Gastric epithelial proliferation and p53 and p21 expression in a general population sample: relations to age, sex, and mucosal changes associated with H. pylori infection

Selective dysfunction of p53 for mitochondrial biogenesis induces cellular proliferation in bronchial smooth muscle from asthmatic patients

BACKGROUND

Increase of bronchial smooth muscle (BSM) mass is a crucial feature of asthma remodeling. The mechanisms of such an increased BSM mass are complex but involve enhanced mitochondrial biogenesis, leading to increased proliferation of BSM cells in asthmatic patients. The major tumor suppressor protein p53 is a key cell regulator involved in cell proliferation and has also been implicated in mitochondrial biogenesis. However, the role of p53 in BSM cell proliferation and mitochondrial biogenesis has not been investigated thus far.

OBJECTIVE

We sought to evaluate the role of p53 in proliferation of BSM cells in asthmatic patients and mitochondrial biogenesis.

METHODS

The expression of p53 was assessed both in vitro by using flow cytometry and Western blotting and ex vivo by using RT-PCR after laser microdissection. The role of p53 was assessed with small hairpin RNA lentivirus in both asthmatic patients and control subjects with BSM cell proliferation by using 5-bromo-2'-deoxyuridine and cell counting and in the expression of p21, BCL2-associated X protein, mitochondrial transcription factor A (TFAM), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α).

RESULTS

Twenty-nine patients with moderate-to-severe asthma and 26 control subjects were enrolled in the study. p53 expression was increased in BSM from asthmatic patients both ex vivo and in vitro, with a decreased interaction with mouse double minute 2 homolog (Mdm2) and an increased phosphorylation of serine 20. p53 did not inhibit the transcription of both TFAM and PGC-1α in BSM cells from asthmatic patients. As a consequence, p53 is unable to slow the increased mitochondrial biogenesis and hence the subsequent increased proliferation of BSM cells in asthmatic patients.

CONCLUSION

This study suggests that p53 might act as a new potential therapeutic target against BSM remodeling in asthmatic patients.

Assessment of p21, p53 expression, and Ki-67 proliferative activities in the gastric mucosa of children with Helicobacter pylori gastritis

BACKGROUND

Helicobacter pylori that is generally acquired in childhood and infects the gastric mucosa is considered to be responsible for many pathobiological changes that are linked to the pathogenesis of gastric cancer. Although the majority of studies on the subject have been carried out in adults, there are a limited number of studies on children that reflect the early period of infection and may be of greater significance.

AIM

We aimed to determine the role of H. pylori infection and/or gastritis in several histopathological changes, p53, p21, and cell proliferation-associated Ki-67 antigen expression in the gastric mucosa.

MATERIALS AND METHODS

We studied 60 patients with a mean age of 7.5 ± 4.5 years at referral. On the basis of endoscopic appearance and the evaluation of the gastric antral specimens, the patients were divided into three groups: patients without gastritis, patients with H. pylori-positive gastritis, and patients with H. pylori-negative gastritis. To determine the expression of p53, Ki-67, and p21 in gastric biopsy specimens, immunohistochemical stains were performed.

RESULTS

The incidence of neutrophil activity, which was one of our histopathologic parameters, was significantly higher in the H. pylori-positive gastritis group than the other two groups. The presence of lymphoid aggregate was more frequent in H. pylori ± gastritis groups than the nongastritis group. p53 expression was found to be significantly higher in the H. pylori-positive gastritis group than the nongastritis group. Ki-67 and p21 expressions were significantly more frequent in the H. pylori-positive gastritis group than the other two groups. When we evaluated the density of H. pylori, as the density of bacteria increases, we found that the expressions of p53, p21, and Ki-67 increased significantly.

CONCLUSION

Expression of the studied precancerous markers in significant amounts indicates the importance of childhood H. pylori infection in the constitution of gastric cancer in adulthood.

Lycopene inhibits Helicobacter pylori-induced ATM/ATR-dependent DNA damage response in gastric epithelial AGS cells

Oxidative stress linked to DNA damage is involved in the pathogenesis of Helicobacter pylori-associated gastric diseases. The DNA damage response (DDR) coordinates cell-cycle transitions, DNA repair, and apoptosis through the activation of ataxia-telangiectasia-mutated (ATM) and ATM and Rad3-related (ATR) and their target proteins. However, neither H. pylori-induced DDR nor the effects of antioxidants on the DNA damage have been established. This study aimed to investigate the detailed process of H. pylori-induced DNA damage and to examine whether lycopene, a natural antioxidant, inhibits DNA damage and cellular response of gastric epithelial AGS cells infected with H. pylori. AGS cells were cultured with H. pylori in Korean isolates and treated with or without lycopene. Cell viability, DNA damage indices, levels of 8-OH-dG, and reactive oxygen species (ROS) as well as cell-cycle distributions were determined. The activation of ATM, ATR, Chk1, and Chk2; histone H2AX focus formation; activation and induction of p53; and levels of Bax and Bcl-2 and poly(ADP-ribose) polymerase-1 (PARP-1) were assessed. The results showed that H. pylori induced apoptosis in AGS cells with increased Bax and decreased Bcl-2 expression as well as PARP-1 cleavage. Culture with H. pylori led to increases in intracellular ROS, 8-OH-dG, double-strand DNA breaks (DSBs), and DNA fragmentation. H. pylori induced activation of the ATM/Chk2 and ATR/Chk1 pathways, phosphorylation of H2AX and p53, and a delay in the progression of the cells entering the S phase. Lycopene inhibited H. pylori-induced increases in ROS, apoptosis, alterations in cell-cycle distribution, DSBs, and ATM- and ATR-mediated DDR in AGS cells. In conclusion, lycopene may be beneficial for treatment of H. pylori-induced gastric diseases associated with oxidative DNA damage.

The effect of age and Helicobacter pylori infection on gastric epithelial cell kinetics

BACKGROUND

Helicobacter pylori infection is a known risk factor for gastric cancer. The aim of the study was to determine the effect of H. pylori and age on gastric epithelial cell kinetics.

METHODS

One hundred and fifty-seven patients (92 men, median age: 58.5 years, range: 18-85) who had undergone upper gastrointestinal endoscopy due to dyspeptic symptoms were enrolled into the study. Six antral biopsy samples were obtained for flow cytometric DNA analysis (expressed as proliferative index [PI], S+G2/M phase), presence of H. pylori (CLO-test, culture and histology), and histopathologic examination.

RESULTS

Eighty-four (53.5%) patients were H. pylori positive and 93.3% of patients had diploid pattern and 6.7% expressed aneuploid pattern. The mean PI was 4.8 ± 0.2 for the whole group studied. PI were 5.14 ± 0.33 and 4.26 ± 0.36 for H. pylori (+) and H. pylori (-) patients respectively (P = 0.017). When age groups were taken into account, PI was found higher in patients over 75 years of age (n = 14, PI = 6.66 ± 1.3) compared to patients under 35 years of age (n = 25, PI = 3.83 ± 0.41, P = 0.014). There was no correlation between histological changes and PI. H. pylori (P = 0.045) and age (P = 0.082) were independent factors for PI.

CONCLUSION

PI of gastric antral mucosa increases in patients with H. pylori infection. Although PI increases by age, H. pylori is the only factor that significantly and independently influences the rate of epithelial cell proliferation.

Characterization of the gastric cardia in volunteers from the general population. Type of mucosa, Helicobacter pylori infection, inflammation, mucosal proliferative activity, p53 and p21 expression, and relations to gastritis

The aim of this research was to characterize the mucosa of the gastric cardia in relation to infection with Helicobacter pylori and the occurrence of chronic gastritis in other parts of the stomach in a sample of the general population. In this study, 80 adult volunteers underwent esophagogastroscopy with biopsies from the gastric cardia, corpus, and antrum. Gastritis was classified according to the Sydney system. Chronic gastritis (cardia excepted) was diagnosed in 35 subjects, 30 with H. pylori infection. Epithelial proliferative activity (Ki-67), p53- and p21 expression were examined quantitatively with cell counting after immunohistochemical stainings. Esophagitis was diagnosed macroscopically. Fourty eight subjects had cardia-type and 32 corpus-type mucosa in the anatomical cardia. The prevalence of esophagitis (nine cases) did not differ between these groups. Carditis was more prevalent among subjects with cardia-type mucosa (73 vs. 28%, P < 0.0001). H. pylori was present in 48% of those with cardia-type and 25% of those with corpus-type mucosa (P = 0.06). Of the 44 subjects with carditis, 31 had H. pylori in this location. The group with H. pylori infection had significantly higher mucosal proliferative activity when compared to uninfected subjects. Among the subjects with H. pylori-associated carditis, more p53-positive epithelial cells were detected compared to both the non-infected group (P = 0.0004) and to subjects with non-H. pylori-associated carditis (P = 0.03). In subjects with cardia-type mucosa, and both carditis and gastritis, the degree of chronic inflammation was higher in the cardia compared to the corpus and antrum and the p53 expression was significantly higher in the cardia compared to the corpus, but similar to that in the antrum. The proliferative activity was significantly higher in the antrum compared to the cardia and corpus, respectively. In conclusion, H. pylori infection, carditis, and increased p53 expression are more common in subjects with cardia- than corpus-type mucosa in the gastric cardia. Carditis is mainly related to H. pylori infection. There are some differences regarding inflammation, proliferative activity, and p53 expression between the cardia and other regions of the stomach, yet the significance of these differences remains to be clarified.

The relation of Helicobacter pylori to gastric adenocarcinoma and lymphoma: pathophysiology, epidemiology, screening, clinical presentation, treatment, and prevention

Helicobacter pylori infection may be the most common chronic bacterial infection worldwide; however, the prevalence varies between countries and is usually linked to socioeconomic conditions. Gastric cancer is one of the most frequent cancers in developing countries and usually about the seventh most common in developed countries. This article explores the relation of H. pylori to gastric adenocarcinoma and lymphoma. The pathophysiology, epidemiology, screening, clinical presentation, treatment, and prevention are discussed.

Aneuploidies, deletion, and overexpression of TP53 gene in intestinal metaplasia of patients without gastric cancer

Gastric carcinogenesis is attributable to interacting environmental and genetic factors, through a sequence of events including intestinal metaplasia. Using a fluorescence in situ hybridization technique, we investigated the occurrence of aneuploidies of chromosomes 3, 7, 8, 9, and 17, TP53 gene deletion, and expression of p53 in 21 intestinal metaplasia (IM) samples from cancer-free patients and in 20 gastric adenocarcinoma samples. Aneuploidies were found in 71% (15/21) of the IM samples. Trisomy of chromosomes 7 and 9 occurred mainly in complete-type IM; in the incomplete type, trisomy of chromosomes 7 and 8 were more commonly found. The TP53 gene deletion was observed in 60% (3/5) of the IM cases, and immunohistochemistry revealed p53 overexpression in 12% (2/17) of the analyzed IM cases. All gastric adenocarcinoma cases presented higher frequencies of trisomy or tetrasomy of chromosomes 3, 7, 8, 9, and 17. The TP53 deletion was found in all three of the gastric adenocarcinoma analyzed for it, and immunohistochemistry detected overexpression of protein p53 in 80% (12/15) of the analyzed cases. Our study revealed for the first time the presence of aneuploidies of chromosomes 7, 8, 9, and 17 and of TP53 gene deletion and overexpression in IM samples from cancer-free patients. These results suggest that IM and gastric adenocarcinoma may share the same genetic alterations.

A novel mitogenic protein that is highly expressed in cells of the gastric antrum mucosa

Human and pig cDNAs for a novel stomach protein, the product of a gene expressed at high levels specifically in cells of the antrum mucosa, have been characterized. The general exon/intron structure of the genomic DNA is conserved in humans and mice. The predicted protein sequences of the human and mouse mRNAs contain 185 and 184 amino acids, respectively. The protein isolated from pig antral extracts has an NH2 terminus consistent with cleavage of a 20-amino acid signal peptide. Human cDNA was expressed in E. coli to generate a protein antigen for antibody production. The antibodies detected polypeptides of approximately 18 kDa in antrum extracts from all mammalian species tested. Immunocytochemistry located antrum mucosal protein (AMP)-18 to surface mucosal cells of the mouse antrum and, specifically, to secretion granules, suggesting that it is cosecreted with mucins. Antrum extracts and recombinant human AMP-18 exhibit growth-promoting activity on epithelial cells that can be blocked by the specific antisera. We suggest that AMP-18 is a "gastrokine" that maintains the integrity of the gastric mucosal epithelium.