Effects of acute administration of selective serotonin reuptake inhibitors on sympathetic nerve activity

Sex differences in Black Veterans with PTSD: women versus men have higher sympathetic activity, inflammation, and blunted cardiovagal baroreflex sensitivity

PURPOSE

Post-traumatic stress disorder (PTSD) is associated with greater risk of incident hypertension and cardiovascular disease (CVD). Inflammation and autonomic derangements are suggested as contributing mechanisms. Women and Black adults have higher CVD risk associated with stress; however, whether there is a sex difference in autonomic and inflammatory mechanisms among Black individuals with PTSD is not known. We hypothesized that Black women with PTSD have higher inflammation, sympathetic nervous system (SNS) activity and impaired baroreflex sensitivity (BRS).

METHODS

In 42 Black Veterans with PTSD (Women, N = 18 and Men, N = 24), we measured inflammatory biomarkers, continuous blood pressure (BP), heart rate (HR) and muscle sympathetic nerve activity (MSNA) at rest and during arterial BRS testing via the modified Oxford technique.

RESULTS

Groups were matched for age and body mass index (BMI). Resting BP was similar between groups, but HR was higher (76 ± 12 vs. 68 ± 9 beats/min, p = 0.021) in women compared to men. Although women had lower PTSD symptoms severity (57 ± 17 vs. 68 ± 12 a.u.), resting MSNA (27 ± 13 vs. 16 ± 5 bursts/min, p = 0.003) was higher in women compared to men, respectively. Likewise, cardiovagal BRS was blunted (p = 0.002) in women (7.6 ± 4.3 ms/mmHg) compared to men (15.5 ± 8.4 ms/mmHg) while sympathetic BRS was not different between groups (p = 0.381). Black women also had higher (p = 0.020) plasma levels of interleukin-2 (IL-2).

CONCLUSION

Black women with PTSD have higher resting HR and MSNA, greater impairment of cardiovagal BRS and possibly higher inflammation. These findings suggest a higher burden of autonomic and inflammatory derangements in Black women compared to Black men with PTSD.

Serotonergic Modulation of Neurovascular Transmission: A Focus on Prejunctional 5-HT Receptors/Mechanisms

5-Hydroxytryptamine (5-HT), or serotonin, plays a crucial role as a neuromodulator and/or neurotransmitter of several nervous system functions. Its actions are complex, and depend on multiple factors, including the type of effector or receptor activated. Briefly, 5-HT can activate: (i) metabotropic (G-protein-coupled) receptors to promote inhibition (5-HT₁, 5-HT₅) or activation (5-HT₄, 5-HT₆, 5-HT₇) of adenylate cyclase, as well as activation (5-HT₂) of phospholipase C; and (ii) ionotropic receptor (5-HT₃), a ligand-gated Na⁺/K⁺ channel. Regarding blood pressure regulation (and beyond the intricacy of central 5-HT effects), this monoamine also exerts direct postjunctional (on vascular smooth muscle and endothelium) or indirect prejunctional (on autonomic and sensory perivascular nerves) effects. At the prejunctional level, 5-HT can facilitate or preclude the release of autonomic (e.g., noradrenaline and acetylcholine) or sensory (e.g., calcitonin gene-related peptide) neurotransmitters facilitating hypertensive or hypotensive effects. Hence, we cannot formulate a specific impact of 5-HT on blood pressure level, since an increase or decrease in neurotransmitter release would be favoured, depending on the type of prejunctional receptor involved. This review summarizes and discusses the current knowledge on the prejunctional mechanisms involved in blood pressure regulation by 5-HT and its impact on some vascular-related diseases.

Paroxetine induced larva zebrafish cardiotoxicity through inflammation response

Paroxetine (PRX) is a common antidepressant drug which widely existence in natural environment. Numerous studies in the past few decades have focused on the beneficial effects of PRX on depression, however, the toxic properties and the potential mechanisms remain unclear. In this study, zebrafish embryos were exposed to 1.0, 5.0, 10 and 20 mg/L of PRX from 4 to 120-hour-post-fertilization (hpf), and it showed that PRX exposure caused adverse effects in zebrafish embryos, including decreased body length, blood flow velocity, cardiac frequency, cardiac output and increased burst activity and atria area. Meanwhile, the Tg (myl7: EGFP) and Tg (lyz: DsRed) transgenic zebrafish were used to detect the cardiotoxicity and inflammation response of PRX. Moreover, the heart development associated genes (vmhc, amhc, hand2, nkx2.5, ta, tbx6, tbx16 and tbx20) and inflammatory genes (IL-10, IL-1β, IL-8 and TNF-α) were up-regulated after PRX challenge. In addition, Aspirin was used to alleviate the PRX-induced heart development disorder. In conclusion, our study verified the PRX induced inflammatory related cardiotoxicity in larva zebrafish. Meanwhile, the current study shown the toxic effects of PRX in aquatic organism, and provide for the environmental safety of PRX.

The results of a unique dietary supplement (nutraceutical formulation) used to treat the symptoms of long-haul COVID

Long-COVID is a syndrome characterized by debilitating symptoms that persist over 3 months after infection with the SARS-CoV-2 virus. It affects 15 to 33% of COVID-19 recovered patients and has no dedicated treatment. First, we found that β-caryophyllene and pregnenolone have a significant synergistic effect in the resolution of LPS-induced sepsis and inflammation in mice. Then we combined these two compounds with seven others and designed a unique dietary supplement formulation to alleviate long COVID inflammatory and neurological disorders. We performed a one-arm open-labeled study at a single site with 51 eligible patients from 18 states. Each participant recorded the severity level of 12 symptoms (including fatigue, weakness, cardiac and neurological symptoms, shortness of breath, gastrointestinal disorders, ageusia or anosmia, anxiety, joint pain, rash, cough, and insomnia) at baseline, 2- and 4-week time points. On average, all the symptoms were significantly milder after 2 weeks, with further improvement after 4 weeks. Importantly, each symptom was significantly attenuated in 72 to 84% of the participants. There were no significant adverse effects. Our data indicate that the use of this nutraceutical product is a safe and significantly efficient option to reduce multiple symptoms of long COVID.

Oral fluoxetine treatment changes serotonergic sympatho-regulation in experimental type 1 diabetes

AIMS

This study investigated whether fluoxetine treatment changes the 5-HT regulation on vascular sympathetic neurotransmission in type 1 diabetes.

MAIN METHODS

Four-week diabetes was obtained by a single alloxan s.c. administration in male Wistar rats, administering fluoxetine for 14 days (10 mg/kg/day; p.o.). Systolic blood pressure, heart rate, glycaemia, body weight (BW) evolution, creatinine, and blood urea nitrogen (BUN) were monitored. Afterward, rats were pithed to perform the vascular sympathetic stimulation. 5-HT_1A/1D/2A receptors expression was analysed by Western blot in thoracic aorta. Both i.v. norepinephrine and the electrical stimulation of the spinal sympathetic drive evoked vasoconstrictor responses.

KEY FINDINGS

Fluoxetine treatment significantly reduced the BW gain, hyperglycaemia, creatinine, and BUN in diabetic rats. The electrical-produced vasopressor responses were greater in untreated than in fluoxetine-treated diabetic rats. 5-HT decreased the sympathetic-produced vasopressor responses. While 5-CT, 8-OH-DPAT and L-694,247 (5-HT_1/7, 5-HT_1A and 5-HT_1D agonists, respectively) reproduced 5-HT-evoked inhibition, the 5-HT₂ activation by α-methyl-5-HT augmented the vasoconstrictions. The 5-CT sympatho-inhibition was reversed by 5-HT_1A plus 5-HT_1D antagonists (WAY-100,635 and LY310762, respectively), whereas ritanserin (5-HT_2A antagonist) blocked the α-methyl-5-HT potentiating effect. Norepinephrine-generated vasoconstrictions were increased or diminished by α-methyl-5-HT or 5-CT, respectively. 5-HT_1A/1D/2A receptors were expressed at vascular level, being 5-HT_1A expression increased by fluoxetine in diabetic rats.

SIGNIFICANCE

Our findings suggest that fluoxetine improves metabolic and renal profiles, changes the vasopressor responses, and 5-HT receptors modulating sympathetic activity in diabetic rats: 5-HT_1A/1D are involved in the sympatho-inhibition, while 5-HT_2A is implicated in the sympatho-potentiation, being both effects pre and/or postjunctional in nature.

Vascular sympathetic neurotransmission and its serotonergic regulation are modified by chronic fluoxetine treatment

Given the interconnection between depressive and cardiovascular disorders, we investigated whether antidepressant treatment (fluoxetine) modifies the serotonergic influence on rat vascular noradrenergic outflow. Twelve-week-old male Wistar rats received fluoxetine treatment (10 mg/kg/day; p.o.) for 14 days; then, they were pithed and prepared for sympathetic stimulation. Vasopressor responses were obtained by electrical stimulation of the sympathetic outflow (0.1, 0.5, 1, and 5 Hz) or i.v. noradrenaline (NA; 0.01, 0.05, 0.1, and 0.5 μg/kg). In fluoxetine-treated group, the electrical-induced vasoconstrictions were lower compared to non-treated rats. Intravenous infusion of 5-HT (10 μg/kg/min) inhibited the sympathetically-induced vasoconstrictions. Only 5-CT, 8-OH-DPAT and L-694,247 (5-HT1/7, 5-HT1A and 5-HT1D agonists, respectively) mimicked 5-HT-induced inhibition, while α-methyl-5-HT (5-HT2 agonist) increased the vasopressor responses. The inhibitory effect of 5-HT was: a) no modified by SB269970 (5-HT7 antagonist); b) abolished by WAY-100,635 (5-HT1A antagonist) plus LY310762 (5-HT1D antagonist); and c) potentiated by ritanserin (5-HT2A receptor antagonist). The vasoconstrictions induced by exogenous NA were not modified by 5-CT but were increased by α-methyl-5-HT. Our results suggest that fluoxetine treatment decreases NA release at vascular level and changes 5-HT modulation on rat vascular noradrenergic neurotransmission, inducing sympatho-inhibition via prejunctional 5-HT1A/1D receptors, and sympatho-potentiation via pre and/or postjunctional 5-HT2A receptors.

Is Fluoxetine Good for Subacute Stroke? A Meta-Analysis Evidenced From Randomized Controlled Trials

Background and Purpose: Fluoxetine is a drug commonly used to treat mental disorders, such as depression and obsessive–compulsive disorder, and some studies have shown that fluoxetine can improve motor and function recovery after stroke. Therefore, we performed a meta-analysis to investigate the efficacy and safety of fluoxetine in the treatment of post-stroke neurological recovery.

Methods: PubMed, Embase, and Cochrane Library were searched for randomized controlled trials (RCTs) that were performed to assess the efficacy and safety of fluoxetine for functional and motor recovery in subacute stroke patients up to October 2020. Review Manager 5.3 software was used to assess the data. The risk ratio (RR) and standardized mean difference (SMD) were analyzed and calculated with a fixed effects model.

Results: We pooled 6,788 patients from nine RCTs. The primary endpoint was modified Rankin Scale (mRS). Fluoxetine did not change the proportion of mRS ≤ 2 (P = 0.47). The secondary endpoints were Fugl-Meyer Motor Scale (FMMS), Barthel Index (BI), and National Institutes of Health Stroke Scale (NIHSS). Fluoxetine improved the FMMS (P < 0.00001) and BI(P < 0.0001) and showed a tendency of improving NIHSS (P = 0.08). In addition, we found that fluoxetine reduced the rate of new-onset depression (P < 0.0001) and new antidepressants (P < 0.0001).

Conclusion: In post-stroke treatment, fluoxetine did not improve participants' mRS and NIHSS but improved FMMS and BI. This difference could result from heterogeneities between the trials: different treatment duration, clinical scales sensitivity, patient age, delay of inclusion, and severity of the deficit.

Selective serotonin reuptake inhibitors (SSRIs) prevent meta-iodobenzylguanidine (MIBG) uptake in platelets without affecting neuroblastoma tumor uptake

Background

The therapeutic use of [¹³¹I]meta-iodobenzylguanidine ([¹³¹I]MIBG) is often accompanied by hematological toxicity, mainly consisting of persistent and severe thrombocytopenia. While MIBG accumulates in neuroblastoma cells via selective uptake by the norepinephrine transporter (NET), the serotonin transporter (SERT) is responsible for cellular uptake of MIBG in platelets. In this study, we have investigated whether pharmacological intervention with selective serotonin reuptake inhibitors (SSRIs) may prevent radiotoxic MIBG uptake in platelets without affecting neuroblastoma tumor uptake.

Methods

To determine the transport kinetics of SERT for [¹²⁵I]MIBG, HEK293 cells were transfected with SERT and uptake assays were conducted. Next, a panel of seven SSRIs was tested in vitro for their inhibitory potency on the uptake of [¹²⁵I]MIBG in isolated human platelets and in cultured neuroblastoma cells. We investigated in vivo the efficacy of the four best performing SSRIs on the accumulation of [¹²⁵I]MIBG in nude mice bearing subcutaneous neuroblastoma xenografts. In ex vivo experiments, the diluted plasma of mice treated with SSRIs was added to isolated human platelets to assess the effect on [¹²⁵I]MIBG uptake.

Results

SERT performed as a low-affinity transporter of [¹²⁵I]MIBG in comparison with NET (K_m = 9.7 μM and 0.49 μM, respectively). Paroxetine was the most potent uptake inhibitor of both serotonin (IC₅₀ = 0.6 nM) and MIBG (IC₅₀ = 0.2 nM) in platelets. Citalopram was the most selective SERT inhibitor of [¹²⁵I]MIBG uptake, with high SERT affinity in platelets (IC₅₀ = 7.8 nM) and low NET affinity in neuroblastoma cells (IC₅₀ = 11.940 nM). The in vivo tested SSRIs (citalopram, fluvoxamine, sertraline, and paroxetine) had no effect on [¹²⁵I]MIBG uptake levels in neuroblastoma xenografts. In contrast, treatment with desipramine, a NET selective inhibitor, resulted in profoundly decreased xenograft [¹²⁵I]MIBG levels (p < 0.0001). In ex vivo [¹²⁵I]MIBG uptake experiments, 100- and 34-fold diluted murine plasma of mice treated with citalopram added to isolated human platelets led to a decrease in MIBG uptake of 54–76%, respectively.

Conclusion

Our study demonstrates for the first time that SSRIs selectively inhibit MIBG uptake in platelets without affecting MIBG accumulation in an in vivo neuroblastoma model. The concomitant application of citalopram during [¹³¹I]MIBG therapy seems a promising strategy to prevent thrombocytopenia in neuroblastoma patients.

Serotonin Selective Reuptake Inhibitors (SSRIs) and Stroke

PURPOSE OF REVIEW

The interest in SSRIs after stroke has increased in the past few years, with better knowledge of post-stroke depression and with the demonstrated capacity of some SSRIs to act on the functional recovery of non-depressed subjects.

RECENT FINDINGS

Arguments for the action of SSRIs in favour of post-stroke neurological function recovery have improved through new elements: basic science and preclinical data, positive clinical trials and repeated series of stroke patient meta-analysis, and confirmation of favourable safety conditions in post-stroke patients. Global coherence is appearing, showing that SSRIs improve stroke recovery in non-depressed patients when given for 3 months after the stroke, with highly favourable safety conditions and a favourable benefit/risk ratio. Large series are still needed.

Psychocardiological disorder and brain serotonin after comorbid myocardial infarction and depression: an experimental study

Objectives We investigated whether trimetazidine pretreatment can regulate central and peripheral serotonin (5-HT) in rats of myocardial infarction (MI) combined with depression. Methods Forty rats were randomly assigned to a sham operation group (n = 10) and a disease model group (n = 30). The sham operation group was pretreated with normal saline for 4 weeks. The disease model group was randomly assigned further into a negative control subgroup, a positive control subgroup, and a treatment subgroup - the groups received saline, sertraline, and trimetazidine pretreatment, respectively, for 4 weeks, then the rats were subjected to MI combined with depression. 5-HT concentrations in the serum, platelet lysate, and cerebral cortex lysate were analyzed with ELISA. Results The levels of serum 5-HT and platelet 5-HT were significantly lower in negative control subgroup than the sham operation group (P < 0.05), but there was no significant difference in brain 5-HT (P > 0.05). Compared with the negative control subgroup, the levels of serum 5-HT and platelet 5-HT in the positive control subgroup and treatment subgroup were significantly higher (P < 0.05). The levels of 5-HT in brain of the positive control subgroup and treatment subgroup were significantly lower than those in the negative control subgroup (P < 0.05). Conclusions Trimetazidine pretreatment can increase serum and platelet 5-HT levels in rats with MI and depression and decrease 5-HT levels in brain tissue. This regulatory effect on central and peripheral 5-HT suggests a role for trimetazidine in the treatment of psychocardiological diseases.

Role of monoaminergic systems and ambient temperature in bath salts constituent 3,4-methylenedioxypyrovalerone (MDPV)-elicited hyperthermia and locomotor stimulation in mice

3,4-Methylenedioxypyrovalerone (MDPV) is a common constituent of illicit bath salts products, and in vitro studies implicate monoamine transporters as mediators of its pharmacological effects. Locomotor and thermoregulatory effects of MDPV depend on ambient temperature, so the current studies aimed to gauge the involvement of dopamine (DA), norepinephrine (NE), and serotonin (5-HT) in MDPV-induced locomotor stimulation and hyperthermia in the mouse at different ambient temperatures. Mice were pretreated with the selective 5-HT-reuptake inhibitor fluoxetine (3 mg/kg), the NE-reuptake inhibitor desipramine (3 mg/kg), the DA-reuptake inhibitor bupropion (10 mg/kg), or saline, followed by 10 mg/kg MDPV while thermoregulation and locomotor activity were monitored via radiotelemetry. In other studies, mice were pretreated for three days with saline, 100 mg/kg of the tryptophan hydroxylase inhibitor para-chlorophenylalanine (p-CPA), or 100 mg/kg of the tyrosine hydroxylase inhibitor α-methyl-para-tyrosine (α-MPT) before receiving 10 mg/kg MDPV on the fourth day. All manipulations were conducted at both 20 °C and 28 °C ambient temperatures. MDPV increased locomotor activity under both ambient conditions and modestly increased core body temperature at 20 °C; however, neither pretreatment with monoamine reuptake inhibitors nor monoamine synthesis inhibitors significantly altered these effects. At 28 °C, MDPV induced a more pronounced hyperthermic effect which was attenuated by bupropion, desipramine, or fluoxetine pretreatment, but not by the monoamine synthesis inhibitors. These results suggest that MDPV may have a more complex pharmacological profile than suggested by in vitro studies, perhaps extending beyond interactions with monoamine transporters. A more thorough binding profile of MDPV at various brain recognition sites should be developed. This article is part of the Special Issue entitled 'Designer Drugs and Legal Highs.'

Selective serotonin reuptake inhibitors to improve outcome in acute ischemic stroke: possible mechanisms and clinical evidence

BACKGROUND

Several clinical studies have indicated that selective serotonin reuptake inhibitors (SSRIs) administered in patients after acute ischemic stroke can improve clinical recovery independently of depression. Due to small sample sizes and heterogeneous study designs interpretability was limited in these studies. The mechanisms of action whereby SSRI might improve recovery from acute ischemic stroke are not fully elucidated.

METHODS

We searched MEDLINE using the PubMed interface to identify evidence of SSRI mediated improvement of recovery from acute ischemic stroke and reviewed the literature on the potential underlying mechanisms of action.

RESULTS

Among identified clinical studies, a well-designed randomized, double-blind, and placebo-controlled study (FLAME - fluoxetine for motor recovery after acute ischemic stroke) demonstrated improved recovery of motor function in stroke patients receiving fluoxetine. The positive effects of SSRIs on stroke recovery were further supported by a meta-analysis of 52 trials in a total of 4060 participants published by the Cochrane collaboration. Based on animal models, the mechanisms whereby SSRIs might ameliorate functional and structural ischemic-brain damage were suggested to include stimulation of neurogenesis with migration of newly generated cells toward ischemic-brain regions, anti-inflammatory neuroprotection, improved regulation of cerebral blood flow, and modulation of the adrenergic neurohormonal system. However, to date, it remains speculative if and to what degree these mechanisms convert into humans and randomized controlled trials in large populations of stroke patients comparing different SSRIs are still lacking.

CONCLUSION

In addition to the need of comprehensive-clinical evidence, further elucidation of the beneficial mechanisms whereby SSRIs may improve structural and functional recovery from ischemic-brain damage is needed to form a basis for translation into clinical practice.