Interferon-γ Induces Senescence in Normal Human Melanocytes

Suiquan Wang,Miaoni Zhou,Aie Xu,Liangjun Lu,Weisong Hong,Yiping Zhu,Dongyin Liu,Fuquan Lin,Arianna L Kim

doi:10.1371/journal.pone.0093232

Suiquan Wang, Miaoni Zhou + Show 7 more

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https://doi.org/10.1371/journal.pone.0093232

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Abstract

BackgroundInterferon-γ (IFN-γ) plays an important role in the proceedings of vitiligo through recruiting lymphocytes to the lesional skin. However, the potential effects of IFN-γ on skin melanocytes and the subsequent contribution to the vitiligo pathogenesis are still unclear.ObjectiveTo investigate the effects of IFN-γ on viability and cellular functions of melanocytes.MethodsPrimary human melanocytes were treated with IFN-γ. Cell viability, apoptosis, cell cycle melanin content and intracellular reactive oxygen species (ROS) level were measured. mRNA expression was examined by real-time PCR. The release of interleukin 6 (IL-6) and heat shock protein 70 (HSP-70) was monitored by ELISA. β-galactosidase staining was utilized to evaluate melanocyte senescence.ResultsPersistent IFN-γ treatment induced viability loss, apoptosis, cell cycle arrest and senescence in melanocytes. Melanocyte senescence was characterized as the changes in pigmentation and morphology, as well as the increase of β-galactosidase activity. Increase of p21Cip1/Waf1 protein was evident in melanocytes after IFN-γ treatment. IFN-γ induction of senescence was attenuated by siRNAs against p21, Janus kinase 2 (JAK2) or signal transducer and activator of transcription 1 (STAT1), but not by JAK1 siRNA nor by p53 inhibitor pifithrin-α. IFN-γ treatment increased the accumulation of intracellular ROS in melanocytes, while ROS scavenger N-acetyl cysteine (NAC) effectively inhibited IFN-γ induced p21 expression and melanocyte senescence. IL-6 and HSP-70 release was significantly induced by IFN-γ treatment, which was largely inhibited by NAC. The increase of IL-6 and HSP-70 release could also be observed in senescent melanocytes.ConclusionIFN-γ can induce senescence in melanocytes and consequently enhance their immuno-competency, leading to a vitiligo-prone milieu.

Highlights

The loss of melanocytes is the cause of skin de-pigmentation in vitiligo, an acquired disfiguring skin disorder which affects 0.5–1% of the worldwide population [1]
The results showed that IFN-c upregulated mRNA level of tyrosinase (TYR) (Fig. 2B), Melan-A (Fig. 2D), melanocyte protein 17 (PMEL17) (Fig. 2E) and microphthalmia-associated transcription factor (MITF) (Fig. 2F)
Despite the existence of accumulating evidence supporting the pathogenic role of oxidative stress, there is a lack of convincing proof indicating the occurrence of cytotoxicity or apoptosis in vitiligo skin in vivo [33]

Summary

Introduction

The loss of melanocytes is the cause of skin de-pigmentation in vitiligo, an acquired disfiguring skin disorder which affects 0.5–1% of the worldwide population [1]. Melanocyte-specific CD8+T lymphocytes-mediated autoimmune response is currently highlighted to be associated with the destruction of the melanocytes in vitiligo [3,4,5]. Since cytokines and the related inflammatory mediators modulate the activation and skin homing of lymphocytes [6,7], they are the important research objectives for elucidating the onset of autoimmune vitiligo. Vitiligo is proposed to be a degenerative disorder, possibly caused by continuous stress which leads to apoptosis or senescence in melanocytes [10]. Interferon-c (IFN-c) plays an important role in the proceedings of vitiligo through recruiting lymphocytes to the lesional skin. The potential effects of IFN-c on skin melanocytes and the subsequent contribution to the vitiligo pathogenesis are still unclear

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Conclusion