Radiolabeled Agents for Molecular Imaging and/or Therapy
George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos in Handbook of Small Animal Imaging, 2018
The neuropeptide vasoactive intestinal peptide (VIP) is a secretin-like peptide, which regulates a broad spectrum of biological activities, including vasodilation, stimulating secretion of various hormones, immunomodulation, and promotion of cell proliferation. Its receptors (VPAC1 and VPAC2) function through two distinct GPCR subtypes that can also be internalized (Shetzline et al. 2002). Only the VPAC1 receptor is found on tumor cells of neuroendocrine origin and neuroblastomas. The proteolytic degradation of VIP in vivo as well as high VPAC receptor expression in normal tissues hampers the applicability of this target for the imaging of neuroendocrine tumors. Recently, a more stable 64Cu-labeled VIP analog has been developed for neuroendocrine and human breast tumors. In vivo studies in athymic BALB/c nude mice bearing subcutaneous VIP expressing estrogen-dependent human T47D breast tumors showed a higher tumor uptake than the 99mTc-labeled VIP analog (Thakur et al. 2004). Recently, a 18F-labeled VIP analog has been developed and evaluated with micro-PET imaging study in C26 colon carcinoma–bearing mice, confirming high tumor specificity and good tumor/muscle radioactivity uptake ratio (Cheng et al. 2013).
Stimulus-Secretion Coupling: Receptors
Stephen W. Carmichael, Susan L. Stoddard in The Adrenal Medulla 1986 - 1988, 2017
Malhotra, Wakade and Wakade (1988b) investigated the molecular mechanism involved in the exocytotic secretion of catecholamines by VIP and the effects of this peptide on radioactive calcium uptake and phosphoinositide breakdown. The omission of calcium from the perfusion medium had almost no effect on vasoactive intestinal peptide-induced secretion; however, the addition of a calcium chelator abolished secretion. Stimulation with the peptide did not result in a net increase in calcium uptake, and uptake was not modified by a protein kinase C activator. All of these effects of vasoactive intestinal peptide were similar to those of muscarine. These and other results led to the conclusion that the inositol 1, 4,5-triphosphate generated on activation of vasoactive intestinal peptide and muscarinic receptors is linked to exocytotic secretion of adrenal catecholamines through release of internal calcium ions.
Host Defense II: Acquired Immunity
Constantin A. Bona, Francisco A. Bonilla in Textbook of Immunology, 2019
Mucosal tissues also possess many cellular specific and non-specific immune elements. The extent to which these areas are different from other lymphoid populations with respect to the activation and regulation of immune effector mechanisms is a subject of intense study. Several neuropeptides which are released in mucosal tissues have activities on various effector cell populations. T cells bear receptors for substance P which can increase antibody production in murine Peyer’s patches; it may also augment natural killer (NK) cell activity. Vasoactive intestinal peptide also exhibits the latter activity. Somatostatin also augments antibody synthesis. Cholecystokinin may increase intestinal mucosal production of IgA.
Biologic and advanced immunomodulating therapeutic options for sarcoidosis: a clinical update
Published in Expert Review of Clinical Pharmacology, 2021
Ogugua Ndili Obi, Elyse E. Lower, Robert P. Baughman
Vasoactive intestinal peptide is a 28-amino acid neuropeptide with multiple effects on smooth muscle contractility and vasodilatation. It is produced by neural cells as well as by Th-2 immune cells (in response to antigen stimulation) and has been identified as a potent anti-inflammatory agent both in the innate and adaptive immune system [359,360]. It has been shown that VIP inhibits the production of inflammatory cytokines and chemokines by macrophages and dendritic cells (including TNF), reduces the stimulation of antigen-specific CD4 T-cells, modulates the action of autoreactive Th1 cells and promotes anti-inflammatory Th-2 responses [359,360]. Several studies also show that VIP upregulates the production of T-reg cells with suppressive activity on effector T-cells in vivo [361,362].
Emerging and potential treatment options for sarcoidosis
Published in Expert Opinion on Orphan Drugs, 2018
Debabrata Bandyopadhyay, Marc A. Judson
Vasoactive intestinal peptide (VIP) is a neuropeptide secreted by hypothalamus which has anti-inflammatory properties. VIP affects both innate and acquired immunity. VIP downregulates several inflammatory mediators, notably TNF-α. The usefulness of inhaled VIP therapy is being explored in many chronic inflammatory conditions, including sarcoidosis. In an open-label, phase II trial of nebulized VIP was used to assess its immunoregulatory activity in sarcoidosis patients with an active alveolitis [180], there was a significant reduction in TNF-α and an increase in T regulatory cells in the BAL. These results suggest that VIP may be of therapeutic value in the treatment of pulmonary sarcoidosis by dampening the immune response.
The impact of chewing gum on postoperative bowel activity and postoperative pain after total laparoscopic hysterectomy
Published in Journal of Obstetrics and Gynaecology, 2020
Ünal Turkay, Arzu Yavuz, İsmet Hortu, Hasan Terzi, Ahmet Kale
The aetiology of postoperative ileus remains controversial. Bowel motility is suppressed postoperatively due to sympathetic hyperactivity and increased concentrations of circulating catecholamine (Jepsen et al. 1986). More recent studies have focussed on neural and humoral factors. Vasoactive intestinal peptide directly inhibits smooth muscle contraction in the intestine, and levels of it are increased after surgery (Carr et al. 1996).Moreover, pain increases the release of substance P, which is also known to inhibit bowel motility (Soffer and Adrian 1992; Stewart et al. 1998).
Related Knowledge Centers
- Gastrointestinal Tract
- Ligand
- Neocortex
- Pancreas
- Peptide Hormone
- Residue
- Amino Acid
- Vasoactivity
- Secretin Family
- G Protein-Coupled Receptor