H2O2-induced Oxidative Conditions Research Articles

Tumoricidal effects of unprimed and curcumin-primed adipose-derived stem cells on human hepatoma HepG2 cells under oxidative conditions

IntroductionAdipose-derived stem cells (ASCs) have been proven to have tumoricidal effects against hepatic cancer cell lines. However, it appears that exposure to oxidative microenvironment compromises the potential outcome of ASCs in real hepatoma. Herein, we aimed to examine the tumoricidal effects of ASCs under oxidative conditions and to investigate the impact of curcumin priming on ASCs’ therapeutic potential. MethodsWe used human hepatoma (HepG2) cells in a coculture system with unprimed or curcumin-primed ASCs (Cur-ASCs) under H2O2-induced oxidative conditions. To investigate HepG2 proliferation and death, MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) and annexin V staining assays were performed. To determine the HepG2 migration and invasion potential, the scratch healing and the transwell invasion assays were performed. To evaluate the expression of apoptosis-protein markers, Western blotting was performed. ResultsCur-ASCs suppressed HepG2 proliferation, migration, and invasion as well as prompted apoptosis more significantly compared to unprimed ASCs under oxidative conditions. Expressional studies also revealed an obvious decline in the BCL-2/BAX ratio in HepG2 cocultured with Cur-ASCs. In addition, we noticed a marked elevation of apoptosis and senescence in unprimed ASCs compared to Cur-ASCs after coculture experiments, which demonstrated that curcumin priming preserved the survival and growth potential of ASCs; hence, Cur-ASCs performed better tumoricidal functions under oxidative conditions. ConclusionOur findings suggest that ASCs have the intrinsic ability to induce cell death in HepG2 cells; however, their functions can be compromised under oxidative conditions. We believe that curcumin priming is an effective approach for improving the therapeutic effectiveness of ASCs in the cancerous microenvironment.

Changing oxidoreduction potential to improve water-soluble yellow pigment production with Monascus ruber CGMCC 10910

BackgroundMonascus pigments are widely used in the food and pharmaceutical industries due to their safety to human health. Our previous study found that glucose concentration induced extracellular oxidoreduction potential (ORP) changes could influence extracellular water-soluble yellow pigment production by Monascus ruber CGMCC 10910 in submerged fermentation. In this study, H2O2 and dithiothreitol (DTT) were used to change the oxidoreduction potential for investigating the effects of oxidative or reductive substances on Monascus yellow pigment production by Monascus ruber CGMCC 10910.ResultsThe extracellular ORP could be controlled by H2O2 and DTT. Both cell growth and extracellular water-soluble yellow pigment production were enhanced under H2O2-induced oxidative (HIO) conditions and were inhibited under dithiothreitol-induced reductive conditions. By optimizing the amount of H2O2 added and the timing of the addition, the yield of extracellular water-soluble yellow pigments significantly increased and reached a maximum of 209 AU, when 10 mM H2O2 was added on the 3rd day of fermentation with M. ruber CGMCC 10910. Under HIO conditions, the ratio of NADH/NAD+ was much lower than that in the control group, and the expression levels of relative pigment biosynthesis genes were up-regulated; moreover, the activity of glucose-6-phosphate dehydrogenase (G6PDH) was increased while 6-phosphofructokinase (PFK) activity was inhibited.ConclusionsOxidative conditions induced by H2O2 increased water-soluble yellow pigment accumulation via up-regulation of the expression levels of relative genes and by increasing the precursors of pigment biosynthesis through redirection of metabolic flux. In contrast, reductive conditions induced by dithiothreitol inhibited yellow pigment accumulation. This experiment provides a potential strategy for improving the production of Monascus yellow pigments.

Protective effect of madecassoside on H2O2-induced oxidative stress and autophagy activation in human melanocytes.

BackgroundCentella asiatica (L.) Urb. is a traditional Chinese medicine that has many medical applications, including wound healing and anti-oxidation. Some traditional Chinese Medicine doctors have found that it has therapeutic effects for external use in the repigmentation of vitiligo and post-inflammatory hypopigmentation. This study was designed to evaluate the effects of madecassoside, a major bioactive component of C. asiatica, on oxidative stress in human melanocytes and its possible mechanism of action.ResultsIn H2O2-induced oxidative conditions, madecassoside inhibited melanocyte dendrite retraction, improved MMP and reduced the accumulation of [Ca2+]i in a concentration-dependent manner. Observations by TEM showed that madecassoside attenuated the damage of mitochondria in human melanocytes caused by oxidative stress. Furthermore, autophagy activation was demonstrated by AO staining and an increased LC3-II/LC3-I ratio.Materials and MethodsNormal human melanocytes were treated with 0.01 mM H2O2 and varying concentrations of madecassoside (0, 10, 50, 100 μg/mL). Subsequently, the retraction velocity of melanocyte dendrites was assessed. Determination of mitochondrial membrane potential (MMP, ΔΨm) was performed by flow cytometry and intracellular calcium ([Ca2+]i) level were measured. Alterations of mitochondrial ultrastructure were observed by transmission electron microscopy (TEM). Acridine orange (AO) staining was used to measure autophagy. The LC3-II/LC3-I ratio, an indicator of autophagosome formation, was analyzed by western blot.ConclusionsThese results demonstrate the antioxidative effect of madecassoside on human melanocytes subjected to oxidative damage via the activation of autophagy. Moreover, madecassoside could be a promising treatment for vitiligo mainly caused by oxidative stress.