Molecular characterization of Helicobacter pylori VacA induction of IL-8 in U937 cells reveals a prominent role for p38MAPK in activating transcription factor-2, cAMP response element binding protein, and NF-κB activation
Molecular characterization of Helicobacter pylori VacA induction of IL-8 in U937 cells reveals a prominent role for p38MAPK in activating transcription factor-2, cAMP response element binding protein, and NF-κB activation
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DOI：
10.4049/jimmunol.180.7.5017
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发表时间：
2008-04-01
影响因子：
4.4
通讯作者：
Hirayama, Toshiya
中科院分区：
文献类型：
--
作者：
Hisatsune, Junzo;Nakayama, Masaaki;Hirayama, Toshiya
幽门螺杆菌VacA对易感细胞诱导多种效应，包括空泡化、线粒体损伤、细胞生长抑制和环氧合酶-2表达增强。评估H. pylori来调节炎症介质的产生，我们研究了VacA增强前单核细胞U937细胞产生IL-8的机制，这证明了测试细胞的最大VacA诱导的IL-8释放。p38 MAPK（SB 203580）、ERK 1/2（PD 98059）、IKBa（（E）-3-（4-甲基苯磺酰基）-2-丙烯腈）、Ca 2+进入（SKF 96365）和细胞内Ca 21通道（丹曲林）的抑制剂可阻断VacA诱导的IL-8产生。此外，细胞内Ca 2+螯合剂（BAPTA-AM），抑制VacA激活的p38 MAPK，导致剂量依赖性减少VacA诱导的IL-8分泌的U937细胞，这意味着细胞内Ca 2 1介导的MAPK和经典NF-κ B途径的激活的作用。VacA刺激NF-κ Bp 65向细胞核的移位，这与通过激活NF-κ B途径增强IL-8表达一致。另外，转录激活因子（ATF）-2或CREB的小干扰RNA（其是p38 MAPK底物并结合到IL-8启动子的AP-1位点）抑制VacA诱导的IL-8产生。VacA激活含有NF-IL-6位点的IL-8启动子，但不激活突变的AP-1或NF-κ B B位点，表明ATF-2/CREB B结合区或NF-κ B结合区直接参与VacA诱导的IL-8启动子激活。因此，在U937细胞中，VacA通过胞内Ca 2+释放激活p38 MAPK直接增加IL-8的产生，导致转录因子ATF-2、CREB和NF-κ B的激活。
Helicobacterpylori VacA induces multiple effects on susceptible cells, including vacuolation, mitochondrial damage, inhibition of cell growth, and enhanced cyclooxygenase-2 expression. To assess the ability of H. pylori to modulate the production of inflammatory mediators, we examined the mechanisms by which VacA enhanced IL-8 production by promonocytic U937 cells, which demonstrated the greatest VacA-induced IL-8 release of the cells tested. Inhibitors of p38 MAPK (SB203580), ERK1/2 (PD98059), IKBa ((E)-3-(4-methylphenyisulfonyl)-2-propenenitrile), Ca2+ entry (SKF96365), and intracellular Ca 21 channels (dantrolene) blocked VacA-induced IL-8 production. Furthermore, an intracellular Ca2+ chelator (BAPTA-AM), which inhibited VacA-activated p38 MAPK, caused a dose-dependent reduction in VacA-induced IL-8 secretion by U937 cells, implying a role for intracellular Ca 21 in mediating activation of MAPK and the canonical NF-kappa B pathway. VacA stimulated translocation of NF-kappa Bp65 to the nucleus, consistent with enhancement of IL-8 expression by activation of the NF-kappa B pathway. In addition, small interfering RNA of activating transcription factor (ATF)-2 or CREB, which is a p38MAPK substrate and binds to the AP-1 site of the IL-8 promoter, inhibited VacA-induced IL-8 production. VacA activated an IL-8 promoter containing an NF-IL-6 site, but not a mutated AP-1 or NF-kappa B site, suggesting direct involvement of the ATF-2/CREB binding region or NF-kappa B-binding regions in VacA-induced IL-8 promoter activation. Thus, in U937 cells, VacA directly increases IL-8 production by activation of the p38 MAPK via intracellular Ca2+ release, leading to activation of the transcription factors, ATF-2, CREB, and NF-kappa B.