players in the pathophysiology of liver disease; however, additional mechanistic insight is needed to understand the signalling pathways involved in the up-regulation of collagen I protein. At present, systems biology approaches are helping to answer the many unresolved questions in this field and are allowing to more comprehensively identify protein networks regulating pathological collagen I deposition in hopes of determining how to prevent the onset of liver fibrosis and/or to slow disease progression. Thus, this review article provides a snapshot on current efforts for identifying pathological protein regulatory networks in the liver using systems biology tools. These approaches hold great promise for future research in liver disease.

Cytoglobin: biochemical, functional and clinical perspective of the newest member of the globin family

Since the discovery of cytoglobin (Cygb) a decade ago, growing amounts of data have been gathered to characterise Cygb biochemistry, functioning and implication in human pathologies. Its molecular roles remain under investigation, but nitric oxide dioxygenase and lipid peroxidase activities have been demonstrated. Cygb expression increases in response to various stress conditions including hypoxia, oxidative stress and fibrotic stimulation. When exogenously overexpressed, Cygb revealed cytoprotection against these factors. Cygb was shown to be upregulated in fibrosis and neurodegenerative disorders and downregulated in multiple cancer types. CYGB was also found within the minimal region of a hereditary tylosis with oesophageal cancer syndrome, and its expression was reduced in tylotic samples. Recently, Cygb has been shown to inhibit cancer cell growth in vitro, thus confirming its suggested tumour suppressor role. This article aims to review the biochemical and functional aspects of Cygb, its involvement in various pathological conditions and potential clinical utility.