R. Dimaline

Neuropeptides in Alzheimer's disease, depression and schizophrenia. A post mortem analysis of vasoactive intestinal peptide and cholecystokinin in cerebral cortex.

Vasoactive intestinal peptide (VIP) and cholecystokinin (CCK) have been measured, by radioimmunoassay, in cerebral cortex obtained at autopsy from patients without neurological or psychiatric disease and from patients with Alzheimers disease, depression and schizophrenia. Sephadex gel filtration indicated that over 90% of the CCK immunoreactivity was associated with the octapeptide in extracted material from the different clinical groups investigated. There were no significant differences from the normal in the overall concentrations of either VIP or CCK in any of the psychiatric groups examined, although differences in Alzheimers disease were apparent when cases were grouped according to postmortem delay.

The use of region-specific antibodies in the characterization and localization of vasoactive intestinal polypeptide-like substances in the rat gastrointestinal tract

Abstract Antisera specific for different regions of porcine VIP have been used in radioimmunoassay and immunohistochemical studies of immunoreactive VIP in rat small and large intestine. Cation exchange chromatography of intestinal extracts separated two major and one minor peak of immunoreactivity. One major peak eluted in a similar position to natural porcine VIP and was read equally by NH 2 -terminal-specific, and mid- and COOH-terminal-specific antisera. A second major peak, and the minor peak, eluted earlier than porcine VIP, and were read significantly less well with mid- and COOH-terminal antisera compared with NH 2 -terminal-specific antisera. All forms of VIP occurred mainly in extracts of muscle layers of the gut, and no antiserum revealed more than trace amounts of immunoreactivity in mucosal extracts. In immunohistochemical studies all antisera demonstrated fluorescent nerve fibres in the enteric plexuses, circular smooth muscle and lamina propria; some antisera demonstrated nerve cell bodies predominantly in the submucous plexus. NH 2 -terminal-specific antisera also demonstrated a sparse population of mucosal endocrine-like cells in the ileum and colon that were not seen with other antisera. It is concluded that VIPergic neurons of the rat gut contain a peptide closely resembling porcine VIP and at least two less basic variants with similar NH 2 -terminal antigenic determinants. VIP-like peptides may also occur in endocrine cells, but since these peptides appearto fact that the majority of neuronal VIP in rat gut exists in a form that is both chromatographically and immunochemically distinct from porcine VIP, and may well possess different biological properties.

A novel vasoactive intestinal peptide (VIP) from elasmobranch intestine has full affinity for mammalian pancreatic VIP receptors

A peptide that cross reacted with N-terminal, but not C-terminal, antisera to vasoactive intestinal peptide (VIP) was isolated from extracts of intestine from the dogfish Scyliorhinus canicula. Microsequence analysis gave the structure His-Ser-Asp-Ala-Val-Phe-Thr-Asp-Asn-Tyr-Ser-Arg-Ile-Arg-Lys-Gln-Met-Ala-Val-Lys - Lys-Tyr-Ile-Asn-Ser-Leu-Leu-Ala-NH2. C-terminal amidation was determined by HPLC analysis of phenylthiocarbamyl amino acid derivatives after carboxypeptidase Y digestion. The peptide differs at five positions from the porcine octacosapeptide. Dogfish VIP was equipotent with its porcine counterpart in inhibiting binding of 125I-labelled VIP to guinea pig dispersed pancreatic acini, and in stimulating amylase secretion by the same preparation. The data indicate a strong conservation of VIP during evolution and permit identification of residues crucial for bioactivity.

Cholecystokinin octapeptide in rat central nervous system: Immunocytochemical studies using a monoclonal antibody that does not react with CGRP

The biological activity of the important neuropeptide cholecystokinin octapeptide (CCK8) resides at the C-terminus. Antibodies with C-terminal specificity have been reported to cross-react with a different neuropeptide, calcitonin gene related peptide (CGRP) and this has frustrated the interpretation of immunohistochemical studies. We describe here the properties of a monoclonal antibody to the CCK-related peptide, caerulein, that reacts with the C-terminal region of CCK8, but does not react with CGRP in radioimmunoassay or immunohistochemistry. The distribution of CCK-like activity revealed by immunohistochemistry using this antibody broadly resembles that described previously with a single major exception: in the dorsal horn of the spinal cord. The results support the suggestion that apparent CCK activity in the terminals of rat primary sensory neurones is due to cross-reactivity with CGRP.

Unique amino terminal structure of rat little gastrin

The heptadecapeptide form of rat gastrin was purified by a combination of DEAE cellulose, Sephadex G50 affinity, and high performance liquid chromatography. An amino terminal pyroglutamyl blocking group was removed by incubation with PCA peptidase. Amino acid analysis before and after the unblocking reaction revealed the presence of one additional residue of arginine and proline compared with porcine gastrin. Microsequencing analysis of the unblocked peptide revealed that the sequence of the remaining hexadecapeptide was RPPMEEEEEAYGWMDF. The corresponding sequence of porcine gastrin is GPWMEEEEEAYGWMDF amide. The presence of carboxyl-terminal amide group in rat gastrin is strongly supported by complete immunoreactivity with antibodies specific for amidated C-terminal sequences of mammalian gastrins. The Arg and Pro substitutions in the amino terminal region can explain poor crossreactivity of rat gastrin with antibodies specific for the amino-terminal portion of porcine or human gastrin and its more basic chromatography pattern on ion exchange resins.

Gastrin stimulates MMP-1 expression in gastric epithelial cells: putative role in gastric epithelial cell migration

The pyloric antral hormone gastrin plays a role in remodeling of the gastric epithelium, but the specific targets of gastrin that mediate these effects are poorly understood. Glandular epithelial cells of the gastric corpus express matrix metalloproteinase (MMP)-1, which is a potential determinant of tissue remodeling; some of these cells express the CCK-2 receptor at which gastrin acts. We have now examined the hypothesis that gastrin stimulates expression of MMP-1 in the stomach. We determined MMP-1 transcript abundance in gastric mucosal biopsies from Helicobacter pylori negative human subjects with normal gastric mucosal histology, who had a range of serum gastrin concentrations due in part to treatment with proton pump inhibitors (PPI). The effects of gastrin were studied on gastric epithelial AGS-GR cells using Western blot and migration assays. In human subjects with increased serum gastrin due to PPI usage, MMP-1 transcript abundance was increased 2-fold; there was also increased MMP-7 transcript abundance but not MMP-3. In Western blots, gastrin increased proMMP-1 abundance, as well that of a minor band corresponding to active MMP-1, in the media of AGS-GR cells, and the response was mediated by protein kinase C and p42/44 MAP kinase. There was also increased MMP-1 enzyme activity. Gastrin-stimulated AGS-GR cell migration in both scratch wound and Boyden chamber assays was inhibited by MMP-1 immunoneutralization. We conclude that MMP-1 expression is a target of gastrin implicated in mucosal remodeling.

A novel gastrin-processing pathway in mammalian antrum

An antiserum, L221, has been developed that is specific for the C-terminal region of the N-terminal tridecapeptide (i.e., 1-13) fragment of the acid-stimulating hormone, G17. In contrast to N-terminal G17 antisera previously used to estimate 1-13 G17, L221 does not cross-react with other N-terminal gastrin fragments or with C-terminal extensions of G17. Using L221 in conjunction with conventional gastrin antisera, and reversed-phase HPLC, it has been possible to identify in addition to 1-13 G17 a further, formerly unrecognised gastrin fragment, 1-11 G17, in stomach extracts. The production of 1-13 G17, 1-11 G17 and other gastrin forms such as the biologically active hexapeptide G6 which is known to occur naturally cannot be explained by tryptic cleavage of progastrin. Instead, their biosynthesis could be explained by the actions of an enzyme with an endopeptidase 24.11-like specificity. In porcine antrum, unsulphated and sulphated G17 are present in similar amounts, but unsulphated 1-13 G17 was about twice as abundant as sulphate 1-13 G17. This is consistent with previous in vitro findings that endopeptidase 24.11 has a higher affinity for the Ala-11-Tyr-12 and Gly-13-Trp-14 bonds in unsulphated G17, than in sulphated G17. The results suggest a novel albeit minor, processing pathway for gastrin biosynthesis in pig antrum involving an enzyme resembling endopeptidase 24.11.

Vasoactive Intestinal Polypeptide and its Relatives: Biochemistry, Distribution, and Functions

Vasoactive intestinal polypeptide (VIP) was first isolated from the small intestine of the pig, the purification being monitored with a bioassay based on the vasoactive properties of the material (Said and Mutt, 1972). The new peptide had been anticipated, for in their pioneering experiments leading to the first discovery of the hormone secretin, Bayliss and Starling (1902) had noted the presence, in intestinal extracts, of a factor with vasodepressor activity. This may be the first recorded evidence of VIP activity.

Vasoactive intestinal polypeptide stimulation of prolactin release and renin activity in normal man and patients with hyperprolactinaemia: effects of pretreatment with bromocriptine and dexamethazone

Abstract. Vasoactive intestinal polypeptide (VIP) was infused into normal volunteers and patients with hyperprolactinaemia. Heart rate increased from 62 pL 3 to 75 pL 3 beats min‐1 (P= 0·001) in controls and from 70 pL 2 to 78 pL 3 beats min‐1 (P= 0·001) in hyperprolactinaemics. Similarly, haematocrit increased from 38 pL 2 to 44 pL 1% (P= 0·001) and from 40 pL 1 to 43 pL 2% (P= 0·002) and plasma renin activity from 910 pL 59 to a peak of 3344 pL 282 pg ml‐1 h‐1 (P= 0·001) and from 1577 pL 671 to a peak of 4954 pL 1364 pg ml‐1 h‐1 (P= 0·001) in the two groups, respectively. Prolactin concentrations rose in the control group only, from 134 pL 11 to a peak of 377 pL 35 mU l‐1 (P= 0·001), whilst in the hyperprolactinaemics little change occurred from the pre‐infusion concentration of 3873 pL 2179 reaching a peak of 3998 pL 2347 mU l‐1 (P > 0·07).