G-CSF-induced mobilization of peripheral blood stem cells for allografting: comparative study of daily single versus divided dose of G-CSF

We conducted a comparative study on a daily single versus a divided dose of G-CSF for G-CSF-induced mobilization of peripheral blood stem cells (PBSC) in eleven HLA-identical sibling donors of allogeneic PBSC transplantation (PBSCT). Six donors received double subcutaneous injections of G-CSF at a dose of 5 micrograms/kg x 2/day for 5 days (Group A), while the remaining five received single subcutaneous injection at a dose of 10 micrograms/kg/day for 5 days (Group B). The numbers of circulating CD34+ cells, myeloid progenitors (CFU-GM) and erythroid progenitors (BFU-E) reached peak values at day 5 of G-CSF administration in both groups. The mean number of CD34+ cells harvested per apheresis was 4.4 x 10(6)/kg (cells/body weight of each donor, range: 0.8-7.9 x 10(6)/kg) in Group A and 5.1 x 10(6)/kg (range: 3.0-9.0 x 10(6)/kg) in Group B. There were no significant differences between these two groups in total numbers of CFU-GM, BFU-E, or T-lymphocytes harvested. Adverse effects including mild to moderate bone pain and thrombocytopenia were transient and well tolerated. No difference was observed in the incidence of adverse effects between the two groups. These observations suggest that there is no difference in G-CSF-induced mobilization of PBSC between daily single and divided dose of G-CSF to collect a sufficient number of PBSC for engraftment after allo-PBSCT.

Conformational changes in G-CSF/Receptor complex as investigated by isotope-edited FTIR spectroscopy

Conformations of G-CSF and the extracellular domain of its receptor as well as their complex have been investigated by employing isotope-edited FTIR spectroscopy. To determine unambiguously the protein conformations of G-CSF and the receptor in the complex, we have prepared uniformly 13C/15N isotope labeled G-CSF to resolve its amide I' band from that of the receptor in the IR spectrum of the complex. By comparing the IR spectra of the isotope-labeled G-CSF and the receptor with that of the complex, we have provided spectral evidence that the AB loop region involving the unique 310 helix segment of G-CSF likely undergoes a conformational change to a regular alpha-helix upon binding to the receptor. The IR data also indicate a possible minor increase in alpha-helical conformation for the receptor in the complex. Furthermore, FTIR spectra of G-CSF, the receptor, and their complex demonstrate clearly that protein conformations of both G-CSF and the receptor have been dramatically stabilized by complex formation. Specifically, the melting transition (Tm value) of the alpha-helix in G-CSF is increased by nearly 30 degrees C and that of the beta-strand in the receptor by nearly 15 degrees C in the G-CSF/receptor complex. We estimate from the current FTIR data that the native conformations of approximately 15% of all receptor residues are stabilized by G-CSF binding. On the other hand, the entire alpha-helical content of G-CSF appears to be stabilized in the complex. Together, these results indicate that formation of the ligand/receptor complex results in not only conformational changes in the receptor but also significant structural changes in the ligand. This adds insight to the general consensus that binding of ligand to cytokine receptors induces mostly structural changes in the receptor which lead to receptor oligomerization and signal transduction. The current data also suggest a possible physiological role of the 310 helix present in G-CSF for its receptor binding activity.

Expression of the human milk protein beta-casein in transgenic potato plants

A 1177 bp cDNA fragment encoding the human milk protein beta-casein was introduced into Solanum tuberosum cells under control of the auxin-inducible, bidirectional mannopine synthase (mas1',2') promoters using Agrobacterium tumefaciens-mediated leaf disc transformation methods. Antibiotic-resistant plants were regenerated and transformants selected based on luciferase activity carried by the expression vector containing the human beta-casein cDNA. The presence of human beta-casein cDNA in the plant genome was detected by PCR and DNA hybridization experiments. Human beta-casein mRNA was identified in leaf tissues of transgenic plants by RT-PCR analysis. Human beta-casein was identified in auxin-induced leaf and tuber tissues of transformed potato plants by immunoprecipitation and immunoblot analysis. Human beta-casein produced in transgenic plants migrated in polyacrylamide gels as a single band with an approximate molecular mass of 30 kDa. Immunoblot experiments identified approximately 0.01% of the total soluble protein of transgenic potato leaf tissue as beta-casein. The above experiments demonstrate the expression of human milk beta-casein as part of an edible food plant. These findings open the way for reconstitution of human milk in edible plants for replacement of bovine milk in baby foods for general improvement of infant nutrition, and for prevention of gastric and intestinal diseases in children.

Putative folding pathway of insulin-like growth factor-I

Insulin-like growth factor-I (IGF-I) has three disulfide bonds and refolding of the fully reduced molecule generates varying ratios of correctly (PII) and incorrectly (PI) folded forms via several intermediates. All of the intermediates have the disulfide bond between Cys18 and 61 formed, indicating that formation of this disulfide is the first step in refolding. In order to further understand the refolding pathway, two intermediate froms, PIII with the additional disulfide Cys(6/47) formed and PIIIa with Cys(6/48) formed, were isolated. The oxidation of the remaining Cys48 and 52 in PIII and Cys47 and 52 in PIIIa would lead to PI and PII, respectively; however, air oxidation of these resulted in a rapid reshuffling into other intermediates as well as folding into the fully oxidized forms, and this occurred whether refolding was started with PIII or PIIIa. When oxidation occurred in the presence of an excess of oxidized glutathione, the predominant species generated were various glutathione adducts regardless of the initial intermediate form, indicating that formation of the last disulfide bond is not a favorable process relative to disulfide exchange when excess disulfides from oxidized glutathione are present. Interestingly, if 80 microM copper sulfate, an oxidant, is added to the refolding buffer, PIII resulted in formation of the PI form alone, whereas PIIIa resulted in the PII form alone. It was concluded from these results that the intermediate forms of IGF-1 can rapidly reshuffle between different disulfide structures, and that formation of the last disulfide bond is not as favorable a process as the conversion to other intermediates. The oxidation to form the last disulfide bond in PIII or PIIIa is accelerated and hence the interconversion to other intermediates is kinetically minimized only in the presence of copper sulfate. It appears, therefore, that the two intermediate forms, PIII and PIIIa, are the precursors of the corresponding fully oxidized forms, but their conversions are not energetically a favorable process.

Oxygen-dependent regulation of the respiration and growth of Escherichia coli by nitric oxide

To elucidate the role of nitric oxide (NO) in the metabolisms of enteric bacteria, its effect on the respiration and growth of Escherichia coli was examined. Respiration of E. coli was reversibly inhibited by NO particularly under low oxygen tensions. Growth of E. coli was also inhibited by NO more strongly under low oxygen tension than at its high concentration. Because the intestinal lumen is anaerobic, even a small amount of NO might strongly inhibit the energy metabolism and growth of E. coli and other enteric bacteria in vivo than in air atmospheric conditions in which oxygen tension is unphysiologically high.

Interleukin-8 stimulates leukocyte migration across a monolayer of cultured rabbit gastric epithelial cells. Effect associated with the impairment of gastric epithelial barrier function

Acute Helicobacter pylori infection produces predominantly neutrophilic infiltration of the gastric mucosa. However, the precise mechanisms and mediators of neutrophil migration are not known. Interleukin-8 (IL-8), a potent chemotactic factor for neutrophils, is present at high concentration in the gastric mucosa of subjects with chronic gastritis caused by H. pylori infection. The aims of this study were to determine whether IL-8 stimulates polymorphonuclear leukocyte (PMN) migration across a cultured monolayer of rabbit gastric epithelial cells and whether PMN migration affects epithelial cell barrier function. Confluent gastric epithelial monolayers grown on the inserts were overlaid with PMNs and various amounts of IL-8 were administered into the well under the insert. Gastric epithelial barrier function was assessed by sodium back diffusion. IL-8 stimulated PMN migration across the monolayer in a dose- and time-dependent manner. PMN transmigration significantly increased sodium back diffusion. In conclusion, IL-8 induces PMN migration across a monolayer of cultured gastric epithelial cells. This IL-8 action is associated with impairment of gastric epithelial barrier function. Since H. pylori infection causes a local mucosal increase of IL-8, our present findings may explain the mechanism of H. pylori-induced PMN infiltration of the gastric glands and mucosal injury.

New aspects of gastric adaptive relaxation, reflex after food intake for more food: involvement of capsaicin-sensitive sensory nerves and nitric oxide

To accommodate the intake of food or liquid, gastric reservoir functions are important as the physiological reflex. There exist two major responses as a reservoir function of the stomach; adaptive and receptive relaxations. Adaptive relaxation is a reflex in which the fundus of the stomach dilates in response to small increases in intragastric pressure when food enters the stomach. Receptive relaxation is a reflex in which the gastric fundus dilates when food passes down the pharynx and the esophagus. The mechanisms of these two types of functional responses are to some extent different, although a nitric oxide (NO) dependent non adrenergic, non cholinergic neural pathway is involved in the both relaxation reflexes. Adaptive relaxation is an intragastric pressure induced reflex. Stretch of the gastric wall activates the mechanoreceptors in gastric mucosa (Mu), which generate impulses carried by the capsaicin-sensitive afferent sensory neuron. The sensory neuron can synapse on the inhibitory efferent neuron directly or activate it via interneurons of the myenteric plexus. This leads to the release of NO from the nitroxergic efferent neuron, which causes relaxation of circular muscle and hence of the fundus. Alternatively, an axon reflex causes the NO release from the sensory neuron, resulting in hexamethonium resistant gastric relaxation. Receptive relaxation is mediated by vagal motor fibers. In contrast with the pressure-induced adaptive relaxation, ganglionic nicotinic transmission is essential in the vagally induced relaxation. VIP and CGRP are important neurotransmitters of the inhibitory sensory neuron, which, however, may not mediate both adaptive and receptive relaxations. Disorders of these reservoir functions result in symptoms of early satiety and anorexia, which are the major symptoms of patients with functional dyspepsia.

Purification and characterization of two new cytochrome P-450 related to CYP2C subfamily from rabbit small intestine microsomes

Two forms of cytochrome P-450, designated P-450id and P-450ie, were purified to specific contents of 14.3 and 15.0 nmol of P-450/mg of protein, respectively, from small intestine mucosa microsomes of rabbits. P-450id and P-450ie showed apparent molecular weights of 50 and 49 kDa, respectively, on SDS-PAGE. Both P-450s catalyzed N-demethylation of nitrosodimethylamine. The NH2-terminal amino acid sequence (first 19 residues) of P-450id exhibited 74-90% identity with those of six members of the rabbit P-450 2C subfamily, except for P-450 2C3. Similarly, the NH2-terminal sequence (first 22 residues) of P-450ie showed 73-86% identity with those of the same members of the rabbit P-450 2C subfamily. The peptide mapping patterns of the two P-450s were quite different from each other. In addition, P-450id did not cross-react with the guinea-pig antibodies against P-450ie. The results indicate that rabbit small intestine mucosa contain two new distinct forms of P-450s, both of which may be classified into the 2C subfamily.

Transcriptional activation of human 12-lipoxygenase gene promoter is mediated through Sp1 consensus sites in A431 cells

The functional 5' flanking region of the human 12-lipoxygenase in epidermoid carcinoma A431 cells was characterized. By a primer extension method, the transcription initiation sites were mapped at -47 adenosine, -48 guanosine and -55 guanosine upstream of the ATG translation start codon. Transient transfection with a series of 5' and 3' deletion constructs showed that the 5' flanking region spanning from -224 to -100 bp was important for the basal expression of 12-lipoxygenase gene. Gel mobility shift assays with antibodies of transcription factors showed that both Sp1 and Sp3 required highly GC-rich Sp1 sites within this region for binding. Disruption of two Sp1 recognition motifs residing at -158 to -150 bp and -123 to -114 bp by site-directed mutagenesis markedly reduced the basal 12-lipoxygenase promoter activity and abolished the retarded bands in a gel-shift assay, indicating that these two Sp1-binding sites were essential for gene expression. The same two Sp1-binding sites in this promoter region were also responsible for epidermal growth factor (EGF)-induced expression of 12-lipoxygenase gene. Moreover, EGF also induced the transcriptional activation of luciferase driven by SV40 early promoter, which contained rich Sp1-binding sites. Taken together, the results suggest that two specific Sp1 consensus sites are involved in the mediation of the basal promoter activity as well as EGF induction of the 12-lipoxygenase gene and that Sp1 and Sp3 transcription factors might have a role in their regulation.

Changes in conformation and stability upon formation of complexes of erythropoietin (EPO) and soluble EPO receptor

Erythropoietin (EPO) is a glycoprotein hormone which belongs to the four-helical-bundle cytokine family and regulates the level of circulating red blood cells. The EPO receptor (EPOR) belongs to the cytokine-receptor family of proteins. While many of the downstream events following receptor/ligand interaction have been defined, both ligand-induced receptor dimerization and conformational changes induced by binding have been implicated as the initial step in signal transduction. In a recent paper [Philo et al. (1996), Biochemistry 38, 1681-1691] we described the formation of both 1:1 and 2:1 EPOR/EPO complexes. In this paper, we examine changes in protein conformation and stability resulting from the formation of both 1:1 and 2:1 complexes of the soluble extracellular domain of EPOR and the recombinant EPO derived from either Chinese hamster ovary cells or from Escherichia coli cells. Occupation of the first binding site results in a slight conformational change that is apparent in both the far- and near-UV circular dichroism spectra. Formation of the 2:1 complex results in an even greater change in conformation which involves the local environment of one or more aromatic amino acids, accompanied perhaps by a small increase in helical content of the complex. This change in local conformation could occur in the EPO molecule, in the EPOR, in both EPOR molecules due to dimerization, or in all molecules in the trimer. The 1:1 complex exhibits increased stability to thermal-induced denaturation relative to the individual protein component; indeed, the E. coli-derived (nonglycosylated) EPO stays folded in the complex at temperatures where the EPO alone would have unfolded and precipitated. Glycosylation of the receptor increases the reversibility of thermal denaturation, but does not affect the temperature at which this unfolding reaction occurs.

Nitric oxide stimulates prostaglandin synthesis in cultured rabbit gastric cells

Both prostaglandins (PGs) and nitric oxide (NO) have cytoprotective and hyperemic effects in the stomach. However, the effect of NO on PG synthesis in gastric mucosal cells is unclear. We examined whether sodium nitroprusside (SNP), a releaser of NO, stimulates PG synthesis in cultured rabbit gastric mucus-producing cells. These cells did not release NO themselves. Co-incubation with SNP (2 x 10(-4), 5 x 10(-4), 10(-3) M) increased PGE2 synthesis, and SNP (10(-3) M) increased PGI2 synthesis in these cells. Hemoglobin, a scavenger of NO, (10(-5) M) eliminated the increase in PGE2 synthesis by SNP, but methylene blue, an inhibitor of soluble guanylate cyclase, (5 x 10(-5) M) did not affect the increase in PGE2 synthesis by SNP. 8-bromo guanosine 3':5'-cyclic monophosphate (8-bromo cGMP), a cGMP analogue, (10(-6), 10(-5), 10(-4), 10(-3) M) did not affect PGE2 synthesis. These findings suggest that NO increased PGE2 and PGI2 synthesis via a cGMP-independent pathway in cultured rabbit gastric cells.

Increased expression of transforming growth factor-beta1 during gastric ulcer healing in rats

This study was done to investigate the expression and localization of transforming growth factor-beta1 (TGF-beta1) in the gastric ulcerated tissues produced by acetic-acid during the healing process, by northern blot analysis and immunohistochemical technique. Ulcerated TGF-beta1 mRNA levels were significantly increased from days 3 to 18, in a similar manner to extracellular matrix proteins, and returned to control levels at the scarred phase. Immunoreactive TGF-beta1 was localized in epithelial cells beneath proliferative zone in intact tissues. In ulcerated tissues, TGF-beta1 was localized in macrophages in the ulcer bed and in fibroblasts or myofibroblasts in the granulation tissues. Treatment with prostaglandin E1 (PGE1) further stimulated ulcerated TGF-beta1 expression, being associated with the acceleration of gastric ulcer healing, while treatment with indomethacin reduced TGF-beta1 expression, being accompanied by the delayed ulcer healing. The combination of PGE1 and indomethacin reversed the indomethacin-induced decrease in ulcerated TGF-beta1. Thus, TGF-beta1 may be implicated in the acceleration of gastric ulcer healing.

Role of neutrophils in a rat model of gastric ulcer recurrence caused by interleukin-1 beta

The production of several cytokines such as interleukin (IL)-1 in gastric mucosa is increased in subjects infected with Helicobacter pylori, a bacterium associated with ulcer recurrence. This study was performed to determine whether the administration of IL-1 beta can cause recurrence of gastric ulcers in rats. Rats with healed ulcers received an injection of IL-1 beta (0.01 to 1 microgram/kg) or vehicle alone. Some rats received an injection of antiserum to rat neutrophils at the same time as 1 microgram/kg IL-1 beta or an injection of monoclonal antibodies against adhesion molecules (anti-intercellular adhesion molecule-1, anti-CD11a, and anti-CD11b) at 0, 12, and 24 hours after the initial injection. At this dose of IL-1 beta, the numbers of neutrophils and monocytes/macrophages infiltrating the scarred mucosa were higher at 12 and 24 hours than without injection of IL-1 beta. By 48 hours, seven of the eight bealed ulcers in the group treated with 1 microgram/kg IL-1 beta had recurred, as had one of the seven healed ulcers in the group given 0.1 microgram/kg IL-1 beta. No recurrence was found in the rats treated with 0.01 microgram/kg IL-1 beta or vehicle alone. Treatment with antiserum to neutrophils or antibodies to adhesion molecules inhibited both neutrophil infiltration into the scarred mucosa and the ulcer recurrence caused by IL-1 beta. These findings suggest possible mechanisms of recurrence of human peptic ulcers.

Relationship between progression of gastric mucosal atrophy and Helicobacter pylori infection: retrospective long-term endoscopic follow-up study

A retrospective long-term endoscopic follow-up study was designed to examine atrophic changes in the gastric mucosa over time in Helicobacter pylori-positive patients. Over a period of 8-17 years (mean, 13.4 years) 22 subjects (5 men, 17 women, mean age, 55 years) without localized gastroduodenal lesions underwent serial endoscopic examinations and serological and microbiological assessments of H. pylori infection. The extent of atrophic mucosa in the gastric body was expressed using the Kimura-Takemoto classification of atrophic pattern. Atrophic patterns were unchanged over time in 7 H. pylori-seronegative and culture-negative subjects with normal stomach, and in 1 seropositive and culture-negative subject with severe atrophy. Seven of 10 H. pylori culture-positive subjects not including three with the O-3 pattern, i.e., open type atrophic pattern, exhibited a cephalad shift of atrophic pattern. The cumulative progression rates of atrophy in the culture-positive subjects excluding O-3 subjects, were 10% after 2 years, 20% after 4 years, 50% after 6 years, and 70% after 8 years. The increases in the extent of the atrophic area were discontinuous, in terms of age, in the H. pylori-positive individuals and occasionally advanced rapidly within periods of several years with no relation to age.

Quality of ulcer healing influences the relapse of gastric ulcers in humans

The usefulness of dye-contrast endoscopy for the evaluation of the quality of gastric ulcer healing and the prediction of relapse was investigated. Sixty consenting patients whose ulcers healed during 3 months of treatment underwent endoscopy for the identification of the pattern of mucosal regeneration. Patients were monitored for relapses for up to 18 months after antiulcer therapy had ended. The pattern of regeneration was flat in 24 patients, nodular in 25 and intermediate in 11. Internal hypoechoic areas seen by endoscopic ultrasonography were less common and histological maturity was better in the patient group with the flat pattern compared with the patient group with the nodular pattern of mucosal regeneration. Prostaglandin E2 synthesis was highest in the group with the flat pattern of mucosal regeneration and the relapse rate was lowest in this group. We conclude that the evaluation of the quality of ulcer healing is possible and that findings in individuals may aid the prediction of relapse for particular patients.

Structural characterization of an alpha-amylase inhibitor from a wild common bean (Phaseolus vulgaris): insight into the common structural features of leguminous alpha-amylase inhibitors

The primary structures of two subunits of an alpha-amylase inhibitor (alpha AI-2) from a wild common bean (Phaseolus vulgaris) were revealed by a comparison of the amino acid sequence previously deduced from the nucleotide sequence with the amino- and carboxyl-terminal amino acid sequences determined by conventional methods. The polypeptide molecular weight of alpha AI-2 obtained by the light-scattering technique, considered together with the sequence molecular weights revealed for the subunits, indicated that alpha AI-2 has the subunit stoichiometry of an alpha 2 beta 2 complex. These structural features were closely similar to those recently elucidated for a white kidney bean (P. vulgaris) alpha-amylase inhibitor, which is quite different in the inhibitory specificity from alpha AI-2. The post-translational processing of the precursor glycoproteins to form the tetrameric structure appeared to require an Arg residue close to the processing site. Further, the proper associations of the subunits into the tetrameric structures seemed to be strictly controlled by a few amino acids on the subunit interfaces.

Dimerization of granulocyte-colony stimulating factor receptor: the Ig plus CRH construct of granulocyte-colony stimulating factor receptor forms a 2:2 complex with a ligand

We have previously shown that the extracellular domain of granulocyte-colony stimulating factor receptor (soluble G-CSFR), prepared from CHO cell conditioned media, dimerizes upon binding its ligand, G-CSF. The most stable ligand-receptor complex occurs at a 2:2 stoichiometry, unlike the growth hormone and erythropoietin systems. In the latter cases, each ligand uses two sites to bring two receptors together. In this study, we have generated a truncated G-CSF receptor, known to be sufficient for high affinity ligand binding, which consists of an Ig-like domain and a cytokine receptor homology module. With an affinity purified receptor, sedimentation equilibrium experiments clearly demonstrated that this truncated form of the receptor behaves very similarly to the entire extracellular domain. The sedimentation equilibrium data are consistent with the model that the truncated receptor has a weak tendency to self-associate into a dimer in the absence of a ligand, this receptor-receptor interaction is enhanced by ligand binding, and the most stable complex occurs at a 2:2 stoichiometry. These results are very different from those described by others for various murine G-CSF receptor constructs from either Escherichia coli or insect expression systems.

Molecular characterization of ALK, a receptor tyrosine kinase expressed specifically in the nervous system

The 2;5 chromosomal translocation is frequently associated with anaplastic large cell lymphomas (ALCLs). The translocation creates a fusion gene consisting of the alk (anaplastic lymphoma kinase) gene and the nucelophosmin (npm) gene: the 3' half of alk derived from chromosome 2 is fused to the 5' portion of npm from chromosome 5. A recent study shows that the product of the npm-alk fusion gene is oncogenic. To help understand how the npm-alk oncogene transform cells, it is important to investigate the normal biological function of the alk gene product, ALK. Here, we show molecular cloning of cDNAs for both the human and mouse ALK proteins. The deduced amino acid sequences reveal that ALK is a novel receptor protein-tyrosine kinase having a putative transmembrane domain and an extracellular domain. These sequences are absent in the product of the transforming npm-alk gene. ALK shows the greatest sequence similarity to LTK (leukocyte tyrosine kinase) whose biological function is presently unknown. RNA blot hybridization analysis of various tissues reveals that the alk mRNA is dominantly detected in the brain and spinal cord. Immunoblotting with anti-ALK antibody shows that ALK is highly expressed in the neonatal brain. Furthermore, RNA in situ hybridization analysis shows that the alk mRNA is dominantly expressed in neurons in specific regions of the nervous system such as the thalamus, mid-brain, olfactory bulb, and ganglia of embryonic and neonatal mice. These data suggest that ALK plays an important role(s) in the development of the brain and exerts its effects on specific neurons in the nervous system.

Epidermal growth factor enhances transcription of human arachidonate 12-lipoxygenase in A431 cells

Epidermal growth factor (EGF), determined by immunoprecipitation and Western blot analysis, increased both enzyme activity and protein level of 12-lipoxygenase in the solubilized microsomes of human epidermoid carcinoma A431 cells, respectively. The EGF-induced expression of 12-lipoxygenase mRNA was inhibited by transcription inhibitors such as actinomycin D and 5,6-dichlorobenzimidazole riboside. Promoters of different lengths for human 12-lipoxygenase gene were used to prepare the luciferase fusion vectors. These construct plasmids were transiently transfected into A431 cells, and the induction of luciferase expression by EGF was examined. A 4- to 6-fold increase in luciferase reporter activity stimulated by EGF for 18 h treatment was observed in plasmids with the 5'-flanking region length of -951 bp and that of -224 bp upstream from translation starting site. The time-dependent induction of luciferase activity by EGF paralleled the EGF-induced enzyme activity and expression of 12-lipoxygenase protein. Taken together, the results of this study indicate that EGF enhanced the transcription of the human 12-lipoxygenase gene, resulting in an increase in the amount and activity of 12-lipoxygenase.

Involvement of capsaicin-sensitive sensory nerves in gastric adaptive relaxation in isolated guinea-pig stomachs

We investigated the role of capsaicin-sensitive sensory nerves (CPSNs), nitric oxide (NO), calcitonin gene-related peptide (CGRP) and vasoactive intestinal peptide (VIP) in gastric adaptive and receptive relaxation in isolated guineapig stomachs. Changes in intragastric volume and pressure were recorded simultaneously in isolated stomachs in baths containing atropine and guanethidine. Adaptive relaxation was induced by luminal distention, and receptive relaxation was induced by electrical vagal stimulation. We found that desensitization to capsaicin inhibited adaptive relaxation, but not vagally induced relaxation. Extraluminal capsaicin induced gastric relaxation. Adaptive relaxation and capsaicin-induced relaxation were reduced by both tetrodotoxin and NG-nitro-L-arginine (LNNA), but not by hexamethonium. The effect of LNNA was partially reversed by co-incubation with L-arginine. Neither CGRP(8-37) nor VIP(10-28) inhibited all responses of adaptive relaxation, vagally induced and capsaicin-induced relaxation. These findings suggest that activation of CPSNs may be involved in adaptive relaxation, and that NO, but not CGRP or VIP, may be involved in the mechanisms of adaptive relaxation and receptive relaxation.

Rapid expression and specific localization of tenascin in gastric ulcer healing in rats

This study was done to investigate the gene expression and localization of tenascin in ulcerated gastric tissues during the healing process with Northern blot analysis and immunohistochemical technique. Gastric ulcers in rats were produced by acetic acid. Tenascin mRNA levels in the ulcerated tissue were significantly increased in a biphasic manner (12 h and day 5), preceding the increase in collagen type IV and laminin mRNA levels, and returned to control levels on day 11. In intact tissues, tenascin was mainly localized in the basement membrane above the proliferative zone, in contrast to the predominant localization of collagen type IV and laminin below the proliferative zone. On the ulcer margin from 12 h to day 5, tenascin was abundantly observed in the lamina propria around nonproliferating new epithelial cells, but collagen type IV and laminin were not seen in this lamina propria. On day 7, tenascin, expressed in the lamina propria, was replaced by collagen type IV and laminin. Thus, the rapid expression and unique localization of tenascin suggest the important role of tenascin in gastric ulcer healing.

Helicobacter pylori culture supernatant inhibits binding and proliferative response of human gastric cells to epidermal growth factor: implications for H.pylori interference with ulcer healing?

Helicobacter pylori (H. pylori) infection of gastric mucosa is strongly associated with gastritis and peptic ulcer disease. However, the mechanisms of the ulcerogenic action of H. pylori and/or the interference of H. pylori with ulcer healing are unknown. Through binding to its receptor, epidermal growth factor (EGF) accelerates cells migration and triggers epithelial cell proliferation which are both important for the healing of gastroduodenal ulcers. H. pylori seems to interfere with ulcer healing, but the cellular and molecular targets and mechanisms of these actions have not been elucidated. In the present study, we tested the effect of H. pylori culture supernatant (dialyzed to remove molecules smaller than 10 kD) on EGF binding to its receptor and on the proliferative response of human gastric Kato III cells to EGF. H. pylori culture supernatant significantly reduced specific binding of EGF to its receptor and reduced EGF-stimulated gastric cell proliferation. Since ulcer healing requires epithelial cell proliferation and cell migration (re-epithelialization), which are both triggered by EGF binding to its receptor, the alteration in these mechanisms by H. pylori product may be the basis of H. pylori-induced interference with ulcer healing.