Eosinophil Supernatant Causes Hyperresponsiveness of Airway Smooth Muscle in Guinea Pig Trachea

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Abstract
To study the role of eosinophils in airway hyperresponsiveness, we studied the effect of supernatant obtained from activated eosinophils on the responses of isolated guinea pig tracheal smooth muscle segments to histamine. Eosinophils obtained from guinea pig peritoneal fluid were purified and activated with Ca2+ ionophore A23187 using a two-stage reaction. Supernatant obtained from different eosinophil cell numbers (3 × 105 to 107 cells) did not alter resting tension but potentiated the contractile response to histamine in a cell number-dependent fashion. Thus, at a cell number of 107, the supernatant decreased the mean (± SE) log histamine concentration producing 50% of maximum contraction significantly from a control value of −5.62 ± 0.10 to −5.99 ± 0.07 M (p < 0.05). The potentiating effect of the supernatant (107 cells) was not altered by either removal of tracheal epithelium or by pretreatment with indomethacin when cells were activated. However, pretreatment with AA 861 completely inhibited the supernatant (107 cells)-induced potentiating effect associated with inhibition of leukotriene C4, D4, and E4 release in the supernatant. The concentrations of exogenous authentic leukotrienes chosen to match concentrations in the supernatant mimicked the supernatant-induced potentiating response to histamine. These results suggest that leukotrienes released from eosinophils cause hyperresponsiveness of airway smooth muscle in vitro.