Plasma neuropeptide Y-like immunoreactivity and catecholamines during various degrees of sympathetic activation in man

Circulating noradrenaline leads to release of neuropeptide Y from cardiac sympathetic nerve terminals via activation of β-adrenergic receptors

Cardiac disease is marked by sympathoexcitation and elevated levels of noradrenaline (NA) and cotransmitter neuropeptide Y (NPY). Increased NPY levels are associated with a greater risk of ventricular arrhythmias and mortality. Nonetheless, the factors that cause NPY release remain poorly understood. We hypothesized that circulating catecholamines might lead to NPY release from myocardial sympathetic nerve terminals via a β-receptor-mediated mechanism that enhances sympathoexcitation. Ventricular interstitial NA and NPY levels were measured in six Yorkshire pigs after i.v. administration of NA (1 mg) and before and after propranolol infusion (1 mg/kg). Real-time interstitial NPY levels were measured using ventricular capacitive immunoprobes (CIs) affixed with NPY antibodies and quantified as the change in CI input current (INPY ) upon binding of NPY. Interstitial NA was measured with adjacent fast-scan cyclic voltammetry probes (INA ). A left ventricular pressure catheter and continuous ECGs were used for haemodynamic recordings, and an epicardial 56-electrode sock was used for measurements of activation recovery interval, a surrogate of action potential duration. Upon administration of NA, heart rate and left ventricular pressure increased, and activation recovery interval shortened. Notably, NA significantly increased interstitial myocardial NPY levels. After propranolol, changes in heart rate and activation recovery interval were largely mitigated. The INA increased to a similar extent post-propranolol vs. pre-propranolol, but changes in INPY were significantly reduced post-propranolol. Coronary sinus plasma analyses confirmed fast-scan cyclic voltammetry and CI findings. Hence, this study demonstrates that circulating NA induces NPY release from ventricular sympathetic nerve terminals, the mechanism for which is mediated via β-adrenergic receptors and can be blocked by the non-selective β-blocker, propranolol. KEY POINTS: Cardiovascular disease is characterized by sympathovagal imbalance, with increased plasma noradrenaline (NA) and neuropeptide Y (NPY) concentrations. Increased NPY levels are associated with increased ventricular arrhythmias and mortality in heart failure. Limited data are available on the specific factors that cause NPY release. In this study, fast-scan cyclic voltammetry and capacitive immunoprobes were used to allow for real-time in vivo measurements of interstitial myocardial neurotransmitters and neuropeptides, respectively. Using an in vivo porcine model with cardiac fast-scan cyclic voltammetry and capacitive immunoprobes, it was shown that systemic NA can increase ventricular interstitial NPY levels, suggesting that NA induces NPY release from postganglionic sympathetic nerves. The release of NPY was blocked by administration of the non-selective β-blocker propranolol, suggesting that release of NPY is dependent on activation of β-adrenergic receptors by NA.

Saxagliptin: A potential doping agent? A randomized, double-blinded, placebo-controlled, and crossover pilot study in young active men

Neuropeptide Ys (NPYs) contribute to sympathetic-adreno stimulation: NPY1-36 potentiates the effects of catecholamines (CATs), whereas NPY3-36 inhibits CAT release. We sought to investigate whether inhibiting dipeptidyl-peptidase-4 (DPP4), cleaving NPY1-36 into NPY3-36, leads to increased NPY1-36 potentiating effects and reduced NPY3-36 inhibitory effects on CATs, thereby improving endurance performance. Seven male participants (age 27 ± 3 years, BMI 23.1 ± 2.4 kg/m² ) performed time-to-exhaustion cycling exercise at 95% of peak power output with either placebo, or saxagliptin, a DPP4 inhibitor. Oxygen consumption (V̇O₂ ), heart rate variability, NPY1-36, NPY3-36, catecholamines, and lactate were measured at several time points before, during, and after exercise. With saxagliptin, DPP4 activity (12.7 ± 1.6 vs. 0.2 ± 0.3 U/L, p = 0.001; d = 10.7) was decreased at rest, while NPY3-36 (1.94 ± 0.88 vs. 0.73 ± 0.22 pm; p < 0.001; d = 2.04) decreased and NPY1-36 increased during exercise (2.64 ± 2.22 vs. 4.59 ± 2.98 pm; p < 0.01; d = 0.19). CATs were unchanged. Time-to-exhaustion was 32% higher with saxagliptin. The difference in time-to-exhaustion between placebo and saxagliptin was correlated with NPY1-36 differences (R = 0.78, p < 0.05). Peak V̇O₂ and other cardio-respiratory values were not different, whereas peak NPY concentrations were higher with saxagliptin. DPP4 blockade improved performance, increased NPY1-36, and decreased NPY3-36 concentrations which may have potentiating effects on the influences of CATs. However, DPP4 is involved in many different actions, thus NPYs are one group of factors that may underly its performance-enhancing effects; further studies are required to determine the exact mechanisms.

Kinetics of neuropeptide Y, catecholamines, and physiological responses during moderate and heavy intensity exercises

Neuropeptide Y 1-36 (NPY1-36) is a vasoconstrictor peptide co-secreted with norepinephrine (NE) by nerve endings during sympathetic activation. NPY1-36 potentiates NE action post-synaptically through the stimulation of the Y1 receptor, whereas its metabolite NPY3-36 resulting from DPP4 action activates Y2 presynaptic receptors, inhibiting NE and acetylcholine secretion. The secretions of NPY1-36 and NPY3-36 in response to sympathetic nervous system activation have not been studied due to the lack of analytical techniques available to distinguish them. We determined in healthy volunteers NPY1-36, NPY3-36 and catecholamine kinetics and how these neurotransmitters modulate the physiological stress response during and after moderate- and heavy-intensity exercises. Six healthy males participated in this randomized, double-blind, saxagliptin vs placebo crossover study. The volunteers performed an orthostatic test, a 30-min exercise at moderate intensity and a 15-min exercise at heavy intensity each followed by 50 min of recovery in two separate sessions with saxagliptin or placebo. Oxygen consumption (V̇O₂), ventilation and heart rate were continuously recorded. NE, epinephrine, NPY1-36 and NPY3-36 were quantified by tandem mass spectrometry. We found that exercise triggers NPY1-36 and NE secretion in an intensity-dependent manner and that NE returns faster to the baseline concentration than NPY1-36 after exercise. NPY3-36 rises during recovery parallel to the decline of NPY1-36. Saxagliptin reverses the NPY1-36/NPY3-36 ratio but does not affect hemodynamics, nor NPY1-36 and catecholamine concentrations. We found that NPY1-36 half-life is considerably shorter than previously established with immunoassays. NPY1-36 and NE secretions are finely regulated to prevent an excessive physiological Y1 stimulating response to submaximal exercise.

Current Insights Into the Role of Neuropeptide Y in Skin Physiology and Pathology

Neuropeptide Y is widely distributed within the body and has long been implicated as a contributor to skin disease based on the correlative clinical data. However, until recently, there have been few empirical investigations to determine whether NPY has a pathophysiological role in the skin. Due to appearance-altering phenotypes of atopic dermatitis, psoriasis, and vitiligo, those suffering from these diseases often face multiple forms of negative social attention. This often results in psychological stress, which has been shown to exacerbate inflammatory skin diseases - creating a vicious cycle that perpetuates disease. This has been shown to drive severe depression, which has resulted in suicidal ideation being a comorbidity of these diseases. Herein, we review what is currently known about the associations of NPY with skin diseases and stress. We also review and provide educated guessing what the effects NPY can have in the skin. Inflammatory skin diseases can affect physical appearance to have significant, negative impacts on quality of life. No cure exists for these conditions, highlighting the need for identification of novel proteins/neuropetides, like NPY, that can be targeted therapeutically. This review sets the stage for future investigations into the role of NPY in skin biology and pathology to stimulate research on therapeutic targeting NPY signaling in order to combat inflammatory skin diseases.

NPY and Gene Therapy for Epilepsy: How, When,... and Y

Neuropeptide Y (NPY) is a neuropeptide abundantly expressed in the mammalian central and peripheral nervous system. NPY is a pleiotropic molecule, which influences cell proliferation, cardiovascular and metabolic function, pain and neuronal excitability. In the central nervous system, NPY acts as a neuromodulator, affecting pathways that range from cellular (excitability, neurogenesis) to circuit level (food intake, stress response, pain perception). NPY has a broad repertoire of receptor subtypes, each activating specific signaling pathways in different tissues and cellular sub-regions. In the context of epilepsy, NPY is thought to act as an endogenous anticonvulsant that performs its action through Y2 and Y5 receptors. In fact, its overexpression in the brain with the aid of viral vectors can suppress seizures in animal models of epilepsy. Therefore, NPY-based gene therapy may represent a novel approach for the treatment of epilepsy patients, particularly for pharmaco-resistant and genetic forms of the disease. Nonetheless, considering all the aforementioned aspects of NPY signaling, the study of possible NPY applications as a therapeutic molecule is not devoid of critical aspects. The present review will summarize data related to NPY biology, focusing on its anti-epileptic effects, with a critical appraisal of key elements that could be exploited to improve the already existing NPY-based gene therapy approaches for epilepsy.

Moderated mediation for exercise maintenance in pain and posttraumatic stress disorder: A randomized trial

This study utilizes the Science of Behavior Change (SOBC) experimental medicine approach to evaluate the effects of a 3-month, individually prescribed progressive exercise training program on neurobiological, cognitive and motivational mechanisms by which our exercise-training paradigm may foster exercise maintenance. We will investigate hypothesized relationships between exercise-training associated augmentation of neuropeptide Y (NPY) system function and improvements in self-regulation and reward sensitivity-cognitive control and motivational processes posited to promote self-efficacy and intrinsic motivation, which have been shown to predict exercise maintenance. This study will recruit Veterans with chronic low back pain and posttraumatic stress disorder (PTSD). Procedures include a baseline, acute cardiopulmonary exercise challenge assessment that will inform the exercise prescription for a 12-week progressive exercise training program comprised of three 45-minute aerobic exercise sessions per week-all of which will be supervised by an exercise physiologist. Additionally, a week-7 and week-14 exercise challenge assessment will track changes in NPY system function and the variables of interest. We hypothesize that increases in the capacity to release NPY in response to acute exercise testing will be associated with improvements in self-regulation and reward sensitivity, which will in turn be associated with self-efficacy and intrinsic motivation to maintain regular exercise. Ninety participants will be randomized either to the "active exercise training condition" or to the "wait list symptom monitoring condition". The study aims to demonstrate the feasibility of procedures and elucidate mechanisms relevant to developing individually prescribed, motivationally based exercise regimens to reduce negative consequences of PTSD and low back pain over the long-term. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Nur77 protects against adverse cardiac remodelling by limiting neuropeptide Y signalling in the sympathoadrenal-cardiac axis

Aims

Cardiac remodelling and heart failure are promoted by persistent sympathetic activity. We recently reported that nuclear receptor Nur77 may protect against sympathetic agonist-induced cardiac remodelling in mice. The sympathetic co-transmitter neuropeptide Y (NPY) is co-released with catecholamines and is a known cardiac modulator and predictor of heart failure mortality. Recently, transcriptome analyses revealed NPY as a putative target of Nur77. In this study, we assess whether Nur77 modulates adverse cardiac remodelling via NPY signalling.

Methods and results

Nur77 represses NPY expression in the PC12 adrenal chromaffin cell line. Accordingly, NPY levels are higher in adrenal gland, plasma, and heart from Nur77-KO compared to wild-type mice. Conditioned medium from Nur77-silenced chromaffin cells and serum from Nur77-KO mice induce marked hypertrophy in cultured neonatal rat cardiomyocytes, which is inhibited by the NPY type 1 receptor (NPY1R) antagonist BIBO3304. In cardiomyocytes from Nur77-KO mice, intracellular Ca2+ is increased partially via the NPY1R. This is independent from elevated circulating NPY since cardiomyocyte-specific Nur77-deficient mice (CM-KO) do not have elevated circulating NPY, but do exhibit BIBO3304-sensitive, increased cardiomyocyte intracellular Ca2+. In vivo, this translates to NPY1R antagonism attenuating cardiac calcineurin activity and isoproterenol-induced cardiomyocyte hypertrophy and fibrosis in full-body Nur77-KO mice, but not in CM-KO mice.

Conclusions

The cardioprotective action of Nur77 can be ascribed to both inhibition of circulating NPY levels and to cardiomyocyte-specific modulation of NPY-NPY1R signalling. These results reveal the underlying mechanism of Nur77 as a promising modifier gene in heart failure.

Stronger correlation with myocardial ischemia of high-sensitivity troponin T than other biomarkers

BACKGROUND

Acute myocardial infarction (AMI) is considered a major cause of death and disability. Myocardial perfusion scintigraphy (MPS) as a non-invasive diagnostic imaging procedure and certain biomarkers associated with myocardial ischemia (ISCH), such as ischemia-modified albumin (IMA), neuropeptide Y (NPY), N-terminal pro b-type natriuretic peptide (NT-proBNP), and high-sensitivity troponin T (hsTnT) could probably aid in the detection of myocardial infarction.

METHODS

Between December 2011 and June 2012, we prospectively analyzed patients who underwent a MPS study with the clinical question of myocardial ISCH. An exercise test was performed along with a MPS. Blood was drawn from the patients before exercise and the within 3 minutes from achieving maximum load and was analyzed for the aforementioned biomarkers.

RESULTS

A total of 71 patients (56 men and 15 women) were enrolled with a mean age of 61 ± 12 years. Twenty-six patients (36.6%) showed reduced uptake on stress MPS images that normalized at rest, a finding consistent with ISCH. Between ISCH and non-ISCH groups, only hsTnT levels showed a significant difference with the highest levels pertaining to the former group both before (0.0075 ng/ml vs 0.0050 ng/ml, P = 0.023) and after stress exercise (0.0085 vs 0.0050, P = 0.015). The most prominent differences were seen in higher stages of the Bruce protocol (stress duration > 9.05 minutes - P < 0.017). None of the IMA, NPY, and NP-pro BNP showed significant differences in time between the two groups.

CONCLUSIONS

Although IMA, NPY, and NT-pro BNP may not detect minor ischemic myocardial insults, serum hsTnT holds a greater ability of detecting not only myocardial infarction but also less severe ischemia. Further studies with larger cohorts of patients are warranted in order to better define the role of hsTnT as a screening tool for myocardial ischemia.

Placental Neuropeptide Y ( NPY) and NPY receptors expressions and serum NPY levels in preeclampsia

IMPACT STATEMENT

Neuropeptide Y (NPY) has been reported as a vasoconstrictive substance which might be associated with preeclampsia. The novel findings of this study were that Y1R, Y2R, and Y5R expressions were significantly lower in the PE than the NP group. Moreover, the NPY receptor expression ratio between the PE/NP groups was lowest for Y2R (0.27) compared to Y1R (0.42) and Y5R (0.40) suggestive of a reduction of this receptor in the preeclampsia group. Our results suggested that decreased Y2R mRNA in the PE group might be associated with abnormalities of placental angiogenesis which probably contributes to the pathophysiology of preeclampsia.

Endogenous dipeptidyl peptidase IV modulates skeletal muscle arteriolar diameter in rats

The purpose of this study is to investigate that dipeptidyl peptidase IV (DPP‐IV) released from skeletal and vascular smooth muscle can increase arteriolar diameter in a skeletal muscle vascular bed by reducing neuropeptide Y (NPY)‐mediated vasoconstriction. We hypothesized that the effect of myokine DPP‐IV would be greatest in the smallest and least in the largest arterioles. Eight male Sprague Dawley rats (age 7–9 weeks; mass, mean ± SD: 258 ± 41 g) were anesthetized and the gluteus maximus dissected in situ for intravital microscopy analysis of arteriolar diameter of the vascular network. Computational modeling was performed on the diameter measurements to evaluate the overall impact of diameter changes on network resistance and flow distribution. In the first set of experiments, whey protein isolate powder was added to physiological saline solution, put in a heated reservoir, and applied to the preparation to induce release of DPP‐IV from the muscle. This resulted in an order‐dependent increase in arteriolar diameter, with the largest change in the 6A arterioles (63% more reactive than 1A arterioles; P < 0.05). This effect was abolished by adding the DPP‐IV inhibitor, Diprotin A. To test if the DPP‐IV released was affecting NPY‐mediated vasoconstriction, we applied NPY and whey protein, which resulted in attenuated vasoconstriction. These findings suggest that DPP‐IV is released from muscle and has a unique effect on blood flow, which appears to act on NPY to attenuate vasoconstriction. The findings suggest that DPP‐IV released from the skeletal or smooth muscle can alter muscle blood flow.

Potential neurobiological benefits of exercise in chronic pain and posttraumatic stress disorder: Pilot study

This pilot study assessed the effects of cardiopulmonary exercise testing and cardiorespiratory fitness on plasma neuropeptide Y (NPY), allopregnanolone and pregnanolone (ALLO), cortisol, and dehydroepiandrosterone (DHEA), and their association with pain sensitivity. Medication-free trauma-exposed participants were either healthy (n = 7) or experiencing comorbid chronic pain/posttraumatic stress disorder (PTSD) (n = 5). Peak oxygen consumption (VO2) during exercise testing was used to characterize cardiorespiratory fitness. Peak VO2 correlated with baseline and peak NPY levels (r = 0.66, p < 0.05 and r = 0.69, p < 0.05, respectively), as well as exercise-induced changes in ALLO (r = 0.89, p < 0.001) and peak ALLO levels (r = 0.71, p < 0.01). NPY levels at the peak of exercise correlated with pain threshold 30 min after exercise (r = 0.65, p < 0.05), while exercise-induced increases in ALLO correlated with pain tolerance 30 min after exercise (r = 0.64, p < 0.05). In contrast, exercise-induced changes in cortisol and DHEA levels were inversely correlated with pain tolerance after exercise (r = -0.69, p < 0.05 and r = -0.58, p < 0.05, respectively). These data suggest that cardiorespiratory fitness is associated with higher plasma NPY levels and increased ALLO responses to exercise, which in turn relate to pain sensitivity. Future work will examine whether progressive exercise training increases cardiorespiratory fitness in association with increases in NPY and ALLO and reductions in pain sensitivity in chronic pain patients with PTSD.

Prevention of unfavourable effects of cigarette smoke on flap viability using botulinum toxin in random pattern flaps: An experimental study

BACKGROUND

There are numerous clinical and experimental studies reporting unfavourable effects of cigarette smoke on skin flaps.

OBJECTIVE

To investigate whether unfavourable effects of cigarette smoke on flap survival could be reduced by botulinum toxin type A.

METHODS

Twenty-eight male Wistar albino rats (15 months of age, mean weight 210 g [range 180 g to 230 g]) were included. They were divided into four groups of seven animals each. The control group underwent the surgical procedure alone. Surgical procedure was performed after administration of botulinum toxin type A in the botulinum toxin (BTX) group, after exposure to cigarette smoke in the cigarette smoke (CS) group, and after BTX type A administration and exposure to CS in the CS+BTX (CS+BTX) group. Random pattern cutaneous flaps (3 cm × 9 cm) were elevated from the dorsum of all rats. Necrosis area was calculated in percentages (%) using Image J computer software. Tissue samples were examined histopathologically.

RESULTS

The mean necrotic area in the control group (26%) and in the BTX group (21%) were similar (P=0.497), whereas administration of BTX type A significantly decreased flap necrosis area in the rats exposed to CS (the mean necrosis areas were 41.5% in the CS group, and 26% in the CS+BTX group; P<0.001). Histopathological examination findings corroborated the unfavourable effects of CS and preventive effects of BTX type A.

CONCLUSION

Preoperative administration of BTX significantly enhanced flap viability in the rats exposed to CS. Further human studies are warranted to verify whether BTX type A could be used as an agent to reduce the risk of flap necrosis in patients who smoke.

Prevention of unfavourable effects of cigarette smoke on flap viability using botulinum toxin in random pattern flaps: An experimental study

Background

There are numerous clinical and experimental studies reporting unfavourable effects of cigarette smoke on skin flaps.

Objective

To investigate whether unfavourable effects of cigarette smoke on flap survival could be reduced by botulinum toxin type A.

Methods

Twenty-eight male Wistar albino rats (15 months of age, mean weight 210 g [range 180 g to 230 g]) were included. They were divided into four groups of seven animals each. The control group underwent the surgical procedure alone. Surgical procedure was performed after administration of botulinum toxin type A in the botulinum toxin (BTX) group, after exposure to cigarette smoke in the cigarette smoke (CS) group, and after BTX type A administration and exposure to CS in the CS+BTX (CS+BTX) group. Random pattern cutaneous flaps (3 cm × 9 cm) were elevated from the dorsum of all rats. Necrosis area was calculated in percentages (%) using Image J computer software. Tissue samples were examined histopathologically.

Results

The mean necrotic area in the control group (26%) and in the BTX group (21%) were similar (P=0.497), whereas administration of BTX type A significantly decreased flap necrosis area in the rats exposed to CS (the mean necrosis areas were 41.5% in the CS group, and 26% in the CS+BTX group; P<0.001). Histopathological examination findings corroborated the unfavourable effects of CS and preventive effects of BTX type A.

Conclusion

Preoperative administration of BTX significantly enhanced flap viability in the rats exposed to CS. Further human studies are warranted to verify whether BTX type A could be used as an agent to reduce the risk of flap necrosis in patients who smoke.

The ratio of low-frequency to high-frequency in ambulatory electrocardiographic monitoring immediately before coronary angiography as a predictor of the presence of coronary artery disease

Background

There is considerable evidence that impaired autonomic control may be associated with the etiology of coronary artery disease (CAD). We hypothesized that the autonomic imbalance as assessed by measuring heart rate variability (HRV) and biological parameters before and after coronary angiography (CAG) may predict the presence of CAD.

Methods

Ambulatory electrocardiographic (ECG) examination using eHEART^® (Parama-Tec) is a novel, rapid, and simple method with which we can measure HRV within 5 min. We selected patients (n = 78, 68 ± 10 y) who underwent CAG and analyzed their ambulatory ECGs and blood levels of neuropeptides at both 1 day and immediately before and after CAG. The patients were divided into the presence (n = 64, CAD group) and absence of CAD (n = 14, non-CAD group).

Results

Although the CAD group showed an increase in blood pressure immediately before CAG, the ratio of low-frequency to high-frequency (LF/HF) was significantly decreased in the CAD group, but not in the non-CAD group. On the other hand, there was no difference in a coefficient of variation of the R-R interval or pulse rate between the two groups. CAD was independently associated with hypertension (P = 0.011), dyslipidemia (P = 0.009), and LF/HF immediately before CAG (P = 0.046) by a logistic regression analysis.

Conclusions

These findings suggest that LF/HF immediately before CAG in addition to hypertension and dyslipidemia might predict the presence of CAD.

Neuropeptide Y in the noradrenergic neurons induces the development of cardiometabolic diseases in a transgenic mouse model

Neuropeptide Y (NPY) is a neuropeptide widely expressed in the brain and a peptide transmitter of sympathetic nervous system (SNS) co-released with noradrenaline (NA) in prolonged stress. Association of a gain-of-function polymorphism in the human NPY gene with dyslipideamia, diabetes and vascular diseases suggests that increased NPY plays a role in the pathogenesis of the metabolic syndrome in humans. In the hypothalamus, NPY plays an established role in the regulation of body energy homeostasis. However, the effects of NPY elsewhere in the brain and in the SNS are less explored. In order to understand the role of NPY co-expressed with NA in the sympathetic nerves and brain noradrenergic neurons, a novel mouse model overexpressing NPY in noradrenergic neurons was generated. The mouse displays metabolic defects such as increased adiposity, hepatosteatosis, and impaired glucose tolerance as well as stress-related hypertension and increased susceptibility to vascular wall hypertrophy. The mouse phenotype closely reflects the findings of the several association studies with human NPY gene polymorphisms, and fits with the previous work on the effects of stress-induced NPY release on metabolism and vasculature. Thus, in addition of promoting feeding and obesity in the hypothalamus, NPY expressed in the noradrenergic neurons in the brain and in the SNS induces the development of cardiometabolic diseases.

The cardiac sympathetic co-transmitter galanin reduces acetylcholine release and vagal bradycardia: implications for neural control of cardiac excitability

The autonomic phenotype of congestive cardiac failure is characterised by high sympathetic drive and impaired vagal tone, which are independent predictors of mortality. We hypothesize that impaired bradycardia to peripheral vagal stimulation following high-level sympathetic drive is due to sympatho-vagal crosstalk by the adrenergic co-transmitters galanin and neuropeptide-Y (NPY). Moreover we hypothesize that galanin acts similarly to NPY by reducing vagal acetylcholine release via a receptor mediated, protein kinase-dependent pathway. Prolonged right stellate ganglion stimulation (10 Hz, 2 min, in the presence of 10 μM metoprolol) in an isolated guinea pig atrial preparation with dual autonomic innervation leads to a significant (p < 0.05) reduction in the magnitude of vagal bradycardia (5 Hz) maintained over the subsequent 20 min (n = 6). Immunohistochemistry demonstrated the presence of galanin in a small number of tyrosine hydroxylase positive neurons from freshly dissected stellate ganglion tissue sections. Following 3 days of tissue culture however, most stellate neurons expressed galanin. Stellate stimulation caused the release of low levels of galanin and significantly higher levels of NPY into the surrounding perfusate (n = 6, using ELISA). The reduction in vagal bradycardia post sympathetic stimulation was partially reversed by the galanin receptor antagonist M40 after 10 min (1 μM, n = 5), and completely reversed with the NPY Y₂ receptor antagonist BIIE 0246 at all time points (1 μM, n = 6). Exogenous galanin (n = 6, 50–500 nM) also reduced the heart rate response to vagal stimulation but had no effect on the response to carbamylcholine that produced similar degrees of bradycardia (n = 6). Galanin (500 nM) also significantly attenuated the release of ³H-acetylcholine from isolated atria during field stimulation (5 Hz, n = 5). The effect of galanin on vagal bradycardia could be abolished by the galanin receptor antagonist M40 (n = 5). Importantly the GalR₁ receptor was immunofluorescently co-localised with choline acetyl-transferase containing neurons at the sinoatrial node. The protein kinase C inhibitor calphostin (100 nM, n = 6) abolished the effect of galanin on vagal bradycardia whilst the protein kinase A inhibitor H89 (500 nM, n = 6) had no effect. These results demonstrate that prolonged sympathetic activation releases the slowly diffusing adrenergic co-transmitter galanin in addition to NPY, and that this contributes to the attenuation in vagal bradycardia via a reduction in acetylcholine release. This effect is mediated by GalR₁ receptors on vagal neurons coupled to protein kinase C dependent signalling pathways. The role of galanin may become more important following an acute injury response where galanin expression is increased.

Morphological and molecular changes of the myocardium after left ventricular mechanical support

Left ventricular assist devices (LVAD) are currently used to either “bridge” patients with terminal congestive heart failure (CHF) until cardiac transplantation is possible or optionally for patients with contraindications for transplantation (“destination therapy”). Mechanical support is associated with a marked decrease of cardiac dilation and hypertrophy as well as numerous cellular and molecular changes (“reverse cardiac remodeling”), which can be accompanied by improved cardiac function (“bridge to recovery”) in a relatively small subset of patients with heart transplantation no longer necessary even after removal of the device (“weaning”). In the recent past, novel pharmacological strategies have been developed and are combined with mechanical support, which has increased the percentage of patients with improved clinical status and cardiac performance. Gene expression profiles have demonstrated that individuals who recover after LVAD show different gene expression compared to individuals who do not respond to unloading. This methodology holds promise for the future to develop read out frames to identify individuals who can recover after support. Aside from describing the morphological changes associated with “reverse cardiac remodeling”, this review will focus on signal transduction, transcriptional regulation, apoptosis, cell stress proteins, matrix remodeling, inflammatory mediators and aspects of neurohormonal activation in the failing human heart before and after ventricular unloading.

A possible role of neuropeptide Y in depression and stress

Neuropeptide Y (NPY) mediates its physiological effects through at least four receptors known as Y(1), Y(2), Y(4), and Y(5). This peptide is one of the most abundant peptides in the central nervous system and is highly conserved throughout evolution. The most abundant receptors of the NPY family, the Y(1) and Y(2) receptors, are densely expressed in the cortex, hippocampus, and amygdala. These brain regions are particularly associated with mood disorders, stress responses, and memory processing. With this in mind, researchers suggested the involvement of NPY as well as the Y(1) and Y(2) receptors in affective disorders. Earlier studies showed that NPY and the Y(1) and Y(2) receptors mediate some aspects of depression-like disorders and stress responses in rodents. Recent research also suggests the involvement of the Y(4) and Y(5) receptors in emotion-related processes in rodents. In addition, human studies have consistently suggested a role for NPY in stress responses, whereas conflicting data have been obtained in relation to the role of NPY in depression-related illnesses. However, novel evidence from polymorphisms in the prepro-NPY gene has shed new light on the potential clinical relevance of NPY in depression. In this article, we review the literature from both animal and human studies regarding the contribution of NPY and its receptors in depression and stress.

Uncoupling of sympathetic nervous system and hypothalamic-pituitary-adrenal axis in cirrhosis

BACKGROUND AND AIM

The hypothalamic-autonomic nervous system (HANS) axis and the hypothalamic-pituitary-adrenal (HPA) axis are stimulated in parallel in response to stress factors under healthy conditions. This physiological synergism of the axes aims at optimizing anti-inflammatory actions. Therefore, we investigated whether this synergism is altered in patients with liver cirrhosis.

METHODS

As a typical marker of the HANS axis neuropeptide Y (NPY is a neurotransmitter of the sympathetic nerve terminal) and of the HPA axis, cortisol together with adrenocorticotropic hormone (ACTH) and cortisol-binding globulin (CBG), were measured in samples from control subjects and patients with liver cirrhosis.

RESULTS

Plasma NPY was found to be increased in cirrhotic patients compared to control subjects (P < 0.01). This increase was observed to be independent of the severity of liver disease (Child class). Serum cortisol was decreased in cirrhotics, particularly in patients with Child A cirrhosis. Plasma NPY was positively correlated with serum cortisol in control subjects (r = 0.32, P < 0.05) reflecting the parallel activation of both axes under the normal condition. However, serum cortisol was not correlated with plasma NPY in cirrhotic patients. For the subgroup of Child A patients, even a negative correlation between NPY and cortisol was observed (r = -0.43, P < 0.05). No significant change in serum levels of ACTH and its positive correlation with serum cortisol was observed in cirrhotic patients.

CONCLUSIONS

The present study demonstrates that the two stress axes seem to act in parallel fashion in control subjects but are uncoupled in liver cirrhosis. We discuss how uncoupling of the two anti-inflammatory axes can occur and may contribute to the increased susceptibility for infections and lethal complications in cirrhotic patients.

Neuropeptide Y signalling on hippocampal stem cells in health and disease

Neuropeptides are emerging as key components in the hippocampal neurogenic niche in health and disease, regulating many aspects of neurogenesis and the synaptic integration of newly generated neurons. This review focuses on the role of neuropeptide Y in the control of stem/precursor cells in the postnatal and adult hippocampus. It is likely that neuropeptide Y releasing interneurons are key sensors of neural activity, modulating neurogenesis appropriately. This is likely to be a fruitful area of research for extending our understanding of the control of stem cells in the normal and diseased brain.

Decreased myocardial chromogranin a expression and colocalization with brain natriuretic peptide during reverse cardiac remodeling after ventricular unloading

AIMS

In chronic heart failure, atrial and brain natriuretic peptide expression is increased and serves as a clinical marker of cardiac hypertrophy. Chromogranin A is also up-regulated during chronic heart failure and associated with disease severity and prognosis. Significant decrease of both natriuretic peptide and hypertrophy after left ventricular assist device (LVAD) treatment was reported. This study investigated whether chromogranin A and neural cell adhesion molecule (NCAM)/CD56 are associated with cardiac hypertrophy and regulated by LVAD.

METHODS

Expression of atrial and brain natriuretic peptide, chromogranin A, and NCAM/CD56 were investigated by immunohistochemistry and morphometrically quantified in 33 paired myocardial samples before and after LVAD. In a different set of patients, chromogranin A was evaluated in the plasma. Cardiomyocyte colocalization of brain natriuretic peptide and chromogranin A was visualized by immunofluorescence doublestaining.

RESULTS

Natriuretic peptide and chromogranin A protein expression is significantly decreased after LVAD (p < 0.05). NCAM/CD56 expression remains unaltered by unloading. In contrast with natriuretic peptide, chromogranin A and NCAM/CD56 expression is not correlated with cardiomyocyte diameters. Although increased compared with controls, no significant differences for chromogranin A plasma levels were found before and after LVAD. Sarcoplasmic colocalization of chromogranin A and brain natriuretic peptide is considerably decreased after LVAD.

CONCLUSIONS

Neither chromogranin A nor CD56 is associated with cardiac hypertrophy. Chromogranin A is significantly decreased by ventricular support. Sarcoplasmic colocalization of brain natriuretic peptide and chromogranin A is diminished after unloading. However, owing to its low expression, the negative regulation of chromogranin A is not reflected by plasma levels and thus does not appear to be an appropriate biomarker of reverse cardiac remodeling after unloading.

Ventricular fibrillation induced by ischemia-reperfusion is not prevented by the NPY Y2 receptor antagonist BIIE0246

Neuropeptide Y is released together with norepinephrine from sympathetic nerve terminals during conditions of increased sympathetic activity. Neuropeptide Y is known to inhibit vagal activity, and accordingly, it might increase the risk for ventricular fibrillation during myocardial ischemia-reperfusion, with concomitant sympathetic stimulation. Counteracting the inhibiting effect of neuropeptide Y by the specific neuropeptide Y2 antagonist, BIIE0246, we expected occurrence of ventricular fibrillation in association with repeated periods of myocardial ischemia-reperfusion to decrease. The midleft anterior descending coronary artery was repeatedly occluded in 16 open-chest pigs. Eight pigs received BIIE0246, and the controls received the vehicle only. Ventricular fibrillation developed in 2 animals of the control group, but in 4 pigs receiving BIIE0246. Occurrence of ventricular fibrillation and ventricular tachycardia did not differ significantly between the 2 groups, and in association with repeated periods of regional myocardial ischemia, did not decline in pigs treated by the specific neuropeptide Y2-receptor antagonist BIIE0246.

Role of NPY for vasoregulation in the splanchnic circulation during portal hypertension

Vascular dysfunction in the splanchnic circulation during portal hypertension is characterized by enhanced NO-mediated vasorelaxation and vascular hyporeactivity to norepinephrine that lead to arterial vasodilation. NPY most likely counteracts both of these key features. Firstly, NPY appears to inhibit Ach- and PNS-induced vasorelaxation in mesenteric arteries. This effect is more pronounced in portal hypertensive rats as compared to control, and most likely reflects the inhibition of increased e- and nNOS-derived NO-synthesis during portal hypertensive conditions. Secondly, NPY sensitizes the mesenteric vasculature to alpha(1)-adrenergic vasoconstriction. Most importantly, in portal hypertensive rats but not in sham rats NPY markedly augments vascular contractility and thereby corrects vascular hyporeactivity. Both actions of NPY increase vascular tone and may well act synergistically in the splanchnic circulation during portal hypertension. Moreover, the vasoconstrictive effects of NPY are most pronounced at particularly high levels of alpha(1)-adrenergic activity. Therefore, it appears that NPY becomes increasingly important for optimizing adrenergic vasoconstriction at particularly high adrenergic drive and also for playing a predominant role for vascular homeostasis. Cirrhotic patients present with elevated circulating plasma levels of NPY, which appears to be independent from the severity of liver dysfunction and to correlate with portal pressure. This finding indicates enhanced NPY release during portal hypertension that may represent a compensatory mechanism aimed at counterbalancing arterial vasodilation by restoring the efficacy of endogenous catecholamines and inhibiting vasodilative drive in the splanchnic circulation.

Neurohumoral changes in patients with left ventricular dysfunction following acute myocardial infarction and the effect of nitrate therapy: a randomized, double-blind, placebo-controlled long-term study

BACKGROUND

Several neurohumoral mechanisms involved in cardiovascular regulation are activated in the failing heart, but only limited information is available regarding the influence of long-term nitrate therapy.

MATERIALS AND METHODS

This was a double-blind, randomized comparison of isosorbide-5-mononitrate (IS-5-MN), 60 mg given orally, once daily for 11 months to patients (n = 47) with left ventricular (LV) dysfunction following acute myocardial infarction (AMI). Forty-five patients received placebo. All patients received ramipril.Plasma natriuretic peptides (atrial [ANP] and brain [BNP] natriuretic peptide), epinephrine, norepinephrine (NEPI), antidiuretic hormone, aldosterone (Aldo), renin activity (PRA), substance P, neuropeptide Y-like immunoreactivity, calcitonin gene-related peptide, and vasoactive intestinal peptide were measured at baseline and at the end of the treatment period. Clinical, echocardiographic, and hemodynamic data were also obtained.

RESULTS AND CONCLUSIONS

Chronic nitrate therapy does not significantly affect the neurohumoral status in patients with LV dysfunction after AMI, apart from a decrease in ANP. Some hormones are more closely associated with diastolic dysfunction/increased volume load (ANP and BNP) and others are more closely associated with systolic dysfunction (PRA, NEPI, Aldo). There is a temporal dissociation of these 2 groups of hormones 1 year post infarction: ANP and BNP decrease, whereas NEPI and Aldo show a slight increase. BNP levels do not reflect all important pathophysiologic mechanisms in heart failure. Consequently, the use of other neurohormonal factors than BNP for monitoring of heart failure therapy should be explored.

Roles of nuclear NPY and NPY receptors in the regulation of the endocardial endothelium and heart functionThis paper is one of a selection of papers published in this Special issue, entitled Second Messengers and Phosphoproteins—12th International Conference

It is now well accepted that the heart is a multifunctional organ in which endothelial cells, and more particularly endocardial endothelial cells (EECs), seem to play an important role in regulating and maintaining cardiac excitation–contraction coupling. Even if major differences exist between vascular endothelial cells (VECs) and EECs, all endothelial cells including EECs release a variety of auto- and paracrine factors such as nitric oxide, endothelin-1, angiotensin II, and neuropeptide Y. All these factors were reported to affect cardiomyocyte contractile performance and rhythmicity. In this review, findings on the morphology of EECs, differences between EECs and other types of endothelial cells, interactions between EECs and the adjacent cardiomyocytes, and effects of NPY on the heart will be presented. We will also show evidence on the presence and localization of NPY and the Y1receptor in the endocardial endothelium and discuss their role in the regulation of cytosolic and nuclear free calcium.

Enhanced Y1-receptor-mediated vasoconstrictive action of neuropeptide Y (NPY) in superior mesenteric arteries in portal hypertension

BACKGROUND/AIMS

Vascular hyporeactivity to catecholamines contributes to arterial vasodilation and hemodynamic dysregulation in portal hypertension. Neuropeptide Y (NPY) is a sympathetic neurotransmitter facilitating adrenergic vasoconstriction via Y1-receptors on the vascular smooth muscle. Therefore, we investigated its role for vascular reactivity in the superior mesenteric artery (SMA) of portal vein ligated (PVL) and sham operated rats.

METHODS

In vitro perfused SMA vascular beds of rats were tested for the cumulative dose-response to NPY dependent on the presence and level of alpha1-adrenergic vascular tone (methoxamine MT: 0.3-10 microM). Moreover, the effect of NPY (50 nM) on vascular responsiveness to alpha1-adrenergic stimulation (MT: 0.3-300 microM) was evaluated. Y1-receptor function was tested by Y1-selective inhibition using BIBP-3226 (1 microM).

RESULTS

NPY dose-dependently and endothelium-independently enhanced MT-pre-constriction in SMA. This potentiation was increasingly effective with increasing adrenergic pre-stimulation and being more pronounced in PVL rats as compared to sham rats at high MT concentrations. NPY enhanced vascular contractility only in PVL rats correcting the adrenergic vascular hyporeactivity. Y1-receptor inhibition completely abolished NPY-evoked vasoconstrictive effects.

CONCLUSIONS

NPY endothelium-independently potentiates adrenergic vasoconstriction via Y1-receptors being more pronounced in portal hypertension improving mesenteric vascular contractility and thereby correcting the splanchnic vascular hyporeactivity. This makes NPY a superior vasoconstrictor counterbalancing arterial vasodilation in portal hypertension.

Influence of endogenous neuropeptide Y (NPY) on the sympathetic-parasympathetic interaction in the canine heart

The purpose of this study was to examine the sympathetic-parasympathetic interactions on heart rate through release of neuropeptide Y (NPY) and its action on prejunctional NPY Y2 receptors on vagal and sympathetic nerve fibers. In other studies on various preparations and in various organs, attenuation of transmitter release has in fact been demonstrated through activation of the NPY Y2 receptor. In the present study on anesthetized dogs we examine, however, for the first time if vagal bradycardia is attenuated by endogenous NPY released during intense cardiac sympathetic stimulation. In addition, we explore if sympathetic transmitter release and heart rate, during moderate sympathetic stimulation, are affected through this receptor system. The significance of the NPY Y2 receptor was revealed by performing experiments before and after administration of its specific receptor antagonist BIIE0246. We found that attenuation of the bradycardia during vagal nerve stimulation was dose-dependently counteracted by BIIE0246 and that the tachycardia elicited by sympathetic stimulation remained unaffected after NPY Y2 receptor blockade. Thus, endogenous NPY appears to attenuate vagal bradycardia by stimulating prejunctional NPY Y2 receptors on cardiac vagal nerve terminals and, less efficiently, to attenuate transmitter release and tachycardia through a feedback loop on the cardiac sympathetic nerve fibers.

Neuropeptide Y1receptor vasoconstriction in exercising canine skeletal muscles

Existing evidence suggests that neuropeptide Y (NPY) acts as a neurotransmitter in vascular smooth muscle and is coreleased with norepinephrine from sympathetic nerves. We hypothesized that release of NPY stimulates NPY Y(1) receptors in the skeletal muscle vasculature to produce vasoconstriction during dynamic exercise. Eleven mongrel dogs were instrumented chronically with flow probes on the external iliac arteries of both hindlimbs and a catheter in one femoral artery. In resting dogs (n = 4), a 2.5-mg bolus of BIBP-3226 (NPY Y(1) antagonist) infused into the femoral artery increased external iliac conductance by 150 +/- 82% (1.80 +/- 0.44 to 3.50 +/- 0.14 ml.min(-1).mmHg(-1); P < 0.05). A 10-mg bolus of BIBP-3226 infused into the femoral artery in dogs (n = 7) exercising on a treadmill at a moderate intensity (6 miles/h) increased external iliac conductance by 28 +/- 6% (6.00 +/- 0.49 to 7.64 +/- 0.61 ml.min(-1).mmHg(-1); P < 0.05), whereas the solvent vehicle did not (5.74 +/- 0.51 to 5.98 +/- 0.43 ml.min(-1).mmHg(-1); P > 0.05). During exercise, BIBP-3226 abolished the reduction in conductance produced by infusions of the NPY Y(1) agonist [Leu(31),Pro(34)]NPY (-19 +/- 3 vs. 0.5 +/- 1%). Infusions of BIBP-3226 (n = 7) after alpha-adrenergic receptor antagonism with prazosin and rauwolscine also increased external iliac conductance (6.82 +/- 0.43 to 8.22 +/- 0.48 ml.min(-1).mmHg(-1); P < 0.05). These data support the hypothesis that NPY Y(1) receptors produce vasoconstriction in exercising skeletal muscle. Furthermore, the NPY Y(1) receptor-mediated tone appears to be independent of alpha-adrenergic receptor-mediated vasoconstriction.

Chronic Stress Induces Rapid Occlusion of Angioplasty-Injured Rat Carotid Artery by Activating Neuropeptide Y and Its Y1 Receptors

OBJECTIVE

We reported previously that neuropeptide Y (NPY) induces an atherosclerotic-like lesion that is significantly reduced by NPY-Y1 and NPY-Y5 receptor (R) inhibitors. Because antagonists also inhibit neointima induced by angioplasty alone, we now test whether stress-induced endogenous NPY release mimic these changes.

METHODS AND RESULTS

Rats were nonstressed or stressed (4 degrees C water; 2 hours per day for 14 days) starting immediately before and continuing after carotid artery angioplasty. Stress acutely and chronically increased blood pressure and doubled plasma NPY levels. After 14 days, angioplasty-induced neointima was markedly greater in stressed (than nonstressed) rats, in which most of the vessels became occluded with an atherosclerotic-like lesion containing macrophages, lipids, thrombus, and microvessels that was similar but more inflammatory than the injury in the NPY-treated vessels. Fourteen days after angioplasty combined with stress or NPY, Y1R and Y5R (mRNA and protein) became upregulated in areas of neointima, microvessels, and macrophages in injured carotid arteries. Stress- and NPY-induced changes were completely prevented by a selective Y1R antagonist (0.02 micromol/kg per minute for 14 days), whereas neointima induced by angioplasty alone was reduced by 60%.

CONCLUSIONS

Because of sympathetic NPY release, stress may be a less-than-appreciated risk factor for restenosis/atherosclerosis, and Y1R antagonists a potential therapy for these conditions.

Increase of sympathetic outflow measured by neuropeptide Y and decrease of the hypothalamic-pituitary-adrenal axis tone in patients with systemic lupus erythematosus and rheumatoid arthritis: another example of uncoupling of response systems

OBJECTIVE

To study in parallel the outflow of the sympathetic nervous system (SNS) and the hypothalamic-pituitary adrenal (HPA) axis tone in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).

METHODS

32 patients with SLE, 62 with RA, and 65 healthy subjects (HS) were included. To measure the tone of the HPA axis, plasma ACTH and serum cortisol were determined. Serum neuropeptide Y (NPY) was used to evaluate the sympathetic outflow.

RESULTS

Patients with SLE had increased NPY levels in comparison with HS, irrespective of prior prednisolone treatment (p<0.001). For patients with RA, only those with prednisolone treatment had increased NPY levels in comparison with HS (p = 0.016). Daily prednisolone dose correlated positively with serum NPY in RA (R(Rank) = 0.356, p = 0.039). In contrast, plasma ACTH levels were generally decreased significantly in comparison with HS in SLE with prednisolone, and in RA with/without prednisolone. Similarly, serum cortisol levels were also decreased in SLE with/without prednisolone, and in RA with prednisolone. The NPY/ACTH ratio was increased in SLE and RA, irrespective of prior prednisolone treatment. The NPY/cortisol ratio was increased in SLE with/without prednisolone, and in RA with prednisolone. Twelve weeks' anti-TNF antibody treatment with adalimumab did not decrease NPY levels in RA, irrespective of prednisolone treatment.

CONCLUSIONS

An increased outflow of the SNS was shown and a decreased tone of the HPA axis in patients with SLE and RA. Low levels of cortisol in relation to SNS neurotransmitters may be proinflammatory because cooperative anti-inflammatory coupling of the two endogenous response axes is missing.

Neuropeptide Y stimulates neuronal precursor proliferation in the post-natal and adult dentate gyrus

Adult dentate neurogenesis is important for certain types of hippocampal-dependent learning and also appears to be important for the maintenance of normal mood and the behavioural effects of antidepressants. Neuropeptide Y (NPY), a peptide neurotransmitter released by interneurons in the dentate gyrus, has important effects on mood, anxiety-related behaviour and learning and memory. We report that adult NPY receptor knock-out mice have significantly reduced cell proliferation and significantly fewer immature doublecortin-positive neurons in the dentate gyrus. We also show that the neuroproliferative effect of NPY is dentate specific, is Y1-receptor mediated and involves extracellular signal-regulated kinase (ERK)1/2 activation. NPY did not exhibit any effect on cell survival in vitro but constitutive loss of the Y1 receptor in vivo resulted in greater survival of newly generated neurons and an unchanged total number of dentate granule cells. These results show that NPY stimulates neuronal precursor proliferation in the dentate gyrus and suggest that NPY-releasing interneurons may modulate dentate neurogenesis.

Psychopharmacological possibilities in the acute disaster setting

This article focuses on possible psychopharmacological interventions in the immediate post disaster setting. As there is little evidence for the efficacy or effectiveness of such interventions-given the difficulty in performing randomized, double-blind, placebo controlled studies with these populations-the article will delineate the neurobiological basis for pathological sequelae and theoretical drug interventions targeting putative disease mechanisms.

Vasoconstriction in exercising skeletal muscles: a potential role for neuropeptide Y?

There is evidence that neuropeptide Y (NPY) acts as a neurotransmitter in vascular smooth muscle and is released with norepinephrine from sympathetic nerves. We hypothesized that NPY Y1 receptor stimulation would produce vasoconstriction in resting and exercising skeletal muscle. Nine mongrel dogs were instrumented chronically with flow probes on the external iliac arteries of both hindlimbs and a catheter in one femoral artery. The selective NPY Y1 receptor agonist [Leu31,Pro34]NPY was infused as a bolus into the femoral artery catheter at rest and during mild, moderate, and heavy exercise. Intra-arterial infusions of [Leu31,Pro34]NPY elicited reductions ( P < 0.05) in vascular conductance of 38 ± 3, 25 ± 2, 17 ± 1, and 11 ± 1% at rest, 3 miles/h, 6 miles/h, and 6 miles/h and 10% grade, respectively. The agonist infusions did not affect ( P > 0.05) blood flow in the contralateral iliac artery. To examine whether nitric oxide (NO) is responsible for the attenuated vasoconstrictor response during exercise to NPY Y1 receptor stimulation, the infusions were repeated after NO synthase blockade. These infusions yielded reductions ( P < 0.05) in vascular conductance of 47 ± 3, 23 ± 2, 19 ± 3, and 12 ± 2% at rest, 3 miles/h, 6 miles/h, and 6 miles/h and 10% grade, respectively. NPY Y1 receptor responsiveness was attenuated ( P < 0.05) during exercise compared with rest. Blockade of NO production did not affect ( P > 0.05) the attenuation of NPY Y1 receptor responsiveness during exercise. These data support the hypothesis that NPY Y1 receptors can produce vasoconstriction in exercising skeletal muscle.

Neuropeptide Y antagonism reduces reflex cutaneous vasoconstriction in humans

Previous studies have provided evidence of a non-noradrenergic contributor to reflex cutaneous vasoconstriction in humans but did not identify the transmitter responsible. To test whether neuropeptide Y (NPY) has a role, in two series of experiments we slowly reduced whole body skin temperature (TSK) from 34.5 to 31.7 degrees C. In protocol 1, Ringer solution and the NPY receptor antagonist BIBP-3226 alone were delivered intradermally via microdialysis. In protocol 2, yohimbine plus propranolol (Yoh + Pro), Yoh + Pro in combination with BIBP-3226, and Ringer solution were delivered to antagonize locally the vasomotor effects of NPY and norepinephrine. Blood flow was measured by laser Doppler flowmetry (LDF). Mean arterial blood pressure (MAP) was monitored at the finger (Finapres). In protocol 1, cutaneous vascular conductance (CVC) fell by 45%, to 55.1 +/- 5.6% of baseline at control sites (P < 0.05). At BIBP-3226-treated sites, CVC fell by 34.1% to 65.9 +/- 5.0% (P < 0.05; P < 0.05 between sites). In protocol 2, during body cooling, CVC at control sites fell by 32.6%, to 67.4 +/- 4.3% of baseline; at sites treated with Yoh + Pro, CVC fell by 18.7%, to 81.3 +/- 4.4% of baseline (P < 0.05 vs. baseline; P < 0.05 vs. control) and did not fall significantly at sites treated with BIBP-3226 + Yoh + Pro (P > 0.05; P < 0.05 vs. other sites). After cooling, exogenous norepinephrine induced vasoconstriction at control sites (P < 0.05) but not at sites treated with Yoh + Pro + BIBP-3226 (P > 0.05). These results indicate that NPY participates in sympathetically mediated cutaneous vasoconstriction in humans during whole body cooling.

Alpha-adrenergic vascular responsiveness during postexercise hypotension in humans

In sedentary individuals, postexercise hypotension following a single bout of aerobic exercise is due to an unexplained peripheral vasodilatation. We tested the hypothesis that alpha-adrenergic responsiveness in the forearm and leg vasculatures is blunted during postexercise hypotension. We studied 12 men and two women before and 30 min after a 60 min bout of cycling at 60 % VO2,peak. In the first five subjects, arterial pressure (brachial artery catheter) and forearm blood flow (plethysmography) were measured and vascular conductance was calculated during intraarterial infusions of the alpha1-agonist phenylephrine and the alpha2-agonist clonidine. Exercise reduced mean arterial pressure (89 +/- 2 vs. 95 +/- 2 mmHg, P < 0.05) and increased forearm vascular conductance 77 +/- 33 % (P < 0.05). Despite these changes in baseline vascular conductance, vasoconstrictor responses in the forearm to phenylephrine and clonidine were similar (or enhanced) postexercise vs. preexercise. In the remaining nine subjects, arterial pressure (femoral artery catheter) and leg blood flow (Doppler ultrasound of the femoral artery) were measured and vascular conductance was calculated during intraarterial infusions of phenylephrine and clonidine. Exercise reduced mean arterial pressure (80 +/- 2 vs. 89 +/- 2 mmHg, P < 0.05) and increased leg vascular conductance 94 +/- 16 % (P < 0.05). Despite these changes in baseline vascular conductance, vasoconstrictor responses in the leg to phenylephrine and clonidine were similar (or enhanced) postexercise vs. preexercise. These results suggest that vascular responsiveness to alpha-adrenergic agonists is maintained during postexercise hypotension in humans. Thus, while postexercise hypotension is associated with increased vascular conductance in the forearm and leg, it does not appear that blunting of alpha-adrenergic responsiveness is the cause.

Functional organization of peripheral vasomotor pathways

AIM

In this article, we review the functional organization of the peripheral autonomic pathways regulating the vasculature.

RESULTS

The final motor neurones in vasomotor pathways tend to be smaller than neurones in other autonomic pathways. This suggests that they have relatively smaller target territories and receive fewer pre-ganglionic inputs than non-vasomotor neurones. Nevertheless, single vasomotor neurones project to large areas of the vasculature separated by up to 7 mm. Different functional pools of vasomotor neurones project to specific segments of the vasculature, allowing for the selective neural control of resistance in vessels in proximal or distal regions of the vascular bed. In many cases, each functional pool of vasomotor neurones utilizes a characteristic combination of cotransmitters. The various pools of final motor neurones in vasomotor pathways receive convergent synaptic input from different pools of pre-ganglionic neurones, many of which also contain neuropeptides which enhance the excitability of the final motor neurones. The excitability of vasomotor neurones regulating gastrointestinal and mesenteric blood flow, also can be increased by the actions of peptides such as substance P that are released from visceral nociceptors.

CONCLUSIONS

We propose that autonomic pathways regulating the vasculature are organized into 'vasomotor units'. Each vasomotor unit consists of a pre-ganglionic neurone, the final motor neurones it innervates, and the blood vessels that they regulate. The vasomotor units are likely to be grouped into functional pools that can be recruited as necessary to provide highly specific, graded control of blood flow both within and between vascular beds.

Neuropeptide-Y and atrial natriuretic peptide as prognostic markers in patients on hemodialysis

We conducted a study of the influence of the vasoactive peptides atrial natriuretic peptide (ANP) and neuropeptide Y (NPY) on survival of patients on hemodialysis and their association and relative importance with cardiac and clinical variables. Thirty-three hemodialysis patients were characterized by age, sex, diagnosis, blood pressure, serum (S)-albumin, serum (S)-urea, hemoglobin, dialysis dose, weight gain, duration of dialysis, cardiac hypertrophy, volume, failure, and ischemia and plasma levels of ANP and NPY. The outcomes were analyzed for early deaths (< 1 year) and for all deaths. The association of the variables to early deaths and all deaths, respectively, was studied in Cox proportional hazard analyses. The variables were also studied in three hierarchical steps: clinical variables only, clinical and cardiac variables, and all variables. For all deaths, the independent variables were plasma NPY (pmol/L) (hazard ratio [HR] = 1.035, p = 0.004), heart volume (ml/m2) (HR = 1.009, p = 0.001), and S-albumin (g/L) (HR = 0.750, p = 0.034). For early deaths, the independent variables were predialysis ANP (pmol/L) (HR = 1.008, p = 0.034) and NPY (pmol/L) (HR = 1.031, p = 0.026). In the hierarchical study, excluding the vasoactive peptides, heart volume, heart failure and S-albumin were independently associated with all deaths, and mean arterial blood pressure was associated with early death. When also excluding the cardiac parameters, S-albumin was associated with all deaths and mean arterial blood pressure with early death. In conclusion, plasma levels of the vasoactive peptides ANP and NPY are the most important group in a hierarchy of variables that predict imminent death in hemodialysis patients, and NPY is associated with late death. ANP and NPY apparently sum up the detrimental influence of many factors in hemodialysis patients.

Botulinum neurotoxin A attenuates release of norepinephrine but not NPY from vasoconstrictor neurons

We examined effects of botulinum neurotoxin A (BoNTA) on sympathetic constrictions of the vena cava and uterine artery from guinea pigs to test the role of soluble NSF attachment protein receptor (SNARE) proteins in release of the cotransmitters norepinephrine (NE) and neuropeptide Y (NPY). Protein extracts of venae cavae and uterine arteries showed partial cleavage of synaptosomal associated protein of 25 kDa (SNAP-25) after treatment in vitro with BoNTA (50-100 nM). The rising phase of isometric contractions of isolated venae cavae to field stimulation at 20 Hz, mediated by NE acting on alpha-adrenoceptors, was reduced significantly by 100 nM BoNTA. However, sustained sympathetic contractions mediated by NPY were not affected by BoNTA. In uterine arteries, noradrenergic contractions to 1-Hz stimulation were almost abolished by BoNTA, and contractions at 10 Hz were reduced by 50-60%. We conclude that SNARE proteins are involved in exocytosis of NE from synaptic vesicles at low frequencies of stimulation but may not be essential for exocytosis of NPY and NE from large vesicles at high stimulation frequencies.

NPY Y1 receptors are present in axonal processes of DRG neurons

Using a sensitive immunohistochemical method, the localization of the neuropeptide Y (NPY) Y1 receptor (Y1R) was studied in contralateral and ipsilateral dorsal root ganglion (DRG) neurons of rats subjected to different unilateral manipulations with focus on their axonal processes and projection areas. Y1R-like immunoreactivity (LI) was observed in the contralateral sciatic nerve and dorsal roots of lesioned rats, and double staining revealed colocalization with calcitonin gene-related peptide (CGRP). Y1R-LI was also seen in fibers close to and even within the epidermis. A fairly small number of nerve endings double-labeled for Y1R and CGRP were present in the dorsal horn. After unilateral crush of the sciatic nerve Y1R- and CGRP-LI accumulated in the same axons proximal to the lesion. After dorsal rhizotomy CGRP-LI was strongly reduced in the ipsilateral dorsal horn. No certain change was observed for Y1R- or NPY-LI, but Y1R/CGRP double-labeled nerve endings disappeared after the lesion. These results strongly suggest centrifugal transport of Y1Rs in DRG neurons, mainly to the peripheral sensory branches. To what extent these Y1Rs are functional has not been analyzed here, but a recent study on Y1R null mice provides evidence for involvement of prejunctional Y1Rs in peripheral sensory functions

Neurohormonal activation in heart failure after acute myocardial infarction treated with beta-receptor antagonists

BACKGROUND

Few studies have described how neurohormonal activation is influenced by treatment with beta-receptor antagonists in patients with heart failure after acute myocardial infarction. The aims were to describe neurohormonal activity in relation to other variables and to investigate treatment effects of a beta(1) receptor-antagonist compared to a partial beta(1) receptor-agonist.

METHODS

Double-blind, randomized comparison of metoprolol 50-100 mg b.i.d. (n=74), and xamoterol 100-200 mg b.i.d (n=67). Catecholamines, neuropeptide Y-like immunoreactivity (NPY-LI), renin activity, and N-terminal pro-atrial natriuretic factor (N-ANF) were measured in venous plasma before discharge and after 3 months. Clinical and echocardiographic variables were assessed.

RESULTS

N-ANF showed the closest correlations to clinical and echocardiographic measures of heart failure severity, e.g. NYHA functional class, furosemide dose, exercise tolerance, systolic and diastolic function. Plasma norepinephrine, dopamine and renin activity decreased after 3 months on both treatments, in contrast to a small increase in NPY-LI which was greater (by 3.9 pmol/l, 95% CI 1.2-6.6) in the metoprolol group. N-ANF increased on metoprolol, and decreased on xamoterol (difference: 408 pmol/l, 95% CI 209-607). Increase above median of NPY-LI (>25.2 pmol/l, odds ratio 2.8, P=0.0050) and N-ANF (>1043 pmol/l, odds ratio 2.8, P=0.0055) were related to long term (mean follow-up 6.8 years) cardiovascular mortality.

CONCLUSIONS

Decreased neurohormonal activity, reflecting both the sympathetic nervous system and the renin-angiotensin system, was found 3 months after an acute myocardial infarction with heart failure treated with beta-receptor antagonists. The small increase in NPY-LI may suggest increased sympathetic activity or reduced clearance from plasma. The observed changes of N-ANF may be explained by changes in cardiac preload, renal function, and differences in beta-receptor mediated inhibition of atrial release of N-ANF. NPY-LI, and N-ANF at discharge were related to long term cardiovascular mortality.

Diminished circadian variation in heart rate variability before surgery in patients developing postoperative atrial fibrillation

OBJECTIVE

To evaluate the role of the autonomic nervous system for the development of atrial fibrillation (AF) after coronary artery bypass surgery.

DESIGN

Eighty patients without a previous history of AF were included. The sympathetic and parasympathetic activity were evaluated by the analysis of heart rate variability (HRV) in the frequency domain from 24-h Holter recordings and by measuring neuropeptides (neuropeptide Y, chromogranin A, chromogranin B, and pancreatic polypeptide (PP)) and catecholamines, obtained pre- and postoperatively.

RESULTS

Preoperatively, patients (36.3%) developing AF postoperatively showed a statistically significant less circadian variation in the HRV variables, the high-frequency (HF) component (p = 0.013) and the low-frequency (LF)/HF ratio (p = 0.007), than patients remaining in sinus rhythm. The HF component and PP. both reflecting parasympathetic activity, and all other variables in the frequency domain, decreased significantly after surgery in both patient groups (p < 0.0001). Although catecholamines increased significantly postoperatively in both patient groups, neither catecholamines nor neuropeptides expressing sympathetic activity, differed between the two groups. PP was, however, significantly higher in patients with postoperative AF than in those with sinus rhythm postoperatively on day 1.

CONCLUSION

The diminished circadian variation in HRV before surgery and the indirect signs of a higher parasympathetic activity in patients developing postoperative AF compared with patients remaining in sinus rhythm, may indicate a propensity for AF.

Thoracic epidural anesthesia does not influence the occurrence of postoperative sustained atrial fibrillation

BACKGROUND

To evaluate whether thoracic epidural anesthesia (TEA) can reduce the incidence of atrial fibrillation (AF) after coronary artery bypass grafting (CABG).

METHODS

Forty-one patients undergoing CABG were treated with TEA intraoperatively and postoperatively. Another 80 patients served as the control group. The sympathetic and parasympathetic activities were evaluated by analysis of neuropeptides, catecholamines and heart rate variability (HRV), preoperatively and postoperatively.

RESULTS

Postoperative AF occurred in 31.7% of the TEA-treated patients and in 36.3% of the untreated patients (p = 0.77). TEA significantly suppressed sympathetic activity, as indicated by a less pronounced increase of norepinephrine and epinephrine (p = 0.03, p = 0.02) and a significant decrease of neuropeptide Y (p = 0.01) postoperatively in TEA-treated patients compared to untreated patients. The HRV variable expressing sympathetic activity was significantly lower and the postoperative increase in heart rate was significantly less in the TEA group than in the control group after surgery (p = 0.01, p < 0.001). Among patients developing AF, the maximal number of supraventricular premature beats per minute increased significantly in untreated patients postoperatively but remained unchanged in TEA-treated patients (p = 0.004 versus p = 0.86).

CONCLUSIONS

TEA has no effect on the incidence of postoperative sustained AF, despite a significant reduction in sympathetic activity.

Nonnoradrenergic mechanism of reflex cutaneous vasoconstriction in men

We tested for a nonnoradrenergic mechanism of reflex cutaneous vasoconstriction with whole body progressive cooling in seven men. Forearm sites (<1 cm(2)) were pretreated with: 1) yohimbine (Yoh; 5 mM id) to antagonize alpha-adrenergic receptors, 2) Yoh plus propranolol (5 mM Yoh-1 mM PR id) to block alpha- and beta-adrenergic receptors, 3) iontophoretic application of bretylium tosylate (BT) to block all sympathetic vasoconstrictor nerve effects, or 4) intradermal saline. Skin blood flow was measured by laser Doppler flowmetry and arterial pressure by finger photoplethysmography; cutaneous vascular conductance (CVC) was indexed as the ratio of the two. Whole body skin temperature (T(SK)) was controlled at 34 degrees C (water-perfused suit) for 10 min and then lowered to 31 degrees C over 15 min. During cooling, vasoconstriction was blocked at BT sites (P > 0.05). CVC at saline sites fell significantly beginning at T(SK) of 33.4 +/- 0.01 degrees C (P <0.05). CVC at Yoh-PR sites was significantly reduced beginning at TSK of 33.0 +/- 0.01 degrees C (P < 0.05). After cooling, iontophoretic application of norepinephrine (NE) confirmed blockade of adrenergic receptors by Yoh-PR. Because the effects of NE were blocked at sites showing significant reflex vasoconstriction, a nonnoradrenergic mechanism in human skin is indicated, probably via a sympathetic cotransmitter.

Postexercise ischemia is associated with increased neuropeptide Y in patients with coronary artery disease

BACKGROUND

Neurohormones may influence vascular tone both during and after exercise. Neuropeptide Y (NPY), which is costored and released with norepinephrine (NE) during sympathetic activity, is a potent vasoconstrictor with a relatively long half-life. We therefore examined its possible association with the ischemic response to exercise in patients with coronary artery disease.

METHODS AND RESULTS

Twenty-nine male patients with effort-induced angina pectoris underwent a symptom-limited exercise test. In addition to conventional ST-segment analysis, we examined ischemia on the basis of heart rate (HR)-adjusted ST-segment changes through calculation of the ST/HR slope during the final 4 minutes of exercise and of the ST/HR recovery loop after exercise. Blood samples were taken before, during, and after exercise for an analysis of several neurohormones. Mean ST-segment depression was -223+/-20.2 microV (P:<0.0001) just before the termination of exercise, followed by a gradual normalization, but it remained significant after 10 minutes (-49+/-8.9 microV, P:<0.0001). At the end of exercise, the ST/HR slope, which reflects myocardial ischemia, was -6.0+/-0.77 microV/HR. In most patients, ST-segment levels at a given HR were lower during recovery than during exercise, here referred to as ST "deficit." Exercise increased the plasma levels of NPY, NE, epinephrine, and N-terminal proatrial natriuretic peptide, but big endothelin remained unchanged. Although NE and epinephrine peaked at maximal exercise, the highest levels of NPY and N-terminal proatrial natriuretic peptide were observed 4 minutes after exercise. The maximal increase in the NPY correlated significantly with ST-segment depression at 3 minutes after exercise (r=-0.61, P:= 0.0005), the ST deficit at the corresponding time point (r=-0.66, P:= 0.0001), and the duration of ST-segment depression after exercise (r= 0.42, P:=0.02). In contrast, no such correlations were found for NE.

CONCLUSIONS

The present study has for the first time demonstrated a correlation between plasma NPY levels and the degree and duration of ST-segment depression after exercise in patients with coronary artery disease, which suggests that NPY may contribute to myocardial ischemia in these patients.

Plasma neuropeptide-Y concentrations in humans exposed to military survival training

BACKGROUND

Neuropeptide-Y (NPY) is present in extensive neuronal systems of the brain and is present in high concentrations in cell bodies and terminals in the amygdala. Preclinical studies have shown that injections of NPY into the central nucleus of the amygdala function as a central anxiolytic and buffer against the effects of stress. The objective of this study was to assess plasma NPY immunoreactivity in healthy soldiers participating in high intensity military training at the U.S. Army survival school. The Army survival school provides a means of observing individuals under high levels of physical, environmental, and psychological stress, and consequently is considered a reasonable analogue to stress incurred as a result of war or other catastrophic experiences.

METHODS

Plasma levels of NPY were assessed at baseline (prior to initiation of training), and 24 hours after the conclusion of survival training in 49 subjects, and at baseline and during the Prisoner of War (P.O.W.) experience (immediately after exposure to a military interrogation) in 21 additional subjects.

RESULTS

Plasma NPY levels were significantly increased compared to baseline following interrogations and were significantly higher in Special Forces soldiers, compared to non-Special Forces soldiers. NPY elicited by interrogation stress was significantly correlated to the subjects' behavior during interrogations and tended to be negatively correlated to symptoms of reported dissociation. Twenty-four hours after the conclusion of survival training, NPY had returned to baseline in Special Forces soldiers, but remained significantly lower than baseline values in non-Special Forces soldiers. NPY was positively correlated with both cortisol and behavioral performance under stress. NPY was negatively related to psychological symptoms of dissociation.

CONCLUSIONS

These results provide evidence that uncontrollable stress significantly increases plasma NPY in humans, and when extended, produces a significant depletion of plasma NPY. Stress-induced alterations of plasma NPY were significantly different in Special Forces soldiers compared to non-Special Forces soldiers. These data support the idea that NPY may be involved in the enhanced stress resilience seen in humans.

Increased concentrations of plasma neuropeptide Y in patients with eclampsia and preeclampsia

OBJECTIVE

Epinephrine and norepinephrine are associated with the hyperstimulation of the sympathetic nervous system. Neuropeptide Y is a potent vasoconstrictive substance that is released in response to sympathetic nerve stimulation.

STUDY DESIGN

The concentrations of plasma neuropeptide Y in pregnant patients with eclampsia (n = 8), preeclampsia (n = 8), and normotension (n = 8) were measured by radioimmunoassay on admission and 6 days after delivery. Correlations between plasma concentration of neuropeptide Y and mean arterial blood pressure were also evaluated in these patients on admission and 6 days after delivery.

RESULTS

The plasma level of neuropeptide Y in women with eclampsia (P <.001) and preeclampsia (P <.003) was found to be significantly elevated with respect to that in normotensive pregnant women. At 6 days after delivery the concentration of plasma neuropeptide Y was significantly decreased in women with eclampsia, women with preeclampsia, and women with normotensive pregnancies compared with the value measured on admission (P <.0001, P <.0001, and P <.002, respectively). At admission the plasma neuropeptide Y level was positively correlated with mean arterial blood pressure in women with eclampsia and preeclampsia. However, no significant correlations were observed between plasma neuropeptide Y concentration and mean arterial blood pressure both at admission and 6 days after delivery in normotensive pregnant women and 6 days after delivery in women with eclampsia and preeclampsia.

CONCLUSION

We have concluded that the level of neuropeptide Y in plasma is increased in women with eclampsia and preeclampsia. Elevated plasma neuropeptide Y levels may play a key role in the development of eclampsia and preeclampsia.

Low baseline and yohimbine-stimulated plasma neuropeptide Y (NPY) levels in combat-related PTSD

BACKGROUND

Consistent with many studies demonstrating enhanced reactivity of the sympathetic nervous system in posttraumatic stress disorder (PTSD), the administration of yohimbine, a noradrenergic alpha(2)-antagonist, has been shown to increase core symptoms of PTSD and to induce greater increases in plasma 3-methyl-4-hydroxy-phenyl-glycol (MHPG) in subjects with PTSD compared with healthy control subjects. In turn, neuropeptide Y (NPY) has been shown to inhibit the release of norepinephrine from sympathetic noradrenergic neurons.

METHODS

In the following study, plasma NPY responses to yohimbine and placebo were measured in a subgroup of 18 subjects with PTSD and 8 healthy control subjects who participated in the previous study of the effect of yohimbine on plasma MHPG.

RESULTS

The PTSD subjects had lower baseline plasma NPY and blunted yohimbine-stimulated increases in plasma NPY compared with the healthy control subjects. Within the PTSD group, baseline plasma NPY levels correlated negatively with combat exposure scale scores, baseline PTSD and panic symptoms, and yohimbine-stimulated increases in MHPG and systolic blood pressure.

CONCLUSIONS

This study suggests that combat stress-induced decreases in plasma NPY may mediate, in part, the noradrenergic system hyperreactivity observed in combat-related PTSD. The persistence of this decrease in plasma NPY may contribute to symptoms of hyperarousal and the expression of exaggerated alarm reactions, anxiety reactions, or both in combat veterans with PTSD long after war.