Selective serotonin reuptake inhibitors and the incidence and outcome of pulmonary hypertension

Exploring the correlation between cardiovascular adverse events and antidepressant use: A retrospective pharmacovigilance analysis based on the FDA Adverse Event Reporting System database

BACKGROUND

The high comorbidity and mutually reinforcing relation between depression and cardiovascular disease have raised concerns about the cardiovascular risk of antidepressants. To gain a better understanding of this correlation, we performed a comprehensive evaluation regarding the types and degrees of cardiovascular adverse events (AEs) associated with 37 commonly prescribed antidepressants.

METHODS

AE reports from January 2004 to December 2023 were retrieved from the FDA Adverse Event Reporting System (FAERS) database. Disproportionality analysis was performed to identify antidepressant-related cardiovascular signals using the reporting odds ratio, proportional reporting ratio, and information component. Influencing factors of cardiovascular death, including age, sex, antidepressant choice, and concomitant medication, were explored. The underlying mechanisms of antidepressant-associated cardiovascular risk related to neurotransmitter transporters/receptors were further explored.

RESULTS

The use of antidepressants was associated with eight categories of Standardized MedDRA Queries of cardiovascular events. Different antidepressants exerted varying types and degrees of cardiovascular risks along with contributions to death in reports with cardiovascular AEs. Among them, monoamine oxidase inhibitors had the highest risk of developing six cardiovascular event categories: torsades de pointes (TdP)/QT prolongation, hypertension, cardiac arrhythmias, cardiomyopathy, pulmonary hypertension, and ischaemic heart disease. Age, male and the use of 24 types of antidepressants and concomitant medications were positively correlated with death in cardiovascular AEs. The highest risk associated with antidepressants was found in amoxapine (OR = 5.00 [2.13, 11.75], P < 0.001), followed by moclobemide (OR = 3.66 [1.85, 7.24], P < 0.001). Correlation analysis indicated the occurrence of antidepressant-related TdP/QT prolongation, hypertension and cardiomyopathy was associated with the binding and uptake inhibition of dopamine and norepinephrine transporters as well as their selectivity over serotonin transporters.

CONCLUSION

The retrospective analysis revealed that cardiovascular AEs were connected with antidepressant use, and the binding/uptake inhibitory potency and selectivity of neurotransmitters of antidepressants played an important role, providing a preliminary basis for further in-depth study of antidepressant-related cardiovascular toxicity. However, as an exploratory study, prospective studies are needed to validate our findings in the future.

Pulmonary Arterial Hypertension Secondary to Drugs and Toxins

Pulmonary arterial hypertension secondary to drugs and toxins is an important subgroup of group 1 pulmonary hypertension associated with significant morbidity and mortality. Many drugs and toxins have emerged as risk factors for pulmonary arterial hypertension, which include anorexigens, illicit agents, and several US Food and Drug Administration-approved therapeutic medications. Drugs and toxins are classified as possible or definite risk factors for pulmonary arterial hypertension. This article reviews agents that have been implicated in the development of pulmonary arterial hypertension, their pathologic mechanisms, and methods to prevent the next deadly outbreak of drug- and toxin-induced pulmonary arterial hypertension.

SSRIs: Applications in inflammatory lung disease and implications for COVID-19

Selective serotonin reuptake inhibitors (SSRIs) have anti-inflammatory properties that may have clinical utility in treating severe pulmonary manifestations of COVID-19. SSRIs exert anti-inflammatory effects at three mechanistic levels: (a) inhibition of proinflammatory transcription factor activity, including NF-κB and STAT3; (b) downregulation of lung tissue damage and proinflammatory cell recruitment via inhibition of cytokines, including IL-6, IL-8, TNF-α, and IL-1β; and (c) direct suppression inflammatory cells, including T cells, macrophages, and platelets. These pathways are implicated in the pathogenesis of COVID-19. In this review, we will compare the pathogenesis of lung inflammation in pulmonary diseases including COVID-19, ARDS, and chronic obstructive pulmonary disease (COPD), describe the anti-inflammatory properties of SSRIs, and discuss the applications of SSRIS in treating COVID-19-associated inflammatory lung disease.

Hemodynamic effects of fluoxetine in pulmonary arterial hypertension: an open label pilot study

In order to evaluate the therapeutic potential of fluoxetine in pulmonary arterial hypertension, 13 patients with pulmonary arterial hypertension underwent catheterization before and after 12 (N = 5) or 24 (N = 8) weeks fluoxetine therapy. No change was seen in the primary endpoint of pulmonary vascular resistance, other hemodynamic values, or any secondary endpoints.

Pulmonary Arterial Hypertension: A Palliative Medicine Review of the Disease, Its Therapies, and Drug Interactions

Pulmonary arterial hypertension (PAH) is often a progressive and ultimately fatal disease. It is characterized by an elevated mean pulmonary arterial pressure because of disease of the small pulmonary arterioles. PAH leads to a constellation of symptoms, including dyspnea, fatigue, syncope, chest discomfort, and peripheral edema. Disease-targeted therapies for PAH produce symptomatic and functional improvement, but long-term survival remains uncommon without lung transplantation. Palliative care is appropriate to support patients with advanced PAH who typically have a high symptom burden. However, palliative care has historically focused on supporting patients with malignant disease, rather than progressive chronic disease such as PAH. Our aim is to provide palliative care clinicians with a background in the classification, pathophysiology, and modern treatment of PAH. This review describes disease-targeted therapies and their effects on symptoms, physical functioning, and health-related quality of life. We also review the unique physiology of PAH and its implication for palliative interventions. Pharmacological interactions with, and precautions related to commonly used palliative care medications, are discussed.

Platelets in Systemic Sclerosis: the Missing Link Connecting Vasculopathy, Autoimmunity, and Fibrosis?

PURPOSE OF REVIEW

Platelets are no longer recognized solely as cell fragments regulating hemostasis. They have pleiotropic functions and they are linked directly or indirectly with the three cornerstones of systemic sclerosis (SSc): vasculopathy, autoimmunity, and fibrosis. In this review, we summarize the current knowledge on the potential role of platelets in the pathogenesis of SSc.

RECENT FINDINGS

Experimental evidence suggests that vasculopathy, a universal and early finding in SSc, may activate platelets which subsequently release several profibrotic mediators such as serotonin and transforming growth factor β (TGFβ). Platelets may also cross-react with the endothelium leading to the release of molecules, such as thymic stromal lymphopoietin (TSLP), that may trigger fibrosis or sustain vascular damage. Finally, activated platelets express CD40L and provide costimulatory help to B cells, something that may facilitate the breach in immune tolerance. Preclinical studies point to the direction that platelets are actively involved in SSc pathogenesis. Targeting platelets may be an attractive therapeutic approach in SSc.

Non-Hormonal Replacement Therapy Regimens: Do they have an Effect on Cardiovascular Risk?

INTRODUCTION

Menopause is associated with adverse effects on quality of life of perimenopausal and post-menopausal women. It also has an impact on the development of cardiovascular disease (CVD). Hormonal treatments are the most effective medications for menopausal symptoms relief. Given the fact that hormonal treatments are contraindicated for many women, non-hormonal treatment, such as Selective Serotonin Reuptake Inhibitors (SSRIs), Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs), gabapentin, pregabalin, clonidine and phytoestrogens, constitute alternative treatments. Nevertheless, little is known about their effects on CVD risk.

METHODS

PubMed, EMBASE and Cochrane Library were searched for the effects of non-hormonal treatment on CVD risk, blood pressure, heart rate, lipids and glucose concentrations, weight gain, cardiovascular events, stroke, mortality and morbidity.

RESULTS

Phytoestrogens, pregabalin and gabapentin seem to have no adverse effects on the cardiovascular system. Phytoestrogens, in particular, seem to reduce CVD risk through many pathways. On the other hand, SSRIs and SNRIs, although effective in reducing menopausal vasomotor symptoms, should be cautiously administered to women with known CVD (e.g. with cardiac arrhythmias, atherosclerotic disease or stroke). As clonidine has been associated with cardiovascular adverse effects, it should be administered only in cases where blood pressure regulation is mandatory.

CONCLUSION

Further research is needed to produce definite conclusions regarding the cardiovascular safety of non-hormonal medications for menopausal symptoms relief.

The role of platelets in the development and progression of pulmonary arterial hypertension

Pulmonary arterial hypertension is a multifactorial disease characterized by vasoconstriction, vascular remodeling, inflammation and thrombosis. Although an increasing number of research confirmed that pulmonary artery endothelial cells, pulmonary artery smooth muscle cells as well as platelets have a role in the pulmonary arterial hypertension pathogenesis, it is still unclear what integrates these factors. In this paper, we review the evidence that platelets through releasing a large variety of chemokines could actively impact the pulmonary arterial hypertension pathogenesis and development. A recent publication revealed that not only an excess of platelet derived cytokines, but also a deficiency may be associated with pulmonary arterial hypertension development and progression. Hence, a simple platelet blockade may not be a correct action to treat pulmonary arterial hypertension. Our review aims to analyse the interactions between the platelets and different types of cells involved in pulmonary arterial hypertension pathogenesis. This knowledge could help to find novel therapeutic options and improve prognosis in this devastating disease.

Drug-associated pulmonary arterial hypertension

INTRODUCTION

While pulmonary arterial hypertension remains an uncommon diagnosis, various therapeutic agents are recognized as important associations. These agents are typically categorized into "definite", "likely", "possible", or "unlikely" to cause pulmonary arterial hypertension, based on the strength of evidence.

OBJECTIVE

This review will focus on those therapeutic agents where there is sufficient literature to adequately comment on the role of the agent in the pathogenesis of pulmonary arterial hypertension.

METHODS

A systematic search was conducted using PubMed covering the period September 1970- 2017. The search term utilized was "drug induced pulmonary hypertension". This resulted in the identification of 853 peer-reviewed articles including case reports. Each paper was then reviewed by the authors for its relevance. The majority of these papers (599) were excluded as they related to systemic hypertension, chronic obstructive pulmonary disease, human immunodeficiency virus, pulmonary fibrosis, alternate differential diagnosis, treatment, basic science, adverse effects of treatment, and pulmonary hypertension secondary to pulmonary embolism. Agents affecting serotonin metabolism (and related anorexigens): Anorexigens, such as aminorex, fenfluramine, benfluorex, phenylpropanolamine, and dexfenfluramine were the first class of medications recognized to cause pulmonary arterial hypertension. Although most of these medications have now been withdrawn worldwide, they remain important not only from a historical perspective, but because their impact on serotonin metabolism remains relevant. Selective serotonin reuptake inhibitors, tryptophan, and lithium, which affect serotonin metabolism, have also been implicated in the development of pulmonary arterial hypertension. Interferon and related medications: Interferon alfa and sofosbuvir have been linked to the development of pulmonary arterial hypertension in patients with other risk factors, such as human immunodeficiency virus co-infection. Antiviral therapies: Sofosbuvir has been associated with two cases of pulmonary artery hypertension in patients with multiple risk factors for its development. Its role in pathogenesis remains unclear. Small molecule tyrosine kinase inhibitors: Small molecule tyrosine kinase inhibitors represent a relatively new class of medications. Of these dasatinib has the strongest evidence in drug-induced pulmonary arterial hypertension, considered a recognized cause. Nilotinib, ponatinib, carfilzomib, and ruxolitinib are newer agents, which paradoxically have been linked to both cause and treatment for pulmonary arterial hypertension. Monoclonal antibodies and immune regulating medications: Several case reports have linked some monoclonal antibodies and immune modulating therapies to pulmonary arterial hypertension. There are no large series documenting an increased prevalence of pulmonary arterial hypertension complicating these agents; nonetheless, trastuzumab emtansine, rituximab, bevacizumab, cyclosporine, and leflunomide have all been implicated in case reports. Opioids and substances of abuse: Buprenorphine and cocaine have been identified as potential causes of pulmonary arterial hypertension. The mechanism by which this occurs is unclear. Tramadol has been demonstrated to cause severe, transient, and reversible pulmonary hypertension. Chemotherapeutic agents: Alkylating and alkylating-like agents, such as bleomycin, cyclophosphamide, and mitomycin have increased the risk of pulmonary veno-occlusive disease, which may be clinically indistinct from pulmonary arterial hypertension. Thalidomide and paclitaxel have also been implicated as potential causes. Miscellaneous medications: Protamine appears to be able to cause acute, reversible pulmonary hypertension when bound to heparin. Amiodarone is also capable of causing pulmonary hypertension by way of recognized side effects.

CONCLUSIONS

Pulmonary arterial hypertension remains a rare diagnosis, with drug-induced causes even more uncommon, accounting for only 10.5% of cases in large registry series. Despite several agents being implicated in the development of PAH, the supportive evidence is typically limited, based on case series and observational data. Furthermore, even in the drugs with relatively strong associations, factors that predispose an individual to PAH have yet to be elucidated.

Identification of a Novel Allosteric Inhibitory Site on Tryptophan Hydroxylase 1 Enabling Unprecedented Selectivity Over all Related Hydroxylases

Pulmonary arterial hypertension (PAH) has demonstrated multi-serotonin receptor dependent pathologies, characterized by increased tone (5-HT_1B receptor) and complex lesions (SERT, 5-HT_1B, 5-HT_2B receptors) of the pulmonary vasculature together with right ventricular hypertrophy, ischemia and fibrosis (5-HT_2B receptor). Selective inhibitors of individual signaling elements – SERT, 5-HT_2A, 5HT_2B, and combined 5-HT2_A/B receptors, have all been tested clinically and failed. Thus, inhibition of tryptophan hydroxylase 1 (TPH1), the rate limiting step in 5-HT synthesis, has been suggested as a more broad, and thereby more effective, mode of 5-HT inhibition. However, selectivity over non-pathogenic enzyme family members, TPH2, phenylalanine hydroxylase, and tyrosine hydroxylase has hampered therapeutic development. Here we describe the site/sequence, biochemical, and biophysical characterization of a novel allosteric site on TPH1 through which selectivity over TPH2 and related aromatic amino acid hydroxylases is achieved. We demonstrate the mechanism of action by which novel compounds selectively inhibit TPH1 using surface plasma resonance and enzyme competition assays with both tryptophan ligand and BH4 co-factor. We demonstrate 15-fold greater potency within a human carcinoid cell line versus the most potent known TPH1/2 non-specific inhibitor. Lastly, we detail a novel canine in vivo system utilized to determine effective biologic inhibition of newly synthesized 5-HT. These findings are the first to demonstrate TPH1-selective inhibition and may pave the way to a truly effective means to reduce pathologic 5-HT and thereby treat complex remodeling diseases such as PAH.

Novel Targets of Drug Treatment for Pulmonary Hypertension

Biomedical advances over the last decade have identified the central role of proliferative pulmonary arterial smooth muscle cells (PASMCs) in the development of pulmonary hypertension (PH). Furthermore, promoters of proliferation and apoptosis resistance in PASMCs and endothelial cells, such as aberrant signal pathways involving growth factors, G protein-coupled receptors, kinases, and microRNAs, have also been described. As a result of these discoveries, PH is currently divided into subgroups based on the underlying pathology, which allows focused and targeted treatment of the condition. The defining features of PH, which subsequently lead to vascular wall remodeling, are dysregulated proliferation of PASMCs, local inflammation, and apoptosis-resistant endothelial cells. Efforts to assess the relative contributions of these factors have generated several promising targets. This review discusses recent novel targets of therapies for PH that have been developed as a result of these advances, which are now in pre-clinical and clinical trials (e.g., imatinib [phase III]; nilotinib, AT-877ER, rituximab, tacrolimus, paroxetine, sertraline, fluoxetine, bardoxolone methyl [phase II]; and sorafenib, FK506, aviptadil, endothelial progenitor cells (EPCs) [phase I]). While substantial progress has been made in recent years in targeting key molecular pathways, PH still remains without a cure, and these novel therapies provide an important conceptual framework of categorizing patients on the basis of molecular phenotype(s) for effective treatment of the disease.

Existing drugs and agents under investigation for pulmonary arterial hypertension

Pulmonary arterial hypertension is a progressive and debilitating disorder with an associated high morbidity and mortality rate. Significant advances in our understanding of the epidemiology, pathogenesis, and pathophysiology of pulmonary hypertension have occurred over the past several decades. This has allowed the development of new therapeutic options in this disease. Today, our selection of therapeutic modalities is broader, including calcium channel blockers, prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors, and soluble guanylate cyclase stimulators, but the disease remains fatal. This underscores the need for a continued search for novel therapies. Several potential pharmacologic agents for the treatment of pulmonary arterial hypertension are under clinical development and some promising results with these treatments have been reported. These agents include rho-kinase inhibitors, long-acting nonprostanoid prostacyclin receptor agonists, tyrosine protein kinase inhibitors, endothelial nitric oxide synthase couplers, synthetically produced vasoactive intestinal peptide, antagonists of the 5-HT2 receptors, and others. This article will review several of these promising new therapies and will discuss the current evidence regarding their potential benefit in pulmonary arterial hypertension.

The use of antidepressants and the risk of idiopathic pulmonary arterial hypertension

BACKGROUND

Serotonin has been implicated in the development of idiopathic pulmonary arterial hypertension (IPAH). Drugs modulating serotonin pathways, including antidepressants, have been associated with the incidence of IPAH, with conflicting reports as to the direction of the effect. We aimed to determine whether antidepressant exposure is associated with the incidence of IPAH.

METHODS

A nested case-control study was conducted using the United Kingdom Clinical Practice Research Datalink and the Hospital Episodes Statistics repository between January 1, 1988 and September 30, 2011. Incident cases of IPAH were identified and matched to all controls in the case's risk set on age, sex, general practice, and date of registration with the practice. Rate ratios (RRs) and 95% confidence intervals (CIs) were estimated for the use of antidepressants on the risk of IPAH, with an 18-month lag period before the diagnosis.

RESULTS

One hundred ninety-five IPAH cases were identified (incidence 3.84/million per year). Use of any antidepressant was associated with a 67% increased risk of IPAH (RR, 1.67; 95% CI, 1.17-2.37). The rate of IPAH was similar across antidepressant classes, whether with selective serotonin reuptake inhibitors (SSRIs) (RR, 1.67; 95% CI, 1.09-2.57) or non-SSRI antidepressants (RR, 1.66; 95% CI, 1.07-2.59). In sensitivity and exploratory analyses, no change in risk was observed with different lag times, serotonin transporter affinities, or durations of exposure.

CONCLUSIONS

The use of antidepressants was associated with a significantly increased risk of IPAH. However, the consistency of this risk across all antidepressants and absence of a dose-response relationship suggests a noncausal association.

An update on medical therapy for pulmonary arterial hypertension

Over the past 20 years, great progress has been made in the treatment of pulmonary arterial hypertension (PAH). Available therapies target one of three principal pathways: the endothelin (ET), nitric oxide (NO) or the prostacyclin (PGI2) pathway. Evidence shows that current drugs, used either as monotherapy or in different combinations, can improve exercise capacity, clinical symptoms, hemodynamics and even survival in PAH. Unfortunately, the disease remains incurable and the prognosis of the disease is still poor. However, existing and novel potent antiproliferative therapies are being explored, and new agents targeting different and/or additional pathways are likely to become available to clinicians in the near future. Promising candidates include tyrosine kinase antagonists (e.g. imatinib); soluble guanylate cyclase stimulators (riociguat); an oral analog of prostacyclin (selexipag); and a tissue targeting endothelin receptor antagonist (macitentan). Phase II or III trials have either been completed or are underway to evaluate the safety and efficacy of these various therapies.

Pharmacologic treatments for pulmonary hypertension: exploring pharmacogenomics

Pulmonary hypertension (PH) is a disease with multiple etiologies and is categorized into five broad groups. Of these groups, pulmonary arterial hypertension (PAH) is the most studied and, therefore, all of the currently available drug classes (prostacyclin analogs, endothelin receptor antagonists and phosphodiesterase type 5 inhibitors) were developed to treat PAH. Thus, limited treatment data exist for the less-studied non-PAH forms of PH. Pharmacogenomics can be a tool to better understand the pathways involved in PH, as well as to improve personalization of therapy. However, little pharmacogenomic research has been carried out on this disease. New treatments for PH are on the horizon, deriving from both repurposed currently available drugs and novel therapeutics.

Novel medical therapies for pulmonary arterial hypertension

Available targeted therapies for pulmonary arterial hypertension are capable only of slowing progression of the disease and a cure remains elusive. However with the improved understanding of the pulmonary vascular remodeling that characterizes the disease, there is optimism that the disconnect between preclinical and clinical studies may be bridged with some of the newer therapies that are now at different stages of clinical evaluation. This article examines the evidence behind these new candidate treatments that may become part of the arsenal available for clinicians managing this devastating disease.

Use of selective serotonin reuptake inhibitors and outcomes in pulmonary arterial hypertension

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) have been suggested to offer therapeutic benefit in patients with pulmonary arterial hypertension (PAH). We conducted two analyses to explore the association between SSRI use and PAH outcomes using the Registry to Evaluate Early and Long-term PAH Disease Management (REVEAL Registry).

METHODS

First, new users (SSRI-naive patients who initiated treatment after enrollment, incident use analysis, n = 220) were matched (1:2) with non-SSRI users (nonusers, n = 440) by enrollment center, sex, date of most recent visit, age, and 6-min walk distance. Second, a cross-sectional design was used to compare nonusers (n = 2,463), high-affinity SSRI users (n = 430), and non-high-affinity SSRI users (n = 125) at enrollment. Mortality and a composite end point defined by events indicative of clinical worsening were evaluated.

RESULTS

New users had a higher risk of death (unadjusted hazard ratio [HR], 1.74; 95% CI, 1.19-2.54; P = .004) and were less likely to be free from the composite end point 2 years after enrollment vs nonusers (25.7% vs 43.2%, respectively; P &lt; .001). Similarly, among prevalent SSRI users (patients with a history of SSRI use at enrollment), high-affinity SSRI users were less likely to be free from the composite end point vs nonusers (unadjusted HR, 1.20; 95% CI, 1.07-1.36; P = .003). In both analyses, differences in outcome were maintained after adjustment for clinical variables previously associated with PAH outcomes.

CONCLUSIONS

In a large population of patients with PAH, incident SSRI use was associated with increased mortality and a greater risk of clinical worsening, although we could not adjust for all potential confounders.

Serotonin contributes to high pulmonary vascular tone in a sheep model of persistent pulmonary hypertension of the newborn

Although past studies demonstrate that altered serotonin (5-HT) signaling is present in adults with idiopathic pulmonary arterial hypertension, whether serotonin contributes to the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN) is unknown. We hypothesized that 5-HT contributes to increased pulmonary vascular resistance (PVR) in a sheep model of PPHN and that selective 5-HT reuptake inhibitor (SSRI) treatment increases PVR in this model. We studied the hemodynamic effects of 5-HT, ketanserin (5-HT2A receptor antagonist), and sertraline, an SSRI, on pulmonary hemodynamics of the late gestation fetal sheep with PPHN caused by prolonged constriction of the ductus arteriosis. Brief intrapulmonary infusions of 5-HT increased PVR from 1.0 ± 0.07 (baseline) to 1.4 ± 0.22 mmHg/ml per minute of treatment (P < 0.05). Ketanserin decreased PVR from 1.1 ± 0.15 (baseline) to 0.82 ± 0.09 mmHg/ml per minute of treatment (P < 0.05). Sertraline increased PVR from 1.1 ± 0.17 (baseline) to 1.4 ± 0.17 mmHg/ml per minute of treatment (P = 0.01). In addition, we studied 5-HT production and activity in vitro in experimental PPHN. Compared with controls, pulmonary artery endothelial cells from fetal sheep with PPHN exhibited increased expression of tryptophan hydroxylase 1 and 5-HT production by twofold and 56%, respectively. Compared with controls, 5-HT2A R expression was increased in lung homogenates and pulmonary artery smooth muscle cell lysates by 35% and 32%, respectively. We concluded that increased 5-HT contributes to high PVR in experimental PPHN through activation of the 5-HT2A receptor and that SSRI infusion further increases PVR in this model.

Targeting the serotonin pathway for the treatment of pulmonary arterial hypertension

As we uncover the complex pathophysiology underlying idiopathic and familial pulmonary arterial hypertension, multiple disease associated pathways, cell types and processes reveal links to elements of the serotonin system. Beyond the original 'serotonin hypothesis' observed with anorexigens, and the latterly demonstrated association with vascular tone and pulmonary artery smooth muscle cell proliferation, recent studies suggest links to BMPR2, PDGF and RhoK pathways, as well as an impact upon more complex lesion formation and pathologic bone marrow progenitor mobilization. Clinical experience with antagonists targeting the various elements of the serotonin pathway has been unsatisfactory, yet perhaps this is less than surprising given our expanding knowledge around serotonin production and signaling biology, which indicate opportunities for novel therapeutic options.

The pharmacological treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening and progressive disease of various origins characterized by pulmonary vascular remodeling that leads to increased pulmonary vascular resistance and pulmonary arterial pressure, most often resulting in right-sided heart failure. The most common symptom at presentation is breathlessness, with impaired exercise capacity as a hallmark of the disease. Advances in understanding the pathobiology over the last 2 decades have led to therapies (endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and prostacyclins or analogs) initially directed at reversing the pulmonary vasoconstriction and more recently directed toward reversing endothelial cell dysfunction and smooth muscle cell proliferation. Despite these advances, disease progression is common even with use of combination regimens targeting multiple mechanistic pathways. Overall 5-year survival for PAH has increased significantly from approximately 30% in the 1980s to approximately 60% at present, yet remains abysmal. This review summarizes the mechanisms of action, clinical data, and regulatory histories of approved PAH therapies and describes the latest agents in late-stage clinical development.

Effects of dapoxetine on cloned Kv1.5 channels expressed in CHO cells

The effects of dapoxetine were examined on cloned Kv1.5 channels stably expressed in Chinese hamster ovary cells using the whole-cell patch clamp technique. Dapoxetine decreased the peak amplitude of Kv1.5 currents and accelerated the decay rate of current inactivation in a concentration-dependent manner with an IC ( 50 ) of 11.6 μM. Kinetic analysis of the time-dependent effects of dapoxetine on Kv1.5 current decay yielded the apparent association (k (+1 )) and dissociation (k (-1 )) rate constants of 2.8 μM(-1) s(-1) and 34.2 s(-1), respectively. The theoretical K ( D ) value, derived by k (-1 )/k (+1 ), yielded 12.3 μM, which was reasonably similar to the IC ( 50 ) value obtained from the concentration-response curve. Dapoxetine decreased the tail current amplitude and slowed the deactivation process of Kv1.5, which resulted in a tail crossover phenomenon. The block by dapoxetine is voltage-dependent and steeply increased at potentials between -10 and +10 mV, which correspond to the voltage range of channel activation. At more depolarized potentials, a weaker voltage dependence was observed (δ=0.31). Dapoxetine had no effect on the steady-state activation of Kv1.5 but shifted the steady-state inactivation curves in a hyperpolarizing direction. Dapoxetine produced a use-dependent block of Kv1.5 at frequencies of 1 and 2 Hz and slowed the time course for recovery of inactivation. These effects were reversible after washout of the drug. Our results indicate that dapoxetine blocks Kv1.5 currents by interacting with the channel in both the open and inactivated states of the channel.

Effect of serotonin reuptake inhibitors on pulmonary hemodynamics in humans

Background

Serotonin promotes pulmonary arterial vasoconstriction and pulmonary arterial smooth muscle cell proliferation, thereby having the potential to increase pulmonary arterial blood pressure. Although serotonin reuptake inhibitors (SRIs) might inhibit further deterioration in patients with manifest pulmonary arterial hypertension, they may induce pulmonary hypertension in healthy newborns after fetal exposure. As it is unclear whether treatment with SRIs affects pulmonary hemodynamics in adults without pulmonary hypertension, the aim of the present study was to investigate the effect of SRIs on pulmonary hemodynamics in such subjects.

Methods

Sixteen patients with stable angina pectoris scheduled for first time coronary artery bypass grafting were included in the study. Of these 8 were currently treated with an SRI (the SRI group) and 8 were not (the control group). Pulmonary arterial pressures were measured before induction of anesthesia by means of a pulmonary artery catheter. Serotonin transporter and 5-HT_2A receptor gene polymorphisms and platelet 5-HT_2A receptor expression were studied to elucidate their possible role as modifying factors.

Results

No patients in any of the groups had pulmonary arterial hypertension. Mean pulmonary artery pressure was 15.0 mmHg in the SRI group and 14.5 mmHg in the control group (P = 0.50; 95% confidence interval for the difference, -2.9 to +3.9 mmHg). Neither were there any significant differences between the groups for any of the other hemodynamic variables studied. The various gene polymorphisms and the extent of platelet 5-HT_2A receptor expression did not influence the hemodynamic variables.

Conclusions

SRI treatment did not significantly influence pulmonary hemodynamics in patients without pulmonary hypertension.

Keywords

Serotonin; Selective serotonin reuptake inhibitors; Pulmonary hemodynamics; Pulmonary hypertension

Selective serotonin reuptake inhibitor use is associated with right ventricular structure and function: the MESA-right ventricle study

PURPOSE

Serotonin and the serotonin transporter have been implicated in the development of pulmonary hypertension (PH). Selective serotonin reuptake inhibitors (SSRIs) may have a role in PH treatment, but the effects of SSRI use on right ventricular (RV) structure and function are unknown. We hypothesized that SSRI use would be associated with RV morphology in a large cohort without cardiovascular disease (N = 4114).

METHODS

SSRI use was determined by medication inventory during the Multi-Ethnic Study of Atherosclerosis baseline examination. RV measures were assessed via cardiac magnetic resonance imaging. The cross-sectional relationship between SSRI use and each RV measure was assessed using multivariable linear regression; analyses for RV mass and end-diastolic volume (RVEDV) were stratified by sex.

RESULTS

After adjustment for multiple covariates including depression and left ventricular measures, SSRI use was associated with larger RV stroke volume (RVSV) (2.75 mL, 95% confidence interval [CI] 0.48-5.02 mL, p = 0.02). Among men only, SSRI use was associated with greater RV mass (1.08 g, 95% CI 0.19-1.97 g, p = 0.02) and larger RVEDV (7.71 mL, 95% 3.02-12.40 mL, p = 0.001). SSRI use may have been associated with larger RVEDV among women and larger RV end-systolic volume in both sexes.

CONCLUSIONS

SSRI use was associated with higher RVSV in cardiovascular disease-free individuals and, among men, greater RV mass and larger RVEDV. The effects of SSRI use in patients with (or at risk for) RV dysfunction and the role of sex in modifying this relationship warrant further study.

Pulmonary vascular effects of serotonin and selective serotonin reuptake inhibitors in the late-gestation ovine fetus

Maternal use of selective serotonin (5-HT) reuptake inhibitors (SSRIs) is associated with an increased risk for persistent pulmonary hypertension of the newborn (PPHN), but little is known about 5-HT signaling in the developing lung. We hypothesize that 5-HT plays a key role in maintaining high pulmonary vascular resistance (PVR) in the fetus and that fetal exposure to SSRIs increases 5-HT activity and causes pulmonary hypertension. We studied the hemodynamic effects of 5-HT, 5-HT receptor antagonists, and SSRIs in chronically prepared fetal sheep. Brief infusions of 5-HT (3-20 μg) increased PVR in a dose-related fashion. Ketanserin, a 5-HT 2A receptor antagonist, caused pulmonary vasodilation and inhibited 5-HT-induced pulmonary vasoconstriction. In contrast, intrapulmonary infusions of GR127945 and SB206553, 5-HT 1B and 5-HT 2B receptor antagonists, respectively, had no effect on basal PVR or 5-HT-induced vasoconstriction. Pretreatment with fasudil, a Rho kinase inhibitor, blunted the effects of 5-HT infusion. Brief infusions of the SSRIs, sertraline and fluoxetine, caused potent and sustained elevations of PVR, which was sustained for over 60 min after the infusion. SSRI-induced pulmonary vasoconstriction was reversed by infusion of ketanserin and did not affect the acute vasodilator effects of acetylcholine. We conclude that 5-HT causes pulmonary vasoconstriction, contributes to maintenance of high PVR in the normal fetus through stimulation of 5-HT 2A receptors and Rho kinase activation, and mediates the hypertensive effects of SSRIs. We speculate that prolonged exposure to SSRIs can induce PPHN through direct effects on the fetal pulmonary circulation.

Pulmonary arterial hypertension in systemic sclerosis

Pulmonary arterial hypertension (PAH) in systemic sclerosis (SSc) is a complex clinical situation resulting from restricted flow through the pulmonary arterial circulation ending in increased pulmonary vascular resistance and right heart failure. PAH is a common and life-threatening complication in connective tissue diseases, specifically in SSc if not treated rapidly and adequately. Based on the emerging knowledge in SSc epidemiology by large scale patient cohorts such as EUSTAR, of PAH pathophysiology and advances in cardiopulmonary diagnostic techniques, several novel treatment approaches have been examined and have proceeded to licensing and daily use in the clinical practice. Amongst them are different endothelin receptor antagonists and PDE-5 inhibitors, but several other ideas are being currently pursued to improve the long-term outcome of the affected patients.

Emerging drugs for pulmonary hypertension

IMPORTANCE OF THE FIELD

Pulmonary arterial hypertension (PAH) is a clinical syndrome characterized by structural narrowing of the small pulmonary arteries that often culminates in fatal right heart failure.

AREAS COVERED IN THIS REVIEW

PubMed was searched for PAH and treatment. Data from scientific meetings and pharmaceutical websites are also included. There are currently eight FDA approved drugs for PAH that fall into one of three classes: prostacyclins, endothelin-receptor antagonists and PDE-5 inhibitors. All have important limitations and morbidity and mortality remain high. Several new agents with similar mechanisms of action are in clinical development. Multiple novel therapeutic targets are being explored. New applications for PAH therapies, such as pulmonary hypertension due to left heart and lung disease, are also being investigated.

WHAT THE READER WILL GAIN

An understanding of currently available drugs and those in clinical development for pulmonary hypertension.

TAKE HOME MESSAGE

Drugs targeting the pulmonary vasculature have been an extremely active area of basic and clinical research for the past 20 years and will continue to be so for the foreseeable future. Considerable progress has been made, and yet there continues to be a great unmet medical need for developing more efficacious therapies.