Genotoxicity, carcinogenicity and acid-suppressing medications

Evaluation of mutagenesis, necrosis and apoptosis induced by omeprazole in stomach cells of patients with gastritis

Background

Gastritis is a superficial and prevalent inflammatory lesion that is considered a public health concern once can cause gastric ulcers and gastric cancer, especially when associated with Helicobacter pylori infection. Proton pump inhibitors, such as omeprazole, are the most widely used drugs to treat this illness. The aim of the study was evaluate cytogenetic effects of omeprazole in stomach epithelial cells of patients with gastritis in presence and absence of H. pylori, through cytogenetic biomarkers and catalse and superoxide dismutase analysis.

Methods

The study included 152 patients from the Gastroenterology Outpatient Clinic of Hospital Getúlio Vargas, Teresina—Brazil, that reported continuous and prolonged omeprazole use in doses of 20, 30 and 40 mg/kg. The participants were divided into groups: (1) patients without gastritis (n = 32); (2) patients without gastritis but with OME use (n = 24); (3) patients with gastritis (n = 26); (4) patients with gastritis undergoing OME therapy (n = 26); (5) patients with gastritis and H. pylori (n = 22) and (6) patients with gastritis and H. pylori on OME therapy (n = 22).

Results

OME induced cytogenetic imbalance in the stomach epithelium through the formation of micronuclei (group 6 > 1, 2, 3, 4, 5; group 5 > 1, 2, 3; group 4 > 1, 2, 3); bridges (groups 4 and 6 > 1, 2, 3, 5 and group 2 > 3, 5); buds (groups 2,4,6 > , 1, 3, 5); binucleated cells (group 6 > 1, 2, 3, 4, 5; group 4 > 1, 2, 3); (groups 2 and 3 > 1); picnoses (group 6 > 1, 2, 3, 4, 5), groups 2 and 5 > 1, 3; group 4 > 1, 2, 3, 5); cariorrexis (groups 6 and 4 > 1, 2, 3, 5; groups 2, 3, 5 > 1) and karyolysis (groups 2, 4, and 6 > 1, 3, 5; groups 3 and 5 > 1). The OME cytogenetic instability was associated with H. pylori infection, indicating clastogenic/aneugenic effects, chromosomes alterations, gene expression changes, cytotoxicity and apoptosis.

Conclusions

The cytogenetic changescan be attributed to several mechanisms that are still unclear, including oxidative damage, as observed by increased catalase and superoxide dismutase expresion. Positive correlations between antioxidant enzymes were found with micronuclei formation, and were negative for picnoses. Thus, the continuous and prolonged omeprazole use induces genetic instability, which can be monitored through cytogenetic analyzes, as precursor for gastric cancer.

Evaluation of antioxidant, enzyme inhibition, and cytotoxic activity of three anthraquinones (alizarin, purpurin, and quinizarin)

OBJECTIVE

The aim of this work was to investigate the cytotoxic, antioxidative, and enzyme inhibition effects of alizarin, quinizarin, and purpurin, which are anthraquinones (AQ).

METHODS

Cytotoxic effects were evaluated with cell inhibition rate by 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide assay. Different chemical assays, including free radical scavenging activity (1,1-diphenyl-2-picrylhydrazyl and 2,2-azino-bis(3-ethylbenzothiazloine-6-sulfonic acid)), phosphomolybdenum and reducing power (ferric reducing antioxidant power and cupric ion reducing activity), were used to evaluate the antioxidant properties. Moreover, enzyme inhibitory activities were analyzed against acetylcholinesterase, butrylcholinesterase, tyrosinase, α-amylase, and α-glucosidase.

RESULTS

These components have antioxidant and enzyme inhibition activity. Especially, purpurin showed the strongest antioxidant and good enzyme inhibitory effects. According to our cytotoxicity results, alizarin, purpurin, and quinizarin induced dose- and time-dependent cell proliferation. Furthermore, when we applied AQs with mitomycin C (MC) on L929 cell line, we demonstrated that cell proliferation in MC-AQ groups compared with MC group was increased. The most effective component was alizarin at 100 µM concentration. These AQs showed positive effects on L929 cell lines with high half-maximal inhibitory concentration values.

CONCLUSION

Our results demonstrate that AQs may be used as antioxidative compounds in food and medicinal applications.

Hydrogen potassium adenosine triphosphatase activity inhibition and downregulation of its expression by bioactive fraction DLBS2411 from Cinnamomum burmannii in gastric parietal cells

This study assessed the gastric acid antisecretory effect of DLBS2411 fractionated from Cinnamomum burmannii. Hydrogen potassium adenosine triphosphatase (H⁺/K⁺ ATPase) activity and its gene expression were observed, and the antioxidant activity of DLBS2411 was also investigated. Treatment of DLBS2411 decreased the level of H⁺/K⁺ ATPase messenger RNA expression on human embryonic kidney 293 cells and rat gastric parietal cells in a dose-dependent manner, in vitro and ex vivo. DLBS2411 also acted as a competitive inhibitor by showing inhibition in gastric H⁺/K⁺ ATPase activity at various pHs. In gastric ulcer animal models induced with indomethacin and ethanol, DLBS2411showed a reduction in the number of petechiae, suggesting that the fraction also confers gastroprotective activity. Moreover, DLBS2411 was also found to have potent antioxidant activity. Taken together, DLBS2411 is a promising novel agent for the management of dyspepsia, a condition of hyperacidity and diseases in the stomach requiring gastroprotection.

Gastroprotective effect of swallow root (Decalepis hamiltonii) extract: possible involvement of H(+)-K(+)-ATPase inhibition and antioxidative mechanism

The present study reports the antiulcer potentials of aqueous extract of swallow root (Decalepis hamiltonii Wight & Arn, SRAE) belonging to the family Asclepiadaceae. Swim stress-induced ulcers with an ulcer index (UI) of 6.0+/-0.01 was protected up to 43% and 72% at 100 and 200mg/kg b.w. of SRAE, respectively, similar to protection offered by ranitidine (79%) at 30mg/kg b.w. Depletion in antioxidant enzymes and increased Thiobarbituric Acid Reactive Substances (TBARS) were observed in ulcer-induced rats while SRAE fed rats showed normal levels. SRAE also normalized approximately 3.1 and 2.4 folds of increased H(+)-K(+)-ATPase and gastric mucin, respectively, in ulcerous animals, similar to the levels found in healthy controls. SRAE also possessed reducing power, free radical scavenging ability with an IC(50) of 0.17microg/mL gallic acid equivalent (GAE), comparable to that of BHA (IC(50)-0.08microg/mL). DNA protection up to 80% at 0.2microg was also observed. Toxicity studies indicated no lethal effects in rats fed up to 5g/kg b.w. Antioxidant, proton pump inhibition as well as boosting of gastric mucin effects of SRAE have been implicated to be responsible for antiulcer property of SRAE.

Omeprazole treatment: genotoxicity biomarkers, and potential to induce CYP1A2 activity in humans

Omeprazole is one of the most used acid-suppressing medications. This fact emphasizes the questions concerning the safety of this compound. Healthy volunteers (n=33) were included in this prospective study. All study subjects were analysed for their CYP2C19 genotype. Of the 33 individuals, 24 were homozygous for the wild type CYP2C19*1 allele, 7 were heterozygous for the CYP2C19*2 variant allele, and 2 were homozygous for the CYP2C19*2 variant allele. Before and after 14 days of omeprazole treatment at a daily dose of 20 mg, one blood sample was taken from each individual to determine five cytogenetic biomarkers of genotoxicity: chromosome aberrations, micronuclei, proliferating rate index, sister chromatid exchanges, and mitotic index. The only significant change was that of a weak increase in micronuclei count after treatment in relation to baseline values (day 0) (P = 0.026). To assess the potential of omeprazole to induce P450 CYP1A2, the urinary ratio AFMU+1X+1U/17U in the interval of 4-5 hours after caffeine intake was calculated twice (days 0 and 15), using the caffeine test in 27 of the 33 individuals. This result suggests that omeprazole does not increase CYP1A2 activity after 14 days of treatment.

Gastroprotective effect of Neem (Azadirachta indica) bark extract: possible involvement of H(+)-K(+)-ATPase inhibition and scavenging of hydroxyl radical

The antisecretory and antiulcer effects of aqueous extract of Neem (Azadirachta indica) bark have been studied along with its mechanism of action, standardisation and safety evaluation. The extract can dose dependently inhibit pylorus-ligation and drug (mercaptomethylimidazole)-induced acid secretion with ED(50) value of 2.7 and 2 mg Kg(-1) b.w. respectively. It is highly potent in dose-dependently blocking gastric ulcer induced by restraint-cold stress and indomethacin with ED(50) value of 1.5 and 1.25 mg Kg(-1) b.w. respectively. When compared, bark extract is equipotent to ranitidine but more potent than omeprazole in inhibiting pylorus-ligation induced acid secretion. In a stress ulcer model, it is more effective than ranitidine but almost equipotent to omeprazole. Bark extract inhibits H(+)-K(+)-ATPase activity in vitro in a concentration dependent manner similar to omeprazole. It offers gastroprotection against stress ulcer by significantly preventing adhered mucus and endogenous glutathione depletion. It prevents oxidative damage of the gastric mucosa by significantly blocking lipid peroxidation and by scavenging the endogenous hydroxyl radical ((z.rad;)OH)-the major causative factor for ulcer. The (z.rad;)OH-mediated oxidative damage of human gastric mucosal DNA is also protected by the extract in vitro. Bark extract is more effective than melatonin, vitamin E, desferrioxamine and alpha-phenyl N-tert butylnitrone, the known antioxidants having antiulcer effect. Standardisation of the bioactive extract by high pressure liquid chromatography indicates that peak 1 of the chromatogram coincides with the major bioactive compound, a phenolic glycoside, isolated from the extract. The pharmacological effects of the bark extract are attributed to a phenolic glycoside which is apparently homogeneous by HPLC and which represents 10% of the raw bark extract. A single dose of 1g of raw extract per kg b.w. (mice) given in one day and application of 0.6g raw extract per kg b.w. per day by oral route over 15 days to a cumulative dose of 9g per kg was well tolerated and was below the LD(50). It is also well tolerated by rats with no significant adverse effect. It is concluded that Neem bark extract has therapeutic potential for the control of gastric hyperacidity and ulcer.

Mutagenic and clastogenic activity of gastric juice in human gastric diseases

To investigate whether subjects with low-acid states are exposed to increased genetic risk with respect to controls, we evaluated mutagenicity and presence of clastogenic factors (CF) in the gastric juice of chronic atrophic gastritis and omeprazole-treated patients. Mutagenic gastric juice was found in 8/15 (53%) chronic atrophic gastritis patients, 8/11 (73%) omeprazole-treated patients, and 2/13 (15%) healthy control subjects. The mean mutagenicity ratio of omeprazole-treated patients (1.52+/-0.48/0.1 ml gastric juice) was significantly higher than those of either controls (1.07+/-0.15; P<0.01) or chronic atrophic gastritis patients (1.16+/-0.21; P<0.05). Only chronic atrophic gastritis patients showed an increased clastogenic index with respect to healthy controls (2.67+/-2.13 versus 0.38+/-0.51; P<0.001). These findings expand our knowledge of gastric disease risk factors, and indicate that there may well be a risk of mucosal DNA damage arising from the presence of mutagenic and CF in the gastric juice.

Review article: current perspectives on hypergastrinaemia and enterochromaffin-like-cell hyperplasia

Rabeprazole, a new benzimidazole proton pump inhibitor (PPI), is among a class of agents known to be very potent inhibitors of gastric acid secretion. PPIs inhibit hydrogen-potassium adenosine triphosphatase activity on the luminal surface of the parietal cell, effectively blocking the final common pathway for gastric acid secretion. Raising gastric pH stimulates the production of gastrin by G cells in the antrum of the stomach, which can lead to enterochromaffin-like (ECL)-cell hyperplasia. In the past, these changes have been viewed with concern, particularly in the light of studies in rats indicating that hypergastrinaemia and ECL-cell hyperplasia induce gastric carcinoid tumour formation. All available clinical data indicate that long-term PPI use does not lead to carcinoid tumour formation in humans. In fact, both serum gastrin elevation and ECL-cell hyperplasia are now generally viewed as normal physiological responses to gastric acid suppression. Serum gastrin concentrations, in particular, correlate well with gastric acid suppression, which has led to the use of gastrin response by some investigators as a surrogate marker of antisecretory effectiveness. Long-term tolerability data indicate that PPIs have a favourable side-effect profile. Data obtained from patients receiving acute or long-term maintenance rabeprazole therapy support this conclusion. Furthermore, neither animal nor human data obtained with rabeprazole suggest a significant risk for neoplastic changes secondary to hypergastrinaemia.