Response of vascular smooth muscle cells to the neuropeptide secretoneurin. A functional role for migration and proliferation in vitro

Transplantation of Exercise-Induced Extracellular Vesicles as a Promising Therapeutic Approach in Ischemic Stroke

Clinical evidence affirms physical exercise is effective in preventive and rehabilitation approaches for ischemic stroke. This sustainable efficacy is independent of cardiovascular risk factors and associates substantial reprogramming in circulating extracellular vesicles (EVs). The intricate journey of pluripotent exercise-induced EVs from parental cells to the whole-body and infiltration to cerebrovascular entity offers several mechanisms to reduce stroke incidence and injury or accelerate the subsequent recovery. This review delineates the potential roles of EVs as prospective effectors of exercise. The candidate miRNA and peptide cargo of exercise-induced EVs with both atheroprotective and neuroprotective characteristics are discussed, along with their presumed targets and pathway interactions. The existing literature provides solid ground to hypothesize that the rich vesicles link exercise to stroke prevention and rehabilitation. However, there are several open questions about the exercise stressors which may optimally regulate EVs kinetic and boost brain mitochondrial adaptations. This review represents a novel perspective on achieving brain fitness against stroke through transplantation of multi-potential EVs generated by multi-parental cells, which is exceptionally reachable in an exercising body.

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

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

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

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

Excitotoxicity Alters Endogenous Secretoneurin Plasma Levels, but Supplementation with Secretoneurin Does Not Protect Against Excitotoxic Neonatal Brain Injury

Excitotoxicity plays an important role in the pathogenesis of developing brain injury. The neuropeptide secretoneurin (SN) has neuroprotective potential. The aim of this study was to investigate SN plasma concentrations following excitotoxicity and to evaluate the effect of SN as therapeutic strategy in excitotoxic newborn brain injury. Baseline SN plasma concentrations were established in healthy animals. To evaluate the effect of an excitotoxic insult on SN levels, mice pups were subjected to an intracranial injection of ibotenic acid and SN plasma concentrations were measured thereafter. To assess SN's neuroprotective potential, a subgroup of animals was randomly assigned to the following groups: i) "single treatment": vehicle 1× phosphate-buffered saline (PBS), SN 0.25 μg/g body weight (bw), SN 2.5 μg/g bw or SN 12.5 μg/g bw in a single dose 1 h after insult; ii) "acute repetitive treatment": vehicle 1× PBS or SN 0.25 μg/g bw every 24 h starting 1 h after insult; iii) "delayed repetitive treatment": vehicle 1× PBS or SN 0.25 μg/g bw every 24 h starting 60 h after insult. Animals subjected to excitotoxic injury showed significantly lower SN plasma concentrations 6 and 120 h after insult in comparison to healthy controls. Administration of SN did not positively affect lesion size, apoptotic cell death, microglial cell activation or cell proliferation. To conclude, endogenous SN plasma levels are lower in newborn mice subjected to an excitotoxic insult than in healthy controls. Supplementation with SN in various treatment regimens is not neuroprotective in the experimental animal model of excitotoxic newborn brain injury.

The Neuropeptide Secretoneurin Exerts a Direct Effect on Arteriogenesis In Vivo and In Vitro

It is well known that nerves modulate the development and remodeling of blood vessels by releasing different neuropeptides and neurotransmitters. Secretoneurin (SN), a neuropeptide located in nerve fibers along blood vessels, acts as a pro-angiogenic agent and induces postnatal vasculogenesis. However, little is known about its involvement in arteriogenesis. In the present study, we tested the hypothesis that SN promotes arteriogenesis in a rat model of hind limb ischemia, as such, we evaluated the effect of this neuropeptide on proliferation and the production of adhesion and chemotaxis molecules in vascular smooth muscle cells (VSMCs), the main component that carries the burden of the transformation of a small arteriole into a large collateral vessel. In vivo, SN-immunoreactive nerve fibers were abundantly distributed in the adventitia of the collateral vessel. Moreover, administration of SN induced cell proliferation in the vascular wall and the infiltration of inflammatory cells/macrophages to promote collateral vessel growth. This was shown by an increased density of arterioles/arteries, together with a well-developed network of collateral vessels, and well-preserved skeletal muscles. In vitro, SN exerted proliferative effects on VSMCs and stimulated these cells to express adhesion molecules. In conclusion, our data demonstrate for the first time that SN acts as a mediator of inflammation, contributing to collateral vessel growth, in addition to directly stimulating cell proliferation in the vascular wall to promote collateral vessel growth in a rat model of hind limb ischemia. Anat Rec, 301:1917-1927, 2018. © 2018 Wiley Periodicals, Inc.

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.

Administration of secretoneurin is protective in hypoxic-ischemic neonatal brain injury predominantly in the hypoxic-only hemisphere

Neonatal brain injury is a problem of global importance. To date, no causal therapies are available. A substance with considerable therapeutic potential is the endogenous neuropeptide secretoneurin (SN), which has proven to be beneficial in adult stroke. The aim of this study was to assess its effect in neonatal hypoxic-ischemic brain injury models. In vitro, primary hippocampal neurons were pre-treated with vehicle, 1µg/ml, 10µg/ml, or 50µg/ml SN and subjected to oxygen-glucose deprivation (OGD) for six hours. Cell death was assessed after a 24-h recovery period. In vivo, seven day-old CD-1 mice underwent unilateral common carotid artery ligation and were exposed to 8% oxygen/nitrogen for 20 min. SN plasma concentrations were serially determined by ELISA after insult. One hour after hypoxia, a subgroup of animals was treated with vehicle or SN. SN plasma concentrations significantly decreased 48h after insult. The number of caspase-3-positive cells was significantly lower in the hypoxic-ischemic hemisphere in the thalamus of SN-treated animals. In the hypoxic-only hemisphere administration of SN significantly reduced the number of caspase-3-positive cells (in cortex, white matter, hippocampus, thalamus and striatum) and inhibited microglial cell activation in the thalamus. SN has neuroprotective potential in neonatal brain injury. Its main action seems to be inhibition of apoptosis in the aftermath of the insult, predominantly in the hypoxic-only hemisphere. This might be explained by the less pronounced injury in this hemisphere, where blood flow and thus nutrient supply are maintained.

Antrodia cinnamomea profoundly exalted the reversion of activated hepatic stellate cells by the alteration of cellular proteins

The direct modulation of Antrodia cinnamomea (AC) on the prominent role of liver fibrosis-hepatic stellate cells (HSCs) in situ remains unclear. Firstly, the administration of A. cinnamomea mycelial extract (ACME) could improve liver morphology and histological changes including collagen formation and GPT activity in the liver of thioacetamide (TAA)-injured rats. The morphology and fatty acid restore of TAA-induced HSCs (THSCs) returned to the non-chemical induced HSCs (NHSCs) type as measured by immunofluorescence and Oil Red O staining. PPARγ was upregulated associated with the lowering of α-SMA protein in NHSC-ACME. ACME inhibited the MMP-2 activity in NHSCs by gelatin Zymography. After LC-MS/MS, the cytoskeleton (tubulin, lamin A) and heat shock protein 8 in NHSC-ACME, and guanylate kinase, brain-specific kinase, SG-II and p55 proteins were downregulated in THSC-ACME. Whereas MHC class II, SMC6 protein, and phospholipase D were upregulated in NHSC-ACME. Furthermore, PKG-1 was downregulated in NHSC-ACME and upregulated in THSC-ACME. SG-II and p55 proteins were downregulated in NHSC-ACME and THSC-ACME by Western blotting. Taken together, the beneficial effect of A. cinnamomea on the induction of HSC cellular proteins is potentially applied as an alternative and complementary medicine for the prevention and amelioration of a liver injury.

Desmoglein 2 depletion leads to increased migration and upregulation of the chemoattractant secretoneurin in melanoma cells

During development and progression of malignant melanoma, an important role has been attributed to alterations of cell-cell adhesions, in particular, to a “cadherin switch” from E- to N-cadherin. We have previously shown that a subtype of melanoma cells express the desmosomal cadherin desmoglein 2 as non-junction-bound cell surface protein in addition to classical cadherins. To study the role of desmoglein 2 in melanoma cells, melanoma lines containing high endogenous amounts of desmoglein 2 were depleted of the protein by RNA interference. Transwell migration and scratch wounding assays showed markedly increased migration upon desmoglein 2 suppression whereas proliferation and viability remained unaltered. In gene expression profiles, desmoglein 2 depletion was associated with overexpression of migration-related genes. Strongest overexpression was found for secretogranin II which has not been reported in melanoma cells before. The bioactive peptide derived from secretogranin II, secretoneurin, is known to exert chemoattractive functions and was demonstrated here to stimulate melanoma cell migration. In summary, we show that desmoglein 2 expression attenuates migration of melanoma cells. The mechanism of desmoglein 2 impaired cell migration is mediated by downregulation of secretogranin II. Loss of desmoglein 2 increases expression of secretogranin II, followed by an enhanced migratory activity of melanoma cells. Our data add a new pathway of regulating melanoma cell migration related to a desmoglein 2 – secretogranin II axis.

The neuropeptide catestatin promotes vascular smooth muscle cell proliferation through the Ca2+-calcineurin-NFAT signaling pathway

The Chromogranin A-derived neuropeptide catestatin is an endogenous nicotinic cholinergic antagonist that acts as a pleiotropic hormone. Since catestatin shares several functions with other members derived from the chromogranin/secretogranin protein family and other neuropeptides which exert proliferative effects on vascular smooth muscle cells (VSMCs), we therefore hypothesized that catestatin would regulate VSMC proliferation. The present study demonstrates that catestatin caused a dose-dependent induction of proliferation in rat aortic smooth muscle cells and furthermore evoked a sustained increase in intracellular calcium. This subsequently leaded to enhanced activation of the Ca(2+)/calmodulin-dependent phosphatase, calcineurin and resulted in an activation of the Ca(2+)-dependent transcription factor, nuclear factor of activated T cells (NFAT), initiating transcription of proliferative genes. In addition, cyclosporin A (CsA), a potent inhibitor of calcineurin, abrogated catestatin-mediated effect on VSMCs, indicating that the calcineurin-NFAT signaling is strongly required for catestatin-induced growth of VSMCs. The present study establishes catestatin as a novel proliferative cytokine on vascular smooth muscle cells and this effect is mediated by the Ca(2+)-calcineurin-NFAT signaling pathway.

VEGF and its role in the early development of the long bone epiphysis

In long bones of murine species, undisturbed development of the epiphysis depends on the generation of vascularized cartilage canals shortly after birth. Despite its importance, it is still under discussion how this event is exactly regulated. It was suggested previously that, following increased hypoxia in the epiphyseal core, angiogenic factors are expressed and hence stimulate the ingrowth of the vascularized canals. In the present study, we tested this model and examined the spatio-temporal distribution of two angiogenic molecules during early development in mice. In addition, we investigated the onset of cartilage hypertrophy and mineralization. Our results provide evidence that the vascular endothelial growth factor is expressed in the epiphyseal resting cartilage prior to the moment of canal formation and is continuously expressed until the establishment of a large secondary ossification centre. Interestingly, we found no expression of secretoneurin before the establishment of the canals although this factor attracts blood vessels under hypoxic conditions. Epiphyseal development further involves maturation of the resting chondrocytes into hypertrophic ones, associated with the mineralization of the cartilage matrix and eventual death of the latter cells. Our results suggest that vascular endothelial growth factor is the critical molecule for the generation of the epiphyseal vascular network in mice long bones. Secretoneurin, however, does not appear to be a player in this event. Hypertrophic chondrocytes undergo cell death by a mechanism interpreted as chondroptosis.

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.

Sensory neuropeptides are potent chemoattractants for human basophils in vitro

The sensory neuropeptides secretoneurin (SN) and substance P (SP) are involved in "neurogenic" inflammatory processes as they occur in bronchial asthma or allergic rhinitis. A possible interaction with basophils has not been reported to date. Basophils were isolated from healthy donors by magnetic cell sorting technique and migration was explored using Boyden microchemotaxis chambers. SN [10(-8)M] and SP [10(-6) to 10(-8)M] proved to be chemoattractants equally potent to FMLP [10(-8)M] or LPS [10 pg/ml]. Specific anti-SN antibodies and a trypsinization preparation of SN were used to determine the specificity of the SN effect on basophils. The preincubation of basophils with neurokinin-1 (NK-1) or -2 (NK-2) receptor antagonists revealed the SP effect to act via NK-1 receptors in basophils. In addition, we were able to show phosphodiesterases and phosphoinositide-3 kinases to be engaged in the downstream signalling pathway. Our observations reveal for the first time a link between basophils, which are engaged in allergic processes, and the neuropeptides SN and SP. Furthermore, our data might suggest phosphodiesterases or phosphoinositide-3 kinases to be new therapeutic targets for the treatment of allergic diseases such as asthma or allergic rhinitis.

Secretoneurin as a hormone regulator in the pituitary

Secretoneurin (SN) is a 33-34 amino acid peptide derived from the most conserved sequence of the secretogranin (SgII) precursor. SgII is a granin protein found in the secretory granules of neuroendocrine tissues. There are two paralogs of teleost SgII that we name here SgIIa and SgIIb. Processing of these proteins would yield SNa and SNb in fish. Secretoneurin immunoreactivity is found within all the major pituitary cell types in mammals. In goldfish, it appears to be mainly expressed in the prolactin cells of the rostral pars distalis. We have investigated the paracrine role of goldfish SN (SNa) to stimulate luteinizing hormone from gonadotrophs in the neighboring proximal pars distalis. Another source of SN is the hypophysiotropic neurons that may deliver SN to target cells by direct pituitary innervation. Little else is known about the neuroendocrine role of SN. We also discuss the evolution, distribution and production of SN in the pituitary.

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.

Gene expression profiling of human mesenchymal stem cells chemotactically induced with CXCL12

In situ tissue engineering is a promising approach in regenerative medicine, with the possibility that adult stem or progenitor cells will be guided chemotactically to a tissue defect and subsequently differentiate into the surrounding tissue type. Mesenchymal stem cells (MSC) represent attractive candidate cells. Chemokines such as CXCL12 (SDF-1alpha) chemoattract MSC, but little is known about the molecular processes involved in the chemotaxis and migration of MSC. In this study, MSC recruitment by CXCL12 was investigated by genome-wide microarray analysis. The dose-dependent migration potential of bone-marrow-derived MSC toward CXCL12 was measured in an in vitro assay, with a maximum being recorded at a concentration of 1,000 nM CXCL12. Microarray analysis of MSC stimulated with CXCL12 and non-stimulated controls showed 30 differentially expressed genes (24 induced and six repressed). Pathway analysis revealed 11 differentially expressed genes involved in cellular movement and cytokine-cytokine receptor interaction, including those for migratory inducers such as the chemokines CXCL8 and CCL26, the leukocyte inhibitory factor, secretogranin II, and prostaglandin endoperoxide synthase 2. These results were confirmed by real-time polymerase chain reaction for selected genes. The obtained data provide further insights into the molecular mechanisms involved in chemotactic processes in cell migration and designate CXCL12 as a promising candidate for in situ recruitment in regenerative therapies.

Measurements of secretogranins II, III, V and proconvertases 1/3 and 2 in plasma from patients with neuroendocrine tumours

INTRODUCTION

Chromogranin (Cg) and secretogranin (Sg) are members of the granin family of proteins, which are expressed in neuroendocrine and nervous tissue. In recent publications we have presented generation of region-specific antibodies against CgA and CgB and also development of several region-specific radioimmunoassays for measurements of specific parts of the Cgs. In this study we describe generation of antibodies against SgII, SgIII, SgV and the proconvertases PC1/3 and PC2 and development of radioimmunoassays for measurements of these proteins.

MATERIALS AND METHODS

Peptides homologous to defined parts of the secretogranin and proconvertase molecules were selected and synthesised. Antibodies were raised, radioimmunoassays were developed and circulating levels of the proteins in plasma samples from 22 patients with neuroendocrine tumours were measured in the assays.

RESULTS

Increased plasma concentrations were recorded in 11, 4 and 3 of the patients with the SgII 154-165 (N-terminal secretoneurin), the SgII 172-186 (C-terminal Secretoneurin) and the SgII 225-242 assays respectively. The SgIII, SgV, PC1/3 and PC2 assays failed to detect increased concentrations in any of the patients.

CONCLUSION

Increased concentrations of SgII, especially the N-terminal part of secretoneurin could be measured in plasma from patients with endocrine pancreatic tumours and in this case this assay was quite comparable to measurements of CgA and CgB. Even though secretoneurin was not as frequently increased as CgA and CgB in patients with carcinoid tumours or pheochromocytoma it may be a useful marker for endocrine pancreatic tumours.

Immunohistochemical staining of human islet cells with region-specific antibodies against secretogranins II and III

Chromogranins and secretogranins belong to the granin family of proteins, which are expressed in neuroendocrine and nervous tissue. In earlier publications we have described the development of region-specific antibodies against CgA and CgB. In this study we describe antibodies to SgII and SgIII and their usefulness for immunohistochemical staining. Peptides homologous to defined parts of secretogranins II and III were selected and synthesized. Antibodies were raised and immunostainings were performed on normal human pancreas. The SgII 154-165 (N-terminal secretoneurin), SgII 172-186 (C-terminal secretoneurin) and SgIII antibodies immunostained all insulin-immunoreactive cells, most of the glucagon cells and some of the pancreatic polypeptide cells. The SgII 225-242 antibody immunostained only the insulin-containing cells. None of the antibodies immunostained the somatostatin cells. This study is the first observation of the expression of SgIII in human tissues, where we show expression of SgIII in three of the four major islet cell types in human pancreas.

Secretoneurin increases monolayer permeability in human coronary artery endothelial cells

BACKGROUND

Secretoneurin (SN), a novel neuropeptide, may play a role in inflammation in the vascular system. However, the interaction between SN and endothelial cells is largely unknown. This study's objective is to investigate the effects of SN on endothelial permeability and its associated molecular mechanisms in human coronary artery endothelial cells (HCAECs).

METHODS

HCAECs were treated with SN. Monolayer permeability was assayed with a transwell system and a Texas Red-labeled dextran tracer. The mRNA and protein levels of endothelial junctional molecules were determined by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. Superoxide anion was determined by fluorescent dye dihydroethidium-based flow cytometry detection. Mitogen-activated protein kinase (MAPK) activation was determined by Bio-Plex immunoassay.

RESULTS

HCAECs were treated with SN (15, 30, and 60 ng/ml) for 24 hours and showed a significant increase of monolayer permeability by 12%, 33%, and 47%, respectively, compared with controls (P < 0.05). SN-treated cells showed a significant reduction of zonula occludens-1 (ZO-1) and occludin at both mRNA and protein levels (P < 0.05). In addition, SN significantly increased superoxide anion in HCAECs (P < 0.05). Furthermore, SN activated MAPKs (JNK and ERK1/2) but not p38. Both antioxidant seleno-L-methionine (SeMet) and specific inhibitors of JNK and ERK1/2 effectively blocked SN-induced monolayer permeability increase in HCAECs.

CONCLUSIONS

SN significantly increases monolayer permeability and reduces the expression of ZO-1 and occludin through oxidative stress and the activation of JNK and ERK1/2 in HCAECs. This study provides direct evidence that SN impairs endothelial barrier function.

Secretoneurin stimulates goldfish pituitary luteinizing hormone production

Secretoneurin (SN), a 33-34 amino acid neuropeptide is derived from endoproteolysis of secretogranin II (SgII), a member protein of the chromogranin family. SN is widely distributed in various tissues of vertebrates especially in pituitary and hypothalamus, and is a potential new hormone. In vivo, i.p. injection of SN increased luteinizing hormone (LH) release in goldfish pretreated with the dopamine antagonist domperidone. In 6-h static incubation of goldfish pituitary fragments, 10 and 100 nM but not 1 nM concentrations of goldfish SN had a direct stimulatory effect to increase LH release by 2.3- and 1.5-fold (p<0.05), respectively. In addition, 500 nM SN induced a 2.6-fold increase in LHbeta subunit messenger RNA (mRNA) levels in pituitary fragments, regardless of whether LHbeta mRNA levels were expressed relative to 18S ribosomal RNA or beta-actin mRNA. We suggest that the stimulatory actions of SN on LH release may be a part of a paracrine or autocrine feedback loop in the pituitary.

Human neuroblastoma cells exposed to hypoxia: induction of genes associated with growth, survival, and aggressive behavior

We have recently found that cells derived from human neuroblastoma, a sympathetic nervous system (SNS) tumor, dedifferentiate and acquire a neural crest-like phenotype when exposed to hypoxia. In the present study, global analysis of gene expression and quantitative PCR of relevant genes showed that hypoxia provokes a general adaptive response in neuroblastoma cells and confirm loss of the neuronal phenotype and gain of stem-cell characteristics. Of the approximately 17,000 genes and ESTs analyzed, 199 were consistently upregulated and 36 were downregulated more than 2-fold by hypoxia. As anticipated, several genes involved in glucose and iron metabolism and neovascularization were upregulated, the latter group we here show to include the gene encoding chromogranin C and its cleavage product, secretoneurin, a vascular smooth muscle cell mitogen. We also observed upregulation of genes implicated in cell survival and growth, such as vascular endothelial growth factor (VEGF), neuropilin 1, adrenomedullin, and IGF-2. Several metallothioneins, which are linked to tumor drug resistance, were upregulated, whereas the expression of MDR1 decreased. In hypoxic neuroblastoma cells, proneuronal lineage specifying transcription factors, and their dimerization partner E2-2, were downregulated, whereas their inhibitors Id2 and HES-1 were induced, providing a molecular mechanism for the hypoxia-provoked dedifferentiation of neuroblastoma cells.

Secretoneurin promotes pertussis toxin-sensitive neurite outgrowth in cerebellar granule cells

The neuropeptide secretoneurin (SN) is an endoproteolytic product of the chromogranin secretogranin II. We investigated the effects of SN on the differentiation of immature cerebellar granule cells derived from the external granular layer (EGL). Secretoneurin caused concentration-dependent increases in neurite outgrowth, reflecting differentiation. The maximum effect was reached at a concentration of 100 nm SN. Secretoneurin immunoneutralization using specific antiserum significantly decreased neurite outgrowth; however, neurite morphology was altered. An affinity chromatography-purified antibody significantly inhibited the outgrowth response to SN (p < 0.001) without altering the morphology. Binding studies suggest the existence of specific G-protein-coupled receptors on the surface of monocytes that recognize SN. Assuming that SN promotes neurite outgrowth in EGL cells by acting through a similar G-protein-coupled mechanism, we treated SN-stimulated EGL cultures with pertussis toxin. Exposure to pertussis toxin (0.1 micro g/mL) showed a significant inhibition of the SN-induced outgrowth. To establish a second messenger pathway we used the protein kinase C inhibitor staurosporine. We found that EGL cell viability was not enhanced following chronic SN treatment for 24 h. These data indicate that SN is a novel trophic substance that can affect cerebellar maturation, primarily by accelerating granule cell differentiation through a signalling mechanism that is coupled to pertussis toxin-sensitive G-proteins.

Myofibroblastic conversion of mesothelial cells

BACKGROUND

The continuous chemical, physical, and inflammatory insults of prolonged continuous ambulatory peritoneal dialysis (CAPD) incite mesothelial cell responses, which may result in peritoneal fibrosis. The transforming growth factor-beta (TGF-beta), especially the isoform TGF-beta 1, has long been known to play crucial role in the fibrogenic process. Although several studies have implicated TGF-beta in peritoneal fibrosis, the underlying mechanism has not been completely elucidated.

METHODS

To test the effects of exogenous TGF-beta 1 on mesothelial cells, we assessed cytoarchitectural changes of human peritoneal mesothelial cells (HPMC) in in vitro culture by light, immunofluorescent, electron and immunoelectron microscopy, and differential gene expression analysis using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and cDNA expression array assays.

RESULTS

The TGF-beta 1-induced myofibroblastic conversion was a transdifferentiation process resulting in characteristic myofibroblastic phenotype that included prominent rough endoplasmic reticuli (rER) with dilated cisternas, conspicuous smooth muscle actin (SMA) myofilaments, frequent intercellular intermediate and gap junctions, and active deposition of extracellular matrix (ECM) and formation of fibronexus. The gene expression array analysis revealed complex modulation of gene expression involving cytoskeletal organization, cell adhesion, ECM production, cell proliferation, innate immunity, cytokine/growth factor signaling, cytoprotection, stress response, and many other essential metabolic processes in mesothelial cells.

CONCLUSION

This report describes myofibroblastic conversion of mesothelial cells, a previously undefined, yet frequently speculated, cell adaptive or pathogenic process. Our study helps to elucidate the complex molecular and cellular events involved in myofibroblastic conversion of mesothelial cells. We propose that differentiated epithelial cells of mesothelium convert or transdifferentiate into myofibroblasts, which implies the recruitment of fibrogenic cells from mesothelium during serosal inflammation and wound healing.

The neuropeptide secretoneurin stimulates adhesion of human monocytes to arterial and venous endothelial cells in vitro

Monocytes appear to play a central role in inflammatory processes like atherogenesis or lung inflammation both as the progenitors of foam cells and as a potential source of factors mediating further inflammatory processes. However, signals mediating the influx of monocytes into the inflammatory focus remain partly unknown. Secretoneurin (SN) is a more recently characterised 33-amino acid neuropeptide that is co-released from afferent nerve endings together with substance P (SP) and calcitonin gene-related peptide (CGRP). Furthermore, SN has been shown to affect human fibroblast, endothelial, smooth muscle, eosinophil and monocyte functions in vitro. An activity of SN on monocyte adhesion to the vascular wall has not yet been reported. The aim of this study was to investigate whether the adhesion properties of human monocytes (U937 and Mono Mac-6) to endothelial cells could be influenced by SN. In an in vitro model of the vascular wall, incubation of arterial (rat aortic endothelial cells) and venous endothelial cells (immortalised human umbilical vein endothelial line: EA.hy 926) with SN resulted in a time- and concentration-dependent increase in monocyte adhesion with a maximal effect seen after 4-6 h at a concentration of 10(-8) M SN. Increased monocyte adhesion seems not to be tissue-specific as SN-induced adhesion was observed on both arterial and venous endothelial cells. A specific antibody preparation against SN completely abolished increased monocyte adhesion toward SN-stimulated endothelium. Since adhesion was enhanced to a similar degree and with similar time kinetics as responses evoked by interleukin-1 (IL-1, 1 ng/ml) or lipopolysaccharide (LPS, 100 ng/ml), involvement of identical adhesion molecules can be suggested. Our observations provide substantial evidence that in inflammatory processes, SN might play a role in recruitment of monocytes to inflamed tissue.

Effects of Ginkgo biloba extract on the proliferation of vascular smooth muscle cells in vitro and on intimal thickening and interleukin-1beta expression after balloon injury in cholesterol-fed rabbits in vivo

Restenosis may develop in response to cytokine activation and smooth muscle cell proliferation. Ginkgo biloba extract (EGb) has been used to treat cardiovascular and cerebrovascular diseases. In the present study, the effects of EGb on the growth of cultured vascular smooth muscle cells (VSMC), as well as on the expression of interleukin-1beta (IL-1beta) and the intimal response in balloon-injured arteries of cholesterol-fed rabbits, were investigated. Using bromodeoxyuridine incorporation as an index of cell proliferation, EGb was found to inhibit serum-induced mitogenesis of cultured rat aorta VSMC in a dose-dependent manner. In vivo, EGb and probucol ( positive control) reduced the atheroma area in thoracic aortas of male New Zealand white rabbits fed a 2% cholesterol diet for 6 weeks with balloon denudation of the abdominal aorta being performed at the end of the third week. Intimal hyperplasia, expressed as the intimal/medial area ratio, in the abdominal aortas was significantly inhibited in the both the EGb group (0.61 +/- 0.06) and the probucol group (0.55 +/- 0.03) compared to the C group (0.87 +/- 0.02). In the balloon-injured abdominal aorta, both EGb and probucol significantly reduced IL-1beta mRNA and protein expression and the percentage of proliferating cells. The inhibitory effects of EGb on the intimal response might be attributed to its antioxidant capacity. EGb may have therapeutic potential for the prevention of restenosis after angioplasty.

Transendothelial migration of leukocytes and signalling mechanisms in response to the neuropeptide secretoneurin

Secretoneurin (SN), a newly discovered neuropeptide, may be implicated in inflammatory responses as it was shown to modulate leukocyte, endothelial and mesenchymal cell functions. Neutrophils placed above pulmonary arterial or venous endothelial monolayers migrated through this cellular barrier in response to apical or basal stimulation with SN in a dose-dependent manner. At optimal concentrations of 10(-6) to 10(-8) M, SN was nearly equally effective in stimulating neutrophil transmigration as was tumor necrosis factor-alpha at 10 ng/ml or a chemotactic gradient of formyl-Met-Leu-Phe (10(-8) M). Stimulation of transendothelial migration appears to be specific, since a trypsin digest of SN was ineffective and excess concentrations of anti-SN antibodies completely abolished the effect. Inhibition of cyclooxygenase or nitric oxide synthase did not affect the action of SN. Preincubation of endothelial cells with pertussistoxin (PTx) or choleratoxin (CTx), and the presence of staurosporine significantly inhibited transmigration, suggesting that SN uses a signalling pathway that is coupled to G-proteins and protein kinase C in endothelium. Moreover, SN treatment resulted in transient elevation of cytoplasmatic calcium concentration in endothelial cells. These data support the hypothesis that SN might contribute to neurogenic inflammation in vivo and reveal signalling mechanisms of SN in endothelial cells.

Secretoneurin: a functional neuropeptide in health and disease

Chromogranins belong to an evolutionarily conserved family of proteins that serve as neuropeptide pro-proteins, besides having other functions. The secretogranin-II-derived peptide secretoneurin is a 33-amino-acid polypeptide generated by proteolytic cleavage at paired dibasic sequences that exerts its effect by binding to specific receptors. Secretoneurin receptors have been kinetically and functionally characterized indicating that they are G-protein linked. Localization of secretoneurin and functional studies have helped to elucidate roles for secretoneurin, ranging from effects in the central nervous system to the modulation of the inflammatory response in the periphery. It has been shown that secretoneurin possesses biologic activities such as stimulation of dopamine release from striatal neurons and activation of monocyte migration, suggesting that the peptide may modulate both neurotransmission and inflammatory response. With an array of actions as diverse as that seen with other sensory neuropeptides, there is scope for numerous studies and therapeutic possibilities.

Vascular actions of brain natriuretic peptide: modulation by atherosclerosis and neutral endopeptidase inhibition

OBJECTIVES

We sought to define the vascular actions of the cardiac hormone brain natriuretic peptide (BNP) on cellular proliferation and cyclic guanosine monophosphate (cGMP) in human aortic vascular smooth muscle cells (HAVSMCs). Secondly, we investigated BNP and acetylcholine (ACh) vasorelaxations in aortic rings from normal and atherosclerotic rabbits in the presence and absence of long-term oral inhibition of neutral endopeptidase (NEP).

BACKGROUND

The vascular actions of BNP are not well defined, despite the presence of its receptor in vascular smooth muscle and the upregulation of NEP, the ectoenzyme that degrades BNP, in the vascular wall in atherosclerosis.

METHODS

HAVSMCs stimulated with fetal calf serum (FCS) were pulsed with bromodeoxyuridine (BrdU) with and without BNP. The HAVSMCs were incubated in the presence and absence of BNP to assess cGMP. Vasorelaxations to BNP and ACh were assessed in rings in normal and atherosclerotic rabbits in the presence and absence of long-term oral inhibition of NEP, together with assessment of atheroma formation.

RESULTS

FCS-stimulated BrdU uptake in HAVSMCs was suppressed with BNP. BNP potentiated cGMP in HAVSMCs. BNP resulted in potent vasorelaxation in normal isolated aortic rings, which were impaired in atherosclerotic versus normal rabbits and preserved with NEP inhibition, which also decreased atheroma formation. Relaxations to ACh, which were also impaired in atherosclerosis, were preserved with inhibition of NEP.

CONCLUSIONS

We conclude that BNP potently inhibits vascular smooth muscle cell proliferation and potentiates the generation of cGMP. BNP potently relaxes the normal rabbit aorta, and this response is impaired in atherosclerosis but preserved with inhibition of NEP, together with a reduction in atheroma formation and preservation of relaxations to ACh.

Distribution and origin of secretoneurin-immunoreactive nerves in the female rat uterus

Secretoneurin is a 33-amino acid peptide derived from secretogranin II. Secretoneurin immunoreactivity has been localized in the peripheral nervous system where it exerts potent chemotactic activity for monocytes and may play a role in inflammation. Secretoneurin could play a role in this process, although the presence and distribution of secretoneurin-immunoreactive neurons in the female reproductive system has not been documented. Thus, this study was undertaken to examine secretoneurin immunoreactivity in nerves of the rat uterus and uterine cervix. A moderate plexus of secretoneurin-immunoreactive nerve fibers was present in the myometrium and endometrium of the uterus as well as in the smooth muscle and endocervix of the cervix. Many of these fibers were associated with the vasculature as well as the myometrium. Secretoneurin immunoreactivity was present in small- to medium-sized neurons of dorsal root and nodose ganglia. Retrograde tracing with FluoroGold indicated that some of these sensory neurons project axons to the cervix and uterine horns. Secretoneurin-immunoreactive terminal-like structures were associated with neurons in the sacral parasympathetic nucleus of the lumbosacral spinal cord. In addition, some secretoneurin terminals were apposed to pelvic parasympathetic neurons in the paracervical ganglia that projected axons to the uterus and cervix. Double-immunostaining indicated co-existence of calcitonin gene-related peptide or substance P with secretoneurin in some sensory neurons, in some terminals of the pelvic ganglia, as well as nerve fibers in the uterine horn and cervix. Finally, fibers in the uterus and cervix were depleted of secretoneurin by capsaicin treatment. This study indicates that secretoneurin is present in the uterus in C-afferent nerve fibers whose cell bodies are located in sensory ganglia. Some of these fibers contain both secretoneurin and calcitonin gene-related peptide or substance P. These substances have functions in inflammatory reactions. Further, secretoneurin could influence postganglionic parasympathetic "uterine-related" neurons in the pelvic ganglia and preganglionic parasympathetic neurons in the lumbosacral spinal cord.

A soluble gradient of the neuropeptide secretoneurin promotes the transendothelial migration of monocytes in vitro

Secretoneurin, derived from the chromogranin secretogranin II, triggers the selective migration of human monocytes, eosinophils, fibroblasts, endothelial and smooth muscle cells. More recently, we located specific binding sites on the human monocytic cell line MonoMac-6. Differentiated U937 transendothelial diapedesis was evaluated using an in vitro model of the vascular wall and specific monoclonal antibodies against CD11/CD18 and the alpha-chains of the very late activation antigen (VLA)-4 were used to evaluate involved adhesion molecules. Results showed a significant migratory response to secretoneurin between 10(-8) to 10(-10) M. Migration was comparable to a maximal effect induced by the monocyte chemotactic agent N-formyl-Met-Leu-Phe (fMLP, 10(-8) M). Rabbit anti-secretoneurin antibodies were able to block the neuropeptide effect but not of fMLP and a trypsinized secretoneurin preparation as well as the secretogranin II-fragment EL-17 were ineffective in eliciting migration. Transmigration of U937 across endothelial-layers toward secretoneurin is inhibited by antibodies to CD11/CD18 adhesion molecules. The novel neuropeptide secretoneurin may play a role in regulating migration of monocytes into the subendothelial space, supposing a role in inflammatory responses.

Formation and sequence analysis of secretoneurin, a neuropeptide derived from secretogranin II, in mammalian, bird, reptile, amphibian and fish brains

Secretoneurin is a recently-characterized neuropeptide derived from secretogranin II, a protein belonging to the class of chromogranins. We investigated the phylogeny of this peptide by immunoblotting and gel-filtration high performance liquid chromatography followed by radioimmunoassay of brain extracts of various species including chicken, lizard, frog and fish. In addition the amino acid sequence of secretoneurin from pig, hamster, rabbit, guinea-pig and chicken was established by reverse transcriptase polymerase chain reaction. Secretoneurin is strongly conserved during evolution, it is not only expressed in various mammalian species but found also in the brain of birds, reptiles, amphibians and fish. In all these species a significant or near complete processing of secretogranin II to secretoneurin was observed. These data provide significant evidence for the neuropeptide nature of the novel functional peptide.

Staurosporine-dependent activation of human endothelial cell monolayers for neutrophil adherence by secretoneurin

Functions of secretoneurin include chemotaxis for monocytes and endothelial cells, and inhibition of endothelial cell proliferation. Inhibition of monocyte chemotaxis by staurosporine indicated involvement of specific signaling mechanisms. We have tested effects of kinase inhibitors on activation of endothelial cells for neutrophil adherence by secretoneurin. Pretreatment of endothelial cells by secretoneurin induced in endothelium increased adhesiveness to neutrophils. Addition of staurosporine, an inhibitor of protein kinase C, completely abolished endothelial cell activation, whereas tyrphostin-23, a tyrosin kinase inhibitor, had no effect. Results on activation of neutrophil-endothelial cell adherence by secretoneurin demonstrate that specific signaling mechanisms are involved in endothelial cell activation.