Lipopolysaccharide induces CXCL2/macrophage inflammatory protein-2 gene expression in enterocytes via NF-kappaB activation: independence from endogenous TNF-alpha and platelet-activating factor.
CXCL2 (macrophage inflammatory protein-2 (MIP-2)), a critical chemokine for neutrophils, has been shown to be produced in the rat intestine in response to platelet-activating factor (PAF) and to mediate intestinal inflammation and injury. The intestinal epithelium, constantly exposed to bacterial products, is the first line of defence against micro-organisms. It has been reported that enterocytes produce proinflammatory mediators, including tumour necrosis factor (TNF) and PAF, and we showed that lipopolysaccharide (LPS) and TNF activate nuclear factor (NF)-kappaB in enterocytes. However, it remains elusive whether enterocytes release CXCL2 in response to LPS and TNF via a NF-kappaB-dependent pathway and whether this involves the endogenous production of TNF and PAF. In this study, we found that TNF and LPS markedly induced CXCL2 gene expression in IEC-6 cells, TNF within 30 min, peaking at 45 min, while LPS more slowly, peaking after 2 hr. TNF- and LPS- induced CXCL2 gene expression and protein release were completely blocked by pyrrolidine dithiocarbamate (PDTC) and helenalin, two potent NF-kappaB inhibitors. NEMO-binding domain peptide, a specific inhibitor of inhibitor protein kappaB kinase (IKK) activation, a major upstream kinase mediating NF-kappaB activation, significantly blocked CXCL2 gene expression and protein release induced by LPS. WEB2170 (PAF antagonist) and anti-TNF antibodies had no effect on LPS-induced CXCL2 expression. In conclusion, CXCL2 gene is expressed in enterocytes in response to both TNF and LPS. LPS-induced CXCL2 expression is dependent on NF-kappaB activation via the IKK pathway. The effect of LPS is independent of endogenous TNF and PAF.
De Plaen
Isabelle G
IG
Department of Pediatrics (Neonatology), Children's Memorial Hospital, Northwestern University Medical School, Chicago, IL 60614, USA. isabelledp@northwestern.edu
Han
Xin-Bing
XB
Liu
Xueli
X
Hsueh
Wei
W
Ghosh
Sankar
S
May
Michael J
MJ
D000818:Animals; D001381:Azepines / Q000494:pharmacology; D002460:Cell Line; D054426:Chemokine CXCL2; D019743:Chemokines, CXC / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D024202:Electrophoretic Mobility Shift Assay; D020895:Enterocytes / Q000187:drug effects / Q000276:immunology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D020672:I-kappa B Proteins / Q000378:metabolism; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000276:immunology*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000276:immunology*; D010972:Platelet Activating Factor / Q000276:immunology; D011759:Pyrrolidines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014158:Transcription, Genetic / Q000187:drug effects; D014230:Triazoles / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
D001381:Azepines; D054426:Chemokine CXCL2; D019743:Chemokines, CXC; C513296:Cxcl2 protein, rat; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; D010972:Platelet Activating Factor; D011759:Pyrrolidines; D012333:RNA, Messenger; D014230:Triazoles; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; C063964:bepafant; C032519:pyrrolidine