Recombinant Helicobacter pylori catalase

AIM: To construct a recombinant strain which highly expresses catalase of Helicobacter pylori (H. pylori) and assay the activity of H. pylori catalase.

METHODS: The catalase DNA was amplified from H. pylori chromosomal DNA with PCR techniques and inserted into the prokaryotie expression vector pET-22b (+), and then was transformed into the BL21 (DE3) E. coli strain which expressed catalase recombinant protein. The activity of H. pylori catalase was assayed by the Beers&Sizers.

RESULTS: DNA sequence analysis showed that the sequence of catalase DNA was the same as GenBank’s research. The catalase recombinant protein amounted to 24.4% of the total bacterial protein after induced with IPTG for 3 hours at 37 °C and the activity of H. pylori catalase was high in the BL21 (DE3) E. coli strain.

CONCLUSION: A clone expressing high activity H. pylori catalase is obtained, laying a good foundation for further studies.

The expression of hTERT mRNA and cellular immunity in gastric cancer and precancerosis

AIM: To observe the expression of Human telomerase reverse transcriptase (hTERT) in gastric carcinomas and precancerosis lesions, to evaluate the immune state of such patients, and to then study the clinical significance of hTERT and immune state for the diagnosis, treatment and prognosis of gastric cancer.

METHODS: In situ hybridization was used to detect the expression of hTERT mRNA in 116 endoscopic of gastric mucosa. Analyzed tissue samples were as follows: 30 cases of chronic superficial gastritis (CSG), 44 of precancerosis lesions (including 27 of chronic atrophic gastritis, 8 of adenomatous polyp and 9 of gastric ulcer) and 42 of gastric cancer (GC). In addition, the T lymphocyte subsets (CD3⁺, CD4⁺, CD8⁺, CD4⁺/CD8⁺) and natural killer cells (NK) in peripheral blood were determined by flow cytometric analysis (FCM) in 30 cases of CSG, 27 of precancerosis (chronic atrophic gastritis, CAG), and 42 of GC. The data were compared with those of normal control (NC).

RESULTS: The detected positive rate of hTERT varied as follows: 86% (36/42) in GC, 36% (16/44) in precancerosis lesions and 0% (0/30) in CSG. The expression of hTERT mRNA was not associated with patient gender, tumor location, macroscopic type, lymph node metastasis, or degree of differentiation. It was found that the CD3⁺, CD4⁺ of the CSG group were lower than that of NC (P < 0.05). Meanwhile, the T lymphocyte subsets (CD3⁺, CD4⁺, CD4⁺/CD8⁺ ratio) and NK cells of CAG were remarkably lower than that of NC and CSG groups (P < 0.05-0.01). Values of T cells and NK cells of the GC group were significantly abnormal when compared with the CAG group (P < 0.05-0.01). Furthermore, with tumor progression, the function of T cells was weakened gradually.

CONCLUSION: The expression of telomerase may be a crucial step in gastric carcinogenesis and increased hTERT mRNA may serve as a novel marker for diagnosis of GC. The immune state of patients with GC and precancerosis was somewhat depressed, which indicates the importance of cellular immunological assays in cancer patients.

Gastrin, somatostatin, G and D cells of gastric ulcer in rats

AIM: To investigate the relationship among gastrin, somatostatin, G and D cells in gastric ulcer and in its healing process in rats.

METHODS: Fourty-nine Wistar rats were divided into 7 groups. The gastric ulcer model was induced by acetic acid successfully. The gastrin and the somatostatin in rat plasma, gastric fluid and antral tissue were measured by radioimmunoassay (RIA). G and D cells in antral mucosa were analyzed with polyclonal antibody of gastrin and somatostatin by immunohistochemical method and Quantimet 500 image analysis system.

RESULTS: In gastric ulcer, the level of gastrin in plasma, gastric fluid, and antral tissue increased, that of somatostatin declined, and the disorder gradually recovered to the normal level in the healing process. Immunohistochemical technique of G and D cells in antral mucosa demonstrated that the number of G cells increased and that of D cells decreased, both areas of G and D cells declined, the ratio of number and area of G/D increased in gastric ulcer, and the disorder gradually recovered in the healing process.

CONCLUSION: In gastric ulcer, the increased gastrin secreted by G cells, the declined somatostatin secreted by D cells, and the disordered G/D cell ratio can lead to gastrointestinal dysfunction.

Effect of L-NAME on nitric oxide and gastrointestinal motility alterations in cirrhotic rats

AIM: To investigate the effect of L-NAME on nitric oxide and gastrointestinal motility alterations in cirrhotic rats.

METHODS: Rats with cirrhosis induced by carbon tetrachloride were randomly divided into two groups, one (n = 13) receiving

0.5 mg·kg^-1 per day of N G-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, for 10 d, whereas the other group (n = 13) and control (n = 10) rats were administrated the same volume of 9 g•L⁻¹ saline. Half gastric emptying time and 2 h residual rate were measured by SPECT, using ^99mTc-DTPA-labeled barium sulfate as test meal. Gastrointestinal transition time was recorded simultaneously. Serum concentration of nitric oxide (NO) was determined by the kinetic cadmium reduction and colorimetric methods. Immunohistochemical SABC method was used to observe the expression and distribution of three types of nitric oxide synthase (NOS) isoforms in the rat gastrointestinal tract. Western blot was used to detect expression of gastrointestinal NOS isoforms.

RESULTS: Half gastric emptying time and trans-gastrointestinal time were significantly prolonged (124.0 ± 26.4 min; 33.7 ± 8.9 min; 72.1 ± 15.3 min; P < 0.01), (12.4 ± 0.5 h; 9.5 ± 0.3 h; 8.2 ± 0.8 h; P < 0.01), 2 h residual rate was raised in cirrhotic rats than in controls and cirrhotic rats treated with L-NAME (54.9% ± 7.6%, 13.7% ± 3.2%, 34.9% ± 10.3%, P < 0.01). Serum concentration of NO was significantly increased in cirrhotic rats than in the other groups (8.20 ± 2.48) μmol•L⁻¹, (5.94 ± 1.07) μmol•L⁻¹, and control (5.66 ± 1.60) μmol•L⁻¹, P < 0.01. NOS staining intensities which were mainly located in the gastrointestinal tissues were markedly lower in cirrhotic rats than in the controls and cirrhotic rats after treated with L-NAME.

CONCLUSION: Gastrointestinal motility was remarkably inhibited in cirrhotic rats, which could be alleviated by L-NAME.Nitric oxide may play an important role in the inhibition of gastrointestinal motility in cirrhotic rats.

Polymorphism of flagellin A gene in Helicobacter pylori

AIM: To study the polymorphism of flagellin A genotype and its significance in Helicobacter pylori (H. pylori).

METHODS: As the template, genome DNA was purified from six clinical isolates of H. pylori from outpatients, and the corresponding flagellin A fragments were amplified by polymerase chain reaction. All these products were sequenced. These sequences were compared with each other, and analyzed by software of FASTA program.

RESULTS: Specific PCR products were amplified from all of these H. pylori isolates and no length divergence was found among them. Compared with each other, the highest ungapped identity is 99.10%, while the lowest is 94.65%. Using FASTA program, the alignments between query and library sequences derived from different H. pylori strains were higher than 90%.

CONCLUSION: The nucleotide sequence of flagellin A in H. pylori is highly conservative with incident divergence. This information may be useful for gene diagnosis and further study on flagellar antigen phenotype.

Apoptosis, proliferation and p53 gene expression of H. pylori associated gastric epithelial lesions

AIM: To study the relationship between Helicobacter pylori (H. pylori) and gastric carcinoma and its possible pathogenesis by H. pylori.

METHODS: DNEL technique and immunohistochemical technique were used to study the state of apoptosis, proliferation and p53 gene expression. A total of 100 gastric mucosal biopsy specimens, including 20 normal mucosa, 30 H. pylori-negative and 30 H. pylori-positive gastric precancerous lesions along with 20 gastric carcinomas were studied.

RESULTS: There were several apoptotic cells in the superficial epithelium and a few proliferative cells within the neck of gastric glands, and no p53 protein expression in normal mucosa. In gastric carcinoma, there were few apoptotic cells, while there were a large number of proliferative cells, and expression of p53 protein significantly was increased. In the phase of metaplasia, the apoptotic index (AI, 4.36% ± 1.95%), proliferative index (PI, 19.11% ± 6. 79%) and positivity of p53 expression (46.7%) in H. pylori-positive group were higher than those in normal mucosa (P < 0.01). AI in H. pylori-positive group was higher than that in H. pylori-negative group (3.81% ± 1.76%), PI in H. pylori-positive group was higher than that in H. pylori-negative group (12.25% ± 5.63%, P < 0.01). In the phase of dysplasia, AI (2.31% ± 1.10%) in H. pylori-positive group was lower (3.05% ± 1.29%) than that in H. pylori-negative group, but PI (33.89% ± 11.65%) was significantly higher (22.09% ± 80.18%, P < 0.01). In phases of metaplasia, dysplasia and gastric cancer in the H. pylori-positive group, AIs had an evidently graduall decreasing trend (P < 0.01), while PIs had an evidently gradual increasing trend (P < 0.05 or P < 0.01), and there was also a trend of gradual increase in the expression of p53 gene.

CONCLUSION: In the course of the formation of gastric carcinoma, proliferation of gastric mucosa can be greatly increased by H. pylori, and H. pylori can induce apoptosis in the phase of metaplasia, but in the phase of dysplasia H. pylori can inhibit cellular apoptosis. And H. pylori infection can strengthen the expression of mutated p53 gene.