Pharmaceutical Pollution Alters the Structure of Freshwater Communities and Hinders Their Recovery from a Fish Predator.

Freshwater ecosystems are under threat from rising pharmaceutical pollution. While such pollutants are known to elicit biological effects on organisms, we have limited knowledge on how these effects might cascade through food-webs, disrupt ecological processes, and shape freshwater communities. In this study, we used a mesocosm experiment to explore how the community impacts of a top-order predator, the eastern mosquitofish (Gambusia holbrooki), are mediated by exposure to environmentally relevant low (measured concentration: ∼10 ng/L) and high concentrations (∼110 ng/L) of the pervasive pharmaceutical pollutant fluoxetine. We found no evidence that exposure to fluoxetine altered the consumptive effects of mosquitofish on zooplankton. However, once mosquitofish were removed from the mesocosms, zooplankton abundance recovered to a greater extent in control mesocosms compared to both low and high fluoxetine-exposed mesocosms. By the end of the experiment, this resulted in fundamental differences in community structure between the control and fluoxetine-treated mesocosms. Specifically, the control mesocosms were characterized by higher zooplankton abundances and lower algal biomass, whereas mesocosms exposed to either low or high concentrations of fluoxetine had lower zooplankton abundances and higher algal biomass. Our results suggest that fluoxetine, even at very low concentrations, can alter aquatic communities and hinder their recovery from disturbances.

Initiation of fluoxetine in a pediatric patient with Mucopolysaccharidosis IIIA: Early observations.

Fluoxetine has been identified as a potential treatment for mucopolysaccharidosis IIIA (MPS IIIA), a debilitating and progressive lysosomal storage disorder for which no treatments are approved. In the MPS IIIA mouse model, fluoxetine decreases the accumulation of glycosaminoglycans and aggregated autophagic substrates, reducing inflammation, and slowing cognitive deterioration. 1 We treated a single patient, 6 years old, under off-label prescription of fluoxetine, a selective serotonin reuptake inhibitor (SSRI). The primary endpoint was safety. Secondary exploratory assessments included urine quantitative heparan sulfate. Fluoxetine was well-tolerated in this patient and the patient continued treatment following the 12-month monitoring period. The patient experienced an increase in daytime somnolence which resolved with rescheduling fluoxetine administration to bedtime. Quantitative heparan sulfate levels remained elevated during treatment. Parents reported improved sleep latency time and less nighttime waking. These findings support general tolerability and further study of fluoxetine as a potential therapy for MPS IIIA.

Evaluating non-monotonic dose-response relationships in ecotoxicological risk assessment: A case study based on a systematic review of data on fluoxetine.

The environmental presence of pharmaceuticals, including the antidepressant fluoxetine, has become a subject of concern. Numerous studies have revealed effects of fluoxetine at environmental concentrations. Some of these studies have reported non-monotonic dose-response curves (NMDRs), leading to discussion because of the inconsistent detection of subtle effects and lack of mechanistic understanding. Nevertheless, investigating NMDRs in risk assessment is important, because neglecting them could underestimate potential risks of chemicals at low levels of exposure. Identification and quantification of NMDRs in risk assessment remains challenging, particularly given the prevalence of single outliers and the lack of sound statistical analyses. In response, the European Food Safety Authority (Beausoleil et al., 2016) presented a framework delineating six checkpoints for the evaluation of NMDR datasets, offering a systematic method for their assessment. The present study applies this framework to the case study of fluoxetine, aiming to assess the weight-of-evidence for the reported NMDR relationships. Through a systematic literature search, 53 datasets were selected for analysis against the six checkpoints. The results reveal that while a minority of these datasets meet all checkpoints, a significant proportion (27%) fulfilled at least five. Notably, many studies did not meet checkpoint 3, which requires NMDRs to be based on more than a single outlier. Overall, the current study points out a number of studies with considerable evidence supporting the presence of NMDRs for fluoxetine, while the majority of studies lacks strong evidence. The suggested framework proved useful for analysing NMDRs in ecotoxicological studies, but it is still imperative to develop further understanding of their biological plausibility.

Clinical effect of acupuncture at ghost points combined with fluoxetine hydrochloride on mild-to-moderate depression.

BACKGROUND: Depression is a common, chronic, and recurrent mood disorder that has become a worldwide health hazard. Fluoxetine hydrochloride, a common treatment method, can inhibit 5-hydroxytryptamine (5-HT) recycling in the presynaptic membrane; however, the efficacy of a single drug is inadequate. At present, mild-to-moderate depression can be treated with acupuncture of ghost caves, but the clinical curative effect of combined therapy with fluoxetine hydrochloride has not been sufficiently reported. AIM: To evaluate the clinical effect of acupuncture at ghost points combined with fluoxetine hydrochloride in the treatment of mild-to-moderate depression. METHODS: This retrospective study included 160 patients with mild-to-moderate depression who were admitted to Shanghai Hospital of Integrated Traditional Chinese and Western Medicine, Affiliated to Shanghai University of Traditional Chinese Medicine, between January 2022 and June 2023. Patients were separated into a single-agent group (fluoxetine hydrochloride treatment, n = 80) and a coalition group (fluoxetine hydrochloride treatment combined with acupuncture at ghost points, n = 80). Pre-treatment symptoms were recorded, and the clinical curative effect and adverse reactions [Asberg Antidepressant Side Effects Scale (SERS)] were assessed. Depression before and after treatment [Hamilton Depression Scale (HAMD)-24], neurotransmitter levels [5-HT, norepinephrine (NE), dopamine (DA)], oxidative stress indicators [superoxide dismutase (SOD), malondialdehyde (MDA)], and sleep quality [Pittsburgh Sleep Quality Index (PSQI)] were compared. RESULTS: The total efficacy rate was 97.50% in the coalition group and 86.25% in the single-agent group (P < 0.05). After 2, 4, 6, and 8 wk of treatment, the HAMD, self-rating depression scale, and SERS scores of the coalition and single-agent groups decreased compared with pre-treatment, and the decrease was more significant in the coalition group (P < 0.05). After 8 wk of treatment, the levels of NE, DA, 5-HT, and SOD in the coalition and single-agent groups increased, while the levels of MDA decreased; the increases and decrease in the coalition group were more significant (P < 0.05). The PSQI scores of the coalition and single-agent groups decreased, and the decrease was more significant in the coalition group (P < 0.05). CONCLUSION: Acupuncture at ghost points combined with paroxetine tablets can safely improve depressive symptoms and sleep disorders, regulate neurotransmitter levels, and reduce stress responses in patients with mild-to-moderate depression.

Effect of depression and the antidepressant fluoxetine on osseointegration-A pre-clinical in vivo experimental study.

OBJECTIVE: The aim of this study was to explore the effect of depression and selective serotonin reuptake inhibitors on implant osseointegration and bone healing. METHODS: Forty-eight 6- to 8-week-old SPF Sprague-Dawley male rats were randomly divided into four groups: the Control group, the Fluoxetine group, the Depression group and the De&Flu group. The rats in the Depression group and the De&Flu group were subjected to a depression modelling process, and the rats in the Control group and the Fluoxetine group were raised normally. Then, a titanium implant was placed in the right tibia of each rat. In the Fluoxetine group and De&Flu group, fluoxetine was injected subcutaneously daily, while subcutaneously injecting physiological saline in the Control group and Depression group. Collecting serum from the rats used for ELISA. The surgical area was cut for microcomputed tomography and histology observation. RESULTS: After 12 weeks, bone mineral density was lower in the De&Flu group than in the Control group, Depression group and Fluoxetine group. Bone mineral density was also lower in the Depression group and the Fluoxetine group than in the Control group. The percentage of bone-implant contact (BIC%) in De&Flu rats was lower than in the Control, Depression and Fluoxetine groups. The BIC% in the Depression group and the Fluoxetine group was lower than in the Control group. CONCLUSIONS: Depression and fluoxetine negatively affect bone density and implant osseointegration independently, and this damaging effect is exacerbated when both factors are present. The mechanism may be related to the dysregulation of the hypothalamic-pituitary-adrenal axis and inflammation in the body.

Fluoxetine Rescues Excessive Myelin Formation and Psychological Behaviors in a Murine PTSD Model.

Posttraumatic stress disorder (PTSD) is a complex mental disorder notable for traumatic experience memory. Although current first-line treatments are linked with clinically important symptom reduction, a large proportion of patients retained to experience considerable residual symptoms, indicating pathogenic mechanism should be illustrated further. Recent studies reported that newly formed myelin could shape neural circuit function and be implicated in fear memory preservation. However, its role in PTSD remains to be elucidated. In this study, we adopted a restraint stress-induced PTSD mouse model and found that PTSD-related neuropsychiatric symptoms were accompanied by increased myelination in the posterior parietal cortex and hippocampus. Fluoxetine, but not risperidone or sertraline, has a more profound rescue effect on neuropsychological behaviors and myelin abnormalities. Further mechanistic experiments revealed that fluoxetine could directly interfere with oligodendroglial differentiation by upregulating Wnt signaling. Our data demonstrated the correlation between PTSD and abnormal myelination, suggesting that the oligodendroglial lineage could be a target for PTSD treatment.

Effects of selective serotonin reuptake inhibitors on endocrine system (Review).

Selective serotonin reuptake inhibitors (SSRIs) are typically prescribed for treating major depressive disorder (MDD) due to their high efficacy. These drugs function by inhibiting the reuptake of serotonin [also termed 5-hydroxytryptamine (5-HT)], which raises the levels of 5-HT in the synaptic cleft, leading to prolonged activation of postsynaptic 5-HT receptors. Despite the therapeutic benefits of SSRIs, this mechanism of action also disturbs the neuroendocrine response. Hypothalamic-pituitary-adrenal (HPA) axis activity is strongly linked to both MDD and the response to antidepressants, owing to the intricate interplay within the serotonergic system, which regulates feeding, water intake, sexual drive, reproduction and circadian rhythms. The aim of the present review was to provide up-to-date evidence for the proposed effects of SSRIs, such as fluoxetine, citalopram, escitalopram, paroxetine, sertraline and fluvoxamine, on the endocrine system. For this purpose, the literature related to the effects of SSRIs on the endocrine system was searched using the PubMed database. According to the available literature, SSRIs may have an adverse effect on glucose metabolism, sexual function and fertility by dysregulating the function of the HPA axis, pancreas and gonads. Therefore, considering that SSRIs are often prescribed for extended periods, it is crucial to monitor the patient closely with particular attention to the function of the endocrine system.

[Antidepressants in psychiatric practice]. / Antidepressanty v psikhiatricheskoi praktike.

The choice of antidepressants for depression or neurotic disorder is analyzed in the article. Drugs of the group of selective serotonin reuptake inhibitors are used for various mental disorders more often than other antidepressants according to clinical recommendations. Drugs of other groups (selective serotonin and norepinephrine reuptake inhibitors, tricyclic antidepressants, tetracyclic antidepressants, monoamine oxidase inhibitors) are used when the effectiveness of selective serotonin reuptake inhibitors is insufficient or the severity of the mental disorder is significant. The duration of therapy, if well tolerated, can range from several months to many years. Antidepressants from Canonpharma Production are successfully used in clinical practice: Sertraline Canon, Fluoxetine Canon, Escitalopram Canon, Duloxetine Canon, Mirtazapine Canon, Agomelatine Canon. These drugs have different mechanisms of action. They are used for various depression and other mental disorders. All antidepressants from Canonpharma Production have been tested for bioequivalence to the original drugs. This fact increases confidence in these medicines. Some features of the use of these antidepressants based on clinical recommendations and personal experience are discussed in the article.

Ketamine and fluoxetine exert similar actions on prelimbic and infralimbic responsivity to lateral septal nucleus stimulation in Wistar rats.

Ketamine is a dissociative anesthetic that has been proposed to be a useful alternative in cases of a poor response to other treatments in patients with depression. Remarkably, beneficial clinical actions of ketamine are detected once its psychotropic actions disappear. Therefore, clinical actions may occur independently of dose. Most current studies focus on actions of ketamine on neurotrophic factors, but few studies have investigated actions of ketamine on neural structures for which actions of antidepressants have been previously explored. Lateral septal nucleus (LSN) stimulation reduces neural activity in the prelimbic cortex (PL) and infralimbic cortex (IL) subregions of the medial prefrontal cortex (mPFC). Fluoxetine increases inhibitory responsivity of the LSN-IL connection. In the present study, actions of an anesthetic dose of ketamine were compared with a high dose of fluoxetine on behavior and neural responsivity 24 h after drug administration. Fluoxetine reduced immobility in the forced swim test without changing locomotor activity in the open field test. Ketamine strongly decreased locomotor activity and did not produce changes in immobility. In another set of Wistar rats that received similar drug treatment regimens, the results indicated that LSN stimulation in saline-treated animals produced a long-lasting inhibitory afterdischarge in these mPFC subregions. Actions of ketamine on the LSN-mPFC connection reproduced actions of fluoxetine, consisting of accentuated inhibition of the LSN action on the mPFC. These findings suggest that independent of different actions on neurotransmission, the common final pathway of antidepressants lies in their actions on forebrain structures that are related to emotional regulation.

Beyond Psychotropic: Potential Repurposing of Fluoxetine toward Cancer Therapy.

Drug repurposing, rebranding an existing drug for a new therapeutic indication, is deemed a beneficial approach for a quick and cost-effective drug discovery process by skipping preclinical, Phase 1 trials and pharmacokinetic studies. Several psychotropic drugs, including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), were studied for their potential application in different diseases, especially in cancer therapy. Fluoxetine (FLX) is one of the most prescribed psychotropic agents from the SSRIs class for the treatment of several neuropsychiatric disorders with a favorable safety profile. FLX exhibited different oncolytic effects via mechanisms distinct from its main serotonergic activity. Taking advantage of its ability to rapidly penetrate the blood-brain barrier, FLX could be particularly useful in brain tumors. This was proved by different in vitro and in vivo experiments using FLX as a monotherapy or combination with temozolomide (TMZ) or radiotherapy. In this review of the literature, we summarize the potential pleiotropic oncolytic roles of FLX against different cancers, highlighting the multifaceted activities of FLX and its ability to interrupt cancer proliferation via several molecular mechanisms and even surmount multidrug resistance (MDR). We elaborated on the successful synergistic combinations such as FXR/temozolomide and FXR/raloxifene for the treatment of glioblastoma and breast cancer, respectively. We showcased beneficial pharmaceutical trials to load FLX onto carriers to enhance its safety and efficacy on cancer cells. This is the first review article extensively summarizing all previous FLX repurposing studies for the management of cancer.

ß-arrestin2 is indispensable for the antidepressant effects of fluoxetine via inhibiting astrocytic pyroptosis in chronic mild stress mouse model for depression.

ß-arrestin2 is a versatile protein for signaling transduction in brain physiology and pathology. Herein, we investigated the involvement of ß-arrestin2 in pharmacological effects of fluoxetine for depression. A chronic mild stress (CMS) model was established using wild-type (WT) and ß-arrestin2-/- mice. Behavioral results demonstrated that CMS mice showed increased immobility time in the tail suspension test and forced swimming test, elevated concentrations of pro-inflammatory factors in peripheral blood, increased expression of pyroptosis-related proteins, and increased co-labeling of glial fibrillary acidic protein and Caspase1 p10 in the hippocampus compared to the CON group. Treatment with fluoxetine (FLX) ameliorated these conditions. However, compared with the ß-arrestin2-/- CMS group, these results of the ß-arrestin2-/- CMS + FLX group showed no significant changes. These results suggested that the above effects of FLX could be eliminated by knocking out ß-arrestin2. Mass spectrometry implying that FLX promoted the binding of ß-arrestin2 to the NLRP2 inflammasome of depressed mice. Subsequently, the results of the cellular experiments suggested that the 5HT2B receptor antagonist may attenuate L-kynurenine + ATP-induced cell pyroptosis by attenuating NLRP2 binding to ß-arrestin2. We further found that the lack of ß-arrestin2 eliminated the anti-pyroptosis effect of fluoxetine. In conclusion, ß-arrestin2 is an essential protein for fluoxetine to alleviate pyroptosis in the hippocampal astrocytes of CMS mice. Mechanistically, we found that the 5-HT2BR-ß-arrestin2-NLRP2 axis is vital for maintaining the antidepressant effects of fluoxetine.

Emerging Therapeutic Potential of Fluoxetine on Cognitive Decline in Alzheimer's Disease: Systematic Review.

Fluoxetine, a commonly prescribed medication for depression, has been studied in Alzheimer's disease (AD) patients for its effectiveness on cognitive symptoms. The aim of this systematic review is to investigate the therapeutic potential of fluoxetine in cognitive decline in AD, focusing on its anti-degenerative mechanisms of action and clinical implications. According to PRISMA, we searched MEDLINE, up to 1 April 2024, for animal and human studies examining the efficacy of fluoxetine with regard to the recovery of cognitive function in AD. Methodological quality was evaluated using the ARRIVE tool for animal AD studies and the Cochrane tool for clinical trials. In total, 22 studies were analyzed (19 animal AD studies and 3 clinical studies). Fluoxetine promoted neurogenesis and enhanced synaptic plasticity in preclinical models of AD, through a decrease in Aß pathology and increase in BDNF, by activating diverse pathways (such as the DAF-16-mediated, TGF-beta1, ILK-AKT-GSK3beta, and CREB/p-CREB/BDNF). In addition, fluoxetine has anti-inflammatory properties/antioxidant effects via targeting antioxidant Nrf2/HO-1 and hindering TLR4/NLRP3 inflammasome. Only three clinical studies showed that fluoxetine ameliorated the cognitive performance of people with AD; however, several methodological issues limited the generalizability of these results. Overall, the high-quality preclinical evidence suggests that fluoxetine may have neuroprotective, antioxidant, and anti-inflammatory effects in AD animal models. While more high-quality clinical research is needed to fully understand the mechanisms underlying these effects, fluoxetine is a promising potential treatment for AD patients. If future clinical trials confirm its anti-degenerative and neuroprotective effects, fluoxetine could offer a new therapeutic approach for slowing down the progression of AD.

Effect of an antidepressant on aquatic ecosystems in the presence of microplastics: A mesocosm study.

Emerging pollutants, such as pharmaceuticals and microplastics have become a pressing concern due to their widespread presence and potential impacts on ecological systems. To assess the ecosystem-level effects of these pollutants within a multi-stressor context, we simulated real-world conditions by exposing a near-natural multi-trophic aquatic food web to a gradient of environmentally relevant concentrations of fluoxetine and microplastics in large mesocosms over a period of more than three months. We measured the biomass and abundance of different trophic groups, as well as ecological functions such as nutrient availability and decomposition rate. To explore the mechanisms underlying potential community and ecosystem-level effects, we also performed behavioral assays focusing on locomotion parameters as a response variable in three species: Daphnia magna (zooplankton prey), Chaoborus flavicans larvae (invertebrate pelagic predator of zooplankton) and Asellus aquaticus (benthic macroinvertebrate), using water from the mesocosms. Our mesocosm results demonstrate that presence of microplastics governs the response in phytoplankton biomass, with a weak non-monotonic dose-response relationship due to the interaction between microplastics and fluoxetine. However, exposure to fluoxetine evoked a strong non-monotonic dose-response in zooplankton abundance and microbial decomposition rate of plant material. In the behavioral assays, the locomotion of zooplankton prey D. magna showed a similar non-monotonic response primarily induced by fluoxetine. Its predator C. flavicans, however, showed a significant non-monotonic response governed by both microplastics and fluoxetine. The behavior of the decomposer A. aquaticus significantly decreased at higher fluoxetine concentrations, potentially leading to reduced decomposition rates near the sediment. Our study demonstrates that effects observed upon short-term exposure result in more pronounced ecosystem-level effects following chronic exposure.

Inhibitory modulation of action potentials in crayfish motor axons by fluoxetine.

The goal of this report is to explore how K2P channels modulate axonal excitability by using the crayfish ventral superficial flexor preparation. This preparation allows for simultaneous recording of motor nerve extracellular action potentials (eAP) and intracellular excitatory junctional potential (EJP) from a muscle fiber. Previous pharmacological studies have demonstrated the presence of K2P-like channels in crayfish. Fluoxetine (50 µM) was used to block K2P channels in this study. The blocker caused a gradual decline, and eventually complete block, of motor axon action potentials. At an intermediate stage of the block, when the peak-to-peak amplitude of eAP decreased to ∼60%-80% of the control value, the amplitude of the initial positive component of eAP declined at a faster rate than that of the negative peak representing sodium influx. Furthermore, the second positive peak following this sodium influx, which corresponds to the after-hyperpolarizing phase of intracellularly recorded action potentials (iAP), became larger during the intermediate stage of eAP block. Finally, EJP recorded simultaneously with eAP showed no change in amplitude, but did show a significant increase in synaptic delay. These changes in eAP shape and EJP delay are interpreted as the consequence of depolarized resting membrane potential after K2P channel block. In addition to providing insights to possible functions of K2P channels in unmyelinated axons, results presented here also serve as an example of how changes in eAP shape contain information that can be used to infer alterations in intracellular events. This type of eAP-iAP cross-inference is valuable for gaining mechanistic insights here and may also be applicable to other model systems.

Nicotine and fluoxetine alter adolescent dopamine-mediated behaviors via 5-HT1A receptor activation.

Introduction: Abuse or misuse of tobacco, e-cigarettes, or antidepressants may have serious clinical consequences during adolescence, a sensitive period during brain development when the distinct neurobiology of adolescent serotonin (5-HT) and dopamine (DA) systems create unique behavioral vulnerabilities to drugs of abuse. Methods: Using a pharmacological approach, we modeled the behavioral and neurochemical effects of subchronic (4-day) nicotine (60µg/kg, i.v.) or fluoxetine (1mg/kg, i.v.) exposure in adolescent and adult male rats. Results: Nicotine and fluoxetine significantly enhance quinpirole-induced locomotor activity and initial cocaine self-administration in adolescents, but not adults. These effects were blocked by serotonin 5-HT1A receptor antagonists, WAY-100,635 (100 µg/kg, i.v.) or S-15535 (300 µg/kg, i.v.). Neurochemical and anatomical autoradiographic analysis of 8-OH-DPAT-stimulated [35S]GTPγS reveal that prior exposure to nicotine and fluoxetine results in both overlapping and distinct effects on regional 5-HT1A receptor activity. Both fluoxetine and nicotine enhance adolescent 5-HT1A receptor activity in the primary motor cortex (M1), whereas fluoxetine alone targets prefrontal cortical neurocircuitry and nicotine alone targets the amygdala. Discussion: Given their different pharmacological profiles, comparison between WAY-100,635 and S-15535 indicates that postsynaptic 5-HT1A receptors mediate the behavioral effects of prior nicotine and fluoxetine exposure. In addition, within the adolescent M1, maladaptive changes in 5-HT signaling and 5-HT1A activity after nicotine or fluoxetine exposure may potentiate hyper-responsiveness to dopaminergic drugs and prime adolescent vulnerability for future substance abuse.

Effect analysis of repeated transcranial magnetic stimulation combined with fluoxetine in the treatment of first-episode adolescent depression.

Objectives: This study aims to evaluate the efficacy of repeated transcranial magnetic stimulation (rTMS) combined with fluoxetine in enhancing the early antidepressant response in first-episode adolescent depression cases, providing insights for patient diagnosis and treatment. Methods: One hundred and thirty-five adolescents experiencing their first depressive episode were randomly assigned to either a sham group treated with fluoxetine or to low or high repetitive transcranial magnetic stimulation (rTMS) groups receiving both rTMS and fluoxetine. Therapeutic effects were assessed by comparing changes in Hamilton Depression Scale (HAMD-17) scores, cognitive function scores from the Wisconsin Card Sorting Test (WCST), and Clinical Global Impression-improvement (CGI-I) scores, along with recording adverse reactions. Results: The total effectiveness rate in the rTMS groups (Low, 95.56%; High, 97.78%) was significantly higher than in the Sham rTMS group (80%) (F = 11.15, P<0.0001). Post-treatment, not only the Low but also the High rTMS group exhibited more significant reductions in HAMD-17 (Low, 21.05; High, 21.45) and CGI-I scores (Low, 3.44; High, 3.60) compared to the Sham rTMS group (HAMD-17, 16.05; CGI-I, 2.57) (two weeks: F = 7.889, P = 0.0006; four weeks: F = 15.900, P<0.0001). Additionally, the two rTMS groups exhibited fewer erroneous responses and persistent errors in the WCST and completed more WCST categorizations than the Sham rTMS group. There was no significant difference in adverse reaction rates between the groups (F=4.421, P=0.0794). Conclusions: The combination of fluoxetine with rTMS demonstrates enhanced therapeutic effectiveness in treating adolescent depression, effectively controlling disease progression, reducing depressive symptoms, and improving cognitive function, making it a valuable clinical approach.

Fluoxetine and ketamine trigger the p75NTR proteolytic pathway and enhance extinction memory and brain plasticity through p75NTR.

BACKGROUND: Diverse antidepressants were recently described to bind to TrkB and drive a positive allosteric modulation of endogenous BDNF. Although neurotrophins such as BDNF can bind to the p75 neurotrophin receptor (p75NTR), their precursors are the high affinity p75NTR ligands. While part of an unrelated receptor family capable of inducing completely opposite physiological changes, TrkB and p75NTR feature a cross-like conformation dimer and carry a cholesterol-recognition and alignment consensus in the transmembrane domain. Since such qualities were found crucial for antidepressants to bind to TrkB and drive behavioral and neuroplasticity effects, we hypothesized that their effects might also depend on p75NTR. METHODS: ELISA-based binding assay and NMR spectroscopy were accomplished to assess whether antidepressants would bind to p75NTR. HEK293T cells and a variety of in vitro assays were used to address whether fluoxetine (FLX) or ketamine (KET) would trigger any α- and γ-secretase-dependent p75NTR proteolysis, and lead to p75NTR nuclear localization. Ocular dominance shift was performed with male and female p75KO mice to study the effects of KET and FLX on brain plasticity, in addition to pharmacological interventions to verifying how p75NTR signaling is important for the effects of KET and FLX in enhancing extinction memory in male WT mice and rats. RESULTS: Antidepressants were found binding to p75NTR, FLX and KET triggered the p75NTR proteolytic pathway and induced p75NTR-dependent behavioral/neuroplasticity changes. CONCLUSION: We thus hypothesize that antidepressants co-opt both BDNF/TrkB and proBDNF/p75NTR systems to induce a more efficient activity-dependent synaptic competition, thereby boosting the brain ability for remodeling.

Effects of esketamine and fluoxetine on depression-like behaviors in chronic variable stress: a role of plasma inflammatory factors.

Mounting evidence has identified the rapid and sustained antidepressive and anxiolytic-like effects of esketamine. However, the underlying mechanism of this no-monoamine target rapid-onset antidepressant is still underexplored. Immune-inflammatory pathways and cell-mediated immune activation, mainly including inflammatory cytokines in plasma, play a pivotal role in the pathogenesis of major depressive disorder and are also a potential therapeutic target for MDD. The current study was designed to clarify the role of esketamine on the expression of plasma cytokines in a depressive-like model introduced by chronic variable stress (CVS). In this study, a 21-day consecutive CVS protocol was applied to produce depressive- and anxiety-like behaviors. After the single dose or 7-day repeated administration of esketamine or fluoxetine, the depressive- and anxiety-like behaviors and the expression of inflammatory cytokines in plasma were examined. Both a single dose of esketamine and 7-days repeated fluoxetine administration elicited anti-depressive and anxiolytic effects in mice exposed to CVS. Additionally, CVS produced significant changes in the plasma inflammatory factors, notably increasing the expression of IL-1ß, IL-6, IL-8, IL-17A, TNFα, IL-4, IL-9, IL-24, IL-37, IFN-ß, and CXCL12, while reducing IL-10 and IL-33. With the administration of esketamine and fluoxetine, CVS-produced inflammatory disturbances were partially normalized. Together, our findings provide a novel insight that acute esketamine treatment could rescue CVS-produced depressive-like and anxiety-like behaviors in mice by normalizing the expression of inflammatory cytokines; this effect was similar to the repeated administration of fluoxetine. These results contributed to the understating of rapid anti-depressant effects elicited by esketamine.

The impact of chronic fluoxetine treatment in adolescence or adulthood on context fear memory and perineuronal nets.

Selective serotonin reuptake inhibitors, such as fluoxetine (Prozac), are commonly prescribed pharmacotherapies for anxiety. Fluoxetine may be a useful adjunct because it can reduce the expression of learned fear in adult rodents. This effect is associated with altered expression of perineuronal nets (PNNs) in the amygdala and hippocampus, two brain regions that regulate fear. However, it is unknown whether fluoxetine has similar effects in adolescents. Here, we investigated the effect of fluoxetine exposure during adolescence or adulthood on context fear memory and PNNs in the basolateral amygdala (BLA), the CA1 subregion of the hippocampus, and the medial prefrontal cortex in rats. Fluoxetine impaired context fear memory in adults but not in adolescents. Further, fluoxetine increased the number of parvalbumin (PV)-expressing neurons surrounded by a PNN in the BLA and CA1, but not in the medial prefrontal cortex, at both ages. Contrary to previous reports, fluoxetine did not shift the percentage of PNNs toward non-PV cells in either the BLA or CA1 in the adults, or adolescents. These findings demonstrate that fluoxetine differentially affects fear memory in adolescent and adult rats but does not appear to have age-specific effects on PNNs.