Glatiramer acetate blocks interleukin-1-dependent nuclear factor-κB activation and RANTES expression in human U-251 MG astroglial cells

Abstract

RANTES is a basic 8-kDa polypeptide of the C–C chemokine subfamily with strong chemoattractant activity for T lymphocytes and monocytes/macrophages that are implicated in the pathogenesis of multiple sclerosis (MS) lesions. Glatiramer acetate is a drug recently approved for the treatment of MS. We therefore investigated the effect of glatiramer acetate on RANTES expression in glial cells in vitro. Treatment of human U-251 MG astroglial cells with glatiramer acetate blocks IL-1β-induced RANTES chemokine production in a dose- and time-dependent manner. Glatiramer acetate also decreased steady-state levels of RANTES mRNA in these cells, which was attributable to reduced transcription, as assessed by nuclear run-on assays. In addition, we showed that NF-κB may be the transcriptional activator responsible for the IL-1β-mediated RANTES gene expression in this system. Our data indicated that the IL-1β-induced increase in RANTES was associated with an increase in in vitro nuclear extract binding activity specific for the NF-κB site in the promoter region of the RANTES gene. The increases in RANTES mRNA and protein expression were suppressed by the NF-κB inhibitors gliotoxin, isohelenin, and pyrrolidine dithiocarbamate (PDTC). Furthermore, we demonstrated that the increase in NF-κB DNA-binding activity was prevented by pretreatment with glatiramer acetate or the NF-κB inhibitors. Our results suggest that glatiramer acetate may inhibit IL-1β-stimulated RANTES expression in human glial cells by blocking NF-κB activation, thus identifying part of the molecular basis for its anti-inflammatory and immunosuppressive effects in demyelinating diseases.