Chromogranin A immunoreactivity in human cerebrospinal fluid: properties, relationship to noradrenergic neuronal activity, and variation in neurologic disease

Cerebrospinal Fluid Levels of Chromogranin A in Parkinson's Disease and Multiple System Atrophy

Background: Chromogranin A (CgA) and other peptides from the chromogranin–secretogranin family have been recently studied as potential biomarkers of various neurodegenerative diseases, including Parkinson’s disease (PD). Methods: We measured CgA in the cerebrospinal fluid (CSF) of 119 PD patients, 18 multiple system atrophy (MSA) patients, and 31 age-matched controls. We also correlated the values with disease duration and levodopa dose equivalent. Results: In the PD patients, CSF CgA tended to be lower than the control group (median 124.5 vs. 185.2 µg/L; p = 0.057); however, the results did not reach statistical significance. CSF CgA levels in MSA were significantly lower compared to the control group (median 104.4 vs. 185.2; p = 0.014). There was no significant difference in CSF CgA between PD and MSA patients (p = 0.372). There was no association between CSF CgA and disease duration or levodopa dose equivalent in PD or in MSA. Conclusions: We observed a tendency toward lower CSF CgA levels in both PD and MSA compared to the control group; however, the difference reached statistical significance only in MSA. Based on these results, CgA may have potential as a biomarker in PD and MSA, but further studies on larger numbers of patients are needed to draw conclusions.

Chromogranins A and B and secretogranin II as prohormones for regulatory peptides from the diffuse neuroendocrine system

Chromogranin A (CgA), chromogranin B (CgB), and secretogranin II (SgII) belong to a family of uniquely acidic secretory proteins in elements of the diffuse neuroendocrine system. These "granins" are characterized by numerous pairs of basic amino acids as potential sites for intra- and extragranular processing. In response to adequate stimuli, the granins are coreleased with neurotransmitters and hormones and appear in the circulation as potential modulators of homeostatic processes. This review is directed towards functional aspects of the secreted CgA, CgB, and SgII and their biologically active sequences. Widely different effects and targets have been reported for granin-derived peptides. So far, the CgA peptides vasostatin-I, pancreastatin, and catestatin, the CgB peptides CgB(1-41) and secretolytin, and the SgII peptide secretoneurin are the most likely candidates for granin-derived regulatory peptides. Most of their effects fit into patterns of direct or indirect modulations of major functions, in particular associated with inflammatory conditions.

Regulatory peptides from chromogranin A and secretogranin II: putative modulators of cells and tissues involved in inflammatory conditions

Chromogranin A (CgA) and secretogranin II (SgII) of the granin family of uniquely acidic proteins secreted from elements of the diffuse neuroendocrine system are also produced by cells involved in inflammation. CgA and the CgA-derived peptides vasostatin-I and catestatin are products of polymorphonuclear neutrophils accumulating at sites of injury or infections while SgII and the Sg II-derived secretoneurin may contribute to neurogenic inflammation when released from sensory nerve terminals. This review is directed towards vasostatin-I, catestatin and secretoneurin as modulators of cells and tissues associated with inflammatory conditions. The accumulated literature indicates that concerted effects of vasostatin-I and catestatin may be relevant for the first-line host-defence against invading microorganisms, contrasting the apparent lack of antibacterial potencies in secretoneurin. Oppositely directed effects of vasostatin-I and secretoneurin on endothelial permeability and transendothelial extravasation are particularly striking. While vasostatin-I protects the integrity of the endothelial barrier against the disruptive effects of proinflammatory agents, secretoneurin activates transendothelial extravasation, chemotaxis and migration of leukocytes. Oppositely directed effects of vasostatin-I and secretoneurin on formation of blood vessels are also indicated, vasostatin-I inhibiting angiogenetic parameters while secretoneurin activates not only angiogenesis but also vascularization.

Cerebrospinal fluid concentrations of peptides derived from chromogranin B and secretogranin II are decreased in multiple sclerosis

Novel biomarkers for multiple sclerosis (MS) could improve diagnosis and provide clues to pathogenesis. In this study surface-enhanced laser desorption/ionization time-of-flight mass spectrometry was used to analyze protein expression in CSF from 46 MS patients, 46 healthy siblings to the patients, and 50 unrelated healthy controls. Twenty-four proteins in the mass range 2-10 kDa were expressed at significantly different levels (p < 0.01) in a robust manner when comparing the three groups. Identities of three proteins were determined using biochemical purification followed by tandem mass spectrometric analysis. Immunoprecipitation experiments confirmed the identities for two peptides derived from chromogranin B (m/z 6252) and from secretogranin II (m/z 3679). These peptides were all decreased in MS when compared with siblings or controls. Radioimmunoassays specific for each peptide confirmed these differences. The lowered concentrations did not correlate to the axonal damage marker neurofilament light protein and may thus reflect functional changes rather than neurodegeneration. Further studies will investigate the involvement of these peptides in MS pathogenesis.

The granin family of uniquely acidic proteins of the diffuse neuroendocrine system: comparative and functional aspects

The chromogranins A (CgA) and B (CgB) and secretogranin II (SgII) constitute the main members of a family of uniquely acidic secretory proteins in elements of the diffuse neuroendocrine system. These genetically distinct proteins, CgA, CgB, SgII and the less well known secretogranins III-VII are collectively referred to as 'granins' and characterised by numerous pairs of basic amino acids as potential cleavage sites for processing by the co-stored prohormone converting enzymes PC 1/3 and PC2. This review is directed towards comparative and functional aspects of the granins with emphasis on their phylogenetically conserved sequences. Recent developments provide ample evidence of widely different effects and targets for the intact granins and their derived peptides, intracellularly in the directed trafficking of storage components during granule maturation and extracellularly in autocrine, paracrine and endocrine interactions. Most of the effects assigned to the granin derived peptides fit into patterns of direct or indirect inhibitory modulations of major functions. So far, peptides derived from CgA (vasostatins, chromacin, pancreastatin, WE-14, catestatin and parastatin), CgB (secretolytin) and SgII (secretoneurin) are the most likely candidates for granin-derived regulatory peptides, of postulated relevance not only for homeostatic processes, but also for tissue assembly and repair, inflammatory responses and the first line of defence against invading microorganisms.

Migraine, but not subarachnoid hemorrhage, is associated with differentially increased NPY-like immunoreactivity in the CSF

To test whether migraine and subarachnoid hemorrhage (SAH) are associated with increased sympathetic tone, we compared the neuropeptide Y-like (NPY-LI) and chromogranin A-like immunoreactivities (LI) of cerebrospinal fluid (CSF) from migraneurs and SAH patients with those from control subjects. Increased sympathetic tone was expected to produce higher co-release of these co-stored peptides and concordant changes in their CSF levels. In addition, we investigated a possible disturbed nitric oxide homeostasis by measuring CSF nitrites (NO). More than 70% of CSF NPY-LI corresponded to the chromatographic peak (HPLC) for the intact molecule in all three groups. Migraneurs had 64% higher CSF NPY-LI, but no significant difference in CSF chromogranin A-LI, as compared to controls. In contrast, SAH patients had 74% less CSF chromogranin A-LI and a trend to lower NPY-LI, as compared to controls. No differences in CSF NO were detected among groups. These results argue against an increased sympathetic tone in patients with either migraine or SAH, and suggest that the higher CSF NPY-LI of migraneurs probably originates from central neurons. Furthermore, our findings in SAH patients argue in favor of a decreased sympathetic tone; this could be a homeostatic response to counterbalance vasoconstriction mediated by other mechanisms.

Chromogranin A in the central nervous system of the rat: pan-neuronal expression of its mRNA and selective expression of the protein

Chromogranin A, a glycoprotein stored in secretory granules of neuroendocrine cells, displays a widespread distribution throughout the central nervous system of a variety of species. In situ hybridization histochemistry was employed to investigate the localization of chromogranin A mRNA in the central nervous system of the rat. The previously characterized monoclonal antibody, LK2H-10, was employed in an immunohistochemical study to compare the topographic localization of the chromogranin A protein with that of its mRNA. Although the latter, as revealed by in situ hybridization, displayed a ubiquitous, pan-neuronal localization throughout the rat brain, LK2H-10 immunoreactive cell bodies and axon terminals were disposed in a widespread, but highly regionally differential, distribution. This discrepancy suggests that chromogranin A is processed in a regionally differential fashion in the rat brain to yield one or multiple variant forms, one of which is specifically recognized by LK2H-10. Catecholaminergic cell groups consistently displayed LK2H-10 immunoreactivity. LK2H-10 immunopositive axon terminals were prominent in the circumventricular organs. In addition, LK2H-10 immunoreactivity was also detected in a subset of astrocytes which demonstrated a widespread, but anatomically restricted, pattern of distribution. Consequently, the variant of chromogranin A labelled by LK2H-10 represents a novel neurochemical marker for regionally differential astrocytic diversity.

Reduction of chromogranin A and B but not C in the cerebrospinal fluid in subjects with schizophrenia

The granins (secretogranins/chromogranins) are a family of soluble proteins stored and released from the secretory large dense-core vesicles of the synapse. Schizophrenia is a common and devastating brain disorder. Although the aetiology of schizophrenia is unknown, data are accumulating that synaptic disturbance or damage may be of importance. The objective of this study was to compare the levels of chromogranin A, B and C in the cerebrospinal fluid (CSF) of patients with schizophrenia and healthy controls. CSF chromogranin levels were measured by RIA in 33 subsequent admissions of patients with psychotic disorder and in 31 healthy controls. The levels of CSF chromogranin A (11.8+/-3.0 vs 14.8+/-4.8 nmol/l, P=0.004), chromogranin B (3.4+/-0.49 vs 3.7+/-0.58 nmol/l, P=0.02), but not chromogranin C (70.2+/-15.7 vs 65.3+/-20.4 pmol/l, P=0.29) were lower in the schizophrenic patients than in the healthy controls. These data indicate that two widespread constituents of large dense-core vesicles, i.e. chromogranin A and chromogranin B, are altered in chronic schizophrenic patients.

CSF of neuroleptic-naive first-episode schizophrenic patients: levels of biogenic amines, substance P, and peptides derived from chromogranin A (GE-25) and secretogranin II (secretoneurin)

Lumbar cerebrospinal fluid (CSF) was collected from controls and neuroleptic-naive patients with their first acute schizophrenic episode. The CSF was analyzed for several biogenic amines and their metabolites [dopamine,dihydroxyphenylacetic acid (DOPAC), noradrenaline, 5-hydroxytryptamine (5-HT), 5-hydroxyindolacetic acid (5-HIAA)]. For these transmitters, which are stored and secreted from synaptic vesicles, there was no significant difference between controls and schizophrenic patients. As constituents of large dense-core vesicles substance P (SP) and GE-25 (derived from chromogranin A)-and secretoneurin (derived from secretogranin 11)-immunoreactivities were determined. SP-like immunoreactivity levels did not differ between controls and patients; however, GE-25 was elevated and especially the GE-25/secretoneurin ratio was significantly (p < .001) higher in patients. Characterization of the immunoreactivities by high-performance liquid chromatography did not reveal any difference between patients (n = 3) and controls in the processing of the two proproteins chromogranin A and secretogranin II. These data indicate that proteolytic processing of the two widespread constituents of large dense-core vesicles, i.e., chromogranin A and secretogranin II, is not altered in schizophrenic patients. The increase in the chromogranin A /secretoneurin ratio in schizophrenic patients deserves further investigation in order to elucidate its possible pathogenetic significance.

Hereditary intermediate phenotypes in African American hypertension

OBJECTIVE

Essential hypertension is a heterogeneous and multifactorial disorder and is at least twice as frequent among African Americans as in the general population. Inheritance of high blood pressure is complex, with the gene(s) responsible for hypertension still remaining elusive. A useful strategy for investigating the heritability of hypertension is to evaluate 'intermediate phenotypes'--simple Mendelian or monogenic traits that are associated with hypertension. These intermediate steps may identify potential pathophysiological factors that antedate the development of high blood pressure and suggest candidate genes. We are attempting to identify and characterize several such intermediate phenotypes, in particular as these might apply to hypertension in African Americans.

METHODS

We studied several physiological and biochemical candidate intermediate phenotypes in untreated black and white patients with essential hypertension and in their normotensive counterparts stratified by genetic risk of hypertension.

RESULTS AND CONCLUSIONS

Promising intermediate phenotypes, which may be useful for studies in African American families, include baroreceptor sensitivity to low and high pressure stimuli, cold pressor test responses, and biochemical markers such as plasma chromogranin A, dopamine-beta-hydroxylase and urinary kallikrein excretion. Identification of genes involved in complex traits such as hypertension may be facilitated by the intermediate phenotype approach, combined with recent advances in quantitative genetics and linkage mapping. Further studies are needed to pinpoint the nature of genes in African American hypertension.

Chromogranin A triggers a phenotypic transformation and the generation of nitric oxide in brain microglial cells

Chromogranin A is an ubiquitous 48,000 mol. wt secretory protein stored and released from many neuroendocrine cells and neurons. In human brain, chromogranin A is a common feature of regions that are known to be affected by various neurodegenerative pathologies such as Alzheimer's, Parkinson's and Pick's diseases. Brain degenerative areas are generally infiltrated by activated microglial cells, the resident macrophage cell population within the central nervous system. Here, we report that both recombinant human chromogranin A and chromogranin A purified from bovine chromaffin granules trigger drastic morphological changes in rat microglial cells maintained in culture. Microglial cells exposed to chromogranin A adopted a flattened amoeboid shape and, this change was associated with an accumulation of actin in the subplasmalemmal region, as observed by immunocytochemistry and confocal laser microscopy. In single microglial cells loaded with indo-1, chromogranin A elicited a rapid and transient increase in [Ca2+]i which preceded the reorganization of actin cytoskeleton. The activity of nitric oxide synthase was estimated by measuring the accumulation of nitrite in the culture medium. Both recombinant human chromogranin A and bovine chromogranin A triggered an important accumulation of nitrite comparable to that induced by lipopolysaccharide, a well-known activator of microglia. The effect of chromogranin A was dose dependent, inhibited by N omega-nitro-L-arginine methyl ester, a competitive inhibitor of nitric oxide synthase, and by cycloheximide, an inhibitor of protein synthesis. These findings suggest that chromogranin A induces an activated phenotype of microglia, and thus may have a role in the pathogenesis of neuronal degeneration in the brain.

Chromogranin A in human hypertension. Influence of heredity

Multiple heritable traits are associated with essential (genetic) hypertension in humans. Because chromogranin A is increased in both human and rodent genetic hypertension, we examined the influence of heredity and blood pressure on chromogranin A in humans. In estimates derived from among- and within-pair variance in monozygotic versus dizygotic twins, plasma chromogranin A displayed significant (F15,18 = 2.93, P = .016) genetic variance (sigma 2 g), and its broad-sense heritability was high (h2B = 0.983). Plasma chromogranin A was increased in essential hypertension (99.9 +/- 6.7 versus 62.8 +/- 4.7 ng/mL, P < .001) but was influenced little by genetic risk for (family history of) hypertension (in normotensive or hypertensive subjects), by race, or by several antihypertensive therapies (angiotensin-converting enzyme inhibitor, diuretic, or beta-adrenergic antagonist). In normotensive subjects at genetic risk for essential hypertension, neither basal nor sympathoadrenal stress-evoked chromogranin A differed from values found in subjects not at risk. In established essential hypertension, plasma chromogranin A responses to adrenal medullary (insulin-evoked hypoglycemia) or sympathetic neuronal (dynamic exercise) activation were exaggerated, whereas responses to sympathoadrenal suppression (ganglionic blockade) were diminished, suggesting increased vesicular stores of chromogranin A and an adrenergic origin of the augmented chromogranin A expression in this disorder. We conclude that plasma chromogranin A displays substantial heritability and is increased in established essential hypertension. Its elevation in established hypertension is associated with evidence of increased vesicular stores of the protein and with adrenergic hyperactivity but is influenced little by customary antihypertensive therapies. However, the chromogranin A elevation is not evident early in the course of genetic hypertension.

Molecular characterization of immunoreactivities of peptides derived from chromogranin A (GE-25) and from secretogranin II (secretoneurin) in human and bovine cerebrospinal fluid

Chromogranin A and secretogranin II are members of the so-called chromogranins, the acidic proteins stored in neuroendocrine large dense-core vesicles. We characterized chromogranin A and secretogranin II immunoreactivities in cerebrospinal fluid by radioimmunoassays using synthetic peptides derived from these components (GE-25 for chromogranin A and secretoneurin for secretogranin II). In lumbar cerebrospinal fluid, high levels (more than 1000 fmol/ml) of these two components were found, whereas in ventricular cerebrospinal fluid the secretoneurin levels were relatively low. The cerebrospinal fluid/serum ratio for secretoneurin was close to 170. High-performance liquid chromatography revealed that in both cerebrospinal fluid and extracts from human brain secretoneurin was the predominant immunoreactive component. In cerebrospinal fluid chromogranin A immunoreactivity was present as intermediate-sized peptides with little intact chromogranin A and free GE-25 peptide. In human brain samples smaller peptides including GE-25 were more predominant. Analogous findings for secretoneurin and chromogranin A were obtained for bovine brain samples. We can conclude that chromogranins are present in cerebrospinal fluid in concentrations much higher than those of classical neuropeptides also stored in large dense-core vesicles. Therefore, their degree of proteolytic processing can be analysed with small samples of cerebrospinal fluid. A possible disturbance of proteolytic processing in large dense-core vesicles in various pathological conditions can now be discovered.