Presence of bronchoalveolar lavage fluid necessary for platelet activating factor-induced ciliary depression

Roxythromycin reinforces epithelial defence function in rabbit trachea

Our study elucidates the effect of roxythromycin (RXM) on airway epithelial defence functions, especially the mucociliary and epithelial barrier functions, in the rabbit trachea. In vitro ciliary activity was not affected in the presence of 3.3 mg/ml of RMX, but was enhanced in the presence of 6.7 mg/ml of RXM. Oral administration of 10 and 100 mg of RXM for 14 days enhanced both ciliary activity and mucociliary transport velocity in the trachea. Epithelial permeability to fluorescein isothiocyanate-dextrans (FD-70s; molecular weight: 70,000 daltons) was not affected by oral administration of 10 mg of RXM for 14 days, but was significantly reduced by oral administration of 100 mg of RXM for 14 days. Inhalation of platelet activating factor (PAF) compromised the function of the mucociliary system and the tight junction barrier. However, pretreatment with 20 mg of RXM significantly alleviated the PAF-induced decrease in mucociliary function and the increase in epithelial permeability to FD-70s. In conclusion, such reinforcement of the epithelial defence functions is likely to be involved in the pharmacological action underlying the clinical efficacy of RXM for chronic airway inflammatory disease.

Effects of platelet activating factor on the tubotympanic mucosa and inner ear in the guinea pig

The effect of platelet activating factor (PAF) was studied to elucidate its role in the pathogenesis of otitis media and sensorineural hearing loss. The PAF alone did not induce a reduction of ciliary activity of the cultured middle ear mucosa. However, a dose-dependent decrease in ciliary activity was observed in the presence of the medium containing both PAF and macrophages. Intravenous injection of PAF did not induce dysfunction of the mucociliary system or morphologic changes of epithelium in the tubotympanum, but cytoplasmic vacuolization and ballooning were observed in the inner ear within 1 hour after injection of PAF. In contrast, intratympanic injection of PAF induced mucociliary dysfunction and some pathologic changes in the tubotympanum. Intratympanic inoculation of PAF induced no pathologic findings in the inner ear. These results suggest that PAF is at least partially involved in the pathogenesis of certain middle ear diseases such as otitis media with effusion. Additionally, PAF might be involved in the pathogenesis of some types of unexplained sensorineural hearing loss.

The herbal medicine, sairei-to, enhances the mucociliary activity of the tubotympanum in the healthy guinea pig

Mucociliary dysfunction in the tubotympanum is deeply reflected in the clinical manifestations of otitis media with effusion (OME), and clinical application of pharmacological agents with ciliostimulatory action might therefore enhance the mucociliary clearance function of the tubotympanum to more effectively eliminate middle ear effusions to the pharynx. A herbal medicine, sairei-to, enhances the in vitro ciliary activity of the middle ear during culture. However, this ciliostimulatory effect is not always applicable to the mucociliary system in situ, which may be deteriorated following oral administration of sairei-to. The present study therefore aimed at investigating the in vivo effect of sairei-to on the mucociliary system in the tubotympanum of the guinea pig. Thirty healthy guinea pigs were used. Ten animals were treated with oral administration of physiologic saline solution for 14 successive days. The remaining animals were treated with oral administration of 120 or 600 mg/kg body weight of sairei-to for 14 successive days. Each animal was used for examination of the ciliary activity and mucociliary clearance time of the tubotympanum, 24 h after the final treatment. No significant changes in either ciliary activity or mucociliary clearance time of the tubotympanum were observed upon administration of 120 mg/kg of sairei-to, which was equivalent to the clinical human dosage. By contrast, oral administration of 600 mg/kg of sairei-to significantly enhanced the ciliary activity, but failed to significantly accelerate mucociliary clearance in the tubotympanum, although the mean value of the clearance time became shorter. Therefore, our results suggest that sairei-to to some extent stimulates the function of the mucociliary system. In conclusion, the herbal medicine, sairei-to, might be useful in the treatment of OME, and preventive administration of this drug may be a new therapy in the treatment of recurrent OME.

Platelet activating factor compromises airway epithelial defense functions

BACKGROUND

The mechanism of disruption of the epithelial defense function observed in asthmatic airways is considered to be largely the result of mediators involved in allergic responses. Platelet activating factor (PAF) might be a key mediator involved in this mechanism.

OBJECTIVE

This study was designed to determine whether PAF is capable of compromising the epithelial defense functions, such as tight junctional barriers and the mucociliary system.

METHODS

A total of 120 healthy rabbits were used. Twenty of them were used as normal controls. Eighty rabbits were treated with inhalation of 10 ml of PAF (200 microg/ml), and 20 animals were used for the examination of epithelial defense functions of the trachea at 1, 10, 20, and 30 days after inhalation of PAF. Epithelial defense functions of the trachea were evaluated by ciliary activity, mucociliary transport velocity, epithelial permeability to fluorescein isothiocyanate dextrans (70,000 d), and electron microscopy of the epithelial structure.

RESULTS

PAF inhalation induced a significant decrease in ciliary activity and mucociliary transport velocity, which persisted for up to 20 days. PAF inhalation also caused a significant 7.4-fold increase in epithelial permeability to fluorescein isothiocyanate dextrans at I and 10 days. This increased epithelial permeability returned to the normal level 20 days after PAF inhalation. However, electron microscopy demonstrated no apparent evidence of epithelial shedding.

CONCLUSIONS

PAF-induced prolonged dysfunction of both the epithelial junctional barrier and the mucociliary system may allow enhanced entry of allergen molecules, as well as bronchoactive agonists to the airway parenchyma and may also significantly contribute to an increased airway responsiveness.