Inhibition of phosphodiesterase 2 reverses gp91phox oxidase-mediated depression- and anxiety-like behavior

Apocynin Prevents Cigarette Smoke-Induced Anxiety-Like Behavior and Preserves Microglial Profiles in Male Mice

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally and is primarily caused by cigarette smoking (CS). Neurocognitive comorbidities such as anxiety and cognitive impairments are common among people with COPD. CS-induced lung inflammation and oxidative stress may "spill-over" into the systemic circulation, driving the onset of these comorbidities. We investigated whether a prophylactic treatment with the NADPH Oxidase 2 (NOX2) inhibitor, apocynin, could prevent CS-induced neurocognitive impairments. Adult male BALB/c mice were exposed to CS (9 cigarettes/day, 5 days/week) or room air (sham) for 8 weeks with co-administration of apocynin (5 mg/kg, intraperitoneal injection once daily) or vehicle (0.01% DMSO in saline). Following 7 weeks of CS exposure, mice underwent behavioral testing to assess recognition and spatial memory (novel object recognition and Y maze, respectively) and anxiety-like behaviors (open field and elevated plus maze). Mice were then euthanized, and blood, lungs, and brains were collected. Apocynin partially improved CS-induced lung neutrophilia and reversed systemic inflammation (C-reactive protein) and oxidative stress (malondialdehyde). Apocynin exerted an anxiolytic effect in CS-exposed mice, which was associated with restored microglial profiles within the amygdala and hippocampus. Thus, targeting oxidative stress using apocynin can alleviate anxiety-like behaviors and could represent a novel strategy for managing COPD-related anxiety disorders.

Opportunities and perspectives of small molecular phosphodiesterase inhibitors in neurodegenerative diseases

Phosphodiesterase (PDE) is a superfamily of enzymes that are responsible for the hydrolysis of two second messengers: cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). PDE inhibition promotes the gene transcription by activating cAMP-response element binding protein (CREB), initiating gene transcription of brain-derived neurotrophic factor (BDNF). The procedure exerts neuroprotective profile, and motor and cognitive improving efficacy. From this point of view, PDE inhibition will provide a promising therapeutic strategy for treating neurodegenerative disorders. Herein, we summarized the PDE inhibitors that have entered the clinical trials or been discovered in recent five years. Well-designed clinical or preclinical investigations have confirmed the effectiveness of PDE inhibitors, such as decreasing Aβ oligomerization and tau phosphorylation, alleviating neuro-inflammation and oxidative stress, modulating neuronal plasticity and improving long-term cognitive impairment.

NADPH-oxidases as potential pharmacological targets for thrombosis and depression comorbidity

There is a complex interrelationship between the nervous system and the cardiovascular system. Comorbidities of cardiovascular diseases (CVD) with mental disorders, and vice versa, are prevalent. Adults with mental disorders such as anxiety and depression have a higher risk of developing CVD, and people with CVD have an increased risk of being diagnosed with mental disorders. Oxidative stress is one of the many pathways associated with the pathophysiology of brain and cardiovascular disease. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is one of the major generators of reactive oxygen species (ROS) in mammalian cells, as it is the enzyme that specifically produces superoxide. This review summarizes recent findings on the consequences of NOX activation in thrombosis and depression. It also discusses the therapeutic effects and pharmacological strategies of NOX inhibitors in CVD and brain disorders. A better comprehension of these processes could facilitate the development of new therapeutic approaches for the prevention and treatment of the comorbidity of thrombosis and depression.

Phosphodiesterase 2 and Its Isoform A as Therapeutic Targets in the Central Nervous System Disorders

Cyclic adenosine monophosphates (cAMP) and cyclic guanosine monophosphate (cGMP) are two essential second messengers, which are hydrolyzed by phosphodiesterase's (PDEs), such as PDE-2. Pharmacological inhibition of PDE-2 (PDE2A) in the central nervous system improves cAMP and cGMP signaling, which controls downstream proteins related to neuropsychiatric, neurodegenerative, and neurodevelopmental disorders. Considering that there are no specific treatments for these disorders, PDE-2 inhibitors' development has gained more attention in the recent decade. There is high demand for developing new-generation drugs targeting PDE2 for treating diseases in the central nervous and peripheral systems. This review summarizes the relationship between PDE-2 with neuropsychiatric, neurodegenerative, and neurodevelopmental disorders as well as its possible treatment, mainly involving inhibitors of PDE2.

An insight into the hepatoprotective role of Velpatasvir and Sofosbuvir per se and in combination against carbon tetrachloride-induced hepatic fibrosis in rats

Hepatitis C is a global health issue. Hepatitis C Virus (HCV) induces fibrosis by redox reactions, which involve the deposition of collagen in extracellular matrix (ECM). This study aimed to examine the antifibrotic effect of direct-acting antivirals; Sofosbuvir and Velpatasvir, per se and in combination against carbon tetrachloride (CCl4)-induced fibrosis in rats. Carbon tetrachloride (intraperitoneal; 0.5 ml/kg) twice weekly for six weeks was used to induce hepatic fibrosis in rats. After two weeks of CCl4, oral administration of Sofosbuvir (20 mg/kg/d) and Velpatasvir (10 mg/kg/d) was administered to rats for the last four weeks. Liver function tests (LFTs), renal function tests (RFTs), oxidative stress markers, and the levels of TNF-a, NF-κB, and IL-6 were measured through ELISA and western blotting at the end of the study. CCl4 significantly ameliorated the values of RFTs, LFTs and lipid profiles in the diseased group, which were normalized by the SOF and VEL both alone and in combination. These drugs produced potent antioxidant effects by significantly increasing antioxidant enzymes. From the histopathology of hepatic tissues of rats treated with drugs, the antifibrotic effect was further manifested, which showed suppression of hepatic stellate cells (HSCs) in treated rats, as compared to the disease control group. The antifibrotic effect was further demonstrated by significantly decreasing the levels of TNF-a, NF-κB and IL-6 in serum and hepatic tissues of treated rats as compared to the disease control group. Sofosbuvir and Velpatasvir alone and in combination showed marked inhibition of fibrosis in the CCl4-induced non-HCV rat model, which was mediated by decreased levels of TNF-a/NF-κB and the IL-6 signaling pathway. Thus, it can be concluded that Sofosbuvir and Velpatasvir might have an antifibrotic effect that appears to be independent of their antiviral activity.

Characterization of 2 Novel Phosphodiesterase 2 Inhibitors Hcyb1 and PF-05180999 on Depression- and Anxiety-Like Behavior

BACKGROUND

Phosphodiesterase 2A (PDE2A) represents a novel target for new therapies addressing psychiatric disorders. To date, the development of PDE2A inhibitors suitable for human clinical evaluation has been hampered by the poor brain accessibility and metabolic stability of the available compounds.

METHODS

Corticosterone (CORT)-induced neuronal cell lesion and restraint stress mouse model were used to measure the neuroprotective effect in cells and antidepressant-like behavior in mice.

RESULTS

The cell-based assay showed that both Hcyb1 and PF were potent in protecting cells against stress hormone CORT insults by stimulating cAMP and cGMP signaling in hippocampal cells (HT-22). Administration of both compounds before treatment of CORT to cells increased cAMP/cGMP, VASP phosphorylation at Ser239 and Ser157, cAMP response element binding protein phosphorylation at Ser133, and brain derived neurotrophic factor BDNF expression. Further in vivo study showed that both Hcyb1 and PF displayed -antidepressant- and anxiolytic-like effects against restraint stress as indicated by reduced immobility time in the forced swimming and tail suspension tasks as well as increased open arm entries and time spent in open arms and holes visit in elevated plus maze and hole-board tests, respectively. The biochemical study confirmed that these antidepressant- and anxiolytic-like effects of Hcyb1 and PF were related to cAMP and cGMP signaling in the hippocampus.

CONCLUSIONS

The results extend the previous studies and validate that PDE2A is a tractable target for drug development in the treatment of emotional disorders such as depression and anxiety.

Phosphodiesterase inhibitors in psychiatric disorders

RATIONALE

Challenges in drug development for psychiatric disorders have left much room for the introduction of novel treatments with better therapeutic efficacies and indices. As a result, intense research has focused on identifying new targets for developing such pharmacotherapies. One of these targets may be the phosphodiesterase (PDE) class of enzymes, which play important roles in intracellular signaling. Due to their critical roles in cellular pathways, these enzymes affect diverse neurobiological functions from learning and memory formation to neuroinflammation.

OBJECTIVES

In this paper, we reviewed studies on the use of PDE inhibitors (PDEIs) in preclinical models and clinical trials of psychiatric disorders including depression, anxiety, schizophrenia, post-traumatic stress disorder (PTSD), bipolar disorder (BP), sexual dysfunction, and feeding disorders.

RESULTS

PDEIs are able to improve symptoms of psychiatric disorders in preclinical models through activating the cAMP-PKA-CREB and cGMP-PKG pathways, attenuating neuroinflammation and oxidative stress, and stimulating neural plasticity. The most promising therapeutic candidates to emerge from these preclinical studies are PDE2 and PDE4 inhibitors for depression and anxiety and PDE1 and PDE10 inhibitors for schizophrenia. Furthermore, PDE3 and 4 inhibitors have shown promising results in clinical trials in patients with depression and schizophrenia.

CONCLUSIONS

Larger and better designed clinical studies of PDEIs in schizophrenia, depression, and anxiety are warranted to facilitate their translation into the clinic. Regarding the other conditions discussed in this review (most notably PTSD and BP), better characterization of the effects of PDEIs in preclinical models is required before clinical studies.

Effects of NADPH Oxidase Isoform-2 (NOX2) Inhibition on Behavioral Responses and Neuroinflammation in a Mouse Model of Neuropathic Pain

NADPH oxidase isoform-2 (NOX2) has been implicated in the pathophysiology of neuropathic pain (NP), mostly through the modulation of neuroinflammation. Since it is also accepted that some neuroimmune mechanisms underlying NP are sex-dependent, we aimed to evaluate the effects of early systemic treatment with the NOX2-selective inhibitor (NOX2i) GSK2795039 on behavioral responses and spinal neuroinflammation in spared nerve injury (SNI)-induced NP in male and female mice. Mechanical sensitivity was evaluated with the von Frey test, while general well-being and anxiety-like behavior were assessed with burrowing and light/dark box tests. Spinal microglial activation and cytokines IL-1β, IL-6, and IL-10, as well as macrophage colony-stimulating factor (M-CSF) were evaluated by immunofluorescence and multiplex immunoassay, respectively. NOX2i treatment reduced SNI-induced mechanical hypersensitivity and early SNI-induced microglial activation in both sexes. SNI-females, but not males, showed a transient reduction in burrowing activity. NOX2i treatment did not improve their burrowing activity, but tendentially reduced their anxiety-like behavior. NOX2i marginally decreased IL-6 in females, and increased M-CSF in males. Our findings suggest that NOX2-selective inhibition may be a potential therapeutic strategy for NP in both male and female individuals, with particular interest in females due to its apparent favorable impact in anxiety-like behavior.

Protective effects of phosphodiesterase 2 inhibitor against Aβ1-42 induced neuronal toxicity

Our previous study suggested that inhibition of Phosphodiesterase 2 ameliorates memory loss upon exposure to oxidative stress. While whether memory enhancing effects of PDE2 inhibition on Alzheimer's disease mouse model are involved in antioxidant defense and neuronal remodeling, are largely unexplored. The present study addressed whether and how PDE2 inhibitor Bay 60-7550 rescued Aβ oligomers (Aβo)-induced neuronal damage and memory impairment. The results suggested that exposure of primary cortical neurons to Aβo induced neuronal cells damage and increased PDE2 expression, which were paralleled to an increase in the oxidative parameter malondialdehyde (MDA) level and cellular apoptosis. However, this Aβo-induced oxidative damage was blocked by pre-treatment with protein kinase A or G (PKA or PKG) inhibitor, suggesting the involvement of cAMP/cGMP signaling. Moreover, microinjection of Aβo into the prefrontal cortex of mice increased the MDA level; while Bay 60-7550 reversed this effect and increased antioxidant and anti-apoptotic factors, i.e. increased trolox-equivalent-antioxidant capacity and Bcl-2/Bax ratio. Bay 60-7550 also rescued Aβo-induced synaptic atrophy and memory deficits, as evidenced by the increased synaptic proteins' levels and spine density in the prefrontal cortex, and improved cognitive behaviors by decreased working memory errors in the eight-arm maze and increased discrimination index in the novel object recognition test. These findings suggest that inhibition of PDE2 contributes to antioxidant defense and neuronal remodeling by regulation of cAMP/cGMP signaling, which provide a theoretical basis for the future use of PDE2 inhibitors as the anti-AD drugs.

Ameliorative effect of ethoxylated chalcone-based MAO-B inhibitor on behavioural predictors of haloperidol-induced Parkinsonism in mice: evidence of its antioxidative role against Parkinson's diseases

Parkinson's disease is a progressive neurodegenerative disorder that affects mostly elderly people above the age of 60. Previously, we have reported that the ethoxylated chalcone derivative (E)-1-(4-ethoxyphenyl)-3-(fluorophenyl)prop-2-en-1-one (E7) showed potent, reversible, and competitive MAO-B inhibition with an IC₅₀ value of 0.053 μm. The present study aims to investigate the anti-Parkinson activity of compound E7 in a haloperidol-induced animal model of mice. The disease was induced with haloperidol (1 mg/kg, intraperitoneal route) once daily for 21 days. E7 was given at dose levels of 10, 20, and 30 mg/kg/day for 21 days, consecutively. Behavioural tests were carried out during and at the end of the study. Biochemical analyses such as oxidative stress biomarkers and neurotransmitters were quantified on the brain homogenate at the end of the study. Behavioural results showed that there is a marked improvement in locomotor activity and motor coordination in the treatment group. Oxidative stress biomarkers such as SOD, CAT, and GSH levels were increased dose-dependently with a maximum at 30 mg/kg, whereas the dose-dependent decrease (30 mg/kg) in the MDA and nitrite levels were observed in the treatment groups. Levels of neurotransmitters, such as dopamine, serotonin, and noradrenaline, were increased in the treatment groups while dopamine and noradrenaline levels were more than in the standard treated group. MAO-B level was also decreased dose dependently in the treatment group in comparison with the control group. Based on the findings, it was concluded that the E7 compound exhibited anti-Parkinson activity which was more evident at 30 mg/kg oral dose as evaluated by the haloperidol-induced animal model of mice.

Phenotypic Trade-Offs: Deciphering the Impact of Neurodiversity on Drug Development in Fragile X Syndrome

Fragile X syndrome (FXS) is the most common single-gene cause of intellectual disability and autism spectrum disorder. Individuals with FXS present with a wide range of severity in multiple phenotypes including cognitive delay, behavioral challenges, sleep issues, epilepsy, and anxiety. These symptoms are also shared by many individuals with other neurodevelopmental disorders (NDDs). Since the discovery of the FXS gene, FMR1, FXS has been the focus of intense preclinical investigation and is placed at the forefront of clinical trials in the field of NDDs. So far, most studies have aimed to translate the rescue of specific phenotypes in animal models, for example, learning, or improving general cognitive or behavioral functioning in individuals with FXS. Trial design, selection of outcome measures, and interpretation of results of recent trials have shown limitations in this type of approach. We propose a new paradigm in which all phenotypes involved in individuals with FXS would be considered and, more importantly, the possible interactions between these phenotypes. This approach would be implemented both at the baseline, meaning when entering a trial or when studying a patient population, and also after the intervention when the study subjects have been exposed to the investigational product. This approach would allow us to further understand potential trade-offs underlying the varying effects of the treatment on different individuals in clinical trials, and to connect the results to individual genetic differences. To better understand the interplay between different phenotypes, we emphasize the need for preclinical studies to investigate various interrelated biological and behavioral outcomes when assessing a specific treatment. In this paper, we present how such a conceptual shift in preclinical design could shed new light on clinical trial results. Future clinical studies should take into account the rich neurodiversity of individuals with FXS specifically and NDDs in general, and incorporate the idea of trade-offs in their designs.

NADPH Oxidase (NOX) Targeting in Diabetes: A Special Emphasis on Pancreatic β-Cell Dysfunction

In type 2 diabetes, metabolic stress has a negative impact on pancreatic β-cell function and survival (T2D). Although the pathogenesis of metabolic stress is complex, an imbalance in redox homeostasis causes abnormal tissue damage and β-cell death due to low endogenous antioxidant expression levels in β-cells. Under diabetogenic conditions, the susceptibility of β-cells to oxidative damage by NADPH oxidase has been related to contributing to β-cell dysfunction. Here, we consider recent insights into how the redox response becomes deregulated under diabetic conditions by NADPH oxidase, as well as the therapeutic benefits of NOX inhibitors, which may provide clues for understanding the pathomechanisms and developing strategies aimed at the treatment or prevention of metabolic stress associated with β-cell failure.

Apocynin Prevents Anxiety-Like Behavior and Histone Deacetylases Overexpression Induced by Sub-Chronic Stress in Mice

Anxiety disorders are common mental health diseases affecting up to 7% of people around the world. Stress is considered one of the major environmental risk factors to promote anxiety disorders through mechanisms involving epigenetic changes. Moreover, alteration in redox balance and increased reactive oxygen species (ROS) production have been detected in anxiety patients and in stressed-animal models of anxiety. Here we tested if the administration of apocynin, a natural origin antioxidant, may prevent the anxiety-like phenotype and reduction of histone acetylation induced by a subchronic forced swimming stress (FSS) paradigm. We found that apocynin prevented the enhanced latency time in the novelty-suppressed feeding test, and the production of malondialdehyde induced by FSS. Moreover, apocynin was able to block the upregulation of p47phox, a key subunit of the NADPH oxidase complex. Finally, apocynin prevented the rise of hippocampal Hdac1, Hdac4 and Hdac5, and the reduction of histone-3 acetylation levels promoted by FSS exposure. In conclusion, our results provide evidence that apocynin reduces the deleterious effect of stress and suggests that oxidative stress may regulate epigenetic mechanisms.

Determining the Biological Mechanisms of Action for Environmental Exposures: Applying CRISPR/Cas9 to Toxicological Assessments

Toxicology is a constantly evolving field, especially in the area of developing alternatives to animal testing. Toxicological research must evolve and utilize adaptive technologies in an effort to improve public, environmental, and occupational health. The most commonly cited mechanisms of toxic action after exposure to a chemical or particle test substance is oxidative stress. However, because oxidative stress involves a plethora of genes and proteins, the exact mechanism(s) are not commonly defined. Exact mechanisms of toxicity can be revealed using an emerging laboratory technique referred to as CRISPR (clustered regularly interspaced short palindromic repeats). This article reviews the most common CRISPR techniques utilized today and how each may be applied in Toxicological Sciences. Specifically, the CRISPR/CRISPR-associated protein complex is used for single gene knock-outs, whereas CRISPR interference/activation is used for silencing or activating (respectively) ribonucleic acid. Finally, CRISPR libraries are used for knocking-out entire gene pathways. This review highlights the application of CRISPR in toxicology to elucidate the exact mechanism through which toxicants perturb normal cellular functions.

Drotaverine Inhibitor of PDE4: Reverses the Streptozotocin Induced Alzheimer's Disease in Mice

Alzheimer's disease (AD) is a progressive neurodegenerative disease associated with decline in memory and cognitive impairments. Phosphodiesterase IV (PDE4) protein, an intracellular cAMP levels regulator, when inhibited act as potent neuroprotective agents by virtue of ceasing the activity of Pro-inflammatory mediators. The complexity of AD etiology has ever since compelled the researchers to discover multifunctional compounds to combat the AD and neurodegeneration. The aim of this study was to probe into role of drotaverine a PDE4 inhibitor in the management of AD. Albino mice were divided into seven groups (n = 10). Group 1 control group received carboxy methyl cellulose (CMC 1 mL/kg), group II diseased group treated with streptozotocin (STZ 3 mg/kg) by intracerebroventricular (ICV) route, group III administered standard drug Piracetam 200 mg/kg and groups IV-VII were given drotaverine (10, 20, 40, and 80 mg/kg i/p respectively). Groups II-VII were given STZ (3 mg/kg, ICV) on 1st and 3rd day of treatment to induce AD. All the groups were given their respective treatments for 23 days. Improvement in learning and memory was evaluated by using behavioral tests like open field test, elevated plus maze test, Morris water maze test and passive avoidance test. Furthermore, brain levels of biochemical markers of oxidative stress, neurotransmitters, β-amyloid and tau protein were also measured. Drotaverine showed statistically significant dose dependent improvement in behavioral and biochemical markers of AD: the maximum response was achieved at a dose level of 80 mg/kg. The Study concluded that drotaverine ameliorates cognitive impairment and as well as exhibited modulated the brain levels of neurotransmitters.

Oxidative Stress at the Crossroads of Aging, Stroke and Depression

Epidemiologic studies have shown that in the aging society, a person dies from stroke every 3 minutes and 42 seconds, and vast numbers of people experience depression around the globe. The high prevalence and disability rates of stroke and depression introduce enormous challenges to public health. Accumulating evidence reveals that stroke is tightly associated with depression, and both diseases are linked to oxidative stress (OS). This review summarizes the mechanisms of OS and OS-mediated pathological processes, such as inflammation, apoptosis, and the microbial-gut-brain axis in stroke and depression. Pathological changes can lead to neuronal cell death, neurological deficits, and brain injury through DNA damage and the oxidation of lipids and proteins, which exacerbate the development of these two disorders. Additionally, aging accelerates the progression of stroke and depression by overactive OS and reduced antioxidant defenses. This review also discusses the efficacy and safety of several antioxidants and antidepressants in stroke and depression. Herein, we propose a crosstalk between OS, aging, stroke, and depression, and provide potential therapeutic strategies for the treatment of stroke and depression.

The role of CCR5 in the protective effect of Esculin on lipopolysaccharide-induced depressive symptom in mice

BACKGROUND

The purpose of this study was to evaluate whether Esculin could improve the depressive symptom induced by LPS in mice and explore the role of CCR5 in its potential mechanism.

METHODS

Mice were stimulated with LPS to establish depression model and treated with Esculin. The emotional alteration was assessed via behavior tests. The ELISA assay and western blot analysis were applied to detect the expressions of inflammatory cytokines and correlative proteins.

RESULTS

As a result, Esculin played a protective role in LPS-induced depressive dysfunction, which was possible through the reduction of M1 microglia, and elevation of M2 microglia by inhibiting TLR4/NF-κB signaling pathway regulated by CCR5. Besides, Esculin led to up-regulation of the CREB/BDNF neuroprotective pathway, and suppression of inflammatory cytokines both in the central and peripheral system. BV2 cells were stimulated with LPS to further elucidate the accordant mechanism in vitro. Molecular docking results suggested that Esc bound to CCR5 at amino acid residues TYR187 and THR105 through hydrogen-bonding.

LIMITATIONS

Transgenic animals might be useful for the further investigation.

CONCLUSIONS

From the overall results, we concluded that Esculin might exert a beneficial effect on LPS-induced depression in mice and represent an effective treatment for depression.

Investigation of anti-Parkinson activity of dicyclomine

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder. The major causative factors that progress the PD are age, genetic abnormalities, environmental factors and degeneration of dopamine neurons in substantia nigra. PD normally exerts a tonic inhibitory effect on striatal cholinergic interneurons. Anticholinergics act by normalizing the disequilibrium between striatal dopamine and acetylcholine-resulted reduction in tremors.

OBJECTIVE

This study sought to evaluate the anti-Parkinson potential of dicyclomine in haloperidol (HAL)- and paraquat (PQT)-induced Parkinsonism models in mice.

MATERIALS AND METHODS

Sixty albino mice were divided into six groups (n = 10) for each model. Group I: received distilled water 1 mL/kg, Group II: diseased group received HAL (1 mg/kg) for consecutive 21 days and PQT (2 mg/kg) every three days for three weeks, Group III: treated with sinemet (20 mg/kg), Group IV-VI: received 40, 80 and 160 mg/kg dose of dicyclomine, respectively, for consecutive 21 days. The effect of treatments on spontaneous locomotor activity and motor co-ordination was evaluated by using open field, rotarod, actophotometer and light and dark box tests. Cataleptic behavior was estimated by the block method and triple horizontal bar apparatus. Biochemical markers of oxidative stress and levels of neurotransmitters were estimated.

RESULTS

Findings from this study showed that dicyclomine at highest dose level of 160 mg/kg prevented HAL- and PQT-induced PD through enhancement of antioxidant defense system.

CONCLUSION

The study concluded that dicyclomine could be the potential drug in the management of Parkinsonism.