Japanese Cedar (Cryptomeria japonica) pollen allergen induces elevation of intracellular calcium in human keratinocytes and impairs epidermal barrier function of human skin ex vivo.

Cry j1 is the major peptide allergen of Japanese cedar (Sugi), Cryptomeria japonica. Since some allergens disrupt epidermal permeability barrier homeostasis, we hypothesized that Cry j1 might have a similar effect. Intracellular calcium level in cultured human keratinocytes was measured with a ratiometric fluorescent probe, Fura-2 AM. Application of Cry j1 significantly increased the intracellular calcium level of keratinocytes, and this increase was inhibited by trypsin inhibitor or a protease-activated receptor 2 (PAR-2) antagonist. We found that Cry j1 itself did not show protease activity, but application of Cry j1 to cultured keratinocytes induced a rapid (within 30 s) and transient increase of protease activity in the medium. This transient increase was blocked by trypsin inhibitor or PAR-2 antagonist. The effect of Cry j1 on transepidermal water loss (TEWL) of cultured human skin was measured in the presence and absence of a trypsin inhibitor and PAR-2 antagonist. Cry j1 significantly impaired the barrier function of human skin ex vivo, and this action was blocked by co-application of trypsin inhibitor or PAR-2 antagonist. Our results suggested that interaction of Cry j1 with epidermal keratinocytes leads to the activation of PAR-2, which induces elevation of intracellular calcium and disruption of barrier function. Blocking the interaction of Cry j1 with epidermal keratinocytes might ameliorate allergic reaction and prevent disruption of epidermal permeability barrier homeostasis.