Nestorone (segesterone acetate) effects on neuroregeneration.

Nestorone® (segesterone acetate) is a progestin with a chemical structure closely related to progesterone with high affinity and selectivity for the progesterone receptor without significant interaction with other steroid receptors. It has been developed for female and male contraception and is FDA-approved in a first long-acting contraceptive vaginal system for female contraception. Its safety has been extensively demonstrated in both preclinical and clinical studies for contraceptive indications. Nestorone was found to display neuroprotective and neuroregenerative activity in animal models of various central nervous system diseases, including multiple sclerosis, stroke, and amyotrophic lateral sclerosis. Reviewed herein are neuroprotective and myelin- regenerating properties of Nestorone in various animal models and its translational potential as a therapeutic agent for debilitating neurological diseases for which limited therapeutic options are available (Table 1).

Early Signs of Neuroinflammation in the Postnatal Wobbler Mouse Model of Amyotrophic Lateral Sclerosis.

The Wobbler mouse is an accepted model of sporadic amyotrophic lateral sclerosis. The spinal cord of clinically symptomatic animals (3-5 months old) shows vacuolar motoneuron degeneration, inflammation, and gliosis accompanied by motor impairment. However, data are not conclusive concerning pathological changes appearing early after birth. To answer this question, we used postnatal day (PND) 6 genotyped Wobbler pups to determine abnormalities of glia and neurons at this early age period in the spinal cord. We found astrogliosis, microgliosis with morphophenotypic changes pointing to active ameboid microglia, enhanced expression of the proinflammatory markers TLR4, NFkB, TNF, and inducible nitric oxide synthase. The astrocytic enzyme glutamine synthase and the glutamate-aspartate transporter GLAST were also reduced in PND 6 Wobbler pups, suggesting excitotoxicity due to impaired glutamate homeostasis. At the neuronal level, PND 6 Wobblers showed swollen soma, increased choline acetyltransferase immunofluorescence staining, and low expression of the neuronal nuclear antigen NeuN. However, vacuolated motoneurons, a typical signature of older clinically symptomatic Wobbler mice, were absent in the spinal cord of PND 6 Wobblers. The results suggest predominance of neuroinflammation and abnormalities of microglia and astrocytes at this early period of Wobbler life, accompanied by some neuronal changes. Data support the non-cell autonomous hypothesis of the Wobbler disorder, and bring useful information with regard to intervening molecular inflammatory mechanisms at the beginning stage of human motoneuron degenerative diseases.

Exposure to endogenous and exogenous sex hormones and reproductive history influence prognosis in women with ALS.

INTRODUCTION/AIMS: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with a higher incidence in men suggesting an influence of sex steroids. Our objective was to investigate past exposure to endogenous and synthetic steroids in female ALS patients and controls. METHODS: We administered a questionnaire to 158 postmenopausal women (75 ALS patients and 83 controls). We calculated reproductive time span (RTS), lifetime endogenous estrogen (LEE) and progesterone exposures (LPE), oral contraceptive pill (OCP) use, and reproductive history. RESULTS: ALS patients showed shorter LEE and LPE, a lower proportion of breast cancer, and 11% showed no history of pregnancies vs. 4% of controls. Odds ratios (ORs) showed that <17 y of LEE and a delayed menarche (>13 y) constitute risk factors for ALS [OR = 2.1 (95% confidence interval {CI}, 1.08-4.2); and OR = 2.4 (95% CI, 1.1-5.1) respectively]. According to Cox survival analysis, for each year the LEE increased over 17 y, it was independently associated with longer survival [hazard ratio (HR) = 0.37 (95% CI, 0.16-0.85)] after adjusting for smoking, age and site of onset. Multivariate regression analysis demonstrated that for each month using OCP for longer than 40 mo increased the risk of ALS [adjusted OR = 4.1 (95% CI, 1.2-13.8)]. DISCUSSION: Thus, longer exposure to endogenous female sex steroids increased survival and reduced ALS susceptibility. In contrast, longer exposure to synthetic sex steroids showed a negative impact by reducing the production of endogenous female sex steroids or due to crossover with other steroid receptors. Given the neuroprotective effects of sex steroids, we suggest that abnormalities of neuroendocrine components may alter motor function in women with ALS.

Spinal Cord Injury Leads to Hippocampal Glial Alterations and Neural Stem Cell Inactivation.

The hippocampus encodes spatial and contextual information involved in memory and learning. The incorporation of new neurons into hippocampal networks increases neuroplasticity and enhances hippocampal-dependent learning performances. Only few studies have described hippocampal abnormalities after spinal cord injury (SCI) although cognitive deficits related to hippocampal function have been reported in rodents and even humans. The aim of this study was to characterize in further detail hippocampal changes in the acute and chronic SCI. Our data suggested that neurogenesis reduction in the acute phase after SCI could be due to enhanced death of amplifying neural progenitors (ANPs). In addition, astrocytes became reactive and microglial cells increased their number in almost all hippocampal regions studied. Glial changes resulted in a non-inflammatory response as the mRNAs of the major pro-inflammatory cytokines (IL-1ß, TNFα, IL-18) remained unaltered, but CD200R mRNA levels were downregulated. Long-term after SCI, astrocytes remained reactive but on the other hand, microglial cell density decreased. Also, glial cells induced a neuroinflammatory environment with the upregulation of IL-1ß, TNFα and IL-18 mRNA expression and the decrease of CD200R mRNA. Neurogenesis reduction may be ascribed at later time points to inactivation of neural stem cells (NSCs) and inhibition of ANP proliferation. The number of granular cells and CA1 pyramidal neurons decreased only in the chronic phase. The release of pro-inflammatory cytokines at the chronic phase might involve neurogenesis reduction and neurodegeneration of hippocampal neurons. Therefore, SCI led to hippocampal changes that could be implicated in cognitive deficits observed in rodents and humans.

Progesterone and Allopregnanolone Neuroprotective Effects in the Wobbler Mouse Model of Amyotrophic Lateral Sclerosis.

Progesterone regulates a number of processes in neurons and glial cells not directly involved in reproduction or sex behavior. Several neuroprotective effects are better observed under pathological conditions, as shown in the Wobbler mouse model of amyotrophic laterals sclerosis (ALS). Wobbler mice are characterized by forelimb atrophy due to motoneuron degeneration in the spinal cord, and include microgliosis and astrogliosis. Here we summarized current evidence on progesterone reversal of Wobbler neuropathology. We demonstrated that progesterone decreased motoneuron vacuolization with preservation of mitochondrial respiratory complex I activity, decreased mitochondrial expression and activity of nitric oxide synthase, increased Mn-dependent superoxide dismutase, stimulated brain-derived neurotrophic factor, increased the cholinergic phenotype of motoneurons, and enhanced survival with a concomitant decrease of death-related pathways. Progesterone also showed differential effects on glial cells, including increased oligodendrocyte density and downregulation of astrogliosis and microgliosis. These changes associate with reduced anti-inflammatory markers. The enhanced neurochemical parameters were accompanied by longer survival and increased muscle strength in tests of motor behavior. Because progesterone is locally metabolized to allopregnanolone (ALLO) in nervous tissues, we also studied neuroprotection by this derivative. Treatment of Wobbler mice with ALLO decreased oxidative stress and glial pathology, increased motoneuron viability and clinical outcome in a progesterone-like manner, suggesting that ALLO could mediate some progesterone effects in the spinal cord. In conclusion, the beneficial effects observed in different parameters support the versatile properties of progesterone and ALLO in a mouse model of motoneuron degeneration. The studies foresee future therapeutic opportunities with neuroactive steroids for deadly diseases like ALS.

Activation of the G Protein-Coupled Estrogen Receptor (GPER) Increases Neurogenesis and Ameliorates Neuroinflammation in the Hippocampus of Male Spontaneously Hypertensive Rats.

It is known that spontaneously hypertensive rats (SHR) present a marked encephalopathy, targeting vulnerable regions such as the hippocampus. Abnormalities of the hippocampus of SHR include decreased neurogenesis in the dentate gyrus (DG), partial loss of neurons in the hilus of the DG, micro and astrogliosis and inflammation. It is also known that 17ß-estradiol (E2) exert neuroprotective effects and prevent hippocampal abnormalities of SHR. The effects of E2 may involve a variety of mechanisms, including intracellular receptors of the ERα and ERß subtypes or membrane-located receptors, such as the G protein-coupled estradiol receptor (GPER). We have now investigated the protective role of GPER in SHR employing its synthetic agonist G1. To accomplish this objective, 5 month-old male SHR received 150 µg/day of G1 during 2 weeks. At the end of this period, we analyzed neuronal progenitors by staining for doublecortin (DCX), and counted the number of glial fibrillary acidic protein (GFAP)-labeled astrocytes and Iba1-stained microglial cells by computerized image analysis. We found that G1 activation of GPER increased DCX+ cells in the DG and reduced GFAP+ astrogliosis and Iba1+ microgliosis in the CA1 region of hippocampus. We also found that the high expression of proinflammatory makers IL1ß and cyclooxygenase 2 (COX2) of SHR was decreased after G1 treatment, which correlated with a change of microglia phenotype from the activated to a resting morphology. Additionally, G1 treatment increased the anti-inflammatory factor TGFß in SHR hippocampus. Altogether, our results suggest that activation of GPER plays a neuroprotective role on the encephalopathy of SHR, an outcome resembling E2 effects but avoiding secondary effects of the natural hormone.

Insights into the Therapeutic Potential of Glucocorticoid Receptor Modulators for Neurodegenerative Diseases.

Glucocorticoids are crucial for stress-coping, resilience, and adaptation. However, if the stress hormones become dysregulated, the vulnerability to stress-related diseases is enhanced. In this brief review, we discuss the role of glucocorticoids in the pathogenesis of neurodegenerative disorders in both human and animal models, and focus in particular on amyotrophic lateral sclerosis (ALS). For this purpose, we used the Wobbler animal model, which mimics much of the pathology of ALS including a dysfunctional hypothalamic-pituitary-adrenal axis. We discuss recent studies that demonstrated that the pathological cascade characteristic for motoneuron degeneration of ALS is mimicked in the genetically selected Wobbler mouse and can be attenuated by treatment with the selective glucocorticoid receptor antagonist (GRA) CORT113176. In long-term treatment (3 weeks) GRA attenuated progression of the behavioral, inflammatory, excitatory, and cell-death-signaling pathways while increasing the survival signal of serine-threonine kinase (pAkt). The action mechanism of the GRA may be either by interfering with GR deactivation or by restoring the balance between pro- and anti-inflammatory signaling pathways driven by the complementary mineralocorticoid receptor (MR)- and GR-mediated actions of corticosterone. Accordingly, GR antagonism may have clinical relevance for the treatment of neurodegenerative diseases.

Introduction to the Special Issue "Neuroactive Steroids".

Steroids are complex molecules, exerting known and still unknown effects in the nervous system. Throughout this volume, the reader will find a wide spectrum of articles, giving an up-to-date account of the molecular, physiological, pharmacological, and clinical aspects of steroid action on the nervous system.

Spinal Cord Injury Impairs Neurogenesis and Induces Glial Reactivity in the Hippocampus.

The incorporation of newborn neurons with increased synaptic remodeling and activity-dependent plasticity in the dentate gyrus enhances hippocampal-dependent learning performances. Astrocytes and microglial cells are components of the neurogenic niche and regulate neurogenesis under normal and neurophatological conditions leading to functional consequences for learning and memory. Although cognitive impairments were reported in patients after spinal cord injury (SCI), only few studies have considered remote changes in brain structures which are not related with sensory and motor cortex. Thus, we examined neurogenesis and glial reactivity by stereological assessment in dentate gyrus sub-regions after three different intensities of thoracic spinal cord compression in rats. Sixty days after injury we observed a decrease in the Basso-Bresnahan-Beattie locomotor scale scores, rotarod performance and volume of spare tissue that correlated with the severity of the compression. Regarding the hippocampus, we observed that neurogenesis and hilar neurons were reduced after severe SCI, while only neurogenesis decreased in the moderately injured group. In addition, severe SCI induced reactive microglia and astrogliosis in all dentate gyrus sub-regions. Furthermore, the density of reactive microglia increased in the hilus whereas astrogliosis developed in the molecular layer after moderate SCI. No changes were observed in the mildly injured rats. These results suggest glial response and neurogenesis are associated with injury intensity. Interestingly, hippocampal neurogenesis is more sensitive to SCI than astrocytes or microglia reaction, as moderate injury impairs the generation of new neurons without changing glial response in the subgranular zone.

Neuroactive Steroids in Acute Ischemic Stroke: Association with Cognitive, Functional, and Neurological Outcomes.

Despite several scientific and technological advances, there is no single neuroprotective treatment that can reverse the brain damage after acute ischemic stroke (AIS). Neuroactive steroids are cholesterol-derived hormones that have the ability to modulate the normal and pathologic nervous system employing genomic and nongenomic mechanisms. In this work, we first investigated if AIS affects the plasma concentration of 5 neuroactive steroids (cortisol, estradiol, progesterone, testosterone, and 3α-androstenediol glucuronide). Second, we studied if levels of circulating steroids associate with neurological, cognitive, and functional outcome in a cohort of 60- to 90 year-old male and female patients with AIS. For this purpose, we recruited patients who were hospitalized at the Emergency Room of the Central Military Hospital within the first 24 h after stroke onset. We designed 2 experimental groups, each one composed of 30 control subjects and 30 AIS patients, both males and females. The assessment of neurological deficit was performed with the NIHSS and the tests used for the functional and cognitive status were: (1) modified Rankin Scale; (2) Photo test, and (3) abbreviated Pfeiffer's mental status questionnaire. We observed a significant difference in plasma concentration of cortisol and estradiol between both experimental groups. In the AIS group, higher levels of these neuroactive steroids were associated with more pronounced neurological, cognitive and functional deficits in women compared to men. We propose that in elderly patients, high levels of circulating neuroactive steroids like cortisol and estradiol could potentiate AIS-mediated neuropathology in the ischemic and penumbra areas.

Stress-induced Neuroinflammation of the Spinal Cord is Restrained by Cort113176 (Dazucorilant), A Specific Glucocorticoid Receptor Modulator.

Glucocorticoids exert antiinflammatory, antiproliferative and immunosupressive effects. Paradoxically they may also enhance inflammation particularly in the nervous system, as shown in Cushing´ syndrome and neurodegenerative disorders of humans and models of human diseases. ."The Wobbler mouse model of amyotrophic lateral sclerosis shows hypercorticoidism and neuroinflammation which subsided by treatment with the glucocorticoid receptor (GR) modulator Dazucorilant (CORT113176). This effect suggests that GR mediates the chronic glucocorticoid unwanted effects. We now tested this hypothesis using a chronic stress model resembling the condition of the Wobbler mouse Male NFR/NFR mice remained as controls or were subjected to a restraining / rotation stress protocol for 3 weeks, with a group of stressed mice receiving CORT113176 also for 3 weeks. We determined the mRNAS or reactive protein for the proinflamatory factors HMGB1, TLR4, NFkB, TNFα, markers of astrogliosis (GFAP, SOX9 and acquaporin 4), of microgliosis (Iba, CD11b, P2RY12 purinergic receptor) as well as serum IL1ß and corticosterone. We showed that chronic stress produced high levels of serum corticosterone and IL1ß, decreased body and spleen weight, produced microgliosis and astrogliosis and increased proinflammatory mediators. In stressed mice, modulation of the GR with CORT113176 reduced Iba + microgliosis, CD11b and P2RY12 mRNAs, immunoreactive HMGB1 + cells, GFAP + astrogliosis, SOX9 and acquaporin expression and TLR4 and NFkB mRNAs vs. stress-only mice. The effects of CORT113176 indicate that glucocorticoids are probably involved in neuroinflammation. Thus, modulation of the GR would become useful to dampen the inflammatory component of neurodegenerative disorders.

Effects of the mineralocorticoid receptor antagonist eplerenone in experimental autoimmune encephalomyelitis.

There is growing evidence indicating that mineralocorticoid receptor (MR) expression influences a wide variety of functions in metabolic and immune response. The present study explored if antagonism of the MR reduces neuroinflammation in the spinal cord of mice with experimental autoimmune encephalomyelitis (EAE). Eplerenone (EPLE) (100 mg/kg dissolved in 30% 2-hydroxypropyl-ß-cyclodextrin) was administered intraperitoneally (i.p.) daily from EAE induction (day 0) until sacrificed on day 17 post-induction. The MR blocker (a) significantly decreased the inflammatory parameters TLR4, MYD88, IL-1ß, and iNOS mRNAs; (b) attenuated HMGB1, NLRP3, TGF-ß mRNAs, microglia, and aquaporin4 immunoreaction without modifying GFAP. Serum IL-1ß was also decreased in the EAE+EPLE group. Moreover, EPLE treatment prevented demyelination and improved clinical signs of EAE mice. Interestingly, MR was decreased and GR remained unchanged in EAE mice while EPLE treatment restored MR expression, suggesting that a dysbalanced MR/GR was associated with the development of neuroinflammation. Our results indicated that MR blockage with EPLE attenuated inflammation-related spinal cord pathology in the EAE mouse model of Multiple Sclerosis, supporting a novel therapeutic approach for immune-related diseases.

Testosterone Reduces Myelin Abnormalities in the Wobbler Mouse Model of Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is a fatal motoneuron degenerative disease that is associated with demyelination. The Wobbler (WR) mouse exhibits motoneuron degeneration, gliosis and myelin deterioration in the cervical spinal cord. Since male WRs display low testosterone (T) levels in the nervous system, we investigated if T modified myelin-relative parameters in WRs in the absence or presence of the aromatase inhibitor, anastrozole (A). We studied myelin by using luxol-fast-blue (LFB) staining, semithin sections, electron microscopy and myelin protein expression, density of IBA1+ microglia and mRNA expression of inflammatory factors, and the glutamatergic parameters glutamine synthetase (GS) and the transporter GLT1. Controls and WR + T showed higher LFB, MBP and PLP staining, lower g-ratios and compact myelin than WRs and WR + T + A, and groups showing the rupture of myelin lamellae. WRs showed increased IBA1+ cells and mRNA for CD11b and inflammatory factors (IL-18, TLR4, TNFαR1 and P2Y12R) vs. controls or WR + T. IBA1+ cells, and CD11b were not reduced in WR + T + A, but inflammatory factors' mRNA remained low. A reduction of GS+ cells and GLT-1 immunoreactivity was observed in WRs and WR + T + A vs. controls and WR + T. Clinically, WR + T but not WR + T + A showed enhanced muscle mass, grip strength and reduced paw abnormalities. Therefore, T effects involve myelin protection, a finding of potential clinical translation.

Beneficial effects of the phytoestrogen genistein on hippocampal impairments of spontaneously hypertensive rats (SHR).

Hippocampal neuropathology is a recognized feature of the spontaneously hypertensive rat (SHR). The hippocampal alterations associate with cognitive impairment. We have shown that hippocampal abnormalities are reversed by 17ß-estradiol, a steroid binding to intracellular receptors (estrogen receptor α and ß subtypes) or the membrane-located G-protein coupled estradiol receptor. Genistein (GEN) is a neuroprotective phytoestrogen which binds to estrogen receptor ß and G-protein coupled estradiol receptor. Here, we investigated whether GEN neuroprotection extends to SHR. For this purpose, we treated 5-month-old SHR for 2 weeks with 10 mg kg-1 daily s.c injections of GEN. We analyzed the expression of doublecortin+ neuronal progenitors, glial fibrillary acidic protein+ astrocytes and ionized calcium-binding adapter molecule 1+ microglia in the CA1 region and dentate gyrus of the hippocampus using immunocytochemistry, whereas a quantitative real-time polymerase chain reaction was used to measure the expression of pro- and anti-inflammatory factors tumor necrosis factor α, cyclooxygenase-2 and transforming growth factor ß. We also evaluated hippocampal dependent memory using the novel object recognition test. The results showed a decreased number of doublecortin+ neural progenitors in the dentate gyrus of SHR that was reversed with GEN. The number of glial fibrillary acidic protein+ astrocytes in the dentate gyrus and CA1 was increased in SHR but significantly decreased by GEN treatment. Additionally, GEN shifted microglial morphology from the predominantly activated phenotype present in SHR, to the more surveillance phenotype found in normotensive rats. Furthermore, treatment with GEN decreased the mRNA of the pro-inflammatory factors tumor necrosis factor α and cyclooxygenase-2 and increased the mRNA of the anti-inflammatory factor transforming growth factor ß. Discrimination index in the novel object recognition test was decreased in SHR and treatment with GEN increased this parameter. Our results indicate important neuroprotective effects of GEN at the neurochemical and behavioral level in SHR. Our data open an interesting possibility for proposing this phytoestrogen as an alternative therapy in hypertensive encephalopathy.

Progesterone prevents mitochondrial dysfunction in the spinal cord of wobbler mice.

In the Wobbler mouse, a mutation of the Vps54 protein increases oxidative stress in spinal motoneurons, associated to toxic levels of nitric oxide and hyperactivity of nitric oxide synthase (NOS). Progesterone neuroprotection has been reported for several CNS diseases, including the Wobbler mouse neurodegeneration. In the present study, we analyzed progesterone effects on mitochondrial-associated parameters of symptomatic Wobbler mice. The activities of mitochondrial respiratory chain complexes I, II-III and IV and protein levels of mitochondrial and cytosolic NOS were determined in cervical and lumbar cords from control, Wobbler and Wobbler mice receiving a progesterone implant for 18 days. We found a significant reduction of complex I and II-III activities in mitochondria and increased protein levels of mitochondrial, but not cytosolic nNOS, in the cervical cord of Wobbler mice. Progesterone treatment prevented the reduction of complex I in the cervical region and the increased level of mitochondrial nNOS. Wobbler motoneurons also showed accumulation of amyloid precursor protein immunoreactivity and decreased activity and immunostaining of MnSOD. Progesterone treatment avoided these abnormalities. Therefore, administration of progesterone to clinically afflicted Wobblers (i) prevented the abnormal increase of mitochondrial nNOS and normalized respiratory complex I; (ii) decreased amyloid precursor protein accumulation, a sign of axonal degeneration, and (iii) increased superoxide dismutation. Thus, progesterone neuroprotection decreases mitochondriopathy of Wobbler mouse cervical spinal cord.

Tibolone restrains neuroinflammation in mouse experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) is an immune-mediated and degenerating disease in which myelin sheaths are damaged as a result of chronic progressive inflammation of the central nervous system. Tibolone [(7α,17α)-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-in-3-one], a synthetic estrogenic compound with tissue-specific actions and used for menopausal hormone therapy, shows neuroprotective and antioxidant properties both in vivo and in vitro. In the present study, we analyzed whether tibolone plays a therapeutic role in experimental autoimmune encephalomyelitis (EAE) mice, a commonly used model of MS. Female C57BL/6 mice were induced with the myelin oligodendrocyte glycoprotein MOG35-55 and received s.c. tibolone (0.08 mg kg-1 ) injection every other day from the day of induction until death on the acute phase of the disease. Reactive gliosis, Toll like receptor 4 (TLR4), high mobility group box protein 1 (HMGB1), inflammasome parameters, activated Akt levels and myelin were assessed by a real-time polymerase chain reaction, immunohistochemistry, and western blot analysis. Our findings indicated that, in the EAE spinal cord, tibolone reversed the astrocytic and microglial reaction, and reduced the hyperexpression of TLR4 and HMGB1, as well as NLR family pyrin domain containing 3-caspase 1-interleukin-1ß inflammasome activation. At the same time, tibolone attenuated the Akt/nuclear factor kappa B pathway and limited the white matter demyelination area. Estrogen receptor expression was unaltered with tibolone treatment. Clinically, tibolone improved neurological symptoms without uterine compromise. Overall, our data suggest that tibolone may serve as a promising agent for the attenuation of MS-related inflammation.

IGF1 Gene Therapy Reversed Cognitive Deficits and Restored Hippocampal Alterations After Chronic Spinal Cord Injury.

The hippocampus is implicated in the generation of memory and learning, processes which involve extensive neuroplasticity. The generation of hippocampal adult-born neurons is particularly regulated by glial cells of the neurogenic niche and the surrounding microenvironment. Interestingly, recent evidence has shown that spinal cord injury (SCI) in rodents leads to hippocampal neuroinflammation, neurogenesis reduction, and cognitive impairments. In this scenario, the aim of this work was to evaluate whether an adenoviral vector expressing IGF1 could reverse hippocampal alterations and cognitive deficits after chronic SCI. SCI caused neurogenesis reduction and impairments of both recognition and working memories. We also found that SCI increased the number of hypertrophic arginase-1 negative microglia concomitant with the decrease of the number of ramified surveillance microglia in the hilus, molecular layer, and subgranular zone of the dentate gyrus. RAd-IGF1 treatment restored neurogenesis and improved recognition and working memory impairments. In addition, RAd-IGF1 gene therapy modulated differentially hippocampal regions. In the hilus and molecular layer, IGF1 gene therapy recovered the number of surveillance microglia coincident with a reduction of hypertrophic microglia cell number. However, in the neurogenic niche, IGF1 reduced the number of ramified microglia and increased the number of hypertrophic microglia, which as a whole expressed arginase-1. In summary, RAd-IGF1 gene therapy might surge as a new therapeutic strategy for patients with hippocampal microglial alterations and cognitive deficits such as those with spinal cord injury and other neurodegenerative diseases.

Developmental expression of genes involved in progesterone synthesis, metabolism and action during the post-natal cerebellar myelination.

Progesterone is involved in dendritogenesis, synaptogenesis and maturation of cerebellar Purkinge cells, major sites of steroid synthesis in the brain. To study a possible time-relationship between myelination, neurosteroidogenesis and steroid receptors during development of the postnatal mouse cerebellum, we determined at postnatal days 5 (P5),18 (P18) and 35 (P35) the expression of myelin basic protein (MBP), components of the steroidogenic pathway, levels of endogenous steroids and progesterone's classical and non-classical receptors. In parallel with myelin increased expression during development, P18 and P35 mice showed higher levels of cerebellar progesterone and its reduced derivatives, higher expression of steroidogenic acute regulatory protein (StAR) mRNA, cholesterol side chain cleavage enzyme (P450scc) and 5α-reductase mRNA vs. P5 mice. Other steroids such as corticosterone and its reduced derivatives and 3ß-androstanodiol (ADIOL) showed a peak increase at P18 compared to P5. Progesterone membrane receptors and binding proteins (PGRMC1, mPRα, mPRß, mPRγ, and Sigma1 receptors) mRNAs levels increased during development while that of classical progesterone receptors (PR) remained invariable. PRKO mice showed similar MBP levels than wild type. Thus, these data suggests that progesterone and its neuroactive metabolites may play a role in postnatal cerebellar myelination.

Progress in progestin-based therapies for neurological disorders.

Hormone therapy, primarily progesterone and progestins, for central nervous system (CNS) disorders represents an emerging field of regenerative medicine. Following a failed clinical trial of progesterone for traumatic brain injury treatment, attention has shifted to the progestin Nestorone for its ability to potently and selectively transactivate progesterone receptors at relatively low doses, resulting in robust neurogenetic, remyelinating, and anti-inflammatory effects. That CNS disorders, including multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), spinal cord injury (SCI), and stroke, develop via demyelinating, cell death, and/or inflammatory pathological pathways advances Nestorone as an auspicious candidate for these disorders. Here, we assess the scientific and clinical progress over decades of research into progesterone, progestins, and Nestorone as neuroprotective agents in MS, ALS, SCI, and stroke. We also offer recommendations for optimizing timing, dosage, and route of the drug regimen, and identifying candidate patient populations, in advancing Nestorone to the clinic.

Progesterone neuroprotection in traumatic CNS injury and motoneuron degeneration.

Studies on the neuroprotective and promyelinating effects of progesterone in the nervous system are of great interest due to their potential clinical connotations. In peripheral neuropathies, progesterone and reduced derivatives promote remyelination, axonal regeneration and the recovery of function. In traumatic brain injury (TBI), progesterone has the ability to reduce edema and inflammatory cytokines, prevent neuronal loss and improve functional outcomes. Clinical trials have shown that short-and long-term progesterone treatment induces a significant improvement in the level of disability among patients with brain injury. In experimental spinal cord injury (SCI), molecular markers of functional motoneurons become impaired, including brain-derived neurotrophic factor (BDNF) mRNA, Na,K-ATPase mRNA, microtubule-associated protein 2 and choline acetyltransferase (ChAT). SCI also produces motoneuron chromatolysis. Progesterone treatment restores the expression of these molecules while chromatolysis subsided. SCI also causes oligodendrocyte loss and demyelination. In this case, a short progesterone treatment enhances proliferation and differentiation of oligodendrocyte progenitors into mature myelin-producing cells, whereas prolonged treatment increases a transcription factor (Olig1) needed to repair injury-induced demyelination. Progesterone neuroprotection has also been shown in motoneuron neurodegeneration. In Wobbler mice spinal cord, progesterone reverses the impaired expression of BDNF, ChAT and Na,K-ATPase, prevents vacuolar motoneuron degeneration and the development of mitochondrial abnormalities, while functionally increases muscle strength and the survival of Wobbler mice. Multiple mechanisms contribute to these progesterone effects, and the role played by classical nuclear receptors, extra nuclear receptors, membrane receptors, and the reduced metabolites of progesterone in neuroprotection and myelin formation remain an exciting field worth of exploration.