Increase In Vasoactive Intestinal Polypeptide Research Articles

Regenerative Therapies to Restore Interneuron Disturbances in Experimental Models of Encephalopathy of Prematurity.

Encephalopathy of Prematurity (EoP) is a major cause of morbidity in (extreme) preterm neonates. Though the majority of EoP research has focused on failure of oligodendrocyte maturation as an underlying pathophysiological mechanism, recent pioneer work has identified developmental disturbances in inhibitory interneurons to contribute to EoP. Here we investigated interneuron abnormalities in two experimental models of EoP and explored the potential of two promising treatment strategies, namely intranasal mesenchymal stem cells (MSCs) or insulin-like growth factor I (IGF1), to restore interneuron development. In rats, fetal inflammation and postnatal hypoxia led to a transient increase in total cortical interneuron numbers, with a layer-specific deficit in parvalbumin (PV)+ interneurons. Additionally, a transient excess of total cortical cell density was observed, including excitatory neuron numbers. In the hippocampal cornu ammonis (CA) 1 region, long-term deficits in total interneuron numbers and PV+ subtype were observed. In mice subjected to postnatal hypoxia/ischemia and systemic inflammation, total numbers of cortical interneurons remained unaffected; however, subtype analysis revealed a global, transient reduction in PV+ cells and a long-lasting layer-specific increase in vasoactive intestinal polypeptide (VIP)+ cells. In the dentate gyrus, a long-lasting deficit of somatostatin (SST)+ cells was observed. Both intranasal MSC and IGF1 therapy restored the majority of interneuron abnormalities in EoP mice. In line with the histological findings, EoP mice displayed impaired social behavior, which was partly restored by the therapies. In conclusion, induction of experimental EoP is associated with model-specific disturbances in interneuron development. In addition, intranasal MSCs and IGF1 are promising therapeutic strategies to aid interneuron development after EoP.

Intestinal dysmotility and enteric neurochemical changes in a Parkinson's disease rat model

Gastrointestinal disorders, constipation in particular, are the most common non-motor dysfunctions affecting Parkinson's disease (PD) patients. We have previously reported that rats bearing unilateral nigrostriatal lesion caused by 6-hydroxydopamine (6-OHDA) stereotaxic injection develop severe constipation together with a region-specific decrease of neuronal nitric oxide synthase (nNOS) in enteric neurons of the lower intestinal tract. Here, we extend these observations on other enteric neuronal subpopulations, investigating also the propulsive activity of isolated colonic specimens. Four weeks post 6-OHDA injection, lesioned rats showed a significant increase of vasoactive intestinal polypeptide (VIP) concomitant with the reduced expression of nNOS in the myenteric plexus of distal ileum and proximal colon; in particular VIP increased in a subpopulation of neurons actively expressing nNOS. On the other hand, choline acetyltransferase (ChAT) was not modified in any of the intestinal segments analyzed. Interestingly, we found a reduced expression of dopamine receptor type 2 (D2R) in proximal (-66.8%) and distal (-54.5%) colon, together with reduced peristalsis efficiency (decrease in intraluminal pressure and frequency of peristaltic events) in the 6-OHDA-lesioned rats. The selective depletion of dopaminergic nigrostriatal neurons is associated with changes in the expression of enteric inhibitory neurotransmitters, as well as of the D2R in intestinal specific regions. Moreover, 6-OHDA-lesioned rats demonstrated altered colon propulsive activity referable to the D2R decrease. Our findings unveil subtle mechanisms underlying the enteric neurochemical plasticity events evoked by disruption of the normal brain-gut cross-talk, giving a peculiar point of view on the pathophysiology of the severe constipation that frequently affects PD patients.

Regulation of neuronal pituitary adenylate cyclase-activating polypeptide expression during culture of guinea-pig cardiac ganglia

The trophic neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) increases in many different neuron types following injury; a response postulated to support cell survival and regeneration. In acutely isolated cardiac ganglia, approximately 1% of the cardiac neurons exhibited PACAP immunoreactivity whereas after 72 h in culture, ∼25% of the neurons were PACAP immunoreactive. In contrast, there was no increase in vasoactive intestinal polypeptide (VIP)-immunoreactive (IR) cells. Using a combination of immunocytochemical and molecular techniques, we have quantified PACAP expression, during explant culture of guinea-pig cardiac ganglia. Using real time polymerase chain reaction, PACAP transcript levels increased progressively up to 48 h in culture with no further increase after 72 h. PACAP transcript levels were reduced by neurturin at 48 h in culture but not after 24 or 72 h in culture. In addition, neurturin partially suppressed the percentage of PACAP-IR neurons after 72 h in culture, an effect mediated by activation of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase signaling pathways. The addition of different known regulatory molecules, including ciliary neurotrophic factor (CNTF), interleukin-1 beta (Il-1β), tumor necrosis factor-alpha (TNFα), fibroblast growth factor basic (bFGF), transforming growth factor-beta (TGF-β) and nerve growth factor (NGF) did not increase the percentage of PACAP-IR neurons after 24 h in culture; a result indicating that the generation and secretion of these factors did not stimulate PACAP expression. The presence of 20 nM PACAP or 10 μM forskolin increased the percentage of PACAP-IR cardiac neurons in 24 h cultures, but not in 72 h cultures. Neither treatment enhanced the number of VIP-IR neurons. The addition of the PACAP selective receptor (PAC1) receptor antagonist, M65 (100 nM) suppressed the 20 nM PACAP-induced increase in percentage of PACAP-IR cells in 24 h cultures indicating the effect of PACAP was mediated through the PAC1 receptor. However, 100 nM M65 had no effect on the percentage of PACAP-IR cells in either 24 or 48 h cultures not treated with exogenous PACAP, suggesting that endogenous release of PACAP likely did not contribute to the enhanced peptide expression. We postulate that the enhanced PACAP expression, which occurs in response to injury is facilitated in the explant cultured cardiac ganglia by the loss of a target-derived inhibitory factor, very likely neurturin. In intact tissues the presence of neurturin would normally suppress PACAP expression. Lastly, our results indicate that many common trophic factors do not enhance PACAP expression in the cultured cardiac neurons. However, the stimulatory role of an, as yet, unidentified factor cannot be excluded.

Pituitary adenylate cyclase-activating polypeptide regulation of vasoactive intestinal polypeptide transcription requires Ca2+ influx and activation of the serine/threonine phosphatase calcineurin.

A >15-fold increase in vasoactive intestinal polypeptide (VIP) mRNA and VIP peptide levels occurred in primary chromaffin cells following exposure to the neurotrophic neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP)-27 with an EC50 of approximately 2 nM. PACAP induction of VIP expression was blocked by methoxyverapamil or by a combination of nimodipine and omega-conotoxin MVIIC, indicating a requirement for PACAP-initiated calcium entry through voltage-dependent calcium channels for regulation of VIP biosynthesis. Ascomycin, which inhibits calcineurin through formation of an ascomycin/FKBP12/calcineurin ternary complex, abolished the PACAP-evoked increase in VIP expression, whereas rapamycin, which also binds to FKBP12 but does not cause inhibition of calcineurin, did not. Cyclosporin A, which inhibits calcineurin through formation of a cyclosporin A/cyclophilin/calcineurin complex, also abolished PACAP-evoked VIP biosynthesis. These data indicate that PACAP regulates the expression of VIP via a signaling pathway that requires calcium influx and activation of calcineurin.

Acrylamide-induced neuropathic changes in rat enteric nerves: Similarities with effects of streptozotocin-diabetes

The effect of acrylamide intoxication (a widely used model for autonomic neuropathy) on the fluorescence intensity and density of catecholamine- and peptide-containing nerve fibres and tissue content of noradrenaline and the peptides vasoactive intestinal polypeptide, calcitonin gene-related peptide, substance P and neuropeptide Y in the enteric nerves of rat ileum was examined. Histochemical and immunohistochemical techniques were used to localize catecholamine- and peptide-containing nerve fibres. The tissue content of noradrenaline was measured using high-performance liquid chromatography, and an enzyme-linked immunosorbent assay technique was used to determine the tissue content of the peptides investigated. Acrylamide intoxication caused a significant decrease in the density of catecholamine-containing nerve fibres and tissue content of noradrenaline in the myenteric plexus of rat ileum. A decrease in tissue content and immunoreactivity of calcitonin gene-related peptide and an increase in vasoactive intestinal polypeptide was seen in the myenteric plexus of ileum from acrylamide-intoxicated rats. In the submucous plexus, the acrylamide treatment caused a decrease in calcitonin gene-related peptide immunoreactivity and an increase in vasoactive intestinal polypeptide and neuropeptide Y immunoreactivity. There was no change in either tissue content or immunoreactivity of substance P in both myenteric and submucous plexuses of the treated rat ileum. These changes have a striking similarity with those found in the enteric nerves of streptozotocin-diabetic rat ileum, suggesting the possible presence of an underlying common mechanism(s) in the development of neuropathic changes in the autonomic nerves of acrylamide-intoxicated and streptozotocin-diabetic rats.

Differential effect of immunosympathectomy on the expression of rat enteric neurotransmitters

The effect of immunosympathectomy on the pattern of distribution of catecholamine- and peptide-containing nerve fibres and neurones in the myenteric and submucous plexuses of rat ileum was investigated. There was an increase in vasoactive intestinal polypeptide (VIP)-, galanin (GAL)- and substance P-like immunoreactivity in the myenteric plexus of ileum from rats treated with nerve growth facter (NGF) antiserum compared with controls. A similar increase in immunoreactivity was observed in VIP-. GAL- and neuropeptide Y (NPY)-containing submucous neurones and nerve fibres. In contrast, the immunosympathectomy had no effect on the pattern of distribution of catecholamine-, calcitonin gene-related peptide (CGRP)- and NPY-containing nerve fibres in the myenteric plexus or on substance P- and CGRP-containing neurones and nerve fibres of the submucous plexus. The findings of the present study suggest that NGF may differentially regulate the expression of enteric neuropeptides at a postnatal stage of development.

The Innervation of the Human Prostate Gland—the Changes Associated with Benign Enlargement

Different regions of the prostate gland, namely prostatic capsule, peripheral prostate and central prostate (subdivided into proximal (near the bladder neck), distal (near the verumontanum) and midway between these areas) were obtained from 32 obstructed (stable obstructed, n = 8; unstable obstructed, n = 13; acute retention, n = 11) and five control patients. The innervation of these tissues was studied both histochemically to localise acetylcholinesterase activity and immunohistochemically for dopamine-β-hydroxylase, 5-hydroxytryptamine, vasoactive intestinal polypeptide, neuropeptide Y, leu- and met-enkephalin, calcitonin gene-related peptide, substance P and somatostatin. In control patients the greatest density of nerves was found in the proximal central prostate, followed by the anterior capsule and distal central prostate, with the least density in the peripheral prostate. The greatest density of nerves were acetylcholinesterase positive and immunoreactive to neuropeptide Y followed (in decreasing order) by nerves immunoreactive to: vasoactive intestinal polypeptide and dopamine β-hydroxylase; leu-enkephalin and 5-hydroxytryptamine; calcitonin gene-related peptide; met-enkephalin; substance P; somatostatin. In addition a group of periacinar 5-hydroxytryptamine-immunoreactive cells and ganglia containing acetylcholinesterase, dopamine β-hydroxylase and all of the peptides studied except somatostatin were identified. In the prostate gland from obstructed patients there was a significant reduction in the density of acetylcholinesterase-positive nerves (p <0.001) when compared with the controls. A similar trend was found for dopamine β-hydroxylase, 5-hydroxytryptamine and all of the putative neuropeptides in most areas of the prostate, the most notable exceptions being in the peripheral prostate, with an increase in dopamine β-hydroxylase- and leu-enkephalin-immunoreactive nerves in all three groups of obstructed patients and an increase in vasoactive intestinal polypeptide- and calcitonin gene-related peptide-immunoreactive nerves in those presenting in urinary retention. The functional significance of these findings is discussed.

Chemical degeneration of intestinal nerves

In 15 dogs, cobalt chloride solutions were infused close intra-arterially to perfuse a short segment of the jejunum. In an additional four dogs, the jejunum was perfused with the aqueous vehicle (perfusion control). All animals were killed after 1 mo and tissue samples from cobalt-treated and from nonperfused intestine (tissue comparison control) were obtained for electron microscopic and immunohistochemical studies. Segments infused with 0.25 g/dl cobalt solution showed minimal changes; the most striking feature was an increase of vasoactive intestinal polypeptide (VIP)- and substance P-containing neurosecretory granules. Cobalt chloride at higher concentrations (0.75-1.5 g/dl) induced degeneration of ganglion cells and axons in both the myenteric and submucosal plexi. In contrast, the smooth muscle and the mucosal cells of the cobalt-perfused intestine showed no histological abnormalities. Immunohistochemical staining of tissues treated with 0.75-1.5 g/dl cobalt solutions revealed absence of substance P, Met-enkephalin, and VIP immunoreactivity in all section studied; control segments showed the presence of all three peptides. Cobalt chloride in concentrations of 0.75-1.5 g/dl causes degeneration of intestinal intramural nerves and provides an experimental model suitable for studying the role of these nerves in small intestinal function.

Neuropeptide expression in rat dorsal root ganglion cells and spinal cord after peripheral nerve injury with special reference to galanin

The temporal course of changes in peptide expression in the dorsal root ganglia L4 and L5 and in the dorsal horn of the spinal cord has been studied in rats subjected to a sciatic nerve transection at a mid-thigh level following different survival times. Galanin-, substance P-, vasoactive intestinal polypeptide-, peptide histidine-isoleucine- and calcitonin gene-related peptide-like immunoreactivities have been studied both by immunohistochemistry and radioimmunoassay. Galanin messenger ribonucleic acid has also been studied by in situ hybridization in the dorsal root ganglia of normal and lesioned animals. In addition, a group of animals with a sciatic nerve crush was studied to compare possible differences in peptide expression after both types of lesions. The results show that the transection induces an increase in the number of cell bodies expressing galanin-like immunoreactivity in the ganglia, and that the galanin levels rise about 120-fold after three and 14 days of survival. This increase reflected increased synthesis of the peptide, since there was a rise in the galanin messenger ribonucleic acid already at 24 h post-lesion, which was maintained for at least 60 days. In the spinal cord there was an increase of staining in the midportion of the outer layers of the dorsal horn that corresponded to fibers thought to arise from cells of the dorsal root ganglia affected by the transection. Also a depletion of substance P-like and an increase in vasoactive intestinal polypeptide and peptide histidine-isoleucine-like immunoreactivities in the dorsal root ganglia were confirmed. These changes were shown to be rapidly detectable and were paralleled by similar changes in the dorsal horn of the spinal cord. For calcitonin gene-related peptide the immunohistochemistry was inconclusive, and the radioimmunoassay showed no detectable changes. After nerve crush a transient increase in the number of galanin immunoreactive neurons was observed, as well as a decrease in the number of neurons showing substance P-like immunoreactivity. These changes were most noticeable between six and 14 days of survival. After this, peptide expression seemed to return slowly to normal, that is by day 45 post-crush only a few cells showed galanin-like, and many sensory neurons expressed substance P-like immunoreactivity. The results demonstrate that when primary sensory neurons are peripherally lesioned they respond in a complex manner, altering their normal production of peptides by increasing or decreasing their synthesis. The possibility that these changes are produced by neurons displaying specific sensory modalities is discussed, and it is suggested that the variation in peptide expression could represent part of an active process turned on as a response to the peripheral injury.

An increase of vasoactive intestinal polypeptide-, but not neuropeptide Y-, substance P- or catecholamine-containing nerves in the iris of the streptozotocin-induced diabetic rat

The distribution of adrenergic and vasoactive intestinal polypeptide-, neuropeptide Y- and substance P-immunoreactive nerves was studied histochemically and immunohistochemically in the irides of rats 8 weeks after the induction of diabetes with streptozotocin. In the control animals, catecholamine-containing, vasoactive intestinal polypeptide- and substance P-immunoreactive nerve fibres were found in the constrictor pupillae, dilator muscle and the ciliary processes. They also formed perivascular nerve plexuses of blood vessels in the dilator muscle. Neuropeptide Y-immunoreactive nerve fibres were only observed in the dilator muscle and ciliary processes. In the irides from diabetic animals, a considerable increase was observed in the fluorescence intensity and/or density of vasoactive intestinal polypeptide-immunoreactive nerves. Some varicosities of the vasoactive intestinal polypeptide-immunoreactive nerves appeared enlarged. In contrast, no apparent change in the density and/or fluorescence intensity of catecholamine-containing, neuropeptide Y- and substance P-immunoreactive nerve fibres was observed in the irides from diabetic animals when compared with controls. The results are discussed in relation to the symptoms of autonomic neuropathy of the irides in diabetes.

Enteric nerves in diabetic rats: Increase in vasoactive intestinal polypeptide but not substance P

The distribution of vasoactive intestinal polypeptide (VIP) and substance P-like immunoreactivities was studied by immunohistochemistry in the myenteric plexus and circular muscle layer of the ileum and proximal colon of rats 8 wk after induction of diabetes with streptozotocin. A consistent increase was observed in fluorescence intensity of VIP-like immunoreactivity in the nerve fibers, and intensely stained cell bodies were significantly more frequent in the myenteric plexus of the ileum (p < 0.001) from diabetic animals. Some varicosities of VIP-like immunoreactive fibers in the myenteric plexus appeared to be enlarged. Vasoactive intestinal polypeptide-like immunoreactivity was increased and VIP-like immunoreactive nerves appeared thicker in the circular muscle layer of both diabetic ileum and proximal colon. The VIP levels were measured biochemically in tissue consisting of the smooth muscle layers and myenteric plexus. A significant increase in the VIP content per centimeter of intestine was found in both the ileum (p < 0.05) and proximal colon (p < 0.01) from diabetic rats. In contrast, no apparent change in substance P innervation was observed immunohistochemically in the myenteric plexus and circular muscle layer of either diabetic ileum or proximal colon when compared with controls. The results are discussed in relation to the symptoms of autonomic neuropathy of the gut in diabetes.

Effect of peripheral nerve section and nerve crush on spinal cord neuropeptides in the rat; increased VIP and PHI in the dorsal horn

An increase in vasoactive intestinal polypeptide (VIP) immunoreactivity in the dorsal lumbar hemisegment L4 of the spinal cord was observed by both radioimmunoassay and immunocytochemistry following sciatic nerve section or crush. Compared to the contralateral control hemisegment there was 125% and 35% more VIP immunoreactivity in the L4 hemisegment ipsilateral to the lesion 14 days following nerve section and crush respectively. The contralateral control hemisegment contained levels similar to L4 hemisegments from unoperated control rats. This increase appeared by immunocytochemistry to be confined to the substantia gelatinosa, in the region of termination of the majority of unmyelinated sciatic nerve afferents. Similar increases to VIP were observed for the peptide PHI, which is closely related to VIP. However, spinal cord substance P and somatostatin immunoreactivities were reduced following nerve section and unchanged following nerve crush whilst neurotensin and bombesin immunoreactivities were not affected following either lesion. Previous studies have shown that peripheral nerve injury produces a number of electrophysiological and biochemical changes in the dorsal horn of the spinal cord, including depletion of substance P in primary afferent neurones. The location of the cell bodies of fibres showing increased immunoreactivity remains to be established. Further studies are required to elucidate how these peptide changes are related to the adaptive processes which occur centrally following peripheral nerve injury.

Unilateral sciatic nerve section induces a significant increase of vasoactive intestinal polypeptide (VIP) in nerves of the ipsilateral dorsal horn of the rat

Unilateral sciatic nerve section induces a significant increase of vasoactive intestinal polypeptide (VIP) in nerves of the ipsilateral dorsal horn of the rat