Tumor necrosis factor-alpha from macrophages enhances LPS-induced clara cell expression of keratinocyte-derived chemokine.
Tumor necrosis factor (TNF)-alpha is a cytokine produced by alveolar macrophages in response to LPS in the lung. Clara cells are bronchiolar epithelial cells that produce a variety of proinflammatory cytokines in response to LPS but not to TNF-alpha. In this study, we examined whether TNF-alpha affects Clara cell cytokine production in the setting of LPS stimulation. Using a transformed murine Clara cell line (C22), we observed that both LPS and TNF-alpha induced production of keratinocyte-derived chemokine (KC) and monocyte chemoattractant protein (MCP)-1. We also found that simultaneous LPS and TNF-alpha stimulation is synergistic for KC production, but additive for MCP-1 production. By using a Transwell coculture system of RAW264.7 macrophages and Clara cells isolated from C57Bl/6 mice, we found that macrophages produce a soluble factor that enhances Clara cell KC production in response to LPS. Cocultures of Clara cells from mice deficient in TNF-alpha receptors with RAW264.7 macrophages demonstrated that the effect of macrophages on Clara cells is mediated primarily via TNF-alpha. To determine whether these findings occur in vivo, we treated wild-type and TNF receptor-deficient mice intratracheally with LPS and examined the expression of KC. LPS-treated, TNF receptor-deficient mice showed much less KC mRNA in airway epithelial cells compared with wild-type mice. In contrast, a similar number of KC-expressing cells was seen in the lung periphery. Thus, upregulation of KC by Clara cells in the setting of LPS stimulation is largely dependent on TNF-alpha originating from alveolar macrophages. These findings shed light on macrophage-Clara cell interactions in regulating the pulmonary inflammatory response to LPS.
Department of Medicine, Washington University School of Medicine, 902 Yalem, Box 8052, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
Arnon
A
Elizur
Tracy L
TL
Adair-Kirk
Diane G
DG
Kelley
Gail L
GL
Griffin
Daphne E
DE
Demello
Robert M
RM
Senior
D000818:Animals; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D018932:Chemokine CCL2 / Q000096:biosynthesis / Q000235:genetics; D054360:Chemokine CXCL1 / Q000096:biosynthesis* / Q000235:genetics; D018920:Coculture Techniques; D004357:Drug Synergism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000819:agonists / Q000494:pharmacology*; D008168:Lung / Q000166:cytology / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000819:agonists / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D054360:Chemokine CXCL1; C475895:Cxcl1 protein, mouse; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha