Cytosolic redistribution of cytochrome c after transient focal cerebral ischemia in rats

Traditional Chinese medicines treat ischemic stroke and their main bioactive constituents and mechanisms

Ischemic stroke (IS) remains one of the leading causes of death and disability in humans. Unfortunately, none of the treatments effectively provide functional benefits to patients with IS, although many do so by targeting different aspects of the ischemic cascade response. The advantages of traditional Chinese medicine (TCM) in preventing and treating IS are obvious in terms of early treatment and global coordination. The efficacy of TCM and its bioactive constituents has been scientifically proven over the past decades. Based on clinical trials, this article provides a review of commonly used TCM patent medicines and herbal decoctions indicated for IS. In addition, this paper also reviews the mechanisms of bioactive constituents in TCM for the treatment of IS in recent years, both domestically and internationally. A comprehensive review of preclinical and clinical studies will hopefully provide new ideas to address the threat of IS.

Use of 31 P magnetisation transfer magnetic resonance spectroscopy to measure ATP changes after 670 nm transcranial photobiomodulation in older adults

Mitochondrial function declines with age, and many pathological processes in neurodegenerative diseases stem from this dysfunction when mitochondria fail to produce the necessary energy required. Photobiomodulation (PBM), long-wavelength light therapy, has been shown to rescue mitochondrial function in animal models and improve human health, but clinical uptake is limited due to uncertainty around efficacy and the mechanisms responsible. Using 31 P magnetisation transfer magnetic resonance spectroscopy (MT-MRS) we quantify, for the first time, the effects of 670 nm PBM treatment on healthy ageing human brains. We find a significant increase in the rate of ATP synthase flux in the brain after PBM in a cohort of older adults. Our study provides initial evidence of PBM therapeutic efficacy for improving mitochondrial function and restoring ATP flux with age, but recognises that wider studies are now required to confirm any resultant cognitive benefits.

Revert total protein normalization method offers a reliable loading control for mitochondrial samples following TBI

Owing to evidence that mitochondrial dysfunction plays a dominant role in the traumatic brain injury (TBI) pathophysiology, the Western blot (WB) based immunoblotting method is widely employed to identify changes in the mitochondrial protein expressions after neurotrauma. In WB method, the housekeeping proteins (HKPs) expression is routinely used as an internal control for sample normalization. However, the traditionally employed HKPs can be susceptible to complex cascades of TBI pathogenesis, leading to their inconsistent expression. Remarkably, our data illustrated here that mitochondrial HKPs, including Voltage-dependent anion channels (VDAC), Complex-IV, Cytochrome C and Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) yielded altered expressions following penetrating TBI (PTBI) as compared to Sham. Therefore, our goal was to identify more precise normalization procedure in WB. Adult male Sprague Dawley rats (N = 6 rats/group) were used to perform PTBI, and the novel REVERT Total Protein (RTP) method was used to quantify mitochondrial protein load consistency between samples at 6 h and 24 h post-injury. Notably, the RTP method displayed superior protein normalization compared to HKPs method with higher sensitivity at both time-points between experimental groups. Our data favors application of RTP based normalization to accurately quantify protein expression where inconsistent HKPs may be evident in neuroscience research.

Mitochondrial pyruvate carrier 1 alleviates hypoxic-ischemic brain injury in rats

AIMS

Mitochondrial dysfunction is a critical pathological change in cerebral ischemia. Mitochondrial pyruvate carrier 1 (MPC1) is a mitochondrial inner membrane protein carrier participating in pyruvate transport. The work is aiming to figure out the effect of MPC1 on cerebral ischemia.

MAIN METHODS

Bilateral internal carotid artery embolization (BICAO) rats model and cells model from oxygen glucose deprivation/reoxygenation (OGD/R) were used to simulate cerebral ischemia in vivo and in vitro. The effect of MPC1 on cerebral ischemia was detected by imaging, behavioral test, immunofluorescence, flow cytometry, transmission electron microscopy, Western blot and RT-Q-PCR. RNA-sequence (RNA-seq) was applied to explore the potential molecular mechanisms underlying the role of MPC1 in cerebral ischemia.

KEY FINDING

After BICAO or OGD/R treatment, MPC1 expression in ischemic cortical neurons was significantly decreased, and MPC1 deficiency significantly reduced cerebral blood flow, decreased locomotion activities, and exacerbated neuronal injury. Moreover, MPC1 deficiency obviously aggravated oxidative stress, structural disruption and dysfunction of mitochondria, autophagy and calcium overload of ischemic cortical neurons. Interestingly, MPC1 overexpression remarkably reversed neuronal loss and persisting neuronal deficits induced by OGD. Using RNA-seq, 38 MPC1-associated differentially expressed genes were involved in oxidative stress, autophagy and calcium overload. Our results further confirmed that MPC1 could alleviate autophagy via the PI3K/Akt/mTOR pathway in the ischemic cortical neurons.

SIGNIFICANCE

MPC1 may exert neuroprotective effects by attenuating oxidative stress, mitochondrial dysfunction, calcium overload and autophagy during cerebral ischemia. MPC1-related genes identified by RNA-seq may be a novel therapeutic target for cerebral ischemia.

The initiator of neuroexcitotoxicity and ferroptosis in ischemic stroke: Glutamate accumulation

Glutamate plays an important role in excitotoxicity and ferroptosis. Excitotoxicity occurs through over-stimulation of glutamate receptors, specifically NMDAR, while in the non-receptor-mediated pathway, high glutamate concentrations reduce cystine uptake by inhibiting the System Xc-, leading to intracellular glutathione depletion and resulting in ROS accumulation, which contributes to increased lipid peroxidation, mitochondrial damage, and ultimately ferroptosis. Oxidative stress appears to crosstalk between excitotoxicity and ferroptosis, and it is essential to maintain glutamate homeostasis and inhibit oxidative stress responses in vivo. As researchers work to develop natural compounds to further investigate the complex mechanisms and regulatory functions of ferroptosis and excitotoxicity, new avenues will be available for the effective treatment of ischaemic stroke. Therefore, this paper provides a review of the molecular mechanisms and treatment of glutamate-mediated excitotoxicity and ferroptosis.

Comparison of oxidative stress-mitochondria-mediated tenderization in two different bovine muscles during aging

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PM suffered from higher levels of ROS earlier than LT.

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The mitochondria swelled and ruptured preferentially in PM compared to LT.

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Faster metabolism of ATP-related compounds appeared in PM compared to LT.

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The caspase-9 activation was earlier than caspase-3 activation in both muscle types.

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MFI may be related to energy metabolism and caspases activities involved in mitochondria.

The aim of this study was to investigate the differences in the effects of mitochondria-involved energy metabolism and caspases activation on postmortem tenderness in different muscle fiber types. Beef Longissimus thoracis (LT) and Psoas major (PM) muscles showed significant difference in mitochondrial function. Our data revealed that PM suffered from higher levels of reactive oxygen species (ROS) earlier than LT, causing faster mitochondrial swelling and rupture. Additionally, faster metabolism of ATP-related compounds and activation of caspase-9 appeared in PM, but the activity of caspase-3 in PM was lower than that in LT. Differences in myofibril fragmentation index (MFI) of LT and PM at different aging stages suggested that energy metabolism and caspases activities may play a role in tenderness at different aging stages. These results indicated that oxidative stress-mitochondria-mediated tenderization process could be muscle-specific.

Pharmacological therapy to cerebral ischemia-reperfusion injury: Focus on saponins

Secondary insult from cerebral ischemia-reperfusion injury (CIRI) is a major risk factor for poor prognosis of cerebral ischemia. Saponins are steroid or triterpenoid glycosides with various pharmacological activities that are effective in treating CIRI. By browsing the literature from 2001 to 2021, 55 references involving 24 kinds of saponins were included. Saponins were shown to relieve CIRI by inhibiting oxidation stress, neuroinflammation, and apoptosis, restoring BBB integrity, and promoting neurogenesis and angiogenesis. This review summarizes and classifies several common saponins and their mechanisms in relieving CIRI. Information provided in this review will benefit researchers to design, research and develop new medicines to treat CIRI-related conditions with saponins.

Post-Ischemic Neurodegeneration of the Hippocampus Resembling Alzheimer's Disease Proteinopathy

In this review, we summarize, inter alia, the protein and gene changes associated with Alzheimer’s disease and their role in post-ischemic hippocampal neurodegeneration. In the hippocampus, studies have revealed dysregulation of the genes for the amyloid protein precursor metabolism and tau protein that is identical in nature to Alzheimer’s disease. Data indicate that amyloid and tau protein, derived from brain tissue and blood due to increased permeability of the blood–brain barrier after ischemia, play a key role in post-ischemic neurodegeneration of the hippocampus, with concomitant development of full-blown dementia. Thus, the knowledge of new neurodegenerative mechanisms that cause neurodegeneration of the hippocampus after ischemia, resembling Alzheimer’s disease proteinopathy, will provide the most important therapeutic development goals to date.

Upregulation of hemeoxygenase enzymes HO-1 and HO-2 following ischemia-reperfusion injury in connection with experimental cardiac arrest and cardiopulmonary resuscitation: Neuroprotective effects of methylene blue

Oxidative stress plays an important role in neuronal injuries after cardiac arrest. Increased production of carbon monoxide (CO) by the enzyme hemeoxygenase (HO) in the brain is induced by the oxidative stress. HO is present in the CNS in two isoforms, namely the inducible HO-1 and the constitutive HO-2. Elevated levels of serum HO-1 occurs in cardiac arrest patients and upregulation of HO-1 in cardiac arrest is seen in the neurons. However, the role of HO-2 in cardiac arrest is not well known. In this review involvement of HO-1 and HO-2 enzymes in the porcine brain following cardiac arrest and resuscitation is discussed based on our own observations. In addition, neuroprotective role of methylene blue- an antioxidant dye on alterations in HO under in cardiac arrest is also presented. The biochemical findings of HO-1 and HO-2 enzymes using ELISA were further confirmed by immunocytochemical approach to localize selective regional alterations in cardiac arrest. Our observations are the first to show that cardiac arrest followed by successful cardiopulmonary resuscitation results in significant alteration in cerebral concentrations of HO-1 and HO-2 levels indicating a prominent role of CO in brain pathology and methylene blue during CPR followed by induced hypothermia leading to superior neuroprotection after return of spontaneous circulation (ROSC), not reported earlier.

Participation of Amyloid and Tau Protein in Post-Ischemic Neurodegeneration of the Hippocampus of a Nature Identical to Alzheimer's Disease

Recent evidence suggests that amyloid and tau protein are of vital importance in post-ischemic death of CA1 pyramidal neurons of the hippocampus. In this review, we summarize protein alterations associated with Alzheimer's disease and their gene expression (amyloid protein precursor and tau protein) after cerebral ischemia, as well as their roles in post-ischemic hippocampus neurodegeneration. In recent years, multiple studies aimed to elucidate the post-ischemic processes in the development of hippocampus neurodegeneration. Their findings have revealed the dysregulation of genes for amyloid protein precursor, β-secretase, presenilin 1 and 2, tau protein, autophagy, mitophagy, and apoptosis identical in nature to Alzheimer's disease. Herein, we present the latest data showing that amyloid and tau protein associated with Alzheimer's disease and their genes play a key role in post-ischemic neurodegeneration of the hippocampus with subsequent development of dementia. Therefore, understanding the underlying process for the development of post-ischemic CA1 area neurodegeneration in the hippocampus in conjunction with Alzheimer's disease-related proteins and genes will provide the most important therapeutic development goals to date.

Neuroprotective roles of HAX-1 in ischemic neuronal injury

Hematopoietic cell-specific protein 1 associated protein X-1 (HAX-1) is a novel mitochondrial protein that regulates oxidative stress-induced apoptosis. However, the roles of HAX-1 in ischemic neuronal injury have not been thoroughly elucidated. In this study, the expression and roles of HAX-1 after ischemic stress were investigated using in vivo and in vitro models. The effect of oxidative stress on the regulation of HAX-1 was examined using knockout mice lacking nicotinamide-adenine dinucleotide phosphate oxidase 2 (NOX2), which is a major source of reactive oxygen species (ROS) after cerebral ischemia. Male C57BL/6 J mice were subjected to transient forebrain ischemia induced by 22-min occlusion of the bilateral common carotid arteries, and striatum samples were analyzed. For in vitro ischemic experiments, oxygen and glucose deprivation (OGD) in a rat pheochromocytoma cell line was utilized. Western blotting and immunofluorescence analysis revealed HAX-1 expression in neuronal mitochondria, which was significantly decreased after ischemia in vivo and in vitro. In NOX2 knockout mice, ischemia-induced decrease in HAX-1 expression and ischemic neuronal injury was significantly alleviated compared to those in wild-type mice. Inhibition of HAX-1 using small interfering RNA significantly increased injury in cultured cells after OGD. These findings suggest that HAX-1 has a neuroprotective effect against ischemic neuronal injury, and downregulation of HAX-1 by NOX2-produced ROS induces apoptosis after cerebral ischemia.

Different Roles of Mitochondria in Cell Death and Inflammation: Focusing on Mitochondrial Quality Control in Ischemic Stroke and Reperfusion

Mitochondrial dysfunctions are among the main hallmarks of several brain diseases, including ischemic stroke. An insufficient supply of oxygen and glucose in brain cells, primarily neurons, triggers a cascade of events in which mitochondria are the leading characters. Mitochondrial calcium overload, reactive oxygen species (ROS) overproduction, mitochondrial permeability transition pore (mPTP) opening, and damage-associated molecular pattern (DAMP) release place mitochondria in the center of an intricate series of chance interactions. Depending on the degree to which mitochondria are affected, they promote different pathways, ranging from inflammatory response pathways to cell death pathways. In this review, we will explore the principal mitochondrial molecular mechanisms compromised during ischemic and reperfusion injury, and we will delineate potential neuroprotective strategies targeting mitochondrial dysfunction and mitochondrial homeostasis.

Protosappanin A Maintains Neuronal Mitochondrial Homeostasis through Promoting Autophagic Degradation of Bax

Cerebral ischemia is accompanied by mitochondrial integrity destruction. Thus, reversion of mitochondrial damage holds great potential for cerebral ischemia therapy. As a crucial Bcl-2 family member, pro-apoptotic Bax protein is a main effector of mitochondrial permeabilization and plays an important role in mitochondrial homeostasis. However, there is still a lack of an effective cerebral protective strategy through selectively targeting Bax. In this study, we reported that natural small-molecule protosappanin A (PTA) showed a significant mitochondrial protective effect on oxygen-glucose deprivation/reperfusion (OGD/R)-induced PC12 cells injury through increasing ATP production and maintaining mitochondrial DNA (mtDNA) content. The mechanism study revealed that PTA selectively induced pro-apoptotic protein Bax degradation, without affecting other Bcl-2 family members such as Bcl-2, Bcl-xl, Bad, Puma, Bid, Bim, and Bik. In addition, we found that PTA promoted the association of autophagosomal marker LC3B to Bax for its degradation via an autophagy-dependent manner but not the ubiquitin-proteasome pathway. Collectively, our findings offered a new pharmacological strategy for maintaining mitochondrial function by inducing autophagic degradation of Bax and also provided a novel drug candidate against ischemic neuronal injury.

Role of 2-Arachidonoyl-Glycerol and CB1 Receptors in Orexin-A-Mediated Prevention of Oxygen-Glucose Deprivation-Induced Neuronal Injury

Orexin-A (OX-A) protects the brain against oxidative stress-mediated ischemic injury. Since the endocannabinoid 2-arachidonoylglycerol (2-AG) and cannabinoid type-1 (CB1) receptors were previously shown to mediate some of the effects of OX-A exerted through the orexin-1 receptor (OX-1R), we investigated the involvement of 2-AG in OX-A-induced neuroprotection following oxygen and glucose deprivation (OGD) in mouse cortical neurons. OGD-induced reactive oxygen species (ROS) accumulation and neuronal death were prevented by both OX-A and arachidonyl-2′-chloroethylamide (ACEA), a synthetic CB1 receptor agonist, in a manner sensitive to OX-1R and CB1 receptor antagonists, SB334867 and AM251. OX-A stimulated 2-AG biosynthesis in cortical neurons. In neurons isolated from monoacylglycerol lipase (MAGL, a 2-AG hydrolyzing enzyme) null mice, 10-fold higher 2-AG concentrations were found and OGD failed to induce ROS production and cell death, whereas AM251 restored these noxious effects. OX-A-induced neuroprotection was mediated by the phosphoinositide-3-kinase/Akt (PI3K/Akt) survival pathway since both OX-A and ACEA induced phosphorylation of Akt and prevented OGD-induced cytochrome c release from the mitochondria, in a manner counteracted by SB334867 or AM251. Administration of OX-A reduced infarct volume and elevated brain 2-AG levels in a mouse model of transient ischemia. These results suggest that 2-AG and CB1 receptor mediate OX-A prevention of ischemia-induced neuronal apoptosis.

Neurovascular protection by peroxisome proliferator-activated receptor α in ischemic stroke

Ischemic stroke is a leading cause of death and disability worldwide. Currently, the only pharmacological therapy for ischemic stroke is thrombolysis with tissue plasminogen activator that has a narrow therapeutic window and increases the risk of intracerebral hemorrhage. New pharmacological treatments for ischemic stroke are desperately needed, but no neuroprotective drugs have successfully made it through clinical trials. Beneficial effects of peroxisome proliferator-activated receptor alpha (PPARα) activation on vascular integrity and function have been reported, and PPARα agonists have clinically been used for many years to manage cardiovascular disease. Thus, PPARα has gained interest in recent years as a target for neurovascular disease such as ischemic stroke. Accumulating preclinical evidence suggests that PPARα activation modulates several pathophysiological hallmarks of stroke such as oxidative stress, blood-brain barrier (BBB) dysfunction, and neuroinflammation to improve functional recovery. Therefore, this review summarizes the various actions PPARα exerts in neurovascular health and disease and the potential of employing exogenous PPARα agonists for future pharmacological treatment of ischemic stroke.

MiR-34a Interacts with Cytochrome c and Shapes Stroke Outcomes

Blood-brain barrier (BBB) dysfunction occurs in cerebrovascular diseases and neurodegenerative disorders such as stroke. Opening of the BBB during a stroke has a negative impact on acute outcomes. We have recently demonstrated that miR-34a regulates the BBB by targeting cytochrome c (CYC) in vitro. To investigate the role of miR-34a in a stroke, we purified primary cerebrovascular endothelial cells (pCECs) from mouse brains following 1 h transient middle cerebral artery occlusion (tMCAO) and measured real-time PCR to detect miR-34a levels. We demonstrate that the miR-34a levels are elevated in pCECs from tMCAO mice at the time point of BBB opening following 1 h tMCAO and reperfusion. Interestingly, knockout of miR-34a significantly reduces BBB permeability, alleviates disruption of tight junctions, and improves stroke outcomes compared to wild-type (WT) controls. CYC is decreased in the ischemic hemispheres and pCECs from WT but not in miR-34a^−/− mice following stroke reperfusion. We further confirmed CYC is a target of miR-34a by a dural luciferase reporter gene assay in vitro. Our study provides the first description of miR-34a affecting stroke outcomes and may lead to discovery of new mechanisms and treatments for cerebrovascular and neurodegenerative diseases such as stroke.

The dual role of KCNQ/M channels upon OGD or OGD/R insults in cultured cortical neurons of mice: Timing is crucial in targeting M-channels against ischemic injur ies

KCNQ/M potassium channels play a vital role in neuronal excitability; however, it is required to explore their pharmacological modulation on N-Methyl- d-aspartic acid receptors (NMDARs)-mediated glutamatergic transmission of neurons upon ischemic insults. In the current study, both presynaptic glutamatergic release and activities of NMDARs were measured by NMDAR-induced miniature excitatory postsynaptic currents (mEPSCs) in cultured cortical neurons of C57 mice undergoing oxygen and glucose deprivation (OGD) or OGD/reperfusion (OGD/R). The KCNQ/M-channel opener, retigabine (RTG), suppressed the overactivation of postsynaptic NMDARs induced by OGD and then NO transient; RTG also decreased OGD-induced neuronal death measured with MTT assay, suggesting the beneficial role of KCNQ/M-channels for the neurons exposed to ischemic insults. However, when the neurons exposed to the subsequent reperfusion, KCNQ/M-channels played a differential role from its protective effect. OGD/R increased presynaptic glutamatergic release, which was further augmented by RTG or decreased by KCNQ/M-channel blocker, XE991. Reactive oxygen species (ROS) were produced partly in a NO-dependent manner. In addition, XE991 decreased neuronal injuries upon reperfusion measured with DCF and PI staining. Meanwhile, the addition of RTG upon OGD or XE991 upon reperfusion can reverse OGD or OGD/R-reduced mitochondrial membrane potential. Our present study indicates the dual role of KCNQ/M-channels in OGD and OGD/R, which will decide the fate of neurons. Provided that activation of KCNQ/M-channels has differential effects on neuronal injuries during OGD or OGD/R, we propose that therapy targeting KCNQ/M-channels may be effective for ischemic injuries but the proper timing is so crucial for the corresponding treatment.

Intracellular S1P Levels Dictate Fate of Different Regions of the Hippocampus following Transient Global Cerebral Ischemia

Sphingosine-1-phosphate (S1P) is a sphingolipid molecule produced by the action of sphingosine kinases (SphK) on sphingosine. It possesses various intracellular functions through its interactions with intracellular proteins or via its action on five G-protein-coupled cell membrane receptors. Following transient global cerebral ischemia (tGCI), only the CA1 subregion of the hippocampus undergoes apoptosis. In this study, we evaluated S1P levels and S1P-processing enzyme expression in different hippocampal areas following tGCI in rats. We found that S1P was upregulated earlier in CA3 than in CA1. This was associated with upregulation of SphK1 in both regions; however, SphK2 was downregulated quickly in CA3. S1P lyase was also downregulated in CA3, but not in CA1. Spinster 2, the S1P exporter, was upregulated early in both regions, but was quickly downregulated in CA3. Together, these effects explain the variable levels of S1P in the CA1 and CA3 areas and indicate that S1P levels play a role in the preferential resistance of the CA3 subregion to tGCI-induced ischemia. FTY720 did not improve neuronal survival in the CA1 subregion, indicating that these effects were due to intracellular S1P accumulation. In conclusion, the findings suggest that intracellular S1P levels affect neuronal cell fate following tGCI.

Implications of Epigenetic Mechanisms and their Targets in Cerebral Ischemia Models

BACKGROUND

Understanding the complexities associated with the ischemic condition and identifying therapeutic targets in ischemia is a continued challenge in stroke biology. Emerging evidence reveals the potential involvement of epigenetic mechanisms in the incident and outcome of stroke, suggesting novel therapeutic options of targeting different molecules related to epigenetic regulation.

OBJECTIVE

This review summarizes our current understanding of ischemic pathophysiology, describes various in vivo and in vitro models of ischemia, and examines epigenetic modifications associated with the ischemic condition.

METHOD

We focus on microRNAs, DNA methylation, and histone modifying enzymes, and present how epigenetic studies are revealing novel drug target candidates in stroke.

CONCLUSION

Finally, we discuss emerging approaches for the prevention and treatment of stroke and post-stroke effects using pharmacological interventions with a wide therapeutic window.

Targeting NMDA receptors in stroke: new hope in neuroprotection

NMDA (N-methyl-d-aspartate) receptors (NMDARs) play a central role in excitotoxic neuronal death caused by ischemic stroke, but NMDAR channel blockers have failed to be translated into clinical stroke treatments. However, recent research on NMDAR-associated signaling complexes has identified important death-signaling pathways linked to NMDARs. This led to the generation of inhibitors that inhibit these pathways downstream from the receptor without necessarily blocking NMDARs. This therapeutic approach may have fewer side effects and/or provide a wider therapeutic window for stroke as compared to the receptor antagonists. In this review, we highlight the key findings in the signaling cascades downstream of NMDARs and the novel promising therapeutics for ischemic stroke.

Calcium uptake and cytochrome c release from normal and ischemic brain mitochondria

At abnormally elevated levels of intracellular Ca²⁺, mitochondrial Ca²⁺ uptake may compromise mitochondrial electron transport activities and trigger membrane permeability changes that allow for release of cytochrome c and other mitochondrial apoptotic proteins into the cytosol. In this study, a clinically relevant canine cardiac arrest model was used to assess the effects of global cerebral ischemia and reperfusion on mitochondrial Ca²⁺ uptake capacity, Ca²⁺ uptake-mediated inhibition of respiration, and Ca²⁺-induced cytochrome c release, as measured in vitro in a K⁺-based medium in the presence of Mg²⁺, ATP, and NADH-linked oxidizable substrates. Maximum Ca²⁺ uptake by frontal cortex mitochondria was significantly lower following 10 min cardiac arrest compared to non-ischemic controls. Mitochondria from ischemic brains were also more sensitive to the respiratory inhibition associated with accumulation of large levels of Ca²⁺. Cytochrome c was released from brain mitochondria in vitro in a Ca²⁺-dose-dependent manner and was more pronounced following both 10 min of ischemia alone and following 24 h reperfusion, in comparison to mitochondria from non-ischemic Shams. These effects of ischemia and reperfusion on brain mitochondria could compromise intracellular Ca²⁺ homeostasis, decrease aerobic and increase anaerobic cerebral energy metabolism, and potentiate the cytochrome c-dependent induction of apoptosis, when re-oxygenated mitochondria are exposed to abnormally high levels of intracellular Ca²⁺.

Establishment of an ideal time window model in hypothermic-targeted temperature management after traumatic brain injury in rats

Although hypothermic-targeted temperature management (HTTM) holds great potential for the treatment of traumatic brain injury (TBI), translation of the efficacy of hypothermia from animal models to TBI patientshas no entire consistency. This study aimed to find an ideal time window model in experimental rats which was more in accordance with clinical practice through the delayed HTTM intervention. Sprague-Dawley rats were subjected to unilateral cortical contusion injury and received therapeutic hypothermia at 15mins, 2 h, 4 h respectively after TBI. The neurological function was evaluated with the modified neurological severity score and Morris water maze test. The brain edema and morphological changes were measured with the water content and H&E staining. Brain sections were immunostained with antibodies against DCX (a neuroblast marker) and GFAP (an astrocyte marker). The apoptosis levels in the ipsilateral hippocampi and cortex were examined with antibodies against the apoptotic proteins Bcl-2, Bax, and cleaved caspase-3 by the immunofluorescence and western blotting. The results indicated that each hypothermia therapy group could improve neurobehavioral and cognitive function, alleviate brain edema and reduce inflammation. Furthermore, we observed that therapeutic hypothermia increased DCX expression, decreased GFAP expression, upregulated Bcl-2 expression and downregulated Bax and cleaved Caspase-3 expression. The above results suggested that HTTM at 2h or even at 4h post-injury revealed beneficial brain protection similarly, despite the best effect at 15min post-injury. These findings may provide relatively ideal time window models, further making the following experimental results more credible and persuasive.

Mitochondrial function in Müller cells - Does it matter?

Growing evidence suggests that mitochondrial dysfunction might play a key role in the pathogenesis of age-related neurodegenerative inner retinal diseases such as diabetic retinopathy and glaucoma. Therefore, the present review provides a perspective on the impact of functional mitochondria in the most predominant glial cells of the retina, the Müller cells. Müller cells span the entire thickness of the neuroretina and are in close proximity to retinal cells including the retinal neurons that provides visual signaling to the brain. Among multiple functions, Müller cells are responsible for the removal of neurotransmitters, buffering potassium, and providing neurons with essential metabolites. Thus, Müller cells are responsible for a stable metabolic dialogue in the inner retina and their crucial role in supporting retinal neurons is indisputable. Müller cell functions require considerable energy production and previous literature has primarily emphasized glycolysis as the main energy provider. However, recent studies highlight the need of mitochondrial ATP production to upheld Müller cell functions. Therefore, the present review aims to provide an overview of the current evidence on the impact of mitochondrial functions in Müller cells.

Mitochondrial iron chelation ameliorates cigarette smoke-induced bronchitis and emphysema in mice

Chronic obstructive pulmonary disease (COPD) is linked to both cigarette smoking and genetic determinants. We have previously identified iron-responsive element-binding protein 2 (IRP2) as an important COPD susceptibility gene and have shown that IRP2 protein is increased in the lungs of individuals with COPD. Here we demonstrate that mice deficient in Irp2 were protected from cigarette smoke (CS)-induced experimental COPD. By integrating RNA immunoprecipitation followed by sequencing (RIP-seq), RNA sequencing (RNA-seq), and gene expression and functional enrichment clustering analysis, we identified Irp2 as a regulator of mitochondrial function in the lungs of mice. Irp2 increased mitochondrial iron loading and levels of cytochrome c oxidase (COX), which led to mitochondrial dysfunction and subsequent experimental COPD. Frataxin-deficient mice, which had higher mitochondrial iron loading, showed impaired airway mucociliary clearance (MCC) and higher pulmonary inflammation at baseline, whereas mice deficient in the synthesis of cytochrome c oxidase, which have reduced COX, were protected from CS-induced pulmonary inflammation and impairment of MCC. Mice treated with a mitochondrial iron chelator or mice fed a low-iron diet were protected from CS-induced COPD. Mitochondrial iron chelation also alleviated CS-induced impairment of MCC, CS-induced pulmonary inflammation and CS-associated lung injury in mice with established COPD, suggesting a critical functional role and potential therapeutic intervention for the mitochondrial-iron axis in COPD.

Crosstalk Between Endoplasmic Reticulum Stress, Oxidative Stress, and Autophagy: Potential Therapeutic Targets for Acute CNS Injuries

Endoplasmic reticulum (ER) stress induces a variety of neuronal cell death pathways that play a critical role in the pathophysiology of stroke. ER stress occurs when unfolded/misfolded proteins accumulate and the folding capacity of ER chaperones exceeds the capacity of ER lumen to facilitate their disposal. As a consequence, a complex set of signaling pathways will be induced that transmit from ER to cytosol and nucleus to compensate damage and to restore the normal cellular homeostasis, collectively known as unfolded protein response (UPR). However, failure of UPR due to severe or prolonged stress leads to cell death. Following acute CNS injuries, chronic disturbances in protein folding and oxidative stress prolong ER stress leading to sustained ER dysfunction and neuronal cell death. While ER stress responses have been well studied after stroke, there is an emerging need to study the association of ER stress with other cell pathways that exacerbate neuronal death after an injury. In this review, we summarize the current understanding of the role for ER stress in acute brain injuries, highlighting the diverse molecular mechanisms associated with ER stress and its relation to oxidative stress and autophagy. We also discussed the existing and developing therapeutic options aimed to reduce ER stress to protect the CNS after acute injuries.

Inhibition of mTOR Pathway by Rapamycin Reduces Brain Damage in Rats Subjected to Transient Forebrain Ischemia

The aims of this study are to clarify the role of mTOR in mediating cerebral ischemic brain damage and the effects of rapamycin on ischemic outcomes. Ten minutes of forebrain ischemia was induced in rats, and their brains were sampled after 3 h, 16 h, and 7 days reperfusion for histology, immunohistochemistry and biochemical analysis. Our data demonstrated that cerebral ischemia resulted in both apoptotic and necrotic neuronal death; cerebral ischemia and reperfusion led to significant increases of mRNA and protein levels of p-mTOR and its downstream p-P70S6K and p-S6; elevation of LC3-II, and release of cytochrome c into the cytoplasm in both the cortex and hippocampus. Inhibition of mTOR by rapamycin markedly reduced ischemia-induced damage; suppressed p-Akt, p-mTOR, p-P70S6K and p-S6 protein levels; decreased LC3-II and Beclin-1; and prevented cytochrome c release in the two structures. All together, these data provide evidence that cerebral ischemia activates mTOR and autophagy pathways. Inhibition of mTOR deactivates the mTOR pathway, suppresses autophagy, prevents cytochrome c release and reduces ischemic brain damage.

Oxidative stress-dependent changes in immune responses and cell death in the substantia nigra after ozone exposure in rat

Parkinson's disease has been associated with the selective loss of neurons in the substantia nigra pars compacta. Increasing evidence suggests that oxidative stress plays a major role. The resulting increase in reactive oxygen species triggers a sequence of events that leads to cell damage, activation of microglia cells and neuroinflammatory responses. Our objective was to study whether chronic exposure to low doses of ozone, which produces oxidative stress itself, induces progressive cell death in conjunction with glial alterations in the substantia nigra. Animals were exposed to an ozone-free air stream (control) or to low doses of ozone for 7, 15, 30, 60, or 90 days. Each group underwent (1) spectrophotometric analysis for protein oxidation; (2) western blot testing for microglia reactivity and nuclear factor kappa B expression levels; and (3) immunohistochemistry for cytochrome c, GFAP, Iba-1, NFkB, and COX-2. Our results indicate that ozone induces an increase in protein oxidation levels, changes in activated astrocytes and microglia, and cell death. NFkB and cytochrome c showed an increase until 30 days of exposure, while cyclooxygenase 2 in the substantia nigra increased from 7 days up to 90 days of repetitive ozone exposure. These results suggest that oxidative stress caused by ozone exposure induces changes in inflammatory responses and progressive cell death in the substantia nigra in rats, which could also be occurring in Parkinson's disease.

miRNAs-19b, -29b-2* and -339-5p show an early and sustained up-regulation in ischemic models of stroke

Stroke, the loss of neurons after ischemic insult to the brain, is one of the leading causes of death and disability worldwide. Despite its prevalence and severity, current therapy is extremely limited, highlighting the importance of further understanding the molecular events underlying ischemia-induced neuronal cell death. An ischemic area can be subdivided into two separate pathophysiological regions: the rapidly dying necrotic core, and the potentially salvageable apoptotic penumbra. Understanding molecular events occurring in the apoptotic ischemic penumbra may give greater insight into mechanisms controlling this salvageable tissue. miRNAs are known to have key roles in the regulation of gene expression in numerous pathological conditions, including the modulation of distinct pathways in stroke. However, previous studies have profiled miRNAs in the whole ischemic infarct, and do not differentiate between miRNA regulation in the necrotic core versus the apoptotic penumbra. We asked if there were unique miRNAs that are differentially regulated following ischemic insults in the salvageable apoptotic penumbra. miRNA expression profiles were compared in the whole infarct from in vivo stroke models, using the three vessel occlusion approach, to an in vitro model of the ischemic penumbra, prior to apoptotic induction. Multiple miRNAs were found to be differentially regulated following ischemic insults in each system. However, miR-19b, miR-29b-2* and miR-339-5p were significantly up-regulated in both model systems. Further, we confirmed these results in a neuroblastoma cell line subjected to a penumbra-like ischemic insult that induced the apoptotic cell death pathway. The data show that miR-19b, miR-29b-2* and miR-339-5p are up-regulated following ischemic insults and may be regulating gene expression to control important cellular pathways in the salvageable ischemic penumbra. Further investigation of their role and mRNA target identification may lead to new insights into the molecular mechanisms taking place in the salvageable apoptotic penumbra.

Activation of caspase-9 and its influencing factors in beef during conditioning

To study the activation of caspase-9 and its potential influence in conditioning, longissimus thoracis (LT), semitendinosus (STN) and psoas minor (PMi) muscles were used to analyze the ratio of pro-apoptotic bax to anti-apoptotic bcl-2 in fresh tissues and observe the changes in ATP, cytosolic cytochrome c and caspase-9 activity levels during storage at 4°C. Caspase-9 activity at 5 h is higher than the activity at 0 and 24 h in the muscles (P<0.001). The ATP content decreased between 0 and 3 h, between 8 and 14 h in the PMi and LT muscles (P<0.0001), whereas between 0 and 5 h, between 8 and 14 h in the STN muscle (P<0.0001). There is 60.2%, 55.3% and 43.1% available ATP in the STN, LT and PMi muscles at 5 h, respectively. The cytosolic cytochrome c level increased during 5 and 24 h storage in the LT and PMi muscles (P<0.0001), during 5 and 96 h in the STN muscle (P<0.0001). The cytosolic cytochrome c at 24 h (P<0.001) and ratio of bax to bcl-2 (P<0.05) was higher in the PMi than in other muscles. We concluded that the increase in cytosolic cytochrome c and available intracellular ATP should be responsible for the increase in caspase-9 activity; the activation of caspase-9 could be limited by the subsequent depletion of ATP; the postmortem release level of cytochrome c could be determined by the ratio of bax to bcl-2 in fresh tissues.

Cytochrome C is tyrosine 97 phosphorylated by neuroprotective insulin treatment

Recent advancements in isolation techniques for cytochrome c (Cytc) have allowed us to discover post-translational modifications of this protein. We previously identified two distinct tyrosine phosphorylated residues on Cytc in mammalian liver and heart that alter its electron transfer kinetics and the ability to induce apoptosis. Here we investigated the phosphorylation status of Cytc in ischemic brain and sought to determine if insulin-induced neuroprotection and inhibition of Cytc release was associated with phosphorylation of Cytc. Using an animal model of global brain ischemia, we found a ∼50% decrease in neuronal death in the CA1 hippocampal region with post-ischemic insulin administration. This insulin-mediated increase in neuronal survival was associated with inhibition of Cytc release at 24 hours of reperfusion. To investigate possible changes in the phosphorylation state of Cytc we first isolated the protein from ischemic pig brain and brain that was treated with insulin. Ischemic brains demonstrated no detectable tyrosine phosphorylation. In contrast Cytc isolated from brains treated with insulin showed robust phosphorylation of Cytc, and the phosphorylation site was unambiguously identified as Tyr97 by immobilized metal affinity chromatography/nano-liquid chromatography/electrospray ionization mass spectrometry. We next confirmed these results in rats by in vivo application of insulin in the absence or presence of global brain ischemia and determined that Cytc Tyr97-phosphorylation is strongly induced under both conditions but cannot be detected in untreated controls. These data suggest a mechanism whereby Cytc is targeted for phosphorylation by insulin signaling, which may prevent its release from the mitochondria and the induction of apoptosis.

The role of PARL and HtrA2 in striatal neuronal injury after transient global cerebral ischemia

The presenilin-associated rhomboid-like (PARL) protein and high temperature requirement factor A2 (HtrA2) are key regulators of mitochondrial integrity and play pivotal roles in apoptosis. However, their roles after cerebral ischemia have not been thoroughly elucidated. To clarify these roles, mice were subjected to transient global cerebral ischemia, and striatal neuronal injury was assessed. Western blot and coimmunoprecipitation analyses revealed that PARL and processed HtrA2 localized to mitochondria, and that PARL was bound to HtrA2 in sham animals. Expression of PARL and processed HtrA2 in mitochondria significantly decreased 6 to 72 hours after ischemia, and the binding of PARL to HtrA2 disappeared after ischemia. In contrast, expression of processed HtrA2 increased 24 hours after ischemia in the cytosol, where HtrA2 was bound to X chromosome-linked inhibitor-of-apoptosis protein (XIAP). Administration of PARL small interfering RNA inhibited HtrA2 processing and worsened ischemic neuronal injury. Our results show that downregulation of PARL after ischemia is a key step in ischemic neuronal injury, and that it decreases HtrA2 processing and increases neuronal vulnerability. In addition, processed HtrA2 released into the cytosol after ischemia contributes to neuronal injury via inhibition of XIAP.

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.

In the eye of the storm: mitochondrial damage during heart and brain ischaemia

We review research investigating mitochondrial damage during heart and brain ischaemia, focusing on the mechanisms and consequences of ischaemia-induced and/or reperfusion-induced: (a) inhibition of mitochondrial respiratory complex I; (b) release of cytochrome c from mitochondria; (c) changes to mitochondrial phospholipids; and (d) nitric oxide inhibition of mitochondria. Heart ischaemia causes inhibition of cytochrome oxidase and complex I, release of cytochrome c, and induction of permeability transition and hydrolysis and oxidation of mitochondrial phospholipids, but some of the mechanisms are unclear. Brain ischaemia causes inhibition of complexes I and IV, but other effects are less clear.

Minocycline-preconditioned neural stem cells enhance neuroprotection after ischemic stroke in rats

Transplantation of neural stem cells (NSCs) offers a novel therapeutic strategy for stroke; however, massive grafted cell death following transplantation, possibly due to a hostile host brain environment, lessens the effectiveness of this approach. Here, we have investigated whether reprogramming NSCs with minocycline, a broadly used antibiotic also known to possess cytoprotective properties, enhances survival of grafted cells and promotes neuroprotection in ischemic stroke. NSCs harvested from the subventricular zone of fetal rats were preconditioned with minocycline in vitro and transplanted into rat brains 6 h after transient middle cerebral artery occlusion. Histological and behavioral tests were examined from days 0-28 after stroke. For in vitro experiments, NSCs were subjected to oxygen-glucose deprivation and reoxygenation. Cell viability and antioxidant gene expression were analyzed. Minocycline preconditioning protected the grafted NSCs from ischemic reperfusion injury via upregulation of Nrf2 and Nrf2-regulated antioxidant genes. Additionally, preconditioning with minocycline induced the NSCs to release paracrine factors, including brain-derived neurotrophic factor, nerve growth factor, glial cell-derived neurotrophic factor, and vascular endothelial growth factor. Moreover, transplantation of the minocycline-preconditioned NSCs significantly attenuated infarct size and improved neurological performance, compared with non-preconditioned NSCs. Minocycline-induced neuroprotection was abolished by transfecting the NSCs with Nrf2-small interfering RNA before transplantation. Thus, preconditioning with minocycline, which reprograms NSCs to tolerate oxidative stress after ischemic reperfusion injury and express higher levels of paracrine factors through Nrf2 up-regulation, is a simple and safe approach to enhance the effectiveness of transplantation therapy in ischemic stroke.

Release of mitochondrial apoptogenic factors and cell death are mediated by CK2 and NADPH oxidase

Activation of the NADPH oxidase subunit, NOX2, and increased oxidative stress are associated with neuronal death after cerebral ischemia and reperfusion. Inhibition of NOX2 by casein kinase 2 (CK2) leads to neuronal survival, but the mechanism is unknown. In this study, we show that in copper/zinc-superoxide dismutase transgenic (SOD1 Tg) mice, degradation of CK2α and CK2α' and dephosphorylation of CK2β against oxidative stress were markedly reduced compared with wild-type (WT) mice that underwent middle cerebral artery occlusion. Inhibition of CK2 pharmacologically or by ischemic reperfusion facilitated accumulation of poly(ADP-ribose) polymers, the translocation of apoptosis-inducing factor (AIF), and cytochrome c release from mitochondria after ischemic injury. The eventual enhancement of CK2 inhibition under ischemic injury strongly increased 8-hydroxy-2'-deoxyguanosine and phosphorylation of H2A.X. Furthermore, CK2 inhibition by tetrabromocinnamic acid (TBCA) in SOD1 Tg and gp91 knockout (KO) mice after ischemia reperfusion induced less release of AIF and cytochrome c than in TBCA-treated WT mice. Inhibition of CK2 in gp91 KO mice subjected to ischemia reperfusion did not increase brain infarction compared with TBCA-treated WT mice. These results strongly suggest that NOX2 activation releases reactive oxygen species after CK2 inhibition, triggering release of apoptogenic factors from mitochondria and inducing DNA damage after ischemic brain injury.

Reactive oxygen/nitrogen species and their functional correlations in neurodegenerative diseases

The continuous production and efflux of reactive oxygen/nitrogen species from endogenous and exogenous sources can damage biological molecules and initiate a cascade of events. Mitochondria are pivotal in controlling cell survival and death. Cumulative oxidative stress, disrupted mitochondrial respiration, and mitochondrial damage are related with various neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and others. Biochemical cascades of apoptosis are mediated in signaling molecules, including protein kinases and transcription factors. The expressions in the pro-apoptotic signal transduction networks may indeed promote cell death and degeneration in brain cells. The regulation of that protein phosphorylation by kinases and phosphatases is emerging as a prerequisite mechanism in the control of the apoptotic cell death program. In this review, we attempt to put forth the evidence for possible mechanistic explanations for involvement of free radicals in the pathogenesis of neurodegenerative diseases.

Effect of polyphenols on oxidative stress and mitochondrial dysfunction in neuronal death and brain edema in cerebral ischemia

Polyphenols are natural substances with variable phenolic structures and are elevated in vegetables, fruits, grains, bark, roots, tea, and wine. There are over 8000 polyphenolic structures identified in plants, but edible plants contain only several hundred polyphenolic structures. In addition to their well-known antioxidant effects, select polyphenols also have insulin-potentiating, anti-inflammatory, anti-carcinogenic, anti-viral, anti-ulcer, and anti-apoptotic properties. One important consequence of ischemia is neuronal death and oxidative stress plays a key role in neuronal viability. In addition, neuronal death may be initiated by the activation of mitochondria-associated cell death pathways. Another consequence of ischemia that is possibly mediated by oxidative stress and mitochondrial dysfunction is glial swelling, a component of cytotoxic brain edema. The purpose of this article is to review the current literature on the contribution of oxidative stress and mitochondrial dysfunction to neuronal death, cell swelling, and brain edema in ischemia. A review of currently known mechanisms underlying neuronal death and edema/cell swelling will be undertaken and the potential of dietary polyphenols to reduce such neural damage will be critically reviewed.

Changes in gene expression in the rat hippocampus after focal cerebral ischemia

OBJECTIVE

The rat middle cerebral artery thread-occlusion model has been widely used to investigate the pathophysiological mechanisms of stroke and to develop therapeutic treatment. This study was conducted to analyze energy metabolism, apoptotic signal pathways, and genetic changes in the hippocampus of the ischemic rat brain.

METHODS

Focal transient cerebral ischemia was induced by obstructing the middle cerebral artery for two hours. After 24 hours, the induction of ischemia was confirmed by the measurement of infarct size using 2,3,5-triphenyltetrazolium chloride staining. A cDNA microarray assay was performed after isolating the hippocampus, and was used to examine changes in genetic expression patterns.

RESULTS

According to the cDNA microarray analysis, a total of 1,882 and 2,237 genes showed more than a 2-fold increase and more than a 2-fold decrease, respectively. When the genes were classified according to signal pathways, genes related with oxidative phosphorylation were found most frequently. There are several apoptotic genes that are known to be expressed during ischemic brain damage, including Akt2 and Tnfrsf1a. In this study, the expression of these genes was observed to increase by more than 2-fold. As energy metabolism related genes grew, ischemic brain damage was affected, and the expression of important genes related to apoptosis was increased/decreased.

CONCLUSION

Our analysis revealed a significant change in the expression of energy metabolism related genes (Atp6v0d1, Atp5g2, etc.) in the hippocampus of the ischemic rat brain. Based on this data, we feel these genes have the potential to be target genes used for the development of therapeutic agents for ischemic stroke.

Stachybotrys microspora triprenyl phenol-7, a novel fibrinolytic agent, suppresses superoxide production, matrix metalloproteinase-9 expression, and thereby attenuates ischemia/reperfusion injury in rat brain

Stachybotrys microspora triprenyl phenol-7 (SMTP-7) is a novel fibrinolytic agent with anti-inflammatory effect. Previous study demonstrated that SMTP-7 further ameliorated infarction volume in a mouse embolic stroke model compared with tissue type plasminogen activator (tPA), but the reason SMTP-7 has more beneficial effect than tPA has not yet been determined. In the present study, we investigated whether SMTP-7 has an intrinsic neuroprotective effect against transient focal cerebral ischemia (tFCI). Sprague-Dawley rats were subjected to tFCI by intraluminal middle cerebral artery occlusion for 2h. Following induction of tFCI, rats were randomized into two groups based on the agent administered: SMTP-7 group and vehicle group. We examined cerebral infarction volume 24h after reperfusion, and evaluated superoxide production, the expressions of nitrotyrosine and matrix metalloproteinase-9 (MMP-9), which play major roles in secondary brain injury and hemorrhagic transformation. The findings showed that SMTP-7 significantly suppressed superoxide production, the expression of nitrotyrosine and MMP-9 after tFCI, and consequently attenuated ischemic neuronal damage. These results suggest that SMTP-7 has an intrinsic neuroprotective effect on ischemia/reperfusion injury through the suppression of oxidative stress and MMP-9 activation.

Activation of protein kinase C delta following cerebral ischemia leads to release of cytochrome C from the mitochondria via bad pathway

BACKGROUND

The release of cytochrome c from the mitochondria following cerebral ischemia is a key event leading to cell death. The goal of the present study was to determine the mechanisms involved in post-ischemic activation of protein kinase c delta (δPKC) that lead to cytochrome c release.

METHODS/FINDINGS

We used a rat model of cardiac arrest as an in vivo model, and an in vitro analog, oxygen glucose deprivation (OGD) in rat hippocampal synaptosomes. Cardiac arrest triggered translocation of δPKC to the mitochondrial fraction at 1 h reperfusion. In synaptosomes, the peptide inhibitor of δPKC blocked OGD-induced translocation to the mitochondria. We tested two potential pathways by which δPKC activation could lead to cytochrome c release: phosphorylation of phospholipid scramblase-3 (PLSCR3) and/or protein phosphatase 2A (PP2A). Cardiac arrest increased levels of phosphorlyated PLSCR3; however, inhibition of δPKC translocation failed to affect the OGD-induced increase in PLSCR3 in synaptosomal mitochondria suggesting the post-ischemic phosphorylation of PLSCR3 is not mediated by δPKC. Inhibition of either δPKC or PP2A decreased cytochrome c release from synaptosomal mitochondria. Cardiac arrest results in the dephosphorylation of Bad and Bax, both downstream targets of PP2A promoting apoptosis. Inhibition of δPKC or PP2A prevented OGD-induced Bad, but not Bax, dephosphorylation. To complement these studies, we used proteomics to identify novel mitochondrial substrates of δPKC.

CONCLUSIONS

We conclude that δPKC initiates cytochrome c release via phosphorylation of PP2A and subsequent dephosphorylation of Bad and identified δPKC, PP2A and additional mitochondrial proteins as potential therapeutic targets for ischemic neuroprotection.

Mechanisms of primary blast-induced traumatic brain injury: insights from shock-wave research

Traumatic brain injury caused by explosive or blast events is traditionally divided into four phases: primary, secondary, tertiary, and quaternary blast injury. These phases of blast-induced traumatic brain injury (bTBI) are biomechanically distinct and can be modeled in both in vivo and in vitro systems. The primary bTBI injury phase represents the response of brain tissue to the initial blast wave. Among the four phases of bTBI, there is a remarkable paucity of information about the cause of primary bTBI. On the other hand, 30 years of research on the medical application of shockwaves (SW) has given us insight into the mechanisms of tissue and cellular damage in bTBI, including both air-mediated and underwater SW sources. From a basic physics perspective, the typical blast wave consists of a lead SW followed by supersonic flow. The resultant tissue injury includes several features observed in bTBI, such as hemorrhage, edema, pseudoaneurysm formation, vasoconstriction, and induction of apoptosis. These are well-described pathological findings within the SW literature. Acoustic impedance mismatch, penetration of tissue by shock/bubble interaction, geometry of the skull, shear stress, tensile stress, and subsequent cavitation formation, are all important factors in determining the extent of SW-induced tissue and cellular injury. Herein we describe the requirements for the adequate experimental set-up when investigating blast-induced tissue and cellular injury; review SW physics, research, and the importance of engineering validation (visualization/pressure measurement/numerical simulation); and, based upon our findings of SW-induced injury, discuss the potential underlying mechanisms of primary bTBI.

Sex differences in the response to poly(ADP-ribose) polymerase-1 deletion and caspase inhibition after stroke

BACKGROUND AND PURPOSE

Emerging data suggest that the molecular cell death pathways triggered by ischemic insults differ in the male and female brain. Cell death in males is initiated by poly(ADP-ribose) polymerase-1 (PARP-1) activation; however, manipulation of this pathway paradoxically increases ischemic damage in females. In contrast, females are exquisitely sensitive to caspase-mediated cell death. The effect of caspase inhibition in PARP-1 knockout mice was evaluated to determine if the detrimental effects of PARP deletion in females were secondary to increased caspase activation.

METHODS

Focal stroke was induced by transient or permanent middle cerebral artery occlusion (MCAO) in wild-type (WT) and PARP-1(-/-) mice of both sexes. The pan-caspase inhibitor, quinoline-Val-Asp(Ome)-CH2-O-phenoxy (Q-VD-OPh), was administered 90 minutes after middle cerebral artery occlusion. Infarct size and neurological sores were assessed. Separate cohorts were used for protein analysis for PAR, Apoptosis inducing factor (AIF), caspase-9, and caspase-3.

RESULTS

WT mice of both sexes had increased nuclear AIF after stroke compared to PARP-1(-/-) mice. PARP-1(-/-) females had higher mitochondrial cytochrome C and activated caspase-9 and -3 levels than WT female mice. PARP-1(-/-) females also had an increase in stroke-induced cytosolic cytochrome C release compared with WT females, which was not seen in males. Q-VD-OPh decreased caspase-9 in both males and females but only led to reduction of infarct in females. PARP-1(-/-) males had smaller infarcts, whereas PARP-1(-/-) females had larger strokes compared with WT. Q-VD-OPh significantly decreased infarct in both WT and PARP-1(-/-) females in both transient and permanent MCAO models, but had no effect in males.

CONCLUSIONS

Deletion of PARP-1 reduces infarct in males but exacerbates injury in females. PARP-1(-/-) females have enhanced caspase activation. The detrimental effects of PARP loss in females can be reversed with caspase inhibition.