Selective Brain-Targeted Antagonism of p38 MAPKα Reduces Hippocampal IL-1β Levels and Improves Morris Water Maze Performance in Aged Rats

Shedding light on microglial dysregulation in Alzheimer's disease: exploring molecular mechanisms and therapeutic avenues

Alzheimer's disease (AD) stands out as the foremost prevalent neurodegenerative disorder, characterized by a complex etiology. Various mechanisms have been proposed to elucidate its onset, encompassing amyloid-beta (Aβ) toxicity, tau hyperphosphorylation, oxidative stress and reactive gliosis. The hallmark of AD comprises Aβ and tau aggregation. These misfolded protein aggregates trigger the activation of glial cells, primarily microglia. Microglial cells serve as a major source of inflammatory mediators and their cytotoxic activation has been implicated in various aspects of AD pathology. Activated microglia can adopt M1 or M2 phenotypes, where M1 promotes inflammation by increasing pro-inflammatory cytokines and M2 suppresses inflammation by boosting anti-inflammatory factors. Overexpressed pro-inflammatory cytokines include interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α) in adjacent brain regions. Furthermore, microglial signaling pathways dysregulated in AD are myeloid differentiation primary-response protein 88 (Myd 88), colony-stimulating factor-1 receptor (CSF1R) and dedicator of cytokinesis 2 (DOCK2), which alter the physiology. Despite numerous findings, the causative role of microglia-mediated neuroinflammation in AD remains elusive. This review concisely explores cellular and molecular mechanisms of activated microglia and their correlation with AD pathogenesis. Additionally, it highlights promising therapeutics targeting microglia modulation, currently undergoing preclinical and clinical studies, for developing effective treatment for AD.

Opposing roles of p38α-mediated phosphorylation and PRMT1-mediated arginine methylation in driving TDP-43 proteinopathy

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder typically characterized by insoluble inclusions of hyperphosphorylated TDP-43. The mechanisms underlying toxic TDP-43 accumulation are not understood. Persistent activation of p38 mitogen-activated protein kinase (MAPK) is implicated in ALS. However, it is unclear how p38 MAPK affects TDP-43 proteinopathy. Here, we show that p38α MAPK inhibition reduces pathological TDP-43 phosphorylation, aggregation, cytoplasmic mislocalization, and neurotoxicity. Remarkably, p38α MAPK inhibition mitigates aberrant TDP-43 phenotypes in diverse ALS patient-derived motor neurons. p38α MAPK phosphorylates TDP-43 at pathological S409/S410 and S292, which reduces TDP-43 liquid-liquid phase separation (LLPS) but allows pathological TDP-43 aggregation. Moreover, we establish that PRMT1 methylates TDP-43 at R293. Importantly, S292 phosphorylation reduces R293 methylation, and R293 methylation reduces S409/S410 phosphorylation. Notably, R293 methylation permits TDP-43 LLPS and reduces pathological TDP-43 aggregation. Thus, strategies to reduce p38α-mediated TDP-43 phosphorylation and promote PRMT1-mediated R293 methylation could have therapeutic utility for ALS and related TDP-43 proteinopathies.

Endosomal traffic disorders: a driving force behind neurodegenerative diseases

Endosomes are crucial sites for intracellular material sorting and transportation. Endosomal transport is a critical process involved in the selective uptake, processing, and intracellular transport of substances. The equilibrium between endocytosis and circulation mediated by the endosome-centered transport pathway plays a significant role in cell homeostasis, signal transduction, and immune response. In recent years, there have been hints linking endosomal transport abnormalities to neurodegenerative diseases, including Alzheimer's disease. Nonetheless, the related mechanisms remain unclear. Here, we provide an overview of endosomal-centered transport pathways and highlight potential physiological processes regulated by these pathways, with a particular focus on the correlation of endosomal trafficking disorders with common pathological features of neurodegenerative diseases. Additionally, we summarize potential therapeutic agents targeting endosomal trafficking for the treatment of neurodegenerative diseases.

Dual inhibition of butyrylcholinesterase and p38α mitogen-activated protein kinase: A new approach for the treatment of Alzheimer's disease

The simultaneous targeting of neuroinflammation and cholinergic hypofunction, the key pathological changes in Alzheimer's disease (AD), is not addressed by drugs currently in clinical trials, highlighting a critical therapeutic gap. We propose that dual-acting small molecules that inhibit butyrylcholinesterase (BChE) and mitogen-activated protein kinase p38α (p38α MAPK) represent a novel strategy to combat AD. This hypothesis is supported by cellular and animal studies as well as in silico modelling showing that it is possible to act simultaneously on both enzymes. Amyloid beta (Aβ) plaques trigger a pro-inflammatory microglial response that overactivates p38α MAPK, leading to increased Aβ synthesis, tau hyperphosphorylation, and altered synaptic plasticity. Overactivated microglia exacerbate neuroinflammation and cholinergic degeneration, ultimately leading to cognitive impairment. Structural similarities between the binding sites of BChE and p38α MAPK provide a promising basis for the development of dual inhibitors that could alleviate AD symptoms and address the underlying pathology.

A small molecule p38α MAPK inhibitor, MW150, attenuates behavioral deficits and neuronal dysfunction in a mouse model of mixed amyloid and vascular pathologies

Background

Inhibition of p38 alpha mitogen activated protein kinase (p38α) has shown great promise as a treatment for Alzheimer's disease (AD) in preclinical tests. However, previous preclinical studies were performed in "pure" models of AD pathology. A vast majority of AD patients have comorbid dementia-contributing pathologies, particularly some form of vascular damage. The present study therefore aimed to test the potential of p38α inhibition to address dysfunction in the context of comorbid amyloid and vascular pathologies.

Methods

An amyloid overexpressing mouse strain (5xFAD) was placed on an 8-week long diet to induce the hyperhomocysteinemia (HHcy) model of small vessel disease. Mice were treated with the brain-penetrant small molecule p38α inhibitor MW150 for the duration of the HHcy diet, and subsequently underwent behavioral, neuroimaging, electrophysiological, or biochemical/immunohistochemical analyses.

Results

MW150 successfully reduced behavioral impairment in the Morris Water Maze, corresponding with attenuation of synaptic loss, reduction in tau phosphorylation, and a partial normalization of electrophysiological parameters. No effect of MW150 was observed on the amyloid, vascular, or neuroinflammatory endpoints measured.

Conclusions

This study provides proof-of-principle that the inhibition of p38α is able to provide benefit even in the context of mixed pathological contributions to cognitive impairment. Interestingly, the benefit was mediated primarily via rescue of neuronal function without any direct effects on the primary pathologies. These data suggest a potential use for p38 inhibitors in the preservation of cognition across contexts, and in particular AD, either alone or as an adjunct to other AD therapies (i.e. anti-amyloid approaches). Future studies to delineate the precise neuronal pathways implicated in the benefit may help define other specific comorbid conditions amenable to this type of approach or suggest future refinement in pharmacological targeting.

Poly-GR repeats associated with ALS/FTD gene C9ORF72 impair translation elongation and induce a ribotoxic stress response in neurons

Hexanucleotide repeat expansion in the C9ORF72 gene is the most frequent inherited cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The expansion results in multiple dipeptide repeat proteins, among which arginine-rich poly-GR proteins are highly toxic to neurons and decrease the rate of protein synthesis. We investigated whether the effect on protein synthesis contributes to neuronal dysfunction and degeneration. We found that the expression of poly-GR proteins inhibited global translation by perturbing translation elongation. In iPSC-differentiated neurons, the translation of transcripts with relatively slow elongation rates was further slowed, and stalled, by poly-GR. Elongation stalling increased ribosome collisions and induced a ribotoxic stress response (RSR) mediated by ZAKα that increased the phosphorylation of the kinase p38 and promoted cell death. Knockdown of ZAKα or pharmacological inhibition of p38 ameliorated poly-GR-induced toxicity and improved the survival of iPSC-derived neurons from patients with C9ORF72-ALS/FTD. Our findings suggest that targeting the RSR may be neuroprotective in patients with ALS/FTD caused by repeat expansion in C9ORF72.

The interplay of p38 MAPK signaling and mitochondrial metabolism, a dynamic target in cancer and pathological contexts

Mitochondria play a crucial role in cellular metabolism and bioenergetics, orchestrating various cellular processes, including energy production, metabolism, adaptation to stress, and redox balance. Besides, mitochondria regulate cellular metabolic homeostasis through coordination with multiple signaling pathways. Importantly, the p38 mitogen-activated protein kinase (MAPK) signaling pathway is a key player in the intricate communication with mitochondria, influencing various functions. This review explores the multifaced interaction between the mitochondria and p38 MAPK signaling and the consequent impact on metabolic alterations. Overall, the p38 MAPK pathway governs the activities of key mitochondrial proteins, which are involved in mitochondrial biogenesis, oxidative phosphorylation, thermogenesis, and iron homeostasis. Additionally, p38 MAPK contributes to the regulation of mitochondrial responses to oxidative stress and apoptosis induced by cancer therapies or natural substances by coordinating with other pathways responsible for energy homeostasis. Therefore, dysregulation of these interconnected pathways can lead to various pathologies characterized by aberrant metabolism. Consequently, gaining a deeper understanding of the interaction between mitochondria and the p38 MAPK pathway and their implications presents exciting forecasts for novel therapeutic interventions in cancer and other disorders characterized by metabolic dysregulation.

Environmental Toxins and Alzheimer's Disease: a Comprehensive Analysis of Pathogenic Mechanisms and Therapeutic Modulation

Alzheimer's disease is a leading cause of mortality worldwide. Inorganic and organic hazards, susceptibility to harmful metals, pesticides, agrochemicals, and air pollution are major environmental concerns. As merely 5% of AD cases are directly inherited indicating that these environmental factors play a major role in disease development. Long-term exposure to environmental toxins is believed to progress neuropathology, which leads to the development of AD. Numerous in-vitro and in-vivo studies have suggested the harmful impact of environmental toxins at cellular and molecular level. Common mechanisms involved in the toxicity of these environmental pollutants include oxidative stress, neuroinflammation, mitochondrial dysfunction, abnormal tau, and APP processing. Increased expression of GSK-3β, BACE-1, TNF-α, and pro-apoptotic molecules like caspases is observed upon exposure to these environmental toxins. In addition, the expression of neurotrophins like BDNF and GAP-43 have been found to be reduced as a result of toxicity. Further, modulation of signaling pathways involving PARP-1, PGC-1α, and MAPK/ERK induced by toxins have been reported to contribute in AD pathogenesis. These pathways are a promising target for developing novel AD therapeutics. Drugs like epigallocatechin-gallate, neflamapimod, salsalate, dexmedetomidine, and atabecestat are in different phases of clinical trials targeting the pathways for possible treatment of AD. This review aims to culminate the correlation between environmental toxicants and AD development. We emphasized upon the signaling pathways involved in the progression of the disease and the therapeutics under clinical trial targeting the altered pathways for possible treatment of AD.

Targeting Lewy body dementia with neflamapimod-rasagiline hybrids

Lewy body dementia (LBD) represents the second most common neurodegenerative dementia but is a quite underexplored therapeutic area. Nepflamapimod (1) is a brain-penetrant selective inhibitor of the alpha isoform of the mitogen-activated serine/threonine protein kinase (MAPK) p38α, recently repurposed for LBD due to its remarkable antineuroinflammatory properties. Neuroprotective propargylamines are another class of molecules with a therapeutical potential against LBD. Herein, we sought to combine the antineuroinflammatory core of 1 and the neuroprotective propargylamine moiety into a single molecule. Particularly, we inserted a propargylamine moiety in position 4 of the 2,6-dichlorophenyl ring of 1, generating neflamapimod-propargylamine hybrids 3 and 4. These hybrids were evaluated using several cell models, aiming to recapitulate the complexity of LBD pathology through different molecular mechanisms. The N-methyl-N-propargyl derivative 4 showed a nanomolar p38α-MAPK inhibitory activity (IC50 = 98.7 nM), which is only 2.6-fold lower compared to that of the parent compound 1, while displaying no hepato- and neurotoxicity up to 25 μM concentration. It also retained a similar immunomodulatory profile against the N9 microglial cell line. Gratifyingly, at 5 μM concentration, 4 demonstrated a neuroprotective effect against dexamethasone-induced reactive oxygen species production in neuronal cells that was higher than that of 1.

Practical Three-Component Regioselective Synthesis of Drug-Like 3-Aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnolines as Potential Non-Covalent Multi-Targeting Inhibitors To Combat Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are one of the prominent health challenges facing contemporary society, and many efforts have been made to overcome and (or) control it. In this research paper, we described a practical one-pot two-step three-component reaction between 3,4-dihydronaphthalen-1(2H)-one (1), aryl(or heteroaryl)glyoxal monohydrates (2a-h), and hydrazine monohydrate (NH2NH2•H2O) for the regioselective preparation of some 3-aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnoline derivatives (3a-h). After synthesis and characterization of the mentioned cinnolines (3a-h), the in silico multi-targeting inhibitory properties of these heterocyclic scaffolds have been investigated upon various Homo sapiens-type enzymes, including hMAO-A, hMAO-B, hAChE, hBChE, hBACE-1, hBACE-2, hNQO-1, hNQO-2, hnNOS, hiNOS, hPARP-1, hPARP-2, hLRRK-2(G2019S), hGSK-3β, hp38α MAPK, hJNK-3, hOGA, hNMDA receptor, hnSMase-2, hIDO-1, hCOMT, hLIMK-1, hLIMK-2, hRIPK-1, hUCH-L1, hPARK-7, and hDHODH, which have confirmed their functions and roles in the neurodegenerative diseases (NDs), based on molecular docking studies, and the obtained results were compared with a wide range of approved drugs and well-known (with IC50, EC50, etc.) compounds. In addition, in silico ADMET prediction analysis was performed to examine the prospective drug properties of the synthesized heterocyclic compounds (3a-h). The obtained results from the molecular docking studies and ADMET-related data demonstrated that these series of 3-aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnolines (3a-h), especially hit ones, can really be turned into the potent core of new drugs for the treatment of neurodegenerative diseases (NDs), and/or due to the having some reactionable locations, they are able to have further organic reactions (such as cross-coupling reactions), and expansion of these compounds (for example, with using other types of aryl(or heteroaryl)glyoxal monohydrates) makes a new avenue for designing novel and efficient drugs for this purpose.

Inflammation and Huntington's disease - a neglected therapeutic target?

INTRODUCTION

Huntington's Disease (HD) is a genetic neurodegenerative disease for which there is currently no disease-modifying treatment. One of several underlying mechanisms proposed to be involved in HD pathogenesis is inflammation; there is now accumulating evidence that the immune system may play an integral role in disease pathology and progression. As such, modulation of the immune system could be a potential therapeutic target for HD.

AREAS COVERED

To date, the number of trials targeting immune aspects of HD has been limited. However, targeting it, may have great advantages over other therapeutic areas, given that many drugs already exist that have actions in this system coupled to the fact that inflammation can be measured both peripherally and, to some extent, centrally using CSF and PET imaging. In this review, we look at evidence that the immune system and the newly emerging area of the microbiome are altered in HD patients, and then present and discuss clinical trials that have targeted different parts of the immune system.

EXPERT OPINION

We then conclude by discussing how this field might develop going forward, focusing on the role of imaging and other biomarkers to monitor central immune activation and response to novel treatments in HD.

Cancer drugs with high repositioning potential for Alzheimer's disease

INTRODUCTION

Despite the recent full FDA approval of lecanemab, there is currently no disease modifying therapy (DMT) that can efficiently slow down the progression of Alzheimer's disease (AD) in the general population. This statement emphasizes the need to identify novel DMTs in the shortest time possible to prevent a global epidemic of AD cases as the world population experiences an increase in lifespan.

AREAS COVERED

Here, we review several classes of anti-cancer drugs that have been or are being investigated in Phase II/III clinical trials for AD, including immunomodulatory drugs, RXR agonists, sex hormone therapies, tyrosine kinase inhibitors, and monoclonal antibodies.

EXPERT OPINION

Given the overall course of brain pathologies during the progression of AD, we express a great enthusiasm for the repositioning of anti-cancer drugs as possible AD DMTs. We anticipate an increasing number of combinatorial therapy strategies to tackle AD symptoms and their underlying pathologies. However, we strongly encourage improvements in clinical trial study designs to better assess target engagement and possible efficacy over sufficient periods of drug exposure.

Inflammatory signaling pathways in the treatment of Alzheimer's disease with inhibitors, natural products and metabolites (Review)

The intricate nature of Alzheimer's disease (AD) pathogenesis poses a persistent obstacle to drug development. In recent times, neuroinflammation has emerged as a crucial pathogenic mechanism of AD, and the targeting of inflammation has become a viable approach for the prevention and management of AD. The present study conducted a comprehensive review of the literature between October 2012 and October 2022, identifying a total of 96 references, encompassing 91 distinct pharmaceuticals that have been investigated for their potential impact on AD by inhibiting neuroinflammation. Research has shown that pharmaceuticals have the potential to ameliorate AD by reducing neuroinflammation mainly through regulating inflammatory signaling pathways such as NF‑κB, MAPK, NLRP3, PPARs, STAT3, CREB, PI3K/Akt, Nrf2 and their respective signaling pathways. Among them, tanshinone IIA has been extensively studied for its anti‑inflammatory effects, which have shown significant pharmacological properties and can be applied clinically. Thus, it may hold promise as an effective drug for the treatment of AD. The present review elucidated the inflammatory signaling pathways of pharmaceuticals that have been investigated for their therapeutic efficacy in AD and elucidates their underlying mechanisms. This underscores the auspicious potential of pharmaceuticals in ameliorating AD by impeding neuroinflammation.

Alzheimer's Disease: Novel Targets and Investigational Drugs for Disease Modification

Novel agents addressing non-amyloid, non-tau targets in Alzheimer's Disease (AD) comprise 70% of the AD drug development pipeline of agents currently in clinical trials. Most of the target processes identified in the Common Alzheimer's Disease Research Ontology (CADRO) are represented by novel agents in trials. Inflammation and synaptic plasticity/neuroprotection are the CADRO categories with the largest number of novel candidate therapies. Within these categories, there are few overlapping targets among the test agents. Additional categories being evaluated include apolipoprotein E [Formula: see text] 4 (APOE4) effects, lipids and lipoprotein receptors, neurogenesis, oxidative stress, bioenergetics and metabolism, vascular factors, cell death, growth factors and hormones, circadian rhythm, and epigenetic regulators. We highlight current drugs being tested within these categories and their mechanisms. Trials will be informative regarding which targets can be modulated to produce a slowing of clinical decline. Possible therapeutic combinations of agents may be suggested by trial outcomes. Biomarkers are evolving in concert with new targets and novel agents, and biomarker outcomes offer a means of supporting disease modification by the putative treatment. Identification of novel targets and development of corresponding therapeutics offer an important means of advancing new treatments for AD.

NF-κB Pathway and Its Inhibitors: A Promising Frontier in the Management of Alzheimer's Disease

The nuclear factor kappa B (NF-κB) pathway has emerged as a pivotal player in the pathogenesis of various diseases, including neurodegenerative illnesses like Alzheimer's disease (AD). The involvement of the NF-κB pathway in immune system responses, inflammation, oxidative stress, and neuronal survival highlights its significance in AD progression. We discuss the advantages of NF-κB pathway inhibition, including the potential to mitigate neuroinflammation, modulate amyloid beta (Aβ) production, and promote neuronal survival. However, we also acknowledge the limitations and challenges associated with this approach. Balancing the fine line between dampening inflammation and preserving physiological immune responses is critical to avoid unintended consequences. This review combines current knowledge on the NF-κB pathway's intricate involvement in AD pathogenesis, emphasizing its potential as a therapeutic target. By evaluating both advantages and limitations, we provide a holistic view of the feasibility and challenges of NF-κB pathway modulation in AD treatment. As the quest for effective AD therapies continues, an in-depth understanding of the NF-κB pathway's multifaceted roles will guide the development of targeted interventions with the potential to improve AD management.

Therapeutic Strategies Aimed at Improving Neuroplasticity in Alzheimer Disease

Alzheimer disease (AD) is the most prevalent form of dementia among elderly people. Owing to its varied and multicausal etiopathology, intervention strategies have been highly diverse. Despite ongoing advances in the field, efficient therapies to mitigate AD symptoms or delay their progression are still of limited scope. Neuroplasticity, in broad terms the ability of the brain to modify its structure in response to external stimulation or damage, has received growing attention as a possible therapeutic target, since the disruption of plastic mechanisms in the brain appear to correlate with various forms of cognitive impairment present in AD patients. Several pre-clinical and clinical studies have attempted to enhance neuroplasticity via different mechanisms, for example, regulating glucose or lipid metabolism, targeting the activity of neurotransmitter systems, or addressing neuroinflammation. In this review, we first describe several structural and functional aspects of neuroplasticity. We then focus on the current status of pharmacological approaches to AD stemming from clinical trials targeting neuroplastic mechanisms in AD patients. This is followed by an analysis of analogous pharmacological interventions in animal models, according to their mechanisms of action.

Kinase Inhibitors Involved in the Regulation of Autophagy: Molecular Concepts and Clinical Implications

All cells and intracellular components are remodeled and recycled in order to replace the old and damaged cells. Autophagy is a process by which damaged, and unwanted cells are degraded in the lysosomes. There are three different types of autophagy: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy has an effect on adaptive and innate immunity, suppression of any tumour, and the elimination of various microbial pathogens. The process of autophagy has both positive and negative effects, and this pertains to any specific disease or its stage of progression. Autophagy involves various processes which are controlled by various signaling pathways, such as Jun N-terminal kinase, GSK3, ERK1, Leucine-rich repeat kinase 2, and PTEN-induced putative kinase 1 and parkin RBR E3. Protein kinases are also important for the regulation of autophagy as they regulate the process of autophagy either by activation or inhibition. The present review discusses the kinase catalyzed phosphorylated reactions, the kinase inhibitors, types of protein kinase inhibitors and their binding properties to protein kinase domains, the structures of active and inactive kinases, and the hydrophobic spine structures in active and inactive protein kinase domains. The intervention of autophagy by targeting specific kinases may form the mainstay of treatment of many diseases and lead the road to future drug discovery.

Omics-based biomarkers discovery for Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorders presenting with the pathological hallmarks of amyloid plaques and tau tangles. Over the past few years, great efforts have been made to explore reliable biomarkers of AD. High-throughput omics are a technology driven by multiple levels of unbiased data to detect the complex etiology of AD, and it provides us with new opportunities to better understand the pathophysiology of AD and thereby identify potential biomarkers. Through revealing the interaction networks between different molecular levels, the ultimate goal of multi-omics is to improve the diagnosis and treatment of AD. In this review, based on the current AD pathology and the current status of AD diagnostic biomarkers, we summarize how genomics, transcriptomics, proteomics and metabolomics are all conducing to the discovery of reliable AD biomarkers that could be developed and used in clinical AD management.

Medicinal Herbs and Their Derived Ingredients Protect against Cognitive Decline in In Vivo Models of Alzheimer’s Disease

Alzheimer’s disease (AD) has pathological hallmarks including amyloid beta (Aβ) plaque formation. Currently approved single-target drugs cannot effectively ameliorate AD. Medicinal herbs and their derived ingredients (MHDIs) have multitarget and multichannel properties, engendering exceptional AD treatment outcomes. This review delineates how in in vivo models MHDIs suppress Aβ deposition by downregulating β- and γ-secretase activities; inhibit oxidative stress by enhancing the antioxidant activities and reducing lipid peroxidation; prevent tau hyperphosphorylation by upregulating protein phosphatase 2A expression and downregulating glycogen synthase kinase-3β expression; reduce inflammatory mediators partly by upregulating brain-derived neurotrophic factor/extracellular signal-regulated protein kinase 1/2-mediated signaling and downregulating p38 mitogen-activated protein kinase (p38 MAPK)/c-Jun N-terminal kinase (JNK)-mediated signaling; attenuate synaptic dysfunction by increasing presynaptic protein, postsynaptic protein, and acetylcholine levels and preventing acetylcholinesterase activity; and protect against neuronal apoptosis mainly by upregulating Akt/cyclic AMP response element-binding protein/B-cell lymphoma 2 (Bcl-2)-mediated anti-apoptotic signaling and downregulating p38 MAPK/JNK/Bcl-2-associated x protein (Bax)/caspase-3-, Bax/apoptosis-inducing factor-, C/EBP homologous protein/glucose-regulated protein 78-, and autophagy-mediated apoptotic signaling. Therefore, MHDIs listed in this review protect against Aβ-induced cognitive decline by inhibiting Aβ accumulation, oxidative stress, tau hyperphosphorylation, inflammation, synaptic damage, and neuronal apoptosis in the cortex and hippocampus during the early and late AD phases.

Preclinical and randomized clinical evaluation of the p38α kinase inhibitor neflamapimod for basal forebrain cholinergic degeneration

The endosome-associated GTPase Rab5 is a central player in the molecular mechanisms leading to degeneration of basal forebrain cholinergic neurons (BFCN), a long-standing target for drug development. As p38α is a Rab5 activator, we hypothesized that inhibition of this kinase holds potential as an approach to treat diseases associated with BFCN loss. Herein, we report that neflamapimod (oral small molecule p38α inhibitor) reduces Rab5 activity, reverses endosomal pathology, and restores the numbers and morphology of BFCNs in a mouse model that develops BFCN degeneration. We also report on the results of an exploratory (hypothesis-generating) phase 2a randomized double-blind 16-week placebo-controlled clinical trial (Clinical trial registration: NCT04001517/EudraCT #2019-001566-15) of neflamapimod in mild-to-moderate dementia with Lewy bodies (DLB), a disease in which BFCN degeneration is an important driver of disease expression. A total of 91 participants, all receiving background cholinesterase inhibitor therapy, were randomized 1:1 between neflamapimod 40 mg or matching placebo capsules (taken orally twice-daily if weight <80 kg or thrice-daily if weight >80 kg). Neflamapimod does not show an effect in the clinical study on the primary endpoint, a cognitive-test battery. On two secondary endpoints, a measure of functional mobility and a dementia rating-scale, improvements were seen that are consistent with an effect on BFCN function. Neflamapimod treatment is well-tolerated with no study drug associated treatment discontinuations. The combined preclinical and clinical observations inform on the validity of the Rab5-based pathogenic model of cholinergic degeneration and provide a foundation for confirmatory (hypothesis-testing) clinical evaluation of neflamapimod in DLB.

Glial Cell-Mediated Neuroinflammation in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder; it is the most common cause of dementia and has no treatment. It is characterized by two pathological hallmarks, the extracellular deposits of amyloid beta (Aβ) and the intraneuronal deposits of Neurofibrillary tangles (NFTs). Yet, those two hallmarks do not explain the full pathology seen with AD, suggesting the involvement of other mechanisms. Neuroinflammation could offer another explanation for the progression of the disease. This review provides an overview of recent advances on the role of the immune cells' microglia and astrocytes in neuroinflammation. In AD, microglia and astrocytes become reactive by several mechanisms leading to the release of proinflammatory cytokines that cause further neuronal damage. We then provide updates on neuroinflammation diagnostic markers and investigational therapeutics currently in clinical trials to target neuroinflammation.

Astrocytic and microglial cells as the modulators of neuroinflammation in Alzheimer's disease

Neuroinflammation is instigated by the misfiring of immune cells in the central nervous system (CNS) involving microglia and astrocytes as key cell-types. Neuroinflammation is a consequence of CNS injury, infection, toxicity, or autoimmunity. It is favorable as well as a detrimental process for neurodevelopment and associated processes. Transient activation of inflammatory response involving release of cytokines and growth factors positively affects the development and post-injury tissue. However, chronic or uncontrolled inflammatory responses may lead to various neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis, and multiple sclerosis. These diseases have variable clinical and pathological features, but are underlaid by the aggregation of misfolded proteins with a cytotoxic effect. Notably, abnormal activation of glial cells could mediate neuroinflammation, leading to the neurodegenerative condition. Microglia, a type of glial cell, a resident immune cell, form the forefront defense of the CNS immune system. Dysfunctional microglia and astrocyte, a different kind of glial cell with homeostatic function, impairs the protein aggregate (amyloid-beta plaque) clearance in AD. Studies have shown that microglia and astrocytes undergo alterations in their genetic profile, cellular and molecular responses, and thus promote dysfunctional immune cross-talk in AD. Hence, targeting microglia and astrocytes-driven molecular pathways could resolve the particular layers of neuroinflammation and set a reliable therapeutic intervention in AD progression.

Predictive effect of Bayes discrimination in the level of serum protein factors and cognitive dysfunction in schizophrenia

Finding molecular biomarkers that can be related to the degree of cognitive dysfunction in schizophrenia remains a challenge. The levels of 6 Serum Protein Factors (NGF, BDNF, IL-6, TNF-α, S100β, GFAP) in peripheral blood of patients with schizophrenia were measured. The cognitive function of patients with schizophrenia was assessed by MATRICS Consensus Cognitive Battery (MCCB), a systematic assessment tool of international gold standard for cognitive function assessment of schizophrenia. To explore the correlation between these 6 biomarkers and the degree of cognitive dysfunction in schizophrenia,78 schizophrenic patients and 71 healthy controls were included in the study. The serum concentrations of BDNF and GFAP were lower in the patient group, but the concentrations of IL-6, TNF-α and S100β were higher. The speed of information processing, word learning, reasoning and problem solving, visual learning T-score of the patient group were lower than the control group. Bayes discriminant function model has a high correct discriminant rate for the severity of cognitive dysfunction in schizophrenia. The level of serum protein factor and clinical symptom score of schizophrenia may forecast the degree of cognitive dysfunction, which is expected to be a potential biomarker to identify the degree of cognitive dysfunction of schizophrenia, and provide objective basis for the clinical diagnosis and treatment of patients with schizophrenia.

Current and Possible Future Therapeutic Options for Huntington's Disease

Huntington's disease (HD) is an autosomal neurodegenerative disease that is characterized by an excessive number of CAG trinucleotide repeats within the huntingtin gene (HTT). HD patients can present with a variety of symptoms including chorea, behavioural and psychiatric abnormalities and cognitive decline. Each patient has a unique combination of symptoms, and although these can be managed using a range of medications and non-drug treatments there is currently no cure for the disease. Current therapies prescribed for HD can be categorized by the symptom they treat. These categories include chorea medication, antipsychotic medication, antidepressants, mood stabilizing medication as well as non-drug therapies. Fortunately, there are also many new HD therapeutics currently undergoing clinical trials that target the disease at its origin; lowering the levels of mutant huntingtin protein (mHTT). Currently, much attention is being directed to antisense oligonucleotide (ASO) therapies, which bind to pre-RNA or mRNA and can alter protein expression via RNA degradation, blocking translation or splice modulation. Other potential therapies in clinical development include RNA interference (RNAi) therapies, RNA targeting small molecule therapies, stem cell therapies, antibody therapies, non-RNA targeting small molecule therapies and neuroinflammation targeted therapies. Potential therapies in pre-clinical development include Zinc-Finger Protein (ZFP) therapies, transcription activator-like effector nuclease (TALEN) therapies and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system (Cas) therapies. This comprehensive review aims to discuss the efficacy of current HD treatments and explore the clinical trial progress of emerging potential HD therapeutics.

Lewy Body Dementias: Controversies and Drug Development

Lewy body dementia (LBD) is one of the most common neurodegenerative dementias. Clinical trials for symptomatic and disease-modifying therapies in LBD remain a national research priority, but there are many challenges in both past and active drug developments in LBD. This review highlights the controversies in picking the appropriate populations, interventions, target selections, and outcome measures, which are all critical components of clinical trial implementation in LBD. The heterogeneity of LBD neuropathology and clinical presentations, limited understanding of core features such as cognitive fluctuations, and lack of validated LBD-specific outcome measures and biomarkers represent some of the major challenges in LBD trials.

Identification of Potential Biomarkers of Depression and Network Pharmacology Approach to Investigate the Mechanism of Key Genes and Therapeutic Traditional Chinese Medicine in the Treatment of Depression

BACKGROUND

To explore the potential target of depression and the mechanism of related traditional Chinese medicine in the treatment of depression.

METHOD

Differential gene expression in depression patients and controls was analyzed in the GEO database. Key genes for depression were obtained by searching the disease databases. The COREMINE Medical database was used to search for Chinese medicines corresponding to the key genes in the treatment of depression, and the network pharmacological analysis was performed on these Chinese medicines. Then, protein-protein interaction analysis was conducted. Prediction of gene phenotypes was based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment scores.

RESULTS

The total number of differentially expressed genes in the GEO database was 147. Combined with the GEO dataset and disease database, a total of 3533 depression-related genes were analyzed. After screening in COREMINE Medical, it was found that the top 4 traditional Chinese medicines with the highest frequency for depression were Paeonia lactiflora Pall., Crocus sativus L., Bupleurum chinense DC., and Cannabis sativa L. The compound target network consisted of 24 compounds and 138 corresponding targets, and the key targets involved PRKACA, NCOA2, PPARA, and so on. GO and KEGG analysis revealed that the most commonly used Chinese medicine could regulate multiple aspects of depression through these targets, related to metabolism, neuroendocrine function, and neuroimmunity. Prediction and analysis of protein-protein interactions resulted in the selection of nine hub genes (ESR1, HSP90AA1, JUN, MAPK1, MAPK14, MAPK8, RB1, RELA, and TP53). In addition, a total of four ingredients (petunidin, isorhamnetin, quercetin, and luteolin) from this Chinese medicine could act on these hub genes.

CONCLUSIONS

Our research revealed the complicated antidepressant mechanism of the most commonly used Chinese medicines and also provided a rational strategy for revealing the complex composition and function of Chinese herbal formulas.

κ-Opioid Receptor Agonist Ameliorates Postoperative Neurocognitive Disorder by Activating the Ca2+/CaMKII/CREB Pathway

Objective

Cardiopulmonary bypass (CPB) is an important cardiac operation and also a high-risk procedure, leading to postoperative neurocognitive disorder. However, there are few effective drugs to treat the aftermath of CPB. Therefore, we observe the effect of kappa opioid receptor (KOR) agonist on cognitive disorders of rats after cardiopulmonary bypass (CPB) and investigate the mechanism of the Ca²⁺/calmodulin-dependent protein kinase (CaMKII)/cAMP responsive element-binding protein (CREB) pathway.

Methods

A total of 40 Sprague Dawley rats were randomly divided into the sham operation group (sham group, n = 10), CPB model group (CPB group, n = 10), CPB + KOR agonist U50488H group (UH group, n = 10), and CPB + specific CaMKII antagonist + U50488H group (CKU group, n = 10). The changes in the rats' cognitive function were evaluated using the Morris water maze, the hippocampal histopathological changes were observed via hematoxylin-eosin (H&E) staining, and the apoptosis rate of neuronal cells was detected through terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. Moreover, enzyme-linked immunosorbent assay (ELISA) was applied to examine the changes in brain injury markers, inflammatory factors, and oxidative stress factors. The hippocampal variations in Ca²⁺ concentration and oxidative stress index (ROS) levels were measured by immunofluorescence staining, and western blotting was performed to determine the expression changes in the Ca²⁺/CaMKII/CREB pathway.

Results

The KOR agonist could shorten latency, increase the swimming distance and residence time in the target quadrant, and ameliorate postoperative neurocognitive disorder (PND). Meanwhile, the KOR agonist relieved CPB-induced hippocampal and oxidative stress injuries, reduced NSE and S-100β expression, decreased the apoptosis rate, and repressed the inflammatory response, which alleviated the brain injury. In addition, U50488H was able to decrease Ca²⁺ influx and glutamate (Glu) level, inhibit N-methyl-D-aspartate receptor (NMDAR) expression, upregulate CaMKII expression, promote CREB phosphorylation, and increase the brain-derived neurotrophic factor (BDNF) level in CPB rats. However, the protective effects of KORs against PND were suppressed following the application of the CaMKII-specific antagonist.

Conclusion

The KOR agonist activates the Ca²⁺/CaMKII/CREB pathway, which improves the brain injury and relieves PND in CPB rats.

A multitude of signaling pathways associated with Alzheimer's disease and their roles in AD pathogenesis and therapy

The exact molecular mechanisms associated with Alzheimer's disease (AD) pathology continue to represent a mystery. In the past decades, comprehensive data were generated on the involvement of different signaling pathways in the AD pathogenesis. However, the utilization of signaling pathways as potential targets for the development of drugs against AD is rather limited due to the immense complexity of the brain and intricate molecular links between these pathways. Therefore, finding a correlation and cross-talk between these signaling pathways and establishing different therapeutic targets within and between those pathways are needed for better understanding of the biological events responsible for the AD-related neurodegeneration. For example, autophagy is a conservative cellular process that shows link with many other AD-related pathways and is crucial for maintenance of the correct cellular balance by degrading AD-associated pathogenic proteins. Considering the central role of autophagy in AD and its interplay with many other pathways, the finest therapeutic strategy to fight against AD is the use of autophagy as a target. As an essential step in this direction, this comprehensive review represents recent findings on the individual AD-related signaling pathways, describes key features of these pathways and their cross-talk with autophagy, represents current drug development, and introduces some of the multitarget beneficial approaches and strategies for the therapeutic intervention of AD.

Therapy for Alzheimer's disease: Missing targets and functional markers?

The development of the next generation therapy for Alzheimer's disease (AD) presents a huge challenge given the number of promising treatment candidates that failed in trials, despite recent advancements in understanding of genetic, pathophysiologic and clinical characteristics of the disease. This review reflects some of the most current concepts and controversies in developing disease-modifying and new symptomatic treatments. It elaborates on recent changes in the AD research strategy for broadening drug targets, and potentials of emerging non-pharmacological treatment interventions. Established and novel biomarkers are discussed, including emerging cerebrospinal fluid and plasma biomarkers reflecting tau pathology, neuroinflammation and neurodegeneration. These fluid biomarkers together with neuroimaging findings can provide innovative objective assessments of subtle changes in brain reflecting disease progression. A particular emphasis is given to neurophysiological biomarkers which are well-suited for evaluating the brain overall neural network integrity and function. Combination of multiple biomarkers, including target engagement and outcome biomarkers will empower translational studies and facilitate successful development of effective therapies.

Kinase drug discovery 20 years after imatinib: progress and future directions

Protein kinases regulate nearly all aspects of cell life, and alterations in their expression, or mutations in their genes, cause cancer and other diseases. Here, we review the remarkable progress made over the past 20 years in improving the potency and specificity of small-molecule inhibitors of protein and lipid kinases, resulting in the approval of more than 70 new drugs since imatinib was approved in 2001. These compounds have had a significant impact on the way in which we now treat cancers and non-cancerous conditions. We discuss how the challenge of drug resistance to kinase inhibitors is being met and the future of kinase drug discovery.

Small molecule therapeutics for neuroinflammation-mediated neurodegenerative disorders

Chronically activated microglia and the resulting cascade of neuroinflammatory mechanisms have been postulated to play a critical role in neurodegenerative disorders. Microglia are the main component of the brain's innate immune system and become activated by infection, injury, misfolded proteins or a multitude of other stimuli. Activated microglia release pro-inflammatory and cytotoxic factors that can damage neurons and transform astrocytes to become toxic to neurons as well. Therapeutic approaches aiming to modulate microglia activation may be beneficial to mitigate the progression of inflammatory-mediated neurodegenerative diseases. In this literature review, we provide an overview of recent progress on key microglia targets and discovery of small molecule compounds advancing in clinical trials to minimize neuroinflammation.

Learning from the Past: A Review of Clinical Trials Targeting Amyloid, Tau and Neuroinflammation in Alzheimer's Disease

Alzheimer's Disease (AD) is the most common neurodegenerative disease and cause of dementia. Characterized by amyloid plaques and neurofibrillary tangles of hyperphosphorylated Tau, AD pathology has been intensively studied during the last century. After a long series of failed trials of drugs targeting amyloid or Tau deposits, currently, hope lies in the positive results of one Phase III trial, highly debated, and on other ongoing trials. In parallel, some approaches target neuroinflammation, another central feature of AD. Therapeutic strategies are initially evaluated on animal models, in which the various drugs have shown effects on the target (decreasing amyloid, Tau and neuroinflammation) and sometimes on cognitive impairment. However, it is important to keep in mind that rodent models have a less complex brain than humans and that the pathology is generally not fully represented. Although they are indispensable tools in the drug discovery process, results obtained from animal models must be viewed with caution. In this review, we focus on the current status of disease-modifying therapies targeting amyloid, Tau and neuroinflammation with particular attention on the discrepancy between positive preclinical results on animal models and failures in clinical trials.

Modulating neuroinflammation in neurodegeneration-related dementia: can microglial toll-like receptors pull the plug?

Neurodegeneration-associated dementia disorders (NADDs), namely Alzheimer and Parkinson diseases, are developed by a significant portion of the elderly population globally. Extensive research has provided critical insights into the molecular basis of the pathological advancements of these diseases, but an efficient curative therapy seems elusive. A common attribute of NADDs is neuroinflammation due to a chronic inflammatory response within the central nervous system (CNS), which is primarily modulated by microglia. This response within the CNS is positively regulated by cytokines, chemokines, secondary messengers or cyclic nucleotides, and free radicals. Microglia mediated immune activation is regulated by a positive feedback loop in NADDs. The present review focuses on evaluating the crosstalk between inflammatory mediators and microglia, which aggravates both the clinical progression and extent of NADDs by forming a persistent chronic inflammatory milieu within the CNS. We also discuss the role of the human gut microbiota and its effect on NADDs as well as the suitability of targeting toll-like receptors for an immunotherapeutic intervention targeting the deflation of an inflamed milieu within the CNS.

When Good Kinases Go Rogue: GSK3, p38 MAPK and CDKs as Therapeutic Targets for Alzheimer's and Huntington's Disease

Alzheimer's disease (AD) is a mostly sporadic brain disorder characterized by cognitive decline resulting from selective neurodegeneration in the hippocampus and cerebral cortex whereas Huntington's disease (HD) is a monogenic inherited disorder characterized by motor abnormalities and psychiatric disturbances resulting from selective neurodegeneration in the striatum. Although there have been numerous clinical trials for these diseases, they have been unsuccessful. Research conducted over the past three decades by a large number of laboratories has demonstrated that abnormal actions of common kinases play a key role in the pathogenesis of both AD and HD as well as several other neurodegenerative diseases. Prominent among these kinases are glycogen synthase kinase (GSK3), p38 mitogen-activated protein kinase (MAPK) and some of the cyclin-dependent kinases (CDKs). After a brief summary of the molecular and cell biology of AD and HD this review covers what is known about the role of these three groups of kinases in the brain and in the pathogenesis of the two neurodegenerative disorders. The potential of targeting GSK3, p38 MAPK and CDKS as effective therapeutics is also discussed as is a brief discussion on the utilization of recently developed drugs that simultaneously target two or all three of these groups of kinases. Multi-kinase inhibitors either by themselves or in combination with strategies currently being used such as immunotherapy or secretase inhibitors for AD and knockdown for HD could represent a more effective therapeutic approach for these fatal neurodegenerative diseases.

A phase 2 double-blind placebo-controlled 24-week treatment clinical study of the p38 alpha kinase inhibitor neflamapimod in mild Alzheimer's disease

BACKGROUND

In preclinical studies, p38⍺ kinase is implicated in Alzheimer's disease (AD) pathogenesis. In animal models, it mediates impaired synaptic dysfunction in the hippocampus, causing memory deficits, and is involved in amyloid-beta (Aβ) production and tau pathology.

METHODS

The REVERSE-SD (synaptic dysfunction) study was a multi-center phase 2, randomized, double-blind, placebo-controlled trial of the p38⍺ kinase inhibitor neflamapimod; conducted December 29, 2017, to June 17, 2019; 464 participants screened, and 161 randomized to either 40 mg neflamapimod (78 study participants) or matching placebo (83 study participants), orally twice daily for 24 weeks. Study participants are as follows: CSF AD-biomarker confirmed, Clinical Dementia Rating (CDR)-global score 0.5 or 1.0, CDR-memory score ≥0.5, and Mini-Mental State Examination (MMSE) 20-28. The primary endpoint was the improvement in episodic memory, assessed by combined change in Z-scores of Hopkins Verbal Learning Test-Revised (HVLT-R) Total and Delayed Recall. Secondary endpoints included change in Wechsler Memory Scale-IV (WMS) Immediate and Delayed Recall composites, CDR-SB, MMSE, and CSF biomarkers [total and phosphorylated tau (T-tau and p-tau₁₈₁), Aβ_1-40, Aβ_1-42, neurogranin, and neurofilament light chain].

RESULTS

At randomization, the mean age is 72, 50% female, 77% with CDR-global score 0.5, and mean MMSE score 23.8. The incidence of discontinuation for adverse events and serious adverse events (all considered unrelated) was 3% each. No significant differences between treatment groups were observed in the primary or secondary clinical endpoints. Significantly reduced CSF levels with neflamapimod treatment, relative to placebo, were evident for T-tau [difference (95% CI): -18.8 (-35.8, -1.8); P=0.031] and p-tau₁₈₁ [-2.0 (-3.6, -0.5); P=0.012], with a trend for neurogranin [-21.0 (-43.6, 1.6); P=0.068]. In pre-specified pharmacokinetic-pharmacodynamic (PK-PD) analyses, subjects in the highest quartile of trough plasma neflamapimod levels demonstrated positive trends, compared with placebo, in HLVT-R and WMS.

CONCLUSIONS AND RELEVANCE

A 24-week treatment with 40 mg neflamapimod twice daily did not improve episodic memory in patients with mild AD. However, neflamapimod treatment lowered CSF biomarkers of synaptic dysfunction. Combined with PK-PD findings, the results indicate that a longer duration study of neflamapimod at a higher dose level to assess effects on AD progression is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03402659 . Registered on January 18, 2018.

Design and Synthesis of Highly Selective Brain Penetrant p38α Mitogen-Activated Protein Kinase Inhibitors

Stress-induced p38α mitogen-activated protein (MAP) kinase activation modulates cytokine overproduction and is associated with neuroinflammation and neurodegeneration. As a potential therapeutic approach, novel Skepinone-based p38α MAP kinase inhibitors were optimized to cross the blood-brain barrier via either amino acid transporters or hydrophobic diffusion. To enhance absorption from the oral route, we used methyl ester prodrugs of the active carboxy analogs. Of these, 3-(8-((2,4-difluorophenyl)amino)-5-oxo-10,11-dihydro-5H-dibenzo[a,d][7]annulene-3-carboxamido)propanoic acid (43; p38α, IC₅₀ = 5.5 nM) and 4-(8-((2,4-difluorophenyl)amino)-5-oxo-10,11-dihydro-5H-dibenzo[a,d][7]annulene-3-carboxamido)butanoic acid (44; p38α, IC₅₀ = 12 nM) had brain-to-plasma ratios of 1.4 and 4.4, respectively. Compound 70, 3-(8-((2-aminophenyl)amino)-5-oxo-10,11-dihydro-5H-dibenzo[a,d][7]annulene-3-carboxamido)propanoic acid (p38α, IC₅₀ = 1.0 nM), the Skepinone-N counterpart of 43, was most present in the mouse brain (brain-to-plasma ratio of 4.7; 0.4 mg/kg p.o., 2 h, 580 nmol/kg). Compounds 43, 44, and 70 were p38α-MAP-kinase-selective, metabolically stable, hERG nonbinding, and able to modulate IL-6 and TNF-α production in cell-based assays.

Neuroinflammation in Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disease associated with human aging. Ten percent of individuals over 65 years have AD and its prevalence continues to rise with increasing age. There are currently no effective disease modifying treatments for AD, resulting in increasingly large socioeconomic and personal costs. Increasing age is associated with an increase in low-grade chronic inflammation (inflammaging) that may contribute to the neurodegenerative process in AD. Although the exact mechanisms remain unclear, aberrant elevation of reactive oxygen and nitrogen species (RONS) levels from several endogenous and exogenous processes in the brain may not only affect cell signaling, but also trigger cellular senescence, inflammation, and pyroptosis. Moreover, a compromised immune privilege of the brain that allows the infiltration of peripheral immune cells and infectious agents may play a role. Additionally, meta-inflammation as well as gut microbiota dysbiosis may drive the neuroinflammatory process. Considering that inflammatory/immune pathways are dysregulated in parallel with cognitive dysfunction in AD, elucidating the relationship between the central nervous system and the immune system may facilitate the development of a safe and effective therapy for AD. We discuss some current ideas on processes in inflammaging that appear to drive the neurodegenerative process in AD and summarize details on a few immunomodulatory strategies being developed to selectively target the detrimental aspects of neuroinflammation without affecting defense mechanisms against pathogens and tissue damage.

Current status and future prospects of p38α/MAPK14 kinase and its inhibitors

P38α (which is also named MAPK14) plays a pivotal role in initiating different disease states such as inflammatory disorders, neurodegenerative diseases, cardiovascular cases, and cancer. Inhibitors of p38α can be utilized for treatment of these diseases. In this article, we reviewed the structural and biological characteristics of p38α, its relationship to the fore-mentioned disease states, as well as the recently reported inhibitors and classified them according to their chemical structures. We focused on the articles published in the literature during the last decade (2011-2020).

Continuous administration of a p38α inhibitor during the subacute phase after transient ischemia-induced stroke in the rat promotes dose-dependent functional recovery accompanied by increase in brain BDNF protein level

There is unmet need for effective stroke therapies. Numerous neuroprotection attempts for acute cerebral ischemia have failed and as a result there is growing interest in developing therapies to promote functional recovery through increasing synaptic plasticity. For this research study, we hypothesized that in addition to its previously reported role in mediating cell death during the acute phase, the alpha isoform of p38 mitogen-activated protein kinase, p38α, may also contribute to interleukin-1β-mediated impairment of functional recovery during the subacute phase after acute ischemic stroke. Accordingly, an oral, brain-penetrant, small molecule p38α inhibitor, neflamapimod, was evaluated as a subacute phase stroke treatment to promote functional recovery. Neflamapimod administration to rats after transient middle cerebral artery occlusion at two dose levels was initiated outside of the previously characterized therapeutic window for neuroprotection of less than 24 hours for p38α inhibitors. Six-week administration of neflamapimod, starting at 48 hours after reperfusion, significantly improved behavioral outcomes assessed by the modified neurological severity score at Week 4 and at Week 6 post stroke in a dose-dependent manner. Neflamapimod demonstrated beneficial effects on additional measures of sensory and motor function. It also resulted in a dose-related increase in brain-derived neurotrophic factor (BDNF) protein levels, a previously reported potential marker of synaptic plasticity that was measured in brain homogenates at sacrifice. Taken together with literature evidence on the role of p38α-dependent suppression by interleukin-1β of BDNF-mediated synaptic plasticity and BDNF production, our findings support a mechanistic model in which inhibition of p38α promotes functional recovery after ischemic stroke by blocking the deleterious effects of interleukin-1β on synaptic plasticity. The dose-related in vivo efficacy of neflamapimod offers the possibility of having a therapy for stroke that could be initiated outside the short time window for neuroprotection and for improving recovery after a completed stroke.

Endosomal Dysfunction Induced by Directly Overactivating Rab5 Recapitulates Prodromal and Neurodegenerative Features of Alzheimer's Disease

Neuronal endosomal dysfunction, the earliest known pathobiology specific to Alzheimer's disease (AD), is mediated by the aberrant activation of Rab5 triggered by APP-β secretase cleaved C-terminal fragment (APP-βCTF). To distinguish pathophysiological consequences specific to overactivated Rab5 itself, we activate Rab5 independently from APP-βCTF in the PA-Rab5 mouse model. We report that Rab5 overactivation alone recapitulates diverse prodromal and degenerative features of AD. Modest neuron-specific transgenic Rab5 expression inducing hyperactivation of Rab5 comparable to that in AD brain reproduces AD-related Rab5-endosomal enlargement and mistrafficking, hippocampal synaptic plasticity deficits via accelerated AMPAR endocytosis and dendritic spine loss, and tau hyperphosphorylation via activated glycogen synthase kinase-3β. Importantly, Rab5-mediated endosomal dysfunction induces progressive cholinergic neurodegeneration and impairs hippocampal-dependent memory. Aberrant neuronal Rab5-endosome signaling, therefore, drives a pathogenic cascade distinct from β-amyloid-related neurotoxicity, which includes prodromal and neurodegenerative features of AD, and suggests Rab5 overactivation as a potential therapeutic target.

Clinically Precedented Protein Kinases: Rationale for Their Use in Neurodegenerative Disease

Kinases are an intensively studied drug target class in current pharmacological research as evidenced by the large number of kinase inhibitors being assessed in clinical trials. Kinase-targeted therapies have potential for treatment of a broad array of indications including central nervous system (CNS) disorders. In addition to the many variables which contribute to identification of a successful therapeutic molecule, drug discovery for CNS-related disorders also requires significant consideration of access to the target organ and specifically crossing the blood-brain barrier (BBB). To date, only a small number of kinase inhibitors have been reported that are specifically designed to be BBB permeable, which nonetheless demonstrates the potential for success. This review considers the potential for kinase inhibitors in the context of unmet medical need for neurodegenerative disease. A subset of kinases that have been the focus of clinical investigations over a 10-year period have been identified and discussed individually. For each kinase target, the data underpinning the validity of each in the context of neurodegenerative disease is critically evaluated. Selected molecules for each kinase are identified with information on modality, binding site and CNS penetrance, if known. Current clinical development in neurodegenerative disease are summarized. Collectively, the review indicates that kinase targets with sufficient rationale warrant careful design approaches with an emphasis on improving brain penetrance and selectivity.

P38α MAPK Signaling-A Robust Therapeutic Target for Rab5-Mediated Neurodegenerative Disease

Multifactorial pathologies, involving one or more aggregated protein(s) and neuroinflammation are common in major neurodegenerative diseases, such as Alzheimer's disease and dementia with Lewy bodies. This complexity of multiple pathogenic drivers is one potential explanation for the lack of success or, at best, the partial therapeutic effects, respectively, with approaches that have targeted one specific driver, e.g., amyloid-beta, in Alzheimer's disease. Since the endosome-associated protein Rab5 appears to be a convergence point for many, if not all the most prominent pathogenic drivers, it has emerged as a major therapeutic target for neurodegenerative disease. Further, since the alpha isoform of p38 mitogen-activated protein kinase (p38α) is a major regulator of Rab5 activity and its effectors, a biology that is distinct from the classical nuclear targets of p38 signaling, brain-penetrant selective p38α kinase inhibitors provide the opportunity for significant therapeutic advances in neurogenerative disease through normalizing dysregulated Rab5 activity. In this review, we provide a brief summary of the role of Rab5 in the cell and its association with neurodegenerative disease pathogenesis. We then discuss the connection between Rab5 and p38α and summarize the evidence that through modulating Rab5 activity there are therapeutic opportunities in neurodegenerative diseases for p38α kinase inhibitors.

Targeting dementias through cancer kinases inhibition

The failures in Alzheimer's disease (AD) therapy strongly suggest the importance of reconsidering the research strategies analyzing other mechanisms that may take place in AD as well as, in general, in other neurodegenerative dementias. Taking into account that in AD a variety of defects result in neurotransmitter activity and signaling efficiency imbalance, neuronal cell degeneration and defects in damage/repair systems, aberrant and abortive cell cycle, glial dysfunction, and neuroinflammation, a target may be represented by the intracellular signaling machinery provided by the kinome. In particular, based on the observations of a relationship between cancer and AD, we focused on cancer kinases for targeting neurodegeneration, highlighting the importance of targeting the intracellular pathways at the intersection between cell metabolism control/duplication, the inhibition of which may stop a progression in neurodegeneration.

Pharmacological approaches to mitigate neuroinflammation in Alzheimer's disease

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases characterized by the formation of extracellular amyloid beta (Aβ) plaques and intracellular neurofibrillary tangles (NFTs). Growing evidence suggested that there is an association between neuronal dysfunction and neuroinflammation (NI) in AD, coordinated by the chronic activation of astrocytes and microglial cells along with the subsequent excessive generation of the proinflammatory molecule. Therefore, a better understanding of the relationship between the nervous and immune systems is important in order to delay or avert the neurodegenerative events of AD. The inflammatory/immune pathways and the mechanisms to control these pathways may provide a novel arena to develop new drugs in order to target NI in AD. In this review, we represent the influence of cellular mediators which are involved in the NI process, with regards to the progression of AD. We also discuss the processes and the current status of multiple anti-inflammatory agents which are used in AD and have gone through or going through clinical trials. Moreover, new prospects for targeting NI in the development of AD drugs have also been highlighted.

A selective p38α/β MAPK inhibitor alleviates neuropathology and cognitive impairment, and modulates microglia function in 5XFAD mouse

Background

Chronic neuroinflammation, aggressive amyloid beta (Aβ) deposition, neuronal cell loss, and cognitive impairment are pathological presentations of Alzheimer’s disease (AD). Therefore, resolution of neuroinflammation and inhibition of Aβ-driven pathology have been suggested to be important strategies for AD therapy. Previous efforts to prevent AD progression have identified p38 mitogen-activated protein kinases (MAPKs) as a promising target for AD therapy. Recent studies showed pharmacological inhibition of p38α MAPK improved memory impairment in AD mouse models.

Methods

In this study, we used an AD mouse model, 5XFAD, to explore the therapeutic potential of NJK14047 which is a novel, selective p38α/β MAPK inhibitor. The mice were injected with 2.5 mg/kg NJK14047 or vehicle every other day for 3 months. Morris water maze task and histological imaging analysis were performed. Protein and mRNA expression levels were measured using immunoblotting and qRT-PCR, respectively. In vitro studies were conducted to measure the cytotoxicity of microglia- and astrocyte-conditioned medium on primary neurons using the MTT assay and TUNEL assay.

Results

NJK14047 treatment downregulated phospho-p38 MAPK levels, decreased the amount of Aβ deposits, and reduced spatial learning memory loss in 9-month-old 5XFAD mice. While the pro-inflammatory conditions were decreased, the expression of alternatively activated microglial markers and microglial phagocytic receptors was increased. Furthermore, NJK14047 treatment reduced the number of degenerating neurons labeled with Fluoro-Jade B in the brains of 5XFAD mice. The neuroprotective effect of NJK14047 was further confirmed by in vitro studies.

Conclusion

Taken together, a selective p38α/β MAPK inhibitor NJK14047 successfully showed therapeutic effects for AD in 5XFAD mice. Based on our data, p38 MAPK inhibition is a potential strategy for AD therapy, suggesting NJK14047 as one of the promising candidates for AD therapeutics targeting p38 MAPKs.

Pharmacological inhibition of p38 potentiates antimicrobial peptide TP4-induced cell death in glioblastoma cells

Glioblastoma is the most common and deadly type of brain cancer. The poor prognosis may be largely attributed to inadequate disease response to current chemotherapeutic agents. Activation of p38 is associated with deleterious outcomes in glioblastoma patients, as its signaling mediates chemoresistance mechanisms. Antimicrobial peptide tilapia piscidin (TP) 4 was identified from Nile tilapia (Oreochromis niloticus) and exhibits strong bactericidal effects on Gram-positive and Gram-negative bacteria. TP4 also has anticancer activity toward human triple-negative breast cancer cells and glioblastoma cells. In the present study, we tested the cytotoxic effects of combined TP4 and p38 inhibitors on glioblastoma U251 cells. We found that the combination of TP4 and p38 inhibitors (SB202190 and VX-745) enhanced cytotoxicity in U251 glioblastoma cells but not noncancerous neural cells. Cytotoxicity from the combination treatments proceeded via necrosis and not apoptosis. Mechanistically, SB202190 potentiated TP4-induced mitochondrial dysfunction, reactive oxygen species generation and unbalanced antioxidant status, which resulted in necrotic cell death. Thus, we demonstrated for the first time that combinations of TP4 and p38 inhibitors have the potential to preferentially target glioblastoma cells, while sparing noncancerous neural cells.

Losmapimod Protected Epileptic Rats From Hippocampal Neuron Damage Through Inhibition of the MAPK Pathway

Objective: This research aimed to validate the therapeutic effect of losmapimod and explore the underlying mechanism in its treatment of epilepsy.

Methods: A rat model of epilepsy was constructed with an injection of pilocarpine. Microarray analysis was performed to screen aberrantly expressed mRNAs and activated signaling pathways between epileptic rats and normal controls. A TdT-mediated dUTP nick-end labeling (TUNEL) assay was used to identify cell apoptosis. Hippocampal cytoarchitecture was visualized with Nissl staining. The secretion of inflammatory factors as well as the marker proteins in the mitogen-activated protein kinase (MAPK) pathway were detected by Western blot. A Morris water maze navigation test evaluated the rats’ cognitive functions.

Results: Activation of the MAPK signaling pathway was observed in epilepsy rats. A decrease in the MAPK phosphorylation level by application of losmapimod protected against epilepsy by reducing neuron loss. Losmapimod effectively improved memory, reduced the frequency of seizures, protected the neuron from damage, and limited the apoptosis of neurons in epilepsy rats.

Conclusion: The application of losmapimod could partly reverse the development of epilepsy.

A Selective and Brain Penetrant p38αMAPK Inhibitor Candidate for Neurologic and Neuropsychiatric Disorders That Attenuates Neuroinflammation and Cognitive Dysfunction

The p38αMAPK is a serine/threonine protein kinase and a key node in the intracellular signaling networks that transduce and amplify stress signals into physiological changes. A preponderance of preclinical data and clinical observations established p38αMAPK as a brain drug discovery target involved in neuroinflammatory responses and synaptic dysfunction in multiple degenerative and neuropsychiatric brain disorders. We summarize the discovery of highly selective, brain-penetrant, small molecule p38αMAPK inhibitors that are efficacious in diverse animal models of neurologic disorders. A crystallography and pharmacoinformatic approach to fragment expansion enabled the discovery of an efficacious hit. The addition of secondary pharmacology screens to refinement delivered lead compounds with improved selectivity, appropriate pharmacodynamics, and efficacy. Safety considerations and additional secondary pharmacology screens drove optimization that delivered the drug candidate MW01-18-150SRM (MW150), currently in early stage clinical trials.