Opening of mitochondrial permeability transition pore (mPTP) was found to have a critical role in cell death from ischemia/reperfusion (I/R) injury experimentally in the late 1980's. Thereafter, tremendous efforts have been made to define the molecular composition of mPTP and underlying mechanisms of its opening. mPTP opening, so far, has been demonstrated with the conformational changes of the mitochondrial protein components including cyclophilin-D, adenine nucleotide translocase, and voltage-dependent anion channel, which were induced by the modification of the levels of Ca2+, phosphate, mitochondrial membrane potential, intracellular pH and adenine nucleotide. At present, genetic modulation of the expression of protein components are being used in the investigation of its properties, presenting novel mechanisms of mPTP opening, including phosphate carrier. For therapeutic intervention, cyclosporin A and its analogues were first to be demonstrated to inhibit the opening of mPTP, affecting cyclophilin-D. There are numerous pharmacological substances that have direct or indirect effects on mPTP opening, including bongkrekic acid, reactive oxygen species scavengers, calcium channel blockers, and Na+/H+ exchanger-1 inhibitors, but only cyclosporin A was clinically tried to limit the myocardial infarction. Conditioning interventions, ischemic or anesthetic, have also been shown to be effective in limiting the detrimental effects of I/R injury. These interventions are commonly related to specific receptors on cell membrane and then signal transduction pathway consisting of many protein kinases, which eventually lead to mitochondria. And being presented are experimental evidences that inhibition of mPTP opening is a primary mechanism of these conditioning interventions. In conclusion, mPTP opening is now presented as primary mechanism and therapeutic target of I/R injury, but precise mechanism and standardized treatment method are needed to be clarified.
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine ; Adenine ; Bongkrekic Acid ; Calcium Channel Blockers ; Cell Death ; Cell Membrane ; Cyclosporine ; Hydrogen-Ion Concentration ; Membrane Potential, Mitochondrial ; Mitochondria ; Mitochondrial ADP, ATP Translocases ; Mitochondrial Membrane Transport Proteins ; Mitochondrial Proteins ; Myocardial Infarction ; Myocardium ; Permeability ; Protein Kinases ; Reactive Oxygen Species ; Reperfusion Injury ; Signal Transduction

One group of Bcl-2 protein family, which shares only the BH3 domain (BH3-only), is critically involved in the regulation of programmed cell death. Herein we demonstrated a novel human BH3-only protein (designated as Bop) which could induce apoptosis in a BH3 domain-dependent manner. Further analysis indicated that Bop mainly localized to mitochondria and used its BH3 domain to contact the loop regions of voltage dependent anion channel 1 (VDAC1) in the outer mitochondrial membrane. In addition, purified Bop protein induced the loss of mitochondrial transmembrane potential (Δψm) and the release of cytochrome c. Furthermore, Bop used its BH3 domain to contact pro-survival Bcl-2 family members (Bcl-2, Bcl-X(L), Mcl-1, A1 and Bcl-w), which could inhibit Bop-induced apoptosis. Bop would be constrained by pro-survival Bcl-2 proteins in resting cells, because Bop became released from phosphorylated Bcl-2 induced by microtubule-interfering agent like vincristine (VCR). Indeed, knockdown experiments indicated that Bop was partially required for VCR induced cell death. Finally, Bop might need to function through Bak and Bax, likely by releasing Bak from Bcl-X(L) sequestration. In conclusion, Bop may be a novel BH3-only factor that can engage with the regulatory network of Bcl-2 family members to process intrinsic apoptotic signaling.
Amino Acid Sequence ; Animals ; Apoptosis ; Cell Line ; Cell Survival ; Humans ; Mice ; Mitochondria ; metabolism ; Mitochondrial Membranes ; metabolism ; Molecular Sequence Data ; Protein Structure, Tertiary ; Protein Transport ; Proto-Oncogene Proteins c-bcl-2 ; chemistry ; metabolism ; Signal Transduction ; Time Factors ; Voltage-Dependent Anion Channel 1 ; metabolism ; bcl-2 Homologous Antagonist-Killer Protein ; metabolism ; bcl-2-Associated X Protein ; metabolism

OBJECTIVES: To study the physical and neuropsychological development of children with Citrin deficiency (CD). METHODS: A total of 93 children, aged 1.9-59.8 months, who were diagnosed with CD by RESULTS: For the 93 children with CD, the incidence rate of failure to thrive was 25% (23 children) and the proportion of small for gestational age was 47% (44 children). For the 100 cases of CD, the incidence rates of growth retardation, underweight, emaciation, overweight, and microcephalus were 23% (23 cases), 14% (14 cases), 4% (4 cases), 8% (8 cases), and 9% (9 cases), respectively. The incidence rate of neuropsychological developmental delay was 25% (25 cases), and the incidence rates of development delay in the five domains of adaptability, gross motor, fine motor, language, and social ability were 7% (7 cases), 15% (15 cases), 7% (7 cases), 9% (9 cases), and 7% (7 cases), respectively. CONCLUSIONS Physical and neuropsychological developmental delay can be observed in children with CD, and physical and neuropsychological development should be regularly assessed.
Child ; Citrullinemia ; Humans ; Infant ; Mitochondrial Membrane Transport Proteins ; Retrospective Studies

OBJECTIVETo introduce a new method for detecting mitochondrial permeability transition pore (PTP) opening with flow cytometry using the resveratrol-inducing PTP opening model.

METHODSMitochondria were isolated from rat livers and selectively labeled with nonyl acridine orange. The mitochondrial membrane potential was detected using flow cytometry with TMRE (tetramethylrhodamine, ethyl ester) labeling. PTP opening induced by resveratrol was represented by the changes of mitochondrial side-scattering (SSC) detected by flow cytometry.

RESULTSFlow cytometry was capable of defining the purity of the mitochondria isolated. The fluorescence intensities and SSC of the mitochondria were decreased after resveratrol treatment, indicating that resveratrol could induce PTP opening. Ciclosporin A inhibited resveratrol-induced PTP opening.

CONCLUSIONFlow cytometric analysis allows accurate and convenient detection of mitochondrial membrane potential, mitochondrial swelling and PTP opening.

Animals ; Apoptosis ; Flow Cytometry ; Membrane Potential, Mitochondrial ; genetics ; Mitochondria, Liver ; metabolism ; Mitochondrial Membrane Transport Proteins ; metabolism ; Rats ; Rhodamines

OBJECTIVE: To explore the clinical and genetic features of an infant with citrin deficiency (CD). METHODS: Clinical data of the patient was collected and analyzed. Genomic DNA was extracted from peripheral blood samples collected from the patient and her parents. Targeted exome sequencing was performed to explore the genetic cause, and Sanger sequencing was used to confirm the detected variants. SLC25A13 mRNA was extracted from peripheral blood lymphocytes of the infant. The effect of novel mutation of SLC25A13 was analyzed by reverse transcription-PCR, cDNA cloning and Sanger sequencing. RESULTS: The SLC25A13 genotype of the patient was determined as c.845_c.848+1delG/c.1841+3_1841+4delAA, with the latter having not been reported. The mutation has affected the splicing of the SLC25A13 mRNA, giving rise to an aberrant transcript [r.1841_1842ins1841+1_1841+67; 1841+3_c.1841+4del]. CONCLUSION A novel SLC25A13 mutation c.1841+3_1841+4delAA and the resultant abnormal splicing variant were discovered by combined DNA sequencing and cDNA cloning. The finding has enabled definite diagnosis of CD and enriched the spectrum of SLC25A13 mutations.
Base Sequence ; Citrullinemia ; Female ; Humans ; Mitochondrial Membrane Transport Proteins ; genetics ; Mutation ; Pedigree

N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity is one of the major causes for neuronal cell death during cerebral ischemic insult. Previously, we reported that the final product of lipid membrane peroxidation 4-hydroxy-2E-nonenal (HNE) synergistically increased NMDA receptor-mediated excitotoxicity (J Neurochem., 2006). In this study, we investigated the mechanism involved in the synergistic neuronal cell death induced by co-treatment with HNE and NMDA. Although neither HNE (1 microM) nor NMDA (2 microM) alone induced the death of cortical neurons, simultaneous treatment of neuronal cells with HNE and NMDA synergistically evoked the death of the cells. However, the synergistic effect on neuronal death was observed only in the presence of calcium. HNE neither increased the cytosolic calcium level ([Ca2+]i) nor altered the NMDA-induced intracellular calcium influx. However, HNE together with NMDA elevated the mitochondrial calcium level and depolarized the mitochondrial transmembrane potential. Furthermore, HNE evoked damage of isolated mitochondria at the cytosolic calcium level (200 nM), which is maximally induced by 2 microM NMDA. Consistently, ATP was depleted in neurons when treated with both HNE and NMDA together. Ciclopirox, a potent inhibitor of mitochondrial permeability transition pore opening (Br. J. Pharmacol., 2005), largely prevented the synergistic damage of mitochondria and death of cortical neurons. Therefore, although low concentrations of HNE and NMDA cannot individually induce neuronal cell death, they can evoke the neuronal cell death by synergistically accelerating mitochondrial dysfunction.
Adenosine Triphosphate ; Calcium ; Cell Death ; Cytosol ; Membrane Potentials ; Membranes ; Mitochondria ; Mitochondrial Membrane Transport Proteins ; N-Methylaspartate ; Neurons ; Permeability ; Pyridones

Citrin deficiency causes autosomal recessive disorders including adult-onset type II citrullinemia (CTLN2) and neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD). The responsive gene of citrin deficiency, SLC25A13, locates on chromosome 7q21.3 and encodes citrin as a liver-type mitochondrial aspartate/glutamate carrier (AGC). The mutations on SLC25A13 will result in deficiency of citrin and CTLN2 or NICCD. Citrin deficiency was found at first in Japan. However, recently, some of cases were identified in China, Korea, Vietnam, Israel, Czech, United States and England, and racial differences of the SLC25A13 mutations were found, suggesting the patients with citrin deficiency maybe exist worldwide. In this article, authors reviewed the progresses in the study on citrin deficiency up to now and put forward authors' considerations for further research on it.
Animals ; Calcium-Binding Proteins ; deficiency ; genetics ; Cholestasis, Intrahepatic ; genetics ; surgery ; Chromosomes, Human, Pair 7 ; Citrullinemia ; etiology ; genetics ; surgery ; Humans ; Liver Transplantation ; Membrane Transport Proteins ; genetics ; Mitochondrial Membrane Transport Proteins ; Mitochondrial Proteins ; genetics ; Organic Anion Transporters ; deficiency ; genetics ; Point Mutation

The three dimensional structures of both pro-apoptotic Bax and anti-apoptotic Bcl-2 are strikingly similar to that of pore-forming domains of diphtheria toxin and E. coli colicins. Consistent with the structural similarity, both Bax and Bcl-2 have been shown to possess pore-forming property in the membrane. However, these pore-forming proteins form pores via different mechanisms. While Bax and diphtheria toxin form pores via oligomerization, the colicin pore is formed only by colicin monomers. Although the oligomers of Bcl-2 proteins have been found in the mitochondria of both healthy and apoptotic cells, it is unknown whether or not oligomerization is involved in the pore formation. To determine the mechanism of Bcl-2 pore formation, we reconstituted the pore-forming process of Bcl-2 using purified proteins and liposomes. We found that Bcl-2 pore size depended on Bcl-2 concentration, and the release of smaller entrapped molecules was faster than that of larger ones from liposomes at a given Bcl-2 concentration. Moreover, the rate of dye release mediated by pre-formed wild-type Bcl-2 oligomers or by the mutant Bcl-2 monomers with a higher homo-association affinity was much higher than that by wild-type Bcl-2 monomers. Together, it is suggested that oligomerization is likely involved in Bcl-2 pore formation.
Apoptosis ; physiology ; Cytosol ; metabolism ; Humans ; Hydrogen-Ion Concentration ; Liposomes ; metabolism ; Mitochondrial Membrane Transport Proteins ; metabolism ; Mitochondrial Membranes ; metabolism ; Protein Multimerization ; Proto-Oncogene Proteins c-bcl-2 ; metabolism

OBJECTIVETo investigate the opening of the mitochondrial permeability transition pores of the cultured hepatocytes in a non-alcoholic fatty liver disease model and its relationship with apoptosis of the cells.

METHODSOleic acid was used to induce cultured L02 hepatocyte steatotic in making a model of NAFLD. The steatotic hepatocytes were detected with oil red O staining; the opening of the mitochondrial permeability transition pores was observed under a fluorescence microscope. The apoptosis of the cells was detected with a flow cytometer.

RESULTSAfter adding oleic acid to the cultured hepatocytes, a model of steatosis of human hepatocytes was established after 24 hours. Oleic acid opened the mitochondrial permeability transition pores of the L02 hepatocytes (72.58%+/-2.78%) more than that in the control group (8.28%+/-4.98%) and the difference was statistically significant (P < 0.01). Apoptosis index of the steatotic hepatocytes at 24 hours and 48 hours were 11.09%+/-4.95% and 15.24%+/-2.45%. They were also higher than those of the control group (4.56%+/-1.25%) (P < 0.05, P < 0.01).

CONCLUSIONOpening the mitochondrial permeability transition pores may be the basis of the apoptosis of steatotic hepatocytes in vitro, and it also may be related to the steatosis of NAFLD in human beings.

Apoptosis ; Cell Line ; Fatty Liver ; metabolism ; pathology ; Hepatocytes ; metabolism ; Humans ; Mitochondria, Liver ; metabolism ; Mitochondrial Membrane Transport Proteins ; metabolism

Early restoration of blood flow to the ischemic myocardium not only saves myocardium but also induces reperfusion injury. While no specific therapy to reduce reperfusion injury has yet been established, recent laboratory studies have shown that G protein-coupled receptor (GPCR) agonists, insulin, and postconditioning can effectively prevent reperfusion injury in various experimental settings and animal species. The potential mechanisms underlying the cardioprotection initiated by these interventions may include activation of the reperfusion injury salvage kinase (RISK) pathway, inactivation of glycogen synthase kinase 3beta (GSK-3beta), and modulation of mitochondrial permeability transition pore (mPTP) opening. These encouraging laboratory findings may help us develop successful clinical strategies to salvage reperfused myocardium in patients with acute myocardial infarction.
Glycogen Synthase Kinase 3 ; metabolism ; Humans ; Mitochondrial Membrane Transport Proteins ; physiology ; Myocardial Infarction ; complications ; Myocardial Reperfusion Injury ; prevention & control ; Myocardium