Glycogen synthase kinase-3 inhibition as a potential pharmacological target for vascular dementia: In silico and in vivo evidence

Abstract

Vascular dementia is a serious problem as it creates significant disability and dependency in the affected person. Lives of these patients can be improved through the advent of novel drug targets which can be targeted by pharmacological therapies. However, finding a precise and druggable target for vascular dementia is experimentally impossible and challenging task owing to a complex and mostly unknown interplay between the cognitive abilities of the brain with a diversity of vascular diseases. To address this issue, we have systematically analyzed the literature reports by using well-known methods and approaches of bioinformatics (viz. network pharmacology, reverse pharmacology, enrichment analysis of KEGG pathways, biological processes of Gene Ontology and DIAMOnD algorithm). Because glycogen synthase kinase-3 (GSK-3) seems to be one of the most promising targets, therefore, we have tested the capacity of lithium carbonate, a classical inhibitor of GSK-3, for treatment of dementia resulting from mild chronic cerebral hypoperfusion in mice. To this end, our study shows in-vivo validation of predicted target, i.e., pharmacological deactivation of GSK-3 enzyme and its impact on cognitive abilities employing a behavioral test battery, i.e., object recognition task, step-through passive avoidance task, elevated plus maze task and water maze task. In this framework, we observed that lithium carbonate attenuates recognition, emotion, spatial and fear-motivated learning and memory impairments along with attenuation of oxidative stress, cholinergic dysfunction and glutamate-induced excitotoxicity in cerebral cortex and hippocampus. In conclusion, we propose GSK-3 as a promising drug target for vascular dementia in light of experimental results and in-silico predictions.

Introduction

Vascular dementia is a heterogeneous syndrome in which underlying cause is a vascular disease in some form, and its ultimate manifestation is a cognitive decline in one or more domains, e.g., learning and memory, language, executive function, and attention. These impairments not only impact individuals who have dementia but also interfere with their families, communities, and societies. Patients with vascular dementia are at significantly high risk of ischemic stroke [1] but no specific medications are available to these patients. For the development of effective medicines discovery of novel, superior and druggable target is warranted. However, the finding of such target is a challenging task because pathophysiology of vascular dementia is mostly unknown and a large volume of clinical and experimental data is being accumulated every year in this research area (approx. 700 PubMed counts for VaD). However, collection, analysis and making sense out of this data became a hurdle.

Past few years have witnessed the successful use of big data in drug discovery. Therefore, we believe that finding diseased target through the lens of bioinformatics can be fruitful for further wet lab validations. To this end, we have collected and analyzed the literature reports by using well-known methods and approaches of bioinformatics (viz. network pharmacology, reverse pharmacology, enrichment analysis of KEGG pathways, biological processes of Gene Ontology & DIAMOnD algorithm). A list of druggable targets related to the treatment of vascular dementia has been predicted based on known gene-vascular dementia associations and known drug targets.

In this list, glycogen synthase kinase-3β (GSK-3β) seems to be a most promising target because it has been implicated in many processes which are relevant to vascular dementia such as thrombosis [2], atherosclerosis [3], diabetes mellitus [4], disruption of blood-brain barrier [5], oxidative stress [6], neuroinflammation [7], neuronal death [8], synaptic plasticity [9], mood [10], learning [11] and memory [12].

Apart from this selection, GSK-3α implicated in many neuronal functions [13] and its inhibition reduces the formation of amyloid plaques and neurofibrillary tangles in Alzheimer's disease [14]. Thus, both isoform of the glycogen synthase kinase-3 seems to be relevant with vascular dementia.

Pharmacological inhibition of these enzymes is possible with the use of a drug having well-established clinical safety, i.e., lithium carbonate [15]. Human observational studies show that treatment with lithium may reduce the risk of dementia among patients with bipolar disorder [16] and may facilitate recovery of spatial learning and memory after transient global ischemia [17]. However, the effect of lithium on recognition, emotion, spatial and fear-motivated learning, and memory remain unexplored under mild chronic cerebral hypoperfusion. Mild chronic cerebral hypoperfusion is a well-recognized cause of cerebral ischemia and vascular dementia [18]. It can be induced in mice by occlusion of the right common carotid artery and mimics core feature of vascular dementia, e.g., cerebral hypoxia, neuroinflammation, white matter lesion and cognitive impairment [19].

We hypothesized that lithium carbonate could treat vascular dementia through deactivation of GSK-3 enzyme involving enlisted pathways (Fig. 11) predicted through the lens of bioinformatics. To this end, present work aimed at in-vivo testing of the selected target. i.e., inhibition of GSK-3 pathway and shows capacity of lithium carbonate, a classical inhibitor of GSK-3, in treatment of vascular dementia induced by occlusion of right common carotid artery in Swiss albino mice employing a behavioral test battery i.e. object recognition test, step-through passive avoidance test, elevated plus maze test and Morris water maze test.