CNS & Neurological Disorders - Drug Targets (Formerly Current Drug Targets - CNS & Neurological Disorders) - Volume 21, Issue 10, 2022

Progressive degeneration in the morphology and functions of neuronal cells leads to multifactorial pathogenesis conditions of oxidative stress, mitochondrial dysfunction, excitotoxicity, nitric oxide toxicity, and neuro-inflammation to mediate heterogeneous types of neurodegenerative diseases, such as Epilepsy, Alzheimer's (AD) and Parkinson's (PD), more prominently among aging populations. In this editorial, complex mechanisms, challenges, and advancements made in the discovery of new neurotherapeutics, as well as designing approaches being adopted to fabricate brain-targeted delivery systems, are discussed.

Neuropathy is the most common complication of diabetes. 50% of adults with diabetes will develop neuropathy in their lifetime. Diabetic peripheral neuropathy (DPN) is the major form of neuropathy found in 75% of diabetic neuropathy incidences. Pharmacological treatments are recommended for pain management in DPN. Anticonvulsants like pregabalin and gabapentin are the preferred first-line treatment, followed by amitriptyline, duloxetine, and venlafaxine. Topical agents like capsaicin and isosorbide dinitrate are also useful in treating the DPN and may be considered for the second or third-line treatment. Opioids and related drugs are suggested for short-term use during the acute exacerbation of pain. Combination therapy may be beneficial in patients who do not respond to monotherapy. However, currently, there is no compelling evidence to suggest any specific combination of agents. Disease-modifying agents such as alpha-lipoic acid and epalrestat appear to improve the disease state but are not recommended by any guideline. This review discusses the available pharmacological therapy for treating DPN. Also, we highlight the recommendations from different guidelines about the pharmacological treatment of DPN.

Background: The complication of Alzheimer’s disease (AD) has made the development of its therapeutic a challenging task. Even after decades of research, we have achieved no more than a few years of symptomatic relief. The inability to diagnose the disease early is the major hurdle behind its treatment. Several studies have aimed to identify potential biomarkers that can be detected in body fluids (CSF, blood, urine, etc.) or assessed by neuroimaging (i.e., PET and MRI). However, the clinical implementation of these biomarkers is incomplete as they cannot be validated. Methods: This study aimed to overcome the limitation of using artificial intelligence along with technical tools that have been extensively investigated for AD diagnosis. For developing a promising artificial intelligence strategy that can diagnose AD early, it is critical to supervise neuropsychological outcomes and imaging-based readouts with a proper clinical review. Conclusion: Profound knowledge, a large data pool, and detailed investigations are required for the successful implementation of this tool. This review will enlighten various aspects of early diagnosis of AD using artificial intelligence.

Alzheimer’s Disease (AD) is one of the most common neurodegenerative diseases, which affects millions of people worldwide. Accumulation of amyloid-β plaques and hyperphosphorylated neurofibrillary tangles are the key mechanisms involved in the etiopathogenesis of AD, characterized by memory loss and behavioural changes. Effective therapies targeting AD pathogenesis are limited, making it the largest unmet clinical need. Unfortunately, the available drugs provide symptomatic relief and primary care, with no substantial impact on the disease pathology. However, in recent years researchers are working hard on several potential therapeutic targets to combat disease pathogenesis, and few drugs have also reached clinical trials. In addition, drugs are being repurposed both in the preclinical and clinical studies for the treatment of AD. For instance, montelukast is the most commonly used leukotriene receptor antagonist for treating asthma and seasonal allergy. Its leukotriene antagonistic action can also be beneficial for the reduction of detrimental effects of leukotriene against neuro-inflammation, a hallmark feature of AD. The available marketed formulations of montelukast present challenges such as poor bioavailability and reduced uptake, reflecting the lack of effectiveness of its desired action in the CNS. While on the other side, targeted drug delivery is a satisfactory approach to surpass the challenges associated with the therapeutic agents. This review will discuss the enhancement of montelukast treatment efficacy and its access to CNS by using new approaches like nano-formulation, nasal gel, solid lipid formulation, nano-structure lipid carrier (NSLC), highlighting lessons learned to target AD pathologies and hurdles that persist.

Pyrimidine is an aromatic and heterocyclic organic compound containing a 6-membered ring consisting of four carbon and two nitrogen atoms on alternative positions. Pyrimidine scaffolds described their existence in the medicinal chemist’s cause for their synthesizing practicability and nonpoisonous nature. However, the reason behind neurological disorders is still an open challenge for scientific research and development organizations. Efficacy voids are widespread before researchers, despite high throughput research in the field of anti-Alzheimer's drugs.Researchers have constantly investigated all the probabilities for restraining the unwanted adverse effects of the anti-Alzheimer’s agents and are focusing more extensively to rehabilitate neurological disorders. The scientific literature on drug development has been an aspiration to medicinal chemists and other researchers to facilitate further research. Therefore, this review emphasizes the structure-activity relationship (SAR) based approach and the pharmacological advancements of pyrimidine moiety in the new era of therapeutics as anti-Alzheimer’s agents.

As a source of therapeutic agents, heterocyclic nitrogen-containing compounds and their derivatives are still interesting and essential. Pyrazole, a five-member heteroaromatic ring with two nitrogen atoms, has a major impact in chemical industries as well as pharmaceutical industries. Due to its wide range of biological activities against various diseases, it has been identified as a biologically important heterocyclic scaffold. The treatment of neurological disorders has always been a difficult task in both the past and present. Therefore, identifying therapeutically effective molecules for neurological conditions remains an open challenge in biomedical research and development. For developing novel entities as neuroprotective agents, recently, pyrazole scaffold has attracted medicinal chemists worldwide. The major focus of research in this area is discovering novel molecules as neuroprotective agents with minimal adverse effects and better effectiveness in improving the neurological condition. This review mainly covers recent developments in the neuropharmacological role of pyrazole incorporated compounds, including their structural-activity relationship (SAR), which also further includes IC50 values (in mM as well as in μM), recent patents, and a brief history as neuroprotective agents.

Significant efforts have been made in research to discover newer neurotherapeutics, however, the rate of reported neurological disorders has been increasing at an alarming speed. Neurotherapeutics delivery in the brain is still posing a significant challenge, owing to the blood-brain barrier and blood-cerebrospinal fluid barrier. These physiological barriers restrict the passage of systemically available fractions of neurotherapeutics into the brain, owing to low permeability and drug localization factors. Neurotherapeutics encapsulating lipid carriers favor a significant increase in bioavailability of poorly water-soluble drugs by enhancing solubility in the gastrointestinal tract and favoring stability. Due to their small size and lipid-based composition, these carriers offer enhanced permeability across the semi-permeable blood-brain barrier to effectively transport encapsulated loads, such as synthetic drugs, nutraceuticals, phytoconstituents, herbal extracts, and peptides, thereby reducing incidences of off-target mediated adverse impacts and toxicity. The most significant advantage of such lipid-based delivery systems is non–invasive nature and targeting of neurotherapeutics to the central nervous system. Critical attributes of lipid-based carriers modulate release rates in rate-controlled manners, enable higher penetration through the blood-brain barrier, and bypass the hepatic first-pass metabolism leading to higher CNS bioavailability neurotherapeutics. The current review discusses a brief and introductory account of the limitations of neurotherapeutics, pharmacological barriers, challenges in brain-targeted delivery, and the potential of nanotechnology- processed lipid-based carriers in the clinical management of neuronal disorders.

Neurodegenerative diseases are a heterogeneous group of disorders among aging populations worldwide characterized by the progressive degeneration of the structure and function of brain cells and the nervous system. Alzheimer's disease and Parkinson's disease are common neurodegenerative diseases (NDs). Classic pathological features of AD are the accumulation of the amyloid betaprotein and aggregates of hyperphosphorylated tau protein around the brain cells. Dopaminergic neuronal death in the midbrain and accumulation of α- synuclein in the neurons are the hallmark of Parkinson’s disease. The pathogenesis is multifactorial, and both neurodegenerative disorders have complex etiology. Oxidative stress closely linked with mitochondrial dysfunction, excitotoxicity, nitric oxide toxicity, and neuro-inflammation, is anticipated to trigger neuronal death. Ample evidence has implicated that oxidative stress and inflammation contribute to the pathology of neurodegeneration in AD and PD. Currently, acetylcholinesterase inhibitors are the main treatment option for AD, while L-DOPA is the gold standard therapy for PD. Along with the main therapy, many endogenous antioxidants, like vitamin E, selenium, etc., are also given to the patients to combat oxidative stress. Current treatment for these NDs is limited due to the blood-brain barrier (BBB) that hinders drug targeting towards neurons. In this review, we emphasize adjunct treatment with anti-inflammatory agents that act at the site of the disease and can halt the disease progression by attenuating the effect of ROS triggering neuro-inflammatory response. Polyphenols, either as purified compounds or extracts from various natural plant sources, have been well studied and documented for anti-inflammatory effects, but their use for ND is limited due to their physicochemical attributes. Nanoparticle-mediated drug delivery system exhibits immense potential to overcome these hurdles in drug delivery to the CNS, enabling nanoparticle-based therapies to directly target the inflammation and release bioactive compounds with anti-inflammatory properties to the site of action.

Herbal medicines are being used by humans since the oldest civilizations and have been an integral part of traditional and alternative medicines. In recent times, pharmaceutical and biomedical scientists are taking interest in developing nutraceutical-based medicines to overcome the side effects and adverse drug reactions caused by allopathic medicines. Nutraceuticals have started occupying the global market. Nutraceuticals have gained widespread acceptance due to their efficacy in treating difficult to treat diseases, low toxicity, low cost, easy accessibility, etc. Safety and efficacy are other important factors in the commercialization process of nutraceuticals. Different novel advanced drug delivery systems have been constantly studied to improve the efficacy and bioavailability of medicines obtained from herbal sources. The transdermal drug delivery system provides a potent alternative to the conventional method of using nutraceuticals. The development of transdermal system-based nutraceuticals could provide the advantage of enhanced bioavailability, improved solubility, bypass of the first-pass metabolism, and targeted delivery of drugs in brain-related disorders. It additionally provides the advantage of being non-invasive. This article reviews the potential effects of various nutraceuticals in brain-related disorders as well as trends in transdermal nano-systems to deliver such nutraceuticals. We have also focused on advantages, applications as well as recent United States-based patents which emphasize emerging interest towards transdermal nutraceuticals in brain disorders.

Epilepsy is known as one of the major challenges for medical science. The sudden appearance of a seizure has been a significant health emergency as it may lead to further complications. Although key advancements have been achieved in terms of pharmacological approaches for epilepsy, many issues remain uncertain. Lipid carriers have been at the forefront, especially in neurodegenerative diseases, such as epilepsy, Alzheimer’s, dementia, etc. The blood-brain barrier still appears to be a major impediment in the successful treatment of epileptic seizures. This is mainly due to the limited bioavailability of most anti-convulsant drugs. The present review encompasses the issues underlying the current approach for epilepsy drug treatment and highlights the newer, novel, and more precise drug delivery system to manage seizures. The advantage of using a lipidbased delivery system is its superior absorption in the brain cells. Ample evidence shows that reducing the particle size also infuses the drug easily through the blood-brain barrier. The application of liposomes, polymeric nanoparticles, metallic nanoparticles, and solid lipid nanoparticles for the treatment and management of epilepsy has been highlighted in the present review. This review provides an overview of the current status of the treatment and recent advances in the treatment of epilepsy.

Major depressive disorder (MDD) is a serious and complex mental illness. Currently, many antidepressants are available in the market for the treatment of MDD. However, these agents are associated with side effects, which restricts their use. This warrants the development of advanced antidepressive medications with a novel mechanism of action or novel targets and with minimal adverse effects. The traditional neurobiological hypothesis of depression, the monoamine hypothesis, is unable to properly explain all the aspects of depressive conditions. In this review, we discuss novel approaches that could be used for the treatment of depression, including glutamatergic and serotonergic system modulation. The pathogenesis of depression is greatly affected by glutamatergic neurotransmission dysfunction. Previous investigations have shown that ketamine, an N-methyl-D-aspartate receptor antagonist, exerts fast and long-lasting antidepressant effects. Several glutamatergic modulators, such as esketamine, sarcosine, and others, have also shown potential antidepressant action in animal as well as clinical studies. Lastly, drugs that alter neurotransmission by NMDA receptors could open up new avenues for more effective treatment of depression. Besides, understanding the underlying mechanisms will aid in the development of novel and fast-acting antidepressant drugs in the future.

The new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease (COVID-19) represents a public health problem worldwide. COVID-19 triggers a maladaptive cytokine release commonly referred to as cytokine storm syndrome with increased production of proinflammatory cytokines, which also appears to contribute to chronic neuroinflammation and neurodegenerative disorders’ appearance, including multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease. In this context, SARS-CoV-2 might enter the central nervous system through binding with the angiotensin converting enzyme 2 receptors which are highly expressed in glial cells and neurons. For this reason, an association between COVID-19, its dependent cytokine storm, and the development and/or progression of neurodegenerative disorders might be evaluated. Therefore, the aim of this review was to assess the impact of COVID-19 on neurodegenerative disorders, focusing on the possible increased mortality risk and/or deterioration of the clinical course of pre-existing chronic neurological diseases in patients with dementia.