Brain organoids engineered to give rise to glia and neural networks after 90 days in culture exhibit human-specific proteoforms

Human brain organoids are emerging as translationally relevant models for the study of human brain health and disease. However, it remains to be shown whether human-specific protein processing is conserved in human brain organoids. Herein, we demonstrate that cell fate and composition of unguided brain organoids are dictated by culture conditions during embryoid body formation, and that culture conditions at this stage can be optimized to result in the presence of glia-associated proteins and neural network activity as early as three-months in vitro. Under these optimized conditions, unguided brain organoids generated from induced pluripotent stem cells (iPSCs) derived from male-female siblings are similar in growth rate, size, and total protein content, and exhibit minimal batch-to-batch variability in cell composition and metabolism. A comparison of neuronal, microglial, and macroglial (astrocyte and oligodendrocyte) markers reveals that profiles in these brain organoids are more similar to autopsied human cortical and cerebellar profiles than to those in mouse cortical samples, providing the first demonstration that human-specific protein processing is largely conserved in unguided brain organoids. Thus, our organoid protocol provides four major cell types that appear to process proteins in a manner very similar to the human brain, and they do so in half the time required by other protocols. This unique copy of the human brain and basic characteristics lay the foundation for future studies aiming to investigate human brain-specific protein patterning (e.g., isoforms, splice variants) as well as modulate glial and neuronal processes in an in situ-like environment.

A role for Shugoshin in human cilia?

We have recently described a novel role for the conserved centromeric/kinetochore protein and cohesin protector, Shugoshin, in cilia of C. elegans. Worms are unusual in that the sole Shugoshin protein ( SGO-1 ) is dispensable for chromosome segregation but required for cilia function in fully differentiated sensory neurons. Depletion of sgo-1 leads to an array of sensory defects observed in other cilia mutants with a compromised diffusion barrier. Accordingly, SGO-1 loads to the base of cilia in sensory neurons and can be observed occupying the transition zone, the critical ciliary domain that regulates trafficking in and out of ciliary compartments. Here we start to address a potential conserved role in cilia for vertebrate Shugoshin by asking whether human Shugoshin can: (1) localize to cilia and (2) rescue defects due to Shugoshin depletion in C. elegans . Our preliminary results suggest that human Shugoshin is detectable in the cilia base but show limited functional conservation when expressed in C. elegans sensory neurons.

CP55940-induced vasorelaxation is endothelial-dependent and mediated by the CB1R through NOS, COX and EDHF pathways in porcine cerebral arteries

Using swine as an experimental model, we chose to examine whether the cannabinoid receptors, e.g. CB1R and the CB2R, could affect vasomotor tone in isolated pial arteries. It was hypothesized that the CB1R would specifically mediate cerebral artery vasorelaxation in an endothelial-dependent manner. First-order pial arteries were isolated from female Landrace pigs (age = 2 months; N = 27) for wire and pressure myography. Arteries were pre-contracted with a thromboxane A₂ analogue (U-46619) and vasorelaxation in response to the CB1R and CB2R receptor mixed agonist CP55940 was examined in the following conditions: 1) untreated; 2) inhibition of the CB1R (AM251); or 3) inhibition of the CB2R receptor (AM630). The data revealed that CP55940 elicits a CB1R-dependent relaxation in pial arteries. CB1R expression was confirmed using immunoblot and immunohistochemical analyses. Subsequently, the role of different endothelial-dependent pathways in the CB1R-mediated vasorelaxation was examined using: 1) denudation (removal of the endothelium); 2) inhibition of cyclooxygenase (COX; Naproxen); 3) inhibition of nitric oxide synthase (NOS; L-NAME); 4) combined inhibition of COX + NOS. The data revealed CB1R-mediated vasorelaxation was endothelial-dependent, with contributions from COX-derived prostaglandins, NO, and endothelium-dependent hyperpolarizing factor (EDHF). Pressurized arteries underwent myogenic curves (20-100 mmHg) under the following conditions: 1) untreated; 2) inhibition of the CB1R. The data revealed CB1R inhibition increased basal myogenic tone, but not myogenic reactivity. As the vascular responses were assessed in isolated pial arteries, this work reveals that the CB1R modulates cerebrovascular tone independently of changes in brain metabolism.

Fundamental Neurochemistry Review: Incorporating a greater diversity of cell types, including microglia, in brain organoid cultures improves clinical translation

Brain organoids have the potential to improve clinical translation, with the added benefit of reducing any extraneous use of experimental animals. As brain organoids are three-dimensional in vitro constructs that emulate the human brain, they bridge in vitro and in vivo studies more appropriately than monocultures. Although many factors contribute to the failure of extrapolating monoculture-based information to animal-based experiments and clinical trials, for the purpose of this review, we will focus on glia (non-neuronal brain cells), whose functions and transcriptome are particularly abnormal in monocultures. As discussed herein, glia require signals from-and contact with-other cell types to exist in their homeostatic state, which likely contributes to some of the differences between data derived from monocultures and data derived from brain organoids and even two-dimensional co-cultures. Furthermore, we highlight transcriptomic differences between humans and mice in regard to aging and Alzheimer's disease, emphasizing need for a model using the human genome-again, a benefit of brain organoids-to complement data derived from animals. We also identify an urgency for guidelines to improve the reporting and transparency of research using organoids. The lack of reporting standards creates challenges for the comparison and discussion of data from different articles. Importantly, brain organoids mark the first human model enabling the study of brain cytoarchitecture and development.

Cardiolipin released by microglia can act on neighboring glial cells to facilitate the uptake of amyloid-β (1-42)

Cardiolipin is a mitochondrial phospholipid that is also detected in serum inferring its extracellular release; however, this process has not been directly demonstrated for any of the brain cell types. Nevertheless, extracellular cardiolipin has been shown to modulate several neuroimmune functions of microglia and astrocytes, including upregulation of their endocytic activity. Low cardiolipin levels are associated with brain aging, and may thus hinder uptake of amyloid-β (Αβ) in Alzheimer's disease. We hypothesized that glial cells are one of the sources of extracellular cardiolipin in the brain parenchyma where this phospholipid interacts with neighboring cells to upregulate the endocytosis of Αβ. Liquid chromatography-mass spectrophotometry identified 31 different species of cardiolipin released from murine BV-2 microglial cells and revealed this process was accelerated by exposure to Aβ42. Extracellular cardiolipin upregulated internalization of fluorescently-labeled Aβ42 by primary murine astrocytes, human U118 MG astrocytic cells, and murine BV-2 microglia. Increased endocytic activity in the presence of extracellular cardiolipin was also demonstrated by studying uptake of Aβ42 and pHrodo™ Bioparticles™ by human induced pluripotent stem cells (iPSCs)-derived microglia, as well as iPSC-derived human brain organoids containing microglia, astrocytes, oligodendrocytes and neurons. Our observations indicate that Aβ42 augments the release of cardiolipin from microglia into the extracellular space, where it can act on microglia and astrocytes to enhance their endocytosis of Aβ42. Our observations suggest that the reduced glial uptake of Aβ due to the decreased levels of cardiolipin could be at least partially responsible for the extracellular accumulation of Aβ in aging and Alzheimer's disease.

Detecting Monoamine Oxidase A and B Proteins: A Western Blotting Protocol and Some Practical Considerations

The expression of the two isoforms of monoamine oxidase (MAO A and MAO B) is often inferred from proxy measures such as mRNA transcript levels or catalytic activity. Yet the literature is clear that the proportionality of protein, mRNA, and activity does not guarantee that any of these measures can be used as a proxy for any of the others. Here we provide a protocol for the detection of MAO proteins in cell lysates that can be adapted readily to tissue preparations. Given that MAOs influence many physiological and pathological processes, we feel it is essential to include measures of protein expression when exploring genetic regulation or catalytic properties of these important enzymes.

An (Immuno) Fluorescence Protocol for Monitoring Monoamine Oxidase A/B Protein Distribution Within the Cell

The influence of a protein is not determined exclusively by its level of expression, but also by its localization within the cell. The literature often refers to the enzyme monoamine oxidase (MAO) as a mitochondrial enzyme, yet there is evidence that mitochondria-independent pools of MAO exist. These pools of MAO could exert distinct influences across physiological as well as pathological phenotypes. Fluorescence microscopy is a powerful tool for spatially resolving target proteins in cell and tissue preparations. This can rely on an antibody-based probe that targets the endogenous protein, e.g., immunofluorescence. In the event that antibodies might not be readily available or if one is interested in characterizing a variant of the wild-type protein, then a recombinant protein with a fluorescent fusion "tag" is preferred. We now describe a protocol for the detection of endogenous MAO using indirect immunofluorescence and a version of the protocol with minor modification for detecting (green) fluorescent protein-tagged MAOs. One observation we can highlight using these easily adaptable approaches is that MAO A and MAO B do not follow similar patterns of distribution throughout the cell, suggesting potential expression of MAO A and MAO B on distinct pools of mitochondria. Furthermore, distinct subcellular compartmentalization is suggested by the fact that a pool of MAO A, but not MAO B, is associated with certain lysosomal compartments. However, directed and quantitative studies will be required before any definitive statement can be made on these intriguing possibilities.

Altered cerebrovascular regulation in low birthweight swine

Full-term low birthweight (LBW) offspring exhibit peripheral vascular dysfunction in the postnatal period; however, whether such impairments extend to the cerebrovasculature remains to be elucidated. We used a swine model to test the hypothesis that LBW offspring would exhibit cerebrovascular dysfunction at later stages of life. Offspring from 14 sows were identified as normal birthweight (NBW) or LBW and were assessed at 28 (similar to end of infancy) and 56 (similar to childhood) days of age. LBW swine had lower absolute brain mass, but demonstrated evidence of brain sparing (increased brain mass scaled to body mass) at 56 days of age. The cerebral pulsatility index, based on transcranial Doppler, was increased in LBW swine. Moreover, arterial myography of isolated cerebral arteries revealed impaired vasoreactivity to bradykinin and reduced contribution of nitric oxide (NO) to vasorelaxation in the LBW swine. Immunoblotting demonstrated a lower ratio of phosphorylated-to-total endothelial NO synthase in LBW offspring. This impairment in NO signaling was greater at 28 vs. 56 days of age. Vasomotor responses to sodium nitroprusside (NO-donor) were unaltered, while Leu³¹, Pro³⁴ neuropeptide Y-induced vasoconstriction was enhanced in LBW swine. Increases in total Y1 receptor protein content in the LBW group were not significant. In summary, LBW offspring displayed signs of cerebrovascular dysfunction at 28 and 56 days of age, evidenced by altered cerebral hemodynamics (reflective of increased impedance) coupled with endothelial dysfunction and altered vasomotor control. Overall, the data reveal that normal variance in birthweight of full-term offspring can influence cerebrovascular function later in life.

Cannabinoids in the management of behavioral, psychological, and motor symptoms of neurocognitive disorders: a mixed studies systematic review

Aim

We undertook this systematic review to determine the efficacy and safety of cannabis-based medicine as a treatment for behavioral, psychological, and motor symptoms associated with neurocognitive disorders.

Methods

We conducted a PRISMA-guided systematic review to identify studies using cannabis-based medicine to treat behavioral, psychological, and motor symptoms among individuals with Alzheimer's disease (AD) dementia, Parkinson’s disease (PD), and Huntington’s disease (HD). We considered English-language articles providing original data on three or more participants, regardless of design.

Findings

We identified 25 studies spanning 1991 to 2021 comprised of 14 controlled trials, 5 pilot studies, 5 observational studies, and 1 case series. In most cases, the cannabinoids tested were dronabinol, whole cannabis, and cannabidiol, and the diagnoses included AD (n = 11), PD (n = 11), and HD (n = 3). Primary outcomes were motor symptoms (e.g., dyskinesia), sleep disturbance, cognition, balance, body weight, and the occurrence of treatment-emergent adverse events.

Conclusions

A narrative summary of the findings from the limited number of studies in the area highlights an apparent association between cannabidiol-based products and relief from motor symptoms in HD and PD and an apparent association between synthetic cannabinoids and relief from behavioral and psychological symptoms of dementia across AD, PD, and HD. These preliminary conclusions could guide using plant-based versus synthetic cannabinoids as safe, alternative treatments for managing neuropsychiatric symptoms in neurocognitive vulnerable patient populations.

Cerebrovascular insufficiency and amyloidogenic signaling in Ossabaw swine with cardiometabolic heart failure

Individuals with heart failure (HF) frequently present with comorbidities, including obesity, insulin resistance, hypertension, and dyslipidemia. Many patients with HF experience cardiogenic dementia, yet the pathophysiology of this disease remains poorly understood. Using a swine model of cardiometabolic HF (Western diet+aortic banding; WD-AB), we tested the hypothesis that WD-AB would promote a multidementia phenotype involving cerebrovascular dysfunction alongside evidence of Alzheimer’s disease (AD) pathology. The results provide evidence of cerebrovascular insufficiency coupled with neuroinflammation and amyloidosis in swine with experimental cardiometabolic HF. Although cardiac ejection fraction was normal, indices of arterial compliance and cerebral blood flow were reduced, and cerebrovascular regulation was impaired in the WD-AB group. Cerebrovascular dysfunction occurred concomitantly with increased MAPK signaling and amyloidogenic processing (i.e., increased APP, BACE1, CTF, and Aβ40 in the prefrontal cortex and hippocampus) in the WD-AB group. Transcriptomic profiles of the stellate ganglia revealed the WD-AB group displayed an enrichment of gene networks associated with MAPK/ERK signaling, AD, frontotemporal dementia, and a number of behavioral phenotypes implicated in cognitive impairment. These provide potentially novel evidence from a swine model that cerebrovascular and neuronal pathologies likely both contribute to the dementia profile in a setting of cardiometabolic HF.

The Aβ(1-38) peptide is a negative regulator of the Aβ(1-42) peptide implicated in Alzheimer disease progression

The pool of β-Amyloid (Aβ) length variants detected in preclinical and clinical Alzheimer disease (AD) samples suggests a diversity of roles for Aβ peptides. We examined how a naturally occurring variant, e.g. Aβ(1-38), interacts with the AD-related variant, Aβ(1-42), and the predominant physiological variant, Aβ(1-40). Atomic force microscopy, Thioflavin T fluorescence, circular dichroism, dynamic light scattering, and surface plasmon resonance reveal that Aβ(1-38) interacts differently with Aβ(1-40) and Aβ(1-42) and, in general, Aβ(1-38) interferes with the conversion of Aβ(1-42) to a β-sheet-rich aggregate. Functionally, Aβ(1-38) reverses the negative impact of Aβ(1-42) on long-term potentiation in acute hippocampal slices and on membrane conductance in primary neurons, and mitigates an Aβ(1-42) phenotype in Caenorhabditis elegans. Aβ(1-38) also reverses any loss of MTT conversion induced by Aβ(1-40) and Aβ(1-42) in HT-22 hippocampal neurons and APOE ε4-positive human fibroblasts, although the combination of Aβ(1-38) and Aβ(1-42) inhibits MTT conversion in APOE ε4-negative fibroblasts. A greater ratio of soluble Aβ(1-42)/Aβ(1-38) [and Aβ(1-42)/Aβ(1-40)] in autopsied brain extracts correlates with an earlier age-at-death in males (but not females) with a diagnosis of AD. These results suggest that Aβ(1-38) is capable of physically counteracting, potentially in a sex-dependent manner, the neuropathological effects of the AD-relevant Aβ(1-42).

An Overview of the Involvement of D-Serine in Cognitive Impairment in Normal Aging and Dementia

Dementia, of which Alzheimer's disease (AD) is the most common form, is characterized by progressive cognitive deterioration, including profound memory loss, which affects functioning in many aspects of life. Although cognitive deterioration is relatively common in aging and aging is a risk factor for AD, the condition is not necessarily a part of the aging process. The N-methyl-D-aspartate glutamate receptor (NMDAR) and its co-agonist D-serine are currently of great interest as potential important contributors to cognitive function in normal aging and dementia. D-Serine is necessary for activation of the NMDAR and in maintenance of long-term potentiation (LTP) and is involved in brain development, neuronal connectivity, synaptic plasticity and regulation of learning and memory. In this paper, we review evidence, from both preclinical and human studies, on the involvement of D-serine (and the enzymes involved in its metabolism) in regulation of cognition. Potential mechanisms of action of D-serine are discussed in the context of normal aging and in dementia, as is the potential for using D-serine as a potential biomarker and/or therapeutic agent in dementia. Although there is some controversy in the literature, it has been proposed that in normal aging there is decreased expression of serine racemase and decreased levels of D-serine and down-regulation of NMDARs, resulting in impaired synaptic plasticity and deficits in learning and memory. In contrast, in AD there appears to be activation of serine racemase, increased levels of D-serine and overstimulation of NMDARs, resulting in cytotoxicity, synaptic deficits, and dementia.

The Nuclear Lamina: Protein Accumulation and Disease

Cellular health is reliant on proteostasis-the maintenance of protein levels regulated through multiple pathways modulating protein synthesis, degradation and clearance. Loss of proteostasis results in serious disease and is associated with aging. One proteinaceous structure underlying the nuclear envelope-the nuclear lamina-coordinates essential processes including DNA repair, genome organization and epigenetic and transcriptional regulation. Loss of proteostasis within the nuclear lamina results in the accumulation of proteins, disrupting these essential functions, either via direct interactions of protein aggregates within the lamina or by altering systems that maintain lamina structure. Here we discuss the links between proteostasis and disease of the nuclear lamina, as well as how manipulating specific proteostatic pathways involved in protein clearance could improve cellular health and prevent/reverse disease.

Female Sex Hormones and Cardiac Pressure Overload Independently Contribute to the Cardiogenic Dementia Profile in Yucatan Miniature Swine

Post-menopausal women with heart failure (HF) frequently exhibit cardiogenic dementia. Using a pre-clinical swine model of post-menopausal HF, we recently demonstrated that experimental menopause (ovariectomy; OVX) and HF (6-month cardiac pressure overload/aortic banding; AB) independently altered cerebral vasomotor control and together impaired cognitive function. The purpose of this study was to examine the prefrontal cortex and hippocampus tissues from these animals to assess whether OVX and HF are associated with neurologic alterations that may contribute to cardiogenic dementia. We hypothesized that OVX and HF would independently alter neuronal cell signaling in swine with post-menopausal cardiogenic dementia. Immunoblot analyses revealed OVX was associated with reduced estrogen receptor-α in both brain regions and HF tended to exacerbate OVX-induced deficits in the hippocampus. Further, OVX was associated with a reduction in the ratio of phosphorylated:total Akt and ERK in the hippocampus as well as decreased total Akt and synaptophysin in the prefrontal cortex. In contrast, HF was associated with a trend toward reduced phosphorylated:total ERK in the prefrontal cortex. In addition, HF was associated with decreased β-amyloid (1-38) in the prefrontal cortex and increased β-amyloid (1-38) in the hippocampus. Regional brain lipid analysis revealed OVX tended to increase total, saturated, and monounsaturated fatty acid content in the prefrontal cortex, with the greatest magnitude of change occurring in the AB-OVX group. The data from this study suggest that OVX and HF are independently associated with regional-specific neurologic changes in the brain that contribute to the cardiogenic dementia profile in this model. This pre-clinical swine model may be a useful tool for better understanding post-menopausal cardiogenic dementia pathology and developing novel therapies.

Design and synthesis of fluorogenic substrate-based probes for detecting Cathepsin B activity

Cathepsin B plays key roles in tumor progression with its overexpression being associated with invasive and metastatic phenotypes and is a primary target of protease activated antibody-directed prodrug therapy. It therefore represents a potential therapeutic and diagnostic target and effort has been made to develop fluorescent probes to report on Cathepsin B activity in cells and animal models of cancer. We have designed, synthesized, and thoroughly evaluated four novel "turn on" probes that employ a lysosomotropic dansylcadaverine dye to report on Cathepsin B activity. Enzyme activity assays using a recombinant human enzyme and cancer cell lysates coupled with confocal microscopy experiments demonstrated that one of the probes, derivatized with the self-immolative prodrug linker p-aminobenzyl alcohol, can selectively report on Cathepsin B in biological samples including live cells.

Dosage Related Efficacy and Tolerability of Cannabidiol in Children With Treatment-Resistant Epileptic Encephalopathy: Preliminary Results of the CARE-E Study

Purpose: There is uncertainty regarding the appropriate dose of Cannabidiol (CBD) for childhood epilepsy. We present the preliminary data of seven participants from the Cannabidiol in Children with Refractory Epileptic Encephalopathy (CARE-E) study. Methods: The study is an open-label, prospective, dose-escalation trial. Participants received escalating doses of a Cannabis Herbal Extract (CHE) preparation of 1:20 Δ⁹-tetrahydrocannabinol (THC): CBD up to 10-12 mg CBD/kg/day. Seizure frequency was monitored in daily logs, participants underwent regular electroencephalograms, and parents filled out modified Quality of Life in Childhood Epilepsy (QOLCE) and Side Effect rating scale questionnaires. Steady-state trough levels (C_{ss, Min}) of selected cannabinoids were quantified. Results: All seven participants tolerated the CHE up to 10-12 mg CBD/kg/day and had improvements in seizure frequency and QOLCE scores. C_{SS, Min} plasma levels for CBD, THC, and cannabichromene (CBC) showed dose-independent pharmacokinetics in all but one participant. C_{SS, Min} CBD levels associated with a >50% reduction in seizures and seizure freedom were lower than those reported previously with purified CBD. In most patients, C_{SS, Min} levels of THC remained lower than what would be expected to cause intoxication. Conclusion: The preliminary data suggest an initial CBD target dose of 5-6 mg/kg/day when a 1:20 THC:CBD CHE is used. Possible non-linear pharmacokinetics of CBD and CBC needs investigation. The reduction in seizure frequency seen suggests improved seizure control when a whole plant CHE is used. Plasma THC levels suggest a low risk of THC intoxication when a 1:20 THC:CBD CHE is used in doses up to 12 mg/kg CBD/kg/day.

Age- and sex-dependent profiles of APP fragments and key secretases align with changes in despair-like behavior and cognition in young APPSwe/Ind mice

Biological sex exerts distinct influences on brain levels of the β-amyloid (Aβ) peptide in both clinical depression and Alzheimer disease (AD), yet studies in animal models focus primarily on males. We examined behavioral 'despair'/depression (using the tail-suspension test) and memory (using the novel object recognition task) in J20 (hAPP_Swe/Ind) mice. Three month-old male (but not female) J20 mice exhibited less despair-like behavior, but more evidence of cognitive deficits. In young J20 mice, only soluble Aβ peptides -primarily Aβ(1-40)- were detected. There was no evidence of an effect on despair-like behavior in the six month-old J20 mice, although cognitive deficits were now evident in both sexes, and coincided with a greater proportion of the neurotoxic Aβ(1-42) species (in soluble as well as insoluble fractions). This age-dependent shift in Aβ peptide profile coincided with reduced expression of glycosylated species of ADAM-10 (α-secretase) and BACE1 (β-secretase), and an increased co-immunoprecipitation of presenilin-1 with nicastrin (components of the γ-secretase complex). Sex-dependent changes in depression-related monoaminergic, e.g. serotonin and dopamine (but not noradrenaline), systems were evident already in young J20 mice. It is critical to acknowledge that sex-dependent APP-related phenotypes might differentially influence modifiable depression-related monoaminergic signalling at some of the earliest pathological stages of clinical AD.

Can Animal Models Inform on the Relationship between Depression and Alzheimer Disease?

The focus on the β-amyloid (Aβ) peptide in clinical Alzheimer disease (AD) as well as in animal models of AD has perhaps biased our understanding of what contributes to the heterogeneity in disease onset and progression. Part of this heterogeneity could reflect the various neuropsychiatric risk factors that present with common symptomatology and can predispose the brain to AD-like changes. One such risk factor is depression. Animal models, particularly mouse models carrying variants of AD-related gene(s), many of which lead to an accumulation of Aβ, suggest that a fundamental shift in depression-related monoaminergic systems (including serotonin and noradrenaline) is a strong indicator of the altered cellular function associated with the earlier(est) stages of AD-related pathology. These changes in monoaminergic neurochemistry could provide for relevant targets for intervention in clinical AD and/or could support a polypharmacy strategy, which might include the targeting of Aβ, in vulnerable populations. Future studies must also include female mice as well as male mice in animal model studies on the relationship between depression and AD.

Molecular characterization of an MLL1 fusion and its role in chromosomal instability

Chromosomal rearrangements involving the mixed‐lineage leukemia (MLL1) gene are common in a unique group of acute leukemias, with more than 100 fusion partners in this malignancy alone. However, do these fusions occur or have a role in solid tumors? We performed extensive network analyses of MLL1‐fusion partners in patient datasets, revealing that multiple MLL1‐fusion partners exhibited significant interactions with the androgen‐receptor signaling pathway. Further exploration of tumor sequence data from TCGA predicts the presence of MLL1 fusions with truncated SET domain in prostate tumors. To investigate the physiological relevance of MLL1 fusions in solid tumors, we engineered a truncated version of MLL1 by fusing it with one of its known fusion partners, ZC3H13, to use as a model system. Functional characterization with cell‐based assays revealed that MLL1‐ZC3H13 fusion induced chromosomal instability, affected mitotic progression, and enhanced tumorsphere formation. The MLL1‐ZC3H13 chimera consistently increased the expression of a cancer stem cell marker (CD44); in addition, we detected potential collateral lethality between DOT1L and MLL1 fusions. Our work reveals that MLL1 fusions are likely prevalent in solid tumors and exhibit a potential pro‐tumorigenic role.

Glycosylation States of Pre- and Post-synaptic Markers of 5-HT Neurons Differ With Sex and 5-HTTLPR Genotype in Cortical Autopsy Samples

The serotonin (5-hydroxytryptamine, 5-HT) transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) is thought to alter 5-HT signaling and contribute to behavioral and cognitive phenotypes in depression as well as Alzheimer disease (AD). We explored how well the short (S) and long (L) alleles of the 5-HTTLPR align with serotoninergic indices in 60 autopsied cortical samples from early-onset AD/EOAD and late-onset AD/LOAD donors, and age- and sex-matched controls. Stratifying data by either diagnosis-by-genotype or by sex-by-genotype revealed that the donor's 5-HTTLPR genotype, i.e., L/L, S/L, or S/S, did not affect 5-HTT mRNA or protein expression. However, the glycosylation of 5-HTT was significantly higher in control female (vs. male) samples and tended to decrease in female EOAD/LOAD samples, but remained unaltered in male LOAD samples. Glycosylated forms of the vesicular monoamine transporter (VMAT2) were lower in both male and female AD samples, while a sex-by-genotype stratification revealed a loss of VMAT2 glycosylation specifically in females with an L/L genotype. VMAT2 and 5-HTT glycosylation were correlated in male samples and inversely correlated in female samples in both stratification models. The S/S genotype aligned with lower levels of 5-HT turnover in females (but not males) and with an increased glycosylation of the post-synaptic 5-HT2C receptor. Interestingly, the changes in presynaptic glycosylation were evident primarily in female carriers of the APOE ε4 risk factor for AD. Our data do not support an association between 5-HTTLPR genotype and 5-HTT expression, but they do reveal a non-canonical association of 5-HTTLPR genotype with sex-dependent glycosylation changes in pre- and post-synaptic markers of serotoninergic neurons. These patterns of change suggest adaptive responses in 5-HT signaling and could certainly be contributing to the female prevalence in risk for either depression or AD.

The protocol for the Cannabidiol in children with refractory epileptic encephalopathy (CARE-E) study: a phase 1 dosage escalation study

BACKGROUND

Initial studies suggest pharmaceutical grade cannabidiol (CBD) can reduce the frequency of convulsive seizures and lead to improvements in quality of life in children affected by epileptic encephalopathies. With limited access to pharmaceutical CBD, Cannabis extracts in oil are becoming increasingly available. Physicians show reluctance to recommend Cannabis extracts given the lack of high quality safety data especially regarding the potential for harm caused by other cannabinoids, such as Δ9-tetrahydrocannabinol (Δ9-THC). The primary aims of the study presented in this protocol are (i) To determine whether CBD enriched Cannabis extract is safe and well-tolerated for pediatric patients with refractory epilepsy, (ii) To monitor the effects of CBD-enriched Cannabis extract on the frequency and duration of seizure types and on quality of life.

METHODS

Twenty-eight children with treatment resistant epileptic encephalopathy ranging in age from 1 to 10 years will be recruited in four Canadian cities into an open-label, dose-escalation phase 1 trial. The primary objectives for the study are (i) To determine if the CBD-enriched Cannabis herbal extract is safe and well-tolerated for pediatric patients with treatment resistant epileptic encephalopathy and (ii) To determine the effect of CBD-enriched Cannabis herbal extract on the frequency and duration of seizures. Secondary objectives include (i) To determine if CBD-enriched Cannabis herbal extracts alter steady-state levels of co-administered anticonvulsant medications. (ii) To assess the relation between dose escalation and quality of life measures, (iii) To determine the relation between dose escalation and steady state trough levels of bioactive cannabinoids. (iv) To determine the relation between dose escalation and incidence of adverse effects.

DISCUSSION

This paper describes the study design of a phase 1 trial of CBD-enriched Cannabis herbal extract in children with treatment-resistant epileptic encephalopathy. This study will provide the first high quality analysis of safety of CBD-enriched Cannabis herbal extract in pediatric patients in relation to dosage and pharmacokinetics of the active cannabinoids.

TRIAL REGISTRATION

http://clinicaltrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). 2016 Dec 16. Identifier NCT03024827, Cannabidiol in Children with Refractory Epileptic Encephalopathy: CARE-E; 2017 Jan 19 [cited 2017 Oct]; Available from: http://clinicaltrials.gov/ct2/show/NCT03024827.

Alzheimer Disease and Selected Risk Factors Disrupt a Co-regulation of Monoamine Oxidase-A/B in the Hippocampus, but Not in the Cortex

Monoamine oxidase-A (MAO-A) and MAO-B have both been implicated in the pathology of Alzheimer disease (AD). We examined 60 autopsied control and AD donor brain samples to determine how well MAO function aligned with two major risk factors for AD, namely sex and APOE ε4 status. MAO-A activity was increased in AD cortical, but not hippocampal, samples. In contrast, MAO-B activity was increased in both regions (with a strong input from female donors) whether sample means were compared based on: (a) diagnosis alone; (b) diagnosis-by-APOE ε4 status (i.e., carriers vs. non-carriers of the ε4 allele); or (c) APOE ε4 status alone (i.e., ignoring ‘diagnosis’ as a variable). Sample means strictly based on the donor’s sex did not reveal any difference in either MAO-A or MAO-B activity. Unexpectedly, we found that cortical MAO-A and MAO-B activities were highly correlated in both males and females (if focussing strictly on the donor’s sex), while in the hippocampus, any correlation was lost in female samples. Stratifying for sex-by-APOE ε4 status revealed a strong correlation between cortical MAO-A and MAO-B activities in both non-carriers and carriers of the allele, but any correlation in hippocampal samples was lost in carriers of the allele. A diagnosis of AD disrupted the correlation between MAO-A and MAO-B activities in the hippocampus, but not the cortex. We observed a novel region-dependent co-regulation of MAO-A and MAO-B mRNAs (but not proteins), while a lack of correlation between MAO activities and the respective proteins corroborated previous reports. Overexpression of human APOE4 increased MAO activity (but not mRNA/protein) in C6 and in HT-22 cell cultures. We identified a novel co-regulation of MAO-A and MAO-B activities that is spared from any influence of risk factors for AD or AD itself in the cortex, but vulnerable to these same factors in the hippocampus. Sex- and region-dependent abilities to buffer influences on brain MAO activities could have significant bearing on ambiguous outcomes when monoaminergic systems are targeted in clinical populations.

Lacunar-canalicular network in femoral cortical bone is reduced in aged women and is predominantly due to a loss of canalicular porosity

The lacunar-canalicular network (LCN) of bone contains osteocytes and their dendritic extensions, which allow for intercellular communication, and are believed to serve as the mechanosensors that coordinate the processes of bone modeling and remodeling. Imbalances in remodeling, for example, are linked to bone disease, including fragility associated with aging. We have reported that there is a reduction in scale for one component of the LCN, osteocyte lacunar volume, across the human lifespan in females. In the present study, we explore the hypothesis that canalicular porosity also declines with age. To visualize the LCN and to determine how its components are altered with aging, we examined samples from young (age: 20–23 y; n = 5) and aged (age: 70–86 y; n = 6) healthy women donors utilizing a fluorescent labelling technique in combination with confocal laser scanning microscopy. A large cross-sectional area of cortical bone spanning the endosteal to periosteal surfaces from the anterior proximal femoral shaft was examined in order to account for potential trans-cortical variation in the LCN. Overall, we found that LCN areal fraction was reduced by 40.6% in the samples from aged women. This reduction was due, in part, to a reduction in lacunar density (21.4% decline in lacunae number per given area of bone), but much more so due to a 44.6% decline in canalicular areal fraction. While the areal fraction of larger vascular canals was higher in endosteal vs. periosteal regions for both age groups, no regional differences were observed in the areal fractions of the LCN and its components for either age group. Our data indicate that the LCN is diminished in aged women, and is largely due to a decline in the canalicular areal fraction, and that, unlike vascular canal porosity, this diminished LCN is uniform across the cortex.

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The lacunar-canalicular network (LCN) is reduced by 40.6% in aged women

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The lacunar density (lacunae number per given area of bone) is reduced by 21.4% in aged women

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The reduction in LCN in aged women is primarily due to a 44.6% loss of canaliculi

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No endosteal vs. periosteal regional differences were observed in the LCN and its components in either young or aged women

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A reduction in canaliculi with age may contribute to bone fragility in aged women

The association of antidepressant drug usage with cognitive impairment or dementia, including Alzheimer disease: A systematic review and meta-analysis

OBJECTIVE

To determine if antidepressant drug usage is associated with cognitive impairment or dementia, including Alzheimer disease (AD).

METHOD

We conducted a systematic search of Medline, PubMed, PsycINFO, Web of Science, Embase, CINAHL, and the Cochrane Library. An initial screen by abstracts and titles was performed, and relevant full articles were then reviewed and assessed for their methodologic quality. Crude effect estimates were extracted from the included articles and a pooled estimate was obtained using a random effects model.

RESULTS

Five articles were selected from an initial pool of 4,123 articles. Use of antidepressant drugs was associated with a significant twofold increase in the odds of some form of cognitive impairment or dementia (OR = 2.17). Age was identified as a likely modifier of the association between antidepressant use and some form of cognitive impairment or AD/dementia. Studies that included participants with an average age equal to or greater than 65 years showed an increased odds of some form of cognitive impairment with antidepressant drug usage (OR = 1.65), whereas those with participants less than age 65 revealed an even stronger association (OR = 3.25).

CONCLUSIONS

Antidepressant drug usage is associated with AD/dementia and this is particularly evident if usage begins before age 65. This association may arise due to confounding by depression or depression severity. However, biological mechanisms potentially linking antidepressant exposure to dementia have been described, so an etiological effect of antidepressants is possible. With this confirmation that an association exists, clarification of underlying etiologic pathways requires urgent attention.

Therapeutic relevance of the protein phosphatase 2A in cancer

Chromosomal Instability (CIN) is regarded as a unifying feature of heterogeneous tumor populations, driving intratumoral heterogeneity. Polo-Like Kinase 1 (PLK1), a serine-threonine kinase that is often overexpressed across multiple tumor types, is one of the key regulators of CIN and is considered as a potential therapeutic target. However, targeting PLK1 has remained a challenge due to the off-target effects caused by the inhibition of other members of the polo-like family. Here we use synthetic dosage lethality (SDL), where the overexpression of PLK1 is lethal only when another, normally non-lethal, mutation or deletion is present. Rather than directly inhibiting PLK1, we found that inhibition of PP2A causes selective lethality to PLK1-overexpressing breast, pancreatic, ovarian, glioblastoma, and prostate cancer cells. As PP2A is widely regarded as a tumor suppressor, we resorted to gene expression datasets from cancer patients to functionally dissect its therapeutic relevance. We identified two major classes of PP2A subunits that negatively correlated with each other. Interestingly, most mitotic regulators, including PLK1, exhibited SDL interactions with only one class of PP2A subunits (PPP2R1A, PPP2R2D, PPP2R3B, PPP2R5B and PPP2R5D). Validation studies and other functional cell-based assays showed that inhibition of PPP2R5D affects both levels of phospho-Rb as well as sister chromatid cohesion in PLK1-overexpressing cells. Finally, analysis of clinical data revealed that patients with high expression of mitotic regulators and low expression of Class I subunits of PP2A improved survival. Overall, these observations point to a context-dependent role of PP2A that warrants further exploration for therapeutic benefits.

Differential expression of mannose-6-phosphate receptor regulates T cell contraction

CD8(+) T cells provide protection against pathogens and cancer. After encountering a pathogenic antigen, CD8(+) T cells undergo a triphasic program of rapid proliferation, contraction, and memory formation. Most (∼90-95%) CD8(+) T cells die after vigorous proliferation in the T cell contraction phase, yet the mechanism that triggers apoptotic T cell death remains elusive. This study tested the hypothesis that differential cell-surface expression of M6PR, a multifunctional receptor that regulates lysozyme biogenesis, but also uptakes apoptosis-inducing serine-protease Gzm-B, critically determines life vs. death decisions in T cells. We demonstrate that M6PR-expression on CD8(+) T cell surfaces is dynamically regulated during LmOVA bacterial infection. Notably, time-lapse, confocal microscopy and flow cytometry confirms that M6PR(low) effectors, but not M6PR(high) effectors, escape Gzm-B lethal-hit derived from CD4(+)25(+) Treg cells. Adoptive cotransfer of M6PR(low) effectors and M6PR(high) effectors sorted from LmOVA-infected, congenic mice at the peak of CD8(+) T cell response, reveals that M6PR(low) effectors with the CD8(+) T cell memory precursor phenotype preferentially survive the CD8(+) T cell contraction and differentiate into functional, long-lasting memory CD8(+) T cells. Taken together, our data provide the first evidence, to our knowledge, that selective M6PR down-regulation has a critical role in CD8(+) T cell survival, and our findings have implications for efficient vaccine design and immunotherapy.

RAGE mediates the inactivation of nAChRs in sympathetic neurons under high glucose conditions

Autonomic dysfunction is a serious complication of diabetes and can lead to cardiovascular abnormalities and premature death. It was recently proposed that autonomic dysfunction is triggered by oxidation-mediated inactivation of neuronal nicotinic acetylcholine receptors (nAChRs), impairing synaptic transmission in sympathetic ganglia and resulting in autonomic failure. We investigated whether the receptor for advanced glycation end products (RAGE) and its role in the generation of reactive oxygen species (ROS) could be contributing to the events that initiate sympathetic malfunction under high glucose conditions. Using biochemical, live imaging and electrophysiological tools we demonstrated that exposure of sympathetic neurons to high glucose increases RAGE expression and oxidative markers, and that incubation with RAGE ligands (e.g. AGEs, S100 and HMGB1) mimics both ROS elevation and nAChR inactivation. In contrast, co-treatment with either antioxidants or an anti-RAGE IgG prevented the inactivation of nAChRs. Lastly, a role for RAGE in this context was corroborated by the lack of sensitivity of sympathetic neurons from RAGE knock-out mice to high glucose. These data define a pivotal role for RAGE in initiating the events associated with exposure of sympathetic neurons to high glucose, and strongly support RAGE signaling as a potential therapeutic target in the autonomic complications associated with diabetes.

Ligand stimulation induces clathrin- and Rab5-dependent downregulation of the kinase-dead EphB6 receptor preceded by the disruption of EphB6-Hsp90 interaction

Ligand-induced internalisation and subsequent downregulation of receptor tyrosine kinases (RTKs) serve to determine biological outputs of their signalling. Intrinsically kinase-deficient RTKs control a variety of biological responses, however, the mechanism of their downregulation is not well understood and its analysis is focused exclusively on the ErbB3 receptor. The Eph group of RTKs is represented by the EphA and EphB subclasses. Each bears one kinase-inactive member, EphA10 and EphB6, respectively, suggesting an important role for these molecules in the Eph signalling network. While EphB6 effects on cell behaviour have been assessed, the mechanism of its downregulation remains elusive. Our work reveals that EphB6 and its kinase-active relative, and signalling partner, EphB4, are downregulated in a similar manner in response to their common ligand, ephrin-B2. Following stimulation, both receptors are internalised through clathrin-coated pits and are degraded in lysosomes. Their targeting for lysosomal degradation relies on the activity of an early endosome regulator, the Rab5 GTPase, as this process is inhibited in the presence of a Rab5 dominant-negative mutant. EphB6 also interacts with the Hsp90 chaperone and EphB6 downregulation is preceded by their rapid dissociation. Moreover, the inhibition of Hsp90 results in EphB6 degradation, mimicking its ligand-induced downregulation. These processes appear to rely on overlapping mechanisms, since Hsp90 inhibition does not significantly enhance ligand-induced EphB6 elimination. Taken together, our observations define a novel mechanism for intrinsically kinase-deficient RTK downregulation and support an intriguing model, where Hsp90 dissociation acts as a trigger for ligand-induced receptor removal.

Recent developments in the regulation of monoamine oxidase form and function: is the current model restricting our understanding of the breadth of contribution of monoamine oxidase to brain [dys]function?

Historically, much of the focus on monoamine oxidases and their substrates has been in the area of depression and the monoamine neurotransmitters serotonin (5-hydroxytryptamine), noradrenaline, and to a lesser extent, dopamine. With both forms of monoamine oxidase (A and B), the production of hydrogen peroxide as a byproduct of the reaction between the monoamine oxidases and their monoamine substrates has also implicated monoamine oxidase-sensitive events in intrinsic cell death pathways, particularly those centered on oxidative stress and peroxyradical-mediated mechanisms. Consequently, and perhaps not unexpectedly, the inhibition of monoamine oxidase has been considered as adjunctive therapy in neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease, both of which involve a significant oxidative stress component. Yet the literature also provides ambiguities; indeed, not all of the functions of monoamine oxidases are dependent on catalytic activity nor can they all be ascribed to expression levels of the monoamine oxidase protein per se. Recent reports strongly suggest that the functions of monoamine oxidases also rely on posttranslational modifications, epigenetic influences, interactions with other proteins, the cell phenotype and its localization to specific subcellular compartments. These recent developments certainly complicate the issue, yet they need to be duly considered when implicating monoamine oxidases and their inhibitors in both in vitro and in vivo pathological contexts.

An update on amine oxidase inhibitors: multifaceted drugs

Although not used as extensively as other antidepressants for the treatment of depression, the monoamine oxidase (MAO) inhibitors continue to hold a niche in psychiatry and to have a relatively broad spectrum with regard to treatment of psychiatric and neurological disorders. Experimental and clinical research on MAO inhibitors has been expanding in the past few years, primarily because of exciting findings indicating that these drugs have neuroprotective properties (often independently of their ability to inhibit MAO). The non-selective and irreversible MAO inhibitors tranylcypromine (TCP) and phenelzine (PLZ) have demonstrated neuroprotective properties in numerous studies targeting elements of apoptotic cascades and neurogenesis. l-Deprenyl and rasagiline, both selective MAO-B inhibitors, are used in the management of Parkinson's disease, but these drugs may be useful in the treatment of other neurodegenerative disorders given that they demonstrate neuroprotective/neurorescue properties in a wide variety of models in vitro and in vivo. Although the focus of studies on the involvement of MAO inhibitors in neuroprotection has been on MAO-B inhibitors, there is a growing body of evidence demonstrating that MAO-A inhibitors may also have neuroprotective properties. In addition to MAO inhibition, PLZ also inhibits primary amine oxidase (PrAO), an enzyme implicated in the etiology of Alzheimer's disease, diabetes and cardiovascular disease. These multifaceted aspects of amine oxidase inhibitors and some of their metabolites are reviewed herein.

Matrix metalloproteinase-2 is activated during ischemia/reperfusion in a model of myocardial infarction

BACKGROUND

The degradation of myosin light chain 1 (MLC1) by matrix metalloproteinase-2 (MMP-2) during ischemia/reperfusion has been implicated in the development of cardiac dysfunction. Our objective was to elucidate the role of MMP-2 and MLC1 in the development of cardiac injury and dysfunction in a model of left anterior descending (LAD) coronary artery occlusion.

METHODS

Adult rats (300-350 g) were anaesthetized, and the isolated hearts were retrogradely perfused in a Langendorff apparatus. The LAD was stabilized for 25 minutes and occluded for either 45 or 90 minutes and then reperfused. Cardiac function (evaluated as rate-pressure product) was significantly decreased in the reperfused hearts subjected to 90 minutes of LAD occlusion in comparison with hearts subjected to either sham or 45 minutes of occlusion. Ninety minutes of occlusion resulted in 60% of infarct.

RESULTS

MMP-2 activity, measured by gelatin zymography, was significantly increased following occlusion as well as reperfusion. An increased degradation of MLC1 was observed at the end of reperfusion, but not at the end of occlusion, which most likely was because of the compensatory increase in tissue inhibitor of matrix metalloproteinases-4 (TIMP-4) during occlusion, but not reperfusion.

CONCLUSION

We demonstrate that MMP-2 activation is an ischemic event that extends into the reperfusion phase, while MLC1 degradation in response to ischemia/reperfusion is strictly a reperfusion event. MLC1 degradation during occlusion is prevented by a compensatory increase in the levels of TIMP-4.

Survival of patients with incident dementia who had a pre-existing psychiatric disorder: a population-based 7-year follow-up study

OBJECTIVES

Although it is widely accepted that psychiatric disorders and dementia coexist and survival data for dementia patients have been published, there is a paucity of information regarding the survival of patients with a psychiatric disorder who develop dementia. This study fills this information gap providing survival data on patients with such comorbidity and identifies mortality risk factors.

METHODS

All residents of Saskatchewan, a Canadian province, diagnosed with psychiatric problems and/or dispensed a psychiatric drug in 2000 and without dementia were followed through to 31 December 2006; the development of incident dementia was noted. Median survival time (in months) and selected predictors of mortality were measured. Analyses used Cox's proportional hazard model. Incidence density of dementia for the year 2000 was also computed.

RESULTS

By December 2006, 5,583 subjects with psychiatric disorders in 2000 had been diagnosed with incident dementia, and 60.65% of them died. Dementia-incidence density in this population for 2000 was 0.01 per 1000 person years at risk among those aged 18-64 years and rapidly increased to 3.13 per 1000 person years at risk among those aged 75 to 84 years. The median survival time from dementia onset to death was 32.66 months (interquartile range 31.21-34.14). Being male, later age of onset of dementia, having a lower income, and a high chronic disease score predicted shorter survival.

CONCLUSIONS

The comorbidity of psychiatric disorders and dementia resulted in shorter survival compared with that reported for patients with dementia only. These findings can be used for prognosis for patients, caregivers, and service providers.

Monoamine oxidase-A physically interacts with presenilin-1(M146V) in the mouse cortex

The concentration of presenilin-1 (PS-1) protein at the mitochondrial-associated aspect of the endoplasmic reticulum supports the potential for a mitochondrial influence of PS-1. Given that carriers of certain Alzheimer's disease (AD)-related PS-1 variants are predisposed to clinical depression and that depression has been historically associated with the mitochondrial enzyme, monoamine oxidase-A (MAO-A), we investigated cortical MAO-A function in the AD-related PS-1(M146V) knock-in mouse. The MAO-A system was clearly altered in the PS-1(M146V) mouse as revealed by (a) a mismatch between MAO-A protein expression and MAO-A activity; (b) changes in MAO-A-mediated monoaminergic neurotransmitter metabolism; (c) changes in non-cognitive behavior following treatment with the irreversible MAO-A inhibitor clorgyline; and (d) an increase in the potency of clorgyline in these same mice. We next investigated whether PS-1(M146V) could be influencing MAO-A directly. We observed (a) an enhanced MAO-A activity in necropsied PS-1(M146V) mouse cortical extracts incubated with DAPT (a PS-1 substrate-competitor); (b) the proximity of PS-1 with MAO-A and mitochondrial markers in cortical sections and in primary cortical neurons; (c) the co-segregation and co-immunoprecipitation of PS-1 and MAO-A within the mitochondrial fraction; and (d) the co-immunoprecipitation of overexpressed PS-1(M146V) and MAO-A proteins from N2a lysates. The PS-1(ΔEx9) and PS-1(D257A) variants, known to have low substrate-binding capacity, co-immunoprecipitated weakly with MAO-A. These combined data support a physical interaction between PS-1 and MAO-A that could influence MAO-A activity and contribute to the monoaminergic disruptions common to disorders as seemingly diverse as depression and AD.

Serine 209 resides within a putative p38(MAPK) consensus motif and regulates monoamine oxidase-A activity

The p38 mitogen-activated protein kinase (MAPK) cascade as well as the enzyme monoamine oxidase-A (MAO-A) have both been associated with oxidative stress. We observed that the specific inhibition of the p38(MAPK) protein [using either a chemical inhibitor or a dominant-negative p38(MAPK) clone] selectively induces MAO-A activity and MAO-A-sensitive toxicity in several neuronal cell lines, including primary cortical neurons. Over-expression of a constitutively active p38(MAPK) results in the phosphorylation of the MAO-A protein and inhibition of MAO-A activity. The MAO-A(Ser209Glu) phosphomimic - bearing a targeted substitution within a putative p38(MAPK) consensus motif - is neither active nor neurotoxic. In contrast, the MAO-A(Ser209Ala) variant (mimics dephosphorylation) does not associate with p38(MAPK), and is both very active and very toxic. Substitution of the homologous serine in the MAO-B isoform, i.e. Ser200, with either Glu or Ala does not affect the catalytic activity of the corresponding over-expressed proteins. These combined in vitro data strongly suggest a direct p38(MAPK)-dependent inhibition of MAO-A function. Based on published observations, this endogenous means of selectively regulating MAO-A function could provide for an adaptive response to oxidative stress associated with disorders as diverse as depression, reperfusion/ischemia, and the early stages of Alzheimer's disease.

Mutagenic probes of the role of Ser209 on the cavity shaping loop of human monoamine oxidase A

The available literature implicating human monoamine oxidase A (MAO A) in apoptotic processes reports levels of MAO A protein that do not correlate with activity, suggesting that unknown mechanisms may be involved in the regulation of catalytic function. Bioinformatic analysis suggests Ser209 as a possible phosphorylation site that may be relevant to catalytic function because it is adjacent to a six-residue loop termed the 'cavity shaping loop' from structural data. To probe the functional role of this site, MAO A Ser209Ala and Ser209Glu mutants were created and investigated. In its membrane-bound form, the MAO A Ser209Glu phosphorylation mimic exhibits catalytic and inhibitor binding properties similar to those of wild-type MAO A. Solubilization in detergent solution and purification of the Ser209Glu mutant results in considerable decreases in these functional parameters. By contrast, the MAO A Ser209Ala mutant exhibits similar catalytic properties to those of wild-type enzyme when purified. Compared to purified wild-type and Ser209Ala MAO A proteins, the Ser209Glu MAO A mutant shows significant differences in covalent flavin fluorescence yield, CD spectra and thermal stability. These structural differences in the purified MAO A Ser209Glu mutant are not exhibited in quantitative structure-activity relationship patterns using a series of para-substituted benzylamine analogs similar to the wild-type enzyme. These data suggest that Ser209 in MAO A does not appear to be the putative phosphorylation site for regulation of MAO A activity and demonstrate that the membrane environment plays a significant role in stabilizing the structure of MAO A and its mutant forms.

The nuclear localization of 3'-phosphoinositide-dependent kinase-1 is dependent on its association with the protein tyrosine phosphatase SHP-1

3'-Phosphoinositide-dependent protein kinase-1 (PDK1), the direct upstream kinase of Akt, can localize to the nucleus during specific signalling events. The mechanism used for its import into the nucleus, however, remains unresolved as it lacks a canonical nuclear localization signal (NLS). Expression of activated Src kinase in C6 glioblastoma cells promotes the association of tyrosylphosphorylated PDK1 with the NLS-containing tyrosine phosphatase SHP-1 as well as the nuclear localization of both proteins. A constitutive nucleo-cytoplasmic SHP-1:PDK1 shuttling complex is supported by several lines of evidence including (i) the distribution of both proteins to similar subcellular compartments following manipulation of the nuclear pore complex, (ii) the nuclear retention of SHP-1 upon overexpression of a PDK1 protein bearing a disrupted nuclear export signal (NES), and (iii) the exclusion of PDK1 from the nucleus upon overexpression of SHP-1 lacking the NLS or following siRNA-mediated knock-down of SHP-1. The latter case results in a perinuclear distribution of PDK1 that corresponds with the distribution of PIP3 (phosphatidylinositol 3,4,5-triphosphate), while a PDK1 protein bearing a mutated PH domain that abrogates PIP3-binding is excluded from the nucleus. Our data suggest that the SHP-1:PDK1 complex is recruited to the nuclear membrane by binding to perinuclear PIP3, whereupon SHP-1 (and its NLS) facilitates active import. Export from the nucleus relies on PDK1 (and its NES). The intact complex contributes to Src kinase-induced, Akt-sensitive podial formation in C6 cells.

Dephosphorylation of Akt in C6 cells grown in serum-free conditions corresponds with redistribution of p85/PI3K to the nucleus

Withdrawal of serum from cell cultures constitutes a useful model for the study of mechanisms involved in the regulation of Akt function in vitro. However, there have been several reports of changes in Akt activity that are not fully explained by the current model of phosphatidylinositol 3'-kinase (PI3K)/Akt signaling. We demonstrate the expected loss of Akt phosphorylation in C6 glioma cells cultured in serum-free conditions, yet we also observed a paradoxical increase in PI3K-lipid kinase activity in the same cultures. These events corresponded with relocalization of p85, the regulatory subunit of PI3K, to the perinuclear region and a local increase in PI3K-lipid kinase products. Treatment with platelet-derived growth factor (PDGF) maintained the association between p85 and the PDGF receptor during serum withdrawal and restored PI3K-lipid production at the plasma membrane. Although this protected Akt from dephosphorylation, it only slightly reversed cell-cycle arrest. These effects were not sensitive to treatment with epidermal growth factor, thus precluding a generalized role for growth factors. Our data suggest that loss of growth factor signaling, including PDGF signaling, may disrupt recruitment and/or anchoring of an active p85(PI3K) complex at the plasma membrane during serum withdrawal, which could account for the concurrent loss of Akt function.

Calcium-sensitive regulation of monoamine oxidase-A contributes to the production of peroxyradicals in hippocampal cultures: implications for Alzheimer disease-related pathology

Background

Calcium (Ca²⁺) has recently been shown to selectively increase the activity of monoamine oxidase-A (MAO-A), a mitochondria-bound enzyme that generates peroxyradicals as a natural by-product of the deamination of neurotransmitters such as serotonin. It has also been suggested that increased intracellular free Ca²⁺ levels as well as MAO-A may be contributing to the oxidative stress associated with Alzheimer disease (AD).

Results

Incubation with Ca²⁺ selectively increases MAO-A enzymatic activity in protein extracts from mouse hippocampal HT-22 cell cultures. Treatment of HT-22 cultures with the Ca²⁺ ionophore A23187 also increases MAO-A activity, whereas overexpression of calbindin-D28K (CB-28K), a Ca²⁺-binding protein in brain that is greatly reduced in AD, decreases MAO-A activity. The effects of A23187 and CB-28K are both independent of any change in MAO-A protein or gene expression. The toxicity (via production of peroxyradicals and/or chromatin condensation) associated with either A23187 or the AD-related β-amyloid peptide, which also increases free intracellular Ca²⁺, is attenuated by MAO-A inhibition in HT-22 cells as well as in primary hippocampal cultures.

Conclusion

These data suggest that increases in intracellular Ca²⁺ availability could contribute to a MAO-A-mediated mechanism with a role in AD-related oxidative stress.

Haloperidol induces the nuclear translocation of phosphatidylinositol 3'-kinase to disrupt Akt phosphorylation in PC12 cells

OBJECTIVE

The antipsychotic drug haloperidol (HAL) has been linked to apoptosis and to inhibition of prosurvival Akt signalling in pheochromocytoma (PC12) and neuronal cell cultures. However, the mechanism involved is unclear.

METHODS

We used HAL to induce cytotoxicity in preneuronal PC12 cells. The expression and the subcellular localization of selected components of the PI3K-Akt survival cascade were monitored with standard biochemical approaches, such as subcellular fractionation, western blot analysis, gene transfer and fluorescence microscopy.

RESULTS

PC12 cell stimulation with the epidermal growth factor (used as a control) results in normal processing of phosphatidylinositol 3'-kinase (PI3K)-Akt signalling (e.g., localization of PI3K to the plasma membrane and phosphorylation of Akt (Ser473). Surprisingly, HAL induces PI3K-generated phosphoinositol [phosphatidylinositol-3,4,5-triphosphate (PIP3), which conflicts with its ability to inhibit Akt. In fact, the production of PIP3s is nuclear, as assessed by the localized concentration of a fluorophore-tagged PIP3-targeting pleckstrin homology protein and a fluorophore-tagged substrate-trapping mutant of the phosphoinositide phosphatase, phosphatase and tensin homologue deleted on chromosome 10 (PTEN). However, phosphoinositide-dependent protein kinase 1 (PDK1, the activating kinase of Akt) does not colocalize to the nucleus with the PI3K complex. This effectively inactivates both cytoplasmic and nuclear pools of Akt.

CONCLUSION

The differential compartmentalization of effectors of the PI3K-PDK1-Akt pathway is a unique means by which HAL disrupts Akt functioning in PC12 cells.

Haloperidol induces apoptosis via the sigma2 receptor system and Bcl-XS

Toxicity of the typical antipsychotic haloperidol (HAL) comprises an apoptotic component that we link to pro-apoptotic Bcl-XS in PC12 preneuronal and N2a neuroblastoma cells. The mitochondrial translocation of Bcl-XS and its interaction with the pore-forming voltage-dependent anion channel (VDAC) correlates with the redistribution of cytochrome c and the cleavage of Poly(ADP-ribose) polymerase. Haloperidol-induced apoptosis is mediated by the sigma2 (sigma2) receptor system and does not involve the expected antagonism of the dopamine D(2) receptor, nor is it influenced by Vitamin E- or p53/Bax-mediated events. Pathological relevance is demonstrated by the cytotoxic synergism between HAL and the Alzheimer disease-related peptide beta-amyloid(1-40), which correlates with Bcl-XS expression and its interaction with VDAC, and with cytosolic cytochrome c translocation. These data provide for a unique apoptotic mechanism that could underscore the clinical risks associated with HAL, particularly following chronic regimens or in the elderly.

Atypical antipsychotics attenuate neurotoxicity of beta-amyloid(25-35) by modulating Bax and Bcl-X(l/s) expression and localization

We have demonstrated recently that atypical antipsychotics possess neuroprotective actions in H2O2-mediated and serum-withdrawal models of cell death. In the present study, we compared the ability of atypical and typical antipsychotics to protect against an insult mediated by Abeta(25-35), an apoptogenic fragment of the Alzheimer's disease-related beta-amyloid (Abeta) peptide. Treatment of PC12 cell cultures with Abeta(25-35) did not significantly alter total cellular expression levels of Bax, a proapoptotic Bcl-2 family member, or levels of Bcl-XL, an antiapoptotic analogue. Treatment with Abeta(25-35), however, did result in mitochondrial translocation of Bax, which effectively increased the mitochondrial ratio of Bax to Bcl-X(L). This relative increase in proapoptotic molecules was reduced by pretreatment with atypical (quetiapine and olanzapine) and typical (haloperidol) antipsychotics. We also observed a selective increase in proapoptotic Bcl-XS immunodetection in haloperidol-treated cells, which was evident particularly in the mitochondrial compartment. This increase in proapoptotic molecules may account for the lower neuroprotective potential of haloperidol, as determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) reduction assay. The disparate neuroprotective effects of atypical and typical antipsychotics/neuroleptics may be due to their respective abilities to regulate pro- and anti-apoptotic protein translocation and expression.

A direct interaction between transforming growth factor (TGF)-betas and amyloid-beta protein affects fibrillogenesis in a TGF-beta receptor-independent manner

Transforming growth factor-beta (TGF-beta) receptor-mediated signaling has been proposed to mediate both the beneficial and deleterious roles for this cytokine in amyloid-beta protein (Abeta) function. In order to assess receptor dependence of these events, we used PC12 cell cultures, which are devoid of TGF-beta receptors. Surprisingly, TGF-beta potentiated the neurotoxic effects of the 40-residue Abeta peptide, Abeta-(1-40), in this model suggesting that there may be a direct, receptor-independent interaction between TGF-beta and Abeta-(1-40). Surface plasmon resonance confirmed that TGF-beta binds with high affinity directly to Abeta-(1-40) and electron microscopy revealed that TGF-beta enhances Abeta-(1-40) oligomerization. Immunohistochemical examination of mouse brain revealed that hippocampal CA1 and dentate gyrus, two regions classically associated with Abeta-mediated pathology, lack TGF-beta Type I receptor immunoreactivity, thus indicating that TGF-beta receptor-mediated signaling would not be favored in these regions. Our observations not only provide for a unique, receptor-independent mechanism of action for TGF-beta, but also help to reconcile the literature interpreting the role of TGF-beta in Abeta function. These data support a critical etiological role for this mechanism in neuropathological amyloidoses.