Background: Myocardial ischemia/reperfusion injury (MI/RI) is a clinical issue in MI therapy that requires effective intervention. Cathepsin B (CTSB) plays an essential role in regulating cell death, inflammatory response and angiogenesis. Ilexsaponin I (ISI), a triterpenoid saponin obtained from Ilex pubescens Hook. et Arn, has anti-inflammatory and cardioprotective effects. However, the effect of ISI on MI/RI is unclear.
Purpose: The study aims to disclose the mechanism of ISI as a potent therapeutic agent for MI/RI.
Methods: Left anterior descending (LAD) coronary artery ligation and oxygen-glucose deprivation and reperfusion (OGD/R) were used to establish MI/RI model in vivo and in vitro. ELISA, western blot and immunofluorescence were carried out to detect CTSB activity and NLRP3 inflammasome activation. Coimmunoprecipitation (Co-IP), molecular docking and surface plasmon resonance (SPR) analysis were used to detect the interaction of CTSB/HSP70 complex. Infarct area determination, echocardiography and hematoxylin and eosin (HE) staining were performed to assess the cardioprotection of ISI in vivo.
Results: Plasma CTSB was elevated in patients after percutaneous coronary intervention (PCI), and was positively correlated with the level of cTnI in plasma, which was also found in MI/RI rat model. ISI significantly suppressed the overexpression and activity of CTSB after MI/RI or OGD/R. ISI remarkably suppressed CTSB triggered-NLRP3 inflammasome activation and reduced the maturation of IL-1β and IL-18. Importantly, we firstly found that ISI promoted CTSB/HSP70 complex formation to disrupt CTSB/NLRP3 complex, leading to NLRP3 inflammasome inactivation. ISI could also limit infarct size, improve cardiac function and reduce inflammatory infiltrates in vivo and protected H9c2 cells against OGD/R insult in vitro. Interrupting the HSP70 and CTSB interaction with HSP70 siRNA blocked the effect of ISI on CTSB, NLRP3 inflammasome activation and the cardioprotective effect.
Conclusion: ISI probably exerts cardioprotective effect against MI/RI by modulating HSP70 competitively bind to CTSB to suppress the activation of the NLRP3 inflammasome.
Keywords: HSP70/Cathepsin B interaction; Ilexsaponin I; Myocardial ischemia/reperfusion injury; NLRP3-mediated pyroptosis.
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