Ohkusu K, Isobe K, Hidaka H, Nakashima I
Department of Immunology, Nagoya University School of Medicine, Japan.
Eur J Immunol. 1995 Nov;25(11):3180-6. doi: 10.1002/eji.1830251129.
MRL-lpr mice are severely impaired in the Fas pathway of apoptosis induction. We here evaluate another pathway of apoptosis induction in MRL-lpr mice which is protein kinase C (PKC) dependent. Despite the defect of the Fas pathway, apoptosis developed during culture in vitro in splenic T lymphocytes from MRL-lpr mice more extensively than in T lymphocytes from MRL-(+/+) mice. Apoptosis induction in the former cells was then found to be greatly promoted by PKC inhibitor H-7, and partially prevented by PKC activator phorbol 12-myristate 13-acetate (PMA). High sensitivity to H-7, but not to PKA inhibitor HA 1004, of these cells for apoptosis induction was confirmed by detailed time course and dose-dependency experiments of the drug effect. Population analysis showed that both CD4+ T lymphocytes and CD8+ T lymphocytes from MRL-lpr mice were highly sensitive to H-7, whereas CD8+ T lymphocytes, but not CD4+ T lymphocytes, from MRL-(+/+) mice were susceptible to the reagent. Interestingly, B220+ Thy-1+ CD4-CD8- T lymphocytes from MRL-lpr mice were most sensitive to H-7 for apoptosis induction. Correspondingly, the membrane-translocated activated PKC-alpha level in splenic T lymphocytes from MRL-lpr was more extensively up-regulated by PMA than in splenic T lymphocytes from MRL-(+/+). These results suggest that some signal consistently activates PKC in MRL-lpr T lymphocytes, and this event is needed for survival of these cells. On the other hand, CD4+ CD8+ thymocytes were deleted by apoptosis in culture with PMA, whether these thymocytes were from MRL-lpr mice or MRL-(+/+) mice. This finding suggested that the apoptosis induction pathway linked to PKC activation is intact in CD4+ CD8+ thymocytes from the Fas-defective MRL-lpr mice. We conclude from these results that the PKC-dependent signal pathways for either cell death or cell activation are intact or even accelerated in lpr mice, which could both compensate for the loss of the Fas pathway and promote the generation of autoreactive T lymphocytes.
MRL-lpr小鼠在Fas凋亡诱导途径中存在严重缺陷。我们在此评估MRL-lpr小鼠中另一条依赖蛋白激酶C（PKC）的凋亡诱导途径。尽管Fas途径存在缺陷，但MRL-lpr小鼠脾T淋巴细胞在体外培养过程中发生的凋亡比MRL-(+/+)小鼠的T淋巴细胞更为广泛。随后发现，PKC抑制剂H-7可极大地促进前一种细胞的凋亡诱导，而PKC激活剂佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）可部分抑制凋亡诱导。通过详细的药物作用时间进程和剂量依赖性实验证实，这些细胞对H-7诱导凋亡高度敏感，但对PKA抑制剂HA 1004不敏感。群体分析表明，MRL-lpr小鼠的CD4+ T淋巴细胞和CD8+ T淋巴细胞对H-7均高度敏感，而MRL-(+/+)小鼠的CD8+ T淋巴细胞（而非CD4+ T淋巴细胞）对该试剂敏感。有趣的是，MRL-lpr小鼠的B220+ Thy-1+ CD4-CD8- T淋巴细胞对H-7诱导凋亡最为敏感。相应地，与MRL-(+/+)小鼠的脾T淋巴细胞相比，PMA对MRL-lpr小鼠脾T淋巴细胞中膜转位活化PKC-α水平的上调作用更为广泛。这些结果表明，某些信号持续激活MRL-lpr T淋巴细胞中的PKC，而这一事件是这些细胞存活所必需的。另一方面，无论这些胸腺细胞来自MRL-lpr小鼠还是MRL-(+/+)小鼠，在PMA培养下，CD4+ CD8+胸腺细胞都会通过凋亡被清除。这一发现表明，与PKC激活相关的凋亡诱导途径在Fas缺陷的MRL-lpr小鼠的CD4+ CD8+胸腺细胞中是完整的。我们从这些结果得出结论，lpr小鼠中依赖PKC的细胞死亡或细胞活化信号通路是完整的，甚至有所加速，这既可以弥补Fas途径的缺失，又可以促进自身反应性T淋巴细胞的产生。
