Tocotrienols improve urban particulate matter-induced skin damages by regulating skin barrier function and ROS/MAPK signalling pathway in keratinocytes
Juvenia Rui En Neo, Zi Ning Teo, Jolene Shi En Yeo, Cassey Kai Sing Ng, Cheryl Wei Ling Teo, Yee Wei Ung, Wei Ney Yap
Abstract
Urban particulate matter (PM) is a major air pollutant that triggers molecular processes and is detrimental to the skin. We investigated the protective effects of tocotrienol-rich fraction (TRF) against urban PM-induced skin ageing, inflammation, and skin barrier dysfunction in human epidermal keratinocytes. Alpha-tocopherol (αTP) and retinoic acid (RA) were used as comparators. Our results showed that TRF significantly restored cell viability and alleviated increased intracellular reactive oxygen radicals in PM-treated keratinocytes. In addition, TRF significantly downregulated the activation of mitogen-activated protein kinases in PM-stimulated keratinocytes. This was substantiated by lower protein expression in the phosphorylation of extracellular signal-regulated kinase, Jun N-terminal kinase, and p38. This resulted in the inhibition of cyclooxygenase-2 expression, which is a downstream inflammatory mediator. TRF significantly protected skin barrier function upon exposure to PM by upregulating filaggrin, transglutaminase-1, and involucrin. In contrast, αTP and RA did not exhibit protective effects against skin damages in the PM-treated keratinocytes. Overall, this study suggests that TRF possesses antioxidant, anti-inflammatory, and skin barrier protective properties, and may serve as a potential ingredient in personal care and cosmeceutical industries to combat skin damage due to air pollution.