Li Hongye, Nord Edward P
Department of Medicine, Div. of Nephrology, School of Medicine, HSC T-16 Rm-080, State Univ. of NY at Stony Brook, Stony Brook, NY 11794, USA.
Am J Physiol Renal Physiol. 2009 Feb;296(2):F438-45. doi: 10.1152/ajprenal.90214.2008. Epub 2008 Jul 30.
Activation of the CD40 receptor by its cognate ligand, CD154, results in interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) production and increased intercellular adhesion molecule-1 (ICAM-1) expression in proximal tubule cells (PTCs). The independent role of these two proinflammatory chemokines, IL-8 and MCP-1, in inciting an inflammatory response in PTCs was explored. Exposure of primary cultures of human renal PTCs to recombinant IL-8 and MCP-1 resulted in increased ICAM-1 expression measured by quantitative real-time PCR, but confirmed only for IL-8 by immunoblot. The mechanism of action of IL-8 was explored in further detail. Immunohistochemistry identified both the CXCR-1 and CXCR-2 receptors, confirmed by RT-PCR, immunoprecipitation, immunoblot, and FACS analysis. IL-8 increased ICAM-1 expression only via the CXCR-1 receptor, which in turn resulted in activation of the p38 mitogen-activated protein kinase (MAPK) pathway; neither the extracellular signal-related kinase (ERK) 1/2 MAPK pathway nor the stress-activated protein kinase (SAPK)/c-Jun NH(2) terminal kinase (JNK) pathway was involved. CD154/CD40-mediated ICAM-1 upregulation was not affected by preincubation of monolayers with the CXCR-1 blocking antibody, indicating that ICAM-1 expression occurs independent of CD154-mediated IL-8 production. Coincubation of monolayers with both CD154 and IL-8 resulted in a greater ICAM-1 response than either compound alone. We conclude that in human renal PTCs, IL-8 upregulates ICAM-1 production by engaging the CXCR-1 receptor and p38 MAPK signaling pathway. This cascade of events is independent of CD40/CD154-mediated IL-8 stimulation and ICAM-1 production and serves to amplify the inflammatory response.
其同源配体CD154激活CD40受体，可导致近端肾小管细胞（PTCs）产生白细胞介素-8（IL-8）和单核细胞趋化蛋白-1（MCP-1），并增加细胞间黏附分子-1（ICAM-1）的表达。本研究探讨了这两种促炎趋化因子IL-8和MCP-1在引发PTCs炎症反应中的独立作用。将人肾PTCs原代培养物暴露于重组IL-8和MCP-1后，通过定量实时PCR检测发现ICAM-1表达增加，但免疫印迹仅证实IL-8可增加ICAM-1表达。进一步详细探讨了IL-8的作用机制。免疫组织化学鉴定出CXCR-1和CXCR-2受体，逆转录聚合酶链反应（RT-PCR）、免疫沉淀、免疫印迹和荧光激活细胞分选（FACS）分析均证实了这一结果。IL-8仅通过CXCR-1受体增加ICAM-1表达，进而激活p38丝裂原活化蛋白激酶（MAPK）途径；细胞外信号调节激酶（ERK）1/2 MAPK途径和应激激活蛋白激酶（SAPK）/c-Jun氨基末端激酶（JNK）途径均未参与。用CXCR-1阻断抗体预孵育单层细胞，并不影响CD154/CD40介导的ICAM-1上调，这表明ICAM-1的表达独立于CD154介导的IL-8产生。将单层细胞与CD154和IL-8共同孵育，所产生的ICAM-1反应比单独使用任何一种化合物时都更强。我们得出结论，在人肾PTCs中，IL-8通过结合CXCR-1受体和p38 MAPK信号通路来上调ICAM-1的产生。这一系列事件独立于CD40/CD154介导的IL-8刺激和ICAM-1产生，起到放大炎症反应的作用。
