Expression of neuropeptide Y and its receptors Y1 and Y2 in the rat heart and its supplying autonomic and spinal sensory ganglia in experimentally induced diabetes

Multiomics analysis of canine myocardium after circumferential pulmonary vein ablation: Effect of neuropeptide Y on long-term reinduction of atrial fibrillation

Catheter ablation (CA) is an essential method for the interventional treatment of atrial fibrillation (AF), and it is very important to reduce long-term recurrence after CA. The mechanism of recurrence after CA is still unclear. We established a long-term model of beagle canines after circumferential pulmonary vein ablation (CPVA). The transcriptome and proteome were obtained using high-throughput sequencing and TMT-tagged LC-MS/LC analysis, respectively. Differentially expressed genes and proteins were screened and enriched, and the effect of fibrosis was found and verified in tissues. A downregulated protein, neuropeptide Y (NPY), was selected for validation and the results suggest that NPY may play a role in the long-term reinduction of AF after CPVA. Then, the molecular mechanism of NPY was further investigated. The results showed that the atrial effective refractory period (AERP) was shortened and fibrosis was increased after CPVA. Atrial myocyte apoptosis was alleviated by NPY intervention, and Akt activation was inhibited in cardiac fibroblasts. These results suggest that long-term suppression of NPY after CPVA may lead to induction of AF through promoting cardiomyocyte apoptosis and activating the Akt pathway in cardiac fibroblasts, which may make AF more likely to reinduce.

Cardiac innervations in diabetes mellitus-Anatomical evidence of neuropathy

The extensive innervations of the heart include a complex network of sympathetic, parasympathetic, and sensory nerves connected in loops that serve to regulate cardiac output. Metabolic dysfunction in diabetes affects many different organ systems, including the cardiovascular system; it causes cardiac arrhythmias, silent myocardial ischemia, and sudden cardiac death, among others. These conditions are associated with damage to the nerves that innervate the heart, cardiac autonomic neuropathy (CAN), which is caused by various pathophysiological mechanisms. In this review, the main facts about the anatomy of cardiac innervations and the current knowledge of CAN, its pathophysiological mechanisms, and its diagnostic approach are discussed. In addition, anatomical evidence for CAN from human and animal studies has been summarized.

Regulation of Prepro-NeuropeptideW/B and Its Receptor in the Heart of ZDF Rats: An Animal Model of Type II DM

Neuropeptide B (NPB) and neuropeptide W (NPW) are neuropeptides, which constitute NPB/W signaling systems together with G-protein coupled receptors NPBWR1. The location and function of NPB/W signaling systems have been predominantly detected and mapped within the CNS, including their role in the modulation of inflammatory pain, neuroendocrine functions, and autonomic nervous systems. The aim of the study is to investigate the impact of diabetes on the neuropeptide B/W signaling system in different heart compartments and neurons which innervates it. In the RT-qPCR analysis, we observed the upregulation of mRNA for preproNPB in RV, for preproNPW in LA, and for NPBWR1 in DRG in diabetic rats. On the contrary, the expression of mRNA for NPBWR1 was downregulated in LV in diabetic rats. In the WB analysis, significant downregulation of NPBWR1 in LV (0.54-fold, p = 0.046) in diabetic rats was observed at the proteomic level. The presence of NPBWR1 was also confirmed in a dissected LCM section of cardiomyocytes and coronary arteries. The positive inotropic effect of NPW described on the diabetic cardiomyocytes in vitro could point to a possible therapeutic target for compensation of the contractile dysfunction in the diabetic heart. In conclusion, the NPB/W signaling system is involved in the regulation of heart functions and long-term diabetes leads to changes in the expression of individual members of this signaling system differently in each cardiac compartment, which is related to the different morphology and function of these cardiac chambers.

Identification of NPB, NPW and Their Receptor in the Rat Heart

Members of neuropeptide B/W signaling system have been predominantly detected and mapped within the CNS. In the rat, this system includes neuropeptide B (NPB), neuropeptide W (NPW) and their specific receptor NPBWR1. This signaling system has a wide spectrum of functions including a role in modulation of inflammatory pain and neuroendocrine functions. Expression of NPB, NPW and NPBWR1 in separate heart compartments, dorsal root ganglia (DRG) and stellate ganglia was proven by RT-qPCR, Western blot (WB) and immunofluorescence. Presence of mRNA for all tested genes was detected within all heart compartments and ganglia. The presence of proteins preproNPB, preproNPW and NPBWR1 was confirmed in all the chambers of heart by WB. Expression of preproNPW and preproNPB was proven in cardiac ganglionic cells obtained by laser capture microdissection. In immunofluorescence analysis, NPB immunoreactivity was detected in nerve fibers, some nerve cell bodies and smooth muscle within heart and both ganglia. NPW immunoreactivity was present in the nerve cell bodies and nerve fibers of heart ganglia. Weak nonhomogenous staining of cardiomyocytes was present within heart ventricles. NPBWR1 immunoreactivity was detected on cardiomyocytes and some nerve fibers. We confirmed the presence of NPB/W signaling system in heart, DRG and stellate ganglia by proteomic and genomic analyses.

Melatonin alleviates cardiac fibrosis via inhibiting lncRNA MALAT1/miR-141-mediated NLRP3 inflammasome and TGF-β1/Smads signaling in diabetic cardiomyopathy

Melatonin is a hormone produced by the pineal gland, and it has extensive beneficial effects on various tissue and organs; however, whether melatonin has any effect on cardiac fibrosis in the pathogenesis of diabetic cardiomyopathy (DCM) is still unknown. Herein, we found that melatonin administration significantly ameliorated cardiac dysfunction and reduced collagen production by inhibiting TGF-β1/Smads signaling and NLRP3 inflammasome activation, as manifested by downregulating the expression of TGF-β1, p-Smad2, p-Smad3, NLRP3, ASC, cleaved caspase-1, mature IL-1β, and IL-18 in the heart of melatonin-treated mice with diabetes mellitus (DM). Similar beneficial effects of melatonin were consistently observed in high glucose (HG)-treated cardiac fibroblasts (CFs). Moreover, we also found that lncRNA MALAT1 (lncR-MALAT1) was increased along with concomitant decrease in microRNA-141 (miR-141) in DM mice and HG-treated CFs. Furthermore, we established NLRP3 and TGF-β1 as target genes of miR-141 and lncR-MALAT1 as an endogenous sponge or ceRNA to limit the functional availability of miR-141. Finally, we observed that knockdown of miR-141 abrogated anti-fibrosis action of melatonin in HG-treated CFs. Our findings indicate that melatonin produces an antifibrotic effect via inhibiting lncR-MALAT1/miR-141-mediated NLRP3 inflammasome activation and TGF-β1/Smads signaling, and it might be considered a potential agent for the treatment of DCM.

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.

Deletion of Neuropeptide Y Attenuates Cardiac Dysfunction and Apoptosis During Acute Myocardial Infarction

Increasing neuropeptide Y (NPY) has been shown to be a risk factor for cardiovascular diseases. However, its role and mechanism in myocardial infarction (MI) have not yet been fully understood. H9c2 cells and neonatal rat ventricular myocytes with loss of function of NPY and rats with global knockout were used in this study. MI model of rats was induced by the ligation of left coronary artery, and the extent of MI was analyzed through echocardiographic, pathological, and molecular analyses. Our data demonstrated that NPY expression was significantly increased in MI rats and hypoxia/hydrogen peroxide (H₂O₂)-treated cardiomyocytes. At the same time, NPY-knockout rats exhibited a remarkable decrease in infarct size, serum lactate dehydrogenase activity, cardiomyocyte apoptosis, and caspase-3 expression and activity and a strong improvement in heart contractile function compared with MI rats. Meanwhile, NPY small interfering RNA (siRNA) inhibited the cell apoptosis in H₂O₂-treated H9c2 cells and hypoxia-treated neonatal rat ventricular myocytes. NPY deletion increased miR-499 expression and decreased FoxO4 expression in MI in vivo and in vitro. Moreover, NPY type 1 receptor antagonist BIBO3304 can reverse miR-499 decrease and FoxO4 increase in H₂O₂-induced cardiomyocytes. NPY siRNA inhibited cell apoptosis in H₂O₂-treated H9c2 cells that were reversed by miR-499 inhibitor. Additionally, FoxO4 was validated as the direct target of miR-499. Moreover, BIBO3304 and FoxO4 siRNA significantly increased the cell activity, inhibited the cell apoptosis, and decreased caspase-3 expression and activity in H₂O₂-treated cardiomyocytes that NPY presented the opposite effect. Collectively, deletion of NPY reduced myocardial ischemia, improved cardiac function, and inhibited cardiomyocyte apoptosis by NPY type 1 receptor–miR-499–FoxO4 axis, which provides a new treatment for MI.

The Role of Neuropeptide Y in Cardiovascular Health and Disease

Neuropeptide Y (NPY) is an abundant sympathetic co-transmitter, widely found in the central and peripheral nervous systems and with diverse roles in multiple physiological processes. In the cardiovascular system it is found in neurons supplying the vasculature, cardiomyocytes and endocardium, and is involved in physiological processes including vasoconstriction, cardiac remodeling, and angiogenesis. It is increasingly also implicated in cardiovascular disease pathogenesis, including hypertension, atherosclerosis, ischemia/infarction, arrhythmia, and heart failure. This review will focus on the physiological and pathogenic role of NPY in the cardiovascular system. After summarizing the NPY receptors which predominantly mediate cardiovascular actions, along with their signaling pathways, individual disease processes will be considered. A thorough understanding of these roles may allow therapeutic targeting of NPY and its receptors.

Substance P Receptor in the Rat Heart and Regulation of Its Expression in Long-Term Diabetes

Substance P (SP) is a neuropeptide engaged in the signal transmission of neural C fibers afferents in the myocardium. The actions of SP in the heart are extensive and they are mediated by the neurokinin 1 receptor (NK1R), a member of the tachykinin subfamily of G-protein coupled receptors. The receptors have been found in the heart, but to our knowledge, their exact localization in the heart has not been described yet. Here, we investigated the presence of NK1R protein in separate rat heart compartments by means of western blot and its tissue distribution by means of immunofluorescence. Specificity of NK1R immunolabeling was controlled by preabsorption of the antiserum with its corresponding peptide. Additionally, we investigated abundance of gene for NK1R in separated heart chambers by means of quantitative real-time PCR (RT-PCR). Relative abundance of NK1R mRNA was expressed as a ratio of target gene Cq value to Cq value of control gene - beta-actin. Finally, we studied abundance of NK1R mRNA in different cell types of heart isolated by laser capture microdissection. Immunofluorescence showed NK1R immunoreactivity on the surface of some intracardiac neurons and smooth muscle cells of coronary vessels. The results of quantitative RT-PCR indicate abundance of mRNA for NK1R in all heart chambers with highest level in the left atrium. The presence of NK1R mRNA was detected in some samples of dissected intracardiac neurons, but not in cardiomyocytes or smooth muscle cells of coronary vessels. In the course of long-term diabetes, a significant downregulation of the NK1R mRNA was seen in the right atrium and upregulation in the right ventricle 53 weeks after the induction of diabetes. Our results indicate localization of NK1R in some intracardiac neurons and smooth muscle cells. Impaired transcription of the NK1R gene in the diabetic heart may be induced by unidentified genes or factors involved in the development of diabetic cardiomyopathy.

Vascularisation for cardiac tissue engineering: the extracellular matrix

Cardiovascular diseases present a major socio-economic burden. One major problem underlying most cardiovascular and congenital heart diseases is the irreversible loss of contractile heart muscle cells, the cardiomyocytes. To reverse damage incurred by myocardial infarction or by surgical correction of cardiac malformations, the loss of cardiac tissue with a thickness of a few millimetres needs to be compensated. A promising approach to this issue is cardiac tissue engineering. In this review we focus on the problem of in vitro vascularisation as implantation of cardiac patches consisting of more than three layers of cardiomyocytes (> 100 μm thick) already results in necrosis. We explain the need for vascularisation and elaborate on the importance to include non-myocytes in order to generate functional vascularised cardiac tissue. We discuss the potential of extracellular matrix molecules in promoting vascularisation and introduce nephronectin as an example of a new promising candidate. Finally, we discuss current biomaterial- based approaches including micropatterning, electrospinning, 3D micro-manufacturing technology and porogens. Collectively, the current literature supports the notion that cardiac tissue engineering is a realistic option for future treatment of paediatric and adult patients with cardiac disease.

Novel role of NPY in neuroimmune interaction and lung growth after intrauterine growth restriction

Individuals with intrauterine growth restriction (IUGR) are at risk for chronic lung disease. Using a rat model, we showed in our previous studies that altered lung structure is related to IL-6/STAT3 signaling. As neuropeptide Y (NPY), a coneurotransmitter of the sympathetic nervous system, regulates proliferation and immune response, we hypothesized that dysregulated NPY after IUGR is linked to IL-6, impaired myofibroblast function, and alveolar growth. IUGR was induced in rats by isocaloric low-protein diet; lungs were analyzed on embryonic day (E) 21, postnatal day (P) 3, P12, and P23. Finally, primary neonatal lung myofibroblasts (pnF) and murine embryonic fibroblasts (MEF) were used to assess proliferation, apoptosis, migration, and IL-6 expression. At E21, NPY and IL-6 expression was decreased, and AKT/PKC and STAT3/AMPKα signaling was reduced. Early reduction of NPY/IL-6 was associated with increased chord length in lungs after IUGR at P3, indicating reduced alveolar formation. At P23, however, IUGR rats exhibited a catch-up of body weight and alveolar growth coupled with more proliferating myofibroblasts. These structural findings after IUGR were linked to activated NPY/PKC, IL-6/AMPKα signaling. Complementary, IUGR-pnF showed increased survival, impaired migration, and reduced IL-6 compared with control-pnF (Co-pnF). In contrast, NPY induced proliferation, migration, and increased IL-6 synthesis in fibroblasts. Additionally, NPY^-/- mice showed reduced IL-6 signaling and less proliferation of lung fibroblasts. Our study presents a novel role of NPY during alveolarization: NPY regulates 1) IL-6 and lung STAT3/AMPKα signaling, and 2) proliferation and migration of myofibroblasts. These new insights in pulmonary neuroimmune interaction offer potential strategies to enable lung growth.

Diabetes mellitus influences the expression of NPY and VEGF in neurons of rat trigeminal ganglion

BACKGROUND

Diabetes mellitus (DM) influences the trigeminal nerve function by changing the pain response and transduction of the orofacial sensory pathways. It affects the inflammatory response via neuropeptide Y (NPY) and vascular endothelial growth factor (VEGF), which could potentially have a relevant role in the pathophysiology of diabetic neuropathy. The aim was to investigate expression of VEGF and NPY in subpopulations of trigeminal ganglion (TG) neurons in rat models of early DM1 and DM2.

METHODS

DM1 model was induced by an intraperitoneal (i.p.) injection of streptozotocin (STZ) (55mg/kg). DM2 rats were fed with a high fat diet (HFD) for two weeks and then received 35mg/kg of STZ i.p. Two weeks and 2months after the STZ-diabetes induction, rats were sacrificed and TG was immunohistochemically analyzed for detection of VEGF and NPY expression, and also double immunofluorescence labeling with isolectin (IB4) was completed.

RESULTS

An increased percentage of NPY+ neurons was observed 2weeks after DM1 and 2months post DM2 induction. NPY immunoreactivity was restricted to IB4-negative small-diameter and IB4+ neurons. Two weeks post induction, DM1 rats showed an increased percentage of VEGF/IB4- large neurons and DM2 rats showed an increased percentage of VEGF/IB4+ neurons. Two months after DM induction, the DM1 group showed a reduced percentage of VEGF/IB4- small neurons.

CONCLUSION

The observed changes may play a critical role in the modulation of nociceptor activity and plasticity of primary sensory trigeminal neurons. The results contribute to the understanding of the basic pathophysiology of trigeminal diabetic neuropathy.

Neuropeptide Y is an angiogenic factor in cardiovascular regeneration

In diabetic cardiomyopathy, there is altered angiogenic signaling and increased oxidative stress. As a result, anti-angiogenic and pro-inflammatory pathways are activated. These disrupt cellular metabolism and cause fibrosis and apoptosis, leading to pathological remodeling. The autonomic nervous system and neurotransmitters play an important role in angiogenesis. Therapies that promote angiogenesis may be able to relieve the pathology in these disease states. Neuropeptide Y (NPY) is the most abundantly produced and expressed neuropeptide in the central and peripheral nervous systems in mammals and plays an important role in promoting angiogenesis and cardiomyocyte remodeling. It produces effects through G-protein-coupled Y receptors that are widely distributed and also present on the myocardium. Some of these receptors are also involved in diseased states of the heart. NPY has been implicated as a potent growth factor, causing cell proliferation in multiple systems while the NPY3-36 fragment is selective in stimulating angiogenesis and cardiomyocyte remodeling. Current research is focusing on developing a drug delivery mechanism for NPY to prolong therapy without having significant systemic consequences. This could be a promising innovation in the treatment of diabetic cardiomyopathy and ischemic heart disease.

Development of neuropeptide Y-mediated heart innervation in rats

Neuropeptide Y (NPY) plays a trophic role in the nervous and vascular systems and in cardiac hypertrophy. However, there is no report concerning the expression of NPY and its receptors in the heart during postnatal development. In the current study, immunohistochemistry and Western blot analysis was used to label NPY, and Y1R, Y2R, and Y5R receptors in the heart tissue and intramural cardiac ganglia from rats of different ages (newborn, 10 days old, 20 days old, 30 days old, 60 days old, 1 year old, and 2 years old).The obtained data suggest age-dependent changes of NPY-mediated heart innervation. The density of NPY-immunoreactive (IR) fibers was the least in newborn animals and increased in the first 20 days of life. In the atria of newborn and 10-day-old rats, NPY-IR fibers were more abundant compared with the ventricles. The vast majority of NPY-IR fibers also contained tyrosine hydroxylase, a key enzyme in catecholamine synthesis.The expression of Y1R increased between 10 and 20 days of life. Faint Y2R immunoreactivity was observed in the atria and ventricles of 20-day-old and older rats. In contrast, the highest level of the expression of Y5R was found in newborn pups comparing with more adult rats. All intramural ganglionic neurons were also Y1R-IR and Y5R-IR and Y2R-negative in all studied animals.Thus, the increasing of density of NPY-containing nerve fibers accompanies changes in relation of different subtypes of NPY receptors in the heart during development.

Cardiomyocyte proliferation in cardiac development and regeneration: a guide to methodologies and interpretations

The newt and the zebrafish have the ability to regenerate many of their tissues and organs including the heart. Thus, a major goal in experimental medicine is to elucidate the molecular mechanisms underlying the regenerative capacity of these species. A wide variety of experiments have demonstrated that naturally occurring heart regeneration relies on cardiomyocyte proliferation. Thus, major efforts have been invested to induce proliferation of mammalian cardiomyocytes in order to improve cardiac function after injury or to protect the heart from further functional deterioration. In this review, we describe and analyze methods currently used to evaluate cardiomyocyte proliferation. In addition, we summarize the literature on naturally occurring heart regeneration. Our analysis highlights that newt and zebrafish heart regeneration relies on factors that are also utilized in cardiomyocyte proliferation during mammalian fetal development. Most of these factors have, however, failed to induce adult mammalian cardiomyocyte proliferation. Finally, our analysis of mammalian neonatal heart regeneration indicates experiments that could resolve conflicting results in the literature, such as binucleation assays and clonal analysis. Collectively, cardiac regeneration based on cardiomyocyte proliferation is a promising approach for improving adult human cardiac function after injury, but it is important to elucidate the mechanisms arresting mammalian cardiomyocyte proliferation after birth and to utilize better assays to determine formation of new muscle mass.

New insights in (inter)cellular mechanisms by heart failure with preserved ejection fraction

Recently, a new paradigm for the development of heart failure with preserved ejection fraction (HFpEF) has been proposed, which identifies a systemic pro-inflammatory state induced by comorbidities as the origin of microvascular endothelial cell inflammation and subsequent concentric cardiac remodeling and dysfunction. This review further discusses the pivotal role of the inflamed endothelium in the pathogenesis of HFpEF-specific cardiac remodeling. The potential importance of reciprocal interactions of the endothelium with cardiac fibroblasts and cardiomyocytes and with the cardiac neurohumoral response in this cardiac remodeling process is outlined.

Autonomic control of the heart: going beyond the classical neurotransmitters

Acute myocardial infarction and congestive cardiac failure are characterized by high levels of cardiac sympathetic drive. In these conditions, sympathetic neurotransmitters such as neuropeptide Y (NPY) can be released in addition to noradrenaline, and plasma levels correlate with infarct size and mortality. Even in the presence of β-blockers, NPY is able to bind to its own receptors located on cholinergic ganglia and ventricular myocytes. In this symposium report, I review the evidence that NPY can inhibit acetylcholine release during vagus nerve stimulation and limit the subsequent bradycardia. I also present preliminary, as yet unpublished data, demonstrating that NPY may be pro-arrhythmic by directly influencing ventricular electrophysiology. Targeting NPY receptors pharmacologically may therefore be a useful therapeutic strategy both to reduce heart rate and to prevent arrhythmias in the setting of myocardial infarction and chronic heart failure. Such medications would be expected to act synergistically with β-blockers, angiotensin-converting enzyme inhibitors and implantable cardiac devices, such as defibrillators and vagus nerve stimulators.

Role of neuropeptides in cardiomyopathies

The role of neuropeptides in cardiomyopathy-associated heart failure has been garnering more attention. Several neuropeptides--Neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), calcitonin gene related peptide (CGRP), substance P (SP) and their receptors have been studied in the various types of cardiomyopathies. The data indicate associations with the strength of the association varying depending on the kind of neuropeptide and the nature of the cardiomyopathy--diabetic, ischemic, inflammatory, stress-induced or restrictive cardiomyopathy. Several neuropeptides appear to alter regulation of genes involved in heart failure. Demonstration of an association is an essential first step in proving causality or establishing a role for a factor in a disease. Understanding the complexity of neuropeptide function should be helpful in establishing new or optimal therapeutic strategies for the treatment of heart failure in cardiomyopathies.

Autonomic neuropathy in experimental models of diabetes mellitus

Autonomic neuropathy complicates diabetes by increasing patient morbidity and mortality. Surprisingly, considering its importance, development and exploitation of animal models has lagged behind the wealth of information collected for somatic symmetrical sensory neuropathy. Nonetheless, animal studies have resulted in a variety of insights into the pathogenesis, neuropathology, and pathophysiology of diabetic autonomic neuropathy (DAN) with significant and, in some cases, remarkable correspondence between rodent models and human disease. Particularly in the study of alimentary dysfunction, findings in intrinsic intramural ganglia, interstitial cells of Cajal and the extrinsic parasympathetic and sympathetic ganglia serving the bowel vie for recognition as the chief mechanism. A body of work focused on neuropathologic findings in experimental animals and human subjects has demonstrated that axonal and dendritic pathology in sympathetic ganglia with relative neuron preservation represents one of the neuropathologic hallmarks of DAN but it is unlikely to represent the entire story. There is a surprising selectivity of the diabetic process for subpopulations of neurons and nerve terminals within intramural, parasympathetic, and sympathetic ganglia and innervation of end organs, afflicting some while sparing others, and differing between vascular and other targets within individual end organs. Rather than resulting from a simple deficit in one limb of an effector pathway, autonomic dysfunction may proceed from the inability to integrate portions of several complex pathways. The selectivity of the diabetic process appears to confound a simple global explanation (e.g., ischemia) of DAN. Although the search for a single unifying pathogenetic hypothesis continues, it is possible that autonomic neuropathy will have multiple pathogenetic mechanisms whose interplay may require therapies consisting of a cocktail of drugs. The role of multiple neurotrophic substances, antioxidants (general or pathway specific), inhibitors of formation of advanced glycosylation end products and drugs affecting the polyol pathway may be complex and therapeutic elements may have both salutary and untoward effects. This review has attempted to present the background and current findings and hypotheses, focusing on autonomic elements including and beyond the typical parasympathetic and sympathetic nervous systems to include visceral sensory and enteric nervous systems.

Local infiltration of neuropeptide Y as a potential therapeutic agent against apoptosis and fibrosis in a swine model of hypercholesterolemia and chronic myocardial ischemia

While the angiogenic effects of Neuropeptide Y (NPY) in myocardial ischemia and hypercholesterolemia have been studied, its effects on altering oxidative stress, fibrosis and cell death are not known. We hypothesized that local infiltration of NPY in a swine model of chronic myocardial ischemia and hypercholesterolemia will induce nerve growth and cell survival, while reducing oxidative stress and fibrosis. Yorkshire mini-swine (n=15) were fed a high cholesterol diet for 5 weeks. Three weeks after surgical induction of focal myocardial ischemia, an osmotic pump was implanted, which delivered NPY (n=8, high cholesterol treated, HCT) or the vehicle (n=7, high cholesterol control, HCC) for 5 weeks. Then myocardium was harvested for analysis. Assessment of myocardial function and perfusion was made the last intervention. Immunoblotting demonstrated significantly decreased levels of MMP-9 (p=0.001) and TGF-β (p=0.05) and significantly increased levels of Ang-1 (p=0.002), MnSOD (p=0.006) and NGF (p=0.01) in HCT. Immunohistochemistry results revealed significantly decreased TUNEL staining (p=0.005) and GLUT4 translocation (p=0.004) in HCT. The functional data showed significantly improved blood flow reserve (p=0.02) and improved diastolic function -dP/dt (p=0.009) in the treated animals. Local infiltration of NPY results in positive remodeling in ischemic myocardium in the setting of hypercholesterolemia. By initiating angio and neurogenesis, NPY infiltration improves blood flow reserve and restoration of fatty acid metabolism. The associated increased cell survival and decreased fibrosis result in improved myocardial diastolic function. NPY may have a potential therapeutic role in patients with hypercholesterolemia associated coronary artery disease.

Remodelling of the intracardiac ganglia in diabetic Goto-Kakizaki rats: an anatomical study

Background

Although cardiac autonomic neuropathy is one of major complications of diabetes mellitus (DM), anatomical data on cardiac innervation of diabetic animal models is scant and controversial. We performed this study to check whether long-term diabetic state impacts the anatomy of intracardiac ganglia in Goto-Kakizaki (GK) rats, a genetic model of type 2 DM.

Methods

Twelve GK rats (276 ± 17 days of age; mean ± standard error) and 13 metabolically healthy Wistar rats (262 ± 5 days of age) as controls were used for this study. Blood glucose was determined using test strips, plasma insulin by radioimmunoassay. Intrinsic ganglia and nerves were visualized by acetylcholinesterase histochemistry on whole hearts. Ganglion area was measured, and the neuronal number was assessed according to ganglion area.

Results

The GK rats had significantly elevated blood glucose level compared to controls (11.0 ± 0.6 vs. 5.9 ± 0.1 mmol/l, p < 0.001), but concentration of plasma insulin did not differ significantly between the two groups (84.0 ± 9.8 vs. 67.4 ± 10.9 pmol/l, p = 0.17). The GK rats contained significantly fewer intracardiac ganglia, decreased total area of intracardiac ganglia (1.4 ± 0.1 vs. 2.2 ± 0.1 mm², p < 0.001) and smaller somata of ganglionic neurons. Mean total number of intracardiac neurons in GK rats was 1461 ± 62, while this number in control rats was higher by 39% and reached 2395 ± 110 (p < 0.001).

Conclusions

Results of our study demonstrate the decreased number of intracardiac neurons in GK rats compared to metabolically healthy Wistar rats of similar age. It is likely that the observed structural remodelling of intracardiac ganglia in GK rats is caused by a long-term diabetic state.

Pre-diabetes augments neuropeptide Y1- and α1-receptor control of basal hindlimb vascular tone in young ZDF rats

BACKGROUND

Peripheral vascular disease in pre-diabetes may involve altered sympathetically-mediated vascular control. Thus, we investigated if pre-diabetes modifies baseline sympathetic Y(1)-receptor (Y(1)R) and α(1)-receptor (α(1)R) control of hindlimb blood flow (Q(fem)) and vascular conductance (VC).

METHODS

Q(fem) and VC were measured in pre-diabetic ZDF rats (PD) and lean controls (CTRL) under infusion of BIBP3226 (Y(1)R antagonist), prazosin (α(1)R antagonist) and BIBP3226+prazosin. Neuropeptide Y (NPY) concentration and Y(1)R and α(1)R expression were determined from hindlimb skeletal muscle samples.

RESULTS

Baseline Q(fem) and VC were similar between groups. Independent infusions of BIBP3226 and prazosin led to increases in Q(fem) and VC in CTRL and PD, where responses were greater in PD (p<0.05). The percent change in VC following both drugs was also greater in PD compared to CTRL (p<0.05). As well, Q(fem) and VC responses to combined blockade (BIBP3226+prazosin) were greater in PD compared to CTRL (p<0.05). Interestingly, an absence of synergistic effects was observed within groups, as the sum of the VC responses to independent drug infusions was similar to responses following combined blockade. Finally, white and red vastus skeletal muscle NPY concentration, Y(1)R expression and α(1)R expression were greater in PD compared to CTRL.

CONCLUSIONS

For the first time, we report heightened baseline Y(1)R and α(1)R sympathetic control of Q(fem) and VC in pre-diabetic ZDF rats. In support, our data suggest that augmented sympathetic ligand and receptor expression in pre-diabetes may contribute to vascular dysregulation.

Expression of Neuropeptide Y, Substance P, and their receptors in the right atrium of diabetic patients

OBJECTIVE

To investigate the expression of neuropeptides and their receptors that play a role in cardiac homeostasis in the right atrium of nondiabetic and diabetic patients undergoing coronary artery bypass graft surgery.

BACKGROUND

The cardioactive neuropeptides and their receptors investigated in this study were Neuropeptide Y (NPY), and its receptors, NPY Receptor1 (NPY1R), NPY Receptor2 (NPY2R), NPY Receptor5 (NPY5R) and Substance P (SP) and its receptor, Neurokinin1R (NK1R).

METHODS

The gene and protein expression of NPY, NPY1R, NPY2R, NPY5R, SP and NK1R from the atrial tissue of 10 nondiabetic and diabetic patients undergoing coronary artery bypass grafting (CABG) was assessed by Q-RTPCR, immunohistochemistry, Western blot, and ELISA.

RESULTS

Gene expression of NPY2R, NPY5R, preproTachykinin A (SP gene), and NK1R and their respective protein expression were significantly reduced whereas that of NPY and NPY1R were unchanged in the right atrium of diabetic patients compared to nondiabetic patients.

CONCLUSIONS

These results demonstrate that the expression of neuropeptides and their receptors in the diabetic heart is significantly impaired, and may be the link between neuropathy and cardiac complications. Further studies are warranted to delineate pathophysiologic mechanisms associated with dysregulation of the cardiac neuropeptide system and the relationship to cardiac complications in diabetes.

Diabetic neuropathy and heart failure: role of neuropeptides

Cardiovascular autonomic neuropathy (CAN), in which patients present with damage of autonomic nerve fibres, is one of the most common complications of diabetes. CAN leads to abnormalities in heart rate and vascular dynamics, which are features of diabetic heart failure. Dysregulated neurohormonal activation, an outcome of diabetic neuropathy, has a significant pathophysiological role in diabetes-associated cardiovascular disease. Key players in neurohormonal activation include cardioprotective neuropeptides and their receptors, such as substance P (SP), neuropeptide Y (NPY), calcitonin-gene-related peptide (CGRP), atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP). These neuropeptides are released from the peripheral or autonomic nervous system and have vasoactive properties. They are further implicated in cardiomyocyte hypertrophy, calcium homeostasis, ischaemia-induced angiogenesis, protein kinase C signalling and the renin-angiotensin-aldosterone system. Therefore, dysregulation of the expression of neuropeptides or activation of the neuropeptide signalling pathways can negatively affect cardiac homeostasis. Targeting neuropeptides and their signalling pathways might thus serve as new therapeutic interventions in the treatment of heart failure associated with diabetes. This review discusses how neuropeptide dysregulation in diabetes might affect cardiac functions that contribute to the development of heart failure.

Chronic type II diabetes mellitus leads to changes in neuropeptide Y receptor expression and distribution in human myocardial tissue

Neuropeptide Y is one of the most abundant neurotransmitters in the myocardium, and is known to influence cardiovascular remodeling. We hypothesized that diabetic neuropathy could possibly be associated with altered neuropeptide Y and its receptor expression levels in myocardium and plasma. Plasma neuropeptide Y levels in diabetic (n=24, HgbA1c 7.9 ± 1.1%) and non-diabetic (n=27, HgbA1c 5.8 ± 0.5%) patients undergoing cardiac surgery utilizing cardiopulmonary bypass were analyzed. Right atrial tissue of these patients was used to determine the expression of neuropeptide Y, the receptors 1-5, and leptin by immunoblotting, real-time PCR and immunofluorescence. Apoptosis signaling and endostatin and angiostatin were measured to determine the effects of leptin. Plasma neuropeptide Y levels were significantly increased in patients with Type II diabetes mellitus as compared to non-diabetic patients (P=0.026). Atrial tissue neuropeptide Y mRNA levels were lower in diabetic patients (P=0.036). There was a significant up-regulation of myocardial Y(2) and Y(5) receptors (P=0.009, P=0.01 respectively) in the diabetic patients. Leptin, involved with apoptosis and angiogenesis, was down regulated in diabetic patients (P=0.05). The levels of caspase-3, endostatin and angiostatin were significantly elevated in diabetic patients (P=0.003, P=0.008, P=0.01 respectively). Y(1) receptors were more likely to be localized within the nuclei of cardiomyocytes and vascular smooth muscle cells. Neuropeptide expression is altered differentially in the serum and myocardium by diabetes. Altered regulation of this system in diabetics may be in part responsible for the decreased angiogenesis, increased apoptosis, and increased vascular smooth muscle proliferation leading to coronary artery disease and heart failure in this patient population.

Neuropeptide Y functions as a facilitator of GDNF-induced budding of the Wolffian duct

Ureteric bud (UB) emergence from the Wolffian duct (WD), the initiating step in metanephric kidney morphogenesis, is dependent on GDNF; however, GDNF by itself is generally insufficient to induce robust budding of the isolated WD in culture. Thus, additional factors, presumably peptides or polypeptide growth factors, might be involved. Microarray data from in vivo budding and non-budding conditions were analyzed using non-negative matrix factorization followed by gene ontology filtering and network analysis to identify sets of genes that are highly regulated during budding. These included the GDNF co-receptors GFRalpha1 and RET, as well as neuropeptide Y (NPY). By using ANOVA with pattern matching, NPY was also found to correlate most significantly to the budded condition with a high degree of connectedness to genes with developmental roles. Exogenous NPY [as well as its homolog, peptide YY (PYY)] augmented GDNF-dependent budding in the isolated WD culture; conversely, inhibition of NPY signaling or perturbation of NPY expression inhibited budding, confirming that NPY facilitates this process. NPY was also found to reverse the decreased budding, the downregulation of RET expression, the mislocalization of GFRalpha1, and the inhibition of AKT phosphorylation that resulted from the addition of BMP4 to the isolated WD cultures, suggesting that NPY acts through the budding pathway and is reciprocally regulated by GDNF and BMP4. Thus, the outgrowth of the UB from the WD might result from a combination of the upregulation of the GDNF receptors together with genes that support GDNF signaling in a feed-forward loop and/or counteraction of the inhibitory pathway regulated by BMP4.