Sympathetic Nerve Terminals Research Articles

Aberrancy in CNS Signals and other Factors Related to Altered Homeostasis, Obesity and Metabolic Syndrome

Introduction: ‘The Obese-Obese World’: The obesity and metabolic syndrome (MetS) are a global epidemic of such magnitude that the today’s health scenario can be summed up as the ‘Obese-obese World’*. Obesity and MetS deteriorate quality of life and alter course of various chronic diseases, and on their own, are risk factors for diabetes, hypertension, cardiovascular disease and stroke, neurological degenerative diseases and cancers. Modern day lifestyle drives for excess calorie intake, comparatively reduced energy expenditure and storage of surplus energy in adipose tissue, an accentuated evolutionary need to fill body nutrients stores, leading to obesity, appended by pathophysiological alterations termed MetS. Cns Regulation of Energy Intake: Specialised neurons in hypothalamus and brainstem primarily regulate energy homeostasis, food intake and body weight, and integrate multiple peripheral metabolic inputs, such as nutrients, gut-derived hormones, and adiposity-related signals. There are several neuropeptides involved, including melanin concentrating hormone (MCH) and the orexins. An abnormal alteration in ghrelin and leptin levels can lead to weight gain and Obesity. Increase in adipose tissue leads to overproduction of leptin and hypothalamus becoming resistant to leptin action. The reward circuitry involves interactions between several systems including opioids, endocannabinoids, serotonin and dopamine. The obese individuals appear to have abnormalities in dopaminergic activity, and an imbalance in the brain circuits promoting reward seeking and those governing cognitive control leads to an overriding stimulus to feeding, even in the absence of an energy deficit. Dorsal striatum is hyperactive in obese and may contribute aberrancy of satiety signals. The genetics involving various mutations contributes up to 70% towards a person’s vulnerability to obesity. Regulation of Energy Expenditure: Energy is consumed in processes of physical activity, basal metabolism, and adaptive thermogenesis, which are modulated by brain, especially hypothalamic melanocortin system. Brown adipose tissue (BAT) plays a major role in thermogenesis. Central regulation of BAT thermogenesis is dependent on sympathetic outflow to BAT. Norepinephrine released from sympathetic nerve terminals binds to β3-adrenergic receptors on adipocytes in BAT to promote enhanced thermogenesis. In addition, many hormonal and nutrient signals, such as glucose, insulin, leptin and GLP-1 also influence sympathetic outflow to BAT. Conclusion - Fallouts of Neurosignal Aberrancy: The obese subjects with BMI > 30 show atrophy in the frontal lobes, anterior cingulate gyrus, hippocampus, and thalamus. MetS affects various cognitive domains including executive functioning, processing speed, and overall intellectual functioning. There is impaired vascular reactivity, endothelial dysfunction, neuro-inflammation, oxidative stress and altered brain metabolism.

VNUT and VMAT2 segregate within sympathetic varicosities and localize near preferred Cav2 isoforms in the rat tail artery.

ATP and norepinephrine (NE) are coreleased from peripheral sympathetic nerve terminals. Whether they are stored in the same vesicles has been debated for decades. Preferential dependence of NE or ATP release on Ca2+ influx through specific voltage-gated Ca2+ channel (Cav2) isoforms suggests that NE and ATP are stored in separate vesicle pools, but simultaneous imaging of NE and ATP containing vesicles within single varicosities has not been reported. We conducted an immunohistochemical study of vesicular monoamine transporter 2 (VMAT2/SLC18A2) and vesicular nucleotide translocase (VNUT/SLC17A9) as markers of vesicles containing NE and ATP in sympathetic nerves of the rat tail artery. A large fraction of varicosities exhibited neighboring, rather than overlapping, VNUT and VMAT2 fluorescent puncta. VMAT2, but not VNUT, colocalized with synaptotagmin 1. Cav2.1, Cav2.2, and Cav2.3 are expressed in nerves in the tunica adventitia. VMAT2 preferentially localized adjacent to Cav2.2 and Cav2.3 rather than Cav2.1. VNUT preferentially localized adjacent to Cav2.3 > Cav2.2 >> Cav2.1. With the use of wire myography, inhibition of field-stimulated vasoconstriction with the Cav2.3 blocker SNX-482 (0.25 µM) mimicked the effects of the P2X inhibitor suramin (100 µM) rather than the α-adrenergic inhibitor phentolamine (10 µM). Variable sensitivity to SNX-482 and suramin between animals closely correlated with Cav2.3 staining. We concluded that a majority of ATP and NE stores localize to separate vesicle pools that use different synaptotagmin isoforms and that localize near different Cav2 isoforms to mediate vesicle release. Cav2.3 appears to play a previously unrecognized role in mediating ATP release in the rat tail artery. NEW & NOTEWORTHY Immunofluorescence imaging of vesicular nucleotide translocase and vesicular monoamine transporter 2 in rat tail arteries revealed that ATP and norepinephrine, classical cotransmitters, localize to well-segregated vesicle pools. Furthermore, vesicular nucleotide translocase and vesicular monoamine transporter 2 exhibit preferential localization with specific Cav2 isoforms. These novel observations address long-standing debates regarding the mechanism(s) of sympathetic neurotransmitter corelease.

GW29-e1585 NADPH oxidase mediates cardiac sympathetic nerve terminal abnormalities in heart failure

Heart failure is characterized by cardiac sympathetic nerve terminal abnormalities, including the decreases of norepinephrine transporter (NET) density and cardiac catecholaminergic and tyrosine hydroxylase (TH) profiles. The alterations in cardiac sympathetic nerve terminals in heart failure are

Imaging the Autonomic Nervous System in Parkinson's Disease.

Patients with Parkinson's disease (PD) often display gastrointestinal and genitourinary autonomic symptoms years or even decades prior to diagnosis. These symptoms are thought to be caused in part by pathological α-synuclein inclusions in the peripheral autonomic and enteric nervous systems. It has been proposed that the initial α-synuclein aggregation may in some PD patients originate in peripheral nerve terminals and then spread centripetally to the spinal cord and brainstem. In vivo imaging methods can directly quantify the degeneration of the autonomic nervous system as well as the functional consequences such as perturbed motility. Here, we review the methodological principles of these imaging techniques and the major findings in patients with PD and atypical parkinsonism. Loss of sympathetic and parasympathetic nerve terminals in PD can be visualized using radiotracer imaging, including 123I-MIBG scintigraphy, and 18F-dopamine and 11C-donepezil PET. Recently, ultrasonographical studies disclosed reduced diameter of the vagal nerves in PD patients. Radiological and radioisotope techniques have demonstrated dysmotility and prolonged transit time throughout all subdivisions of the gastrointestinal tract in PD. The prevalence of objective dysfunction as measured with these imaging methods is often considerably higher compared to the prevalence of subjective symptoms experienced by the patients. Degeneration of the autonomic nervous system may play a key role in the pathogenesis of PD. In vivo imaging techniques provide powerful and noninvasive tools to quantify the degree and extent of this degeneration and its functional consequences.

Circulating epinephrine is not required for chronic stress to enhance metastasis

Signaling through β-adrenergic receptors drives cancer progression and β-blockers are being evaluated as a novel therapeutic strategy to prevent metastasis. Orthotopic mouse models of breast cancer show that β-adrenergic signaling induced by chronic stress accelerates metastasis, and that β2-adrenergic receptors on tumor cells are critical for this. Endogenous catecholamines are released during chronic stress: norepinephrine from the adrenal medulla and sympathetic nerves, and epinephrine from the adrenal medulla. β2-adrenergic receptors are much more sensitive to epinephrine than to norepinephrine. To determine if epinephrine is necessary in the effects of stress on cancer progression, we used a denervation strategy to eliminate circulating epinephrine, and quantified the effect on metastasis. Using both human xenograft and immune-intact murine models of breast cancer, we show that circulating epinephrine is dispensable for the effects of chronic stress on cancer progression. Measured levels of circulating norepinephrine were sufficiently low that they were unlikely to influence β2-adrenergic signaling, suggesting a possible role for norepinephrine release from sympathetic nerve terminals.

Assessment of myocardial sympathetic innervation by PET in patients with heart failure: a review of the most recent advances and future perspectives

Life-threatening ventricular arrhythmias (VA) are a major cause of death in patients with congestive heart failure (HF). Among various factors, the sympathetic nervous system may give rise to VA in several pathophysiological pathways due to an impaired function of presynaptic sympathetic nerve terminals. Positron emission tomography (PET) with labeled catecholamine analogues represents a reliable tool to assess the sympathetic innervation activity. This review aims at summarising the most relevant and recent literature findings on the current role of PET in the evaluation of cardiac sympathetic activity in patients with heart failure. A comprehensive literature search strategy using PubMed databases was carried out looking for articles on the role of Positron emission tomography/Computed Tomography (PET/CT) in the assessment of myocardial sympathetic innervation in patients with heart failure. The literature search limited to the last 5 years retrieved 40 papers. Most of the papers dealt with PET studies with 11C-HED. 19 pre-clinical, first-in-human and clinical studies highlighting the current role of PET and future perspectives resulted eligible for inclusion in the present review. The assessment of myocardial sympathetic activity in patients with heart failure with PET will play a pivotal role in clinical practice. Its capability to predict the occurrence of life-threatening VA and the effectiveness of resynchronization therapy makes this technique ideal in the era of personalized medicine.

β-Adrenoceptors Trigger Melatonin Synthesis in Phagocytes.

Melatonin (5-methoxy-N-acetylserotonin), the pineal hormone, is also synthesized by immune-competent cells. The pineal hormone signals darkness, while melatonin synthesized on demand by activated macrophages at any hour of the day acts locally, favoring regulatory/tolerant phenotypes. Activation of β-adrenoceptors in pinealocytes is the main route for triggering melatonin synthesis. However, despite the well-known role of β-adrenoceptors in the resolution macrophage phenotype (M2), and the relevance of macrophage synthesized melatonin in facilitating phagocytic activity, there is no information regarding whether activation of β-adrenoceptors would induce melatonin synthesis by monocytes. Here we show that catecholamines stimulate melatonin synthesis in bone marrow-derived dendritic cells and RAW 264.7 macrophages. Activation of β-adrenoceptors promotes the synthesis of melatonin by stimulating cyclic AMP/protein kinase A (PKA) pathway and by activating the nuclear translocation of NF-κB. Considering the great number of macrophages around sympathetic nerve terminals, and the relevance of this system for maintaining macrophages in stages compatible to low-grade inflammation, our data open the possibility that extra-pineal melatonin acts as an autocrine/paracrine signal in macrophages under resolution or tolerant phenotypes.

Clinical Implications

HomeHypertensionVol. 71, No. 4Clinical Implications Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBClinical Implications Originally published1 Apr 2018https://doi.org/10.1161/HYPERTENSIONAHA.118.10969Hypertension. 2018;71:539Socioeconomic Status and Hypertension in Africa (p 577)Download figureDownload PowerPointSystemic hypertension is a rapidly growing epidemic in Africa. Our study represents the first multination report on socioeconomic status and uncontrolled hypertension from Sub-Saharan Africa. Our results demonstrate the overall strikingly high proportion of uncontrolled blood pressure in low- and middle-income countries (77.4%), of which 61.7% had hypertension of grade 2 or 3. We further observed that the rate and severity (hypertension grade) of uncontrolled hypertension was proportional to individual wealth. This was observed in low-income but not middle-income countries, suggesting that the combination of individual poverty with a poor health system is particularly detrimental to achieving the goal of adequate blood pressure control. Hypertension is probably the easiest chronic noncommunicable disease to treat because blood pressure measurement for diagnosis and monitoring is simple, drug regimens are mainly once daily and inexpensive, and treatments generally do not need laboratory monitoring. According to World Health Organization estimations, the African region has the highest prevalence world rate of hypertension, afflicting 46% of the adult population aged ≥25 years. With >9 million deaths from hypertension worldwide each year, the potential effect of improved treatment of hypertension, particularly if combined with population-wide measures, would be substantial. Strategies for improving hypertension control in Sub-Saharan Africa should focus on people belonging to the lowest wealth groups with a particular focus on those living in low-income countries.Antifibrotic Effects of Finerenone (p 599)Download figureDownload PowerPointIn this study, we demonstrate that the new nonsteroidal mineralocorticoid receptor antagonist finerenone prevents cardiac fibrosis and improves global longitudinal strain parameters in a mouse model of early subendocardial damage. In addition, we identify a new pharmacological mechanism of selective mineralocorticoid receptor modulation which distinguishes nonsteroidal mineralocorticoid receptor antagonists from steroidal mineralocorticoid receptor antagonists based on selective mineralocorticoid receptor–cofactor binding. It has been shown previously by other groups that finerenone also exerts antifibrotic action in the kidney. The efficacy and safety of finerenone in patients with type 2 diabetes mellitus and the clinical diagnosis of diabetic kidney disease is currently being investigated in 2 large phase 3 outcome trials in patients with diabetic kidney disease (FIGARO-DKD [Efficacy and Safety of Finerenone in Subjects With Type 2 Diabetes Mellitus and the Clinical Diagnosis of Diabetic Kidney Disease], URL: http://www.clinicaltrials.gov. Unique identifier: NCT02545049; FIDELIO-DKD [Efficacy and Safety of Finerenone in Subjects With Type 2 Diabetes Mellitus and Diabetic Kidney Disease], URL: http://www.clinicaltrials.gov. Unique identifier: NCT02540993). FIGARO-DKD is a 6400 patient trial that will examine the time to the first occurrence of the composite end point of cardiovascular death and nonfatal cardiovascular events, whereas FIDELIO-DKD is a 4800 patient trial that will compare the effects of finerenone versus placebo on the time to the first occurrence of the composite end point of kidney failure, decrease of estimated glomerular filtration rate ≥40% from baseline, or renal death. The marked cardiorenal antifibrotic effects of finerenone shown in our study and by others are likely to be substantial for finerenone’s clinical effects currently tested in these trials.MiR-30c-5p Pathway in Cocaine-Induced Hypertension (p 752)Download figureDownload PowerPointThe use of cocaine remains the leading cause for all illicit drug-related emergency department visits, with the majority of these visits resulting from cardiovascular complaints, including chest pain. Cocaine exposure has short-term effects on the cardiovascular system, such as increasing blood pressure and inducing arrhythmias, but also negatively impacts long-term cardiovascular health by increasing the risk for hypertension, aortic stiffness, and atherosclerosis. It is well-known that cocaine inhibits catecholamine reuptake at sympathetic nerve terminals, stimulates central sympathetic outflow, and increases the sensitivity of adrenergic nerve endings to norepinephrine. It has been assumed that these cocaine-associated sympathetic nervous system effects are wholly responsible for hypertension and other cardiovascular effects resulting from cocaine exposure. However, recent studies have suggested that other mechanisms may be governing the effects of cocaine on the cardiovascular system. To better understand the molecular mechanisms underlying cocaine-induced cardiovascular toxicities, we analyzed microRNAs whose expression was altered in mouse aortas in response to cocaine exposure. We have identified a key pathway, the miR-30c–Me1 (malic enzyme 1) axis, that is involved in regulating reactive oxygen species levels, crucial factors in the pathogenesis of hypertension, vascular aging, and atherosclerosis. Inhibition of this pathway suppresses cocaine-induced elevation of blood pressure and augmentation of aortic stiffness in mice, providing new molecular targets for the development of therapeutic strategies as well as the rationale for the use of an antioxidant, such as N-acetylcysteine, to treat cocaine-associated cardiovascular toxicities. Previous Back to top Next FiguresReferencesRelatedDetails April 2018Vol 71, Issue 4 Advertisement Article InformationMetrics © 2018 American Heart Association, Inc.https://doi.org/10.1161/HYPERTENSIONAHA.118.10969 Originally publishedApril 1, 2018 PDF download Advertisement

Cutaneous adrenergic nerve blockade attenuates sweating response during incremental exercise in habitually trained and untrained men

Human eccrine sweat glands are governed by adrenergic nerves and noradrenergic agonists can elicit sweating. However, it remained unknown whether this neural adrenergic mechanism functionally contributes to sweat production during exercise. To clarify the mechanisms of adrenergic sweat production during exercise associated with habitual exercise training, this study examined 1) whether a blockade of cutaneous noradrenaline release from adrenergic nerve terminals attenuates sweating response during incremental exercise, and 2) whether the neural adrenergic sweating, if any, would be greater in habitually trained individuals relative to untrained counterparts. Nine habitually trained and 10 untrained males (VO2max: 57.6±5.1 and 38.9±6.7 ml kg−1 min−1, respectively, P < 0.05) performed incremental semi‐recumbent cycling (20W min−1) until exhaustion. Sweat rates (ventilated capsule) were measured at two bilateral forearm skin sites that were transdermally administered via iontophoresis with either 10 mM bretylium tosylate (BT, an inhibitor of noradrenaline release from sympathetic adrenergic nerve terminals) or saline (Control). Ninety min after the iontophoresis, foot cold water immersion was performed for 2 min to verify bretylium tosylate abolishes adrenergic cutaneous vasoconstriction associated with cold stress. Sweat rate was evaluated as a function of relative (percentage of maximum workload) exercise intensities. Trained individuals exhibited higher sweat production compared with untrained counterparts at exercise intensity of ≥70% relative workload (all P < 0.05). In trained individuals, sweat rate at the BT site was attenuated compared to the Control at relative exercise intensities of 70% (0.12±0.16 vs. 0.24±0.22 ml cm−2 min−1), 80% (0.32±0.25 vs. 0.48±0.28ml cm−2 min−1), 90% (0.48±0.29 vs. 0.66±0.29 ml cm−2 min−1), and 100% (0.60±0.29 vs. 0.77±0.29ml cm−2 min−1), respectively (all P < 0.05). Similarly, sweat rate measured in untrained group was reduced at BT vs. Control site at relative exercise intensities of 80% (0.04±0.08 vs. 0.10±0.09 ml cm−2 min−1), 90% (0.12±0.14 vs. 0.20±0.14 ml cm−2 min−1), and 100% (0.22±0.17 vs. 0.30±0.19 ml cm−2 min−1), respectively (all P < 0.05). BT‐induced reduction in sweat rate was greater in trained than in untrained individuals during exercise at the intensities of 70% (−0.12±0.11 vs. 0.00±0.03 ml cm−2 min−1), 80% (−0.16±0.12 vs. −0.06±0.10 ml cm−2 min−1), and 90% (−0.18±0.14 vs. −0.08±0.14 ml cm−2 min−1), respectively (all P < 0.05). To the best of our knowledge, this is the first study demonstrating noradrenaline release from sympathetic adrenergic nerve terminal does modulate sweating during high intensity exercise (i.e., >70% maximum) with habitually trained males exhibiting greater adrenergic sweating in comparison to untrained counterparts.Support or Funding InformationThis study was supported by a Grant‐in‐Aid for Scientific Research (no. 16K16521) from the Japan Society for the Promotion of Science from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The nature of catecholamine-containing neurons in the enteric nervous system in relationship with organogenesis, normal human anatomy and neurodegeneration.

The gastrointestinal tract is provided with extrinsic and intrinsic innervation. The extrinsic innervation includes the classic vagal parasympathetic and sympathetic components, with afferent sensitive and efferent secretomotor fibers. The intrinsic innervations is represented by the enteric nervous system (ENS), which is recognized as a complex neural network controlling a variety of cell populations, including smooth muscle cells, mucosal secretory cells, endocrine cells, microvasculature, immune and inflammatory cells. This is finalized to regulate gastrointestinal secretion, absorption and motility. In particular, this network is organized in several plexuses each one providing quite autonomous control of gastrointestinal functions (hence the definition of "second brain"). The similarity between ENS and CNS is further substantiated by the presence of local sensitive pseudo- unipolar ganglionic neurons with both peripheral and central branching which terminate in the enteric wall. A large variety of neurons and neurotransmitters takes part in the ENS. However, the nature of these neurons and their role in the regulation of gastrointestinal functions is debatable. In particular, the available literature reporting the specific nature of catecholamine- containing neurons provides conflicting evidence. This is critical both for understanding the specific role of each catecholamine in the gut and, mostly, to characterize specifically the enteric neuropathology occurring in a variety of diseases. An emphasis is posed on neurodegenerative disorders, such as Parkinson's disease, which is associated with the loss of catecholamine neurons. In this respect, the recognition of the nature of such neurons within the ENS would contribute to elucidate the pathological mechanisms which produce both CNS and ENS degeneration and to achieve more effective therapeutic approaches. Despite a great emphasis is posed on the role of noradrenaline to regulate enteric activities only a few reports are available on the anatomy and physiology of enteric dopamine neurons. Remarkably, this review limits the presence of enteric noradrenaline (and adrenaline) only within extrinsic sympathetic nerve terminals. This is based on careful morphological studies showing that the only catecholamine-containing neurons within ENS would be dopaminergic. This means that enteric pathology of catecholamine neurons should be conceived as axon pathology for noradrenaline neurons and whole cell pathology for dopamine neurons which would be the sole catecholamine cell within intrinsic circuitries affecting gut motility and secretions.The gastrointestinal tract is provided with extrinsic and intrinsic innervation. The extrinsic innervation includes the classic vagal parasympathetic and sympathetic components, with afferent sensitive and efferent secretomotor fibers. The intrinsic innervations is represented by the enteric nervous system (ENS), which is recognized as a complex neural network controlling a variety of cell populations, including smooth muscle cells, mucosal secretory cells, endocrine cells, microvasculature, immune and inflammatory cells. This is finalized to regulate gastrointestinal secretion, absorption and motility. In particular, this network is organized in several plexuses each one providing quite autonomous control of gastrointestinal functions (hence the definition of "second brain"). The similarity between ENS and CNS is further substantiated by the presence of local sensitive pseudounipolar ganglionic neurons with both peripheral and central branching which terminate in the enteric wall. A large variety of neurons and neurotransmitters takes part in the ENS. However, the nature of these neurons and their role in the regulation of gastrointestinal functions is debatable. In particular, the available literature reporting the specific nature of catecholamine-containing neurons provides conflicting evidence. This is critical both for understanding the specific role of each catecholamine in the gut and, mostly, to characterize specifically the enteric neuropathology occurring in a variety of diseases. An emphasis is posed on neurodegenerative disorders, such as including Parkinson's disease, which is associated with the loss of catecholamine neurons. In this respect, the recognition of the nature of such neurons within the ENS would contribute to elucidate the pathological mechanisms which produce both CNS and ENS degeneration and to achieve more effective therapeutic approaches. Despite a great emphasis is posed on the role of noradrenaline to regulate enteric activities only a few reports are available on the anatomy and physiology of enteric dopamine neurons. Remarkably, this review limits the presence of enteric noradrenaline (and adrenaline) only within extrinsic sympathetic nerve terminals. This is based on careful morphological studies showing that the only catecholamine-containing neurons within ENS would be dopaminergic. This means that enteric pathology of catecholamine neurons should be conceived as axon pathology for noradrenaline neurons and whole cell pathology for dopamine neurons which would be the sole catecholamine cell within intrinsic circuitries affecting gut motility and secretions.

Age-related regulation of bone formation by the sympathetic cannabinoid CB1 receptor.

The endocannabinoid (eCB) system, including its receptors, ligands, and their metabolizing enzymes, plays an important role in bone physiology. Skeletal cannabinoid type 1 (CB1) receptor signaling transmits retrograde signals that restrain norepinephrine (NE) release, thus transiently stimulating bone formation following an acute challenge, suggesting a feedback circuit between sympathetic nerve terminals and osteoblasts. To assess the effect of chronic in vivo occurrence of this circuit, we characterized the skeletal phenotype of mice with a conditional deletion of the CB1 receptor in adrenergic/noradrenergic cells, including sympathetic nerves. Whereas the deletion of the CB1 receptor did not affect bone mass accrual in the distal femoral metaphysis and in vertebral bodies of young, 12-week-old mice, it substantially increased bone mass in aged, 35-week-old mutant mice as compared to wild-type controls. Contrary to our expectations, specific deficiency of the CB1 receptor in sympathetic neurons led to a markedly increased bone mass phenotype, associated with an enhanced bone formation rate and reduced osteoclastogenesis. Mechanistically, the reduced skeletal eCB 'tone' in the null mice did not reflect in increased sympathetic tone and reduced bone formation, suggesting that constitutive genetic inactivation of sympathetic CB1 receptor disrupts the negative feedback loop between eCBs and NE signaling in bone.

Changes in neurofilament 200 and tyrosine hydroxylase expression in the cardiac innervation of diabetic rats during aging.

Changes in sensory and sympathetic innervation during diabetes mellitus (DM) can be a predictor of arrhythmias, silent myocardial ischemia, and chronic heart failure, but knowledge about these changes is still unsatisfactory. We analyzed whether prolonged DM induces changes in density of sensory and sympathetic nerve terminals of rat's heart and whether it contributes to cardiomyopathy during aging. DM was induced by i/p injecting 55 mg/kg streptozotocin to male Sprague-Dawley rats, while a control group received a citrate buffer. DM in the rats was validated by measuring blood glucose level. Animals were sacrificed after 2 weeks, 2 months, 6 months, and 12 months. Five areas of cardiac sections were analyzed. Antibodies raised against tyrosine hydroxylase (TH) and neurofilament 200 kDa (NF 200) were used to detect sympathetic and sensory fibers. TH immunoreactive fiber density increased in DM groups 2 weeks after induction, reaching a peek after 2 months, while in the later stages of DM (6 and 12 months), there was no significant difference compared to control. NF 200 immunoreactive fiber density increased 2 weeks after induction compared to control. There was no consistent pattern of change during the given period in both the DM or control groups. In the DM group, we found thickening of the left ventricle wall (P<.05) as the sign of cardiomyopathy. Our findings suggest that hyperglycemia as a hallmark of DM in early stages can lead to proliferation of sympathetic and sensory nerve terminals. This finding can contribute to a better understanding of the occurrence of arrhythmias and silent myocardial ischemia in DM.

The binding of botulinum neurotoxins to different peripheral neurons

Botulinum neurotoxins are the most potent toxins known. The double receptor binding modality represents one of the most significant properties of botulinum neurotoxins and largely accounts for their incredible potency and lethality. Despite the high affinity and the very specific binding, botulinum neurotoxins are versatile and multi-tasking toxins. Indeed they are able to act both at the somatic and at the autonomic nervous system.In spite of the preference for cholinergic nerve terminals botulinum neurotoxins have been shown to inhibit to some extent also the noradrenergic postganglionic sympathetic nerve terminals and the afferent nerve terminals of the sensory neurons inhibiting the release of neuropeptides and glutamate, which are responsible of nociception. Therefore, there is increasing evidence that the therapeutic effect in both motor and autonomic disorders is based on a complex mode of botulinum neurotoxin action modulating the activity of efferent as well as afferent nerve fibres.

Electrophysiological Investigation of the Subcellular Fine Tuning of Sympathetic Neurons by Hydrogen Sulfide.

H2S is well-known as hypotensive agent, whether it is synthetized endogenously or administered systemically. Moreover, the H2S donor NaHS has been shown to inhibit vasopressor responses triggered by stimulation of preganglionic sympathetic fibers. In contradiction with this latter result, NaHS has been reported to facilitate transmission within sympathetic ganglia. To resolve this inconsistency, H2S and NaHS were applied to primary cultures of dissociated sympathetic ganglia to reveal how this gasotransmitter might act at different subcellular compartments of such neurons. At the somatodendritic region of ganglionic neurons, NaHS raised the frequency, but not the amplitudes, of cholinergic miniature postsynaptic currents via a presynaptic site of action. In addition, the H2S donor as well as H2S itself caused membrane hyperpolarization and decreased action potential firing in response to current injection. Submillimolar NaHS concentrations did not affect currents through Kυ7 channels, but did evoke currents through KATP channels. Similarly to NaHS, the KATP channel activator diazoxide led to hyperpolarization and decreased membrane excitability; the effects of both, NaHS and diazoxide, were prevented by the KATP channel blocker tolbutamide. At postganglionic sympathetic nerve terminals, H2S and NaHS enhanced noradrenaline release due to a direct action at the level of vesicle exocytosis. Taken together, H2S may facilitate transmitter release within sympathetic ganglia and at sympatho-effector junctions, but causes hyperpolarization and reduced membrane excitability in ganglionic neurons. As this latter action was due to KATP channel gating, this channel family is hereby established as another previously unrecognized determinant in the function of sympathetic ganglia.

Neuroanatomy of the spleen: Mapping the relationship between sympathetic neurons and lymphocytes.

The nervous system plays a profound regulatory role in maintaining appropriate immune responses by signaling to immune cells. These immune cells, including B- and T-cells, can further act as intermediary messengers, with subsets of B- and T-cells expressing choline acetyltransferase (ChAT), the enzyme required for acetylcholine (ACh) synthesis. Neural control of ACh release from ChAT+ T-cells can have powerful immune implications, regulating lymphocyte trafficking, inflammation, and prevent death due to experimental septic shock. Although ACh release from T-cells has been proposed to occur following norepinephrine (NE) released from sympathetic nerve terminals in the spleen, it is unknown how this communication occurs. While it was proposed that tyrosine hydroxylase (TH+) axons form synapse-like structures with ChAT+ T-cells, there is scant evidence to support or refute this phenomenon. With this in mind, we sought to determine the relative abundance of ChAT+ B- and T-cells in close proximity to TH+ axons, and determine what factors contribute to their localization in the spleen. Using confocal microscopy of tissue sections and three-dimensional imaging of intact spleen, we confirmed that ChAT+ B-cells exceed the number of ChAT+ T-cells, and overall few ChAT+ B- or T-cells are located close to TH+ fibers compared to total numbers. The organized location of ChAT+ lymphocytes within the spleen suggested that these cells were recruited by chemokine gradients. We identified ChAT+ B- and T-cells express the chemokine receptor CXCR5; indicating that these cells can respond to CXCL13 produced by stromal cells expressing the β2 adrenergic receptor in the spleen. Our findings suggest that sympathetic innervation contributes to organization of ChAT+ immune cells in the white pulp of the spleen by regulating CXCL13. Supporting this contention, chemical sympathectomy significantly reduced expression of this chemokine. Together, we demonstrated that there does not appear to be a basis for synaptic neuro-immune communication, and that sympathetic innervation can modulate immune function through altering stromal cell chemokine production.

Pure autonomic failure.

Pure autonomic failure is a degenerative disorder of the peripheral autonomic nervous system. Patients experience symptomatic hypotension that requires them to sit, squat or lie down to prevent syncope. It is associated with characteristic histopathological findings, resulting in neuronal cytoplasmic inclusions in the peripheral autonomic nerves. These lesions are responsible for defects in the synthesis and release of norepinephrine from sympathetic nerve terminals, resulting in significant hypotension. Patients with autonomic failure also have exaggerated blood pressure responses to common stimuli such as food or fluid intake, heat, exercise and medications. Tilt table (head-up) testing is probably the test most commonly used to establish the diagnosis. However, simple office testing is also useful, such as having the patient stand after lying supine with blood pressure monitoring. Treatment options range from simply increasing fluid and salt intake, and using compressive garments, to medications administered orally, subcutaneously or intravenously in more severe cases.

The neuropeptide galanin promotes an anti-thrombotic phenotype on endocardial endothelial cells from heart failure patients.

Thromboembolic complications are a significant cause of mortality and re-hospitalization in heart failure (HF) patients. One source of thrombi is the ventricular endocardial surface that becomes increasingly pro-thrombotic as HF progresses. Anticoagulation comes with bleeding risks so identifying therapeutic agents for improving cardiac endothelial health are of critical clinical importance. Endocardial endothelial cells are closely apposed to cardiac sympathetic nerves. In HF, cardiac sympathetic nerves are dysregulated and promote disease progression. Whether endocardial endothelial health and function is impacted by sympathetic dysregulation in HF is unknown. Also unexplored is the impact of neuropeptides, such as galanin and neuropeptide Y (NPY), co-released from sympathetic nerve terminals, on endothelial health. In this study we examined the effect of sympathetic nerve-released neurotransmitters and neuropeptides on the procoagulant phenotype of cultured human endocardial endothelial cells from HF patients. As a functional readout of procoagulant state we examined thrombin-mediated von Willebrand factor (vWF) extrusion and multimer expression. We demonstrate that vWF extrusion and multimer expression is promoted by thrombin, that isoproterenol (a beta-adrenergic receptor agonist) augments this effect, whereas co-treatment with the beta-blockers propranolol and carvedilol blocks this effect. We also show that vWF extrusion and multimer expression is attenuated by treatment with the neuropeptide galanin, but not with NPY. Our results are consistent with a protective role of beta-blockers and galanin on endocardial endothelial health in heart failure. Improving endothelial health through galanin therapy is a future clinical application of this study.

Pathophysiology of Takotsubo Syndrome

Originally described by Japanese authors in the 1990s, Takotsubo syndrome (TTS) generally presents as an acute myocardial infarction characterized by severe left ventricular dysfunction. TTS, however, differs from an acute coronary syndrome because patients have generally a normal coronary angiogram and left ventricular dysfunction, which extends beyond the territory subtended by a single coronary artery and recovers within days or weeks. The prognosis was initially thought to be benign, but subsequent studies have demonstrated that both short-term mortality and long-term mortality are higher than previously recognized. Indeed, mortality reported during the acute phase in hospitalized patients is ≈4% to 5%, a figure comparable to that of ST-segment-elevation myocardial infarction in the era of primary percutaneous coronary interventions. Despite extensive research, the cause and pathogenesis of TTS remain incompletely understood. The aim of the present review is to discuss the pathophysiology of TTS with particular emphasis on the role of the central and autonomic nervous systems. Different emotional or psychological stressors have been identified to precede the onset of TTS. The anatomic structures that mediate the stress response are found in both the central and autonomic nervous systems. Acute stressors induce brain activation, increasing bioavailability of cortisol and catecholamine. Both circulating epinephrine and norepinephrine released from adrenal medullary chromaffin cells and norepinephrine released locally from sympathetic nerve terminals are significantly increased in the acute phase of TTS. This catecholamine surge leads, through multiple mechanisms, that is, direct catecholamine toxicity, adrenoceptor-mediated damage, epicardial and microvascular coronary vasoconstriction and/or spasm, and increased cardiac workload, to myocardial damage, which has a functional counterpart of transient apical left ventricular ballooning. The relative preponderance among postmenopausal women suggests that estrogen deprivation may play a facilitating role, probably mediated by endothelial dysfunction. Despite the substantial improvement in our understanding of the pathophysiology of TTS, a number of knowledge gaps remain.

Modulation of experimental arthritis by vagal sensory and central brain stimulation

Articular inflammation is a major clinical burden in multiple inflammatory diseases, especially in rheumatoid arthritis. Biological anti-rheumatic drug therapies are expensive and increase the risk of systemic immunosuppression, infections, and malignancies. Here, we report that vagus nerve stimulation controls arthritic joint inflammation by inducing local regulation of innate immune response. Most of the previous studies of neuromodulation focused on vagal regulation of inflammation via the efferent peripheral pathway toward the viscera. Here, we report that vagal stimulation modulates arthritic joint inflammation through a novel “afferent” pathway mediated by the locus coeruleus (LC) of the central nervous system. Afferent vagal stimulation activates two sympatho-excitatory brain areas: the paraventricular hypothalamic nucleus (PVN) and the LC. The integrity of the LC, but not that of the PVN, is critical for vagal control of arthritic joint inflammation. Afferent vagal stimulation suppresses articular inflammation in the ipsilateral, but not in the contralateral knee to the hemispheric LC lesion. Central stimulation is followed by subsequent activation of joint sympathetic nerve terminals inducing articular norepinephrine release. Selective adrenergic beta-blockers prevent the effects of articular norepinephrine and thereby abrogate vagal control of arthritic joint inflammation. These results reveals a novel neuro-immune brain map with afferent vagal signals controlling side-specific articular inflammation through specific inflammatory-processing brain centers and joint sympathetic innervations.

Effects of Intranasal NPY on Cardiovascular Parameters and Activity in SPS Model of PTSD: Telemetric Studies

Single prolonged stress (SPS) is a rodent model of PTSD with high construct and face validity. Our previous studies revealed that early intervention with neuropeptide Y (NPY) delivered to the brain by intranasal pathways is very effective to prevent development of many of the SPS‐elicited impairments in behavioral and neuroendocrine functions, demonstrating its therapeutic potential. However, there are conflicting findings regarding the effect of NPY on the cardiovascular system. On one hand, NPY is co‐released with norepinephrine from the sympathetic nerve terminals in the periphery and can enhance norepinephrine's vaso constrictive effects. On the other hand several studies indicate that delivery of NPY to selective brain regions may elicit hypotensive effects.Therefore, we examined whether intranasal NPY affects the major cardiovascular responses to SPS. Telemetric probes (TA11PA‐C40, Data Sciences) were implanted to measure blood pressure (BP), heart rate (HR) and activity in male Sprague Dawley rats. After recovery from the surgery data was collected every 10 min. When basal parameters were established, animals were subjected to SPS stressors and infused with 150 μg NPY or vehicle (water). They were returned to the receivers and data measured, every 2 min for 2 hrs and every 10 min subsequently for 6 days afterwards.SPS stressors led to significant elevation of mean arterial pressure (MAP) and HR in all groups. MAP was elevated in both the vehicle and NPY treated group by (20.5 ±2.3 mHg, p=0.01; 25.7 ±6.1 mmHg, p&lt;0.001 respectively) with no significant difference between them. The MAP returned towards basal levels by the following day; however MAP in the vehicle‐treated group MAP remained significantly elevated for several of the days following exposure to SPS stressors.A large elevation in heart rate (HR) in response to SPS was observed in both groups. However, the elevation in the NPY treated group (116 ±5 bpm p&lt;0.001) was significantly (p&lt;0.05) lower than in the vehicle treated group (139 ±7 bpm, p&lt;0.001). In the week following SPS stressors, the HR was similar to basal levels during the light phase, but lower than basal levels during the dark phase (normally active phase) with no difference between NPY‐ or vehicle‐treated groups.SPS triggered pronounced effects on activity. In vehicle, but not NPY‐treated group, activity was elevated above basal levels immediately following exposure to SPS stressors. In the days following SPS, activity was significantly reduced from baseline in both groups, especially during the dark (normally active) phase. Dark phase activity gradually returned towards basal levels in the NPY group, and 6 days post‐SPS stressors was still depressed in the vehicle‐treated animals.The results indicate that while intranasal NPY may be slightly beneficial for immediate changes in HR and long‐term effects on activity and MAP, overall it does not markedly alter the cardiovascular response to traumatic stress in animal model of PTSD.Support or Funding InformationSupported by grant W81XWH‐16‐1‐0016 from US Army MOMRP