Fingerprinting of the TLR4-induced acute inflammatory response

Abstract

Intensive scientific efforts in the past decades have helped shed light into the pathogenesis of endotoxin-induced inflammation. We have used multiplexing bead-based assays to characterize the responses in two models of in vivo LPS challenge. C57BL/6 mice were either injected intraperitoneally (endotoxemia) or intratracheally (acute lung injury; ALI) with lipopolysaccharide (LPS). The time courses (1h-24h) of the following 20 inflammatory mediators in plasma or broncho-alveolar lavages were simultaneously analyzed: IL-1α, IL-1β, IL-2, IL-3, IL-4, IL-5, IL-6, IL-9, IL-12(p40), IL-13, Eotaxin (CCL11), G-CSF, GM-CSF, IFN-γ, KC (CXCL1), MCP-1 (CCL2), MIP-1α (CCL3), MIP-1β (CCL4), RANTES (CCL5) and TNF-α. While significant inductions of all mediators were found, substantial differences in their absolute concentrations, time points of maximal concentrations and clearances were observed. There were also notable variations in the patterns of several cytokines/chemokines when samples from endotoxemia and LPS-ALI were compared. These data may be helpful in defining analytic strategies including selection of optimal time points for studying the host immune response to endotoxin.

Figure 1

Release of inflammatory mediators following intraperitoneal challenge with LPS (endotoxemia). Male C57BL/6J mice (n=4–6 mice per group and at each time point) were injected with LPS and plasma at different time points analyzed for the concentrations (expressed as pg/ml) of 20 cytokines/chemokines by multiplexing bead-based assays. Sham indicates normal C57BL/6J mice injected with PBS i.p. only. Student t-test, * P < 0.05 as compared to sham.

Figure 2

Release of inflammatory mediators following intrapulmonary challenge with LPS (LPS-ALI). Male C57BL/6J mice (n=5 per group and at each time point) were injected with LPS intratracheally. Broncho-alveolar lavage fluids were collected at different time points and the concentrations (expressed as pg/ml) of 20 mediators detected by multiplexing bead-based assays. Sham mice received PBS intratracheally. Student t-test, * P < 0.05 as compared to sham.