Dominique Stephan

Endothelium-dependent relaxation in the isolated rat kidney : impairment by cyclosporine A

The therapeutical use of cyclosporine A (CsA) is hampered by the development of nephrotoxicity characterized by a marked increase in renal vascular resistance (RVR). We investigated vascular functions in kidneys of rats treated with CsA. The ex vivo vascular reactivity of kidneys from control rats and animals treated subacutely with CsA [50 mg/kg/day subcutaneously (s.c.) for 16-21 days] or an olive oil vehicle (1 ml/kg) was analyzed in male Wistar rats. The right kidney was isolated and perfused with Tyrodes or Krebs solution in an open circuit. The effects of acetylcholine (Ach), fenoldopam (FEN), and sodium nitroprusside (SNP) on norepinephrine (NE) preconstricted kidneys were studied. In control kidneys (untreated or vehicle-treated), Ach induced a relaxation (EC50 = 0.56 +/- 0.05 x 10(-9)M; Emax = 88.2 +/- 2.1% decrease in the vascular tone restored by NE) which was endothelium-dependent [near-complete abolition after treatment with a detergent, 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propane-sulfonate (CHAPS) treatment] but only partially inhibited by indomethacin (EC50 = 1.71 +/- 0.39 x 10(-9)M, p < 0.05; Emax = 87.1 +/- 4.9%, NS) or indomethacin with NG-nitro-L-arginine methyl ester (L-NAME: EC50 = 1.04 +/- 0.38 x 10(-9)M, NS; Emax = 63.8 +/- 2.5%, p < 0.01). CsA treatment induced a marked decrease in creatinine clearance and natriuresis measured in vivo but had no effect on systolic blood pressure (SBP). In CsA-treated rats, Ach-induced renal relaxation was partially blunted (EC50 = 1.88 +/- 0.34 x 10(-9)M, p < 0.01; Emax = 82.8 +/- 4.6, NS), with both a defect in prostaglandin (PG) and nitric oxide (NO)-related responses. CsA treatment had no effect on endothelium-independent relaxations induced by FEN and SNP. These results show that subacute CsA treatment selectively impairs renal endothelium-dependent relaxation related to PGs and NO release.

Vascular effects of loop diuretics: an in vivo and in vitro study in the rat

The vascular effects of loop diuretics were studied in two models designed to eliminate hemodynamic repercussions linked to sodium and water depletion: in vivo, in unilaterally nephrectomized rats with a contralateral uretero-venous shunt, and in vitro, in the isolated perfused rat kidney.In anesthetized rats, local vascular resistance was calculated from the simultaneous recording of blood pressure and renal, iliac and carotid blood flows (electromagnetic flowmeter, Skalar). Furosemide and piretanide (10 to 80 mg/kg i. v.) induced a comparable dose-dependent decrease in renal vascular resistance, which was not modified by reserpine and indomethacin pre-treatment. The iliac relaxing response was blunted by vasoconstriction, which disappeared after combined treatment with reserpine and indomethacin. The relaxation induced in the iliac and carotid vasculature persisted after bilateral nephrectomy.In vitro, the vasorelaxing effect of diuretics in isolated rat kidneys perfused in an open circuit was studied after vascular tone had been re-established by a continuous perfusion of PGF2α. Furosemide, piretanide and ozolinone induced a concentration-dependent decrease in renal tone (EC50 = 0.47 × 10-4 mol/l, 1.03 × 10−4 mol/l and 2.07 × 10−4 mol/l respectively) in Wistar rats. A similar response to piretanide was found in spontaneously hypertensive stroke-prone rats (EC50 = 0.32 × 10−4 mol/l) and in their normotensive controls (ECSO = 0.74 × 10−4 mol/l).Our results show that loop diuretics induce a direct relaxation in the renal, iliac and carotid vasculature. This vascular effect, which appears at relatively high concentrations of the drugs, is prostaglandin independent and persists after bilateral nephrectomy.

Plasma renin activity and changes in tissue angiotensin converting enzyme.

Objectives Recent evidence suggests that tissue generation of angiotensins I and II depends on the level of the plasma components of the renin-angiotensin system and on tissue-specific processes. The present study was undertaken to clarify the possible relationship between plasma renin activity (PRA) and tissue angiotensin converting enzyme (ACE) activity in the heart, lung, kidney cortex and kidney medulla of Wistar-Kyoto rats. In the kidney cortex particular attention was focused on renal brush-border ACE. Methods Different experimental models known to have opposite effects on PRA were used: changes in salt intake, deoxycorticosterone acetate (DOCA) with or without salt supplements, and the Coldblatt two-kidney, one clip (2-K,1 C) model. Two weeks after the start of the experiments the rats were killed, and PRA, and plasma and tissue ACE activity, were measured. Results At the end of the study the blood pressure in the treated rats was not significantly different from control. As expected, the PRA were highest in the 2-K, 1C and depleted-salt groups and lowest in the DOCA, DOCA-salt and high-salt groups. ACE responses were different in different types of tissue, with no relationship between PRA and plasma or tissue ACE activity. For example, DOCA treatment led to increased ACE activity in the heart and the kidney only if the rats were maintained on a high salt intake. DOCA or salt alone failed to have this effect. In the 2-K, 1C model the undipped kidneys did not show any significant variation in ACE activity, but the clipped kidneys exhibited increased ACE activity compared with sham-operated rats. This increase, coupled with increased renal renin secretion, could play a role in the acceleration of local angiotensin II formation, and could thus initiate and sustain the development of hypertension in this model. Conclusion The present results show that variations in ACE activity were organ-specific and were not linked either to hypertension or to changes in PRA.

Effects of Dopamine Prodrugs and Fenoldopam on Glomerular Hyperfiltration in Streptozotocin-Induced Diabetes in Rats

The effects of dopamine (DA) prodrugs (L-dopa and gludopa) and of a D1-selective agonist (fenol-dopam) on glomerular hyperfiltration were studied in the early stage of diabetes in rats. Wistar rats received one injection of streptozotocin (STZ) and were treated 1 week later with L-dopa (2 ± 10 mg/kg/day, s.c.), gludopa (2 ± 3 or 2 ± 10 mg/kg/day, s.c.), or fenoldopam (2 ± 0.3 or 2 ± 1 mg/kg/day, s.c.). Their renal functions were compared with those of untreated diabetic and nondiabetic control rats. STZ injection led to hyperglycemia that was kept moderate (20–25 mmol/L) by daily insulin therapy (2–4 U of NPH insulin). Within 2 weeks, glomerular hyperfiltration (polyfructosan clearance) developed in diabetic rats (30% increase vs. nondiabetic control). A rise in renal plasma flow (PAH clearance) was sometimes observed. One week of treatment with either L-dopa, gludopa, or fenoldopam normalized the glomerular filtration rate and decreased filtration fraction, These corrections occurred despite similar metabolic disturbance and kidney hypertrophy. Gludopa was less well tolerated by diabetic rats than L-dopa. Results with L-dopa showed that the normalization of glomerular hyperfiltration was linked to DA synthesis and stimulation of D1 receptors, since it was reversed by carbidopa, a dopa decarboxylase inhibitor, and by SCH 23390, a D1-selective antagonist. These data show that DA prodrugs and a D1 agonist can suppress diabetic glomerular hyperfiltration in the very early course of the disease in rats.

Mono-hydrofluorination of electrophilic alkynes by the liquid biphasic CsF–H2O–DMF system (DMF = N,N-dimethylformamide)

CsF induces the addition of HF in fair yields to activated acetylenic triple bonds in a DMF–water biphasic medium (DMF = N,N-dimethylformamide); in a homogeneous DMF–water mixture, no addition is observed.

Antiangiogenic effects of spironolactone and other potassium-sparing diuretics in human umbilical vein endothelial cells and in fibrin gel chambers implanted in rats

Objective Potassium-sparing diuretics have different effects on angiogenesis that may mediate some abilities to treat cardiovascular diseases. The aim of the current study was to compare the effects of spironolactone and an active metabolite, canrenone, or a derivative, eplerenone, and amiloride, a diuretic without affecting mineralocorticoid activity, on the proliferation of human umbilical vein endothelial cells (HUVEC) and on angiogenesis in fibrin gel chambers implanted in rats. Materials and methods We measured the effects of spironolactone, canrenone, eplerenone, and amiloride on the proliferation of HUVEC in the presence or absence of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). We also examined the effects of these compounds on migration and capillary tube formation by HUVEC. Finally, the effects of the compounds on neovessel formation in vivo were investigated by implanting Wistar rats for 14 days with perforated Plexiglas chambers containing rat fibrin. Results Spironolactone and amiloride inhibited the proliferation of HUVEC, but canrenone and eplerenone had no effect. The inhibitory effect of spironolactone was not prevented by VEGF or bFGF. Aldosterone had no effect on spironolactone-induced inhibition of HUVEC proliferation. Spironolactone induced a dose-dependent reduction of both cell chemotaxis and capillary tube formation. In fibrin gel chambers, spironolactone and amiloride significantly reduced the numbers of both peripheral and central neovessels. Canrenone and eplerenone, in contrast, had no antiangiogenic effect. Conclusion Spironolactone and amiloride significantly inhibited angiogenesis in vitro and in the fibrin gel chamber in vivo. Spironolactone antiangiogenic effects are unrelated to antimineralocorticoid activity.

A critical appraisal of the guidelines from France, the UK, Europe and the USA for the management of hypertension in adults

Hypertension is the leading cause of death in developed countries; its management is the subject of guidelines that are regularly reviewed and updated. However, the guidelines from France, the UK, Europe and the USA differ. Some recommendations are graded, whereas others are not. All recommendations emphasize the role of alternative methods for clinical measurement of blood pressure, such as ambulatory blood pressure measurement (ABPM) or self-measurement. The UK guideline recommends that the diagnosis of hypertension should be established by ABPM. The USA guideline recommends a target of ≤ 150/90 mmHg for patients aged >60 years. The French guideline recommends that the target blood pressure remains at <140/90 mmHg, with <150 mmHg for patients aged >80 years. Systolic blood pressure between 130 and 139 mmHg and diastolic blood pressure <90 mmHg are recommended for diabetic patients and those with chronic kidney disease. The French Society of Hypertension (SFHTA) guideline is unique in recommending a dedicated consultation to announce the diagnosis to the patient. In the French and European guidelines, diuretics, beta-blockers, calcium antagonists, angiotensin-converting enzyme (ACE) inhibitors and angiotensin II type 1 receptor blockers (ARBs) remain indicated as first-line therapy for hypertension; if the target blood pressure is not achieved, they recommend combining two active substances. The UK guideline recommends ACE inhibitors or ARBs as first-line therapy for patients aged <55 years; calcium antagonists are advised for patients aged >55 years and for black patients. The USA guideline advises treating non-black patients, including those with diabetes, with thiazides, calcium antagonists, ACE inhibitors or ARBs; for black patients, including those with diabetes, it recommends thiazide and calcium antagonists.

Volumineux œdèmes des mains chez des patients toxicomanes intraveineux au long cours

Resume La toxicomanie intra-veineuse peut s’accompagner de complications systemiques et locales. L’injection intra-veineuse de drogues induit des thromboses, des complications septiques ou emboliques. Le syndrome des mains bouffies est une complication peu connue d’une toxicomanie intra-veineuse au long cours. Nous rapportons trois cas de patients toxicomanes au long cours souffrant d’un syndrome des mains bouffies. Il s’agissait de deux hommes et une femme (26-37, âge moyen 30,6 ans) toxicomanes au long cours (4-12, duree moyenne 7,3 ans), ayant arrete l’intoxication par l’heroine depuis 3 a 5 ans (duree moyenne 4,6 ans) et beneficiant ou ayant beneficie d’une substitution par buprenorphine. Les troubles etaient apparus plusieurs annees apres l’intoxication (1,5-5 ans, 2,3 ans). Typiquement, l’œdeme etait bilateral touchant la face dorsale de la main et la racine des doigts, s’etendant vers l’avant-bras. L’œdeme touchait les pieds et les jambes chez un patient. L’œdeme etait elastique, prenant peu le godet et non modifie par la surelevation des membres. L’echographie veineuse des membres etait normale. La lymphoscintigraphie pratiquee chez un patient montrait une absence de progression du traceur dans un membre en faveur d’une obstruction des troncs de drainage. Le syndrome des mains bouffies constituerait l’expression ultime de l’occlusion lymphatique. L’obstruction et la destruction progressive des troncs lymphatiques resulteraient du drainage des impuretes presentes dans la drogue lors d’injections en dehors de la veine. La buprenorphine est souvent utilisee par les toxicomanes en injection intra-veineuse. Cependant ce medicament est peu soluble, et c’est le drainage de fragments de l’excipient lors d’injections en dehors des veines qui pourrait expliquer l’obstruction lymphatique. Le syndrome des mains bouffies, pour lequel il n’existe pas de traitement curatif, ne doit pas etre confondu avec une infection des espaces profonds de la main qui necessite incision et drainage. (J Mal Vasc 2004 ;29 : 201-204).

A facile access to masked isobenzofurans ; High exo-stereoselectivity in the Diels-Alder reactions of 4,7-dihydro-4,7-ethanoisobenzofuran.

Abstract The isobenzofuran derivatives precursors 4 a-c are readily prepared from 1 ; their Diels-Alder adducts with cis-dienophiles present a stereochemistry endoexo from 4 b,c and, interestingly, only exo (towards the furan moiety) from 4 a.

Rivaroxaban versus standard anticoagulation for symptomatic venous thromboembolism (REMOTEV observational study): Analysis of 6-month outcomes

BACKGROUND This study aimed to provide safety and efficacy data of rivaroxaban in routine patient care in a non-selected symptomatic venous thromboembolism (VTE) population. METHODS AND RESULTS REMOTEV is a prospective, non-interventional study of patients with acute symptomatic VTE, treated with oral rivaroxaban, VKA or parenteral heparin/fondaparinux alone for at least 3months and who are followed up for 6months. From Nov. 2013 to July 2015, 499 consecutive patients were retained for baseline analysis and 445 for safety analysis. The mean age was 65.1years, 7.6% had previously known active cancer, 18.6% had creatinine clearance 30≤CrCl<60mL/min, and 87.8% had pulmonary embolism with or without deep venous thrombosis. The major and clinically relevant bleeding rate was 5.4% (15/280) in the rivaroxaban group, 9.4%/(9/96) in the VKA group and 7.2% (5/69) in the heparin/fondaparinux group. The recurrent VTE rate was 1.4% (4/280) in the rivaroxaban group, 3.1% (3/96) in the VKA group and 11.6% (8/69) in the heparin/fondaparinux group. In the propensity score-adjusted samples, major and clinically relevant non-major bleeding (HR 0.37 [95% CI, 0.15 to 0.93], p<0.05), all-cause death (HR 0.21 [95% CI, 0.06 to 0.66], p<0.01) and the composite of recurrent VTE, major and clinically relevant non-major bleeding and all-cause mortality (HR 0.35 [95% CI, 0.17 to 0.71], p<0.01), were significantly lower in the rivaroxaban group compared to the VKA group. CONCLUSION In REMOTEV 6-month outcomes are consistent with the findings of the phase 3 randomized trials and post-marketing data, with low rates of major bleeding and symptomatic recurrent VTE.