Challenges and new strategies for therapeutic peptide delivery to the CNS

Effects of amyloid precursor protein peptide APP96-110, alone or with human mesenchymal stromal cells, on recovery after spinal cord injury

Delivery of a peptide (APP96-110), derived from amyloid precursor protein (APP), has been shown to elicit neuroprotective effects following cerebral stroke and traumatic brain injury. In this study, the effect of APP96-110 or a mutant version of this peptide (mAPP96-110) was assessed following moderate (200 kdyn, (2 N)) thoracic contusive spinal cord injury (SCI) in adult Nude rats. Animals received a single tail vein injection of APP96-110 or mAPP96-110 at 30 minutes post-SCI and were then assessed for functional improvements over the next 8 weeks. A cohort of animals also received transplants of either viable or non-viable human mesenchymal stromal cells (hMSCs) into the SC lesion site at one week post-injury to assess the effect of combining intravenous APP96-110 delivery with hMSC treatment. Rats were perfused 8 weeks post-SCI and longitudinal sections of spinal cord analyzed for a number of factors including hMSC viability, cyst size, axonal regrowth, glial reactivity and macrophage activation. Analysis of sensorimotor function revealed occasional significant differences between groups using Ladderwalk or Ratwalk tests, however there were no consistent improvements in functional outcome after any of the treatments. mAPP96-110 alone, and APP96-110 in combination with both viable and non-viable hMSCs significantly reduced cyst size compared to SCI alone. Combined treatments with donor hMSCs also significantly increased βIII tubulin⁺, glial fibrillary acidic protein (GFAP⁺) and laminin⁺ expression, and decreased ED1⁺ expression in tissues. This preliminary study demonstrates that intravenous delivery of APP96-110 peptide has selective, modest neuroprotective effects following SCI, which may be enhanced when combined with hMSC transplantation. However, the effects are less pronounced and less consistent compared to the protective morphological and cognitive impact that this same peptide has on neuronal survival and behaviour after stroke and traumatic brain injury. Thus while the efficacy of a particular therapeutic approach in one CNS injury model may provide justification for its use in other neurotrauma models, similar outcomes may not necessarily occur and more targeted approaches suited to location and severity are required. All animal experiments were approved by The University of Western Australia Animal Ethics Committee (RA3/100/1460) on April 12, 2016.

Brain Pathogenesis and Potential Therapeutic Strategies in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy that affects multiple systems including the muscle and heart. The mutant CTG expansion at the 3′-UTR of the DMPK gene causes the expression of toxic RNA that aggregate as nuclear foci. The foci then interfere with RNA-binding proteins, affecting hundreds of mis-spliced effector genes, leading to aberrant alternative splicing and loss of effector gene product functions, ultimately resulting in systemic disorders. In recent years, increasing clinical, imaging, and pathological evidence have indicated that DM1, though to a lesser extent, could also be recognized as true brain diseases, with more and more researchers dedicating to develop novel therapeutic tools dealing with it. In this review, we summarize the current advances in the pathogenesis and pathology of central nervous system (CNS) deficits in DM1, intervention measures currently being investigated are also highlighted, aiming to promote novel and cutting-edge therapeutic investigations.

Current strategies for therapeutic drug delivery after traumatic CNS injury

Therapeutic strategies for traumatic injuries in the central nervous system (CNS) are largely limited to the efficiency of drug delivery. Despite the disrupted blood-CNS barrier during the early phase after injury, the drug administration faces a variety of obstacles derived from homeostatic imbalance at the injury site. In the late phase after CNS injury, the restoration of the blood-CNS barrier integrity varies depending on the injury severity resulting in inconsistent delivery of therapeutics. This review intends to characterize those different challenges of the therapeutic delivery in acute and chronic phases after injury and discuss recent advances in various approaches to explore novel strategies for the treatment of traumatic CNS injury.

Established and Emerging Strategies for Drug Delivery Across the Blood-Brain Barrier in Brain Cancer

Brain tumors are characterized by very high mortality and, despite the continuous research on new pharmacological interventions, little therapeutic progress has been made. One of the main obstacles to improve current treatments is represented by the impermeability of the blood vessels residing within nervous tissue as well as of the new vascular net generating from the tumor, commonly referred to as blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB), respectively. In this review, we focused on established and emerging strategies to overcome the blood-brain barrier to increase drug delivery for brain cancer. To date, there are three broad strategies being investigated to cross the brain vascular wall and they are conceived to breach, bypass, and negotiate the access to the nervous tissue. In this paper, we summarized these approaches highlighting their working mechanism and their potential impact on the quality of life of the patients as well as their current status of development.

Fighting against depression with TREK-1 blockers: Past and future. A focus on spadin

Depression is a devastating mood disorder and a leading cause of disability worldwide. Depression affects approximately one in five individuals in the world and represents heavy economic and social burdens. The neurobiological mechanisms of depression are not fully understood, but evidence highlights the role of monoamine neurotransmitter balance. Several antidepressants (ADs) are marketed to treat depression and related mood disorders. However, despite their efficacy, they remain nonspecific and unsafe because they trigger serious adverse effects. Therefore, developing new molecules for new targets in depression has become a real necessity. Eight years ago, spadin was described as a natural peptide with AD properties. This 17-amino acid peptide blocks TREK-1 channels, an original target in depression. Compared to the classical AD drugs such as fluoxetine, which requires 3-4 weeks for the AD effect to manifest, spadin acts rapidly within only 4 days of treatment. The AD properties are associated with increased neurogenesis and synaptogenesis in the brain. Despite the advantages of this fast-acting AD, the in vivo stability is weak and does not last for >7 h. The present review summarizes different strategies such as retro-inverso strategy, cyclization, and shortening the spadin sequence that has led to the development and optimization of spadin as an AD. Shortened spadin analogs present increased inhibition potency for TREK-1, an improved AD activity, and prolonged in vivo bioavailability. Finally, we also discuss about other inhibitors of TREK-1 channels with a proven efficacy in treating depression in the clinic, such as fluoxetine.

Asn194Lys mutation in RVG29 peptide increases GFP transgene delivery by endocytosis to neuroblastoma and astrocyte cells

OBJECTIVES

A cell-penetrating peptide-based delivery system could target specific types of cells for therapeutic genes delivery. To increase the gene delivery efficiency into neuronal phenotype cells, we introduced an Asn194Lys mutation to RVG29 peptide derived from rabies virus glycoprotein and added a nuclear localization signal to enhance its nuclear import.

METHODS

Mutant RVG or wild-type RVG peptide, a karyophilic peptide (KP) and a plasmid encoding green fluorescent protein (pGL) were bound by electrostatic charges to form four different kinds of RVG complexes. Immunofluorescence was used to assess the gene transfection efficiency into astrocytes, oligodendrocyte precursor cells (OPCs), SH-SY5Y, HeLa and NIH/3T3 cells. The cellular uptake mechanism of RVG29 complexes was examined using endocytosis inhibitors.

KEY FINDINGS

The mRVG29 peptide has the ability to enhance the nuclear import of plasmids. The Asn194Lys mutation in RVG29 peptide of the pGL-mRVG29 complex and the addition of KP to the pGL-RVG29-KP complex increased the capacity to deliver DNA by endocytosis in astrocytes and SH-SY5Y cells.

CONCLUSIONS

The complexes pGL-mRVG29 and pGL-RVG29-KP have specificity for transfecting astrocytes and SH-SY5Y cells. The karyophilic capacity of this new mRVG peptide render it promising candidate to act as gene delivery vector into the brain cells.

Myotonic Dystrophies: State of the Art of New Therapeutic Developments for the CNS

Myotonic dystrophies are multisystemic diseases characterized not only by muscle and heart dysfunction but also by CNS alteration. They are now recognized as brain diseases affecting newborns and children for myotonic dystrophy type 1 and adults for both myotonic dystrophy type 1 and type 2. In the past two decades, much progress has been made in understanding the mechanisms underlying the DM symptoms allowing development of new molecular therapeutic tools with the ultimate aim of curing the disease. This review describes the state of the art for the characterization of CNS related symptoms, the development of molecular strategies to target the CNS as well as the available tools for screening and testing new possible treatments.

Nanotechnology-based drug delivery systems for Alzheimer's disease management: Technical, industrial, and clinical challenges

Alzheimer's disease (AD) is a neurodegenerative disease with high prevalence in the rapidly growing elderly population in the developing world. The currently FDA approved drugs for the management of symptomatology of AD are marketed mainly as conventional oral medications. Due to their gastrointestinal side effects and lack of brain targeting, these drugs and dosage regiments hinder patient compliance and lead to treatment discontinuation. Nanotechnology-based drug delivery systems (NTDDS) administered by different routes can be considered as promising tools to improve patient compliance and achieve better therapeutic outcomes. Despite extensive research, literature screening revealed that clinical activities involving NTDDS application in research for AD are lagging compared to NTDDS for other diseases such as cancers. The industrial perspectives, processability, and cost/benefit ratio of using NTDDS for AD treatment are usually overlooked. Moreover, active and passive immunization against AD are by far the mostly studied alternative AD therapies because conventional oral drug therapy is not yielding satisfactorily results. NTDDS of approved drugs appear promising to transform this research from 'paper to clinic' and raise hope for AD sufferers and their caretakers. This review summarizes the recent studies conducted on NTDDS for AD treatment, with a primary focus on the industrial perspectives and processability. Additionally, it highlights the ongoing clinical trials for AD management.

Structural Elucidation of the Cell-Penetrating Penetratin Peptide in Model Membranes at the Atomic Level: Probing Hydrophobic Interactions in the Blood-Brain Barrier

Cell-penetrating peptides (CPPs) have shown promise in nonpermeable therapeutic drug delivery, because of their ability to transport a variety of cargo molecules across the cell membranes and their noncytotoxicity. Drosophila antennapedia homeodomain-derived CPP penetratin (RQIKIWFQNRRMKWKK), being rich in positively charged residues, has been increasingly used as a potential drug carrier for various purposes. Penetratin can breach the tight endothelial network known as the blood-brain barrier (BBB), permitting treatment of several neurodegenerative maladies, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. However, a detailed structural understanding of penetratin and its mechanism of action is lacking. This study defines structural features of the penetratin-derived peptide, DK17 (DRQIKIWFQNRRMKWKK), in several model membranes and describes a membrane-induced conformational transition of the DK17 peptide in these environments. A series of biophysical experiments, including high-resolution nuclear magnetic resonance spectroscopy, provides the three-dimensional structure of DK17 in different membranes mimicking the BBB or total brain lipid extract. Molecular dynamics simulations support the experimental results showing preferential binding of DK17 to particular lipids at atomic resolution. The peptide conserves the structure of the subdomain spanning residues Ile6-Arg11, despite considerable conformational variation in different membrane models. In vivo data suggest that the wild type, not a mutated sequence, enters the central nervous system. Together, these data highlight important structural and functional attributes of DK17 that could be utilized in drug delivery for neurodegenerative disorders.