IL-1 beta and IL-6 gene expression in alveolar macrophages: modulation by extracellular matrices

Interleukin-1 (IL-1) and interleukin-6 (IL-6) are two cytokines involved in a variety of host inflammatory reactions. The alveolar macrophage (AM), a predominant cell source for IL-1 and IL-6, exists in a microenvironment in which there are abundant extracellular matrix (ECM) components, and it is likely that ECM may participate in the inflammatory response in the lung by modulating the effector activities of AMs. To investigate this hypothesis, we cultured rat AMs on different substrates including plastic, collagen, and airways fibroblast-derived ECM (fECM) and assessed IL-1 beta and IL-6 gene expression in these cells. Our study demonstrates that cytokine gene expression in AMs is affected by the conditions of culture. IL-1 gene expression is stimulated by adherence to plastic and exposure to endotoxin, whereas IL-6 mRNA is detectable only in the cells stimulated by endotoxin. Coating the plastic with collagen or fECM modifies cytokine gene expression. At early time points, collagen enhances gene expression. At later times (5 days), actin and cytokine gene expression are predominantly maintained in the endotoxin-stimulated cells cultured on fECM. These findings suggest an extracellular environment-directed mechanism of regulation of cytokine expression in alveolar macrophages.