Department of Molecular Medicine, College of Medicine, Keimyung University, Dalseo-gu, Daegu 704-701, Republic of Korea.
Int J Mol Med. 2014 Mar;33(3):695-702. doi: 10.3892/ijmm.2013.1595. Epub 2013 Dec 19.
Evidence suggests that solar ultraviolet B (UVB) radiation inhibits growth and/or induces apoptosis of human skin cells. However, mechanisms underlying the UVB-induced anti-survival and pro-apoptotic effects on human skin cells remain unclear. In this study, we investigated the effect of UVB radiation on survival and apoptosis of HaCaT human keratinocytes and determined possible molecular, cellular and signaling mechanisms including cross-regulation, which are responsible for the UVB's anti-survival and/or pro-apoptotic effects. The results showed that UVB radiation at 400 mJ/cm² for 8 h largely decreased cell survival and induced DNA fragmentation, an index of apoptosis, in HaCaT human keratinocytes. On a mechanistic level, UVB radiation triggered the activation of caspase-9, cleavage of poly(ADP-ribose) polymerase, and downregulation of myeloid cell leukemia-1 (Mcl-1), human inhibitor of apoptosis protein-1 (HIAP-1), X-linked IAP (XIAP), and protein kinase B (PKB), but did not affect the expression of B-cell lymphoma-2 in HaCaT cells. UVB radiation also upregulated the expression of glucose-regulated protein 78 (GRP78), an endoplasmic reticulum (ER) stress marker, in HaCaT cells. Of note, results of pharmacological inhibition studies have demonstrated that pretreatment with z-VAD-fmk, a pan-caspase inhibitor strongly attenuated UVB-induced apoptosis, the activation of caspase-9, downregulation of Mcl-1, XIAP and PKB (but not HIAP-1), and upregulation of GRP78, while pretreatment with GF109203 or GO6983, pan-PKC inhibitors, substantially blocked the UVB-induced reduction of cell survival, activation of caspase-9, downregulation of HIAP-1, XIAP, and PKB (but not Mcl-1), and GRP78 upregulation in HaCaT cells. Collectively, these results demonstrated that UVB has strong anti-survival and pro-apoptotic effects on HaCaT cells and the effects were largely mediated via the activation of caspase-9 and protein kinase Cs, which subsequently downregulated PKB, XIAP, HIAP-1 and Mcl-1, and triggered ER stress.
有证据表明，太阳紫外线 B（UVB）辐射会抑制人体皮肤细胞的生长和/或诱导其凋亡。然而，UVB 诱导的人体皮肤细胞抗生存和促凋亡作用的机制尚不清楚。在这项研究中，我们研究了 UVB 辐射对 HaCaT 人角质形成细胞生存和凋亡的影响，并确定了可能的分子、细胞和信号转导机制，包括交叉调节，这些机制负责 UVB 的抗生存和/或促凋亡作用。结果表明，400mJ/cm² 的 UVB 辐射 8 小时后，大大降低了 HaCaT 人角质形成细胞的存活率，并诱导了 DNA 片段化，这是凋亡的一个指标。在机制水平上，UVB 辐射触发了半胱天冬酶-9 的激活、多聚（ADP-核糖）聚合酶的切割以及髓细胞白血病-1（Mcl-1）、人凋亡蛋白抑制剂-1（HIAP-1）、X 连锁凋亡抑制剂（XIAP）和蛋白激酶 B（PKB）的下调，但不影响 HaCaT 细胞中 B 细胞淋巴瘤-2 的表达。UVB 辐射还上调了内质网（ER）应激标志物葡萄糖调节蛋白 78（GRP78）在 HaCaT 细胞中的表达。值得注意的是，药理学抑制研究的结果表明，用广谱半胱天冬酶抑制剂 z-VAD-fmk 预处理强烈减弱了 UVB 诱导的凋亡、半胱天冬酶-9 的激活、Mcl-1、XIAP 和 PKB（但不是 HIAP-1）的下调以及 GRP78 的上调，而用 pan-PKC 抑制剂 GF109203 或 GO6983 预处理则大大阻断了 UVB 诱导的细胞存活率降低、半胱天冬酶-9 激活、HIAP-1、XIAP 和 PKB（但不是 Mcl-1）下调以及 HaCaT 细胞中 GRP78 上调。总之，这些结果表明，UVB 对 HaCaT 细胞具有很强的抗生存和促凋亡作用，这些作用主要通过半胱天冬酶-9 和蛋白激酶 C 的激活介导，随后下调 PKB、XIAP、HIAP-1 和 Mcl-1，并引发内质网应激。
