Ibuki Yuko, Goto Rensuke
Laboratory of Radiation Biology, Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, Japan.
Photochem Photobiol. 2002 May;75(5):495-502. doi: 10.1562/0031-8655(2002)075<0495:aeibdw>2.0.co;2.
Cells receive signals for survival as well as for death, and the balance between the two ultimately determines the fate of the cells. UV-triggered apoptotic signaling has been well documented, whereas UV-induced survival effects have received little attention. We have reported previously that UVB irradiation prevented apoptosis, which is partly dependent on activation of the phosphatidylinositol 3-kinase (PI3-kinase)-Akt pathway (Ibuki Y. and Goto, R. [2000] Biochem. Biophys. Res. Commun. 279, 872-878). In this study, antiapoptotic effects and survival signals of UV with different wavelength ranges, UVA, UVB and UVC, were examined. NIH3T3 cells showed apoptotic cell death by detachment from the extracellular matrix under serum-free conditions, which was prevented by all wavelengths. However, the effect of UVA was less than those of UVB and UVC, as determined by metabolism of fluoresceine diacetate and the appearance of chromatin-condensed cells. Furthermore, the effects of three wavelengths of UV on the apoptotic pathway upstream of the nuclear signals were examined. Reduction of mitochondrial transmembrane potential (delta psi) and activation of caspase-9 and -3 were suppressed by all three wavelengths of UV, showing wavelength-dependent effects as mentioned previously. Shorter wavelengths showed stronger inhibitory effects on caspase-8 activity. The P13-kinase inhibitor wortmannin partially inhibited the UVB- and UVC-induced suppression of apoptosis but not the inhibitory effect of UVA. Furthermore, normal delta psi maintained by UVA was not changed in the presence of wortmannin, but those by UVB and UVC were reduced. Akt was clearly phosphorylated by all three wavelengths. The phosphorylation by UVB and UVC was completely inhibited by addition of wortmannin, but that by UVA was not, in agreement with the results of survival and of delta psi. These results suggested the existence of two different survival pathways leading to suppression of apoptosis, one for UVA that is independent of the PI3-kinase-Akt pathway and the other for UVB and UVC that is dependent on this pathway.
细胞会接收存活信号以及死亡信号，而这两者之间的平衡最终决定了细胞的命运。紫外线引发的凋亡信号已得到充分记录，然而紫外线诱导的存活效应却很少受到关注。我们之前曾报道，中波紫外线（UVB）照射可预防细胞凋亡，这在一定程度上依赖于磷脂酰肌醇3-激酶（PI3-激酶）-Akt信号通路的激活（Ibuki Y.和Goto, R. [2000] Biochem. Biophys. Res. Commun. 279, 872 - 878）。在本研究中，我们检测了不同波长范围的紫外线，即长波紫外线（UVA）、中波紫外线（UVB）和短波紫外线（UVC）的抗凋亡效应和存活信号。在无血清条件下，NIH3T3细胞会因与细胞外基质脱离而发生凋亡性细胞死亡，而所有波长的紫外线均可预防这种情况。然而，通过二乙酸荧光素代谢和染色质浓缩细胞的出现确定，UVA的作用小于UVB和UVC。此外，我们还检测了三种波长的紫外线对核信号上游凋亡途径的影响。所有三种波长的紫外线均抑制了线粒体跨膜电位（Δψ）的降低以及半胱天冬酶-9和-3的激活，呈现出如前所述的波长依赖性效应。较短波长对半胱天冬酶-8活性的抑制作用更强。PI3-激酶抑制剂渥曼青霉素部分抑制了UVB和UVC诱导的凋亡抑制，但对UVA的抑制作用无效。此外，在渥曼青霉素存在的情况下，UVA维持的正常Δψ没有变化，但UVB和UVC维持的Δψ降低。所有三种波长均能使Akt明显磷酸化。渥曼青霉素的添加完全抑制了UVB和UVC诱导的磷酸化，但对UVA诱导的磷酸化没有抑制作用，这与存活和Δψ的结果一致。这些结果表明存在两种不同的导致凋亡抑制的存活途径，一种是UVA所特有的，不依赖于PI3-激酶-Akt信号通路，另一种是UVB和UVC所共有的，依赖于该信号通路。
