Platelet activating factor induced respiratory mucosal damage

Ultrastructural changes in platelet activating factor-induced epithelial damage in rabbit maxillary sinus mucosa

Platelet activating factor (PAF), a potent chemical mediator in inflammation and allergic reaction, has been thought to induce mucociliary inhibition and epithelial damage in the airway mucosa. However, several recent papers have reported that PAF may not readily damage the airway epithelium. The aim of this study was to elucidate the pathogenesis of PAF-induced epithelial damage in terms of ultrastructural changes. Sixteen micrograms of PAF (1 mL of 16 microg/mL) was administered into the maxillary sinuses of rabbits. The rabbits were divided into 2 groups according to time intervals, and the antral mucosa was taken 1 and 3 days after administration of PAF. The tissue was processed for routine transmission electron microscopy. No epithelial degeneration was observed other than platelet aggregation, red blood cell stasis, and swelling of the endothelial cells 1 day after administration of PAF. Migration of inflammatory cells into the perivascular connective tissue, infiltration of eosinophils into the subepithelial and intraepithelial spaces, and vacuolar degeneration of the epithelial cells with focal loss of cilia were seen 3 days after administration of PAF. In conclusion, PAF induced infiltration of eosinophils into the epithelium, and resulted in epithelial degeneration that varied according to the time interval. Our findings suggest that PAF may cause epithelial damage through a series of secondary events, probably due to cytotoxicity of eosinophils infiltrating the epithelium.

Effect of leukotriene C4 exposure on ciliated cells of the nasal mucosa

To clarify the effects of leukotriene C4 (LTC4) on human ciliated epithelium, ciliary activity of the ethmoid sinus mucosa was measured photoelectrically in tissue culture. At concentrations ranging from 10(-6)M to 10(-9)M, LTC4 showed minimal effects on the ciliated epithelium during the initial 30 minutes of exposure; thereafter, ciliary inhibition was observed in a concentration- and time-dependent manner. Irrigation of the mucosa with culture medium 15 minutes after exposure prevented the LTC4-induced ciliary inhibition. However, irrigation 60 minutes after exposure failed to inhibit 10(-8)M LTC4-induced ciliary dysfunction and mucosal damage. The LTC4-induced ciliary inhibition was blocked in the presence of FPL-55712 and/or Ly-171883, both leukotriene receptor antagonists. L-serine and sodium tetraborate complex (SBC), a gamma-glutamyl transpeptidase (gamma-GTP) inhibitor, also inhibited the LTC4-induced ciliary inhibition. These findings indicate that LTC4 is converted to LTD4 by gamma-GTP during 60 minutes of exposure, and LTC4 itself has minimal direct effects on the ciliated cells.

Eosinophil cationic protein in perennial allergic rhinitis

For a quantitative investigation of eosinophil activation in perennial allergic rhinitis, eosinophil cationic protein (ECP) concentrations were measured by a radioimmunoassay in serum, nasal secretions (ECPWN) and in the supernatant of these nasal secretions (ECPsup) obtained from normal subjects and allergic patients. Levels of ECPWN and ECPsup were higher than that of ECPserum. ECPsup showed a positive correlation with clinical severity, despite the lack of a significant correlation with eosinophilia in nasal smears. ECPWN and ECPserum showed no significant correlation with any of these clinical parameters. There was a weak tendency toward an increase in histamine sensitivity of the nasal mucosa of allergic patients with higher ECPsup although this was not statistically significant. These results suggest accumulation and activation of eosinophils in the allergic nasal mucosa, and also indicate that ECPsup may be a clinical parameter of perennial allergic rhinitis.

Leukotriene D4-induced mucosal damage during long observation periods in vitro

The effect of leukotriene D4 (LTD4) on human paranasal sinus mucosa was investigated for over 1 hour up to 24 hours using a VTR system at 2,500 X in vitro. Ethmoidal sinus mucosal specimens were incubated in tissue culture, and after exposure to LTD4 the mucosal surface profile was viewed under an inverted phase-contrast microscope equipped with a VTR system on a TVscreen. LTD4-induced ultrastructural alterations, ciliostasis, alterations consisted of a coarse profile and epithelial cell exfoliation. Ciliary activity was photoelectorically measured on the screen hourly. The mucosal specimens were morphologically examined before and after exposure to LTD4 by transmission electron microscopy. LTD4 inhibited ciliary activity in a time- and dose-dependent manner at concentrations ranging from 10(-6)M to 10(-10)M, whereas LTE4 had a minimal effect on the mucosa even at the concentration of 10(-6) M. Irrigation of the mucosa with culture medium after 5-min of exposure to 10(-8) M LTD4 delayed appearance of ciliary inhibition and alteration of the mucosal surface profile, but had no effect after 15-min exposure. These effects of LTD4 on the mucosa were blocked by preincubation with the LT antagonists, FPL-55712 and Ly-171883. These results demonstrate the cytotoxic effect of LTD4 on human airway epithelium in vitro.

Clinical efficacy of Tranilast on otitis media with effusion in children

In this open randomized study, we evaluated the efficacy of Tranilast, one of the anti-inflammatory drugs, on otitis media with effusion in children. Sixty-two patients (103 ears) were divided into two groups: Group A was given Tranilast and local treatment (nasal and tubal); Group B only received local treatment (control for Group A). The overall improvement rating assessed as "moderately improved or above" for Group A was 63.6%, Group B 47.9%. There was a significant improvement in Group A as compared to Group B (p < 0.05). In subjects who suffered from otitis media with effusion for over 2 months. Group A exhibited 50.0% of efficacy while Group B only 15.4% (p < 0.05).

Study on the metabolism of lyso-platelet activating factor (lyso-PAF) in human paranasal sinus mucosa. The cultured ciliated epithelium can convert lyso-PAF to PAF

The conversion of lyso-platelet activating factor (lyso-PAF) to PAF in cultured paranasal sinus mucosa obtained from normal human subjects was studied. The PAF concentration in the medium was determined after addition of lyso-PAF. PAF became detectable at 10 minutes after the addition of 10(-8)M lyso-PAF, and reached a maximum concentration (3.25 x 10(-9)M) at 20 minutes. The PAF level then gradually declined to become undetectable at 60 minutes after addition of lyso-PAF. Thus PAF is very unstable having a half-life calculated to be 12.8 minutes with an elimination constant of k = 0.05377 minutes-1. In contrast, lyso-PAF is known to be a stable metabolite of PAF as well as a precursor of PAF. The results obtained from this study suggest that the turnover of lyso-PAF to PAF may play a role in evoking prolonged inflammation in target organs or tissues.