S-allylcysteine inhibits free radical production, lipid peroxidation and neuronal damage in rat brain ischemia

The efficacy of S-allylcysteine (SAC) as a free radical scavenger was studied using rat brain ischemia models. In a middle cerebral artery occlusion model, preischemic administration of SAC had the following effects: it improved motor performance and memory impairment and reduced water content and the infarct size. In a transient global ischemia model, the time course of free radical (alkoxyl radical) formation as studied by electron paramagnetic resonance (EPR) spectroscopy and alpha-phenyl-N-tert-butylnitrone (PBN) was biphasic; the first peak occurred at 5 min and the second at 20 min after reperfusion. Although SAC did not attenuate the first peak, it did affect the second peak, which is related to lipid peroxidation. The lipid peroxidation as estimated by thiobarbituric acid reactive substances (TBARS) increased significantly at 20 min after reperfusion. SAC decreased TBARS to the levels found without ischemia. These results suggest that SAC could have beneficial effects in brain ischemia and that the major protective mechanism may be the inhibition of free radical-mediated lipid peroxidation.

In vitro effects of aged garlic extract and other nutritional supplements on sickle erythrocytes

In the circulation of sickle cell anemia patients, a certain population of erythrocytes has an elevated density. These abnormally dense cells are believed to be at the root of the painful crisis and anemia of the patients. We have developed an in vitro method for the preparation of these heavier erythrocytes by a repeated deoxy-oxy cycling of erythrocytes from sickle cell anemia patients. By using this method, we studied whether certain nutritional supplements would inhibit the formation of dense cells in vitro. It was found that aged garlic extract (AGE) as well as its components with antioxidant activity, i.e., S-allylcysteine and N alpha-(1-deoxy-D-fructos-1-yl)-L-arginine (fructosyl arginine), inhibited the formation of dense cells in vitro. Vitamin C, vitamin E and the spin-trapping agents, 5-diethoxyphophoryl-5-methyl-1-pyrroline-N-oxide and alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone were all found to inhibit the formation of dense cells in vitro. These results suggest that, when extremely stretched sickle-shaped cells are formed by the repeated deoxy-oxy cycling, the erythrocyte membrane becomes susceptible to oxidative injury by reactive oxygen species. The protection of the erythrocyte membrane from such an oxidative injury would prevent the membranes from becoming leaky to the calcium ion, thus inhibiting the activation of the calcium-activated potassium efflux channel and the formation of dense cells. We also developed a new ex vivo method of studying the possible efficacy of antioxidants taken orally on the dense cell formation in sickle cell patients. It involved the use of blood plasma taken from a healthy donor (with normal hemoglobin) of AB blood type who had consumed different types of antioxidants orally. By suspending sickle erythrocytes in such plasma and exposing them to the deoxy-oxy cycling, the degree of dense cell formation was determined. The degree of inhibition in vitro by antioxidants taken orally may be related to their efficacy in inhibiting dense cell formation in the patients. On the basis of these in vivo and ex vivo studies, we propose that a cocktail of antioxidants would have beneficial effects in lessening the incidence and severity of crisis and reducing anemia in sickle cell disease.

Green tea extract and aged garlic extract inhibit anion transport and sickle cell dehydration in vitro

Both green tea extract (GTE or tea polyphenols) and aged garlic extract (AGE) effectively inhibited in vitro dehydration of sickle red blood cells induced by K-Cl cotransport or red cell storage. For K-Cl cotransport induced by 500 mM urea, 0.3 mg/ml EGCg (epigallocatechin gallate; a major component in GTE) almost completely inhibited dehydration, and 6 mg/ml AGE inhibited dehydration to 30% of the control level. Both vitamins E and C had no effect at the level of 2 mM. Different tea extracts had different degrees of inhibition, but the inhibitory activity increased when the number of hydroxyl groups in the compounds increased. With storage of sickle cells at 4 degrees C for 6 days, the cells started to undergo spontaneous dehydration when incubated at 37 degrees C. Neither inhibitors for Ca-induced K efflux nor K-Cl cotransport could inhibit cell dehydration of stored sickle cells, but both GTE and AGE effectively inhibited it. Chloride efflux measurements using a chloride electrode demonstrated that both GTE and AGE inhibited anion transport in red blood cells. The inhibitory mechanism of these compounds may be related to anion transport inhibition, although involvement of their antioxidant activities can not yet be ruled out.

Hypoxia-induced generation of nitric oxide free radicals in cerebral cortex of newborn guinea pigs

Previous studies have shown that brain tissue hypoxia results in increased N-methyl-D-aspartate (NMDA) receptor activation and receptor-mediated increase in intracellular calcium which may activate Ca++-dependent nitric oxide synthase (NOS). The present study tested the hypothesis that tissue hypoxia will induce generation of nitric oxide (NO) free radicals in cerebral cortex of newborn guinea pigs. Nitric oxide free radical generation was assayed by electron spin resonance (ESR) spectroscopy. Ten newborn guinea pigs were assigned to either normoxic (FiO2 = 21%, n = 5) or hypoxic (FiO2 = 7%, n = 5) groups. Prior to exposure, animals were injected subcutaneously with the spin trapping agents diethyldithiocarbamate (DETC, 400 mg/kg), FeSO4.7H2O (40 mg/kg) and sodium citrate (200mg/kg). Pretreated animals were exposed to either 21% or 7% oxygen for 60 min. Cortical tissue was obtained, homogenized and the spin adducts extracted. The difference of spectra between 2.047 and 2.027 gauss represents production of NO free radical. In hypoxic animals, there was a difference (16.75+/-1.70 mm/g dry brain tissue) between the spectra of NO spin adducts identifying a significant increase in NO free radical production. In the normoxic animals, however, there was no difference between the two spectra. We conclude that hypoxia results in Ca2+-dependent NOS mediated increase in NO free radical production in the cerebral cortex of newborn guinea pigs. Since NO free radicals produce peroxynitrite in presence of superoxide radicals that are abundant in the hypoxic tissue, we speculate that hypoxia-induced generation of NO free radical will lead to nitration of a number of cerebral proteins including the NMDA receptor, a potential mechanism of hypoxia-induced modification of the NMDA receptor resulting in neuronal injury.

Sickle cell anemia: a potential nutritional approach for a molecular disease

A certain population of red blood cells in patients with sickle cell anemia has an elevated density and possesses an abnormal membrane. These "dense cells" have a tendency to adhere to neutrophils, platelets, and vascular endothelial cells, and, thus, they could trigger vasoocclusion and the subsequent painful crisis from which these patients suffer. We developed a laboratory method of preparing such dense cells and found that nutritional antioxidant supplements, hydroxyl radical scavengers, and iron-binding agents could inhibit the formation of dense cells in vitro. The concentrations at which effective nutritional supplements could inhibit dense cell formation by 50% were 4.0 mg/mL for aged garlic extract, 0.38 mg/mL for black tea extract, 0.13 mg/mL for green tea extract, 0.07 mg/mL for Pycnogenol, 930 microM for alpha-lipoic acid, 270 microM for vitamin E, 45 microM for coenzyme Q(10), and 32 microM for beta-carotene. Both an ex vivo study and a pilot clinical trial demonstrated that a cocktail consisting of daily doses of 6 g of aged garlic extract, 4-6 g of vitamin C, and 800 to 1200 IU of vitamin E may indeed be beneficial to the patients.

S-allylcysteine ameliorates doxorubicin toxicity in the heart and liver in mice

Doxorubicin, a potent anticancer drug, is effective against a wide range of human neoplasms. However, the clinical uses of doxorubicin have been limited due to its serious cardiotoxic effects, which are likely the result of generation of free radicals and lipid peroxidation. S-Allylcysteine (SAC), an organosulfur compound purified from garlic, has been reported to have antioxidant and radical scavenging effects. Thus, we examined the effect of SAC on doxorubicin toxicity in mice. Severe doxorubicin toxicity was induced in mice by a single intraperitoneal injection (15 mg/kg body weight). SAC (30 mg/kg) was injected intraperitoneally daily for 5 days, starting two days prior to the administration of doxorubicin. Body weight was measured every alternate day. A measurement of serum creatine phosphokinase (CPK) and a histopathological analysis of the heart and liver was performed 6 days after the administration of doxorubicin. Death of any of the animals was recorded during the observation period. Doxorubicin injection induced a mortality rate of 58%, with SAC treatment reducing the doxorubicin-induced mortality rate to 30%. The severe body weight loss caused by doxorubicin (13%) was also significantly attenuated by SAC treatment (9%). Although an elevation of the level of serum CPK was observed following doxorubicin injection (5472 +/- 570 i.u./L), treatment with SAC significantly reduced the level of CPK (1923 +/- 635 i.u./L). Histological analysis demonstrated that heart and liver damage was significantly less severe in SAC treated mice than in mice receiving only doxorubicin. These results suggest that SAC research may ultimately lead to a resolution of the adverse effects of doxorubicin treatment in cancer chemotherapy.

Oxygen free radical generation during in-utero hypoxia in the fetal guinea pig brain: the effects of maturity and of magnesium sulfate administration

Previous studies have shown, employing direct measurements with electron spin resonance (ESR) spectroscopy, that hypoxia induces an increased production of oxygen free radicals (OFR) in the brain of the guinea pig fetus. The present study using the same approach, investigated the effects of maturity and Mg2+-pretreatment on hypoxia-induced OFR formation in the guinea pig fetal brain. The normoxic and the hypoxic groups were exposed for 60 min to 21% or 7% oxygen, respectively. The control group consisted of term fetuses exposed to normoxia (n=7) and hypoxia (n=7). The experimental groups consisted of the following: (a) for the investigation on maturity effect, preterm fetuses (40 days) exposed to normoxia (n=6) or hypoxia (n=6); and (b) for the Mg2+-pretreatment investigation, term fetuses (60 days) exposed to normoxia (n=6) or hypoxia (n=6) following maternal pretreatment with Mg2+ which consisted of an initial bolus of MgSO4 (600 mg/kg, i.p.) 1 h prior to hypoxia followed by a second dose (300 mg/kg, i.p.). Oxygen free radicals were measured by ESR spectroscopy in the fetal cerebral cortical tissue utilizing phenyl-N-tert-butylnitrone (PBN) spin trapping. Fetal brain tissue hypoxia was documented biochemically by decreased tissue levels of ATP and phosphocreatine. In the control group of term fetuses, the cortical tissue from hypoxic fetuses showed a significant increase in spin adducts (71% increase, p<0.01). In the preterm group, the cortical tissue from hypoxic fetuses showed a 33% increase in spin adducts (p<0.001). The baseline free radical generation during normoxia was 22.5% higher at preterm than at term (41.4+/-3.5 units/g issue vs. 33.8+/-9.3 units/g tissue, p<0.05). In Mg2+-treated groups, spin adduct levels in cortical tissue from hypoxic fetuses did not significantly differ from those of the normoxic group (30.2+/-9.9 units/g tissue, normoxic-Mg2+ vs. 30. 6+/-8.1 units/g tissue, hypoxic-Mg2+). The results indicate that the fetal brain at term may be more susceptible to hypoxia-induced free radical damage than at preterm and that Mg2+ administration significantly decreased the hypoxia-induced increase in oxygen free radical generation in the term fetal guinea pig brain in comparison with non-treated hypoxic group.

Deleterious brain cell membrane effects after NMDA receptor antagonist administration to newborn piglets

Previous studies have shown that administration of the N-methyl-d-aspartate (NMDA) receptor antagonist 3-(2-carboxypiperazin-4-yl)-1-phosphonic acid (CPP) reduces NMDA-mediated neurotoxicity in animal models of hypoxia/ischemia but also may induce brain tissue vacuolization and alter glucose metabolism. The present study tests the hypothesis that CPP administration alters brain cell membrane structure and function in the cerebral cortex of normoxic newborn piglets through the generation of oxygen free radicals and induction of lipid peroxidation. Twenty six anesthetized, ventilated newborn piglets-13 treated with 2 mg/kg i.v. CPP and 13 untreated controls-were studied. ATP and phosphocreatine (PCr) levels were measured as an index of cellular energy metabolism and tissue glucose levels determined. Na+, K+-ATPase activity was measured as an index of brain cell membrane function and the lipid peroxidation products conjugated dienes (CD) and fluorescent compounds (FC) measured. Free radical generation was detected on cortical biopsies homogenized with alpha-phenyl-N-tert-butyl-nitrone (PBN) through electron spin resonance spectroscopy. Signal height of spectrum was divided by dry tissue weight and expressed as mm/g tissue. In the two groups brain tissue ATP and PCr levels were not different. Tissue glucose levels were higher in the CPP group (24+/-5 mg/dl) than in controls (14+/-3 mg/dl), p<0.05, whereas Na+,K+-ATPase activity was lower in the CPP group than in controls (34+/-4 vs. 43+/-6 micromol Pi/mg protein/h), p<0.05. Lipid peroxidation products were higher in the CPP group (CD: 57+/-19 nmol/g brain, FC: 1.5+/-0.3 microg/g brain) than in controls (CD: 0+/-0 nmol/g brain, FC: 0.9+/-0.2 microg/g brain), p<0. 05. Free radical intensity was higher in the CPP group (493+/-397 mm/g tissue) than in controls (51+/-83 mm/g tissue), p<0.05. In vitro administration of CPP to brain cell membranes did not change Na+,K+-ATPase activity or the generation of lipid peroxidation products. The data demonstrate that administration of CPP induces lipid peroxidation, results in free radical generation, decreases brain cell membrane Na+,K+-ATPase activity and alters glucose metabolism in the cerebral cortex of newborn piglets. Since CPP is a potent antagonist of the NMDA receptor, we speculate that CPP generates free radicals through a pathway independent of the NMDA receptor by altering cellular metabolism and possibly glucose utilization during normoxia in newborn piglets.

Pulmonary vascular stress from carbon monoxide

Studies were conducted with rats to investigate whether exposure to carbon monoxide (CO) at concentrations frequently found in the environment caused lung injury mediated by nitric oxide (*NO)-derived oxidants. Lung capillary leakage was significantly increased 18 h after rats had been exposed to CO at concentrations of 50 ppm or more for 1 h. An elevation of *NO during CO exposure was demonstrated by electron paramagnetic resonance spectroscopy. There was a 2.6-fold increase of *NO over control in the lungs of rats exposed to 100 ppm CO. A qualitative increase in the concentration of H2O2 was also detected in lungs during CO exposure, and this change was caused by *NO as it was inhibited in rats pretreated with the nitric oxide synthase inhibitor, Nomega nitro-l-arginine methyl ester (l-NAME). Production of *NO-derived oxidants during CO exposure was indicated by an elevated concentration of nitrotyrosine in lung homogenates. The CO-associated elevations in lung capillary leakage and nitrotyrosine concentration did not occur when rats were pretreated with l-NAME. CO exposure did not change the concentrations of endothelial or inducible nitric oxide synthase in lung and leukocyte sequestration was not detected as a consequence of CO exposure. CO-mediated lung leak and nitrotyrosine elevation were not affected by neutropenia. We conclude that CO exposure elevates the steady-state concentration of *NO in lungs. Consequences from this change include increases in the concentration of reactive oxygen species, production of *NO-derived oxidants such as peroxynitrite, and physiological evidence of lung injury.

Direct measurement of oxygen free radicals during in utero hypoxia in the fetal guinea pig brain

The present study tested the hypothesis that maternal hypoxia induces oxygen free radical generation in the fetal guinea pig brain utilizing techniques of electron spin resonance spectroscopy and alpha-phenyl-tert-butyl nitrone (PBN) spin trapping. Pregnant guinea pigs of 60 days gestation were divided into normoxic and hypoxic groups and exposed to 21% or 7% oxygen for 60 min. Free radical generation was documented by measuring the signal of PBN spin adducts. Fluorescent compounds were determined as an index of lipid peroxidation and the activity of Na+,K+-ATPase was determined as an index of brain cell membrane function. Hypoxic fetal cerebral cortical tissue showed a significant increase in spin adducts (normoxic: 33.8+/-9.3 units/g tissue vs. hypoxic: 57.9+/-9.2 units/g tissue, p<0.01) and fluorescent compounds (normoxic: 0.639+/-0.054 microg quinine sulfate/g brain vs. 0.810+/-0.102 microg quinine sulfate/g brain, p<0.01) and a decrease in Na+,K+-ATPase activity (normoxic: 43.04+/-2.50 micromol Pi/mg protein/h vs. hypoxic: 33. 80+/-3.51 micromol Pi/mg protein/h, p<0.001). These results demonstrate an increased free radical generation during hypoxia in the fetal guinea pig brain. The spectral characteristics of the radicals were consistent with those of alkoxyl radicals. The increased level of fluorescent compounds and decreased activity of Na+,K+-ATPase indicated hypoxia induced brain cell membrane lipid peroxidation and dysfunction, respectively. These results directly demonstrate an increased oxygen free radical generation during hypoxia and suggest that hypoxia-induced increase in lipid peroxidation and decrease in membrane function, as indicated by a decrease in Na+,K+-ATPase activity, are consequences of increased free radicals. The nature of predominantly present alkoxyl radical indicates ongoing lipid peroxidation during hypoxia. The direct demonstration of oxygen free radical generation during hypoxia is the critical missing link in the mechanism of hypoxia-induced brain cell membrane dysfunction and damage.

DNA strand scission by polycyclic aromatic hydrocarbon o-quinones: role of reactive oxygen species, Cu(II)/Cu(I) redox cycling, and o-semiquinone anion radicals,

In previous studies, benzo[a]pyrene-7,8-dione (BPQ), a polycyclic aromatic hydrocarbon (PAH) o-quinone, was found to be 200-fold more potent as a nuclease than (+/-)-anti-7,8-dihydroxy-9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene, a suspect human carcinogen. The mechanism of strand scission mediated by naphthalene-1,2-dione (NPQ) and BPQ was further characterized using either phiX174 DNA or poly(dG).poly(dC) as the target DNA. Strand scission was extensive, dependent on the concentration of o-quinone (0-10 microM), and required the presence of NADPH (1 mM) and CuCl2 (10 microM). The production of reactive species, i.e., superoxide anion radical, o-semiquinone anion (SQ) radical, hydrogen peroxide (H2O2), hydroxyl radical (OH.), and Cu(I), was measured in the incubation mixtures. The formation of SQ radicals was measured by EPR spectroscopy under anaerobic conditions in the presence of NADPH. A Cu(II)/Cu(I) redox cycle was found to be critical for DNA cleavage. No strand scission occurred in the absence of Cu(II) or when Cu(I) was substituted, yet Cu(I) was required for OH* production. Both DNA strand scisson and OH. formation were decreased to an equal extent, albeit not completely, by the inclusion of OH. scavengers (mannitol, soduim benzoate, and formic acid) or Cu(I) chelators (bathocuproine and neocuproine). In contrast, although the SQ radical signals of NPQ and BPQ were quenched by DNA, no strand scission was observed. When calf thymus DNA was treated with PAH o-quinones, malondialdehyde (MDA) was released by acid hydrolysis. The formation of MDA was inhibited by OH. scavengers suggesting that OH* cleaved the 2'-deoxyribose moiety in the DNA to produce base propenals. These studies indicate that for PAH o-quinones to act as nucleases, NADPH, Cu(II), Cu(I), H2O2, and OH*, were necessary and that the primary species responsible for DNA fragmentation was OH., generated by a Cu(I)-catalyzed Fenton reaction. The genotoxicity of PAH o-quinones may play a role in the carcinogenicity and mutagenicity of the parent hydrocarbons.

8-epi PGF2 alpha generation during coronary reperfusion. A potential quantitative marker of oxidant stress in vivo

BACKGROUND

Myocardial reperfusion is believed to be associated with free radical injury. However, indexes of oxidative stress in vivo have been limited by their poor specificity and sensitivity. Isoprostanes are stable products of arachidonic acid formed in a nonenzymatic, free radical-catalyzed manner. We have developed a sensitive and specific assay for one of these compounds, 8-epi prostaglandin (PG) F2 alpha.

METHODS AND RESULTS

To address its utility as an index of oxidative stress during coronary reperfusion, we measured urinary levels by gas chromatography/mass spectrometry in a canine model of coronary thrombolysis, in patients with acute myocardial infarction treated with thrombolytic therapy, and in patients after elective coronary artery bypass surgery. Urinary 8-epi PGF2 alpha was unchanged after circumflex artery occlusion in a canine model of coronary thrombolysis (n = 13; 437.2 +/- 56.4 versus 432.7 +/- 55.2 pmol/mmol creatinine) but increased significantly (P < .05) immediately after reperfusion (553.8 +/- 64.7 pmol/mmol). Urinary levels were increased (P < .001) in patients (n = 12) with acute myocardial infarction given lytic therapy (265.8 +/- 40.8 pmol/mmol) compared with age-matched control subjects (n = 20; 91.5 +/- 11.8 pmol/mmol) and patients with stable coronary disease (n = 20; 95.7 +/- 6.3 pmol/mmol). Preoperative levels rose from 113.2 +/- 11.8 to 248.2 +/- 86.3 pmol/mmol at 30 minutes into revascularization to 332.2 +/- 82.6 pmol/mmol by 15 minutes after global myocardial reperfusion (P < .05) and dropped to 181.2 +/- 50.4 pmol/mmol at 30 minutes and 120.2 +/- 9.9 pmol/mmol at 24 hours after bypass surgery (n = 5). Corresponding changes in spin adduct formation, found with electron paramagnetic resonance, were noted in 2 patients.

CONCLUSIONS

These data support the hypothesis that free radical generation occurs during myocardial reperfusion. Measurement of isoprostane production may serve as a noninvasive index of oxidative stress.

Prevention of experimental allergic encephalomyelitis by targeting nitric oxide and peroxynitrite: implications for the treatment of multiple sclerosis

In this study we provide further evidence associating activated cells of the monocyte lineage with the lesions of multiple sclerosis (MS). Using a combination of immunohistochemistry and reverse transcriptase-dependent in situ polymerase chain reaction analysis, we have identified monocytes expressing inducible nitric oxide synthase (iNOS) to be prevalent in the plaque areas of post mortem brain tissue from patients with MS. In addition, we have obtained evidence of the nitration of tyrosine residues in brain areas local to accumulations of iNOS-positive cells. In parallel studies we have assessed the effects of inhibitors of iNOS induction, as well as scavengers of nitric oxide and peroxynitrite in the experimental allergic encephalomyelitis model. Significant therapeutic effects were seen with the inhibitor of iNOS induction, tricyclodecan-9-xyl-xanthogenate, a nitric oxide scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and a peroxynitrite scavenger, uric acid. In particular, treatment with high doses of uric acid virtually prevented clinical symptoms of the disease. Together with our demonstration of the presence of activated macrophages expressing high levels of iNOS and evidence of peroxynitrite formation in brain tissue from patients with MS, these findings are of importance in the development of approaches to treat this disease.

Attenuation of rat ischemic brain damage by aged garlic extracts: a possible protecting mechanism as antioxidants

Effects of an aged garlic extract and its thioallyl components on rat brain ischemia were examined using a middle cerebral artery occlusion model and a transient global ischemia model. In focal ischemia, an aged garlic extract, S-allyl cysteine (SAC), Allyl sulfide (AS) or Allyl disulfide (ADS) was administered 30 min prior to ischemic insult. Three days after ischemic insult, water contents of both ischemic and contralateral hemispheres were measured to assess the degree of ischemic damage. The water content of the ischemic control (no drug treatment) group was 81.50 +/- 0.07% (mean +/- SEM). It was significantly reduced with the administration of 300 mg/kg of SAC; the water content was 80.66 +/- 0.11% (P < 0.001). The histological observation using 2,3,5-triphenyltetrazolium chloride staining demonstrated that the administration of SAC reduced infarct volume. Neither AS nor ADS was effective. In global ischemia, the production of reactive oxygen species (ROS) was measured ex vivo using a spin-trapping agent, alpha-phenyl-N-tert-butylnitrone, and electron paramagnetic resonance spectroscopy. The production of ROS had two peaks; first at 5 min and second at 20 min after reperfusion. Both SAC and 7-nitro indazole, a nitric oxide synthase inhibitor, did not attenuate the amount of ROS produced at the first peak, but did the amount of the second peak. A possible involvement of peroxinitrite, which may be formed from superoxide and nitric oxide and is known to be highly toxic in ischemia/reperfusion injury of the brain, was suggested.

Inhibition of ozone-induced nitric oxide synthase expression in the lung by endotoxin

Inhalation of the pulmonary irritant ozone is associated with an accumulation of macrophages in the lung. These cells, along with type II epithelial cells, are activated to release increased quantities of hydrogen peroxide and nitric oxide, two reactive mediators that have been implicated in tissue injury. In the present studies we determined whether pretreatment of rats with bacterially derived endotoxin, which modulates oxidant levels in tissues, could abrogate the effects of ozone on lung injury and nitric oxide production. Acute exposure of rats to ozone (2 parts per million, 3 h) resulted in nitric oxide production in the lung as measured by electron paramagnetic resonance spin trapping. This was correlated with expression of inducible nitric oxide synthase (iNOS) mRNA in the lung as determined by in situ hybridization. Particularly high levels of iNOS were evident in alveolar macrophages and type II cells. Alveolar macrophages isolated from ozone-treated rats also expressed increased iNOS mRNA and protein as measured by Northern and Western blotting, respectively, and produced more nitric oxide compared with cells from air-exposed animals. Treatment of rats with endotoxin (5 mg/kg, intravenously), 30 min prior to ozone, was found to abrogate ozone-induced increases in iNOS mRNA and protein expression, as well as nitric oxide production by alveolar macrophages. This was associated with a reduction in ozone-induced tissue injury as determined by levels of lung lavage fluid protein. Ozone inhalation also resulted in a reduction in intracellular glutathione in alveolar macrophages, an effect that was blocked by endotoxin administration. Taken together, these data provide evidence that the protective effects of endotoxin against ozone-induced injury are mediated, at least in part, by alterations in levels of lung oxidants and antioxidants.

Nitric oxide production and perivascular nitration in brain after carbon monoxide poisoning in the rat

Nitric oxide is a short-lived free radical and physiological mediator which has the potential to cause cytotoxicity. Studies were conducted to investigate whether nitric oxide, and the potent oxidant peroxynitrite, were generated in brain during experimental carbon monoxide (CO) poisoning in the rat. Nitric oxide production was documented by electron paramagnetic resonance spectroscopy, and found to be increased by ninefold immediately after CO poisoning. Evidence that peroxynitrite was generated was sought by looking for nitrotyrosine in the brains of CO-poisoned rats. Nitrotyrosine was found deposited in vascular walls, and also diffusely throughout the parenchyma in inummocytochemical studies. The affinity and specificity of an anti-nitrotyrosine antibody was investigated and a solid phase immunoradiochemical assay was developed to quantity nitrotyrosine in brain homogenates. A 10-fold increase in nitrotyrosine was found in the brains of CO-poisoned rats. Platelets were involved with production of nitrotyrosine in the early phase of exposure to CO. However, nitrotyrosine formation and leukocyte sequestration were not decreased in thrombocytopenic rats poisoned with CO according to the standard model. When rats were pre-treated with the nitric oxide synthase inhibitor, L-nitroarginine methyl ester, formation of both nitric oxide and nitrotyrosine in response to CO poisoning were abolished, as well as leukocyte sequestration in the microvasculature, endothelial xanthine dehydrogenase conversion to xanthine oxidase, and brain lipid peroxidation. We conclude that perivascular reactions mediated by peroxynitrite are important in the cascade of events which lead to brain oxidative stress in CO poisoning.

Generation of reactive oxygen species during the enzymatic oxidation of polycyclic aromatic hydrocarbon trans-dihydrodiols catalyzed by dihydrodiol dehydrogenase

Dihydrodiol dehydrogenase (DD; EC 1.3.1.20) catalyzes the oxidation of polycyclic aromatic hydrocarbon (PAH) trans-dihydrodiols (proximate carcinogens) to catechols which rapidly autoxidize to yield o-quinones (Smithgall, T. E., Harvey, R. G., and Penning, T. M. (1988) J. Biol. Chem 263, 1814-1820). Although this pathway suppresses the formation of the PAH anti- and syn-diol epoxides (ultimate carcinogens), the process of autoxidation is anticipated to yield reactive oxygen species (ROS). We now show that the NADP+ dependent oxidation of (+/-)-trans-1,2-dihydroxy-1,2-dihydronaphthalene (Npdiol) and (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (Bpdiol) catalyzed by homogeneous DD is accompanied by the consumption of molecular oxygen and the production of H2O2. With both trans-dihydrodiol substrates, oxygen consumption was stoichiometric with H2O2 production consistent with the reaction: QH2 + O2 = H2O2 + Q, where QH2 is the catechol and Q is the o-quinone. Using Npdiol or Bpdiol as substrates, a burst of superoxide anion production is catalyzed by DD which can be detected as the rate of cyt c reduction that is inhibited by superoxide dismutase. Using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as spin-trapping agent, secondary spin adducts corresponding to DMPO-CH3 were formed during the enzymatic oxidation of Npdiol and Bpdiol. The formation of the CH3. radical arises from the OH. attack of DMSO, which was used as cosolvent. These spin adducts were attenuated by superoxide dismutase and catalase, implying that O2-. and H2O2 are obligatory for the formation of DMPO-CH3. It is proposed that O2-. is the radical that propagates autoxidation and that the resultant H2O2 undergoes Fenton chemistry to produce the OH. radical. Identical spin adducts were observed using a superoxide anion generating system (hypoxanthine/xanthine oxidase) and DMPO as spin-trapping agent in the presence of DMSO. The ability of DD to generate ROS during the oxidation of PAH trans-dihydrodiols (proximate carcinogens) may have important implications for tumor initiation and promotion.

Three-dimensional imaging of nitric oxide production in the rat brain subjected to ischemia-hypoxia

By the systemic administration of diethyldithiocarbamate and iron into the rat, nitric oxide radicals produced in the brain during ischemia-hypoxia were trapped. The right hemisphere of the brain was then removed and frozen with liquid nitrogen. With use of recently developed electron paramagnetic resonance imaging instrumentation and techniques, three-dimensional imaging of the production of the nitric oxide radicals in several brains was performed. The results suggest that nitric oxide radicals were produced and trapped in the areas that are known to have high nitric oxide synthase activity, such as cortex, hippocampus, hypothalamus, amygdala, and substantia nigra. In this ischemia-hypoxia model, which did not interrupt the posterior circulation, the production and trapping of nitric oxide in the cerebellum were approximately 30% of those in the cerebrum.

Hepatic nitric oxide production following acute endotoxemia in rats is mediated by increased inducible nitric oxide synthase gene expression

In the present studies, we analyzed the effects of acute endotoxemia on hepatocyte nitric oxide production and functional activity. Treatment of rats with 5 mg/kg of lipopolysaccharide (LPS), which induces acute endotoxemia, caused an increase in nitric oxide production in the liver, as measured by electron paramagnetic spin trapping, which was evident within 6 hours. This was associated with expression of inducible nitric oxide synthase (iNOS) messenger (m) RNA in hepatocytes and in sinusoidal cells throughout the liver lobule. Acute endotoxemia also caused alterations in hepatic structure, including hypertrophy, vacuolization, and chromosomal emargination, however these changes were not apparent for 24 to 48 hours. Hepatocytes isolated from endotoxemic rats released increased amounts of nitric oxide, measured by nitrite production, in response to interferon gamma (gamma-IFN) alone or in combination with LPS, tumor necrosis factor alpha, macrophage-colony stimulating factor, granulocyte/macrophage-colony stimulating factor, or hepatocyte growth factor. These results show that hepatocytes are sensitized by acute endotoxemia to respond to inflammatory mediators and growth factors. Increased nitrite production by hepatocytes was due to increased expression of iNOS mRNA and protein and was correlated with the time following induction of acute endotoxemia. Thus, cells isolated 48 hours after induction of acute endotoxemia released significantly more nitrite than cells recovered after 6 hours, a response that was not due to alterations in hepatocyte viability. Hepatocytes isolated from endotoxemic rats also exhibited a marked increase in proliferative capacity when compared with cells from control rats. Nitric oxide production by hepatocytes in vitro was associated with inhibition of cell growth and protein synthesis, which was reversed by the nitric oxide synthase inhibitor, NG-monomethyl-l-arginine (L-NMMA). Agarose gel electrophoresis showed extensive cytoplasmic DNA fragmentation in hepatocytes treated with LPS and gamma-IFN, a characteristic of apoptosis, which was also reversed by L-NMMA. These results, together with our findings that treatment of rats with an inhibitor of nitric oxide synthase partially reversed the structural alterations in the liver associated with acute endotoxemia suggest that nitric oxide may contribute to the pathophysiologic response to this bacterially derived toxin.

Local nitric oxide production in viral and autoimmune diseases of the central nervous system

Because of the short half-life of NO, previous studies implicating NO in central nervous system pathology during infection had to rely on the demonstration of elevated levels of NO synthase mRNA or enzyme expression or NO metabolites such as nitrate and nitrite in the infected brain. To more definitively investigate the potential causative role of NO in lesions of the central nervous system in animals infected with neurotropic viruses or suffering from experimental allergic encephalitis, we have determined directly the levels of NO present in the central nervous system of such animals. Using spin trapping of NO and electron paramagnetic resonance spectroscopy, we confirm here that copious amounts of NO (up to 30-fold more than control) are elaborated in the brains of rats infected with rabies virus or borna disease virus, as well as in the spinal cords of rats that had received myelin basic protein-specific T cells.

Production of nitric oxide and peroxynitrite in the lung during acute endotoxemia

Nitric oxide is a short-lived cytotoxic mediator that has been implicated in the pathogenesis of endotoxin-induced tissue injury and septic shock. In the present studies we determined whether this mediator is produced in the lung during acute endotoxemia. We found that intravenous injection of rats with bacterially derived lipopolysaccharide (LPS), a condition that induces acute endotoxemia, caused a time-dependent increase in inducible nitric oxide synthase (iNOS) mRNA expression in the lung, which reached a maximum after 24 h. This was correlated with nitric oxide production in the lung as measured by electron paramagnetic spin trapping, which was detectable within 6 h. Alveolar macrophages (AMs) and interstitial macrophages (IMs) isolated from rats 6-12 h after induction of acute endotoxemia were also found to exhibit increased nitric oxide production in response to in vitro stimulation with interferon-gamma (IFN-gamma) and LPS measured by nitrite accumulation in the culture medium. The effects of acute endotoxemia on nitric oxide production by these cells were, however, transient and returned to control levels by 24 h in AMs and 36 h in IMs. Interestingly, although nitrite accumulation in the culture medium of IMs isolated 48 h after induction of acute endotoxemia and stimulated with low concentrations of IFN-gamma and LPS was reduced, when compared with cells from control animals, these cells, as well as AMs, continued to express high levels of iNOS protein and mRNA. This was correlated with increased peroxynitrite production by the cells. Peroxynitrite has been shown to act as a nitrating agent and can generate nitrotyrosine residues in proteins. Using a specific antibody and immunohistochemistry, we found evidence of nitrotyrosine residues in sections of lungs 48 h after treatment of rats with endotoxin. These data suggest that nitric oxide produced by IMs and AMs can react with superoxide anion to form peroxynitrite. Taken together, the present studies demonstrate that AMs and IMs are activated following acute endotoxemia to produce reactive nitrogen intermediates and that both cell types contribute to inflammatory responses in the lung.

Role of nitric oxide in brain ischemia

In order to study the role of nitric oxide (NO) in rat brain ischemia, an in vivo spin trapping technique was applied. The results showed that NO was produced not only during ischemia but also during reperfusion. The role of NO production during ischemia may be to increase cerebral blood flow. The NO production during reperfusion seems to be related to tissue damage.

Electron paramagnetic resonance (EPR) detection of nitric oxide produced during forebrain ischemia of the rat

To detect if nitric oxide (NO) is produced in rat forebrain ischemia, we applied an electron paramagnetic resonance (EPR) NO-trapping technique. We also performed a detailed characterization of the technique. Diethyldithiocarbamate (DETC) and Fe-citrate were used as NO-trapping reagents. Under controlled ventilation, forebrain ischemia was produced by occlusion of both carotid arteries combined with hemorrhagic hypotension at 50 mm Hg for 15 min. DETC and Fe were administered 30 min prior to the onset of ischemia. During ischemia, the cerebral cortex was removed, and EPR samples were prepared. At liquid nitrogen temperatures, the NO-Fe-DETC signal (a triplet signal centered at g = 2.039 with the hyperfine coupling constant aN of 13 G) was detected overlapping Cu-DETC signals. By perfusing various concentrations of an NO-generating agent, 1,1-diethyl-2-hydroxy-2-nitrosohydrazine, into the rat brains, the amount of the "trapped NO" was calibrated. The size of the NO-Fe-DETC signal was well correlated with the NO concentrations in the perfusate (correlation coefficient r = 0.998, p < 0.01). Based on this calibration curve, it was found that the amount of trapped NO during forebrain ischemia increased to seven times that of the control (control n = 5, forebrain ischemia n = 4, p < 0.005).

Nitric oxide released by platelets inhibits neutrophil B2 integrin function following acute carbon monoxide poisoning

Carbon monoxide (CO) poisoning has been reported to temporarily inhibit B2 integrin adherence molecules on leukocytes in previous studies in a rat model. The aim of this study was to investigate the mechanism for this effect. Studies were conducted using blood obtained from rats after they were exposed to CO and also with blood cells exposed to CO in vitro. Initial investigations indicated that inhibition of neutrophil (polymorphonuclear leukocyte, PMN) B2 integrin function was linked to the platelets in blood, as the effect was resolved by decreasing platelet number before PMN adherence was tested. The platelet effect could also be shown by incubating either platelet-rich plasma or whole blood with CO in vitro. The effect of platelets was blocked by superoxide radicals and by NG-nitro-L-arginine methyl ester, an inhibitor of nitric oxide (NO) synthase. These observations suggested that CO caused platelets to release NO, an agent known to inhibit the function of B2 integrins. The concentration of NO measured in suspensions of platelets from rats poisoned with CO according to the established model (exposure to 1000 ppm CO for 40 min and 3000 ppm CO for 20 min) was 47 nmol/10(8) platelets, in contrast to only 0.3 nmol NO/10(8) platelets from control rats. Enhanced NO release occurred despite a 60% inhibition of NO synthase activity, assessed by measuring conversion of [14C]L-arginine to citrulline. Exposure to only 1000 ppm CO for 1 hr caused platelets to release 74 nmol NO/10(8) platelets, and no inhibition of NO synthase occurred. Enhanced NO release, and inhibition of PMN adherence, did not occur after platelets were exposed to light from a quartz lamp to photodissociate CO from heme proteins. The data suggest that the NO flux from platelets increased when CO became bound to heme-containing platelet proteins, which normally scavage intraplatelet NO and thus prevent diffusion beyond the platelet membrane.

Electron paramagnetic resonance study on nitric oxide production during brain focal ischemia and reperfusion in the rat

The production of nitric oxide (NO) during brain focal ischemia and reperfusion was measured using diethyldithiocarbamate (DETC)/Fe-citrate, NO trapping reagents, and electron paramagnetic resonance spectroscopy. The NO production is potentiated after 5 min of ischemia, and is continued during 60 min of ischemia. During the reperfusion period after 60 min of ischemia, NO was also produced. However, its production during reperfusion was not observed when the ischemia time was less than 15 min. The NO signal during reperfusion after 60 min of ischemia decreased after 15 min of reperfusion. These results suggest that NO production during ischemia is a physiological reaction for increasing cerebral blood flow, while NO production during reperfusion may be related to cellular damage.

Protective effects of an aged garlic extract on doxorubicin‐induced cardiotoxicity in the mouse

Protective effects of an aged garlic extract on the cardiotoxicity of doxorubicin (DOX) was evaluated using the mouse. DOX (1.5 mg/kg body wt i.p.) was administered three times per week for 40 days. An aged garlic extract, WG-1 (a preserved stock solution; Wakunaga Pharmaceutical) was administered intraperitoneally six times weekly. DOX caused changes in the electrocardiogram. In the control mice, the width of the QRS complex was 20 +/- 2.8 milliseconds, the R-R interval was 130 +/- 2.8 milliseconds, and the P-Q interval was 30 +/- 1.4 milliseconds. In mice treated with DOX for 40 days, the width of the QRS complex was 50 +/- 10 milliseconds (p < 0.05), the R-R interval was 240 +/- 30 milliseconds (p < 0.05), and the P-Q interval was 45 +/- 1.0 milliseconds (p < 0.01). These values were significantly smaller in mice treated with WG-1 + DOX than in mice treated with DOX. The width of the QRS complex was 29.3 +/- 5.8 milliseconds (p < 0.05), the R-R interval was 145.8 +/- 17.9 milliseconds (p < 0.01), and the P-Q interval was 37.8 +/- 3.5 milliseconds (p < 0.05). The lipid peroxidation in the heart homogenates prepared from DOX-treated mice, as measured by thiobarbituric acid-reactive substance (TBARS, nmol malondialdehyde/100 mg protein) was 332.5 +/- 67.0, which was significantly larger than that in the control mice (186.6 +/- 42.2) (p < 0.05). WG-1 decreased the level of TBARS in DOX-treated mice significantly. In the mice treated with WG-1 + DOX, TBARS was 221.3 +/- 31.6, which was significantly smaller than that of DOX-treated mice (p < 0.05). Histological study demonstrated that the heart treated with DOX had vacuolization in muscle cells, disrupted myofibrils, and swollen mitochondria. Mice that received WG-1 + DOX had no significant pathological lesions in the heart.

Beneficial effects of a non-protein diet on renal function of rats exposed to ischemic and nephrotoxic insults

We investigated the effects of a non-protein diet on renal recovery in rats following 45-minute renal ischemia and mercuric chloride (3 mg/kg BW:S.C.) poisoning. The rats were fed a non-protein diet for one week before the renal insults. Renal functions were measured 24 hours after renal ischemia or 6 hours after mercuric chloride administration. In the ischemia investigation, the glomerular filtration rate (GFR), the renal plasma flow rate (RPFR) and the percent fractional sodium excretion (%FENa) of rats fed a regular diet (19.6% protein) were 25 +/- 7 microliters/min/g KW, 0.19 +/- 0.1 ml/min/g KW and 14.8 +/- 2.0, respectively. These values in the rats fed a non-protein diet showed better recovery, returning to a GFR of 114 +/- 32 microliters/min/g KW, an RPFR of 0.37 +/- 0.1 ml/min/g KW, and a %FENa of 2.43 +/- 0.6, respectively (p < 0.05). Furthermore, the seven-day survival rate was improved from 17% in the regular diet group to 100% in the non-protein diet group. In the mercuric chloride investigation, the renal functions in rats on a regular diet were shown by a GFR of 461 +/- 51 microliters/min/g KW, an RPFR of 1.91 +/- 0.2 ml/min/g KW, and a %FENa of 2.22 +/- 0.5. One-week feeding with a non-protein diet ameliorated the decrease in renal function, resulting in a GFR of 604 +/- 84 microliters/min/g KW, an RPFR of 2.15 +/- 0.5 ml/min/g KW, and a %FENa of 2.20 +/- 0.6. Consequently, there was a distinct beneficial effect on the survival of these rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of nitric oxide formation following bilateral carotid occlusion and focal cerebral ischemia in the rat: in vivo detection of the nitric oxide radical by electron paramagnetic resonance spin trapping

We have directly demonstrated in vivo that nitric oxide (NO) is produced in the ischemic rat brain. Using diethyldithiocarbamate and Fe as spin-trapping agents, NO spin adducts were detected by cryogenic electron paramagnetic resonance. The cerebral cortex which was exposed to focal ischemia or bilateral carotid artery occlusion generated an increased amount of spin-adducts of NO radicals (g = 2.039, a hyperfine coupling constant aN = 13 gauss). This signal disappeared by the preischemic administration of NG-nitro-L-arginine methylester, a NO synthase inhibitor.

Reversal of chloroquine resistance in murine malaria parasites by prostaglandin derivatives

An oligomeric ester of prostaglandin B2 (OC-5186) was found to reverse chloroquine resistance in the murine malarial parasite Plasmodium berghei. When mice were infected with either chloroquine-sensitive or -resistant P. berghei on day 0 (by intraperitoneal injection of 1 x 10(6) parasitized erythrocytes), they died before day 23. When treated with 15 mg/kg/day of chloroquine for the first four days of infection, all mice infected with the sensitive-strain survived, while all those infected with the resistant strain died before day 23. When OC-5186 (3-12 mg/kg/day) was administered in combination with chloroquine for the first four days, 60% of the animals infected with the resistant strain survived. The differences in the survival rate between the group treated with chloroquine only and the group treated with a combination of drugs (chloroquine plus 3-12 mg/kg/day of OC-5186) were significant. There was also a significant inhibition of parasitemia in the group treated with the combination of drugs. The combinations of chloroquine and a monomer ester of prostaglandin B2 (OC-5181) had some antimalarial activity, but the differences between the chloroquine-treated group and the combination treatment group were not significant in terms of both the parasitemia and the survival rate. Another oligomeric ester of prostaglandin E1 (MR-356) as well as unesterified monomer prostaglandins (PGA2 and PGB2) were ineffective by themselves and in combination with chloroquine.

EPR spin-trapping study of nitric oxide formation during bilateral carotid occlusion in the rat

The formation of nitric oxide (NO) radicals was demonstrated by electron paramagnetic resonance spectroscopy in the rat during varying degrees of brain ischemia. Diethyldithiocarbamate and Fe-citrate were used as in vivo spin-trapping reagents. The signal of NO spin adducts increased in accordance with the degree of ischemic insults. The formation of NO radicals was inhibited by NG-nitro-L-arginine methyl ester.

Inhibition of lipid peroxidation by some dihydropyridine derivatives

The efficacy of dihydropyridine derivatives in inhibiting lipid peroxidation was studied using modified Buege and Aust's method. The method first involves keeping a decapitated rat head at 37 degrees C for 30 min in order to induce global ischemia. Then, the cortex is removed and homogenized, and the homogenate is subsequently exposed to air for 30 min for reoxygenation. Finally, the amount of thiobarbituric acid-reactive substances (TBAR) is measured. With this method, nisoldipine, nimodipine, nitrendipine, nifedipine and nicardipine were all shown to have an antioxidant activity that correlated with their lipophilicity, which was determined by their octanol/water partition coefficients.

Protein-restricted diet prior to renal insult improves the recovery of renal function following ischemia

The effects of a protein-restricted diet on renal recovery following renal ischemia were studied. The renal function was assessed by measuring the inulin clearance (CIN), the p-aminohippurate clearance (CPAH), and the percent fractional sodium excretion (%FENa) 24 h after 45 min renal ischemia. In rats fed with a regular diet (containing 19.6% protein), CIN was 10.0 +/- 2.2 microL/min/100 g body weight (BW), CPAH 0.08 +/- 0.02 mL/min/100 g BW, and %FENa 14.8 +/- 2.0, 24 h after renal ischemia. In contrast, feeding rats with a no-protein diet (0% protein) for 1 week prior to the ischemic insult significantly improved renal recovery (CIN 48.0 +/- 9.3 microL/min/100 g BW, CPAH 0.16 +/- 0.04 mL/min/100 g BW, and %FENa 2.43 +/- 0.58). Feeding rats with a no-protein diet for 3 weeks prior to ischemic insult further improved the renal recovery (CIN 113 +/- 30 microL/min/100 g BW, CPAH 0.47 +/- 0.17 mL/min/100 g BW, and %FENa 1.55 +/- 0.29). When rats fed with a regular diet were exposed to 45 min of ischemia, the survival rate on day 7 was 16.7%. In rats fed with the no-protein diet for 1 week and for 3 weeks, the 7-day survival rate was 100% in each case. The survival rate of rats fed for 3 days instead of 7 days with the no-protein diet was 87.5%. When a no-protein feeding was shortened to 1 day, no beneficial effects were observed and survival rate was 14.3%. (ABSTRACT TRUNCATED AT 250 WORDS)

Protective effects of a prostaglandin E1 oligomer on taurocholate-induced rat pancreatitis

Effects of prostaglandin E (PGE) on acute pancreatitis have been controversial. This study shows the effects of PGE1 oligomer, MR-356, on trypsin-taurocholate-induced acute pancreatitis in rats. Divided intraperitoneal doses of 0.6 mg/rat were administered, which increased 24 h survival rates when the oligomer was given both at 1 h before and after (group A) and immediately and 3 h after (group B) induction of pancreatitis. In group A MR-356 significantly improved the survival rates at 18 h (94 vs 61%, P < 0.05) and 24 h (68 vs 33%, P < 0.05) when compared with controls. MR-356 improved the survival rates dose-dependently up to 0.6 mg/rat when given by the same protocol of group A. In group B MR-356 also improved the survival rate (72 vs 39%, P < 0.05) only at 24 h, while other parameters failed to improve. The present results suggest that the PGE1 oligomer may play a beneficial role in bile-induced pancreatitis, probably through its proposed effects of stabilization of lysosomal membranes, maintenance of microcirculation and inhibition of protease in the pancreas.

Free radical formation during splanchnic artery occlusion shock

Free radical (FR) formation in the rat intestinal lumen was measured using the spin-trapping technique and electron paramagnetic resonance spectroscopy. Intestinal ischemia was produced by occluding the celiac and the superior mesenteric arteries for 30 min followed by reperfusion. The lumen was filled with a solution of PBN (N-tert-butyl-alpha-phenyl-nitrone) and the intestine was squeezed to enhance the interaction between the PBN solution and the intestinal mucosal cells. Free radicals were produced upon reperfusion, with peaks at 5 and 90 min. Post-ischemic treatment with superoxide dismutase (20 mg.kg(-1)) inhibited the increase of FR production during the second peak by 36%. In a single study in a group of leucocytopenic rats (WBC < 1500/mm(3)), the increase of FR production during the second peak was decreased by 80%. However, these treatments did not inhibit the FR production during the first peak in either group. In contrast, pretreatment with allopurinol (40 and 100 mg.kg(-1) injection at 24 and 3 hours before ischemia, respectively) inhibited the FR production during the first peak by 76%, but did not inhibit during the second peak. The changes in lipid peroxidation in the intestinal mucosa, specific gravity of the intestine and in the hematocrit were correlated to the FR production in the second peak. These results suggest that a major cause of tissue injury after reperfusion in the ischemic intestine may largely be produced by neutrophils.

Protective effect of a prostaglandin oligomer on liver mitochondria in situ: time-shared measurements of fluorescence and reflectance in the cold-preserved rat liver

The protective effect of a new oligomeric derivative of prostaglandin B2, known as OC-5186, was evaluated using time-sharing spectrofluorometry in the cold-preserved rat liver. Experiments were divided into three groups: in group A, a 5000 ng dose of OC-5186 was administered via the peripheral vein, 1000 ng via the portal vein, and 200 ng/ml in University of Wisconsin (UW) solution; in group B, the OC-5186 dosage was ten times greater than that in group A; in group C (control group), liver procurement and storage were performed without OC-5186. At 0, 12, and 24 h after cold preservation at 4 degrees C, the liver was perfused for 30 min at 12 degrees C with oxygenized Krebs-Henseleit solution, after which the perfusate was switched to deoxygenized Krebs-Henseleit solution. Time sharing spectrofluorometry was used to follow NADH fluorescence at 450 nm with a 360-nm excitation wavelength, as well as the reflectance of cytochrome aa3 with 605 minus 620 nm from oxidation to reduction. Rate constants of NADH fluorescence and cytochrome aa3 reflectance were used as indices of integrity of the mitochondrial respiratory chain. In group C, the rate constant of NADH fluorescence decreased significantly (P < 0.05) from the control value of 8.31 +/- 0.21 x 10(-3) (sec-1) to 4.97 +/- 0.15 x 10(-3) and 5.58 +/- 0.16 x 10(-3) (mean +/- SEM) at 12 and 24 h after cold preservation, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of lipid peroxidation by prostaglandin oligomeric derivatives

The inhibition of lipid peroxidation by oligomeric derivatives synthesized from prostaglandin E1 (PGE1) and PGB2 was studied using two rat models. In an in vitro model, the brain was exposed to decapitation-ischemia, the cortex was removed and homogenized, and the formation of thiobarbituric acid reactive substances (TBAR) was measured after exposing the homogenate to in vitro reoxygenation either in the presence or absence of oligomers. It was found that these oligomers could inhibit lipid peroxidation, and that their activities were higher than that of superoxide dismutase (SOD). In an in vivo administration model, either the oligomer or the vehicle was injected i.p. 30 min before decapitation. The brain was exposed to decapitation-ischemia, the cortex was homogenized and exposed to 'in vitro' reoxygenation, after which TBAR value was determined. Ester-type compounds had a greater activity than free-acid type compounds in inhibiting lipid peroxidation. A possible mechanism of the protective effect of these oligomers in ischemia/reperfusion injury may be to scavenge oxygen free radicals.

Inhibitory effect of prostaglandin oligomeric derivatives on 9,10-dimethyl-1,2-benzanthracene-induced hamster lingual carcinomas

The inhibitory effects of prostaglandin oligomeric derivatives OC-3186 and OC-5186 were examined in hamster lingual carcinoma induced by 9,10-dimethyl-1,2-benzanthracene (DMBA). These compounds caused a regression of 40-90% in the size of lingual carcinomas in the hamster within several days after systemic or local administration.

Biologically significant physico-chemical properties of antioxidative prostaglandin derivatives

A monomeric derivative and several oligomeric derivatives were synthesized from prostaglandin B2. Their lipid solubility was studied by measuring their octanol-water partition coefficients. With EPR spectroscopy, the oligomeric derivatives were shown to have g = 2 signal, indicating these compounds have intrinsic free radicals. Measuring the rate of adenochrome formation, it was shown that these derivatives could scavenge superoxide anions. Using a spin-trapping technique employing DMPO, we found that these oligomers could also scavenge hydroxyl radicals. The calcium chelating activity of these compounds were also studied. In an in vitro rat model, these compounds inhibited lipid peroxidation as measured by the production of thiobarbituric acid reacting substances. Other prostaglandin oligomeric derivatives synthesized from PGE1 were also studied, and their properties were compared with these new compounds. Results suggest that both the water solubility and the chelating activity for calcium ions may not be related to their protective effects in ischemic or traumatic injury.

Chronic alcoholism impedes the recovery of renal function following renal ischemia

The recovery of renal function following renal ischemia was studied using rats fed for 1-, 3-, and 5-week periods with an alcoholic diet (ethanol provided 36% of total calories). Renal ischemia was produced by clamping the renal artery and vein for 20 min. Renal function was determined 24 hr after the ischemia. In the absence of ischemic insult, the renal function of rats fed with an alcoholic diet for 1, 3, and 5 weeks was not significantly different from those of nonalcoholic rats. In nonalcoholic rats, renal function (24 hr postischemia) were: glomerular filtration rate (GFR) 430.4 +/- 29.6 microliters/min/g KW (kidney weight), renal plasma flow rate (RPFR) 1.4 +/- 0.17 ml/min/g KW, and fractional sodium excretion (FENa) 2.0 +/- 0.04% (mean +/- SE). Postischemic renal function of rats on 1- and 3-week alcoholic diets were essentially the same as that of the control rats. However, the 24-hr postischemic renal function of 5-week alcoholic diet rats was significantly depressed. The values were only 117.2 +/- 35.2 microliters/min/g KW (p less than 0.05) for GFR, 0.31 +/- 0.12 ml/min/g KW (p less than 0.05) for RPFR, and 7.46 +/- 3.59% for FENa. The present results demonstrate that the rat kidney subjected to prolonged alcohol ingestion was more susceptible to renal insult than a nonalcoholic kidney.

Relationship between free radical production and lipid peroxidation during ischemia-reperfusion injury in the rat brain

Forebrain ischemia was produced in the rat by bilateral occlusion of the common carotid arteries combined with hemorrhagic hypotension (30 mmHg). The whole cerebral cortex was homogenized in the presence of the spin trap agent N-tert-butyl-alpha-phenyl-nitrone, followed by a Folch extract. Spin-adducts were detected using electron spin resonance spectroscopy. The lipid peroxidation was estimated from both the amount of thiobarbituric acid reactive substance and the formation of conjugated diene. After 10 or 20 min of ischemia, reperfusion was initiated which induced an abrupt burst of free radical formation. The formation peaked at 5 min, and the peak value increased with the ischemia time. The degree of lipid peroxidation, which was measured after 20 min of reperfusion, also increased with the ischemia time. The results suggest that the lipid peroxidation may be the direct consequence of the action of free radicals formed during ischemia and reperfusion periods.

[31P]MRS study of the protective effects of prostaglandin oligomers on forebrain ischemia in rats

Two ester-type prostaglandin oligomeric compounds were synthesized, one from prostaglandin E1 (termed MR-356) and the other from prostaglandin B2 (termed OC-5186). Using in vivo [31P]MRS, the protective effects of these oligomers on forebrain ischemia (15 min) were evaluated in a rat model. Forebrain ischemia caused a decrease in intracellular high energy phosphates and intracellular pH (pHi) in the control and compounds-treated groups, but changes of these values in the OC-5186-treated group were significantly smaller than those in the control group. Moreover, the cerebral energy metabolism of the OC-5186-treated group returned to the preischemia level more rapidly than in the control group after forebrain ischemia. MR-356 had some effects, but the differences were not significant.

Why does halothane relax cardiac muscle but contract malignant hyperthermic skeletal muscle?

We have studied the question of the possible role of sarcoplasmic reticulum (SR) in the interaction of volatile anesthetics (such as halothane, enflurane and isoflurane) with muscle. We used two cardiac muscle models, i.e., isolated rat myocytes and Langendorff perfused rat hearts. We compared the results with those for skeletal muscle SR from rabbits, rats and pigs susceptible to malignant hyperthermia (MH). In both skeletal and cardiac muscle SR, volatile anesthetics enhanced the calcium release from the SR. In cardiac muscle, these agents are known to decrease contractility (negative inotropism). We found that caffeine, a well-known agent which releases calcium from the SR, also had a negative inotropic effect in cardiac muscle, raising the possibility of an unexpected link between the potentiation of calcium release and mechanism underlying the observed negative inotropism. Current understanding of anesthetic mechanisms does not include this possibility. We further found that both volatile anesthetics and caffeine decrease the content of calcium in the SR, suggesting that the increase of calcium permeability results in the decrease of calcium ions in the SR which are available for excitation-contraction (E-C) coupling. In MH-susceptible skeletal muscle, a similar increase in calcium permeability does not cause a decrease of contractility, but rather may contribute to a fatal syndrome of temperature increase provoked by abnormal contracture. This difference may be because in skeletal myoplasm calcium ions recycle internally, while in the cardiac muscle cell they are in dynamic equilibrium with extracellular calcium ions.

Protective effect of a new anti-oxidant on the rat brain exposed to ischemia-reperfusion injury: inhibition of free radical formation and lipid peroxidation

A new oligomeric derivative was synthesized from prostaglandin B2 and ascorbic acid, and its effect on rat brain ischemia-reperfusion injury was studied. Brain ischemia was produced in the rat by the combination of bilateral common carotid artery occlusion and hemorrhagic hypotension (30 mmHg, 20 min). The cerebral cortex was homogenized in the presence of the spin trap agent, N-tert-butyl-alpha-phenyl-nitrone (PBN). Spin-adducts were detected using an electron spin resonance spectrometer (EPR). Lipid peroxidation was estimated from the amounts of both thiobarbituric acid reactive substances (TBAR) and conjugated diene. In control experiments, reperfusion induced a burst of free radical formation which peaked at 5 min reperfusion time (238 +/- 41%). Lipid peroxidation increased significantly after 20 min of reperfusion (TBAR, 161 +/- 50%; conjugated diene, 160 +/- 29%). When the oligomeric derivative was administered (9 mg/kg i.p. 30 min before ischemic insult), it significantly reduced both spin adduct formation (103 +/- 13%) and lipid peroxidation (TBAR, 109 +/- 14%; conjugated diene, 97 +/- 33%).

Studies on the permeability of potassium ions across the dura and arachnoid mater of the rat spinal cord

A combined impounder-surface K+ electrode was developed to measure change in K+ ion concentration of the cerebrospinal fluid (CSF) across the dura and arachnoid maters. To determine whether K+ permeability of the rat dura and arachnoid maters is due to an intrinsic permeability, a study was conducted using an atraumatic laminectomy model. Dorsal laminectomy was performed at T7-8, T12, and L1. Artificial CSF containing 4.2 mM, 24.2 mM, or 54.2 mM of K+ was administered by anterograde subdural infusion into the subarachnoid space from the proximal laminectomy site (T7-8), with effluent overflow at the distal laminectomy site (L1). K+ concentration on the dorsal aspect of the central laminectomy site (T12) was measured. It was found that changes in K+ concentrations of the infused solution were detected by the epidural surface electrode. This suggests that the intact rat spinal cord dura and arachnoid maters may be permeable to K+ in this laminectomy model. This study supports the use of the combined impounder-K+ electrode for measuring changes in K+ ion concentration of the CSF that can result from spinal cord trauma and ischemia.

Pharmacologic protection of perfused rat heart against global ischemia

Using a Langendorff rat heart model, studies were performed on the effects of three drugs in protecting the heart against global ischemia. The drugs used were: (a) MR-256, a prostaglandin oligomeric derivative, which is a calcium chelating agent and at the same time, is an inhibitor of phospholipase A2 activity, (b) chlorpromazine which is not a calcium chelator, but is a calmodulin antagonist and is an inhibitor of phospholipase A2 activity, and (c) BAPTA/AM, a calcium chelating agent, but which is not an inhibitor of phospholipase A2 activity. The perfused heart was exposed to 15 minutes of global ischemia. In control experiments (no drug), the ventricular pressure recovered to 26.4 +/- 6.7% (n = 22) of the original level. With pretreatment of (a) MR-256 (b) chlorpromazine, and (c) BAPTA/AM, maximum recoveries were 0.5 +/- 6.7% (n = 5), 88.7 +/- 8.5% (n = 5), 45.3 +/- 26.6% (n = 5), respectively. MR-256 and chlorpromazine were found to react with free radicals. The modes of action of these three different types of drugs are discussed.

Effects of membrane acting-drugs on plasmodium species and sickle cell erythrocytes

The effects of several membrane-acting drugs on malaria and sickle cell anemia was studied. In the initial experiments, propranolol and W-7 were shown to increase red cell density. In vitro, these drugs inhibited the growth of P. falciparum. However, in vivo experiments using the murine malarial parasite, P. vinckei, demonstrated little, if any, anti-parasite activity with the doses of drugs employed. Subsequently, prostaglandin oligomeric derivatives were found to inhibit the growth of P. falciparum in vitro and P. vinckei in vivo. Since prostaglandin oligomers inhibited the formation of dense, dehydrated cells (irreversible sickle cells), they may also have therapeutic efficacy in sickle cell anemia.

Prostaglandin oligomeric derivatives inhibit in vitro formation of dehydrated cells from sickle red cells

Two types of oligomeric derivatives of prostaglandin E1 were synthesized, a free-acid type and a lipophilic ester type. Neither compound inhibited sickling of red blood cells from sickle cell anaemia patients. However, both were found to inhibit the in vitro formation of dehydrated, dense cells (DC) caused by repeated cycles of sickling and unsickling of sickle cells. Both inhibited the formation of DC in a dose-related manner, but the ester type compound was more effective than the acid-type compound. Concentrations at which these compounds inhibit the DC formation by 50% were 5.2 microM and 40 microM for ester and free-acid compounds, respectively. A possible inhibition mechanism is discussed.

Inhibition of ischemic brain edema formation by post-ischemic administration of a prostaglandin oligomer

We studied the efficacy of an oligomeric derivative of prostaglandin E1 in protecting the rat brain against focal ischemia. The degree of ischemic damage was evaluated from three parameters, namely, the degree of edema formation, reduction of motor performance, and memory disturbance as measured by a passive avoidance test. The pre-ischemic administration of the drug (6 mg/kg i.p.) had some effects, but the differences were not significant. The post-ischemic administration (6 mg/kg i.p.) produced significant improvement in all three parameters. The increase of water content of the ischemic hemisphere was reduced (p less than 0.05); the total motor score was improved (p less than 0.01); and the memory disturbance as estimated by the passive avoidance test was reduced (p less than 0.01). A possible mechanism of protection is discussed.

Studies of the cation binding properties of an oligomeric derivative of prostaglandin B1

The ionophoretic activity of PGBx, an oligomeric mixture synthesized from 15-dehydro PGB1, with different cations was measured using arsenazo III-entrapped liposomes. The order of ionophoretic activity was Zn2+ greater than Co2+ greater than Mn2+ greater than Cu2+ greater than Ca2+ greater than Ba2+ greater than Sr2+ greater than Mg2+. The intrinsic fluorescence of PGBx was quenched by the binding of divalent cations as well as by La3+ and H+. Quenching by K+ and Na+ was minimal. The order of quenching strength of divalent cations was Zn2+ greater than Co2+ greater than Cu2+ = Mn2+ greater than Ca2+ greater than Ba2+ greater than Sr2+ greater than Mg2+. Binding affinities of these cations determined by a murexide indicator method were in good agreement with that determined by the fluorescence quenching reaction. The cation binding affinity of PGBx in aqueous solutions correlates with the ionophoretic activity in liposomes. The binding affinity for K+ was estimated from the inhibition by K+ of Ca2+ binding by PGBx. Although PGBx has a lower selectivity for divalent cation binding than the ionophore A23187, the characteristics of the binding affinity of these two compounds for various ions were similar. The pK of PGBx as determined by fluorescence quenching was 6.7. The molecular weight of the divalent cation binding unit was estimated to be about 680, with each PGBx molecule having three such binding sites. The binding of Ca2+ to such a site is one-to-one.