Androgen regulates neuritin mRNA levels in an in vivo model of steroid-enhanced peripheral nerve regeneration

Neuritin improves cognitive impairments in APP/PS1 Alzheimer's disease mice model by mitigating neuronal ferroptosis via PI3K/Akt activation

The neurotrophic factor Neuritin is known to enhance cognitive capacity and to mitigate synaptic impairments in the APP/PS1 Alzheimer's disease (AD) mouse model, suggesting therapeutic potential for clinical treatment. However, the core molecular mechanisms remain elusive. Ferroptosis, a form of programmed cell death linked to iron dysregulation and oxidative stress, contributes to neurodegeneration in AD in part by accelerating amyloid-β deposition and neurofibrillary tangle formation. Here we examined if Neuritin can mitigate cognitive decline and neural degeneration in AD model mice by suppressing ferroptosis. Age-dependent cognitive decline was associated with Neuritin downregulation and increased ferroptosis in the hippocampus. Intracerebroventricular injection of exogenous Neuritin mitigated spatial and fear learning deficits as well as neural oxidative stress, apoptosis, and ferroptosis in the hippocampus without causing deleterious side effects. Neuritin injection also upregulated the activity of NAD+ kinase (NADK), the enzyme responsible for converting NAD to anti-ferroptotic NADPH, in the hippocampus of AD mice as well as in cultured hippocampal neurons. Reduced Neuritin expression in the hippocampus AD mice was associated with reduced phosphorylation (activation) of Akt (p-Akt), and Neuritin administration enhanced p-Akt expression in both HT22 cells and AD model mice. Conversely, blocking the PI3K/Akt pathway in HT22 cells reversed the Neuritin-induced increase in NADK activity and reduction in ferroptosis, indicating that Neuritin protects neurons from AD-induced damage by enhancing NADK activity through the PI3K/Akt pathway. Collectively, our results support Neuritin upregulation as a potential therapeutic strategy for early-phase AD.

Fusion with CTP increases the stability of recombinant neuritin

Neuritin is a vital neurotrophin that plays an essential role in recovery from nerve injury and neurodegenerative diseases and may become a new target for treating these conditions. However, improving neuritin protein stability is an urgent problem. In this study, to obtain active and stable neuritin proteins, we added a carboxyl-terminal peptide (CTP) sequence containing four O-linked glycosylation sites to the C-terminus of neuritin and cloned it into the Chinese hamster ovary (CHO) expression system. The neuritin-CTP protein was purified using a His-Tag purification strategy after G418 screening of stable high-expression cell lines. Ultimately, we obtained neuritin-CTP protein with a purity >90%. Functional analyses showed that the purified neuritin-CTP protein promoted the neurite outgrowth of PC12 cells, and stability experiments showed that neuritin stability was increased by adding CTP. These results indicate that neuritin protein-CTP fusion effectively increases stability without affecting secretion and activity. This study offers a sound strategy for improving the stability of neuritin protein and provides material conditions for further study of the function of neuritin.

Involvement of histone methylation in the regulation of neuronal death

Neuronal death occurs in various physiological and pathological processes, and apoptosis, necrosis, and ferroptosis are three major forms of neuronal death. Neuronal apoptosis, necrosis, and ferroptosis are widely identified to involve the progress of stroke, Parkinson's disease, and Alzheimer's disease. A growing body of evidence has pointed out that neuronal death is tightly associated with expression of related genes and alteration of signaling molecules. In addition, recently, epigenetics has been increasingly focused on as a vital regulatory mechanism for neuronal apoptosis, necrosis, and ferroptosis, providing a new direction for treating nervous system diseases. Moreover, growing researches suggest that histone methylation or demethylation is involved in the processes of neuronal apoptosis, necrosis, and ferroptosis. These researches may imply that studying the potential roles of histone methylation is essential for treating the nervous system diseases. Here, we review potential roles of histone methylation and demethylation in neuronal death, which may give us a new direction in treating the nervous system diseases.

Neuritin affects the activity of neuralized-like 1 by promoting degradation and weakening its affinity for substrate

Neuritin plays a key role in neural development and regeneration by promoting neurite outgrowth and synapse maturation. Our previous research revealed the mechanism by which neuritin inhibits Notch signaling through interaction with neuralized-like 1 (Neurl1) to promote neurite growth. However, how neuritin regulates Notch signaling through Neurl1 has not been elucidated. Here, we first confirm that neuritin is an upstream regulator of Neurl1 and inhibits Notch signaling through Neurl1. Neurl1 is an E3 ubiquitin ligase that can promote ubiquitination and endocytosis of the Notch1 ligand Jagged1. Therefore, we observe the effect of neuritin on the ligase activity of Neurl1. The results indicate that neuritin inhibits Neurl1 activity by reducing the ubiquitination level and endocytosis of the target protein Jagged1. Moreover, we find that decreased activity of Neurl1 results in reduced expression of Notch receptor Notch intracellular domain (NICD) and downstream target gene hairy and enhancer of split-1 ( HES1). Furthermore, we investigate how neuritin affects Neurl1 enzyme activity. The results show that neuritin not only weakens the affinity between Neurl1 and Jagged1 but also promotes the degradation of Neurl1 by the 26S proteasome pathway. Taken together, our results suggest that neuritin negatively regulates Notch signaling by inhibiting the activity of Neurl1, promoting the degradation of Neurl1 and weakening the affinity of Neurl1 for Jagged1. Our study clarifies the molecular mechanisms of neuritin in regulating the Notch signaling pathway and provides new clues about how neuritin mediates neural regeneration and plasticity.

The role of ubiquitination in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is a neurodegenerative and neuromuscular genetic disease caused by the expansion of a polyglutamine-encoding CAG tract in the androgen receptor (AR) gene. The AR is an important transcriptional regulator of the nuclear hormone receptor superfamily; its levels are regulated in many ways including by ubiquitin-dependent degradation. Ubiquitination is a post-translational modification (PTM) which plays a key role in both AR transcriptional activity and its degradation. Moreover, the ubiquitin-proteasome system (UPS) is a fundamental component of cellular functioning and has been implicated in diseases of protein misfolding and aggregation, including polyglutamine (polyQ) repeat expansion diseases such as Huntington's disease and SBMA. In this review, we discuss the details of the UPS system, its functions and regulation, and the role of AR ubiquitination and UPS components in SBMA. We also discuss aspects of the UPS that may be manipulated for therapeutic effect in SBMA.

Gasdermin D in peripheral nerves: the pyroptotic microenvironment inhibits nerve regeneration

Wallerian degeneration (WD) involves the recruitment of macrophages for debris clearance and nerve regeneration, and the cause of the foamy macrophages that are frequently observed in peripheral transection injuries is unknown. Recent studies indicated that these foamy cells are generated by gasdermin D (GSDMD) via membrane perforation. However, whether these foamy cells are pyroptotic macrophages and whether their cell death elicits immunogenicity in peripheral nerve regeneration (PNR) remain unknown. Therefore, we used GSDMD-deficient mice and mice with deficiencies in other canonical inflammasomes to establish a C57BL/6 J mouse model of sciatic nerve transection and microanastomosis (SNTM) and evaluate the role of GSDMD-executed pyroptosis in PNR. In our study, the GSDMD^−/− mice with SNTM showed a significantly diminished number of foamy cells, better axon regeneration, and a favorable functional recovery, whereas irregular axons or gaps in the fibers were found in the wild-type (WT) mice with SNTM. Furthermore, GSDMD activation in the SNTM model was dependent on the NLRP3 inflammasome and caspase-1 activation, and GSDMD-executed pyroptosis resulted in a proinflammatory environment that polarized monocytes/macrophages toward the M1 (detrimental) but not the M2 (beneficial) phenotype. In contrast, depletion of GSDMD reversed the proinflammatory microenvironment and facilitated M2 polarization. Our results suggested that inhibition of GSDMD may be a potential treatment option to promote PNR.

miR‑199a decreases Neuritin expression involved in the development of Alzheimer's disease in APP/PS1 mice

Neuritin plays an important role in neural development and plasticity. A recent study demonstrated that increasing Neuritin levels attenuated synaptic damage in mice with Alzheimer's disease (AD), which exhibit a decreased Neuritin expression. However, it remains unclear as to whether Neuritin expression is regulated by microRNAs (miRNAs or miRs) in AD. In the present study, it was found that miR-199a decreased Neuritin expression and was therefore involved in the development of AD. Subsequently, differentially expressed miRNAs in AD from datasets and the literature were recruited, and those that could bind Neuritin were predicted using bioinformatics analysis. The present study then focused on the candidate miRNAs that were highly associated with Neuritin and were upregulated in AD. The expression patterns of the candidate miRNAs and Neuritin in the hippocampus and cortex of APP/PS1 (AD model) mice at different stages were then detected and analyzed. It was found that miR-199a expression was significantly increased in the early stages of AD and was negatively associated with Neuritin expression. Furthermore, it was revealed that the decreased Neuritin expression was due to the direct targeting of the Neuritin 3′-UTR by miR-199a. Finally, the association between the spatial memory capacity of APP/PS1 mice and the changes in miR-199a and Neuritin expression protein was investigated. On the whole, the data of the present study suggest that miR-199a is involved in the development of AD by regulating Neuritin expression.

The Role of Sex and Sex Hormones in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are a wide class of disorders of the central nervous system (CNS) with unknown etiology. Several factors were hypothesized to be involved in the pathogenesis of these diseases, including genetic and environmental factors. Many of these diseases show a sex prevalence and sex steroids were shown to have a role in the progression of specific forms of neurodegeneration. Estrogens were reported to be neuroprotective through their action on cognate nuclear and membrane receptors, while adverse effects of male hormones have been described on neuronal cells, although some data also suggest neuroprotective activities. The response of the CNS to sex steroids is a complex and integrated process that depends on (i) the type and amount of the cognate steroid receptor and (ii) the target cell type-either neurons, glia, or microglia. Moreover, the levels of sex steroids in the CNS fluctuate due to gonadal activities and to local metabolism and synthesis. Importantly, biochemical processes involved in the pathogenesis of NDs are increasingly being recognized as different between the two sexes and as influenced by sex steroids. The aim of this review is to present current state-of-the-art understanding on the potential role of sex steroids and their receptors on the onset and progression of major neurodegenerative disorders, namely, Alzheimer's disease, Parkinson's diseases, amyotrophic lateral sclerosis, and the peculiar motoneuron disease spinal and bulbar muscular atrophy, in which hormonal therapy is potentially useful as disease modifier.

Production of polyclonal antibody against human Neuritin and its application of immunodetection

OBJECTIVE

To date, a commercial antibody to human Neuritin for immunoprecipitation is still limited. In this study, we aimed to develop a specific antibody for further research on the potential function of Neuritin.

METHODS AND RESULTS

By epitope prediction of recombinant human Neuritin, the active fragment of human Neuritin that could be used as an excellent immunogen. Soluble His-tagged Neuritin was expressed and purified from Pichia pastoris. Polyclonal antibody against Neuritin was obtained by immunizing Sprague-Dawley rats with purified recombinant human Neuritin. Affinity-purified polyclonal antibody against Neuritin was characterized with indirect enzyme-linked immunosorbent assay, immunoblotting, immunoprecipitation, and immunofluorescence. The results demonstrated that the polyclonal antibody against Neuritin had been prepared successfully. The prepared antibody bound to both exogenous and endogenous Neuritin. Importantly, the anti-Neuritin polyclonal antibody could be used in immunoprecipitation assays.

CONCLUSIONS

The prepared polyclonal antibody could be used in immunoprecipitation and provide researchers with a useful tool for further investigating the function and mechanism of Neuritin.

Neuroprotective Effects on the Morphology of Somatic Motoneurons Following the Death of Neighboring Motoneurons: A Role for Microglia?

Partial depletion of spinal motoneuron populations induces dendritic atrophy in neighboring motoneurons, and treatment with testosterone protects motoneurons from induced dendritic atrophy. We explored a potential mechanism for this induced atrophy and protection by testosterone, examining the microglial response to partial depletion of motoneurons. Motoneurons innervating the vastus medialis muscles of adult male rats were killed by intramuscular injection of cholera toxin-conjugated saporin; some saporin-injected rats were treated with testosterone. Microglia were later visualized via immunohistochemical staining, classified as monitoring or activated, and counted stereologically. Partial motoneuron depletion increased the number of activated microglia in the quadriceps motor pool, and this increase was attenuated with testosterone treatment. The attenuation in microglial response could reflect an effect of testosterone on suppressing microglia activation, potentially sparing motoneuron dendrites. Alternatively, testosterone could be neuroprotective, sparing motoneuron dendrites, secondarily resulting in reduced microglial activation. To discriminate between these hypotheses, following partial motoneuron depletion, rats were treated with minocycline to inhibit microglial activation. Motoneurons innervating the ipsilateral vastus lateralis muscle were later labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed. Reduction of microglial activation by minocycline did not prevent induced dendritic atrophy following partial motoneuron depletion. Further, reduction of microglial activation by minocycline treatment resulted in dendritic atrophy in intact animals. Together, these findings indicate that the neuroprotective effect of testosterone on dendrites following motoneuron death is not due to inhibiting microglial activation, and that microglial activity contributes to the normal maintenance of dendritic arbors.

Protective effects of gonadal hormones on spinal motoneurons following spinal cord injury

Spinal cord injury (SCI) results in lesions that destroy tissue and disrupt spinal tracts, producing deficits in locomotor and autonomic function. The majority of treatment strategies after SCI have concentrated on the damaged spinal cord, for example working to reduce lesion size or spread, or encouraging regrowth of severed descending axonal projections through the lesion, hoping to re-establish synaptic connectivity with caudal targets. In our work, we have focused on a novel target for treatment after SCI, surviving spinal motoneurons and their target musculature, with the hope of developing effective treatments to preserve or restore lost function following SCI. We previously demonstrated that motoneurons, and the muscles they innervate, show pronounced atrophy after SCI. Importantly, SCI-induced atrophy of motoneuron dendrites can be attenuated by treatment with gonadal hormones, testosterone and its active metabolites, estradiol and dihydrotestosterone. Similarly, SCI-induced reductions in muscle fiber cross-sectional areas can be prevented by treatment with androgens. Together, these findings suggest that regressive changes in motoneuron and muscle morphology seen after SCI can be ameliorated by treatment with gonadal hormones, further supporting a role for steroid hormones as neurotherapeutic agents in the injured nervous system.

What does the research say about androgen use and cerebrovascular events?

Many studies have investigated the benefits of androgen therapy and neurosteroids in aging men, while concerns remain about the potential associations of exogenous steroids and incidents of cerebrovascular events and ischemic stroke (IS). Testosterone is neuroprotective, neurotrophic and a potent stimulator of neuroplasticity. These benefits are mediated primarily through conversion of a small amount of testosterone to estradiol by the catalytic activity of estrogen synthetase (aromatase cytochrome P450 enzyme). New studies suggest that abnormal serum levels of the nonaromatized potent metabolite of testosterone, either high or low dihydrotestosterone (DHT), is a risk factor for stroke. Associations between pharmacologic androgen use and the incidence of IS are questionable, because a significant portion of testosterone is converted to DHT. There is also insufficient evidence to reject a causal relationship between the pro-testosterone adrenal androgens and incidence of IS. Moreover, vascular intima-media thickness, which is a predictor of stroke and myocardial symptoms, has correlations with sex hormones. Current diagnostic and treatment criteria for androgen therapy for cerebrovascular complications are unclear. Confounding variables, including genetic and metabolic alterations of the key enzymes of steroidogenesis, ought to be considered. Information extracted from pharmacogenetic testing may aid in expounding the protective-destructive properties of neurosteroids, as well as the prognosis of androgen therapy, in particular their cerebrovascular outcomes. This investigative review article addresses relevant findings of the clinical and experimental investigations of androgen therapy, emphasizes the significance of genetic testing of androgen responsiveness towards individualized therapy in post-IS injuries as well as identifying pertinent questions.

Protective Effects of Estradiol and Dihydrotestosterone following Spinal Cord Injury

Spinal cord injury (SCI) results in lesions that destroy tissue and disrupt spinal tracts, producing deficits in locomotor and autonomic function. We previously demonstrated that motoneurons and the muscles they innervate show pronounced atrophy after SCI, and these changes are prevented by treatment with testosterone. Here, we assessed whether the testosterone active metabolites estradiol and dihydrotestosterone have similar protective effects after SCI. Young adult female rats received either sham or T9 spinal cord contusion injuries and were treated with estradiol, dihydrotestosterone, both, or nothing via Silastic capsules. Basso-Beattie-Bresnahan locomotor testing was performed weekly and voiding behavior was assessed at 3 weeks post-injury. Four weeks after SCI, lesion volume and tissue sparing, quadriceps muscle fiber cross-sectional area, and motoneuron dendritic morphology were assessed. Spontaneous locomotor behavior improved after SCI, but hormone treatments had no effect. Voiding behavior was disrupted after SCI, but was significantly improved by treatment with either estradiol or dihydrotestosterone; combined treatment was maximally effective. Treatment with estradiol reduced lesion volume, but dihydrotestosterone alone and estradiol combined with dihydrotestosterone were ineffective. SCI-induced decreases in motoneuron dendritic length were attenuated by all hormone treatments. SCI-induced reductions in muscle fiber cross-sectional areas were prevented by treatment with either dihydrotestosterone or estradiol combined with dihydrotestosterone, but estradiol treatment was ineffective. These findings suggest that deficits in micturition and regressive changes in motoneuron and muscle morphology seen after SCI are ameliorated by treatment with estradiol or dihydrotestosterone, further supporting a role for steroid hormones as neurotherapeutic agents in the injured nervous system.

Dihydrotestosterone Treatment Accelerates Autograft Reversal Sciatic Nerve Regeneration in Rats

Neuroactive steroids such as progesterone, testosterone, and their derivatives have been widely studied for their neuroprotective roles in the nervous system. Autologous nerve transplantation is considered as the gold standard repair technique when primary suture is impossible; nevertheless, this method is far from ideal. In this study, we aimed to explore the impact of dihydrotestosterone (DHT), a 5α-reduced derivative of testosterone, on the recovery of peripheral nerve injury treated with autologous nerve transplantation. Sprague-Dawley rats were subjected to a 10-mm right side sciatic nerve reversed autologous nerve transplantation and randomly divided into groups that received DHT or DHT + flutamide (an androgen receptor blocker) daily for 8 weeks after operation. Our results demonstrated that DHT could speed up the rate of axonal regeneration and increase the expression of myelin protein zero (P0) in autograft reversal sciatic nerves. Thus, our study provided new insights into improving the prognosis of patients with long gap peripheral nerve defects.

Expression of hNeuritin protein in a baculovirus expression system and the analysis of its activity

Neuritin plays an important role in the development and regeneration of the nervous system, and shows good prospects in the treatment and protection of the nervous system. To characterize neuritin function, we constructed a baculovirus expression system of neuritin, and identified the biological activity of the neuritin protein. The results and showed that the expression product could promote the neurite growth of dorsal root ganglion in chicken embryos. The neuritin open reading frame was amplified and cloned into the plasmid pFastBac™HTA. The pFastBac™HTA-neuritin was confirmed to be correct by PCR and DNA sequencing, and then transformed into Escherichia coli DH10Bac. The high purity recombinant Bacmid-neuritin (shuttle vectors) was obtained from DH10Bac through screening and identification. Recombinant virus, including the neuritin gene (virus-neuritin), was produced by transfection of SF9 cells using the bacmid-neuritin, and then amplified repeatedly to express the neuritin fusion protein. Finally, we identified the fusion protein with SDS-PAGE and western blotting, and optimized the best expression time of the neuritin fusion protein. We also analyzed the activity of the expressed protein by dorsal root ganglion from chicken embryos.

Neuritin Inhibits Notch Signaling through Interacted with Neuralized to Promote the Neurite Growth

Neuritin plays a key role in neural development and regeneration by promoting neurite outgrowth and synapse maturation. However, the mechanism of neuritin in modulating neurite growth has not been elucidated. Here, using yeast two-hybrid we screened and discovered the interaction of neuritin and neuralized (NEURL1), which is an important regulator that can activate Notch signaling through promoting endocytosis of Notch ligand. And then we identified the interaction of neuritin and neuralized by co-immunoprecipitation (IP) assays, and clarified that neuritin and NEURL1 were co-localized on the cell membrane of SH-SY5Y cells. Moreover, neuritin significantly suppressed Notch ligand Jagged1 (JAG1) endocytosis promoted by NEURL1, and then inhibited the activation of Notch receptor Notch intracellular domain (NICD) and decreased the expression of downstream gene hairy and enhancer of split-1 (HES1). Importantly, the effect of neuritin on inhibiting Notch signaling was rescued by NEURL1, which indicated that neuritin is an upstream and negative regulator of NEURL1 to inhibit Notch signaling through interaction with NEURL1. Notably, recombinant neuritin restored the retraction of neurites caused by activation of Notch, and neurite growth stimulated by neuritin was partially blocked by NEURL1. These findings establish neuritin as an upstream and negative regulator of NEURL1 that inhibits Notch signaling to promote neurite growth. This mechanism connects neuritin with Notch signaling, and provides a valuable foundation for further investigation of neuritin's role in neurodevelopment and neural plasticity.

Recombinant hNeuritin Promotes Structural and Functional Recovery of Sciatic Nerve Injury in Rats

Neuritin is a new neurotropic factor implicated in nervous system development and plasticity. Studies have shown that Neuritin is upregulated in injured nerves, suggesting that it is involved in nerve repair. To test this hypothesis, we investigated whether recombinant human Neuritin could restore nerve structure and function in a rat model of sciatic nerve injury. Neuritin treatment had a dose-dependent effect on functional recovery 4 weeks after injury, as determined by the walking-track test. Similar trends were observed for gastrocnemius muscular strength and nerve conduction velocity. Additionally, sciatic nerve fiber density and organization as well as degree of remyelination were increased, while growth-associated protein 43 and neurofilament 200 expression was upregulated upon treatment with Neuritin. These findings demonstrate that Neuritin stimulates nerve regeneration and functional recovery and thus promotes the repair of injured sciatic nerves.

Preventing the Androgen Receptor N/C Interaction Delays Disease Onset in a Mouse Model of SBMA

Spinal and bulbar muscular atrophy (SBMA) is a neurodegenerative disease caused by a polyglutamine expansion in the androgen receptor (AR) and is associated with misfolding and aggregation of the mutant AR. We investigated the role of an interdomain interaction between the amino (N)-terminal FxxLF motif and carboxyl (C)-terminal AF-2 domain in a mouse model of SBMA. Male transgenic mice expressing polyQ-expanded AR with a mutation in the FxxLF motif (F23A) to prevent the N/C interaction displayed substantially improved motor function compared with N/C-intact AR-expressing mice and showed reduced pathological features of SBMA. Serine 16 phosphorylation was substantially enhanced by the F23A mutation; moreover, the protective effect of AR F23A was dependent on this phosphorylation. These results reveal an important role for the N/C interaction on disease onset in mice and suggest that targeting AR conformation could be a therapeutic strategy for patients with SBMA.

A molecular analysis provides novel insights into androgen receptor signalling in breast cancer

BACKGROUND

Androgen Receptor (AR) is an essential transcription factor for the development of secondary sex characteristics, spermatogenesis and carcinogenesis. Recently AR has been implicated in the development and progression of breast and prostate cancers. Although some of the functions of the AR are known but the mechanistic details of these divergent processes are still not clear. Therefore understanding the regulatory mechanisms of the functioning of the AR in ER-/AR+ breast cancer will provide many novel targets for the purpose of therapeutic intervention.

METHODS/RESULTS

Using bioinformatics tools, we have identified 75 AR targets having prominent roles in cell cycle, apoptosis and metabolism. Herein, we validated 10 genes as AR targets by studying the regulation of these genes in MDA-MB-453 cell line on stimulation by androgens like 5α-dihydrotestosterone (DHT), using RT-qPCR and ChIP assay. It was observed that all the identified genes involved in cell cycle except MAD1L1 were found to be up regulated whereas expression of apoptosis related genes was decreased in response to DHT treatment. We performed an exhaustive, rigid-body docking between individual ARE and DNA binding domain (DBD) of the AR protein and it was found that novel residues K567, K588, K591 and R592 are involved in the process of DNA binding. To verify these specific DNA-protein interactions electrostatic energy term calculations for each residue was determined using the linearized Poisson-Boltzmann equation. Our experimental data showed that treatment of breast cancer cells with DHT promotes cell proliferation and decreases apoptosis. It was observed that bicalutamide treatment was able to reverse the effect of DHT.

CONCLUSION

Taken together, our results provide new insights into the mechanism by which AR promotes breast cancer progression. Moreover our work proposes to use bicalutamide along with taxanes as novel therapy for the treatment of TNBCs, which are positive for downstream AR signalling.

Drug delivery systems, CNS protection, and the blood brain barrier

Present review highlights various drug delivery systems used for delivery of pharmaceutical agents mainly antibiotics, antineoplastic agents, neuropeptides, and other therapeutic substances through the endothelial capillaries (BBB) for CNS therapeutics. In addition, the use of ultrasound in delivery of therapeutic agents/biomolecules such as proline rich peptides, prodrugs, radiopharmaceuticals, proteins, immunoglobulins, and chimeric peptides to the target sites in deep tissue locations inside tumor sites of brain has been explained. In addition, therapeutic applications of various types of nanoparticles such as chitosan based nanomers, dendrimers, carbon nanotubes, niosomes, beta cyclodextrin carriers, cholesterol mediated cationic solid lipid nanoparticles, colloidal drug carriers, liposomes, and micelles have been discussed with their recent advancements. Emphasis has been given on the need of physiological and therapeutic optimization of existing drug delivery methods and their carriers to deliver therapeutic amount of drug into the brain for treatment of various neurological diseases and disorders. Further, strong recommendations are being made to develop nanosized drug carriers/vehicles and noninvasive therapeutic alternatives of conventional methods for better therapeutics of CNS related diseases. Hence, there is an urgent need to design nontoxic biocompatible drugs and develop noninvasive delivery methods to check posttreatment clinical fatalities in neuropatients which occur due to existing highly toxic invasive drugs and treatment methods.

The effects of exercise on synaptic stripping require androgen receptor signaling

Following peripheral nerve injury, synapses are withdrawn from axotomized motoneurons. Moderate daily treadmill exercise, which promotes axon regeneration of cut peripheral nerves, also influences this synaptic stripping. Different exercise protocols are required to promote axon regeneration in male and female animals, but the sex requirements for an effect of exercise on synaptic stripping are unknown. In male and female C57BL/6 mice, the sciatic nerve was transected in the mid-thigh. Mice were then exercised five days per week for two weeks, beginning on the third post-transection day. Half of the exercised mice were trained by walking slowly (10 M/min) on a level treadmill for one hour per day (continuous training). Other mice were interval trained; four short (two min) sprints at 20 M/min separated by five minute rest periods. A third group was untrained. The extent of synaptic contacts made by structures immunoreactive to vesicular glutamate transporter 1 and glutamic acid decarboxylase 67 onto axotomized motoneurons was studied in confocal images of retrogradely labeled cells. Both types of presumed synaptic contacts were reduced markedly in unexercised mice following nerve transection, relative to intact mice. No significant reduction was found in continuous trained males or interval trained females. Reductions in these contacts in interval trained males and continuous trained females were identical to that observed in untrained mice. Treatments with the anti-androgen, flutamide, blocked the effect of sex-appropriate exercise on synaptic contacts in both males and females. Moderate daily exercise has a potent effect on synaptic inputs to axotomized motoneurons. Successful effects of exercise have different requirements in males and females, but require androgen receptor signaling in both sexes.

Neuritin: A therapeutic candidate for promoting axonal regeneration

Following injury, the axons of the mammalian central nervous system do not regenerate. Many studies have aimed at understanding the mechanisms that prevent axonal regeneration and at designing ways to overcome the obstacles preventing axonal regrowth. These studies have identified numerous proteins as promoters of axonal regeneration. In this minireviews, we focus on neuritin as a therapeutic candidate for promoting axonal regeneration. Neuritin was first identified as a neuronal-activity-inducible gene product in the rat brain. The overexpression of neuritin in neurons or the application of neuritin to neurons induces neuritogenesis, neurite arborization, and axonal elongation both in vitro and in vivo. These morphological changes are often observed during the first step of axonal regeneration. Indeed, neuritin expression increases during axonal regeneration in the peripheral nervous system (PNS). Conversely, in a mouse model of diabetes mellitus, neuritin expression decreases in the PNS, and this reduced expression may result in deficient axonal regeneration. Neuritin is induced in the hippocampal dentate gyrus after temporal lobe epilepsy or brain ischemia; however, in these conditions, neuritin induction may exacerbate brain dysfunction through mossy fiber sprouting. Together, these findings support the hypothesis that tightly controlled regulation of neuritin may be required for the treatment of each unique axonal pathology.

Axonal localization of neuritin/CPG15 mRNA in neuronal populations through distinct 5' and 3' UTR elements

Many neuronal mRNAs are actively transported into distal axons. The 3' untranslated regions (UTRs) of axonal mRNAs often contain cues for their localization. The 3' UTR of neuritin mRNA was shown to be sufficient for localization into axons of hippocampal neurons. Here, we show that neuritin mRNA localizes into axons of rat sensory neurons, but this is predominantly driven by the 5' rather than 3' UTR. Neuritin mRNA shifts from cell body to axon predominantly after nerve crush injury, suggesting that it encodes a growth-associated protein. Consistent with this, overexpression of neuritin increases axon growth but only when its mRNA localizes into the axons.

Supraphysiological doses of performance enhancing anabolic-androgenic steroids exert direct toxic effects on neuron-like cells

Anabolic-androgenic steroids (AAS) are lipophilic hormones often taken in excessive quantities by athletes and bodybuilders to enhance performance and increase muscle mass. AAS exert well known toxic effects on specific cell and tissue types and organ systems. The attention that androgen abuse has received lately should be used as an opportunity to educate both athletes and the general population regarding their adverse effects. Among numerous commercially available steroid hormones, very few have been specifically tested for direct neurotoxicity. We evaluated the effects of supraphysiological doses of methandienone and 17-α-methyltestosterone on sympathetic-like neuron cells. Vitality and apoptotic effects were analyzed, and immunofluorescence staining and western blot performed. In this study, we demonstrate that exposure of supraphysiological doses of methandienone and 17-α-methyltestosterone are toxic to the neuron-like differentiated pheochromocytoma cell line PC12, as confirmed by toxicity on neurite networks responding to nerve growth factor and the modulation of the survival and apoptosis-related proteins ERK, caspase-3, poly (ADP-ribose) polymerase and heat-shock protein 90. We observe, in contrast to some previous reports but in accordance with others, expression of the androgen receptor (AR) in neuron-like cells, which when inhibited mitigated the toxic effects of AAS tested, suggesting that the AR could be binding these steroid hormones to induce genomic effects. We also note elevated transcription of neuritin in treated cells, a neurotropic factor likely expressed in an attempt to resist neurotoxicity. Taken together, these results demonstrate that supraphysiological exposure to the AAS methandienone and 17-α-methyltestosterone exert neurotoxic effects by an increase in the activity of the intrinsic apoptotic pathway and alterations in neurite networks.

Neuroprotective effects of testosterone on motoneuron and muscle morphology following spinal cord injury

Treatment with testosterone is neuroprotective/neurotherapeutic after a variety of motoneuron injuries. Here we assessed whether testosterone might have similar beneficial effects after spinal cord injury (SCI). Young adult female rats received either sham or T9 spinal cord contusion injuries and were implanted with blank or testosterone-filled Silastic capsules. Four weeks later, motoneurons innervating the vastus lateralis muscle of the quadriceps were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Soma volume, motoneuron number, lesion volume, and tissue sparing were also assessed, as were muscle weight, fiber cross-sectional area, and motor endplate size and density. Contusion injury resulted in large lesions, with no significant differences in lesion volume, percent total volume of lesion, or spared white or gray matter between SCI groups. SCI with or without testosterone treatment also had no effect on the number or soma volume of quadriceps motoneurons. However, SCI resulted in a decrease in dendritic length of quadriceps motoneurons in untreated animals, and this decrease was completely prevented by treatment with testosterone. Similarly, the vastus lateralis muscle weights and fiber cross-sectional areas of untreated SCI animals were smaller than those of sham-surgery controls, and these reductions were both prevented by testosterone treatment. No effects on motor endplate area or density were observed across treatment groups. These findings suggest that regressive changes in motoneuron and muscle morphology seen after SCI can be prevented by testosterone treatment, further supporting a role for testosterone as a neurotherapeutic agent in the injured nervous system.

Differential gene expression in the axotomized facial motor nucleus of presymptomatic SOD1 mice

Previously, we compared molecular profiles of one population of wild-type (WT) mouse facial motoneurons (FMNs) surviving with FMNs undergoing significant cell death after axotomy. Regardless of their ultimate fate, injured FMNs respond with a vigorous pro-survival/regenerative molecular response. In contrast, the neuropil surrounding the two different injured FMN populations contained distinct molecular differences that support a causative role for glial and/or immune-derived molecules in directing contrasting responses of the same cell types to the same injury. In the current investigation, we utilized the facial nerve axotomy model and a presymptomatic amyotrophic lateral sclerosis (ALS) mouse (SOD1) model to experimentally mimic the axonal die-back process observed in ALS pathogenesis without the confounding variable of disease onset. Presymptomatic SOD1 mice had a significant decrease in FMN survival compared with WT, which suggests an increased susceptibility to axotomy. Laser microdissection was used to accurately collect uninjured and axotomized facial motor nuclei of WT and presymptomatic SOD1 mice for mRNA expression pattern analyses of pro-survival/pro-regeneration genes, neuropil-specific genes, and genes involved in or responsive to the interaction of FMNs and non-neuronal cells. Axotomized presymptomatic SOD1 FMNs displayed a dynamic pro-survival/regenerative response to axotomy, similar to WT, despite increased cell death. However, significant differences were revealed when the axotomy-induced gene expression response of presymptomatic SOD1 neuropil was compared with WT. We propose that the increased susceptibility of presymptomatic SOD1 FMNs to axotomy-induced cell death and, by extrapolation, disease progression, is not intrinsic to the motoneuron, but rather involves a dysregulated response by non-neuronal cells in the surrounding neuropil.

Use of laser microdissection in the investigation of facial motoneuron and neuropil molecular phenotypes after peripheral axotomy

The mechanism underlying axotomy-induced motoneuron loss is not fully understood, but appears to involve molecular changes within the injured motoneuron and the surrounding local microenvironment (neuropil). The mouse facial nucleus consists of six subnuclei which respond differentially to facial nerve transection at the stylomastoid foramen. The ventromedial (VM) subnucleus maintains virtually full facial motoneuron (FMN) survival following axotomy, whereas the ventrolateral (VL) subnucleus results in significant FMN loss with the same nerve injury. We hypothesized that distinct molecular phenotypes of FMN existed within the two subregions, one responsible for maintaining cell survival and the other promoting cell death. In this study, we used laser microdissection to isolate VM and VL facial subnuclear regions for molecular characterization. We discovered that, regardless of neuronal fate after injury, FMN in either subnuclear region respond vigorously to injury with a characteristic "regenerative" profile and additionally, the surviving VL FMN appear to compensate for the significant FMN loss. In contrast, significant differences in the expression of pro-inflammatory cytokine mRNA in the surrounding neuropil response were found between the two subnuclear regions of the facial nucleus that support a causative role for glial and/or immune-derived molecules in directing the contrasting responses of the FMN to axonal transection.

Neuroprotective effects of testosterone on regenerating spinal cord motoneurons in rats

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

Toll-like receptor 2 and facial motoneuron survival after facial nerve axotomy

We have previously demonstrated that CD4(+) Th2 lymphocytes are required to rescue facial motoneuron (FMN) survival after facial nerve axotomy through interaction with peripheral antigen presenting cells, as well as CNS resident microglia. Furthermore, the innate immune molecule, toll-like receptor 2 (TLR2), has been implicated in the development of Th2-type immune responses and can be activated by intracellular components released by dead or dying cells. The role of TLR2 in the FMN response to axotomy was explored in this study, using a model of facial nerve axotomy at the stylomastoid foramen in the mouse, in which blood-brain-barrier (BBB) permeability does not occur. After facial nerve axotomy, TLR2 mRNA was significantly upregulated in the facial motor nucleus and co-immunofluorescence localized TLR2 to CD68(+) microglia, but not GFAP(+) astrocytes. Using TLR2-deficient (TLR2(-/-)) mice, it was determined that TLR2 does not affect FMN survival levels after axotomy. These data contribute to understanding the role of innate immunity after FMN death and may be relevant to motoneuron diseases, such as amyotrophic lateral sclerosis (ALS).

Validated treatments and therapeutics prospectives regarding pharmacological products for sarcopenia

Loss of physical function in older adults may be, at least in part, explained by sarcopenia, a phenomenon characterized by a reduction in number and size of muscle fibres and by increase in interstitial fat and connective tissue. Lifestyle intervention (i.e. physical activity and nutrition) have shown to impact on sarcopenia. However, several drugs were suggested, with various levels of scientific evidence, to have an impact on muscle outcomes. In this study we reviewed the effect of six classes of drugs on sarcopenia and muscular outcomes in older adults. We decided to focus our review on two commonly drugs which have recently showed promising effects on muscular outcomes in older adults (ACE inhibitors and statins) and on four drugs whose effect on skeletal muscle was already largely studied (creatine, Growth Hormone, testosterone, estrogens and tibolone).

Neuroprotective actions of androgens on motoneurons

Androgens have a variety of protective and therapeutic effects in both the central and peripheral nervous systems. Here we review these effects as they related specifically to spinal and cranial motoneurons. Early in development, androgens are critical for the formation of important neuromuscular sex differences, decreasing the magnitude of normally occurring cell death in select motoneuron populations. Throughout the lifespan, androgens also protect against motoneuron death caused by axonal injury. Surviving motoneurons also display regressive changes to their neurites as a result of both direct axonal injury and loss of neighboring motoneurons. Androgen treatment enhances the ability of motoneurons to recover from these regressive changes and regenerate both axons and dendrites, restoring normal neuromuscular function. Androgens exert these protective effects by acting through a variety of molecular pathways. Recent work has begun to examine how androgen treatment can interact with other treatment strategies in promoting recovery from motoneuron injury.

Neuroprotective effects of testosterone on the morphology and function of somatic motoneurons following the death of neighboring motoneurons

Motoneuron loss is a significant medical problem, capable of causing severe movement disorders or even death. We have previously shown that partial depletion of motoneurons from sexually dimorphic, highly androgen-sensitive spinal motor populations induces dendritic atrophy in remaining motoneurons, and this atrophy is attenuated by treatment with testosterone. To test whether testosterone has similar effects in more typical motoneurons, we examined potential neuroprotective effects in motoneurons innervating muscles of the quadriceps. Motoneurons innervating the vastus medialis muscle were selectively killed by intramuscular injection of cholera toxin-conjugated saporin. Simultaneously, some saporin-injected rats were given implants containing testosterone or left untreated. Four weeks later, motoneurons innervating the ipsilateral vastus lateralis muscle were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Compared with intact normal males, partial motoneuron depletion resulted in decreased dendritic length in remaining quadriceps motoneurons, and this atrophy was attenuated by testosterone treatment. To examine the functional consequences of the induced dendritic atrophy, and its attenuation with testosterone treatment, the activation of remaining quadriceps motoneurons was assessed using peripheral nerve recording. Partial motoneuron depletion resulted in decreased amplitudes of motor nerve activity, and these changes were attenuated by treatment with testosterone, providing a functional correlate to the neuroprotective effects of testosterone treatment on quadriceps motoneuron morphology. Together these findings suggest that testosterone has neuroprotective effects on morphology and function in both highly androgen-sensitive as well as more typical motoneuron populations, further supporting a role for testosterone as a neurotherapeutic agent in the injured nervous system.