Bacterial peptidoglycan signalling in microglia: Activation by MDP via the NF-κB/MAPK pathway.

Bacterial peptidoglycan (PGN) fragments are commonly studied in the context of bacterial infections. However, PGN fragments recently gained recognition as signalling molecules from the commensal gut microbiota in the healthy host. Here we focus on the minimal bioactive PGN motif muramyl dipeptide (MDP), found in both Gram-positive and Gram-negative commensal bacteria, which signals through the Nod2 receptor. MDP from the gut microbiota translocates to the brain and is associated with changes in neurodevelopment and behaviour, yet there is limited knowledge about the underlying mechanisms. In this study we demonstrate that physiologically relevant doses of MDP induce rapid changes in microglial gene expression and lead to cytokine and chemokine secretion. In immortalised microglial (IMG) cells, C-C Motif Chemokine Ligand 5 (CCL5/RANTES) expression is acutely sensitive to the lowest physiologically prevalent dose (0.1 µg/ml) of MDP. As CCL5 plays an important role in memory formation and synaptic plasticity, microglial CCL5 might be the missing link in elucidating MDP-induced alterations in synaptic gene expression. We observed that a higher physiological dose of MDP elevates the expression of cytokines TNF-α and IL-1ß, indicating a transition toward a pro-inflammatory phenotype in IMG cells, which was validated in primary microglial cultures. Furthermore, MDP induces the translocation of NF-κB subunit p65 into the nucleus, which is blocked by MAPK p38 inhibitor SB202190, suggesting that an interplay of both the NF-κB and MAPK pathways is responsible for the MDP-specific microglial phenotype. These findings underscore the significance of different MDP levels in shaping microglial function in the CNS and indicate MDP as a potential mediator for early inflammatory processes in the brain. It also positions microglia as an important target in the gut microbiota-brain-axis pathway through PGN signalling.

Chronic inflammation with microglia senescence at basal forebrain: impact on cholinergic deficit in Alzheimer's brain haemodynamics.

Cholinergic innervation in the brain is involved in modulating neurovascular function including cerebral blood flow haemodynamics in response to neuronal activity. Cholinergic deficit is associated with pathophysiology in Alzheimer's disease, albeit the aetiology remains to be clarified. In the current study, neocortex cerebral blood flow response to acetylcholine was evaluated by Laser-Doppler Flowmetry (LDF) in 3xTgAD Alzheimer's disease model) and wild-type mice of two age groups. The peak of cerebral blood flow to acetylcholine (i.v.) from baseline levels (% ΔrCBF) was higher in young 3xTgAD versus in wild-type mice (48.35; 95% CI:27.03-69.67 versus 22.70; CI:15.5-29.91, P < 0.05); this was reversed in old 3xTgAD mice (21.44; CI:2.52-40.35 versus 23.25; CI:23.25-39). Choline acetyltransferase protein was reduced in neocortex, while cerebrovascular reactivity to acetylcholine was preserved in young 3×TgAD mice. This suggests endogenous acetylcholine deficit and possible cholinergic denervation from selected cholinergic nuclei within the basal forebrain. The early deposition of tauopathy moieties (mutant hTau and pTau181) and its coincidence in cholinergic cell clusters (occasionaly), were observed at the basal forebrain of 3xTgAD mice including substantia innominate, nucleus Basalis of Meynert and nucleus of horizontal limb diagonal band of Broca. A prominent feature was microglia interacting tauopathy and demonstrated a variety of morphology changes particularly when located in proximity to tauopathy. The microglia ramified phenotype was reduced as evaluated by the ramification index and Fractal analysis. Increased microglia senescence, identified as SASP (senescence-associated secretory phenotype), was colocalization with p16Ink4ɑ, a marker of irreversible cell-cycle arrest in old 3xTgAD versus wild-type mice (P = 0.001). The p16Ink4ɑ was also observed in neuronal cells bearing tauopathy within the basal forebrain of 3xTgAD mice. TNF-ɑ, the pro-inflammatory cytokine elevated persistently in microglia (Pearson's correlation coefficient = 0.62) and the loss of cholinergic cells in vulnerable basal forebrain environment, was indicated by image analysis in 3xTgAD mice, which linked to the cholinergic deficits in neocortex rCBF haemodynamics. Our study revealed the early change of CBF haemodynamics to acetylcholine in 3xTgAD model. As a major effector of brain innate immune activation, microglia SASP with age-related disease progression is indicative of immune cell senescence, which contributes to chronic inflammation and cholinergic deficits at the basal forebrain. Targeting neuroinflammation and senescence may mitigate cholinergic pathophysiology in Alzheimer's disease.

Type 2 diabetes mellitus/obesity drugs: A neurodegenerative disorders savior or a bridge too far?

Glucagon-like peptide-1 (GLP-1) receptor agonist-based drugs (incretin mimetics) have meaningfully impacted current treatment of type 2 diabetes mellitus (T2DM), and their actions on satiety and weight loss have led to their use as an obesity medication. With multiple pleotropic actions beyond their insulinotropic and weight loss ones, including anti-inflammatory and anti-insulin-resistant effects selectively mediated by their receptors present within numerous organs, this drug class offers potential efficacy for an increasing number of systemic and neurological disorders whose current treatment is inadequate. Among these are a host of neurodegenerative disorders that are prevalent in the elderly, such as Parkinson's and Alzheimer's disease, which have bucked previous therapeutic approaches. An increasing preclinical, clinical, and epidemiological literature suggests that select incretin mimetics may provide an effective treatment strategy, but 'which ones' for 'which disorders' and 'when' remain key open questions.

Excitotoxic glutamate levels cause the secretion of resident endoplasmic reticulum proteins.

Dysregulation of synaptic glutamate levels can lead to excitotoxicity such as that observed in stroke, traumatic brain injury, and epilepsy. The role of increased intracellular calcium (Ca2+ ) in the development of excitotoxicity is well established. However, less is known regarding the impact of glutamate on endoplasmic reticulum (ER)-Ca2+ -mediated processes such as proteostasis. To investigate this, we expressed a secreted ER Ca2+ modulated protein (SERCaMP) in primary cortical neurons to monitor exodosis, a phenomenon whereby ER calcium depletion causes the secretion of ER-resident proteins that perform essential functions to the ER and the cell. Activation of glutamatergic receptors (GluRs) led to an increase in SERCaMP secretion indicating that normally ER-resident proteins are being secreted in a manner consistent with ER Ca2+ depletion. Antagonism of ER Ca2+ channels attenuated the effects of glutamate and GluR agonists on SERCaMP release. We also demonstrate that endogenous proteins containing an ER retention/retrieval sequence (ERS) are secreted in response to GluR activation supporting that neuronal activation by glutamate promotes ER exodosis. Ectopic expression of KDEL receptors attenuated the secretion of ERS-containing proteins caused by GluR agonists. Taken together, our data indicate that excessive GluR activation causes disruption of neuronal proteostasis by triggering the secretion of ER-resident proteins through ER Ca2+ depletion and describes a new facet of excitotoxicity.

The RhoA-ROCK1/ROCK2 Pathway Exacerbates Inflammatory Signaling in Immortalized and Primary Microglia.

Neuroinflammation is a unifying factor among all acute central nervous system (CNS) injuries and chronic neurodegenerative disorders. Here, we used immortalized microglial (IMG) cells and primary microglia (PMg) to understand the roles of the GTPase Ras homolog gene family member A (RhoA) and its downstream targets Rho-associated coiled-coil-containing protein kinases 1 and 2 (ROCK1 and ROCK2) in neuroinflammation. We used a pan-kinase inhibitor (Y27632) and a ROCK1- and ROCK2-specific inhibitor (RKI1447) to mitigate a lipopolysaccharide (LPS) challenge. In both the IMG cells and PMg, each drug significantly inhibited pro-inflammatory protein production detected in media (TNF-α, IL-6, KC/GRO, and IL-12p70). In the IMG cells, this resulted from the inhibition of NF-κB nuclear translocation and the blocking of neuroinflammatory gene transcription (iNOS, TNF-α, and IL-6). Additionally, we demonstrated the ability of both compounds to block the dephosphorylation and activation of cofilin. In the IMG cells, RhoA activation with Nogo-P4 or narciclasine (Narc) exacerbated the inflammatory response to the LPS challenge. We utilized a siRNA approach to differentiate ROCK1 and ROCK2 activity during the LPS challenges and showed that the blockade of both proteins may mediate the anti-inflammatory effects of Y27632 and RKI1447. Using previously published data, we show that genes in the RhoA/ROCK signaling cascade are highly upregulated in the neurodegenerative microglia (MGnD) from APP/PS-1 transgenic Alzheimer's disease (AD) mice. In addition to illuminating the specific roles of RhoA/ROCK signaling in neuroinflammation, we demonstrate the utility of using IMG cells as a model for primary microglia in cellular studies.

Microglial Nogo delays recovery following traumatic brain injury in mice.

Nogo-A, B, and C are well described members of the reticulon family of proteins, most well known for their negative regulatory effects on central nervous system (CNS) neurite outgrowth and repair following injury. Recent research indicates a relationship between Nogo-proteins and inflammation. Microglia, the brain's immune cells and inflammation-competent compartment, express Nogo protein, although specific roles of the Nogo in these cells is understudied. To examine inflammation-related effects of Nogo, we generated a microglial-specific inducible Nogo KO (MinoKO) mouse and challenged the mouse with a controlled cortical impact (CCI) traumatic brain injury (TBI). Histological analysis shows no difference in brain lesion sizes between MinoKO-CCI and Control-CCI mice, although MinoKO-CCI mice do not exhibit the levels of ipsilateral lateral ventricle enlargement as injury matched controls. Microglial Nogo-KO results in decreased lateral ventricle enlargement, microglial and astrocyte immunoreactivity, and increased microglial morphological complexity compared to injury matched controls, suggesting decreased tissue inflammation. Behaviorally, healthy MinoKO mice do not differ from control mice, but automated tracking of movement around the home cage and stereotypic behavior, such as grooming and eating (termed cage "activation"), following CCI is significantly elevated. Asymmetrical motor function, a deficit typical of unilaterally brain lesioned rodents, was not detected in CCI injured MinoKO mice, while the phenomenon was present in CCI injured controls 1-week post-injury. Overall, our studies show microglial Nogo as a negative regulator of recovery following brain injury. To date, this is the first evaluation of the roles microglial specific Nogo in a rodent injury model.

A New Generation of IMiDs as Treatments for Neuroinflammatory and Neurodegenerative Disorders.

The immunomodulatory imide drug (IMiD) class, which includes the founding drug member thalidomide and later generation drugs, lenalidomide and pomalidomide, has dramatically improved the clinical treatment of specific cancers, such as multiple myeloma, and it combines potent anticancer and anti-inflammatory actions. These actions, in large part, are mediated by IMiD binding to the human protein cereblon that forms a critical component of the E3 ubiquitin ligase complex. This complex ubiquitinates and thereby regulates the levels of multiple endogenous proteins. However, IMiD-cereblon binding modifies cereblon's normal targeted protein degradation towards a new set of neosubstrates that underlies the favorable pharmacological action of classical IMiDs, but also their adverse actions-in particular, their teratogenicity. The ability of classical IMiDs to reduce the synthesis of key proinflammatory cytokines, especially TNF-α levels, makes them potentially valuable to reposition as drugs to mitigate inflammatory-associated conditions and, particularly, neurological disorders driven by an excessive neuroinflammatory element, as occurs in traumatic brain injury, Alzheimer's and Parkinson's diseases, and ischemic stroke. The teratogenic and anticancer actions of classical IMiDs are substantial liabilities for effective drugs in these disorders and can theoretically be dialed out of the drug class. We review a select series of novel IMiDs designed to avoid binding with human cereblon and/or evade degradation of downstream neosubstrates considered to underpin the adverse actions of thalidomide-like drugs. These novel non-classical IMiDs hold potential as new medications for erythema nodosum leprosum (ENL), a painful inflammatory skin condition associated with Hansen's disease for which thalidomide remains widely used, and, in particular, as a new treatment strategy for neurodegenerative disorders in which neuroinflammation is a key component.

Glucagon-like peptide-1 (GLP-1) receptor agonists and neuroinflammation: Implications for neurodegenerative disease treatment.

Chronic, excessive neuroinflammation is a key feature of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). However, neuroinflammatory pathways have yet to be effectively targeted in clinical treatments for such diseases. Interestingly, increased inflammation and neurodegenerative disease risk have been associated with type 2 diabetes mellitus (T2DM) and insulin resistance (IR), suggesting that treatments that mitigate T2DM pathology may be successful in treating neuroinflammatory and neurodegenerative pathology as well. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that promotes healthy insulin signaling, regulates blood sugar levels, and suppresses appetite. Consequently, numerous GLP-1 receptor (GLP-1R) stimulating drugs have been developed and approved by the US Food and Drug Administration (FDA) and related global regulatory authorities for the treatment of T2DM. Furthermore, GLP-1R stimulating drugs have been associated with anti-inflammatory, neurotrophic, and neuroprotective properties in neurodegenerative disorder preclinical models, and hence hold promise for repurposing as a treatment for neurodegenerative diseases. In this review, we discuss incretin signaling, neuroinflammatory pathways, and the intersections between neuroinflammation, brain IR, and neurodegenerative diseases, with a focus on AD and PD. We additionally overview current FDA-approved incretin receptor stimulating drugs and agents in development, including unimolecular single, dual, and triple receptor agonists, and highlight those in clinical trials for neurodegenerative disease treatment. We propose that repurposing already-approved GLP-1R agonists for the treatment of neurodegenerative diseases may be a safe, efficacious, and cost-effective strategy for ameliorating AD and PD pathology by quelling neuroinflammation.

Role of chronic neuroinflammation in neuroplasticity and cognitive function: A hypothesis.

OBJECTIVE: Evaluating the efficacy of 3,6'-dithioPomalidomide in 5xFAD Alzheimer's disease (AD) mice to test the hypothesis that neuroinflammation is directly involved in the development of synaptic/neuronal loss and cognitive decline. BACKGROUND: Amyloid-ß (Aß) or tau-focused clinical trials have proved unsuccessful in mitigating AD-associated cognitive impairment. Identification of new drug targets is needed. Neuroinflammation is a therapeutic target in neurodegenerative disorders, and TNF-α a pivotal neuroinflammatory driver. NEW HYPOTHESIS: AD-associated chronic neuroinflammation directly drives progressive synaptic/neuronal loss and cognitive decline. Pharmacologically mitigating microglial/astrocyte activation without altering Aß generation will define the role of neuroinflammation in AD progression. MAJOR CHALLENGES: Difficulty of TNF-α-lowering compounds reaching brain, and identification of a therapeutic-time window to preserve the beneficial role of neuroinflammatory processes. LINKAGE TO OTHER MAJOR THEORIES: Microglia/astroglia are heavily implicated in maintenance of synaptic plasticity/function in healthy brain and are disrupted by Aß. Mitigation of chronic gliosis can restore synaptic homeostasis/cognitive function.

The metabolite GLP-1 (9-36) is neuroprotective and anti-inflammatory in cellular models of neurodegeneration.

Glucagon-like peptide-1 (GLP-1) is best known for its insulinotropic action following food intake. Its metabolite, GLP-1 (9-36), was assumed biologically inactive because of low GLP-1 receptor (GLP-1R) affinity and non-insulinotropic properties; however, recent studies contradict this assumption. Increased use of FDA approved GLP-1 analogues for treating metabolic disorders and neurodegenerative diseases raises interest in GLP-1 (9-36)'s biological role. We use human SH-SY5Y neuroblastoma cells and a GLP-1R over-expressing variety (#9), in both undifferentiated and differentiated states, to evaluate the neurotrophic/neuroprotective effects of GLP-1 (9-36) against toxic glutamate exposure and other oxidative stress models (via the MTS, LDH or ROS assays). In addition, we examine GLP-1 (9-36)'s signaling pathways, including cyclic-adenosine monophosphate (cAMP), protein kinase-A (PKA), and 5' adenosine monophosphate-activated protein kinase (AMPK) via the use of ELISA, pharmacological inhibitors, or GLP-1R antagonist. Human HMC3 and mouse IMG microglial cell lines were used to study the anti-inflammatory effects of GLP-1 (9-36) against lipopolysaccharide (LPS) (via ELISA). Finally, we applied GLP-1 (9-36) to primary dissociation cultures challenged with α-synuclein or amyloid-ß and assessed survival and morphology via immunochemistry. We demonstrate evidence of GLP-1R, cAMP, PKA, and AMPK-mediated neurotrophic and neuroprotective effects of GLP-1 (9-36). The metabolite significantly reduced IL-6 and TNF-α levels in HMC3 and IMG microglial cells, respectively. Lastly, we show mild but significant effects of GLP-1 (9-36) in primary neuron cultures challenged with α-synuclein or amyloid-ß. These studies enhance understanding of GLP-1 (9-36)'s effects on the nervous system and its potential as a primary or complementary treatment in pathological contexts.

Neuronal delivery of antibodies has therapeutic effects in animal models of botulism.

Botulism is caused by a potent neurotoxin that blocks neuromuscular transmission, resulting in death by asphyxiation. Currently, the therapeutic options are limited and there is no antidote. Here, we harness the structural and trafficking properties of an atoxic derivative of botulinum neurotoxin (BoNT) to transport a function-blocking single-domain antibody into the neuronal cytosol where it can inhibit BoNT serotype A (BoNT/A1) molecular toxicity. Post-symptomatic treatment relieved toxic signs of botulism and rescued mice, guinea pigs, and nonhuman primates after lethal BoNT/A1 challenge. These data demonstrate that atoxic BoNT derivatives can be harnessed to deliver therapeutic protein moieties to the neuronal cytoplasm where they bind and neutralize intracellular targets in experimental models. The generalizability of this platform might enable delivery of antibodies and other protein-based therapeutics to previously inaccessible intraneuronal targets.

PT320, Sustained-Release Exendin-4, Mitigates L-DOPA-Induced Dyskinesia in a Rat 6-Hydroxydopamine Model of Parkinson's Disease.

BACKGROUND: We previously demonstrated that subcutaneous administration of PT320, a sustained-release (SR) form of exendin-4, resulted in the long-term maintenance of steady-state exenatide (exendin-4) plasma and target levels in 6-hydroxydopamine (6-OHDA)-pretreated animals. Additionally, pre- or post-treatment with PT320 mitigated the early stage of 6-OHDA-induced dopaminergic neurodegeneration. The purpose of this study was to evaluate the effect of PT320 on L-3,4-dihydroxyphenylalanine (L-DOPA)-induced abnormal involuntary movements (AIMs) in the rat 6-OHDA model of Parkinson's disease. METHODS: Adult male Sprague-Dawley rats were unilaterally lesioned in the right medial forebrain bundle by 6-OHDA. L-DOPA and benserazide were given daily for 22 days, starting from 4 weeks after lesioning. PT320 was co-administered weekly for 3 weeks. AIM was evaluated on days 1, 16, and 22 after initiating L-DOPA/benserazide + PT320 treatment. Brain tissues were subsequently collected for HPLC measurements of dopamine (DA) and metabolite concentrations. RESULTS: L-DOPA/benserazide increased AIMs of limbs and axial as well as the sum of all dyskinesia scores (ALO) over 3 weeks. PT320 significantly reduced the AIM scores of limbs, orolingual, and ALO. Although PT320 did not alter DA levels in the lesioned striatum, PT320 significantly attenuated 6-OHDA-enhanced DA turnover. CONCLUSION: PT320 attenuates L-DOPA/benserazide-induced dyskinesia in a 6-OHDA rat model of PD and warrants clinical evaluation to mitigate Parkinson's disease in humans.

Glucagon-like peptide-1 (GLP-1)-based receptor agonists as a treatment for Parkinson's disease.

INTRODUCTION: Accumulating evidence supports the evaluation of glucagon-like peptide-1 (GLP-1) receptor (R) agonists for the treatment of the underlying pathology causing Parkinson's Disease (PD). Not only are these effects evident in models of PD and other neurodegenerative disorders but recently in a randomized, double-blind, placebo-controlled clinical trial, a GLP-1R agonist has provided improved cognition motor functions in humans with moderate PD. AREAS COVERED: In this mini-review, we describe the development of GLP-1R agonists and their potential therapeutic value in treating PD. Many GLP-1R agonists are FDA approved for the treatment of metabolic disorders, and hence can be rapidly repositioned for PD. Furthermore, we present preclinical data offering insights into the use of monomeric dual- and tri-agonist incretin-based mimetics for neurodegenerative disorders. These drugs combine active regions of GLP-1 with those of glucose-dependent insulinotropic peptide (GIP) and/or glucagon (Gcg). EXPERT OPINION: GLP-1Ragonists offer a complementary and enhanced therapeutic value to other drugs used to treat PD. Moreover, the use of the dual- or tri-agonist GLP-1-based mimetics may provide combinatory effects that are even more powerful than GLP-1R agonism alone. We advocate for further investigations into the repurposing of GLP-1R agonists and the development of classes of multi-agonists for PD treatment.

(-)-Phenserine tartrate (PhenT) as a treatment for traumatic brain injury.

AIM: Traumatic brain injury (TBI) is one of the most common causes of morbidity and mortality of both young adults and the elderly, and is a key contributing factor in about 30% of all injury-associated deaths occurring within the United States of America. Albeit substantial impact has been made to improve our comprehension of the mechanisms that underpin the primary and secondary injury stages initiated by a TBI incident, this knowledge has yet to successfully translate into the development of an effective TBI pharmacological treatment. Developing consent suggests that a TBI can concomitantly trigger multiple TBI-linked cascades that then progress in parallel and, if correct, the multifactorial nature of TBI would make the discovery of a single effective mechanism-targeted drug unlikely. DISCUSSION: We review recent data indicating that the small molecular weight drug (-)-phenserine tartrate (PhenT), originally developed for Alzheimer's disease (AD), effectively inhibits a broad range of mechanisms pertinent to mild (m) and moderate (mod)TBI, which in combination underpin the ensuing cognitive and motor impairments. In cellular and animal models at clinically translatable doses, PhenT mitigated mTBI- and modTBI-induced programmed neuronal cell death (PNCD), oxidative stress, glutamate excitotoxicity, neuroinflammation, and effectively reversed injury-induced gene pathways leading to chronic neurodegeneration. In addition to proving efficacious in well-characterized animal TBI models, significantly mitigating cognitive and motor impairments, the drug also has demonstrated neuroprotective actions against ischemic stroke and the organophosphorus nerve agent and chemical weapon, soman. CONCLUSION: In the light of its tolerability in AD clinical trials, PhenT is an agent that can be fast-tracked for evaluation in not only civilian TBI, but also as a potentially protective agent in battlefield conditions where TBI and chemical weapon exposure are increasingly jointly occurring.

Neurotrophic and neuroprotective effects of a monomeric GLP-1/GIP/Gcg receptor triagonist in cellular and rodent models of mild traumatic brain injury.

A synthetic monomeric peptide triple receptor agonist, termed "Triagonist" that incorporates glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and glucagon (Gcg) actions, was previously developed to improve upon metabolic and glucose regulatory benefits of single and dual receptor agonists in rodent models of diet-induced obesity and type 2 diabetes. In the current study, the neurotrophic and neuroprotective actions of this Triagonist were probed in cellular and mouse models of mild traumatic brain injury (mTBI), a prevalent cause of neurodegeneration in both the young and elderly. Triagonist dose- and time-dependently elevated cyclic AMP levels in cultured human SH-SY5Y neuronal cells, and induced neurotrophic and neuroprotective actions, mitigating oxidative stress and glutamate excitotoxicity. These actions were inhibited only by the co-administration of antagonists for all three receptor types, indicating the balanced co-involvement of GLP-1, GIP and Gcg receptors. To evaluate physiological relevance, a clinically translatable dose of Triagonist was administered subcutaneously, once daily for 7 days, to mice following a 30 g weight drop close head injury. Triagonist fully mitigated mTBI-induced visual and spatial memory deficits, evaluated at 7 and 30 days post injury. These results establish Triagonist as a novel neurotrophic/protective agent worthy of further evaluation as a TBI treatment strategy.

Incretin Mimetics as Rational Candidates for the Treatment of Traumatic Brain Injury.

Traumatic brain injury (TBI) is becoming an increasing public health issue. With an annually estimated 1.7 million TBIs in the United States (U.S) and nearly 70 million worldwide, the injury, isolated or compounded with others, is a major cause of short- and long-term disability and mortality. This, along with no specific treatment, has made exploration of TBI therapies a priority of the health system. Age and sex differences create a spectrum of vulnerability to TBI, with highest prevalence among younger and older populations. Increased public interest in the long-term effects and prevention of TBI have recently reached peaks, with media attention bringing heightened awareness to sport and war related head injuries. Along with short-term issues, TBI can increase the likelihood for development of long-term neurodegenerative disorders. A growing body of literature supports the use of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and glucagon (Gcg) receptor (R) agonists, along with unimolecular combinations of these therapies, for their potent neurotrophic/neuroprotective activities across a variety of cellular and animal models of chronic neurodegenerative diseases (Alzheimer's and Parkinson's diseases) and acute cerebrovascular disorders (stroke). Mild or moderate TBI shares many of the hallmarks of these conditions; recent work provides evidence that use of these compounds is an effective strategy for its treatment. Safety and efficacy of many incretin-based therapies (GLP-1 and GIP) have been demonstrated in humans for the treatment of type 2 diabetes mellitus (T2DM), making these compounds ideal for rapid evaluation in clinical trials of mild and moderate TBI.

Pharmacokinetics and efficacy of PT302, a sustained-release Exenatide formulation, in a murine model of mild traumatic brain injury.

Traumatic brain injury (TBI) is a neurodegenerative disorder for which no effective pharmacological treatment is available. Glucagon-like peptide 1 (GLP-1) analogues such as Exenatide have previously demonstrated neurotrophic and neuroprotective effects in cellular and animal models of TBI. However, chronic or repeated administration was needed for efficacy. In this study, the pharmacokinetics and efficacy of PT302, a clinically available sustained-release Exenatide formulation (SR-Exenatide) were evaluated in a concussive mild (m)TBI mouse model. A single subcutaneous (s.c.) injection of PT302 (0.6, 0.12, and 0.024 mg/kg) was administered and plasma Exenatide concentrations were time-dependently measured over 3 weeks. An initial rapid regulated release of Exenatide in plasma was followed by a secondary phase of sustained-release in a dose-dependent manner. Short- and longer-term (7 and 30 day) cognitive impairments (visual and spatial deficits) induced by weight drop mTBI were mitigated by a single post-injury treatment with Exenatide delivered by s.c. injection of PT302 in clinically translatable doses. Immunohistochemical evaluation of neuronal cell death and inflammatory markers, likewise, cross-validated the neurotrophic and neuroprotective effects of SR-Exenatide in this mouse mTBI model. Exenatide central nervous system concentrations were 1.5% to 2.0% of concomitant plasma levels under steady-state conditions. These data demonstrate a positive beneficial action of PT302 in mTBI. This convenient single, sustained-release dosing regimen also has application for other neurological disorders, such as Alzheimer's disease, Parkinson's disease, multiple system atrophy and multiple sclerosis where prior preclinical studies, likewise, have demonstrated positive Exenatide actions.

Author Correction: Post-treatment with PT302, a long-acting Exendin-4 sustained release formulation, reduces dopaminergic neurodegeneration in a 6-Hydroxydopamine rat model of Parkinson's disease.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Post-treatment with PT302, a long-acting Exendin-4 sustained release formulation, reduces dopaminergic neurodegeneration in a 6-Hydroxydopamine rat model of Parkinson's disease.

We previously demonstrated that pretreatment with Exendin-4, a glucagon-like peptide-1 (GLP-1) receptor agonist, reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) -mediated dopaminergic neurodegeneration. The use of GLP-1 or Exendin-4 for Parkinson's disease (PD) patients is limited by their short half-lives. The purpose of this study was to evaluate a new extended release Exendin-4 formulation, PT302, in a rat model of PD. Subcutaneous administration of PT302 resulted in sustained elevations of Exendin-4 in plasma for >20 days in adult rats. To define an efficacious dose within this range, rats were administered PT302 once every 2 weeks either before or following the unilaterally 6-hydroxydopamine lesioning. Pre- and post-treatment with PT302 significantly reduced methamphetamine-induced rotation after lesioning. For animals given PT302 post lesion, blood and brain samples were collected on day 47 for measurements of plasma Exendin-4 levels and brain tyrosine hydroxylase immunoreactivity (TH-IR). PT302 significantly increased TH-IR in the lesioned substantia nigra and striatum. There was a significant correlation between plasma Exendin-4 levels and TH-IR in the substantia nigra and striatum on the lesioned side. Our data suggest that post-treatment with PT302 provides long-lasting Exendin-4 release and reduces neurodegeneration of nigrostriatal dopaminergic neurons in a 6-hydroxydopamine rat model of PD at a clinically relevant dose.