The chromogranin A-derived peptides vasostatin-I and catestatin as regulatory peptides for cardiovascular functions

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.

Catestatin-A Potential New Therapeutic Target for Women with Preeclampsia? An Analysis of Maternal Serum Catestatin Levels in Preeclamptic Pregnancies

BACKGROUND

Catestatin has been identified as an important factor in blood pressure control in non-pregnant adults. A possible impact on the development of hypertensive disorders of pregnancy has been indicated. Data on catestatin levels in pregnancy are scarce. The aim of this study was to investigate a potential association of maternal serum catestatin levels to the pathogenesis of preeclampsia.

METHODS

We evaluated serum catestatin levels of 50 preeclamptic singleton pregnancies and 50 healthy gestational-age-matched pregnancies included in the obstetric biobank registry of the Medical University of Vienna. Receiver operating characteristic curves and logistic regression models were performed to investigate an association between catestatin levels and development of preeclampsia.

RESULTS

Catestatin levels were significantly decreased in women with preeclampsia compared to healthy controls (median CST: 3.03 ng/mL, IQR [1.24-7.21 ng/mL] vs. 4.82 ng/mL, IQR [1.82-10.02 ng/mL]; p = 0.010), indicating an association between decreased catestatin values and the development of preeclampsia. There was no significant difference in catestatin values between early-onset preeclampsia and late-onset preeclampsia. Modelling the occurrence of preeclampsia via logistic regression was improved when adding catestatin as a predictive factor.

CONCLUSIONS

Decreased serum catestatin levels are associated with the presence of preeclampsia. Further investigations into the diagnostic value and possible therapeutic role of catestatin in preeclampsia are warranted.

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.

Reduction in CgA-Derived CST Protein Level in HTR-8/SVneo and BeWo Trophoblastic Cell Lines Caused by the Preeclamptic Environment

One of the most dangerous complications of pregnancy is preeclampsia (PE), a disease associated with a high risk of maternal and fetal mortality and morbidity. Although its etiology remains unknown, the placenta is believed to be at the center of ongoing changes. One of the hormones produced by the placenta is chromogranin A (CgA). Thus far, its role in pregnancy and pregnancy-related disorders is enigmatic, yet it is known that both CgA and its derived peptide catestatin (CST) are involved in the majority of the processes that are disturbed in PE, such as blood pressure regulation or apoptosis. Therefore, in this study, the influence of the preeclamptic environment on the production of CgA using two cell lines, HTR-8/SVneo and BeWo, was investigated. Furthermore, the capacity of trophoblastic cells to secrete CST to the environment was tested, as well as the correlation between CST and apoptosis. This study provided the first evidence that CgA and CST proteins are produced by trophoblastic cell lines and that the PE environment has an impact on CST protein production. Furthermore, a strong negative correlation between CST protein level and apoptosis induction was found. Hence, both CgA and its derived peptide CST may play roles in the complex process of PE pathogenesis.

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.

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.

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.

Serum Vasostatin-1 Level is Increased in Women with Preeclampsia

OBJECTIVE

To evaluate the serum vasostatin-1 levels in preeclamptic and non-preeclamptic pregnant women.

MATERIALS AND METHODS

Thirty consecutive women with mild preeclampsia and sixty consecutive women with severe preeclampsia were compared with ninety gestational age-matched (±1 week) non-preeclamptic pregnant women with an appropriate-for-gestational-age (AGA) fetus.

RESULTS

Mean serum vasostatin-1 was significantly higher in women with preeclampsia than gestational age-matched controls. Mean serum vasostatin-1 was significantly higher in the mild preeclampsia group compared to its gestational age-matched control group, and in the severe preeclampsia group compared to its gestational age-matched control group. There was no significant difference in mean serum vasostatin-1 levels between the mild and severe preeclampsia groups, and in severe early- and severe late-onset preeclampsia groups. Serum vasostatin-1 had positive correlations with systolic and diastolic blood pressure.

CONCLUSION

Serum vasostatin-1 was significantly higher in women with preeclampsia compared to those of the gestational age-matched controls. There was no significant difference in mean serum vasostatin-1 levels between the mild and severe preeclampsia groups and severe early- and severe late-onset preeclampsia groups.

Serum catestatin level is increased in women with preeclampsia

Catestatin can inhibit catecholamine release from chromaffin cells and adrenergic neurons. Catestatin can also have a strong vasodilator effect. This may be useful in understanding the pathophysiology of preeclampsia and its treatment. In this study, we investigated the serum catestatin levels in pregnant women with and without preeclampsia. Fifty consecutive women with mild preeclampsia, 50 consecutive women with severe preeclampsia, and 100 consecutive pregnant women with a gestational age-matched (±1 week) uncomplicated pregnancy were evaluated in a cross-sectional study. Mean serum catestatin was significantly increased in the preeclampsia group compared to the control group (290.7 ± 95.5 pg/mL vs. 182.8 ± 72.0 pg/mL). Mean serum catestatin was comparable in mild and severe preeclampsia groups (282.7 ± 97.9 pg/mL vs. 298.7 ± 93.4 pg/mL, p = .431). Serum catestatin levels had positive correlations with systolic and diastolic blood pressure, urea, uric acid, and creatinine. In conclusion, serum catestatin levels are increased in preeclamptic pregnancies compared to gestational age-matched controls.IMPACT STATEMENTWhat is already known on this subject? The role of autonomic nervous system dysregulation in the pathophysiology of preeclampsia is known. The most obvious part of this dysregulation is the sympathetic nervous system activation. The adrenal medulla is one of the locations of the sympathetic nervous system in the body.What do the results of this study add? Serum catestatin levels were found to be correlated with clinical and laboratory data of preeclampsia. This highlights the importance of chromaffin cell secretions in the adrenal medulla in preeclampsia.What are the implications of these findings for clinical practice and/or further research? This study will help understand the role of the adrenal medulla in the autonomic nervous system dysregulation in preeclampsia. Also, control of serum catestatin levels may support the treatment of hypertension in preeclampsia.

Catestatin prevents endothelial inflammation and promotes thrombus resolution in acute pulmonary embolism in mice

Catestatin (CTS), a catecholamine-release inhibitory peptide, exerts pleiotropic cardiac protective effects. Pulmonary embolism caused by deep vein thrombosis involving vascular dysfunction. The present study aims to investigate the effects of CTS on thrombus formation that may inhibit the development of pulmonary embolism and its potential pathway. Acute pulmonary embolism (APE) model was developed as an in vivo model. The effects of CTS on mice with APE were examined. Human pulmonary artery endothelial cells (HPAECs) were pretreated with CTS before thrombin stimulation, and endothelial inflammation and underlying mechanisms were evaluated in vitro. That plasma CTS level was decreased in APE mice, while the number of platelets was significantly increased. The decreased circulating CTS level negatively associated with the number of platelets. CTS administration increased the survival rate of APE mice and protected against microvascular thrombosis in lung. APE-induced the increase in platelets number and plasma von Willebrand factor (VWF) were inhibited by CTS. Platelets from CTS-treated APE mice showed impaired agonist-induced platelets aggregation and spreading. CTS also ameliorated APE-induced the systemic inflammatory response. In in vivo study, thrombin-induced the increase in inflammation, TLR-4 expression and p38 phosphorylation were abrogated by CTS in HPAECs. Furthermore, TLR-4 overexpression inhibited the effect of CTS on VWF release and inflammation in HPAECs. Collectively, CTS increases thrombus resolution by attenuating endothelial inflammation at partially via inhibiting TLR-4-p38 pathway. The present study may provide a novel approach for anti-thrombosis.

The chromogranin A-derived peptides catestatin and vasostatin in dogs with myxomatous mitral valve disease

Background

The protein chromogranin A (CgA) is stored and co-released with catecholamines from the stimulated adrenal glands. Increased plasma concentrations of CgA have been shown in people with heart disease. The aim of the study was to investigate whether plasma concentrations of the CgA-derived biologically active peptides catestatin and vasostatin were associated with the severity of myxomatous mitral valve disease (MMVD) in dogs and to assess potential associations between these blood variables and dog characteristics, echocardiographic variables, heart rate (HR), blood pressure (BP) and plasma N-terminal-proBNP (NT-proBNP) concentration. Sixty-seven privately owned dogs with or without MMVD were included. The dogs underwent physical examination, blood pressure measurement, blood sample collection, and echocardiographic examination. Plasma concentrations of catestatin and vasostatin were analyzed using radioimmunoassay.

Results

Catestatin concentration decreased with increasing left atrial and ventricular size (R² ≤ 0.09, P ≤ 0.019), and increased with increasing systolic and diastolic blood pressures (R² ≤ 0.08, P ≤ 0.038). Regression analyses showed no significant associations for vasostatin. No differences in plasma concentrations of catestatin or vasostatin were found between the disease severity groups used in the study.

Conclusions

In the present dog population, the catestatin concentration showed weak negative associations with left atrial and ventricular sizes, both of which are known to increase with increasing severity of MMVD. Furthermore, the catestatin concentration showed weak positive associations with blood pressure.

Chromogranin A in the early steps of the neurosecretory pathway

Chromogranin A (CgA) is a soluble glycoprotein stored with hormones and neuropeptides in secretory granules (SG) of most (neuro)endocrine cells and neurons. Since its discovery in 1967, many studies have reported its structural characteristics, biological roles, and mechanisms of action. Indeed, CgA is both a precursor of various biologically active peptides and a granulogenic protein regulating the storage and secretion of hormones and neuropeptides. This review emphasizes the findings and theoretical concepts around the CgA-linked molecular machinery controlling hormone/neuropeptide aggregation and the interaction of CgA-hormone/neuropeptide aggregates with the trans-Golgi membrane to allow hormone/neuropeptide targeting and SG biogenesis. We will also discuss the intriguing alteration of CgA expression and secretion in various neurological disorders, which could provide insights to elucidate the molecular mechanisms underlying these pathophysiological conditions.

Adrenal gland-released vasostatin-I is a myocardial depressant factor

Pheochromocytoma crisis is an exceptional consequence of the release of storage vesicles of the adrenal medulla. It is complicated by fulminant adrenergic myocarditis. It offers a unique opportunity to detect inotropic negative factors from neuroendocrine origin. Our objectives were (a) to describe a pheochromocytoma crisis, (b) to investigate in vivo myocardial depressant activities for the N-terminal 1-76 Chromogranin A-derived peptide, vasostatin-I (VS-I). A patient with a pheochromocytoma crisis was treated, including extracorporeal membrane oxygenation, until mass resection. Plasma concentrations of VS-I were time-dependently assessed with a specific immunoassay; correlations with invasive cardiovascular parameters were investigated. Increased VS-I concentrations were observed over 7 days until tumour resection. VS-I concentrations correlated positively with Chromogranin A levels, negatively with cardiac output and left ventricular stroke work index, but not with heart rate. This case illustrates the pharmacokinetics of VS-I in a pheochromocytoma crisis. It highlights myocardial depressant activity for this peptide at high concentrations.

Decreased circulating catestatin levels are associated with coronary artery disease: The emerging anti-inflammatory role

BACKGROUND AND AIMS

The neuropeptide catestatin (CST) is an endogenous nicotinic cholinergic antagonist that acts as pleiotropic cardiac protective hormone. This study investigated the association between CST and coronary artery disease (CAD) and the underlying mechanisms.

METHODS AND RESULTS

The serum concentration of CST among 224 CAD patients and 204 healthy controls was compared, and its association with atherosclerosis severity in 921 CAD patients was further analyzed. Compared to healthy subjects, serum CST concentration was lower in patients with CAD [1.14 (1.05-1.24) ng/mL vs. 2.15 (1.92-2.39) ng/mL, p < 0.001] and was inversely correlated with disease severity (r = -0.208, p < 0.001). In cultured endothelial cells, CST suppressed TNF-α-elicited expression of inflammatory cytokines and adhesion molecules by activating angiotensin-converting enzyme-2 (ACE2). Administration of CST reduced leukocyte-endothelium interactions in vitro and in vivo, and attenuated the development of atherosclerotic in ApoE^-/- mice fed a high-fat diet. These protective effects by CST were blocked by an ACE2 inhibitor.

CONCLUSIONS

Serum CST concentration is lower in CAD patients and is inversely associated with the severity of atherosclerosis. CST acts as a novel anti-atherogenic peptide that inhibits inflammatory response and EC-leukocyte interactions via an ACE2-dependent mechanism.

Inhibitory effects of vasostatin-1 against atherogenesis

Vasostatin-1, a chromogranin A (CgA)-derived peptide (76 amino acids), is known to suppress vasoconstriction and angiogenesis. A recent study has shown that vasostatin-1 suppresses the adhesion of human U937 monocytes to human endothelial cells (HECs) via adhesion molecule down-regulation. The present study evaluated the expression of vasostatin-1 in human atherosclerotic lesions and its effects on inflammatory responses in HECs and human THP-1 monocyte-derived macrophages, macrophage foam cell formation, migration and proliferation of human aortic smooth muscle cells (HASMCs) and extracellular matrix (ECM) production by HASMCs, and atherogenesis in apolipoprotein E-deficient (ApoE^-/-) mice. Vasostatin-1 was expressed around Monckeberg's medial calcific sclerosis in human radial arteries. Vasostatin-1 suppressed lipopolysaccharide (LPS)-induced up-regulation of monocyte chemotactic protein-1 (MCP-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin in HECs. Vasostatin-1 suppressed inflammatory M1 phenotype and LPS-induced interleukin-6 (IL-6) secretion via nuclear factor-κB (NF-κB) down-regulation in macrophages. Vasostatin-1 suppressed oxidized low-density lipoprotein (oxLDL)-induced foam cell formation associated with acyl-CoA:cholesterol acyltransferase-1 (ACAT-1) and CD36 down-regulation and ATP-binding cassette transporter A1 (ABCA1) up-regulation in macrophages. In HASMCs, vasostatin-1 suppressed angiotensin II (AngII)-induced migration and collagen-3 and fibronectin expression via decreasing ERK1/2 and p38 phosphorylation, but increased elastin expression and matrix metalloproteinase (MMP)-2 and MMP-9 activities via increasing Akt and JNK phosphorylation. Vasostatin-1 did not affect the proliferation and apoptosis in HASMCs. Four-week infusion of vasostatin-1 suppressed the development of aortic atherosclerotic lesions with reductions in intra-plaque inflammation, macrophage infiltration, and SMC content, and plasma glucose level in ApoE^-/- mice. These results indicate the inhibitory effects of vasostatin-1 against atherogenesis. The present study provided the first evidence that vasostatin-1 may serve as a novel therapeutic target for atherosclerosis.

What's New in Endocrinology: The Chromaffin Cell

Recent advances in understanding the intracellular and intercellular features of adrenal chromatin cells as stress transducers are reviewed here, along with their implications for endocrine function in other tissues and organs participating in endocrine regulation in the mammalian organism.

Role of the neuroendocrine antimicrobial peptide catestatin in innate immunity and pain

Catestatin (CST) is a neuroendocrine peptide which is derived from the chromogranin A. It has been demonstrated that CST can affect a wide range of processes, such as innate immunity, inflammatory and autoimmune reactions, and several homeostatic regulations. Furthermore, CST is positive against several kinds of bacterial strains at micromolecular range, which shows its antimicrobial activity. Recently, the role of CST in acute and chronic pain has attracted much attention. In this review, we discussed the latest research findings of CST and its role in innate immunity and pain.

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 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.

Association of decreased serum vasostatin-2 level with ischemic chronic heart failure and with MACE in 3-year follow-up: Vasostatin-2 prevents heart failure in myocardial infarction rats

BACKGROUND

We investigated whether serum vasostatin-2 level is related to chronic heart failure (CHF) in patients with previous myocardial infarction (MI) and MACE in 3-year follow-up. The biological effect of vasostatin-2 on ischemic HF was evaluated in animal experiments.

METHODS

After exclusion of the subjects not eligible, this study included 450 patients with CHF and previous MI, and 149 healthy controls. Serum vasostatin-2 level was analyzed. CHF patients were followed up for three years and major adverse cardiac events (MACE) were recorded, defined as reinfarction, target-vessel revascularization, cardiovascular death and refractory HF requiring hospitalizations.

RESULTS

Notably, serum vasostatin-2 level was decreased in CHF patients than in controls, and significant difference was observed between CHF patients with MACE and those without (both P<0.05). Vasostatin-2 level was correlated with HF stages (Spearman's r=-0.288, P<0.05), LVEF (r=0.377, P<0.05) and pro-BNP level (r=-0.294, P<0.05). Multivariable logistic regression analysis suggested that vasostatin-2, conventional risk factors, severity of HF stages and LVEF were independently associated with MACE in CHF patients. Vasostatin-2 (100μg) or PBS was injected intraperitoneally every other day in MI rats, follow by echocardiography, hemodynamic analysis after 2months. Compared with PBS, vasostatin-2 treatment prevented ischemic HF in MI rats, accompanied with reduction of infarct size, remodeling, fibrosis and inflammation, mainly through inhibition of Rho, Wnt and TLR-4 pathways and modulation of renin-angiotensin system.

CONCLUSION

Decreased serum vasostatin-2 level is associated with ischemic CHF and with MACE in three-year follow-up. Intraperitoneal injection of vasostatin-2 protects against ischemic HF in MI rats.

Secretoneurin is a novel prognostic cardiovascular biomarker associated with cardiomyocyte calcium handling

BACKGROUND

Secretoneurin (SN) levels are increased in patients with heart failure (HF), but whether SN provides prognostic information and influences cardiomyocyte function is unknown.

OBJECTIVES

This study sought to evaluate the merit of SN as a cardiovascular biomarker and assess effects of SN on cardiomyocyte Ca(2+) handling.

METHODS

We assessed the association between circulating SN levels and mortality in 2 patient cohorts and the functional properties of SN in experimental models.

RESULTS

In 143 patients hospitalized for acute HF, SN levels were closely associated with mortality (n = 66) during follow-up (median 776 days; hazard ratio [lnSN]: 4.63; 95% confidence interval: 1.93 to 11.11; p = 0.001 in multivariate analysis). SN reclassified patients to their correct risk strata on top of other predictors of mortality. In 155 patients with ventricular arrhythmia-induced cardiac arrest, SN levels were also associated with short-term mortality (n = 51; hazard ratio [lnSN]: 3.33; 95% confidence interval: 1.83 to 6.05; p < 0.001 in multivariate analysis). Perfusing hearts with SN yielded markedly increased myocardial levels and SN internalized into cardiomyocytes by endocytosis. Intracellularly, SN reduced Ca(2+)/calmodulin (CaM)-dependent protein kinase II δ (CaMKIIδ) activity via direct SN-CaM and SN-CaMKII binding and attenuated CaMKIIδ-dependent phosphorylation of the ryanodine receptor. SN also reduced sarcoplasmic reticulum Ca(2+) leak, augmented sarcoplasmic reticulum Ca(2+) content, increased the magnitude and kinetics of cardiomyocyte Ca(2+) transients and contractions, and attenuated Ca(2+) sparks and waves in HF cardiomyocytes.

CONCLUSIONS

SN provided incremental prognostic information to established risk indices in acute HF and ventricular arrhythmia-induced cardiac arrest.

Catestatin exerts direct protective effects on rat cardiomyocytes undergoing ischemia/reperfusion by stimulating PI3K-Akt-GSK3β pathway and preserving mitochondrial membrane potential

Catestatin (Cst) is a 21-amino acid peptide deriving from Chromogranin A. Cst exerts an overall protective effect against an excessive sympathetic stimulation of cardiovascular system, being able to antagonize catecholamine secretion and to reduce their positive inotropic effect, by stimulating the release of nitric oxide (NO) from endothelial cells. Moreover, Cst reduces ischemia/reperfusion (I/R) injury, improving post-ischemic cardiac function and cardiomyocyte survival. To define the cardioprotective signaling pathways activated by Cst (5 nM) we used isolated adult rat cardiomyocytes undergoing simulated I/R. We evaluated cell viability rate with propidium iodide labeling and mitochondrial membrane potential (MMP) with the fluorescent probe JC-1. The involvement of Akt, GSK3β, eNOS and phospholamban (PLN) cascade was studied by immunofluorescence. The role of PI3K-Akt/NO/cGMP pathway was also investigated by using the pharmacological blockers wortmannin (Wm), L-NMMA and ODQ. Our experiments revealed that Cst increased cell viability rate by 65% and reduced cell contracture in I/R cardiomyocytes. Wm, L-NMMA and ODQ limited the protective effect of Cst. The protective outcome of Cst was related to its ability to maintain MMP and to increase AktSer473, GSK3βSer9, PLNThr17 and eNOSSer1179 phosphorylation, while treatment with Wm abolished these effects. Thus, the present results show that Cst is able to exert a direct action on cardiomyocytes and give new insights into the molecular mechanisms involved in its protective effect, highlighting the PI3K/NO/cGMP pathway as the trigger and the MMP preservation as the end point of its action.

Decreased plasma Chromogranin A361-372 (Catestatin) but not Chromogranin A17-38 (Vasostatin) in female dogs with bacterial uterine infection (pyometra)

Background

Pyometra often induces systemic inflammatory response syndrome (SIRS) and early diagnosis is crucial for survival. Chromogranin A (CgA) is a neuroendocrine secretory protein that is co-released with catecholamines from the adrenal medulla and sympathetic nerve endings. A prognostic value of CgA has been found in humans that are critically ill or that have SIRS associated with infection. CgA has not yet been studied in dogs with bacterial infection. The aim of the study was to investigate CgA, measured by Chromogranin A361-372 (Catestatin; Cst) and Chromogranin A17-38 (Vasostatin; VS) in healthy dogs and in dogs with pyometra.

Results

Fifty dogs with pyometra, sampled prior to surgery and 64 healthy female dogs were included. In 19 pyometra cases, blood samples were also collected postoperatively. Concentrations of Cst and VS were measured in heparinised plasma and Cst also measured in EDTA plasma, by in-house radioimmunoassays. Student’s t-test and Wilcoxon two-sample test was used to test for differences between dog groups. Pre- and postoperative samples in dogs with pyometra were analysed by paired t-test. Pearson correlation was used to investigate associations of laboratory variables and hospitalization. P < 0.05 was considered significant.

Concentrations of Cst were decreased in pyometra dogs (mean ± SE, 1.01 ± 0.05 nmol/L) compared to healthy dogs (mean ± SE, 1.70 ± 0.03 nmol/L) (p ≤ 0.0001). VS concentrations did not differ significantly between dogs with pyometra (0.40 ± 0.04 nmol/L) and healthy dogs (0.42 ± 0.03 nmol/L). Mean ± SE pre- and postoperative concentration of Cst (1.0 ± 0.04 nmol/L and 0.9 ± 0.2 nmol/L) and VS (0.36 ± 0.04 nmol/L and 0.36 ± 0.04 nmol/L) in dogs with pyometra did not differ significantly. Neither Cst nor VS concentrations were associated with duration of hospitalization and were not significantly different in the four dogs with pyometra that had prolonged (≥3 d) postoperative hospitalization.

Conclusion

Concentrations of Cst, but not VS, were decreased in pyometra. Cst and VS concentrations before and after ovariohysterectomy did not differ significantly and were not associated with duration of hospitalization. Further studies are warranted to evaluate a possible diagnostic or prognostic value for Cst and VS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0328-6) contains supplementary material, which is available to authorized users.

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.

The use of low-level electromagnetic fields to suppress atrial fibrillation

BACKGROUND

Extremely low-level electromagnetic fields have been proposed to cause significant changes in neural networks.

OBJECTIVE

We sought to investigate whether low-level electromagnetic fields can suppress atrial fibrillation (AF).

METHODS

In 17 pentobarbital anesthetized dogs, bilateral thoracotomies allowed the placement of multielectrode catheters in both atria and at all pulmonary veins. AF was induced by rapid atrial pacing (RAP) or programmed atrial extrastimulation. At baseline and end of each hour of RAP, during sinus rhythm, atrial programmed stimulation gave both the effective refractory period (ERP) and the width of the window of vulnerability. The latter was a measure of AF inducibility. Microelectrodes inserted into the anterior right ganglionated plexi recorded neural firing. Helmholtz coils were powered by a function generator inducing an electromagnetic field (EMF; 0.034 μG, 0.952 Hz). The study sample was divided into 2 groups: group 1 (n = 7)-application of EMF to both cervical vagal trunks; group 2 (n = 10)-application of EMF across the chest so that the heart was located in the center of the coil.

RESULTS

In group 1, EMF induced a progressive increase in AF threshold at all pulmonary vein and atrial sites (all P < .05). In group 2, the atrial ERP progressively shortened and ERP dispersion and window of vulnerability progressively increased (P < .05 compared to baseline values) during 3 hours of RAP and then returned to baseline values during 3 hours of combined application of RAP and EMF (P < .05 compared to the end of the third hour of RAP). The frequency and amplitude of the neural activity recorded from the anterior right ganglionated plexi were markedly suppressed by EMF in both groups.

CONCLUSION

Pulsed EMF applied to the vagal trunks or noninvasively across the chest can significantly reverse AF inducibility.

The important role of catestatin in cardiac remodeling

Catestatin (CST) was first discovered as a potent non-competitive and reversible inhibitor of catecholamine secretion. Recent reports on plasma CST level in heart diseases suggested a cardioprotective role for this peptide. Given that cardiac remodeling is the dominant pathologic process in cardiac dysfunction, we propose that CST participates in the regulation of concern pathways and contributes to the inhibition of cardiac remodeling. In this minireview, the potential mechanism of cardiac remodeling involving CST will be discussed from three aspects: hypertrophy, fibrosis, and apoptosis.

Obligatory role for endothelial heparan sulphate proteoglycans and caveolae internalization in catestatin-dependent eNOS activation

The chromogranin-A peptide catestatin modulates a wide range of processes, such as cardiovascular functions, innate immunity, inflammation, and metabolism. We recently found that the cardiac antiadrenergic action of catestatin requires a PI3K-dependent NO release from endothelial cells, although the receptor involved is yet to be identified. In the present work, based on the cationic properties of catestatin, we tested the hypothesis of its interaction with membrane heparan sulphate proteoglycans, resulting in the activation of a caveolae-dependent endocytosis. Experiments were performed on bovine aortic endothelial cells. Endocytotic vesicles trafficking was quantified by confocal microscopy using a water-soluble membrane dye; catestatin colocalization with heparan sulphate proteoglycans and caveolin 1 internalization were studied by fluorimetric measurements in live cells. Modulation of the catestatin-dependent eNOS activation was assessed by immunofluorescence and immunoblot analysis. Our results demonstrate that catestatin (5 nM) colocalizes with heparan sulphate proteoglycans and induces a remarkable increase in the caveolae-dependent endocytosis and caveolin 1 internalization, which were significantly reduced by both heparinase and wortmannin. Moreover, catestatin was unable to induce Ser¹¹⁷⁹ eNOS phosphorylation after pretreatments with heparinase and methyl-β-cyclodextrin. Taken together, these results highlight the obligatory role for proteoglycans and caveolae internalization in the catestatin-dependent eNOS activation in endothelial cells.

The relationship of plasma catestatin concentrations with metabolic and vascular parameters in untreated hypertensive patients: Influence on high-density lipoprotein cholesterol

OBJECTIVE

Catestatin has several cardiovascular actions, in addition to diminished sympatho-adrenal flow. Decreased plasma catestatin levels may reflect a predisposition for the development of hypertension and metabolic disorders. We planned to investigate the possible roles of catestatin in untreated hypertensive patients. As a secondary objective, we compared catestatin concentrations of healthy subjects with those of hypertensive patients in order to understand whether catestatin is increased reactively or diminished at onset.

METHODS

Our study was cross-sectional and observational. The patient group, comprising 109 consecutive untreated hypertensive patients without additional systemic or coronary heart disease, underwent evaluations of plasma catestatin, waist circumference, lipid parameters, left ventricular mass, carotid intima-media thickness, and flow-mediated dilation of the brachial artery. Additionally, we measured catestatin concentrations of 38 apparently healthy subjects without any disease using a commercial enzyme-linked immunosorbent assay kit.

RESULTS

We documented increased catestatin concentrations in previously untreated hypertensive patients compared to healthy controls (2.27±0.83 vs. 1.92±0.49 ng/mL, p=0.004). However, this association became insignificant after adjustments for age, gender, height, and weight. Within the patient group, catestatin levels were significantly higher in females. Among all study parameters, age, high-density lipoprotein cholesterol (HDL-C) correlated positively to plasma catestatin, whereas triglycerides, hemoglobin, and left ventricular mass correlated negatively to plasma catestatin. We could not detect an association between vascular parameters and catestatin. Catestatin levels were significantly elevated with increasing HDL-C (1.91±0.37, 2.26±0.79, and 3.1±1.23 ng/mL in patients with HDL-C <40, 40-60, and >60 mg/dL, respectively). Multiple linear regression analysis revealed age (beta: 0.201, p=0.041) and HDL-C (beta: 0.390, p<0.001) as independent correlates of plasma catestatin concentration. Additionally, male gender (beta:-0.330, p=0.001) and plasma catestatin (beta: 0.299, p=0.002) were significantly associated with HDL-C concentrations.

CONCLUSION

We documented that plasma catestatin is an independent predictor of high-density lipoprotein cholesterol. In addition to antihypertensive effects, catestatin appears to be related to improved lipid and metabolic profiles. Coexistence of low catestatin levels with low HDL-C may provide a probable mechanism for the predictive value of low HDL-C for increased hypertension and cardiovascular events.

Naturally occurring variants of the dysglycemic peptide pancreastatin: differential potencies for multiple cellular functions and structure-function correlation

Pancreastatin (PST), a chromogranin A-derived peptide, is a potent physiological inhibitor of glucose-induced insulin secretion. PST also triggers glycogenolysis in liver and reduces glucose uptake in adipocytes and hepatocytes. Here, we probed for genetic variations in PST sequence and identified two variants within its functionally important carboxyl terminus domain: E287K and G297S. To understand functional implications of these amino acid substitutions, we tested the effects of wild-type (PST-WT), PST-287K, and PST-297S peptides on various cellular processes/events. The rank order of efficacy to inhibit insulin-stimulated glucose uptake was: PST-297S > PST-287K > PST-WT. The PST peptides also displayed the same order of efficacy for enhancing intracellular nitric oxide and Ca(2+) levels in various cell types. In addition, PST peptides activated gluconeogenic genes in the following order: PST-297S ≈ PST-287K > PST-WT. Consistent with these in vitro results, the common PST variant allele Ser-297 was associated with significantly higher (by ∼17 mg/dl, as compared with the wild-type Gly-297 allele) plasma glucose level in our study population (n = 410). Molecular modeling and molecular dynamics simulations predicted the following rank order of α-helical content: PST-297S > PST-287K > PST-WT. Corroboratively, circular dichroism analysis of PST peptides revealed significant differences in global structures (e.g. the order of propensity to form α-helix was: PST-297S ≈ PST-287K > PST-WT). This study provides a molecular basis for enhanced potencies/efficacies of human PST variants (likely to occur in ∼300 million people worldwide) and has quantitative implications for inter-individual variations in glucose/insulin homeostasis.

Chromogranin A and its fragments as regulators of small intestinal neuroendocrine neoplasm proliferation

INTRODUCTION

Chromogranin A is a neuroendocrine secretory product and its loss is a feature of malignant NEN de-differentiation. We hypothesized that chromogranin A fragments were differentially expressed during NEN metastasis and played a role in the regulation of NEN proliferation.

METHODS

Chromogranin A mRNA (PCR) and protein (ELISA/western blot) were studied in 10 normal human mucosa, 5 enterochromaffin cell preparations, 26 small intestinal NEN primaries and 9 liver metastases. Cell viability (WST-1 assay), proliferation (bromodeoxyuridine ELISA) and expression of AKT/AKT-P (CASE ELISA/western blot) in response to chromogranin A silencing, inhibition of prohormone convertase and mTOR inhibition (RAD001/AKT antisense) as well as different chromogranin A fragments were examined in 4 SI-NEN cell lines.

RESULTS

Chromogranin A mRNA and protein levels were increased (37-340 fold, p<0.0001) in small intestinal NENs compared to normal enterochromaffin cells. Western blot identified chromogranin A-associated processing bands including vasostatin in small intestinal NENs as well as up-regulated expression of prohormone convertase in metastases. Proliferation in small intestinal NEN cell lines was decreased by silencing chromogranin A as well as by inhibition of prohormone convertase (p<0.05). This inhibition also decreased secretion of chromogranin A (p<0.05) and 5-HT (p<0.05) as well as expression of vasostatin. Metastatic small intestinal NEN cell lines were stimulated (50-80%, p<0.05) and AKT phosphorylated (Ser473: p<0.05) by vasostatin I, which was completely reversed by RAD001 (p<0.01) and AKT antisense (p<0.05) while chromostatin inhibited proliferation (~50%, p<0.05).

CONCLUSION

Chromogranin A was differentially regulated in primary and metastatic small intestinal NENs and cell lines. Chromogranin A fragments regulated metastatic small intestinal NEN proliferation via the AKT pathway indicating that CgA plays a far more complex role in the biology of these tumors than previously considered.

Mass spectrometry identification of granins and other proteins secreted by neuroblastoma cells

We used mass spectrometry-based protein identification to determine the presence of granins and other proteins in the mouse neuroblastoma secretome. We detected polypeptides derived from four members of the granin family: chromogranin A, chromogranin B, secretogranin III, and VGF. Many of them are derived from previously described biologically active regions; however, for VGF and CgB, we detected peptides not related to known bioactivities. Along with granins, we identified 115 other proteins secreted by mouse neuroblastoma cells, belonging to different functional categories. Fifty-six out of 119 detected proteins possess the signal fragments required for translocation into endoplasmic reticulum. Sequences of remaining 63 proteins were analyzed using SecretomeP algorithm to determine probability of nonclassical secretion. Identified proteins are involved in the regulation of cell cycle, proliferation, apoptosis, angiogenesis, proteolysis, and cell adhesion.

Multi-marker network in ST-elevation myocardial infarction patients undergoing primary percutaneous coronary intervention: when and what to measure

BACKGROUND

Data on the correlations between biomarkers to suggest cost-effective multi-marker (MM) panels predictive for ST-elevation myocardial infarction (STEMI) patients are lacking. We sought to explore the relationship between cardiac troponin I (cTnI), C-reactive protein (CRP), B-type natriuretic peptide (BNP), and chromogranin A (CgA) accounting for biomarkers' profiles detected within 48h from successful primary percutaneous coronary intervention (PPCI).

METHODS

In 73 STEMI patients cTnI, CRP, BNP, and CgA were measured before PPCI and 6, 24, and 48h later. STATIS methods generalizing Principal Component Analysis on three-way data sets were employed to extract information about: 1) similarities between patients, 2) contribution of each time of sampling and 3) correlations between biomarkers' profiles.

RESULTS

STEMI patients who underwent successful PPCI emerged to have a homogeneous profile tailored on biomarkers' evaluation within 48h. Their measurements at 24h contributed the most variability and information both to patients' and to biomarkers' profiles. BNP and cTnI were highly correlated and explained the 40.1% of the total variance, whereas CgA resulted independent and explained the 26.3% of the total variance.

CONCLUSIONS

Markers' measurements at 24h after PPCI contributed most information to the definition of patients' profile. BNP and cTnI resulted interchangeable in a MM panel for reporting about the extent of necrosis.

Catestatin reduces myocardial ischaemia/reperfusion injury: involvement of PI3K/Akt, PKCs, mitochondrial KATP channels and ROS signalling

Catestatin (CST) limits myocardial ischaemia/reperfusion (I/R) injury with unknown mechanisms. Clearly phosphoinositide-3-kinase (PI3K), protein kinase C (PKC) isoforms, including intra-mitochondrial PKCε, mitochondrial KATP (mitoKATP) channels and subsequent reactive oxygen species (ROS)-signalling play important roles in postconditioning cardioprotection, preventing mitochondrial permeability transition pore (mPTP) opening. Therefore, we studied the role of these extra- and intra-mitochondrial factors in CST-induced protection. Isolated rat hearts and H9c2 cells underwent I/R and oxidative stress, respectively. In isolated hearts CST (75nM, CST-Post) given in early-reperfusion significantly reduced infarct size, limited post-ischaemic contracture, and improved recovery of developed left ventricular pressure. PI3K inhibitor, LY-294002 (LY), large spectrum PKC inhibitor, Chelerythrine (CHE), specific PKCε inhibitor (εV1-2), mitoKATP channel blocker, 5-Hydroxydecanoate (5HD) or ROS scavenger, 2-mercaptopropionylglycine (MPG) abolished the infarct-sparing effect of CST. Notably the CST-induced contracture limitation was maintained during co-infusion of 5HD, MPG or εV1-2, but it was lost during co-infusion of LY or CHE. In H9c2 cells challenged with H2O2, mitochondrial depolarization (an index of mPTP opening studied with JC1-probe) was drastically limited by CST (75nM). Our results suggest that the protective signalling pathway activated by CST includes mitoKATP channels, ROS signalling and prevention of mPTP opening, with a central role for upstream PI3K/Akt and PKCs. In fact, all inhibitors completely abolished CST-infarct-sparing effect. Since CST-anti-contracture effect cannot be explained by intra-mitochondrial mechanisms (PKCε activation and mitoKATP channel opening) or ROS signalling, it is proposed that these downstream signals are part of a reverberant loop which re-activates upstream PKCs, which therefore play a pivotal role in CST-induced protection.

Secretogranin II; a protein increased in the myocardium and circulation in heart failure with cardioprotective properties

BACKGROUND

Several beneficial effects have been demonstrated for secretogranin II (SgII) in non-cardiac tissue. As cardiac production of chromogranin A and B, two related proteins, is increased in heart failure (HF), we hypothesized that SgII could play a role in cardiovascular pathophysiology.

METHODOLOGY/PRINCIPAL FINDINGS

SgII production was characterized in a post-myocardial infarction heart failure (HF) mouse model, functional properties explored in experimental models, and circulating levels measured in mice and patients with stable HF of moderate severity. SgII mRNA levels were 10.5 fold upregulated in the left ventricle (LV) of animals with myocardial infarction and HF (p<0.001 vs. sham-operated animals). SgII protein levels were also increased in the LV, but not in other organs investigated. SgII was produced in several cell types in the myocardium and cardiomyocyte synthesis of SgII was potently induced by transforming growth factor-β and norepinephrine stimulation in vitro. Processing of SgII to shorter peptides was enhanced in the failing myocardium due to increased levels of the proteases PC1/3 and PC2 and circulating SgII levels were increased in mice with HF. Examining a pathophysiological role of SgII in the initial phase of post-infarction HF, the SgII fragment secretoneurin reduced myocardial ischemia-reperfusion injury and cardiomyocyte apoptosis by 30% and rapidly increased cardiomyocyte Erk1/2 and Stat3 phosphorylation. SgII levels were also higher in patients with stable, chronic HF compared to age- and gender-matched control subjects: median 0.16 (Q1-3 0.14-0.18) vs. 0.12 (0.10-0.14) nmol/L, p<0.001.

CONCLUSIONS

We demonstrate increased myocardial SgII production and processing in the LV in animals with myocardial infarction and HF, which could be beneficial as the SgII fragment secretoneurin protects from ischemia-reperfusion injury and cardiomyocyte apoptosis. Circulating SgII levels are also increased in patients with chronic, stable HF and may represent a new cardiac biomarker.

Catestatin (chromogranin A(352-372)) and novel effects on mobilization of fat from adipose tissue through regulation of adrenergic and leptin signaling

Chromogranin A knock-out (Chga-KO) mice display increased adiposity despite high levels of circulating catecholamines and leptin. Consistent with diet-induced obese mice, desensitization of leptin receptors caused by hyperleptinemia is believed to contribute to the obese phenotype of these KO mice. In contrast, obesity in ob/ob mice is caused by leptin deficiency. To characterize the metabolic phenotype, Chga-KO mice were treated with the CHGA-derived peptide catestatin (CST) that is deficient in these mice. CST treatment reduced fat depot size and increased lipolysis and fatty acid oxidation. In liver, CST enhanced oxidation of fatty acids as well as their assimilation into lipids, effects that are attributable to the up-regulation of genes promoting fatty acid oxidation (Cpt1α, Pparα, Acox, and Ucp2) and incorporation into lipids (Gpat and CD36). CST did not affect basal or isoproterenol-stimulated cAMP production in adipocytes but inhibited phospholipase C activation by the α-adrenergic receptor (AR) agonist phenylephrine, suggesting inhibition of α-AR signaling by CST. Indeed, CST mimicked the lipolytic effect of the α-AR blocker phentolamine on adipocytes. Moreover, CST reversed the hyperleptinemia of Chga-KO mice and improved leptin signaling as determined by phosphorylation of AMPK and Stat3. CST also improved peripheral leptin sensitivity in diet-induced obese mice. In ob/ob mice, CST enhanced leptin-induced signaling in adipose tissue. In conclusion, our results implicate CST in a novel pathway that promotes lipolysis and fatty acid oxidation by blocking α-AR signaling as well as by enhancing leptin receptor signaling.

Antiarrhythmic effects of vasostatin-1 in a canine model of atrial fibrillation

BACKGROUND

We examined the antiarrhythmic effects of vasostatin-1, a recently identified cardioregulatory peptide, in canine models of atrial fibrillation (AF).

METHODS AND RESULTS

In 13 pentobarbital-anesthetized dogs bilateral thoracotomies allowed the attachment of multielectrode catheters to superior and inferior pulmonary veins and atrial appendages (AA). Rapid atrial pacing (RAP) was maintained for 6 hours. Each hour, programmed stimulation was performed to determine the window of vulnerability (WOV), a measure of AF inducibility, at all sites. During the last 3 hours, vasostatin-1, 33 nM, was injected into the anterior right (AR) ganglionated plexus (GP) and inferior right (IR) GP every 30 minutes (n = 6). Seven dogs underwent 6 hours of RAP only (controls). At baseline, acetylcholine, 100 mM, was applied on the right AA and AF duration was recorded before and after injection of vasostatin-1, 33 nM, into the ARGP and IRGP. In separate experiments (n = 8), voltage-sinus rate response curves (surrogate for GP function) were constructed by applying high-frequency stimulation to the ARGP with incremental voltages with or without vasostatin-1. Vasostatin-1 significantly decreased the duration of acetylcholine-induced AF (11.0 ± 4.1 vs 5.5 ± 2.6 min, P = 0.02). The cumulative WOV (the sum of individual WOVs) significantly increased (P < 0.0001) during the first 3 hours and decreased toward baseline in the presence of vasostatin-1 (P < 0.0001). Cumulative WOV in controls steadily increased. Vasostatin-1 blunted the slowing of sinus rate with increasing stimulation voltage of ARGP.

CONCLUSIONS

Vasostatin-1 suppresses AF inducibility, likely by inhibiting GP function. These data may provide new insights into the role of peptide neuromodulators for AF therapy.

Salivary chromogranin A, but not α-amylase, correlates with cardiovascular parameters during high-intensity exercise

INTRODUCTION

Several studies have shown that activation of the sympathetic nervous system results in the increased secretion of α-amylase (sAA), an enzyme produced by salivary glands. Recently, chromogranin A (CgA), a soluble protein costored and coreleased with catecholamines from the adrenal medulla and sympathetic nerve endings, has been proposed as a marker of sympathoadrenal medullary system (SAM) activity. The aim of this study was to investigate the behaviour of salivary chromogranin A (sCgA) and sAA during high-intensity exercise and to analyse their possible correlation with cardiovascular and psychological parameters.

METHODS

Before and during a standardized treadmill stress test, and at 5, 15 and 30 min during the recovery phase, sCgA and sAA were monitored in 21 healthy men. The double product (DP) of blood pressure and heart rate responses, and the product of the subjective ratings of perceived exertion recorded at the final step (RPE) and the exercise duration were used as indices of cardiovascular and exercise intensity, respectively.

RESULTS

With respect to baseline, significant (P < 0·001) increases in peak sCgA (median 64%) and sAA (median 86%) were observed at the end of exercise. During the recovery phase, sAA levels fell abruptly, whereas sCgA remained elevated (P < 0·001). Significant correlations emerged only for sCgA with respect to %DP (r = 0·84; P < 0·001) and last step-RPE (r = 0·82; P = 0·024).

CONCLUSIONS

These data suggest sCgA as a reliable marker of SAM activation. Furthermore, the relationship between sCgA and exercise intensity highlights the potential use of this noninvasive parameter in monitoring the adrenergic response during intense physical stress.

The extended granin family: structure, function, and biomedical implications

The chromogranins (chromogranin A and chromogranin B), secretogranins (secretogranin II and secretogranin III), and additional related proteins (7B2, NESP55, proSAAS, and VGF) that together comprise the granin family subserve essential roles in the regulated secretory pathway that is responsible for controlled delivery of peptides, hormones, neurotransmitters, and growth factors. Here we review the structure and function of granins and granin-derived peptides and expansive new genetic evidence, including recent single-nucleotide polymorphism mapping, genomic sequence comparisons, and analysis of transgenic and knockout mice, which together support an important and evolutionarily conserved role for these proteins in large dense-core vesicle biogenesis and regulated secretion. Recent data further indicate that their processed peptides function prominently in metabolic and glucose homeostasis, emotional behavior, pain pathways, and blood pressure modulation, suggesting future utility of granins and granin-derived peptides as novel disease biomarkers.

Vasostatin I (CgA17-76) vasoconstricts rat splanchnic vascular bed but does not affect central cardiovascular function

Vasostatin I (CgA(1-76)) is a naturally occurring biologically active peptide derived from chromogranin A (CgA), and is so named for its inhibitory effects on vascular tension. CgA mRNA is expressed abundantly in sympathoexcitatory catecholaminergic neurons of the rostral ventrolateral medulla (RVLM). CgA microinjection into the RVLM decreases blood pressure (BP), heart rate (HR) and sympathetic nerve activity (SNA). Proteolytic fragments of CgA are thought to be responsible for the cardiovascular effects observed. We hypothesised that vasostatin I is one of the fragments responsible for the central effects of CgA. We examined the role of a vasostatin I fragment, CgA(17-76) (VS-I((CgA17-76))), containing the portion important for biological effects. The effects of VS-I((CgA17-76)) delivered by intrathecal injection, or microinjection into the RVLM, on cardio-respiratory function in urethane anaesthetised, vagotomised, mechanically ventilated Sprague-Dawley rats (n=21) were evaluated. The effects of intrathecal VS-I((CgA17-76)) on the somato-sympathetic, baroreceptor and peripheral chemoreceptor reflexes were also examined. At the concentrations used (10, 100 or 200 μM, intrathecal; or 5 μM, RVLM microinjection) VS-I((CgA17-76)) produced no change in mean arterial pressure, HR, splanchnic SNA, phrenic nerve amplitude or phrenic nerve frequency. All reflexes examined were unchanged following intrathecal VS-I((CgA17-76)). In the periphery, VS-I((CgA17-76)) potentiated the contractile effects of noradrenaline on rat mesenteric arteries (n=6), with a significant left-shift in the dose response curve to noradrenaline (3.7×10(-7) vs 7.7×10(-7)). Our results indicate that VS-I((CgA17-76)) is active in the periphery but not centrally, and is not a central modulator of cardiorespiratory function and physiological reflexes.

Chromogranin peptides in brain diseases

Synaptic disturbances may play a key role in the pathophysiology of neuropsychiatric diseases. In this article, we review immunohistological findings of chromogranin peptides in neurodegenerative and neurodevelopmental disorders, with particular emphasis on Alzheimer's disease, the disorder chromogranins have been studied most extensively. Data was collected from existing and new experimental data and medline research. This review focuses on synaptic changes elicited by chromogranin peptides immunoreactivity in Alzheimer's disease, as well in schizophrenia and amyotrophic lateral sclerosis (ALS). An imbalanced availability of chromogranin peptides may be responsible for impaired neurotransmission and a reduced functioning of dense core vesicles. Since chromogranin A was postulated as a potent proinflammatory agent, we focused on chromogranin A in neuroinflammation in Alzheimer's disease and ALS. Further understanding of role and function of chromogranin peptides in neuropathological conditions is still required.

The chromogranin A- derived N-terminal peptide vasostatin-I: In vivo effects on cardiovascular variables in the rabbit

This study is the first to report on vascular effect of the chromogranin A derived Vasostatin-I (CgA(1-76)) in vivo. Cardiovascular parameters were recorded in 29 rabbits with sympathetically decentralized right carotid vascular bed. The recombinant human STA CgA(1-78) (VS-1) was infused at 480 μg/kg over 25 min. Group I was kept awake while groups II-V were anesthetized with Ketamine-xylazine. VS-1 was given alone in groups I-II while in presence of either phentolamine, phentolamine plus propranolol or hexamethonium in groups III-V. Serum VS-1 peaked at 2 μg/ml (200 nM) before onset of vascular effects and declined rapidly to ~200 ng/ml within 30 min. In all groups but III and IV VS-1 induced a brief vasoconstriction, being larger in intact than in sympathetically decentralized beds. The VS-1 induced vasoconstriction was not altered by hexamethonium but was abolished by phentolamine. In presence of the α-adrenergic blocker a long lasting vasodilatation, unaffected by propranolol, was apparent on both innervated and decentralized sides. In conclusion, VS-1 induced an α-adrenoceptor-mediated vasoconstriction presumably brought about by noradrenaline release from sympathetic nerves when infused at a dose giving an initial serum concentration of ~200 nM. This initial vasoconstriction masked a persistent adrenoceptor-independent vasodilatation, consistent with previous reports from in vitro models.

Catestatin improves post-ischemic left ventricular function and decreases ischemia/reperfusion injury in heart

The Chromogranin A (CgA)-derived anti-hypertensive peptide catestatin (CST) antagonizes catecholamine secretion, and is a negative myocardial inotrope acting via a nitric oxide-dependent mechanism. It is not known whether CST contributes to ischemia/reperfusion injury or is a component of a cardioprotective response to limit injury. Here, we tested whether CST by virtue of its negative inotropic activity improves post-ischemic cardiac function and cardiomyocyte survival. Three groups of isolated perfused hearts from adult Wistar rats underwent 30-min ischemia and 120-min reperfusion (I/R, Group 1), or were post-conditioned by brief ischemic episodes (PostC, 5-cycles of 10-s I/R at the beginning of 120-min reperfusion, Group 2), or with exogenous CST (75 nM for 20 min, CST-Post, Group-3) at the onset of reperfusion. Perfusion pressure and left ventricular pressure (LVP) were monitored. Infarct size was evaluated with nitroblue-tetrazolium staining. The CST (5 nM) effects were also tested in simulated ischemia/reperfusion experiments on cardiomyocytes isolated from young-adult rats, evaluating cell survival with propidium iodide labeling. Infarct size was 61 ± 6% of risk area in hearts subjected to I/R only. PostC reduced infarct size to 34 ± 5%. Infarct size in CST-Post was 36 ± 3% of risk area (P < 0.05 respect to I/R). CST-Post reduced post-ischemic rise of diastolic LVP, an index of contracture, and significantly improved post-ischemic recovery of developed LVP. In isolated cardiomyocytes, CST increased the cell viability rate by about 65% after simulated ischemia/reperfusion. These results suggest a novel cardioprotective role for CST, which appears mainly due to a direct reduction of post-ischemic myocardial damages and dysfunction, rather than to an involvement of adrenergic terminals and/or endothelium.

Regulatory peptides from chromogranin A and secretogranin II

This commentary is focusing on novel aspects on the secreted CgA- and SgII-derived peptides, vasostatin-I (bovine and human CgA_1–76, VS-I), WE-14 (CgA_316–329), catestatin (bovine CgA_344–366, human CgA_352–372, Cts) and the SgII-derived secretoneurin (SgII_180–204) as significant regulators of inflammatory reactions.

Reprint of: Chromogranin A: a new proposal for trafficking, processing and induction of granule biogenesis

Chromogranin A (CgA), a member of the granin family serves several important cell biological roles in (neuro)endocrine cells which are summarized in this review. CgA is a "prohormone" that is synthesized at the rough endoplasmic reticulum and transported into the cisternae of this organelle via its signal peptide. It is then trafficked to the Golgi complex and then to the trans-Golgi network (TGN) where CgA aggregates at low pH in the presence of calcium. The CgA aggregates provide the physical driving force to induce budding of the TGN membrane resulting in dense core granule (DCG) formation. Within the granule, a small amount of the CgA is processed to bioactive peptides, including a predicted C-terminal peptide, serpinin. Upon stimulation, DCGs undergo exocytosis and CgA and its derived peptides are released. Serpinin, acting extracellularly is able to signal the increase in transcription of a serine protease inhibitor, protease nexin-1 (PN-1) that protects DCG proteins against degradation in the Golgi complex, which then enhances DCG biogenesis to replenish those that were released. Thus CgA and its derived peptide, serpinin, plays a significant role in granule formation and regulation of granule biogenesis, respectively, in (neuro) endocrine cells.