Sunburn Cell Formation, Dendritic Cell Migration, and Immunomodulatory Factor Production After Solar-Simulated Irradiation of Sunscreen-Treated Human Skin Explants In Vitro

Abstract

Using human skin explants, we investigated the effects of two different sunscreen preparations containing a chemical UVB filter alone [sun protection factor (SPF) 5.2] or UVA+UVB filter [SPF 6.2] on sunburn cell formation, dendritic cell (DC) migration, CD86- and CD1a-positive cell number, and tumor necrosis factor alpha (TNFalpha) and interleukin (IL)-1, IL-10, and IL-12 production in the skin after irradiation with different doses of solar-simulated UV radiation. Sunscreen- or placebo-treated skin explants were irradiated with solar-simulated UV radiation at 0.5, 1, and 2 minimal erythematous dose equivalents (MEDE) (as determined in an in vivo human study) multiplied by the SPF of the placebo or sunscreens. After irradiation, skin explants were floated on RMPI medium for 48 h. Cells that had emigrated and the skin explants were histologically analyzed, and the soluble mediators were measured in the supernatants by ELISA. Exposure to UV radiation led to concentration-dependent increases in sunburn cell formation and TNFalpha production but a concentration-dependent decrease in DC migration and CD86- and CD1a-positive cell number in the epidermis. Both chemical sunscreens protected against those alterations. The immunoprotective capacity of the sunscreens correlated with their SPF but was independent of the sunscreens' UVA protection capacity, suggesting that UVA is not a major factor for immunosuppression under the conditions used in the model. UV irradiation did not significantly affect the vitality of emigrated DC; the expression of HLA, CD80, and lag on emigrated cells; the number of CD1a-positive cells in the dermis; or the production of IL-1, IL-10, and IL-12. We conclude that our model may be useful in determining the immunoprotective capacity of sunscreens.

Endogenous Phospholipid Metabolite Containing Topical Product Inhibits Ultraviolet Light-Induced Inflammation and DNA Damage in Human Skin

“…Sunscreens are applied 15-20 min before irradiation, a time interval which is sufficient to exert their effect [7,[25][26][27] . As there was no suppression of skin erythema when the Physiogel AI was applied 20 min before UV irradiation we suggest that these substances have no direct sunblocker effects.…”

Decreased human epidermal antigen-presenting cell activity after ultraviolet A exposure: dose–response effects and protection by sunscreens

“…1,2 The role of UVA (wavelengths 320-400 nm) in these processes and the protection afforded by sunscreens are still debated. [3][4][5][6] Indeed, some studies showed that UVA radiation was immunosuppressive, [7][8][9][10][11][12] whereas others suggested that it had no effects on immune functions 3,[13][14][15] or was immunoprotective. 3,16,17 Potential explanation for these conflicting results mainly lies in the source and doses of UVA as well as the protocols used to evaluate the cutaneous immune effects.…”

“…Ultraviolet (UV) radiation‐mediated immunosuppression is thought to be one of the most important factors for the development of skin cancer 1,2 . The role of UVA (wavelengths 320–400 nm) in these processes and the protection afforded by sunscreens are still debated 3–6 . Indeed, some studies showed that UVA radiation was immunosuppressive, 7–12 whereas others suggested that it had no effects on immune functions 3,13–15 or was immunoprotective 3,16,17 .…”

Radiation Sources Providing Increased UVNUVB Ratios Induce Photoprotection Dependent on the UVA Dose in Hairless Mice

“…However, a small number of studies provide the opposite evidence. For example, a comparison in human skin explants of the protection provided by two sunscreens matched for sun protection factor but with differing UVA transmission found that neither the number of SSUV‐induced apoptotic sunburn cells, the expression of the cytokines IL‐1, IL‐10, IL‐12 or TNF‐α nor the migration of epidermal dendritic cells differed (17). Furthermore, Liardet et al .…”