Potential role of PUMA in delayed death of hippocampal CA1 neurons after transient global cerebral ischemia

An innovative metabolic index for insulin resistance correlates with early neurological deterioration following intravenous thrombolysis in minor acute ischemic stroke patients

Background and purpose

The composite score for insulin resistance (IR), known as the Metabolic Score of Insulin Resistance (METS-IR), serves as an assessment tool for IR and has been previously linked to symptomatic intracranial hemorrhage and poor functional outcomes in patients with acute ischemic stroke (AIS). Despite these associations, the impact of METS-IR on early neurological deterioration (END) in patients with minor AIS who underwent intravenous administration of recombinant tissue-type plasminogen activator (IV-rtPA) remains inadequately established. This investigation explored the link between METS-IR and END in patients with minor AIS receiving IV-rtPA treatment.

Methods

In this study, a cohort comprising 425 consecutive patients with National Institutes of Health Stroke Scale Score (NIHSS)≤5 who underwent IV-rtPA treatment was included. The METS-IR was computed using the formula ln METS-IR=ln (2 × FBG + TG) × BMI/ln (HDL). END was defined as a NIHSS ≥2 within 24 h post IV-rtPA administration, while poor functional outcome was defined as a modified Rankin Scale (mRS) of 2-6. Multivariate logistical regression was performed to investigate the association between METS-IR and both poor functional outcomes and END.

Results

Among the 425 enrolled patients, 64 (15.1 %) patients experienced END, while 80 (18.8 %) had poor functional outcomes three months post-discharge. Upon adjusting for confounding factors, a higher METS-IR emerged as an independent predictor for both END and poor functional outcomes. Similarly, noteworthy findings were observed when METS-IR was defined as a categorical group. The restricted cubic spline (RCS) analysis indicated a linear relationship between METS-IR and END (P = 0.593 for non-linearity, P = 0.034 for overall). The incorporation of METS-IR into the conventional model resulted in a significant enhancement of predictive accuracy for both END and poor functional outcomes.

Conclusion

METS-IR emerges as an independent predictor for END and poor functional outcome at three months post-discharge in patients with minor AIS subjected to IV-rtPA. Considering its simplicity and clinical accessibility as an indicator of IR, METS-IR may hold guiding significance in clinical practice.

Involvement of Proteasomal and Endoplasmic Reticulum Stress in Neurodegeneration After Global Brain Ischemia

A brief period of transient global brain ischemia leads to selective ischemic neurodegeneration associated with death of hippocampal CA1 pyramidal neurons days after reperfusion. The mechanism of such selective and delayed neurodegeneration is still uncertain. Our work aimed to study the involvement of proteasomal and endoplasmic reticulum (ER) stress in ischemic neurodegeneration. We have performed laser scanning confocal microscopy analysis of brain slices from control and experimental animals that underwent global brain ischemia for 15 min and varying times of reperfusion. We have focused on ubiquitin, PUMA, a proapoptotic protein of the Bcl-2 family overexpressed in response to both proteasomal and ER stress, and p53, which controls expression of PUMA. We have also examined the expression of HRD1, an E3 ubiquitin ligase that was shown to be overexpressed after ER stress. We have also examined potential crosstalk between proteasomal and ER stress using cellular models of both proteasomal and ER stress. We demonstrate that global brain ischemia is associated with an appearance of distinct immunoreactivity of ubiquitin, PUMA and p53 in pyramidal neurons of the CA1 layer of the hippocampus 72 h after ischemic insults. Such changes correlate with a delay and selectivity of ischemic neurodegeneration. Immunoreactivity of HRD1 observed in all investigated regions of rat brain was transiently absent in both CA1 and CA3 pyramidal neurones 24 h after ischemia in the hippocampus, which does not correlate with a delay and selectivity of ischemic neurodegeneration. We do not document significant crosstalk between proteasomal and ER stress. Our results favour dysfunction of the ubiquitin proteasome system and consequent p53-induced expression of PUMA as the main mechanisms responsible for selective and delayed degeneration of pyramidal neurons of the hippocampal CA1 layer in response to global brain ischemia.

Reverse Electron Transport at Mitochondrial Complex I in Ischemic Stroke, Aging, and Age-Related Diseases

Stroke is one of the leading causes of morbidity and mortality worldwide. A main cause of brain damage by stroke is ischemia-reperfusion (IR) injury due to the increased production of reactive oxygen species (ROS) and energy failure caused by changes in mitochondrial metabolism. Ischemia causes a build-up of succinate in tissues and changes in the mitochondrial NADH: ubiquinone oxidoreductase (complex I) activity that promote reverse electron transfer (RET), in which a portion of the electrons derived from succinate are redirected from ubiquinol along complex I to reach the NADH dehydrogenase module of complex I, where matrix NAD+ is converted to NADH and excessive ROS is produced. RET has been shown to play a role in macrophage activation in response to bacterial infection, electron transport chain reorganization in response to changes in the energy supply, and carotid body adaptation to changes in the oxygen levels. In addition to stroke, deregulated RET and RET-generated ROS (RET-ROS) have been implicated in tissue damage during organ transplantation, whereas an RET-induced NAD+/NADH ratio decrease has been implicated in aging, age-related neurodegeneration, and cancer. In this review, we provide a historical account of the roles of ROS and oxidative damage in the pathogenesis of ischemic stroke, summarize the latest developments in our understanding of RET biology and RET-associated pathological conditions, and discuss new ways to target ischemic stroke, cancer, aging, and age-related neurodegenerative diseases by modulating RET.

Hippocampal region-specific endogenous neuroprotection as an approach in the search for new neuroprotective strategies in ischemic stroke. Fiction or fact?

Ischemic stroke is the leading cause of death and long-term disability worldwide, and, while considerable progress has been made in understanding its pathophysiology, the lack of effective treatments remains a major concern. In that context, receiving more and more consideration as a promising therapeutic method is the activation of natural adaptive mechanisms (endogenous neuroprotection) - an approach that seeks to enhance and/or stimulate the endogenous processes of plasticity and protection of the neuronal system that trigger the brain's intrinsic capacity for self-defence. Ischemic preconditioning is a classic example of endogenous neuroprotection, being the process by which one or more brief, non-damaging episodes of ischemia-reperfusion (I/R) induce tissue resistance to subsequent prolonged, damaging ischemia. Another less-known example is resistance to an I/R episode mounted by the hippocampal region consisting of CA2, CA3, CA4 and the dentate gyrus (here abbreviated to CA2-4, DG). This can be contrasted with the ischemia-vulnerable CA1 region. There is not yet a good understanding of these different sensitivities of the hippocampal regions, and hence of the endogenous neuroprotection characteristic of CA2-4, DG. However, this region is widely reported to have properties distinct from CA1, and capable of generating resistance to an I/R episode. These include activation of neurotrophic and neuroprotective factors, greater activation of anti-excitotoxic and anti-oxidant mechanisms, increased plasticity potential, a greater energy reserve and improved mitochondrial function. This review seeks to summarize properties of CA2-4, DG in the context of endogenous neuroprotection, and then to assess the potential utility of these properties to therapeutic approaches. In so doing, it appears to represent the first such addressing of the issue of ischemia resistance attributable to CA2-4, DG.

MDMX elevation by a novel Mdmx-p53 interaction inhibitor mitigates neuronal damage after ischemic stroke

Mdmx and Mdm2 are two major suppressor factors for the tumor suppressor gene p53. In central nervous system, Mdmx suppresses the transcriptional activity of p53 and enhances the binding of Mdm2 to p53 for degradation. But Mdmx dynamics in cerebral infarction remained obscure. Here we investigated the role of Mdmx under ischemic conditions and evaluated the effects of our developed small-molecule Protein-Protein Interaction (PPI) inhibitors, K-181, on Mdmx-p53 interactions in vivo and in vitro. We found ischemic stroke decreased Mdmx expression with increased phosphorylation of Mdmx Serine 367, while Mdmx overexpression by AAV-Mdmx showed a neuroprotective effect on neurons. The PPI inhibitor, K-181 attenuated the neurological deficits by increasing Mdmx expression in post-stroke mice brain. Additionally, K-181 selectively inhibited HDAC6 activity and enhanced tubulin acetylation. Our findings clarified the dynamics of Mdmx in cerebral ischemia and provide a clue for the future pharmaceutic development of ischemic stroke.

Neuroprotective Mechanism of Icariin on Hypoxic Ischemic Brain Damage in Neonatal Mice

Objective

Our previous results showed that icariin (ICA) could inhibit apoptosis and provide neuroprotection against hypoxic-ischemic brain damage (HIBD) in neonatal mice, but the specific mechanism of its neuroprotective effect remains unknown. This study aims at exploring whether ICA plays a neuroprotective role in apoptosis inhibition by regulating autophagy through the estrogen receptor α (ERα)/estrogen receptor β (ERβ) pathway in neonatal mice with HIBD.

Methods

A neonatal mouse model of HIBD was constructed in vivo, and an oxygen and glucose deprivation (OGD) model in HT22 cells from the hippocampal neuronal system was constructed in vitro. The effects of ICA pretreatment on autophagy and the expression of ERα and ERβ were detected in vitro and in vivo, respectively. ICA pretreatment was also supplemented with the autophagy inhibitor 3-methyladenine (3-MA), ERα inhibitor methylpiperidino pyrazole (MPP), and ERβ inhibitor 4-(2-phenyl-5,7-bis (trifluoromethyl) pyrazolo [1,5-a] pyramidin-3-yl) phenol (PHTPP) to further detect whether ICA pretreatment can activate the ERα/ERβ pathway to promote autophagy and reduce HIBD-induced apoptosis to play a neuroprotective role against HIBD in neonatal mice.

Results

ICA pretreatment significantly promoted autophagy in HIBD mice. Treatment with 3-MA significantly inhibited the increase in autophagy induced by ICA pretreatment, reversed the neuroprotective effect of ICA pretreatment, and promoted apoptosis. Moreover, ICA pretreatment significantly increased the expression levels of the ERα and ERβ proteins in HIBD newborn mice. Both MPP and PHTPP administration significantly inhibited the expression levels of the ERα and ERβ proteins activated by ICA pretreatment, reversed the neuroprotective effects of ICA pretreatment, inhibited the increase in autophagy induced by ICA pretreatment, and promoted apoptosis.

Conclusion

ICA pretreatment may promote autophagy by activating the ERα and ERβ pathways, thus reducing the apoptosis induced by HIBD and exerting a neuroprotective effect on neonatal mice with HIBD.

Regulation and Role of Neuron-Derived Hemoglobin in the Mouse Hippocampus

Hemoglobin (Hb) is the oxygen transport protein in erythrocytes. In blood, Hb is a tetramer consisting of two Hb-alpha (Hb-α) chains and two Hb-beta (Hb-β) chains. A number of studies have also shown that Hb-α is also expressed in neurons in both the rodent and human brain. In the current study, we examined for age-related regulation of neuronal Hb-α and hypoxia in the hippocampus and cerebral cortex of intact male and female mice. In addition, to confirm the role and functions of neuronal Hb-α, we also utilized lentivirus CRISPR interference-based Hb-α knockdown (Hb-α CRISPRi KD) in the non-ischemic and ischemic mouse hippocampus and examined the effect on neuronal oxygenation, as well as induction of hypoxia-inducible factor-1α (HIF-1α) and its downstream pro-apoptotic factors, PUMA and NOXA, and on neuronal survival and neurodegeneration. The results of the study revealed an age-related decrease in neuronal Hb-α levels and correlated increase in hypoxia in the hippocampus and cortex of intact male and female mice. Sex differences were observed with males having higher neuronal Hb-α levels than females in all brain regions at all ages. In vivo Hb-α CRISPRi KD in the mouse hippocampus resulted in increased hypoxia and elevated levels of HIF-1α, PUMA and NOXA in the non-ischemic and ischemic mouse hippocampus, effects that were correlated with a significant decrease in neuronal survival and increased neurodegeneration. As a whole, these findings indicate that neuronal Hb-α decreases with age in mice and has an important role in regulating neuronal oxygenation and neuroprotection.

Proteasome and Neuroprotective Effect of Hyperbaric Oxygen Preconditioning in Experimental Global Cerebral Ischemia in Rats

Objectives

We investigated the involvement of the proteasome in the mechanism of preconditioning with hyperbaric oxygen (HBO-PC).

Methods

The experiments were performed on male Wistar rats subjected to a transient global cerebral ischemia of 5 min duration (2-vessel occlusion model) and preconditioned or not with HBO for 5 preceding days (1 h HBO at 2.5 atmosphere absolute [ATA] daily). In subgroups of preconditioned rats, the proteasome inhibitor MG132 was administered 30 min prior to each preconditioning session. Twenty-four hours and 7 days post-ischemia, after neurobehavioral assessment, the brains were collected and evaluated for morphological changes and quantitative immunohistochemistry of cell markers and apoptosis-related proteins.

Results

We observed reduced damage of CA1 pyramidal cells in the HBO preconditioned group only at 7 days post-ischemia. However, both at early (24 h) and later (7 days) time points, HBO-PC enhanced the tissue expression of 20S core particle of the proteasome and of the nestin, diminished astroglial reactivity, and reduced p53, rabbit anti-p53 upregulated modulator of apoptosis (PUMA), and rabbit anti-B cell lymphoma-2 interacting mediator of cell death (Bim) expressions in the hippocampus and cerebral cortex. HBO-PC also improved T-maze performance at 7 days. Proteasome inhibitor abolished the beneficial effects of HBO-PC on post-ischemic neuronal injury and functional impairment and reduced the ischemic alterations in the expression of investigated proteins.

Significance

Preconditioning with hyperbaric oxygen-induced brain protection against severe ischemic brain insult appears to involve the proteasome, which can be linked to a depletion of apoptotic proteins and improved regenerative potential.

Cross-Talk between Amyloid, Tau Protein and Free Radicals in Post-Ischemic Brain Neurodegeneration in the Form of Alzheimer’s Disease Proteinopathy

Recent years have seen remarkable progress in research into free radicals oxidative stress, particularly in the context of post-ischemic recirculation brain injury. Oxidative stress in post-ischemic tissues violates the integrity of the genome, causing DNA damage, death of neuronal, glial and vascular cells, and impaired neurological outcome after brain ischemia. Indeed, it is now known that DNA damage and repair play a key role in post-stroke white and gray matter remodeling, and restoring the integrity of the blood-brain barrier. This review will present one of the newly characterized mechanisms that emerged with genomic and proteomic development that led to brain ischemia to a new level of post-ischemic neuropathological mechanisms, such as the presence of amyloid plaques and the development of neurofibrillary tangles, which further exacerbate oxidative stress. Finally, we hypothesize that modified amyloid and the tau protein, along with the oxidative stress generated, are new key elements in the vicious circle important in the development of post-ischemic neurodegeneration in a type of Alzheimer’s disease proteinopathy.

Dexmedetomidine attenuates ischemia and reperfusion-induced cardiomyocyte injury through p53 and forkhead box O3a (FOXO3a)/p53-upregulated modulator of apoptosis (PUMA) signaling signaling

Dexmedetomidine (DEX) has been reported to attenuate the ischemia and reperfusion (I/R) induced cardiomyocyte apoptosis. However, mechanisms underlying these protective effect remain to be fully elucidated. Cardiomyocyte apoptosis is associated with ischemic heart disease. Here we investigated the role of DEX in I/R -induced cardiomyocyte apoptosis. Mice and H9c2 cardiomyocyte cells were subjected to cardiomyocyte I/R injury and hypoxia/reoxygenation (H/R) injury, respectively. The roles and mechanisms of DEX on H9c2 cardiomyocyte cells and mice cardiomyocyte cells exposured to H/R or I/R injury were explored. The results showed that DEX attenuates H/R injury-induced H9c2 cell apoptosis and alleviated mitochondrial oxidative stress; it also reduced myocardial infarct size and protected the cardiac function following cardiomyocyte I/R injury. In addition, H/R and I/R injury increased p53 expression and forkhead box O3a (FOXO3a)/p53-upregulated modulator of apoptosis (PUMA) signaling in H9c2 cardiomyocyte cells and cardiomyocytes. Targeting p53 expression or FOXO3a/PUMA signaling inhibited cell apoptosis and protected against H/R injury in H9c2 cardiomyocyte cells and cardiomyocytes. Pretreatment with DEX reduced the H/R or I/R injury-induced activation of p53 expression and FOXO3a/PUMA signaling, and alleviated H/R or I/R injury-induced apoptosis and mitochondrial oxidative stress. Therefore, DEX could alleviate H/R- or I/R-induced cardiomyocytes injury by reducing cell apoptosis and blocking p53 expression and FOXO3a/PUMA signaling. Targeting p53 or/and FOXO3a/PUMA signaling could alleviate cardiomyocyte I/R injury.

Integrated Stress Response in Neuronal Pathology and in Health

Neurodegeneration involves progressive pathological loss of a specific population of neurons, glial activation, and dysfunction of myelinating oligodendrocytes leading to cognitive impairment and altered movement, breathing, and senses. Neuronal degeneration is a hallmark of aging, stroke, drug abuse, toxic chemical exposure, viral infection, chronic inflammation, and a variety of neurological diseases. Accumulation of intra- and extracellular protein aggregates is a common characteristic of cell pathologies. Excessive production of reactive oxygen species and nitric oxide, induction of endoplasmic reticulum stress, and accumulation of misfolded protein aggregates have been shown to trigger a defensive mechanism called integrated stress response (ISR). Activation of ISR is important for synaptic plasticity in learning and memory formation. However, sustaining of ISR may lead to the development of neuronal pathologies and altered patterns in behavior and perception.

Insulin resistance in ischemic stroke: Mechanisms and therapeutic approaches

The pathological condition of insulin resistance prevents the neuroprotective effects of insulin. Numerous studies have demonstrated that insulin resistance, as an independent risk factor for ischemic stroke, accelerates the formation of thrombosis and promotes the development of atherosclerosis, both of which are major mechanisms of ischemic stroke. Additionally, insulin resistance negatively affects the prognosis of patients with ischemic stroke regardless of whether the patient has diabetes, but the mechanisms are not well studied. We explored the association between insulin resistance and the primary mechanisms of brain injury in ischemic stroke (inflammation, oxidative stress, and neuronal damage), looking for potential causes of poor prognosis in patients with ischemic stroke due to insulin resistance. Furthermore, we summarize insulin resistance therapeutic approaches to propose new therapeutic directions for clinically improving prognosis in patients with ischemic stroke.

How cytosolic compartments play safeguard functions against neuroinflammation and cell death in cerebral ischemia

Ischemic stroke is the second leading cause of mortality and disability globally. Neuronal damage following ischemic stroke is rapid and irreversible, and eventually results in neuronal death. In addition to activation of cell death signaling, neuroinflammation is also considered as another pathogenesis that can occur within hours after cerebral ischemia. Under physiological conditions, subcellular organelles play a substantial role in neuronal functionality and viability. However, their functions can be remarkably perturbed under neurological disorders, particularly cerebral ischemia. Therefore, their biochemical and structural response has a determining role in the sequel of neuronal cells and the progression of disease. However, their effects on cell death and neuroinflammation, as major underlying mechanisms of ischemic stroke, are still not understood. This review aims to provide a comprehensive overview of the contribution of each organelle on these pathological processes after ischemic stroke.

Combining Growth Factor and Stem Cell Therapy for Stroke Rehabilitation, A Review

Stroke is a serious, life-threatening condition demanding vigorous search for new therapies. Recent research has focused on stem cell-based therapies as a viable choice following ischemic stroke, based on studies displaying that stem cells transplanted to the brain not only survive but also cause functional recovery. Growth factors defined as polypeptides that regulate the growth and differentiation of many cell types. Many studies have demonstrated that combined use of growth factors may increase results by the stimulation of endogenous neurogenesis, anti-inflammatory, neuroprotection properties, and enhancement of stem cell survival rates and so may be more effective than a single stem cell therapy. This paper reviews and discusses the most promising new stroke recovery research, including combination treatment.

Expression and inhibitory effects of p53-upregulated modulator of apoptosis in gallbladder carcinoma

The p53-upregulated modulator of apoptosis (PUMA) has been reported to be involved in various types of cancer. However, its potential biological role in gallbladder carcinoma (GBC) has not been fully elucidated. The present study aimed to determine the expression levels of PUMA and its biological effects on GBC. The mRNA and protein expression levels of PUMA in GBC tissues and cell lines were measured using reverse transcription-quantitative PCR and western blotting, respectively. The effects of PUMA overexpression on cell viability, proliferation and invasive ability were determined in vitro using the MTT, colony formation and Transwell invasion assays, respectively. The apoptotic rates were detected using the Annexin V-FITC apoptosis detection kit. Furthermore, follow-up of patients with GBC was performed to identify the association between PUMA expression levels and GBC prognosis. The results of the present study demonstrated that the expression levels of PUMA were significantly lower in the GBC tissues and cell lines compared with those in adjacent normal gallbladder tissues and normal gallbladder cells, respectively. Further experiments indicated that overexpression of PUMA inhibited the viability, proliferation and invasive ability of GBC cells compared with those in the control-transfected GBC cells. In addition, overexpression of PUMA significantly promoted apoptosis in GBC cells. Furthermore, overexpression of PUMA inhibited epithelial-mesenchymal transition, and promoted Bax upregulation and Bcl-2 downregulation compared with those in the control group. Low PUMA expression levels were associated with a short overall survival time in patients with GBC. In conclusions, PUMA may act as a tumor suppressor in GBC and may serve as a potential novel treatment target for human GBC.

Mesenchymal Stem Cell-Mediated Mitochondrial Transfer: a Therapeutic Approach for Ischemic Stroke

Stroke is the leading cause of death and adult disability worldwide. Mitochondrial dysfunction is one of the hallmarks of stroke-induced neuronal death, and maintaining mitochondrial function is essential in cell survival and neurological progress following ischemic stroke. Stem cell-mediated mitochondrial transfer represents an emerging therapeutic approach for ischemic stroke. Accumulating evidence suggests that mesenchymal stem cells (MSCs) can directly transfer healthy mitochondria to damaged cells, and rescue mitochondrial damage-provoked tissue degeneration. This review summarizes the research on MSCs-mediated mitochondrial transfer as a therapeutic strategy against ischemic stroke.

Cell Death and Recovery in Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of morbidity and mortality worldwide. Although TBI leads to mechanical damage during initial impact, secondary damage also occurs as results from delayed neurochemical process and intracellular signaling pathways. Accumulated animal and human studies demonstrated that apoptotic mechanism contributes to overall pathology of TBI. Apoptotic cell death has been identified within contusional brain lesion at acute phase of TBI and in region remote from the site directly injured in days to weeks after trauma. TBI is also dynamic conditions that cause neuronal decline overtime and is likely due to neurodegenerative mechanisms years after trauma. Current studies have even suggested association of neuronal damage through apoptotic pathway with mild TBI, which contributes chronic persistent neurological symptoms and cognitive deficits. Thus, a better understanding of the acute and chronic consequences of apoptosis following TBI is required. The purpose of this review is to describe (1) neuronal apoptotic pathway following TBI, (2) contribution of apoptosis to acute and chronic phase of TBI, and (3) current treatment targeting on apoptotic pathway.

Mode of action of granulocyte-colony stimulating factor (G-CSF) as a novel therapy for stroke in a mouse model

BACKGROUND

The FDA approved drug granulocyte-colony stimulating factor (G-CSF) displays anti-apoptotic and immunomodulatory properties with neurogenesis and angiogenic functions. It is known to demonstrate neuroprotective mechanisms against ischemic global stroke. Autophagy is a method for the degradation of intracellular components and in particular, unrestrained autophagy may lead to uncontrolled digestion of affected neurons as well as neuronal death in cerebral ischemia. Mitochondrial dynamics is vital for the regulation of cell survival and death after cerebral ischemia and an early upstream event in neuronal death is mitochondrial fission. We examined the pro-survival mechanisms of G-CSF against apoptosis resulting from autophagy, mitochondrial stress and endoplasmic reticulum (ER) stress.

METHODS

Male Swiss Webster mice (20 weeks of age) were subjected to bilateral common carotid artery occlusion (BCAO) for 30 min. After occlusion, mice were injected with G-CSF (50 μg/kg) subcutaneously for 4 days. Behavioral analysis was carried out using the corner test and locomotor activity test before animals were sacrificed on day 4 or day 7. Key proteins in ER stress, autophagy and mitochondrial stress induced apoptosis were analyzed by immunoblotting.

RESULTS

G-CSF improved neurological deficits and improved behavioral performance on corner and locomotor test. G-CSF binds to G-CSF receptors and its activation leads to upregulation of Akt phosphorylation (P-Akt) which in turn decreases levels of the ER stress sensor, GRP 78 and expression of proteins involved in ER stress apoptosis pathway; ATF6, ATF4, eIF2α, XBP1, Caspase 12 and CHOP. G-CSF treatment significantly decreased Beclin-1, an autophagy marker, and decreased mitochondrial stress biomarkers DRP1 and P53. G-CSF also up-regulated the mitochondrial fusion protein, OPA1 and anti-apoptotic protein Bcl-2 while down-regulating the pro-apoptotic proteins Bax, Bak and PUMA.

CONCLUSIONS

G-CSF is an endogenous ligand in the CNS that has a dual activity that is beneficial both in reducing acute neuronal degeneration and adding to long-term plasticity after cerebral ischemia. G-CSF treatment exerts neuroprotective effects on damaged neurons through the suppression of the ER stress and mitochondrial stress and maintains cellular homeostasis by decreasing pro-apoptotic proteins and increasing of anti-apoptotic proteins.

Neuroprotective effects of minocycline on focal cerebral ischemia injury: a systematic review

To review the neuroprotective effects of minocycline in focal cerebral ischemia in animal models. By searching in the databases of PubMed, ScienceDirect, and Scopus, and considering the inclusion and exclusion criteria of the study. Studies were included if focal cerebral ischemia model was performed in mammals and including a control group that has been compared with a minocycline group. Written in languages other than English; duplicate data; in vitro studies and combination of minocycline with other neuroprotective agents were excluded. Neurological function of patients was assessed by National Institute of Health Stroke Scale, modified Rankin Scale, and modified Barthel Index. Neuroprotective effects were assessed by detecting the expression of inflammatory cytokines. We examined 35 papers concerning the protective effects of minocycline in focal cerebral ischemia in animal models and 6 clinical trials which had evaluated the neuroprotective effects of minocycline in ischemic stroke. These studies revealed that minocycline increases the viability of neurons and decreases the infarct volume following cerebral ischemia. The mechanisms that were reported in these studies included anti-inflammatory, antioxidant, as well as anti-apoptotic effects. Minocycline also increases the neuronal regeneration following cerebral ischemia. Minocycline has considerable neuroprotective effects against cerebral ischemia-induced neuronal damages. However, larger clinical trials may be required before using minocycline as a neuroprotective drug in ischemic stroke.

Down-regulation of cyclin-dependent kinase 5 attenuates p53-dependent apoptosis of hippocampal CA1 pyramidal neurons following transient cerebral ischemia

Abnormal activation of cyclin-dependent kinase 5 (Cdk5) is associated with pathophysiological conditions. Ischemic preconditioning (IPC) can provide neuroprotective effects against subsequent lethal ischemic insult. The objective of this study was to determine how Cdk5 and related molecules could affect neuroprotection in the hippocampus of gerbils after with IPC [a 2-min transient cerebral ischemia (TCI)] followed by 5-min subsequent TCI. Hippocampal CA1 pyramidal neurons were dead at 5 days post-TCI. However, treatment with roscovitine (a potent inhibitor of Cdk5) and IPC protected CA1 pyramidal neurons from TCI. Expression levels of Cdk5, p25, phospho (p)-Rb and p-p53 were increased in nuclei of CA1 pyramidal neurons at 1 and 2 days after TCI. However, these expressions were attenuated by roscovitine treatment and IPC. In particular, Cdk5, p-Rb and p-p53 immunoreactivities in their nuclei were decreased. Furthermore, TUNEL-positive CA1 pyramidal neurons were found at 5 days after TCI with increased expression levels of Bax, PUMA, and activated caspase-3. These TUNEL-positive cells and increased molecules were decreased by roscovitine treatment and IPC. Thus, roscovitine treatment and IPC could protect CA1 pyramidal neurons from TCI through down-regulating Cdk5, p25, and p-p53 in their nuclei. These findings indicate that down-regulating Cdk5 might be a key strategy to attenuate p53-dependent apoptosis of CA1 pyramidal neurons following TCI.

Pretreated Oenanthe Javanica extract increases anti-inflammatory cytokines, attenuates gliosis, and protects hippocampal neurons following transient global cerebral ischemia in gerbils

Recently, we have reported that Oenanthe javanica extract (OJE) displays strong neuroprotective effect against ischemic damage after transient global cerebral ischemia. However, neuroprotective mechanisms of OJE have not been fully identified. Thus, this study investigated the neuroprotection of OJE in the hippocampal CA1 area and its anti-inflammatory activity in gerbils subjected to 5 minutes of transient global cerebral ischemia. We treated the animals by intragastrical injection of OJE (100 and 200 mg/kg) once daily for 1 week prior to transient global cerebral ischemia. Neuroprotection of OJE was observed by immunohistochemistry for neuronal nuclear antigen and histofluorescence staining for Fluoro-Jade B. Immunohistochemistry of glial fibrillary acidic protein and ionized calcium-binding adapter molecule 1 was done for astrocytosis and microgliosis, respectively. To investigate the neuroprotective mechanisms of OJE, we performed immunohistochemistry of tumor necrosis factor-alpha and interleukin-2 for pro-inflammatory function and interleukin-4 and interleukin-13 for anti-inflammatory function. When we treated the animals by intragastrical administration of 200 mg/kg of OJE, hippocampal CA1 pyramidal neurons were protected from transient global cerebral ischemia and cerebral ischemia-induced gliosis was inhibited in the ischemic hippocampal CA1 area. We also found that interleukin-4 and -13 immunoreactivities were significantly increased in pyramidal neurons of the ischemic CA1 area after OJE pretreatment, and the increased immunoreactivities were sustained in the CA1 pyramidal neurons after transient global cerebral ischemia. However, OJE pretreatment did not increase interleukin-2 and tumor necrosis factor-alpha immunoreactivities in the CA1 pyramidal neurons. Our findings suggest that pretreatment with OJE can protect neurons and attenuate gliosis from transient global cerebral ischemia via increasing expressions of interleukin-4 and -13. The experimental plan of this study was reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) in Kangwon National University (approval No. KW-160802-1) on August 10, 2016.

Inhibiting aberrant p53-PUMA feedback loop activation attenuates ischaemia reperfusion-induced neuroapoptosis and neuroinflammation in rats by downregulating caspase 3 and the NF-κB cytokine pathway

Background

Ischaemia reperfusion (IR) induces multiple pathophysiological changes. In addition to its classical role in regulating tumourigenesis, the feedback loop formed by p53 and its driven target p53-upregulated modulator of apoptosis (PUMA) was recently demonstrated to be the common node tightly controlling various cellular responses during myocardial IR. However, the roles of the p53-PUMA feedback loop in the spinal cord remain unclear. This study aimed to elucidate the roles of p53-PUMA feedback interactions in the spinal cord after IR, specifically investigating their regulation of caspase 3-mediated apoptosis and nuclear factor (NF)-κB-mediated cytokine release.

Methods

SD rats subjected to 12 min of aortic arch occlusion served as IR models. Neurological assessment as well as p53 and PUMA mRNA and protein expression analyses were performed at 12-h intervals during a 48-h reperfusion period. The cellular distributions of p53 and PUMA were determined via double immunofluorescence staining. The effects of the p53-PUMA feedback loop on modulating hind-limb function; the number of TUNEL-positive cells; and protein levels of caspase 3, NF-κB and cytokines interleukin (IL)-1β and tumour necrosis factor (TNF)-α, were evaluated by intrathecal treatment with PUMA-specific or scramble siRNA and pifithrin (PFT)-α. Blood-spinal cord barrier (BSCB) breakdown was examined by Evans blue (EB) extravasation and water content analyses.

Results

IR induced significant behavioural deficits as demonstrated by deceased Tarlov scores, which displayed trends opposite those of PUMA and p53 protein and mRNA expression. Upregulated PUMA and p53 fluorescent labels were widely distributed in neurons, astrocytes and microglia. Injecting si-PUMA and PFT-α exerted significant anti-apoptosis effects as shown by the reduced number of TUNEL-positive cells, nuclear abnormalities and cleaved caspase 3 levels at 48 h post-IR. Additionally, p53 colocalized with NF-κB within the cell. Similarly, injecting si-PUMA and PFT-α exerted anti-inflammatory effects as shown by the decreased NF-κB translocation and release of IL-1β and TNF-α. Additionally, injecting si-PUMA and PFT-α preserved the BSCB integrity as determined by decreased EB extravasation and spinal water content. However, injecting si-Con did not induce any of the abovementioned effects.

Conclusions

Inhibition of aberrant p53-PUMA feedback loop activation by intrathecal treatment with si-PUMA and PFT-α prevented IR-induced neuroapoptosis, inflammatory responses and BSCB breakdown by inactivating caspase 3-mediated apoptosis and NF-κB-mediated cytokine release.

Diverse roles of mitochondria in ischemic stroke

Stroke is the leading cause of adult disability and mortality in most developing and developed countries. The current best practices for patients with acute ischemic stroke include intravenous tissue plasminogen activator and endovascular thrombectomy for large-vessel occlusion to improve clinical outcomes. However, only a limited portion of patients receive thrombolytic therapy or endovascular treatment because the therapeutic time window after ischemic stroke is narrow. To address the current shortage of stroke management approaches, it is critical to identify new potential therapeutic targets. The mitochondrion is an often overlooked target for the clinical treatment of stroke. Early studies of mitochondria focused on their bioenergetic role; however, these organelles are now known to be important in a wide range of cellular functions and signaling events. This review aims to summarize the current knowledge on the mitochondrial molecular mechanisms underlying cerebral ischemia and involved in reactive oxygen species generation and scavenging, electron transport chain dysfunction, apoptosis, mitochondrial dynamics and biogenesis, and inflammation. A better understanding of the roles of mitochondria in ischemia-related neuronal death and protection may provide a rationale for the development of innovative therapeutic regimens for ischemic stroke and other stroke syndromes.

•

Review of current treatment of ischemic stroke indicates deficiency in the contemporary methods.

•

Discuss the mitochondrial ROS-related signaling that affect neuronal fate after ischemic stroke.

•

Mechanisms of mitochondrial dynamics and mitophagy could be pivotal for ischemic stroke.

•

Inhibiting mitochondrion-induced inflammatory response is a potential treatment for ischemic stroke.

bFGF plays a neuroprotective role by suppressing excessive autophagy and apoptosis after transient global cerebral ischemia in rats

Transient global cerebral ischemia (tGCI) is a cerebrovascular disorder that can cause apoptotic neuronal damage and functional deficits. Basic fibroblast growth factor (bFGF) was reported to be highly expressed in the central nervous system (CNS) and to exert neuroprotective effects against different CNS diseases. However, the effects of bFGF on tGCI have not been studied intensively. This study was conducted to investigate the effect of bFGF and its underlying mechanism in an animal model of tGCI. After intracerebroventricular (i.c.v.) injection of bFGF, functional improvement was observed, and the number of viable neurons increased in the ischemia-vulnerable hippocampal CA1 region. Apoptosis was induced after tGCI and could be attenuated by bFGF treatment via inhibition of p53 mitochondrial translocation. In addition, autophagy was activated during this process, and bFGF could inhibit activation of autophagy through the mTOR pathway. Rapamycin, an activator of autophagy, was utilized to explore the relationship among bFGF, apoptosis, and autophagy. Apoptosis deteriorated after rapamycin treatment, which indicated that excessive autophagy could contribute to the apoptosis process. In conclusion, these results demonstrate that bFGF could exert neuroprotective effects in the hippocampal CA1 region by suppressing excessive autophagy via the mTOR pathway and inhibiting apoptosis by preventing p53 mitochondrial translocation. Furthermore, our results suggest that bFGF may be a promising therapeutic agent to for treating tGCI in response to major adverse events, including cardiac arrest, shock, extracorporeal circulation, traumatic hemorrhage, and asphyxiation.

Free Radical Damage in Ischemia-Reperfusion Injury: An Obstacle in Acute Ischemic Stroke after Revascularization Therapy

Acute ischemic stroke is a common cause of morbidity and mortality worldwide. Thrombolysis with recombinant tissue plasminogen activator and endovascular thrombectomy are the main revascularization therapies for acute ischemic stroke. However, ischemia-reperfusion injury after revascularization therapy can result in worsening outcomes. Among all possible pathological mechanisms of ischemia-reperfusion injury, free radical damage (mainly oxidative/nitrosative stress injury) has been found to play a key role in the process. Free radicals lead to protein dysfunction, DNA damage, and lipid peroxidation, resulting in cell death. Additionally, free radical damage has a strong connection with inducing hemorrhagic transformation and cerebral edema, which are the major complications of revascularization therapy, and mainly influencing neurological outcomes due to the disruption of the blood-brain barrier. In order to get a better clinical prognosis, more and more studies focus on the pharmaceutical and nonpharmaceutical neuroprotective therapies against free radical damage. This review discusses the pathological mechanisms of free radicals in ischemia-reperfusion injury and adjunctive neuroprotective therapies combined with revascularization therapy against free radical damage.

Hsp27 reduces cold ischemia-reperfusion injury in heart transplantation through regulation of NF-κB and PUMA signaling

BACKGROUND AND OBJECTIVE

Global myocardial ischemia-reperfusion (I/R) injury after heart transplantation is believed to impair graft function and aggravate episodes of both acute and chronic rejection. The 27-kDa heat shock protein (Hsp27) has a potent ability to alleviate I/R after cardiac transplantation. The aim of this study was to investigate the anti-I/R injury effect of Hsp27 to elucidate the underling mechanisms.

METHODS

Heart grafts from BALB/c mice were preserved in University of Wisconsin (UW) solution (control) or UW solution containing pAAV-Hsp27 (Hsp27 solution) at 4°C for 48 h and subsequently transplanted into syngeneic recipients for 72 h. The heart grafts were then collected for histopathological and gene expression analyses. An in vitro I/R model (H9c2 cells or H9c2/Hsp27 cells) was constructed. Then, protein and mRNA expression of Hsp27, p65, p53 upregulated modulator of apoptosis (PUMA), interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α in heart tissues and H9c2 cells were detected with western blot and reverse transcription polymerase chain reaction analyses. Caspase-3 activity was detected using a commercial assay, while protein levels of IL-6, IL-1β, and TNF-α were detected using specific enzyme-linked immunosorbent assays. NF-κB activity was detected with an electrophoretic mobility shift assay. Cell apoptosis was detected with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and flow cytometric analysis.

RESULTS

Cold I/R caused severe morphologic myocardial injury of heart grafts from wild type C57BL/c mice, whereas grafts from Hsp27 preservation showed less damage as demonstrated by decreased cell apoptosis/death and the preservation of the normal structure of the heart. Hsp27 inhibited I/R-induced injury as indicated by the reduction in cardiac troponin I activities and decreased cardiac tissue levels of the proinflammatory factors TNF-α, IL-1β, and IL-6. Hsp27 was further demonstrated to significantly inhibit nuclear translocation of p65 and p53 upregulated modulator of apoptosis (PUMA) expression.

CONCLUSIONS

These results suggested that the cardioprotective effect of Hsp27 could be due to the suppression of the myocardial inflammatory response and apoptosis by blocking the NF-κB-dependent pro-inflammatory and NF-κB-dependent PUMA signaling pathways.

PUMA decreases the growth of prostate cancer PC-3 cells independent of p53

PUMA (p53 upregulated modulator of apoptosis), a member of the B-cell lymphoma 2 (Bcl-2) protein family, is a pro-apoptotic protein. PUMA expression is modulated by the tumor suppressor p53. PUMA has a role in rapid cell death via p53-dependent and -independent mechanisms. To evaluate whether p53 is required for PUMA-mediated apoptosis in prostate cancer cells, p53 protein was silenced in human prostate cancer PC-3 cells by using p53 small interfering RNA (siRNA). The interference efficiency of p53 on RNA and protein levels was detected by reverse transcription-quantitative polymerase chain reaction and western blotting. Cell proliferation and p21 expression were subsequently examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and western blot analysis, respectively. p53-silenced or control PC-3 cells were transfected with pCEP4-(hemagglutinin)-PUMA plasmid, or non-carrier plasmid. Enzyme-linked immunosorbent assay was used to determine cell apoptosis by measuring histone release and caspase-3 activation, and MTT assay was used to measure cell viability. In addition, the expression of pro-apoptosis protein Bax and anti-apoptosis protein Bcl-2 were evaluated. The results of the present study revealed that p53 siRNA significantly suppressed p53 RNA and protein expression in PC-3 cells. Deficiency of p53 increased the cell growth rate and decreased p21 expression. However, PUMA overexpression remained able to induce apoptosis in p53-silenced and control cells by increasing Bax expression and decreasing Bcl-2 expression, leading to the activation of caspase-3. These results suggest that PUMA may mediate apoptosis of prostate cancer PC-3 cells, potentially independently of p53. Furthermore, PUMA gene treatment to induce cancer cell apoptosis may be more efficient compared with p53-dependent apoptosis, where loss of p53 expression or function may lead to limited efficacy of PUMA expression. Therefore, the present study proposes the significant hypothesis that increasing PUMA expression may be an effective approach for the treatment of prostate cancer, regardless of p53 status.

miR-29a differentially regulates cell survival in astrocytes from cornu ammonis 1 and dentate gyrus by targeting VDAC1

Neurons in the cornu ammonis 1 (CA1) region of the hippocampus are vulnerable to cerebral ischemia, while dentate gyrus (DG) neurons are more resistant. This effect is mediated by local astrocytes, and may reflect differences in subregional hippocampal expression of miR-29a. We investigated the role of miR-29a on survival of hippocampal astrocytes cultured selectively from CA1 and DG in response to glucose deprivation (GD). CA1 astrocytes exhibited more cell death and a greater decrease in miR-29a than DG astrocytes. A reciprocal change was observed in the mitochondrial voltage dependent cation channel-1 (VDAC1), a regulator of mitochondria and target of miR-29a. In CA1 astrocytes, increasing miR-29a decreased VDAC1 and improved cell survival, while knockdown of VDAC1 improved survival. Finally, the protective effect of miR-29a was eliminated by inhibition of miR-29a/VDAC1 binding. These findings suggest that the selective vulnerability of the CA1 to injury may be due in part to a limited miR-29a response in CA1 astrocytes, allowing a greater increase in VDAC1-mediated cellular dysfunction in CA1 astrocytes.

Post-traumatic administration of the p53 inactivator pifithrin-α oxygen analogue reduces hippocampal neuronal loss and improves cognitive deficits after experimental traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Neuronal apoptosis in the hippocampus has been detected after TBI. The hippocampal dysfunction may result in cognitive deficits in learning, memory, and spatial information processing. Our previous studies demonstrated that a p53 inhibitor, pifithrin-α oxygen analogue (PFT-α (O)), significantly reduced cortical cell death, which is substantial following controlled cortical impact (CCI) TBI, and improved neurological functional outcomes via anti-apoptotic mechanisms. In the present study, we examined the effect of PFT-α (O) on CCI TBI-induced hippocampal cellular pathophysiology in light of this brain region's role in memory. To investigate whether p53-dependent apoptosis plays a role in hippocampal neuronal loss and associated cognitive deficits and to define underlying mechanisms, SD rats were subjected to experimental CCI TBI followed by the administration of PFT-α or PFT-α (O) (2mg/kg, i.v.) or vehicle at 5h after TBI. Magnetic resonance imaging (MRI) scans were acquired at 24h and 7days post-injury to assess evolving structural hippocampal damage. Fluoro-Jade C was used to stain hippocampal sub-regions, including CA1 and dentate gyrus (DG), for cellular degeneration. Neurological functions, including motor and recognition memory, were assessed by behavioral tests at 7days post injury. p53, p53 upregulated modulator of apoptosis (PUMA), 4-hydroxynonenal (4-HNE), cyclooxygenase-IV (COX IV), annexin V and NeuN were visualized by double immunofluorescence staining with cell-specific markers. Levels of mRNA encoding for caspase-3, p53, PUMA, Bcl-2, Bcl-2-associated X protein (BAX) and superoxide dismutase (SOD) were measured by RT-qPCR. Our results showed that post-injury administration of PFT-α and, particularly, PFT-α (O) at 5h dramatically reduced injury volumes in the ipsilateral hippocampus, improved motor outcomes, and ameliorated cognitive deficits at 7days after TBI, as evaluated by novel object recognition and open-field test. PFT-α and especially PFT-α (O) significantly reduced the number of FJC-positive cells in hippocampus CA1 and DG subregions, versus vehicle treatment, and significantly decreased caspase-3 and PUMA mRNA expression. PFT-α (O), but not PFT-α, treatment significantly lowered p53 and elevated SOD2 mRNA expression. Double immunofluorescence staining demonstrated that PFT-α (O) treatment decreased p53, annexin V and 4-HNE positive neurons in the hippocampal CA1 region. Furthermore, PUMA co-localization with the mitochondrial maker COX IV, and the upregulation of PUMA were inhibited by PFT-α (O) after TBI. Our data suggest that PFT-α and especially PFT-α (O) significantly reduce hippocampal neuronal degeneration, and ameliorate neurological and cognitive deficits in vivo via antiapoptotic and antioxidative properties.

Cardiac arrest triggers hippocampal neuronal death through autophagic and apoptotic pathways

The mechanism of neuronal death induced by ischemic injury remains unknown. We investigated whether autophagy and p53 signaling played a role in the apoptosis of hippocampal neurons following global cerebral ischemia-reperfusion (I/R) injury, in a rat model of 8-min asphyxial cardiac arrest (CA) and resuscitation. Increased autophagosome numbers, expression of lysosomal cathepsin B, cathepsin D, Beclin-1, and microtubule-associated protein light chain 3 (LC3) suggested autophagy in hippocampal cells. The expression of tumor suppressor protein 53 (p53) and its target genes: Bax, p53-upregulated modulator of apoptosis (PUMA), and damage-regulated autophagy modulator (DRAM) were upregulated following CA. The p53-specific inhibitor pifithrin-α (PFT-α) significantly reduced the expression of pro-apoptotic proteins (Bax and PUMA) and autophagic proteins (LC3-II and DRAM) that generally increase following CA. PFT-α also reduced hippocampal neuronal damage following CA. Similarly, 3-methyladenine (3-MA), which inhibits autophagy and bafilomycin A1 (BFA), which inhibits lysosomes, significantly inhibited hippocampal neuronal damage after CA. These results indicate that CA affects both autophagy and apoptosis, partially mediated by p53. Autophagy plays a significant role in hippocampal neuronal death induced by cerebral I/R following asphyxial-CA.

Neuroprotection by triptolide against cerebral ischemia/reperfusion injury through the inhibition of NF-κB/PUMA signal in rats

Triptolide, an active compound extracted from the Chinese herb thunder god vine (Tripterygium wilfordii Hook F.), has potent antitumor activity. Recently, triptolide was found to have protective effects against acute cerebral ischemia/reperfusion (I/R) injury through inhibition of cell apoptosis. However, the regulatory mechanism of the effect remains unclear. We hypothesize that the regulatory mechanisms of triptolide are mediated by nuclear factor κB (NF-κB) and p53-upregulated-modulator-of-apoptosis signal inhibition. To verify this hypothesis, we occluded the middle cerebral artery in male rats to establish focal cerebral I/R model. The rats received triptolide or vehicle at the onset of reperfusion following middle cerebral artery occlusion. At 24 hours after reperfusion, neurological deficits, infarct volume, and cell apoptosis were evaluated. The expression levels of NF-κBp65, PUMA, and caspase-3 were determined by Western blot. Real-time polymerase chain reaction was used to determine the levels of NF-κBp65 mRNA, PUMA mRNA, and caspase-3 mRNA. NF-κB activity was determined by electrophoretic mobility shift assay. Apoptotic cells were detected using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. In I/R group, neurological deficit scores, cerebral infarct volume, expression of NF-κBp65, PUMA, caspase-3, NF-κB activity, and TUNEL-positive cells were found to be increased at 24 hours after I/R injury. The I/R/triptolide rats showed significantly better neurological deficit scores, decreased neural apoptosis, and reduced cerebral infarct volume. In addition, the expression of NF-κBp65, PUMA, caspase-3, and NF-κB activity was suppressed in the I/R/triptolide rats. These results indicate that the neuroprotective effects of triptolide during acute cerebral I/R injury are possibly related to the inhibition of apoptosis through suppression of NF-κB/PUMA signaling pathway.

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.

Exogenous p53 upregulated modulator of apoptosis (PUMA) decreases growth of lung cancer A549 cells

PURPOSE

To investigate the influence of exogenous p53 upregulated modulator of apoptosis (PUMA) expression on cell proliferation and apoptosis in human non-small cell lung cancer A549 cells and transplanted tumor cell growth in nude mice.

MATERIALS AND METHODS

A549 cells were divided into the following groups: control, non- carrier (NC), PUMA (transfected with pCEP4- (HA) 2-PUMA plasmid), DDP (10 μg/mL cisplatin treatment) and PUMA+DDP (transfected with pCEP4-(HA)2-PUMA plasmid and 10 μg/mL cisplatin treatment). The MTT method was used to detect the cell survival rate. Cell apoptosis rates were measured by flow cytometry, and PUMA, Bax and Bcl-2 protein expression levels were measured by Western blotting.

RESULTS

Compared to the control group, the PUMA, DDP and PUMA+DDP groups all had significantly decreased A549 cell proliferation (p<0.01), with the largest reduction in the PUMA+DDP group. Conversely, the apoptosis rates of the three groups were significantly increased (P<0.01), and the PUMA and DDP treatments were synergistic. Moreover, Bax protein levels significantly increased (p<0.01), while Bcl-2 protein levels significantly decreased (p<0.01). Finally, both the volume and the weights of transplanted tumors were significantly reduced (p<0.01), and the inhibition ratio of the PUMA+DDP group was significantly higher than in the single DDP or PUMA groups.

CONCLUSIONS

Exogenous PUMA effectively inhibited lung cancer A549 cell proliferation and transplanted tumor growth by increasing Bax protein levels and reducing Bcl-2 protein levels.

Pifithrin-α provides neuroprotective effects at the level of mitochondria independently of p53 inhibition

Impaired mitochondrial integrity and function are key features of intrinsic death pathways in neuronal cells. Therefore, key regulators of intrinsic death pathways acting upstream of mitochondria are potential targets for therapeutic approaches of neuroprotection. The tumor suppressor p53 is a well-established regulator of cellular responses towards different kinds of lethal stress, including oxidative stress. Recent reports suggested that p53 may affect mitochondrial integrity and function through both, transcriptional activation of mitochondria-targeted pro-death proteins and direct effects at the mitochondrial membrane. In the present study, we compared the effects of pharmacological inhibition of p53 by pifithrin-α with those of selective p53 gene silencing by RNA interference. Using MTT assay and real-time cell impedance measurements we confirmed the protective effect of both strategies against glutamate-induced oxidative stress in immortalized mouse hippocampal HT-22 neurons. Further, we observed full restoration of mitochondrial membrane potential and inhibition of glutamate-induced mitochondrial fragmentation by pifithrin-α which was, in contrast, not achieved by p53 gene silencing. Downregulation of p53 by siRNA decreased p53 transcriptional activity and reduced expression levels of p21 mRNA, while pifithrin-α did not affect these endpoints. These results suggest a neuroprotective effect of pifithrin-α which occurred at the level of mitochondria and independently of p53 inhibition.

Post-trauma administration of the pifithrin-α oxygen analog improves histological and functional outcomes after experimental traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Programmed death of neuronal cells plays a crucial role in acute and chronic neurodegeneration following TBI. The tumor suppressor protein p53, a transcription factor, has been recognized as an important regulator of apoptotic neuronal death. The p53 inactivator pifithrin-α (PFT-α) has been shown to be neuroprotective against stroke. A previous cellular study indicated that PFT-α oxygen analog (PFT-α (O)) is more stable and active than PFT-α. We aimed to investigate whether inhibition of p53 using PFT-α or PFT-α (O) would be a potential neuroprotective strategy for TBI. To evaluate whether these drugs protect against excitotoxicity in vitro, primary rat cortical cultures were challenged with glutamate (50mM) in the presence or absence of various concentrations of the p53 inhibitors PFT-α or PFT-α (O). Cell viability was estimated by LDH assay. In vivo, adult Sprague Dawley rats were subjected to controlled cortical impact (CCI, with 4m/s velocity, 2mm deformation). Five hours after injury, PFT-α or PFT-α (O) (2mg/kg, i.v.) was administered to animals. Sensory and motor functions were evaluated by behavioral tests at 24h after TBI. The p53-positive neurons were identified by double staining with cell-specific markers. Levels of mRNA encoding for p53-regulated genes (BAX, PUMA, Bcl-2 and p21) were measured by reverse transcription followed by real time-PCR from TBI animals without or with PFT-α/PFT-α (O) treatment. We found that PFT-α(O) (10 μM) enhanced neuronal survival against glutamate-induced cytotoxicity in vitro more effectively than PFT-α (10 μM). In vivo PFT-α (O) treatment enhanced functional recovery and decreased contusion volume at 24h post-injury. Neuroprotection by PFT-α (O) treatment also reduced p53-positive neurons in the cortical contusion region. In addition, p53-regulated PUMA mRNA levels at 8h were significantly reduced by PFT-α (O) administration after TBI. PFT-α (O) treatment also decreased phospho-p53 positive neurons in the cortical contusion region. Our data suggest that PFT-α (O) provided a significant reduction of cortical cell death and protected neurons from glutamate-induced excitotoxicity in vitro, as well as improved neurological functional outcome and reduced brain injury in vivo via anti-apoptotic mechanisms. The inhibition of p53-induced apoptosis by PFT-α (O) provides a useful tool to evaluate reversible apoptotic mechanisms and may develop into a novel therapeutic strategy for TBI.

Buyang Huanwu Decoction fraction protects against cerebral ischemia/reperfusion injury by attenuating the inflammatory response and cellular apoptosis

Buyang Huanwu Decoction fraction extracted from Buyang Huanwu Decoction contains saponins of Astragalus, total paeony glycoside and safflower flavones. The aim of this study was to demonstrate the neuroprotective effect and mechanism of Buyang Huanwu Decoction fraction on ischemic injury both in vivo and in vitro. In vivo experiments showed that 50-200 mg/kg Buyang Huanwu Decoction fraction reduced infarct volume and pathological injury in ischemia/reperfusion rats, markedly inhibited expression of nuclear factor-κB and tumor necrosis factor-α and promoted nestin protein expression in brain tissue. Buyang Huanwu Decoction fraction (200 mg/kg) exhibited significant effects, which were similar to those of 100 mg/kg Ginkgo biloba extract. In vitro experimental results demonstrated that 10-100 mg/L Buyang Huanwu Decoction fraction significantly improved cell viability, decreased the release of lactate dehydrogenase and malondialdehyde levels, and inhibited the rate of apoptosis in HT22 cells following oxygen-glucose deprivation. Buyang Huanwu Decoction fraction (100 mg/L) exhibited significant effects, which were similar to those of 100 mg/L Ginkgo biloba extract. These findings suggest that Buyang Huanwu Decoction fraction may represent a novel, protective strategy against cerebral ischemia/reperfusion injury in rats and oxygen-glucose deprivation-induced damage in HT22 cells in vitro by attenuating the inflammatory response and cellular apoptosis.

Postconditioning mitigates cell death following oxygen and glucose deprivation in PC12 cells and forebrain reperfusion injury in rats

Postconditioning mitigates ischemia-induced cellular damage via a modified reperfusion procedure. Mitochondrial permeability transition (MPT) is an important pathophysiological change in reperfusion injury. This study explores the role of MPT modulation underlying hypoxic postconditioning (HPoC) in PC12 cells and studies the neuroprotective effects of ischemic postconditioning (IPoC) on rats. Oxygen-glucose deprivation (OGD) was performed for 10 hr on PC12 cells. HPoC was induced by three cycles of 10-min reoxygenation/10-min rehypoxia after OGD. The MPT inhibitor N-methyl-4-isoleucine cyclosporine (NIM811) and the MPT inducer carboxyatractyloside (CATR) were administered to selective groups before OGD. Cellular death was evaluated by flow cytometry and Western blot analysis. JC-1 fluorescence signal was used to estimate the mitochondrial membrane potential (△Ψm ). Transient global cerebral ischemia (tGCI) was induced via the two-vessel occlusion and hypotension method in male Sprague Dawley rats. IPoC was induced by three cycles of 10-sec reperfusion/10-sec reocclusion after index ischemia. HPoC and NIM811 administration attenuated cell death, cytochrome c release, and caspase-3 activity and maintained △Ψm of PC12 cells after OGD. The addition of CATR negated the protection conferred by HPoC. IPoC reduced neuronal degeneration and cytochrome c release and cleaved caspase-9 expression of hippocampal CA1 neurons in rats after tGCI. HPoC protected PC12 cells against OGD by modulating the MPT. IPoC attenuated degeneration of hippocampal neurons after cerebral ischemia.

The essential role of p53-up-regulated modulator of apoptosis (Puma) and its regulation by FoxO3a transcription factor in β-amyloid-induced neuron death

Neurodegeneration underlies the pathology of Alzheimer disease (AD). The molecules responsible for such neurodegeneration in AD brain are mostly unknown. Recent findings indicate that the BH3-only proteins of the Bcl-2 family play an essential role in various cell death paradigms, including neurodegeneration. Here we report that Puma (p53-up-regulated modulator of apoptosis), an important member of the BH3-only protein family, is up-regulated in neurons upon toxic β-amyloid 1-42 (Aβ(1-42)) exposure both in vitro and in vivo. Down-regulation of Puma by specific siRNA provides significant protection against neuron death induced by Aβ(1-42). We further demonstrate that the activation of p53 and inhibition of PI3K/Akt pathways induce Puma. The transcription factor FoxO3a, which is activated when PI3K/Akt signaling is inhibited, directly binds with the Puma gene and induces its expression upon exposure of neurons to oligomeric Aβ(1-42). Moreover, Puma cooperates with another BH3-only protein, Bim, which is already implicated in AD. Our results thus suggest that Puma is activated by both p53 and PI3K/Akt/FoxO3a pathways and cooperates with Bim to induce neuron death in response to Aβ(1-42).

Role of Astrocytes in Delayed Neuronal Death: GLT-1 and its Novel Regulation by MicroRNAs

Astrocytes have been shown to protect neurons from delayed neuronal death and increase their survival in cerebral ischemia. One of the main mechanisms of astrocyte protection is rapid removal of excess glutamate from synaptic sites by astrocytic plasma membrane glutamate transporters such as GLT-1/EAAT-2, reducing excitotoxicity. Astrocytic mitochondrial function is essential for normal GLT-1 function. Manipulating astrocytic mitochondrial and GLT-1 function is thus an important strategy to enhance neuronal survival and improve outcome following cerebral ischemia. Increasing evidence supports the involvement of microRNAs (miRNA), some of them being astrocyte-enriched, in the regulation of cerebral ischemia. This chapter will first update the information about astrocytes, GLT-1, astrocytic mitochondria, and delayed neuronal death. Then we will focus on two recently reported astrocyte-enriched miRNAs (miR-181 and miR-29 families), their effects on astrocytic mitochondria and GLT-1 as well as on outcome after cerebral ischemia.

MicroRNAs affect BCL-2 family proteins in the setting of cerebral ischemia

The BCL-2 family is centrally involved in the mechanism of cell death after cerebral ischemia. It is well known that the proteins of the BCL-2 family are key regulators of apoptosis through controlling mitochondrial outer membrane permeabilization. Recent findings suggest that many BCL-2 family members are also directly involved in controlling transmission of Ca(2+) from the endoplasmic reticulum (ER) to mitochondria through a specialization called the mitochondria-associated ER membrane (MAM). Increasing evidence supports the involvement of microRNAs (miRNAs), some of them targeting BCL-2 family proteins, in the regulation of cerebral ischemia. In this mini-review, after highlighting current knowledge about the multiple functions of BCL-2 family proteins and summarizing their relationship to outcome from cerebral ischemia, we focus on the regulation of BCL-2 family proteins by miRNAs, especially miR-29 which targets multiple BCL-2 family proteins.

Astrocyte-enriched miR-29a targets PUMA and reduces neuronal vulnerability to forebrain ischemia

Following transient forebrain ischemia, astrocytes play a key role in determining whether or not neurons in the hippocampal CA1 sector go on to die in a delayed fashion. MicroRNAs (miRNAs) are a novel class of RNAs that control gene expression at the post-transcriptional level and the miR-29 family is highly expressed in astrocytes. In this study we assessed levels of miR-29 in hippocampus following forebrain ischemia and found that after transient forebrain ischemia and short periods of reperfusion, miR-29a significantly increased in the resistant dentate gyrus, but decreased in the vulnerable CA1 region of the hippocampus. We demonstrate that miR-29a targets BH3-only proapoptotic BCL2 family member PUMA by luciferase reporter assay and by Western blot. Comparing primary neuron and astrocyte cultures, and postnatal brain, we verified the strongly astrocytic expression of miR-29a. We further found that miR-29a mimic protects and miR-29a inhibitor aggravates cell injury and mitochondrial function after ischemia-like stresses in vitro. Lastly, by overexpressing and reducing miR-29a we demonstrate the protective effect of miR-29a on CA1 delayed neuronal death after forebrain ischemia. Our data suggest that by targeting a pro-apoptotic BCL2 family member, increasing levels of miR-29a might emerge as a strategy for protection against ischemia-reperfusion injury.

microRNAs: innovative targets for cerebral ischemia and stroke

Stroke is one of the leading causes of death and disability worldwide. Because stroke is a multifactorial disease with a short therapeutic window many clinical stroke trials have failed and the only currently approved therapy is thrombolysis. MicroRNAs (miRNA) are endogenously expressed noncoding short single-stranded RNAs that play a role in the regulation of gene expression at the post-transcriptional level, via degradation or translational inhibition of their target mRNAs. The study of miRNAs is rapidly growing and recent studies have revealed a significant role of miRNAs in ischemic disease. miRNAs are especially important candidates for stroke therapeutics because of their ability to simultaneously regulate many target genes and since to date targeting single genes for therapeutic intervention has not yet succeeded in the clinic. Although there are already quite a few review articles about miRNA in ischemic heart disease, much less is currently known about miRNAs in cerebral ischemia. This review summarizes current knowledge about miRNAs and cerebral ischemia, focusing on the role of miRNAs in ischemia, both changes in expression and identification of potential targets, as well as the potential of miRNAs as biomarkers and therapeutic targets in cerebral ischemia.

Defining the role of the Bcl-2 family proteins in Huntington's disease

B-cell lymphoma 2 (Bcl-2) family proteins regulate survival, mitochondria morphology dynamics and metabolism in many cell types including neurons. Huntington's disease (HD) is a neurodegenerative disorder caused by an expanded CAG repeat tract in the IT15 gene that encodes for the protein huntingtin (htt). In vitro and in vivo models of HD and HD patients' tissues show abnormal mitochondrial function and increased cell death rates associated with alterations in Bcl-2 family protein expression and localization. This review aims to draw together the information related to Bcl-2 family protein alterations in HD to decipher their potential role in mutated htt-related cell death and mitochondrial dysfunction.

Role of neural precursor cells in promoting repair following stroke

Stem cell-based therapies for the treatment of stroke have received considerable attention. Two broad approaches to stem cell-based therapies have been taken: the transplantation of exogenous stem cells, and the activation of endogenous neural stem and progenitor cells (together termed neural precursors). Studies examining the transplantation of exogenous cells have demonstrated that neural stem and progenitor cells lead to the most clinically promising results. Endogenous activation of neural precursors has also been explored based on the fact that resident precursor cells have the inherent capacity to proliferate, migrate and differentiate into mature neurons in the uninjured adult brain. Studies have revealed that these neural precursor cell behaviours can be activated following stroke, whereby neural precursors will expand in number, migrate to the infarct site and differentiate into neurons. However, this innate response is insufficient to lead to functional recovery, making it necessary to enhance the activation of endogenous precursors to promote tissue repair and functional recovery. Herein we will discuss the current state of the stem cell-based approaches with a focus on endogenous repair to treat the stroke injured brain.

Increased vulnerability of hippocampal CA1 neurons to hypoperfusion in ataxia and male sterility (AMS) mouse

The nna1 gene mutation is associated with spontaneous degeneration of cerebellar Purkinje cells and germ cells in Ataxia and Male Sterility (AMS) mouse. Since nna1 is also expressed in hippocampal neurons, we investigated their vulnerability to hypoperfusion in AMS mouse. Eight-week-old male wild type (WT) and AMS mice were subjected to bilateral common carotid artery occlusion (BCCAO) for 10 min and sacrificed 1, 3, 7 and 28 days after BCCAO. Nissl staining revealed the neuronal cell loss and pyknotic change in the CA1 of AMS mice. TUNEL(+) apoptotic cells were found in the area at 7 days in AMS mice. Bcl-2 mRNA and protein in WT hippocampus were increased, while they were not increased in AMS. Bax mRNA was increased in AMS. Moreover, Bax activation was immunohistochemically demonstrated only in AMS at 3 and 7 days after BCCAO. An oxidative DNA damage marker, 8-hydroxydeoxyguanosine-positive cells were increased in both strains at 1 day; decreased in WT at 3 days but remained high in AMS. BCCAO increased glutathione, an antioxidant, in WT, but not in AMS at 3 days. The mRNA level of mitochondrial uncoupling protein 2, a regulator of oxidative stress, was increased only in WT at 1 day. Nna1 mRNA was similarly expressed in WT and AMS, but the protein was undetectable in AMS. Thus, our results indicate the increased vulnerability of hippocampal CA1 neurons of AMS mice to cerebral hypoperfusion could be due to an imbalance between oxidative stress and antioxidative defense system.

Neuronal oxidative stress in acute ischemic stroke: sources and contribution to cell injury

Oxidative stress has emerged as a key deleterious factor in brain ischemia and reperfusion. Malfunction of the oxidative respiratory chain in mitochondria combines with the activation of cytoplasmic oxidases to generate a burst of reactive oxygen species that cannot be neutralised by the cell's antioxidant mechanisms. As a result, oxidative stress contributes directly to necrosis and apoptosis through a number of pathways in ischemic tissue. Pharmacological intervention with antioxidants or enhancers of endogenous antioxidant molecules is proving to be difficult due to the speed and scope of the oxidative impact. Additionally, the knowledge that neuronal fate in ischemic stroke is tightly linked to other brain cells like endothelial cells and astrocytes has shifted the focus of study from isolated neurons to the neurovascular unit. For this reason, recent efforts have been directed towards understanding the sources of oxidative stress in ischemic stroke and attempting to block the generation of oxygen radicals.