Marine fungal DHICA as a UVB protectant: Assessment under in vitro and in vivo conditions

The present study explores UVB protective role of a melanin precursor namely DHICA (5,6- Dihydroxyindole-2-carboxylic acid) expressed by the marine imperfect fungus Aspergillus nidulans. In brief, A. nidulans grown in a modified growth medium for the period of 5 days at 25 °C under shaking conditions and the extracellular medium free from fungal biomass used for the extraction of DHICA. The extracted DHICA further exposed to partial purification and subjected to UVB protection studies using HaCaT cells and Balb/c mice independently. DHICA obtained in the present study found soluble in water. Experiments on HaCaT cell compatibility revealed nil cell death up to 500 μM concentration of DHICA. UVB protection studies under in vitro conditions emphasizes DHICA significantly protect HaCaT cells from UVB exposure by quenching the generated ROS, reducing cell apoptosis, maintain the cellular integrity and sequentially down regulating the LPO (Lipid peroxidation) and up-regulating the antioxidant enzyme (SOD (Superoxide Dismutase), Catalase, GPx (Glutathione peroxidase)) respectively. Further, experiments on cell cycle arrest analysis, gelatin zymography, and western blot analysis on COX-2 and TNF-alpha, IHC (Immunohistochemistry) on apoptotic markers (Bax, Bcl2) substantiate the protective role of DHICA. Furthermore, in vivo studies on BALB/c mice carried out and compared with the sunscreen cream with sun protective factor (SPF) of 20. Analysis of skin sections of experimental samples revealed that an appreciable reduction in the epidermal thickness of the skin samples of mice pre-exposed to DHICA followed by UVB exposure compared to UVB exposure alone. RT-PCR results on various inflammatory apoptotic markers also suggested that DHICA has UVB protective potential. The observations made in the present study explore the possible application of DHICA alone as a sun-protective agent for skin care.