Wu Shengnan, Xing Da, Gao Xuejuan, Chen Wei R
MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, South China Normal University, Guangzhou, China.
J Cell Physiol. 2009 Mar;218(3):603-11. doi: 10.1002/jcp.21636.
High fluence low-power laser irradiation (HF-LPLI) can induce cell apoptosis via the mitochondria/caspase-3 pathway. Here, we further investigated the mechanism involved in the apoptotic process in human lung adenocarcinoma cells (ASTC-a-1) at a laser irradiation fluence of 120 J/cm(2) (633 nm). Cytochrome c release was ascribed to mitochondrial permeability transition (MPT) because the release was prevented by cyclosporine (CsA), a specific inhibitor of MPT. Furthermore, mitochondrial permeability for calcein (approximately 620 Da) was another evidence for the MPT induction under HF-LPLI treatment. A high-level intracellular reactive oxygen species (ROS) generation was observed after irradiation. The photodynamically produced ROS caused onset of MPT, as the ROS scavenger docosahexaenoic acid (DHA) prevented the MPT. However, CsA failed to prevented cell death induced by HF-LPLI, indicating the existence of other signaling pathways. Following laser irradiation, Bax activation occurred after mitochondrial depolarization and cytochrome c release, indicating Bax activation was a downstream event. In the presence of CsA, Bax was still activated at the end-stage of apoptotic process caused by HF-LPLI, suggesting that Bax was involved in an alternative-signaling pathway, which was independent of MPT. Under HF-LPLI treatment, cell viabilities due to pre-treatment with DHA, CsA, or Bax small interfering RNA (siRNA) demonstrated that the MPT signaling pathway was dominant, while Bax signaling pathway was secondary, and more importantly ROS mediated both pathways. Taken together, these results showed that HF-LPLI induced cell apoptosis via the CsA-sensitive MPT, which was ROS-dependent. Furthermore, there existed a secondary signaling pathway through Bax activation. The observed link between MPT and triggering ROS could be a fundamental phenomenon in HF-LPLI-induced cell apoptosis.
高能量密度低功率激光照射（HF-LPLI）可通过线粒体/半胱天冬酶-3途径诱导细胞凋亡。在此，我们进一步研究了在激光照射能量密度为120 J/cm²（633 nm）时，人肺腺癌细胞（ASTC-a-1）凋亡过程中的相关机制。细胞色素c的释放归因于线粒体通透性转换（MPT），因为该释放可被环孢素（CsA）（一种MPT的特异性抑制剂）所抑制。此外，钙黄绿素（约620 Da）的线粒体通透性是HF-LPLI处理下MPT诱导的另一证据。照射后观察到细胞内活性氧（ROS）大量生成。光动力产生的ROS导致MPT的发生，因为ROS清除剂二十二碳六烯酸（DHA）可阻止MPT。然而，CsA未能阻止HF-LPLI诱导的细胞死亡，表明存在其他信号通路。激光照射后，Bax激活发生在线粒体去极化和细胞色素c释放之后，表明Bax激活是一个下游事件。在存在CsA的情况下，Bax在HF-LPLI引起的凋亡过程末期仍被激活，这表明Bax参与了一条独立于MPT的替代信号通路。在HF-LPLI处理下，用DHA、CsA或Bax小干扰RNA（siRNA）预处理后的细胞活力表明，MPT信号通路占主导，而Bax信号通路是次要的，更重要的是ROS介导了这两条通路。综上所述，这些结果表明HF-LPLI通过CsA敏感的MPT诱导细胞凋亡，该过程依赖于ROS。此外，还存在一条通过Bax激活的次要信号通路。观察到的MPT与触发ROS之间的联系可能是HF-LPLI诱导细胞凋亡的一个基本现象。
