Metformin and fluoxetine improve depressive-like behavior in a murine model of Parkinsońs disease through the modulation of neuroinflammation, neurogenesis and neuroplasticity

Effects of astrocytes in the dorsal hippocampus on anxiety-like and depressive-like behaviors in hemiparkinsonian rats

Anxiety and depression are the most common neuropsychiatric manifestations of Parkinson's disease (PD) patients. Growing evidence have shown that the dorsal hippocampus (dHIPP) and astrocytes (AS) may be involved in regulating depression and anxiety, but the role and mechanism are still unclear, especially in PD-related depression and anxiety. Unilateral 6-hydroxydopamine lesions of the substantia nigra pars compacta (SNc) were used to establish the rat model of PD. Behavioral tests and measurement of monoamine levels in the depression and anxiety related brain regions were performed to investigate the effects of chemogenetic activation or inhibition of dHIPP AS on PD-related anxiety and depression. The present results showed that unilateral lesions of the SNc induced anxiety-like and depressive-like behaviors, decreased dopamine (DA) levels in some related brain regions, but did not change the density of glial fibrillary acidic protein-positive AS in the CA1, CA3 and dentate gyrus in rats. Chemogenetic inhibition of dHIPP AS significantly improved anxiety-like and depressive-like behaviors only in the lesioned rats, while chemogenetic activation of dHIPP AS had no effects on anxiety-like and depressive-like behaviors in sham-operated and the lesioned rats. Chemogenetic activation of dHIPP AS only decreased DA level in the ventral hippocampus (vHIPP) in sham-operated rats, while inhibition of dHIPP AS increased 5-hydroxytryptamine (5-HT) levels in the medial prefrontal cortex (mPFC) and vHIPP in sham-operated rats and also in the amygdala, mPFC, lateral habenula, dHIPP and vHIPP in the lesioned rats. These results indicate that chemogenetic inhibition of dHIPP AS improves the anxiety-like and depressive-like behaviors in the lesioned rats through the changes in monoamine in some brain regions.

Dysregulation of serotonergic neurotransmission in Parkinson disease: A key duet

Parkinson's disease (PD) is the most common movement disorder, affecting approximately 1% of the general population over 65 years of age. PD is commonly associated with the development of motor and non-motor symptoms. Non-motor symptoms arise decades earlier than motor symptoms due to the degeneration of GABAergic, serotonergic, and other neurons involved in autonomic regulation. However, motor symptoms in PD are developed due to degeneration of the dopaminergic neurons in the substantia nigra pars compacta (SNpc) of midbrain. The PD neuropathology is related to the progressive loss of the dopaminergic neurons in the SNpc of midbrain. Particularly, dysfunction of serotonergic system is implicated in the development of non-motor symptoms such as sleep disorders, cognitive dysfunction, depression and anxiety. In addition, dysfunction of serotonergic neurons which affects the dopaminergic neurons in the SNpc leads to the development of motor symptoms. Moreover, dysfunction of serotonergic neurons is associated with the development of L-dopamine (L-DOPA)-induced dyskinesia. Consistently, administration of serotonin (5-HT) receptor agonist attenuates the development of L-DOPA-induced dyskinesia. These findings emphasized the possible role of serotonergic system in PD. However, the underlying mechanisms that mediate the latent effect of 5-HT in PD are not completely elucidated. Therefore, this mini-review aims to discuss the exact role of 5-HT in PD, and how the 5-HT modulators affect PD neuropathology.

Metformin attenuated depressive-like behaviors by suppressing TRPV1/NLRP3 mediated neuroinflammation in the hypothalamus of allergic rhinitis mice

In addition to nasal symptoms, allergic rhinitis (AR) has increasingly been reported to be associated with depression-like behaviors. Recent evidence suggests that neuroinflammation in the hypothalamus may cause these depressive symptoms in AR. However, the precise mechanisms and effective treatments remain to be elucidated. This study investigated the ameliorative effects of metformin on neuroinflammation in the hypothalamus, depressive-like behavior and the underlying molecular mechanisms of AR mice. Mice were administered ovalbumin (OVA) intranasally to induce allergic rhinitis and subsequently subjected to behavioral experiments to detect depressive-like behavior. The roles of the TRPV1/NLRP3 pathway in depression-like behaviors in AR were examined in vivo. Additionally, the mechanism of TRPV1/NLRP3-mediated neuroinflammation was investigated in vitro. Finally, metformin was utilized to explore its possible mechanisms and efficacy in treating depressive-like behavior in AR. AR mice exhibited significant depressive-like behavior, which was attenuated by metformin. The number of Iba-1+ microglia significantly increased in the hypothalamus of AR mice. The expression of NLRP3 was significantly upregulated in the hypothalamus, activating microglia. Metformin ameliorated the neuropsychiatric symptoms by reducing NLRP3 expression in the hypothalamus. Moreover, metformin inhibited LPS-induced upregulation of the TRPV1/NLRP3 signaling pathway in microglial cell line, an effect that can be reversed by the TRPV1-specific agonist capsaicin. Increased TRPV1 expression activates the NLRP3 inflammasome in hypothalamic microglia, promoting the pathological process of depressive-like behavior in AR mice. Metformin could effectively treat neuroinflammation by regulating microglia via TRPV1 downregulation, indicating its potential as a treatment for depressive-like behaviors in AR.

Hesperidin produces antidepressant effects by activating AMPA receptor: enhancing synaptic proteins to promote hippocampal neuronal activities

Hesperidin treatments reduce depressive symptoms in mouse models of depression, but the mechanism that mediates its antidepressant effects is unclear. This study shows that hesperidin exerts its antidepressant effects by activating α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor to promote synaptic and neuronal function in the hippocampus. The optimal dose of hesperidin (10 mg/kg) for the antidepressant potential was determined after 7 consecutive days of treatments, demonstrating decreased latency to eat and increased food consumption in novelty suppressed feeding, and decreased immobility time in tail suspension test (TST). Moreover, the optimal dose also reversed the depressive phenotypes of Institute of Cancer Research mice exposed to chronic unpredictable mild stress (CUMS), including reduced immobility time in the TST and increased sucrose preference in the sucrose preference test. In addition, hesperidin increased the expression of AMPA receptor protein (Glur1) and synaptic proteins (BDNF, PSD95, synapsin1) in the hippocampus of CUMS-exposed mice. Furthermore, inhibition of AMPA receptor activity by NBQX blocked the effect of hesperidin in reversing the depressive phenotypes, upregulated the expression of synaptic proteins (BDNF, PSD95, synapsin1) and cFOS-positive cells in the hippocampus, and increased the number of Ki67-positive cells in the dentate gyrus of the hippocampus of CUMS-exposed mice. These results help to further understand the antidepressant mechanism of hesperidin and provide new ideas for the future development of antidepressant drugs.

Metformin as a potential antidepressant: Mechanisms and therapeutic insights in depression

Depression is one of the most disabling psychiatric disorders, whose pathophysiology has not been fully understood. Increasing numbers of preclinical studies have highlighted that metformin, as the first-line hypoglycaemic agent, has a potential pleiotropic effect on depression. Moreover, there is emerging evidence that metformin shows antidepressant activity and improves depressive symptoms in rodent models of depression. However, the exact role and underlying mechanism of metformin in depression remain unclear and still need to be investigated. Recent studies suggest that metformin not only improves neuronal damage and structural plasticity in the hippocampus but also enhances the antidepressant effect of antidepressants. Therefore, in this review, we summarize the existing evidence for the use of metformin as a psychopharmaceutical and elaborate on the underlying mechanisms of metformin in mitigating the onset and progression of depression, as well as the associated biochemical signaling pathways and targets involved in the pathogenesis of depression. After reviewing several studies, we conclude that metformin helps reduce depressive symptoms by targeting multiple pathways, including the regulation of neurotransmitters, enhanced neurogenesis, anti-inflammatory effects, and changes in gut microbiota. We aim to gain a deeper understanding of the mechanism of action of metformin and provide new insights into its clinical value in the prevention and therapy of depression.

Comparing psilocybin to metformin as neuroprotective agents against Parkinson's dementia: A systematic review of evidence and efficacy

BACKGROUND & AIM

Treatment of Parkinson's disease (PD) has remained largely unchanged and focuses primarily on symptomatic relief through activation of dopaminergic pathways. Currently, there are no proven prophylactic approaches to the prevention of PD. This systematic review seeks to compare two separate compounds, metformin (MTF) and psilocybin, as potential prophylactic therapeutics against the development of PD.

METHODS

The authors conducted a systematic review focusing on primary studies that test these compounds on cell and animal models to determine if they might have any neuroprotective or neuroplastic effects.

RESULTS

The results of this review found that MTF may halt the progression of diseases such as PD through multiple mechanisms including reduced oxidative stress at the level of the mitochondria, thereby reducing α-synuclein related damage. Psilocybin, on the other hand, may increase repair of damaged neurons through psychoplastogenic activation of serotonergic pathways, particularly 5-HT2A receptor activation, ultimately increasing the release of brain derived neurotropic factor (BDNF) and the reduction of α-synuclein accumulation.

CONCLUSION

Implications of this study include a need for further research in off-label use of MTF as well as further research into serotonergic compounds such as psilocybin for the treatment and prevention of neurodegenerative diseases.

Emerging Pro-neurogenic Therapeutic Strategies for Neurodegenerative Diseases: A Review of Pre-clinical and Clinical Research

The neuroscience community has largely accepted the notion that functional neurons can be generated from neural stem cells in the adult brain, especially in two brain regions: the subventricular zone of the lateral ventricles and the subgranular zone in the dentate gyrus of the hippocampus. However, impaired neurogenesis has been observed in some neurodegenerative diseases, particularly in Alzheimer's, Parkinson's, and Huntington's diseases, and also in Lewy Body dementia. Therefore, restoration of neurogenic function in neurodegenerative diseases emerges as a potential therapeutic strategy to counteract, or at least delay, disease progression. Considering this, the present study summarizes the different neuronal niches, provides a collection of the therapeutic potential of different pro-neurogenic strategies in pre-clinical and clinical research, providing details about their possible modes of action, to guide future research and clinical practice.

Hyperglycemia-Driven Insulin Signaling Defects Promote Parkinson's Disease-like Pathology in Mice

This study aims to determine the effect of chronic hyperglycemia, induced by a high-fat diet and STZ-induced diabetes, on the development of Parkinson's disease-like characteristics. Understanding this relationship is crucial in pharmacology, neurology, and diabetes, as it could potentially lead to developing new therapeutic strategies for Parkinson's disease. Our study employed a comprehensive approach to investigate the effect of hyperglycemia on Parkinson's disease-like characteristics. Hyperglycemia was induced by a high-fat diet for 6- and 9-week duration with a single intraperitoneal STZ (100 mg/kg) injection at week 5 in C57/BL6 mice. Rotenone (10 mg/kg p.o.) was administered to C57/BL6 mice for 6 and 9 weeks. Time-dependent behavioral studies (wire-hang tests, pole tests, Y-maze tests, and round beam walk tests) were carried out to monitor pathology progression and deficits. Molecular protein levels (GLP1, PI3K, AKT, GSK-3β, NF-κB, and α-syn), oxidative stress (GSH and MDA) parameters, and histopathological alterations (H&E and Nissl staining) were determined after 6 weeks as well as 9 weeks. After 9 weeks of study, molecular protein expression (p-AKT and p-α-syn) was determined. Hyperglycemia induced by HFD and STZ induced significant motor impairment in mice, correlated with the rotenone group. Insulin receptor signaling (GLP1/PI3K/AKT) was found to be disrupted in the HFD+STZ group and also in rotenone-treated mice, which further enhanced phosphorylation of α-syn, suggesting its role in α-syn accumulation. Histopathological alterations indicating neuroinflammation and neurodegeneration were quite evident in the HFD+STZ and rotenone groups. Exposure to hyperglycemia induced by HFD+STZ administration exhibits PD-like characteristics after 9 weeks of duration, which was correlative with rotenone-induced PD-like symptoms.

The therapeutic potential of traditional Chinese medicine in depression: focused on the modulation of neuroplasticity

Depression, a mood disorder characterized by a persistent low mood and lack of enjoyment, is considered the leading cause of non-fatal health losses worldwide. Neuroplasticity refers to the brain's ability to adapt to external or internal stimuli, resulting in functional and structural changes. This process plays a crucial role in the development of depression. Traditional Chinese Medicine (TCM) shows significant potential as a complementary and alternative therapy for neurological diseases, including depression. However, there has been no systematic summary of the role of neuroplasticity in the pathological development of depression and TCM Interventions currently. This review systematically summarized recent literature on changes in neuroplasticity in depression and analyzed the regulatory mechanisms of active metabolites in TCM and TCM formulas on neuroplasticity in antidepressant treatment. Additionally, this review discussed the limitations of current research and the application prospects of TCM in regulating neuroplasticity in antidepressant research.

Comparing the effect of fluoxetine, escitalopram, and sertraline, on the level of BDNF and depression in preclinical and clinical studies: a systematic review

Brain-derived neurotrophic factor (BDNF) dysfunction is one of the most important mechanisms underlying depression. It seems that selective serotonin reuptake inhibitors (SSRIs) improve depression via affecting BDNF level. In this systematic review, for the first time, we aimed to review the effect of three SSRIs including fluoxetine, escitalopram, and sertraline, on both depression and BDNF level in preclinical and clinical studies. PubMed electronic database was searched, and 193 articles were included in this study. After reviewing all manuscripts, only one important difference was found: subjects. We found that SSRIs induce different effects in animals vs. humans. Preclinical studies showed many controversial effects, while human studies showed only two effects: improvement of depression, with or without the improvement of BDNF. However, most studies used chronic SSRIs treatment, while acute SSRIs were not effectively used and evaluated. In conclusion, it seems that SSRIs are reliable antidepressants, and the improvement effect of SSRIs on depression is not dependent to BDNF level (at least in human studies).

Promising use of metformin in treating neurological disorders: biomarker-guided therapies

Neurological disorders are a diverse group of conditions that affect the nervous system and include neurodegenerative diseases (Alzheimer's disease, multiple sclerosis, Parkinson's disease, Huntington's disease), cerebrovascular conditions (stroke), and neurodevelopmental disorders (autism spectrum disorder). Although they affect millions of individuals around the world, only a limited number of effective treatment options are available today. Since most neurological disorders express mitochondria-related metabolic perturbations, metformin, a biguanide type II antidiabetic drug, has attracted a lot of attention to be repurposed to treat neurological disorders by correcting their perturbed energy metabolism. However, controversial research emerges regarding the beneficial/detrimental effects of metformin on these neurological disorders. Given that most neurological disorders have complex etiology in their pathophysiology and are influenced by various risk factors such as aging, lifestyle, genetics, and environment, it is important to identify perturbed molecular functions that can be targeted by metformin in these neurological disorders. These molecules can then be used as biomarkers to stratify subpopulations of patients who show distinct molecular/pathological properties and can respond to metformin treatment, ultimately developing targeted therapy. In this review, we will discuss mitochondria-related metabolic perturbations and impaired molecular pathways in these neurological disorders and how these can be used as biomarkers to guide metformin-responsive treatment for the targeted therapy to treat neurological disorders.

Metformin role in Parkinson's disease: a double-sword effect

Parkinson's disease (PD) is a common neurodegenerative disease developed due to the degeneration of dopaminergic neurons in the substantia nigra. There is no single effective treatment in the management of PD. Therefore, repurposing effective and approved drugs like metformin could be an effective strategy for managing PD. However, the mechanistic role of metformin in PD neuropathology was not fully elucidated. Metformin is an insulin-sensitizing agent used as a first-line therapy in the management of type 2 diabetes mellitus (T2DM) and has the ability to reduce insulin resistance (IR). Metformin may have a beneficial effect on PD neuropathology. The neuroprotective effect of metformin is mainly mediated by activating adenosine monophosphate protein kinase (AMPK), which reduces mitochondrial dysfunction, oxidative stress, and α-synuclein aggregation. As well, metformin mitigates brain IR a hallmark of PD and other neurodegenerative diseases. However, metformin may harm PD neuropathology by inducing hyperhomocysteinemia and deficiency of folate and B12. Therefore, this review aimed to find the potential role of metformin regarding its protective and detrimental effects on the pathogenesis of PD. The mechanistic role of metformin in PD neuropathology was not fully elucidated. Most studies regarding metformin and its effectiveness in PD neuropathology were observed in preclinical studies, which are not fully translated into clinical settings. In addition, metformin effect on PD neuropathology was previously clarified in T2DM, potentially linked to an increasing PD risk. These limitations hinder the conclusion concerning the therapeutic efficacy of metformin and its beneficial and detrimental role in PD. Therefore, as metformin does not cause hypoglycemia and is a safe drug, it should be evaluated in non-diabetic patients concerning PD risk.

Merazin hydrate produces rapid antidepressant effects by activating CaMKII to promote neuronal activities and proliferation in hippocampus

In our previous studies, we demonstrated that merazin hydrate (MH) had rapid antidepressant effects, but the deep mechanism needed to be further investigated. In this study, we used depressive-like model, behavioral tests, molecular biology and pharmacological interventions to reveal the underlying mechanisms of MH's rapid antidepressants. We found that a single administration of MH was able to produce rapid antidepressant effects in chronic unpredictable mild stress (CUMS) exposed mice at 1 day later, similar to ketamine. Moreover, MH could not only significantly up-regulated the expressions of cFOS, but also obviously increased the number of Ki67 positive cells in hippocampal dentate gyrus (DG). Furthermore, we also found that the phosphorylated expression of calcium/calmodulin-dependent protein kinase II (CaMKII) was significantly reduced by CUMS in hippocampus, which was also reversed by MH. In addition, pharmacological inhibition of CaMKII by using KN-93 (a CaMKII antagonist) blocked the MH's up-regulation of cFOS and Ki67 in hippocampal DG. To sum up, this study demonstrated that MH produced rapid antidepressant effects by activating CaMKII to promote neuronal activities and proliferation in hippocampus.

The Antidiabetic Drug Metformin Attenuated Depressive and Anxiety-like Behaviors and Oxidative Stress in the Brain in a Rodent Model of Inflammation Induced by Lipopolysaccharide in Male Rats

BACKGROUND

Inflammation is considered to be a link between diabetes and central nervous system (CNS) disorders, including depression and anxiety. Metformin is suggested to have antioxidant, anti-inflammatory, and mood-improving effects. The aim of the current research was to investigate the effects of the antidiabetic drug metformin on depressive- and anxiety- like behaviors and oxidative stress in the brain in a rodent model of inflammation induced by lipopolysaccharide (LPS) in male rats.

MATERIALS AND METHODS

The rats were treated as follows: (1) Vehicle instead of metformin and lipopolysaccharide, (2) Lipopolysaccharide (1 mg/ kg) + vehicle instead of metformin, (3-5) Lipopolysaccharide + 50, 100, or 150 mg/ kg of metformin. After the behavioral tests, including open field (OF), elevated pulse maze (EPM), and force swimming (FS) tests, the brains were removed, and malondialdehyde (MDA), nitric oxide (NO) metabolites, total thiol, catalase (CAT) activity, interleukin-6 (IL-6) and superoxide dismutase (SOD) activity were determined.

RESULTS

In the EPM, metformin increased the open arm time and entry and decreased closed arm time and entry. In the FS test, metformin lowered the immobility and increased active time compared to lipopolysaccharide. In the OF test, metformin increased total crossing and total distance, time spent, traveled distance, and crossing number in the central zone. As a result of metformin administration, IL-6, MDA, and NO metabolites were decreased while thiol content, SOD, and CAT activity were increased.

CONCLUSION

The results indicated that the well-known antidiabetic drug metformin attenuated depressive- and anxiety-like behaviors induced by inflammation in rats. These beneficial effects are suggested to be due to their attenuating effects on neuroinflammation, oxidative stress, and NO in the brain.

Adult hippocampal neurogenesis: pharmacological mechanisms of antidepressant active ingredients in traditional Chinese medicine

Depression is characterized by prominent indicators and manifestations, such as anhedonia, which refers to the inability to experience pleasure, and persistent feelings of hopelessness. In clinical practice, the primary treatment approach involves the utilization of selective serotonin reuptake inhibitors (SSRIs) and related pharmacological interventions. Nevertheless, it is crucial to recognize that these agents are associated with significant adverse effects. Traditional Chinese medicine (TCM) adopts a multifaceted approach, targeting diverse components, multiple targets, and various channels of action. TCM has potential antidepressant effects. Anomalies in adult hippocampal neurogenesis (AHN) constitute a pivotal factor in the pathology of depression, with the regulation of AHN emerging as a potential key measure to intervene in the pathogenesis and progression of this condition. This comprehensive review presented an overview of the pharmacological mechanisms underlying the antidepressant effects of active ingredients found in TCM. Through examination of recent studies, we explored how these ingredients modulated AHN. Furthermore, we critically assessed the current limitations of research in this domain and proposed novel strategies for preclinical investigation and clinical applications in the treatment of depression in future.

Metformin Improves Comorbid Depressive Symptoms in Mice with Allergic Rhinitis by Reducing Olfactory Bulb Damage

Allergic rhinitis (AR) is a widespread disease that is frequently comorbid with depression. However, the mechanisms and treatments for depression in AR remain underexplored. Metformin, a widely used antidiabetic drug, has shown antidepressant effects. The aim of this study was to explore the effects and potential mechanisms of metformin on depression-like behaviors in an AR mouse model. In the present study, mice were sensitized and challenged with ovalbumin (OVA) to induce AR. Results showed that mice with AR exhibited significant depression-like behavior which was attenuated by metformin. In addition, the levels of expression of synaptic plasticity markers (anti-microtubule-associated protein 2, synaptophysin, postsynaptic density protein 95), neurogenesis markers (doublecortin and Ki-67), and brain-derived neurotrophic factor were decreased in the olfactory bulb (OB) of mice with AR, while metformin ameliorated all these alterations and reduced apoptosis in the OB of these mice. Furthermore, it enhanced the phosphorylation of AMP-activated kinase (AMPK) and the levels of ten-eleven translocation 2 (TET2) and 5-hydroxymethylcytosine in the OB. In conclusion, our findings suggest that metformin might be a viable strategy for treating AR-related depression, possibly by modulating neuroplasticity, neurogenesis, apoptosis, and BDNF signaling in the OB via the AMPK/TET2 pathway.

Poly (ADP-Ribose) polymerase 1 and parthanatos in neurological diseases: From pathogenesis to therapeutic opportunities

Poly (ADP-ribose) polymerase-1 (PARP-1) is the most extensively studied member of the PARP superfamily, with its primary function being the facilitation of DNA damage repair processes. Parthanatos is a type of regulated cell death cascade initiated by PARP-1 hyperactivation, which involves multiple subroutines, including the accumulation of ADP-ribose polymers (PAR), binding of PAR and apoptosis-inducing factor (AIF), release of AIF from the mitochondria, the translocation of the AIF/macrophage migration inhibitory factor (MIF) complex, and massive MIF-mediated DNA fragmentation. Over the past few decades, the role of PARP-1 in central nervous system health and disease has received increasing attention. In this review, we discuss the biological functions of PARP-1 in neural cell proliferation and differentiation, memory formation, brain ageing, and epigenetic regulation. We then elaborate on the involvement of PARP-1 and PARP-1-dependant parthanatos in various neuropathological processes, such as oxidative stress, neuroinflammation, mitochondrial dysfunction, excitotoxicity, autophagy damage, and endoplasmic reticulum (ER) stress. Additional highlight contains PARP-1's implications in the initiation, progression, and therapeutic opportunities for different neurological illnesses, including neurodegenerative diseases, stroke, autism spectrum disorder (ASD), multiple sclerosis (MS), epilepsy, and neuropathic pain (NP). Finally, emerging insights into the repurposing of PARP inhibitors for the management of neurological diseases are provided. This review aims to summarize the exciting advancements in the critical role of PARP-1 in neurological disorders, which may open new avenues for therapeutic options targeting PARP-1 or parthanatos.

Is metformin neuroprotective against diabetes mellitus-induced neurodegeneration? An updated graphical review of molecular basis

Diabetes mellitus (DM) is a metabolic disease that activates several molecular pathways involved in neurodegenerative disorders. Metformin, an anti-hyperglycemic drug used for treating DM, has the potential to exert a significant neuroprotective role against the detrimental effects of DM. This review discusses recent clinical and laboratory studies investigating the neuroprotective properties of metformin against DM-induced neurodegeneration and the roles of various molecular pathways, including mitochondrial dysfunction, oxidative stress, inflammation, apoptosis, and its related cascades. A literature search was conducted from January 2000 to December 2022 using multiple databases including Web of Science, Wiley, Springer, PubMed, Elsevier Science Direct, Google Scholar, the Core Collection, Scopus, and the Cochrane Library to collect and evaluate peer-reviewed literature regarding the neuroprotective role of metformin against DM-induced neurodegenerative events. The literature search supports the conclusion that metformin is neuroprotective against DM-induced neuronal cell degeneration in both peripheral and central nervous systems, and this effect is likely mediated via modulation of oxidative stress, inflammation, and cell death pathways.

Metformin mitigates amyloid β1-40-induced cognitive decline via attenuation of oxidative/nitrosative stress and neuroinflammation

Metformin is an antidiabetic medicine widely used for management of type 2 diabetes with neuroprotective effects and promising potential to attenuate cognitive impairment. The efficacy of metformin in attenuation of Alzheimer's disease (AD) pathology has not been well-documented. Thus, this study was designed to assess protective effect of metformin against Aβ_1-40-instigared cognitive impairment. After intra-CA1 microinjection of aggregated Aβ_1-40, rats received oral metformin (50 and/or 200 mg/kg/day) for two weeks. Cognition function was analyzed in various behavioral tasks besides measurement of hippocampal oxidative stress, apoptosis, and inflammation along with H&E staining and 3-nitrotyrosine (3-NT) immunohistochemistry. Obtained data showed significant improvement of discrimination score in novel object recognition test, higher alternation score in Y maze, greater latency in passive avoidance task, and lower working and reference memory errors in radial arm maze in metformin-treated Aβ-injured group. Moreover, metformin treatment attenuated hippocampal levels of nitrite, MDA, protein carbonyl, ROS, TNFα, GFAP, DNA fragmentation intensity, caspase 3 activity, AChE activity, and increased SOD activity and level of IL-10 as an anti-inflammatory factor. In addition, metformin treatment was associated with lower CA1 neuronal loss and it also decreased intensity of 3-NT immunoreactivity as an indicator of nitrosative stress. Taken together, obtained findings showed neuroprotective and anti-dementia property of metformin in male rats and this may have potential benefit in attenuation of cognitive decline and related complications in patients with neurodegenerative disorders such as AD besides diabetes mellitus.

PARP1 and OGG1 in Medicated Patients With Depression and the Response to ECT

BACKGROUND

Oxidative stress and oxidation-induced DNA damage may contribute to the pathophysiology of depression. Two key mediators of base excision repair (BER) in response to oxidative damage of DNA are OGG1 and PARP1. Few studies have examined changes in OGG1 or PARP1 mRNA in patients with depression or following antidepressant treatment. We examined PARP1 and OGG1 mRNA levels in patients with depression at baseline/pre-electroconvulsive therapy (baseline/pre-ECT) vs in healthy controls and in patients following a course of ECT.

METHODS

PARP1 and OGG1 were examined in whole blood samples from medicated patients with depression and controls using quantitative real-time polymerase chain reaction. Exploratory subgroup correlational analyses were performed to determine associations between PARP1 and OGG1 and mood (Hamilton Depression Rating Scale 24-item version) scores as well as with vitamin B3, SIRT1, PGC1α, and tumor necrosis factor alpha levels, as previously reported on in this cohort.

RESULTS

PARP1 levels were reduced in samples from patients with depression vs controls (P = .03), though no difference was noted in OGG1. ECT had no effect on PARP1 or OGG1. Higher baseline PARP1 weakly correlated with greater mood improvement post ECT (P = .008). Moreover, PARP1 positively correlated with SIRT1 at baseline and post ECT, and positive correlations were noted between change in PARP1 and change in OGG1 with change in tumor necrosis factor alpha post ECT.

CONCLUSIONS

To our knowledge, this is the first study to examine the effect of ECT on BER enzymes. A better understanding of BER enzymes and DNA repair in depression could unearth new mechanisms relevant to the pathophysiology of this condition and novel antidepressant treatments.

The pathobiological basis of depression in Parkinson disease: challenges and outlooks

Depression, with an estimated prevalence of about 40% is a most common neuropsychiatric disorder in Parkinson disease (PD), with a negative impact on quality of life, cognitive impairment and functional disability, yet the underlying neurobiology is poorly understood. Depression in PD (DPD), one of its most common non-motor symptoms, can precede the onset of motor symptoms but can occur at any stage of the disease. Although its diagnosis is based on standard criteria, due to overlap with other symptoms related to PD or to side effects of treatment, depression is frequently underdiagnosed and undertreated. DPD has been related to a variety of pathogenic mechanisms associated with the underlying neurodegenerative process, in particular dysfunction of neurotransmitter systems (dopaminergic, serotonergic and noradrenergic), as well as to disturbances of cortico-limbic, striato-thalamic-prefrontal, mediotemporal-limbic networks, with disruption in the topological organization of functional mood-related, motor and other essential brain network connections due to alterations in the blood-oxygen-level-dependent (BOLD) fluctuations in multiple brain areas. Other hypothetic mechanisms involve neuroinflammation, neuroimmune dysregulation, stress hormones, neurotrophic, toxic or metabolic factors. The pathophysiology and pathogenesis of DPD are multifactorial and complex, and its interactions with genetic factors, age-related changes, cognitive disposition and other co-morbidities awaits further elucidation.

Metformin improves depressive-like behavior in experimental Parkinson's disease by inducing autophagy in the substantia nigra and hippocampus

Parkinson's disease (PD) remains a disease of little known etiology. In addition to the motor symptoms, depression is present in about 40% of patients, contributing to the loss of quality of life. Recently, the involvement of the autophagy mechanism in the pathogenesis of depression has been studied, in addition to its involvement in PD as well. In this study, we tested the effects of metformin, an antidiabetic drug also with antidepressant effects, on depressive-like behavior in a rotenone-induced PD model and on the autophagy process. Mice 8-week-old male C57BL/6 were induced with rotenone for 20 consecutive days (2.5 mg/kg/day) and treated with metformin (200 mg/kg/day) from the 5th day of induction. All the animals were submitted to rotarod, sucrose preference and tail suspension tests. After euthanasia, the substantia nigra and hippocampus were removed for analysis by western blotting or fixed and analyzed by immunofluorescence. The results show that there was an impairment of autophagy in animals induced by rotenone both in nigral and extranigral regions as well as a depressive-like behavior. Metformin was able to inhibit depressive-like behavior and increase signaling pathway proteins, transcription factors and autophagosome-forming proteins, thus inducing autophagy in both the hippocampus and the substantia nigra. In conclusion, we show that metformin has an antidepressant effect in a rotenone-induced PD model, which may result, at least in part, from the induction of the autophagy process.

Curcumin can improve Parkinson's disease via activating BDNF/PI3k/Akt signaling pathways

Parkinson's disease is a common progressive neurodegenerative disease, and presently has no curative agent. Curcumin, as one of the natural polyphenols, has great potential in neurodegenerative diseases and other different pathological settings. The brain-derived neurotrophic factor (BDNF) and phosphatidylinositol 3 kinase (PI3k)/protein kinase B (Akt) signaling pathways are significantly involved nerve regeneration and anti-apoptotic activities. Currently, relevant studies have confirmed that curcumin has an optimistic impact on neuroprotection via regulating BDNF and PI3k/Akt signaling pathways in neurodegenerative disease. Here, we summarized the relationship between BDNF and PI3k/Akt signaling pathway, the main biological functions and neuroprotective effects of curcumin via activating BDNF and PI3k/Akt signaling pathways in Parkinson's disease. This paper illustrates that curcumin, as a neuroprotective agent, can delay the progression of Parkinson's disease by protecting nerve cells.

Hippocampal miR-124 Participates in the Pathogenesis of Depression via Regulating the Expression of BDNF in a Chronic Social Defeat Stress Model of Depression

OBJECTIVE

As one of the most prevalent psychiatric disorders, the exact pathogenesis of depression remains elusive. Therefore, there is an urgent need to identify novel antidepressants for effective treatment. MicroRNA-124 (miR-124), the most abundant miRNA in brain tissue, plays a key effect on adult neurogenesis and neuronal differentiation. However, the mechanism of miR-124 in depression has not been clarified so far. The aim of this study is to provide broad insight into the mechanisms underlying depression.

METHODS

In the study, we used the forced swim test (FST), the tail suspension test (TST), and a Chronic Social Defeat Stress (CSDS) mice model of depression. Quantitative real-time reverse transcription PCR (qRT-PCR), western blotting, immunofluorescence and virus-mediated gene transfer were used together. The level of plasma corticosterone in mice was analyzed by Enzyme Linked Immunosorbent Assay (ELISA).

RESULTS

It was found that CSDS robustly increased the level of miR-124 in the hippocampus. Genetic knockdown of hippocampal miR-124 produced significant antidepressant-like effects in the CSDS model of depression. Furthermore, AAV-siR-124-EGFP treatment increased the level of plasma corticosterone in CSDS-induced mice. Moreover, it was found that the antidepressant-like effects induced by miR-124 inhibition required the hippocampal BDNF-TrkB system.

CONCLUSION

Hippocampal miR-124 participated in the pathogenesis of depression by regulating BDNF biosynthesis and was a feasible antidepressant target.

The anxiolytic Drug Buspirone Prevents Rotenone-Induced Toxicity in a Mouse Model of Parkinson’s Disease

A pharmacological and genetic blockade of the dopamine D3 receptor (D3R) has shown to be neuroprotective in models of Parkinson’s disease (PD). The anxiolytic drug buspirone, a serotonin receptor 1A agonist, also functions as a potent D3R antagonist. To test if buspirone elicited neuroprotective activities, C57BL/6 mice were subjected to rotenone treatment (10mg/kg i.p for 21 days) to induce PD-like pathology and were co-treated with increasing dosages of buspirone (1, 3, or 10 mg/kg i.p.) to determine if the drug could prevent rotenone-induced damage to the central nervous system (CNS). We found that high dosages of buspirone prevented the behavioural deficits caused by rotenone in the open field test. Molecular and histological analyses confirmed that 10 mg/kg of buspirone prevented the degeneration of TH-positive neurons. Buspirone attenuated the induction of interleukin-1β and interleukin-6 expression by rotenone, and this was paralleled by the upregulation of arginase-1, brain-derived neurotrophic factor (BDNF), and activity-dependent neuroprotective protein (ADNP) in the midbrain, striatum, prefrontal cortex, amygdala, and hippocampus. Buspirone treatment also improved mitochondrial function and antioxidant activities. Lastly, the drug prevented the disruptions in the expression of two neuroprotective peptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP). These results pinpoint the neuroprotective efficacy of buspirone against rotenone toxicity, suggesting its potential use as a therapeutic agent in neurodegenerative and neuroinflammatory diseases, such as PD.