Radioimmunoassay of chromogranin A in plasma as a measure of exocytotic sympathoadrenal activity in normal subjects and patients with pheochromocytoma

The uterine secretory cycle: recurring physiology of endometrial outputs that setup the uterine luminal microenvironment

Conserved in female reproduction across all mammalian species is the estrous cycle and its regulation by the hypothalamic-pituitary-gonadal (HPG) axis, a collective of intersected hormonal events that are crucial for ensuring uterine fertility. Nonetheless, knowledge of the direct mediators that synchronously shape the uterine microenvironment for successive yet distinct events, such as the transit of sperm and support for progressive stages of preimplantation embryo development, remain principally deficient. Toward understanding the timed endometrial outputs that permit luminal events as directed by the estrous cycle, we used Bovidae as a model system to uniquely surface sample and study temporal shifts to in vivo endometrial transcripts that encode for proteins destined to be secreted. The results revealed the full quantitative profile of endometrial components that shape the uterine luminal microenvironment at distinct phases of the estrous cycle (estrus, metestrus, diestrus, and proestrus). In interpreting this comprehensive log of stage-specific endometrial secretions, we define the "uterine secretory cycle" and extract a predictive understanding of recurring physiological actions regulated within the uterine lumen in anticipation of sperm and preimplantation embryonic stages. This repetitive microenvironmental preparedness to sequentially provide operative support was a stable intrinsic framework, with only limited responses to sperm or embryos if encountered in the lumen within the cyclic time period. In uncovering the secretory cycle and unraveling realistic biological processes, we present novel foundational knowledge of terminal effectors controlled by the HPG axis to direct a recurring sequence of vital functions within the uterine lumen.NEW & NOTEWORTHY This study unravels the recurring sequence of changes within the uterus that supports vital functions (sperm transit and development of preimplantation embryonic stages) during the reproductive cycle in female Ruminantia. These data present new systems knowledge in uterine reproductive physiology crucial for setting up in vitro biomimicry and artificial environments for assisted reproduction technologies for a range of mammalian species.

Biochemical Assessment of Pheochromocytoma and Paraganglioma

Pheochromocytoma and paraganglioma (PPGL) require prompt consideration and efficient diagnosis and treatment to minimize associated morbidity and mortality. Once considered, appropriate biochemical testing is key to diagnosis. Advances in understanding catecholamine metabolism have clarified why measurements of the O-methylated catecholamine metabolites rather than the catecholamines themselves are important for effective diagnosis. These metabolites, normetanephrine and metanephrine, produced respectively from norepinephrine and epinephrine, can be measured in plasma or urine, with choice according to available methods or presentation of patients. For patients with signs and symptoms of catecholamine excess, either test will invariably establish the diagnosis, whereas the plasma test provides higher sensitivity than urinary metanephrines for patients screened due to an incidentaloma or genetic predisposition, particularly for small tumors or in patients with an asymptomatic presentation. Additional measurements of plasma methoxytyramine can be important for some tumors, such as paragangliomas, and for surveillance of patients at risk of metastatic disease. Avoidance of false-positive test results is best achieved by plasma measurements with appropriate reference intervals and preanalytical precautions, including sampling blood in the fully supine position. Follow-up of positive results, including optimization of preanalytics for repeat tests or whether to proceed directly to anatomic imaging or confirmatory clonidine tests, depends on the test results, which can also suggest likely size, adrenal vs extra-adrenal location, underlying biology, or even metastatic involvement of a suspected tumor. Modern biochemical testing now makes diagnosis of PPGL relatively simple. Integration of artificial intelligence into the process should make it possible to fine-tune these advances.

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.

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.

The antimicrobial peptides secreted by the chromaffin cells of the adrenal medulla link the neuroendocrine and immune systems: From basic to clinical studies

The increasing resistance to antibiotic treatments highlights the need for the development of new antimicrobial agents. Antimicrobial peptides (AMPs) have been studied to be used in clinical settings for the treatment of infections. Endogenous AMPs represent the first line defense of the innate immune system against pathogens; they also positively interfere with infection-associated inflammation. Interestingly, AMPs influence numerous biological processes, such as the regulation of the microbiota, wound healing, the induction of adaptive immunity, the regulation of inflammation, and finally express anti-cancer and cytotoxic properties. Numerous peptides identified in chromaffin secretory granules from the adrenal medulla possess antimicrobial activity: they are released by chromaffin cells during stress situations by exocytosis via the activation of the hypothalamo-pituitary axis. The objective of the present review is to develop complete informations including (i) the biological characteristics of the AMPs produced after the natural processing of chromogranins A and B, proenkephalin-A and free ubiquitin, (ii) the design of innovative materials and (iii) the involvement of these AMPs in human diseases. Some peptides are elective biomarkers for critical care medicine, may play an important role in the protection of infections (alone, or in combination with others or antibiotics), in the prevention of nosocomial infections, in the regulation of intestinal mucosal dynamics and of inflammation. They could play an important role for medical implant functionalization, such as catheters, tracheal tubes or oral surgical devices, in order to prevent infections after implantation and to promote the healing of tissues.

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.

Modulation of magnetoencephalography alpha band activity by radiofrequency electromagnetic field depicted in sensor and source space

Several studies reported changes in spontaneous electroencephalogram alpha band activity related to radiofrequency electromagnetic fields, but findings showed both an increase and a decrease of its spectral power or no effect. Here, we studied the alpha band modulation after 900 MHz mobile phone radiofrequency exposure and localized cortical regions involved in these changes, via a magnetoencephalography (MEG) protocol with healthy volunteers in a double-blind, randomized, counterbalanced crossover design. MEG was recorded during eyes open and eyes closed resting-state before and after radiofrequency exposure. Potential confounding factors, known to affect alpha band activity, were assessed as control parameters to limit bias. Entire alpha band, lower and upper alpha sub-bands MEG power spectral densities were estimated in sensor and source space. Biochemistry assays for salivary biomarkers of stress (cortisol, chromogranin-A, alpha amylase), heart rate variability analysis and high-performance liquid chromatography for salivary caffeine concentration were realized. Results in sensor and source space showed a significant modulation of MEG alpha band activity after the radiofrequency exposure, with different involved cortical regions in relation to the eyes condition, probably because of different attention level with open or closed eyes. None of the control parameters reported a statistically significant difference between experimental sessions.

Quantification of chromogranin A using a surface plasmon resonance-based biosensor

The chromogranin A (CgA) level in the blood is an important biomarker for neuroendocrine tumors and other diseases. Traditional methods for detecting CgA are expensive and time-consuming with low reproducibility. In this study, surface plasmon resonance (SPR), a simple and label-free technique, was validated for quantifying CgA. CgA antibody (CgA-Ab) was immobilized on the CM5 sensor chip (CgA-Ab-CM5) at optimal conditions (pH 5.0, 10 μg mL^-1). Next, different concentrations of CgA were measured by CgA-Ab-CM5. The binding and regeneration conditions were optimized and used in each measurement. A binding time of 240 s, and flow rate of 30 μL min^-1 were chosen as the optimal binding conditions. A pH of 1.75 was the optimal regeneration condition. Compared to the detection range of 23.4-187 ng mL^-1 for enzyme-linked immunosorbent assay (ELISA), a linear range of 0.2-187 ng mL^-1 was detected based on the response unit (RU), showing high sensitivity and reliability of SPR. Finally, the reproducibility of the CgA-Ab-CM5 chip was accessed by consecutive binding-regeneration cycles for 300 times. In conclusion, the SPR-based CgA-Ab-CM5 chip is a sensitive and reproducible method for quantifying CgA levels in a real-time manner.

The Emerging Roles of Chromogranins and Derived Polypeptides in Atherosclerosis, Diabetes, and Coronary Heart Disease

Chromogranin A (CgA), B (CgB), and C (CgC), the family members of the granin glycoproteins, are associated with diabetes. These proteins are abundantly expressed in neurons, endocrine, and neuroendocrine cells. They are also present in other areas of the body. Patients with diabetic retinopathy have higher levels of CgA, CgB, and CgC in the vitreous humor. In addition, type 1 diabetic patients have high CgA and low CgB levels in the circulating blood. Plasma CgA levels are increased in patients with hypertension, coronary heart disease, and heart failure. CgA is the precursor to several functional peptides, including catestatin, vasostatin-1, vasostatin-2, pancreastatin, chromofungin, and many others. Catestatin, vasostain-1, and vasostatin-2 suppress the expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 in human vascular endothelial cells. Catestatin and vasostatin-1 suppress oxidized low-density lipoprotein-induced foam cell formation in human macrophages. Catestatin and vasostatin-2, but not vasostatin-1, suppress the proliferation and these three peptides suppress the migration in human vascular smooth muscles. Chronic infusion of catestatin, vasostatin-1, or vasostatin-2 suppresses the development of atherosclerosis of the aorta in apolipoprotein E-deficient mice. Catestatin, vasostatin-1, vasostatin-2, and chromofungin protect ischemia/reperfusion-induced myocardial dysfunction in rats. Since pancreastatin inhibits insulin secretion from pancreatic β-cells, and regulates glucose metabolism in liver and adipose tissues, pancreastatin inhibitor peptide-8 (PSTi8) improves insulin resistance and glucose homeostasis. Catestatin stimulates therapeutic angiogenesis in the mouse hind limb ischemia model. Gene therapy with secretoneurin, a CgC-derived peptide, stimulates postischemic neovascularization in apolipoprotein E-deficient mice and streptozotocin-induced diabetic mice, and improves diabetic neuropathy in db/db mice. Therefore, CgA is a biomarker for atherosclerosis, diabetes, hypertension, and coronary heart disease. CgA- and CgC--derived polypeptides provide the therapeutic target for atherosclerosis and ischemia-induced tissue damages. PSTi8 is useful in the treatment of diabetes.

NETest is superior to chromogranin A in neuroendocrine neoplasia: a prospective ENETS CoE analysis

INTRODUCTION

The absence of a reliable, universal biomarker is a significant limitation in neuroendocrine neoplasia (NEN) management. We prospectively evaluated two CgA assays, (NEOLISA, EuroDiagnostica) and (CgA ELISA, Demeditec Diagnostics (DD)) and compared the results to the NETest.

METHODS

NEN cohort (n = 258): pancreatic, n = 67; small intestine, n = 40; appendiceal, n = 10; rectal, n = 45; duodenal, n = 9; gastric, n = 44; lung, n = 43. Image-positive disease (IPD) (n = 123), image & histology- negative (IND) (n = 106), and image-negative and histology positive (n = 29). CgA metrics: NEOLISA, ULN: 108 ng/mL, DD: ULN: 99 ng/mL. Data mean ± s.e.m. NETest: qRT-PCR - multianalyte analyses, ULN: 20. All samples de-identified and assessed blinded. Statistics: Mann-Whitney U-test, Pearson correlation and McNemar-test.

RESULTS

CgA positive in 53/258 (NEOLISA), 32 (DD) and NETest-positive in 157/258. In image- positive disease (IPD, n = 123), NEOLISA-positive: 33% and DD: 19%. NETest-positive: 122/123 (99%; McNemar's Chi2= 79-97, P < 0.0001). NEOLISA was more accurate than DD (P = 0.0003). In image- negative disease (IND), CgA was NEOLISA-positive (11%), DD (8%), P = NS, and NETest (33%). CgA assays could not distinguish progressive (PD) from stable disease (SD) or localized from metastatic disease (MD). NETest was significantly higher in PD (47 ± 5) than SD (29 ± 1, P = 0.0009). NETest levels in MD (35 ± 2) were elevated vs localized disease (24 ± 1.3, P = 0.008).

CONCLUSIONS

NETest, a multigenomic mRNA biomarker, was ~99% accurate in the identification of NEN disease. The CgA assays detected NEN disease in 19-33%. Multigenomic blood analysis using NETest is more accurate than CgA and should be considered the biomarker standard of care.

Catestatin peptide of chromogranin A as a potential new target for several risk factors management in the course of metabolic syndrome

Obesity, lipodystrophy, diabetes, and hypertension collectively constitute the main features of Metabolic Syndrome (MetS), together with insulin resistance (IR), which is considered as a defining element. MetS generally leads to the development of cardiovascular disease (CVD), which is a determinant cause of mortality and morbidity in humans and animals. Therefore, it is essential to implement and put in place adequate management strategies for the treatment of this disease. Catestatin is a bioactive peptide with 21 amino acids, which is derived through cleaving of the prohormone chromogranin A (CHGA/CgA) that is co-released with catecholamines from secretory vesicles and, which is responsible for hepatic/plasma lipids and insulin levels regulation, improves insulin sensitivity, reduces hypertension and attenuates obesity in murine models. In humans, there were few published studies, which showed that low levels of catestatin are significant risk factors for hypertension in adult patients. These accumulating evidence documents clearly that catestatin peptide (CST) is linked to inflammatory and metabolic syndrome diseases and can be a novel regulator of insulin and lipid levels, blood pressure, and cardiac function. The goal of this review is to provide an overview of the CST effects in metabolic syndrome given its role in metabolic regulation and thus, provide new insights into the use of CST as a diagnostic marker and therapeutic target.

The clinical applications of a multigene liquid biopsy (NETest) in neuroendocrine tumors

PURPOSE

There are few effective biomarkers for neuroendocrine tumors. Precision oncology strategies have provided liquid biopsies for real-time and tailored decision-making. This has led to the development of the first neuroendocrine tumor liquid biopsy (the NETest). The NETest represents a transcriptomic signature of neuroendocrine tumor (NETs) that captures tumor biology and disease activity. The data have direct clinical application in terms of identifying residual disease, disease progress and the efficacy of treatment. In this overview we assess the available published information on the metrics and clinical efficacy of the NETest.

MATERIAL AND METHODS

Published data on the NETest have been collated and analyzed to understand the clinical application of this multianalyte biomarker in NETs.

RESULTS

NETest assay has been validated as a standardized and reproducible clinical laboratory measurement. It is not affected by demographic characteristics, or acid suppressive medication. Clinical utility of the NETest has been documented in gastroenteropancreatic, bronchopulmonary NETs, in paragangliomas and pheochromocytomas. The test facilitates accurate diagnosis of a NET disease, and real-time monitoring of the disease status (stable/progressive disease). It predicts aggressive tumor behavior, identifies operative tumor resection, and efficacy of the medical treatment (e.g. somatostatin analogues), or peptide receptor radionuclide therapy (PRRT). NETest metrics and clinical applications out-perform standard biomarkers like chromogranin A.

CONCLUSIONS

The NETest exhibits clinically competent metrics as an effective biomarker for neuroendocrine tumors. Measurement of NET transcripts in blood is a significant advance in neuroendocrine tumor management and demonstrates that blood provides a viable source to identify and monitor tumor status.

Endogenous Sympathetic Activity in CAPD Patients: Its Relationship to Peritoneal Diffusion Capacity

Endogenous agents, as catecholamines, may influence peritoneal mass transport by modifying peritoneal blood flow. Such endogenous mechanisms could explain certain functional peculiarities of the peritoneum in CAPD patients. In 27 randomly selected patients on CAPD we calculated peritoneal mass-transfer coefficient (MTC) for urea, creatinine, uric acid and parathormone (PTH) using mathematical modelling techniques. Also we measured simultaneously the renin-angiotensin and catecholamine levels in blood and dialysate.

The dialysate level of catecholamines and especially noradrenaline was significantly higher than the blood levels. Most of these patients had higher renin and aldosterone blood levels than the controls; we found no renin activity in the dialysate of any of these patients; (Plasma) aldosterone values correlated directly with renin activity. Multivariant analysis provided no evidence that the MTCs values were affected by two or more variables. Linear regression analysis of all variables studied showed direct correlation between dialysate noradrenaline and MTCs, and negative relationship between noradrenaline and ultrafiltration capacity. The catecholamine plasma levels, which were within the normal range, did not correlate with MTCs or with ultrafiltration.

Our findings suggest that, in some cases, noradrenaline produced in the peritoneum may influence peritoneal mass transport through a vasoactive effect. Dialysate catecholamine levels correlate with that of plasma, but the latter does not influence peritoneal transport.

Prognostic role of chromogranin A in castration-resistant prostate cancer: A meta-analysis

We aimed to investigate the prognostic value of chromogranin A (CgA) in castration-resistant prostate cancer (CRPC). We conducted a systematic literature search of PubMed, Web of Science, and EMBASE for citations published prior to September 2017 that described CgA and CRPC and performed a standard meta-analysis on survival outcomes. Our meta-analysis included eight eligible studies with 686 patients. The results were as follows: progression-free survival (PFS) was associated with CgA level (hazard ratio [HR] = 2.47, 95% confidence interval [CI]: 1.47-4.14, P = 0.0006); PFS was relative to CgA change (HR = 9.22, 95% CI: 3.03-28.05, P < 0.0001); and overall survival (OS) was relative to CgA level (HR = 1.47, 95% CI: 1.15-1.87, P = 0.002). When we divided the patients into two groups according to therapy status, the result for OS relative to CgA level was an HR of 1.26 (95% CI: 1.09-1.45, P = 0.001) in the first-line hormonal therapy group, and an HR of 2.33 (95% CI: 1.40-3.89, P = 0.001) in the second-line hormonal therapy or chemotherapy group. This meta-analysis indicated that a high CgA level had a negative influence on OS and PFS in CRPC patients. In addition, CRPC patients with a rising CgA had a shorter PFS. Further studies are needed to verify the prognostic value of CgA in CRPC.

Chromogranin A and its fragments in cardiovascular, immunometabolic, and cancer regulation

Chromogranin A (CgA)-the index member of the chromogranin/secretogranin secretory protein family-is ubiquitously distributed in endocrine, neuroendocrine, and immune cells. Elevated levels of CgA-related polypeptides, consisting of full-length molecules and fragments, are detected in the blood of patients suffering from neuroendocrine tumors, heart failure, renal failure, hypertension, rheumatoid arthritis, and inflammatory bowel disease. Full-length CgA and various CgA-derived peptides, including vasostatin-1, pancreastatin, catestatin, and serpinin, are expressed at different relative levels in normal and pathological conditions and exert diverse, and sometime opposite, biological functions. For example, CgA is overexpressed in genetic hypertension, whereas catestatin is diminished. In rodents, the administration of catestatin decreases hypertension, cardiac contractility, obesity, atherosclerosis, and inflammation, and it improves insulin sensitivity. By contrast, pancreastatin is elevated in diabetic patients, and the administration of this peptide to obese mice decreases insulin sensitivity and increases inflammation. CgA and the N-terminal fragment of vasostatin-1 can enhance the endothelial barrier function, exert antiangiogenic effects, and inhibit tumor growth in animal models, whereas CgA fragments lacking the CgA C-terminal region promote angiogenesis and tumor growth. Overall, the CgA system, consisting of full-length CgA and its fragments, is emerging as an important and complex player in cardiovascular, immunometabolic, and cancer regulation.

Modulation of the coronary tone in the expanding scenario of Chromogranin-A and its derived peptides

The cardiac function critically depends on an adequate myocardial oxygenation and on a correct coronary blood flow. Endothelial, hormonal and extravascular factors work together generating a fine balance between oxygen supply and oxygen utilization through the coronary circulation. Among the regulatory factors that contribute to the coronary tone, increasing attention is paid to the cardiac endocrines, such as chromogranin A, a prohormone for many biologically active peptides, including vasostatin and catestatin. In this review, we will summarize the available evidences about the coronary effects of these molecules, and their putative mechanism of action. Laboratory and clinical data on chromogranin A and its derived fragments will be analyzed in relation to the scenario of the endocrine heart, and of its putative clinical perspectives.

Biogenesis of the Insulin Secretory Granule in Health and Disease

The secretory granules of pancreatic beta cells are specialized organelles responsible for the packaging, storage and secretion of the vital hormone insulin. The insulin secretory granules also contain more than 100 other proteins including the proteases involved in proinsulin-to insulin conversion, other precursor proteins, minor co-secreted peptides, membrane proteins involved in cell trafficking and ion translocation proteins essential for regulation of the intragranular environment. The synthesis, transport and packaging of these proteins into nascent granules must be carried out in a co-ordinated manner to ensure correct functioning of the granule. The process is regulated by many circulating nutrients such as glucose and can change under different physiological states. This chapter discusses the various processes involved in insulin granule biogenesis with a focus on the granule composition in health and disease.

Catestatin as a Target for Treatment of Inflammatory Diseases

It is increasingly clear that inflammatory diseases and cancers are influenced by cleavage products of the pro-hormone chromogranin A (CgA), such as the 21-amino acids long catestatin (CST). The goal of this review is to provide an overview of the anti-inflammatory effects of CST and its mechanism of action. We discuss evidence proving that CST and its precursor CgA are crucial for maintaining metabolic and immune homeostasis. CST could reduce inflammation in various mouse models for diabetes, colitis and atherosclerosis. In these mouse models, CST treatment resulted in less infiltration of immune cells in affected tissues, although in vitro monocyte migration was increased by CST. Both in vivo and in vitro, CST can shift macrophage differentiation from a pro- to an anti-inflammatory phenotype. Thus, the concept is emerging that CST plays a role in tissue homeostasis by regulating immune cell infiltration and macrophage differentiation. These findings warrant studying the effects of CST in humans and make it an interesting therapeutic target for treatment and/or diagnosis of various metabolic and immune diseases.

Chromogranin a Measurement in Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are rare neoplasms characterized by a low proliferative index and, in some cases, a favorable prognosis. These tumors often overproduce and release biologically active substances that are responsible for severe syndromes. Tumor marker measurement provides the clinician with useful information for the management of NET patients. The substances released by overproducing tumors are currently used as biomarkers, but there is a need for sensitive markers also for the “biochemically silent” NETs. The most effective and reliable blood marker available today is chromogranin A (CgA). Because of its high sensitivity and specificity, this glycoprotein can be used for the diagnosis, prognosis and follow-up of NETs. Furthermore, CgA measurement can be used for monitoring those tumors not overproducing or releasing any hormones or biological amines. This paper is a synthetic review on the value of CgA in NET management and reports our experiences with CgA measurement in NET patients.

Accuracy and Clinical Correlates of Two Different Methods for Chromogranin A Assay in Neuroendocrine Tumors

Measurement of chromogranin A (CgA) plays a major role in the management of neuroendocrine tumors (NET); however, reliable assaying of CgA is made difficult by the rapid hydrolysis following its release into the bloodstream. This study was aimed at the assessment of two assays for CgA in NET patients. CgA was measured in 93 patients by means of an enzyme-linked immunosorbent assay (ELISA) and an immunoradiometric assay (IRMA). The specificity and sensitivity of CgA were evaluated in relation to tumor histology. The clinical accuracy of the two assays was evaluated by receiver-operating characteristic (ROC) curve analysis. Regression analysis demonstrated different immunoreactivity for CgA of the antibodies used in the two kits (r=0.61). The two assays had different accuracy also in classifying patients according to their clinical condition (91% vs 64% specificity and 79% vs 79% sensitivity for the ELISA and IRMA assay, respectively) and tumor histology (81% vs 85% sensitivity for the ELISA and IRMA assays, respectively, in carcinoids; 92% vs 67% sensitivity for the ELISA and IRMA assays, respectively, in pancreatic islet cell tumors). The different clinical accuracy of the two assays was confirmed by the ROC analysis (AUC=0.90 vs AUC=0.87 for the ELISA and IRMA assays, respectively). In conclusion, because of the poor standardization of the commercially available measurement tools the clinical accuracy of CgA measurement depends on the assay used. This makes it difficult to compare CgA values measured with different kits and affects the clinical accuracy of the different assays for CgA.

Catestatin, vasostatin, cortisol, and visual analog scale scoring for stress assessment in healthy dogs

The neuroendocrine glycoprotein chromogranin A is a useful biomarker for stress in humans. Chromogranin A epitopes catestatin and vasostatin can be measured in dogs using radioimmunoassays. The objective of this study was to evaluate catestatin and vasostatin as canine stress biomarkers in a clinical setting. Blood and saliva were collected from 33 healthy dogs that were familiar with sampling procedures and the animal hospital environment (control group) and 30 healthy dogs that were unacquainted (stress group). During sampling, stress behavior was scored by the same observer using visual analog scale (VAS). Plasma was analyzed for catestatin and vasostatin, serum for cortisol, and saliva for catestatin. Differences between groups were analyzed using two-sample t-tests and P<0.05 was considered significant. Stress behavior VAS score in the control group was significantly lower than in the stress group during blood (P=0.002) and saliva (P=0.0009) sampling. Serum cortisol and saliva catestatin concentrations in the stress group were higher than the control group (P=0.003 and P<0.0001, respectively). Serum cortisol concentrations were correlated with those of saliva (r=0.34, P=0.04) and plasma catestatin (r=0.29, P=0.03). Plasma catestatin and vasostatin did not differ significantly between groups. In conclusion, concentrations of saliva catestatin, and serum cortisol, and stress behavior VAS scores were significantly higher in the stress group. The results indicate that saliva catestatin may be useful as a biomarker for acute psychological stress in dogs.

Old and emerging concepts on adrenal chromaffin cell stimulus-secretion coupling

The chromaffin cells (CCs) of the adrenal medulla play a key role in the control of circulating catecholamines to adapt our body function to stressful conditions. A huge research effort over the last 35 years has converted these cells into the Escherichia coli of neurobiology. CCs have been the testing bench for the development of patch-clamp and amperometric recording techniques and helped clarify most of the known molecular mechanisms that regulate cell excitability, Ca²⁺ signals associated with secretion, and the molecular apparatus that regulates vesicle fusion. This special issue provides a state-of-the-art on the many well-known and unsolved questions related to the molecular processes at the basis of CC function. The issue is also the occasion to highlight the seminal work of Antonio G. García (Emeritus Professor at UAM, Madrid) who greatly contributed to the advancement of our present knowledge on CC physiology and pharmacology. All the contributors of the present issue are distinguished scientists who are either staff members, external collaborators, or friends of Prof. García.

Circulating chromogranin A and its fragments as diagnostic and prognostic disease markers

Chromogranin A (CgA), a secretory protein released in the blood by neuroendocrine cells and neurons, is the precursor of various bioactive fragments involved in the regulation of the cardiovascular system, metabolism, innate immunity, angiogenesis, and tissue repair. After the original demonstration that circulating CgA can serve as a biomarker for a wide range of neuroendocrine tumors, several studies have shown that increased levels of CgA can be present also in the blood of patients with cardiovascular, gastrointestinal, and inflammatory diseases with, in certain cases, important diagnostic and prognostic implications. Considering the high structural and functional heterogeneity of the CgA system, comprising precursor and fragments, it is not surprising that the different immunoassays used in these studies led, in some cases, to discrepant results. Here, we review these notions and we discuss the importance of measuring total-CgA, full-length CgA, specific fragments, and their relative levels for a more thorough assessment of the pathophysiological function and diagnostic/prognostic value of the CgA system.

Chromogranins: from discovery to current times

The discovery in 1953 of the chromaffin granules as co-storage of catecholamines and ATP was soon followed by identification of a range of uniquely acidic proteins making up the isotonic vesicular storage complex within elements of the diffuse sympathoadrenal system. In the mid-1960s, the enzymatically inactive, major core protein, chromogranin A was shown to be exocytotically discharged from the stimulated adrenal gland in parallel with the co-stored catecholamines and ATP. A prohormone concept was introduced when one of the main storage proteins collectively named granins was identified as the insulin release inhibitory polypeptide pancreastatin. A wide range of granin-derived biologically active peptides have subsequently been identified. Both chromogranin A and chromogranin B give rise to antimicrobial peptides of relevance for combat of pathogens. While two of the chromogranin A-derived peptides, vasostatin-I and pancreastatin, are involved in modulation of calcium and glucose homeostasis, respectively, vasostatin-I and catestatin are important modulators of endothelial permeability, angiogenesis, myocardial contractility, and innate immunity. A physiological role is now evident for the full-length chromogranin A and vasostatin-I as circulating stabilizers of endothelial integrity and in protection against myocardial injury. The high circulating levels of chromogranin A and its fragments in patients suffering from various inflammatory diseases have emerged as challenges for future research and clinical applications.

Granin-derived peptides

The granin family comprises altogether 7 different proteins originating from the diffuse neuroendocrine system and elements of the central and peripheral nervous systems. The family is dominated by three uniquely acidic members, namely chromogranin A (CgA), chromogranin B (CgB) and secretogranin II (SgII). Since the late 1980s it has become evident that these proteins are proteolytically processed, intragranularly and/or extracellularly into a range of biologically active peptides; a number of them with regulatory properties of physiological and/or pathophysiological significance. The aim of this comprehensive overview is to provide an up-to-date insight into the distribution and properties of the well established granin-derived peptides and their putative roles in homeostatic regulations. Hence, focus is directed to peptides derived from the three main granins, e.g. to the chromogranin A derived vasostatins, betagranins, pancreastatin and catestatins, the chromogranin B-derived secretolytin and the secretogranin II-derived secretoneurin (SN). In addition, the distribution and properties of the chromogranin A-derived peptides prochromacin, chromofungin, WE14, parastatin, GE-25 and serpinins, the CgB-peptide PE-11 and the SgII-peptides EM66 and manserin will also be commented on. Finally, the opposing effects of the CgA-derived vasostatin-I and catestatin and the SgII-derived peptide SN on the integrity of the vasculature, myocardial contractility, angiogenesis in wound healing, inflammatory conditions and tumors will be discussed.

Catestatin, vasostatin, cortisol, and pain assessments in dogs suffering from traumatic bone fractures

Background

Traumatic bone fractures cause moderate to severe pain, which needs to be minimized for optimal recovery and animal welfare, illustrating the need for reliable objective pain biomarkers for use in a clinical setting. The objectives of this study were to investigate catestatin (CST) and vasostatin (VS) concentrations as two new potential biomarkers, and cortisol concentrations, scores of the short form of the Glasgow composite measure pain scale (CMPS-SF), and visual analog scale (VAS) in dogs suffering from traumatic bone fractures before and after morphine administration in comparison with healthy dogs.

Methods

Fourteen dogs with hind limb or pelvic fractures and thirty healthy dogs were included. Dogs with fractures were divided into four groups according to analgesia received before participation. Physical examination, CMPS-SF, pain and stress behavior VAS scores were recorded in all dogs. Saliva and blood were collected once in healthy dogs and in dogs with fractures before and 35–70 min after morphine administration. Blood samples were analyzed for CST, VS, and cortisol. Saliva volumes, however, were insufficient for analysis.

Results

Catestatin and cortisol concentrations, and CMPS-SF, and VAS scores differed significantly between dogs with fractures prior to morphine administration and healthy dogs. After morphine administration, dogs with fractures had significantly decreased CMPS-SF and VAS scores and, compared to healthy dogs, CST concentrations, CMPS-SF, and VAS scores still differed significantly. However, CST concentrations remained largely within the normal range. Absolute delta values for CST significantly correlated with delta values for CMPS-SF. Catestatin and cortisol did not differ significantly before and after morphine administration. Vasostatin concentrations did not differ significantly between groups.

Conclusions

Catestatin and cortisol concentrations, CMPS-SF, and VAS scores differed significantly in the dogs with traumatic bone fractures compared to the healthy dogs. Morphine treatment partially relieved pain and stress according to the subjective but not according to the objective assessments performed. However, because of the large degree of overlap with normal values, our results suggest that plasma CST concentrations have a limited potential as a clinically useful biomarker for pain-induced stress.

Catestatin and vasostatin concentrations in healthy dogs

Background

The neuroendocrine glycoprotein chromogranin A is a useful biomarker in humans for neuroendocrine tumors and stress. Chromogranin A can be measured in both blood and saliva. The objective of this study was to investigate concentrations of and correlation between the chromogranin A epitopes catestatin and vasostatin in healthy dogs accustomed to the sample collection procedures. Blood and saliva samples were collected from 10 research Beagle dogs twice daily for 5 consecutive days, and from 33 privately-owned blood donor dogs in association with 50 different blood donation occasions. All dogs were familiar with sample collection procedures. During each sampling, stress behavior was scored by the same observer using a visual analog scale (VAS) and serum cortisol concentrations. Catestatin and vasostatin were analyzed using radioimmunoassays for dogs.

Results

The dogs showed minimal stress behavior during both saliva sampling and blood sampling as monitored by VAS scores and serum cortisol concentrations. Few and insufficient saliva volumes were obtained and therefore only catestatin could be analyzed. Catestatin concentrations differed significantly and did not correlate significantly with vasostatin concentrations (P < 0.0001). Age, gender, breed, and time of sample collection did not significantly affect concentrations of plasma catestatin, vasostatin, and saliva catestatin.

Conclusions

The normal ranges of plasma catestatin (0.53–0.98 nmol/l), vasostatin (0.11–1.30 nmol/l), and saliva catestatin (0.31–1.03 nmol/l) concentrations in healthy dogs accustomed to the sampling procedures were determined. Separate interpretation of the different chromogranin A epitopes from either saliva or plasma is recommended.

Chromogranin A Regulation of Obesity and Peripheral Insulin Sensitivity

Chromogranin A (CgA) is a prohormone and granulogenic factor in endocrine and neuroendocrine tissues, as well as in neurons, and has a regulated secretory pathway. The intracellular functions of CgA include the initiation and regulation of dense-core granule biogenesis and sequestration of hormones in neuroendocrine cells. This protein is co-stored and co-released with secreted hormones. The extracellular functions of CgA include the generation of bioactive peptides, such as pancreastatin (PST), vasostatin, WE14, catestatin (CST), and serpinin. CgA knockout mice (Chga-KO) display: (i) hypertension with increased plasma catecholamines, (ii) obesity, (iii) improved hepatic insulin sensitivity, and (iv) muscle insulin resistance. These findings suggest that individual CgA-derived peptides may regulate different physiological functions. Indeed, additional studies have revealed that the pro-inflammatory PST influences insulin sensitivity and glucose tolerance, whereas CST alleviates adiposity and hypertension. This review will focus on the different metabolic roles of PST and CST peptides in insulin-sensitive and insulin-resistant models, and their potential use as therapeutic targets.

Catestatin, vasostatin, cortisol, temperature, heart rate, respiratory rate, scores of the short form of the Glasgow composite measure pain scale and visual analog scale for stress and pain behavior in dogs before and after ovariohysterectomy

Background

The stress reaction induced by surgery and associated pain may be detrimental for patient recovery and should be minimized. The neuropeptide chromogranin A (CGA) has shown promise as a sensitive biomarker for stress in humans. Little is known about CGA and its derived peptides, catestatin (CST) and vasostatin (VS), in dogs undergoing surgery. The objectives of this study were to investigate and compare concentrations of CGA epitopes CST and VS, cortisol, body temperature, heart rate, respiratory rate, scores of the short form of the Glasgow composite measure pain scale (CMPS-SF) and visual analog scales (VAS) for stress and pain behavior in dogs before and after ovariohysterectomy.

Methods

Thirty healthy privately owned female dogs admitted for elective ovariohysterectomy were included. Physical examination, CMPS-SF, pain behavior VAS, and stress behavior VAS were recorded and saliva and blood samples were collected before surgery, 3 h after extubation, and once at recall 7–15 days after surgery. Dogs were premedicated with morphine and received carprofen as analgesia for 7 days during the postoperative period.

Results

At 3 h after extubation, CMPS-SF and pain behavior VAS scores had increased (p < 0.0001) and stress behavior VAS scores, temperature, respiratory rate (p < 0.0001), plasma CST concentrations (p = 0.002) had decreased significantly compared to before surgery. No significant differences were observed in the subjective and physiological parameters between before surgery and at recall, but plasma CST (p = 0.04) and serum cortisol (p = 0.009) were significantly lower at recall. Plasma VS, saliva CST, and heart rate did not differ significantly at any observed time.

Conclusion

Study parameters for evaluating surgery-induced stress and pain changed in dogs subjected to ovariohysterectomy. To further evaluate CST and VS usefulness as pain biomarkers, studies on dogs in acute painful situations are warranted.

Pancreatic neuroendocrine tumors: Challenges in an underestimated disease

Pancreatic neuroendocrine tumours (PanNETs) are considered a relatively unusual oncologic entity. Due to its relative good prognosis, surgery remains the goal standard therapy not only in localized disease but also in the setting of locally or metastatic disease. Most of the patients are diagnosed in metastatic scenario, where multidisciplinary approach based on surgery, chemotherapies, liver-directed and/or molecular targeted therapies are commonly used. Owing to a deeper molecular knowledge of this disease, these targeted therapies are nowadays widely implemented, being the likely discovery of predictive biomarkers that would allow its use in other settings. This review is focused on describing the different classifications, etiology, prognostic biomarkers and multidisciplinary approaches that are typically used in PanNET.

Salivary function impairment in type 2 Diabetes patients associated with concentration and genetic polymorphisms of chromogranin A

OBJECTIVES

The purpose of this study was to evaluate the effect of type 2 diabetes mellitus (T2DM) on salivary function impairments according to glycemic control status and subsequently compare the concentration of chromogranin A (CHGA) with its genetic profile.

MATERIALS AND METHODS

Thirty-six patients with controlled T2DM, 36 with poorly controlled T2DM, and 38 nondiabetic subjects underwent salivary flow rate measurements by means of unstimulated labial (ULS), unstimulated whole (UWS), and stimulated whole saliva (SWS) collections. CHGA concentrations were determined in saliva and plasma with ELISA, and two CHGA polymorphisms (T-415C and Glu264Asp) were analyzed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

T2DM patients presented significantly lower ULS and UWS flow rates regardless of glycemic control status compared to controls (P = 0.002 and P = 0.027, respectively). The SWS flow rate in the poorly controlled T2DM was the lowest among the groups (P = 0.026). Significantly higher plasma and salivary CHGA levels were found in T2DM groups (P = 0.019 and P < 0.001, respectively). CHGA gene variants (T-415C and Glu264Asp) revealed significant differences between diabetics and control subjects when associated with lower salivary flow and higher salivary CHGA production (P < 0.05).

CONCLUSIONS

T2DM causes abnormalities in the function of salivary glands. However, poorly controlled T2DM has the most influence on SWS flow rates. Our findings indicate an association between plasma and salivary CHGA levels and T2DM patients. Furthermore, the results suggest that CGHA polymorphisms might be associated with salivary gland hypofunction and higher salivary CHGA production in T2DM patients. Nevertheless, further epidemiological studies are required to elucidate this clinical implication.

CLINICAL RELEVANCE

Salivary impairments and high levels of CHGA are associated with T2DM patients. In addition, CGHA polymorphisms might be associated with salivary gland hypofunction and higher salivary CHGA production in T2DM patients. This could be a significant insight to establish a role for salivary CHGA as a potential clinical biomarker to T2DM.

Impact of glycemic control on oral health status in type 2 diabetes individuals and its association with salivary and plasma levels of chromogranin A

OBJECTIVE

To evaluate the effect of glycemic control status in type 2 diabetes mellitus (T2DM) individuals on clinical oral health indicators and to compare the concentrations of plasma and salivary chromogranin A (CHGA) among nondiabetic subjects and T2DM patients, exploring their associations.

DESIGN

In this cross-sectional study, 32 patients with controlled T2DM, 31 with poorly controlled T2DM and 37 nondiabetic subjects underwent a clinical and periodontal examination. CHGA concentrations were determined in saliva and plasma with ELISA.

RESULTS

Poorly controlled T2DM group exhibited significantly higher mean buffering capacity, plaque index and bleeding on probing than other groups (P<0.05). No difference was found to DMFT (decayed, missed and filled teeth) index between groups. Sites with clinical attachment loss (CAL) of 4 and 5-6mm were significantly higher in both diabetic groups compared to control group (P<0.05). Poorly controlled T2DM group had significantly higher sites with CAL ≥ 7 mm than other groups (P=0.001). Significantly higher plasma and salivary CHGA levels were found in T2DM groups (P<0.05). In both diabetic groups, probing depths 5-6mm and CAL 5-6mm were associated with higher salivary CHGA concentration (P<0.05).

CONCLUSIONS

The findings revealed that T2DM patients were more prone to periodontal tissue damage than to caries risk. The results also provide some evidence that the degree of attachment loss deteriorates significantly with poor glycemic control in T2DM (CAL ≥ 7 mm). Moreover, the results suggest that high concentrations of salivary CHGA are associated with worse periodontal parameters and T2DM, and this could be related to the pathogenesis of both diseases.

Diagnostic value of circulating chromogranin a for neuroendocrine tumors: a systematic review and meta-analysis

Background

In previous decades, chromogranin A (CgA) has been demonstrated to be the most promising biomarker for the diagnosis of neuroendocrine tumors (NETs), but its diagnostic value is still controversial. This meta-analysis aimed to estimate the potential diagnostic value of circulating CgA for NETs.

Methods

We collected relevant studies from several electronic databases as well as from reference lists. Diagnostic indices of CgA were pooled with random effects models. Pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and summary receiver operating characteristic (SROC) curves for the diagnosis of NETs were used to estimate the overall diagnostic efficiency.

Results

Through a search strategy, 13 studies met the inclusion criteria and were included. These studies contained 1260 patients with NETs and 967 healthy controls in the total sample. As a result, the overall sensitivity, specificity and diagnostic odds ratio (DOR) were 0.73 (95% CI: 0.71 to 0.76), 0.95 (95% CI: 0.93 to 0.96) and 56.29 (95% CI: 25.27 to 125.38), respectively, while the summary positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 14.56 (95% CI: 6.62 to 32.02) and 0.26 (95% CI: 0.18 to 0.38), respectively. In addition, the area under the curve (AUC) of the circulating CgA in the diagnosis of NETs was 0.8962.

Conclusions

These data demonstrate that circulating CgA is an efficient biomarker for the diagnosis of NETs with high sensitivity and specificity, which indicates that it may be helpful for the clinical management of NETs. However, further studies are needed to clarify this issue.

Chromogranin A: a paradoxical player in angiogenesis and vascular biology

Half a century after the discovery of chromogranin A as a secreted product of the catecholamine storage granules in the bovine adrenal medulla, the physiological role for the circulating pool of this protein has been recently coined, namely as an important player in vascular homeostasis. While the circulating chromogranin A since 1984 has proved to be a significant and useful marker of a wide range of pathophysiological and pathological conditions involving the diffuse neuroendocrine system, this protein has now been assigned a physiological "raison d'etre" as a regulator in vascular homeostasis. Moreover, chromogranin A processing in response to tissue damage and blood coagulation provides the first indication of a difference in time frame of the regulation of angiogenesis evoked by the intact chromogranin A and its two major peptide products, vasostatin-1 and catestatin. The impact of these discoveries on vascular homeostasis, angiogenesis, cancer, tissue repair and cardio-regulation will be discussed.

Biochemical prognostic indicators for pancreatic neuroendocrine tumors and small bowel neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) and small bowel neuroendocrine tumors (SBNETs) are rare tumors that are frequently diagnosed late in the course of the disease. Several biomarkers have been proposed in the literature as prognostic factors for patients with these tumors. This article discusses a recent publication in Annals of Surgical Oncology from the University of Iowa analyzing the effect of different biomarkers on survival in patients with PNETs and SBNETs.

Levels of the antimicrobial proteins lactoferrin and chromogranin in the saliva of individuals with oral dryness

STATEMENT OF PROBLEM

Many individuals in an aging society experience oral dryness. Maintaining the flow of saliva and the presence of antimicrobial substances is important to maintain oral health. The inhibition of the secretion of antimicrobial substances could lead to oral dryness.

PURPOSE

The purpose of this study was to evaluate the antimicrobial substances lactoferrin and chromogranin A in the saliva of elderly individuals with oral dryness.

MATERIAL AND METHODS

The study included 25 controls and 28 participants with subjective oral dryness. The levels of lactoferrin and chromogranin A were determined in unstimulated whole saliva with an enzyme-linked immunosorbent assay method. The differences in secretion of lactoferrin and chromogranin A between the controls and the participants with oral dryness were analyzed with the Mann-Whitney U test (α=.05).

RESULTS

The flow rate of lactoferrin and chromogranin A was lower in the group of participants with oral dryness (lactoferrin, 7.43 ±7.08 ng/min; chromogranin A, 0.24 ±0.24 ng/min) than in the control group (lactoferrin, 21.52 ±7.67 ng/min; chromogranin A, 0.97 ±0.69 ng/min) (P<.01). The ratio of both antimicrobial proteins to total protein was also lower in participants with oral dryness than in the controls.

CONCLUSIONS

The results of this study indicated that the levels of lactoferrin and chromogranin A were lower in those with oral dryness. A reduction in the secretion of these antimicrobial substances may be associated with oral dryness.

Full-length human chromogranin-A cardioactivity: myocardial, coronary, and stimulus-induced processing evidence in normotensive and hypertensive male rat hearts

Plasma chromogranin-A (CgA) concentrations correlate with severe cardiovascular diseases, whereas CgA-derived vasostatin-I and catestatin elicit cardiosuppression via an antiadrenergic/nitric oxide-cGMP mediated mechanism. Whether these phenomena are related is unknown. We here investigated whether and to what extent full-length CgA directly influences heart performance and may be subjected to stimulus-elicited intracardiac processing. Using normotensive and hypertensive rats, we evaluated the following: 1) direct myocardial and coronary effects of full-length CgA; 2) the signal-transduction pathway involved in its action mechanism; and 3) CgA intracardiac processing after β-adrenergic [isoproterenol (Iso)]- and endothelin-1(ET-1)-dependent stimulation. The study was performed by using a Langendorff perfusion apparatus, Western blotting, affinity chromatography, and ELISA. We found that CgA (1-4 nM) dilated coronaries and induced negative inotropism and lusitropism, which disappeared at higher concentrations (10-16 nM). In spontaneously hypertensive rats (SHRs), negative inotropism and lusitropism were more potent than in young normotensive rats. We found that perfusion itself, Iso-, and endothelin-1 stimulation induced intracardiac CgA processing in low-molecular-weight fragments in young, Wistar Kyoto, and SHR rats. In young normotensive and adult hypertensive rats, CgA increased endothelial nitric oxide synthase phosphorylation and cGMP levels. Analysis of the perfusate from both Wistar rats and SHRs of untreated and treated (Iso) hearts revealed CgA absence. In conclusion, in normotensive and hypertensive rats, we evidenced the following: 1) full-length CgA directly affects myocardial and coronary function by AkT/nitric oxide synthase/nitric oxide/cGMP/protein kinase G pathway; and 2) the heart generates intracardiac CgA fragments in response to hemodynamic and excitatory challenges. For the first time at the cardiovascular level, our data provide a conceptual link between systemic and intracardiac actions of full-length CgA and its fragments, expanding the knowledge on the sympathochromaffin/CgA axis under normal and physiopathological conditions.

The biochemical utility of chromogranin A, chromogranin B and cocaine- and amphetamine-regulated transcript for neuroendocrine neoplasia

Neuroendocrine neoplasia (NEN) is a heterogeneous group of tumours and often represents a therapeutic challenge to clinicians. The peptides chromogranin A (CgA), chromogranin B (CgB) and cocaine- and amphetamine-regulated transcript (CART) are widely distributed throughout the neuroendocrine system. CgA and CgB have been used as general NEN biomarkers for many years, while CART has only recently been identified. Of these biomarkers, CgA is the most commonly used. However, circulating CgA concentrations exhibit considerable intra-individual biological variation, are altered by proton pump inhibitors (PPIs) and somatostatin analogues and are elevated in non-NEN malignancies. Therefore, interpretation of CgA results must be in the context of these confounding factors. The effects of treatment and non-NEN conditions on circulating CgB and CART concentrations are less well understood. CgB is less affected by impaired renal function and PPIs than CgA; while, circulating CART concentrations lack a diurnal variation in humans and are more reliable markers of pancreatic NEN malignancy than CgA. The utility of circulating CgA measurements in NEN prognosis, surveillance and disease recurrence has been widely investigated. However, the utility of CgB and CART in NEN management is yet to be elucidated. Further studies are needed to establish whether CgB and CART are useful alternatives to CgA.

A new chromogranin A-dependent angiogenic switch activated by thrombin

Angiogenesis, the formation of blood vessels from pre-existing vasculature, is regulated by a complex interplay of anti and proangiogenic factors. We found that physiologic levels of circulating chromogranin A (CgA), a protein secreted by the neuroendocrine system, can inhibit angiogenesis in various in vitro and in vivo experimental models. Structure-activity studies showed that a functional anti-angiogenic site is located in the C-terminal region, whereas a latent anti-angiogenic site, activated by cleavage of Q76-K77 bond, is present in the N-terminal domain. Cleavage of CgA by thrombin abrogated its anti-angiogenic activity and generated fragments (lacking the C-terminal region) endowed of potent proangiogenic activity. Hematologic studies showed that biologically relevant levels of forms of full-length CgA and CgA1-76 (anti-angiogenic) and lower levels of fragments lacking the C-terminal region (proangiogenic) are present in circulation in healthy subjects. Blood coagulation caused, in a thrombin-dependent manner, almost complete conversion of CgA into fragments lacking the C-terminal region. These results suggest that the CgA-related circulating polypeptides form a balance of anti and proangiogenic factors tightly regulated by proteolysis. Thrombin-induced alteration of this balance could provide a novel mechanism for triggering angiogenesis in pathophysiologic conditions characterized by prothrombin activation.

The novel chromogranin A-derived serpinin and pyroglutaminated serpinin peptides are positive cardiac β-adrenergic-like inotropes

Three forms of serpinin peptides, serpinin (Ala26Leu), pyroglutaminated (pGlu)-serpinin (pGlu23Leu), and serpinin-Arg-Arg-Gly (Ala29Gly), are derived from cleavage at pairs of basic residues in the highly conserved C terminus of chromogranin A (CgA). Serpinin induces PN-1 expression in neuroendocrine cells to up-regulate granule biogenesis via a cAMP-protein kinase A-Sp1 pathway, while pGlu-serpinin inhibits cell death. The aim of this study was to test the hypothesis that serpinin peptides are produced in the heart and act as novel β-adrenergic-like cardiac modulators. We detected serpinin peptides in the rat heart by HPLC and ELISA methods. The peptides included predominantly Ala29Gly and pGlu-serpinin and a small amount of serpinin. Using the Langendorff perfused rat heart to evaluate the hemodynamic changes, we found that serpinin and pGlu-serpinin exert dose-dependent positive inotropic and lusitropic effects at 11-165 nM, within the first 5 min after administration. The pGlu-serpinin-induced contractility is more potent than that of serpinin, starting from 1 nM. Using the isolated rat papillary muscle preparation to measure contractility in terms of tension development and muscle length, we further corroborated the pGlu-serpinin-induced positive inotropism. Ala29Gly was unable to affect myocardial performance. Both pGlu-serpinin and serpinin act through a β1-adrenergic receptor/adenylate cyclase/cAMP/PKA pathway, indicating that, contrary to the β-blocking profile of the other CgA-derived cardiosuppressive peptides, vasostatin-1 and catestatin, these two C-terminal peptides act as β-adrenergic-like agonists. In cardiac tissue extracts, pGlu-serpinin increased intracellular cAMP levels and phosphorylation of phospholamban (PLN)Ser16, ERK1/2, and GSK-3β. Serpinin and pGlu-serpinin peptides emerge as novel β-adrenergic inotropic and lusitropic modulators, suggesting that CgA and the other derived cardioactive peptides can play a key role in how the myocardium orchestrates its complex response to sympathochromaffin stimulation.

Chromogranin A and derived peptides in health and disease

Chromogranin A (CgA) is a member of the granins, a family of acidic proteins found in abundance in (neuro)endocrine cells (e.g., in chromaffin cells) and in some tumors. Like other granins, CgA has a granulogenic role in secretory granule biogenesis and is stored in these organelles. CgA is partially processed differentially in various cell types to yield biologically active peptides, such as vasostatin, pancreastatin, catestatin, and serpinins. In this review, we describe the roles of CgA and several of its derived peptides. CgA, which is elevated in the blood of cancer patients, inhibits angiogenesis and exerts protective effects on the endothelial barrier function in tumors, thus affecting response to chemotherapy. Recent studies indicate that the serpinins promote cell survival and myocardial contractility and relaxation. Other peptides such as pancreastatin were found to have significant effects on inhibition of glucose-stimulated insulin secretion and glucose up-take, induction of glycogenolysis in hepatocytes, and inhibition of lipogenesis. In contrast, catestatin has opposite effects to that of pancreastatin in glucose metabolism and lipogenesis. Catestatin appears to also play a significant role in cardiac function, blood pressure regulation, and mutations in the catestatin domain of the CgA gene are associated with hypertension in humans.

Chromogranin A regulates tumor self-seeding and dissemination

Cancer progression involves the seeding of malignant cells in circulation and the colonization of distant organs. However, circulating neoplastic cells can also reinfiltrate the tumor of origin. This process, called "tumor-self seeding," can select more aggressive cells that may contribute to cancer progression. Here, using mouse mammary adenocarcinoma models, we observed that both tumor self-seeding and organ colonization were inhibited by chromogranin A (CgA), a protein present in variable amounts in the blood of cancer patients. Mechanism studies showed that CgA inhibited the shedding of cancer cells in circulation from primary tumors, as well as the reinfiltration of tumors and the colonization of lungs by circulating tumor cells. CgA reduced gap formation induced by tumor cell-derived factors in endothelial cells, decreased vascular leakage in tumors, and inhibited the transendothelial migration of cancer cells. Together, our findings point to a role for circulating CgA in the regulation of tumor cell trafficking from tumor-to-blood and from blood-to-tumor/normal tissues. Inhibition of the multidirectional trafficking of cancer cells in normal and neoplastic tissues may represent a novel strategy to reduce cancer progression.

Chromogranin A restricts drug penetration and limits the ability of NGR-TNF to enhance chemotherapeutic efficacy

NGR-TNF is a derivative of TNF-α that targets tumor blood vessels and enhances penetration of chemotherapeutic drugs. Because of this property, NGR-TNF is being tested in combination with chemotherapy in various phase II and III clinical trials. Here we report that chromogranin A (CgA), a protein present in variable amounts in the blood of normal subjects and cancer patients, inhibits the synergism of NGR-TNF with doxorubicin and melphalan in mouse models of lymphoma and melanoma. Pathophysiologically relevant levels of circulating CgA blocked NGR-TNF-induced drug penetration by enhancing endothelial barrier function and reducing drug extravasation in tumors. Mechanistic investigations done in endothelial cell monolayers in vitro showed that CgA inhibited phosphorylation of p38 MAP kinase, disassembly of VE-cadherin-dependent adherence junctions, paracellular macromolecule transport, and NGR-TNF-induced drug permeability. In this system, the N-terminal fragment of CgA known as vasostatin-1 also inhibited drug penetration and NGR-TNF synergism. Together, our results suggest that increased levels of circulating CgA and its fragments, as it may occur in certain cancer patients with nonneuroendocrine tumors, may reduce drug delivery to tumor cells particularly as induced by NGR-TNF. Measuring CgA and its fragments may assist the selection of patients that can respond better to NGR-TNF/chemotherapy combinations in clinical trials.

Morphological and molecular changes of the myocardium after left ventricular mechanical support

Left ventricular assist devices (LVAD) are currently used to either “bridge” patients with terminal congestive heart failure (CHF) until cardiac transplantation is possible or optionally for patients with contraindications for transplantation (“destination therapy”). Mechanical support is associated with a marked decrease of cardiac dilation and hypertrophy as well as numerous cellular and molecular changes (“reverse cardiac remodeling”), which can be accompanied by improved cardiac function (“bridge to recovery”) in a relatively small subset of patients with heart transplantation no longer necessary even after removal of the device (“weaning”). In the recent past, novel pharmacological strategies have been developed and are combined with mechanical support, which has increased the percentage of patients with improved clinical status and cardiac performance. Gene expression profiles have demonstrated that individuals who recover after LVAD show different gene expression compared to individuals who do not respond to unloading. This methodology holds promise for the future to develop read out frames to identify individuals who can recover after support. Aside from describing the morphological changes associated with “reverse cardiac remodeling”, this review will focus on signal transduction, transcriptional regulation, apoptosis, cell stress proteins, matrix remodeling, inflammatory mediators and aspects of neurohormonal activation in the failing human heart before and after ventricular unloading.

Chromogranin A: a novel factor acting at the cross road between the neuroendocrine and the cardiovascular systems

Chromogranin A (CHGA) is a secretory protein stored in and released from neurons and cells of the diffuse neuroendocrine system. Cells of the adrenal medulla and adrenergic terminals are a main source of CHGA but also myocardial cells produce it under stress conditions. After secretion, CHGA is cleaved into several biologically active fragments, including vasostatins and catestatin. CHGA and its proteolytic peptides exert a broad spectrum of activities on the cardiovascular system. They act on blood pressure by controlling the vascular tone and the cardiac inotropic and chronotropic function. CHGA revealed to be a sensitive marker of myocardial dysfunction, with a high predictive power of morbidity and mortality in heart failure and ischemic heart disease. In addition, CHGA has been involved in the control of sustained endothelial inflammation and has been shown to be a good marker of persistent vascular inflammation in rheumatologic disorders affecting vessels.

Chromogranin A as a crucial factor in the sorting of peptide hormones to secretory granules

Chromogranin A (CgA) is a soluble glycoprotein stored along with hormones and neuropeptides in secretory granules of endocrine cells. In the last four decades, intense efforts have been concentrated to characterize the structure and the biological function of CgA. Besides, CgA has been widely used as a diagnostic marker for tumors of endocrine origin, essential hypertension, various inflammatory diseases, and neurodegenerative disorders such as amyotrophic lateral sclerosis and Alzheimer's disease. CgA displays peculiar structural features, including numerous multibasic cleavage sites for prohormone convertases as well as a high proportion of acidic residues. Thus, it has been proposed that CgA represents a precursor of biologically active peptides, and a "granulogenic protein" that plays an important role as a chaperone for catecholamine storage in adrenal chromaffin cells. The widespread distribution of CgA throughout the neuroendocrine system prompted several groups to investigate the role of CgA in peptide hormone sorting to the regulated secretory pathway. This review summarizes the findings and theoretical concepts around the molecular machinery used by CgA to exert this putative intracellular function. Since CgA terminal regions exhibited strong sequence conservation through evolution, our work focused on the implication of these domains as potential functional determinants of CgA. Characterization of the molecular signals implicating CgA in the intracellular traffic of hormones represents a major biological issue that may contribute to unraveling the mechanisms defining the secretory competence of neuroendocrine cells.

Granins and their derived peptides in normal and tumoral chromaffin tissue: Implications for the diagnosis and prognosis of pheochromocytoma

Pheochromocytomas are rare catecholamine-secreting tumors that arise from chromaffin tissue within the adrenal medulla and extra-adrenal sites. Typical clinical manifestations are sustained or paroxysmal hypertension, severe headaches, palpitations and sweating resulting from hormone excess. However, their presentation is highly variable and can mimic many other diseases. The diagnosis of pheochromocytomas depends mainly upon the demonstration of catecholamine excess by 24-h urinary catecholamines and metanephrines or plasma metanephrines. Occurrence of malignant pheochromocytomas can only be asserted by imaging of metastatic lesions, which are associated with a poor survival rate. The characterization of tissue, circulating or genetic markers is therefore crucial for the management of these tumors. Proteins of the granin family and their derived peptides are present in dense-core secretory vesicles and secreted into the bloodstream, making them useful markers for the identification of neuroendocrine cells and neoplasms. In this context, we will focus here on reviewing the distribution and characterization of granins and their processing products in normal and tumoral chromaffin cells, and their clinical usefulness for the diagnosis and prognosis of pheochromocytomas. It appears that, except SgIII, all members of the granin family i.e. CgA, CgB, SgII, SgIV-SgVII and proSAAS, and most of their derived peptides are present in adrenomedullary chromaffin cells and in pheochromocytes. Moreover, besides the routinely used CgA test assays, other assays have been developed to measure concentrations of tissue and/or circulating granins or their derived peptides in order to detect the occurrence of pheochromocytomas. In most cases, elevated levels of these entities were found, in correlation with tumor occurrence, while rarely discriminating between benign and malignant neoplasms. Nevertheless, measurement of the levels of granins and derived peptides improves the diagnostic sensitivity and may therefore provide a complementary tool for the management of pheochromocytomas. However, the existing data need to be substantiated in larger groups of patients, particularly in the case of malignant disease.