The powerhouse takes control of the cell: is the mitochondrial permeability transition a viable therapeutic target against neuronal dysfunction and death?

CD3ζ-Mediated Signaling Protects Retinal Ganglion Cells in Glutamate Excitotoxicity of the Retina

Excessive levels of glutamate activity could potentially damage and kill neurons. Glutamate excitotoxicity is thought to play a critical role in many CNS and retinal diseases. Accordingly, glutamate excitotoxicity has been used as a model to study neuronal diseases. Immune proteins, such as major histocompatibility complex (MHC) class I molecules and their receptors, play important roles in many neuronal diseases, while T-cell receptors (TCR) are the primary receptors of MHCI. We previously showed that a critical component of TCR, CD3ζ, is expressed by mouse retinal ganglion cells (RGCs). The mutation of CD3ζ or MHCI molecules compromises the development of RGC structure and function. In this study, we investigated whether CD3ζ-mediated molecular signaling regulates RGC death in glutamate excitotoxicity. We show that mutation of CD3ζ significantly increased RGC survival in NMDA-induced excitotoxicity. In addition, we found that several downstream molecules of TCR, including Src (proto-oncogene tyrosine-protein kinase) family kinases (SFKs) and spleen tyrosine kinase (Syk), are expressed by RGCs. Selective inhibition of an SFK member, Hck, or Syk members, Syk or Zap70, significantly increased RGC survival in NMDA-induced excitotoxicity. These results provide direct evidence to reveal the underlying molecular mechanisms that control RGC death under disease conditions.

Evaluation of the neuroprotective efficacy of the gramine derivative ITH12657 against NMDA-induced excitotoxicity in the rat retina

Purpose

The aim of this study was to investigate, the neuroprotective effects of a new Gramine derivative named: ITH12657, in a model of retinal excitotoxicity induced by intravitreal injection of NMDA.

Methods

Adult Sprague Dawley rats received an intravitreal injection of 100 mM NMDA in their left eye and were treated daily with subcutaneous injections of ITH12657 or vehicle. The best dose-response, therapeutic window study, and optimal treatment duration of ITH12657 were studied. Based on the best survival of Brn3a + RGCs obtained from the above-mentioned studies, the protective effects of ITH12657 were studied in vivo (retinal thickness and full-field Electroretinography), and ex vivo by quantifying the surviving population of Brn3a + RGCs, αRGCs and their subtypes α-ONsRGCs, α-ONtRGCs, and α-OFFRGCs.

Results

Administration of 10 mg/kg ITH12657, starting 12 h before NMDA injection and dispensed for 3 days, resulted in the best significant protection of Brn3a + RGCs against NMDA-induced excitotoxicity. In vivo, ITH12657-treated rats showed significant preservation of retinal thickness and functional protection against NMDA-induced retinal excitotoxicity. Ex vivo results showed that ITH12657 afforded a significant protection against NMDA-induced excitotoxicity for the populations of Brn3a + RGC, αRGC, and αONs-RGC, but not for the population of αOFF-RGC, while the population of α-ONtRGC was fully resistant to NMDA-induced excitotoxicity.

Conclusion

Subcutaneous administration of ITH12657 at 10 mg/kg, initiated 12 h before NMDA-induced retinal injury and continued for 3 days, resulted in the best protection of Brn3a + RGCs, αRGC, and αONs-RGC against excitotoxicity-induced RGC death. The population of αOFF-RGCs was extremely sensitive while α-ONtRGCs were fully resistant to NMDA-induced excitotoxicity.

Zinc oxide nanoparticles trigger dysfunction of mitochondrial respiratory complexes and repair dynamics in human alveolar cells

Zinc oxide nanoparticles (ZnO NP) are commonly used engineered NPs with extensive usage in consumer products, thus leading to direct exposure to humans. The direct route of exposure is through inhalation. Once inhaled, these particles accumulate in the lungs, increasing the chances of respiratory tract illness through cellular organelle damage. Zinc oxide nanoparticle-treated lung cells are reported to display cytotoxicity, increase DNA damage, and induce oxidative stress. The current study focused on the effects of ZnO NPs on mitochondrial dynamics (fission and fusion) in human lung epithelial cells (A549). The lung cells were exposed to ZnO NPs at 50 and 100 μg/ml concentrations, and their mitochondrial dynamics were assessed to understand the effects of the NPs. Treatment with ZnO NPs reduced the activity of mitochondrial complex I and complex III and altered mitochondrial structural and functional characteristics in a concentration-dependent manner. Zinc oxide nanoparticles exposure showed an increase in small and round-shaped mitochondria. The expression of various fission proteins (Drp1 and Fis1) and fusion proteins (Mfn1, Mfn2, and OPA1) was altered upon exposure to ZnO NPs. Our studies showed dysfunction of the mitochondria induced by ZnO NPs. In fibroblast mitochondrial dynamics, fission symbolizes threshold damage. In this paper, we have shown that the mitochondrial fission phenotype increased upon exposure to ZnO NPs. The paper emphasizes that these particles enter mitochondria, triggering a stress response that results in the removal of mitochondria via fission. It provides relevant data for safety guidelines to ensure the safer use of these particles.

Tetrahydrocurcumin-Related Vascular Protection: An Overview of the Findings from Animal Disease Models

Tetrahydrocurcumin (THC), one of the major metabolites of CUR, possesses several CUR-like pharmacological effects; however, its mechanisms of action are largely unknown. This manuscript aims to summarize the literature on the preventive role of THC on vascular dysfunction and the development of hypertension by exploring the effects of THC on hemodynamic status, aortic elasticity, and oxidative stress in vasculature in different animal models. We review the protective effects of THC against hypertension induced by heavy metals (cadmium and iron), as well as its impact on arterial stiffness and vascular remodeling. The effects of THC on angiogenesis in CaSki xenografted mice and the expression of vascular endothelial growth factor (VEGF) are well documented. On the other hand, as an anti-inflammatory and antioxidant compound, THC is involved in enhancing homocysteine-induced mitochondrial remodeling in brain endothelial cells. The experimental evidence regarding the mechanism of mitochondrial dysfunction during cerebral ischemic/reperfusion injury and the therapeutic potential of THC to alleviate mitochondrial cerebral dysmorphic dysfunction patterns is also scrutinized and explored. Overall, the studies on different animal models of disease suggest that THC can be used as a dietary supplement to protect against cardiovascular changes caused by various factors (such as heavy metal overload, oxidative stress, and carcinogenesis). Additionally, the reviewed literature data seem to confirm THC's potential to improve mitochondrial dysfunction in cerebral vasculature during ischemic stroke through epigenetic mechanisms. We suggest that further preclinical studies should be implemented to demonstrate THC's vascular-protective, antiangiogenic, and anti-tumorigenic effects in humans. Applying the methods used in the presently reviewed studies would be useful and will help define the doses and methods of THC administration in various disease settings.

Leukocyte mitochondrial DNA copy number in schizophrenia

OBJECTIVE

Schizophrenia is a complex neuropsychiatric disorder with significant genetic predisposition. In a subset of schizophrenia patients, mitochondrial dysfunction could be explained by the genomic defects like mitochondrial DNA Copy Number Variations, which are considered as a sensitive index of cellular oxidative stress. Given the high energy demands for neuronal functions, altered Mitochondrial DNA copy number (mtDNAcn) and consequent impaired mitochondrial physiology would significantly influence schizophrenia pathogenesis. In this context, we have made an attempt to study mitochondrial dysfunction in schizophrenia by assessing mtDNAcn in antipsychotic-naïve/free schizophrenia patients.

METHOD

mtDNAcn was measured in 90 antipsychotic-naïve / free schizophrenia (SCZ) patients and 147 Healthy Controls (HC). The relative mtDNAcn was determined by quantitative real-time polymerase chain reaction (qPCR) using TaqMan® multiplex assay method.

RESULT

A statistically significant difference between groups [t = 5.22, P < 0.001] was observed, with significantly lower mtDNAcn in SCZ compared to HC. The group differences persisted even after controlling for age and sex [F (4, 232) = 22.68, P < 0.001, η2 = 0.09].

CONCLUSION

Lower mtDNAcn in SCZ compared to HC suggests that mtDNAcn may hold potential to serve as an important proxy marker of mitochondrial function in antipsychotic-naïve/free SCZ patients.

Going the Extra (Synaptic) Mile: Excitotoxicity as the Road Toward Neurodegenerative Diseases

Excitotoxicity is a phenomenon that describes the toxic actions of excitatory neurotransmitters, primarily glutamate, where the exacerbated or prolonged activation of glutamate receptors starts a cascade of neurotoxicity that ultimately leads to the loss of neuronal function and cell death. In this process, the shift between normal physiological function and excitotoxicity is largely controlled by astrocytes since they can control the levels of glutamate on the synaptic cleft. This control is achieved through glutamate clearance from the synaptic cleft and its underlying recycling through the glutamate-glutamine cycle. The molecular mechanism that triggers excitotoxicity involves alterations in glutamate and calcium metabolism, dysfunction of glutamate transporters, and malfunction of glutamate receptors, particularly N-methyl-D-aspartic acid receptors (NMDAR). On the other hand, excitotoxicity can be regarded as a consequence of other cellular phenomena, such as mitochondrial dysfunction, physical neuronal damage, and oxidative stress. Regardless, it is known that the excessive activation of NMDAR results in the sustained influx of calcium into neurons and leads to several deleterious consequences, including mitochondrial dysfunction, reactive oxygen species (ROS) overproduction, impairment of calcium buffering, the release of pro-apoptotic factors, among others, that inevitably contribute to neuronal loss. A large body of evidence implicates NMDAR-mediated excitotoxicity as a central mechanism in the pathogenesis of many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and epilepsy. In this review article, we explore different causes and consequences of excitotoxicity, discuss the involvement of NMDAR-mediated excitotoxicity and its downstream effects on several neurodegenerative disorders, and identify possible strategies to study new aspects of these diseases that may lead to the discovery of new therapeutic approaches. With the understanding that excitotoxicity is a common denominator in neurodegenerative diseases and other disorders, a new perspective on therapy can be considered, where the targets are not specific symptoms, but the underlying cellular phenomena of the disease.

The Susceptibility of Retinal Ganglion Cells to Optic Nerve Injury is Type Specific

Retinal ganglion cell (RGC) death occurs in many eye diseases, such as glaucoma and traumatic optic neuropathy (TON). Increasing evidence suggests that the susceptibility of RGCs varies to different diseases in an RGC type-dependent manner. We previously showed that the susceptibility of several genetically identified RGC types to N-methyl-D-aspartate (NMDA) excitotoxicity differs significantly. In this study, we characterize the susceptibility of the same RGC types to optic nerve crush (ONC). We show that the susceptibility of these RGC types to ONC varies significantly, in which BD-RGCs are the most resistant RGC type while W3-RGCs are the most sensitive cells to ONC. We also show that the survival rates of BD-RGCs and J-RGCs after ONC are significantly higher than their survival rates after NMDA excitotoxicity. These results are consistent with the conclusion that the susceptibility of RGCs to ONC varies in an RGC type-dependent manner. Further, the susceptibilities of the same types of RGCs to ONC and NMDA excitotoxicity are significantly different. These are valuable insights for understanding of the selective susceptibility of RGCs to various pathological insults and the development of a strategy to protect RGCs from death in disease conditions.

Effects of aging and exercise training on mitochondrial function and apoptosis in the rat heart

Aging is associated with vulnerability to cardiovascular diseases, and mitochondrial dysfunction plays a critical role in cardiovascular disease pathogenesis. Exercise training is associated with benefits against chronic cardiac diseases. The purpose of this study was to determine the effects of aging and treadmill exercise training on mitochondrial function and apoptosis in the rat heart. Fischer 344 rats were divided into young sedentary (YS; n = 10, 4 months), young exercise (YE; n = 10, 4 months), old sedentary (OS; n = 10, 20 months), and old exercise (OE; n = 10, 20 months) groups. Exercise training groups ran on a treadmill at 15 m/min (young) or 10 m/min (old), 45 min/day, 5 days/week for 8 weeks. Morphological parameters, mitochondrial function, mitochondrial dynamics, mitophagy, and mitochondria-mediated apoptosis were analyzed in cardiac muscle. Mitochondrial O₂ respiratory capacity and Ca²⁺ retention capacity gradually decreased, and mitochondrial H₂O₂ emitting potential significantly increased with aging. Exercise training attenuated aging-induced mitochondrial H₂O₂ emitting potential and mitochondrial O₂ respiratory capacity, while protecting Ca²⁺ retention in the old groups. Aging triggered imbalanced mitochondrial dynamics and excess mitophagy, while exercise training ameliorated the aging-induced imbalance in mitochondrial dynamics and excess mitophagy. Aging induced increase in Bax and cleaved caspase-3 protein levels, while decreasing Bcl-2 levels. Exercise training protected against the elevation of apoptotic signaling markers by decreasing Bax and cleaved caspase-3 and increasing Bcl-2 protein levels, while decreasing the Bax/Bcl-2 ratio and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive myonuclei. These data demonstrate that regular exercise training prevents aging-induced impairment of mitochondrial function and mitochondria-mediated apoptosis in cardiac muscles.

Melanopsin+RGCs Are fully Resistant to NMDA-Induced Excitotoxicity

We studied short- and long-term effects of intravitreal injection of N-methyl-d-aspartate (NMDA) on melanopsin-containing (m⁺) and non-melanopsin-containing (Brn3a⁺) retinal ganglion cells (RGCs). In adult SD-rats, the left eye received a single intravitreal injection of 5µL of 100nM NMDA. At 3 and 15 months, retinal thickness was measured in vivo using Spectral Domain-Optical Coherence Tomography (SD-OCT). Ex vivo analyses were done at 3, 7, or 14 days or 15 months after damage. Whole-mounted retinas were immunolabelled for brain-specific homeobox/POU domain protein 3A (Brn3a) and melanopsin (m), the total number of Brn3a⁺RGCs and m⁺RGCs were quantified, and their topography represented. In control retinas, the mean total numbers of Brn3a⁺RGCs and m⁺RGCs were 78,903 ± 3572 and 2358 ± 144 (mean ± SD; n = 10), respectively. In the NMDA injected retinas, Brn3a⁺RGCs numbers diminished to 49%, 28%, 24%, and 19%, at 3, 7, 14 days, and 15 months, respectively. There was no further loss between 7 days and 15 months. The number of immunoidentified m⁺RGCs decreased significantly at 3 days, recovered between 3 and 7 days, and were back to normal thereafter. OCT measurements revealed a significant thinning of the left retinas at 3 and 15 months. Intravitreal injections of NMDA induced within a week a rapid loss of 72% of Brn3a⁺RGCs, a transient downregulation of melanopsin expression (but not m⁺RGC death), and a thinning of the inner retinal layers.

Proteomics Reveals Profound Metabolic Changes in the Alcohol Use Disorder Brain

Changes in brain metabolism are a hallmark of alcohol use disorder (AUD). Determining how AUD changes the brain proteome is critical for understanding the effects of alcohol consumption on biochemical processes in the brain. We used data-independent acquisition mass spectrometry proteomics to study differences in the abundance of proteins associated with AUD in prefrontal lobe and motor cortex from autopsy brain. AUD had a substantial effect on the overall brain proteome exceeding the inherent differences between brain regions. Proteins associated with glycolysis, trafficking, the cytoskeleton, and excitotoxicity were altered in abundance in AUD. We observed extensive changes in the abundance of key metabolic enzymes, consistent with a switch from glucose to acetate utilization in the AUD brain. We propose that metabolic adaptations allowing efficient acetate utilization contribute to ethanol dependence in AUD.

The Susceptibility of Retinal Ganglion Cells to Glutamatergic Excitotoxicity Is Type-Specific

Retinal ganglion cells (RGCs) are the only output neurons that conduct visual signals from the eyes to the brain. RGC degeneration occurs in many retinal diseases leading to blindness and increasing evidence suggests that RGCs are susceptible to various injuries in a type-specific manner. Glutamate excitotoxicity is the pathological process by which neurons are damaged and killed by excessive stimulation of glutamate receptors and it plays a central role in the death of neurons in many CNS and retinal diseases. The purpose of this study is to characterize the susceptibility of genetically identified RGC types to the excitotoxicity induced by N-methyl-D-aspartate (NMDA). We show that the susceptibility of different types of RGCs to NMDA excitotoxicity varies significantly, in which the αRGCs are the most resistant type of RGCs to NMDA excitotoxicity while the J-RGCs are the most sensitive cells to NMDA excitotoxicity. These results strongly suggest that the differences in the genetic background of RGC types might provide valuable insights for understanding the selective susceptibility of RGCs to pathological insults and the development of a strategy to protect RGCs from death in disease conditions. In addition, our results show that RGCs lose dendrites before death and the sequence of the morphological and molecular events during RGC death suggests that the initial insult of NMDA excitotoxicity might set off a cascade of events independent of the primary insults. However, the kinetics of dendritic retraction in RGCs does not directly correlate to the susceptibility of type-specific RGC death.

Tetrahydrocurcumin epigenetically mitigates mitochondrial dysfunction in brain vasculature during ischemic stroke

The objectives of this study are to identify the mechanism of mitochondrial dysfunction during cerebral ischemic/reperfusion (I/R) injury and the therapeutic potential of tetrahydrocurcumin (THC) to mitigate mitochondrial dysfunction in experimental stroke model. In our study, 8-10 weeks old male C57BL/6 wild-type mice were subjected to middle cerebral artery occlusion (MCAO) for 40 min, followed by reperfusion for 72 h. THC (25mg/kg-BW/day) was injected intraperitoneally once daily for 3 days after 4 h of ischemia. The experimental groups were: (i) sham, (ii) I/R and (iii) I/R + THC. We noticed that THC treatment in ischemic mice significantly improved the functional capacity and motor co-ordination along with reduced neuroscore, infarct volume, brain edema and microvascular leakage in brain parenchyma. The study revealed that level of total homocysteine (tHcy), homocysteine metabolizing enzymes, mitochondrial oxidative stress were significantly altered in I/R mice compared to sham. We also observed alteration in mitochondrial transition pore, ATP production and O₂ consumption in the ischemic brain as compared to sham. Further, elevated matrix metalloproteinases-9 (MMP-9) activity and reduced tight junction protein expressions intensified the brain vascular impairment in I/R mice compared to sham. Interestingly, we found that levels of mitophagy markers, fusion and fission proteins were significantly altered. However THC treatment in I/R mice almost normalized the above functional and molecular changes. Mechanistic study demonstrated that DNA Methyltransferase 1 (DNMT1) expression was higher and was associated with reduced mitochondrial tissue inhibitor of metalloproteinases 2 (TIMP-2) expression through hyper-methylation of CpG island of TIMP-2 promoter in I/R mice compared to sham. However, administration of epigenetic inhibitor, 5-Azacytidine (5-Aza) abrogated I/R induced hyper-methylation of TIMP-2 promoter and maintaining the extracellular matrix (ECM) integrity. In conclusion, this study suggests that THC epigenetically ameliorates mitochondrial dysfunction in brain vasculature during Ischemic Stroke.

Memory and Learning Dysfunction Following Copper Toxicity: Biochemical and Immunohistochemical Basis

The prototype disease of Cu toxicity in human is Wilson disease, and cognitive impairment is the presenting symptom of it. There is no study correlating Cu-induced excitotoxicity, apoptosis, and astrocytic reaction with memory dysfunction. We report excitotoxicity, apoptosis, and astrocytic reaction of the hippocampus and frontal cortex with memory dysfunction in rat model of Cu toxicity. Thirty-six rats were divided into group I (control) and group II (100 mg/kgBwt/day CuSO₄ orally). Y-maze was performed for memory and learning at 0, 30, 60, and 90 days. Frontal and hippocampal free Cu concentration, oxidative stress markers [glutathione (GSH), total antioxidant toxicity (TAC), and malondialdehyde (MDA)], and glutamate were measured by atomic absorption spectroscopy, spectrophotometry, and ELISA, respectively. N-methyl-D-aspartate receptors (NMDARs) NR1, NR2A, and NR2B were done by real-time polymerase chain reaction. Immunohistochemistry for caspase-3 and glial fibrillary acidic protein (GFAP) were done and quantified using the ImageJ software. The glutamate level in hippocampus was increased, and NMDAR expression was decreased at 30, 60, and 90 days in group II compared to group I. In the frontal cortex, glutamate was increased at 90 days, but NMDARs were not significantly different in group II compared to group I. Caspase-3 and GFAP expressions were also higher in group II compared to group I, and these changes were more marked in hippocampus than frontal cortex. These changes correlated with respective free tissue Cu, oxidative stress, and Y-maze attention score. Cu toxicity induces apoptosis and astrocytosis of the hippocampus and frontal cortex through direct or glutamate and oxidative stress pathways, and results in impaired memory and learning.

Abnormal Capillary Vasodynamics Contribute to Ictal Neurodegeneration in Epilepsy

Seizure-driven brain damage in epilepsy accumulates over time, especially in the hippocampus, which can lead to sclerosis, cognitive decline, and death. Excitotoxicity is the prevalent model to explain ictal neurodegeneration. Current labeling technologies cannot distinguish between excitotoxicity and hypoxia, however, because they share common molecular mechanisms. This leaves open the possibility that undetected ischemic hypoxia, due to ictal blood flow restriction, could contribute to neurodegeneration previously ascribed to excitotoxicity. We tested this possibility with Confocal Laser Endomicroscopy (CLE) and novel stereological analyses in several models of epileptic mice. We found a higher number and magnitude of NG2+ mural-cell mediated capillary constrictions in the hippocampus of epileptic mice than in that of normal mice, in addition to spatial coupling between capillary constrictions and oxidative stressed neurons and neurodegeneration. These results reveal a role for hypoxia driven by capillary blood flow restriction in ictal neurodegeneration.

Inorganic polyphosphate (polyP) as an activator and structural component of the mitochondrial permeability transition pore

Mitochondrial permeability transition pore (mPTP) is a large channel located in the mitochondrial inner membrane. The opening of mPTP during pathological calcium overload leads to the membrane depolarization and disruption of ATP production. mPTP activation has been implicated as a central event during the process of stress-induced cell death. mPTP is a supramolecular complex composed of many proteins. Recent studies suggest that mitochondrial ATPase plays the central role in the formation of mPTP. However, the structure of the central conducting pore part of mPTP (mPTPore) remains elusive. Here we review current models proposed for the mPTPore and involvement of polyP in its formation and regulation. We discuss the underestimated role of polyP as an effector and a putative structural component of the mPTPore. We propose the hypothesis that inclusion of polyP can explain such properties of mPTP activity as calcium activation, selectivity and voltage-dependence.

Beyond muscles: The untapped potential of creatine

Creatine is widely used by both elite and recreational athletes as an ergogenic aid to enhance anaerobic exercise performance. Older individuals also use creatine to prevent sarcopenia and, accordingly, may have therapeutic benefits for muscle wasting diseases. Although the effect of creatine on the musculoskeletal system has been extensively studied, less attention has been paid to its potential effects on other physiological systems. Because there is a significant pool of creatine in the brain, the utility of creatine supplementation has been examined in vitro as well as in vivo in both animal models of neurological disorders and in humans. While the data are preliminary, there is evidence to suggest that individuals with certain neurological conditions may benefit from exogenous creatine supplementation if treatment protocols can be optimized. A small number of studies that have examined the impact of creatine on the immune system have shown an alteration in soluble mediator production and the expression of molecules involved in recognizing infections, specifically toll-like receptors. Future investigations evaluating the total impact of creatine supplementation are required to better understand the benefits and risks of creatine use, particularly since there is increasing evidence that creatine may have a regulatory impact on the immune system.

Preparation of purified perikaryal and synaptosomal mitochondrial fractions from relatively small hypothalamic brain samples

In order to measure the activity of neuronal mitochondria, a representative proof of neuronal processes, physiologically relevant mitochondrial samples need to be gained as simply as possible. Existing methods are, however, either for tissue samples of large size and/or homogenous microstructures only, or are not tested for mitochondrial function measurements. In the present article we describe a gradient fractionation method to isolate viable and well-coupled mitochondria from relatively heterogeneous histological microstructures such as the hypothalamus. With this new method, we are able to isolate a sufficient amount of functional mitochondria for determination of respiratory activity, in a short period of time, using affordable equipment. •Verified by electron microscopy, our method separates highly enriched and well-preserved perikaryal and synaptosomal mitochondria. Both fractions contain minimal cell debris and no myelin. Respiratory measurements (carried out by Clark-type electrode) confirmed undisturbed mitochondrial function providing well-evaluable records. The demonstrated protocol yields highly viable mitochondrial subfractions within 3 h from small brain areas for high-precision examinations. Using this procedure, brain regions with relatively heterogeneous histological microstructure (hypothalamus) can also be efficiently sampled.•Up to our present knowledge, our method is the shortest available procedure with the lowest sample size to gain debris-free, fully-viable mitochondria.

HIV-1, methamphetamine and astrocytes at neuroinflammatory Crossroads

As a popular psychostimulant, methamphetamine (METH) use leads to long-lasting, strong euphoric effects. While METH abuse is common in the general population, between 10 and 15% of human immunodeficiency virus-1 (HIV-1) patients report having abused METH. METH exacerbates the severity and onset of HIV-1-associated neurocognitive disorders (HAND) through direct and indirect mechanisms. Repetitive METH use impedes adherence to antiretroviral drug regimens, increasing the likelihood of HIV-1 disease progression toward AIDS. METH exposure also directly affects both innate and adaptive immunity, altering lymphocyte numbers and activity, cytokine signaling, phagocytic function and infiltration through the blood brain barrier. Further, METH triggers the dopamine reward pathway and leads to impaired neuronal activity and direct toxicity. Concurrently, METH and HIV-1 alter the neuroimmune balance and induce neuroinflammation, which modulates a wide range of brain functions including neuronal signaling and activity, glial activation, viral infection, oxidative stress, and excitotoxicity. Pathologically, reactive gliosis is a hallmark of both HIV-1- and METH-associated neuroinflammation. Significant commonality exists in the neurotoxic mechanisms for both METH and HAND; however, the pathways dysregulated in astroglia during METH exposure are less clear. Thus, this review highlights alterations in astrocyte intracellular signaling pathways, gene expression and function during METH and HIV-1 comorbidity, with special emphasis on HAND-associated neuroinflammation. Importantly, this review carefully evaluates interventions targeting astrocytes in HAND and METH as potential novel therapeutic approaches. This comprehensive overview indicates, without a doubt, that during HIV-1 infection and METH abuse, a complex dialog between all neural cells is orchestrated through astrocyte regulated neuroinflammation.

The Mitochondrial Permeability Transition Pore: Channel Formation by F-ATP Synthase, Integration in Signal Transduction, and Role in Pathophysiology

The mitochondrial permeability transition (PT) is a permeability increase of the inner mitochondrial membrane mediated by a channel, the permeability transition pore (PTP). After a brief historical introduction, we cover the key regulatory features of the PTP and provide a critical assessment of putative protein components that have been tested by genetic analysis. The discovery that under conditions of oxidative stress the F-ATP synthases of mammals, yeast, and Drosophila can be turned into Ca(2+)-dependent channels, whose electrophysiological properties match those of the corresponding PTPs, opens new perspectives to the field. We discuss structural and functional features of F-ATP synthases that may provide clues to its transition from an energy-conserving into an energy-dissipating device as well as recent advances on signal transduction to the PTP and on its role in cellular pathophysiology.

Protein kinase CK2 inhibition induces cell death via early impact on mitochondrial function

CK2 (official acronym for casein kinase 2 or II) is a potent suppressor of apoptosis in response to diverse apoptotic stimuli-thus its molecular downregulation or activity inhibition results in potent induction of cell death. CK2 downregulation is known to impact mitochondrial apoptotic circuitry but the underlying mechanism(s) remain unclear. Utilizing prostate cancer cell lines subjected to CK2-specific inhibitors which cause loss of cell viability, we have found that CK2 inhibition in cells causes rapid early decrease in mitochondrial membrane potential (Δψm). Cells treated with the CK2 inhibitors TBB (4,5,6,7-tetrabromobenzotriazole) or TBCA (tetrabromocinnamic acid) demonstrate changes in Δψm which become apparent within 2 h, that is, significantly prior to evidence of activation of other mitochondrial apoptotic signals whose temporal expression ensues subsequent to loss of Δψm. Further, we have demonstrated the presence of CK2 in purified mitochondria and it appears that the effect on Δψm evoked by inhibition of CK2 may involve mitochondrial localized CK2. Results also suggest that alterations in Ca(2+) signaling may be involved in the CK2 mediated regulation of Δψm and mitochondrial permeability. Thus, we propose that a key mechanism of CK2 impact on mitochondrial apoptotic circuitry and cell death involves early loss of Δψm which may be a primary trigger for apoptotic signaling and cell death resulting from CK2 inhibition.

Targeted nanoparticles in mitochondrial medicine

Mitochondria, the so-called 'energy factory of cells' not only produce energy but also contribute immensely in cellular mortality management. Mitochondrial dysfunctions result in various diseases including but not limited to cancer, atherosclerosis, and neurodegenerative diseases. In the recent years, targeting mitochondria emerged as an attractive strategy to control mitochondrial dysfunction-related diseases. Despite the desire to direct therapeutics to the mitochondria, the actual task is more difficult due to the highly complex nature of the mitochondria. The potential benefits of integrating nanomaterials with properties such as biodegradability, magnetization, and fluorescence into a single object of nanoscale dimensions can lead to the development of hybrid nanomedical platforms for targeting therapeutics to the mitochondria. Only a handful of nanoparticles based on metal oxides, gold nanoparticles, dendrons, carbon nanotubes, and liposomes were recently engineered to target mitochondria. Most of these materials face tremendous challenges when administered in vivo due to their limited biocompatibility. Biodegradable polymeric nanoparticles emerged as eminent candidates for effective drug delivery. In this review, we highlight the current advancements in the development of biodegradable nanoparticle platforms as effective targeting tools for mitochondrial medicine.

Electrophysiological and molecular mechanisms of protection by iron sucrose against phosphine-induced cardiotoxicity: a time course study

The present study was designed for determining the exact mechanism of cytotoxic action of aluminum phosphide (AlP) in the presence of iron sucrose as the proposed antidote. Rats received AlP (12 mg/kg) and iron sucrose (5-30 mg/kg) in various sets and were connected to cardiovascular monitoring device. After identification of optimum doses of AlP and iron sucrose, rats taken in 18 groups received AlP (6 mg/kg) and iron sucrose (10 mg/kg), treated at six different time points, and then their hearts were surgically removed and used for evaluating a series of mitochondrial parameters, including cell lipid peroxidation, antioxidant power, mitochondrial complex activity, ADP/ATP ratio and process of apoptosis. ECG changes of AlP poisoning, including QRS, QT, P-R, ST, BP and HR were ameliorated by iron sucrose (10 mg/kg) treatment. AlP initiated its toxicity in the heart mitochondria through reducing mitochondrial complexes (II, IV and V), which was followed by increasing lipid peroxidation and the ADP/ATP ratio and declining mitochondrial membrane integrity that ultimately resulted in cell death. AlP in acute exposure (6 mg/kg) resulted in an increase in hydroxyl radicals and lipid peroxidation in a time-dependent fashion, suggesting an interaction of delivering electrons of phosphine with mitochondrial respiratory chain and oxidative stress. Iron sucrose, as an electron receiver, can compete with mitochondrial respiratory chain complexes and divert electrons to another pathway. The present findings supported the idea that iron sucrose could normalize the activity of mitochondrial electron transfer chain and cellular ATP level as vital factors for cell escaping from AlP poisoning.

EAAC1 gene deletion increases neuronal death and blood brain barrier disruption after transient cerebral ischemia in female mice

EAAC1 is important in modulating brain ischemic tolerance. Mice lacking EAAC1 exhibit increased susceptibility to neuronal oxidative stress in mice after transient cerebral ischemia. EAAC1 was first described as a glutamate transporter but later recognized to also function as a cysteine transporter in neurons. EAAC1-mediated transport of cysteine into neurons contributes to neuronal antioxidant function by providing cysteine substrates for glutathione synthesis. Here we evaluated the effects of EAAC1 gene deletion on hippocampal blood vessel disorganization after transient cerebral ischemia. EAAC1-/- female mice subjected to transient cerebral ischemia by common carotid artery occlusion for 30 min exhibited twice as much hippocampal neuronal death compared to wild-type female mice as well as increased reduction of neuronal glutathione, blood-brain barrier (BBB) disruption and vessel disorganization. Pre-treatment of N-acetyl cysteine, a membrane-permeant cysteine prodrug, increased basal glutathione levels in the EAAC1-/- female mice and reduced ischemic neuronal death, BBB disruption and vessel disorganization. These findings suggest that cysteine uptake by EAAC1 is important for neuronal antioxidant function under ischemic conditions.

Vitamin D as a potential therapy in amyotrophic lateral sclerosis

Vitamin D has been demonstrated to influence multiple aspects of amyotrophic lateral sclerosis (ALS) pathology. Both human and rodent central nervous systems express the vitamin D receptor (VDR) and/or its enzymatic machinery needed to fully activate the hormone. Clinical research suggests that vitamin D treatment can improve compromised human muscular ability and increase muscle size, supported by loss of motor function and muscle mass in animals following VDR knockout, as well as increased muscle protein synthesis and ATP production following vitamin D supplementation. Vitamin D has also been shown to reduce the expression of biomarkers associated with oxidative stress and inflammation in patients with multiple sclerosis, rheumatoid arthritis, congestive heart failure, Parkinson's disease and Alzheimer's disease; diseases that share common pathophysiologies with ALS. Furthermore, vitamin D treatment greatly attenuates hypoxic brain damage in vivo and reduces neuronal lethality of glutamate insult in vitro; a hallmark trait of ALS glutamate excitotoxicity. We have recently shown that high-dose vitamin D3 supplementation improved, whereas vitamin D3 restriction worsened, functional capacity in the G93A mouse model of ALS. In sum, evidence demonstrates that vitamin D, unlike the antiglutamatergic agent Riluzole, affects multiple aspects of ALS pathophysiology and could provide a greater cumulative effect.

Low-level laser therapy (810 nm) protects primary cortical neurons against excitotoxicity in vitro

Excitotoxicity describes a pathogenic process whereby death of neurons releases large amounts of the excitatory neurotransmitter glutamate, which then proceeds to activate a set of glutamatergic receptors on neighboring neurons (glutamate, N-methyl-D-aspartate (NMDA), and kainate), opening ion channels leading to an influx of calcium ions producing mitochondrial dysfunction and cell death. Excitotoxicity contributes to brain damage after stroke, traumatic brain injury, and neurodegenerative diseases, and is also involved in spinal cord injury. We tested whether low level laser (light) therapy (LLLT) at 810 nm could protect primary murine cultured cortical neurons against excitotoxicity in vitro produced by addition of glutamate, NMDA or kainate. Although the prevention of cell death was modest but significant, LLLT (3 J/cm(2) delivered at 25 mW/cm(2) over 2 min) gave highly significant benefits in increasing ATP, raising mitochondrial membrane potential, reducing intracellular calcium concentrations, reducing oxidative stress and reducing nitric oxide. The action of LLLT in abrogating excitotoxicity may play a role in explaining its beneficial effects in diverse central nervous system pathologies.

Protective effect of Aloe vera gel on the permeability transition pore in the inner membrane of rat liver mitochondria in vitro

OBJECTIVE

Aloe vera is a perennial drought resisting, succulent plant belonging to the zanthorrhoeaceae family which historically has been used for a variety of medicinal purposes. This study seeks to determine the effect of varying concentrations of Aloe vera gel (50, 100, 150, 250, and 350 µg/ml) on mitochondrial permeability transition pore (MPTP) in rat liver mitochondria (RLM) (in vitro).

METHODS

Fresh Aloe gel was prepared daily from the Aloe vera leaf and the effect of the gel on mitochondrial membrane permeability transition pore opening was estimated in vitro using the spectrophotometric method of Lapidus and Sokolove.

RESULTS

Varying concentrations of Aloe vera gel (50, 100, 150, 250, and 350 µg/ml) induced (insignificantly at p < 0.05) the opening of the mitochondrial permeability transition pore in a concentration dependent manner in the absence of calcium (Δ540 nm as -0.020 ± 0.008, -0.021 ± 0.009, -0.031 ± 0.013, -0.031 ± 0.014, -0.034 ± 0.014 respectively) when compared with the control (-0.016 ± 0.009). In the presence of calcium, the various concentrations of Aloe vera gel further opened the MMPT pore with the highest effect noticed at 350 µg/ml concentration.

CONCLUSIONS

These findings indicate that Aloe vera gel modulates the mitochondrial pore opening by further increasing the effect of calcium. This effect is needed in situations that requires tissue wastage such as in cancer treatment.

Phosphorylation of DYNLT1 at serine 82 regulates microtubule stability and mitochondrial permeabilization in hypoxia

Hypoxia-induced microtubule disruption and mitochondrial permeability transition (mPT) are crucial events leading to fatal cell damage and recent studies showed that microtubules (MTs) are involved in the modulation of mitochondrial function. Dynein light chain Tctex-type 1 (DYNLT1) is thought to be associated with MTs and mitochondria. Previously we demonstrated that DYNLT1 knockdown aggravates hypoxia-induced mitochondrial permeabilization, which indicates a role of DYNLT1 in hypoxic cytoprotection. But the underlying regulatory mechanism of DYNLT1 remains illusive. Here we aimed to investigate the phosphorylation alteration of DYNLT1 at serine 82 (S82) in hypoxia (1% O2). We therefore constructed recombinant adenoviruses to generate S82E and S82A mutants, used to transfect H9c2 and HeLa cell lines. Development of hypoxia-induced mPT (MMP examining, Cyt c release and mPT pore opening assay), hypoxic energy metabolism (cellular viability and ATP quantification), and stability of MTs were examined. Our results showed that phosph-S82 (S82-P) expression was increased in early hypoxia; S82E mutation (phosphomimic) aggravated mitochondrial damage, elevated the free tubulin in cytoplasm and decreased the cellular viability; S82A mutation (dephosphomimic) seemed to diminish the hypoxia-induced injury. These data suggest that DYNLT1 phosphorylation at S82 is involved in MTs and mitochondria regulation, and their interaction and cooperation contribute to the cellular hypoxic tolerance. Thus, we provide new insights into a DYNLT1 mechanism in stabilizing MTs and mitochondria, and propose a potential therapeutic target for hypoxia cytoprotective studies.

Mitochondrial dysfunction and NAD(+) metabolism alterations in the pathophysiology of acute brain injury

Mitochondrial dysfunction is commonly believed to be one of the major players in mechanisms of brain injury. For several decades, pathologic mitochondrial calcium overload and associated opening of the mitochondrial permeability transition (MPT) pore were considered a detrimental factor causing mitochondrial damage and bioenergetics failure. Mitochondrial and cellular bioenergetic metabolism depends on the enzymatic reactions that require NAD(+) or its reduced form NADH as cofactors. Recently, it was shown that NAD(+) also has an important function as a substrate for several NAD(+) glycohydrolases whose overactivation can contribute to cell death mechanisms. Furthermore, downstream metabolites of NAD(+) catabolism can also adversely affect cell viability. In contrast to the negative effects of NAD(+)-catabolizing enzymes, enzymes that constitute the NAD(+) biosynthesis pathway possess neuroprotective properties. In the first part of this review, we discuss the role of MPT in acute brain injury and its role in mitochondrial NAD(+) metabolism. Next, we focus on individual NAD(+) glycohydrolases, both cytosolic and mitochondrial, and their role in NAD(+) catabolism and brain damage. Finally, we discuss the potential effects of downstream products of NAD(+) degradation and associated enzymes as well as the role of NAD(+) resynthesis enzymes as potential therapeutic targets.

Excitotoxicity: bridge to various triggers in neurodegenerative disorders

Glutamate is one of the most prominent neurotransmitter in the body, present in over 50% of nervous tissue and plays an important role in neuronal excitation. This neuronal excitation is short-lived and is followed by depression. Multiple abnormal triggers such as energy deficiency, oxidative stress, mitochondrial dysfunction, calcium overload, etc can lead to aberration in neuronal excitation process. Such an aberration, serves as a common pool or bridge between abnormal triggers and deleterious signaling processes with which central neurons cannot cope up, leading to death. Excitotoxicity is the pathological process by which nerve cells are damaged and killed by excessive stimulation by neurotransmitters such as glutamate and similar substances. Such excitotoxic neuronal death has been implicated in spinal cord injury, stroke, traumatic brain injury, hearing loss and in neurodegenerative diseases of the central nervous system such as stroke, epilepsy, multiple sclerosis, Alzheimer disease, Amyltropic lateral sclerosis, Parkinson's disease, Huntington disease and alcohol withdrawal. This review mainly emphasizes the triggering events which sustain neuronal excitation, role of calcium, mitochondrial dysfunction, ROS, NO, chloride homeostasis and eicosanoids pathways. Further, a brief introduction about the recent research occurring in the treatment of various neurodegenerative diseases, including a summary of the presumed physiologic mechanisms behind the pharmacology of these disorders.

Ultrastructural and biochemical alterations in rats exposed to crude extract of Carex baccans and Potentilla fulgens

The use of plants as a source of medicine is an important component of the health care system in rural India. Carex baccans (Cyperaceae) and Potentilla fulgens (Rosaceae) have been known since ancient times in northeast India for their antitumor, antidiabetic, and antihelmintic properties. The present study was designed to determine the subacute toxicity profile of the root tuber extract of C. baccans and root-peel extract of P. fulgens in Wistar rats. The subacute oral toxicity was conducted using sublethal doses of 40, 50, 100, 150, 200, and 400 mgkg-1 body weights. Surface topographical and ultrastructural observations of liver and intestinal microvilli showed remarkable deformation and disruption, accompanied by quantitative changes in the liver enzymes, i.e., aspartate aminotransferase and alanine aminotransferase in comparison to those of the control group. Apoptotic cell death was observed in the liver cells of rats exposed to both of the plant extracts. A significant increase in splenic lymphocyte count was also observed in rats exposed to the highest concentration of both extracts. The results showed that consumption of the plant extracts at higher doses may cause toxicological effect if treatment continues for a long time.

Dietary Omega-3 Fatty Acids Do Not Change Resistance of Rat Brain or Liver Mitochondria to Ca(2+) and/or Prooxidants

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) block apoptotic neuronal cell death and are strongly neuroprotective in acute and chronic neurodegeneration. Theoretical considerations, indirect data, and consideration of parsimony lead to the hypothesis that modulation of mitochondrial pathway(s) underlies at least some of the neuroprotective effects of n-3 PUFAs. We therefore systematically tested this hypothesis on healthy male FBFN1 rats fed for four weeks with isocaloric, 10% fat-containing diets supplemented with 1, 3, or 10% fish oil (FO). High resolution mass spectrometric analysis confirmed expected diet-driven increases in docosahexaenoic acid (DHA, 22:6, n-3) and eicosapentaenoic acid (EPA, 20:5, n-3) in sera, liver and nonsynaptosomal brain mitochondria. We further evaluated the resistance of brain and liver mitochondria to Ca(2+) overload and prooxidants. Under these conditions, neither mitochondrial resistance to Ca(2+) overload and prooxidants nor mitochondrial physiology is altered by diet, despite the expected incorporation of DHA and EPA in mitochondrial membranes and plasma. Collectively, the data eliminate one of the previously proposed mechanism(s) that n-3 PUFA induced augmentation of mitochondrial resistance to the oxidant/calcium-driven dysfunction. These data furthermore allow us to define a specific series of follow-up experiments to test related hypotheses about the effect of n-3 PUFAs on brain mitochondria.

Coenzyme depletion by members of the aerolysin family of pore-forming toxins leads to diminished ATP levels and cell death

Recent studies demonstrated that a variety of bacterial pore-forming toxins induce cell death through a process of programmed necrosis characterized by the rapid depletion of cellular ATP. However, events leading to the necrosis and depletion of ATP are not thoroughly understood. We demonstrate that ATP-depletion induced by two pore-forming toxins, the Clostridium perfringens epsilon-toxin and the Aeromonas hydrophila aerolysin toxin, is associated with decreased mitochondrial membrane potential and opening of the mitochondrial permeability transition pore. To gain further insight into the toxin-induced metabolic changes contributing to necrosis and depletion of ATP, we analyzed the biochemical profiles of 251 distinct compounds by GC/MS or LC/MS/MS following exposure of a human kidney cell line to the epsilon-toxin. As expected, numerous biochemicals were seen to increase or decrease in response to epsilon-toxin. However, the pattern of these changes was consistent with the toxin-induced disruption of major energy-producing pathways in the cell including disruptions to the beta-oxidation of lipids. In particular, treatment with epsilon-toxin led to decreased levels of key coenzymes required for energy production including carnitine, NAD (and NADH), and coenzyme A. Independent biochemical assays confirmed that epsilon-toxin and aerolysin induced the rapid decrease of these coenzymes or their synthetic precursors. Incubation of cells with NADH or carnitine-enriched medium helped protect cells from toxin-induced ATP depletion and cell death. Collectively, these results demonstrate that members of the aerolysin family of pore-forming toxins lead to decreased levels of essential coenzymes required for energy production. The resulting loss of energy substrates is expected to contribute to dissipation of the mitochondrial membrane potential, opening of the mitochondrial permeability transition pore, and ultimately cell death.

Visualizing cell death in experimental focal cerebral ischemia: promises, problems, and perspectives

One of the hallmarks of stroke pathophysiology is the widespread death of many different types of brain cells. As our understanding of the complex disease that is stroke has grown, it is now generally accepted that various different mechanisms can result in cell damage and eventual death. A plethora of techniques is available to identify various pathological features of cell death in stroke; each has its own drawbacks and pitfalls, and most are unable to distinguish between different types of cell death, which partially explains the widespread misuse of many terms. The purpose of this review is to summarize the standard histopathological and immunohistochemical techniques used to identify various pathological features of stroke. We then discuss how these methods should be properly interpreted on the basis of what they are showing, as well as advantages and disadvantages that require consideration. As there is much interest in the visualization of stroke using noninvasive imaging strategies, we also specifically discuss how these techniques can be interpreted within the context of cell death.

Dipyrone inhibits neuronal cell death and diminishes hypoxic/ischemic brain injury

BACKGROUND

Dipyrone is an analgesic and antipyretic drug usually prescribed for patients with inflammatory conditions. We recently identified dipyrone as an antiapoptotic agent by screening a library of 1040 compounds for their ability to inhibit cytochrome c release from isolated mitochondria.

OBJECTIVE

We investigated the potential neuroprotective properties of dipyrone in cerebral ischemia.

METHODS

We evaluated the protective effects of dipyrone in experimental models of neuronal hypoxia/ischemia, including an oxygen/glucose deprivation model in primary cerebrocortical neurons and a focal cerebral ischemia model in mice.

RESULTS

Dipyrone reduced hypoxia/ischemia injury in both cellular and animal models. Dipyrone inhibited the release of cytochrome c and other mitochondrial apoptogenic factors from mitochondria into the cytoplasm, and attenuated subsequent caspase-9 and caspase-3 activation both in vitro and in vivo. Moreover, dipyrone prevented ischemia-induced changes in Bcl-2 and tBid, and ameliorated oxygen/glucose deprivation-mediated loss of mitochondrial membrane potential. Dipyrone also inhibited ischemia-induced reactive microgliosis. In the cellular models evaluated, dipyrone did not inhibit oxygen/glucose deprivation-induced cyclooxygenase-2 activation.

CONCLUSION

Dipyrone is remarkably neuroprotective in cerebral ischemia, and its cyclooxygenase-independent protective properties are, at least in part, due to the inhibition of mitochondrial cell death cascades.

The melatonin MT1 receptor axis modulates mutant Huntingtin-mediated toxicity

Melatonin mediates neuroprotection in several experimental models of neurodegeneration. It is not yet known, however, whether melatonin provides neuroprotection in genetic models of Huntington's disease (HD). We report that melatonin delays disease onset and mortality in a transgenic mouse model of HD. Moreover, mutant huntingtin (htt)-mediated toxicity in cells, mice, and humans is associated with loss of the type 1 melatonin receptor (MT1). We observe high levels of MT1 receptor in mitochondria from the brains of wild-type mice but much less in brains from HD mice. Moreover, we demonstrate that melatonin inhibits mutant htt-induced caspase activation and preserves MT1 receptor expression. This observation is critical, because melatonin-mediated protection is dependent on the presence and activation of the MT1 receptor. In summary, we delineate a pathologic process whereby mutant htt-induced loss of the mitochondrial MT1 receptor enhances neuronal vulnerability and potentially accelerates the neurodegenerative process.

MAP4 mechanism that stabilizes mitochondrial permeability transition in hypoxia: microtubule enhancement and DYNLT1 interaction with VDAC1

Mitochondrial membrane permeability has received considerable attention recently because of its key role in apoptosis and necrosis induced by physiological events such as hypoxia. The manner in which mitochondria interact with other molecules to regulate mitochondrial permeability and cell destiny remains elusive. Previously we verified that hypoxia-induced phosphorylation of microtubule-associated protein 4 (MAP4) could lead to microtubules (MTs) disruption. In this study, we established the hypoxic (1% O₂) cell models of rat cardiomyocytes, H9c2 and HeLa cells to further test MAP4 function. We demonstrated that increase in the pool of MAP4 could promote the stabilization of MT networks by increasing the synthesis and polymerization of tubulin in hypoxia. Results showed MAP4 overexpression could enhance cell viability and ATP content under hypoxic conditions. Subsequently we employed a yeast two-hybrid system to tag a protein interacting with mitochondria, dynein light chain Tctex-type 1 (DYNLT1), by hVDAC1 bait. We confirmed that DYNLT1 had protein-protein interactions with voltage-dependent anion channel 1 (VDAC1) using co-immunoprecipitation; and immunofluorescence technique showed that DYNLT1 was closely associated with MTs and VDAC1. Furthermore, DYNLT1 interactions with MAP4 were explored using a knockdown technique. We thus propose two possible mechanisms triggered by MAP4: (1) stabilization of MT networks, (2) DYNLT1 modulation, which is connected with VDAC1, and inhibition of hypoxia-induced mitochondrial permeabilization.

Mitochondrial dysfunction and nicotinamide dinucleotide catabolism as mechanisms of cell death and promising targets for neuroprotection

Both acute and chronic neurodegenerative diseases are frequently associated with mitochondrial dysfunction as an essential component of mechanisms leading to brain damage. Although loss of mitochondrial functions resulting from prolonged activation of the mitochondrial permeability transition (MPT) pore has been shown to play a significant role in perturbation of cellular bioenergetics and in cell death, the detailed mechanisms are still elusive. Enzymatic reactions linked to glycolysis, the tricarboxylic acid cycle, and mitochondrial respiration are dependent on the reduced or oxidized form of nicotinamide dinucleotide [NAD(H)] as a cofactor. Loss of mitochondrial NAD(+) resulting from MPT pore opening, although transient, allows detrimental depletion of mitochondrial and cellular NAD(+) pools by activated NAD(+) glycohydrolases. Poly(ADP-ribose) polymerase (PARP) is considered to be a major NAD(+) degrading enzyme, particularly under conditions of extensive DNA damage. We propose that CD38, a main cellular NAD(+) level regulator, can significantly contribute to NAD(+) catabolism. We discuss NAD(+) catabolic and NAD(+) synthesis pathways and their role in different strategies to prevent cellular NAD(+) degradation in brain, particularly following an ischemic insult. These therapeutic approaches are based on utilizing endogenous intermediates of NAD(+) metabolism that feed into the NAD(+) salvage pathway and also inhibit CD38 activity.

Modulation of methylmercury uptake by methionine: prevention of mitochondrial dysfunction in rat liver slices by a mimicry mechanism

Methylmercury (MeHg) is an ubiquitous environmental pollutant which is transported into the mammalian cells when present as the methylmercury-cysteine conjugate (MeHg-Cys). With special emphasis on hepatic cells, due to their particular propensity to accumulate an appreciable amount of Hg after exposure to MeHg, this study was performed to evaluate the effects of methionine (Met) on Hg uptake, reactive species (RS) formation, oxygen consumption and mitochondrial function/cellular viability in both liver slices and mitochondria isolated from these slices, after exposure to MeHg or the MeHg-Cys complex. The liver slices were pre-treated with Met (250 μM) 15 min before being exposed to MeHg (25 μM) or MeHg-Cys (25 μM each) for 30 min at 37 °C. The treatment with MeHg caused a significant increase in the Hg concentration in both liver slices and mitochondria isolated from liver slices. Moreover, the Hg uptake was higher in the group exposed to the MeHg-Cys complex. In the DCF (dichlorofluorescein) assay, the exposure to MeHg and MeHg-Cys produced a significant increase in DFC reactive species (DFC-RS) formation only in the mitochondria isolated from liver slices. As observed with Hg uptake, DFC-RS levels were significantly higher in the mitochondria treated with the MeHg-Cys complex compared to MeHg alone. MeHg exposure also caused a marked decrease in the oxygen consumption of liver slices when compared to the control group, and this effect was more pronounced in the liver slices treated with the MeHg-Cys complex. Similarly, the loss of mitochondrial activity/cell viability was greater in liver slices exposed to the MeHg-Cys complex when compared to slices treated only with MeHg. In all studied parameters, Met pre-treatment was effective in preventing the MeHg- and/or MeHg-Cys-induced toxicity in both liver slices and mitochondria. Part of the protection afforded by Met against MeHg may be related to a direct interaction with MeHg or to the competition of Met with the complex formed between MeHg and endogenous cysteine. In summary, our results show that Met pre-treatment produces pronounced protection against the toxic effects induced by MeHg and/or the MeHg-Cys complex on mitochondrial function and cell viability. Consequently, this amino acid offers considerable promise as a potential agent for treating acute MeHg exposure.

Long-term treatment with danshen-gegen decoction protects the myocardium against ischemia/reperfusion injury via the redox-sensitive protein kinase C-ε/mK(ATP) pathway in rats

Danshen-Gegen (DG) decoction, an herbal formulation comprised of radix Salvia Miltiorrhiza and radix Puerariae Lobata, is prescribed for the treatment of coronary heart disease in Chinese medicine. Experimental and clinical studies have indicated that DG decoction can reduce the extent of atherosclerosis. In the present study, using an ex vivo rat model of myocardial ischemia/reperfusion (I/R) injury, we investigated the myocardial preconditioning effect of an aqueous DG extract prepared from an optimized weight-to-weight ratio of danshen and gegen. Long-term treatment with DG extract at increasing doses (including the equivalent of a human dose) protected against myocardial I/R injury in rats. The cardioprotection afforded by DG pretreatment was paralleled by enhancements in mitochondrial antioxidant status and membrane integrity, as well as a decrease in the sensitivity of mitochondria to Ca(2+)-stimulated permeability transition in vitro, particularly under I/R conditions. Long-term treatment with the DG extract enhanced the translocation of protein kinase C-epsilon (PKCε) from the cytosol to mitochondria in rat myocardium, and this translocation was inhibited by α-tocopherol co-treatment with DG extract in rats. Long-term DG treatment may precondition the myocardium via a redox-sensitive PKCε/mK(ATP) pathway, with resultant inhibition of the mitochondrial permeability transition. The results suggest that clinical studies examining the effectiveness of DG extract given prophylactically in affording protection against myocardial I/R injury would be warranted.

Superoxide dismutase mimics: chemistry, pharmacology, and therapeutic potential

Oxidative stress has become widely viewed as an underlying condition in a number of diseases, such as ischemia-reperfusion disorders, central nervous system disorders, cardiovascular conditions, cancer, and diabetes. Thus, natural and synthetic antioxidants have been actively sought. Superoxide dismutase is a first line of defense against oxidative stress under physiological and pathological conditions. Therefore, the development of therapeutics aimed at mimicking superoxide dismutase was a natural maneuver. Metalloporphyrins, as well as Mn cyclic polyamines, Mn salen derivatives and nitroxides were all originally developed as SOD mimics. The same thermodynamic and electrostatic properties that make them potent SOD mimics may allow them to reduce other reactive species such as peroxynitrite, peroxynitrite-derived CO(3)(*-), peroxyl radical, and less efficiently H(2)O(2). By doing so SOD mimics can decrease both primary and secondary oxidative events, the latter arising from the inhibition of cellular transcriptional activity. To better judge the therapeutic potential and the advantage of one over the other type of compound, comparative studies of different classes of drugs in the same cellular and/or animal models are needed. We here provide a comprehensive overview of the chemical properties and some in vivo effects observed with various classes of compounds with a special emphasis on porphyrin-based compounds.

Isolation of mitochondria from the CNS

This unit contains a protocol describing the isolation of brain mitochondria by using discontinuous Percoll gradient centrifugation. The Percoll density gradient centrifugation separates synaptosomes, myelin, and free nonsynaptic mitochondria released from cells during tissue homogenization into individual fractions. Mitochondria entrapped in synaptosomes (synaptic mitochondria) can be liberated using nitrogen cavitation and then further purified by Percoll gradient centrifugation. These methods yield mitochondria that exhibit good respiratory coupling and high respiratory rates.

Reactive gamma-ketoaldehydes formed via the isoprostane pathway disrupt mitochondrial respiration and calcium homeostasis

Isoketals (IsoKs) are gamma-ketoaldehydes formed via the isoprostane pathway of arachidonic acid peroxidation and are among the most reactive by-products of lipid peroxidation. IsoKs selectively adduct to protein lysine residues and are highly cytotoxic, but the targets and molecular events involved in IsoK-induced cell death are poorly defined. Our previous work established that physiologically relevant aldehydes induce mitochondrial dysfunction (Kristal et al., J. Biol. Chem.271:6033-6038; 1996). We therefore examined whether IsoKs induced mitochondrial dysfunction. Incubation of mitochondria with synthetic IsoKs in the presence or absence of Ca(2+) was associated with alterations in mitochondrial respiration, membrane potential (DeltaPsi), and pyridine nucleotide redox state. IsoKs dose dependently (0.5-4microM) accelerated liver mitochondria swelling induced by low concentrations of Ca(2+) and Zn(2+) or by the prooxidant tert-butylhydroperoxide, and release of cytochrome c, with similar observations in heart/brain mitochondria. The mitochondrial permeability transition (mPT) inhibitor cyclosporine A delayed IsoK-induced mitochondria dysfunction. The actions of IsoKs are consistent with interactions with cytochrome c, a protein rich in lysine residues. Direct reaction of IsoKs with select lysines in cytochrome c was demonstrated using high-resolution mass spectrometry. Overall, these results suggest that IsoKs may, in part, mediate their cytotoxic effects through induction of the mPT and subsequent activation of downstream cell death cascades.