Role of caspase-3 activation in cerebral ischemia-induced neurodegeneration in adult and neonatal brain

Serum Caspase-3 Levels as a Predictive Molecular Biomarker for Acute Ischemic Stroke

Caspases are key players in the apoptotic process and have been found to contribute to the pathogenesis of a variety of diseases, including neurological disorders such as ischemic stroke. This study aimed to investigate the serum levels of Caspase-3 in patients with acute ischemic stroke (AIS) and in control patients without ischemic events. Moreover, we explored any potential associations with the clinical outcomes of AIS. We enrolled 69 consecutive patients with clinical signs and symptoms of AIS in the presence of a negative CT scan who presented themselves at the Clinical Neurological Department from the Emergency Clinical Hospital of Galati within the first 24 h of symptom onset. The control group comprised 68 patients without cerebral ischemic pathologies. A comparison of the two groups showed significantly higher levels of caspase-3 at 24 and 48 h after hospital admission. No significant associations between caspase-3 levels and clinical features of AIS were seen. However, in a subgroup analysis conducted on patients with moderate/severe and severe stroke, lower levels of caspase-3 were associated with early mortality. Caspase-3 levels did not directly correlate with AIS severity or prognosis when considering all AIS patients. In patients with moderate to severe National Institute of Health Stroke Scale (NIHSS) scores, caspase-3 might be a prognostic indicator of early death. Further studies are required to confirm these results and further explore the mechanisms behind these findings.

Pathophysiological Mechanisms Involved in Overactive Bladder/Detrusor Overactivity

Purpose of Review

To examine the latest published findings on the pathophysiological mechanisms involved in the development of overactive bladder (OAB) and detrusor overactivity (DO), and to identify common pathways linked to the risk factors associated with these conditions.

Recent Findings

Evidence is accumulating, both clinical and experimental, that many of the factors linked to the development of OAB/DO, including ageing, bladder outlet obstruction, psychological stress, and obesity are associated with reduced bladder blood flow. This induces local tissue inflammation with cytokine release and enhanced oxidative stress, ultimately resulting in altered detrusor sensitivity, detrusor hypertrophy and fibrosis, together with afferent hypersensitivity. These mechanisms would explain the symptoms of urgency and frequency observed in OAB patients. Although not a characteristic of OAB, undetected low level bacterial infections of the bladder have been proposed to explain the OAB symptoms in patients resistant to standard treatments. In this condition, inflammatory responses without reductions in perfusion activate the inflammatory pathways.

Summary

Evidence is mounting that poor bladder perfusion and local inflammatory responses are central mechanisms involved in the development of OAB/DO. As our understanding of these pathophysiological mechanisms advances, new avenues for drug development will be identified and ultimately treatment may become more individualized depending on the particular pathway involved and the drugs available.

Neuroprotective effect of a novel brain-derived peptide, HIBDAP, against oxygen-glucose deprivation through inhibition of apoptosis in PC12 cells

BACKGROUND

The effect of a novel brain-derived peptide, hypoxic-ischemic brain damage associated peptide (HIBDAP), on apoptosis after oxygen-glucose deprivation (OGD) in PC12 cells was investigated.

METHODS

The HIBDAP sequence (HSQFIGYPITLFVEKER) was coupled with the carrier peptide of the transactivator of transcription (TAT) sequence (YGRKKRRQRRR). FITC-labelled TAT-HIBDAP was observed by fluorescence microscopy. After TAT-HIBDAP treatment and OGD treatment, the PC12 cell apoptosis rate was analysed using lactate dehydrogenase (LDH) leakage and Annexin V-fluorescein isothiocyanate (FITC) assays. Mitochondrial membrane potential (ΔΨm) was examined by fluorescence microscopy. Protein expression of apoptotic factors was examined by Western blotting.

RESULTS

FITC-labelled TAT-HIBDAP entered the PC12 cell nucleus. Compared with the OGD group, TAT-HIBDAP at low concentrations (1 µM, 5 µM, 10 µM) significantly reduced the apoptosis rate of PC12 cells (except at 20 µM); 5 µM TAT-HIBDAP had the most obvious effect. There were remarkable increases in ΔΨm at different concentrations (1 µM, 5 µM, 10 µM, 20 µM) of TAT-HIBDAP pretreatment, and 5 µM TAT-HIBDAP also had the most obvious effect. TAT-HIBDAP reversed the increased ratio of Bax/Bcl-2 and activation of Caspase-3 induced by OGD.

CONCLUSION

TAT-HIBDAP is resistant to OGD-induced PC12 cell apoptosis by regulating the Bax/Bcl-2/Caspase-3 pathway, which may provide a novel therapeutic strategy for neonatal HIBD.

Formation of Double Stranded RNA Provokes Smooth Muscle Contractions and Structural Modifications in Bladder Ischemia

Purpose

Growing evidence suggests that ischemia provokes detrusor overactivity and degenerative responses in the bladder. Underlying mechanisms appear to involve modification of smooth muscle contractile rudiments by hypoxia, redox, cellular stress and cell survival signaling. Downstream pathways of cellular stress and stress response molecules eliciting bladder dysfunction in ischemia remain largely elusive. Our goal was to define the role of double stranded RNA (dsRNA), a stress response molecule provoked by redox, in ischemia mediated bladder dysfunction.

Methods

A rat model of pelvic ischemia along with a cell culture hypoxia model were used to investigate the expression levels, functional consequences, structural aspects, and regulatory mechanisms of dsRNA in the bladder. Gene and protein expression were examined by reverse transcription polymerase chain reaction (RT-PCR), dot blot, and Western blotting, respectively. Tissue structure and function were assessed using histological staining and organ bath. Regulatory mechanisms were analyzed in cultured bladder smooth muscle cells.

Results

The data presented here provide the first evidence of the formation of dsRNA in the overactive bladder. dsRNA is a cellular stress response molecule that sensitizes smooth muscle and regulates inflammatory and degenerative rejoinders. Our data suggest that the production of dsRNA in the bladder is provoked by ischemia. Formation of dsRNA appears to augment bladder smooth muscle contractions and provoke fibrotic and apoptotic responses. Downstream actions of dsRNA in the bladder may involve upregulation of dsRNA-activated protein kinase R (PKR) and caspase-3, the executioner of apoptosis.

Conclusion

Activation of dsRNA/PKR pathway may play a role in sensitization of bladder smooth muscle cells to contractile stimuli, whereas dsRNA and caspase-3 crosstalk appear to modulate cellular stress and instigate degenerative responses in bladder ischemia. These observations suggest the role of dsRNA in bladder dysfunction and may open new perspectives to overcome overactive smooth muscle contractions and structural damage in the bladder.

Polydatin as a therapeutic alternative for central nervous system disorders: A systematic review of animal studies

Polydatin, or piceid, is a natural stilbene found in grapes, peanuts, and wines. Polydatin presents pharmacological activities, including neuroprotective properties, exerting preventive and/or therapeutic effects in central nervous system (CNS) disorders. In the present study, we summarize and discuss the neuroprotective effects of polydatin in CNS disorders and related pathological conditions in preclinical animal studies. A systematic review was performed by searching online databases, returning a total of 110 records, where 27 articles were selected and discussed here. The included studies showed neuroprotective effects of polydatin in experimental models of neurological disorders, including cerebrovascular disorders, Parkinson's disease, traumatic brain injuries, diabetic neuropathy, glioblastoma, and neurotoxicity induced by chemical agents. Most studies were focused on stroke (22.2%) and conducted in male rodents. The intervention protocol with polydatin was mainly acute (66.7%), with postdamage induction treatment being the most commonly used regimen (55.2%). Overall, polydatin ameliorated behavioral dysfunctions and/or promoted neurological function by virtue of its antioxidant and antiinflammatory properties. In summary, this review offers important scientific evidence for the neuroprotective effects and distinct pharmacological mechanisms of polydatin that not only enhances the present understanding but is also useful for the development of future preclinical and clinical investigations.

Macamide B Pretreatment Attenuates Neonatal Hypoxic-Ischemic Brain Damage of Mice Induced Apoptosis and Regulates Autophagy via the PI3K/AKT Signaling Pathway

Lepidium meyenii (maca) is an annual or biennial herb from South America that is a member of the genus Lepidium L. in the family Cruciferae. This herb possesses antioxidant and antiapoptotic activities, enhances autophagy functions, prevents cell death, and protects neurons from ischemic damage. Macamide B, an effective active ingredient of maca, exerts a neuroprotective effect on neonatal hypoxic-ischemic brain damage (HIBD), but the mechanism underlying its neuroprotective effect is not yet known. The purpose of this study was to explore the effect of macamide B on HIBD-induced autophagy and apoptosis and its potential neuroprotective mechanism. The modified Rice-Vannucci method was used to induce HIBD in 7-day-old (P7) macamide B- and vehicle-pretreated pups. TTC staining was performed to evaluate the cerebral infarct volume in pups, the brain water content was measured to evaluate the neurological function of pups, neurobehavioural testing was conducted to assess functional recovery after HIBD, TUNEL and FJC staining was performed to detect cellular autophagy and apoptosis, and Western blot analysis was used to detect the levels of proteins in the pro-survival phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) signaling pathway and autophagy and apoptosis-related proteins. Macamide B pretreatment significantly decreases brain damage and improves the recovery of neural function after HIBD. At the same time, macamide B pretreatment activates the PI3K/AKT signaling pathway after HIBD, enhances autophagy, and reduces hypoxic-ischemic (HI)-induced apoptosis. In addition, 3-methyladenine (3-MA), an inhibitor of the PI3K/AKT signaling pathway, significantly inhibits the increase in autophagy levels, aggravates HI-induced apoptosis, and reverses the neuroprotective effect of macamide B on HIBD. Our data indicate that a macamide B pretreatment might regulate autophagy through the PI3K/AKT signaling pathway, thereby reducing HIBD-induced apoptosis and exerting neuroprotective effects on neonatal HIBD. Macamide B may become a new drug for the prevention and treatment of HIBD.

Cellular Stress and Molecular Responses in Bladder Ischemia

The concept of bladder ischemia as a contributing factor to detrusor overactivity and lower urinary tract symptoms (LUTS) is evolving. Bladder ischemia as a consequence of pelvic arterial atherosclerosis was first documented in experimental models and later in elderly patients with LUTS. It was shown that early-stage moderate ischemia produces detrusor overactivity, while prolonged severe ischemia provokes changes consistent with detrusor underactivity. Recent studies imply a central role of cellular energy sensors, cellular stress sensors, and stress response molecules in bladder responses to ischemia. The cellular energy sensor adenosine monophosphate-activated protein kinase was shown to play a role in detrusor overactivity and neurodegeneration in bladder ischemia. The cellular stress sensors apoptosis signal-regulating kinase 1 and caspase-3 along with heat shock proteins were characterized as important contributing factors to smooth muscle structural modifications and apoptotic responses in bladder ischemia. Downstream pathways seem to involve hypoxia-inducible factor, transforming growth factor beta, vascular endothelial growth factor, and nerve growth factor. Molecular responses to bladder ischemia were associated with differential protein expression, the accumulation of non-coded amino acids, and post-translational modifications of contractile proteins and stress response molecules. Further insight into cellular stress responses in bladder ischemia may provide novel diagnostic and therapeutic targets against LUTS.

Green tea and its active compound epigallocathechin-3-gallate (EGCG) inhibit neuronal apoptosis in a middle cerebral artery occlusion (MCAO) model

OBJECTIVES

To determine the effect of green tea with the active ingredient epigallocathechin-3-gallate (EGCG) on the inhibition of apoptosis in the middle cerebral artery occlusion (MCAO) model.

METHODS

Four month old male Rattus norvegicus rats with a body weight of 200-275 g was used for the MCAO model and divided into five groups, and the treatment was carried out for 7 days. Before being sacrificed, the subject had 1 cc of blood drawn for high mobility group box 1 (HMGB-1) examination using enzyme-linked immunosorbent assay (ELISA), and after being sacrificed, the brain tissue specimen was taken to examine caspase-3 and B-cell lymphoma 3 (BCL-3) using immunohistochemistry methods.

RESULTS

There was no significant difference in HMGB-1 results for the treatment group compared to the control group (P1: 384.20 ± 231.72 [p = 0.553]; P2: 379.11 ± 268.4 [p = 0.526]; P3: 284, 87 ± 276.19 [p = 0.140]; P4: 435.32 ± 279.95 [p = 0.912]). There is a significant increase in BCL-2 expression between the treatment group compared to the control group (P1: 2.58 ± 0.51 [p = 0.04]; P2: 3.36 ± 0.50 [p<0.001]; P3: 4.00 ± 0.42 [p<0.001]; P4: 3.60 ± 0.52 [p<0.001]). There was a significant difference in caspase-3 expression compared to the control group in the P3 group (P1: 4.33 ± 0.49 [p = 0.652]; P2: 4.09 ± 0.30 [p = 0.136]; P3: 3.58 ± 0.51 [p = 0.01]; P4: 3.89 ± 0.42 [p = 0.063]). There is no correlation between HMGB-1 and caspase-3 (r = -0.063; p = 0.613) or BCL-2 (r = -0.106; p = 0.396). There is significant negative correlation between caspase-3 and BCL-2 (r = -0.459; p = 0.000).

CONCLUSIONS

Green tea with the active ingredient EGCG can inhibit neuronal cell death through the apoptotic pathway and not through the activation of HMGB-1.

Regulation of Cellular Stress Signaling in Bladder Ischemia

Introduction

The etiology of lower urinary tract symptoms in patients with non-obstructed non-neurogenic bladder remains largely unknown. Clinical studies divulged a significant correlation between reduced bladder blood flow and low bladder compliance. Animal models of bladder ischemia displayed structural modifications, characterized by loss of smooth muscle cells and accumulation of connective tissue in the bladder wall. The underlying mechanisms contributing to structural damage in bladder ischemia remain largely elusive. We previously reported that structural modifications in bladder ischemia correlate with upregulated stress proteins and cell survival signaling, suggesting the potential role of cellular stress in ischemic damage. However, stress response molecules and downstream pathways eliciting bladder damage in ischemia remain largely undetermined.

Methods

Using a rat model of bladder ischemia along with a cell culture hypoxia model, we investigated stress signaling molecules in the ischemic bladder tissues and hypoxic bladder smooth muscle cells.

Results

Our data suggest simultaneous upregulation of two major cellular stress-sensing molecules, namely apoptosis signal-regulating kinase 1 (ASK1) and caspase-3, implying degenerative insult via stress signaling pathway in bladder ischemia. Consistent with bladder ischemia, incubation of cultured human bladder smooth muscle cells at low oxygen tension increased both ASK1 and caspase-3 expression, insinuating hypoxia as an essential factor in ASK1 and caspase-3 upregulation. Gene deletion of ASK1 by ASK1 siRNA in cultured smooth muscle cells prevented caspase-3 upregulation by hypoxia, suggesting caspase-3 regulation by ASK1 under the ischemic/hypoxic conditions. Upregulation of ASK1 and caspase-3 in rat bladder ischemia and human bladder smooth muscle cell hypoxia was associated with subcellular structural modifications consistent with the initial stages of apoptotic insult.

Conclusion

Our data suggest that stress sensing by ASK1 and caspase-3 may contribute to subcellular structural damage and low bladder compliance. The ASK1/caspase-3 pathway may provide therapeutic targets against cellular stress and degenerative responses in bladder ischemia.

Bioactivity of Marine Natural Product Xyloketals

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Oceans can play a major role in supplying life-saving medicines in the world in future. Although considerable progress has been made in finding new medicines from marine sources, large efforts are still necessary to examine such molecules for clinical applications. Xyloketals are an important group of natural products with various powerful and prominent bioactivities such as inhibition of acetylcholine esterase, antioxidant activity, inhibition of L-calcium channels, radicalscavenging behavior, suppression of cell proliferation, reduction of neonatal hypoxic-ischemic brain injury, etc. This review describes the isolation and structural characterization of all xyloketal natural products giving major emphasis on their bioactivity.

Lupeol Alleviates Cerebral Ischemia-Reperfusion Injury in Correlation with Modulation of PI3K/Akt Pathway

BACKGROUND/AIM

This study aimed to investigate the effect and mechanism of lupeol on cerebral ischemia-reperfusion injury in rats.

METHODS

The effects of lupeol on cerebral infarction, cerebral water content, neurological symptoms and cerebral blood flow in rats were evaluated. Nissl staining was carried out to assess the neuronal damage of ischemic brain after I/R in rats. Apoptosis of ischemic brain neurons after I/R was detected by TUNEL staining. Western blotting was carried out to detect the effects of lupeol on the expression of p-PDK1, p-Akt, pc-Raf, p-BAD, cleaved caspase-3 and p-PTEN.

RESULTS

Lupeol significantly increased cerebral blood flow after I/R in rats, reduced brain water content and infarct volume, and decreased neurological function scores. It significantly reduced neuronal damage after I/R in rats, and significantly reduced neuronal cell loss. PI3K inhibitor (LY294002) can eliminate the effect of lupeol on I/R in rats. In addition, lupeol significantly increased the protein expression of p-PDK1, p-Akt, pc-Raf, p-BAD, and down-regulated the expression of cleaved caspase-3. LY294002 reversed the effects of lupeol on the expression of PI3K/Akt signaling pathway-related proteins and cleaved caspase-3 after I/R in rats.

CONCLUSION

Lupeol had significant neuroprotective effects on brain I/R injury and neuronal apoptosis, and its mechanism may be related to the activation of PI3K/Akt signaling pathway.

Propofol Suppresses Proliferation, Migration, Invasion And Promotes Apoptosis By Upregulating microRNA-140-5p In Gastric Cancer Cells

Purpose

This study aimed to investigate the anti-tumor effect of propofol on gastric cancer (GC) and its underlying mechanisms.

Patients and methods

SGC-7901 and MKN45 cells were transfected and divided into the following groups: Control group, Propofol group, Propofol+miR-140-5p inhibitor group and miR-140-5p inhibitor group. Moreover, cell proliferation, apoptosis, migration and invasion of SGC-7901 and MKN45 cells were evaluated by BrdU incorporation assay, Annexin V-FITC/PI double staining assay, wound healing assay and transwell assay, respectively. The mRNA expressions of matrix metalloproteinase 2 (MMP-2) and MMP-9 were detected by qRT-PCR. Cleaved caspase-3, Bcl-2, MMP-2 and MMP-9 expressions were detected by Western blot.

Results

Propofol inhibited cell proliferation, migration and invasion, but promoted cell apoptosis in SGC-7901 and MKN45 cells. Propofol also elevated the expression of miR-140-5p. Suppression of miR-140-5p could reverse the effects of propofol on the biological behavior of SGC-7901 and MKN45 cells. Meanwhile, propofol treatment increased the expression of cleaved caspase-3 but decreased Bcl-2, MMP-2 and MMP-9 in SGC-7901 and MKN45 cells. The expression of cleaved caspase-3 was downregulated while Bcl-2, MMP-2 and MMP-9 were upregulated by miR-140-5p suppression.

Conclusion

Propofol could inhibit cell proliferation, migration and invasion, as well as promote cell apoptosis by upregulating miR-140-5p in gastric cancer cells.

Cleaved β-Actin May Contribute to DNA Fragmentation Following Very Brief Focal Cerebral Ischemia

Our previous study demonstrated caspase independent DNA fragmentation after very brief cerebral ischemia, the mechanism of which was unclear. In this study, we explore whether actin is cleaved following focal cerebral ischemia, and whether these structural changes of actin might modulate DNA fragmentation observed following focal ischemia. Results showed that a cleaved β-actin fragment was identified in brains of rats 24 hours following 10-minute and 2-hour focal ischemia. Though granzyme B and caspase-3 cleaved β-actin in vitro, the fragment size of β-actin cleaved by granzyme B was the same as those found after 10-minute and 2-hour focal ischemia. This was consistent with increases of granzyme B activity after 10-minute and 2-hour ischemia compared with controls. Cerebral extracts from 10-minute and 2-hour ischemic brains degraded DNA in vitro. Adding intact β-actin to these samples completely abolished DNA degradation from the 10-minute ischemia group but not from the 2-hour ischemia group. We concluded that β-actin is likely cleaved by granzyme B by 24 hours following 10-minute and 2-hour focal cerebral ischemia. Intact β-actin inhibits DNase, and cleavage of β-actin activates DNase, which leads to DNA fragmentation observed in the brain following very brief focal ischemia.

Regulation of apoptosis in health and disease: the balancing act of BCL-2 family proteins

The loss of vital cells within healthy tissues contributes to the development, progression and treatment outcomes of many human disorders, including neurological and infectious diseases as well as environmental and medical toxicities. Conversely, the abnormal survival and accumulation of damaged or superfluous cells drive prominent human pathologies such as cancers and autoimmune diseases. Apoptosis is an evolutionarily conserved cell death pathway that is responsible for the programmed culling of cells during normal eukaryotic development and maintenance of organismal homeostasis. This pathway is controlled by the BCL-2 family of proteins, which contains both pro-apoptotic and pro-survival members that balance the decision between cellular life and death. Recent insights into the dynamic interactions between BCL-2 family proteins and how they control apoptotic cell death in healthy and diseased cells have uncovered novel opportunities for therapeutic intervention. Importantly, the development of both positive and negative small-molecule modulators of apoptosis is now enabling researchers to translate the discoveries that have been made in the laboratory into clinical practice to positively impact human health.

Hyperbaric Oxygen Protects Against Cerebral Damage in Permanent Middle Cerebral Artery Occlusion Rats and Inhibits Autophagy Activity

BACKGROUND

To investigate the effects of hyperbaric oxygen (HBO) on brain damage and autophagy levels in a rat model of middle cerebral artery occlusion.

METHODS

Neurologic injury and infarcted areas were evaluated according to the modified neurological severity score and 2,3,5-triphenyltetrazolium chloride staining. Western blots were used to determine beclin1, caspase-3 and fodrin1 protein expression. Beclin1 protein expression (an autophagy marker), positive terminal dUTP nick-end labeling (TUNEL) staining (an apoptosis marker) and positive propidium iodide (PI) staining (a necrosis marker) were detected by immunofluorescence.

RESULTS

Our results indicated that HBO could decrease the infarct volume and speed up the recovery of the neurological deficit scores in ischemic rats. Beclin1 was down-regulated after HBO treatment. HBO treatment inhibited fodrin1 protein expression and decreased the number of PI-positive cells. HBO also down-regulated caspase-3 and decreased the number of TUNEL-positive cells.

CONCLUSION

Cerebral ischemia caused early neuronal death due to necrosis, followed by delayed neuronal death due to apoptosis. Consequently, autophagy might be involved in all processes of ischemia. HBO could protect the brain against ischemic injury, and the possible mechanisms might be correlated with decreased autophagy activity and decreased apoptosis and necrosis levels.

Neuronal Cell Death

Neuronal cell death occurs extensively during development and pathology, where it is especially important because of the limited capacity of adult neurons to proliferate or be replaced. The concept of cell death used to be simple as there were just two or three types, so we just had to work out which type was involved in our particular pathology and then block it. However, we now know that there are at least a dozen ways for neurons to die, that blocking a particular mechanism of cell death may not prevent the cell from dying, and that non-neuronal cells also contribute to neuronal death. We review here the mechanisms of neuronal death by intrinsic and extrinsic apoptosis, oncosis, necroptosis, parthanatos, ferroptosis, sarmoptosis, autophagic cell death, autosis, autolysis, paraptosis, pyroptosis, phagoptosis, and mitochondrial permeability transition. We next explore the mechanisms of neuronal death during development, and those induced by axotomy, aberrant cell-cycle reentry, glutamate (excitoxicity and oxytosis), loss of connected neurons, aggregated proteins and the unfolded protein response, oxidants, inflammation, and microglia. We then reassess which forms of cell death occur in stroke and Alzheimer's disease, two of the most important pathologies involving neuronal cell death. We also discuss why it has been so difficult to pinpoint the type of neuronal death involved, if and why the mechanism of neuronal death matters, the molecular overlap and interplay between death subroutines, and the therapeutic implications of these multiple overlapping forms of neuronal death.

Vitexin protects against hypoxic-ischemic injury via inhibiting Ca2+/Calmodulin-dependent protein kinase II and apoptosis signaling in the neonatal mouse brain

Neonatal hypoxic-ischemic is a major cause of death and disability in neonates. In this study, we suggest for the first time that pretreatment with vitexin may suppress a pro-apoptotic signaling pathway in hypoxic-ischemic neuronal injury in neonates by inhibition of the phosphorylation of Ca²⁺/Calmodulin-dependent protein kinase II. Here we found that vitexin pretreatment reduced brain infarct volume in a dose-dependent manner. In addition, vitexin decreased the number of TUNEL-positive cells and brain atrophy. Furthermore, vitexin improved neurobehavioral outcomes. Vitexin also reduced oxygen glucose deprivation-induced neuronal injury and calcium entry. Vitexin pretreatment increased the Bcl-2/Bax protein ratio and decreased phosphorylation of Ca²⁺/Calmodulin-dependent protein kinase II and NF-κB, cleaved caspase-3 protein expression 24 hours after injury. Our data indicate that pretreatment with vitexin protects against neonatal hypoxic-ischemic brain injury and thus has potential as a treatment for hypoxic-ischemic brain injury.

Cell Death in the Developing Brain after Hypoxia-Ischemia

Perinatal insults such as hypoxia–ischemia induces secondary brain injury. In order to develop the next generation of neuroprotective therapies, we urgently need to understand the underlying molecular mechanisms leading to cell death. The cell death mechanisms have been shown to be quite different in the developing brain compared to that in the adult. The aim of this review is update on what cell death mechanisms that are operating particularly in the setting of the developing CNS. In response to mild stress stimuli a number of compensatory mechanisms will be activated, most often leading to cell survival. Moderate-to-severe insults trigger regulated cell death. Depending on several factors such as the metabolic situation, cell type, nature of the stress stimulus, and which intracellular organelle(s) are affected, the cell undergoes apoptosis (caspase activation) triggered by BAX dependent mitochondrial permeabilzation, necroptosis (mixed lineage kinase domain-like activation), necrosis (via opening of the mitochondrial permeability transition pore), autophagic cell death (autophagy/Na⁺, K⁺-ATPase), or parthanatos (poly(ADP-ribose) polymerase 1, apoptosis-inducing factor). Severe insults cause accidental cell death that cannot be modulated genetically or by pharmacologic means. However, accidental cell death leads to the release of factors (damage-associated molecular patterns) that initiate systemic effects, as well as inflammation and (regulated) secondary brain injury in neighboring tissue. Furthermore, if one mode of cell death is inhibited, another route may step in at least in a scenario when upstream damaging factors predominate over protective responses. The provision of alternative routes through which the cell undergoes death has to be taken into account in the hunt for novel brain protective strategies.

Poststroke Induction of α-Synuclein Mediates Ischemic Brain Damage

α-Synuclein (α-Syn), one of the most abundant proteins in the CNS, is known to be a major player in the neurodegeneration observed in Parkinson's disease. We currently report that transient focal ischemia upregulates α-Syn protein expression and nuclear translocation in neurons of the adult rodent brain. We further show that knockdown or knock-out of α-Syn significantly decreases the infarction and promotes better neurological recovery in rodents subjected to focal ischemia. Furthermore, α-Syn knockdown significantly reduced postischemic induction of phospho-Drp1, 3-nitrotyrosine, cleaved caspase-3, and LC-3 II/I, indicating its role in modulating mitochondrial fragmentation, oxidative stress, apoptosis, and autophagy, which are known to mediate poststroke neuronal death. Transient focal ischemia also significantly upregulated serine-129 (S129) phosphorylation (pα-Syn) of α-Syn and nuclear translocation of pα-Syn. Furthermore, knock-out mice that lack PLK2 (the predominant kinase that mediates S129 phosphorylation) showed better functional recovery and smaller infarcts when subjected to transient focal ischemia, indicating a detrimental role of S129 phosphorylation of α-Syn. In conclusion, our studies indicate that α-Syn is a potential therapeutic target to minimize poststroke brain damage.

SIGNIFICANCE STATEMENT

Abnormal aggregation of α-synuclein (α-Syn) has been known to cause Parkinson's disease and other chronic synucleinopathies. However, even though α-Syn is linked to pathophysiological mechanisms similar to those that produce acute neurodenegerative disorders, such as stroke, the role of α-Syn in such disorder is not clear. We presently studied whether α-Syn mediates poststroke brain damage and more importantly whether preventing α-Syn expression is neuroprotective and leads to better physiological and functional outcome after stroke. Our study indicates that α-Syn is a potential therapeutic target for stroke therapy.

Neonatal hypoxic ischemic encephalopathy: an update on disease pathogenesis and treatment

INTRODUCTION

Hypoxic ischemic encephalopathy (HIE) is the most important reason for morbidity and mortality in term-born infants. Understanding pathophysiology of the brain damage is essential for the early detection of patients with high risk for HIE and development of strategies for their treatments. Areas covered: This review discusses pathophysiology of the neonatal HIE and its treatment options, including hypothermia, melatonin, allopurinol, topiramate, erythropoietin, N-acetylcyctein, magnesium sulphate and xenon. Expert commentary: Several clinical studies have been performed in order to decrease the risk of brain injury due to difficulties in the early diagnosis and treatment, and to develop strategies for better long-term outcomes. Although currently standard treatment methods include therapeutic hypothermia for neonates with moderate to severe HIE, new supportive options are needed to enhance neuroprotective effects of the hypothermia, which should aim to reduce production of the free radicals and to have anti-inflammatory and anti-apoptotic actions.

Tideglusib, a chemical inhibitor of GSK3β, attenuates hypoxic-ischemic brain injury in neonatal mice

BACKGROUND

Hypoxia-ischemia is an important cause of brain injury and neurological morbidity in the newborn infants. The activity of glycogen synthase kinase-3β (GSK-3β) is up-regulated following neonatal stroke. Tideglusib is a GSK-3β inhibitor which has neuroprotective effects against neurodegenerative diseases in clinical trials. However, the effect of tideglusib on hypoxic-ischemic (HI) brain injury in neonates is still unknown.

METHODS

Postnatal day 7 (P7) mouse pups subjected to unilateral common carotid artery ligation followed by 1h of hypoxia or sham surgery was performed. HI animals were administered tideglusib (5mg/kg) or vehicle intraperitoneally 20min prior to the onset of ischemia. The brain infarct volume and whole brain images, were used in conjunction with Nissl staining to evaluate the protective effects of tideglusib. Protein levels of glial fibrillary acidic protein (GFAP), Notch1, cleaved caspase-3/9, phosphorylated signal transducer and activator of transcription 3 (STAT3), GSK-3β and protein kinase B (Akt) were detected to identify potentially involved molecules.

RESULTS

Tideglusib significantly reduced cerebral infarct volume at both 24h and 7days after HI injury. Tideglusib also increased phosphorylated GSK-3β(Ser9) and Akt(Ser473), and reduced the expression of GFAP and p-STAT3(Tyr705). In addition, pretreatment with tideglusib also enhanced the protein level of Notch1. Moreover, tideglusib reduced the cleavage of pro-apoptotic signal caspase proteins, including caspase 3 and caspase 9 following HI.

CONCLUSION

These results indicate that tideglusib shows neuroprotection against hypoxic-ischemic brain injury in neonatal mice.

GENERAL SIGNIFICANCE

Tideglusib is a potential compound for the prevention or treatment of hypoxic-ischemic brain injury in neonates.

Neuronal death after perinatal cerebral hypoxia-ischemia: Focus on autophagy-mediated cell death

Neonatal hypoxic-ischemic encephalopathy is a critical cerebral event occurring around birth with high mortality and neurological morbidity associated with long-term invalidating sequelae. In view of the great clinical importance of this condition and the lack of very efficacious neuroprotective strategies, it is urgent to better understand the different cell death mechanisms involved with the ultimate aim of developing new therapeutic approaches. The morphological features of three different cell death types can be observed in models of perinatal cerebral hypoxia-ischemia: necrotic, apoptotic and autophagic cell death. They may be combined in the same dying neuron. In the present review, we discuss the different cell death mechanisms involved in neonatal cerebral hypoxia-ischemia with a special focus on how autophagy may be involved in neuronal death, based: (1) on experimental models of perinatal hypoxia-ischemia and stroke, and (2) on the brains of human neonates who suffered from neonatal hypoxia-ischemia.

Matrine attenuates focal cerebral ischemic injury by improving antioxidant activity and inhibiting apoptosis in mice

Matrine, an active constituent of the Chinese herb, Sophora flavescens Ait., and it is known for its antioxidant, anti-inflammatory and antitumor activities. It has been demonstrated that matrine exerts protective effects against heart failure by decreasing the expression of caspase-3 and Bax, and increasing Bcl-2 levels. In this study, we aimed to determine whether these protective effects of matrine can be applied to cerebral ischemia. Following 7 successive days of treatment with matrine (7.5, 15 and 30 mg/kg) and nimodipine (1 mg/kg) by intraperitoneal injection, male Institute of Cancer Research (ICR) mice were subjected to middle cerebral artery occlusion (MCAO). Following reperfusion, the neurobehavioral score and brain infarct volume were estimated, and morphological changes were analyzed by hematoxylin and eosin (H&E) staining and electron microscopy. The percentage of apoptotic neurons was determined by flow cytometry. The levels of oxidative stress were assessed by measuring the levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT), and the total antioxidant capacity (T-AOC). Western blot analysis and immunofluorescence staining were used to examine the expression of the apoptosis-related proteins, caspase-3, Bax and Bcl-2. Our results revealed that pre-treatment with matrine significantly decreased the infarct volume and improved the neurological scores. Matrine also reduced the percentage of apoptotic neurons and relieved neuronal morphological damage. Furthermore, matrine markedly decreased the MDA levels, and increased SOD, GSH-Px and CAT activity, and T-AOC. Western blot analysis and immunofluorescence staining revealed a marked decrease in caspase-3 expression and an increase in the Bcl-2/Bax ratio in the group pre-treated with matrine (30 mg/kg) as compared with the vehicle-treated group. The findings of the present study demonstrate that matrine exerts neuroprotective effects against cerebral ischemic injury and that these effects are associated with its antioxidant and anti-apoptotic properties.

The role of excitotoxic programmed necrosis in acute brain injury

Excitotoxicity involves the excessive release of glutamate from presynaptic nerve terminals and from reversal of astrocytic glutamate uptake, when there is excessive neuronal depolarization. N-methyl-d-aspartate (NMDA) receptors, a subtype of glutamate receptor, are activated in postsynaptic neurons, opening their receptor-operated cation channels to allow Ca^2 + influx. The Ca^2 + influx activates two enzymes, calpain I and neuronal nitric oxide synthase (nNOS). Calpain I activation produces mitochondrial release of cytochrome c (cyt c), truncated apoptosis-inducing factor (tAIF) and endonuclease G (endoG), the lysosomal release of cathepsins B and D and DNase II, and inactivation of the plasma membrane Na⁺–Ca^2 + exchanger, which add to the buildup of intracellular Ca^2 +. tAIF is involved in large-scale DNA cleavage and cyt c may be involved in chromatin condensation; endoG produces internucleosomal DNA cleavage. The nuclear actions of the other proteins have not been determined. nNOS forms nitric oxide (NO), which reacts with superoxide (O₂⁻) to form peroxynitrite (ONOO⁻). These free radicals damage cellular membranes, intracellular proteins and DNA. DNA damage activates poly(ADP-ribose) polymerase-1 (PARP-1), which produces poly(ADP-ribose) (PAR) polymers that exit nuclei and translocate to mitochondrial membranes, also releasing AIF. Poly(ADP-ribose) glycohydrolase hydrolyzes PAR polymers into ADP-ribose molecules, which translocate to plasma membranes, activating melastatin-like transient receptor potential 2 (TRPM-2) channels, which open, allowing Ca^2 + influx into neurons. NADPH oxidase (NOX1) transfers electrons across cellular membranes, producing O₂⁻. The result of these processes is neuronal necrosis, which is a programmed cell death that is the basis of all acute neuronal injury in the adult brain.

TRPM7 inhibitor carvacrol protects brain from neonatal hypoxic-ischemic injury

BACKGROUND

Our previous study found that suppression of TRPM7 reduced neuronal death in adult rat ischemic brain injury. It was reported that carvacrol blocked TRPM7 and attenuated brain injury in an adult rat MCAO model. The effects of carvacrol on neonatal stroke remain unknown. This study investigated the effects of carvacrol on neuronal injury and behavioral impairment after hypoxia-ischemia in neonatal mice and the potential signaling pathway underlying these effects.

RESULTS

Carvacrol inhibited TRPM7 current in HEK293 cells over-expressing TRPM7 and TRPM7-like current in hippocampal neurons in a dose-dependent manner. Carvacrol (>200 μM) reduced OGD-induced neuronal injury in cortical neurons. 24 hours after HI, TRPM7 protein level in the ipsilateral hemisphere was significantly higher than in the contralateral hemisphere. Carvacrol (30 and 50 mg/kg) pre-treatment reduced brain infarct volume 24 hours after HI in a dose-dependent manner. Carvacrol pre-treatment also improved neurobehavioral outcomes. Furthermore, animals pre-treated with carvacrol had fewer TUNEL-positive cells in the brain compared to vehicle-treated animals 3 days after HI. Carvacrol pre-treatment also increased Bcl-2/Bax and p-Akt/t-Akt protein ratios and decreased cleaved caspase-3 protein expression 24 hours after HI.

CONCLUSIONS

Carvacrol pre-treatment protects against neonatal hypoxic-ischemic brain injury by reducing brain infarct volume, promoting pro-survival signaling and inhibiting pro-apoptotic signaling, as well as improving behavioral outcomes. The neuroprotective effect may be mediated by the inhibition of TRPM7 channel function. Carvacrol is a potential drug development target for the treatment of neonatal stroke.

Neuroprotection of Sevoflurane Against Ischemia/Reperfusion-Induced Brain Injury Through Inhibiting JNK3/Caspase-3 by Enhancing Akt Signaling Pathway

In this study, we investigated the neuroprotective effect of sevoflurane against ischemic brain injury and its underlying molecular mechanisms. Transient global brain ischemia was induced by 4-vessel occlusion in adult male Sprague-Dawley rats. The rats were pretreated with sevoflurane alone or sevoflurane combined with LY294002/wortmannin (selective inhibitor of PI3K) before ischemia. Cresyl violet staining was used to examine the survival of hippocampal CA1 pyramidal neurons. Immunoblotting and immunoprecipitation were performed to measure the phosphorylation of Akt1, PRAS40, ASK1, and JNK3 and the expression of cleaved-caspase-3. The results demonstrated that a moderate dose of sevoflurane inhalation of 2% for 2 h had significant neuroprotective effects against ischemia/reperfusion induced hippocampal neuron death. Sevoflurane significantly increased Akt and PRAS40 phosphorylation and decreased the phosphorylation of ASK1 at 6 h after reperfusion and the phosphorylation of JNK3 at 3 days after reperfusion following 15 min of transient global brain ischemia. Conversely, LY294002 and wortmannin significantly inhibited the effects of sevoflurane. Taken together, the results suggest that sevoflurane could suppress ischemic brain injury by downregulating the activation of the ASK1/JNK3 cascade via increasing the phosphorylation of Akt1 during ischemia/reperfusion.

Marine compound xyloketal B reduces neonatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic encephalopathy causes neurodegeneration and brain injury, leading to sensorimotor dysfunction. Xyloketal B is a novel marine compound isolated from a mangrove fungus Xylaria species (no. 2508) with unique antioxidant effects. In this study, we investigated the effects and mechanism of xyloketal B on oxygen-glucose deprivation-induced neuronal cell death in mouse primary cortical culture and on hypoxic-ischemic brain injury in neonatal mice in vivo. We found that xyloketal B reduced anoxia-induced neuronal cell death in vitro, as well as infarct volume in neonatal hypoxic-ischemic brain injury model in vivo. Furthermore, xyloketal B improved functional behavioral recovery of the animals following hypoxic-ischemic insult. In addition, xyloketal B significantly decreased calcium entry, reduced the number of TUNEL-positive cells, reduced the levels of cleaved caspase-3 and Bax proteins, and increased the level of Bcl-2 protein after the hypoxic-ischemic injury. Our findings indicate that xyloketal B is effective in models of hypoxia-ischemia and thus has potential as a treatment for hypoxic-ischemic brain injury.

Mechanisms of perinatal arterial ischemic stroke

The incidence of perinatal stroke is high, similar to that in the elderly, and produces a significant morbidity and severe long-term neurologic and cognitive deficits, including cerebral palsy, epilepsy, neuropsychological impairments, and behavioral disorders. Emerging clinical data and data from experimental models of cerebral ischemia in neonatal rodents have shown that the pathophysiology of perinatal brain damage is multifactorial. These studies have revealed that, far from just being a smaller version of the adult brain, the neonatal brain is unique with a very particular and age-dependent responsiveness to hypoxia-ischemia and focal arterial stroke. In this review, we discuss fundamental clinical aspects of perinatal stroke as well as some of the most recent and relevant findings regarding the susceptibility of specific brain cell populations to injury, the dynamics and the mechanisms of neuronal cell death in injured neonates, the responses of neonatal blood-brain barrier to stroke in relation to systemic and local inflammation, and the long-term effects of stroke on angiogenesis and neurogenesis. Finally, we address translational strategies currently being considered for neonatal stroke as well as treatments that might effectively enhance repair later after injury.

Mitochondria: hub of injury responses in the developing brain

Progress in the field of mitochondrial biology in the past few years has shown that mitochondrial activities go beyond bioenergetics. These new aspects of mitochondrial physiology and pathophysiology have important implications for the immature brain. A picture emerges in which mitochondrial biogenesis, mitophagy, migration, and morphogenesis are crucial for brain development and synaptic pruning, and play a part in recovery after acute insults. Mitochondria also affect brain susceptibility to injury, and mitochondria-directed interventions can make the immature brain highly resistant to acute injury. Finally, the mitochondrion is a platform for innate immunity, contributes to inflammation in response to infection and acute damage, and participates in antiviral and antibacterial defence. Understanding of these new aspects of mitochondrial function will provide insights into brain development and neurological disease, and enable discovery and development of new strategies for treatment.

Short-term treadmill exercise preserves sensory-motor function through inhibiting apoptosis in the hippocampus of hypoxic ischemia injury rat pups

Perinatal hypoxic ischemia injury is a common cause of morbidity and mortality in neonates. Physical exercise may ameliorate neurological impairment by impeding neuronal loss following various brain insults. In the present study, the effect of treadmill exercise on sensory-motor function in relation with hippocampal apoptosis following hypoxic ischemia brain injury was investigated. Sensory-motor function was determined by walking initiation test and apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining and caspase-3 immunohistochemistry. On postnatal 7 day, left common carotid artery of the neonatal rats was ligated for two hours and then the neonatal rats were exposed to hypoxia conditions for one hour. The rat pups in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 10 days, starting 22 days after induction of hypoxic ischemia brain injury. Hypoxic ischemia caused sensory-motor disturbance with enhancement of apoptosis in the hippocampus. Short-term treadmill exercise suppressed hypoxic ischemia injury-induced apoptosis in the hippocampus, and preserved sensory-motor function of hypoxic ischemia injury rat pups.

Mitochondrial dysfunction induced by nuclear poly(ADP-ribose) polymerase-1: a treatable cause of cell death in stroke

Many drugs targeting excitotoxic cell death have demonstrated robust neuroprotective effects in animal models of cerebral ischemia. However, these neuroprotective effects have almost universally required drug administration at relatively short time intervals after ischemia onset. This finding has translated to clinical trial results; interventions targeting excitotoxicity have had no demonstrable efficacy when initiated hours after ischemia onset, but beneficial effects have been reported with more rapid initiation. Consequently, there continues to be a need for interventions with efficacy at later time points after ischemia. Here, we focus on mitochondrial dysfunction as both a relatively late event in ischemic neuronal death and a recognized cause of delayed neuronal death. Activation of poly(ADP-ribose) polymerase-1 (PARP-1) is a primary cause of mitochondrial depolarization and subsequent mitochondria-triggered cell death in ischemia reperfusion. PARP-1 consumes cytosolic NAD(+), thereby blocking both glycolytic ATP production and delivery of glucose carbon to mitochondria for oxidative metabolism. However, ketone bodies such as pyruvate, beta- and gamma-hydroxybutyrate, and 1,4-butanediol can fuel mitochondrial metabolism in cells with depleted cytosolic NAD(+) as long as the mitochondria remain functional. Ketone bodies have repeatedly been shown to be highly effective in preventing cell death in animal models of ischemia, but a rigorous study of the time window of opportunity for this approach remains to be performed.

Neuroprotective therapies after perinatal hypoxic-ischemic brain injury

Hypoxic-ischemic (HI) brain injury is one of the main causes of disabilities in term-born infants. It is the result of a deprivation of oxygen and glucose in the neural tissue. As one of the most important causes of brain damage in the newborn period, the neonatal HI event is a devastating condition that can lead to long-term neurological deficits or even death. The pattern of this injury occurs in two phases, the first one is a primary energy failure related to the HI event and the second phase is an energy failure that takes place some hours later. Injuries that occur in response to these events are often manifested as severe cognitive and motor disturbances over time. Due to difficulties regarding the early diagnosis and treatment of HI injury, there is an increasing need to find effective therapies as new opportunities for the reduction of brain damage and its long term effects. Some of these therapies are focused on prevention of the production of reactive oxygen species, anti-inflammatory effects, anti-apoptotic interventions and in a later stage, the stimulation of neurotrophic properties in the neonatal brain which could be targeted to promote neuronal and oligodendrocyte regeneration.

Targeting neonatal ischemic brain injury with a pentapeptide-based irreversible caspase inhibitor

Brain protection of the newborn remains a challenging priority and represents a totally unmet medical need. Pharmacological inhibition of caspases appears as a promising strategy for neuroprotection. In a translational perspective, we have developed a pentapeptide-based group II caspase inhibitor, TRP601/ORPHA133563, which reaches the brain, and inhibits caspases activation, mitochondrial release of cytochrome c, and apoptosis in vivo. Single administration of TRP601 protects newborn rodent brain against excitotoxicity, hypoxia-ischemia, and perinatal arterial stroke with a 6-h therapeutic time window, and has no adverse effects on physiological parameters. Safety pharmacology investigations, and toxicology studies in rodent and canine neonates, suggest that TRP601 is a lead compound for further drug development to treat ischemic brain damage in human newborns.

Pharmacological neuroprotection after perinatal hypoxic-ischemic brain injury

Perinatal hypoxia-ischemia (HI) is an important cause of neonatal brain injury. Recent progress in the search for neuroprotective compounds has provided us with several promising drugs to reduce perinatal HI-induced brain injury. In the early stage (first 6 hours after birth) therapies are concentrated on prevention of the production of reactive oxygen species or free radicals (xanthine-oxidase-, nitric oxide synthase-, and prostaglandin inhibition), anti-inflammatory effects (erythropoietin, melatonin, Xenon) and anti-apoptotic interventions (nuclear factor kappa B- and c-jun N-terminal kinase inhibition); in a later stage stimulation of neurotrophic properties in the neonatal brain (erythropoietin, growth factors) can be targeted to promote neuronal and oligodendrocyte regeneration. Combination of pharmacological means of treatment with moderate hypothermia, which is accepted now as a meaningful therapy, is probably the next step in clinical treatment to fight post-asphyxial brain damage. Further studies should be directed at a more rational use of therapies by determining the optimal time and dose to inhibit the different potentially destructive molecular pathways or to enhance endogenous repair while at the same time avoiding adverse effects of the drugs used.

miR-23a regulation of X-linked inhibitor of apoptosis (XIAP) contributes to sex differences in the response to cerebral ischemia

It is increasingly recognized that the mechanisms underlying ischemic cell death are sexually dimorphic. Stroke-induced cell death in males is initiated by the mitochondrial release of apoptosis-inducing factor, resulting in caspase-independent cell death. In contrast, ischemic cell death in females is primarily triggered by mitochondrial cytochrome c release with subsequent caspase activation. Because X-linked inhibitor of apoptosis (XIAP) is the primary endogenous inhibitor of caspases, its regulation may play a unique role in the response to injury in females. XIAP mRNA levels were higher in females at baseline. Stroke induced a significant decrease in XIAP mRNA in females, whereas no changes were seen in the male brain. However, XIAP protein levels were decreased in both sexes after stroke. MicroRNAs (miRNAs) predominantly induce translational repression and are emerging as a major regulators of mRNA and subsequent protein expression after ischemia. The miRNA miR-23a was predicted to bind XIAP mRNA. miR-23a directly bound the 3' UTR of XIAP, and miR-23a inhibition led to an increase in XIAP mRNA in vitro, demonstrating that XIAP is a previously uncharacterized target for miR-23a. miR-23a levels differed in male and female ischemic brains, providing evidence for sex-specific miRNA expression in stroke. Embelin, a small-molecule inhibitor of XIAP, decreased the interaction between XIAP and caspase-3 and led to enhanced caspase activity. Embelin treatment significantly exacerbated stroke-induced injury in females but had no effect in males, demonstrating that XIAP is an important mediator of sex-specific responses after stroke.

Pharmacological neuroprotection after perinatal asphyxia

Recent progress has provided us with several promising neuroprotective compounds to reduce perinatal hypoxic-ischemic (HI) brain injury. In the early post HI phase, therapies can be concentrated on ion channel blockage (Xenon), anti-oxidation (allopurinol, 2-iminobiotin, and indomethacin), anti-inflammation (erythropoietin [EPO], melatonin), and anti-apoptosis (nuclear factor kappa B [NF-&#x03BA;B]and c-jun N-terminal kinase [JNK] inhibitors); in the later phase, therapies should be targeted to promote neuronal regeneration by stimulation of neurotrophic properties of the neonatal brain (EPO, growth factors, stem cells transplantation). Combination of pharmacological interventions with moderate hypothermia, which is the only established therapy for post HI brain injury, is probably the next step to fight HI brain damage in the clinical setting. Further studies should be concentrated on more rational pharmacological strategies by determining the optimal time and dose to inhibit the various potentially destructive molecular pathways and/or to enhance endogenous repair meanwhile avoiding the adverse effects.

Caspase inhibition by cardiotrophin-1 prevents neuronal death in vivo and in vitro

Our previous studies showed that cardiotrophin-1 (CT-1), a cytokine in the interleukin-6 family, protected the developing rat brain against focal cerebral ischemia (FCI) in vivo and prevented cortical neuron death in vitro. However, the mechanisms by which CT-1 prevents neuronal death are not clearly understood. This in vivo study focused on whether CT-1 treatment prevented FCI-induced brain injuries in the postnatal day 7 (P7) rat through modulating activation of the initiator caspase-8 (C-8) and the downstream effector caspase-3 (C-3). FCI caused a significant increase in expressions of cleaved C-8 and C-3 and, meanwhile, a significant decrease in expression of microtubule-associated protein-2 (MAP2) in the left ischemic cortex of the P7 rat brain after FCI. Exogenous treatment of CT-1 significantly reduced the expression of cleaved C-8 or C-3 and attenuated the decline in MAP2 expression in the ischemic cortex from 12 to 24 hr after FCI. Subsequent in vitro experiments demonstrated that CT-1 treatment inhibited sodium nitroprusside (SNP)-induced activation of C-8 and C-3 and loss of MAP2-positive neurons in cortical neuron cultures. More importantly, CT-1 activated several pathways, including Janus kinase 2, signal transducers and activators of transcription 3, nuclear factor kappa B, mitogen-activated protein kinase (MAPK), and MAPK kinase in the cultures exposed to SNP. This is the first suggestion that CT-1 prevents neuronal injury in the developing central nervous system possibly through mediating multiple signal pathways, inhibiting activation of C-8 and C-3.

A highly toxic cellular prion protein induces a novel, nonapoptotic form of neuronal death

Several different deletions within the N-terminal tail of the prion protein (PrP) induce massive neuronal death when expressed in transgenic mice. This toxicity is dose-dependently suppressed by coexpression of full-length PrP, suggesting that it results from subversion of a normal physiological activity of cellular PrP. We performed a combined biochemical and morphological analysis of Tg(DeltaCR) mice, which express PrP carrying a 21-aa deletion (residues 105-125) within a highly conserved region of the protein. Death of cerebellar granule neurons in Tg(DeltaCR) mice is not accompanied by activation of either caspase-3 or caspase-8 or by increased levels of the autophagy marker, LC3-II. In electron micrographs, degenerating granule neurons displayed a unique morphology characterized by heterogeneous condensation of the nuclear matrix without formation of discrete chromatin masses typical of neuronal apoptosis. Our data demonstrate that perturbations in PrP functional activity induce a novel, nonapoptotic, nonautophagic form of neuronal death whose morphological features are reminiscent of those associated with excitotoxic stress.

Mitochondrial damage: a target for new therapeutic horizons

Traumatic brain injury (TBI) represents a leading cause of death and morbidity, as well as a considerable social and economical burden in western countries, and has thus emerged as a formidable therapeutic challenge. Yet despite tremendous efforts enlightening the mechanisms of neuronal death, hopes for the "magic bullet" have been repeatedly deceived, and TBI management has remained focused on the control of increased intracranial pressure. Indeed, impairment of cerebral metabolism is traditionally attributed to impaired oxygen delivery mediated by reduced cerebral perfusion in the swollen cerebral parenchyma. Although intuitively appealing, this hypothesis is not entirely supported by physiological facts and does not take into consideration mitochondrial dysfunction that has been repeatedly reported in both human and animal TBI. Although the nature and origin of the events leading to mitochondrial damage may be different, most share a permeabilization of mitochondrial membrane, which therefore may represent a logical target for new therapeutic strategies. Therefore, the proteins mediating these events may represent promising targets for new TBI therapies. Furthermore, mimicking anti-apoptotic proteins, such as Bcl-2 or XIAP, or inhibiting mitochondrial pro-apoptotic proteins, such as Smac/DIABLO, Omi/HTRA2, and ARTS (septin 4 isoform 2) may represent useful novel therapeutic strategies. This review focuses on mechanisms of the mitochondrial membrane permeabilization and its consequences and discusses the current and possible future therapeutic implications of this key event of neuronal death.

Hypoxic-ischemic encephalopathy in the term infant

Hypoxia-ischemia in the perinatal period is an important cause of cerebral palsy and associated disabilities in children. There has been significant research progress in hypoxic-ischemic encephalopathy over the last 2 decades, and many new molecular mechanisms have been identified. Despite all these advances, therapeutic interventions are still limited. In this article the authors discuss several molecular pathways involved in hypoxia-ischemia, and potential therapeutic targets.

Calpain 1 and Calpastatin expression is developmentally regulated in rat brain

Calpains and caspases are cysteine endopeptidases which share many similar substrates. Caspases are essential for caspase-dependent apoptotic death where calpains may play an augmentive role, while calpains are strongly implicated in necrotic cell death morphologies. Previous studies have demonstrated a down-regulation in the expression of many components of the caspase-dependent cell death pathway during CNS development. We therefore sought to determine if there is a corresponding upregulation of calpains. The major CNS calpains are the mu-and m-isoforms, composed of the unique 80 kDa calpain 1 and 2 subunits, respectively, and the shared 28 kDa small subunit. In rat brain, relative protein and mRNA levels of calpain 1, calpain 2, caspase 3, and the endogenous calpain inhibitor-calpastatin, were evaluated using western blot and real-time RT-PCR. The developmental time points examined ranged from embryonic day 18 until postnatal day 90. Calpain 1 and calpastatin protein and mRNA levels were low at early developmental time points and increased dramatically by P30. Conversely, caspase-3 expression was greatest at E18, and was rapidly downregulated by P30. Calpain 2 protein and mRNA levels were relatively constant throughout the E18-P90 age range examined. The inverse relationship of calpain 1 and caspase 3 levels during CNS development is consistent with the shift from caspase-dependent to caspase-independent cell death mechanisms following CNS injury in neonatal vs. adult rat brain.

Mitochondria, oxidative metabolism and cell death in stroke

Stroke most commonly results from occlusion of a major artery in the brain and typically leads to the death of all cells within the affected tissue. Mitochondria are centrally involved in the development of this tissue injury due to modifications of their major role in supplying ATP and to changes in their properties that can contribute to the development of apoptotic and necrotic cell death. In animal models of stroke, the limited availability of glucose and oxygen directly impairs oxidative metabolism in severely ischemic regions of the affected tissue and leads to rapid changes in ATP and other energy-related metabolites. In the less-severely ischemic "penumbral" tissue, more moderate alterations develop in these metabolites, associated with near normal glucose use but impaired oxidative metabolism. This tissue remains potentially salvageable for at least the first few hours following stroke onset. Early restoration of blood flow can result in substantial recovery of energy-related metabolites throughout the affected tissue. However, glucose oxidation is markedly decreased due both to lower energy requirements in the post-ischemic tissue and limitations on the mitochondrial oxidation of pyruvate. A secondary deterioration of mitochondrial function subsequently develops that may contribute to progression to cell loss. Mitochondrial release of multiple apoptogenic proteins has been identified in ischemic and post-ischemic brain, mostly in neurons. Pharmacological interventions and genetic modifications in rodent models strongly implicate caspase-dependent and caspase-independent apoptosis and the mitochondrial permeability transition as important contributors to tissue damage, particularly when induced by short periods of temporary focal ischemia.

Apoptotic mechanisms in the immature brain: involvement of mitochondria

Brain injury after hypoxic-ischemic encephalopathy often develops with delayed appearance, opening a therapeutic window. Clinical studies in newborns show that post-hypoxic-ischemic hypothermia improves outcome. This has generated renewed interest in the molecular mechanisms of hypoxic-ischemic brain injury. In this brief review, we propose that mitochondrial permeabilization is crucial for injury to advance beyond the point of no return. We suggest that excitatory amino acids, nitric oxide, inflammation, trophic factor withdrawal, and an increased pro- versus antiapoptotic Bcl-2 protein ratio will trigger Bax-dependent mitochondrial outer membrane permeabilization. Mitochondrial outer membrane permeabilization, in turn, elicits mitochondrial release of cytochrome C, apoptosis-inducing factor, second mitochondria-derived activator of caspase/Diablo, and HtrA2/Omi. Cytochrome C efflux activates caspase-9/-3, leading to DNA fragmentation. Apoptosis-inducing factor interacts with cyclophilin A and induces chromatinolysis. Blockage of mitochondrial outer membrane permeabilization holds promise as a strategy for perinatal brain protection.