Virág L, Szabó C
Inotek Corporation, Beverly, MA 01915, USA.
Free Radic Biol Med. 2000 Oct 15;29(8):704-13. doi: 10.1016/s0891-5849(00)00359-2.
In thymocytes, peroxynitrite induces poly(ADP-ribose) synthetase (PARS) activation, which results in necrotic cell death. In the absence of PARS, however, peroxynitrite-treated thymocytes die by apoptosis. Because Bcl-2 has been reported to inhibit not only apoptotic but also some forms of necrotic cell death, here we have investigated how Bcl-2 regulates the peroxynitrite-induced apoptotic and necrotic cell death. We have found that Bcl-2 did not provide protection against peroxynitrite-induced necrotic death, as characterized by propidium iodide uptake, mitochondrial membrane potential decrease, secondary superoxide production, and cardiolipin loss. In the presence of a PARS inhibitor, peroxynitrite-treated thymocytes from Bcl-2 transgenic mice showed no caspase activation or DNA fragmentation and displayed smaller mitochondrial membrane potential decrease. These data show that Bcl-2 protects thymocytes from peroxynitrite-induced apoptosis at a step proximal to mitochondrial alterations but fails to prevent PARS-mediated necrotic cell death. Activation of tissue transglutaminase (tTG) occurs in various forms of apoptosis. Peroxynitrite did not induce transglutaminase activity in thymocytes and did not have a direct inhibitory effect on the purified tTG. Basal tTG was not different in Bcl-2 transgenic and wild type cells.
在胸腺细胞中，过氧亚硝酸盐可诱导聚（ADP - 核糖）合成酶（PARS）激活，进而导致细胞坏死性死亡。然而，在缺乏PARS的情况下，经受过氧亚硝酸盐处理的胸腺细胞则通过凋亡死亡。由于据报道Bcl - 2不仅能抑制凋亡，还能抑制某些形式的坏死性细胞死亡，因此我们在此研究了Bcl - 2如何调节过氧亚硝酸盐诱导的凋亡和坏死性细胞死亡。我们发现，Bcl - 2并不能保护细胞免受由过氧亚硝酸盐诱导的坏死性死亡，其特征为碘化丙啶摄取、线粒体膜电位降低、继发性超氧阴离子产生以及心磷脂丢失。在存在PARS抑制剂的情况下，来自Bcl - 2转基因小鼠的经受过氧亚硝酸盐处理的胸腺细胞未显示半胱天冬酶激活或DNA片段化，并且线粒体膜电位降低幅度较小。这些数据表明，Bcl - 2在靠近线粒体改变的步骤中保护胸腺细胞免受由过氧亚硝酸盐诱导的凋亡，但无法阻止PARS介导的坏死性细胞死亡。组织转谷氨酰胺酶（tTG）的激活发生在各种形式的凋亡中。过氧亚硝酸盐未在胸腺细胞中诱导转谷氨酰胺酶活性，并且对纯化的tTG没有直接抑制作用。Bcl - 2转基因细胞和野生型细胞中的基础tTG没有差异。
