Redox state and methods to evaluate oxidative stress in liver damage: From bench to bedside.

 Oxidative stress is importantly involved in the pathophysiology of various liver diseases. The redox state participates on the course of the inflammatory, metabolic and proliferative liver diseases. The main sources of the reactive oxygen species (ROS) are represented by the mitochondria and cytochrome P450 enzymes in the hepatocyte, Kupffer cells and neutrophils. Cells are provided with efficient molecular strategies to strictly control the intracellular ROS level and to maintain the balance between oxidant and antioxidant molecules. Hepatocyte's proteins, lipids and DNA are among the cellular structures to be affected primarily by ROS and reactive nitrogen species (RNS). This process disrupts at cellular and molecular level the structure-function relationship on liver cells at different sites. Therefore, further studies on the molecular mechanisms of the oxidative stress pathways on liver diseases are urgently required, because they could explain the pathogenesis of various liver disorders. Moreover, new methods to evaluate oxidative stress like the oxidative markers among hepatocytes offers the potential to diagnose the degree of liver injury and ultimately to assess the response to pharmacological therapies. In this review, we discuss the molecular, metabolic and aging aspects of the oxidative stress, and the methods to evaluate oxidative stress on liver damage.

Coffee attenuates fibrosis by decreasing the expression of TGF-ß and CTGF in a murine model of liver damage.

This study was performed to evaluate the antifibrotic properties of coffee in a model of liver damage induced by repeated administration of thioacetamide (TAA) in male Wistar rats. In this study, cirrhosis was induced by chronic TAA administration and the effects of co-administration of conventional caffeinated coffee or decaffeinated coffee (CC, DC, respectively) for 8 weeks were evaluated. TAA administration elevated serum alkaline phosphatase (AP), γ-glutamyl transpeptidase (γ-GTP) and alanine aminotransferase (ALAT), liver lipid peroxidation, collagen content, depleted liver glycogen and glutathione peroxidase (GPx) activity. Additionally increased levels of a number of proteins were detected including transforming growth factor-beta (TGF-ß), connective tissue growth factor (CTGF) and alpha-smooth muscle actin (α-SMA), and matrix metalloproteinase (MMP)-2, 9 and 13. Coffee suppressed most of the changes produced by TAA. Histopathological analysis was in agreement with biochemical and molecular findings. These results indicate that coffee attenuates experimental cirrhosis; the action mechanisms are probably associated with its antioxidant properties and mainly by its ability to block the elevation of the profibrogenic cytokine TGF-ß and its downstream effector CTGF. Various components of coffee that have been related to such a favorable effect include caffeine, coffee oils kahweol, cafestol and antioxidant substances; however, no definite evidence for the role of these components has been established. These results support earlier findings suggesting a beneficial effect of coffee on the liver. However, more basic clinical studies must be performed to confirm this hypothesis.

Coffee consumption prevents fibrosis in a rat model that mimics secondary biliary cirrhosis in humans.

Investigations demonstrated that oxidative stress plays an important role in injury promotion in cholestatic liver disease. We hypothesized that coffee attenuates cholestasis-induced hepatic necrosis and fibrosis via its antioxidant, anti-inflammatory, and antifibrotic properties. The major aim of this study was to evaluate the hepatoprotective properties of coffee and caffeine in a model of chronic bile duct ligation (BDL) in male Wistar rats. Liver injury was induced by 28-day BDL, and conventional coffee, decaffeinated coffee, or caffeine was administered daily. After treatment, the hepatic oxidative status was estimated by measuring lipid peroxidation, the reduced to oxidized glutathione ratio, and glutathione peroxidase. Fibrosis was assessed by measuring the liver hydroxyproline content. The transforming growth factor-ß, connective tissue growth factor, α-smooth muscle actin, collagen 1, and interleukin-10 proteins and mRNAs were measured by Western blot and polymerase chain reaction, respectively. Conventional coffee suppressed most of the changes produced by BDL; however, caffeine showed better antifibrotic effects. Coffee demonstrated antioxidant properties by restoring the redox equilibrium, and it also prevented the elevation of liver enzymes as well as hepatic glycogen depletion. Interestingly, coffee and caffeine administration prevented collagen increases. Western blot assays showed decreased expression levels of transforming growth factor-ß, connective tissue growth factor, α-smooth muscle actin, and collagen 1 in the coffee- and caffeine-treated BDL groups. Similarly, coffee decreased the mRNA levels of these proteins. We conclude that coffee prevents liver cirrhosis induced by BDL by attenuating the oxidant processes, blocking hepatic stellate cell activation, and downregulating the main profibrotic molecules involved in extracellular matrix deposition.

Naringenin prevents experimental liver fibrosis by blocking TGFß-Smad3 and JNK-Smad3 pathways.

AIM: To study the molecular mechanisms involved in the hepatoprotective effects of naringenin (NAR) on carbon tetrachloride (CCl4)-induced liver fibrosis. METHODS: Thirty-two male Wistar rats (120-150 g) were randomly divided into four groups: (1) a control group (n = 8) that received 0.7% carboxy methyl-cellulose (NAR vehicle) 1 mL/daily p.o.; (2) a CCl4 group (n = 8) that received 400 mg of CCl4/kg body weight i.p. 3 times a week for 8 wk; (3) a CCl4 + NAR (n = 8) group that received 400 mg of CCl4/kg body weight i.p. 3 times a week for 8 wk and 100 mg of NAR/kg body weight daily for 8 wk p.o.; and (4) an NAR group (n = 8) that received 100 mg of NAR/kg body weight daily for 8 wk p.o. After the experimental period, animals were sacrificed under ketamine and xylazine anesthesia. Liver damage markers such as alanine aminotransferase (ALT), alkaline phosphatase (AP), γ-glutamyl transpeptidase (γ-GTP), reduced glutathione (GSH), glycogen content, lipid peroxidation (LPO) and collagen content were measured. The enzymatic activity of glutathione peroxidase (GPx) was assessed. Liver histopathology was performed utilizing Masson's trichrome and hematoxylin-eosin stains. Zymography assays for MMP-9 and MMP-2 were carried out. Hepatic TGF-ß, α-SMA, CTGF, Col-I, MMP-13, NF-κB, IL-1, IL-10, Smad7, Smad3, pSmad3 and pJNK proteins were detected via western blot. RESULTS: NAR administration prevented increases in ALT, AP, γ-GTP, and GPx enzymatic activity; depletion of GSH and glycogen; and increases in LPO and collagen produced by chronic CCl4 intoxication (P < 0.05). Liver histopathology showed a decrease in collagen deposition when rats received NAR in addition to CCl4. Although zymography assays showed that CCl4 produced an increase in MMP-9 and MMP-2 gelatinase activity; interestingly, NAR administration was associated with normal MMP-9 and MMP-2 activity (P < 0.05). The anti-inflammatory, antinecrotic and antifibrotic effects of NAR may be attributed to its ability to prevent NF-κB activation and the subsequent production of IL-1 and IL-10 (P < 0.05). NAR completely prevented the increase in TGF-ß, α-SMA, CTGF, Col-1, and MMP-13 proteins compared with the CCl4-treated group (P < 0.05). NAR prevented Smad3 phosphorylation in the linker region by JNK since this flavonoid blocked this kinase (P < 0.05). CONCLUSION: NAR prevents CCl4 induced liver inflammation, necrosis and fibrosis, due to its antioxidant capacity as a free radical inhibitor and by inhibiting the NF-κB, TGF-ß-Smad3 and JNK-Smad3 pathways.

Nicotinic acid prevents experimental liver fibrosis by attenuating the prooxidant process.

UNLABELLED: Liver fibrosis is the excessive accumulation of extracellular matrix proteins that occurs in most chronic liver diseases. Nicotinamide treatment has been shown to prevent collagen accumulation and fibrogenesis in a bleomycin model of lung fibrosis. In this study, we evaluated the effects of nicotinic acid (NA) on experimental liver fibrosis and investigated its underlying mechanism. METHODS: Fibrosis was induced by chronic TAA administration and the effects of co-administration with NA for 8 weeks were evaluated, including control groups. RESULTS: TAA administration induced liver fibrosis, which was prevented by nicotinic acid. NA prevented the elevation of liver enzymes and prevented hepatic glycogen depletion. Liver histopathology and hydroxyproline levels were significantly lower in the rats treated with TAA plus NA compared with TAA only. NA demonstrated antioxidant properties by restoring the redox equilibrium (lipid peroxidation and GPx levels). Western blot assays showed decreased expression levels of TGF-ß and its downstream inductor CTGF. Additionally, NA prevented hepatic stellate cell activation due by blocking the expression of α-SMA. Zymography assays showed that NA decreased the activity of matrix metalloproteinases 2 and 9. CONCLUSIONS: NA prevents experimental fibrosis; the mechanisms of action are associated with its antioxidant properties and the reduction in TGF-ß expression. The decrease in TGF-ß levels may be associated with the attenuation of the oxidative processes, thus resulting in a reduction in HSC activation and ECM deposition. The findings suggest a possible role for NA as an antifibrotic agent for liver injury.

Caffeine prevents experimental liver fibrosis by blocking the expression of TGF-ß.

BACKGROUND: There is a growing body of evidence that caffeine exerts beneficial effects on the liver; however, the molecular mechanisms by which caffeine exerts beneficial effects on the liver are poorly defined. AIMS: The aim of the present study was to examine the efficacy of caffeine in preventing thioacetamide (TAA)-induced cirrhosis in rats. MATERIALS AND METHODS: Cirrhosis was induced by chronic TAA administration and the effects of coadministration of caffeine for 8 weeks were evaluated, including control groups. RESULTS: The administration of TAA induced liver cirrhosis, which was inhibited by caffeine. Caffeine prevents elevation of liver enzymes. Liver histopathology and hydroxyproline levels were significantly lower in the rats treated with TAA plus caffeine compared with TAA only. Caffeine shows antioxidant properties by restoring the redox equilibrium [lipid peroxidation and glutathione peroxidase (GPx) levels]. Western blot assays showed blockade of the expression of transforming growth factor-ß and its downstream inductor connective tissue growth factor. Similarly, caffeine decreases messenger RNA levels of these profibrogenic proteins. In addition, caffeine inhibits hepatic stellate cells because of blockade of the expression of α-smooth muscle actin; in the western blot assay, we also found low levels of mRNA of collagen α1. Zymography assays showed that caffeine had an effect on the activity of matrix metalloproteinases 2 and 9, but no effect on the expression of tissue inhibitor of metalloproteinases-1, using RT-PCR. CONCLUSION: Our results show that caffeine prevents experimental cirrhosis; the mechanisms of action are associated with its antioxidant properties and mainly by its ability to block the elevation of the profibrogenic cytokine transforming growth factor-ß, which may be associated with attenuation of the inflammatory and fibrotic processes.

Coffee and liver diseases.

Coffee consumption is worldwide spread with few side effects. Interestingly, coffee intake has been inversely related to the serum enzyme activities gamma-glutamyltransferase, and alanine aminotransferase in studies performed in various countries. In addition, epidemiological results, taken together, indicate that coffee consumption is inversely related with hepatic cirrhosis; however, they cannot demonstrate a causative role of coffee with prevention of liver injury. Animal models and cell culture studies indicate that kahweol, diterpenes and cafestol (some coffee compounds) can function as blocking agents by modulating multiple enzymes involved in carcinogenic detoxification; these molecules also alter the xenotoxic metabolism by inducing the enzymes glutathione-S-transferase and inhibiting N-acetyltransferase. Drinking coffee has been associated with reduced risk of hepatic injury and cirrhosis, a major pathogenic step in the process of hepatocarcinogenesis, thus, the benefit that produces coffee consumption on hepatic cancer may be attributed to its inverse relation with cirrhosis, although allowance for clinical history of cirrhosis did not completely account for the inverse association. Therefore, it seems to be a continuum of the beneficial effect of coffee consumption on liver enzymes, cirrhosis and hepatocellular carcinoma. At present, it seems reasonable to propose experiments with animal models of liver damage and to test the effect of coffee, and/or isolated compounds of this beverage, not only to evaluate the possible causative role of coffee but also its action mechanism. Clinical prospective double blind studies are also needed.