NF-κB translocation and endothelial cell activation is potentiated by macrophage-released signals co-secreted with TNF-α and IL-1β

Abstract.

Objective and Methods: Over-expression of the immune response can lead to pathological conditions such as septic shock or chronic inflammation. Endothelial cell activation by pro-inflammatory products of activated macrophages plays a key role in these conditions. Here we examine the response of primary human endothelial cells (HUVEC) to conditioned media (CM) obtained from LPS-activated macrophages. We further characterized the translocation of NF-κB in the presence of CM by studying the degradation rate of individual IκB isoforms.

Results: We show that, as expected, CM induced NF-κB translocation, as well as adhesion capacity in HUVEC. We further show that this response is critically dependent on TNF-α and IL1β naturally present in the CM. However, both the amplitude of NF-κB translocation and adhesiveness observed with CM were well beyond the saturation levels attained after the sole stimulation with recombinant TNF-α and IL-1β, either separately or together. Our results show that CM induced a faster degradation of the IκB-β and IκB-ɛ isoforms than the recombinant cytokines, leading to an enhanced recruitment of NF-κB activity.

Conclusions: The above results suggest that the physiological context of factors co-secreted by LPS-activated macrophages enhances TNF-α mediated endothelial activation.