Cyclophilin D ablation is associated with increased end-ischemic mitochondrial hexokinase activity
Rianne Nederlof1, Mark A M van den Elshout1, Anneke Koeman1
1Laboratory of Experimental Intensive Care and Anesthesiology, Department of Anesthesiology, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
Insights
Absence of cyclophilin D (CypD) protects the heart from ischemia/reperfusion injury. CypD deficiency increases mitochondrial hexokinase II (mtHKII) activity in a multi-substrate perfusion model, enhancing protection.
Area of Science:
- Cardiovascular Biology
- Mitochondrial Biochemistry
- Ischemia-Reperfusion Injury
Background:
- Cyclophilin D (CypD) absence and mitochondrial hexokinase II (mtHKII) presence protect the heart against ischemia/reperfusion (I/R) injury.
- The relationship between CypD and mtHKII levels in the heart remains unclear.
Purpose of the Study:
- To investigate whether CypD influences mitochondrial hexokinase (mtHK) levels in isolated mouse hearts under normoxic, ischemic, and preconditioned conditions.
Main Methods:
- Isolated wild-type (WT) and CypD knockout (CypD-/-) mouse hearts were perfused with either glucose only or a multi-substrate solution (glucose, glutamine, pyruvate, lactate).
- Hearts were subjected to 25 minutes of ischemia followed by reperfusion.
- Mitochondrial hexokinase (mtHK) levels and activity were assessed.
Main Results:
- In glucose-only perfused hearts, CypD ablation protected against I/R injury and enhanced ischemic preconditioning (IPC) effects without altering end-ischemic mtHK levels.
- In multi-substrate perfused hearts, CypD deficiency provided greater protection against I/R injury, associated with increased mtHK activity.
- IPC offered limited additional protection in multi-substrate perfused CypD knockout hearts.
Conclusions:
- CypD deletion is not linked to end-ischemic mtHK binding in glucose-only perfused hearts.
- In a physiologically relevant multi-substrate model, CypD deficiency is associated with increased mtHK activity, potentially explaining enhanced protection against I/R injury.
Abstract:
Both the absence of cyclophilin D (CypD) and the presence of mitochondrial bound hexokinase II (mtHKII) protect the heart against ischemia/reperfusion (I/R) injury. It is unknown whether CypD determines the amount of mtHKII in the heart. We examined whether CypD affects mtHK in normoxic, ischemic and preconditioned isolated mouse hearts. Wild type (WT) and CypD-/- mouse hearts were perfused with glucose only and subjected to 25 min ischemia and reperfusion. At baseline, cytosolic and mtHK was similar between hearts. CypD ablation protected against I/R injury and increased ischemic preconditioning (IPC) effects, without affecting end-ischemic mtHK. When hearts were perfused with glucose, glutamine, pyruvate and lactate, the preparation was more stable and CypD ablation-resulted in more protection that was associated with increased mtHK activity, leaving little room for additional protection by IPC. In conclusion, in glucose only-perfused hearts, deletion of CypD is not associated with end-ischemic mitochondrial-HK binding. In contrast, in the physiologically more relevant multiple-substrate perfusion model, deletion of CypD is associated with an increased mtHK activity, possibly explaining the increased protection against I/R injury.
