Nambiar Madhusoodana P, Fisher Carolyn U, Enyedy Edith J, Warke Vishal G, Kumar Anil, Tsokos George C
Department of Cellular Injury, Walter Reed Army Institute of Research, Silver Spring, MD 20910-7500, USA.
Cell Immunol. 2002 Feb;215(2):151-61. doi: 10.1016/s0008-8749(02)00006-0.
Exposure of human T-lymphocytes to heat downregulates TCR zeta chain expression and inhibits (TCR)/CD3-mediated production of inositol triphosphate and Ca(2+) signaling. Here we investigated whether oxidative stress is involved in the heat-induced downregulation of TCR/CD3-mediated signaling. To this end, we have studied the effect of a thiol antioxidant, N-acetyl-L-cysteine (NAC), and a non-thiol antioxidant, allopurinol, on heat-induced downregulation of TCR/CD3-mediated signaling. We found that preincubation of cells with 10mM NAC significantly reversed the downregulation of TCR/CD3-mediated Ca(2+) response and restored the suppression of TCR zeta chain protein expression as well as prevented its increased membrane distribution in heat-treated cells. NAC also reversed the downregulation of TCR zeta chain mRNA expression and the active 94kDa TCR zeta chain transcription factor, Elf-1, in heat-treated cells. Consistent with the increase in the TCR zeta chain, preincubation with NAC increased the levels of antigen receptor-induced tyrosine phosphorylation of several cytosolic proteins. Finally, treatment with NAC was able to reverse the suppression of IL-2 production in heat-treated cells. Inactive analog, N-acetylserine, failed to reverse the heat-induced downregulation of TCR/CD3-mediated signaling. Allopurinol, another potent non-thiol antioxidant, also restored the TCR/CD3-mediated Ca(2+) response in heat-treated cells. These results demonstrate that antioxidants restore the expression of TCR zeta chain and reverse the TCR/CD3-mediated signaling abnormalities associated with heat stress and suggest that heat shock-induced oxidative stress is a mediator of the heat-induced biochemical damage that leads to downregulation of signaling in human T-lymphocytes.
将人类T淋巴细胞暴露于热环境会下调TCR ζ链的表达，并抑制（TCR）/CD3介导的肌醇三磷酸生成和[Ca(2+)]i信号传导。在此，我们研究了氧化应激是否参与热诱导的TCR/CD3介导信号传导的下调。为此，我们研究了硫醇抗氧化剂N-乙酰-L-半胱氨酸（NAC）和非硫醇抗氧化剂别嘌呤醇对热诱导的TCR/CD3介导信号传导下调的影响。我们发现，用10mM NAC预孵育细胞可显著逆转TCR/CD3介导的[Ca(2+)]i反应的下调，恢复TCR ζ链蛋白表达的抑制，并防止其在热处理细胞中的膜分布增加。NAC还逆转了热处理细胞中TCR ζ链mRNA表达和活性94kDa TCR ζ链转录因子Elf-1的下调。与TCR ζ链的增加一致，用NAC预孵育可增加几种胞质蛋白的抗原受体诱导的酪氨酸磷酸化水平。最后，用NAC处理能够逆转热处理细胞中IL-2产生的抑制。无活性类似物N-乙酰丝氨酸未能逆转热诱导的TCR/CD3介导信号传导的下调。另一种有效的非硫醇抗氧化剂别嘌呤醇也恢复了热处理细胞中TCR/CD3介导的[Ca(2+)]i反应。这些结果表明，抗氧化剂可恢复TCR ζ链的表达，并逆转与热应激相关的TCR/CD3介导的信号异常，提示热休克诱导的氧化应激是热诱导的生化损伤的介质，导致人类T淋巴细胞信号传导下调。
