Central Nervous System Targets Research Articles

Building on Success: A Bright Future for Peptide Therapeutics

The primary aim of this review article is to highlight current exciting and future looking areas of research in peptide science as applied to the discovery and development of novel therapeutics. Among the strengths of peptides as drug candidates are their high potency, specificity, and good safety profile. These positive attributes of peptides along with advances in drug delivery technologies have generated renewed interest in the discovery, optimization, and development of peptides as therapeutics. The intent of this review is to demonstrate that peptides have broad applicability in many therapeutic areas by examining some of the most compelling indications and targets for peptide therapeutics. For example, target selection for peptide therapeutics is challenging due to the inherent properties of peptides; therefore, identifying a clear differentiation strategy for a new peptide program over a small molecule or antibody program from the outset is critical for successful navigation of drug development hurdles. In this review, some of the latest techniques that accentuate the advantages and overcome the druggability limitations of peptides will be covered. Emerging technologies for enhancing the pharmacokinetics of peptides to achieve sufficient in vivo half-lives will be described and evaluated, as well as novel technologies for getting peptides across cell membranes to reach intracellular targets and across the blood-brain-barrier to reach central nervous system targets.

Silver nanoparticle-induced expression of proteins related to oxidative stress and neurodegeneration in an in vitro human blood-brain barrier model

Silver nanoparticles (AgNPs) have been reported to penetrate the central nervous system (CNS) and induce neurotoxicity. However, there is a paucity of understanding of the toxicity of AgNPs and their effect on the blood-brain barrier (BBB) including the underlying molecular mechanism(s) of action. Such information is important for the formulation of new strategies for delivery of biological therapeutics to central nervous system (CNS) targets. Using an in vitro BBB model and mass spectrometry-based proteomics, we investigated alterations in the proteomes of brain endothelial cells and astrocytes at different time points after AgNPs exposure (24 and 48 h). Our data showed that several proteins involved in neurodisorders and neurodegeneration were significantly upregulated in endothelial cells (e.g. 7-dehydrocholesterol reductase, zinc transporters 1 and 6), while proteins responsible for maintaining brain homeostasis were significantly downregulated (e.g anti-oxidative proteins glutathione peroxidase 1 and glutathione peroxidase 4). Many inflammatory pathways were significantly upregulated at 24 h post-AgNPs exposure (C9 pathway), while at 48 h proteins involved in BBB damage and anti-inflammatory responses were upregulated (quinoneoxidoreductase1 and glutamate cysteine ligase catalytic subunit) suggesting that by the later time point, cellular protection pathways had been activated to rescue the cells from AgNPs-induced toxicity. Our study suggests that in the initial stage of exposure, AgNPs exerted direct cellular stress on the endothelial cells by triggering a pro-inflammatory cascade. This study provides detailed insight into the toxic potency of AgNPs on in vitro BBB model and adds to the understanding of the adaptive role of BBB with regards to AgNPs-mediated toxicity.

Diazepam is not a direct allosteric modulator of α1-adrenoceptors, but modulates receptor signaling by inhibiting phosphodiesterase-4.

α1A‐ and α1B‐adrenoceptors (ARs) are G protein‐coupled receptors (GPCRs) that are activated by adrenaline and noradrenaline to modulate smooth muscle contraction in the periphery, and neuronal outputs in the central nervous system (CNS). α1A‐ and α1B‐AR are clinically targeted with antagonists for hypertension and benign prostatic hyperplasia and are emerging CNS targets for treating neurodegenerative diseases. The benzodiazepines midazolam, diazepam, and lorazepam are proposed to be positive allosteric modulators (PAMs) of α1‐ARs. Here, using thermostabilized, purified, α1A‐ and α1B‐ARs, we sought to identify the benzodiazepine binding site and modulatory mechanism to inform the design of selective PAMs. However, using a combination of biophysical approaches no evidence was found for direct binding of several benzodiazepines to purified, stabilized α1A‐ and α1B‐ARs. Similarly, in cell‐based assays expressing unmodified α1A‐ and α1B‐ARs, benzodiazepine treatment had no effect on fluorescent ligand binding, agonist‐stimulated Ca2+ release, or G protein activation. In contrast, several benzodiazepines positively modulated phenylephrine stimulation of a cAMP response element pathway by α1A‐ and α1B‐ARs; however, this was shown to be caused by off‐target inhibition of phosphodiesterases, known targets of diazepam. This study highlights how purified, stabilized GPCRs are useful for validating allosteric ligand binding and that care needs to be taken before assigning new targets to benzodiazepines.

Molecular cross-talk in a unique parasitoid manipulation strategy

Envenomation of cockroach cerebral ganglia by the parasitoid Jewel wasp, Ampulex compressa, induces specific, long-lasting behavioural changes. We hypothesized that this prolonged action results from venom-induced changes in brain neurochemistry. Here, we address this issue by first identifying molecular targets of the venom, i.e., proteins to which venom components bind and interact with to mediate altered behaviour. Our results show that venom components bind to synaptic proteins and likely interfere with both pre- and postsynaptic processes. Since behavioural changes induced by the sting are long-lasting and reversible, we hypothesized further that long-term effects of the venom must be mediated by up or down regulation of cerebral ganglia proteins. We therefore characterize changes in cerebral ganglia protein abundance of stung cockroaches at different time points after the sting by quantitative mass spectrometry. Our findings indicate that numerous proteins are differentially expressed in cerebral ganglia of stung cockroaches, many of which are involved in signal transduction, such as the Rho GTPase pathway, which is implicated in synaptic plasticity. Altogether, our data suggest that the Jewel wasp commandeers cockroach behaviour through molecular cross-talk between venom components and molecular targets in the cockroach central nervous system, leading to broad-based alteration of synaptic efficacy and behavioural changes that promote successful development of wasp progeny.

Multiple target tissue effects of GLP-1 analogues on non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH).

Accumulating experimental and clinical evidences over the last decade indicate that GLP-1 analogues have a series of central nervous system and peripheral target tissues actions which are able to significantly influence the liver metabolism. GLP-1 analogues pleiotropic effects proved to be efficacious in T2DM subjects not only reducing liver steatosis and ameliorating NAFLD and NASH, but also in lowering plasma glucose and liver inflammation, improving cardiac function and protecting from kidney dysfunction. While the experimental and clinical data are robust, the precise mechanisms of action potentially involved in these protective multi-target effects need further investigation. Here we present a systematic review of the most recent literature data on the multi-target effects of GLP-1 analogues on the liver, on adipose and muscular tissue and on the nervous system, all capable of influencing significant aspects of the fatty liver disease physiopathology. From this analysis, we can conclude that the multi-target beneficial action of the GLP-1 analogues could explain the positive effects observed in animal and human models on progression of NAFLD to NASH.

Inhibitory effects of cannabidiol on voltage-dependent sodium currents

Cannabis sativa contains many related compounds known as phytocannabinoids. The main psychoactive and nonpsychoactive compounds are Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), respectively. Much of the evidence for clinical efficacy of CBD-mediated antiepileptic effects has been from case reports or smaller surveys. The mechanisms for CBD's anticonvulsant effects are unclear and likely involve noncannabinoid receptor pathways. CBD is reported to modulate several ion channels, including sodium channels (Nav). Evaluating the therapeutic mechanisms and safety of CBD demands a richer understanding of its interactions with central nervous system targets. Here, we used voltage-clamp electrophysiology of HEK-293 cells and iPSC neurons to characterize the effects of CBD on Nav channels. Our results show that CBD inhibits hNav1.1–1.7 currents, with an IC50 of 1.9–3.8 μm, suggesting that this inhibition could occur at therapeutically relevant concentrations. A steep Hill slope of ∼3 suggested multiple interactions of CBD with Nav channels. CBD exhibited resting-state blockade, became more potent at depolarized potentials, and also slowed recovery from inactivation, supporting the idea that CBD binding preferentially stabilizes inactivated Nav channel states. We also found that CBD inhibits other voltage-dependent currents from diverse channels, including bacterial homomeric Nav channel (NaChBac) and voltage-gated potassium channel subunit Kv2.1. Lastly, the CBD block of Nav was temperature-dependent, with potency increasing at lower temperatures. We conclude that CBD's mode of action likely involves 1) compound partitioning in lipid membranes, which alters membrane fluidity affecting gating, and 2) undetermined direct interactions with sodium and potassium channels, whose combined effects are loss of channel excitability.

P3.13-17 A Retrospective Study: Central Nervous System Response to Osimertinib in Patients with Advanced NSCLC

Central nervous system (CNS) metastases are common in patients with non-small-cell lung cancer (NSCLC). More than 30% of patients who progress during or after treatment with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) have CNS metastases. Osimertinib, a third-generation EGFR-TKI, has been demonstrated promising intracranial efficacy in patients with advanced NSCLC from several large scale randomized control trials. We aimed to explore clinical impact of osimertinib for patients with CNS metastases, advanced NSCLC in real world setting. Patients with advanced NSCLC who received osimertinib after progression of prior EGFR-TKIs and CNS metastases on baseline brain scan were retrospectively collected from Cancer Hospital Chinese Academy of Medical Sciences. Primary outcome was objective response rate (ORR) and secondary objectives were disease control rate (DCR), progression-free survival (PFS), time to tumor response, median best percentage change from baseline in CNS target lesion (TL) size and safety. Between Apr 1, 2017, and Dec 30, 2017, 22 patients met selection criteria, 15 with ≥1 measurable CNS lesion (RECIST 1.1) were included in CNS evaluable for response (cEFR) set. The median duration of follow-up was 6.5 months. For overall 22 patients, ORR and DCR were 40.9% and 86.4%, respectively, with median PFS of 8.5 months (95% CI 4.1, 13.0). Of 15 patients in cEFR set, CNS ORR was 53.3% with complete responses reported in 3 patients (20.0%). Median best percentage change from baseline in CNS TL size was -40% (range: -100% ∼ +60%) and median time to CNS tumor response was 1.3 months. CNS DCR was 80.0%. Median CNS PFS was not reached. Safety profile was acceptable and no new unexpected findings were found. This real world analysis further confirmed that osimertinib was indeed demonstrated clinically meaningful efficacy against CNS metastases in Chinese patients with advanced NSCLC.

Multimodal General Anesthesia: Theory and Practice.

Balanced general anesthesia, the most common management strategy used in anesthesia care, entails the administration of different drugs together to create the anesthetic state. Anesthesiologists developed this approach to avoid sole reliance on ether for general anesthesia maintenance. Balanced general anesthesia uses less of each drug than if the drug were administered alone, thereby increasing the likelihood of its desired effects and reducing the likelihood of its side effects. To manage nociception intraoperatively and pain postoperatively, the current practice of balanced general anesthesia relies almost exclusively on opioids. While opioids are the most effective antinociceptive agents, they have undesirable side effects. Moreover, overreliance on opioids has contributed to the opioid epidemic in the United States. Spurred by concern of opioid overuse, balanced general anesthesia strategies are now using more agents to create the anesthetic state. Under these approaches, called “multimodal general anesthesia,” the additional drugs may include agents with specific central nervous system targets such as dexmedetomidine and ones with less specific targets, such as magnesium. It is postulated that use of more agents at smaller doses further maximizes desired effects while minimizing side effects. Although this approach appears to maximize the benefit-to-side effect ratio, no rational strategy has been provided for choosing the drug combinations. Nociception induced by surgery is the primary reason for placing a patient in a state of general anesthesia. Hence, any rational strategy should focus on nociception control intraoperatively and pain control postoperatively. In this Special Article, we review the anatomy and physiology of the nociceptive and arousal circuits, and the mechanisms through which commonly used anesthetics and anesthetic adjuncts act in these systems. We propose a rational strategy for multimodal general anesthesia predicated on choosing a combination of agents that act at different targets in the nociceptive system to control nociception intraoperatively and pain postoperatively. Because these agents also decrease arousal, the doses of hypnotics and/or inhaled ethers needed to control unconsciousness are reduced. Effective use of this strategy requires simultaneous monitoring of antinociception and level of unconsciousness. We illustrate the application of this strategy by summarizing anesthetic management for 4 representative surgeries.

Class I Histone Deacetylase Inhibition by Tianeptinaline Modulates Neuroplasticity and Enhances Memory.

Through epigenetic and other regulatory functions, the histone deacetylase (HDAC) family of enzymes has emerged as a promising therapeutic target for central nervous system and other disorders. Here we report on the synthesis and functional characterization of new HDAC inhibitors based structurally on tianeptine, a drug used primarily to treat major depressive disorder (MDD) that has a poorly understood mechanism of action. Since the chemical structure of tianeptine resembles certain HDAC inhibitors, we profiled the in vitro HDAC inhibitory activity of tianeptine and demonstrated its ability to inhibit the lysine deacetylase activity of a subset of class I HDACs. Consistent with a model of active site Zn2+ chelation by the carboxylic acid present in tianeptine, newly synthesized analogues containing either a hydroxamic acid or ortho-aminoanilide exhibited increased potency and selectivity among the HDAC family. This in vitro potency translated to improved efficacy in a panel of high-content imaging assays designed to assess HDAC target engagement and functional effects on critical pathways involved in neuroplasticity in both primary mouse neurons and, for the first time, human neurons differentiated from pluripotent stem cells. Most notably, tianeptinaline, a class I HDAC-selective analogue of tianeptine, but not tianeptine itself, increased histone acetylation, and enhanced CREB-mediated transcription and the expression of Arc (activity-regulated cytoskeleton-associated protein). Systemic in vivo administration of tianeptinaline to mice confirmed its brain penetration and was found to enhance contextual fear conditioning, a behavioral test of hippocampal-dependent memory. Tianeptinaline and its derivatives provide new pharmacological tools to dissect chromatin-mediated neuroplasticity underlying memory and other epigenetically related processes implicated in health and disease.

Clinical Benefits of Renal Denervation besides Blood Pressure Reduction

Hypertension (HTN) is currently one of the most common chronic diseases, among which some cases are poorly controlled and defined as resistant HTN (RH). Through years of exploration, it has been discovered that hyperactivity in the sympathetic nervous system and the renin–angiotensin system (RAS) initiates the development of RH, followed by other chain reactions in inflammation and oxidative injury. Attributed to their shared pathogenesis with communal cytokines and factors, other comorbidities of HTN, usually associated with cardiovascular and metabolic pathophysiology, often occur alongside primary symptoms, namely, atherosclerosis, heart failure, arrhythmia, and glucose metabolic disorder. Renal denervation (RDN) was first introduced as an alternative measure to help alleviate RH. Renal denervation's clinical relevance comes from directly cutting down afferent and efferent renal nerves, resulting in fewer nerve impulses transmitted to central nervous system and peripheral target organs, and less RAS activation, resulting in lower blood pressure. However, the practical effects of RDN have extended beyond lowering blood pressure and and and plays a role in anti-inflammation and antioxidation pathways. In this review, we briefly summarize the possible mechanism and beneficial clinical effect of RDN treatment in atherosclerosis improvement, cardioprotection, and diabetes remission.

Intranasal delivery of antibodies bypasses the blood‐brain barrier and results in significantly higher central nervous system levels than systemic administration

Passive immunotherapy has become a prominent therapeutic strategy for the treatment of many different neurological disorders. Antibodies can be targeted to the pathogenic proteins of diseases such as Alzheimer's (e.g., beta‐amyloid and phosphorylated tau), Parkinson's (e.g., alpha‐synuclein), and multiple sclerosis (e.g., CD20 marker on B cells). However, delivery of antibodies to the central nervous system (CNS) following systemic administration is significantly impeded as a result of the blood‐brain barrier (BBB) and blood‐cerebrospinal‐fluid barriers (BCSFBs). The intranasal route has been hypothesized to circumvent the BBB and BCSFBs and allow entry into the brain via extracellular pathways along cranial nerves and the perivascular spaces (PVS) of cerebral blood vessels (Thorne et al. Neuroscience 2004 & 2008; Lochhead et al. J. Cereb. Blood Flow & Metab. 2015). Here, we demonstrate the potential of intranasal delivery as a non‐invasive strategy to bypass the BBB and BCSFBs to rapidly target full length immunoglobulin G (IgG) antibodies to the CNS. Quantitative distribution studies of radiolabeled IgG in the CNS of anesthetized rats revealed that intranasal delivery achieved significantly higher antibody levels in both the CNS and CSF compared to systemic delivery at doses resulting in matched blood exposure via either route. Additional experiments exploring the intactness of radiolabeled IgG in the brain following intranasal delivery were conducted to identify the biochemical conditions necessary for IgG intactness in vivo. Finally, by utilizing fluorophore‐labeled IgG, we provide direct evidence of intranasal IgG transport along perineural and perivascular pathways that directly connect the nasal mucosa to CNS target sites. Our results suggest olfactory and trigeminal nerve‐associated perineural channels provide direct pathways to the olfactory bulbs and brainstem, respectively. Once within the brain, further distribution along perivascular spaces of cerebral blood vessels is capable of transporting IgG to widespread regions of the brain. Our findings highlight that the intranasal route can provide a non‐invasive, direct, and rapid method for targeting antibodies to the CNS, bypassing the BBB and BCSFBs in a way that merits further consideration for the treatment of neurological diseases.Support or Funding InformationSupported by the University of Wisconsin‐Madison School of Pharmacy, the Graduate School at the University of Wisconsin, the Michael J. Fox Foundation for Parkinson's Research, the Parkinson's Foundation, the Wisconsin Alzheimer's Disease Research Center (NIH P50‐AG033514), the Wisconsin institute for Clinical and Translational Research (Clinical and Translational Science Award program through the NIH National Center for Advancing Translational Sciences, grant UL1TR000427), and the Wisconsin Alumni Research Foundation grant 135 PRJ82AZ.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Central pharmacodynamic activity of solanezumab in mild Alzheimer's disease dementia

IntroductionSolanezumab treatment was previously shown to significantly increase total (bound + unbound) cerebrospinal fluid (CSF) levels of amyloid β (Aβ)1–40 and Aβ1–42 in patients with mild to moderate Alzheimer's disease dementia yet did not produce meaningful cognitive effects. This analysis assessed solanezumab's central nervous system target engagement by evaluating changes in CSF total and free Aβ isoforms and their relationship with solanezumab exposure. MethodsCSF Aβ isoform concentrations were measured in patients with mild Alzheimer's disease dementia from a pooled EXPEDITION + EXPEDITION2 population and from EXPEDITION3. CSF solanezumab concentrations were determined from EXPEDITION3. ResultsSolanezumab produced statistically significant increases in CSF total Aβ isoforms versus placebo, which correlated with CSF solanezumab concentration. Inconsistent effects on free Aβ isoforms were observed. Solanezumab penetration into the central nervous system was low. DiscussionSolanezumab administration engaged the central molecular target, and molar ratio analyses demonstrated that higher exposures may further increase CSF total Aβ concentrations.

Nature, nurture, and microbes: The development of multiple sclerosis.

This paper argues that multiple sclerosis (MS) is the result of an autoimmune attack against components of the central nervous system (CNS). The effector cells involved in the pathogenic process are CNS-autoreactive T cells present in the healthy immune system in a resting state. Upon activation, these cells cross the blood-brain barrier and attack the CNS target tissue. Recent evidence indicates that autoimmune activation may happen in the intestine, following an interaction of bacterial components of the gut flora with local CNS autoreactive T cells. The consequences of this concept are discussed.

Region-Specific Suppression of Hypothalamic Responses to Insulin To Adapt to Elevated Maternal Insulin Secretion During Pregnancy.

As part of the adaptation of maternal glucose regulation during pregnancy to ensure glucose provision to the fetus, maternal insulin concentrations become elevated. However, increased central actions of insulin, such as suppression of appetite, would be maladaptive during pregnancy. We hypothesized that central nervous system targets of insulin become less responsive during pregnancy to prevent overstimulation by the increased circulating insulin concentrations. To test this hypothesis, we have measured insulin-induced phosphorylation of Akt (pAkt) in specific hypothalamic nuclei as an index of hypothalamic insulin responsiveness. Despite higher endogenous insulin concentrations following feeding, arcuate nucleus pAkt levels were significantly lower in the pregnant group compared with the nonpregnant group. In response to an intracerebroventricular injection of insulin, insulin-induced pAkt was significantly reduced in the arcuate nucleus and ventromedial nucleus of pregnant rats compared with nonpregnant rats. Similar levels of insulin receptor β and PTEN, a negative regulator of the phosphoinositide 3-kinase/Akt pathway, were detected in hypothalamic areas of nonpregnant and pregnant rats. In the ventromedial nucleus, however, levels of phosphorylated PTEN were significantly lower in pregnancy, suggesting that reduced inactivation of PTEN may contribute to the attenuated insulin signaling in this area during pregnancy. In conclusion, these results demonstrate region-specific changes in responsiveness to insulin in the hypothalamus during pregnancy that may represent an adaptive response to minimize the impact of elevated circulating insulin on the maternal brain.

Preclinical Evaluation of 18F-RO6958948, 11C-RO6931643, and 11C-RO6924963 as Novel PET Radiotracers for Imaging Tau Aggregates in Alzheimer Disease.

Tau aggregates and amyloid-β (Aβ) plaques are key histopathologic features in Alzheimer disease (AD) and are considered targets for therapeutic intervention as well as biomarkers for diagnostic in vivo imaging agents. This article describes the preclinical in vitro and in vivo characterization of 3 novel compounds-RO6958948, RO6931643, and RO6924963-that bind specifically to tau aggregates and have the potential to become PET tracers for future human use. Methods: RO6958948, RO6931643, and RO6924963 were identified as high-affinity competitors at the 3H-T808 binding site on native tau aggregates in human late-stage AD brain tissue. Binding of tritiated compounds to brain tissue sections of AD patients and healthy controls was analyzed by macro- and microautoradiography and by costaining of tau aggregates and Aβ plaques on the same tissue section using specific antibodies. All 3 tracer candidates were radiolabeled with a PET nuclide and tested in vivo in tau-naïve baboons to assess brain uptake, distribution, clearance, and metabolism. Results:3H-RO6958948, 3H-RO6931643, and 3H-RO6924963 bound with high affinity and specificity to tau aggregates, clearly lacking affinity for concomitant Aβ plaques in human AD Braak V tissue sections. The specificity of all 3 radioligands for tau aggregates was supported, first, by binding patterns in AD sections comparable to the tau-specific radioligand 3H-T808; second, by very low nonspecific binding in brain tissue devoid of tau pathology, excluding significant radioligand binding to any other central nervous system target; and third, by macroscopic and microscopic colocalization and quantitative correlation of radioligand binding and tau antibody staining on the same tissue section. RO6958948, RO6931643, and RO6924963 were successfully radiolabeled with a PET nuclide at high specific activity, radiochemical purity, and yield. After intravenous administration of 18F-RO6958948, 11C-RO6931643, and 11C-RO6924963 to baboons, PET scans indicated good brain entry, rapid washout, and a favorable metabolism pattern. Conclusion:18F-RO6958948, 11C-RO6931643, and 11C-RO6924963 are promising PET tracers for visualization of tau aggregates in AD. Head-to-head comparison and validation of these tracer candidates in AD patients and healthy controls will be reported in due course.

Action sequencing in the spontaneous swimming behavior of zebrafish larvae - implications for drug development

All motile organisms need to organize their motor output to obtain functional goals. In vertebrates, natural behaviors are generally composed of a relatively large set of motor components which in turn are combined into a rich repertoire of complex actions. It is therefore an experimental challenge to investigate the organizational principles of natural behaviors. Using the relatively simple locomotion pattern of 10 days old zebrafish larvae we have here characterized the basic organizational principles governing the swimming behavior. Our results show that transitions between different behavioral states can be described by a model combining a stochastic component with a control signal. By dividing swimming bouts into a limited number of categories, we show that similar types of swimming behavior as well as stand-stills between bouts were temporally clustered, indicating a basic level of action sequencing. Finally, we show that pharmacological manipulations known to induce alterations in the organization of motor behavior in mammals, mainly through basal ganglia interactions, have related effects in zebrafish larvae. This latter finding may be of specific relevance to the field of drug development given the growing importance of zebrafish larvae in phenotypic screening for novel drug candidates acting on central nervous system targets.

Hello from the Other Side: How Autoantibodies Circumvent the Blood-Brain Barrier in Autoimmune Encephalitis.

Antibodies against neuronal receptors and synaptic proteins are associated with autoimmune encephalitides (AE) that produce movement and psychiatric disorders. In order to exert their pathological effects on neural circuits, autoantibodies against central nervous system (CNS) targets must gain access to the brain and spinal cord by crossing the blood–brain barrier (BBB), a tightly regulated gateway formed by endothelial cells lining CNS blood vessels. To date, the pathogenic mechanisms that underlie autoantibody-triggered encephalitic syndromes are poorly understood, and how autoantibodies breach the barrier remains obscure for almost all AE syndromes. The relative importance of cellular versus humoral immune mechanisms for disease pathogenesis also remains largely unexplored. Here, we review the proposed triggers for various autoimmune encephalopathies and their animal models, as well as basic structural features of the BBB and how they differ among various CNS regions, a feature that likely underlies some regional aspects of autoimmune encephalitis pathogenesis. We then discuss the routes that antibodies and immune cells employ to enter the CNS and their implications for AE. Finally, we explore future therapeutic strategies that may either preserve or restore barrier function and thereby limit immune cell and autoantibody infiltration into the CNS. Recent mechanistic insights into CNS autoantibody entry indicate promising future directions for therapeutic intervention beyond current, short-lived therapies that eliminate circulating autoantibodies.

CNS Physicochemical Property Space Shaped by a Diverse Set of Molecules with Experimentally Determined Exposure in the Mouse Brain.

Understanding the "limits and boundaries" of the central nervous system (CNS) property space is a critical aspect of modern CNS drug design. Medicinal chemists are often guided by the physicochemical properties of marketed CNS drugs, which are heavily biased toward "traditional" aminergic targets and commonly described as small lipophilic amines. This miniperspective describes the statistical analysis of the calculated physicochemical properties for a diverse set of ligands for mostly "nontraditional" CNS targets and classified as either "brain penetrant" or "peripherally restricted" on the basis of the experimental mouse brain exposure. The results suggested that (a) the physicochemical property space conducive to brain exposure is larger than the one defined by the marketed CNS drugs and (b) the most critical brain exposure determinants are descriptors of the molecular size and hydrogen bond capacity. These findings led to a modified version of the CNS MPO scoring algorithm, termed CNS MPO.v2.

Microdialysis: the Key to Physiologically Based Model Prediction of Human CNS Target Site Concentrations

Despite the enormous research efforts that have been put into the development of central nervous system (CNS) drugs, the success rate in this area is still disappointing. To increase the successful rate in the clinical trials, first the problem of predicting human CNS drug distribution should be solved. As it is the unbound drug that equilibrates over membranes and is able to interact with targets, especially knowledge on unbound extracellular drug concentration-time profiles in different CNS compartments is important. The only technique able to provide such information in vivo is microdialysis. Also, obtaining CNS drug distribution data from human subjects is highly limited, and therefore, we have to rely on preclinical approaches combined with physiologically based pharmacokinetic (PBPK) modeling, taking unbound drug CNS concentrations into account. The next step is then to link local CNS pharmacokinetics to target interaction kinetics and CNS drug effects. In this review, system properties and small-molecule drug properties that together govern CNS drug distribution are summarized. Furthermore, the currently available approaches on prediction of CNS pharmacokinetics are discussed, including in vitro, in vivo, ex vivo, and in silico approaches, with special focus on the powerful combination of in vivo microdialysis and PBPK modeling. Also, sources of variability on drug kinetics in the CNS are discussed. Finally, remaining gaps and challenges are highlighted and future directions are suggested.

Impacts of the retinal environment and photoreceptor type on functional regeneration.

Retinal regeneration is a promising central nervous system (CNS) target amongst the various stem cell therapy pursuits, due to its accessibility for manipulation and its disposition towards longitudinal monitoring of treatment safety and efficacy. We offer our perspective on current hurdles towards functional regeneration of cone photoreceptors. Cones are key: For patients suffering vision loss, cone photoreceptors are a required cellular component to restoring daytime vision, colour vision, and high acuity vision. The challenges of regenerating cones contrast with logistic challenges of regenerating rod photoreceptors, which underlines the importance of evaluating context in degeneration and regeneration studies. Foundational research is required to delineate the factors required to generate a diversity of cones in the human macula, and to coax both remaining and newly regenerating cones to rewire towards restoring daytime colour vision. A complex interplay between cell-intrinsic factors and the retinal environment determine both the specification of cone fates and the synaptic plasticity enabling their functional integration. Recent revelations that cellular materials are transferred amongst photoreceptor progenitors further emphasize the critical role of neighbouring cells in directing stem cell fates. From our vantage point, translation of stem cell therapies to restore the cone-rich human macula must be borne upon foundational research in cone-rich retinas. Research frameworks centered on patient outcomes should prioritize animal models and functional outputs that enable and report functional restoration of cone-mediated vision.