Targeting Extracellular Heat Shock Protein 70 Ameliorates Doxorubicin-Induced Heart Failure Through Resolution of Toll-Like Receptor 2-Mediated Myocardial Inflammation.

Background Heart failure (HF) is one of the most significant causes of morbidity and mortality for the cardiovascular risk population. We found previously that extracellular HSP70 (heat shock protein) is an important trigger in cardiac hypertrophy and fibrosis, which are associated with the development of heart dysfunction. However, the potential role of HSP70 in response to HF and whether it could be a target for the therapy of HF remain unknown. Methods and Results An HF mouse model was generated by a single IP injection of doxorubicin at a dose of 15 mg/kg. Ten days later, these mice were treated with an HSP70 neutralizing antibody for 5 times. We observed that doxorubicin treatment increased circulating HSP70 and expression of HSP70 in myocardium and promoted its extracellular release in the heart. Blocking extracellular HSP70 activity by its antibody significantly ameliorated doxorubicin-induced left ventricular dilation and dysfunction, which was accompanied by a significant inhibition of cardiac fibrosis. The cardioprotective effect of the anti-HSP70 antibody was largely attributed to its ability to promote the resolution of myocardial inflammation, as evidenced by its suppression of the toll-like receptor 2-associated signaling cascade and modulation of the intracellular distribution of the p50 and p65 subunits of nuclear factor-κB. Conclusions Extracellular HSP70 serves as a noninfectious inflammatory factor in the development of HF, and blocking extracellular HSP70 activity may provide potential therapeutic benefits for the treatment of HF.

[Blocking extracellular HMGB1 activity protects against doxorubicin induced cardiac injury in mice].

This study aims to investigate the preventive role and potential mechanisms of blocking extracellular HMGB1 function on doxorubicin induced cardiac injury. Mice were treated with HMGB1 blocker glycyrrhizin 1 h before and one time every day (intraperitoneal, 10 mg per mouse) after doxorubicin injection, and sacrificed on the day 14 after doxorubicin challenge. Cardiac function was evaluated by echocardiography and hemodynamic measurement. Myocardial inflammation and collagen deposition were analyzed by immunohistochemistry and picrosirius red staining. The interaction of HMGB1 and TLR2 was assessed by co-immunoprecipitation and confocal microscopy. The protein contents of HMGB1, MyD88, p65NF-kappaB and phospho-p65NF-kappaB were measured by Immunoblot. Compared with mice treated with saline, doxorubicin treatment led to an upregulation in HMGB1 expression. Blocking HMGB1 activity with glycyrrhizin protected mice against cardiac dysfunction, inflammatory response, and cardiac fibrosis induced by doxorubicin challenge. Glycyrrhizin inhibited the interaction of HMGB1 and TLR2, and blocked the downstream signaling of TLR2. In conclusion, blocking HMGB1 protected against doxorubicin induced cardiac injury by inhibiting TLR2 signaling pathway.