MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
Free Radic Biol Med. 2011 Jul 1;51(1):53-68. doi: 10.1016/j.freeradbiomed.2011.03.042. Epub 2011 Apr 8.
Lysosomal photosensitizers have been used in photodynamic therapy. The combination of such photosensitizers and light causes lysosomal photodamage, inducing cell death. Lysosomal disruption can lead to apoptosis but its signaling pathways remain to be elucidated. In this study, N-aspartyl chlorin e6 (NPe6), an effective photosensitizer that preferentially accumulates in lysosomes, was used to study the mechanism of apoptosis caused by lysosomal photodamage. Apoptosis in living human lung adenocarcinoma cells (ASTC-a-1) after NPe6-photodynamic treatment (NPe6-PDT) was studied using real-time single-cell analysis. Our results demonstrated that NPe6-PDT induced rapid generation of reactive oxygen species (ROS). The photodynamically produced ROS caused a rapid destruction of lysosomes, leading to release of cathepsins, and the ROS scavengers vitamin C and NAC prevent the effects. Then the following spatiotemporal sequence of cellular events was observed during cell apoptosis: Bcl-2-associated X protein (Bax) activation, cytochrome c release, and caspase-9/-3 activation. Importantly, the activation of Bax proved to be a crucial event in this apoptotic machinery, because suppressing the endogenous Bax using siRNA could significantly inhibit cytochrome c release and caspase-9/-3 activation and protect the cell from death. In conclusion, this study demonstrates that PDT with lysosomal photosensitizer induces Bax activation and subsequently initiates the mitochondrial apoptotic pathway.
溶酶体光敏剂已被用于光动力疗法。这种光敏剂与光的结合会导致溶酶体光损伤，从而诱导细胞死亡。溶酶体破裂可导致细胞凋亡，但其中的信号通路仍有待阐明。在这项研究中，N-天冬氨酰氯乙酮（NPe6）是一种有效的光敏剂，它优先积聚在溶酶体中，用于研究溶酶体光损伤引起的细胞凋亡机制。使用实时单细胞分析研究了 NPe6 光动力治疗（NPe6-PDT）后活的人肺腺癌细胞（ASTC-a-1）中的细胞凋亡。我们的结果表明，NPe6-PDT 诱导了活性氧（ROS）的快速产生。光动力产生的 ROS 迅速破坏溶酶体，导致组织蛋白酶的释放，而 ROS 清除剂维生素 C 和 NAC 可预防这些影响。然后在细胞凋亡过程中观察到以下细胞事件的时空顺序：Bcl-2 相关 X 蛋白（Bax）的激活、细胞色素 c 的释放和 caspase-9/-3 的激活。重要的是，Bax 的激活被证明是这个凋亡机制中的一个关键事件，因为使用 siRNA 抑制内源性 Bax 可以显著抑制细胞色素 c 的释放和 caspase-9/-3 的激活，并保护细胞免于死亡。总之，这项研究表明，溶酶体光敏剂的光动力疗法诱导 Bax 激活，随后引发线粒体凋亡途径。
