[Possible use of zinc ions for anti-pigmentation and anti-wrinkling skin care].

Active studies of skin science have gradually clarified the underlying mechanisms of skin problems regarding skin beauty. The major skin problems are the alterations in appearance such as the hyperpigmentation and wrinkling caused by age. Those skin alterations are accelerated by solar light, particularly by ultraviolet rays, and it has been reported that reactive oxygen species (ROS) also involves in most of those processes. Thus, the reduction of oxidative stress induced by intracellular ROS is one approach to prevent and improve hyperpigmentation and wrinkling. Zn(2+) is well-known as an inducer of MT (metallothionein) and γGCS (γ-glutamyl cysteinyl synthetase: a rate-limiting enzyme of glutathione synthesis) via the up-regulation of their mRNAs through a metal transcription factor. The inductions of both MT and glutathione are expected to reduce oxidative stress due to the more effective scavenging of intracellular ROS. Several complexes of Zn(2+) and amino acids were synthesized and then evaluated for effects on MT synthesis in HaCaT keratinocytes. Among the complexes tested, we found a superior induction by a Zn(2+) glycine complex, Zn(Gly)(2). The anti-pigmentation and anti-wrinkling effects of Zn(Gly)(2) are introduced in this paper.