Effect Of Vasoactive Intestinal Peptide Research Articles

Vasoactive intestinal peptide stimulates melanogenesis in B16F10 mouse melanoma cells via CREB/MITF/tyrosinase signaling

Vasoactive intestinal peptide (VIP), one of the major skin neuropeptides, has been suggested to have active roles in the pathogenesis of inflammatory skin disorders such as atopic dermatitis and psoriasis, which can commonly cause post-inflammatory hyperpigmentation. However, the effect of VIP on melanogenesis remains unknown. In this study, we showed that the melanin contents, tyrosinase activity, and gene expression of tyrosinase and microphthalmia-associated transcription factor (MITF) were significantly increased by treatment with VIP in B16F10 mouse melanoma cells and the stimulatory melanogenic effect was further examined in human epidermal melanocytes (HEMns). In addition, phosphorylated levels of CRE-binding protein (CREB) and protein kinase A (PKA) were markedly increased after VIP treatment, but not p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), or Akt, indicating the possible PKA-CREB signaling pathway involved in VIP-induced melanogenesis. This result was further verified by the fact that VIP induced increased melanin synthesis, and protein levels of phosphorylated CREB, MITF, tyrosinase were significantly attenuated by H89 (a specific PKA inhibitor). These data suggest that VIP-induced upregulation of tyrosinase through the CREB-MITF signaling pathway plays an important role in finding new treatment strategy for skin inflammatory diseases related pigmentation disorders.

Effect of vasoactive intestinal peptide on cell migration and invasion and epithelial-mesenchymal transition in prostate cancer DU145 cells

Objective To observe the effect of intestinal peptide on cell migration and invasion of the DU145 cells, and explore the mechanism of epithelial-mesenchymal transition. Methods DU145 cells were treated with VIP at concentrations of 0, 25, 50 and 100 μmol/L, respectively. E-cadherin, Vimentin, and Snail mRNA and protein were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting respectively at 24 h. The cell mobility, migration and invasion ability of DU145 cells were respectively measured by wound-healing assay, Transwell migration and invasion assays at 48 h. Results With the increases of concentrations of VIP for 24 h, the expression levels of E-cadherin, Vimentin, and Snail mRNA in PC-3 cells were increased at 24 h (0.897±0.053, 0.715±0.041, 0.521±0.036, 0.343±0.029; 0.586±0.061, 0.827±0.089, 1.329±0.107, 1.764±0.135; 0.645±0.055, 0.917±0.074, 1.383±0.097, 1.725±0.124; P<0.05). Meanwhile, the cell mobility was increased, the number of migrative cells and invasive cells was significantly increased gradually with the increased concentrations of VIP [(76.7±5.8), (104.5±6.7), (128.3±10.4), (147.7±12.6) cells; (84.2±6.4), (118.3±10.3), (142.1±13.7), (173.6±15.4) cells; P<0.01]. Conclusion VIP can increase ability of movement, migration and invasion of prostate cancer DU145 cells by epithelial-mesenchymal transition. Key words: Vasoactive intestinal peptide; Prostate carcinoma; Tumor metastasis; Epithelial-mesenchymal transition

PACAP and VIP Inhibit the Invasiveness of Glioblastoma Cells Exposed to Hypoxia through the Regulation of HIFs and EGFR Expression.

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) through the binding of vasoactive intestinal peptide receptors (VIPRs), perform a wide variety of effects in human cancers, including glioblastoma multiforme (GBM). This tumor is characterized by extensive areas of hypoxia, which triggers the expression of hypoxia-inducible factors (HIFs). HIFs not only mediate angiogenesis but also tumor cell migration and invasion. Furthermore, HIFs activation is linked to epidermal growth factor receptor (EGFR) overexpression. Previous studies have shown that VIP interferes with the invasive nature of gliomas by regulating cell migration. However, the role of VIP family members in GBM infiltration under low oxygen tension has not been clarified yet. Therefore, in the present study we have investigated, for the first time, the molecular mechanisms involved in the anti-invasive effect of PACAP or VIP in U87MG glioblastoma cells exposed to hypoxia induced by treatment with desferrioxamine (DFX). The results suggest that either PACAP or VIP exert an anti-infiltrative effect under low oxygen tension by modulating HIFs and EGFR expression, key elements involved in cell migration and angiogenesis. These peptides act through the inhibition of PI3K/Akt and MAPK/ERK signaling pathways, which are known to have a crucial role in HIFs regulation.

Vinpocetine and Vasoactive Intestinal Peptide Attenuate Manganese-Induced Toxicity in NE-4C Cells.

Increased concentration of manganese (Mn) in the brain is known to be associated with excitotoxicity and neuroinflammation. Vinpocetine, an alkaloid derived from the plant Vinca minor L., basically shows its effect via phosphodiesterase inhibition and voltage-dependent Na+ channels. Vasoactive intestinal peptide (VIP) has gastrointestinal, vasomotor, muscular, and neuroprotective effects. The aim of this study was to examine the potential protective effects of vinpocetine and VIP against Mn toxicity in NE-4C neural stem cells (NSCs). VIP treatment at 1μM and vinpocetine treatment at 2μM concentrations were sufficient to yield maximum protection, and these concentrations were adopted in the following experiments. In this study, Mn treatment significantly increased lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) production, and triggered cell death in NE-4C cultures. However, significant reduction in LDH release was observed following vinpocetine or VIP treatments when compared with control. Similar to these findings, vinpocetine or VIP treatments significantly reduced membrane degradation induced by Mn (p<0.001). Moreover, vinpocetine attenuated Mn-induced decrease of mitochondrial membrane potential. Similarly, proapoptotic protein bax and ROS production significantly decreased in cells after incubation with vinpocetine (p=0.01) or VIP in the presence of Mn (p<0.001). Our study provides the evidence that both vinpocetine and VIP may exert protective effects via modulating oxidative stress and apoptosis in Mn-induced neurodegeneration in NE-4C cells.

Vasoactive Intestinal Peptide modulates trophoblast-derived cell line function and interaction with phagocytic cells through autocrine pathways.

Trophoblast cells migrate and invade the decidual stroma in a tightly regulated process to maintain immune homeostasis at the maternal-placental interface during the first weeks of pregnancy. Locally synthesized factors modulate trophoblast cell function and their interaction with maternal leukocytes to promote the silent clearance of apoptotic cells. The vasoactive intestinal peptide (VIP) is a pleiotropic polypeptide with trophic and anti-inflammatory effects in murine pregnancy models. We explored the effect of VIP on two human first trimester trophoblast cell lines, particularly on their migration, invasiveness and interaction with phagocytic cells, and the signalling and regulatory pathways involved. We found that VIP enhanced trophoblast cell migration and invasion through the activation of high affinity VPAC receptors and PKA-CRE signalling pathways. VIP knocked-down trophoblast cells showed reduced migration in basal and leukemic inhibitor factor (LIF)-elicited conditions. In parallel, VIP-silenced trophoblast cells failed to induce the phagocytosis of apoptotic bodies and the expression of immunosuppressant markers by human monocytes. Our results suggest that VIP-mediated autocrine pathways regulate trophoblast cell function and contribute to immune homeostasis maintenance at placentation and may provide new clues for therapeutic intervention in pregnancies complicated by defective deep placentation.

Modulation of Corpus Striatal Neurochemistry by Astrocytes and Vasoactive Intestinal Peptide (VIP) in Parkinsonian Rats.

The neurotoxin 6-hydroxydopamine (6-OHDA) is widely used in animal models of Parkinson's disease. In various neurodegenerative diseases, astrocytes play direct, active, and critical roles in mediating neuronal survival and functions. Vasoactive intestinal peptide (VIP) has neurotrophic actions and modulates a number of astrocytic activities. In this study, the effects of VIP on the striatal neurochemistry were investigated in parkinsonian rats. Adult Sprague-Dawley rats were divided into sham-operated, unilaterally 6-OHDA-lesioned, and lesioned + VIP-administered (25ng/kgi.p.) groups. VIP was first injected 1h after the intrastriatal 6-OHDA microinjection and then every 2days throughout 15days. Extracellular striatal concentration of glutathione (GSH), gamma-aminobutyric acid (GABA), glutamate (GLU), and lactate were measured in microdialysates by high-performance liquid chromatography (HPLC). Quantification of GABA and activity dependent neuroprotective protein (ADNP)-expressing cells were determined by glutamic acid decarboxylase (GAD)/ADNP + glial fibrillary acidic protein (GFAP) double immunohistochemistry. Our results demonstrated that a 6-OHDA lesion significantly increased the density of astrocytes in the striatum and VIP treatment slightly reduced the gliosis. Extracellular concentration of GABA, GLU, and lactate levels did not change, but GSH level significantly increased in the striatum of parkinsonian rats. VIP treatment reduced GSH level comparable to sham-operated groups, but enhanced GABA and GLU levels. Our double labeling results showed that VIP primarily acts on neurons to increase ADNP and GAD expression for protection. These results suggest that, in the 6-OHDA-induced neurodegeneration model, astrocytes were possibly activated for forefront defensiveness by modulating striatal neurochemistry.

VIP protects human retinal microvascular endothelial cells against high glucose-induced increases in TNF-α and enhances RvD1

PurposeThe purpose of our study was to evaluate the therapeutic effect of VIP on human retinal endothelial cells (HREC) under high glucose conditions. Diabetes affects almost 250 million people worldwide. Over 40% of diabetics are expected to develop diabetic retinopathy, which remains the leading cause of visual impairment/blindness. Currently, treatment is limited to late stages of retinopathy with no options available for early stages. To this end, the purpose of the current study is to evaluate the therapeutic effect of vasoactive intestinal peptide (VIP) on HREC under high glucose conditions. MethodsPrimary HREC were cultured in normal (5mM) or high (25mM) glucose medium +/− VIP treatment. Protein levels of TNF-α, resolvin D1 (RvD1), formyl peptide receptor 2 (FPR2), G protein-coupled receptor 32 (GPR32), VEGF, and VIP receptors, VPAC1 and VPAC2 were measured. ResultsHigh glucose-induced changes in TNF-α and RvD1 were restored to control levels with VIP treatment. RvD1 receptors, ALX/FPR2 and GPR32, were partially rescued with VIP treatment. VPAC2 expression appeared to be the major receptor involved in VIP signaling in HREC, as VPAC1 receptor was not detected. In addition, VIP did not induce HREC secretion of VEGF under high glucose conditions. ConclusionsOur results demonstrate that VIP’s therapeutic effect on HREC, occurs in part, through the balance between the pro-inflammatory cytokine, TNF-α, and the pro-resolving mediator, RvD1. Although VPAC1 is considered the major VIP receptor, VPAC2 is predominantly expressed on HREC under both normal and high glucose conditions.

Effect of vasoactive intestinal peptide on the wound healing of alkali-burned corneas.

To study the effect of vasoactive intestinal peptide (VIP) on wound healing in experimental alkali burns of the cornea. Twenty-seven albino rabbits, weighing 3.2±0.75 kg were used. Alkali burns were induced on corneas by applying 10 mm Whatman paper No:50 soaked in 1 mol/L NaOH. They have further classified into 5 groups as follows: 1) control group given no treatment (n=5); 2) VIP given subconjunctivally (n=6); 3) VIP injected into anterior chamber (n=6); 4) NaCl 0.9% given subconjunctivally (n=5); 5) NaCl 0.9% given into the anterior chamber (n=5). All treatment protocols except control group were followed by topical eye drops composed of VIP at two hourly intervals for one week from 8 a.m. to 6 p.m. VIP treated groups of rabbits with alkali burns were found to have better wound healing findings histo-pathologically when compared to those of control group who have received no treatment on day 30. No differences were observed between groups in respect to degree of polymorphonuclear leukocytes (PMNL) infiltration and degree of loss of amorphous substrate on day 15. However, PMNL infiltration and degree of loss of amorphous substrate were lower in Groups 2 and 3 when compared to that of control group on day 30 (P<0.05). We have shown that VIP has positive effects on alkali induced corneal burns. VIP may inhibit PMNL migration to cornea through an immunomodulatory effect. Inhibition of PMNL migration might reduce the release of collagenases and this might prevent the extracellular amorphous substance loss.

VIP and PACAP analogs regulate therapeutic targets in high-risk neuroblastoma cells

Neuroblastoma (NB) is a pediatric cancer. New therapies for high-risk NB aim to induce cell differentiation and to inhibit MYCN and ALK signaling in NB. The vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase-activating polypeptide (PACAP) are 2 related neuropeptides sharing common receptors. The level of VIP increases with NB differentiation. Here, the effects of VIP and PACAP analogs developed for therapeutic use were studied in MYCN-amplified NB SK-N-DZ and IMR-32 cells and in Kelly cells that in addition present the F1174L ALK mutation. As previously reported by our group in IMR-32 cells, VIP induced neuritogenesis in SK-N-DZ and Kelly cells and reduced MYCN expression in Kelly but not in SK-N-DZ cells. VIP decreased AKT activity in the ALK-mutated Kelly cells. These effects were PKA-dependent. IMR-32, SK-NDZ and Kelly cells expressed the genes encoding the 3 subtypes of VIP and PACAP receptors, VPAC1, VPAC2 and PAC1. In parallel to its effect on MYCN expression, VIP inhibited invasion in IMR-32 and Kelly cells. Among the 3 PACAP analogs tested, [Hyp2]PACAP-27 showed higher efficiency than VIP in Kelly cells. These results indicate that VIP and PACAP analogs act on molecular and cellular processes that could reduce aggressiveness of high-risk NB.

Effects of Vasoactive Intestinal Polypeptide and Forskolin on mRNA Expression of Prolactin and Prolactin Regulatory Element-Binding Protein in the Anterior Pituitary Gland of Chicken Embryo and Laying Hens.

Vasoactive intestinal peptide (VIP) treatment induced mRNA expression of Prolactin (PRL) in the chicken anterior pituitary gland. VIP responsive element (VRE) of the PRL promoter was identified in the various bird species. However, transcription factor, which binds to VRE, has not yet been identified. Prolactin regulatory element-binding protein (PREB) gene cloned as a candidate transcription factor binds to VRE. Increases of mRNA levels of PRL and PREB during embryogenesis were identified. However, whether VIP affects levels of PRL and PREB mRNA during embryogenesis remains unknown. The effects of VIP and forskolin on mRNA expression of PRL and PREB in the embryonic anterior pituitary gland were assessed. Furthermore, administration of VIP to laying hens was conducted to examine the relationship between VIP and PREB mRNA expression. At day 14 of the embryonic growth stage, VIP treatment did not affect mRNA levels of either PRL or PREB, whereas forskolin treatment induced the increase of these mRNA levels. At day 20, both VIP and forskolin induced an increase of PRL and PREB mRNA levels. The administration of VIP significantly increased mRNA levels of PRL and PREB in the anterior pituitary gland of White Leghorn and Nagoya. These results indicate that the effects of VIP on PRL and PREB mRNA expression levels of VIP receptor may in turn affect PRL and PREB mRNA levels in the chicken anterior pituitary gland.

Vasoactive intestinal peptide administration after stroke in rats enhances neurogenesis and improves neurological function

The aim of this study was to investigate the effects of vasoactive intestinal peptide (VIP) on neurogenesis and neurological function after cerebral ischemia. Rats were intracerebroventricular administered with VIP after a 2h middle cerebral artery occlusion (MCAO) and sacrificed at 7, 14 and 28 days after MCAO. Functional outcome was studied with the modified neurological severity score. The infarct volume was evaluated via histology. Neurogenesis, angiogenesis and the protein expression of vascular endothelial growth factor (VEGF) were measured by immunohistochemistry and Western blotting analysis, respectively. The treatment with VIP significantly reduced the neurological severity score and the infarc volume, and increased the numbers of bromodeoxyuridine (BrdU) immunoreactive cells and doublecortin immunoreactive area in the subventricular zone (SVZ) at 7, 14 and 28 days after ischemia. The cerebral protein levels of VEGF and VEGF expression in the SVZ were also enhanced in VIP-treated rats at 7 days after stroke. VIP treatment obviously increased the number of BrdU positive endothelial cells in the SVZ and density of cerebral microvessels in the ischemic boundary at 28 days after ischemia. Our study suggests that in the ischemic rat brain VIP reduces brain damage and promotes neurogenesis by increasing VEGF. VIP-enhanced neurogenesis is associated with angiogenesis. These changes may contribute to improvement in functional outcome.

Vasoactive intestinal peptide reduces the inflammatory profile in mice infected with Trypanosoma cruzi

Vasoactive intestinal peptide (VIP) has gained great prominence because of its therapeutic potential, which is ascribed to its ability to regulate innate immunity, inhibit antigen-specific Th1 cell responses, and generate T regulatory cells. Additionally, VIP may act as a natural antimicrobial peptide, killing bacteria, fungi, and infective forms of Trypanosoma brucei. Despite the possible relevance of VIP during the course of Chagas disease, studies regarding this in human and experimental Trypanosoma cruzi infections remain poorly characterized. In this work, we evaluated the effects of VIP on systemic and cardiac immune responses during experimental acute infection. C57BL/6 mice were infected with 5000 trypomastigotes of the VL-10 strain of T. cruzi and treated with intraperitoneal VIP injection every other day for one month. After 30 days, we observed no reduction in parasitemia levels. However, we observed a reduction in serum levels of IFN-gamma and IL-2 and an increase in that of IL-4. These data suggest that VIP treatment modified immune responses to favor the Th2 response, which had no impact on parasitemia levels although the serum level of IFN-gamma was reduced. However, this change in immune balance reduced heart damage, as noted by the smaller cardiac volume and the moderate inflammatory infiltrate observed in VIP-treated mice. Our results indicate that VIP treatment reduced the inflammatory response at the cardiac site of mice that were experimentally infected with T. cruzi. These data suggest a protective role for VIP in the heart of infected mice.

Vasoactive intestinal peptide represses activation of tumor-associated macrophages in gastric cancer via regulation of TNFα, IL-6, IL-12 and iNOS.

Vasoactive intestinal peptide (VIP) has been regarded as deactivator for macrophages. However, the depressive effect of VIP on tumor-associated macrophages (TAM) has not been recognized. In the present study, we investigated the effect of VIP on gastric cancer via TAM by suppressing expression levels of TNFα, IL-6, IL-12 and iNOS. Real-time PCR was carried out to examine the expression of CD68 to determine the levels of TAM. The effect of VIP on cell activities was assayed by proliferation assay, colony formation and flow cytometry analysis. The co-culture of TAM and human gastric cancer cell line MKN-45 were performed to understand whether the VIP affects the gastric cancer cells via TAM. Further, the tumor formation in a nude mouse model and VIP injection were performed to illustrate the effect on tumor progression in vivo. CD68 was high expressed in gastric cancer indicating high level of TAM in gastric cancer. Treatment with VIP significantly depressed TAM activation. Moreover, the expression of TNFα, IL-6, IL-12 and iNOS in TAM were depressed by VIP treatment, and the VIP treated TAM depressed gastric cancer cells. The experiment in the nude mouse model also suggested that by injection with TAM+VIP, the tumor volume and tumor weight were both decreased significantly. These data suggest that treatment with VIP inhibits gastric cancer.

Vasoactive intestinal peptide (VIP) differentially affects inflammatory immune responses in human monocytes infected with viable Salmonella or stimulated with LPS

We compared the effect of VIP on human blood monocytes infected with Salmonella typhimurium 4/74 or stimulated with LPS. VIP (10−7M) increased monocyte viability by 24% and 9% when cultured for 24h with 4/74 or Salmonella LPS (100ng/ml), respectively. Significantly increased (P<0.05) numbers of 4/74 were also recovered from monocytes co-cultured with VIP after 6h post-infection (pi) and this remained high after 24h pi. Both 4/74 and LPS increased (P<0.05) the concentration of TNF-α, IL-1β and IL-6 measured in monocyte supernatants. However, LPS induced this effect more rapidly while, with the exception of IL-6, 4/74 induced higher concentrations (P<0.05). VIP significantly decreased (P<0.05) TNF-α and IL-1β production by 4/74-infected monocytes after 6 pi, but only after 24h in LPS-cultured monocytes. This trend was reversed for IL-6 production. However, TNF-α and IL-1β production by 4/74-infected monocytes, cultured with VIP, still remained higher (P<0.05) than concentrations measured in supernatants cultured only with LPS. VIP also increased (P<0.05) production of anti-inflammatory IL-10 in both 4/74 and LPS cultures after 24h. We also show a differential effect of VIP on the expression of TNFα and IL-6 receptors, since VIP was only able to decreased expression in LPS-stimulated monocytes but not in 4/74-infected monocytes.In conclusion, we show a differential effect of VIP on human monocytes infected with virulent Salmonella or stimulated with LPS. Our study suggests that the use of VIP in bacteraemia and/or sepsis may be limited to an adjunctive therapy to antibiotic treatment.

VIP boosts regulatory T cell induction by trophoblast cells in an in vitro model of trophoblast-maternal leukocyte interaction.

Inducible regulatory T cells (Tregs) exert a timely and efficient immunosuppressive action at the critical peri-implantation stage essential for maternal tolerance to the conceptus. Vasoactive intestinal peptide (VIP) promotes anti-inflammatory and tolerogenic profiles through binding to VIP receptors on immune cells. We evaluated whether VIP produced by trophoblast cells induces Tregs during the early interaction of maternal leukocytes with trophoblast cells, thus contributing to maternal tolerance. We used an in vitro model of maternal leukocyte-trophoblast cell interaction represented by cocultures of fertile women's PBMCs with a human trophoblast cell line (Swan-71) and evaluated the effect of VIP added exogenously and of the endogenous polypeptide. VIP increased the frequency of CD4(+)CD25(+)FoxP3(+) cells after coculture, and these cells were able to suppress the maternal alloresponse. VIP also increased the frequency of CD4(+)IL10(+) and CD4(+)TGFβ(+) cells, but it did not modulate IFN-γ or IL-17 production. Swan-71 secreted VIP, and their coculture with maternal PBMCs significantly increased the frequency of Tregs. This effect was even more pronounced if the trophoblast cells had been pretreated with VIP. In both situations, the VIP antagonist prevented the increase in the frequency of CD4(+)Foxp3(+) cells, reflecting a specific effect of the polypeptide after the interaction with Swan-71 cells. Finally, the increase in CD4(+)CD25(+)FoxP3(+) frequency was prevented by an anti-TGF-β Ab and a VIP antagonist. These results suggest that VIP could have an active role in the immunoregulatory processes operating in the maternal-placental interface by contributing to the induction of Tregs through a mechanism involving TGF-β1.

Immune homeostasis maintenance from decidualization to implantation: macrophages, dendritic cells and Treg network

Immune homeostasis maintenance from decidualization to implantation: macrophages, dendritic cells and Treg network

VIP induces NF-κB1-nuclear localisation through different signalling pathways in human tumour and non-tumour prostate cells

The nuclear factor κB (NF-κB) is a powerful activator of angiogenesis, invasion and metastasis. Transactivation and nuclear localisation of NF-κB is an index of recurrence in prostate cancer. Vasoactive intestinal peptide (VIP) exerts similar effects in prostate cancer models involving increased expression of vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2) which are related to NF-κB transactivation. Here we studied differential mechanisms of VIP-induced NF-κB transactivation in non-tumour RWPE-1 and tumour LNCaP and PC3 human prostate epithelial cells. Immunofluorescence studies showed that VIP increases translocation of the p50 subunit of NF-κB1 to the nucleus, an effect that was inhibited by curcumin. The signalling transduction pathways involved are different depending on cell transformation degree. In control cells (RWPE1), the effect is mediated by protein kinase A (PKA) activation and does not implicate extracellular signal-regulated kinase (ERK) or phosphoinositide 3-kinase (PI3-K) pathways whereas the opposite is true in tumour LNCaP and PC3 cells. Exchange protein directly activated by cAMP (EPAC) pathway is involved in transformed cells but not in control cells. Curcumin blocks the activating effect of VIP on COX-2 promoter/prostaglandin E2 (PGE2) production and VEGF expression and secretion. The study incorporates direct observation on COX-2 promoter and suggests that VIP effect on VEGF may be indirectly mediated by PGE2 after being synthesised by COX-2, thus amplifying the initial signal. We show that the signalling involved in VIP effects on VEGF is cAMP/PKA in non-tumour cells and cAMP/EPAC/ERK/PI3K in tumour cells which coincides with pathways mediating p50 nuclear translocation. Thus, VIP appears to use different pathways for NF-κB1 (p50) transactivation in prostate epithelial cells depending on whether they are transformed or not. Transformed cells depend on pro-survival and pro-proliferative signalling pathways involving ERK, PI3-K and cAMP/EPAC which supports the potential therapeutic value of these targets in prostate cancer.

The cyclic AMP effects and neuroprotective activities of PACAP and VIP in cultured astrocytes and neurons exposed to oxygen-glucose deprivation

BackgroundPituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are endogenous peptides, widely expressed in the central and peripheral nervous system. The adenylyl cyclase (AC)/cyclic AMP (cAMP) is their main intracellular signal transduction pathway. Numerous data suggest that PACAP and VIP have considerable neuroprotective potential, indicating the possibility for their use as new therapeutic strategies in stroke treatment. The aim of this study was to evaluate the effect of oxygen-glucose deprivation (OGD) – an established in vitro model for ischemic cell stress – on PACAP and VIP-evoked receptor-mediated cAMP generation in glial and neuronal cells, and to determine whether PACAP and VIP have neuroprotective activity under these conditions. MethodsThe formation of [3H]cAMP by PACAP, VIP and forskolin (a direct activator of AC) was measured in [3H]adenine prelabeled primary rat glial and neuronal cells under normoxia and OGD conditions. The effects of PACAP and VIP on cell viability were measured using the MTT conversion method, and were compared to tacrolimus (FK506), a well known neuroprotective agent. ResultsThe OGD model inhibited the PACAP and VIP-induced cAMP formation in rat astrocytes and neurons. Incubation of neuronal cells with PACAP prevented OGD-induced cell death, more efficiently than VIP and FK506. ConclusionThe obtained results showed that hypoxia/ischemia may trigger down-regulation of the brain AC-coupled PACAP/VIP receptors, with a consequent decrease of PACAP- and/or VIP-ergic-dependent cAMP-driven signaling. Moreover, our findings indicate that PACAP and VIP can prevent the deleterious effect of OGD on rat neuronal cells.

Modulatory effect of VIP injected into hippocampal CA1 area on anxiety in olfactory bulbectomized rats.

Vasoactive intestinal peptide (VIP) is a neuropeptide, which is widely distributed in the central nervous system and peripheral tissues, acting both as a neurotransmitter and neuromodulator. Despite its extensive expression in the hippocampus, amygdala and other limbic system structures, the effects of VIP on anxiety and depression have not yet been fully investigated. The aim of the present study was to evaluate the involvement of VIP and VIP receptors in the mechanism of anxiety in rats with a model of depression (bilateral olfactory bulbectomy), using the elevated plus-maze test. VIP and a non-specific antagonist of VIP receptors (VIP6-28) were administered unilaterally into the hippocampal CA1 area of bulbectomized (OBX) rats. VIP (10 ng) showed a tendency for an anxiety-modulatory effect upon right side injection, by reducing significantly the closed arm time and increasing the open arm time. VIP (100 ng) injected unilaterally (left or right) into CA1 area induced an anxiolytic-like effect on the activity of OBX rats (increased the number of open arms entries, open arm time and the ratio open/total number of entries). VIP6-28 failed to antagonize the anxiety-related behavior of OBX rats in the plus maze. An unexpected finding in our study was that upon pretreatment with VIP6-28, VIP (10 ng), injected unilaterally (left or right) exerted an anti-anxiety like effect (increased the number of open arm entries, open arm time and the ratio open/total number of entries). Our data point to a possible involvement of hippocampal VIP-ergic neurons in modulating emotional processes or adaptive responses to stressful stimuli in a rat model of depression.

Recent advances in the regulation of pancreatic secretion.

This review highlights recent progress made in the field of pancreatic secretion. This review summarizes a number of recent studies demonstrating the intracellular pathways by which hormones and neural inputs regulate pancreatic exocrine and endocrine secretion. In particular, the effects of vasoactive intestinal peptide and secretin on intra-acinar cell adenosine 3',5'-cyclic monophosphate are explored. Considerable attention is paid to regulation of β-cell function and includes studies detailing the mechanisms of regulation of insulin by somatostatin, serotonin, and melanocortins. These studies emphasize the critical role that hormonal, paracrine, and neural factors play in glucose homeostasis. Exocrine and endocrine pancreatic secretions are regulated by hormonal and neural mechanisms, and understanding these pathways will enable the discovery and design of new and improved therapies for prevention and control of diabetes and perhaps exocrine insufficiency.