TGF-beta 1, IL-10 and IL-4 differentially modulate the cytokine-induced expression of IL-6 and IL-8 in human endothelial cells.

Multiple cytokines and growth factors are present at sites of inflammation, and each of these can potentially influence the nature of the inflammatory response. Vascular endothelial cells (ECs) must integrate the signals generated by these multiple factors to effectively regulate the immune response and homeostasis. IL-6 and IL-8 and endothelial-derived products which play an important role as regulators of these processes. As a model for how ECs respond to signals from multiple cytokines, we have examined the effects of pretreatment with TGF-beta 1, IL-10 or IL-4 on TNF-alpha, IL-1 beta- or LPS-induced expression of IL-6 and IL-8 in human umbilical vein endothelial cells (HUVEC). Treatment of HUVEC with TGB-beta 1 or IL-10 significantly inhibited, but did not completely abolish, the TNF-alpha-, IL-1 beta- or LPS-induced expression of IL-6 and IL-8 protein. Maximal inhibition was achieved with physiologically relevant doses (1-2 ng/ml) of either TGF-beta 1 or IL-10. The inhibitory effects of TGF-beta and IL-10 were additive in nature. In contrast, pretreatment with IL-4 amplified the production of IL-6 in TNF-alpha-, IL-1 beta- or LPS-activated ECs, but inhibited IL-8 expression. Addition of TGF-beta 1 completely reversed the effects of IL-4 on IL-6 expression, whilst augmenting inhibition of IL-8. These studies demonstrate that multiple cytokines can act in concert to differentially regulate the endothelial expression of cytokines important to the inflammatory response. Modulation of endothelial cytokine production may contribute to the progression or resolution of the inflammatory response.