On March 11, 2011, an earthquake led to major problems at the Fukushima Daiichi Nuclear Power Plant. A 14-m high tsunami triggered by the earthquake disabled all AC power to Units 1, 2, and 3 of the Power Plant, and carried off fuel tanks for emergency diesel generators. Despite many efforts, cooling systems did not work and hydrogen explosions damaged the facilities, releasing a large amount of radioactive material into the environment. In this review, we describe the environmental impact of the nuclear accident, and the fundamental biological effects, acute and late, of the radiation. Possible medical countermeasures to radiation exposure are also discussed.
NADPH oxidase is a superoxide (O2•−)-generating enzyme first identified in phagocytes, essential for their bactericidal activities. Later, in non-phagocytes, production of O2•− was also demonstrated in an NADPH-dependent manner. In the last decade, several non-phagocyte-type NADPH oxidases have been identified. The catalytic subunit of these oxidases, NOX, constitutes the NOX family. There are five homologs in the family, NOX1 to NOX5, and two related enzymes, DUOX1 and DUOX2. Transgenic or gene-disrupted mice of the NOX family have also been established. NOX/DUOX proteins possess distinct features in the dependency on other components for their enzymatic activities, tissue distributions, and physiological functions. This review summarized the characteristics of the NOX family proteins, especially focused on their functions clarified through studies using gene-modified mice.
Thioredoxin binding protein −2/ thioredoxin interacting protein is an α-arrestin protein that has attracted much attention as a multifunctional regulator. Thioredoxin binding protein −2 expression is downregulated in tumor cells and the level of thioredoxin binding protein is correlated with clinical stage of cancer. Mice with mutations or knockout of the thioredoxin binding protein −2 gene are much more susceptible to carcinogenesis than wild-type mice, indicating a role for thioredoxin binding protein −2 in cancer suppression. Studies have also revealed roles for thioredoxin binding protein −2 in metabolic control. Enhancement of thioredoxin binding protein −2 expression causes impairment of insulin sensitivity and glucose-induced insulin secretion, and β-cell apoptosis. These changes are important characteristics of type 2 diabetes mellitus. Thioredoxin binding protein −2 regulates transcription of metabolic regulating genes. Thioredoxin binding protein −2-like inducible membrane protein/ arrestin domain containing 3 regulates endocytosis of receptors such as the β2-adrenergic receptor. The α-arrestin family possesses PPXY motifs and may function as an adaptor/scaffold for NEDD family ubiquitin ligases. Elucidation of the molecular mechanisms of α-arrestin proteins would provide a new pharmacological basis for developing approaches against cancer and type 2 diabetes mellitus.
The stomach is a sensitive digestive organ that is susceptible and exposed to exogenous pathogens from the diet. In response to such pathogens, the stomach induces oxidative stress, which might be related to the development of gastric organic disorders such as gastritis, gastric ulcers, and gastric cancer, as well as functional disorders such as functional dyspepsia. In particular, the bacterium Helicobacter pylori plays a major role in eliciting and confronting oxidative stress in the stomach. The present paper summarizes the pathogenesis of oxidative stress in the stomach during the development of various stomach diseases.
Temperature-dependent free radical reactions were investigated using nitroxyl radicals as redox probes. Reactions of two types of nitroxyl radicals, TEMPOL (4-hydroxyl-2,2,6,6-tetramethylpiperidine-N-oxyl) and carbamoyl-PROXYL (3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl), were tested in this paper. Heating a solution containing a nitroxyl radical and a reduced form of glutathione (GSH) caused temperature-dependent decay of electron paramagnetic resonance (EPR) signal of the nitroxyl radical. Heating a solution of the corresponding hydroxylamine form of the nitroxyl radical showed EPR signal recovery. The GSH-dependent reduction of nitroxyl radicals at 70°C was suppressed by antioxidants, spin trapping agents, and/or bubbling N2 gas, although heating carbamoyl-PROXYL with GSH showed temporarily enhanced signal decay by bubbling N2 gas. Since SOD could restrict the GSH-dependent EPR signal decay of TEMPOL, O2•− is related with this reaction. O2•− was probably generated from dissolved oxygen in the reaction mixture. Oxidation of the hydroxylamines at 70°C was also suppressed by bubbling N2 gas. Heating a solution of spin trapping agent, DMPO (5,5-dimethyl-1-pyrroline-N-oxide) showed a temperature-dependent increase of the EPR signal of the hydroxyl radical adduct of DMPO. Synthesis of hydroxyl radical adduct of DMPO at 70°C was suppressed by antioxidants and/or bubbling N2 gas. The results suggested that heating an aqueous solution containing oxygen can generate O2•−.
Nε-(Hexanoyl)lysine, formed by the reaction of lysine with n-6 lipid hydroperoxide, is a lipid peroxidation marker during the initial stage of oxidative stress. The aim of the present study is to indentify Nε-(hexanoyl)lysine-modified proteins in neoplastic transformed gastric mucosal cells by N-methyl-N’-nitro-N-nitrosoguanidine, and to compare the levels of these proteins between gastric mucosal cells and normal gastric cells. Much greater fluorescence of 2-[6-(4'-hydroxy)phenoxyl-3H-xanthen-3-on-9-yl]benzoic acid, an index of the intracellular levels of reactive oxygen species, was observed for gastric mucosal cells compared to normal gastric cells. Nε-(Hexanoyl)lysine-modified proteins were detected by SDS-PAGE or two-dimensional electrophoresis and Western blotting using anti-Nε-(hexanoyl)lysine polyclonal antibody, and a protein band of between 30–40 kDa was clearly increased in gastric mucosal cells compared to normal gastric cells. Two Nε-(hexanoyl)lysine-modified protein spots in gastric mucosal cells were identified as the tropomyosin 1 protein by mass spectrometry using a MASCOT search. The existence of Nε-(hexanoyl)lysine modification in tropomyosin 1 was confirmed by Western blotting of SDS-PAGE-separated or two-dimensional electrophoresis-separated proteins as well as by the immunoprecipitation with anti-tropomyosin 1 antibody. These data indicate that Nε-(hexanoyl)lysine modification of tropomyosin 1 may be related to neoplastic transformation by N-methyl-N'-nitro-N-nitrosoguanidine in gastric epithelial cells.
Excess production of nitric oxide by activated macrophages via inducible nitric oxide synthase leads to the development of various inflammatory diseases. Heme oxygenase-1 expression via activation of nuclear factor-erythroid 2-related factor 2 inhibits nitric oxide production and inducible nitric oxide synthase expression in activated macrophages. Okanin is one of the most abundant chalcones found in the genus Bidens (Asteraceae) that is used as various folk medications in Korea and China for treating inflammation. Here, we found that okanin (possessing the α-β unsaturated carbonyl group) induced heme oxygenase-1 expression via nuclear factor-erythroid 2-related factor 2 activation in RAW264.7 macrophages. 3-Penten-2-one, of which structure, as in okanin, possesses the α-β unsaturated carbonyl group, also induced nuclear factor-erythroid 2-related factor 2-dependent heme oxygenase-1 expression, while both 2-pentanone (lacking a double bond) and 2-pentene (lacking a carbonyl group) were virtually inactive. In lipopolysaccharide-activated RAW264.7 macrophages, both okanin and 3-penten-2-one inhibited nitric oxide production and inducible nitric oxide synthase expression via heme oxygenase-1 expression. Collectively, our findings suggest that by virtue of its α-β unsaturated carbonyl functional group, okanin can inhibit nitric oxide production and inducible nitric oxide synthase expression via nuclear factor-erythroid 2-related factor 2-dependent heme oxygenase-1 expression in lipopolysaccharide-activated macrophages.
In inflammatory bowel diseases, interleukin-1β production is accelerated. Butyrate, a short chain fatty acid, plays an important role in inflammatory bowel diseases. We investigated the effect of butyrate on interleukin-1β production in macrophage and elucidated its underlying mechanism. We stimulated THP-1 cells, a human premonocytic cell line, by lipopolysaccharide alone and by butyrate with lipopolysaccharide. Butyrate with lipopolysaccharide increased interleukin-1β production more than lipopolysaccharide alone. Butyrate with lipopolysaccharide increased caspase-1 activity more than lipopolysaccharide alone. As for the phosphorylation pathway, PD98059 (ERK1/2 inhibitor), SB203580 (p38 MAPK inhibitor), SP600125 (JNK1/2 inhibitor) decreased caspase-1 activity and interleukin-1β production to approximately 50% of the controls. Pertussis toxin (G protein-coupled signal transduction pathway inhibitor) also reduced interleukin-1β production to approximately 50%. Butyrate with lipopolysaccharide increased reactive oxygen species levels more than lipopolysaccharide alone. The addition of N-acetyl L-cysteine reduced reactive oxygen species levels to a level similar to that of lipopolysaccharide alone. Butyrate with lipopolysaccharide increased nitric oxide production more than lipopolysaccharide alone, and the addition of N-acetyl L-cysteine reduced the elevated amount of nitric oxide. In conclusions, butyrate enhances interleukin-1β production by activating caspase-1, via reactive oxygen species, the phosphorylation of MAPK, and G protein mediated pathways in lipopolysaccharide stimulated THP-1 cells.
We examined whether continuous supplementation with branched-chain amino acids phosphorylates ribosomal protein S6, a downstream effector of mammalian target of rapamycin, and improves hypoalbuminemia of rats with chronic liver disease. Sprague-Dawley rats were fed a casein diet (control group) or a branched-chain amino acid-supplemented casein diet (branched-chain amino acid group) for 11 weeks with repeated injections of carbon tetrachloride. Throughout this experimental period, no significant difference in plasma albumin concentration was seen between groups. The percentage of reduced albumin within total plasma albumin gradually decreased in both control and branched-chain amino acid groups. After 11 weeks with supplementation, phosphorylation of ribosomal protein S6 was significantly increased in the liver of rats in the branched-chain amino acid group compared with the control group. Furthermore, the percentage of reduced albumin within total albumin was significantly higher in the branched-chain amino acid group than in the control group. These results indicate that continuous supplementation with branched-chain amino acids in rats with chronic liver disease induces phosphorylation of hepatic ribosomal protein S6 and attenuates decreases in the percentage of reduced albumin, although levels of plasma albumin are not increased.
This study aimed to evaluate the relationship between gut probiotic flora and nonalcoholic fatty liver disease in a diet-induced rat model, and to compare the effects of two different probiotic strains on nonalcoholic fatty liver disease. Forty male Sprague-Dawley rats were randomized into 4 groups for 12 weeks: control (standard rat chow), model (fat-rich diet), Lactobacillus (fat-rich diet plus Lactobacillus acidophilus), and Bifidobacterium (fat-rich diet plus Bifidobacterium longum) groups. Probiotics were provided to rats in drinking water (1010/ml). Gut bifidobacteria and lactobacilli were obviously lower at weeks 8 and 10, respectively, in the model group compared with the control group. Supplementation with Bifidobacterium significantly attenuated hepatic fat accumulation (0.10 ± 0.03 g/g liver tissue) compared with the model group (0.16 ± 0.03 g/g liver tissue). However, there was no improvement in intestinal permeability in either the Lactobacillus or the Bifidobacterium group compared with the model group. In all 40 rats, the hepatic total lipid content was negatively correlated with gut Lactobacillus (r = −0.623, p = 0.004) and Bifidobacterium (r = −0.591, p = 0.008). Oral supplementation with probiotics attenuates hepatic fat accumulation. Further, Bifidobacterium longum is superior in terms of attenuating liver fat accumulation than is Lactobacillus acidophilus.
The vascular endothelium is important for the early and late effects observed in lethally irradiated tissue and organs. We examined the effects of exogenously added superoxide dismutase on cell survival and angiogenesis in lethally irradiated human primary umbilical vein endothelial cells. Cell survival was significantly improved in superoxide dismutase-treated cells; the addition of superoxide dismutase to cells after irradiation was also effective for increased survival, as it was before irradiation. Moreover, treatment of cells with superoxide dismutase enhanced the phosphorylation of mitogen-activated protein/extracellular signal-regulated kinase/extracellular signal regulated kinases 1 and 2 in human primary umbilical vein endothelial cells. The addition of superoxide dismutase to cells after irradiation attenuated the reduction of angiogenesis by irradiation, and inhibition of the mitogen-activated protein/extracellular signal-regulated kinase/extracellular signal regulated kinases signaling pathway abrogated the rescue effect of superoxide dismutase. Our results suggest that superoxide dismutase rescues human primary umbilical vein endothelial cells from endothelial dysfunction caused by irradiation via a pathway requiring activation of mitogen-activated protein/extracellular signal-regulated kinase/extracellular signal regulated kinases 1 and 2.
The cholesterol ozonolysis products secosterol-A and its aldolization product secosterol-B were recently detected in human atherosclerotic tissues and brain specimens, and have been postulated to play pivotal roles in the pathogenesis of atherosclerosis and neurodegenerative diseases. We examined several oxidized cholesterol metabolites including secosterol-A, secosterol-B, 25-hydroxycholesterol, 5β,6β-epoxycholesterol and 7-ketocholesterol for their effects on the activities of three nitric oxide synthases. In contrast to other oxidized metabolites, secosterol-A was found to be a potent inhibitor against the neuronal- and endothelial-type, but not the inducible-type nitric oxide synthase, with IC50 values of 22 ± 1 and 50 ± 5 μM, respectively. The calmodulin-binding regions of the neuronal- and endothelial-nitric oxide synthases contain lysine residues which are not present in the inducible-type nitric oxide synthase. Secosterol-A modifies proteins through the formation of a Schiff base with the lysine epsilon-amino group. It is possible that secosterol-A modifies lysine residues of constitutive nitric oxide synthases, leading to the inhibition of enzymatic activities. As nitric oxide is a critical signaling molecule in vascular function and in long-term potentiation, its reduced production through inhibition of constitutive nitric oxide synthases by secosterol-A may contribute to the development of atherosclerosis and memory impairment in particular neurodegenerative diseases.