H2O2-dependent hyperoxidation of peroxiredoxin 6 (Prdx6) plays a role in cellular toxicity via up-regulation of iPLA2 activity

Peroxiredoxin 6 (Prdx6) is a bifunctional enzyme with peroxidase activity and Ca2+-independent phospholipase A2 (iPLA2) activity. Here, we report that H2O2-induced cellular toxicity acts through Prdx6 hyperoxidation. Under high concentrations of H2O2 (> 100 microm), Prdx6, and 2-Cys Prdxs were hyperoxidized. Contrary to hyperoxidation of 2-Cys Prdxs, hyperoxidation of Prdx6 was irreversible in vivo. Surprisingly, H2O2-induced cell cycle arrest at the G2/M transition correlated with hyperoxidation and increased iPLA2 activity of Prdx6. This arrest was also associated with up-regulation of p53 and p21 and with down-regulation of cyclin B1. Furthermore, the H2O2-mediated increase in iPLA2 activity was dramatically abolished in a hyperoxidation mutant (C47A), an iPLA2 mutant (S32A), and a double mutant (C47A/S32A) of Prdx6, demonstrating the essential requirement of Prdx6 C47 hyperoxidation for its iPLA2 activity. Together, our results demonstrate that H2O2-mediated hyperoxidation of Prdx6 induces cell cycle arrest at the G2/M transition through up-regulation of iPLA2 activity.     

Antizyme suppression leads to an increment of the cellular redox potential and an induction of HIF-1alpha: its involvement in resistance to gamma-radiation

The mammalian antizyme (AZ) promotes ubiqutin-independent degradation of ornithine decarboxylase, a key enzyme in polyamine biosynthesis. This study shows that AZ suppression in human lung carcinoma A549 cells caused growth defects and death, but made the cells resistant to DNA damaging agents such as gamma-radiation and cisplatin. In these cells, the cellular redox potential (glutathione/glutathione disulfide [GSH/GSSG] ratio) was increased and thus intracellular reactive oxygen species were severely diminished, which might cause growth defects and cell death. The increase of cellular redox potential was mainly caused by dramatic increase of the cytoplasmic nicotinamide adenine dinucleotide phosphate (NADP)(+)-dependent isocitrate dehydrogenase, which generates the reducing equivalents NADPH. In the AZ-suppressed cells, the hypoxia inducible factor 1alpha (HIF-1alpha) was also increased. As in other cases which showed an increment of HIF-1alpha and the cellular redox potential, the AZ-suppressed cells showed resistance to gamma-radiation and anticancer drugs. Therefore, these facts might be considered as important for the use of radio- and chemotherapy on tumor cells which show an unbalance in their polyamine levels.     

Role of Arabidopsis CHL27 protein for photosynthesis, chloroplast development and gene expression profiling

In Chl biosynthesis, aerobic Mg-protoporphyrin IX monomethyl ester (MPE) cyclase is a key enzyme involved in the synthesis of protochlorophyllide a, and its membrane-bound component is known to be encoded by homologs of CHL27 in photosynthetic bacteria, green algae and plants. Here, we report that the Arabidopsis chl27-t knock-down mutant exhibits retarded growth and chloroplast developmental defects that are caused by damage to PSII reaction centers. The mutant contains a T-DNA insertion within the CHL27 promoter that dramatically reduces the CHL27 mRNA level. chl27-t mutant plants grew slowly with a pale green appearance, suggesting that they are defective in Chl biosynthesis. Chl fluorescence analysis showed significantly low photosynthetic activity in chl27-t mutants, indicating damage in their PSII reaction centers. The chl27-t mutation also conferred severe defects in chloroplast development, including the unstacking of thylakoid membranes. Microarray analysis of the chl27-t mutant showed repression of numerous nuclear genes involved in photosynthesis, including those encoding components of light-harvesting complex I (LHCI) and LHCII, and PSI and PSII, which accounts for the defects in photosynthetic activity and chloroplast development. In addition, the microarray data also revealed the significant repression of genes such as PORA and AtFRO6 for Chl biosynthesis and iron acquisition, respectively, and, furthermore, implied that there is cross-talk in the Chl biosynthetic pathway among the PORA, AtFRO6 and CHL27 proteins.     

Time-course Changes in Immunoreactivities of Glucokinase and Glucokinase Regulatory Protein in the Gerbil Hippocampus Following Transient Cerebral Ischemia

Glucose is a main energy source for normal brain functions. Glucokinase (GK) plays an important role in glucose metabolism as a glucose sensor, and GK activity is modulated by glucokinase regulatory protein (GKRP). In this study, we examined the changes of GK and GKRP immunoreactivities in the gerbil hippocampus after 5 min of transient global cerebral ischemia. In the sham-operated-group, GK and GKRP immunoreactivities were easily detected in the pyramidal neurons of the stratum pyramidale of the hippocampus. GK and GKRP immunoreactivities in the pyramidal neurons were distinctively decreased in the hippocampal CA1 region (CA), not CA2/3, 3 days after ischemia–reperfusion (I–R). Five days after I–R, GK and GKRP immunoreactivities were hardly detected in the CA1, not CA2/3, pyramidal neurons; however, at this point in time, GK and GKRP immunoreactivities were newly expressed in astrocytes, not microglia, in the ischemic CA1. In brief, GK and GKRP immunoreactivities are changed in pyramidal neurons and newly expressed in astrocytes in the ischemic CA1 after transient cerebral ischemia. These indicate that changes of GK and GKRP expression may be related to the ischemia-induced neuronal damage/death.     

Prevalence of and Factors Associated with Albuminuria in the Korean Adult Population: The 2011 Korea National Health and Nutrition Examination Survey

Background

Microalbuminuria is associated with increased risk of renal disease and cardiovascular diseases even in non-diabetic subjects. High incidence rates of microalbuminuria have been found in a number of population-based studies. However, the prevalence and risk factors associated with microalbuminuria in the general population in Korea are unclear.

Objectives

The present study was performed to estimate the prevalence of microalbuminuria and investigate the associated risk factors in the general adult population using the Fifth Korea National Health and Nutrition Examination Survey (KNHANES V-2) data from 2011.

Methods

A total of 5,202 participants (mean age, 45.6 years; men, 2,337; women, 2,865) were included in the analysis. Microalbuminuria was evaluated in participants of KNHANES V-2 based on the urine albumin–creatinine ratio. Estimated glomerular filtration rate was calculated using the Modification of Diet in Renal Disease study equation.

Results

The weighted prevalence of microalbuminuria was 5.2% (95% CI, 4.4–6.1) in the general population. The prevalence of albuminuria is increased with age. After adjustment for age and sex, the presence of albuminuria was associated with increased waist circumference, systolic and diastolic blood pressure, aspartate aminotransferase, triglyceride, fasting plasma glucose, and the presence of hypertension and diabetes. In logistic regression analyses, older age, female sex, diabetes, hypertension, and serum aspartate aminotransferase were independently associated with the presence of albuminuria.

Conclusion

The prevalence of microalbuminuria was found to be 5.2%, and conventional risk factors for cardiovascular diseases are closely related to the presence of microalbuminuria in Korea. Microalbuminuria may be a useful marker to identify individuals with increased risk of cardiovascular disease.     

BetaDock: Shape-Priority Docking Method Based on Beta-Complex

Abstract

This paper presents an approach and a software, BetaDock, to the docking problem by putting the priority on shape complementarity between a receptor and a ligand. The approach is based on the theory of the β-complex. Given the Voronoi diagram of the receptor whose topology is stored in the quasi-triangulation, the β-complex corresponding to water molecule is computed. Then, the boundary of the β-complex defines the β-shape which has the complete proximity information among all atoms on the receptor boundary. From the β-shape, we first compute pockets where the ligand may bind. Then, we quickly place the ligand within each pocket by solving the singular value decomposition problem and the assignment problem. Using the conformations of the ligands within the pockets as the initial solutions, we run the genetic algorithm to find the optimal solution for the docking problem. The performance of the proposed algorithm was verified through a benchmark test and showed that BetaDock is superior to a popular docking software AutoDock 4.     

Calpain inhibitory flavonoids isolated from Orostachys japonicus

The n-butanol (n-BuOH) fraction of Orostachys japonicus A. Berger (Crassulaceae) significantly inhibited calpain activity. Through the activity-guided isolation from the n-BuOH fraction, herbacetin 8-O-α-D-ribopyranoside (1), kaempferol (2), quercetin (3), afzelin (4), astragalin (5), isoquercetin (6) and quercitrin (7) were obtained. Their structures were determined by spectroscopic techniques. Among them, compound 3 and 5 had significant calpain inhibitory activities.