Abstract:
Ultraviolet B (UVB) (290-320nm) is the foremost cause of photoaging, sunburn, wrinkles and skin cancer. Photoprotection against harmful UVB rays is essential through various means including the use of skincare products. Carrageenan, a polysaccharide which makes up the cell wall of red algae mostly of the genera Chondrus, Eucheuma, Gigartina and Iridae is widely used excipient in cosmetics and skincare products. However, its effects on normal skin keratinocyte or as a photoprotection agent have not been well established. The primary aim of this study was to assess the photoprotective, apoptotic and mutagenic effects of carrageenan in UVB-induced immortalized normal human keratinocytes (HaCaT cells). Results showed that the number of cell killing increased linearly with UVB dose of 10, 50, 100, 222 and 1000 mJ/cm², indicating phototoxicity. Four isomers of carrageenan, namely iota 2 [ι (ІІ)], iota 5 [ι (V)], lambda (λ) and kappa (κ) carrageenan were used in this study. Vitamin E was used as positive control. Carrageenan did not exhibit cytotoxicity at dosages <200 µg/ml and it showed ability to quench 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. Carrageenan showed significant protection against detrimental effects of UVB-induced cell killing and reactive oxygen species (ROS) release based on 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) and 2',7'-dichlorfluorescein-diacetate (DCFH-DA) assays respectively. Apoptosis was significantly favoured than necrosis in carrageenan pre-treated cells after being exposed to 10, 50 and 100 mJ/cm² UVB. Carrageenan and vitamin E pre-treated cells showed lower interleukin 1-α release after irradiation compared to non-pre-treated cells, thereby reducing inflammation. Iota 2 [ι (II)] and lambda (λ) carrageenan significantly (p<0.05) reduced cyclobutane pyrimidine dimers (CPD) and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs). Exon 6 in all carrageenan pre-treated samples was not deleted. Exon 3 was not detected except in non-irradiated and carrageenan-pre-treated cells without irradiation. Carragenan did protect hprt gene but not via deletions of exon 3 or 6. The presence of sulphur moieties, vital minerals and ions is postulated to contribute to the photoprotective potential of carrageenan. The ability of carrageenan to protect against UVB as evidenced from the reduction ROS and photoproduct liberation has added new knowledge which warrants further investigations on its added value in photodamage prevention.
