High-mobility group box 1 (HMGB1) impaired cardiac excitation-contraction coupling by enhancing the sarcoplasmic reticulum (SR) Ca(2+) leak through TLR4-ROS signaling in cardiomyocytes

J Mol Cell Cardiol. 2014 Sep;74:260-73. doi: 10.1016/j.yjmcc.2014.06.003. Epub 2014 Jun 14.

Abstract

High-mobility group box 1 (HMGB1) is a proinflammatory mediator playing an important role in the pathogenesis of cardiac dysfunction in many diseases. In this study, we explored the effects of HMGB1 on Ca(2+) handling and cellular contractility in cardiomyocytes to seek for the mechanisms underlying HMGB1-induced cardiac dysfunction. Our results show that HMGB1 increased the frequency of Ca(2+) sparks, reduced the sarcoplasmic reticulum (SR) Ca(2+) content, and decreased the amplitude of systolic Ca(2+) transient and myocyte contractility in dose-dependent manners in adult rat ventricular myocytes. Inhibiting high-frequent Ca(2+) sparks with tetracaine largely inhibited the alterations of SR load and Ca(2+) transient. Blocking Toll-like receptor 4 (TLR4) with TAK-242 or knockdown of TLR4 by RNA interference remarkably inhibited HMGB1 induced high-frequent Ca(2+) sparks and restored the SR Ca(2+) content. Concomitantly, the amplitude of systolic Ca(2+) transient and myocyte contractility had significantly increased. Furthermore, HMGB1 increased the level of intracellular reactive oxygen species (ROS) and consequently enhanced oxidative stress and CaMKII-activated phosphorylation (pSer2814) in ryanodine receptor 2 (RyR2). TAK-242 pretreatment significantly decreased intracellular ROS levels and oxidative stress and hyperphosphorylation in RyR2, similar to the effects of antioxidant MnTBAP. Consistently, MnTBAP normalized HMGB1-impaired Ca(2+) handling and myocyte contractility. Taken together, our findings suggest that HMGB1 enhances Ca(2+) spark-mediated SR Ca(2+) leak through TLR4-ROS signaling pathway, which causes partial depletion of SR Ca(2+) content and hence decreases systolic Ca(2+) transient and myocyte contractility. Prevention of SR Ca(2+) leak may be an effective therapeutic strategy for the treatment of cardiac dysfunction related to HMGB1 overproduction.

Keywords: Ca(2+) transient; HMGB1; Reactive oxygen species (ROS); SR Ca(2+) content; Sarcoplasmic reticulum (SR) Ca(2+) leak; Toll-like receptor (TLR) 4.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Calcium / metabolism*
  • Calcium Signaling
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2 / genetics
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2 / metabolism
  • Excitation Contraction Coupling / genetics*
  • Female
  • Gene Expression Regulation
  • HMGB1 Protein / genetics
  • HMGB1 Protein / metabolism*
  • Heart Ventricles / cytology
  • Heart Ventricles / drug effects
  • Heart Ventricles / metabolism
  • Male
  • Metalloporphyrins / pharmacology
  • Myocytes, Cardiac / cytology
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / metabolism*
  • Primary Cell Culture
  • Rats
  • Rats, Sprague-Dawley
  • Reactive Oxygen Species / metabolism
  • Ryanodine Receptor Calcium Release Channel / genetics
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Sarcoplasmic Reticulum / drug effects
  • Sarcoplasmic Reticulum / metabolism*
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / antagonists & inhibitors
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / genetics
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism
  • Sulfonamides / pharmacology
  • Tetracaine / pharmacology
  • Toll-Like Receptor 4 / antagonists & inhibitors
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / metabolism*

Substances

  • HMGB1 Protein
  • Hbp1 protein, rat
  • Metalloporphyrins
  • Reactive Oxygen Species
  • Ryanodine Receptor Calcium Release Channel
  • Sulfonamides
  • Tlr4 protein, rat
  • Toll-Like Receptor 4
  • ethyl 6-(N-(2-chloro-4-fluorophenyl)sulfamoyl)cyclohex-1-ene-1-carboxylate
  • manganese(III)-tetrakis(4-benzoic acid)porphyrin
  • Tetracaine
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium