Poststroke neuronal rescue and synaptogenesis mediated in vivo by protein kinase C in adult brains

Bryostatin-1: a promising compound for neurological disorders

The central nervous system (CNS) is the most complex system in human body, and there is often a lack of effective treatment strategies for the disorders related with CNS. Natural compounds with multiple pharmacological activities may offer better options because they have broad cellular targets and potentially produce synergic and integrative effects. Bryostatin-1 is one of such promising compounds, a macrolide separated from marine invertebrates. Bryostatin-1 has been shown to produce various biological activities through binding with protein kinase C (PKC). In this review, we mainly summarize the pharmacological effects of bryostatin-1 in the treatment of multiple neurological diseases in preclinical studies and clinical trials. Bryostatin-1 is shown to have great therapeutic potential for Alzheimer's disease, multiple sclerosis, fragile X syndrome, stroke, traumatic brain injury, and depression. It exhibits significant rescuing effects on the deficits of spatial learning, cognitive function, memory and other neurological functions caused by diseases, producing good neuroprotective effects. The promising neuropharmacological activities of bryostatin-1 suggest that it is a potential candidate for the treatment of related neurological disorders although there are still some issues needed to be addressed before its application in clinic.

Aptamer-based expansion microscopy platform enables signal-amplified imaging of dendritic spines

Super-resolution imaging of dendritic spines (DS) can provide valuable information for mechanistic studies related to synaptic physiology and neural plasticity, but challenged by their small dimension (50-200 nm) below the spatial resolution of conventional optical microscopes. In this work, by combining the molecular recognition specificity of aptamer with high programmability of DNA nanotechnology, we developed an expansion microscopy (ExM) platform for imaging DS with enhanced spatial resolution and amplified signal output. Our results demonstrated that the aptamer probe could specifically bind to DS of primary hippocampal neurons. With physical expansion, the DS structure could be effectively enlarged by 4-5 folds, leading to the generation of more structural information. Meantime, the aptamer binding signal could be readily amplified by the introduction of DNA signal amplification strategy, overcoming the drawback of fluorescence dilution during the ExM treatment. This platform enabled evaluation of ischemia-induced early stroke based on the morphological change of DS, highlighting a promising avenue for studying nanoscale structures in biological systems.

Cholinergic Internal and Projection Systems of Hippocampus and Neocortex Critical for Early Spatial Memory Consolidation in Normal and Chronic Cerebral Hypoperfusion Conditions in Rats with Different Abilities to Consolidation: The Role of Cholinergic Interneurons of the Hippocampus

The role of cholinergic projection systems of the neocortex and hippocampus in memory consolidation in healthy and neuropathological conditions has been subject to intensive research. On the contrary, the significance of cholinergic cortical and hippocampal interneurons in learning has hardly been studied. We aimed to evaluate the role of both cholinergic projection neurons and interneurons of the neocortex and hippocampus at an early stage of spatial memory consolidation (2s1) in normal and chronic brain hypoperfusion conditions. Control rats and rats subjected to permanent two-vessel occlusion were trained with the Morris water maze, and the activity of membrane-bound and water-soluble choline acetyltransferase was evaluated in the sub-fractions of ‘light’ and ‘heavy’ synaptosomes of the neocortex and hippocampus, in which the presynapses of cholinergic projections and interneurons, respectively, are concentrated. Animals were ranked into quartiles according to their performance on stage 2s1. We found: (1) quartile-dependent cholinergic composition of 2s1 function and dynamics of cholinergic synaptic plasticity under cerebral hypoperfusion; (2) cholinergic hippocampal interneurons are necessary for successful 2s1 consolidation; (3) cholinergic neocortical interneurons and projections can be critical for 2s1 consolidation in less learning rats. We conclude that targeted modulation of cholinergic synaptic activity in the hippocampus and neocortex can be effective in reversing the cognitive disturbance of cerebral hypoperfusion. We discuss the possible ways to restore the impaired spatial memory 2s1 in the presence of cerebral hypoperfusion.

Individuals with Higher Levels of Physical Activity after Stroke Show Comparable Patterns of Myelin to Healthy Older Adults

Background

Myelin asymmetry ratios (MARs) relate and contribute to motor impairment and function after stroke. Physical activity (PA) may induce myelin plasticity, potentially mitigating hemispheric myelin asymmetries that can occur after a stroke.

Objective

The aim of this study was to determine whether individuals with higher levels of PA showed lower MAR compared to individuals with lower levels of PA.

Methods

Myelin water fraction was obtained from 5 bilateral motor regions in 22 individuals with chronic stroke and 26 healthy older adults. Activity levels were quantified with wrist accelerometers worn for a period of 72 hours (3 days). Higher and lower PA levels were defined by a cluster analysis within each group.

Results

MAR was similar regardless of PA level within the older adult group. Compared to the higher PA stroke group, lower PA stroke participants displayed greater MAR. There was no difference in MAR between the stroke and older adult higher PA groups. Within the lower PA groups, individuals with stroke showed greater MAR compared to the older adults. Arm impairment, lesion volume, age, time since stroke, and preferential arm use were not different between the PA stroke groups, suggesting that motor impairment severity and extent of brain damage did not drive differences in PA.

Conclusion

Individuals who have had a stroke and are also physically active display lower MAR (i.e., similar myelin in both hemispheres) in motor regions. High levels of PA may be neuroprotective and mitigate myelin asymmetries once a neurological insult, such as a stroke, occurs. Alternately, it is possible that promoting high levels of PA after a stroke may reduce myelin asymmetries.

Bryostatin-1 Attenuates Ischemia-Elicited Neutrophil Transmigration and Ameliorates Graft Injury after Kidney Transplantation

Ischemia reperfusion injury (IRI) is a form of sterile inflammation whose severity determines short- and long-term graft fates in kidney transplantation. Neutrophils are now recognized as a key cell type mediating early graft injury, which activates further innate immune responses and intensifies acquired immunity and alloimmunity. Since the macrolide Bryostatin-1 has been shown to block neutrophil transmigration, we aimed to determine whether these findings could be translated to the field of kidney transplantation. To study the effects of Bryostatin-1 on ischemia-elicited neutrophil transmigration, an in vitro model of hypoxia and normoxia was equipped with human endothelial cells and neutrophils. To translate these findings, a porcine renal autotransplantation model with eight hours of reperfusion was used to study neutrophil infiltration in vivo. Graft-specific treatment using Bryostatin-1 (100 nM) was applied during static cold storage. Bryostatin-1 dose-dependently blocked neutrophil activation and transmigration over ischemically challenged endothelial cell monolayers. When applied to porcine renal autografts, Bryostatin-1 reduced neutrophil graft infiltration, attenuated histological and ultrastructural damage, and improved renal function. Our novel findings demonstrate that Bryostatin-1 is a promising pharmacological candidate for graft-specific treatment in kidney transplantation, as it provides protection by blocking neutrophil infiltration and attenuating functional graft injury.

Further insights for the role of Morin in mRTBI: Implication of non-canonical Wnt/PKC-α and JAK-2/STAT-3 signaling pathways

The slightly available data about the pathogenesis process of mild repetitive traumatic brain injury (mRTBI) indicates to the necessity of further exploration of mRTBI consequences. Several cellular changes are believed to contribute to the cognitive disabilities, and neurodegenerative changes observed later in persons subjected to mRTBI. We investigated glial fibrillary acidic protein (GFAP), the important severity related biomarker, where it showed further increase after multiple trauma compared to single one. To authenticate our aim, Morin (10 mg/kg loading dose, then twice daily 5 mg/kg for 7 days), MK-801 (1 mg/kg; i.p) and their combination were used. The results obtained has shown that all the chosen regimens opposed the upregulated dementia markers (Aβ1-40,p(Thr231)Tau) and inflammatory protein contents/expression of p(Ser53s6)NF-κBp65, TNF-α, IL-6,and IL-1β and the elevated GFAP in immune stained cortex sections. Additionally, they exerted anti-apoptotic activity by decreasing caspase-3 activity and increasing Bcl-2 contents. Saving brain tissues was evident after these therapeutic agents via upregulating the non-canonical Wnt-1/PKC-α cue and IL-10/p(Tyr(1007/1008))JAK-2/p(Tyr705)STAT-3 signaling pathway to confirm enhancement of survival pathways on the molecular level. Such results were imitated by correcting the injury dependent deviated behavior, where Morin alone or in combination enhanced behavior outcome. On one side, our study refers to the implication of two survival signaling pathways; viz.,the non-canonical Wnt-1/PKC-α and p(Tyr(1007/1008))JAK-2/p(Tyr705)STAT-3 in single and repetitive mRTBI along with distorted dementia markers, inflammation and apoptotic process that finally disrupted behavior. On the other side, intervention through affecting all these targets by Morin alone or with MK-801 affords a promising neuroprotective effect.

Morphine pretreatment protects against cerebral ischemic injury via a cPKCγ-mediated anti-apoptosis pathway

It has been reported that morphine pretreatment (MP) can exert neuroprotective effects, and that protein kinase C (PKC) participates in the initiation and development of ischemic/hypoxic preconditioning in the brain. However, it remains unknown whether PKC is involved in MP-induced neuroprotection. The aim of the present study, which included in vivo and in vitro experiments, was to determine whether the conventional γ isoform of PKC (cPKCγ) was involved in the protective effects of MP against cerebral ischemic injury. The present study included an in vivo experiment using a mouse model of middle cerebral artery occlusion and an in vitro experiment using neuroblastoma N2a cells with oxygen-glucose deprivation (OGD). Furthermore, a cPKCγ antagonist, Go6983, was used to determine the involvement of cPKCγ in the protective effects of MP against cerebral ischemic injury. In the in vivo experiment, neurological deficits, ischemic infarct volume, neural cell damage, apoptosis and caspase-3 activation were evaluated. In the in vitro experiment, flow cytometry was used to determine the activation of caspase-3 in N2a cells with OGD. It was found that MP protected against cerebral ischemic injury. However, intracerebroventricular injection of the cPKCγ antagonist before MP attenuated the neuroprotective effect of MP and increased the activation of cleaved caspase-3. These findings suggested that MP may provide protection against cerebral ischemic injury via a cPKCγ-mediated anti-apoptosis pathway.

Anti-Alzheimer's Molecules Derived from Marine Life: Understanding Molecular Mechanisms and Therapeutic Potential

Alzheimer’s disease (AD) is a devastating neurodegenerative disease and the most common cause of dementia. It has been confirmed that the pathological processes that intervene in AD development are linked with oxidative damage to neurons, neuroinflammation, tau phosphorylation, amyloid beta (Aβ) aggregation, glutamate excitotoxicity, and cholinergic deficit. Still, there is no available therapy that can cure AD. Available therapies only manage some of the AD symptoms at the early stages of AD. Various studies have revealed that bioactive compounds derived from marine organisms and plants can exert neuroprotective activities with fewer adverse events, as compared with synthetic drugs. Furthermore, marine organisms have been identified as a source of novel compounds with therapeutic potential. Thus, there is a growing interest regarding bioactive compounds derived from marine sources that have anti-AD potentials. Various marine drugs including bryostatin-1, homotaurine, anabaseine and its derivative, rifampicins, anhydroexfoliamycin, undecylprodigioisin, gracilins, 13-desmethyl spirolide-C, and dictyostatin displayed excellent bioavailability and efficacy against AD. Most of these marine drugs were found to be well-tolerated in AD patients, along with no significant drug-associated adverse events. In this review, we focus on the drugs derived from marine life that can be useful in AD treatment and also summarize the therapeutic agents that are currently used to treat AD.

AhR/miR-23a-3p/PKCα axis contributes to memory deficits in ovariectomized and normal aging female mice

The mechanism of estrogen deficiency-induced cognitive impairment is still not fully elucidated. In this study, we assessed the effect of microRNA (miRNA) on the memory of long-term estrogen-deficient mice after ovariectomy (OVX) and normal aging. We observed that 5-month OVX and 22-month-old normal aging female mice showed significantly impaired spatial and object recognition memory, declined hippocampal long-term potentiation (LTP), and decreased hippocampal protein kinase C α (PKCα) protein. Quantitative real-time PCR analysis showed upregulated miRNA-23a-3p (miR-23a-3p) in the hippocampus of 5-month OVX and 22-month-old female mice. In vitro, overexpression of miR-23a-3p downregulated PKCα by binding the 3¢ UTRs of Prkca mRNAs, which was prevented by its antisense oligonucleotide AMO-23a. In vivo, adeno-associated virus-mediated overexpression of miR-23a-3p (AAV-pre-miR-23a-3p) suppressed hippocampal PKCα and impaired the memory of mice. Chromatin immunoprecipitation analysis showed that aryl hydrocarbon receptor (AhR) binds the promoter region of miR-23a-3p. The AhR-dependent downregulation of PKCα could be prevented by AMO-23a as well. Furthermore, knockdown of miR-23a-3p using AAV-AMO-23a rescued the cognitive and electrophysiological impairments of OVX and normal aging female mice. We conclude that long-term estrogen deficiency impairs cognition and hippocampal LTP by activating the AhR/miR-23a-3p/PKCα axis. The knockdown of miR-23a-3p may be a potentially valuable therapeutic strategy for estrogen deficiency-induced memory deficits.

Preclinical and Clinical Studies on Bryostatins, A Class of Marine-Derived Protein Kinase C Modulators: A Mini-Review

Bryostatins are complex macrolactones isolated from marine organisms Bryozoan Bugula neritina. They are potent modulators of protein kinase C isozymes (PKCα: ki = 1.3-188 nM), and are one of the most extensively investigated marine natural products in clinical trials. Although ~21 natural bryostatins have been isolated, however only bryostatin-1 (1) has received much interest among medicinal chemists and clinicians. The structure-activity relationship of bryostatins has been well established, with the identification of key pharmacophoric features important for PKC modulation. The low natural abundance and the long synthetic route have prompted medicinal chemists to come-up with simplified analogs. Bryostatin skeleton comprises three pyran rings connected to each other to form a macrocyclic lactone. The simplest analog 27 contains only one pyran, which is also able to modulate the PKCα activity; however, the cyclic framework appears to be essential for the desired level of potency. Another simplified analog 17 ("picolog") exhibited potent and in-vivo efficacy against lymphoma. Bryostatin-1 (1) has shown an acceptable intravenous pharmacokinetic profile in mice and displayed promising in-vivo efficacy in mice models of various cancers and Alzheimer's disease. Bryostatin-1 was investigated in numerous Phase I/II oncology clinical trials; it has shown minimal effect as a single agent, however, provided encouraging results in combination with other chemotherapy agents. FDA has granted orphan drug status to bryostatin-1 in combination with paclitaxel for esophageal cancer. Bryostatin-1 has also received orphan drug status for fragile X syndrome. Bryostatin-1 was also investigated in clinical studies for Alzheimer's disease and HIV infection. In a nutshell, the natural as well as synthetic bryostatins have generated a strong hope to emerge as treatment for cancer along with many other diseases.

The Combination of Astragalus membranaceus and Ligustrazine Protects Against Thrombolysis-Induced Hemorrhagic Transformation Through PKCδ/Marcks Pathway in Cerebral Ischemia Rats

Astragalus membranaceus (Ast) and ligustrazine (Lig) have a protective effect on lower hemorrhagic transformation induced by pharmaceutical thrombolysis. The cerebral ischemia rat model was induced with autologous blood clot injections. A combination of Ast and Lig, or a protein kinase C delta (PKCδ) inhibitor—rottlerin, or a combination of Ast, Lig, and rottlerin was administered immediately after recombinant tissue plasminogen activator injection. The cerebral infarct area, neurological deficits, cerebral hemorrhage status, neuronal damage and tight junctions’ changes in cerebral vessels, and the messenger RNA and protein levels of PKCδ, myristoylated alanine-rich C kinase substrate (Marcks), and matrix metallopeptidase 9 (MMP9) were determined after 3 h and 24 h of thrombolysis. The ultrastructure of the neuronal damage and tight junctions was examined under a transmission electron microscope. The expression levels of PKCδ, Marcks, and MMP9 were assessed by immunohistochemistry, western blot, and quantitative real-time polymerase chain reaction . Administration of Ast and Lig not only significantly decreased neurological deficit scores, infarct volumes, and cerebral hemorrhage but also inhibited the disruption due to neuronal dysfunction and the tight junction integrity in the cerebral vessel. Treatment with a combination of Ast and Lig effectively protected ischemia-induced microhemorrhage transformation through PKCδ/Marcks pathway suppression.

Bryostatin 1 Promotes Synaptogenesis and Reduces Dendritic Spine Density in Cortical Cultures through a PKC-Dependent Mechanism

The marine natural product bryostatin 1 has demonstrated procognitive and antidepressant effects in animals and has been entered into human clinical trials for treating Alzheimer's disease (AD). The ability of bryostatin 1 to enhance learning and memory has largely been attributed to its effects on the structure and function of hippocampal neurons. However, relatively little is known about how bryostatin 1 influences the morphology of cortical neurons, key cells that also support learning and memory processes and are negatively impacted in AD. Here, we use a combination of carefully designed chemical probes and pharmacological inhibitors to establish that bryostatin 1 increases cortical synaptogenesis while decreasing dendritic spine density in a protein kinase C (PKC)-dependent manner. The effects of bryostatin 1 on cortical neurons are distinct from those induced by neural plasticity-promoting psychoplastogens such as ketamine. Compounds capable of increasing synaptic density with concomitant loss of immature dendritic spines may represent a unique pharmacological strategy for enhancing memory by improving signal-to-noise ratio in the central nervous system.

The Phylum Bryozoa: From Biology to Biomedical Potential

Less than one percent of marine natural products characterized since 1963 have been obtained from the phylum Bryozoa which, therefore, still represents a huge reservoir for the discovery of bioactive metabolites with its ~6000 described species. The current review is designed to highlight how bryozoans use sophisticated chemical defenses against their numerous predators and competitors, and which can be harbored for medicinal uses. This review collates all currently available chemoecological data about bryozoans and lists potential applications/benefits for human health. The core of the current review relates to the potential of bryozoan metabolites in human diseases with particular attention to viral, brain, and parasitic diseases. It additionally weighs the pros and cons of total syntheses of some bryozoan metabolites versus the synthesis of non-natural analogues, and explores the hopes put into the development of biotechnological approaches to provide sustainable amounts of bryozoan metabolites without harming the natural environment.

Neuro-regeneration Therapeutic for Alzheimer's Dementia: Perspectives on Neurotrophic Activity

Alzheimer's disease (AD), the leading disorder of memory impairment in our aging population, is increasing at an alarming rate. AD is currently identified by three 'gold standard criteria': (i) dementia in life, (ii) amyloid plaques at autopsy, and (iii) neurofibrillary tangles at autopsy. Several autopsy studies have indicated that dementia in life is a consequence of lost synaptic networks in the brain, while many clinical trials targeting neurotoxic amyloid beta (Aβ) have consistently failed to produce therapeutic effects on memory function in AD patients. Restoring cognitive function(s) by activating endogenous repairing/regenerating mechanisms that are synaptogenic and antiapoptotic (preventing neuronal death), however, is emerging as a necessary disease-modifying therapeutic strategy against AD and possibly for other degenerative dementias, such as Parkinson's disease and multi-infarct dementia.

G, Calderon O, Moreno-Gonzalez I. Modifiable Risk Factors for Alzheimer's Disease

Since first described in the early 1900s, Alzheimer's disease (AD) has risen exponentially in prevalence and concern. Research still drives to understand the etiology and pathogenesis of this disease and what risk factors can attribute to AD. With a majority of AD cases being of sporadic origin, the increasing exponential growth of an aged population and a lack of treatment, it is imperative to discover an easy accessible preventative method for AD. Some risk factors can increase the propensity of AD such as aging, sex, and genetics. Moreover, there are also modifiable risk factors-in terms of treatable medical conditions and lifestyle choices-that play a role in developing AD. These risk factors have their own biological mechanisms that may contribute to AD etiology and pathological consequences. In this review article, we will discuss modifiable risk factors and discuss the current literature of how each of these factors interplay into AD development and progression and if strategically analyzed and treated, could aid in protection against this neurodegenerative disease.

Neuronal activity-dependent myelin repair after stroke

Brain tissue undergoes substantial activity-dependent reorganisation after stroke due to neuronal plasticity, leading to partial functional recovery in patients. Concurrent myelin repair is crucial for proper neuronal network function and reorganisation. Myelin repair after stroke might occur as myelin plasticity or as remyelination through the recruitment and differentiation of oligodendrocyte precursor cells (OPCs), which become myelin-forming oligodendrocytes (OLs). These two processes might share a similar guiding mechanism, which is postulated to depend on neuronal activity and glutamate signaling to OPCs. However, with ageing, the ability of OPCs to differentiate into myelinating OLs decreases due to changes in their ion channel and neurotransmitter receptor expression profile, rendering them less sensitive to neuronal activity. Because of their unique ability to replace damaged OLs, OPCs represent a potential therapeutic target for myelin repair in the context of stroke.

Deep Brain Stimulation Rescues Memory and Synaptic Activity in a Rat Model of Global Ischemia

Deep brain stimulation (DBS) is remarkably effective in treating Parkinson's disease and is currently under investigation for the treatment of neuropsychiatric disorders including Alzheimer's disease. Until now, DBS has not been examined for its cognitive benefits in the context of hypoxic-ischemic injuries. Here, we investigated the effect of DBS in a rat model of global ischemia (GI) that mimics the neurological consequences occurring after a cardiac arrest. We show that DBS rescues memory deficits induced by GI and produces changes in synaptic activity in the hippocampus. Novel approaches to improve neurological outcomes after stroke are urgently needed; therefore, the present study highlights a possible role for DBS in the treatment of cognitive impairment associated with ischemia.

Regulation of Neural Stem Cell Fate by Natural Products

Neural stem cells (NSCs) can proliferate and differentiate into multiple cell types that constitute the nervous system. NSCs can be derived from developing fetuses, embryonic stem cells, or induced pluripotent stem cells. NSCs provide a good platform to screen drugs for neurodegenerative diseases and also have potential applications in regenerative medicine. Natural products have long been used as compounds to develop new drugs. In this review, natural products that control NSC fate and induce their differentiation into neurons or glia are discussed. These phytochemicals enable promising advances to be made in the treatment of neurodegenerative diseases.

A Randomized, Double-Blind, Placebo-Controlled, Phase II Study Assessing Safety, Tolerability, and Efficacy of Bryostatin in the Treatment of Moderately Severe to Severe Alzheimer's Disease

BACKGROUND

Bryostatin-activated PKC epsilon pre-clinically induces synaptogenesis, anti-apoptosis, anti-amyloid-β oligomers, and anti-hyperphosphorylated tau.

OBJECTIVES

To investigate bryostatin safety, tolerability, and efficacy to improve cognition in advanced Alzheimer's disease (AD) patients.

METHODS

A double-blind, randomized, placebo-controlled Phase II, 12-week trial of i.v. bryostatin for 150 advanced AD patients (55-85) with MMSE-2 of 4-15, randomized 1:1:1 into 20 μg and 40 μg bryostatin, and placebo arms. The Full Analysis Set (FAS) and the Completer Analysis Set (CAS) were pre-specified alternative assessments (1-sided, p < 0.1 for primary efficacy, and 2-sided, p < 0.05 for pre-specified and post hoc exploratory analyses).

RESULTS

The safety profile was similar for 20 μg treatment and placebo patients. The 40 μg patients showed safety and drop-out issues, but no efficacy. Primary improvement of Severe Impairment Battery (SIB) scores at 13 weeks was not significant (p = 0.134) in the FAS, although in the CAS, the SIB comparison favored 20 μg bryostatin compared to placebo patients (p < 0.07). Secondary analyses at weeks 5 and 15 (i.e., 30 days post-final dosing) also favored 20 μg bryostatin compared to placebo patients. A pre-specified ANCOVA for baseline memantine blocking bryostatin and positive post-hoc trend analyses were statistically significant (2-sided, p < 0.05).

CONCLUSION

Although the primary endpoint was not significant in the FAS, primary and secondary analyses in the CAS, and pre-specified and post-hoc exploratory analyses did favor bryostatin 20 μg compared to the placebo cohort. These promising Phase II results support further trials of 20 μg bryostatin- without memantine- to treat AD.

RLIPostC protects against cerebral ischemia through improved synaptogenesis in rats

OBJECTIVE

Remote limb ischemic post-conditioning (RLIPostC) has been shown to be neuroprotective in cerebral ischemia, whereas the effect of RLIPostC on synaptogenesis remains elusive. In the present study, we investigated the effects of RLIPostC on synaptogenesis in an experimental stroke rat model.

METHODS

Sprague-Dawley rats were subjected to left middle cerebral artery occlusion (MCAO) and were randomly divided into a control group, an RLIPostC group and a sham group. The RLIPostC group received three cycles of RLIPostC treatment immediately after reperfusion (ten minutes ischemia and ten minutes reperfusion in bilateral femoral artery). The neurological function was assessed by neurological deficit scores and the foot fault test at days 7 and 14 after MCAO. At day 14 after MCAO, the infarct volume and oedema were determined by cresyl violet (CV) staining and by measuring brain water content, respectively. Synaptogenesis was evaluated by western blotting and immunofluorescence staining.

RESULTS

Our results showed that RLIPostC treatment significantly promoted the recovery of behavioural function, reduced infarct volume and brain oedema, and increased the expressions of SYN1, PSD95 and GAP43.

CONCLUSIONS

These results confirmed that RLIPostC treatment for cerebral ischemia was safe and effective. A possible molecular mechanism of the beneficial effects of RLIPostC treatment may be the promotion of synaptogenesis.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.

Inhibition of Inflammation, Suppression of Matrix Metalloproteinases, Induction of Neurogenesis, and Antioxidant Property Make Bryostatin-1 a Therapeutic Choice for Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease characterized by inflammation and myelin damage. Pro-inflammatory cytokines, oxidative stress, high level of matrix metalloproteinases (MMPs) activity and blood-brain barrier (BBB) damage, immune-mediated destruction of myelin and neuron loss are involved in the pathogenesis of MS. The currently approved treatments for MS include injectable drugs (interferon-β and glatiramer acetate), oral drugs (fingolimod), and monoclonal antibodies (natalizumab). The mentioned therapeutic choices are mostly focused on the inhibition of inflammation. Therefore, the search for a multi-target therapeutic choice remains unchallenged. It seems that a drug with anti-inflammatory, oxidative stress inhibitory, reduction of MMPs activity, and neurogenesis stimulatory properties may be effective for treatment of MS. In this regard, Bryostatin-1 as a macrolide and marine natural product has been selected as a therapeutic choice. Studies indicate that Bryostatin-1 has anti-inflammatory and antioxidant properties and decreases MMPs level and BBB damage. Furthermore, Bryostatin-1 has a neuroprotective effect and promotes neurogenesis and differentiation of oligodendrocyte progenitor stem cells as a critical step for remyelination/myelogenesis. Based on these properties, we hypothesized here that Bryostatin-1 is an effective treatment in MS.

Hippocampal microvasculature changes in association with oxidative stress in Alzheimer's disease

Vascular endothelial dysfunction is a primary phenotype of aging, and microvascular (MV) lesion is mainly associated with Alzheimer's disease (AD). Here we have studied the correlation of MV wall thickness and CA1 pyramidal neuronal pathology in autopsy-confirmed AD brains. Both hyaline (h-MV) and increased cell number (c-MV) associated MV wall thickening was found in age-matched control (AC) hippocampus without significant change in Aβ level (Braak stages 0-III). AC neurons neighboring the h-MV showed lower levels of oxidative DNA/RNA damage and Aβ precursor protein (APP), while the neurons around c-MV showed higher oxidative DNA/RNA damage with increased APP expression. Neurons in AC hippocampus without MV wall thickening (thin wall) showed increased DNA/RNA damage and APP levels compared to AC cases with h-MV and c-MV walls. In the AD hippocampus neurons neighboring h-MV walls showed increased levels of Aβ and decreased number of dendritic spines (at Braak stages IV-VI). C-MV neighboring neurons in the AD cases showed higher levels of DNA/RNA damage with increased APP at stages II - III, followed by lower levels of oxidative DNA/RNA damage, decreased APP and increased Aβ levels with loss of dendritic spines at stages IV-VI. Prolonged treatment of primary human fetal hippocampal neurons with tert-butyl hydroperoxide (TBHP) induced oxidative DNA damage with a sustained increase in APP. Aβ increased rapidly and then decreased overtime. Short-term TBHP treated neurons showed lower levels of superoxide (O₂^{• -}) without significant DNA damage. Short-term TBHP treatment induced a gradual decrease in APP but an increase in Aβ levels over time. In conclusion this study indicates that AD hippocampus at Braak stages II-III are characterized by strong oxidative DNA/RNA damage with increased APP in neurons associated with c-MV, while stages IV-VI are characterized by a slow increase in Aβ in neurons neighboring both h-MV and c-MV.

Exposure to far-infrared rays attenuates methamphetamine-induced recognition memory impairment via modulation of the muscarinic M1 receptor, Nrf2, and PKC

We demonstrated that activation of protein kinase Cδ (PKCδ) and inactivation of the glutathione peroxidase-1 (GPx-1)-dependent systems are critical for methamphetamine (MA)-induced recognition memory impairment. We also demonstrated that exposure to far-infrared rays (FIR) causes induction of the glutathione (GSH)-dependent system, including induction of the GPx-1 gene. Here, we investigated whether exposure to FIR rays affects MA-induced recognition memory impairment and whether it modulates PKC, cholinergic receptors, and the GSH-dependent system. Because the PKC activator bryostatin-1 mainly induces PKCα, PKCε, and PKCδ, we assessed expression of these proteins after MA treatment. MA treatment selectively increased PKCδ expression and its phosphorylation. Exposure to FIR rays significantly attenuated MA-induced increases in PKCδ phosphorylation. Importantly, bryostatin-1 potentiated MA-induced phosphorylation of PKCδ. MA treatment significantly decreased M1, M3, and M4 muscarinic acetylcholine receptors (mAChRs) and β2 nicotinic acetylcholine receptor expression. Of these, the decrease was most pronounced in M1 mAChR. Exposure to FIR significantly attenuated MA-induced decreases in the M1 mAChR and phospho-ERK_1/2, while it facilitated Nrf2-dependent GSH induction. Dicyclomine, an M1 mAChR antagonist, and l-buthionine-(S, R)-sulfoximine (BSO), an inhibitor of GSH synthesis, counteracted against the protective potentials mediated by FIR. More importantly, the memory-enhancing potential of FIR rays was significantly counteracted by bryostatin-1, dicyclomine, and BSO. Our results suggest that exposure to FIR rays attenuates MA-induced impairment in recognition memory via up-regulation of M1 mAChR, Nrf2-dependent GSH induction, and ERK_1/2 phosphorylation by inhibiting PKCδ phosphorylation by bryostatin-1.

Bryostatin Effects on Cognitive Function and PKCɛ in Alzheimer's Disease Phase IIa and Expanded Access Trials

Bryostatin 1, a potent activator of protein kinase C epsilon (PKCɛ), has been shown to reverse synaptic loss and facilitate synaptic maturation in animal models of Alzheimer’s disease (AD), Fragile X, stroke, and other neurological disorders. In a single-dose (25 μg/m²) randomized double-blind Phase IIa clinical trial, bryostatin levels reached a maximum at 1-2 h after the start of infusion. In close parallel with peak blood levels of bryostatin, an increase of PBMC PKCɛ was measured (p = 0.0185) within 1 h from the onset of infusion. Of 9 patients with a clinical diagnosis of AD, of which 6 received drug and 3 received vehicle within a double-blind protocol, bryostatin increased the Mini-Mental State Examination (MMSE) score by +1.83±0.70 unit at 3 h versus –1.00±1.53 unit for placebo. Bryostatin was well tolerated in these AD patients and no drug-related adverse events were reported. The 25 μg/m² administered dose was based on prior clinical experience with three Expanded Access advanced AD patients treated with bryostatin, in which return of major functions such as swallowing, vocalization, and word recognition were noted. In one Expanded Access patient trial, elevated PKCɛ levels closely tracked cognitive benefits in the first 24 weeks as measured by MMSE and ADCS-ADL psychometrics. Pre-clinical mouse studies showed effective activation of PKCɛ and increased levels of BDNF and PSD-95. Together, these Phase IIa, Expanded Access, and pre-clinical results provide initial encouragement for bryostatin 1 as a potential treatment for AD.

Bryostatin and its synthetic analog, picolog rescue dermal fibroblasts from prolonged stress and contribute to survival and rejuvenation of human skin equivalents

Skin health is associated with the day-to-day activity of fibroblasts. The primary function of fibroblasts is to synthesize structural proteins, such as collagen, extracellular matrix proteins, and other proteins that support the structural integrity of the skin and are associated with younger, firmer, and more elastic skin that is better able to resist and recover from injury. At sub-nanomolar concentrations (0.03-0.3 nM), bryostatin-1 and its synthetic analog, picolog (0.1-10 nM) sustained the survival and activation of human dermal fibroblasts cultured under the stressful condition of prolonged serum deprivation. Bryostatin-1 treatment stabilized human skin equivalents (HSEs), a bioengineered combination of primary human skin cells (keratinocytes and dermal fibroblasts) on an extracellular matrix composed of mainly collagen. Fibroblasts activated by bryostatin-1 protected the structural integrity of HSEs. Bryostatin-1 and picolog prolonged activation of Erk in fibroblasts to promote cell survival. Chronic stress promotes the progression of apoptosis. Dermal fibroblasts constitutively express all components of Fas associated apoptosis, including caspase-8, an initiator enzyme of apoptosis. Prolong bryostatin-1 treatment reduced apoptosis by decreasing caspase-8 and protected dermal fibroblasts. Our data suggest that bryostatin-1 and picolog could be useful in anti-aging skincare, and could have applications in tissue engineering and regenerative medicine.

Chronic stress causes protein kinase C epsilon-aldehyde dehydrogenase 2 signaling pathway perturbation in the rat hippocampus and prefrontal cortex, but not in the myocardium

Chronic stress is strongly associated with the occurrence and development of depression and cardiovascular disease. Stress can induce altered mitochondrial function and activation of apoptosis in the cardio-cerebral system. However, it is unknown whether the protein kinase C ε (PKCε)-aldehyde dehydrogenase 2 (ALDH2) pathway is altered under chronic stress, and this study sought to address this question. A rat model of depression was established using a chronic unpredictable mild stress (CUMS) protocol. After experiencing CUMS for 4 weeks, the sucrose preference test and the forced swim test verified depressive-like behaviors. Enzyme linked immunosorbent assays showed that ALDH2 activity was decreased in the rat hippocampus and prefrontal cortex, but was not altered in the myocardium. Western blot assays demonstrated reduced levels of ALDH2 and PKCε, but increased levels of 4-hydroxy-2-nonenal (4HNE) adducts. Caspase-3 expression did not obviously alter, but active forms of caspase-3 were increased in the hippocampus and prefrontal cortex. In the myocardium, expression of ALDH2, PKCε and 4HNE adducts did not remarkably alter; while caspase-3 expression was reduced and the active forms of caspase-3 were upregulated. Pearson’s correlation test demonstrated that expression of 4HNE adducts was positively correlated with levels of the active forms of caspase-3 in the hippocampus and prefrontal cortex, but not in the myocardium. In conclusion, chronic stress can damage the PKCε-ALDH2 signaling pathway in the hippocampus and prefrontal cortex, but not in the myocardium. Moreover, 4HNE is associated with active forms of caspase-3 in the hippocampus and prefrontal cortex.

Potential Therapeutics for Vascular Cognitive Impairment and Dementia

BACKGROUND

As the human lifespan increases, the number of people affected by agerelated dementia is growing at an epidemic pace. Vascular pathology dramatically affects cognitive profiles, resulting in dementia and cognitive impairment. While vascular dementia itself constitutes a medical challenge, hypo-perfusion/vascular risk factors enhance amyloid toxicity and other memory- damaging factors and hasten Alzheimer's disease (AD) and other memory disorders' progression, as well as negatively affect treatment outcome.

METHODS

Research and online content related to vascular cognitive impairment and dementia is reviewed, specifically focusing on the potential treatment of the disorder.

RESULTS

Few therapeutic options are currently available to improve the prognosis of patients with vascular dementia and cognitive impairment, mixed AD dementia with vascular pathology, or other memory disorders. Emerging evidence, however, indicates that, like AD and other memory disorders, synaptic impairment underlies much of the memory impairment in the cognitive decline of vascular cognitive impairment and vascular dementia.

CONCLUSION

Effective rescues of the memory functions might be achieved through synaptic and memory therapeutics, targeting distinct molecular signaling pathways that support the formation of new synapses and maintaining their connections. Potential therapeutic agents include: 1) memory therapeutic agents that rescue synaptic and memory functions after the brain insults; 2) antipathologic therapeutics and an effective management of vascular risk factors; and 3) preventative therapeutic agents that achieve memory therapy through functional enhancement. These therapeutic agents are also likely to benefit patients with AD and/or other types of memory disorders.

Protein kinase C epsilon delays latency until anoxic depolarization through arc expression and GluR2 internalization

Global cerebral ischemia is a debilitating injury that damages the CA1 region of the hippocampus, an area important for learning and memory. Protein kinase C epsilon (PKCɛ) activation is a critical component of many neuroprotective treatments. The ability of PKCɛ activation to regulate AMPA receptors (AMPARs) remains unexplored despite the role of AMPARs in excitotoxicity after brain ischemia. We determined that PKCɛ activation increased expression of a protein linked to learning and memory, activity-regulated cytoskeleton-associated protein (arc). Also, arc is necessary for neuroprotection and confers protection through decreasing AMPAR currents via GluR2 internalization. In vivo, activation of PKCɛ increased arc expression through a BDNF/TrkB pathway, and decreased GluR2 mRNA levels. In hippocampal cultured slices, PKCɛ activation decreased AMPAR current amplitudes in an arc- and GluR2-dependent manner. Additionally, PKCɛ activation triggered an arc- and GluR2 internalization-dependent delay in latency until anoxic depolarization. Inhibiting arc also blocked PKCɛ-mediated neuroprotection against lethal oxygen and glucose deprivation. These data characterize a novel PKCɛ-dependent mechanism that for the first time defines a role for arc and AMPAR internalization in conferring neuroprotection.

Transformation of the B Ring to the C Ring of Bryostatins by Csp3-H Amination and Z to E Isomerization

An interesting approach to transform the B ring of bryostatins to the C ring has been developed. The key tactics of the approach feature an intramolecular Csp³-H bond amination to form spirocyclic hemiaminal, which undergoes ring opening to afford the C ring found in bryostatin 17. The subsequent epoxidation/oxidation sequence results in Z to E isomerization of the exo-cyclic enoate, delivering the common precursor, which could be transformed into the C ring found in bryostatins 1, 2, 4-9, 12, 14, and 15.

Cell-based and pharmacological neurorestorative therapies for ischemic stroke

Ischemic stroke remains one of most common causes of death and disability worldwide. Stroke triggers a cascade of events leading to rapid neuronal damage and death. Neuroprotective agents that showed promise in preclinical experiments have failed to translate to the clinic. Even after decades of research, tPA remains the only FDA approved drug for stroke treatment. However, tPA is effective when administered 3-4.5 h after stroke onset and the vast majority of stroke patients do not receive tPA therapy. Therefore, there is a pressing need for novel therapies for ischemic stroke. Since stroke induces rapid cell damage and death, neuroprotective strategies that aim to salvage or replace injured brain tissue are challenged by treatment time frames. To overcome the barriers of neuroprotective therapies, there is an increasing focus on neurorestorative therapies for stroke. In this review article, we provide an update on neurorestorative treatments for stroke using cell therapy such as bone marrow derived mesenchymal stromal cells (BMSCs), human umbilical cord blood cells (HUCBCs) and select pharmacological approaches including Minocycline and Candesartan that have been employed in clinical trials. This review article discusses the present understanding of mechanisms of neurorestorative therapies and summarizes ongoing clinical trials. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Applications of Keck allylation in the synthesis of natural products

This review highlights the applications of the versatile Keck allylation reaction in the construction of important key fragments of medicinally important natural products.

Cognitive training and Bacopa monnieri: Evidence for a combined intervention to alleviate age associated cognitive decline

As the elderly population grows the impact of age associated cognitive decline as well as neurodegenerative diseases such as Alzheimer's disease and dementia will increase. Ageing is associated with consistent impairments in cognitive processes (e.g., processing speed, memory, executive function and learning) important for work, well-being, life satisfaction and overall participation in society. Recently, there has been increased effort to conduct research examining methods to improve cognitive function in older citizens. Cognitive training has been shown to improve performance in some cognitive domains; including memory, processing speed, executive function and attention in older adults. These cognitive changes are thought to be related to improvements in brain connectivity and neural circuitry. Bacopa monnieri has also been shown to improve specific domains of cognition, sensitive to age associated cognitive decline (particularly processing speed and memory). These Bacopa monnieri dependent improvements may be due to the increase in specific neuro-molecular mechanisms implicated in the enhancement of neural connections in the brain (i.e. synaptogenesis). In particular, a number of animal studies have shown Bacopa monnieri consumption upregulates calcium dependent kinases in the synapse and post-synaptic cell, crucial for strengthening and growing connections between neurons. These effects have been shown to occur in areas important for cognitive processes, such as the hippocampus. As Bacopa monnieri has shown neuro-molecular mechanisms that encourage synaptogenesis, while cognitive training enhances brain connectivity, Bacopa monnieri supplementation could theoretically enhance and strengthen synaptic changes acquired through cognitive training. Therefore, the current paper hypothesises that the combination of these two interventions could improve cognitive outcomes, over and above the effects of administrating these interventions independently, as an effective treatment to ameliorate age associated cognitive decline.

Synthesis and Biological Evaluation of Several Bryostatin Analogues Bearing a Diacylglycerol Lactone C-Ring

As an initial step in designing a simplified bryostatin hybrid molecule, three bryostatin analogues bearing a diacylglycerol lactone-based C-ring, which possessed the requisite pharmacophores for binding to protein kinase C (PKC) together with a modified bryostatin-like A- and B-ring region, were synthesized and evaluated. Merle 46 and Merle 47 exhibited binding affinity to PKC alpha with Ki values of 7000 ± 990 and 4940 ± 470 nM, respectively. Reinstallation of the trans-olefin and gem-dimethyl group present in bryostatin 1 in Merle 48 resulted in improved binding affinity, 363 ± 42 nM. While Merle 46 and 47 were only marginally active biologically, Merle 48 showed sufficient activity on the U937 cells to confirm that it was PMA-like for growth and attachment, as predicted by the substitution pattern of its A- and B-rings.

Protein Kinase Cϵ (PKCϵ) Promotes Synaptogenesis through Membrane Accumulation of the Postsynaptic Density Protein PSD-95

Protein kinase Cϵ (PKCϵ) promotes synaptic maturation and synaptogenesis via activation of synaptic growth factors such as BDNF, NGF, and IGF. However, many of the detailed mechanisms by which PKCϵ induces synaptogenesis are not fully understood. Accumulation of PSD-95 to the postsynaptic density (PSD) is known to lead to synaptic maturation and strengthening of excitatory synapses. Here we investigated the relationship between PKCϵ and PSD-95. We show that the PKCϵ activators dicyclopropanated linoleic acid methyl ester and bryostatin 1 induce phosphorylation of PSD-95 at the serine 295 residue, increase the levels of PSD-95, and enhance its membrane localization. Elimination of the serine 295 residue in PSD-95 abolished PKCϵ-induced membrane accumulation. Knockdown of either PKCϵ or JNK1 prevented PKCϵ activator-mediated membrane accumulation of PSD-95. PKCϵ directly phosphorylated PSD-95 and JNK1 in vitro Inhibiting PKCϵ, JNK, or calcium/calmodulin-dependent kinase II activity prevented the effects of PKCϵ activators on PSD-95 phosphorylation. Increase in membrane accumulation of PKCϵ and phosphorylated PSD-95 (p-PSD-95(S295)) coincided with an increased number of synapses and increased amplitudes of excitatory post-synaptic potentials (EPSPs) in adult rat hippocampal slices. Knockdown of PKCϵ also reduced the synthesis of PSD-95 and the presynaptic protein synaptophysin by 30 and 44%, respectively. Prolonged activation of PKCϵ increased synapse number by 2-fold, increased presynaptic vesicle density, and greatly increased PSD-95 clustering. These results indicate that PKCϵ promotes synaptogenesis by activating PSD-95 phosphorylation directly through JNK1 and calcium/calmodulin-dependent kinase II and also by inducing expression of PSD-95 and synaptophysin.

Simplified Bryostatin Analogues Protect Cells from Chikungunya Virus-Induced Cell Death

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus showing a recent resurgence and rapid spread worldwide. While vaccines are under development, there are currently no therapies to treat this disease, except for over-the-counter (OTC) analgesics, which alleviate the devastating arthritic and arthralgic symptoms. To identify novel inhibitors of the virus, analogues of the natural product bryostatin 1, a clinical lead for the treatment of cancer, Alzheimer's disease, and HIV eradication, were investigated for in vitro antiviral activity and were found to be among the most potent inhibitors of CHIKV replication reported to date. Bryostatin-based therapeutic efforts and even recent anti-CHIKV strategies have centered on modulation of protein kinase C (PKC). Intriguingly, while the C ring of bryostatin primarily drives interactions with PKC, A- and B-ring functionality in these analogues has a significant effect on the observed cell-protective activity. Significantly, bryostatin 1 itself, a potent pan-PKC modulator, is inactive in these assays. These new findings indicate that the observed anti-CHIKV activity is not solely mediated by PKC modulation, suggesting possible as yet unidentified targets for CHIKV therapeutic intervention. The high potency and low toxicity of these bryologs make them promising new leads for the development of a CHIKV treatment.

Isolation, analytical measurements, and cell line studies of the iron-bryostatin-1 complex

Bryostatin-1 is a marine natural product that has demonstrated medicinal activity in pre-clinical and clinical trials for the treatment of cancer, Alzheimer's disease, effects of stroke, and HIV. In this study, iron-bryostatin-1 was obtained using a pharmaceutical aquaculture technique developed by our lab that cultivates marine bacteria for marine natural product extraction. Analytical measurements (1)H and (13)C NMR, mass spectrometry, and flame atomic absorption were utilized to confirm the presence of an iron-bryostatin-1 complex. The iron-bryostatin-1 complex produced was then tested against the National Cancer Institute's 60 cell line panel. Adding iron to bryostatin-1 lowered the anti-cancer efficacy of the compound.

Bryostatin-1 Restores Blood Brain Barrier Integrity following Blast-Induced Traumatic Brain Injury

Recent wars in Iraq and Afghanistan have accounted for an estimated 270,000 blast exposures among military personnel. Blast traumatic brain injury (TBI) is the 'signature injury' of modern warfare. Blood brain barrier (BBB) disruption following blast TBI can lead to long-term and diffuse neuroinflammation. In this study, we investigate for the first time the role of bryostatin-1, a specific protein kinase C (PKC) modulator, in ameliorating BBB breakdown. Thirty seven Sprague-Dawley rats were used for this study. We utilized a clinically relevant and validated blast model to expose animals to moderate blast exposure. Groups included: control, single blast exposure, and single blast exposure + bryostatin-1. Bryostatin-1 was administered i.p. 2.5 mg/kg after blast exposure. Evan's blue, immunohistochemistry, and western blot analysis were performed to assess injury. Evan's blue binds to albumin and is a marker for BBB disruption. The single blast exposure caused an increase in permeability compared to control (t = 4.808, p < 0.05), and a reduction back toward control levels when bryostatin-1 was administered (t = 5.113, p < 0.01). Three important PKC isozymes, PKCα, PKCδ, and PKCε, were co-localized primarily with endothelial cells but not astrocytes. Bryostatin-1 administration reduced toxic PKCα levels back toward control levels (t = 4.559, p < 0.01) and increased the neuroprotective isozyme PKCε (t = 6.102, p < 0.01). Bryostatin-1 caused a significant increase in the tight junction proteins VE-cadherin, ZO-1, and occludin through modulation of PKC activity. Bryostatin-1 ultimately decreased BBB breakdown potentially due to modulation of PKC isozymes. Future work will examine the role of bryostatin-1 in preventing chronic neurodegeneration following repetitive neurotrauma.

Acyl Ghrelin Improves Synapse Recovery in an In Vitro Model of Postanoxic Encephalopathy

Comatose patients after cardiac arrest have a poor prognosis. Approximately half never awakes as a result of severe diffuse postanoxic encephalopathy. Several neuroprotective agents have been tested, however without significant effect. In the present study, we used cultured neuronal networks as a model system to study the general synaptic damage caused by temporary severe hypoxia and the possibility to restrict it by ghrelin treatment. Briefly, we applied hypoxia (pO₂ lowered from 150 to 20 mmHg) during 6 h in 55 cultures. Three hours after restoration of normoxia, half of the cultures were treated with ghrelin for 24 h, while the other, non-supplemented, were used as a control. All cultures were processed immunocytochemically for detection of the synaptic marker synaptophysin. We observed that hypoxia led to drastic decline of the number of synapses, followed by some recovery after return to normoxia, but still below the prehypoxic level. Additionally, synaptic vulnerability was selective: large- and small-sized neurons were more susceptible to synaptic damage than the medium-sized ones. Ghrelin treatment significantly increased the synapse density, as compared with the non-treated controls or with the prehypoxic period. The effect was detected in all neuronal subtypes. In conclusion, exogenous ghrelin has a robust impact on the recovery of cortical synapses after hypoxia. It raises the possibility that ghrelin or its analogs may have a therapeutic potential for treatment of postanoxic encephalopathy.

Stress: perspectives on its impact on cognition and pharmacological treatment

Stress in life is unavoidable, affecting everyone on a daily basis. Psychological stress in mammals triggers a rapidly organized response for survival, but it may also cause a variety of behavioral disorders and damage cognitive function. Stress is associated with biases in cognitive processing; some of the most enduring memories are formed by traumatic events. Our understanding of how cognition is shaped by stress is still relatively primitive; however, evidence is rapidly accumulating that the 'mature' brain has a great capacity for plasticity and that there are numerous ways through which pharmacological therapeutics could rescue cognitive function and regain cognitive balance. In this review, we discuss recent advances in our understanding of the interplay between stress and cognitive processes and potential therapeutic approaches to stress-related behavioral and cognitive disorders.

Toward a biorelevant structure of protein kinase C bound modulators: design, synthesis, and evaluation of labeled bryostatin analogues for analysis with rotational echo double resonance NMR spectroscopy

Protein kinase C (PKC) modulators are currently of great importance in preclinical and clinical studies directed at cancer, immunotherapy, HIV eradication, and Alzheimer's disease. However, the bound conformation of PKC modulators in a membrane environment is not known. Rotational echo double resonance (REDOR) NMR spectroscopy could uniquely address this challenge. However, REDOR NMR requires strategically labeled, high affinity ligands to determine interlabel distances from which the conformation of the bound ligand in the PKC-ligand complex could be identified. Here we report the first computer-guided design and syntheses of three bryostatin analogues strategically labeled for REDOR NMR analysis. Extensive computer analyses of energetically accessible analogue conformations suggested preferred labeling sites for the identification of the PKC-bound conformers. Significantly, three labeled analogues were synthesized, and, as required for REDOR analysis, all proved highly potent with PKC affinities (∼1 nM) on par with bryostatin. These potent and strategically labeled bryostatin analogues are new structural leads and provide the necessary starting point for projected efforts to determine the PKC-bound conformation of such analogues in a membrane environment, as needed to design new PKC modulators and understand PKC-ligand-membrane structure and dynamics.

Selective estrogen receptor modulators (SERMs) enhance neurogenesis and spine density following focal cerebral ischemia

Selective estrogen receptor modulators (SERMs) have been reported to enhance synaptic plasticity and improve cognitive performance in adult rats. SERMs have also been shown to induce neuroprotection against cerebral ischemia and other CNS insults. In this study, we sought to determine whether acute regulation of neurogenesis and spine remodeling could be a novel mechanism associated with neuroprotection induced by SERMs following cerebral ischemia. Toward this end, ovariectomized adult female rats were either implanted with pellets of 17β-estradiol (estrogen) or tamoxifen, or injected with raloxifene. After one week, cerebral ischemia was induced by the transient middle-cerebral artery occlusion (MCAO) method. Bromodeoxyuridine (BrdU) was injected to label dividing cells in brain. We analyzed neurogenesis and spine density at day-1 and day-5 post MCAO. In agreement with earlier findings, we observed a robust induction of neurogenesis in the ipsilateral subventricular zone (SVZ) of both the intact as well as ovariectomized female rats following MCAO. Interestingly, neurogenesis in the ipsilateral SVZ following ischemia was significantly higher in estrogen and raloxifene-treated animals compared to placebo-treated rats. In contrast, this enhancing effect on neurogenesis was not observed in tamoxifen-treated rats. Finally, both SERMs, as well as estrogen significantly reversed the spine density loss observed in the ischemic cortex at day-5 post ischemia. Taken, together these results reveal a profound structural remodeling potential of SERMs in the brain following cerebral ischemia. This article is part of a Special Issue entitled "Sex steroids and brain disorders".