Is arbutin an effective antioxidant for the discount of oxidative and nitrosative stress in Hep-G2 cells exposed to tert-butyl hydroperoxide?

AIM

Oxidative and nitrosative stress triggers an extensive damage to the tissues. Many herbal and chemical medicines have claimed to possess antioxidant properties. Arbutin exists in some plants such as Pyrus Biossierana Bushe. In this study, an inhibitory effect of arbutin against tert-butyl hydroperoxide induced cytotoxicity was studied using SYTOX TM Green assay for cell viability. The antioxidant effects of arbutin on the generation of malondialdehyde, nitric oxide, activity of oxidative enzyme (Superoxide dismutase and catalyze) and the amount of total thiol in Hep-G2 cells exposed to tert-butyl hydroperoxide were evaluated.

METHODS

Hep-G2 cells were cultured in 24-well plates. After 24 hours, the cells were pretreated with the arbutin at different concentrations (0, 100 and 150 µM). 24 hours later, tert-butyl hydroperoxide at different concentrations (0, 150, 200 and 250 µM) was added into the culture media.

RESULTS

Arbutin was able to decrease malondialdehyde and nitric oxide concentrations in arbutin treated group in comparison with the control group (p < 0.00001). The catalase and superoxide dismutase enzymes in these cells were significantly decreased in a dose depend manner in the presence of arbutin in comparison with the control group (p < 0.00001). In addition, arbutin was capable of increasing the tert-butyl hydroperoxide mediated reduction in the total thiol amount in comparison with the control group (p < 0.00001.) CONCLUSION: Our investigation demonstrated that tert-butyl hydroperoxide evoked a reactive oxygen and nitrogen species overproduction in Hep-G2 cells. The cells treated with arbutin showed a dose-dependent reduction of tert-butyl hydroperoxide induced reactive oxygen and nitrogen species generation (Fig. 6, Ref. 34).

Evaluation of frxA and rdxA gene mutations in clinical metronidazole resistance Helicobacter pylori isolates

Metronidazole resistance is an important factor related to failure in the treatment of Helicobacter pylori. The mutation in the rdxA and frxA genes is the most important cause of resistance to metronidazole. Since the resistance rate of metronidazole is high in our region, we decided to assess the frequency of these mutations among H. pylori clinical isolates. Antral gastric biopsy specimens were cultured and minimal inhibitory concentrations (MICs) of metronidazole were determined by the E-test method. The rdxA and frxA genes were amplified in all isolates through the use of PCR with the specific primers. PCR products were purified for sequencing. The resultant sequences were compared with the wild type reference sequences to find any possible mutations. According to our findings, the rate of metronidazole resistance was 77%, with the MICs ranging from 0.25-1 µg/ml for metronidazolesensitive group and from 16-256 µg/ml for resistance group. H. pylori isolates containing a single mutation in rdxA or frxA genes demonstrated a low MIC (8-16 µg/ml), while those containing mutations in both genes showed a higher MIC (32-256 µg/ml). In this study, all resistant H. pylori isolates contained single or multiple nucleotide substitutions in the mentioned genes. Nevertheless, no nucleotide substitutions were found in the sensitive clinical isolates. The results of our study showed that the mutations in rdxA are mostly related to metronidazole resistance, and mutations in frxA are able to enhance H. pylori resistance.

Co-inhibition of Notch and NF-κB Signaling Pathway Decreases Proliferation through Downregulating IκB-α and Hes-1 Expression in Human Ovarian Cancer OVCAR-3 Cells

Background: Ovarian cancer is one of the most lethal gynecological malignancies and numerous changes in signaling cascades are involved in the initiation and progression of ovarian cancerous cells. Here, we investigated the role of NF-κB and Notch pathways inhibition on human ovarian cancer OVCAR-3 cells proliferation and IκB-α and Hes-1 expression as 2 key genes in these pathways regulation. Methods: The effects of Bay 11-7085 and DAPT, NF-κB and Notch pathways specific inhibitors, on cell proliferation were evaluated using MTT assay. In addition, the cells were transfected by Notch and IKK-β siRNAs. mRNA and protein levels of target genes were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot after 48 h incubation with inhibitors and siRNAs. Results: Bay 11-7085 and DAPT significantly decreased the cell proliferation OVCAR-3. IκB-α and Hes-1 mRNA levels decreased to 5 or 3% and 6% or 2% after treatment with Bay 11-7085 or DAPT, respectively (p<0.05). We also found that combination treatment exert a more potent effects on the expression of these gene (p<0.05). Moreover, siRNA transfection caused a significant reduction in IκB-α and Hes-1 mRNA levels (p<0.05). In the protein level, OVCAR-3 cell treatment with both chemichal inhibitors and specific siRNA cause a significant decrease in the expression of target genes (p<0.05) Conclusion: Our findings suggest that inhibition of NF-κB and Notch signaling pathways can effectively reduce OVCAR-3 cells proliferation. Therefore, pharmacological targeting of the NF-κB and Notch signaling pathway could be a promising future treatment of ovarian cancer.