GC content of vertebrate exome landscapes reveal areas of accelerated protein evolution.

BACKGROUND: Rapid accumulation of vertebrate genome sequences render comparative genomics a powerful approach to study macro-evolutionary events. The assessment of phylogenic relationships between species routinely depends on the analysis of sequence homology at the nucleotide or protein level. RESULTS: We analyzed mRNA GC content, codon usage and divergence of orthologous proteins in 55 vertebrate genomes. Data were visualized in genome-wide landscapes using a sliding window approach. Landscapes of GC content reveal both evolutionary conservation of clustered genes, and lineage-specific changes, so that it was possible to construct a phylogenetic tree that closely matched the classic "tree of life". Landscapes of GC content also strongly correlated to landscapes of amino acid usage: positive correlation with glycine, alanine, arginine and proline and negative correlation with phenylalanine, tyrosine, methionine, isoleucine, asparagine and lysine. Peaks of GC content correlated strongly with increased protein divergence. CONCLUSIONS: Landscapes of base- and amino acid composition of the coding genome opens a new approach in comparative genomics, allowing identification of discrete regions in which protein evolution accelerated over deep evolutionary time. Insight in the evolution of genome structure may spur novel studies assessing the evolutionary benefit of genes in particular genomic regions.

Anomalous dynamics of DNA hairpin folding.

By means of computer simulations of a coarse-grained DNA model we show that the DNA hairpin zippering dynamics is anomalous; i.e., the characteristic time τ scales nonlinearly with N, the hairpin length, τ ∼ N(α) with α>1. This is in sharp contrast to the prediction of the zipper model for which τ ∼ N. We show that the anomalous dynamics originates from an increase in the friction during zippering due to the tension built in the closing strands. From a simple polymer model we get α = 1+ν ≈ 1.59 with ν being the Flory exponent, a result which is in agreement with the simulations. We discuss transition path times data where such effects should be detected.

Response to intranasal fluticasone propionate in perennial allergic rhinitis not associated with glucocorticoid receptor characteristics.

BACKGROUND: The reduction of symptoms due to treatment with corticosteroids varies among patients with perennial rhinitis. Most patients will respond but a few patients respond less to these drugs. OBJECTIVE: To investigate the association in reduction of symptoms due to glucocorticoids and glucocorticoid receptor characteristics in patients with perennial allergic rhinitis, in vitro glucocorticoid receptor binding studies were performed with peripheral blood mononuclear cells using dexamethasone and in vitro production of mediators were measured. METHODS: During a double-blind placebo-controlled crossover study, 200 micrograms fluticasone propionate aqueous nasal spray (in the active treatment period) and placebo (in the placebo treatment period) were administered twice daily for 2 weeks to 22 patients allergic to house dust mite. At the end of both treatment periods symptoms were scored after allergen provocation (100, 1000, 10000 BU/mL) and during the 9.5 hours after this challenge. Receptor binding studies with dexamethasone were performed with peripheral blood mononuclear cells. Leukotriene B4 produced by monocytes in vitro and soluble interleukin-2 receptor released by lymphocytes in vitro and cortisol levels in plasma were determined. RESULTS: No significant partial correlations of the number of the peripheral blood mononuclear cell glucocorticoid receptors (6821 +/- 5669 binding sites per cell) and the affinity (Kd: 16.5 +/- 13.51 nmol/L) for the glucocorticoid receptors with the symptom score (placebo: 4.3 +/- 2.45 pts; fluticasone: 2.4 +/- 1.55 pts) after active treatment were found. Also no significant partial correlations of the levels of leukotriene B4 (45.6 +/- 105.3 ng/10(6) cells) produced by monocytes in vitro, soluble interleukin-2 receptor (734 +/- 237 ng/10(6) cells) released by lymphocytes in vitro and cortisol levels (571 +/- 236 ng/mL) in plasma with the symptom score after active treatment were found. CONCLUSIONS: The reduction of symptoms due to topical fluticasone propionate in patients with rhinitis and allergy to house dust mite is not correlated with the characteristics of the glucocorticoid receptor.

The relationships between nasal hyperreactivity, quality of life, and nasal symptoms in patients with perennial allergic rhinitis.

BACKGROUND: A clinical test that could inform the clinician about the severity of a patient's nasal symptoms and health-related quality of life (QOL) would be very useful. OBJECTIVE: We attempted to determine whether, in patients with perennial allergic rhinitis, nasal challenge with histamine could be used to estimate daily symptoms and QOL. METHODS: Forty-eight patients with perennial allergic rhinitis were challenged with histamine to determine nasal hyperreactivity. Nasal response was monitored by the number of sneezes, the amount of secretion, and a symptom score. Daily nasal symptoms were recorded during the 2 preceding weeks. Patients also completed a rhinitis QOL questionnaire. RESULTS: Responsiveness to histamine and total daily nasal symptoms were moderately correlated (r = 0.51, p = 0.001). Comparison of total daily nasal symptoms with the overall QOL score showed a moderate correlation (r = 0.59, p < 0.001). Nasal response to histamine and overall QOL score were also correlated (r = 0.43, p = 0.002). However, overall QOL and daily nasal symptoms could be predicted by wide 95% confidence intervals only for each decade of nasal responsiveness to histamine (expressed as a composite symptom score). CONCLUSION: In patients with perennial allergic rhinitis nasal hyperreactivity as determined by histamine challenge, QOL, and daily nasal symptoms are moderately correlated. Therefore nasal histamine challenge can be used as a tool for estimating the severity of daily nasal symptoms and QOL, although it cannot predict nasal symptoms and QOL very accurately.

Selective effect of levocabastine on histamine receptor and histamine release from human leukocytes and guinea pig isolated tissue.

BACKGROUND: Levocabastine is a potent histamine H1 receptor antagonist used topically in the treatment of patients with allergic rhinitis. It has been suggested that antihistamines also have anti-inflammatory properties. OBJECTIVE: The present study was performed to investigate whether levocabastine, in addition to the anti-H1 receptor activity, has anti-inflammatory properties and thus is able to modulate the release of histamine and cytokines, such as interleukin 5 from human leukocytes and isolated tissues. METHODS: Leukocytes suspensions were prepared by dextran sedimentation of peripheral venous blood drawn from allergic and healthy volunteers. Leukocytes obtained from allergic volunteers were preincubated for 30 minutes with levocabastine (doses 10(-8) M to 10(-6) M) and thereafter incubated with allergen. Leukocytes obtained from healthy volunteers were incubated for zero to three hours with levocabastine (doses 10(-14) M to 10(-3) M). Histamine release was measured by an automated fluorometric method. Interleukin-5 release was measured by enzyme linked immunoassay. Contractile responses to histamine on guinea pig trachea and lung parenchyma as well as the release of histamine and interleukin-5 by the tissues were investigated in the absence or presence of levocabastine and/or the histamine H2 receptor antagonist cimetidine. RESULTS: Levocabastine did not influence allergen-induced histamine release from leukocytes obtained from allergic volunteers. High concentrations (10(-4)and 10(-3) M) of levocabastine, however, caused release of histamine from leukocytes obtained from healthy volunteers as well as guinea pig airway smooth muscle tissues. Pretreatment with levocabastine dose-dependently decreased the contractile response to histamine, showing an irreversible competitive mechanism. Interleukin 5 release from human leukocytes and by guinea pig airway smooth muscle was not detectable. CONCLUSIONS: These findings indicate that the H1 receptor blocker, levocabastine, has probably no anti-inflammatory properties, measured as histamine release, and that the histamine release from both human leukocytes and guinea pig trachea and lung parenchyma is significantly increased by the drug only at high concentrations.

Effect of topical levocabastine on nasal response to allergen challenge and nasal hyperreactivity in perennial rhinitis.

BACKGROUND: It has been demonstrated that some oral antihistamines reduce nasal nonspecific reactivity and that topical levocabastine reduces cellular influx after nasal allergen challenge. This suggests that antihistamines possess other properties besides classical H1-receptor antagonism. OBJECTIVE: To evaluate the effect of 1 week's treatment with topical levocabastine on the nasal clinical response, inflammatory mediators, and nasal hyperreactivity. METHODS: In a double-blind, placebo-controlled, 2-period, 2-treatment, crossover study, 21 rhinitic patients allergic to house dust mite participated. After each treatment period patients were challenged with house dust mite extract. Symptom scores and nasal lavages were collected for nine and one-half hours after challenge. Allergen-induced nasal hyperreactivity was determined by nasal methacholine challenge 24 hours after allergen challenge. A nasal histamine challenge was performed as well. RESULTS: Patients showed only an immediate nasal response. Levocabastine significantly reduced the symptom score after 100 (P = .0063), 1000 (P = .0035), and 10,000 biological units (BU)/mL (P = .0013) of house dust mite extract. Albumin influx and tryptase release were not significantly reduced by levocabastine. No release of histamine and eosinophil cationic protein was seen. Levocabastine did not reduce nasal response to methacholine. Active treatment significantly reduced histamine-induced nasal secretion (P = .0009) and the number of sneezes (P = .0001). CONCLUSION: A significant effect of levocabastine was shown on the immediate clinical response to house dust mite and to histamine challenge only. Our findings suggest that levocabastine is an effective H1-receptor antagonist without anti-inflammatory properties.

Interleukin-5 and eosinophil cationic protein in nasal lavages of rhinitis patients.

The production of interleukin-5 and eosinophil cationic protein (ECP) in the nasal cavity was examined in 24 patients with rhinitis who were allergic to the house dust mite. During a double-blind placebo-controlled cross-over study, fluticasone propionate aqueous nasal spray (200 micrograms) was administered twice daily for 2 weeks. After four basal nasal lavages provocation with house dust mite extract was performed and nasal lavages were collected every hour for 9.5 h. Interleukin-5 was present in detectable amounts in nasal lavages from patients allergic to house dust mite. Nasal challenge with house dust mite extract caused immediate nasal symptoms and increased levels of interleukin-5. Between 3.5 and 8.5 h after the challenge symptoms recurred and interleukin-5 levels increased, reflecting a late phase reaction. Eosinophil cationic protein, a marker of activated eosinophils, was released between 6.5 and 9.5 h after challenge. Treatment with fluticasone propionate (as an aqueous nasal spray) significantly decreased the evoked interleukin-5 and ECP levels in the late phase reaction. This response was correlated with an improved symptom score. This could indicate that the number and activity of eosinophils are increased during the late phase allergic reaction, a response that is inhibited by corticosteroids.

Effect of Fluticasone propionate Aqueous Nasal Spray Treatment on Platelet Activating Factor and Eicosanoid Production By nasal Mucosa in Patients with A house Dust Mite Allergy.

The relationship between the release of platelet activating factor (PAF), leukotriene C(4)/D(4)/E(E) (LTC(4)/D(4)/E(4)) and prostaglandin D(2) (PGD(2)) from nasal mucosa in vivo was examined in 24 rhinitis patients allergic to the house dust mite (HDM). During a double blind placebo controlled cross-over study 200 mug fluticasone propionate aqueous nasal spray (FPANS) was administered twice daily for two weeks. In response to allergen provocation (100, 1 000, 10 000 Bu/ml) and during the 9.5 h after this challenge the nasal fluid was obtained by washing the nose with saline and the levels of PAF, LTC(4)/D(4)/E(4) and PGD(2), as indicators of mediator release, were measured at the following time-points: baseline (t = - 1/2), allergen provocation with 10 000 Bu/ml (t = 0), 3.5 and 7.5 h (late phase). After allergen provocation the levels of the mediators increased in the nasal fluids of placebo treated patients (x-fold increase to baseline: PAF, 15; LTC(4)/D(4)/E(4), 12; PGD(2), 1.5). In fluids of patients treated with FPANS these levels tended to decrease. At the time of provocation the levels of PAF, LTC(4)/D(4)/E(4) and PGD(2) showed a significant correlation. The results indicate that these mediators can be used as markers of allergic reactions against house dust mites and that fluticasone propionate aqueous nasal spray tended to reduce the release of mediators of inflammation correlated with beneficial effects on clinical symptoms in this type of allergic reactions.