Kristin Schmerbach

Charité Universitätsmedizin Berlin, Berlín, Berlin, Germany

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Publications (22)66.44 Total impact

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    ABSTRACT: Atherosclerosis is the most common cause of cardiovascular disease. The ApoB mouse is a model for human familial hypercholesterolemia and has a lipoprotein profile similar to that of humans with atherosclerosis. Therefore, it is a suitable model to investigate the changes in vasoreactivity during atherogenesis. This study investigates contractile and dilatative properties of arteries in this model in relation to age. Male ApoB mice and B6, WT, mice were examined at age 4 or 18 month. Isometric measurements of 2 mm ring preparations of the aorta thoracica were performed by using a wire myograph. Histological and biochemical methods served to determine atherosclerosis, lipid status and endothelial markers, respectively. Morphometric analysis showed that all old ApoB mice had severe atherosclerosis in the aorta. Atherosclerotic alteration of the aorta of the ApoB mice coincided with a diminished vasodilatation to acetylcholine. The phenylephrine response was significantly attenuated already to the same degree in the non-atherosclerotic aorta of the young ApoB mice as in the atherosclerotic aorta of the older ApoB mice. Serum parameters showed a rise in total cholesterol and triglycerides in the ApoB strain compared to WT mice. sICAM-1 and sVCAM-1 were increased in old compared to young ApoB mice. The study shows that reduced acetylcholine-induced dilatation is related to the presence of atherosclerosis in old ApoB mice. Remarkably, the impaired vessel reactivity to phenylephrine already in young ApoB mice indicates early changes in vascular function in this model. This article is protected by copyright. All rights reserved.
    Acta Physiologica 02/2014; 211(1). DOI:10.1111/apha.12262 · 4.25 Impact Factor
  • K Schmerbach, A Patzak
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    ABSTRACT: Today, eating habits in Western societies are to a large extent mirrored by the abundance and easy access to palatable food rich in fat and sugar (Bellisle et al. 2012). Consequently, the global prevalence of the metabolic syndrome in children, adolescents and adults is increasing at an alarming rate (Symonds et al. 2009). An unhealthy diet together with a sedentary lifestyle has been claimed responsible for the dramatic rise in obesity and metabolic syndrome (Kongsted et al. 2014). This article is protected by copyright. All rights reserved.
    Acta Physiologica 01/2014; DOI:10.1111/apha.12230 · 4.25 Impact Factor
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    ABSTRACT: Iodinated contrast media (CM) have adverse effects which may result in contrast induced acute kidney injury. Oxidative stress is believed to play a role in CM induced kidney injury. We test the hypothesis that oxidative stress and reduced nitric oxide in tubules are consequences of CM-induced direct cell damage, and that increased local oxidative stress may increase tubulo-glomerular feedback. Rat thick ascending limbs (TAL) were isolated and perfused. Superoxide and nitric oxide were quantified using fluorescence techniques. Cell death rate was estimated using propidium iodide and trypan blue. The function of macula densa and tubulo-glomerular feedback responsiveness were measured in isolated perfused juxta-glomerular apparatuses (JGA) of rabbits. The expression of genes related to oxidative stress and the activity of superoxide dismutase (SOD) were investigated in the renal medulla of rats which received CM. CM increased superoxide concentration and reduced NO bioavailability in TAL. Propidium iodide fluorescence and trypan blue uptake increased more in CM perfused TAL than in controls, indicating increased rate of cell death. There were no marked acute changes in the expression of genes related to oxidative stress in medullary segments of Henle's loop. SOD activity did not differ between CM and control groups. The tubulo-glomerular feedback in isolated JGA was increased by CM. Tubular cell damage and accompanying oxidative stress in our model are consequences of CM-induced direct cell damage, which also modifies the tubulo-vascular interaction at the macula densa, and may therefore contribute to disturbances of renal perfusion and filtration.
    AJP Renal Physiology 01/2014; 306(8). DOI:10.1152/ajprenal.00302.2013 · 4.42 Impact Factor
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    Kristin Schmerbach, Andreas Patzak
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    ABSTRACT: In recent years, popularity of adventure travel and mountain activities has strongly increased. For example, since the 1980s a real break out of Mount Everest euphoria (Tibetan Chomolungma, Nepalese Sagarmatha, Chinese Qomolangma, 8.848 m) took place, which led to a significant increase in the number of ascents to the summit. Whereas in 1979 - within 27 years since the initial ascent - only 99 people reached the summit, between 1980 and 1985 there was a doubling in reaching the summit in just six years. In the record season of 2007 the highest point of 633 mountaineers was achieved (2013). This article is protected by copyright. All rights reserved.
    Acta Physiologica 10/2013; DOI:10.1111/apha.12175 · 4.25 Impact Factor
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    ABSTRACT: Genetic factors strongly contribute to the pathogenesis of sporadic Alzheimer's disease (AD). Nevertheless, genome-wide association studies only yielded single nucleotide polymorphism loci of moderate importance. In contrast, microsatellite repeats are functionally less characterized structures within our genomes. Previous work has shown that endothelin-converting enzyme-1 (ECE-1) is able to reduce amyloid β content. Here we demonstrate that a CpG-CA repeat within the human ECE-1c promoter is highly polymorphic, harbors transcriptional start sites, is able to recruit the transcription factors poly(ADP-ribose) polymerase-1 and splicing factor proline and glutamine-rich, and is functional regarding haplotype-specific promoter activity. Furthermore, genotyping of 403 AD patients and 444 controls for CpG-CA repeat length indicated shifted allelic frequency distributions. Sequencing of 245 haplotype clones demonstrated that the overall CpG-CA repeat composition of AD patients and controls is distinct. Finally, we show that human and chimpanzee [CpG](m)-[CA](n) ECE-1c promoter repeats are genetically and functionally distinct. Our data indicate that a short genomic repeat structure constitutes a novel core promoter element, coincides with human evolution, and contributes to the pathogenesis of AD.
    The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 11/2012; 32(47):16807-16820. DOI:10.1523/JNEUROSCI.2636-12.2012 · 6.75 Impact Factor
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    ABSTRACT: Background/Aims: Putative in vitro-in vivo correlations of pharmacokinetic (PK) parameters are regarded as a prerequisite to filter hits derived from high-throughput screening (HTS) approaches for subsequent murine in vivo PK studies. Methods: In this study, we assessed stabilities in rat and human microsomes of 121 compounds from an early, academic drug discovery programme targeting the (pro)renin receptor and correlated the respective data with single-dose, in vivo PK parameters of 22 hits administered intravenously in rats. Results: After transformation of in vitro half-lives to predicted in vivo hepatic clearances, r(2) regarding in vitro-in vivo clearance correlations were 0.31 and 0.27 for the rat and human species, respectively. Conclusions: Our data concerning structurally diverse real-world compounds indicate that microsomal stability testing is not a tool to triage early compounds for in vivo PK testing.
    Pharmacology 10/2012; 90(5-6):307-315. DOI:10.1159/000343241 · 1.58 Impact Factor
  • K Schmerbach, A Patzak
    Acta Physiologica 08/2012; 205(4):453-5. DOI:10.1111/j.1748-1716.2012.02449.x · 4.25 Impact Factor
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    ABSTRACT: Background: The ONTARGET trial revealed an association of ACEI/ARB combination treatment (telmisartan and ramipril) with adverse renal outcome versus respective monotherapy; preclinical evidence regarding renal outcome in ACEI/ARB combination treatment is scarce. Methods: Spontaneously hypertensive stroke prone rats (SHR-SP) rats on a salt-rich diet were randomly allocated to 4 groups: SHR (untreated, n = 24), SHR + telmisartan (SHR-T, 2.39 +/- 0.69 mg/kg bw; n = 27), SHR + ramipril (SHR-R, 6.28 +/- 3.48 mg/kg bw; n = 27) and combination treatment (SHR-TR, 0.51 +/- 0.14 mg/kg bw; same dose for telmisartan and ramipril; n = 26). Study duration was 12 weeks, blood pressure was assessed weekly and doses were adjusted to maintain equal blood pressure. Finally, blood and urine samples were obtained and kidneys were harvested for histological studies. Results: Blood pressure in untreated rats rose to a maximum of 239 mmHg, whereas in all treatment groups it remained stable betvveen 140 and 150 mmHg. Mortality was 50% in the untreated group, whereas all treatment groups survived completely. Renal function - as indicated by plasma urea and cystatin c - was significantly worse in SHR-TR animals compared to all other groups. With plasma creatinine a similar trend was observed. All treatment options significantly decreased albuminuria. Renal glomerulosclerosis was decreased by monotherapy, whereas combination therapy failed to have a significant effect. Interstitial fibrosis was decreased to a similar extent by all treatment options. Conclusions: ACEI/ARB combination treatment failed to render significant additional benefits on renal outcome in hypertensive rats when compared to monotherapy. Instead our data indicate that dual RAAS blockade might have an adverse effect on kidney function and histology when compared to monotherapy in salt-loaded SHR-SP. (Clin. Lab. 2012;58:625-633. DOI: 10.7754/Clin.Lab.2011.110622)
    Clinical laboratory 01/2012; 58(7-8):625-633. DOI:10.7754/Clin.Lab.2011.110622 · 1.08 Impact Factor
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    ABSTRACT: The effects of AT1 receptor blocker, telmisartan, and the ACE inhibitor, ramipril, were tested head-to head and in combination on stroke prevention in hypertensive rats and on potential neuroprotection in acute cerebral ischemia in normotensive rats. Prevention study: Stroke-prone spontaneously hypertensive rats (SHR-SP) were subjected to high salt and randomly assigned to 4 groups: (1) untreated (NaCl, n = 24), (2) telmisartan (T; n = 27), (3) ramipril (R; n = 27) and (4) telmisartan + ramipril (T+R; n = 26). Drug doses were selected to keep blood pressure (BP) at 150 mmHg in all groups. Neurological signs and stroke incidence at 50% mortality of untreated SHR-SP were investigated. Intervention study: Normotensive Wistar rats were treated s.c. 5 days prior to middle cerebral artery occlusion (MCAO) for 90 min with reperfusion. Groups (n = 10 each): (1) sham, (2) vehicle (V; 0.9% NaCl), (3) T (0.5 mg/kg once daily), (4) R (0.01 mg/kg twice daily), (5) R (0.1 mg/kg twice daily) or (6) T (0.5 mg/kg once daily) plus R (0.01 mg/kg twice daily). Twenty-four and 48 h after MCAO, neurological outcome (NO) was determined. Forty-eight h after MCAO, infarct volume by MRI, neuronal survival, inflammation factors and neurotrophin receptor (TrkB) were analysed. Stroke incidence was reduced, survival was prolonged and neurological outcome was improved in all treated SHR-SP with no differences between treated groups. In the acute intervention study, T and T+R, but not R alone, improved NO, reduced infarct volume, inflammation (TNFα), and induced TrkB receptor and neuronal survival in comparison to V. T, R or T+R had similar beneficial effects on stroke incidence and NO in hypertensive rats, confirming BP reduction as determinant factor in stroke prevention. In contrast, T and T+R provided superior neuroprotection in comparison to R alone in normotensive rats with induced cerebral ischemia.
    PLoS ONE 08/2011; 6(8):e23646. DOI:10.1371/journal.pone.0023646 · 3.53 Impact Factor
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    ABSTRACT: Stroke is one of the major medical burdens in industrialized countries. Animal experiments indicate that blockade of the angiotensin AT1 receptor (AT1R) improves neurological outcome after cerebral ischemia. These protective effects are partially mediated by the angiotensin AT2 receptor (AT2R). The transcription factor promyelocytic leukemia zinc finger (PLZF) was identified as a direct adapter protein of the AT2R. Furthermore, our group was able to demonstrate that PLZF also directly binds and mediates the effects of the human (pro)renin receptor [(P)RR] which is involved in brain development. Therefore, we hypothesized that PLZF is involved in neuroprotection. Here we show that PLZF and its receptors (P)RR and AT2R exhibited an ubiquitous expression pattern in different brain regions. Furthermore, stable PLZF overexpression in human neuronal cells was able to mediate neuroprotection in a glutamate toxicity model in vitro. Consistently, PLZF mRNA and protein were downregulated on the ipsilateral side in a stroke model in vivo, whereas the neurodetrimental PLZF target genes cyclin A2 and BID were upregulated under this condition. Further analyses indicated that the neuroprotective AT2R is upregulated upon stable PLZF overexpression in cultured neuronal cells. Finally, reporter gene assays demonstrated the functionality of (P)RR promoter polymorphisms regarding basal and PLZF-induced activity.
    Brain Pathology 01/2011; 21(1):31-43. DOI:10.1111/j.1750-3639.2010.00427.x · 4.35 Impact Factor
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    ABSTRACT: Pre-treatment with angiotensin receptor blockers is known to improve neurological outcome after stroke. This study investigated for the first time, whether the renin inhibitor aliskiren has similar neuroprotective effects. Since aliskiren specifically blocks human renin, double transgenic rats expressing human renin and angiotensinogen genes were used. To achieve a systolic blood pressure of 150 or 130 mmHg animals were treated with aliskiren (7.5 or 12.5 mg/kg*d) or candesartan (1.5 or 10 mg/kg*d) via osmotic minipump starting five days before middle cerebral artery occlusion with reperfusion. Infarct size was determined by magnetic resonance imaging. mRNA of inflammatory marker genes was studied in different brain regions. The mortality of 33.3% (7 of 21 animals) in the vehicle group was reduced to below 10% by treatment with candesartan or aliskiren (p<0.05). Aliskiren-treated animals had a better neurological outcome 7 days post-ischemia, compared to candesartan (Garcia scale: 9.9±0.7 vs. 7.3±0.7; p<0.05). The reduction of infarct size in the aliskiren group did not reach statistical significance compared to candesartan and vehicle (24 h post-ischemia: 314±81 vs. 377±70 and 403±70 mm(3) respectively). Only aliskiren was able to significantly reduce stroke-induced gene expression of CXC chemokine ligand 1, interleukin-6 and tumor necrosis factor-alpha in the ischemic core. Head-to-head comparison suggests that treatment with aliskiren before and during cerebral ischemia is at least as effective as candesartan in double transgenic rats. The improved neurological outcome in the aliskiren group was blood pressure independent. Whether this effect is due to primary anti-inflammatory mechanisms has to be investigated further.
    PLoS ONE 11/2010; 5(11):e15052. DOI:10.1371/journal.pone.0015052 · 3.53 Impact Factor
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    ABSTRACT: Ceftriaxone has been reported to reduce neuronal damage in amyotrophic lateral sclerosis and in an in-vitro model of neuronal ischaemia through increased expression and activity of the glutamate transporter, GLT1. We tested the effects of ceftriaxone on mortality, neurological outcome, and infarct size in experimental stroke in rats and looked for underlying mechanisms. Male normotensive Wistar rats received ceftriaxone (200 mg/kg intraperitoneal) as a single injection 90 min after middle cerebral artery occlusion (90 min with reperfusion). Forty-eight hours after middle cerebral artery occlusion, infarct size (MRI) and neurological deficits were estimated. GLT1 expression was determined by real time RT-PCR, immunoblotting and promoter reporter assay, astrocyte GLT1 activity by measuring glutamate uptake. Bacterial load in various organs was measured by real time RT-PCR, neurotrophins and IL-6 by immunoblotting. Ceftriaxone dramatically reduced early (24-h) mortality from 34.5% (vehicle treatment, n = 29) to 0% (P < 0.01, n = 19). In a subgroup, followed up for 4 weeks, mortality persisted at 0%. Ceftriaxone strongly tended to reduce infarct size, it significantly improved neuronal survival within the penumbra, reduced neurological deficits (P < 0.001) and led to an upregulation of neurotrophins (P < 0.01) in the peri-infarct zone. Ceftriaxone did not increase GLT1 expression, but increased GLT1 activity (P < 0.05). Ceftriaxone causes a significant reduction in acute stroke mortality in a poststroke treatment regimen in animal studies. Improved neurological performance and survival may be due to neuroprotection by activation of GLT1 and a stimulation of neurotrophins resulting in an increased number of surviving neurons in the penumbra.
    Journal of Hypertension 01/2009; 26(12):2426-35. DOI:10.1097/HJH.0b013e328313e403 · 4.22 Impact Factor
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    ABSTRACT: Angiotensin AT1 receptor blockers (ARBs) and thiazolidinediones (TZDs) have become well established drugs for the treatment of major risk factors of stroke. Since several studies provided evidence that ARBs and TZDs also have additional anti-inflammatory effects, we hypothesized that a combined treatment with the ARB, candesartan, and the TZD, pioglitazone, ameliorates ischemia-induced brain injury and inflammation by synergistic anti-inflammatory actions. Normotensive Wistar rats were pre-treated for 5 days with vehicle (0.9% NaCl), 0.2 mg/kg/day candesartan (s.c.), and/or 2 and/or 20 mg/kg/day pioglitazone (p.o.), respectively and underwent 90 min of middle cerebral artery occlusion (MCAO) with successive reperfusion. Neurological deficits and infarct size were determined 24 h and 48 h after MCAO, respectively, followed by tissue sampling. Animals treated with candesartan, pioglitazone, and the combination of candesartan and pioglitazone had reduced neurological deficits 24 h and 48 h after MCAO, respectively (P<0.05-0.01). Infarct size was reduced by treatment of candesartan, pioglitazone, and their respective combination (each P<0.05) 48 h after stroke compared to vehicle. Treatment with candesartan, pioglitazone, and their combination resulted in significantly reduced mRNA expression of the inflammatory markers CXCL1 and TNFalpha in vivo (P<0.01). The combination of candesartan plus pioglitazone is equally effective compared to their single applications concerning neuroprotection and attenuation of inflammation after MCAO. Therefore, we conclude that a direct synergistic neuroprotective action of parallel ARB and TZD treatment is unlikely.
    Brain Research 06/2008; 1208:225-33. DOI:10.1016/j.brainres.2008.02.032 · 2.83 Impact Factor
  • Kristin Schmerbach, Thomas Unger
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    ABSTRACT: Hypertension is a major public health problem, being one of the leading causes of death and disability worldwide and a major risk factor for cardiovascular disease. The renin-angiotensin-aldosterone system plays an important role in volume homeostasis and blood pressure regulation, and is a target for several groups of pharmaceutical agents. Telmisartan, a highly selective AT1 receptor antagonist, fulfills all new criteria for antihypertensive agents: high effectiveness, high specificity, high compliance and fewer adverse effects. Several clinical trials and the clinical practice setting indicate substantial evidence that telmisartan, either as monotherapy or in combination with other antihypertensive drugs, provides long-term antihypertensive efficacy. In fact, telmisartan has the property to sustain blood pressure control throughout the 24-h dosage interval. Furthermore, telmisartan can play an important role in improving compliance, because of its documented good tolerability profile, which limits the adverse effects. This article provides the most recent data of the pharmacoeconomic position of telmisartan and its treatment effects on quality of life.
    Expert Review of Pharmacoeconomics & Outcomes Research 10/2007; 7(5):435-44. DOI:10.1586/14737167.7.5.435 · 1.87 Impact Factor
  • Hypertension 10/2007; 50(4):802-802. · 7.63 Impact Factor
  • Hypertension 10/2006; 48(4):778-778. · 7.63 Impact Factor