The mitochondrial permeability transition pore

Effects of mild hypercapnia on myocardial injury after out-of-hospital cardiac arrest. A sub-study of the TAME trial

PURPOSE

Mild hypercapnia did not improve neurological outcomes for resuscitated out-of-hospital cardiac arrest (OHCA) patients in the Targeted Therapeutic Mild Hypercapnia After Resuscitated Cardiac Arrest (TAME) trial. However, the effects of hypercapnic acidosis on myocardial injury in patients with cardiac arrest is unexplored. We investigated whether mild hypercapnia compared to normocapnia, following emergency coronary intervention, increased myocardial injury in comatose OHCA-patients with AMI.

METHODS

Single-centre, prospective, pre-planned sub-study of the TAME trial. Patients were randomised to targeted mild hypercapnia (PaCO2 = 6.7-7.3 kPa) or normocapnia (PaCO2 = 4.7-6.0 kPa) for 24 h. Myocardial injury was assessed with high-sensitive cardiac troponin T (hs-cTnT) measured at baseline, 24, 48 and 72 h. Haemodynamics were assessed with right heart catheterisation and blood-gas analyses every 4th hour for 48 h.

RESULTS

We included 125 OHCA-patients. 57 (46%) had an AMI, with 31 and 26 patients randomised to hypercapnia and normocapnia, respectively. Median peak hs-cTnT in AMI-patients was 58% lower in the hypercapnia-group: 2136 (IQR: 861-4462) versus 5165 ng/L (IQR: 2773-7519), p = 0.007. Lower average area under the hs-cTnT curve was observed in the hypercapnia-group: 2353 (95% CI 1388-3319) versus 4953 ng/L (95% CI 3566-6341), P-group = 0.002. Hypercapnia was associated with increased cardiac power output (CPO) and lower lactate levels in patients with AMI (P-group < 0.05). hs-cTnT, lactate and CPO were not significantly different between intervention groups in OHCA-patients without AMI (p > 0.05).

CONCLUSIONS

Mild hypercapnia was not associated with increased myocardial injury in resuscitated OHCA-patients. In AMI-patients, mild hypercapnia was associated with lower hs-cTnT and lactate, and improved cardiac performance.

TRIAL REGISTRATION NUMBER

NCT03114033.

Endoplasmic Reticulum Stress of Gut Enterocyte and Intestinal Diseases

The endoplasmic reticulum, a vast reticular membranous network from the nuclear envelope to the plasma membrane responsible for the synthesis, maturation, and trafficking of a wide range of proteins, is considerably sensitive to changes in its luminal homeostasis. The loss of ER luminal homeostasis leads to abnormalities referred to as endoplasmic reticulum (ER) stress. Thus, the cell activates an adaptive response known as the unfolded protein response (UPR), a mechanism to stabilize ER homeostasis under severe environmental conditions. ER stress has recently been postulated as a disease research breakthrough due to its significant role in multiple vital cellular functions. This has caused numerous reports that ER stress-induced cell dysfunction has been implicated as an essential contributor to the occurrence and development of many diseases, resulting in them targeting the relief of ER stress. This review aims to outline the multiple molecular mechanisms of ER stress that can elucidate ER as an expansive, membrane-enclosed organelle playing a crucial role in numerous cellular functions with evident changes of several cells encountering ER stress. Alongside, we mainly focused on the therapeutic potential of ER stress inhibition in gastrointestinal diseases such as inflammatory bowel disease (IBD) and colorectal cancer. To conclude, we reviewed advanced research and highlighted future treatment strategies of ER stress-associated conditions.

Mitochondria are specifically vulnerable to 420nm light in drosophila which undermines their function and is associated with reduced fly mobility

Increased blue light exposure has become a matter of concern as it has a range of detrimental effects, but the mechanisms remain unclear. Mitochondria absorb short wavelength light but have a specific absorbance at 420nm at the lower end of the human visual range. This 420nm absorption is probably due to the presence of porphyrin. We examine the impact of 420nm exposure on drosophila melanogaster mitochondria and its impact on fly mobility. Daily 15 mins exposures for a week significantly reduced mitochondrial complex activities and increased mitochondrial inner membrane permeability, which is a key metric of mitochondrial health. Adenosine triphosphate (ATP) levels were not significantly reduced and mobility was unchanged. There are multiple options for energy/time exposure combinations, but we then applied single 420nm exposure of 3h to increase the probability of an effect on ATP and mobility, and both were significantly reduced. ATP and mitochondrial membrane permeability recovered and over corrected at 72h post exposure. However, despite this, normal mobility did not return. Hence, the effect of short wavelengths on mitochondrial function is to reduce complex activity and increasing membrane permeability, but light exposure to reduce ATP and to translate into reduced mobility needs to be sustained.

Calcium influx through the mitochondrial calcium uniporter holocomplex, MCUcx

Ca2+ flux into the mitochondrial matrix through the MCU holocomplex (MCUcx) has recently been measured quantitatively and with milliseconds resolution for the first time under physiological conditions in both heart and skeletal muscle. Additionally, the dynamic levels of Ca2+ in the mitochondrial matrix ([Ca2+]m) of cardiomyocytes were measured as it was controlled by the balance between influx of Ca2+ into the mitochondrial matrix through MCUcx and efflux through the mitochondrial Na+ / Ca2+ exchanger (NCLX). Under these conditions [Ca2+]m was shown to regulate ATP production by the mitochondria at only a few critical sites. Additional functions attributed to [Ca2+]m continue to be reported in the literature. Here we review the new findings attributed to MCUcx function and provide a framework for understanding and investigating mitochondrial Ca2+ influx features, many of which remain controversial. The properties and functions of the MCUcx subunits that constitute the holocomplex are challenging to tease apart. Such distinct subunits include EMRE, MCUR1, MICUx (i.e. MICU1, MICU2, MICU3), and the pore-forming subunits (MCUpore). Currently, the specific set of functions of each subunit remains non-quantitative and controversial. The more contentious issues are discussed in the context of the newly measured native MCUcx Ca2+ flux from heart and skeletal muscle. These MCUcx Ca2+ flux measurements have been shown to be a highly-regulated, tissue-specific with femto-Siemens Ca2+ conductances and with distinct extramitochondrial Ca2+ ([Ca2+]i) dependencies. These data from cardiac and skeletal muscle mitochondria have been examined quantitatively for their threshold [Ca2+]i levels and for hypothesized gatekeeping function and are discussed in the context of model cell (e.g. HeLa, MEF, HEK293, COS7 cells) measurements. Our new findings on MCUcx dependent matrix [Ca2+]m signaling provide a quantitative basis for on-going and new investigations of the roles of MCUcx in cardiac function ranging from metabolic fuel selection, capillary blood-flow control and the pathological activation of the mitochondrial permeability transition pore (mPTP). Additionally, this review presents the use of advanced new methods that can be readily adapted by any investigator to enable them to carry out quantitative Ca2+ measurements in mitochondria while controlling the inner mitochondrial membrane potential, ΔΨm.

ATP synthase c-subunit ring as the channel of mitochondrial permeability transition: Regulator of metabolism in development and degeneration

The mitochondrial permeability transition pore (mPTP) or mitochondrial megachannel is arguably one of the most mysterious phenomena in biology today. mPTP has been at the center of ongoing extensive scientific research for the last several decades. In this review we will discuss recent advances in the field that enhance our understanding of the molecular composition of mPTP, its regulatory mechanisms and its pathophysiological role. We will describe our recent findings on the role of ATP synthase c-subunit ring as a central player in mitochondrial permeability transition and as an important metabolic regulator during development and in degenerative diseases.

Closing the Mitochondrial Permeability Transition Pore in hiPSC-Derived Endothelial Cells Induces Glycocalyx Formation and Functional Maturation

Human induced pluripotent stem cells (hiPSCs) are used to study organogenesis and model disease as well as being developed for regenerative medicine. Endothelial cells are among the many cell types differentiated from hiPSCs, but their maturation and stabilization fall short of that in adult endothelium. We examined whether shear stress alone or in combination with pericyte co-culture would induce flow alignment and maturation of hiPSC-derived endothelial cells (hiPSC-ECs) but found no effects comparable with those in primary microvascular ECs. In addition, hiPSC-ECs lacked a luminal glycocalyx, critical for vasculature homeostasis, shear stress sensing, and signaling. We noted, however, that hiPSC-ECs have dysfunctional mitochondrial permeability transition pores, resulting in reduced mitochondrial function and increased reactive oxygen species. Closure of these pores by cyclosporine A improved EC mitochondrial function but also restored the glycocalyx such that alignment to flow took place. These results indicated that mitochondrial maturation is required for proper hiPSC-EC functionality.

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hiPSC-ECs lack a functional glycocalyx and fail to align to flow

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hiPSC-ECs have reduced mitochondrial function and increased leakage of ROS

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Closing the mPTP with cyclosporine A induces mitochondrial maturation

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Improved mitochondrial function restores the glycocalyx and alignment to flow

Disturbance of mitochondrial functions associated with permeability transition pore opening induced by cis-5-tetradecenoic and myristic acids in liver of adolescent rats

Patients affected by very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency commonly present liver dysfunction whose pathogenesis is poorly known. We demonstrate here that major metabolites accumulating in this disorder, namely cis-5-tetradecenoic acid (Cis-5) and myristic acid (Myr), markedly impair mitochondrial respiration, decreasing ATP production in liver mitochondrial preparations from adolescent rats. Other parameters of mitochondrial homeostasis such as membrane potential (ΔΨm) and Ca²⁺retention capacity were strongly compromised by these fatty acids, involving induction of mitochondrial permeability transition. The present data indicate that disruption of mitochondrial bioenergetics and Ca²⁺homeostasis may contribute to the liver dysfunction of VLCAD deficient patients.

Uncoupling Effect of F16 Is Responsible for Its Mitochondrial Toxicity and Anticancer Activity

As a novel delocalized lipophilic cation, F16 selectively accumulates in mitochondria of carcinoma cells and shows a broad spectrum of antiproliferative action towards cancer cell lines. In order to reveal the mode of action and molecular mechanism of F16 inducing cytotoxicity, we investigated the effects of F16 on cancer cells and isolated mitochondria relative to its precursor compound (E)-3-(2-(pyridine-4yl)vinyl)-1 H-indole (PVI), which has a similar structure without positive charge. It was found that PVI did not accumulate in mitochondria, and exhibited lower cytotoxicity compared to F16. However, when they were directly incubated with mitochondria, both F16 and PVI were observed to induce damage to mitochondrial structure and function. Moreover, it was found that F16 as well as PVI acted as uncouplers on mitochondria, and further rescue experiments revealed that the addition of adenosine 5'-triphosphate was the most effective way to recover the cell viability decreased by F16. Thus it was concluded that the decreased intracellular adenosine 5'-triphosphate availability induced by the uncoupling effect of F16 was a major factor in F16-mediated cytotoxicity. Futhermore, the results indicated that the uncoupling effect of F16 is attributed to its chemical stucture in common with PVI but independent of its positive charge. The study may shed light on understanding the underlying mechanism of action for F16, and providing suggestions for the design of new mitochondria-targeted antitumor molecules.

Estrogen receptor beta modulates permeability transition in brain mitochondria

Recent evidence highlights a role for sex and hormonal status in regulating cellular responses to ischemic brain injury and neurodegeneration. A key pathological event in ischemic brain injury is the opening of a mitochondrial permeability transition pore (MPT) induced by excitotoxic calcium levels, which can trigger irreversible damage to mitochondria accompanied by the release of pro-apoptotic factors. However, sex differences in brain MPT modulation have not yet been explored. Here, we show that mitochondria isolated from female mouse forebrain have a lower calcium threshold for MPT than male mitochondria, and that this sex difference depends on the MPT regulator cyclophilin D (CypD). We also demonstrate that an estrogen receptor beta (ERβ) antagonist inhibits MPT and knockout of ERβ decreases the sensitivity of mitochondria to the CypD inhibitor, cyclosporine A. These results suggest a functional relationship between ERβ and CypD in modulating brain MPT. Moreover, co-immunoprecipitation studies identify several ERβ binding partners in mitochondria. Among these, we investigate the mitochondrial ATPase as a putative site of MPT regulation by ERβ. We find that previously described interaction between the oligomycin sensitivity-conferring subunit of ATPase (OSCP) and CypD is decreased by ERβ knockout, suggesting that ERβ modulates MPT by regulating CypD interaction with OSCP. Functionally, in primary neurons and hippocampal slice cultures, modulation of ERβ has protective effects against glutamate toxicity and oxygen glucose deprivation, respectively. Taken together, these results reveal a novel pathway of brain MPT regulation by ERβ that could contribute to sex differences in ischemic brain injury and neurodegeneration.

Mevalonolactone disrupts mitochondrial functions and induces permeability transition pore opening in rat brain mitochondria: Implications for the pathogenesis of mevalonic aciduria

Mevalonic aciduria (MVA) is caused by severe deficiency of mevalonic kinase activity leading to tissue accumulation and high urinary excretion of mevalonic acid (MA) and mevalonolactone (ML). Patients usually present severe neurologic symptoms whose pathophysiology is poorly known. Here, we tested the hypothesis that the major accumulating metabolites are toxic by investigating the in vitro effects of MA and ML on important mitochondrial functions in rat brain and liver mitochondria. ML, but not MA, markedly decreased mitochondrial membrane potential (ΔΨm), NAD(P)H content and the capacity to retain Ca²⁺ in the brain, besides inducing mitochondrial swelling. These biochemical alterations were totally prevented by the classical inhibitors of mitochondrial permeability transition (MPT) cyclosporine A and ADP, as well as by ruthenium red in Ca²⁺-loaded mitochondria, indicating the involvement of MPT and an important role for mitochondrial Ca²⁺ in these effects. ML also induced lipid peroxidation and markedly inhibited aconitase activity, an enzyme that is highly susceptible to free radical attack, in brain mitochondrial fractions, indicating that lipid and protein oxidative damage may underlie some of ML-induced deleterious effects including MTP induction. In contrast, ML and MA did not compromise oxidative phosphorylation in the brain and all mitochondrial functions evaluated in the liver, evidencing a selective toxicity of ML towards the central nervous system. Our present study provides for the first time evidence that ML impairs essential brain mitochondrial functions with the involvement of MPT pore opening. It is therefore presumed that disturbance of brain mitochondrial homeostasis possibly contributes to the neurologic symptoms in MVA.

pH-sensitive micelles for the intracellular co-delivery of curcumin and Pluronic L61 unimers for synergistic reversal effect of multidrug resistance

Pluronic L61 unimers, which are biomacromolecular modulators, and curcumin, a small-molecule modulator, were co-formulated into pH-sensitive micelles to reveal the full synergistic potential of combination drug treatments to reverse multidrug resistance (MDR). Compared to monotherapy, combined therapy significantly improved the cytotoxicity, cellular uptake and apoptotic effects of doxorubicin (DOX) against MCF-7/ADR cells. In mechanistic studies, both L61 and curcumin enhanced the cytotoxic effect by acting on mitochondrial signalling pathways. The compounds selectively accumulated in the mitochondria and disabled the mitochondria by dissipating the mitochondrial membrane potential, decreasing the ATP levels, and releasing cytochrome c, which initiated a cascade of caspase-9 and caspase-3 reactions. Furthermore, both curcumin and L61 down-regulated the expression and function of P-gp in response to drug efflux from the MCF-7/ADR cells. In the MCF-7/ADR tumour-bearing mouse model, intravenous administration of the combined therapy directly targeted the tumour, as revealed by the accumulation of DiR in the tumour site, which led to a significant inhibition of tumour growth without measurable side effects. In conclusion, co-formulation consisting of L61 and curcumin in pH-sensitive micelles induced significant synergistic effects on the reversal of MDR. Therefore, the intracellular co-delivery of various MDR modulators has great potential to reverse MDR in tumours.

Bioenergetics and metabolism: a bench to bedside perspective

'Metabolism' refers to the vast collection of chemical processes that occur within a living organism. Within this broad designation, one can identify metabolism events that relate specifically to energy homeostasis, whether they occur at the subcellular, cellular, organ, or whole organism level. This review operationally refers to this type of metabolism as 'energy metabolism' or 'bioenergetics.' Changes in energy metabolism/bioenergetics have been linked to brain aging and a number of neurodegenerative diseases, and research suggests mitochondria may uniquely contribute to this. Interventions that manipulate energy metabolism/bioenergetic function and mitochondria may have therapeutic potential and efforts intended to accomplish this are playing out at basic, translational, and clinical levels. This review follows evolving views of energy metabolism's role in neurodegenerative diseases but especially Alzheimer's disease, with an emphasis on the bench-to-bedside process whose ultimate goal is to develop therapeutic interventions. It further considers challenges encountered during this process, which include linking basic concepts to a medical question at the initial research stage, adapting conceptual knowledge gained to a disease-associated application in the translational stage, extending what has been learned to the clinical arena, and maintaining support for the research at each of these fundamentally linked but functionally distinct stages. A bench-to-bedside biomedical research process is discussed that moves through conceptual, basic, translational, and clinical levels. For example, herein a case was made that bioenergetics is a valid Alzheimer's disease therapeutic target. Following this, a fundamental strategy for manipulating bioenergetics was defined, potential implications studied, and the approach extended to the clinical arena. This article is part of the 60th Anniversary special issue.

Targeting Kv1.3 channels to reduce white matter pathology after traumatic brain injury

Axonal injury is present in essentially all clinically significant cases of traumatic brain injury (TBI). While no effective treatment has been identified to date, experimental TBI models have shown promising axonal protection using immunosuppressants FK506 and Cyclosporine-A, with treatment benefits attributed to calcineurin inhibition or protection of mitochondrial function. However, growing evidence suggests neuroprotective efficacy of these compounds may also involve direct modulation of ion channels, and in particular Kv1.3. The present study tested whether blockade of Kv1.3 channels, using Clofazimine (CFZ), would alleviate TBI-induced white matter pathology in rodents. Postinjury CFZ administration prevented suppression of compound action potential (CAP) amplitude in the corpus callosum of adult rats following midline fluid percussion TBI, with injury and treatment effects primarily expressed in unmyelinated CAPs. Kv1.3 protein levels in callosal tissue extracts were significantly reduced postinjury, but this loss was prevented by CFZ treatment. In parallel, CFZ also attenuated the injury-induced elevation in pro-inflammatory cytokine IL1-β. The effects of CFZ on glial function were further studied using mixed microglia/astrocyte cell cultures derived from P3-5 mouse corpus callosum. Cultures of callosal glia challenged with lipopolysaccharide exhibited a dramatic increase in IL1-β levels, accompanied by reactive morphological changes in microglia, both of which were attenuated by CFZ treatment. These results support a cell specific role for Kv1.3 signaling in white matter pathology after TBI, and suggest a treatment approach based on the blockade of these channels. This therapeutic strategy may be especially efficacious for normalizing neuro-glial interactions affecting unmyelinated axons after TBI.

Disturbance of mitochondrial functions provoked by the major long-chain 3-hydroxylated fatty acids accumulating in MTP and LCHAD deficiencies in skeletal muscle

The pathogenesis of the muscular symptoms and recurrent rhabdomyolysis that are commonly manifested in patients with mitochondrial trifunctional protein (MTP) and long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) deficiencies is still unknown. In this study we investigated the effects of the major long-chain monocarboxylic 3-hydroxylated fatty acids (LCHFA) accumulating in these disorders, namely 3-hydroxytetradecanoic (3HTA) and 3-hydroxypalmitic (3HPA) acids, on important mitochondrial functions in rat skeletal muscle mitochondria. 3HTA and 3HPA markedly increased resting (state 4) and decreased ADP-stimulated (state 3) and CCCP-stimulated (uncoupled) respiration. 3HPA provoked similar effects in permeabilized skeletal muscle fibers, validating the results obtained in purified mitochondria. Furthermore, 3HTA and 3HPA markedly diminished mitochondrial membrane potential, NAD(P)H content and Ca(2+) retention capacity in Ca(2+)-loaded mitochondria. Mitochondrial permeability transition (mPT) induction probably underlie these effects since they were totally prevented by cyclosporin A and ADP. In contrast, the dicarboxylic analogue of 3HTA did not alter the tested parameters. Our data strongly indicate that 3HTA and 3HPA behave as metabolic inhibitors, uncouplers of oxidative phosphorylation and mPT inducers in skeletal muscle. It is proposed that these pathomechanisms disrupting mitochondrial homeostasis may be involved in the muscle alterations characteristic of MTP and LCHAD deficiencies.

Minimal systems analysis of mitochondria-dependent apoptosis induced by cisplatin

Recently, it was reported that the role of mitochondria-reactive oxygen species (ROS) generating pathway in cisplatin-induced apoptosis is remarkable. Since a variety of molecules are involved in the pathway, a comprehensive approach to delineate the biological interactions of the molecules is required. However, quantitative modeling of the mitochondria-ROS generating pathway based on experiment and systemic analysis using the model have not been attempted so far. Thus, we conducted experiments to measure the concentration changes of critical molecules associated with mitochondrial apoptosis in both human mesothelioma H2052 and their ρ(0) cells lacking mitochondrial DNA (mtDNA). Based on the experiments, a novel mathematical model that can represent the essential dynamics of the mitochondrial apoptotic pathway induced by cisplatin was developed. The kinetic parameter values of the mathematical model were estimated from the experimental data. Then, we have investigated the dynamical properties of this model and predicted the apoptosis levels for various concentrations of cisplatin beyond the range of experiments. From parametric perturbation analysis, we further found that apoptosis will reach its saturation level beyond a certain critical cisplatin concentration.

LYG-202 exerts antitumor effect on PI3K/Akt signaling pathway in human breast cancer cells

In this study, we aimed to investigate the antitumor effect of LYG-202, a newly synthesized piperazine-substituted derivative of flavonoid on human breast cancer cells and illustrate the potential mechanisms. LYG-202 induced apoptosis in MCF-7, MDA-MB-231 and MDA-MB-435 cells. LYG-202 triggered the activation of mitochondrial apoptotic pathway through multiple steps: increasing Bax/Bcl-2 ratio, decreasing mitochondrial membrane potential (ΔΨ(m)), activating caspase-9 and caspase-3, inducing cleavage of poly(ADP-ribose) polymerase, cytochrome c release and apoptosis-inducing factor translocation. Furthermore, LYG-202 inhibited cell cycle progression at the G1/S transition via targeting Cyclin D, CDK4 and p21(Waf1/Cip1). Additionally, LYG-202 increased the generation of intracellular ROS. N-Acetyl cysteine, an antioxidant, reversed LYG-202-induced apoptosis suggesting that LYG-202 induces apoptosis by accelerating ROS generation. Further, we found that LYG-202 deactivated the PI3K/Akt pathway, activated Bad phosphorylation, increased Cyclin D and Bcl-xL expression, and inhibited NF-κB nuclear translocation. Activation of PI3K/Akt pathway by IGF-1 attenuated LYG-202-induced apoptosis and cell cycle arrest. Our in vivo study showed that LYG-202 exhibited a potential antitumor effect in nude mice inoculated with MCF-7 tumor through similar mechanisms identified in cultured cells. In summary, our results demonstrated that LYG-202 induced apoptosis and cell cycle arrest via targeting PI3K/Akt pathway, indicating that LYG-202 is a potential anticancer agent for breast cancer.

Modeling calcium regulation of contraction, energetics, signaling, and transcription in the cardiac myocyte

Calcium (Ca(2+)) plays many important regulatory roles in cardiac muscle cells. In the initial phase of the action potential, influx of Ca(2+) through sarcolemmal voltage-gated L-type Ca(2+) channels (LCCs) acts as a feed-forward signal that triggers a large release of Ca(2+) from the junctional sarcoplasmic reticulum (SR). This Ca(2+) drives heart muscle contraction and pumping of blood in a process known as excitation-contraction coupling (ECC). Triggered and released Ca(2+) also feed back to inactivate LCCs, attenuating the triggered Ca(2+) signal once release has been achieved. The process of ECC consumes large amounts of ATP. It is now clear that in a process known as excitation-energetics coupling, Ca(2+) signals exert beat-to-beat regulation of mitochondrial ATP production that closely couples energy production with demand. This occurs through transport of Ca(2+) into mitochondria, where it regulates enzymes of the tricarboxylic acid cycle. In excitation-signaling coupling, Ca(2+) activates a number of signaling pathways in a feed-forward manner. Through effects on their target proteins, these interconnected pathways regulate Ca(2+) signals in complex ways to control electrical excitability and contractility of heart muscle. In a process known as excitation-transcription coupling, Ca(2+) acting primarily through signal transduction pathways also regulates the process of gene transcription. Because of these diverse and complex roles, experimentally based mechanistic computational models are proving to be very useful for understanding Ca(2+) signaling in the cardiac myocyte.

Deregulation of mitochondrial functions provoked by long-chain fatty acid accumulating in long-chain 3-hydroxyacyl-CoA dehydrogenase and mitochondrial permeability transition deficiencies in rat heart--mitochondrial permeability transition pore opening as a potential contributing pathomechanism of cardiac alterations in these disorders

Mitochondrial trifunctional protein and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiencies are fatty acid oxidation disorders biochemically characterized by tissue accumulation of long-chain fatty acids and derivatives, including the monocarboxylic long-chain 3-hydroxy fatty acids (LCHFAs) 3-hydroxytetradecanoic acid (3HTA) and 3-hydroxypalmitic acid (3HPA). Patients commonly present severe cardiomyopathy for which the pathogenesis is still poorly established. We investigated the effects of 3HTA and 3HPA, the major metabolites accumulating in these disorders, on important parameters of mitochondrial homeostasis in Ca(2+) -loaded heart mitochondria. 3HTA and 3HPA significantly decreased mitochondrial membrane potential, the matrix NAD(P)H pool and Ca(2+) retention capacity, and also induced mitochondrial swelling. These fatty acids also provoked a marked decrease of ATP production reflecting severe energy dysfunction. Furthermore, 3HTA-induced mitochondrial alterations were completely prevented by the classical mitochondrial permeability transition (mPT) inhibitors cyclosporin A and ADP, as well as by ruthenium red, a Ca(2+) uptake blocker, indicating that LCHFAs induced Ca(2+)-dependent mPT pore opening. Milder effects only achieved at higher doses of LCHFAs were observed in brain mitochondria, implying a higher vulnerability of heart to these fatty acids. By contrast, 3HTA and docosanoic acids did not change mitochondrial homeostasis, indicating selective effects for monocarboxylic LCHFAs. The present data indicate that the major LCHFAs accumulating in mitochondrial trifunctional protein and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiencies induce mPT pore opening, compromising Ca(2+) homeostasis and oxidative phosphorylation more intensely in the heart. It is proposed that these pathomechanisms may contribute at least in part to the severe cardiac alterations characteristic of patients affected by these diseases.

Inhibition of NAADP signalling on reperfusion protects the heart by preventing lethal calcium oscillations via two-pore channel 1 and opening of the mitochondrial permeability transition pore

Aims

In the heart, a period of ischaemia followed by reperfusion evokes powerful cytosolic Ca²⁺ oscillations that can cause lethal cell injury. These signals represent attractive cardioprotective targets, but the underlying mechanisms of genesis are ill-defined. Here, we investigated the role of the second messenger nicotinic acid adenine dinucleotide phosphate (NAADP), which is known in several cell types to induce Ca²⁺ oscillations that initiate from acidic stores such as lysosomes, likely via two-pore channels (TPCs, TPC1 and 2).

Methods and results

An NAADP antagonist called Ned-K was developed by rational design based on a previously existing scaffold. Ned-K suppressed Ca²⁺ oscillations and dramatically protected cardiomyocytes from cell death in vitro after ischaemia and reoxygenation, preventing opening of the mitochondrial permeability transition pore. Ned-K profoundly decreased infarct size in mice in vivo. Transgenic mice lacking the endo-lysosomal TPC1 were also protected from injury.

Conclusion

NAADP signalling plays a major role in reperfusion-induced cell death and represents a potent pathway for protection against reperfusion injury.

Uncoupling, metabolic inhibition and induction of mitochondrial permeability transition in rat liver mitochondria caused by the major long-chain hydroxyl monocarboxylic fatty acids accumulating in LCHAD deficiency

Patients with long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) deficiency commonly present liver dysfunction whose pathogenesis is unknown. We studied the effects of long-chain 3-hydroxylated fatty acids (LCHFA) that accumulate in LCHAD deficiency on liver bioenergetics using mitochondrial preparations from young rats. We provide strong evidence that 3-hydroxytetradecanoic (3HTA) and 3-hydroxypalmitic (3HPA) acids, the monocarboxylic acids that are found at the highest tissue concentrations in this disorder, act as metabolic inhibitors and uncouplers of oxidative phosphorylation. These conclusions are based on the findings that these fatty acids decreased ADP-stimulated (state 3) and uncoupled respiration, mitochondrial membrane potential and NAD(P)H content, and, in contrast, increased resting (state 4) respiration. We also verified that 3HTA and 3HPA markedly reduced Ca2+ retention capacity and induced swelling in Ca2+-loaded mitochondria. These effects were mediated by mitochondrial permeability transition (MPT) induction since they were totally prevented by the classical MPT inhibitors cyclosporin A and ADP, as well as by ruthenium red, a Ca2+ uptake blocker. Taken together, our data demonstrate that the major monocarboxylic LCHFA accumulating in LCHAD deficiency disrupt energy mitochondrial homeostasis in the liver. It is proposed that this pathomechanism may explain at least in part the hepatic alterations characteristic of the affected patients.

Oxidative stress damage in the protozoan parasite Trypanosoma cruzi is inhibited by Cyclosporin A

Cyclosporin A (CsA) specifically inhibits the mitochondrial permeability transition pore (mPTP). Opening of the mPTP, which is triggered by high levels of matrix [Ca2+] and/or oxidative stress, leads to mitochondrial dysfunction and thus to cell death by either apoptosis or necrosis. In the present study, we analysed the response of Trypanosoma cruzi epimastigote parasites to oxidative stress with 5 mm H2O2, by studying several features related to programmed cell death and the effects of pre-incubation with 1 μm of CsA. We evaluated TcPARP cleavage, DNA integrity, cytochrome c translocation, Annexin V/propidium iodide staining, reactive oxygen species production. CsA prevented parasite oxidative stress damage as it significantly inhibited DNA degradation, cytochrome c translocation to cytosol and TcPARP cleavage. The calcein-AM/CoCl2 assay, used as a selective indicator of mPTP opening in mammals, was also performed in T. cruzi parasites. H2O2 treatment decreased calcein fluorescence, but this decline was partially inhibited by pre-incubation with CsA. Our results encourage further studies to investigate if there is a mPTP-like pore and a mitochondrial cyclophilin involved in this protozoan parasite.

Regulation of ceramide channel formation and disassembly: Insights on the initiation of apoptosis

Sphingolipid research has surged in the past two decades and has produced a wide variety of evidence supporting the role of this class of molecules in mediating cellular growth, differentiation, senescence, and apoptosis. Ceramides are a subgroup of sphingolipids (SLs) that are directly involved in the process of initiation of apoptosis. We, and others, have recently shown that ceramides are capable of the formation of protein-permeable channels in mitochondrial outer membranes under physiological conditions. These pores are indeed good candidates for the pathway of release of pro-apoptotic proteins from the mitochondrial intermembrane space (IMS) into the cytosol to initiate intrinsic apoptosis. Here, we review recent findings on the regulation of ceramide channel formation and disassembly, highlighting possible implications on the initiation of the intrinsic apoptotic pathway.

The mitochondrial permeability transition pore and its role in myocardial ischemia reperfusion injury

Ischemic heart disease (IHD) remains the leading cause of death and disability worldwide. For patients presenting with an acute myocardial infarction, the most effective treatment for limiting myocardial infarct (MI) size is timely reperfusion. However, in addition to the injury incurred during acute myocardial ischemia, the process of reperfusion can itself induce myocardial injury and cardiomyocyte death, termed 'myocardial reperfusion injury', the combination of which can be referred to as acute ischemia-reperfusion injury (IRI). Crucially, there is currently no effective therapy for preventing this form of injury, and novel cardioprotective therapies are therefore required to protect the heart against acute IRI in order to limit MI size and preserve cardiac function. The opening of the mitochondrial permeability transition pore (MPTP) in the first few minutes of reperfusion is known to be a critical determinant of IRI, contributing up to 50% of the final MI size. Importantly, preventing its opening at this time using MPTP inhibitors, such as cyclosporin-A, has been reported in experimental and clinical studies to reduce MI size and preserve cardiac function. However, more specific and novel MPTP inhibitors are required to translate MPTP inhibition as a cardioprotective strategy into clinical practice. In this article, we review the role of the MPTP as a mediator of acute myocardial IRI and as a therapeutic target for cardioprotection. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease".

Novel therapeutic strategies for ischemic heart disease

Despite significant advances in the physician's ability to initiate myocardial reperfusion and salvage heart tissue, ischemic heart disease remains one of the leading causes of death in the United States. Consequently, alternative therapeutic strategies have been intensively investigated, especially methods of enhancing the heart's resistance to ischemic cell death - so called "cardioprotective" interventions. However, although a great deal has been learned regarding the methods and mechanisms of cardioprotective interventions, an efficacious therapy has yet to be successfully implemented in the clinical arena. This review discusses the current understanding of cardioprotection in the context of ischemic heart disease pathophysiology, highlighting those elements of ischemic heart disease pathophysiology that have received less attention as potential targets of cardioprotective intervention.

The mitochondrial permeability transition: a current perspective on its identity and role in ischaemia/reperfusion injury

The mitochondrial permeability transition pore (MPTP) is a non-specific pore that opens in the inner mitochondrial membrane (IMM) when matrix [Ca(2+)] is high, especially when accompanied by oxidative stress, high [Pi] and adenine nucleotide depletion. Such conditions occur during ischaemia and subsequent reperfusion, when MPTP opening is known to occur and cause irreversible damage to the heart. Matrix cyclophilin D facilitates MPTP opening and is the target of its inhibition by cyclosporin A that is cardioprotective. Less certainty exists over the composition of the pore itself, with structural and/or regulatory roles proposed for the adenine nucleotide translocase, the phosphate carrier and the FoF1 ATP synthase. Here we critically review the supporting data for the role of each and suggest that they may interact with each other through their bound cardiolipin to form the ATP synthasome. We propose that under conditions favouring MPTP opening, calcium-triggered conformational changes in these proteins may perturb the interface between them generating the pore. Proteins associated with the outer mitochondrial membrane (OMM), such as members of the Bcl-2 family and hexokinase (HK), whilst not directly involved in pore formation, may regulate MPTP opening through interactions between OMM and IMM proteins at "contact sites". Recent evidence suggests that cardioprotective protocols such as preconditioning inhibit MPTP opening at reperfusion by preventing the loss of mitochondrial bound HK2 that stabilises these contact sites. Contact site breakage both sensitises the MPTP to [Ca(2+)] and facilitates cytochrome c loss from the intermembrane space leading to greater ROS production and further MPTP opening. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease".

Protective effects of panax notoginseng saponins on cardiovascular diseases: a comprehensive overview of experimental studies

Panax notoginseng saponins (PNS) are one of the most important compounds derived from roots of the herb Panax notoginseng which are traditionally used as a hemostatic medicine to control internal and external bleeding in China for thousands of years. To date, at least twenty saponins were identified and some of them including notoginsenoside R1, ginsenoside Rb1, and ginsenoside Rg1 were researched frequently in the area of cardiovascular protection. However, the protective effects of PNS on cardiovascular diseases based on experimental studies and its underlying mechanisms have not been reviewed systematically. This paper reviewed the pharmacology of PNS and its monomers Rb1, Rg1, and R1 in the treatment for cardiovascular diseases.

Nitrosothiol signaling and protein nitrosation in cell death

Nitric oxide, a reactive free radical, is an important signaling molecule that can lead to a plethora of cellular effects affecting homeostasis. A well-established mechanism by which NO manifests its effect on cellular functions is the post-translational chemical modification of cysteine thiols in substrate proteins by a process known as S-nitrosation. Studies that investigate regulation of cellular functions through NO have increasingly established S-nitrosation as the primary modulatory mechanism in their respective systems. There has been a substantial increase in the number of reports citing various candidate proteins undergoing S-nitrosation, which affects cell-death and -survival pathways in a number of tissues including heart, lung, brain and blood. With an exponentially growing list of proteins being identified as substrates for S-nitrosation, it is important to assimilate this information in different cell/tissue systems in order to gain an overall view of protein regulation of both individual proteins and a class of protein substrates. This will allow for broad mapping of proteins as a function of S-nitrosation, and help delineate their global effects on pathophysiological responses including cell death and survival. This information will not only provide a much better understanding of overall functional relevance of NO in the context of various disease states, it will also facilitate the generation of novel therapeutics to combat specific diseases that are driven by NO-mediated S-nitrosation.

Mitochondrial reactive oxygen species (ROS) in animal cells: relevance to aging and normal physiology

In animal mitochondria, the four electron reduction of molecular oxygen to produce water at respiratory complex IV is the terminal step in substrate oxidation. However, respiratory complexes I, II, and III can participate in the single electron reduction of oxygen to produce the radical species superoxide. This progenitor reactive oxygen species (ROS) participates in a number of reactions that generate other ROS. These molecules may react with, and damage, intracellular macromolecules, leading to cellular dysfunction. Mitochondrial ROS production is often considered from this perspective of macromolecular damage and is central to the “oxidative damage theory of aging”, which suggests the accumulation of oxidative damage in animal cells underlies the aging phenotype and limits lifespan. In this review, we discuss some experimental results accumulated over the past decade that are inconsistent with this theory. A limitation of the theory is that it presupposes mitochondrial ROS are inherently harmful. However, it is increasingly apparent that some basic cellular functions are physiologically regulated by normal levels of mitochondrial ROS. For example, cell growth and division, the apoptotic pathway, and mitochondrial fusion–fission dynamics all appear to be redox-regulated by mitochondrial ROS and perhaps the matrix manganese superoxide dismutase (MnSOD). Therefore, it is less clear how the balance between ROS regulation of normal cellular activities and ROS-mediated macromolecular damage is maintained and how this relates to aging and longevity in animals.

Mitochondrial bioenergetics deregulation caused by long-chain 3-hydroxy fatty acids accumulating in LCHAD and MTP deficiencies in rat brain: a possible role of mPTP opening as a pathomechanism in these disorders?

Long-chain 3-hydroxylated fatty acids (LCHFA) accumulate in long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) and mitochondrial trifunctional protein (MTP) deficiencies. Affected patients usually present severe neonatal symptoms involving cardiac and hepatic functions, although long-term neurological abnormalities are also commonly observed. Since the underlying mechanisms of brain damage are practically unknown and have not been properly investigated, we studied the effects of LCHFA on important parameters of mitochondrial homeostasis in isolated mitochondria from cerebral cortex of developing rats. 3-Hydroxytetradecanoic acid (3 HTA) reduced mitochondrial membrane potential, NAD(P)H levels, Ca(2+) retention capacity and ATP content, besides inducing swelling, cytochrome c release and H2O2 production in Ca(2+)-loaded mitochondrial preparations. We also found that cyclosporine A plus ADP, as well as ruthenium red, a Ca(2+) uptake blocker, prevented these effects, suggesting the involvement of the mitochondrial permeability transition pore (mPTP) and an important role for Ca(2+), respectively. 3-Hydroxydodecanoic and 3-hydroxypalmitic acids, that also accumulate in LCHAD and MTP deficiencies, similarly induced mitochondrial swelling and decreased ATP content, but to a variable degree pending on the size of their carbon chain. It is proposed that mPTP opening induced by LCHFA disrupts brain bioenergetics and may contribute at least partly to explain the neurologic dysfunction observed in patients affected by LCHAD and MTP deficiencies.

Reactive oxygen species in inflammation and tissue injury

Abstract Reactive oxygen species (ROS) are key signaling molecules that play an important role in the progression of inflammatory disorders. An enhanced ROS generation by polymorphonuclear neutrophils (PMNs) at the site of inflammation causes endothelial dysfunction and tissue injury. The vascular endothelium plays an important role in passage of macromolecules and inflammatory cells from the blood to tissue. Under the inflammatory conditions, oxidative stress produced by PMNs leads to the opening of inter-endothelial junctions and promotes the migration of inflammatory cells across the endothelial barrier. The migrated inflammatory cells not only help in the clearance of pathogens and foreign particles but also lead to tissue injury. The current review compiles the past and current research in the area of inflammation with particular emphasis on oxidative stress-mediated signaling mechanisms that are involved in inflammation and tissue injury.

Ethylmalonic acid induces permeability transition in isolated brain mitochondria

Predominant accumulation of ethylmalonic acid (EMA) in tissues and biological fluids is a characteristic of patients affected by short chain acyl-CoA dehydrogenase deficiency and ethylmalonic encephalopathy. Neurological abnormalities are frequently found in these disorders, but the mechanisms underlying the brain injury are still obscure. Since hyperlacticacidemia is also found in many affected patients indicating a mitochondrial dysfunction; in the present work, we evaluated the in vitro and ex vivo effects of EMA plus Ca(2+) on mitochondrial integrity and redox balance in succinate-supported brain organelles. We verified that the evaluated parameters were disturbed only when EMA was associated with exogenous micromolar Ca(2+) concentrations. Thus, we found that this short chain organic acid plus Ca(2+) dissipated the membrane potential and provoked mitochondrial swelling, as well as impaired the mitochondrial Ca(2+) retention capacity, resulting in a rapid Ca(2+) release and decreased NAD(P)H matrix content. In contrast, EMA was not able to stimulate mitochondrial hydrogen peroxide generation. We also observed that all these effects were prevented by the mitochondrial Ca(2+) uptake inhibitor ruthenium red and the mitochondrial permeability transition (MPT) inhibitors cyclosporin A (CsA) and ADP. Furthermore, mitochondria isolated from rat brains after in vivo intrastriatal administration of EMA was more susceptible to Ca(2+)-induced swelling, which was fully prevented by CsA and ADP. Finally, EMA significantly decreased striatal slice viability, which was attenuated by CsA. The data strongly indicate that EMA reduced the mitochondrial threshold for Ca(2+)-induced MPT reinforcing the role of this cation in EMA-induced disruption of mitochondrial bioenergetics. It is, therefore, presumed that EMA acting synergistically with Ca(2+) compromises mitochondrial energy homeostasis in the central nervous system that may explain at least in part the neurologic alterations presented by patients with abnormal levels of this organic acid.

Permeability transition pore-mediated mitochondrial superoxide flashes mediate an early inhibitory effect of amyloid beta1-42 on neural progenitor cell proliferation

Cellular damage by reactive oxygen species and altered neurogenesis are implicated in the etiology of AD and the pathogenic actions of amyloid β-peptide (Aβ); the underlying mechanisms and the early oxidative intracellular events triggered by Aβ are not established. In the present study, we found that mouse embryonic cortical neural progenitor cells exhibit intermittent spontaneous mitochondrial superoxide (SO) flashes that require transient opening of mitochondrial permeability transition pores (mPTPs). The incidence of mitochondria SO flash activity in neural progenitor cells (NPCs) increased during the first 6-24 hours of exposure to aggregating amyloid β-peptide (Aβ1-42), indicating an increase in transient mPTP opening. Subsequently, the SO flash frequency progressively decreased and ceased between 48 and 72 hours of exposure to Aβ1-42, during which time global cellular reactive oxygen species increased, mitochondrial membrane potential decreased, cytochrome C was released from mitochondria and the cells degenerated. Inhibition of mPTPs and selective reduction in mitochondrial SO flashes significantly ameliorated the negative effects of Aβ1-42 on NPC proliferation and survival. Our findings suggest that mPTP-mediated bursts of mitochondrial SO production is a relatively early and pivotal event in the adverse effects of Aβ1-42 on NPCs. If Aβ inhibits NPC proliferation in the brains of AD patients by a similar mechanism, then interventions that inhibit mPTP-mediated superoxide flashes would be expected to protect NPCs against the adverse effects of Aβ.

Growth hormone secretagogues exert differential effects on skeletal muscle calcium homeostasis in male rats depending on the peptidyl/nonpeptidyl structure

The orexigenic and anabolic effects induced by ghrelin and the synthetic GH secretagogues (GHSs) are thought to positively contribute to therapeutic approaches and the adjunct treatment of a number of diseases associated with muscle wasting such as cachexia and sarcopenia. However, many questions about the potential utility and safety of GHSs in both therapy and skeletal muscle function remain unanswered. By using fura-2 cytofluorimetric technique, we determined the acute effects of ghrelin, as well as of peptidyl and nonpeptidyl synthetic GHSs on calcium homeostasis, a critical biomarker of muscle function, in isolated tendon-to-tendon male rat skeletal muscle fibers. The synthetic nonpeptidyl GHSs, but not peptidyl ghrelin and hexarelin, were able to significantly increase resting cytosolic calcium [Ca²⁺]i. The nonpeptidyl GHS-induced [Ca²⁺]i increase was independent of GHS-receptor 1a but was antagonized by both thapsigargin/caffeine and cyclosporine A, indicating the involvement of the sarcoplasmic reticulum and mitochondria. Evaluation of the effects of a pseudopeptidyl GHS and a nonpeptidyl antagonist of the GHS-receptor 1a together with a drug-modeling study suggest the conclusion that the lipophilic nonpeptidyl structure of the tested compounds is the key chemical feature crucial for the GHS-induced calcium alterations in the skeletal muscle. Thus, synthetic GHSs can have different effects on skeletal muscle fibers depending on their molecular structures. The calcium homeostasis dysregulation specifically induced by the nonpeptidyl GHSs used in this study could potentially counteract the beneficial effects associated with these drugs in the treatment of muscle wasting of cachexia- or other age-related disorders.

Mitochondrial morphology transitions and functions: implications for retrograde signaling?

In response to cellular and environmental stresses, mitochondria undergo morphology transitions regulated by dynamic processes of membrane fusion and fission. These events of mitochondrial dynamics are central regulators of cellular activity, but the mechanisms linking mitochondrial shape to cell function remain unclear. One possibility evaluated in this review is that mitochondrial morphological transitions (from elongated to fragmented, and vice-versa) directly modify canonical aspects of the organelle's function, including susceptibility to mitochondrial permeability transition, respiratory properties of the electron transport chain, and reactive oxygen species production. Because outputs derived from mitochondrial metabolism are linked to defined cellular signaling pathways, fusion/fission morphology transitions could regulate mitochondrial function and retrograde signaling. This is hypothesized to provide a dynamic interface between the cell, its genome, and the fluctuating metabolic environment.

VDAC: old protein with new roles in diabetes

A decrease in capillary density due to an increase in endothelial cell apoptosis in the heart is implicated in cardiac ischemia in diabetes. The voltage-dependent anion channel (VDAC) plays a crucial role in the regulation of mitochondrial metabolic function and mitochondria-mediated apoptosis. This study is designed to examine the role of VDAC in coronary endothelial dysfunction in diabetes. Endothelial cells (ECs) were more apoptotic in diabetic left ventricle of diabetic mice and mouse coronary ECs (MCECs) isolated from diabetic mice exhibited significantly higher mitochondrial Ca(2+) concentration and VDAC protein levels than control MCECs. The expression of VDAC-short hairpin RNA (shRNA) not only decreased the resting mitochondrial Ca(2+) concentration but also attenuated mitochondrial Ca(2+) uptake in diabetic MCECs. Furthermore, the downregulation of VDAC in diabetic MCECs significantly decreased mitochondrial superoxide anion (O(2)(-)) production and the activity of the mitochondrial permeability transition pore (mPTP) opening (an indirect indicator of cell apoptosis) toward control levels. These data suggest that the increased VDAC level in diabetic MCECs is responsible for increased mitochondrial Ca(2+) concentration, mitochondrial O(2)(-) production, and mPTP opening activity. Normalizing VDAC protein level may help to decrease endothelial cell apoptosis, increase capillary density in the heart, and subsequently decrease the incidence of cardiac ischemia in diabetes.

Mitochondrial function in vascular endothelial cell in diabetes

Micro- and macrovascular complications are commonly seen in diabetic patients and endothelial dysfunction contributes to the development and progression of the complications. Abnormal functions in endothelial cells lead to the increase in vascular tension and atherosclerosis, followed by systemic hypertension as well as increased incidence of ischemia and stroke in diabetic patients. Mitochondria are organelles serving as a source of energy production and as regulators of cell survival (e.g., apoptosis and cell development) and ion homeostasis (e.g., H(+), Ca(2+)). Endothelial mitochondria are mainly responsible for generation of reactive oxygen species (ROS) and maintaining the Ca(2+) concentration in the cytosol. There is increasing evidence that mitochondrial morphological and functional changes are implicated in vascular endothelial dysfunction. Enhanced mitochondrial fission and/or attenuated fusion lead to mitochondrial fragmentation and disrupt the endothelial physiological function. Abnormal mitochondrial biogenesis and disturbance of mitochondrial autophagy increase the accumulation of damaged mitochondria, such as irreversibly depolarized or leaky mitochondria, and facilitate cell death. Augmented mitochondrial ROS production and Ca(2+) overload in mitochondria not only cause the maladaptive effect on the endothelial function, but also are potentially detrimental to cell survival. In this article, we review the physiological and pathophysiological role of mitochondria in endothelial function with special focus on diabetes.

Yeast mitochondrial interactosome model: metabolon membrane proteins complex involved in the channeling of ADP/ATP

The existence of a mitochondrial interactosome (MI) has been currently well established in mammalian cells but the exact composition of this super-complex is not precisely known, and its organization seems to be different from that in yeast. One major difference is the absence of mitochondrial creatine kinase (MtCK) in yeast, unlike that described in the organization model of MI, especially in cardiac, skeletal muscle and brain cells. The aim of this review is to provide a detailed description of different partner proteins involved in the synergistic ADP/ATP transport across the mitochondrial membranes in the yeast Saccharomyces cerevisiae and to propose a new mitochondrial interactosome model. The ADP/ATP (Aacp) and inorganic phosphate (PiC) carriers as well as the VDAC (or mitochondrial porin) catalyze the import and export of ADP, ATP and Pi across the mitochondrial membranes. Aacp and PiC, which appear to be associated with the ATP synthase, consist of two nanomotors (F₀, F₁) under specific conditions and form ATP synthasome. Identification and characterization of such a complex were described for the first time by Pedersen and co-workers in 2003.