Pivotal Advance: Inhibition of HMGB1 nuclear translocation as a mechanism for the anti-rheumatic effects of gold sodium thiomalate

Cecilia K. Zetterström^*^,^,1, Weiwen Jiang^,1, Heidi Wähämaa^*^,, Therese Östberg^*^,, Ann-Charlotte Aveberger^*, Hanna Schierbeck^*, Michael T. Lotze, Ulf Andersson^*^,^,2, David S. Pisetsky and Helena Erlandsson Harris

^* Departments of Woman and Child Health, Pediatric Rheumatology Research Unit, and
Medicine, Rheumatology Unit, Karolinska Institutet/Karolinska University Hospital, Stockholm, Sweden;
Division of Rheumatology and Immunology, Department of Medicine, Duke University, Durham, North Carolina, USA; and
Surgery and Bioengineering, DAMP Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA

² Correspondence: Department of Woman and Child Health, Astrid Lindgren Children’s Hospital, Q1:02, S-17176 Stockholm, Sweden. E-mail: ulf.andersson{at}ki.se

ABSTRACT

Gold compounds such as gold sodium thiomalate (GST) can reducethe symptoms of rheumatoid arthritis (RA), although their mechanismof action is not well defined. As the proinflammatory mediatorhigh mobility group box chromosomal protein 1 (HMGB1) may playa role in the pathogenesis of RA, we have performed in vitrostudies to investigate whether GST inhibits HMGB1 release asthe basis of its mode of action. Murine RAW 264.7 or human THP-1macrophage cells were stimulated in culture with agents causingextracellular HMGB1 release, including LPS, IFN- ${gamma}$ , polyinosinic:polycytidylicacid, IFN-β, or NO in the presence of GST, ranging from0 µM to 250 µM. Secretion and intracellular locationof HMGB1 were assessed by Western blotting, HMGB1-specific ELISPOTassay, and immunofluorescent staining. In parallel, TNF andIFN-β levels were analyzed by ELISPOT and/or ELISA. SupernatantNO production was analyzed by the Griess method. At pharmacologicallyrelevant doses, GST inhibited the extracellular release of HMGB1from activated macrophages and caused the nuclear retentionof this protein; in contrast, no effects were observed on thesecretion or production of TNF. Release of the key endogenousmediators of HMGB1 translocation, IFN-β and NO, was inhibitedby GST. This inhibition required gold, as sodium thiomalatedid not affect the responses measured. Furthermore, gold chloridealso inhibited release of HMGB1. Together, these results suggesta new mechanism for the anti-rheumatic effects of gold saltsin RA and the potential of drugs, which interfere with intracellularHMGB1 transport mechanisms, as novel agents to treat RA.

Key Words: gold salts • arthritis • inflammation • therapy • cytokines • immunomodulation • TNF • IFN-β • nitric oxide