Inst. of Pharmacology, University Medical Center Benjamin Franklin
The Free University Berlin, Berlin,Germany
Study Information and Results:
Nitric oxide (NO) has been identified as an important mediator in various physiological and pathophysiological processes of the skin, such as regulation of blood flow, melanogenesis, wound healing, and hyperproliferative skin diseases. However, little is known about the role of NO in the human hair follicle and in hair cycling processes.
By measuring nitrate and nitrite levels in culture supernatants we demonstrate that dermal papilla cells (DPC) derived from human hair follicles spontaneously produce NO. This biomolecule is apparently formed by the endothelial isoform of nitric oxide synthase (NOS), which could be detected by reverse transcription polymerase chain reaction (RT-PCR) and immunological protein analysis.
Remarkably, basal NO level was markedly enhanced by stimulating DPC with 5-dihydrotestosterone (DHT) but not by testosterone.
Addition of N-(3-(aminomethyl)benzyl-acetamidine (1400W), a highly selective inhibitor of human inducible NOS, restrained the elevation of NO level induced by DHT. Analysis of androgen-stimulated cells on RNA as well as on protein level, respectively, confirmed the expression of inducible NOS. Thus, we suggest that endothelial NOS accounts as a constitutive enzyme for a physiological role of NO in hair follicle cells, whereas, upregulation of NO production by androgens via stimulating inducible NOS expression may indicate an involvement of NO in the pathogenesis of androgen-dependent hair loss, such as androgenetic alopecia.
These findings indicate that NO could be part of an important signaling pathway in the human hair follicle.