Role of imbalance of eicosanoid pathways and staphylococcal superantigens in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a multifactorial disease of the upper airways with a high prevalence (approximately 11%) in the general population. Different immune and inflammatory mechanisms are involved in its pathogenesis. Alterations in the arachidonic acid pathway (leading to an imbalanced production of eicosanoids) have been linked to the pathophysiology of different diseases especially nasal polyposis, asthma, and aspirin-exacerbated respiratory disease. Furthermore, viral and bacterial infections have been identified as important factors amplifying the pro-inflammatory reactions in these pathologies. This review summarizes the impact of an imbalance in the eicosanoid pathway and the effect of Staphylococcus aureus enterotoxins on the regulation of the pro-inflammatory network in CRS and their translation into disease severity.

Clinical and immunological determinants of severe/refractory asthma (SRA): association with Staphylococcal superantigen-specific IgE antibodies

BACKGROUND

Demographic and immunological determinants of severe refractory asthma (SRA) are not well characterized. Because Staphylococcus aureus enterotoxins with superantigenic activity have been associated with upper and lower airway inflammation, we aimed to evaluate the association of sensitization to Staphylococcal enterotoxins with asthma severity and various asthma phenotypes.

METHODS

The study included 109 patients with SRA diagnosed according to the American Thoracic Society Workshop 2000, and 101 patients with nonsevere asthma, followed for at least 12 months. Specific IgE to Staphylococcus enterotoxins and total IgE and eosinophil cationic protein concentrations were measured in serum with immunoassays.

FINDINGS

A significant risk for severe asthma was associated with female gender [Odds Ratio (OR) = 2.04], history of wheezing in childhood (OR = 2.47), presence of hypersensitivity to aspirin (OR = 1.96) and with body mass index (OR = 3.08). The mean level of enterotoxin-specific IgE was 3-fold higher in patients with severe asthma when compared to patients with nonsevere asthma (P = 0.01). Serum-specific IgE to enterotoxins was significantly associated with low respiratory function parameters (FEV₁, FEV₁/FVC and MEF 25/75) and increased airway reversibility in response to albuterol. The presence of specific IgE to enterotoxin carried a significant risk for patients to have serum total IgE level above 100 kU/l (OR = 7.84).

INTERPRETATION

Specific immunological response to enterotoxins is associated with clinical and immunological parameters of asthma severity, suggesting a role for Staphylococcal enterotoxins in the asthma pathogenesis.

CRTH2 mediates the activation of human Th2 cells in response to PGD(2) released from IgE/anti-IgE treated nasal polyp tissue

BACKGROUND

Mast cells release mediators upon stimulation that contribute to the pathogenesis of chronic airway disease, including the recruitment and activation of Th2 lymphocytes. The objective was to determine the involvement of prostaglandin D(2) (PGD(2)) and its receptors in the chemotaxis of Th2 cells, using nasal polyp tissue.

METHODS

Tissue explants from ten patients with nasal polyposis were incubated with RPMI alone or RPMI containing IgE/anti-IgE for 30 min. Some samples were treated with diclofenac to inhibit the production of PGD(2). Supernatants were assayed for PGD(2) content and for their ability to promote human Th2 cell chemotaxis in the presence and absence of a CRTH2 antagonist. Transcript levels of D protanoid receptor type 1 (DP(1)), chemoattractant receptor-homologous receptor expressed on Th2 cells (CRTH2) and PGD(2) synthase were analysed by real time PCR.

RESULTS

Increased release of PGD(2) by nasal polyp tissue treated with IgE/anti-IgE was significantly inhibited by preincubation of the tissue with diclofenac. Transcript levels of PGD(2) synthase, DP(1) and CRTH2 receptors increased after stimulation with IgE/anti-IgE. Supernatants from IgE/anti-IgE-stimulated nasal polyp tissue caused significantly increased chemotaxis of Th2 cells. The levels of PGD(2) produced and the degree of Th2 cell chemotaxis were highly correlated. Diclofenac inhibited the production of Th2 cell chemotactic activity, and the chemotactic effect of the supernatant on Th2 cells was inhibited by the CRTH2 antagonist ramatroban.

CONCLUSION

These data suggest that in immunologically activated nasal polyp tissue, PGD(2) produced by mast cells promotes the migration of Th2 cells through a CRTH2 dependent mechanism.