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  • Title: The effect of in vitro exposure to histamine on mononuclear leucocyte phosphodiesterase activity in atopic dermatitis.
    Author: Holden CA, Yuen CT, Coulson IH.
    Journal: Clin Exp Dermatol; 1989 May; 14(3):186-90. PubMed ID: 2556225.
    Abstract:
    Increased cyclic AMP (cAMP) phosphodiesterase activity (PDE) is present in the peripheral blood mononuclear leucocytes (MNL) of patients suffering from atopic dermatitis. It is unknown whether this is a primary abnormality or whether it is a consequence of MNL exposure to inflammatory mediators. In this study we have compared the responses of MNL PDE from untreated atopic dermatitis patients, patients on prolonged therapy with topical fluorinated steroids, and normal controls following exposure in vitro to low concentrations of histamine. We have confirmed that PDE activity is elevated in the MNL of patients suffering from atopic dermatitis who have used emollients only for 1 week. However, patients on therapy with topical fluorinated steroids have MNL PDE activity similar to normal controls in spite of the persistence of some active eczema. Exposure to histamine in vitro results in a similar increase of MNL PDE in untreated patients and normal controls. However, treated patients show no elevation of MNL PDE activity following in vitro histamine exposure. The results suggest that the normal MNL PDE values seen in patients treated with topical fluorinated steroids may not be the consequence of reduced cutaneous inflammation, but the result of a direct action of topical steroids on MNL. This action abrogates any in vitro response to histamine and presumably acts in a similar fashion in vivo.
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