Ethyl pyruvate inhibits HMGB1 phosphorylation and release by chelating calcium

Mol Med. 2015 Mar 13;20(1):649-57. doi: 10.2119/molmed.2014.00039.

Abstract

Ethyl pyruvate (EP), a simple aliphatic ester of pyruvic acid, has been shown to have antiinflammatory effects and to confer protective effects in various pathological conditions. Recently, a number of studies have reported EP inhibits high mobility group box 1 (HMGB1) secretion and suggest this might contribute to its antiinflammatory effect. Since EP is used in a calcium-containing balanced salt solution (Ringer solution), we wondered if EP directly chelates Ca(2+) and if it is related to the EP-mediated suppression of HMGB1 release. Calcium imaging assays revealed that EP significantly and dose-dependently suppressed high K(+)-induced transient [Ca(2+)]i surges in primary cortical neurons and, similarly, fluorometric assays showed that EP directly scavenges Ca(2+) as the peak of fluorescence emission intensities of Mag-Fura-2 (a low-affinity Ca(2+) indicator) was shifted in the presence of EP at concentrations of ≥7 mmol/L. Furthermore, EP markedly suppressed the A23187-induced intracellular Ca(2+) surge in BV2 cells and, under this condition, A23187-induced activations of Ca(2+)-mediated kinases (protein kinase Cα and calcium/calmodulin-dependent protein kinase IV), HMGB1 phosphorylation and subsequent secretion of HMGB1 also were suppressed. (A23187 is a calcium ionophore and BV2 cells are a microglia cell line.) Moreover, the above-mentioned EP-mediated effects were obtained independent of cell death or survival, which suggests that they are direct effects of EP. Together, these results indicate that EP directly chelates Ca(2+), and that it is, at least in part, responsible for the suppression of HMGB1 release by EP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcimycin / pharmacology
  • Calcium / metabolism*
  • Cell Line
  • Cells, Cultured
  • HMGB1 Protein / antagonists & inhibitors*
  • HMGB1 Protein / metabolism
  • Mice
  • N-Methylaspartate / pharmacology
  • Neurons / drug effects
  • Phosphorylation
  • Pyruvates / pharmacology*

Substances

  • HMGB1 Protein
  • Pyruvates
  • ethyl pyruvate
  • Calcimycin
  • N-Methylaspartate
  • Calcium