Beneficial behavioral, neurochemical and molecular effects of 1-(R)-aminoindan in aged mice

Monoamine Oxidase-B Inhibitors for the Treatment of Parkinson's Disease: Past, Present, and Future

Monoamine oxidase-B (MAO-B) inhibitors are commonly used for the symptomatic treatment of Parkinson’s disease (PD). MAO-B inhibitor monotherapy has been shown to be effective and safe for the treatment of early-stage PD, while MAO-B inhibitors as adjuvant drugs have been widely applied for the treatment of the advanced stages of the illness. MAO-B inhibitors can effectively improve patients’ motor and non-motor symptoms, reduce “OFF” time, and may potentially prevent/delay disease progression. In this review, we discuss the effects of MAO-B inhibitors on motor and non-motor symptoms in PD patients, their mechanism of action, and the future development of MAO-B inhibitor therapy.

A comprehensive review of monoamine oxidase inhibitors as Anti-Alzheimer's disease agents: A review

Monoamine oxidases (MAO-A and MAO-B) are mammalian flavoenzyme, which catalyze the oxidative deamination of several neurotransmitters like norepinephrine, dopamine, tyramine, serotonin, and some other amines. The oxidative deamination produces several harmful side products like ammonia, peroxides, and aldehydes during the biochemical reaction. The concentration of biochemical neurotransmitter alteration in the brain by MAO is directly related with several neurological disorders like Alzheimer's disease and Parkinson's disease (PD). Activated MAO also contributes to the amyloid beta (Aβ) aggregation by two successive cleft β-secretase and γ-secretase of amyloid precursor protein (APP). Additionally, activated MAO is also involved in aggregation of neurofibrillary tangles and cognitive destruction through the cholinergic neuronal damage and disorder of the cholinergic system. MAO inhibition has general anti-Alzheimer's disease effect as a consequence of oxidative stress reduction prompted by MAO enzymes. In this review, we outlined and addressed recent understanding on MAO enzymes such as their structure, physiological function, catalytic mechanism, and possible therapeutic goals in AD. In addition, it also highlights the current development and discovery of potential MAO inhibitors (MAOIs) from various chemical scaffolds.

Rasagiline delays retinal degeneration in a mouse model of retinitis pigmentosa via modulation of Bax/Bcl-2 expression

AIMS

Retinitis pigmentosa (RP) is an inherited disease characterized by a progressive degeneration of rod photoreceptors. An imbalance between pro- and antiapoptotic factors, such as Bax/Bcl-2, has been involved in retinal degeneration. To date, no cure or effective treatments are available for RP. Rasagiline is an antiparkinsonian drug that has shown neuroprotective effects in part attributed to a modulation of Bax/Bcl-2 expression. In this study, we have evaluated the use of rasagiline as a potential treatment for RP.

METHODS

Newborn rd10 mice, a RP model, were treated with oral rasagiline during 30 days followed by a functional and morphological characterization of their mouse retinas.

RESULTS

Treated animals showed a significant improvement in visual acuity and in the electrical responses of photoreceptors to light stimuli. Rasagiline delayed photoreceptor degeneration, which was confirmed not only by a high photoreceptor nuclei counting, but also by a sustained expression of photoreceptor-specific markers. In addition, the expression of proapoptotic Bax decreased, whereas the antiapoptotic factor Bcl-2 increased after rasagiline treatment.

CONCLUSION

This study provides new evidences regarding the neuroprotective effect of rasagiline in the retina, and it brings new insight into the development of future clinical trials using this well-established antiparkinsonian drug to treat RP.

Citalopram restores short-term memory deficit and non-cognitive behaviors in APP/PS1 mice while halting the advance of Alzheimer's disease-like pathology

Alzheimer's disease (AD) is the most common cause of dementia. In addition to cognitive impairments, deficits in non-cognitive behaviors are also common neurological sequelae in AD. Here, we show that complex behavioral deficits in 7-month-old APPswe/PSEN1dE9 (APP/PS1) mice include impairments in object recognition, deficient social interaction, increased depression and buried marbles. Citalopram, one of the selective serotonin reuptake inhibitors (SSRIs), ameliorated the amyloid deposition in AD patients and transgenic animal models. After treatment for 4 weeks, citalopram rescued the deficits in short-term memory, sociability and depression in these mice. Further immunohistochemical analysis showed chronic citalopram treatment significantly attenuated β-amyloid deposition and microglial activation in the brains of APP/PS1 mice as demonstrated previously. Parvalbumin (PV) interneurons, which are the primary cellular subtype of GABAergic neurons and considered indispensable for short-term memory and social interaction, also contributed to the progress of depression. Additionally, we found the citalopram could significantly increase the PV-positive neurons in the cortex of APP/PS1 mice without alteration in the hippocampus, which might contribute to the improvement of behavioral performance. Our findings suggest that citalopram might be a potential candidate for the early treatment of AD.

Protective effect of betulinic acid against intracerebroventricular streptozotocin induced cognitive impairment and neuronal damage in rats: Possible neurotransmitters and neuroinflammatory mechanism

BACKGROUND

The purpose of the study was to explore the therapeutic potential of Betulinic acid (BA) in streptozotocin (STZ) induced memory damage in experimental rats.

METHODS

STZ (3mg/kg bilaterally) as intracerebroventrical (icv) route was administered on day 1 and 3 in rats. Donepezil (5mg/kg/day po), used as standard, and BA (5, 10 and 15mg/kg/day po) were administered after 1h of 1st STZ infusion up to 21days. Object recognition task (ORT) for non-spatial, Morris water maze (MWM) for spatial and locomotor activity were performed to evaluate behavioral changes in rats. On 22nd day, animals were decapitated and hippocampus was separated to perform biochemical (AChE, LPO, GSH, nitrite), neuroinflammatory (TNF-α, IL-1β, and IL-6), neurotransmitters (NTs) (dopamine, norepinephrine and serotonin) analysis.

RESULTS

STZ infusion significantly impaired memory as observed in MWM and ORT, increased oxidative stress, pro-inflammatory cytokine's level and altered NTs level. Moreover, BA demonstrated a neuroprotective effect in a dose-dependent manner. BA dose dependently (5, 10 and 15mg/kg) significantly restore STZ induced memory changes and pathological abnormalities in rat brain.

CONCLUSIONS

The findings of the current study suggests that BA protect rat brain from STZ induced neuronal damage via acting through multiple mechanisms and would be used to curb cognitive decline associated with neurodegenerative disorders especially AD.

Inhibitors of MAO-A and MAO-B in Psychiatry and Neurology

Inhibitors of MAO-A and MAO-B are in clinical use for the treatment of psychiatric and neurological disorders respectively. Elucidation of the molecular structure of the active sites of the enzymes has enabled a precise determination of the way in which substrates and inhibitor molecules are metabolized, or inhibit metabolism of substrates, respectively. Despite the knowledge of the strong antidepressant efficacy of irreversible MAO inhibitors, their clinical use has been limited by their side effect of potentiation of the cardiovascular effects of dietary amines (“cheese effect”). A number of reversible MAO-A inhibitors which are devoid of cheese effect have been described in the literature, but only one, moclobemide, is currently in clinical use. The irreversible inhibitors of MAO-B, selegiline and rasagiline, are used clinically in treatment of Parkinson's disease, and a recently introduced reversible MAO-B inhibitor, safinamide, has also been found efficacious. Modification of the pharmacokinetic characteristics of selegiline by transdermal administration has led to the development of a new drug form for treatment of depression. The clinical potential of MAO inhibitors together with detailed knowledge of the enzyme's binding site structure should lead to future developments with these drugs.

Design, synthesis and evaluation of novel dual monoamine-cholinesterase inhibitors as potential treatment for Alzheimer's disease

Current novel therapeutic approach suggests that multifunctional compounds with diverse biological properties and a single bioavailability and pharmacokinetic metabolism, will produce higher significant advantages in treatment of neurodegenerative diseases, such as Alzheimer's disease (AD). Based on this rational, a new class of cholinesterase (ChE)-monoamine oxidase (MAO) inhibitors were designed and synthesized by amalgamating the propargyl moiety of the irreversible selective MAO-B inhibitor, neuroprotective/neurorestorative anti-Parkinsonian drug, rasagiline, into the "N-methyl" position of the ChE inhibitor, anti-AD drug rivastigmine. Initially, we examined the MAO and ChE inhibitory effect of these novel compounds, MT series in vitro and in vivo. Among MT series, MT-031 exhibited higher potency as a dual MAO-A and ChE inhibitor compared to other compounds in acute-treated mice. Additionally, MT-031 was found to increase the striatal levels of dopamine (DA), serotonin (5-HT) and norepinephrine (NE), and prevent the metabolism of DA and 5-HT. Finally, we have demonstrated that MT-031 exerted neuroprotective effect against H2O2-induced neurotoxicity and reactive oxygen species generation in human neuroblastoma SH-SY5Y cells. These findings provide evidence that MT-031 is a potent brain permeable novel multifunctional, neuroprotective and MAO-A/ChE inhibitor, preserves in one molecule entity some of the beneficial properties of its parent drugs, rasagiline and rivastigmine, and thus may be indicated as novel therapeutic approach for AD.