Photoprotective effect of a Polyopes affinis (Harvey) Kawaguchi and Wang (Halymeniaceae)-derived ethanol extract on human keratinocytes

Abstract

Purpose: To investigate the photoprotective effect of the ethanol extract of the red marine alga, Polyopes affinis (PAE) against ultraviolet B (UVB) radiation on cultured human keratinocytes. Methods: The 2′,7′-dichlorodihydrofluorescein diacetate method was used to detect intracellular reactive oxygen species (ROS) generated by H2O2 treatment or UVB radiation. Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Superoxide anion or hydroxyl radical was detected using an electron spin resonance spectrometer after reaction with the nitrone spin trap. Lipid peroxidation was assayed by determining the level of 8-isoprostane. Protein carbonyl formation was determined using a protein carbonyl ELISA kit. The degree of oxidative DNA damage was determined using an alkaline comet assay. Apoptosis was assessed by apoptotic bodies and DNA fragmentation. Results: PAE significantly scavenged the free radical 1,1-diphenyl-2-picrylhydrazyl, as well as hydrogen peroxide- and UVB-induced intracellular ROS. Furthermore, PAE showed 23 % scavenging effect of the superoxide anion and 33 % of the hydroxyl radical. PAE also absorbed UVB rays in the 280 - 320 nm range. PAE significantly decreased cellular damage resulting from UVB-induced oxidative stress to lipids, proteins, and DNA. Furthermore, PAE-treated keratinocytes showed significant reduction in UVB-induced apoptosis, as exemplified by fewer apoptotic bodies and reduced DNA fragmentation. Conclusion: These results suggest that PAE protects keratinocytes against UVB-induced oxidative stress by absorbing UVB rays and scavenging ROS, thereby reducing injury to cellular constituents. © Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria.