Dose-dependent modulation of apoptotic processes by fluoxetine in maturing neuronal cells: an in vitro study

Fluoxetine induces direct inhibitory effects on mesenchymal stem cell‑derived osteoprogenitor cells independent of serotonin concentration

Selective serotonin reuptake inhibitors are the most commonly prescribed antidepressants worldwide, which have been reported to exert potential detrimental effects on bone mineral density and increase the risk of developing fractures. The present study aimed to investigate the pathways underlying the negative effects of fluoxetine on bone using mesenchymal stem cells (MSCs) derived from rat adipose tissue as a source of osteoprogenitor cells. MSCs were harvested from adipose tissue using a collagenase enzyme digestion method and were allowed to differentiate into osteoprogenitor cells. Various concentrations of fluoxetine were added to the cells, which were harvested and analyzed by flow cytometry to detect apoptotic markers Annexin V and caspase-3, in order to assess the levels of apoptosis. The levels of endogenous serotonin released in the extracellular matrix were measured using a serotonin ELISA kit. The underlying molecular pathways associated with the effects of fluoxetine on bone were investigated with reverse transcription-quantitative polymerase chain reaction. The results of the present study revealed a significant dose-dependent increase in apoptosis in response to increasing doses of fluoxetine, which was independent of serotonin levels in the culture supernatant. These findings indicated that fluoxetine exerted a direct inhibitory effect on bone cells via an apoptosis-dependent pathway. Furthermore, the expression levels of serotonergic genes, including serotonin 1B receptor, serotonin 2A receptor (HTR2A), serotonin 2B receptor and serotonin transporter, were down regulated; of these genes, HTR2A exhibited the highest expression levels. Further in vitro and in vivo studies are required to verify this association and to determine the molecular pathways involved in fluoxetine-induced bone loss. Fluoxetine-induced apoptosis of osteoprogenitor cells may be the mechanism underlying the increased incidence of bone loss observed in patients treated with fluoxetine.

Fluoxetine Inhibits Canonical Wnt Signaling to Impair Embryoid Body Morphogenesis: Potential Teratogenic Mechanisms of a Commonly Used Antidepressant

Fluoxetine is one of the most commonly prescribed antidepressants in the selective serotonin reuptake inhibitor (SSRI) class. Epidemiologic studies have suggested a link between maternal fluoxetine use during pregnancy and an increased incidence of birth defects. However, the mechanisms by which fluoxetine adversely impacts embryonic developments are unknown. Here, we used the mouse P19C5 embryoid body (EB) as a 3D morphogenesis model to investigate the developmental toxicity of fluoxetine. Morphological and molecular changes in P19C5 EBs replicate the processes of axial elongation and patterning seen in early embryos, and these changes are specifically and sensitively altered by exposure to developmental toxicants. Treatment with fluoxetine, or its major metabolite, norfluoxetine, adversely affected EB morphogenesis at concentrations of 6 µM and above. Treatment with other serotonin reuptake inhibitors or serotonin itself did not impair EB morphogenesis, suggesting that the adverse effects of fluoxetine are independent of serotonin signaling. Gene expression analyses showed that various key developmental regulators were affected by fluoxetine, particularly those involved in mesodermal differentiation. Reporter assays demonstrated that fluoxetine inhibited canonical Wnt signaling, and that the pharmacologic activation of canonical Wnt signaling partially alleviated the morphogenetic effects of fluoxetine. Fluoxetine also exhibited cytostatic effects independently of inhibition of the serotonin transporter or canonical Wnt signaling. These results suggest that the SSRI-independent actions of fluoxetine, namely inhibition of canonical Wnt signaling and reduction of cellular proliferation, are largely responsible for the observed adverse morphogenetic impacts. This study provides mechanistic insight for further investigations on the teratogenicity of fluoxetine.

Fluoxetine protects against IL-1β-induced neuronal apoptosis via downregulation of p53

Fluoxetine, a selective serotonin reuptake inhibitor, exerts neuroprotective effects in a variety of neurological diseases including stroke, but the underlying mechanism remains obscure. In the present study, we addressed the molecular events in fluoxetine against ischemia/reperfusion-induced acute neuronal injury and inflammation-induced neuronal apoptosis. We showed that treatment of fluoxetine (40 mg/kg, i.p.) with twice injections at 1 h and 12 h after transient middle cerebral artery occlusion (tMCAO) respectively alleviated neurological deficits and neuronal apoptosis in a mouse ischemic stroke model, accompanied by inhibiting interleukin-1β (IL-1β), Bax and p53 expression and upregulating anti-apoptotic protein Bcl-2 level. We next mimicked neuroinflammation in ischemic stroke with IL-1β in primary cultured cortical neurons and found that pretreatment with fluoxetine (1 μM) prevented IL-1β-induced neuronal apoptosis and upregulation of p53 expression. Furthermore, we demonstrated that p53 overexpression in N2a cell line abolished the anti-apoptotic effect of fluoxetine, indicating that p53 downregulation is required for the protective role of fluoxetine in IL-1β-induced neuronal apoptosis. Fluoxetine downregulating p53 expression could be mimicked by SB203580, a specific inhibitor of p38, but blocked by anisomycin, a p38 activator. Collectively, our findings have revealed that fluoxetine protects against IL-1β-induced neuronal apoptosis via p38-p53 dependent pathway, which give us an insight into the potential of fluoxetine in terms of opening up novel therapeutic avenues for neurological diseases including stroke.

Fluoxetine Maintains a State of Heightened Responsiveness to Motor Training Early After Stroke in a Mouse Model

BACKGROUND AND PURPOSE

Data from both humans and animal models suggest that most recovery from motor impairment after stroke occurs in a sensitive period that lasts only weeks and is mediated, in part, by an increased responsiveness to training. Here, we used a mouse model of focal cortical stroke to test 2 hypotheses. First, we investigated whether responsiveness to training decreases over time after stroke. Second, we tested whether fluoxetine, which can influence synaptic plasticity and stroke recovery, can prolong the period over which large training-related gains can be elicited after stroke.

METHODS

Mice were trained to perform a skilled prehension task to an asymptotic level of performance after which they underwent stroke induction in the caudal forelimb area. The mice were then retrained after a 1- or 7-day delay with and without fluoxetine.

RESULTS

Recovery of prehension after a caudal forelimb area stroke was complete if training was initiated 1 day after stroke but incomplete if it was delayed by 7 days. In contrast, if fluoxetine was administered at 24 hours after stroke, then complete recovery of prehension was observed even with the 7-day training delay. Fluoxetine seemed to mediate its beneficial effect by reducing inhibitory interneuron expression in intact premotor cortex rather than through effects on infarct volume or cell death.

CONCLUSIONS

There is a gradient of diminishing responsiveness to motor training over the first week after stroke. Fluoxetine can overcome this gradient and maintain maximal levels of responsiveness to training even 7 days after stroke.

Fluoxetine prevents acetylcholine-induced excitotoxicity blocking human endplate acetylcholine receptor

INTRODUCTION

Fluoxetine is an open channel blocker of fetal muscle acetylcholine (ACh) receptor (AChR) and slow-channel mutant AChRs. It is used commonly to treat patients with slow-channel congenital myasthenic syndromes. Fluoxetine effects on adult wild-type endplate AChR are less characterized, although muscle AChR isoforms are differentially modulated by some drugs.

METHODS

Excitotoxicity assays and patch clamp recordings were performed in human embryonic kidney 293 (HEK) cells expressing wild-type or slow-channel mutant human AChRs.

RESULTS

Fluoxetine (2-10 μM) abolished ACh-induced death and decreased ACh-activated whole-cell currents in cells expressing all AChR types. In outside-out patches, fluoxetine rapidly curtailed ACh evoked unitary activity and macroscopic currents. The effect was increased if fluoxetine was applied before ACh.

CONCLUSIONS

Fluoxetine is an open channel blocker, but it also affects AChR in the closed state. AChR blockade likely underlies the rescue of HEK cells from ACh-induced death.

Selective serotonin reuptake inhibitors inhibit human osteoclast and osteoblast formation and function

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) are widely used antidepressants and one of the most commonly used medications. There is growing concern that SSRIs, which sequester in bone marrow at higher concentrations than brain or blood, increase bone fragility and fracture risk. However, their mechanism of action on human osteoclasts (OC) and osteoblasts (OB) differentiation remains unclear.

METHODS

Expression of serotonin receptors (5-HTR), transporter (5-HTT), and tryptophan hydroxylase 1 (TPH1) was assessed in human OC (precursors and mature) and OB (nonmineralizing and mineralizing) by polymerase chain reaction. OC formation and resorption was measured in the presence of 5 SSRIs. OBs cultured with SSRIs for 28 days were assessed for alkaline phosphatase (ALP) and bone mineralization. Cell viability and apoptosis were determined by annexin V flow cytometry.

RESULTS

OCs and OB expressed TPH1, 5-HTT, and 5-HTR1B. The 5-HTR2A was expressed only in OB, whereas 5-HTR2B expression increased from precursor to mature OC. All SSRIs (except citalopram) dose-dependently inhibited OC formation and resorption between 1 μmol/L and 10 μmol/L; order of potency: sertraline > fluoxetine > paroxetine > fluvoxamine > citalopram. Similarly, SSRIs (except citalopram) inhibited ALP and bone mineralization by OB but only at 30 μmol/L. Apoptosis was induced by SSRIs in OC and OB in an identical pattern to inhibitory effects. Serotonin treatment had no effect on either OC or OB parameters.

CONCLUSIONS

These data demonstrate that SSRIs differentially inhibit bone cell function via apoptosis. This may explain the mechanisms of bone loss with chronic use and aid clinical choices.

Cost effectiveness of pharmacotherapies for attention-deficit hyperactivity disorder: a systematic literature review

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is a common psychiatric disorder that impairs the quality of life for patients and their families and is associated with considerable direct and indirect costs. Pharmacotherapies for ADHD, including stimulants and non-stimulants, are often used to treat patients with ADHD. However, the costs, effectiveness and adverse effects of these agents vary. Therefore, information regarding the cost effectiveness of different pharmacological treatments is needed to better inform payers in the allocation of limited resources.

OBJECTIVES

The objectives of this study were to conduct a systematic literature review of economic evaluations of pharmacotherapies for ADHD treatments and to assess the cost effectiveness of different interventions based on the existing studies.

METHODS

A systematic literature review of economic evaluations of pharmacotherapies for ADHD was conducted in MEDLINE, the National Health Services (NHS) Economic Evaluation database and EMBASE. For inclusion in this review, studies had to compare two or more ADHD interventions with at least one pharmacotherapy, assess both costs and outcomes, and be conducted between 1990 and 2011 in North America, Europe, Australia or New Zealand. Studies were excluded if they were not original research, were presented only as conference proceedings or abstracts or did not report costs associated with specific interventions. The study quality was assessed using the British Medical Journal (BMJ) health economics checklist. The literature search, data extraction and quality assessment were performed by one author and independently checked for accuracy by a second author. Discrepancies were resolved by consensus and referring to the original article. If necessary, a third reviewer was consulted.

RESULTS

The initial search returned 93 citations from MEDLINE, 10 from the NHS Economic Evaluation database and 377 from EMBASE. Thirteen papers met the inclusion/exclusion criteria and were included in the review. Based on the BMJ checklist, all these studies were considered to be of sufficient quality to be included in the literature review, but they varied substantially in target population, methodology and effectiveness measures. Identified pharmacotherapies were cost effective compared with no treatment, placebo, behavioural therapy or community care among children and adolescents with ADHD. Studies comparing non-stimulants with stimulants and amfetamine with methylphenidate stimulants showed inconsistent findings. A limited number of studies indicated that methylphenidate Osmotic-controlled Release Oral delivery System (OROS) was cost effective compared with short-acting methylphenidate. There were no published studies on the cost effectiveness of pharmacotherapy in the adult ADHD population, comparing stimulants, non-stimulants or adjuvant therapy. There is limited evidence on the long-term cost effectiveness of pharmacotherapies.

CONCLUSIONS

Among children and adolescents with ADHD, there was consistent evidence that pharmacotherapies are cost effective compared with no treatment or behavioural therapy. Adequate data are lacking to draw conclusions regarding the relative cost effectiveness of different pharmacological agents. More economic evaluations with standardized methods, such as effectiveness measures and cost components, are warranted. To better inform payers about the economic value of existing medications, future studies should also consider identifying subgroups that may have heterogeneous responses to different treatments, including analyses of recently approved treatments (e.g. lisdexamfetamine, guanfacine extended-release and clonidine extended-release) and expanding the time horizon to incorporate long-term outcomes.