Anorectic drugs and pulmonary hypertension from the bedside to the bench

Mutually reinforcing effects of genetic variants and interferon-β 1a therapy for pulmonary arterial hypertension development in multiple sclerosis patients

Based on a small number of cases, interferon beta (IFN-β) has been added to the list of drugs that might induce pulmonary arterial hypertension (PAH) in the current European guidelines for the diagnosis and treatment of pulmonary hypertension. Here, we propose that multiple sclerosis patients who are genetically predisposed to PAH may be at higher risk to develop disease when treated with IFN-β. We included two patients with multiple sclerosis who developed a manifest PAH after five amd eight years on IFN-β 1a therapy, respectively (without confirmed right heart catheterization). In both patients, PAH markedly improved after discontinuation of IFN-β 1a and initiation of targeted PAH therapy. For genetic analysis, we used a PAH-gene panel based on next-generation sequencing of 16 PAH and 38 candidate genes. In one of the two patients, we could identify a nonsense variant in the PAH gene ATP13A3. The second patient showed a missense variant of the CYP1B1 gene, which might be linked to PAH predisposition. The results of this study support the hypothesis that multiple sclerosis patients who receive IFN-β 1a therapy might be at higher risk for the development of manifest PAH, if they carry a pathogenic variant or sequence variant genetically predisposing to the disease. However, further studies are necessary to systematically investigate the presence of predisposing PAH gene variants in these patients.

Pulmonary vascular dysfunction in metabolic syndrome

Metabolic syndrome is a critically important precursor to the onset of many diseases, such as cardiovascular disease, and cardiovascular disease is the leading cause of death worldwide. The primary risk factors of metabolic syndrome include hyperglycaemia, abdominal obesity, dyslipidaemia, and high blood pressure. It has been well documented that metabolic syndrome alters vascular endothelial and smooth muscle cell functions in the heart, brain, kidney and peripheral vessels. However, there is less information available regarding how metabolic syndrome can affect pulmonary vascular function and ultimately increase an individual's risk of developing various pulmonary vascular diseases, such as pulmonary hypertension. Here, we review in detail how metabolic syndrome affects pulmonary vascular function.

Centrally Acting Agents for Obesity: Past, Present, and Future

For many years, obesity was believed to be a condition of overeating that could be resolved through counseling and short-term drug treatment. Obesity was not recognized as a chronic disease until 1985 by the scientific community, and 2013 by the medical community. Pharmacotherapy for obesity has advanced remarkably since the first class of drugs, amphetamines, were approved for short-term use. Most amphetamines were removed from the obesity market due to adverse events and potential for addiction, and it became apparent that obesity pharmacotherapies were needed that could safely be administered over the long term. This review of central nervous system (CNS) acting anti-obesity drugs evaluates current therapies such as phentermine/topiramate, which act through multiple neurotransmitter pathways to reduce appetite. In the synergistic mechanism of bupropion/naltrexone, naltrexone blocks the feed-back inhibitory circuit of bupropion to give greater weight loss. Lorcaserin, a selective agonist of a serotonin receptor that regulates food intake, and the glucagon-like-peptide-1 (GLP-1) receptor agonist liraglutide are reviewed. Future drugs include tesofensine, a potent triple reuptake inhibitor in Phase III trials for obesity, and semaglutide, an oral GLP-1 analog approved for diabetes and currently in trials for obesity. Another potential new pharmacotherapy, setmelanotide, is a melanocortin-4 receptor agonist, which is still in an early stage of development. As our understanding of the communication between the CNS, gut, adipose tissue, and other organs evolves, it is anticipated that obesity drug development will move toward new centrally acting combinations and then to drugs acting on peripheral target tissues.

Nitric Oxide and Other Novel Therapies for Pulmonary Hypertension

Pulmonary hypertension is an uncommon, yet devastating, syndrome with a complex underlying pathobiology. Hypoxia, inflammation, and increased shear stress appear to be the primary pathogenic events; however, mechanisms by which these processes lead to pulmonary hypertension remain incompletely understood. The ultimate increase in pulmonary vascular resistance is attributed to remodelling of the walls of resistance vessels, which can lead to encroachment on and reduction of the vascular lumen. The number of blood vessels per unit of cross-sectional area in the hypertensive lung is also reduced, which can contribute to increased vascular resistance. Regardless of its etiology, endothelial dysfunction underlies pulmonary hypertension, one manifestation of which is the attenuated production of bioactive nitric oxide. Nitric oxide administration can exert beneficial effects at various stages of the disease. Here we review the known pathobiology of pulmonary hypertension, with a principal focus on endothelial nitric oxide, and also summarize the data on nitric oxide replacement therapy and other novel therapies that relate to nitric oxide as one approach to treatment.

Evolution of pharmacological obesity treatments: focus on adverse side-effect profiles

Pharmacotherapy directed toward reducing body weight may provide benefits for both curbing obesity and lowering the risk of obesity-associated comorbidities; however, many weight loss medications have been withdrawn from the market because of serious adverse effects. Examples include pulmonary hypertension (aminorex), cardiovascular toxicity, e.g. flenfluramine-induced valvopathy, stroke [phenylpropanolamine (PPA)], excess non-fatal cardiovascular events (sibutramine), and neuro-psychiatric issues (rimonabant; approved in Europe, but not in the USA). This negative experience has helped mould the current drug development and approval process for new anti-obesity drugs. Differences between the US Food and Drug Administration (FDA) and the European Medicines Agency, however, in perceptions of risk-benefit considerations for individual drugs have resulted in discrepancies in approval and/or withdrawal of weight-reducing medications. Thus, two drugs recently approved by the FDA, i.e. lorcaserin and phentermine + topiramate extended release, are not available in Europe. In contrast, naltrexone sustained release (SR)/bupropion SR received FDA approval, and liraglutide 3.0 mg was recently approved in both the USA and Europe. Regulatory strategies adopted by the FDA to manage the potential for uncommon but potentially serious post-marketing toxicity include: (i) risk evaluation and mitigation strategy programmes; (ii) stipulating post-marketing safety trials; (iii) considering responder rates and limiting cumulative exposure by discontinuation if weight loss is not attained within a reasonable timeframe; and (iv) requiring large cardiovascular outcome trials before or after approval. We chronicle the adverse effects of anti-obesity pharmacotherapy and consider how the history of high-profile toxicity issues has shaped the current regulatory landscape for new and future weight-reducing drugs.

Obesity and pulmonary hypertension: a review of pathophysiologic mechanisms

Pulmonary hypertension (PH) is a potentially life-threatening condition arising from a wide variety of pathophysiologic mechanisms. Effective treatment requires a systematic diagnostic approach to identify all reversible mechanisms. Many of these mechanisms are relevant to those afflicted with obesity. The unique mechanisms of PH in the obese include obstructive sleep apnea, obesity hypoventilation syndrome, anorexigen use, cardiomyopathy of obesity, and pulmonary thromboembolic disease. Novel mechanisms of PH in the obese include endothelial dysfunction and hyperuricemia. A wide range of effective therapies exist to mitigate the disability of PH in the obese.

Multi tyrosine kinase inhibitor dasatinib as novel cause of severe pre-capillary pulmonary hypertension?

Background

Pulmonary hypertension (PH) is a life-threatening disease with poor prognosis. Encouraging efforts have been made to target the main vasoproliferative aspects of the disease. Promising emerging therapeutics are tyrosine kinase inhibitors such as imatinib.

Case presentation

Here, we discuss the relevance of previously published cases and add another well-characterised patient who developed pre-capillary PH under long-term therapy with the multi-tyrosine kinase inhibitor dasatinib approved for therapy of chronic myeloic leukaemia (CML) and Philadelphia chromosome positive acute lymphocytic leukaemia (mean time of all patients on dasatinib: 26 months). Hence, we discuss the possibility of dasatinib itself causing PH after long-term therapy and turn specialist's attention to this possible severe side effect.

At present, the true incidence of dasatinib-associated PH remains illusive and systematic data regarding haemodynamics are missing.

Conclusion

We therefore recommend systematic screening of dasatinib-treated patients for pulmonary hypertension and subsequent collection of haemodynamic data.

Comparison of body habitus in patients with pulmonary arterial hypertension enrolled in the Registry to Evaluate Early and Long-term PAH Disease Management with normative values from the National Health and Nutrition Examination Survey

OBJECTIVE

To investigate the correlation between body mass index (BMI) and pulmonary artery systolic pressure in a large population of patients with pulmonary arterial hypertension (PAH).

PATIENTS AND METHODS

The BMI of patients with group 1 PAH enrolled in the Registry to Evaluate Early and Long-term PAH Disease Management (REVEAL) was compared with that of age- and sex-matched controls in the National Health and Nutrition Examination Survey (NHANES) to clarify whether obesity is linked with PAH. The diagnosis of PAH was defined in REVEAL by right-sided heart catheterization. Differences in BMI and the percentage of patients considered obese (BMI ≥30) and underweight (BMI <18.5) in various subgroups of patients enrolled in REVEAL from March 30, 2006, through September 11, 2007, were determined.

RESULTS

Mean BMI was no different for patients with PAH (n=2141) than for the NHANES normal comparison group; however, the proportion of obese and underweight patients was increased in patients with PAH. Subgroup analysis demonstrated that subgroups with idiopathic PAH and those with PAH associated with drugs and toxins had both higher BMI and percentage of obese patients, whereas 3 other subgroups (those with PAH associated with congenital heart disease, connective tissue disease, and human immunodeficiency virus) had lower mean BMI.

CONCLUSION

Mean BMI of the REVEAL patients was the same as that of the NHANES normal comparison group; however, there were higher percentages of obese and underweight patients in REVEAL. This discrepancy can be explained by the balancing effect of more overweight and underweight patients in different PAH subgroups. The reason for the increased frequency of obesity in idiopathic PAH is unknown, and additional study is needed.

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.

Review paper: Current strategies in the development of anti-obesity drugs and their safety concerns

Obesity is a well-established risk factor for hypertension, hyperlipidemia, type II diabetes, coronary heart disease, stroke, obstructive sleep apnea, asthma, orthopedic disorders, and certain cancers. Despite this risk, the prevalence of obesity continues to increase worldwide, and there is a growing demand for safe and effective antiobesity drugs. Previous antiobesity drugs or anorexigens, particularly centrally acting agents, have poor safety records. Life-threatening safety issues led to the withdrawal of aminorex in 1968, fenfluramine and dexfenfluramine in 1997, and phenylpropanolamine in 2000. Many of the safety issues, such as valvulopathy with fenfluramine and pulmonary arterial hypertension with aminorex, were initially not predicted by routine preclinical toxicology studies. To date, there are no validated animal models or preclinical and/or toxicologic screens to accurately predict anorexigen-induced valvulopathy and pulmonary arterial hypertension in humans. This review covers the current state of antiobesity drugs and their safety concerns, and highlights new therapeutic targets and scientific advances toward the development of appropriate animal models by using novel techniques that will aid in understanding pathogenesis and pathophysiology of anorexigen-related safety issues.

Valvular regurgitation and surgery associated with fenfluramine use: an analysis of 5743 individuals

BACKGROUND

Use of fenfluramines for weight loss has been associated with the development of characteristic plaques on cardiac valves causing regurgitation. However, previously published studies of exposure to fenfluramines have been limited by relatively small sample size, short duration of follow-up, and the lack of any estimate of the frequency of subsequent valvular surgery. We performed an observational study of 5743 users of fenfluramines examined by echocardiography between July 1997 and February 2004 in a single large cardiology clinic.

RESULTS

The prevalence of at least mild aortic regurgitation (AR) or moderate mitral regurgitation (MR) was 19.6% in women and 11.8% in men (p < 0.0001 for gender difference). Duration of use was strongly predictive of mild or greater AR (p < 0.0001 for trend), MR (p = 0.002), and tricuspid regurgitation (TR) (p < 0.0001), as was earlier scan date (p < 0.0001 for those scanned prior to 1 January 2000 versus later). Increasing age was also independently associated with increased risk of AR and MR (both p < 0.0001). With mean follow-up of 30.3 months, AR worsened in 15.2%, remained the same in 63.1%, and improved in 21.7%. Corresponding values for MR were 24.8%, 47.4% and 27.9%. Pulmonary hypertension was strongly associated with MR but not AR. Valve surgery was performed on 38 patients (0.66% of 5743), 25 (0.44%) with clear evidence of fenfluramine-related etiology.

CONCLUSION

Regurgitant valvulopathy was common in individuals exposed to fenfluramines, more frequent in females, and associated with duration of use in all valves assessed. Valve surgery was performed as frequently for aortic as mitral valves and some tricuspid valve surgeries were also performed. The incidence of surgery appeared to be substantially increased compared with limited general population data.

Pharmacokinetics and effects of aminorex in horses

OBJECTIVE

To investigate the pharmacokinetics and behavioral effects of aminorex administered IV and PO in horses.

ANIMALS

7 Thoroughbreds.

PROCEDURES

In a cross-over design, aminorex (0.03 mg/kg) was administered IV or PO. Plasma and urinary aminorex concentrations were determined via liquid chromatography- mass spectrometry.

RESULTS

Decrease of aminorex from plasma following IV administration was described by a 3-compartment pharmacokinetic model. Median (range) values of alpha, beta, and gamma half-lives were 0.04 (0.01 to 0.28), 2.30 (1.23 to 3.09), and 18.82 (8.13 to 46.64) hours, respectively. Total body and renal clearance, the area under the plasma time curve, and initial volume of distribution were 37.26 (28.61 to 56.24) mL x min/kg, 1.25 (0.85 to 2.05) mL x min/kg, 13.39 (8.82 to 17.37) ng x h/mL, and 1.44 (0.10 to 3.64) L/kg, respectively. Oral administration was described by a 2-compartment model with first-order absorption, elimination from the central compartment, and distribution into peripheral compartments. The absorption half-life was 0.29 (0.12 to 1.07) hours, whereas the beta and gamma elimination phases were 1.93 (1.01 to 3.17) and 23.57 (15.16 to 47.45) hours, respectively. The area under the curve for PO administration was 10.38 (4.85 to 13.40) ng.h/mL and the fractional absorption was 81.8% (33.8% to 86.9%).

CONCLUSIONS AND CLINICAL RELEVANCE

Aminorex administered IV had a large volume of distribution, initial rapid decrease, and an extended terminal elimination. Following PO administration, there was rapid absorption, rapid initial decrease, and an extended terminal elimination. At a dose of 0.03 mg/kg, the only effects detected were transient and central in origin and were observed only following IV administration.

Challenges in pulmonary risk assessment and perioperative management in bariatric surgery patients

Bariatric surgery has serious associated medical comorbidity and procedure-related risks and is, thus, considered an intermediate-to-high-risk non-cardiac surgery. Altered respiratory mechanics, obstructive sleep apnea (OSA), and less often, pulmonary hypertension and postoperative pulmonary embolism are the major contributors to poor pulmonary outcomes in obese patients. Attention to posture and positioning is critical in patients with OSA. Suspected OSA patients requiring intravenous narcotics should be kept in a monitored setting with frequent assessments and naloxone kept at the bedside. Use of reverse Tredelenburg position, preinduction, maintenance of positive end-expiratory pressure, and use of continuous positive airway pressure can help improve oxygenation in the perioperative period.

Genetics and mediators in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is an uncommon disorder of the pulmonary vasculature characterized by remodeling of the smallest pulmonary arteries, leading to a progressive increase in pulmonary vascular resistance. Various forms of PAH exist, including familial (FPAH) and idiopathic (IPAH) forms and associated conditions. FPAH transmits as an autosomal dominant trait that exhibits genetic anticipation but also markedly reduced penetrance (20%). The primary genetic defect of FPAH, identifiable in more than 70% of cases of FPAH, is a mutation in the gene encoding bone morphogenetic protein receptor type 2 (BMPR2), a member of the transforming growth factor beta superfamily. The true prevalence of BMPR2 mutations in IPAH is unknown, with reports ranging from 10% to 40% of patients. The cause of the variable phenotypic expression of PAH among carriers of mutated BMPR2 genes and patients is unclear, and likely related to environmental and genetic modifiers of disease not yet fully elucidated. Although BMPR2-related pathways seem to be pivotal, many other mediator pathways participate in the pathogenesis of different forms of PAH and are being actively investigated, both independently and in combination. As understanding of the molecular basis of this devastating disease improves, opportunities for earlier diagnosis, additional therapeutic regimens, and perhaps disease prevention will emerge.

Dual dopamine/serotonin releasers as potential medications for stimulant and alcohol addictions

We have advocated the idea of agonist therapy for treating cocaine addiction. This strategy involves administration of stimulant-like medications (eg, monoamine releasers) to alleviate withdrawal symptoms and prevent relapse. A major limitation of this approach is that many candidate medicines possess significant abuse potential because of activation of mesolimbic dopamine (DA) neurons in central nervous system reward circuits. Previous data suggest that serotonin (5-HT) neurons can provide an inhibitory influence over mesolimbic DA neurons. Thus, it might be predicted that the balance between DA and 5-HT transmission is important to consider when developing medications with reduced stimulant side effects. In this article, we discuss several issues related to the development of dual DA/5-HT releasers for the treatment of substance use disorders. First, we discuss evidence supporting the existence of a dual deficit in DA and 5-HT function during withdrawal from chronic cocaine or alcohol abuse. Then we summarize studies that have tested the hypothesis that 5-HT neurons can dampen the effects mediated by mesolimbic DA. For example, it has been shown that pharmacological manipulations that increase extracellular 5-HT attenuate stimulant effects produced by DA release, such as locomotor stimulation and self-administration behavior. Finally, we discuss our recently published data about PAL-287 (naphthylisopropylamine), a novel non-amphetamine DA-/5-HT-releasing agent that suppresses cocaine self-administration but lacks positive reinforcing properties. It is concluded that DA/5-HT releasers might be useful therapeutic adjuncts for the treatment of cocaine and alcohol addiction, obesity, and even attention deficit disorder and depression.

Pulmonary Arterial Hypertension

The first description of the circulation of blood through the lungs has been attributed to Ibn Nafis (1210–1288).1 The concept was rediscovered by Michael Servetus, a Spanish physician during the Renaissance (1511–1553) and recorded, oddly enough, in two pages of his religious treatise, Christianismi Restitutio (1553).2 The definitive exposition of the pulmonary circulation was made by William Harvey in DeMotu Cordis (1628).3 The first observation of the pulmonary capillaries was first reported by Marcellus Malpighi (1661).4 Heart catheterization in humans, driven by a desire to obtain the perfect mixed venous specimen and measure cardiac output, was first performed in 1929 by the German urologist Forssmann,5 using a ureteral catheter to access his own right atrium. Over a decade later, Cournand and Richards at Columbia University in New York subsequently used right heart catheterization to record pulmonary artery pressure (PAP) in patients with shock and secondary forms of pulmonary hypertension (PHT). For these accomplishments, which were inspired by an interest in the pulmonary circulation and PHT related to mitral stenosis, Forssmann, Cournand, and Richards received the Nobel Prize in 1956.

Dual dopamine-5-HT releasers: potential treatment agents for cocaine addiction

Biogenic amine transporters (BATs) are integral membrane proteins that translocate biogenic amine neurotransmitters [norepinephrine, dopamine (DA) and 5-hydroxytryptamine (5-HT)] across cell membranes. BATs are the principal sites of action for many psychotropic drugs, including abused stimulants such as cocaine and methamphetamine. Preclinical and human data demonstrate that withdrawal from long-term cocaine administration produces a dual deficit of synaptic DA and 5-HT in the brain, indicating the advantage of developing medications that normalize impairments in both neurotransmitter systems. In this article, we review data supporting the notion that stimulant effects normally produced by increased levels of extracellular DA can be antagonized by concurrent increases in levels of extracellular 5-HT. Accordingly, nonselective BAT substrates that can release both DA and 5-HT, such as the novel compound PAL287, have low abuse potential while maintaining the ability to suppress drug-seeking behavior. The collective findings indicate that such drugs will provide neurochemical normalization therapy for cocaine addiction and might also be useful for treating depression, obsessive-compulsive disorder, attention deficit disorder and obesity.

Safety of drug therapies used for weight loss and treatment of obesity

Some of the medications used for weight loss in the management of obesity have been associated with unacceptable morbidity and mortality. Safety concerns have led to the withdrawal of aminorex, followed by the fenfluramines in 1997, and phenylpropanolamine (norephedrine) in 2000. Aminorex was associated with an increased prevalence of primary pulmonary hypertension (PPH), fenfluramines with an increased prevalence of PPH and valvulopathy, and phenylpropanolamine with an increased risk of haemorrhagic stroke. Several studies have investigated the safety of the fenfluramines, yet the benefit-risk profile has not been conclusively quantified. This is due to several deficiencies in the published studies, including a lack of data on the baseline prevalences of comorbid conditions in obese subjects, and potential confounders and biases in the study designs. Although several studies and systematic reviews support an increased risk of PPH and valvulopathy in patients who have taken fenfluramines, without knowledge of the background prevalence it is not possible to determine if the exposure preceded the outcome. The population at higher risk of these adverse effects includes those taking higher doses or with a longer duration of exposure to fenfluramines and those with pre-existing cardiac disease or a genetic predisposition. Patients exposed to fenfluramines continue to be monitored, with some follow-up studies indicating no overall worsening in valvulopathy over time. There are limited efficacy and safety data for amfepramone (diethylpropion) and phentermine and their approval for the management of obesity is limited to short-term use. Orlistat and sibutramine are the only currently approved medications for long-term management of obesity. Although the benefit-risk profiles of sibutramine and orlistat appear positive, sibutramine continues to be monitored because of long-term safety concerns. The safety and efficacy of currently approved drug therapies have not been evaluated in children and elderly patient populations and there is limited information in adolescents, whilst the long-term safety of current and potential new drug therapies in adults will require several years of postmarketing surveillance to fully elucidate their adverse effect profiles.

Serotonin induces pulmonary artery smooth muscle cell migration

The chronic phase of pulmonary arterial hypertension (PAH) is associated with vascular remodeling, especially thickening of the smooth muscle layer of large pulmonary arteries and muscularization of small pulmonary vessels, which normally have no associated smooth muscle. Serotonin (5-hydroxytryptamine, 5-HT) has been shown to induce proliferation and hypertrophy of pulmonary artery smooth muscle cells (PASMC), and may be important for in vivo pulmonary vascular remodeling. Here, we show that 5-HT stimulates migration of pulmonary artery PASMC. Treatment with 5-HT for 16h increased migration of PASMC up to four-fold as monitored in a modified Boyden chamber assay. Increased migratory responses were associated with cellular morphological changes and reorganization of the actin cytoskeleton. 5-HT-induced alterations in morphology were previously shown in our laboratory to require cAMP [Lee SL, Fanburg BL. Serotonin produces a configurational change of cultured smooth muscle cells that is associated with elevation of intracellular cAMP. J Cell Phys 1992;150(2):396-405], and the 5-HT4 receptor was pharmacologically determined to be the primary activator of cAMP in bovine PASMC [Becker BN, Gettys TW, Middleton JP, Olsen CL, Albers FJ, Lee SL, et al. 8-Hydroxy-2-(di-n-propylamino)tetralin-responsive 5-hydroxytryptamine4-like receptor expressed in bovine pulmonary artery smooth muscle cells. Mol Pharmacol 1992;42(5):817-25]. We examined the role of the 5-HT4 receptor and cAMP in 5-HT-induced bovine PASMC migration. PASMC express 5-HT4 receptor mRNA, and a 5-HT4 receptor antagonist and a cAMP antagonist completely blocked 5-HT-induced cellular migration. Consistent with our previous report that a cAMP-dependent Cl(-) channel is required for 5-HT-induced morphological changes in PASMC, phenylanthranilic acid, a Cl(-) channel blocker, inhibited actin cytoskeletal reorganization and migration produced by 5-HT. We conclude that 5-HT stimulates PASMC migration and associated cytoskeletal reorganization through the 5-HT4 receptor and cAMP activation of a chloride channel.

Phobic memory and somatic vulnerabilities in anorexia nervosa: a necessary unity?

Anorexia nervosa is a clinically significant illness that may be associated with permanent medical complications involving almost every organ system. The paper raises a question whether some of them are associated with premorbid vulnerability such as subcellular ion channel abnormalities ('channelopathy') that determines the clinical expression of the bodily response to self-imposed malnutrition. Aberrant channels emerge as a tempting, if rather speculative alternative to the notion of cognitively-driven neurotransmitter modulation deficit in anorexia nervosa. The concept of channelopathies is in keeping with some characteristics of anorexia nervosa, such as a genetically-based predisposition to hypophagia, early onset, cardiac abnormalities, an appetite-enhancing efficacy of some antiepileptic drugs, and others. The purpose of this article is to stimulate further basic research of ion channel biophysics in relation to restrictive anorexia.

The NO − K+ Channel Axis in Pulmonary Arterial Hypertension

The prognosis of patients with pulmonary arterial hypertension (PAH) is poor. Available therapies (Ca(++)-channel blockers, epoprostenol, bosentan) have limited efficacy or are expensive and associated with significant complications. PAH is characterized by vasoconstriction, thrombosis in-situ and vascular remodeling. Endothelial-derived nitric oxide (NO) activity is decreased, promoting vasoconstriction and thrombosis. Voltage-gated K+ channels (Kv) are downregulated, causing depolarization, Ca(++)-overload and PA smooth muscle cell (PASMC) contraction and proliferation. Augmenting the NO and Kv pathways should cause pulmonary vasodilatation and regression of PA remodeling. Several inexpensive oral treatments may be able to enhance the NO axis and/or K+ channel expression/function and selectively decrease pulmonary vascular resistance (PVR). Oral L-Arginine, NOS' substrate, improves NO synthesis and functional capacity in humans with PAH. Most of NO's effects are mediated by cyclic guanosine-monophosphate (c-GMP). cGMP causes vasodilatation by activating K+ channels and lowering cytosolic Ca++. Sildenafil elevates c-GMP levels by inhibiting type-5 phosphodiesterase, thereby opening BK(Ca). channels and relaxing PAs. In PAH, sildenafil (50 mg-po) is as effective and selective a pulmonary vasodilator as inhaled NO. These benefits persist after months of therapy leading to improved functional capacity. 3) Oral Dichloroacetate (DCA), a metabolic modulator, increases expression/function of Kv2.1 channels and decreases remodeling and PVR in rats with chronic-hypoxic pulmonary hypertension, partially via a tyrosine-kinase-dependent mechanism. These drugs appear safe in humans and may be useful PAH therapies, alone or in combination.

The role of the NO axis and its therapeutic implications in pulmonary arterial hypertension

Pulmonary Arterial Hypertension (PAH) is a disease of the pulmonary vasculature leading to vasoconstriction and remodeling of the pulmonary arteries. The resulting increase in the right ventricular afterload leads to right ventricular failure and death. The treatment options are limited, expensive and associated with significant side effects. The nitric oxide (NO) pathway in the pulmonary circulation provides several targets for the development of new therapies for this disease. However, the NO pathway is modulated at multiple levels including transcription and expression of the NO synthase gene, regulation of the NO synthase activity, regulation of the production of cyclic guanomonophosphate (cGMP) by phosphodiesterases, postsynthetic oxidation of NO, etc. This makes the study of the role of the NO pathway very difficult, unless one uses multiple complementary techniques. Furthermore, there are significant differences between the pulmonary and the systemic circulation which make extrapolation of data from one circulation to the other very difficult. In addition, the role of NO in the development of pulmonary hypertension varies among different models of the disease. This paper reviews the role of the NO pathway in both the healthy and diseased pulmonary circulation and in several animal models and human forms of the disease. It focuses on the role of recent therapies that target the NO pathway, including L-Arginine, inhaled NO, the phosphodiesterase inhibitor sildenafil and gene therapy.

Function of the serotonin 5-hydroxytryptamine 2B receptor in pulmonary hypertension

Primary pulmonary hypertension is a progressive and often fatal disorder in humans that results from an increase in pulmonary blood pressure associated with abnormal vascular proliferation. Dexfenfluramine increases the risk of pulmonary hypertension in humans, and its active metabolite is a selective serotonin 5-hydroxytryptamine 2B (5-HT(2B)) receptor agonist. Thus, we investigated the contribution of the 5-HT(2B)receptor to the pathogenesis of pulmonary hypertension. Using the chronic-hypoxic-mouse model of pulmonary hypertension, we found that the hypoxia-dependent increase in pulmonary blood pressure and lung remodeling are associated with an increase in vascular proliferation, elastase activity and transforming growth factor-beta levels, and that these parameters are potentiated by dexfenfluramine treatment. In contrast, hypoxic mice with genetically or pharmacologically inactive 5-HT(2B)receptors manifested no change in any of these parameters. In both humans and mice, pulmonary hypertension is associated with a substantial increase in 5-HT(2B) receptor expression in pulmonary arteries. These data show that activation of 5-HT(2B) receptors is a limiting step in the development of pulmonary hypertension.

Therapeutic and adverse actions of serotonin transporter substrates

A variety of drugs release serotonin (5-HT, 5-hydroxytryptamine) from neurons by acting as substrates for 5-HT transporter (SERT) proteins. This review summarizes the neurochemical, therapeutic, and adverse actions of substrate-type 5-HT-releasing agents. The appetite suppressant (+/-)-fenfluramine is composed of (+) and (-) isomers, which are N-de-ethylated in the liver to yield the metabolites (+)- and (-)-norfenfluramine. Fenfluramines and norfenfluramines are potent 5-HT releasers. (+/-)-3,4-Methylenedioxymethamphetamine ((+/-)-MDMA, "ecstasy") and m-chlorophenylpiperazine (mCPP) are substrate-type 5-HT releasers. Fenfluramines, (+/-)-MDMA, and mCPP release neuronal 5-HT by a common non-exocytotic diffusion-exchange mechanism involving SERTs. (+)-Norfenfluramine is a potent 5-HT(2B) and 5-HT(2C) receptor agonist. The former activity may increase the risk of valvular heart disease, whereas the latter activity is implicated in the anorexic effect of systemic fenfluramine. Appetite suppressants that increase the risk for developing primary pulmonary hypertension (PPH) are all SERT substrates, but these drugs vary considerably in their propensity to increase this risk. For example, fenfluramine and aminorex are clearly linked to the occurrence of PPH, whereas other anorectics are not. Similarly, some SERT substrates deplete brain tissue 5-HT in animals (e.g., fenfluramine), while others do not (e.g., mCPP). In addition to the established indication of obesity, 5-HT releasers may help treat psychiatric disorders, such as drug and alcohol dependence, depression, and premenstrual syndrome. Viewed collectively, we believe new medications can be developed that selectively release 5-HT without increasing the risk for adverse effects of valvular heart disease, PPH, and neurotoxicity. Such agents may be useful for treating a variety of psychiatric disorders.

Nondrug interventions in hypertension prevention and control

This review was undertaken to address the relation of various factors to HBP and their potential for preventing and controlling this widespread problem. With respect to salt intake and BP, the 1999 Workshop on Sodium and Blood Pressure of the (US) National Heart, Lung, and Blood Institute [5] will serve the reader well as a point of departure. The body of the present review provides more detailed discussion especially of recent epidemiologic research, including the DASH-Sodium trial, published more recently than the proceedings of that workshop. The DASH-Sodium trial demonstrates significant increases in SBP and DBP, with sodium intake greater than 65 mmol/d (= 3.7 g NaCl--see equivalencies in Appendix A) and with the usual American diet (versus the DASH diet). These results provide substantial evidence against current dietary practices in many populations where daily intakes of salt are much higher than recommended. We also have addressed alcohol consumption, micronutrients/macronutrients, physical activity and inactivity, obesity, cigarette smoking, and alternative approaches to treatment such as stress reduction/biofeedback, yoga/meditation, and acupuncture. Evidence for the efficacy of certain nonpharmacologic approaches to preventing and controlling HBP is strong. This evidence offers a basis for public health policies and clinical approaches that can greatly affect the incidence and consequences of HBP in the population at large. What is needed now is implementation of the policies and practices addressed here. Unless such action is taken on a large scale, we will have made poor use of the knowledge accrued over decades of research. The clinician is referred to the National Heart, Lung and Blood Institute Web site at www.nhlbi.gov/health/prof/heart/index.htm for resource and guideline information for hypertension. Patients and the general public are referred to the sister web page at www.nhlbi.gov\health\public\heart\index.htm for educational fact sheets and general information on hypertension.

Anorectic drugs and vascular disease: the role of voltage-gated K+ channels

Anorectic drugs are widely used for the treatment of obesity. They are thought to decrease appetite through their effects on catecholamine or 5-hydroxytryptamine (5-HT) levels in the brain. Their use has been associated with epidemics of pulmonary hypertension and the development of valvular heart disease, hypertension, stroke and digital or mesenteric ischemia. Understanding the mechanism of the cardiovascular toxicity of anorectic drugs is important because of the modern epidemic of obesity and the resulting plethora of new anorexigens, many of which share similar mechanisms with those that have previously caused cardiovascular disease. In addition, the mechanism by which anorexigens cause vascular disease has relevance to the etiology and treatment of pulmonary and systemic hypertension. Recent discoveries have clarified how the anorexigens cause vasoconstriction and hypertension. Most anorexigens directly inhibit voltage-gated K+ (KV) channels in vascular smooth muscle cells (SMCs). This reduced K+ efflux leads to depolarization, the opening of voltage-sensitive Ca2+ channels, an increase in intracellular Ca2+ and vasoconstriction. Endothelial dysfunction appears to be a predisposing factor for the development of anorectic-induced vascular complications. Vasoconstriction is weak at clinically relevant doses of anorectic drugs. However, when nitric oxide synthase is inhibited, vasoconstriction is significantly enhanced. Anorexigens are the only drugs in widespread clinical use that have KV-channel-blocking properties and it is probable that much of their cardiovascular toxicity relates to this mechanism. Investigators need to examine new anorexigens and other therapeutic molecules for inhibitory effects on KV channels, as this effect may be a marker of drugs that will elicit vascular complications.

Insights into the structure and function of 5-HT(2) family serotonin receptors reveal novel strategies for therapeutic target development

5-HT(2) family serotonin receptors, principal sites of action of serotonin in the brain, represent major molecular targets for drugs used in treating a variety of diseases including schizophrenia, depression, anxiety, eating disorders, obsessive-compulsive disorder, chronic pain conditions and obesity. The 5-HT(2) family of receptors has three members: 5-HT(2A), 5-HT(2B) and 5-HT(2C). Therefore, it is likely that subtype-selective compounds will be needed to avoid serious side effects and to enhance therapeutic indices. Unfortunately, recent insights into the structure and function of 5-HT(2A) receptors have revealed that structurally-diverse agonists and antagonists have distinct modes of interacting with 5-HT(2A) receptors, complicating efforts at structure-based drug-design. These distinct binding modes would not have been predicted based on conventional structure-activity relationships or static docking models. Fortunately, these complicated binding modes can be predicted and simulated using molecular dynamics, allowing for the possibility of structure-based drug design. Thus, provided appropriately sophisticated drug design strategies are employed, it is likely that uniquely valuable medications will result which could have great potential for treating a variety of mental and physical illnesses.