Th1 cytokines stimulate RANTES chemokine secretion by human astroglial cells depending on de novo transcription.

Beta-chemokines induce the directional migration of monocytes and T lymphocytes that are implicated in the pathogenesis of multiple sclerosis (MS) lesions. RANTES is a member of the beta-chemokine family that has been detected in the lesions of MS patients. However, the cellular sources of RANTES message and the molecular basis for the regulation of its production in MS lesions are not well understood. Glial cells may be a major source of RANTES in vivo and have been shown to produce RANTES in vitro. Thus, the objective of this study was to establish a model system for studying the regulation of RANTES expression by cytokines in cultured human glial cells, and to determine the mechanism involved in the process. We show that the Th1 cytokines TNF-alpha and IL-1beta independently induce RANTES mRNA and chemokine levels in human U-251 MG astroglial cells, and that these effects are time- and concentration-dependent. In addition, we demonstrate that both cytokines increased the rate of transcription of the RANTES gene, as estimated by in vitro nuclear transcript elongation assays. The transcriptional activity in TNF-alpha-treated U-251 MG cells started to increase at 2 h and peaked at 8 h, with levels more than 14 times greater than controls. We further show that NF-kappaB may play a critical role in the up-regulation of human RANTES gene expression in this system. Gel shift assays revealed an induction of in vitro nuclear extract binding activity to the NF-kappaB element of RANTES in cells incubated with the Th1 cytokines. These observations suggest that human astroglia, within diseased brain, may be stimulated to produce RANTES chemokine in response to TNF-alpha and IL-1beta, and that this effect of the Th1 cytokines is attributed to increase of transcription.