Long-Term Functionality of Transversal Intraneural Electrodes Is Improved By Dexamethasone Treatment

Neuroprostheses aimed to restore lost functions after a limb amputation are based on the interaction with the nervous system by means of neural interfaces. Among the different designs, intraneural electrodes implanted in peripheral nerves represent a good strategy to stimulate nerve fibers to send sensory feedback and to record nerve signals to control the prosthetic limb. However, intraneural electrodes, as any device implanted in the body, induce a foreign body reaction (FBR) that results in the tissue encapsulation of the device. The FBR causes a progressive decline of the electrode functionality over time due to the physical separation between the electrode active sites and the axons to interface. Modulation of the inflammatory response has arisen as a good strategy to reduce the FBR and maintain electrode functionality. In this study transversal intraneural multi-channel electrodes (TIMEs) were implanted in the rat sciatic nerve and tested for 3 months to evaluate stimulation and recording capabilities under chronic administration of dexamethasone. Dexamethasone treatment significantly reduced the threshold for evoking muscle responses during the follow-up compared to saline-treated animals, without affecting the selectivity of stimulation. However, dexamethasone treatment did not improve the signal-to-noise ratio of the recorded neural signals. Dexamethasone treatment allowed to maintain more working active sites along time than saline treatment. Thus, systemic administration of dexamethasone appears as a useful treatment in chronically implanted animals with neural electrodes as it increases the number of functioning contacts of the implanted TIME and reduces the intensity needed to stimulate the nerve.

Fascicular nerve stimulation and recording using a novel double-aisle regenerative electrode

OBJECTIVE

As artificial prostheses become more refined, they are most often used as a therapeutic option for hand amputation. By contrast to extra- or intraneural interfaces, regenerative nerve electrodes are designed to enable electrical interfaces with regrowing axonal bundles of injured nerves, aiming to achieve high selectivity for recording and stimulation. However, most of the developed designs pose an obstacle to the regrowth mechanisms due to low transparency and cause impairment to the nerve regeneration.

APPROACH

Here we present the double-aisle electrode, a new type of highly transparent, non-obstructive regenerative electrode. Using a double-side thin-film polyimide planar multi-contact electrode, two nerve fascicles can regenerate without physical impairment through two electrically isolated aisles.

MAIN RESULTS

We show that this electrode can be used to selectively record and stimulate fascicles, acutely as well as chronically, and allow regeneration in nerve gaps of several millimeters without impairment.

SIGNIFICANCE

This multi-aisle regenerative electrode may be suitable for neuroprosthetic applications, such as prostheses, for the restoration of hand function after amputation or severe nerve injuries.

Identification of a founder BRCA1 mutation in the Moroccan population

Breast cancer (BC) is the most frequent cancer among women in Morocco. However, the role of the most prevalent BC-predisposing genes, BRCA1 and BRCA2, has been largely unexplored. To help define the role of BRCA1 in BC in Morocco, we characterized the first potential BRCA1 founder mutation in this population. Genetic testing of BRCA1 and BRCA2 in BC high-risk families identified mutation BRCA1 c.5309G>T, p.(Gly1770Val) or G1770V in five independent families from Morocco, suggesting a founder effect. To confirm this hypothesis, haplotype construction was performed using seven intragenic and flanking BRCA1 microsatellite markers. Clinical data were also compiled. Clinical data from carriers of mutation G1770V correspond to data from carriers of BRCA1 pathogenic mutations. Microsatellite analysis showed a common haplotype for the five families in a region comprising 1.54 Mb, confirming G1770V as the first specific founder BRCA1 mutation in the Moroccan population. Our findings contribute to a better understanding of BC genetics in the Moroccan population. Nevertheless, comprehensive studies of mutation G1770V in large series of BC patients from Morocco are needed to assess the real prevalence of this mutation and to improve genetic testing and risk assessment in this population.

Status of Competency-Based Medical Education in Endoscopy Training: A Nationwide Survey of US ACGME-Accredited Gastroenterology Training Programs

OBJECTIVES

The Accreditation Council for Graduate Medical Education (ACGME) emphasizes the importance of medical trainees meeting specific performance benchmarks and demonstrating readiness for unsupervised practice. The aim of this study was to examine the readiness of Gastroenterology (GI) fellowship programs for competency-based evaluation in endoscopic procedural training.

METHODS

ACGME-accredited GI program directors (PDs) and GI trainees nationwide completed an online survey of domains relevant to endoscopy training and competency assessment. Participants were queried about current methods and perceived quality of endoscopy training and assessment of competence. Participants were also queried about factors deemed important in endoscopy competence assessment. Five-point Likert items were analyzed as continuous variables by an independent t-test and χ(2)-test was used for comparison of proportions.

RESULTS

Survey response rate was 64% (94/148) for PDs and 47% (546/1,167) for trainees. Twenty-three percent of surveyed PDs reported that they do not have a formal endoscopy curriculum. PDs placed less importance (1—very important to 5—very unimportant) on endoscopy volume (1.57 vs. 1.18, P<0.001), adenoma detection rate (2.00 vs. 1.53, P<0.001), and withdrawal times (1.96 vs. 1.68, P=0.009) in determining endoscopy competence compared with trainees. A majority of PDs report that competence is assessed by procedure volume (85%) and teaching attending evaluations (96%). Only a minority of programs use skills assessment tools (30%) or specific quality metrics (28%). Specific competencies are mostly assessed by individual teaching attending feedback as opposed to official documentation or feedback from a PD. PDs rate the overall quality of their endoscopy training and assessment of competence as better than overall ratings by trainees.

CONCLUSIONS

Although the majority of PDs and trainees nationwide believe that measuring specific metrics is important in determining endoscopy competence, most programs still rely on procedure volume and subjective attending evaluations to determine overall competence. As medical training transitions from an apprenticeship model to competency-based education, there is a need for improved endoscopy curricula which are better suited to demonstrate readiness for unsupervised practice.

Amyloid and tau pathology of familial Alzheimer's disease APP/PS1 mouse model in a senescence phenotype background (SAMP8)

The amyloid precursor protein/presenilin 1 (APP/PS1) mouse model of Alzheimer's disease (AD) has provided robust neuropathological hallmarks of familial AD-like pattern at early ages, whereas senescence-accelerated mouse prone 8 (SAMP8) has a remarkable early senescence phenotype with pathological similarities to AD. The aim of this study was the investigation and characterization of cognitive and neuropathological AD markers in a novel mouse model that combines the characteristics of the APP/PS1 transgenic mouse model with a senescence-accelerated background of SAMP8 mice. Initially, significant differences were found regarding amyloid plaque formation and cognitive abnormalities. Bearing these facts in mind, we determined a general characterization of the main AD brain molecular markers, such as alterations in amyloid pathway, neuroinflammation, and hyperphosphorylation of tau in these mice along their lifetimes. Results from this analysis revealed that APP/PS1 in SAMP8 background mice showed alterations in the pathways studied in comparison with SAMP8 and APP/PS1, demonstrating that a senescence-accelerated background exacerbated the amyloid pathology and maintained the cognitive dysfunction present in APP/PS1 mice. Changes in tau pathology, including the activity of cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3 β (GSK3β), differs, but not in a parallel manner, with amyloid disturbances.

A three-dimensional self-opening intraneural peripheral interface (SELINE)

OBJECTIVE

In this study we present the development and testing in a rat model of the self-opening neural interface (SELINE), a novel flexible peripheral neural interface.

APPROACH

This polyimide-based electrode has a three-dimensional structure that provides an anchorage system to the nerve and confers stability after implant. This geometry has been achieved by means of the plastic deformation of polyimide. Mechanical and electrochemical characterizations have been performed to prove the integrity of the electrode with very good results. Functionality of SELINEs for fascicular stimulation has been tested during in vivo acute experiments in the rat. Chronic implants were made to test the biocompatibility of the device.

MAIN RESULTS

Results showed that SELINEs significantly improve mechanical anchorage to the nerve. Stimulation stability is considerably enhanced compared to common planar transversal electrodes and stimulation selectivity is increased for some motor fascicles. Chronic experimental results showed that SELINEs neither produce changes in the fascicular organization of sciatic nerves nor signs of nerve degeneration.

SIGNIFICANCE

The presented three-dimensional electrode provides an effective anchorage system to the nervous tissue that can improve the stability of the implant for acute and chronic studies.

Macroautophagic process was differentially modulated by long-term moderate exercise in rat brain and peripheral tissues

The autophagic process is a lysosomal degradation pathway, which is activated during stress conditions, such as starvation or exercise. Regular exercise has beneficial effects on human health, including neuroprotection. However, the cellular mechanisms underlying these effects are incompletely understood. Endurance and a single bout of exercise induce autophagy not only in brain but also in peripheral tissues. However, little is known whether autophagy could be modulated in brain and peripheral tissues by long-term moderate exercise. Here, we examined the effects on macroautophagy process of long-term moderate treadmill training (36 weeks) in adult rats both in brain (hippocampus and cerebral cortex) and peripheral tissues (skeletal muscle, liver and heart). We assessed mTOR activation and the autophagic proteins Beclin 1, p62, LC3B (LC3B-II/LC3B-I ratio) and the lysosomal protein LAMP1, as well as the ubiquitinated proteins. Our results showed in the cortex of exercised rats an inactivation of mTOR, greater autophagy flux (increased LC3-II/LC3-I ratio and reduced p62) besides increased LAMP1. Related with these effects a reduction in the ubiquitinated proteins was observed. No significant changes in the autophagic pathway were found either in hippocampus or in skeletal and cardiac muscle by exercise. Only in the liver of exercised rats mTOR phosphorylation and p62 levels increased, which could be related with beneficial metabolic effects in this organ induced by exercise. Thus, our findings suggest that long-term moderate exercise induces autophagy specifically in the cortex.

Identification of a founder EPCAM deletion in Spanish Lynch syndrome families

Germline deletions at the 3'-end of EPCAM have been involved in the etiology of Lynch syndrome (LS). The aim of this study was to characterize at the molecular level Spanish families harboring EPCAM deletions. Non-commercial multiplex ligation-dependent probe amplification (MLPA) probes and long-range polymerase chain reaction (PCR) amplification were used to characterize each deletion. Haplotyping was performed by analyzing eight microsatellite markers and five MSH2single nucleotide polymorphisms (SNPs). Methylation of MSH2 was analyzed by methylation specific-MLPA. Tumors diagnosed in seven Spanish families harboring EPCAM deletions were almost exclusively colorectal. Mosaicism in MSH2 methylation was observed in EPCAM deletion carrier samples, being average methylation levels higher in normal colon and colorectal tumors (27.6% and 31.1%), than in lymphocytes and oral mucosa (1.1% and 0.7%). Three families shared the deletion c.858 + 2568_*4596del, with a common haplotype comprising 9.9 Mb. In two families the novel EPCAM deletion c.858 + 2488_*7469del was identified. This study provides knowledge on the clinical and molecular characteristics of mosaic MSH2 epimutations. The identification of an EPCAM founder mutation has useful implications for the molecular diagnosis of LS in Spain.

Common variants at 12p11, 12q24, 9p21, 9q31.2 and in ZNF365 are associated with breast cancer risk for BRCA1 and/or BRCA2 mutation carriers

INTRODUCTION

Several common alleles have been shown to be associated with breast and/or ovarian cancer risk for BRCA1 and BRCA2 mutation carriers. Recent genome-wide association studies of breast cancer have identified eight additional breast cancer susceptibility loci: rs1011970 (9p21, CDKN2A/B), rs10995190 (ZNF365), rs704010 (ZMIZ1), rs2380205 (10p15), rs614367 (11q13), rs1292011 (12q24), rs10771399 (12p11 near PTHLH) and rs865686 (9q31.2).

METHODS

To evaluate whether these single nucleotide polymorphisms (SNPs) are associated with breast cancer risk for BRCA1 and BRCA2 carriers, we genotyped these SNPs in 12,599 BRCA1 and 7,132 BRCA2 mutation carriers and analysed the associations with breast cancer risk within a retrospective likelihood framework.

RESULTS

Only SNP rs10771399 near PTHLH was associated with breast cancer risk for BRCA1 mutation carriers (per-allele hazard ratio (HR) = 0.87, 95% CI: 0.81 to 0.94, P-trend = 3 × 10-4). The association was restricted to mutations proven or predicted to lead to absence of protein expression (HR = 0.82, 95% CI: 0.74 to 0.90, P-trend = 3.1 × 10-5, P-difference = 0.03). Four SNPs were associated with the risk of breast cancer for BRCA2 mutation carriers: rs10995190, P-trend = 0.015; rs1011970, P-trend = 0.048; rs865686, 2df-P = 0.007; rs1292011 2df-P = 0.03. rs10771399 (PTHLH) was predominantly associated with estrogen receptor (ER)-negative breast cancer for BRCA1 mutation carriers (HR = 0.81, 95% CI: 0.74 to 0.90, P-trend = 4 × 10-5) and there was marginal evidence of association with ER-negative breast cancer for BRCA2 mutation carriers (HR = 0.78, 95% CI: 0.62 to 1.00, P-trend = 0.049).

CONCLUSIONS

The present findings, in combination with previously identified modifiers of risk, will ultimately lead to more accurate risk prediction and an improved understanding of the disease etiology in BRCA1 and BRCA2 mutation carriers.

Novel (60%) and recurrent (40%) androgen receptor gene mutations in a series of 59 patients with a 46,XY disorder of sex development

BACKGROUND

Androgen receptor (AR) gene mutations are the most frequent cause of 46,XY disorders of sex development (DSD) and are associated with a variety of phenotypes, ranging from phenotypic women [complete androgen insensitivity syndrome (CAIS)] to milder degrees of undervirilization (partial form or PAIS) or men with only infertility (mild form or MAIS).

OBJECTIVE

The aim of the study was to characterize the contribution of the AR gene to the molecular cause of 46,XY DSD in a series of Spanish patients.

SETTING

We studied a series of 133 index patients with 46,XY DSD in whom gonads were differentiated as testes, with phenotypes including varying degrees of undervirilization, and in whom the AR gene was the first candidate for a molecular analysis.

METHODS

The AR gene was sequenced (exons 1 to 8 with intronic flanking regions) in all patients and in family members of 61% of AR-mutated gene patients.

RESULTS

AR gene mutations were found in 59 individuals (44.4% of index patients), of whom 46 (78%) were CAIS and 13 (22%) PAIS. Fifty-seven different mutations were found: 21.0% located in exon 1, 15.8% in exons 2 and 3, 57.9% in exons 4-8, and 5.3% intronic. Twenty-three mutations (40.4%) had been previously described and 34 (59.6%) were novel.

CONCLUSIONS

AR gene mutation is the most frequent cause of 46,XY DSD, with a clearly higher frequency in the complete phenotype. Mutations spread along the whole coding sequence, including exon 1. This series shows that 60% of mutations detected during the period 2002-2009 were novel.

Insulin resistance is associated with liver stiffness in HIV/HCV co-infected patients

BACKGROUND

The factors that influence liver fibrosis progression in patients co-infected with human immunodeficiency virus/hepatitis C virus (HIV/HCV) are not completely understood. It is not known if insulin resistance (IR), a condition that promotes liver fibrosis in HCV mono-infected individuals, is one of these factors.

OBJECTIVE

To evaluate the association between IR and liver stiffness (LS).

DESIGN

Multicentre cross-sectional study.

PATIENTS

330 patients co-infected with HIV/HCV.

METHODS

LS was assessed by transient elastography, which has shown a high accuracy to predict significant fibrosis in patients co-infected with HIV/HCV. The outcome variable of the study was LS. Patients with LS> or =9 kPa were considered as having significant fibrosis. IR was calculated using the HOMA method.

RESULTS

LS was > or =9 kPa in 150 (45%) patients. HOMA correlated with LS (Spearman's rho correlation coefficient, 0.37; p<0.0001). The median (Q1-Q3) HOMA in patients with LS> or =9 kPa was 3.30 (2.17-5.16) while it was 2.09 (1.37-3.22) in patients with LS <9 kPa (p<0.0001). Ninety-six (39%) individuals with a HOMA <4 and 54 (63%) with a HOMA > or =4 showed LS> or =9 kPa (p<0.0001). Analyses after excluding patients with cirrhosis yielded similar results. After multivariate analyses, age > or =40 years (adjusted odds ratio (AOR), 1.85; 95% confidence interval (CI), 1.03 to 3.29; p = 0.03), CD4 cell count <200 cells/ml (AOR, 3.45; 95% CI, 1.67 to 7.11; p = 0.001), hepatitis B virus co-infection (AOR, 9.25; 95% CI, 2.42 to 35.31; p = 0.001), and HOMA > or =4 (AOR, 5.33; 95% CI, 2.70 to 10.49; p<0.0001) were the independent predictors of LS> or =9 kPa.

CONCLUSION

IR is associated with LS in patients co-infected with HIV/HCV.

Functional role of protein kinase B/Akt in gastric acid secretion

Epidermal growth factor (EGF) stimulates gastric acid secretion and H(+)/K(+)-ATPase alpha-subunit gene expression. Because EGF activates the serine-threonine protein kinase Akt, we explored the role of Akt in gastric acid secretion. Akt phosphorylation and activation were measured by kinase assays and by Western blots with an anti-phospho-Akt antibody, using lysates of purified (>95%) canine gastric parietal cells in primary culture. EGF induced Akt phosphorylation and activation, whereas carbachol had no effect. LY294002, an inhibitor of phosphoinositide 3-kinase, completely blocked EGF induction of Akt phosphorylation, whereas the MEK1 inhibitor PD98059 and the protein kinase C inhibitor GF109203X had no effect. We examined the role of Akt in H(+)/K(+)-ATPase gene expression by Northern blotting using a canine H(+)/K(+)-ATPase alpha-subunit cDNA probe. The parietal cells were transduced with a multiplicity of infection of 100 of the adenoviral vector Ad.Myr-Akt, which overexpresses a constitutively active Akt gene, or with the control vector Ad.CMV-beta-gal, which expresses beta-galactosidase. Ad.Myr-Akt induced H(+)/K(+)-ATPase alpha-subunit gene expression 3-fold, whereas it failed to stimulate the gene cyclooxygenase-2, which was potently induced by carbachol in the same parietal cells. Ad.Myr-Akt induced aminopyrine uptake 4-fold, and it potentiated the stimulatory action of carbachol 3-fold. In contrast, Ad.Myr-Akt failed to induce changes in either parietal cell actin content, measured by Western blots with an anti-actin antibody or in the organization of the actin cellular cytoskeleton, visualized by fluorescein phalloidin staining and confocal microscopy. Transduction of the parietal cells with a multiplicity of infection of 100 of the adenoviral vector Ad.dom.neg.Akt, which overexpresses an inhibitor of Akt, blocked the stimulatory effect of EGF on both aminopyrine uptake and H(+)/K(+)-ATPase production, measured by Western blots with an anti-H(+)/K(+)-ATPase alpha-subunit antibody. Thus, EGF induces a cascade of events in the parietal cells that results in the activation of Akt. The functional role of Akt appears to be stimulation of gastric acid secretion through induction of H(+)/K(+)-ATPase expression.

TNF-alpha and interleukin 1 activate gastrin gene expression via MAPK- and PKC-dependent mechanisms

Helicobacter pylori and proinflammatory cytokines have a direct stimulatory effect on gastrin release from isolated G cells, but little is known about the mechanism by which these factors regulate gastrin gene expression. We explored whether tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 directly regulate gastrin gene expression and, if so, by what mechanism. TNF-alpha and IL-1 significantly increased gastrin mRNA in canine G cells to 181 +/- 18% and 187 +/- 28% of control, respectively, after 24 h of treatment. TNF-alpha and IL-1 stimulated gastrin promoter activity to a maximal level of 285 +/- 12% and 415 +/- 26% of control. PD-98059 (a mitogen-activated protein kinase kinase inhibitor), SB-202190 (a p38 kinase inhibitor), and GF-109203 (a protein kinase C inhibitor) inhibited the stimulatory action of both cytokines on the gastrin promoter. In conclusion, both cytokines can directly regulate gastrin gene expression via a mitogen-activated protein kinase- and protein kinase C-dependent mechanism. These data suggest that TNF-alpha and IL-1 may play a direct role in Helicobacter pylori-induced hypergastrinemia.

Molecular cloning of the orphanin FQ receptor gene and differential tissue expression of splice variants in rat

Pharmacological and receptor-ligand binding studies of the cloned orphanin FQ (OFQ) receptor suggest that multiple forms of this receptor may exist. To further characterize the OFQ receptor (OFQR), we attempted to isolate the gene encoding this receptor in rat. The OFQR gene exceeds 10 kb in length and contains six exons ranging from 34 to 524 bp that are interrupted by five introns. The ATG translation initiation codon is located in exon 2, and the open reading frame consists of 1283 bp. Primer extension analysis of the gene revealed two major transcription initiation sites: one in the 5' flanking region and the other in intron 1. The rat OFQR gene appeared to be alternatively spliced to yield multiple mRNAs. Four splice variants deleted for exon 1 were expressed only in brain. In contrast, five isoforms containing exon 1 were expressed in various tissues, such as brain, testes, and gastrointestinal tract. These data suggest that unique regions in intron 1 and in the 5' flanking region of the OFQR gene contribute to the regulation of its expression in different tissues.

Histamine H2 receptor mediated dual signaling: mapping of structural requirements using beta2 adrenergic chimeric receptors

Previously we demonstrated that the histamine H2 receptor can activate both the adenylate cyclase and phosphoinositide/protein kinase (PKC) signaling pathways. Although dual coupling occurs via separate GTP-dependent mechanisms the structural components of the H2 receptor directing differential signaling have not been established. We explored this question by attempting to confer to the beta2-adrenergic receptor (betaAR), which is known to stimulate cAMP formation, the ability to activate PKC through the construction of beta2/H2 chimeric receptors. Intracytoplasmic domains of the human beta2 adrenergic receptor were substituted with the corresponding sequences of the human H2 receptor and stably expressed in HEK-293 cells. Binding of [(3)H]-CGP to chimeric wild type beta2 receptors was comparable. Substitution of the second intracellular loop (2i) of the betaAR led to a significant decrease in coupling to adenylate cyclase while leading to a 139.5 +/- 9.4% control increase in epinephrine mediated PKC activation. Introduction of the H2 receptor 3i also led to a decrease in betaAR mediated cAMP generation but provided the latter with the ability to stimulate PKC (182.2 +/- 8% of control). Concomitant expression of both 2i and 3i led to a substantial increase in epinephrine mediated PKC activation (201.8 +/- 10.5% of control). Addition of the carboxyl terminal tail did not facilitate stimulation of PKC. In summary, the third intracellular loop of the H2 receptor plays an essential role in activating PKC with maximal efficiency conferred by the second intracellular domain.

Host specificity of Helicobacter pylori strains and host responses in experimentally challenged nonhuman primates

BACKGROUND & AIMS

The specificity of colonization by Helicobacter pylori and complex host-bacterium interactions cannot be readily examined in humans. The aim of this study was to perform such analyses in rhesus monkeys.

METHODS

Four animals that had been cured of natural H. pylori colonization were challenged with a mixture of 7 strains of human origin, and bacteria recovered during periodic videogastroscopy were DNA fingerprinted.

RESULTS

Three animals carried mixtures of several strains for 4 months, after which strain J166 predominated. In the fourth animal, only strain J238 was isolated from the earliest phase of colonization through 7 months, but strain J166 again became predominant by 10 months after the challenge. Gastritis scores and plasma gastrin and anti-H. pylori immunoglobulin G titers reached levels observed in naturally colonized animals by 4 months after the challenge; however, no plasma immunoglobulin A response was observed up to 10 months.

CONCLUSIONS

These results show that (1) natural colonization does not elicit protective immunity against subsequent H. pylori challenge; (2) individuals differ in susceptibility to different H. pylori strains during initial stages of colonization; and (3) certain strains are better suited than others for long-term survival in different hosts. These observations show the complexity of H. pylori-host interactions.

Regulation of c-Jun NH2-terminal kinases in isolated canine gastric parietal cells

c-Jun NH2-terminal kinases (JNKs) are protein kinases that are activated by a wide variety of extracellular signals. This study investigated the expression and regulation of JNKs in isolated gastric canine parietal cells. Western blot analysis of cell lysates from highly purified (>95%) parietal cells with an antibody recognizing JNK1 and to a lesser degree JNK2 revealed the presence of two bands of 46 and 54 kDa, respectively. JNK1 activity was quantitated by immunoprecipitation and in-gel kinase assays. Of the different agents tested, carbachol was the most potent inducer of JNK1 activity, whereas histamine and epidermal growth factor induced weaker responses. The proinflammatory cytokine tumor necrosis factor-alpha stimulated JNK1 but had no effect on extracellular signal-regulated kinase (ERK2) induction, suggesting that activation of JNK1 might represent an important event in mediation of the inflammatory response in the stomach. The action of carbachol was dose (0.1-100 microM) and time dependent, with a maximal stimulatory effect (fourfold) detected after 30 min of incubation and sustained for 2 h. Addition of the specific protein kinase C (PKC) inhibitor GF109203X did not affect the stimulatory action of carbachol. The intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid-AM inhibited carbachol induction of JNK1 activity by 60%. Thapsigargin (1 microM), an intracellular Ca2+-rising agent, induced JNK1 activity more than threefold. Carbachol activation of JNK1 resulted in induction of c-Jun (protein) transcriptional activity and in stimulation of parietal cell mRNA content of c-jun. In conclusion, our data indicate that carbachol induces JNK activity in gastric parietal cells via intracellular Ca2+-dependent, PKC-independent pathways, leading to induction of c-jun gene expression via phosphorylation and transcriptional activation of c-Jun.

Characterization of the histamine H2 receptor structural components involved in dual signaling

We previously demonstrated that the histamine H2 receptor can activate both adenylate cyclase (AC) and phospholipase C (PLC) signaling pathways via separate GTP-dependent mechanisms. We examined whether H2 receptor-specific peptides corresponding to the amino (N) or carboxyl terminus (C) of the second (2i) or third (3i) intracytoplasmic loops or the carboxyl terminal tail (P4iN) could effect histamine- stimulated AC and PLC activity in cell membranes prepared from HEPA cells stably transfected to express the canine H2 histamine receptor cDNA. Tiotidine binding and basal signaling were not altered by the synthetic peptides. H2P2iN, H2P2iC, H2P3iN and H2P4iN did not effect histamine stimulated AC activity although H2P3iC (10(-4) M) significantly inhibited this parameter (65.6 +/- 7.2% of maximal stimulation) (n = 6). Combination of the five peptides (H2P2iN, H2P2iC, H2P3iN, H2P3iC and H2P4iN) abolished histamine stimulated AC activity. Although all of the peptides inhibited histamine-stimulated PLC activity to a moderate degree individually, H2P3iC (10(-4) M) had the greatest effect, decreasing PLC activation to 20.8 +/- 6.3% of maximal stimulation (IC50 = 7.5 X 10(-7) M) (n = 6). H2P3iC and the peptide combination did not alter, forskolin, GTP gamma s or epinephrine-stimulated AC activity nor GTP gamma s and vasopressin-stimulated PLC. These studies demonstrate that both the second and third intracytoplasmic loops of the histamine H2 receptor are linked to separate signaling pathways in a differential manner.

Activation of the human histamine H2 receptor is linked to cell proliferation and c-fos gene transcription

We examined whether histamine could regulate cell proliferation and expression of the early response gene c-fos in HEK-293 cells stably transfected with the human H2 receptor (HEK-H2). Histamine stimulated [3H]thymidine incorporation [50% effective concentration (EC50) = 3.6 x 10(-6) M] in HEK-H2 cells in a cimetidine-sensitive manner and increased c-fos mRNA in a time-dependent fashion, reaching maximal induction after 30 min. Histamine induced luciferase activity in HEK-H2 cells transiently transfected with a construct containing the luciferase reporter gene (Luc) coupled to the serum response element (SRE) of the c-fos gene promoter (EC50 = 1.5 x 10(-6) M) or a plasmid containing the SRE core fragment (bases -320 to -298). The protein kinase C (PKC) inhibitor staurosporine and long-term pretreatment of HEK cells with phorbol ester inhibited the effect of histamine on PKC activation, SRE-Luc activity, and [3H]thymidine incorporation. We have demonstrated that activation of the human H2 receptor can lead to induction of c-fos gene transcription and cell proliferation through a PKC-dependent mechanism.

Novel insights into histamine H2 receptor biology

Histamine exerts multiple biological actions through one of three receptor subtypes (H1, H2, and H3). This review focuses on new developments regarding the structure and function of the H2 receptor. In addition to the important role this receptor plays in stimulating gastric acid secretion, recent studies have demonstrated that it is also involved in regulating gastrointestinal motility and intestinal secretion. The potential role of the H2 receptor in regulating cell growth and differentiation has also been added to the list of actions this biogenic amine may exert in both normal and transformed tissues. Molecular cloning of the gene indicates that it has the structural characteristics of a heptahelical G protein-linked receptor. Site-directed mutagenesis studies of this receptor reveal the presence of key amino acids within the third and fifth transmembrane domains that are critical for ligand recognition. Molecular approaches have also shed light on the structural components of the H2 receptor important in regulating desensitization and internalization. Although the H2 receptor was classically thought to couple to the adenylate cyclase pathway, recent work with the cloned receptor indicates that it can also activate the phosphoinositide signaling cascade through an independent G protein-dependent mechanism. The novel observation that histamine may stimulate c-fos gene expression lends further support to the possible role of this receptor in regulating cell growth and differentiation.

Effect of Helicobacter pylori products and recombinant cytokines on gastrin release from cultured canine G cells

BACKGROUND & AIMS

The pathophysiology of hypergastrinemia in Helicobacter pylori infection is undefined, but the infected antrum shows a marked inflammatory response with local production of cytokines. Hypergastrinemia and inflammatory infiltrate clear with successful eradication. The aim of this study was to examine whether the cytokines tumor necrosis factor alpha or interleukin 8 (IL-8), which are produced in the gastric mucosa of patients with H. pylori-induced peptic disease or H. pylori products, can stimulate gastrin release from isolated cultured canine G cells.

METHODS

Canine G cells were isolated by collagenase digestion, enriched by centrifugal elutriation, incubated with cytokines, bacterial components, or both, and gastrin release was measured by radioimmunoassay.

RESULTS

IL-8 (1 and 10 nmol/L) stimulated gastrin release by 34% +/- 13% and 43% +/- 23% (P < 0.05) above basal, respectively. H. pylori sonicates, water extract preparations, and lipopolysaccharide had no stimulatory actions, but the sonicates from two of four strains potentiated the effects of IL-8, leading to maximal gastrin release of 230% +/- 130% and 232% +/- 33% above basal, respectively (P < 0.05).

CONCLUSIONS

IL-8 stimulated gastrin release from isolated G cells, and the effect was potentiated by H. pylori products. The interaction of cytokines and H. pylori may contribute to the hypergastrinemia seen in vivo.

EGF receptor activation stimulates endogenous gastrin gene expression in canine G cells and human gastric cell cultures

Gastrin release from the antral gastrin-expressing cell (G cell) is regulated by bombesin and luminal factors. Yet, these same extracellular regulators do not stimulate expression of the gene. Since the gastric mucosa expresses large quantities of EGF receptor ligands such as TGFalpha, we examined whether EGF receptor ligands stimulate gastrin gene expression in gastrin-expressing cell cultures. EGF receptor activation of primary cultures stimulated gastrin gene expression about twofold; whereas bombesin treatment of antral G cell cultures stimulated gastrin release but not gene expression. EGF and TGFalpha were weak stimulants of gastrin release. EGF receptor activation of AGS human gastric adenocarcinoma cell line stimulated gastrin gene expression nearly fourfold; and gastrin reporter constructs transfected into AGS cells were stimulated more than fourfold by EGF. EGF induction was conferred by the previously defined GC-rich gastrin EGF response element (gERE) element located at -68 to -53 bp upstream from the cap site since a mutation of the gERE element abolished both basal and EGF induction. Moreover, EGF treatment of AGS cells stimulated binding of the transcription factor Sp1 to this element. Collectively, these results demonstrate that gastrin gene expression and gastrin release are regulated by different signaling pathways: gene expression by EGF receptor activation and gastrin secretion by neuropeptides and luminal factors.

Results at 43 months' follow-up of a double-blind, randomized, prospective clinical trial using intravesical interferon alpha-2b in the prophylaxis of stage pT1 transitional cell carcinoma of the bladder

OBJECTIVES

To assess the intravesical efficacy of 60 million units of interferon (IFN) alpha-2b in preventing recurrences of Stage pT1 transitional cell carcinoma of the bladder, as well as to assess its local and systemic toxicity.

METHODS

A total of 90 patients were included in a double-blind, randomized, prospective clinical trial and divided into two groups of 45 patients. After complete transurethral resection, 60 million units IFN alpha-2b was instilled in one group; in the other, double-distilled water was used. The therapeutic regimen consisted of weekly instillation for 12 weeks, followed by once-monthly instillation until patients had completed 1 year of treatment.

RESULTS

Only 78 patients were evaluable. After 12 months of follow-up, the relapse rate was 28.2% (11 of 39) for the IFN group and 35.8% (14 of 39) for the control group (P = NS). After 43 months (range 9 to 67), relapse rates were 53.8% (21 of 39) and 51.2% (20 of 39), respectively (P = NS). Progression, mortality, and local or systemic toxicity were similar in both groups. Flu-like syndrome was not reported.

CONCLUSIONS

At the dose used in this study, IFN alpha-2b proved ineffective in the prophylaxis of Stage pT1 transitional cell carcinoma of the bladder compared with a control group. Toxicity was virtually absent.

Intestinal intraepithelial lymphocytes influence the production of somatostatin

BACKGROUND

We have previously demonstrated that intestinal intraepithelial lymphocytes (iIELs) inhibit lymphocyte proliferation. Because somatostatin also prevents lymphocyte proliferation, we hypothesized that iIELs may influence production of somatostatin.

METHODS

Isolates of intestinal epithelium that were obtained from Brown Norway (BN) rats and contained an iIEL-enriched population (defined as CD45+) were incubated with irradiated Lewis splenocytes for allogeneic stimulation. BN rat splenocytes incubated with irradiated Lewis splenocytes served as a control. Supernatants were harvested after 4 days and assayed for somatostatin by using a radioimmunoassay.

RESULTS

The somatostatin level in the intestinal epithelium-conditioned supernatant was significantly higher than that of the control group (176 +/- 60 versus 10 +/- 2 fmol/ml; p < 0.05). Removal of the CD45+ cell subset resulted in a fifteenfold reduction in somatostatin levels. The CD45+ cell lysates had significantly higher levels of somatostatin than did CD45+ depleted cells (1304 +/- 531 versus 128 +/- 41 fmol/ml; p < 0.05).

CONCLUSIONS

The isolates of intestinal epithelium produced significant amounts of somatostatin. Removal of the CD45+ cells caused a significant loss of somatostatin production. Intracellular levels of somatostatin appeared to be highest in the CD45+ subpopulation. These data suggest that iIELs (that is, CD45+ cells) may have a significant influence on the production of somatostatin and may be a source of somatostatin production. Production of somatostatin by iIELs may help modulate immune responses in gut-associated lymphoid tissue.

Epidermal growth factor and transforming growth factor-alpha directly inhibit parietal cell function through a similar mechanism

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) are naturally occurring peptides which are present throughout the gastrointestinal tract and are capable of inhibiting gastric acid secretion. Although previous studies have suggested that TGF-alpha may serve as an autocrine factor regulating parietal cell function, the cellular mechanisms by which it exerts its inhibitory action have not been fully elucidated. In addition, no systematic comparison has been undertaken of the effects of EGF and TGF-alpha on parietal cell function. The aims of the present studies were to compare the actions of EGF and TGF-alpha on basal and stimulated acid secretion by isolated rabbit parietal cells and to elucidate the intracellular mechanisms by which these growth factors inhibit acid secretion stimulated by agents that activate the adenylate cyclase and cyclic AMP second messenger system. Although EGF and TGF-alpha did not alter basal parietal cell function, they both inhibited histamine-stimulated [14C]aminopyrine accumulation in a identical time- and dose-dependent fashion. The maximal effect of approximately 40% inhibition for histamine-stimulated action was achieved with concentrations of 10(-6) M for both EGF and TGF-alpha. The inhibitory effect of EGF and TGF-alpha appeared to be at the postreceptor level as neither growth factor significantly altered binding of histamine to its receptor (H2) on parietal cells. Consistent with this postulated mechanism of action, both EGF and TGF-alpha dose-dependently inhibited forskolin-stimulated aminopyrine uptake with IC50 similar to those required for inhibiting the stimulatory effect of histamine. Of note, neither growth factor inhibited parietal cell activity stimulated by dibutyryl cyclic AMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of immunoreactive cholecystokinin precursor to amacrine cells and bipolar cells of the macaque monkey retina

We used antisera that recognized precursors of the neuropeptide cholecystokinin extended at the carboxyl terminus in an immunocytochemical study of the macaque retina. A subpopulation of bipolar cells with long, obliquely oriented dendrites was labeled. Their axons terminated exclusively in the fifth stratum of the inner plexiform layer, where they contacted processes of amacrine and ganglion cells. Based on their morphology, these cells appeared to be the type that contacts short-wavelength cones selectively. Two types of amacrine cells were also labeled, and processes from both types formed dense plexuses in the second and fourth strata of the inner plexiform layer. The majority of their synaptic connections were with other amacrine cells, but they had more contacts with bipolar cell axons and retinal ganglion cell dendrites than any other peptidergic cells in the macaque retina. We studied extracts of macaque retina with gel-filtration chromatography and radioimmunoassays to confirm our immunohistochemical results. We found cholecystokinin octapeptide and other immunoreactive forms that were amidated at their carboxyl termini and were therefore likely to be biologically active. Unlike most other regions of the CNS, however, the retina had relatively low concentrations of amidated forms, and forms with extended carboxyl termini that are presumably their precursors were far more abundant. These findings suggest that the rate of cholecystokinin synthesis in the retina is quite high, as we would expect if the peptide were found in tonically active neurons.

Carbonic anhydrase II gene expression in isolated canine gastric parietal cells

The participation of carbonic anhydrase (CA II) in the gastric acid secretory process has been the subject of considerable controversy. We utilized a cDNA probe for CA II to measure CA II gene expression in canine gastric parietal cells that had been stimulated with the three principal acid secretagogues, carbachol, gastrin, and histamine. Hybridization to dot blots of total parietal cell RNA showed a significant increase in specific CA II mRNA content within minutes of secretagogue addition: carbachol stimulation led to an increase of 52 +/- 8.9%, reaching a maximum within 20 min; gastrin stimulation led to an increase within 60 min of 104 +/- 10.6%; stimulation with histamine was followed within 20 min by an increase of 30 +/- 7.2%. We also measured transcription rates for the CA II gene in cells stimulated by each agent and found an increase within 15 min. Our results show that CA II gene expression is regulated by agents that stimulate the parietal cell to secrete acid and that the accumulation of CA II mRNA subsequent to the initial interaction of stimulant appears to result from new transcription of the CA II gene. These data suggest the participation of CA II in the acid secretory response of the parietal cell to secretagogues.

Progastrin and its glycine-extended posttranslational processing intermediates in human gastrointestinal tissues

We examined the posttranslational modification of gastrin in human gastrointestinal and Zollinger-Ellison tumor tissues using antibodies specific for progastrin and its glycine-extended processing intermediates. Gel filtration of antral and duodenal extracts on Sephadex G-50 revealed multiple molecular forms of immunoreactive glycine-extended processing intermediates corresponding to known molecular forms of gastrin and cholecystokinin. Immunoaffinity chromatography studies of antral mucosal and gastrinoma extracts identified a molecular form of glycine-extended processing intermediates that was characterized by an amino terminus identical to that of gastrin heptadecapeptide. Large differences in the relative contents of precursors and products of gastrin synthesis were found in gastrinoma tissue as compared to gastrointestinal mucosal extracts. These studies suggest the potential importance of glycine-extended peptides as intermediates in the posttranslational processing of gastrin and cholecystokinin in humans and indicate that gastrin processing mechanisms may be altered in Zollinger-Ellison tumors.