Kimio Konno

Effect of clarithromycin on sputum production and its rheological properties in chronic respiratory tract infections.

Macrolide antibiotics possess a variety of actions other than antimicrobial activities. To determine the effects of long-term administration of clarithromycin (CAM) on the amount and physical properties of sputum in patients with clinical conditions associated with excessive airway secretions, we conducted the present study in a parallel, double-blind, placebo-controlled fashion. Patients were divided into two groups: the first group (n = 16) received CAM (100 mg, twice a day) for 8 weeks, and the second group (n = 15) received placebo. In evaluating airway secretion, the daily amount of expectorated sputum, solid composition, viscoelastic properties (including elastic modulus and dynamic viscosity), and sputum microbiology were assessed. CAM decreased sputum production from 51 +/- 6 to 24 +/- 3 g/day after treatment, whereas placebo had no effect. The bacterial density and sputum flora were unaltered. In the group receiving CAM, the percent solid composition and elastic modulus increased from 2.44% +/- 0.29% to 3.01% +/- 0.20% and 66 +/- 7 to 87 +/- 8 dyne/cm2 (P < 0.05), respectively, but the dynamic viscosity remained unchanged. These results suggest that long-term treatment with CAM reduces the amount of sputum production, probably by inhibiting airway secretions, and increases sputum elasticity.

Erythromycin shortens neutrophil survival by accelerating apoptosis.

Erythromycin is reported to have an anti-inflammatory action, which may account for its clinical effectiveness in the treatment of chronic inflammatory diseases such as diffuse panbronchiolitis. To evaluate the anti-inflammatory action of erythromycin, we examined the survival of isolated neutrophils with and without erythromycin. Erythromycin shortened neutrophil survival in a dose-dependent fashion, with a maximum effect at 10 micrograms/ml [corrected] and above. Survival at 24 h was 63.4% in medium with 10 micrograms of erythromycin per ml compared with 82.7% in control medium (P < 0.01). This shortening of survival was brought about by acceleration of apoptosis, as evidenced by transmission electron microscopy. In a manner similar to that of erythromycin, other macrolide antibiotics, i.e., clarithromycin, roxithromycin, and midecamycin, also shortened neutrophil survival, but neither the beta-lactams ampicillin and cefazolin nor the aminoglycoside gentamicin affected their survival. Erythromycin increased intracellular levels of cyclic AMP (cAMP) to 150% of control levels in neutrophils. Forskolin, rolipram, and dibutyryl-cAMP, which are known to increase intracellular cAMP levels, also shortened neutrophil survival. H-89, an inhibitor of cAMP-dependent protein kinase A, partially blocked the survival-shortening effect of erythromycin. Our findings suggest that erythromycin shortens neutrophil survival at least in part through elevation of intracellular cAMP levels.

Nicotine prolongs neutrophil survival by suppressing apoptosis

Neutrophil accumulation in the lung is implicated in the pathogenesis of pulmonary emphysema and chronic bronchitis associated with cigarette smoking. To determine whether nicotine contributes to this accumulation through the prolongation of neutrophil survival, we examined the survival rates of isolated neutrophils cultured with or without nicotine. We found that nicotine prolonged neutrophil survival in a dose-dependent fashion, with a maximum effect at 10(-6) mol/L. The survival rate at 72 hours was 35.6% +/- 1.2% in medium with 10(-6) mol/L nicotine, compared with 15.5% +/- 0.5% in control medium (mean +/- SEM; p < 0.01), as determined by trypan blue dye exclusion. This prolongation was brought about by suppression of apoptosis, as evidenced by both transmission electron and fluorescence microscopy, and was associated with the preservation of neutrophil functions such as chemotaxis and O2- generation. The prolongation of survival caused by nicotine was abrogated by the addition of Pro-Lys-Arg-NH2, a competitive inhibitor of the specific binding of nicotine to noncholinergic receptors on neutrophils. However, the prolongation of survival caused by nicotine was not suppressed in the presence of K-252b, an inhibitor of protein kinase C. These findings suggest that nicotine prolongs neutrophil survival through noncholinergic nicotine receptors and new protein synthesis, without activation of protein kinase C.

Effects of macrolide antibiotics on neurally mediated contraction of human isolated bronchus

BACKGROUND Long-term administration of macrolide antibiotic substances is an alternative therapy used in the treatment of asthma and airway hyperresponsiveness, but neither its mechanism of action nor whether this substance exerts an immediate action in the airways is known. METHODS Contractile responses of human isolated bronchial strips to electrical field stimulation (EFS) and acetylcholine were assessed under isometric conditions in the absence and presence of erythromycin, roxithromycin, or clarithromycin. RESULTS Incubation of tissues with erythromycin (3 x 10(-5) mol/L) attenuated the contractile responses to EFS so that the stimulus frequency required to produce 50% of the maximal contraction increased from 4.1 +/- 0.5 to 10.1 +/- 0.7 Hz (mean +/- SE; p < 0.001). In contrast, contractile responses to acetylcholine were not changed. Erythromycin reduced the EFS-induced contraction in a concentration-dependent fashion; the maximal decrease from the baseline response was 92.8% +/- 3.6% (p < 0.001). This inhibitory effect was not altered by propranolol, indomethacin, ouabain, charybdotoxin, or mechanical removal of the epithelium. Roxithromycin and clarithromycin likewise inhibited neurally mediated contraction. CONCLUSIONS These results suggest that macrolides may inhibit cholinergic neuroeffector transmission in the human airway smooth muscle, probably by reducing exocytotic release of acetylcholine from the nerve terminals.

Effect of macrolide antibiotics on ciliary motility in rabbit airway epithelium in‐vitro

Abstract— We have studied ciliary beat frequency (CBF) of rabbit cultured tracheal epithelium by a photoelectric method in‐vitro. Addition of erythromycin and roxithromycin increased CBF in a dose‐dependent fashion, whereas clarithromycin was without effect. The rank order potency of macrolide was roxithromycin > erythromycin » clarithromycin. The roxithromycin‐induced increase in CBF was not altered by propranolol, AA‐861, or verapamil, but partially attenuated by indomethacin. Roxithromycin increased intracellular cAMP concentrations. These results suggest that certain macrolides can stimulate airway ciliary motility probably via prostaglandin‐ and cAMP‐dependent regulatory pathways, which may affect mucociliary transport function in the respiratory tract.

Histamine H2 receptor-mediated airway goblet cell secretion and its modulation by histamine-degrading enzymes

BACKGROUND Airway goblet cell hypersecretion may contribute to the pathophysiology of asthma. However, it is unknown whether histamine affects goblet cell secretion and, if so, which subtype of histamine receptor is involved and whether endogenous histamine-degrading enzymes modulate these actions. METHODS We morphometrically assessed goblet cell secretion in the guinea pig trachea stained with alcian blue and periodic acid Schiff stains by measuring the mucus score, which was inversely related to the degree of mucus glycoprotein discharge. RESULTS Inhalation of histamine caused a dose-dependent decrease in mucus score, an effect that was inhibited by pretreatment with the H2-receptor antagonist cimetidine but not with the H1-receptor antagonist mepyramine or the H3-receptor antagonist thioperamide. Inhaled Dimaprit, a selective H2-receptor agonist, likewise decreased mucus score; whereas stimulation of H1- and H3-receptors with 2-methylhistamine and (R)-alpha-methylhistamine, respectively, had no effect. Pretreatment with the histamine N-methyltransferase inhibitor SKF 91488, but not the diamine oxidase inhibitor aminoguanidine, potentiated the dose-dependent effect of histamine on goblet cell secretion, causing a decrease in the concentration of inhaled histamine required to produce a half-maximal effect from 0.80 +/- 0.12 to 0.48 +/- 0.09 mg/ml (p < 0.01). The histamine methyltransferase activity in the tracheal mucosa was 29 times higher than diamine oxidase activity. CONCLUSION These findings suggest that histamine stimulates airway goblet cell secretion through H2-receptors and that this effect may be modulated principally by endogenous histamine methyltransferase through a degradation of histamine.

Lipoxin A4 inhibits cholinergic neurotransmission through nitric oxide generation in the rabbit trachea

The effect of lipoxin A4 and lipoxin B4 on cholinergic neurotransmission in rabbit tracheal segments was studied under isometric conditions in vitro. Lipoxin A4 attenuated the contractile responses to electrical field stimulation and caused a rightward shift of the frequency-response curves, so that the stimulus frequency required to produce a half-maximal effect (ES50) increased from 8.1 +/- 0.8 to 25.7 +/- 1.9 Hz (P < 0.001), whereas lipoxin B4 had no effect. In contrast, lipoxin A4 did not alter the contractile responses to acetylcholine. Pretreatment of tissues with NG-nitro-L-arginine methylester inhibited the effect of lipoxin A4 on electrical field stimulation, but NG-nitro-D-arginine methylester did not. This inhibition by NG-nitro-L-arginine methylester was reversed by L-arginine but not by D-arginine. These results suggest that lipoxin A4 prejunctionally reduces the vagal nerve-mediated contraction of airway smooth muscle, probably by inhibiting the release of acetylcholine, and that this effect may be exerted through stimulation of nitric oxide generation.

Macrolide antibiotics protect against endotoxin-induced vascular leakage and neutrophil accumulation in rat trachea.

We studied the effects of macrolides on lipopolysaccharide (LPS)-induced airway inflammation in the rat tracheal mucosa. Erythromycin and roxithromycin dose dependently inhibited microvascular leakage and neutrophil recruitment induced by LPS. This inhibitory action on vascular permeability was abolished by neutrophil depletion.

Stimulation of ciliary motility mediated by atypical β-adrenoceptor in canine bronchial epithelium

The effects of catecholamines on ciliary motility of canine bronchial epithelium was studied by a photoelectric method in vitro. Addition of beta-adrenoceptor agonists increased ciliary beat frequency, a rank order of potency being salbutamol > or = BRL 37344, a selective beta 3-adrenoceptor agonist > norepinephrine. The response to BRL 37344 was relatively resistant to the blockade of beta 1- and beta 2-adrenoceptors but was competitively antagonized by the beta 3-adrenoceptor antagonist cyanopindolol, with the pA2 value being lower than that when salbutamol was used as an agonist. These results suggest that beta 3-adrenoceptors exist in canine bronchial epithelium and that stimulation of this receptor subtype may enhance ciliary motility and, hence, mucociliary transport in the airway.

Effects of Nicotinamide and Niacin on Bleomycin-Induced Acute Injury and Subsequent Fibrosis in Hamster Lungs

Nicotinamide (500 or 250 mg/kg body wt) or niacin (100 or 50 mg/kg body wt) was administered to hamsters given an intratracheal injection of bleomycin (BLM). At 7 days after the BLM injection, when compared with BLM-control animals, both nicotinamide- and niacin-treated animals showed similar acute lung injury, recognized as increases in the wet-to-dry lung weight ratio, intraalveolar albumin concentration, inflammatory cell number, and elastase activity. At 30 days after the BLM injection, both nicotinamide and niacin attenuated the development of pulmonary fibrosis, as indicated by fewer fibrotic changes and a decreased amount of lung hydroxyproline. Histologic examination revealed that, compared with nicotinamide, niacin had more potent antifibrotic effects. Lung nicotinamide-adenine-dinucleotide (NAD) was less depleted in nicotinamide-treated animals than in BLM-control animals. Nicotinamide- and niacin-treated animals had more intraalveolar cells than the BLM-control animals. These findings suggest that the development of pulmonary fibrosis induced by BLM was prevented through maintaining NAD by the administration of nicotinamide or niacin. Since neither nicotinamide nor niacin attenuated the inflammatory response to acute lung injury, the amelioration of fibrosis by these treatments appears to be independent of the early events.