Low environmental pH is responsible for the induction of nitric-oxide synthase in macrophages -: Evidence for involvement of nuclear factor-κB activation
Low environmental pH is responsible for the induction of nitric-oxide synthase in macrophages -: Evidence for involvement of nuclear factor-κB activation
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DOI：
10.1074/jbc.273.9.5086
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发表时间：
1998-02-27
影响因子：
4.8
通讯作者：
Baud, L
中科院分区：
文献类型：
--
作者：
Bellocq, A;Suberville, S;Baud, L
用内毒素和/或细胞因子刺激巨噬细胞负责一氧化氮合酶（MOS）的诱导型同种型的表达。由于巨噬细胞暴露于炎性病变的微环境内的低pH，因此研究了酸性pH作为iNOS的额外调节剂的潜在作用。用pH 7.0的培养基替代pH 7.4的大鼠腹膜巨噬细胞的培养基上调了iNOS活性，如亚硝酸盐积累增加2.5倍所反映的，iNOS活性的增加与iNOS mRNA表达的类似增加相关，这反映了iNOS mRNA合成的增加而不是稳定性，低pH环境诱导的iNOS基因转录与核因子-κ B的激活有关（NF-κ B）转录因子的表达增加，这既增加了核中NF-κ B B结合活性，又增强了NF-κ B驱动的报告基因表达。此外，用吡咯烷二硫代氨基甲酸酯或N-乙酰基-亮氨酰-亮氨酰-正亮氨酸处理巨噬细胞，两种药物均能阻止NF-κ B B向细胞核的转位，消除低pH诱导的亚硝酸盐蓄积，其总体机制需要肿瘤坏死因子α（TNF α）的合成。事实上，1）在暴露于pH 7.0的巨噬细胞的培养基中观察到升高的TNF α生物活性，和2）巨噬细胞与中和性抗TNF α抗体的孵育损害了NF-κ B活化和响应于酸攻击的亚硝酸盐积累。总之，巨噬细胞暴露于炎性病变中的酸性微环境，通过激活NF-κ B导致iNOS活性上调，kappa B。
Stimulation of macrophages with endotoxin and/or cytokines is responsible for the expression of the inducible isoform of nitric oxide synthase (MOS). Because macrophages are exposed to low pH within the microenvironment of inflammatory lesions, the potential role of acidic pH as an additional regulator of iNOS was investigated, Substitution of the culture medium of rat peritoneal macrophages at pH 7.4 with medium at pH 7.0 up-regulated iNOS activity, as reflected by a 2.5-fold increase in nitrite accumulation, The increase in iNOS activity was associated with a similar increase in iNOS mRNA expression that reflected an increase in iNOS mRNA synthesis rather than stability, Low environmental pH-induced iNOS gene transcription involved the activation of nuclear factor-kappa B (NF-kappa B) transcription factor since exposure of macrophages to low environmental pH both increased NF-kappa B binding activity in the nucleus and enhanced NF-kappa B-driven reporter gene expression, In addition, treatment of macrophages with pyrrolidine dithiocarbamate or n-acetyl-leucinyl-leucinyl-norleucinal, two drugs preventing NF-kappa B translocation to the nucleus, canceled low pH-induced nitrite accumulation, The overall mechanism required the synthesis of tumor necrosis factor alpha (TNF alpha). Indeed, 1) elevated TNF alpha bioactivity was observed in the medium of macrophages exposed to pH 7.0, and 2) incubation of macrophages with a neutralizing anti-TNF alpha antibody impaired both NF-kappa B activation and nitrite accumulation in response to acid challenge, In summary, exposure of macrophages to acidic microenvironment in inflammatory lesions leads to the up-regulation of iNOS activity through the activation of NF-kappa B.