There is an apparent overlap between areas in the USA where the herbicide, atrazine (ATZ), is heavily used and obesity-prevalence maps of people with a BMI over 30. Given that herbicides act on photosystem II of the thylakoid membrane of chloroplasts, which have a functional structure similar to mitochondria, we investigated whether chronic exposure to low concentrations of ATZ might cause obesity or insulin resistance by damaging mitochondrial function. Sprague-Dawley rats (n = 48) were treated for 5 months with low concentrations (30 or 300 µg kg−1 day−1) of ATZ provided in drinking water. One group of animals was fed a regular diet for the entire period, and another group of animals was fed a high-fat diet (40% fat) for 2 months after 3 months of regular diet. Various parameters of insulin resistance were measured. Morphology and functional activities of mitochondria were evaluated in tissues of ATZ-exposed animals and in isolated mitochondria. Chronic administration of ATZ decreased basal metabolic rate, and increased body weight, intra-abdominal fat and insulin resistance without changing food intake or physical activity level. A high-fat diet further exacerbated insulin resistance and obesity. Mitochondria in skeletal muscle and liver of ATZ-treated rats were swollen with disrupted cristae. ATZ blocked the activities of oxidative phosphorylation complexes I and III, resulting in decreased oxygen consumption. It also suppressed the insulin-mediated phosphorylation of Akt. These results suggest that long-term exposure to the herbicide ATZ might contribute to the development of insulin resistance and obesity, particularly where a high-fat diet is prevalent.

Abbreviations: HIF-1α, hypoxia inducible factor-1α; STAT3, signal transducer and activator of transcription 3; VHL, von Hippel-Lindau Abstract Hypoxia-inducible factor 1α (HIF-1α) is rapidly degraded by the ubiquitin-proteasome pathway under normoxic conditions. Ubiquitination of HIF-1α is mediated by interaction with von Hippel-Lindau tumor suppressor protein (pVHL). In our previous report, we found that hypoxia-induced active signal transducer and activator of transcription3 (STAT3) accelerated the accumulation of HIF-1α protein and prolonged its half-life in solid tumor cells. However, its specific mechanisms are not fully understood. Thus, we examined the role of STAT3 in the mechanism of pVHL-mediated HIF-1α stability. We found that STAT3 interacts with C-terminal domain of HIF-1α and stabilizes HIF-1α by inhibition of pVHL binding to HIF-1α. The binding between HIF-1α and pVHL, negative regulator of HIF-1α stability, was interfered dose-dependently by overexpressed constitutive active STAT3. Moreover, we found that the enhanced HIF-1α protein levels by active STAT3 are due to decrease of poly-ubiquitination of HIF-1α protein via inhibition of interaction between pVHL and HIF-1α. Taken together, our results suggest that STAT3 decreases the pVHL-mediated ubiquitination of HIF-1α through competition with pVHL for binding to HIF-1 α, and then stabilizes HIF-1α protein levels.

Reactive oxygen species (ROS) attack guanine bases in DNA easily and form 8-hydroxydeoxyguanosine (8-OHdG), which can bind to thymidine rather than cytosine, based on which, the level of 8-OHdG is generally regarded as a biomarker of mutagenesis consequent to oxidative stress. For example, higher levels of 8-OHdG are noted in Helicobacter pylori-associated chronic atrophic gastritis as well as gastric cancer. However, we have found that exogenous 8-OHdG can paradoxically reduce ROS production, attenuate the nuclear factor-κB signaling pathway, and ameliorate the expression of proinflammatory mediators such as interleukin (IL)-1, IL-6, cyclo-oxygenase-2, and inducible nitric oxide synthase in addition to expression of nicotinamide adenine dinucleotide phosphate oxidase (NOX)-1, NOX organizer-1 and NOX activator-1 in various conditions of inflammation-based gastrointestinal (GI) diseases including gastritis, inflammatory bowel disease, pancreatitis, and even colitis-associated carcinogenesis. Our recent finding that exogenous 8-OHdG was very effective in either inflammation-based or oxidative-stress-associated diseases of stress-related mucosal damage has inspired the hope that synthetic 8-OHdG can be a potential candidate for the treatment of inflammation-based GI diseases, as well as the prevention of inflammation-associated GI cancer. In this editorial review, the novel fact that exogenous 8-OHdG can be a functional molecule regulating oxidative-stress-induced gastritis through either antagonizing Rac-guanosine triphosphate binding or blocking the signals responsible for gastric inflammatory cascade is introduced.

The tracheal tumors were eccentric, well-defined, polypoid masses in all cases. The endobronchial tumors were masses confined within the bronchus in all cases, and atelectasis or pneumonia of the distal parenchyma was frequently associated. Of the six hamartomas, one was a fatty mass, and two were nodules with calcification. The others were soft-tissue-density nodules. The lipomas manifested as fat density on CT scans in both cases. The other benign tumors were low-attenuating, soft-tissue-density masses without characteristic findings on CT scans.

OBJECTIVE -The production of reactive oxygen species is increased in diabetic patients, especially in those with poor glycemic control. We have investigated oxidative damage in type 2 diabetic patients using serum 8-hydroxyguanine (8-OHG) as a biomarker.RESEARCH DESIGN AND METHODS -We studied 41 type 2 diabetic patients and compared them with 33 nondiabetic control subjects. Serum 8-OHG concentration was assayed using high-pressure liquid chromatography.RESULTS -The type 2 diabetic patients had significantly higher concentrations of 8-OHG in their serum than the control subjects (5.03 Ϯ 0.69 vs. 0.96 Ϯ 0.15 pmol/ml; P Ͻ 0.01). There was no association between the levels of 8-OHG and HbA 1c . We also could not find any correlation between serum 8-OHG levels and age, duration of diabetes, serum lipids, or creatinine or albumin excretion rate. Creatinine clearance showed marginal correlation with serum 8-OHG levels (P ϭ 0.06). Among the diabetic patients, those with proliferative retinopathy had significantly higher 8-OHG levels than those with nonproliferative retinopathy or without retinopathy. Likewise, the serum 8-OHG levels in patients who had advanced nephropathy (azotemia) were higher than in patients with normoalbuminuria, microalbuminuria, or overt proteinuria.CONCLUSIONS -Our findings show that measuring serum 8-OHG is a novel convenient method for evaluating oxidative DNA damage. Diabetic patients, especially those with advanced microvascular complications, had significantly higher serum 8-OHG levels; this suggests that such changes may contribute to the development of microvascular complications of diabetes. Diabetes Care 24:733-737, 2001C onsiderable evidence has been accumulated to suggest that the production of reactive oxygen species (ROS) is increased in diabetic patients, especially in those with poor glycemic control (1-3). Excessive ROS can accelerate oxidative damage to macromolecules, including lipids and proteins, as well as to DNA. An increased production of malondialdehyde (MDA), a marker of lipid peroxidation, has been demonstrated in the erythrocyte membranes of diabetic patients, along with a depressed erythrocyte content of reduced glutathione (4). Moreover, there is a significant relationship between markers of lipid peroxidation and metabolic control in both type 1 and type 2 diabetic patients (5). Although there are fewer data regarding the oxidation of protein, a recent study by Suzuki et al. (6) demonstrated local oxidative stress and carbonyl modification of proteins in diabetic glomerulopathy.8-Hydroxydeoxyguanosine (8-OHdG), an ROS-induced modification of a purine residue in DNA, is a sensitive index of oxidative DNA damage (7). 8-OHdG in plasma increases with age (8), with cigarette smoking (9), and during tumorigenesis (10). The urinary level of this molecule is now considered a biomarker of the total systemic oxidative stress in vivo. Dandona et al. (11) demonstrated that type 1 and type 2 diabetic patients had a significantly higher concentration of 8-OH-dG in their monon...

The p53-inducible gene 3 (PIG3) is originally isolated as a p53 downstream target gene, but its function remains unknown. Here, we report a role of PIG3 in the activation of DNA damage checkpoints, after UV irradiation or radiomimetic drug neocarzinostatin (NCS). We show that depletion of endogenous PIG3 sensitizes cells to DNA damage agents, and impaired DNA repair. PIG3 depletion also allows for UV-and NCS-resistant DNA synthesis and permits cells to progress into mitosis, indicating that PIG3 knockdown can suppress intra-S phase and G2/M checkpoints. PIG3-depleted cells show reduced Chk1 and Chk2 phosphorylation after DNA damage, which may directly contribute to checkpoint bypass. PIG3 exhibited diffuse nuclear staining in the majority of untreated cells and forms discrete nuclear foci in response to DNA damage. PIG3 colocalizes with c-H2AX and 53BP1 to sites of DNA damage after DNA damage, and binds to a c-H2AX. Notably, PIG3 depletion decreases the efficient induction and maintenance of H2AX phosphorylation after DNA damage. Moreover, PIG3 contributes to the recruitment of 53BP1, Mre11, Rad50 and Nbs1 to the sites of DNA break lesions in response to DNA damage. Our combined results suggest that PIG3 is a critical component of the DNA damage response pathway and has a direct role in the transmission of the DNA damage signal from damaged DNA to the intra-S and G2/M checkpoint machinery in human cells.

Cumulating evidence suggests that enhanced oxidative stress may contribute to diabetic angiopathy. The levels of 8-hydroxydeoxyguanosine (8-OHdG) and 8-hydroxyguanine (8-OHG), indicators of oxidative DNA damage, in tissue or body fluid are increased in diabetic patients. However, it is unclear whether plasma 8-OHG correlates with tissue 8-OHdG and whether insulin or antioxidant treatment reduces plasma 8-OHG in diabetic state. In this study, we measured the 8-OHG levels in plasma as well as the 8-OHdG levels in liver and kidney in streptozotocin-induced diabetic rats (DR) treated with insulin (DR؉I), insulin and probucol (DR؉I/P), or insulin and vitamin E (DR؉I/E). There was a correlation between plasma 8-OHG levels and tissue 8-OHdG levels (plasma 8-OHG vs. liver 8-OHdG: r ‫؍‬ 0.64, P < 0.001; plasma 8-OHG vs. kidney 8-OHdG: r ‫؍‬ 0.38, P ‫؍‬ 0.06). DR had levels of plasma 8-OHG that were three times higher than control rats (CR), whereas they had levels of tissue 8-OHdG that were ϳ1.5-2 times higher. Plasma 8-OHG levels in DR were almost normalized by insulin treatment, although insulin partially corrected hyperglycemia (plasma 8-OHG: CR 3.3 ؎ 2.7 pmol/ml; DR 10.4 ؎ 2.3 pmol/ml, P < 0.05 vs. CR; DR with insulin 3.6 ؎ 1.0 pmol/ml, P < 0.05 vs. DR). However, tissue 8-OHdG levels in DR were significantly decreased by combined treatment with insulin and antioxidant (probucol or vitamin E), but not by insulin treatment alone. This data suggests that plasma 8-OHG could be a useful biomarker of oxidative DNA damage in diabetic subjects. The mechanism of differential response of plasma 8-OHG and tissue 8-OHdG to insulin and antioxidant treatment remains to be elucidated.

BackgroundIntestinal epithelium is essential for maintaining normal intestinal homeostasis; its breakdown leads to chronic inflammatory pathologies, such as inflammatory bowel diseases (IBDs). Although high concentrations of S100A9 protein and interleukin-6 (IL-6) are found in patients with IBD, the expression mechanism of S100A9 in colonic epithelial cells (CECs) remains elusive. We investigated the role of IL-6 in S100A9 expression in CECs using a colitis model.MethodsIL-6 and S100A9 expression, signal transducer and activator of transcription 3 (STAT3) phosphorylation, and infiltration of immune cells were analyzed in mice with dextran sulfate sodium (DSS)-induced colitis. The effects of soluble gp130-Fc protein (sgp130Fc) and S100A9 small interfering (si) RNA (si-S100A9) on DSS-induced colitis were evaluated. The molecular mechanism of S100A9 expression was investigated in an IL-6-treated Caco-2 cell line using chromatin immunoprecipitation assays.ResultsIL-6 concentrations increased significantly in the colon tissues of DSS-treated mice. sgp130Fc or si-S100A9 administration to DSS-treated mice reduced granulocyte infiltration in CECs and induced the down-regulation of S100A9 and colitis disease activity. Treatment with STAT3 inhibitors upon IL-6 stimulation in the Caco-2 cell line demonstrated that IL-6 mediated S100A9 expression through STAT3 activation. Moreover, we found that phospho-STAT3 binds directly to the S100A9 promoter. S100A9 may recruit immune cells into inflamed colon tissues.ConclusionsElevated S100A9 expression in CECs mediated by an IL-6/STAT3 signaling cascade may play an important role in the development of colitis.