A deficiency of apoptosis inducing factor (AIF) in Harlequin mouse heart mitochondria paradoxically reduces ROS generation during ischemia-reperfusion

Abstract

Background and Aims: AIF (apoptosis inducing factor) is a flavin and NADH containing protein located within mitochondria required for optimal function of the respiratory chain. AIF may function as an antioxidant within mitochondria, yet when released from mitochondria it activates caspase-independent cell death. The Harlequin (Hq) mouse has a markedly reduced content of AIF, providing an experimental model to query if the main role of AIF in the exacerbation of cell death is enhanced mitochondrial generation of reactive oxygen species (ROS) or the activation of cell death programs. We asked if the ROS generation is altered in Hq heart mitochondria at baseline or following ischemia-reperfusion (IR).Methods: Buffer perfused mouse hearts underwent 30 min ischemia and 30 min reperfusion. Mitochondrial function including oxidative phosphorylation and H2O2 generation was measured. Immunoblotting was used to determine the contents of AIF and PAR [poly(ADP-ribose)] in cell fractions.Results: There were no differences in the release of H2O2 between wild type (WT) and Hq heart mitochondria at baseline. IR increased H2O2 generation from WT but not from Hq mitochondria compared to corresponding time controls. The complex I activity was decreased in WT but not in Hq mice following IR. The relocation of AIF from mitochondria to nucleus was increased in WT but not in Hq mice. IR activated PARP-1 only in WT mice. Cell injury was decreased in the Hq mouse heart following in vitro IR.Conclusion: A deficiency of AIF within mitochondria does not increase ROS production during IR, indicating that AIF functions less as an antioxidant within mitochondria. The decreased cardiac injury in Hq mouse heart accompanied by less AIF translocation to the nucleus suggests that AIF relocation, rather than the AIF content within mitochondria, contributes to cardiac injury during IR.

Caspase-Dependent and Caspase-Independent Pathways Are Involved in Cadmium-Induced Apoptosis in Primary Rat Proximal Tubular Cell Culture

“…Under different stimuli, PARP-1 [poly (ADP-ribose) polymerase-1] activation triggers mitochondrial AIF release and translocation to the nucleus [50–52]. PARP-1 activation produces PAR in the nucleus, which is released into the cytosol and colocalizes with the mitochondria to induce AIF release [53].…”

Hippocampal Neuroprotection by Minocycline and Epigallo‐Catechin‐3‐Gallate Against Cardiopulmonary Bypass‐Associated Injury

“…ROS and peroxynitrite, which are part of ischemia and reperfusion injury at the end lead to nitrosylated proteins, DNA damage, AIF and caspase‐3 activation. In a very recent study it was demonstrated in a mouse model of reduced AIF expression that cardiac ischemic/reperfusion injury was significantly attenuated if AIF translocation was shut down even if ROS levels were not altered . Thus, AIF relocation seems to be important in the development of tissue damage.…”

High-Resolution Respirometry for Simultaneous Measurement of Oxygen and Hydrogen Peroxide Fluxes in Permeabilized Cells, Tissue Homogenate and Isolated Mitochondria

“…When the cellular antioxidant capacity is overwhelmed, ROS concentrations may increase dramatically and the resulting oxidative stress can cause substantial cell damage and ultimately cell death. Hence, both oxidative stress originating from mitochondrial activity and mitochondrial dysfunction ensuing from related oxidative damage have been shown to play important roles in aging and the pathogenesis of various disease states such as ischemia, neurodegeneration, diabetes and atherosclerosis (reviewed in [ 2 , 3 , 4 ]).…”