An accumulation of glucosylceramide in the stratum corneum due to attenuated activity of beta-glucocerebrosidase is associated with the early phase of UVB-induced alteration in cutaneous barrier function.

Epidermal glucosylceramide (GlcCer) metabolism is essential to the maintenance of skin homeostasis. Although exposure of the skin to ultraviolet (UV) radiation elicits dramatic physiological and biological changes in the epidermis attributable to barrier perturbation, wrinkle formation and inflammation, little is known about UV-induced changes in GlcCer metabolism. In this study, we have assessed beta-glucocerebrosidase (GlcCer'ase) activity in murine epidermis before and after a single UVB irradiation and have compared it with GlcCer and ceramide (Cer) levels. GlcCer'ase enzymatic activity was significantly suppressed in a dose-dependent manner one day after UVB (70 mJ/cm(2)) irradiation despite a significant increase in GlcCer'ase mRNA. The marked decrease in enzyme activity was followed by an accumulation of GlcCer in the stratum corneum, which peaked at day 2. This decreased level of GlcCer'ase activity returned to 80% of the control level by day 3 followed by a return of GlcCer level to the control level by day 4. In the whole epidermis, significant increases in Cer and GlcCer levels occurred on day 3 and on day 2, respectively. These results suggest that UVB irradiation dramatically affects the metabolism of GlcCer to Cer in the epidermis (including the stratum corneum) and that this may be closely associated with the early and minor phase of UVB-induced alteration in cutaneous barrier function.