Oral administration of triptolide ameliorates the clinical signs of experimental autoimmune encephalomyelitis (EAE) by induction of HSP70 and stabilization of NF-κB/IκBα transcriptional complex

Abstract

Available treatments for multiple sclerosis (MS) require frequent injections and have significant side effects. In this study, we examined the immunomodulatory properties of orally administered triptolide, a major diterpenoid triepoxide isolated from a twining vine Tripterygium wilfordii. SJL/J mice were primed with PLP 139–151 peptide and orally treated with triptolide (100 μg/kg per day) from the day of EAE induction (preventive regime) and after the onset of clinical signs (therapeutic regime). Triptolide delayed disease onset, reduced clinical symptoms, decreased the relapse rate, and suppressed inflammation and demyelination in CNS tissue of EAE mice when compared to vehicle-treated animals. Molecular analysis revealed a marked increase of heat shock protein 70 (Hsp70) mRNA and protein in the CNS tissue of triptolide-treated animals. Cytokine and chemokine expression analysis from EAE tissues and in vitro macrophages detected a decrease of key pro-inflammatory mRNAs. Triptolide inhibited IκBα phosphorylation and NF-κB nuclear translocation by stabilization of NF-κB/IκBα complex, possibly due to a direct physical interaction between NF-κB and Hsp70 proteins. Lymph node cell proliferation assay in EAE confirmed the immunosuppressive efficacy of triptolide. Our data indicate that daily oral administration of triptolide exhibits not only a preventive but also a therapeutic effect on EAE. These effects might be explained by the increase in Hsp70 levels driven by triptolide and stabilization of the NF-κB/IκBα complex leading to an attenuated inflammatory response.