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Biomedical subjects

M Böhm

Publications and source records attributed to M Böhm.

At least 109 records · Page 6Linked to original sources
PubMed2001

Exploration of novel aryl binding sites of farnesyltransferase using molecular modeling and benzophenone-based farnesyltransferase inhibitors.

Most non-thiol CAAX-peptidomimetic farnesyltransferase inhibitors bear nitrogen-containing heterocycles in place of the terminal cysteine which are supposed to coordinate the enzyme-bound zinc. However, it has been shown that those nitrogen-containing heterocycles can be replaced by carbocyclic aromatic moieties which are unable to coordinate the zinc ion, a conclusion that resulted in the postulation of one or two hitherto unknown aryl binding sites. No indication has been given about the spatial location of these novel binding sites. Employing flexible docking of several non-thiol farnesyltransferase inhibitors known from the literature and some model compounds based on our benzophenone scaffold as well as performing GRID searches, we have identified two regions in the farnesyltransferase's active site which we suggest being the postulated aryl binding sites. One aryl binding region is located in close proximity to the zinc ion and is defined by the aromatic side chains of Tyr 300beta, Trp 303beta, Tyr 361beta, and Tyr 365beta. The second aryl binding site is defined by the side chains of Tyr 300beta, Leu 295beta, Lys 294beta, Lys 353beta, and Lys 356beta. This second aryl binding site has been used for the design of a non-thiol farnesyltransferase inhibitor (9c) with an IC(50) of 35 nM.

Acrylamides↗
PubMed2001

Effect of inhaled iloprost plus oral sildenafil in patients with primary pulmonary hypertension.

BACKGROUND: The application of iloprost, a stable prostacyclin analogue, by inhalation has been shown to improve hemodynamic variables in patients with primary pulmonary hypertension. However, repetitive inhalations are required due to its short-term effects. One potential approach to prolong and increase the vasorelaxant effects of aerosolized iloprost might be to combine use with phosphodiesterase inhibitors. METHODS AND RESULTS: The short-term effects of 8.4 to 10.5 microgram of aerosolized iloprost, the phosphodiesterase type 5 inhibitor sildenafil, and the combination thereof were compared in 5 patients with primary pulmonary hypertension. Aerosolized iloprost resulted in a more pronounced decrease in mean pulmonary arterial pressure (PAP) than sildenafil alone (9.4+/-1.3 versus 6.4+/-1.1 mm Hg; P<0.05). The reduction in mean PAP after sildenafil was maximal after the first dose (25 mg). The combination of sildenafil plus iloprost lowered mean PAP significantly more than iloprost alone (13.8+/-1.4 versus 9.4+/-1.3 mm Hg; P<0.009). No significant changes in heart rate or systemic arterial pressure were observed during any treatment. The treatments were well tolerated, without major adverse effects. CONCLUSIONS: Sildenafil caused a long-lasting reduction in mean PAP and pulmonary vascular resistance, with a further additional improvement after iloprost inhalation. These data suggest that small doses of a phosphodiesterase type 5 inhibitor may be a useful adjunct to inhaled iloprost in the management of pulmonary hypertension.

Administration, Inhalation↗
PubMed2001

Synthesis, molecular modeling, and structure-activity relationship of benzophenone-based CAAX-peptidomimetic farnesyltransferase inhibitors.

Because of the involvement of farnesylated proteins in oncogenesis, inhibition of the protein-modifying enzyme farnesyltransferase is considered a major emerging strategy in cancer therapy. Here, we describe the structure-activity relationship of a novel class of CAAX-peptidomimetic farnesyltransferase inhibitors based on the benzophenone scaffold. 4'-Methyl, 4'-chloro, 4'-bromo, and 4'-nitrophenylacetic acid as substituents at the 2-amino group of the benzophenone core structure yield farnesyltransferase inhibitors active in the nanomolar range. Using diphenylacetic acid in this position further improves activity. SEAL superimposition of inhibitor 12a to the enzyme-bound conformation of a CAAX-peptide shows a markedly good resemblance of the molecular properties of the peptide. FlexX docking of 12a confirms the good fit of the molecule into the peptide binding site of farnesyltransferase. The novel benzophenone-based AAX-peptidomimetic substructure described here will be useful for the design of some novel types of farnesyltransferase inhibitors.

Alkyl and Aryl Transferases↗
PubMed2001

Mitogen-activated protein kinases control p27/Kip1 expression and growth of human melanoma cells.

The mitogen-activated protein kinases (MAPKs) extracellular signal-regulated protein kinase (ERK)1 and ERK2, involved in regulating cell growth and differentiation, are constitutively active in A375 and WM239 human melanoma cells. Using PD098059, an inhibitor of MAPK kinase (MEK), we investigated the role of persistently activated ERK1/2 in cell growth. The inhibition of MAPK activity induced a dose-dependent growth arrest in G(0)/G(1) phase. Correspondingly, we observed the up-regulation of the cyclin-dependent kinase (Cdk) inhibitor p27/Kip1 and hypophosphorylation of the retinoblastoma protein. Further studies showed that PD098059 treatment significantly decreased Cdk2 kinase activity, most probably owing to an augmented level of p27/Kip1 associated with cyclin E-Cdk2 complexes. The accumulation of p27/Kip1 protein in A375 cells was attributed to its increased stability. Our findings suggest that constitutively active ERK1/2 kinases contribute to the growth of melanoma cells by negative regulation of the p27/Kip1 inhibitor.

CDC2-CDC28 Kinases↗
PubMed2001

Immunohistological changes in dilated cardiomyopathy induced by immunoadsorption therapy and subsequent immunoglobulin substitution.

BACKGROUND: Immunoadsorption (IA) and subsequent immunoglobulin (Ig) G substitution represent an additional therapeutic approach in dilated cardiomyopathy (DCM). It remains to be elucidated whether this treatment modulates myocardial inflammation, which is possibly a causal factor of ventricular dysfunction. METHODS AND RESULTS: From 25 DCM patients (EF <30%), 12 patients were randomized for IA therapy and subsequent IgG substitution at 1-month intervals until month 3. Before (<7 days) and after IA therapy, right ventricular biopsies were obtained from all patients. Biopsies were also obtained at intervals of 3 months from 13 patients without IA/IgG treatment (controls). IA/IgG treatment induced improvement in left ventricular ejection fraction from 21.3+/-1.7% (+/-SEM) to 27.0+/-1.3% (P<0.01 versus baseline/controls) and reduction of the beta-receptor autoantibody serum levels (P<0.01 versus baseline/controls). The number of CD3 cells decreased from 5.7+/-0.8 to 2.9+/-0.5 cells/mm(2) (P<0.01 versus baseline/controls). This decline was paralleled by a decrease in CD4 (P<0.01 versus baseline/controls) and CD8 (P<0.05 versus baseline/controls) lymphocytes. The number of leukocyte common antigen-positive cells (leukocytes) was reduced from 20.0+/-3.2 to 9.9+/-2.8 cells/mm(2) (P<0.01 versus baseline/P<0.05 versus controls). HLA class II expression decreased from 2.1+/-0.7% to 1.1+/-0.4% (P<0.05 versus controls/baseline). The number of immunopositive cells and the expression of HLA class II in controls remained stable. In both groups, the degree of fibrosis remained unchanged. CONCLUSIONS: IA and subsequent IgG substitution mitigate myocardial inflammation in DCM.

Autoantibodies↗
PubMed2001

Photooxygenation of the helimers of (-)-isocolchicine: regio- and facial selectivity of the [4 + 2] cycloaddition with singlet oxygen and surprising endoperoxide transformations.

Photooxygenation of the helimeric mixture of (-)-(M,7S)/(P,7S)-isocolchicine (6) with the superdienophile singlet oxygen has been studied. Cycloaddition occurred with high regioselectivity at the 7a,11-positions of the alkaloid and predominantly at the diene face anti to the amidic substituent at the stereogenic center C-7, leading to two endoperoxides 7 (syn) and 8 (anti) with an 1:7 ratio. The structure of the minor product 7 was established by X-ray analysis. Investigation of the triethylamine induced transformation of the predominant endoperoxide 8 furnished a mixture of two isomers (M,7S)-10a/(M,7S)-10b in a 2:1 ratio possibly with constitutional interconversion and with (M,7S)-9 as plausible intermediate. Treatment of this mixture with silica gel/ethyl acetate at ambient temperature surprisingly led to an atropenantiomerically pure colchicinoid (M,7S)-12 characterized by an eightmembered oxocine B-ring, the structure and absolute configuration of which could be determined by X-ray analysis. For the unprecedented formation of the novel colchicinoid (M,7S)-12 a plausible reaction pathway is suggested, involving a complete transfer of the (M) helical asymmetry of the intermediate (M)-11 into (S) asymmetry of the newly formed carbon center of (M,7S)-12. Prerequisite for such a scenario is the configurational stability of the intermediate pseudobiaryl (M)-11, under the conditions employed, allowing to transmit the axial chirality onto the chiral center of the product (M,7S)-12.

Journal Article↗
PubMed2001

Differential effects of carvedilol and metoprolol on isoprenaline-induced changes in beta-adrenoceptor density and systolic function in rat cardiac myocytes.

OBJECTIVE: beta-Blockers improve cardiac function and survival in heart failure patients. The underlying mechanisms are not completely elucidated. Differences between agents might be important for the development of more specific therapeutical approaches. This study investigated whether metoprolol or carvedilol alter beta-adrenergic signaling differently. METHODS: beta-Adrenoceptor density and systolic function were determined in rat adult ventricular cardiac myocytes. RESULTS: 12 h isoprenaline-treatment (Iso, 1 micromol/l) reduced beta-adrenoceptor density by 33% (P<0.01). The effect was abolished by incubation with isoprenaline plus metoprolol (3 micromol/l), but was more pronounced after coincubation with carvedilol (0.003 micromol/l, P<0.05 Carv vs. Iso). Metoprolol alone had no effect on beta-adrenoceptor density, but carvedilol induced a decrease in receptor density even in absence of isoprenaline (P<0.05 Carv vs. ctr.). The isoprenaline (0.0003-10 micromol/l) induced concentration-dependent increase in myocyte shortening was blunted after 12 h preincubation with Iso (1 micromol/l, P<0.001). This reduction was abolished or partly prevented by coincubation with metoprolol or carvedilol, respectively. Carvedilol decreased the number of receptors which had to be occupied by isoprenaline in order to obtain 50% and 90% increase in myocyte cell shortening. Comparison of guanine nucleotide-dependent binding characteristics of isoprenaline, carvedilol and metoprolol revealed beta-receptor agonist like binding characteristics for carvedilol, but antagonist like binding characteristics for metoprolol. CONCLUSION: Metoprolol but not carvedilol prevents isoprenaline-induced downregulation of myocyte beta-adrenoceptors. The difference might be due to specific binding properties of the beta-blockers. Restoration of isoprenaline responsiveness by carvedilol might be due to improved coupling of beta-receptors to postreceptor effects.

Adrenergic beta-Antagonists↗
PubMed2001

Endothelial dysfunction and oxidative stress during estrogen deficiency in spontaneously hypertensive rats.

BACKGROUND: Postmenopausal estrogen deficiency is associated with an increased cardiovascular risk, hypertension, and oxidative stress. Angiotensin type 1 (AT(1)) receptor regulation is involved in the pathogenesis of atherosclerosis. To characterize vascular function, oxidative stress, and AT(1) receptor regulation during estrogen deficiency, ovariectomized spontaneously hypertensive rats (SHR) were investigated in comparison with sham-operated animals and with ovariectomized rats receiving estrogen replacement therapy with 17beta-estradiol. METHODS AND RESULTS: Arterial blood pressure was similar in all 3 groups investigated. Five weeks after ovariectomy, endothelial dysfunction in aortic rings was observed, which was reversed by estrogen replacement therapy. Estrogen deficiency led to an enhanced vasoconstriction by angiotensin II. Vascular superoxide production was significantly increased compared with that in sham-operated rats, as measured by lucigenin chemiluminescence assays. Estrogen substitution normalized the production of free radicals in the vessel wall. Vascular AT(1) receptor expression was significantly upregulated by estrogen deficiency, as shown by quantitative reverse transcription-polymerase chain reaction, whereas endothelial NO synthase mRNA expression and NO release were unchanged. Five-week treatment of the animals with the AT(1) receptor antagonist irbesartan prevented endothelial dysfunction in ovariectomized rats and normalized the vascular production of free radicals. CONCLUSIONS: In SHR, estrogen deficiency leads to increased vascular free radical production and enhanced angiotensin II-induced vasoconstriction via increased vascular AT(1) receptor expression, resulting in endothelial dysfunction. Estrogen replacement therapy and AT(1) receptor antagonism prevent these pathological changes. Therefore, estrogen deficiency-induced AT(1) receptor overexpression and oxidative stress may play an important role in cardiovascular diseases associated with menopause.

Angiotensin II↗
PubMed2001

Intra-aortic counterpulsation during carotid stenting.

Postprocedural hypotension following endovascular stent placement of carotid artery disease (CAS) predicts increased in-hospital complications and long-term risk of death. Intra-aortic balloon counterpulsation (IABP) both increases mean arterial pressure and cerebral blood flow and therefore possibly reduces complications due to hemodynamic instability during and after CAS. In this study, we describe the use of IABP in a patient with severe depression of left ventricular function due to diffuse coronary artery disease undergoing CAS. Controlled studies are necessary to demonstrate a potentially protective role of IABP in high-risk CAS patients.

Aorta↗
PubMed2001

[Cyclic neutropenia. Detection of a mutation in the gene for neutrophil elastase (ELA2)].

BACKGROUND AND OBJECTIVE: Cyclic neutropenia is a rare congenital hematopoietic disease which occurs sporadically or as an autosomal dominantly inherited disorder. Recently, the locus for cyclic neutropenia was mapped to chromosome 19p13.3. Autosomal dominant and sporadic cyclic neutropenia are now attributable to mutations of the ELA2 gene encoding neutrophil elastase. PATIENTS/METHODS: Based on a case report we review the clinical picture and diagnostic criteria of cyclic neutropenia and report about the recent molecular biological findings and current treatment options. RESULTS: Serial blood cell counts revealed the characteristic oscillations of the circulating neutrophils with 21-day periodicity from near normal to extremely low levels. The neutrophil nadir lasted 3-5 days. The neutropenia was associated with fever, malaise, painful oral aphthous ulcers and lymphadenopathy. Mutational analysis of the patient's genomic DNA revealed a single base-pair transition (nt 4716, G-->A) in intron 4 of ELA2. Since the initiation of therapy with subcutaneous recombinant human granulocyte-stimulating colony factor (rHuG-CSF) 24 months ago, the patient has been free of symptoms. CONCLUSIONS: Despite the typical medical history with onset of the symptoms in early infancy the diagnosis of cyclic neutropenia was not established until the age of 9 years. A common reason for the delayed diagnosis of cyclic neutropenia may be unawareness of the rare but distinctive disorder and the practice of obtaining screening blood counts without leukocyte differentials. Patients with cyclic neutropenia should be enrolled to the Severe Chronic Neutropenia International Registry (SCNIR).

Base Pairing↗
PubMed2001

[Pharmacotherapeutical approaches to insomnia patients with cardiac diseases and after heart transplantation].

Insomnia in patients with heart transplantation and cardiac disease is a common problem. Organic factors, immunodepressant medication (e.g. ciclosporine and steroids) and psychological factors may account for this symptom. The article reviews different hypnotic drugs and their value in the treatment of insomnia. For short-time treatment, medication with benzodiazepine hypnotics may be useful. If the problems of drug dependence and rebound insomnia are taken into consideration, treatment with non-benzodiazepine hypnotics offers more safety and comfort. If insomnia is part of a depressive syndrome, pharmacotherapeutical intervention with antidepressive sedative medication is required. With regard to cardiac disease, treatment with mirtazapine, nefazodone or trazodone should be preferred because of the chinidine-like effect of tricyclic antidepressants (TCA). Sedative neuroleptic medication (e.g. melperone) is commonly given to geriatric patients; nevertheless, patients with chronic insomnia may also benefit from this medication. The risks and benefits of hypnotic drugs are discussed especially in relation to pharmacological interaction (cytochrome system) and cardiac disease.

Adult↗
PubMed2001

Alcohol and the risk of myocardial infarction.

Epidemiological studies have repeatedly demonstrated a beneficial effect of moderate alcohol consumption on the incidence of coronary heart disease, myocardial infarction and overall mortality. The latter increases with excessive alcohol consumption. Although most epidemiological studies demonstrate a beneficial effect of alcohol consumption independent from the specific kind of alcoholic beverage, there is increasing evidence that wine and in particular red wine might contain pharmacological substances, which prevent atherosclerosis and myocardial infarction independent from the wine ethanol. Pathophysiological mechanisms mediating these beneficial effects include effects of wine phenols and tannins on LDL-cholesterol oxidation status, thrombocyte aggregation, endothelial function and smooth muscle cell proliferation. Identification and characterization of the pharmacologically active substances might provide the stage for the development of new substances to be used in the prevention of coronary artery disease and myocardial infarction.

Alcohol Drinking↗
PubMed2001

Prospective crossover comparison of carvedilol and metoprolol in patients with chronic heart failure.

OBJECTIVES: This study investigates the effects of a change of beta-adrenergic blocking agent treatment from metoprolol to carvedilol and vice versa in patients with heart failure (HF). BACKGROUND: Beta-blockers improve ventricular function and prolong survival in patients with HF. It has recently been suggested that carvedilol has more pronounced effects on left ventricular ejection fraction (LVEF) compared with metoprolol. It is uncertain whether a change from one beta-blocker to the other is safe and leads to any change of left ventricular function. METHODS: Forty-four patients with HF due to ischemic (n = 17) or idiopathic cardiomyopathy (n = 27) that had responded well to long-term treatment with either metoprolol (n = 20) or carvedilol (n = 24) were switched to an equivalent dose of the respective other beta-blocker. Before and six months after crossover of treatment, echocardiography, radionuclide ventriculography and dobutamine stress echocardiography were performed. RESULTS: Six months after crossover of beta-blocker treatment, LVEF had further improved with both carvedilol and metoprolol (carvedilol: 32 +/- 3% to 36 +/- 4%; metoprolol: 27 +/- 4% to 30 +/- 5%; both p < 0.05 vs. baseline), without interindividual differences. There were no changes in either New York Heart Association functional class or any other hemodynamic parameters at rest. Dobutamine stress echocardiography revealed a more pronounced increase of heart rate after dobutamine infusion in metoprolol- compared with carvedilol-treated patients. After dobutamine infusion, LVEF increased in the carvedilol- but not in the metoprolol-treated group. CONCLUSIONS: When switching treatment from one beta-blocker to the other, improvement of LVEF in patients with HF is maintained. Despite similar long-term effects on hemodynamics at rest, beta-adrenergic responsiveness is different in both treatments.

Adrenergic beta-Antagonists↗
PubMed2001

Characterization of beta(1)-selectivity, adrenoceptor-G(s)-protein interaction and inverse agonism of nebivolol in human myocardium.

Intrinsic activity and beta(1)-selectivity are important features of beta-blockers in the treatment of patients with coronary syndromes and heart failure. In human myocardium, intrinsic activity and beta(1)-selectivity of the novel beta-adrenoceptor antagonist nebivolol have not yet been determined. The study examines intrinsic activity, beta-adrenoceptor-G-protein coupling and beta(1)-selectivity of nebivolol and bisoprolol in human ventricular myocardium. Furthermore, intrinsic activity of both compounds is compared to the one of bucindolol, carvedilol and metoprolol in human atrial myocardium. Radioligand binding studies ([(125)I]-lodocyanopindolol) were performed on membrane preparations of human failing and nonfailing myocardium and on COS-7 cells transfected with human beta(1)- and beta(2)-adrenoceptors, respectively. Functional experiments were carried out on isolated muscle preparations of human left ventricular and right atrial myocardium from failing and nonfailing hearts. Radioligand binding studies reveal 3 - 4 fold beta(1)-selectivity for nebivolol and 16 - 20 fold beta(1)-selectivity for bisoprolol in human myocardium. In COS-7-cells, beta(1)-selectivity is 3 fold for nebivolol and 15 fold for bisoprolol. Neither the binding of nebivolol nor of bisoprolol is affected by the presence of guanylylimidodiphosphate (Gpp(NH)p). Nebivolol and bisoprolol exert similar inverse agonist activity in human ventricular as well as atrial myocardium. In atrial myocardium, inverse agonism of both compounds is higher compared to bucindolol, equal to carvedilol and lower compared to metoprolol. Favourable haemodynamic effects of nebivolol in humans are not due to beta(1)-selectivity or partial agonist activity of this agent. Other mechanisms, i.e. the production of nitric oxide, may thus be responsible for its unique haemodynamic profile.

Adrenergic beta-Agonists↗
PubMed2001

Reduction of oxidative stress and AT1 receptor expression by the selective oestrogen receptor modulator idoxifene.

1. The beneficial vasoprotective effects of oestrogens are hampered by their side effects on secondary sexual organs. Selective oestrogen receptor modulators (SERM) such as idoxifene may exert beneficial vascular effects without influencing cancerogenesis in breast or uterus. 2. In order to investigate vascular effects of selective oestrogen receptor modulators, we examined the impact of idoxifene on production of reactive oxygen species as well as AT1 receptor expression in vascular smooth muscle cells (VSMC). 3. Idoxifene caused a concentration- and time-dependent down-regulation of AT1 receptor mRNA expression, as assessed by Northern analysis. The maximal effect was reached with 10 micromol l(-1) idoxifene after a 4 h incubation period (33+/-7% of control levels). Western blots showed a similar down-regulation of AT1 receptor protein to 36+/-11% of control levels. 4. Confocal laserscanning microscopy using the redox sensitive marker 2',7'-dichlorofluorescein (DCF) and measurement of NAD(P)H oxidase activity in cell homogenates revealed that idoxifene effectively blunted the angiotensin II-induced production of reactive oxygen species. 5. In order to investigate the signal transduction involved in SERM-induced modulation of AT1 receptor expression, VSMC were preincubation with PD98059, genistein, wortmannin, or N(omega)-Nitro-L-arginine. The results suggested that idoxifene caused AT1 receptor down-regulation through nitric oxide-dependent pathways. 6. In conclusion, idoxifene reduces angiotensin II-evoked oxidative stress in VSMC. This could in part be explained by idoxifene-induced down-regulation of AT1 receptor expression. These results demonstrate that the selective oestrogen receptor modulator idoxifene may exert beneficial vascular effects which could be useful for therapeutic regimen in postmenopausal women at risk for cardiovascular diseases.

Angiotensin Receptor Antagonists↗
PubMed2001

Interleukin-6-resistant melanoma cells exhibit reduced activation of STAT3 and lack of inhibition of cyclin E-associated kinase activity.

Development of cytokine resistance is an important feature of melanoma cells during tumor progression. To study the mechanisms of interleukin-6 resistance, we examined an interleukin-6 sensitive (WM35) and an interleukin-6 unresponsive cell line (WM9). Interleukin-6 treatment resulted in rapid inhibition of cyclin-dependent kinase 2/cyclin E activity and accumulation of the hypophosphorylated retinoblastoma protein in WM35 but not in WM9 cells. In contrast to previous reports, no differences in the expression of the cyclin-dependent kinase 2 inhibitor p21Cip1/WAF1 upon interleukin-6 treatment were found in both cell lines. Interleukin-6-induced inhibition of cyclin-dependent kinase 2 was also not due to changes in protein expression of cyclin-dependent kinase 2, cyclin E, p27Kip1 and cdc25A, a phosphatase positively regulating cyclin-dependent kinase 2 activity. As it is established that interleukin-6 resistance of WM9 cells is not caused by differential interleukin-6 receptor expression, we studied whether this is due to defective interleukin-6 signaling in which activation of signal transducer and activator of transcription 3 is a critical step. WM9 cells showed reduced tyrosine phosphorylation, DNA binding, and delayed nuclear translocation of signal transducer and activator of transcription 3 as compared with WM35 cells. The kinase upstream of signal transducer and activator of transcription 3, Janus kinase 1, was constitutively tyrosine-phosphorylated in WM9 cells and did not respond to interleukin-6 with increased phosphorylation. As compared with WM35 cells, interleukin-6 treatment of WM9 cells was not paralleled by reduced activity of the mitogen-activated protein kinase kinase-1, which suppresses activation of signal transducer and activator of transcription 3. Our data suggest that resistance of advanced melanoma cells to interleukin-6 is associated with reduced inhibition of cyclin-dependent kinase 2, which appears to be a consequence of a complex alteration in interleukin-6 signal transduction.

CDC2-CDC28 Kinases↗