Separovic D, Mann K J, Oleinick N L
Department of Radiation Oncology, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4942, USA.
Photochem Photobiol. 1998 Jul;68(1):101-9.
Ceramide, a stress-induced second messenger, has been associated with apoptosis in several malignant and non-malignant cell lines. We have shown that photodynamic treatment (PDT), using the phthalocyanine photosensitizer Pc 4 (HOSiPcOSi[CH3]2[CH2]3N[CH3]2), causes increased ceramide generation and subsequent induction of apoptosis in L5178Y-R (LY-R) mouse lymphoma cells. To test further if ceramide generation accompanies photocytotoxicity, we treated various cell lines with a PDT dose producing a 99-99.9% loss of clonogenicity. Like LY-R cells, human leukemia (U937) cells underwent rapid DNA fragmentation initiating within 1 h after PDT. Similarly, Chinese hamster ovary (CHO) cells showed rapid DNA laddering, beginning 1 h following the treatment. In contrast, mouse radiation-induced fibrosarcoma (RIF-1) cells showed no apoptosis within 24 h post-PDT, as judged by the absence of 50 kbp and oligonucleosome size DNA fragments, as well as no annexin V binding to cells with preserved membrane integrity. Using the same doses of PDT, we observed a time-dependent ceramide accumulation in all three cell lines. While a significant increase in ceramide levels was reached within 1 and 10 min in U937 and CHO cells, respectively, elevated ceramide production was measured only after 30 min in RIF-1 cells. In addition, exogenous N-acetyl-sphingosine was able to mimic PDT-induced apoptosis in U937 and CHO cells. We suggest that ceramide accumulation is associated with PDT-induced apoptosis and photocytotoxicity.
神经酰胺是一种应激诱导的第二信使，已被证明与多种恶性和非恶性细胞系的凋亡有关。我们已经表明，使用酞菁光敏剂Pc 4（HOSiPcOSi[CH3]2[CH2]3N[CH3]2）的光动力治疗（PDT）可导致L5178Y-R（LY-R）小鼠淋巴瘤细胞中神经酰胺生成增加，并随后诱导细胞凋亡。为了进一步测试神经酰胺生成是否伴随光细胞毒性，我们用产生99-99.9%克隆形成能力丧失的PDT剂量处理了各种细胞系。与LY-R细胞一样，人白血病（U937）细胞在PDT后1小时内开始迅速发生DNA片段化。同样，中国仓鼠卵巢（CHO）细胞在处理后1小时开始出现快速的DNA梯状条带。相比之下，小鼠辐射诱导的纤维肉瘤（RIF-1）细胞在PDT后24小时内未显示凋亡，这通过缺乏50 kbp和寡核小体大小的DNA片段以及膜联蛋白V未与膜完整性保留的细胞结合来判断。使用相同剂量的PDT，我们在所有三种细胞系中观察到了时间依赖性的神经酰胺积累。虽然U937和CHO细胞分别在1分钟和10分钟内神经酰胺水平显著增加，但RIF-1细胞仅在30分钟后才检测到神经酰胺生成增加。此外，可以模拟PDT诱导的U937和CHO细胞凋亡。我们认为神经酰胺积累与PDT诱导的细胞凋亡和光细胞毒性有关。
