DHEA-neuroprotection and -neurotoxicity after transient cerebral ischemia in rats

Steroid Metabolomic Signature in Term and Preterm Infants

Adrenal function is essential for survival and well-being of preterm babies. In addition to glucocorticoids, it has been hypothesized that C19-steroids (DHEA-metabolites) from the fetal zone of the adrenal gland may play a role as endogenous neuroprotective steroids. In 39 term-born (≥37 weeks gestational age), 42 preterm (30-36 weeks) and 51 early preterm (<30 weeks) infants 38 steroid metabolites were quantified by GC-MS in 24-h urinary samples. In each gestational age group, three distinctive cluster were identified by pattern analysis (k-means clustering). Individual steroidal fingerprints and clinical phenotype were analyzed at the 3rd day of life. Overall, the excretion rates of C21-steroids (glucocorticoid precursors, cortisol, and cortisone metabolites) were low (<99 μg/kg body weight/d) whereas the excretion rates of C19-steroids were up to 10 times higher. There was a shift to higher excretion rates of C19-steroids in both preterm groups compared to term infants but only minor differences in the distribution of C21-steroids. Comparable metabolic patterns were found between gestational age groups: Cluster 1 showed mild elevation of C21- and C19-steroids with the highest incidence of neonatal morbidities in term and severe intraventricular hemorrhage in early preterm infants. In cluster 2 lowest excretion in general was noted but no clinically unique phenotype. Cluster 3 showed highest elevation of C21-steroids and C19-steroids but no clinically unique phenotype. Significant differences in steroid metabolism between clusters are only partly reflected by gestational age and disease severity. In early preterm infants, higher excretion rates of glucocorticoids and their precursors were associated with severe cerebral hemorrhage. High excretion rates of C19-steroids in preterm infants may indicate a biological significance.

Treatment of Stroke at a Delayed Timepoint with a Repurposed Drug Targeting Sigma 1 Receptors

Sigma 1 receptors are intracellular chaperone proteins that have been explored as a subacute treatment to enhance post-stroke recovery. We recently identified the antitussive oxeladin as a selective sigma 1 receptor agonist with the ability to stimulate the release of brain-derived neurotrophic factor from neurons in vitro. In this study, we hypothesized that oral oxeladin citrate would stimulate BDNF secretion and improve stroke outcomes when administered to male rats starting 48 h after transient middle cerebral artery occlusion. Oxeladin did not alter blood clotting and crossed the blood brain barrier within 30 min of oral administration. Rats underwent 90 min of transient middle cerebral artery occlusion. Forty-eight hours later rats began receiving daily oxeladin (135 mg/kg) for 11 days. Oxeladin significantly improved neurological function on days 3, 7, and 14 following MCAO. Infarct size was not altered by a single dose, but the final extent of infarct after 14 days was decreased. However, there was no significant reduction in astrogliosis or microgliosis compared to vehicle-treated control rats. In agreement with in vitro studies, oxeladin increased the amount of mature BDNF in the cerebral cortex 2, 6, and 24 h after single oral dose. However, the increase in BDNF did not result in increases in cellular proliferation in the subventricular zone or dentate gyrus when compared to vehicle-treated controls. These results suggest that oxeladin may reduce the extent of infarct expansion in the subacute phase of stroke, although this action does not appear to involve a reduction in inflammation or increased cell proliferation.

Younger age and early puberty are associated with cognitive function decline in children with Cushing disease

OBJECTIVE

To investigate the effect of hypercortisolism on the developing brain we performed clinical, cognitive, and psychological evaluation of children with Cushing disease (CD) at diagnosis and 1 year after remission.

STUDY DESIGN

Prospective study of 41 children with CD. Children completed diverse sets of cognitive measures before and 1 year after remission. Neuropsychological evaluation included the Wechsler Intelligence Scale, California Verbal Learning Test, Trail Making Test, the combined subset scores of Wide Range Achievement Test and Woodcock-Johnson Psychoeducational Battery Test of Achievement, and the Behavioral Assessment System for Children.

RESULTS

Comprehensive cognitive evaluations at baseline and 1 year following cure revealed significant decline mostly in nonverbal skills. Decrements occurred in most of the various indices that measure all aspects of cognitive function and younger age and early pubertal stage largely contributed to most of this decline. Results indicated that age at baseline was associated with positive regression weights for changes in scores for verbal, performance, and full intelligence quotient (IQ) scores and for subtests arithmetic, picture completion, coding, block design, scores; indicating that older age at baseline was associated with less of a deterioration in cognitive scores from pre- to posttreatment.

CONCLUSION

Our findings suggest that chronic glucocorticoid excess and accompanying secondary hormonal imbalances followed by eucortisolemia have detrimental effects on cognitive function in the developing brain; younger age and pubertal stage are risk factors for increased vulnerability, while older adolescents have cognitive vulnerabilities like that of adult patients affected with CD.

Neurosteroids: A novel promise for the treatment of stroke and post-stroke complications

Stroke is the primary reason for death and disability worldwide, with few treatment strategies to date. Neurosteroids, which are natural molecules in the brain, have aroused great interest in the field of stroke. Neurosteroids are a kind of steroid that acts on the nervous system, and are synthesized in the mitochondria of neurons or glial cells using cholesterol or other steroidal precursors. Neurosteroids mainly include estrogen, progesterone (PROG), allopregnanolone, dehydroepiandrosterone (DHEA), and vitamin D (VD). Most of the preclinical studies have confirmed that neurosteroids can decrease the risk of stroke, and improve stroke outcomes. In the meantime, neurosteroids have been shown to have a positive therapeutic significance in some post-stroke complications, such as epilepsy, depression, anxiety, cardiac complications, movement disorders, and post-stroke pain. In this review, we report the historical background, modulatory mechanisms of neurosteroids in stroke and post-stroke complications, and emphasize on the application prospect of neurosteroids in stroke therapy.

Impact of Gestational and Postmenstrual Age on Excretion of Fetal Zone Steroids in Preterm Infants Determined by Gas Chromatography-Mass Spectrometry

CONTEXT

Fetal zone steroids (FZSs) are excreted in high concentrations in preterm infants. Experimental data suggest protective effects of FZSs in models of neonatal disease.

OBJECTIVE

We aimed to characterize the postnatal FZS metabolome of well preterm and term infants.

METHODS

Twenty-four-hour urinary FZS excretion rates were determined in early preterm (<30 weeks' gestation), preterm (30-36 weeks), and term (>37 weeks) infants. Pregnenolone and 17-OH-pregnenolone metabolites (n = 5), and dehydroepiandrosterone sulfate and metabolites (n = 12) were measured by gas chromatography mass spectrometry. Postnatal concentrations of FZSs were compared with already published prenatal concentrations in amniotic fluid.

RESULTS

Excretion rates of total FZSs and most of the single metabolites were highest in early preterm infants. In this group, excretion rates approach those of term infants at term equivalent postmenstrual age. Preterm infants of 30-36 weeks had more than half lower median excretion rates of FZSs than early preterm infants at the same time of postmenstrual age. Postnatal concentrations of FZSs were partly more than 100-fold higher in all gestational age groups than prenatal concentrations in amniotic fluid at midgestation.

CONCLUSION

The excretion rates of FZSs as a proxy of the involution of the fetal zone of the most immature preterm infants approached those of term infants at term equivalent. In contrast, the fetal zone in more mature preterm infants undergoes more rapid involution. These data in exclusively well neonates can serve as a basis to investigate the effects of illness on the FZS metabolome in future studies.

Endocrine disruptors also function as nervous disruptors and can be renamed endocrine and nervous disruptors (ENDs)

Endocrine disruption (ED) and endocrine disruptors (EDs) emerged as scientific concepts in 1995, after numerous chemical pollutants were found to be responsible for reproductive dysfunction. The World Health Organization established in the United Nations Environment Programme a list of materials, plasticizers, pesticides, and various pollutants synthesized from petrochemistry that impact not only reproduction, but also hormonal functions, directly or indirectly. Cells communicate via either chemical or electrical signals transmitted within the endocrine or nervous systems. To investigate whether hormone disruptors may also interfere directly or indirectly with the development or functioning of the nervous system through either a neuroendocrine or a more general mechanism, we examined the scientific literature to ascertain the effects of EDs on the nervous system, specifically in the categories of neurotoxicity, cognition, and behaviour. To date, we demonstrated that all of the 177 EDs identified internationally by WHO are known to have an impact on the nervous system. Furthermore, the precise mechanisms underlying this neurodisruption have also been established. It was previously believed that EDs primarily function via the thyroid. However, this study presents substantial evidence that approximately 80 % of EDs operate via other mechanisms. It thus outlines a novel concept: EDs are also neurodisruptors (NDs) and can be collectively termed endocrine and nervous disruptors (ENDs). Most of ENDs are derived from petroleum residues, and their various mechanisms of action are similar to those of "spam" in electronic communications technologies. Therefore, ENDs can be considered as an instance of spam in a biological context.

Disassembly of Death-associated Protein Kinase and DANGER Interaction Mediates Hippocampal CA1 Neuron Death in Rat Cerebral Ischemic Reperfusion

Death-associated protein kinase (DAPK) is a Ca²⁺/CaM-regulated protein kinase that is involved in cell death processes by multiple pathways. It has been reported that DAPK may play a role in brain ischemia-induced neuronal death, but this mechanism is not well understood. DANGER, a membrane-associated protein that binds to DAPK physiologically, inhibits DAPK activation. In the present study, we used a transient global brain ischemia and reperfusion (I/R) rat model to investigate whether the interaction between DAPK and DANGER is involved in neuronal cell death following brain ischemia, and to reveal the mechanism of action. Our results indicate that the DAPK/DANGER interaction in the hippocampal CA1 region was significantly reduced after I/R with a peak reduction at 6 h. We further demonstrate that the NMDA inhibitor MK-801, DAPK inhibitor, or calcineurin inhibitor FK-506 prevented the dissociation of DANGER from DAPK 6 h after I/R. This was accompanied by a significantly decreased I/R-induced dephosphorylation of DAPK^(ser-308), inhibiting DAPK catalytic activity. Moreover, the expression of DANGER and the interaction between DANGER and IP₃R on the endoplasmic reticulum was significantly increased at I/R 6 h, which may be related to a reduction of DAPK/DANGER binding under I/R condition. Furthermore, MK-801, DAPK inhibitor and FK-506 had neuroprotective effects against hippocampal CA1 neuronal death 5 days after I/R. In conclusion, our data suggest that the dissociation of DANGER from DAPK may mediate DAPK activation, which is involved in DAPK-related neuronal death following I/R injury.

Molecular Alterations and Effects of Acute Dehydroepiandrosterone Treatment Following Brief Bilateral Common Carotid Artery Occlusion: Relevance to Transient Ischemic Attack

Transient ischemic attack (TIA) represents brief neurological dysfunction of vascular origin without detectable infarction. Despite major clinical relevance characterization of post-TIA molecular changes using appropriate experimental model is lacking and no therapeutic agent has been established yet. Neurosteroid dehydroepiandrosterone (DHEA) arose as one of the candidates for cerebral ischemia treatment but its effects on TIA-like condition remain unknown. Seeking an animal model applicable for investigation of molecular alterations in mild ischemic conditions such as TIA, 15-min bilateral common carotid artery occlusion with 24-h reperfusion was performed to induce ischemia/ reperfusion (I/R) injury in adult male Wistar rats. Additionally, effects of 4-h post-operative DHEA treatment (20 mg/kg) were investigated in physiological and I/R conditions in hippocampus (HIP) and prefrontal cortex (PFC). The study revealed absence of sensorimotor deficits, cerebral infarcts and neurodegeneration along with preserved HIP and PFC overall neuronal morphology and unaltered malondialdehyde and reduced glutathione level following I/R and/or DHEA treatment. I/R induced nitric oxide burst in HIP and PFC was accompanied with increased neuronal nitric oxide synthase protein level exclusively in HIP. DHEA had no effects in physiological conditions, while increase of Bax/Bcl2 ratio and dissipation of mitochondrial membrane potential in treated I/R group suggested DHEA-mediated exacerbation of post-ischemic changes that might lead to pro-apoptotic events in HIP. Interestingly, DHEA restored I/R-induced NO to the control level in PFC. Obtained results indicated that I/R may serve as an appropriate model for investigation of molecular changes and treatment outcome following mild ischemic conditions such as TIA.

Molecular Interplay Between the Sigma-1 Receptor, Steroids, and Ion Channels

Cell excitability is tightly regulated by the activity of ion channels that allow for the passage of ions across cell membranes. Ion channel activity is controlled by different mechanisms that change their gating properties, expression or abundance in the cell membrane. The latter can be achieved by forming complexes with a diversity of proteins like chaperones such as the Sigma-1 receptor (Sig-1R), which is one with unique features and exhibits a role as a ligand-operated chaperone. This molecule also displays high intracellular mobility according to its activation level since, depletion of internal Ca⁺² stores or the presence of specific ligands, produce Sig-1R’s mobilization from the endoplasmic reticulum toward the plasma membrane or nuclear envelope. The function of the Sig-1R as a chaperone is regulated by synthetic and endogenous ligands, with some of these compounds being a steroids and acting as key endogenous modifiers of the actions of the Sig-1R. There are cases in the literature that exemplify the close relationship between the actions of steroids on the Sig-1R and the resulting negative or positive effects on ion channel function/abundance. Such interactions have been shown to importantly influence the physiology of mammalian cells leading to changes in their excitability. The present review focuses on describing how the Sig-1R regulates the functional properties and the expression of some sodium, calcium, potassium, and TRP ion channels in the presence of steroids and the physiological consequences of these interplays at the cellular level are also discussed.

A tale of two steroids: The importance of the androgens DHEA and DHEAS for early neurodevelopment

DHEA and DHEAS are neuroactive neurosteroids that interact with several major receptor systems in the brain, including sigma (σ), glutamate, and GABA-A receptors. It has been recognized as early as 1952, that the loss of DHEA/DHEAS in adult life is associated with neuropsychiatric disorders (eg schizophrenia, depression). However, the mechanistic role for DHEA/DHEAS in any of these domains remains speculative, not the least because the presence of these androgens in the adrenal gland and brain is largely confined to humans and only some non-human primates. DHEA and DHEAS are dynamically regulated from before birth and before the onset of puberty, and therefore an understanding of the synthesis, regulation, and functions of this important androgen pathway warrants attention. Here, we draw attention to the possible modulating influence of DHEA/DHEAS in early brain development from fetal life to the remarkable increase of these steroids in early childhood - the adrenarche. We propose that the pre-pubertal DHEA/DHEAS surge plays a key role in modulating early brain development, perhaps by prolonging brain plasticity during childhood to allow the pre-adolescent brain to adapt and re-wire in response to new, and ever-changing social challenges. Nonetheless, the aetiology of neurodevelopmental phenomena in relation to DHEA/DHEAS synthesis and action cannot be easily studied in humans due to the obvious ethical restrictions on mechanistic studies, the uncertainty of predicting the future mental characteristics of individuals, and the difficulty of conducting retrospective investigations based on pre-birth and/or neonatal complications. We discuss new opportunities for animal studies to resolve these important questions.

Sigma-1 receptor protects against endoplasmic reticulum stress-mediated apoptosis in mice with cerebral ischemia/reperfusion injury

Reports have showed that Sigma-1 receptor (Sig-1R) activation can protect neurons against cerebral ischemia/reperfusion (I/R) injury in mice and alleviate endoplasmic reticulum (ER) stress in cultured cells, but little known is about the protective role of Sig-1R on ER stress induced by cerebral I/R. The purpose of this study was to determine whether Sig-1R exerts a protective effect against ER stress-mediated apoptosis in cerebral I/R using a 15-min bilateral common carotid artery occlusion (BCCAO) mouse model. At 72 h after reperfusion in BCCAO mice, we found that Sig-1R knockout (Sig-1R KO) significantly increased terminal dUTP nick-end labeling (TUNEL)-positive cells and nuclear structural damage in cortical neurons. Treatment with the Sig-1R agonist PRE084 once daily for three consecutive days reduced the number of TUNEL-positive cells and improved the ultrastructural damage of neurons in the cerebral cortex. These protective effects could be blocked by the Sig-1R antagonist BD1047. Then, we used BCCAO mice at 24 h after reperfusion to detect the expression of ER stress-mediated apoptotic pathway proteins. We found that expression of the pro-apoptotic proteins p-PERK, p-eIF2α, ATF, CHOP, p-IRE, p-JNK, Bim, PUMA, cleaved-caspase-12 and cleaved-caspase-3 was significantly increased and that expression of the anti-apoptotic protein Bcl-2 was significantly decreased in Sig-1R KO-BCCAO mice compared with BCCAO mice. Meanwhile, we found that treatment with PRE084 twice a day decreased pro-apoptotic protein expression and increased anti-apoptotic protein expression. The effects of PRE084 were blocked by the Sig-1R antagonist BD1047. These results suggest that Sig-1R activation inhibits ER stress-mediated apoptosis in BCCAO mice, indicating that Sig-1R may be a therapeutic target for neuroprotection particularly relevant to ER stress-induced apoptosis after cerebral I/R injury.

Role of DHEA and cortisol in prefrontal-amygdalar development and working memory

There is accumulating evidence that both dehydroepiandrosterone (DHEA) and cortisol play an important role in regulating physical maturation and brain development. High DHEA levels tend to be associated with neuroprotective and indirect anabolic effects, while high cortisol levels tend to be associated with catabolic and neurotoxic properties. Previous literature has linked the ratio between DHEA and cortisol levels (DC ratio) to disorders of attention, emotional regulation and conduct, but little is known as to the relationship between this ratio and brain development. Due to the extensive links between the amygdala and the cortex as well as the known amygdalar involvement in emotional regulation, we examined associations between DC ratio, structural covariance of the amygdala with whole-brain cortical thickness, and validated report-based measures of attention, working memory, internalizing and externalizing symptoms, in a longitudinal sample of typically developing children and adolescents 6-22 years of age. We found that DC ratio predicted covariance between amygdalar volume and the medial anterior cingulate cortex, particularly in the right hemisphere. DC ratio had a significant indirect effect on working memory through its impact on prefrontal-amygdalar covariance, with higher DC ratios associated with a prefrontal-amygdalar covariance pattern predictive of higher scores on a measure of working memory. Taken together, these findings support the notion, as suggested by animal and in vitro studies, that there are opposing effects of DHEA and cortisol on brain development in humans, and that these effects may especially target prefrontal-amygdalar development and working memory, in a lateralized fashion.

The role of oligodendrocytes and their progenitors on neural interface technology: A novel perspective on tissue regeneration and repair

Oligodendrocytes and their precursors are critical glial facilitators of neurophysiology, which is responsible for cognition and behavior. Devices that are used to interface with the brain allow for a more in-depth analysis of how neurons and these glia synergistically modulate brain activity. As projected by the BRAIN Initiative, technologies that acquire a high resolution and robust sampling of neural signals can provide a greater insight in both the healthy and diseased brain and support novel discoveries previously unobtainable with the current state of the art. However, a complex series of inflammatory events triggered during device insertion impede the potential applications of implanted biosensors. Characterizing the biological mechanisms responsible for the degradation of intracortical device performance will guide novel biomaterial and tissue regenerative approaches to rehabilitate the brain following injury. Glial subtypes which assist with neuronal survival and exchange of electrical signals, mainly oligodendrocytes, their precursors, and the insulating myelin membranes they produce, are sensitive to inflammation commonly induced from insults to the brain. This review explores essential physiological roles facilitated by oligodendroglia and their precursors and provides insight into their pathology following neurodegenerative injury and disease. From this knowledge, inferences can be made about the impact of device implantation on these supportive glia in order to engineer effective strategies that can attenuate their responses, enhance the efficacy of neural interfacing technology, and provide a greater understanding of the challenges that impede wound healing and tissue regeneration during pathology.

Central intracrine DHEA synthesis in ageing-related neuroinflammation and neurodegeneration: therapeutic potential?

It is a well-known fact that DHEA declines on ageing and that it is linked to ageing-related neurodegeneration, which is characterised by gradual cognitive decline. Although DHEA is also associated with inflammation in the periphery, the link between DHEA and neuroinflammation in this context is less clear. This review drew from different bodies of literature to provide a more comprehensive picture of peripheral vs central endocrine shifts with advanced age—specifically in terms of DHEA. From this, we have formulated the hypothesis that DHEA decline is also linked to neuroinflammation and that increased localised availability of DHEA may have both therapeutic and preventative benefit to limit neurodegeneration. We provide a comprehensive discussion of literature on the potential for extragonadal DHEA synthesis by neuroglial cells and reflect on the feasibility of therapeutic manipulation of localised, central DHEA synthesis.

Protective effect of a novel sigma-1 receptor agonist is associated with reduced endoplasmic reticulum stress in stroke male mice

Sigma-1 receptor (Sig-1R) is expressed at endoplasmic reticulum (ER) membranes, where it regulates a variety of specific physiological functions. However, the profile and exact roles of ER stress-related molecules after Sig-1R agonist treatment in an in vivo stroke model are largely unknown. The aim of this study is to investigate the effect of a novel Sig-1R agonist, aniline derivative compound (Comp-AD), on the ER stress response following ischemic stroke. Male C57BL/6J mice received transient middle cerebral artery occlusion for 90 min, and were then treated with vehicle saline or Comp-AD at reperfusion. At 3 hr, 1 day, and 7 days after reperfusion, immunohis- tochemistry was performed for Sig-1R and ER stress-related proteins including phospho protein kinase RNA-like endoplasmic reticulum kinase (p-PERK), phospho inositol requiring enzyme 1α (p- IRE1α), and activating transcription factor 6 (ATF6). Neurobehavioral analysis showed improved functional recovery at 1 day and 7 days after reperfusion, and the infarct volume was significantly smaller at 7 days (p < .05), in the Comp-AD group compared with the vehicle group. Comp-AD treatment upregulated Sig-1R immunoreactivity at 3 hr and 1 day (p < .05), and reduced p-PERK and p-IRE1α expression at 1 day (p < .05, respectively), in the peri-ischemic region compared with the vehicle group. Treatment with the novel Sig-1R agonist Comp-AD was neuroprotective after transient middle cerebral artery occlusion, and was associated with upregulation of Sig-1R and a reduction of ER stress.

What does the research say about androgen use and cerebrovascular events?

Many studies have investigated the benefits of androgen therapy and neurosteroids in aging men, while concerns remain about the potential associations of exogenous steroids and incidents of cerebrovascular events and ischemic stroke (IS). Testosterone is neuroprotective, neurotrophic and a potent stimulator of neuroplasticity. These benefits are mediated primarily through conversion of a small amount of testosterone to estradiol by the catalytic activity of estrogen synthetase (aromatase cytochrome P450 enzyme). New studies suggest that abnormal serum levels of the nonaromatized potent metabolite of testosterone, either high or low dihydrotestosterone (DHT), is a risk factor for stroke. Associations between pharmacologic androgen use and the incidence of IS are questionable, because a significant portion of testosterone is converted to DHT. There is also insufficient evidence to reject a causal relationship between the pro-testosterone adrenal androgens and incidence of IS. Moreover, vascular intima-media thickness, which is a predictor of stroke and myocardial symptoms, has correlations with sex hormones. Current diagnostic and treatment criteria for androgen therapy for cerebrovascular complications are unclear. Confounding variables, including genetic and metabolic alterations of the key enzymes of steroidogenesis, ought to be considered. Information extracted from pharmacogenetic testing may aid in expounding the protective-destructive properties of neurosteroids, as well as the prognosis of androgen therapy, in particular their cerebrovascular outcomes. This investigative review article addresses relevant findings of the clinical and experimental investigations of androgen therapy, emphasizes the significance of genetic testing of androgen responsiveness towards individualized therapy in post-IS injuries as well as identifying pertinent questions.

An exploratory pilot investigation of neurosteroids and self-reported pain in female Iraq/Afghanistan-era Veterans

Female Veterans are the most rapidly growing segment of new users of the Veterans Health Administration (VHA), and a significant proportion of female Veterans receiving treatment from VHA primary care providers report persistent pain symptoms. Currently, available data characterizing the neurobiological underpinnings of pain disorders are limited. Preclinical data suggest that neurosteroids may be involved in the modulation of pain symptoms, potentially via actions at gamma-aminobutyric acid (GABA) and N-methyl-D-aspartate (NMDA) receptors. Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) are neurosteroids that modulate inhibitory GABA receptors and excitatory NMDA receptors, producing complex neuronal effects. Emerging evidence from male Iraq/Afghanistan-era Veterans suggests that reductions in neurosteroid levels are associated with increased pain symptoms and that neurosteroids may be promising biomarker candidates. The current exploratory study thus examined associations between self-reported pain symptoms in 403 female Iraq/Afghanistan-era Veterans and serum DHEAS and DHEA levels. Serum DHEAS levels were inversely correlated with low back pain in female Veterans (Spearman r = -0.103; p = 0.04). Nonparametric analyses indicate that female Veterans reporting moderate/extreme low back pain demonstrated significantly lower DHEAS levels than those reporting no/little low back pain (|Z| = 2.60; p = 0.009). These preliminary findings support a role for DHEAS in pain physiology of low back pain and the rationale for neurosteroid therapeutics in pain analgesia.

Regional-specific effects of cerebral ischemia/reperfusion and dehydroepiandrosterone on synaptic NMDAR/PSD-95 complex in male Wistar rats

Excessive glutamate efflux and N-methyl-D-aspartate receptor (NMDAR) over-activation represent well-known hallmarks of cerebral ischemia/reperfusion (I/R) injury, still, expression of proteins involved in this aspect of I/R pathophysiology show inconsistent data. Neurosteroid dehydroepiandrosterone (DHEA) has been proposed as potent NMDAR modulator, but its influence on I/R-induced changes up to date remains questionable. Therefore, I/R-governed alteration of vesicular glutamate transporter 1 (vGluT1), synaptic NMDAR subunit composition, postsynaptic density protein 95 (PSD-95) and neuronal morphology alone or following DHEA treatment were examined. For that purpose, adult male Wistar rats were treated with a single dose of vehicle or DHEA (20 mg/kg i.p.) 4 h following sham operation or 15 min bilateral common carotid artery occlusion. Western blot was used for analyses of synaptic protein expressions in hippocampus and prefrontal cortex, while neuronal morphology was assessed using Nissl staining. Regional-specific postischemic changes were detected on protein level i.e. signs of neuronal damage in CA1 area was accompanied with hippocampal vGluT1, NR1, NR2B enhancement and PSD-95 decrement, while histological changes observed in layer III were associated with decreased NR1 subunit in prefrontal cortex. Under physiological conditions DHEA had no effect on protein and histological appearance, while in ischemic milieu it restored hippocampal PSD-95 and NR1 in prefrontal cortex to the control level. Along with intact neurons, ones characterized by morphology observed in I/R group were also present. Future studies involving NMDAR-related intracellular signaling and immunohistochemical analysis will reveal precise effects of I/R and DHEA treatment in selected brain regions.

Astrocyte Neuroprotection and Dehydroepiandrosterone

Dehydroepiandrosterone (DHEA) and its sulfate ester (DHEAS) are the most abundant steroid hormones in the systemic circulation of humans. Due to their abundance and reduced production during aging, these hormones have been suggested to play a role in many aspects of health and have been used as drugs for a multiple range of therapeutic actions, including hormonal replacement and the improvement of aging-related diseases. In addition, several studies have shown that DHEA and DHEAS are neuroprotective under different experimental conditions, including models of ischemia, traumatic brain injury, spinal cord injury, glutamate excitotoxicity, and neurodegenerative diseases. Since astrocytes are responsible for the maintenance of neural tissue homeostasis and the control of neuronal energy supply, changes in astrocytic function have been associated with neuronal damage and the progression of different pathologies. Therefore, the aim of this chapter is to discuss the neuroprotective effects of DHEA against different types of brain and spinal cord injuries and how the modulation of astrocytic function by DHEA could represent an interesting therapeutic approach for the treatment of these conditions.

Developmental effects of androgens in the human brain

Neuroendocrine theories of brain development posit that androgens play a crucial role in sex-specific cortical growth, although little is known about the differential effects of testosterone and dehydroepiandrosterone (DHEA) on cortico-limbic development and cognition during adolescence. In this context, the National Institutes of Health Study of Normal Brain Development, a longitudinal study of typically developing children and adolescents aged 4-24 years (n=433), offers a unique opportunity to examine the developmental effects of androgens on cortico-limbic maturation and cognition. Using data from this sample, our group found that higher testosterone levels were associated with left-sided decreases in cortical thickness (CTh) in post-pubertal boys, particularly in the prefrontal cortex, compared to right-sided increases in CTh in somatosensory areas in pre-pubertal girls. Prefrontal-amygdala and prefrontal-hippocampal structural covariance (considered to reflect structural connectivity) also varied according to testosterone levels, with the testosterone-related brain phenotype predicting higher aggression levels and lower executive function, particularly in boys. By contrast, DHEA was associated with a pre-pubertal increase in CTh of several regions involved in cognitive control in both boys and girls. Covariance within several cortico-amygdalar structural networks also varied as a function of DHEA levels, with the DHEA-related brain phenotype predicting improvements in visual attention in both boys and girls. DHEA-related cortico-hippocampal structural covariance, on the other hand, predicted higher scores on a test of working memory. Interestingly, there were significant interactions between testosterone and DHEA, such that DHEA tended to mitigate the anti-proliferative effects of testosterone on brain structure. In sum, testosterone-related effects on the developing brain may lead to detrimental effects on cortical functions (ie, higher aggression and lower executive function), whereas DHEA-related effects may optimise cortical functions (ie, better attention and working memory), perhaps by decreasing the influence of amygdalar and hippocampal afferents on cortical functions.

Neurosteroid dehydroepiandrosterone enhances activity and trafficking of astrocytic GLT-1 via σ1 receptor-mediated PKC activation in the hippocampal dentate gyrus of rats

Neurosteroid dehydroepiandrosterone (DHEA) has been reported to exert a potent neuroprotective effect against glutamate-induced excitotoxicity. However, the underlying mechanism remains to be elucidated. One of the possible mechanisms may be an involvement of astrocytic glutamate transporter subtype-1 (GLT-1) that can quickly clear spilled glutamate at the synapse to prevent excitotoxicity. To examine the effect of DHEA on GLT-1 activity, we measured synaptically induced glial depolarization (SIGD) in the dentate gyrus (DG) of adult rats by applying an optical recording technique to the hippocampal slices stained with voltage-sensitive dye RH155. Bath-application of DHEA for 10 min dose-dependently increased SIGD without changing presynaptic glutamate releases, which was sensitive to the GLT-1 blocker DHK. Patch-clamp recordings in astrocytes showed that an application of 50 μM DHEA increased glutamate-evoked inward currents (Iglu) by approximately 1.5-fold, which was dependent on the GLT-1 activity. In addition, the level of biotinylated GLT-1 protein in the surface of astrocytes was significantly elevated by DHEA. The DHEA-increased SIGD, Iglu, and GLT-1 translocation to the cell surface were blocked by the σ₁ R antagonist NE100 and mimicked by the σ₁ R agonist PRE084. DHEA elevated the phosphorylation level of PKC in a σ₁ R-dependent manner. Furthermore, the PKC inhibitor chelerythrine could prevent the DHEA-increased SIGD, Iglu, and GLT-1 translocation. Collectively, present results suggest that DHEA enhances the activity and translocation to cell surface of astrocytic GLT-1 mainly via σ₁ R-mediated PKC cascade.

Activation of σ1 and σ2 receptors by afobazole increases glial cell survival and prevents glial cell activation and nitrosative stress after ischemic stroke

Activation of sigma receptors at delayed time points has been shown to decrease injury following ischemic stroke. The mixed σ1/σ2 receptor agonist, 5-ethoxy-2-[2-(morpholino)-ethylthio]benzimidazole (afobazole), provides superior long-term outcomes compared to other σ ligands in the rat middle cerebral artery occlusion (MCAO) stroke model. Experiments using the MCAO model were carried out to determine the molecular mechanism involved in the beneficial effects of afobazole. Administration of afobazole (3 mg/kg) at delayed time points post-stroke significantly increased the number of microglia and astrocytes detected in the ipsilateral hemisphere at 96 h post-surgery. Morphological analysis of the microglia indicated that a greater number of these cells were found in the ramified resting state in MCAO animals treated with afobazole relative to MCAO vehicle controls. Similarly, fewer reactive astrocytes were detected in the injured hemisphere of afobazole-treated animals. Both the enhanced survival and reduced activation of glial cells were abolished by co-application of either a σ1 (BD-1063) or a σ2 (SM-21) receptor antagonist with afobazole. To gain further insight into the mechanisms by which afobazole lessens stroke injury, we probed the brain sections for markers of neuroinflammation (tumor necrosis factor α) and nitrosative stress (S-nitrosocysteine). Data show that afobazole significantly reduces S-nitrosocysteine levels, but does not alter tumor necrosis factor α expression 96 h after an ischemic stroke. Taken together our data indicate that afobazole acting via both σ1 and σ2 receptors decreases stroke injury by enhancing glial cell survival, blocking ischemia-induced glial cell activation, and decreasing nitrosative stress.

Cortisol/DHEA ratio and hippocampal volume: A pilot study in major depression and healthy controls

Structural imaging studies investigating the relationship between hippocampal volume (HCV) and peripheral measures of glucocorticoids (GCs) have produced conflicting results in both normal populations and in individuals with MDD, raising the possibility of other modulating factors. In preclinical studies, dehydroepiandrosterone (DHEA) and its sulfate ester (DHEAS; together abbreviated, DHEA(S)) have been shown to antagonize the actions of GCs on the central nervous system. Therefore, considering the relationship of HCV to both of these hormones simultaneously may be important, although it has rarely been done in human populations. Using high-resolution magnetic resonance imaging (MRI), the present pilot study examined the relationship between morning serum cortisol, DHEA(S), and HCV in nineteen normal controls and eighteen unmedicated subjects with Major Depressive Disorder (MDD). Serum cortisol and DHEA(S) were not significantly correlated with HCV across all subjects (cortisol: r=-0.165, p=0.33; DHEA: r=0.164, p=0.35; DHEAS: r=0.211, p=0.22, respectively). However, the ratios of cortisol/DHEA(S) were significantly negatively correlated with HCV in combined group (Cortisol/DHEA: r=-0.461, p=0.005; Cortisol/DHEAS: r=-0.363, p=0.03). Significant or near-significant correlations were found between some hormonal measurements and HCV in the MDDs alone (DHEA: r=0.482, p=0.059; DHEAS: r=0.507, p=0.045; cort/DHEA: r=-0.589, p=0.02; cort/DHEAS: r=-0.424p=0.10), but not in the controls alone (DHEA: r=0.070, p=0.79; DHEAS: r=0.077, p=0.77; cort/DHEA: r=-0.427, p=0.09; cort/DHEAS: r=-0.331, p=0.19). However, Group (MDDs vs controls) did not have a significant effect on the relationship between cortisol, DHEA(S), and their ratios with HCV (p>0.475 in all analyses). Although the exact relationship between serum and central steroid concentrations as well as their effects on the human hippocampus remains not known, these preliminary results suggest that the ratio of cortisol to DHEA(S), compared to serum cortisol alone, may convey additional information about "net steroid activity" with relation to HCV.

The developmental relationship between DHEA and visual attention is mediated by structural plasticity of cortico-amygdalar networks

Humans and the great apes are the only species demonstrated to exhibit adrenarche, a key developmental event leading to increased production of dehydroepiandrosterone (DHEA), suggesting that this hormone may play an important evolutionary role. Similarly, visual attention networks have been shown to evolve in a human-specific manner, with some anatomical connections and elements of cortical organization exclusive to our species. Existing studies of human brain development support the notion that DHEA shows significant uptake in cortical structures and the amygdala, and as such, could be involved in the bottom-up regulation of visual attention. Here we examined associations between DHEA, structural covariance of the amygdala with whole-brain cortical thickness, and tests of visual attention, in a longitudinal sample of typically developing children and adolescents 6-22 years of age. We found that DHEA predicted covariance between amygdalar volume and the left occipital pole, right somatosensory parietal cortex and right anterior cingulate cortex. Amygdala-occipital covariance predicted visual awareness; amygdala-parietal covariance predicted visuo-motor dexterity and processing speed; amygdala-prefrontal covariance predicted global attentional impairment. Further, effects of DHEA were above and beyond those of age and sex, as well as distinct from those of pubertal stage, estradiol and testosterone. These findings support the notion that DHEA may play a unique role in shaping amygdala-dependent cortical plasticity and in regulating 'bottom-up' visual attention processes from childhood to young adulthood.

Antioxidant Protection of NADPH-Depleted Oligodendrocyte Precursor Cells Is Dependent on Supply of Reduced Glutathione

The pentose phosphate pathway is the main source of NADPH, which by reducing oxidized glutathione, contributes to antioxidant defenses. Although oxidative stress plays a major role in white matter injury, significance of NADPH for oligodendrocyte survival has not been yet investigated. It is reported here that the NADPH antimetabolite 6-amino-NADP (6AN) was cytotoxic to cultured adult rat spinal cord oligodendrocyte precursor cells (OPCs) as well as OPC-derived oligodendrocytes. The 6AN-induced necrosis was preceded by increased production of superoxide, NADPH depletion, and lower supply of reduced glutathione. Moreover, survival of NADPH-depleted OPCs was improved by the antioxidant drug trolox. Such cells were also protected by physiological concentrations of the neurosteroid dehydroepiandrosterone (10⁻⁸ M). The protection by dehydroepiandrosterone was associated with restoration of reduced glutathione, but not NADPH, and was sensitive to inhibition of glutathione synthesis. A similar protective mechanism was engaged by the cAMP activator forskolin or the G protein-coupled estrogen receptor (GPER/GPR30) ligand G1. Finally, treatment with the glutathione precursor N-acetyl cysteine reduced cytotoxicity of 6AN. Taken together, NADPH is critical for survival of OPCs by supporting their antioxidant defenses. Consequently, injury-associated inhibition of the pentose phosphate pathway may be detrimental for the myelination or remyelination potential of the white matter. Conversely, steroid hormones and cAMP activators may promote survival of NADPH-deprived OPCs by increasing a NADPH-independent supply of reduced glutathione. Therefore, maintenance of glutathione homeostasis appears as a critical effector mechanism for OPC protection against NADPH depletion and preservation of the regenerative potential of the injured white matter.

Dehydroepiandrosterone protects male and female hippocampal neurons and neuroblastoma cells from glucose deprivation

Dehydroepiandrosterone (DHEA) modulates neurogenesis, neuronal function, neuronal survival and metabolism, enhancing mitochondrial oxidative capacity. Glucose deprivation and hypometabolism have been implicated in the mechanisms that mediate neuronal damage in neurological disorders, and some studies have shown that these mechanisms are sexually dimorphic. It was also demonstrated that DHEA is able to attenuate the hypometabolism that is related to some neurodegenerative diseases, eliciting neuroprotective effects in different experimental models of neurodegeneration. The aim of this study was to evaluate the effect of DHEA on the viability of male and female hippocampal neurons and SH-SY5Y neuroblastoma cells exposed to glucose deprivation. It was observed that after 12h of pre-treatment, DHEA was able to protect SH-SY5Y cells from glucose deprivation for 6h (DHEA 10(-12), 10(-8) and 10(-6)M) and 8h (DHEA 10(-8)M). In contrast, DHEA was not neuroprotective against glucose deprivation for 12 or 24h. DHEA (10(-8)M) also protected SH-SY5Y cells when added together or even 1h after the beginning of glucose deprivation (6h). Furthermore, DHEA (10(-8)M) also protected primary neurons from both sexes against glucose deprivation. In summary, our findings indicate that DHEA is neuroprotective against glucose deprivation in human neuroblastoma cells and in male and female mouse hippocampal neurons. These results suggest that DHEA could be a promising candidate to be used in clinical studies aiming to reduce neuronal damage in people from both sexes.

Resveratrol protects CA1 neurons against focal cerebral ischemic reperfusion-induced damage via the ERK-CREB signaling pathway in rats

Ischemic stroke is a primary cause of mortality and disability in the aged population. Resveratrol (Res), a natural polyphenol enriched in plants, presents diverse biological activities, e.g., antiinflammatory and anti-oxidation effects. Here, we evaluated whether Res pretreatment influenced focal cerebral ischemia-induced cognitive impairment, and we explored the underlying mechanisms in rats. The results showed that a single administration of Res (30mg/kg, i.p.) at 1 or 4h, but not at 24h before focal cerebral ischemia exerted significant neuroprotective effects, including a reduction in hippocampal CA1 neuronal death and spatial cognition deficits caused by ischemia. The neuroprotective effects of Res were suppressed by pretreatment with MK801, an NMDA receptor blocker, or U0126, an extracellular signal regulated kinase 1/2 (ERK1/2) kinase inhibitor. A western blot analysis revealed that Res treatment at 1h before ischemia significantly increased ERK1/2 phosphorylation and cyclic-AMP response element binding protein (CREB) phosphorylation in the CA1 region of the hippocampus, which can be prevented with U0126 pretreatment. The results showed that the NMDA receptor-mediated ERK-CREB signaling pathway might participates in Res-induced neuroprotection in rats with focal cerebral ischemia.

Effects of Acute Systemic Hypoxia and Hypercapnia on Brain Damage in a Rat Model of Hypoxia-Ischemia

Therapeutic hypercapnia has the potential for neuroprotection after global cerebral ischemia. Here we further investigated the effects of different degrees of acute systemic hypoxia in combination with hypercapnia on brain damage in a rat model of hypoxia and ischemia. Adult wistar rats underwent unilateral common carotid artery (CCA) ligation for 60 min followed by ventilation with normoxic or systemic hypoxic gas containing 11%O2,13%O2,15%O2 and 18%O2 (targeted to PaO2 30-39 mmHg, 40-49 mmHg, 50-59 mmHg, and 60-69 mmHg, respectively) or systemic hypoxic gas containing 8% carbon dioxide (targeted to PaCO2 60-80 mmHg) for 180 min. The mean artery pressure (MAP), blood gas, and cerebral blood flow (CBF) were evaluated. The cortical vascular permeability and brain edema were examined. The ipsilateral cortex damage and the percentage of hippocampal apoptotic neurons were evaluated by Nissl staining and terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL) assay as well as flow cytometry, respectively. Immunofluorescence and western blotting were performed to determine aquaporin-4 (AQP4) expression. In rats treated with severe hypoxia (PaO2 < 50 mmHg), hypercapnia augmented the decline of MAP with cortical CBF and damaged blood-brain barrier permeability (p < 0.05). In contrast, in rats treated with mild to moderate hypoxia (PaO2 > 50 mmHg), hypercapnia protected against these pathophysiological changes. Moreover, hypercapnia treatment significantly reduced brain damage in the ischemic ipsilateral cortex and decreased the percentage of apoptotic neurons in the hippocampus after the CCA ligated rats were exposed to mild or moderate hypoxemia (PaO2 > 50 mmHg); especially under mild hypoxemia (PaO2 > 60 mmHg), hypercapnia significantly attenuated the expression of AQP4 protein with brain edema (p < 0.05). Hypercapnia exerts beneficial effects under mild to moderate hypoxemia and augments detrimental effects under severe hypoxemia on brain damage in a rat model of hypoxia-ischemia.

Dehydroepiandrosterone administration improves memory deficits following transient brain ischemia through sigma-1 receptor stimulation

Dehydroepiandrosterone (DHEA) is the most abundant neurosteroid synthesized de novo in the central nervous system. Oral DHEA administration elicits neuroprotection and cognitive improvement, but mechanisms underlying these functions in cerebral ischemia have remained unclear. Since DHEA is the endogenous ligand for the sigma-1 receptor (σ1R), we determined whether oral DHEA administration prevents neuronal cell death and improves cognition via σ1R stimulation in brain ischemia using a 20-min bilateral common carotid artery occlusion (BCCAO) mouse model. Twenty-four hours after BCCAO ischemia, mice were administered DHEA (15 or 30mg/kg p.o.) daily for 11 consecutive days. Memory deficits following brain ischemia were improved by DHEA administration dose-dependently. Accordingly, DHEA administration significantly prevented neuronal cell death in the hippocampal CA1 region in BCCAO mice. Interestingly, DHEA administration rescued decreases in Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation and phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) in the CA1 region. Moreover, DHEA administration significantly ameliorated decreases in adenosine 5'-triphosphate (ATP) levels and decreased σ1R expression levels in CA1 following BCCAO ischemia. Finally, co-treatment of mice with the σ1R antagonist NE-100 (1mg/kg, p.o.) blocked DHEA effects on memory improvement and neuroprotection in ischemic mice. Taken together, DHEA prevents neuronal cell death and activates CaMKII via σ1R stimulation, thereby improving cognitive deficits following brain ischemia.

Sigma 1 receptor activation regulates brain-derived neurotrophic factor through NR2A-CaMKIV-TORC1 pathway to rescue the impairment of learning and memory induced by brain ischaemia/reperfusion

RATIONALE

Sigma-1 receptor (Sig-1R) agonists showed anti-amnesic properties in Alzheimer's disease models and anti-inflammatory properties in cerebrum ischaemia models. The agonist of Sig-1R was reported to up-regulate brain-derived neurotrophic factor (BDNF) levels in the hippocampus of mice. Here, we investigate whether the activation of Sig-1R attenuates the learning and memory impairment induced by ischaemia/reperfusion and how it affects the expression of BDNF.

OBJECTIVES

Bilateral common carotid artery occlusion (BCCAO) was induced for 20 min in C57BL/6 mice.

MATERIALS AND METHODS

Sig-1R agonist, PRE084, sigma 1/2 non-selective agonist, DTG, Sig-1R antagonist and BD1047 were injected once daily throughout the experiment. Behavioural tests were performed from day 8. On day 22 after BCCAO, mice were sacrificed for biochemical analysis.

RESULTS

PRE084 and DTG ameliorated learning and memory impairments in the Y maze, novel object recognition, and water maze tasks and prevented the decline of synaptic proteins and BDNF expression in the hippocampus of BCCAO mice. Furthermore, PRE084 and DTG up-regulated the level of NMDA receptor 2A (NR2A), calcium/calmodulin-dependent protein kinase type IV (CaMKIV) and CREB-specific co-activator transducer of regulated CREB activity 1 (TORC1). Additionally, the effects of PRE084 and DTG were antagonised by the co-administration of BD1047.

CONCLUSIONS

Sig-1R activation showed an attenuation in the ischaemia/reperfusion model and the activation of Sig-1R increased the expression of BDNF, possibly through the NR2A-CaMKIV-TORC1 pathway, and Sig-1R agonists might function as neuroprotectant agents in vascular dementia.

Sigma-1 (σ₁) receptor deficiency reduces β-amyloid(25-35)-induced hippocampal neuronal cell death and cognitive deficits through suppressing phosphorylation of the NMDA receptor NR2B

In early Alzheimer's disease (AD) brain, reduction of sigma-1 receptors (σ1R) is detected. In this study, we employed male heterozygous σ1R knockout (σ1R(+/-)) mice showing normal cognitive performance to investigate association of σ1R deficiency with AD risk. Herein we report that a single injection (i.c.v.) of Aβ(25-35) impaired spatial memory with approximately 25% death of pyramidal cells in the hippocampal CA1 region of WT mice (Aβ(25-35)-WT mice), whereas it did not cause such impairments in σ1R(+/-) mice (Aβ(25-35)-σ1R(+/-) mice). Compared with WT mice, Aβ(25-35)-WT mice showed increased levels of NMDA-activated currents (INMDA) and NR2B phosphorylation (phospho-NR2B) in the hippocampal CA1 region at 48 h after Aβ25-35-injection (post-Aβ(25-35)) followed by approximately 40% decline at 72 h post-Aβ(25-35) of their respective control levels, which was inhibited by the σ1R antagonist NE100. In Aβ(25-35)-WT mice, the administration of NR2B inhibitor Ro25-6981 or NE100 on day 1-4 post-Aβ(25-35) attenuated the memory deficits and loss of pyramidal cells. By contrast, Aβ(25-35)-σ1R(+/-) mice showed a slight increase in the INMDA density and the phospho-NR2B at 48 h or 72 h post-Aβ25-35 compared to σ1R(+/-) mice. Treatment with σ1R agonist PRE084 in Aβ(25-35)-σ1R(+/-) mice caused the same changes in the INMDA density and the phospho-NR2B as those in Aβ(25-35)-WT mice. Furthermore, Aβ(25-35)-σ1R(+/-) mice treated with the NMDA receptor agonist NMDA or PRE084 on day 1-4 post-Aβ(25-35) showed a loss of neuronal cells and memory impairment. These results indicate that the σ1R deficiency can reduce Aβ(25-35)-induced neuronal cell death and cognitive deficits through suppressing Aβ(25-35)-enhanced NR2B phosphorylation.

Neuroprotective effects of therapeutic hypercapnia on spatial memory and sensorimotor impairment via anti-apoptotic mechanisms after focal cerebral ischemia/reperfusion

A number of studies have demonstrated that therapeutic hypercapnia ameliorates neurological deficits and attenuates the histological damage of cerebral ischemia-reperfusion injury. However, the effects of therapeutic hypercapnia on impaired spatial memory have not been reported. Here we aimed to investigate the effects and mechanisms of therapeutic hypercapnia on spatial memory in a rat model of focal cerebral ischemia induced by middle cerebral artery occlusion/reperfusion (MCAO/R). Adult male rats were randomly assigned into three experimental groups: sham (sham operation), IR (MCAO/R), and hypercapnia [arterial blood CO2 tension (PaCO2) 80-100 mmHg+IR] groups. Sensorimotor deficits and spatial memory testing were evaluated by an 18-point scoring system and an 8-arm radial maze task, respectively. The hippocampal histological damage and the percentage of apoptotic neurons were evaluated by hematoxylin and eosin (HE) staining as well as flow cytometry. Western blotting was used to investigate the changes of the apoptosis-related Bcl-2 and Bax proteins. The results indicated that hypercapnia treatment significantly improved the abilities of impaired sensorimotor and spatial memory after MCAO/R. Moreover, hypercapnia treatment significantly increased the percentage of surviving neurons and decreased the percentage of apoptotic neurons in the hippocampus after MCAO/R damage. The expressions of anti-apoptotic protein Bcl-2 and pro-apoptotic protein Bax were significantly increased and decreased in the hypercapnia treated rats, respectively. These findings suggest that therapeutic hypercapnia can attenuate neuronal apoptosis and improve impaired spatial memory and sensorimotor after MCAO/R, which may be attributable to its anti-apoptotic effects through modulation of apoptosis-related protein.

Major cardiac surgery induces an increase in sex steroids in prepubertal children

While the neuroprotective benefits of estrogen and progesterone in critical illness are well established, the data regarding the effects of androgens are conflicting. Surgical repair of congenital heart disease is associated with significant morbidity and mortality, but there are scant data regarding the postoperative metabolism of sex steroids in this setting. The objective of this prospective observational study was to compare the postoperative sex steroid patterns in pediatric patients undergoing major cardiac surgery (MCS) versus those undergoing less intensive non-cardiac surgery. Urinary excretion rates of estrogen, progesterone, and androgen metabolites (μg/mmol creatinine/m(2) body surface area) were determined in 24-h urine samples before and after surgery using gas chromatography-mass spectrometry in 29 children undergoing scheduled MCS and in 17 control children undergoing conventional non-cardiac surgery. Eight of the MCS patients had Down's syndrome. There were no significant differences in age, weight, or sex between the groups. Seven patients from the MCS group showed multi-organ dysfunction after surgery. Before surgery, the median concentrations of 17β-estradiol, pregnanediol, 5α-dihydrotestosterone (DHT), and dehydroepiandrosterone (DHEA) were (control/MCS) 0.1/0.1 (NS), 12.4/11.3 (NS), 4.7/4.4 (NS), and 2.9/1.1 (p=0.02). Postoperatively, the median delta 17β-estradiol, delta pregnanediol, delta DHT, and delta DHEA were (control/MCS) 0.2/6.4 (p=0.0002), -3.2/23.4 (p=0.013), -0.6/3.7 (p=0.0004), and 0.5/4.2 (p=0.004). Postoperative changes did not differ according to sex. We conclude that MCS, but not less intensive non-cardiac surgery, induced a distinct postoperative increase in sex steroid levels. These findings suggest that sex steroids have a role in postoperative metabolism following MCS in prepubertal children.

Interactive effects of dehydroepiandrosterone and testosterone on cortical thickness during early brain development

Humans and the great apes are the only species demonstrated to exhibit adrenarche, a key endocrine event associated with prepubertal increases in the adrenal production of androgens, most significantly dehydroepiandrosterone (DHEA) and to a certain degree testosterone. Adrenarche also coincides with the emergence of the prosocial and neurobehavioral skills of middle childhood and may therefore represent a human-specific stage of development. Both DHEA and testosterone have been reported in animal and in vitro studies to enhance neuronal survival and programmed cell death depending on the timing, dose, and hormonal context involved, and to potentially compete for the same signaling pathways. Yet no extant brain-hormone studies have examined the interaction between DHEA- and testosterone-related cortical maturation in humans. Here, we used linear mixed models to examine changes in cortical thickness associated with salivary DHEA and testosterone levels in a longitudinal sample of developmentally healthy children and adolescents 4-22 years old. DHEA levels were associated with increases in cortical thickness of the left dorsolateral prefrontal cortex, right temporoparietal junction, right premotor and right entorhinal cortex between the ages of 4-13 years, a period marked by the androgenic changes of adrenarche. There was also an interaction between DHEA and testosterone on cortical thickness of the right cingulate cortex and occipital pole that was most significant in prepubertal subjects. DHEA and testosterone appear to interact and modulate the complex process of cortical maturation during middle childhood, consistent with evidence at the molecular level of fast/nongenomic and slow/genomic or conversion-based mechanisms underlying androgen-related brain development.

Temporal changes of cytochrome P450 (Cyp) and eicosanoid-related gene expression in the rat brain after traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) induces arachidonic acid (ArA) release from cell membranes. ArA metabolites form a class of over 50 bioactive eicosanoids that can induce both adaptive and/or maladaptive brain responses. The dynamic metabolism of ArA to eicosanoids, and how they affect the injured brain, is poorly understood due to their diverse activities, trace levels, and short half-lives. The eicosanoids produced in the brain postinjury depend upon the enzymes present locally at any given time. Eicosanoids are synthesized by heme-containing enzymes, including cyclooxygenases, lipoxygenases, and arachidonate monoxygenases. The latter comprise a subset of the cytochrome P450 "Cyp" gene family that metabolize fatty acids, steroids, as well as endogenous and exogenous toxicants. However, for many of these genes neither baseline neuroanatomical nor injury-related temporal expression have been studied in the brain.In a rat model of parietal cortex TBI, Cyp and eicosanoid-related mRNA levels were determined at 6 h, 24 h, 3d, and 7d postinjury in parietal cortex and hippocampus, where dynamic changes in eicosanoids have been observed. Quantitative real-time polymerase chain reaction with low density arrays were used to assay 62 rat Cyps, 37 of which metabolize ArA or other unsaturated fatty acids; 16 eicosanoid-related enzymes that metabolize ArA or its metabolites; 8 eicosanoid receptors; 5 other inflammatory- and recovery-related genes, plus 2 mouse Cyps as negative controls and 3 highly expressed "housekeeping" genes.

RESULTS

Sixteen arachidonate monoxygenases, 17 eicosanoid-related genes, and 12 other Cyps were regulated in the brain postinjury (p < 0.05, Tukey HSD). Discrete tissue levels and distinct postinjury temporal patterns of gene expression were observed in hippocampus and parietal cortex.

CONCLUSIONS

The results suggest complex regulation of ArA and other lipid metabolism after TBI. Due to the temporal nature of brain injury-induced Cyp gene induction, manipulation of each gene (or its products) at a given time after TBI will be required to assess their contributions to secondary injury and/or recovery. Moreover, a better understanding of brain region localization and cell type-specific expression may be necessary to deduce the role of these eicosanoid-related genes in the healthy and injured brain.

Prognostic value of dehydroepiandrosterone-sulfate and other parameters of adrenal function in acute ischemic stroke

Background and Purpose

Acute stroke has a high morbidity and mortality. We evaluated the predictive value of adrenal function testing in acute ischemic stroke.

Methods

In a cohort of 231 acute ischemic stroke patients, we measured dehydroepiandrosterone (DHEA), DHEA-Sulfate (DHEAS), cortisol at baseline and 30 minutes after stimulation with 1 ug ACTH. Delta cortisol, the amount of rise in the 1 ug ACTH-test, was calculated. Primary endpoint was poor functional outcome defined as modified Rankin scale 3–6 after 1 year. Secondary endpoint was nonsurvival after 1 year.

Results

Logistic regression analysis showed that DHEAS (OR 1.21, 95% CI 1.01–1.49), but not DHEA (OR 1.01, 95% CI 0.99–1.04), was predictive for adverse functional outcome. Neither DHEA (OR 0.99, 95% CI 0.96–1.03) nor DHEAS (OR 1.10, 95% CI 0.82–1.44) were associated with mortality. Baseline and stimulated cortisol were predictive for mortality (OR 1.41, 95% CI 1.20–1.71; 1.35, 95% CI 1.15–1.60), but only basal cortisol for functional outcome (OR 1.20, 95% CI 1.04–1.38). Delta cortisol was not predictive for functional outcome (OR 0.86, 95% CI 0.71–1.05) or mortality (OR 0.92, 95% CI 0.72–1.17). The ratios cortisol/DHEA and cortisol/DHEAS discriminated between favorable outcome and nonsurvival (both p<0.0001) and between unfavorable outcome and nonsurvival (p = 0.0071 and 0.0029), but are not independent predictors for functional outcome or mortality in multivariate analysis (adjusted OR for functional outcome for both 1.0 (95% CI 0.99–1.0), adjusted OR for mortality for both 1.0 (95% CI 0.99–1.0 and 1.0–1.01, respectively)).

Conclusion

DHEAS and the cortisol/DHEAS ratio predicts functional outcome 1 year after stroke whereas cortisol levels predict functional outcome and mortality.

Trial Registration

ClinicalTrials.gov NCT00390962 (Retrospective analysis of this cohort).

Adrenarche and middle childhood

Middle childhood, the period from 6 to 12 years of age, is defined socially by increasing autonomy and emotional regulation, somatically by the development of anatomical structures for subsistence, and endocrinologically by adrenarche, the adrenal production of dehydroepiandrosterone (DHEA). Here I suggest that DHEA plays a key role in the coordinated development of the brain and body beginning with middle childhood, via energetic allocation. I argue that with adrenarche, increasing levels of circulating DHEA act to down-regulate the release of glucose into circulation and hence limit the supply of glucose which is needed by the brain for synaptogenesis. Furthermore, I suggest the antioxidant properties of DHEA may be important in maintaining synaptic plasticity throughout middle childhood within slow-developing areas of the cortex, including the insula, thamalus, and anterior cingulate cortex. In addition, DHEA may play a role in the development of body odor as a reliable social signal of behavioral changes associated with middle childhood.

Resveratrol attenuates brain damage in a rat model of focal cerebral ischemia via up-regulation of hippocampal Bcl-2

A number of studies have demonstrated that resveratrol (Res), a natural polyphenol compound found in plants, shows potent neuroprotective, anti-inflammatory and antioxidant effects; however, its ability to prevent ischemia-induced brain damage remains unclear. Here we tested whether Res played a neuroprotective role in a rat brain ischemia model induced by middle cerebral artery occlusion (MCAO). Adult male rats were randomly assigned into four experimental groups: sham operation (sham), ischemia treatment (MCAO), Res-treated MCAO (Res+MCAO) and Res alone group (Res+sham). The brain damage size and hippocampal apoptotic neurons in each rat were evaluated by triphenyltetrazolium chloride (TTC) staining and terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) staining, respectively. Long-term potentiation (LTP) induced by high-frequency stimulation (HFS) in the hippocampus was assessed with extracellular recording. The expression of apoptosis-related proteins, i.e., Bcl-2 and Bax, in the hippocampus was detected by western blot. Our results revealed that Res treatment significantly reduced brain infarct volume of MCAO rats as compared to MCAO rats without Res treatment. A significant increase in TUNEL-positive neurons in the hippocampal CA1 region was visualized in the MCAO rats as compared to that of the sham group, but this increase was attenuated with Res treatment. Functionally, extracellular recordings revealed that MCAO operation impaired LTP in the hippocampal CA1 region and the basal synaptic transmission between the Schaffer collaterals, whereas Res treatment rescued the impaired LTP and facilitated synaptic transmission in the CA1 region of the MCAO rats. Res treatment increased the expression of anti-apoptotic protein Bcl-2 and decreased the expression of pro-apoptotic protein Bax in the MCAO rats. The findings suggest that Res can attenuate the deleterious effects of focal cerebral ischemia/reperfusion-induced brain injury and function as a potential neuroprotective agent. The neuroprotective qualities of Res, based on our data, may be attributable to the up-regulation of Bcl-2 expression and down-regulation of Bax expression.

Severity and outcome of acute stroke in women: relation to adrenal sex steroid levels

Adrenal sex steroids exert diverse metabolic and neurobiological actions. Their levels have been associated with cardiovascular disease, but data concerning cerebrovascular disease are lacking. The objective of our study was to investigate the role of adrenal sex steroids in a female population suffering an acute stroke. We addressed the question of whether their levels are associated with disease severity and prognosis. A 2-year cohort study was performed in 2 tertiary hospitals, where we prospectively studied 302 consecutive postmenopausal female patients hospitalized for an acute stroke. Neurological severity on admission was assessed by the National Institutes of Health Stroke Scale; and handicap 1 month after stroke, with the modified Rankin Scale. Δ4-androstenedione levels were positively and dehydroepiandrosterone sulfate was inversely associated with stroke severity (r = 0.142, P = .014 and r = -0.153, P = .008, respectively), and both parameters remained as significant determinants even after entering other confounders in the multivariate model (r = 0.118, P = .039 and r = -0.150, P = .011, respectively). Levels of Δ4-androstenedione were significantly associated with 1-month mortality in the multivariate analysis (odds ratio with 95% confidence intervals: 1.540 [1.107-2.138)], P = .010). Δ4-androstenedione and dehydroepiandrosterone sulfate levels were associated with poor outcome in the univariate analysis, that is, combined severe handicap (modified Rankin Scale ≥4) and death, 1 month poststroke, although this was not significant in the multivariate analysis. Adrenal sex steroids, and especially Δ4-androstenedione, are significantly associated with stroke severity on admission and short-term prognosis among female stroke subjects. Well-designed prospective studies will further clarify their role in cerebrovascular disease.

2-(Cyclohexylamino)-1-(4-cyclopentylpiperazin-1-yl)-2-methylpropan-1-one, a novel compound with neuroprotective and neurotrophic effects in vitro

Focusing on development of novel drug candidates for the treatment of neurodegenerative diseases, we developed and synthesized a new compound, 2-(cyclohexylamino)-1-(4-cyclopentylpiperazin-1-yl)-2-methylpropan-1-one (amido-piperizine 1). The compound demonstrated robust neuroprotective properties after both glutamate excitotoxicity and peroxide induced oxidative stress in primary cortical cultures. Furthermore, amido-piperizine 1 was found to significantly induce neurite outgrowth in vitro which could suggest central reparative and regenerative potential of the compound. With these potential beneficial effects in CNS, the ability of the amido-piperizine 1 to penetrate the blood-brain barrier was tested using MDR1-MDCK cells. Amido-piperizine 1 was found not to be a P-gp substrate and to have a high blood-brain barrier penetration potential, indicating excellent availability to the CNS. Moreover, amido-piperizine 1 had a fast metabolic clearance rate in vitro, suggesting that parenteral in vivo administration seems preferable. As an attempt to elucidate a possible mechanism of action, we found that amido-piperizine 1 bound in nano-molar range to the sigma-1 receptor, which could explain the observed neuroprotective and neurotrophic properties, and with a 100-fold lower affinity to the sigma-2 receptor. These results propose that amido-piperizine 1 may hold promise as a drug candidate for the treatment of stroke/traumatic brain injury or other neurodegenerative diseases.

Baifuzi reduces transient ischemic brain damage through an interaction with the STREX domain of BKCa channels

Stroke is a long-term disability and one of the leading causes of death. However, no successful therapeutic intervention is available for the majority of stroke patients. In this study, we explored a traditional Chinese medicine Baifuzi (Typhonium giganteum Engl.). We show, at first, that the ethanol extract of Baifuzi exerts neuroprotective effects against brain damage induced by transient global or focal cerebral ischemia in rats and mice. Second, the extract activated large-conductance Ca(2+)-activated K(+) channel (BK(Ca)) channels, and BK(Ca) channel blockade suppressed the neuroprotection of the extract, suggesting that the BK(Ca) is the molecular target of Baifuzi. Third, Baifuzi cerebroside (Baifuzi-CB), purified from its ethanol extract, activated BK(Ca) channels in a manner similar to that of the extract. Fourth, the stress axis hormone-regulated exon (STREX) domain of the BK(Ca) channel directly interacted with Baifuzi-CB, and its deletion suppressed channel activation by Baifuzi-CB. These results indicate that Baifuzi-CB activated the BK(Ca) channel through its direct interaction with the STREX domain of the channel and suggests that Baifuzi-CB merits exploration as a potential therapeutic agent for treating brain ischemia.

Neuroprotective actions of neurosteroids

Neurosteroids were initially defined as steroid hormones locally synthesized within the nervous tissue. Subsequently, they were described as steroid hormone derivatives that devoid hormonal action but still affect neuronal excitability through modulation of ionotropic receptors. Neurosteroids are further subdivided into natural (produced in the brain) and synthetic. Some authors distinguish between hormonal and regular neurosteroids in the group of natural ones. The latter group, including hormone metabolites like allopregnanolone or tetrahydrodeoxycorticosterone, is devoid of hormonal activity. Both hormones and their derivatives share, however, most of the physiological functions. It is usually very difficult to distinguish the effects of hormones and their metabolites. All these substances may influence seizure phenomena and exhibit neuroprotective effects. Neuroprotection offered by steroid hormones may be realized in both genomic and non-genomic mechanisms and involve regulation of the pro- and anti-apoptotic factors expression, intracellular signaling pathways, neurotransmission, oxidative, and inflammatory processes. Since regular neurosteroids show no affinity for steroid receptors, they may act only in a non-genomic mode. Multiple studies have been conducted so far to show efficacy of neurosteroids in the treatment of the central and peripheral nervous system injury, ischemia, neurodegenerative diseases, or seizures. In this review we focused primarily on neurosteroid mechanisms of action and their role in the process of neurodegeneration. Most of the data refers to results obtained in experimental studies. However, it should be realized that knowledge about neuroactive steroids remains still incomplete and requires confirmation in clinical conditions.

Dehydroepiandrosterone effects on Akt signaling modulation in central nervous system of young and aged healthy rats

Dehydroepiandrosterone (DHEA) is a steroid synthesized in adrenal cortex as well as in the nervous system. DHEA effects on central nervous system (CNS) have been associated with several brain functions such as marked neurotrophic and neuroprotective activity. DHEA plasma concentration decreases steadily with aging and studies have reported an inverse correlation between levels of DHEA and neurological diseases age-associated. Nonetheless, its mechanisms of action are not yet fully understood. Akt signaling pathway is one protein kinase which has been related to be DHEA modulated. The goal of this study was to investigate whether short-term (6 or 24h) or chronic (5 weeks) DHEA treatment modulates Akt in CNS of adult (3 months) and aged (18 and 24 months) healthy rats. Hypothalamus and hippocampus homogenates were prepared to quantify total-Akt and phosphorylated Akt at Ser(473) (pAkt). The results here presented have shown that acute (50mg/kg) and chronic (10mg/kg) DHEA injections modulate total and pAkt levels. This effect was dose and time-dependent as well as age and tissue-dependent. In addition, the age variable also intervenes on total and pAkt levels expression independently of DHEA treatment.

Isoflurane preconditioning neuroprotection in experimental focal stroke is androgen-dependent in male mice

Isoflurane preconditioning neuroprotection in experimental stroke is male-specific. The role of androgens in the ischemic sensitivity of isoflurane preconditioned male brain and whether androgen effects are androgen receptor dependent were assessed. Male C57BL/6 mice were implanted with flutamide (androgen receptor antagonist), or castrated and implanted with testosterone, dihydrotestosterone, flutamide, letrozole (aromatase inhibitor), or vehicle 7-13 days before preconditioning. P450 estrogen aromatase wild-type and knockout mice were also evaluated. All mice were preconditioned for 4 h with 0% (sham preconditioning) or 1% isoflurane (isoflurane preconditioning) and recovered for 24 h. Mice then underwent 2 h of middle cerebral artery occlusion and were evaluated 22 h later for infarct volume. For neurobehavioral outcomes, sham and isoflurane preconditioned castrated male+/-dihydrotestosterone groups underwent 1 h of middle cerebral artery occlusion followed by 9 days of reperfusion. Isoflurane preconditioning neuroprotection relative to infarct volume outcomes were testosterone and dihydrotestosterone dose-specific and androgen receptor-dependent. Relative to long-term neurobehavioral outcomes, front paw sensorimotor function improved in isoflurane preconditioned mice regardless of androgen status while androgen replacement independently improved sensorimotor function. In contrast, isoflurane preconditioning improved cognitive function in castrates lacking endogenous androgens, but this improvement was absent in androgen replaced mice. Our findings suggest that androgen availability during isoflurane preconditioning may influence infarct volume and neurobehavioral outcomes in male mice following experimental stroke.

The pharmacology of sigma-1 receptors

Originally considered an enigmatic protein, the sigma-1 receptor has recently been identified as a unique ligand-regulated molecular chaperone in the endoplasmic reticulum of cells. This discovery causes us to look back at the many proposed roles of this receptor, even before its molecular function was identified, in many diseases such as methamphetamine or cocaine addiction, amnesia, pain, depression, Alzheimer's disease, stroke, retinal neuroprotection, HIV infection, and cancer. In this review, we examine the reports that have clearly shown an agonist-antagonist relationship regarding sigma-1 receptors in models of those diseases and also review the relatively known mechanisms of action of sigma-1 receptors in an attempt to spur the speculation of readers on how the sigma-1 receptor at the endoplasmic reticulum might relate to so many diseases. We found that the most prominent action of sigma-1 receptors in biological systems including cell lines, primary cultures, and animals is the regulation and modulation of voltage-regulated and ligand-gated ion channels, including Ca(2+)-, K(+)-, Na(+), Cl(-), and SK channels, and NMDA and IP3 receptors. We found that the final output of the action of sigma-1 receptor agonists is to inhibit all above-mentioned voltage-gated ion channels, while they potentiate ligand-gated channels. The inhibition or potentiation induced by agonists is blocked by sigma-1 receptor antagonists. Other mechanisms of action of sigma-1 receptors, and to some extent those of sigma-2 receptors, were also considered. We conclude that the sigma-1 and sigma-2 receptors represent potential fruitful targets for therapeutic developments in combating many human diseases.