Neuropathological protection after traumatic brain injury in intact female rats versus males or ovariectomized females

Effects of Female Sex Steroids Administration on Pathophysiologic Mechanisms in Traumatic Brain Injury

Secondary brain damage following initial brain damage in traumatic brain injury (TBI) is a major cause of adverse outcomes. There are many gaps in TBI research and a lack of therapy to limit debilitating outcomes in TBI or enhance the neurogenesis, despite pre-clinical and clinical research performed in TBI. Females show harmful outcomes against brain damage including TBI less than males, independent of different TBI occurrence. A significant reduction in secondary brain damage and improvement in neurologic outcome post-TBI has been reported following the use of progesterone and estrogen in many experimental studies. Although useful features of sex steroids including progesterone have been identified in TBI clinical trials I and II, clinical trials III have been unsuccessful. This review article focuses on evidence of secondary injury mechanisms and neuroprotective effects of estrogen and progesterone in TBI. Understanding these mechanisms may enable researchers to achieve greater success in TBI clinical studies. It seems that the design of clinical studies should be revised due to translation loss of animal studies to clinical studies. The heterogeneous and complex nature of TBI, the endogenous levels of sex hormones at the time of taking these hormones, the therapeutic window of the drug, the dosage of the drug, the selection of appropriate targets in evaluation, the determination of responsive population, gender and age based on animal studies should be considered in the design of TBI human studies in future.

Estrogens as neuroprotectants: Estrogenic actions in the context of cognitive aging and brain injury

There is ample empirical evidence to support the notion that the biological impacts of estrogen extend beyond the gonads to other bodily systems, including the brain and behavior. Converging preclinical findings have indicated a neuroprotective role for estrogen in a variety of experimental models of cognitive function and brain insult. However, the surprising null or even detrimental findings of several large clinical trials evaluating the ability of estrogen-containing hormone treatments to protect against age-related brain changes and insults, including cognitive aging and brain injury, led to hesitation by both clinicians and patients in the use of exogenous estrogenic treatments for nervous system outcomes. That estrogen-containing therapies are used by tens of millions of women for a variety of health-related applications across the lifespan has made identifying conditions under which benefits with estrogen treatment will be realized an important public health issue. Here we provide a summary of the biological actions of estrogen and estrogen-containing formulations in the context of aging, cognition, stroke, and traumatic brain injury. We have devoted special attention to highlighting the notion that estrogen appears to be a conditional neuroprotectant whose efficacy is modulated by several interacting factors. By developing criteria standards for desired beneficial peripheral and neuroprotective outcomes among unique patient populations, we can optimize estrogen treatments for attenuating the consequences of, and perhaps even preventing, cognitive aging and brain injury.

New method to induce mild traumatic brain injury in rodents produces differential outcomes in female and male Sprague Dawley rats

BACKGROUND

Mild traumatic brain injuries (mTBI) are an increasing health concern due to persistent behavioral and neurological effects. To better understand these effects, researchers frequently rely on animal injury models. Existing models, however, may not adequately reproduce the mechanism of injury as it occurs in humans.

NEW METHOD

Our new model for inducing mTBI in rodents entails acceleration of the animal toward a stationary impact zone to produce rapid rotational movement of the head. The aim of the present experiment was to characterize the effects of this injury in female and male rats on behavior, cognition, and neural plasticity.

RESULTS

mTBI produced the most widespread effects in females: they were more active during recovery within minutes of mTBI and more active in the center of the open field 4days after mTBI. Spatial learning deficits in the water maze were mild but persistent and accompanied by reduced numbers of immature neurons in the hippocampus along with reductions in sera levels of the neurotrophin, BDNF. By contrast, male mTBI rats mainly exhibited mild spatial learning deficits, with no other observed effects.

COMPARISON WITH EXISTING METHODS

Our model induced effects on behavior and biology in rats that aligned with existing models. However, new patterns were observed, particularly when comparing females and males.

CONCLUSIONS

Taken together, these findings confirm the validity of this model and point to key differences between females and males in symptom severity and type. Additionally, our model adds a novel injury mechanism that complements existing rodent models.

Comparable impediment of cognitive function in female and male rats subsequent to daily administration of haloperidol after traumatic brain injury

Antipsychotic drugs, such as haloperidol (HAL), are prescribed in the clinic to manage traumatic brain injury (TBI)-induced agitation. While preclinical studies have consistently shown that once-daily administration of HAL hinders functional recovery after TBI in male rats, its effects in females are unknown. Hence, the objective of this study was to directly compare neurobehavioral and histological outcomes in both sexes to determine whether the reported deleterious effects of HAL extend to females. Anesthetized adult female and male rats received either a controlled cortical impact (CCI) or sham injury and then were randomly assigned to a dosing regimen of HAL (0.5mg/kg, i.p.) or vehicle (VEH; 1mL/kg, i.p.) that was initiated 24h after injury and continued once daily for 19 consecutive days. Motor function was tested using established beam-balance/walk protocols on post-operative days 1-5 and acquisition of spatial learning was assessed with a well-validated Morris water maze task on days 14-19. Cortical lesion volume was quantified at 21days. No statistical differences were revealed between the HAL and VEH-treated sham groups and thus they were pooled for each sex. HAL only impaired motor recovery in males (p<0.05), but significantly diminished spatial learning in both sexes (p<0.05). Females, regardless of treatment, exhibited smaller cortical lesions vs VEH-treated males (p<0.05). Taken together, the data show that daily HAL does not prohibit motor recovery in females, but does negatively impact cognition. These task-dependent differential effects of HAL in female vs male rats may have clinical significance as they can direct therapy.

Sexual dimorphism in the inflammatory response to traumatic brain injury

The activation of resident microglial cells, alongside the infiltration of peripheral macrophages, are key neuroinflammatory responses to traumatic brain injury (TBI) that are directly associated with neuronal death. Sexual disparities in response to TBI have been previously reported; however it is unclear whether a sex difference exists in neuroinflammatory progression after TBI. We exposed male and female mice to moderate-to-severe controlled cortical impact injury and studied glial cell activation in the acute and chronic stages of TBI using immunofluorescence and in situ hybridization analysis. We found that the sex response was completely divergent up to 7 days postinjury. TBI caused a rapid and pronounced cortical microglia/macrophage activation in male mice with a prominent activated phenotype that produced both pro- (IL-1β and TNFα) and anti-inflammatory (Arg1 and TGFβ) cytokines with a single-phase, sustained peak from 1 to 7 days. In contrast, TBI caused a less robust microglia/macrophage phenotype in females with biphasic pro-inflammatory response peaks at 4 h and 7 days, and a delayed anti-inflammatory mRNA peak at 30 days. We further report that female mice were protected against acute cell loss after TBI, with male mice demonstrating enhanced astrogliosis, neuronal death, and increased lesion volume through 7 days post-TBI. Collectively, these findings indicate that TBI leads to a more aggressive neuroinflammatory profile in male compared with female mice during the acute and subacute phases postinjury. Understanding how sex affects the course of neuroinflammation following brain injury is a vital step toward developing personalized and effective treatments for TBI.

Development of a systems-based in situ multiplex biomarker screening approach for the assessment of immunopathology and neural tissue plasticity in male rats after traumatic brain injury

Traumatic brain injuries (TBIs) pose a massive burden of disease and continue to be a leading cause of morbidity and mortality throughout the world. A major obstacle in developing effective treatments is the lack of comprehensive understanding of the underlying mechanisms that mediate tissue damage and recovery after TBI. As such, our work aims to highlight the development of a novel experimental platform capable of fully characterizing the underlying pathobiology that unfolds after TBI. This platform encompasses an empirically optimized multiplex immunohistochemistry staining and imaging system customized to screen for a myriad of biomarkers required to comprehensively evaluate the extent of neuroinflammation, neural tissue damage, and repair in response to TBI. Herein, we demonstrate that our multiplex biomarker screening platform is capable of evaluating changes in both the topographical location and functional states of resident and infiltrating cell types that play a role in neuropathology after controlled cortical impact injury to the brain in male Sprague-Dawley rats. Our results demonstrate that our multiplex biomarker screening platform lays the groundwork for the comprehensive characterization of changes that occur within the brain after TBI. Such work may ultimately lead to the understanding of the governing pathobiology of TBI, thereby fostering the development of novel therapeutic interventions tailored to produce optimal tissue protection, repair, and/or regeneration with minimal side effects, and may ultimately find utility in a wide variety of other neurological injuries, diseases, and disorders that share components of TBI pathobiology.

Genistein inhibits hypoxia, ischemic-induced death, and apoptosis in PC12 cells

A hypoxia/ischemia neuronal model was established in PC12 cells using oxygen-glucose deprivation (OGD). OGD-induced neuronal death, apoptosis, glutamate receptor subunit GluR2 expression, and potassium channel currents were evaluated in the present study to determine the effects of genistein in mediating the neuronal death and apoptosis induced by hypoxia and ischemia, as well as its underlying mechanism. OGD exposure reduced the cell viability, increased apoptosis, decreased the GluR2 expression, and decreased the voltage-activated potassium currents. Genistein partially reversed the effects induced by OGD. Therefore, genistein may prevent hypoxia/ischemic-induced neuronal apoptosis that is mediated by alterations in GluR2 expression and voltage-activated potassium currents.

Head Injury as a Risk Factor for Dementia and Alzheimer's Disease: A Systematic Review and Meta-Analysis of 32 Observational Studies

BACKGROUND

Head injury is reported to be associated with increased risks of dementia and Alzheimer's disease (AD) in many but not all the epidemiological studies. We conducted a systematic review and meta-analysis to estimate the relative effect of head injury on dementia and AD risks.

METHODS

Relevant cohort and case-control studies published between Jan 1, 1990, and Mar 31, 2015 were searched in PubMed, Web of Science, Scopus, and ScienceDirect. We used the random-effect model in this meta-analysis to take into account heterogeneity among studies.

RESULTS

Data from 32 studies, representing 2,013,197 individuals, 13,866 dementia events and 8,166 AD events, were included in the analysis. Overall, the pooled relative risk (RR) estimates showed that head injury significantly increased the risks of any dementia (RR = 1.63, 95% CI 1.34-1.99) and AD (RR = 1.51, 95% CI 1.26-1.80), with no evidence of publication bias. However, when considering the status of unconsciousness, head injury with loss of consciousness did not show significant association with dementia (RR = 0.92, 95% CI 0.67-1.27) and AD (RR = 1.49, 95% CI 0.91-2.43). Additionally, this positive association did not reach statistical significance in female participants.

CONCLUSIONS

The findings from this meta-analysis indicate that head injury is associated with increased risks of dementia and AD.

Lack of eye discipline during headers in high school girls soccer: A possible mechanism for increased concussion rates

The sport of soccer is the fastest growing and most popular sport worldwide. With this growth and popularity, attention needs to be given to this athletic population. Sports related concussions is a topic that has gained attention both in the media and by governmental organizations, with growing initiatives in diagnosis, prevention and treatment. The act of soccer heading is thought to contribute to increased concussion incidence. Current evidence reveals that within the high school soccer athletic population, female athletes incur a higher concussion rate than males. This is often attributed to many things including differing cervical spinal musculature, skull thickness, etc., but a definitive reason has not yet been found. Other behaviors, such as field awareness and eye discipline™ on the field of play, may also be contributing factors that result in females incurring a greater concussion rate than males. For the purposes of this paper we define eye discipline™ as the ability to keep the eyes engaged in sporting activity with high risk potential. We present our hypothesis that high school female soccer players are more likely to have their eyes closed when in position for heading the ball as compared to high school male soccer players and this lack of visual awareness may increase the risk of concussion. Should these differences be substantiated between males and females, it may initiate and promote discussion of the need for vision training in the high school athletic setting. As a tool for injury prevention, vision training may improve specific visual parameters improving athletes' abilities to process the field of play and prepare for or avoid injury causing situations. Through ocular motor and visual conditioning, an athlete may become more eye disciplined™, and more likely to have their eyes open during heading of the ball, and more likely to avoid concussions.

A heads up on concussions: are there sex-related differences?

Head injuries are a major concern for physicians in athletes of all ages. Specifically, sports-related concussions are becoming an all-too-common injury among female athletes. The incidence of concussions among female athletes has likely increased over the past few decades because of an increase in sports participation afforded by Title IX. It would be useful for physicians to have general knowledge of concussions and their potential sex-related differences. This review article summarizes the current body of research concerning sex-related differences in concussion epidemiology and outcomes. A literature search was performed using PubMed and included all articles published from 1993 to present, with a predominant focus on research conducted over the past fifteen years. Additional articles were found using the bibliography from articles found through the PubMed search. Several articles have compared incidence, severity of neurological deficit, constellation of symptoms, and length of recovery post-concussion in males and females. However, the literature does not unanimously support a significant sex-related difference in concussions. Lack of consensus in the literature can be attributed to differences between patient populations, different tools used to study concussions, including subjective or objective measures, and differences in mechanisms of injury. We conclude that concussions are a serious injury in both male and female athletes, and physicians should have a very high index of suspicion regardless of sex, because there currently is not sufficient consensus in the literature to institute sex-related changes to concussion management. Current research may suggest a sex-related difference pertaining to sports-related concussions, but further evaluation is needed on this topic.

Sex differences in orbitofrontal connectivity in male and female veterans with TBI

More female soldiers are now serving in combat theaters than at any other time. However, little is known about possible sex differences underlying the neuropathology and manifestation of one of modern war’s signature injuries, traumatic brain injury (TBI). The paucity of information regarding sex differences in TBI is particularly evident when examining changes in executive function and emotion regulation associated with post concussive events. The current study objective was to observe whether patterns of orbitofrontal (OFC) functional connectivity would differ between female veterans with TBI and their male counterparts. The study further sought to determine whether OFC connectivity might be differentially associated with clinical measures of aggression and hostility. Seventeen female veterans and 24 male veterans, age 18 to 25, who met criteria for TBI completed resting state magnetic resonance imaging (MRI) and clinical assessment measures. Imaging data were analyzed using left and right seed regions of the OFC, and regression analyses were conducted to observe the relationship between resting state connectivity and self-reported aggression. Females and males in this study differed in OFC connectivity, with females demonstrating greater connectivity between left and right OFC and parietal and occipital regions and males demonstrating greater connectivity between left and right OFC and frontal and temporal regions. Significant associations between resting state connectivity and clinical measures were found only in male veterans. These findings suggest that TBI may interact with sex-specific patterns of brain connectivity in male and female veterans and exert divergent effects on clinical profiles of aggression post-injury.

Genistein improves sensorimotor gating: Mechanisms related to its neuroprotective effects on the striatum

Huntington's disease (HD) is a neurodegenerative disorder, characterized by selective atrophy in the striatum, particularly the medium spiny GABAergic efferent neurons. This results in striatal sensorimotor gating deficits. Systemic administration of 3-nitropropionic acid (3-NPA) produces selective lesions mimicking those of HD. Males were found to be more susceptible to 3-NPA-induced neurotoxicity than females, suggesting neuroprotective effects of estrogens. Phytoestrogens, including genistein, are good estrogenic alternatives that keep their beneficial effects on non-reproductive organs and lack the potential hazardous side effects. The current study was designed to investigate the potential beneficial effects of genistein in 3-NPA-induced HD in ovariectomized rats. Results showed that 3-NPA (20 mg/kg) administration caused significant disruption of the rats' locomotor activity and prepulse inhibition. In addition, it decreased striatal ATP levels and increased oxidative stress, inflammatory and apoptotic markers with striatal focal hemorrhage and gliosis. Pretreatment with 17β-estradiol (2.5 mg/kg) or genistein (20 mg/kg) led to a significant improvement of behavioral parameters, increased ATP production, decreased oxidative stress, attenuated inflammation and apoptosis. Therefore, this study suggests potential neuroprotective effects of genistein in ovariectomized rats challenged with 3-NPA.

Development and application of cognitive-pragmatic language ability assessment protocol for traumatic brain injury

The study aim was to introduce a newly-developed multifaceted cognitive-pragmatic language assessment protocol. This study was also designed to assess the reliability and validity of the assessment protocol in the discrimination between mild traumatic brain injury (mTBI) and normal control. Individuals in this study were 25 to 64 years old. Ten mTBIs and twenty-two control group were recruited for the preliminary study. Their mean ages were 45.20 and 41.23, respectively. For the main study, we recruited 39 mTBIs and 100 healthy individuals whose mean ages were 44.67 and 40.84, respectively. The newly-developed protocol was completed through a systematic review based on an item analysis. We administered the CAPTBI based on nine domains, 22 subcategories, and 57 items. All nine domains of the CAPTBI were found to be significant variables by which mTBI individuals can be distinguished from normal individuals (p < .001). We also presented the cut-off points by education level to maximize the validity of differentiating the two groups. This study is the first attempt to evaluate mTBI by means of the cognitive-linguistic protocol with multiple domains. The CAPTBI is an appropriate tool for differentiating the cognitive-pragmatic language abilities between mTBI and control group.

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.

Does being female provide a neuroprotective advantage following spinal cord injury?

It has been controversial whether gender has any effect on recovery following spinal cord injury (SCI). Past experimental and clinical research aimed at addressing this subject has led to constrasting findings on whether females hold any advantage in locomotor recovery. Additionally, for studies supporting the notion of a female gender related advantage, a definite cause has not been explained. In a recent study, using large sample sizes for comparative male and female spinal cord injury cohorts, we reported that a significant gender advantage favoring females existed in both tissue preservation and functional recovery after taking into consideration discrepancies in age and weight of the animals across sexes. Prior animal research frequently used sample sizes that were too small to determine significance with certainty and also did not account for two other factors that influence locomotor performance: age and weight. Our finding is important in light of controversy surrounding the effect of gender on outcome and the fact that SCI affects more than ten thousand new individuals annually, a population that is disproportionately male. By deepening our understanding of why a gender advantage exists, potential new therapeutics can be designed to improve recovery for the male population following the initial trauma or putatively augment the neuroprotective privilege in females for enhanced outcomes.

Modeling Chronic Traumatic Encephalopathy: The Way Forward for Future Discovery

Despite the extensive media coverage associated with the diagnosis of chronic traumatic encephalopathy (CTE), our fundamental understanding of the disease pathophysiology remains in its infancy. Only recently have scientific laboratories and personnel begun to explore CTE pathophysiology through the use of preclinical models of neurotrauma. Some studies have shown the ability to recapitulate some aspects of CTE in rodent models, through the use of various neuropathological, biochemical, and/or behavioral assays. Many questions related to CTE development, however, remain unanswered. These include the role of impact severity, the time interval between impacts, the age at which impacts occur, and the total number of impacts sustained. Other important variables such as the location of impacts, character of impacts, and effect of environment/lifestyle and genetics also warrant further study. In this work, we attempt to address some of these questions by exploring work previously completed using single- and repetitive-injury paradigms. Despite some models producing some deficits similar to CTE symptoms, it is clear that further studies are required to understand the development of neuropathological and neurobehavioral features consistent with CTE-like features in rodents. Specifically, acute and chronic studies are needed that characterize the development of tau-based pathology.

Performance of Male and Female C57BL/6J Mice on Motor and Cognitive Tasks Commonly Used in Pre-Clinical Traumatic Brain Injury Research

To date, clinical trials have failed to find an effective therapy for victims of traumatic brain injury (TBI) who live with motor, cognitive, and psychiatric complaints. Pre-clinical investigators are now encouraged to include male and female subjects in all translational research, which is of particular interest in the field of neurotrauma given that circulating female hormones (progesterone and estrogen) have been demonstrated to exert neuroprotective effects. To determine whether behavior of male and female C57BL6/J mice is differentially impaired by TBI, male and cycling female mice were injured by controlled cortical impact and tested for several weeks with functional assessments commonly employed in pre-clinical research. We found that cognitive and motor impairments post-TBI, as measured by the Morris water maze (MWM) and rotarod, respectively, were largely equivalent in male and female animals. However, spatial working memory, assessed by the y-maze, was poorer in female mice. Female mice were generally more active, as evidenced by greater distance traveled in the first exposure to the open field, greater distance in the y-maze, and faster swimming speeds in the MWM. Statistical analysis showed that variability in all behavioral data was no greater in cycling female mice than it was in male mice. These data all suggest that with careful selection of tests, procedures, and measurements, both sexes can be included in translational TBI research without concern for effect of hormones on functional impairments or behavioral variability.

Biomechanics of head impacts associated with diagnosed concussion in female collegiate ice hockey players

Epidemiological evidence suggests that female athletes may be at a greater risk of concussion than their male counterparts. The purpose of this study was to examine the biomechanics of head impacts associated with diagnosed concussions in a cohort of female collegiate ice hockey players. Instrumented helmets were worn by 58 female ice hockey players from 2 NCAA programs over a three year period. Kinematic measures of single impacts associated with diagnosed concussion and head impact exposure on days with and without diagnosed concussion were evaluated. Nine concussions were diagnosed. Head impact exposure was greater in frequency and magnitude on days of diagnosed concussions than on days without diagnosed concussion for individual athletes. Peak linear accelerations of head impacts associated with diagnosed concussion in this study are substantially lower than those previously reported in male athletes, while peak rotational accelerations are comparable. Further research is warranted to determine the extent to which female athletes' biomechanical tolerance to concussion injuries differs from males.

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.

Combining Enriched Environment, Progesterone, and Embryonic Neural Stem Cell Therapy Improves Recovery after Brain Injury

Millions of persons every year are affected by traumatic brain injury (TBI), and currently no therapies have shown efficacy in improving outcomes clinically. Recent research has suggested that enriched environments (EE), embryonic neural stem cells (eNSC), and progesterone (PROG) improve functional outcomes after TBI, and further, several investigators have suggested that a polytherapuetic approach may have greater efficacy than a single therapy. The purpose of the current study was to determine if varying combinations of post-injury EE, progesterone therapy, or eNSC transplantation would improve functional outcomes over just a single therapy. A controlled cortical impact was performed in rats to create a lesion in the medial frontal cortex. The rats were then placed in either EE or standard environments and administered 10 mg/kg progesterone or vehicle injections 4 h post-injury and every 12 h for 72 h after the initial injection. Seven days after the surgery, rats were transplanted with either eNSCs or media. Rats were then tested on the open field test, Barnes maze, Morris water maze, and Rotor-Rod tasks. Improved functional outcomes were shown on a majority of the behavioral tasks in animals that received a combination of therapies. This effect was especially prominent with therapies that were combined with EE. Immunohistochemistry showed that the transplanted eNSCs survived, migrated, and displayed neural phenotypes. These data suggest that a poly-therapeutic approach after TBI improves functional recovery to a greater magnitude. Moreover, when polytherapies are combined with EE, the effects on recovery are enhanced, leading to greater recovery of function.

Progesterone for neuroprotection in pediatric traumatic brain injury

OBJECTIVE

To provide an overview of the preclinical literature on progesterone for neuroprotection after traumatic brain injury and to describe unique features of developmental brain injury that should be considered when evaluating the therapeutic potential for progesterone treatment after pediatric traumatic brain injury.

DATA SOURCES

National Library of Medicine PubMed literature review.

STUDY SELECTION

The mechanisms of neuroprotection by progesterone are reviewed, and the preclinical literature using progesterone treatment in adult animal models of traumatic brain injury is summarized. Unique features of the developing brain that could either enhance or limit the efficacy of neuroprotection by progesterone are discussed, and the limited preclinical literature using progesterone after acute injury to the developing brain is described. Finally, the current status of clinical trials of progesterone for adult traumatic brain injury is reviewed.

DATA EXTRACTION AND DATA SYNTHESIS

Progesterone is a pleiotropic agent with beneficial effects on secondary injury cascades that occur after traumatic brain injury, including cerebral edema, neuroinflammation, oxidative stress, and excitotoxicity. More than 40 studies have used progesterone for treatment after traumatic brain injury in adult animal models, with results summarized in tabular form. However, very few studies have evaluated progesterone in pediatric animal models of brain injury. To date, two human phase II trials of progesterone for adult traumatic brain injury have been published, and two multicenter phase III trials are underway.

CONCLUSIONS

The unique features of the developing brain from that of a mature adult brain make it necessary to independently study progesterone in clinically relevant, immature animal models of traumatic brain injury. Additional preclinical studies could lead to the development of a novel neuroprotective therapy that could reduce the long-term disability in head-injured children and could potentially provide benefit in other forms of pediatric brain injury (global ischemia, stroke, and statue epilepticus).

Regulation of brain microglia by female gonadal steroids

Microglial cells are the primary mediators of the CNS immune defense system and crucial for shaping inflammatory responses. They represent a highly dynamic cell population which is constantly moving and surveying their environment. Acute brain damage causes a local attraction and activation of this immune cell type which involves neuron-to-glia and glia-to-glia interactions. The prevailing view attributes microglia a "negative" role such as defense and debris elimination. More topical studies also suggest a protective and "positive" regulatory function. Estrogens and progestins exert anti-inflammatory and neuroprotective effects in the CNS in acute and chronic brain diseases. Recent work revealed that microglial cells express subsets of classical and non-classical estrogen and progesterone receptors in a highly dynamic way. In this review article, we would like to stress the importance of microglia for the spreading of neural damage during hypoxia, their susceptibility to functional modulation by sex steroids, the potency of sex hormones to switch microglia from a pro-inflammatory M1 to neuroprotective M2 phenotype, and the regulation of pro- and anti-inflammatory properties including the inflammasome. We will further discuss the possibility that the neuroprotective action of sex steroids in the brain involves an early and direct modulation of local microglia cell function. This article is part of a Special Issue entitled 'Sex steroids and brain disorders'.

Progesterone protects mitochondrial function in a rat model of pediatric traumatic brain injury

Progesterone has been studied extensively in preclinical models of adult traumatic brain injury (TBI), and has advanced to clinical trials in adults with TBI. However, there are very few preclinical studies in pediatric TBI models investigating progesterone for neuroprotection. Immature male and female rats (postnatal day, PND 17-21) underwent controlled cortical impact (CCI) to the left parietal cortex. Rats received either progesterone (10 mg/kg) at 1 h (i.p.) and 6 h (s.c.) after TBI or vehicle (22.5 % cyclohexdrin), and were compared to naïve, age-matched littermates. At 24 h after CCI, brain mitochondria were isolated from the ipsilateral hemisphere. Active (State 3) and resting (State 4) mitochondrial respiration were measured, and mitochondrial respiratory control ratio (RCR, State 3/State 4) was determined. Total mitochonidral glutathione content was measured. A separate group of rats were studied for histology, and received progesterone or vehicle every 24 h (s.c.) for 7 days. In male rats, TBI reduced mitochondrial RCR, and progesterone preserved mitochondrial RCR. This improvement of RCR was predominantly through significant decreases in State 4 respiratory rates. In female rats, post-injury treatment with progesterone did not significantly improve mitochondrial RCR. Normal (uninjured) male rats had lower mitochondrial glutathione content than normal female rats. After TBI, progesterone prevented loss of mitochondrial glutathione in male rats only. Tissue loss was reduced in progesterone treated female rats at 7d after CCI. Future studies will be directed at correlation with neurologic outcome testing. These preclinical studies could provide information for planning future clinical trials of progesterone treatment in children with TBI.

Complications of trauma patients admitted to the ICU in level I academic trauma centers in the United States

BACKGROUND

The aims of this study were to evaluate the complications that occur after trauma and the characteristics of individuals who develop complications, to identify potential risk factors that increase their incidence, and finally to investigate the relationship between complications and mortality.

METHODS

We did a population-based retrospective study of trauma patients admitted to ICUs of a level I trauma center. Logistic regression analyses were performed to determine independent predictors for complications.

RESULTS

Of the 11,064 patients studied, 3,451 trauma patients developed complications (31.2%). Complications occurred significantly more in younger male patients. Length of stay was correlated with the number of complications (R = 0.435, P < 0.0001). The overall death rate did not differ between patients with or without complications. The adjusted odds ratio (OR) of developing complication for patients over age 75 versus young adults was 0.7 (P < 0.0001). Among males, traumatic central nervous system (CNS) injury was an important predictor for complications (adjusted OR 1.24).

CONCLUSIONS

Complications after trauma were found to be associated with age, gender, and traumatic CNS injury. Although these are not modifiable factors, they may identify subjects at high risk for the development of complications, allowing for preemptive strategies for prevention.

Mouse model of intrauterine inflammation: sex-specific differences in long-term neurologic and immune sequelae

Preterm infants, especially those that are exposed to prenatal intrauterine infection or inflammation, are at a major risk for adverse neurological outcomes, including cognitive, motor and behavioral disabilities. We have previously shown in a mouse model that there is an acute fetal brain insult associated with intrauterine inflammation. The objectives of this study were: (1) to elucidate long-term (into adolescence and adulthood) neurological outcomes by assessing neurobehavioral development, MRI, immunohistochemistry and flow cytometry of cells of immune origin and (2) to determine whether there are any sex-specific differences in brain development associated with intrauterine inflammation. Our results have shown that prenatal exposure appeared to lead to changes in MRI and behavior patterns throughout the neonatal period and during adulthood. Furthermore, we observed chronic brain inflammation in the offspring, with persistence of microglial activation and increased numbers of macrophages in the brain, ultimately resulting in neuronal loss. Moreover, our study highlights the sex-specific differences in long-term sequelae. This study, while extending the growing literature of adverse neurologic outcomes following exposure to inflammation during early development, presents novel findings in the context of intrauterine inflammation.

Macrophagic and microglial responses after focal traumatic brain injury in the female rat

BACKGROUND

After central nervous system injury, inflammatory macrophages (M1) predominate over anti-inflammatory macrophages (M2). The temporal profile of M1/M2 phenotypes in macrophages and microglia after traumatic brain injury (TBI) in rats is unknown. We subjected female rats to severe controlled cortical impact (CCI) and examined the postinjury M1/M2 time course in their brains.

METHODS

The motor cortex (2.5 mm left laterally and 1.0 mm anteriorly from the bregma) of anesthetized female Wistar rats (ages 8 to 10 weeks; N = 72) underwent histologically moderate to severe CCI with a 5-mm impactor tip. Separate cohorts of rats had their brains dissociated into cells for flow cytometry, perfusion-fixed for immunohistochemistry (IHC) and ex vivo magnetic resonance imaging or flash-frozen for RNA and protein analysis. For each analytical method used, separate postinjury times were included for 24 hours; 3 or 5 days; or 1, 2, 4 or 8 weeks.

RESULTS

By IHC, we found that the macrophagic and microglial responses peaked at 5 to 7 days post-TBI with characteristics of mixed populations of M1 and M2 phenotypes. Upon flow cytometry examination of immunological cells isolated from brain tissue, we observed that peak M2-associated staining occurred at 5 days post-TBI. Chemokine analysis by multiplex assay showed statistically significant increases in macrophage inflammatory protein 1α and keratinocyte chemoattractant/growth-related oncogene on the ipsilateral side within the first 24 hours after injury relative to controls and to the contralateral side. Quantitative RT-PCR analysis demonstrated expression of both M1- and M2-associated markers, which peaked at 5 days post-TBI.

CONCLUSIONS

The responses of macrophagic and microglial cells to histologically severe CCI in the female rat are maximal between days 3 and 7 postinjury. The response to injury is a mixture of M1 and M2 phenotypes.

Continual naringin treatment benefits the recovery of traumatic brain injury in rats through reducing oxidative and inflammatory alterations

Naringin is neuroprotective in ischemia and other disease models. However, the effects of naringin are unknown after traumatic brain injury (TBI). The present study explored the role of naringin for neuroprotection in TBI rats. TBI was performed with the weight drop technique, and naringin was given orally at a dose of 100 mg/kg/day. The neurological scores, tissue edema, and oxidative stress/inflammation parameters [malondialdehyde (MDA), superoxide dismutase, nitric oxide, inducible nitric oxide synthase (iNOS), as well as interleukin-1β (IL-1β)] were measured. Compared to sham controls, TBI rats displayed obvious sensorimotor dysfunction, significant brain edema, and elevated oxidative and inflammatory molecules. Although a 7-day pre-treatment of naringin was unable to reverse these pathological changes, a 14-day continual treatment (7 days before and 7 days after the TBI) attenuated the increases in MDA and nitric oxide; enhanced the activation of superoxide dismutase; depressed the over-activation of iNOS; down-regulated the over-expression of IL-1β; and reduced the cortex edema. Additionally, the TBI-induced behavioral dysfunction was reduced. These results suggest that naringin treatment can attenuate cellular and histopathological alterations and improve the sensorimotor dysfunction of TBI rats, which may be partly due to the attenuation of oxidative and inflammatory damages.

17β-estradiol confers protection after traumatic brain injury in the rat and involves activation of G protein-coupled estrogen receptor 1

Abstract Traumatic brain injury (TBI) is a significant public health problem in the United States. Despite preclinical success of various drugs, to date all clinical trials investigating potential therapeutics have failed. Recently, sex steroid hormones have sparked interest as possible neuroprotective agents after traumatic injury. One of these is 17β-estradiol (E2), the most abundant and potent endogenous vertebrate estrogen. The goal of our study was to investigate the acute potential protective effects of E2 or the specific G protein-coupled estrogen receptor 1 (GPER) agonist G-1 when administered in an intravenous bolus dose 1 hour post-injury in the lateral fluid percussion (LFP) rodent model of TBI. The results of this study show that, when assessed at 24 hours post-injury, E2 or G-1 confers protection in adult male rats subjected to LFP brain injury. Specifically, we found that an acute bolus dose of E2 or G-1 administered intravenously 1 hour post-TBI significantly increases neuronal survival in the ipsilateral CA 2/3 region of the hippocampus and decreases neuronal degeneration and apoptotic cell death in both the ipsilateral cortex and CA 2/3 region of the hippocampus. We also report a significant reduction in astrogliosis in the ipsilateral cortex, hilus, and CA 2/3 region of the hippocampus. Finally, these effects were observed to be chiefly dose-dependent for E2, with the 5 mg/kg dose generating a more robust level of protection. Our findings further elucidate estrogenic compounds as a clinically relevant pharmacotherapeutic strategy for treatment of secondary injury following TBI, and intriguingly, reveal a novel potential therapeutic target in GPER.

Progesterone's role in neuroprotection, a review of the evidence

The sex hormone progesterone has been shown to improve outcomes in animal models of a number of neurologic diseases, including traumatic brain injury, ischemia, spinal cord injury, peripheral nerve injury, demyelinating disease, neuromuscular disorders, and seizures. Evidence suggests it exerts its neuroprotective effects through several pathways, including reducing edema, improving neuronal survival, and modulating inflammation and apoptosis. In this review, we summarize the functional outcomes and pathophysiologic mechanisms attributed to progesterone treatment in neurologic disease. We then comment on the breadth of evidence for the use of progesterone in each neurologic disease family. Finally, we provide support for further human studies using progesterone to treat several neurologic diseases.

The evolution of traumatic brain injury in a rat focal contusion model

Serial MRI facilitates the in vivo analysis of the intra- and intersubject evolution of traumatic brain injury lesions. Despite the availability of MRI, the natural history of experimental focal contusion lesions in the controlled cortical impact (CCI) rat model has not been well described. We performed CCI on rats and MRI during the acute to chronic stages of cerebral injury to investigate the time course of changes in the brain. Female Wistar rats underwent CCI of their left motor cortex with a flat impact tip driven by an electromagnetic piston. In vivo MRI was performed at 7 T serially over 6 weeks post-CCI. The appearances of CCI-induced lesions and lesion-associated cortical volumes were variable on MRI, with the percentage change in cortical volume of the CCI ipsilateral side relative to the contralateral side ranging from 18% within 2 h of injury on day 0 to a peak of 35% on day 1, and a trough of -28% by week 5/6, with an average standard deviation of ± 14% at any given time point. In contrast, the percentage change in cortical volume of the ipsilateral side relative to the contralateral side in control rats was not significant (1 ± 2%). Hemorrhagic conversion within and surrounding the CCI lesion occurred between days 2 and 9 in 45% of rats, with no hemorrhage noted on the initial scan. Furthermore, hemorrhage and hemosiderin within the lesion were positive for Prussian blue and highly autofluorescent on histological examination. Although some variation in injuries may be technique related, the divergence of similar lesions between initial and final scans demonstrates the inherent biological variability of the CCI rat model.

Effect of gender on recovery after spinal cord injury

Spinal cord injury (SCI) is a debilitating condition that affects thousands of new individuals each year, the majority of which are males. Males with SCI tend to be injured at an earlier age, mostly during sports or motor vehicle accidents, whereas females tend be injured later in life, particularly in the age group 65 and older. In both experimental and clinical studies, the question as to whether gender affects outcome has been addressed in a variety of patient groups and animal models. Results from experimental paradigms have suggested that a gender bias in outcome exists that favors females and appears to involve the advantageous or disadvantageous effects of the gonadal sex hormones estrogen and progesterone or testosterone, respectively. However, other studies have shown an absence of gender differences in outcome in specific SCI models and work has also questioned the involvement of female sex hormones in the observed outcome improvements in females. Similar controversy exists clinically, in studies that have examined gender disparities in outcome after SCI. The current review examines the experimental and clinical evidence for a gender bias in outcome following SCI and discusses issues that have made it difficult to conclusively answer this question.

Environmental enrichment promotes robust functional and histological benefits in female rats after controlled cortical impact injury

Environmental enrichment (EE) consistently induces marked benefits in male rats after traumatic brain injury (TBI), but whether similar efficacy extends to females is not well established. Hence, the aim of this study was to reassess the effect of EE on functional and histological outcome in female rats after brain trauma. Twenty-four normal cycling adult female rats underwent verification of estrous stage prior to controlled cortical impact (CCI) or sham injury and then were assigned to EE or standard (STD) housing. Motor function was assessed with beam-balance/beam-walk and rotarod tasks on post-operative days 1-5 and every other day from 1-19, respectively. Spatial learning/memory was evaluated in a Morris water maze on days 14-19. Morphologically intact hippocampal CA(1/3) cells and cortical lesion volume were quantified 3 weeks after injury. No differences were observed between the EE and STD sham groups in any endpoint measure and thus the data were pooled. In the TBI groups, EE improved beam-balance, beam-walk, rotarod, and spatial learning performance vs. STD (p's<0.05). EE also provided significant histological protection as confirmed by increased CA(1/3) cell survival and decreased cortical lesion size vs. STD. These data demonstrate that EE confers robust benefits in female rats after CCI injury, which parallels numerous studies in males and lends further credence for EE as a preclinical model of neurorehabilitation.

Sports Neuropsychology With Diverse Athlete Populations: Contemporary Findings and Special Considerations

This paper aims to familiarize readers with the contemporary scientific literature available on sports concussion as it relates to populations divergent from adult males who play football and hockey. Herein, we focus on important issues such as age, gender, culture, language, sport type, and premorbid conditions (such as learning disabilities [LD] and attention deficit/hyperactive disorder [ADHD]) that can influence concussion incidence, severity, and recovery.

Gender-specific differences in the central nervous system's response to anesthesia

Males and females are physiologically distinct in their responses to various anesthetic agents. The brain and central nervous system (CNS), the main target of anesthesia, are sexually dimorphic from birth and continue to differentiate throughout life. Accordingly, gender has a substantial impact on the influence of various anesthetic agents in the brain and CNS. Given the vast differences in the male and female CNS, it is surprising to find that females are often excluded from basic and clinical research studies of anesthesia. In animal research, males are typically studied to avoid the complication of breeding, pregnancy, and hormonal changes in females. In clinical studies, females are also excluded for the variations that occur in the reproductive cycle. Being that approximately half of the surgical population is female, the exclusion of females in anesthesia-related research studies leaves a huge knowledge gap in the literature. In this review, we examine the reported sex-specific differences in the central nervous system's response to anesthesia. Furthermore, we suggest that anesthesia researchers perform experiments on both sexes to further evaluate such differences. We believe a key goal of research studying the interaction of the brain and anesthesia should include the search for knowledge of sex-specific mechanisms that will improve anesthetic care and management in both sexes.

Animal modelling of traumatic brain injury in preclinical drug development: where do we go from here?

Traumatic brain injury (TBI) is the leading cause of death and disability in young adults. Survivors of TBI frequently suffer from long-term personality changes and deficits in cognitive and motor performance, urgently calling for novel pharmacological treatment options. To date, all clinical trials evaluating neuroprotective compounds have failed in demonstrating clinical efficacy in cohorts of severely injured TBI patients. The purpose of the present review is to describe the utility of animal models of TBI for preclinical evaluation of pharmacological compounds. No single animal model can adequately mimic all aspects of human TBI owing to the heterogeneity of clinical TBI. To successfully develop compounds for clinical TBI, a thorough evaluation in several TBI models and injury severities is crucial. Additionally, brain pharmacokinetics and the time window must be carefully evaluated. Although the search for a single-compound, 'silver bullet' therapy is ongoing, a combination of drugs targeting various aspects of neuroprotection, neuroinflammation and regeneration may be needed. In summary, finding drugs and prove clinical efficacy in TBI is a major challenge ahead for the research community and the drug industry. For a successful translation of basic science knowledge to the clinic to occur we believe that a further refinement of animal models and functional outcome methods is important. In the clinical setting, improved patient classification, more homogenous patient cohorts in clinical trials, standardized treatment strategies, improved central nervous system drug delivery systems and monitoring of target drug levels and drug effects is warranted.

Sex differences in concussion symptoms of high school athletes

CONTEXT

More than 1.6 million sport-related concussions occur every year in the United States, affecting greater than 5% of all high school athletes who participate in contact sports. As more females participate in sports, understanding possible differences in concussion symptoms between sexes becomes more important.

OBJECTIVE

To compare symptoms, symptom resolution time, and time to return to sport between males and females with sport-related concussions.

DESIGN

Descriptive epidemiology study.

SETTING

Data were collected from 100 high schools via High School RIO (Reporting Information Online).

PATIENTS OR OTHER PARTICIPANTS

Athletes from participating schools who sustained concussions while involved in interscholastic sports practice or competition in 9 sports (boys' football, soccer, basketball, wrestling, and baseball and girls' soccer, volleyball, basketball, and softball) during the 2005-2006 and 2006-2007 school years. A total of 812 sport concussions were reported (610 males, 202 females).

MAIN OUTCOME MEASURE(S)

Reported symptoms, symptom resolution time, and return-to-play time.

RESULTS

No difference was found between the number of symptoms reported (P  =  .30). However, a difference was seen in the types of symptoms reported. In year 1, males reported amnesia (exact P  =  .03) and confusion/disorientation (exact P  =  .04) more frequently than did females. In year 2, males reported more amnesia (exact P  =  .002) and confusion/disorientation (exact P  =  .002) than did females, whereas females reported more drowsiness (exact P  =  .02) and sensitivity to noise (exact P  =  .002) than did males. No differences were observed for symptom resolution time (P  =  .40) or return-to-play time (P  =  .43) between sexes.

CONCLUSIONS

The types of symptoms reported differed between sexes after sport-related concussion, but symptom resolution time and return-to-play timelines were similar.

Progesterone, administered before kainic acid, prevents decrements in cognitive performance in the Morris Water Maze

The nature of progesterone (P₄)'s neuroprotective effects is of interest. We investigated effects of P₄ when administered before, or after, kainic acid, which produces ictal activity and damage to the hippocampus, to mediate effects on spatial performance. The hypothesis was that P₄, compared with vehicle, would reduce decrements in Morris Water Maze performance induced by kainic acid. Experiment 1: We examined the effects of kainic acid on plasma stress hormone, corticosterone, and progestogen (P₄ and its metabolites) levels in plasma and the hippocampus after subcutaneous (s.c.) P₄ administration to ovariectomized rats. Rats administered kainic acid had the highest corticosterone levels immediately following injection. P₄ is 5α-reduced to dihydroprogesterone (DHP) and subsequently metabolized to 5α-pregnan-3α-ol-20-one (3α,5α-THP) by 3α-hydroxysteroid dehydrogenase. The regimen of P₄ used produced circulating and hippocampal levels of P₄, DHP, and 3α,5α-THP within a physiological range, which declined at 14 hours postinjection and were not altered by kainic acid. Experiment 2: The physiological P₄ regimen was administered to rats before, or after, kainic acid-induced seizures, and later effects on water maze performance were compared with that of rats administered vehicle. Rats administered kainic acid had significantly poorer performance in the water maze (i.e., increased latencies and distances to the hidden platform) than did rats administered vehicle. Administration of P₄ before, but not after, kainic acid prevented these performance deficits. Thus, these data suggest that a physiological regimen of P₄ can prevent some of the deficits in water maze performance produced by kainic acid.

Sex shapes experimental ischemic brain injury

Biologic sex and sex steroids are important factors in clinical and experimental stroke. This review evaluates key evidence that biological sex strongly alters mechanisms and outcomes from cerebral ischemia. The role of androgens in male stroke is understudied and important to pursue given that male sex is a well known risk factor for human stroke. To date, male sex steroids remain largely evaluated at the bench rather than the bedside. We review recent advances in our understanding of androgens in the context of ischemic cell death and neuroprotection. We also highlight some possible molecular mechanisms by which androgens impact ischemic outcomes.

Resveratrol attenuates behavioral impairments and reduces cortical and hippocampal loss in a rat controlled cortical impact model of traumatic brain injury

Resveratrol (3,5,4'-trihydroxystilbene) is a plant-derived small molecule that is protective against multiple neurological and systemic insults. To date, no studies have explored the potential for resveratrol to provide behavioral protection in adult animals in the setting of traumatic brain injury (TBI). Using 50 male Sprague-Dawley rats, we employed the controlled cortical impact (CCI) model to ascertain whether post-injury administration of resveratrol would reduce the severity of the well-described cognitive and motor deficits associated with the model. Contusion volumes and hippocampal neuronal numbers were also measured to characterize the tissue and neuronal-sparing properties, respectively, of resveratrol. We found that 100 mg/kg, but not 10 mg/kg, of intraperitoneal resveratrol administered after injury provides significant behavioral protection in rats sustaining CCI. Specifically, rodents treated with 100 mg/kg of resveratrol showed improvements in motor performance (beam balance and beam walking) and testing of visuospatial memory (Morris water maze). Behavioral protection was correlated with significantly reduced contusion volumes, preservation of CA1 and CA3 hippocampal neurons, and protection from overt hippocampal loss as a result of incorporation into the overlying cortical contusion in resveratrol-treated animals. Although the mechanisms by which resveratrol mediates its neuroprotection is unclear, the current study adds to the growing literature identifying resveratrol as a potential therapy for human brain injury.

Neuroprotective effects of testosterone on regenerating spinal cord motoneurons in rats

Degeneration in the CNS and peripheral nervous system consists of degradation and phagocytosis of axons and their myelin sheath distal to the site of injury. Testosterone is a gonadal sex steroid hormone that plays an important role in CNS development. One of the lesser-known testosterone actions is neuroprotection. In the present study, the authors investigated the neuroprotectective effect of intracerebral ventricular injection of testosterone on the number of spinal motoneurons after sciatic nerve crush. In all, 32 male Wistar rats were divided to 4 groups (control, compression, compression + castration, compression + testosterone injections; n = 8). Four weeks after compression the lumber segments of spinal cord were sampled, processed, sectioned serially, and stained with toluidine blue (pH = 4.65) by using steriological quantitative technique (physical dissector), the number of alpha motoneurons in the right ventral horns of spinal cord were counted and compared between groups. Statistical analyses showed that testosterone injections (1 microl icv, 4 times, 1 week interval between injections) significantly (p < .05) reduced neuronal damage. These results indicated that testosterone has an obvious neuroprotective effect on lumbar spinal motoneurons.

Sex bias in neuroscience and biomedical research

Female mammals have long been neglected in biomedical research. The NIH mandated enrollment of women in human clinical trials in 1993, but no similar initiatives exist to foster research on female animals. We reviewed sex bias in research on mammals in 10 biological fields for 2009 and their historical precedents. Male bias was evident in 8 disciplines and most prominent in neuroscience, with single-sex studies of male animals outnumbering those of females 5.5 to 1. In the past half-century, male bias in non-human studies has increased while declining in human studies. Studies of both sexes frequently fail to analyze results by sex. Underrepresentation of females in animal models of disease is also commonplace, and our understanding of female biology is compromised by these deficiencies. The majority of articles in several journals are conducted on rats and mice to the exclusion of other useful animal models. The belief that non-human female mammals are intrinsically more variable than males and too troublesome for routine inclusion in research protocols is without foundation. We recommend that when only one sex is studied, this should be indicated in article titles, and that funding agencies favor proposals that investigate both sexes and analyze data by sex.

Sex differences in outcome after mild traumatic brain injury

The objective of this study was to estimate the independent association of sex with outcome after mild traumatic brain injury (mTBI). We performed an analysis of a subset of an established cohort involving 1425 mTBI patients presenting to an academic emergency department (ED). The associations between sex and three outcomes determined 3 months after the initial ED visit were examined: post-concussive symptom (PCS) score (0, 1-5, 6-16, and >16), the number of days to return of normal activities (0, 1-7, and >7), and the number of days of work missed (0, 1-7,and >7). Logistic regression analyses were used to determine the relationship between sex and each outcome after controlling for 12 relevant subject-level variables. Of the 1425 subjects, 643 (45.1%) were female and 782 (54.9%) were male. Three months after mTBI, males had significantly lower odds of being in a higher PCS score category (odds ratio [OR] 0.62, 95% confidence interval [CI]: 0.50, 0.78); this association appeared to be more prominent during child-bearing years for females. Males and females did not significantly differ with respect to the odds of poorer outcome as defined by the number of days to return of normal activities or the number of days of work missed. Female sex is associated with significantly higher odds of poor outcome after mTBI, as measured by PCS score, after control for appropriate confounders. The observed pattern of peak disability for females during the child-bearing years suggests disruption of endogenous estrogen or progesterone production. Attempts to better understand how mTBI affects production of these hormones acutely after injury and during the recovery period may shed light on the mechanism behind poorer outcome among females and putative therapeutic interventions.

Activation of transgenic estrogen receptor-beta by selected phytoestrogens in a stably transduced rat serotonergic cell line

Many flavonoids, a major group of phenolic plant-derived secondary metabolites, are known to possess estrogen-like bioactivities. However, little is known about their estrogenic properties in the central nervous system due to the lack of suitable cellular models expressing sufficient amounts of functional estrogen receptor beta (ERbeta). To overcome this deficit, we have created a cellular model, which is serotonergic in origin, to study properties of estrogenic substances by stably transducing RN46A-B14 cells derived from raphe nuclei region of the rat brain with a lentiviral vector encoding a human ERbeta. We clearly showed that the transgenic human ERbeta is a spontaneously expressed and a functional receptor. We have further assessed the estrogenicity of three different isoflavones and four different naringenin-type flavanones in this cell line utilizing a luciferase reporter gene assay. Genistein (GEN), Daidzein (DAI), Equol (EQ), Naringenin (NAR) and 8-prenylnaringenin (8-PN) showed strong estrogenic activity in a concentration-dependent manner as compared to 7-(O-prenyl)naringenin-4'-acetate (7-O-PN) which was only slightly estrogenic and 6-(1,1-dimethylallyl)naringenin (6-DMAN) that neither showed estrogenic nor anti-estrogenic activity in our model. All observed effects could be antagonized by the anti-estrogen fulvestrant. Moreover, co-treatment of cells with 17beta-estradiol (E2) and either GEN or DAI showed a slight additive effect as compared to EQ. On the other hand, 8-PN in addition to 7-O-PN, but not NAR and 6-DMAN, were able to slightly antagonize the responses triggered by E2. Our newly established cellular model may prove to be a useful tool in explicating basic physiological properties of ERbeta in the brain and may help unravel molecular and cellular mechanisms involved in serotonergic mood regulation by estrogen or potential plant-derived secondary metabolites.

Scaled cortical impact in immature swine: effect of age and gender on lesion volume

The piglet scaled cortical impact model creates a focal contusion using a skull-mounted, spring-loaded blunt indentation device scaled to achieve identical tissue strains in subjects with different brain sizes. Preliminary data showed that contusion size increased proportional to subject age. This study details the results from a new, larger series of subjects of three ages, and compares the effect of age and additional host and physiologic variables on injury response. Sixty-seven subjects, including infant (5- to 7-day-old), "toddler" (1-month-old), and early adolescent (4-month-old) swine underwent scaled cortical impact under strict anesthetic protocols. Serum glucose, testosterone, and 17beta-estradiol levels were measured. Lesion size was measured at 1 week post injury, as the ratio of the lesion area over the area of the contralateral hemisphere. Adolescent subjects had lesions over eight times larger than infants (p < 0.0001). Lesion volumes were larger in toddlers than in infants, most significantly for males (p < 0.05). Adolescent subjects were warmer on average, but there was no correlation between temperature and lesion volume within any age group. Serum glucose did not differ among ages. Infant males had the highest levels of circulating sex steroids. In this model, age was the most robust predictor of lesion size. Temperature had an effect, but did not explain all the variability seen among age groups. There was an interaction among gender, hormone levels, and lesion size in younger subjects. Characterization of these variables allows use of this model for treatment trials for subjects at different stages of maturation.