Respiratory syncytial virus and TNF alpha induction of chemokine gene expression involves differential activation of Rel A and NF-kappa B1.
BACKGROUND
Respiratory syncytial virus (RSV) infection of airway epithelial cells stimulates the expression and secretion of a variety of cytokines including the chemotactic cytokines interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and RANTES (regulated upon activation, normal T cell expressed and secreted). Chemokines are important chemoattractants for the recruitment of distinct sets of leukocytes to airway sites of inflammation.


RESULTS
We have shown previously that chemokine expression is regulated in airway epithelial cells (A549) in a stimulus-specific manner in part through the redox-responsive transcription factors AP-1 and NF-kappaB. In this study, we examined the NF-kappaB-mediated effects of RSV and the proinflammatory cytokine TNFalpha on the induction of IL-8, MCP-1 and RANTES chemokine gene expression in A549 epithelial cells. The results demonstrate that RSV induces chemokine expression with distinct kinetics that is associated with a specific pattern of NF-kappaB binding activity. This distinction was further demonstrated by the differential effects of the NF-kappaB inhibitors dexamethasone (DEX) and N-acetyl-L-cysteine (NAC). NAC preferentially inhibited RSV induced chemokine expression, whereas DEX preferentially inhibited TNFalpha induced chemokine expression. DNA binding studies using NF-kappaB subunit specific binding ELISA demonstrated that RSV and TNFalpha induced different NF-kappaB binding complexes containing Rel A (p65) and NF-kappaB1 (p50). Both TNFalpha and RSV strongly induced Rel A the activation subunit of NF-kappaB, whereas only TNFalpha was able to substantially induce the p50 subunit. Consistent with the expression studies, RSV but not TNFalpha induction of Rel A and p50 were markedly inhibited by NAC, providing a mechanism by which TNFalpha and RSV can differentially activate chemokine gene expression via NF-kappaB.


CONCLUSIONS
These data suggest that RSV induction of chemokine gene expression, in contrast to TNFalpha, involves redox-sensitive NF-kappaB complexes containing predominantly Rel A.
Carpenter
Laura R
LR
Department of Immunology/Microbiology, Rush-Presbyterian-St, Luke's Medical Center Chicago, IL 60612, USA. lcarpent@rush.edu
Moy
James N
JN
Roebuck
Kenneth A
KA
D000111:Acetylcysteine / Q000494:pharmacology; D000998:Antiviral Agents / Q000494:pharmacology; D018925:Chemokines / Q000096:biosynthesis / Q000235:genetics*; D003907:Dexamethasone / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology*; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D010084:Oxidation-Reduction; D012136:Respiratory Syncytial Viruses / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*
D000998:Antiviral Agents; D018925:Chemokines; D016166:Free Radical Scavengers; D005938:Glucocorticoids; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone; D000111:Acetylcysteine