Differential induction of interleukin-6 production by monocytes, endothelial cells and smooth muscle cells.

Studying the production of IL-6 by monocytes, endothelial cells and smooth muscle cells we observed that cytokine inducers like IL-1, TNF alpha, LPS, SAC and PMA could be divided roughly into two categories. One, that consisted of LPS and SAC, which had a potent IL-6 inducing effect on monocytes and minor or no effect on endothelial- and smooth muscle cells. The other category, consisting of IL-1, TNF alpha and PMA, induced IL-6 production in endothelial- and smooth muscle cells and of which IL-1 also induced IL-6 in monocytes. Only IL-1 induced IL-6 production in monocytes as well as in endothelial cells and smooth muscle cells. Besides IL-6, also IL-1 and TNF alpha were produced by monocytes however with different kinetics. None of the stimuli had any inhibitory effect on IL-6 production with the exception of PMA. Whereas PMA induced IL-6 production in endothelial cells and it potentiated the induction of IL-6 by IL-1 in these cells, it inhibited LPS-stimulated IL-6 production in monocytes. In line with the effects of PMA, staurosporin induced IL-6 production in monocytes and it inhibited IL-1 driven IL-6 production by endothelial cells.