PROTECTIVE EFFECT OF NUTRACEUTICALS AGAINST UVB-INDUCED DAMAGE IN HUMAN KERATINOCYTES

Ultraviolet B (UVB) radiation is a major external stimulus that initiates a cascade of damaging events in the human skin. It causes oxidative stress, DNA damage, inflammation, mitochondrial dysfunction, and disrupts the epidermal homeostasis and cytoskeletal organization. These events finally contribute to photoaging and photocarcinogenesis by initiation of a multistep process. Human keratinocytes respond to these events by activating cell cycle arrest and cell death, thus acting as the first line of defense. Therefore, HaCaT cells were used as an in vitro model in this study. Nutraceuticals have gained attention as a photoprotective strategy due to their high levels of phenolic and flavonoid compounds. In this study, we have explored the protective effect of LifeMel™ honey (LMH) on HaCaT cells exposed to UVB irradiation (180 mJ/cm²), including its chemical characterization using HPLC-MS/MS and spectrophotometric assays to evaluate its polyphenolic composition and antioxidant capacity. LMH is derived from bees feeding on sixteen medicinal herbs, reported to have antioxidant and anti-inflammatory properties. We have found that LMH is non-cytotoxic to human keratinocytes. Moreover, it significantly protected the cells from UVB-induced loss of viability and oxidative stress. Immunofluorescence analysis also demonstrated the altered distribution of cellular Nrf2 after UVB exposure and LMH pre-treatment. Furthermore, LMH pretreatment protected the cytoskeletal organization and mitochondria from UVB exposure, as observed by confocal microscopy. Ultrastructural analysis using a scanning and transmission electron microscope (SEM/TEM) also confirmed the preservation of cell membrane integrity and the structure of intracellular organelles. Besides, LMH downregulated the expression of UVB-induced pro-inflammatory cytokines (IL1β, IL-6, IL-8, and TNF-α), suggesting mitigation of inflammatory responses. Flow cytometry analysis revealed that LMH modulates the UVB-induced cell death and cell cycle arrest. LMH does not inhibit cell death but promotes a more regulated cellular response. Overall, this study explains the anti-inflammatory, antioxidative, and cytoprotective effects of LMH against UVB-induced damage, establishing it as a promising choice for skin photoprotection and dermo-nutrition. Further in vivo studies are required to substantiate these results.