Dihydrotestosterone Induces Keratinocyte Apoptosis by Activating ERK Signaling

BACKGROUND/AIM: Dihydrotestosterone (DHT) plays a critical role in hair loss. However, research on DHT has mostly focused on its effects on dermal papilla cells expressing androgen receptor (AR). Accordingly, studies on the roles of DHT in keratinocytes, which undergo active proliferation and cell death during hair cycle progression, are lacking. This study investigated the effects of DHT on extracellular signal-regulated kinase (ERK) and Wnt/β-catenin signaling, which are involved in cell proliferation, cell death, and hair cycle regulation. MATERIALS AND METHODS: Changes in human immortalized keratinocyte (HaCaT) cell proliferation were investigated by WST assay after treatment with DHT without fetal bovine serum. Apoptosis induction was investigated using Hoechst33342 staining, immunoblotting, and Annexin V/7AAD staining. The involvement of specific signaling pathways was analyzed using WST assay with AR antagonist, Ras/Raf/mitogen-activated protein kinase kinase (MEK) inhibitor, or glycogen synthase kinase-3β (GSK3β) inhibitors. Changes in mRNA levels were analyzed using quantitative reverse transcription-polymerase chain reaction. RESULTS: apoptosis induction. The AR antagonist bicalutamide had no effect on DHT-induced proliferation inhibition. DHT treatment increased phospho-ERK levels, which was attenuated by pretreatment with the MEK inhibitor U0126. Pretreatment with U0126 suppressed DHT-induced increase in cleaved caspase-3 and poly (ADP-ribose) polymerase (PARP) levels. U0126 restored DHT-induced decrease in HaCaT cell proliferation. Further, DHT increased dickkopf-1 and CXXC-type zinc finger protein 5 levels but decreased total and cytoplasmic β-catenin levels. Moreover, GSK3β inhibitors (LiCl and CHIR99021) did not prevent DHT-induced proliferation inhibition. CONCLUSION: DHT induces apoptosis in HaCaT cells through ERK activation, independently of AR, and Wnt/β-catenin pathways. These findings provide a basis for understanding the effects of DHT on hair follicle keratinocytes.