Evaluation of nitrite/nitrate levels in relation to oxidative stress parameters in liver cirrhosis

Microfluidic/HPLC combination to study carnosine protective activity on challenged human microglia: Focus on oxidative stress and energy metabolism

Carnosine (β-alanyl-L-histidine) is a naturally occurring endogenous peptide widely distributed in excitable tissues such as the brain. This dipeptide possesses well-demonstrated antioxidant, anti-inflammatory, and anti-aggregation properties, and it may be useful for treatment of pathologies characterized by oxidative stress and energy unbalance such as depression and Alzheimer's disease (AD). Microglia, the brain-resident macrophages, are involved in different physiological brain activities such synaptic plasticity and neurogenesis, but their dysregulation has been linked to the pathogenesis of numerous diseases. In AD brain, the activation of microglia towards a pro-oxidant and pro-inflammatory phenotype has found in an early phase of cognitive decline, reason why new pharmacological targets related to microglia activation are of great importance to develop innovative therapeutic strategies. In particular, microglia represent a common model of lipopolysaccharides (LPS)-induced activation to identify novel pharmacological targets for depression and AD and numerous studies have linked the impairment of energy metabolism, including ATP dyshomeostasis, to the onset of depressive episodes. In the present study, we first investigated the toxic potential of LPS + ATP in the absence or presence of carnosine. Our studies were carried out on human microglia (HMC3 cell line) in which LPS + ATP combination has shown the ability to promote cell death, oxidative stress, and inflammation. Additionally, to shed more light on the molecular mechanisms underlying the protective effect of carnosine, its ability to modulate reactive oxygen species production and the variation of parameters representative of cellular energy metabolism was evaluated by microchip electrophoresis coupled to laser-induced fluorescence and high performance liquid chromatography, respectively. In our experimental conditions, carnosine prevented LPS + ATP-induced cell death and oxidative stress, also completely restoring basal energy metabolism in human HMC3 microglia. Our results suggest a therapeutic potential of carnosine as a new pharmacological tool in the context of multifactorial disorders characterize by neuroinflammatory phenomena including depression and AD.

High Meat Consumption Is Prospectively Associated with the Risk of Non-Alcoholic Fatty Liver Disease and Presumed Significant Fibrosis

Non-alcoholic fatty liver disease (NAFLD) has been associated with meat consumption in cross-sectional studies. However, only a few prospective studies have been conducted, and they did not test for liver fibrosis. We aimed to assess the association between meat consumption changes and the incidence and remission of NAFLD and significant liver fibrosis. We used a prospective cohort study design, including 316 subjects aged 40–70 years, participating in baseline and follow-up evaluations at Tel-Aviv Medical Center. NAFLD was determined by liver ultrasound or controlled attenuation parameter (CAP), and liver fibrosis was determined by FibroScan. Meat consumption (g/day) was assessed by a food frequency questionnaire (FFQ). In multivariable-adjusted analyses, high consumption of red and/or processed meat (≥gender-specific median) was associated with a higher risk of NAFLD with elevated alanine aminotransferase (ALT) (OR = 3.75, 1.21–11.62, p = 0.022). Consistently high (in both baseline and follow-up evaluations) total meat consumption was associated with 2.55-fold (95% CI 1.27–5.12, p = 0.009) greater odds for new onset and/or persistence of NAFLD compared to consistently low meat consumption. A similar association was shown for consistently high consumption of red and/or processed meat (OR = 2.12, 95% CI 1.11–4.05, p = 0.022). Consistently high red and/or processed meat consumption was associated with 4.77-fold (95% CI 1.36–16.69, p = 0.014) greater odds for significant fibrosis compared to consistently low consumption. Minimizing the consumption of red and/or processed meat may help prevent NAFLD and significant fibrosis.

Antioxidant, Hypoglycemic, and Neurobehavioral Effects of a Leaf Extract of Avicennia marina on Autoimmune Diabetic Mice

Diabetes mellitus (DM) is a metabolic disease that can affect the central nervous system and behavioral traits in animals. Streptozotocin-induced diabetes is considered an autoimmune disease. The aim of the current study was to determine whether supplementation with the alcoholic extract of Avicennia marina leaves could improve diabetes-associated pathological changes. The animals were divided into four groups: a control group (A), an A. marina receiving nondiabetic group (B), a diabetic group (C), and a DM group orally supplemented with A. marina alcoholic leaf extract (D). The DM group of animals receiving the alcoholic extract of A. marina leaves had reduced blood glucose levels, improved blood picture, and organ functions. This group also showed improvement in locomotory behavior. The results of this study showed that supplementation with the alcoholic extract of A. marina leaves reduced oxidative stress and blood sugar levels, protected the liver, and improved the neurobehavioral changes associated with diabetes in mice. Introducing alcoholic leaf extract of A. marina to diabetic mice decreased inflammatory cells aggregation, vacuolation, and hemorrhage. Additionally, a positive effect of the alcoholic leaf extract on the histopathological changes was observed in the testicular tissue of treated mice.

Possible Synergistic Effects of Glutathione and C-Reactive Protein in the Progression of Liver Cirrhosis

Liver cirrhosis is often associated with increased inflammatory responses and changes of glutathione (GSH) status. The possible interactions between these two factors in mediating damages of liver function remain unclear. Here, we measured the inflammatory responses and GSH status in liver cirrhotic patients and compared them with healthy subjects. In addition, we assessed the relationship of the GSH status and levels of inflammatory markers with the severity of the disease. This was a cross-sectional study. In total, we recruited 63 liver cirrhotic patients with Child⁻Turcotte⁻Pugh class A scores, and 12 patients with class B⁻C scores, together with 110 healthy subjects. Patients with class B⁻C scores showed the highest level of high-sensitivity C-reactive protein (hs-CRP) when compared with class A patients or healthy subjects. Patients in class A group had significantly higher GSH levels when compared with class B⁻C group or healthy subjects. After adjusting for potential confounders and each other, serum hs-CRP levels showed positive association with the Child⁻Turcotte⁻Pugh scores, while GSH levels showed negative association with Child⁻Turcotte⁻Pugh scores. Interactions were found between levels of plasma GSH and serum hs-CRP (β = 0.004, p = 0.016). CRP and GSH levels, which had showed interactions, were associated with the severity of liver cirrhosis.

Involvement of Cholinergic and Adrenergic Receptors in Pathogenesis and Inflammatory Response Induced by Alpha-Neurotoxin Bot III of Scorpion Venom

Bot III neurotoxin is the most lethal α neurotoxin purified from Buthus occitanus tunetanus scorpion venom. This toxin binds to the voltage-gated sodium channel of excitable cells and blocks its inactivation, inducing an increased release of neurotransmitters (acetylcholine and catecholamines). This study aims to elucidate the involvement of cholinergic and adrenergic receptors in pathogenesis and inflammatory response triggered by this toxin. Injection of Bot III to animals induces an increase of peroxidase activities, an imbalance of oxidative status, tissue damages in lung parenchyma, and myocardium correlated with metabolic disorders. The pretreatment with nicotine (nicotinic receptor agonist) or atropine (muscarinic receptor antagonist) protected the animals from almost all disorders caused by Bot III toxin, especially the immunological alterations. Bisoprolol administration (selective β1 adrenergic receptor antagonist) was also efficient in the protection of animals, mainly on tissue damage. Propranolol (non-selective adrenergic receptor antagonist) showed less effect. These results suggest that both cholinergic and adrenergic receptors are activated in the cardiopulmonary manifestations induced by Bot III. Indeed, the muscarinic receptor appears to be more involved than the nicotinic one, and the β1 adrenergic receptor seems to dominate the β2 receptor. These results showed also that the activation of nicotinic receptor leads to a significant protection of animals against Bot III toxin effect. These findings supply a supplementary data leading to better understanding of the mechanism triggered by scorpionic neurotoxins and suggest the use of drugs targeting these receptors, especially the nicotinic one in order to counteract the inflammatory response observed in scorpion envenomation.

Involvement of Kallikrein-Kinin System on Cardiopulmonary Alterations and Inflammatory Response Induced by Purified Aah I Toxin from Scorpion Venom

Bradykinins are released from kininogen by kallikrein. They increase capillary lung permeability after their binding to β1 and especially β2 receptors before being metabolized by kininase enzyme. This study was performed to evaluate cardiopulmonary damages and inflammatory response on injected rats with Aah I toxin of scorpion venom and the involvement of Kallikrein-Kinin system in this pathogenesis. Obtained results revealed that Aah I toxin induces inflammatory cell infiltration accompanied by cellular peroxidase activities, a release of cytokine levels, pulmonary and myocardial damage, with altered metabolic activities and imbalanced redox status. Administration of aprotinin (bradykinin inhibitor) and especially icatibant (bradykinin β2 receptor antagonist) seemed to be able to protect animals against the toxicity of Aah I; nevertheless, the use of captopril (kininase II inhibitor) reduced partially some cardiac disorders. These findings indicate that the kallikrein-kinin system may contribute to the physiopathological effect and lung edema formation induced by toxin, which suggests a potential use of drugs with significant anti-kinin properties.

The role of iNOS in cholesterol-induced liver fibrosis

Accumulation of cholesterol in the liver is associated with the development of non-alcoholic steatohepatitis-related fibrosis. However, underlying mechanisms are not well understood. The present study investigated the role of inducible nitric oxide synthase (iNOS) in cholesterol-induced liver fibrosis by feeding wild-type (WT) and iNOS-deficient mice with control or high-cholesterol diet (HCD) for 6 weeks. WT mice fed with HCD developed greater liver fibrosis, compared with iNOS-deficient mice, as evident by Sirius red staining and higher expression levels of profibrotic genes. Enhanced liver fibrosis in the presence of iNOS was associated with hypoxia-inducible factor-1α stabilization, matrix metalloproteinase-9 expression, and enhanced hepatic DNA damage. The profibrotic role of iNOS was also demonstrated in vivo using a selective inhibitor of iNOS as well as in vitro in a rat liver stellate cell line (HSC-T6). In conclusion, these findings suggest that iNOS is an important mediator in HCD-induced liver fibrosis.

Beneficial effects of Androctonus australis hector venom and its non-toxic fraction in the restoration of early hepatocyte-carcinogenesis induced by FB1 mycotoxin: Involvement of oxidative biomarkers

Some venom components are known to present potential biological activities that are useful as tools in therapeutics. In this study anti-tumoral activity of Androctonus australis hector (Aah) venom and its purified fraction on early step of hepato-carcinogenesis initiated by Fumonisin (FB1), was tested. Initiated hepatic tumor was assessed in mice by decreased doses of Fumonisin B1 associated to phenobarbital. Scorpion venom was used to investigate its activity on initiated tumor by FB1. Evaluation of oxidative unbalance, enzymatic activities and DNA quantification in the liver were correlated with tissue analysis. Obtained results showed that the initiated pathogenesis by FB1 at seven months was characterized by tissue alterations and biomarker variations. These alterations were characterized by atypical lesions such as muffled nucleus, karyo- and cyto-megaly; up normal and large number of nuclei into hepatocytes. These alterations were confirmed by DNA alteration. An unbalance of oxidative status was also observed, characterized by an increased levels of respectively oxidant (NO and MDA) and antioxidant (GSH and catalase activity) mediators. Aah venom and its non-toxic fraction used at low doses seemed to be able to restore partially the hepatic altered tissue induced by FB1. Decreased levels of oxidative and anti-oxidative mediators were also observed. DNA in hepatocytes returned also to the physiological values. Structure of hepatic tissue showed restoration of some alterations such as karyo- and cyto-megaly; decrease of polyploidy hepatocytes induced by FB1. Aah venom and its non-toxic fraction seem to contain some bioactive components with anti-tumoral activity. Purification of this activity from non-toxic fraction F1 could be of interest to identify the components with anti-tumoral activities.

Induction of systemic oxidative stress leads to brain oedema in portacaval shunted rats

BACKGROUND & AIMS

The pathogenesis of hepatic encephalopathy (HE) is multifactorial and often associated with the development of brain oedema. In addition to ammonia playing a central role, systemic oxidative stress is believed to aggravate the neuropsychological effects of ammonia in patients with chronic liver disease (CLD). The aim of this study was to (i) induce systemic oxidative stress in hyperammonaemic portacaval anastomosed (PCA) rats by inhibiting the antioxidant glutathione using Dimethyl maleate (DEM) and (ii) investigate whether a synergistic relationship between ammonia and oxidative stress contributes to the pathogenesis of brain oedema in CLD.

METHODS

Four-week PCA and sham-operated rats received DEM (0.4-4 mg/kg/day) for the last 10 days before sacrifice when oxidative stress markers [reactive oxygen species (ROS) and malondialdehyde (MDA)] were assessed in blood and frontal cortex. Brain water content was measured using a specific gravimetric technique.

RESULTS

Dimethyl maleate induced an increase in ROS and MDA in the blood, but not in the brain, of the PCA rats, compared with non-treated PCA rats. This was accompanied with an increase in brain water content (PCA+DEM: 78.45 ± 0.13% vs. PCA: 77.38 ± 0.11%, P < 0.001). Higher doses of DEM induced systemic oxidative stress in sham-operated controls, but brain oedema did not develop.

CONCLUSIONS

Dimethyl maleate provoked systemic, not central, oxidative stress in PCA rats, resulting in the development of brain oedema. Independently, hyperammonaemia and systemic oxidative stress do not precipitate brain oedema; therefore, our findings sustain that a synergistic effect between hyperammonaemia and systemic oxidative stress is responsible for the development of brain oedema in HE.

Liver exhibits thermal variations according to the stage of fibrosis progression: A novel use of modulated-differential scanning calorimetry for research in hepatology

AIM

Liver fibrosis results in a disproportion of the hepatic composition and architecture, characterized by a progressive accumulation of fibrillar proteins at the liver parenchyma. Modulated-differential scanning calorimetry (mDSC) is an experimental methodology able to determine the specific thermal signature from any biological substance, based on the variation in heat flow and heat capacity. As these physicochemical properties are directly influenced by compositional and structural changes, we decided to study the thermal behavior of the liver during fibrosis using mDSC.

METHODS

Liver fibrosis was induced in rats by bile duct ligation or carbon tetrachloride administration. Degree of liver fibrosis was determined by histological examination using the Masson-trichrome stain, accompanied by hepatic expression of α-smooth muscle actin. The thermal analysis was performed in a modulated-differential scanning calorimeter using 20 mg of fresh liver mass.

RESULTS

The liver showed a characteristic thermal signature in control animals, which progressively differed among mild (F1), moderate (F2) and advanced (F3-F4) liver fibrosis. For heat flow, the hepatic thermal signature from F3-F4 rats exhibited significant differences when compared with F1, F2 and controls. In terms of heat capacity, liver specimens provided a specific thermal signature for each stage of disease, characterized by a transition temperature onset at 95°C for controls, whereas in F1, F2 and F3-F4 animals this temperature significantly decreased to 93°C, 84°C and 75°C, respectively.

CONCLUSION

Because the liver shows a differential thermal signature according to the degree of fibrosis, mDSC could be a novel tool in the study of liver fibrosis progression.

Astragaloside IV suppresses collagen production of activated hepatic stellate cells via oxidative stress-mediated p38 MAPK pathway

Oxidative stress is involved in hepatic fibrogenesis. Activation of hepatic stellate cells (HSCs), the key effectors in hepatic fibrogenesis, is characterized by overproduction of extracellular matrix. Astragaloside IV, the active component of Radix Astragali, has antioxidant properties and antifibrotic potential in renal fibrosis. Little is known about the role of astragaloside IV in liver and its involvement in hepatic fibrosis. This study aims at evaluating the antifibrotic potential of astragaloside IV and characterizing involved signal transduction pathways in culture-activated HSCs. Our results show that astragaloside IV attenuates oxidative stress in culture-activated HSCs, as demonstrated by scavenging reactive oxygen species and reducing lipid peroxidation, and elevates the level of cellular glutathione by stimulating Nrf2gene expression. Depletion of cellular glutathione by buthionine sulfoximine or abrogation of p38 MAPK by SB-203580 evidently eliminates the inhibitory effects of astragaloside IV on genes relevant to HSC activation. These results demonstrate that astragaloside IV inhibits HSC activation by inhibiting generation of oxidative stress and associated p38 MAPK activation and provide novel insights into the mechanisms of astragaloside IV as an antifibrogenic candidate in the prevention and treatment of liver fibrosis.

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.

Th2-associated alternative Kupffer cell activation promotes liver fibrosis without inducing local inflammation

Cirrhosis is the final outcome of liver fibrosis. Kupffer cell-mediated hepatic inflammation is considered to aggravate liver injury and fibrosis. Alternatively-activated macrophages are able to control chronic inflammatory events and trigger wound healing processes. Nevertheless, the role of alternative Kupffer cell activation in liver harm is largely unclear. Thus, we evaluated the participation of alternatively-activated Kupffer cells during liver inflammation and fibrosis in the murine model of carbon tetrachloride-induced hepatic damage. To stimulate alternative activation in Kupffer cells, 20 Taenia crassiceps (Tc) larvae were inoculated into BALBc/AnN female mice. Six weeks post-inoculation, carbon tetrachloride or olive oil were orally administered to Tc-inoculated and non-inoculated mice twice per week during other six weeks. The initial exposure of animals to T. crassiceps resulted in high serum concentrations of IL-4 accompanied by a significant increase in the hepatic mRNA levels of Ym-1, with no alteration in iNOS expression. In response to carbon tetrachloride, recruitment of inflammatory cell populations into the hepatic parenchyma was 5-fold higher in non-inoculated animals than Tc-inoculated mice. In contrast, carbon tetrachloride-induced liver fibrosis was significantly less in non-inoculated animals than in the Tc-inoculated group. The latter showed elevated IL-4 serum levels and low IFN-γ concentrations during the whole experiment, associated with hepatic expression of IL-4, TGF-β, desmin and α-sma, as well as increased mRNA levels of Arg-1, Ym-1, FIZZ-1 and MMR in Kupffer cells. These results suggest that alternative Kupffer cell activation is favored in a Th2 microenvironment, whereby such liver resident macrophages could exhibit a dichotomic role during chronic hepatic damage, being involved in attenuation of the inflammatory response but at the same time exacerbation of liver fibrosis.