Condition of asthma in patients with asthma and concomitant seasonal allergic rhinitis (SAR) deteriorates during the Japanese cedar pollen (JCP) season. However, the underlying mechanisms remain unclear.
We analyzed seasonal variations in eicosanoid levels in the airways of patients with asthma and concomitant SAR sensitized to JCP (N = 29, BA-SAR-JCP group) and those not sensitized (N = 13, BA-AR-non-JCP group) during the JCP season. The association between changes in eicosanoid concentrations and pulmonary function was assessed. Exhaled breath condensate (EBC) was collected, and pulmonary function tests were performed during the JCP and non-JCP seasons. The cysteinyl leukotriene (CysLT), thromboxane B (TXB), prostaglandin D-methoxime (PGD-MOX), and leukotriene B (LTB) levels in the collected EBC were measured via enzyme-linked immunosorbent immunoassays.
The log CysLT levels significantly increased in the BA-SAR-JCP group during the JCP season compared with the non-JCP season (1.78 ± 0.55, 1.39 ± 0.63 pg/mL, mean ± standard deviation, respectively, p = 0.01) and those in the BA-AR-non-JCP group during the JCP season (1.39 ± 0.38 pg/mL, p = 0.04). Moreover, the log TXB levels seemed to increase. However, the log LTB and log PGD-MOX levels did not increase. The changes in the log CysLT levels during the two seasons were negatively correlated to forced expiratory volume in one second (FEV) in the BA-SAR-JCP group (r = -0.52, p < 0.01).
In the BA-SAR-JCP group, seasonal increases in eicosanoid levels in the airway likely promoted deterioration in pulmonary function despite optimal maintenance treatment.

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