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Biomedical subjects

Tobias Welte

Publications and source records attributed to Tobias Welte.

At least 55 records · Page 3Linked to original sources
PubMed2005

Penetration of ertapenem into different pulmonary compartments of patients undergoing lung surgery.

Ertapenem is approved for the treatment of community-acquired pneumonia (CAP), but its in vivo penetration into lung tissue (LT), epithelial lining fluid (ELF), and alveolar cells (AC) is unknown. Fifteen patients undergoing thoracotomy were treated with 1 g intravenously for perioperative prophylaxis. Bronchoalveolar lavage was performed 1, 3, and 5 hours after ertapenem infusion. Normal LT was sampled at the time of lung extraction. Blood was collected before and at different time points up to 24 hours after infusion. Mean concentrations of ertapenem in plasma, ELF, and AC were at 1.0 hour, 63.1, 4.06, 0.004 mg/L; at 3.0 hours, 39.7, 2.59, 0.003 mg/L; and at 5.0 hours, 27.2, 2.83, 0.007 mg/L. Mean (range) concentration in LT was 7.60 (2.5-19.4) mg/kg tissue 1.5 to 4.5 hours after infusion. In plasma, ertapenem exhibited a Cmax of 94.7 +/- 23.3 mg/L and an AUC(0-last) of 501.1 +/- 266.3 mg x h/L. These results, combined with the reported (MIC)90 of most CAP bacteria, support the previously observed clinical efficacy of ertapenem in the treatment of CAP.

Adult↗
PubMed2005

The pulmonary immune effects of mechanical ventilation in patients undergoing thoracic surgery.

UNLABELLED: Mechanical ventilation (MV) may induce an inflammatory alveolar response. One-lung ventilation (OLV) with tidal volumes (Vt) as used during two-lung ventilation is a suggested algorithm but may impose mechanical stress of the dependent lung and potentially aggravate alveolar mediator release. We studied whether ventilation with different Vt modifies pulmonary immune function, hemodynamics, and gas exchange. Thirty-two patients undergoing open thoracic surgery were randomized to receive either MV with Vt = 10 mL/kg (n = 16) or Vt = 5 mL/kg (n = 16) adjusted to normal Pa(CO2) during and after OLV. Fiberoptic bronchoalveolar lavage of the ventilated lung was performed, and cells, protein, tumor necrosis factor (TNF)-alpha, interleukin (IL)-8, soluble intercellular adhesion molecule (sICAM)-1, IL-10, and elastase were determined in the bronchoalveolar lavage. Data were analyzed by parametric or nonparametric tests, as indicated. In all patients, an increase of proinflammatory variables was found. The time courses of intra-alveolar cells, protein, albumin, IL-8, elastase, and IL-10 did not differ between the groups after OLV and postoperatively. TNF-alpha (8.4 versus 5.0 microg/mL) and sICAM-1 (52.7 versus 27.5 microg/mL) concentrations were significantly smaller after OLV with Vt = 5 mL/kg. These results indicate that MV may induce epithelial damage and a proinflammatory response in the ventilated lung. Reduction of tidal volume during OLV may reduce alveolar concentrations of TNF-alpha and of sICAM-1. IMPLICATIONS: Reductions of tidal volume, with subsequently decreased peak airway pressures, may reduce some alveolar inflammatory responses seen with mechanical ventilation.

Adult↗
PubMed2005

Cost analyses of community-acquired pneumonia from the hospital perspective.

STUDY OBJECTIVES: Community-acquired pneumonia (CAP) is a widespread disease with important implications for health-care systems worldwide. This study investigated direct costs, treatment patterns, and outcomes associated with two patient cohorts hospitalized with CAP. DESIGN: The study design was naturalistic, prospective, and open. PATIENTS: The study enrolled 580 patients. Two hundred sixty-one patients were treated initially with IV moxifloxacin (45%, cohort M); the remaining 319 patients received nonstandardized treatment (cohort S). SETTING: Twenty-two hospitals in Germany. RESULTS: Clinical success rates were similar between treatment groups (cohort M, 242 of 256 patients, 95%; cohort S, 286 of 312 patients, 92%; p = 0.208). Mean +/- SD length of hospital stay was 10.8 +/- 5.2 days, with cohort M having a significantly shorter hospital stay (10.0 +/- 4 days) compared to cohort S (11.5 +/- 6 days; p < 0.001). Median of all direct costs was dollar 1,333 (minimum, dollar 127; maximum, dollar 9,488), with direct costs of dollar 1,250 in cohort M (minimum, dollar 372; maximum, dollar 9,488) and dollar 1,409 in cohort S (minimum, dollar 127; maximum, dollar 9,366) per treated episode of CAP (p = 0.066). CONCLUSIONS: Major determinants of costs were length of hospital stay and ICU admission, whereas costs for staff and hotel were major contributors to direct costs. Initial antibiotic therapy with moxifloxacin resulted in similar clinical efficacy and direct costs compared to nonstandardized therapy; however, patients treated with moxifloxacin benefited with an earlier hospital discharge.

Aged↗
PubMed2005

Bosentan therapy for inoperable chronic thromboembolic pulmonary hypertension.

STUDY OBJECTIVES: We performed an open-label multicenter study to evaluate the safety and efficacy of the dual endothelin receptor antagonist bosentan in patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH). PATIENTS: Nineteen patients with inoperable CTEPH were enrolled. MEASUREMENTS: The primary end point was a change in pulmonary vascular resistance (PVR). Secondary end points included 6-min walk test, peak oxygen uptake (V(O2)), New York Heart Association functional class, serum levels of N-terminal-pro brain natriuretic peptide (NT-pro-BNP), and various other hemodynamic parameters. RESULTS: After 3 months of treatment with bosentan, PVR decreased from 914 +/- 329 to 611 +/- 220 dyne.s.cm(-5) (p < 0.001). Functional class and peak V(O2) remained unchanged, but 6-min walk distance increased from 340 +/- 102 to 413 +/- 130 m (p = 0.009), and serum NT-pro BNP levels improved from 2,895 +/- 2,620 to 2,179 +/- 2,301 (p = 0.027). One patient died, presumably from influenza A infection, and another patient experienced progressive fluid retention despite reduction of PVR. Other than that, treatment was well tolerated by all patients. CONCLUSIONS: This open-label pilot trial suggests that bosentan may offer a therapeutic option for patients with inoperable CTEPH. Randomized controlled trials are warranted to confirm these findings.

Aged↗
PubMed2005

Effects of enteral feeding on the oral bioavailability of moxifloxacin in healthy volunteers.

BACKGROUND AND OBJECTIVE: Moxifloxacin is a new generation fluoroquinolone antimicrobial agent used worldwide. In clinical practice in intensive care units, moxifloxacin may be frequently administered through a nasogastric feeding tube. In the absence of an oral liquid formulation and since the multivalent cations contained in enteral feeds may potentially impair absorption of moxifloxacin administered via this route, we studied the effect of concomitant enteral feeding on the pharmacokinetics and tolerability of moxifloxacin administered as a crushed tablet through the nasogastric tube. PARTICIPANTS AND METHODS: This was a single-centre, open-label, randomised, controlled, nonblinded, three-way crossover study. Twelve young healthy volunteers (nine females and three males) aged 20-42 years were included in the study. Each participant received three separate treatment regimens in a randomised fashion: an intact moxifloxacin 400 mg tablet (regimen A, reference treatment), a crushed moxifloxacin 400 mg tablet as a suspension through a nasogastric tube with water (regimen B) and a crushed moxifloxacin 400 mg tablet as a suspension through a nasogastric tube with enteral feeding (regimen C). A washout period of 1-week followed each treatment. Concentrations of moxifloxacin in serum were measured by a validated high-performance liquid chromatography method. Pharmacokinetic parameters were calculated by noncompartmental methods. Additionally, the primary parameters indicative for changes in absorption (area under the serum concentration-time curve from time zero to infinity [AUC(infinity)] and peak serum concentration [C(max)]), were tested for bioequivalence, assuming log-normally distributed data using ANOVA. RESULTS: All moxifloxacin treatment regimens were well tolerated. The AUC(infinity) was slightly, but not statistically significantly, decreased in treatments with regimens B and C. AUC(infinity) (geometric means 39.6 [regimen A] vs 36.1 [regimen B] vs 36.1 mg.h/L [regimen C] and point estimates 91% for B : A and C : A) indicated bioequivalence of the treatments. Bioequivalence criteria of AUC(infinity) and C(max) were met upon retrospective statistical analysis. Likewise C(max) after moxifloxacin administration through nasogastric tube with water (regimen B) and with tube feed (regimen C) were slightly decreased (geometric means 3.20 [regimen A] vs 3.05 [regimen B] vs 2.83 mg/L [regimen C]; point estimates 88% for B : A, and 95% for C : A). They were within the range seen in other studies conducted with oral administration of the drug. No statistically significant differences were observed in time to reach C(max) (t(max); median 1.75 [regimen A] vs 1.00 [regimen B] vs 1.75 hours [regimen C]). Thus, the rate of absorption of moxifloxacin was not affected by administration through a nasogastric tube. This route of ingestion seems to be associated with a slight loss of bioavailability independent of the carrier medium used (water vs enteral feed); no clinically relevant interaction with the multivalent cations contained in the enteral feed was observed, indicating that moxifloxacin and enteral nutrition can be administered concomitantly. CONCLUSION: There was no clinically relevant effect of enteral feeding on the pharmacokinetics of oral moxifloxacin in healthy volunteers. This result has to be evaluated in patients, particularly those from the intensive care unit, who are characterised by severe infectious and/or concomitant diseases that might influence absorption of moxifloxacin.

Absorption↗
PubMed2004

Protease-activated receptor-1 in human lung fibroblasts mediates a negative feedback downregulation via prostaglandin E2.

Among the four protease-activated receptors (PARs), PAR-1 plays an important role in normal lung functioning and in the development of lung diseases, including fibrosis. We compared the expression and functional activity of PARs in normal and fibrotic human lung fibroblasts. Both normal and fibrotic cells express PAR-1, -2, and -3, with PAR-2 showing the lowest level. There was no significant difference between normal and fibrotic fibroblasts in expression levels of PAR-1 and PAR-3, whereas a fourfold higher expression level of PAR-2 was observed in fibrotic cells compared with normal cells. Ca(2+) imaging studies revealed apparently only PAR-1-induced Ca(2+) signaling in lung fibroblasts. PAR-1 agonists, thrombin and synthetic activating peptide, induced concentration-dependent Ca(2+) mobilization with EC(50) values of 5 nM and 1 microM, respectively. The neutrophil protease cathepsin G produced a transient Ca(2+) response followed by disabling PAR-1, whereas elastase did not affect Ca(2+) level. PAR-1 activation by thrombin or receptor-activating peptide downregulated expression of all three PARs in lung fibroblasts, with maximal effect at 3-6 h, whereas expression returned toward basal level after 24 h. Furthermore, PAR-1 agonists dose dependently increased PGE(2) secretion from lung fibroblasts and induction of cyclooxygenase-2 expression. We then found that PGE(2) downregulated expression of all three PARs. The effect of PGE(2) was continuously growing with time. Furthermore, PGE(2) exerts its effect through the EP2 receptor that was confirmed using the selective EP2 agonist butaprost. This novel autocrine feedback mechanism of PGE(2) in lung fibroblasts seems to be an important regulator in lung physiology and pathology.

Calcium↗
PubMed2004

Life after corpse engulfment: phagocytosis of apoptotic cells leads to VEGF secretion and cell growth.

Removal of apoptotic cells by neighboring viable cells or professional phagocytes is essential for the maintenance of tissue homeostastis. Here we show that the phagocytosis of apoptotic Jurkat T cells by mouse epithelial cells (HC-11) and peritoneal macrophages leads to the secretion of growth and survival factors. We characterized VEGF as one of these factors which subsequently promote the proliferation of endothelial cells. Further we demonstrate that the phagocytosis of apoptotic bodies inhibits both spontanous and UV-irradiation-induced apoptosis in endothelial and epithelial cells. These effects were not observed when phagocytes had been exposed to viable or necrotic Jurkat T cells. We conclude that phagocytosis of apoptotic cells leads to secretion of growth and survival factors by phagocytes that represents a new form of life-promoting cell-cell interaction.

Animals↗
PubMed2004

Clinical proteomics in lung diseases.

Proteomics is a relatively new approach for understanding the pathology and pathogenesis of various diseases. It has also been used for characterizing the modifications in protein expression during the development of interstitial lung diseases, in lung tumors, or following exposure to exogenous stress signals. We compared the protein composition of primary human lung fibroblasts derived from patients with lung fibrosis and control fibroblasts of unaffected lung tissues. We found a predominant modulation in proteins related to the cytoskeleton, including decreased expression of vimentin and lamin A/C, and increased expression of moesin. Furthermore, we observed lower levels of components of the antioxidative system, such as omega class glutathione S-transferase and an up-regulation of an intracellular chloride channel. In fibroblasts obtained from fibrotic lungs, the expression of a major histocompatibility complex class I C was decreased, and so was the expression of tripeptidyl-peptidase-I-precursor, a collagen-degrading exopeptidase. Our results and the studies reviewed in this paper represent just the beginning of detailed studies that should unravel the relevance and the functional consequences of differential protein expressions in the diseased lung.

Animals↗
PubMed2004

Pivotal role of cathepsin K in lung fibrosis.

The paramount importance of the homeostasis of the extracellular matrix for pulmonary function is exemplified by two opposing extremes: emphysema and pulmonary fibrosis. This study examined the putative role of cathepsin K (catK) in the pathology of lung fibrosis in mice and its relevance to the human disease activity. We compared the induction of lung fibrosis by administration of bleomycin. CTSK(-/-) mice deposited significantly more extracellular matrix than control mice. Primary lung fibroblasts derived from CTSK(-/-) mice showed a decreased collagenolytic activity indicating the role of catK in collagen degradation. Interestingly, CTSK(+/+) control mice revealed an increased expression of catK in fibrotic lung regions suggesting a protective role of catK to counter the excessive deposition of collagen matrix in the diseased lung. Similarly, in lung specimens obtained from patients with lung fibrosis fibroblasts expressed larger amounts of catK than those obtained from normal lungs. Activation of human pulmonary fibroblasts in primary cell cultures led to an increased activity of catK through enhanced gene transcription and protein expression and to increased intracellular collagenolytic activity. We believe that this is the first study to show that catK plays a pivotal role in lung matrix homeostasis under physiological and pathological conditions.

Animals↗
PubMed2004

Effect of physical exercise on platelet activity and the von-Willebrand-factor in patients with persistent lone atrial fibrillation.

BACKGROUND: The risk of stroke is of great clinical importance in patients with atrial fibrillation (AF). It is not known whether physical exercise influences plasma coagulation and platelet aggregability during AF. The purpose of this study was to assess the effect of physical exercise on platelet activity, thrombin generation, and levels of von-Willebrand-factor in patients with persistent AF. METHODS: Thirteen patients with lone AF (>or=1 year) were compared with 13 matched patients in sinus rhythm. Patients with AF were anticoagulated effectively with coumarin. All patients underwent bicycle ergometry using a respiratory gas exchange technique for 20 min at one-third of the age-adjusted maximal workload. Thereafter, workload was increased until maximal exercise capacity was reached. Platelet factor-4 (PF-4), beta-thromboglobulin (beta-TG; marker for platelet activation), von-Willebrand-factor (vWF; marker for endothelial dysfunction), prothrombin fragment F1 + 2 (F1 + 2; marker for thrombin generation) and fibrinogen levels were determined throughout the study in all patients. RESULTS: Gas exchange variables, hemodynamic parameters and norepinephrine levels were comparable in the groups during moderate (45 +/- 5 W) and heavy exercise (198 +/- 38 W). In contrast to moderate exercise, PF-4 and beta-TG levels increased to 212 +/- 56% ( p < 0.05) and to 145 +/- 24% ( p < 0.05), respectively, in patients with AF during heavy exercise. In contrast, physical exercise had no significant effect on platelet activity in patients with sinus rhythm. Levels of vWF increased by delta24% ( p < 0.05) in all patients during maximal exercise, whereas F1 + 2 levels increased only in patients with sinus rhythm. CONCLUSIONS: Heavy physical activity increases platelet activity and vWF levels during AF, whereas moderate exercise has no procoagulatory effect. Coumarin therapy prevents exercise-induced thrombin generation only. Future studies are needed to prove the hypothesis that heavy physical exercise is a risk factor for thromboembolic events in patients with AF.

Aged↗
PubMed2004

Recurrent tendinitis after treatment with two different fluoroquinolones.

Tendinopathies with and without tendon rupture are rare adverse events, occurring mainly following older fluoroquinolones, but recently also to an increasing extent following levofloxacin. We report the first case of tendinitis after treatment with moxifloxacin, and of recurrent tendinitis after treatment with 2 different fluoroquinolones. From these findings we conclude hitherto unexplained class effect of fluoroquinolones in respect of the development of tendinitis.

Achilles Tendon↗
PubMed2004

Cathepsin L is involved in cathepsin D processing and regulation of apoptosis in A549 human lung epithelial cells.

Cathepsins are implicated in a multitude of physiological and pathophysiological processes. The aim of the present study was to investigate the function of cathepsin L (catL) in the proteolytic network of human lung epithelial cells and its role in the regulation of apoptosis. We found that catL-deficient A549 cells as well as lung tissue extracts of catL(-/-) mice express increased amounts of single-chain cathepsin D (catD). Degradation experiments indicate that catL specifically degrades the single-chain isoform of catD. Furthermore, we found that catL-deficient cells showed increased sensitivity to apoptosis. Finally, we demonstrate that the inhibition of catD activity by pepstatin A decreased the number of apoptotic cells in catL-deficient A549 cells after anti-Fas treatment. In conclusion, catL is involved in catD processing and the accumulation of catD isoforms in catL-deficient cells is associated with increased rates of spontaneous and anti-Fas-induced apoptosis.

Animals↗
PubMed2003

Nitric oxide-dependent vasorelaxation and endothelial cell damage caused by mercury chloride.

Mercury and its derivatives are known to constrict vascular smooth muscle cells. However, little is known about the role of endothelial cells in mercury-induced vasoreactivity. Using isolated, norepinephrine preconstricted rat aorta and pulmonary artery rings with intact endothelium, we demonstrate that mercury chloride (HgCl2) induces an endothelial-dependent vasorelaxation which was totally blocked by the nitric oxide inhibitor L-NAME. Besides this vasorelaxant effect, treatment with HgCl2 resulted in functional and morphological alterations of the endothelial cells. On aortic rings, endothelial cells were partly lifted from the basal membrane when incubated for 20 min in HgCl2 (10(-7) M)-containing buffer. At a concentration of 10(-6) M, the endothelial cells were completely denuded and acetylcholine vasorelaxation was abolished. Endothelial cell structure and function was preserved by incubating the vessels in HgCl2-containing rat blood instead of buffer. We conclude that HgCl2 induces an endothelial-dependent vasorelaxation and alters structure and function of vascular endothelial cells.

Animals↗
PubMed2003

[Fixed Combination of a Long-Acting beta(2)-Agonist and an Inhaled Steroid. A Therapeutic Option for COPD?].

BACKGROUND: The introduction of long-acting bronchodilators (beta(2)-agonists and anticholinergics) has essentially changed the therapy of chronic obstructive pulmonary disease (COPD) in the last years. Furthermore, the understanding of the pathophysiology of the disease has improved, leading to a reevaluation of essential therapeutic principles. Especially, the significance of inhaled steroids in elder and sicker patients is now being acknowledged. COMBINED TREATMENT OF COPD: For a long time, the use of the fixed combination of an inhaled steroid and a long-acting beta(2)-agonist seemed to be reserved for the therapy of bronchial asthma, as there was clinical as well as pharmacologic evidence of a synergism of the therapy components, i. e., increase in beta(2)-receptor density and responsiveness by the steroid and activation of the glucocorticoid receptor by the beta(2)-agonist. However, first studies in COPD showed significant, clinically relevant improvement of the classic outcome parameter pulmonary function as well as of symptoms, especially dyspnea, quality of life and incidence of severe exacerbations, exceeding solely additive effects of the monosubstances. CONCLUSION: According to clinical data, the supposed synergism is very likely, even though pharmacodynamic evidence is not yet available. However, the beneficial effect of combination therapy could be demonstrated for older patients with more severe disease (FEV(1) < 50%, history of frequent exacerbations) only. Further studies will be needed to clarify, if other patient groups will benefit from this therapy option and which dosage is to be regarded as optimal.

Administration, Inhalation↗
PubMed2003

P2Y receptor specific for diadenosine tetraphosphate in lung: selective inhibition by suramin, PPADS, Ip5I, and not by MRS-2197.

Extracellular dinucleotides, which act as signaling molecules in a variety of systems, may regulate fluid homeostasis in the human lung by activation of a specific P2Y receptor subtype. Previously, we presented evidence for a G protein-coupled P2Y receptor with high affinity for dinucleotides in both rat and human lung tissue. In a human bronchial epithelial cell line (HBE-1), diadenosine polyphosphates (Ap(n)A, n=2-6) increase intracellular Ca(2+). The aim of the present work was to find additional evidence that, in these cells, the receptors selectively activated by diadenosine polyphosphates are distinct from already known P2Y receptors, which are activated by the mononucleotides ATP or UTP. We tested antagonists suitable to classify P2Y receptor subtypes. The P2Y(1) receptor-selective antagonist 2'-deoxy-N(6)-methyl adenosine 3',5'-diphosphate (MRS-2197) did not affect Ca(2+) mobilization induced by diadenosine tetraphosphate (Ap(4)A). However, suramin, pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) (PPADS) and diinosine pentaphosphate (Ip(5)I) inhibited the Ca(2+) response by 96%, 92% and 32%, respectively. Moreover, these results were confirmed by assessing the specific binding of [3H]Ap(4)A to membranes from human and rat lung. Suramin (100 microM), PPADS (400 microM) and Ip(5)I (200 microM), reduced [3H]Ap(4)A binding in lung membrane preparations by 66%, 77% and 80%, respectively. The Ap(4)A-induced Ca(2+) response in HBE-1 cells was inhibited to a much greater extent by these antagonists than the ATP- or UTP-evoked Ca(2+) rise. Thus, Ap(4)A in lung epithelial cells also activates a still unidentified P2Y receptor that is specific for dinucleotides over mononucleotides.

Adenosine Diphosphate↗
PubMed2003

ATP- and UTP-activated P2Y receptors differently regulate proliferation of human lung epithelial tumor cells.

The involvement of P2Y receptors, which are activated by extracellular nucleotides, in proliferative regulation of human lung epithelial cells is unclear. Here we show that extracellular ATP and UTP stimulate bromodeoxyuridine (BrdU) incorporation into epithelial cell lines. The nucleotide efficacy profile [ATP = ADP > UDP >or= UTP > adenosine >or= 2-methylthioadenosine-5'-diphosphate, with alpha,beta-methylene adenosine 5'-triphosphate, 2',3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate, AMP, UMP, and ATPalphaS inactive] and PCR analysis indicate involvement of P2Y2 and P2Y6 receptors. The signal transduction pathway, which, via the P2Y2 receptor, transmits the proliferative activity of ATP or UTP in A549 cells downstream of phospholipase C, depends on Ca2+/calmodulin-dependent protein kinase II and nuclear factor-kappaB, but not on protein kinase C. Signaling does not involve the mitogen-activated protein kinases extracellular signal-regulated kinases-1 and -2, the phosphatidylinositol 3-kinase pathway, or Src kinases. Thus nucleotides regulate proliferation of human lung epithelial cells by a novel pathway. The stimulatory effect of UTP, but not ATP, in A549 cells is attenuated by preincubation with interleukin-1beta and interleukin-6, but not tumor necrosis factor-alpha. This indicates an important role for the pyrimidine-activated P2Y receptor in the inflammatory response of lung epithelia. ATP antagonizes the antiproliferative effect of the anticancer drugs paclitaxel and etoposide, whereas it enhances the activity of cisplatin about fourfold. Thus pathways activated by extracellular nucleotides differentially control proliferation of lung epithelial tumor cells.

Adenosine Triphosphate↗