ABSTRACT
Thioredoxin reductase (TrxR) is one class of the most important antioxidant selenoproteins and is involved in regulating tumor genesis and progression. It has been reported that naphthoquinones can target and inhibit TrxR1 activity therefore produce reactive oxygen species (ROS) mediated by TrxR1, resulting into cellular redox imbalance and making the naphthoquinone compounds to become potential antitumor chemotherapy drugs. The purpose of this work is to explore the interaction between TrxR1 and menadione using biochemical and mass-spectrometric (MS) analyses, to further reveal the detailed mechanisms of TrxR1-mediated naphthoquinone reduction and inhibition of TrxR1 by naphthoquinone compounds. Using the site-directed mutagenesis and recombinantly expressed TrxR1 variants, we measured the steady-state kinetic parameters of menadione reduction mediated by TrxR1 and its variants, performed the inhibition analysis of menadione on TrxR1 activity, and eventually identified the interaction between menadione and TrxR1 through MS analysis. We found that Sec-to-Cys mutation at residue of 498 significantly enhanced the efficiency of TrxR1-mediated menadione reduction, though the Sec⁴⁹⁸ is capable to catalyze the menadione reduction, indicating that TrxR1-mediated menadione reduction is dominantly in a Se-independent manner. Mutation experiments showed that Cys⁴⁹⁸ is mainly responsible for menadione catalysis in comparison to Cys⁴⁹⁷, while the N-terminal Cys⁶⁴ is slightly stronger than Cys⁵⁹ regarding the menadione reduction. LC-MS results detected that TrxR1 was arylated with one molecule of menadione, suggesting that menadione irreversibly modified the hyper-reactive Sec residue at the C-terminus of selenoprotein TrxR1. This study revealed that TrxR1 catalyzes the reduction of menadione in a Se-independent manner meanwhile its activity is irreversibly inhibited by menadione. Hereby it will be useful for the research and development of naphthoquinone anticancer drugs targeting TrxR1.
Subject(s)
Catalysis , Drug Development , Oxidation-Reduction , Thioredoxin Reductase 1/metabolism , Vitamin K 3/metabolismABSTRACT
@#To investigate the inhibitory effect of sildenafil on Caco-2 cell proliferation and its anti-inflammatory effect on menadione-induced NCM460 cell inflammation model, MTT assay was used to determine cell proliferation. Intracellular reactive oxygen species(ROS)and nitric oxide(NO)levels were detected by fluorescent probe. Western blot was used to detect the expression of eNOS/ERK/JNK pathway related proteins in Caco-2 cells and correlated inflammatory cytokines in NCM460 cells. The effect of sildenafil on the growth of two probiotics was determined by spectrophotometry. Results showed that sildenafil signi-ficantly inhibited the proliferation of Caco-2 cells and enhanced the expression levels of eNOS, p-eNOS, p-JNK1/2 and p-ERK1/2 proteins in Caco-2 cells; while after adding NG-nitro-L-arginine methyl ester(L-NAME), the expression levels of eNOS, p-eNOS, p-JNK1/2 and p-ERK1/2 proteins were significantly lower than those of the sildenafil group. Compared with the menadione group, sildenafil significantly reduced ROS levels in NCM460 cells and inhibited the expression levels of IL-6, IL-1β, p62, and TNF-α. Moreover, high concentrations of sildenafil had no obvious toxic effects on Lactobacillus casei and Lactobacillus rhamnosus. Thus, the results indicated that sildenafil could effectively inhibit the intestinal inflammatory response without affecting the balance of the intestinal flora, and prevent colorectal cancer by reducing the oxidative stress responses in the intestinal cells.
ABSTRACT
Vitamins are vital for normal growth and survival of living organisms and they are distributed in feedstuffs in small quantities. This review is focused on the liposoluble vitamins (A, D, E and K) in the diets and metabolic responses of the Argentine penaeoid shrimps Pleoticus muelleri and Artemesia longinaris, distributed along the South American coast line. Growth, survival and histological analyses serve as indicators of the nutritional value derived from vitamin deficiency. Liposoluble vitamins are also related to stress, antioxidant defense and immune response of shrimps. Effective diet for shrimp culture that provide not only macronutrients including protein and lipid but also micronutrients such as vitamins for optimal growth is an ever improving subject. This review may help formulating suitable feeds for shrimps.
ABSTRACT
Candida glabrata is an opportunistic fungal pathogen that can cause severe invasive infections and can evade phagocytic cell clearance. We are interested in understanding the virulence of this fungal pathogen, in particular its oxidative stress response. Here we investigated C. glabrata, Saccharomyces cerevisiae and Candida albicans responses to two different oxidants: menadione and cumene hydroperoxide (CHP). In log-phase, in the presence of menadione, C. glabrata requires Cta1p (catalase), while in a stationary phase (SP), Cta1p is dispensable. In addition, C. glabrata is less resistant to menadione than C. albicans in SP. The S. cerevisiae laboratory reference strain is less resistant to menadione than C. glabrata and C. albicans; however S. cerevisiaeclinical isolates (CIs) are more resistant than the lab reference strain. Furthermore, S. cerevisiae CIs showed an increased catalase activity. Interestingly, in SP C. glabrata and S. cerevisiae are more resistant to CHP than C. albicans and Cta1p plays no apparent role in detoxifying this oxidant.