Microarray and suppression subtractive hybridization analyses of gene expression in pheochromocytoma cells reveal pleiotropic effects of pituitary adenylate cyclase-activating polypeptide on cell proliferation, survival, and adhesion

The Potential of the Nose-to-Brain Delivery of PACAP for the Treatment of Neuronal Disease

Research on the neuroprotective effect of pituitary adenylate cyclase-activating polypeptide (PACAP) and its use as a therapeutic agent has grown over the past 30 years. Both in vitro and in vivo experiments have shown that PACAP exerts a strong neuroprotective effect in many central and peripheral neuronal diseases. Various delivery routes have been employed from intravenous (IV) injections to intracerebroventricular (ICV) administration, leading either to systemic or topical delivery of the peptide. Over the last decade, a growing interest in the use of intranasal (IN) administration of PACAP and other therapeutic agents has emerged as an alternative delivery route to target the brain. The aim of this review is to summarize the findings on the neuroprotective effect of PACAP and to discuss how the IN administration of PACAP could contribute to target the effects of this pleiotropic peptide.

The Heterogeneity of Response of PC12 Cells from Different Laboratories to Nerve Growth Factor and Pituitary Adenylate Cyclase-Activating Polypeptide Questions the Reproducibility of Studies Carried Out with Tumor Cell Lines

BACKGROUND

PC12 pheochromocytoma tumor cell lines are widely used to decipher the intracellular signaling mechanisms mediating the effects of some growth factors. Nevertheless, the disparity in appearance of some PC12 cell lines used in the different publications questions our ability to compare the results obtained by the numerous laboratories which use them. This led us to analyze the phenotypic aspect and transcriptomic expression of 5 PC12 cell lines from different origins under control conditions and after treatment with nerve growth factor (NGF) or pituitary adenylate cyclase-activating polypeptide (PACAP).

METHODS

Characterization of the 5 PC12 cell lines was conducted using imaging techniques and high-throughput real-time PCR combined with bioinformatics analysis.

RESULTS

The results show that the 5 cell lines are very variable in terms of shape, proliferation rate, motility, adhesion to the substrate, and gene expression. This high heterogeneity of the cell lines is also found when looking at their response to NGF or PACAP on gene expression or differentiation, with even in some cases opposite effects, as, for example, on cell proliferation. Actually, only 2 of the cell lines tested exhibited some phenotypic similarities with each other, even though the transcriptomic analyses show that they are far from identical.

DISCUSSION/CONCLUSION

As this issue of cell heterogenicity is not restricted to PC12 cells, the present results highlight the need to facilitate the supply of cell lines at low cost, the necessity to standardize practices regarding the use of cell lines, and the requirement to define precise markers of established cell lines which should be monitored in every publication. Regarding this latter point, the present data show that transcriptomic analysis by real-time PCR using a panel of genes of interest is easy to implement and provides a reliable method to control the possible drift of the cells over time in culture. Transcriptomic phenotyping combined with bioinformatics analysis can also be a useful approach to predict the response of the cells to treatments in terms of cell signaling activation, which can help to choose among several cell lines the most appropriate one for the investigation of a particular mechanism. Taken together, the results from this study highlight the need to use well-characterized cell lines with standardized protocols to generate reproducible results from 1 laboratory to the other.

ERK-dependent induction of the immediate-early gene Egr1 and the late gene Gpr50 contribute to two distinct phases of PACAP Gs-GPCR signaling for neuritogenesis

Gs-coupled GPCR-stimulated neuritogenesis in PC12 and NS-1 - cells depends on activation of the MAP kinase ERK. Here, we examine changes in ERK activation (phosphorylation), and the time course of ERK-dependent gene induction, to seek transcriptional determinants for this process. Quenching of ERK activation by inhibition of MEK with U0126 at any time point for at least 24 h following addition of PACAP resulted in arrest of neurite formation. Changes in the transcriptome profile throughout this time period revealed at least two phases of gene induction: an early phase dominated by induction of immediate-early genes, and a later phase of gene induction after 4-6 h of exposure to PACAP with persistent elevation of phospho-ERK levels. Genes induced by PACAP in both phases consisted in those whose induction was dependent on ERK (i.e., blocked by U0126), and some whose induction was blocked by the protein kinase A inhibitor H89. ERK-dependent "late gene" transcripts included Gpr50, implicated earlier in facilitation of NGF-induced neurite formation in NS-1 cells. Gpr50 induction by PACAP, but not NGF, was dependent on the guanine nucleotide exchange factor RapGEF2, which has been shown to be required for PACAP-induced neuritogenesis in NS-1 cells. Expression of a Gpr50-directed shRNA lowered basal levels of Gpr50 mRNA and attenuated Gpr50 mRNA and GPR50 protein induction by PACAP, with a corresponding attenuation of PACAP-induced neuritogenesis. Gs-GPCR-stimulated neuritogenesis first requires immediate-early gene induction, including that of Egr1 (Zif268/NGF1A/Krox24) as previously reported. This early phase of gene induction, however, is insufficient to maintain the neuritogenic process without ERK-dependent induction of additional late genes, including Gpr50, upon continuous exposure to neurotrophic neuropeptide. Early (Egr1) and late (Gpr50) gene induction by NGF, like that for PACAP, was inhibited by U0126, but was independent of RapGEF2, confirming distinct modes of ERK activation by Gs-coupled GPCRs and neurotrophic tyrosine receptor kinases, converging on a final common ERK-dependent signaling pathway for neuritogenesis.

Pituitary Adenylate Cyclase-Activating Polypeptide: A Promising Neuroprotective Peptide in Stroke

The search for viable, effective treatments for acute stroke continues to be a global priority due to the high mortality and morbidity. Current therapeutic treatments have limited effects, making the search for new treatments imperative. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a well-established cytoprotective neuropeptide that participates in diverse neural physiological and pathological activities, such as neuronal proliferation, differentiation, and migration, as well as neuroprotection. It is considered a promising treatment in numerous neurological diseases. Thus, PACAP bears potential as a new therapeutic strategy for stroke treatment. Herein, we provide an overview pertaining to the current knowledge of PACAP, its receptors, and its potential neuroprotective role in the setting of stroke, as well as various mechanisms of neuroprotection involving ionic homeostasis, excitotoxicity, cell edema, oxidative stress, inflammation, and cell death, as well as the route of PACAP administration.

Selenoprotein T protects against cisplatin-induced acute kidney injury through suppression of oxidative stress and apoptosis

Previously, selenoprotein T (SelT) expression was shown to be induced in nervous, endocrine, and metabolic tissues during ontogenetic and regenerative processes. However, whether SelT plays a critical role in renal diseases remains unclear. Here, we explored the role of SelT in cisplatin-induced acute kidney injury (AKI). Results revealed that SelT was highly expressed in renal tubules, but its expression was significantly reduced in cisplatin-induced AKI. Importantly, knocking down of SelT expression in kidney cells in vitro resulted in cisplatin-induced cell apoptosis, as indicated by the elevation of cleaved-PARP and Bax expression, Caspase-3 activity, and number of TUNEL-positive cells. Moreover, SelT silencing-induced reactive oxygen species (ROS) production, accompanied by a decrease in intracellular superoxide dismutase (SOD) and catalase (CAT) activity and increase in malondialdehyde (MDA) content. Notably, the protein and mRNA levels of Nox4 were increased in response to SelT downregulation. Furthermore, suppression of Nox4 expression by GKT137831 partially alleviated SelT knockdown-induced ROS generation and cell apoptosis in cisplatin-treated kidney cells. Taken together, our findings provide the first evidence that SelT protects against cisplatin-induced AKI by suppression of oxidative stress and apoptosis.

Progress in the emerging role of selenoproteins in cardiovascular disease: focus on endoplasmic reticulum-resident selenoproteins

Cardiovascular diseases represent one of the most important health problems of developed countries. One of the main actors involved in the onset and development of cardiovascular diseases is the increased production of reactive oxygen species that, through lipid peroxidation, protein oxidation and DNA damage, induce oxidative stress and cell death. Basic and clinical research are ongoing to better understand the endogenous antioxidant mechanisms that counteract oxidative stress, which may allow to identify a possible therapeutic targeting/application in the field of stress-dependent cardiovascular pathologies. In this context, increasing attention is paid to the glutathione/glutathione-peroxidase and to the thioredoxin/thioredoxin-reductase systems, among the most potent endogenous antioxidative systems. These key enzymes, belonging to the selenoprotein family, have a well-established function in the regulation of the oxidative cell balance. The aim of the present review was to highlight the role of selenoproteins in cardiovascular diseases, introducing the emerging cardioprotective role of endoplasmic reticulum-resident members and in particular one of them, namely selenoprotein T or SELENOT. Accumulating evidence indicates that the dysfunction of different selenoproteins is involved in the susceptibility to oxidative stress and its associated cardiovascular alterations, such as congestive heart failure, coronary diseases, impaired cardiac structure and function. Some of them are under investigation as useful pathological biomarkers. In addition, SELENOT exhibited intriguing cardioprotective effects by reducing the cardiac ischemic damage, in terms of infarct size and performance. In conclusion, selenoproteins could represent valuable targets to treat and diagnose cardiovascular diseases secondary to oxidative stress, opening a new avenue in the field of related therapeutic strategies.

Selenoprotein T is a key player in ER proteostasis, endocrine homeostasis and neuroprotection

Selenoprotein T (SELENOT, SELT) is a thioredoxin-like enzyme anchored at the endoplasmic reticulum (ER) membrane, whose primary structure is highly conserved during evolution. SELENOT is abundant in embryonic tissues and its activity is essential during development since its gene knockout in mice is lethal early during embryogenesis. Although its expression is repressed in most adult tissues, SELENOT remains particularly abundant in endocrine organs such as the pituitary, pancreas, thyroid and testis, suggesting an important role of this selenoprotein in hormone production. Our recent studies showed indeed that SELENOT plays a key function in insulin and corticotropin biosynthesis and release by regulating ER proteostasis. Although SELENOT expression is low or undetectable in most cerebral structures, its gene conditional knockout in brain provokes anatomical alterations that impact mice behavior. This suggests that SELENOT also plays an important role in brain development and function. In addition, SELENOT is induced after injury in brain or liver and exerts a cytoprotective effect. Thus, the data gathered during the last ten years of intense investigation of this newly discovered thioredoxin-like enzyme point to an essential function during development and in adult endocrine organs or lesioned brain, most likely by regulating ER redox circuits that control homeostasis and survival of cells with intense metabolic activity.

Induction of serpinb1a by PACAP or NGF is required for PC12 cells survival after serum withdrawal

PC12 cells are used to study the signaling mechanisms underlying the neurotrophic and neuroprotective activities of pituitary adenylate cyclase-activating polypeptide (PACAP) and nerve growth factor (NGF). Previous microarray experiments indicated that serpinb1a was the most induced gene after 6 h of treatment with PACAP or NGF. This study confirmed that serpinb1a is strongly activated by PACAP and NGF in a time-dependent manner with a maximum induction (~ 50-fold over control) observed after 6 h of treatment. Co-incubation with PACAP and NGF resulted in a synergistic up-regulation of serpinb1a expression (200-fold over control), suggesting that PACAP and NGF act through complementary mechanisms. Consistently, PACAP-induced serpinb1a expression was not blocked by TrkA receptor inhibition. Nevertheless, the stimulation of serpinb1a expression by PACAP and NGF was significantly reduced in the presence of extracellular signal-regulated kinase, calcineurin, protein kinase A, p38, and PI3K inhibitors, indicating that the two trophic factors share some common pathways in the regulation of serpinb1a. Finally, functional investigations conducted with siRNA revealed that serpinb1a is not involved in the effects of PACAP and NGF on PC12 cell neuritogenesis, proliferation or body cell volume but mediates their ability to block caspases 3/7 activity and to promote PC12 cell survival.

Pituitary adenylate cyclase activating polypeptide modulates catecholamine storage and exocytosis in PC12 cells

A number of efforts have been made to understand how pituitary adenylate cyclase activating polypeptide (PACAP) functions as a neurotrophic and neuroprotective factor in Parkinson's disease (PD). Recently its effects on neurotransmission and underlying mechanisms have generated interest. In the present study, we investigate the effects of PACAP on catecholamine storage and secretion in PC12 cells with amperometry and transmission electron microscopy (TEM). PACAP increases quantal release induced by high K+ without significantly regulating the frequency of vesicle fusion events. TEM data indicate that the increased volume of the vesicle is mainly the result of enlargement of the fluidic space around the dense core. Moreover, the number of docked vesicles isn't modulated by PACAP. When cells are acutely treated with L-DOPA, the vesicular volume and quantal release both increase dramatically. It is likely that the characteristics of amperometric spikes from L-DOPA treated cells are associated with increased volume of individual vesicles rather than a direct effect on the mechanics of exocytosis. Treatment with PACAP versus L-DOPA results in different profiles of the dynamics of exocytosis. Release via the fusion pore prior to full exocytosis was observed with the same frequency following treatment with PACAP and L-DOPA. However, release events have a shorter duration and higher average current after PACAP treatment compared to L-DOPA. Furthermore, PACAP reduced the proportion of spikes having rapid decay time and shortened the decay time of both fast and slow spikes. In contrast, the distributions of the amperometric spike decay for both fast and slow spikes were shifted to longer time following L-DOPA treatment. Compared to L-DOPA, PACAP may produce multiple favorable effects on dopaminergic neurons, including protecting dopaminergic neurons against neurodegeneration and potentially regulating dopamine storage and release, making it a promising therapeutic agent for the treatment of PD.

The PACAP-regulated gene selenoprotein T is abundantly expressed in mouse and human β-cells and its targeted inactivation impairs glucose tolerance

Selenoproteins are involved in the regulation of redox status, which affects several cellular processes, including cell survival and homeostasis. Considerable interest has arisen recently concerning the role of selenoproteins in the regulation of glucose metabolism. Here, we found that selenoprotein T (SelT), a new thioredoxin-like protein of the endoplasmic reticulum, is present at high levels in human and mouse pancreas as revealed by immunofluorescence and quantitative PCR. Confocal immunohistochemistry studies revealed that SelT is mostly confined to insulin- and somatostatin-producing cells in mouse and human islets. To elucidate the role of SelT in β-cells, we generated, using a Cre-Lox strategy, a conditional pancreatic β-cell SelT-knockout C57BL/6J mice (SelT-insKO) in which SelT gene disruption is under the control of the rat insulin promoter Cre gene. Glucose administration revealed that male SelT-insKO mice display impaired glucose tolerance. Although insulin sensitivity was not modified in the mutant mice, the ratio of glucose to insulin was significantly higher in the SelT-insKO mice compared with wild-type littermates, pointing to a deficit in insulin production/secretion in mutant mice. In addition, morphometric analysis showed that islets from SelT-insKO mice were smaller and that their number was significantly increased compared with islets from their wild-type littermates. Finally, we found that SelT is up-regulated by pituitary adenylate cyclase-activating polypeptide (PACAP) in β-pancreatic cells and that SelT could act by facilitating a feed-forward mechanism to potentiate insulin secretion induced by the neuropeptide. Our findings are the first to show that the PACAP-regulated SelT is localized in pancreatic β- and δ-cells and is involved in the control of glucose homeostasis.

Pituitary adenylate cyclase-activating polypeptide (PACAP) promotes both survival and neuritogenesis in PC12 cells through activation of nuclear factor κB (NF-κB) pathway: involvement of extracellular signal-regulated kinase (ERK), calcium, and c-REL

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a trophic factor that promotes neuronal survival and neurite outgrowth. However, the signaling pathways and the transcriptional mechanisms involved are not completely elucidated. Our previous studies aimed at characterizing the transcriptome of PACAP-differentiated PC12 cells revealed an increase in the expression of nuclear factor κB2 (NF-κB2) gene coding for p100/p52 subunit of NF-κB transcription factor. Here, we examined the role of the NF-κB pathway in neuronal differentiation promoted by PACAP. We first showed that PACAP-driven survival and neuritic extension in PC12 cells are inhibited following NF-κB pathway blockade. PACAP stimulated both c-Rel and p52 NF-κB subunit gene expression and nuclear translocation, whereas c-Rel down-regulation inhibited cell survival and neuritogenesis elicited by the neuropeptide. PACAP-induced c-Rel nuclear translocation was inhibited by ERK1/2 and Ca(2+) blockers. Furthermore, the neuropeptide stimulated NF-κB p100 subunit processing into p52, indicative of activation of the NF-κB alternative pathway. Taken together, our data show that PACAP promotes both survival and neuritogenesis in PC12 cells by activating NF-κB pathway, most likely via classical and alternative signaling cascades involving ERK1/2 kinases, Ca(2+), and c-Rel/p52 dimers.

STC1 induction by PACAP is mediated through cAMP and ERK1/2 but not PKA in cultured cortical neurons

The neuroprotective actions of PACAP (pituitary adenylate cyclase-activating polypeptide) in vitro and in vivo suggest that activation of its cognate G protein coupled receptor PAC1 or downstream signaling molecules,and thus activation of PACAP target genes, could be of therapeutic benefit. Here, we show that cultured rat cortical neurons predominantly expressed the PAC1hop and null variants. PACAP receptor activation resulted in the elevation of the two second messengers cAMP and Ca(2+) and expression of the putative neuroprotectant stanniocalcin 1(STC1). PACAP signaling to the STC1 gene proceeded through the extracellular signal-regulated kinases 1 and 2(ERK1/2), but not through the cAMP-dependent protein kinase (PKA), and was mimicked by the adenylate cyclase activator forskolin. PACAP- and forskolin-mediated activation of ERK1/2 occurred through cAMP, but not PKA.These results suggest that STC1 gene induction proceeds through cAMP and ERK1/2, independently of PKA, the canonical cAMP effector. In contrast, PACAP signaling to the BDNF gene proceeded through PKA, suggesting that two different neuroprotective cAMP pathways co-exist in differentiated cortical neurons. The selective activation of a potentially neuroprotective cAMP-dependent pathway different from the canonical cAMP pathway used in many physiological processes, such as memory storage, has implications for pharmacological activation of neuroprotection in vivo.

Signaling through the neuropeptide GPCR PAC₁ induces neuritogenesis via a single linear cAMP- and ERK-dependent pathway using a novel cAMP sensor

Both cAMP and ERK are necessary for neuroendocrine cell neuritogenesis, and pituitary adenylate cyclase-activating polypeptide (PACAP) activates each. It is important to know whether cAMP and ERK are arranged in a novel, linear pathway or in two parallel pathways using known signaling mechanisms. Native cellular responses [cAMP elevation, ERK phosphorylation, cAMP responsive element binding (CREB) phosphorylation, and neuritogenesis] and promoter-reporter gene activation after treatment with forskolin, cAMP analogs, and PACAP were measured in Neuroscreen-1 (NS-1) cells, a PC12 variant enabling simultaneous morphological, molecular biological, and biochemical analysis. Forskolin (25 μM) and cAMP analogs (8-bromo-cAMP, dibutyryl-cAMP, and 8-chlorophenylthio-cAMP) stimulated ERK phosphorylation and neuritogenesis in NS-1 cells. Both ERK phosphorylation and neuritogenesis were MEK dependent (blocked by 10 μM U0126) and PKA independent (insensitive to 30 μM H-89 or 100 nM myristoylated protein kinase A inhibitor). CREB phosphorylation induced by PACAP was blocked by H-89. The exchange protein activated by cAMP (Epac)-selective 8-(4-chlorophenylthio)-2'-O-Me-cAMP (100-500 μM) activated Rap1 without affecting the other cAMP-dependent processes. Thus, PACAP-38 potently stimulated two distinct and independent cAMP pathways leading to CREB or ERK activation in NS-1 cells. Drug concentrations for appropriate effect were derived from control data for all compounds. In summary, a novel PKA- and Epac-independent signaling pathway: PACAP → adenylate cyclase → cAMP → ERK → neuritogenesis has been identified.

The PACAP-regulated gene selenoprotein T is highly induced in nervous, endocrine, and metabolic tissues during ontogenetic and regenerative processes

Selenoproteins contain the essential trace element selenium whose deficiency leads to major disorders including cancer, male reproductive system failure, or autoimmune thyroid disease. Up to now, 25 selenoprotein-encoding genes were identified in mammals, but the spatiotemporal distribution, regulation, and function of some of these selenium-containing proteins remain poorly documented. Here, we found that selenoprotein T (SelT), a new thioredoxin-like protein, is regulated by the trophic neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) in differentiating but not mature adrenomedullary cells. In fact, our analysis revealed that, in rat, SelT is highly expressed in most embryonic structures, and then its levels decreased progressively as these organs develop, to vanish in most adult tissues. In the brain, SelT was abundantly expressed in neural progenitors in various regions such as the cortex and cerebellum but was undetectable in adult nervous cells except rostral migratory-stream astrocytes and Bergmann cells. In contrast, SelT expression was maintained in several adult endocrine tissues such as pituitary, thyroid, or testis. In the pituitary gland, SelT was found in secretory cells of the anterior lobe, whereas in the testis, the selenoprotein was present only in spermatogenic and Leydig cells. Finally, we found that SelT expression is strongly stimulated in liver cells during the regenerative process that occurs after partial hepatectomy. Taken together, these data show that SelT induction is associated with ontogenesis, tissue maturation, and regenerative mechanisms, indicating that this PACAP-regulated selenoprotein may play a crucial role in cell growth and activity in nervous, endocrine, and metabolic tissues.

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) impairs the regulation of apoptosis in megakaryocytes by activating NF-κB: a proteomic study

We previously showed that the Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and its receptor VPAC1 are negative regulators of megakaryopoiesis and platelet function, but their downstream signaling pathway that inhibits this process still remained unknown. A combined proteomic, transcriptomic, and bioinformatic approach was here used to elucidate the molecular mechanisms underlying PACAP signaling via VPAC1 in megakaryocytes. Two-dimensional difference gel electrophoresis and tandem MS were applied to detect differentially expressed proteins in megakaryocytic CHRF cells stimulated with PACAP. The majority of the 120 proteins modulated by PACAP belong to the class of "cell cycle and apoptosis" proteins. The up- or down-regulated expression of some proteins was confirmed by immunoblot and immunohistochemical analysis. A meta-analysis of our data and 12 other published studies was performed to evaluate signaling pathways involved in different cellular models of PACAP response. From 2384 differentially expressed genes/proteins, 83 were modulated by PACAP in at least three independent studies and Ingenuity Pathway Analysis further identified apoptosis as the highest scored network with NF-κB as a key-player. PACAP inhibited serum depletion-induced apoptosis of CHRF cells via VPAC1 stimulation. In addition, PACAP switched on NF-κB dependent gene expression since higher nuclear levels of the active NF-κB p50/p65 heterodimer were found in CHRF cells treated with PACAP. Finally, a quantitative real time PCR apoptosis array was used to study RNA from in vitro differentiated megakaryocytes from a PACAP overexpressing patient, leading to the identification of 15 apoptotic genes with a 4-fold change in expression and Ingenuity Pathway Analysis again revealed NF-κB as the central player. In conclusion, our findings suggest that PACAP interferes with the regulation of apoptosis in megakaryocytes, probably via stimulation of the NF-κB pathway.

Maternal perinatal undernutrition has long-term consequences on morphology, function and gene expression of the adrenal medulla in the adult male rat

Epidemiological studies suggest that maternal undernutrition sensitises to the development of chronic adult diseases, such as type 2 diabetes, hypertension and obesity. Although the physiological mechanisms involved in this 'perinatal programming' remain largely unknown, alterations of stress neuroendocrine systems such as the hypothalamic-pituitary-adrenal (HPA) and sympathoadrenal axes might play a crucial role. Despite recent reports showing that maternal perinatal undernutrition disturbs chromaffin cells organisation and activity in male rats at weaning, its long-term effects on adrenal medulla in adult animals are unknown. Using a rat model of maternal perinatal 50% food restriction (FR50) from the second week of gestation until weaning, histochemistry approaches revealed alterations in noradrenergic chromaffin cells aggregation and in cholinergic innervation in the adrenal medulla of 8-month-old FR50 rats. Electron microscopy showed that chromaffin cell granules exhibited ultrastructural changes in FR50 rats. These morphological changes were associated with reduced circulating levels and excretion of catecholamines. By contrast, catecholamine plasma levels were significantly increased after a 16 or 72 h of fasting, indicating that the responsiveness of the sympathoadrenal system to food deprivation was accentuated in FR50 adult rats. Among 384 pituitary adenylate cyclase-activating polypeptide-sensitive genes, we identified 129 genes (33.6%) that were under expressed (ratio < 0.7) in FR50 animals. A large number of these genes are involved in cytoskeleton remodelling and vesicle trafficking. Taken together, our results show that maternal perinatal undernutrition programmes adrenomedullary function and gene expression in adult male rats. Because catecholamines contribute to metabolic homeostasis, as well as arterial blood pressure regulation, the alterations observed in the adrenal medulla of adult male FR50 rats may participate in the programming of chronic adult diseases.

Proteomics of rat hypothalamus, hippocampus and pre-frontal/frontal cortex after central administration of the neuropeptide PACAP

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide that exerts pleiotropic functions, acting as a hypophysiotropic factor, a neurotrophic and a neuroprotective agent. The molecular pathways activated by PACAP to exert its physiological roles in brain are incompletely understood. In this study, adrenocorticotropic hormone (ACTH), prolactin, luteinising hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), brain-derived neurotrophic factor and corticosterone blood levels were determined before and 20, 40, 60, and 120 min after PACAP intracerebroventricular administration. PACAP treatment increased ACTH, corticosterone, LH and FSH blood concentrations, while it decreased TSH levels. A proteomics investigation was carried out in hypothalamus, hippocampus and pre-frontal/frontal cortex (P/FC) using 2-dimensional gel electrophoresis at 120 min, the end-point suggested by studies on PACAP hypophysiotropic activities. Spots showing statistically significant alterations after PACAP treatment were identified by Matrix-assisted laser desorption/ionization-Time of flight mass spectrometry. Identified proteins were consistent with PACAP involvement in different molecular processes in brain. Altered expression levels were observed for proteins involved in cytoskeleton modulation and synaptic plasticity: actin in the hypothalamus; stathmin, dynamin, profilin and cofilin in hippocampus; synapsin in P/FC. Proteins involved in cellular differentiation were also modulated: glutathione-S-transferase α and peroxiredoxin in hippocampus; nucleoside diphosphate kinase in P/FC. Alterations were detected in proteins involved in neuroprotection, neurodegeneration and apoptosis: ubiquitin carboxyl-terminal hydrolase isozyme L1 and heat shock protein 90-β in hypothalamus; α-synuclein in hippocampus; glyceraldehyde-3-phosphate dehydrogenase and prohibitin in P/FC. This proteomics study identified new proteins involved in molecular mechanisms mediating PACAP functions in the central nervous system.

Pituitary adenylate cyclase-activating polypeptide and its receptors: 20 years after the discovery

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a 38-amino acid C-terminally alpha-amidated peptide that was first isolated 20 years ago from an ovine hypothalamic extract on the basis of its ability to stimulate cAMP formation in anterior pituitary cells (Miyata et al., 1989. PACAP belongs to the vasoactive intestinal polypeptide (VIP)-secretin-growth hormone-releasing hormone-glucagon superfamily. The sequence of PACAP has been remarkably well conserved during evolution from protochordates to mammals, suggesting that PACAP is involved in the regulation of important biological functions. PACAP is widely distributed in the brain and peripheral organs, notably in the endocrine pancreas, gonads, respiratory and urogenital tracts. Characterization of the PACAP precursor has revealed the existence of a PACAP-related peptide, the activity of which remains unknown. Two types of PACAP binding sites have been characterized: type I binding sites exhibit a high affinity for PACAP and a much lower affinity for VIP, whereas type II binding sites have similar affinity for PACAP and VIP. Molecular cloning of PACAP receptors has shown the existence of three distinct receptor subtypes: the PACAP-specific PAC1-R, which is coupled to several transduction systems, and the PACAP/VIP-indifferent VPAC1-R and VPAC2-R, which are primarily coupled to adenylyl cyclase. PAC1-Rs are particularly abundant in the brain, the pituitary and the adrenal gland, whereas VPAC receptors are expressed mainly in lung, liver, and testis. The development of transgenic animal models and specific PACAP receptor ligands has strongly contributed to deciphering the various actions of PACAP. Consistent with the wide distribution of PACAP and its receptors, the peptide has now been shown to exert a large array of pharmacological effects and biological functions. The present report reviews the current knowledge concerning the pleiotropic actions of PACAP and discusses its possible use for future therapeutic applications.

Functional whole-genome analysis identifies Polo-like kinase 2 and poliovirus receptor as essential for neuronal differentiation upstream of the negative regulator alphaB-crystallin

This study aimed at identifying transcriptional changes associated to neuronal differentiation induced by six distinct stimuli using whole-genome microarray hybridization analysis. Bioinformatics analyses revealed the clustering of these six stimuli into two categories, suggesting separate gene/pathway dependence. Treatment with specific inhibitors demonstrated the requirement of both Janus kinase and microtubule-associated protein kinase activation to trigger differentiation with nerve growth factor (NGF) and dibutyryl cAMP. Conversely, activation of protein kinase A, phosphatidylinositol-3-kinase alpha, and mammalian target of rapamycin, although required for dibutyryl cAMP-induced differentiation, exerted a negative feedback on NGF-induced differentiation. We identified Polo-like kinase 2 (Plk2) and poliovirus receptor (PVR) as indispensable for NGF-driven neuronal differentiation and alphaB-crystallin (Cryab) as an inhibitor of this process. Silencing of Plk2 or PVR blocked NGF-triggered differentiation and Cryab down-regulation, while silencing of Cryab enhanced NGF-induced differentiation. Our results position both Plk2 and PVR upstream of the negative regulator Cryab in the pathway(s) leading to neuronal differentiation triggered by NGF.

Transcriptome profiling of neuronal model cell PC12 from rat pheochromocytoma

GeneChip microarray is a cutting-edge technology being used to study the expression patterns of genes with in a particular cell type. In this study, the Affymetrix RAE230A platform was used to profile stably expressed mRNA transcripts from PC12 cells at passage 5 and 15. The whole-cell PC12 transcriptome revealed that a total of 7,531 stable transcripts (P < 0.05), corresponding to 6,785 genes, were found to be consistently expressed between passage 5 and 15. The data analysis revealed 3,080 functional proteins, belonging to 13 families, which indicate that about 65% of the proteins expressed in PC12 cells are uncharacterized. By using our custom-built rat neuronal reference genome database, we mapped endogenously expressed stable neuronal transcripts from PC12 cells comprising about 765 genes responsible for neuronal function and disease. These neuronal transcripts were further analyzed to provide a genetic blueprint that can be used by neurobiologist to unravel the complex cellular and molecular mechanisms underlying biological functions and their associated signalling networks for diseases affecting the nervous system.

Calmodulin interacts with PAC1 and VPAC2 receptors and regulates PACAP-induced FOS expression in human neuroblastoma cells

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) mediates its physiological functions through activation of PAC1, VPAC1 and VPAC2 receptors, and the ubiquitous Ca(2+)-sensor calmodulin has been implicated in PACAP-induced signaling. The immediate early response gene FOS is a well-known marker of neuronal activation, so we used a human neuroblastoma cell line NB-1 to explore the role of calmodulin in PACAP-induced FOS gene expression. We observed both short-term and prolonged altered PACAP-mediated activation of the FOS gene in the presence of the calmodulin-antagonist W-7. NB-1 cells were shown to express PAC1 and VPAC2 receptors, and immunoprecipitation of both receptors displayed a co-association with calmodulin in the absence of Ca(2+). Our findings indicate a novel mechanism of calmodulin in regulating PACAP signaling by possible interaction with the inactive state of PAC1 and VPAC2 receptors.

Discovery of pituitary adenylate cyclase-activating polypeptide-regulated genes through microarray analyses in cell culture and in vivo

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an evolutionarily well conserved neuropeptide with multiple functions in the nervous, endocrine, and immune systems. PACAP provides neuroprotection from ischemia and toxin exposure, is anti-inflammatory in gastric inflammatory disease and sepsis, controls proliferative signaling pathways involved in neural cell transformation, and modulates glucohomeostasis. PACAP-based, disease-targeted therapeutics might thus be both effective and benign, enhancing homeostatic responses to behavioral, metabolic, oncogenic, and inflammatory stressors. PACAP signal transduction employs synergistic regulation of calcium and cyclic adenosine monophosphate (cAMP), and noncanonical activation of both calcium- and cAMP-dependent processes. Pharmacological activation of PACAP signaling should consequently have highly specific effects even in vivo. Here, a combined cellular biochemical, pharmacologic, transcriptomic, and bioinformatic approach to understanding PACAP signal transduction by identifying PACAP target genes with oligonucleotide- and cDNA-based microarray is described. Calcium- and cAMP-dependent PACAP signaling pathways for regulation of genes encoding proteins required for neuritogenesis, changes in cell morphology, and cell survival have been traced in PC12 cells. Pharmacological experiments have linked gene expression to cell physiological responses in this system, in which gene silencing can also be employed to confirm the functional significance of induction of specific transcripts. Differential transcriptional responses to metabolic, ischemic, and other stressors in wild type compared to PACAP-deficient mice establish in principle which PACAP-responsive transcripts in culture are PACAP-dependent in vivo. Bioinformatic approaches aid in creating a pipeline for identifying neuropeptide-regulated genes, validating their cellular functions, and defining their expression in the context of neuropeptide signaling physiology, required for discovery of new targets for drug action.

PACAP prevents toxicity induced by cisplatin in rat and primate neurons but not in proliferating ovary cells: involvement of the mitochondrial apoptotic pathway

Cisplatin is a chemotherapeutic agent whose use is limited by side effects including neuropathies. In proliferating cells, toxic action of cisplatin is based on DNA interactions, while, in quiescent cells, it can induce apoptosis by interacting with proteins. In the present study, we compared cytotoxic mechanisms activated by cisplatin in primate and rodent neurons and in ovary cells in order to determine whether the anti-apoptotic peptide PACAP could selectively reduce neurotoxicity. In quiescent neurons, JNK and sphingomyelinase inhibitors blocked cisplatin-induced cell death. Toxicity was associated with DNA laddering, caspase-3 and -9 activations and Bax induction. These effects were prevented by PACAP. In proliferating cells, cisplatin activated caspase-8 but had no effect on caspase-9. PACAP exerted no protective effect. These data indicate that cisplatin activates distinct apoptotic pathways in quiescent neurons and proliferating cells and that PACAP may reduce neurotoxicity of cisplatin without affecting its chemotherapeutic efficacy.

Cells silenced for SDHB expression display characteristic features of the tumor phenotype

Recently, enzymes of the tricarboxylic acid (TCA) cycle have emerged as novel tumor suppressors. In particular, mutations in the nuclear-encoded subunits of succinate dehydrogenase (SDHB, SDHC, and SDHD) cause paragangliomas and pheochromocytomas. Although the mechanism(s) by which disruption of mitochondrial metabolism leads to neoplasia is largely unknown, increasing evidence points to an activation of pseudohypoxia. In this study, we have shown that silencing of SDHB using DNA-based small interfering RNA resulted in major impairments in cellular proliferation, respiration, and a corresponding shift to glycolysis. The levels of reactive oxygen species, however, were unchanged. As expected, hypoxia-inducible factor-1 alpha (HIF-1 alpha) and HIF-2alpha were up-regulated in chronically silenced cells, suggesting that a pseudohypoxic state was attained. In addition, the c-Jun amino-terminal kinase and p38 kinase stress signaling proteins were hyperphosphorylated in SDHB-silenced cells. Microarray analysis showed that >400 genes were influenced (6-fold or more up-regulation or down-regulation) by silencing of SDHB, confirming the importance of the TCA cycle in cellular metabolism. Examples of dysregulated genes included those involved in proliferation, adhesion, and the hypoxia pathway. Of interest, SDHB-silenced cells had a greater capacity to adhere to extracellular matrix components, including fibronectin and laminin, than control cells, thus suggesting a possible mechanism of tumor initiation. Although transient silencing of the HIF-1 alpha transcription factor in SDHB-silenced cells had little effect on the expression of a subset of up-regulated genes, it partially reversed the adhesion phenotype to fibronectin, pointing to a potentially important role for HIF-1 in this process.

Pituitary adenylate cyclase-activating polypeptide (PACAP) alters parasympathetic neuron gene expression in a time-dependent fashion

Neuropeptides, including pituitary adenylate cyclase-activating polypeptide (PACAP), can influence diverse cellular processes over a broad temporal range. In ciliary ganglion (CG) neurons, for example, PACAP binding to high-affinity PAC1 receptors triggers transduction cascades that both rapidly modulate nicotinic receptors and synapses and support long-term survival. Since PACAP/PAC1 signaling recruits intracellular messengers and effectors that potently alter transcription, we examined its activation of the transcription factor CREB and then tested for changes in gene expression. PACAP/PAC1 signaling rapidly induced prolonged CREB activation in CG neurons by a phospholipase C -independent mechanism supported by Ca2+-influx, adenylate cyclase, and effectors, including protein kinase C (PKC) and possibly PKA. Since PACAP is abundant in the CG and released from depolarized presynaptic terminals, it is well suited to regulate gene expression relevant to neuronal and synaptic development. Gene array screens conducted using RNA from CG cultures grown with PACAP for 1/4, 24, or 96 h revealed a time-dependent pattern of > 600 regulated transcripts, including several encoding proteins implicated in synaptic function, neuronal survival, and development. The results underscore rapid, neuromodulatory, and long-term, neurotrophic consequences of PAC1 signaling in CG neurons and suggest that PACAP exerts such diverse influences by altering the expression of specific gene transcripts in a time-dependent fashion.

Selenoprotein T is a PACAP-regulated gene involved in intracellular Ca2+ mobilization and neuroendocrine secretion

Selenoproteins contain the essential trace element selenium, the deficiency of which is associated with cancer or accelerated aging. Although selenoproteins are thought to be instrumental for the effects of selenium, the biological function of many of these proteins remains unknown. Here, we studied the role of selenoprotein T (SelT), a selenocysteine (Sec) -containing protein with no known function, which we have identified as a novel target gene of the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) during PC12 cell differentiation. SelT was found to be ubiquitously expressed throughout embryonic development and in adulthood in rat. Immunocytochemical analysis revealed that SelT is mainly localized to the endoplasmic reticulum through a hydrophobic domain. PACAP and cAMP induced a rapid and long-lasting increase in SelT gene expression in PC12 cells, in a Ca(2+)-dependent manner. These results suggested a possible role of SelT in PACAP signaling during PC12 cell differentiation. Indeed, overexpression of SelT in PC12 cells provoked an increase in the concentration of intracellular Ca(2+) ([Ca(2+)](i)) that was dependent on the Sec residue. Conversely, SelT gene knockdown inhibited the PACAP-induced increase in [Ca(2+)](i) and reduced hormone secretion. These findings demonstrate the implication of a selenoprotein in the regulation of Ca(2+) homeostasis and neuroendocrine secretion in response to a cAMP-stimulating trophic factor.

Role of PACAP in the physiology and pathology of the sympathoadrenal system

Sympathetic neurons and chromaffin cells derive from common sympathoadrenal precursors which arise from the neural crest. Cells from this lineage migrate to their final destination and differentiate by acquiring a catecholaminergic phenotype in response to different environmental factors. It has been shown that the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) and its PAC1 receptor are expressed at early stages of sympathetic development, and participate to the control of neuroblast proliferation and differentiation. PACAP also acts as a neurotransmitter to stimulate catecholamine and neuropeptide biosynthesis and release from sympathetic neurons and chromaffin cells, during development and in adulthood. In addition, PACAP and its receptors have been described in neuroblastoma and pheochromocytoma, and the neuropeptide regulates the differentiation and activity of sympathoadrenal-derived tumoral cell lines, suggestive of an important role in the pathophysiology of the sympathoadrenal lineage. Transcriptome studies uncovered genes and pathways of known and unknown roles that underlie the effects of PACAP in the sympathoadrenal system.

PACAP and its receptor VPAC1 regulate megakaryocyte maturation: therapeutic implications

Megakaryocytes and platelets express the Gs-coupled VPAC1 receptor, for which the pituitary adenylyl cyclase-activating peptide (PACAP) and the vasointestinal peptide (VIP) are agonists. We here demonstrate a regulatory role for VPAC1 signaling during megakaryopoiesis. A total of 2 patients with trisomy 18p with PACAP overexpression and transgenic mice overexpressing PACAP in megakaryocytes have thrombopathy, a mild thrombocytopenia, and a reduced number of mature megakaryocytes in their bone marrow. In vitro differentiation of hematopoietic stem cells from the patient and transgenic mice shows a reduced number of megakaryocyte colonies compared with controls. The addition of PACAP, VIP, or the adenylyl cyclase activator forskolin to CD34(+) cells inhibits megakaryocyte differentiation. In contrast, neutralizing monoclonal anti-PACAP (PP1A4) or anti-VPAC1 (23A11) antibodies inhibit cAMP formation and stimulate megakaryopoiesis in a thrombopoietin-independent manner. Moreover, wild-type mice obtain an increased platelet count after subcutaneous injection of PP1A4 or 23A11. These antibodies also elevate platelet numbers in animal models of myelosuppressive therapy and in GATA1-deficient mice with congenital thrombocytopenia. Furthermore, 23A11 stimulates the in vitro megakaryocyte differentiation of both normal and GATA1-deficient human CD34(+) cells. Together, our data strongly suggest that VPAC1 signaling tempers normal megakaryopoiesis, and that inhibition of this pathway stimulates megakaryocyte differentiation, enhancing platelet recovery after myelosuppressive therapy and in GATA1 deficiency.

Microarray analyses of pituitary adenylate cyclase activating polypeptide (PACAP)-regulated gene targets in sympathetic neurons

The high and preferential expression of the PAC(1)(short)HOP1 receptor in postganglionic sympathetic neurons facilitates microarray studies for mechanisms underlying PACAP-mediate neurotrophic signaling in a physiological context. Replicate primary sympathetic neuronal cultures were treated with 100 nM PACAP27 either acutely (9 h) or chronically (96 h) before RNA extraction and preparation for Affymetrix microarray analysis. Compared to untreated control cultures, acute PACAP treatment modulated significantly the expression of 147 transcripts of diverse functional groups, including peptides, growth factors/cytokines, transcriptional factors, receptors/signaling effectors and cell cycle regulators, that collectively appeared to facilitate neuronal plasticity, differentiation and/or regeneration processes. Some regulated transcripts, for example, were related to BDNF/TrkB, IL-6/Jak2/Socs2 and TGF/follistatin signaling; many transcripts affected bioactive peptide and polyamine biosynthesis. Although chronic PACAP treatments altered the expression of 109 sympathetic transcripts, only 43 transcripts were shared between the acute and chronic treatment data sets. The PACAP-mediated changes in transcript expression were corroborated independently by quantitative PCR measurement. The PACAP-regulated transcripts in sympathetic neurons did not bear strong resemblance to those in PACAP-treated pheochromocytoma cells. However, many PACAP-targeted sympathetic transcripts, especially those related to peptide plasticity and nerve regeneration processes, coincided significantly with genes altered after peripheral nerve injury. The ability for sympathetic PAC(1)(short)HOP1 receptors to engage multiple downstream signaling cascades appeared to be reflected in the number and diversity of genes targeted in a multifaceted strategy for comprehensive neurotrophic responses.

Meta-analysis of microarray-derived data from PACAP-deficient adrenal gland in vivo and PACAP-treated chromaffin cells identifies distinct classes of PACAP-regulated genes

Initial PACAP-regulated transcriptomes of PACAP-treated cultured chromaffin cells, and the adrenal gland of wild-type versus PACAP-deficient mice, have been assembled using microarray analysis. These were compared to previously acquired PACAP-regulated transcriptome sets from PC12 cells and mouse central nervous system, using the same microarray platform. The Ingenuity Pathways Knowledge Base was then employed to group regulated transcripts into common first and second messenger regulatory clusters. The purpose of our meta-analysis was to identify sets of genes regulated distinctly or in common by the neurotransmitter/neurotrophin PACAP in specific physiological contexts. Results suggest that PACAP participates in both the basal differentiated expression, and the induction upon physiological stimulation, of distinct sets of transcripts in neuronal and endocrine cells. PACAP in both developmental and acute regulatory paradigms acts on target genes also regulated by either TNFalpha or TGFbeta, two first messengers acting on transcription mainly through NFkappaB and Smads, respectively.

Pheochromocytomas in Nf1 knockout mice express a neural progenitor gene expression profile

Pheochromocytomas are adrenal medullary tumors that typically occur in adult patients, with increased frequency in multiple endocrine neoplasia type 2, von Hippel-Lindau disease, familial paraganglioma syndromes and neurofibromatosis type 1 (NF1). Pheochromocytomas arise in adult mice with a heterozygous knockout mutation of exon 31 of the murine Nf1 gene, providing a mouse model for pheochromocytoma development in NF1. We performed a microarray-based gene expression profiling study comparing mouse pheochromocytoma tissue to normal adult mouse adrenal medulla to develop a basis for studying the pathobiology of these tumors. The findings demonstrate that pheochromocytomas from adult neurofibromatosis knockout mice express multiple developmentally regulated genes involved in early development of both the CNS and peripheral nervous system. One of the most highly overexpressed genes is receptor tyrosine kinase Ret, which is known to be transiently expressed in the developing adrenal gland, down-regulated in adult adrenals and often overexpressed in human pheochromocytomas. Real-time polymerase chain reaction validated the microarray results and immunoblots confirmed the overexpression of Ret protein. Other highly expressed validated genes include Sox9, which is a neural crest determinant, and Hey 1, which helps to maintain the progenitor status of neural precursors. The findings are consistent with the recently proposed concept that persistent neural progenitors might give rise to pheochromocytomas in adult mouse adrenals and suggest that events predisposing to tumor development might occur before formation of the adrenal medulla or migration of cells from the neural crest. However, the competing possibility that developmentally regulated neural genes arise secondarily to neoplastic transformation cannot be ruled out. In either case, the unique profile of gene expression opens the mouse pheochromocytoma model to new applications pertinent to neural stem cells and suggests potential new targets for treatment of pheochromocytomas or eradication of their precursors.

Development of novel tools for the diagnosis and prognosis of pheochromocytoma using peptide marker immunoassay and gene expression profiling approaches

Pheochromocytomas (PHEOs) are rare catecholamine-producing neoplasias that arise from chromaffin cells of the adrenal medulla or from extra-adrenal locations. These neuroendocrine tumors are usually benign, but may also present as or develop into a malignancy. There are currently no means to predict or to cure malignant tumors which have a poor prognosis. We have recently validated several assays for the measurement of peptides derived from chromogranin A (CgA) and secretogranin II (SgII) in order to determine whether these secreted neuroendocrine products could provide useful, complementary markers for the diagnosis and prognosis of PHEOs. Both the CgA-derived peptide WE14 and the SgII-derived peptide EM66 proved to be sensitive circulating markers for the diagnosis of PHEO. In addition, much higher EM66 levels were measured in benign than in malignant tumoral tissues, suggesting that this peptide could represent a valuable tool for the prognosis of PHEO. We have also initiated a comparative microarray study of benign and malignant PHEOs, which allowed the identification of a set of about 100 genes that were differentially expressed and best discriminated the two types of tumors. A large majority of these genes were expressed at lower levels in the malignant disease and were associated with various characteristics of chromaffin cells, such as hormone secretion signaling and machinery, peptide maturation, and cellular morphology. Altogether, these studies provide novel tools for the management of PHEO, and new insights for the understanding of tumorigenesis in chromaffin cells, which may offer potential therapeutic strategies.

Functional genomics approaches for the study of sporadic adrenal tumor pathogenesis: clinical implications

Although sporadic adrenal tumors are frequently encountered in the general population their pathogenesis is not well elucidated. The advent of functional genomics/bioinformatics tools enabling large scale comprehensive genome expression profiling should contribute to significant progress in this field. Some studies have already been published describing gene expression profiles of benign and malignant adrenocortical tumors and phaeochromocytomas. Several genes coding for growth factors and their receptors, enzymes involved in steroid hormone biosynthesis, genes related to the regulation of cell cycle, cell proliferation, adhesion and intracellular metabolism have been found to be up- or downregulated in various tumors. Some alterations in gene expression appear so specific for certain tumor types that their application in diagnosis, determination of prognosis and the choice of therapy can be envisaged. In this short review, the authors will present a synopsis of these recent findings that seem to open new perspectives in adrenal tumor pathogenesis, with emphasis on changes in steroidogenic enzyme expression profiles and highlighting possible clinical implications.

Possible implication of the transcriptional regulator Id3 in PACAP-induced pro-survival signaling during PC12 cell differentiation

PACAP inhibits cell proliferation and promotes cell survival and neurite outgrowth of pheochromocytoma PC12 cells. Transcriptome analysis of PACAP-treated PC12 cells allowed to identify potential genes implicated in this differentiation process. Among the genes whose expression is up-regulated by PACAP, we identified the Inhibitor of DNA binding 3 (Id3). Id3 is a member of the helix-loop-helix (HLH) family of transcription factors which acts as a negative dominant inhibitor of basic HLH factors. Time-course studies revealed that Id3 is an early PACAP response gene (8-fold after 1 h of stimulation), and that the up-regulation of its expression persists over 12 h after the onset of PACAP treatment. The stimulatory effect of PACAP on Id3 mRNA levels was mimicked by adenylate cyclase/PKA activators like forskolin and dibutyryl cyclic AMP. Moreover, PACAP-induced Id3 gene expression was inhibited by phosphatidylinositol 3'-OH-kinase and p38 MAP kinase blockers. Northern blot analysis of Id3 distribution in rat tissues showed a strong expression of this gene in the adrenal medulla. Overexpression of Id3 increased the number of living PC12 cells, in basal condition and after exposure to oxidative stress. These results indicate that Id3 is a cAMP-responsive gene whose up-regulation could be involved in PACAP-induced pro-survival signaling during sympathoadrenal cell differentiation.

The neurotrophic effects of PACAP in PC12 cells: control by multiple transduction pathways

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are closely related members of the secretin superfamily of neuropeptides expressed in both the brain and peripheral nervous system, and they exhibit neurotrophic and neurodevelopmental effects in vivo. Like the index member of the Trk receptor ligand family, nerve growth factor (NGF), PACAP promotes the differentiation of PC12 cells, a well-established cell culture model, to investigate neuronal differentiation, survival and function. Stimulation of catecholamine secretion and enhanced neuropeptide biosynthesis are effects exerted by PACAP at the adrenomedullary synapse in vivo and on PC12 cells in vitro through stimulation of the specific PAC1 receptor. Induction of neuritogenesis, growth arrest, and promotion of cell survival are effects of PACAP that occur in developing cerebellar, hippocampal and cortical neurons, as well as in the more tractable PC12 cell model. Study of the mechanisms through which PACAP exerts its various effects on cell growth, morphology, gene expression and survival, i.e. its actions as a neurotrophin, in PC12 cells is the subject of this review. The study of neurotrophic signalling by PACAP in PC12 cells reveals that multiple independent pathways are coordinated in the PACAP response, some activated by classical and some by novel or combinatorial signalling mechanisms.

Cycloheximide treatment to identify components of the transitional transcriptome in PACAP-induced PC12 cell differentiation

Pituitary adenylate cyclase-activating polypeptide (PACAP) promotes neurite outgrowth, reduces proliferation and inhibits apoptosis of PC12 cells. We have partially characterized the transcriptome changes induced by PACAP after 6 h of treatment, when commitment to differentiation has occurred. Here, we have investigated the effects of a 6-h treatment with PACAP (10(-7) m) in the presence of cycloheximide (5 microm) to identify, via superinduction, components of the transitional transcriptome initially induced by PACAP and potentially participating in the regulation of late-response genes required for differentiation. Approximately 100 new transcripts were identified in this screen, i.e. as many individual genes as make up the 6-h PACAP differentiation transcriptome itself. Six known transcripts in this cohort were then measured at several time points between 0 and 6 h by real-time PCR to determine whether these transcripts are induced early following PACAP treatment in the absence of cycloheximide, and therefore may be of functional importance in differentiation. Five out of the six transcripts were indeed induced by PACAP alone soon (between 30 min and 3 h) after cell treatment. beta-Cell translocation gene 2, antiproliferative (Btg2), serum/glucocorticoid-regulated kinase (Sgk), nuclear factor for the kappa chain of B-cells (NFkappaB), seven in absentia homologue 2 (Siah2) and FBJ osteosarcoma related oncogene (Fos) showed a 2.5-200-fold induction by PACAP between 15 min and 3 h, and mRNA levels returned either to baseline or near baseline after 6 h. This work provides new information concerning genes whose transient regulation early after PACAP exposure may contribute to the expression of the differentiated transcriptome in PC12 cells, and should help to elucidate the molecular mechanisms involved in the control of nerve cell survival and differentiation.

Maternal perinatal undernutrition alters neuronal and neuroendocrine differentiation in the rat adrenal medulla at weaning

Epidemiological studies suggest that chronic adult diseases, such as type 2 diabetes and hypertension, can be programmed during fetal and early postnatal life. The nervous system regions governing vegetative functions and the hypothalamic-pituitary-adrenal axis are particularly sensitive to the perinatal nutritional status. Despite recent reports demonstrating that the activity of the sympathoadrenal system can be altered by early life events, the effects of maternal nutrient restriction on the adrenal medulla remain unknown. Using a rat model of maternal perinatal 50% food restriction (FR50) from the second week of gestation until weaning, immunohistochemical experiments revealed alterations in chromaffin cell aggregation and in nerve fiber fasciculation in the adrenal medulla of FR50 pups. These morphological changes were associated with enhanced circulating levels of catecholamines after decapitation (epinephrine by 55% and norepinephrine by 41%). Using macroarrays, we identified several genes whose expression was affected by maternal nutrient restriction. Semiquantitative RT-PCR confirmed the overexpression of four genes involved in neuroendocrine differentiation and neuronal plasticity (chromogranin B, growth-associated protein 43, neurofilament 3, and Slit2) in the adrenal glands of FR50 rats. Using in situ hybridization, we showed that these genes are solely expressed in the adrenal medulla. Together, our results suggest that perinatal maternal undernutrition markedly alters the differentiation of the adrenal medulla during postnatal life, resulting in enhanced activity of chromaffin cells at weaning. These alterations may persist in adulthood and participate to the programming of chronic adult diseases.

Pituitary adenylate cyclase activating polypeptide protects cardiomyocytes against oxidative stress-induced apoptosis

Pituitary adenylate cyclase activating polypeptide (PACAP) has well-known neuroprotective effects, and one of the main factors leading to neuroprotection seems to be its anti-apoptotic effects. The peptide and its receptors are present also in the heart, but whether PACAP can be protective in cardiomyocytes, is not known. Therefore, the aim of the present study was to investigate the effects of PACAP on oxidative stress-induced apoptosis in cardiomyocytes. Our results show that PACAP increased cell viability by attenuating H2O2-induced apoptosis in a cardiac myocyte culture. PACAP also decreased caspase-3 activity and increased the expression of the anti-apoptotic markers Bcl-2 and phospho-Bad. These effects of PACAP were counteracted by the PACAP antagonist PACAP6-38. In summary, our results show that PACAP is able to attenuate oxidative stress-induced cardiomyocyte apoptosis.

Endogenous Ligands of PACAP/VIP Receptors in the Autocrine–Paracrine Regulation of the Adrenal Gland

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are the main endogenous ligands of a class of G protein-coupled receptors (Rs). Three subtypes of PACAP/VIP Rs have been identified and named PAC(1)-Rs, VPAC(1)-Rs, and VPAC(2)-Rs. The PAC(1)-R almost exclusively binds PACAP, while the other two subtypes bind with about equal efficiency VIP and PACAP. VIP, PACAP, and their receptors are widely distributed in the body tissues, including the adrenal gland. VIP and PACAP are synthesized in adrenomedullary chromaffin cells, and are released in the adrenal cortex and medulla by VIPergic and PACAPergic nerve fibers. PAC(1)-Rs are almost exclusively present in the adrenal medulla, while VPAC(1)-Rs and VPAC(2)-Rs are expressed in both the adrenal cortex and medulla. Evidence indicates that VIP and PACAP, acting via VPAC(1)-Rs and VPAC(2)-Rs coupled to adenylate cyclase (AC)- and phospholipase C (PLC)-dependent cascades, stimulate aldosterone secretion from zona glomerulosa (ZG) cells. There is also proof that they can also enhance aldosterone secretion indirectly, by eliciting the release from medullary chromaffin cells of catecholamines and adrenocorticotropic hormone (ACTH), which in turn may act on the cortical cells in a paracrine manner. The involvement of VIP and PACAP in the regulation of glucocorticoid secretion from inner adrenocortical cells is doubtful and surely of minor relevance. VIP and PACAP stimulate the synthesis and release of adrenomedullary catecholamines, and all three subtypes of PACAP/VIP Rs mediate this effect, PAC(1)-Rs being coupled to AC, VPAC(1)-Rs to both AC and PLC, and VPAC(2)-Rs only to PLC. A privotal role in the catecholamine secretagogue action of VIP and PACAP is played by Ca(2+). VIP and PACAP may also modulate the growth of the adrenal cortex and medulla. The concentrations attained by VIP and PACAP in the blood rule out the possibility that they act as true circulating hormones. Conversely, their adrenal content is consistent with a local autocrine-paracrine mechanism of action.

Identification of novel growth factor-responsive genes in neuroendocrine gastrointestinal tumour cells

Targeting growth-regulatory pathways is a promising approach in cancer treatment. A prerequisite to the development of such therapies is characterisation of tumour growth regulation in the particular tumour cell type of interest. In order to gain insight into molecular mechanisms underlying proliferative responses in neuroendocrine (NE) gastrointestinal (GI) tumours, we investigated gene expression in human carcinoid BON cells after exposure to gastrin, hepatocyte growth factor (HGF), pituitary adenylate cyclase-activating polypeptide or epidermal growth factor. We particularly focused on gastrin- and HGF-induced gene expression, and identified 95 gastrin- and 101 HGF-responsive genes. The majority of these genes are known mediators of processes central in tumour biology, and a number of them have been associated with poor prognosis and metastasis in cancer patients. Furthermore, we identified 12 genes that were regulated by all four factors, indicating that they may be universally regulated during NE GI tumour cell proliferation. Our findings provide useful hypotheses for further studies aimed to search for new therapeutic targets as well as tumour markers in NE GI tumours.

Transcriptome of pituitary adenylate cyclase-activating polypeptide-differentiated PC12 cells

Addition of pituitary adenylate cyclase-activating polypeptide (PACAP) into the cultured PC12 cells secreted dopamine and promoted neurite outgrowth of the cells, indicating cell differentiation. To characterize the PACAP-differentiated PC12 cell transcriptome, we applied DNA macroarray techniques, using Atlas Rat 1.2 Array membranes (BD Biosciences Clontech) that have 1176 cDNA. RNA samples were harvested from PC12 cells before and at a time of 6 h treatment with 1 nM PACAP, when neuritogenesis was remarkably observed under the condition used. Several genes regulated by PACAP have been associated with neuritogenesis (i.e. villin 2 and tissue plasminogen activator) or cell growth/differentiation (i.e. cyclin or ornitine decarboxylase). Also, cytoskeleton proteins such as actin or tubulin were up-regulated for cell morphology remodeling. A message of vehicle trafficking molecule (synaptotagmin IV) was more remarkably increased (3.95-6.85-fold). Signaling molecules such as small G proteins (rab12, rab16, or ral), IkappaB, or STAT3 were altered by PACAP. It is noteworthy that PACAP inhibited the expression of galanin receptor 2, whose ligand was shown to inhibit tyrosine hydroxylase activity. Thus, in this study the transcriptome of PACAP-differentiated PC12 was established, leading to the elucidation of the molecular mechanism of neuritogenesis by the neuropeptide.

Dicyclohexylphthalate causes hyperactivity in the rat concomitantly with impairment of tyrosine hydroxylase immunoreactivity

Endocrine disruptors possibly exert effects on neuronal functions leading, in particular, to behavioural alterations. In this study, we examined the effects of dicyclohexylphthalate (DCHP), an endocrine disruptor, on rat behavioural and cellular responses. Single intracisternal administration of DCHP (0.87-87 nmol) into 5-day-old male Wistar rats caused significant hyperactivity at 4-5 weeks of age. It was about 1.4-fold more active in the nocturnal phase after administration of 87 nmol of DCHP than control rats (p < 0.001). The response had a tendency to be dose-dependent. Based on DNA macoarray analyses, DCHP down-regulated the levels of gene expression of the dopamine D4 receptor at 4 weeks old in both the midbrain and the striatum, and the dopamine transporter in the midbrain at 8 weeks old 1.7- to 2-fold. The gene expression of several subtypes of glutamate receptors was facilitated in the striatum at 4 weeks old and in the midbrain at 8 weeks old. Some normalization and/or compensatory changes seemed to occur in gene expression of GABA or glycine transmission. Furthermore, DCHP abolished immunoreactivity of tyrosine hydroxylase in the substantia nigra at 8 weeks of age, where TUNEL-positive cells were seen. We conclude that DCHP affected the developing rat brain, resulting in hyperactivity, probably as a result of degeneration of mesencephalic tyrosine hydroxylase rather than alteration of the level of gene expression.

p-Nitrotoluene causes hyperactivity in the rat

It has not been known which endocrine disruptors exert their effects on neuronal functions, particularly leading to behavioral alterations. To address this, we examined the effects of p-nitrotoluene, an endocrine disruptor, on rat behavior and gene expression. Single intracisternal administration of p-nitrotoluene (ca. 10 microg) into 5-day-old male Wistar rats caused significant hyperactivity at 4-5 weeks of age. They were about 1.4-fold more active in the nocturnal phase after administration of p-nitrotoluene than control rats. Based on DNA array analyses, p-nitrotoluene decreased more than two-fold the levels of gene expression of the mesencephalic dopamine transporter at 8 weeks old. Thus, it was demonstrated for the first time that p-nitrotoluene definitely affected the developing brain, resulting in hyperactivity in the rat.

Combinatorial code of growth factors and neuropeptides define neuroendocrine differentiation in PC12 cells

Adrenal chromaffin cells constitute one of the first cell types to have been defined as a neuroendocrine cell type. Since they produce dopamine, these cells have been proposed for the treatment of neuronal deficits in human Parkinson's disease. However, the factors involved in the development of chromaffin cells are still poorly understood. Based on recent insights from stem cell research, we decided to study the role of extracellular matrices, growth factors and neuropeptides on the neuroendocrine differentiation in a serum-free medium of PC12 cells. Employing immunohistochemistry, quantitative PCR and HPLC analysis, neuroendocrine differentiation was determined by evaluating neurite outgrowth, catecholamine biosynthesis and release as well as neuropeptide and vesicular protein mRNA expression. The combination of bFGF, NGF and PACAP could prevent the inhibition of neurite process development induced by dexamethasone in PC12 cells cultured on ECM. Whereas glucocorticoids were essential in the regulation of enzymes of catecholamine biosynthesis and metabolism, growth factors and PACAP were more efficient in inducing neuropeptide and chromogranin B expression as well as release of dopamine and 3-methoxytyramine. Therefore, in addition to glucocorticoids, chromaffin cells need a gradient of matrix, growth factors, and neuropeptides to develop the full functional phenotype of a neuroendocrine cell.