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. 2019 Jul 5;8(7):207.
doi: 10.3390/antiox8070207.

Sesamol Inhibited Ultraviolet Radiation-Induced Hyperpigmentation and Damage in C57BL/6 Mouse Skin

Ya-Jhen You  1 , Po-Yuan Wu  2   3 , Yi-Jung Liu  1   4 , Chien-Wei Hou  5 , Chin-Sheng Wu  1 , Kuo-Ching Wen  1 , Chien-Yih Lin  6 , Hsiu-Mei Chiang  7   8
Affiliations

Sesamol Inhibited Ultraviolet Radiation-Induced Hyperpigmentation and Damage in C57BL/6 Mouse Skin

Ya-Jhen You et al. Antioxidants (Basel). .

Abstract

Melanin is synthesized through a series of oxidative reactions initiated with tyrosine and catalyzed by melanogenesis-related proteins such as tyrosinase, tyrosinase-related protein-1 (TRP-1), dopachrome tautomerase (TRP-2), and microphthalmia-associated transcription factor (MITF). Our previous study demonstrated that sesamol inhibited melanin synthesis through the inhibition of the melanocortin 1 receptor (MC1R)/MITF/tyrosinase pathway in B16F10 cells. In this study, sesamol was applied to C57BL/6 mouse skin to understand its activity with respect to skin pigmentation. The results indicated that ultraviolet (UV) B-induced hyperpigmentation in the C57BL/6 mouse skin was significantly reduced by topical application of sesamol for 4 weeks. Sesamol reduced the melanin index and melanin content of the skin. In addition, sesamol elevated the brightness (L* value) of the skin. Sesamol also reduced UVB-induced hyperplasia of epidermis and collagen degradation in dermis. In immunohistochemical staining, topical application of sesamol reduced UVB-induced tyrosinase, TRP-1, TRP-2, and MITF expression in the epidermis of the skin. These results demonstrated that sesamol is a potent depigmenting agent in the animal model.

Keywords: melanogenesis; microphthalmia-associated transcription factor; sesamol; tyrosinase; tyrosinase-related protein-1.

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Conflict of interest statement

The authors state no conflict of interest.

Figures

Figure 1
Figure 1
Implementation process of animal experimentation.
Figure 2
Figure 2
Body weight variation of C57BL/6 mice receiving topical application of sesamol during the 4-week study period.
Figure 3
Figure 3
Effect of sesamol on the melanin index of C57BL/6 mouse ear skin post UVB irradiation in the fourth week. UVB irradiation increased the melanin index, whereas topical application of sesamol decreased the melanin index. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB-irradiated group: ***, p < 0.001.).
Figure 4
Figure 4
Effect of sesamol on L* values (brightness) of C57BL/6 mouse ear skin after UVB irradiation in the fourth week. UVB irradiation decreased L* values, whereas topical application of sesamol increased L* values. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 5
Figure 5
Photographs illustrate the skin lightening effect of sesamol after topical application for 4 weeks on UVB-irradiation-induced hyperpigmentation in C57BL/6 mice.
Figure 6
Figure 6
Effect of sesamol on UVB-irradiation-induced hyperpigmentation in C57BL/6 mice ear skin. Melanin pigments (as indicated by the arrows) were stained black by Fontana-Masson staining (400X). Topical application of sesamol reduced melanin pigments. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 6
Figure 6
Effect of sesamol on UVB-irradiation-induced hyperpigmentation in C57BL/6 mice ear skin. Melanin pigments (as indicated by the arrows) were stained black by Fontana-Masson staining (400X). Topical application of sesamol reduced melanin pigments. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 7
Figure 7
Effect of sesamol on UVB-irradiation-induced histopathological changes in C57BL/6 mouse ear skin. Tissue morphology was visualized through hematoxylin and eosin (H&E) staining (400X). UVB irradiation caused hyperplasia in the skin, whereas topical application of sesamol once a day to the ear skin reduced the thickness of the epidermis. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 7
Figure 7
Effect of sesamol on UVB-irradiation-induced histopathological changes in C57BL/6 mouse ear skin. Tissue morphology was visualized through hematoxylin and eosin (H&E) staining (400X). UVB irradiation caused hyperplasia in the skin, whereas topical application of sesamol once a day to the ear skin reduced the thickness of the epidermis. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 8
Figure 8
Light micrographs of histological sections stained with Masson’s trichrome in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. The collagen content decreased in the UVB-irradiated group, whereas topical application of sesamol once a day to the ear skin restored the collagen level.
Figure 8
Figure 8
Light micrographs of histological sections stained with Masson’s trichrome in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. The collagen content decreased in the UVB-irradiated group, whereas topical application of sesamol once a day to the ear skin restored the collagen level.
Figure 9
Figure 9
Light micrographs of histological sections stained with antibodies against tyrosinase in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. The tyrosinase level increased in the UVB-irradiated group, whereas topical application of sesamol reduced the effect. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 9
Figure 9
Light micrographs of histological sections stained with antibodies against tyrosinase in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. The tyrosinase level increased in the UVB-irradiated group, whereas topical application of sesamol reduced the effect. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 10
Figure 10
Light micrographs of histological sections stained with tyrosinase-related protein-1 (TRP-1) in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. The TRP-1 level increased in the UVB-irradiated group, whereas topical application of sesamol reduced the effect. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 10
Figure 10
Light micrographs of histological sections stained with tyrosinase-related protein-1 (TRP-1) in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. The TRP-1 level increased in the UVB-irradiated group, whereas topical application of sesamol reduced the effect. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 11
Figure 11
Light micrographs of histological sections stained with dopachrome tautomerase (TRP-2) in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. The TRP-2 level increased in the UVB-irradiated group, whereas topical application of sesamol reduced the effect. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 11
Figure 11
Light micrographs of histological sections stained with dopachrome tautomerase (TRP-2) in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. The TRP-2 level increased in the UVB-irradiated group, whereas topical application of sesamol reduced the effect. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: ***, p < 0.001.).
Figure 12
Figure 12
Light micrographs of histological sections stained with microphthalmia-associated transcription factor (MITF) in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: *, p < 0.05, **, p < 0.01, ***, p < 0.001.).
Figure 12
Figure 12
Light micrographs of histological sections stained with microphthalmia-associated transcription factor (MITF) in UVB-irradiated C57BL/6 mice that received topical application of sesamol once a day to the ear skin. (Significant difference versus control: ###, p < 0.001. Significant difference versus UVB treated group: *, p < 0.05, **, p < 0.01, ***, p < 0.001.).
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