Glucocorticoids: do we know how they work?
It is not known to what extent glucocorticoid hormones cause their anti-inflammatory actions and their undesirable side effects by the same or different molecular mechanisms. Glucocorticoids combine with a cytoplasmic receptor that alters gene expression in two ways. One way is dependent on the receptor's binding directly to DNA and acting (positively or negatively) as a transcription factor. The other is dependent on its binding to and interfering with other transcription factors. Both mechanisms could underlie suppression of inflammation. The liganded receptor binds and inhibits the inflammatory transcription factors activator protein-1 and NF-kappaB. It also directly induces anti-inflammatory genes such as that encoding the protein inhibitor of NF-kappaB. Recent work has shown that glucocorticoids inhibit signalling in the mitogen-activated protein kinase pathways that mediate the expression of inflammatory genes. This inhibition is dependent on de novo gene expression. It is important to establish the significance of these different mechanisms for the various physiological effects of glucocorticoids, because it may be possible to produce steroid-related drugs that selectively target the inflammatory process.