Fernandez A, Kiefer J, Fosdick L, McConkey D J
Department of Cell Biology, University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
J Immunol. 1995 Dec 1;155(11):5133-9.
Glucocorticoid hormones stimulate apoptosis in thymocytes via a mechanism that involves changes in intracellular Ca2+, and exogenous Ca2+ can also directly promote the nuclear alterations of apoptosis (lamin degradation and chromatin cleavage) in isolated nuclei. Here we report that glucocorticoid treatment resulted in the production of reactive oxygen species and the depletion of reduced glutathione. Separation of apoptotic cells on Percoll gradients demonstrated that both effects selectively occurred in thymocytes undergoing apoptosis. Moreover, glucocorticoid-induced endonuclease activation was partially blocked by the antioxidant N-acetyl-L-cysteine. Although abrogation of methylprednisolone-induced Ca2+ increases using the intracellular Ca2+ buffer 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid resulted in inhibition of endonuclease activation, it failed to prevent GSH depletion. However, N-acetyl-L-cysteine almost completely blocked methylprednisolone-induced elevations in cytosolic calcium levels, indicating that oxidative stress was playing a role in the Ca2+ response. Our results support the idea that oxidative stress is a key component of the apoptotic effector pathway in thymocytes, and that it interacts, at least in part, with the Ca2+ response.
糖皮质激素通过一种涉及细胞内Ca2+变化的机制刺激胸腺细胞凋亡，外源性Ca2+也能直接促进分离细胞核中凋亡的核改变（核纤层蛋白降解和染色质裂解）。我们在此报告，糖皮质激素处理导致活性氧的产生和还原型谷胱甘肽的消耗。在Percoll梯度上分离凋亡细胞表明，这两种效应均选择性地发生在正在经历凋亡的胸腺细胞中。此外，抗氧化剂N-乙酰-L-半胱氨酸部分阻断了糖皮质激素诱导的核酸内切酶激活。尽管使用细胞内Ca2+缓冲剂1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸消除甲泼尼龙诱导的Ca2+增加会导致核酸内切酶激活受到抑制，但它未能阻止谷胱甘肽的消耗。然而，N-乙酰-L-半胱氨酸几乎完全阻断了甲泼尼龙诱导的胞质钙水平升高，表明氧化应激在Ca2+反应中起作用。我们的结果支持这样一种观点，即氧化应激是胸腺细胞凋亡效应途径的关键组成部分，并且它至少部分地与Ca2+反应相互作用。
