Role of mitochondrial function in the protective effects of ischaemic postconditioning on ischaemia/reperfusion cerebral damage

Mitochondrial ferritin alleviates apoptosis by enhancing mitochondrial bioenergetics and stimulating glucose metabolism in cerebral ischemia reperfusion

Oxidative stress and deficient bioenergetics are key players in the pathological process of cerebral ischemia reperfusion injury (I/R). As a mitochondrial iron storage protein, mitochondrial ferritin (FtMt) plays a pivotal role in protecting neuronal cells from oxidative damage under stress conditions. However, the effects of FtMt in mitochondrial function and activation of apoptosis under cerebral I/R are barely understood. In the present study, we found that FtMt deficiency exacerbates neuronal apoptosis via classical mitochondria-depedent pathway and the endoplasmic reticulum (ER) stress pathway in brains exposed to I/R. Conversely, FtMt overexpression significantly inhibited oxygen and glucose deprivation and reperfusion (OGD/R)-induced apoptosis and the activation of ER stress response. Meanwhile, FtMt overexpression rescued OGD/R-induced mitochondrial iron overload, mitochondrial dysfunction, the generation of reactive oxygen species (ROS) and increased neuronal GSH content. Using the Seahorse and O2K cellular respiration analyser, we demonstrated that FtMt remarkably improved the ATP content and the spare respiratory capacity under I/R conditions. Importantly, we found that glucose consumption was augmented in FtMt overexpressing cells after OGD/R insult; overexpression of FtMt facilitated the activation of glucose 6-phosphate dehydrogenase and the production of NADPH in cells after OGD/R, indicating that the pentose-phosphate pathway is enhanced in FtMt overexpressing cells, thus strengthening the antioxidant capacity of neuronal cells. In summary, our results reveal that FtMt protects against I/R-induced apoptosis through enhancing mitochondrial bioenergetics and regulating glucose metabolism via the pentose-phosphate pathway, thus preventing ROS overproduction, and preserving energy metabolism.

The creation of unilateral intermittent and unintermittent renal ischemia-reperfusion models in rats

Background and Aim:

This study aims to establish unilateral intermittent and unintermittent partial nephrectomy-like renal ischemia-reperfusion (I-R) model in rats and to compare the results with biochemical findings.

Material and Methods:

The study was conducted on 24 adult 8-week-old male Wistar-Albino rats, each weighing s200–250 g. The rats were divided into three groups. In the Sham group (n = 8), the kidney was surgically exposed and closed. We designed experimental I-R models in the second group (n = 8, a total of 30-min ischemia model in the manner of 3 intermittent sets 8 minutes clamping and 2 min unclamping) and in the third group (n = 8, one session of 30-min unintermittent ischemia). In postoperative day 1, the rats were sacrificed, and the effects of I-R models on the renal tissue were comparatively assessed by evaluating serum Neutrophil Gelatinase-Associated Lipocalin (NGAL), serum kidney injury molecule-1 (KIM-1), urinary NGAL, urinary KIM-1, and serum creatinine levels.

Results:

Urinary NGAL and KIM-1 levels were significantly higher in the continuous ischemia group when compared to those in the sham and intermittent ischemia groups (P < 0.05). In the intermittent ischemia group, urinary NGAL and urinary KIM-1 levels were significantly higher than those in the sham group (P < 0.05). Although the results of serum NGAL, serum KIM-1, and serum creatinine levels seemed to be in parallel to the results of urinary markers, no statistically significant difference was found.

Conclusion:

Renal injury was significantly less in the intermittent I-R model when compared to that in the unintermittent I-R model in our experimental rat study.

Advances in intervention methods and brain protection mechanisms of in situ and remote ischemic postconditioning

Ischemic postconditioning (PostC) conventionally refers to a series of brief blood vessel occlusions and reperfusions, which can induce an endogenous neuroprotective effect and reduce cerebral ischemia/reperfusion (I/R) injury. Depending on the site of adaptive ischemic intervention, PostC can be classified as in situ ischemic postconditioning (ISPostC) and remote ischemic postconditioning (RIPostC). Many studies have shown that ISPostC and RIPostC can reduce cerebral IS injury through protective mechanisms that increase cerebral blood flow after reperfusion, decrease antioxidant stress and anti-neuronal apoptosis, reduce brain edema, and regulate autophagy as well as Akt, MAPK, PKC, and KATP channel cell signaling pathways. However, few studies have compared the intervention methods, protective mechanisms, and cell signaling pathways of ISPostC and RIPostC interventions. Thus, in this article, we compare the history, common intervention methods, neuroprotective mechanisms, and cell signaling pathways of ISPostC and RIPostC.

Restoration of L-OPA1 alleviates acute ischemic stroke injury in rats via inhibiting neuronal apoptosis and preserving mitochondrial function

BACKGROUND

Ischemic stroke can induce changes in mitochondrial morphology and function. As a regulatory gene in mitochondria, optic atrophy 1 (OPA1) plays a pivotal role in the regulation of mitochondrial dynamics and other related functions. However, its roles in cerebral ischemia-related conditions are barely understood.

METHODS

Cultured rat primary cortical neurons were respectively transfected with OPA1-v1ΔS1-encoding and OPA1-v1-encoding lentivirus before exposure to 2-h oxygen-glucose deprivation (OGD) and subsequent reoxygenation (OGD/R). Adult male SD rats received an intracranial injection of AAV-OPA1-v1ΔS1 and were subjected to 90 min of transient middle cerebral artery occlusion (tMCAO) followed by reperfusion. OPA1 expression and function were detected by in vitro and in vivo assays.

RESULTS

OPA1 was excessively cleaved after cerebral ischemia/reperfusion injury, both in vitro and in vivo. Under OGD/R condition, compared with that of the LV-OPA1-v1-treated group, the expression of OPA1-v1ΔS1 efficiently restored L-OPA1 level and alleviated neuronal death and mitochondrial morphological damage. Meanwhile, the expression of OPA1-v1ΔS1 markedly improved cerebral ischemia/reperfusion-induced motor function damage, attenuated brain infarct volume, neuronal apoptosis, mitochondrial bioenergetics deficits, oxidative stress, and restored the morphology of mitochondrial cristae and mitochondrial length. It also preserved the mitochondrial integrity and reinforced the mtDNA content and expression of mitochondrial biogenesis factors in ischemic rats.

INTERPRETATION

Our results demonstrate that the stabilization of L-OPA1 protects ischemic brains by reducing neuronal apoptosis and preserving mitochondrial function, suggesting its significance as a promising therapeutic target for stroke prevention and treatment.

Angelica sinensis extract protects against ischemia-reperfusion injury in the hippocampus by activating p38 MAPK-mediated p90RSK/p-Bad and p90RSK/CREB/BDNF signaling after transient global cerebral ischemia in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Angelica sinensis (Oliv.) Diels, commonly known as Dang Gui (DG), is one of the most popular traditional Chinese herbal medicines for the treatment of stroke. However, the effects of DG on transient global cerebral ischemia (GCI) and its precise mechanisms remain unclear.

AIM OF THE STUDY

This study aimed to investigate the effects of the DG extract on ischemia-reperfusion (I/R) injury in the hippocampus 7 d after transient GCI and to identify the potential mitogen-activated protein kinase (MAPK)-related signaling pathway in the hippocampus involved in the effects.

MATERIALS AND METHODS

Rats were intragastrically administered DG at doses of 0.25 g/kg (DG-0.25g), 0.5 g/kg (DG-0.5g), or 1 g/kg (DG-1g) 1, 3, and 5 d after GCI.

RESULTS

DG-0.5g and DG-1g treatments effectively promoted hippocampal cornu ammonis 1 (CA1) neuronal survival. DG-0.5g and DG-1g treatments markedly increased phospho-p38 MAPK (p-p38 MAPK), phospho-90-kDa ribosomal S6 kinase (p-p90RSK), cytosolic and mitochondrial phospho-Bad (p-Bad), phospho-cAMP response element-binding protein (p-CREB), brain-derived neurotrophic factor (BDNF), and p-CREB/BDNF expression; decreased 4-hydroxy-2-nonenal, cytochrome c (Cytc), and cleaved caspase-3 expression, and inhibited apoptosis in the hippocampal CA1 region. Pretreatment with a specific inhibitor of p38 MAPK, SB203580, completely blocked the effects of DG-1g on the expression of the aforementioned proteins.

CONCLUSIONS

DG-0.5g and DG-1g treatments exerted neuroprotective effects on I/R injury by activating p38 MAPK-mediated p90RSK/p-Bad-induced anti-apoptotic-Cytc/caspase-3-related and p90RSK/CREB/BDNF survival signaling in the hippocampus 7 d after transient GCI.

Danhong injection facilitates recovery of post-stroke motion deficit via Parkin-enhanced mitochondrial function

BACKGROUND

A cerebral ischemic stroke involves mitochondrial dysfunction, motor deficits, and paralysis; and Danhong injection (DHI) might possess mitochondrial protection and functional recovery in a stroke subject through promoting expression of parkin, a ubiquitin ligase playing a key role in the regulation of proteins and mitochondria quality control.

OBJECTIVE

To investigate the therapeutic effects of DHI on the histological, cellular, and functional recovery of Wistar rats after middle cerebral artery occlusion/reperfusion (MCAO/R).

METHODS

One hundred and twenty healthy male Wistar rats (250-300 g), were randomly assigned to six groups (twenty rats/group). Rats were subjected to 1 h MCAO/R and subsequently administered the intravenous doses of DHI (0.75, 1.5, and 3 mL/kg) to the respective groups (twice a day for 14 days). Unlike the other groups, the sham group received surgery without vessel occlusion. All the animals were tested for gait behavior using the CatWalk system. The body weight/survival rates were recorded daily for 14 days. The parkin protein expression of the brain tissue was quantified by immunohistochemistry analysis. Additionally, cultured cortical neurons were incubation with DHI or minocycline (MC) and then deprived of oxygen and glucose for 2 h (to resemble ischemic/reperfusion), followed by 4 h reoxygenation. Cellular and mitochondrial phenotypes were assayed by high content analysis.

RESULTS

Neurological integrity and paw parameters of the animals were altered in the model group but significantly ameliorated by DHI administration. Also, the infarct volume and survival rate were significantly improved in DHI groups. DHI enhanced the expression of parkin protein in the brain and improved the relative mitochondrial reductase activity of the cultured neurons.

CONCLUSIONS

The overall result shows that daily intervention with DHI provides neuroprotection and survival to improve gait motion in Wistar rats.

Gerontoxanthone I and Macluraxanthone Induce Mitophagy and Attenuate Ischemia/Reperfusion Injury

Mitophagy is a crucial process in controlling mitochondrial biogenesis. Balancing mitophagy and mitochondrial functions is required for maintaining cellular homeostasis. In this study, we found that Gerontoxanthone I (GeX1) and Macluraxanthone (McX), xanthone derivatives isolated from Garcinia bracteata C. Y. Wu ex Y. H. Li, induced Parkin puncta accumulation and promoted mitophagy. GeX1 and McX treatment induced the degradation of mitophagy-related proteins such as Tom20 and Tim23. GeX1 and McX directly stabilized PTEN-induced putative kinase 1 (PINK1) on the outer membrane of the mitochondria, and then recruited Parkin to mitochondria. This significantly induced phosphorylation and ubiquitination of Parkin, suggesting that GeX1 and McX mediate mitophagy through the PINK1-Parkin pathway. Transfecting ParkinS65A or pretreated MG132 abolished the induction effects of GeX1 and McX on mitophagy. Furthermore, GeX1 and McX treatment decreased cell death and the level of ROS in an ischemia/reperfusion (IR) injury model in H9c2 cells compared to a control group. Taken together, our data suggested that GeX1 and McX induce PINK1-Parkin–mediated mitophagy and attenuate myocardial IR injury in vitro.

Application of ischemic postconditioning's algorithms in tissues protection: response to methodological gaps in preclinical and clinical studies

Ischaemic postconditioning (IPostC) was introduced for the first time by Zhao et al. as a feasible method for reduction of myocardial ischaemia–reperfusion (IR) injury. The cardioprotection by this protocol has been extensively evaluated in various species. Then, further research revealed that IPostC is a safe and convenient approach in limiting IR injury of non‐myocardial tissues such as lung, liver, kidney, intestine, skeletal muscle, brain and spinal cord. IPostC has been conducted with different algorithms, resulting in diverse effects. The possible important factors leading to these differences are the difference in activation levels of signalling pathways and protective mediators by any algorithm, presence or absence of IPostC effectors in each tissue, or intrinsic characteristics of the tissues as well as the methodological biases. Also, the conflicting results have been shown with the application of the same algorithm of IPostC in certain tissues or animal species. The effectiveness of IPostC may depend upon various parameters including the species and the tissues characteristics. For example, different heart rates and metabolic rates of the species and unequal amounts of perfusion and blood flow of the tissues should be considered as the important determinants of IPostC effectiveness and should be thought about in designing IPostC algorithms for future studies. Due to these discrepancies, there is still no optimal single IPostC algorithm applicable to any tissue or any species. This issue is the main topic of the present article.

Progesterone induces neuroprotection following reperfusion-promoted mitochondrial dysfunction after focal cerebral ischemia in rats

Organelle damage and increases in mitochondrial permeabilization are key events in the development of cerebral ischemic tissue injury because they cause both modifications in ATP turnover and cellular apoptosis/necrosis. Early restoration of blood flow and improvement of mitochondrial function might reverse the situation and help in recovery following an onset of stroke. Mitochondria and related bioenergetic processes can be effectively used as pharmacological targets. Progesterone (P4), one of the promising neurosteroids, has been found to be neuroprotective in various models of neurological diseases, through a number of mechanisms. This influenced us to investigate the possible role of P4 in the mitochondria-mediated neuroprotective mechanism in an ischemic stroke model of rat. In this study, we have shown the positive effect of P4 administration on behavioral deficits and mitochondrial health in an ischemic stroke injury model of transient middle cerebral artery occlusion (tMCAO). After induction of tMCAO, the rats received an initial intraperitoneal injection of P4 (8 mg/kg body weight) or vehicle at 1 h post-occlusion followed by subcutaneous injections at 6, 12 and 18 h. Behavioral assessment for functional deficits included grip strength, motor coordination and gait analysis. Findings revealed a significant improvement with P4 treatment in tMCAO animals. Staining of isolated brain slices from P4-treated rats with 2,3,5-triphenyltetrazolium chloride (TTC) showed a reduction in the infarct area in comparison to the vehicle group, indicating the presence of an increased number of viable mitochondria. P4 treatment was also able to attenuate mitochondrial reactive oxygen species (ROS) production, as well as block the mitochondrial permeability transition pore (mPTP), in the tMCAO injury model. In addition, it was also able to ameliorate the altered mitochondrial membrane potential and respiration ratio in the ischemic animals, thereby suggesting that P4 has a positive effect on mitochondrial bioenergetics. In conclusion, these results demonstrate that P4 treatment is beneficial in preserving the mitochondrial functions that are altered in cerebral ischemic injury and thus can help in defining better therapies.

Summary: Progesterone treatment is beneficial in preserving the altered mitochondrial functions in cerebral ischemic injury and thus can help in defining better therapies.

Mitochondrial dysfunction and cell death in neurodegenerative diseases through nitroxidative stress

Mitochondria are important for providing cellular energy ATP through the oxidative phosphorylation pathway. They are also critical in regulating many cellular functions including the fatty acid oxidation, the metabolism of glutamate and urea, the anti-oxidant defense, and the apoptosis pathway. Mitochondria are an important source of reactive oxygen species leaked from the electron transport chain while they are susceptible to oxidative damage, leading to mitochondrial dysfunction and tissue injury. In fact, impaired mitochondrial function is commonly observed in many types of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, alcoholic dementia, brain ischemia-reperfusion related injury, and others, although many of these neurological disorders have unique etiological factors. Mitochondrial dysfunction under many pathological conditions is likely to be promoted by increased nitroxidative stress, which can stimulate post-translational modifications (PTMs) of mitochondrial proteins and/or oxidative damage to mitochondrial DNA and lipids. Furthermore, recent studies have demonstrated that various antioxidants, including naturally occurring flavonoids and polyphenols as well as synthetic compounds, can block the formation of reactive oxygen and/or nitrogen species, and thus ultimately prevent the PTMs of many proteins with improved disease conditions. Therefore, the present review is aimed to describe the recent research developments in the molecular mechanisms for mitochondrial dysfunction and tissue injury in neurodegenerative diseases and discuss translational research opportunities.

Mitochondrial DNA Copy Number in Sleep Duration Discordant Monozygotic Twins

STUDY OBJECTIVES

Mitochondrial DNA (mtDNA) copy number is an important component of mitochondrial function and varies with age, disease, and environmental factors. We aimed to determine whether mtDNA copy number varies with habitual differences in sleep duration within pairs of monozygotic twins.

SETTING

Academic clinical research center.

PARTICIPANTS

15 sleep duration discordant monozygotic twin pairs (30 twins, 80% female; mean age 42.1 years [SD 15.0]).

DESIGN

Sleep duration was phenotyped with wrist actigraphy. Each twin pair included a "normal" (7-9 h/24) and "short" (< 7 h/24) sleeping twin. Fasting peripheral blood leukocyte DNA was assessed for mtDNA copy number via the n-fold difference between qPCR measured mtDNA and nuclear DNA creating an mtDNA measure without absolute units. We used generalized estimating equation linear regression models accounting for the correlated data structure to assess within-pair effects of sleep duration on mtDNA copy number.

MEASUREMENTS AND RESULTS

Mean within-pair sleep duration difference per 24 hours was 94.3 minutes (SD 62.6 min). We found reduced sleep duration (β = 0.06; 95% CI 0.004, 0.12; P < 0.05) and sleep efficiency (β = 0.51; 95% CI 0.06, 0.95; P < 0.05) were significantly associated with reduced mtDNA copy number within twin pairs. Thus every 1-minute decrease in actigraphy-defined sleep duration was associated with a decrease in mtDNA copy number of 0.06. Likewise, a 1% decrease in actigraphy-defined sleep efficiency was associated with a decrease in mtDNA copy number of 0.51.

CONCLUSIONS

Reduced sleep duration and sleep efficiency were associated with reduced mitochondrial DNA copy number in sleep duration discordant monozygotic twins offering a potential mechanism whereby short sleep impairs health and longevity through mitochondrial stress.

Neuroprotective effects of quercetin in a mouse model of brain ischemic/reperfusion injury via anti-apoptotic mechanisms based on the Akt pathway

The present study provided experimental evidence for the neuroprotective effects of quercetin using a rat model of global brain ischemic/reperfusion (I/R) injury. Pre‑treatment with quercetin (5 or 10 mg/kg orally (p.o.); once daily) induced a dose‑dependent reduction in I/R‑induced hippocampal neuron cell loss, with 10 mg/kg/day being the lowest dose that achieved maximal neuroprotection. Administration of 10 mg/kg quercetin over at least 3 days prior to I/R was required to improve the survival rate of I/R rats. Fluorescence‑assisted cell sorting, hematoxylin and eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling indicated neuronal cell loss in the CA1 hippocampus. Rats that had undergone transient global cerebral ischemia for 15 min followed by 1 h of reperfusion exhibited a significant increase in reactive oxygen species (ROS) production in the hippocampus. The I/R‑induced ROS overproduction in the hippocampus at 1, 12 and 24 h following I/R was significantly decreased by quercetin pre‑treatment. Western blot analysis revealed that the neuroprotective effects of quercetin (5 and 10 mg/kg/day, p.o.) were associated with an upregulation of the I/R‑induced suppression of B‑cell lymphoma‑2 (Bcl‑2), Bcl extra large and survivin expression as well as phosphorylation of Bcl‑2‑associated death promoter. Furthermore, the neuroprotective effects of quercetin (5, 10 mg/kg/day) in the brain were associated with an upregulation of Akt signaling. These findings suggested that the inhibition of I/R‑induced brain injury by quercetin likely involves a transcriptional mechanism to enhance anti‑apoptotic signaling.

Protection of ischemic postconditioning against neuronal apoptosis induced by transient focal ischemia is associated with attenuation of NF-κB/p65 activation

Background and Purpose

Accumulating evidences have demonstrated that nuclear factor κB/p65 plays a protective role in the protection of ischemic preconditioning and detrimental role in lethal ischemia-induced programmed cell death including apoptosis and autophagic death. However, its role in the protection of ischemic postconditioning is still unclear.

Methods

Rat MCAO model was used to produce transient focal ischemia. The procedure of ischemic postconditioning consisted of three cycles of 30 seconds reperfusion/reocclusion of MCA. The volume of cerebral infarction was measured by TTC staining and neuronal apoptosis was detected by TUNEL staining. Western blotting was used to analyze the changes in protein levels of Caspase-3, NF-κB/p65, phosphor- NF-κB/p65, IκBα, phosphor- IκBα, Noxa, Bim and Bax between rats treated with and without ischemic postconditioning. Laser scanning confocal microscopy was used to examine the distribution of NF-κB/p65 and Noxa.

Results

Ischemic postconditioning made transient focal ischemia-induced infarct volume decrease obviously from 38.6%±5.8% to 23.5%±4.3%, and apoptosis rate reduce significantly from 46.5%±6.2 to 29.6%±5.3% at reperfusion 24 h following 2 h focal cerebral ischemia. Western blotting analysis showed that ischemic postconditioning suppressed markedly the reduction of NF-κB/p65 in cytoplasm, but elevated its content in nucleus either at reperfusion 6 h or 24 h. Moreover, the decrease of IκBα and the increase of phosphorylated IκBα and phosphorylated NF-κB/p65 at indicated reperfusion time were reversed by ischemic postconditioning. Correspondingly, proapoptotic proteins Caspase-3, cleaved Caspase-3, Noxa, Bim and Bax were all mitigated significantly by ischemic postconditioning. Confocal microscopy revealed that ischemic postconditioning not only attenuated ischemia-induced translocation of NF-κB/p65 from neuronal cytoplasm to nucleus, but also inhibited the abnormal expression of proapoptotic protein Noxa within neurons.

Conclusions

We demonstrated in this study that the protection of ischemic postconditioning on neuronal apoptosis caused by transient focal ischemia is associated with attenuation of the activation of NF-κB/p65 in neurons.

Ginsenoside Rb1 attenuates oxygen-glucose deprivation-induced apoptosis in SH-SY5Y cells via protection of mitochondria and inhibition of AIF and cytochrome c release

To investigate the role of mitochondria in the protective effects of ginsenoside Rb1 on cellular apoptosis caused by oxygen-glucose deprivation, in this study, MTT assay, TUNEL staining, flow cytometry, immunocytochemistry and western blotting were used to examine the cellular viability, apoptosis, ROS level, mitochondrial membrane potential, and the distribution of apoptosis inducing factor, cytochrome c, Bax and Bcl-2 in nucleus, mitochondria and cytoplasm. We found that pretreatment with GRb1 improved the cellular viability damaged by OGD. Moreover, GRb1 inhibited apoptosis in SH-SY5Y cells induced by OGD. Further studies showed that the elevation of cellular reactive oxygen species levels and the reduction of mitochondrial membrane potential caused by OGD were both counteracted by GRb1. Additionally, GRb1 not only suppressed the translocation of apoptosis inducing factor into nucleus and cytochrome c into cytoplasm, but also inhibited the increase of Bax within mitochondria and alleviated the decrease of mitochondrial Bcl-2. Our study indicates that the protection of GRb1 on OGD-induced apoptosis in SH-SY5Y cells is associated with its protection on mitochondrial function and inhibition of release of AIF and cytochrome c.