Expression and activities of three inducible enzymes in the healing of gastric ulcers in rats

AIM: To explore the roles of nitric oxide synthase (NOS),heme oxygenase (HO) and cyclooxygenase (COX) in gastric ulceration and to investigate the relationships of the expression and activities of these enzymes at different stages of gastric ulceration.METHODS: Gastric ulcers (kissing ulcers) were induced by luminal application of acetic acid. Gastric tissue samples were obtained from the ulcer base, ulcer margin, and nonulcerated area around the ulcer margin at different time intervals after ulcer induction. The mRNA expression and protein levels of inducible and constitutive isoforms of NOS,HO and COX were analyzed with RT-PCR and Western blotting methods. The activities of the total NOS, inducible NOS (iNOS), HO, and COX were also determined.RESULTS: Differential expression of inducible iNOS, HO-1and COX-2 and enzyme activities of NOS, HO and COX were found in the gastric ulcer base. High iNOS expression and activity were observed on day 1 to day 3 in severely inflamed ulcer tissues. Maximum expressions of HO-1 and COX-2 and enzyme activities of HO and COX lagged behind that of iNOS,and remained at high levels during the healing phase.CONCLUSION: The expression and activities of inducible NOS, HO-1 and COX-2 are found to be correlated to different stages of gastric ulceration. Inducible NOS may contribute to ulcer formation while HO-1 and COX-2 may promote ulcer healing.

Preparation of magnetic polybutylcyanoacrylate nanospheres encapsulated with aclacinomycin A and its effect on gastric tumor

AIM: To evaluate the effect of aclacinomycin A-loaded magnetic polybutylcyanoacrylate nanoparticles on gastric tumor growth in vivo and in vitro.METHODS: Magnetic polybutylcyanoacrylate (PBCA)nanospheres encapsulated with aclacinomycin A (MPNS-ACM) were prepared by interracial polymerization. Particle size, shape and drug content were examined. Female BABL/c nude mice were implanted with MKN-45 gastric carcinoma tissues subcutaneously to establish human gastric carcinoma model. The mice were randomly divided into 5 groups of 6 each: ACM group (8 mg/kg bin); group of high dosage of MPNS-ACM (8 mg/kg bin); group of low dosage of MPNS-ACM (1.6 mg/kg bin); group of magnetic PBCA nanosphere (MPNS) and control group(normal saline). Magnets (2.5 T) were implanted into the tumor masses in all of the mice one day before the therapy.Above-mentioned drugs were administered intravenously to the mice of every group on the first day and sixth day.When the mice were sacrificed, tumor weight was measured, and the assay of granulocyte- macrophage colony forming-unit (CFU-GM) was performed on semi-solid culture. White blood cell, alanine aminotransferase and creatine were examined. 3-[4-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) was used to examine the viability of MKN-45 cells afger incubation with different concentrations of ACM, MPNS and MPNS-ACM suspension respectively for 48 h.RESULTS: Content of ACM in MPNS-ACM was 12.0% and the average diameter of the particles was 210 nm. The inhibitory rates of ACM (8 mg/kg bin), high dosage of MPNS-ACM (8 mg/kg bin), low dosage of MPNS-ACM (1.6 mg/kg bin)and MPNS on human gastric carcinoma in nude mice were 22.63%, 52.55%, 30.66% and 10.22%, respectively. There was a significant decrease in the number of CFU-GM of bone marrow in ACM group compared with control group,whereas no obvious change was observed in that of the nanosphere groups. The values of 50% inhibition concentration (IC50) of ACM, MPNS and MPNS-ACM were 0.09, 97.78 and 1.07 μg/mL, respectively.CONCLUSION: The tumor inhibitory rate of MPNS-ACM was much higher than that of ACM under magnetic field and the inhibition on bone marrow was alleviated significantly compared with ACM group.