Investigations on the antifatigue and antihypoxic effects of Paecilomyces hepiali extract.

Paecilomyces hepiali, one of the most valuable and effective Chinese medicinal herbs, possesses potential antioxidant, immunomodulatory, antitumor and anti­inflammatory properties. The present study aimed to investigate the antifatigue and antihypoxic effects of Paecilomyces hepiali extract (PHC) in a mouse model. Using a rotating rod, forced swimming and running assessment, the antifatigue activity of PHC was determined. PHC administration for 7 days had no effect on mouse horizontal or vertical movement, indicating no neurotoxicity at the selected doses was observed. Using a normobaric hypoxia, sodium nitrite toxicosis and acute cerebral ischemia assessments, PHC was confirmed to possess antihypoxic effects. PHC treatment for 7 days significantly enhanced the serum and liver levels of adenosine triphosphate, superoxide dismutase and glutathione peroxidase, prior to and following 60 min of swimming. The levels of antioxidant­associated proteins in the livers of the mice were analyzed using western blotting. PHC effectively increased the expression levels of phosphorylated (p)­5'­monophosphate (AMP)­activated protein kinase (AMPK), p­protein kinase B (AKT) and p­mammalian target of rapamycin (mTOR). The results of the present study demonstrated that PHC efficiently enhanced endurance from fatigue and had antihypoxic effects through elevation of the antioxidant capacity in the serum and liver, at least in part through the AMPK and AKT/mTOR pathways. These results indicate the potential of this natural product as an antioxidant in the treatment of fatigue, hypoxia and their associated diseases.

Chemical composition and biological activities of trans-Himalayan alga Spirogyra porticalis (Muell.) Cleve.

The freshwater alga Spirogyra porticalis (Muell.) Cleve, a filamentous charophyte, collected from the Indian trans-Himalayan cold desert, was identified on the basis of morpho-anatomical characters. Extracts of this alga were made using solvents of varying polarity viz. n-hexane, acetonitrile, methanol and water. The antioxidant capacities and phenolic profile of the extracts were estimated. The methanol extract showing highest antioxidant capacity and rich phenolic attributes was further investigated and phytochemical profiling was conducted by gas chromatography-mass spectrometry (GC/MS) hyphenated technique. The cytotoxic activity of methanol extract was evaluated on human hepatocellular carcinoma HepG2 and colon carcinoma RKO cell lines. The anti-hypoxic effect of methanol extract of the alga was tested on in vivo animal system to confirm its potential to ameliorate oxidative stress. The antioxidant assays viz. ferric reducing antioxidant power (FRAP), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide (NO) radical scavenging capacities, ß-carotene-linoleic acid bleaching property and lipid peroxidation exhibited analogous results, wherein the algal extracts showed significantly high antioxidant potential. The extracts were also found to possess high content of total proanthocyanidin, flavonoid and polyphenol. GC/MS analysis revealed the presence of thirteen chemotypes in the methanol extract representing different phytochemical groups like fatty acid esters, sterols, unsaturated alcohols, alkynes etc. with substantial phyto-pharmaceutical importance. The methanol extract was observed to possess anticancer activity as revealed from studies on HepG2 and RKO cell lines. In the present study, S. porticalis methanol extract also provided protection from hypoxia-induced oxidative stress and accelerated the onset of adaptative changes in rats during exposure to hypobaric hypoxia. The bioactive phytochemicals present in this trans-Himalayan alga are of enormous interest and can be utilized sustainably for discovery of novel drugs against oxidative stress.

[DYNAMICS OF GLUTAMINE SYNTHASE ACTIVITY IN RAT BRAIN IN PRENATAL HYPOXIA MODEL].

Prenatal ontogenesis is a period of high sensitivity to stressful impact, so any stressor can lead to changes of physiological, biochemical indicators, behavioral and cognitive functions. The most common and clinically significant stress factor, which the embryo may be exposed during embryonic development, is hypoxia. In this case pathological changes in the central nervous system depend on the duration and severity of hypoxic exposure, individual tolerance and the stage of prenatal development, at each of which in the brain take place the basic histogenetic processes. By activating energetically disadvantageous anaerobic glycolysis hypoxia leads to excess of glutamate emission and cell apoptosis. Glutamine synthase is a basic enzyme that regulates metabolism of glutamate, catalyzing conversion of glutamate to glutamine with ammonia detoxification. The aim of the presented work was to reveal changes in the activity of one of the key enzyme of glutamate metabolism- glutamine synthetase in the brain of offspring of white rats undergone to hypoxia at different stages of prenatal ontogenesis. Hypoxia was created by placing female rats at stages of the pregnancy, corresponding to progestation period of organogenesis and fetal period of prenatal development, in the hypobaric chamber with exposure to 5% oxygen and 95% nitrogen gas mixture during 30 minutes per day. The offspring obtained from females of control and experimental groups were used for biochemical determinations in the age of 1 and 3 month. It has been established that hypoxia exposed to pregnant females during embryonic organogenesis causes significant changes in enzyme activity, particularly pronounced in the cerebral cortex and cerebellum, as compared with progestational and fetal hypoxia. Enzyme activity decreased in a greater degree in one-month-old rats undergone to prenatal hypoxia, than three- month-old animals. Thus, stress during intensive processes of proliferation and migration of cells of the forming brain violates glutamate metabolism of the brain.

Effect of panax notoginseng saponins injection on the p38MAPK pathway in lung tissue in a rat model of hypoxic pulmonary hypertension.

OBJECTIVE: To investigate the effect of panax notoginseng saponins (PNS) injection on pulmonary artery pressure and the expression of p38MAPK in lung tissue of rats subjected to chronic hypoxia. METHODS: Thirty adult male Sprague Dawley rats were randomly divided into three groups (ten in each group): rats in control group were exposed to normoxic condition and the rats in hypoxia group and PNS group were subjected to 4-week hypoxia, and PNS injection (50 mg · kg(-1) · d(-1)) was administrated intraperitoneally at 30 min in the PNS group daily before the rats were kept in the hypoxic chamber, while rats in the other two groups received equal dose of normal saline instead. After chronic hypoxia, mean pulmonary artery pressure (mPAP) and mean carotid artery pressure (mCAP) were measured. The heart and lung tissues were harvested, and right ventricle (RV) and left ventricle plus ventricular septum (LV+S) were weighed to calculate the ratio of RV/(LV+S). The expression of p38MAPK mRNA was determined by reverse transcription-polymerase chain reaction, the quantity of phosphorylated p38MAPK (p-p38MAPK) in rat lung tissues and pulmonary arterioles was determined by Western blot and immunohistochemistry. RESULTS: Compared with the control group, mPAP and the ratio of RV/(LV+S) in the hypoxia group were increased, the expression of p-p38MAPK in pulmonary arterioles and p38MAPK mRNA in the lung were higher (P<0.05). The changes of these parameters in the hypoxia group were significantly attenuated by PNS treatment (P<0.05). CONCLUSION: PNS injection was shown to prevent hypoxic pulmonary hypertension at least partly by regulating p38MAPK pathway.

Overexpression of extracellular superoxide dismutase protects against brain injury induced by chronic hypoxia.

Extracellular superoxide dismutase (EC-SOD) is an isoform of SOD normally found both intra- and extra-cellularly and accounting for most SOD activity in blood vessels. Here we explored the role of EC-SOD in protecting against brain damage induced by chronic hypoxia. EC-SOD Transgenic mice, were exposed to hypoxia (FiO2.1%) for 10 days (H-KI) and compared to transgenic animals housed in room air (RA-KI), wild type animals exposed to hypoxia (H-WT or wild type mice housed in room air (RA-WT). Overall brain metabolism evaluated by positron emission tomography (PET) showed that H-WT mice had significantly higher uptake of 18FDG in the brain particularly the hippocampus, hypothalamus, and cerebellum. H-KI mice had comparable uptake to the RA-KI and RA-WT groups. To investigate the functional state of the hippocampus, electrophysiological techniques in ex vivo hippocampal slices were performed and showed that H-KI had normal synaptic plasticity, whereas H-WT were severely affected. Markers of oxidative stress, GFAP, IBA1, MIF, and pAMPK showed similar values in the H-KI and RA-WT groups, but were significantly increased in the H-WT group. Caspase-3 assay and histopathological studies showed significant apoptosis/cell damage in the H-WT group, but no significant difference in the H-KI group compared to the RA groups. The data suggest that EC-SOD has potential prophylactic and therapeutic roles in diseases with compromised brain oxygenation.

Silibinin inhibits VEGF secretion and age-related macular degeneration in a hypoxia-dependent manner through the PI-3 kinase/Akt/mTOR pathway.

BACKGROUND AND PURPOSE: Hypoxia-mediated neovascularization plays an important role in age-related macular degeneration (AMD). There are few animal models or effective treatments for AMD. Here, we investigated the effects of the flavonoid silibinin on hypoxia-induced angiogenesis in a rat AMD model. EXPERIMENTAL APPROACH: Retinal pigmented epithelial (RPE) cells were subjected to hypoxia in vitro and the effects of silibinin on activation of key hypoxia-induced pathways were examined by elucidating the hypoxia-inducible factor-1 alpha (HIF-1α) protein level by Western blot. A rat model of AMD was developed by intravitreal injection of VEGF in Brown Norway rats, with or without concomitant exposure of animals to hypoxia. Animals were treated with oral silibinin starting at day 7 post-VEGF injection and AMD changes were followed by fluorescein angiography on days 14 and 28 post-injection. KEY RESULTS: Silibinin pretreatment of RPE cells increased proline hydroxylase-2 expression, inhibited HIF-1α subunit accumulation, and inhibited VEGF secretion. Silibinin-induced HIF-1α and VEGF down-regulation required suppression of hypoxia-induced phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (mTOR) pathway. In the rat model of AMD, silibinin administration prevented VEGF- and VEGF plus hypoxia-induced retinal oedema and neovascularization. CONCLUSION AND IMPLICATIONS: The effects of silibinin, both in vitro and in vivo, support its potential as a therapeutic for the prevention of neovascular AMD.

Blueberry extracts protect testis from hypobaric hypoxia induced oxidative stress in rats.

Exposure to hypobaric hypoxia causes oxidative damage to male rat reproductive function. The aim of this study was to evaluate the protective effect of a blueberry extract (BB-4) in testis of rats exposed to hypobaric hypoxia. Morphometric analysis, cellular DNA fragmentation, glutathione reductase (GR), and superoxide dismutase (SOD) activities were evaluated. Our results showed that supplementation of BB-4 reduced lipid peroxidation, decreased apoptosis, and increased GR and SOD activities in rat testis under hypobaric hypoxia conditions (P < 0.05). Therefore, this study demonstrates that blueberry extract significantly reduced the harmful effects of oxidative stress caused by hypobaric hypoxia in rat testis by affecting glutathione reductase and superoxide dismutase activities.

[Protective effects and mechanisms of OSR on primary cultured hippocampus neurons subjected to anoxic injury in neonatal rat].

OBJECTIVE: To investigate the protective effects of oxysophoridine (OSR) on primary cultured hippocampus neurons subjected to anoxia injury in neonatal rats and its mechanism. METHOD: The model of anoxia injury of hippocampus neurons in neonatal rats were primarily cultured in vitro by physical oxygen deficiency using glucose-free culture fluid. The survival rate of neurons, the leaking rate of lactate dehydrogenase (LDH), the intracellular contents of malondialdehyde (MDA) and nitric oxide (NO), the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and nitric oxide synthase (NOS) were measured. The intracellular free calcium concentration ([Ca2+]i) in hippocampus neurons were detected with Ca(2+)-sensitive dual wavelength fluorescence spectrophotometer. RESULT: Neuron death occurred in the anoxia injury model group with increase of LDH leaking rate, the contents of NO, MDA, intracellular [Ca2+] and the elevated activity of NOS while decreased activities of SOD and GSH-PX. The hippocampus neurons subjected to anoxia injury were alleviated in OSR (0.625, 5, 10 microg x L(-1)) group. CONCLUSION: OSR has significant protective effects on hippocampus neurons subjected to anoxic injury. The mechanism of its protective effect may relate to its reduction of calcium overload and against oxidation injury.

Catalytic subunits atpα and atpß from the Pacific white shrimp Litopenaeus vannamei F(O)F (1) ATP-synthase complex: cDNA sequences, phylogenies, and mRNA quantification during hypoxia.

In the mitochondrial F(O)F(1) ATP-synthase/ATPase complex, subunits α and ß are part of the extrinsic portion that catalyses ATP synthesis. Since there are no reports about genes and proteins from these subunits in crustaceans, we analyzed the cDNA sequences of both subunits in the whiteleg shrimp Litopenaeus vannamei and their phylogenetic relationships. We also investigated the effect of hypoxia on shrimp by measuring changes in the mRNA amounts of atpα and atpß. Our results confirmed highly conserved regions for both subunits and underlined unique features among others. The ATPß deduced protein of shrimp was less conserved in size and sequence than ATPα. The relative mRNA amounts of atpα and atpß changed in shrimp pleopods; hypoxia at 1.5 mg/L caused an increase in atpß transcripts and a subsequent decrease when shrimp were re-oxygenated. Results confirm that changes in the mRNAs of the ATP-synthase subunits are part of the mechanisms allowing shrimp to deal with the metabolic adjustment displayed to tolerate hypoxia.

Superoxide dismutase functional regulation in neonatal hypoxia: effect of glucose, oxygen and epinephrine.

Hypoxia is one of the major causes of damage to the fetal and neonatal brain and cardiac functions. In earlier studies, we have reported the brain damage caused by hypoxia and resuscitation with oxygen and epinephrine and have found that glucose treatment to hypoxic rats and hypoxic rats treated with oxygen shows a reversal of brain damage. The neonatal rats are shown to be deficient in free radical scavenging system, which offers a high risk of oxidative stress. In the present study, we induced hypoxia in neonatal Wistar rats and resuscitated with glucose, oxygen and epinephrine. Heart tissue and cerebral cortex were used to study the kinetics of superoxide dismutase activity in experimental groups of rats to assess the free radical status. Results showed that glucose supplementation in hypoxia (Hx + G) and hypoxic + oxygen (Hx + O) had an efficient free radical scavenging capability, compared to all other experimental groups. The observation was ascertained by studying the activity of catalase, another antioxidant enzyme in the body. Our results suggested that in neonatal rats during hypoxic condition, damage to heart and brain was more prominent in all groups, except when supplemented with glucose. These findings may have clinical significance in the proper management of heart and brain function.

Molecular cloning, characterization and expression of two tryptophan hydroxylase (TPH-1 and TPH-2) genes in the hypothalamus of Atlantic croaker: down-regulation after chronic exposure to hypoxia.

Recently we discovered that hypoxia causes marked impairment of reproductive neuroendocrine function in Atlantic croaker, a marine teleost, which is due to a decline in hypothalamic serotonergic activity. As a first step in understanding the molecular responses of the hypothalamic serotonergic system to hypoxia, we cloned and characterized the genes for the enzymes regulating the rate-limiting step in serotonin biosynthesis, tryptophan hydroxylase (TPH-1 and TPH-2) in the croaker brain. The full-length croaker TPH-1 and TPH-2 cDNAs contain open reading frames encoding proteins with 479 and 487 amino acids, respectively, which are highly homologous to the TPH-1 (76-93%) and TPH-2 (64-92%) proteins of other vertebrates. Croaker TPH-1 and TPH-2 mRNA expression was detected throughout the brain but was greatest in the hypothalamic region. Both Northern blot analysis and real-time PCR showed that TPH-1 (transcript size approximately 2.1 kb) and TPH-2 ( approximately 1.9 kb) mRNA levels were significantly decreased in the hypothalami of croaker exposed for 2 weeks to hypoxic conditions compared with those in fish exposed to normoxic conditions. Immunohistochemistry of hypothalamic neurons with TPH antibodies showed reduced expression of TPHs in hypoxia-exposed fish compared with normoxic fish. Western blot analysis confirmed that hypoxia caused a marked decline in hypothalamic TPH protein levels, which was associated with decreases in hypothalamic TPH enzyme activity and 5-hydroxytryptophan levels. These results suggest that TPH is a major site of hypoxia-induced down-regulation of serotonergic function in croaker brains. Moreover, they provide the first evidence that hypoxia decreases the expression of TPH transcripts in vertebrate brains.

High hopes at high altitudes: pharmacotherapy for acute mountain sickness and high-altitude cerebral and pulmonary oedema.

The pharmacotherapy of prevention and treatment of acute altitude- related problems - acute mountain sickness, high-altitude cerebral oedema and high-altitude pulmonary oedema - is reviewed. Drug therapy is only part of the answer to the medical problems of high altitude; prevention should include slow ascent and treatment of the more severe illnesses should include appropriate descent. Carbonic anhydrase inhibitors, in particular acetazolamide, remain the most effective drugs in preventing, to a large extent, the symptoms of acute mountain sickness, and can be used in the immediate management of the more severe forms of altitude-related illnesses. Glucocorticoids in relatively large doses are also effective preventative drugs, but at present are largely reserved for the treatment of the more severe acute mountain sickness and acute cerebral oedema. Calcium channel blockers and PDE-5 inhibitors are effective in the management of acute pulmonary oedema. Further work is required to establish the role of antioxidants and anticytokines in these syndromes.

Dietary polyunsaturated fatty acids alter myocardial protein kinase C expression and affect cardioprotection induced by chronic hypoxia.

We examined the influence of dietary fatty acid (FA) classes on the expression of protein kinase C (PKC) delta and epsilon in relation to the cardioprotective effects of chronic intermittent hypoxia (CIH). Adult male Wistar rats were fed a nonfat diet enriched with 10% lard (saturated FA [SFA]), fish oil (n-3 polyunsaturated FA [n-3 PUFA]), or corn oil (n-6 PUFA) for 10 weeks. After 4 weeks on the diet, each group was divided into two subgroups that were either exposed to CIH in a barochamber (7000 m, 8 hrs/ day) or kept at normoxia for an additional 5-6 weeks. A FA phospholipid profile and Western blot analysis of PKC were performed in left ventricles. Infarct size was assessed in anesthetized animals subjected to 20-min coronary artery occlusion and 3-hr reperfusion. CIH decreased the n-6/n-3 PUFA ratio in all groups by 23% independently of the initial value set by various diets. The combination of n-3 diet and CIH had a stronger antiarrhythmic effect during reperfusion than the n-3 diet alone; this effect was less pronounced in rats fed the n-6 diet. The normoxic n-6 group exhibited smaller infarctions (by 22%) than the n-3 group. CIH decreased the infarct size in n-3 and SFA groups (by 20% and 23%, respectively) but not in the n-6 group. Unlike PKC epsilon, the abundance of PKC delta in the myocardial particulate fraction was increased by CIH except for the n-6 group. Myocardial infarct size was negatively correlated (r=- 0.79) with the abundance of PKC delta in the particulate fraction. We conclude that lipid diets modify the infarct size-limiting effect of CIH by a mechanism that involves the PKC delta-dependent pathway.

Differential effects of phosphodiesterase-5 inhibitors on hypoxic pulmonary vasoconstriction and pulmonary artery cytokine expression.

BACKGROUND: Perioperative pulmonary hypertension is a challenging clinical problem with numerous etiologies including hypoxia, adrenergic stimulation, and local inflammation. New oral phosphodiesterase-5 (PDE-5) inhibitors used for the treatment of erectile dysfunction may have beneficial effects on the pulmonary vasculature owing to the abundance of PDE-5 receptors in the lung. The purpose of this study was to compare the efficacy of sildenafil, vardenafil, and tadalafil in preventing acute hypoxic pulmonary vasoconstriction and hypoxia-induced pulmonary artery tumor necrosis factor-alpha (TNF-alpha) and interleukin-1-beta (IL-1beta) expression. METHODS: Isolated rat pulmonary arteries suspended in physiologic organ baths for measurement of isometric force transduction were treated with vehicle (dimethyl sulfoxide), sildenafil, vardenafil, or tadalafil to assess (1) pulmonary artery relaxation; (2) inhibition of phenylephrine-induced pulmonary artery contraction; (3) inhibition of hypoxic pulmonary vasoconstriction (pO2 = 30-35 mm Hg); and (4) hypoxia-induced pulmonary artery TNF-alpha and IL-1beta expression (reverse transcriptase-polymerase chain reaction). RESULTS: Sildenafil, vardenafil, and tadalafil resulted in dose-dependent pulmonary artery relaxation and inhibited phenylephrine-induced pulmonary artery contraction, but only tadalafil significantly inhibited hypoxic pulmonary vasoconstriction (52.08% +/- 7.65% tadalafil versus 88.63% +/- 8.96% vehicle; 98.61% +/- 10.04% sildenafil; 68.46% +/- 15.84% vardenafil). Hypoxia-induced upregulation of TNF-alpha and IL-1beta mRNA in pulmonary artery was significantly decreased by tadalafil, but not sildenafil or vardenafil pretreatment. CONCLUSIONS: We conclude that sildenafil, vardenafil, and tadalafil were equally efficacious in causing pulmonary artery relaxation, but only tadalafil inhibited hypoxic pulmonary vasoconstriction and attenuated hypoxia-induced pulmonary artery TNF-alpha and IL-1beta expression.

Antioxidant enzymes during hypoxia-anoxia signaling events in Crocus sativus L. corm.

The activity of reactive oxygen species (ROS)-scavenging enzymes, catalase, superoxide dismutase (SOD), glutathione peroxidase, o-dianisidine and ascorbate peroxidases, was investigated in Crocus sativus L. corms cultivated in normoxic and hypoxic-anoxic conditions. The activity of the ROS-scavenging enzymes studied varied during cultivation. However, the pattern of ROS-scavenging enzymes production was different in corms cultivated in normoxic and hypoxic-anoxic conditions. In normoxic conditions, only the activities of peroxidases and SOD were stimulated. In dormant corms placed under hypoxia-anoxia, the activities of catalase, SOD, and glutathione peroxidase were stimulated, with the highest stimulation observed for catalase, followed by SOD, and then glutathione peroxidase. In corms that had been rooted for 3 days before being placed in hypoxia-anoxia, the activities of all ROS-scavenging enzymes studied were stimulated with the highest stimulation still observed for catalase, followed by the peroxidases, and finally SOD. Thus catalase was the prevailing enzyme produced under hypoxia-anoxia.

Oxidative stress and antioxidant status in patients undergoing prolonged exposure to hyperbaric oxygen.

OBJECTIVES: To evaluate the condition of oxidative stress in patients undergoing prolonged exposure to hyperbaric oxygen (HBO) and the possible modifications of the antioxidant defense systems in the absence of antioxidant supplementation. DESIGN AND METHODS: Twelve patients exposed to 15 HBO treatments for pathological conditions related to hypoxia were included in the study. Oxidative stress indices as well as plasma and erythrocyte antioxidant levels were measured in blood samples collected both at the 1st and 15th HBO session. RESULTS: The repeated exposures to HBO led to a significant accumulation of plasmatic reactive oxygen metabolites (ROM) and malondialdehyde (MDA). After 15 HBO sessions, no relevant differences were detected for reduced glutathione (GSH), alpha-tocopherol, and retinol plasma levels; however, a significant decrease in erythrocyte superoxide dismutase (SOD) and catalase (CAT) activity was observed when compared to the 1st HBO exposure; glutathione peroxidase (GPx) activity remained almost unchanged. CONCLUSIONS: In the absence of antioxidant supplementation, the prolonged HBO treatment leads to a condition of oxidative stress that seems to affect in particular the response of the enzymatic antioxidant defense system; the possible relationship between the chemical modifications of the enzymes caused by oxygen reactive species and the consequent inactivation of the proteins is under investigation.

Methylprednisolone inhibits low-flow hypoxia-induced mitochondrial dysfunction in isolated perfused rat liver.

OBJECTIVE: To investigate the mechanism by which methylprednisolone protects the liver from hypoxia-induced injury. DESIGN: Prospective control study using the isolated rat liver. SETTING: Animal research facility. SUBJECTS: Male, fasted, pathogen-free Sprague-Dawley rats. INTERVENTIONS: Low-flow hypoxia was produced by reducing afferent perfusate pressure from 10 to 2.5 cm H(2)O; isolated livers were portally perfused for 2 hrs. MEASUREMENTS AND MAIN RESULTS: We measured mitochondrial membrane potential and hydrogen peroxide production by imaging rhodamine 123 and 2'-7'-dichlorofluorescein fluorescence, respectively. Leakage of mitochondrial enzymes was also monitored by assaying mitochondrial aspartate aminotransferase activity in the outflow perfusate, and the radical-scavenging effect of methylprednisolone was assessed by measuring luminol-dependent hydrogen peroxide chemiluminescence. Apoptosis in liver cells was determined by using terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling. Rhodamine 123 fluorescence was significantly diminished in the hypoxic liver, especially in the region of the terminal hepatic venules, which is indicative of membrane depolarization in the mitochondria in those areas. Hypoxia-induced mitochondrial dysfunction was indicated by leakage of aspartate aminotransferase into the outflow perfusate, and increased 2'-7'-dichlorofluorescein fluorescence indicated increased hydrogen peroxide levels, particularly in the midzone. Pretreatment with 30, 10, or 3 mg/kg of methylprednisolone inhibited the hypoxia-induced mitochondrial membrane depolarization and enzyme leakage, although hydrogen peroxide levels and apoptosis in sinusoidal endothelial cells were unaffected. CONCLUSIONS: Methylprednisolone does not protect the liver from hypoxia-induced injury by suppressing hydrogen peroxide production. Instead, the beneficial effect of methylprednisolone seems to be related to its ability to protect against mitochondrial membrane depolarization under hypoxic conditions.

[Effect of lycium barbarum L on defending free radicals of mice caused by hypoxia].

The effect of Lycium Barbarum L. (LB) on the free radical defending system during hypoxia was tested. Fifty six mice were divided into 3 groups. Experimental mice were fed with LB and the control mice were fed with distilled water by tube feeding for 16 days. Animals were put into each enclosed bottle for testing the effect of hypoxia. The results showed that LB treatment could not prolong the survival time (P > 0.05), but increase the activities of superoxide dismutase (SOD), catalase(CAT) and total anti-oxidative capacity as compared with the control group(P < 0.05). The study indicated that LB could not increase the hypoxic tolerance, but it might have a protective effect on free radical injury caused by hypoxia.

The ability of hypoxia to modify the gene expression of thymidylate synthase in tumour cells in vivo.

PURPOSE: Hypoxic cells in tumours are resistant to 5-fluorouracil (5-FU). This in vivo study investigated the ability of hypoxia to regulate the gene expression of thymidylate synthase (TS), the target enzyme of 5-FU. MATERIALS AND METHODS: C3H mammary carcinomas, grown in the feet of female CDF1 mice, were used for all experiments. Mice were placed in a 10% oxygen environment for various time periods and the tumour oxygen status was determined with an Eppendorf oxygen electrode. The animals were then injected with BrdU (100 mg/kg, i.p.). Tumours were excised and immediately frozen (-80 degrees C) until isolation of total RNA. The mRNA was reversibly transcribed to complementary DNA and the resulting cDNA amplified in a multiplex PCR reaction, with beta-actin as the internal reference gene. RESULTS: One hour of low oxygen breathing made tumours significantly more hypoxic. This increase was maintained for a maximum incubation period of 48 h. In the same tumours, no change in TS gene expression was seen with up to 3 h of low oxygen breathing. At longer times it decreased, reaching significance at 12-24 h and remaining at this lower level for up to 48 h. BrdU labelling was significantly reduced after breathing low O2 for 24 h (p = 0.001). CONCLUSION: Hypoxia-induced down-regulation of TS gene expression was observed. This would be expected to make hypoxic tumour cells more sensitive to 5-FU. Other mechanisms must be responsible for the previously reported resistance to this drug.