Intricacies of the Molecular Machinery of Catecholamine Biosynthesis and Secretion by Chromaffin Cells of the Normal Adrenal Medulla and in Pheochromocytoma and Paraganglioma

Role of epigenetic regulation on catecholamine synthesis in pheochromocytoma and paraganglioma

INTRODUCTION

Pheochromocytomas and paragangliomas (PPGLs) typically secrete catecholamines and their metabolites (metanephrines [MN] and normetanephrine [NMN]). Catecholamines are synthesized by several enzymes: phenylalanine hydroxylase (encoded by PAH), tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (DDC), dopamine β-hydroxylase (DBH), and phenylethanolamine N-methyltransferase (PNMT). MN/NMN secretion varies between anatomical and molecular subgroups. The aim of this study was to assess the correlation between DNA methylation of catecholamine synthesis genes and MN/NMN secretion.

METHODS

Gene promoter methylation of PAH, TH, AADC, DBH, and PNMT were extracted and calculated based on publicly available data. Comparisons and correlation analysis were performed between MN ± NMN (MN/NMN), NMN only, and neither/unknown secretion patterns. Methylation levels and MN/NMN patterns were compared by three genetic alteration subgroups: pseudohypoxia (PH), kinase signaling (KS), and others.

RESULTS

A total of 178 cases were included. Methylation of PAH CpGs negatively correlated with probability for MN/NMN secretion (p < .05 for all CpGs) and positively with NMN-only secretion. NMN-only secreting tumors had significantly higher promoter methylation of PAH, DBH, and PNMT compared with MN/NMN-secreting tumors. MN/NMN-secreting PPGLs had mainly KS alterations (52.1%), whereas NMN-only PPGLs had PH alterations (41.9%). PPGLs in the PH versus KS group had gene promoter hypermethylation of PAH (p = .002), DBH (p = .02), and PNMT (p = .003).

CONCLUSIONS

Promoter methylation of genes encoding catecholamine synthesis enzymes is strongly and inversely correlated with MN/NMN patterns in PPGLs. KS and PH-related tumors have distinct methylation patterns. These results imply that methylation is a key regulatory mechanism of catecholamine synthesis in PPGLs.

Update on clinical characteristics in the evaluation of phaeochromocytoma and paraganglioma

Pheochromocytomas and sympathetic paragangliomas (PPGL) are rare neuroendocrine tumors originating from chromaffin tissue of the adrenal medulla and extra-adrenal sympathetic paraganglia. Historically, many of these tumors were diagnosed postmortem, earning pheochromocytomas the moniker "great mimic" due to their diverse clinical manifestations that can resemble various other conditions. Over time, the clinical presentation of PPGL has evolved, with a shift from symptomatic or postmortem diagnoses to more frequent incidental discoveries or diagnoses through screening, with postmortem identification now being rare. The development of a clinical scoring system has improved the identification of patients at increased risk for PPGL. Notably, the proportion of PPGL patients with normal blood pressure ranges from 15 % to 40 %, varying based on the clinical context. Despite the tumor's reputation, PPGL is an exceedingly rare cause of resistant hypertension. Management of a pheochromocytoma crisis has advanced, with several classes of drugs available for treatment. However, PPGL during pregnancy remains a significant concern, associated with substantial maternal and fetal mortality rates. Additionally, PPGL can present as rare disorders, including catecholamine-induced cardiomyopathy, Cushing syndrome, and urinary bladder PGL. Given these varied presentations, heightened awareness and prompt recognition of PPGL are crucial for timely diagnosis and treatment, ultimately improving patient outcomes. In this article, we offer an in-depth analysis of the diverse clinical presentations of PPGL, highlighting their complexity and the associated diagnostic and treatment strategies.

Mechanical Strain Induces and Increases Vesicular Release Monitored by Microfabricated Stretchable Electrodes

Exocytosis involving the fusion of intracellular vesicles with cell membrane, is thought to be modulated by the mechanical cues in the microenvironment. Single-cell electrochemistry can offer unique information about the quantification and kinetics of exocytotic events; however, the effects of mechanical force on vesicular release have been poorly explored. Herein, we developed a stretchable microelectrode with excellent electrochemical stability under mechanical deformation by microfabrication of functionalized poly(3,4-ethylenedioxythiophene) conductive ink, which achieved real-time quantitation of strain-induced vesicular exocytosis from a single cell for the first time. We found that mechanical strain could cause calcium influx via the activation of Piezo1 channels in chromaffin cell, initiating the vesicular exocytosis process. Interestingly, mechanical strain increases the amount of catecholamines released by accelerating the opening and prolonging the closing of fusion pore during exocytosis. This work is expected to provide revealing insights into the regulatory effects of mechanical stimuli on vesicular exocytosis.

Effects of chronic stress on cancer development and the therapeutic prospects of adrenergic signaling regulation

Long-term chronic stress is an important factor in the poor prognosis of cancer patients. Chronic stress reduces the tissue infiltration of immune cells in the tumor microenvironment (TME) by continuously activating the adrenergic signaling, inhibits antitumor immune response and tumor cell apoptosis while also inducing epithelial-mesenchymal transition (EMT) and tumor angiogenesis, promoting tumor invasion and metastasis. This review first summarizes how adrenergic signaling activates intracellular signaling by binding different adrenergic receptor (AR) heterodimers. Then, we focused on reviewing adrenergic signaling to regulate multiple functions of immune cells, including cell differentiation, migration, and cytokine secretion. In addition, the article discusses the mechanisms by which adrenergic signaling exerts pro-tumorigenic effects by acting directly on the tumor itself. It also highlights the use of adrenergic receptor modulators in cancer therapy, with particular emphasis on their potential role in immunotherapy. Finally, the article reviews the beneficial effects of stress intervention measures on cancer treatment. We think that enhancing the body's antitumor response by adjusting adrenergic signaling can enhance the efficacy of cancer treatment.

Increasing Catecholamine Secretion Through NPY in Pheochromocytomas With False-Negative 123 I-MIBG Scintigraphy

INTRODUCTION

123 I-MIBG has been well established as a functional imaging tool, and 131 I-MIBG therapy is being considered for catecholamine-secreting tumors. Tumors with the characteristics of a noradrenergic biochemical phenotype, small, malignant, metastatic, extra-adrenal, bilateral, and hereditary, especially SDHx -related tumors, are reported to correlate with reduced MIBG uptake. However, the potential molecular mechanisms influencing MIBG uptake have been poorly studied.

PATIENTS AND METHODS

To identify critical genes that may enhance MIBG accumulation in pheochromocytomas (PCCs), we performed RNA-seq analyses for 16 operated patients with PCCs (6 MIBG-negative and 10 MIBG-positive) combined with RT-qPCR for 27 PCCs (5 MIBG-negative and 22 MIBG-positive) and examined primary cultures of the surgical tissues.

RESULTS

In the present study, 6 adrenal nodules of 66 nodules surgically removed from 63 patients with PCCs (9%) were MIBG negative. MIBG, a guanethidine analog of norepinephrine, can enter chromaffin cells through active uptake via the cellular membrane, be deposited in chromaffin granules, and be released via Ca 2+ -triggered exocytosis from adrenal chromaffin cells. When we compared expression of several catecholamine biosynthesis and secretion-associated genes between MIBG-negative and MIBG-positive tumors using transcriptome analyses, we found that neuropeptide Y, which is contained in chromaffin granules, was significantly increased in MIBG-negative tumors. NPY stimulated norepinephrine secretion dose-dependently in primary cell culture derived from MIBG-positive PCC. In our study, MIBG-negative PCCs were all norepinephrine-hypersecreting tumors.

CONCLUSIONS

These data indicate that NPY upregulation in PCCs may stimulate chromaffin granule catecholamine secretion, which is associated with false-negative 123 I-MIBG scintigraphy.

Tumor metabolism in pheochromocytomas: clinical and therapeutic implications

Pheochromocytomas and paragangliomas (PPGLs) have emerged as one of the most common endocrine tumors. It epitomizes fascinating crossroads of genetic, metabolic, and endocrine oncology, providing a canvas to explore the molecular intricacies of tumor biology. Predominantly rooted in the aberration of metabolic pathways, particularly the Krebs cycle and related enzymatic functionalities, PPGLs manifest an intriguing metabolic profile, highlighting elevated levels of oncometabolites like succinate and fumarate, and furthering cellular malignancy and genomic instability. This comprehensive review aims to delineate the multifaceted aspects of tumor metabolism in PPGLs, encapsulating genetic factors, oncometabolites, and potential therapeutic avenues, thereby providing a cohesive understanding of metabolic disturbances and their ramifications in tumorigenesis and disease progression. Initial investigations into PPGLs metabolomics unveiled a stark correlation between specific genetic mutations, notably in the succinate dehydrogenase complex (SDHx) genes, and the accumulation of oncometabolites, establishing a pivotal role in epigenetic alterations and hypoxia-inducible pathways. By scrutinizing voluminous metabolic studies and exploiting technologies, novel insights into the metabolic and genetic aspects of PPGLs are perpetually being gathered elucidating complex interactions and molecular machinations. Additionally, the exploration of therapeutic strategies targeting metabolic abnormalities has burgeoned harboring potential for innovative and efficacious treatment modalities. This review encapsulates the profound metabolic complexities of PPGLs, aiming to foster an enriched understanding and pave the way for future investigations and therapeutic innovations in managing these metabolically unique tumors.

The 3D in vitro Adrenoid cell model recapitulates the complexity of the adrenal gland

The crosstalk between the chromaffin and adrenocortical cells is essential for the endocrine activity of the adrenal glands. This interaction is also likely important for tumorigenesis and progression of adrenocortical cancer and pheochromocytoma. We developed a unique in vitro 3D model of the whole adrenal gland called Adrenoid consisting in adrenocortical carcinoma H295R and pheochromocytoma MTT cell lines. Adrenoids showed a round compact morphology with a growth rate significantly higher compared to MTT-spheroids. Confocal analysis of differential fluorescence staining of H295R and MTT cells demonstrated that H295R organized into small clusters inside Adrenoids dispersed in a core of MTT cells. Transmission electron microscopy confirmed the strict cell-cell interaction occurring between H295R and MTT cells in Adrenoids, which displayed ultrastructural features of more functional cells compared to the single cell type monolayer cultures. Adrenoid maintenance of the dual endocrine activity was demonstrated by the expression not only of cortical and chromaffin markers (steroidogenic factor 1, and chromogranin) but also by protein detection of the main enzymes involved in steroidogenesis (steroidogenic acute regulatory protein, and CYP11B1) and in catecholamine production (tyrosine hydroxylase and phenylethanolamine N-methyltransferase). Mass spectrometry detection of steroid hormones and liquid chromatography measurement of catecholamines confirmed Adrenoid functional activity. In conclusion, Adrenoids represent an innovative in vitro 3D-model that mimics the spatial and functional complexity of the adrenal gland, thus being a useful tool to investigate the crosstalk between the two endocrine components in the pathophysiology of this endocrine organ.

Role of the Adrenal Medulla in Hypoglycaemia-Associated Autonomic Failure-A Diabetic Perspective

Hypoglycaemia-associated autonomic failure (HAAF) is characterised by an impairment in adrenal medullary and neurogenic symptom responses following episodes of recurrent hypoglycaemia. Here, we review the status quo of research related to the regulatory mechanisms of the adrenal medulla in its response to single and recurrent hypoglycaemia in both diabetic and non-diabetic subjects with particular focus given to catecholamine synthesis, enzymatic activity, and the impact of adrenal medullary peptides. Short-term post-transcriptional modifications, particularly phosphorylation at specific residues of tyrosine hydroxylase (TH), play a key role in the regulation of catecholamine synthesis. While the effects of recurrent hypoglycaemia on catecholamine synthetic enzymes remain inconsistent, long-term changes in TH protein expression suggest species-specific responses. Adrenomedullary peptides such as neuropeptide Y (NPY), galanin, and proenkephalin exhibit altered gene and protein expression in response to hypoglycaemia, suggesting a potential role in the modulation of catecholamine secretion. Of note is NPY, since its antagonism has been shown to prevent reductions in TH protein expression. This review highlights the need for further investigation into the molecular mechanisms involved in the adrenal medullary response to hypoglycaemia. Despite advancements in our understanding of HAAF in non-diabetic rodents, a reliable diabetic rodent model of HAAF remains a challenge.

Unilateral chemical ablation of the adrenal gland lowers blood pressure and alleviates target organ damage in spontaneously hypertensive rats

Adrenal gland hormones play a critical role in the development and maintenance of hypertension. Adrenal ablation has been used to treat primary aldosteronism but not essential hypertension. The present study aimed to investigate the effectiveness and safety of unilateral adrenal gland ablation in treating spontaneously hypertensive rats (SHR). SHR and Wistar-Kyoto rats (WKY) were subjected to unilateral adrenal ablation with injection of anhydrous ethanol or a sham procedure. Blood pressure was monitored by both tail-cuff plethysmography and telemetry until 6 months after the procedure. Adrenal ablation significantly lowered systolic and diastolic blood pressure of the SHR (P < 0.05 or P < 0.01) but not WKY from 4 to 24 weeks after the procedure. Adrenal ablation substantially damaged adrenal cortex and medulla with fibrosis in SHR and WKY rats. The ablation procedure remarkably reduced the levels of renin, angiotensin II, aldosterone, cortisol, noradrenaline, and epinephrine in SHR (all P < 0.05) but not in WKY. Hypokalemia in SHR was significantly improved by adrenal ablation (P < 0.05), while the serum sodium levels were not affected by adrenal ablation in either SHR or WKY rats. Additionally, adrenal ablation improved cardiac, renal, and vascular remodeling and function measured 3 months after the procedure in SHR. In conclusion, the present study shows that ethanol ablation of adrenal gland can effectively lower blood pressure and prevent target organ damage in SHR. These findings suggest that unilateral debulking of the adrenal gland using ethanol ablation is a promising therapeutic strategy for treating hypertension.

METHODS

Spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were subjected to unilateral adrenal ablation with injection of ethanol or a sham procedure. Blood pressure was monitored for 24 weeks.

RESULTS

Adrenal ablation significantly lowered systolic and diastolic blood pressure of SHR but not WKY from 4 to 24 weeks after the procedure.

CONCLUSION

Unilateral debulking of the adrenal gland using ethanol ablation is a promising therapeutic strategy for treating hypertension.

Early short-term effects on catecholamine levels and pituitary function in patients with pheochromocytoma or paraganglioma treated with [177Lu]Lu-DOTA-TATE therapy

Purpose

While there are reports of treatment-related endocrine disruptions and catecholamine surges in pheochromocytoma/paraganglioma (PPGL) patients treated with [177Lu]Lu-DOTA-TATE therapy, the spectrum of these abnormalities in the immediate post-treatment period (within 48 hours) has not been previously evaluated and is likely underestimated.

Methods

The study population included patients (≥18 years) enrolled in a phase 2 trial for treatment of somatostatin receptor (SSTR)-2+ inoperable/metastatic pheochromocytoma/paraganglioma with [177Lu]Lu-DOTA-TATE (7.4 GBq per cycle for 1 - 4 cycles). Hormonal measurements [adrenocorticotropic hormone (ACTH), cortisol, thyroid stimulating hormone (TSH), free thyroxine (FT4), follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone, estradiol, growth hormone, prolactin], catecholamines, and metanephrines were obtained on days-1, 2, 3, 30, and 60 per cycle as per trial protocol, and were retrospectively analyzed.

Results

Among the 27 patients (age: 54 ± 12.7 years, 48.1% females) who underwent hormonal evaluation, hypoprolactinemia (14.1%), elevated FSH (13.1%), and elevated LH (12.5%) were the most frequent hormonal abnormalities across all 4 cycles combined. On longitudinal follow-up, significant reductions were noted in i. ACTH without corresponding changes in cortisol, ii. TSH, and FT4, and iii. prolactin at or before day-30 of [177Lu]Lu-DOTA-TATE. No significant changes were observed in the gonadotropic axis and GH levels. Levels of all hormones on day-60 were not significantly different from day-1 values, suggesting the transient nature of these changes. However, two patients developed clinical, persistent endocrinopathies (primary hypothyroidism: n=1 male; early menopause: n=1 female). Compared to day-1, a significant % increase in norepinephrine, dopamine, and normetanephrine levels were noted at 24 hours following [177Lu]Lu-DOTA-TATE dose and peaked within 48 hours.

Conclusions

[177Lu]Lu-DOTA-TATE therapy is associated with alterations in endocrine function likely from radiation exposure to SSTR2+ endocrine tissues. However, these changes may sometimes manifest as clinically significant endocrinopathies. It is therefore important to periodically assess endocrine function during [177Lu]Lu-DOTA-TATE therapy, especially among symptomatic patients.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT03206060?term=NCT03206060&draw=2&rank=1, identifier NCT03206060.

PD-L1 Expression is Linked to Tumor-Infiltrating T-Cell Exhaustion and Adverse Pathological Behavior in Pheochromocytoma/Paraganglioma

Pheochromocytoma/paraganglioma (PPGL) is an endocrine-related tumor associated with excessive catecholamine release and has limited treatment options once metastasis occurs. Although recent phase 2 clinical trials of immune checkpoint inhibitors in the treatment of PPGL have preliminarily shown promising results, the fundamentals of immunotherapy for PPGL have not yet been established. In the early research, using bulk RNA sequencing of tumor samples from 7 PPGL patients, we found that PPGL tumor tissues exhibited high PD-L1 mRNA expression compared with adjacent normal adrenal medulla tissues, and this was related to T-cell exhaustion biomarkers. To further validate the association, in this study (n = 60), we first stratified all PPGL samples according to PD-L1 expression as determined by immunohistochemical staining, and then subjected 23 fresh PPGL tumor samples from the cohort to a quantitative polymerase chain reaction (n = 16), flow cytometry (n = 7), and multiplex-immunofluorescence staining. Subsequently, we evaluated the pathological manifestations of all 60 PPGL tumor samples and analyzed the correlation among PD-L1 expression, adverse pathological behavior, various clinicopathological data, and genotypes in PPGL. The results showed that PD-L1-positive expression correlated with the exhaustion of tumor-infiltrating T cells, preoperative abnormal elevation of plasma norepinephrine, high Ki67 index, and adverse pathological behavior in PPGL but not with genetic mutation or metastatic disease, possibly due to the limitation of the small number of patients with metastatic disease (n = 4) in the study cohort. In conclusion, our findings reveal that PD-L1 expression is associated with T-cell exhaustion and adverse pathological behavior in PPGL. These results are expected to provide a new theoretical basis and clinical guidance for the treatment of PPGL.

Forty years of the adrenal chromaffin cell through ISCCB meetings around the world

This historical review focuses on the evolution of the knowledge accumulated during the last two centuries on the biology of the adrenal medulla gland and its chromaffin cells (CCs). The review emerged in the context of a series of meetings that started on the Spanish island of Ibiza in 1982 with the name of the International Symposium on Chromaffin Cell Biology (ISCCB). Hence, the review is divided into two periods namely, before 1982 and from this year to 2022, when the 21st ISCCB meeting was just held in Hamburg, Germany. The first historical period extends back to 1852 when Albert Kölliker first described the fine structure and function of the adrenal medulla. Subsequently, the adrenal staining with chromate salts identified the CCs; this was followed by the establishment of the embryological origin of the adrenal medulla, and the identification of adrenaline-storing vesicles. By the end of the nineteenth century, the basic morphology, histochemistry, and embryology of the adrenal gland were known. The twentieth century began with breakthrough findings namely, the experiment of Elliott suggesting that adrenaline was the sympathetic neurotransmitter, the isolation of pure adrenaline, and the deciphering of its molecular structure and chemical synthesis in the laboratory. In the 1950s, Blaschko isolated the catecholamine-storing vesicles from adrenal medullary extracts. This switched the interest in CCs as models of sympathetic neurons with an explosion of studies concerning their functions, i.e., uptake of catecholamines by chromaffin vesicles through a specific coupled transport system; the identification of several vesicle components in addition to catecholamines including chromogranins, ATP, opioids, and other neuropeptides; the calcium-dependence of the release of catecholamines; the underlying mechanism of exocytosis of this release, as indicated by the co-release of proteins; the cross-talk between the adrenal cortex and the medulla; and the emission of neurite-like processes by CCs in culture, among other numerous findings. The 1980s began with the introduction of new high-resolution techniques such as patch-clamp, calcium probes, marine toxins-targeting ion channels and receptors, confocal microscopy, or amperometry. In this frame of technological advances at the Ibiza ISCCB meeting in 1982, 11 senior researchers in the field predicted a notable increase in our knowledge in the field of CCs and the adrenal medulla; this cumulative knowledge that occurred in the last 40 years of history of the CC is succinctly described in the second part of this historical review. It deals with cell excitability, ion channel currents, the exocytotic fusion pore, the handling of calcium ions by CCs, the kinetics of exocytosis and endocytosis, the exocytotic machinery, and the life cycle of secretory vesicles. These concepts together with studies on the dynamics of membrane fusion with super-resolution imaging techniques at the single-protein level were extensively reviewed by top scientists in the field at the 21st ISCCB meeting in Hamburg in the summer of 2022; this frontier topic is also briefly reviewed here. Many of the concepts arising from those studies contributed to our present understanding of synaptic transmission. This has been studied in physiological or pathophysiological conditions, in CCs from animal disease models. In conclusion, the lessons we have learned from CC biology as a peripheral model for brain and brain disease pertain more than ever to cutting-edge research in neurobiology. In the 22nd ISCCB meeting in Israel in 2024 that Uri Asheri is organizing, we will have the opportunity of seeing the progress of the questions posed in Ibiza, and on other questions that undoubtedly will arise.

Massive Biochemically Silent Pheochromocytoma Masquerading as Nonfunctioning Adrenocortical Cancer

Pheochromocytomas are rare catecholamine-secreting neuroendocrine tumors of the adrenal medulla chromaffin cells, usually associated with features of catecholamine excess. Clinically and biochemically silent pheochromocytoma without adrenergic symptoms or elevated catecholamine concentrations are rare. A 71-year-old female presented with acute right flank pain with abdominal computed tomography (CT) scan revealing a hemorrhagic right adrenal mass. She had no preceding adrenergic symptoms, and normal serum electrolytes, on a background of well-controlled hypertension on amlodipine monotherapy. After conservative management and discharge, an outpatient CT adrenal scan confirmed an 88 × 64 mm right adrenal mass demonstrating intense avidity (maximum standardized uptake value, 20.2) on fluorodeoxyglucose F 18-positron emission tomography (FDG-PET)/CT scan. Biochemical screening supported a nonfunctional adrenal lesion with normal-range plasma normetanephrines and metanephrines. She underwent a right adrenalectomy for presumed nonfunctioning adrenocortical cancer; however, histopathology demonstrated a 120-mm pheochromocytoma. Succinate dehydrogenase subunit B (SDHB) and fumarate hydratase (FH) staining were retained; however, weakly positive 2SC staining raised concerns for FH-deficient pheochromocytoma. Germline DNA sequencing was negative for pathogenic RET, VHL, SDHB, SDHD, or FH variants. Tumor cells stained positive for tyrosine hydroxylase and negative for dopamine β hydroxylase. Four months postoperatively, progress FDG-PET/CT scan demonstrated no focal avidity. Massive biochemically silent pheochromocytomas are exceedingly rare, and we discuss various mechanisms that may predispose patients to this phenomenon.

Metabolic Signatures of Youth Exposure to Mixtures of Per- and Polyfluoroalkyl Substances: A Multi-Cohort Study

BACKGROUND

Exposure to per- and polyfluoroalkyl substances (PFAS) is ubiquitous and has been associated with an increased risk of several cardiometabolic diseases. However, the metabolic pathways linking PFAS exposure and human disease are unclear.

OBJECTIVE

We examined associations of PFAS mixtures with alterations in metabolic pathways in independent cohorts of adolescents and young adults.

METHODS

Three hundred twelve overweight/obese adolescents from the Study of Latino Adolescents at Risk (SOLAR) and 137 young adults from the Southern California Children's Health Study (CHS) were included in the analysis. Plasma PFAS and the metabolome were determined using liquid-chromatography/high-resolution mass spectrometry. A metabolome-wide association study was performed on log-transformed metabolites using Bayesian regression with a g-prior specification and g-computation for modeling exposure mixtures to estimate the impact of exposure to a mixture of six ubiquitous PFAS (PFOS, PFHxS, PFHpS, PFOA, PFNA, and PFDA). Pathway enrichment analysis was performed using Mummichog and Gene Set Enrichment Analysis. Significance across cohorts was determined using weighted Z -tests.

RESULTS

In the SOLAR and CHS cohorts, PFAS exposure was associated with alterations in tyrosine metabolism (meta-analysis p = 0.00002 ) and de novo fatty acid biosynthesis (p = 0.03 ), among others. For example, when increasing all PFAS in the mixture from low (∼ 30 th percentile) to high (∼ 70 th percentile), thyroxine (T4), a thyroid hormone related to tyrosine metabolism, increased by 0.72 standard deviations (SDs; equivalent to a standardized mean difference) in the SOLAR cohort (95% Bayesian credible interval (BCI): 0.00, 1.20) and 1.60 SD in the CHS cohort (95% BCI: 0.39, 2.80). Similarly, when going from low to high PFAS exposure, arachidonic acid increased by 0.81 SD in the SOLAR cohort (95% BCI: 0.37, 1.30) and 0.67 SD in the CHS cohort (95% BCI: 0.00, 1.50). In general, no individual PFAS appeared to drive the observed associations.

DISCUSSION

Exposure to PFAS is associated with alterations in amino acid metabolism and lipid metabolism in adolescents and young adults. https://doi.org/10.1289/EHP11372.

Applications of spatially resolved omics in the field of endocrine tumors

Endocrine tumors derive from endocrine cells with high heterogeneity in function, structure and embryology, and are characteristic of a marked diversity and tissue heterogeneity. There are still challenges in analyzing the molecular alternations within the heterogeneous microenvironment for endocrine tumors. Recently, several proteomic, lipidomic and metabolomic platforms have been applied to the analysis of endocrine tumors to explore the cellular and molecular mechanisms of tumor genesis, progression and metastasis. In this review, we provide a comprehensive overview of spatially resolved proteomics, lipidomics and metabolomics guided by mass spectrometry imaging and spatially resolved microproteomics directed by microextraction and tandem mass spectrometry. In this regard, we will discuss different mass spectrometry imaging techniques, including secondary ion mass spectrometry, matrix-assisted laser desorption/ionization and desorption electrospray ionization. Additionally, we will highlight microextraction approaches such as laser capture microdissection and liquid microjunction extraction. With these methods, proteins can be extracted precisely from specific regions of the endocrine tumor. Finally, we compare applications of proteomic, lipidomic and metabolomic platforms in the field of endocrine tumors and outline their potentials in elucidating cellular and molecular processes involved in endocrine tumors.

Novel Germline PHD2 Variant in a Metastatic Pheochromocytoma and Chronic Myeloid Leukemia, but in the Absence of Polycythemia

Background: Pheochromocytoma (Pheo) and paraganglioma (PGL) are rare tumors, mostly resulting from pathogenic variants of predisposing genes, with a genetic contribution that now stands at around 70%. Germline variants account for approximately 40%, while the remaining 30% is attributable to somatic variants. Objective: This study aimed to describe a new PHD2 (EGLN1) variant in a patient affected by metastatic Pheo and chronic myeloid leukemia (CML) without polycythemia and to emphasize the need to adopt a comprehensive next-generation sequencing (NGS) panel. Methods: Genetic analysis was carried out by NGS. This analysis was initially performed using a panel of genes known for tumor predisposition (EGLN1, EPAS1, FH, KIF1Bβ, MAX, NF1, RET, SDHA, SDHAF2, SDHB, SDHC, SDHD, TMEM127, and VHL), followed initially by SNP-CGH array, to exclude the presence of the pathogenic Copy Number Variants (CNVs) and the loss of heterozygosity (LOH) and subsequently by whole exome sequencing (WES) comparative sequence analysis of the DNA extracted from tumor fragments and peripheral blood. Results: We found a novel germline PHD2 (EGLN1) gene variant, c.153G>A, p.W51*, in a patient affected by metastatic Pheo and chronic myeloid leukemia (CML) in the absence of polycythemia. Conclusions: According to the latest guidelines, it is mandatory to perform genetic analysis in all Pheo/PGL cases regardless of phenotype. In patients with metastatic disease and no evidence of polycythemia, we propose testing for PHD2 (EGLN1) gene variants. A possible correlation between PHD2 (EGLN1) pathogenic variants and CML clinical course should be considered.

A Case of 123I-Metaiodobenzylguanidine Scintigraphy-Negative Pheochromocytoma with a Tumor-Developing Mutation in the RET Gene

Pheochromocytoma (PCC) is rare catecholamine-producing endocrine tumor that metastasizes in approximately 10% of cases. As a functional imaging of PCC, 123I-metaiodobenzylguanidine (MIBG) scintigraphy was established, and some cases of PCC exhibit negative accumulation on MIBG scintigraphy, indicating a high risk of metastasis. Additionally, germline genetic variants of PCC are evident in approximately 30% of cases, although the genotype-phenotype correlation in PCC, especially the association between genetic mutations and MIBG scintigraphy, remains unclear. A 33-year-old man was admitted to our hospital for further examination for hypertension. He was diagnosed with sporadic PCC, and left adrenalectomy was performed. The adrenal tumor was negative on MIBG scintigraphy. Histology of the tumor revealed a moderately differentiated PCC. Target gene testing revealed a mutation in RET (c.2071G > A). This mutation has been reported to be a tumor-developing gene involved in the pathogenesis of PCC. Moreover, the RET mutation is the only gene mutation reported in a previous study of PCC with negative results on MIBG scintigraphy, except for the SDHB gene mutation, which is a common mutation in metastatic PCC. Correctively, the present RET gene mutation may be associated to MIBG-scintigraphy negative PCC and its pathophysiology. Clinicians should follow such cases more cautiously in clinical practice.

Silent pheochromocytoma and paraganglioma: Systematic review and proposed definitions for standardized terminology

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors with heterogeneous clinical presentations and potential lethal outcomes. The diagnosis is based on clinical suspicion, biochemical testing, imaging and histopathological confirmation. Increasingly widespread use of imaging studies and surveillance of patients at risk of PPGL due to a hereditary background or a previous tumor is leading to the diagnosis of these tumors at an early stage. This has resulted in an increasing use of the term "silent" PPGL. This term and other variants are now commonly found in the literature without any clear or unified definition. Among the various terms, "clinically silent" is often used to describe the lack of signs and symptoms associated with catecholamine excess. Confusion arises when these and other terms are used to define the tumors according to their ability to synthesize and/or release catecholamines in relation to biochemical test results. In such cases the term "silent" and other variants are often inappropriately and misleadingly used. In the present analysis we provide an overview of the literature and propose standardized terminology in an attempt at harmonization to facilitate scientific communication.

Low number of neurosecretory vesicles in neuroblastoma impairs massive catecholamine release and prevents hypertension

INTRODUCTION

Neuroblastoma (NB) is a pediatric cancer of the developing sympathetic nervous system. It produces and releases metanephrines, which are used as biomarkers for diagnosis in plasma and urine. However, plasma catecholamine concentrations remain generally normal in children with NB. Thus, unlike pheochromocytoma and paraganglioma (PHEO/PGL), two other non-epithelial neuroendocrine tumors, hypertension is not part of the usual clinical picture of patients with NB. This suggests that the mode of production and secretion of catecholamines and metanephrines in NB is different from that in PHEO/PGL, but little is known about these discrepancies. Here we aim to provide a detailed comparison of the biosynthesis, metabolism and storage of catecholamines and metanephrines between patients with NB and PHEO.

METHOD

Catecholamines and metanephrines were quantified in NB and PHEO/PGL patients from plasma and tumor tissues by ultra-high pressure liquid chromatography tandem mass spectrometry. Electron microscopy was used to quantify neurosecretory vesicles within cells derived from PHEO tumor biopsies, NB-PDX and NB cell lines. Chromaffin markers were detected by qPCR, IHC and/or immunoblotting.

RESULTS

Plasma levels of metanephrines were comparable between NB and PHEO patients, while catecholamines were 3.5-fold lower in NB vs PHEO affected individuals. However, we observed that intratumoral concentrations of metanephrines and catecholamines measured in NB were several orders of magnitude lower than in PHEO. Cellular and molecular analyses revealed that NB cell lines, primary cells dissociated from human tumor biopsies as well as cells from patient-derived xenograft tumors (NB-PDX) stored a very low amount of intracellular catecholamines, and contained only rare neurosecretory vesicles relative to PHEO cells. In addition, primary NB expressed reduced levels of numerous chromaffin markers, as compared to PHEO/PGL, except catechol O-methyltransferase and monoamine oxidase A. Furthermore, functional assays through induction of chromaffin differentiation of the IMR32 NB cell line with Bt2cAMP led to an increase of neurosecretory vesicles able to secrete catecholamines after KCl or nicotine stimulation.

CONCLUSION

The low amount of neurosecretory vesicles in NB cytoplasm prevents catecholamine storage and lead to their rapid transformation by catechol O-methyltransferase into metanephrines that diffuse in blood. Hence, in contrast to PHEO/PGL, catecholamines are not secreted massively in the blood, which explains why systemic hypertension is not observed in most patients with NB.

A high sensitivity LC-MS/MS method for measurement of 3-methoxytyramine in plasma and associations between 3-methoxytyramine, metanephrines, and dopamine

•

3-methoxytyramine (3MT) aids diagnosis of dopamine-producing tumors and metastases.

•

A sensitive and specific LC-MS/MS method was developed to measure 3MT in plasma.

•

3MT was elevated in 46% of samples with elevated metanephrine and normetanephrine.

•

3MT concentrations correlated the strongest with normetanephrine concentrations.

Introduction

Diagnosis of pheochromocytoma and paraganglioma (PPGL) is aided by the measurement of metanephrine (MN) and normetanephrine (NMN). Research suggests that 3-methoxytyramine (3MT), a dopamine (DA) metabolite, may serve as a biomarker of metastasis in patients with paraganglioma. Considering the very low endogenous plasma 3MT concentrations (<0.1 nM), highly sensitive and specific methods for 3MT are needed.

Methods

We developed a simple method for measurement of 3MT. Sample preparation was performed using solid phase micro-extraction with the eluates injected directly onto the LC-MS/MS. Data acquisition was performed in multiple reaction monitoring mode with an instrumental analysis time of 3 min per sample. We evaluated the method’s performance and analyzed samples from healthy individuals and pathological specimens.

Results

The limit of quantitation and upper limit of linearity were 0.03 nM and 20 nM, respectively. The intra-/inter-day imprecision for pooled plasma samples at concentrations of 0.04 nM, 0.2 nM, and 2 nM was 10.7%/18.3%, 4.5%/8.9%, and 3.1%/0.9%, respectively. Among samples with MN, NMN, or both MN and NMN above the reference intervals (RIs), 0%, 16% and 46%, respectively, showed 3MT greater than the proposed upper RI value of 0.1 nM; 12% of samples with DA above the RI had 3MT above 0.1 nM.

Conclusions

The developed method allowed accurate quantitation of 3MT in patient samples and would provide valuable information to clinicians diagnosing or monitoring patients with PPGL. High 3MT concentrations in patient samples with MN and NMN within the respective RIs may alert clinicians of the possibility of a DA-producing tumor.

HIF2α regulates the synthesis and release of epinephrine in the adrenal medulla

The adrenal gland and its hormones regulate numerous fundamental biological processes; however, the impact of hypoxia signaling on adrenal function remains poorly understood. Here, we reveal that deficiency of HIF (hypoxia inducible factors) prolyl hydroxylase domain protein-2 (PHD2) in the adrenal medulla of mice results in HIF2α-mediated reduction in phenylethanolamine N-methyltransferase (PNMT) expression, and consequent reduction in epinephrine synthesis. Simultaneous loss of PHD2 in renal erythropoietin (EPO)-producing cells (REPCs) stimulated HIF2α-driven EPO overproduction, excessive RBC formation (erythrocytosis), and systemic hypoglycemia, which is necessary and sufficient to enhance exocytosis of epinephrine from the adrenal medulla. Based on these results, we propose that the PHD2-HIF2α axis in the adrenal medulla regulates the synthesis of epinephrine, whereas in REPCs, it indirectly induces the release of this hormone. Our findings are also highly relevant to the testing of small molecule PHD inhibitors in phase III clinical trials for patients with renal anemia. KEY MESSAGES: HIF2α and not HIF1α modulates PNMT during epinephrine synthesis in chromaffin cells. The PHD2-HIF2α-EPO axis induces erythrocytosis and hypoglycemia. Reduced systemic glucose facilitates exocytosis of epinephrine from adrenal gland.

Adrenal medulla development and medullary-cortical interactions

The mammalian adrenal gland is composed of two distinct tissue types in a bidirectional connection, the catecholamine-producing medulla derived from the neural crest and the mesoderm-derived cortex producing steroids. The medulla mainly consists of chromaffin cells derived from multipotent nerve-associated descendants of Schwann cell precursors. Already during adrenal organogenesis, close interactions between cortex and medulla are necessary for proper differentiation and morphogenesis of the gland. Moreover, communication between the cortex and the medulla ensures a regular function of the adult adrenal. In tumor development, interfaces between the two parts are also common. Here, we summarize the development of the mammalian adrenal medulla and the current understanding of the cortical-medullary interactions under development and in health and disease.

Case Report: Pheochromocytoma in a 59-Year-Old Woman Presenting With Hypotension

Background: Pheochromocytoma patients who present with shock are extremely rare. Here, we report a patient who presented with shock and was diagnosed with pheochromocytoma. Case Summary: A 59-year-old woman with a history of hypertension without any treatment for 5 years presented with chest tightness. Vital signs on arrival indicated blood pressure of 78/50 mmHg. Twelve-lead electrocardiogram indicated ST-segment depression in leads II, III, aVF, and V3-V6 and QT prolongation. Coronary angiogram revealed no evidence of coronary artery disease. Contrast-enhanced computed tomography demonstrated an inhomogeneous right adrenal mass (2.5 × 3.0 cm). Her 24-h urinary norepinephrine and catecholamine levels were elevated. The patient underwent laparoscopic right adrenalectomy. Histopathology confirmed adrenal pheochromocytoma with residual necrosis. The patient was diagnosed with pheochromocytoma. During the 2-year follow-up, the patient was asymptomatic, and her blood pressure remained normal without medication. ECG showed that the ST-segment depression in leads II, III, aVF, and V3-V6 and the QT prolongation had disappeared. The patient showed no signs of recurrence, with normal urine norepinephrine and catecholamine levels. Conclusion: Patients with pheochromocytoma can present with hypotension or even shock. Clinicians should suspect pheochromocytoma when a patient with a history of hypertension has sudden hypotension or even shock.

HIF-Prolyl Hydroxylase Domain Proteins (PHDs) in Cancer-Potential Targets for Anti-Tumor Therapy?

Solid tumors are typically associated with unbridled proliferation of malignant cells, accompanied by an immature and dysfunctional tumor-associated vascular network. Consequent impairment in transport of nutrients and oxygen eventually leads to a hypoxic environment wherein cells must adapt to survive and overcome these stresses. Hypoxia inducible factors (HIFs) are central transcription factors in the hypoxia response and drive the expression of a vast number of survival genes in cancer cells and in cells in the tumor microenvironment. HIFs are tightly controlled by a class of oxygen sensors, the HIF-prolyl hydroxylase domain proteins (PHDs), which hydroxylate HIFs, thereby marking them for proteasomal degradation. Remarkable and intense research during the past decade has revealed that, contrary to expectations, PHDs are often overexpressed in many tumor types, and that inhibition of PHDs can lead to decreased tumor growth, impaired metastasis, and diminished tumor-associated immune-tolerance. Therefore, PHDs represent an attractive therapeutic target in cancer research. Multiple PHD inhibitors have been developed that were either recently accepted in China as erythropoiesis stimulating agents (ESA) or are currently in phase III trials. We review here the function of HIFs and PHDs in cancer and related therapeutic opportunities.

Pathophysiology and Acute Management of Tachyarrhythmias in Pheochromocytoma: JACC Review Topic of the Week

Pheochromocytomas, arising from chromaffin cells, produce catecholamines, epinephrine and norepinephrine. The tumor biochemical phenotype is defined by which of these exerts the greatest influence on the cardiovascular system when released into circulation in high amounts. Action on the heart and vasculature can cause potentially lethal arrhythmias, often in the setting of comorbid blood pressure derangements. In a review of electrocardiograms obtained on pheochromocytoma patients (n = 650) treated at our institution over the last decade, severe and refractory sinus tachycardia, atrial fibrillation, and ventricular tachycardia were found to be the most common or life-threatening catecholamine-induced tachyarrhythmias. These arrhythmias, arising from catecholamine excess rather than from a primary electrophysiologic substrate, require special considerations for treatment and complication avoidance. Understanding the synthesis and release of catecholamines, the adrenoceptors catecholamines bind to, and the cardiac and vascular response to epinephrine and norepinephrine underlies optimal management in catecholamine-induced tachyarrhythmias.

The Inhibition Effects of Shenmai Injection on Acetylcholine-Induced Catecholamine Synthesis and Secretion by Modulating Nicotinic Acetylcholine Receptor Ion Channels in Cultured Bovine Adrenal Medullary Cells

Shenmai injection (SMI) has been widely used for the treatment of cardiovascular diseases in China. Cardiovascular disorders are often related to excessive catecholamine (CA) secretion. Here, we report the effects of SMI on CA secretion and synthesis in cultured bovine adrenal medullary cells. We found that SMI significantly reduced CA secretion induced by 300 μM acetylcholine (ACh). Cotreatment with SMI (10 μL/mL) and either of the ACh receptor α-subunit inhibitors, HEX (α3) or DhβE (α4β2), did not produce any further inhibition, indicating that SMI may play a role through α3 and α4β2 channels. Furthermore, SMI reduced tyrosine hydroxylase (TH) activity induced by ACh by inhibiting the phosphorylation of TH at Ser19 and Ser40. TH is phosphorylated at Ser19 by Ca²⁺/calmodulin-dependent protein kinase II (CaM kinase II) and at Ser40 by protein kinase A (PKA). KN-93 and H89, the antagonists of CaM kinase II and PKA, respectively, inhibited the ACh-induced phosphorylation at Ser19 and Ser40, and the addition of SMI did not augment the inhibitory effect. Taken together, our results show that SMI likely inhibits CA secretion by blocking TH activity at its Ser19 and Ser40 sites.

Activation of RAS Signalling is Associated with Altered Cell Adhesion in Phaeochromocytoma

Phaeochromocytomas and paragangliomas (PPGLs) are neuroendocrine catecholamine-producing tumours that may progress into inoperable metastatic disease. Treatment options for metastatic disease are limited, indicating a need for functional studies to identify pharmacologically targetable pathophysiological mechanisms, which require biologically relevant experimental models. Recently, a human progenitor phaeochromocytoma cell line named “hPheo1” was established, but its genotype has not been characterised. Performing exome sequencing analysis, we identified a KIF1B T827I mutation, and the oncogenic NRAS Q61K mutation. While KIF1B mutations are recurring somatic events in PPGLs, NRAS mutations have hitherto not been detected in PPGLs. Therefore, we aimed to assess its implications for the hPheo1 cell line, and possible relevance for the pathophysiology of PPGLs. We found that transient downregulation of NRAS in hPheo1 led to elevated expression of genes associated with cell adhesion, and enhanced adhesion to hPheo1 cells’ extracellular matrix. Analyses of previously published mRNA data from two independent PPGL patient cohorts (212 tissue samples) revealed a subcluster of PPGLs featuring hyperactivated RAS pathway-signalling and under-expression of cell adhesion-related gene expression programs. Thus, we conclude that NRAS activity in hPheo1 decreases adhesion to their own extracellular matrix and mirrors a transcriptomic RAS-signalling-related phenomenon in PPGLs.

Correlation Between Telomere Attrition of Zona Fasciculata and Adrenal Weight Reduction in Older Men

CONTEXT

Although numerous theories are reported on sex differences in longevity, the underlying biological mechanisms remain unknown. We previously reported that telomere length in the zona reticularis cells of the human adrenal cortex was significantly longer in older than that in younger subjects. However, we could not evaluate sex differences in the telomere lengths.

OBJECTIVE

To compare the telomere lengths of adrenocortical and adrenal medullar cells between men and women from infancy through older adulthood.

METHODS

Adrenal glands of 30 male (aged 0 to 100 years) and 25 female (aged 0 to 104 years) autopsied subjects were retrieved from autopsy files. Using quantitative fluorescence in situ hybridization, relative telomere lengths were determined in the parenchymal cells of the 3 adrenocortical zones and medulla. Age-related changes in the weight of adrenal glands were also investigated.

MAIN RESULTS

Older male subjects (aged 65 years or older) had significantly shorter telomere lengths in zona fasciculata (ZF) cells compared to the corresponding female subjects. In men, older subjects exhibited a significant age-related reduction in adrenal weight; however, no age-related changes in adrenal weight were detected in women.

CONCLUSION

Telomere attrition of ZF cells was correlated with adrenal weight reduction in older men but not in older women, suggesting a decreased number of ZF cells in older men. This may help us understand the possible biological mechanisms of sex difference in longevity of humans.

Pheochromocytoma (PHEO) and Paraganglioma (PGL)

This series of 23 articles (17 original articles, six reviews) is presented by international leaders in pheochromocytoma and paraganglioma (PPGL) [...].