[The effect of mitochondrial oxidative stress and the expression of Bcl-2 and Bax proteins on cardiomyocyte apoptosis during hypoxia postconditioning].

Abstract

OBJECTIVE:

To investigate mitochondrial oxidative stress on cardiomyocyte apoptosis and the expression of Bcl-2 and Bax proteins in cardiac sarcolemma and mitochondria after application of hypoxia postconditioning and free radical scavengers.

METHODS:

Primary cultured neonatal rat cardiomyocytes were exposed to 3 h hypoxia (H) followed by (1) 6 h of reoxygenation (R) (H/R), (2) 3 intermittent cycles of 5 min H and R before 6 h of R (PC), (3) application of superoxide dismutase (SOD) before PC (SOD+PC), (4) application of catalase (CAT) before PC (CAT+PC), and (5) application of SOD plus CAT before PC (SOD+CAT+PC). Cardiac sarcolemma and mitochondria were isolated by differential centrifugation. Mitochondrial reactive oxygen species (ROS) was detected with fluorescent probes (DCFH-DA) and cardiomyocyte apoptosis was detected with flow cytometry. The expressions of Bcl-2 and Bax proteins in cardiac sarcolemma and mitochondria were measured by Western blot.

RESULTS:

Mitochondrial ROS reduced significantly in PC, SOD+PC, CAT+PC and especially in SOD+CAT+PC groups (all P<0.01). The number of apoptotic cardiomyocytes reduced significantly in PC, SOD+PC and CAT+PC (all P<0.01) but not in SOD+CAT+PC groups. Bcl-2 levels increased while Bax levels decreased in cardiac sarcolemma and mitochondria in PC, SOD+PC and CAT+PC groups (all P<0.01), Bcl-2 levels decreased and Bax levels increased in H/R and PC+SOD+CAT groups (all P<0.01).

CONCLUSIONS:

PC attenuated H/R induced ROS and cardiomyocyte apoptosis, which might be mediated by upregulating the expression of Bcl-2 and downregulating the Bax in mitochondria and sarcolemma; SOD or CAT alone did not but SOD plus CAT attenuate the anti-apoptotic effect of hypoxia postconditioning; mitochondrial ROS thus plays an important role in PC's cardioprotection.

• Authors: Rong-hui Tu, Li Chen, Guo-qiang Zhong, Zhi-yu Zeng, Qing-jie Li, Yan He, Yan He, Jin-yi Li
• Journal: Zhonghua xin xue guan bing za zhi (Zhonghua Xin Xue Guan Bing Za Zhi) Vol. 40 Issue 6 Pg. 516-21 (Jun 2012) ISSN: 0253-3758 [Print] China
• PMID: 22943649 (Publication Type: English Abstract, Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Bax protein, rat
• Proto-Oncogene Proteins c-bcl-2
• Reactive Oxygen Species
• bcl-2-Associated X Protein

Topics

• Animals
• Apoptosis
• Cell Hypoxia
• Cells, Cultured
• Mitochondria (metabolism)
• Myocytes, Cardiac (cytology, metabolism)
• Oxidative Stress
• Proto-Oncogene Proteins c-bcl-2 (metabolism)
• Rats
• Rats, Sprague-Dawley
• Reactive Oxygen Species (metabolism)
• bcl-2-Associated X Protein (metabolism)