The chromogranin-secretogranin family

Biochemical Markers for Neuroendocrine Tumors: Traditional Circulating Markers and Recent Development-A Comprehensive Review

Neuroendocrine neoplasms (NENs) are a heterogeneous group of neoplasms presenting unique challenges in diagnosis and management. Traditional markers such as chromogranin A (CgA), pancreatic polypeptide (PP), and neuron-specific enolase (NSE) have limitations in terms of specificity and sensitivity. Specific circulating markers such as serotonin and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) and various gastrointestinal hormones such as gastrin, glucagon, somatostatin, and vasoactive intestinal peptide (VIP) have a role in identifying functional NENs. Recent advances in molecular and biochemical markers, also accounting for novel genomic and proteomic markers, have significantly improved the landscape for the diagnosis and monitoring of NENs. This review discusses these developments, focusing on both traditional markers such as CgA and NSE, as well as specific hormones like gastrin, insulin, somatostatin, glucagon, and VIP. Additionally, it covers emerging genomic and proteomic markers that are shaping current research. The clinical applicability of these markers is highlighted, and their role in improving diagnostic accuracy, predicting surgical outcomes, and monitoring response to treatment is demonstrated. The review also highlights the need for further research, including validation of these markers in larger studies, development of standardized assays, and integration with imaging techniques. The evolving field of biochemical markers holds promise for improving patient outcomes in the treatment of NENs, although challenges in standardization and validation remain.

Human iN neuronal model of schizophrenia displays dysregulation of chromogranin B and related neuropeptide transmitter signatures

Schizophrenia (SZ) is a serious mental illness and neuropsychiatric brain disorder with behavioral symptoms that include hallucinations, delusions, disorganized behavior, and cognitive impairment. Regulation of such behaviors requires utilization of neurotransmitters released to mediate cell-cell communication which are essential to brain functions in health and disease. We hypothesized that SZ may involve dysregulation of neurotransmitters secreted from neurons. To gain an understanding of human SZ, induced neurons (iNs) were derived from SZ patients and healthy control subjects to investigate peptide neurotransmitters, known as neuropeptides, which represent the major class of transmitters. The iNs were subjected to depolarization by high KCl in the culture medium and the secreted neuropeptides were identified and quantitated by nano-LC-MS/MS tandem mass spectrometry. Several neuropeptides were identified from schizophrenia patient-derived neurons, including chromogranin B (CHGB), neurotensin, and natriuretic peptide. Focusing on the main secreted CHGB neuropeptides, results revealed differences in SZ iNs compared to control iN neurons. Lower numbers of distinct CHGB peptides were found in the SZ secretion media compared to controls. Mapping of the peptides to the CHGB precursor revealed peptides unique to either SZ or control, and peptides common to both conditions. Also, the iNs secreted neuropeptides under both KCl and basal (no KCl) conditions. These findings are consistent with reports that chromogranin B levels are reduced in the cerebrospinal fluid and specific brain regions of SZ patients. These findings suggest that iNs derived from SZ patients can model the decreased CHGB neuropeptides observed in human SZ.

The potential roles of salivary biomarkers in neurodegenerative diseases

Current research efforts on neurodegenerative diseases are focused on identifying novel and reliable biomarkers for early diagnosis and insight into disease progression. Salivary analysis is gaining increasing interest as a promising source of biomarkers and matrices for measuring neurodegenerative diseases. Saliva collection offers multiple advantages over the currently detected biofluids as it is easily accessible, non-invasive, and repeatable, allowing early diagnosis and timely treatment of the diseases. Here, we review the existing findings on salivary biomarkers and address the potential value in diagnosing neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease and Amyotrophic lateral sclerosis. Based on the available research, β-amyloid, tau protein, α-synuclein, DJ-1, Huntington protein in saliva profiles display reliability and validity as the biomarkers of neurodegenerative diseases.

Immunohistochemical field parcellation of the human hippocampus along its antero-posterior axis

The primate hippocampus includes the dentate gyrus, cornu ammonis (CA), and subiculum. CA is subdivided into four fields (CA1-CA3, plus CA3h/hilus of the dentate gyrus) with specific pyramidal cell morphology and connections. Work in non-human mammals has shown that hippocampal connectivity is precisely patterned both in the laminar and longitudinal axes. One of the main handicaps in the study of neuropathological semiology in the human hippocampus is the lack of clear laminar and longitudinal borders. The aim of this study was to explore a histochemical segmentation of the adult human hippocampus, integrating field (medio-lateral), laminar, and anteroposterior longitudinal patterning. We provide criteria for head-body-tail field and subfield parcellation of the human hippocampus based on immunodetection of Rabphilin3a (Rph3a), Purkinje-cell protein 4 (PCP4), Chromogranin A and Regulation of G protein signaling-14 (RGS-14). Notably, Rph3a and PCP4 allow to identify the border between CA3 and CA2, while Chromogranin A and RGS-14 give specific staining of CA2. We also provide novel histological data about the composition of human-specific regions of the anterior and posterior hippocampus. The data are given with stereotaxic coordinates along the longitudinal axis. This study provides novel insights for a detailed region-specific parcellation of the human hippocampus useful for human brain imaging and neuropathology.

Diagnostic value of CSF chromogranin A to discriminate between Alzheimer's disease and dementia with Lewy bodies

BACKGROUND

Chromogranin A (CgA) seems to be involved in the pathophysiology of different neurodegenerative pathologies such as Alzheimer's disease (AD) and dementia with Lewy Bodies (DLB). CgA is present in the aggregates of amyloid plaques and in Lewy bodies but CgA also has a function in neuroinflammatory processes via microglia. Our objective was to determine if there is a difference in the CgA concentration in the cerebrospinal fluid (CSF) of AD and DLB patients and whether the CgA concentration can discriminate between the two diseases.

METHODS

Using the previously described AlphaLewyMA cohort, we included 117 patients with a CSF CgA assay: 15 control subjects (CS group), 64 DLB patients, 17 AD patients and 21 patients with both AD and probable DLB criteria (AD/DLB group). CgA concentration was assessed using the MSD platform.

RESULTS

CSF CgA was increased in the AD and AD/DLB groups compared with the DLB group (p = 0.0006 between AD and DLB, p = 0.0013 between AD/DLB and DLB). No significant difference in CgA concentration was found between DLB and CS. ROC curve analysis showed an area under the curve of 0.791 between AD and DLB. CgA concentrations were correlated with t-Tau and P-Tau regardless of the pathology (for Tau: p = 0.022 for AD; p < 0.0001 for DLB; p = 0.004 for AD/DLB; for P-Tau: p = 0.032 for AD; p < 0.0001 for DLB; p = 0.0009 for AD/DLB). Aβ42 was positively correlated with CgA in the DLB group but not in the AD and AD/DLB groups (for DLB: p < 0.0001; for AD: p = 0.57; for AD/DLB: p = 0.58).

CONCLUSIONS

CSF CgA concentrations are increased in AD but not in DLB and correlate with P-Tau and Tau whatever the disease. These results suggest a link between tauopathy/neurodegeneration and CgA.

The angiogenic neuropeptide catestatin exerts beneficial effects on human coronary vascular cells and cardiomyocytes

INTRODUCTION

Myocardial infarction (MI) induces irreversible tissue damage, eventually leading to heart failure. Exogenous induction of angiogenesis positively influences ventricular remodeling after MI. Recently, we could show that therapeutic angiogenesis by the neuropeptide catestatin (CST) restores perfusion in the mouse hind limb ischemia model by the induction of angio-, arterio- and vasculogenesis. Thus, we assumed that CST might exert beneficial effects on cardiac cells.

METHODS/RESULTS

To test the effect of CST on cardiac angiogenesis in-vitro matrigel assays with human coronary artery endothelial cells (HCAEC) were performed. CST significantly mediated capillary like tube formation comparable to vascular endothelial growth factor (VEGF), which was used as positive control. Interestingly, blockade of bFGF resulted in abrogation of observed effects. Moreover, CST induced proliferation of HCAEC and human coronary artery smooth muscle cells (HCASMC) as determined by BrdU-incorporation. Similar to the matrigel assay blockade of bFGF attenuated the effect. Consistent with these findings western blot assays revealed a bFGF-dependent phosphorylation of extracellular-signal regulated kinase (ERK) 1/2 by CST in these cell lines. Finally, CST protected human cardiomyocytes in-vitro from apoptosis.

CONCLUSION

CST might qualify as potential candidate for therapeutic angiogenesis in MI.

Ten-Fold Elevation of Chromogranin A Level Unrelated to a Neuroendocrine Tumor: A Case Report of the Diagnostic Interference of Proton Pump Inhibitors

Chromogranin A (CgA) is a well-known biomarker for neuroendocrine tumors (NETs). However, due to its non-specificity, a proper assessment of CgA test results requires a detailed knowledge of the factors, conditions, and medications influencing its serum concentration. We describe a case of a 61-year-old patient presenting with a mass suspicious of a gastrointestinal NET and an exceedingly high level of serum CgA persistent after mass resection. Following a thorough review of patient's medical history and clinical presentation, along with radiographic and pathological findings, no evidence of a NET was detected. A trial of proton-pump inhibitor (PPI) withdrawal led to a dramatic normalization of CgA level, marking it as the culprit causing this tumor marker elevation. This case highlights the significant impact of PPI use on CgA level, and should incentivize clinicians to provide proper education to patients prior to testing.

Cell-specific secretory granule sorting mechanisms: the role of MAGEL2 and retromer in hypothalamic regulated secretion

Intracellular protein trafficking and sorting are extremely arduous in endocrine and neuroendocrine cells, which synthesize and secrete on-demand substantial quantities of proteins. To ensure that neuroendocrine secretion operates correctly, each step in the secretion pathways is tightly regulated and coordinated both spatially and temporally. At the trans-Golgi network (TGN), intrinsic structural features of proteins and several sorting mechanisms and distinct signals direct newly synthesized proteins into proper membrane vesicles that enter either constitutive or regulated secretion pathways. Furthermore, this anterograde transport is counterbalanced by retrograde transport, which not only maintains membrane homeostasis but also recycles various proteins that function in the sorting of secretory cargo, formation of transport intermediates, or retrieval of resident proteins of secretory organelles. The retromer complex recycles proteins from the endocytic pathway back to the plasma membrane or TGN and was recently identified as a critical player in regulated secretion in the hypothalamus. Furthermore, melanoma antigen protein L2 (MAGEL2) was discovered to act as a tissue-specific regulator of the retromer-dependent endosomal protein recycling pathway and, by doing so, ensures proper secretory granule formation and maturation. MAGEL2 is a mammalian-specific and maternally imprinted gene implicated in Prader-Willi and Schaaf-Yang neurodevelopmental syndromes. In this review, we will briefly discuss the current understanding of the regulated secretion pathway, encompassing anterograde and retrograde traffic. Although our understanding of the retrograde trafficking and sorting in regulated secretion is not yet complete, we will review recent insights into the molecular role of MAGEL2 in hypothalamic neuroendocrine secretion and how its dysregulation contributes to the symptoms of Prader-Willi and Schaaf-Yang patients. Given that the activation of many secreted proteins occurs after they enter secretory granules, modulation of the sorting efficiency in a tissue-specific manner may represent an evolutionary adaptation to environmental cues.

Genome-wide association study in 404,302 individuals identifies 7 significant loci for reaction time variability

Reaction time variability (RTV), reflecting fluctuations in response time on cognitive tasks, has been proposed as an endophenotype for many neuropsychiatric disorders. There have been no large-scale genome-wide association studies (GWAS) of RTV and little is known about its genetic underpinnings. Here, we used data from the UK Biobank to conduct a GWAS of RTV in participants of white British ancestry (n = 404,302) as well as a trans-ancestry GWAS meta-analysis (n = 44,873) to assess replication. We found 161 genome-wide significant single nucleotide polymorphisms (SNPs) distributed across 7 genomic loci in our discovery GWAS. Functional annotation of the variants implicated genes involved in synaptic function and neural development. The SNP-based heritability (h2SNP) estimate for RTV was 3%. We investigated genetic correlations between RTV and selected neuropsychological traits using linkage disequilibrium score regression, and found significant correlations with several traits, including a positive correlation with mean reaction time and schizophrenia. Despite the high genetic correlation between RTV and mean reaction time, we demonstrate distinctions in the genetic underpinnings of these traits. Lastly, we assessed the predictive ability of a polygenic score (PGS) for RTV, calculated using PRSice and PRS-CS, and found that the RTV-PGS significantly predicted RTV in independent cohorts, but that the generalisability to other ancestry groups was poor. These results identify genetic underpinnings of RTV, and support the use of RTV as an endophenotype for neurological and psychiatric disorders.

Cellular and molecular mechanisms of the organogenesis and development, and function of the mammalian parathyroid gland

Serum calcium homeostasis is mainly regulated by parathormone (PTH) secreted by the parathyroid gland. Besides PTH and Gcm2, a master gene for parathyroid differentiation, many genes are expressed in the gland. Especially, calcium-sensing receptor (CaSR), vitamin D receptor (VDR), and Klotho function to prevent increased secretion of PTH and hyperplasia of the parathyroid gland under chronic hypocalcemia. Parathyroid-specific dual deletion of Klotho and CaSR induces a marked enlargement of the glandular size. The parathyroid develops from the third and fourth pharyngeal pouches except murine species in which the gland is derived from the third pouch only. The development of the murine parathyroid gland is categorized as follows: (1) formation and differentiation of the pharyngeal pouches, (2) appearance of parathyroid domain in the third pharyngeal pouch together with thymus domain, (3) migration of parathyroid primordium attached to the top of thymus, and (4) contact with the thyroid lobe and separation from the thymus. The transcription factors and signaling molecules involved in each of these developmental stages are elaborated. In addition, mesenchymal neural crest cells surrounding the pharyngeal pouches and parathyroid primordium and invading the parathyroid parenchyma participate in the development of the gland.

An Overview of Circulating Biomarkers in Neuroendocrine Neoplasms: A Clinical Guide

Neuroendocrine neoplasms (NENs) are a heterogeneous group of diseases that are characterized by different behavior and clinical manifestations. The diagnosis and management of this group of tumors are challenging due to tumor complexity and lack of precise and widely validated biomarkers. Indeed, the current circulating mono-analyte biomarkers (such as chromogranin A) are ineffective in describing such complex tumors due to their poor sensitivity and specificity. In contrast, multi-analytical circulating biomarkers (including NETest) are emerging as more effective tools to determine the real-time profile of the disease, both in terms of accurate diagnosis and effective treatment. In this review, we will analyze the capabilities and limitations of different circulating biomarkers focusing on three relevant questions: (1) accurate and early diagnosis; (2) monitoring of disease progression and response to therapy; and (3) detection of early relapse.

Chromogranin A and its derived peptides: potential regulators of cholesterol homeostasis

Chromogranin A (CHGA), a member of the granin family of proteins, has been an attractive therapeutic target and candidate biomarker for several cardiovascular, neurological, and inflammatory disorders. The prominence of CHGA stems from the pleiotropic roles of several bioactive peptides (e.g., catestatin, pancreastatin, vasostatins) generated by its proteolytic cleavage and by their wide anatomical distribution. These peptides are emerging as novel modulators of cardiometabolic diseases that are often linked to high blood cholesterol levels. However, their impact on cholesterol homeostasis is poorly understood. The dynamic nature of cholesterol and its multitudinous roles in almost every aspect of normal body function makes it an integral component of metabolic physiology. A tightly regulated coordination of cholesterol homeostasis is imperative for proper functioning of cellular and metabolic processes. The deregulation of cholesterol levels can result in several pathophysiological states. Although studies till date suggest regulatory roles for CHGA and its derived peptides on cholesterol levels, the mechanisms by which this is achieved still remain unclear. This review aims to aggregate and consolidate the available evidence linking CHGA with cholesterol homeostasis in health and disease. In addition, we also look at common molecular regulatory factors (viz., transcription factors and microRNAs) which could govern the expression of CHGA and genes involved in cholesterol homeostasis under basal and pathological conditions. In order to gain further insights into the pathways mediating cholesterol regulation by CHGA/its derived peptides, a few prospective signaling pathways are explored, which could act as primers for future studies.

A Comprehensive Review on Neuroendocrine Neoplasms: Presentation, Pathophysiology and Management

Neuroendocrine neoplasms (NENs) are a group of heterogeneous tumors with neuroendocrine differentiation that can arise from any organ. They account for 2% of all malignancies in the United States. A significant proportion of NEN patients experience endocrine imbalances consequent to increased amine or peptide hormone secretion, impacting their quality of life and prognosis. Over the last decade, pathologic categorization, diagnostic techniques and therapeutic choices for NENs-both well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs)-have appreciably evolved. Diagnosis of NEN mostly follows a suspicion from clinical features or incidental imaging findings. Hormonal or non-hormonal biomarkers (like serum serotonin, urine 5-HIAA, gastrin and VIP) and histology of a suspected NEN is, therefore, critical for both confirmation of the diagnosis and classification as an NET or NEC. Therapy for NENs has progressed recently based on a better molecular understanding, including the involvement of mTOR, VEGF and peptide receptor radionuclide therapy (PRRT), which add to the growing evidence supporting the possibility of treatment beyond complete resection. As the incidence of NENs is on the rise in the United States and several other countries, physicians are more likely to see these cases, and their better understanding may support earlier diagnosis and tailoring treatment to the patient. We have compiled clinically significant evidence for NENs, including relevant changes to clinical practice that have greatly updated our diagnostic and therapeutic approach for NEN patients.

Single-cell sequencing of entorhinal cortex reveals widespread disruption of neuropeptide networks in Alzheimer's disease

INTRODUCTION

Abnormalities of neuropeptides (NPs) that play important roles in modulating neuronal activities are commonly observed in Alzheimer's disease (AD). We hypothesize that NP network disruption is widespread in AD brains.

METHODS

Single-cell transcriptomic data from the entorhinal cortex (EC) were used to investigate the NP network disruption in AD. Bulk RNA-sequencing data generated from the temporal cortex by independent groups and machine learning were employed to identify key NPs involved in AD. The relationship between aging and AD-associated NP (ADNP) expression was studied using GTEx data.

RESULTS

The proportion of cells expressing NPs but not their receptors decreased significantly in AD. Neurons expressing higher level and greater diversity of NPs were disproportionately absent in AD. Increased age coincides with decreased ADNP expression in the hippocampus.

DISCUSSION

NP network disruption is widespread in AD EC. Neurons expressing more NPs may be selectively vulnerable to AD. Decreased expression of NPs participates in early AD pathogenesis. We predict that the NP network can be harnessed for treatment and/or early diagnosis of AD.

Prognostic value of secretoneurin in chronic heart failure. Data from the GISSI-Heart Failure trial

BACKGROUND

Circulating secretoneurin (SN) concentrations have been found to provide prognostic information in patients with acute heart failure. We wanted to assess whether SN would improve prognostication also in patients with chronic heart failure (HF) in a large multicenter trial.

METHODS

We measured plasma SN concentrations at randomization (n=1224) and after 3 months (n=1103) in patients with chronic, stable HF from the GISSI-HF study. The co-primary endpoints were (1) time to death or (2) admission to hospital for cardiovascular reasons.

RESULTS

Mean age was 67 years and 80% were male. Median (quartile 1-3) SN concentrations were 42.6 (35.0-62.8) pmol/L on randomization and 42.0 (34.5-53.1) pmol/L after 3 months, which are higher than SN concentrations in healthy subjects. Higher SN concentrations at randomization were associated with lower body-mass index (BMI), lower systolic blood pressure, lower estimated glomerular filtration rate (eGFR), higher B-type natriuretic peptide (BNP) concentrations, and diagnosis of chronic obstructive pulmonary disease. During median follow-up of 3.9 years, 344 patients (27.0%) died. After adjusting for age, sex, left ventricular ejection fraction, BMI, functional class, ischemic etiology, heart rate, blood pressure, eGFR, bilirubin, comorbidities, and BNP concentrations, logarithmically transformed SN concentrations on randomization were associated with mortality (HR 2.60 (95% CI 1.01-6.70), p=0.047). SN concentrations were also associated with admission to hospital for cardiovascular reasons, but the association was attenuated and no longer significant in multivariable analysis.

CONCLUSION

Plasma SN concentrations provided incremental prognostic information to established risk indices and biomarkers in a large cohort of chronic HF patients.

NOD mouse dorsal root ganglia display morphological and gene expression defects before and during autoimmune diabetes development

Introduction

During the development of Autoimmune Diabetes (AD) an autoimmune attack against the Peripheral Nervous System occurs. To gain insight into this topic, analyses of Dorsal Root Ganglia (DRG) from Non-Obese Diabetic (NOD) mice were carried out.

Methods

Histopathological analysis by electron and optical microscopy in DRG samples, and mRNA expression analyzes by the microarray technique in DRG and blood leukocyte samples from NOD and C57BL/6 mice were performed.

Results

The results showed the formation of cytoplasmic vacuoles in DRG cells early in life that could be related to a neurodegenerative process. In view of these results, mRNA expression analyses were conducted to determine the cause and/or the molecules involved in this suspected disorder. The results showed that DRG cells from NOD mice have alterations in the transcription of a wide range of genes, which explain the previously observed alterations. In addition, differences in the transcription genes in white blood cells were also detected.

Discussion

Taken together, these results indicate that functional defects are not only seen in beta cells but also in DRG in NOD mice. These results also indicate that these defects are not a consequence of the autoimmune process that takes place in NOD mice and suggest that they may be involved as triggers for its development.

The Regulated Secretion and Models of Intracellular Transport: The Goblet Cell as an Example

Transport models are extremely important to map thousands of proteins and their interactions inside a cell. The transport pathways of luminal and at least initially soluble secretory proteins synthesized in the endoplasmic reticulum can be divided into two groups: the so-called constitutive secretory pathway and regulated secretion (RS) pathway, in which the RS proteins pass through the Golgi complex and are accumulated into storage/secretion granules (SGs). Their contents are released when stimuli trigger the fusion of SGs with the plasma membrane (PM). In specialized exocrine, endocrine, and nerve cells, the RS proteins pass through the baso-lateral plasmalemma. In polarized cells, the RS proteins secrete through the apical PM. This exocytosis of the RS proteins increases in response to external stimuli. Here, we analyze RS in goblet cells to try to understand the transport model that can be used for the explanation of the literature data related to the intracellular transport of their mucins.

Function of secretoneurin in regulating the expression of reproduction-related genes in ovoviviparous black rockfish (Sebastes schlegelii)

Secretoneurin (SN), a conserved peptide derived from secretogranin-2 (scg2), also known as secretogranin II or chromogranin C, plays an important role in regulating gonadotropin in the pituitary, which affects the reproductive system. This study aimed to clarify the mode of action of scg2 in regulating gonad development and maturation and the expression of mating behavior-related genes. Two scg2 cDNAs were cloned from the ovoviviparity teleost black rockfish (Sebastes schlegelii). In situ hybridization detected positive scg2 mRNA signals in the telencephalon and hypothalamus, where sgnrh and kisspeptin neurons were reported to be located and potentially regulated by scg2. In vivo, intracerebral ventricular injections of synthetic black rockfish SNa affected brain cgnrh, sgnrh, kisspeptin1, pituitary lh and fsh and gonad steroidogenesis-related gene expression levels with sex dimorphism. In vitro, a similar effect was found in primary cultured brain and pituitary cells. Thus, SN could contribute to the regulation of gonadal development, as well as reproductive behaviors, including mating and parturition.

Small bowel neuroendocrine tumors: An analysis of clinical presentation, diagnostic workup and surgical approach—A single center retrospective study

Background

Neurocrine neoplasms (NEN) of the small bowel (SBNEN) are a rare entity and mostly asymptomatic. The aim of this study was to explore trends in the clinical presentation, diagnostic workup, surgical approach and oncological outcome in patients with SBNEN at our surgical department.

Materials and methods

All patients who underwent surgical resection for SBNEN from 2004 to 2020 at our department were enrolled in this single center retrospective study.

Results

A total of 32 patients were included in this study. In most cases, the diagnosis was based on incidental findings during endoscopy or radiographic imaging (n = 23; 72%). Twenty cases had a G1 tumor and 12 cases a G2 tumor. The 1-, 3- and 5-year overall survival (OS) were 96%, 86% and 81%, respectively. Patients with a tumor more than 30 mm had a significantly lower OS (p = 0.01). For G1 tumors, the estimated disease-free survival (DFS) was 109 months. Again, the DFS was significantly lower when the tumor had more than 30 mm in diameter (p = 0.013).

Conclusion

Due to the mostly asymptomatic presentation, the diagnostic workup can be difficult. An aggressive approach and a strict follow-up seem to be important for the oncological outcome.

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.

Chromogranin A: An Endocrine Factor of Pregnancy

Pregnancy is a state of physiological and hormonal changes. One of the endocrine factors involved in these processes is chromogranin A, an acidic protein produced, among others, by the placenta. Although it has been previously linked to pregnancy, no existing articles have ever managed to clarify the role of this protein regarding this subject. Therefore, the aim of the present study is to gather knowledge of chromogranin A's function with reference to gestation and parturition, clarify elusive information, and, most importantly, to formulate hypotheses for the future studies to verify.

Serum Catestatin Concentrations Are Increased in Patients with Atrial Fibrillation

The autonomic nervous system is crucial in initiating and maintaining atrial fibrillation (AF). Catestatin is a multipurpose peptide that regulates cardiovascular systems and reduces harmful, excessive activity of the sympathetic nervous system by blocking the release of catecholamines. We aimed to determine whether serum catestatin concentrations are associated with AF severity, duration indices, and various clinical and laboratory indicators in these individuals to better define the clinical value of catestatin in patients with AF. The present single center study enrolled 73 participants with AF and 72 healthy age-matched controls. Serum catestatin concentrations were markedly higher in AF patients than controls (14.11 (10.21-26.02) ng/mL vs. 10.93 (5.70-20.01) ng/mL, p = 0.013). Furthermore, patients with a more severe form of AF had significantly higher serum catestatin (17.56 (12.80-40.35) vs. 10.98 (8.38-20.91) ng/mL, p = 0.001). Patients with higher CHA₂DS₂-VASc scores (17.58 (11.89-37.87) vs. 13.02 (8.47-22.75) ng/mL, p = 0.034) and higher NT-proBNP levels (17.58 (IQR 13.91-34.62) vs. 13.23 (IQR 9.04-22.61), p = 0.036) had significantly higher serum catestatin concentrations. Finally, AF duration correlated negatively with serum catestatin levels (r = -0.348, p = 0.003). The results of the present study implicate the promising role of catestatin in the intricate pathophysiology of AF, which should be explored in future research.

Quantification of Chromogranin A and Its Fragments in Biological Fluids

Human chromogranin A (CgA), a 439-residue long neurosecretory protein, can serve as a circulating biomarker for a wide range of neuroendocrine tumors. Increased levels of immunoreactive CgA are also present in the blood of patients with cardiovascular, gastrointestinal, or inflammatory diseases with, in certain cases, important diagnostic and prognostic implications. A growing body of evidence suggest that CgA and various CgA-derived fragments have complex roles in the regulation of cardiovascular system, metabolism, innate immunity, angiogenesis, and tissue repair, sometime with opposite biological effects. For example, while full-length CgA (CgA_1-439) inhibits angiogenesis, the CgA_1-373 fragment, at certain doses, is proangiogenic. Thus, the selective quantification of CgA and its fragments in the blood of patients (and in other biological fluids) is of great experimental and clinical interest. Here, we describe methods to produce CgA_1-439 and CgA_1-373 and to develop ELISAs capable of detecting these polypeptides in a very selective manner. The same approach can be used, in principle, also for developing assays for other fragments.

Secretoneurin as a Novel Biomarker of Cardiovascular Episodes: Are We There Yet? A Narrative Review

Secretoneurin (SN) is a 33 amino-acid evolutionary conserved neuropeptide from the chromogranin peptide family. SN's main effects may be cardioprotective and are believed to be mediated through its inhibition of calmodulin-dependent kinase II (CaMKII), which influences intracellular calcium handling. SN inhibition of CaMKII suppresses calcium leakage from the sarcoplasmic reticulum through the ryanodine receptor. This action may reduce the risk of ventricular arrhythmias and calcium-dependent remodelling in heart failure. SN is also involved in reducing the intracellular reactive oxygen species concentration, modulating the immune response, and regulating the cell cycle, including apoptosis. SN can predict mortality in different disease states, beyond the classical risk factors and markers of myocardial injury. Plasma SN levels are elevated soon after an arrhythmogenic episode. In summary, SN is a novel biomarker with potential in cardiovascular medicine, and probably beyond.

The immunomodulatory functions of chromogranin A-derived peptide pancreastatin

Chromogranin A (CgA) is a 439 amino acid protein secreted by neuroendocrine cells. Proteolytic processing of CgA results in the production of different bioactive peptides. These peptides have been associated with inflammatory bowel disease, diabetes, and cancer. One of the chromogranin A-derived peptides is ∼52 amino acid long Pancreastatin (PST: human (h)CgA250-301, murine (m)CgA263-314). PST is a glycogenolytic peptide that inhibits glucose-induced insulin secretion from pancreatic islet β-cells. In addition to this metabolic role, evidence is emerging that PST also has inflammatory properties. This review will discuss the immunomodulatory properties of PST and its possible mechanisms of action and regulation. Moreover, this review will discuss the potential translation to humans and how PST may be an interesting therapeutic target for treating inflammatory diseases.

Neuropilin-1 and Integrins as Receptors for Chromogranin A-Derived Peptides

Human chromogranin A (CgA), a 439 residue-long member of the "granin" secretory protein family, is the precursor of several peptides and polypeptides involved in the regulation of the innate immunity, cardiovascular system, metabolism, angiogenesis, tissue repair, and tumor growth. Despite the many biological activities observed in experimental and preclinical models for CgA and its most investigated fragments (vasostatin-I and catestatin), limited information is available on the receptor mechanisms underlying these effects. The interaction of vasostatin-1 with membrane phospholipids and the binding of catestatin to nicotinic and b2-adrenergic receptors have been proposed as important mechanisms for some of their effects on the cardiovascular and sympathoadrenal systems. Recent studies have shown that neuropilin-1 and certain integrins may also work as high-affinity receptors for CgA, vasostatin-1 and other fragments. In this case, we review the results of these studies and discuss the structural requirements for the interactions of CgA-related peptides with neuropilin-1 and integrins, their biological effects, their mechanisms, and the potential exploitation of compounds that target these ligand-receptor systems for cancer diagnosis and therapy. The results obtained so far suggest that integrins (particularly the integrin avb6) and neuropilin-1 are important receptors that mediate relevant pathophysiological functions of CgA and CgA fragments in angiogenesis, wound healing, and tumor growth, and that these interactions may represent important targets for cancer imaging and therapy.

Lysosomal solute and water transport

Lysosomes mediate hydrolase-catalyzed macromolecule degradation to produce building block catabolites for reuse. Lysosome function requires an osmo-sensing machinery that regulates osmolytes (ions and organic solutes) and water flux. During hypoosmotic stress or when undigested materials accumulate, lysosomes become swollen and hypo-functional. As a membranous organelle filled with cargo macromolecules, catabolites, ions, and hydrolases, the lysosome must have mechanisms that regulate its shape and size while coordinating content exchange. In this review, we discussed the mechanisms that regulate lysosomal fusion and fission as well as swelling and condensation, with a focus on solute and water transport mechanisms across lysosomal membranes. Lysosomal H+, Na+, K+, Ca2+, and Cl- channels and transporters sense trafficking and osmotic cues to regulate both solute flux and membrane trafficking. We also provide perspectives on how lysosomes may adjust the volume of themselves, the cytosol, and the cytoplasm through the control of lysosomal solute and water transport.

Comparison of two chromogranin A assays and investigation of nonlinear specimens

Background

As a marker for functional and non-functional neuroendocrine tumors, serum chromogranin A (CgA) concentrations have shown value for detecting and monitoring disease. Here we describe a comparison between an established micro-titer plate assay (Cisbio CgA ELISA) and an analyzer-based assay (B·R·A·H·M·S CgA II KRYPTOR). Reference limits were established along with a performance evaluation of the KRYPTOR assay. Nonlinearity observed in approximately 0.03% of patients was also investigated.

Methods

Samples were tested according to kit manufacturer's protocols. Reference limits were established for both assays testing the same cohort of healthy volunteers. Potential causes of nonlinearity investigated were HAMA, macromolecule effects and elevated serum creatinine.

Results

KRYPTOR vs. Cisbio: slope=0.692, y-intercept=−40.0 (r²=0.967, n=186). Upper reference limits were 160 and 103 ng/mL for the Cisbio and KRYPTOR assays, respectively. Linearity: slope=1.012 (r²=0.998) with 95.0–105.5% recoveries. Precision: repeatability ≤2.4%, within-laboratory ≤3.1% (79 and 738 ng/mL). Limit of detection: 8 ng/mL. Strong nonlinear specimens (n=6) retested for HAMA interference generated differences (block-no block) ranging −3.2–4.2%. Polyethylene glycol precipitation recoveries ranged from 157 to >5714% for affected specimens versus 71–79% for normal specimens. Eight of 14 nonlinear specimens (57%) had elevated serum creatinine results (>1.20 mg/dL).

Conclusions

The CgA II KRYPTOR assay performs acceptably for quantifying CgA in human serum. While adequate correlation is observed against the Cisbio ELISA, there is significant disagreement overall. Efforts to identify a cause of the nonlinearity observed in a small percentage of patients were inconclusive, but neither HAMA interference, macromolecule effects nor renal failure appear as major factors.

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The Cisbio Chromoa® ELISA is a well-established assay for measuring chromogranin A.

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The CgA II KRYPTOR® performs acceptably for quantifying chromogranin A in serum.

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Studies of the CgA II KRYPTOR vs. the established Cisbio Chomoa ELISA are lacking.

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Agreement between the Cisbio Chromoa CgA ELISA and the CgA II KRYPTOR is suboptimal.

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Causes for the nonlinearity in approximately 0.02–0.03% of specimens remain unclear.

Mutated lncRNA increase the risk of type 2 diabetes by promoting β cell dysfunction and insulin resistance

Islet β cell dysfunction and insulin resistance are the main pathogenesis of type 2 diabetes (T2D), but the mechanism remains unclear. Here we identify a rs3819316 C > T mutation in lncRNA Reg1cp mainly expressed in islets associated with an increased risk of T2D. Analyses in 16,113 Chinese adults reveal that Mut-Reg1cp individuals had higher incidence of T2D and presented impaired insulin secretion as well as increased insulin resistance. Mice with islet β cell specific Mut-Reg1cp knock-in have more severe β cell dysfunction and insulin resistance. Mass spectrometry assay of proteins after RNA pulldown demonstrate that Mut-Reg1cp directly binds to polypyrimidine tract binding protein 1 (PTBP1), further immunofluorescence staining, western blot analysis, qPCR analysis and glucose stimulated insulin secretion test reveal that Mut-Reg1cp disrupts the stabilization of insulin mRNA by inhibiting the phosphorylation of PTBP1 in β cells. Furthermore, islet derived exosomes transfer Mut-Reg1cp into peripheral tissue, which then promote insulin resistance by inhibiting AdipoR1 translation and adiponectin signaling. Our findings identify a novel mutation in lncRNA involved in the pathogenesis of T2D, and reveal a new mechanism for the development of T2D.

Role of Chromogranin A in the Diagnosis and Follow-up of Neuroendocrine Tumors: Real-World Experience

OBJECTIVE

The aim of this study was to assess the utility of serum chromogranin A (CgA) along the clinical pathway of patients with neuroendocrine tumors (NETs).

METHODS

A retrospective review of medical records was conducted of patients with NET who had at least 1 measurement of CgA between January 2015 and April 2021 at a large metropolitan Australian hospital. Chromogranin A was classified as increased or decreased if there was at least a 25% change in sequential levels and was compared with disease response by anatomical or functional imaging if within 6 weeks (considered concurrent).

RESULTS

Of 102 patients with NETs, 67 had at least 1 serum CgA level: 50 had been ordered during diagnostic workup, of which 33 were elevated (sensitivity: 66%; 95% confidence interval, 51%-79%). Of 129 CgA results concurrent with imaging, the sensitivity for detecting progressive disease was 28% (95% confidence interval, 15%-44%).

CONCLUSIONS

Our findings support previous concerns that CgA adds little value in clinical decision-making.

Tuning the Size of Large Dense-Core Vesicles and Quantal Neurotransmitter Release via Secretogranin II Liquid-Liquid Phase Separation

Large dense-core vesicles (LDCVs) are larger in volume than synaptic vesicles, and are filled with multiple neuropeptides, hormones, and neurotransmitters that participate in various physiological processes. However, little is known about the mechanism determining the size of LDCVs. Here, it is reported that secretogranin II (SgII), a vesicle matrix protein, contributes to LDCV size regulation through its liquid-liquid phase separation in neuroendocrine cells. First, SgII undergoes pH-dependent polymerization and the polymerized SgII forms phase droplets with Ca²⁺ in vitro and in vivo. Further, the Ca²⁺ -induced SgII droplets recruit reconstituted bio-lipids, mimicking the LDCVs biogenesis. In addition, SgII knockdown leads to significant decrease of the quantal neurotransmitter release by affecting LDCV size, which is differently rescued by SgII truncations with different degrees of phase separation. In conclusion, it is shown that SgII is a unique intravesicular matrix protein undergoing liquid-liquid phase separation, and present novel insights into how SgII determines LDCV size and the quantal neurotransmitter release.

Exploring the genetic relationship between deep vein thrombosis and plasma protein: a new research idea

BACKGROUND

The aim of this article is to scan and analyze the genetic correlation between plasma proteome and deep venous thrombosis(DVT), and to explore the correlation between plasma protein and DVT.

RESEARCH DESIGN AND METHODS

GWAS data of DVT and plasma proteins were analyzed with linkage disequilibrium scores, and plasma proteins that were genetically associated with DVT were screened out. To ascertain the causal link between potential plasma proteins and DVT, a Mendelian randomized (MR) study was used. This study used STRING to examine the pathogenesis of DVT in connection with the gene encoding plasma protein.

RESULTS

Several suggestive plasma proteins were detected for DVT, such as Complement factor B (correlation coefficient =0.3883 P value=0.0177), Chromogranin-A (correlation coefficient =-0.4786, P value=0.0158). Through MR analysis, we found that there was a significant positive causal relationship between Chromogranin-A (exposure) and DVT (outcome) (β=-0.0117, SE=0.0013, P<0.0001). Our STRING analysis revealed that hsa04610 was associated with coagulation cascade in the KEGG pathway of Complement factor B(P<0.0001), which was based on GO and KEGG analysis of 8 selected plasma proteins.

CONCLUSIONS

A genetic link between plasma protein and DVT was thoroughly investigated. Our findings provide a fresh perspective on the genetics and pathogenesis of DVT.

Changes in colonic enteroendocrine cells of patients with irritable bowel syndrome following fecal microbiota transplantation

OBJECTIVES

The aim was to investigate the effect of fecal microbiota transplantation (FMT) on colonic enteroendocrine cells densities in patients with irritable bowel syndrome (IBS).

MATERIALS AND METHODS

This study is connected to the REFIT study, a double-blinded placebo-controlled trial to investigate using FMT for IBS treatment. Eighty-three subjects received either donor-FMT or placebo FMT (own feces) by colonoscope to cecum. Biopsies were obtained from sigmoid colon. Ten responders and ten non-responders consented to new biopsy one-year after FMT. Sixteen patients received donor-FMT and four received placebo FMT. Biopsies were immunostained for all of the colonic enteroendocrine cells and were quantified using computerized image analysis.Allocation sequence was revealed after obtaining re-biopsies and cells quantification.

RESULTS

Scores for IBS-SSS (mean ± SEM) of responders (eight of 10 patients who received donor FMT) and non-responders changed from baseline to one year after FMT (297 ± 11 and 81 ± 16, p < .0001, and 270 ± 17 and 291 ± 16, p = .15, respectively). Using paired t-test to compare enteroendocrine cells densities one-year after FMT to baseline showed significant increase only in somatostatin immunoreactive cells density in the total IBS responders group (p = .023) and who received donor-FMT (p = .038). The densities of peptide YY and enteroglucagon immunoreactive cells increased significantly (p = .04 and .035, respectively) in donor-FMT recipients. No significant changes were noted in placebo FMT or nonresponders subgroups.

CONCLUSION

This study shows that colonic enteroendocrine cells densities significantly change in responders group that received donor-FMT. The mechanisms for the cross talks between gut microbiota and colonic enteroendocrine cells remain to be investigated.

Single-cell transcriptomic analysis of neuroepithelial cells and other cell types of the gills of zebrafish (Danio rerio) exposed to hypoxia

The fish gill is a multifunctional organ involved in numerous physiological processes, such as gas exchange and sensing of hypoxia by respiratory chemoreceptors, called neuroepithelial cells (NECs). Many studies have focused on zebrafish (Danio rerio) to investigate the structure, function and development of the gills, yet the transcriptomic profile of most gill cells remains obscure. We present the results of a comprehensive transcriptomic analysis of the gills of zebrafish using single-cell RNA sequencing (scRNA‐seq). Gill cells from ETvmat2:EGFP zebrafish were individually labelled before scRNA‐seq library construction using 10× Genomics Chromium technology. 12,819 cells were sequenced with an average depth of over 27,000 reads per cell. We identified a median of 485 genes per cell and 16 cell clusters, including NECs, neurons, pavement cells, endothelial cells and mitochondrion-rich cells. The identity of NECs was confirmed by expression of slc18a2, encoding the vesicular monoamine transporter, Vmat2. Highly differentially-expressed genes in NECs included tph1a, encoding tryptophan hydroxylase, sv2 (synaptic vesicle protein), and proteins implicated in O₂ sensing (ndufa4l2a, cox8al and epas1a). In addition, NECs and neurons expressed genes encoding transmembrane receptors for serotonergic, cholinergic or dopaminergic neurotransmission. Differential expression analysis showed a clear shift in the transcriptome of NECs following 14 days of acclimation to hypoxia. NECs in the hypoxia group showed high expression of genes involved in cell cycle control and proliferation. The present article provides a complete cell atlas for the zebrafish gill and serves as a platform for future studies investigating the molecular biology and physiology of this organ.

Enhancer of Zeste Homolog 2 (EZH2) Is a Marker of High-Grade Neuroendocrine Neoplasia in Gastroenteropancreatic and Pulmonary Tract and Predicts Poor Prognosis

Simple Summary

Neuroendocrine neoplasms most frequently arise in the gastroenteropancreatic and pulmonary tract and show an increasing incidence and prevalence. The prognosis and treatment depend on tumor proliferation and clinical behavior. Highly proliferating grade 3 neoplasms especially, show a wildly divergent therapy response and prognosis. In particular, it is crucial to securely separate the more indolent G3 tumors from the more aggressive carcinomas. Currently, this distinction is based on a combination of clinical, morphologic, immunohistochemical, and molecular biomarkers. However, none of these markers allow for a reliable distinction, and additional markers are needed. EZH2 has attracted increasing interest in different tumor entities. We aimed to analyze the expression of EZH2 in different neuroendocrine neoplasms and to correlate the expression with clinical parameters and survival. We demonstrate that EZH2 is nearly exclusively expressed in highly proliferative neoplasms and is a robust biomarker for identifying aggressive G3 tumors with poor prognosis.

Abstract

Tumor grading is a robust prognostic predictor in patients with neuroendocrine neoplasms (NEN) and guides therapy, especially in tumors with high proliferation. NEN can be separated into well-differentiated and poorly differentiated types. The more aggressive NEN have been further separated into neuroendocrine tumors (NET G3) with a better prognosis and neuroendocrine carcinomas (NEC) with a worse prognosis. Despite this distinction’s tremendous clinical and therapeutic relevance, optimal diagnostic biomarkers are still lacking. In this study, we analyzed the protein expression and prognostic impact of Enhancer of Zeste Homolog 2 (EZH2) by immunohistochemistry in 219 tissue samples of gastroenteropancreatic (GEP-NEN) and pulmonary NEN (P-NEN). EZH2 was almost exclusively expressed in NEN with a proliferation rate above 20% (G3), while all low-grade tumors were nearly negative. Among high-grade NEN, 65% showed high and 35% low expression of EZH2. In this group, the high expression of EZH2 was significantly associated with poor overall survival and NEC histology. Interestingly, EZH2 seems to act independently of Polycomb Repressive Complex 2 (PRC2) in NEN. In conclusion, we propose EZH2 as a robust biomarker for distinguishing between NET G3 and NEC among gastroenteropancreatic and pulmonary NEN.

Single-cell RNA sequencing in silent corticotroph tumors confirms impaired POMC processing and provides new insights into their invasive behavior

Objective

Provide insights into the defective POMC processing and invasive behavior in silent pituitary corticotroph tumors.

Design and methods

Single-cell RNAseq was used to compare the cellular makeup and transcriptome of silent and active corticotroph tumors.

Results

A series of transcripts related to hormone processing peptidases and genes involved in the structural organization of secretory vesicles were reduced in silent compared to active corticotroph tumors. Most relevant to their invasive behavior, silent corticotroph tumors exhibited several features of epithelial-to-mesenchymal transition, with increased expression of mesenchymal genes along with the loss of transcripts that regulate hormonal biogenesis and secretion. Silent corticotroph tumor vascular smooth muscle cell and pericyte stromal cell populations also exhibited plasticity in their mesenchymal features.

Conclusions

Our findings provide novel insights into the mechanisms of impaired POMC processing and invasion in silent corticotroph tumors and suggest that a common transcriptional reprogramming mechanism simultaneously impairs POMC processing and activates tumor invasion.

Differential Expression of Secretogranins II and III in Canine Adrenal Chromaffin Cells and Pheochromocytomas

Secretogranin II (SgII) and III (SgIII) function within peptide hormone-producing cells and are involved in secretory granule formation. However, their function in active amine-producing cells is not fully understood. In this study, we analyzed the expression profiles of SgII and SgIII in canine adrenal medulla and pheochromocytomas by immunohistochemical staining. In normal adrenal tissues, the intensity of coexpression of these two secretogranins (Sgs) differed from each chromaffin cell, although a complete match was not observed. The coexpression of vesicular monoamine transporter 2 (VMAT2) with SgIII was similar to that with chromogranin A, but there was a subpopulation of VMAT2-expressing cells that were negative or hardly detectable for SgII. These results are the first to indicate that there are distinct expression patterns for SgII and SgIII in adrenal chromaffin cells. Furthermore, the expression of these two Sgs varied in intensity among pheochromocytomas and did not necessarily correlate with clinical plasma catecholamine levels in patients. However, compared with SgIII, the expression of SgII was shown to be strong at the single-cell level in some tumor tissues. These findings provide a fundamental understanding of the expression differences between SgII and SgIII in normal adrenal chromaffin cells and pheochromocytomas.

Catestatin induces glycogenesis by stimulating the phosphoinositide 3-kinase-AKT pathway

AIM

Defects in hepatic glycogen synthesis contribute to post-prandial hyperglycaemia in type 2 diabetic patients. Chromogranin A (CgA) peptide Catestatin (CST: hCgA352-372 ) improves glucose tolerance in insulin-resistant mice. Here, we seek to determine whether CST induces hepatic glycogen synthesis.

METHODS

We determined liver glycogen, glucose-6-phosphate (G6P), uridine diphosphate glucose (UDPG) and glycogen synthase (GYS2) activities; plasma insulin, glucagon, noradrenaline and adrenaline levels in wild-type (WT) as well as in CST knockout (CST-KO) mice; glycogen synthesis and glycogenolysis in primary hepatocytes. We also analysed phosphorylation signals of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), phosphatidylinositol-dependent kinase-1 (PDK-1), GYS2, glycogen synthase kinase-3β (GSK-3β), AKT (a kinase in AKR mouse that produces Thymoma)/PKB (protein kinase B) and mammalian/mechanistic target of rapamycin (mTOR) by immunoblotting.

RESULTS

CST stimulated glycogen accumulation in fed and fasted liver and in primary hepatocytes. CST reduced plasma noradrenaline and adrenaline levels. CST also directly stimulated glycogenesis and inhibited noradrenaline and adrenaline-induced glycogenolysis in hepatocytes. In addition, CST elevated the levels of UDPG and increased GYS2 activity. CST-KO mice had decreased liver glycogen that was restored by treatment with CST, reinforcing the crucial role of CST in hepatic glycogenesis. CST improved insulin signals downstream of IR and IRS-1 by enhancing phospho-AKT signals through the stimulation of PDK-1 and mTORC2 (mTOR Complex 2, rapamycin-insensitive complex) activities.

CONCLUSIONS

CST directly promotes the glycogenic pathway by (a) reducing glucose production, (b) increasing glycogen synthesis from UDPG, (c) reducing glycogenolysis and (d) enhancing downstream insulin signalling.

Chromogranin A plasma levels predict mortality in COVID-19

Background

Chromogranin A (CgA) and its fragment vasostatin I (VS-I) are secreted in the blood by endocrine/neuroendocrine cells and regulate stress responses. Their involvement in Coronavirus 2019 disease (COVID-19) has not been investigated.

Methods

CgA and VS-I plasma concentrations were measured at hospital admission from March to May 2020 in 190 patients. 40 age- and sex-matched healthy volunteers served as controls. CgA and VS-I levels relationship with demographics, comorbidities and disease severity was assessed through Mann Whitney U test or Spearman correlation test. Cox regression analysis and Kaplan Meier survival curves were performed to investigate the impact of the CgA and VS-I levels on in-hospital mortality.

Results

Median CgA and VS-I levels were higher in patients than in healthy controls (CgA: 0.558 nM [interquartile range, IQR 0.358–1.046] vs 0.368 nM [IQR 0.288–0.490] respectively, p = 0.0017; VS-I: 0.357 nM [IQR 0.196–0.465] vs 0.144 nM [0.144–0.156] respectively, p<0.0001). Concentration of CgA, but not of VS-I, significantly increased in patients who died (n = 47) than in survivors (n = 143) (median 0.948 nM [IQR 0.514–1.754] vs 0.507 nM [IQR 0.343–0.785], p = 0.00026). Levels of CgA were independent predictors of in-hospital mortality (hazard ratio 1.28 [95% confidence interval 1.077–1.522], p = 0.005) when adjusted for age, number of comorbidities, respiratory insufficiency degree, C-reactive protein levels and time from symptom onset to sampling. Kaplan Meier curves revealed a significantly increased mortality rate in patients with CgA levels above 0.558 nM (median value, log rank test, p = 0.001).

Conclusion

Plasma CgA levels increase in COVID-19 patients and represent an early independent predictor of mortality.

Simultaneous Counting of Molecules in the Halo and Dense-Core of Nanovesicles by Regulating Dynamics of Vesicle Opening

We report the discovery that in the presence of chaotropic anions (SCN⁻) the opening of nanometer biological vesicles at an electrified interface often becomes a two‐step process (around 30 % doublet peaks). We have then used this to independently count molecules in each subvesicular compartment, the halo and protein dense‐core, and the fraction of catecholamine binding to the dense‐core is 68 %. Moreover, we differentiated two distinct populations of large dense‐core vesicles (LDCVs) and quantified their content, which might correspond to immature (43 %) and mature (30 %) LDCVs, to reveal differences in their biogenesis. We speculate this is caused by an increase in the electrostatic attraction between protonated catecholamine and the negatively charged dense‐core following adsorption of SCN⁻.

Histological, histochemical, ultrastructural and immunohistochemical identification and characterization of the neurosecretory cells of the adult rabbit's adrenal medulla

The present investigation was conducted on the adrenal glands of 40 adult New Zealand rabbits of both sexes to characterize and identify the histological, histochemical, ultrastructural, and immunohistochemical features of the neurosecretory cells of the adrenal medulla. The obtained specimens of adrenal medulla were subjected to routine histological techniques and then stained with different histological stains, including general, non-specific, specific, and highly specific stains for neurosecretory cells, in addition to immunohistochemical reactions. The obtained results showed two types of adrenal medullary neurosecretory cells containing secretory granules (SGs) of different electron densities: adrenaline and noradrenaline (NA) secreting cells. These secretory granules showed a strong positive reaction to the Grimelius silver impregnation technique. Sections stained with Gomori's chrome alum haematoxylin stain, and the secretory granules showed a strong dark blackish-blue positive colour. The medullary cells showed typical chromaffin reactions when stained by H&E and Giemsa stains after formol dichromate 'Ortha's fluid' fixation. The noradrenaline secretory granules gave a strong positive Schmorl's test, while the adrenaline ones showed a moderate reaction. Immunohistochemically, the adrenal medullary cells were subjected to anti-chromogranin A (CHGA) antibody using the PAP technique, which gave positive reactions.

Endocrine secretory granule production is caused by a lack of REST and intragranular secretory content and accelerated by PROX1

Endocrine secretory granules (ESGs) are morphological characteristics of endocrine/neuroendocrine cells and store peptide hormones/neurotransmitters. ESGs contain prohormones and ESG-related molecules, mainly chromogranin/secretogranin family proteins. However, the precise mechanism of ESG formation has not been elucidated. In this study, we experimentally induced ESGs in the non-neuroendocrine lung cancer cell line H1299. Since repressive element 1 silencing transcription factor (REST) and prospero homeobox 1 (PROX1) are closely associated with the expression of ESG-related molecules, we edited the REST gene and/or transfected PROX1 and then performed molecular biology, immunocytochemistry, and electron and immunoelectron microscopy assays to determine whether ESG-related molecules and ESGs were induced in H1299 cells. Although chromogranin/secretogranin family proteins were induced in H1299 cells by knockout of REST and the induction was accelerated by the PROX1 transgene, the ESGs could not be defined by electron microscopy. However, a small number of ESGs were detected in the H1299 cells lacking REST and expressing pro-opiomelanocortin (POMC) by electron microscopy. Furthermore, many ESGs were produced in the REST-lacking and PROX1- and POMC-expressing H1299 cells. These findings suggest that a lack of REST and the expression of genes related to ESG content are indispensable for ESG production and that PROX1 accelerates ESG production.

Trial registration: Not applicable.

Small disulfide loops in peptide hormones mediate self-aggregation and secretory granule sorting

Unlike constitutively secreted proteins, peptide hormones are stored in densely packed secretory granules, before regulated release upon stimulation. Secretory granules are formed at the TGN by self-aggregation of prohormones as functional amyloids. The nonapeptide hormone vasopressin, which forms a small disulfide loop, was shown to be responsible for granule formation of its precursor in the TGN as well as for toxic fibrillar aggregation of unfolded mutants in the ER. Several other hormone precursors also contain similar small disulfide loops suggesting their function as a general device to mediate aggregation for granule sorting. To test this hypothesis, we studied the capacity of small disulfide loops of different hormone precursors to mediate aggregation in the ER and the TGN. They indeed induced ER aggregation in Neuro-2a and COS-1 cells. Fused to a constitutively secreted reporter protein, they also promoted sorting into secretory granules, enhanced stimulated secretion, and increased Lubrol insolubility in AtT20 cells. These results support the hypothesis that small disulfide loops act as novel signals for sorting into secretory granules by self-aggregation.

Role of Somatostatin Signalling in Neuroendocrine Tumours

Somatostatin (SST) is a small peptide that exerts inhibitory effects on a wide range of neuroendocrine cells. Due to the fact that somatostatin regulates cell growth and hormone secretion, somatostatin receptors (SSTRs) have become valuable targets for the treatment of different types of neuroendocrine tumours (NETs). NETs are a heterogeneous group of tumours that can develop in various parts of the body, including the digestive system, lungs, and pituitary. NETs are usually slow growing, but they are often diagnosed in advanced stages and can display aggressive behaviour. The mortality rate of NETs is not outstandingly increased compared to other malignant tumours, even in the metastatic setting. One of the intrinsic properties of NETs is the expression of SSTRs that serve as drug targets for SST analogues (SSAs), which can delay tumour progression and downregulate hormone overproduction. Additionally, in many NETs, it has been demonstrated that the SSTR expression level provides a prognostic value in predicting a therapeutic response. Furthermore, higher a SSTR expression correlates with a better survival rate in NET patients. In recent studies, other epigenetic regulators affecting SST signalling or SSA–mTOR inhibitor combination therapy in NETs have been considered as novel strategies for tumour control. In conclusion, SST signalling is a relevant regulator of NET functionality. Alongside classical SSA treatment regimens, future advanced therapies and treatment modalities are expected to improve the disease outcomes and overall health of NET patients.

Serum chromogranin A correlated with albuminuria in diabetic patients and is associated with early diabetic nephropathy

BACKGROUND

The kidney is the main site for the removal of chromogranin A (CgA). Previous studies have found that patients with renal impairment displayed elevated concentrations of CgA in plasma and that CgA concentrations reflect a deterioration of renal function. In this study, we aimed to estimate serum CgA levels and to evaluate the role of serum CgA in the early diagnosis of diabetic nephropathy (DN).

METHODS

A total of 219 patients with type 2 diabetes mellitus (T2DM) were included in this cross-sectional study. These patients were classified into normoalbuminuria (n = 121), microalbuminuria (n = 73), or macroalbuminuria (n = 25) groups based on their urine albumin to creatinine ratios (UACRs). The degree of DN is reflected by UACR. A control group consisted of 45 healthy subjects. The serum CgA levels were measured by ELISA, and other key parameters were assayed.

RESULTS

Serum CgA levels were higher in patients with T2DM than in control subjects, and a statistically significant difference among the studied subgroups regarding CgA was found (P < 0.05). The levels of serum CgA increased gradually with the degree of DN (P < 0.001). Serum CgA levels showed a moderate-intensity positive correlation with UACRs (P < 0.001). A cutoff level of 3.46 ng/ml CgA showed 69.86% sensitivity and 66.12% specificity to detect DN in the early stage.

CONCLUSION

The levels of serum CgA increased gradually with the degree of DN and can be used as a biomarker in the early detection of DN.

Use of saliva stress biomarkers to estimate novice male endoscopist's stress during training in a high-end simulator

OBJECTIVE

Simulated endoscopic training can be challenging and stressful for the novice trainee. The absence of a reliable stress detection method during simulated endoscopic training makes estimating trainees' mental stress difficult to quantify. This study concomitantly measures the responses of four saliva stress biomarkers and compares them to the video score (VS) achieved by novice endoscopists in a reproducibly stressful simulation environment.

METHODS

Thirty-six male endoscopy naïve surgery residents were enrolled. After an orientation phase, a saliva specimen was collected for cortisol (sC), alpha-amylase (sAA), Chromogranin A (sCgA), and immunoglobulin A (sIgA) measurements (baseline phase, BL). Thereafter, the simulation exercise phase (E) started, practicing in the Fundamentals of Endoscopic Surgery Skills module (GI-Bronch Mentor). Immediately after, a second saliva sample for measuring the above-cited biomarkers was collected. The whole experiment was videotaped, and the VS was calculated. The percentage (E-BL)_diff of each of the four saliva biomarkers was calculated and examined for correlation to VS.

RESULTS

sCgA_diff showed the best correlation with VS, followed by sAA_diff.

CONCLUSIONS

sCgA and sAA, are saliva stress biomarkers that are easy to collect non-invasively and showed the best correlation with novice endoscopist's performance in our simulation setting, and therefore, they could be used for monitoring stress.