Progesterone protects against lipid peroxidation following traumatic brain injury in rats

Protein Citrullination: A Proposed Mechanism for Pathology in Traumatic Brain Injury

Protein citrullination is a calcium-driven post-translational modification proposed to play a causative role in the neurodegenerative disorders of Alzheimer’s disease, multiple sclerosis (MS), and prion disease. Citrullination can result in the formation of antigenic epitopes that underlie pathogenic autoimmune responses. This phenomenon, which is best understood in rheumatoid arthritis, may play a role in the chronic dysfunction following traumatic brain injury (TBI). Despite substantial evidence of aberrations in calcium signaling following TBI, there is little understanding of how TBI alters citrullination in the brain. The present investigation addressed this gap by examining the effects of TBI on the distribution of protein citrullination and on the specific cell types involved. Immunofluorescence revealed that controlled cortical impact in rats profoundly up-­regulated protein citrullination in the cerebral cortex, external capsule, and hippocampus. This response was exclusively seen in astrocytes; no such effects were observed on the status of protein citrullination in neurons, oligodendrocytes or microglia. Further, proteomic analyses demonstrated that the effects of TBI on citrullination were confined to a relatively small subset of neural proteins. Proteins most notably affected were those also reported to be citrullinated in other disorders, including prion disease and MS. In vivo findings were extended in an in vitro model of simulated TBI employing normal human astrocytes. Pharmacologically induced calcium excitotoxicity was shown to activate the citrullination and breakdown of glial fibrillary acidic protein, producing a novel candidate TBI biomarker and potential target for autoimmune recognition. In summary, these findings demonstrate that the effects of TBI on protein citrullination are selective with respect to brain region, cell type, and proteins modified, and may contribute to a role for autoimmune dysfunction in chronic pathology following TBI.

Current Neurogenic and Neuroprotective Strategies to Prevent and Treat Neurodegenerative and Neuropsychiatric Disorders

The adult central nervous system is commonly known to have a very limited regenerative capacity. The presence of functional stem cells in the brain can therefore be seen as a paradox, since in other organs these are known to counterbalance cell loss derived from pathological conditions. This fact has therefore raised the possibility to stimulate neural stem cell differentiation and proliferation or survival by either stem cell replacement therapy or direct administration of neurotrophic factors or other proneurogenic molecules, which in turn has also originated regenerative medicine for the treatment of otherwise incurable neurodegenerative and neuropsychiatric disorders that take a huge toll on society. This may be facilitated by the fact that many of these disorders converge on similar pathophysiological pathways: excitotoxicity, oxidative stress, neuroinflammation, mitochondrial failure, excessive intracellular calcium and apoptosis. This review will therefore focus on the most promising achievements in promoting neuroprotection and neuroregeneration reported to date.

Neuroprotective actions of progesterone in an in vivo model of retinitis pigmentosa

Progesterone has been shown to have neuroprotective effects in experimental acute brain injury models, but little is known about the effects of steroid sex hormones in models of retinitis pigmentosa (RP). The aim of this study was to asses whether progesterone had a protective effect in one animal model of RP (the rd1 mice), and whether its action was due at least in part, to its ability to reduce free radical damage or to increase antioxidant defences. Rd1 and wild type (wt) mice received an oral administration of 100 mg/kg body/weight of progesterone on alternate days starting at postnatal day 7 (PN7) and were sacrificed at different postnatal days. Our results show that progesterone decreases cell death, as the number of TUNEL-positive cells were decreased in the ONL of the retina from treated rd1 mice. At PN15, treatment with progesterone increased values of ERG b-wave amplitude (p<0,5) when compared with untreated mice. Progesterone also decreased the observed gliosis in RP, though this effect was transient. Treatment with progesterone significantly reduced retinal glutamate concentrations at PN15 and PN17. To clarify the mechanism by which progesterone is able to decrease retinal glutamate concentration, we examined expression levels of glutamine synthase (GS). Our results showed a significant increase in GS in rd1 treated retinas at PN13. Treatment with progesterone, significantly increase not only GSH but also oxidized glutathione retinal concentrations, probably because progesterone is able to partially increase glutamate cysteine ligase c subunit (GCLC) at PN15 and PN17 (p<0,05). In summary, our results demonstrate that oral administration of progesterone appears to act on multiple levels to delay photoreceptor death in this model of RP.

Emerging pharmacotherapy for treatment of traumatic brain injury: targeting hypopituitarism and inflammation

INTRODUCTION

Traumatic brain injury (TBI) is a common cause of morbidity and mortality in the developed world. In particular, TBI is an important cause of death and disability in young adults with consequences ranging from physical disabilities to long-term cognitive, behavioural, psychological and social defects.

AREAS COVERED

There is a large body of evidence that suggest that TBI conditions may adversely affect pituitary function in both the acute and chronic phases of recovery. Prevalence of hypopituitarism, from total to isolated pituitary deficiency, ranges from 5 to 90%. The time interval between TBI and pituitary function evaluation is one of the major factors responsible for variations in the prevalence of hypopituitarism reported. Diagnosis of hypopituitarism and accurate treatment of pituitary disorders offers the opportunity to improve mortality and outcome in TBI conditions.

EXPERT OPINION

The aim of this paper is to review the history and pathophysiology of TBI and to summarize the best evidence of TBI as a cause of pituitary deficiency. Moreover, in this article we will describe the multiple changes which occur within the hypothalamic-pituitary-thyroid axis in critical illness, giving rise to 'sick euthyroid syndrome', focus our attention on thyroid hormones circulating levels from the initial insult to critical illness.

Estrogens and progestins: molecular effects on brain cells

Sex steroids are known to regulate brain function and their role is so important that several diseases are strictly correlated with the onset of menopause when estrogen-progesterone deficiency makes neural cells much more vulnerable to toxic stimuli. Although in the past years several scientists have focused their studies on in vitro and in vivo effects of sex steroids on the brain, we are still far from complete knowledge. Indeed, contrasting results from large clinical trials have made the entire issue much more complicated. Currently we know that protective effects exerted by sex steroids depend on several factors among which the dose, the health of the cells and the type of molecule being used. In this review, we present an overview of the direct and indirect effects of estrogen and progesterone on the brain with specific focus on the molecular mechanisms by which these molecules act on neural cells.

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).

Neuroprotection for traumatic brain injury

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. Despite extensive preclinical research supporting the effectiveness of neuroprotective therapies for brain trauma, there have been no successful randomized controlled clinical trials to date. TBI results in delayed secondary tissue injury due to neurochemical, metabolic and cellular changes; modulating such effects has provided the basis for neuroprotective interventions. To establish more effective neuroprotective treatments for TBI it is essential to better understand the complex cellular and molecular events that contribute to secondary injury. Here we critically review relevant research related to causes and modulation of delayed tissue damage, with particular emphasis on cell death mechanisms and post-traumatic neuroinflammation. We discuss the concept of utilizing multipotential drugs that target multiple secondary injury pathways, rather than more specific "laser"-targeted strategies that have uniformly failed in clinical trials. Moreover, we assess data supporting use of neuroprotective drugs that are currently being evaluated in human clinical trials for TBI, as well as promising emerging experimental multipotential drug treatment strategies. Finally, we describe key challenges and provide suggestions to improve the likelihood of successful clinical translation.

Protein carbonylation after traumatic brain injury: cell specificity, regional susceptibility, and gender differences

Protein carbonylation is a well-documented and quantifiable consequence of oxidative stress in several neuropathologies, including multiple sclerosis, Alzheimer׳s disease, and Parkinson׳s disease. Although oxidative stress is a hallmark of traumatic brain injury (TBI), little work has explored the specific neural regions and cell types in which protein carbonylation occurs. Furthermore, the effect of gender on protein carbonylation after TBI has not been studied. The present investigation was designed to determine the regional and cell specificity of TBI-induced protein carbonylation and how this response to injury is affected by gender. Immunohistochemistry was used to visualize protein carbonylation in the brains of adult male and female Sprague-Dawley rats subjected to controlled cortical impact (CCI) as an injury model of TBI. Cell-specific markers were used to colocalize the presence of carbonylated proteins in specific cell types, including astrocytes, neurons, microglia, and oligodendrocytes. Results also indicated that the injury lesion site, ventral portion of the dorsal third ventricle, and ventricular lining above the median eminence showed dramatic increases in protein carbonylation after injury. Specifically, astrocytes and limited regions of ependymal cells adjacent to the dorsal third ventricle and the median eminence were most susceptible to postinjury protein carbonylation. However, these patterns of differential susceptibility to protein carbonylation were gender dependent, with males showing significantly greater protein carbonylation at sites distant from the lesion. Proteomic analyses were also conducted and determined that the proteins most affected by carbonylation in response to TBI include glial fibrillary acidic protein, dihydropyrimidase-related protein 2, fructose-bisphosphate aldolase C, and fructose-bisphosphate aldolase A. Many other proteins, however, were not carbonylated by CCI. These findings indicate that there is both regional and protein specificity in protein carbonylation after TBI. The marked increase in carbonylation seen in ependymal layers distant from the lesion suggests a mechanism involving the transmission of a cerebral spinal fluid-borne factor to these sites. Furthermore, this process is affected by gender, suggesting that hormonal mechanisms may serve a protective role against oxidative stress.

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.

Pharmacotherapy of traumatic brain injury: state of the science and the road forward: report of the Department of Defense Neurotrauma Pharmacology Workgroup

Despite substantial investments by government, philanthropic, and commercial sources over the past several decades, traumatic brain injury (TBI) remains an unmet medical need and a major source of disability and mortality in both developed and developing societies. The U.S. Department of Defense neurotrauma research portfolio contains more than 500 research projects funded at more than $700 million and is aimed at developing interventions that mitigate the effects of trauma to the nervous system and lead to improved quality of life outcomes. A key area of this portfolio focuses on the need for effective pharmacological approaches for treating patients with TBI and its associated symptoms. The Neurotrauma Pharmacology Workgroup was established by the U.S. Army Medical Research and Materiel Command (USAMRMC) with the overarching goal of providing a strategic research plan for developing pharmacological treatments that improve clinical outcomes after TBI. To inform this plan, the Workgroup (a) assessed the current state of the science and ongoing research and (b) identified research gaps to inform future development of research priorities for the neurotrauma research portfolio. The Workgroup identified the six most critical research priority areas in the field of pharmacological treatment for persons with TBI. The priority areas represent parallel efforts needed to advance clinical care; each requires independent effort and sufficient investment. These priority areas will help the USAMRMC and other funding agencies strategically guide their research portfolios to ensure the development of effective pharmacological approaches for treating patients with TBI.

New aspects of progesterone interactions with the actin cytoskeleton and neurosteroidogenesis in the cerebellum and the neuronal growth cone

The impact of progesterone on neuronal tissues in the central (CNS) and peripheral (PNS) nervous system is of significant scientific and therapeutic interest. Glial and neuronal cells of vertebrates express steroidogenic enzymes, and are able to synthesize progesterone de novo from cholesterol. Progesterone is described to have neuroprotective, neuroreparative, anti-degenerative, and anti-apoptotic effects in the CNS and the PNS. Thus, the first clinical studies promise new therapeutic options using progesterone in the treatment of patients with traumatic brain injury. Additionally, experimental data from different animal models suggest further positive effects of progesterone on neurological diseases such as cerebral ischemia, peripheral nerve injury and amyothropic lateral sclerosis. In regard to this future clinical use of progesterone, we discuss in this review the underlying physiological principles of progesterone effects in neuronal tissues. Mechanisms leading to morphological reorganizations of neurons in the CNS and PNS affected by progesterone are addressed, with special focus on the actin cytoskeleton. Furthermore, new aspects of a progesterone-dependent regulation of neurosteroidogenesis mediated by the recently described progesterone binding protein PGRMC1 in the nervous system are discussed.

Sex differences in cognitive impairment and Alzheimer's disease

Studies have shown differences in specific cognitive ability domains and risk of Alzheimer's disease between the men and women at later age. However it is important to know that sex differences in cognitive function during adulthood may have their basis in both organizational effects, i.e., occurring as early as during the neuronal development period, as well as in activational effects, where the influence of the sex steroids influence brain function in adulthood. Further, the rate of cognitive decline with aging is also different between the sexes. Understanding the biology of sex differences in cognitive function will not only provide insight into Alzheimer's disease prevention, but also is integral to the development of personalized, gender-specific medicine. This review draws on epidemiological, translational, clinical, and basic science studies to assess the impact of sex differences in cognitive function from young to old, and examines the effects of sex hormone treatments on Alzheimer's disease in men and women.

Anti-inflammatory effects of progesterone in lipopolysaccharide-stimulated BV-2 microglia

Female sex is associated with improved outcome in experimental brain injury models, such as traumatic brain injury, ischemic stroke, and intracerebral hemorrhage. This implies female gonadal steroids may be neuroprotective. A mechanism for this may involve modulation of post-injury neuroinflammation. As the resident immunomodulatory cells in central nervous system, microglia are activated during acute brain injury and produce inflammatory mediators which contribute to secondary injury including proinflammatory cytokines, and nitric oxide (NO) and prostaglandin E₂ (PGE₂), mediated by inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), respectively. We hypothesized that female gonadal steroids reduce microglia mediated neuroinflammation. In this study, the progesterone’s effects on tumor necrosis factor alpha (TNF-α), iNOS, and COX-2 expression were investigated in lipopolysaccharide (LPS)-stimulated BV-2 microglia. Further, investigation included nuclear factor kappa B (NF-κB) and mitogen activated protein kinase (MAPK) pathways. LPS (30 ng/ml) upregulated TNF-α, iNOS, and COX-2 protein expression in BV-2 cells. Progesterone pretreatment attenuated LPS-stimulated TNF-α, iNOS, and COX-2 expression in a dose-dependent fashion. Progesterone suppressed LPS-induced NF-κB activation by decreasing inhibitory κBα and NF-κB p65 phosphorylation and p65 nuclear translocation. Progesterone decreased LPS-mediated phosphorylation of p38, c-Jun N-terminal kinase and extracellular regulated kinase MAPKs. These progesterone effects were inhibited by its antagonist mifepristone. In conclusion, progesterone exhibits pleiotropic anti-inflammatory effects in LPS-stimulated BV-2 microglia by down-regulating proinflammatory mediators corresponding to suppression of NF-κB and MAPK activation. This suggests progesterone may be used as a potential neurotherapeutic to treat inflammatory components of acute brain injury.

Progesterone protects blood-brain barrier function and improves neurological outcome following traumatic brain injury in rats

Inflammatory responses are associated with blood-brain barrier (BBB) dysfunction and neurological deficits following traumatic brain injury (TBI). The aim of the present study was to investigate the effects of progesterone on the expression of the inflammatory mediators prostaglandin E2 (PGE2), cyclooxygenase-2 (COX-2), nuclear factor κB (NF-κB) and tumor necrosis factor-α (TNF-α) in the brain, BBB permeability, cerebral edema and neurological outcome, as well as to explore the mechanism of its neuroprotective effect. In this study, male rats were randomly divided into three groups: a sham-operated group (SHAM), a TBI group (TBI) and a progesterone treatment group (TBI-PROG). The TBI model was established using a modified Feeney’s weight-dropping method. Brain samples were extracted 24 h following injury. The expression levels of COX-2 and NF-κB were examined using immunohistochemistry, whilst the expression levels of PGE2 and TNF-α were detected by enzyme-linked immunosorbent assay. BBB permeability was analyzed using Evans blue and cerebral edema was determined using the dry-wet method. The neurological outcome was evaluated using the modified neurological severity score test. The results revealed that progesterone treatment significantly reduced post-injury inflammatory response, brain edema and Evans blue dye extravasation, and improved neurological scores compared with those in the TBI group. In conclusion, the inhibition of inflammation may be an important mechanism by which progesterone protects the BBB and improves neurological outcome.

Antioxidants: The new frontier for translational research in cerebroprotection

It is important for the anesthesiologist to understand the etiology of free radical damage and how free-radical scavengers attenuate this, so that this knowledge can be applied to diverse neuro-pathological conditions. This review will concentrate on the role of reactive species of oxygen in the pathophysiology of organ dysfunction, specifically sub arachnoid hemorrhage (SAH), traumatic brain injury (TBI) as well as global central nervous system (CNS) hypoxic, ischemic and reperfusion states. We enumerate potential therapeutic modalities that are been currently investigated and of interest for future trials. Antioxidants are perhaps the next frontier of translational research, especially in neuro-anesthesiology.

Female ovarian steroids in epilepsy: a cause or remedy

In this article, we review published preclinical and clinical studies that examine the role of female ovarian steroids (estrogen and progesterone) in epilepsy. Its effects on the reproductive and endocrine system are well known but a large and growing body of evidences indicates that the hormones also exert neuroprotective effects on the central nervous system. Estrogen crosses the blood-brain barrier due to its low molecular weight and lipophilic properties and easily reaches the neuronal tissue. Estrogens and progesterone influence neuronal activity and are important for normal brain functions. It is commonly accepted that estrogens may increase neuronal excitability and thus mediate proconvulsant effects whereas in case of progesterone, various preclinical and clinical studies have proved that progesterone shows anticonvulsant effects. To concise our review we concluded that the effects of estrogens and progesterone on seizures depend on various factors, such as treatment duration and latency prior to the seizure testing, dose, hormonal status, the seizure type/model used and sex.

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.

Progesterone and its metabolites as therapeutic targets in psychiatric disorders

INTRODUCTION

Neurosteroids are molecules that regulate physiological functions of the CNS. There is increasing evidence suggesting that impaired neurosteroid biosynthesis has been associated with distinct psychiatric disorders. This review summarizes data from studies that have investigated the relationship between progesterone (PROG) and psychiatric disorders as well as the mechanisms potentially involved in PROG-induced neuroprotection.

AREAS COVERED

The review covers the role of PROG and its metabolites in psychiatric disorders, focusing on results from preclinical and some clinical studies that support the relationship between alterations on PROG levels and pathophysiology of psychiatric illness. We also discussed the main mechanisms underlying the neuroprotective effects of PROG metabolites.

EXPERT OPINION

Our review points out the possible relationship between PROG and its metabolites and the pathophysiology of psychiatric disorders. Furthermore, both preclinical and clinical studies show that certain treatments (antidepressants or antipsychotics) may normalize the levels of PROG, suggesting that the amelioration of psychiatric symptoms may occur due to upregulation of PROG metabolites. Therefore, these results give support to new possibilities of treatment for patients with psychiatric symptoms from anxiety- and depressive-like behaviors to aggressive behaviors.

TBI and sex: crucial role of progesterone protecting the brain in an omega-3 deficient condition

We assessed whether the protective action of progesterone on traumatic brain injury (TBI) could be influenced by the consumption of omega-3 fatty acids during early life. Pregnant Sprague-Dawley rats were fed on omega-3 adequate or deficient diet from 3rd day of pregnancy and their female offspring were kept on the same diets up to the age of 15 weeks. Ovariectomy was performed at the age of 12 weeks to deprive animals from endogenous steroids until the time of a fluid percussion injury (FPI). Dietary n-3 fatty acid deficiency increased anxiety in sham animals and TBI aggravated the effects of the deficiency. Progesterone replacement counteracted the effects of TBI on the animals reared under n-3 deficiency. A similar pattern was observed for markers of membrane homeostasis such as 4-Hydroxynonenal (HNE) and secreted phospholipases A2 (sPLA2), synaptic plasticity such as brain derived neurotrophic factor (BDNF), syntaxin (STX)-3 and growth associated protein (GAP)-43, and for growth inhibitory molecules such as myelin-associated glycoprotein (MAG) and Nogo-A. Results that progesterone had no effects on sham n-3 deficient animals suggest that the availability of progesterone is essential under injury conditions. Progesterone treatment counteracted several parameters related to synaptic plasticity and membrane stability reduced by FPI and n-3 deficiency suggest potential targets for therapeutic applications. These results reveal the importance of n-3 preconditioning during early life and the efficacy of progesterone therapy during adulthood to counteract weaknesses in neuronal and behavioral plasticity.

Improved cognitive outcome after progesterone administration is associated with protecting hippocampal neurons from secondary damage studied in vitro and in vivo

Previous studies reported that progesterone could improve cognitive outcome following TBI. Moreover, some evidence implied that the hippocampus is associated with cognitive function. The aim of this study was to investigate the neuroprotective effects of progesterone on hippocampal neurons in vitro and in vivo, and its influence on the cognitive outcome. In vitro, the model of primary cultured hippocampal neurons against glutamate-induced excitotoxic damage was used. After 10-day culture, neurons were pretreated with progesterone in a concentration 10 ng/ml, 48 h before a 5-min exposure to 200 μmol/l glutamate. Then 24h after glutamate exposure, the nerve cells were observed and LDH was detected. The results showed progesterone protected the cultured hippocampal neurons morphology and significantly reduced the amount of LDH. In vivo, the model of TBI was established by modified Feeney's weight-dropping method. The progesterone was given in a dose of 16 mg/kg by intraperitoneal injection 1h post injury and subsequent injections subcutaneously at 6h and 12h after TBI. Brain samples were extracted at 24h after injury. Histology and the iNOS expression were examined by Nissl stain, immunohistochemistry and Western blot. The cognitive outcome was assessed by Morris water maze test (MWM). The results revealed that the neuronal cell damage and the expression of iNOS in the hippocampus CA1 were significantly decreased after progesterone administration. Progesterone significantly improved cognitive outcome after TBI. The results suggest that the positive effects of progesterone on cognitive outcome may be linked to protecting hippocampal neurons from secondary damage.

Neuroprotective strategies for traumatic brain injury: improving clinical translation

Traumatic brain injury (TBI) induces secondary biochemical changes that contribute to delayed neuroinflammation, neuronal cell death, and neurological dysfunction. Attenuating such secondary injury has provided the conceptual basis for neuroprotective treatments. Despite strong experimental data, more than 30 clinical trials of neuroprotection in TBI patients have failed. In part, these failures likely reflect methodological differences between the clinical and animal studies, as well as inadequate pre-clinical evaluation and/or trial design problems. However, recent changes in experimental approach and advances in clinical trial methodology have raised the potential for successful clinical translation. Here we critically analyze the current limitations and translational opportunities for developing successful neuroprotective therapies for TBI.

Traumatic Brain Injury pathophysiology and treatments: early, intermediate, and late phases post-injury

Traumatic Brain Injury (TBI) affects a large proportion and extensive array of individuals in the population. While precise pathological mechanisms are lacking, the growing base of knowledge concerning TBI has put increased emphasis on its understanding and treatment. Most treatments of TBI are aimed at ameliorating secondary insults arising from the injury; these insults can be characterized with respect to time post-injury, including early, intermediate, and late pathological changes. Early pathological responses are due to energy depletion and cell death secondary to excitotoxicity, the intermediate phase is characterized by neuroinflammation and the late stage by increased susceptibility to seizures and epilepsy. Current treatments of TBI have been tailored to these distinct pathological stages with some overlap. Many prophylactic, pharmacologic, and surgical treatments are used post-TBI to halt the progression of these pathologic reactions. In the present review, we discuss the mechanisms of the pathological hallmarks of TBI and both current and novel treatments which target the respective pathways.

The neuroprotective effects of progesterone on traumatic brain injury: current status and future prospects

Traumatic brain injury is the leading cause of morbidity and mortality in young adults. The secondary injury in traumatic brain injury consists of a complex cascade of processes that simultaneously react to the primary injury to the brain. This cascade has been the target of numerous therapeutic agents investigated over the last 30 years, but no neuroprotective treatment option is currently available that improve neurological outcome after traumatic brain injury. Progesterone has long been considered merely a female reproductive hormone. Numerous studies, however, show that progesterone has substantial pleiotropic properties as a neuroprotective agent in both animal models and humans. Here, we review the increasing evidence that progesterone can act as a neuroprotective agent to treat traumatic brain injury and the mechanisms underlying these effects. Additionally, we discuss the current progress of clinical studies on the application of progesterone in the treatment of traumatic brain injuries.

Effect of progesterone administration on prognosis of patients with diffuse axonal injury due to severe head trauma

OBJECTIVE

Severe traumatic brain injury (TBI) has a major role in mortality rate among the other types of trauma. The aim of this clinical study was to assess the effect of progesterone on the improvement of neurologic outcome in patients with acute severe TBI.

METHODS

A total of 76 patients who had arrived within 8h of injury with a Glasgow Coma Score≤8 were enrolled in the study. In a randomized style 38 received progesterone (1mg/kg per 12h for 5 days) and 38 did not.

RESULTS

There was a better recovery rate and GOS score for the patients who were given progesterone than for those in the control group in a 3-months follow-up period (50% vs. 21%); subgroup analysis showed a significant difference in the percentage of favorable outcome between the two groups with GCS of 5-8 (p=0.03).

CONCLUSION

The use of progesterone may significantly improve neurologic outcome of patients suffering severe TBI up to 3 months after injury, especially those with 5≤GCS≤8, providing a potential benefit to the treatment of acute severe TBI patients. Considering this drug had no significant side effects, so progesterone could be used in patients with severe TBI as a neuro-protective drug.

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.

Progesterone antagonism of neurite outgrowth depends on microglial activation via Pgrmc1/S2R

Neuronal plasticity is regulated by the ovarian steroids estradiol (E2) and progesterone (P4) in many normal brain functions, as well as in acute response to injury and chronic neurodegenerative disease. In a female rat model of axotomy, the E2-dependent compensatory neuronal sprouting is antagonized by P4. To resolve complex glial-neuronal cell interactions, we used the "wounding-in-a-dish" model of neurons cocultured with astrocytes or mixed glia (microglia to astrocytes, 1:3). Although both astrocytes and mixed glia supported E2-enhanced neurite outgrowth, P4 antagonized E2-induced neurite outgrowth only with mixed glia, but not astrocytes alone. We now show that P4-E2 antagonism of neurite outgrowth is mediated by microglial expression of progesterone receptor (Pgr) membrane component 1 (Pgrmc1)/S2R, a putative nonclassical Pgr mediator with multiple functions. The P4-E2 antagonism of neurite outgrowth was restored by add-back of microglia to astrocyte-neuron cocultures. Because microglia do not express the classical Pgr, we examined the role of Pgrmc1, which is expressed in microglia in vitro and in vivo. Knockdown by siRNA-Pgrmc1 in microglia before add-back to astrocyte-neuron cocultures suppressed the P4-E2 antagonism of neurite outgrowth. Conditioned media from microglia restored the P4-E2 activity, but only if microglia were activated by lipopolysaccharide or by wounding. Moreover, the microglial activation was blocked by Pgmrc1-siRNA knockdown. These findings explain why nonwounded cultures without microglial activation lack P4 antagonism of E2-induced neurite outgrowth. We suggest that microglial activation may influence brain responses to exogenous P4, which is a prospective therapy in traumatic brain injury.

Progesterone-estrogen interactions in synaptic plasticity and neuroprotection

17ß-Estradiol and progesterone exert a number of physiological effects throughout the brain due to interactions with several types of receptors belonging to the traditional family of intracellular hormonal receptors as well as to membrane-bound receptors. In particular, both hormones elicit rapid modifications of neuronal excitability that have been postulated to underlie their effects on synaptic plasticity and learning and memory. Likewise, both hormones have been shown to be neuroprotective under certain conditions, possibly due to the activation of pro-survival pathways and the inhibition of pro-apoptotic cascades. Because of the similarities in their cellular effects, there have been a number of questions raised by numerous observations that progesterone inhibits the effects of estrogen. In this manuscript, we first review the interactions between 17ß-estradiol (E2) and progesterone (P4) in synaptic plasticity, and conclude that, while E2 exerts a clear and important role in long-term potentiation of synaptic transmission in hippocampal neurons, the role of P4 is much less clear, and could be accounted by the direct or indirect regulation of GABAA receptors. We then discuss the neuroprotective roles of both hormones, in particular against excitotoxicity. In this case, the neuroprotective effects of these hormones are very similar to those of the neurotrophic factor BDNF. Interestingly, P4 antagonizes the effects of E2, possibly through the regulation of estrogen receptors or of proteins associated with the receptors or interactions with signaling pathways activated by E2. Overall, this review emphasizes the existence of common molecules and pathways that participate in the regulation of both synaptic plasticity and neurodegeneration.

Oxidative stress, DNA damage, and the telomeric complex as therapeutic targets in acute neurodegeneration

Oxidative stress has been identified as an important contributor to neurodegeneration associated with acute CNS injuries and diseases such as spinal cord injury (SCI), traumatic brain injury (TBI), and ischemic stroke. In this review, we briefly detail the damaging effects of oxidative stress (lipid peroxidation, protein oxidation, etc.) with a particular emphasis on DNA damage. Evidence for DNA damage in acute CNS injuries is presented along with its downstream effects on neuronal viability. In particular, unchecked oxidative DNA damage initiates a series of signaling events (e.g. activation of p53 and PARP-1, cell cycle re-activation) which have been shown to promote neuronal loss following CNS injury. These findings suggest that preventing DNA damage might be an effective way to promote neuronal survival and enhance neurological recovery in these conditions. Finally, we identify the telomere and telomere-associated proteins (e.g. telomerase) as novel therapeutic targets in the treatment of neurodegeneration due to their ability to modulate the neuronal response to both oxidative stress and DNA damage.

Progesterone and neuroprotection

Numerous studies aimed at identifying the role of estrogen on the brain have used the ovariectomized rodent as the experimental model. And while estrogen intervention in these animals has, at least partially, restored cholinergic, neurotrophin and cognitive deficits seen in the ovariectomized animal, it is worth considering that the removal of the ovaries results in the loss of not only circulating estrogen but of circulating progesterone as well. As such, the various deficits associated with ovariectomy may be attributed to the loss of progesterone as well. Similarly, one must also consider the fact that the human menopause results in the precipitous decline of not just circulating estrogens, but in circulating progesterone as well and as such, the increased risk for diseases such as Alzheimer's disease during the postmenopausal period could also be contributed by this loss of progesterone. In fact, progesterone has been shown to exert neuroprotective effects, both in cell models, animal models and in humans. Here, we review the evidence that supports the neuroprotective effects of progesterone and discuss the various mechanisms that are thought to mediate these protective effects. We also discuss the receptor pharmacology of progesterone's neuroprotective effects and present a conceptual model of progesterone action that supports the complementary effects of membrane-associated and classical intracellular progesterone receptors. In addition, we discuss fundamental differences in the neurobiology of progesterone and the clinically used, synthetic progestin, medroxyprogesterone acetate that may offer an explanation for the negative findings of the combined estrogen/progestin arm of the Women's Health Initiative-Memory Study (WHIMS) and suggest that the type of progestin used may dictate the outcome of either pre-clinical or clinical studies that addresses brain function.

Progesterone-induced neuroprotection: factors that may predict therapeutic efficacy

Both progesterone and estradiol have well-described neuroprotective effects against numerous insults in a variety of cell culture models, animal models and in humans. However, the efficacy of these hormones may depend on a variety of factors, including the type of hormone used (ex. progesterone versus medroxyprogesterone acetate), the duration of the postmenopausal period prior to initiating the hormone intervention, and potentially, the age of the subject. The latter two factors relate to the proposed existence of a "window of therapeutic opportunity" for steroid hormones in the brain. While such a window of opportunity has been described for estrogen, there is a paucity of information to address whether such a window of opportunity exists for progesterone and its related progestins. Here, we review known cellular mechanisms likely to underlie the protective effects of progesterone and furthermore, describe key differences in the neurobiology of progesterone and the synthetic progestin, medroxyprogesterone acetate (MPA). Based on the latter, we offer a model that defines some of the key cellular and molecular players that predict the neuroprotective efficacy of progesterone. Accordingly, we suggest how changes in the expression or function of these cellular and molecular targets of progesterone with age or prolonged duration of hormone withdrawal (such as following surgical or natural menopause) may impact the efficacy of progesterone. This article is part of a Special Issue entitled Hormone Therapy.

A comparison of the effects of nicotinamide and progesterone on functional recovery of cognitive behavior following cortical contusion injury in the rat

The primary goal of this study was to compare clinically relevant doses of progesterone and nicotinamide within the same injury model. Progesterone has been shown to reduce edema and inflammation and improve functional outcomes following brain injury. Nicotinamide has also been shown to be an effective neuroprotective agent in a variety of neurological injury models. In the current study, nicotinamide was administered beginning 4 h post-cortical contusion injury (CCI) with a loading dose (75 mg/kg, i.p.) combined with continuous infusion (12 mg/h/kg, s.c.) for 72 h post-injury. Progesterone was administered beginning 4 h post-CCI at a dose of 10 or 20 mg/kg, i.p. every 12 h for 72 h. This resulted in the following groups: Injured-nicotinamide treated, Injured-progesterone-10 treated, Injured-progesterone-20 treated, Injured-vehicle treated, and Sham. Functional recovery was assessed with two spatial memory tasks in the Morris water maze (MWM) the acquisition of a reference memory task and a reversal learning task. Neuropathological assessments were conducted in the cortex and hippocampus. It was found that both progesterone (10 mg/kg) and nicotinamide improved reference memory acquisition and reversal learning in the MWM compared with vehicle treatment. The lower dose of progesterone and nicotinamide also reduced tissue loss in the injured cortex and ipsilateral hippocampus compared with vehicle. The beneficial effects of progesterone appear to be dose dependent with the lower 10 mg/kg dose producing significant effects that were not observed at the higher dose. Direct comparison between nicotinamide and low dose progesterone appears to suggest that both are equally effective. The general findings of this study suggest that both nicotinamide and progesterone produce significant improvements in recovery of function following CCI.

Neuroinflammation after traumatic brain injury: opportunities for therapeutic intervention

Traumatic brain injury (TBI) remains one of the leading causes of mortality and morbidity worldwide, yet despite extensive efforts to develop neuroprotective therapies for this devastating disorder there have been no successful outcomes in human clinical trials to date. Following the primary mechanical insult TBI results in delayed secondary injury events due to neurochemical, metabolic and cellular changes that account for many of the neurological deficits observed after TBI. The development of secondary injury represents a window of opportunity for therapeutic intervention to prevent progressive tissue damage and loss of function after injury. To establish effective neuroprotective treatments for TBI it is essential to fully understand the complex cellular and molecular events that contribute to secondary injury. Neuroinflammation is well established as a key secondary injury mechanism after TBI, and it has been long considered to contribute to the damage sustained following brain injury. However, experimental and clinical research indicates that neuroinflammation after TBI can have both detrimental and beneficial effects, and these likely differ in the acute and delayed phases after injury. The key to developing future anti-inflammatory based neuroprotective treatments for TBI is to minimize the detrimental and neurotoxic effects of neuroinflammation while promoting the beneficial and neurotrophic effects, thereby creating optimal conditions for regeneration and repair after injury. This review outlines how post-traumatic neuroinflammation contributes to secondary injury after TBI, and discusses the complex and varied responses of the primary innate immune cells of the brain, microglia, to injury. In addition, emerging experimental anti-inflammatory and multipotential drug treatment strategies for TBI are discussed, as well as some of the challenges faced by the research community to translate promising neuroprotective drug treatments to the clinic.

Progesterone for acute traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of death and disability. Progesterone is a potential neuroprotective drug to treat patients with TBI.

OBJECTIVES

To assess the effectiveness and safety of progesterone in people with acute TBI.

SEARCH METHODS

We searched: the Cochrane Injuries Group's Specialised Register (13 July 2012), Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 7, 2012), MEDLINE (Ovid) (1950 to August week 1, 2012), EMBASE (Ovid) (1980 to week 32 2012), LILACS (12 August 2012), Zetoc (13 July 2012), Clinicaltrials.gov (12 August 2012), Controlled-trials.com (12 August 2012).

SELECTION CRITERIA

We included published and unpublished randomised controlled trials (RCTs) of progesterone versus no progesterone (or placebo) for the treatment of people with acute TBI.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened search results to identify the full texts of potentially relevant studies for inclusion. From the results of the screened searches two review authors independently selected trials meeting the inclusion criteria, with no disagreement.

MAIN RESULTS

Three studies were included with a total of 315 people. Two included studies were of high methodological quality, with low risk of bias in allocation concealment, blinding and incomplete outcome data. One study did not use blinding and had unclear risk of bias in allocation concealment and incomplete outcome data. All three studies reported the effects of progesterone on mortality. The pooled risk ratio (RR) for mortality at end of follow-up was 0.61, 95% confidence interval (CI) 0.40 to 0.93. Three studies measured disability and found the RR of death or severe disability in patients treated with progesterone to be 0.77, 95% CI 0.62 to 0.96. Data from two studies showed no difference in mean intracranial pressure or the rate of adverse and serious adverse events among people in either group. One study presented blood pressure and temperature data, and there were no differences between the people in the progesterone or control groups. There was no substantial evidence for the presence of heterogeneity.

AUTHORS' CONCLUSIONS

Current clinical evidence from three small RCTs indicates progesterone may improve the neurologic outcome of patients suffering TBI. This evidence is still insufficient and further multicentre randomised controlled trials are required.

Therapeutic role of toll-like receptor modification in cardiovascular dysfunction

Toll-like receptors (TLR) are key pattern recognition receptors in the innate immune system. The TLR-mediated immune response against pathogens is usually protective however inappropriate TLR activation may lead to excessive tissue damage. It is well recognised that TLRs respond to a variety of endogenous as well as exogenous ligands. By responding to endogenous ligands that are exposed during cellular damage, TLRs have been implicated in a range of pathological conditions associated with cardiovascular dysfunction. Increasing knowledge on the mechanisms involved in TLR signalling has encouraged the exploration of therapeutic pharmacological modulation of TLR activation in conditions such as atherosclerosis, ischaemic heart disease, heart failure and ischaemic reperfusion injury. The aim of this review is to explore the translational potentials of TLR modification in cardiovascular dysfunction, where these agents have been studied.

Comparison of the administration of progesterone versus progesterone and vitamin D in improvement of outcomes in patients with traumatic brain injury: A randomized clinical trial with placebo group

Background:

Due to the heterogeneity of traumatic brain injury (TBI), many of single treatments have not been successful in prevention and cure of these kinds of injuries. The neuroprotective effect of progesterone drug on severe brain injuries has been identified, and recently, the neuroprotective effect of vitamin D has also been studied as the combination of these two drugs has shown better effects on animal samples in some studies. This study was conducted to examine the effect of vitamin D and progesterone on brain injury treatment after brain trauma.

Materials and Methods:

This study was performed on patients with severe brain trauma (Glasgow Coma Scale (GCS) ≤ 8) from April to September, 2011. The patients were divided to 3 groups (placebo, progesterone, progesterone-vitamin D), each with 20 people. Upon the patients’ admission, their GCS and demographic information were recorded. After 3 months, they were reassessed, and their GCS and GOS (Glasgow outcome scale) were recorded. The collected data were analyzed using SPSS 18 software (SPSS Inc., Chicago IL, USA).

Results:

Before intervention, GCS mean of the placebo, progesterone, and progesterone-vitamin D groups were 6.3 ± 0.88, 6.31 ± 0.87, and 6 ± 0.88, respectively. They increased to 9.16 ± 1.11, 10.25 ± 1.34, and 11.27 ± 2.27, respectively 3 months after intervention. There was a significant difference among GCS means of the 3 groups (P-value = 0.001). GOS was classified to 2 main categories of favorable and unfavorable recovery, of which, favorable recovery in placebo, progesterone, and progesterone-vitamin D was 25%, 45%, and 60%, respectively which showed a statistical significant difference among the groups (P-value = 0.03).

Conclusion:

The results showed that recovery rate in patients with severe brain trauma in the group receiving progesterone and vitamin D together was significantly higher than that of progesterone group, which was in turn higher than that of placebo group.

Trichostatin A enhances glutamate transporter GLT-1 mRNA levels in C6 glioma cells via neurosteroid-mediated cell differentiation

The neurotoxic effects of excitatory amino acids (EAAs) are suggested to be connected with the chronic loss of neuronal cells, thereby being responsible for the age-related neurodegenerative diseases. Therefore, it seems conceivable that the excitatory amino acid transporters may contribute to the protection of neuronal cells against the excitotoxic damage by facilitating the removal of EAAs from the brain tissue. On the other hand, previous studies have suggested that glial cell differentiation may be involved in the protection and recovery of neural function probably through the elevation of BDNF gene expression in the brain. Based on these findings, histone deacetylase (HDAC) inhibitors are assumed to induce glutamate transporter-1 (GLT-1) gene expression probably through the promotion of glial cell differentiation. Then, we examined the effects of HDAC inhibitors on GLT-1 mRNA levels in rat C6 glioma cells and found that trichostatin A can induce GLT-1 gene transcription following steroid 5α-reductase and GFAP gene expression. Therefore, it seems conceivable that glial cell differentiation may play a potential role in the removal of EAAs probably through the expression of GLT-1, thereby being involved in the protection of neuronal cells against the chronic excitotoxic insults in the brain.

Water-soluble progesterone analogues are effective, injectable treatments in animal models of traumatic brain injury

After more than 30 years of research and 30 failed clinical trials with as many different treatments, progesterone is the first agent to demonstrate robust clinical efficacy as a treatment for traumatic brain injuries. It is currently being investigated in two, independent phase III clinical trials in hospital settings; however, it presents a formidable solubility challenge that has so far prevented the identification of a formulation that would be suitable for emergency field response use or battlefield situations. Accordingly, we have designed and tested a novel series of water-soluble analogues that address this critical need. We report here the synthesis of C-20 oxime conjugates of progesterone as therapeutic agents for traumatic brain injuries with comparable efficacy in animal models of traumatic brain injury and improved solubility and pharmacokinetic profiles. Pharmacodynamic analysis reveals that a nonprogesterone steroidal analogue may be primarily responsible for the observed activity.

Sex steroids and their receptors: molecular actions on brain cells

Sex steroids exert actions of paramount importance on brain cells. They contribute to shape the central nervous system during embryo development. They modulate the formation and the turnover of the interconnections between neurons. They control the function of glial cells. And they do it through a signaling machinery that is apparently simple, but that hides a level of complexity that has been unveiled only in part. Different receptor isoforms, different interactions between receptors and co-regulators, chains of events originating at the cell membrane and leading to effects in the nucleus (or the other way around) all interact to determine selective modulations of brain cells. All these actions end up in phenomenal effects on brain function that change through adolescence, pregnancy, adulthood, up to menopause and ageing. Many of these actions are relevant for degenerative processes and research may offer soon new strategies to counteract these diseases.

Novel actions of progesterone: what we know today and what will be the scenario in the future?

Objectives

This article is aimed to review the novel actions of progesterone, which otherwise is considered as a female reproductive hormone. The article focuses on its important physiological actions in males too and gives an overview of its novel perspectives in disorders of central and peripheral nervous system.

Key findings

Progesterone may have a potential benefit in treatment of traumatic brain injury, various neurological disorders and male related diseases like benign prostatic hypertrophy (BPH), prostate cancer and osteoporosis. Norethisterone (NETA), a progesterone derivative, decreases bone mineral loss in male castrated mice suggesting its role in osteoporosis. In the future, progesterone may find use as a male contraceptive too, but still needs confirmatory trials for safety, tolerability and acceptability. Megestrol acetate, a progesterone derivative is preferred in prostatic cancer. Further, it may find utility in nicotine addiction, traumatic brain injury (recently entered Phase III trial) and Alzheimer's disease, diabetic neuropathy and crush injuries. Studies also suggest role of progesterone in stroke, for which further clinical trials are needed. The non genomic actions of progesterone may be in part responsible for these novel actions.

Summary

Although progesterone has shown promising role in various non-hormonal benefits, further clinical studies are needed to prove its usefulness in conditions like stroke, traumatic brain injury, neuropathy and crush injury. In male related illnesses like BPH and prostatic Ca, it may prove a boon in near future. New era of hormonal male contraception may be initiated by use of progesterone along with testosterone.

Antioxidant strategies in neurocritical care

An increase in oxidative stress and overproduction of oxidizing reactive species plays an important role in the pathophysiology of several conditions encountered in the neurocritical care setting including: ischemic and hemorrhagic strokes, traumatic brain injury, acute respiratory distress syndrome, sepsis, and organ failure. The presence of oxidative stress in these conditions is supported by a large body of pre-clinical and clinical studies, and provides a rationale to support a potential therapeutic role for antioxidants. The purpose of this article is to briefly review the basic mechanisms and molecular biology of oxidative stress, summarize its role in critically ill neurological patients, and review available data regarding the potential role of antioxidant strategies in neurocritical care and future directions.

The role of estrogen and progesterone, administered alone and in combination, in modulating cytokine concentration following traumatic brain injury

Cytokines play an important role in the pathophysiology of traumatic brain injury (TBI). This study was designed to determine the effects of administering progesterone (P) and estrogen (E), alone and in combination, on brain water content, blood-brain barrier (BBB) disturbance, and brain level of cytokines following diffuse TBI. Ovariectomized rats were divided into 9 groups, treated with vehicle, E1, E2, P1, P2, E1+P1, E1+P2, E2+P1, and E2+P2. Levels of BBB disruption (5 h), cytokines, and water content (24 h) were evaluated after TBI induced by the Marmarou method. Physiological (E1 and P1) and pharmacological (E2 and P2) doses of estrogen and progesterone were administered 30 min after TBI. Water content in the E1+P2-treated group was higher than in the E1-treated group. The inhibitory effect of E2 on water content was reduced by adding progesterone. The inhibitory effect of E1 and E2 on Evans blue content was reduced by treatment with E1+P1 and E2+P2, respectively. The brain level of IL-1β was reduced in E1 and E2, after TBI. In the E2+P2-treated group, this level was higher than in the E2-treated group. The brain level of TGF-β was also elevated by the administration of progesterone and estrogen alone, and reduced when the hormones were administered in combination. In conclusion, a combined administration of progesterone and estrogen inhibited the decreasing effects of administration of progesterone and estrogen alone on water content and BBB disruption that mediated to change the proinflammatory cytokines.

Investigation of the mechanisms of progesterone protection following oxygen-glucose deprivation in organotypic hippocampal slice cultures

This study aimed to test the hypothesis that progesterone is neuroprotective against oxygen-glucose deprivation (OGD) through its conversion to the active metabolite allopregnanolone (AlloP) and the potentiation of GABA(A) receptors. Organotypic hippocampal cultures were exposed to 2h of OGD and the resulting cell death was quantified 24h later using combined propidium iodide and Hoechst immunostaining. Initially, we confirmed, that both progesterone and AlloP were protective in terms of reducing cell death following OGD in hippocampal cultures and for both, the optimal level of protection was observed at a concentration of 0.1μM. However, the protective effect of progesterone was absent in the presence of finasteride (10μM) which inhibits the metabolism of progesterone to active metabolites, including AlloP. In addition, the concurrent application of picrotoxin (100μM), a potent GABA(A) receptor antagonist, prevented the protection previously seen by either progesterone or AlloP alone. These results indicate that progesterone protects hippocampal cultures from cell death following OGD largely due to its conversion to AlloP and that GABA(A) receptors are important mediators of the protective effects of both progesterone and AlloP.

Potential age-dependent effects of estrogen on neural injury

In 2000, approximately 10 million women were receiving hormone replacement therapy (HRT) for alleviation of menopausal symptoms. A number of prior animal studies suggested that HRT may be neuroprotective and cardioprotective. Then, in 2003, reports from the Women's Health Initiative (WHI) indicated that long-term estrogen/progestin supplementation led to increased incidence of stroke. A second branch of the WHI in women with prior hysterectomy found an even stronger correlation between estrogen supplementation alone and stroke incidence. Follow-up analyses of the data, as well as data from other smaller clinical trials, have also demonstrated increased stroke severity in women receiving HRT or estrogen alone. This review examines the studies indicating that estrogen is neuroprotectant in animal models and explores potential reasons why this may not be true in postmenopausal women. Specifically, age-related differences in estrogen receptors and estrogenic actions in the brain are discussed, with the conclusion that animal models of disease must closely mimic human disease to produce clinically relevant results.