Anti-inflammatory effects of ladostigil and its metabolites in aged rat brain and in microglial cells

Ladostigil Reduces the Adenoside Triphosphate/Lipopolysaccharide-Induced Secretion of Pro-Inflammatory Cytokines from Microglia and Modulate-Immune Regulators, TNFAIP3, and EGR1

Treatment of aging rats for 6 months with ladostigil (1 mg/kg/day) prevented a decline in recognition and spatial memory and suppressed the overexpression of gene-encoding pro-inflammatory cytokines, TNFα, IL1β, and IL6 in the brain and microglial cultures. Primary cultures of mouse microglia stimulated by lipopolysaccharides (LPS, 0.75 µg/mL) and benzoyl ATPs (BzATP) were used to determine the concentration of ladostigil that reduces the secretion of these cytokine proteins. Ladostigil (1 × 10-11 M), a concentration compatible with the blood of aging rats in, prevented memory decline and reduced secretion of IL1β and IL6 by ≈50%. RNA sequencing analysis showed that BzATP/LPS upregulated 25 genes, including early-growth response protein 1, (Egr1) which increased in the brain of subjects with neurodegenerative diseases. Ladostigil significantly decreased Egr1 gene expression and levels of the protein in the nucleus and increased TNF alpha-induced protein 3 (TNFaIP3), which suppresses cytokine release, in the microglial cytoplasm. Restoration of the aberrant signaling of these proteins in ATP/LPS-activated microglia in vivo might explain the prevention by ladostigil of the morphological and inflammatory changes in the brain of aging rats.

Coordinated Transcriptional Waves Define the Inflammatory Response of Primary Microglial Culture

The primary role of microglia is to maintain homeostasis by effectively responding to various disturbances. Activation of transcriptional programs determines the microglia's response to external stimuli. In this study, we stimulated murine neonatal microglial cells with benzoyl ATP (bzATP) and lipopolysaccharide (LPS), and monitored their ability to release pro-inflammatory cytokines. When cells are exposed to bzATP, a purinergic receptor agonist, a short-lived wave of transcriptional changes, occurs. However, only combining bzATP and LPS led to a sustainable and robust response. The transcriptional profile is dominated by induced cytokines (e.g., IL-1α and IL-1β), chemokines, and their membrane receptors. Several abundant long noncoding RNAs (lncRNAs) are induced by bzATP/LPS, including Ptgs2os2, Bc1, and Morrbid, that function in inflammation and cytokine production. Analyzing the observed changes through TNF (Tumor necrosis factor) and NF-κB (nuclear factor kappa light chain enhancer of activated B cells) pathways confirmed that neonatal glial cells exhibit a distinctive expression program in which inflammatory-related genes are upregulated by orders of magnitude. The observed capacity of the microglial culture to activate a robust inflammatory response is useful for studying neurons under stress, brain injury, and aging. We propose the use of a primary neonatal microglia culture as a responsive in vitro model for testing drugs that may interact with inflammatory signaling and the lncRNA regulatory network.

IKZF3 modulates cerebral ischemia/reperfusion injury by inhibiting neuroinflammation

Neuroinflammation is a key mediator to the pathogenic cascades induced by cerebral ischemia-reperfusion (I/R) injury. IKZF3, a key zinc finger transcription factor in the Ikaros family, has already been shown to modulate a wide range of cell functions and the production of inflammatory mediators. However, the effects of IKZF3 on inflammation and the potential mechanism after cerebral I/R injury remain unclear. In this study, we evaluated the effect of IKZF3 on HT-22 cells under oxygen-glucose deprivation and reoxygenation (OGD/R) in vitro and in mice with MACO in vivo. We found that IKZF3 expression peaked at 12 h after MCAO and OGD/R, and there was high expression of IKZF3 in brain tissues and HT-22 cells. IKZF3 knockdown exacerbated the damage by OGD-induced HT-22 cells injury and MCAO-induced brain injury in mice by regulating the production of inflammatory factors, which promoted the phosphorylation and nuclear transfer of NF-ĸB and may bind with NF-ĸB-p65 in vivo and in vitro. Our results suggested that IKZF3 may provide a new target in improve neurological recovery and reducing neuroinflammation after cerebral I/R injury.

Oxidative Stress and Its Modulation by Ladostigil Alter the Expression of Abundant Long Non-Coding RNAs in SH-SY5Y Cells

Neurodegenerative disorders, brain injury, and the decline in cognitive function with aging are accompanied by a reduced capacity of cells in the brain to cope with oxidative stress and inflammation. In this study, we focused on the response to oxidative stress in SH-SY5Y, a human neuroblastoma cell line. We monitored the viability of the cells in the presence of oxidative stress. Such stress was induced by hydrogen peroxide or by Sin1 (3-morpholinosydnonimine) that generates reactive oxygen and nitrogen species (ROS and RNS). Both stressors caused significant cell death. Our results from the RNA-seq experiments show that SH-SY5Y cells treated with Sin1 for 24 h resulted in 94 differently expressed long non-coding RNAs (lncRNAs), including many abundant ones. Among the abundant lncRNAs that were upregulated by exposing the cells to Sin1 were those implicated in redox homeostasis, energy metabolism, and neurodegenerative diseases (e.g., MALAT1, MIAT, GABPB1-AS1, NEAT1, MIAT, GABPB1-AS1, and HAND2-AS1). Another group of abundant lncRNAs that were significantly altered under oxidative stress included cancer-related SNHG family members. We tested the impact of ladostigil, a bifunctional reagent with antioxidant and anti-inflammatory properties, on the lncRNA expression levels. Ladostigil was previously shown to enhance learning and memory in the brains of elderly rats. In SH-SY5Y cells, several lncRNAs involved in transcription regulation and the chromatin structure were significantly induced by ladostigil. We anticipate that these poorly studied lncRNAs may act as enhancers (eRNA), regulating transcription and splicing, and in competition for miRNA binding (ceRNA). We found that the induction of abundant lncRNAs, such as MALAT1, NEAT-1, MIAT, and SHNG12, by the Sin1 oxidative stress paradigm specifies only the undifferentiated cell state. We conclude that a global alteration in the lncRNA profiles upon stress in SH-SY5Y may shift cell homeostasis and is an attractive in vitro system to characterize drugs that impact the redox state of the cells and their viability.

Monoamine Oxidase-B Inhibitor Reduction in Pro-Inflammatory Cytokines Mediated by Inhibition of cAMP-PKA/EPAC Signaling

Mucosal epithelial cell integrity is an important component of innate immunity and it protects the host from an environment rich in microorganisms. Virulence factors from Gram-negative bacteria [e.g. lipopolysaccharide (LPS)] induce significant pro-inflammatory cytokine expression. Monoamine oxidase (MAO) inhibitors reduce cytokine expression in a variety of inflammatory models and may therefore have therapeutic potential for a number of inflammatory diseases. We tested the anti-inflammatory therapeutic potential of a recently developed reversible MAO-B inhibitor (RG0216) with reduced transport across the blood–brain barrier. In an epithelial cell culture model, RG0216 significantly decreased LPS-induced interleukin (IL)-6 and IL-1β gene and protein expression and was as effective as equimolar concentrations of deprenyl (an existing irreversible MAO-B inhibitor). Hydrogen peroxide and modulating dopamine receptor signaling had no effect on cytokine expression. We showed that LPS-induced expression of IL-6 and IL-1β was cAMP dependent, that IL-6 and IL-1β expression were induced by direct cAMP activation (forskolin) and that RG0216 and deprenyl effectively reduced cAMP-mediated cytokine expression. Targeted protein kinase A (PKA) and Exchange Protein Activated by cAMP (EPAC) activation regulated IL-6 and IL-1β expression, albeit in different ways, but both cytokines were effectively decreased with RG0216. RG0216 reduction of LPS-induced cytokine expression occurred by acting downstream of the cAMP-PKA/EPAC signaling cascade. This represents a novel mechanism by which MAO-B selective inhibitors regulate LPS-induced IL-6 and IL-1β expression.

Ladostigil Attenuates Induced Oxidative Stress in Human Neuroblast-like SH-SY5Y Cells

A hallmark of the aging brain is the robust inflammation mediated by microglial activation. Pathophysiology of common neurodegenerative diseases involves oxidative stress and neuroinflammation. Chronic treatment of aging rats by ladostigil, a compound with antioxidant and anti-inflammatory function, prevented microglial activation and learning deficits. In this study, we further investigate the effect of ladostigil on undifferentiated SH-SY5Y cells. We show that SH-SY5Y cells exposed to acute (by H₂O₂) or chronic oxidative stress (by Sin1, 3-morpholinosydnonimine) induced apoptotic cell death. However, in the presence of ladostigil, the decline in cell viability and the increase of oxidative levels were partially reversed. RNA-seq analysis showed that prolonged oxidation by Sin1 resulted in a simultaneous reduction of the expression level of endoplasmic reticulum (ER) genes that participate in proteostasis. By comparing the differential gene expression profile of Sin1 treated cells to cells incubated with ladostigil before being exposed to Sin1, we observed an over-expression of Clk1 (Cdc2-like kinase 1) which was implicated in psychophysiological stress in mice and Alzheimer’s disease. Ladostigil also suppressed the expression of Ccpg1 (Cell cycle progression 1) and Synj1 (Synaptojanin 1) that are involved in ER-autophagy and endocytic pathways. We postulate that ladostigil alleviated cell damage induced by oxidation. Therefore, under conditions of chronic stress that are observed in the aging brain, ladostigil may block oxidative stress processes and consequently reduce neurotoxicity.

Recent Updates in the Alzheimer's Disease Etiopathology and Possible Treatment Approaches: A Narrative Review of Current Clinical Trials

BACKGROUND

Alzheimer's disease (AD) is the most frequent subtype of incurable neurodegenerative dementias and its etiopathology is still not clearly elucidated.

OBJECTIVE

Outline the ongoing clinical trials (CTs) in the field of AD, in order to find novel master regulators.

METHODS

We strictly reviewed all scientific reports from Clinicaltrials.gov and PubMed databases from January 2010 to January 2019. The search terms were "Alzheimer's disease" or "dementia" and "medicine" or "drug" or "treatment" and "clinical trials" and "interventions". Manuscripts that met the objective of this study were included for further evaluations.

RESULTS

Drug candidates have been categorized into two main groups including antibodies, peptides or hormones (such as Ponezumab, Interferon β-1a, Solanezumab, Filgrastim, Levemir, Apidra, and Estrogen), and naturally-derived ingredients or small molecules (such as Paracetamol, Ginkgo, Escitalopram, Simvastatin, Cilostazo, and Ritalin-SR). The majority of natural candidates acted as anti-inflammatory or/and anti-oxidant and antibodies exert their actions via increasing amyloid-beta (Aβ) clearance or decreasing Tau aggregation. Among small molecules, most of them that are present in the last phases act as specific antagonists (Suvorexant, Idalopirdine, Intepirdine, Trazodone, Carvedilol, and Risperidone) or agonists (Dextromethorphan, Resveratrol, Brexpiprazole) and frequently ameliorate cognitive dysfunctions.

CONCLUSION

The presences of a small number of candidates in the last phase suggest that a large number of candidates have had an undesirable side effect or were unable to pass essential eligibility for future phases. Among successful treatment approaches, clearance of Aβ, recovery of cognitive deficits, and control of acute neuroinflammation are widely chosen. It is predicted that some FDA-approved drugs, such as Paracetamol, Risperidone, Escitalopram, Simvastatin, Cilostazoand, and Ritalin-SR, could also be used in off-label ways for AD. This review improves our ability to recognize novel treatments for AD and suggests approaches for the clinical trial design for this devastating disease in the near future.

Monoamine Oxidase Inhibitors: A Review of Their Anti-Inflammatory Therapeutic Potential and Mechanisms of Action

Chronic inflammatory diseases are debilitating, affect patients' quality of life, and are a significant financial burden on health care. Inflammation is regulated by pro-inflammatory cytokines and chemokines that are expressed by immune and non-immune cells, and their expression is highly controlled, both spatially and temporally. Their dysregulation is a hallmark of chronic inflammatory and autoimmune diseases. Significant evidence supports that monoamine oxidase (MAO) inhibitor drugs have anti-inflammatory effects. MAO inhibitors are principally prescribed for the management of a variety of central nervous system (CNS)-associated diseases such as depression, Alzheimer's, and Parkinson's; however, they also have anti-inflammatory effects in the CNS and a variety of non-CNS tissues. To bolster support for their development as anti-inflammatories, it is critical to elucidate their mechanism(s) of action. MAO inhibitors decrease the generation of end products such as hydrogen peroxide, aldehyde, and ammonium. They also inhibit biogenic amine degradation, and this increases cellular and pericellular catecholamines in a variety of immune and some non-immune cells. This decrease in end product metabolites and increase in catecholamines can play a significant role in the anti-inflammatory effects of MAO inhibitors. This review examines MAO inhibitor effects on inflammation in a variety of in vitro and in vivo CNS and non-CNS disease models, as well as their anti-inflammatory mechanism(s) of action.

Monoamine Oxidase Inhibitors: From Classic to New Clinical Approaches

Monoamine oxidases (MAOs) are involved in the oxidative deamination of different amines and neurotransmitters. This pointed them as potential targets for several disorders and along the last 70 years a wide variety of MAO inhibitors have been developed as successful drugs for the treatment of complex diseases, being the first drugs approved for depression in the late 1950s. The discovery of two MAO isozymes (MAO-A and B) with different substrate selectivity and tissue expression patterns led to novel therapeutic approaches and to the development of new classes of inhibitors, such as selective irreversible and reversible MAO-B inhibitors and reversible MAO-A inhibitors. Significantly, MAO-B inhibitors constitute a widely studied group of compounds, some of them approved for the treatment of Parkinson's disease. Further applications are under development for the treatment of Alzheimer's disease, amyotrophic lateral sclerosis, and cardiovascular diseases, among others. This review summarizes the most important aspects regarding the development and clinical use of MAO inhibitors, going through mechanistic and structural details, new indications, and future perspectives. Monoamine oxidases (MAOs) catalyze the oxidative deamination of different amines and neurotransmitters. The two different isozymes, MAO-A and MAO-B, are located at the outer mitochondrial membrane in different tissues. The enzymatic reaction involves formation of the corresponding aldehyde and releasing hydrogen peroxide (H₂O₂) and ammonia or a substituted amine depending on the substrate. MAO's role in neurotransmitter metabolism made them targets for major depression and Parkinson's disease, among other neurodegenerative diseases. Currently, these compounds are being studied for other diseases such as cardiovascular ones.

Effect of ladostigil treatment of aging rats on gene expression in four brain areas associated with regulation of memory

Episodic and spatial memory decline in aging and are controlled by the hippocampus, perirhinal, frontal and parietal cortices and the connections between them. Ladostigil, a drug with antioxidant and anti-inflammatory activity, was shown to prevent the loss of episodic and spatial memory in aging rats. To better understand the molecular effects of aging and ladostigil on these brain regions we characterized the changes in gene expression using RNA-sequencing technology in rats aged 6 and 22 months. We found that the changes induced by aging and chronic ladostigil treatment were brain region specific. In the hippocampus, frontal and perirhinal cortex, ladostigil decreased the overexpression of genes regulating calcium homeostasis, ion channels and those adversely affecting synaptic function. In the parietal cortex, ladostigil increased the expression of several genes that provide neurotrophic support, while reducing that of pro-apoptotic genes and those encoding pro-inflammatory cytokines and their receptors. Ladostigil also decreased the expression of axonal growth inhibitors and those impairing mitochondrial function. Together, these actions could explain the protection by ladostigil against age-related memory decline.

Controlled ozone therapy modulates the neurodegenerative changes in the frontal cortex of the aged albino rat

Aging is a normal process associated with neurodegenerative changes resulting in decline of cognitive and motor functions. Oxidative stress plays an important role. Controlled ozone (O₃) therapy has been proved to induce oxidative preconditioning thus reversing oxidative stress. To the best of our knowledge, this research is the first attempt to investigate whether the antioxidant properties of O₃ can ameliorate age-associated structural alterations of the cerebral cortex. Ozone administration (at a dose of 0.7mg/kg intraperitonially, three times a week for eight weeks) produced significant downregulation of tissue malondialdehyde (MDA) and upregulation of glutathione, superoxide dismutase (SOD) and catalase (CAT) within the frontal cortex of aged rats. Sections of the frontal cortex from adult and aged rats were stained with hematoxylin and eosin and analyzed using light microscopy. In addition, quantitative immunohistochemical assessments of the expression of inducible nitric oxide synthase (iNOS), caspase-3, glial fibrillary acidic protein (GFAP), Ki67 and acetylcholinesterase (AChE) were performed. Our results revealed the beneficial effect of O₃ in improving the neurodegenerative changes of the cerebral cortex of aged rats. Moreover, this study clarified that O₃ exerted its effects via reducing oxidative stress, apoptosis, gliosis as well as improving neurogenesis and cholinergic plasticity. This work added to the previously proved aging - associated neurodegenerative effects and provided a new insight into the promising role of O₃ to ameliorate these effects.

Low-dose ladostigil for mild cognitive impairment: A phase 2 placebo-controlled clinical trial

OBJECTIVE

Ladostigil reduces oxidative stress and microglial activation in aging rats. We assessed its safety and potential efficacy in a 3-year, randomized, double-blind, placebo-controlled phase 2 clinical trial in patients with mild cognitive impairment (MCI) and medial temporal lobe atrophy.

METHODS

Patients 55 to 85 years of age with MCI, Clinical Dementia Rating (CDR) score of 0.5, Mini-Mental State Examination (MMSE) score >24, Wechsler Memory Scale-Revised Verbal Paired Associates I score ≤18, and Medial Temporal Lobe Atrophy Scale score >1 were stratified by APOE ε4 genotype and randomly assigned (1:1) to ladostigil 10 mg/d or placebo. Primary outcomes were safety and onset of Alzheimer disease dementia. Secondary endpoints were Neuropsychological Test Battery (NTB) composite, Disability Assessment in Dementia (DAD), and Geriatric Depression Scale (GDS) scores. Exploratory outcomes were NTB component, CDR, and MMSE scores. Biomarkers included MRI-derived whole-brain, hippocampus, and entorhinal cortex volumes.

RESULTS

Two hundred ten patients from 15 sites in Austria, Germany, and Israel were randomly allocated to placebo (107 patients) or ladostigil (103 patients). After 36 months, 21 of 103 patients on placebo and 14 of 99 patients receiving ladostigil progressed to Alzheimer disease (log-rank test p = 0.162). There were no significant effects on the NTB composite, DAD, or GDS score. Whole-brain and hippocampus volumes decreased more in the placebo than in the ladostigil group (whole brain, p = 0.025, Cohen d = 0.43; hippocampus, p = 0.043, d = 0.43). Serious adverse events were reported by 28 of 107 patients treated with placebo and 26 of 103 with ladostigil.

CONCLUSION

Ladostigil was safe and well tolerated but did not delay progression to dementia. Its association with reduced brain and hippocampus volume loss suggests a potential effect on atrophy.

CLINICALTRIALSGOV IDENTIFIER

NCT01429623.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that for patients with MCI and medial temporal lobe atrophy, ladostigil did not significantly decrease the risk of the development of Alzheimer disease.

Neuroinflammation Signaling Modulated by ASS234, a Multitarget Small Molecule for Alzheimer's Disease Therapy

There is clear evidence that neuroinflammation plays a crucial role in the pathogenesis of Alzheimer's disease. Consequently, modulating the inflammatory environment in brain has become a powerful and attractive strategy to deal with Alzheimer's disease physiopathology. In spite of the neuroprotective capacity shown by ASS234, a multitarget propargylamine targeted for Alzheimer's disease, its regulation of inflammation in the brain still remains unexplored. Therefore, we aimed to characterize possible anti-inflammatory effects of ASS234, counteracting induced inflammatory effects in RAW 264.7 cells and evaluating seven neuroinflammation related genes expression profiling (IL-6, IL-10, IL1β, NF-κB, TNF-α, TNFR1, and TGF-β), after ASS234 (5 μM) treatment in SH-SY5Y cells. The analysis of the obtained fold changes lead us to conclude that ASS234 may play an important role facing the neuroinflammatory environment in Alzheimer's disease pathology.

Design, synthesis and evaluation of indole derivatives as multifunctional agents against Alzheimer's disease

A series of indole derivatives was designed and synthesised to improve on activity and circumvent pharmacokinetic limitations experienced with the structurally related compound, ladostigil. The compounds consisted of a propargylamine moiety (a known MAO inhibitor and neuroprotector) at the N1 position and a ChE inhibiting diethyl-carbamate/urea moiety at the 5 or 6 position of the indole ring. In order to prevent or slow down the in vivo hydrolysis and deactivation associated with the carbamate function of ladostigil, a urea moeity was incorporated into selected compounds to obtain more metabolically stable structures. The majority of the synthesised compounds showed improved MAO-A inhibitory activity compared to ladostigil. The compounds possessing the propargylamine moiety showed good MAO-B inhibitory activity with 6 and 8 portraying IC₅₀ values between 14-20 fold better than ladostigil. The ChE assay results indicated that the compounds have non-selective inhibitory activities on eeAChE and eqBuChE regardless of the type or position of substitution (IC₅₀: 2-5 μM). MAO-A and MAO-B docking results showed that the propargylamine moiety was positioned in close proximity to the FAD cofactor suggesting that the good inhibitory activity may be attributed to the propargylamine moiety and irreversible inhibition as confirmed in the reversibility studies. Docking results also indicated that the compounds have interactions with important amino acids in the AChE and BuChE catalytic sites. Compound 6 was the most potent multifunctional agent showing better inhibitory activity than ladostigil in vitro on all enzymes tested (hMAO-A IC₅₀ = 4.31 μM, hMAO-B IC₅₀ = 2.62 μM, eeAChE IC₅₀ = 3.70 μM, eqBuChE IC₅₀ = 2.82 μM). Chemical stability tests confirmed the diethyl-urea containing compound 6 to be more stable than its diethyl-carbamate containing counterpart compound 8. Compound 6 also exerted significant neuroprotection (52.62% at 1 μM) against MPP⁺ insult to SH-SY5Y neural cells and has good in silico predicted ADMET properties. The favourable neuronal enzyme inhibitory activity, likely improved pharmacokinetic properties in vivo and the potent neuroprotective ability of compound 6 make it a promising compound for further development.

M30 Antagonizes Indoleamine 2,3-Dioxygenase Activation and Neurodegeneration Induced by Corticosterone in the Hippocampus

Monoamine oxidases (MAO), downstream targets of glucocorticoid, maintain the turnover and homeostasis of monoamine neurotransmitters; yet, its pathophysiological role in monoamine deficiency, oxidative stress and neuroinflammation remains controversial. Protective effects of M30, a brain selective MAO inhibitor with iron-chelating antioxidant properties, have been shown in models of neurodegenerative diseases. This study aims to examine the neuroprotective mechanism of M30 against depressive-like behavior induced by corticosterone (CORT). Sprague-Dawley rats were given CORT subcutaneous injections with or without concomitant M30 administration for two weeks. CORT-treated rats exhibited depressive-like behavior with significant elevated levels of MAO activities, serotonin turnover, oxidative stress, neuroinflammation and apoptosis in the hippocampus with significant losses of synaptic proteins when compared to the control. The expression and activity of cytokine-responsive indoleamine 2,3-dioxygenase (IDO-1), a catabolic enzyme of serotonin and tryptophan, was significantly increased in the CORT-treated group with lowered levels of serotonin. Besides, CORT markedly reduced dendritic length and spine density. Remarkably, M30 administration neutralized the aberrant changes in the hippocampus and prevented the induction of depressive-like behavior induced by CORT. Our results suggest that M30 is neuroprotective against CORT-induced depression targeting elevated MAO activities that cause oxidative stress and neuroinflammation, resulting in IDO-1 activation, serotonin deficiency and neurodegeneration.

Neuroprotective effects of multifaceted hybrid agents targeting MAO, cholinesterase, iron and β-amyloid in ageing and Alzheimer's disease

Alzheimer's disease (AD) is accepted nowadays as a complex neurodegenerative disorder with multifaceted cerebral pathologies, including extracellular deposition of amyloid β peptide-containing plaques, intracellular neurofibrillary tangles, progressive loss of cholinergic neurons, metal dyshomeostasis, mitochondrial dysfunction, neuroinflammation, glutamate excitoxicity, oxidative stress and increased MAO enzyme activity. This may explain why it is currently widely accepted that a more effective therapy for AD would result from the use of multifunctional drugs, which may affect more than one brain target involved in the disease pathology. The current review will discuss the potential benefits of novel multimodal neuroprotective, brain permeable drugs, recently developed by Youdim and collaborators, as a valuable therapeutic approach for AD treatment. The pharmacological and neuroprotective properties of these multitarget-directed ligands, which target MAO enzymes, the cholinergic system, iron accumulation and amyloid β peptide generation/aggregation are described, with a special emphasis on their potential therapeutic value for ageing and AD-associated cognitive functions. This review is conceived as a tribute to the broad neuropharmacology work of Professor Moussa Youdim, Professor Emeritus in the Faculty of Medicine and Director of Eve Topf Center of Excellence in Technion-Israel Institute of Technology, and Chief Scientific Officer of ABITAL Pharma Pipeline Ltd., at the occasion of his 75th birthday.

LINKED ARTICLES

This article is part of a themed section on Updating Neuropathology and Neuropharmacology of Monoaminergic Systems. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.13/issuetoc.

Neuroprotective and neurorestorative potential of propargylamine derivatives in ageing: focus on mitochondrial targets

The mitochondrial theory of ageing proposes that accumulation of damage to mitochondrial function and DNA mutation lead to ageing of humans and animals. It has been suggested that mitochondria play dynamic roles in regulating synaptogenesis and morphological/functional responses of synaptic activity, and thus, deteriorating of mitochondrial function (e.g., deficits of the mitochondrial respiratory enzymes, reduced calcium influx, increased accumulation of mitochondrial DNA defects/apoptotic proteins and impairment of mitochondrial membrane potential) can lead to severe neuronal energy deficit, and in the long run, to modifications in neuronal synapses and neurodegeneration in the ageing brain. Hence, considering the mechanisms by which mitochondrial impairment can lead to neuronal death, the development of neuroprotective molecules that target various mitochondrial pathogenic processes can be effective in the treatment of ageing and age-related neurodegenerative diseases. This review addresses several aspects of the neuroprotective effects of propargylamine derivatives (e.g., the monoamine oxidase-B inhibitors, selegiline and rasagiline and the multifunctional drugs, ladostigil, M30 and VAR10303) in ageing with a special focus on mitochondrial molecular protective mechanisms.

Protective roles of N-benzylcinnamide on cortex and hippocampus of aged rat brains

Brain aging has been associated with oxidative stress leading to inflammation and apoptosis. The protective effects and underlying mechanisms of N-benzylcinnamide (PT-3), purified from Piper submultinerve, on brains of 90-week-old Wistar rats were investigated following daily intraperitoneal injection with 1.5 mg of PT-3/kg of body weight for 15 days. PT-3 treatment improved spatial learning and memory of aged rats and caused significant changes in brain frontal cortex, hippocampus, and temporal cortex in parameters associated with oxidative stress (decreased reactive oxygen species production and iNOS and nNOS levels), inflammation (reduced levels of IL-1β and IL-6), apoptosis (reduced levels of Bax and activated caspase-3, and elevated level of Bcl-2), and signaling pathways related to inflammation and apoptosis (decreased amounts of phospho-JNK and -p38, increased phospho-Akt level and no change in phospho-ERK1/2 content) compared to controls. PT-3 treatment also inhibited aged rat brain AChE activity. These results suggest that PT-3 with its intrinsic antioxidant and AChE inhibitory properties has therapeutic potential in ameliorating, in part, age-associated damages to the brain.

Dose-limiting inhibition of acetylcholinesterase by ladostigil results from the rapid formation and fast hydrolysis of the drug-enzyme complex formed by its major metabolite, R-MCPAI

Ladostigil is a pseudo reversible inhibitor of acetylcholinesterase (AChE) that differs from other carbamates in that the maximal enzyme inhibition obtainable does not exceed 50-55%. This could explain the low incidence of cholinergic adverse effects induced by ladostigil in rats and human subjects. The major metabolite, R-MCPAI is believed to be responsible for AChE inhibition by ladostigil in vivo. Therefore we determined whether the ceiling in AChE inhibition resulted from a limit in the metabolism of ladostigil to R-MCPAI by liver microsomal enzymes, or from the kinetics of enzyme inhibition by R-MCPAI. Ladostigil reduces TNF-α in lipopolysaccharide-activated microglia. In vivo, it may also reduce pro-inflammatory cytokines by inhibiting AChE and increasing the action of ACh on macrophages and splenic lymphocytes. We also assessed the contribution of AChE inhibition in the spleen of LPS-injected mice to the anti-inflammatory effect of ladostigil. As in other species, AChE inhibition by ladostigil in spleen, brain and plasma did not exceed 50-55%. Since levels of R-MCPAI increased with increasing doses of ladostigil we concluded that there was no dose or rate limitation of metabolism. The kinetics of enzyme inhibition by R-MCPAI are characterized by a rapid formation of the drug-enzyme complex and fast hydrolysis which limits the attainable degree of AChE inhibition. Ladostigil and its metabolites (1-100 nM) decreased TNF-α in lipopolysaccharide-activated macrophages. Ladostigil (5 and 10mg/kg) also reduced TNF-α in the spleen after injection of lipopolysaccharide in mice. However, AChE inhibition contributed to the anti-inflammatory effect only at a dose of 10mg/kg.

Functional connectivity in prenatally stressed rats with and without maternal treatment with ladostigil, a brain-selective monoamine oxidase inhibitor

Stress during pregnancy in humans is known to be a risk factor for neuropsychiatric disorders in the offspring. Prenatal stress in rats caused depressive-like behavior that was restored to that of controls by maternal treatment with ladostigil (8.5 mg/kg per day), a brain-selective monoamine oxidase (MAO) inhibitor that prevented increased anxiety-like behavior in stressed mothers. Ladostigil inhibited maternal striatal MAO-A and -B by 45-50% at the time the pups were weaned. Using resting state-functional connectivity magnetic resonance imaging on rat male offspring of control mothers, and mothers stressed during gestation with and without ladostigil treatment, we identified neuronal connections that differed between these groups. The percentage of significant connections within a predefined predominantly limbic network in control rats was 23.3 within the right and 22.0 within the left hemisphere. Prenatal stress disturbed hemispheric symmetry, resulting in 30.2 and 21.6%, significant connections in the right and left hemispheres, respectively, but this was fully restored in the maternal ladostigil group to 24.6% in both hemispheres. All connections that were modified in prenatally stressed rats and restored by maternal drug treatment were associated with the dopaminergic system. Specifically, we observed that restoration of the connections of the right nucleus accumbens shell with frontal areas, the cingulate, septum and motor and sensory cortices, and those of the right globus pallidus with the infra-limbic and the dentate gyrus, were most important for prevention of depressive-like behavior.

Dose-dependent effects of ladostigil on microglial activation and cognition in aged rats

The current study determined the effects of chronic treatment of aging rats with ladostigil, a cholinesterase (ChE) and monoamine oxidase (MAO) inhibitor, at doses of 1 and 8.5 mg/kg/day, on novel object recognition (NOR) and reference memory in the Morris water maze (MWM). A dose of (1 mg/kg/day) did not inhibit ChE or MAO but prevented the loss of NOR and reference memory in the MWM that occurs at 20.5 months of age. This anti-aging effect was associated with a reduction in the expression of CD11b, a marker of microglial activation, in the fornix and parietal cortex and restoration of microglial morphology to that in young adult rats. Ladostigil (8.5 mg/kg/day) inhibited brain ChE by ≈30 % and MAO A and B by 55-59 %, and had a similar, or greater effect than the low dose on microglia, but was less effective in preventing the decline in NOR. Ladostigil (8.5 mg/kg/day) may have caused too much cortical ChE inhibition and acetylcholine elevation at 16 months when NOR was intact. In support of this suggestion we showed that acute administration of ladostigil (8.5 mg/kg) worsened NOR at this age. However, at 20 months, when NOR was impaired and brain acetylcholine levels are 40 % below normal, ladostigil (8.5 mg/kg) reversed the memory deficit.

CONCLUSION

Ladostigil (1 mg/kg/day) prevents the development of age-related memory deficits by a combination of immunomodulatory and antioxidant effects. A dose causing 30 % ChE inhibition is necessary in order to reverse existing memory deficits at 20 months of age.