Prevention of ultraviolet radiation‑induced immunosuppression by sunscreen in Candida albicans‑induced delayed‑type hypersensitivity

Abstract

Ultraviolet (UV) radiation-induced immunosuppression leading to skin cancer has received increased attention in previous years. The present study aimed to investigate the immunoprotection offered by Anthelios sunscreen in a mouse model of Candida albicans‑induced delayed‑type hypersensitivity. Anthelios sunscreen was applied to the skin on the dorsal skin of BALB/c mice treated with a sub‑erythema dose of solar‑simulated radiation. Delayed‑type hypersensitivity was induced by immunization with Candida albicans. Changes in the skin thickness of the foot pads were measured, and immunosuppression rates were also evaluated. The expression levels of CD207, CD80 and CD86 in the Langerhans cells were semi‑quantitatively detected using Western blotting and immunohistochemical assays. The delayed‑type hypersensitivity mouse model was successfully established. The minimal erythema doses of UVA and UVB exposure to the mice were 2,000 and 145 mJ/cm2, respectively. The immunosuppression rates in the sunscreen group and non‑sunscreen group were 24.39 and 65.85%, respectively (P<0.01). The results of the Western blotting and immunohistochemistry showed that the expression levels of CD207 (P<0.01), CD80 (P<0.05) and CD86 (P<0.01) were higher in the sunscreen group, compared with those in the non‑sunscreen group. UV exposure reduced Candida albicans antigen‑induced delayed‑type hypersensitivity. Anthelios sunscreen was found to protect the skin from immunosuppression through the activation of epidermal Langerhans cells.

Figure 1

Schematic diagram showing the experimental design of the present study. Mice were randomly divided into four groups (n=10): Group A (sunscreen+UV+immunization), Group B (UV+immunization), Group C (positive control) and Group D (negative control). Mice were anesthetized and prepared for UV radiation. For the UV groups, 0.7X minimal erythema dose was repeatedly administered to the individual animals for 5 days. On the fifth day, the mice were immunized by subcutaneous injection of 10⁷ formalin-fixed Candida albicans to each foot pad. Additional mice were treated with UV treatment only or immunization only as a negative control and positive control, respectively. At 24 h-post challenge, the thickness of each foot was measured using vernier calipers and the mean footpad swelling for each mouse was calculated. The increase in skin thickness from that in the negative control was used to normalize data. UV, ultraviolet.

Figure 2

Dose-response curve showing the increase in skin thickness against UVR. Mice were randomly divided into a sunscreen group and a non-sunscreen group. Each group was divided into six subgroups (n=10), each treated with a different dose of UVR. Prior to UVR, an area of ~8 cm² of the dorsal skin of the mice was covered with, or without, sunscreen (2 mg/cm²). The dorsal skin was then exposed to a sunlight system at various ssUVR doses (UVA, 1,000–3,500 mJ/cm²; UVB, 30–1,200 mJ/cm²) for 60 sec. (A) The increases in skin thickness were plotted to obtain the response curves against various ssUVR doses under a constant sunscreen dose. The minimum dose of ssUVR required to cause a significant increase (^*P<0.05) in skin thickness in the sunscreen group, compared with the non-sunscreen group, was used for further experiments, (factor of 0.7). (B) The immunosuppresion rate of the sunscreen and non-sunscreen groups were 24.39 and 65.85%, respectively. ^*P<0.05 vs. sunscreen (+). The data are presented as the mean ± standard deviation. UVR, ultraviolet radiation. ssUVR, solar-stimulated UVR.

Figure 3

Comparison of the increase in skin thickness between different groups. Mice in treated with or without sunscreen were injected with formalin-fixed Candida albicans. At 24 h-post challenge, the thickness of each foot was measured using vernier calipers and the mean footpad swelling of each mouse was calculated as follows: Mean swelling = (left foot swelling + right foot swelling) / 2. The increase in skin thickness from that of the negative control was used to normalize data. Data are presented as the mean ± standard deviation. ^#P<0.01, compared with the non-sunscreen group. UV, ultraviolet.

Figure 4

Western blot analyses of the expression levels of CD207, CD80 and CD86. Compared with the positive control, the expression level of (A) CD207, (B) CD80 and (C) CD86 in the non-sunscreen group was significantly decreased, whereas the use of sunscreen upregulated the expression of CD207, CD80 and CD86 (P<0.05). Data are presented as the mean ± standard deviation. ^*P<0.05 and ^#P<0.01, compared with the non-sunscreen group. UV, ultraviolet.

Figure 5

Immunohistochemical analysis demonstrating the expression levels of CD207, CD80 and CD86. CD207, CD80 and CD86 were highly expressed in the positive control (immunization group), and markedly suppressed by UVR treatment, while the expression levels of these immune molecules were recovered by the sunscreen treatment. Sections were examined by light microscopy (magnification, ×100; scale bar=50 µm). UVR, ultraviolet radiation.