Responses of growth performance and tryptophan metabolism to oxidative stress induced by diquat in weaned pigs

During many pathological conditions, the tryptophan concentration in blood may be reduced. However, the effects of oxidative stress on tryptophan metabolism remain unknown. In this study, we investigated the effects of oxidative stress on growth performance and tryptophan metabolism in weaned pigs. A total of 24 weaned pigs were assigned to one of three treatments that included pigs fed ad libitum (control), pigs challenged with diquat at a dose of 10 mg/kg BW and fed ad libitum (oxidative stress) or pigs pair-fed to receive the same amount of feed as the diquat-challenged pigs. The trial lasted for 7 days. The growth performance and activities of antioxidant enzymes were declined in diquat-challenged pigs. The diquat challenge decreased the tryptophan concentration in serum and the 5-hydroxytryptamine concentration in the hypothalamus, and increased large neutral amino acids, kynurenine (Kyn) and malondialdehyde in serum. The 544-bp porcine partial mRNA sequence of the tryptophan 2,3-dioxygenase (TDO) gene was obtained according to the conserved region in the human gene sequence. In addition, the oxidative stress induced by the diquat challenge stimulated TDO-relative mRNA abundance in the liver and γ-glutamyl transpeptidase activity in intestinal mucosa, but did not affect the mRNA levels of Na+-neutral amino acid transporter B0. These results suggested that oxidative stress induced by diquat depressed growth performance and increased metabolism of tryptophan via Kyn pathway that upregulated TDO mRNA expression in weaned pigs.     

Melatonin protects against taurolithocholic‐induced oxidative stress in rat liver

Cholestasis, encountered in a variety of clinical disorders, is characterized by intracellular accumulation of toxic bile acids in the liver. Furthermore, oxidative stress plays an important role in the pathogenesis of bile acids. Taurolithocholic acid (TLC) was revealed in previous studies as the most pro‐oxidative bile acid. Melatonin, a well‐known antioxidant, is a safe and widely used therapeutic agent. Herein, we investigated the hepatoprotective role of melatonin on lipid and protein oxidation induced by TLC alone and in combination with FeCl₃ and ascorbic acid in rat liver homogenates and hepatic membranes. The lipid peroxidation products, malondialdehyde and 4‐hydroxyalkenals (MDA + 4‐HDA), and carbonyl levels were quantified as indices of oxidative damage to hepatic lipids and proteins, respectively. In the current study, the rise in MDA + 4‐HDA levels induced by TLC was inhibited by melatonin in a concentration‐dependent manner in both liver homogenates and in hepatic membranes. Melatonin also had protective effects against structural damage to proteins induced by TLC in membranes. These results suggest that the indoleamine melatonin may potentially act as a protective agent in the therapy of those diseases that involve bile acid toxicity. J. Cell. Biochem. 110: 1219–1225, 2010. Published 2010 Wiley‐Liss, Inc.     

Effect of melatonin on cholestatic oxidative stress under constant light exposure

This study was designed to evaluate the effect of melatonin on cholestatic oxidative stress under constant light exposure. Cholestasis was induced by double ligature and section of the extra-hepatic bile duct. Melatonin was injected i.p.(1000 microg kg(-1) day(-1)). Malondialdehyde, reduced glutathione, catalase, superoxide dismutase, glutathione reductase, peroxidase and transferase were determined in liver. After bile-duct obstruction and under constant light exposure, an increase in malondialdehyde (p < 0.05) and a slight decrease in reduced glutathione were seen. Enzyme activity, with the exception of glutathione reductase, had significantly diminished. After melatonin administration, malondialdehyde fell (p < 0.001), whereas there was an increase in reduced glutathione (p < 0.0001) compared with untreated controls. Constant light exposure was associated with an increase in hepatic oxidative stress. Treatment with melatonin decreased lipid peroxide synthesis, and permitted a recovery of both reduced glutathione and scavenger enzyme activity.     

Melatonin attenuates methotrexate‐induced oxidative stress and renal damage in rats

Nephrotoxicity is an adverse side effect of methotrexate (MTX) chemotherapy. The present study verifies whether melatonin, an endogenous antioxidant prevents MTX‐induced renal damage. Adult rats were administered 7 mg/kg body weight MTX intraperitoneally for 3 days. In the melatonin pretreated rats, 40 mg/ kg body weight melatonin was administered daily intraperitoneally 1 h before the administration of MTX. The rats were killed 12 h after the final dose of MTX/vehicle. The kidneys were used for light microscopic and biochemical studies. The markers of oxidative stress were measured along with the activities of the antioxidant enzymes and myeloperoxidase activity in the kidney homogenates. Pretreatment with melatonin reduced MTX induced renal damage both histologically and biochemically as revealed by normal plasma creatinine levels. Melatonin pretreatment reduced MTX induced oxidative stress, alteration in the activity of antioxidant enzymes as well as elevation in myeloperoxidase activity. The results suggest that melatonin has the potential to reduce MTX induced oxidative stress, neutrophil infiltration as well as renal damage. As melatonin is an endogenous antioxidant and is non‐toxic even in high doses it is suggested that melatonin may be beneficial in minimizing MTX induced renal damage in humans. Copyright © 2010 John Wiley & Sons, Ltd.     

Tryptophan metabolism and oxidative stress in patients with Huntington's disease

Abnormalities in the kynurenine pathway may play a role in Huntington's disease (HD). In this study, tryptophan depletion and loading were used to investigate changes in blood kynurenine pathway metabolites, as well as markers of inflammation and oxidative stress in HD patients and healthy controls. Results showed that the kynurenine : tryptophan ratio was greater in HD than controls in the baseline state and after tryptophan depletion, indicating increased indoleamine dioxygenase activity in HD. Evidence for persistent inflammation in HD was provided by elevated baseline levels of C-reactive protein, neopterin and lipid peroxidation products compared with controls. The kynurenate : kynurenine ratio suggested lower kynurenine aminotransferase activity in patients and the higher levels of kynurenine in patients at baseline, after depletion and loading, do not result in any differences in kynurenic acid levels, providing no supportive evidence for a compensatory neuroprotective role for kynurenic acid. Quinolinic acid showed wide variations in blood levels. The lipid peroxidation data indicate a high level of oxidative stress in HD patients many years after disease onset. Levels of the free radical generators 3-hydroxykynurenine and 3-hydroxyanthranilic acid were decreased in HD patients, and hence did not appear to contribute to the oxidative stress. It is concluded that patients with HD exhibit abnormal handling of tryptophan metabolism and increased oxidative stress, and that these factors could contribute to ongoing brain dysfunction.     

Melatonin effect on renal oxidative stress under constant light exposure

Recently, numerous studies have shown antioxidant actions of melatonin. Melatonin at both physiological and pharmacological levels stimulates glutathione peroxidase, glutathione reductase and superoxide dismutase activities in the brains of rats and chickens. This study was designed to evaluate the effect of melatonin on nephropathy and oxidative stress under constant light exposure. Nephropathy was induced by adriamycin administered in a single dose (25 mg kg(-1) b.w., i.p.). Melatonin was injected i.p. (1,000 microg kg(-1) b.w./day). Malondialdehyde, reduced glutathione, glutathione peroxidase, glutathione reductase, glutathione transferase, catalase and superoxide dismutase were determined in kidney. Urea, creatinine and total proteins in plasma and proteinuria were evaluated and melatonin was determined. Results show a decrease in melatonin levels. Similar effects occurred with the antioxidant enzyme activities and reduced glutathione. Likewise, adriamycin and constant light induced significant enhancement of malondialdehyde. All changes induced both by adriamycin and constant light were reverted to normal by melatonin administration. Constant light exposure was associated with an increase in oxidative stress and nephropathy induced by adriamycin. Treatment with melatonin decreased lipid peroxides, and permitted a recovery of reduced glutathione, scavenger enzyme activity and parameters of renal function.     

Hepatitis B virus replication is cell cycle independent during liver regeneration in transgenic mice.

The content of hepatitis B virus (HBV) replicative forms and HBV core protein in the liver of HBV transgenic mice is transiently reduced during massive liver regeneration following partial hepatectomy while the steady-state content of viral RNA is unchanged. This antiviral effect is triggered by interferon and tumor necrosis factor that are induced in the liver following hepatectomy and either prevent the formation or accelerate the degradation of viral nucleocapsids in the cytoplasm of the hepatocyte. Despite massive hepatocellular turnover, this effect is independent of liver cell division, indicating that HBV replicates efficiently in resting and dividing hepatocytes.     

Walker-256 tumor growth causes oxidative stress in rat brain

The elevated rate of oxygen consumption and high amount of polyunsaturated fatty acids make the central nervous system vulnerable to oxidative stress. The effect of Walker-256 tumor growth on oxi-reduction indexes in the hypothalamus (HT), cortex (CT), hippocampus (HC) and cerebellum (CB) of male Wistar rats was investigated. The presence of the tumor caused an increase in thiobarbituric acid reactant substances (TBARs) in the HT, CB and HC. Due to tumor growth, the activity of glucose-6-phosphate dehydrogenase increased in the HT and CB, whereas citrate synthase activity was reduced in the HT, CT and CB. Therefore, the potential for generation of reducing power is increased in the cytosol and decreased in the mitochondria of various brain regions of Walker-256 tumor-bearing rats. These changes occurred concomitantly with an unbalance in the brain enzymatic antioxidant system. The tumor decreased the activities of catalase in the HT and CB and of glutathione peroxidase in the HT, CB and HC, and raised the CuZn-superoxide dismutase activity in the HT, CB and HC. These combined findings indicate that Walker-256 tumor growth causes oxidative stress in the brain.     

Protective effect of hypoglycemic granule against diabetes-induced liver injury by alleviating glycolipid metabolic disorder and oxidative stress

The current study was designed to explore the therapeutic effect and mechanism of different extraction, which came from hypoglycemic granule on diabetes-induced liver injury. The ethanol fraction (HGEF) and aqueous fraction (HGAF) from hypoglycemic granule were prepared and administered p.o. to diabetic mice for 17 weeks after 6 weeks of constructing the model. Hematoxylin-eosin (HE) staining and periodic acid-Schiff (PAS) staining were individually applied to observe the morphological change and glycogen deposition. In addition, Oil Red O staining was adopted in lipid droplets detection. Western blot analysis was performed to evaluate the protein expression. The commercial biochemical kits were used to determine the fasting blood glucose value, enzyme activity, and some biochemical indicators. HGEF not only significantly decreased the levels of blood glucose, the content of triglycerides, total cholesterol, low-density lipoprotein, and lipid droplet accumulation, but also remarkably enhanced the high-density lipoprotein, glycogen synthesis, and further improved the hepatic function in diabetic mice. Moreover, HGEF increased the superoxide dismutase (SOD) activity and inhibited the malondialdehyde production, so did HGAF. HGAF performed potential to modulate lipid metabolism via decreasing TG and LDL levels. Further, the protein expressions of SOD, nuclear factor erythroid 2-related factor 2 (Nrf2), and forkhead box O3 (Foxo3a) were increased by HGEF, whereas the receptor-interacting serine-threonine kinase 3 (RIP3), calcium/calmodulin-dependent protein kinase II (CaMKII), and cytochrome c (Cyt c) expressions were inhibited. Our present results suggest that HGEF has superiority in ameliorating oxidative stress via modulating hepatic glycolipid metabolism homeostasis in low-dose streptozotocin-induced liver tissue of diabetic mice.     

The effect of melatonin on glycoprotein levels and oxidative liver injury in experimental diabetes

In this present study, the duration of melatonin (Mel) administered to diabetic rats was prolonged so as to examine its effects on the biochemical liver parameters of diabetic rats. In the experiment, Male Sprague Dawley rats were divided randomly into five groups; the control, diabetic + Mel, diabetic, diabetic + insulin, and diabetic + Mel + insulin. Diabetes mellitus was induced by administration of a single dose of streptozotocin (60 mg/kg) intraperitoneally and rats were given vehicle as a solvent for Mel every day for 12 weeks. In the diabetic + Mel group, diabetic rats were administered Mel (10 mg/kg/day) for 12 weeks to treat diabetes. The diabetic + insulin group were diabetic rats given insulin (6 U/kg) subcutaneously for 12 weeks. The diabetic + Mel + insulin rats received insulin and Mel at the same dose and time. At the end of the experiment, the animals were decapitated and liver tissues were taken. The protective effect of Mel on liver tissue of diabetic rats was investigated, total antioxidant status, total oxidant status, reactive oxygen species, oxidative stress index, adenosine deaminase, xanthine oxidase, paraoxonase 1, sodium/potassium ATPase, myeloperoxidase, γ-glutamyl transferase, sorbitol dehydrogenase, tumor necrosis factor-alpha, homocysteine, nitric oxide, glucose-6-phosphate dehydrogenase, and glycoprotein levels were determined in liver tissues. Treatment with Mel and/or insulin has been found to have a protective effect on biochemical parameters. The results showed that administration of Mel to diabetic rats prevented the distortion of the studied biochemical parameters of liver tissues.     

Neuroprotective effect of melatonin on radiation-induced oxidative stress and apoptosis in the brainstem of rats

This study aimed to determine the effects of melatonin on irradiation-induced apoptosis and oxidative stress in the brainstem region of Wistar rats. Therefore, the animals underwent whole-brain X-radiation with a single dose of 25 Gy in the presence or absence of melatonin pretreatment at a concentration of 100 mg/kg BW. The rats were allocated into four groups (10 rats in each group): namely, vehicle control (VC), 100 mg/kg of melatonin alone (MLT), irradiation-only (RAD), and irradiation plus 100 mg/kg of melatonin (RAM). An hour before irradiation, the animals received intraperitoneal (IP) melatonin and then were killed after 6 hr, followed by measurement of nitric oxide (NO), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and total antioxidant capacity (TAC) in the brainstem region. Furthermore, the western blot analysis technique was performed to assess the caspase-3 expression level. Results showed significantly higher MDA and NO levels in the brainstem tissues for the RAD group when compared with the VC group (p < .001). Moreover, the irradiated rats exhibited a significant decrease in the levels of CAT, SOD, GPx, and TAC (p < .01, p < .001, p < .001, and p < .001, respectively) in comparison to the VC group. The results of apoptosis assessment revealed that the expression level of caspase-3 significantly rose in the RAD group in comparison with the VC group (p < .001). Pretreatment with melatonin ameliorated the radiation-induced adverse effects by decreasing the MDA and NO levels (p < .001) and increasing the antioxidant enzyme activities (p < .001). Consequently, the caspase-3 protein expression level in the RAM group showed a significant reduction in comparison with the RAD group (p < .001). In conclusion, melatonin approximately showed a capacity for neuroprotective activity in managing irradiation-induced oxidative stress and apoptosis in the brainstem of rats; however, the use of melatonin as a neuroprotective agent in humans requires further study, particularly clinical trials.     

Correction: Hepatitis B virus infection and replication in human bone marrow mesenchymal stem cells

ABSTRACT: Correction After publication of this work (Virol J 2011, 8:486), we noted that D of Figure 1 was incorrect. Now the correct figure has been provided with this correction.     

Hepatitis B virus X protein stimulates the mitochondrial translocation of Raf-1 via oxidative stress

The human hepatitis B virus (HBV) X protein (HBx) plays a crucial role(s) in the viral life cycle and contributes to the onset of hepatocellular carcinoma (HCC). HBx caused the mitochondrial translocation of Raf-1 kinase either alone or in the context of whole-viral-genome transfections. Mitochondrial translocation of Raf-1 is mediated by HBx-induced oxidative stress and was dependent upon the phosphorylation of Raf-1 at the serine338/339 and Y340/341 residues by p21-activated protein kinase 1 and Src kinase, respectively. These studies provide an insight into the mechanisms by which HBV induces intracellular events relevant to liver disease pathogenesis, including HCC.     

The protective effect of melatonin against cypermethrin-induced oxidative stress damage in Spodoptera litura (Lepidoptera: Noctuidae)

Antioxidant enzymes form the first-line defense against free radicals damage in organisms. Their regulation depends mainly on the oxidant and antioxidant status of the cell, given that oxidants are their principal modulators. Therefore, the aim of the present study was to investigate the effect of melatonin on synthetic pyrethroid insecticide-induced antioxidative enzymes activity in Spodoptera litura larvae. In addition, activities of enzymatic antioxidants viz. superoxide dismutase (SOD), glutathione S-transferase (GST), catalase (CAT), glutathione reductase (GR), α, β-esterase, and acetylcholine esterase (AChE) were assessed. There was no significant change in GST levels in the melatonin-treated groups. Melatonin modulates cypermethrin-induced changes in the activities of esterase and AChE, whereas SOD, CAT, and GR activity was significantly increased in melatonin-treated samples when compared to control. In conclusion, the results of the current study revealed that SP toxicity activated oxidant systems in all antioxidant systems in some tissues of insects. Melatonin administration led to a marked increase in antioxidant activity and inhibited GST and AChE in most of the tissues studied.     

Role of oxidative stress in the pathogenesis of alcohol-induced liver disease

Abstract

Chronic alcohol consumption is a well-known risk factor for liver disease, which represents a major cause of morbidity and mortality worldwide. The pathological process of alcohol-induced liver disease is characterized by a broad spectrum of morphological changes ranging from steatosis with minimal injury to more advanced liver damage, including steato-hepatitis and fibrosis/cirrhosis. Experimental and clinical studies increasingly show that the oxidative damage induced by ethanol contribute in many ways to the pathogenesis of alcohol hepatotoxicity. This article describes the contribution of oxidative mechanisms to liver damage by alcohol.     

Melatonin reverses the oxidative stress and mitochondrial dysfunction caused by LETM1 silencing

LETM1 is a mitochondrial inner‐membrane protein, which is encoded by a gene present in a locus of 4p, which, in turn, is deleted in the Wolf–Hirschhorn Syndrome, and is assumed to be related to its pathogenesis. The cellular damage caused by the deletion is presumably related to oxidative stress. Melatonin has many beneficial roles in protecting mitochondria by scavenging reactive oxygen species, maintaining membrane potential, and improving functions. The aim of this study was to investigate the effects of melatonin administration to LETM1‐silenced mouse embryonic fibroblast cells as a cellular model for LETM1 deficiency. We transfected mouse embryonic fibroblast cells with a pair of siRNA against LETM1 and monitored the oxidative stress and mitochondrial functions with or without melatonin addition. MnSOD expression and aconitase activity decreased and oxidized protein levels increased in LETM1‐silenced cells. LETM1 suppression did not alter the expression of OXPHOS complexes, but the oxygen consumption rates decreased significantly; however, this change was not related to complex I but instead involved complex IV and complex II. Melatonin supplementation effectively normalized the parameters studied, including the oxygen consumption rate. Our findings identified a novel effect of LETM1 deficiency on cellular respiration via complex II as well as a potential beneficial role of melatonin treatment. On the other hand, these effects may be specific to the cell line used and need to be verified in other cell lines.     

Mutant U2AF1-induced differential alternative splicing causes an oxidative stress in bone marrow stromal cells

Alternative splicing (AS) is a critical regulatory process of gene expression. In bone marrow microenvironment, AS plays a critical role in mesenchymal stem cells fate determination by forming distinct isoforms of important regulators. As a spliceosome factor, U2AF1 is essential for the catalysis of pre-mRNA splicing, and its mutation can cause differential AS events. In the present study, by forced expression of mutant U2AF1 (U2AF1S34F) in the mouse bone marrow stroma OP9 cells, we determine AS changes in U2AF1S34F transduced OP9 cells and investigate their role in stroma cell biological functions. We find that abundant differential RNA splicing events are induced by U2AF1S34F in OP9 cells. U2AF1S34F causes increased generation of hydrogen peroxide, promotes production of cytokines and chemokines. U2AF1S34F transduced OP9 cells also exhibit dysfunction of mitochondria. RNA-seq data, gene ontology (GO), and gene set enrichment analysis reveal that differentially expressed genes downregulated in response to U2AF1S34F are enriched in peroxisome component and function. U2AF1S34F can also cause release of hydrogen peroxide from OP9 cells. Furthermore, we investigate the influence of U2AF1S34F-induced oxidative stress in stromal cells on hematopoietic cells. When co-culturing mouse bone marrow mononuclear cells with OP9 cells, the U2AF1S34F expressing OP9 cells induce phosphorylation of histone H2AX in hematopoietic cells. Collectively, our results reveal that mutant U2AF1-induced differential AS events cause oxidative stress in bone marrow stromal cells and can further lead to DNA damage and genomic instability in hematopoietic cells.