Long-Term Treatment with Fluvoxamine Decreases Nonmotor Symptoms and Dopamine Depletion in a Postnatal Stress Rat Model of Parkinson's Disease

Neonatal stress disrupts the glymphatic system development and increases the susceptibility to Parkinson's disease in later life

INTRODUCTION

Neonatal stress disrupts brain development and increases the risk of neurological disorders later in life. However, the impact of neonatal stress on the development of the glymphatic system and susceptibility to Parkinson's disease (PD) remains largely unknown.

METHODS

Neonatal maternal deprivation (NMD) was performed on mice for 14 consecutive days to model chronic neonatal stress. Adeno-associated virus expressing A53T-α-synuclein (α-syn) was injected into the substantia nigra to establish PD model mice. Glymphatic activity was determined using in vivo magnetic resonance imaging, ex vivo fluorescence imaging and microplate assay. The transcription and expression of aquaporin-4 (AQP4) and other molecules were evaluated by qPCR, western blotting, and immunofluorescence. Animal's responses to NMD and α-syn overexpression were observed using behavioral tests.

RESULTS

Glymphatic activity was impaired in adult NMD mice. AQP4 polarization and platelet-derived growth factor B (PDGF-B) signaling were reduced in the frontal cortex and hippocampus of both young and adult NMD mice. Furthermore, exogenous α-syn accumulation was increased and PD-like symptoms were aggravated in adult NMD mice.

CONCLUSION

The results demonstrated that NMD could disrupt the development of the glymphatic system through PDGF-B signaling and increase the risk of PD later in life, indicating that alleviating neonatal stress could be beneficial in protecting the glymphatic system and reducing susceptibility to neurodegeneration.

Investigation of non-invasive focused ultrasound efficacy on depressive-like behavior in hemiparkinsonian rats

Depression is a common non-motor symptom in Parkinson's disease (PD) that includes anhedonia and impacts quality of life but is not effectively treated with conventional antidepressants clinically. Vagus nerve stimulation improves treatment-resistant depression in the general population, but research about its antidepressant efficacy in PD is limited. Here, we administered peripheral non-invasive focused ultrasound to hemiparkinsonian ('PD') and non-parkinsonian (sham) rats to mimic vagus nerve stimulation and assessed its antidepressant-like efficacy. Following 6-hydroxydopamine (6-OHDA) lesion, akinesia-like immobility was assessed in the limb-use asymmetry test, and despair- and anhedonic-like behaviors were evaluated in the forced swim test and sucrose preference test, respectively. After, tyrosine hydroxylase immuno-staining was employed to visualize and quantify dopaminergic degeneration in the substantia nigra pars compacta, ventral tegmental area, and striatum. We found that PD rats exhibited akinesia-like immobility and > 90% reduction in tyrosine hydroxylase immuno-staining ipsilateral to the lesioned side. PD rats also demonstrated anhedonic-like behavior in the sucrose preference test compared to sham rats. No 6-OHDA lesion effect on immobility in the forced swim test limited conclusions about the efficacy of ultrasound on despair-like behavior. However, ultrasound improved anhedonic-like behavior in PD rats and this efficacy was sustained through the end of the 1-week recovery period. The greatest number of animals demonstrating increased sucrose preference was in the PD group receiving ultrasound. Our findings here are the first to posit that peripheral non-invasive focused ultrasound to the celiac plexus may improve anhedonia in PD with further investigation needed to reveal its potential for clinical applicability.

"The wrong tools for the right job": a critical meta-analysis of traditional tests to assess behavioural impacts of maternal separation

RATIONALE

Unconditioned tasks in rodents have been the mainstay of behavioural assessment for decades, but their validity and sensitivity to detect the behavioural consequences of early life stress (ELS) remains contentious and highly variable.

OBJECTIVES

In the present study, we carried out a meta-analysis to investigate whether persistent behavioural effects, as assessed using unconditioned procedures in rats, are a reliable consequence of early repeated maternal separation, a commonly used procedure in rodents to study ELS.

METHODS

A literature search identified 100 studies involving maternally separated rats and the following unconditioned procedures: the elevated plus maze (EPM); open field test (OFT); sucrose preference test (SPT) and forced swim task (FST). Studies were included for analysis if the separation of offspring from the dam was at least 60 min every day during the pre-weaning period prior to the start of adolescence.

RESULTS

Our findings show that unconditioned tasks are generally poor at consistently demonstrating differences between control and separated groups with pooled effect sizes that were either small or non-existent (EPM: Hedge's g =  - 0.35, p = 0.01, OFT: Hedge's g =  - 0.32, p = 0.05, SPT: Hedge's g =  - 0.33, p = 0.21, FST: Hedge's g = 0.99, p = 0.0001). Despite considerable procedural variability between studies, heterogeneity statistics were low; indicating the lack of standardization in the maternal separation protocol was the not the cause of these inconsistent effects.

CONCLUSIONS

Our findings indicate that in general, unconditioned tests of depression and anxiety are not sufficient to reveal the full behavioural repertoire of maternal separation stress should not be relied upon in isolation. We argue that more objective tasks that sensitively detect specific cognitive processes are better suited for translational research on stress-related disorders such as depression.

Rhabdomyolysis in a male adolescent associated with monotherapy of fluvoxamine

Rhabdomyolysis is a syndrome resulting from striated muscular breakdown, which may occur due to drug therapy with agents such as selective serotonin reuptake inhibitors (SSRIs). Although studies have shown that fluvoxamine can rarely cause myalgia, there are no reported cases of rhabdomyolysis due to fluvoxamine monotherapy. Here we describe a case of rhabdomyolysis due to fluvoxamine monotherapy for obsessive-compulsive disorder. The young adolescent developed pain in the extremities, and an increase in serum creatine kinase (CK) and myoglobin during fluvoxamine treatment. These adverse reactions were reversed immediately after the medicine was changed to another SSRI-sertraline. This is the first reported case of fluvoxamine-associated rhabdomyolysis. It is advisable to determine serum CK levels before starting fluvoxamine treatment, and then at regular intervals, to avoid the occurrence of severe acute kidney injury with possible life-threatening complications.

A new perspective on hippocampal synaptic plasticity and post-stroke depression

Post-stroke depression, a common complication after stroke, severely affects the recovery and quality of life of patients with stroke. Owing to its complex mechanisms, post-stroke depression treatment remains highly challenging. Hippocampal synaptic plasticity is one of the key factors leading to post-stroke depression; however, the precise molecular mechanisms remain unclear. Numerous studies have found that neurotrophic factors, protein kinases and neurotransmitters influence depressive behaviour by modulating hippocampal synaptic plasticity. This review further elaborates on the role of hippocampal synaptic plasticity in post-stroke depression by summarizing recent research and analysing possible molecular mechanisms. Evidence for the correlation between hippocampal mechanisms and post-stroke depression helps to better understand the pathological process of post-stroke depression and improve its treatment.

Neurobiology of depression in Parkinson's disease: Insights into epidemiology, molecular mechanisms and treatment strategies

Parkinson's disease (PD) is characterized mainly by motor dysfunctions due to the progressive loss of dopaminergic neurons. However, PD patients experience a multitude of debilitating non-motor symptoms, including depression, which may have deleteriously detrimental effects on life. Depression is multifactorial and exhibits a bimodal progression in PD, but its underlying molecular mechanisms are poorly understood. Studies demonstrating the pathophysiology of depression in PD and the specific treatment strategies for depression-like symptoms in PD patients are largely lacking, often underrated, under-recognized and, consequently, inadequately/under-treated. Nevertheless, reports suggest that the incidence of depression is approximately 20-30% of PD patients and may precede the onset of motor symptoms. Diagnosing depression in PD becomes difficult due to the clinical overlap in symptomatology between the two diseases, and the nigrostriatal dysfunction alone is insufficient to explain depressive symptoms in PD. Therefore, the current study provides an overview of the molecular mechanisms underlying the development of depression in PD and new insights into developing current antidepressant strategies to treat depression in PD. This review will identify and understand the molecular pathological mechanisms of depression in PD that will fundamentally help tailoring therapeutic interventions for depressive symptoms in PD.

Transplantation of ERK gene-modified bone marrow mesenchymal stem cells ameliorates cognitive deficits in a 6-hydroxydopamine rat model of Parkinson's disease

The study aimed to investigate bone marrow mesenchymal stem cells (BMSCs) and extracellular signal-regulated kinase (ERK) gene-modified BMSCs (ERK-BMSCs) transplantation in ameliorating cognitive deficits in Parkinson's disease (PD). The PD rat model was built by 6-hydroxydopamine (6-OHDA) injection into the right striatum for 8 weeks, then successful PD rats were randomly divided into three groups and respectively transplanted in the same position of striatum as modeling with PBS, BMSCs and ERK-BMSCs for another 8 weeks. The 6-OHDA-induced PD rat model was successfully established, as demonstrated by reduced active avoidance response (AAR) times, percentage of time exploring in the light area (Ltime%) and platform quadrant time (PQT), as well as p-ERK expression. Compared with PBS rats, both BMSCs and ERK-BMSCs transplantation significantly reduced the left turn number, while increased AAR, Ltime%, PQT and p-ERK expression, suggesting improved cognitive abilities through restoring p-ERK expression. In addition, ERK-BMSCs injection exhibited higher therapeutic efficacy against cognitive deficits compared with BMSCs injection. These results demonstrated that BMSCs transplantation ameliorated cognitive deficits, and ERK-BMSCs exerted synergistic effects, which may prove beneficial against cognitive impairments in PD.

Therapeutic Approaches to Non-Motor Symptoms of Parkinson's Disease: A Current Update on Preclinical Evidence

Despite being classified as a movement disorder, Parkinson's disease (PD) is characterized by a wide range of non-motor symptoms that significantly affect the patients' quality of life. However, clear evidence-based therapy recommendations for non-motor symptoms of PD are uncommon. Animal models of PD have previously been shown to be useful for advancing the knowledge and treatment of motor symptoms. However, these models may provide insight into and assess therapies for non-motor symptoms in PD. This paper highlights non-motor symptoms in preclinical models of PD and the current position regarding preclinical therapeutic approaches for these non-motor symptoms. This information may be relevant for designing future preclinical investigations of therapies for nonmotor symptoms in PD.

Enduring effects of early-life adversity on reward processes: A systematic review and meta-analysis of animal studies

Two-thirds of individuals experience adversity during childhood such as neglect, abuse or highly-stressful events. Early-life adversity (ELA) increases the life-long risk of developing mood and substance use disorders. Reward-related deficits has emerged as a key endophenotype of such psychiatric disorders. Animal models are invaluable for studying how ELA leads to reward deficits. However, the existing literature is heterogenous with difficult to reconcile findings. To create an overview, we conducted a systematic review containing multiple meta-analyses regarding the effects of ELA on reward processes overall and on specific aspects of reward processing in animal models. A comprehensive search identified 120 studies. Most studies omitted key details resulting in unclear risk of bias. Overall meta-analysis showed that ELA significantly reduced reward behaviors (SMD: -0.42 [-0.60; -0.24]). The magnitude of ELA effects significantly increased with longer exposure. When reward domains were analyzed separately, ELA only significantly dampened reward responsiveness (SMD: -0.525[-0.786; -0.264]) and social reward processing (SMD: -0.374 [-0.663; -0.084]), suggesting that ELA might lead to deficits in specific reward domains.

Application of Neurotoxin-Induced Animal Models in the Study of Parkinson's Disease-Related Depression: Profile and Proposal

Depression can be a non-motor symptom, a risk factor, and even a co-morbidity of Parkinson's disease (PD). In either case, depression seriously affects the quality of life of PD patients. Unfortunately, at present, a large number of clinical and basic studies focused on the pathophysiological mechanism of PD and the prevention and treatment of motor symptoms. Although there has been increasing attention to PD-related depression, it is difficult to achieve early detection and early intervention, because the clinical guidelines mostly refer to depression developed after or accompanied by motor impairments. Why is there such a dilemma? This is because there has been no suitable preclinical animal model for studying the relationship between depression and PD, and the assessment of depressive behavior in PD preclinical models is as well a very challenging task since it is not free from the confounding from the motor impairment. As a common method to simulate PD symptoms, neurotoxin-induced PD models have been widely used. Studies have found that neurotoxin-induced PD model animals could exhibit depression-like behaviors, which sometimes manifested earlier than motor impairments. Therefore, there have been attempts to establish the PD-related depression model by neurotoxin induction. However, due to a lack of unified protocol, the reported results were diverse. For the purpose of further promoting the improvement and optimization of the animal models and the study of PD-related depression, we reviewed the establishment and evaluation strategies of the current animal models of PD-related depression based on both the existing literature and our own research experience, and discussed the possible mechanism and interventions, in order to provide a reference for future research in this area.

Early-Life Stress Induces Prodromal Features of Parkinsonism in Ageing Rats

Early-life stress (ELS) can cause long-term effects on human health, ranging from adolescence to adulthood, and even to gerontic. Although clinical retrospective data suggest that ELS may be related to senile neurodegenerative diseases such as Parkinson's disease (PD), there are few prospective investigations to explore its real contribution to PD. Here, we investigated the behavioral, histochemical, neuromorphological, and transcriptional changes induced by maternal separation (MS), an ELS model. Without neurotoxin, MS rats showed behavioral alterations in olfaction, locomotion, and gait characters after depression compared with control rats. Based on neuroimaging and histochemistry, although we found that the dopaminergic system in the striatum was impaired after MS, the decrease of striatal dopamine level was ~33%. Consistently, tyrosine hydroxylase immunostaining positive neurons of MS rats in the substantia nigra showed deficit by about 20% in cell counting. Furthermore, using transcriptome sequencing, we discovered many differentially expressed genes (DEGs) of MS rats in the striatum significantly enriched in the pathway of dopaminergic synapse, and the biological process of locomotion and neuromuscular process controlling balance. Encouragingly, some representative DEGs relating to PD were singled out. These results suggest that ELS-depression rats potentially mimic some key features of prodromal stage of PD during natural senescence. In conclusion, our findings provide some novel insights into the future pathogenesis and therapeutic studies for PD related to depression.

Highlighting Immune System and Stress in Major Depressive Disorder, Parkinson's, and Alzheimer's Diseases, with a Connection with Serotonin

There is recognition that both stress and immune responses are important factors in a variety of neurological disorders. Moreover, there is an important role of several neurotransmitters that connect these factors to several neurological diseases, with a special focus in this paper on serotonin. Accordingly, it is known that imbalances in stressors can promote a variety of neuropsychiatric or neurodegenerative pathologies. Here, we discuss some facts that link major depressive disorder, Alzheimer’s, and Parkinson’s to the stress and immune responses, as well as the connection between these responses and serotonergic signaling. These are important topics of investigation which may lead to new or better treatments, improving the life quality of patients that suffer from these conditions.

Resveratrol against 6-OHDA-induced damage of PC12 cells via PI3K/Akt

Objective

Our previous in vivo study found that resveratrol (Res), which is a phytoalexin, attenuated 6-hydroxydopamine (6-OHDA)-induced motor dysfunction by activating the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway in rats. Therefore, we further explored the protective effect of Res on 6-OHDA-induced damage to PC12 cells in vitro with respect to the PI3K/Akt signaling pathway.

Methods

We incubated PC12 cells with 75 μM 6-OHDA for 24 h, and Res was then added at a final concentration of 25 μM; the protective effect was examined via MTT and lactate dehydrogenase (LDH) assays. In addition, the PI3K inhibitor LY294002 was used to investigate the potential mechanism. JC-1 staining was used to detect the mitochondrial membrane potential (MMP), and western blotting (WB) was used to detect the phosphorylation of Akt-Ser473.

Results

Compared with that in the control, the cell viability, total superoxide dismutase (SOD) activity, MMP, and p-Akt-Ser473 level of 6-OHDA-treated PC12 cells were significantly decreased, while the leakage rate of LDH was increased. And after treatment with 25 μM Res, the cell viability, total SOD activity, MMP, and p-Akt-Ser473 level of 6-OHDA-treated PC12 cells were significantly increased compared with those of the control cells, while the leakage rate of LDH was decreased. These effects of Res were antagonized by LY294002.

Conclusions

Res ameliorates 6-OHDA-induced damage to PC12 cells via activation of the PI3K/Akt signaling pathway.