Prostaglandin content in human middle ear effusions

Lipopolysaccharide induces proinflammatory cytokines and chemokines in experimental otitis media through the prostaglandin D2 receptor (DP)-dependent pathway

Otitis media is one of the most common and intractable ear diseases, and is the major cause of hearing loss, especially in children. Multiple factors affect the onset or development of otitis media. Prostaglandin D₂ is the major prostanoid involved in infection and allergy. However, the role of prostaglandin D₂ and prostaglandin D2 receptors on the pathogenesis of otitis media remains to be determined. Recent studies show that D prostanoid receptor (DP) and chemoattractant receptor-homologous molecule expressed on T helper type 2 (Th2) cells (CRTH2) are major prostaglandin D₂ receptors. In this study, homozygous DP single gene-deficient (DP⁻(/)⁻) mice, CRTH2 single gene-deficient (CRTH2⁻(/)⁻) mice and DP/CRTH2 double gene-deficient (DP⁻(/)⁻ CRTH2⁻(/)⁻) mice were used to investigate the role of prostaglandin D₂ and its receptors in otitis media. We demonstrate that prostaglandin D₂ is induced by lipopolysaccharide (LPS), a major component of Gram-negative bacteria, and that transtympanic injection of prostaglandin D₂ up-regulates macrophage inflammatory protein 2 (MIP-2), interleukin (IL)-1β and IL-6 in the middle ear. We also show that middle ear inflammatory reactions, including infiltration of inflammatory cells and expression of MIP-2, IL-1β and IL-6 induced by LPS, are reduced significantly in DP⁻(/)⁻ mice and DP⁻(/)⁻ CRTH2⁻(/)⁻ mice. CRTH2⁻(/)⁻ mice display inflammatory reactions similar to wild-type mice. These findings indicate that prostaglandin D₂ may play significant roles in LPS-induced experimental otitis media via DP.

Successful treatment of eosinophilic otitis media using ramatroban: Report of two cases

OBJECTIVE

The pathogenesis of eosinophilic otitis media is not yet fully understood. The purpose of this paper is to describe the clinical course of our two patients with eosinophilic otitis media and to discuss the pathogenesis and treatment of this intractable condition.

METHODS

Two cases of eosinophilic otitis media were treated with ramatroban.

RESULTS

The middle ear effusion has been well controlled in both patients for more than 1 year with minimal corticosteroid therapy.

CONCLUSIONS

Our experience suggests that the pathogenesis of eosinophilic otitis media is related to the pharmaceutical effects of ramatroban, i.e., inhibition of the thromboxane A2 receptor (TP) and the chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2).

Biochemical evidence of platelet-activating factor (PAF) in human middle ear effusions

Platelet-activating factor (PAF) is one of the most potent biological lipid mediators. This is especially true in relation to inflammation. In order to characterize the biochemical features of otitis media with effusion, the authors characterized and determined the concentration of the PAF present in human middle ear effusions obtained from 23 patients with otitis media with effusion. Each sample of middle ear effusion was divided into two groups: serous (n = 12) and mucoid effusions (n = 11). The platelet-activating factor activity was found mainly in mucoid middle ear effusions, and the amounts of PAF were higher in mucoid type (3.55 +/- 1.19 ng/g, mean +/- standard deviation [SD]) than in the serous type (0.44 +/- 0.19 ng/g). Phospholipids obtained from the middle ear effusions contained a large amount of lyso-platelet-activating factor, the biologically inactive precursor or breakdown product of platelet-activating factor. Based on these findings, it is suggested that platelet-activating factor may play an important role as a mediator of the inflammatory responses in the pathogenesis of otitis media with effusion.

Presence of dipeptidyl peptidase II, dipeptidyl peptidase IV, and prolyl endopeptidase in effusion from patients with serous otitis media

We have measured for the first time, using specific substrates and specific fluorometric analyses, activities of three pathophysiologically important peptidases, i.e., dipeptidyl peptidase II, dipeptidyl peptidase IV, and prolyl endopeptidase in effusions from 45 patients with chronic otitis media with effusion. In 20 patients, DPP II and DPP IV were assayed simultaneously in effusions and sera. Activity of PEP was also estimated in effusions and sera from 25 patients. The mean values (+/- SD) of DPP II and DPP IV (n = 45) and PEP (n = 25) in effusion from patients with OME were 0.020 +/- 0.007, 0.66 +/- 0.04, and 0.040 +/- 0.006 nmole/min/mg protein, and 0.21 +/- 0.01, 16.2 +/- 1.87, and 1.90 +/- 0.23 nmole/min/ml of effusion, respectively. The mean values (+/- SD) for DPP II, DPP IV, and PEP in sera were 2.82 +/- 0.18, 54.8 +/- 1.23, and 3.73 +/- 0.33 nmole/min/ml of serum, respectively, which were similar to our previously reported values. Activities of DPP II, DPP IV, and PEP of serous effusions were comparable to those in serum. However, there was no significant correlation between their activities in serum and effusion. This may suggest that the major source of these enzymes in effusions may not be serum but the cells in the middle ear.