Sleep deprivation and cellular responses to oxidative stress

STUDY OBJECTIVES: It has been hypothesized that sleep deprivation represents an oxidative challenge for the brain and that sleep may have a protective role against oxidative damage. This study was designed to test this hypothesis by measuring in rats the effects of sleep loss on markers of oxidative stress (oxidant production and antioxidant enzyme activities) as well as on markers of cellular oxidative damage (lipid peroxidation and protein oxidation). DESIGN: The analyses were performed in the brain and in peripheral tissues (liver and skeletal muscle), after short-term sleep deprivation (8 hours), after long-term sleep deprivation (3-14 days), and during recovery sleep after 1 week of sleep loss. Short-term sleep deprivation was performed by gentle handling; long-term sleep deprivation was performed using the disk-over-water method. SETTING: Sleep research laboratory at University of Wisconsin-Madison. PARTICIPANTS AND INTERVENTIONS: Adult male Wistar Kyoto rats (n = 69) implanted for polygraphic (electroencephalogram, electromyogram) recording. MEASUREMENTS AND RESULTS: Aliquots of brain, liver, or skeletal muscle homogenate were used to assess oxidant production, superoxide dismutase activity, lipid peroxidation, and protein oxidation. No evidence of oxidative damage was observed at the lipid and/or at the protein level in long-term sleep-deprived animals relative to their yoked controls, nor in the cerebral cortex or in peripheral tissues. Also, no consistent change in antioxidant enzymatic activities was found after prolonged sleep deprivation, nor was any evidence of increased oxidant production in the brain or in peripheral tissues. CONCLUSION: The available data do not support the assumption that prolonged wakefulness may cause oxidative damage, nor that it can represent an oxidative stress for the brain or for peripheral tissue such as liver and skeletal muscle.     

Sleep Deprivation Alters Gene Expression and Antioxidant Enzyme Activity in Mice Splenocytes

Cellular defence against the formation of reactive oxygen species (ROS) involves a number of mechanisms in which antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD) play an important role. The relation between sleep deprivation and oxidative stress has not yet been completely elucidated. Although some authors did not find evidence of this relationship, others found alterations in some oxidative stress markers in response to sleep deprivation. Thus, the objective of this study was to identify changes induced by sleep deprivation in the activity and gene expression of antioxidant enzymes in mice splenocytes, ideally corroborating a better understanding of the observed effects related to sleep deprivation, which could be triggered by oxidative imbalance. Splenocytes from mice sleep deprived for 72 h showed no significant difference in CAT and CuZnSOD gene expression compared with normal sleep mice. However, sleep‐deprived mice did show higher MnSOD gene expression than the control group. Concerning enzymatic activity, CuZnSOD and MnSOD significantly increased after sleep deprivation, despite the expression in CuZnSOD remained unchanged. Moreover, CAT activity was significantly lower after sleep deprivation. The data suggest that the antioxidant system is triggered by sleep deprivation, which in turn could influence the splenocytes homoeostasis, thus interfering in physiological responses.     

Effects of Lipoic Acid on Proliferation and Apoptosis of Liver Cells in Rats with Metabolic Stress

Lipoic acid stimulated expression of heat shock proteins 25, 70, and 90 in liver cells of Wistar rats with metabolic stress (5 days of food deprivation followed by complete resumption of nutrition). Lipoic acid in a dose of 25 mg/kg reduced proliferation of hepatic lymphocytes during fasting, while after resumption of feeding it stimulated hepatocyte proliferation due to differentiated regulation of the expression of cyclin D1 and Rb protein in these cell populations.     

Effects of S-adenosyl-L-methionine on lipid peroxidation and glutathione levels in rat brain slices exposed to reoxygenation after oxygen-glucose deprivation.

We analyzed the effects of S-adenosyl-L-methionine (AdoMet) on tissue oxidative stress in rat brain slices exposed to reoxygenation after oxygen-glucose deprivation. The thiobarbituric acid reactive substances (TBARS), total and oxidized glutathione, and lactate-dehydrogenase efflux (LDH) from tissue to the incubation medium, were measured. Brain slices were incubated without glucose and with N2, then glucose was added and O2 was perfused. After the anoxic-reoxygenation period, increase in TBARS, oxidized glutathione and LDH efflux, and decrease in total glutathione levels, were observed. The incubation with AdoMet before the anoxic period reduced TBARS (31-1000 micromol/l), glutathione production was increased (31-1000 micromol/l), LDH efflux decreased 6.41% with 15 micromol/l and 61.5% with 500 micromol/l). In the ex vivo experiments, we administered 50 mg/kg per day p.o., AdoMet for 3 days, then brain slices were collected and the anoxia-reoxygenation experiment was carried out. AdoMet led to the inhibition of brain lipid peroxidation and increased total glutathione production, after 3 h-reoxygenation. The increase of LDH efflux in non-treated rats was reduced by 77%. We conclude that AdoMet exerts citoprotective effects in an experimental model of brain slices reoxygenation after oxygen-glucose deprivation.     

睡眠剥夺对抑郁模型大鼠海马CREB表达的影响

目的:探讨睡眠剥夺通过影响海马区CREB含量及活性而产生的快速抗抑郁机制。方法:将40只SD大鼠随机分为正常对照组、抑郁模型组、睡眠剥夺组和水环境对照组。用改良多平台睡眠剥夺法(MMPM)对用慢性不可预见性应激抑郁模型方法建立的抑郁大鼠模型进行睡眠剥夺。用旷场实验和强迫游泳实验测试其行为变化,以及用免疫组化法测试海马CREB、P-CREB的含量。结果:①睡眠剥夺组大鼠与抑郁模型组相比旷场实验的水平得分与垂直得分均明显升高,潜伏期明显缩短。②海马CA1、CA3、DG区的CREB及p-CREB平均光密度值比较中,抑郁模型组均显著低于正常对照组,睡眠剥夺组均显著高于抑郁模型组。结论:睡眠剥夺可明显改善抑郁大鼠的抑郁样行为;海马部位CREB含量及活性的增高可能参与了睡眠剥夺的快速抗抑郁作用。     

Age-dependent effects of maternal deprivation on oxidative stress in infant rat brain

Developing brain is much more sensitive to all kind of stressors than the developed brain. Early maternal deprivation causes some behavioural and physiological effects on rats. After the birth, there is no endocrinological response to stressors between post-natal 4 and 14th days, which is called stress-hyporesponsive period (SHRP) in rats. This hypo-responsiveness is time- and stressor-specific, as some more severe stressors have been shown to induce a stress response. The present study examined the effects of maternal deprivation on oxidative stress in the hippocampus, prefrontal cortex (PFC) and striatum regions of the brain both during and after SHRP of the infant rats. The results showed that maternal deprivation in SHRP increased antioxidant enzyme activities and reduced lipid peroxidation in infant rat brain. However, by the termination of SHRP, maternal deprivation reduced enzyme activities and increased lipid peroxidation. The results indicated that infant brain might be protected in SHRP from maternal deprivation-induced oxidative stress.     

Oxidative stress and quality of life in elderly patients with obstructive sleep apnea syndrome: are there differences after six months of Continuous Positive Airway Pressure treatment?

OBJECTIVES:

This study evaluated the effect of Continuous Positive Airway Pressure treatment on oxidative stress parameters and the quality of life of elderly patients with obstructive sleep apnea syndrome.

METHODS:

In total, 30 obstructive sleep apnea syndrome patients and 27 subjects without obstructive sleep apnea syndrome were included in this study. Both groups underwent quality of life and oxidative stress evaluations at baseline and after six months. Polysomnography was performed in both groups at baseline and a second time in the obstructive sleep apnea syndrome group after six months of Continuous Positive Airway Pressure treatment. All of the variables were compared between the control and obstructive sleep apnea syndrome groups in this prospective case-control study.

RESULTS:

The baseline concentrations of the antioxidant enzyme catalase were higher in the obstructive sleep apnea syndrome group than the control group. After Continuous Positive Airway Pressure treatment, the obstructive sleep apnea syndrome group exhibited a reduction in the level of oxidative stress, as indicated by a decrease in the level of lipid peroxidation measured by the malondialdehyde (MDA) concentration [pre: 2.7 nmol malondialdehyde/mL (95% 1.6-3.7) vs. post: 1.3 nmol MDA/mL (0.7-1.9), p<0.01]. Additionally, improvements were observed in two domains covered by the SF-36 questionnaire: functional capacity [pre: 77.4 (69.2-85.5) vs. post: 83.4 (76.9-89.9), p = 0.002] and pain [pre: 65.4 (52.8-78.1) vs. post: 77.8 (67.2-88.3), p = 0.004].

CONCLUSION:

Our study demonstrated that the use of Continuous Positive Airway Pressure to treat obstructive sleep apnea syndrome in elderly patients reduced oxidative stress and improved the quality of life.     

Bisphenol A impairs mitochondrial function in the liver at doses below the no observed adverse effect level

Bisphenol A (BPA) has been reported to possess hepatic toxicity. We investigated the hypothesis that BPA, below the no observed adverse effect level (NOAEL), can induce hepatic damage and mitochondrial dysfunction by increasing oxidative stress in the liver. Two doses of BPA, 0.05 and 1.2 mg/kg body weight/day, were administered intraperitoneally for 5 days to mice. Both treatments impaired the structure of the hepatic mitochondria, although oxygen consumption rate and expression of the respiratory complex decreased only at the higher dose. The hepatic levels of malondialdehyde (MDA), a naturally occurring product of lipid peroxidation, increased, while the expression of glutathione peroxidase 3 (GPx3) decreased, after BPA treatment. The expression levels of proinflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) also increased. In HepG2 cells, 10 or 100 nM of BPA also decreased the oxygen consumption rate, ATP production, and the mitochondrial membrane potential. In conclusion, doses of BPA below the NOAEL induce mitochondrial dysfunction in the liver, and this is associated with an increase in oxidative stress and inflammation.     

Effects of benzo(a)pyrene on the expression of heat shock proteins, pro-inflammatory cytokines and antioxidant enzymes in hepatic tumors induced by rat hepatoma N1-S1 cells

Benzo(a)pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) that is easily introduced to humans via consumption of grilled or smoked meat. BaP causes harmful oxidative effects on cell development, growth and survival through an increase in membrane lipid peroxidation, oxidative DNA damage and mutagenesis. Therefore, the present study was conducted to evaluate the synergistic effects of BaP on oxidative stress in hepatic tumors. In this study, we established a hepatic tumor model by injecting rat hepatoma N1-S1 cells into healthy rats. Changes in the abundance of heat shock proteins (HSPs), antioxidant enzymes and pro-inflammatory cytokines were then investigated by western blot analysis. In addition, we examined changes in oxidative stress levels. Injection of N1-S1 cells or concomitant injection of BaP and N1-S1 cells resulted in the formation of hepatic tumors at the injection site. Evaluation of rat plasma reveals that hepatic tumors induced by BaP and N1-S1 cells expresses higher levels of Hsp27, superoxide dismutase (SOD), and tumor necrosis factor-α (TNF-α) when compared to those induced by N1-S1 cells only. The collective results of this study suggest that BaP exerts synergistic effects on the expression of HSP, cytokines and antioxidant enzymes in hepatic tumors induced by rat hepatoma N1-S1 cells.     

A social conflict increases EEG slow-wave activity during subsequent sleep.

Electroencephalogram (EEG) slow-wave activity (SWA) during non-rapid eye movement (NREM) sleep is widely viewed as an indicator of sleep debt and sleep intensity. In a previous study, we reported a strong increase in SWA during NREM sleep after a social conflict in rats. To test whether this increase in SWA reflects normal physiological sleep or an unrelated by-product of the stress, we now measured the effect of a conflict in combination with extended sleep deprivation by means of gentle handling. We anticipated that if the social defeat-induced SWA reflects a true sleep debt, the drive for it would persist during the extended wakefulness. Male rats were subjected to a 1-h social conflict followed by 5 h of sleep deprivation by gentle handling or to 6 h gentle handling alone. The manipulations took place during the second half of the dark phase and recovery sleep was recorded during the subsequent light phase. Neither of the two procedures caused a significant change in the total duration of NREM or REM sleep thereafter. Yet, both modes of sleep deprivation induced a strong increase in SWA during NREM sleep. This SWA was significantly higher for 6 h after sleep deprivation consisting of a social conflict followed by gentle handling, as compared to sleep deprivation by handling alone. Thus, the SWA increasing effect of the conflict persisted during the extended wakefulness. The data confirm that social defeat stress accelerates the build up of sleep debt and support the notion that sleep debt and subsequent NREM sleep intensity not only depend on the duration of prior wakefulness but also on what animals experience during that waking.     

Effect of binge ethanol treatment on prooxidant-antioxidant balance in rat heart tissue

Binge drinking of alcohol is known to cause cardiac dysfunction in some drinkers. This study was designed to examine the effect of ethanol on rat heart tissue with an experimental model mimicking human binge drinking. Female Sprague-Dawley rats were given ethanol diluted with normal saline (40%, v:v) by gavage at the dose of 5.0g/kg every 12h for 3 doses as total. Serum activities of lactate dehydrogenase (LDH), creatine phosphokinase (CK) and aspartate transaminase (AST) were determined. Endogenous lipid peroxidation was assessed by measuring the levels of malondialdehyde (MDA) in heart homogenates. In vitro susceptibility of tissues to oxidative stress was assessed by using two different media. Tissue glutathione (GSH) and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione transferase (GST) activities were determined. All serum enzymatic activities were found markedly elevated in ethanol group. Binge ethanol administration significantly enhanced endogenous lipid peroxidation and caused an enhanced in vitro susceptibility to lipid peroxidation. Levels of reduced GSH and GSH-Px and GST activities were found unchanged as compared to controls. SOD activity was found significantly increased. As a conclusion, binge ethanol consumption which was applied to rats to investigate acute tissue injury, appeared to confirm the generation of oxidative stress in rat hearts.     

Hepatic gluconeogenesis and Krebs cycle fluxes in a CCl4 model of acute liver failure

Acute liver failure was induced in rats by CCl4 administration and its effects on the hepatic Krebs cycle and gluconeogenic fluxes were evaluated in situ by 13C NMR isotopomer analysis of hepatic glucose following infusion of [U-13C]propionate. In fed animals, CCl4 injury caused a significant increase in relative gluconeogenic flux from 0.80+/-0.10 to 1.34 +/-0.24 times the flux through citrate synthase (p<0.01). In 24-h fasted animals, CCl4-injury also significantly increased relative gluconeogenic flux from 1.36+/-0.16 to 1.80+/-0.22 times the flux through citrate synthase (p<0.01). Recycling of PEP via pyruvate and oxaloacetate was extensive under all conditions and was not significantly altered by CCl4 injury. CCl4 injury significantly reduced hepatic glucose output by 26% (42.8+/-7.3 vs 58.1+/-2.4 micromol/kg/min, p=0.005), which was attributed to a 26% decrease in absolute gluconeogenic flux from PEP (85.6+/-14.6 vs 116+/-4.8 micromol/kg/min, p<0.01). These changes were accompanied by a 47% reduction in absolute citrate synthase flux (90.6+/-8.0 to 47.6+/-8.0 micromol/kg/min, p<0.005), indicating that oxidative Krebs cycle flux was more susceptible to CCl4 injury. The reduction in absolute fluxes indicate a significant loss of hepatic metabolic capacity, while the significant increases in relative gluconeogenic fluxes suggest a reorganization of metabolic activity towards preserving hepatic glucose output.     

Lipoperoxidation products and thiol antioxidants in chromium exposed workers

Hexavalent chromium is an established carcinogenic agent, which is not directly reactive with DNA. Its genotoxicity involves a reduction step, producing reactive oxygen species and radicals, and also lower valence forms which form stable complexes with intracellular macromolecules. The trivalent form of chromium may directly react with the genetic material and has also been shown to generate oxidative damage in vitro. To further evaluate the importance of in vivo oxidative DNA damage in the toxicity of each valence form, we conducted a comparative study on hexavalent and trivalent chromium-exposed workers (manual metal arc stainless steel welders and leather tanning workers), focusing on the total oxidative status by quantifying the level of lipoperoxidation products in urine. Thiol antioxidants are important in response to oxidative stress, and therefore, the concentration of glutathione and cysteine in peripheral blood lymphocytes was also determined. Chromium exposure was evaluated by quantifying total chromium in plasma and urine. Both groups had a significant increase in lipid peroxidation products expressed as malondialdehyde (MDA) in urine (tanners 1.42 +/- 0.61 micromol/g creatinine, welders 1.67 +/- 1.13 micromol/g creatinine versus controls 0.81 +/- 0.26 micromol/g creatinine, P < 0.005 in both cases) but only welders had a significant decrease in glutathione concentration in lymphocytes. There was a positive correlation between chromium in plasma and urinary MDA in welders, but not in tanners. This work is part of a larger study of which major results have been published previously including cytogenetics and DNA-protein cross-links in workers exposed to the two different forms of chromium. These results are compared with the results of oxidative damage from this study.     

Time-dependent modulation of rat serum paraoxonase 1 activity by fasting

High-density lipoprotein-associated paraoxonase 1 (PON1) protects the endothelium from the pro-oxidant activity of oxidised low-density lipoprotein. Whereas fasting has been related to increased oxidative stress, intermittent fasting and caloric restriction are associated to increased resistance to oxidative injury. Taking into consideration that serum PON1 activity is modulated by a restriction of caloric intake and because there is no evidence regarding PON1 response to total food deprivation, we investigated whether PON1 activity is involved in the response aimed to counteract the greater oxidative stress associated to fasting and whether serum PON1 activity is altered by the length of food deprivation. Male Wistar rats were randomly divided into five groups: fed and 6-, 12-, 24- or 48-h fasted rats. Serum PON1 activity increases within the first hours of fasting, representing a prompt adaptation designed to attenuate blood lipid peroxidation that cannot be sustained when fasting is prolonged. This PON1 response to early fasting could be part of the mechanisms triggered by periodically repeated short periods of food deprivation—intermittent fasting—which result in increased resistance to stress by stimulating antioxidant defences.     

Regulation of oxidative stress and inflammation by hepatic adiponectin receptor 2 in an animal model of nonalcoholic steatohepatitis

The pathogenesis of nonalcoholic steatohepatitis (NASH) is not well understood; however, the progression of fatty liver to NASH has been linked to oxidative stress and lipid peroxidation in the liver, leading to inflammation. Although the adiponectin receptor 2 (AdipoR2) has been identified as a modulator of oxidative stress and inflammation in the liver, it remains unclear whether the receptor has hepatic antioxidant and anti-inflammatory effects in NASH. In this study, we used an animal model of NASH to examine hepatic AdipoR2. Obese fa/fa Zucker rats fed a high-fat and high-cholesterol (HFC) diet spontaneously developed fatty liver with inflammation and fibrosis, characteristic of NASH, after 4, 8, or 12 weeks of HFC diet consumption. AdipoR2 expression was significantly decreased, whereas the expression of genes related to NADPH oxidase complex were increased. As a result of the decrease in AdipoR2 expression, the mRNA expression of genes located downstream of AdipoR2, i.e., Cu-Zn superoxide dismutase (Cu-Zn SOD) and Mn-SOD, also decreased. Furthermore, the expression of genes related to inflammation was increased. Increased oxidative stress and inflammation by down-regulation of AdipoR2 may contribute to the progression of NASH. Thus, the AdipoR2 might be a crucially important regulator of hepatic oxidative stress and inflammation in NASH.     

Alpha-lipoic Acid modulates heat shock factor-1 expression in streptozotocin-induced diabetic rat kidney

Increased oxidative stress and impaired heat shock protein (HSP) synthesis may contribute to diabetic nephropathy. The question of whether 8-week thiol antioxidant alpha-lipoic acid (LA) supplementation modulates HSP response and oxidative stress was studied in the kidney of streptozotocin-induced diabetic (SID) and nondiabetic rats. SID caused a histological mesangial expansion, tubular dilatation, and increased levels of transforming growth factor-beta (TGF-beta), a mediator of glomerulosclerosis. SID increased 4-hydroxynonenal (4-HNE) protein adduct formation, a marker of lipid peroxidation, and heme oxygenase-1 (HO-1), also a marker of oxidative stress. Moreover, SID increased the DNA-binding activity of heat shock factor-1 (HSF-1) and expression of heat shock protein 60 (HSP60). In contrast, LA supplementation partially reversed histological findings of glomerulosclerosis and decreased TGF-beta. LA also increased HSF-1 and decreased HO-1 protein expression, without affecting 4-HNE protein adduct levels. At the mRNA level, LA increased expression of HSF-1, HSP90, and glucose-regulated protein (GRP75) in both control and diabetic animals and HSP72 in SID rats. However, LA supplementation did not affect these HSPs at the protein level. These findings suggest that in addition to its antiglomerulosclerotic effects, LA can induce cytoprotective response in SID.     

Evaluation of epirubicin-induced acute oxidative stress toxicity in rat liver cells and mitochondria,and the prevention of toxicity through quercetin administration

Anticancer therapy with epirubicin (EPI) results in acute hepatotoxicity, likely due to the generation of free radicals. However, the oxidative status of rat liver cells and mitochondria after EPI toxicity has not been investigated. In the present study, we first investigated the pro-oxidant effect of EPI on both hepatic cells and mitochondrial function. Injection of EPI into rats at a dose of 9 mg/kg (cumulative dose in human chemotherapy), induced hepatic dysfunction, as revealed by a significant increase in serum glutamate oxaloacetate transaminases (SGOT) and glutamate pyruvate transaminases (SGPT). Oxidative stress in liver cells and mitochondria was provoked by EPI because a statistically significant reduction of catalase (CAT), superoxide dismutase (SOD) and cytosolic glutathione (GSH) levels, and a significant increase in malonedialdehyde (MDA) levels – an indicator of lipid peroxidation that can perforate biological membranes – were observed. Second, the protective effect of quercetin (QE) (0.33 mg/kg) against EPI-induced oxidative stress was also investigated. Indeed, the pretreatment of rats with QE protected liver cells and mitochondria from oxidative stress. This treatment prevented hepatic dysfunction by maintaining normal levels of serum transaminases following the inhibition of their hepatic leakage by preventing lipid peroxidation. Thus, QE works through the prevention of cellular membrane perforation and the antioxidant defense system of mitochondria from liver cells, which represent compartments for the permanent production of reactive oxygen species (ROS) through the respiratory chain.     

Sleep deprivation in the pigeon using the Disk-Over-Water method

A well-defined sleep deprivation (SD) syndrome has been observed in studies with rats under conditions of severe sleep loss on the Disk-Over-Water (DOW) apparatus. Observation of the sleep deprivation syndrome across taxa would assist in the elucidation of the function of sleep. In the present study, the effects of total sleep deprivation were assessed in pigeons, a biologically relevant choice given that birds are the only non-mammalian taxon known to exhibit unequivocal rapid-eye-movement (REM) sleep and non-REM (NREM) sleep. Pigeons were deprived of sleep for 24-29 days on the DOW by rotating the disk and requiring them to walk whenever sleep was initiated. Control (C) birds were also housed on the DOW and required to walk only when the deprived (D) birds were required to walk due to sleep initiation. NREM and REM sleep amounts were reduced from baseline during the deprivation for both D and C birds, although D birds obtained less NREM sleep than controls. Across the deprivation, D birds had their total sleep reduced by 54% of baseline (scored in 4 s epochs), whereas previous studies in rats on the DOW reported total sleep reduction of as much as 91% (scored in 30 s epochs). Pigeons proved to be more resistant to sleep deprivation by the DOW method and were much more difficult to deprive over the course of the experiment. Overall, the pigeons showed recovery sleep patterns similar to those seen in rats; i.e., rebound sleep during recovery was disproportionately composed of REM sleep. They did not, however, show the obvious external physical signs of the SD syndrome nor the large metabolic and thermoregulatory changes associated with the syndrome. The DOW method was thus effective in producing sleep loss in the pigeon, but was not as effective as it is in rats. The absence of the full SD syndrome is discussed in the context of limitations of the DOW apparatus and the possibility of species-specific adaptations that birds may possess to withstand or adapt to conditions of limited sleep opportunity.     

Oxidized low-density-lipoprotein accumulation is associated with liver fibrosis in experimental cholestasis

OBJECTIVE: The aim of the present study was to examine the probable relationship between the accumulation of oxLDL and hepatic fibrogenesis in cholestatic rats. INTRODUCTION: There is growing evidence to support the current theories on how oxidative stress that results in lipid peroxidation is involved in the pathogenesis of cholestatic liver injury and fibrogenesis. One of the major and early lipid peroxidation products, OxLDL, is thought to play complex roles in various immuno-inflammatory mechanisms. METHODS: A prolonged (21-day) experimental bile duct ligation was performed on Wistar-albino rats. Biochemical analysis of blood, histopathologic evaluation of liver, measurement of the concentration of malondialdehyde (MDA) and superoxide-dismutase (SOD) in liver tissue homogenates, and immunofluorescent staining for oxLDL in liver tissue was conducted in bile-duct ligated (n=8) and sham-operated rats (n=8). RESULTS: Significantly higher levels of MDA and lower concentrations of SOD were detected in jaundiced rats than in the sham-operated rats. Positive oxLDL staining was also observed in liver tissue sections of jaundiced rats. Histopathological examination demonstrated that neither fibrosis nor other indications of hepatocellular injury were found in the sham-operated group, while features of severe hepatocellular injury, particularly fibrosis, were found in jaundiced rats. CONCLUSION: Our results support the finding that either oxLDLs are produced as an intermediate agent during exacerbated oxidative stress or they otherwise contribute to the various pathomechanisms underlying the process of liver fibrosis. Whatever the mechanism, it is clear that an association exists between elevated oxLDL levels and hepatocellular injury, particularly with fibrosis. Further studies are needed to evaluate the potential effects of oxLDLs on the progression of secondary biliary cirrhosis.     

Relationship between oxidative stress and hepatic phosphoglucomutase activity in rats.

The relationship between the oxidative stress and inactivation of hepatic enzymes was examined in rats. An intake of lipid peroxidation products or pro-oxidative drugs provokes oxidative stress in the living body. Secondary peroxidation products of linoleic acid were administered orally, and the oxidative stress was evaluated by thiobarbituric acid (TBA) and haemoglobin-methylene blue (HMB) tests, and by the reduction in tocopherol level. A specific decrease in hepatic phosphoglucomutase activity was found following the oxidative stress caused by the dose with secondary products. Then, ten pro-oxidative drugs were administered intraperitoneally and the effects on the enzymatic activity were determined. Among the ten drugs, CCl4, alcohol, paraquat, phenobarbital, thiopental and methylcholanthrene caused the TBA values to increase, and the phosphoglucomutase activity to decrease, in the liver 24 h after the doses. It was attempted to clarify the inactivation mechanism by using parenchymal hepatocytes. When the cells were cultured in medium containing aldehydic products originating from lipid peroxidation, these aldehydes significantly suppressed the induction of phosphoglucomutase by dexamethasone as compared with the cells in aldehyde-free medium. We consider that aldehydes inhibit the hormonal induction of phosphoglucomutase in the rat liver.