Water-Soluble Organic Germanium Promotes Both Cornified Cell Envelope Formation and Ceramide Synthesis in Cultured Keratinocytes

We investigated whether 3-(trihydroxygermyl) propionic acid increases the formation of cornified cell envelopes and the level of ceramide in cultured epidermal keratinocytes and in a three-dimensional human epidermis model. The activity and mRNA expression of transglutaminase were increased when 3-(trihydroxygermyl) propionic acid was added to the cell cultures. The formation of cornified cell envelopes in cultured human epidermal keratinocytes was increased in the presence of 3-(trihydroxygermyl) propionic acid. Ceramide levels were increased in the presence of 3-(trihydroxygermyl) propionic acid. The activity of serine palmitoyltransferase and mRNA levels of serine palmitoyltransferase 2 were also increased when 3-(trihydroxygermyl) propionic acid was added to the cultures. The extent to which ceramide levels were increased in the presence of 3-(trihydroxygermyl) propionic acid appeared dependent on serine palmitoyltransferase 2 upregulation. These results suggest that 3-(trihydroxygermyl) propionic acid can promote cornified cell envelope formation by inducing transglutaminase expression and ceramide synthesis via the induction of serine palmitoyltransferase activity, thereby improving the barrier function and moisture of dry, rough skin.