Estrogen as a neuroprotective agent in the treatment of spinal cord injury

Sex hormone supplementation improves breathing and restores respiratory neuroplasticity following C2 hemisection in rats

In addition to loss of sensory and motor function below the level of the lesion, traumatic spinal cord injury (SCI) may reduce circulating steroid hormones that are necessary for maintaining normal physiological function for extended time periods. For men, who comprise nearly 80% of new SCI cases each year, testosterone is the most abundant circulating sex steroid. SCI often results in significantly reduced testosterone production and may result in chronic low testosterone levels. Testosterone plays a role in respiratory function and the expression of respiratory neuroplasticity. When testosterone levels are low, young adult male rats are unable to express phrenic long-term facilitation (pLTF), an inducible form of respiratory neuroplasticity invoked by acute, intermittent hypoxia (AIH). However, testosterone replacement can restore this respiratory neuroplasticity. Complicating the interpretation of this finding is that testosterone may exert its influence in three possible ways: 1) directly through androgen receptor (AR) activation, 2) through conversion to dihydrotestosterone (DHT) by way of the enzyme 5α-reductase, or 3) through conversion to 17β-estradiol (E2) by way of the enzyme aromatase. DHT signals via AR activation similar to testosterone, but with higher affinity, while E2 activates local estrogen receptors. Evidence to date supports the idea that exogenous testosterone supplementation exerts its influence through estrogen receptor signaling under conditions of low circulating testosterone. Here we explored both recovery of breathing function (measured with whole body barometric plethysmography) and the expression of AIH-induced pLTF in male rats following C2-hemisection SCI. One week post injury, rats were supplemented with either E2 or DHT for 7 days. We hypothesized that E2 would enhance ventilation and reveal pLTF following AIH in SCI rats. To our surprise, though E2 did beneficially impact overall breathing recovery following C2-hemisection, both E2 supplementation and DHT restored the expression of AIH-induced pLTF 2 weeks post-SCI.

Sex hormone mediated change on flexion reflex

It has been shown that estrogen and progesterone receptors are expressed in the spinal cord; therefore, fluctuation in their concentrations may affect the spinal network and modulate the control of movement. Herein, we assessed the neuro-modulatory effect of sex hormones on the polysynaptic spinal network by using a flexion reflex network as a model system. Twenty-four healthy eumenorrheic women (age 21-37 years) were tested every other day for one menstrual cycle. Serum estradiol and progesterone were acquired at the time of testing. The flexion reflex of the tibialis anterior was elicited by sending an innocuous electrical stimulus directly to the posterior tibial nerve or plantar cutaneous afferent. Analyses were performed for each menstrual cycle phase: the follicular phase and the luteal phase. Increases in estradiol or progesterone concentrations were not associated with reflex duration or root mean squared (RMS) amplitude in either the follicular or luteal phases. In the luteal phase, an increase in the estradiol concentration was associated with a longer latency of the reflex (b = 0.23, p = 0.038). The estradiol × progesterone interaction was found towards significance (b = -0.017, p = 0.081). These results highlight the potential synergistic effect of estradiol and progesterone and may provide indirect confirmatory evidence of the observed modulatory effect.

Protective Effects of Estrogen via Nanoparticle Delivery to Attenuate Myelin Loss and Neuronal Death after Spinal Cord Injury

Spinal cord injury (SCI) is associated with devastating neurological deficits affecting more than 11,000 Americans each year. Although several therapeutic agents have been proposed and tested, no FDA-approved pharmacotherapy is available for SCI treatment. We have recently demonstrated that estrogen (E2) acts as an antioxidant and anti-inflammatory agent, attenuating gliosis in SCI. We have also demonstrated that nanoparticle-mediated focal delivery of E2 to the injured spinal cord decreases lesion size, reactive gliosis, and glial scar formation. The current study tested in vitro effects of E2 on reactive oxygen species (ROS) and calpain activity in microglia, astroglia, macrophages, and fibroblasts, which are believed to participate in the inflammatory events and glial scar formation after SCI. E2 treatment decreased ROS production and calpain activity in these glial cells, macrophages, and fibroblast cells in vitro. This study also tested the efficacy of fast- and slow-release nanoparticle-E2 constructs in a rat model of SCI. Focal delivery of E2 via nanoparticles increased tissue distribution of E2 over time, attenuated cell death, and improved myelin preservation in injured spinal cord. Specifically, the fast-release nanoparticle-E2 construct reduced the Bax/Bcl-2 ratio in injured spinal cord tissues, and the slow-release nanoparticle-E2 construct prevented gliosis and penumbral demyelination distal to the lesion site. These data suggest this novel E2 delivery strategy to the lesion site may decrease inflammation and improve functional outcomes following SCI.

Acute Dose-Dependent Neuroprotective Effects of Poly(pro-17β-estradiol) in a Mouse Model of Spinal Contusion Injury

17β-Estradiol (E2) confers neuroprotection in preclinical models of spinal cord injury when administered systemically. The goal of this study was to apply E2 locally to the injured spinal cord for a sustained duration using poly(pro-E2) film biomaterials. Following contusive spinal cord injury in adult male mice, poly(pro-E2) films were implanted subdurally and neuroprotection was assessed using immunohistochemistry 7 days after injury and implantation. In these studies, poly(pro-E2) films modestly improved neuroprotection without affecting the inflammatory response when compared to the injured controls. To increase the E2 dose released, bolus-releasing poly(pro-E2) films were fabricated by incorporating unbound E2 into the poly(pro-E2) films. However, compared to the injured controls, bolus-releasing poly(pro-E2) films did not significantly enhance neuroprotection or limit inflammation at either 7 or 21 days post-injury. Future work will focus on developing poly(pro-E2) biomaterials capable of more precisely releasing therapeutic doses of E2.

Cellular therapy for treatment of spinal cord injury in Zebrafish model

Spinal cord injury is a serious problem with a high rate of morbidity and mortality for all persons, especially young people (15-25 years old). Due to the large burden and the costs incurred on the government, finding the best therapeutic approach is necessary. In this respect, treatment strategies based on the disease mechanism can be effective. After the first trauma of spinal cord cascades, cellular events happen one after the other known as secondary trauma. The mechanism of secondary events of spinal cord injury could be helpful for target therapy as trying to stop the secondary trauma. Herein, some medical and surgical therapy has been introduced and cell therapy strategy was considered as a recent method. Actually, cell therapy is defined as the application of different cells including mesenchymal stem cells, embryonic stem cells, induced pluripotent stem cells, and some others to replace or reconstruct the damaged tissues and restore their functions. However, as a newly emerged therapeutic method, cell therapy should be used through various subclinical studies in animal models to assess the efficacy of the treatment under controlled conditions. In this review, the role of Zebrafish as a recommended model has been discussed and combinatory approach as the probably most useful treatment has been suggested.

Pathophysiology, Biomarkers, and Therapeutic Modalities Associated with Skeletal Muscle Loss Following Spinal Cord Injury

A spinal cord injury (SCI) may lead to loss of strength, sensation, locomotion and other body functions distal to the lesion site. Individuals with SCI also develop secondary conditions due to the lack of skeletal muscle activity. As SCI case numbers increase, recent studies have attempted to determine the best options to salvage affected musculature before it is lost. These approaches include pharmacotherapeutic options, immunosuppressants, physical activity or a combination thereof. Associated biomarkers are increasingly used to determine if these treatments aid in the protection and reconstruction of affected musculature.

Nanoparticle-Based Estrogen Delivery to Spinal Cord Injury Site Reduces Local Parenchymal Destruction and Improves Functional Recovery

Spinal cord injury (SCI) patients sustain significant functional impairments; this is causally related to restricted neuronal regeneration after injury. The ensuing reactive gliosis, inflammatory cascade, and glial scar formation impede axonal regrowth. Although systemic anti-inflammatory agents (steroids) have been previously administered to counteract this, no current therapeutic is approved for post-injury neuronal regeneration, in part because of related side effects. Likewise, therapeutic systemic estrogen levels exhibit neuroprotective properties, but dose-dependent side effects are prohibitive. The current study thus uses low-dose estrogen delivery to the spinal cord injury (SCI) site using an agarose gel patch embedded with estrogen-loaded nanoparticles. Compared to controls, spinal cords from rodents treated with nanoparticle site-directed estrogen demonstrated significantly decreased post-injury lesion size, reactive gliosis, and glial scar formation. However, axonal regeneration, vascular endothelial growth factor production, and glial-cell-derived neurotrophic factor levels were increased with estrogen administration. Concomitantly improved locomotor and bladder functional recovery were observed with estrogen administration after injury. Therefore, low-dose site-directed estrogen may provide a future approach for enhanced neuronal repair and functional recovery in SCI patients.

Vastly extended drug release from poly(pro-17β-estradiol) materials facilitates in vitro neurotrophism and neuroprotection

Central nervous system (CNS) injuries persist for years, and currently there are no therapeutics that can address the complex injury cascade that develops over this time-scale. 17β-estradiol (E2) has broad tropism within the CNS, targeting and inducing beneficial phenotypic changes in myriad cells following injury. To address the unmet need for vastly prolonged E2 release, we report first-generation poly(pro-E2) biomaterial scaffolds that release E2 at nanomolar concentrations over the course of 1-10 years via slow hydrolysis in vitro. As a result of their finely tuned properties, these scaffolds demonstrate the ability to promote and guide neurite extension ex vivo and protect neurons from oxidative stress in vitro. The design and testing of these materials reported herein demonstrate the first step towards next-generation implantable biomaterials with prolonged release and excellent regenerative potential.

Sex Differences and Role of Gonadal Hormones on Glutamate LevelAfter Spinal Cord Injury in Rats: A Microdialysis Study

Introduction:

Sex differences in outcomes of Spinal Cord Injury (SCI) suggest a sex-hormone-mediated effect on post-SCI pathological events, including glutamate excitotoxicity. This study aimed to investigate the importance of gonadal hormones on glutamate release subsequent to SCI in rats.

Methods:

After laminectomy at T8–T9, an electrolytic lesion was applied to the spinothalamic tracts of male and female rats. Using spinal microdialysis, we assessed glutamate levels at the site of lesion in both intact and gonadectomized rats for 4 hours. In this way, we examined the sex differences in the glutamate concentrations.

Results:

The peak retention time of glutamate level was 10.6 min and spinal glutamate concentration reached a maximum level 40 min following SCI. In male SCI rats, gonadectomy caused a significant elevation of glutamate level (P<0.001) following injury which was maximum 40 min post-SCI as well. However, no significant alterations were seen in gonadectomized female rats.

Conclusion:

The significant differences in glutamate levels between both intact and gonadectomized SCI male and female rats show the sex-hormone-related mechanisms underlying the molecular events in the second phase of SCI. It seems that the role of male gonadal hormones to prevent glutamate excitotoxicity is more prominent. The exact mechanisms of these hormones on the functional recovery after SCI should be clarified in further studies.

Effects of estrogen on Survival and Neuronal Differentiation of adult human olfactory bulb neural stem Cells Transplanted into Spinal Cord Injured Rats.. [DOI: 10.1101/571950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

In the present study we developed an excitotoxic spinal cord injury (SCI) model using kainic acid (KA) to evaluate of the therapeutic potential of human olfactory bulb neural stem cells (h-OBNSCs) for spinal cord injury (SCI). In a previous study, we assessed the therapeutic potential of these cells for SCI; all transplanted animals showed successful engraftment. These cells differentiated predominantly as astrocytes, not motor neurons, so no improvement in motor functions was detected. In the current study we used estrogen as neuroprotective therapy before transplantation of OBNSCs to preserve some of endogenous neurons and enhance the differentiation of these cells towards neurons. The present work demonstrated that the h-GFP-OBNSCs were able to survive for more than eight weeks after sub-acute transplantation into injured spinal cord. Stereological quantification of OBNSCs showed approximately a 2.38-fold increase in the initial cell population transplanted. 40.91% of OBNSCs showed differentiation along the neuronal lineages, which was the predominant fate of these cells. 36.36% of the cells differentiated into mature astrocytes; meanwhile 22.73% of the cells differentiated into oligodendrocytes. Improvement in motor functions was also detected after cell transplantation.

Histoarchitecture restoration of cerebellar sub-layers as a response to estradiol treatment following Kainic acid-induced spinal cord injury

One of the major impacts of spinal cord injury (SCI) is the cerebellar neurological malfunction and deformation of its sub-layers. This could be due to the enormous innervation of the spinocerebellar tract from the posterior gray horn in the spinal cord to the ipsilateral cerebellum. Although the neuroprotective role of estradiol in spinal cord (SC) injuries, as well as its ability to delay secondary cell death changes, is well-known, its effect on cerebellar layers is not fully investigated. In this study, a SCI model was achieved by injection of Kainic acid into SC of adult Male Wistar rats in order to assess the effects of SCI on the cerebellum. The animals were classified into SCI group (animals with SCI), estradiol-treated group (animals with SCI and received estradiol), control groups, and sham control group. The microscopical examination 24 h after induction of SCI revealed that KA induced the most characteristics of neurodegeneration including astrocytic propagation and microglial activation. The estradiol was injected intraperitoneally 20 min after induction of SCI, and the samples were collected at 1, 3, 7, 14, and 30 days. Histologically, the estradiol reduced the inflammatory response, enhanced the recovery of molecular, granular, and Purkinje cell layers, and therefore aided in the restoration of layer organization. These findings were also confirmed by immunohistochemical staining and gene expression profiling.

Expression of aromatase and estrogen receptors in lumbar motoneurons of mice

Estrogen exerts protective roles in amyotrophic lateral sclerosis (ALS). However, the expression of aromatase (ARO) and estrogen receptors (ERs) in the motoneurons of spinal cord, has not yet been elucidated. By immunohistochemistry, we found that ARO and ERs were present in the ventral horn of adult mice lumbar spinal cord, and colocalized with SMI-32, a motoneuron specific marker. Within motoneurons, we observed that ARO is detected primarily in the cytoplasm, with fewer ARO in the nucleus; ERα and ERβ mainly localized in the nucleus with less in the cytoplasm; while GPR30 is located in soma and processes. In conclusion, we found that ERs and ARO are expressed in the motoneurons of lumbar spinal cord in adult mice. These findings suggest that estrogen may be useful as a promising therapeutic agent for prevention of damage and improvement of locomotor function in ALS.

Identifying the Long-Term Role of Inducible Nitric Oxide Synthase after Contusive Spinal Cord Injury Using a Transgenic Mouse Model

Inducible nitric oxide synthase (iNOS) is a potent mediator of oxidative stress during neuroinflammation triggered by neurotrauma or neurodegeneration. We previously demonstrated that acute iNOS inhibition attenuated iNOS levels and promoted neuroprotection and functional recovery after spinal cord injury (SCI). The present study investigated the effects of chronic iNOS ablation after SCI using inos-null mice. iNOS^-/- knockout and wild-type (WT) control mice underwent a moderate thoracic (T8) contusive SCI. Locomotor function was assessed weekly, using the Basso Mouse Scale (BMS), and at the endpoint (six weeks), by footprint analysis. At the endpoint, the volume of preserved white and gray matter, as well as the number of dorsal column axons and perilesional blood vessels rostral to the injury, were quantified. At weeks two and three after SCI, iNOS^-/- mice exhibited a significant locomotor improvement compared to WT controls, although a sustained improvement was not observed during later weeks. At the endpoint, iNOS^-/- mice showed significantly less preserved white and gray matter, as well as fewer dorsal column axons and perilesional blood vessels, compared to WT controls. While short-term antagonism of iNOS provides histological and functional benefits, its long-term ablation after SCI may be deleterious, blocking protective or reparative processes important for angiogenesis and tissue preservation.

Molecular mechanisms of estrogen for neuroprotection in spinal cord injury and traumatic brain injury

Estrogen (EST) is a steroid hormone that exhibits several important physiological roles in the human body. During the last few decades, EST has been well recognized as an important neuroprotective agent in a variety of neurological disorders in the central nervous system (CNS), such as spinal cord injury (SCI), traumatic brain injury (TBI), Alzheimer’s disease, and multiple sclerosis. The exact molecular mechanisms of EST-mediated neuroprotection in the CNS remain unclear due to heterogeneity of cell populations that express EST receptors (ERs) in the CNS as well as in the innate and adaptive immune system. Recent investigations suggest that EST protects the CNS from injury by suppressing pro-inflammatory pathways, oxidative stress, and cell death, while promoting neurogenesis, angiogenesis, and neurotrophic support. In this review, we have described the currently known molecular mechanisms of EST-mediated neuroprotection and neuroregeneration in SCI and TBI. At the same time, we have emphasized on the recent in vitro and in vivo findings from our and other laboratories, implying potential clinical benefits of EST in the treatment of SCI and TBI.

Administration of low dose estrogen attenuates gliosis and protects neurons in acute spinal cord injury in rats

Spinal cord injury (SCI) is a debilitating condition with neurological deficits and loss of motor function that, depending on the severity, may lead to paralysis. The only treatment currently available is methylprednisolone, which is widely used and renders limited efficacy in SCI. Therefore, other therapeutic agents must be developed. The neuroprotective efficacy of estrogen in SCI was studied with a pre-clinical and pro-translational perspective. Acute SCI was induced in rats that were treated with low doses of estrogen (1, 5, 10, or 100 μg/kg) and compared with vehicle-treated injured rats or laminectomy control (sham) rats at 48 h post-SCI. Changes in gliosis and other pro-inflammatory responses, expression and activity of proteolytic enzymes (e.g., calpain, caspase-3), apoptosis of neurons in SCI, and cell death were monitored via Western blotting and immunohistochemistry. Negligible pro-inflammatory responses or proteolytic events and very low levels of neuronal death were found in sham rats. In contrast, vehicle-treated SCI rats showed profound pro-inflammatory responses with reactive gliosis, elevated expression and activity of calpain and caspase-3, elevated Bax:Bcl-2 ratio, and high levels of neuronal death in lesion and caudal regions of the injured spinal cord. Estrogen treatment at each dose reduced pro-inflammatory and proteolytic activities and protected neurons in the caudal penumbra in acute SCI. Estrogen treatment at 10 μg was found to be as effective as 100 μg in ameliorating the above parameters in injured animals. Results from this investigation indicated that estrogen at a low dose could be a promising therapeutic agent for treating acute SCI. Experimental studies with low dose estrogen therapy in acute spinal cord injury (SCI) demonstrated the potential for multi-active beneficial outcomes. Estrogen has been found to ameliorate several degenerative pathways following SCI. Thus, such early protective effects may even lead to functional recovery in long term injury. Studies are underway in chronic SCI in a follow up manuscript.

Effects of estrogen on functional and neurological recovery after spinal cord injury: An experimental study with rats

OBJECTIVES

To evaluate the functional and histological effects of estrogen as a neuroprotective agent after a standard experimentally induced spinal cord lesion.

METHODS

In this experimental study, 20 male Wistar rats were divided into two groups: one group with rats undergoing spinal cord injury (SCI) at T10 and receiving estrogen therapy with 17-beta estradiol (4mg/kg) immediately following the injury and after the placement of skin sutures and a control group with rats only subjected to SCI. A moderate standard experimentally induced SCI was produced using a computerized device that dropped a weight on the rat's spine from a height of 12.5 mm. Functional recovery was verified with the Basso, Beattie and Bresnahan scale on the 2nd, 7th, 14th, 21st, 28th, 35th and 42nd days after injury and by quantifying the motor-evoked potential on the 42nd day after injury. Histopathological evaluation of the SCI area was performed after euthanasia on the 42nd day.

RESULTS

The experimental group showed a significantly greater functional improvement from the 28th to the 42nd day of observation compared to the control group. The experimental group showed statistically significant improvements in the motor-evoked potential compared with the control group. The results of pathological histomorphometry evaluations showed a better neurological recovery in the experimental group, with respect to the proportion and diameter of the quantified nerve fibers.

CONCLUSIONS

Estrogen administration provided benefits in neurological and functional motor recovery in rats with SCI beginning at the 28th day after injury.

The Incremental Induction of Neuroprotective Properties by Multiple Therapeutic Strategies for Primary and Secondary Neural Injury

Neural diseases including injury by endogenous factors, traumatic brain injury, and degenerative neural injury are eventually due to reactive oxygen species (ROS). Thus ROS generation in neural tissues is a hallmark feature of numerous forms of neural diseases. Neural degeneration and the neural damage process is complex, involving a vast array of tissue structure, transcriptional/translational, electrochemical, metabolic, and functional events within the intact neighbors surrounding injured neural tissues. During aging, multiple changes involving physical, chemical, and biochemical processes occur from the molecular to the morphological levels in neural tissues. Among many recommended therapeutic candidates, melatonin also plays a role in protecting the nervous system from anti-inflammation and efficiently safeguards neuronal cells via antioxidants and other endogenous/exogenous beneficial factors. Therefore, given the wide range of mechanisms responsible for neuronal damage, multi-action drugs or therapies for the treatment of neural injury that make use of two or more agents and target several pathways may have greater efficacy in promoting functional recovery than a single therapy alone.

Female Rats Demonstrate Improved Locomotor Recovery and Greater Preservation of White and Gray Matter after Traumatic Spinal Cord Injury Compared to Males

The possibility of a gender-related difference in recovery after spinal cord injury (SCI) remains a controversial subject. Current empirical animal research lacks sizable test groups to definitively determine whether significant differences exist. Evaluating locomotor recovery variances between sexes following a precise, clinically relevant spinal cord contusion model can provide valuable insight into a possible gender-related advantage in outcome post-SCI. In the current study, we hypothesized that by employing larger sample sizes in a reproducible contusive SCI paradigm, subtle distinctions in locomotor recovery between sexes, if they exist, would be elucidated through a broad range of behavioral tests. During 13 weeks of functional assessment after a thoracic (T8) contusive SCI in rat, significant differences owing to gender existed for the Basso, Beattie, and Bresnahan score and CatWalk hindlimb swing, support four, and single stance analyses. Significant differences in locomotor performance were noticeable as early as 4 weeks post-SCI. Stereological tissue-volume analysis determined that females, more so than males, also exhibited greater volumes of preserved gray and white matter within the injured cord segment as well as more spared ventral white matter area at the center of the lesion. The stereological tissue analysis differences favoring females directly correlated with the female rats' greater functional improvement observed at endpoint.

Impact of treatment duration and lesion size on effectiveness of chondroitinase treatment post-SCI

The effects of 2weeks of intralesional chondroitinase abc (ch'abc) treatment on anatomical plasticity and behavioral recovery are examined in adult cats and compared to results achieved with 4weeks of treatment following tightly controlled lateral hemisection injuries. Analyses also were completed using 35 cats with a range of hemisection magnitudes to assess relationships between treatment duration, lesion size and functional recovery. Results indicate that both 2 and 4weeks of treatment significantly increased the number of rubrospinal tract (RuST) neurons with axons below the lesion, but neither affected the number of corticospinal tract neurons. Similarly, both treatment periods also accelerated recovery of select motor tasks, which carries considerable importance with respect to human health care and rehabilitation. Four weeks of treatment promoted recovery beyond that seen with 2weeks in its significant impact on accuracy of movement critical for placement of the ipsilateral hindlimb onto small support surfaces during the most challenging locomotor tasks. Analyses, which extended to a larger group of cats with a range of lesion magnitudes, indicate that 4weeks of ch'abc treatment promoted earlier recovery as well as significantly greater targeting accuracy even in cats with larger lesions. Together, these results support the potential for ch'abc to promote anatomical and behavioral recovery and suggest that intraspinal treatment with ch'abc continues to enhance motor recovery and performance beyond the subacute injury period and diminishes the impact of lesion size.

Estradiol attenuates spinal cord injury-related central pain by decreasing glutamate levels in thalamic VPL nucleus in male rats

Central neuropathic pain (CNP) is a complicated medical problem that involves both the spinal and supraspinal regions of the central nervous system. Estrogen, a neuroprotective agent, has been considered a possible candidate for CNP treatment. In this study, we examined the effects of a single dose of 17β-estradiol on glutamate levels in the ventral posterolateral (VPL) nucleus of the rat thalamus. Furthermore, we determined whether there was a correlation between glutamate levels and neuropathic pain induced by unilateral electrolytic spinothalamic tract (STT) lesion. STT lesioning was performed in male Wistar rats at the T8-T9 vertebrae; rats were then administered 17β-estradiol (4 mg/kg, i.p.) 30 min after injury. Glutamate samples were collected using a microdialysis probe and quantified by high performance liquid chromatography. Mechanical allodynia (MA) and thermal hyperalgesia (TH) thresholds were measured pre-injury and 7, 14, and 28 days post-injury. We found that STT lesion significantly increased glutamate levels in the ipsilateral VPL nucleus 14 and 28 days post-injury; this was accompanied by allodynia and hyperalgesia in the hind paws of the rats. Administering 17β-estradiol to the rats decreased glutamate levels in the ipsilateral VPL nucleus and significantly increased MA and TH thresholds. These results suggest that glutamate in the VPL nucleus of the thalamus is involved in the pathology of neuropathic pain after STT injury; furthermore, 17β-estradiol may attenuate this neuropathic pain by decreasing glutamate levels.

Tamoxifen and estradiol improved locomotor function and increased spared tissue in rats after spinal cord injury: their antioxidant effect and role of estrogen receptor alpha

17β-Estradiol is a multi-active steroid that imparts neuroprotection via diverse mechanisms of action. However, its role as a neuroprotective agent after spinal cord injury (SCI), or the involvement of the estrogen receptor-alpha (ER-α) in locomotor recovery, is still a subject of much debate. In this study, we evaluated the effects of estradiol and of Tamoxifen (an estrogen receptor mixed agonist/antagonist) on locomotor recovery following SCI. To control estradiol cyclical variability, ovariectomized female rats received empty or estradiol filled implants, prior to a moderate contusion to the spinal cord. Estradiol improved locomotor function at 7, 14, 21, and 28 days post injury (DPI), when compared to control groups (measured with the BBB open field test). This effect was ER-α mediated, because functional recovery was blocked with an ER-α antagonist. We also observed that ER-α was up-regulated after SCI. Long-term treatment (28 DPI) with estradiol and Tamoxifen reduced the extent of the lesion cavity, an effect also mediated by ER-α. The antioxidant effects of estradiol were seen acutely at 2 DPI but not at 28 DPI, and this acute effect was not receptor mediated. Rats treated with Tamoxifen recovered some locomotor activity at 21 and 28 DPI, which could be related to the antioxidant protection seen at these time points. These results show that estradiol improves functional outcome, and these protective effects are mediated by the ER-α dependent and independent-mechanisms. Tamoxifen׳s effects during late stages of SCI support the use of this drug as a long-term alternative treatment for this condition.

MiR-7-1 potentiated estrogen receptor agonists for functional neuroprotection in VSC4.1 motoneurons

Protection of motoneurons is an important goal in the treatment of spinal cord injury (SCI). We tested whether neuroprotective microRNAs (miRs) like miR-206, miR-17, miR-21, miR-7-1, and miR-106a could enhance efficacy of estrogen receptor (ER) agonists such as 1,3,5-tris (4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT, ERα agonist), Way200070 (WAY, ERβ agonist), and estrogen (EST, ERα and ERβ agonist) in preventing apoptosis in the calcium ionophore (CI)-insulted ventral spinal cord 4.1 (VSC4.1) motoneurons. We determined that 200 nM CI induced 70% cell death. Treatment with 50 nM PPT, 100 nM WAY, and 150 nM EST induced overexpression of ERα, ERβ, and both receptors, respectively, at mRNA and protein levels. Treatment with ER agonists significantly upregulated miR-206, miR-17, and miR-7-1 in the CI-insulted VSC4.1 motoneurons. Transfection with miR-206, miR-17, or miR-7-1 mimic potentiated WAY or EST to inhibit apoptosis in the CI-insulted VSC4.1 motoneurons. Overexpression of miR-7-1 maximally increased efficacy of WAY and EST for down regulation of pro-apoptotic Bax and upregulation of anti-apoptotic Bcl-2. A search using microRNA database (miRDB) indicated that miR-7-1 could inhibit the expression of L-type Ca(2+) channel protein alpha 1C (CPα1C). miR-7-1 overexpression and WAY or EST treatment down regulated CPα1C but upregulated p-Akt to trigger cell survival signaling. The same therapeutic strategy increased expression of the Ca(2+)/calmodulin-dependent protein kinase II beta (CaMKIIβ) and the phosphorylated cAMP response element binding protein (p-CREB) so as to promote Bcl-2 transcription. Whole cell membrane potential and mitochondrial membrane potential studies indicated that miR-7-1 highly potentiated EST to preserve functionality in the CI-insulted VSC4.1 motoneurons. In conclusion, our data indicated that miR-7-1 most significantly potentiated efficacy of EST for functional neuroprotection and this therapeutic strategy could be used in the future to attenuate apoptosis of motoneurons in SCI.

Estrone is neuroprotective in rats after traumatic brain injury

In various animal and human studies, early administration of 17β-estradiol, a strong antioxidant, anti-inflammatory, and anti-apoptotic agent, significantly decreases the severity of injury in the brain associated with cell death. Estrone, the predominant estrogen in postmenopausal women, has been shown to be a promising neuroprotective agent. The overall goal of this project was to determine if estrone mitigates secondary injury following traumatic brain injury (TBI) in rats. Male rats were given either placebo (corn oil) or estrone (0.5 mg/kg) at 30 min after severe TBI. Using a controlled cortical impact device in rats that underwent a craniotomy, the right parietal cortex was injured using the impactor tip. Non-injured control and sham animals were also included. At 72 h following injury, the animals were perfused intracardially with 0.9% saline followed by 10% phosphate-buffered formalin. The whole brain was removed, sliced, and stained for TUNEL-positive cells. Estrone decreased cortical lesion volume (p<0.01) and neuronal injury (p<0.001), and it reduced cerebral cortical levels of TUNEL-positive staining (p<0.0001), and decreased numbers of TUNEL-positive cells in the corpus callosum (p<0.03). We assessed the levels of β-amyloid in the injured animals and found that estrone significantly decreased the cortical levels of β-amyloid after brain injury. Cortical levels of phospho-ERK1/2 were significantly (p<0.01) increased by estrone. This increase was associated with an increase in phospho-CREB levels (p<0.021), and brain-derived neurotrophic factor (BDNF) expression (p<0.0006). In conclusion, estrone given acutely after injury increases the signaling of protective pathways such as the ERK1/2 and BDNF pathways, decreases ischemic secondary injury, and decreases apoptotic-mediated cell death. These results suggest that estrone may afford protection to those suffering from TBI.

17β-estradiol attenuates neural cell apoptosis through inhibition of JNK phosphorylation in SCI rats and excitotoxicity induced by glutamate in vitro

We investigated whether 17β-estradiol (E2) treatment could prevent the apoptosis of neural cells after spinal cord injury (SCI) and cultured cortical cells through inhibition of JNK (c-Jun N-terminal kinase) phosphorylation. SCI-induced rats were randomly divided into three groups: control, E2-treated, and sham-treated. Five rats from each group were sacrificed at 2, 4, 6, 12, or 24 h postinjury. Apoptotic neural cells were assessed using the TUNEL method. JNK phosphorylation was detected with immunohistochemistry. Cultured cortical cells were pretreated with E2 and the specific JNK inhibitor SP600125 and then treated with glutamate-induced cytotoxicity in vitro. Neuron viability was determined with an methyl thiazolyl tetrazolium (MTT) assay, morphology of apoptotic cells was observed with 4',6-diamidino-2-phenylindole (DAPI) staining, and JNK phosphorylation was detected using Western blot analysis. Treatment with E2 reduced neuron apoptosis and inhibited JNK phosphorylation. Moreover, the number of apoptotic cells was correlated with JNK phosphorylation 24 h after the rats suffered the SCI. Pretreatment with E2 significantly maintained neural cell viability, attenuated apoptosis, and inhibited JNK phosphorylation induced by glutamate in vitro. These neuroprotective effects of E2 on neural cells were blocked by the co-administration of SP600125. Our results suggest that neuroprotection from E2 is partially mediated by the inhibition of JNK phosphorylation.

Low dose estrogen prevents neuronal degeneration and microglial reactivity in an acute model of spinal cord injury: effect of dosing, route of administration, and therapy delay

Spinal cord injury (SCI), depending on the severity of injury, leads to neurological dysfunction and paralysis. Methylprednisolone, the only currently available therapy renders limited protection in SCI. Therefore, other therapeutic agents must be tested to maximize neuroprotection and functional recovery. Previous data from our laboratory indicate that estrogen (17β-estradiol) at a high dose may attenuate multiple damaging pathways involved in SCI and improve locomotor outcome. Since use of high dose estrogen may have detrimental side effects and therefore may never be used in the clinic, the current study investigated the efficacy of this steroid hormone at very low doses in SCI. In particular, we tested the impact of dosing (1-10 μg/kg), mode of delivery (intravenous vs. osmotic pump), and delay in estrogen application (15 min-4 h post-SCI) on microgliosis and neuronal death in acute SCI in rats. Treatment with 17β-estradiol (1-10 μg/kg) significantly reduced microglial activation and also attenuated apoptosis of neurons compared to untreated SCI animals. The attenuation of cell death and inflammation by estrogen was observed regardless of mode and time of delivery following injury. These findings suggest estrogen as a potential agent for the treatment of individuals with SCI.

Gender issues in multiple sclerosis: an update

Although multiple sclerosis (MS) affects both women and men, women are more susceptible to MS than men. Accumulating evidence indicates that the incidence and prevalence of MS is increasing, more so in women than in men. Owing to pregnancy, differing hormonal states and distinct social roles, the impact of MS differs between women and men. Since Patricia K Coyle published a review on gender issues in MS, multiple studies have added to the body of knowledge. This update will summarize the current thinking on gender-related issues in MS and we will address incidence and prevalence, hormonal factors, pregnancy and breastfeeding, genetics, course and prognosis, imaging, treatment and psychosocial aspects. Future progression within this field will help elucidate the cause of and define the treatment of MS.

Estrogen receptor agonists and estrogen attenuate TNF-α-induced apoptosis in VSC4.1 motoneurons

Tumor necrosis factor-alpha (TNF-α) may cause apoptosis and inflammation in amyotrophic lateral sclerosis (ALS) and spinal cord injury (SCI). Recent studies suggest that estrogen (EST) provides neuroprotection against SCI. We tested whether 1,3,5-tris (4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT) (EST receptor alpha (ERα) agonist), 2,3-bis (4-hydroxyphenyl) propionitrile (DPN) (EST receptor beta (ERβ) agonist), or EST itself would prevent apoptosis in VSC4.1 motoneurons following exposure to TNF-α. Cells were exposed to TNF-α and 15 min later treated with PPT, DPN, or EST. Posttreatment with 50 nM PPT, 50 nM DPN, or 150 nM EST prevented cell death in VSC4.1 motoneurons. Treatment of VSC4.1 motoneurons with PPT, DPN, or EST induced overexpression of ERα, ERβ, or both, which contributed to neuroprotection by upregulating expression of anti-apoptotic proteins (p-AKT, p-CREB, Bcl-2, and p-Src). Our analyses also revealed that EST agonists and EST increased phosphorylation of extracellular signal-regulated kinase (ERK). The L-type Ca(2+) channel inhibitor, nifedipine (10 μM), partially inhibited EST agonist and EST-induced increase in phosphorylated ERK expression. The mitogen-activated protein kinase inhibitor, PD98059 (5 μM), partially prevented ER agonists and EST from providing neuroprotection to TNF-α toxicity. Presence of the nuclear ER antagonist, ICI 182 780 (10 μM), blocked the neuroprotection provided by all three ER agonists tested. Taken together, our data indicate that both ERα and ERβ contribute to PPT, DPN, or EST-mediated neuroprotection with similar signaling profiles. Our data strongly imply that PPT, DPN, or EST can be used as effective neuroprotective agents to attenuate motoneuron death in ALS and SCI.

Sex differences in autoimmune diseases

Women are more susceptible to a variety of autoimmune diseases including systemic lupus erythematosus (SLE), multiple sclerosis (MS), primary biliary cirrhosis, rheumatoid arthritis and Hashimoto's thyroiditis. This increased susceptibility in females compared to males is also present in animal models of autoimmune diseases such as spontaneous SLE in (NZBxNZW)F1 and NZM.2328 mice, experimental autoimmune encephalomyelitis (EAE) in SJL mice, thyroiditis, Sjogren's syndrome in MRL/Mp-lpr/lpr mice and diabetes in non-obese diabetic mice. Indeed, being female confers a greater risk of developing these diseases than any single genetic or environmental risk factor discovered to date. Understanding how the state of being female so profoundly affects autoimmune disease susceptibility would accomplish two major goals. First, it would lead to an insight into the major pathways of disease pathogenesis and, secondly, it would likely lead to novel treatments which would disrupt such pathways.

Neuroprotective effects of tamoxifen on experimental spinal cord injury in rats

The aim of this study was to evaluate the effects of tamoxifen on tumor necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) levels and ultrastructural changes in rats with spinal cord injury. Rats were divided into four groups: control group (laminectomy only), trauma group (laminectomy+spinal trauma), tamoxifen group (laminectomy+spinal trauma+tamoxifen), and vehicle group (laminectomy+spinal trauma+vehicle). Spinal cords were extirpated at the T(7)-T(12) level and tissue samples from the spinal cords were gathered for TNF-alpha and IL-1beta measurements at 1 and 6hours. Spinal cords harvested at 6 hours were evaluated for ultrastructural changes. TNF-alpha and IL-1beta levels at 6 hours were significantly lower in the tamoxifen group than in the trauma group. Electron microscopic examination of tissue from the trauma group revealed gross cell deformities with widespread edema of all structures as well as severe edema in the neuropil. At 6 hours after trauma, these ultrastructural changes were less marked in the tamoxifen group. Our findings support a neuroprotective and restorative role for tamoxifen in the context of secondary pathological biochemical events after SCI.

Postinjury estrogen treatment of chronic spinal cord injury improves locomotor function in rats

Spinal cord injury (SCI) causes loss of neurological function and, depending on serverity, may cause paralysis. The only recommended pharmacotherapy for the treatment of SCI is high-dose methylprednisolone, and its use is controversial. We have previously shown that estrogen treatment attenuated cell death, axonal and myelin damage, calpain and caspase activities, and inflammation in acute SCI. The aim of this study was to examine whether posttreatment of SCI with estrogen would improve locomotor function by protecting cells and axons and reducing inflammation during the chronic phase following injury. Moderately severe injury (40 g . cm force) was induced in male Sprague-Dawley rats following laminectomy at T10. Three groups of animals were used: sham (laminectomy only), vehicle (dimethyl sulfoxide; DMSO)-treated injury group, and estrogen-treated injury group. Animals were treated with 4 mg/kg estrogen at 15 min and 24 hr postnjury, followed by 2 mg/kg estrogen daily for the next 5 days. After treatment, animals were sacrificed at the end of 6 weeks following injury, and 1-cm segments of spinal cord (lesion, rostral to lesion, and caudal to lesion) were removed for biochemical analyses. Estrogen treatment reduced COX-2 activity, blocked nuclear factor-kappaB translocation, prevented glial reactivity, attenuated neuron death, inhibited activation and activity of calpain and caspase-3, decreased axonal damage, reduced myelin loss in the lesion and penumbra, and improved locomotor function compared with vehicle-treated animals. These findings suggest that estrogen may be useful as a promising therapeutic agent for prevention of damage and improvement of locomotor function in chronic SCI. (c) 2010 Wiley-Liss, Inc.

Estrogen treatment in multiple sclerosis

Currently available treatments for multiple sclerosis (MS) reduce inflammatory lesions on MRI and decrease clinical relapses but have limited effects on disability. Novel treatment options that target both the inflammatory as well as the neurodegenerative component of the disease are therefore needed. A growing body of evidence from basic science and clinical studies supports the therapeutic potential of estrogens in MS. Mechanisms of action include both immunomodulatory and directly neuroprotective pathways. A first pilot trial of oral estriol treatment showed encouraging results. There are now several phase II trials underway to further determine the efficacy of estrogen treatment in MS.

Estrogen attenuates glutamate-induced cell death by inhibiting Ca2+ influx through L-type voltage-gated Ca2+ channels

Estrogen-mediated neuroprotection is observed in neurodegenerative disease and neurotrauma models; however, determining a mechanism for these effects has been difficult. We propose that estrogen may limit cell death in the nervous system tissue by inhibiting increases in intracellular free Ca(2+). Here, we present data using VSC 4.1 cell line, a ventral spinal motoneuron and neuroblastoma hybrid cell line. Treatment with 1 mM glutamate for 24 h induced apoptosis. When cells were pre-treated with 100 nM 17beta-estradiol (estrogen) for 1 h and then co-treated with glutamate, apoptotic death was significantly attenuated. Estrogen also prevented glutamate-mediated changes in resting membrane potential and membrane capacitance. Treatment with either 17 alpha-estradiol or cell impermeable estrogen did not mimic the findings seen with estrogen. Glutamate treatment significantly increased both intracellular free Ca(2+) and the activities of downstream proteases such as calpain and caspase-3. Estrogen attenuated both the increases in intracellular free Ca(2+) and protease activities. In order to determine the pathway responsible for estrogen-mediated inhibition of these increases in intracellular free Ca(2+), cells were treated with several Ca(2+) entry inhibitors, but only the L-type Ca(2+) channel blocker nifedipine demonstrated cytoprotective effects comparable to estrogen. To expand these findings, cells were treated with the L-type Ca(2+) channel agonist FPL 64176, which increased both cell death and intracellular free Ca(2+), and estrogen inhibited both effects. From these observations, we conclude that estrogen limits glutamate-induced cell death in VSC 4.1 cells through effects on L-type Ca(2+) channels, inhibiting Ca(2+) influx as well as activation of the pro-apoptotic proteases calpain and caspase-3.

Traumatic spinal cord injury mortality, 1981-1998

BACKGROUND

We aim to assess the long-term trend of and identify risk factors for traumatic spinal cord injury (TSCI) mortality from 1981 through 1998 in the state of South Carolina (SC).

METHODS

We analyzed data from the TSCI surveillance system in SC. Poisson regression analyses were used to examine trends in TSCI mortality rates across subpopulations of interest. Multiple logistic regression was used to identify risk factors for TSCI mortality.

RESULTS

The rate of TSCI mortality was 27.4 per million population between 1981 and 1998. A significant 3% annual decrease in the TSCI mortality rate was found from 1981 through 1998. Specifically, TSCI mortality rates declined the most per year in motor vehicle crashes, males, and whites. Adjusted for covariates, individuals of older ages, black race, with a cervical TSCI, and with a more severe injury, as defined by both Frankel grade and Abbreviated Injury Scale, were associated with higher odds of in-hospital mortality. Females had lower odds of in-hospital mortality than males.

CONCLUSION

Although mortality rate is decreasing, TSCI remains a significant public health problem, with SC having higher rates of TSCI mortality than the United States. The association between gender and in-hospital mortality needs further exploration.

Estrogen and testosterone therapies in multiple sclerosis

It has been known for decades that females are more susceptible than men to inflammatory autoimmune diseases, including multiple sclerosis (MS), rheumatoid arthritis, and psoriasis. In addition, female patients with these diseases experience clinical improvements during pregnancy with a temporary "rebound" exacerbation postpartum. These clinical observations indicate an effect of sex hormones on disease and suggest the potential use of the male hormone testosterone and the pregnancy hormone estriol, respectively, for the treatment of MS. A growing number of studies using the MS animal model experimental autoimmune encephalomyelitis (EAE) support a therapeutic effect of these hormones. Both testosterone and estriol have been found to induce anti-inflammatory as well as neuroprotective effects. Findings from two recent pilot studies of transdermal testosterone in male MS patients and oral estriol in female MS patients are encouraging. In this paper, we review the preclinical and clinical evidence for sex hormone treatments in MS and discuss potential mechanisms of action.

Effect of 17beta-estradiol on signal transduction pathways and secondary damage in experimental spinal cord trauma

Because studies have shown that 17beta-estradiol (E2) produces anti-inflammatory effects after various adverse circulatory conditions, we examined whether administration of E2 before spinal cord injury (SCI) has any salutary effects in reducing SCI. Spinal cord injury was induced by the application of vascular clips (force of 24 g) to the dura via a four-level T5-T8 laminectomy. To gain a better insight into the mechanism of action of the anti-inflammatory effects of E2, the following end points of the inflammatory process were evaluated: (1) spinal cord inflammation and tissue injury (histological score); (2) neutrophil infiltration (myeloperoxidase activity); (3) expression of iNOS, nitrotyrosine, and COX-2; (4) apoptosis (terminal deoxynucleotidyltransferase-mediated UTP end labeling staining and Bax and Bcl-2 expression); and (5) tissue TNF-alpha, IL-6, IL-1beta, and monocyte chemoattractant protein 1 levels. In another set of experiments, the pretreatment or posttreatment with E2 significantly ameliorates the recovery of limb function (evaluated by motor recovery score). To elucidate whether the protective effects of E2 were mediated via the estrogen receptors, we investigated the effect of an estrogen receptor antagonist, ICI 182,780, on the protective effects of E2. ICI 182,780 (500 microg/kg, s.c., 1 h before treatment with E2) significantly antagonized the effect of the E2 and abolished the protective effect against SCI. Taken together, our results clearly demonstrate that administration of E2 before SCI reduces the development of inflammation and tissue injury associated with spinal cord trauma.

More than a decade of estrogen neuroprotection

Considerable evidence has emerged through more than a decade of research supporting the neuroprotective and cognition-preserving effects of estrogens. Such basic research coupled with various epidemiological studies led quickly to the assessment of Premarin for the treatment of mild to moderate Alzheimer's disease (AD), initiated by the Alzheimer's Disease Cooperative Study Group and headed by Dr. Leon Thal. While this and subsequent trials with Premarin (Wyeth Research, Monmouth Junction, New Jersey) and PremPro (Wyeth Research), a conjugated equine estrogen preparation plus medoxyprogresterone acetate, have not supported the use of estrogens in treating advanced AD, considerable inferences have been made from these placebo controlled trials of estrogens. Here, we aimed to put these AD trials of estrogens in perspective by considering the potential mechanisms of these potent neuroprotective estrogens, the role of estrogens in other neurodegenerative conditions, such as cerebral ischemia, and based on our current understanding of estrogen neurobiology, offer insight into the design of future clinical trails of estrogens for neuronal protection.

Differential neuroprotective and antiinflammatory effects of estrogen receptor (ER)alpha and ERbeta ligand treatment

Treatment with either estradiol or an estrogen receptor (ER)alpha ligand has been shown to be both antiinflammatory and neuroprotective in a variety of neurological disease models, but whether neuroprotective effects could be observed in the absence of an antiinflammatory effect has remained unknown. Here, we have contrasted effects of treatment with an ERalpha vs. an ERbeta ligand in experimental autoimmune encephalomyelitis, the multiple sclerosis model with a known pathogenic role for both inflammation and neurodegeneration. Clinically, ERalpha ligand treatment abrogated disease at the onset and throughout the disease course. In contrast, ERbeta ligand treatment had no effect at disease onset but promoted recovery during the chronic phase of the disease. ERalpha ligand treatment was antiinflammatory in the systemic immune system, whereas ERbeta ligand treatment was not. Also, ERalpha ligand treatment reduced CNS inflammation, whereas ERbeta ligand treatment did not. Interestingly, treatment with either the ERalpha or the ERbeta ligand was neuroprotective, as evidenced by reduced demyelination and preservation of axon numbers in white matter, as well as decreased neuronal abnormalities in gray matter. Thus, by using the ERbeta selective ligand, we have dissociated the antiinflammatory effect from the neuroprotective effect of estrogen treatment and have shown that neuroprotective effects of estrogen treatment do not necessarily depend on antiinflammatory properties. Together, these findings suggest that ERbeta ligand treatment should be explored as a potential neuroprotective strategy in multiple sclerosis and other neurodegenerative diseases, particularly because estrogen-related toxicities such as breast and uterine cancer are mediated through ERalpha.

Chondroitinase ABC improves basic and skilled locomotion in spinal cord injured cats

Chondroitin sulfate proteoglycans (CSPGs) are upregulated in the central nervous system following injury. Chondroitin sulfate glycosaminoglycan (CS GAG) side chains substituted on this family of molecules contribute to the limited functional recovery following injury by restricting axonal growth and synaptic plasticity. In the current study, the effects of degrading CS GAGs with Chondroitinase ABC (Ch'ase ABC) in the injured spinal cords of adult cats were assessed. Three groups were evaluated for 5 months following T10 hemisections: lesion-only, lesion+control, and lesion+Ch'ase ABC. Intraspinal control and Ch'ase ABC treatments to the lesion site began immediately after injury and continued every other day, for a total of 15 treatments, using an injectable port system. Delivery and in vivo cleavage were verified anatomically in a subset of cats across the treatment period. Recovery of skilled locomotion (ladder, peg, and beam) was significantly accelerated, on average, by >3 weeks in Ch'ase ABC-treated cats compared to controls. Ch'ase ABC-treated cats also showed greater recovery of specific skilled locomotor features including intralimb movement patterns and significantly greater paw placement onto pegs. Although recovery of basic locomotion (bipedal treadmill and overground) was not accelerated, intralimb movement patterns were more normal in the Ch'ase ABC-treated cats. Qualitative assessment of serotonergic immunoreactivity also suggested that Ch'ase ABC treatment enhanced plasticity. Finally, analyses using fluorophore-assisted carbohydrate electrophoresis (FACE) indicate CS GAG content is similar in cat and human. These findings show, for the first time, that intraspinal cleavage of CS GAGs can enhance recovery of function following spinal cord injury in large animals with sophisticated motor behaviors and axonal growth requirements similar to those encountered in humans.

Gender differences in spinal cord injury are not estrogen-dependent

Recent attention has been given to gender differences in neurotrauma, and the anecdotal suggestion is that females have better outcomes than males, suggesting that circulating levels of estrogen (E(2)) may be neuroprotective. In order to address this issue, both young adult male and ovariectomized female rats were subjected to a T10 spinal cord injury (SCI), and E2 levels were maintained at chronic, constant circulating levels. Animals were clinically evaluated for locomotor changes using the Basso-Beattie-Bresnahan (BBB) scoring system. Morphologic differences were evaluated with unbiased stereology. Data analysis failed to reveal any significant benefit for the E2 therapy in either males or females. We did find a non-estrogen-dependent difference between male and female rats in length of injury, and percent of spared tissue, with female outcomes more favorable. These results suggest that E(2) does not provide a viable therapy following SCI.

Estrogen treatment of spinal cord injury attenuates calpain activation and apoptosis

Spinal cord injury (SCI) is a devastating neurologic injury, and currently, the only recommended pharmacotherapy is high-dose methylprednisolone, which has limited efficacy. Estrogen is a multi-active steroid with anti-oxidant and anti-apoptotic effects. Estrogen may modulate intracellular Ca2+ and prevent inflammation. For this study, male rats were divided into three groups. Sham-group animals received a laminectomy at T12. Injured rats received both laminectomy and 40 gram centimeter force SCI. Estrogen-group rats received 4 mg/kg 17beta-estradiol (estrogen) at 15 min and 24 hr post-injury, and vehicle-group rats received equal volumes of dimethyl sulfoxide. Animals were sacrificed at 48 hr post-injury, and 1-cm segments of the lesion, rostral penumbra, and caudal penumbra were excised. The degradation of 68 kD neurofilament protein (NFP) and estrogen receptors (ER) was examined by Western blot analysis. Protein levels of calpain and the activities of calpain and caspase-3 were also examined. Levels of cytochrome c were determined in both cytosolic and mitochondrial fractions. Cell death with DNA fragmentation was examined using the TUNEL assay. At the lesion, samples from both vehicle and estrogen treated animals showed increased levels of 68 kD NFP degradation, calpain content, calpain activity, cytochrome c release, and degradation of ERalpha and ERbeta, as compared to sham. In the caudal penumbra, estrogen treatment significantly attenuated 68 kD NFP degradation, calpain content, calpain activity, levels of cytosolic cytochrome c, and ERbeta degradation. At the lesion, vehicle-treated animals displayed more TUNEL+ cells, and estrogen treatment significantly attenuated this cell death marker. We conclude that estrogen may inhibit cell death in SCI through calpain inhibition.

Treatment with an estrogen receptor alpha ligand is neuroprotective in experimental autoimmune encephalomyelitis

Multiple sclerosis is an inflammatory, neurodegenerative disease for which experimental autoimmune encephalomyelitis (EAE) is a model. Treatments with estrogens have been shown to decrease the severity of EAE through anti-inflammatory mechanisms. Here we investigated whether treatment with an estrogen receptor alpha (ERalpha) ligand could recapitulate the estrogen-mediated protection in clinical EAE. We then went on to examine both anti-inflammatory and neuroprotective mechanisms. EAE was induced in wild-type, ERalpha-, or ERbeta-deficient mice, and each was treated with the highly selective ERalpha agonist, propyl pyrazole triol, to determine the effect on clinical outcomes, as well as on inflammatory and neurodegenerative changes. ERalpha ligand treatment ameliorated clinical disease in both wild-type and ERbeta knock-out mice, but not in ERalpha knock-out mice, thereby demonstrating that the ERalpha ligand maintained ERalpha selectivity in vivo during disease. ERalpha ligand treatment also induced favorable changes in autoantigen-specific cytokine production in the peripheral immune system [decreased TNFalpha, interferon-gamma, and interleukin-6, with increased interleukin-5] and decreased CNS white matter inflammation and demyelination. Interestingly, decreased neuronal staining [NeuN+ (neuronal-specific nuclear protein)/beta3-tubulin+/Nissl], accompanied by increased immunolabeling of microglial/monocyte (Mac 3+) cells surrounding these abnormal neurons, was observed in gray matter of spinal cords of EAE mice at the earliest stage of clinical disease, 1-2 d after the onset of clinical signs. Treatment with either estradiol or the ERalpha ligand significantly reduced this gray matter pathology. In conclusion, treatment with an ERalpha ligand is highly selective in vivo, mediating both anti-inflammatory and neuroprotective effects in EAE.

Estrogen prevents glutamate-induced apoptosis in C6 glioma cells by a receptor-mediated mechanism

Estrogen-mediated neuroprotection is well established; however, no single mechanism of action for this effect has yet been established. As glial cells are integral for both the intact and injured nervous system, we hypothesized that estrogen-mediated neuroprotection may partly be attributed to attenuation of glial cell apoptosis, allowing them to protect neurons following injury. To assess the protective effects of estrogen on glia, C6 rat glioma cells were treated for 24 h with 500 microM glutamate. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and apoptosis was confirmed by cell morphology and DNA fragmentation. Pretreatment with 10 nM 17beta-estradiol (estrogen) increased cell viability and attenuated apoptosis. Treatment with the stereoisomer 17alpha-estradiol, or estrogen plus estrogen receptor antagonist ICI 182,780, was significantly less effective, indicating that cytoprotection was receptor-mediated. Estrogen treatment upregulated expression of estrogen receptor alpha. Cell impermeable bovine serum albumin-conjugated estrogen was also protective, indicating activation of estrogen receptors on the cell membrane. Intracellular free [Ca2+] was increased after glutamate treatment. This increase was attenuated in cells pretreated with estrogen. Glutamate increased the activity of pro-apoptotic proteases, such as calpain and caspase-3, and these protease activities were significantly attenuated by estrogen. The mechanism by which estrogen decreased intracellular Ca2+ was examined by assaying cell viability after using inhibitors that either blocked extracellular Ca2+ influx or prevented the release of intracellular Ca2+ stores. While several inhibitors increased cell viability in glutamate-treated cells, none were as protective as estrogen, and estrogen co-treatment significantly increased cell viability. These findings indicate that estrogen-mediated cytoprotection may be related to effects on Ca2+ entry but that these effects are not limited to any one of these Ca2+ entry points alone.

Molecular targets in spinal cord injury

The spinal cord can be compared to a highway connecting the brain with the different body levels lying underneath, with the axons being the ultimate carriers of the electrical impulse. After spinal cord injury (SCI), many cells are lost because of the injury. To reconstitute function, damaged axons from surviving neurons have to grow through the lesion site to their initial targets. However, the territory they have to traverse has changed: the highway is full of inhibitory signals (myelin and scar components); the pavement itself has become bumpy (demyelination); and specialized cells are recruited to clear the way (inflammatory cells). Thus, actual strategies to treat spinal injuries aim at providing a permissive environment for regenerating axons and boosting the endogenous potential of axons to regenerate while limiting progression of secondary damage. Here we review some of the strategies currently under consideration to treat spinal injuries.

The effects of gender on clinical and neurological outcomes after acute cervical spinal cord injury

The potential clinical relevance of gender on clinical and neurological outcome after spinal cord injury (SCI) has received little attention. In order to address this issue, we examined all consecutive cases of acute traumatic cervical SCI admitted to our institution from 1998 to 2000. There were 38 males (ages 17-89 years, mean of 51.6) and 17 females (ages 18-84 years, mean of 63.2). Both groups were comparable regarding level (C1 to C7) and severity of SCI (ASIA A to D) at admission. Age differences between the groups approached significance (p = 0.057), and thus this factor was treated as a covariate in the analysis. Co-morbidities were as frequent in men (86.8%) as in women (76.5%). The therapeutic approaches, length-of-stay in the acute care unit, mortality, and discharge disposition were similar in men and women. During hospitalization, 44.7% of men and 52.9% of women developed post-SCI secondary complications without any significant gender-related differences. Both groups showed a similar incidence of infections, cardiovascular complications, thromboembolism, and pressure sores. Univariate analysis revealed a trend for higher incidence of psychiatric complications (p = 0.054) and deep venous thrombosis (p = 0.092) in women, which was confirmed by multivariate analysis. Neurological outcome was not correlated with gender. A similar number of males and females (42.1%, 47.1%) showed evidence of neurological recovery as revealed by an improvement in ASIA scores. Moreover, 18.4% of males and 29.4% of females recovered to ASIA E status. Our data suggest a shift in the demographics of acute SCI with an increasing incidence in elderly women. Although neurological outcomes were not significantly related to gender, we observed a trend for higher rates of reactive depression and deep venous thrombosis in women. These issues may be of key clinical importance in developing improved management protocols for SCI so as to maximize functional recovery and quality-of-life.

Microglia overexpressing the macrophage colony-stimulating factor receptor are neuroprotective in a microglial-hippocampal organotypic coculture system

Microglia with increased expression of the macrophage colony-stimulating factor receptor (M-CSFR; c-fms) are found surrounding plaques in Alzheimer's disease (AD) and in mouse models for AD and after ischemic or traumatic brain injury. Increased expression of M-CSFR causes microglia to adopt an activated state that results in proliferation, release of cytokines, and enhanced phagocytosis. To determine whether M-CSFR-induced microglial activation affects neuronal survival, we assembled a coculture system consisting of BV-2 microglia transfected to overexpress the M-CSFR and hippocampal organotypic slices treated with NMDA. Twenty-four hours after assembly of the coculture, microglia overexpressing M-CSFR proliferated at a higher rate than nontransfected control cells and exhibited enhanced migration toward NMDA-injured hippocampal cultures. Surprisingly, coculture with c-fms-transfected microglia resulted in a dramatic reduction in NMDA-induced neurotoxicity. Similar results were observed when cocultures were treated with the teratogen cyclophosphamide. Biolistic overexpression of M-CSFR on microglia endogenous to the organotypic culture also rescued neurons from excitotoxicity. Furthermore, c-fms-transfected microglia increased neuronal expression of macrophage colony-stimulating factor (M-CSF), the M-CSFR, and neurotrophin receptors in the NMDA-treated slices, as determined with laser capture microdissection. In the coculture system, direct contact between the exogenous microglia and the slice was necessary for neuroprotection. Finally, blocking expression of the M-CSF ligand by exogenous c-fms-transfected microglia with a hammerhead ribozyme compromised their neuroprotective properties. These results demonstrate a protective role for microglia overexpressing M-CSFR in our coculture system and suggest under certain circumstances, activated microglia can help rather than harm neurons subjected to excitotoxic and teratogen-induced injury.

Estrogen attenuated markers of inflammation and decreased lesion volume in acute spinal cord injury in rats

Spinal cord injury (SCI) is a devastating neurologic injury with functional deficits for which the only currently recommended pharmacotherapy is high-dose methylprednisolone, which has limited efficacy. Estrogen is a multi-active steroid that has shown antiinflammatory and antioxidant effects, and estrogen may modulate intracellular Ca(2+) and attenuate apoptosis. For this study, male rats were divided into three groups. Sham group animals received a laminectomy at T12. Injured rats received both laminectomy and 40 g x cm force SCI. Estrogen-group rats received 4 mg/kg 17beta-estradiol (estrogen) at 15 min and 24 hr post-injury, and vehicle-group rats received equal volumes of dimethyl sulfoxide (vehicle). Animals were sacrificed at 48 hr post-injury, and 1-cm-long segments of the lesion, rostral penumbra, and caudal penumbra were excised. Inflammation was assessed by examining tissue edema, infiltration of macrophages/microglia, and levels of cytosolic and nuclear NFkappaB and inhibitor of kappa B (IkappaBalpha). Myelin integrity was examined using Luxol fast blue staining. When compared to sham, vehicle-treated animals revealed increased tissue edema, increased infiltration of inflammatory cells, decreased cytosolic levels of NFkappaB and IkappaBalpha, increased levels of nuclear NFkappaB, and increased myelin loss. Treatment of SCI rats with estrogen reduced edema and decreased inflammation and myelin loss in the lesion and penumbral areas, suggesting its potential as a therapeutic agent. Further work needs to be done, however, to elucidate the neuroprotective mechanism of estrogen.

17beta-estradiol attenuates glutamate-induced apoptosis and preserves electrophysiologic function in primary cortical neurons

Glutamate toxicity causes neuronal death in neurodegenerative diseases; hence, there is a need for therapeutic agents rendering functional neuroprotection. We tested the effects of 17beta-estradiol (estrogen) in rat primary cortical neurons after glutamate exposure. Wright staining and ApopTag assays indicated that 0.5 microM glutamate for 24 hr caused apoptosis. Glutamate-induced apoptosis correlated with upregulation of calpain, a proapoptotic shift in the Bax:Bcl-2 ratio, and increased activation of caspase-3. Pretreatment with 10 nM estrogen prevented apoptosis, attenuated calpain upregulation, shifted the Bax:Bcl-2 ratio toward survival, and decreased caspase-3 activation. Single-cell voltage-clamp techniques were used to record whole-cell currents associated with Na+ channels, N-methyl-D-aspartate receptor channels, and kainate receptor channels. No significant differences were recorded in membrane capacitance at -70 mV in neurons treated with estrogen or estrogen plus glutamate, relative to controls. Notably, no changes in capacitance indicated that neurons treated with estrogen and glutamate did not experience apoptosis-associated cell shrinkage. No membrane potential could be recorded in the neurons treated with glutamate due to apoptosis. All recorded currents were similar in amplitude and activation/inactivation kinetics in control neurons and neurons treated with estrogen plus glutamate. Estrogen thus preserved both neuronal viability and function in this in vitro glutamate toxicity model.