Expression of substance P receptors in normal and psoriatic skin

Recently, substance P receptors (SPR) have been detected in neonatal foreskin. Our purpose was to determine the expression of SPR in other localizations than neonatal foreskin. As SP has been implicated in the pathogenesis of inflammatory cutaneous lesions, we wondered whether SPR localization was modified in psoriatic lesions. In normal skin, SP binding sites were detected using biotinylated SP and abrogated by a specific NK1 antagonist (spantide) on blood vessels, sweat glands and hair follicles. In the normal epidermis, SPR were usually observed on granular layers but may also be observed on other cell layers. The SP binding processed on cultured keratinocytes demonstrated that SPR were expressed in the epidermis, except basal cell layers, confirming that keratinocytes constitutively express SPR. In skin lesions of psoriatic patients, SP binding sites were expressed on the uppermost keratinocytes which are not granular cells, and seem to be overexpressed. Our results raise the question of the role of SPR on psoriatic keratinocytes.