Skin-Derived Precursors against UVB-Induced Apoptosis via Bcl-2 and Nrf2 Upregulation.

Jianqiao Zhong,Li Li

doi:10.1155/2016/6894743

Jianqiao Zhong, Li Li

Open Access

https://doi.org/10.1155/2016/6894743

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Abstract

Bcl-2 and Nrf2 are critical factors in protecting cells against UVB-induced apoptosis. Hair-follicle-bulge stem cells could resist ionization through Bcl-2 upregulation. Skin-derived precursors (SKPs) dwelling on the bulge may be against UVB irradiation. Initially, SKPs were isolated and identified. Then, SKPs were exposed to UVB and grew in medium for 24 hours. CCK-8 assay, TUNEL, and Ki67 staining evaluated cells apoptosis/proliferation, while SA-βgal staining evaluated cells senescence and pH2AX immunostaining evaluated DNA damage. Meanwhile, Bcl-2, Nrf2, HO-1, Bax, and Bak expressions were assessed by qRT-PCR and western blot. Two weeks later, floating spheres appeared and were identified as SKPs. After UVB radiation, SKPs maintained spherical colonies and outnumbered unirradiated ones, showing high Ki67 expression and low TUNEL, SA-βgal, and pH2AX expression. Fibroblasts (FBs), however, displayed deformation, senescence, and reduction, with increased TUNEL, SA-βgal, and pH2AX expression. Moreover, Bcl-2 and Nrf2 mRNA expression were significantly higher than Bak and Bax in irradiated SKPs. Conversely, Bcl-2 and Nrf2 mRNA levels greatly decreased compared with Bax and Bak in irradiated FBs. Interestingly, SKPs showed higher protein levels of Bcl-2, Nrf2, and HO-1 than FBs. SKPs exert a beneficial effect on resisting UVB-induced apoptosis, which may be associated with Bcl-2 and Nrf2 upregulation.

Highlights

Cumulative Ultraviolet B (UVB) radiation can damage the skin, encourage photoaging, and even induce tumorigenesis [1, 2]
After 3-week induction, skinderived precursors (SKPs) could differentiate into osteocytes and adipocytes (Figures 3(a) and 3(b)); this phenomenon, did not occur when these cells were cultured in medium without inducer (Figures 3(c) and 3(d))
In our previous [23] and current studies, we both successfully isolated SKP-shaped spheres from the dermis and identified them as SKPs based on the fact that these cells present the key markers such as Nestin and Sox2 and have the ability to differentiate into osteocytes or adipocyte

Summary

Introduction

Cumulative Ultraviolet B (UVB) radiation can damage the skin, encourage photoaging, and even induce tumorigenesis [1, 2]. Apoptosis and repair mechanisms are involved in UVBinduced DNA damage or apoptosis, in which Bcl-2 and transcription factor NF-E2-related factor (Nrf2) play pivotally protective roles [3, 4]. Both of them are critical genes to alleviate UV-associated skin damage or skin aging [3, 5, 6]. Some reports indicated that after hair-follicle-bulge stem cells (SCs) or embryonic stem (ES) cells were exposed to a certain dose of ionizing radiation (IR), cells biological activity and viability were rarely affected, let alone their differentiation or senescence, the mechanism of which was associated with Bcl-2 upregulation [16, 17]. In order to test this hypothesis, we isolated SKPs from mouse dermis, observed the changes of SKPs after exposure to UVB, and detected the levels of bcl family and Nrf

Materials and Methods

Reagent Setup

SKPs Identification

UVB Irradiation on Cells

Results and Discussion

Conclusions