Jauhonen Hanna-Mari, Kauppinen Anu, Paimela Tuomas, Laihia Jarmo K, Leino Lasse, Salminen Antero, Kaarniranta Kai
Department of Ophthalmology, Kuopio University Hospital, Kuopio, Finland.
Mol Vis. 2011;17:2311-7. Epub 2011 Aug 27.
The cornea is sensitive to ultraviolet B (UV-B) radiation-induced oxidative stress and inflammation. Its clinical manifestations are photokeratitis and climatic droplet keratopathy. Urocanic acid (UCA) is a major endogenous UV-absorbing chromophore in the epidermis and it is also an efficacious immunosuppressant. We have previously shown that cis-UCA can suppress UV-B-induced interleukin-6 and -8 secretion and cytotoxicity in human corneal epithelium (HCE) cells. In the current study, we further wanted to investigate the effects of cis-UCA on UV-B-induced inflammatory and apoptotic responses in HCE-2 cells, focusing on the nuclear factor kappa B (NF-κB) and AP-1 (subunits c-Fos and c-Jun) signaling pathways.
After exposing HCE-2 cells to UV-B and cis-UCA, DNA binding of c-Fos, c-Jun and NF-κB was measured with ELISA. In addition, the endogenous levels of phosphorylated stress-activated protein kinase/c-Jun N-terminal kinase (phospho-SAPK/JNK) and phospho-c-Jun were determined. The proliferative capacity of HCE-2 cells was also quantified, and the cytotoxicity of the cis-UCA and UV-B treatments was monitored by measuring the release of lactate dehydrogenase enzyme in the culture medium.
UV-B irradiation induced the binding of transcription factors c-Jun, c-Fos, and NF-κB to DNA. Cis-UCA inhibited the binding of c-Jun and c-Fos but not that of NF-κB. Moreover, UV-B increased the levels of phospho-c-Jun and phospho-JNK, and the expression of both was attenuated by cis-UCA. Cis-UCA also alleviated the UV-B-induced apoptosis and proliferative decline in human corneal cells.
The results from this study suggest that cis-UCA suppresses JNK signaling pathway, which provides potential for treating UV-B-induced inflammatory defects in human corneal cells.
角膜对紫外线B（UV-B）辐射诱导的氧化应激和炎症敏感。其临床表现为光角膜炎和气候性点状角膜病变。尿刊酸（UCA）是表皮中主要的内源性紫外线吸收发色团，也是一种有效的免疫抑制剂。我们之前已经表明，顺式UCA可以抑制UV-B诱导的人角膜上皮（HCE）细胞中白细胞介素-6和-8的分泌以及细胞毒性。在本研究中，我们进一步想研究顺式UCA对UV-B诱导的HCE-2细胞炎症和凋亡反应的影响，重点关注核因子κB（NF-κB）和AP-1（亚基c-Fos和c-Jun）信号通路。
将HCE-2细胞暴露于UV-B和顺式UCA后，用酶联免疫吸附测定法（ELISA）测量c-Fos、c-Jun和NF-κB的DNA结合情况。此外，还测定了磷酸化应激激活蛋白激酶/c-Jun氨基末端激酶（磷酸化-SAPK/JNK）和磷酸化c-Jun的内源性水平。还对HCE-2细胞的增殖能力进行了定量，并通过测量培养基中乳酸脱氢酶的释放来监测顺式UCA和UV-B处理的细胞毒性。
UV-B照射诱导转录因子c-Jun、c-Fos和NF-κB与DNA结合。顺式UCA抑制c-Jun和c-Fos的结合，但不抑制NF-κB的结合。此外，UV-B增加了磷酸化c-Jun和磷酸化JNK的水平，而顺式UCA减弱了两者的表达。顺式UCA还减轻了UV-B诱导的人角膜细胞凋亡和增殖下降。
本研究结果表明，顺式UCA抑制JNK信号通路，这为治疗UV-B诱导的人角膜细胞炎症缺陷提供了潜力。
