P-09   SUPPRESSIVE EFFECT OF A NEUTRAL ENDOPEPTIDASE (EC 3.4.24.11) INHIBITOR ON HAIR GROWTH IN MICE AND IN HUMANS

S. Moriwaki, N. Tsuji, A. Ohuchi, Y. Shibuya, Y. Takema Biological Science Laboratories, Kao Corporation.

The purpose of this study was to identify inhibitors of neutral endopeptidase(NEP)which could inhibit its increased activity during the early anagen phase of hair growth, and to evaluate the effects on hair growth in mice and in humans. We screened NEP inhibitors from various botanical extracts. NEP enzyme activity was measured in samples prepared from cultured human skin fibroblasts using Glu-(Ala)2-Phe-4-methoxy-2-naphthylamine as a substrate. C3H mice were treated daily with the NEP inhibitor on their dorsal skin after depilation. Photographs of dorsal skin were taken at a standard magnification over the time course of the experiment, and areas of newly grown hair were measured by image analysis. Hair was also removed from human legs by depilatory tape, and the legs were treated daily with the NEP inhibitor. Numbers, length and thickness of newly grown hairs were measured by image analysis. A Ginger extract was identified as an effective NEP inhibitor. When we applied it to the depilated dorsal skin of C3H mice, hair growth was significantly suppressed compared with the vehicle control. In the case of human leg skin, the Ginger extract suppressed the hair number and hair thickness, but did not affect the hair length. These data show that an NEP inhibitor suppresses the growth of hair in mice and in humans, and suggest that NEP plays an important role in the process of hair regeneration.