A role of melatonin in neuroectodermal-mesodermal interactions: the hair follicle synthesizes melatonin and expresses functional melatonin receptors.
Since mammalian skin expresses the enzymatic apparatus for melatonin synthesis, it may be an extrapineal site of melatonin synthesis. However, evidence is still lacking that this is really the case in situ. Here, we demonstrate melatonin-like immunoreactivity (IR) in the outer root sheath (ORS) of mouse and human hair follicles (HFs), which corresponds to melatonin, as shown by radioimmunoassay and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The melatonin concentration in organ-cultured mouse skin, mouse vibrissae follicles, and human scalp HFs far exceeds the respective melatonin serum level and is significantly increased ex vivo by stimulation with norepinephrine (NE), the key stimulus for pineal melatonin synthesis. By real-time PCR, transcripts for the melatonin membrane receptor MT2 and for the nuclear mediator of melatonin signaling, retinoid orphan receptor alpha (ROR)alpha, are detectable in murine back skin. Transcript levels for these receptors fluctuate in a hair cycle-dependent manner, and are maximal during apoptosis-driven HF regression (catagen). Melatonin may play a role in hair cycle regulation, since its receptors (MT2 and RORalpha) are expressed in murine skin in a hair cycle-dependent manner, and because it inhibits keratinocyte apoptosis and down-regulates ERalpha expression. Therefore, the HF is both, a prominent extrapineal melatonin source, and an important peripheral melatonin target tissue. Regulated intrafollicular melatonin synthesis and signaling may play a previously unrecognized role in the endogenous controls of hair growth, for example, by modulating keratinocyte apoptosis during catagen and by desensitizing the HF to estrogen signaling. As a prototypic neuroectodermal-mesodermal interaction model, the HF can be exploited for dissecting the obscure role of melatonin in such interactions in peripheral tissues.
Kobayashi
Hiromi
H
Department of Dermatology, University Hospital Schleswig-Holstein, Campus Lübeck, University of Lübeck, Lübeck, Germany.
Kromminga
Arno
A
Dunlop
Thomas W
TW
Tychsen
Birte
B
Conrad
Franziska
F
Suzuki
Naoto
N
Memezawa
Ai
A
Bettermann
Albrecht
A
Aiba
Setsuya
S
Carlberg
Carsten
C
Paus
Ralf
R
D000818:Animals; D017209:Apoptosis; D002853:Chromatography, Liquid; D015536:Down-Regulation; D004475:Ectoderm / Q000378:metabolism*; D047628:Estrogen Receptor alpha / Q000378:metabolism; D005260:Female; D006197:Hair / Q000502:physiology; D018859:Hair Follicle / Q000196:embryology* / Q000378:metabolism; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000378:metabolism; D013058:Mass Spectrometry; D008550:Melatonin / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008648:Mesoderm / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism*; D009924:Organ Culture Techniques / Q000379:methods; D012333:RNA, Messenger / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases; D057050:Receptor Tyrosine Kinase-like Orphan Receptors; D011956:Receptors, Cell Surface / Q000378:metabolism; D044094:Receptors, Melatonin / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D012867:Skin / Q000166:cytology / Q000378:metabolism
D047628:Estrogen Receptor alpha; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D044094:Receptors, Melatonin; C078716:ROR1 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D057050:Receptor Tyrosine Kinase-like Orphan Receptors; D008550:Melatonin