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.
Elizur
Arnon
A
Department of Medicine, Washington University School of Medicine, 902 Yalem, Box 8052, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
Adair-Kirk
Tracy L
TL
Kelley
Diane G
DG
Griffin
Gail L
GL
Demello
Daphne E
DE
Senior
Robert M
RM
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