Heat Shock Protein 27 Attenuated Lipopolysaccharide-induced Murine Cardiac Dysfunction

Background: Cardiac protection of heat shock protein 27 (Hsp27) have been observed in myocardial ischemia/reperfusion injury and doxorubicin-induced heart failure. However, the role of Hsp27 in endotoxin-induced cardiac dysfunction, a lethal complication during sepsis/septic shock, has not been investigated.Objective: To investigate overexpression of Hsp27 will attenuate endotoxin-induced cardiac dysfunction and its related machanisms.Methods: 1. Male C57BL/6J mice were randomly divided into LPS group (intraperitoneal injection with LPS 10mg/kg) and saline control group. The expression of TLR4 signaling molecule targets were detected at5min, 10min, 30min, 1h, 2h, 6h, 12h, 24h(n=3)after treatment by westem blotting. 2. Transgenic mice overexpressing Hsp27 solely in heart (TG) and wild type littermate controls (WT) were challenged with LPS (10mg/kg, IP). 6h and 24h after LPS exposure, left ventricular (LV) function was determined by Echo (n=6/group). 3.24h after LPS exposure, the activation of the TLR4-mediated MyD88-dependent NFκB pathway was examined by western blotting (n=4/group). 4. The H9c2 cardiac myoblasts, overexpressing Hsp27 or stable transfected with the vector alone, was stimulated with LPS for 15min, 30min, 1h and 2h. The unstimulated cells were used as control. At each time point after stimulation, the myoblasts were collected, the protein was extracted, and the activation of IκB was determined. The H9c2 cardiac myoblasts transiently transfected with NFκB-1uc,pEGFP-C3 or pEGFP-C3/Hsp27 vector were challenged with LPS for 2h, 4h and 24h. And the control groups of unstimulated cells were also established. At each time point, the cells were collected, and the report gene of NF-κB was exanmined.Results: 1. The pathway of TLR4-MyD88-IκBαsignaling was activated 5min after LPS injection, reached the peak at 2h, then decreased (P＜0.05). 2. LPS challenge resulted in significant cardiac dysfunction in WT mice. 6h after LPS, HR, CO, SV, EF and FS in WT mice and TG mice were 373.554±25.068 vs. 457.159±15.125, 0.271±0.038 vs. 0.383±0.032, 0.043±0.004 vs. 0.049±0.004, 37.555±4.961 vs. 47.419±4.706, 15.394±2.384 vs. 20.337±2.509 (P＜0.05). 24h, they were 303.069±8.590 vs. 403.20614.645, 0.193±0.019 vs. 0.350±0.028, 0.038±0.003 vs. 0.054±0.004, 46.272±2.254 vs.58.918±2.624, 19.420±1.214 vs. 26.622±1.638 (P＜0.05). 6h later, LVIDs and ESV were 3.049±0.160 vs. 2.784±0.141, 0.076±0.011 vs. 0.058±0.008 (P＜0.05). AV VTI,PV VTI were 11.158±1.398 vs. 21.400±3.894, 23.451±2.549 vs. 34.229±1.567 6h later (P＜0.05), 13.581±1.714 vs. 23.995±1.434, 23.449±2.205 vs. 32.959±1.426 24h later (P＜0.05). 3. In addition, LPS administration significantly increased the expression of TLR4 and MyD88 and caused IκBαdegradation, resulting in NFκd3 nuclear translocation in the myocardium of WT mice. In LPS challenged TG mice, LPS-induced activation of the TLR4-mediated NFκB pathway was significantly attenuated. 4. We also observed that overexpression of Hsp27 in H9c2 cardiac myoblasts significantly inhibited LPS-induced IκB degradation and NFκB activation.Conclusion: Our findings suggest that Hsp27 plays an important role in attenuation of endotoxin-induced cardiac dysfunction and the mechanism involves down-regulation of LPS-induced activation of TLR4/NFκB pathway.