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

Glycosylated Chromogranin A in Heart Failure: Implications for Processing and Cardiomyocyte Calcium Homeostasis

BACKGROUND

Chromogranin A (CgA) levels have previously been found to predict mortality in heart failure (HF), but currently no information is available regarding CgA processing in HF and whether the CgA fragment catestatin (CST) may directly influence cardiomyocyte function.

METHODS AND RESULTS

CgA processing was characterized in postinfarction HF mice and in patients with acute HF, and the functional role of CST was explored in experimental models. Myocardial biopsies from HF, but not sham-operated mice, demonstrated high molecular weight CgA bands. Deglycosylation treatment attenuated high molecular weight bands, induced a mobility shift, and increased shorter CgA fragments. Adjusting for established risk indices and biomarkers, circulating CgA levels were found to be associated with mortality in patients with acute HF, but not in patients with acute exacerbation of chronic obstructive pulmonary disease. Low CgA-to-CST conversion was also associated with increased mortality in acute HF, thus, supporting functional relevance of impaired CgA processing in cardiovascular disease. CST was identified as a direct inhibitor of CaMKIIδ (Ca²⁺/calmodulin-dependent protein kinase IIδ) activity, and CST reduced CaMKIIδ-dependent phosphorylation of phospholamban and the ryanodine receptor 2. In line with CaMKIIδ inhibition, CST reduced Ca²⁺ spark and wave frequency, reduced Ca²⁺ spark dimensions, increased sarcoplasmic reticulum Ca²⁺ content, and augmented the magnitude and kinetics of cardiomyocyte Ca²⁺ transients and contractions.

CONCLUSIONS

CgA-to-CST conversion in HF is impaired because of hyperglycosylation, which is associated with clinical outcomes in acute HF. The mechanism for increased mortality may be dysregulated cardiomyocyte Ca²⁺ handling because of reduced CaMKIIδ inhibition.

Chromogranin A regulates vesicle storage and mitochondrial dynamics to influence insulin secretion

Chromogranin A (CgA) is a prohormone and a granulogenic factor that regulates secretory pathways in neuroendocrine tissues. In β-cells of the endocrine pancreas, CgA is a major cargo in insulin secretory vesicles. The impact of CgA deficiency on the formation and exocytosis of insulin vesicles is yet to be investigated. In addition, no literature exists on the impact of CgA on mitochondrial function in β-cells. Using three different antibodies, we demonstrate that CgA is processed to vasostatin- and catestatin-containing fragments in pancreatic islet cells. CgA deficiency in Chga-KO islets leads to compensatory overexpression of chromogranin B, secretogranin II, SNARE proteins and insulin genes, as well as increased insulin protein content. Ultrastructural studies of pancreatic islets revealed that Chga-KO β-cells contain fewer immature secretory granules than wild-type (WT) control but increased numbers of mature secretory granules and plasma membrane-docked vesicles. Compared to WT control, CgA-deficient β-cells exhibited increases in mitochondrial volume, numerical densities and fusion, as well as increased expression of nuclear encoded genes (Ndufa9, Ndufs8, Cyc1 and Atp5o). These changes in secretory vesicles and the mitochondria likely contribute to the increased glucose-stimulated insulin secretion observed in Chga-KO mice. We conclude that CgA is an important regulator for coordination of mitochondrial dynamics, secretory vesicular quanta and GSIS for optimal secretory functioning of β-cells, suggesting a strong, CgA-dependent positive link between mitochondrial fusion and GSIS.

Prognostic Value of Secretoneurin in Critically Ill Patients With Infections

OBJECTIVES

Secretoneurin is produced in neuroendocrine cells, and the myocardium and circulating secretoneurin levels provide incremental prognostic information to established risk indices in cardiovascular disease. As myocardial dysfunction contributes to poor outcome in critically ill patients, we wanted to assess the prognostic value of secretoneurin in two cohorts of critically ill patients with infections.

DESIGN

Two prospective, observational studies.

SETTING

Twenty-four and twenty-five ICUs in Finland.

PATIENTS

A total of 232 patients with severe sepsis (cohort #1) and 94 patients with infections and respiratory failure (cohort #2).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured secretoneurin levels by radioimmunoassay in samples obtained early after ICU admission and compared secretoneurin with other risk indices. In patients with severe sepsis, admission secretoneurin levels (logarithmically transformed) were associated with hospital mortality (odds ratio, 3.17 [95% CI, 1.12-9.00]; p = 0.030) and shock during the hospitalization (odds ratio, 2.17 [1.06-4.46]; p = 0.034) in analyses that adjusted for other risk factors available on ICU admission. Adding secretoneurin levels to age, which was also associated with hospital mortality in the multivariate model, improved the risk prediction as assessed by the category-free net reclassification index: 0.35 (95% CI, 0.06-0.64) (p = 0.02). In contrast, N-terminal pro-B-type natriuretic peptide levels were not associated with mortality in the multivariate model that included secretoneurin measurements, and N-terminal pro-B-type natriuretic peptide did not improve patient classification on top of age. Secretoneurin levels were also associated with hospital mortality after adjusting for other risk factors and improved patient classification in cohort #2. In both cohorts, the optimal cutoff for secretoneurin levels at ICU admission to predict hospital mortality was ≈ 175 pmol/L, and higher levels were associated with mortality also when adjusting for Simplified Acute Physiology Score II and Sequential Organ Failure Assessment scores.

CONCLUSIONS

Secretoneurin levels provide incremental information to established risk indices for the prediction of mortality and shock in critically ill patients with severe infections.

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.

SNAP-25 gene family members differentially support secretory vesicle fusion

Neuronal dense-core vesicles (DCVs) transport and secrete neuropeptides necessary for development, plasticity and survival, but little is known about their fusion mechanism. We show that Snap-25-null mutant (SNAP-25 KO) neurons, previously shown to degenerate after 4 days in vitro (DIV), contain fewer DCVs and have reduced DCV fusion probability in surviving neurons at DIV14. At DIV3, before degeneration, SNAP-25 KO neurons show normal DCV fusion, but one day later fusion is significantly reduced. To test if other SNAP homologs support DCV fusion, we expressed SNAP-23, SNAP-29 or SNAP-47 in SNAP-25 KO neurons. SNAP-23 and SNAP-29 rescued viability and supported DCV fusion in SNAP-25 KO neurons, but SNAP-23 did so more efficiently. SNAP-23 also rescued synaptic vesicle (SV) fusion while SNAP-29 did not. SNAP-47 failed to rescue viability and did not support DCV or SV fusion. These data demonstrate a developmental switch, in hippocampal neurons between DIV3 and DIV4, where DCV fusion becomes SNAP-25 dependent. Furthermore, SNAP-25 homologs support DCV and SV fusion and neuronal viability to variable extents - SNAP-23 most effectively, SNAP-29 less so and SNAP-47 ineffectively.

Pharmacological and Biochemical Characterization of TLQP-21 Activation of a Binding Site on CHO Cells

VGF is a propeptide of 617 amino acids expressed throughout the central and the peripheral nervous system. VGF and peptides derived from its processing have been found in dense core vesicles and are released from neuronal and neuroendocrine cells via the regulated secretory pathway. Among VGF-derived neuropeptides, TLQP-21 (VGF^556-576) has raised a huge interest and is one of most studied. TLQP-21 is a multifunctional neuropeptide involved in the control of several physiological functions, potentially including energy homeostasis, pain modulation, stress responsiveness and reproduction. Although little information is available about its receptor and the intracellular mechanisms mediating its biological effects, recent reports suggest that TLQP-21 may bind to the complement receptors C3aR1 and/or gC1qR. The first aim of this study was to ascertain the existence and nature of TLQP-21 binding sites in CHO cells. Secondly, we endeavored to characterize the ligand binding to these sites by using a small panel of VGF-derived peptides. And finally, we investigated the influence of TLQP-21 on selected intracellular signaling pathways. We report that CHO cells express a single class of saturable and specific binding sites for TLQP-21 with an affinity and capacity of K_d = 0.55 ± 0.05 × 10^-9 M and B_{max =} 81.7 ± 3.9 fmol/mg protein, respectively. Among the many bioactive products derived from the C-terminal region of VGF that we tested, TLQP-21 was the most potent in stimulating intracellular calcium mobilization in CHO cells; this effect is primarily due to its C-terminal fragment (HFHH-10). TLQP-21 induced rapid and transient dephosphorylation of phospholipase Cγ1 and phospholipase A2. Generation of IP₃ and diacylglycerol was crucial for TLQP-21 bioactivity. In conclusion, our results suggest that the receptor stimulated by TLQP-21 belongs to the family of the G_q-coupled receptors, and its activation first increases membrane-lipid derived second messengers which thereby induce the mobilization of Ca²⁺ from the endoplasmic reticulum followed by a slower store-operated Ca²⁺ entry from outside the cell.

Neuropeptide VGF Promotes Maturation of Hippocampal Dendrites That Is Reduced by Single Nucleotide Polymorphisms

The neuropeptide VGF (non-acronymic) is induced by brain-derived neurotrophic factor and promotes hippocampal neurogenesis, as well as synaptic activity. However, morphological changes induced by VGF have not been elucidated. Developing hippocampal neurons were exposed to VGF through bath application or virus-mediated expression in vitro. VGF-derived peptide, TLQP-62, enhanced dendritic branching, and outgrowth. Furthermore, VGF increased dendritic spine density and the proportion of immature spines. Spine formation was associated with increased synaptic protein expression and co-localization of pre- and postsynaptic markers. Three non-synonymous single nucleotide polymorphisms (SNPs) were selected in human VGF gene. Transfection of N2a cells with plasmids containing these SNPs revealed no relative change in protein expression levels and normal protein size, except for a truncated protein from the premature stop codon, E525X. All three SNPs resulted in a lower proportion of N2a cells bearing neurites relative to wild-type VGF. Furthermore, all three mutations reduced the total length of dendrites in developing hippocampal neurons. Taken together, our results suggest VGF enhances dendritic maturation and that these effects can be altered by common mutations in the VGF gene. The findings may have implications for people suffering from psychiatric disease or other conditions who may have altered VGF levels.

A potential role for the secretogranin II-derived peptide EM66 in the hypothalamic regulation of feeding behaviour

EM66 is a conserved 66-amino acid peptide derived from secretogranin II (SgII), a member of the granin protein family. EM66 is widely distributed in secretory granules of endocrine and neuroendocrine cells, as well as in hypothalamic neurones. Although EM66 is abundant in the hypothalamus, its physiological function remains to be determined. The present study aimed to investigate a possible involvement of EM66 in the hypothalamic regulation of feeding behaviour. We show that i.c.v. administration of EM66 induces a drastic dose-dependent inhibition of food intake in mice deprived of food for 18 hours, which is associated with an increase of hypothalamic pro-opiomelanocortin (POMC) and melanocortin-3 receptor mRNA levels and c-Fos immunoreactivity in the POMC neurones of the arcuate nucleus. By contrast, i.c.v. injection of EM66 does not alter the hypothalamic expression of neuropeptide Y (NPY), or that of its Y1 and Y5 receptors. A 3-month high-fat diet (HFD) leads to an important decrease of POMC and SgII mRNA levels in the hypothalamus, whereas NPY gene expression is not affected. Finally, we show that a 48 hours of fasting in HFD mice decreases the expression of POMC and SgII mRNA, which is not observed in mice fed a standard chow. Taken together, the present findings support the view that EM66 is a novel anorexigenic neuropeptide regulating hypothalamic feeding behaviour, at least in part, by activating the POMC neurones of the arcuate nucleus.

JMV5656, A Novel Derivative of TLQP-21, Triggers the Activation of a Calcium-Dependent Potassium Outward Current in Microglial Cells

TLQP-21 (TLQPPASSRRRHFHHALPPAR) is a multifunctional peptide that is involved in the control of physiological functions, including feeding, reproduction, stress responsiveness, and general homeostasis. Despite the huge interest in TLQP-21 biological activity, very little is known about its intracellular mechanisms of action. In microglial cells, TLQP-21 stimulates increases of intracellular Ca²⁺ that may activate functions, including proliferation, migration, phagocytosis and production of inflammatory molecules. Our aim was to investigate whether JMV5656 (RRRHFHHALPPAR), a novel short analogue of TLQP-21, stimulates intracellular Ca²⁺ in the N9 microglia cells, and whether this Ca²⁺ elevation is coupled with the activation Ca²⁺-sensitive K⁺ channels. TLQP-21 and JMV5656 induced a sharp, dose-dependent increment in intracellular calcium. In 77% of cells, JMV5656 also caused an increase in the total outward currents, which was blunted by TEA (tetraethyl ammonium chloride), a non-selective blocker of voltage-dependent and Ca²⁺-activated potassium (K⁺) channels. Moreover, the effects of ion channel blockers charybdotoxin and iberiotoxin, suggested that multiple calcium-activated K⁺ channel types drove the outward current stimulated by JMV5656. Additionally, inhibition of JMV5656-stimulated outward currents by NS6180 (4-[[3-(trifluoromethyl)phenyl]methyl]-2H-1,4 benzothiazin-3(4H)-one) and TRAM-34 (triarylmethane-34), indicated that K_Ca3.1 channels are involved in this JMV5656 mechanisms of action. In summary, we demonstrate that, in N9 microglia cells, the interaction of JMV5656 with the TLQP-21 receptors induced an increase in intracellular Ca²⁺, and, following extracellular Ca²⁺ entry, the opening of K_Ca3.1 channels.

Muscle injury, impaired muscle function and insulin resistance in Chromogranin A-knockout mice

Chromogranin A (CgA) is widely expressed in endocrine and neuroendocrine tissues as well as in the central nervous system. We observed CgA expression (mRNA and protein) in the gastrocnemius (GAS) muscle and found that performance of CgA-deficient Chga-KO mice in treadmill exercise was impaired. Supplementation with CgA in Chga-KO mice restored exercise ability suggesting a novel role for endogenous CgA in skeletal muscle function. Chga-KO mice display (i) lack of exercise-induced stimulation of pAKT, pTBC1D1 and phospho-p38 kinase signaling, (ii) loss of GAS muscle mass, (iii) extensive formation of tubular aggregates (TA), (iv) disorganized cristae architecture in mitochondria, (v) increased expression of the inflammatory cytokines Tnfα, Il6 and Ifnγ, and fibrosis. The impaired maximum running speed and endurance in the treadmill exercise in Chga-KO mice correlated with decreased glucose uptake and glycolysis, defects in glucose oxidation and decreased mitochondrial cytochrome C oxidase activity. The lack of adaptation to endurance training correlated with the lack of stimulation of p38MAPK that is known to mediate the response to tissue damage. As CgA sorts proteins to the regulated secretory pathway, we speculate that lack of CgA could cause misfolding of membrane proteins inducing aggregation of sarcoplasmic reticulum (SR) membranes and formation of tubular aggregates that is observed in Chga-KO mice. In conclusion, CgA deficiency renders the muscle energy deficient, impairs performance in treadmill exercise and prevents regeneration after exercise-induced tissue damage.

Circulating chromogranin B levels in patients with acute respiratory failure: data from the FINNALI Study

PURPOSE

Circulating chromogranin B (CgB) levels are increased in situations characterized by systemic and myocardial stress, but whether CgB provides prognostic information in patients with acute respiratory failure (ARF) is unknown.

METHODS

We included 584 patients with ARF, defined as ventilatory support >6 h, and with blood samples available on Intensive Care Unit (ICU) admission and day 3 (n = 479). CgB levels were measured by radioimmunoassay and follow-up was 90 days.

RESULTS

One-hundred-sixty-nine patients (29%) died during follow-up. Admission CgB levels separated non-survivors from survivors: median 1234 (Q1-3 989-1742) vs. 917 (753-1224) pmol/L, respectively, p < 0.001. CgB levels on ICU admission (logarithmically transformed) were associated with time to death after adjustment for established risk indices available on ICU admission, including N-terminal pro-B-type natriuretic levels: HR 2.62 (95%C.I. 1.82-3.77), p < 0.001. Admission CgB levels also improved prognostication on top of SOFA and SAPS II scores as assessed by Cox regression analyses and the category-free net reclassification index. The area under the curve (AUC) for admission CgB levels to separate survivors and non-survivors was 0.72 (95%CI 0.67-0.76), while the AUC on day 3 was 0.60 (0.54-0.66).

CONCLUSIONS

CgB levels measured on ICU admission provided additional prognostic information to established risk indices in ARF patients.

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.

Prognostic Value of Secretoneurin in Patients with Acute Respiratory Failure: Data from the FINNALI Study

BACKGROUND

We examined whether secretoneurin (SN), a biomarker associated with cardiomyocyte Ca2+ handling, provides prognostic information in patients with acute respiratory failure (ARF).

METHODS

We included 490 patients with ARF, defined as ventilatory support &gt;6 h, with blood samples available on admission to the intensive care unit (ICU). SN concentrations were measured by RIA.

RESULTS

A total of 209 patients (43%) were hospitalized with cardiovascular (CV)-related ARF, and 90-day mortality rates were comparable between CV- and non–CV-related ARF (n = 281): 31% vs 24%, P = 0.11. Admission SN concentrations were higher in nonsurvivors than in survivors in both CV-related (median 148 [quartile 1–3, 117–203] vs 108 [87–143] pmol/L, P &lt; 0.001) and non–CV-related ARF (139 [115–184] vs 113 [91–139] pmol/L, P &lt; 0.001). In patients with CV-related ARF, SN concentrations on ICU admission were associated with 90-day mortality [odds ratio (OR) 1.97 (95% CI, 1.04–3.73, P = 0.04)] after adjusting for established risk indices, including N-terminal-pro-B-type natriuretic peptide (NT-proBNP) concentrations. SN also improved patient classification in CV-related ARF as assessed by the net reclassification index: 0.32 (95% CI, 0.04–0.59), P = 0.03. The area under the curve (AUC) of SN to predict mortality in patients with CV-related ARF was 0.72 (95% CI, 0.65–0.79), and the AUC of NT-proBNP was 0.64 (0.56–0.73). In contrast, SN concentrations on ICU admission did not provide incremental prognostic value to established risk indices in patients with non–CV-related ARF, and the AUC was 0.67 (0.60–0.75).

CONCLUSIONS

SN concentrations measured on ICU admission provided incremental prognostic information to established risk indices in patients with CV-related ARF, but not in patients with non–CV-related ARF.

Excitatory and Inhibitory Neurons in the Hippocampus Exhibit Molecularly Distinct Large Dense Core Vesicles

Hippocampal interneurons comprise a diverse family of inhibitory neurons that are critical for detailed information processing. Along with gamma-aminobutyric acid (GABA), interneurons secrete a myriad of neuroactive substances via secretory vesicles but the molecular composition and regulatory mechanisms remain largely unknown. In this study, we have carried out an immunohistofluorescence analysis to describe the molecular content of vesicles in distinct populations of hippocampal neurons. Our results indicate that phogrin, an integral protein of secretory vesicles in neuroendocrine cells, is highly enriched in parvalbumin-positive interneurons. Consistently, immunoelectron microscopy revealed phogrin staining in axon terminals of symmetrical synapses establishing inhibitory contacts with cell bodies of CA1 pyramidal neurons. Furthermore, phogrin is highly expressed in CA3 and dentate gyrus (DG) interneurons which are both positive for PV and neuropeptide Y. Surprisingly, chromogranin B a canonical large dense core vesicle marker, is excluded from inhibitory cells in the hippocampus but highly expressed in excitatory CA3 pyramidal neurons and DG granule cells. Our results provide the first evidence of phogrin expression in hippocampal interneurons and suggest the existence of molecularly distinct populations of secretory vesicles in different types of inhibitory neurons.

Identification of prohormones and pituitary neuropeptides in the African cichlid, Astatotilapia burtoni

Background

Cichlid fishes have evolved remarkably diverse reproductive, social, and feeding behaviors. Cell-to-cell signaling molecules, notably neuropeptides and peptide hormones, are known to regulate these behaviors across vertebrates. This class of signaling molecules derives from prohormone genes that have undergone multiple duplications and losses in fishes. Whether and how subfunctionalization, neofunctionalization, or losses of neuropeptides and peptide hormones have contributed to fish behavioral diversity is largely unknown. Information on fish prohormones has been limited and is complicated by the whole genome duplication of the teleost ancestor. We combined bioinformatics, mass spectrometry-enabled peptidomics, and molecular techniques to identify the suite of neuropeptide prohormones and pituitary peptide products in Astatotilapia burtoni, a well-studied member of the diverse African cichlid clade.

Results

Utilizing the A. burtoni genome, we identified 148 prohormone genes, with 21 identified as a single copy and 39 with at least 2 duplicated copies. Retention of prohormone duplicates was therefore 41 %, which is markedly above previous reports for the genome-wide average in teleosts. Beyond the expected whole genome duplication, differences between cichlids and mammals can be attributed to gene loss in tetrapods and additional duplication after divergence. Mass spectrometric analysis of the pituitary identified 620 unique peptide sequences that were matched to 120 unique proteins. Finally, we used in situ hybridization to localize the expression of galanin, a prohormone with exceptional sequence divergence in cichlids, as well as the expression of a proopiomelanocortin, prohormone that has undergone an additional duplication in some bony fish lineages.

Conclusion

We characterized the A. burtoni prohormone complement. Two thirds of prohormone families contain duplications either from the teleost whole genome duplication or a more recent duplication. Our bioinformatic and mass spectrometric findings provide information on a major vertebrate clade that will further our understanding of the functional ramifications of these prohormone losses, duplications, and sequence changes across vertebrate evolution. In the context of the cichlid radiation, these findings will also facilitate the exploration of neuropeptide and peptide hormone function in behavioral diversity both within A. burtoni and across cichlid and other fish species.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2914-9) contains supplementary material, which is available to authorized users.

Chronic Administration of Catestatin Improves Autonomic Function and Exerts Cardioprotective Effects in Myocardial Infarction Rats

Catestatin (CST), which is emerging as a novel cardiac modulator, can protect the heart against excessive sympathetic drive in hypertensive cardiomyopathy. The aim of this study is to investigate whether exogenous CST decreases excessive cardiac sympathetic drive and improves autonomic function and exerts cardioprotective effects in myocardial infarction (MI) rats. Rats were divided into a sham group, MI group, and MI plus CST (MI + CST) group. Four weeks later, the autonomic function of the animals was assessed by analyzing heart rate variability (HRV) and measuring plasma catecholamine. Cardiac function was evaluated via echocardiography. Electrophysiological characteristics were assessed in Langendorff-perfused hearts. Compared to the MI group, the chronic administration of CST significantly increased the standard deviation of normal–normal intervals ( P < .01) and low-frequency (LF) and high-frequency (HF) HRV and decreased the ratio of LF–HF HRV ( P < .01 for all). Additionally, the level of plasma catecholamine was reduced in the MI + CST group compared to the MI group ( P < .01). Treatment with CST significantly increased ejection fraction (EF) and fraction shorting (FS) and significantly decreased the left ventricular end-systolic diameter and left ventricular end-diastolic diameter at 28 days postmyocardial infraction ( P < .05 for all). After MI, the ventricular repolarization duration, such as QTc intervals and action potential duration (APD) at 90% repolarization, was prolonged, and this prolongation could be decreased by CST ( P < .05 for all). The CST also increased the threshold of ADP alternans ( P < .01). Moreover, ventricular arrhythmias were induced in 83% of the MI group but only 33% of the MI + CST group ( P < .05). These results suggested that the chronic administration of CST plays a role in cardioprotection in MI rats, which may function by decreasing the cardiac sympathetic drive and improving autonomic function.

Population-based metagenomics analysis reveals markers for gut microbiome composition and diversity

Deep sequencing of the gut microbiomes of 1135 participants from a Dutch population-based cohort shows relations between the microbiome and 126 exogenous and intrinsic host factors, including 31 intrinsic factors, 12 diseases, 19 drug groups, 4 smoking categories, and 60 dietary factors. These factors collectively explain 18.7% of the variation seen in the interindividual distance of microbial composition. We could associate 110 factors to 125 species and observed that fecal chromogranin A (CgA), a protein secreted by enteroendocrine cells, was exclusively associated with 61 microbial species whose abundance collectively accounted for 53% of microbial composition. Low CgA concentrations were seen in individuals with a more diverse microbiome. These results are an important step toward a better understanding of environment-diet-microbe-host interactions.

Stimulatory effect of the secretogranin-ll derived peptide secretoneurin on food intake and locomotion in female goldfish (Carassius auratus)

Secretoneurin (SN) is a conserved peptide derived by proteolytic processing from the middle domain of the ∼600 amino acid precursor secretogranin-II (SgII). Secretoneurin is widely distributed in secretory granules of endocrine cells and neurons and has important roles in reproduction as it stimulates luteinizing hormone release from the pituitary. A potential new role of SN in goldfish feeding is the subject of this study. Firstly, we established that acute (26 h; p<0.0001) and short-term (72 h; p=0.016) fasting increased SgIIa precursor mRNA levels 1.25-fold in the telencephalon, implicating SN in the control of feeding. Secondly, we determined that intracerebroventricular injections of the type A SN (SNa; 0.2 and 1 ng/g BW) increased food intake and locomotor behavior by 60 min. Fish injected with the lower and higher doses of SNa (0.2 and 1 ng/g) respectively exhibited significant 1.77- and 2.58-fold higher food intake (p<0.0001) than the saline-injected control fish. Locomotor behavior was increased by 1.35- and 2.26-fold for 0.2 ng/g SNa (p=0.0001) and 1 ng/g SNa (p<0.0001), respectively. Injection of 1 ng/g SNa increased mRNA levels of hypothalamic neuropeptide Y 1.36-fold (p=0.038) and decreased hypothalamic cocaine-and amphetamine-regulated transcript by 33% (p=0.01) at 2h and 5h post-injection, respectively. These data suggest interactions of SNa with stimulatory and inhibitory pathways of food intake control in fish.

Carboxypeptidase E and Secretogranin III Coordinately Facilitate Efficient Sorting of Proopiomelanocortin to the Regulated Secretory Pathway in AtT20 Cells

Proopiomelanocortin (POMC) is a multivalent prohormone that can be processed into at least 7 biologically active peptide hormones. Processing can begin in the trans-Golgi network (TGN) and continues in the secretory granules of the regulated secretory pathway (RSP). Sorting of POMC into these granules is a complex process. Previously, a membrane-associated form of carboxypeptidase E (CPE) was shown to bind to POMC and facilitate its trafficking into these granules. More recently, secretogranin III (SgIII) was also found to affect POMC trafficking. Here, we show by RNA silencing that CPE and SgIII play a synergistic role in the trafficking of POMC to granules of the RSP in AtT20 cells. Reduction of either protein resulted in increased constitutive secretion of POMC and chromogranin A, which was increased even further when both proteins were reduced together, indicative of missorting at the TGN. In SgIII-reduced cells, POMC accumulated in a compartment that cofractionated and colocalized with syntaxin 6, a marker of the TGN, on sucrose density gradients and in immunocytochemistry, respectively, indicating an accumulation of this protein in the presumed sorting compartment. Regulated secretion of ACTH, as a measure of sorting and processing of POMC in mature granules, was reduced in the SgIII down-regulated cells but was increased in the CPE down-regulated cells. These results suggest that multiple sorting systems exist, providing redundancy to ensure the important task of continuous and accurate trafficking of prohormones to the granules of the RSP for the production of peptide hormones.

A genome-wide association study of asthma symptoms in Latin American children

Background

Asthma is a chronic disease of the airways and, despite the advances in the knowledge of associated genetic regions in recent years, their mechanisms have yet to be explored. Several genome-wide association studies have been carried out in recent years, but none of these have involved Latin American populations with a high level of miscegenation, as is seen in the Brazilian population.

Methods

1246 children were recruited from a longitudinal cohort study in Salvador, Brazil. Asthma symptoms were identified in accordance with an International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Following quality control, 1 877 526 autosomal SNPs were tested for association with childhood asthma symptoms by logistic regression using an additive genetic model. We complemented the analysis with an estimate of the phenotypic variance explained by common genetic variants. Replications were investigated in independent Mexican and US Latino samples.

Results

Two chromosomal regions reached genome-wide significance level for childhood asthma symptoms: the 14q11 region flanking the DAD1 and OXA1L genes (rs1999071, MAF 0.32, OR 1.78, 95 % CI 1.45–2.18, p-value 2.83 × 10⁻⁸) and 15q22 region flanking the FOXB1 gene (rs10519031, MAF 0.04, OR 3.0, 95 % CI 2.02–4.49, p-value 6.68 × 10⁻⁸ and rs8029377, MAF 0.03, OR 2.49, 95 % CI 1.76–3.53, p-value 2.45 × 10⁻⁷). eQTL analysis suggests that rs1999071 regulates the expression of OXA1L gene. However, the original findings were not replicated in the Mexican or US Latino samples.

Conclusions

We conclude that the 14q11 and 15q22 regions may be associated with asthma symptoms in childhood.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0296-7) contains supplementary material, which is available to authorized users.

pGlu-serpinin protects the normotensive and hypertensive heart from ischemic injury

Serpinin peptides derive from proteolytic cleavage of Chromogranin-A at C-terminus. Serpinin and the more potent pyroglutaminated-serpinin (pGlu-Serp) are positive cardiac β-adrenergic-like modulators, acting through β1-AR/AC/cAMP/PKA pathway. Because in some conditions this pathway and/or other pro-survival pathways, activated by other Chromogranin-A fragments, may cross-talk and may be protective, here we explored whether pGlu-Serp cardioprotects against ischemia/reperfusion injury under normotensive and hypertensive conditions. In the latter condition, cardioprotection is often blunted because of the limitations on pro-survival Reperfusion Injury Salvage Kinases (RISK) pathway activation. The effects of pGlu-Serp were evaluated on infarct size (IS) and cardiac function by using the isolated and Langendorff perfused heart of normotensive (Wistar Kyoto, WKY) and spontaneously hypertensive (SHR) rats exposed to ischemic pre-conditioning (PreC) and post-conditioning (PostC). In both WKY and SHR rat, pGlu-Serp induced mild cardioprotection in both PreC and PostC. pGlu-Serp administered at the reperfusion (Serp-PostC) significantly reduced IS, being more protective in SHR than in WKY. Conversely, left ventricular developed pressure (LVDevP) post-ischemic recovery was greater in WKY than in SHR. pGlu-Serp-PostC reduced contracture in both strains. Co-infusion with specific RISK inhibitors (PI3K/Akt, MitoKATP channels and PKC) blocked the pGlu-Serp-PostC protective effects. To show direct effect on cardiomyocytes, we pre-treated H9c2 cells with pGlu-Serp, which were thus protected against hypoxia/reoxygenation. These results suggest pGlu-Serp as a potential modulatory agent implicated in the protective processes that can limit infarct size and overcome the hypertension-induced failure of PostC.

Impact of Chromogranin A deficiency on catecholamine storage, catecholamine granule morphology and chromaffin cell energy metabolism in vivo

Chromogranin A (CgA) is a prohormone and granulogenic factor in neuroendocrine tissues with a regulated secretory pathway. The impact of CgA depletion on secretory granule formation has been previously demonstrated in cell culture. However, studies linking the structural effects of CgA deficiency with secretory performance and cell metabolism in the adrenomedullary chromaffin cells in vivo have not previously been reported. Adrenomedullary content of the secreted adrenal catecholamines norepinephrine (NE) and epinephrine (EPI) was decreased 30-40 % in Chga-KO mice. Quantification of NE and EPI-storing dense core (DC) vesicles (DCV) revealed decreased DCV numbers in chromaffin cells in Chga-KO mice. For both cell types, the DCV diameter in Chga-KO mice was less (100-200 nm) than in WT mice (200-350 nm). The volume density of the vesicle and vesicle number was also lower in Chga-KO mice. Chga-KO mice showed an ~47 % increase in DCV/DC ratio, implying vesicle swelling due to increased osmotically active free catecholamines. Upon challenge with 2 U/kg insulin, there was a diminution in adrenomedullary EPI, no change in NE and a very large increase in the EPI and NE precursor dopamine (DA), consistent with increased catecholamine biosynthesis during prolonged secretion. We found dilated mitochondrial cristae, endoplasmic reticulum and Golgi complex, as well as increased synaptic mitochondria, synaptic vesicles and glycogen granules in Chga-KO mice compared to WT mice, suggesting that decreased granulogenesis and catecholamine storage in CgA-deficient mouse adrenal medulla is compensated by increased VMAT-dependent catecholamine update into storage vesicles, at the expense of enhanced energy expenditure by the chromaffin cell.

Catecholamine-secreting paraganglioma: the challenges of perioperative management

An asymptomatic 48-year-old man presented with a right-sided neck mass. A CT scan demonstrated a lesion at the carotid bifurcation and an angiogram showed splaying of the carotid arteries. His plasma metanephrines were raised confirming a catecholamine-secreting paraganglioma. Metaiodobenzylguanidine single-photon emission CT showed focal high tracer uptake in the right of the neck. Histology revealed a tumour, arising within a nerve, composed of oval-shaped cells arranged in nested (zellballen) as well as in trabecular patterns. Immunohistochemistry was positive for neuroendocrine markers chromogranin A, synaptophysin and CD56. Preoperative management included an endocrinologist initiating α-adrenergic and β-adrenergic blockers. Intraoperatively, acute hypertension occurred whenever the tumour was manipulated. Close communication between the surgeons and the anaesthetist allowed for these episodes to be predicted and treated with fast-acting antihypertensives such as sodium nitroprusside. Postoperatively, the patient recovered well and his antihypertensives were discontinued.

VGF and Its C-Terminal Peptide TLQP-62 Regulate Memory Formation in Hippocampus via a BDNF-TrkB-Dependent Mechanism

Regulated expression and secretion of BDNF, which activates TrkB receptor signaling, is known to play a critical role in cognition. Identification of additional modulators of cognitive behavior that regulate activity-dependent BDNF secretion and/or potentiate TrkB receptor signaling would therefore be of considerable interest. In this study, we show in the adult mouse hippocampus that expression of the granin family gene Vgf and secretion of its C-terminal VGF-derived peptide TLQP-62 are required for fear memory formation. We found that hippocampal VGF expression and TLQP-62 levels were transiently induced after fear memory training and that sequestering secreted TLQP-62 peptide in the hippocampus immediately after training impaired memory formation. Reduced VGF expression was found to impair learning-evoked Rac1 induction and phosphorylation of the synaptic plasticity markers cofilin and synapsin in the adult mouse hippocampus. Moreover, TLQP-62 induced acute, transient activation of the TrkB receptor and subsequent CREB phosphorylation in hippocampal slice preparations and its administration immediately after training enhanced long-term memory formation. A critical role of BDNF-TrkB signaling as a downstream effector in VGF/TLQP-62-mediated memory consolidation was further revealed by posttraining activation of BDNF-TrkB signaling, which rescued impaired fear memory resulting from hippocampal administration of anti-VGF antibodies or germline VGF ablation in mice. We propose that VGF is a critical component of a positive BDNF-TrkB regulatory loop and, upon its induced expression by memory training, the TLQP-62 peptide rapidly reinforces BDNF-TrkB signaling, regulating hippocampal memory consolidation.

SIGNIFICANCE STATEMENT

Identification of the cellular and molecular mechanisms that regulate long-term memory formation and storage may provide alternative treatment modalities for degenerative and neuropsychiatric memory disorders. The neurotrophin BDNF plays a prominent role in cognitive function, and rapidly and robustly induces expression of VGF, a secreted neuronal peptide precursor. VGF knock-out mice have impaired fear and spatial memory. Our study shows that VGF and VGF-derived peptide TLQP-62 are transiently induced after fear memory training, leading to increased BDNF/TrkB signaling, and that sequestration of hippocampal TLQP-62 immediately after training impairs memory formation. We propose that TLQP-62 is a critical component of a positive regulatory loop that is induced by memory training, rapidly reinforces BDNF-TrkB signaling, and is required for hippocampal memory consolidation.

Differential Reovirus-Specific and Herpesvirus-Specific Activator Protein 1 Activation of Secretogranin II Leads to Altered Virus Secretion

Viruses utilize host cell machinery for propagation and manage to evade cellular host defense mechanisms in the process. Much remains unknown regarding how the host responds to viral infection. We recently performed global proteomic screens of mammalian reovirus TIL- and T3D-infected and herpesvirus (herpes simplex virus 1 [HSV-1])-infected HEK293 cells. The nonenveloped RNA reoviruses caused an upregulation, whereas the enveloped DNA HSV-1 caused a downregulation, of cellular secretogranin II (SCG2). SCG2, a member of the granin family that functions in hormonal peptide sorting into secretory vesicles, has not been linked to virus infections previously. We confirmed SCG2 upregulation and found SCG2 phosphorylation by 18 h postinfection (hpi) in reovirus-infected cells. We also found a decrease in the amount of reovirus secretion from SCG2 knockdown cells. Similar analyses of cells infected with HSV-1 showed an increase in the amount of secreted virus. Analysis of the stress-activated protein kinase (SAPK)/Jun N-terminal protein kinase (JNK) pathway indicated that each virus activates different pathways leading to activator protein 1 (AP-1) activation, which is the known SCG2 transcription activator. We conclude from these experiments that the negative correlation between SCG2 quantity and virus secretion for both viruses indicates a virus-specific role for SCG2 during infection.

IMPORTANCE

Mammalian reoviruses affect the gastrointestinal system or cause respiratory infections in humans. Recent work has shown that all mammalian reovirus strains (most specifically T3D) may be useful oncolytic agents. The ubiquitous herpes simplex viruses cause common sores in mucosal areas of their host and have coevolved with hosts over many years. Both of these virus species are prototypical representatives of their viral families, and investigation of these viruses can lead to further knowledge of how they and the other more pathogenic members of their respective families interact with the host. Here we show that secretogranin II (SCG2), a protein not previously studied in the context of virus infections, alters virus output in a virus-specific manner and that the quantity of SCG2 is inversely related to amounts of infectious-virus secretion. Herpesviruses may target this protein to facilitate enhanced virus release from the host.

Research Resource: A Chromogranin A Reporter for Serotonin and Histamine Secreting Enteroendocrine Cells

Chromogranin A (ChgA) is an acidic protein found in large dense-core secretory vesicles and generally considered to be expressed in all enteroendocrine cells of the gastrointestinal (GI) tract. Here, we characterize a novel reporter mouse for ChgA, ChgA-humanized Renilla reniformis (hr)GFP. The hrGFP reporter was found in the monoamine-storing chromaffin cells of the adrenal medulla, where ChgA was originally discovered. hrGFP also was expressed in enteroendocrine cells throughout the GI tract, faithfully after the expression of ChgA, as characterized by immunohistochemistry and quantitative PCR analysis of fluorescence-activated cell sorting-purified cells, although the expression in the small intestine was weak compared with that of the stomach and colon. In the stomach, hrGFP was highly expressed in almost all histamine-storing enterochromaffin (EC)-like cells, at a lower level in the majority of serotonin-storing EC cells and ghrelin cells, in a small fraction of somatostatin cells, but was absent from gastrin cells. In the small intestine, the hrGFP reporter was selectively, but weakly expressed in EC cells, although not in any peptide-storing enteroendocrine cells. In the colon, hrGFP was exclusively expressed in EC cells but absent from the peptide-storing enteroendocrine cells. In contrast, in the pancreas, hrGFP was expressed in β-cells, α-cells, and a fraction of pancreatic polypeptide cells. It is concluded that ChgA-hrGFP in the GI tract functions as an effective reporter, particularly for the large populations of still poorly characterized monoamine-storing enteroendocrine cells. Furthermore, our findings substantiate the potential function of ChgA as a monoamine-binding protein that facilitates the regulated endocrine secretion of large amounts of monoamines from enteroendocrine cells.

The VGF-derived peptide TLQP-62 modulates insulin secretion and glucose homeostasis

Insulin secretion control is critical for glucose homeostasis. Paracrine and autocrine molecules secreted by cells of the islet of Langerhans, as well as by intramural and autonomic neurons, control the release of different hormones that modulate insulin secretion. In pancreatic islets, the abundant presence of the granin protein VGF (nonacronymic; unrelated to VEGF) suggests that some of its proteolytically derived peptides could modulate hormone release. Thus, in the present study, we screened several VGF-derived peptides for their ability to induce insulin secretion, and we identified the VGF C-terminal peptide TLQP-62 as the most effective fragment. TLQP-62 induced a potent increase in basal insulin secretion as well as in glucose-stimulated insulin secretion in several insulinoma cell lines. We found that this peptide stimulated insulin release via increased intracellular calcium mobilization and fast expression of the insulin 1 gene. Moreover, the peripheral injection of TLQP-62 in mice improved glucose tolerance. Together, the present findings suggest that TLQP-62, acting as an endocrine, paracrine, or autocrine factor, can be considered a new, strong insulinotropic peptide that can be targeted for innovative antidiabetic drug discovery programs.

Expression of Secretogranin III in Chicken Endocrine Cells: Its Relevance to the Secretory Granule Properties of Peptide Prohormone Processing and Bioactive Amine Content

The expression of secretogranin III (SgIII) in chicken endocrine cells has not been investigated. There is limited data available for the immunohistochemical localization of SgIII in the brain, pituitary, and pancreatic islets of humans and rodents. In the present study, we used immunoblotting to reveal the similarities between the expression patterns of SgIII in the common endocrine glands of chickens and rats. The protein-protein interactions between SgIII and chromogranin A (CgA) mediate the sorting of CgA/prohormone core aggregates to the secretory granule membrane. We examined these interactions using co-immunoprecipitation in chicken endocrine tissues. Using immunohistochemistry, we also examined the expression of SgIII in a wide range of chicken endocrine glands and gastrointestinal endocrine cells (GECs). SgIII was expressed in the pituitary, pineal, adrenal (medullary parts), parathyroid, and ultimobranchial glands, but not in the thyroid gland. It was also expressed in GECs of the stomach (proventriculus and gizzard), small and large intestines, and pancreatic islet cells. These SgIII-expressing cells co-expressed serotonin, somatostatin, gastric inhibitory polypeptide, glucagon-like peptide-1, glucagon, or insulin. These results suggest that SgIII is expressed in the endocrine cells that secrete peptide hormones, which mature via the intragranular enzymatic processing of prohormones and physiologically active amines in chickens.

Role of VGF-derived carboxy-terminal peptides in energy balance and reproduction: analysis of "humanized" knockin mice expressing full-length or truncated VGF

Targeted deletion of VGF, a secreted neuronal and endocrine peptide precursor, produces lean, hypermetabolic, and infertile mice that are resistant to diet-, lesion-, and genetically-induced obesity and diabetes. Previous studies suggest that VGF controls energy expenditure (EE), fat storage, and lipolysis, whereas VGF C-terminal peptides also regulate reproductive behavior and glucose homeostasis. To assess the functional equivalence of human VGF(1-615) (hVGF) and mouse VGF(1-617) (mVGF), and to elucidate the function of the VGF C-terminal region in the regulation of energy balance and susceptibility to obesity, we generated humanized VGF knockin mouse models expressing full-length hVGF or a C-terminally deleted human VGF(1-524) (hSNP), encoded by a single nucleotide polymorphism (rs35400704). We show that homozygous male and female hVGF and hSNP mice are fertile. hVGF female mice had significantly increased body weight compared with wild-type mice, whereas hSNP mice have reduced adiposity, increased activity- and nonactivity-related EE, and improved glucose tolerance, indicating that VGF C-terminal peptides are not required for reproductive function, but 1 or more specific VGF C-terminal peptides are likely to be critical regulators of EE. Taken together, our results suggest that human and mouse VGF proteins are largely functionally conserved but that species-specific differences in VGF peptide function, perhaps a result of known differences in receptor binding affinity, likely alter the metabolic phenotype of hVGF compared with mVGF mice, and in hSNP mice in which several C-terminal VGF peptides are ablated, result in significantly increased activity- and nonactivity-related EE.

VGF, Which Is Induced Transcriptionally in Stroke Brain, Enhances Neurite Extension and Confers Protection Against Ischemia In Vitro

Ischemic stroke is a devastating neural event as currently no therapies other than physical rehabilitation are available to enhance recovery after stroke. To identify endogenous mediators to repair stroke brain, we performed the expression profiling analysis of transcripts in the mouse photothrombotic stroke brain. Based on real-time PCR analysis, we found VGF, identified as a nerve growth factor (NGF)-regulated transcript, was induced transcriptionally in stroke brain at 1-7 days after insult. The immunoreactivites of VGF were observed in the neurons around the ischemic core of stroke brain. Experiments with various inhibitors and plasmid transfections indicated that cAMP response element binding protein-mediated complex signaling pathways are possibly implicated in the NGF-mediated VGF expressions in vitro. Furthermore, the over-expression of VGF promoted neurite extensions and conferred protections from ischemic stress in vitro. These findings raise the possibility the application of VGF could be one of the promising therapeutic strategies to enhance recovery after stroke.

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.

Chromogranin A and cortisol at intraoperative repeated noxious stimuli: Surgical stress in a dog model

Objectives:

Biomarkers representing sympathetic tone and the surgical stress response are measured to objectively evaluate surgical techniques and anaesthetic protocols. If a part of the intraoperative procedure is repeated on the contralateral organ, one animal may potentially serve as its own control and, if so, may minimize the problem of individual differences of the stress response to anaesthesia and surgery. This study aimed to investigate the use of chromogranin A for measurement of the intraoperative sympathetic tone. Additional aims were to investigate chromogranin A and cortisol as indicators of the intraoperative surgical stress response caused by repeated noxious stimuli in dogs subjected to ovariohysterectomy and thereby to investigate the possibility of one dog serving as its own control.

Methods:

Experiments were carried out on 10 dogs subjected to ovariohysterectomy. Perioperative blood samples (0–6) were collected after premedication, immediately before induction of anaesthesia (0), after induction of anaesthesia and before incision (1), before (2) and after (3) removal of the first ovary, after a 15-min pause before removal of the second ovary (4), after removal of the second ovary (5) and after closing the abdomen (6). Plasma chromogranin A and cortisol were analysed.

Results:

Plasma chromogranin A did not change. Plasma cortisol concentration did not change between before anaesthesia and opening of the abdomen. Plasma cortisol increased at removal of the first ovary. Cortisol did not change at removal of the second ovary but remained increased compared to initial sample.

Conclusion:

The results suggest chromogranin A is a poor indicator of intraoperative sympathetic tone during elective surgery in dogs. Cortisol measurement was useful for assessment of intraoperative noxious stimuli. However, at these test conditions, neither plasma chromogranin A nor plasma cortisol was useful for assessment of repeated intraoperative noxious stimuli where one dog served as its own control.

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.

A common genetic variant of the chromogranin A-derived peptide catestatin is associated with atherogenesis and hypertension in a Japanese population

Chromogranin A (CHGA) is a major protein in the secretory granules of chromaffin cells. CHGA also gives rise to cardiovascular/metabolism regulatory peptides, such as catestatin (CST) and pancreastatin (PST). While CST is a potent inhibitor of catecholamine secretion, PST is a potent physiological inhibitor of glucose-induced insulin secretion. Recently, several SNPs were identified in the CST and PST domains of CHGA locus in different populations. Among the discovered SNPs, CST variant allele Ser-364 was associated with blood pressure alteration and PST variant allele Ser-297 was associated with significantly higher plasma glucose level. In this study, we examined whether these CST and PST variant alleles exist and influence cardiovascular and metabolic phenotypes in Japanese population. Our study comprised of 343 Japanese subjects aged 45-85 years (143 men and 200 women, mean age 66 ± 8 years). We determined the genotypes of CST and PST by PCR-direct sequencing method and carried out genotype-phenotype association analysis. In 343 participants, the minor allele frequency of CST variant Ser-364 was 6.10%. On the other hand, we did not detect the PST variant Ser-297 in this entire study population. The presence of Ser-364 allele was associated with increased in baPWV (an index of systemic arterial stiffness) that suggests an initiation and/or progression atherogenesis and hypertension. The Ser-364 allele was also associated with elevated systolic blood pressure and pulse pressure, consistent with increased baPWV. In conclusion, the CST Ser-364 allele may increase the risk for cardiovascular diseases in Japanese population.

Pancreastatin-dependent inflammatory signaling mediates obesity-induced insulin resistance

Chromogranin A knockout (Chga-KO) mice exhibit enhanced insulin sensitivity despite obesity. Here, we probed the role of the chromogranin A-derived peptide pancreastatin (PST: CHGA(273-301)) by investigating the effect of diet-induced obesity (DIO) on insulin sensitivity of these mice. We found that on a high-fat diet (HFD), Chga-KO mice (KO-DIO) remain more insulin sensitive than wild-type DIO (WT-DIO) mice. Concomitant with this phenotype is enhanced Akt and AMPK signaling in muscle and white adipose tissue (WAT) as well as increased FoxO1 phosphorylation and expression of mature Srebp-1c in liver and downregulation of the hepatic gluconeogenic genes, Pepck and G6pase. KO-DIO mice also exhibited downregulation of cytokines and proinflammatory genes and upregulation of anti-inflammatory genes in WAT, and peritoneal macrophages from KO mice displayed similarly reduced proinflammatory gene expression. The insulin-sensitive, anti-inflammatory phenotype of KO-DIO mice is masked by supplementing PST. Conversely, a PST variant peptide PSTv1 (PST-NΔ3: CHGA(276-301)), lacking PST activity, simulated the KO phenotype by sensitizing WT-DIO mice to insulin. In summary, the reduced inflammation due to PST deficiency prevented the development of insulin resistance in KO-DIO mice. Thus, obesity manifests insulin resistance only in the presence of PST, and in its absence obesity is dissociated from insulin resistance.

GNAS mutations in Pseudohypoparathyroidism type 1a and related disorders

Pseudohypoparathyroidism type 1a (PHP1a) is characterized by hypocalcaemia and hyperphosphatemia due to parathyroid hormone resistance, in association with the features of Albright's hereditary osteodystrophy (AHO). PHP1a is caused by maternally inherited inactivating mutations of Gs-alpha, which is encoded by a complex imprinted locus termed GNAS. Paternally inherited mutations can lead either to pseudopseudohypoparathyroidism (PPHP) characterized by AHO alone, or to progressive osseous heteroplasia (POH), characterized by severe heterotopic ossification. The clinical aspects and molecular genetics of PHP1a and its related disorders are reviewed together with the 343 kindreds with Gs-alpha germline mutations reported so far in the literature. These 343 (176 different) mutations are scattered throughout the 13 exons that encode Gs-alpha and consist of 44.9% frameshift, 28.0% missense, 14.0% nonsense, and 9.0% splice-site mutations, 3.2% in-frame deletions or insertions, and 0.9% whole or partial gene deletions. Frameshift and other highly disruptive mutations were more frequent in the reported 37 POH kindreds than in PHP1a/PPHP kindreds (97.3% vs. 68.7%, P < 0.0001). This mutation update and respective genotype-phenotype data may be of use for diagnostic and research purposes and contribute to a better understanding of these complex disorders.

The TLQP-21 peptide activates the G-protein-coupled receptor C3aR1 via a folding-upon-binding mechanism

TLQP-21, a VGF-encoded peptide is emerging as a novel target for obesity-associated disorders. TLQP-21 is found in the sympathetic nerve terminals in the adipose tissue and targets the G-protein-coupled receptor complement-3a receptor1 (C3aR1). The mechanisms of TLQP-21-induced receptor activation remain unexplored. Here, we report that TLQP-21 is intrinsically disordered and undergoes a disorder-to-order transition, adopting an α-helical conformation upon targeting cells expressing the C3aR1. We determined that the hot spots for TLQP-21 are located at the C terminus, with mutations in the last four amino acids progressively reducing the bioactivity and, a single site mutation (R21A) or C-terminal amidation abolishing its function completely. Additionally, the human TLQP-21 sequence carrying a S20A substitution activates the human C3aR1 receptor with lower potency compared to the rodent sequence. These studies reveal the mechanism of action of TLQP-21 and provide molecular templates for designing agonists and antagonists to modulate C3aR1 functions.

Quantitative proteomics of delirium cerebrospinal fluid

Delirium is a common cause and complication of hospitalization in older people, being associated with higher risk of future dementia and progression of existing dementia. However relatively little data are available on which biochemical pathways are dysregulated in the brain during delirium episodes, whether there are protein expression changes common among delirium subjects and whether there are any changes which correlate with the severity of delirium. We now present the first proteomic analysis of delirium cerebrospinal fluid (CSF), and one of few studies exploring protein expression changes in delirium. More than 270 proteins were identified in two delirium cohorts, 16 of which were dysregulated in at least 8 of 17 delirium subjects compared with a mild Alzheimer's disease neurological control group, and 31 proteins were significantly correlated with cognitive scores (mini-mental state exam and acute physiology and chronic health evaluation III). Bioinformatics analyses revealed expression changes in several protein family groups, including apolipoproteins, secretogranins/chromogranins, clotting/fibrinolysis factors, serine protease inhibitors and acute-phase response elements. These data not only provide confirmatory evidence that the inflammatory response is a component of delirium, but also reveal dysregulation of protein expression in a number of novel and unexpected clusters of proteins, in particular the granins. Another surprising outcome of this work is the level of similarity of CSF protein profiles in delirium patients, given the diversity of causes of this syndrome. These data provide additional elements for consideration in the pathophysiology of delirium as well as potential biomarker candidates for delirium diagnosis.

Identification of chondroitin sulfate linkage region glycopeptides reveals prohormones as a novel class of proteoglycans

Vertebrates produce various chondroitin sulfate proteoglycans (CSPGs) that are important structural components of cartilage and other connective tissues. CSPGs also contribute to the regulation of more specialized processes such as neurogenesis and angiogenesis. Although many aspects of CSPGs have been studied extensively, little is known of where the CS chains are attached on the core proteins and so far, only a limited number of CSPGs have been identified. Obtaining global information on glycan structures and attachment sites would contribute to our understanding of the complex proteoglycan structures and may also assist in assigning CSPG specific functions. In the present work, we have developed a glycoproteomics approach that characterizes CS linkage regions, attachment sites, and identities of core proteins. CSPGs were enriched from human urine and cerebrospinal fluid samples by strong-anion-exchange chromatography, digested with chondroitinase ABC, a specific CS-lyase used to reduce the CS chain lengths and subsequently analyzed by nLC-MS/MS with a novel glycopeptide search algorithm. The protocol enabled the identification of 13 novel CSPGs, in addition to 13 previously established CSPGs, demonstrating that this approach can be routinely used to characterize CSPGs in complex human samples. Surprisingly, five of the identified CSPGs are traditionally defined as prohormones (cholecystokinin, chromogranin A, neuropeptide W, secretogranin-1, and secretogranin-3), typically stored and secreted from granules of endocrine cells. We hypothesized that the CS side chain may influence the assembly and structural organization of secretory granules and applied surface plasmon resonance spectroscopy to show that CS actually promotes the assembly of chromogranin A core proteins in vitro. This activity required mild acidic pH and suggests that the CS-side chains may also influence the self-assembly of chromogranin A in vivo giving a possible explanation to previous observations that chromogranin A has an inherent property to assemble in the acidic milieu of secretory granules.

The surging role of Chromogranin A in cardiovascular homeostasis

Together with Chromogranin B and Secretogranins, Chromogranin A (CGA) is stored in secretory (chromaffin) granules of the diffuse neuroendocrine system and released with noradrenalin and adrenalin. Co-stored within the granule together with neuropeptideY, cardiac natriuretic peptide hormones, several prohormones and their proteolytic enzymes, CGA is a multifunctional protein and a major marker of the sympatho-adrenal neuroendocrine activity. Due to its partial processing to several biologically active peptides, CGA appears an important pro-hormone implicated in relevant modulatory actions on endocrine, cardiovascular, metabolic, and immune systems through both direct and indirect sympatho-adrenergic interactions. As a part of this scenario, we here illustrate the emerging role exerted by the full-length CGA and its three derived fragments, i.e., Vasostatin 1, catestatin and serpinin, in the control of circulatory homeostasis with particular emphasis on their cardio-vascular actions under both physiological and physio-pathological conditions. The Vasostatin 1- and catestatin-induced cardiodepressive influences are achieved through anti-beta-adrenergic-NO-cGMP signaling, while serpinin acts like beta1-adrenergic agonist through AD-cAMP-independent NO signaling. On the whole, these actions contribute to widen our knowledge regarding the sympatho-chromaffin control of the cardiovascular system and its highly integrated “whip-brake” networks.

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.

Zebrafish pituitary gene expression before and after sexual maturation

Sexual maturation and somatic growth cessation are associated with adolescent development, which is precisely controlled by interconnected neuroendocrine regulatory pathways in the endogenous endocrine system. The pituitary gland is one of the key regulators of the endocrine system. By analyzing the RNA sequencing (RNA-seq) transcriptome before and after sexual maturation, in this study, we characterized the global gene expression patterns in zebrafish pituitaries at 45 and 90 days post-fertilization (dpf). A total of 15 043 annotated genes were expressed in the pituitary tissue, 3072 of which were differentially expressed with a greater than or equal to twofold change between pituitaries at 45 and 90 dpf. In the pituitary transcriptome, the most abundant transcript was gh. The expression levels of gh remained high even after sexual maturation at 90 dpf. Among the eight major pituitary hormone genes, lhb was the only gene that exhibited a significant change in its expression levels between 45 and 90 dpf. Significant changes in the pituitary transcripts included genes involved in the regulation of immune responses, bone metabolism, and hormone secretion processes during the juvenile-sexual maturity transition. Real-time quantitative PCR analysis was carried out to verify the RNA-seq transcriptome results and demonstrated that the expression patterns of the eight major pituitary hormone genes did not exhibit a significant gender difference at 90 dpf. For the first time, we report the quantitative global gene expression patterns at the juvenile and sexual maturity stages. These expression patterns may account for the dynamic neuroendocrine regulation observed in body metabolism.

The VGF-derived peptide TLQP-21 contributes to inflammatory and nerve injury-induced hypersensitivity

VGF (nonacronymic) is a granin-like protein that is packaged and proteolytically processed within the regulated secretory pathway. VGF and peptides derived from its processing have been implicated in neuroplasticity associated with learning, memory, depression, and chronic pain. In sensory neurons, VGF is rapidly increased following peripheral nerve injury and inflammation. Several bioactive peptides generated from the C-terminus of VGF have pronociceptive spinal effects. The goal of the present study was to examine the spinal effects of the peptide TLQP-21 and determine whether it participates in spinal mechanisms of persistent pain. Application of exogenous TLQP-21 induced dose-dependent thermal hyperalgesia in the warm-water immersion tail-withdrawal test. This hyperalgesia was inhibited by a p38 mitogen-activated protein kinase inhibitor, as well as inhibitors of cyclooxygenase and lipoxygenase. We used immunoneutralization of TLQP-21 to determine the function of the endogenous peptide in mechanisms underlying persistent pain. In mice injected intradermally with complete Freund adjuvant, intrathecal treatment with anti-TLQP-21 immediately prior to or 5hours after induction of inflammation dose-dependently inhibited tactile hypersensitivity and thermal hyperalgesia. Intrathecal anti-TL21 administration also attenuated the development and maintenance of tactile hypersensitivity in the spared nerve injury model of neuropathic pain. These results provide evidence that endogenous TLQP-21 peptide contributes to the mechanisms of spinal neuroplasticity after inflammation and nerve injury.

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.

Cryptic collagen IV promotes cell migration and adhesion in myeloid leukemia

Previously, we showed that discoidin domain receptor 1 (DDR1), a class of collagen-activated receptor tyrosine kinase (RTK) was highly upregulated on bone marrow (BM)-derived CD33+ leukemic blasts of acute myeloid leukemia (AML) patients. Herein as DDR1 is a class of collagen-activated RTK, we attempt to understand the role of native and remodeled collagen IV in BM microenvironment and its functional significance in leukemic cells. Exposure to denatured collagen IV significantly increased the migration and adhesion of K562 cells, which also resulted in increased activation of DDR1 and AKT. Further, levels of MMP9 were increased in conditioned media (CM) of denatured collagen IV exposed cells. Mass spectrometric liquid chromatography/tandem mass spectrometry QSTAR proteomic analysis revealed exclusive presence of Secretogranin 3 and InaD-like protein in the denatured collagen IV CM. Importantly, BM samples of AML patients exhibited increased levels of remodeled collagen IV compared to native as analyzed via anti-HUIV26 antibody. Taken together, for the first time, we demonstrate that remodeled collagen IV is a potent activator of DDR1 and AKT that also modulates both migration and adhesion of myeloid leukemia cells. Additionally, high levels of the HUIV26 cryptic collagen IV epitope are expressed in BM of AML patients. Further understanding of this phenomenon may lead to the development of therapeutic agents that directly modulate the BM microenvironment and attenuate leukemogenesis.