The VIPoma: further confirmation of VIP as the hormonal agent in the WDHA syndrome

The WDHA syndrome characterized by watery diarrhea, hypokalemia, and achlorhydria is being diagnosed with increasing frequency. The diagnosis has been made to date only due to severe clinical symptomatology. In a review of the literature gastrin, secretin, glucagon, enteroglucagon, gastric inhibitory peptide (GIP), vasoactive intestinal peptide (VIP), and prostaglandins have been variously suggested as a possible etiologic agent for this syndrome. A case of the WDHA syndrome is reported in which hormonal assays of the serum preoperatively and two years postoperatively and tumor for many of the proposed agents is performed. A discussion of possible cross-reactivity among these similary structured polypeptides in the radioimmunoassays systems is used to explain the multitude of possible hormonal agents presented in the literature. Standardization of the VIP assays will result in increasing diagnosis of this diseases state prior to its fulminant clinical presentation.     

Occurrence of human pancreatic polypeptide in pancreatic endocrine tumors. Possible implication in the watery diarrhea syndrome

Eighteen endocrine pancreatic tumors were examined for the occurrence of cells producing insulin, glucagon, gastrin, human pancreatic polypeptide (HPP), and vasoactive intestinal polypeptide (VIP) and for A1 cells. More than half of the tumors were mixed, i.e., they contained more than one type of hormone-producing cell. The clinical symptoms were attributable only to one of the hormones produced by the mixed tumors. Three of four tumors causing the watery diarrhea syndrome contained both VIP and HPP cells. In one such tumor there was a strong predominance of HPP cells; the serum HPP levels of this patient were a thousandfold elevated, whereas her VIP levels were within the normal range. Several lines of evidence point to HPP as a possible agent causing the watery diarrhea syndrome. In many of our patients, HPP cells hyperplasia was present in the extratumoral pancreas. Such hyperplasia may give rise to the raised serum HPP levels seen in many patients having endocrine pancreatic tumors.     

Comparison of a videokeratoscope and an autokeratometer as predictors of the optimum back surface curves of rigid corneal contact lenses

Vasoactive intestinal polypeptide (VIP) is reported to exert an autocrine control on neuroblastoma cell tumours: VIP is produced by the tumour and stimulates cell differentiation. This study tested the hypothesis that the parent peptide; the pituitary adenylate cyclase activating polypeptide (PACAP) may have a similar role. It was found that PACAP mRNA and PACAP were expressed in 12/12 tumours; it was also observed that PACAP receptor mRNA and functional PACAP receptors were expressed in 12/12 and 5/9 tumours, respectively. VIP mRNA and VIP were detected in 9/12 tumours. VIP receptor mRNA was expressed in 5/12 tumours and functional VIP receptors were never demonstrated. The tumours having the highest VIP levels also had the highest PACAP contents and were associated with a watery diarrhoea syndrome due to activation of intestinal VIP receptors. As PACAP recognizes the PACAP receptors and the VIP receptors with the same high affinity it may contribute to the syndrome and is a likely candidate for an autocrine control of neuroblastoma cell growth and differentiation.     

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activation polypeptide (PACAP) protect mice from lethal endotoxemia through the inhibition of TNF-alpha and IL-6

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) down-regulate cytokine production. Because human septic shock involves excessive cytokine production, the effect of VIP/PACAP was investigated in a high endotoxemia murine model. Both peptides protect against endotoxin-induced lethality and prevent septic shock-associated histopathological alterations. VIP/PACAP reduce serum and peritoneal TNF-alpha and IL-6, suggesting that the protective effect is exerted by inhibiting the production of endogenous TNF-alpha/IL-6. Consistent with this mechanism, VIP does not protect against septic shock induced by exogenous TNF-alpha. The immunomodulatory role of VIP in vivo is supported by the appearance of high levels of VIP in serum and peritoneal fluid following LPS administration. Thus, the neuropeptides VIP/PACAP protect from the lethal effect of high endotoxemia, presumably by down-regulating TNF-alpha and IL-6 production, and may offer an alternative in the treatment of human septic shock syndrome.     

Location of a VIPoma by iodine-123-vasoactive intestinal peptide scintigraphy

A major problem in patients with small endocrine tumors is the difficulty in localizing the primary tumor site. Many endocrine tumors possess larger amounts of high affinity vasoactive intestinal peptide (VIP) binding sites compared with normal tissue or blood cells. We used radiolabeled VIP to localize the tumor site in a patient with Verner-Morrison syndrome (VMS). Under octreotide therapy, the VIP levels had declined in this patient, but a tumor site could not be detected by conventional techniques or by radiolabeled octreotide. However, using 123I-VIP, the tumor was detectable in the pancreatic tail. Surgical resection of the tumor was followed by complete remission of the VMS. Expression of VIP binding sites in the tumor was confirmed by a radioreceptor assay and showed cross-competition between VIP and octreotide. The identity of the VIP binding site in the tumor was analyzed by Northern blotting and revealed the expression of somatostatin receptor subtype 3, which binds both somatostatin-14 and VIP with higher affinity than octreotide. Iodine-123-VIP scintigraphy would be an effective tracer to identity the tumor site in VMS patients.     

Use of octreotide acetate for control of symptoms in patients with islet cell tumors

Gut tumor syndromes are rare, occurring in less than two cases per million population per year: Insulinomas are most common and gastrinomas are less common; all the others are extremely rare. Conventional treatment of the symptoms caused by these tumors has included surgery, hepatic arterial embolization, and chemotherapy; some patients with Zollinger-Ellison syndrome (ZES) have been treated with specific agents such as gastric antisecretory drugs. The development of octreotide, a synthetic, long-acting analogue of the natural peptide somatostatin, has offered an alternative to such therapies. Octreotide has a half life of > 100 minutes and inhibits both physiological- and tumor release of many peptides. It also has direct effects on the gut that modify secretion and motility. Octreotide has been shown to be particularly useful for the symptoms of tumors producing vasoactive intestinal peptide (VIP), and of the carcinoid syndrome. It is also useful in patients with glucagonomas, with growth hormone-releasing hormone producing tumors, and in some patients with Cushing's syndrome and unresectable insulinomas. Octreotide is effective in patients with ZES, but alternative therapies such as omeprazole are more effective, safer, and more convenient for those patients. Side effects of octreotide have not been troublesome in these patients, but the incidence of long term effects is still not entirely clear. Octreotide has proved to be a significant advance in the treatment of patients with islet cell tumors.     

Vasoactive intestinal peptide enhances its own expression in sympathetic neurons after injury

Neurons in the adult rat superior cervical sympathetic ganglion (SCG) dramatically increase their content of vasoactive intestinal peptide (VIP) and its mRNA after axotomy in vivo and after explantation. Because the VIP gene contains a functional cAMP response element, the effects of cAMP-elevating agents on VIP expression were examined. VIP, forskolin, or isoproterenol increased cAMP accumulation in explanted ganglia. Secretin, a peptide chemically related to VIP, or forskolin increased VIP levels above those seen in ganglia cultured in control medium, whereas treatment with VIP or secretin increased the level of peptide histidine isoleucine (PHI), a peptide coded for by the same mRNA that encodes VIP. VIP or forskolin also increased VIP-PHI mRNA. In contrast, isoproterenol did not alter levels of VIP, PHI, or VIP-PHI mRNA. Although VIP or forskolin increased cAMP levels in both dissociated neurons and in non-neuronal cells, isoproterenol significantly stimulated cAMP accumulation only in the latter. VIP6-28 was an effective antagonist of the actions of exogenous VIP on cAMP and VIP-PHI mRNA in neuron-enriched cultures. When adult SCG explants were cultured in defined medium, endogenous VIP immunoreactivity was released. When VIP6-28 was added to such cultures, it significantly inhibited the increase in VIP-PHI mRNA that normally occurs. These data indicate that VIP, or a closely related molecule, produced by adult neurons after injury can enhance the expression of VIP. Such a mechanism may prolong the period during which VIP is elevated after axonal damage. The possibility is also discussed that, because VIP is present in preganglionic neurons in normal animals, its release during periods of increased sympathetic nerve activity could alter VIP expression in the SCG.     

Evidence that cellular immune responses to soluble and membrane associated antigens are independently regulated during human schistosomiasis mansoni

The glucagonoma syndrome is a rare disorder characterized by weight loss, necrolytic migratory erythema (NME), diabetes, stomatitis, and diarrhea. We identified 21 patients with the glucagonoma syndrome evaluated at the Mayo Clinic from 1975 to 1991. Although NME and diabetes help identify patients with glucagonomas, other manifestations of malignant disease often lead to the diagnosis. If the diagnosis is made after the tumor is metastatic, the potential for cure is limited. The most common presenting symptoms of the glucagonoma syndrome were weight loss (71%), NME (67%), diabetes mellitus (38%), cheilosis or stomatitis (29%), and diarrhea (29%). Although only 8 of the 21 patients had diabetes at presentation, diabetes eventually developed in 16 patients, 75% of whom required insulin therapy. Symptoms other than NME or diabetes mellitus led to the diagnosis of an islet cell tumor in 7 patients. The combination of NME and diabetes mellitus led to a more rapid diagnosis (7 months) than either symptom alone (4 years). Ten patients had diabetes mellitus before the onset of NME. No patients had NME clearly preceding diabetes mellitus. Increased levels of secondary hormones, such as gastrin (4 patients), vasoactive intestinal peptide (1 patient), serotonin (5 patients), insulin (6 patients, clinically significant in 1 only), human pancreatic polypeptide (2 patients), calcitonin (2 patients) and adrenocorticotropic hormone (2 patients), contributed to clinical symptoms leading to the diagnosis of an islet cell tumor before the onset of the full glucagonoma syndrome in 2 patients. All patients had metastatic disease at presentation. Surgical debulking, chemotherapy, somatostatin, and hepatic artery embolization offered palliation of NME, diabetes, weight loss, and diarrhea. Despite the malignant potential of the glucagonomas, only 9 of 21 patients had tumor-related deaths, occurring an average of 4.91 years after diagnosis. Twelve patients were still alive, with an average age follow-up of 3.67 years.     

Evidence from confocal fluorescence microscopy for a dense, reciprocal innervation between AVP-, somatostatin-, VIP/PHI-, GRP-, and VIP/PHI/GRP-immunoreactive neurons in the rat suprachiasmatic nucleus

The rat suprachiasmatic nucleus (SCN) consists of several classes of neurons which can be identified by their transmitter content. Knowledge of putative interaction between these different cell types is essential in order to understand the possibilities of information processing within the SCN. The aim of the present study was therefore to obtain more information about the mutual innervation between the main cell classes in the rat SCN, viz. those containing the neuropeptides arginine vasopressin (AVP), vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), gastrin-releasing peptide (GRP) and somatostatin respectively. For this purpose, vibratome sections were double-immunolabelled for seven different peptide combinations and subsequently analysed by high-resolution confocal laser scanning fluorescence microscopy. Attention was focused on axosomatic appositions, the occurrence and frequency of which were quantitatively estimated. Our analysis of double-immunolabelled sections demonstrated that some of the VIP- and some of the GRP-immunoreactive nerve cells and endings showed colocalization. Assuming, on the basis of literature data, that VIP and PHI are always colocalized at the cellular level, the five main cell classes in the SCN appeared to be interconnected, at least axosomatically, in the following reciprocal way: AVP <--> VIP/PHI, AVP <--> GRP, AVP <--> somatostatin, somatostatin <--> VIP/PHI, somatostatin <--> GRP, VIP/PHI <--> GRP, VIP/PHI/GRP <--> GRP, VIP/PHI/GRP <--> VIP/ PHI. In addition to this heterologous axosomatic innervation, these cell groups also showed substantial homologous innervation. Supported by electron microscope data from the literature showing the existence of axodendritic synapses for some of these peptide combinations, our findings strongly suggest that the rat SCN comprises a complex synaptic network with strong interactive capabilities, which is probably a requisite for its biological clock function.     

A diffuse T lymphocytic gastrointestinal mucosal infiltration associated with Sj?gren's syndrome resulting in a watery diarrhea syndrome and responsive to immunosuppressive therapy

We report the case of a 45-yr-old white man, investigated for chronic diarrhea, malabsorption and weight loss associated with sicca syndrome. Endoscopic and x-ray examinations showed normal macroscopic mucosa in gastrointestinal tract (GIT). Immunohistochemistry showed diffuse polyclonal T cell lymphocytes infiltrating either epithelium and lamina propria in GIT. There was no villous atrophy in the jejunum and ileum. Corticosteroids, azathioprine, and cyclosporine failed to improve symptoms. Monthly intravenous cyclophosphamide administered over 1 yr, stopped the diarrhea and weight loss. The patient is free of symptoms up to a 5-yr follow-up.     

Vasoactive intestinal peptide stimulation of human trabecular meshwork cell growth

PURPOSE: To demonstrate that vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide, is a growth factor of human trabecular meshwork (TM) cells in culture and in a corneoscleral explant organ culture treated with laser trabeculoplasty (LTP). METHODS: Proliferating human TM cells in cell cultures were incubated with VIP for 20 hours, followed by total cell number determination, using a Coulter counter. The percentage of proliferating TM cells was assessed, using an antibody against the proliferating cell nuclear antigen (PCNA). To test the growth effect of VIP on TM cells in situ, corneoscleral explants in organ cultures were first treated with argon LTP to initiate TM-cell proliferation and then were exposed to VIP for 48 hours. The mitotic TM cells were demonstrated immunocytochemically, using anti-PCNA in paraffin sections of the explants; and the total number of TM cells was determined after paraffin sections were counterstained by hematoxylin. RESULTS: Vasoactive intestinal peptide dose-dependently stimulated the proliferation of TM cells in cell culture. Treatment with 5 x 10(-10) M VIP resulted in a maximal increase of 40% in cell number. The effect of VIP was blocked by a VIP antagonist. The number of PCNA-stained TM cells and the total cell number in the TM in LTP-treated corneoscleral explants were increased by VIP. CONCLUSIONS: Exogenously applied VIP stimulated the proliferation of human TM cells in subconfluent cultures and in LTP-treated corneoscleral explants. In that LTP has been shown to increase the number of TM cells in situ, the growth stimulatory effect of VIP may help enhance this therapy.     

Intractable diarrhea. Intestinal perfusion studies and plasma VIP concentrations in patients with pancreatic cholera syndrome and surreptitious ingestion of laxatives and diuretics

Small-intestinal perfusion studies with a triple-lumen tube were performed in the jejunum and ileum of 11 patients with a presumptive diagnosis of pancreatic cholera syndrome (PCS). Ultimately PCS was proven to be present in only 3 patients, whereas 6 were discovered to be taking either laxatives or diuretics surreptitiously. In 2 of the 11 patients the cause of the diarrhea could not be determined. In PCS the major abnormality which we observed was that the jejunal mucosa secreted rather than absorbed when perfused with a plasma-like solution. By contrast, the ileum of the PCS patients absorbed a plasma-like solution in a normal fashion; however, one patient failed to absorb sodium and chloride when a solution with low (50 mM) sodium chloride concentration was perfused in the ileum. The volume of endogenous fluid was high in both the jejunum and ileum, presumably because of proximal small-intestinal secretion. Glucose stimulated sodium movement in an absorptive direction in each patient. Studies were repeated in one PCS patient after tumor removal, and his intestinal absorption of water and electrolytes was normal. Patients with diarrhea due to surreptitious ingestion of laxatives and diuretics showed normal absorption in the jejunum and ileum. This study shows that proximal small-bowel secretion was the major cause for diarrhea in our 3 patients with PCS. This cannot be a consequence of diarrhea per se since it was not found in patients with long-standing diarrhea due to surrepitious drug ingestion. Small-intestinal perfusion studies may be helpful in the diagnosis and management of selected cases of severe chronic diarrhea. On the other hand, measurement of plasma VIP concentration, especially by methods currently used in the United States, is of little use and may be misleading.     

VIP and PACAP potentiate the action of glutamate on BDNF expression in mouse cortical neurones

In view of the neurotrophic effect of vasoactive intestinal peptide (VIP), the regulation of brain-derived neurotrophic factor (BDNF) expression by VIP and the related peptide pituitary adenylate cyclase-activating polypeptide (PACAP) was analysed by Northern blot in primary cultures of cortical neurones. Results reported in this article demonstrate that VIP and PACAP stimulate the expression of BDNF mRNA in primary cultures of cortical neurones and astrocytes. In primary cultures of cortical neurones, induction of BDNF mRNA by VIP and PACAP is completely inhibited by the N-methyl-D-aspartate (NMDA) receptor antagonists MK-801 and AP5, therefore indicating that VIP and PACAP do not stimulate BDNF expression directly but rather by potentiating the effect of glutamate tonically released by neurones and acting at NMDA receptors. In addition to its neurotrophic effects, BDNF has been shown to be involved in neuronal plasticity and results reported here suggest that by stimulating BDNF expression, VIP and PACAP could modulate synaptic plasticity in the cerebral cortex.     

Neurobehavioral development of neonatal mice following blockade of VIP during the early embryonic period

Previous work has shown that blockade of VIP function in the early postimplantation embryo results in growth retardation and microcephaly. In the present work, the neurobehavioral development of neonatal mice was examined following treatment of dams with a VIP antagonist during this period. Inhibition of VIP functions during early embryogenesis impaired the performance of 5 of 10 developmental behaviors. These behaviors included developmental milestones (first appearance of ear twitch and eye opening) and complex motor behaviors (negative geotaxis, surface righting, and air righting). The retardation of neurobehavioral development produced by inhibition of VIP action indicates that this peptide is important to the progression of embryonic development.     

Stabilization of vasoactive intestinal peptide by lipids

An anionic phospholipid, phosphatidylglycerol (PG), induced vasoactive intestinal peptide (VIP) to adopt a helical conformation, determined by circular dichroism studies. PG inhibited the trypsin-catalyzed, antibody-catalyzed and uncatalyzed cleavage of VIP, measured by radiometric and HPLC methods. Phosphatidylcholine, a neutral lipid, did not alter the circular dichroism spectra of VIP, and it was without detectable effect on the rates of VIP cleavage. Trypsin-catalyzed cleavage of Boc-Ile-Glu-Arg-methylcoumarinamide, a substrate unrelated in sequence to VIP, proceeded at equivalent rates in the absence and presence of PG, which suggests that the phospholipid did not exert a nonspecific inhibitory effect on the enzyme. Study of the kinetics of antibody-catalyzed VIP cleavage indicated that the inhibition by PG was due to decreased affinity for VIP, suggested by observations of increased K(m) values and unaltered Vmax values. Incorporation of VIP in the liposomes and the liposomal surface permitted maintenance of the peptide in essentially undegraded form at 37 degrees C for 8 days. The longevity of liposomal VIP administered i.v. to mice was increased by about 5-fold compared with aqueous VIP. These observations indicate that certain phospholipids and liposomes can be applied to circumvent the rapid loss of VIP in vitro and in vivo due to degradative processes.     

Neuroprotective strategy for Alzheimer disease: intranasal administration of a fatty neuropeptide

Neurodegenerative diseases, in which neuronal cell disintegrate, bring about deteriorations in cognitive functions as is evidenced in millions of Alzheimer patients. A major neuropeptide, vasoactive intestinal peptide (VIP), has been shown to be neuroprotective and to play an important role in the acquisition of learning and memory. A potent lipophilic analogue to VIP now has been synthesized, [stearyl-norleucine17]VIP ([St-Nle17]VIP), that exhibited neuroprotection in model systems related to Alzheimer disease. The beta-amyloid peptide is a major component of the cerebral amyloid plaque in Alzheimer disease and has been shown to be neurotoxic. We have found a 70% loss in the number of neurons in rat cerebral cortical cultures treated with the beta-amyloid peptide (amino acids 25-35) in comparison to controls. This cell death was completely prevented by cotreatment with 0.1 pM [St-Nle17]VIP. Furthermore, characteristic deficiencies in Alzheimer disease result from death of cholinergic neurons. Rats treated with a cholinergic blocker (ethylcholine aziridium) have been used as a model for cholinergic deficits. St-Nle-VIP injected intracerebroventricularly or delivered intranasally prevented impairments in spatial learning and memory associated with cholinergic blockade. These studies suggest both an unusual therapeutic strategy for treatment of Alzheimer deficiencies and a means for noninvasive peptide administration to the brain.     

Stable expression of the recombinant human VIP1 receptor in clonal Chinese hamster ovary cells: pharmacological, functional and molecular properties

We stably transfected Chinese hamster ovary (CHO) cells with the recombinant human vasoactive intestinal peptide (VIP)1 receptor. A clone referred to as Clone 15 was isolated and studied for receptor properties. The following data were obtained: (1) one class of binding site was identified by Scatchard analysis of [125I]VIP binding to cell membranes with a Kd of 0.41 nM and a Bmax of 1.62 pmol/mg protein; (2) the constant Ki for the inhibition of [125I]VIP binding by VIP and related peptides was: VIP (0.9 nM) = pituitary adenylate cyclase-activating peptide (PACAP)-27 (1.3 nM) < PACAP-38 (6.8 nM) < helodermin (46.0 nM) < human growth hormone-releasing factor (GRF) (0.6 microM) < peptide histidine methionineamide (2.0 microM) < secretin (> 10 microM); (3) cross-linking experiments using [125I]VIP identified a single M(r) 67000 recombinant receptor; (4) VIP stimulated cAMP production in Clone 15 cells with an EC50 of 0.20 nM; (5) some previously described VIP receptor antagonists including [4-Cl-D-Phe6, Leu17]VIP, [Ac-Tyr1,D-Phe2]GRF-(1-29) amide and VIP-(10-28) inhibited [125I]VIP binding with a Ki of 0.7, 1.6 and 2.5 microM, respectively. They failed to stimulate cAMP production in Clone 15 cells and inhibited, at least partially, the VIP (0.3 nM)-evoked cAMP production; (6) exposure of Clone 15 cells to 10 nM VIP for 24 h resulted in a sharp decrease in Bmax in Clone 15 cells (0.43 vs. 1.62 pmol/mg protein in control cells) and in the potency and efficacy of VIP in stimulating cAMP. Moreover, immunofluorescence studies using confocal microscopy indicated that the receptor was internalized and sequestered in vesicular structures within the cells. It is concluded that Clone 15 cells provide a valuable tool to further characterize various functional and pharmacological aspects of the human VIP1 receptor.     

Vasoactive intestinal peptide, but not pituitary adenylate cyclase-activating peptide, modulates the responsiveness of the gonadotroph to LHRH in man

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are hypothalamic peptides sharing considerable sequence homology which are postulated to be hypophysiotrophic releasing factors. When infused into man, PACAP has no effect on anterior pituitary hormone levels, while VIP causes a significant increase in circulating prolactin concentrations. However, PACAP has recently been shown to augment the release of LH and FSH in response to LHRH in rat anterior pituitary cell culture. In order to ascertain if either peptide has a similar effect in man, PACAP and VIP were infused at 3.6 pmol/kg per min into six healthy male volunteers, and an LHRH test was performed 30 min after the infusion was commenced. Infusion of PACAP did not alter the gonadotrophin response to LHRH significantly. However, VIP augmented the release of LH significantly, both during the infusion and for 30 min thereafter, although there was no effect on FSH release. Thus VIP, but not PACAP, potentiates the release of LH after LHRH injection in man.     

Small-cell lung carcinoma: inhibition of proliferation by vasoactive intestinal peptide and helodermin and enhancement of inhibition by anti-bombesin antibody

Small-cell lung cancer (SCLC) is a common and highly fatal malignancy for which there is no satisfactory treatment. The amphibian peptide bombesin and its mammalian counterpart, gastrin-releasing peptide, serve as autocrine growth factors for the SCLC cells, but little is known about endogenous substances that inhibit the growth and proliferation of these tumor cells. We report that the neuropeptide vasoactive intestinal peptide (VIP) markedly inhibits the growth and multiplication of SCLC cell lines NCI-H345 and NCI-H69, and that the closely related peptide helodermin inhibits the proliferation of NCI-H345 cells with even higher efficacy. In the latter cells, the inhibition by VIP and isobutyl methyl xanthine paralleled their ability to stimulate cyclic adenosine monophosphate production within the cells. The peptide-induced suppression of SCLC proliferation is enhanced in the presence of an anti-bombesin monoclonal antibody. The antimitogenic activities of VIP and helodermin, and their enhancement by anti-bombesin antibody, offer the potential for a new approach to the pharmacologic control of SCLC.