Ischemia-reperfusion induces inhibition of mitochondrial protein synthesis and cytochrome c oxidase activity in rat hippocampus

Long-Term Region-Specific Mitochondrial Functionality Changes in Both Cerebral Hemispheres after fMCAo Model of Ischemic Stroke

Cerebral ischemia/reperfusion (I/R) refers to a secondary brain injury that results in mitochondrial dysfunction of variable extent, leading to neuronal cell damage. The impact of this process has mainly been studied in the short term, from the early hours up to one week after blood flow reperfusion, and in the ischemic hemisphere only. The focus of this study was to assess the long-term impacts of I/R on mitochondrial functionality using high-resolution fluorespirometry to evaluate state-dependent activities in both ischemic (ipsilateral) and non-ischemic (contralateral) hemispheres of male mice 60, 90, 120, and 180 days after I/R caused by 60-min-long filament-induced middle cerebral artery occlusion (fMCAo). Our results indicate that in cortical tissues, succinate-supported oxygen flux (Complex I&II OXPHOS state) and H2O2 production (Complex II LEAK state) were significantly decreased in the fMCAo (stroke) group ipsilateral hemisphere compared to measurements in the contralateral hemisphere 60 and 90 days after stroke. In hippocampal tissues, during the Complex I&II ET state, mitochondrial respiration was generally lower in the ipsilateral compared to the contralateral hemisphere 90 days following stroke. An aging-dependent impact on mitochondria oxygen consumption following I/R injury was observed 180 days after surgery, wherein Complex I&II activities were lowest in both hemispheres. The obtained results highlight the importance of long-term studies in the field of ischemic stroke, particularly when evaluating mitochondrial bioenergetics in specific brain regions within and between separately affected cerebral hemispheres.

Intermittent hypoxia differentially affects metabolic and oxidative stress responses in two species of cyprinid fish

Oxygen fluctuations are common in freshwater habitats and aquaculture and can impact ecologically and economically important species of fish like cyprinids. To gain insight into the physiological responses to oxygen fluctuations in two common cyprinid species, we evaluated the impact of short-term intermittent hypoxia on oxidative stress and metabolic parameters (including levels of prooxidants and oxidative lesions, antioxidants, mitochondrial enzyme activities, mitochondrial swelling, markers of apoptosis, autophagy and cytotoxicity) in silver carp Hypophthalmichthys molitrix and gibel carp Carassius gibelio. During hypoxia, gibel carp showed higher baseline levels of antioxidants and less pronounced changes in oxidative and metabolic biomarkers in the tissues than silver carp. Reoxygenation led to a strong shift in metabolic and redox-related parameters and tissue damage, indicating high cost of post-hypoxic recovery in both species. Species-specific differences were more strongly associated with oxidative stress status, whereas metabolic indices and nitrosative stress parameters were more relevant to the response to hypoxia-reoxygenation. Overall, regulation of energy metabolism appears more critical than the regulation of antioxidants in the response to oxygen deprivation in the studied species. Further research is needed to establish whether prioritizing metabolic over redox regulation during hypoxia-reoxygenation stress is common in freshwater cyprinids.

MicroRNA-338 inhibition protects against focal cerebral ischemia and preserves mitochondrial function in vitro in astrocytes and neurons via COX4I1

Brain-enriched microRNA-338 (miR-338) is known to play a central role in brain mitochondrial function, however the role of miR-338 in stroke injury remains unknown. This study investigated the role of miR-338 in injury from transient focal cerebral ischemia in mice, and in cell survival and mitochondrial function after in vitro ischemia in astrocyte and neuronal cultures. Pre-treatment of mice with intracerebroventricular injection of miR-338 antagomir 24 h prior to 1 h of middle cerebral artery occlusion (MCAO) significantly reduced infarct size and improved neurological score at both 24 h and 7d after injury. Levels of the miR-338 target cytochrome-c oxidase subunit 4I1 (COX4I1), which plays an essential role in maintaining brain mitochondrial ATP production, were increased in miR-338 antagomir-treated mice. Mouse primary astrocyte cell cultures subjected to glucose deprivation exhibited increased cell survival when pre-treated with miR-338 inhibitor, and greater cell death with miR-338 mimic. Decreased miR-338 levels were associated with increased ATP production, augmented cytochrome c oxidative (CcO) activity and preservation of COX4I1. In vitro protection with miR-338 inhibitor was blocked by concurrent knockdown of COX4I1 with small interfering RNA. Parallel studies in mouse neuronal N2a cultures resulted in preserved ATP content and CcO activity with miR-338 inhibition, indicating a shared miR-338-dependent response to ischemic stress between brain cell types. These results suggest that miR-338 inhibition and/or COX4I1-targeted therapies may be novel clinical strategies to protect against stroke injury via preservation of mitochondrial function in multiple cell types.

Inhibition of JNK Alleviates Chronic Hypoperfusion-Related Ischemia Induces Oxidative Stress and Brain Degeneration via Nrf2/HO-1 and NF-κB Signaling

Cerebral ischemia is one of the leading causes of neurological disorders. The exact molecular mechanism related to chronic unilateral cerebral ischemia-induced neurodegeneration and memory deficit has not been precisely elucidated. In this study, we examined the effect of chronic ischemia on the induction of oxidative stress and c-Jun N-terminal kinase-associated detrimental effects and unveiled the inhibitory effect of specific JNK inhibitor (SP600125) on JNK-mediated brain degeneration in adult mice. Our behavioral, biochemical, and immunofluorescence studies revealed that chronic ischemic injuries sustained increased levels of oxidative stress-induced active JNK for a long time, whereas SP600125 significantly reduced the elevated level of active JNK and further regulated Nrf2/HO-1 and NF-κB signaling, which have been confirmed in vivo. Neuroinflammatory mediators and loss of neuronal cells was significantly reduced with the administration of SP600125. Ischemic brain injury caused synaptic dysfunction and memory impairment in mice. However, these were significantly improved with SP600125. On the whole, these findings suggest that elevated ROS-mediated JNK is a key mediator in chronic ischemic conditions and has a crucial role in neuroinflammation, neurodegeneration, and memory dysfunction. Our findings suggest that chronic oxidative stress associated JNK would be a potential target in time-dependent studies of chronic ischemic conditions induced brain degeneration.

Protective effects of combined treatment with mild hypothermia and edaravone against cerebral ischemia/reperfusion injury via oxidative stress and Nrf2 pathway regulation

Mild hypothermia (MH) and edaravone (EDA) exert neuroprotective effects against cerebral ischemia/reperfusion (I/R) injury through activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. However, whether MH and EDA exert synergistic effects against cerebral I/R injury remains unknown. The aim of the present study was to investigate the effects and mechanism of action of MH in combination with EDA in cerebral I/R injury. A rat cerebral I/R injury model was constructed by middle cerebral artery occlusion (MCAO) followed by reperfusion, and the mice were treated by MH, EDA or the inhibitor of the Nrf2 signaling pathway brusatol (Bru). It was observed that mice treated by MCAO had higher neurological deficit scores and oxidative stress levels, and low spatial learning and memory capacity; moreover, the CA1 region of the hippocampi of the mice exhibited reduced neuronal density and viability, and reduced mitochondrial dysfunction. However, MH in combination with EDA reversed the effects of MCAO, which were blocked by Bru injection. The levels of glutathione (GSH), GSH peroxidase, catalase and superoxide dismutase in rat ischemic hemisphere tissues were reduced by Bru. Western blotting demonstrated that the combined treatment with MH and EDA promoted the nuclear localization of Nrf2, and increased the levels of NAD(P)H quinone oxidoreductase and heme oxygenase (HO)-1. In conclusion, MH combined with EDA exerted synergistic neuroprotective effects against cerebral I/R injury involving changes in the Nrf2/HO-1 pathway.

COX5A over-expression protects cortical neurons from hypoxic ischemic injury in neonatal rats associated with TPI up-regulation

BACKGROUND

Neonatal hypoxic-ischemic encephalopathy (HIE) represents as a major cause of neonatal morbidity and mortality. However, the underlying molecular mechanisms in brain damage are still not fully elucidated. This study was conducted to determine the specific potential molecular mechanism in the hypoxic-ischemic induced cerebral injury.

METHODS

Here, hypoxic-ischemic (HI) animal models were established and primary cortical neurons were subjected to oxygen-glucose deprivation (OGD) to mimic HIE model in vivo and in vitro. The HI-induced neurological injury was evaluated by Zea-longa scores, Triphenyte-trazoliumchloride (TTC) staining the Terminal Deoxynucleotidyl Transferased Utp Nick End Labeling (TUNEL) and immunofluorescent staining. Then the expression of Cytochrome c oxidase subunit 5a (COX5A) was determined by immunohistochemistry, western blotting (WB) and quantitative real time Polymerase Chain Reaction (qRT-PCR) techniques. Moreover, HSV-mediated COX5A over-expression virus was transducted into OGD neurons to explore the role of COX5A in vitro, and the underlying mechanism was predicted by GeneMANIA, then verified by WB and qRT-PCR.

RESULTS

HI induced a severe neurological dysfunction, brain infarction, and cell apoptosis as well as obvious neuron loss in neonatal rats, in corresponding to the decrease on the expression of COX5A in both sides of the brain. What's more, COX5A over-expression significantly promoted the neuronal survival, reduced the apoptosis rate, and markedly increased the neurites length after OGD. Moreover, Triosephosephate isomerase (TPI) was predicted as physical interactions with COX5A, and COX5A over-expression largely increased the expressional level of TPI.

CONCLUSIONS

The present findings suggest that COX5A plays an important role in promoting neurological recovery after HI, and this process is related to TPI up-regulation.

Deactivation of mitochondrial complex I after hypoxia-ischemia in the immature brain

Mortality from perinatal hypoxic-ischemic (HI) brain injury reached 1.15 million worldwide in 2010 and is also a major factor for neurological disability in infants. HI directly influences the oxidative phosphorylation enzyme complexes in mitochondria, but the exact mechanism of HI-reoxygenation response in brain remains largely unresolved. After induction of HI-reoxygenation in postnatal day 10 rats, activities of mitochondrial respiratory chain enzymes were analysed and complexome profiling was performed. The effect of conformational state (active/deactive (A/D) transition) of mitochondrial complex I on H₂O₂ release was measured simultaneously with mitochondrial oxygen consumption. In contrast to cytochrome c oxidase and succinate dehydrogenase, HI-reoxygenation resulted in inhibition of mitochondrial complex I at 4 h after reoxygenation. Immediately after HI, we observed a robust increase in the content of deactive (D) form of complex I. The D-form is less active in reactive oxygen species (ROS) production via reversed electron transfer, indicating the key role of the deactivation of complex I in ischemia/reoxygenation. We describe a novel mechanism of mitochondrial response to ischemia in the immature brain. HI induced a deactivation of complex I in order to reduce ROS production following reoxygenation. Delayed activation of complex I represents a novel mitochondrial target for pathological-activated therapy.

Fetal Programming and Sexual Dimorphism of Mitochondrial Protein Expression and Activity of Hearts of Prenatally Hypoxic Guinea Pig Offspring

Chronic intrauterine hypoxia is a programming stimulus of cardiovascular dysfunction. While the fetal heart adapts to the reduced oxygenation, the offspring heart becomes vulnerable to subsequent metabolic challenges as an adult. Cardiac mitochondria are key organelles responsible for an efficient energy supply but are subject to damage under hypoxic conditions. We propose that intrauterine hypoxia alters mitochondrial function as an underlying programming mechanism of contractile dysfunction in the offspring. Indices of mitochondrial function such as mitochondrial DNA content, Complex (C) I-V expression, and CI/CIV enzyme activity were measured in hearts of male and female offspring at 90 days old exposed to prenatal hypoxia (10.5% O2) for 14 d prior to term (65 d). Both left ventricular tissue and cardiomyocytes exhibited decreased mitochondrial DNA content, expression of CIV, and CI/CIV activity in male hearts. In female cardiomyocytes, hypoxia had no effect on protein expression of CI-CV nor on CI/CIV activity. This study suggests that chronic intrauterine hypoxia alters the intrinsic properties of select respiratory complexes as a programming mechanism of cardiac dysfunction in the offspring. Sex differences in mitochondrial function may underlie the increased vulnerability of age-matched males compared to females in cardiovascular disease and heart failure.

Anti-amyloidgenic and neurotrophic effects of tetrahydroxystilbene glucoside on a chronic mitochondrial dysfunction rat model induced by sodium azide

Alzheimer's disease (AD) is an irreversible neurodegenerative brain disorder with complex pathogenesis. Emerging evidence indicates that there is a tight relationship between mitochondrial dysfunction and β-amyloid (Aβ) formation. 2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside (TSG) is one of the main active components extracted from Polygonum multiflorum. The purpose of the present study was to investigate the effects of TSG on Aβ production and neurotrophins in the brains of rats by using a mitochondrial dysfunction rat model induced by sodium azide (NaN₃), an inhibitor of mitochondrial cytochrome c oxidase (COX). NaN₃ was administered to rats by continuous subcutaneous infusion for 28 days via implanted osmotic minipumps to establish the animal model. TSG was intragastrically administered starting 24 h after the operation. The activity of mitochondrial COX was measured by a biochemical method. The content of Aβ 1-42 was detected by ELISA. The expression of neurotrophic factors was determined by Western blot and immunohistochemistry. The results showed that NaN₃ infusion for 28 days induced a decrease in mitochondrial COX activity, an increase in Aβ 1-42 content and the expression of amyloidogenic β-amyloid precursor protein (APP), beta-site APP cleaving enzyme 1 (BACE1) and presenilin 1 (PS1), and a decline in the expression of neurotrophins in the hippocampus of rats. Intragastrical administration of TSG elevated mitochondrial COX activity, decreased Aβ 1-42 content and the expression of APP, BACE1 and PS1, and enhanced the expression of nerve growth factor, brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase B (TrkB) in the hippocampus of NaN₃-infused rats. These findings suggest that TSG may be beneficial in blocking or slowing the progression of AD by enhancing mitochondrial function, decreasing Aβ production and increasing neurotrophic factors at some extent.

Mitochondrial Quality Control and Disease: Insights into Ischemia-Reperfusion Injury

Mitochondria are key regulators of cell fate during disease. They control cell survival via the production of ATP that fuels cellular processes and, conversely, cell death via the induction of apoptosis through release of pro-apoptotic factors such as cytochrome C. Therefore, it is essential to have stringent quality control mechanisms to ensure a healthy mitochondrial network. Quality control mechanisms are largely regulated by mitochondrial dynamics and mitophagy. The processes of mitochondrial fission (division) and fusion allow for damaged mitochondria to be segregated and facilitate the equilibration of mitochondrial components such as DNA, proteins, and metabolites. The process of mitophagy are responsible for the degradation and recycling of damaged mitochondria. These mitochondrial quality control mechanisms have been well studied in chronic and acute pathologies such as Parkinson's disease, Alzheimer's disease, stroke, and acute myocardial infarction, but less is known about how these two processes interact and contribute to specific pathophysiologic states. To date, evidence for the role of mitochondrial quality control in acute and chronic disease is divergent and suggests that mitochondrial quality control processes can serve both survival and death functions depending on the disease state. This review aims to provide a synopsis of the molecular mechanisms involved in mitochondrial quality control, to summarize our current understanding of the complex role that mitochondrial quality control plays in the progression of acute vs chronic diseases and, finally, to speculate on the possibility that targeted manipulation of mitochondrial quality control mechanisms may be exploited for the rationale design of novel therapeutic interventions.

Maternal high-fat diet impairs cardiac function in offspring of diabetic pregnancy through metabolic stress and mitochondrial dysfunction

Offspring of diabetic pregnancies are at risk of cardiovascular disease at birth and throughout life, purportedly through fuel-mediated influences on the developing heart. Preventative measures focus on glycemic control, but the contribution of additional offenders, including lipids, is not understood. Cellular bioenergetics can be influenced by both diabetes and hyperlipidemia and play a pivotal role in the pathophysiology of adult cardiovascular disease. This study investigated whether a maternal high-fat diet, independently or additively with diabetes, could impair fuel metabolism, mitochondrial function, and cardiac physiology in the developing offspring's heart. Sprague-Dawley rats fed a control or high-fat diet were administered placebo or streptozotocin to induce diabetes during pregnancy and then delivered offspring from four groups: control, diabetes exposed, diet exposed, and combination exposed. Cardiac function, cellular bioenergetics (mitochondrial stress test, glycolytic stress test, and palmitate oxidation assay), lipid peroxidation, mitochondrial histology, and copy number were determined. Diabetes-exposed offspring had impaired glycolytic and respiratory capacity and a reduced proton leak. High-fat diet-exposed offspring had increased mitochondrial copy number, increased lipid peroxidation, and evidence of mitochondrial dysfunction. Combination-exposed pups were most severely affected and demonstrated cardiac lipid droplet accumulation and diastolic/systolic cardiac dysfunction that mimics that of adult diabetic cardiomyopathy. This study is the first to demonstrate that a maternal high-fat diet impairs cardiac function in offspring of diabetic pregnancies through metabolic stress and serves as a critical step in understanding the role of cellular bioenergetics in developmentally programmed cardiac disease.

Renal adaptation during hibernation

Hibernators periodically undergo profound physiological changes including dramatic reductions in metabolic, heart, and respiratory rates and core body temperature. This review discusses the effect of hypoperfusion and hypothermia observed during hibernation on glomerular filtration and renal plasma flow, as well as specific adaptations in renal architecture, vasculature, the renin-angiotensin system, and upregulation of possible protective mechanisms during the extreme conditions endured by hibernating mammals. Understanding the mechanisms of protection against organ injury during hibernation may provide insights into potential therapies for organ injury during cold storage and reimplantation during transplantation.

Azadirachta indica mitigates behavioral impairments, oxidative damage, histological alterations and apoptosis in focal cerebral ischemia-reperfusion model of rats

Azadirachta indica Linn. (Meliaceae) has been used from ancient times as a remedy for various ailments. The present study was designed to investigate the antioxidant and anti-apoptotic properties of A. indica seed extract (ASE) in transient middle cerebral artery occlusion (MCAO) rat model. Antioxidant potential of ASE was determined in vitro. Further, ASE was evaluated against neurological deficits, histological alterations (TTC, CV and H&E) and oxidative damage (TBARS, GSH and nitrite) in MCAO rats. Moreover, caspase-3 and -9 were analyzed to evaluate the anti-apoptotic activity of ASE. ASE has shown potent in vitro reducing power (126.2 mg AsAE/g extract) and free radical scavenging activities (DPPH 171.0 and NO 176.0 μg/ml). Furthermore, ASE inhibited oxidative stress and decreased the activities of caspase-3 (26.7 %, p < 0.05) and caspase-9 (31.2 %, p < 0.01) thus, reduced neuronal loss in MCAO rats. Our data revealed that ASE has potent antioxidant and anti-apoptotic properties, and may be explored for its active constituents against neurodegenerative diseases.

A role for dorsal and ventral hippocampus in response learning

The hippocampus and the striatum have been traditionally considered as part of different and independent memory systems despite growing evidence supporting that both brain regions may even compete for behavioral control in particular learning tasks. In this regard, it has been reported that the hippocampus could be necessary for the use of idiothetic cues in several types of spatial learning tasks. Accordingly, the ventral striatum receives strong anatomical projections from the hippocampus, suggesting a participation of both regions in goal-directed behavior. Our work examined the role of the dorsal and ventral hippocampus on a response learning task. Cytochrome c oxidase (C.O.) quantitative histochemistry was used as an index of brain oxidative metabolism. In addition, determination of C.O. subunit I levels in the hippocampus by western blot analysis was performed to assess the contribution of this subunit to overall C.O. activity. Increased brain oxidative metabolism was found in most of the studied hippocampal subregions when experimental group was compared with a swim control group. However, no differences were found in the amount of C.O. subunit I expressed in the hippocampus by western blot analysis. Our results support that both the dorsal and ventral hippocampus are associated with the use of response strategies during response learning.

Effects of sinapic Acid of 4 vessel occlusion model-induced ischemia and cognitive impairments in the rat

Objective

Sinapic acid (SA, Sinapine), small naturally occurring hydroxycinnamic acid, has a GABA(A) receptor agonistic property and free radical scavenging activity. We examined potential neuroprotective effects of sinapic acid (SA) using global cerebral ischemia animal model.

Methods

MTT assay was performed to determine cytotoxic effects of SA. To examine the neuroprotective effects of SA, SA was administrated for 14 d before 4-vessel occlusion. Also, to determine whether SA prevents cognitive impairment, Morris water maze was performed.

Results

In this study, the efficacy of SA for the prevention of neuronal damage and for the reduction of memory impairment was investigated.

Conclusion

The results indicate that SA confers significant neuroprotection especially for ischemic hippocampal neurons.

The power of life--cytochrome c oxidase takes center stage in metabolic control, cell signalling and survival

Mitochondrial dysfunction is increasingly recognized as a major factor in the etiology and progression of numerous human diseases, such as (neuro-)degeneration, ischemia reperfusion injury, cancer, and diabetes. Cytochrome c oxidase (COX) represents the rate-limiting enzyme of the mitochondrial respiratory chain and is thus predestined for being a central site of regulation of oxidative phosphorylation, proton pumping efficiency, ATP and reactive oxygen species production, which in turn affect cell signaling and survival. A unique feature of COX is its regulation by various factors and mechanisms interacting with the nucleus-encoded subunits, whose actual functions we are only beginning to understand.

Postconditioning in focal cerebral ischemia: role of the mitochondrial ATP-dependent potassium channel

INTRODUCTION

Ischemic postconditioning (IpostC) has been described in both heart and brain. The first aim of this study was to evaluate the effects of IpostC on brain infarct size and neurological function in the middle cerebral artery occlusion (MCAO) model. The second aim was to determine the involvement of the mitochondrial potassium ATP-dependent channel (mitoK(ATP)) opening and its capacity to improve mitochondrial dysfunction induced by ischemia-reperfusion.

METHODS

Wistar rats were subjected to 60min MCAO followed by 24-h reperfusion. Postconditioning was performed by 3 cycles of 30-s occlusion-reperfusion at the onset of reperfusion. Three behavioral tests were performed following 24h of reperfusion. Involvement of mitoK(ATP) was determined by the modulation of IpostC effects by 5-hydroxydecanoate (5-HD) and diazoxide. Mitochondrial function after 24h of reperfusion on isolated mitochondria was assessed through mitochondrial oxygen consumption, mitochondrial membrane potential and calcium retention capacity to evaluate impact of IpostC on mitochondrial permeability transition pore (MPTP) opening.

RESULTS

IpostC resulted in a 40% decrease in infarct size and improved neurological outcome. These effects were lost when IpostC was delayed by 5min. The administration of diazoxide resulted in a 60% in infarct size. The beneficial effects of IpostC and diazoxide were blocked by 5-HD. Furthermore, 5-HD also blocked the inhibition of MPTP opening by IpostC and diazoxide. The hyperpolarization induced by ischemia-reperfusion was corrected by IpostC without any effect on oxidative phosphorylation.

CONCLUSION

Our results confirm ischemic postconditioning-induced neuroprotection. They also support the involvement of mitoK(ATP) opening and its role in inhibiting the opening of MTPT induced by postconditioning.

Region-specific sensitivity of the spinal cord to ischemia/reperfusion: the dynamic of changes in catalytic NOS activity

This study was designed in order to consider whether the release of neuronally derived nitric oxide (NO) in the lumbosacral spinal cord during ischemia/reperfusion is region-specific and whether changes in Ca(2+)-dependent NO synthase (cNOS) activity paralell with functional outcome. The cNOS activity was measured in the spinal cord regions after 13-, 15- and 17-min ischemia alone and that followed by 24 h of reperfusion. In addition, the Tarlov's criteria were applied to define the neurological consequences of ischemia/reperfusion in experimental animals. Based on the results, it is evident that only the 17-min ischemia alone was quite sufficient to cause changes in cNOS activity, however, without alterations in functional outcomes. On the other hand, the ischemic episodes followed by reperfusion caused dynamic, region-specific alterations in cNOS activity and consequently led to deterioration of motor function of hindlimbs in affected animals. Our results indicate that the motoneurons in the ventral horns respond more sensitively to ischemia/reperfusion than do neurons localized in the other spinal cord regions and that changes in cNOS activity may also influence the axonal conductance in the white matter and account for the impairment of motoneuronal activity in affected animals.