Neuroprotection with noninvasive neurotrophin delivery to the brain

Electrical stimulation: a potential alternative to positively impact cerebral health?

An increasing body of evidence confirms the effectiveness of physical exercise (PE) in promoting brain health by preventing age-related cognitive decline and reducing the risk of neurodegenerative diseases. The benefits of PE are attributed to neuroplasticity processes which have been reported to enhance cerebral health. However, moderate to high-intensity PE is necessary to induce these responses and these intensities cannot always be achieved especially by people with physical limitations. As a countermeasure, electrical stimulation (ES) offers several benefits, particularly for improving physical functions, for various neurological diseases. This review aims to provide an overview of key mechanisms that could contribute to the enhancement in brain health in response to ES-induced exercise, including increases in cerebral blood flow, neuronal activity, and humoral pathways. This narrative review also focuses on the effects of ES protocols, applied to both humans and animals, on cognition. Despite a certain paucity of research when compared to the more classical aerobic exercise, it seems that ES could be of interest for improving cerebral health, particularly in people who have difficulty engaging in voluntary exercise.

Comparing in vitro affinity measurements of antibodies to TfR1: Surface plasmon resonance versus on-cell affinity

Despite years of utilizing the transferrin receptor 1 (TfR1) to transport large biomolecules into the brain, there is no consensus on how to optimally measure affinity to it. The aim of this study was to compare different methods for measuring the affinities of anti-TfR1 antibodies. Antibodies 15G11, OX26 and 8D3 are known to successfully carry large biologics across the blood-brain barrier in humans, rats, and mice, respectively. The affinity to their respective species of TfR1 was measured with different surface plasmon resonance setups in Biacore and an on-cell assay. When the antibody was captured and TfR1 was the analyte, the dissociation in Biacore was very slow. The dissociation was faster when the antibody was the analyte and TfR1 was the ligand. The Biacore setup with capture of N-terminal FLAG-tag TfR1 yielded the most similar apparent affinities as the cell assay. In conclusion, it is important to evaluate assay parameters including assay orientation, surface capture method, and antibody-format when comparing binding kinetics for TfR1 antibodies. Although it seems possible to determine relative affinities of TfR1 antibodies using the methods described here, both the FLAG-tag TfR1 capture setup and cell assays likely yield apparent affinities that are most translatable in vivo.

Neurotrophic Factors as Regenerative Therapy for Neurodegenerative Diseases: Current Status, Challenges and Future Perspectives

Neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), multiple sclerosis (MS), spinal cord injury (SCI), and amyotrophic lateral sclerosis (ALS), are characterized by acute or chronic progressive loss of one or several neuronal subtypes. However, despite their increasing prevalence, little progress has been made in successfully treating these diseases. Research has recently focused on neurotrophic factors (NTFs) as potential regenerative therapy for neurodegenerative diseases. Here, we discuss the current state of knowledge, challenges, and future perspectives of NTFs with a direct regenerative effect in chronic inflammatory and degenerative disorders. Various systems for delivery of NTFs, such as stem and immune cells, viral vectors, and biomaterials, have been applied to deliver exogenous NTFs to the central nervous system, with promising results. The challenges that currently need to be overcome include the amount of NTFs delivered, the invasiveness of the delivery route, the blood-brain barrier permeability, and the occurrence of side effects. Nevertheless, it is important to continue research and develop standards for clinical applications. In addition to the use of single NTFs, the complexity of chronic inflammatory and degenerative diseases may require combination therapies targeting multiple pathways or other possibilities using smaller molecules, such as NTF mimetics, for effective treatment.

ImmunoPET imaging of amyloid-beta in a rat model of Alzheimer's disease with a bispecific, brain-penetrating fusion protein

BACKGROUND

Hijacking the transferrin receptor (TfR) is an effective strategy to transport amyloid-beta (Aβ) immuno-positron emission tomography (immunoPET) ligands across the blood-brain barrier (BBB). Such ligands are more sensitive and specific than small-molecule ligands at detecting Aβ pathology in mouse models of Alzheimer's disease (AD). This study aimed to determine if this strategy would be as sensitive in rats and to assess how TfR affinity affects BBB transport of bispecific immunoPET radioligands.

METHODS

Two affinity variants of the rat TfR antibody, OX26, were chemically conjugated to a F(ab')₂ fragment of the anti-Aβ antibody, bapineuzumab (Bapi), to generate two bispecific fusion proteins: OX26₅-F(ab')₂-Bapi and OX26₇₆-F(ab')₂-Bapi. Pharmacokinetic analyses were performed 4 h and 70 h post-injection of radioiodinated fusion proteins in wild-type (WT) rats. [¹²⁴I]I-OX26₅-F(ab')₂-Bapi was administered to TgF344-AD and WT rats for in vivo PET imaging. Ex vivo distribution of injected [¹²⁴I]I-OX26₅-F(ab')₂-Bapi and Aβ pathology were assessed.

RESULTS

More [¹²⁵I]I-OX26₅-F(ab')₂-Bapi was taken up into the brain 4 h post-administration than [¹²⁴I]I-OX26₇₆-F(ab')₂-Bapi. [¹²⁴I]I-OX26₅-F(ab')₂-Bapi PET visualized Aβ pathology with significantly higher signals in the TgF344-AD rats than in the WT littermates without Aβ pathology. The PET signals significantly correlated with Aβ levels in AD animals.

CONCLUSION

Affinity to TfR affects how efficiently a TfR-targeting bispecific fusion protein will cross the BBB, such that the higher-affinity bispecific fusion protein crossed the BBB more efficiently. Furthermore, bispecific immunoPET imaging of brain Aβ pathology using TfR-mediated transport provides good imaging contrast between TgF344-AD and WT rats, suggesting that this immunoPET strategy has the potential to be translated to higher species.

Treatment of rat brain ischemia model by NSCs-polymer scaffold transplantation

Neural stem cells (NSCs) transplantation is a promising therapeutic strategy for ischemic stroke. However, significant cell death after transplantation greatly limits its effectiveness. Poly (trimethylene carbonate)15-F127-poly (trimethylene carbonate)15 (PTMC15-F127-PTMC15, PFP) is a biodegradable thermo-sensitive hydrogel biomaterial, which can control drug release and provide permissive substrates for donor NSCs. In our study, we seeded NSCs into PFP polymer scaffold loaded with three neurotrophic factors, including brain-derived neurotrophic factor, nerve growth factor, and Neurotrophin-3. And then we transplanted this NSCs-polymer scaffold in rat brains 14 days after middle cerebral artery occlusion. ELISA assay showed that PFP polymer scaffold sustained releasing three neurotrophic factors for at least 14 days. Western Blot and fluorescence immunostaining revealed that NSCs-polymer scaffold transplantation significantly reduced apoptosis of ischemic penumbra and promoted differentiation of the transplanted NSCs into mature neurons. Furthermore, infarct size was reduced, and neurological performance of the animals were improved by the transplanted NSCs-polymer scaffold. These results demonstrate that PFP polymer scaffold loaded with neurotrophic factors can enhance the effectiveness of stem cell transplantation therapy, which provides a new way for cell transplantation therapy in ischemic stroke.

Mucopolysaccharidoses and the blood-brain barrier

Mucopolysaccharidoses comprise a set of genetic diseases marked by an enzymatic dysfunction in the degradation of glycosaminoglycans in lysosomes. There are eight clinically distinct types of mucopolysaccharidosis, some with various subtypes, based on which lysosomal enzyme is deficient and symptom severity. Patients with mucopolysaccharidosis can present with a variety of symptoms, including cognitive dysfunction, hepatosplenomegaly, skeletal abnormalities, and cardiopulmonary issues. Additionally, the onset and severity of symptoms can vary depending on the specific disorder, with symptoms typically arising during early childhood. While there is currently no cure for mucopolysaccharidosis, there are clinically approved therapies for the management of clinical symptoms, such as enzyme replacement therapy. Enzyme replacement therapy is typically administered intravenously, which allows for the systemic delivery of the deficient enzymes to peripheral organ sites. However, crossing the blood-brain barrier (BBB) to ameliorate the neurological symptoms of mucopolysaccharidosis continues to remain a challenge for these large macromolecules. In this review, we discuss the transport mechanisms for the delivery of lysosomal enzymes across the BBB. Additionally, we discuss the several therapeutic approaches, both preclinical and clinical, for the treatment of mucopolysaccharidoses.

Overcoming the blood-brain barrier for the therapy of malignant brain tumor: current status and prospects of drug delivery approaches

Besides the broad development of nanotechnological approaches for cancer diagnosis and therapy, currently, there is no significant progress in the treatment of different types of brain tumors. Therapeutic molecules crossing the blood-brain barrier (BBB) and reaching an appropriate targeting ability remain the key challenges. Many invasive and non-invasive methods, and various types of nanocarriers and their hybrids have been widely explored for brain tumor treatment. However, unfortunately, no crucial clinical translations were observed to date. In particular, chemotherapy and surgery remain the main methods for the therapy of brain tumors. Exploring the mechanisms of the BBB penetration in detail and investigating advanced drug delivery platforms are the key factors that could bring us closer to understanding the development of effective therapy against brain tumors. In this review, we discuss the most relevant aspects of the BBB penetration mechanisms, observing both invasive and non-invasive methods of drug delivery. We also review the recent progress in the development of functional drug delivery platforms, from viruses to cell-based vehicles, for brain tumor therapy. The destructive potential of chemotherapeutic drugs delivered to the brain tumor is also considered. This review then summarizes the existing challenges and future prospects in the use of drug delivery platforms for the treatment of brain tumors.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Neurotrophin Signaling Impairment by Viral Infections in the Central Nervous System

Neurotrophins, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT-3), NT-4, and NT-5, are proteins involved in several important functions of the central nervous system. The activation of the signaling pathways of these neurotrophins, or even by their immature form, pro-neurotrophins, starts with their recognition by cellular receptors, such as tropomyosin receptor kinase (Trk) and 75 kD NT receptors (p75NTR). The Trk receptor is considered to have a high affinity for attachment to specific neurotrophins, while the p75NTR receptor has less affinity for attachment with neurotrophins. The correct functioning of these signaling pathways contributes to proper brain development, neuronal survival, and synaptic plasticity. Unbalanced levels of neurotrophins and pro-neurotrophins have been associated with neurological disorders, illustrating the importance of these molecules in the central nervous system. Furthermore, reports have indicated that viruses can alter the normal levels of neurotrophins by interfering with their signaling pathways. This work discusses the importance of neurotrophins in the central nervous system, their signaling pathways, and how viruses can affect them.

New Drug Delivery Systems Developed for Brain Targeting

The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (B_CSF) are two of the most complex and sophisticated concierges that defend the central nervous system (CNS) by numerous mechanisms. While they maintain the neuro-ecological homeostasis through the regulated entry of essential biomolecules, their conservative nature challenges the entry of most of the drugs intended for CNS delivery. Targeted delivery challenges for a diverse spectrum of therapeutic agents/drugs (non-small molecules, small molecules, gene-based therapeutics, protein and peptides, antibodies) are diverse and demand specialized delivery and disease-targeting strategies. This review aims to capture the trends that have shaped the current brain targeting research scenario. This review discusses the physiological, neuropharmacological, and etiological factors that participate in the transportation of various drug delivery cargoes across the BBB/B_CSF and influence their therapeutic intracranial concentrations. Recent research works spanning various invasive, minimally invasive, and non-invasive brain- targeting approaches are discussed. While the pre-clinical outcomes from many of these approaches seem promising, further research is warranted to overcome the translational glitches that prevent their clinical use. Non-invasive approaches like intranasal administration, P-glycoprotein (P-gp) inhibition, pro-drugs, and carrier/targeted nanocarrier-aided delivery systems (alone or often in combination) hold positive clinical prospects for brain targeting if explored further in the right direction.

Enhancing autophagy in Alzheimer's disease through drug repositioning

Alzheimer's disease (AD) is one of the biggest human health threats due to increases in aging of the global population. Unfortunately, drugs for treating AD have been largely ineffective. Interestingly, downregulation of macroautophagy (autophagy) plays an essential role in AD pathogenesis. Therefore, targeting autophagy has drawn considerable attention as a therapeutic approach for the treatment of AD. However, developing new therapeutics is time-consuming and requires huge investments. One of the strategies currently under consideration for many diseases is "drug repositioning" or "drug repurposing". In this comprehensive review, we have provided an overview of the impact of autophagy on AD pathophysiology, reviewed the therapeutics that upregulate autophagy and are currently used in the treatment of other diseases, including cancers, and evaluated their repurposing as a possible treatment option for AD. In addition, we discussed the potential of applying nano-drug delivery to neurodegenerative diseases, such as AD, to overcome the challenge of crossing the blood brain barrier and specifically target molecules/pathways of interest with minimal side effects.

The 5-HT1A receptor as a serotonergic target for neuroprotection in cerebral ischemia

Cerebral ischemia due to stroke or cardiac arrest greatly affects daily functioning and the quality of life of patients and has a high socioeconomic impact due to the surge in their prevalence. Advances in the identification of an effective pharmacotherapy to promote neuroprotection and recovery after a cerebral ischemic insult are, however, limited. The serotonin 1A (5-HT_1A) receptor has been implicated in the regulation of several brain functions, including mood, emotions, memory, and neuroplasticity, all of which are deleteriously affected by cerebral ischemia. This review focuses on the specific roles and mechanisms of 5-HT_1A receptors in neuroprotection in experimental models of cerebral ischemia. We present experimental evidence that 5-HT_1A receptor agonists can prevent neuronal damage and promote functional recovery induced by focal and transient global ischemia in rodents. However, indiscriminate activation of pre-and postsynaptic by non-biased 5-HT_1A receptor agonists may be a limiting factor in the anti-ischemic clinical efficacy of these compounds since 5-HT_1A receptors in different brain regions can mediate diverging or even contradictory responses. Current insights are presented into the 'biased' 5-HT_1A post-synaptic heteroreceptor agonist NLX-101 (also known as F15599), a compound that preferentially and potently stimulates postsynaptic cortical pyramidal neurons without inhibiting firing of serotoninergic neurons, as a potential strategy providing neuroprotection in cerebral ischemic conditions.

Neurotrophic Factors in Parkinson's Disease: Clinical Trials, Open Challenges and Nanoparticle-Mediated Delivery to the Brain

Neurotrophic factors (NTFs) are small secreted proteins that support the development, maturation and survival of neurons. NTFs injected into the brain rescue and regenerate certain neuronal populations lost in neurodegenerative diseases, demonstrating the potential of NTFs to cure the diseases rather than simply alleviating the symptoms. NTFs (as the vast majority of molecules) do not pass through the blood-brain barrier (BBB) and therefore, are delivered directly into the brain of patients using costly and risky intracranial surgery. The delivery efficacy and poor diffusion of some NTFs inside the brain are considered the major problems behind their modest effects in clinical trials. Thus, there is a great need for NTFs to be delivered systemically thereby avoiding intracranial surgery. Nanoparticles (NPs), particles with the size dimensions of 1-100 nm, can be used to stabilize NTFs and facilitate their transport through the BBB. Several studies have shown that NTFs can be loaded into or attached onto NPs, administered systemically and transported to the brain. To improve the NP-mediated NTF delivery through the BBB, the surface of NPs can be functionalized with specific ligands such as transferrin, insulin, lactoferrin, apolipoproteins, antibodies or short peptides that will be recognized and internalized by the respective receptors on brain endothelial cells. In this review, we elaborate on the most suitable NTF delivery methods and envision "ideal" NTF for Parkinson's disease (PD) and clinical trial thereof. We shortly summarize clinical trials of four NTFs, glial cell line-derived neurotrophic factor (GDNF), neurturin (NRTN), platelet-derived growth factor (PDGF-BB), and cerebral dopamine neurotrophic factor (CDNF), that were tested in PD patients, focusing mainly on GDNF and CDNF. We summarize current possibilities of NP-mediated delivery of NTFs to the brain and discuss whether NPs have impact in improving the properties of NTFs and delivery across the BBB. Emerging delivery approaches and future directions of NTF-based nanomedicine are also discussed.

Manickam D. Targeting the blood-brain barrier for the delivery of stroke therapies

A variety of neuroprotectants have shown promise in treating ischemic stroke, yet their delivery to the brain remains a challenge. The endothelial cells lining the blood-brain barrier (BBB) are emerging as a dynamic factor in the response to neurological injury and disease, and the endothelial-neuronal matrix coupling is fundamentally neuroprotective. In this review, we discuss approaches that target the endothelium for drug delivery both across the BBB and to the BBB as a viable strategy to facilitate neuroprotective effects, using the example of brain-derived neurotrophic factor (BDNF). We highlight the advances in cell-derived extracellular vesicles (EVs) used for CNS targeting and drug delivery. We also discuss the potential of engineered EVs as a potent strategy to deliver BDNF or other drug candidates to the ischemic brain, particularly when coupled with internal components like mitochondria that may increase cellular energetics in injured endothelial cells.

Evolving new-age strategies to transport therapeutics across the blood-brain-barrier

A basic understanding of the blood-brain barrier (BBB) is essential for the novel advancements in targeting drugs specific to the brain. Neoplasm compromising the internal structure of BBB that results in impaired vasculature is called as blood tumor barrier (BTB). Besides, the BBB serves as a chief hindrance to the passage of a drug into the brain parenchyma. The small and hydrophilic drugs majorly display an absence of desired molecular characteristics required to cross the BBB. Furthermore, all classes of biologics have failed in the clinical trials of brain diseases over the past years since these biologics are large molecules that do not cross the BBB. Also, new strategies have been discovered that use the Trojan horse technology with the re-engineered biologics for BBB transport. Thus, this review delivers information about the different grades of tumors (I-IV) i.e. examples of BBB/BTB heterogenicity along with the different mechanisms for transporting the therapeutics into the brain tumors by crossing BBB. This review also provides insights into the emerging approaches of peptide delivery and the non-invasive and brain-specific molecular Trojan horse targeting technologies. Also, the several challenges in the clinical development of BBB penetrating IgG fusion protein have been discussed.

Human iPSC-Based Modeling of Central Nerve System Disorders for Drug Discovery

A high-throughput drug screen identifies potentially promising therapeutics for clinical trials. However, limitations that persist in current disease modeling with limited physiological relevancy of human patients skew drug responses, hamper translation of clinical efficacy, and contribute to high clinical attritions. The emergence of induced pluripotent stem cell (iPSC) technology revolutionizes the paradigm of drug discovery. In particular, iPSC-based three-dimensional (3D) tissue engineering that appears as a promising vehicle of in vitro disease modeling provides more sophisticated tissue architectures and micro-environmental cues than a traditional two-dimensional (2D) culture. Here we discuss 3D based organoids/spheroids that construct the advanced modeling with evolved structural complexity, which propels drug discovery by exhibiting more human specific and diverse pathologies that are not perceived in 2D or animal models. We will then focus on various central nerve system (CNS) disease modeling using human iPSCs, leading to uncovering disease pathogenesis that guides the development of therapeutic strategies. Finally, we will address new opportunities of iPSC-assisted drug discovery with multi-disciplinary approaches from bioengineering to Omics technology. Despite technological challenges, iPSC-derived cytoarchitectures through interactions of diverse cell types mimic patients' CNS and serve as a platform for therapeutic development and personalized precision medicine.

Treating brain diseases using systemic parenterally-administered protein therapeutics: Dysfunction of the brain barriers and potential strategies

The parenteral administration of protein therapeutics is increasingly gaining importance for the treatment of human diseases. However, the presence of practically impermeable blood-brain barriers greatly restricts access of such pharmaceutics to the brain. Treating brain disorders with proteins thus remains a great challenge, and the slow clinical translation of these therapeutics may be largely ascribed to the lack of appropriate brain delivery system. Exploring new approaches to deliver proteins to the brain by circumventing physiological barriers is thus of great interest. Moreover, parallel advances in the molecular neurosciences are important for better characterizing blood-brain interfaces, particularly under different pathological conditions (e.g., stroke, multiple sclerosis, Parkinson's disease, and Alzheimer's disease). This review presents the current state of knowledge of the structure and the function of the main physiological barriers of the brain, the mechanisms of transport across these interfaces, as well as alterations to these concomitant with brain disorders. Further, the different strategies to promote protein delivery into the brain are presented, including the use of molecular Trojan horses, the formulation of nanosystems conjugated/loaded with proteins, protein-engineering technologies, the conjugation of proteins to polymers, and the modulation of intercellular junctions. Additionally, therapeutic approaches for brain diseases that do not involve targeting to the brain are presented (i.e., sink and scavenging mechanisms).

Plasma Exosomal Brain-Derived Neurotrophic Factor Correlated with the Postural Instability and Gait Disturbance-Related Motor Symptoms in Patients with Parkinson's Disease

Brain-derived neurotrophic factor (BDNF) is an essential neurotrophin, responsible for neuronal development, function, and survival. Assessments of peripheral blood BDNF in patients with Parkinson's disease (PD) previously yielded inconsistent results. Plasma exosomes can carry BDNF, so this study investigated the role of plasma exosomal BDNF level as a biomarker of PD. A total of 114 patients with mild to moderate PD and 42 non-PD controls were recruited, and their clinical presentations were evaluated. Plasma exosomes were isolated with exoEasy Maxi Kits, and enzyme-linked immunosorbent assay was used to assess plasma exosomal BDNF levels. Statistical analysis was performed using SPSS version 19.0, and findings were considered significant at p < 0.05. The analysis revealed no significant differences in plasma exosomal BDNF levels between patients with PD and controls. Patients with PD with low plasma exosomal BDNF levels (in the lowest quartile) exhibited a significant association with daily activity dysfunction but not with cognition/mood or overall motor symptoms as assessed using the Unified Parkinson's Disease Rating Scale (UPDRS). Investigation of UPDRS part III subitems revealed that low plasma exosomal BDNF level was significantly associated with increased motor severity of postural instability and gait disturbance (PIGD)-associated symptoms (rising from a chair, gait, and postural stability) after adjustment for age and sex. In conclusion, although plasma exosomal BDNF level could not distinguish patients with PD from controls, the association with PIGD symptoms in patients with PD may indicate its potential role as a biomarker. Follow-up studies should investigate the association between plasma exosomal BDNF levels and changes in clinical symptoms.

Functional Network Mapping Reveals State-Dependent Response to IGF1 Treatment in Rett Syndrome

Rett Syndrome (RTT) is a neurodevelopmental disorder associated with mutations in the gene MeCP2, which is involved in the development and function of cortical networks. The clinical presentation of RTT is generally severe and includes developmental regression and marked neurologic impairment. Insulin-Like growth factor 1 (IGF1) ameliorates RTT-relevant phenotypes in animal models and improves some clinical manifestations in early human trials. However, it remains unclear whether IGF1 treatment has an impact on cortical electrophysiology in line with MeCP2’s role in network formation, and whether these electrophysiological changes are related to clinical response. We performed clinical assessments and resting-state electroencephalogram (EEG) recordings in eighteen patients with classic RTT, nine of whom were treated with IGF1. Among the treated patients, we distinguished those who showed improvements after treatment (responders) from those who did not show any changes (nonresponders). Clinical assessments were carried out for all individuals with RTT at baseline and 12 months after treatment. Network measures were derived using statistical modelling techniques based on interelectrode coherence measures. We found significant interaction between treatment groups and timepoints, indicating an effect of IGF1 on network measures. We also found a significant effect of responder status and timepoint, indicating that these changes in network measures are associated with clinical response to treatment. Further, we found baseline variability in network characteristics, and a machine learning model using these measures applied to pretreatment data predicted treatment response with 100% accuracy (100% sensitivity and 100% specificity) in this small patient group. These results highlight the importance of network pathology in RTT, as well as providing preliminary evidence for the potential of network measures as tools for the characterisation of disease subtypes and as biomarkers for clinical trials.

Antioxidants and Nanotechnology: Promises and Limits of Potentially Disruptive Approaches in the Treatment of Central Nervous System Diseases

Many central nervous system (CNS) diseases are still incurable and only symptomatic treatments are available. Oxidative stress is suggested to be a common hallmark, being able to cause and exacerbate the neuronal cell dysfunctions at the basis of these pathologies, such as mitochondrial impairments, accumulation of misfolded proteins, cell membrane damages, and apoptosis induction. Several antioxidant compounds are tested as potential countermeasures for CNS disorders, but their efficacy is often hindered by the loss of antioxidant properties due to enzymatic degradation, low bioavailability, poor water solubility, and insufficient blood-brain barrier crossing efficiency. To overcome the limitations of antioxidant molecules, exploitation of nanostructures, either for their delivery or with inherent antioxidant properties, is proposed. In this review, after a brief discussion concerning the role of the blood-brain barrier in the CNS and the involvement of oxidative stress in some neurodegenerative diseases, the most interesting research concerning the use of nano-antioxidants is introduced and discussed, focusing on the synthesis procedures, functionalization strategies, in vitro and in vivo tests, and on recent clinical trials.

Brain-Derived Neurotrophic Factor and Its Potential Therapeutic Role in Stroke Comorbidities

With the rise in the aging global population, stroke comorbidities have become a serious health threat and a tremendous economic burden on human society. Current therapeutic strategies mainly focus on protecting neurons from cytotoxic damage at the acute phase upon stroke onset, which not only is a difficult way to ameliorate stroke symptoms but also presents a challenge for the patients to receive effective treatment in time. The brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain, which possesses a remarkable capability to repair brain damage. Recent promising preclinical outcomes have made BDNF a popular late-stage target in the development of novel stroke treatments. In this review, we aim to summarize the latest progress in the understanding of the cellular/molecular mechanisms underlying stroke pathogenesis, current strategies and difficulties in drug development, the mechanism of BDNF action in poststroke neurorehabilitation and neuroplasticity, and recent updates in novel therapeutic methods.

Noninvasive Brain Delivery and Efficacy of BDNF to Stimulate Neuroregeneration and Suppression of Disease Relapse in EAE Mice

The number of FDA-approved protein drugs (biologics), such as antibodies, antibody-drug conjugates, hormones, and enzymes, continues to grow at a rapid rate; most of these drugs are used to treat diseases of the peripheral body. Unfortunately, most of these biologics cannot be used to treat brain diseases such as Alzheimer's disease (AD), multiple sclerosis (MS), and brain tumors in a noninvasive manner due to their inability to permeate the blood-brain barrier (BBB). Therefore, there is a need to develop an effective method to deliver protein drugs into the brain. Here, we report a proof of concept to deliver a recombinant brain-derived neurotrophic factor (BDNF) to the brains of healthy and experimental autoimmune encephalomyelitis (EAE) mice via intravenous (iv) injections by co-administering BDNF with a BBB modulator (BBBM) peptide ADTC5. Western blot evaluations indicated that ADTC5 enhanced the brain delivery of BDNF in healthy SJL/elite mice compared to BDNF alone and triggered the phosphorylation of TrkB receptors in the brain. The EAE mice treated with BDNF + ADTC5 suppressed EAE relapse compared to those treated with BDNF alone, ADTC5 alone, or vehicle. We further demonstrated that brain delivery of BDNF induced neuroregeneration via visible activation of oligodendrocytes, remyelination, and ARC and EGR1 mRNA transcript upregulation. In summary, we have demonstrated that ADTC5 peptide modulates the BBB to permit noninvasive delivery of BDNF to exert its neuroregeneration activity in the brains of EAE mice.

Development of liposomal drug formulations: quality attributes and methods for quality control

The use of nanostructured components in drug manufacturing and, more specifically, targeted drug delivery has recently become a major trend in the pharmaceutical industry. Nanodrugs encompass a wide range of pharmaceutical agents containing dendrimers, nanocrystals, micelles, liposomes, and polymer nanoparticles. Liposomes are the most well-studied nanoparticles and effective drug carriers. However, the more complex their structure is, the more process controls are needed and the more quality attributes have to be monitored, including the chemical properties of the liposomal fraction such as the shape, size and charge of the nanoparticle, conjugation efficacy, and distribution of the active ingredient. We believe that quality control of key liposome characteristics should rely on dynamic and laser light scattering coupled with electrophoresis, differential scanning calorimetry, cryo-electron microscopy, nuclear magnetic resonance, laser diffraction analysis, and gel filtration chromatography.

Biologically-derived nanomaterials for targeted therapeutic delivery to the brain

Delivery of imaging agents and pharmaceutical payloads to the central nervous system (CNS) is essential for efficient diagnosis and treatment of brain diseases. However, therapeutic delivery is often restricted by the blood-brain barrier (BBB), which prevents transport of clinical compounds to their region of interest. This review discusses the methods that have been used to avoid or overcome this barrier, presenting the use of biologically-derived nanomaterial systems as an efficient strategy for the diagnosis and treatment of CNS diseases. Biological nanomaterials have many advantages over synthetic systems, including being biodegradable, biocompatible, easily surface functionalised for conjugation of targeting moieties, and are often able to self-assemble. These abilities are discussed in relation to various systems, including liposomes, dendrimers, and viral nanoparticles.

The pharmacological perturbation of brain zinc impairs BDNF-related signaling and the cognitive performances of young mice

Zinc (Zn2+) is a pleiotropic modulator of the neuronal and brain activity. The disruption of intraneuronal Zn2+ levels triggers neurotoxic processes and affects neuronal functioning. In this study, we investigated how the pharmacological modulation of brain Zn2+ affects synaptic plasticity and cognition in wild-type mice. To manipulate brain Zn2+ levels, we employed the Zn2+ (and copper) chelator 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol, CQ). CQ was administered for two weeks to 2.5-month-old (m.o.) mice, and effects studied on BDNF-related signaling, metalloproteinase activity as well as learning and memory performances. CQ treatment was found to negatively affect short- and long-term memory performances. The CQ-driven perturbation of brain Zn2+ was found to reduce levels of BDNF, synaptic plasticity-related proteins and dendritic spine density in vivo. Our study highlights the importance of choosing "when", "where", and "how much" in the modulation of brain Zn2+ levels. Our findings confirm the importance of targeting Zn2+ as a therapeutic approach against neurodegenerative conditions but, at the same time, underscore the potential drawbacks of reducing brain Zn2+ availability upon the early stages of development.

Constitutive PGC-1α Overexpression in Skeletal Muscle Does Not Improve Morphological Outcome in Mouse Models of Brain Irradiation or Cortical Stroke

Physical exercise can improve morphological outcomes after ischemic stroke and ameliorate irradiation-induced reduction of hippocampal neurogenesis in rodents, but the mechanisms underlying these effects remain largely unknown. The transcription factor peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is considered to be one of the central factors responsible for exercise-induced benefits in skeletal muscle, including the release of neurotrophic factors into the circulation. In order to test if PGC-1α overexpression in skeletal muscle could simulate the exercise-induced effects on recovery after cranial irradiation and stroke, we used male adult transgenic mice overexpressing murine PGC-1α under the control of muscle creatinine kinase promoter and subjected them to either whole brain irradiation at a dose of 4 Gy or photothrombotic stroke to the sensory motor cortex. Muscular PGC-1α overexpression did not ameliorate irradiation-induced reduction of newborn BrdU-labeled cells in the dentate gyrus, immature neurons, or newborn mature neurons. In the stroke model, muscular overexpression of PGC-1α resulted in an increased infarct size without any changes in microglia activation or reactive astrocytosis. No difference could be detected in the number of migrating neural progenitor cells from the subventricular zone to the lesioned neocortex or in vascular density of the contralateral neocortex in comparison to wildtype animals. We conclude that forced muscular overexpression of PGC-1α does not have a beneficial effect on hippocampal neurogenesis after irradiation, but rather a detrimental effect on the infarct volume after stroke in mice. This suggests that artificial muscle activation through the PGC-1α pathway is not sufficient to mimic exercise-induced recovery after cranial irradiation and stroke.

Strategies for Enhancing the Permeation of CNS-Active Drugs through the Blood-Brain Barrier: A Review

Background: The blood brain barrier (BBB) is a dynamic and functional structure which poses a vast challenge in the development of drugs acting on the central nervous system (CNS). While most substances are denied BBB crossing, selective penetration of substances mainly occurs through diffusion, carrier mediated transport, or receptor mediated transcytosis. Methods: Strategies in enhancing BBB penetration have been reviewed and summarized in accordance with their type of formulation. Highlights in monoclonal antibodies, peptide-vectors, nanoparticles, and simple prodrugs were included. Conclusion: Nanoparticles and simple prodrugs, for example, can be used for efficient BBB penetration through inhibition of efflux mechanisms, however, monoclonal antibodies are the most promising strategy in BBB penetration. Close follow-up of future development in this area should confirm our expectation.

Neurotrophic Factors: An Overview

The neurotrophins are a family of closely related proteins that were first identified as survival factors for sympathetic and sensory neurons and have since been shown to control a number of aspects of survival, development, and function of neurons in both the central and peripheral nervous systems. Limiting quantities of neurotrophins during development control the numbers of surviving neurons to ensure a match between neurons and the requirement for a suitable density of target innervation. Biological effects of each of the four mammalian neurotrophins are mediated through activation of one or more of the three members of the tropomyosin-related kinase (Trk) family of receptor tyrosine kinases (TrkA, TrkB, and TrkC). In addition, all neurotrophins activate the p75 neurotrophin receptor (p75^NTR), a member of the tumor necrosis factor receptor superfamily. Neurotrophin engagement of Trk receptors leads to activation of Ras, phosphatidylinositol 3-kinase, phospholipase C-γ1, and signaling pathways controlled through these proteins, including the mitogen-activated protein kinases. Neurotrophin availability is required into adulthood, where they control synaptic function and plasticity and sustain neuronal cell survival, morphology, and differentiation. This article will provide an overview of neurotrophin biology, their receptors, and signaling pathways.

Cannabidiol reduces neuroinflammation and promotes neuroplasticity and functional recovery after brain ischemia

This study investigated the effects of cannabidiol (CBD), a non-psychotomimetic phytochemical present in Cannabis sativa, on the cognitive and emotional impairments induced by bilateral common carotid artery occlusion (BCCAO) in mice. Using a multi-tiered behavioral testing battery during 21days, we found that BCCAO mice exhibited long-lasting functional deficits reflected by increase in anxiety-like behavior (day 9), memory impairments (days 12-18) and despair-like behavior (day 21). Short-term CBD 10mg/kg treatment prevented the cognitive and emotional impairments, attenuated hippocampal neurodegeneration and white matter (WM) injury, and reduced glial response that were induced by BCCAO. In addition, ischemic mice treated with CBD exhibited an increase in the hippocampal brain derived neurotrophic factor (BDNF) protein levels. CBD also stimulated neurogenesis and promoted dendritic restructuring in the hippocampus of BCCAO animals. Collectively, the present results demonstrate that short-term CBD treatment results in global functional recovery in ischemic mice and impacts multiple and distinct targets involved in the pathophysiology of brain ischemic injury.

Effect of Single and Double Administration of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Following Focal Cerebral Ischemia in Rats

Stem cell therapies are administered during the acute phase of stroke to preserve the penumbral tissues from ischemic injury. However, the effect of repeated cell therapy during the acute phase remains unclear. In this study, we investigated and compared the functional outcome of single (two days post-injury) and repeated (two and nine days post-injury) treatment with human umbilical cord derived mesenchymal stem cells (hUCB-MSCs) after middle cerebral artery occlusion (MCAO). The rotarod and limb placement tests were utilized to investigate functional outcomes, while infarct volume and tissue damage were measured by immunofluorescent staining for neovascularization, neurogenesis, apoptosis, and inflammation in the penumbral zones. We observed notable motor dysfunction and a significant decrease in infarcted brain volume, as well as increases in neurons and vessels in both single and repeated hUCB-MSC treatments compared to the control group. Interestingly, repeated administration of hUCB-MSCs was not found to elicit additional or synergistic improvements over monotherapy. This study suggests that a clearer understanding of the therapeutic window after stroke will facilitate the development of more efficient treatment protocols in the clinical application of stem cell therapy.

Synapse Loss and Regeneration: A Mechanism for Functional Decline and Recovery after Cerebral Ischemia?

Little is known of the mechanisms governing functional recovery after ischemic brain injury, and there is no clinical therapy established to restore neurologic function after ischemic injury is complete. Even so, pronounced spontaneous recovery of function is often observed in a subset of patients. Resolution of neurological deficits after ischemia must occur through replacement of lost tissue via production of new neurons, or through changes in the structure, function, or connectivity of surviving neurons. This review focuses on the neuronal synapse as a potential locus for functional recovery. Selective disruption of synaptic elements is a characteristic feature of hypoxic-ischemic brain injury, such as that seen in ischemic stroke or cardiac arrest. Ischemic damage to synapses occurs even in the absence of neuronal loss, and therefore might underlie the clinical disability observed in patients following mild or transient ischemia. We review evidence that recovery of lost synapses occurs after ischemic injury and that this recovery may be a necessary step for restoration of neurological function. The process of synapse loss and recovery can be examined in neuronal cultures and experimental stroke models. Such studies may help to gain a better understanding of the extracellular factors and intracellular cascades that facilitate recovery of synapses, and may result in therapeutic approaches to improve function after cerebral ischemia.

Antibody-based PET imaging of amyloid beta in mouse models of Alzheimer's disease

Owing to their specificity and high-affinity binding, monoclonal antibodies have potential as positron emission tomography (PET) radioligands and are currently used to image various targets in peripheral organs. However, in the central nervous system, antibody uptake is limited by the blood-brain barrier (BBB). Here we present a PET ligand to be used for diagnosis and evaluation of treatment effects in Alzheimer's disease. The amyloid β (Aβ) antibody mAb158 is radiolabelled and conjugated to a transferrin receptor antibody to enable receptor-mediated transcytosis across the BBB. PET imaging of two different mouse models with Aβ pathology clearly visualize Aβ in the brain. The PET signal increases with age and correlates closely with brain Aβ levels. Thus, we demonstrate that antibody-based PET ligands can be successfully used for brain imaging.

Targeted delivery of growth factors in ischemic stroke animal models

INTRODUCTION

Ischemic stroke is caused by reduced blood supply and leads to loss of brain function. The reduced oxygen and nutrient supply stimulates various physiological responses, including induction of growth factors. Growth factors prevent neuronal cell death, promote neovascularization, and induce cell growth. However, the concentration of growth factors is not sufficient to recover brain function after the ischemic damage, suggesting that delivery of growth factors into the ischemic brain may be a useful treatment for ischemic stroke.

AREAS COVERED

In this review, various approaches for the delivery of growth factors to ischemic brain tissue are discussed, including local and targeting delivery systems.

EXPERT OPINION

To develop growth factor therapy for ischemic stroke, important considerations should be taken into account. First, growth factors may have possible side effects. Thus, concentration of growth factors should be restricted to the ischemic tissues by local administration or targeted delivery. Second, the duration of growth factor therapy should be optimized. Growth factor proteins may be degraded too fast to have a high enough therapeutic effect. Therefore, delivery systems for controlled release or gene delivery may be useful. Third, the delivery systems to the brain should be optimized according to the delivery route.

Illness Severity, Social and Cognitive Ability, and EEG Analysis of Ten Patients with Rett Syndrome Treated with Mecasermin (Recombinant Human IGF-1)

Rett Syndrome (RTT) is a severe neurodevelopmental disorder characterized by an apparently normal development followed by an arrest and subsequent regression of cognitive and psychomotor abilities. At present, RTT has no definitive cure and the treatment of RTT represents a largely unmet clinical need. Following partial elucidation of the underlying neurobiology of RTT, a new treatment has been proposed, Mecasermin (recombinant human Insulin-Like Growth Factor 1), which, in addition to impressive evidence from preclinical murine models of RTT, has demonstrated safety in human studies of patients with RTT. The present clinical study examines the disease severity as assessed by clinicians (International Scoring System: ISS), social and cognitive ability assessed by two blinded, independent observers (RSS: Rett Severity Score), and changes in brain activity (EEG) parameters of ten patients with classic RTT and ten untreated patients matched for age and clinical severity. Significant improvement in both the ISS (p = 0.0106) and RSS (p = 0.0274) was found in patients treated with IGF1 in comparison to untreated patients. Analysis of the novel RSS also suggests that patients treated with IGF1 have a greater endurance to social and cognitive testing. The present clinical study adds significant preliminary evidence for the use of IGF-1 in the treatment of RTT and other disorders of the autism spectrum.

Physical Exercise as a Diagnostic, Rehabilitation, and Preventive Tool: Influence on Neuroplasticity and Motor Recovery after Stroke

Stroke remains a leading cause of adult motor disabilities in the world and accounts for the greatest number of hospitalizations for neurological disease. Stroke treatments/therapies need to promote neuroplasticity to improve motor function. Physical exercise is considered as a major candidate for ultimately promoting neural plasticity and could be used for different purposes in human and animal experiments. First, acute exercise could be used as a diagnostic tool to understand new neural mechanisms underlying stroke physiopathology. Indeed, better knowledge of stroke mechanisms that affect movements is crucial for enhancing treatment/rehabilitation effectiveness. Secondly, it is well established that physical exercise training is advised as an effective rehabilitation tool. Indeed, it reduces inflammatory processes and apoptotic marker expression, promotes brain angiogenesis and expression of some growth factors, and improves the activation of affected muscles during exercise. Nevertheless, exercise training might also aggravate sensorimotor deficits and brain injury depending on the chosen exercise parameters. For the last few years, physical training has been combined with pharmacological treatments to accentuate and/or accelerate beneficial neural and motor effects. Finally, physical exercise might also be considered as a major nonpharmacological preventive strategy that provides neuroprotective effects reducing adverse effects of brain ischemia. Therefore, prestroke regular physical activity may also decrease the motor outcome severity of stroke.

A Peptide Uncoupling BDNF Receptor TrkB from Phospholipase Cγ1 Prevents Epilepsy Induced by Status Epilepticus

The BDNF receptor tyrosine kinase, TrkB, underlies nervous system function in both health and disease. Excessive activation of TrkB caused by status epilepticus promotes development of temporal lobe epilepsy (TLE), revealing TrkB as a therapeutic target for prevention of TLE. To circumvent undesirable consequences of global inhibition of TrkB signaling, we implemented a novel strategy aimed at selective inhibition of the TrkB-activated signaling pathway responsible for TLE. Our studies of a mouse model reveal that phospholipase Cγ1 (PLCγ1) is the dominant signaling effector by which excessive activation of TrkB promotes epilepsy. We designed a novel peptide (pY816) that uncouples TrkB from PLCγ1. Treatment with pY816 following status epilepticus inhibited TLE and prevented anxiety-like disorder yet preserved neuroprotective effects of endogenous TrkB signaling. We provide proof-of-concept evidence for a novel strategy targeting receptor tyrosine signaling and identify a therapeutic with promise for prevention of TLE caused by status epilepticus in humans.

Strategies for delivery of therapeutics into the central nervous system for treatment of lysosomal storage disorders

Lysosomal storage disorders (LSDs) are a group of about fifty life-threatening conditions caused by genetic defects affecting lysosomal components. The underscoring molecular deficiency leads to widespread cellular dysfunction through most tissues in the body, including peripheral organs and the central nervous system (CNS). Efforts during the last few decades have rendered a remarkable advance regarding our knowledge, medical awareness, and early detection of these genetic defects, as well as development of several treatment modalities. Clinical and experimental strategies encompassing enzyme replacement, gene and cell therapies, substrate reduction, and chemical chaperones are showing considerable potential in attenuating the peripheral pathology. However, a major drawback has been encountered regarding the suboptimal impact of these approaches on the CNS pathology. Particular anatomical and biochemical constraints of this tissue pose a major obstacle to the delivery of therapeutics into the CNS. Approaches to overcome these obstacles include modalities of local administration, strategies to enhance the blood-CNS permeability, intranasal delivery, use of exosomes, and those exploiting targeting of transporters and transcytosis pathways in the endothelial lining. The later two approaches are being pursued at the time by coupling therapeutic agents to affinity moieties and drug delivery systems capable of targeting these natural transport routes. This approach is particularly promising, as using paths naturally active at this interface may render safe and effective delivery of LSD therapies into the CNS.

BBB-targeting, protein-based nanomedicines for drug and nucleic acid delivery to the CNS

The increasing incidence of diseases affecting the central nervous system (CNS) demands the urgent development of efficient drugs. While many of these medicines are already available, the Blood Brain Barrier and to a lesser extent, the Blood Spinal Cord Barrier pose physical and biological limitations to their diffusion to reach target tissues. Therefore, efforts are needed not only to address drug development but specially to design suitable vehicles for delivery into the CNS through systemic administration. In the context of the functional and structural versatility of proteins, recent advances in their biological fabrication and a better comprehension of the physiology of the CNS offer a plethora of opportunities for the construction and tailoring of plain nanoconjugates and of more complex nanosized vehicles able to cross these barriers. We revise here how the engineering of functional proteins offers drug delivery tools for specific CNS diseases and more transversally, how proteins can be engineered into smart nanoparticles or 'artificial viruses' to afford therapeutic requirements through alternative administration routes.

Systemic administration of fibroblast growth factor-2 (FGF2) reduces BACE1 expression and amyloid pathology in APP23 mice

There is an emerging evidence that growth factors may have a potential beneficial use in the treatment of Alzheimer's disease (AD) because of their neuroprotective properties and effects on neuronal proliferation. Basic fibroblast growth factor or fibroblast growth factor-2 (FGF2) is an anti-inflammatory, angiogenic, and neurotrophic factor that is expressed in many cell types, including neurons and glial cells. Here, we explored whether subcutaneous administration of FGF2 could have therapeutic effects in the APP 23 transgenic mouse, a model of amyloid pathology. FGF2 treatment attenuated spatial memory deficits, reduced amyloid-β (Aβ) and tau pathologies, decreased inducible nitric oxide synthase expression, and increased the number of astrocytes in the dentate gyrus in APP 23 mice compared with the vehicle-treated controls. The decrease in Aβ deposition was associated with a reduction in the expression of BACE1, the main enzyme responsible for Aβ generation. These results were confirmed in a neuroblastoma cell line, which demonstrated that incubation with FGF2 regulates BACE1 transcription. In addition, and in contrast with what has been previously published, the levels of FGF2 were reduced in postmortem brains from AD patients compared with controls. These data, therefore, suggest that systemic administration of FGF2 could have a potential therapeutic application in AD.

Pluronic modified leptin with increased systemic circulation, brain uptake and efficacy for treatment of obesity

Modification of hydrophilic proteins with amphiphilic block copolymers capable of crossing cell membranes is a new strategy to improve protein delivery to the brain. Leptin, a candidate for the treatment of epidemic obesity, has failed in part because of impairment in its transport across the blood-brain barrier (BBB) that develops with obesity. We posit that modification of leptin with poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), Pluronic P85 (P85) might permit this protein to penetrate the BBB independently of its transporter, thereby overcoming peripheral leptin resistance. Here we report that peripherally administered leptin-P85 conjugates exhibit biological activity by reducing food intake in mouse models of obesity (ob/ob, and diet-induced obese mouse). We further generated two new leptin-P85 conjugates: one, Lep(ss)-P85(L), containing one P85 chain and another, Lep(ss)-P85(H), containing multiple P85 chains. We report data on their purification, analytical characterization, peripheral and brain pharmacokinetics (PK). Lep(ss)-P85(L) crosses the BBB using the leptin transporter, and exhibits improved peripheral PK along with increased accumulation in the brain compared to unmodified leptin. Lep(ss)-P85(H) also has improved peripheral PK but in a striking difference to the first conjugate penetrates the BBB independently of the leptin transporter via a non-saturable mechanism. The results demonstrate that leptin analogs can be developed through chemical modification of the native leptin with P85 to overcome leptin resistance at the level of the BBB, thus improving the potential for the treatment of obesity.

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.

Functional recovery with recombinant human IGF1 treatment in a mouse model of Rett Syndrome

Rett Syndrome is a neurodevelopmental disorder that arises from mutations in the X-linked gene methyl-CpG binding protein 2 (MeCP2). MeCP2 has a large number of targets and a wide range of functions, suggesting the hypothesis that functional signaling mechanisms upstream of synaptic and circuit maturation may contribute to our understanding of the disorder and provide insight into potential treatment. Here, we show that insulin-like growth factor-1 (IGF1) levels are reduced in young male Mecp2-null (Mecp2(-/y)) mice, and systemic treatment with recombinant human IGF1 (rhIGF1) improves lifespan, locomotor activity, heart rate, respiration patterns, and social and anxiety behavior. Furthermore, Mecp2-null mice treated with rhIGF1 show increased synaptic and activated signaling pathway proteins, enhanced cortical excitatory synaptic transmission, and restored dendritic spine densities. IGF1 levels are also reduced in older, fully symptomatic heterozygous (Mecp2(-/+)) female mice, and short-term treatment with rhIGF1 in these animals improves respiratory patterns, reduces anxiety levels, and increases exploratory behavior. In addition, rhIGF1 treatment normalizes abnormally prolonged plasticity in visual cortex circuits of adult Mecp2(-/+) female mice. Our results provide characterization of the phenotypic development of Rett Syndrome in a mouse model at the molecular, circuit, and organismal levels and demonstrate a mechanism-based therapeutic role for rhIGF1 in treating Rett Syndrome.

Impact of BDNF -196 G>A and BDNF -270 C>T polymorphisms on stroke rehabilitation outcome: sex and age differences

BACKGROUND

Genetic factors, including gene polymorphisms, are promising in determining stroke rehabilitation outcome. Brain-derived neurotrophic factor (BDNF) is one of the most attractive because of its role in neuroplasticity and brain repair.

OBJECTIVE

The aim of present study was to assess the role of BDNF -196 G≯A (val66met) and -270 C≯T on clinical parameters and functional outcome in patients with ischemic and hemorrhagic stroke. Additional analyses according to sex and age (≤55 and ≯55 years) were performed.

METHODS

Three hundred thirty-eight patients (287 with ischemic and 51 with hemorrhagic stroke) were evaluated in terms of neurological deficit (National Institute of Heath Stroke Scale [NIHSS]), activities of daily living (Barthel Index [BI]), and everyday functionality (Rankin score [RS]) before and after rehabilitation. BDNF polymorphism genotyping was performed by polymerase chain reaction restriction fragment length polymorphism analysis.

RESULTS

In multivariative analysis, unfavorable outcome of stroke rehabilitation (RS ≥2) was associated with independent factors: ischemic stroke (odds ratio [OR], 2.59; 95% CI, 1.03-6.47), female gender (OR, 2.80; 95% CI, 1.39-5.64), depression (OR, 4.24; 95% CI, 1.45-12.35), falls (OR, 2.61; 95% CI, 1.16-5.87), and BDNF -196 GG polymorphism (OR, 2.18; 95% CI, 1.09-4.35). The differences of functional parameters measured with BI and RS on admission and at discharge are apparent only for comparisons between patients ≤55 and ≯55 years old carrying BDNF -196 GA+AA genotypes but not in those carrying -196 GG genotype; the differences were evident in women but not in men.

CONCLUSIONS

BDNF -196 G≯A polymorphism might affect functional outcome of stroke rehabilitation, but this hypothesis needs further verification.

Green tea catechins potentiate the neuritogenic action of brain-derived neurotrophic factor: role of 67-kDa laminin receptor and hydrogen peroxide

Delivery of optimal amounts of brain-derived neurotrophic factor (BDNF) to regions of the brain affected by neurodegenerative diseases is a daunting task. Using natural products with neuroprotective properties, such as green tea polyphenols, would be a highly useful complementary approach for inexpensive long-term treatment of these diseases. In this study, we used PC12(TrkB) cells which ectopically express TrkB, a high affinity receptor for BDNF. They differentiate and induce neurite outgrowth in response to BDNF. Using this model, we show for the first time that treatment with extremely low concentrations (<0.1 μg/ml) of unfractionated green tea polyphenols (GTPP) and low concentrations (<0.5 μM) of their active ingredient, epigallocatechin-3-gallate (EGCG), potentiated the neuritogenic ability of a low concentration (2 ng/ml) of BDNF. A synergistic interaction was observed between GTPP constituents, where epigallocatechin and epicatechin, both individually lacking this activity, promoted the action of EGCG. GTPP-induced potentiation of BDNF action required the cell-surface associated 67 kDa laminin receptor (67LR) to which EGCG binds with high affinity. A cell-permeable catalase abolished GTPP/EGCG-induced potentiation of BDNF action, suggesting the possible involvement of H2O2 in the potentiation. Consistently, exogenous sublethal concentrations of H2O2, added as a bolus dose (5 μM) or more effectively through a steady-state generation (1 μM), potentiated BDNF action. Collectively, these results suggest that EGCG, dependent on 67 LR and H2O2, potentiates the neuritogenic action of BDNF. Intriguingly, this effect requires only submicromolar concentrations of EGCG. This is significant as extremely low concentrations of polyphenols are believed to reach the brain after drinking green tea.