Selective regulation of MAP kinases and Chemokine expression after ligation of ICAM-1 on human airway epithelial cellsReport as inadecuate

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Respiratory Research

, 7:12

First Online: 23 January 2006Received: 28 April 2005Accepted: 23 January 2006


BackgroundIntercellular adhesion molecule 1 ICAM-1 is an immunoglobulin-like cell adhesion molecule expressed on the surface of multiple cell types, including airway epithelial cells. It has been documented that cross-linking ICAM-1 on the surface of leukocytes results in changes in cellular function through outside-inside signaling; however, the effect of cross-linking ICAM-1 on the surface of airway epithelial cells is currently unknown. The objective of this study was to investigate whether or not cross-linking ICAM-1 on the surface of airway epithelial cells phosphorylated MAP kinases or stimulated chemokine expression and secretion.

MethodsThe human lung adenocarcinoma A549 cells and primary cultures of normal human bronchial epithelial NHBE cells were used in these studies. To increase ICAM-1 surface expression, cultures were stimulated with TNFα to enhance ICAM-1 surface expression. Following ICAM-1 upregulation, ICAM-1 was ligated with a murine anti-human ICAM-1 antibody and subsequently cross-linked with a secondary antibody anti-mouse IgGab-2 in the presence or absence of the MAP kinase inhibitors. Following treatments, cultures were assessed for MAPK activation and chemokine gene expression and secretion. Control cultures were treated with murine IgG1 antibody or murine IgG1 antibody and anti-mouse IgGab-2 to illustrate specificity. Data were analyzed for significance using a one-way analysis of variance ANOVA with Bonferroni post-test correction for multiple comparisons, and relative gene expression was analyzed using the 2T method.

ResultsICAM-1 cross-linking selectively phosphorylated both ERK and JNK MAP kinases as detected by western blot analysis. In addition, cross-linking resulted in differential regulation of chemokine expression. Specifically, IL-8 mRNA and protein secretion was not altered by ICAM-1 cross-linking, in contrast, RANTES mRNA and protein secretion was induced in both epithelial cultures. These events were specifically inhibited by the ERK inhibitor PD98059. Data indicates that ICAM-1 cross-linking stimulates a synergistic increase in TNFα-mediated RANTES production involving activation of ERK in airway epithelial cells.

ConclusionResults demonstrate that cytokine induced ICAM-1 on the surface of airway epithelial cells induce outside-inside signaling through cross-linking ICAM-1, selectively altering intracellular pathways and cytokine production. These results suggest that ICAM-1 cross-linking can contribute to inflammation in the lung via production of the chemokine RANTES.

AbbreviationsRANTESregulated on activation normal T cell expressed and secreted

NHBEnormal human bronchial epithelial

TNFαtumor necrosis factor alpha

ICAM-1intercellular adhesion molecule 1

BEGMbronchial epithelial cell growth medium

DMEM-HDulbecco-s modified Eagle-s medium with high glucose

EGFepidermal growth factor

MAPmitogen-activated protein

MEKMAP kinase kinase

PBSphosphate buffered saline

RT-PCRreverse transcriptase-polymerase chain reaction

mAbmonoclonal antibody.

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Author: Thomas M Krunkosky - Carla L Jarrett


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