Dexfenfluramine and Pergolide Cause Heart Valve Disease via Valve Metabolic Reprogramming and Ongoing Matrix Remodeling.

Several clinical reports indicate that the use of amphetaminic anorectic drugs or ergot derivatives could cause valvular heart disease (VHD). We sought to investigate whether valvular lesions develop in response to long-term oral administration of these drugs and to identify drug-targeted biological processes that may lead to VHD. Treatment of New Zealand White rabbits with pergolide, dexfenfluramine, or high-dose serotonin for 16 weeks induced valvular alterations characterized by extracellular matrix remodeling. Transcriptome profiling of tricuspid valves using RNA sequencing revealed distinct patterns of differentially expressed genes (DEGs) that clustered according to the different treatments. Genes that were affected by the three treatments were functionally enriched for reduced cell metabolism processes. The two drugs yielded more changes in gene expression than serotonin and shared most of the DEGs. These DEGs were mostly enriched for decreased biosynthetic processes, increased cell-matrix interaction, and cell response to growth factors, including TGF-ß, which was associated with p38 MAPK activation. Treatment with pergolide specifically affected genes involved in homeostasis, which was corroborated by the activation of the master regulator of cell energy homeostasis, AMPK-α, as well as decreased levels of metabolism-related miR-107. Thus, both pergolide and dexfenfluramine may cause VHD through valve metabolic reprogramming and matrix remodeling.

Cardiovascular safety of low-dose fenfluramine in Dravet syndrome: a review of its benefit-risk profile in a new patient population.

OBJECTIVE: Dravet syndrome (DS) is a rare, treatment-resistant epilepsy syndrome for which current treatment regimens are often ineffective. Fenfluramine is currently in development for treatment of DS, based on reports in the 1980s and 1990s of its anti-epileptic activity in pediatric patients with intractable epilepsy. However, fenfluramine was withdrawn from global markets in 1997 following reports of its association with pulmonary hypertension and heart valve disease in adult patients treated for obesity. This review was conducted to assess cardiac safety of fenfluramine when used at lower doses for treatment of DS. METHODS: Pubmed was searched for clinical studies of fenfluramine in obese adults who reported incidence of heart valve disease. These data were reviewed against published results from Belgian patients with DS who have been treated with low-dose fenfluramine for up to 28 years. RESULTS: Nine controlled studies of fenfluramine and related compounds (dexfenfluramine and/or phentermine) which assessed incidence and severity of cardiac valve disease in 3,268 treated patients and 2,017 control subjects have been reported. Mild or greater aortic valve regurgitation was found in 9.6% of treated patients compared with 3.9% of control subjects, and moderate or greater mitral valve regurgitation was found in 3.1% of treated patients and 2.5% of control subjects. Nineteen DS patients have been treated for up to 28 years with 10-20 mg/day fenfluramine, with no clinical signs or symptoms of cardiac valve disease or pulmonary hypertension. Slight and clinically unimportant changes in valve structure have been seen on echocardiography in five patients at some time during the observation period. CONCLUSIONS: A different benefit-risk relationship appears to be emerging when fenfluramine is used at low doses for extended periods in young patients with DS. Continued cardiac assessments during ongoing Phase 3 clinical trials will provide additional safety information for this potential new and effective treatment.

Clinical and echographic characteristics of patients exposed to fenfluramin or its derivatives: Results of a prospective, single-centre, observational study.

BACKGROUND: Fenfluramine and its derivatives have been associated with significant risk of developing valvular heart disease but its exact prevalence and severity are still debated. AIM: To evaluate the clinical and echocardiographic characteristics of patients hospitalized in a cardiology centre and who had past exposure to these drugs. METHODS: Between July 2011 and February 2012, patients admitted to the hospitalization and intensive care units at the University Centre of Montpellier, France were questioned about past exposure to fenfluramine or its derivatives. In patients who reported exposure, a questionnaire assessing prescribing patterns and medical history was proposed and echocardiography performed. All of the usual echocardiographic variables were analysed. We applied criteria from a French multicentre registry for diagnosis of drug-induced valvulopathy: leaflets and subvalvular apparatus thickening and retraction, leaflets loss of coaptation, no calcification, and no stenosis. RESULTS: Ninety-five patients exposed to these drugs were included. The majority were female (n=62, 65.3%), 53.2% (n=50) had diabetes and 90.5% (n=86) were exposed to benfluorex. Mean treatment duration was 52.3months (95% confidence interval [CI] 39.0-65.6). Valvular regurgitations were observed in 64.0% of patients (n=57) while 19.8% (n=17) had pulmonary hypertension. Highly probable fenfluramine-induced regurgitations were present in 18.6% (n=16) of patients, possibly fenfluramine-induced regurgitations in 38.2% (n=34) of patients, and unlikely fenfluramine-induced regurgitations in 25.8% (n=23) of patients. Highly probable fenfluramine-induced regurgitations were mild to moderate in severity in all except three patients. CONCLUSION: Considering the frequency of probable or possible fenfluramine-induced regurgitations and in the absence of definite knowledge about the evolution of drug-induced valvular disease, systematic questioning about fenfluramine use may be advisable in hospitalized cardiac patients.

Pulmonary arterial hypertension in a patient with Cowden syndrome and anorexigen exposure.

We report a case of pulmonary arterial hypertension (PAH) occurring in a patient with Cowden syndrome with a mutation in the phosphatase and tensin (PTEN) tumor suppressor gene, in the context of exposure to the appetite suppressant dexfenfluramine. Anorexigen exposure is known to be a risk factor for PAH. However, the role of PTEN in cell function and the development of pulmonary vascular remodeling and histopathologic signs of PAH in mice with a Pten depletion in smooth muscle cells suggest that the association of PAH and Cowden syndrome may be relevant. In this case report, we hypothesize that PTEN mutations may be a predisposing factor for the development of PAH, with anorexigen exposure as a potential trigger.

Development, validation, and use of quantitative structure-activity relationship models of 5-hydroxytryptamine (2B) receptor ligands to identify novel receptor binders and putative valvulopathic compounds among common drugs.

Some antipsychotic drugs are known to cause valvular heart disease by activating serotonin 5-HT(2B) receptors. We have developed and validated binary classification QSAR models capable of predicting potential 5-HT(2B) actives. The classification accuracies of the models built to discriminate 5-HT(2B) actives from the inactives were as high as 80% for the external test set. These models were used to screen in silico 59,000 compounds included in the World Drug Index, and 122 compounds were predicted as actives with high confidence. Ten of them were tested in radioligand binding assays and nine were found active, suggesting a success rate of 90%. All validated actives were then tested in functional assays, and one compound was identified as a true 5-HT(2B) agonist. We suggest that the QSAR models developed in this study could be used as reliable predictors to flag drug candidates that are likely to cause valvulopathy.

The serotonin hypothesis of pulmonary hypertension revisited.

The serotonin hypothesis of pulmonary arterial hypertension (PAH) arose after an outbreak of PAH in patients taking the anorexigenic drugs aminorex and dexfenfluramine. Both of these drugs are serotonin transporter (SERT) substrates and indirect serotinergic agonists. There is now a wealth of evidence to support a role for serotonin in the pathobiology of PAH. Synthesis of serotonin can occur in pulmonary artery endothelial cells by the enzyme tryptophan hydroxylase 1 (TPH1). Serotonin then acts at the 5-HT(1B) receptor and the SERT to mediate constriction and proliferation of pulmonary artery smooth muscle cells. Downstream signalling molecules which play a role in serotonin-induced constriction and proliferation include reactive oxygen species (ROS), Rho-kinase (ROCK) p38 and extracellular signal-regulated kinase (ERK). There is also evidence to suggest that serotonin may interact with the bone morphogenetic receptor type II (BMPRII) to provide a 'second hit' risk factor for PAH.

Drug-induced fibrotic valvular heart disease.

The initial association between the development of valvular heart disease and drugs stems from observations made during the use of methysergide and ergotamine for migraine prophylaxis in the 1960s. Since then, the appetite suppressants fenfluramine and dexfenfluramine, the dopamine agonists pergolide and cabergoline, and more recently, the recreational drug ecstasy (3,4 methylenedioxymethamphetamine; MDMA) have been implicated. Results from clinical trials show that drug dose and treatment duration affect both the risk of developing the disease and its severity. The natural history of the disease remains unclear, although regression of valvular lesions after the end of treatment has been reported. Interference with serotonin metabolism and its associated receptors and transporter gene seems a likely mechanism for development of the drug-induced valvular heart disease. Physicians need to balance the benefits of continued therapy with these drugs against possible risks. Further investigation is needed to assist with treatment decisions. Continued vigilance is necessary because several commonly prescribed treatments interact with serotonergic pathways.

Dexfenfluramine discontinuous treatment does not worsen hypoxia-induced pulmonary vascular remodeling but activates RhoA/ROCK pathway: consequences on pulmonary hypertension.

The anorectic drug, dexfenfluramine has been associated with an increase in the relative risk of developing pulmonary hypertension. 5-hydroxytryptamine (5-HT) is a mitogen for smooth muscle cell, an effect that relies on 5-HT transporter expression and which has been proposed to explain pulmonary side effect of dexfenfluramine, and more particularly its effect on vascular remodeling. However recent data supported a major role of pulmonary artery vasoconstriction through the RhoA/Rho-kinase pathway. We questioned whether or not anorectic treatment aggravates pulmonary hypertension through vascular remodeling and if RhoA/Rho-kinase (ROCK) was potentially involved. In rats exposed to hypoxia, concomitant dexfenfluramine treatment (5 mg/kg/day, i.v.) for 4 weeks had no effect on pulmonary hypertension development. When exposure to 2 weeks of chronic hypoxia followed discontinuation of dexfenfluramine treatment (dexfenfluramine-hypoxic rats), echocardiographic parameters of pulmonary artery flow and right ventricle were further altered (P<0.05) as well as right ventricle systolic pressure was further increased (P<0.001) when compared to hypoxic rats treated with vehicle (hypoxic rats). However, the total number of muscularized distal pulmonary arteries artery was similar in dexfenfluramine-hypoxic vs. hypoxic rats (P>0.05). Western blot, RT-PCR and immunofluorescence analysis revealed a greater expression of 5-HT transporter and ROCK, as well as a greater activation of RhoA in dexfenfluramine-hypoxic rats compared to hypoxic rats. These data show that increased 5-HT transporter expression that follows dexfenfluramine discontinuation is not associated to a greater vascular remodeling despite worsening the development of pulmonary hypertension. Furthermore dexfenfluramine discontinuation promotes a greater RhoA/ROCK pathway activation. This pathway, involved in many cardiovascular diseases, might explain the cardiac and pulmonary toxicity of serotoninergic agonists.

End of the line for cannabinoid receptor 1 as an anti-obesity target?

A wave of terminations of development programmes for cannabinoid receptor 1 blockers for obesity indicates the demise of a drug class that was once anticipated to yield blockbusters. Nevertheless, lessons learned might help salvage something for future such approaches.

Converging evidence in support of the serotonin hypothesis of dexfenfluramine-induced pulmonary hypertension with novel transgenic mice.

BACKGROUND: The incidence of pulmonary arterial hypertension secondary to the use of indirect serotinergic agonists such as aminorex and dexfenfluramine led to the "serotonin hypothesis" of pulmonary arterial hypertension; however, the role of serotonin in dexfenfluramine-induced pulmonary arterial hypertension remains controversial. Here, we used novel transgenic mice lacking peripheral serotonin (deficient in tryptophan hydroxylase-1; Tph1(-/-) mice) or overexpressing the gene for the human serotonin transporter (SERT; SERT(+) mice) to investigate this further. METHODS AND RESULTS: Dexfenfluramine administration (5 mg x kg(-1) x d(-1) PO for 28 days) increased systolic right ventricular pressure and pulmonary vascular remodeling in wild-type mice but not in Tph1(-/-) mice, which suggests that dexfenfluramine-induced pulmonary arterial hypertension is dependent on serotonin synthesis. Dexfenfluramine was also administered to normoxic SERT(+) mice and SERT(+) mice exposed to chronic hypoxia. Dexfenfluramine and SERT overexpression had additive effects in increasing pulmonary vascular remodeling; however, in hypoxic SERT(+) mice, dexfenfluramine reduced both systolic right ventricular pressure and pulmonary vascular remodeling. Pulmonary arterial fibroblasts from SERT(+) mice, but not wild-type mice, proliferated in response to hypoxia. Dexfenfluramine inhibited hypoxia-induced proliferation of pulmonary arterial fibroblasts derived from SERT(+) mice in a manner dependent on SERT activity. Dexfenfluramine also inhibited the hypoxia-mediated increase in phosphorylation of p38 mitogen-activated protein kinase in SERT(+) pulmonary arterial fibroblasts. CONCLUSIONS: The results suggest that peripheral serotonin is critical for the development of dexfenfluramine-induced pulmonary arterial hypertension and that dexfenfluramine and SERT overexpression have additive effects on pulmonary vascular remodeling. We propose that dexfenfluramine can also inhibit hypoxia-induced pulmonary vascular remodeling via SERT activity and inhibition of hypoxia-induced p38 mitogen-activated protein kinase.

Pulmonary hypertension and the serotonin hypothesis: where are we now?

In the 1960s, serotonin (5HT) was associated with pulmonary arterial hypertension (PAH) caused by certain diet pills, but has recently been the subject of renewed interest in the field of PAH. Serotonin can be synthesised in the pulmonary endothelium with the rate-limiting step being the activity of tryptophan hydroxylase1 (Tph1). The serotonin is released and can then: (i) pass into the underlying pulmonary smooth muscle cells through the serotonin transporter (SERT) to initiate proliferation and/or (ii) activate serotonin receptors on pulmonary smooth muscle cells to evoke proliferation and/or contraction. Serotonin may also mediate pulmonary fibroblast proliferation via the SERT and/or serotonin receptors. Here we will unravel, discuss and update the 'serotonin hypothesis' of PAH in light of recent advances in the field. In conclusion, the activity of serotonin receptors, the SERT and Tph1 can all be elevated in clinical and experimental PAH and each offers a potentially unique therapeutic target.

Quantitative positron emission tomography studies of the serotonin transporter in humans previously treated with the appetite suppressants fenfluramine or dexfenfluramine.

PURPOSE: The appetite suppressants fenfluramine and dexfenfluramine were widely prescribed before being withdrawn from the market in 1997. Both drugs are known to have the potential to damage brain serotonin (5-HT) axons and axon terminals in animals, including nonhuman primates. This study used quantitative positron emission tomography (PET) with [(11)C] McN5652, a serotonin transporter (SERT) ligand to determine whether humans previously exposed to fenfluramines showed reductions in SERT binding parameters. PROCEDURES: Subjects previously treated with fenfluramines for weight loss (N = 15) and age-matched controls (N = 17) underwent PET studies with [(11)C] McN5652. Global and regional distribution volumes (DVs) of [(11)C] McN5652 were compared in the two subject groups using parametric statistical analyses. RESULTS: Compared to controls, subjects previously exposed to fenfluramines had significant reductions in [(11)C]McN5652 binding in 14 of 15 regions of interest, more than four years after drug discontinuation. CONCLUSIONS: These results are the first to provide direct evidence for fenfluramine-induced 5-HT neurotoxicity in humans.