Changes in environmental humidity affect the water-holding property of the stratum corneum and its free amino acid content, and the expression of filaggrin in the epidermis of hairless mice.
BACKGROUND
Seasonal changes affect the condition of skin and may trigger various cutaneous disorders.


OBJECTIVE
To clarify the effects of the environmental humidity on the skin pathology, we studied the effects of the humidity on a water-holding function of the stratum corneum.


METHODS
We evaluated the skin surface conductance, amino acid in the stratum corneum, and immunoreactivity of filaggrin of the epidermis of hairless mice kept in different environmental humidity.


RESULTS
Skin surface conductance in the stratum corneum of hairless mice 3-7 days after transfer from a humid environment (>80% relative humidity) to a dry (<10% relative humidity) environment, was significantly lower than that of the mice transferred from a normal environment (relative humidity=40-70%) to a dry environment. The free amino acid content in the stratum corneum significantly decreased 24 h after we transferred the mice from a normal to a dry condition, then it recovered to the original level within 3 days, while the mice transferred from a humid to a dry condition showed a significantly lower amino acid content even 7 days after the transfer. No obvious change was observed in the relative composition of the major components of the free amino acids during the experiments. Immunoreactivity of filaggrin, which is the main precursor of free amino acids in the stratum corneum, also became faint in the epidermis of the mice transferred from a humid or normal to a dry environment.


CONCLUSIONS
These results suggested that a drastic decrease in the environmental humidity reduced the total free amino acid generation and consequently induced skin surface dryness in the stratum corneum.
Katagiri
Chika
C
Shiseido Life Science Research Center, Yokohama, Japan.
Sato
Junko
J
Nomura
Junko
J
Denda
Mitsuhiro
M
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001834:Body Water / Q000378:metabolism*; D004777:Environment; D004817:Epidermis / Q000378:metabolism*; D000091344:Filaggrin Proteins; D006813:Humidity; D007150:Immunohistochemistry; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D051379:Mice; D008812:Mice, Hairless; D014018:Tissue Distribution
D000596:Amino Acids; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins