Overview of the brain polyamine-stress-response: regulation, development, and modulation by lithium and role in cell survival

Comparative brain metabolomics reveals shared and distinct metabolic alterations in Alzheimer's disease and progressive supranuclear palsy

BACKGROUND

Metabolic dysregulation is a hallmark of neurodegenerative diseases, including Alzheimer's disease (AD) and progressive supranuclear palsy (PSP). Although metabolic dysregulation is a common link between these two tauopathies, a comprehensive brain metabolic comparison of the diseases has not yet been performed.

METHODS

We analyzed 342 postmortem brain samples from the Mayo Clinic Brain Bank and examined 658 metabolites in the cerebellar cortex and the temporal cortex between the two tauopathies.

RESULTS

Our findings indicate that both diseases display oxidative stress associated with lipid metabolism, mitochondrial dysfunction linked to lysine metabolism, and an indication of tau-induced polyamine stress response. However, specific to AD, we detected glutathione-related neuroinflammation, deregulations of enzymes tied to purines, and cognitive deficits associated with vitamin B.

DISCUSSION

Our findings underscore vast alterations in the brain's metabolome, illuminating shared neurodegenerative pathways and disease-specific traits in AD and PSP.

HIGHLIGHTS

First high-throughput metabolic comparison of Alzheimer's diesease (AD) versus progressive supranuclear palsy (PSP) in brain tissue. Cerebellar cortex (CER) shows substantial AD-related metabolic changes, despite limited proteinopathy. AD impacts both CER and temporal cortex (TCX); PSP's changes are primarily in CER. AD and PSP share metabolic alterations despite major pathological differences.

The contribution of polyamine pathway to determinations of diagnosis for treatment-resistant depression: A metabolomic analysis

OBJECTIVES

Approximately one-third of major depressive disorder (MDD) patients do not respond to standard antidepressants and develop treatment-resistant depression (TRD). We aimed to reveal metabolic differences and discover promising potential biomarkers in TRD.

METHODS

Our study recruited 108 participants including healthy controls (n = 40) and patients with TRD (n = 35) and first-episode drug-naive MDD (DN-MDD) (n = 33). Plasma samples were presented to ultra performance liquid chromatography-tandem mass spectrometry. Then, a machine-learning algorithm was conducted to facilitate the selection of potential biomarkers.

RESULTS

TRD appeared to be a distinct metabolic disorder from DN-MDD and healthy controls (HCs). Compared to HCs, 199 and 176 differentially expressed metabolites were identified in TRD and DN-MDD, respectively. Of all the metabolites that were identified, spermine, spermidine, and carnosine were considered the most promising biomarkers for diagnosing TRD and DN-MDD patients, with the resulting area under the ROC curve of 0.99, 0.99, and 0.93, respectively. Metabolic pathway analysis yielded compelling evidence of marked changes or imbalances in both polyamine metabolism and energy metabolism, which could potentially represent the primary altered pathways associated with MDD. Additionally, L-glutamine, Beta-alanine, and spermine were correlated with HAMD score.

CONCLUSIONS

A more disordered metabolism structure is found in TRD than in DN-MDD and HCs. Future investigations should prioritize the comprehensive analysis of potential roles played by these differential metabolites and disturbances in polyamine pathways in the pathophysiology of TRD and depression.

A metabolomics study in aqueous humor discloses altered arginine metabolism in Parkinson's disease

BACKGROUND

The lack of accessible and informative biomarkers results in a delayed diagnosis of Parkinson's disease (PD), whose symptoms appear when a significant number of dopaminergic neurons have already disappeared. The retina, a historically overlooked part of the central nervous system (CNS), has gained recent attention. It has been discovered that the composition of cerebrospinal fluid influences the aqueous humor composition through microfluidic circulation. In addition, alterations found in the brain of patients with PD have a correlate in the retina. This new paradigm highlights the potential of the aqueous humor as a sample for identifying differentially concentrated metabolites that could, eventually, become biomarkers if also found altered in blood or CSF of patients. In this research we aim at analyzing the composition of the aqueous humor from healthy controls and PD patients.

METHODS

A targeted metabolomics approach with concentration determination by mass spectrometry was used. Statistical methods including principal component analysis and linear discriminants were used to select differentially concentrated metabolites that allow distinguishing patients from controls.

RESULTS

In this first metabolomics study in the aqueous humor of PD patients, elevated levels of 16 compounds were found; molecules differentially concentrated grouped into biogenic amines, amino acids, and acylcarnitines. A biogenic amine, putrescine, alone could be a metabolite capable of differentiating between PD and control samples. The altered levels of the metabolites were correlated, suggesting that the elevations stem from a common mechanism involving arginine metabolism.

CONCLUSIONS

A combination of three metabolites, putrescine, tyrosine, and carnitine was able to correctly classify healthy participants from PD patients. Altered metabolite levels suggest altered arginine metabolism. The pattern of metabolomic disturbances was not due to the levodopa-based dopamine replacement medication because one of the patients was not yet taking levodopa but a dopamine receptor agonist.

The impact of amino acid metabolism on adult neurogenesis

Adult neurogenesis is a multistage process during which newborn neurons are generated through the activation and proliferation of neural stem cells (NSCs) and integrated into existing neural networks. Impaired adult neurogenesis has been observed in various neurological and psychiatric disorders, suggesting its critical role in cognitive function, brain homeostasis, and neural repair. Over the past decades, mounting evidence has identified a strong association between metabolic status and adult neurogenesis. Here, we aim to summarize how amino acids and their neuroactive metabolites affect adult neurogenesis. Furthermore, we discuss the causal link between amino acid metabolism, adult neurogenesis, and neurological diseases. Finally, we propose that systematic elucidation of how amino acid metabolism regulates adult neurogenesis has profound implications not only for understanding the biological underpinnings of brain development and neurological diseases, but also for providing potential therapeutic strategies to intervene in disease progression.

The Polyamine Spermine Potentiates the Propagation of Negatively Charged Molecules through the Astrocytic Syncytium

The interest in astrocytes, the silent brain cells that accumulate polyamines (PAs), is growing. PAs exert anti-inflammatory, antioxidant, antidepressant, neuroprotective, and other beneficial effects, including increasing longevity in vivo. Unlike neurons, astrocytes are extensively coupled to others via connexin (Cx) gap junctions (GJs). Although there are striking modulatory effects of PAs on neuronal receptors and channels, PA regulation of the astrocytic GJs is not well understood. We studied GJ-propagation using molecules of different (i) electrical charge, (ii) structure, and (iii) molecular weight. Loading single astrocytes with patch pipettes containing membrane-impermeable dyes, we observed that (i) even small molecules do not easily permeate astrocytic GJs, (ii) the ratio of the charge to weight of these molecules is the key determinant of GJ permeation, (iii) the PA spermine (SPM) induced the propagation of negatively charged molecules via GJs, (iv) while no effects were observed on propagation of macromolecules with net-zero charge. The GJ uncoupler carbenoxolone (CBX) blocked such propagation. Taken together, these findings indicate that SPM is essential for astrocytic GJ communication and selectively facilitates intracellular propagation via GJs for negatively charged molecules through glial syncytium.

Versatile roles of polyamines in improving abiotic stress tolerance of plants

In recent years, extreme environmental cues such as abiotic stresses, including frequent droughts with irregular precipitation, salinity, metal contamination, and temperature fluctuations, have been escalating the damage to plants' optimal productivity worldwide. Therefore, yield maintenance under extreme events needs improvement in multiple mechanisms that can minimize the influence of abiotic stresses. Polyamines (PAs) are pivotally necessary for a defensive purpose under adverse abiotic conditions, but their molecular interplay in this remains speculative. The PAs' accretion is one of the most notable metabolic responses of plants under stress challenges. Recent studies reported the beneficial roles of PAs in plant development, including metabolic and physiological processes, unveiling their potential for inducing tolerance against adverse conditions. This review presents an overview of research about the most illustrious and remarkable achievements in strengthening plant tolerance to drought, salt, and temperature stresses by the exogenous application of PAs. The knowledge of underlying processes associated with stress tolerance and PA signaling pathways was also summarized, focusing on up-to-date evidence regarding the metabolic and physiological role of PAs with exogenous applications that protect plants under unfavorable climatic conditions. Conclusively, the literature proposes that PAs impart an imperative role in abiotic stress tolerance in plants. This implies potentially important feedback on PAs and plants' stress tolerance under unfavorable cues.

Postinfection Metabolic Reprogramming of the Murine Trigeminal Ganglion Limits Herpes Simplex Virus-1 Replication

Herpes simplex virus type-1 (HSV-1) infections are known to alter the host metabolism for efficient propagation in vitro. However, in vivo metabolic perturbations upon prolonged HSV-1 infection remain poorly understood. We used high-resolution liquid chromatography coupled with mass spectrometry (LC-MS) and functional assays to determine the state of the trigeminal ganglion (TG) tissue metabolism upon prolonged corneal HSV-1 infection in a murine model. The metabolomics data indicated significant alterations in the host metabolic profile. After HSV-1 infection, the TG microenvironment assumed downregulation of central carbon metabolism and nucleotide synthesis pathways. We validated our observations using in vitro and ex vivo models through targeted inhibition of crucial metabolic polyamine pathways identified in our metabolomics screen. Our findings collectively suggested that HSV-1 infection altered the host metabolic product regulations that limit the energy and macromolecular precursors required for viral replication.

The Involvement of Polyamines Catabolism in the Crosstalk between Neurons and Astrocytes in Neurodegeneration

In mammalian cells, the content of polyamines is tightly regulated. Polyamines, including spermine, spermidine and putrescine, are involved in many cellular processes. Spermine oxidase specifically oxidizes spermine, and its deregulated activity has been reported to be linked to brain pathologies involving neuron damage. Spermine is a neuromodulator of a number of ionotropic glutamate receptors and types of ion channels. In this respect, the Dach-SMOX mouse model overexpressing spermine oxidase in the neocortex neurons was revealed to be a model of chronic oxidative stress, excitotoxicity and neuronal damage. Reactive astrocytosis, chronic oxidative and excitotoxic stress, neuron loss and the susceptibility to seizure in the Dach-SMOX are discussed here. This genetic model would help researchers understand the linkage between polyamine dysregulation and neurodegeneration and unveil the roles of polyamines in the crosstalk between astrocytes and neurons in neuroprotection or neurodegeneration.

Altered Brain Arginine Metabolism and Polyamine System in a P301S Tauopathy Mouse Model: A Time-Course Study

Altered arginine metabolism (including the polyamine system) has recently been implicated in the pathogenesis of tauopathies, characterised by hyperphosphorylated and aggregated microtubule-associated protein tau (MAPT) accumulation in the brain. The present study, for the first time, systematically determined the time-course of arginine metabolism changes in the MAPT P301S (PS19) mouse brain at 2, 4, 6, 8 and 12 months of age. The polyamines putrescine, spermidine and spermine are critically involved in microtubule assembly and stabilization. This study, therefore, further investigated how polyamine biosynthetic and catabolic enzymes changed in PS19 mice. There were general age-dependent increases of L-arginine, L-ornithine, putrescine and spermidine in the PS19 brain (particularly in the hippocampus and parahippocampal region). While this profile change clearly indicates a shift of arginine metabolism to favor polyamine production (a polyamine stress response), spermine levels were decreased or unchanged due to the upregulation of polyamine retro-conversion pathways. Our results further implicate altered arginine metabolism (particularly the polyamine system) in the pathogenesis of tauopathies. Given the role of the polyamines in microtubule assembly and stabilization, future research is required to understand the functional significance of the polyamine stress response and explore the preventive and/or therapeutic opportunities for tauopathies by targeting the polyamine system.

The Role of Polyamines in the Mechanisms of Cognitive Impairment

Abstract—As the population ages, age-related cognitive impairments are becoming an increasingly pressing problem. Currently, the role of polyamines (putrescine, spermidine, and spermine) in the pathogenesis of cognitive impairments of various origin is actively discussed. It was shown that the content of polyamines in the brain tissue decreases with age. Exogenous administration of polyamines makes it possible to avoid cognitive impairment and/or influence the pathogenetic processes associated with disease progression. There are 3 known ways that polyamines can enter the human body: food, synthesis by intestinal bacteria, and biosynthesis in the body. Currently, one of the most promising approaches to the prevention of cognitive impairment is the use of foods with a high content of polyamines, as well as the use of various probiotics that affect intestinal bacteria that synthesize polyamines. Since 2018, in a number of European countries projects have been launched aimed at evaluation of the impact of a diet high in polyamines on cognitive processes. The review, based on analysis of modern scientific literature and the authors' own data, presents material on the effect of polyamines on cognitive processes and the role of polyamines in the regulation of neurotransmitter processes, and discusses the role of polyamines in cognitive disorders in mental and neurological diseases.

Alzheimer's disease as a chronic maladaptive polyamine stress response

Polyamines are nitrogen-rich polycationic ubiquitous bioactive molecules with diverse evolutionary-conserved functions. Their activity interferes with numerous genes' expression resulting in cell proliferation and signaling modulation. The intracellular levels of polyamines are precisely controlled by an evolutionary-conserved machinery. Their transient synthesis is induced by heat stress, radiation, and other traumatic stimuli in a process termed the polyamine stress response (PSR). Notably, polyamine levels decline gradually with age; and external supplementation improves lifespan in model organisms. This corresponds to cytoprotective and reactive oxygen species scavenging properties of polyamines. Paradoxically, age-associated neurodegenerative disorders are characterized by upsurge in polyamines levels, indicating polyamine pleiotropic, adaptive, and pathogenic roles. Specifically, arginase overactivation and arginine brain deprivation have been shown to play an important role in Alzheimer's disease (AD) pathogenesis. Here, we assert that a universal short-term PSR associated with acute stimuli is beneficial for survival. However, it becomes detrimental and maladaptive following chronic noxious stimuli, especially in an aging organism. Furthermore, we regard cellular senescence as an adaptive response to stress and suggest that PSR plays a central role in age-related neurodegenerative diseases' pathogenesis. Our perspective on AD proposes an inclusive reassessment of the causal relationships between the classical hallmarks and clinical manifestation. Consequently, we offer a novel treatment strategy predicated upon this view and suggest fine-tuning of arginase activity with natural inhibitors to preclude or halt the development of AD-related dementia.

Is carbonyl/AGE/RAGE stress a hallmark of the brain aging?

Recent studies have linked carbonyl stress to many physiological processes. Increase in the levels of carbonyl compounds, derived from both endogenous and exogenous sources, is believed to accompany normal age-related decline as well as different pathologies. Reactive carbonyl species (RCS) are capable of damaging biomolecules via their involvement in a net of nonspecific reactions. In the advanced stages of RCS metabolism, variety of poorly degraded adducts and crosslinks, collectively named advanced glycoxidation end products (AGEs), arises. They are accumulated in an age-dependent manner in different tissues and organs and can contribute to inflammatory processes. In particular, detrimental effects of the end products are realized via activation of the specific receptor for AGEs (RAGE) and RAGE-dependent inflammatory signaling cascade. Although it is unclear, whether carbonyl stress is causal for age-associated impairments or it results from age- and disease-related cell damages, increased levels of RCS and AGEs are tightly related to inflammaging, and therefore, attenuation of the RAGE signaling is suggested as an effective approach for the treatment of inflammation and age-related disorders. The question raised in this review is whether specific metabolism in the aging brain related to carbonyl/RCS/AGE/RAGE stress.

Radiosynthesis and evaluation of N5-(2-18F-fluoropropanyl) ornithine as a potential agent for tumor PET imaging

OBJECTIVE

Studies have confirmed that tumorigenesis is related to an imbalance of polyamine metabolism and over-expression of oncogenes resulting in the up-regulation of ornithine decarboxylase (ODC, the first rate-limiting enzyme for regulating intracellular polyamines biosynthesis), which has become a target for anti-tumor therapy. In this study, an ornithine derivative, N5-(2-[18F]fluoropropionyl) ornithine (N5-[18F]FPO), has been prepared and its potential utility for tumor PET imaging evaluated.

METHODS

N5-[18F]FPO was successfully prepared via a nucleophilic fluorination reaction and a subsequent efficient deprotection step. The in vitro and in vivo stability were determined by HPLC conducted in fetal bovine serum, saline and rat urine. Cellular uptake studies were conducted in HepG2 cells and the biodistribution and micro-PET/CT imaging performed in normal ICR mice and three tumor-bearing mice models, respectively.

RESULTS

Total synthesis time of N5-[18F]FPO was about 80 min with a radiochemical yield of 15% ± 6% (uncorrected, based on 18F-, n = 6) and a high radiochemical stability can be seen in vitro and vivo. The N5-[18F]FPO exhibited fast uptake in HepG2 cells and the cellular uptake ability of N5-[18F]FPO can be inhibited by L-ornithine and DFMO, which indicated that the transport pathway of N5-[18F]FPO is similar to that of L-ornithine, interacting with ODC after being transported into the cell. The biodistribution and micro-PET/CT images demonstrate that N5-[18F]FPO was excreted by the urinary system, and excellent tumor visualization with high tumor-to-background ratios can be observed in the three tumor-bearing mice models studied.

CONCLUSION

All the above results suggest that N5-[18F]FPO has the potential to be a novel radiotracer for imaging ODC expression in solid tumors.

Aberrant AZIN2 and polyamine metabolism precipitates tau neuropathology

Tauopathies display a spectrum of phenotypes from cognitive to affective behavioral impairments; however, mechanisms promoting tau pathology and how tau elicits behavioral impairment remain unclear. We report a unique interaction between polyamine metabolism, behavioral impairment, and tau fate. Polyamines are ubiquitous aliphatic molecules that support neuronal function, axonal integrity, and cognitive processing. Transient increases in polyamine metabolism hallmark the cell's response to various insults, known as the polyamine stress response (PSR). Dysregulation of gene transcripts associated with polyamine metabolism in Alzheimer's disease (AD) brains were observed, and we found that ornithine decarboxylase antizyme inhibitor 2 (AZIN2) increased to the greatest extent. We showed that sustained AZIN2 overexpression elicited a maladaptive PSR in mice with underlying tauopathy (MAPT P301S; PS19). AZIN2 also increased acetylpolyamines, augmented tau deposition, and promoted cognitive and affective behavioral impairments. Higher-order polyamines displaced microtubule-associated tau to facilitate polymerization but also decreased tau seeding and oligomerization. Conversely, acetylpolyamines promoted tau seeding and oligomers. These data suggest that tauopathies launch an altered enzymatic signature that endorses a feed-forward cycle of disease progression. Taken together, the tau-induced PSR affects behavior and disease continuance, but may also position the polyamine pathway as a potential entry point for plausible targets and treatments of tauopathy, including AD.

Dysregulation of multiple metabolic networks related to brain transmethylation and polyamine pathways in Alzheimer disease: A targeted metabolomic and transcriptomic study

BACKGROUND

There is growing evidence that Alzheimer disease (AD) is a pervasive metabolic disorder with dysregulation in multiple biochemical pathways underlying its pathogenesis. Understanding how perturbations in metabolism are related to AD is critical to identifying novel targets for disease-modifying therapies. In this study, we test whether AD pathogenesis is associated with dysregulation in brain transmethylation and polyamine pathways.

METHODS AND FINDINGS

We first performed targeted and quantitative metabolomics assays using capillary electrophoresis-mass spectrometry (CE-MS) on brain samples from three groups in the Baltimore Longitudinal Study of Aging (BLSA) (AD: n = 17; Asymptomatic AD [ASY]: n = 13; Control [CN]: n = 13) (overall 37.2% female; mean age at death 86.118 ± 9.842 years) in regions both vulnerable and resistant to AD pathology. Using linear mixed-effects models within two primary brain regions (inferior temporal gyrus [ITG] and middle frontal gyrus [MFG]), we tested associations between brain tissue concentrations of 26 metabolites and the following primary outcomes: group differences, Consortium to Establish a Registry for Alzheimer's Disease (CERAD) (neuritic plaque burden), and Braak (neurofibrillary pathology) scores. We found significant alterations in concentrations of metabolites in AD relative to CN samples, as well as associations with severity of both CERAD and Braak, mainly in the ITG. These metabolites represented biochemical reactions in the (1) methionine cycle (choline: lower in AD, p = 0.003; S-adenosyl methionine: higher in AD, p = 0.005); (2) transsulfuration and glutathione synthesis (cysteine: higher in AD, p < 0.001; reduced glutathione [GSH]: higher in AD, p < 0.001); (3) polyamine synthesis/catabolism (spermidine: higher in AD, p = 0.004); (4) urea cycle (N-acetyl glutamate: lower in AD, p < 0.001); (5) glutamate-aspartate metabolism (N-acetyl aspartate: lower in AD, p = 0.002); and (6) neurotransmitter metabolism (gamma-amino-butyric acid: lower in AD, p < 0.001). Utilizing three Gene Expression Omnibus (GEO) datasets, we then examined mRNA expression levels of 71 genes encoding enzymes regulating key reactions within these pathways in the entorhinal cortex (ERC; AD: n = 25; CN: n = 52) and hippocampus (AD: n = 29; CN: n = 56). Complementing our metabolomics results, our transcriptomics analyses also revealed significant alterations in gene expression levels of key enzymatic regulators of biochemical reactions linked to transmethylation and polyamine metabolism. Our study has limitations: our metabolomics assays measured only a small proportion of all metabolites participating in the pathways we examined. Our study is also cross-sectional, limiting our ability to directly test how AD progression may impact changes in metabolite concentrations or differential-gene expression. Additionally, the relatively small number of brain tissue samples may have limited our power to detect alterations in all pathway-specific metabolites and their genetic regulators.

CONCLUSIONS

In this study, we observed broad dysregulation of transmethylation and polyamine synthesis/catabolism, including abnormalities in neurotransmitter signaling, urea cycle, aspartate-glutamate metabolism, and glutathione synthesis. Our results implicate alterations in cellular methylation potential and increased flux in the transmethylation pathways, increased demand on antioxidant defense mechanisms, perturbations in intermediate metabolism in the urea cycle and aspartate-glutamate pathways disrupting mitochondrial bioenergetics, increased polyamine biosynthesis and breakdown, as well as abnormalities in neurotransmitter metabolism that are related to AD.

The Role of Epigenetic Dysregulation in Suicidal Behaviors

Suicidal behaviors have been associated with both heritable genetic variables and environmental risk factors. Epigenetic processes, such as DNA methylation, have important roles in mediating the effects of the environment on behavior. Dysregulation of these processes has been observed in many psychiatric disorders, and evidence suggests that they may also be involved in suicidal behaviors. Herein, we have summarized candidate gene and epigenome-wide studies which have investigated DNA methylation in relation to suicidal behaviors, as well as discussed some of the limitations of the field to date.

Electrophysiological evaluation of extracellular spermine and alkaline pH on synaptic human GABAA receptors

Polyamines have fundamental roles in brain homeostasis as key modulators of cellular excitability. Several studies have suggested alterations in polyamine metabolism in stress related disorders, suicide, depression, and neurodegeneration, making the pharmacological modulation of polyamines a highly appealing therapeutic strategy. Polyamines are small aliphatic molecules that can modulate cationic channels involved in neuronal excitability. Previous indirect evidence has suggested that polyamines can modulate anionic GABA_A receptors (GABA_ARs), which mediate inhibitory signaling and provide a direct route to reduce hyperexcitability. Here, we attempted to characterize the effect that spermine, the polyamine with the strongest reported effect on GABA_ARs, has on human postmortem native GABA_ARs. We microtransplanted human synaptic membranes from the dorsolateral prefrontal cortex of four cases with no history of mental or neurological disorders, and directly recorded spermine effects on ionic GABA_ARs responses on microtransplanted oocytes. We show that in human synapses, inhibition of GABA_ARs by spermine was better explained by alkalization of the extracellular solution. Additionally, spermine had no effect on the potentiation of GABA-currents by diazepam, indicating that even if diazepam binding is enhanced by spermine, it does not translate to changes in functional activity. Our results clearly demonstrate that while extracellular spermine does not have direct effects on human native synaptic GABA_ARs, spermine-mediated shifts of pH inhibit GABA_ARs. Potential spermine-mediated increase of pH in synapses in vivo may therefore participate in increased neuronal activity observed during physiological and pathological states, and during metabolic alterations that increase the release of spermine to the extracellular milieu.

Altered polyamine profiling in the hair of patients with androgenic alopecia and alopecia areata

Hair follicles are among the most highly proliferative tissues. Polyamines are associated with proliferation, and several polyamines including spermidine and spermine play anti-inflammatory roles. Androgenic alopecia results from increased dihydrotestosterone metabolism, and alopecia areata is an autoimmune disease. This study aimed to investigate differences in polyamine profiles in hair samples between patients with androgenic alopecia and alopecia areata. Polyamine concentrations were determined through high-performance liquid chromatography-mass spectrometry. Hair samples were derivatized with isobutyl chloroformate. Differences in polyamine levels were observed between androgenic alopecia and alopecia areata compared with normal controls. In particular, polyamine levels were higher in alopecia areata patients than in normal controls. Certain polyamines displayed different concentrations between the androgenic alopecia and alopecia areata groups, suggesting that some polyamines, particularly N-acetyl putrescine (P = 0.007) and N-acetyl cadaverine (P = 0.0021), are significantly different in androgenic alopecia. Furthermore, spermidine (P = 0.021) was significantly different in alopecia areata. Our findings suggest that non-invasive quantification of hair polyamines may help distinguish between androgenic alopecia and alopecia areata. Our study provides novel insights into physiological alterations in patients with androgenic alopecia and those with alopecia areata and reveals some differences in polyamine levels in hair loss diseases with two different modes of action.

Pituitary disease in pediatric brain tumor survivors

INTRODUCTION

Treatment of childhood brain tumors, including surgical resection and especially external beam radiation, often results in endocrine complications manifested by hypopituitarism, which can involve growth hormone deficiency, hypothyroidism, adrenal insufficiency, disorders of puberty, diabetes insipidus, and hypothalamic obesity.

AREAS COVERED

A comprehensive literature search was conducted on Medline (publications from the 1990s to 01/2019) including systematic reviews, meta-analyses, longitudinal controlled studies, retrospective cohort studies, and case reports. Herein, we present an up-to-date review of the current literature regarding endocrine sequellae of childhood brain tumor survivors.

EXPERT OPINION

Late endocrine sequellae can arise many years after the initial treatment of tumor, so at least annual surveillance of growth, puberty, weight, development, and endocrine status is recommended for at least 10 years after tumor therapy. This follow up should encompass childhood and adulthood among survivors. If found early, outcomes of endocrinopathies are favorable when treated appropriately. Newer tumor therapy modalities, such as proton beam radiation, offer the potential for fewer endocrine complications, but such benefit has yet to be demonstrated, and more research into short- and long-term outcomes is needed.

Spermidine/spermine-N1-acetyltransferase ablation impacts tauopathy-induced polyamine stress response

BACKGROUND

Tau stabilizes microtubules; however, in Alzheimer's disease (AD) and tauopathies, tau becomes hyperphosphorylated, aggregates, and results in neuronal death. Our group recently uncovered a unique interaction between polyamine metabolism and tau fate. Polyamines exert an array of physiological effects that support neuronal function and cognitive processing. Specific stimuli can elicit a polyamine stress response (PSR), resulting in altered central polyamine homeostasis. Evidence suggests that elevations in polyamines following a short-term stressor are beneficial; however, persistent stress and subsequent PSR activation may lead to maladaptive polyamine dysregulation, which is observed in AD, and may contribute to neuropathology and disease progression.

METHODS

Male and female mice harboring tau P301L mutation (rTg4510) were examined for a tau-induced central polyamine stress response (tau-PSR). The direct effect of tau-PSR byproducts on tau fibrillization and oligomerization were measured using a thioflavin T assay and a N2a split superfolder GFP-Tau (N2a-ssGT) cell line, respectively. To therapeutically target the tau-PSR, we bilaterally injected caspase 3-cleaved tau truncated at aspartate 421 (AAV9 Tau ΔD421) into the hippocampus and cortex of spermidine/spermine-N¹-acetyltransferase (SSAT), a key regulator of the tau-PSR, knock out (SSAT-/-), and wild type littermates, and the effects on tau neuropathology, polyamine dysregulation, and behavior were measured. Lastly, cellular models were employed to further examine how SSAT repression impacted tau biology.

RESULTS

Tau induced a unique tau-PSR signature in rTg4510 mice, notably in the accumulation of acetylated spermidine. In vitro, higher-order polyamines prevented tau fibrillization but acetylated spermidine failed to mimic this effect and even promoted fibrillization and oligomerization. AAV9 Tau ΔD421 also elicited a unique tau-PSR in vivo, and targeted disruption of SSAT prevented the accumulation of acetylated polyamines and impacted several tau phospho-epitopes. Interestingly, SSAT knockout mice presented with altered behavior in the rotarod task, the elevated plus maze, and marble burying task, thus highlighting the impact of polyamine homeostasis within the brain.

CONCLUSION

These data represent a novel paradigm linking tau pathology and polyamine dysfunction and that targeting specific arms within the polyamine pathway may serve as new targets to mitigate certain components of the tau phenotype.

Metabolomic study of polyamines in rat urine following intraperitoneal injection of γ-hydroxybutyric acid

INTRODUCTION

Recently, illegal abuse of γ-hydroxybutyric acid (GHB) has increased in drug-facilitated crimes, but the determination of GHB exposure and intoxication is difficult due to rapid metabolism of GHB. Its biochemical mechanism has not been completely investigated. And a metabolomic study by polyamine profile and pattern analyses was not performed in rat urine following intraperitoneal injection with GHB.

OBJECTIVES

Urinary polyamine (PA) profiling by gas chromatography-tandem mass spectrometry was performed to monitor an altered PA according to GHB administration.

METHODS

Polyamine profiling analysis by gas chromatography-mass spectrometry combined with star pattern recognition analysis was performed in this study. The multivariate statistical analysis was used to evaluate discrimination among control and GHB administration groups.

RESULTS

Six polyamines were determined in control, single and multiple GHB administration groups. Star pattern showed distorted hexagonal shapes with characteristic and readily distinguishable patterns for each group. N¹-Acetylspermine (p < 0.001), putrescine (p < 0.006), N¹-acetylspermidine (p < 0.009), and spermine (p < 0.027) were significantly increased in single administration group but were significantly lower in the multiple administration group than in the control group. N¹-Acetylspermine was the main polyamine for discrimination among control, single and multiple administration groups. Spermine showed similar levels in single and multiple administration groups.

CONCLUSIONS

The polyamine metabolic pattern was monitored in GHB administration groups. N¹-Acetylspermine and spermine were evaluated as potential biomarkers of GHB exposure and addiction.

Adolescent Suicide as a Failure of Acute Stress-Response Systems

Suicide is the second leading cause of death worldwide for adolescents. Despite decades of research on correlates and risk factors for adolescent suicide, we know little about why suicidal ideation and behavior frequently emerge in adolescence and how to predict, and ultimately prevent, suicidal behavior among youths. In this review, we first discuss knowledge regarding correlates, risk factors, and theories of suicide. We then review why adolescence is a period of unique vulnerability, given changing biology and social network reorganization. Next, we present a conceptual model through which to interpret emerging findings in adolescent suicide research. We suggest that a promising area for future research is to examine adolescent suicide as a failure of biological responses to acute stress in the proximal moments of a suicidal crisis. After reviewing initial evidence for this conceptualization, we review future directions for studies on adolescent suicide.

Polyamine Regulator AMD1 Promotes Cell Migration in Epidermal Wound Healing

Wound healing is a dynamic process involving gene-expression changes that drive re-epithelialization. Here, we describe an essential role for polyamine regulator AMD1 in driving cell migration at the wound edge. The polyamines, putrescine, spermidine, and spermine are small cationic molecules that play essential roles in many cellular processes. We demonstrate that AMD1 is rapidly upregulated following wounding in human skin biopsies. Knockdown of AMD1 with small hairpin RNAs causes a delay in cell migration that is rescued by the addition of spermine. We further show that spermine can promote cell migration in keratinocytes and in human ex vivo wounds, where it significantly increases epithelial tongue migration. Knockdown of AMD1 prevents the upregulation of urokinase-type plasminogen activator/urokinase-type plasminogen activator receptor on wounding and results in a failure in actin cytoskeletal reorganization at the wound edge. We demonstrate that keratinocytes respond to wounding by modulating polyamine regulator AMD1 in order to regulate downstream gene expression and promote cell migration. This article highlights a previously unreported role for the regulation of polyamine levels and ratios in cellular behavior and fate.

Putrescine as indicator of manganese neurotoxicity: Dose-response study in human SH-SY5Y cells

Disrupted polyamine metabolism with elevated putrescine is associated with neuronal dysfunction. Manganese (Mn) is an essential nutrient that causes neurotoxicity in excess, but methods to evaluate biochemical responses to high Mn are limited. No information is available on dose-response effects of Mn on putrescine abundance and related polyamine metabolism. The present research was to test the hypothesis that Mn causes putrescine accumulation over a physiologically adequate to toxic concentration range in a neuronal cell line. We used human SH-SY5Y neuroblastoma cells treated with MnCl2 under conditions that resulted in cell death or no cell death after 48 h. Putrescine and other metabolites were analyzed by liquid chromatography-ultra high-resolution mass spectrometry. Putrescine-related pathway changes were identified with metabolome-wide association study (MWAS). Results show that Mn caused a dose-dependent increase in putrescine over a non-toxic to toxic concentration range. MWAS of putrescine showed positive correlations with the polyamine metabolite N8-acetylspermidine, methionine-related precursors, and arginine-associated urea cycle metabolites, while putrescine was negatively correlated with γ-aminobutyric acid (GABA)-related and succinate-related metabolites (P < 0.001, FDR < 0.01). These data suggest that measurement of putrescine and correlated metabolites may be useful to study effects of Mn intake in the high adequate to UL range.

Healthy brain aging: Interplay between reactive species, inflammation and energy supply

Brains' high energy expenditure with preferable utilization of glucose and ketone bodies, defines the specific features of its energy homeostasis. The extensive oxidative metabolism is accompanied by a concomitant generation of high amounts of reactive oxygen, nitrogen, and carbonyl species, which will be here collectively referred to as RONCS. Such metabolism in combination with high content of polyunsaturated fatty acids creates specific problems in maintaining brains' redox homeostasis. While the levels of products of interaction between RONCS and cellular components increase slowly during the first two trimesters of individuals' life, their increase is substantially accelerated towards the end of life. Here we review the main mechanisms controlling the redox homeostasis of the mammalian brain, their age-dependencies as well as their adaptive potential, which might turn out to be much higher than initially assumed. According to recent data, the organism seems to respond to the enhancement of aging-related toxicity by forming a new homeostatic set point. Therefore, further research will focus on understanding the properties of the new set point(s), the general nature of this phenomenon and will explore the limits of brains' adaptivity.

Neuropathology of suicide: recent findings and future directions

Suicide is a major public health concern and a leading cause of death in most societies. Suicidal behaviour is complex and heterogeneous, likely resulting from several causes. It associates with multiple factors, including psychopathology, personality traits, early-life adversity and stressful life events, among others. Over the past decades, studies in fields ranging from neuroanatomy, genetics and molecular psychiatry have led to a model whereby behavioural dysregulation, including suicidal behaviour (SB), develops as a function of biological adaptations in key brain systems. More recently, the unravelling of the unique epigenetic processes that occur in the brain has opened promising avenues in suicide research. The present review explores the various facets of the current knowledge on suicidality and discusses how the rapidly evolving field of neurobehavioural epigenetics may fuel our ability to understand, and potentially prevent, SB.

Agmatine: multifunctional arginine metabolite and magic bullet in clinical neuroscience?

Agmatine, the decarboxylation product of arginine, was largely neglected as an important player in mammalian metabolism until the mid-1990s, when it was re-discovered as an endogenous ligand of imidazoline and α2-adrenergic receptors. Since then, a wide variety of agmatine-mediated effects have been observed, and consequently agmatine has moved from a wallflower existence into the limelight of clinical neuroscience research. Despite this quantum jump in scientific interest, the understanding of the anabolism and catabolism of this amine is still vague. The purification and biochemical characterization of natural mammalian arginine decarboxylase and agmatinase still are open issues. Nevertheless, the agmatinergic system is currently one of the most promising candidates in order to pharmacologically interfere with some major diseases of the central nervous system, which are summarized in the present review. Particularly with respect to major depression, agmatine, its derivatives, and metabolizing enzymes show great promise for the development of an improved treatment of this common disease.

Targets of polyamine dysregulation in major depression and suicide: Activity-dependent feedback, excitability, and neurotransmission

Major depressive disorder (MDD) is a leading cause of disability worldwide characterized by altered neuronal activity in brain regions involved in the control of stress and emotion. Although multiple lines of evidence suggest that altered stress-coping mechanisms underlie the etiology of MDD, the homeostatic control of neuronal excitability in MDD at the molecular level is not well established. In this review, we examine past and current evidence implicating dysregulation of the polyamine system as a central factor in the homeostatic response to stress and the etiology of MDD. We discuss the cellular effects of abnormal metabolism of polyamines in the context of their role in sensing and modulation of neuronal, electrical, and synaptic activity. Finally, we discuss evidence supporting an allostatic model of depression based on a chronic elevation in polyamine levels resulting in self-sustained stress response mechanisms maintained by maladaptive homeostatic mechanisms.

Isoform-level brain expression profiling of the spermidine/spermine N1-Acetyltransferase1 (SAT1) gene in major depression and suicide

Low brain expression of the spermidine/spermine N-1 acetyltransferase (SAT1) gene, the rate-limiting enzyme involved in catabolism of polyamines that mediate the polyamine stress response (PSR), has been reported in depressed suicides. However, it is unknown whether this effect is associated with depression or with suicide and whether all or only specific isoforms expressed by SAT1, such as the primary 171 amino acid protein-encoding transcript (SSAT), or an alternative splice variant (SSATX) that is involved in SAT1 regulated unproductive splicing and transcription (RUST), are involved. We applied next generation sequencing (RNA-seq) to assess gene-level, isoform-level, and exon-level SAT1 expression differences between healthy controls (HC, N = 29), DSM-IV major depressive disorder suicides (MDD-S, N = 21) and MDD non-suicides (MDD, N = 9) in the dorsal lateral prefrontal cortex (Brodmann Area 9, BA9) of medication-free individuals postmortem. Using small RNA-seq, we also examined miRNA species putatively involved in SAT1 post-transcriptional regulation. A DSM-IV diagnosis was made by structured interview. Toxicology and history ruled out recent psychotropic medication. At the gene-level, we found low SAT1 expression in both MDD-S (vs. HC, p = 0.002) and MDD (vs. HC, p = 0.002). At the isoform-level, reductions in MDD-S (vs. HC) were most pronounced in four transcripts including SSAT and SSATX, while reductions in MDD (vs. HC) were pronounced in three transcripts, one of which was reduced in MDD relative to MDD-S (all p < 0.1 FDR corrected). We did not observe evidence for differential exon-usage (i.e. splicing) nor differences in miRNA expression. Results replicate the finding of low SAT1 brain expression in depressed suicides in an independent sample and implicate low SAT1 brain expression in MDD independent of suicide. Low expressions of both SSAT and SATX isoforms suggest that shared transcriptional mechanisms involved in RUST may account for low SAT1 brain expression in depressed suicides. Future studies are required to understand the functions and regulation of SAT1 isoforms, and how they relate to the pathogenesis of MDD and suicide.

The role of glia in stress: polyamines and brain disorders

This review focuses on the roles of glia and polyamines (PAs) in brain function and dysfunction, highlighting how PAs are one of the principal differences between glia and neurons. The novel role of PAs, such as putrescine, spermidine, and spermine and their precursors and derivatives, is discussed. However, PAs have not yet been a focus of much glial research. They affect many neuronal and glial receptors, channels, and transporters. They are therefore key elements in the development of many diseases and syndromes, thus forming the rationale for PA-focused and glia-focused therapy for these conditions.

Suicide and the polyamine system

Suicide is a significant worldwide public health problem. Understanding the neurobiology is important as it can help us to better elucidate underlying etiological factors and provide opportunities for intervention. In recent years, many lines of research have suggested that the polyamine system may be dysregulated in suicidal behaviors. Initial research in animals provided evidence of a dysfunctional polyamine stress response system, while later work using post-mortem human brain tissue has suggested that molecular mechanisms may be at play in the suicide brain. In this review, we will describe the research that suggests the presence of alterations in the polyamine system in mental disorders and behavioral phenotypes, with particular attention to work on suicide. In addition, we will also describe potential avenues for future work.

The molecular bases of the suicidal brain

Suicide ranks among the leading causes of death around the world and takes a heavy emotional and public health toll on most societies. Both distal and proximal factors contribute to suicidal behaviour. Distal factors - such as familial and genetic predisposition, as well as early-life adversity - increase the lifetime risk of suicide. They alter responses to stress and other processes through epigenetic modification of genes and associated changes in gene expression, and through the regulation of emotional and behavioural traits. Proximal factors are associated with the precipitation of a suicidal event and include alterations in key neurotransmitter systems, inflammatory changes and glial dysfunction in the brain. This Review explores the key molecular changes that are associated with suicidality and discusses some promising avenues for future research.

Epigenetics and suicidal behavior research pathways

Suicide and suicidal behaviors are complex, heterogeneous phenomena that are thought to result from the interactions among distal factors increasing predisposition and proximal factors acting as precipitants. Epigenetic factors are likely to act both distally and proximally. Aspirational Goal 1 aims to find clear targets for suicide and suicidal behavior intervention through greater understanding of the interplay among the biological, psychological, and social risk and protective factors associated with suicide. This paper discusses Aspirational Goal 1, focusing on the research pathway related to epigenetics, suicide, and suicidal behaviors. Current knowledge on epigenetic factors associated with suicide and suicidal behaviors is reviewed and avenues for future research are discussed. Epigenetic factors are a promising area of further investigation in the understanding of suicide and suicidal behaviors and may hold clues to identifying targets or avenues for intervention.

Stabilization of neuronal connections and the axonal cytoskeleton

Stabilization of axonal connections is an underappreciated, but critical, element in development and maintenance of neuronal functions. The ability to maintain the overall architecture of the brain for decades is essential for our ability to process sensory information efficiently, coordinate motor activity, and retain memories for a lifetime. While the importance of the neuronal cytoskeleton in this process is acknowledged, little has been known about specializations of the axonal cytoskeleton needed to stabilize neuronal architectures. A novel post-translational modification of tubulin that stabilizes normally dynamic microtubules in axons has now been identified. Polyamination appears to be enriched in axons and is developmentally regulated with a time course that correlates with increased microtubule stabilization. Identifying one of the molecular mechanisms for maintaining neuronal connections creates new research avenues for understanding the role of stabilizing neuronal architecture in neuronal function and in neuropathology.

Regulatory role of miRNAs in polyamine gene expression in the prefrontal cortex of depressed suicide completers

MicroRNAs (miRNAs) are small, non-coding RNA molecules that play an important role in the post-transcriptional regulation of mRNA. These molecules have been the subject of growing interest as they are believed to control the regulation of a large number of genes, including those expressed in the brain. Evidence suggests that miRNAs could be involved in the pathogenesis of neuropsychiatric disorders. Alterations in metabolic enzymes of the polyamine system have been reported to play a role in predisposition to suicidal behaviour. We have previously shown the expression of the polyamine genes SAT1 and SMOX to be down-regulated in the brains of suicide completers. In this study, we hypothesized that the dysregulation of these genes in depressed suicide completers could be influenced by miRNA post-transcriptional regulation. Using a stringent target prediction analysis, we identified several miRNAs that target the 3'UTR of SAT1 and SMOX. We profiled the expression of 10 miRNAs in the prefrontal cortex (BA44) of suicide completers (N = 15) and controls (N = 16) using qRT-PCR. We found that several miRNAs showed significant up-regulation in the prefrontal cortex of suicide completers compared to psychiatric healthy controls. Furthermore, we demonstrated a significant correlation between these miRNAs and the expression levels of both SAT1 and SMOX. Our results suggest a relationship between miRNAs and polyamine gene expression in the suicide brain, and postulate a mechanism for SAT1 and SMOX down-regulation by post-transcriptional activity of miRNAs.

Differential effect of lithium on spermidine/spermine N1-acetyltransferase expression in suicidal behaviour

An altered polyamine system has been suggested to play a key role in mood disorders and suicide, a hypothesis corroborated by the evidence that lithium inhibits the polyamine mediated stress response in the rat brain. Recent post-mortem studies have shown that spermidine/spermine N1-acetyltransferase (SAT1), the key regulator of cellular polyamine content, is under-expressed in brains from suicide victims compared to controls. In our study we tested the effect of in vitro lithium treatment on SAT1 gene and protein expression in B lymphoblastoid cell lines (BLCLs) from bipolar disorder (BD) patients who committed suicide (and for which BLCLs were collected prior to their death), BD patients with high and low risk of suicide and a sample of non-psychiatric controls. Baseline mRNA levels were similar in the four groups of subjects (p > 0.05). Lithium had no effect in suicide completers (p > 0.05) while it significantly increased SAT1 expression in the high risk (p < 0.001) and low risk (p < 0.01) groups as well as in controls (p < 0.001). Protein and mRNA levels were not correlated; lithium significantly reduced protein levels only in the control sample (p < 0.05). Our findings suggest that SAT1 transcription is influenced by lithium and that this effect is altered in BD patients who completed suicide, further supporting a role for polyamines in suicide.

Glutamatergic GRIN2B and polyaminergic ODC1 genes in suicide attempts: associations and gene-environment interactions with childhood/adolescent physical assault

The complex etiology of suicidal behavior has frequently been investigated in relation to monoaminergic neurotransmission, but other neurosystems have shown alterations as well, involving excitatory glutamatergic and inhibitory γ-aminobutyric acid (GABA) molecular components, together with the modulating polyamines. Sufficiently powered and family-based association studies of glutamatergic and GABAergic genes with suicidal behavior are nonexistent, but several studies have been reported for polyamines. We therefore conducted, for the first time ever, an extensive family-based study of 113 candidate single-nucleotide polymorphisms (SNPs) located in 24 glutamatergic and GABA genes, in addition to interrelated polyaminergic genes, on the outcome of severe suicide attempts (SAs). The family-based analysis (n=660 trios) was supplemented with gene-environment interaction (G × E), case-control (n=519 controls) and subgroup analyses. The main observations were the previously unreported association and linkage of SNPs rs2268115 and rs220557 in GRIN2B, as well as of SNPs rs1049500 and rs2302614 in ODC1 (P<10(-2)). Furthermore, GRIN2B haplotypic associations were observed, in particular with a four-SNP AGGC haplotype (rs1805247-rs1806201-rs1805482-rs2268115; P<10(-5)), and a third SNP rs7559979 in ODC1 showed G × E with serious childhood/adolescent physical assault (P<10(-4)). SA subjects were characterized by transdiagnostic trait anger and past year alcohol-drug use disorders, but not by alcohol-drug use at SA, depression, anxiety or psychosis diagnoses. We also discuss a first ever confirmatory observation of SNP rs6526342 (polyaminergic SAT1) in SA, originally identified in completed suicides. The results suggest that specific genetic variants in a subset of glutamatergic (GRIN2B) and polyaminergic (ODC1) neurosystem genes may be of importance in certain suicidal subjects.

Adapting to environmental stresses: the role of the microbiota in controlling innate immunity and behavioral responses

Mammals are subject to colonization by an astronomical number of mutualistic and commensal microorganisms on their environmental exposed surfaces. These mutualistic species build up a complex community, called the indigenous microbiota, which aid their hosts in several physiological activities. In this review, we show that the transition between a non-colonized and a colonized state is associated with modification on the pattern of host inflammatory and behavioral responsiveness. There is a shift from innate anti-inflammatory cytokine production to efficient release of proinflammatory mediators and rapid mobilization of leukocytes upon infection or other stimuli. In addition, host responses to hypernociceptive and stressful stimuli are modulated by indigenous microbiota, partly due to the altered pattern of innate and acquired immune responsiveness of the non-colonized host. These altered responses ultimately lead to significant alteration in host behavior to environmental threats. Therefore, host colonization by indigenous microbiota modifies the way the host perceives and reacts to environmental stimuli, improving resilience of the entire host-microorganism consortium to environmental stresses.

Glucocorticoid and polyamine interactions in the plasticity of glutamatergic synapses that contribute to ethanol-associated dependence and neuronal injury

Stress contributes to the development of ethanol dependence and is also a consequence of dependence. However, the complexity of physiological interactions between activation of the hypothalamic-pituitary-adrenal (HPA) axis and ethanol itself is not well delineated. Emerging evidence derived from examination of corticotropin-releasing factor systems and glucocorticoid receptor systems in ethanol dependence suggests a role for pharmacological manipulation of the HPA axis in attenuating ethanol intake, though it is not clear how activation of the HPA axis may promote ethanol dependence or contribute to the neuroadaptative changes that accompany the development of dependence and the severity of ethanol withdrawal. This review examines the role that glucocorticoids, in particular, have in promoting ethanol-associated plasticity of glutamatergic synapses by influencing expression of endogenous linear polyamines and polyamine-sensitive polypeptide subunits of N-methyl-D-aspartate (NMDA)-type glutamate receptors. We provide evidence that interactions among glucocorticoid systems, polyamines and NMDA receptors are highly relevant to both the development of ethanol dependence and to behavioral and neuropathological sequelae associated with ethanol withdrawal. Examination of these issues is likely to be of critical importance not only in further elucidating the neurobiology of HPA axis dysregulation in ethanol dependence, but also with regard to identification of novel therapeutic targets that may be exploited in the treatment of ethanol dependence.

The polyamine inhibitor alpha-difluoromethylornithine modulates hippocampus-dependent function after single and combined injuries

Exposure to uncontrolled irradiation in a radiologic terrorism scenario, a natural disaster or a nuclear battlefield, will likely be concomitantly superimposed on other types of injury, such as trauma. In the central nervous system, radiation combined injury (RCI) involving irradiation and traumatic brain injury may have a multifaceted character. This may entail cellular and molecular changes that are associated with cognitive performance, including changes in neurogenesis and the expression of the plasticity-related immediate early gene Arc. Because traumatic stimuli initiate a characteristic early increase in polyamine metabolism, we hypothesized that treatment with the polyamine inhibitor alpha-difluoromethylornithine (DFMO) would reduce the adverse effects of single or combined injury on hippocampus structure and function. Hippocampal dependent cognitive impairments were quantified with the Morris water maze and showed that DFMO effectively reversed cognitive impairments after all injuries, particularly traumatic brain injury. Similar results were seen with respect to the expression of Arc protein, but not neurogenesis. Given that polyamines have been found to modulate inflammatory responses in the brain we also assessed the numbers of total and newly born activated microglia, and found reduced numbers of newly born cells. While the mechanisms responsible for the improvement in cognition after DFMO treatment are not yet clear, the present study provides new and compelling data regarding the potential use of DFMO as a potential countermeasure against the adverse effects of single or combined injury.

Global gene expression profiling of the polyamine system in suicide completers

In recent years, gene expression, genetic association, and metabolic studies have implicated the polyamine system in psychiatric conditions, including suicide. Given the extensive regulation of genes involved in polyamine metabolism, as well as their interconnections with the metabolism of other amino acids, we were interested in further investigating the expression of polyamine-related genes across the brain in order to obtain a more comprehensive view of the dysregulation of this system in suicide. To this end, we examined the expression of genes related to polyamine metabolism across 22 brain regions in a sample of 29 mood-disordered suicide completers and 16 controls, and identified 14 genes displaying differential expression. Among these, altered expression of spermidine/spermine N1-acetyltransferase, spermine oxidase, and spermine synthase, has previously been observed in brains of suicide completers, while the remainder of the genes represent novel findings. In addition to genes with direct involvement in polyamine metabolism, including S-adenosylmethionine decarboxylase, ornithine decarboxylase antizymes 1 and 2, and arginase II, we identified altered expression of several more distally related genes, including aldehyde dehydrogenase 3 family, member A2, brain creatine kinase, mitochondrial creatine kinase 1, glycine amidinotransferase, glutamic-oxaloacetic transaminase 1, and arginyl-tRNA synthetase-like. Many of these genes displayed altered expression across several brain regions, strongly implying that dysregulated polyamine metabolism is a widespread phenomenon in the brains of suicide completers. This study provides a broader view of the nature and extent of the dysregulation of the polyamine system in suicide, and highlights the importance of this system in the neurobiology of suicide.

New perspectives in glutamate and anxiety

Anxiety and stress-related disorders, namely posttraumatic stress disorder (PTSD), generalized anxiety disorder (GAD), obsessive-compulsive disorder (ODC), social and specific phobias, and panic disorder, are a major public health issue. A growing body of evidence suggests that glutamatergic neurotransmission may be involved in the biological mechanisms underlying stress response and anxiety-related disorders. The glutamatergic system mediates the acquisition and extinction of fear-conditioning. Thus, new drugs targeting glutamatergic neurotransmission may be promising candidates for new pharmacological treatments. In particular, N-methyl-d-aspartate receptors (NMDAR) antagonists (AP5, AP7, CGP37849, CGP39551, LY235959, NPC17742, and MK-801), NMDAR partial agonists (DCS, ACPC), α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors (AMPARs) antagonists (topiramate), and several allosteric modulators targeting metabotropic glutamate receptors (mGluRs) mGluR1, mGluR2/3, and mGluR5, have shown anxiolytic-like effects in several animal and human studies. Several studies have suggested that polyamines (agmatine, putrescine, spermidine, and spermine) may be involved in the neurobiological mechanisms underlying stress-response and anxiety-related disorders. This could mainly be attributed to their ability to modulate ionotropic glutamate receptors, especially NR2B subunits. The aim of this review is to establish that glutamate neurotransmission and polyaminergic system play a fundamental role in the onset of anxiety-related disorders. This may open the way for new drugs that may help to treat these conditions.

Association of polyaminergic loci with anxiety, mood disorders, and attempted suicide

BACKGROUND

The polyamine system has been implicated in a number of psychiatric conditions, which display both alterations in polyamine levels and altered expression of genes related to polyamine metabolism. Studies have identified associations between genetic variants in spermidine/spermine N1-acetyltransferase (SAT1) and both anxiety and suicide, and several polymorphisms appear to play important roles in determining gene expression.

METHODOLOGY/PRINCIPAL FINDINGS

We genotyped 63 polymorphisms, spread across four polyaminergic genes (SAT1, spermine synthase (SMS), spermine oxidase (SMOX), and ornithine aminotransferase like-1 (OATL1)), in 1255 French-Canadian individuals who have been followed longitudinally for 22 years. We assessed univariate associations with anxiety, mood disorders, and attempted suicide, as assessed during early adulthood. We also investigated the involvement of gene-environment interactions in terms of childhood abuse, and assessed internalizing and externalizing symptoms as endophenotypes mediating these interactions. Overall, each gene was associated with at least one main outcome: anxiety (SAT1, SMS), mood disorders (SAT1, SMOX), and suicide attempts (SAT1, OATL1). Several SAT1 polymorphisms displayed disease-specific risk alleles, and polymorphisms in this gene were involved in gene-gene interactions with SMS to confer risk for anxiety disorders, as well as gene-environment interactions between childhood physical abuse and mood disorders. Externalizing behaviors demonstrated significant mediation with regards to the association between OATL1 and attempted suicide, however there was no evidence that externalizing or internalizing behaviors were appropriate endophenotypes to explain the associations with mood or anxiety disorders. Finally, childhood sexual abuse did not demonstrate mediating influences on any of our outcomes.

CONCLUSIONS/SIGNIFICANCE

These results demonstrate that genetic variants in polyaminergic genes are associated with psychiatric conditions, each of which involves a set of separate and distinct risk alleles. As several of these polymorphisms are associated with gene expression, these findings may provide mechanisms to explain the alterations in polyamine metabolism which have been observed in psychiatric disorders.

Genetic and epigenetic influences on expression of spermine synthase and spermine oxidase in suicide completers

Alterations in the levels of spermine synthase (SMS) and spermine oxidase (SMOX), two enzymes involved in polyamine metabolism, have previously been observed in brains of suicide completers. To characterize the roles played by genetic and epigenetic factors in determining expression levels of these genes, as well as to identify potential mechanisms by which to explain our findings in suicide completers, we (1) assessed the role of promoter polymorphisms in determining expression in the brain and in vitro, and (2) examined CpG methylation and levels of methylated histone H3 lysine-27 in the promoter regions of these genes in the prefrontal cortex of suicide completers and healthy controls. We identified several promoter haplotypes in SMS and SMOX, but found no consistent effects of haplotype on expression levels in either the brain or in reporter gene assays performed in three different cell lines. We also found no overall effects of epigenetic factors in determining expression, with the exception of a relationship between CpG methylation at one site in the promoter of SMOX and its expression in Brodmann area 8/9. In conclusion, the genetic and epigenetic factors examined in this study show little influence on the expression levels of SMS and SMOX, and do not appear to be responsible for the dysregulated expression of these genes in suicide completers.