Search

BACKGROUND High carbon dioxide (CO2) level from indoor environments, such as classrooms and offices, might cause sick building syndrome. Excessive indoor CO2 level increases CO2 level in the blood, and over-accumulation of CO2 induces an adaptive response that requires modulation of gene expression. This study aimed to investigate the adaptive transcriptional response toward hypoxia and oxidative stress in human peripheral blood mononuclear cells (PBMCs) exposed to elevated CO2 level in vitro and its association with cell viability. METHODS PBMCs were treated in 5% CO2 and 15% CO2, representatives a high CO2 level condition for 24 and 48 hours. Extracellular pH (pHe) was measured with a pH meter. The levels of reactive oxygen species were determined by measuring superoxide and hydrogen peroxide with dihydroethidium and dichlorofluorescin-diacetate assay. The mRNA expression levels of hypoxia-inducible factor (HIF)-1α, HIF-2α, nuclear factor (NF)-κB, and manganese superoxide dismutase (MnSOD) were analyzed using a realtime reverse transcriptase-polymerase chain reaction (qRT-PCR). Cell survival was determined by measuring cell viability. RESULTS pHe increased in 24 hours after 15% CO2 treatment, and then decreased in 48 hours. Superoxide and hydrogen peroxide levels increased after the 24- and 48-hour of high CO2 level condition. The expression levels of NF-κB, MnSOD, HIF-1α, and HIF-2α decreased in 24 hours and increased in 48 hours. The increased antioxidant mRNA expression in 48 hours showed that the PBMCs were responsive under high CO2 conditions. Elevated CO2 suppressed cell viability significantly in 48 hours. CONCLUSIONS After 48 hours of high CO2 level condition, PBMCs showed an upregulation in genes related to hypoxia and oxidative stress to overcome the effects of CO2 elevation. [ABSTRACT FROM AUTHOR]

Introduction: Aldehyde dehydrogenase 1-positive (ALDH1+) breast cancer stem cells (BCSCs) are a small population of tumor cells with high capacity of tumorigenicity and oxidative stress. Manganese superoxide dismutase (MnSOD) is specifically expressed in mitochondria as the primary defense against superoxides, which are one of the causes of oxidative stress in cells. The aim of this study was to determine the impact of suppressing MnSOD expression using small interfering RNA (siRNA) on the stemness, tumorigenicity, and viability of BCSCs. Materials and Methods: In vitro transfection of ALDH1+ BCSCs was performed using 33 and 66 µM specific MnSOD siRNA under standard culture conditions. Total RNA and protein were extracted from the transfected cells using TriPure® Isolation Reagent and RIPA® lysis buffer. Cell viability was measured using a trypan blue exclusion assay. The relative expression of MnSOD and OCT4 mRNAs was analyzed using one-step quantitative reverse transcription polymerase chain reaction. MnSOD activity was determined by xanthine oxidase inhibition assay (RanSOD® kit). Cellular superoxides were measured using a dihydroethidium assay, and tumorigenicity was observed with mammosphere-forming unit. Results: After siRNA incubation for 48 h, MnSOD was suppressed by 0.176-fold (P < 0.01), MnSOD enzyme-specific activity was reduced 70.4%, cellular superoxide levels increased by 1.13-fold, OCT4 expression was suppressed by 1.98-fold (P < 0.05), and mammosphere-forming unit decreased by 36.5% (P < 0.05) compared with the corresponding negative controls. The viability of the ALDH1+ BCSCs was reduced 75% (P < 0.05). Conclusion: Our results suggest that suppression of MnSOD expression may be a promising target to reduce stemness and tumorigenicity of ALDH1+ BCSCs. [ABSTRACT FROM AUTHOR]

Recombinant hybrid Manganese superoxide dismutase from Staphyloccus saphropyticus/S. equorum (rMnSODSeq) exhibits stability at high temperatures. The enzyme occurs as a dimer that dissociates around 52 °C prior to unfolding of the monomer around 64 °C, demonstrating contribution of the dimeric form to stability. Here, structure – activity relationship of rMnSODSeq was evaluated on the basis of its activity and stability in the presence of inhibitors, NaCl, denaturants, detergents, reducing agents, and at different pH values. The activity was evaluated at both 37 °C and 52 °C, which the latter is the temperature for dissociation of the dimer. Dimer to monomer transition coincided with significant decrease in residual activity at 52 °C. However, the activity assay results at 52 °C and 37 °C suggest spontaneous re-association of the monomer into dimer. Intriguingly, various new species with melting temperature ( T M ) values other than those of the dimer or monomer were observed. These species displayed medium to comparable level of residual activities to the native at 37 °C. This report suggests that dimer to monomer transition may be not the only explanation for activity loss or decrease. [ABSTRACT FROM AUTHOR]

Background: It has been widely reported that breast cancer aggressiveness may be driven by breast cancer stem cells (BCSCs). BCSCs display stemness properties that include self-renewal, tumourigenicity and pluripotency. The regulation of gene expression may have important roles in BCSC stemness and aggressiveness. Thus, the aim of this study was to examine the stemness and aggressiveness gene expression profile of BCSCs compared to MCF-7 and MDA-MB-231 breast cancer cells., Methods: Human ALDH1+ BCSCs were grown in serum-free Dulbecco's Modified Eagle Medium (DMEM)/F12, while MCF-7 and MDA-MB-231 were cultured in DMEM supplemented with 10% foetal bovine serum under standard conditions. Total RNA was extracted using the Tripure Isolation Reagent. The relative mRNA expressions of OCT4, ALDH1A1 and CD44 associated with stemness as well as TGF-β1, TβR1, ERα1 and MnSOD associated with aggressiveness in BCSCs and MCF-7 cells were determined using the quantitative real-time PCR (qRT-PCR)., Results: The mRNA expressions of OCT4 (5.19-fold ± 0.338; P = 0.001), ALDH1A1 (3.67-fold ± 0.523; P = 0.006), CD44 (2.65-fold ± 0.307; P = 0.006), TGF -β 1 (22.89-fold ± 6.840; P = 0.015), TβR1 (3.74-fold ± 1.446; P = 0.045) and MnSOD (4.6-fold ± 1.096; P = 0.014) were higher in BCSCs than in MCF-7 but were almost similar to MDA-MB-231 cells. In contrast, the ERα1 expression of BCSCs (0.97-fold ± 0.080; P = 0.392) was similar to MCF-7 cells, indicating that BSCSs are oestrogen-dependent breast cancer cells., Conclusion: The oestrogen-dependent BCSCs express stemness and aggressiveness genes at a higher level compared to oestrogen-dependent MCF-7 but are almost similar to oestrogen-independent MDA-MB-231 cells., Competing Interests: Conflict of Interest None., (© Penerbit Universiti Sains Malaysia, 2019.)