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chromaffin tissue [keywords]
- Immunocytochemical markers of neuronal maturation in human diagnostic neuropathology. [JOURNAL ARTICLE]
- Cell Tissue Res 2014 Sep 17.
Histological descriptions of morphogenesis in human fetal brain and in malformations and tumours can now be supplemented by the timing and sequence of the maturation of individual neurons. In human neuropathology, this is principally achieved by immunocytochemical reactivities used as maturational markers of neuronal properties denoted by molecules and cell products. Cytological markers can appear early and then regress, often being replaced by more mature molecules, or might not exhibit the onset of immunoreactivity until a certain stage of neuronal differentiation is achieved, some early, others intermediate and some late during the maturational process. Inter-specific differences occur in some structures of the brain. The classification of markers of neuronal maturation can be based, in addition to those mentioned above, on several criteria: cytological localisation, water solubility, biochemical nature of the antigen, specificity and various technical factors. The most useful immunocytochemical markers of neuronal maturation in human neuropathology are NeuN, synaptophysin, calretinin and other calcium-binding molecules, various microtubule-associated proteins and chromogranins. Non-antibody histochemical stains that denote maturational processes include luxol fast blue for myelination, acridine orange fluorochrome for nucleic acids, mitochondrial respiratory chain enzymes and argentophilic impregnations. Neural crest derivatives of the peripheral nervous system, including chromaffin and neuroendocrine cells, have special features that are shared and others that differ greatly between lineages. Other techniques used in human diagnostic neuropathology, particularly as applied to tumours, include chromosomal and genetic analyses, the mTOR signalling pathway, BRAF V600E and other tumour-suppressor gene products, transcription products of developmental genes and the proliferation index of the tumour cells and of mitotic neuroepithelial cells.
- Low-intensity aerobic exercise mitigates exercise-induced bronchoconstriction by improving the function of adrenal medullary chromaffin cells in asthmatic rats. [Journal Article]
- Tohoku J Exp Med 2014; 234(2):99-110.
Exercise is one of the most common triggers of bronchoconstriction in patients with asthma. The low levels of circulating epinephrine produced by the adrenal medullary chromaffin cells (AMCCs) are associated with exercise-induced bronchoconstriction (EIB) in asthmatics. In the present study, we tested the hypothesis that low-intensity aerobic exercise may ameliorate EIB using a rat model of asthma. Male Sprague-Dawley rats at 7 weeks of age, sensitized with ovalbumin or treated with saline, were subjected to low or moderate exercise training (50 or 75% of maximum velocity) for one hour in a treadmill 30 min after ovalbumin or saline inhalation. The exercise capacity, airway responsiveness, lung morphology, the morphological changes and endocrine function of AMCCs were measured in both groups of rats after exercise training for 6 weeks. Either low-intensity or moderate-intensity exercise mitigated EIB and increased exercise capacity in ovalbumin-sensitized (asthmatic) rats. Low-intensity aerobic exercise reduced the vacuolar degeneration degrees, lipid contents, neuronal peripherin and neurofilament-68 expression, demolished neurites, but increased the chromaffin granule density, endocrine chromogranin A and phenylethanolamine N-methyltransferase expression in the adrenal medullary tissues, accompanied by increased levels of circulating epinephrine and corticosterone, but decreased nerve growth factor in asthmatic rats. Finally, low-intensity aerobic exercise significantly reduced the relative levels of phosphorylated extracellular signal-regulated kinase and phosphorylated cAMP responsive element-binding protein and the relative mRNA expression levels of downstream molecules, including c-FOS and c-JUN in the adrenal medullary of asthmatic rats. We suggest that low-intensity aerobic exercise improves the endocrine dysfunction of AMCCs and mitigates EIB.
- Nuclear imaging to characterize adrenal tumors: Comparison with MRI. [Journal Article]
- World J Radiol 2014 Jul 28; 6(7):493-501.
To describe the role of nuclear imaging modalities using nor-cholesterol, metaiodobenzylguanidine (MIBG) and fluorine-deoxy-glucose (FDG) in adrenal tumors for lesion characterization in comparison with magnetic resonance (MR).Population was classified in group 1 consisting of 30 patients with non-hypersecreting unilateral adrenal masses, in group 2 consisting of 34 patients with hypersecreting (n = 19) or non-hypersecreting (n = 15) adrenal adenomas and in group 3 consisting of 18 patients with chromaffin-tissue tumors (CTT), of which 14 were pheochromocytomas while 4 were paragangliomas (n = 4). All patients underwent MR and nuclear studies (nor-cholesterol, MIBG and FDG). Pathology samples (n = 63) or follow-up data in adenomas (n = 19) were used as standard of reference for imaging studies interpretation.In group 1, MR findings were not highly accurate for lesion characterization, while the results of nuclear scans showed abnormal nor-cholesterol, MIBG and FDG concentration in all cases of adenomas, pheos and malignant tumors, respectively. In group 2, no differences in MR parameters were found between hyperfunctioning and non-hyperfunctioning adenomas, while nor-cholesterol uptake was significantly higher in hyperfunctioning compared to non-hyperfunctioning lesions. In group 3, no differences in MR parameters were found between benign and malignant CCT, while MIBG uptake was significantly higher in malignant compared to benign tumors.On the basis of our findings, nuclear imaging modalities using specific target agents are able to better characterize adrenal tumors, compared with MR. In particular, radionuclide techniques are able to identify the nature of adrenal incidentalomas and to differentiate between hypersecreting and non-hypersecreting adenomas as well as between benign and malignant CTT.
- Adrenal adrenoceptors in heart failure. [Journal Article, Review]
- Front Physiol 2014.:246.
Heart failure (HF) is a chronic clinical syndrome characterized by the reduction in left ventricular (LV) function and it represents one of the most important causes of morbidity and mortality worldwide. Despite considerable advances in pharmacological treatment, HF represents a severe clinical and social burden. Sympathetic outflow, characterized by increased circulating catecholamines (CA) biosynthesis and secretion, is peculiar in HF and sympatholytic treatments (as β-blockers) are presently being used for the treatment of this disease. Adrenal gland secretes Epinephrine (80%) and Norepinephrine (20%) in response to acetylcholine stimulation of nicotinic cholinergic receptors on the chromaffin cell membranes. This process is regulated by adrenergic receptors (ARs): α2ARs inhibit CA release through coupling to inhibitory Gi-proteins, and β ARs (mainly β2ARs) stimulate CA release through coupling to stimulatory Gs-proteins. All ARs are G-protein-coupled receptors (GPCRs) and GPCR kinases (GRKs) regulate their signaling and function. Adrenal GRK2-mediated α2AR desensitization and downregulation are increased in HF and seem to be a fundamental regulator of CA secretion from the adrenal gland. Consequently, restoration of adrenal α2AR signaling through the inhibition of GRK2 is a fascinating sympatholytic therapeutic strategy for chronic HF. This strategy could have several significant advantages over existing HF pharmacotherapies minimizing side-effects on extra-cardiac tissues and reducing the chronic activation of the renin-angiotensin-aldosterone and endothelin systems. The role of adrenal ARs in regulation of sympathetic hyperactivity opens interesting perspectives in understanding HF pathophysiology and in the identification of new therapeutic targets.
- Pre-operative (68)Ga-DOTANOC somatostatin receptor PET/CT imaging demonstrating multiple synchronous lesions in a patient with head and neck paraganglioma. [JOURNAL ARTICLE]
- Rev Esp Med Nucl Imagen Mol 2014 Jul 17.
Paragangliomas, or glomus tumors, are neoplasms arising from extra-adrenal chromaffin tissue. They frequently cause symptoms by over-production of catecholamines with known predilection to multicentricity. We describe the case of a patient with bilateral carotid body tumor who underwent a preoperative (68)Gallium labeled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-NaI3-Octreotide ((68)Ga-DOTANOC) positron emission tomography/computed tomography (PET/CT) imaging for staging. This is a unique case in which multiple paraganglioma and pheochromocytoma were demonstrated in a single patient using (68)Ga-DOTANOC PET/CT.
- Segregation of neuronal and neuroendocrine differentiation in the sympathoadrenal lineage. [JOURNAL ARTICLE]
- Cell Tissue Res 2014 Jul 20.
Neuronal and neuroendocrine cells possess the capacity for Ca(2+)-regulated discharge of messenger molecules, which they release into synapses or the blood stream, respectively. The neural-crest-derived sympathoadrenal lineage gives rise to the sympathetic neurons of the autonomic nervous system and the neuroendocrine chromaffin cells of the adrenal medulla. These cells provide an excellent model system for studying common and distinct developmental mechanisms underlying the acquisition of neuroendocrine and neuronal properties. As catecholaminergic cells, they possess common markers related to noradrenaline synthesis, storage and release, but they also display diverging gene expression patterns and are morphologically and functionally different. The precise mechanisms that underlie the diversification of sympathoadrenal cells into neurons and neuroendocrine cells are not fully understood. However, in the past we could show that the establishment of a chromaffin phenotype does not depend on signals from the adrenal cortex and that chromaffin cells and sympathetic neurons apparently differ from the onset of their catecholaminergic differentiation. Nevertheless, the cues that specifically induce neuroendocrine features remain elusive. The early development of the progenitors of chromaffin cells and sympathetic neurons depends on a common set of transcription factors with overlapping but distinct influences on their development. In addition to the well-defined role of transcription factors as developmental regulators, our understanding of post-transcriptional gene regulation by microRNAs has substantially increased within the last few decades. This review highlights the major similarities and differences between chromaffin cells and sympathetic neurons, summarizes our current knowledge of the roles of selected transcription factors, microRNAs and environmental signals for the neuroendocrine differentiation of sympathoadrenal cells, and draws comparisons with the development of other endocrine and neuronal cells.
- Lumenal Protein within Secretory Granules Affects Fusion Pore Expansion. [Journal Article]
- Biophys J 2014 Jul 1; 107(1):26-33.
It is often assumed that upon fusion of the secretory granule membrane with the plasma membrane, lumenal contents are rapidly discharged and dispersed into the extracellular medium. Although this is the case for low-molecular-weight neurotransmitters and some proteins, there are numerous examples of the dispersal of a protein being delayed for many seconds after fusion. We have investigated the role of fusion-pore expansion in determining the contrasting discharge rates of fluorescent-tagged neuropeptide-Y (NPY) (within 200 ms) and tissue plasminogen activator (tPA) (over many seconds) in adrenal chromaffin cells. The endogenous proteins are expressed in separate chromaffin cell subpopulations. Fusion pore expansion was measured by two independent methods, orientation of a fluorescent probe within the plasma membrane using polarized total internal reflection fluorescence microscopy and amperometry of released catecholamine. Together, they probe the continuum of the fusion-pore duration, from milliseconds to many seconds after fusion. Polarized total internal reflection fluorescence microscopy revealed that 71% of the fusion events of tPA-cer-containing granules maintained curvature for >10 s, with approximately half of the structures likely connected to the plasma membrane by a short narrow neck. Such events were not commonly observed upon fusion of NPY-cer-containing granules. Amperometry revealed that the expression of tPA-green fluorescent protein (GFP) prolonged the duration of the prespike foot ∼2.5-fold compared to NPY-GFP-expressing cells and nontransfected cells, indicating that expansion of the initial fusion pore in tPA granules was delayed. The t1/2 of the main catecholamine spike was also increased, consistent with a prolonged delay of fusion-pore expansion. tPA added extracellularly bound to the lumenal surface of fused granules. We propose that tPA within the granule lumen controls its own discharge. Its intrinsic biochemistry determines not only its extracellular action but also the characteristics of its presentation to the extracellular milieu.
- Protein mobility within secretory granules. [Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't]
- Biophys J 2014 Jul 1; 107(1):16-25.
We investigated the basis for previous observations that fluorescent-labeled neuropeptide Y (NPY) is usually released within 200 ms after fusion, whereas labeled tissue plasminogen activator (tPA) is often discharged over many seconds. We found that tPA and NPY are endogenously expressed in small and different subpopulations of bovine chromaffin cells in culture. We measured the mobility of these proteins (tagged with fluorophore) within the lumen of individual secretory granules in living chromaffin cells, and related their mobilities to postfusion release kinetics. A method was developed that is not limited by standard optical resolution, in which a bright flash of strongly decaying evanescent field (∼64 nm exponential decay constant) produced by total internal reflection (TIR) selectively bleaches cerulean-labeled protein proximal to the glass coverslip within individual granules. Fluorescence recovery occurred as unbleached protein from distal regions within the 300 nm granule diffused into the bleached proximal regions. The fractional bleaching of tPA-cerulean (tPA-cer) was greater when subsequently probed with TIR excitation than with epifluorescence, indicating that tPA-cer mobility was low. The almost equal NPY-cer bleaching when probed with TIR and epifluorescence indicated that NPY-cer equilibrated within the 300 ms bleach pulse, and therefore had a greater mobility than tPA-cer. TIR-fluorescence recovery after photobleaching revealed a significant recovery of tPA-cer (but not NPY-cer) fluorescence within several hundred milliseconds after bleaching. Numerical simulations, which take into account bleach duration, granule diameter, and the limited number of fluorophores in a granule, are consistent with tPA-cer being 100% mobile, with a diffusion coefficient of 2 × 10(-10) cm(2)/s (∼1/3000 of that for a protein of similar size in aqueous solution). However, the low diffusive mobility of tPA cannot alone explain its slow postfusion release. In the accompanying study, we suggest that, additionally, tPA itself stabilizes the fusion pore with dimensions that restrict its own exit.
- HIF signaling pathway in pheochromocytoma and other neuroendocrine tumors. [JOURNAL ARTICLE]
- Physiol Res 2014 Jun 6; 63(Supplementum 2):S251-S262.
Hypoxia-inducible factors (HIFs) are transcription factors controlling energy, iron metabolism, erythropoiesis, and development. Dysregulation of these proteins contributes to tumorigenesis and cancer progression. Recent findings revealed the important role of HIFs in the pathogenesis of neuroendocrine tumors, especially pheochromocytoma (PHEO) and paraganglioma (PGL). PHEOs and PGLs are catecholamine-producing tumors arising from sympathetic- or parasympathetic-derived chromaffin tissue. To date, eighteen PHEO/PGL susceptibility genes have been identified. Based on the main signaling pathways, PHEOs/PGLs have been divided into two clusters, pseudohypoxic cluster 1 and cluster 2, rich in kinase receptor signaling and protein translation pathways. Recent data suggest that both clusters are interconnected via the HIF signaling and its role in tumorigenesis is supported by newly described somatic and germline mutations in HIF2A gene in patients with PHEOs/PGLs associated with polycythemia, and in some of them also with somatostatinoma. Moreover, HIFalpha signaling has also been shown to be upregulated in neuroendocrine tumors other than PHEO/PGL. Some of these tumors are components of hereditary tumor syndromes which can be associated with PHEO/PGL, but also in ileal carcinoids or melanoma. HIF signaling appears to be one of the crucial players in tumorigenesis, which could suggest new therapeutic approaches for treatment of neuroendocrine tumors.
- Chronic opioids regulate KATP channel subunit Kir6.2 and carbonic anhydrase I & II expression in rat adrenal chromaffin cells via HIF-2α and protein kinase A. [JOURNAL ARTICLE]
- Am J Physiol Cell Physiol 2014 Jun 4.
At birth, asphyxial stressors such as hypoxia and hypercapnia are important physiological stimuli for adrenal catecholamine release that is critical for the proper transition to extra-uterine life. We recently showed that chronic opioids blunt chemosensitivity of neonatal rat adrenomedullary chromaffin cells (AMCs) to hypoxia and hypercapnia. This blunting was attributable to increased KATP channel and decreased carbonic anhydrase (CA) I, II expression respectively, and involved μ- and δ-opioid receptor signaling pathways. To address underlying molecular mechanisms, we first exposed an O2- and CO2-sensitive, immortalized rat chromaffin cell line (MAH cells) to combined μ- (DALDA) and δ- (DPDPE) opioid agonists (2 μM) for ~7 days. Western blot and QPCR analysis revealed that chronic opioids increased KATP channel subunit Kir6.2, and decreased CAII expression; both effects were blocked by naloxone and were absent in hypoxia inducible factor (HIF)-2α-deficient MAH cells. Chronic opioids also stimulated HIF-2α accumulation along a time-course similar to Kir6.2. Chromatin immunoprecipitation assays on opioid-treated cells revealed the binding of HIF-2α to a hypoxia response element in the promoter region of the Kir6.2 gene. The opioid-induced regulation of Kir6.2 and CAII was dependent on PKA, but not PKC or CaM kinase, activity. Interestingly, a similar pattern of HIF-2α, Kir6.2, and CAII regulation (including downregulation of CAI) was replicated in chromaffin tissue obtained from rat pups, born to dams exposed to morphine throughout gestation. Collectively, these data reveal novel mechanisms by which chronic opioids blunt asphyxial chemosensitivity in AMCs, thereby contributing to abnormal arousal responses in the offspring of opiate-addicted mothers.