Cyclophilin D is a component of mitochondrial permeability transition and mediates neuronal cell death after focal cerebral ischemia

Abstract

Mitochondrial permeability transition (PT) is a phenomenon induced by high levels of matrix calcium and is characterized by the opening of the PT pore (PTP). Activation of the PTP results in loss of mitochondrial membrane potential, expansion of the matrix, and rupture of the mitochondrial outer membrane. Consequently, PT has been implicated in both apoptotic and necrotic cell death. Cyclophilin D (CypD) appears to be a critical component of the PTP. To investigate the role of CypD in cell death, we created a CypD-deficient mouse. In vitro, CypD-deficient mitochondria showed an increased capacity to retain calcium and were no longer susceptible to PT induced by the addition of calcium. CypD-deficient primary mouse embryonic fibroblasts (MEFs) were as susceptible to classical apoptotic stimuli as the WT, suggesting that CypD is not a central component of cell death in response to these specific death stimuli. However, CypD-deficient MEFs were significantly less susceptible than their WT counterparts to cell death induced by hydrogen peroxide, implicating CypD in oxidative stress-induced cell death. Importantly, CypD-deficient mice displayed a dramatic reduction in brain infarct size after acute middle cerebral artery occlusion and reperfusion, strongly supporting an essential role for CypD in an ischemic injury model in which calcium overload and oxidative stress have been implicated. mitochondria ͉ oxidative stress ͉ calcium homeostasis N umerous toxic stimuli convert mitochondria from a lifesustaining organelle to an inducer of cell death (1-3). In response to cell death stimuli, prodeath proteins sequestered in the inner mitochondrial membrane space are released into the cytosol upon disruption of the mitochondrial outer membrane (MOM) (4-6). The proapoptotic BCL-2 family members BAX and BAK constitute a ''gateway'' to the apoptotic program by regulating events leading to disruption of the MOM (7). BCL-2 family members not only function at the MOM but also are located at the endoplasmic reticulum (ER), where they regulate calcium fluxes. By controlling steady-state calcium levels in the ER, BCL-2 family members regulate the amount of calcium released from the ER to transmit a death signal mediated by mitochondrial calcium uptake (8-11).Sequestration of high levels of calcium by mitochondria can also lead to disruption of the MOM, which, mechanistically, is thought to occur by means of the phenomenon of permeability transition (PT). PT is described as an abrupt increase of inner membrane permeability to solutes with molecular masses of Ͻ1,500 Da. These events are caused by the opening of a highly regulated channel [PT pore (PTP)], which leads to dissipation of the mitochondrial transmembrane potential and an influx of solutes, causing expansion of the matrix (reviewed in ref. 12). The latter event may result in sufficient swelling to rupture the MOM and cause cytochrome c release and subsequent caspase activation, resulting in apoptosis. However, dissipation of the membrane potential can also lead to a sudden d...

Intracellular ASIC1a regulates mitochondrial permeability transition-dependent neuronal death

“…[18][19][20][21] Previous findings showed that CypD is an important regulator of MPT pores. 20,21 Importantly, because of the impaired MPT, CypD-deficient mice displayed a strong resistance against brain ischemic damage and motor neurons degeneration, 17,20 reminiscent of the ASIC1a-deficient mice. 5,6 Therefore, we tested the hypothesis that ASIC1a is a regulator (or even a structural component) of the MPT pore, presumably through association with CypD.…”

“…13 Mitochondrial permeability transition (MPT) is a key event that occurs in most forms of cell demise (apoptotic, necrotic, autophagic or mitotic), determining the life and death of cells. [14][15][16] The opening of MPT pores causes an abrupt increase of inner mitochondrial membrane permeability to solutes with molecular masses of o1500 Da, 14,16,17 leading to mitochondrial swelling, disruption of the mitochondrial outer membranes and mitochondrial dysfunction. 14-16 Keywords: mitochondria; ASIC1a; MPT; oxidative cell death Abbreviations: Aldh7a1, aldehyde dehydrogenase 7 family member a1; AMI, amiloride; ANT, adenine nucleotide translocase; ASIC1a, acid-sensing ion channel 1a; [Ca 2 þ ] em , extramitochondrial Ca 2 þ concentrations; CRC, Ca 2 þ retention capacity; CsA, cyclosporin A; CTB, Cell-Titer Blue; CypD, cyclophilin D; Cyt C, cytochrome c; DNP, dinitrophenol; DC m , mitochondrial membrane potential; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; Gpd2, glycerol-3-phosphate dehydrogenase 2; Hibch, 3-hydroxyisobutyryl-CoA hydrolase; H 2 O 2 , hydrogen peroxide; MCU, mitochondrial Ca 2 þ uniporter; Mito-DsRed, mitochondrion-targeting red fluorescent protein; MPT, mitochondrial permeability transition; mtASIC1a, mitochondrial ASIC1a; MTCO2, cytochrome c oxidase subunit 2; Mterfd2, mitochondria transcription termination factor domain containing 2; PcTX1, psalmotoxin 1; PDI, protein disulfide isomerase; PI, propidium iodide; Pick1, protein interacting with protein kinase C 1; PIN1peptidylprolyl cis/trans isomerase NIMA-interacting 1; ROS, reactive oxygen species; Slc25a25, solute carrier family 25 member 25; TMRM, tetramethylrhodamine methylester; VDAC, voltage-dependent anion channel…”

“…13 Mitochondrial permeability transition (MPT) is a key event that occurs in most forms of cell demise (apoptotic, necrotic, autophagic or mitotic), determining the life and death of cells. [14][15][16] The opening of MPT pores causes an abrupt increase of inner mitochondrial membrane permeability to solutes with molecular masses of o1500 Da, 14,16,17 leading to mitochondrial swelling, disruption of the mitochondrial outer membranes and mitochondrial dysfunction. [14][15][16] During brain ischemia, the lack of oxygen and glucose causes mitochondrial dysfunction, disrupted intracellular Ca 2 þ homeostasis, increased reactive oxygen species (ROS) production and decreased ATP levels.…”

“…Moreover, deletion of cyclophilin D (CypD), a key regulator of the MPT pore, effectively rescued the ischemic damage. 17 Although the pathophysiological importance of MPT has been extensively described in vivo and in vitro, its structural components still remain largely unknown. 16,[18][19][20][21] Recently, F 0 F 1 -ATP synthase was reported to form MPT pores.…”

Molecular mechanism and therapy application of necrosis during myocardial injury

“…Cypd seems to be crucial for MPTP−induced cell death as deficiency in Cypd protects neuron, cardiomyocytes and kidney in mice from ischaemia injury. Deficiency in Cypd protected MEF from necrosis induced by calcium overload or H 2 O 2 treatment 49. Cypd−mediated necrosis is also observed in the context of I/R linked pathologies as deficiency in Cypd will dramatically reduced the infarct size 49, 50.…”