Alcohol-induced generation of lipid peroxidation products in humans

To address the hypothesis that elevated blood alcohol increases systemic oxidant stress, we measured urinary excretion of isoprostanes (iPs), free radical-catalyzed products of arachidonic acid. Ten healthy volunteers received acute doses of alcohol (Everclear-R) or placebo under randomized, controlled, double-blind conditions. Urinary iPF2a-III increased in a time- and dosage-dependent manner after dosing with alcohol, with the peak urinary iPF2a-III excretion correlating with the rise in blood alcohol. To determine whether oxidant stress was associated with alcohol-induced liver disease (ALD), we then studied the excretion of iP in individuals with a documented history of alcohol-induced hepatitis or alcohol-induced chronic liver disease (AC). Both urinary iPF2a-III and urinary iPF2a-VI were markedly increased in patients with acute alcoholic hepatitis. In general, urinary iPF2a-III was significantly elevated in cirrhotic patients, relative to controls, but excretion was more pronounced when cirrhosis was induced by alcohol than by hepatitis C. Excretion of iPF2a-VI, as well as 4-hydroxynonenal and the iPF2a-III metabolite, 2,3-dinor-5, 6-dihydro-iPF2a-III, was also increased in AC. Vitamin C, but not aspirin, reduced urinary iPs in AC. Thus, vasoactive iPs, which serve as indices of oxidant stress, are elevated in the urine in both acute and chronic ALD. Increased generation of iPs by alcohol in healthy volunteers is consistent with the hypothesis that oxidant stress precedes and contributes to the evolution of ALD.

Wheat bran decreases aberrant crypt foci, preserves normal proliferation, and increases intraluminal butyrate levels in experimental colon cancer

BACKGROUND

Dietary wheat bran protects against colon cancer, but the mechanism(s) of this effect is not known. Butyrate, produced by colonic bacterial fermentation of dietary polysaccharides, such as wheat bran, induces apoptosis and decreases proliferation in colon cancer cell lines. Whether similar effects occur in vivo is not well defined. We hypothesized that wheat bran's antineoplastic effects in vivo may be mediated in part by butyrate's modulation of apoptosis and proliferation.

METHODS

Male F344 rats were fed wheat bran-supplemented or an isocaloric, isonitrogenous fiber-free diet. Rats were treated with one dose of the carcinogen azoxymethane or vehicle with sacrifice after 5 days (tumor initiation); or two doses (days O and 7) with sacrifice after 56 days (tumor promotion). Study variables included fecal butyrate levels and the intermediate biomarkers of colon carcinogenesis, aberrant crypt foci (ACF), and changes in crypt cell proliferation and apoptosis.

RESULTS

During tumor initiation, wheat bran produced greater apoptosis (p = .01), a trend toward less proliferation, and preserved the normal zone of proliferation (p = .01). At tumor promotion, wheat bran decreased the number of ACF (proximal colon, p = .005; distal colon, p = .047) and maintained the normal proliferative zone. The fiber-free diet shifted the zone of proliferation into the premalignant pattern in both studies. Wheat bran produced significantly higher fecal butyrate (p = .01; .004, .00001) levels than the fiber-free diet throughout the tumor promotion study.

CONCLUSIONS

Wheat bran increased apoptosis and controlled proliferation during tumor initiation and resulted in decreased ACF. Wheat bran's antineoplastic effects occurred early after carcinogen exposure, and were associated with increased fecal butyrate levels.

The myth of the in situ graft: superiority in infrainguinal bypass surgery?

OBJECTIVES

to compare the clinical outcome of in situ and reversed bypass grafting.

DESIGN

multicentre, prospective, non-randomised study.

PATIENTS AND METHODS

five-hundred patients with an in situ graft and 955 patients with a reversed graft were compared regarding graft occlusion, the need for graft revision, and limb salvage.

RESULTS

two-year assisted primary patency of femoropopliteal bypass procedures was 82% for in situ and 82% for reversed grafts. The corresponding hazard ratio (HR) for occlusion was 1.27 (95% CI 0. 91-1.77). The 2-year assisted primary patency of femorocrural bypass procedures was 69% for in situ vs. 70% for reversed grafts. The corresponding HR was 1.13 (95% CI 0.73-1.75). Adjustment for relevant baseline variables did not change the results. More reinterventions were needed to maintain integrity and patency of the in situ graft especially in crural bypasses. No differences in limb salvage rates were seen.

CONCLUSIONS

reversed and in situ vein grafts have similar patency and limb salvage rates for both femoropopliteal and femorocrural bypass procedures. The in situ graft needs more secondary interventions.

Basal transepidermal water loss is increased in platelet-type 12-lipoxygenase deficient mice

The roles of fatty acids in the skin have been under investigation since early reports of the phenotypic abnormalities of mice fed a diet deficient in essential fatty acids. Little is known about the functional significance of fatty acid metabolism by lipoxygenases in epidermis. Here, we have examined the role of platelet-type 12-lipoxygenase which converts arachidonic acid to the oxygenated metabolite 12-hydroperoxyeicosatetraenoic acid, in the skin using platelet-type 12-lipoxygenase-deficient mice generated by gene targeting. Platelet-type 12-lipoxygenase in wild-type mice was localized to the stratum granulosum by immunohistochemical analysis. Platelet-type 12-lipoxygenase-deficient mice lacked immunodetectable platelet-type 12-lipoxygenase in platelets and epidermis, appeared grossly normal, and exhibited an increase in basal transepidermal water loss without alteration in basal mitotic activity. Water loss and mitotic activity in mice with an acetone-disrupted membrane barrier were normal. No defect in ultrastructural properties or content of major fatty acids in dorsal skin or ear inflammation response was apparent in platelet-type 12-lipoxygenase-deficient mice. These results indicate that the platelet-type 12-lipoxygenase pathway in mice is partly responsible for normal permeability barrier function but the mechanism awaits further elucidation.

Inhibition of Fas receptor (CD95)-induced hepatic caspase activation and apoptosis by acetaminophen in mice

The mechanism of liver cell injury induced by an overdose of the analgesic acetaminophen (AAP) remains controversial. Recently, it was hypothesized that a significant number of hepatocytes die by apoptosis. Since caspases have been implicated as critical signal and effector proteases in apoptosis, we investigated their potential role in the pathophysiology of AAP-induced liver injury. Male C3Heb/FeJ mice were fasted overnight and then treated with 500 mg/kg AAP. Liver injury became apparent at 4 h and was more severe at 6 h (plasma ALT activities: 4110 +/- 320 U/liter; centrilobular necrosis). DNA fragmentation increased parallel to the increase of plasma ALT values. At 6 h there was a 420% increase of DNA fragmentation and a 74-fold increase of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells located predominantly around central veins. However, the activity of the proapoptotic caspase-3 was not increased at any time after AAP. In contrast, injection of the anti-Fas antibody Jo-2 (positive control) caused a 28-fold increase of caspase-3 activity and severe DNA fragmentation before significant ALT release. Treatment with the caspase inhibitor ZVAD-CHF2 had no effect on AAP toxicity but completely prevented Jo-mediated apoptosis. In contrast, Jo-induced caspase activation and apoptosis could be inhibited by AAP treatment in a time- and dose-dependent manner. We conclude that AAP-induced DNA fragmentation does not involve caspases, suggesting a direct activation of endonucleases through elevated Ca2+ levels. In addition, electrophilic metabolites of AAP may inactivate caspases or their activation pathway. This indicates that AAP metabolism has the potential to inhibit signal transduction mechanisms of receptor-mediated apoptosis.

Quality of life after infrainguinal bypass grafting surgery. Dutch Bypass Oral Anticoagulants or Aspirin (BOA) Study Group

PURPOSE

The purpose of this study was to compare quality of life in patients with and without various ischemic complications after infrainguinal bypass grafting surgery for occlusive vascular disease.

METHODS

A sample of patients (n = 746) randomized in the Dutch BOA study (n = 2645), a multicenter trial that compared the effectiveness of oral anticoagulant therapy with aspirin in the prevention of infrainguinal bypass graft occlusions, was entered in this study. On the basis of clinical outcomes of the trial, the patients were grouped as follows: patients with patent grafts (n = 409); patients with nontreated graft occlusions, subdivided into an asymptomatic group (n = 32) and a symptomatic group (n = 65); patients with subsequent revascularizations (n = 194); patients with amputations (n = 36); and patients with failed secondary revascularizations followed by secondary amputation (n = 38). In case an outcome event occurred, the patients were regrouped accordingly. Every half year, the patients completed a Short Form-36 and a EuroQol questionnaire. A multilevel model was used for repeated measure analysis.

RESULTS

The mean follow-up time was 21 months. The quality of life in patients with nontreated asymptomatic occlusions was roughly similar to the quality of life in patients with patent grafts. Patients with symptomatic nontreated occlusions had the lowest outcome with regard to pain as compared with the other groups. Furthermore, physical and social functioning was lower for these patients than for patients with patent grafts. Revascularizations, successful or not, negatively affected pain, social functioning, and physical and emotional role. After successful revascularization, some improvement was observed in pain, physical and social functioning, and general and mental health as compared with the group with nontreated symptomatic occlusions. Amputation deteriorated physical functioning strikingly, especially after failed secondary revascularization. These patients also had the lowest scores of all the groups in the dimensions of social functioning, physical and emotional role, and mental health. EuroQol score showed deterioration of quality of life after all events, except for asymptomatic occlusions. The same patterns emerged if we stratified our analysis according to the indication for the initial operation: claudication or limb salvage. Quality of life was constant over time in all the groups in the observed period.

CONCLUSION

Quality of life in patients with asymptomatic occluded grafts is similar to quality of life in patients with patent grafts. Revascularization of symptomatic occluded grafts improves quality of life to a certain extent. Amputation, in particular after failed secondary revascularization, seemed to be the lowest possible outcome. The results of the Short Form-36 and EuroQol measurements were in line with the clinical expectations. The association of disease severity with scores on the instruments supports the construct validity of these outcome measures for an objective assessment of quality of life in controlled studies.

Inhibition of advanced glycation endproduct formation by acetaldehyde: role in the cardioprotective effect of ethanol

Epidemiological studies suggest that there is a beneficial effect of moderate ethanol consumption on the incidence of cardiovascular disease. Ethanol is metabolized to acetaldehyde, a two-carbon carbonyl compound that can react with nucleophiles to form covalent addition products. We have identified a biochemical modification produced by the reaction of acetaldehyde with protein-bound Amadori products. Amadori products typically arise from the nonenzymatic addition of reducing sugars (such as glucose) to protein amino groups and are the precursors to irreversibly bound, crosslinking moieties called advanced glycation endproducts, or AGEs. AGEs accumulate over time on plasma lipoproteins and vascular wall components and play an important role in the development of diabetes- and age-related cardiovascular disease. The attachment of acetaldehyde to a model Amadori product produces a chemically stabilized complex that cannot rearrange and progress to AGE formation. We tested the role of this reaction in preventing AGE formation in vivo by administering ethanol to diabetic rats, which normally exhibit increased AGE formation and high circulating levels of the hemoglobin Amadori product, HbA1c, and the hemoglobin AGE product, Hb-AGE. In this model study, diabetic rats fed an ethanol diet for 4 weeks showed a 52% decrease in Hb-AGE when compared with diabetic controls (P < 0.001). Circulating levels of HbA1c were unaffected by ethanol, pointing to the specificity of the acetaldehyde reaction for the post-Amadori, advanced glycation process. These data suggest a possible mechanism for the so-called "French paradox," (the cardioprotection conferred by moderate ethanol ingestion) and may offer new strategies for inhibiting advanced glycation.

Glutathione peroxidase-deficient mice are more susceptible to neutrophil-mediated hepatic parenchymal cell injury during endotoxemia: importance of an intracellular oxidant stress

Neutrophils contribute to hepatocellular injury in a number of acute inflammatory reactions. However, the molecular mechanism of parenchymal cell injury remains controversial. To address the issue of whether or not reactive oxygen species (ROS) are important in the injury process, we used the galactosamine/endotoxin (Gal/ET) model of acute liver failure, which involves a neutrophil-mediated parenchymal cell injury. In C3Heb/FeJ mice, Gal/ET induced a significant increase of hepatic and plasma levels of glutathione disulfide (GSSG), an indicator of oxidant stress, selectively during the neutrophil-mediated injury phase. In glutathione peroxidase-deficient mice (Gpx1(-/-)), Gal/ET or Gal/tumor necrosis factor alpha (TNF-alpha) caused more severe neutrophil-mediated liver injury compared with wild-type animals. However, there was no significant difference in other critical parameters, e.g., activation of the transcription factor, nuclear factor-kappaB (NF-kappaB), and soluble intercellular adhesion molecule-1 (sICAM-1), parenchymal cell apoptosis, and neutrophil sequestration in the liver. Our results suggest that neutrophil-derived ROS are responsible for an intracellular oxidant stress in hepatocytes after Gal/ET treatment. Because of the higher susceptibility of Gpx1(-/-) mice to a neutrophil-mediated injury, we conclude that peroxides generated by neutrophils diffused into hepatocytes and contributed to parenchymal cell death in vivo. Thus, strengthening defense mechanisms against ROS in target cells can attenuate excessive inflammatory injury without affecting host defense reactions.

Systemic biosynthesis of prostacyclin by cyclooxygenase (COX)-2: the human pharmacology of a selective inhibitor of COX-2

Prostaglandins (PG) are synthesized by two isoforms of the enzyme PG G/H synthase [cyclooxygenase (COX)]. To examine selectivity of tolerated doses of an inhibitor of the inducible COX-2 in humans, we examined the effects of celecoxib on indices of COX-1-dependent platelet thromboxane (Tx) A2 and on systemic biosynthesis of prostacyclin in vivo. Volunteers received doses of 100, 400, or 800 mg of celecoxib or 800 mg of a nonselective inhibitor, ibuprofen. Ibuprofen, but not celecoxib, significantly inhibited TxA2-dependent aggregation, induced ex vivo by arachidonic acid (83 +/- 11% vs. 11. 9 +/- 2.2%; P < 0.005) and by collagen. Neither agent altered aggregation induced by thromboxane mimetic, U46619. Ibuprofen reduced serum TxB2 (-95 +/- 2% vs. -6.9 +/- 4.2%; P < 0.001) and urinary excretion of the major Tx metabolite, 11-dehydro TxB2 (-70 +/- 9.9% vs. -20.3 +/- 5.3%; P < 0.05) when compared with placebo. Despite a failure to suppress TxA2-dependant platelet aggregation, celecoxib had a modest but significant inhibitory effect on serum TxB2 4 hr after dosing. By contrast, both ibuprofen and celecoxib suppressed a biochemical index of COX-2 activity (endotoxin induced PGE2 in whole blood ex vivo) to a comparable degree (-93.3 +/- 2% vs. -83 +/- 6.1%). There was no significant difference between the doses of celecoxib on COX-2 inhibition. Celecoxib and ibuprofen suppressed urinary excretion of the prostacyclin metabolite 2,3 dinor 6-keto PGF1alpha. These data suggest that (i) platelet COX-1-dependent aggregation is not inhibited by up to 800 mg of celecoxib; (ii) comparable COX-2 inhibition is attained by celecoxib (100-800 mg) and ibuprofen (800 mg) after acute dosing; and (iii) COX-2 is a major source of systemic prostacyclin biosynthesis in healthy humans.

K+ channel blockers: natriuretic potency correlates to vascular ATP-sensitive K+ channel blockade

Using analogs of known vascular ATP-sensitive K+ channel (KATP) blockers, we identified compounds with a wide range of potencies (over 500-fold) in their capacity to block the hypotensive response of 0.2 mg/kg pinacidil in rats. The most potent of these, U-97025E, belongs to a newly disclosed class of compounds, the cyanoguanidines. U-97025E at 0.04 mg/kg blocked 50% of the depressor response induced by 0.2 mg/kg pinacidil. The maximal natriuresis induced by U-97025E (0.4 mg/kg i.v.) increased Na+ excretion by approximately 60%. This natriuresis is of the same magnitude as that induced by thiazide without any effect on K+ excretion. We found a high degree of correlation between natriuretic potency and the capacity to block the blood pressure lowering effects of pinacidil, both among closely related analogs and dissimilar compounds. These findings imply an obligatory rather than incidental relationship between vascular KATP blockade and natriuresis. The exact molecular link of the vascular and renal effects remains to be determined.

A randomized, placebo-controlled, crossover study of E5510 and aspirin in healthy volunteers

Platelet inhibition significantly reduces the risk of cardiovascular mortality and morbidity. However, current antiplatelet therapies have limitations, and more efficacious agents are needed. E5510 is a novel compound that has multiple platelet inhibitory effects in in vitro studies. We compared the in vivo, pharmacodynamic effects of maximal antiplatelet doses of E5510 (20 mg) with 300 mg aspirin in a placebo-controlled, triple crossover trial in nine healthy volunteers. Collagen-induced platelet aggregation and serum thromboxane B2 (TxB2) were similarly inhibited by both compounds in the first 12 h but showed recovery at 24 h in the E5510 group only (p < 0.05). Thrombin and U46619-induced platelet aggregation, as well as basal and prostaglandin E2 (PGE2)-stimulated platelet cyclic adenosine monophosphate (cAMP) levels were unchanged after ingestion of either agent. E5510 and aspirin reduced systemic thromboxane formation without affecting prostacyclin biosynthesis. Neither E5510 nor aspirin inhibited the excretion of 8-epi PGF2alpha and 5,6-DHET, two indices of cyclooxygenase-independent arachidonate metabolism. In conclusion, (a) E55 10 in vivo most likely induces a reversible inhibition of cyclooxygenase, without affecting thromboxane synthetase, phosphodiesterase, thrombin, or thromboxane receptor-mediated signaling; (b) single doses of aspirin or E5510 affect thromboxane/prostacyclin profiles favorably, supporting their use in acute coronary syndromes. This study outlines a comprehensive and minimally invasive approach for the assessment of the in vivo mechanism of action of novel antiplatelet agents.

ILAE-defined epilepsy syndromes in children: correlation with quantitative MRI

PURPOSE

The role of quantitative magnetic resonance imaging (MRI) in evaluation of childhood epilepsy remains poorly defined, with minimal published data. Previous work from our center questioned the specificity of hippocampal asymmetry (HA) in an outpatient group whose epilepsy was defined by using clinical and interictal data only. By using childhood volunteer controls and defining epilepsy syndromes using video-EEG monitoring, we readdressed the utility of HA in differentiating mesial temporal lobe epilepsy (MTLE) from other partial and generalized epileptic syndromes in children.

METHODS

Seventy children were enrolled; entry criteria were age younger than 18 years with predominant seizure type recorded on video-EEG telemetry with volumetric MRI in all cases. Thirty healthy child volunteers had volumetric MRI. Epilepsy syndrome classification was according to ILAE.

RESULTS

Control data revealed symmetric hippocampi, mean smaller/larger ratio of 0.96 (0.95-0.97, 95% CI) with no gender or right/left predominance. Overall 23% of patients had significant HA. Mean hippocampal ratio for MTLE was 0.78 (95% CI, 0.70-0.86), significantly lower than controls and from all other epilepsy syndromes. HA was highly specific (85%) to the syndrome of MTLE. Other potential epileptogenic lesions were found in 27 (39%) patients, lowest yield in frontal and mesial temporal syndromes. Dual pathology was present in 10% of patients. There was no significant association between HA and risk factors.

CONCLUSIONS

In this study, we found that HA in children with a well-defined epilepsy syndrome is highly sensitive and specific for MTLE. Whether this will correlate with surgical outcome, as in adults, is the subject of ongoing study.

Identification of two major F2 isoprostanes, 8,12-iso- and 5-epi-8, 12-iso-isoprostane F2alpha-VI, in human urine

Isoprostanes (iPs) are nonenzymatic, free radical-derived compounds isomeric with enzymatically formed eicosanoids such as prostaglandins, leukotrienes, and thromboxanes. One group formed by the auto-oxidation of arachidonic acid, the F2-iPs, consists of four classes of isomers of prostaglandin F2alpha (PGF2alpha). They are relatively abundant in human urine. This fact, along with their chemical stability and excellent characteristics for quantitation by gas chromatography/mass spectrometry, has made them attractive indices of oxidative stress in humans. We developed a specific assay using gas chromatography/mass spectrometry for the first identified F2-iP, iPF2alpha-III (previously called 8-iso-PGF2alpha or 8-epi-PGF2alpha), which demonstrated the utility of monitoring a specific isomer. Recently, we described an assay for another isomer, iPF2alpha-VI, which is present in urine in greater concentration than iPF2alpha-III and which is particularly amenable to quantitation. We now describe the identification in human urine of two more isomers, 8,12-iso-iPF2alpha-VI and 5-epi-8, 12-iso-iPF2alpha-VI, using high performance liquid chromatography/tandem mass spectrometry and gas chromatography/mass spectrometry. These compounds are each present in approximately 5-fold greater concentrations than iPF2alpha-VI (approximately 20-fold greater than iPF2alpha-III). They share the unique chemical characteristics of class VI compounds, which make them attractive targets for quantitation by gas chromatography/mass spectrometry and immunoassay development.

Parenchymal cell apoptosis as a signal for sinusoidal sequestration and transendothelial migration of neutrophils in murine models of endotoxin and Fas-antibody-induced liver injury

Endotoxin (ET) induces neutrophil sequestration in hepatic sinusoids, the activation of proinflammatory transcription factors (nuclear factor KB [NF-kappaB]) with up-regulation of adhesion molecules on sinusoidal endothelial cells and hepatocytes. However, if galactosamine (Gal) is co-administered with ET, neutrophils transmigrate and attack parenchymal cells. This suggests that a signal from parenchymal cells triggers neutrophil transmigration. In this study, we tested the hypothesis that parenchymal cell apoptosis may induce neutrophil transendothelial migration in the Gal/ET model. Treatment of C3Heb/FeJ mice with 700 mg/kg Gal and 100 microg/kg ET induced tumor necrosis factor alpha (TNF-alpha) formation (13.25 +/- 0.75 ng/mL) and hepatic NF-kappaB activation at 90 minutes; the generation of the C-X-C chemokine KC (2.86 +/- 0.30 ng/mL at 5 hours); sinusoidal neutrophil sequestration (380 +/- 21 polymorphonuclear leukocytes/50 high-power fields) and apoptosis (925% +/- 29% increase of DNA fragmentation; and a 45-fold increase of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells) at 6 hours, followed by transmigration of neutrophils and development of substantial necrosis (38% +/- 3% of hepatocytes; alanine transaminase [ALT]: 1,500 +/- 300 U/L) at 7 hours. Administration of uridine (1,000 mg/kg) did not reduce plasma levels of TNF-alpha and KC, NF-kappaB activation, or polymorphonuclear leukocyte sequestration, but attenuated apoptosis by 90% to 94%. In these livers, neutrophils did not transmigrate and liver injury was prevented (necrosis: < 5%; ALT: 40 +/- 3 U/L). However, massive apoptosis and liver injury initiated by the anti-Fas antibody, Jo2, did not recruit neutrophils into the liver. We conclude that excessive parenchymal cell apoptosis represents an important signal for transmigration of primed neutrophils sequestered in sinusoids during endotoxemia in vivo. However, apoptosis per se does not cause neutrophil sequestration in the liver vasculature.

Prostaglandin F2alpha (PGF2alpha) and the isoprostane, 8, 12-iso-isoprostane F2alpha-III, induce cardiomyocyte hypertrophy. Differential activation of downstream signaling pathways

Prostaglandin receptors may be activated by their cognate ligand or by free radical catalyzed isoprostanes, products of arachidonic acid peroxidation. For example, prostaglandin F2alpha (PGF2alpha) causes hypertrophy of neonatal rat ventricular myocytes, via the PGF2alpha receptor (FP). However, the FP may also be activated by the isoprostane, 8,12-iso-iPF2alpha-III (Kunapuli, P., Lawson, J. A., Rokach, J., and FitzGerald, G. A. (1997) J. Biol. Chem. 272, 27147-27154). Both ligands induce myocyte hypertrophy with overlapping potencies. Interestingly, the hypertrophic effects of these two agonists on cardiomyocytes are additive. Furthermore, the preference of these two agonists for activation of intracellular signal transduction pathways differs in several respects. Thus, PGF2alpha and 8,12-iso-iPF2alpha-III stimulate inositol phosphate formation with EC50 values of 50 +/- 12 nM and 3.5 +/- 0.6 microM, respectively. Moreover, PGF2alpha causes a robust activation ( approximately 50-fold) of Erk2, whereas 8,12-iso-iPF2alpha-III has no effect. Similarly, PGF2alpha causes translocation of cytosolic phospholipase A2 and also results in a 7-fold increment in the formation of 6-keto-PGF1alpha, whereas 8,12-iso-iPF2alpha-III exerts no effect on this pathway. On the other hand, both agonists are equally potent in activating JNK1 and c-Jun, whereas neither activates the p38 kinase. Both PGF2alpha and 8,12-iso-iPF2alpha-III activate the p70S6 kinase (p70(S6K)), but not Akt, downstream of phosphatidylinositol-3-kinase (PI3K). However, both wortmannin, a PI3K inhibitor, and rapamycin, an inhibitor of p70(S6K) activity, inhibit 8,12-iso-iPF2alpha-III -induced myocyte hypertrophy, with IC50 values of 60 +/- 12 and 3 +/- 1.7 nM, respectively, whereas neither compound abrogates the PGF2alpha-mediated response. Thus, both PGF2alpha and 8,12-iso-iPF2alpha-III induce myocyte hypertrophy via discrete signaling pathways. Although both agonists signal via the JNK pathway to initiate changes in c-Jun-dependent gene transcription, PGF2alpha preferentially activates the MEK-Erk2- cytosolic phospholipase A2 pathway. In contrast, the PI3K-p70(S6K) pathway appears to be essential for 8,12-iso-iPF2alpha-III-induced myocyte hypertrophy.

Total synthesis of 17,17,18,18-d4-iPF2alpha-VI and quantification of iPF2alpha-VI in human urine by gas chromatography/mass spectrometry

Isoprostanes are a new class of natural products formed in humans as a result of free-radical-catalyzed lipid peroxidation of polyunsaturated fatty acids. These endogenous compounds are isomeric with biologically active prostaglandins and have great promise as markers of oxidant stress in vivo. iPF2alpha-III (previously 8-iso-PGF2alpha), an isoprostane from Class III (previously known as Class IV), has been used as an index of free-radical-induced oxidative stress. This isoprostane is also produced by the cyclooxygenase enzymes COX1 and COX2. We are proposing a new reliable index of oxidative stress based on iPF2alpha-VI (previously IPF2alpha-I), a new Class VI isoprostane we recently discovered. The advantages of iPF2alpha-VI are that it is several fold more abundant in urine than iPF2alpha-III, hence allowing more accurate determinations. Equally, the proximity of the C-5 OH function to the carboxylic acid allows the formation of the lactone 35 which is easier to purify from other iPs which cannot form such lactones. We have performed the first total synthesis of d4-iPF2alpha-VI by using two synthons, (3,3,4,4-d4)-hexylphosphonium bromide 23 prepared from 5-hexynol and syn-anti-syn lactone 25 synthesized from d-glucose. We have developed two variants of a sensitive GC/MS assay using the synthetic d4-iPF2alpha-VI as an internal standard to determine the levels of endogenous iPF2alpha-VI in biological fluids. Quantification of iPF2alpha-VI formed in vivo may be a more reliable index to assess oxidant stress in humans.

Differential effect of 2-aminoethyl-isothiourea, an inhibitor of the inducible nitric oxide synthase, on microvascular blood flow and organ injury in models of hepatic ischemia-reperfusion and endotoxemia

The vasodilator nitric oxide (NO) is involved in the regulation of systemic blood pressure and local organ blood flow. Inhibitors of the constitutively expressed nitric oxide synthase in endothelial cells (eNOS), e.g., Nomega-nitro-L-arginine methyl ester hydrochloride (L-NAME), aggravated liver injury in a variety of models. On the other hand, inhibitors of the inducible NOS (iNOS), e.g., 2-aminoethyl-isothiourea (AET), were found to be beneficial during endotoxemia. The aim of this investigation was to study the effect of AET compared with L-NAME on liver microvascular blood flow and injury in more complex models with multiple insults, i.e., ischemia (20 min)-reperfusion (8 h) in combination with .5 mg/kg endotoxin (IRE). Male Fisher rats were treated with 10 mg/kg AET or L-NAME and subjected to IRE. At 8 h, liver injury (plasma ALT: 1320+/-164 U/L) was significantly increased in AET-treated (5,018+/-1,379 U/L) and L-NAME-treated groups (2,429+/-228 U/L). Each inhibitor attenuated microvascular blood flow (assessed by laser Doppler flowmetry) to a similar degree. In striking contrast, AET completely reversed the endotoxin-induced impairment of the microvascular blood flow and significantly protected against an endotoxin-induced liver injury (plasma ALT: 3,007+/-268 U/L (ET); 460+/-39 U/L (ET+AET)). Infusion of endothelin-1 reduced microvascular blood flow by 50-60% and caused liver injury. Our data demonstrated that an inhibitor of eNOS (L-NAME) has a consistent detrimental effect on liver injury during ischemia-reperfusion and endotoxemia mainly because it can cause additional ischemia by reducing the microvascular blood flow. However, selective inhibitors of iNOS (AET) can impair hepatic blood flow and aggravate the injury or improve blood flow and attenuate organ injury depending on the experimental model. These results suggest that iNOS inhibitors may not be universally beneficial and should be tested in a variety of experimental models of sepsis/endotoxemia before used in clinical settings.

Activation of caspase 3 (CPP32)-like proteases is essential for TNF-alpha-induced hepatic parenchymal cell apoptosis and neutrophil-mediated necrosis in a murine endotoxin shock model

Endotoxin (ET)-induced liver failure is characterized by parenchymal cell apoptosis and inflammation leading to liver cell necrosis. Members of the caspase family have been implicated in the signal transduction pathway of apoptosis. The aim of this study was to characterize ET-induced hepatic caspase activation and apoptosis and to investigate their effect on neutrophil-mediated liver injury. Treatment of C3Heb/FeJ mice with 700 mg/kg galactosamine (Gal) and 100 microg/kg Salmonella abortus equi ET increased caspase 3-like protease activity (Asp-Val-Glu-Asp-substrate) by 1730 +/- 140% at 6 h. There was a parallel enhancement of apoptosis (assessed by DNA fragmentation ELISA and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay). In contrast, activity of caspase 1 (IL-1beta-converting enzyme)-like proteases (Tyr-Val-Ala-Asp-substrate) did not change throughout the experiment. Caspase 3-like protease activity and apoptosis was not induced by Gal/ET in ET-resistant mice (C3H/HeJ). Furthermore, only murine TNF-alpha but not IL-1alphabeta increased caspase activity and apoptosis. Gal/ET caused neutrophil-dependent hepatocellular necrosis at 7 h (area of necrosis, 45 +/- 3%). Delayed treatment with the caspase 3-like protease inhibitor Z-Val-Ala-Asp-CH2F (Z-VAD) (10 mg/kg at 3 h) attenuated apoptosis by 81 to 88% and prevented liver cell necrosis (< or = 5%). Z-VAD had no effect on the initial inflammatory response, including the sequestration of neutrophils in sinusoids. However, Z-VAD prevented neutrophil transmigration and necrosis. Our data indicate that activation of the caspase 3 subfamily of cysteine proteases is critical for the development of parenchymal cell apoptosis. In addition, excessive hepatocellular apoptosis can be an important signal for transmigration of primed neutrophils sequestered in sinusoids.

IPF2alpha-I: an index of lipid peroxidation in humans

Isoprostanes are prostaglandin isomers produced from arachidonic acid by a free radical-catalyzed mechanism. Urinary excretion of 8-iso-prostaglandin F2alpha, an isomer of the PGG/H synthase (cyclooxygenase or COX) enzyme product, prostaglandin F2alpha (PGF2alpha), has exhibited promise as an index of oxidant stress in vivo. We have developed a quantitative method to measure isoprostane F2alpha-I, (IPF2alpha-I) a class I isomer (8-iso-PGF2alpha is class IV), using gas chromatography/mass spectrometry. IPF2alpha-I is severalfold as abundant in human urine as 8-iso-PGF2alpha, with mean values of 737 +/- 20.6 pg/mg creatinine. Both isoprostanes are formed in a free radical-dependent manner in low density lipoprotein oxidized by copper in vitro. However, IPF2alpha-I, unlike 8-iso-PGF2alpha, is not formed in a COX-dependent manner by platelets activated by thrombin or collagen in vitro. Similarly, COX inhibition in vivo has no effect on IPF2alpha-I. Neither serum IPF2alpha-I, an index of cellular capacity to generate the isoprostane, nor urinary excretion of IPF2alpha-I, an index of actual generation in vivo, is depressed by aspirin or indomethacin. In contrast, both serum thromboxane B2 and urinary excretion of its 11-dehydro metabolite are depressed by the COX inhibitors. Although serum 8-iso-PGF2alpha formation is substantially depressed by COX inhibitors, urinary excretion of the compound is unaffected. Urinary IPF2alpha-I is elevated in cigarette smokers compared with controls (1525 +/- 180 versus 740 +/- 40 pg/mg creatinine; P < 0.01) and is highly correlated with urinary 8-iso-PGF2alpha (r = 0.9; P < 0.001). Urinary IPF2alpha-I is a novel index of lipid peroxidation in vivo, which can be measured with precision and sensitivity. It is an abundant F2-isoprostane formed in a free radical- but not COX-dependent manner. Although 8-iso-PGF2alpha may be formed as a minor product of COX, this pathway contributes trivially, if at all, to levels in urine. Urinary excretion of both isoprostanes is elevated in cigarette smokers.

The natriuretic activity of the K+ channel blocker U-37883A displays an ADH-dependence

We reported previously that K+ channel blockers induce diuresis and natriuresis in conscious and anesthetized rats. Free-water clearance studies suggested that K+ channel blockers inhibit NaCl reabsorption in the thick ascending limb (TAL) by blocking K+ recycling through a low-conductance, usually open, apical ATP-sensitive K+ channel. In the present study, we measured the effect of U-37883A (15 mg/kg, i.v.) on Na+ reabsorption in rats preconditioned to alter ADH levels. In water-loaded animals with suppressed ADH levels, U-37883A was 50% less natriuretic than in saline-loaded rats. Infusion of ADH to water-loaded rats restored the natriuretic response to a level comparable to saline-loaded rats. Loss of natriuretic efficacy was not secondary to changes in GFR or renal perfusion pressure since GFRs did not vary before or after drug administration in any of the respective groups. Decreases in blood pressure were not significantly different in saline-loaded, water-loaded and water-loaded/ADH rats. The natriuretic response of U-37883A as varied by ADH levels may be the first observation, in vivo, to support the observation that the cotransporter in TAL can exist in two modes as previously observed in vitro by Hebert and colleagues.

Eicosanoids and isoeicosanoids: indices of cellular function and oxidant stress

Arachidonic acid (AA) is an unsaturated fatty acid constituent of the phospholipid domain of cell membranes. It is subject to release via mobilization of phospholipases, particularly a cytoplasmic phospholipase A2. Thereafter, it may be metabolized by at least two cyclooxygenase (COX) isoforms to prostaglandins and related compounds, via lipoxygenases to leukotrienes and via p450-catalyzed metabolism to epoxyeicosatrienoic acids. Collectively, these bioactive lipids are termed eicosanoids. All of these lipids express potent bioactivity in vitro. Clinical studies have already demonstrated the importance of COX and lipoxygenase (LOX) products in human disease. The generation of models of COX, LOX and prostaglandin receptor gene inactivation is likely to broaden our insight into the importance of these compounds in vivo. Crystallization of the biosynthetic enzymes is likely to facilitate the development of highly specific inhibitors, as is the case already for COX-2. AA possesses intrinsic biological properties. It is also subject to free radical attack, generating isomeric eicosanoid species, the isoeicosanoids. These compounds may also express biological activity in vitro, although their importance in vivo is unclear. Development of specific assays for these compounds in urine suggests their utility as noninvasive indices of oxidant stress in vivo.

Nomenclature of isoprostanes: a proposal

We have proposed a nomenclature system for the isoprostanes, a new class of natural products formed in vivo by the free-radical peroxidation of polyunsaturated fatty acids. Our proposed nomenclature is based on the assignment of four isoprostanes, 1, 9, 17, and 25, as representatives of the four classes of isoprostanes derived from arachidonic acid (AA). We have attempted as much as possible to retain elements from the familiar prostaglandin nomenclature. In this proposal, we have used the abbreviation i.p. for isoprostane. We have classified isoprostane classes or types based on omega-carbon as being the starting reference. Roman numerals I-VI refer the six types of isoprostanes derived from eicosapentaenoic acid (EPA) and III-VI refer to the four types derived from AA. This nomenclature can be applied to isoprostanes derived from other PUFAs also.

The isoprostanes: a perspective

The isoprostanes are a new class of natural products produced in vivo by a non-enzymatic free-radical-induced peroxidation of polyunsaturated fatty acid. In the case of arachidonic acid, for example, four classes of isoprostanes can be produced. Because of the specific structural features distinguishing them from other free-radical-generated products, e.g., HETEs, etc., the isoprostanes can provide an exclusive and selective index for the oxidant component of several inflammatory and degenerative diseases. The possible mechanisms of formation of the individual isoprostanes is discussed in detail. Class III products, such as 8-iso-PGF2 alpha and 8-iso-PGE2 have been shown to be vasoconstrictors and modulate platelet function. Several synthetic representatives from the four classes of arachidonic-acid-derived isoprostanes have already been prepared by total synthesis. These synthetic standards have been used for the identification and quantitation of these isoprostanes in biological fluids using gas chromatography/mass spectrometry methodology.

Quantitative MRI in outpatient childhood epilepsy

PURPOSE

In adult studies, MRI volumetrics is a proven technique in presurgical assessment of epilepsy. Hippocampal volume loss is maximal in the syndrome of mesial temporal lobe epilepsy. We aimed (a) to validate this methodology in a pediatric outpatient epilepsy population (b) to determine the relationship of hippocampal asymmetry (HA) to epileptic syndromes and risk factors.

METHODS

Two neurologists classified the epileptic syndrome in 79 pediatric outpatients, according to the International Classification of Epilepsies and Epileptic Syndromes (ILAE). Hippocampal volumetrics were performed in all patients. HA was defined according to adult control values.

RESULTS

Inter-rater variability on measurement of HA was very small (Correlation of test retest of 0.97 on 17 children <3 years old). The rate of HA was 44/79 (57%). In 21 patients, (27%) potentially epileptogenic lesions (other than HA) were identified (cerebral dysgenesis n = 11). HA was present in 9/15 (60%) of temporal lobe epilepsy and in 15/28 (54%) extratemporal onset epilepsy and 5/11 (46%) of generalized symptomatic epilepsy. Analysis confined to <13 years also showed HA was not specific for epileptic syndrome. There was no significant association of febrile convulsions (13%) with HA or temporal lobe epilepsy.

CONCLUSIONS

There is a high incidence of HA in childhood epilepsy. HA was not confined to clinically defined temporal lobe epilepsy. The poor correlation of epileptic syndrome to quantitative MRI findings may be due to the inadequacies of epilepsy classification in the younger child, with the clinical semiology providing misleading localizing information. Normative childhood data for hippocampal volumes and symmetry is needed.