Spermine promotes the survival of primary cultured brain neurons

Possible Role of Cellular Polyamine Metabolism in Neuronal Apoptosis

Recent studies have shown that cellular levels of polyamines (PAs) are significantly altered in neurodegenerative diseases. Evidence from in vivo animal and in vitro cell experiments suggests that the cellular levels of various PAs may play important roles in the central nervous system through the regulation of oxidative stress, mitochondrial metabolism, cellular immunity, and ion channel functions. Dysfunction of PA metabolism related enzymes also contributes to neuronal injury and cognitive impairment in many neurodegenerative diseases. Therefore, in the current work, evidence was collected to determine the possible associations between cellular levels of PAs, and related enzymes and the development of several neurodegenerative diseases, which could provide a new idea for the treatment of neurodegenerative diseases in the future.

Hormesis: A potential strategic approach to the treatment of neurodegenerative disease

This review describes neuroprotective effects mediated by pre- and post-conditioning-induced processes that act via the quantitative features of the hormetic dose response. These lead to the development of acquired resilience that can protect neuronal systems from endogenous and exogenous stresses and insult. Particular attention is directed to issues of dose optimization, inter-individual variation, and potential ways to further study and employ hormetic-based preconditioning approaches in medical and public health efforts to treat and prevent neurodegenerative disease.

Temporal Characterization of Neuronal Migration Behavior on Chemically Patterned Neuronal Circuits in a Defined in Vitro Environment

Directed control of neuronal migration, facilitating the correct spatial positioning of neurons, is crucial to the development of a functional nervous system. An understanding of neuronal migration and positioning on patterned surfaces in vitro would also be beneficial for investigators seeking to design culture platforms capable of mimicking the complex functional architectures of neuronal tissues for drug development as well as basic biomedical research applications. This study used coplanar self-assembled monolayer patterns of cytophilic, N-1[3-(trimethoxysilyly)propyl] diethylenetriamine (DETA) and cytophobic, tridecafluoro-1,1,2,2-tetrahydrooctyl-1-trichlorosilane (13F) to assess the migratory behavior and physiological characteristics of cultured neurons. Analysis of time-lapse microscopy data revealed a dynamic procedure underlying the controlled migration of neurons, in response to extrinsic geometric and chemical cues, to promote the formation of distinct two-neuron circuits. Immunocytochemical characterization of the neurons highlights the organization of actin filaments (phalloidin) and microtubules (β-tubulin) at each migration stage. These data have applications in the development of precise artificial neuronal networks and provide a platform for investigating neuronal migration as well as neurite identification in differentiating cultured neurons. Importantly, the cytoskeletal arrangement of these cells identifies a specific mode of neuronal migration on these in vitro surfaces characterized by a single process determining the direction of cell migration and mimicking somal translocation behavior in vivo. Such information provides valuable additional insight into the mechanisms controlling neuronal development and maturation in vitro and validates the biochemical mechanisms underlying this behavior as representative of neuronal positioning phenomena in vivo.

Modulation of learning and memory by natural polyamines

Spermine and spermidine are natural polyamines that are produced mainly via decarboxylation of l-ornithine and the sequential transfer of aminopropyl groups from S-adenosylmethionine to putrescine by spermidine synthase and spermine synthase. Spermine and spermidine interact with intracellular and extracellular acidic residues of different nature, including nucleic acids, phospholipids, acidic proteins, carboxyl- and sulfate-containing polysaccharides. Therefore, multiple actions have been suggested for these polycations, including modulation of the activity of ionic channels, protein synthesis, protein kinases, and cell proliferation/death, within others. In this review we summarize these neurochemical/neurophysiological/morphological findings, particularly those that have been implicated in the improving and deleterious effects of spermine and spermidine on learning and memory of naïve animals in shock-motivated and nonshock-motivated tasks, from a historical perspective. The interaction with the opioid system, the facilitation and disruption of morphine-induced reward and the effect of polyamines and putative polyamine antagonists on animal models of cognitive diseases, such as Alzheimer's, Huntington, acute neuroinflammation and brain trauma are also reviewed and discussed. The increased production of polyamines in Alzheimer's disease and the biphasic nature of the effects of polyamines on memory and on the NMDA receptor are also considered. In light of the current literature on polyamines, which include the description of an inborn error of the metabolism characterized by mild-to moderate mental retardation and polyamine metabolism alterations in suicide completers, we can anticipate that polyamine targets may be important for the development of novel strategies and approaches for understanding the etiopathogenesis of important central disorders and their pharmacological treatment.

Morphological and functional characterization of human induced pluripotent stem cell-derived neurons (iCell Neurons) in defined culture systems

Pre-clinical testing of drug candidates in animal models is expensive, time-consuming, and often fails to predict drug effects in humans. Industry and academia alike are working to build human-based in vitro test beds and advanced high throughput screening systems to improve the translation of preclinical results to human drug trials. Human neurons derived from induced pluripotent stems cells (hiPSCs) are readily available for use within these test-beds and high throughput screens, but there remains a need to robustly evaluate cellular behavior prior to their incorporation in such systems. This study reports on the characterization of one source of commercially available hiPSC-derived neurons, iCell(®) Neurons, for their long-term viability and functional performance to assess their suitability for integration within advanced in vitro platforms. The purity, morphology, survival, identity, and functional maturation of the cells utilizing different culture substrates and medium combinations were evaluated over 28 days in vitro (DIV). Patch-clamp electrophysiological data demonstrated increased capacity for repetitive firing of action potentials across all culture conditions. Significant differences in cellular maturity, morphology, and functional performance were observed in the different conditions, highlighting the importance of evaluating different surface types and growth medium compositions for application in specific in vitro protocols.

Hormesis: its impact on medicine and health

This article offers a broad assessment of the hormetic dose response and its relevance to biomedical researchers, physicians, the pharmaceutical industry, and public health scientists. This article contains a series of 61 questions followed by relatively brief but referenced responses that provides support for the conclusion that hormesis is a reproducible phenomenon, commonly observed, with a frequency far greater than other dose-response models such as the threshold and linear nonthreshold dose-response models. The article provides a detailed background information on the historical foundations of hormesis, its quantitative features, mechanistic foundations, as well as how hormesis is currently being used within medicine and identifying how this concept could be further applied in the development of new therapeutic advances and in improved public health practices.

Neuroprotective effects of spermine following hypoxia‐ischemia‐induced brain damage: A mechanistic study

The polyamines (spermine, putrescine, and spermidine) can have neurotoxic or neuroprotective properties in models of neurodegeneration. However, assessment in a model of hypoxia-ischemia (HI) has not been defined. Furthermore, the putative mechanisms of neuroprotection have not been elucidated. Therefore, the present study examined the effects of the polyamines in a rat pup model of HI and determined effects on key enzymes involved in inflammation, namely, nitric oxide synthase (NOS) and arginase. In addition, effects on mitochondrial function were investigated. The polyamines or saline were administered i.p. at 10mg/kg/day for 6 days post-HI. Histological assessment 7 days post-HI revealed that only spermine significantly (P<0.01) reduced infarct size from 46.14 +/- 10.4 mm3 (HI + saline) to 4.9 +/- 2.7 mm3. NOS activity was significantly increased following spermine treatment in the left (ligated) hemisphere compared with nonintervention controls (P<0.01) and HI + saline (P<0.05). In contrast, spermine decreased arginase activity compared with HI + saline but was still significantly elevated in comparison to nonintervention controls (P<0.01). Assessment of mitochondrial function in the HI + saline group, revealed significant and extensive damage to complex-I (P<0.01) and IV (P<0.001) and loss of citrate synthase activity (P<0.05). No effect on complex II-III was observed. Spermine treatment significantly prevented all these effects. This study has therefore confirmed the neuroprotective effects of spermine in vivo. However, for the first time, we have shown that this effect may, in part, be due to increased NOS activity and preservation of mitochondrial function.

Polyamines in a genetic animal model of paroxysmal dyskinesia

Previous studies suggested that glutamatergic overactivity contributes to the manifestation of dystonia in the dt(sz) mutant hamster, a model of idiopathic paroxysmal dyskinesia in which dystonic episodes occur in response to mild stress. Therefore, the role of polyamines, known as positive modulators of NMDA receptors, was examined in the present study. The levels of polyamines (putrescine, spermidine, spermine) were determined in forebrain, cerebellum and brainstem in dt(sz) hamsters at an age of most marked expression of dystonia (32 days) and in age-matched non-dystonic control hamsters. Spermine was found to be significantly increased in the forebrain (35%) of dystonic animals, while spermidine was unaltered in dystonic brains and only a moderate increase in putrescine (12%) was detected in the cerebellum of dt(sz) mutants. In view of enhanced spermine levels, the effect of the putative polyamine receptor antagonist ifenprodil on the severity of dystonia was examined in dystonic hamsters. Ifenprodil (5-40 mg/kg i.p.) failed to exert a beneficial effect, but even aggravated dystonia in the dt(sz) mutant at higher doses. These data together with previous pharmacological findings in mutant hamsters do not completely exclude a pathophysiological role of enhanced polyamine levels but suggest that overstimulation of NMDA receptors which contain NR2B subunits by enhanced spermine levels is not involved in the dystonic syndrome.

Spermine is neuroprotective against anoxia and N-methyl-D-aspartate in hippocampal slices

Polyamines were implicated as either neurotoxic or neuroprotective in several models of stroke. Spermine augments the excitotoxicity mediated by the N-methyl-D-aspartate (NMDA) receptor because this receptor is activated at micromolar spermine concentrations. However, at higher concentrations, spermine could be neuroprotective because it blocks the NMDA receptor and voltage-activated Ca(2+) channels. In this work, acute hippocampal slices were exposed to 1 mM spermine and either 10 min of anoxia or 0.5 mM NMDA. The percent recovery of population spikes was the measure of neuroprotection. One millimolar spermine was robustly neuroprotective; however, 0.1 mM spermine and 1 mM putrescine were not. The neuroprotective concentration of spermine was higher than the physiological concentration of free spermine. However, during an excitotoxic episode, extracellular Ca(2+) is decreased, enabling the inhibitory activity of lower spermine concentration. In addition, several noxious stimuli trigger the release of intracellular spermine and could raise local levels of spermine. Therefore, it is possible that spermine has a neuroprotective role in vivo.

Exogenous spermine reduces ischemic damage in a model of focal cerebral ischemia in the rat

Alterations in polyamine metabolism during and after global or focal cerebral ischemia can produce a multiplicity of effects on brain such as modification in mitochondria calcium buffering capacity, exacerbating glutamate-mediated neurotoxicity, and impairment of the blood-brain barrier. In this study, the endogenous polyamine spermine was administered intravenously 30 min prior to temporary focal cerebral ischemia in rats induced by clipping of the left middle cerebral and bilateral common carotid arteries for 3 h. Three days after removal of the microclips, intracardiac perfusion with 2% 2,3,5-triphenyl tetrazolium chloride was performed. Coronal slices were cut, photographed, and examined for cortical infarct volume. Spermine reduced infarct volume in a dose-dependent fashion. This study demonstrates that the use of polyamines may be considered as a powerful tool in prevention of ischemic tissue damage following focal cerebral ischemia.

Allixin, a phytoalexin produced by garlic, and its analogues as novel exogenous substances with neurotrophic activity

Effects of allixin, a phytoalexin of garlic, and its analogues were studied on the survival and morphology of primary cultured neurons from fetal rat brain. Addition of allixin (1-100 ng/ml) to medium significantly promoted the survival of neurons derived from various regions of brain and increased the number of branching points per axon in hippocampal neurons. Allixin, however, was cytotoxic at higher concentrations (>1 microg/ml). Among the analogues of allixin, 2,6-dimethyl-3-hydroxy-4H-pyran-4-one (DHP) possessed potent neurotrophic activity at concentrations over 10 ng/ml without any obvious cytotoxicity up to 10 microg/ml. DHP also retained the activity to promote axonal branching. These results indicate that DHP is a novel exogenous low molecular weight neurotrophic substance without apparent cytotoxicity. This compound may be a useful prototype leading chemical for developing therapeutic and/or prophylactic drugs for neurodegenerative disorders.

Spermine partially normalizes in vivo antioxidant defense potential in certain brain regions in transiently hypoperfused rat brain

Activities of the antioxidant enzymes such as superoxide dismutase (Cu,Zn-SOD), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R) as well as the level of reduced glutathione and the concentration of thiobarbituric acid-reactive substance (TBARS) in brain regions in transiently hypoperfused rat brain with or without intravenous infusion of spermine were evaluated. Cerebral hypoperfusion was induced by temporary occlusion of common carotid arteries for 30 min and subsequently, by reperfusion for 60 min. Infusion of spermine reversed the decrease in SOD activity in the cerebral cortex, striatum, hippocampus, hypothalamus and midbrain, and amounted to 50.1 U, 61.5 U, 50.3 U, 30.0 U, 38.0 U, respectively, while GSH-Px restored to normal values only in the cerebral cortex and striatum and amounted to 100 U and 110 U, respectively. During hypoperfusion/reperfusion and after use of spermine no changes in GSSG-R were seen in the hypothalamus and midbrain. The activity of GSSG-R was in accordance with the control for the striatum and amounted to 39.0 IU after using spermine. GSH content returned to normal values in the striatum and midbrain after i.v. use of spermine and amounted to 210 and 240 nmol/g of wet tissue, respectively. In addition, the production of TBARS dropped markedly (P < 0.05) in the hippocampus and midbrain and amounted to 100 and 105 mumol/g of wet tissue, respectively. Partially beneficial effect of spermine could result from the inhibition of free radical generation and capability of chelate formation with iron ions.

HSP70 is essential to the neuroprotective effect of heat-shock

Many kinds of injuries induce 72 kDa heat-shock protein (HSP70) in the central nervous system. We investigated the role of HSP70 in promoting the survival of rat hippocampal neurons in primary culture. Heat-shock (42 degrees C for 30 min) significantly increased the number of surviving neurons independently of the initial density of plated cells, suggesting a direct effect on the neurons. Immunohistochemical detection revealed that HSP70 was expressed in virtually all cells six hours after the heat-shock and the immunostaining became stronger during the observation period of 72 h. HSP70 immunoreactivity was localized in the nucleus at 24 h after the heat-shock, but was diffused throughout the cytoplasm at 72 h. Addition of an antisense oligonucleotide to the medium significantly suppressed the neuroprotective effect of the heat-shock to control level, while a sense oligonucleotide had no effect. HSP70 immunoreactivity was completely abolished in the presence of the antisense oligonucleotide. These results indicate that HSP70 is essential for neuroprotection by heat-shock.

NMDA antagonist blockade of AT8 tau immunoreactive changes in neuronal cultures

Antagonists at four distinct regulatory sites on the N-methyl-D-aspartate (NMDA) receptor were tested for their ability to attenuate NMDA-mediated chronic excitotoxicity and the consequences on AT8 tau immunoreactivity in neuronal cultures. Excitotoxicity was monitored in cultures by diacetate fluorescein staining. Immunoreactivity of tau phosphorylated at serine 202 was quantified by laser confocal microscopy. The NMDA-receptor antagonists MK801, AP7 and 7-chlorokynurenate significantly blocked NMDA-induced cell death and significantly reduced AT8 tau immunoreactivity. NMDA antagonism by the polyamine site antagonist, ifenprodil, did not completely reverse the increase in AT8 tau immunolabeling induced by NMDA and did not completely protect NMDA-sensitive neurons, suggesting an heterogeneity in the NMDA receptor population.

Polyamines induce blood-brain barrier disruption and edema formation in the rat

Polyamines (PA) are derived from ornithine by the enzyme ornithine decarboxylase (ODC), which is activated very rapidly as acute and delayed responses to brain ischemia and trauma. Polyamines play a role in the disruption of the blood-brain barrier (BBB) in different pathological states. This study examined the effect of exogenous polyamines, administered intracerebrally (i.c.v.) or intracarotidly on BBB function. Putrescine, spermidine and spermine, given individually, were found to disrupt BBB integrity within 15 min of i.c.v. administration (p = 0.03; p = 0.0013; p = 0.042 vs saline treated rats, respectively). The effect was still evident after 1 h; however, since the saline treated rats also showed increased permeability of Evans blue at this time, there was no statistical difference between polyamines or saline treated rats 1 h post injection. When injected into the carotid artery, rapid increase in BBB permeability was found 1 min after putrescine and spermidine (p < 0.01 vs saline), with a slight decline at 15 min. A slower effect was noticed after spermine administration which reached significance only at 15 min. These results suggest a role for PA as mediators of vasogenic edema formation in the brain soon after brain injuries which induce increased production of these compounds.

Effects of vitamin B6 and its related compounds on survival of cultured brain neurons

The effects of pyridoxine and its derived cofacter, pyridoxal phosphate (PLP) on the survival of primary cultured neurons from fetal rat brain were investigated. Pyridoxine and PLP significantly promoted the neuronal survival of various brain regions in high cell density culture (10(5) cells/cm2), but showed no positive effects on hippocampal neurons in low cell density culture (5 x 10(3) cells/cm2). This neurotrophic effect of PLP was remarkably suppressed by picrotoxin and ifenprodil. Aminooxyacetic acid (AOAA), an inhibitor of PLP dependent enzymes, caused significant neuronal loss by itself, and largely counteracted the neurotrophic effect of PLP. Taken together, we presume that vitamin B6 afforded the survival-promoting activities of cultured neurons by virtue of its crucial coenzymatic actions in the biosynthesis of putative neurotransmitters.

Antagonistic effect of N-(3-Aminopropyl)cyclohexylamine on neurotrophic action of spermine in primary cultured rat hippocampal and cerebellar neurons

We previously found that spermine potently promotes the neuronal survival and regeneration of primary cultured brain neurons. N-(3-Aminopropyl)cyclohexylamine (APCHA) was originally developed as a spermine synthase inhibitor. To test if endogenous spermine biosynthesis contributes to neuronal survival and morphogenesis, we examined the effects of APCHA in primary cultured rat hippocampal and cerebellar neurons. APCHA at concentrations up to 10(-6) M did not affect the neuronal survival, but significantly blocked the survival-promoting effect of spermine (10(-8) M). APCHA also blocked the spermine-induced promotion of neurite regeneration following axotomy. Unlike APCHA, another cyclohexylamine derivative trans-4-methylcyclohexylamine did not affect the neurotrophic effect of spermine. These results suggest that in primary cultured brain neurons, APCHA works as a spermine antagonist rather than as a spermine synthesis inhibitor.

Polyamines promote regeneration of injured axons of cultured rat hippocampal neurons

Axons of cultured rat hippocampal neurons were injured by local irradiation of laser beam, and the effects of spermine, spermidine and putrescine on neurite regeneration following axonal injury were investigated. The axonal growth was stopped by laser irradiation, but addition of spermine remarkably promoted the axonal re-elongation from the injured site. Spermine affected neither the neurite branching at proximal part of injured axons nor the growth of uninjured dendrites. The effect of spermine was concentration dependent and seen maximally at a concentration of 10(-8) M. Spermidine and putrescine also promoted the axonal re-elongation in a concentration-dependent manner. The effects of three polyamines were very similar, and no additivity was observed when maximally effective concentrations of polyamines were added together, suggesting that they act through a common mechanism. Unlike polyamines, basic fibroblast growth factor (bFGF) did not promote the axonal re-elongation from the injured site, but rather stimulated the formation of axonal branches at proximal part of injured axons, supporting that the promotion of axonal re-elongation is a specific action of polyamines. Concomitant addition of spermine and bFGF additively or synergistically promoted both the axonal re-elongation from the injured site and the branch formation at proximal part of injured axons. These data suggest that polyamines have a capability of promoting axonal regeneration of brain neurons after lesioning.

Structural requirement for neurotrophic activity of spermine in cultured rat hippocampal neurons

We investigated the structure-activity relationship for the neurotrophic activity of spermine by comparing the effects of several synthetic spermine analogues on the survival of cultured rat hippocampal neurons. N,N'-bis(3-aminopropyl)-1,6-hexanediamine and N,N'-bis(3-aminopropyl)-1,3-propanediamine did not promote the neuronal survival, suggesting that the central butanediamine structure is essential for the neurotrophic activity. Furthermore, N1,N12-bis(ethyl)spermine significantly promoted the neuron survival, but its maximum effect was smaller than that of spermine, indicating that two terminal primary amines are required for full agonist activity. The structural requirement for the neurotrophic activity of spermine was different from those for any other reported activities of polyamines.

Polyamines promote neurite elongation of cultured rat hippocampal neurons

The effects of spermine, spermidine and putrescine on the survival and morphology of hippocampal neurons obtained from rat embryos were investigated using low cell density culture. The number of surviving neurons gradually decreased in the control cultures, while addition of spermine significantly promoted neuronal survival. The survival-promoting effect of spermine was seen maximally at a concentration of 10(-8) M. On the other hand, spermidine and putrescine showed no significant effect on neuronal survival. The axon length of neurons cultured in the presence of spermine was significantly longer than that in the medium with no added spermine, indicating that spermine promotes process elongation. The concentration-effect curve for spermine was bell-shaped with the maximum effect at a concentration of 10(-8) M. However, the number of processes per soma, the elongation of dendrites and the process branching in axons were not significantly affected by the presence of spermine. Addition of spermidine and putrescine also promoted the axon elongation of cultured neurons, without affecting the branching number. The effects of spermidine and putrescine on neuronal growth were very similar to that of spermine in terms of the effective concentrations and the patterns of morphological changes. Since spermine specifically promoted neuronal survival while three polyamines affected the neuronal morphology in a similar manner, it is possible that the effects of polyamines on neuronal survival and neurite elongation are mediated by different mechanisms.