Panax notoginseng saponins inhibit ischemia-induced apoptosis by activating PI3K/Akt pathway in cardiomyocytes
Graphical abstract
Introduction
Myocardial ischemia is a pathological process that results in extensive cell death. Cardiomyocytes death involves apoptotic and necrotic cell death, and apoptosis is one of the main causes of ischemia injury (Saraste et al., 1997, Ohno et al., 1998). Exploring anti-apoptotic agents is a novel therapeutic opportunity for ischemia diseases (Feuerstein, 2001).
Panax notoginseng saponins (PNS) are the main effective constituents of Panax notoginseng [(Burk.) F.H. Chen] (Sanqi or Tianqi in Chinese). A wide range of pharmacological activities of PNS in cardiovascular, immune, endocrine and central nervous system had been reported previously (Ng, 2006). The heart protective effect of PNS on rat model of coronary artery ligation-induced ischemic and reperfusion arrhythmias had been well documented (Gao et al., 1992, Chan et al., 2002, Wan et al., 2009). PNS also decreased the size of myocardial infarcts, and protected against CaCl2-Ach induced atrial fibrillation and flutter in mice (Gao et al., 1992). Although PNS have been shown to protect against ischemic heart diseases in animal model, the involved mechanism is still unclear.
It is of importance to explore the action mechanism of PNS as a novel therapeutics for ischemic diseases (Feuerstein, 2001). In present study, we investigated the therapeutic effects and potential mechanism of PNS on ischemia-induced myocardial injury in H9c2 cells in vitro and in rat myocardial ischemia injury model in vivo, especially focusing the effect of PNS on PI3K/Akt pathway. The PI3K/Akt is a powerful survival signaling pathway in many systems (Mullonkal and Toledo-Pereyra, 2007, Steelman et al., 2008). Activated PI3K and Akt are each sufficient to protect hypoxic cardiomyocytes against apoptosis in vitro (Matsui et al., 1999). Inhibition of PI3K accelerated apoptosis, and activation of Akt blocked apoptosis (Kennedy et al., 1997). Activation of the PI3K/Akt pathway may be useful to promote myocytes survival in the damaged heart (Fujio et al., 2000).
We hypothesized that PNS might inhibit cell apoptosis caused by ischemia in cardiomyocytes in vitro and in vivo through activating PI3K/Akt signaling pathway.
Section snippets
Drug and reagents
Panax notoginseng saponins (PNS) were supplied by Livzon Pharmaceutical Group Inc. (batch number 0711129). The phosphor-Akt (Ser473) (D9E) rabbit mAb and Akt (pan) (C67E7) rabbit mAb were purchased from Cell Signaling Technology. β-Actin antibody was purchased from Santa Cruz Biotechnology.Annexin-V/PI kit was purchased from Bender MdeSystems. LY294002 was purchased from CALBIOCHEM. Complete Lysis-M, EDTA-free and PhosSTOP were purchased from Roche. ECL was purchased from Invitrogen.
Cells grouping
The H9c2
PNS inhibited H9c2 cells from apoptosis induced by SGOD
H9c2 cells were subjected to SGOD and treated with/without PNS for 72 h. As shown in Fig. 1, the percentage of apoptotic cells in model group was 65.71%, whereas 8.01% in the normal control group. SGOD treatment for 72 h obviously induced H9c2 cells apoptosis. PNS did not change the apoptotic ratio at the concentration of 0.05 g/L, but significantly decreased (p < 0.01) the ratio at the concentration of 0.25 g/L. The anti-apoptotic effect of PNS was especially obvious at the concentration of 2.25 g/L.
Discussion
Accumulated evidence indicated that apoptosis contributes significantly to post-ischemic myocardial cell death, suggesting that therapeutic interventions that inhibit apoptotic cell death may attenuate ischemic-induced heart injury (Feuerstein, 1999, Feuerstein, 2001, Jacotot et al., 2006, Caroppi et al., 2009). PNS, as the effective components of panax notoginseng, have been used in clinic for treatment of cardiovascular diseases and stroke in China. The anti-apoptotic effect of PNS on
Acknowledgments
We thank Dr. Feng Xu (Zhujing Hospital of Southern Medical University) and Dr. Shilong Zhong (Medical Research Center, Guangdong General Hospital, Guangdong Academy of Medical Sciences) for the critical reading of the manuscript. This study was supported by Administration of Traditional Chinese Medicine of Guangdong Province, China (NO. 2008206), Science and Technology Planning Project of Guangdong Province, China (N0. 2009B080701054) and Cardiovascular Drug Research Fund of Guangdong Province,
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