# Rosmarinic Acid Protects Skin Keratinocytes from Particulate Matter 2.5-Induced Apoptosis

## TL;DR

Rosmarinic acid protects skin cells from damage caused by PM2.5 pollution by reducing oxidative stress and preventing cell death.

## Contribution

This study reveals rosmarinic acid's novel protective mechanism against PM2.5-induced apoptosis in keratinocytes.

## Key findings

- Rosmarinic acid reduced PM2.5-induced lipid peroxidation, protein carbonylation, and DNA damage.
- RA attenuated apoptosis by modulating Bcl-2 family proteins and MAPK signaling pathway activation.
- RA and MAPK inhibitors both showed protective effects against PM2.5-induced cell death.

## Abstract

Background: The exposure of the human skin to particulate matter 2.5 (PM2.5) results in adverse health outcomes, such as skin aging, wrinkle formation, pigment spots, and atopic dermatitis. It has previously been shown that rosmarinic acid (RA) can protect keratinocytes from ultraviolet B radiation by enhancing cellular antioxidant systems and reducing oxidative damage; however, its protective action against the adverse effects of PM2.5 on skin cells remains unclear. Therefore, in this study, we explored the mechanism underlying the protective effects of RA against PM2.5-mediated oxidative stress in HaCaT keratinocytes.

Methods: HaCaT keratinocytes were pretreated with RA and exposed to PM2.5. Thereafter, reactive oxygen species (ROS) production, protein carbonylation, lipid peroxidation, DNA damage, and cellular apoptosis were investigated using various methods, including confocal microscopy, western blot analysis, and flow cytometry.

Results: RA significantly inhibited PM2.5-induced lipid peroxidation, protein carbonylation, DNA damage, increases in intracellular Ca2+ level, and mitochondrial depolarization. It also significantly attenuated PM2.5-induced apoptosis by downregulating Bcl-2-associated X, cleaved caspase-9, and cleaved caspase-3 protein levels, while upregulating B-cell lymphoma 2 protein level. Further, our results indicated that PM2.5-induced apoptosis was associated with the activation of the mitogen-activated protein kinase (MAPK) signaling pathway and that MAPK inhibitors as well as RA exhibited protective effects against PM2.5-induced apoptosis.

Conclusion: RA protected HaCaT cells from PM2.5-induced apoptosis by lowering oxidative stress.