Fluoxetine induces changes in the testicle and testosterone in adult male rats exposed via placenta and lactation

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.

Role of serotonin, estrogen, and TNF-α in the paroxetine-impaired steroidogenesis and testicular macrophages polarization

BACKGROUND

Paroxetine, a selective serotonin reuptake inhibitor (SSRI) antidepressant, has caused male sexual dysfunction; however, the paroxetine mechanisms of action in testes are still unclear.

OBJECTIVES

Paroxetine serotonergic effects in testes were evaluated, focusing on steroidogenesis and the correlation between macrophages population and possible TNF-α-derived oxidative stress. We also verified whether the changes are reversible following treatment interruption.

MATERIALS AND METHODS

Adult rats received paroxetine (PG35 and PG65) or tap water (CG) for 35 days. PG65 was maintained without treatment for 30 more days. Intratesticular testosterone (IT), nitrite, and malondialdehyde concentrations were measured. To confirm serotonergic and estrogenic effects, Htr1b and Esr1 expressions were analyzed. The daily sperm production (DSP), frequency of abnormal seminiferous tubules (ST), SC number, ST area, and Leydig cells nuclear area (LCnu) were evaluated. TUNEL+ germ cells, M1 (CD68+ ), and M2 (Perls+ ) macrophages were quantified. 17β-HSD7, CYP19A1, NDRG2, oxytocin, TNF-α, and iNOS were evaluated by immunoreactions. Oxytocin and NDRG2 protein levels as well as Tnfa mRNA expression were also analyzed.

RESULTS

The Htr1b downregulation in testes confirmed the paroxetine serotonergic effect. The testicular sections showed abnormal ST frequency, ST atrophy and reduction of DSP, LCnu, SC number and Perls+ macrophages. TUNEL+ germ cells and LC were associated with strong NDRG2 immunoexpression. Paroxetine reduced IT levels and 17β-HSD7 immunoexpression in parallel to increased CYP19A1, oxytocin, TNF-α and iNOS. Esr1 and Tnfa overexpression and increased number of CD68+ macrophages were also observed together with high nitrite and malondialdehyde levels. Most parameters were not recovered in PG65.

CONCLUSIONS

Paroxetine serotonergic effect impairs LC steroidogenesis, via aromatization, increasing estrogen/testosterone ratio, which in turn upregulate NDRG2, promoting apoptosis, and impairing sperm production. Serotonin-estrogen pathways may be responsible for M2/M1 polarization, Tnfa upregulation, and induction of oxidative stress. The unrecovered testicular changes after treatment discontinuation are due to persistent paroxetine serotonin/estrogen effects.

Olanzapine treatment of lactating females causes testicular atrophy in prepuberal rat offspring

The antipsychotic drug, olanzapine, is prescribed for postpartum psychosis. Possible adverse effects on fertility of offspring are unclear. We investigated the effects of administering olanzapine via lactation on testicular development and endocrine function of prepuberal male rats. Olanzapine was administered to mothers at 2.5, 5 or 10 mg/kg. We found in male offspring increased body weight, decreased gonadosomatic index, testicular weight and epididymal weight. The volume of seminiferous tubules, seminiferous epithelium, Leydig cells, intertubule tissue and lymphatic space was reduced in rat pups exposed to olanzapine. Tubule diameter and length, seminiferous epithelium height, Leydig cell size and nuclear diameter also were reduced. Testosterone levels were reduced in the groups exposed to olanzapine, while prolactin levels were increased. We observed histopathology in testes of animals whose mothers had been treated with 2.5 mg/kg olanzapine; more severe pathology was observed in offspring whose mothers were administered higher doses. Administration of olanzapine to mothers during lactation produced testicular and endocrine pathology in prepuberal rats in a dose-dependent manner.

The effects of selective serotonin reuptake inhibitors on male and female fertility: a brief literature review

Objective: The aim of this review was to determine whether selective serotonin reuptake inhibitors (SSRIs) affect the ability to conceive in men and women of reproductive age, as well as to find out whether there are certain differencies between them in terms of effects on fertility. Methods: Our review was based on systematic search of literature in four online databases: Medline (PubMed), Scopus, Web of Science and SCIndex (Serbian Citation Index). Results: Several clinical studies reported that SSRIs can decrease the number and viability of sperm, and cause a disruption of their morphological structure. Regarding the effect of these antidepressants on female fertility, some experimental findings suggest that paroxetine and escitalopram may have a negative effect on the ability to conceive due to their stimulatory effect on fallopian tube motility. However, several observational studies favor the use of SSRIs in women with depression/anxiety undergoing in vitro fertilization (IVF) given their efficiency in suppressing these unpleasant symptoms without a relevant negative impact on IVF outcomes. Conclusions: SSRIs should be avoided male patients of reproductive age who wish to conceive, while the use of these antidepressants seems to be justified in women with depression or anxiety who have undergone IVF.Key pointsSSRIs could cause dose and duration-dependent reversible adverse effects on male fertility parameters.In depressed or anxious male patients of reproductive age who wish to conceive mirtazapine or bupropion should be used because of their lower potential to cause sexual side effects.The results of certain experimental studies indicate that paroxetine and escitalopram may have a negative effect on the fertility of female patients.The use of SSRIs in women with depression or anxiety who have undergone IVF seems to be justified, because these psychiatric disorders reduce the likelihood of becoming pregnant.

The antidepressant Sertraline inhibits CatSper Ca2+ channels in human sperm

STUDY QUESTION

Do selective serotonin reuptake inhibitor (SSRI) antidepressants affect the function of human sperm?

SUMMARY ANSWER

The SSRI antidepressant Sertraline (e.g. Zoloft) inhibits the sperm-specific Ca²⁺ channel CatSper and affects human sperm function in vitro.

WHAT IS KNOWN ALREADY

In human sperm, CatSper translates changes of the chemical microenvironment into changes of the intracellular Ca²⁺ concentration ([Ca²⁺]_i) and swimming behavior. CatSper is promiscuously activated by oviductal ligands, but also by synthetic chemicals that might disturb the fertilization process. It is well known that SSRIs have off-target actions on Ca²⁺, Na⁺ and K⁺ channels in somatic cells. Whether SSRIs affect the activity of CatSper is, however, unknown.

STUDY DESIGN, SIZE, DURATION

We studied the action of the seven drugs belonging to the most commonly prescribed class of antidepressants, SSRIs, on resting [Ca²⁺]_i and Ca²⁺ influx via CatSper in human sperm. The SSRI Sertraline was selected for in-depth analysis of its action on steroid-, prostaglandin-, pH- and voltage-activation of human CatSper. Moreover, the action of Sertraline on sperm acrosomal exocytosis and penetration into viscous media was evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The activity of CatSper was investigated in sperm of healthy volunteers, using kinetic Ca²⁺ fluorimetry and patch-clamp recordings. Acrosomal exocytosis was investigated using Pisum sativum agglutinin and image cytometry. Sperm penetration in viscous media was evaluated using the Kremer test.

MAIN RESULTS AND THE ROLE OF CHANCE

Several SSRIs affected [Ca²⁺]_i and attenuated ligand-induced Ca²⁺ influx via CatSper. In particular, the SSRI Sertraline almost completely suppressed Ca²⁺ influx via CatSper. Remarkably, the drug was about four-fold more potent to suppress prostaglandin- versus steroid-induced Ca²⁺ influx. Sertraline also suppressed alkaline- and voltage-activation of CatSper, indicating that the drug directly inhibits the channel. Finally, Sertraline impaired ligand-induced acrosome reaction and sperm penetration into viscous media.

LIMITATIONS, REASONS FOR CAUTION

This is an in vitro study. Future studies have to assess the physiological relevance in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

The off-target action of Sertraline on CatSper in human sperm might impair the fertilization process. In a research setting, Sertraline may be used to selectively inhibit prostaglandin-induced Ca²⁺ influx.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Swiss Centre for Applied Human Toxicology (SCAHT), the Département de l’Instruction Publique of the State of Geneva, the German Research Foundation (CRU326), the Interdisciplinary Center for Clinical Research, Münster (IZKF; Str/014/21), the Innovation Fund Denmark (grant numbers 14-2013-4) and the EDMaRC research grant from the Kirsten and Freddy Johansen’s Foundation. The authors declare that no conflict of interest could be perceived as prejudicing the impartiality of the research reported.

TRIAL REGISTRATION NUMBER

NA.

Effect of fluoxetine on the testes of adult albino rats and the possible protective role of curcumin

Fluoxetine (FLX) is extensively used for the treatment of a diversity of psychiatric disorders, mainly depression. However, it can adversely affect male fertility. This study was done to clarify the changes which take place in the testes after the oral administration of FLX and to evaluate the possible preventative role of curcumin. Seventy-six adult male albino rats were randomly divided into four equal groups. Control group: kept without any treatment. Curcumin group: received daily dose of curcumin (150 mg/kg body weight) through oral gavage for 8 weeks. FLX group. They were given daily dose of FLX (10 mg/kg body weight) given through oral gavage for 8 weeks. FLX and curcumin group. They were given FLX together with curcumin with the same previous doses through oral gavage daily for 8 weeks. By the end of the experiment, blood samples were collected for the biochemical study of testosterone. All the animals were anaesthetized by ether inhalation, and the testis specimens were dissected out and weighed. The specimens were subjected to histopathological, immunohistochemical, and morphometrical evaluation. FLX decreased serum testosterone, diminished both epithelial height and diameter of seminiferous tubules, increased collagen fiber deposition in testicular tissue and induced positive immune reaction to B-cell lymphoma-2-associated X protein. In the FLX and curcumin group, the FLX-induced changes were less remarkable. Exposure to FLX led to pronounced testicular alterations. Co-administration of curcumin with FLX ameliorated these changes.

The adverse effects of psychotropic drugs as an endocrine disrupting chemicals on the hypothalamic-pituitary regulation in male

Adverse effects of drugs on male reproductive system can be categorized as pre-testicular, testicular, and post-testicular. Pre-testicular adverse effects disrupt the hypothalamic-pituitary-gonadal (HPG) axis, generally by interfering with endocrine function. It is known that the HPG axis has roles in the maintenance of spermatogenesis and sexual function. The hypothalamus secretes gonadotropin-releasing hormone (GnRH) which enters the hypophyseal portal system to stimulate the anterior pituitary. The anterior pituitary secretes gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) which are vital for spermatogenesis, into the blood. The FSH stimulates the Sertoli cells for the production of regulatory molecules and nutrients needed for the maintenance of spermatogenesis, while the LH stimulates the Leydig cells to produce and secrete testosterone. Many neurotransmitters influence the hypothalamic-pituitary regulation, consequently the HPG axis, and can consequently affect spermatogenesis and sexual function. Psychotropic drugs including antipsychotics, antidepressants, and mood stabilizers that all commonly modulate dopamine, serotonin, and GABA, can affect male spermatogenesis and sexual function by impairment of the hypothalamic-pituitary regulation, act like endocrine-disrupting chemicals. Otherwise, studies have shown the relationship between decreased sperm quality and psychotropic drugs treatment. Therefore, it is important to investigate the adverse reproductive effects of psychotropic drugs which are frequently used during reproductive ages in males and to determine the role of the hypothalamic-pituitary regulation axis on possible pathologies.

The effects of exposure to fluoxetine during lactation on testicular tissue and sperm parameters in mice offspring

Fluoxetine is a selective serotonin reuptake inhibitor is commonly prescribed to treat maternal depression in pregnancy and lactation. This study aimed to investigate the effects of maternal exposure to fluoxetine via lactation on testicular tissue, sperm parameters including count, motility, viability, and normal morphology and testicular oxidative stress status in male mice offspring. Ten mice dams were divided into control and experimental groups. The control group received water and the experimental group received fluoxetine (20.00 mg kg^-1) by gavage daily from postnatal days of 0-21. Histology of testis, sperm parameters and oxidative stress in the testicular tissue were analyzed at 80 days after birth in their male offspring (n = 8). Significant reductions in the body and testes weights were observed in animals exposed to fluoxetine. Additionally, fluoxetine exposure significantly reduced all sperm parameters, tubular diameter and epithelial height of the seminiferous tubules as well as Leydig cells number. Significant increases in the testicular malondialdehyde levels and percentage of sperm with chromatin/DNA damage were observed in mice exposed to fluoxetine compared to control. These findings suggest that maternal exposure to fluoxetine during lactation in mice has a negative effect on the testicular tissue of their offspring and impairs the spermatogenesis process which in turn can induce infertility.

Developmental effects on hypothalamic, hypophyseal, testicular and steroidogenic patterns of sertraline-exposed male rats by accumulated doses from juvenile to puberty

Since the enduring exposure to selective serotonin reuptake inhibitors medications from juvenile period to puberty poses a growing concern, the aim is an attempt to evaluate the reproductive aspects of sertraline-treated postnatal male rats. Total 80 male rats were orally given 1.2 mg/kg bw/day from postnatal day 28 to puberty (balano-preputial separation). Necropsy takes place at 56th, 84th, 126th postnatal day (SGII, SGIII, and SGIV, respectively), along with the control group (SGI). Final body weight, weight gain, and weights of liver, kidneys, testes and epididymis were significantly decreased in the SGIII and SGIV groups compared to the controls. Levels of LH, FSH, and testosterone and 17β-HSD concentrations were significantly decreased in all groups. Male rats in SGIV group displayed a significant decline in sperm counts, motility and viability and increase in sperm morphological defects compared to control. The cumulative dose of 1.2 mg/kg of sertraline at the 126th postnatal days produced a significant depression in male virility (mating and fertility indices) compared to the control group. In addition, the cumulative treatment significantly increased the number of fetal resorptions in outcomes of female rats copulated by males in the SGIV group and decrease in both the number of implant sites and the viable fetuses. It is concluded that the sertraline-mediated reproductive deficits could entirely dependent on the robust spreading of the serotonergic receptors in the Leydig, Sertoli and germ cells, testis, epididymis, and vas deferens and simultaneously on the developmental-mediated timing of reproductive processes during the postnatal period to puberty.

Fluoxetine-induced androgenic failure impairs the seminiferous tubules integrity and increases ubiquitin carboxyl-terminal hydrolase L1 (UCHL1): Possible androgenic control of UCHL1 in germ cell death?

The selective serotonin reuptake inhibitor fluoxetine has been used for the treatment of depression. Although sexual disorders have been reported in male patients, few studies have demonstrated the fluoxetine effect on the reproductive histophysiology, and the target of this antidepressant in testes is unknown. We evaluated the impact of short-term treatment with fluoxetine on the adult rat testes, focusing on steroidogenesis by Leydig cells (LC) and androgen-dependent testicular parameters, including Sertoli cells (SC) and peritubular myoid cells (PMC). Since UCHL1 (ubiquitincarboxyl-terminal hydrolase L1) seems to control spermatogenesis, the immunoexpression of this hydrolase was also analyzed. Adult male rats received 20 mg/kg BW of fluoxetine (FG) or saline (CG) for eleven days. In historesin-embedded testis sections, the seminiferous tubule (ST) and epithelial (Ep) areas, and the LC nuclear diameter (LCnu) were measured. The number of abnormal ST, androgen-dependent ST, SC and PMC was quantified. Testicular β-tubulin levels and peritubular actin immunofluorescence were evaluated. Serum testosterone levels (STL) and steroidogenesis by 17β-HSD6 immunofluorescence were analyzed, and either UCHL1-immunolabeled or TUNEL-positive germ cells were quantified. In FG, abnormal ST frequency increased whereas ST and Ep areas, androgen-dependent ST number, LCnu, 17β-HSD6 activity and STL reduced significantly. TUNEL-positive PMC and SC was related to decreased number of these cells and reduction in peritubular actin and β-tubulin levels. In FG, uncommon UCHL1-immunoexpression was found in spermatocytes and spermatids, and the number of UCHL1-immunolabeled and TUNEL-positive germ cells increased in this group. These findings indicate that LC may be a fluoxetine target in testes, impairing PMC-SC integrity and disturbing spermatogenesis. The increase of UCHL1 in the damaged tubules associated with high incidence of cell death confirms that this hydrolase regulates germ cell death and may be controlled by androgens. The fertility in association with the androgenic status of patients treated with fluoxetine should be carefully evaluated.

The antidepressant fluoxetine alters mechanisms of pre- and post-copulatory sexual selection in the eastern mosquitofish (Gambusia holbrooki)

Contamination of aquatic habitats with pharmaceuticals is a major environmental concern. Recent studies have detected pharmaceutical pollutants in a wide array of ecosystems and organisms, with many of these contaminants being highly resistant to biodegradation and capable of eliciting sub-lethal effects in non-target species. One such pollutant is fluoxetine, a widely prescribed antidepressant, which is frequently detected in surface waters globally and can alter physiology and behaviour in aquatic organisms. Despite this, relatively little is known about the potential for fluoxetine to disrupt mechanisms of sexual selection. Here, we investigate the impacts of 30-day exposure to two environmentally realistic levels of fluoxetine (low and high) on mechanisms of pre- and post-copulatory sexual selection in the eastern mosquitofish (Gambusia holbrooki). We tested 1) male mating behaviour in the absence or presence of a competitor male, and 2) sperm quality and quantity. We found that high-fluoxetine exposure increased male copulatory behaviour in the absence of a competitor, while no effect was detected under male-male competition. Further, fluoxetine exposure at both concentrations increased total sperm count relative to males from the control group, while no significant change in sperm quality was observed. Lastly, low-fluoxetine males showed a significant reduction in condition index (mass relative to length). Our study is the first to show altered mechanisms of both pre- and post-copulatory sexual selection in an aquatic species resulting from environmentally realistic fluoxetine exposure, highlighting the capacity of pharmaceutical pollution to interfere with sensitive reproductive processes in wildlife.

Fluoxetine treatment of prepubertal male rats uniformly diminishes sex hormone levels and, in a subpopulation of animals, negatively affects sperm quality

Fluoxetine (Flx) is a selective serotonin reuptake inhibitor that alters the male reproductive system when administered at the adult stage or after maternal exposure. In the present study we evaluated the effects of Flx administration on reproductive parameters during juvenile–peripubertal development when treated male rats reached adulthood. Groups of rats were treated daily with Flx (5 mg kg−1, i.p.) or saline (0.9% NaCl), or were left untreated. Rats were treated between 30 and 53 days of age and were killed at 65 days of age. Serotonin concentrations were determined in the hypothalamus, hypophysis and testis. Gonadotrophins, sex steroids and sperm quality (membrane integrity, sperm with functional mitochondria, sperm density, sperm motility and morphological abnormalities) were also evaluated. Flx did not affect bodyweight, but significantly diminished LH, FSH, progesterone and testosterone serum concentrations. After graphical analysis, a subgroup of rats was identified whose sperm quality parameters were greatly affected by Flx. In the present study we show that Flx administered to juvenile rats disrupts the hypothalamic–hypophyseal–testicular axis and its effects on sperm quality are not homogeneous in adults. In contrast, Flx altered concentrations of gonadotrophins and sexual steroids in all treated rats. These results suggest caution should be exercised in the prescription of Flx to prepubertal males.

Fluoxetine and its active metabolite norfluoxetine disrupt estrogen synthesis in a co-culture model of the feto-placental unit

The effects of fluoxetine, one of the most prescribed selective serotonin-reuptake inhibitors (SSRIs) during pregnancy, and its active metabolite norfluoxetine were studied on placental aromatase (CYP19) and feto-placental steroidogenesis. Fluoxetine did not alter estrogen secretion in co-culture of fetal-like adrenocortical (H295R) and trophoblast-like (BeWo) cells used as a model of the feto-placental unit, although it induced CYP19 activity, apparently mediated by the serotonin (5-HT)_2A receptor/PKC signaling pathway. Norfluoxetine decreased estrogen secretion in the feto-placental co-culture and competitively inhibited catalytic CYP19 activity in BeWo cells. Decreased serotonin transporter (SERT) activity in the co-culture was comparable to 17β-estradiol treatment of BeWo cells. This work shows that the complex interaction of fluoxetine and norfluoxetine with placental estrogen production, involves 5-HT-dependent and -independent mechanisms. Considering the crucial role of estrogens during pregnancy, our results raise concern about the impact of SSRI treatment on placental function and fetal health.

Recovery effect of pre-germinated brown rice on the alteration of sperm quality, testicular structure and androgen receptor expression in rat model of depression

Depression and antidepressant drugs induce adverse effects in male reproduction. Therefore, it is important to investigate alternative treatment for depression without adverse effects on the male reproductive system. The aim of this study was to determine the effect of pre-germinated brown rice (PGBR) on sperm quality, testicular structure and androgen receptor (AR) expression in rat model of depression. Male Sprague Dawley rats were divided into five groups including control (distilled water only), depression induced by forced swimming test (FST), FST + fluoxetine (antidepressant drug), FST + GABA (gamma-aminobutyric acid) (standard) and FST + PGBR. When compared with the control, sperm motility showed a significant decrease in FST + fluoxetine group. Sperm morphology also decreased significantly in depression and FST + fluoxetine groups. The morphological changes of seminiferous tubules showed significant increases in depression and FST + fluoxetine groups, while AR expression showed significant decreases in depression, FST + fluoxetine and FST + GABA groups. Interestingly, there were no significant differences in all sperm quality parameters, testicular structure and AR expression in FST + PGBR group. These findings reflect the recovery effects of PGBR treatment on sperm quality, morphological changes of seminiferous tubules and AR expression in stress-induced rats. Therefore, PGBR may potentially develop for the treatment for depression without adverse effect on male reproduction.

Estrogenic/antiestrogenic activity of selected selective serotonin reuptake inhibitors

BACKGROUND AND AIMS

Selective serotonin reuptake inhibitors (SSRIs) are one of the most prescribed classes of psychotropics. Even though the SSRI class consists of 6 molecules (citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine and sertraline), only fluoxetine was intensively studied for endocrine disruptive effects, while the other SSRIs received less attention. This study was designed to evaluate the estrogenic/antiestrogenic effect of fluoxetine, sertraline and paroxetine.

METHODS

The in vitro (anti)estrogenic activity was assessed using a firefly luciferase reporter construct in the T47D-KBluc breast cancer cell line. These cells express nuclear estrogen receptors that can activate the transcription of the luciferase reporter gene upon binding of estrogen receptor agonists.

RESULTS

All three compounds were found to interact with the estrogen receptor. Fluoxetine had dual properties, weak estrogenic at lower concentrations and antiestrogenic effect at higher concentrations. Sertraline shared the same properties with fluoxetine, but also increased the estradiol-mediated transcriptional activity. Paroxetine presented only one type of effect, the ability to increase the estradiol-mediated transcriptional activity.

CONCLUSIONS

Overall, our results indicate a possible interaction of SSRIs with the estrogen receptor. As SSRIs are being used by all categories of population, including pregnant women or children, establishing whether they can affect the endocrine mediated mechanisms should be a priority.

In vitro modulation of estrogen receptor activity by norfluoxetine

Background and aims

Selective serotonin reuptake inhibitors (SSRIs) are antidepressants increasingly prescribed for pregnancy and postpartum depression. However, these compounds can cross the placenta and also pass into breast milk, thus reaching the fetus and infant during critical developmental stages, potentially causing adverse effects. Fluoxetine, a widely used SSRI, has been shown to affect (neuro)endocrine signaling in various organisms, including humans. This compound can also interact with estrogen receptors in vitro and cause an estrogen-dependent uterotrophic response in rodents. Consequently, the aim of the present study was to assess if the active metabolite of fluoxetine, namely norfluoxetine (NFLX), shares the same capacity for estrogen receptor interaction.

Methods

The in vitro (anti)estrogenic activity of norfluoxetine was assessed using a firefly luciferase reporter construct in the T47D-Kbluc breast cancer cell line. These cells express nuclear estrogen receptors (ERs) that can activate the transcription of the luciferase reporter gene upon binding of ER agonists. Light emission was monitored in case of cells exposed to norfluoxetine or mixtures of norfluoxetine-estradiol. Cell viability was assessed using a resazurin-based assay.

Results

During individual testing, NFLX was able to induce a significant increase in luciferase activity compared to control, but only at the highest concentration tested (10 μM). In binary mixtures with estradiol (30 pM constant concentration) a significant increase in luminescence was observed at low submicromolar norfluoxetine concentrations compared to estradiol alone.

Conclusion

Norfluoxetine can induce estrogenic effects in vitro and can potentiate the activity of estradiol. However, further studies are needed to clarify if these observed estrogenic effects may have detrimental consequences for human exposure.