Related Experiment Videos
BNip3 and signal-specific programmed death in the heart
Keith A Webster1, Regina M Graham, Nanette H Bishopric
1Department of Molecular and Cellular Pharmacology, University of Miami Medical Center, 1600 NW 10th Avenue, RMSB 6038, Miami, FL 33136, USA. kwebster@chroma.med.miami.edu
Journal of Molecular and Cellular Cardiology
|December 30, 2004
Summary
BNip3, a Bcl-2 family protein, triggers cardiac myocyte death during ischemia via an atypical pathway. Hypoxia and acidosis induce BNip3, leading to mitochondrial dysfunction and cell death, independent of caspases.
Area of Science:
- Cardiology
- Cell Biology
- Biochemistry
Background:
- The Bcl-2 family regulates cell death, with BH3-only proteins like BNip3 modulating apoptosis.
- Cardiac myocytes are resistant to neutral hypoxia but die when pH drops.
- BNip3 is a key player in programmed cell death pathways.
Purpose of the Study:
- Investigate BNip3's role in cardiac myocyte apoptosis during ischemia.
- Elucidate the signaling pathway activated by BNip3 under hypoxic and acidic conditions.
- Determine if BNip3 triggers classical apoptosis or an alternative cell death mechanism.
Main Methods:
- Cardiac myocytes cultured under hypoxic conditions with varying pH.
- Microarray analysis to identify hypoxia-inducible genes.
- Western blotting for BNip3 protein levels.
- Mitochondrial association studies.
- Inhibition studies using caspase inhibitors, antisense BNip3, and MPTP inhibitors.
Main Results:
- Hypoxia with acidosis caused extensive cardiac myocyte death.
- BNip3 mRNA and protein levels significantly increased under hypoxia, further enhanced by acidosis.
- BNip3 tightly associated with mitochondria at acid pH, coinciding with MPTP opening.
- Cell death was not blocked by caspase inhibitors but was inhibited by BNip3 knockdown and MPTP inhibitors.
Conclusions:
- BNip3 is a critical mediator of cardiac myocyte death induced by hypoxia and acidosis.
- BNip3 activates a non-apoptotic programmed cell death pathway involving MPTP.
- This pathway explains cardiac myocyte resistance to neutral hypoxia but susceptibility to acidic conditions.