Nitrotyrosine formation and heme oxygenase-1 expression in endotoxemic cirrhotic rats

Effect of curcumin on hepatic heme oxygenase 1 expression in high fat diet fed rats: is there a triangular relationship?

High fat diet (HFD) is associated with oxidative stress induced fatty liver. Curcumin, an extract of Curcuma longa, has been shown to possess potent antioxidant and hypolipidemic properties. In this study, we investigated the effect of curcumin treatment on hepatic heme oxygenase-1 (HO-1) expression along with pro-oxidant-antioxidant status and lipid accumulation in rats fed an HFD. Male Sprague-Dawley rats were distributed among 4 groups: Group 1, which was fed the control diet (10% of total calories from fat); Group 2, which was fed the HFD (60% of total calories from fat); and groups 3 and 4, which received the HFD supplemented with curcumin and the control diet supplemented with curcumin (1 g/kg diet; w/w), respectively, for 16 weeks. HFD caused increases in hepatic lipid levels, production of reactive oxygen species, and lipid peroxidation. Further, HO-1 expression was significantly decreased. Histopathological examination showed hepatic fat accumulation and slight fibrotic changes. Curcumin treatment reduced hepatic lipids and oxidative stress parameters, and HO-1 expression was significantly increased. These findings suggest that increased HO-1 expression, along with suppressed oxidative stress as well as reduced hepatic fat accumulation and fibrotic changes, contribute to the beneficial effects of curcumin in attenuating the pathogenesis of fatty liver induced metabolic diseases.

Effects of modulating M3 muscarinic receptor activity on azoxymethane-induced liver injury in mice

Previously, we reported that azoxymethane (AOM)-induced liver injury is robustly exacerbated in M3 muscarinic receptor (M3R)-deficient mice. We used the same mouse model to test the hypothesis that selective pharmacological modulation of M3R activity regulates the liver injury response. Initial experiments confirmed that giving a selective M3R antagonist, darifenacin, to AOM-treated mice mimicked M3R gene ablation. Compared to vehicle controls, mice treated with the M3R antagonist had reduced survival and increased liver nodularity and fibrosis. We next assessed AOM-induced liver injury in mice treated with a selective M3R agonist, pilocarpine. After pilocarpine treatment, stimulation of post-M3R signaling in the liver was evidenced by ERK and AKT activation. In contrast to the damaging effects of the M3R antagonist, administering pilocarpine to AOM-treated mice significantly attenuated hepatic stellate cell activation, collagen deposition, bile ductule proliferation, and liver fibrosis and nodularity. As anticipated from these findings, livers from pilocarpine-treated mice exhibited reduced expression of key players in fibrosis (α1 collagen, α-smooth muscle actin, TGF-β1, PGDF, TGF-β1R, PGDFR) and decreased mRNA levels for molecules that regulate extracellular matrix formation (TIMP-1, TIMP-2, MMP-2, MMP-13). Cleaved caspase-3, nitrotyrosine and BrdU immunostaining provided evidence that pilocarpine treatment reduced hepatocyte apoptosis and oxidative stress, while increasing hepatocyte proliferation. Collectively, these findings identify several downstream mechanisms whereby M3R activation ameliorates toxic liver injury. These novel observations provide a proof-of-principle that selectively stimulating M3R activation to prevent or diminish liver injury is a therapeutic strategy worthy of further investigation.

Biomarkers of oxidative stress in vascular dementia patients

OBJECTIVE

Little is known about the role of oxidative stress in the pathogenesis of vascular dementia (VaD). The aim of this study was to investigate the biomarkers of oxidative stress in urine, as reflected by 8-hydroxydeoxyguanosine (8-OHdG), 8-isoprostaglandin F(2a) (8-isoPGF(2a)) and nitrotyrosine (NT) levels, in a group of well characterized VaD patients and in two control groups of Vascular Not Demented (VaND) patients and health y subjects.

METHODS

Ninety-six subjects from the Tianjin municipality in China were recruited. Forty-six patients were in the VaD group, 24 patients with VaND and 26 persons with no signs of cognitive disorder were employed as control groups. Urinary 8-OHdG and 8-isoPGF(2a) was performed using enzyme-linked immunosorbent assay (ELISA), and urinary NT levels were measured by chemiluminescence detection.

RESULTS

Significantly higher urinary 8-OHdG levels were detected in VaD patients compared to VaND patients and healthy control subjects. In contrast, urinary 8-isoPGF(2a) levels were significantly lower in VaD patients compared with two control groups. For NT levels, no statistically significant differences were observed among the three groups.

CONCLUSION

Increased urinary 8-OHdG level was a potential marker of oxidative stress in VaD patients. Furthermore, it is also important to take into account potential confounders in order to improve the identification of changes in the status of oxidative stress as related to VaD.

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

BACKGROUND AND OBJECTIVE

Nitric oxide and reactive oxygen species have been implicated in several pathophysiological events leading to fibrosis and cirrhosis. The aim of the present study was to investigate the possible contribution of peroxynitrite (formed by the interaction of nitric oxide and superoxide anion) in the pathophysiology of cirrhosis.

METHODS

Twenty-six cirrhotic patients classified as Child-Pugh A, and seven as Child-Pugh B, were included in the study, and nine healthy volunteers served as controls. Levels of nitrite/nitrate (NOx), thiobarbituric acid-reactive substances (TBARS), nitrotyrosine (peroxynitrite marker), superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) were measured in blood samples.

RESULTS

NOx, TBARS, CAT, SOD and GSH levels were higher in cirrhosis patients than in the controls (NOx: 0.17 ± 0.02, 0.95 ± 0.12, 1.3 ± 0.1; TBARS: 2.0 ± 0.05, 4.6 ± 0.3, 5 ± 0.3; CAT: 1.8 ± 0.1, 4 ± 0.3, 4.5 ± 0.4; SOD: 1.8 ± 0.2, 4.8 ± 0.5, 7 ± 0.4; and GSH: 1.3 ± 0.05, 3.6 ± 0.3, 4.5 ± 0.6 in controls, and Child-Pugh A and B patients, respectively). However, there were no differences in nitrotyrosine levels across these groups (controls: 11.4 ± 0.4; Child-Pugh A: 11.1 ± 0.4; Child-Pugh B: 11.9 ± 1.6). NOx levels showed significant and strongly positive correlations with TBARS, SOD, CAT and GSH levels. In contrast, no correlations were found between either NOx or TBARS and nitrotyrosine levels.

CONCLUSION

Nitric oxide and reactive oxygen species, but not peroxynitrite, are overproduced in patients with cirrhosis in spite of evidence of an increase in antioxidant defenses. This suggests that therapeutic measures aimed at attenuating oxidative stress as well as increasing antioxidant defenses may well benefit patients with cirrhosis.

Honokiol rescues sepsis-associated acute lung injury and lethality via the inhibition of oxidative stress and inflammation

PURPOSE

Sepsis has a high mortality rate despite the recent advances in intensive care medicine and antibiotics. Honokiol, a low molecular weight natural product, is known to possess anti-inflammatory activity. Here, we investigate whether honokiol can ameliorate acute lung injury and lethal response in murine models of sepsis.

METHODS

Mice were intraperitoneally given vehicle or honokiol 30 min after the induction of sepsis by cecal ligation and puncture (CLP) and endotoxemia by administration of E. coli lipopolysaccharide (LPS).

RESULTS

The productions of serum tumor necrosis factor-α (TNF-α), nitric oxide (NO), and high mobility group box 1 (HMGB 1) were increased in mice during sepsis, which could be reversed by honokiol. Honokiol could also effectively reduce the increased blood lipid peroxidation and nitrotyrosine in septic mice. Honokiol significantly reversed the inductions of inducible NO synthase and nuclear factor-κB (NF-κB) activation in the lungs of mice during sepsis. Honokiol also effectively rescued the lung edema, lung pathological changes, and lethality in septic mice.

CONCLUSIONS

These findings suggest that honokiol is capable of suppressing the lethal response and acute lung injury associated with sepsis, and support the potential use of honokiol as a therapeutic agent for the conditions associated with septic shock.

Increased plasma malondialdehyde in patients with viral cirrhosis and its relationships to plasma nitric oxide, endotoxin, and portal pressure

BACKGROUND AND AIM

Increased oxidative stress is involved in the development of portal hypertension in cirrhosis. Our study aimed to assess the relationship between oxidative stress and hemodynamic parameters in cirrhotic patients.

METHODS

Forty-two patients with viral cirrhosis and 24 normal controls were enrolled. Measurements of plasma levels of malondialdehyde (MDA), nitrite/nitrate (NOx), endotoxin, and activities of superoxide dismutase (SOD) were carried out in all subjects. Systemic and splanchnic hemodynamic measurements were carried out in cirrhotic patients.

RESULTS

Plasma levels of MDA, endotoxin, and NOx were significantly higher in cirrhotic patients than in normal controls (900 +/- 751 versus 226 +/- 16 nM, P < 0.01; 62.0 +/- 26.0 versus 14.8 +/- 4.1 pg/mL, P < 0.01; 50.5 +/- 22.6 versus 15.0 +/- 9.2 nM, P < 0.01, respectively). Activities of SOD were significantly decreased in cirrhotic patients compared with in normal controls (2.62 +/- 0.7 versus 6.8 +/- 0.4 U/mL). Further, plasma levels of MDA in cirrhotic patients were significantly positively associated with hepatic venous pressure gradient (HVPG) (r = 0.35; P = 0.025), wedge hepatic venous pressure (WHVP) (r = 0.42; P = 0.007), and hepatic sinusoid resistance (HSR) (r = 0.33; P = 0.033). Plasma MDA levels also correlated positively with plasma endotoxin (r = 0.71, P < 0.001) and NOx (r = 0.55, P < 0.001) levels in the cirrhotic patients. Multiregression analysis showed that the independent and strongest factors to predict HVPG, WHVP, and HSR are plasma levels of NOx, MDA, and endotoxin, respectively.

CONCLUSION

This study suggests a close interaction among MDA, endotoxin, and NOx and that these substances are also associated with hemodynamic derangement in cirrhosis.

Oxidative and nitrosative stress and apoptosis in the liver of rats fed on high methionine diet: protective effect of taurine

OBJECTIVE

There are few reports about the direct toxic effects of hyperhomocysteinemia on the liver. We investigated oxidative and nitrosative stresses and apoptotic and necrotic changes in the liver of rats fed a high-methionine (HM) diet (2%, w/w) for 6 mo. We also investigated whether taurine, an antioxidant amino acid, is protective against an HM-diet-induced toxicity in the liver.

METHODS

Lipid peroxide levels, nitrotyrosine formation, and non-enzymatic and enzymatic antioxidants were determined in livers of rats fed an HM diet. In addition, apoptosis-related proteins, proapoptotic Bax and antiapoptotic B-cell lymphoma-2 expressions, apoptotic cell count, histopathologic appearance in the liver, and alanine transaminase and aspartate transaminase activities in the serum were investigated.

RESULTS

Plasma homocysteine levels and serum alanine transaminase and aspartate transaminase activities were increased after the HM diet. This diet resulted in increases in lipid peroxide and nitrotyrosine levels and decreases in non-enzymatic and enzymatic antioxidants in liver homogenates in rats. Bax expression increased, B-cell lymphoma-2 expression decreased, and apoptotic cell number increased in livers of rats fed an HM diet. Inflammatory reactions, microvesicular steatosis, and hepatocyte degeneration were observed in the liver after the HM diet. Taurine (1.5%, w/v, in drinking water) administration and the HM diet for 6 mo was found to decrease serum alanine transaminase and aspartate transaminase activities, hepatic lipid peroxide levels, and nitrotyrosine formation without any change in serum homocysteine levels. Decreases in Bax expression, increases in B-cell lymphoma-2 expression, decreases in apoptotic cell number, and amelioration of histopathologic findings were observed in livers of rats fed with the taurine plus HM diet.

CONCLUSION

Our results indicate that taurine has protective effects on hyperhomocysteinemia-induced toxicity by decreasing oxidative and nitrosative stresses, apoptosis, and necrosis in the liver.

Preventive effects of ME3738 on hepatic fibrosis induced by bile duct ligation in rats

AIM

The aim of this study was to examine the preventive effects of ME3738 on hepatic fibrosis induced by bile duct ligation (BDL) in rats.

METHODS

ME3738 (20 mg/day) was administered orally for 21 days immediately after BDL. Fibrosis was assessed by measuring hepatic hydroxyproline (Hyp) content. Activated hepatic stellate cells (HSCs) were assessed by alpha-smooth muscle actin (alpha-SMA) immunostaining. Hepatic thiobarbituric acid-reactive substance (TBARS), 4-hydroxy-2-nonenal (4-HNE) and 8-hydroxy-2-deoxyguanosine (8-OHdG) immunostaining were used to analyze oxidative stress. The gene expressions of collagen-I, transforming growth factor-beta1 (TGF-beta1), tissue inhibitor of metalloproteinases-1 (TIMP-1), interleukin-6 (IL-6) and heme oxygenase-1 (HO-1) in the liver were examined by real-time reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Hepatic Hyp content and the area of hepatic fibrosis in BDL rats treated with ME3738 were reduced by 24% and 39% compared with non-treated BDL rats (hepatic Hyp, 9.40 +/- 2.85 vs. 12.39 +/- 3.91 mg/liver; P = 0.036; area of hepatic fibrosis, 13.1 +/- 3.8 vs. 21.5 +/- 10.9; P = 0.045). Furthermore, alpha-SMA-positive cells were significantly reduced by 40% (22.3 +/- 14.8 vs. 37.6 +/- 14.2; P = 0.011), collagen-I mRNA by 83% (6.5 +/- 2.2 vs. 38.3 +/- 9.1; P = 0.002), HO-1 mRNA by 58% (4.13 +/- 1.22 vs. 9.73 +/- 1.80; P = 0.018) and hepatic HO-1 content by 26% (2.13 +/- 0.80 vs. 2.87 +/- 0.19; P = 0.01) following ME3738 treatment. The hepatic expression of TBARS, 4-HNE, 8-OHdG and mRNA levels of TGF-beta1, TIMP-1 and IL-6 in the liver were unchanged by ME3738 treatment.

CONCLUSION

Oral ME3738 administration may prevent the progression of hepatic fibrosis in BDL rats through suppression of the activation and collagen synthesis of HSC and, in part, oxidative stress. ME3738 has potential as a therapeutic drug for cholestatic liver fibrosis.