Biomedical subjects

Kurt Racké

Publications and source records attributed to Kurt Racké.

9 recordsLinked to original sources

PubMed2006

New evidence of H1-receptor independent COX-2 inhibition by fexofenadine HCl in vitro.

BACKGROUND/AIMS: Fexofenadine HCl (FEX) has previously been shown to have anti-inflammatory properties in relieving nasal congestion in allergic rhinitis. The objective of this study was to further elucidate the mechanism of action behind the anti-inflammatory properties of FEX in addition to its H(1)-receptor antagonism. METHODS: The effects of two antihistamines, FEX and loratadine (LOR), were investigated on cyclooxygenase (COX)-1 and -2 enzymes in vitro. FEX (10(-9)-10(-3) mol/l) and LOR (10(-9)-10(-4) mol/l) were incubated with arachidonic acid in a COX screening assay with either ovine COX-1 or COX-2 or human COX-2. COX-2 enzyme inhibitory activity for the antihistamines was compared with the known selective COX-2 inhibitor DuP-679. RESULTS: High concentrations of FEX (10(-3) mol/l) significantly inhibited arachidonic acid-mediated ovine COX-1 activity, but low concentrations had no effect. Low concentrations of FEX (10(-8) mol/l) inhibited ovine COX-2 activity, and this inhibition decreased with increasing concentrations. The inhibition of COX-2 activity by FEX was similar to that seen with the selective COX-2 inhibitor, DuP-679. Conversely, LOR inhibited COX-1 activity at low concentrations (10(-8) mol/l), but had little inhibitory effect on COX-1 at high concentrations. LOR (10(-5) mol/l) markedly stimulated COX-2 activity. CONCLUSION: FEX showed selective arachidonic acid-mediated COX-2 inhibitory enzyme activity, which differed markedly from the COX inhibitory enzyme activity of LOR. This selective COX-2 inhibitor activity by FEX may contribute to its anti-inflammatory properties in relieving nasal congestion in allergic rhinitis.

Animals↗

PubMed2006

Muscarinic receptors mediate stimulation of human lung fibroblast proliferation.

Airway remodeling is a structural alteration associated with chronic inflammatory and obstructive airway diseases, wherein fibroblasts are crucially involved. The present study investigates whether lung fibroblast proliferation is influenced by muscarinic mechanisms. For this purpose, expression of muscarinic receptors in MRC-5 human lung fibroblasts was characterized by semiquantitative RT-PCR, and the effects of muscarinic agonists and antagonists on ((3)H)-thymidine incorporation as a measure of proliferative activity were studied under different culture conditions. MRC-5 fibroblasts express mRNA encoding different subtypes of muscarinic receptors (M(2) > M(3) > M(4), traces for M(5) and no M(1)). Expression of M(2) and M(3) receptors was confirmed at the protein level by immunoblot analysis. Under different culture conditions, carbachol (up to 10 microM) or oxotremorine (10 microM) stimulated ((3)H)-thymidine incorporation, with maximum increases between about 40 and 100%. The stimulatory effect of 10 microM carbachol was prevented by pretreatment with pertussis toxin and antagonized in a concentration-dependent manner by the muscarinic receptor antagonists tiotropium, AQ-RA 741, AF-DX 384, 4-diphenylacetoxy-N-methylpiperidine methoiodide, himbacine, p-fluorohexahydrosiladifenidol, and pirenzepine, with concentrations producing 50% inhibition of 14 pM, 24, 64, 127, 187, 452 nM, and 1.5 microM, respectively. Primary human lung fibroblasts were also found to express mRNA for muscarinic receptors (M(2) > M(1) > M(3), traces for M(4) and no M(5)), and showed a pertussis toxin-sensitive proliferative response to muscarinic receptor stimulation. In conclusion, proliferation of human lung fibroblasts can be stimulated by activation of muscarinic receptors with a pharmacologic profile correlating best to M(2) receptors.

Cell Line↗

PubMed2006

Decreased systemic bioavailability of L-arginine in patients with cystic fibrosis.

BACKGROUND: L-arginine is the common substrate for nitric oxide synthases and arginases. Increased arginase levels in the blood of patients with cystic fibrosis may result in L-arginine deficiency and thereby contribute to low airway nitric oxide formation and impaired pulmonary function. METHODS: Plasma amino acid and arginase levels were studied in ten patients with cystic fibrosis before and after 14 days of antibiotic treatment for pulmonary exacerbation. Patients were compared to ten healthy non-smoking controls. RESULTS: Systemic arginase levels measured by ELISA were significantly increased in cystic fibrosis with exacerbation compared to controls (17.3 +/- 12.0 vs. 4.3 +/- 3.4 ng/ml, p < 0.02). Arginase levels normalized with antibiotic treatment. Plasma L-arginine was significantly reduced before (p < 0.05) but not after treatment. In contrast, L-ornithine, proline, and glutamic acid, all downstream products of arginase activity, were normal before, but significantly increased after antibiotic therapy. Bioavailability of L-arginine was significantly reduced in cystic fibrosis before and after exacerbation (p < 0.05, respectively). CONCLUSION: These observations provide further evidence for a disturbed balance between the L-arginine metabolic pathways in cystic fibrosis.

Journal Article↗

PubMed2006

Control by cholinergic mechanisms.

In the respiratory tract acetylcholine is neurotransmitter in ganglia and postganglionic parasympathetic nerves, but in addition is paracrine mediator released from various non-neuronal cells. Almost every cell type present in the respiratory tract expresses nicotinic and muscarinic receptors and therefore appears to be a target for acetylcholine. The present review describes the mechanisms of synthesis and release of acetylcholine from neuronal and non-neuronal cells and the differential control mechanisms. The different cholinoceptors, multiple nicotinic and muscarinic receptors and their signalling are outlined and their involvement in the modulation of the function of various target cells, smooth muscles, nerves, surface epithelial, secretory cells, fibroblasts and inflammatory cells is discussed in detail.

Acetylcholine↗

PubMed2005

Differential effects of fexofenadine on arachidonic acid metabolism in cultured human monocytes.

The relief of nasal congestion with the antihistamine fexofenadine in seasonal allergic rhinitis is thought to be due to its additional anti-inflammatory properties. The objective of this study was to evaluate the in vitro effects of fexofenadine on stimulated arachidonic acid metabolism. Human monocytes, isolated from blood and donated by 5 healthy volunteers, were either incubated for 20 h with 10 microg/ml lipopolysaccharide, with and without fexofenadine (10(-8)-10(-3) mol/l, n = 8-19), or were incubated for 20 h, with and without fexofenadine, and then stimulated with 0.5 mg/ml zymosan for 2 h. Leukotriene B4 (LTB4), LTC4, LTD4 and LTE4, prostaglandin E2 (PGE2) and F2alpha (PGF2alpha) production was determined by enzyme immunoassay. Zymosan-stimulated production of LTC4, LTD4 and LTE4 was significantly inhibited by clinically relevant concentrations of fexofenadine HCl: 10(-7) mol/l (22% inhibition vs. control, p = 0.008) and 10(-6) mol/l (24% inhibition vs. control, p = 0.020). Higher concentrations of fexofenadine (10(-4) and 10(-3) mol/l) inhibited LTB(4) generation. Lipopolysaccharide-stimulated production of PGE2 was significantly inhibited by fexofenadine HCl 10(-6) mol/l (26% inhibition, p = 0.035) and 10(-5) mol/l (40% inhibition, p = 0.001). Higher concentrations of fexofenadine HCl (10(-4) and 10(-3) mol/l) significantly inhibited PGF2alpha production by 50% (p = 0.026) and 63% (p = 0.001), respectively. Fexofenadine, at both clinically relevant and higher concentrations, inhibits LTC4, LTD4, LTE4 and PGE2 in cultured human monocytes. These additional anti-inflammatory properties may underlie the relief of nasal congestion observed in clinical studies.

Anti-Allergic Agents↗

PubMed2005

Increased arginase activity in cystic fibrosis airways.

RATIONALE: Airway nitric oxide concentrations are reduced in cystic fibrosis (CF). Arginases compete for L-arginine, the substrate of nitric oxide synthesis. OBJECTIVES: We hypothesized that increased arginase activity may be one factor contributing to nitric oxide deficiency in CF. MEASUREMENTS: We therefore studied sputum arginase activity, exhaled nitric oxide, and pulmonary function in patients with cystic fibrosis. RESULTS: Mean (+/- SEM) sputum arginase activity was significantly higher in patients admitted for pulmonary exacerbation compared with patients with stable disease (1.032 +/- 0.148 vs. 0.370 +/- 0.091 U/mg protein, p = 0.004). Fourteen days of intravenous antibiotic treatment resulted in significantly decreased sputum arginase activity in all patients (p = 0.0002). However, arginase activity was still significantly (p = 0.0001) higher in CF sputum after treatment for exacerbation compared with induced sputum from healthy control subjects (0.026 +/- 0.006 U/mg protein). Negative correlations were found for sputum arginase activity at admission with FEV1 (r = -0.41, p = 0.01), as well as changes in arginase activity with percent change in FEV1 during antibiotic therapy (r = -0.4, p < 0.01) in CF. Exhaled nitric oxide in CF was positively correlated to FEV1 (r = 0.34, p = 0.007), and in patients admitted for pulmonary exacerbation negatively correlated to sputum arginase activity (r = -0.45, p = 0.03). CONCLUSIONS: These data suggest that increased sputum arginase activity contributes to nitric oxide deficiency in CF lung disease and may be relevant in the pathogenesis of CF airway disease.

Adolescent↗

PubMed2004

Inhibitory activity of 1,8-cineol (eucalyptol) on cytokine production in cultured human lymphocytes and monocytes.

BACKGROUND: The therapeutic value of secretolytic agents in COPD and asthma is still disputed. For this reason, in a preclinical study we aimed to test the potential anti-inflammatory efficacy of 1,8-cineol (eucalyptol) in inhibiting polyclonal stimulated cytokine production by human unselected lymphocytes and LPS-stimulated monocytes. METHODS: Cytokine production was determined following 20 h of incubation cells with 1,8-cineol simultaneously with the stimuli in culture supernatants by enzyme immunoassay. RESULTS: Therapeutic concentrations of 1,8-cineol (1.5 microg/ml=10(-5)M) inhibited significantly (n=13-19, p=0.0001) cytokine production in lymphocytes of TNF-alpha > IL-1beta> IL-4> IL-5 by 92, 84, 70, and 65%, respectively. Cytokine production in monocytes of TNF-alpha > IL-1beta> IL-6> IL-8 was also significantly (n=7-16, p<0.001) inhibited by 99, 84, 76, and 65%, respectively. In the presence of 1,8-cineol (0.15 microg/ml=10(-6)M) production of TNF-alpha>IL-1beta by monocytes and of IL-1beta> TNF-alpha by lymph-ocytes was significantly inhibited by 77, 61 and by 36, 16%, respectively. 1,8-cineol (10(-6)M) had a larger impact on TNF-alpha and IL-1beta-production in monocytes compared to lymphocytes (p<0.03) and similar effects (p>0.59) at therapeutically relevant concentrations of 1,8-Cineol (10(-5)M). CONCLUSION: These results characterize 1,8-cineol as strong inhibitor of TNF-alpha and IL-1beta and suggest smaller effects on chemotactic cytokines. This is increasing evidence for the role of 1,8-cineol to control airway mucus hypersecretion by cytokine inhibition, suggesting long-term treatment to reduce exacerbations in asthma, sinusitis and COPD.

Anti-Inflammatory Agents↗

PubMed2003

Glucocorticoid inhibition of interleukin-4 (IL-4) and interleukin-13 (IL-13) induced up-regulation of arginase in rat airway fibroblasts.

Arginase appears to play a significant role in the pathogenesis of inflammatory and obstructive airway diseases by interfering with NO synthesis (hyperreactivity) and by providing substrate for collagen synthesis (remodelling). IL-4 and IL-13 are key proinflammatory cytokines in asthma, and their effects on arginase in rat primary airway fibroblasts in culture were studied. Airway fibroblasts showed significant arginase activity, which was higher when the culture medium contained 10% fetal calf serum (FCS) (20 mU/mg protein) compared to 5% FCS (6 mU/mg protein). In presence of 10% FCS addition of IL-4 or IL-13 (10 ng/ml each) for 20 h or 40 h caused an increase in arginase activity by 76% and 160% (IL-4) and by 134% and 213% (IL-13), respectively. Using RT-PCR mRNA for arginase I was clearly detectable with 30 PCR cycles, whereas mRNA for arginase II was hardly detectable with 35 PCR cycles. IL-4 and IL-13 caused a clear increase in the mRNA of both arginase isoenzymes. Dexamethasone (1 microM) did not affect basal arginase activity, but largely opposed the stimulatory effects of IL-4 and IL-13. In conclusion, IL-4 and IL-13 can cause a marked up-regulation of arginase activity in rat airway fibroblasts and these effects can be inhibited by glucocorticoids.

Animals↗

PubMed2003

Effects of phosphodiesterase inhibitors on L-arginine pathways in rat alveolar macrophages.

Effects of phosphodiesterase inhibitors on L-arginine-dependent pathways in rat alveolar macrophages, inducible nitric oxide (NO) synthase (iNOS) and arginase, were studied. Culture of rat alveolar macrophages in the presence of lipopolysaccharides (20 h) caused an increase of arginase activity (by 135%) and nitrite concentration (fourfold). The nonselective phosphodiesterase inhibitor IBMX (2-isobutyl-1-methylxanthine) enhanced arginase activity by 35% and nitrite accumulation by 130%. IBMX caused a clear increase in iNOS protein levels and a relatively smaller increase in iNOS mRNA. The effect of IBMX on nitrite accumulation was largely attenuated by the protein kinase A inhibitor K 5720. The phosphodiesterase 4 inhibitor rolipram enhanced nitrite accumulation more effectively than the phosphodiesterase 3 inhibitor siguadozan (about 50% and 20% of IBMX effect, respectively), whereas the phosphodiesterase 3/4 inhibitor benzafendrine was as effective as IBMX. In conclusion, in rat alveolar macrophages, phosphodiesterase 4 and, to a smaller extent, phosphodiesterase 3 play a role in the control of iNOS-mediated NO synthesis.

Animals↗