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H P Bennett

Publications and source records attributed to H P Bennett.

At least 19 recordsLinked to original sources
PubMed2000

Anti-inflammatory drugs protect against Alzheimer disease at low doses.

CONTEXT: Anti-inflammatory medications have an inverse association with Alzheimer disease (AD). OBJECTIVES: To examine at what doses this anti-inflammatory drug effect occurs and whether other medications and/or International Classification of Diseases, Ninth Revision, Clinical Modification diagnoses affect the association. DESIGN: Subjects 75 years and older from a random population sample were classified by consensus using International Classification of Diseases, Ninth Revision, Clinical Modification diagnoses. Drug associations with different types of dementia with and without the International Classification of Diseases, Ninth Revision, Clinical Modification diagnoses as well as dosage data were analyzed. SETTING: The Centre for Education and Research on Aging, Concord Hospital, Concord, Australia. PATIENTS: The Sydney Older Persons Study recruited 647 subjects (average age, 81 years). A total of 163 patients were given diagnoses placing them in different dementia categories and were compared with 373 control subjects. Of the patients with dementia, 78 had AD without vascular dementia, 45 had vascular dementia (permissive of other dementia diagnoses), and 40 had other dementia diagnoses (without AD or vascular dementia). MAIN OUTCOME MEASURES: Fifty drugs or drug groups were subjected to a 2 (drug used vs drug not used) x 4 (dementia and control groups) chi(2) analysis. Drugs with inverse associations were identified and potential confounders (logistic regression) and dosage data (exact small sample 1-tailed tests) analyzed. RESULTS: As expected, there was an inverse association between nonsteroidal anti-inflammatory drugs and aspirin (and unexpectedly angiotensin-converting enzyme inhibitors) and AD. This association was not observed with vascular dementia or any other diagnoses. Analysis showed no evidence for a dosage effect, ie, responses were equivalent for low and high doses. CONCLUSIONS: This study does not support a high-dose anti-inflammatory action of nonsteroidal anti-inflammatory drugs or aspirin in AD. Potential mechanisms for the beneficial effects of these medications are discussed.

Aged↗
PubMed2000

Infusion of N-proopiomelanocortin-(1-77) increases adrenal weight and messenger ribonucleic acid levels of cytochrome P450 17alpha-hydroxylase in the sheep fetus during late gestation.

In the sheep there is a rapid increase in fetal adrenal growth and steroidogenesis during the last 10-15 days gestation (term = 147+/-3 days gestation). In the rat, peptides derived from the N-terminal region of POMC play a role in compensatory adrenal growth and in potentiation of ACTH-induced steroidogenesis. We therefore investigated the effects of infusion of bovine N-POMC-(1-77) and its biosynthetic derivative, N-POMC-(1-49) on adrenal growth and on the expression of adrenal steroidogenic enzymes in the late gestation sheep fetus. Twenty-seven pregnant ewes were used in this study. Fetal vascular catheters were inserted between 116-125 days gestation, and purified bovine N-POMC-(1-77) (2 microg/ml x h), N-POMC-(1-49) (2 microg/ml x h) and saline were each infused for 48 h between 136 and 138 days gestation. Intrafetal infusion of N-POMC-(1-77) resulted in an increased adrenal/fetal body weight ratio (94.6+/-5.7 mg/kg) compared with that in saline-infused (75.6+/-1.8 mg/kg), but not N-POMC-(1-49)-infused (82.7+/-6.1 mg/kg), fetal sheep. The ratio of CYP17 messenger RNA (mRNA) to 18S ribosomal RNA was also significantly higher in fetal adrenals ofthe N-POMC-(1-77)-infused group (49.1+/-4.7) compared with that in either the N-POMC-(1-49)-infused (20.4+/-6.4) or saline-infused (15.2+/-4.4) group. There was no difference, however, in the ratios of adrenal CYP11A1 mRNA/3beta-hydroxysteroid dehydrogenase/delta5,delta4-isomerase mRNA and CYP21A1 mRNA/18S ribosomal RNA among the N-POMC-(1-77)-, N-POMC-(1-49)-, and saline-infused groups. There was also no significant change in either plasma cortisol or ACTH concentrations in response to the infusion of either N-POMC-(1-77) or N-POMC-(1-49). In summary, intrafetal infusion of N-POMC-(1-77) stimulated fetal adrenal growth and resulted in a specific increase in adrenal CYP17 gene expression in late gestation. N-POMC-(1-77) may therefore play a modulatory role in the increase in fetal adrenal growth and steroidogenesis that occurs before birth.

Adrenal Glands↗
PubMed2000

N-proopiomelanocortin (1-77) suppresses expression of steroidogenic acute regulatory protein (StAR) mRNA in the adrenal gland of the fetal sheep.

In the sheep, there is a rapid increase in fetal adrenal growth and steroidogenesis during the last 10-15 days gestation. Recently, we have shown that infusion of POMC (1-77) increases fetal adrenal growth and expression of CYP17 mRNA but does not significantly alter fetal plasma cortisol concentrations [1]. We therefore investigated the effects of infusion of bovine POMC (1-77) and its biosynthetic derivative POMC (1-49) on adrenal StAR mRNA expression. At 136d gestation, POMC (1-77) (n=5 fetuses; 2microg/ml/h), POMC (1-49) (n=5 fetuses, 2microg/ml/h) or Saline (n=5 fetuses, 1ml/h) was infused for 48h. At 138d, fetal adrenal glands were collected and frozen in liquid N2 until RNA was extracted. Northern blot analyses demonstrated a major transcript for StAR mRNA at 3.0kb in fetal adrenal glands from all treatments. The membrane was stripped and re-probed with a P-labelled rat 18S rRNA oligo-probe to verify equal RNA loading. Infusion of POMC (1-77), but not POMC (1-49), resulted in a suppression of fetal adrenal StAR mRNA:18S rRNA when compared to adrenal StAR mRNA:18S rRNA from saline-infused controls. Our data suggest POMC (1-77) may act via separate mechanisms to increase fetal adrenal growth and to limit adrenal steroidogenesis through suppression of StAR mRNA.

Adrenal Glands↗
PubMed1999

Peptide hormone precursor processing: getting sorted?

Processing of proproteins to biologically active peptides and, in the case of peptide hormones and neuropeptides, their sorting to granules of the regulated secretory pathway, requires the concerted action of a cascade of enzymes and chaperones. The purpose of this review is to summarize the recent emerging knowledge of how these molecules affect specific endocrine systems. This has come about through the study of gene knockout mice as well as endocrinopathies resulting from mutated genes in humans.

Animals↗
PubMed1999

Characterization of the inhibitory effect of boiled rice on intestinal chloride secretion in guinea pig crypt cells.

BACKGROUND & AIMS: When rice is incorporated into oral rehydration therapy for patients with secretory diarrhea, clinical outcomes improve. We have shown that a factor purified from boiled rice (RF) blocks the secretory response of intestinal crypt cells to adenosine 3',5'-cyclic monophosphate (cAMP). Now we report that the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel is the cellular target for this rice inhibitor. METHODS: We used RF, the same previously described extract prepared from boiled rice, to assess chloride channel activation in vitro, measuring (1) cell volume regulation of guinea pig intestinal crypt epithelial cell suspensions using standard Coulter counter technology, (2) transepithelial chloride current in monolayers of T84 cells mounted in Ussing chambers, and (3) whole-cell and single-channel currents using the patch-clamp technique in cells transfected to express CFTR. RESULTS: RF inhibited activation by cAMP of CFTR chloride channels in all experimental preparations; RF did not block volume-stimulated Cl- secretion, suggesting that its effect might be specific for CFTR chloride channels. RF inhibited transepithelial cAMP-stimulated Cl- current in T84 cells and inhibited forskolin (i.e., cAMP)-induced current in cells transfected with CFTR. Excised patch and single-channel patch-clamp recordings supported the view that the response was a direct effect on CFTR rather than on cAMP signal transduction. CONCLUSIONS: RF exerts a specific inhibitory effect on CFTR chloride channels, blocking activation from the luminal surface of the cell and reversing established activation. Many major diarrheal states are based on cAMP-induced CFTR activation, leading to excessive gut secretion; our findings could have clinical relevance.

Animals↗
PubMed1999

A 30-residue fragment of the carp granulin-1 protein folds into a stack of two beta-hairpins similar to that found in the native protein.

Upon air oxidation, a peptide corresponding to the 30-residue N-terminal subdomain of carp granulin-1 spontaneously formed the disulfide pairing observed in the native protein. Structural characterization using NMR showed the presence of a defined secondary structure within this peptide. The chemical shifts for most of the alphaCH protons of the peptide and the protein are very similar, and the observed NOE contacts of the peptide strongly resemble those in the protein. A structure calculation of the peptide using NOE distance constraints indicates that the peptide fragment adopts the same conformation as formed within the native protein. The 30-residue N-terminal peptide of carp granulin-1 is the first example of an independently folded stack of two beta-hairpins reinforced by two interhairpin disulfide bonds. Two key areas of the structure show a clustering of hydrophobic residues that may account for its exceptional conformational stability.

Amino Acid Sequence↗
PubMed1999

Processing of rat preprocortistatin in mouse AtT-20 cells.

Preprocortistatin (PPCST) has been recently identified as a novel somatostatin (SST)-related gene expressed only in brain. PPCST shares 11 of 14 residues with SST-14 at its C-terminal segment, where it features Lys-Lys and Lys-Arg basic sites for cleavage to putative cortistatin (CST)-14 and CST-29 peptides, respectively. Although synthetic replicates of the two putative CST peptides interact with SST receptors, they also display novel effects suggesting independent biological functions. Nothing is currently known about the naturally occurring mature cleavage products of PPCST posttranslational processing. Here we have cloned rat PPCST cDNA, stably expressed it in AtT-20 pituitary cells, and characterized the cellular and releasable products of PPCST processing by HPLC and radioimmunoassay using a SST-14 antibody that recognizes synthetic CST-14 and CST-29. Transfected cells released 120 +/- 21 pg of total CST-LI per plate basally, with an increase to 204 +/- 33 pg per plate with forskolin stimulation (p < 0.05). HPLC chromatograms of cell extracts revealed three peaks corresponding to CST-14, CST-29, and unprocessed PPCST (ratio, 41:55:4.5). CST was released preferentially as CST-14 (63-70%) compared with CST-29 (30-37%) under basal and forskolin-stimulated conditions. These studies demonstrate efficient processing of PPCST to both CST-14 and CST-29 through putative cleavage at both C-terminal dibasic sites of PPCST. Although the two peptides are synthesized approximately equally, CST-14 is released preferentially via the regulated secretory pathway.

Animals↗
PubMed1999

Proparathyroid hormone processing by the proprotein convertase-7: comparison with furin and assessment of modulation of parathyroid convertase messenger ribonucleic acid levels by calcium and 1,25-dihydroxyvitamin D3.

We previously showed that the processing of proparathyroid hormone (proPTH) to PTH was accomplished most efficiently by furin (17). Colocalization studies demonstrated that furin is expressed in the parathyroid, whereas proprotein convertase (PC)1 and PC2 are not. Since that time, another member of the PC family, called PC7, has been identified. Here we show, using coinfection studies, that PC7, as well as furin, can appropriately cleave PTH from proPTH. ProPTH and PTH were purified from cell extracts by reversed-phase HPLC and were identified by Western blot analysis and delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Colocalization studies, using Northern blot and reverse transcriptase-PCR analyses, showed that PC7 messenger RNA (mRNA) is expressed in the parathyroid gland. Therefore, PC7, like furin, has the potential to be involved in the physiological processing of proPTH to PTH. The two major regulators of parathyroid cell synthetic and secretory activity are the extracellular fluid calcium and 1,25-dihydroxyvitamin D [1,25(OH)2D] levels. We investigated whether either of these agents might modulate processing of proPTH to PTH by altering parathyroid convertase gene expression. In both in vitro and in vivo systems in which regulation of PTH mRNA levels were clearly apparent, there was no effect of either calcium or 1,25(OH)2D3 on parathyroid furin or PC7 mRNA levels. This is in contrast to the processing of proinsulin to insulin in the pancreatic beta-cell, which is up-regulated by glucose stimulation of PC1 and PC2 synthesis.

Animals↗
PubMed1998

Isolation of a member of the neurotoxin/cytotoxin peptide family from Xenopus laevis skin which activates dihydropyridine-sensitive Ca2+ channels in mammalian epithelial cells.

We have used a sensitive bioassay of calcium-mediated volume changes in mammalian absorptive intestinal epithelial cells to screen extracts of the skin of the amphibian Xenopus laevis for the presence of factors affecting ion transport. A 66-residue peptide, purified using reversed-phase high performance liquid chromatography techniques, caused isotonic volume reduction of guinea pig jejunal villus cells in suspension. This volume reduction required extracellular Ca2+ and was prevented by the dihydropyridine-sensitive Ca2+ channel blocker niguldipine. Structural analysis demonstrated the presence of eight cysteines and a primary structure homologous to that of the neurotoxin/cytotoxin family found in the venom of certain poisonous snakes. The structure of the peptide was identical to that of xenoxin-1 purified from dorsal gland secretions of X. laevis (Kolbe, M., Huber A., Cordier, P., Rasmussen, U., Bouchon, B., Jaquinod, M., Blasak, R., Detot, E., and Kreil, G. (1993) J. Biol. Chem. 268, 16458-16464). Xenoxin-1 (10 nM) caused volume changes that required extracellular Ca2+ and were comparable in magnitude and direction to changes caused by BayK-8644 (100 nM), a dihydropyridine-sensitive Ca2+ channel agonist. The initial rate of dihydropyridine-sensitive 45Ca2+ influx was substantially increased by xenoxin-1. Staurosporine (10 nM) prevented volume changes caused by ATP (250 microM) but had no effect on volume changes caused by BayK-8644 or xenoxin-1. We conclude that xenoxin-1 directly activated dihydropyridine-sensitive Ca2+ channels in villus cells and that a mammalian homologue to xenoxin-1 may exist.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1998

Cloning of human PEX cDNA. Expression, subcellular localization, and endopeptidase activity.

Mutations in the PEX gene are responsible for X-linked hypophosphatemic rickets. To gain insight into the role of PEX in normal physiology we have cloned the human full-length cDNA and studied its tissue expression, subcellular localization, and peptidase activity. We show that the cDNA encodes a 749-amino acid protein structurally related to a family of neutral endopeptidases that include neprilysin as prototype. By Northern blot analysis, the size of the full-length PEX transcript is 6.5 kilobases. PEX expression, as determined by semi-quantitative polymerase chain reaction, is high in bone and in tumor tissue associated with the paraneoplastic syndrome of renal phosphate wasting. PEX is glycosylated in the presence of canine microsomal membranes and partitions exclusively in the detergent phase from Triton X-114 extractions of transiently transfected COS cells. Immunofluorescence studies in A293 cells expressing PEX tagged with a c-myc epitope show a predominant cell-surface location for the protein with its COOH-terminal domain in the extracellular compartment, substantiating the assumption that PEX, like other members of the neutral endopeptidase family, is a type II integral membrane glycoprotein. Cell membranes from cultured COS cells transiently expressing PEX efficiently degrade exogenously added parathyroid hormone-derived peptides, demonstrating for the first time that recombinant PEX can function as an endopeptidase. PEX peptidase activity may provide a convenient target for pharmacological intervention in states of altered phosphate homeostasis and in metabolic bone diseases.

Adult↗
PubMed1998

In vitro cleavage of internally quenched fluorogenic human proparathyroid hormone and proparathyroid-related peptide substrates by furin. Generation of a potent inhibitor.

The cleavage of parathyroid hormone (PTH) from its precursor proparathyroid hormone (pro-PTH) is accomplished efficiently by the proprotein convertase furin (Hendy, G. N., Bennett, H. P. J., Gibbs, B. F., Lazure, C., Day, R., and Seidah, N. G. (1995) J. Biol. Chem. 270, 9517-9525). We also showed that a synthetic peptide comprising the -6 to +7 sequence of human pro-PTH is appropriately cleaved by purified furin in vitro. The human pro-PTH processing site Lys-Ser-Val-Lys-Lys-Arg differs from the consensus furin site Arg-Xaa-(Lys/Arg)-Arg that is represented by Arg-Arg-Leu-Lys-Arg in the cleavage site of pro-PTH-related peptide (pro-PTHrP). An earlier study demonstrated that an internally quenched fluorogenic substrate bearing an O-aminobenzoyl fluorescent donor at the NH2 terminus and an acceptor 3-nitrotyrosine near the COOH terminus was appropriately cleaved by the convertases furin and PC1 (Jean, F., Basak, A., DiMaio, J., Seidah, N. G., and Lazure, C. (1995) Biochem. J. 307, 689-695). Here, we have synthesized a series of internally quenched fluorogenic substrates based upon the pro-PTH and pro-PTHrP sequences to determine which residues are important for furin cleavage. Purified recombinant furin and PC1 cleaved the human pro-PTH internally quenched substrate at the appropriate site in an identical manner to that observed with the nonfluorescent peptide. Several substitutions in the P6-P3 sequence were well tolerated; however, replacement of the Lys at the P6 position with Gly and replacement of the P3 Lys by an acidic residue led to markedly compromised cleavage by furin. Furin activity was very sensitive to substitution in P' positions. Replacement of Ser at P1' with Gly and Val at P2' with Ala generated substrates that were less well cleaved. Substitution at the P1' position of Val for Ser in conjunction with Ala for Val at P2', as well as a single substitution of Lys for Val at P2', generated specific inhibitors of furin cleavage. The findings of this study open the way to the rational design of inhibitors of furin with therapeutic potential.

Amino Acid Sequence↗
PubMed1998

Health habits and risk of cognitive impairment and dementia in old age: a prospective study on the effects of exercise, smoking and alcohol consumption.

Previous research has yielded inconsistent results on the effects of exercise, smoking and alcohol use on cognitive impairment and dementia in old age. We analysed data from the Sydney Older Persons Study to see if these health habits were associated with cognitive functioning, dementia or Alzheimer's disease. Health habits were assessed in Wave 1 of the study, when the subjects were aged 75 years or over. Three years later, the subjects were tested for cognitive functioning and clinically examined for dementia and Alzheimer's disease. The analysis was restricted to the 327 subjects examined in Wave 2 who were non-demented in Wave 1. There were few significant associations between health habits and cognitive performance and these were not found consistently across cognitive measures. No associations were found with dementia or Alzheimer's disease. While these health habits do not affect risk for dementia and cognitive impairment in the very elderly, who are at highest risk for these disorders, we cannot discount a role at younger ages.

Aged↗
PubMed1998

Granulins: the structure and function of an emerging family of growth factors.

The granulin/epithelin motif defines a family of structurally unique proteins, of great evolutionary antiquity, which have been implicated as regulators of cell growth. Recurrent in granulin research are the surprising parallels between the granulin and EGF systems. Both are cysteinerich peptides of approximately 6 kDa that can modify cell growth. They show similar, but not identical, biological activities, although granulin/epithelin peptides do not bind EGF receptors; the three-dimensional folds of granulin and EGF are partially superimposible; and the precursors for mammalian granulin/epithelins and EGF are both organized as multiple repeats of conserved cysteine modules. Given the dissimilarity between amino acid sequences of members of the granulin/epithelin family and EGF-related peptides, the parallelism between the two systems probably represents convergent evolution towards related solutions to common biological problems. The granulin/epithelin precursor gene is expressed throughout the body, but its expression is predominantly in epithelial and haematopoietic cells. There is a great deal of versatility in the means by which cells process and handle the granulin/epithelin precursor. In some instances, the precursor is secreted intact (Zhou et al. 1993), and in others it is stored in a vesicular organelle, such as the sperm acrosome (Baba et al. 1993a). It may be processed into small 6-kDa peptides, which, in the neutrophil, can also be stored in vesicles (Bateman et al. 1990, Couto et al. 1992). The 6-kDa peptide forms, the intact precursor, and related proteins such as TGFe, regulate the growth of epithelial and mesenchymal cells. Epithelial cells express putative receptors for granulin/epithelin peptides and TGFe (Culouscou et al. 1993, Parnell et al. 1995). Thus, although much remains to be clarified, granulin/epithelin polypeptides and related proteins are emerging as widely distributed potential autocrine and paracrine growth modulating factors for epithelial and mesenchymal cells.

Amino Acid Sequence↗
PubMed1995

Inhibition of intestinal secretion by rice.

Rates of stool output are reduced when cooked rice is incorporated into oral rehydration solutions. We found that a fraction extracted from rice inhibited the response of intestinal epithelial crypt cells to adenosine 3'5'-cyclic monophosphate, a major intracellular mediator of secretion. This response to rice was seen as an inhibition of cell shrinkage and of chloride efflux in fresh suspended guinea pig crypt cells. The active fraction was of low molecular weight (< 1.5 kDa), hydrophobic, and not a peptide or glycoprotein. It may be chloride-channel blocker.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Proparathyroid hormone is preferentially cleaved to parathyroid hormone by the prohormone convertase furin. A mass spectrometric study.

Parathyroid hormone (PTH), an 84-amino acid peptide, is the major regulator of blood calcium homeostasis. Its mRNA, in addition to encoding the mature peptide, also encodes a "pre" sequence of 25 amino acids and a basic "pro" hexapeptide. To assess which of the subtilisin-like prohormone convertases can process proPTH to PTH we coinfected cells with a vaccinia virus construct expressing human preproPTH and vaccinia virus constructs expressing furin, PC1 or PC2. BSC-40 cells, having a constitutive secretory pathway, and GH4C1 cells, having a regulated secretory pathway, were used. PTH biosynthetic products in cell extracts and media were purified by high performance liquid chromatography, identified by radioimmunoassay, and unambiguously defined as either proPTH or PTH by ion-spray mass spectrometry. In both cell types, furin was the most effective in processing proPTH to PTH. In all cases only PTH was released into the medium. In addition, partially purified furin and PC1 were tested for their ability to appropriately cleave a tridecapeptide spanning the prohormone cleavage site found in proPTH. Here too furin was much more effective at cleaving at the correct site. Northern blot analysis and in situ hybridization showed that furin and preproPTH mRNA are co-expressed in the parathyroid, whereas PC1, PC2, and PC5 are not and PACE4 is expressed only at very low levels. Taken together these studies strongly suggest that furin is the enzyme responsible for the physiological processing of proPTH to PTH.

Amino Acid Sequence↗
PubMed1995

Mass spectrometric and biological characterization of guinea-pig corticotrophin.

Guinea-pig ACTH has been found to be distinct from other mammalian ACTHs in having an alanine for proline substitution at position 24 and in having superagonist aldosterone-stimulating activity relative to synthetic ACTH(1-24) in an isolated rat glomerulosa cell bioassay. We have purified ACTH from extracts of guinea-pig anterior pituitary and confirmed its unusual structural characteristics by amino acid analysis and mass spectrometry. Using isolated rat adrenal fasciculata-reticularis and glomerulosa cell bioassays, guinea pig ACTH was found to have similar activity to that of human ACTH with respect to corticosterone- and aldosterone-stimulating activity, in terms of maximal steroid output but was slightly more potent in terms of the concentration which elicited half-maximal steroid secretion. Under the assay conditions used, guinea-pig ACTH appeared not to be a superagonist as previously suggested. Various biosynthetic derivatives of guinea-pig pro-opiomelanocortin were identified by amino acid analysis and mass spectrometry. Joining peptide, a major product of pro-opiomelanocortin processing, was found in extracts of both anterior and neurointermediate lobes of the pituitary. Post-translational modification of other products of intermediate lobe processing were observed. N- and O-acetylation of alpha-melanotropin, partial O-phosphorylation of corticotropin-like intermediate lobe peptide and carboxyl-terminal amidation of beta-melanotropin were identified.

Adrenocorticotropic Hormone↗