Lipopolysaccharide induces cyclooxygenase-2 in intestinal epithelium via a noncanonical p38 MAPK pathway
Lipopolysaccharide induces cyclooxygenase-2 in intestinal epithelium via a noncanonical p38 MAPK pathway
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DOI：
10.4049/jimmunol.176.1.580
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发表时间：
2006-01-01
影响因子：
4.4
通讯作者：
Ford, HR
中科院分区：
文献类型：
--
作者：
Grishin, AV;Wang, J;Ford, HR
坏死性小肠结肠炎（NEC）是新生儿中一种严重的肠道炎症，发生在肠道细菌定植之后。lps诱导的未成熟肠细胞炎症因子的产生可能是NEC的一个因素。之前，我们描述了lps诱导大鼠IEC-6细胞中p38 mapk依赖性环氧化酶-2 （COX-2）的表达。在这项研究中，我们检测了COX-2在新生大鼠肠上皮中的表达，并进一步表征了COX-2在肠细胞中的调节机制。配方喂养/缺氧诱导NEC可增加肠黏膜磷酸化-p38和COX-2水平。选择性COX-2抑制剂塞来昔布加重了疾病，提示COX-2具有保护作用。体内和离体LPS诱导肠上皮COX-2。后一种反应可被p38抑制剂SB202190减弱，但不能被ERK、JNK或NF-kappa b的抑制剂减弱。在IEC-6肠细胞中，COX-2可被MAPK激酶3ee （MKK3EE）的表达诱导，MKK3EE是p38的组成激活剂，而不是ERK或JNK途径的激活剂。然而，已知的p38上游激酶MKK3/6和MKK4均未被LPS激活。显性阴性的MKK3或MKK4或SB202190不能阻止lps诱导的p38活化磷酸化，排除了这些激酶或p38自磷酸化的重要作用。LPS增加COX-2和激活p38磷酸化，具有相似的剂量效应。SB202190阻断lps诱导的COX-2荧光素酶报告基因的表达和破坏COX-2信息的稳定，表明p38在转录和mRNA稳定性水平上调控COX-2。我们的数据表明，p38介导的COX-2表达通过一种新的上游途径进行，并支持新生儿肠细胞作为细菌传感器的作用。
Necrotizing enterocolitis (NEC), a severe intestinal inflammation in neonates, occurs following bacterial colonization of the gut. LPS-induced production of inflammatory factors in immature enterocytes may be a factor in NEC. Previously, we described LPS-induced p38 MAPK-dependent expression of cyclooxygenase-2 (COX-2) in rat IEC-6 cells. In this study, we examine COX-2 expression in newborn rat intestinal epithelium and further characterize the mechanisms of COX-2 regulation in enterocytes. Induction of NEC by formula feeding/hypoxia increased phospho-p38 and COX-2 levels in the intestinal mucosa. Celecoxib, a selective COX-2 inhibitor, exacerbated the disease, suggesting a protective role for COX-2. COX-2 was induced in the intestinal epithelium by LPS in vivo and ex vivo. The latter response was attenuated by the p38 inhibitor SB202190, but not by inhibitors of ERK, JNK, or NF-kappa B. In IEC-6 enterocytes, COX-2 was induced by the expression of MAPK kinase 3 EE (MKK3EE), a constitutive activator of p38, but not of activators of ERK or JNK pathways. However, neither MKK3/6 nor MKK4, the known p38 upstream kinases, were activated by LPS. Dominant-negative MKK3 or MKK4 or SB202190 failed to prevent LPS-induced, p38-activating phosphorylation, ruling out important roles of these kinases or p38 autophosphorylation. LPS increased COX-2 and activating phosphorylation of p38 with similar dose-response. Blockade of LPS-induced expression of COX-2-luciferase reporter and destabilization of COX-2 message by SB202190 indicate that p38 regulates COX-2 at transcription and mRNA stability levels. Our data indicate that p38-mediated expression of COX-2 proceeds through a novel upstream pathway and support the role of the neonate's enterocytes as bacterial sensors.