Past, Present and Future of Human Chromaffin Cells: Role in Physiology and Therapeutics

Urinary neurotransmitter analysis and canine behavior assessment

Behavioral problems are highly prevalent in domestic dogs, negatively affecting the quality of life of dogs and their owners. In humans and dogs, neuropsychological or neurobehavioral disorders can be associated with deviations in various neurotransmitter systems. Previous evidence has revealed correlations between urinary neurotransmitters and various behavioral disorders; however, a causal relationship has not yet been conclusively demonstrated. Non-invasive urinary neurotransmitter analysis may identify specific biomarkers, which enable a more differentiated assessment of canine behavioral disorders in the future and contribute to more effective neuromodulatory treatment decisions and monitoring. This approach could offer new insights into underlying pathomechanisms of canine neurobehavioral disorders. This study assessed urinary neurotransmitter levels and the descriptive behavior profile of 100 dogs using established rating scales (Canine Behavioral Assessment and Research Questionnaire, Attention Deficit Hyperactivity Disorder Rating Scale, Dog Personality Questionnaire, Canine Cognitive Dysfunction Rating Scale), and explored relationships between these variables. No correlation was found between urinary neurotransmitters and the assessed behavior profiles; however, age-, sex- and neuter-related influences were identified. The lack of correlation could be explained by the many confounding factors influencing both behavior and urinary neurotransmitter excretion, including age, sex and neuter status effects, and methodological issues e.g., low discriminatory power between anxiety and aggression in the descriptive behavior evaluation. Urinary neurotransmitter testing could not be validated as a tool for canine behavior evaluation in this study. However, reliable assessment methods with low susceptibility to human biases could be valuable in the future to support behavioral-phenotype diagnoses.

Perioperative Evaluation and Management of Patients on Glucocorticoids

Myriad questions regarding perioperative management of patients on glucocorticoids (GCs) continue to be debated including which patients are at risk for adrenal insufficiency (AI), what is the correct dose and duration of supplemental GCs, or are they necessary for everyone? These questions remain partly unanswered due to the heterogeneity and low quality of data, studies with small sample sizes, and the limited number of randomized trials. To date, we know that although all routes of GC administration can result in hypothalamic-pituitary-adrenal (HPA) axis suppression, perioperative adrenal crisis is rare. Correlation between biochemical testing for AI and clinical events is lacking. Some of the current perioperative management recommendations based on daily GC dose and duration of therapy may be difficult to follow in clinical practice. The prospective and retrospective studies consistently report that continuing the daily dose of GCs perioperatively is not associated with a higher risk for adrenal crises in patients with GC-induced AI. Considering that oral GC intake may be unreliable in the early postoperative period, providing the daily GC plus a short course of IV hydrocortisone 25 to 100 mg per day based on the degree of surgical stress seems reasonable. In patients who have stopped GC therapy before surgery, careful assessment of the HPA axis is necessary to avoid an adrenal crisis. In conclusion, our literature review indicates that lower doses and shorter duration of supplemental GCs perioperatively are sufficient to maintain homeostasis. We emphasize the need for well-designed randomized studies on this frequently encountered clinical scenario.

Urinary Neurotransmitter Patterns Are Altered in Canine Epilepsy

Epilepsy is the most common chronic neurological disease in humans and dogs. Epilepsy is thought to be caused by an imbalance of excitatory and inhibitory neurotransmission. Intact neurotransmitters are transported from the central nervous system to the periphery, from where they are subsequently excreted through the urine. In human medicine, non-invasive urinary neurotransmitter analysis is used to manage psychological diseases, but not as yet for epilepsy. The current study aimed to investigate if urinary neurotransmitter profiles differ between dogs with epilepsy and healthy controls. A total of 223 urine samples were analysed from 63 dogs diagnosed with idiopathic epilepsy and 127 control dogs without epilepsy. The quantification of nine urinary neurotransmitters was performed utilising mass spectrometry technology. A significant difference between urinary neurotransmitter levels (glycine, serotonin, norepinephrine/epinephrine ratio, ɤ-aminobutyric acid/glutamate ratio) of dogs diagnosed with idiopathic epilepsy and the control group was found, when sex and neutering status were accounted for. Furthermore, an influence of antiseizure drug treatment upon the urinary neurotransmitter profile of serotonin and ɤ-aminobutyric acid concentration was revealed. This study demonstrated that the imbalances in the neurotransmitter system that causes epileptic seizures also leads to altered neurotransmitter elimination in the urine of affected dogs. Urinary neurotransmitters have the potential to serve as valuable biomarkers for diagnostics and treatment monitoring in canine epilepsy. However, more research on this topic needs to be undertaken to understand better the association between neurotransmitter deviations in the brain and urine neurotransmitter concentrations in dogs with idiopathic epilepsy.

Nanoskiving fabrication of size-controlled Au nanowire electrodes for electroanalysis

Nanoskiving, benefiting from its simple operation and high reproducibility, is a promising method to fabricate nanometer-size electrodes. In this work, we report the fabrication of Au nanowire electrodes with different shapes and well-controlled sizes through nanoskiving. Au nanowire block electrodes, membrane electrodes and tip electrodes are prepared with good reproducibility. Steady-state cyclic voltammograms (CVs) demonstrate that all these electrodes behave well as nanoband ultramicroelectrodes. A fast heterogeneous electron transfer rate constant can be extracted reliably from steady-state CVs at various size Au nanowire block electrodes by the Koutecký-Levich (K-L) method. The Au nanowire membrane electrodes demonstrate good sensitivity toward the oxidation of catecholamine and could monitor catecholamine released from rat adrenal chromaffin cells stimulated by high K⁺.

A defined, controlled culture system for primary bovine chromaffin progenitors reveals novel biomarkers and modulators

We present a method to efficiently culture primary chromaffin progenitors from the adult bovine adrenal medulla in a defined, serum-free monolayer system. Tissue is dissociated and plated for expansion under support by the mitogen basic fibroblast growth factor (bFGF). The cultures, although not homogenous, contain a subpopulation of cells expressing the neural stem cell marker Hes3 that also propagate. In addition, Hes3 is also expressed in the adult adrenal medulla from where the tissue is taken. Differentiation is induced by bFGF withdrawal and switching to Neurobasal medium containing B27. Following differentiation, Hes3 expression is lost, and cells acquire morphologies and biomarker expression patterns of chromaffin cells and dopaminergic neurons. We tested the effect of different treatments that we previously showed regulate Hes3 expression and cell number in cultures of fetal and adult rodent neural stem cells. Treatment of the cultures with a combination of Delta4, Angiopoietin2, and a Janus kinase inhibitor increases cell number during the expansion phase without significantly affecting catecholamine content levels. Treatment with cholera toxin does not significantly affect cell number but reduces the ratio of epinephrine to norepinephrine content and increases the dopamine content relative to total catecholamines. These data suggest that this defined culture system can be used for target identification in drug discovery programs and that the transcription factor Hes3 may serve as a new biomarker of putative adrenomedullary chromaffin progenitor cells.

Syndapin 3 modulates fusion pore expansion in mouse neuroendocrine chromaffin cells

Adrenal neuroendocrine chromaffin cells receive excitatory synaptic input from the sympathetic nervous system and secrete hormones into the peripheral circulation. Under basal sympathetic tone, modest amounts of freely soluble catecholamine are selectively released through a restricted fusion pore formed between the secretory granule and the plasma membrane. Upon activation of the sympathoadrenal stress reflex, elevated stimulation drives fusion pore expansion, resulting in increased catecholamine secretion and facilitating release of copackaged peptide hormones. Thus regulated expansion of the secretory fusion pore is a control point for differential hormone release of the sympathoadrenal stress response. Previous work has shown that syndapin 1 deletion alters transmitter release and that the dynamin 1-syndapin 1 interaction is necessary for coupled endocytosis in neurons. Dynamin has also been shown to be involved in regulation of fusion pore expansion in neuroendocrine chromaffin cells through an activity-dependent association with syndapin. However, it is not known which syndapin isoform(s) contributes to pore dynamics in neuroendocrine cells. Nor is it known at what stage of the secretion process dynamin and syndapin associate to modulate pore expansion. Here we investigate the expression and localization of syndapin isoforms and determine which are involved in mediating fusion pore expansion. We show that all syndapin isoforms are expressed in the adrenal medulla. Mutation of the SH3 dynamin-binding domain of all syndapin isoforms shows that fusion pore expansion and catecholamine release are limited specifically by mutation of syndapin 3. The mutation also disrupts targeting of syndapin 3 to the cell periphery. Syndapin 3 exists in a persistent colocalized state with dynamin 1.

The effects of nanomaterials as endocrine disruptors

In recent years, nanoparticles have been increasingly used in several industrial, consumer and medical applications because of their unique physico-chemical properties. However, in vitro and in vivo studies have demonstrated that these properties are also closely associated with detrimental health effects. There is a serious lack of information on the potential nanoparticle hazard to human health, particularly on their possible toxic effects on the endocrine system. This topic is of primary importance since the disruption of endocrine functions is associated with severe adverse effects on human health. Consequently, in order to gather information on the hazardous effects of nanoparticles on endocrine organs, we reviewed the data available in the literature regarding the endocrine effects of in vitro and in vivo exposure to different types of nanoparticles. Our aim was to understand the potential endocrine disrupting risks posed by nanoparticles, to assess their underlying mechanisms of action and identify areas in which further investigation is needed in order to obtain a deeper understanding of the role of nanoparticles as endocrine disruptors. Current data support the notion that different types of nanoparticles are capable of altering the normal and physiological activity of the endocrine system. However, a critical evaluation of these findings suggests the need to interpret these results with caution since information on potential endocrine interactions and the toxicity of nanoparticles is quite limited.

Differences in the H2S-induced quantal release of catecholamine in adrenal chromaffin cells of neonatal and adult rats

Both catecholamine (CA) released from adrenal chromaffin cells and hydrogen sulfide (H2S) have been shown to play critical roles in the regulation of hypoxic stress response. Our previous study has demonstrated that exogenous H2S directly induced quantal CA released from adult rat adrenal chromaffin cells (ARACCs) by inhibiting Ca(2+)-activated K(+) current [IK(Ca) current]. However, it is not clear now whether H2S can also directly induce quantal CA released from neonatal rat adrenal chromaffin cells (NRACCs). In the present study, we investigated whether exogenous H2S can stimulate quantal CA released from NRACCs, and whether there were differences in the kinetics of H2S-induced quantal CA released between ARACCs and NRACCs. Using carbon-fiber amperometry and whole-cell patch clamping techniques, our experimental results showed: (1) H2S can directly induce quantal CA released from NRACCs; (2) H2S induced the depolarization of membrane potential and inhibited IK(Ca) current; (3) compared with ARACCs, much smaller quantal size and faster quantal release were showed in NRACCs through the kinetic analysis of the single-vesicle secretion induced by H2S. Our results may not only help to further understand the H2S-induced CA released from adrenal chromaffin cells in the aspect of development, but also provide the insights for the clinical prevention and therapy for hypoxic stress-induced injury in neonates at birth.

Activity-dependent fusion pore expansion regulated by a calcineurin-dependent dynamin-syndapin pathway in mouse adrenal chromaffin cells

Neuroendocrine chromaffin cells selectively secrete a variety of transmitter molecules into the circulation as a function of sympathetic activation. Activity-dependent release of transmitter species is controlled through regulation of the secretory fusion pore. Under sympathetic tone, basal synaptic excitation drives chromaffin cells to selectively secrete modest levels of catecholamine through a restricted secretory fusion pore. In contrast, elevated sympathetic activity, experienced under stress, results in fusion pore expansion to evoke maximal catecholamine release and to facilitate release of copackaged peptide transmitters. Therefore, fusion pore expansion is a key control point for the activation of the sympatho-adrenal stress response. Despite the physiological importance of this process, the molecular mechanism by which it is regulated remains unclear. Here we employ fluorescence imaging with electrophysiological and electrochemical-based approaches to investigate the role of dynamin I in the regulation of activity-mediated fusion pore expansion in mouse adrenal chromaffin cells. We show that under elevated stimulation, dynamin I is dephosphorylated at Ser-774 by calcineurin. We also demonstrate that disruption of dynamin I-syndapin binding, an association regulated by calcineurin-dependent dynamin dephosphorylation, limits fusion pore expansion. Last, we show that perturbation of N-WASP function (a syndapin substrate) limits activity-mediated fusion pore expansion. Our results suggest that fusion pore expansion is regulated by a calcineurin-dependent dephosphorylation of dynamin I. Dephosphorylated dynamin I acts via a syndapin/N-WASP signaling cascade to mediate pore expansion.

Chromaffin cells: the peripheral brain

Chromaffin cells probably are the most intensively studied of the neural crest derivates. They are closely related to the nervous system, share with neurons some fundamental mechanisms and thus were the ideal model to study the basic mechanisms of neurobiology for many years. The lessons we have learned from chromaffin cell biology as a peripheral model for the brain and brain diseases pertain more than ever to the cutting edge research in neurobiology. Here, we highlight how studying this cell model can help unravel the basic mechanisms of cell renewal and regeneration both in the central nervous system (CNS) and neuroendocrine tissue and also can help in designing new strategies for regenerative therapies of the CNS.

Native α6β4* nicotinic receptors control exocytosis in human chromaffin cells of the adrenal gland

In the present study, we have electrophysiologically characterized native nicotinic acetylcholine receptors (nAChRs) in human chromaffin cells of the adrenal gland as well as their contribution to the exocytotic process. α-Conotoxin AuIB blocked by 14 ± 1% the acetylcholine (ACh)-induced nicotinic current. α-Conotoxin MII (α-Ctx MII) exhibited an almost full blockade of the nicotinic current at nanomolar concentrations (IC(50)=21.6 nM). The α6*-preferring α-Ctx MII mutant analogs, α-Ctx MII[H9A,L15A] and α-Ctx MII[S4A,E11A,L15A], blocked nAChR currents with an IC(50) of 217.8 and 33 nM, respectively. These data reveal that nAChRs in these cells include the α6* subtype. The washout of the blockade exerted by α-conotoxin BuIA (α-Ctx BuIA; 1 μM) on ACh-evoked currents was slight and slow, arguing in favor of the presence of a β4 subunit in the nAChR composition. Exocytosis was almost fully blocked by 1 μM α-Ctx MII, its mutant analogs, or α-Ctx BuIA. Finally, the fluorescent analog Alexa Fluor 546-BuIA showed distinct staining in these cells. Our results reveal that α6β4* nAChRs are expressed and contribute to exocytosis in human chromaffin cells of the adrenal gland, the main source of adrenaline under stressful situations.