Torsten Schlüter
University of Greifswald
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Featured researches published by Torsten Schlüter.
Cardiovascular Research | 2008
Torsten Schlüter; Antje Steinbach; Anja Steffen; Rainer Rettig; Olaf Grisk
AIMS The present study was designed to test the hypothesis that NADPH oxidase inhibition with apocynin would lower blood pressure and improve endothelial function in spontaneously hypertensive rats (SHRs). Although apocyin effectively dilated arterial segments in vitro, it failed to lower blood pressure or improve endothelial function. Further experiments were performed in normotensive rats and in NADPH oxidase subunit knock-out mice to test if apocynin-induced vasodilation depends on NADPH oxidase inhibition at all. METHODS AND RESULTS SHRs were treated with apocynin orally or i.v. Arterial pressure was recorded directly. Rat and mouse arterial function was investigated in vitro by small vessel wire myography. NADPH oxidase activity was measured in human granulocytes and in rat vascular preparations. Rho kinase activity was determined by Western blot analysis. Apocynin did not reduce arterial pressure acutely in SHR when given at 50, 100, or 150 mg kg(-1) day(-1) orally over 1-week intervals or when given i.v. Apocynin potently inhibited granulocyte NADPH oxidase but not vascular NADPH-oxidase-dependent oxygen radical formation unless exogenous peroxidase was added to vascular preparations. Apocynin dilated rat intrarenal and coronary arteries independently of pharmacological interventions that reduce vascular superoxide radical abundance and actions. Aortic rings from p47phox(-/-) mice were more sensitive to apocynin-induced dilation than wild-type aortic rings. Rho kinase inhibition reduced or prevented the inhibitory effect of apocynin on agonist-induced vasoconstriction and apocynin inhibited the phosphorylation of Rho kinase substrates. CONCLUSION Apocynin per se does not inhibit vascular NADPH-oxidase-dependent superoxide formation. Its in vitro vasodilator actions are not due to NADPH oxidase inhibition but may be explained at least in part by inhibition of Rho kinase activity. The discrepancy between apocynin-induced vasodilation in vitro and the failure of apocynin to lower arterial pressure in SHR suggests opposing effects on arterial pressure-regulating systems in vivo. Its use as a pharmacological tool to investigate vascular NADPH oxidase should be discontinued.
American Journal of Physiology-regulatory Integrative and Comparative Physiology | 2009
Ulla C. Kopp; Olaf Grisk; Michael Z. Cicha; Lori A. Smith; Antje Steinbach; Torsten Schlüter; Nicole Mähler; Tomas Hökfelt
Increasing efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which in turn decreases ERSNA via activation of the renorenal reflexes in the overall goal of maintaining low ERSNA. We now examined whether the ERSNA-induced increases in ARNA are modulated by dietary sodium and the role of endothelin (ET). The ARNA response to reflex increases in ERSNA was enhanced in high (HNa)- vs. low-sodium (LNa) diet rats, 7,560 +/- 1,470 vs. 900 +/- 390%.s. The norepinephrine (NE) concentration required to increase PGE(2) and substance P release from isolated renal pelvises was 10 pM in HNa and 6,250 pM in LNa diet rats. In HNa diet pelvises 10 pM NE increased PGE(2) release from 67 +/- 6 to 150 +/- 13 pg/min and substance P release from 6.7 +/- 0.8 to 12.3 +/- 1.8 pg/min. In LNa diet pelvises 6,250 pM NE increased PGE(2) release from 64 +/- 5 to 129 +/- 22 pg/min and substance P release from 4.5 +/- 0.4 to 6.6 +/- 0.7 pg/min. In the renal pelvic wall, ETB-R are present on unmyelinated Schwann cells close to the afferent nerves and ETA-R on smooth muscle cells. ETA-receptor (R) protein expression in the renal pelvic wall is increased in LNa diet. In HNa diet, renal pelvic administration of the ETB-R antagonist BQ788 reduced ERSNA-induced increases in ARNA and NE-induced release of PGE(2) and substance P. In LNa diet, the ETA-R antagonist BQ123 enhanced ERSNA-induced increases in ARNA and NE-induced release of substance P without altering PGE(2) release. In conclusion, activation of ETB-R and ETA-R contributes to the enhanced and suppressed interaction between ERSNA and ARNA in conditions of HNa and LNa diet, respectively, suggesting a role for ET in the renal control of ERSNA that is dependent on dietary sodium.
Journal of Hypertension | 2012
Olaf Grisk; Torsten Schlüter; Nico Reimer; Uwe Zimmermann; Elpiniki Katsari; Oliver Plettenburg; Matthias Löhn; Hans-Georg Wollert; Rainer Rettig
Objectives: Increased renal vascular resistance contributes to the pathogenesis of hypertension. The new Rho kinase (ROCK) inhibitor SAR407899 more potently lowers arterial pressure than the commercially available ROCK inhibitor Y27623. We tested whether ROCK inhibition more effectively reduced agonist-induced vasoconstriction in renal than in nonrenal resistance arteries and if SAR407899 more potently inhibits agonist-induced vasoconstriction than Y27632. Methods: The effects of the ROCK inhibitors on endothelin-1 (ET-1) induced vasoconstriction were investigated in isolated renal and coronary arteries from lean, normotensive Dark Agouti and obese, type 2 diabetic Zucker diabetic fatty (ZDF) rats as well as in isolated human resistance arteries from the kidney and thymus. Vascular ROCK mRNA abundance was studied by real-time PCR (RT-PCR). Results: ET-1-induced constriction depended more on ROCK in rat and human renal resistance arteries than in rat coronary or human thymic arteries, respectively. SAR407899 was more effective than Y27632 in reducing ET-1-induced vasoconstriction in ZDF rat renal resistance arteries. Maximum ET-1-induced vasoconstriction in SAR407899-treated and Y27632-treated human renal resistance arteries was 23 ± 5 and 48 ± 6% of control values, respectively. Transcripts of both ROCK isoforms were detected in rat and human renal resistance arteries. In human thymic arteries, only the ROCK2 transcript was found. Conclusion: ET-1-induced vasoconstriction is more ROCK-dependent in renal than in nonrenal resistance arteries. SAR407899 causes a greater inhibition of ET-1-induced vasoconstriction in renal resistance arteries from ZDF rats and patients than Y27632. The greater efficacy in renal vessels may contribute to the higher antihypertensive potency of SAR407899 compared with Y27632.
Pharmacogenetics and Genomics | 2009
Olaf Grisk; Antje Steinbach; Sabine Ciecholewski; Torsten Schlüter; Ingrid Klöting; Helmut Schmidt; Eike Dazert; Elke Schaeffeler; Leif Steil; Stefan Gauer; Gabriele Jedlitschky; Matthias Schwab; Gerd Geisslinger; Ingeborg A. Hauser; Uwe Völker; Heyo K. Kroemer; Rainer Rettig
Objectives We tested the effect of kidney-specific multidrug resistance-related protein (MRP2, ABCC2) deficiency on renal organic solute disposition as well as on renal protein and gene expression. Furthermore, we investigated whether a particular kidney donor ABCC2 genotype is associated with delayed graft function in patients. Methods A new MRP2-deficient rat strain was established. Renal cross-transplantations were performed between congenic MRP2-deficient and wild-type rats. Renal disposition of MRP2 substrates was investigated in native and transplanted rats. Proteomic analyses and transcriptional profiling were performed in rat kidney graft cortices. Ninety-eight human kidney donor–recipient pairs were genotyped for five ABCC2 polymorphisms. The relationship between delayed graft function and ABCC2 genetic variants in donors and recipients was analyzed by backward stepwise logistic regression. Results In rats, the absence of renal MRP2 reduced renal bilirubin glucuronide excretion at pathologic plasma concentrations, modified renal p-aminohippurate excretion and did not affect renal morphine-6-glucuronide excretion. Renal MRP2 deficiency led to renal cortical protein or mRNA upregulation of glutathione transferase isoenzymes, glutaredoxin 2, and heme oxygenase-1. In patients, a particular donor ABCC2 genotype was associated with an increased incidence of delayed graft function. Conclusion Kidney graft-specific MRP2 deficiency has mild effects on the renal excretion of some organic solutes under experimental conditions and induces a protein and gene expression pattern indicative of activated antioxidant defense mechanisms. This suggests that MRP2 is a determinant of the redox status in tubular epithelial cells and thus of the susceptibility to renal damage under conditions of treatment with multiple drugs and increased oxygen radical formation.
Cardiovascular Research | 2010
Torsten Schlüter; Uwe Zimmermann; Chris Protzel; Bärbel Miehe; Klaus-Jürgen Klebingat; Rainer Rettig; Olaf Grisk
AIMS The present study was performed to investigate the contribution of NADPH oxidases (Nox) to superoxide formation in human renal proximal resistance arteries and to test whether superoxide formation contributes to acute vasoconstrictor responses and endothelium-dependent vasodilation in these vessels. METHODS AND RESULTS Arcuate and proximal interlobular artery segments were from patients who underwent nephrectomy because of a renal tumour. Vessels were dissected from tumour-free parts of the kidneys. Additional intrarenal arteries were obtained from rats. Superoxide formation was measured by lucigenin-enhanced chemiluminescence, expression of Nox isoforms was analysed by RT-PCR, and functional studies were performed by small vessel wire myography. Sixty per cent of superoxide formation in human arcuate and proximal interlobular arteries was due to Nox activity. mRNA expression analyses revealed the presence of Nox2 and Nox4 but not Nox1. Phenylephrine and endothelin-1 induced powerful concentration-dependent vasoconstrictions that were unaffected by superoxide scavengers. Vasopressin elicited small and variable vasoconstrictions with signs of tachyphylaxis. Endothelium-dependent vasodilation was blunted by tiron and Nomega-nitro-L-arginine methyl ester but not by superoxide dismutase or catalase. Exogenous hydrogen peroxide elicited vasoconstriction. CONCLUSION Nox activity is the major source of superoxide formation in renal proximal resistance arteries from elderly patients. Acute vasoconstrictor responses to alpha1-adrenoreceptor activation and to endothelin-1 do not depend on superoxide formation, while endothelium-dependent vasodilation in intrarenal arteries is reactive oxygen species-dependent.
American Journal of Physiology-heart and Circulatory Physiology | 2009
Jörg Peters; Torsten Schlüter; Thomas Riegel; Barbara Peters; Andreas Beineke; Ulrike Maschke; Norbert Hosten; John J. Mullins; Rainer Rettig
The aim of the present study was to test the hypothesis that elevation of prorenin in plasma is sufficient to induce cardiac fibrosis. Normotensive cyp1a1ren-2 transgenic rats with normal plasma prorenin and aldosterone levels were given 0.125% indole-3-carbinol (I3C) orally for a period of 12 wk. Plasma prorenin and aldosterone levels were determined in 4-wk intervals, and cardiac marker enzymes for hypertrophy, fibrosis, and oxidative stress as well as cardiac pathology were investigated. In I3C-treated cyp1a1 ren-2 transgenic rats, plasma prorenin concentrations were >100-fold elevated (≥7.1 ± 2.6 μg ANG I·ml−1·h−1 vs. ≤0.07 ± 0.1; P < 0.001), whereas active renin levels were suppressed (0.09 ± 0.02 vs. 0.2 ± 0.1; P < 0.05). Aldosterone concentrations were elevated three- to fourfold for a period of >4 wk (574 ± 51 vs. 160 ± 68 pg/ml; P < 0.01). After 12 wk of I3C, rats exhibited moderate cardiac hypertrophy (heart weight/body weight 2.5 ± 0.04 vs. 3.1 ± 0.1 mg/g; P < 0.01). There was a slight increase in mRNA contents of endothelin 1 (1.21 ± 0.08 vs. 0.75 ± 0.007; P < 0.001), NADP oxidase-2 (1.03 ± 0.006 vs. 0.76 ± 0.04; P < 0.001), transforming growth factor-β (0.99 ± 0.06 vs. 0.84 ± 0.04; P < 0.05), collagen type I (1.32 ± 0.32 vs. 0.94 ± 0.18; P < 0.05), and intercellular adhesion molecule-1 (1.12 ± 0.12 vs. 0.84 ± 0.08; P < 0.05). These genes are known to be stimulated by the renin-angiotensin system. There were no histological signs of fibrosis in the heart. We found that prorenin and aldosterone alone are not sufficient to induce considerable cardiac fibrosis in the absence of sodium load.
Journal of Hypertension | 2010
Torsten Schlüter; Robert Rohsius; Heike Wanka; Catherina Schmid; Anja Siepelmeyer; Rainer Rettig; Jörg Peters; Olaf Grisk
Objective The epithelial sodium channel (ENaC) is expressed in the renal vasculature, where it may be involved in the control of vascular tone and arterial pressure. Using a rat model with an inducible mouse renin transgene (cyp1a1ren-2 transgenic rats), we tested the hypothesis that stimulation of the renin–angiotensin–aldosterone system (RAAS) for 3 weeks is associated with an impairment of renal vascular function that is sensitive to treatment with the ENaC blocker amiloride. Methods Rats were randomized to control, transgene induction, or transgene induction plus amiloride treatment (n = 7–10 per group). Additional control animals were treated with amiloride. Arterial pressure was measured telemetrically. Sodium balance was determined in metabolic cages. Renal vascular function was investigated in vitro (wire myography) and in vivo (ultrasound flow probe). ENaC mRNA expression was determined by real-time PCR. Results Transgene induction caused an increase in plasma aldosterone levels associated with a sustained elevation in arterial pressure. Amiloride elicited a transient decrease in renal sodium balance and effectively lowered arterial pressure. Neither transgene induction nor amiloride treatment significantly affected phenylephrine or acetylcholine-induced renal vascular responses. Similarly, small renal artery compliance and renal vascular resistance remained unaltered. Amiloride treatment caused an increase in α-ENaC mRNA abundance in renal cortical tissue but not in intrarenal arteries. Conclusion Amiloride reduces arterial pressure in cyp1a1ren-2 transgenic rats in association with increased renal sodium excretion without affecting renal vascular function. In this model of hypertension sustained activation of the RAAS does not lead to increased ENaC expression in small intrarenal arteries.
American Journal of Physiology-regulatory Integrative and Comparative Physiology | 2010
Olaf Grisk; Martin Packebusch; Antje Steinbach; Torsten Schlüter; Ulla C. Kopp; Rainer Rettig
Upper urinary tract peristalsis is generated in the proximal renal pelvis that connects to the renal parenchyma at the pelvis-kidney junction. It may be exposed to the high renal endothelin-1 (ET-1) concentrations. Dietary NaCl restriction increases renal pelvic ET(A) receptor expression. We investigated the contribution of ET(A) and ET(B) receptors to ET-1-stimulated rat renal pelvic contractions and whether the sensitivity of renal pelvic contractile activity to ET-1 stimulation increases with dietary NaCl restriction. We tested whether ET-1-induced contractile activity depends on cyclooxygenase (COX)-1 or -2 and to what extent spontaneous as well as agonist-induced peristalsis depends on Rho kinases (ROCK). Contractions of isolated renal pelvises were investigated by myography. ET-1 concentration-dependently increased pelvic contractile activity up to 400% of basal activity. ET(A) but not ET(B) receptor blockade inhibited ET-1-induced pelvic contractions. Basal and ET-1-stimulated contractions were similar in renal pelvises from rats on a high-NaCl diet or on a NaCl-deficient diet. COX-1 inhibition reduced spontaneous and almost completely blocked the ET-1-induced pelvic contractions. ROCK inhibition reduced spontaneous and ET-1 stimulated pelvic contractile activity by 90%. RT-PCR revealed that both ROCK isoenzymes are present in the renal pelvic wall. Western blot analyses did not show increased phosphorylation of ROCK substrates myosin phosphatase target subunit 1, ezrin, radixin, and moesin in ET-1-treated isolated renal pelvises. ET-1 is a powerful ET(A) receptor-dependent activator of renal pelvic contractions. COX-1 and ROCK activity are required for the ET-1 effects on pelvic contractions, which are not significantly affected by dietary NaCl intake.
Journal of Hypertension | 2016
Philipp Heumann; Anna Koenen; Olga Zavaritskaya; Konrad Schütze; André Ramm; Torsten Schlüter; Antje Steinbach; Rainer Rettig; Rudolf Schubert; Olaf Grisk
Objectives: Sympathetic denervation enhances agonist-induced vasoconstriction. This effect may involve altered function of signaling mechanisms such as Rho kinase (Rock) and L-type Ca2+ channels downstream from vasoconstrictor receptors. We tested if enhanced Rock and L-type calcium channel activation contribute to exaggerated norepinephrine-induced vasoconstrictions in renal and mesenteric resistance arteries after sympathectomy. Methods: Rats underwent neonatal sympathectomy or sham sympathectomy. Resistance arteries were investigated by small vessel myography. Vascular Rock and L-type Ca2+ channel expression as well as Rock activation were investigated by quantitative real-time PCR and Western blot. Vascular smooth muscle cell (VSMC) membrane potential was recorded with microelectrodes. Results: Sympathetic denervation enhanced norepinephrine sensitivity in renal and mesenteric arteries. Both, Rock inhibition or L-type Ca2+ inhibition shifted the norepinephrine concentration–response curve to the right. This effect was more pronounced in renal than in mesenteric arteries from sympathectomized vs. sham-sympathectomized animals. The L-type Ca2+ channel activator S-(-)-BayK8644 elicited strong vasoconstrictions only in renal arteries from sympathectomized rats. Rock activity and L-type Ca2+ channel &agr;-subunit expression were similar in renal arteries from sympathectomized and sham-sympathectomized animals. VSMC membrane potential was −57.5 ± 2.0 and −64.3 ± 0.3 mV (P < 0.01), respectively, in renal arteries from sympathectomized and from sham-sympathectomized rats. Depolarization enhanced and KATP channel activation abolished S-(-)-BayK8644-induced contractions in renal arteries from sympathectomized rats. Conclusion: Sympathetic denervation enhances L-type Ca2+ channel-dependent signaling in renal but not in mesenteric arteries. This effect may be partly explained by the decreased VSMC membrane potential in denervated renal arteries.
Pharmacogenetics and Genomics | 2012
Nicole Mähler; Martin Freyer; Rene Kauschke; Torsten Schlüter; Antje Steinbach; Stefan Oswald; Bärbel Miehe; Alexander Krebs; Rainer Rettig; Olaf Grisk
ObjectiveMultidrug resistance-related protein 2 (Mrp2) is expressed in apical membranes of renal proximal tubular cells and contributes to the renal secretion of cyclosporine A (CsA). Mrp2 deficiency may lead to local renal CsA accumulation. We investigated whether kidney-specific Mrp2 deficiency enhances acute CsA nephrotoxicity in rats. MethodsKidney-specific Mrp2 deletion was achieved by bilateral nephrectomy and transplantation of a congenic Mrp2-deficient kidney into wild-type recipients. Controls received a wild-type kidney. Animals were treated with CsA (10 or 30 mg/kg/day) for 7 days. Renal hemodynamics and renal cortical mRNA expression profile, oxidative stress, and the abundance of multidrug resistance protein 1 (Mdr1) and Mrp2 were assessed. ResultsCsA accumulation and CsA-induced reduction in glomerular filtration rate were similar in wild-type and Mrp2−/− kidneys. Renal vascular resistance and agonist-induced renal vascular responses were similar in both groups. A PCR array on 84 genes involved in the biotransformation and antioxidant defense revealed increased CsA-induced mRNA expression of genes involved in oxidative and metabolic stress, inflammation, and apoptosis. This gene expression pattern was similar in wild-type and Mrp2−/− kidneys. CsA increased the renal cortical oxidized glutathione, did not affect xanthine oxidase-dependent superoxide formation, and decreased renal cortical NADPH oxidase-dependent superoxide formation. Furthermore, CsA increased Mdr1 protein abundance to a greater extent in Mrp2−/− than in wild-type kidneys. ConclusionMrp2 is not critical for renal CsA disposition and its deficiency does not enhance acute CsA nephrotoxicity. The high Mdr1 abundance may at least in part prevent exaggerated CsA accumulation in Mrp2-/- kidneys.