Abstract
Hibiscus syriacus L. is distributed widely throughout Eastern and Southern Asia and considered as the national flower of South Korea. The extraction of several plant parts of H. syriacus L. is currently used as a natural remedy for several diseases, including breast and lung cancer, microbial infection, and chronic inflammation. However, the effect of the anthocyanin extract of H. syriacus L. petals (PS) in oxidative stress conditions has not been studied. In this study, we evaluated the cytoprotective effect of PS against H2O2-induced oxidative stress in HaCaT keratinocytes. In this study, we found that PS significantly inhibited H2O2-induced apoptosis of HaCaT keratinocytes. We also revealed that PS mediated-cytoprotective effect was associated with the increased expression of heme oxygenase-1 (HO-1) arising from the activation of nuclear factor erythroid 2-related factor-2 (Nrf2). PS also decreased H2O2-induced excessive intracellular ROS generation and restored H2O2-induced mitochondrial depolarization through the downregulation of mitochondrial ROS production. Furthermore, H2O2-induced Bax and caspase-3 expression was markedly abolished in the presence of PS. The inhibition of HO-1 by zinc protoporphyrin significantly attenuated the cytoprotective effect of PS in H2O2-treated HaCaT keratinocytes along with ROS generation, indicating that HO-1 crucially affects PS-mediated cytoprotective properties. Collectively, our results suggested that, under H2O2-mediated oxidative stress conditions, PS sustained a normal level of mitochondrial membrane potential and ROS generation in HaCaT keratinocytes by activating the Nrf2/HO-1 axis, exerting cytoprotective effects against oxidative stress.
Highlights
Keratinocytes are the predominant cell type of the epidermis, and primarily play an important role in the formation of cellular barriers against environmental stresses such as ultraviolet (UV) radiation, heat, water loss, and chemical irritation [1]
To evaluate whether the cytoprotective effect of PS results from anti-oxidative activity, we investigated the expression of anti-apoptotic proteins, such as poly (ADP-ribose) polymerase (PARP) and B-cell lymphoma 2 (Bcl-2), and pro-apoptotic proteins, such as Bcl-2 associated protein x (Bax) and caspase-3 in H2 O2 -treated HaCaT keratinocytes
Consistent with data on the nuclear translocation of nuclear factor erythroid 2-related factor-2 (Nrf2), PS considerably increased the phosphorylation of PI3K and Akt. These results suggested that PS activates the nuclear translocation of Nrf2 in HaCaT keratinocytes by stimulating
Summary
Keratinocytes are the predominant cell type of the epidermis, and primarily play an important role in the formation of cellular barriers against environmental stresses such as ultraviolet (UV) radiation, heat, water loss, and chemical irritation [1]. During skin damage and infections, keratinocytes recognize damage- and pathogen-associated molecular patterns through the pattern recognition receptors, resulting in the promotion of wound healing and the transduction of danger signals [2]. The death or damage of keratinocytes in the epidermis causes the loss of the first line immune defense system. Redox balance has been shown to maintain the proper cellular and tissue homeostasis in keratinocytes through the regulation of reactive oxygen species (ROS). ROS stimulates both wound healing and the immune defense mechanisms in keratinocytes; an excess of ROS promotes oxidative stress in keratinocytes, causing cellular damage and apoptosis [4]. Antioxidants help keratinocytes to maintain normal function in oxidative stress conditions by suppressing ROS generation
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