Depressing Mitochondria-Reticulum Interactions Protects Cardiomyocites from Lethal Hypoxia-Reoxygenation Injury
Background—Under physiological conditions, Ca2+ transfer from the endoplasmic reticulum (ER) to mitochondria might occur at least in part at contact points between the two organelles, and involves the VDAC1/Grp75/IP3R1 complex. Accumulation of Ca2+into the mitochondrial matrix may activate the mitochondrial chaperone cyclophilin D (CypD) and trigger permeability transition pore (PTP) opening, whose role in ischemia-reperfusion injury is well recognized. We questioned here whether the transfer of Ca2+ from ER to mitochondria might play a role in cardiomyocyte death after hypoxia-reoxygenation.
Methods and Results—We report that CypD interacts with the VDAC1/Grp75/IP3R1 complex in cardiomyocytes. Genetic or pharmacologic inhibition of CypD in both H9c2 cardiomyoblasts and adult cardiomyocytes decreased the Ca2+ transfer from ER to mitochondria through IP3R under normoxic conditions. During hypoxia-reoxygenation (HR), the interaction between CypD and the IP3R1 Ca2+ channeling complex increased concomitantly with mitochondrial Ca2+ content. Inhibition of either CypD, IP3R1 or Grp75 decreased protein interaction within the complex, attenuated mitochondrial Ca2+ overload and protected cells from HR. Genetic or pharmacological inhibition of CypD provided similar effect in adult mice cardiomyocytes. Noteworthy, disruption of ER-mitochondria interaction via the down-regulation of Mfn2 similarly reduced the interaction between CypD and the IP3R1 complex and protected against HR injury.
Conclusions—Our data point first, to a new role of CypD at the ER-mitochondria interface, and second, suggest that decreasing ER-mitochondria interaction at reperfusion can protect cardiomyocytes against lethal reperfusion injury through the reduction of mitochondrial Ca2+ overload via the CypD/VDAC1/Grp75/IP3R1 complex.
- mitochondria-associated membranes
- ischemia reperfusion injury
- sarcoplasmic reticulum
- Received May 16, 2013.
- Revision received August 5, 2013.
- Accepted August 9, 2013.