Regulation of neutrophil interleukin 8 gene expression and protein secretion by LPS, TNF-alpha, and IL-1 beta.
Neutrophils are possibly involved in the pathogenesis of various lung diseases through the release of numerous mediators. In the present study, we studied the regulation of IL-8 gene induction and protein secretion in human blood neutrophils. Northern blot analysis revealed that LPS increased IL-8 mRNA levels in neutrophils, with a maximal fivefold increase by 2 h. IL-8 mRNa levels returned to baseline values within 12 h. In contrast, LPS-stimulated monocytes demonstrated a sustained increase of IL-8 mRNA levels for more than 24 h. TNF-alpha, IL-1 beta, and phorbol myristate acetate also increased IL-8 mRNA levels in neutrophils. Immunohistochemical analysis confirmed that IL-8 was localized within stimulated neutrophils. IL-8 secretion by neutrophils and monocytes was quantified using a specific ELISA for IL-8. Resting neutrophils secreted minimal IL-8 activity. However when cells were stimulated with LPS, TNF-alpha, or IL-1B, neutrophils secreted IL-8. IL-8 secretion was most marked during the first 2 h after stimulation and decreased thereafter. In contrast, monocytes maintained a high rate of IL-8 secretion over 12 h. Although a single monocyte secreted 70-fold more IL-8 than did a single neutrophil after 4 h of incubation, the high abundance of neutrophils in peripheral blood made the neutrophil-secreted IL-8 more significant. During the first 2 h, neutrophils secreted approximately 40% of the IL-8 released by monocytes in the same volume of blood. This ratio decreased to 9% after 12 h. Neutrophil-secreted IL-8 may play an autocrine or paracrine role during the initial stage of inflammation.
Fujishima
S
S
Department of Medicine Stanford University Medical Center, California 94305-5236.
Hoffman
A R
AR
Vu
T
T
Kim
K J
KJ
Zheng
H
H
Daniel
D
D
Kim
Y
Y
Wallace
E F
EF
Larrick
J W
JW
Raffin
T A
TA
D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009000:Monocytes / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D007375:Interleukin-1; D016209:Interleukin-8; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D013755:Tetradecanoylphorbol Acetate