Biophysical and morphological changes in the stratum corneum lipids induced by UVB irradiation.

Background: UV irradiation induces a variety of responses in the epidermis, including sunburn cell formation, epidermal hyperplasia, and epidermal permeability barrier disruption.

Objective: The aim of present study was to assess the effects of UVB irradiation in the intercellular lipids in murine stratum corneum.

Methods: Adult hairless mice were exposed to a single UVB dose (0.15 J/cm(2)), the Fourier transform infrared (FT-IR) spectroscopic study was performed to investigate the effect on the biophysical changes in the stratum corneum lipids, barrier function was monitored by transepidermal water loss (TEWL) measurement, and the morphological alterations of stratum corneum was examined by electron microscopy using ruthenium tetroxide postfixation.

Results: The FT-IR spectroscopic study revealed that there was the shift to higher wavenumbers of the symmetric and asymmetric stretching peaks near 2850 and 2920 cm(-1) respectively at days 3-4 after a single UVB irradiation, reflecting to the increase in motional freedom of lipids hydrocarbon chains, call as disordering of lipids. Moreover, A single UVB irradiation also caused a significant increase in TEWL, the increase in TEWL began after 2 days and peaked at day 4. Electron microscopic observations revealed that marked morphological abnormalities in the intercellular domains, including abnormal profile of lamellar granules and its contents at the interface between stratum corneum and stratum granulosum and the persistence of the nuclei in the stratum corneum. Moreover, the separated fragmentary lipid lamellae, excessive numbers of lamellae in stacks, both the elongated and enlarged lacuna as well as the extracellular whorls were present within the widen space of the stratum corneum.

Conclusion: The both of biophysical and morphological changes of the stratum corneum lipids may reflect to the mechanisms of perturbation of the epidermal permeability barrier induced by UVB irradiation.