The Serotonin Transporter Gene Polymorphisms and Risk of Ischemic Stroke

Predicting mortality among ischemic stroke patients using pathways-derived polygenic risk scores

We aim to determine whether ischemic stroke(IS)-related PRSs are also associated with and further predict 3-year all-cause mortality. 1756 IS patients with European ancestry were randomly split into training (n = 1226) and testing (n = 530) groups with 3-year post-event observations. Univariate Cox proportional hazards regression model (CoxPH) was used for primary screening of individual prognostic PRSs. Only the significantly associated PRSs and clinical risk factors with the same direction for a causal relationship with IS were used to construct a multivariate CoxPH. Feature selection was conducted by the LASSO method. After feature selection, a prediction model with 11 disease-associated pathway-specific PRSs outperformed the base model, as demonstrated by a higher concordance index (0.751, 95%CI [0.693–0.809] versus 0.729, 95%CI [0.676–0.782]) in the testing sample. A PRS derived from endothelial cell apoptosis showed independent predictability in the multivariate CoxPH (Hazard Ratio = 1.193 [1.027–1.385], p = 0.021). These PRSs fine-tuned the model by better stratifying high, intermediate, and low-risk groups. Several pathway-specific PRSs were associated with clinical risk factors in an age-dependent manner and further confirmed some known etiologies of IS and all-cause mortality. In conclusion, Pathway-specific PRSs for IS are associated with all-cause mortality, and the integrated multivariate risk model provides prognostic value in this context.

Effects of wheel-running on anxiety and depression-relevant behaviours in the MCAO mouse model of stroke: moderation of brain-derived neurotrophic factor and serotonin receptor gene expression

Stroke continues to be a major cause of mortality globally. Post-stroke treatment is complicated by the heterogenous nature of pathology and the emergence of secondary psychological symptoms are an additional challenge to the recovery process. Poststroke depression (PSD) is a common co-morbidity and is a major impediment to recovery. While selective serotonin reuptake inhibitors (SSRIs) have proven to be clinically efficacious in treating PSD, the pathogenic processes that underlie the manifestation of depressive mood post-stroke remains unclear. Furthermore, the use of SSRIs is associated with risks of intracerebral haemorrhage, so alternative treatment options need to be continuously explored. Exercise has been demonstrated to be beneficial for improving mood in humans and preclinical models of neurological conditions. Little is known of the mood-related benefits of physical exercise post-stroke. Using the middle cerebral artery occlusion (MCAO) mouse model of cerebral ischaemia, we investigated whether behavioural deficits emerge post-MCAO and could be rescued by voluntary wheel-running. We report that MCAO induced hypo-locomotion and anhedonia-related behaviours, with some improvements conferred by wheel-running. Serotonin transporter gene expression was increased in the MCAO hippocampus and frontal cortex, but this increase remained despite wheel-running. Wheel-running associated up-regulation of BDNF gene expression was unaffected in MCAO mice, reflecting conservation of key neuroplasticity molecular pathways. Taken together, our results highlight the need for further research into serotonergic modulation of the affective symptoms of stroke.

Platelet, Plasma, Urinary Tryptophan-Serotonin-Kynurenine Axis Markers in Hyperacute Brain Ischemia Patients: A Prospective Study

Background and Purpose: Ischemic stroke is one of the most common causes of morbidity and mortality and has numerous clinical mimics. Previous studies have suggested a potential role of the tryptophan-serotonin (5-HT)-kynurenine (TSK) axis in ischemic stroke. Studies assessing this axis in the hyperacute phase of ischemic stroke (<4.5 h) are lacking. This prospective study thus evaluates the TSK axis in transient ischemic attack (TIA) and hyperacute ischemic stroke (AIS) patients.

Methods: This study included 28 patients (24 AIS and 4 TIA) and 29 controls. The blood and urine samples of patient were collected within 4.5 h of symptoms onset (day 0, D0), then at 24 h and 3 months. Control blood and urine samples were collected once (D0). The TSK axis markers measured were platelet serotonin transporter (SERT) and 5-HT_2A receptor (5-HT_2AR) densities and platelet, plasma, and urinary 5-HT, plasma and urinary 5-hydroxyindole acetic acid (5-HIAA), and plasma kynurenine and tryptophan (TRP) levels.

Results: At D0, patients exhibited a lower (p = 10⁻⁵) platelet SERT density, higher (p < 10⁻⁶) platelet 5-HT_2AR density, higher (p = 10⁻⁵) plasma kynurenine/tryptophan (K/T) ratio, and higher urinary 5-HT (p = 0.011) and 5-HIAA (p = 0.003) levels than controls.

Conclusions: We observed, for the first time, a hyperacute dysregulation of the serotonergic axis, and hyperacute and long-lasting activation of the tryptophan-kynurenine pathway in brain ischemia.

Cardiovascular serotonergic system: Evolution, receptors, transporter, and function

The serotonergic system, serotonin (5HT), serotonin transporter (SERT), and serotonin receptors (5HT-x), is an evolutionarily ancient system that has clear physiological advantages to all life forms from bacteria to humans. This review focuses on the role of platelet/plasma serotonin and the cardiovascular system with minor references to its significant neurotransmitter function. Platelets transport and store virtually all plasma serotonin in dense granules. Stored serotonin is released from activated platelets and can bind to serotonin receptors on platelets and cellular components of the vascular wall to augment aggregation and induce vasoconstriction or vasodilation. The vascular endothelium is critical to the maintenance of cardiovascular homeostasis. While there are numerous ligands, neurological components, and baroreceptors that effect vascular tone it is proposed that serotonin and nitric oxide (an endothelium relaxing factor) are major players in the regulation of systemic blood pressure. Signals not fully defined, to date, that direct serotonin binding to one of the 15 identified 5HT receptors versus the transporter, and the role platelet/plasma serotonin plays in regulating hypertension within the cardiovascular system remain important issues to better understand many diseases and to develop new drugs. Also, expanded research of these pathways in lower life-forms may serve as important model systems to further our understanding of the evolution and mechanisms of action of serotonin.

Predictors for wellbeing and characteristics of mental health after stroke

BACKGROUND

Poor mental health after stroke is common and complex. We aimed to identify predictors of poor wellbeing and to examine the overlap of poor wellbeing, fatigue, and depression.

METHOD

Consecutive first-ever ischemic stroke-patients filled in questionnaires on wellbeing, fatigue, and depression at baseline and at one and six months. The World Health Organization 5-Item Wellbeing-Index (WHO-5), the Major Depression Inventory, and the Multidimensional Fatigue Inventory were used. Patients were genotyped according to serotonin-transporter gene polymorphisms. Multivariable logistic regression was used to identify potential predictors of poor wellbeing (WHO-5 score <50). Overlap between wellbeing, fatigue, and depression was examined using an Euler diagram.

RESULTS

We included 919 patients. The prevalence of poor wellbeing was 279 (30.4%) six months after stroke. Living alone at stroke onset was the strongest predictor of poor wellbeing with a mutually adjusted odds ratio of 1.53 (95% confidence interval (CI): 1.03 to 2.28) at one month and 1.77 (CI: 1.13 to 2.76) at six months. Severe stroke at admission also predicted poor wellbeing at six months. Abnormal fatigue occurred in half and incorporated almost all patients with poor wellbeing. Less than 5% fulfilled the criteria for depression at any point and almost all of these patients had poor wellbeing and abnormal fatigue. Antidepressants were used by 292 (31.8%) during follow-up.

LIMITATIONS

Cognitive impairment was not measured and could interact with wellbeing post-stroke.

CONCLUSION

Living alone strongly predicted poor wellbeing after stroke. Satisfactory mental health-recovery seems to require psychosocial interventions when indicated in combination with antidepressant treatment.

Association of Antidepressant Medication Type With the Incidence of Cardiovascular Disease in the ARIC Study

Background

The association of antidepressant medication type with the risk of cardiovascular disease (CVD) is unclear. We hypothesized that selective serotonin reuptake inhibitors (SSRIs) are associated with lower risks of CVD events relative to tricyclics and other non‐SSRI antidepressants.

Methods and Results

We studied 2027 participants from the ARIC (Atherosclerosis Risk in Communities) study (mean age 63±10 years; 29% men; 78% white) treated with antidepressants at some time between 1987 and 2013. Antidepressant usage was confirmed by participants bringing pill bottles to study visits. CVD events in the study sample were identified, including atrial fibrillation, heart failure, myocardial infarction, and ischemic stroke. Hazard ratios were used to compare CVD events adjusted for sociodemographic and clinical risk factors in SSRIs users (47%) versus non‐SSRI users. Participants were followed from antidepressant initiation up to 2016 for a median of 13.5 years. We identified 332 atrial fibrillation, 365 heart failure, 174 myocardial infarction and 119 ischemic stroke events. CVD risk was similar for SSRIs and non‐SSRI antidepressant users (hazard ratio, 1.10; 95% CI, 0.86–1.41 for atrial fibrillation; hazard ratio, 0.98; 95% CI, 0.77–1.25 for heart failure; hazard ratio, 0.91; 95% CI, 0.64–1.29 for myocardial infarction; and hazard ratio, 1.07; 95% CI, 0.70–1.63 for ischemic stroke).

Conclusions

SSRI use was not associated with reduced risk of incident CVD compared with non‐SSRI antidepressant use. These results do not provide evidence supporting the use of SSRIs compared with tricyclics and other non‐SSRI antidepressants in relation to CVD risk.

Potential Role of Selective Serotonin Reuptake Inhibitors in Improving Functional Outcome after Stroke

The great advances in acute stroke treatment during the last decades have changed life after stroke considerably. However, the use of intravenous thrombolysis and endovascular thrombectomy is limited by a relatively narrow time window or contraindications for treatment. Further, patients receiving acute reperfusion therapies may still have cognitive and emotional complications due to underlying brain infarcts even though physical problems may almost disappear. Consequently, stroke is still a frequent cause of adult disability and death worldwide, and an effort to identify additional treatments to enhance recovery, preferably also feasible in the time after the acute phase, is warranted. Albeit several drugs and treatment modalities have been studied for their potential to enhance recovery after stroke, no treatment has unambiguously proven to potentiate the rehabilitation process. A promising candidate for pharmacological treatment is selective serotonin reuptake inhibitors (SSRIs), a group of commonly used antidepressants that may also possess neuro-regenerative properties. The current paper reviews the evidence for SSRIs as potential enhancers of stroke recovery and discusses the potential mechanisms behind the effects reported and the implications for the management of patients post-stoke, including potential adverse events and drug-drug interactions.

Executive (dys)function after stroke: special considerations for behavioral pharmacology

Stroke is a worldwide leading cause of death and long-term disability with concurrent secondary consequences that are largely comprised of mood dysfunction, as well as sensory, motor, and cognitive deficits. This review focuses on the cognitive deficits associated with stroke specific to executive dysfunction (including decision making, working memory, and cognitive flexibility) in humans, nonhuman primates, and additional animal models. Further, we review some of the cellular and molecular underpinnings of the individual components of executive dysfunction and their neuroanatomical substrates after stroke, with an emphasis on the changes that occur during biogenic monoamine neurotransmission. We concentrate primarily on changes in the catecholaminergic (dopaminergic and noradrenergic) and serotonergic systems at the levels of neurotransmitter synthesis, distribution, reuptake, and degradation. We also discuss potential secondary stroke-related behavioral deficits (specifically, poststroke depression as well as drug-abuse potential and addiction) and their relationship with stroke-induced deficits in executive function, an especially important consideration given that the average age of the human stroke population is decreasing. In the final sections, we address pharmacological considerations for the treatment of ischemia and the subsequent functional impairment, as well as current limitations in the field of stroke and executive function research.