The Photoprotective Effects of Almond Polyphenols and alpha-Tocopherol in a Three-Dimensional Human Skin Tissue Model.
Introduction: Almonds contain the nutrients alpha-tocopherol (AT) and almond polyphenols
(AP), which have shown promise as photoprotectants in skin. Our study aims were: 1)
assess the feasibility of nutrient studies in a 3-dimensinal (3D) human skin tissue
model and 2) determine the photoprotection of AT and AP from ultraviolet-A (UVA)
irradiation using this model. Methods and Mater... read moreials: AT or AP was applied to medium (25
and 5 uM, respectively) or topically (1 mg/cm2 and 14 ug/cm2, respectively). Optimal
dose and incubation time for each treatment were selected based on maximal nutrient
absorption while maintaining healthy skin tissue parameters (morphology, proliferation
and apoptosis). Skin absorption of AT was quantified in dermis and epidermis by HPLC
with UV detection after proteolysis and standard lipid extraction. After nutrient
incubation, tissues were UVA irradiated (35 J/cm2) and photodamage was assessed in
comparison to control tissues after 96 h. Photodamage was assessed by morphological
outcomes (basal layer organization, fibroblast presence, epidermal development) in
hemotoxylin and eosin-stained tissue cross-sections; proliferation of basal cells by
bromodeoxyuridine incorporation assay; apoptosis by TUNEL assay; differentiation by
cytokeratin-10 immunohistochemistry; and protein secretion of growth factors,
interleukin 1alpha; (IL-1alpha) and matrix metalloprotease (MMP)-2 by ELISA. Morphology
and differentiation comparisons were qualitative while semi-quantitative comparisons
were made for other outcome measures. Results: After 48 h medium incubation with AT,
dermal and epidermal concentrations of AT were approximately 3 and 30 ng/mg wet weight,
respectively. After 2 h incubation with topical AT, dermal and epidermal concentrations
of AT were 1 and 37 ug/mg wet weight, respectively. Nutrient treatments alone did not
induce changes in the percentage of apoptotic fibroblasts or morphologic parameters.
Topical AP tended to increase percent proliferating basal keratinocytes. Topical AT
treatment tended to stimulate hepatocyte growth factor (HGF), keratinocyte growth factor
(KGF) and IL-1alpha. However, UVA irradiation tended to increase apoptotic fibroblasts
and decrease proliferating basal keratinocytes, compared to control tissues. Negative
morphologic changes were also observed at 96 h after irradiation, including
disappearance of fibroblasts in the upper dermis, disorganized basal layer and less
developed epithelium. UVA delayed keratinocyte differentiation and tended to suppress
secretion of HGF and induce secretion of MMP-2. Tissues pretreated with all nutrient
treatments tended to have increased proliferating basal keratinocytes and decreased
apoptotic fibroblasts, compared to corresponding vehicle treated tissues after UVA
irradiation. Morphological deterioration was partially prevented and delayed
keratinocyte differentiation was attenuated by pretreatment of all nutrient applications
to UVA-irradiated tissue. Pretreatment with medium and topical AT tended to stimulate
HGF secretion, compared to corresponding vehicle controls after UVA irradiation.
Pretreatment with medium AT, topical AT and topical AP modulated MMP-2, compared to
corresponding vehicle controls after UVA irradiation. Conclusions: Our 3D skin tissue
model is a feasible tool to assess nutrient photoprotection. AT absorption into dermal
and epidermal compartments of this model was time and dose-dependent with concentrations
reaching those found in vivo. All four nutrient treatments provided some degree of
photoprotection from UVA as assessed by morphology, proliferation, apoptosis,
differentiation and protein secretion. These data may have positive implications for the
use of dietary and topical almond phytonutrients to prevent sun damage. This model
allows for further investigation into the mechanisms by which nutrition may play a role
in skin health.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Biochemical and Molecular Nutrition.
Advisor: Elizabeth Johnson.
Committee: C.-Y. Oliver Chen, Jonathan Garlick, and Xiang-Dong Wang.
Keyword: Nutrition.read less