Molecular cloning of neonate/infant-specific pepsinogens from rat stomach mucosa and their expressional change during development

Human gastric cancer risk screening: From rat pepsinogen studies to the ABC method

We examined the development of gastric cancer risk screening, from rat pepsinogen studies in an experimental rat gastric carcinogenesis model induced with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and human pepsinogen studies in the 1970s and 1980s to the recent "ABC method" for human gastric cancer risk screening. First, decreased expression or absence of a major pepsinogen isozyme, PG1, was observed in the rat gastric mucosa from the early stages of gastric carcinogenesis to adenocarcinomas following treatment with MNNG. In the 1980s, decreases in PGI in the human gastric mucosa and serum were identified as markers of atrophic gastritis. In the 1990s, other researchers revealed that chronic infection with Helicobacter pylori (Hp) causes atrophic gastritis and later gastric cancer. In the 2000s, a gastric cancer risk screening method combining assays to detect serum anti-Hp IgG antibody and serum PGI and PGII levels, the "ABC method", was established. Eradication of Hp and endoscopic follow-up examination after the ABC method are recommended to prevent gastric cancer.

Immediate and Late Effects of Early Weaning on Rat Gastric Cell Differentiation

Background: Gastric glands grow and cells reach differentiation at weaning in rats. By considering that early weaning (EW) can affect the timing of development, we aimed to compare molecular and cellular markers of differentiation in pups and adults. Methods: Wistar rats were separated into suckling-control (S) and EW groups at 15 days. Stomachs were collected at 15, 18, and 60 days for RNA and protein extraction, and morphology. Results: After EW, the expression of genes involved in differentiation (Atp4b, Bhlha15 and Pgc) augmented (18 days), and Atp4b and Gif were high at 60 days. EW increased the number of zymogenic cells (ZC) in pups and adults and augmented mucous neck cells only at 18 days, whereas parietal and transition cells (TC) were unchanged. Conclusions: EW affected the gastric mucosa mostly in a transient manner as the changes in gene expression and distribution of differentiated cells that were detected in pups were not fully maintained in adults, except for the size of ZC population. We concluded that though most of EW effects were immediate, such nutritional change in the infancy might affect part of gastric digestive functions in a permanent manner, as some markers were kept unbalanced in the adulthood.

A time-resolved multi-omic atlas of the developing mouse stomach

The mammalian stomach is structurally highly diverse and its organ functionality critically depends on a normal embryonic development. Although there have been several studies on the morphological changes during stomach development, a system-wide analysis of the underlying molecular changes is lacking. Here, we present a comprehensive, temporal proteome and transcriptome atlas of the mouse stomach at multiple developmental stages. Quantitative analysis of 12,108 gene products allows identifying three distinct phases based on changes in proteins and RNAs and the gain of stomach functions on a longitudinal time scale. The transcriptome indicates functionally important isoforms relevant to development and identifies several functionally unannotated novel splicing junction transcripts that we validate at the peptide level. Importantly, many proteins differentially expressed in stomach development are also significantly overexpressed in diffuse-type gastric cancer. Overall, our study provides a resource to understand stomach development and its connection to gastric cancer tumorigenesis.

Neonatal- maternal separation primes zymogenic cells in the rat gastric mucosa through glucocorticoid receptor activity

Neonatal- Maternal Separation (NMS) deprives mammals from breastfeeding and maternal care, influencing growth during suckling- weaning transition. In the gastric mucosa, Mist1 (encoded by Bhlha15 gene) and moesin organize the secretory apparatus for pepsinogen C in zymogenic cells. Our current hypothesis was that NMS would change corticosterone activity through receptors (GR), which would modify molecules involved in zymogenic cell differentiation in rats. We found that NMS increased corticosterone levels from 18 days onwards, as GR decreased in the gastric mucosa. However, as nuclear GR was detected, we investigated receptor binding to responsive elements (GRE) and observed an augment in NMS groups. Next, we demonstrated that NMS increased zymogenic population (18 and and 30 days), and targeted Mist1 and moesin. Finally, we searched for evolutionarily conserved sequences that contained GRE in genes involved in pepsinogen C secretion, and found that the genomic regions of Bhlha15 and PgC contained sites highly likely to be responsive to glucocorticoids. We suggest that NMS triggers GR- GRE to enhance the expression and to prime genes that organize cellular architecture in zymogenic population for PgC function. As pepsinogen C- pepsin is essential for digestion, disturbance of parenting through NMS might alter functions of gastric mucosa in a permanent manner.

Calcium-binding protein S100A14 induces differentiation and suppresses metastasis in gastric cancer

S100A14 is a calcium-binding protein involved in cell proliferation and differentiation as well as the metastasis of human tumors. In this study, we characterized the regulation of S100A14 expression between biological signatures and clinical pathological features in gastric cancer (GC). Our data demonstrated that S100A14 induced the differentiation of GC by upregulating the expression of E-cadherin and PGII. Moreover, S100A14 expression negatively correlated with cell migration and invasion in in vitro and in vivo experimental models. Interestingly, S100A14 blocked the store-operated Ca²⁺ influx by suppressing Orai1 and STIM1 expression, leading to FAK expression activation, focal adhesion assembly and MMP downregulation. Taken together, our results indicate that S100A14 may have a role in the induction of differentiation and inhibition of cell metastasis in GC.

Identification of Novel Placentally Expressed Aspartic Proteinase in Humans

This study presents pioneering data concerning the human pregnancy-associated glycoprotein-Like family, identified in the genome, of the term placental transcriptome and proteome. RNA-seq allowed the identification of 1364 bp hPAG-L/pep cDNA with at least 56.5% homology with other aspartic proteinases (APs). In silico analyses revealed 388 amino acids (aa) of full-length hPAG-L polypeptide precursor, with 15 aa-signal peptide, 47 aa-blocking peptide and 326 aa-mature protein, and two Asp residues (D), specific for a catalytic cleft of the APs (VVFDTGSSNLWV91-102 and AIVDTGTSLLTG274-285). Capillary sequencing identified 9330 bp of the hPAG-L gene (Gen Bank Acc. No. KX533473), composed of nine exons and eight introns. Heterologous Western blotting revealed the presence of one dominant 60 kDa isoform of the hPAG-L amongst cellular placental proteins. Detection with anti-pPAG-P and anti-Rec pPAG2 polyclonals allowed identification of the hPAG-L proteins located within regions of chorionic villi, especially within the syncytiotrophoblast of term singleton placentas. Our novel data extend the present knowledge about the human genome, as well as placental transcriptome and proteome during term pregnancy. Presumably, this may contribute to establishing a new diagnostic tool for examination of some disturbances during human pregnancy, as well as growing interest from both scientific and clinical perspectives.

Corticosterone activity during early weaning reprograms molecular markers in rat gastric secretory cells

Gastric epithelial cells differentiate throughout the third postnatal week in rats, and become completely functional by weaning time. When suckling is interrupted by early weaning (EW), cell proliferation and differentiation change in the gastric mucosa, and regulatory mechanisms might involve corticosterone activity. Here we used EW and RU486 (glucocorticoid receptor antagonist) to investigate the roles of corticosterone on differentiation of mucous neck (MNC) and zymogenic cells (ZC) in rats, and to evaluate whether effects persisted in young adults. MNC give rise to ZC, and mucin 6, Mist1, pepsinogen a5 and pepsinogen C are produced to characterize these cells. We found that in pups, EW augmented the expression of mucins, Mist1 and pepsinogen C at mRNA and protein levels, and it changed the number of MNC and ZC. Corticosterone regulated pepsinogen C expression, and MNC and ZC distributions. Further, the changes on MNC population and pepsinogen C were maintained until early- adult life. Therefore, by using EW as a model for altered corticosterone activity in rats, we demonstrated that the differentiation of secretory epithelial cells is sensitive to the type of nutrient in the lumen. Moreover, this environmental perception activates corticosterone to change maturation and reprogram cellular functions in adulthood.

Mitogen-activated protein kinase activator with WD40 repeats (MAWD) and MAWD-binding protein induce cell differentiation in gastric cancer

Background

Our previous proteomic analysis revealed that mitogen-activated protein kinase activator with WD40 repeats (MAWD) and MAWD-binding protein (MAWBP) were downregulated in gastric cancer (GC) tissues. These proteins interacted and formed complexes in GC cells. To investigate the role of MAWD and MAWBP in GC differentiation, we analyzed the relationship between MAWD/MAWBP and clinicopathologic characteristics of GC tissues and examined the expression of E-cadherin and pepsinogen C (PGC)—used as gastric mucosa differentiation markers—in MAWD/MAWBP-overexpressing GC cells and xenografts.

Methods

We measured MAWD, MAWBP, transforming growth factor-beta (TGF-beta), E-cadherin, and PGC expression in 223 GC tissues and matched-adjacent normal tissues using tissue microarray and immunohistochemistry (IHC) analyses, and correlated these expression levels with clinicopathologic features. MAWD and MAWBP were overexpressed alone or together in SGC7901 cells and then E-cadherin, N-cadherin, PGC, Snail, and p-Smad2 levels were determined using western blotting, semiquantitative RT-PCR, and immunofluorescence analysis. Alkaline phosphatase (AKP) activity was measured to investigate the differentiation level of various transfected cells, and the transfected cells were used in tumorigenicity assays and for IHC analysis of protein expression in xenografts.

Results

MAWD/MAWBP positive staining was significantly lower in GC tissues than in normal samples (P < 0.001), and the expression of these proteins was closely correlated with GC differentiation grade. Kaplan–Meier survival curves indicated that low MAWD and MAWBP expression was associated with poor patient survival (P < 0.05). The differentiation-related proteins E-cadherin and PGC were expressed in GC tissues at a lower level than in normal tissues (P < 0.001), but were upregulated in MAWD/MAWBP-overexpressing cells. N-cadherin and Snail expression was strongr in vector-expressing cells and comparatively weaker in MAWD/MAWBP co-overexpressing cells. MAWD/MAWBP co-overexpression inhibited Smad2 phosphorylation and nuclear translocation (P < 0.05), and AKP activity was lowest in MAWD/MAWBP coexpressing cells and highest in vector-expressing cells (P < 0.001). TGF-beta, E-cadherin, and PGC expression in xenograft tumors derived from MAWD/MAWBP coexpressing cells was higher than that in control.

Conclusions

MAWD and MAWBP were downregulated and associated with the differentiation grade in GC tissues. MAWD and MAWBP might induce the expression of differentiation-related proteins by modulating TGF-beta signaling in GC cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1637-7) contains supplementary material, which is available to authorized users.

Recurrent gene loss correlates with the evolution of stomach phenotypes in gnathostome history

The stomach, a hallmark of gnathostome evolution, represents a unique anatomical innovation characterized by the presence of acid- and pepsin-secreting glands. However, the occurrence of these glands in gnathostome species is not universal; in the nineteenth century the French zoologist Cuvier first noted that some teleosts lacked a stomach. Strikingly, Holocephali (chimaeras), dipnoids (lungfish) and monotremes (egg-laying mammals) also lack acid secretion and a gastric cellular phenotype. Here, we test the hypothesis that loss of the gastric phenotype is correlated with the loss of key gastric genes. We investigated species from all the main gnathostome lineages and show the specific contribution of gene loss to the widespread distribution of the agastric condition. We establish that the stomach loss correlates with the persistent and complete absence of the gastric function gene kit--H(+)/K(+)-ATPase (Atp4A and Atp4B) and pepsinogens (Pga, Pgc, Cym)--in the analysed species. We also find that in gastric species the pepsinogen gene complement varies significantly (e.g. two to four in teleosts and tens in some mammals) with multiple events of pseudogenization identified in various lineages. We propose that relaxation of purifying selection in pepsinogen genes and possibly proton pump genes in response to dietary changes led to the numerous independent events of stomach loss in gnathostome history. Significantly, the absence of the gastric genes predicts that reinvention of the stomach in agastric lineages would be highly improbable, in line with Dollo's principle.

The co-expression of functional gastric proteins in dynamic gastric diseases and its clinical significance

Background

Pepsinogen C (PGC) and mucin1 (MUC1) are important physiologically functional gastric proteins; Mucin2 (MUC2) is an “ectopic” functional protein in intestinal metaplasia of gastric mucosa. We analyzed the co-expression of the above-mentioned three proteins in dynamic gastric diseases {superficial gastritis (SG)-atrophic gastritis (AG)--gastric cancer (GC)} as well as different histological types of gastric cancer in order to find molecular phenotypes of gastric cancer and precancerous disease and further explore the potential co-function of PGC, MUC1 and MUC2 in the occurrence and development of gastric cancer.

Methods

The SG-AG-GC sequence was 57-57-70 cases in this case–control study, respectively. Different histological types of GC were 28 cases of highly and moderately differentiated aden ocarcinoma (HMDA)、30 of poorly differentiated adenocarcinoma (PDA) and 12 of mucinous adenocarcinoma (MA) or signet ring cell carcinoma (SRCC). PGC, MUC1 and MUC2 expression in situ were detected in all 184 cases using immunohistochemistry.

Results

Both PGC and MUC1 had a significantly decreased expression in GC than in SG and AG (P < 0.0001 and P < 0.01, respectively); While MUC2 had a significant increased expression in AG than in SG and GC (P < 0.0001). Seven phenotypes of PGC, MUC1 and MUC2 co-expression were found in which PGC+/MUC1+/MUC2- phenotype took 94.7%(54/57) in SG group; PGC+/MUC1+/MUC2+ and PGC-/MUC1+/MUC2+ phenotype took 43.9% (25/57) and 52.6% (30/57) in AG; the phenotypes in GC group appeared variable; extraordinarily, PGC-/MUC1-/MUC2+ phenotype took 100% (6/6) in MA or SRCC group and had a statistical significance compared with others (P < 0.05).

Conclusions

Phenotypes of PGC, MUC1 and MUC2 co-expression in dynamic gastric diseases are variable. In SG group it always showed PGC+/MUC1+/MUC2- phenotype and AG group showed two phenotypes (PGC+/MUC1+/MUC2+ and PGC-/MUC1+/MUC2+); the phenotypes in GC group appeared variable but the phenotype of PGC-/MUC1-/MUC2+ may be a predictive biomarker for diagnosing MA or SRCC, or distinguishing histological MA or SRCC from tubular adenocarcinoma accompanied by mucinous secretion or signet ring cell scattered distribution.

Comparison of gastric expression and serum levels of PGC in patients with various gastric diseases

AIM: To detect the gastric expression levels of pepsinogen C (PGC) and serum levels of sPGA and sPGC in patients with various gastric diseases and to analyze their correlation.

METHODS: Gastric PGC were measured by immunohistochemistry, and serum levels of sPGA, sPGC were measured by ELISA in patients with various gastric diseases, respectively. The data were analyzed for significance using the SPSS16.0 software.

RESULTS: There were significant differences in gastric PGC expression among patients with different gastric diseases (P = 0.000). The positive rate of PGC expression was highest in patients with superficial gastritis (SG), followed by those with atrophic gastritis (AG), intestinal metaplasia (IM), dysplasia (DYS) and gastric carcinoma (Ca). The positive rate of PGC was significantly higher in SG than in other lesions (P = 0.035, 0.000, 0.000, 0.000), in AG than in IM, DYS and Ca (P = 0.000, 0.000, 0.031). There were also significant differences in serum levels of sPGA and sPGC among different patient groups (both P = 0.000). Similar to PGC expression, serum levels of sPGA also decreased in an order of SG-AG-IM-DYS-Ca. In contrast, serum levels of sPGC in Ca were significantly higher than those in other lesions (P = 0.000, 0.000, 0.003, 0.001). The positive rate of PGC expression had a positive correlation with serum levels of sPGA and a negative correlation with serum levels of sPGC (r = 0.956, P = 0.011 vs sPGA; r = -0.968, P = 0.007 vs sPGC).

CONCLUSION: Tissue expression of PGC is negatively associated with the malignant degree of gastric mucosa cells and positively with the development of gastric mucosal diseases. Combined detection of sPG and PGC expression can help screen and diagnose gastric mucosal diseases.

Characterization of the peptidase activity of recombinant porcine pregnancy-associated glycoprotein-2

The pregnancy-associated glycoproteins (PAGs) belong to the aspartic peptidase family. They are expressed exclusively in trophoblasts of even-toed ungulates such as swine, cattle, sheep, etc. In pigs, two distinct PAG transcripts (and some variants) have been described. One of the transcripts, porcine PAG-1 (poPAG-1) may not be capable of acting as a peptidase. The second transcript, poPAG-2, possesses a conserved catalytic centre and has been predicted, but not shown, to have proteolytic activity. The thrust of this work was to test such a possibility. PoPAG-2 was expressed as a recombinant protein with an amino-terminal 'FLAG-tag' in a Baculoviral expression system. The expressed proteins were affinity purified by using an anti-FLAG antibody. The purified preparations were then analysed for proteolytic activity against a fluorescent substrate. Porcine PAG-2 had optimal proteolytic activity around pH 3.5. Against this substrate, it had a k(cat)/K(m) of 1.2 microM(-1) s(-1) and was inhibited by the aspartic peptidase inhibitor, pepstatin A, with a K(i) of 12.5 nM. Since the proteolytic activity of PAGs in the pig has now been established, the search for putative substrates to gain insight into the physiological role of PAGs will likely be the focus of future investigations.

Western analyses of pregnancy-associated glycoprotein family (PAG) in placental extracts of various mammals

The present study was conducted in order to analyze the immunoreactivity of placental extracts of several animal species and humans against the following three groups of PAG antisera: anti-boPAG-I (R#497), -boPAG-II (R#435), and -caPAG (R#706). Placental proteins were obtained after extraction at neutral pH, followed by ammonium sulfate (A.S.) precipitation, dialysis, and lyophilization. The immunoreactivity of different placental extracts was revealed by the use of monodimensional SDS-PAGE, followed by blotting on nitrocellulose membrane and the identification of immunoreactive proteins after incubation with PAG antisera (Western blot technique). A strong immunoreactivity of proteins from synepitheliochorial placenta (cattle, sheep, goat, bison, buffalo, and deer) was demonstrated in both 20-50% and 50-80% A.S. fractions using the three antisera. Proteins from species with epitheliochorial placenta presented variable profiles of detected PAG-like proteins: in the sow, many immunoreactive forms were revealed by antisera boPAG-I and boPAG-II, whereas in the dromedary, only two forms were revealed by anti-boPAG-II. Concerning other species, our protocols showed for the first time a cross-reaction between PAG antisera with proteins extracted from dog, alpaca, dromedary, sea lion, and human placenta.

Characterization of pepsinogen C as a potential biomarker for gastric cancer using a histo-proteomic approach

We analyzed 74 cryostat sections of central gastric tumor, tumor margin, and normal gastric epithelium using ProteinChip Arrays and SELDI-TOF MS. One peak was significantly down-regulated in tumor tissue (P = 1.43 x 10(-6)) and identified as pepsinogen C using MS/MS analysis and immunodepletion. This signal was further characterized by immunohistochemistry. This work demonstrates that differentially expressed signals can be identified and assessed using a proteomic approach comprising tissue-microdissection, protein profiling, and immunohistochemistry.

Gastric antibacterial efficiency is different for pepsin A and C

The gastric lumen represents a bactericidal barrier, whose major components are an acidic pH and a family of isoenzymes of the gastric aspartate protease, pepsin. To evaluate whether specific pepsins are specialized in antibacterial protection, we tested their effects on the gastric pathogen Helicobacter pylori. In a recent study we found pepsin to affect the motility of the bacteria, one of its most important virulence factors. We were able to show that the antibacterial effect of pepsin occurs in two phases: rapid loss of motility and subsequent destruction. In the present study we used the rapid pepsin-induced bacterial immobilization as a marker of antibacterial efficiency. The proteolytic activity of different pepsins was normalized to values between 2 and 200 U/ml in the hemoglobin degradation test of Anson, performed at pH 2 and 5. We found that pepsin C completely inactivates H. pylori at proteolytic activities of 2 (pH 5) and 20 (pH 2) U/ml. In contrast, the activities of pepsin A and chymosin required to affect Helicobacter motility were ten times higher.

Chorionic mRNA expression and N-glycodiversity of pregnancy-associated glycoprotein family (PAG) of the European bison (Bison bonasus)

Placental PAG mRNA expression and N-glycodiversity of multiple PAG proteins secreted in vitro by trophectoderm (chorion epithelium) of wild pecoran Bovidae taxons was not examined previously. The study on European bison (Eb) aimed: (1) to determine placental PAG mRNA expression by in situ hybridisation; (2) to identify a profile of pecoran PAG protein family secreted in vitro by cotyledonary (CT) explants; (3) to examine N-glycodiversity of the PAG proteins in this wild taxon. In addition, we compared (4) a profile and N-glycodiversity of the PAG protein family secreted in vitro by CT and interCT-trophectoderm (intCT-TRD) explants of domestic ruminants. Cotyledonary sections of the Eb were used for in situ hybridisation (ISH) with (35)S-labelled probes produced with porcine PAG cDNA as templates. Various CT and intCT-TRD explants were long-term cultured in vitro. Chorionic proteins were isolated from media, ultra-filtrated (>10 kDa MWCO) and analysed by PAGE-Western blotting with various polyclonal anti-PAG sera. Protein samples with or without enzymatic deglycosylation were examined after different times of explant cultures. Released chorionic proteins were deglycosylated by N-glycanase F (PNGase F+) and compared to glycosylated forms (PNGase F-). This is the first paper demonstrating the PAG-like mRNA transcript expression (by ISH) and N-glycodiversity of immuno-reactive PAG-like proteins (produced in vitro by chorionic explants) of European bison. Various PAG proteins of Eb (EbPAG) were secreted by CT explants during long-term in vitro studies. Major approximately 78, approximately 67 and approximately 65 kDa EbPAG-like proteins were reduced by enzymatic deglycosylation (at least by 10 kDa). Considerably smaller amounts of approximately 45 kDa EbPAG-like proteins were also observed. In addition, we have found that various PAG proteins (30-73 kDa) were secreted by bovine CT explants, during long-term in vitro cultures. Corresponding amounts of PAG proteins, similar in M(r), were also secreted by intCT-TRD explants, whose tissues were not utilised for PAG protein extraction during other scientists' previous studies. It seems that the M(r)-heterogeneity and N-glycodiversity of the PAG protein family can play very important role during feto-placental interactions in Bovidae species.

In situ expression and serum level of pepsinogen C in different gastric mucosa diseases

AIM: To explore the matching degree of in situ expression and serum level of pepsinogen C (PGC) in different gastric mucosal biopsies, and to evaluate its value in the diagnosis of gastric cancer.

METHODS: A total of 129 gastric mucosa biopsies and its corresponding serum specimens were collected from patients with superficial gastritis (n = 30), gastric ulcer or erosion (n = 35), atrophic gastritis (29), and gastric cancer (n = 35). The expression of PGC in the gastric mucosa was detected by immunohistochemistry, and the concentration of serum pepsinogen A (sPGA) and pepsinogen C (sPGC) were determined by enzyme linked immunosorbent assay (ELISA).

RESULTS: The positive rate of PGC antigen expression decreased in the tissues of superficial gastritis (100%), gastric ulcer or erosion (80.00%), atrophic gastritis (34.48%), and gastric cancer (11.43%) in sequence (P <0.05). The expression rate decreased as the increase of the disease severity. There was no statistical difference in the concentration of sPGA and sPGC among the above 4 groups. The ratio of sPGA to sPGC in the superficial gastritis, gastric ulcer or erosion, atrophic gastritis, and gastric cancer was 11.55±0.69, 9.39±0.86, 8.86±0.63, and 6.83±0.68, respectively (P <0.05), and decreased as the reduction of the PGC expression. There was specific correlation between the expression of PGC in gastric mucosa and the ratio of sPGA to sPGC in the serum (r = 0.297, P = 0.001).

CONCLUSION: Tissue expression of PGC has nega-tive correlation with the severity of the gastric mucosal disease. The ratio of sPGA to sPGC is closely related with the tissue expression of PGC antigen, and it is a convenient and economic index for the screening and diagnosis of gastric cancer.

Dynamic expression of pepsinogen C in gastric cancer, precancerous lesions and Helicobacter pylori associated gastric diseases

AIM

To investigate the relationship between the expression of pepsinogen C (PGC) and gastric cancer, precancerous diseases, and Helicobacter pylori (H pylori) infection.

METHODS

The expression of PGC was determined by immunohistochemistry method in 430 cases of gastric mucosa. H pylori infection was determined by HE staining, PCR and ELISA in 318 specimens.

RESULTS

The positive rate of PGC expression in 54 cases of normal gastric mucosa was 100%. The positive rates of PGC expression in superficial gastritis or gastric ulcer or erosion, atrophic gastritis or gastric dysplasia and gastric cancer decreased significantly in sequence (P<0.05; 100%/89.2% vs 14.3%/15.2% vs 2.4%). The over-expression rate of PGC in group of superficial gastritis with H pylori infection was higher than that in group without H pylori infection (P<0.05; chi2= 0.032 28/33 vs 15/25). The positive rate of PGC expression in group of atrophic gastritis with H pylori infection was lower than that in group without H pylori infection (P<0.01; chi2= 0.003 4/61 vs 9/30), and in dysplasia and gastric cancer.

CONCLUSION

The level of PGC expression has a close relationship with the degree of malignancy of gastric mucosa and development of gastric lesions. There is a relationship between H pylori infection and expression of antigen PGC in gastric mucosa, the positive rate of PGC expression increases in early stage of gastric lesions with H pylori infection such as gastric inflammation and decreases during the late stage such as precancerous diseases and gastric cancer. PGC-negative cases with H pylori-positive gastric lesions should be given special attention.

Expression of pepsinogen C in Helicobacter pylori-associated gastric lesions

AIM: To investigate the expression of pepsinogen C and its relation with H. pylori infection in gastric cancer and precancerous lesions.

METHODS: The method of immunohistochemistry was used to examine the expression of pepsinogen C in 318 cases of stomach mucosa; the H. pylori infection was determined by H-E stain, PCR and ELISA.

RESULTS: The rate of PGC over-expression in group of superficial gastritis of H. pylori infection was higher than that of non-infection (P < 0.05, 28/33 vs 15/25). The positive rate of PGC in group of atrophic gastritis of H. pylori infection was lower than that of non-infection (P < 0.01, 4/61 vs 9/30) and so were in dysplasia and gastric cancer.

CONCLUSION: There is a relationship between the H. pylori infection and the expression of PGC in gastric mucosa. The expression of PGC increases in superficial gastritis and decreases in atrophic gastritis, dysplasia and gastric cancer with H. pylori infection.

Postnatal changes and effects of glucocorticoid on MUC5AC mRNA expression in the rat stomach

Mucus is an important factor in gastric mucosal protection against acid, pepsin and various factors such as alcohol and nonsteroidal anti-inflammatory drugs. MUC5AC is a gel-forming mucin secreted from gastric surface mucous cells. However, little is known about expression of the MUC5AC gene. We examined developmental changes in rat MUC5AC mRNA expression and the effect of glucocorticoid on MUC5AC mRNA expression in infant rat gastric mucosa. Expression levels of MUC5AC mRNA in the stomach of 0 to 30-d-old and 8-week-old (adult) rats were evaluated by reverse transcription polymerase chain reaction (RT-PCR) and by in situ hybridization. We also examined pepsinogen C (PgC) and F (PgF) mRNA expression by RT-PCR. The expression of MUC5AC mRNA increased from 10 d of age, which was about one week earlier than that of PgC mRNA. The expression of PgF mRNA decreased as that of PgC mRNA increased. The injection of hydrocortisone induced PgC mRNA expression in the infant rat stomach, whereas MUC5AC and PgF mRNA expression decreased. These results suggest that developmental changes of MUC5AC mRNA expression differ from those of Pgs, and are not induced by glucocorticoid.

Activities of gastric, pancreatic, and intestinal brush-border membrane enzymes during postnatal development of dogs

OBJECTIVE

To measure activities of digestive enzymes during postnatal development in dogs.

SAMPLE POPULATION

Gastrointestinal tract tissues obtained from 110 Beagles ranging from neonatal to adult dogs.

PROCEDURE

Pepsin and lipase activities were measured in gastric contents, and amylase, lipase, trypsin, and chymotrypsin activities were measured in small intestinal contents and pancreatic tissue. Activities of lactase, sucrase, 4 peptidases, and enteropeptidase were assayed in samples of mucosa obtained from 3 regions of the small intestine.

RESULTS

Gastric pH was low at all ages. Pepsin was not detected until day 21, and activity increased between day 63 and adulthood. Activities of amylase and lipase in contents of the small intestine and pancreatic tissue were lower during suckling than after weaning. Activities of trypsin and chymotrypsin did not vary among ages for luminal contents, whereas activities associated with pancreatic tissue decreased between birth and adulthood for trypsin but increased for chymotrypsin. Lactase and gamma-glutamyltranspeptidase activities were highest at birth, whereas the activities of sucrase and the 4 peptidases increased after birth. Enteropeptidase was detected only in the proximal region of the small intestine at all ages.

CONCLUSIONS AND CLINICAL RELEVANCE

Secretions in the gastrointestinal tract proximal to the duodenum, enzymes in milk, and other digestive mechanisms compensate for low luminal activities of pancreatic enzymes during the perinatal period. Postnatal changes in digestive secretions influence nutrient availability, concentrations of signaling molecules, and activity of antimicrobial compounds that inhibit pathogens. Matching sources of nutrients to digestive abilities will improve the health of dogs during development.

Association between pepsinogen C gene polymorphism and genetic predisposition to gastric cancer

AIM: To identify a molecular marker for gastric cancer, and to investigate the relationship between the polymorphism of pepsinogen C (PGC) gene and the genetic predisposition to gastric cancer.

METHODS: A total of 289 cases were involved in this study. 115 cases came from Shenyang area, a low risk area of gastric cancer, including 42 unrelated controls and 73 patients with gastric cancer. 174 cases came from Zhuanghe area, a high-risk area of gastric cancer, including 113 unrelated controls, and 61 cases from gastric cancer kindred families. The polymorphism of PGC gene was detected by polymerase chain reaction (PCR) and the relation between the genetic polymorphism of PGC and gastric cancer was examined.

RESULTS: Four alleles, 310 bp (allele 1), 400 bp (allele 2), 450 bp (allele 3), and 480 bp (allele 4) were detected by PCR. The frequency of allele 1 was higher in patients with gastric cancer than that in controls. Genotypes containing homogenous allele 1 were significantly more frequent in patients with gastric cancer than that in controls (0.33, 0.14, χ² = 3.86, P < 0.05). There was no significant difference between the control group of Zhuanghe and the group of gastric cancer kindred. But the frequency of allele 1 was higher in control group of Zhuanghe area than that in control group of Shenyang area and genotypes containing homogenous allele 1 were significantly more frequent in the control group of Zhuanghe area than those in control group of Shenyang area (0.33, 0.14, χ² = 4.32, P < 0.05). In the group of gastric cancer kindred the frequency of allele 1 was significantly higher than that in control group of Shenyang area (0.5164, 0.3571, χ² = 4.47, P < 0.05). Genotypes containing homogenous allele 1 were significantly more frequent in the group of gastric cancer kindred than those in control group of Shenyang area (0.36, 0.14, χ² = 4.91, P < 0.05).

CONCLUSION: These results suggest that there is some relation between pepsinogen C gene polymorphism and gastric cancer, and the person with homogenous allele 1 predisposes to gastric cancer than those with other genotypes. Pepsinogen C gene polymorphism may be used as a genetic marker for a genetic predisposition to gastric cancer. The distribution of pepsinogen C gene polymorphism in Zhuanghe, a high-risk area of gastric cancer, is different from that in Shenyang, a low risk area of gastric cancer.

Primary structure, unique enzymatic properties, and molecular evolution of pepsinogen B and pepsin B

Purification of pepsinogen B from dog stomach was achieved. Activation of pepsinogen B to pepsin B is likely to proceed through a one-step pathway although the rate is very slow. Pepsin B hydrolyzes various peptides including beta-endorphin, insulin B chain, dynorphin A, and neurokinin A, with high specificity for the cleavage of the Phe-X bonds. The stability of pepsin B in alkaline pH is noteworthy, presumably due to its less acidic character. The complete primary structure of pepsinogen B was clarified for the first time through the molecular cloning of the respective cDNA. Molecular evolutional analyses show that pepsinogen B is not included in other known pepsinogen groups and constitutes an independent cluster in the consensus tree. Pepsinogen B might be a sister group of pepsinogen C and the divergence of these two zymogens seems to be the latest event of pepsinogen evolution.

Cellular expression of gut chitinase mRNA in the gastrointestinal tract of mice and chickens

Recently, the second mammalian chitinase, designated acidic mammalian chitinase (AMCase), has been identified in human, mouse, and cow. In contrast to the earlier identified macrophage-derived chitinase (chitotriosidase), this chitinase is richly expressed in the gastrointestinal (GI) tract, suggesting its role in digestion of chitin-containing foods as well as defense against chitin-coated microorganisms and parasites. This in situ hybridization study first revealed cellular localization of the gut-type chitinase in the mouse and chicken. In adult mice, the parotid gland, von Ebner's gland, and gastric chief cells, all of which are exocrine cells of the serous type, expressed the gut chitinase mRNA. In the chicken, oxyntico-peptic cells in glandular stomach (proventriculus) and hepatocytes expressed the chitinase mRNA. Because cattle produce the gut chitinase (chitin-binding protein b04) only in the liver, the gut chitinases in mammals and birds have three major sources of production, i.e., the salivary gland, stomach, and liver. During ontogenetic development, the expression level in the parotid gland and stomach of mice increased to the adult level before weaning, whereas in the stomach of chickens intense signals were detectable in embryos from incubation day 7.

Development and characterization of conditionally immortalized gastric epithelial cell lines from transgenic rats harboring temperature-sensitive simian virus 40 large T-antigen gene

Conditionally immortalized gastric epithelial cell lines were established from transgenic rats harboring temperature-sensitive simian virus 40 (tsSV40) large T-antigen gene. Gastric mucosal cells and epithelial tissues isolated from the stomach of the transgenic rats were cultured at permissive temperature (33 degrees C), and proliferative cells were cloned by colony formation. Six cell lines (designated as RGE1-01, RGE1-02, RGE1-03, RGE1-21, RGE1-22 and RGE2-01) showing epithelial-like morphology have been established. All cells grew at 33 degrees C, but did not at nonpermissive temperature (39 degrees C). High expression level of large T-antigen in the nuclei was observed at 33 degrees C, whereas the expression level was gradually decreased in a time-dependent manner at 39 degrees C. These results suggest that the temperature-sensitive growth characteristics arise as a result of a function of the tsSV40 large T-antigen. None of the cell lines were transformed as judged by anchorage-independent growth assay. Immunocytochemical findings indicated that all cells expressed epithelial cell markers including cytoskeletal (cytokeratin and actin), basement membrane (laminin and collagen type IV) and junctional complex (ZO-1 and desmoplakin I+II) proteins at 33 degrees C. All cells expressed mRNA of cathepsin E, a pit cell marker. Moreover, transepithelial resistance was observed between apical and basolateral sides in the cells. RGE1-22 cells produced prostaglandin E(2). Levels of mRNA for cathepsin E, transepithelial resistance and prostaglandin E(2) were influenced by the nonpermissive temperature. Thus, these conditionally immortalized gastric cell lines which preserve some epithelial cell characteristics will provide a useful in vitro model of gastric epithelium.

An aspartic proteinase expressed in the yolk sac and neonatal stomach of the mouse

A murine aspartic proteinase, described herein, is intermediate in amino acid sequence identity between the placentally produced pregnancy-associated glycoproteins (PAGs) and gastric pepsins. While PAGs are secreted products of placental trophoblast tissue of ungulates and most are not believed to function proteolytically, pepsins are digestive enzymes. The cDNA for this aspartic proteinase was amplified by reverse transcription-polymerase chain reaction from RNA extracted from murine placentas and neonatal stomachs. The open reading frame encoded a 387-amino acid polypeptide with a 15-residue signal sequence. The enzyme most resembled pepsinogen F (a protein identified in the stomachs of neonatal rabbits and rats) and PAG-like proteins cloned from equine and feline placentae. In the stomach, both its mRNA and protein were expressed in gastric chief cells of preweaned neonates. Within the placenta, its mRNA was present in both the parietal and visceral yolk sacs. However, the protein was most prevalent in the visceral yolk sac, with little detectable in the parietal yolk sac. The recombinant protein was expressed in Escherichia coli. This protein was capable of self-activation and exhibited proteolytic activity toward casein. The presence of this enzyme in two organs involved in the selective transcellular transport of proteins suggests that it has specialized digestive functions.

Regulation of human and mouse procathepsin E gene expression

Cathepsin E is an intracellular aspartic proteinase that is considered to have a number of physiological roles including antigen processing. Quantitation of procathepsin E mRNA by LightCyclertrade mark technology indicated that the gene was transcribed in lung but not in kidney of both human and mouse origin. In contrast, the transcript was present in mouse spleen and alveolar macrophages but not in the counterpart tissue/cells from humans. Regulation of human and mouse procathepsin E gene expression was shown not to be influenced by the extent of CpG methylation but depended on the recognition of potential binding motifs in each promoter region by transcription factors such as GATA1, PU1 and YY1, as revealed by functional analysis using a series of promoter/luciferase reporter gene fusion constructs. Thus the extent to which the procathepsin E gene is expressed in a particular cell type may depend on the balance between the effects produced by positive-acting, cell-specific transcription factors such as GATA1 and PU1 and the negative influence of the ubiquitous YY1 factor. In this way, the relative abundance and influence of general and cell-specific transcription factors can govern the production of cathepsin E and thereby account for the sporadic cell and tissue distribution of this enzyme in different species.

A basic residue at position 36p of the propeptide is not essential for the correct folding and subsequent autocatalytic activation of prochymosin

Position 36p in the propeptides of gastric aspartic proteinases is generally occupied by lysine or arginine. This has led to the conclusion that a basic residue at this position, which interacts with the active-site aspartates, is essential for folding and activation of the zymogen. Lamb prochymosin has been shown by cDNA cloning to possess glutamic acid at 36p. To investigate the effect of this natural mutation which appears to contradict the proposed role of this residue, calf and lamb prochymosins and their two reciprocal mutants, K36pE and E36pK, respectively, were expressed in Escherichia coli, refolded in vitro, and autoactivated at pH 2 and 4.7. All four zymogens could be activated to active chymosin and, at both pH values, the two proteins with Glu36p showed higher activation rates than the two Lys36p forms. Glu36p was also demonstrated in natural prochymosin isolated from the fourth stomach of lamb, as well as being encoded in the genomes of sheep, goat and mouflon, which belong to the subfamily Caprinae. A conserved basic residue at position 36p of prochymosin is thus not obligatory for its folding or autocatalytic activation. The apparently contradictory results for porcine pepsinogen A [Richter, C., Tanaka, T., Koseki, T. & Yada, R.Y. (1999) Eur. J. Biochem. 261, 746-752] can be reconciled with those for prochymosin. Lys/Arg36p is involved in stabilizing the propeptide-enzyme interaction, along with residues nearer the N-terminus of the propeptide, the sequence of which varies between species. The relative contribution of residue 36p to stability differs between pepsinogen and prochymosin, being larger in the former.

Molecular organization, expression and chromosomal localization of the mouse pronapsin gene

Napsins have been identified only very recently as new aspartic proteinases of the pepsin family. Isolation, sequencing and functional analysis of the mouse genomic locus indicates that the organization of the pronapsin gene into nine exons is identical to that of other mammalian aspartic proteinase precursors, including pepsinogen. However, the additional C-terminal residues, which are a distinguishing feature of napsins, are encoded within exon 9 and not within an additional exon. Quantitation of pronapsin mRNA using RT-PCR indicates that the gene is transcribed in lung, kidney and spleen but not in heart. Regulation of gene expression was not influenced by the extent of CpG methylation but depended on the recognition of potential binding motifs in the promoter region by specific transcription factors such as YY-1. The single copy of the mouse pronapsin gene was located on chromosome 7. In humans, there are two pronapsin genes and, based on the mouse information, preliminary structures were deduced for these from sequences in the human genome databases. They appear to be located together on chromosome 19.