Leukotriene B4: early mediator of atherosclerosis in obstructive sleep apnoea?

Severity of oxygen desaturation is predictive of early atherosclerosis in obstructive sleep apnoea (OSA). Leukotriene (LT)B(4) is a lipid mediator involved in atherogenesis. In 40 non-obese OSA patients, free of a cardiovascular history, and 20 healthy volunteers, the following were evaluated: 1) LTB(4) production by polymorphonuclear leukocytes (PMNs) stimulated with A23187; and 2) the relationships between LTB(4) production and both OSA severity and infraclinical atherosclerosis markers. The effect of continuous positive airway pressure (CPAP) on LTB(4) production was also studied. An overnight sleep study was followed by first-morning blood sampling. Isolated PMNs were stimulated with A23187 in order to induce LTB(4) production, which was measured by liquid chromatography-tandem mass spectrometry. Carotid intima-media thickness (IMT) and luminal diameter were measured in subset groups of 28 OSA patients and 11 controls. LTB(4) production was increased in OSA patients compared with controls. LTB(4) levels correlated with the mean and minimal arterial oxygen saturation (S(a,O(2))). LTB(4) production correlated with luminal diameter data in patients with a mean S(a,O(2)) of < or = 94% but not with IMT. Lastly, CPAP significantly reduced LTB(4) production by 50%. Leukotriene B(4) production is increased in obstructive sleep apnoea in relation to oxygen desaturation. Leukotriene B(4) could promote early vascular remodelling in moderate-to-severe hypoxic obstructive sleep apnoea patients.

5-lipoxygenase expression and activity in aorta from streptozotocin-induced diabetic rats

We previously reported an activation of the 5-lipoxygenase pathway in aorta from streptozotocin-induced diabetic rats. The aim of this study was to investigate whether this activation was associated with an increased expression of 5-lipoxygenase, an increased cysteinyl leukotriene (CysLT) production in response to arachidonic acid or calcium ionophore A23187 and/or a hypersensitivity of the aorta to CysLTs in streptozotocin-induced diabetic rats. In aorta from diabetic and control rats, reverse transcriptase-PCR and western blot analysis with a specific 5-lipoxygenase antibody provided evidence for the presence of 5-lipoxygenase in aorta. However, the expression of 5-lipoxygenase was not significantly different between diabetic and control rats. Challenge by A23187 (10 microM) and arachidonic acid (10 microM and 0.1 mM) with or without A23187 (10 micromol/l) induced a significant increase of CysLT release (measured by enzyme immunoassay) that was in the same range in aorta from control and diabetic rats. In contrast, aortas from diabetic rats showed a greater sensitivity to LTC4 and LTD4 contractile effects. These data suggested that the activation of the 5-lipoxygenase pathway previously reported in streptozotocin-induced diabetic rats could be explained by an augmented sensitivity to CysLTs of the diabetic aorta.

Chronic intermittent hypoxia increases infarction in the isolated rat heart

Coronary heart disease is frequently associated with obstructive sleep apnea syndrome and treating obstructive sleep apnea appears to significantly improve the outcome in coronary heart disease. Thus we have developed a rat model of chronic intermittent hypoxia (IH) to study the influence of this condition on myocardial ischemia-reperfusion tolerance and on functional vascular reactivity. Wistar male rats were divided in three experimental groups ( n = 12 each) subjected to chronic IH (IH group), normoxia (N group), or control conditions (control group). IH consisted of repetitive cycles of 1 min (40 s with inspired O2fraction 5% followed by 20 s normoxia) and was applied for 8 h during daytime, for 35 days. Normoxic cycles were applied in the same conditions, inspired O2fraction remaining constant at 21%. On day 36, mean arterial blood pressure (MABP) was measured before isolated hearts were submitted to an ischemia-reperfusion protocol. The thoracic aorta and left carotid artery were also excised for functional reactivity studies. MABP was not significantly different between the three experimental groups. Infarct sizes (in percent of ventricles) were significantly higher in IH group (46.9 ± 3.6%) compared with N (26.1 ± 2.8%) and control (21.7 ± 2.1%) groups. Vascular smooth muscle function was similar in aorta and carotid arteries from all groups. The endothelium-dependent relaxation in response to acetylcholine was also similar in aorta and carotid arteries from all groups. Chronic IH increased heart sensitivity to infarction, independently of a significant increase in MABP, and did not affect vascular reactivity of aorta and carotid arteries.

6-tioguanine monitoring in steroid-dependent patients with inflammatory bowel diseases receiving azathioprine

BACKGROUND

6-Thioguanine (6-tioguanine) nucleotides are the active metabolites of azathioprine.

AIM

The aim of the study was to evaluate the rate of clinical remission without steroids in steroid-dependent Crohn's disease and ulcerative colitis patients receiving azathioprine, the medium- and long-term efficacy and the predictive factors of clinical response when monitoring 6-tioguanine.

METHODS

Steroid-dependent Crohn's disease and ulcerative colitis patients receiving either azathioprine or not (treated later with a daily dose of 2.5 mg/kg) were prospectively included. 6-tioguanine was monitored at 1 and 2 months and every 3 months thereafter for 1 year. The azathioprine dose was adapted to reach a 6-tioguanine level of >250 pmol/8 x 10(8) red blood cells. Thiopurine methyltransferase genotype/phenotype was evaluated in some patients.

RESULTS

A total of 106 patients were prospectively included (70 Crohn's disease, 36 ulcerative colitis). The clinical remission rate without steroids in patients receiving azathioprine, in intention-to-treat analysis, was 72% and 59% at 6 and 12 months, respectively. The remission rate was significantly higher in patients with 6-tioguanine >250 pmol/8 x 10(8) RBC (86% and 69% at 6 and 12 months, respectively; P < 0.01). No significant difference was observed between Crohn's disease and ulcerative colitis patients whether treated by azathioprine or not on inclusion. In the univariate analysis, the absence of Crohn's disease stenosis, a 6-tioguanine level >250 pmol/8 x 10(8) RBC, and an increase of erythrocyte mean corpuscular volume were the factors predictive of a favourable clinical response. In the multivariate analysis, only a 6-tioguanine level of >250 pmol/8 x 10(8) red blood cells was a predictive factor of favourable clinical remission.

CONCLUSIONS

Clinical remission without steroids is significantly more likely when monitoring 6-tioguanine so as to reach a level of >250 pmol/8 x 10(8) red blood cells in steroid-dependent Crohn's disease and ulcerative colitis patients receiving azathioprine (86% and 69% at 6 and 12 months, respectively).

Mass spectrometric determination of acromelic acid A from a new poisonous mushroom: Clitocybe amoenolens

As Clitocybe acromelalga, the mushroom Clitocybe amoenolens is responsible for erythermalgia. Acromelic acids isolated from C. acromelalga have been suspected to be to some extend the active principles. The objective was to develop a specific and sensitive liquid chromatographic-mass spectrometric method that would allow acromelic acid A identification and quantification in mushrooms. The method involved a single-step methanol-water extraction followed by a selective cleanup of the extract with solid-phase extraction cartridges (strong-anion exchange). The chromatographic separation was achieved on a porous graphitic carbon column with acetonitrile-water-formic acid as mobile phase. Detection was done with a mass analyzer equipped with a TurboIonSpray source, operated in the negative ionization mode. Acromelic acid A concentration was determined in dried mushroom at around 325 ng/mg in C. amoenolens and 283 ng/mg in C. acromelalga.

Oxidative stress and baroreflex sensitivity in healthy subjects and patients with mild-to-moderate hypertension

Decreased baroreflex sensitivity (BRS) is a prognostic marker in essential hypertension. Animal experiments suggest that decreased BRS is related to increased oxidative stress. Our study was aimed at testing whether oxidative stress, estimated by isoprostane 15-F(2t)-IsoP urinary levels, is correlated to BRS variation in healthy subjects as well as in patients suffering from essential hypertension. Urinary 15-F(2t)-IsoP levels and BRS were evaluated in two groups of subjects: healthy volunteers (n=64) and patients with untreated mild-to-moderate hypertension (n=33). Data were analysed in 61 and 31 subjects, respectively, BRS analysis being impossible in three and two subjects, respectively. 15-F(2t)-IsoP levels were measured using gas chromatography/mass spectrometry. BRS was measured using the sequence method [PS+/RR+ and PS-/RR-] and crossspectral analysis (CSP) (MF gain) at rest, lying down. No significant correlation was found between basal urinary 15-F(2t)-IsoP levels and BRS (sequence method and CSP) in either healthy controls or hypertensive patients. Our study shows that oxidative stress is not involved in interindividual variations of BRS in healthy subjects and patients suffering from mild-to-moderate hypertensionJournal of Human Hypertension (2004) 18, 517-521. doi:10.1038/sj.jhh.1001684 Published online 12 February 2004

Drug interaction between infliximab and azathioprine in patients with Crohn's disease

BACKGROUND

A drug interaction has been observed between infliximab and methotrexate in rheumatoid arthritis.

AIM

To look for an interaction between infliximab and azathioprine in Crohn's disease patients using the active metabolites of azathioprine: 6-tioguanine nucleotides.

METHODS

Patients receiving azathioprine who required infliximab for ileo-colonic or ano-perineal Crohn's disease were recruited prospectively. 6-tioguanine nucleotide levels were evaluated before infusion, within 1-3 weeks after the first infusion and 3 months after the first infusion. The clinical outcome was evaluated by the Harvey-Bradshaw index or the closure of ano-perineal fistulas.

RESULTS

Thirty-two patients were included (17 received one infusion and 15 received three infusions). The mean 6-tioguanine nucleotide level was comparable before and 3 months after the first infusion, but a significant increase was observed within 1-3 weeks after the first infusion (P < 0.001). In parallel, a significant decrease in leucocyte count and increase in mean corpuscular volume were observed; these modifications were normalized 3 months after infusion. An increase in 6-tioguanine nucleotide level of greater than 400 pmol/8 x 108 erythrocytes was strongly related to good tolerance and a favourable response to infliximab, with a predictive value of 100%.

CONCLUSIONS

This prospective study provides evidence for a drug interaction between azathioprine and infliximab.

Automated solid-phase extraction and liquid chromatography-electrospray ionization-mass spectrometry for the determination of flunitrazepam and its metabolites in human urine and plasma samples

A sensitive and specific method using reversed-phase liquid chromatography coupled with electrospray ionization-mass spectrometry (LC-ESI-MS) has been developed for the quantitative determination of flunitrazepam (F) and its metabolites 7-aminoflunitrazepam (7-AF), N-desmethylflunitrazepam (N-DMF) and 3-hydroxyflunitrazepam (3-OHF) in biological fluids. After the addition of deuterium labelled standards of F,7-AF and N-DMF, the drugs were isolated from urine or plasma by automated solid-phase extraction, then chromatographed in an isocratic elution mode with a salt-free eluent. The quantification was performed using selected ion monitoring of protonated molecular ions (M+H(+)). Experiments were carried out to improve the extraction recovery (81-100%) and the sensitivity (limit of detection 0.025 ng/ml for F and 7-AF, 0.040 ng/ml for N-DMF and 0.200 ng/ml for 3-OHF). The method was applied to the determination of F and metabolites in drug addicts including withdrawal urine samples and in one date-rape plasma and urine sample.

[Leukotrienes and 12-HETE: key mediators of angiotensin II-mediated vascular effects.Rol in hypertension]

Arachidonic acid metabolism-derived products are key mediators of angiotensin II-mediated vascular effects. The modulatory effect of cyclooxygenase derived products--in particular thromboxane A2 and prostaglandin H2--in angiotensin II-mediated vascular effects is well established. In contrast, few studies have assessed the involvement of lipoxygenase-derived products in the vascular effects of angiotensin II. Cysteinyl leukotrienes (5-lipoxygenase-derived products) and 12-hydroxyeicosatetraenoic acids (12-HETE) (12-lipoxygenase-derived products) are potent proinflammatory and vasomotor mediators. Their biosynthesis is increased in various models of hypertension. In addition, compelling evidence has suggested that they might contribute to the vasoconstrictor, hypertrophic and mitogenic effects of angiotensin II. The demonstration of their contribution to angiotensin II-mediated vascular effects may explain, at least in part, the vascular inflammatory complications associated with hypertension.

Relaxation and modulation of cyclic AMP production in response to atrial natriuretic peptides in guinea pig tracheal smooth muscle

Relaxation and modulation of cyclic AMP production in response to atrial natriuretic peptides were investigated in epithelium-denuded guinea pig tracheal rings, treated with indomethacin (5 microM) and phosphoramidon (1 microM) and contracted with histamine (3 microM). Atrial natriuretic peptide (ANP) was a more potent relaxant than C-type natriuretic peptide whereas ANP-(4-23) was inactive suggesting the involvement of ANP(A) receptors in the relaxant effect of ANP. ODQ (1H-[1,2,4]oxadiazolo[4,3-A]quinoxalin-1-one, 10 microM), a selective inhibitor of soluble guanylyl cyclase, markedly inhibited the relaxant response to sodium nitroprusside. The relaxant response to ANP was not altered by ODQ demonstrating the involvement of particulate guanylyl cyclase. ANP-induced relaxations, as well as sodium nitroprusside-induced relaxations, were similarly potentiated by rolipram (4-(3-(cyclopentyloxy)-4-methoxyphenyl)pyrrolidin-2-one, 3 microM), a type IV phosphodiesterase inhibitor, and by zaprinast (2-(2-propyloxyphenyl)-8-azapurin-6-one, 10 microM), a type V phosphodiesterase inhibitor. ANP-mediated response was unaffected by glibenclamide (10 microM), a selective blocker of ATP-sensitive K(+) channels, and by apamin (1 microM), a selective blocker of small-conductance Ca(2+)-activated K(+) channels. Iberiotoxin (100 nM) extensively prevented the relaxant effect of ANP suggesting the activation of large-conductance Ca(2+)-activated K(+) channels. In addition, ANP (10 nM) and ANP-(4-23) (100 nM) significantly reduced forskolin (1 microM)-stimulated cAMP accumulation suggesting, for the first time, the presence of functional ANP(C) receptors in guinea pig airway smooth muscle. However, relaxations to forskolin and to isoproterenol were not altered in the presence of ANP-(4-23) or ANP demonstrating that the inhibitory effect of ANP-(4-23) and ANP on adenylyl cyclase was not sufficient to alter the functional response induced by these two activators of adenylyl cyclase.

Cysteinyl leukotrienes modulate angiotensin II constrictor effects on aortas from streptozotocin-induced diabetic rats

Angiotensin II (Ang II) is a vasopressor peptide involved in the pathogenesis of cardiovascular diseases associated with diabetes mellitus. We have previously reported that the 5-lipoxygenase-derived products, particularly the cysteinyl leukotrienes (CysLTs), are involved in Ang II-induced contraction. In this study, we demonstrated that CysLTs contribute to the contraction elicited by Ang II in isolated aortas from streptozotocin-induced diabetic (SS) rats but not from insulin-treated diabetic rats, fructose-fed rats, or control rats. In an organ bath, pretreatment with the 5-lipoxygenase inhibitor (AA861, 10 micromol/L) reduced by 37.6+/-8.2% and 30.1+/-10.9% the Ang II-induced contractions in intact and endothelium-denuded aortic rings, respectively, from SS rats. In contrast, the CysLT(1) receptor antagonist (MK571, 1 micromol/L) or the dual CysLT(1)/CysLT(2) receptor antagonist (BAY-u9773, 0.1 micromol/L) did not affect Ang II-induced contraction. In addition, Ang II induced a 6.2+/-1.5-fold increase in CysLT release through the stimulation of the Ang II type 1 receptor. Furthermore, the urinary excretion of leukotriene E(4) was increased in SS rats (leukotriene E(4), 13.7+/-2.9 ng/24 h [SS rats, n=10] versus 1.5+/-0.5 ng/24 h [control rats, n=6]; P<0.0004). These data suggest the activation of the 5-lipoxygenase pathway in SS rats and the involvement of 5-lipoxygenase-derived products, particularly the CysLTs, in Ang II-induced contraction in aortas from SS rats through stimulation of CysLT receptors different from the well-characterized CysLT(1) or CysLT(2) receptor.

Increased lipid peroxidation in patients with pulmonary hypertension

Isoprostanes are chemically stable lipid peroxidation products of arachidonic acid, the quantification of which provides a novel approach to the assessment of oxidative stress in vivo. The main objective of this study was to quantify the urinary levels of isoprostaglandin F(2alpha) type III (iPF(2alpha)-III), an F(2)-isoprostane, in patients with pulmonary hypertension (PHT) in comparison with healthy controls. The secondary objective was to test whether baseline iPF(2alpha)-III levels correlate to the reversibility of pulmonary hypertension in response to inhaled NO challenge. Urinary iPF(2alpha)-III levels were measured by gas chromatography-mass spectrometry in 25 patients with PHT, 14 of whom were investigated for response to inhaled NO challenge. Urinary iPF(2alpha)-III levels in PHT patients (225 +/- 27 pmol/mmol creatinine) were 2.3 times as high as in controls (97 +/- 7 pmol/mmol creatinine, p < 0.001). The mean pulmonary arterial pressure variation and the pulmonary vascular resistance variation in response to inhaled NO were correlated to basal iPF(2alpha)-III levels. This study shows that oxidative stress is increased in patients with pulmonary hypertension. Furthermore, iPF(2alpha)-III levels inversely correlate to pulmonary vasoreactivity. These observations are consistent with the hypothesis that free radical generation is involved in PHT pathogenesis.

Formation of isoprostanes in children with type IIa hypercholesterolemia

F2-isoprostanes are stable lipid peroxidation products of arachidonic acid and their quantification provides a novel approach to the assessment of oxidative stress in vivo. F2-isoprostanes are present in increased amounts in adult hypercholesterolemia, but no data exist concerning children. We investigated urinary isoprostaglandin F2, type III production as an index of lipid peroxidation in 15 children presenting with type IIa hypercholesterolemia (serum total cholesterol, 290 [SD +/- 70] mg/dl; low-density lipoprotein cholesterol, 210 [SD +/- 90] mg/dl) compared with 15 sex- and age-paired control children (serum total cholesterol, 160 [SD +/- 20] mg/dl). Urinary levels of isoprostaglandin F2alpha type III were measured by gas chromatography mass spectrometry. Urinary concentrations did not differ significantly in hypercholesterolemic children compared with control children (84.7 [SD +/- 37] vs. 96 [SD +/- 35] pmol/mmol creatinine, respectively). No significant correlation was found with total cholesterol, low-density-lipoprotein and high-density-lipoprotein cholesterol, and apolipoprotein B and A1 serum levels. F2-isoprostane urinary levels in children with type IIa hypercholesterolemia do not differ from those of age- and sex-matched control children and are not correlated to blood lipid parameters, suggesting that hypercholesterolemia is not associated with increased lipid peroxidation in childhood.

Enhanced in vivo lipid peroxidation in scleroderma spectrum disorders

OBJECTIVE

A new family of prostaglandin F2 isomers called F2-isoprostanes, produced by free radical peroxidation of arachidonic acid, has recently been described in vivo. Its quantification has been suggested to be a reliable measure of oxidant injury in vivo. The purpose of this study was to investigate urinary F2-isoprostane formation as an index of lipid peroxidation in scleroderma spectrum disorders.

METHODS

Urine samples were obtained from 52 patients with systemic sclerosis (SSc; n = 37) or undifferentiated connective tissue diseases (UCTD; n = 15) and from 20 healthy volunteers. Urinary isoprostaglandin F2alpha type III (iPF2alpha-III) and 11-dehydro thromboxane B2 (11-dehydroTXB2) concentrations were determined using enzyme immunoassays.

RESULTS

The urinary concentration of iPF2alpha-III was approximately twice as high in patients (mean +/- SEM 229+/-16 pmoles/mmoles creatinine) as in controls (116+/-9 pmoles/mmoles creatinine) (P < 0.0001). However, the urinary concentration of iPF2alpha-III was not significantly different among patients with UCTD, limited SSc, and diffuse SSc (mean +/- SEM 221+/-27 versus 245+/-32 versus 220+/-25 pmoles/mmoles creatinine, respectively). No significant correlation was found between the urinary concentrations of iPF2alpha-III and 11-dehydroTXB2.

CONCLUSION

This study provides evidence of enhanced lipid peroxidation in both SSc and UCTD, and suggests a rationale for antioxidant treatment of SSc. Formation of F2-isoprostanes has to be investigated as a means for the evaluation of such therapy.

Determination of isoprostaglandin F2alpha type III in human urine by gas chromatography-electronic impact mass spectrometry. Comparison with enzyme immunoassay

F2-Isoprostanes are stable lipid peroxidation products of arachidonic acid, the quantification of which provides an index of oxidative stress in vivo. We describe a method for analysing isoprostaglandin F2alpha type III (15-F2t-IsoP) in biological fluids. The method involves solid-phase extraction on octadecyl endcapped and aminopropyl cartridges. After conversion to trimethylsilyl ester trimethylsilyl ether derivatives, isoprostaglandin F2alpha type III is analysed by mass spectrometry, operated in electronic impact selected ion monitoring mode. We have compared enzyme immunoassay (EIA; Cayman, Ann Arbor, MI, USA) to this method with 30 human urine aliquots following the same extraction procedure in order to determine the agreement between both methods. Isoprostaglandin F2alpha type III concentrations determined with gas chromatography-mass spectrometry (GC-MS) did not agree with those determined with EIA. Our results suggest that GC-MS and EIA do not measure the same compounds. As a consequence, comparison of clinical results using GC-MS and EIA should be avoided.

Using a WWW-based module for problem-based learning in a cardiovascular pharmacology course

The authors have constructed a problem-based learning (PBL) computer program that makes full use of Internet facilities, and is aimed at providing a stimulating supplement to standard teaching practices. The authors report on students' reactions to this new method of teaching.

Isoprostaglandin E2 type-III (8-iso-prostaglandin E2) evoked contractions in the human internal mammary artery

E2-isoprostanes are recently discovered compounds that are produced in vivo from free radical-catalysed peroxidation of arachidonic acid. One such compound whose formation is favoured by this mechanism is isoprostaglandin E2 type III (iPE2-III, also named 8-iso-prostaglandin E2 or 15-E2t-isoprostaglandin). The aim of this study was to evaluate the vasomotor properties of iPE2-III in isolated human internal mammary artery. In organ bath, iPE2-III was approximately 10 times more potent than isoprostaglandin F2alpha-III and 27 times more potent than prostaglandin E2, whereas both isoprostaglandin F3alpha-III and 15-epi-isoprostaglandin F2alpha-II induced weak contractions. The responses to iPE2-III were inhibited in a concentration-dependent manner by the thromboxane A2 receptor antagonist GR 32191 (3.10(-9) to 3.10(-7) M). Indomethacin, a cyclooxygenase inhibitor and phosphoramidon, an endothelin converting enzyme inhibitor, did not affect iPE2-III response. These data shows that iPE2-III is a more potent vasoconstrictor of human internal mammary arteries than isoprostaglandin F2alpha-III. These effects are mediated by TP receptors, but involve neither cyclooxygenase products nor endothelins. iPE2-III production may induce more pronounced vasomotor effects than isoprostaglandin F2alpha-III in situations of oxidative stress, and in particular may modulate internal mammary artery tone following coronary bypass surgery.

Vascular biology of the isoprostanes

Isoprostanes are a family of compounds produced from polyunsaturated fatty acids via a free-radical-catalysed mechanism. F(2)-isoprostanes are prostaglandin F(2alpha) isomers derived from arachidonic acid. These compounds induce potent vasoconstriction, mediated primarily by TP receptor stimulation, and in some vessels by the release of cyclooxygenase products. This vasoconstriction may be modulated by the endothelium through the release of NO. Potent vasoconstriction is also observed with E(2)-isoprostanes. Experimental and clinical data suggest a role for F(2)-isoprostanes in atherogenesis. These compounds can be detected in free forms in biological fluids as well as esterified in low-density lipoproteins or cell membranes. Their quantification represents a reliable marker of lipid peroxidation. Elevated levels of F(2)-isoprostanes in biological fluids in pathological conditions including atherosclerosis, ischaemia-reperfusion injury, and inflammatory vascular diseases, suggest a relationship between lipid peroxidation and such diseases. F(2)-isoprostanes are currently being investigated as non-invasive quantitative markers to monitor the response to anti-oxidant treatment.

Urinary F2-isoprostanes formation in kidney transplantation

BACKGROUND

Oxygen free-radical mediated lipid peroxidation has been implicated in many diseases such as chronic renal failure, hemodialysis and chronic kidney transplant rejection. However, insight into the role of free radical generation in kidney transplantation has been constrained by the limitations of current indexes of oxidant stress in vivo. Isoprostaglandin F2alpha type-III (iPF2alpha-III, formerly known as 8-iso-prostaglandin F2alpha) is emerging as a reliable marker of oxidant stress in vivo. The purpose of our study was to investigate iPF2alpha-III formation as an index of lipid peroxidation in the 5 d following kidney transplantation.

METHODS

Urinary iPF2alpha-III measurements were performed by enzyme immunoassay from day I to 5 in 11 patients undergoing kidney transplantation. Results were compared with 11 healthy volunteers matched in sex, age and cigarette smoking.

RESULTS

Urinary excretion of iPF2alpha-III at day 1 did not significantly differ between control and transplant group (111 +/- 17 vs. 92 +/- 10 pM/ mM creatinine, respectively, NS). Urinary iPF2alpha-III levels did not differ between day 1 to 5, and were not correlated to cold ischaemia time.

CONCLUSION

Our study shows no evidence of enhanced lipid peroxidation in the first 5 d following kidney transplantation.

Cysteinyl leukotrienes are involved in angiotensin II-induced contraction of aorta from spontaneously hypertensive rats

OBJECTIVE

Non specific lipoxygenase inhibitors have been reported to reduce the in vitro constrictor response and the in vivo pressor effect of angiotensin II in rats. The aim of this study was to assess the role of cysteinyl leukotrienes, in the vascular response to angiotensin II in spontaneously hypertensive rats (SHR).

METHODS

Rings of thoracic aorta from SHR and normotensive Wistar-Kyoto rats (WKY) were compared in terms of contractile responses and release of cysteinyl leukotrienes in response to angiotensin II.

RESULTS

Pretreatment with the specific 5-lipoxygenase inhibitor AA861 10 microM reduced the efficacy of angiotensin II in intact and endothelium-denuded aorta from SHR (% inhibition vs. control: 65+/-12.6% with endothelium (n=6), P<0.05; 43+/-7.2% without endothelium (n=6), P<0.05) but not in aorta from WKY. In addition, in aorta from SHR, the CysLT(1) receptor antagonist MK571 1 microM reduced by 55+/-6.1% (n=6, P<0.05) the contractile effects of angiotensin II in rings with endothelium but not in endothelium-denuded rings. Angiotensin II induced a 8.6+/-2.1-fold increase in cysteinyl leukotriene production in aorta rings from SHR with endothelium which was prevented by the AT(1) receptor antagonist losartan 1 microM but not by the AT(2) receptor antagonist PD123319 0.1 microM. In aorta rings from WKY, cysteinyl leukotriene production remained unchanged after exposition to angiotensin II. The cysteinyl leukotrienes (up to 0.1 microM) induced contractions in aorta rings from SHR but not from WKY.

CONCLUSIONS

These data suggest that cysteinyl leukotrienes, acting at least in part on endothelial CysLT(1) receptors, are involved in the contractile response to angiotensin II in isolated aorta from SHR but not from WKY.

Cyclosporine A and cremophor EL induce contractions of human saphenous vein: involvement of thromboxane A2 receptor-dependent pathway

Chronic treatment with Sandimmune (cyclosporine A [CsA] dissolved in Cremophor EL [CrEL]) is often associated with hypertension and nephrotoxicity. The aims of the present study were to assess the effect of Sandimmune and its two main components (CsA and CrEL) on human saphenous veins and to study the underlying mechanism of their contractile responses. In organ bath, concentration-response curves for Sandimmune (36 ng/ml-120 microg/ml of CsA). CsA (36 ng/ml-120 microg/ml), or CrEL (2.4 microg/ml-8 mg/ml) were elicited in the presence of a thromboxane A2 (TXA2) receptor antagonist (GR32191, 0.3 microM), a cyclooxygenase inhibitor (indomethacin, 1 microM), a 5-lipoxygenase inhibitor (AA861, 10 microM), or their respective vehicles. In addition, the production of TXA2 after CsA challenge was assessed by enzyme immunoassay. Sandimmune, CsA, and CrEL induced concentration-dependent contractions on human saphenous veins. In terms of potency, CsA was a more potent vasoconstrictor agent than CrEL (EC50 values: 11.9+/-3.7 microg/ml (CsA, n = 12) vs. 1.2+/-0.4 mg/ml (CrEL, n = 16), p < 0.05). In contrast, in terms of efficacy, CrEL induced greater contractions than CsA (Emax (% of KCl 90 mM-induced contraction): 98.1+/-16.1% (CrEL, n = 16) vs. 17.0+/-4.3% (CsA, n = 12) p < 0.05). Pretreatment with GR32191 significantly reduced by 85% and 56% the contractions elicited by CsA and CrEL, respectively, whereas indomethacin had no effect. Finally, CsA (12 and 120 microg/ml) failed to stimulate TXA2 production. These in vitro data suggest that Sandimmune-induced contractions on human vascular smooth muscle appear to be mediated by CsA in the therapeutic ranges of doses and by both CsA and CrEL, which, in supratherapeutic doses, acted through a TXA2 receptor-dependent pathway.

Angiotensin II-induced contractions in human internal mammary artery: effects of cyclooxygenase and lipoxygenase inhibition

OBJECTIVE

This study investigated, in isolated human internal mammary artery, the involvement of the cyclooxygenase and the lipoxygenase pathways of arachidonic acid metabolism in the contraction induced by angiotensin II.

METHODS

Rings of human internal mammary arteries were suspended in organ baths for recording of isometric tension. In addition, the release of eicosanoids in response to angiotensin II (0.3 microM) was measured by enzyme immunoassay.

RESULTS

In human arterial rings without endothelial dependent relaxation in response to substance P or acetylcholine, the angiotensin II-induced contractions were significantly (P<0.05) reduced by 27% in the presence of GR32191 0.3 microM (thromboxane A(2) (TXA(2)) receptor antagonist) but remained unchanged in the presence of dazoxiben 100 microM (thromboxane synthase inhibitor). In addition, angiotensin II failed to modify TXB(2) and 6-keto-PGF(1alpha) production. These results suggest the contribution of a TXA(2)/PGH(2) agonist other than TXA(2) in angiotensin II-induced contractions. However, indomethacin increased (P<0.05) angiotensin II-mediated contractile response and cysteinyl leukotriene production, suggesting a redirection of arachidonic acid metabolism from the cyclooxygenase pathway to the lipoxygenase pathway. Indeed, the contractions induced by angiotensin II were inhibited (P<0.05) by phenidone 100 microM (cyclooxygenase and lipoxygenase inhibitor), baicalein 100 microM (5-, 12- and 15-lipoxygenases inhibitor), AA861 10 microM (5-lipoxygenase inhibitor) and MK571 1 microM (CysLT(1) receptor antagonist). Cysteinyl leukotrienes were released in response to angiotensin II (pg/mg dry weight tissue: 32+/-9 (basal, n=6) vs. 49+/-9 (angiotensin II 0.3 microM, n=6), P<0.05). LTD(4), and at a lesser degree LTC(4), induced contractions of internal mammary artery and MK571 1 microM abolished the contraction to LTD(4).

CONCLUSIONS

This study suggests that the in vitro vasoconstrictor effects of angiotensin II in human internal mammary artery are enhanced at least in part by eicosanoids produced by the cyclooxygenase pathway, probably PGH(2), acting on TXA(2)/PGH(2) receptors, and by lipoxygenase-derived products, particularly cysteinyl leukotrienes acting on CysLT(1) receptors.

Human internal mammary artery contraction by isoprostaglandin f(2alpha) type-III [8-iso-prostaglandin F(2alpha)]

Isoprostaglandin F(2alpha) type-III (formerly known as 8-iso-prostaglandin F(2alpha)) is produced in large quantities in vivo in clinical situations associated with oxidant stress such as atherosclerosis, hypercholesterolemia, and myocardial reperfusion. Isoprostaglandin F(2alpha) type-III may alter smooth muscle and platelet functions. The aim of this study was to evaluate the effects of isoprostaglandin F(2alpha) type-III on isolated human internal mammary arteries, and to characterise the signalling underlying mechanisms. In organ baths, concentration-dependent contractions of human internal mammary arteries were obtained in response to isoprostaglandin F(2alpha) type-III stimulation. The responses to isoprostaglandin F(2alpha) type-III were inhibited in a concentration-dependent manner by the thromboxane A(2) receptor antagonist, GR 32191 ([1R-[1 alpha(Z), 2beta,3beta,5 alpha(+)-7-[[1, 1'-biphenyl)-4-yl]methoxy]-3-hydroxy-2-(1-piperidinyl) cyclo pentyl]-4-4heptanoic acid], hydrochloride), 3x10(-9) to 3x10(-7) M). However, this effect was associated with a decreased maximal contraction. AH 6809 (6-isopropoxy-9-oxoxanthene-2-carboxylic acid, 10(-6) to 3x10(-5) M), an EP(1)-DP receptor antagonist had no effect on isoprostaglandin F(2alpha) type-III-induced contractions. The maximal responses to isoprostaglandin F(2alpha) type-III were significantly reduced in the presence of the cyclooxygenase inhibitor indomethacin (10(-5) M) (E(max): 147+/-20% vs. 213+/-19% in control group, P<0.05). Isoprostaglandin F(2alpha) type-III stimulated thromboxane B(2) release (5.7-fold increase) from human internal mammary arteries. Baicaleine, a non-specific lipoxygenase inhibitor, (10(-4) M) and AA 861 (2,3,5-trimethyl-6-(12-hydroxy-5, 10-dodecadiynyl)-1,4 benzoquinone), a 5-lipoxygenase inhibitor (10(-5) M) did not affect isoprostaglandin F(2alpha) type-III response. In conclusion, this study shows that (1) isoprostaglandin F(2alpha) type-III is a vasoconstrictor in human internal mammary arteries, with a potency equivalent to prostaglandin F(2alpha), (2) the contractions induced by isoprostaglandin F(2alpha) type-III are mediated by TP receptor but not EP(1)-DP-receptor activation, (3) thromboxane A(2) but not cysteinyl leukotrienes production is involved in the vascular effects of isoprostaglandin F(2alpha) type-III. Isoprostaglandin F(2alpha) type-III, produced at sites of free radical generation, may play an important role in internal mammary artery spasm in situations of oxidant stress such as coronary bypass surgery.

Vasoconstrictor effects of iso-prostaglandin F2alpha type-III (8-iso-prostaglandin F2alpha) on human saphenous veins

Free radical generation can initiate the peroxidation of arachidonic acid, resulting in a non-cyclooxygenase-dependent production of bioactive prostaglandin F2-like compounds. We have investigated the effects of iso-prostaglandin F2alpha type III, (iPF2alpha-III, formerly named 8-iso prostaglandin F2alpha) on human saphenous veins, and characterized the underlying mechanisms. In organ baths, the contractile effects of iPF2alpha-III were tested on saphenous vein rings coming from 22 patients. iPF2alpha-III induced concentration-dependent contractions of isolated human saphenous veins. The maximal contraction did not differ significantly from that of prostaglandin F2alpha (PGF2alpha). The pD2 values for iPF2alpha-III, PGF2alpha, endothelin-1 (ET-1), and U46619 (a stable thromboxane A2 mimetic) were 6.31+/-0.12, 5.66+/-0.13, 7.37+/-0.08, and 7.99+/-0.31, respectively (p < 0.001 for U46619 vs. iPF2alpha-III and PGF2alpha; and ET-1 vs. PGF2alpha). Emax values of iPF2alpha-III, PGF2alpha, ET-1, and U46619 were 137.7+/-24.3%, 145.9+/-7.5%, 92.9+/-16.8%, and 238.7+/-23.7%, respectively (p < 0.001 for U46619 vs. iPF2alpha-III, PGF2alpha and ET-1; and for PGF2alpha vs. ET-1). The responses to iPF2alpha-III were inhibited by GR 32191 10(-7) M, a TP-receptor antagonist, without affecting the maximal response (pD2 values were 5.98+/-0.06 in the absence, and 5.22+/-0.05 in the presence of GR32191; p < 0.001). Concentration-effect curves to iPF2alpha-III were not affected by phosphoramidon 10(-5) M (an endothelin converting enzyme inhibitor), BQ123 10(-6) M (a selective ET(A)-receptor antagonist), BQ788 10(-6) M (a selective ET(B)-receptor antagonist), and indomethacin 10(-5) M (a cyclooxygenase inhibitor). Finally, the contractile response of iPF2alpha-III did not involve the release of thromboxane B2 and ET-1, measured using enzyme immunoassays. This study demonstrates that iPF2alpha-III is a vasoconstrictor of human saphenous veins, with a potency fourfold greater than that of PGF2alpha, and 50 times less than that of the thromboxane A2 mimetic, U46619. These effects are mediated at least in part by TP-receptor stimulation, but do not involve thromboxane A2 or ET-1 release.

Furosemide inhibits thromboxane A2-induced contraction in isolated human internal mammary artery and saphenous vein

Evidence suggests that, in addition to its diuretic property, furosemide also may exert direct vascular effects. Because thromboxane A2 (TXA2) has a role in the control of vascular tone, we investigated the effect of furosemide on the contraction induced by U46619 (a stable TXA2 mimetic) on isolated human internal mammary artery (IMA) and saphenous vein (SV). Concentration-response curves to U46619 were performed in the absence (vehicle) or the presence of furosemide (0.1-1 mM) on rings of IMA and SV. In addition, the relaxant effect of furosemide (0.1 microM-1 mM) also was evaluated on U46619-precontracted IMA and SV. The participation of cyclooxygenase derivatives was studied by pretreatment with indomethacin. Furosemide (0.1-1.0 mM) caused parallel rightward shifts of U46619 concentration-response curves without affecting the maximal responses in both IMA and SV. Treatment with indomethacin (1 microM) modified neither the inhibitory effect of furosemide on U46619-induced contractions, nor the relaxant effect of furosemide on U46619-induced contractions, nor the relaxant effect of furosemide on U46619-precontracted IMA and SV. In conclusion, furosemide at high concentrations inhibited U46619-induced contraction in human isolated IMA and SV and relaxed U46619-precontracted IMA and SV by mechanisms independent of the release of relaxant prostaglandins. These results suggest that blockade of TXA2 receptors by furosemide may contribute to explaining the therapeutic effects of furosemide in the treatment of severe heart failure.

[Isoprostanes: new markers of oxidative stress in human diseases]

BACKGROUND

Most of the traditional methods used to assess oxidative stress in clinical setting are non specific, unreliable or inaccurate. Recently, a novel family of prostaglandin F2 isomers, called F2-isoprostanes, produced in vivo by a free radical peroxidation of arachidonic acid, has been described. These compounds may produce physiological or pathological effects due to their ability to alter smooth muscle and platelet functions. The quantification of the two major isoforms (isoprostaglandin F2 alpha type-III and VI) in biological fluids and tissues as markers of lipid peroxidation appears to be an important advance in our ability to explore the role of free radicals in the pathogenesis of human disease.

CLINICAL DATA

Urinary excretion of F2-isoprostanes is correlated with age, indicating increased oxidative stress during the normal aging process. High F2-isoprostanes concentration has been described in diseases such as ischemic heart disease, diabetes, Alzheimer's disease and hepatic cirrhosis. The correlation of F2-isoprostane concentrations and human diseases severity in hepatic cirrhosis, cardiac failure and diabetes suggest that these compounds may be of interest as predictive markers.

PERSPECTIVES

Preliminary studies suggest the use of F2-isoprostanes as prognosis markers. In addition, F2-isoprostanes quantification offers promising potential as intermediate endpoints for clinical studies of antioxidant therapies.

[Isoprostanes: new markers of oxidative stress. Fundamental and clinical aspects]

A novel family of prostaglandin F2 isomers, called F2-isoprostanes, produced in large quantities in vivo by a free radical peroxidation of arachidonic acid, has recently been described. The quantification of the two major isoforms (isoprostaglandin F2alpha type-III and VI) in biological fluids and tissues as markers of lipid peroxidation appears to be an important advance in our ability to explore the role of free radicals in the pathogenesis of human disease. In addition, F2-isoporstanes quantification seems promising as intermediate endpoints for clinical studies of antioxidant therapies.

Thromboxane A(2) modulates cyclic AMP relaxation and production in human internal mammary artery

Two forms of thromboxane A(2) (TP) receptors, TPalpha and TPbeta receptors, have recently been cloned. These receptors regulate adenylate cyclase activity in two opposite ways: TPalpha receptors activate, whereas TPbeta receptors inhibit adenylate cyclase and cAMP generation. The aim of this study was to examine the effects of the thromboxane A(2) analogue, U46619 (9,11-dideoxy-9alpha,11 alpha-methanoepoxy-prostaglandin F(2alpha)), on forskolin-induced relaxation and cAMP accumulation in human internal mammary artery (IMA) and saphenous vein (SV). In organ baths, IMA rings precontracted with U46619 (3.10(-9) and 3.10(-8) M) were less sensitive to forskolin than rings precontracted with methoxamine (3. 10(-6) M). In contrast, the sensitivity to forskolin was similar in SV rings contracted with the same concentrations of these agonists. U46619 reduced significantly the ten-fold increase in cAMP induced by forskolin in IMA but not in SV rings. Sensitivity and maximal relaxation in response to sodium nitroprusside were not altered in either IMA or SV. In summary, stimulation of TP receptors with the thromboxane A(2) analogue, U46619, inhibited the cAMP pathway of relaxation through the inhibition of cAMP synthesis in human IMA but not in SV. It is suggested that thromboxane A(2) may play a role in the control of muscle tone in IMA both by its potent contractile effect and by its inhibitory effect on the cAMP pathway of relaxation.

Are isoprostanes a clinical marker for antioxidant drug investigation?

Numerous pathological conditions are suspected to involve free radical production as part of their pathogenic process. Therefore, a pharmacological control of oxidative stress could probably benefit many vascular, inflammatory or degenerative diseases. However, the development of antioxidant drugs and their clinical evaluation are limited by the absence of an accurate, reliable and easy-to-handle marker of tissue oxidative events. Isoprostanes (isoPs), a prostaglandin-related series of metabolites, are emerging as major candidates for clinical measurement of oxidative stress. They are chemically stable products of lipid peroxidation, formed in cellular membranes and subsequently released and excreted in the urine. Many recent clinical studies have reported that urinary and plasma levels of isoPs (in particular the iPF2alpha-III isomer also called 8-epi-PGF2alpha) are increased in clinical conditions where oxidative stress is suspected to play a pathogenic role. Moreover, isoPs have been detected in tissue extracts from atherosclerotic plaques and Alzheimer patients brain tissue. Finally, antioxidant treatments such as vitamin E supplementation appear to reduce isoPs levels in biological fluids of treated patients. These preliminary observations argue for a further investigation of isoPs as a practical pharmacodynamic endpoint for the clinical evaluation of antioxidant therapies.

[In vitro study of of the effects of cysteinyl leukotrienes on human vascular preparations]

Leukotrienes are 5-lipoxygenase-derived arachidonic acid metabolites. In addition to their bronchoconstrictor effects, leukotrienes are also important modulators of the vascular tone which may exert paradoxical effects. Indeed, depending on the vascular tone (in either the basal or norepinephrine-precontracted state), leukotrienes are capable of inducing either contraction or relaxation. These paradoxical effects of leukotrienes depend on the vascular bed and the species investigated. Since urinary LTE4 excretion is increased in various cardiovascular diseases, including arterial pulmonary hypertension or cardiac ischaemia, the study of the effects of leukotrienes on human vascular preparations is of interest. This article reviews the in vitro evidence linking cysteinyl leukotrienes to the modulation of the vascular tone on human vascular preparations.

Vasorelaxant actions of enoximone, dobutamine, and the combination on human arterial coronary bypass grafts

Enoximone (a type III-selective phosphodiesterase inhibitor) and dobutamine (a beta-receptor agonist) are positive inotropic drugs frequently used in the postoperative management of coronary bypass surgery. The purpose of this study was to characterize their relaxant effects on the human internal mammary artery (IMA) and the gastroepiploic artery (GEA) and to test the hypothesis that their combination may have greater than additive relaxant effects. In organ baths, the relaxant effects of enoximone and dobutamine were tested on rings of IMA (n = 86) precontracted with U46619 (a thromboxane A2 mimetic), norepinephrine (NE), or KCl. The relaxant effects of dobutamine and enoximone also were tested on rings of GEA (n = 42) precontracted with U46619 and NE. The effect of the combination of enoximone and dobutamine were tested on rings of IMA (n = 24) precontracted with U46619 or NE. With respect to maximal relaxations induced by papaverine (10(-4) M), enoximone (< or =10(-3) M) caused full relaxations of IMA precontracted with NE, U46619, or KCI. Dobutamine (< or =10(-3) M) caused full relaxations of IMA precontracted with NE or KCI but only 46% (95% CI, 27-65) relaxation in the rings precontracted with U46619. Similar patterns of relaxation were observed in GEA rings, with dobutamine inducing partial relaxation in GEA precontracted with U46619. The pD2 values of enoximone and dobutamine were both significantly lower in segments precontracted with U46619. The in vitro threshold relaxant concentrations were in the upper limits or over the range of therapeutic plasma concentrations. The relaxant effect of the combination was significantly more important than the theoretic additive effect in IMA contracted with U46619 or NE. Enoximone and dobutamine are potent in vitro vasodilators but exert weak relaxant effects in IMA and GEA at concentrations in the therapeutic range. There is, however, a greater than additive vasorelaxant effect of the combination, suggesting that the vasorelaxant effect of the combination, in addition to the additive inotropic effect, may be beneficial to patients undergoing coronary bypass grafting.

Reactivity of the Human Internal Mammary Artery and the Gastroepiploic Artery to Constrictor Substances

The internal mammary artery (IMA) and the gastroepiploic artery (GEA) are frequently used to construct coronary artery bypass grafts. In order to determine and to compare their contractile properties, we studied the effects of constricting agents which are liberated or infused during coronary bypass surgery. IMA and GEA were arranged as ring segments and suspended in organ baths at optimal stretch using a normalization procedure. Concentration-contraction curves to angiotensin II, norepinephrine, U-46619, endothelin-1, leukotriene C(4) and KCl were performed. The sensitivity (pD(2)) of GEA and IMA to all the agents did not differ. However, GEA developed stronger maximal contraction force than IMA to angiotensin II (P < 0.001), norepinephrine (P < 0.05), U-46619 (P = 0.06), endothelin-1 (P < 0.01), and KCl (P < 0.01), whereas leukotriene C(4) did not induce a significant contraction on GEA and IMA. The higher contractility of GEA may explain that it is more prone to spasm than IMA in the clinical setting. This study reinforces IMA as a first-choice conduit for coronary artery bypass and emphasizes the need for antispastic drugs particularly when GEA is used as bypass vessel.http://link.springer-ny.com/link/service/journals/00547/bibs/8n4p187.html</hea

Antagonistic effects of losartan on thromboxane A2-receptors in human isolated gastroepiploic artery and saphenous vein

In addition to its AT1-receptor antagonist activity, losartan has been shown to antagonize thromboxane A2 (TXA2)-induced contraction of animal vessels. We investigated for the first time in human isolated gastroepiploic artery (GEA) and saphenous vein (SV) the TXA2/PGH2-receptor antagonist activity of losartan in the presence of indomethacin (1 microM) and N(omega)-nitro-L-arginine (100 microg). Losartan at concentrations of > or =1 microM on GEA and from 10 microM on SV significantly shifted U46619-induced contractions to the right. In addition, 100 microM losartan decreased by 34% the amplitude of the contraction to U46619 on both GEA and SV. The potency of losartan for the TXA2 receptor was 50- and 80-fold lower than that for the AT1 receptor on human GEA and SV, respectively. This inhibitory effect of losartan appeared selective for angiotensin II and TXA2-induced contractions because 100 microM losartan did not modify either endothelin-1- or KCl-induced contraction in human SV, although a reduction of norepinephrine- and 5-hydroxytryptamine-induced contraction was observed in human GEA and SV, respectively. In conclusion, losartan is an antagonist of TXA2 receptor on human GEA and SV. However, this antagonist activity occurred for a relative high dose of losartan, suggesting that it contributes at a low level, if any, to its antihypertensive effect.

Functional comparison of the human isolated femoral artery, internal mammary artery, gastroepiploic artery, and saphenous vein

Human femoral, internal mammary, and gastroepiploic arteries and saphenous veins are used as bypass grafts for coronary surgery or for reconstruction in arterial occlusive disease. We have characterized the contractile responses of these vessels to various agents that are liberated during cardiac or vascular surgery. In organ baths, U46619 (a stable thromboxane A2 mimetic), norepinephrine, endothelin-1, angiotensin II, and KCl caused concentration-dependent contractions in all vessels tested. Leukotriene C4 did not induce any contraction in the arteries, whereas a contraction was obtained in the saphenous vein rings. U46619 induced the most powerful contraction in all vessels tested. The pD2 values for each agent did not differ among the different vessels. When responses were expressed as a percentage of KCl-induced contraction, the contraction of endothelin-1 (151+/-5%) and leukotriene C4 (43+/-5%) was more significant on saphenous veins than on arteries. In conclusion, thromboxane A2 appears to be the most potent endogenous constricting agent on different human vascular beds. Our second finding is that saphenous veins are more sensitive to contract to leukotriene C4 and endothelin-1 than arteries. These properties may influence early and (or) long-term vein graft patency.

New calcium antagonists: synthesis, X-ray analysis, and smooth muscle relaxing effect of 3-[O-(benzyl-substituted)-oximino-ethers]-hexahydroazepin-2,3- diones

A series of new Z and E 3-[O-(benzyl-substituted)-oximino-ether]-hexahydroazepin-2,3 -diones was prepared from the corresponding hexahydroazepin-2,3-diones and examined as smooth muscle relaxants. E and Z structures were assigned by NMR analysis and confirmed for 16 (E and Z) by an X-ray diffraction using synchrotron radiations. The nitrobenzyl derivative 16 was the most potent in vitro as relaxant of rat trachea precontracted with acetylcholine. The E isomer 16b was more potent than the Z isomer 16a. E isomer 16b is more potent than aminophylline to relax both rat trachea and human bronchus. This derivative acts mainly by inhibiting cellular influx of extracellular calcium since it inhibits potently and dose-dependently the contractions of rat trachea to high concentrations of KCI and to CaCl2 in a depolarizing medium. It appears to act weakly by inducing cGMP and cAMP synthesis. Moreover, its relaxing activity is not related to an inhibition of phosphodiesterases, to opening of potassium channels or to induction of prostaglandin synthesis. Therefore, 16b appears to work mainly as a potent calcium antagonist.

Functional assessment of rat aorta after cold storage in different media

Cold storage is frequently used to store isolated blood vessels for a limited period of time. However preservation of vascular smooth muscle and endothelial functions is time and medium-dependent. The present study was designed to compare the reactivity of rat aorta before and after cold storage for 24 and 48 h in one of four different solutions consisting of Hepes-buffered Krebs solution, Belzer solution, Krebs solution, and Eurocollins solution. Smooth muscle and endothelial functions of the rat aorta were assessed using in vitro isometric tension measurement. The results obtained for vessels preserved for 24 and 48 h were compared with those for vessels studied immediately after harvesting. Sensitivity and maximum contraction to KCl and norepinephrine were not altered in rat aorta preserved up to 48 h in Hepes-Krebs and Belzer solutions. In contrast, the amplitude of contraction elicited by KCl was significantly reduced by 50% and 77% in aorta stored for 24 and 48 h in Krebs solution and by 77% and 96% in those stored in Eurocollins solutions. Similarly, the maximal contraction elicited by norepinephrine was significantly reduced by 60% and 45% in arteries stored for 24 and 48 h in Krebs solution and by 34% and 86% in those stored in Eurocollins solution. In contrast, cold storage in the different media did not alter the relaxations elicited by sodium nitroprusside and forskolin. The endothelium-dependent relaxations in response to acetylcholine were not statistically modified after preservation up to 48 h in Hepes-Krebs solution. In contrast, the maximal relaxations to acetylcholine were significantly decreased after storage for 24 and 48 h in Belzer, Krebs and Eurocollins solutions. These results suggest that among the four media studied, Hepes-Krebs solution is the most suitable medium for the storage of blood vessels under hypothermic conditions.

Determination of buprenorphine and norbuprenorphine in urine and hair by gas chromatography-mass spectrometry

Buprenorphine, which is used in France as a substitution drug for opioid addiction, is widely abused, and several fatal cases have been reported. In order to confirm a recent intoxication or to establish retrospectively chronic abuse, a simple and reliable gas chromatographic-mass spectrometric method was developed and validated for quantitation of buprenorphine and its active metabolite norbuprenorphine in urine and hair. Two milliliters of urine or 50 mg of pulverized hair was submitted to a pretreatment (enzymatic hydrolysis for urine and decontamination with dichloromethane followed by incubation in 0.1 M HCI for hair). Buprenorphine-d4 was chosen as the internal standard. Selective solid-phase extraction with Bond Elut Certify columns provided recoveries higher than 85% for urine and 43% for hair. By using a mixture of MSTFA/TMSIM/TMCS (100:2:5), buprenorphine and norbuprenorphine produced stable silylated derivatives. The detection was carried out with a quadrupole mass detector working in El selected ion monitoring mode. Ions at m/z 450 and 468 were chosen for the quantitation of buprenorphine and norbuprenorphine, respectively (m/z 454 was used for the internal standard). Limits of quantitation were 0.25 and 0.20 ng/mL, respectively, for buprenorphine and norbuprenorphine in urine and 0.005 ng/mg for the two compounds in hair. Calibration curves were linear from 0 to 50 ng/mL in urine and from 0 to 0.4 ng/mg in hair. Between-day and within-day precisions were less than 8.4% in hair and 6.1% in urine for both molecules in all cases. This method was applied to urine and hair samples collected from patients in a withdrawal treatment program and demonstrated its good applicability in routine analysis and its benefit for clinicians. This technique, which requires instruments already available to many toxicology laboratories, offers an attractive alternative to more sophisticated techniques.

[Endothelin-1 and cardiovascular diseases]

INTRODUCTION

Endothelins are peptides released from endothelial cells. According to both their structure and receptor affinity, three isoforms may be identified. Endothelin-1 is secreted abluminally by endothelial cells, and binds ETA and ETB2 receptors expressed on vascular smooth muscle cells, and ETB1 expressed on endothelial cells. ETA and ETB2 receptors stimulation induces smooth muscle contraction and proliferation, whereas ETB1 receptors stimulation induces relaxation.

CURRENT KNOWLEDGE AND KEY POINTS

Endothelin-1 plays an important role in maintaining peripheral vascular tone and systemic blood pressure. It is recognized to have a role in various diseases associated with vasoconstriction and vascular hypertrophy.

FUTURE PROSPECTS AND PROJECTS

Recent development of endothelin receptor antagonists seems promising for the treatment of heart failure and systemic hypertension, with interesting results obtained from short-term clinical trials. However, better evaluation of these drugs requires further long-term studies regarding not only the above mentioned diseases but also ischemic heart disease or pulmonary hypertension. Endothelin antagonists are therefore new therapeutic agents able to inhibit a vasoconstricting system that has been recently discovered. Results of ongoing clinical studies are awaited with interest.

Frusemide inhibits angiotensin II-induced contraction on human vascular smooth muscle

AIMS

Frusemide is widely used in the treatment of acute pulmonary oedema, chronic congestive heart failure and, to a lesser degree, in the treatment of hypertension. Evidence suggests that frusenuide exerts an anti-vasoconstrictor effect independent of its diuretic properties. Since angiotensin II is a highly potent vasoconstrictor involved in the pathophysiology of these diseases, we have investigated the effect of frusemide on the contraction elicited by angiotensin II on human internal mammary artery (IMA) and saphenous vein (SV).

METHODS

Rings of IMA and SV were suspended for isometric tension recording in organ baths. Concentration-response curves to angiotensin II were performed in the absence (control) or in the presence of frusemide (10(-6) to 10(-3) M). In addition, the effect of frusemide was evaluated after cyclooxygenase inhibition by indomethacin (10(-6) M) and was compared with those of the other loop diuretic bumetanide (10(-4) M).

RESULTS

Frusemide induced a concentration-dependent decrease of the contraction elicited by angiotensin II on IMA and SV. On both vessels, the inhibitory effect on the maximal contraction to angiotensin II was significant with concentrations of frusemide from 10(-5) to 10(-3) M. Angiotensin II potency (pD2) was only reduced by 10(-3) M frusemide. The effect of frusemide was not altered in the presence of indomethacin. Bumetanide was less potent than frusemide in inhibiting angiotensin II-induced contractions in both IMA and SV.

CONCLUSIONS

Frusemide, at concentrations in the therapeutic range (10(-5) M), inhibits angiotensin II-induced contraction on human isolated IMA and SV. This inhibitory effect is cyclooxygenase independent and appears mediated, at least in part, by inhibition of Na+/K+/2Cl- symport. Reduction in the vasoconstrictor effect of angiotensin 1 may be involved in the therapeutic efficacy of frusemide.

Functional assessment of human femoral arteries after cryopreservation

PURPOSE

An established method of cryostorage that might preserve the vascular and endothelial responses of human femoral arteries (HFAs) to be transplanted as allografts was studied.

METHODS

HFAs were harvested from multiorgan donors and stored at 4 degrees C in Belzer solution before cryostorage. One hundred eleven HFA rings were isolated and randomly assigned to 1 control group of unfrozen HFAs and 2 groups of HFAs cryopreserved for 7 and 30 days, respectively. Cryopreservation was performed in Elohes solution containing dimethyl sulfoxide (1.8 mmol/L), and the rate of cooling was 1.6 degrees C/min, until -141 degrees C was reached. The contractile and relaxant responses of unfrozen and frozen/thawed arteries were assessed in organ bath by measurement of isometric force generated by the HFAs.

RESULTS

After thawing, the maximal contractile responses to all the contracting agonists tested (KCl, U46619 [a thromboxane A2-mimetic], norepinephrine, serotonin, and endothelin-1) were in the range of 7% to 34% of the responses in unfrozen HFAs. The endothelium-independent relaxant responses to forskolin and verapamil were weakly altered, whereas the endothelium-independent relaxant responses to sodium nitroprusside were markedly reduced. Cryostorage of HFAs also resulted in a loss of the endothelium-dependent relaxant response to acetylcholine. The vascular and endothelial responses were similarly altered in the HFAs cryopreserved for 7 and 30 days.

CONCLUSION

The cryopreservation method used provided a limited preservation of HFAs contractility, a good preservation of the endothelium-independent relaxant responses, but no apparent preservation of the endothelium-dependent relaxation. It is possible that further refinements of the cryopreservation protocol, such as a slower rate of cooling and a more controlled stepwise addition of dimethyl sulfoxide, might allow better post-thaw functional recovery of HFAs.

Glibenclamide inhibits thromboxane A2-induced contraction in human internal mammary artery and saphenous vein

Glibenclamide, like other hypoglycemic sulfonylurea derivatives, is a potent blocker of ATP-regulated K+ channels. In addition, it is reported to inhibit prostanoid-induced contractions of isolated vascular smooth muscle from different animal species. We investigated the effect of glibenclamide on the thromboxane A2-mimetic U-46619 (9,11-dideoxy-9alpha,11alpha-methanoepoxy-prostaglandin F2alpha)-induced contractions in human isolated internal mammary arteries and saphenous veins. In the two vascular preparations, glibenclamide (3, 10 and 30 microM) caused a concentration-dependent shift to the right of the U-46619 contraction-response curve with a reduction, at the highest concentrations, in the maximal responses. This inhibitory effect appears selective for thromboxane A2-induced contractions since glibenclamide (30 microM) did not alter the contraction of internal mammary arteries in response to norepinephrine and of saphenous veins in response to 5-hydroxytryptamine (5-HT) and endothelin-1. However, glibenclamide reduced the endothelin-1-induced contraction in internal mammary arteries. The endothelin-1-induced contractions were similarly inhibited by GR 32191 ([1R-[1alpha(Z),2beta,3beta,5alpha]]-(+)-7-[5-([1,1'-b iphenyl]-4-ylmethoxy)-3-hydroxy-2-(1-piperidinyl)cyclopentyl]-4-++ +heptonoic acid, a thromboxane A2 receptor antagonist. These results suggest that glibenclamide also reduced the endothelin-1-induced contractions by inhibiting a thromboxane A2 receptor-mediated component of the contraction elicited by this peptide. In conclusion, glibenclamide clearly appears to exert a specific inhibitory influence on prostanoid-induced contractions in human internal mammary arteries and saphenous veins.

Inhibitory effects of large Ca2+-activated K+ channel blockers on beta-adrenergic- and NO-donor-mediated relaxations of human and guinea-pig airway smooth muscles

In human bronchi, relaxations to salbutamol and sodium nitroprusside were performed in the presence or absence of blockers of the large Ca2+-activated K+-channels (BKCa): charybdotoxin (Chtx), iberiotoxin (Ibtx) or tetraethylammonium (TEA). In bronchi under basal tone in presence of indomethacin (1 microM) or precontracted with acetylcholine (in presence or absence of indomethacin), the relaxations to salbutamol or sodium nitroprusside were unaffected or weakly inhibited by pretreatment with the BKca blockers (Chtx (100 nM), Ibtx (100 and 300 nM) and TEA (1 mM)). Significant inhibitions were mainly observed with TEA (1 mM) and iberiotoxin at high concentration (300 nM). These results contrasts with the potent inhibitory effects exerted by Chtx (100 nM) or Ibtx (100 nM) in guinea-pig trachea precontracted with acetylcholine in absence or presence of indomethacin indicating that human airways are less susceptible to BKCa blockade than guinea-pig airways. In addition, the BKCa blockers induced slowly developing contractions of human bronchi at basal tone. The contraction induced by TEA (1 mM) was abolished by verapamil (10 microM) suggesting that BKca blockade promotes an increase in membrane Ca2+-conductance through activation of voltage-gated Ca2+-channels. Verapamil also reversed the effects of TEA on salbutamol-induced relaxations in human bronchi as well as the effects of Ibtx on salbutamol- or sodium nitroprusside-induced relaxations in guinea-pig trachea. These data suggest that BKCa blockers induce activation of voltage-gated Ca2+-channels and therefore influx of Ca2+ which in turn cause a functional antagonism of beta2-adrenoceptor-agonist- and NO-donor-induced relaxations. Moreover, the BKCa opener, NS-1619, induced weak relaxations in human bronchi and guinea-pig trachea which were not blocked by TEA or Ibtx suggesting that BKCa opening is of minor significance for the relaxation of human airway smooth muscles. In conclusion, although a wealth of studies have demonstrated that beta-adrenoceptor agonists or NO-donors activate BKCa, the present study provides evidence that in human bronchi, as recently suggested in guinea-pig trachea, opening of BKCa does not appear to functionally participate in the relaxation to these relaxant agents.

Characterization of the production of acetaldehyde by astrocytes in culture after ethanol exposure

The nervous system is one of the main targets of ethanol toxicity. Astrocytes might play an important role in ethanol-induced brain toxicity, because their integrity is essential for the normal growth and functioning of neurons. On the other hand, acetaldehyde has been implicated as a mediator in some of the biochemical, pharmacological, and behavioral effects of ethanol. The present study aimed at demonstrating the ability of astrocytes in culture to produce acetaldehyde from ethanol. Significant metabolization of ethanol with production of acetaldehyde was demonstrated in the primary culture of astrocytes. This production was quite low, compared with that usually observed in hepatocytes, but was in the same range as that measured in whole brain homogenates and corresponded to biologically active levels. Such a demonstration could bring new elements for understanding of ethanol neurotoxicity.

[Leukotriene antagonists: a new approach in the treatment of asthma]

Inflammation plays an essential role in the genesis of airflow obstruction and bronchial hyper-reactivity in the early stages of clinical asthma. The treatment of bronchial inflammation has become an essential element in the therapeutic strategy and principally rests on inhaled glucocorticoids. Amongst a number of inflammatory mediators leukotrienes occupy a privileged place by the power of their inflammatory and constrictor effects on bronchial smooth muscles. These properties have justified the clinical development of inhibitors of their synthesis and of specific antagonists to their receptors. Leukotriene antagonists are specific for a sub type of leukotriene receptors C4, D4 and E4 which is implicated in the majority of the bronchial constrictor and inflammatory effects of leukotrienes. The antagonists of Cys-LT1 receptor but also the inhibitors of the leukotriene synthesis exert an additive bronchodilator effect to those of B2 stimulants confirming an efficacious protection vis a vis bronchial provocation tests and above all they improve the clinical scores, lung function and also enable a decrease in the consumption of beta 2 agonists. The marketing of these products represents a major event because it corresponds to the advent of a new therapeutic class. The ease of administration by the oral route, their demonstrated efficacy and their good tolerance profile (in particular for ICI 204.219, and antagonists to Cys-LT1 receptors) are elements which foresee a success for this new asthmatic treatment. However numerous studies, notably comparative studies vis a vis reference treatments will be necessary to define their place in the strategic approach to the treatment of asthma.