Lipopolysaccharide Induces Expression of Granulocyte/Macrophage Colony-stimulating Factor, Interleukin-8, and Interleukin-6 in Human Nasal, but Not Lung, Fibroblasts: Evidence for Heterogeneity within the Respiratory Tract
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Fibroblasts play an indirect augmenting effector role in the inflammatory response by releasing growth and differentiation factors and other inflammatory mediators after activation by inflammatory cytokines such as interleukin (IL)-1, but whether direct activation occurs by exogenous agents such as endotoxin (lipopolysaccharide, LPS) remains controversial. Using a number of primary human airways tissue-derived fibroblast lines, we demonstrate that in contrast to IL-1 alpha, LPS significantly induced gene expression and production of granulocyte/macrophage colony-stimulating factor (GM-CSF), IL-8, and IL-6 only in nasal but not bronchial or lung tissue-derived fibroblasts. Enhanced expression was dose- and time-dependent, and the minimal stimulatory dose was 10 ng LPS/ml. Polymyxin B entirely abrogated increased cytokine expression by LPS. Actinomycin D treatment largely inhibited expression, and LPS markedly increased an IL-6 gene promoter-driven luciferase reporter response in transfected nasal fibroblasts, suggesting enhanced expression may involve transcriptional regulation. Secondary protein or IL-1 synthesis requirement seemed unlikely since cycloheximide superinduced LPS-stimulated cytokine expression and anti-IL-1 alpha/beta antibodies failed to abrogate the response. Thus our data show that GM-CSF, IL-8, and IL-6 are directly inducible in nasal fibroblasts by LPS, and establish heterogeneous responsiveness to LPS by different fibroblast populations in the airways.
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