Apolipoprotein E Mimetic Promotes Functional and Histological Recovery in Lysolecithin-Induced Spinal Cord Demyelination in Mice

Prophylactic treatment with CN-105 improves functional outcomes in a murine model of closed head injury

The treatment of traumatic brain injury (TBI) in military populations is hindered by underreporting and underdiagnosis. Clinical symptoms and outcomes may be mitigated with an effective pre-injury prophylaxis. This study evaluates whether CN-105, a 5-amino acid apolipoprotein E (ApoE) mimetic peptide previously shown to modify the post-traumatic neuroinflammatory response, would maintain its neuroprotective effects if administered prior to closed-head injury in a clinically relevant murine model. CN-105 was synthesized by Polypeptide Inc. (San Diego, CA) and administered to C57-BL/6 mice intravenously (IV) and/or by intraperitoneal (IP) injection at various time points prior to injury while vehicle treated animals received IV and/or IP normal saline. Animals were randomized following injury and behavioral observations were conducted by investigators blinded to treatment. Vestibulomotor function was assessed using an automated Rotarod (Ugo Basile, Comerio, Italy), and hippocampal microglial activation was assessed using F4/80 immunohistochemical staining in treated and untreated mice 7 days post-TBI. Separate, in vivo assessments of the pharmacokinetics was performed in healthy CD-1. IV CN-105 administered prior to head injury improved vestibulomotor function compared to vehicle control-treated animals. CN-105 co-administered by IP and IV dosing 6 h prior to injury also improved vestibulomotor function up to 28 days following injury. Microglia counted in CN-105 treated specimens were significantly fewer (P = 0.03) than in vehicle specimens. CN-105 improves functional outcomes and reduces hippocampal microglial activation when administered prior to injury and could be adapted as a pre-injury prophylaxis for soldiers at high risk for TBI.

Cationic Arginine-Rich Peptides (CARPs): A Novel Class of Neuroprotective Agents With a Multimodal Mechanism of Action

There are virtually no clinically available neuroprotective drugs for the treatment of acute and chronic neurological disorders, hence there is an urgent need for the development of new neuroprotective molecules. Cationic arginine-rich peptides (CARPs) are an expanding and relatively novel class of compounds, which possess intrinsic neuroprotective properties. Intriguingly, CARPs possess a combination of biological properties unprecedented for a neuroprotective agent including the ability to traverse cell membranes and enter the CNS, antagonize calcium influx, target mitochondria, stabilize proteins, inhibit proteolytic enzymes, induce pro-survival signaling, scavenge toxic molecules, and reduce oxidative stress as well as, having a range of anti-inflammatory, analgesic, anti-microbial, and anti-cancer actions. CARPs have also been used as carrier molecules for the delivery of other putative neuroprotective agents across the blood-brain barrier and blood-spinal cord barrier. However, there is increasing evidence that the neuroprotective efficacy of many, if not all these other agents delivered using a cationic arginine-rich cell-penetrating peptide (CCPPs) carrier (e.g., TAT) may actually be mediated largely by the properties of the carrier molecule, with overall efficacy further enhanced according to the amino acid composition of the cargo peptide, in particular its arginine content. Therefore, in reviewing the neuroprotective mechanisms of action of CARPs we also consider studies using CCPPs fused to a putative neuroprotective peptide. We review the history of CARPs in neuroprotection and discuss in detail the intrinsic biological properties that may contribute to their cytoprotective effects and their usefulness as a broad-acting class of neuroprotective drugs.

Dynamic response of microglia/macrophage polarization following demyelination in mice

BACKGROUND

The glial response in multiple sclerosis (MS), especially for recruitment and differentiation of oligodendrocyte progenitor cells (OPCs), predicts the success of remyelination of MS plaques and return of function. As a central player in neuroinflammation, activation and polarization of microglia/macrophages (M/M) that modulate the inflammatory niche and cytokine components in demyelination lesions may impact the OPC response and progression of demyelination and remyelination. However, the dynamic behaviors of M/M and OPCs during demyelination and spontaneous remyelination are poorly understood, and the complex role of neuroinflammation in the demyelination-remyelination process is not well known. In this study, we utilized two focal demyelination models with different dynamic patterns of M/M to investigate the correlation between M/M polarization and the demyelination-remyelination process.

METHODS

The temporal and spatial features of M/M activation/polarization and OPC response in two focal demyelination models induced by lysolecithin (LPC) and lipopolysaccharide (LPS) were examined in mice. Detailed discrimination of morphology, sensorimotor function, diffusion tensor imaging (DTI), inflammation-relevant cytokines, and glial responses between these two models were analyzed at different phases.

RESULTS

The results show that LPC and LPS induced distinctive temporal and spatial lesion patterns. LPS produced diffuse demyelination lesions, with a delayed peak of demyelination and functional decline compared to LPC. Oligodendrocytes, astrocytes, and M/M were scattered throughout the LPS-induced demyelination lesions but were distributed in a layer-like pattern throughout the LPC-induced lesion. The specific M/M polarization was tightly correlated to the lesion pattern associated with balance beam function.

CONCLUSIONS

This study elaborated on the spatial and temporal features of neuroinflammation mediators and glial response during the demyelination-remyelination processes in two focal demyelination models. Specific M/M polarization is highly correlated to the demyelination-remyelination process probably via modulations of the inflammatory niche, cytokine components, and OPC response. These findings not only provide a basis for understanding the complex and dynamic glial phenotypes and behaviors but also reveal potential targets to promote/inhibit certain M/M phenotypes at the appropriate time for efficient remyelination.

Apolipoprotein E as a novel therapeutic neuroprotection target after traumatic spinal cord injury

Apolipoprotein E (apoE), a plasma lipoprotein well known for its important role in lipid and cholesterol metabolism, has also been implicated in many neurological diseases. In this study, we examined the effect of apoE on the pathophysiology of traumatic spinal cord injury (SCI). ApoE-deficient mutant (apoE^-/-) and wild-type mice received a T9 moderate contusion SCI and were evaluated using histological and behavioral analyses after injury. At 3days after injury, the permeability of spinal cord-blood-barrier, measured by extravasation of Evans blue dye, was significantly increased in apoE^-/- mice compared to wild type. The inflammation and spared white matter was also significantly increased and decreased, respectively, in apoE^-/- mice compared to the wild type ones. The apoptosis of both neurons and oligodendrocytes was also significantly increased in apoE^-/- mice. At 42days after injury, the inflammation was still robust in the injured spinal cord in apoE^-/- but not wild type mice. CD45+ leukocytes from peripheral blood persisted in the injured spinal cord of apoE^-/- mice. The spared white matter was significantly decreased in apoE^-/- mice compared to wild type ones. Locomotor function was significantly decreased in apoE^-/- mice compared to wild type ones from week 1 to week 8 after contusion. Treatment of exogenous apoE mimetic peptides partially restored the permeability of spinal cord-blood-barrier in apoE^-/- mice after SCI. Importantly, the exogenous apoE peptides decreased inflammation, increased spared white matter and promoted locomotor recovery in apoE^-/- mice after SCI. Our results indicate that endogenous apoE plays important roles in maintaining the spinal cord-blood-barrier and decreasing inflammation and spinal cord tissue loss after SCI, suggesting its important neuroprotective function after SCI. Our results further suggest that exogenous apoE mimetic peptides could be a novel and promising neuroprotective reagent for SCI.

Apolipoprotein E mimetic peptide, CN-105, improves outcomes in ischemic stroke

Objective

At present, the absence of a pharmacological neuroprotectant represents an important unmet clinical need in the treatment of ischemic and traumatic brain injury. Recent evidence suggests that administration of apolipoprotein E mimetic therapies represent a viable therapeutic strategy in this setting. We investigate the neuroprotective and anti‐inflammatory properties of the apolipoprotein E mimetic pentapeptide, CN‐105, in a microglial cell line and murine model of ischemic stroke.

Methods

Ten to 13‐week‐old male C57/BL6 mice underwent transient middle cerebral artery occlusion and were randomly selected to receive CN‐105 (0.1 mg/kg) in 100 μL volume or vehicle via tail vein injection at various time points. Survival, motor‐sensory functional outcomes using rotarod test and 4‐limb wire hanging test, infarct volume assessment using 2,3,5‐Triphenyltetrazolium chloride staining method, and microglial activation in the contralateral hippocampus using F4/80 immunostaining were assessed at various time points. In vitro assessment of tumor necrosis factor‐alpha secretion in a microglial cell line was performed, and phosphoproteomic analysis conducted to explore early mechanistic pathways of CN‐105 in ischemic stroke.

Results

Mice receiving CN‐105 demonstrated improved survival, improved functional outcomes, reduced infarct volume, and reduced microglial activation. CN‐105 also suppressed inflammatory cytokines secretion in microglial cells in vitro. Phosphoproteomic signals suggest that CN‐105 reduces proinflammatory pathways and lower oxidative stress.

Interpretation

CN‐105 improves functional and histological outcomes in a murine model of ischemic stroke via modulation of neuroinflammatory pathways. Recent clinical trial of this compound has demonstrated favorable pharmacokinetic and safety profile, suggesting that CN‐105 represents an attractive candidate for clinical translation.

Phase 1 Randomized, Double-Blind, Placebo-Controlled Study to Determine the Safety, Tolerability, and Pharmacokinetics of a Single Escalating Dose and Repeated Doses of CN-105 in Healthy Adult Subjects

Spontaneous intracranial hemorrhage (ICH) remains a devastating stroke subtype, affecting as many as 80,000 people annually in the United States and associated with extremely high mortality. In the absence of any pharmacological interventions demonstrated to improve outcome, care for patients with ICH remains largely supportive. Thus, despite advances in the understanding of ICH and brain injury, there remains an unmet need for interventions that improve neurologic recovery and outcomes. Recent research suggesting inflammation and APOE genotype play a role in modifying neurologic outcome after brain injury has led to the development of an APOE-derived peptide agent (CN-105). Preclinical studies have demonstrated that CN-105 effectively downregulates the inflammatory response in acute brain injury, including ICH. Following Investigational New Drug (IND) enabling studies in murine models, this first-in-human single escalating dose and multiple dose placebo-controlled clinical trial was performed to define the safety and pharmacokinetics (PK) of CN-105. A total of 48 subjects (12 control, 36 active) were randomized in this study; all subjects completed the study. No significant safety issues were identified with both dosing regimens, and PK analysis revealed linearity without significant drug accumulation. The median half-life in the terminal elimination phase of CN-105 following a single or repeated dosing regimen did not change (approximately 3.6 hours). With the PK and preliminary safety of CN-105 established, the drug is now poised to begin first-in-disease phase 2 clinical trials in patients with ICH who urgently need new therapeutic options.

Low-density lipoprotein receptor-related protein 1 is a novel modulator of radial glia stem cell proliferation, survival, and differentiation

The LDL family of receptors and its member low-density lipoprotein receptor-related protein 1 (LRP1) have classically been associated with a modulation of lipoprotein metabolism. Current studies, however, indicate diverse functions for this receptor in various aspects of cellular activities, including cell proliferation, migration, differentiation, and survival. LRP1 is essential for normal neuronal function in the adult CNS, whereas the role of LRP1 in development remained unclear. Previously, we have observed an upregulation of LewisX (LeX) glycosylated LRP1 in the stem cells of the developing cortex and demonstrated its importance for oligodendrocyte differentiation. In the current study, we show that LeX-glycosylated LRP1 is also expressed in the stem cell compartment of the developing spinal cord and has broader functions in the developing CNS. We have investigated the basic properties of LRP1 conditional knockout on the neural stem/progenitor cells (NSPCs) from the cortex and the spinal cord, created by means of Cre-loxp-mediated recombination in vitro. The functional status of LRP1-deficient cells has been studied using proliferation, differentiation, and apoptosis assays. LRP1 deficient NSPCs from both CNS regions demonstrated altered differentiation profiles. Their differentiation capacity toward oligodendrocyte progenitor cells (OPCs), mature oligodendrocytes and neurons was reduced. In contrast, astrocyte differentiation was promoted. Moreover, LRP1 deletion had a negative effect on NSPCs proliferation and survival. Our observations suggest that LRP1 facilitates NSPCs differentiation via interaction with apolipoprotein E (ApoE). Upon ApoE4 stimulation wild type NSPCs generated more oligodendrocytes, but LRP1 knockout cells showed no response. The effect of ApoE seems to be independent of cholesterol uptake, but is rather mediated by downstream MAPK and Akt activation. GLIA 2016 GLIA 2016;64:1363-1380.