The human skin has previously been described to be affected by light; however, the underlying mechanism remains unknown. OPN4 (melanopsin) expression was first identified in the skin of amphibians; however, whether it is also expressed and functioned in the human skin has not yet been identified. Here, we show that OPN4 was expressed in the human skin tissue and cultures of isolated keratinocytes, melanocytes and fibroblasts. Additionally, Ca2+ influx in vitro and ex vivo and phosphorylation of extracellular signal-regulated kinases 1/2 in human fibroblasts were observed by stimulation of blue light irradiation. Notably, our findings showed that this Ca2+ influx and phosphorylation of extracellular signal-regulated kinases 1/2 are promoted in an intensity-dependent manner, indicating that the light signal is converted to an intracellular signal via OPN4 in the human skin. Overall, in this study we showed that the human skin functions as a photoreceptor by demonstrating that in human skin, the photoreceptive protein was expressed, and photoreception was conducted via photoreceptive protein.

中文翻译：

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OPN4属于人类皮肤的感光系统。

先前已经描述了人类皮肤会受到光的影响。但是，其潜在机制仍然未知。首先在两栖动物的皮肤中鉴定出OPN4（黑素蛋白）的表达。但是，还没有确定它是否也在人的皮肤中表达和起作用。在这里，我们显示OPN4在人类皮肤组织和分离的角质形成细胞，黑素细胞和成纤维细胞的培养物中表达。另外，通过刺激蓝光，观察到了Ca 2+在体外和离体的流入以及人成纤维细胞中细胞外信号调节激酶1/2的磷酸化。值得注意的是，我们的研究结果表明，这种Ca2 +内流和细胞外信号调节激酶1/2的磷酸化以强度依赖的方式促进，表明光信号通过人皮肤中的OPN4转换为细胞内信号。总体而言，在本研究中，我们通过证明在人体皮肤中表达了感光蛋白，并通过感光蛋白进行了感光，从而表明人体皮肤具有感光功能。