Composite paraganglioma-ganglioneuroma with atypical catecholamine profile and phenylethanolamine N-methyltransferase expression: a case report and literature review

Pheochromocytomas and paragangliomas (PPGLs) are rare tumors that secrete catecholamines and arise from the adrenal medulla or extra-adrenal sympathetic ganglia. These tumors secrete adrenaline and noradrenaline, but paragangliomas usually produce only noradrenaline because of the lack of phenylethanolamine N-methyltransferase (PNMT) expression. Composite paragangliomas, which are complex tumors consisting of multiple types of neuroblastic cells, are extremely rare. We present the case of a 46-year-old woman with an atypical catecholamine profile who was preoperatively diagnosed with pheochromocytoma. However, postoperative pathology revealed that the patient had an extra-adrenal paraganglioma accompanied by a ganglioneuroma, which led to the diagnosis of a composite tumor. Interestingly, PNMT is expressed in both paragangliomas and ganglioneuromas. In addition, we reviewed reported composite paragangliomas and compared their clinical features with those of composite pheochromocytomas. We also discuss various aspects of the etiology of composite paragangliomas and the mechanism by which PNMT is expressed in tumors.

miR-375 mediates the CRF signaling pathway to regulate catecholamine biosynthesis by targeting Sp1 in porcine adrenal gland

Corticotropin-releasing-factor (CRF) is a key regulator of catecholamines (CATs) biosynthesis in the adrenal gland. Furthermore, miR-375 has been confirmed to be localized in the mouse adrenal gland. However, the relationships between miR-375 and CRF in regulating CATs biosynthesis remain to be established. This study was designed to investigate the relationship between CRF and miR-375 in the regulation of CATs biosynthesis in the porcine adrenal gland. Eight adult female pigs (four controls; four injected intracerebroventricularly with 50 μg of CRF) were used for the in vivo experiments in this study. The results showed that miR-375 was exclusively localized in porcine adrenal medullary cells. Functional studies showed that miR-375 negatively regulated CATs synthesis in primary cells by affecting the expression of the CATs synthetases tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT). CRF up-regulated the expression of CATs synthetase in primary adrenal medullary cells under basal conditions and upon endogenous miR-375 inhibition; the enhanced effects vanished when cellular miR-375 was overexpressed by transfecting miR-375-mic. CRF decreased the expression of miR-375 both in vivo and in vitro. Our in vitro results showed that CRF significantly decreased the expression of miR-375, perhaps by binding to CRFR1. miR-375 functions by directly binding to the 3'-UTR region of specificity protein 1 (Sp1), which is involved in regulating Th and Dbh expression. These data collectively indicate that miR-375 plays an important role in regulating CATs synthesis and mediates the CRF signaling pathway in porcine adrenal medullary cells.

Three-dimensional image reconstruction of distribution of Pnmt+ cell-derived cells in murine heart

Elucidating the function of specific cell types in a highly complex multicellular system such as the heart often requires detailed anatomic reconstruction. We recently described a distinctive class of phenylethanolamine n-methyltransferase (Pnmt+) cell-derived cardiomyocytes (PdCMs), a new cardiomyocyte population with a potential endocrine role. In this dataset, a 3D reconstruction was carried out to visualise the distribution of PdCMs throughout the murine heart. Rigid registration (stiff rotation and translation) was applied to properly align the fused heart slice images based on landmarks using TrakEM2, an open source plug-in in Fiji. The registered slices were then analysed and reconstructed using MATLAB (MATLAB®. Version 8.3.0.532). The final reconstructed 3D volume was 561×866×48 pixels (corresponding to spatial resolutions of 5.8, 8.9 and 2.5 mm in the x-, y- and z-direction respectively), and visualised in Paraview. The reconstruction allows for detailed analyses of morphology, projections and cellular features of different cell types, enabling further geometrical and topological analyses. Image data can be accessed and viewed through Figshare.

Stress-induced alterations in catecholamine enzymes gene expression in the hypothalamic dorsomedial nucleus are modulated by caudal brain and not hypothalamic paraventricular nucleus neurons

The hypothalamic dorsomedial nucleus (DMN) represents an important coordinate center for regulation of autonomic and neuroendocrine systems, especially during stress response. The present study was focused on the gene expression of catecholamine-synthesizing enzymes and the protein levels of tyrosine hydroxylase in DMN, both in control and stressed rats. Moreover, pathways modulating the gene expression of tyrosine hydroxylase in DMN during immobilization (IMO) stress were also investigated. Gene expressions of all catecholamine-synthesizing enzymes were detected in DMN samples. While the levels of tyrosine hydroxylase and phenylethanolamine N-methyltransferase mRNA were increased in IMO rats, aromatic L-amino acid decarboxylase and dopamine-beta-hydroxylase mRNA remained unchanged. Tyrosine hydroxylase protein levels were significantly elevated in the DMN only after repeated IMO stress. Postero-lateral deafferentations of the DMN, or transections of the ascending catecholaminergic pathways originating in the lower brainstem abolished the IMO-induced increase of tyrosine hydroxylase gene expression in the DMN. Nevertheless, postero-lateral deafferentations of the hypothalamic paraventricular nucleus (PVN), which separate the DMN from the PVN, had no effect on IMO-induced elevation of tyrosine hydroxylase mRNA in the DMN. The present data indicate that certain DMN neurons synthesize mRNA of catecholamine enzymes. The stress-induced increase of tyrosine hydroxylase and phenylethanolamine N-methyltransferase mRNA in DMN neurons indicates the involvement of these catecholaminergic neurons in stress response. The gene expression of tyrosine hydroxylase in DMN is modulated by lower brainstem and/or spinal cord, but not by PVN afferents.

Radioenzymatic determination of phenylpropanolamine in plasma

We modified a norepinephrine radioenzymatic method (C. R. Lake, M. G. Ziegler, and I. J. Kopin, 1976, Life Sci. 18, 1315-1326) for determination of plasma phenylpropanolamine (PPA) concentrations. PPA is converted to N[methyl-3H]ephedrine ([3H]EPD) by the enzyme phenylethanolamine N-methyltransferase (PNMT) and S-[methyl-3H]adenosyl-L-methionine ([3H]AdoMet). The product, [3H]EPD, is isolated from unreacted [3H]AdoMet and labeled side products by an organic extraction and a TLC procedure. In addition, a preincubation organic extraction procedure is included to remove inhibitors of PNMT from plasma and to concentrate the sample for enhanced enzymatic conversion. In order to accurately quantitate PPA across the wide range of possible concentrations, the assay is conducted at two plasma volumes. PPA concentrations between 0.3 and 50 micrograms/liter can be detected with 1 ml of plasma, while concentrations between 4 and 1500 micrograms/liter can be detected with 0.1 ml of plasma. The intra-assay coefficients of variation (CVs) are 9.3 and 5.7% at 0.5 and 1500 micrograms/liter, respectively, while the mean interassay CV is 13.8%.

Radioenzymatic assay of catecholamines: real and apparent losses of labelled product

In the radioenzymatic assay of catecholamines, using catechol-O-methyltransferase, the yield of labelled product is frequently less than the expected value. This has been attributed by some workers to losses during the periodate oxidation of the O-methylated derivatives. Using spectrophotometric methods, we have demonstrated that there is no oxidative demethylation of the methoxycatecholamines during periodate oxidation. In a novel technique designed to determine the specific activity of small quantities of tritiated S-adenosylmethionine, high performance liquid chromatography with electrochemical detection was used to measure the amount of adrenaline formed from unlabelled noradrenaline, in the presence of phenylethanolamine-N-methyltransferase and tritiated S-adenosylmethionine. As well as the real losses occurring during solvent extraction and thin layer chromatography (demonstrated spectrophotometrically), apparent 'loss' of radiolabelled product may be due to the assumption that the value for the specific activity of the tritiated S-adenosylmethionine and the determination of the product's radioactivity are both absolutely accurate, with no allowance being made for the normal and expected experimental errors in such measurements.

Radioenzymatic assay measurement of yohimbine's influence on adrenergic neurotransmission of rat vas deferens: unique consequence of using normetanephrine as an uptake2-blocking agent

The effect of the alpha 2-receptor antagonist, yohimbine on norepinephrine overflow was studied in the transmural-stimulated isolated rat vas deferens. A radioenzymatic assay was used to measure the endogenous norepinephrine overflow. In initial studies conducted in the presence of uptake1 blocker desipramine (10(-6) M) and uptake 2 blocker, normetanephrine (10(-5) M) there was an apparent uncoupling of the influence of yohimbine on nerve-stimulated contractile response from norepinephrine overflow. These results were found to be due to the electrolytic O-demethylation of normetanephrine with the resultant generation of large quantities of norepinephrine obscuring the influence of yohimbine on nerve-stimulated norepinephrine overflow from the vas deferens. These findings serve as a warming to the use of normetanephrine as an uptake1 blocker when radioenzymatic assay is used to measure norepinephrine overflow from transmural-stimulated isolated tissue preparations. Yohimbine (10(-6) M), in the absence of uptake blockade, causes a 3-fold enhancement of nerve-stimulated norepinephrine overflow at 1 Hz and a 2-fold enhancement at 10 Hz. This report demonstrates utilization of a radioenzymatic assay to study endogenous norepinephrine overflow from rat vas deferens. Results for yohimbine are complementary to others using measurement of 3H-label overflow from [3H]norepinephrine prelabeled isolated tissue.

A radioenzymatic method for determination of normetanephrine in blood plasma

A radioenzymatic assay for determination of normetanephrine in blood plasma is described. It was based on N-methylation of normetanephrine by phenylethanolamine-N-methyltransferase using S-adenosyl[methyl-3]methionine as the methyl donor. 2981 +/- 85 cpm (mean +/- s mean, n = 32) were obtained from 1 ng normetanephrine. Blank values corresponded to 27 +/- 3 pg (n = 7). Normetanephrine levels measured in the blood plasma of 12 persons ranged from 1.3 to 9.6 ng/ml.

Increased plasma and urinary normetanephrine in young patients with primary hypertension

1. Normetanephrine was measured in small samples of plasma and urine of hypertensive patients and normal volunteers (age 20-60 years) by a specific radioenzymatic assay with bovine adrenal phenylethanolamine N-methyltransferase and tritiated S-adenosylmethionine. 2. Noradrenaline was measured simultaneously in plasma and urine. 3. Plasma normetanephrine and noradrenaline concentrations varied in direct proportion to activation or suppression of sympathetic nerve function. 4. Both plasma and urinary normetanephrine concentrations were elevated in patients with phaeochromocytoma. 5. Plasma normetanephrine concentrations were related to plasma noradrenaline concentrations of hypertensive subjects. 6. Plasma normetanephrine and noradrenaline concentrations and urinary normetanephrine excretion rates were increased in some young patients with primary hypertension, suggesting that sympathetic nerve hyperactivity is a pathogenic factor in these patients.

A selective radioenzymatic assay for the determination of octopamine and phenylethanolamine in plasma and cerebrospinal fluid. Preliminary results in human and experimental hepatic encephalopathy

A sensitive radioenzymatic assay for the simultaneous determination of phenylethanolamine and octopamine in biological fluids is described. It is derived from the radioenzymatic assay originally described by Molinoff et al. (1969) and subsequently modified by Saavedra (1974). The enzymatic reaction is based upon the methylation of phenylethanolamine and octopamine by phenylethanolamine-N-methyl transferase using 14C-S-adenosylmethionine as the methyl donor. The N-methyl derivatives of the two amines are separately extracted and estimated. Selectivity is increased by optimization of extraction and evaporation and by subsequent extraction of the two compounds. Phenylethanolamine and octopamine levels were determined in plasma of human subjects and in plasma and CSF of dogs. The levels were found significantly elevated both in human and experimental hepatic encephalopathy.

[Radioenzymatic assay for catecholamines (author's transl)]

Catecholamines are neurotransmitters produced and secreted by the central and autonomic nervous systems. In addition to being neurotransmitters, amines produced mainly by the adrenal medulla also act as hormones. Fluorometric measurements of amines yield variable results because of the poor sensitivity of the techniques, and the low concentration of these amines in tissues and biological fluids. The lack of specific and sensitive analytical methods has been an obstacle to resolving the mechanism of action of these neurotransmitters and hormones. The possibility of achieving qualitative and quantitative determination of picomole or femtomole amounts of these amines is a major need. Recently, radioenzymatic procedures for catecholamine assay have been developed and there has been a significant improvement in both sensitivity and accuracy of catecholamine assays. In this article, details of these radioenzymatic assay methods are reviewed.

Radioenzymatic estimation of noradrenalin in small plasma samples without prior extraction

We have developed a radioenzymatic method for the estimation of noradrenalin in small plasma samples by utilizing partly purified phenylethanolamine-N-methyltransferase. Noradrenalin can be estimated in deproteinised plasma without prior extraction. The sensitivity of the assay is better than 2.5 pg. Inclusion of an internal standard with each sample is necessary as the enzyme reaction is slightly influenced by some components of the plasma. Prior extraction with alumina severely decreases the sensitivity of the assay.

Effects of vinblastine on catecholamine-biosynthetic enzymes in heart, sympathetic ganglion and adrenal glands of rats

1. The effect of vinblastine on the activities of dopamine-beta-hydroxylase (DBH) in heart, superior cervical ganglion and adrenal glands of rats and tyrosine hydroxylase (TH) and phenylethanolamine-N-methyl transferase (PNMT) in adrenal glands was examined.2. In the superior cervical ganglion and heart, DBH activity decreased within hours, reached a minimum in 3 to 5 days and slowly returned towards normal over the next 2 weeks.3. There was an increase in the activities of TH, DBH and PNMT in adrenal glands which was prevented by adrenal denervation.4. When the same total dose of vinblastine was administered subdivided over a period of 5 days, enzyme activities in heart, superior cervical ganglion or adrenal glands remained unchanged.