Shane W. Rau

Estradiol protects against ischemic injury.

Clinical studies demonstrate that estrogen replacement therapy in postmenopausal women may enhance cognitive function and reduce neurodegeneration associated with Alzheimers disease and stroke, This study assesses whether physiologic levels of estradiol prevent brain injury in an in vivo model of permanent focal ischemia. Sprague-Dawley rats were ovariectomized; they then were implanted, immediately or at the onset of ischemia, with capsules that produced physiologically low or physiologically high 17β-estradiol levels in serum (10 or 60 pg/mL, respectively), One week after ovariectomy, ischemia was induced. Estradiol pretreatment significantly reduced overall infarct volume compared with oil-pretreated controls (mean ± SD: oil = 241 ± 88; low = 139 ± 91; high = 132 ±88 mm3); this protective effect was regionally specific to the cortex, since no protection was observed in the striatum. Baseline and ischemic regional CBF did not differ between oil and estradiol pretreated rats, as measured by laser Doppler flowmetry. Acute estradiol treatment did not protect against ischemic injury. Our finding that estradiol pretreatment reduces injury demonstrates that physiologic levels of estradiol can protect against neurodegeneration.

Estrogens: Trophic and protective factors in the adult brain

Our appreciation that estrogens are important neurotrophic and neuroprotective factors has grown rapidly. Although a thorough understanding of the molecular and cellular mechanisms that underlie this effect requires further investigation, significant progress has been made due to the availability of animal models in which we can test potential candidates. It appears that estradiol can act via mechanisms that require classical intracellular receptors (estrogen receptor alpha or beta) that affect transcription, via mechanisms that include cross-talk between estrogen receptors and second messenger pathways, and/or via mechanisms that may involve membrane receptors or channels. This area of research demands attention since estradiol may be an important therapeutic agent in the maintenance of normal neural function during aging and after injury.

Intranasal oxytocin reduces psychotic symptoms and improves Theory of Mind and social perception in schizophrenia

Oxytocin has numerous prosocial and antipsychotic-like effects in animals. Prosocial effects of acute intranasal oxytocin administration have also been reported in human subjects. We conducted a randomized, placebo-controlled trial testing the effects of twice daily intranasal oxytocin treatment for 14 days on psychotic symptoms and social cognition in patients with schizophrenia. PANSS scores declined significantly and several social cognition measures improved significantly or nearly significantly in oxytocin (N=11) but not placebo (N=9) recipients. Our results suggest that, in addition to reducing classic psychotic symptoms, oxytocin may diminish certain social cognition deficits that are not improved by current antipsychotic medications.

Minireview: Neuroprotective Effects of Estrogen—New Insights into Mechanisms of Action

An accumulating body of evidence clearly establishes that estradiol is a potent neuroprotective and neurotrophic factor in the adult: it influences memory and cognition, decreases the risk and delays the onset of neurological diseases such as Alzheimer’s disease, and attenuates the extent of cell death that results from brain injuries such as cerebrovascular stroke and neurotrauma. Thus, estradiol appears to act at two levels: 1) it decreases the risk of disease or injury; and/or 2) it decreases the extent of injury incurred by suppressing the neurotoxic stimulus itself or increasing the resilience of the brain to a given injury. During the past century, the average life span of women has increased dramatically, whereas the time of the menopause has remained essentially constant. Thus, more women will live a larger fraction of their lives in a postmenopausal, hypoestrogenic state than ever before. Clearly, it is critical for us understand the circumstances under which estradiol exerts protective actions a...

Estradiol is a protective factor in the adult and aging brain: understanding of mechanisms derived from in vivo and in vitro studies

We have shown that 17beta-estradiol exerts profound protective effects against stroke-like ischemic injury in female rats. These effects are evident using physiological levels of estradiol replacement in ovariectomized rats and require hormone treatment prior to the time of injury. The protective actions of estradiol appear to be most prominent in the cerebral cortex, where cell death is not apparent until at least 4 h after the initiation of ischemic injury and where cell death is thought to be apoptotic in nature. Middle-aged rats remain equally responsive to the protective actions of estradiol. The maintenance of responsiveness of the cerebral cortex to the neuroprotective actions of estradiol was unexpected since responsiveness of the hypothalamus to estradiol decreases dramatically by the time animals are middle-aged. We believe that the protective actions of estradiol require the estrogen receptor-alpha, since estradiol does not protect in estrogen receptor-alpha knockout mice. We have also implemented a method of culturing cerebral cortical explants to assess the protective effects of estradiol in vitro. This model exhibits remarkable parallelisms with our in vivo model of brain injury. We have found that 17beta-estradiol decreases the extent of cell death and that this protective effect requires hormone pretreatment. Finally, 17alpha-estradiol, which does not interact effectively with the estrogen receptor, does not protect; and addition of ICI 182,780, an estrogen receptor antagonist, blocks the protective actions of estradiol. We have begun to explore the molecular and cellular mechanisms of estradiol-mediated protection. In summary, our findings demonstrate that estradiol exerts powerful protective effects both in vivo and in vitro and suggest that these actions are mediated by estrogen receptors.

Estradiol enhances neurogenesis following ischemic stroke through estrogen receptors α and β

Neurogenesis persists throughout life under normal and degenerative conditions. The adult subventricular zone (SVZ) generates neural stem cells capable of differentiating to neuroblasts and migrating to the site of injury in response to brain insults. In the present study, we investigated whether estradiol increases neurogenesis in the SVZ in an animal model of stroke to potentially promote the ability of the brain to undergo repair. Ovariectomized C57BL/6J mice were implanted with capsules containing either vehicle or 17β‐estradiol, and 1 week later they underwent experimental ischemia. We utilized double‐label immunocytochemistry to identify the phenotype of newborn cells (5‐bromo‐2′‐deoxyuridine‐labeled) with various cellular markers; doublecortin and PSA‐NCAM as the early neuronal marker, NeuN to identify mature neurons, and glial fibrillary acidic protein to identify astrocytes. We report that low physiological levels of estradiol treatment, which exert no effect in the uninjured state, significantly increase the number of newborn neurons in the SVZ following stroke injury. This effect of estradiol is limited to the dorsal region of the SVZ and is absent from the ventral SVZ. The proliferative actions of estradiol are confined to neuronal precursors and do not influence gliosis. Furthermore, we show that both estrogen receptors α and β play pivotal functional roles, insofar as knocking out either of these receptors blocks the ability of estradiol to increase neurogenesis. These findings clearly demonstrate that estradiol stimulates neurogenesis in the adult SVZ, thus potentially facilitating the brain to remodel and repair after injury. J. Comp. Neurol. 500:1064–1075, 2007.

Estradiol Attenuates Programmed Cell Death after Stroke-Like Injury

Estradiol is a known neurotrophic and neuroprotective factor. Our previous work demonstrated that replacement with physiological concentrations of estradiol protects the cortex against middle cerebral artery occlusion (MCAO)-induced cell death. The cerebral cortex exhibits caspase-dependent programmed cell death (PCD) in many models of focal cerebral ischemia. We hypothesized that estradiol attenuates PCD during stroke injury. The current study explored the temporospatial pattern of markers of PCD, their relationship to the evolution of injury, and their modulation by estradiol. Rats were ovariectomized and treated with either estradiol or vehicle. One week later, rats underwent MCAO, and brains were collected at 1, 4, 8, 16, and 24 hr. We assessed the temporospatial evolution of infarction volume, DNA fragmentation, and levels of spectrin cleavage products in ischemic cortex. Estradiol led to a delay and attenuation of injury-mediated DNA fragmentation as early as 8 hr after MCAO. Estradiol also dramatically reduced the level of the 120 kDa caspase-mediated spectrin breakdown product (SBDP120) at 4 hr but not at 8 or 16 hr. The SBDP150, produced by caspase and calpain, showed peak levels at 16 hr but was not altered by estradiol. These results strongly suggest that estradiol protects the ischemic cortex by attenuating PCD, thereby reducing caspase activity, DNA fragmentation, and subsequently, overall cell death. These studies deepen our understanding of the mechanisms underlying estrogen-mediated neuroprotection.

Intranasal Oxytocin Blocks Alcohol Withdrawal in Human Subjects

BACKGROUND The neuropeptide, oxytocin (OT), has been reported to block tolerance formation to alcohol and decrease withdrawal symptoms in alcohol-dependent rodents. Numerous recent studies in human subjects indicate that OT administered by the intranasal route penetrates into and exerts effects within the brain. METHODS In a randomized, double-blind clinical trial, intranasal OT (24 IU/dose, N = 7) or placebo (N = 4) was given twice daily for 3 days in alcohol-dependent subjects admitted to a research unit for medical detoxification using Clinical Institute Withdrawal Assessment for Alcohol (CIWA) score-driven PRN administration of lorazepam. Subjects rated themselves on the Alcohol Withdrawal Symptom Checklist (AWSC) each time CIWA scores were obtained. Subjects also completed the Penn Alcohol Craving Scale, an Alcohol Craving Visual Analog Scale (ACVAS) and the Profile of Mood States (POMS) on inpatient days 2 and 3. RESULTS All subjects had drunk heavily each day for at least 2 weeks prior to study and had previously experienced withdrawal upon stopping/decreasing alcohol consumption. OT was superior to placebo in reducing alcohol withdrawal as evidenced by: less total lorazepam required to complete detoxification (3.4 mg [4.7, SD] vs. 16.5 [4.4], p = 0.0015), lower mean CIWA scores on admission day 1 (4.3 [2.3] vs. 11.8 [0.4], p < 0.0001) and day 2 (3.4 [2.2] vs. 11.1 [3.6], p < 0.002), lower AWSC scores on days 1 and 2 (p < 0.02; p = 0.07), and lower ACVAS ratings (p = 0.01) and lower POMS Tension/Anxiety subscale scores on day 2 (p < 0.01). CONCLUSIONS This is the first demonstration that OT treatment may block alcohol withdrawal in human subjects. Our results are consistent with previous findings in rodents that OT inhibits neuroadaptation to and withdrawal from alcohol. OT could have advantages over benzodiazepines in managing alcohol withdrawal because it may reverse rather than maintain sedative-hypnotic tolerance. It will be important to test whether OT treatment is effective in reducing drinking in alcohol-dependent outpatients.

Estradiol is a neuroprotective factor in in vivo and in vitro models of brain injury

Many clinical studies suggest that estrogen enhances memory and cognition and protects against neurodegenerative diseases and injury associated with stroke or stress. These results are strongly supported by experiments performed in animal models using both in vivo and in vitro methods. We present here data from our lab that establishes that physiological levels of estradiol exert profound protective actions against ischemic injury. Further we will present evidence that these effects may be mediated through estrogen receptors that may influence the bcl-2 family of genes.

Stimulus-secretion coupling in porcine adrenal chromaffin cells: Effect of dexamethasone

Recent studies from this laboratory established that dexamethasone (DEX) potentiates Ca2+ current via voltage‐gated Ca2+ channels (VGCC), and as a consequence potentiates agonist‐induced cytosolic Ca2+ transients in rat adrenal chromaffin cells. The present study examined whether DEX can also modulate VGCC activity and agonist‐induced cytosolic Ca2+ transients in porcine adrenal medullary chromaffin (PAMC) cells, and if so whether this results in alterations in catecholamine secretion. Forty‐eight‐hr exposure to 1 μM DEX significantly increased peak Ca2+ current (Δ + 138%; n = 6; P < 0.05) in PAMC cells. DEX treatment also significantly potentiated the increase in cytosolic Ca2+ in response to membrane depolarization with KCl (Δ + 20%; n = 29; P < 0.05), but did not affect the amplitude of Ca2+ transients elicited by nicotine or acetylcholine. Despite the potentiation of intracellular Ca2+, DEX treatment had no effect on KCl‐induced secretion of either norepinephrine or epinephrine. These data demonstrate that as in the rat chromaffin cell, DEX can also increase VGCC activity in PAMC cells. However, the subsequent potentiation of selected agonist‐induced increases in intracellular Ca2+ does not appear to be sufficient to alter catecholamine secretion. J. Neurosci. Res. 49:416–424, 1997.