Oral administration of a GSK3 inhibitor increases brain insulin-like growth factor I levels

Choroid plexus extracellular vesicle transport of blood-borne insulin-like growth factor 1 to the hippocampus of the immature brain

Reduced serum level of insulin-like growth factor 1 (IGF-1), a major regulator of perinatal development, in extremely preterm infants has been shown to be associated with neurodevelopmental impairment. To clarify the mechanism of IGF-1 transport at the blood-cerebrospinal fluid (CSF) barrier of the immature brain, we combined studies of in vivo preterm piglet and rabbit models with an in vitro transwell cell culture model of neonatal primary murine choroid plexus epithelial (ChPE) cells. We identified IGF-1-positive intracellular vesicles in ChPE cells and provided data indicating a directional transport of IGF-1 from the basolateral to the apical media in extracellular vesicles (EVs). Exposure of the ChPE cells to human IGF-1 on the basolateral side increased the secretion of IGF-1-positive EVs in the apical media. Mass spectrometry analysis displayed similarities in protein content between EVs derived from preterm piglet CSF-derived and ChPE cell-derived EVs. Furthermore, exposure of ChPE cells to human IGF-1 caused an enrichment of human IGF-1 and transmembrane p24 trafficking protein 2, proteins important for perinatal development, in apical media-derived EVs. Moreover, intraventricular injections of ChPE cell-derived EVs in preterm rabbit pups resulted in an uptake of EVs in the brain, displaying penetration through the ependymal lining and deep into the hippocampus. Finally, exposure of rat hippocampus neurons to ChPE cell-derived EVs resulted in internalization of the EVs in hippocampal soma and neurites. In summary, we describe a transport pathway for blood-borne IGF-1 in EVs through the blood-CSF barrier to the hippocampus in the immature brain.

Synthesis and Antimicrobial Activity of 3-Alkylidene-2-Indolone Derivatives

The escalating threat of antibiotic-resistant bacteria and fungi underscores an urgent need for new antimicrobial agents. This study aimed to synthesize and evaluate the antimicrobial activities of two series of 3-alkylidene-2-indolone derivatives. We synthesized 32 target compounds, among which 25 exhibited moderate to high antibacterial or antifungal activities. Notably, compounds 10f, 10g, and 10h demonstrated the highest antibacterial activity with a minimum inhibitory concentration (MIC) of 0.5 μg/mL, matching the activity of the positive control gatifloxacin against three Gram-positive bacterial strains: Staphylococcus aureus ATCC 6538, 4220, and Methicillin-resistant Staphylococcus aureus ATCC 43300. Moreover, the three most active compounds 10f, 10g, and 10h were evaluated for their in vitro cytotoxicity in the HepG2 cancer cell line and L-02; only compound 10h was found to exert some level of cytotoxicity. These findings suggest that the synthesized 3-alkylidene-2-indolone derivatives hold potential for further development as antibacterial agents.

Insulin-Like Growth Factor Signaling in Alzheimer's Disease: Pathophysiology and Therapeutic Strategies

Alzheimer's disease (AD) is the leading cause of dementia among the elderly population, posing a significant public health challenge due to limited therapeutic options that merely delay cognitive decline. AD is associated with impaired energy metabolism and reduced neurotrophic signaling. The insulin-like growth factor (IGF) signaling pathway, crucial for central nervous system (CNS) development, metabolism, repair, cognition, and emotion regulation, includes IGF-1, IGF-2, IGF-1R, IGF-2R, insulin receptor (IR), and six insulin-like growth factor binding proteins (IGFBPs). Research has identified abnormalities in IGF signaling in individuals with AD and AD models. Dysregulated expression of IGFs, receptors, IGFBPs, and disruptions in downstream phosphoinositide 3-kinase-protein kinase B (PI3K/AKT) and mitogen-activated protein kinase (MAPK) pathways collectively increase AD susceptibility. Studies suggest modulating the IGF pathway may ameliorate AD pathology and cognitive decline. This review explores the CNS pathophysiology of IGF signaling in AD progression and assesses the potential of targeting the IGF system as a novel therapeutic strategy. Further research is essential to elucidate how aberrant IGF signaling contributes to AD development, understand underlying molecular mechanisms, and evaluate the safety and efficacy of IGF-based treatments.

Insulin-like growth factor binding protein-2 in at-risk adults and autopsy-confirmed Alzheimer brains

Insulin, insulin-like growth factors (IGF) and their receptors are highly expressed in the adult hippocampus. Thus, disturbances in the insulin-IGF signalling pathway may account for the selective vulnerability of the hippocampus to nascent Alzheimer's disease (AD) pathology. In the present study, we examined the predominant IGF-binding protein in the CSF, IGFBP2. CSF was collected from 109 asymptomatic members of the parental history-positive PREVENT-AD cohort. CSF levels of IGFBP2, core AD and synaptic biomarkers were measured using proximity extension assay, ELISA and mass spectrometry. Cortical amyloid-beta (Aβ) and tau deposition were examined using 18F-NAV4694 and flortaucipir. Cognitive assessments were performed during up to 8 years of follow-up, using the Repeatable Battery for the Assessment of Neuropsychological Status. T1-weighted structural MRI scans were acquired, and neuroimaging analyses were performed on pre-specified temporal and parietal brain regions. Next, in an independent cohort, we allocated 241 dementia-free ADNI-1 participants into four stages of AD progression based on the biomarkers CSF Aβ42 and total-tau (t-tau). In this analysis, differences in CSF and plasma IGFBP2 levels were examined across the pathological stages. Finally, IGFBP2 mRNA and protein levels were examined in the frontal cortex of 55 autopsy-confirmed AD and 31 control brains from the Quebec Founder Population (QFP) cohort, a unique population isolated from Eastern Canada. CSF IGFBP2 progressively increased over 5 years in asymptomatic PREVENT-AD participants. Baseline CSF IGFBP2 was positively correlated with CSF AD biomarkers and synaptic biomarkers, and negatively correlated with longitudinal changes in delayed memory (P = 0.024) and visuospatial abilities (P = 0.019). CSF IGFBP2 was negatively correlated at a trend-level with entorhinal cortex volume (P = 0.082) and cortical thickness in the piriform (P = 0.039), inferior temporal (P = 0.008), middle temporal (P = 0.014) and precuneus (P = 0.033) regions. In ADNI-1, CSF (P = 0.009) and plasma (P = 0.001) IGFBP2 were significantly elevated in Stage 2 [CSF Aβ(+)/t-tau(+)]. In survival analyses in ADNI-1, elevated plasma IGFBP2 was associated with a greater rate of AD conversion (hazard ratio = 1.62, P = 0.021). In the QFP cohort, IGFBP2 mRNA was reduced (P = 0.049); however, IGFBP2 protein levels did not differ in the frontal cortex of autopsy-confirmed AD brains (P = 0.462). Nascent AD pathology may induce an upregulation in IGFBP2 in asymptomatic individuals. CSF and plasma IGFBP2 may be valuable markers for identifying CSF Aβ(+)/t-tau(+) individuals and those with a greater risk of AD conversion.

Therapeutic Targeting of the GSK3β-CUGBP1 Pathway in Myotonic Dystrophy

Myotonic Dystrophy type 1 (DM1) is a neuromuscular disease associated with toxic RNA containing expanded CUG repeats. The developing therapeutic approaches to DM1 target mutant RNA or correct early toxic events downstream of the mutant RNA. We have previously described the benefits of the correction of the GSK3β-CUGBP1 pathway in DM1 mice (HSALR model) expressing 250 CUG repeats using the GSK3 inhibitor tideglusib (TG). Here, we show that TG treatments corrected the expression of ~17% of genes misregulated in DM1 mice, including genes involved in cell transport, development and differentiation. The expression of chloride channel 1 (Clcn1), the key trigger of myotonia in DM1, was also corrected by TG. We found that correction of the GSK3β-CUGBP1 pathway in mice expressing long CUG repeats (DMSXL model) is beneficial not only at the prenatal and postnatal stages, but also during adulthood. Using a mouse model with dysregulated CUGBP1, which mimics alterations in DM1, we showed that the dysregulated CUGBP1 contributes to the toxicity of expanded CUG repeats by changing gene expression and causing CNS abnormalities. These data show the critical role of the GSK3β-CUGBP1 pathway in DM1 muscle and in CNS pathologies, suggesting the benefits of GSK3 inhibitors in patients with different forms of DM1.

Sulfur-containing therapeutics in the treatment of Alzheimer's disease

Sulfur is widely existent in natural products and synthetic organic compounds as organosulfur, which are often associated with a multitude of biological activities. OBenzothiazole, in which benzene ring is fused to the 4,5-positions of the thiazolerganosulfur compounds continue to garner increasing amounts of attention in the field of medicinal chemistry, especially in the development of therapeutic agents for Alzheimer's disease (AD). AD is a fatal neurodegenerative disease and the primary cause of age-related dementia posing severe societal and economic burdens. Unfortunately, there is no cure for AD. A lot of research has been conducted on sulfur-containing compounds in the context of AD due to their innate antioxidant potential and some are currently being evaluated in clinical trials. In this review, we have described emerging trends in the field, particularly the concept of multi-targeting and formulation of disease-modifying strategies. SAR, pharmacological targets, in vitro/vivo ADMET, efficacy in AD animal models, and applications in clinical trials of such sulfur compounds have also been discussed. This article provides a comprehensive review of organosulfur-based AD therapeutic agents and provides insights into their future development.

Targeting the Choroid Plexuses for Protein Drug Delivery

Delivery of therapeutic agents to the central nervous system is challenged by the barriers in place to regulate brain homeostasis. This is especially true for protein therapeutics. Targeting the barrier formed by the choroid plexuses at the interfaces of the systemic circulation and ventricular system may be a surrogate brain delivery strategy to circumvent the blood-brain barrier. Heterogenous cell populations located at the choroid plexuses provide diverse functions in regulating the exchange of material within the ventricular space. Receptor-mediated transcytosis may be a promising mechanism to deliver protein therapeutics across the tight junctions formed by choroid plexus epithelial cells. However, cerebrospinal fluid flow and other barriers formed by ependymal cells and perivascular spaces should also be considered for evaluation of protein therapeutic disposition. Various preclinical methods have been applied to delineate protein transport across the choroid plexuses, including imaging strategies, ventriculocisternal perfusions, and primary choroid plexus epithelial cell models. When used in combination with simultaneous measures of cerebrospinal fluid dynamics, they can yield important insight into pharmacokinetic properties within the brain. This review aims to provide an overview of the choroid plexuses and ventricular system to address their function as a barrier to pharmaceutical interventions and relevance for central nervous system drug delivery of protein therapeutics. Protein therapeutics targeting the ventricular system may provide new approaches in treating central nervous system diseases.

Drug Repurposing in Dentistry; towards Application of Small Molecules in Dentin Repair

One of the main goals of dentistry is the natural preservation of the tooth structure following damage. This is particularly implicated in deep dental cavities affecting dentin and pulp, where odontoblast survival is jeopardized. This activates pulp stem cells and differentiation of new odontoblast-like cells, accompanied by increased Wnt signaling. Our group has shown that delivery of small molecule inhibitors of GSK3 stimulates Wnt/β-catenin signaling in the tooth cavity with pulp exposure and results in effective promotion of dentin repair. Small molecules are a good therapeutic option due to their ability to pass across cell membranes and reach target. Here, we investigate a range of non-GSK3 target small molecules that are currently used for treatment of various medical conditions based on other kinase inhibitory properties. We analyzed the ability of these drugs to stimulate Wnt signaling activity by off-target inhibition of GSK3. Our results show that a c-Met inhibitor, has the ability to stimulate Wnt/β-catenin pathway in dental pulp cells in vitro at low concentrations. This work is an example of drug repurposing for dentistry and suggests a candidate drug to be tested in vivo for natural dentin repair. This approach bypasses the high level of economical and time investment that are usually required in novel drug discoveries.

Neuronal megalin mediates synaptic plasticity-a novel mechanism underlying intellectual disabilities in megalin gene pathologies

Donnai-Barrow syndrome, a genetic disorder associated to LRP2 (low-density lipoprotein receptor 2/megalin) mutations, is characterized by unexplained neurological symptoms and intellectual deficits. Megalin is a multifunctional endocytic clearance cell-surface receptor, mostly described in epithelial cells. This receptor is also expressed in the CNS, mainly in neurons, being involved in neurite outgrowth and neuroprotective mechanisms. Yet, the mechanisms involved in the regulation of megalin in the CNS are poorly understood. Using transthyretin knockout mice, a megalin ligand, we found that transthyretin positively regulates neuronal megalin levels in different CNS areas, particularly in the hippocampus. Transthyretin is even able to rescue megalin downregulation in transthyretin knockout hippocampal neuronal cultures, in a positive feedback mechanism via megalin. Importantly, transthyretin activates a regulated intracellular proteolysis mechanism of neuronal megalin, producing an intracellular domain, which is translocated to the nucleus, unveiling megalin C-terminal as a potential transcription factor, able to regulate gene expression. We unveil that neuronal megalin reduction affects physiological neuronal activity, leading to decreased neurite number, length and branching, and increasing neuronal susceptibility to a toxic insult. Finally, we unravel a new unexpected role of megalin in synaptic plasticity, by promoting the formation and maturation of dendritic spines, and contributing for the establishment of active synapses, both in in vitro and in vivo hippocampal neurons. Moreover, these structural and synaptic roles of megalin impact on learning and memory mechanisms, since megalin heterozygous mice show hippocampal-related memory and learning deficits in several behaviour tests. Altogether, we unveil a complete novel role of megalin in the physiological neuronal activity, mainly in synaptic plasticity with impact in learning and memory. Importantly, we contribute to disclose the molecular mechanisms underlying the cognitive and intellectual disabilities related to megalin gene pathologies.

Glycogen synthase kinase 3 β activity is essential for Polo-like kinase 2- and Leucine-rich repeat kinase 2-mediated regulation of α-synuclein

Parkinson's disease (PD) is a currently incurable disease and the number of patients is expected to increase due to the extended human lifespan. α-Synuclein is a pathological hallmark of PD and variations and triplications of the gene encoding α-synuclein are strongly correlated with the risk of developing PD. Decreasing α-synuclein is therefore a promising therapeutic strategy for the treatment of PD. We have previously demonstrated that Polo-like kinase 2 (PLK-2) regulates α-synuclein protein levels by modulating the expression of α-synuclein mRNA. In this study, we further expand the knowledge on this pathway and show that it depends on down-stream modulation of Glycogen-synthase kinase 3 β (GSK-3β). We show that PLK-2 inhibition only increases α-synuclein levels in the presence of active GSK-3β in both cell lines and primary neuronal cultures. Furthermore, direct inhibition of GSK-3β decreases α-synuclein protein and mRNA levels in our cell model and overexpression of Leucine-rich repeat kinase 2, known to activate GSK-3β, increases α-synuclein levels. Finally, we show an increase in endogenous α-synuclein in primary neurons when increasing GSK-3β activity. Our findings demonstrate a not previously described role of endogenous GSK-3β activity in the PLK-2 mediated regulation of α-synuclein levels. This finding opens up the possibility of GSK-3β as a novel target for decreasing α-synuclein levels by the use of small molecule compounds, hereby serving as a disease modulating strategy.

Selective Ablation of Megalin in the Retinal Pigment Epithelium Results in Megaophthalmos, Macromelanosome Formation and Severe Retina Degeneration

Purpose

Mutations in the megalin-encoding gene, LRP2, cause high myopia as seen in patients suffering from Donnai-Barrow/facio-oculo-acoustico-renal syndrome. Megalin is present in both the nonpigmented epithelium of the ciliary body and in the RPE. In this study, we set out to establish an animal model to study the mechanisms underlying the ocular phenotype and to establish if high myopia/megaophthalmos is induced by postnatal megalin-deficiency in the RPE.

Methods

Postnatal RPE-specific deletion of megalin was generated by crossing mice bearing a homozygous loxP-flanked Lrp2 allele with transgenic mice expressing the Cre recombinase driven by the BEST1 promotor. The model was investigated by immunohistologic techniques, and transmission electron microscopy.

Results

Mice with postnatal RPE-specific loss of megalin developed a megaophthalmos phenotype with dramatic increase in ocular size and severe retinal thinning associated with compromised vision. This phenotype was present at postnatal day 14, indicating rapid development in the period from onset of BEST1 promotor activity at postnatal day 10. Additionally, RPE melanosomes exhibited abnormal size and morphology, suggested by electron tomography to be caused by fusion events between multiple melanosomes.

Conclusions

Postnatal loss of megalin in the RPE induces dramatic and rapid ocular growth and retinal degeneration compatible with the high myopia observed in Donnai-Barrow patients. The morphologic changes of RPE melanosomes, believed to be largely inert and fully differentiated at birth, suggested a continued plasticity of mature melanosomes and a requirement for megalin to maintain their number and morphology.

The Role of Insulin-Like Growth Factors and Insulin-Like Growth Factor-Binding Proteins in the Nervous System

The insulin-like growth factors (IGF-I and IGF-II) and their receptors are widely expressed in nervous tissue from early embryonic life. They also cross the blood brain barriers by active transport, and their regulation as endocrine factors therefore differs from other tissues. In brain, IGFs have paracrine and autocrine actions that are modulated by IGF-binding proteins and interact with other growth factor signalling pathways. The IGF system has roles in nervous system development and maintenance. There is substantial evidence for a specific role for this system in some neurodegenerative diseases, and neuroprotective actions make this system an attractive target for new therapeutic approaches. In developing new therapies, interaction with IGF-binding proteins and other growth factor signalling pathways should be considered. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

Small molecules targeting glycogen synthase kinase 3 as potential drug candidates for the treatment of retinitis pigmentosa

Retinitis pigmentosa (RP) is an inherited retinal dystrophy that courses with progressive degeneration of retinal tissue and loss of vision. Currently, RP is an unpreventable, incurable condition. We propose glycogen synthase kinase 3 (GSK-3) inhibitors as potential leads for retinal cell neuroprotection, since the retina is also a part of the central nervous system and GSK-3 inhibitors are potent neuroprotectant agents. Using a chemical genetic approach, diverse small molecules with different potency and binding mode to GSK-3 have been used to validate and confirm GSK-3 as a pharmacological target for RP. Moreover, this medicinal chemistry approach has provided new leads for the future disease-modifying treatment of RP.

Nuclear GSK3β promotes tumorigenesis by phosphorylating KDM1A and inducing its deubiquitylation by USP22

Emerging evidences have shown that GSK3β plays oncogenic roles in multiple tumor types; however, the underlying mechanisms remain largely unknown. Herein, we show that nuclear GSK3β is responsible for the accumulation of the histone demethylase KDM1A and critically regulates histone H3K4 methylation during tumorigenesis. GSK3β phosphorylates KDM1A serine 683 upon priming phosphorylation of KDM1A serine 687 by CK1α. Phosphorylation of KDM1A induces its binding with and deubiquitination by USP22, leading to KDM1A stabilization. GSK3β and USP22-dependent KDM1A stabilization is required for the demethylation of histone H3K4, thereby repression of BMP2, CDKN1A, and GATA6 transcription, cancer stem cell self-renewal, and glioblastoma tumorigenesis. In human glioblastoma specimens, KDM1A levels are correlated with nuclear GSK3β and USP22 levels. Furthermore, a GSK3 inhibitor tideglusib sensitizes tumor xenograft to chemotherapy in mice via KDM1A down-regulation and improves survival. Our findings demonstrate that nuclear GSK3β and USP22-mediated KDM1A stabilization is essential for glioblastoma tumorigenesis.

Circulating insulin-like growth factor 1 and insulin-like growth factor binding protein-3 level in Alzheimer's disease: a meta-analysis

It has been reported that the associations between circulating insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) and Alzheimer's disease (AD) are controversial. Thus, present meta-analysis was carried out to confirm the probable associations. We searched "PubMed", "Springer" and "Medline" databases using the term ("insulin-like growth factor-1" or "IGF-1" or "insulin-like growth factor binding protein-3" or "IGFBP-3") and ("Alzheimer's disease") until April 2016. Furthermore, standard mean differences (SMDs) were calculated. A total of seven reports involving 1342 percipients were pooled. SMDs were -0.25 (P = 0.22) and -0.33 (P = 0.08) for IGF-1 and IGFBP-3, respectively. Furthermore, the circulating IGF-1 levels in AD patients were lower than controls when studies with the difference of mean age ≤1 year (SMD -0.57, P = 0.007) or 2 years (SMD -0.58, P = 0.02) or difference of mean MMSE scores ≤10 scores (SMD -0.94, P < 0.00001), or studies from Europe (SMD -0.89, P < 0.00001) were excluded. In addition, the circulating IGFBP-3 levels in AD patients were lower than controls when studies with the difference of mean age ≤2 years (SMD -0.62, P = 0.006) or difference of mean MMSE scores ≤6 scores (SMD -0.48, P = 0.0004), 7 scores (SMD -0.58, P = 0.02), or 8 scores (SMD -0.80, P = 0.03) were excluded. Even though no significant difference of circulating IGF-1 and IGFBP-3 levels in AD patients comparing with controls was found in present meta-analysis, the current study provided the evidence that the circulating IGF-1 and IGFBP-3 level in AD patients were influenced by the difference of mean age as well as MMSE scores. Furthermore, circulating IGFBP-3 levels in AD patients may be decreased earlier than IGF-1.

Central IGF-I Receptors in the Brain are Instrumental to Neuroprotection by Systemically Injected IGF-I in a Rat Model for Ischemic Stroke

AIM

Insulin-like growth factor I (IGF-I) is a neuroprotective agent in animal models of ischemic stroke. The purpose of this study was to determine whether systemically injected IGF-I exerts its neuroprotective action by binding to IGF-I receptors in the brain after crossing the blood-brain barrier, or via peripheral effects.

METHODS

To differentiate the central effects of IGF-I from systemic effects, ischemic stroke was induced in conscious male Wistar Kyoto rats by the injection of endothelin-1 adjacent to the middle cerebral artery in the right hemisphere, while either the IGF-I receptor antagonist JB-1 or vehicle was introduced into the right lateral ventricle.

RESULTS

Intravenous injection of recombinant human (rh)IGF-I resulted in 50% reduction in infarct size, which was counteracted by the central administration of JB-1. Furthermore, rhIGF-I was detected in both the ischemic and nonischemic hemisphere.

CONCLUSIONS

Systemically injected rhIGF-I passes the blood-brain barrier and protects neurons via IGF-I receptors in the brain in rats with an ischemic stroke.

Meta-Analysis of Serum Insulin-Like Growth Factor 1 in Alzheimer's Disease

Insulin-like growth factor 1 (IGF-1) serum levels have been reported to be altered in Alzheimer's disease patients, and it was suggested that the changes in IGF-1 serum level may play a role in disease pathology and progression. However, this notion remained controversial due to conflicting findings. We conducted a meta-analysis to determine the relationship between IGF-1 serum levels and Alzheimer's disease. We searched the databases PUBMED, Ovid SP, and Cochrane library for relevant studies. The primary data analyzed was serum IGF-1 from Alzheimer's disease subjects and controls. Pooled weighted mean difference using a random effects model was used to determine the relationship between serum levels and disease state. Nine studies were included in the meta-analysis compromising a total of 1639 subjects. The pooled weighted mean difference was -2.27ng/ml (95% CI: [-22.221, 17.66]) with a P value of 0.82. Thus our finding did not show clear relationship between low IGF-1 and Alzheimer's disease subjects. We did not find evidence of publication bias by analyzing a funnel plot as well as Egger's and Begg's tests. While eight out of the nine studies included in this meta-analysis detected a statistically significant increase or decrease in serum levels of IGF-1 in Alzheimer's disease subjects, the analysis as a whole did not show a significant trend in either direction. Thus, IGF-1 level is likely a critical personalized factor. A large database of clinical trials is required for better understanding the relationship between IGF-1 levels and Alzheimer's disease.

Abundance of megalin and Dab2 is reduced in syncytiotrophoblast during placental malaria, which may contribute to low birth weight

Placental malaria caused by Plasmodium falciparum contributes to ~200,000 child deaths annually, mainly due to low birth weight (LBW). Parasitized erythrocyte sequestration and consequent inflammation in the placenta are common attributes of placental malaria. The precise molecular details of placental changes leading to LBW are still poorly understood. We hypothesized that placental malaria may disturb maternofetal exchange of vitamins, lipids, and hormones mediated by the multi-ligand (n ~ 50) scavenging/signaling receptor megalin, which is abundantly expressed in placenta but was not previously analyzed in pregnancy outcomes. We studied abundance of megalin and its intracellular adaptor protein Dab2 by immunofluorescence microscopy in placental biopsies from Ugandan women with (n = 8) and without (n = 20) active placental malaria. We found that: (a) abundances of both megalin (p = 0.01) and Dab2 (p = 0.006) were significantly reduced in brush border of syncytiotrophoblast of infected placentas; (b) amounts of megalin and Dab2 were strongly correlated (Spearman's r = 0.53, p = 0.003); (c) abundances of megalin and Dab2 (p = 0.046) were reduced in infected placentas from women with LBW deliveries. This study provides first evidence that placental malaria infection is associated with reduced abundance of megalin transport/signaling system and indicate that these changes may contribute to the pathology of LBW.

Low Density Lipoprotein Receptor Related Proteins as Regulators of Neural Stem and Progenitor Cell Function

The central nervous system (CNS) is a highly organised structure. Many signalling systems work in concert to ensure that neural stem cells are appropriately directed to generate progenitor cells, which in turn mature into functional cell types including projection neurons, interneurons, astrocytes, and oligodendrocytes. Herein we explore the role of the low density lipoprotein (LDL) receptor family, in particular family members LRP1 and LRP2, in regulating the behaviour of neural stem and progenitor cells during development and adulthood. The ability of LRP1 and LRP2 to bind a diverse and extensive range of ligands, regulate ligand endocytosis, recruit nonreceptor tyrosine kinases for direct signal transduction and signal in conjunction with other receptors, enables them to modulate many crucial neural cell functions.

Peptidergic drugs for the treatment of traumatic brain injury

Traumatic brain injury (TBI) is a devastating medical condition that has an enormous socioeconomic impact because it affects more than 10 million people annually worldwide and is associated with high rates of hospitalization, mortality and disability. Although TBI survival has improved continuously for decades, particularly in developing countries, implementation of an effective drug therapy for TBI represents an unmet clinical need. All confirmatory trials conducted to date with drugs targeting a single TBI pathological pathway failed to show clinical efficacy, probably because TBI pathophysiology involves multiple cellular and molecular mechanisms of secondary brain damage. According to current scientific evidence of the participation of peptide-mediated mechanisms in the processes of brain injury and repair after TBI, peptidergic drugs represent a multimodal therapy alternative to improve acute outcome and long-term recovery in TBI patients. Preliminary randomized-controlled clinical trials and open-label studies conducted to date with the peptidergic drug Cerebrolysin® (Ever Neuro Pharma GmbH, Unterach, Austria) and with the endogenous neuropeptides progesterone and erythropoietin, showed positive clinical results. Cerebrolysin-treated patients had a faster clinical recovery, a shorter hospitalization time and a better long-term outcome. Treatment with progesterone showed advantages over placebo regarding TBI mortality and clinical outcome, whereas erythropoietin only reduced mortality. Further validation of these promising findings in confirmatory randomized-controlled clinical trials is warranted. This article reviews the scientific basis and clinical evidence on the development of multimodal peptidergic drugs as a therapeutic option for the effective treatment of TBI patients.

Unraveling 50-Year-Old Clues Linking Neurodegeneration and Cancer to Cycad Toxins: Are microRNAs Common Mediators?

Recognition of overlapping molecular signaling activated by a chemical trigger of cancer and neurodegeneration is new, but the path to this discovery has been long and potholed. Six conferences (1962–1972) examined the puzzling neurotoxic and carcinogenic properties of a then-novel toxin [cycasin: methylazoxymethanol (MAM)-β-d-glucoside] in cycad plants used traditionally for food and medicine on Guam where a complex neurodegenerative disease plagued the indigenous population. Affected families showed combinations of amyotrophic lateral sclerosis (ALS), parkinsonism (P), and/or a dementia (D) akin to Alzheimer’s disease (AD). Modernization saw declining disease rates on Guam and remarkable changes in clinical phenotype (ALS was replaced by P-D and then by D) and in two genetically distinct ALS-PDC-affected populations (Kii-Japan, West Papua-Indonesia) that used cycad seed medicinally. MAM forms DNA lesions – repaired by O⁶-methylguanine methyltransferase (MGMT) – that perturb mouse brain development and induce malignant tumors in peripheral organs. The brains of young adult MGMT-deficient mice given a single dose of MAM show DNA lesion-linked changes in cell-signaling pathways associated with miRNA-1, which is implicated in colon, liver, and prostate cancers, and in neurological disease, notably AD. MAM is metabolized to formaldehyde, a human carcinogen. Formaldehyde-responsive miRNAs predicted to modulate MAM-associated genes in the brains of MGMT-deficient mice include miR-17-5p and miR-18d, which regulate genes involved in tumor suppression, DNA repair, amyloid deposition, and neurotransmission. These findings marry cycad-associated ALS-PDC with colon, liver, and prostate cancer; they also add to evidence linking changes in microRNA status both to ALS, AD, and parkinsonism, and to cancer initiation and progression.

Endocytic Receptors in the Renal Proximal Tubule

Protein reabsorption is a predominant feature of the renal proximal tubule. Animal studies show that the ability to rescue plasma proteins relies on the endocytic receptors megalin and cubilin. Recently, studies of patients with syndromes caused by dysfunctional receptors have supported the importance of these for protein clearance of human ultrafiltrate. This review focuses on the molecular biology and physiology of the receptors and their involvement in renal pathological conditions.

Clinical utility of neuroprotective agents in neurodegenerative diseases: current status of drug development for Alzheimer's, Parkinson's and Huntington's diseases, and amyotrophic lateral sclerosis

INTRODUCTION

According to the definition of the Committee to Identify Neuroprotective Agents in Parkinson's Disease (CINAPS), "neuroprotection would be any intervention that favourably influences the disease process or underlying pathogenesis to produce enduring benefits for patients" [Meissner W, et al. Trends Pharmacol Sci 2004;25:249-253]. Preferably, neuroprotective agents should be used before or eventually during the prodromal phase of the diseases that could start decades before the appearance of symptoms. Although several symptomatic drugs are available, a disease-modifying agent is still elusive.

AREAS COVERED

The aim of the present review is to give an overview of neuroprotective agents being currently investigated for the treatment of AD, PD, HD and ALS in clinical phases.

EXPERT OPINION

Development of effective neuroprotective therapies resulting in clinically meaningful results is hampered by several factors in all research stages, both conceptual and methodological. Novel solutions might be offered by evaluation of new targets throughout clinical studies, therapies emerging from drug repositioning approaches, multi-target approaches and network pharmacology.

Neuroglialpharmacology: myelination as a shared mechanism of action of psychotropic treatments

Current psychiatric diagnostic schema segregate symptom clusters into discrete entities, however, large proportions of patients suffer from comorbid conditions that fit neither diagnostic nor therapeutic schema. Similarly, psychotropic treatments ranging from lithium and antipsychotics to serotonin reuptake inhibitors (SSRIs) and acetylcholinesterase inhibitors have been shown to be efficacious in a wide spectrum of psychiatric disorders ranging from autism, schizophrenia (SZ), depression, and bipolar disorder (BD) to Alzheimer's disease (AD). This apparent lack of specificity suggests that psychiatric symptoms as well as treatments may share aspects of pathophysiology and mechanisms of action that defy current symptom-based diagnostic and neuron-based therapeutic schema. A myelin-centered model of human brain function can help integrate these incongruities and provide novel insights into disease etiologies and treatment mechanisms. Available data are integrated herein to suggest that widely used psychotropic treatments ranging from antipsychotics and antidepressants to lithium and electroconvulsive therapy share complex signaling pathways such as Akt and glycogen synthase kinase-3 (GSK3) that affect myelination, its plasticity, and repair. These signaling pathways respond to neurotransmitters, neurotrophins, hormones, and nutrition, underlie intricate neuroglial communications, and may substantially contribute to the mechanisms of action and wide spectra of efficacy of current therapeutics by promoting myelination. Imaging and genetic technologies make it possible to safely and non-invasively test these hypotheses directly in humans and can help guide clinical trial efforts designed to correct myelination abnormalities. Such efforts may provide insights into novel avenues for treatment and prevention of some of the most prevalent and devastating human diseases.

The many faces of insulin-like peptide signalling in the brain

Central and peripheral insulin-like peptides (ILPs), which include insulin, insulin-like growth factor 1 (IGF1) and IGF2, exert many effects in the brain. Through their actions on brain growth and differentiation, ILPs contribute to building circuitries that subserve metabolic and behavioural adaptation to internal and external cues of energy availability. In the adult brain each ILP has distinct effects, but together their actions ultimately regulate energy homeostasis - they affect nutrient sensing and regulate neuronal plasticity to modulate adaptive behaviours involved in food seeking, including high-level cognitive operations such as spatial memory. In essence, the multifaceted activity of ILPs in the brain may be viewed as a system organization involved in the control of energy allocation.

GSK-3 Inhibitors: Preclinical and Clinical Focus on CNS

Inhibiting glycogen synthase kinase-3 (GSK-3) activity via pharmacological intervention has become an important strategy for treating neurodegenerative and psychiatric disorders. The known GSK-3 inhibitors are of diverse chemotypes and mechanisms of action and include compounds isolated from natural sources, cations, synthetic small-molecule ATP-competitive inhibitors, non-ATP-competitive inhibitors, and substrate-competitive inhibitors. Here we describe the variety of GSK-3 inhibitors with a specific emphasis on their biological activities in neurons and neurological disorders. We further highlight our current progress in the development of non-ATP-competitive inhibitors of GSK-3. The available data raise the hope that one or more of these drug design approaches will prove successful at stabilizing or even reversing the aberrant neuropathology and cognitive deficits of certain central nervous system disorders.

Therapeutic targets in Alzheimer's disease and related tauopathies

Alzheimer's disease is a progressive neurodegenerative disease that is characterized histopathologically by the presence of plaques, mainly composed of Abeta amyloid and the tangles, mainly composed of hyperphosphorylated tau. To date, there is no treatment that can reverse the disease, and all the current therapeutics is directed to cope with the symptoms of the disease. Here we describe the efforts dedicated to attack the plaques and, in more detail, the process of neurofibrillary degeneration, linked to the presence of the hyperphosphorylated microtubule associated protein tau. We have identified the different putative targets for therapeutics and the current knowledge on them.

Glycogen synthase kinase 3 inhibitors in the next horizon for Alzheimer's disease treatment

Glycogen synthase kinase 3 (GSK-3), a proline/serine protein kinase ubiquitously expressed and involved in many cellular signaling pathways, plays a key role in the pathogenesis of Alzheimer's disease (AD) being probably the link between β-amyloid and tau pathology. A great effort has recently been done in the discovery and development of different new molecules, of synthetic and natural origin, able to inhibit this enzyme, and several kinetics mechanisms of binding have been described. The small molecule called tideglusib belonging to the thiadiazolidindione family is currently on phase IIb clinical trials for AD. The potential risks and benefits of this new kind of disease modifying drugs for the future therapy of AD are discussed in this paper.

The cycad genotoxin MAM modulates brain cellular pathways involved in neurodegenerative disease and cancer in a DNA damage-linked manner

Methylazoxymethanol (MAM), the genotoxic metabolite of the cycad azoxyglucoside cycasin, induces genetic alterations in bacteria, yeast, plants, insects and mammalian cells, but adult nerve cells are thought to be unaffected. We show that the brains of adult C57BL6 wild-type mice treated with a single systemic dose of MAM acetate display DNA damage (O⁶-methyldeoxyguanosine lesions, O⁶-mG) that remains constant up to 7 days post-treatment. By contrast, MAM-treated mice lacking a functional gene encoding the DNA repair enzyme O⁶-mG DNA methyltransferase (MGMT) showed elevated O⁶-mG DNA damage starting at 48 hours post-treatment. The DNA damage was linked to changes in the expression of genes in cell-signaling pathways associated with cancer, human neurodegenerative disease, and neurodevelopmental disorders. These data are consistent with the established developmental neurotoxic and carcinogenic properties of MAM in rodents. They also support the hypothesis that early-life exposure to MAM-glucoside (cycasin) has an etiological association with a declining, prototypical neurodegenerative disease seen in Guam, Japan, and New Guinea populations that formerly used the neurotoxic cycad plant for food or medicine, or both. These findings suggest environmental genotoxins, specifically MAM, target common pathways involved in neurodegeneration and cancer, the outcome depending on whether the cell can divide (cancer) or not (neurodegeneration). Exposure to MAM-related environmental genotoxins may have relevance to the etiology of related tauopathies, notably, Alzheimer's disease.

Regulation of cell survival mechanisms in Alzheimer's disease by glycogen synthase kinase-3

A pivotal role has emerged for glycogen synthase kinase-3 (GSK3) as an important contributor to Alzheimer's disease pathology. Evidence for the involvement of GSK3 in Alzheimer's disease pathology and neuronal loss comes from studies of GSK3 overexpression, GSK3 localization studies, multiple relationships between GSK3 and amyloid β-peptide (Aβ), interactions between GSK3 and the microtubule-associated tau protein, and GSK3-mediated apoptotic cell death. Apoptotic signaling proceeds by either an intrinsic pathway or an extrinsic pathway. GSK3 is well established to promote intrinsic apoptotic signaling induced by many insults, several of which may contribute to neuronal loss in Alzheimer's disease. Particularly important is evidence that GSK3 promotes intrinsic apoptotic signaling induced by Aβ. GSK3 appears to promote intrinsic apoptotic signaling by modulating proteins in the apoptosis signaling pathway and by modulating transcription factors that regulate the expression of proteins involved in apoptosis. Thus, GSK3 appears to contribute to several neuropathological mechanisms in Alzheimer's disease, including apoptosis-mediated neuronal loss.

Disrupted energy metabolism and neuronal circuit dysfunction in cognitive impairment and Alzheimer's disease

Epidemiological, neuropathological, and functional neuroimaging evidence implicates global and regional disruptions in brain metabolism and energetics in the pathogenesis of cognitive impairment. Nerve cell microcircuits are modified by excitatory and inhibitory synaptic activity and neurotrophic factors. Ageing and Alzheimer's disease cause perturbations in cellular energy metabolism, level of excitation or inhibition, and neurotrophic factor release, which overwhelm compensatory mechanisms and result in dysfunction of neuronal microcircuits and brain networks. A prolonged positive energy balance impairs the ability of neurons to adapt to oxidative and metabolic stress. Results from experimental studies in animals show how disruptions caused by chronic positive energy balance, such as diabetes, lead to accelerated cognitive ageing and Alzheimer's disease. Therapeutic interventions to allay cognitive dysfunction that target energy metabolism and adaptive stress responses (such as neurotrophin signalling) have been effective in animal models and in preliminary studies in humans.

IGF-I and the aging mammalian brain

Insulin-like growth factors (IGFs) are important modulators of organismal life-span all along phylogeny. These growth factors are widely viewed as detrimental for long life by reducing tissue resistance to oxidative stress. However, IGF-I has been consistently shown to be a potent neuroprotective factor in mammals, and as such, a deterrent of brain aging. Conversely, recent data suggest that IGF-I may contribute to amyloid neurodegeneration underlying Alzheimer's disease. These opposing observations underline an incomplete understanding of the significance of this ancestral hormone pathway in relation to brain aging. It is possible that these opposite results are the consequence of using different experimental approaches. Thus, brain amyloid injury is reduced in mutant mice partially defective in IGF-I receptor function, whereas IGF-I is neuroprotective when administered to animal models of neurodegenerative disease or normal brain aging. This approach-dependent effect of IGF-I highlights a fundamental gap in our knowledge of the relationship between peripheral and brain IGF-I function and the actual biological impact of experimental modulation of brain IGF-I function. We suggest to directly address brain IGF-I function in the varying experimental approaches used to confirm that changes have taken place in the desired way.