Neuroprotective pentapeptide CN-105 is associated with reduced sterile inflammation and improved functional outcomes in a traumatic brain injury murine model

At present, there are no proven pharmacological treatments demonstrated to improve long term functional outcomes following traumatic brain injury(TBI). In the setting of non-penetrating TBI, sterile brain inflammatory responses are associated with the development of cerebral edema, intracranial hypertension, and secondary neuronal injury. There is increasing evidence that endogenous apolipoprotein E(apoE) modifies the neuroinflammatory response through its role in downregulating glial activation, however, the intact apoE holoprotein does not cross the blood-brain barrier due to its size. To address this limitation, we developed a small 5 amino acid apoE mimetic peptide(CN-105) that mimics the polar face of the apoE helical domain involved in receptor interactions. The goal of this study was to investigate the therapeutic potential of CN-105 in a murine model of closed head injury. Treatment with CN-105 was associated with a durable improvement in functional outcomes as assessed by Rotarod and Morris Water Maze and a reduction in positive Fluoro-Jade B stained injured neurons and microglial activation. Administration of CN-105 was also associated with reduction in mRNA expression of a subset of inflammatory and immune-related genes.

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.

Tau Protein Mediates APP Intracellular Domain (AICD)-Induced Alzheimer's-Like Pathological Features in Mice

Amyloid precursor protein (APP) is cleaved by gamma-secretase to simultaneously generate amyloid beta (Aβ) and APP Intracellular Domain (AICD) peptides. Aβ plays a pivotal role in Alzheimer's disease (AD) pathogenesis but recent studies suggest that amyloid-independent mechanisms also contribute to the disease. We previously showed that AICD transgenic mice (AICD-Tg) exhibit AD-like features such as tau pathology, aberrant neuronal activity, memory deficits and neurodegeneration in an age-dependent manner. Since AD is a tauopathy and tau has been shown to mediate Aβ-induced toxicity, we examined the role of tau in AICD-induced pathological features. We report that ablating endogenous tau protects AICD-Tg mice from deficits in adult neurogenesis, seizure severity, short-term memory deficits and neurodegeneration. Deletion of tau restored abnormal phosphorylation of NMDA receptors, which is likely to underlie hyperexcitability and associated excitotoxicity in AICD-Tg mice. Conversely, overexpression of wild-type human tau aggravated receptor phosphorylation, impaired adult neurogenesis, memory deficits and neurodegeneration. Our findings show that tau is essential for mediating the deleterious effects of AICD. Since tau also mediates Aβ-induced toxic effects, our findings suggest that tau is a common downstream factor in both amyloid-dependent and-independent pathogenic mechanisms and therefore could be a more effective drug target for therapeutic intervention in AD.

Increased 4R-Tau Induces Pathological Changes in a Human-Tau Mouse Model

Pathological evidence for selective four-repeat (4R) tau deposition in certain dementias and exon 10-positioned MAPT mutations together suggest a 4R-specific role in causing disease. However, direct assessments of 4R toxicity have not yet been accomplished in vivo. Increasing 4R-tau expression without change to total tau in human tau-expressing mice induced more severe seizures and nesting behavior abnormality, increased tau phosphorylation, and produced a shift toward oligomeric tau. Exon 10 skipping could also be accomplished in vivo, providing support for a 4R-tau targeted approach to target 4R-tau toxicity and, in cases of primary MAPT mutation, eliminate the disease-causing mutation.

Anti-inflammatory effects of progesterone in lipopolysaccharide-stimulated BV-2 microglia

Female sex is associated with improved outcome in experimental brain injury models, such as traumatic brain injury, ischemic stroke, and intracerebral hemorrhage. This implies female gonadal steroids may be neuroprotective. A mechanism for this may involve modulation of post-injury neuroinflammation. As the resident immunomodulatory cells in central nervous system, microglia are activated during acute brain injury and produce inflammatory mediators which contribute to secondary injury including proinflammatory cytokines, and nitric oxide (NO) and prostaglandin E₂ (PGE₂), mediated by inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), respectively. We hypothesized that female gonadal steroids reduce microglia mediated neuroinflammation. In this study, the progesterone’s effects on tumor necrosis factor alpha (TNF-α), iNOS, and COX-2 expression were investigated in lipopolysaccharide (LPS)-stimulated BV-2 microglia. Further, investigation included nuclear factor kappa B (NF-κB) and mitogen activated protein kinase (MAPK) pathways. LPS (30 ng/ml) upregulated TNF-α, iNOS, and COX-2 protein expression in BV-2 cells. Progesterone pretreatment attenuated LPS-stimulated TNF-α, iNOS, and COX-2 expression in a dose-dependent fashion. Progesterone suppressed LPS-induced NF-κB activation by decreasing inhibitory κBα and NF-κB p65 phosphorylation and p65 nuclear translocation. Progesterone decreased LPS-mediated phosphorylation of p38, c-Jun N-terminal kinase and extracellular regulated kinase MAPKs. These progesterone effects were inhibited by its antagonist mifepristone. In conclusion, progesterone exhibits pleiotropic anti-inflammatory effects in LPS-stimulated BV-2 microglia by down-regulating proinflammatory mediators corresponding to suppression of NF-κB and MAPK activation. This suggests progesterone may be used as a potential neurotherapeutic to treat inflammatory components of acute brain injury.

Tumor necrosis factor α antagonism improves neurological recovery in murine intracerebral hemorrhage

Background

Intracerebral hemorrhage (ICH) is a devastating stroke subtype characterized by a prominent neuroinflammatory response. Antagonism of pro-inflammatory cytokines by specific antibodies represents a compelling therapeutic strategy to improve neurological outcome in patients after ICH. To test this hypothesis, the tumor necrosis factor alpha (TNF-α) antibody CNTO5048 was administered to mice after ICH induction, and histological and functional endpoints were assessed.

Methods

Using 10 to 12-week-old C57BL/6J male mice, ICH was induced by collagenase injection into the left basal ganglia. Brain TNF-α concentration, microglia activation/macrophage recruitment, hematoma volume, cerebral edema, and rotorod latency were assessed in mice treated with the TNF-α antibody, CNTO5048, or vehicle.

Results

After ICH induction, mice treated with CNTO5048 demonstrated reduction in microglial activation/macrophage recruitment compared to vehicle-treated animals, as assessed by unbiased stereology (P = 0.049). This reduction in F4/80-positive cells was associated with a reduction in cleaved caspase-3 (P = 0.046) and cerebral edema (P = 0.026) despite similar hematoma volumes, when compared to mice treated with vehicle control. Treatment with CNTO5048 after ICH induction was associated with a reduction in functional deficit when compared to mice treated with vehicle control, as assessed by rotorod latencies (P = 0.024).

Conclusions

Post-injury treatment with the TNF-α antibody CNTO5048 results in less neuroinflammation and improved functional outcomes in a murine model of ICH.

The apoE-mimetic peptide, COG1410, improves functional recovery in a murine model of intracerebral hemorrhage

BACKGROUND

Apolipoprotein E has previously been demonstrated to modulate acute brain injury responses, and administration of COG1410, an apoE-mimetic peptide derived from the receptor-binding region of apoE, improves outcome in preclinical models of acute neurological injury. In the current study, we sought to establish the optimal dose and timing of peptide administration associated with improved functional outcome in a murine model of intracerebral hemorrhage (ICH).

METHODS

Ten to twelve-week-old C57/BL6 male mice were injured by collagenase-induced ICH and randomly selected to receive either vehicle or one of four doses of COG1410 (0.5, 1, 2, or 4 mg/kg) via tail vein injection at 30 min after injury and then daily for 5 days. The injured mice were euthanized at various time points to assess inflammatory mediators, cerebral edema, and hematoma volume. Over the first 5 days following injury, vestibulomotor function was tested via Rotorod (RR) latency. After an optimal dose was demonstrated, a final cohort of animals was injured with ICH and randomly assigned to receive the first dose of COG1410 or vehicle at increasingly longer treatment initiation times after injury. The mice were then assessed for functional deficit via RR testing over the first 5 days following injury.

RESULTS

The mice receiving 2 mg/kg of COG1410 after injury demonstrated reduced functional deficit, decreased brain concentrations of inflammatory proteins, and less cerebral edema, although hematoma volume did not vary. The improved RR performance was maintained when peptide administration was delayed for up to 2 h after ICH.

CONCLUSIONS

COG1410 administered at a dose of 2 mg/kg within 2 h after injury improves functional recovery in a murine model of ICH.

Statins improve outcome in murine models of intracranial hemorrhage and traumatic brain injury: a translational approach

Traumatic brain injury (TBI) and intracerebral hemorrhage (ICH) are leading causes of neurological mortality and disability in the U.S. However, therapeutic options are limited and clinical management remains largely supportive. HMG-CoA reductase inhibitors (statins) have pleiotropic mechanisms of action in the setting of acute brain injury, and have been demonstrated to improve outcomes in preclinical models of ICH and TBI. To facilitate translation to clinical practice, we now characterize the optimal statin and dosing paradigm in murine models of ICH and TBI. In a preclinical model of TBI, mice received vehicle, simvastatin, and rosuvastatin at doses of 1 mg/kg and 5 mg/kg for 5 days after the impact. Immunohistochemistry, differential gene expression, and functional outcomes (rotarod and Morris water maze testing) were assessed to gauge treatment response. Following TBI, administration of rosuvastatin 1 mg/kg was associated with the greatest improvement in functional outcomes. Rosuvastatin treatment was associated with histological evidence of reduced neuronal degeneration at 24 h post-TBI, reduced microgliosis at day 7 post-TBI, and preserved neuronal density in the CA3 region at 35 days post-injury. Administration of rosuvastatin following TBI was also associated with downregulation of inflammatory gene expression in the brain. Following ICH, treatment with simvastatin 1 mg/kg was associated with the greatest improvement in functional outcomes, an effect that was independent of hemorrhage volume. Clinically relevant models of acute brain injury may be used to define variables such as optimal statin and dosing paradigms to facilitate the rational design of pilot clinical trials.

Tau--an inhibitor of deacetylase HDAC6 function

Analysis of brain microtubule protein from patients with Alzheimer's disease showed decreased alpha tubulin levels along with increased acetylation of the alpha tubulin subunit, mainly in those microtubules from neurons containing neurofibrillary tau pathology. To determine the relationship of tau protein and increased tubulin acetylation, we studied the effect of tau on the acetylation-deacetylation of tubulin. Our results indicate that tau binds to the tubulin-deacetylase, histone deacetylase 6 (HDAC6), decreasing its activity with a consequent increase in tubulin acetylation. As expected, increased acetylation was also found in tubulin from wild-type mice compared with tubulin from mice lacking tau because of the tau-mediated inhibition of the deacetylase. In addition, we found that an excess of tau protein, as a HDAC6 inhibitor, prevents induction of autophagy by inhibiting proteasome function.

The tau N279K exon 10 splicing mutation recapitulates frontotemporal dementia and parkinsonism linked to chromosome 17 tauopathy in a mouse model

Intracellular tau deposits are characteristic of several neurodegenerative disorders called tauopathies. The tau protein regulates the stability and assembly of microtubules by binding to microtubules through three or four microtubule-binding repeats (3R and 4R). The number of microtubule-binding repeats is determined by the inclusion or exclusion of the second microtubule-binding repeat encoded by exon 10 of the TAU gene. TAU gene mutations that alter the inclusion of exon 10, and hence the 4R:3R ratio, are causal in the tauopathy frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). A mutation located in exon 10 has been identified in several FTDP-17 families that present with increased exon 10 inclusion in both mRNA and protein, parkinsonism, movement disorders, and dementia. We have engineered a human tau minigene construct that was designed to allow alternative splicing of the tau exon 10. Here we demonstrate that transgenic mice expressing human tau protein with this mutation develop neurodegeneration as result of aberrant splicing. The mice recapitulate many of the disease hallmarks that are seen in patients with this mutation, including increased tau exon 10 inclusion in both mRNA and protein, motor and behavioral deficits, and tau protein accumulation in neurons and tufted astrocytes. Furthermore, these mice present with degeneration of the nigrostriatal dopaminergic pathway, suggesting a possible mechanism for parkinsonism in FTDP-17. Additionally, activated caspase-3 immunoreactivity in both neurons and astrocytes implicates the involvement of the apoptotic pathway in the pathology of these mice.

Quantitative measurement of postural sway in mouse models of human neurodegenerative disease

Detection of motor dysfunction in genetic mouse models of neurodegenerative disease requires reproducible, standardized and sensitive behavioral assays. We have utilized a center of pressure (CoP) assay in mice to quantify postural sway produced by genetic mutations that affect motor control centers of the brain. As a positive control for postural instability, wild type mice were injected with harmaline, a tremorigenic agent, and the average areas of the 95% confidence ellipse, which measures 95% of the CoP trajectory values recorded in a single trial, were measured. Ellipse area significantly increased in mice treated with increasing doses of harmaline and returned to control values after recovery. We also examined postural sway in mice expressing mutations that mimic frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17) (T-279, P301L or P301L-nitric oxide synthase 2 (NOS2)(-/-) mice) and that demonstrate motor symptoms. These mice were then compared with a mouse model of Alzheimer's disease (APPSwDI mice) that demonstrates cognitive, but not motor deficits. T-279 and P301L-NOS2(-/-) mice demonstrated a significant increase in CoP ellipse area compared with appropriate wild type control mice or to mice expressing the P301L mutation alone. In contrast, postural instability was significantly reduced in APPSwDI mice that have cognitive deficits but do not have associated motor deficits. The CoP assay provides a simple, sensitive and quantitative tool to detect motor deficits resulting from postural abnormalities in mice and may be useful in understanding the underlying mechanisms of disease.

Tau is essential to beta -amyloid-induced neurotoxicity

Senile plaques and neurofibrillary tangles, the two hallmark lesions of Alzheimer's disease, are the results of the pathological deposition of proteins normally present throughout the brain. Senile plaques are extracellular deposits of fibrillar beta-amyloid peptide (Abeta); neurofibrillary tangles represent intracellular bundles of self-assembled hyperphosphorylated tau proteins. Although these two lesions are often present in the same brain areas, a mechanistic link between them has yet to be established. In the present study, we analyzed whether tau plays a key role in fibrillar Abeta-induced neurite degeneration in central neurons. Cultured hippocampal neurons obtained from wild-type, tau knockout, and human tau transgenic mice were treated with fibrillar Abeta. Morphological analysis indicated that neurons expressing either mouse or human tau proteins degenerated in the presence of Abeta. On the other hand, tau-depleted neurons showed no signs of degeneration in the presence of Abeta. These results provide direct evidence supporting a key role for tau in the mechanisms leading to Abeta-induced neurodegeneration in the central nervous system. In addition, the analysis of the composition of the cytoskeleton of tau-depleted neurons suggested that the formation of more dynamic microtubules might confer resistance to Abeta-mediated neurodegeneration.

Inhibition of neuronal maturation in primary hippocampal neurons from τ deficient mice

Conflicting evidence supports a role for τ as an essential neuronal cytoskeletal protein or as a redundant protein whose function can be fulfilled by other microtubule-associated proteins. To investigate the function of τ in axonogenesis, we created τ deficient mice by disrupting the TAU gene. The engineered mice do not express the τ protein, appear physically normal and are able to reproduce. In contrast to a previously reported τ knockout mouse, embryonic hippocampal cultures from τ deficient mice show a significant delay in maturation as measured by axonal and neuritic extensions. The classic technique of selectively enhancing axonal growth by growth on laminin substrates failed to restore normal neuronal maturation of τ knockout neurons. By mating human TAU-gene transgenic and τ knockout mice, we reconstituted τ-deficient neurons with human τ proteins and restored a normal pattern of axonal growth and neuronal maturation. The ability of human τ proteins to rescue τ-deficient mouse neurons confirms that τ expression affects the rate of neurite extension.

Stable Transformation of Chlorella: Rescue of Nitrate Reductase-Deficient Mutants with the Nitrate Reductase Gene

Unicellular green algae, like Chlorella, offer a potentially useful system for the expression of heterologous proteins. However, the development of Chlorella as a bioreactor has been delayed owing to the lack of a stable transformation technique. Here we report on the use of micro-projectile bombardment to introduce the nitrate reductase (NR) gene from Chlorella vulgaris into NR-deficient Chlorella sorokiniana mutants, resulting in stable transformants. The stable transformants were able to grow on nitrate medium after repeated passages between selective and nonselective medium and exhibited inducible nitrate reductase activity comparable to that of wild-type cells. Southern analysis suggests homologous recombination occurs with insertion of the wild type gene into the mutated gene and that the genes of the two Chlorellaspecies used are very similar. Specific RNase protection assays, selecting for a poorly conserved region of the gene, identified the presence of the C. vulgaris NR transcript only in the transformed C. sorkiniana mutant and not in the mutant.

Cloning and characterization of the nitrate reductase-encoding gene from Chlorella vulgaris: structure and identification of transcription start points and initiator sequences

The reduction of nitrate to nitrite catalyzed by nitrate reductase (NR) is considered to be the rate-limiting and regulated step of nitrate assimilation, a major metabolic pathway occurring in a wide range of organisms which in turn supply the nutritional nitrogen requirements for other forms of life. Chlorella vulgaris NR mRNA levels are very responsive to changes in nitrogen source. In the presence of ammonia as the sole nitrogen source, under repressed conditions, NR mRNA is undetectable. Under inducing conditions, the removal of ammonia and addition of nitrate, rapid NR mRNA synthesis occurs. We are studying the elements involved in regulating the expression of this important gene. Two overlapping genomic clones (NRS1 and NR5') were isolated from a cosmid library. The two clones were sequenced and their sequences were aligned with that of a full-length NR cDNA. The gene is approximately 8 kb long and consists of 19 exons and 18 introns. Unlike NR isolated from other species, the exons which code for the functional domains of C. vulgaris are separated by introns. Two transcription start points (tsp) were identified and each is surrounded by potential initiator sequences. No TATA, CAAT or GC-rich promoter elements were located. A time course of NR induction revealed that while transcription initiation from one tsp remains at a constant level from the point of induction through steady state, the level of initiation from another tsp is high upon induction, but decreases as steady state is attained.