Interaction of Nitric Oxide with Glutathione or Cysteine Generates Reactive Oxygen Species Causing DNA Single Strand Breaks

GSH threshold requirement for NO-mediated expression of the Arabidopsis AtFer1 ferritin gene in response to iron

Iron treatment of Arabidopsis cultured cells promotes a rapid NO burst within chloroplasts, necessary for up-regulation of the AtFer1 ferritin gene expression. The same occurs in Arabidopsis leaf chloroplasts, and is dependent upon the GSH content of plants. A leaf GSH concentration threshold between 10 and 50 nmol GSHg(-1) FW is required for full induction of AtFer1 gene expression in response to iron.

Increased singlet oxygen-induced secondary ROS production in the serum of cancer patients

Photodynamic therapy (PDT) generates singlet oxygen ((1)O(2)) and Reactive Oxygen Species (ROS) that are counteracted by patient's defenses. As cancer treatments are among the most important PDT applications the aim of this pilot study was to determine whether the serum of cancer patients produces more or less secondary ROS or peroxides after a photoreaction as compared to healthy persons. Fifty-three volunteers and 105 cancer patients were recruited. The capacity of (1)O(2) or secondary oxidant production was found to be increased in 6 healthy donors and 36 cancer patients (23/69 women and 13/31 men p<0.007 and p<0.04) with a mean value of 1.52 as compared to 1.29 in the healthy subjects (p<0.05) when considering values higher than the normal range (norm=1±10%) or 1.1 vs. 0.85 (p<0.01) in the whole cohort. This increase correlated with a poor prognosis, TNM and SBR classification. Serum (1)O(2) deactivation capacity was impaired and secondary ROS were more produced during cancer progression. Although it is currently unclear whether this is the cause or effect of cancer, this finding may hold interest as a potential marker of cancer severity. It would also support the interest of PDT as an adjuvant for cancer treatment, even for aggressive tumors particularly when associated to surgery for bulk removal.

Serum resistance to singlet oxygen in patients with diabetes mellitus in comparison to healthy donors

Diabetes mellitus causes endothelial injury through oxidative stress involving reactive oxygen species and peroxides as well as inflammation, both of which consume antioxidant defenses. Singlet oxygen ((1)O(2)) is produced by leukocytes during inflammatory and biochemical reactions and deactivated by producing reactive oxygen species and peroxides. To determine whether serum was capable of deactivating (1)O(2), we triggered a photo reaction in sera from 53 healthy donors and 52 diabetic patients. Immediately after light delivery, dichlorofluorescein was added and then its fluorescence was recorded. The mean capacity of (1)O(2) or secondary oxidant deactivation was reduced in patients with diabetes mellitus. Hemolysis reduced deactivation of (1)O(2)-induced secondary oxidants in both healthy and diabetic patients. Body mass index, age, platelet counts, and blood cell numbers exerted a nonlinear influence. High levels of glycated hemoglobin were associated with an increased deactivation of oxidative species, whereas high-density lipoprotein cholesterol, total cholesterol, and the total cholesterol to high-density lipoprotein cholesterol ratio decreased the serum deactivation capacity. Oral antidiabetics bore no influence on deactivation, which was restored by insulin in women. Deactivation capacity was lower in women, who had half the complications found in men, suggesting that, with more severe diabetes mellitus, protection was maintained against complications. Resistance to (1)O(2) should be considered during the monitoring of diabetes mellitus.

Increased hydrogen peroxide concentration in the exhaled breath condensate of stable COPD patients after nebulized N-acetylcysteine

BACKGROUND

The oxidative burden in the airways is a hallmark of chronic obstructive pulmonary disease (COPD).

AIMS

This prospective, cross-over, placebo (PL)-controlled study was designed to investigate the effect of N-acetyl-l-cysteine (NAC) on hydrogen peroxide (H(2)O(2)), nitrites and nitrates (NO(2)(-)+NO(3)(-)), and thiol (RSH) concentrations in exhaled breath condensate (EBC) in stable COPD patients (n=19, aged 52.6+/-15.6 years, 10 females, mean FEV(1) 95.2+/-23.8%, FEV(1)/FVC 69.1+/-11.4%).

METHODS

H(2)O(2), NO(2)(-)+NO(3)(-) and RSH concentrations in EBC were determined with homovanillic acid, NADPH-nitrite reductase assays and Ellman's reaction, respectively.

RESULTS

Thirty minutes after nebulization, H(2)O(2) concentration increased if levels after NAC (0.45+/-0.25microM) and PL (0.17+/-0.17microM) were compared in COPD patients (p=0.002). This increased H(2)O(2) level in EBC was no longer observed either after 90min: 0.16+/-0.09microM (PL 0.17+/-0.15microM) or 3h: 0.12+/-0.07microM (PL 0.21+/-0.23microM) (p=0.5 and 0.2, respectively). The levels of NO(2)(-) and NO(3)(-) did not differ between NAC and PL. There was no significant difference in RSH levels between nebulized NAC and PL. After nebulized NAC, however, exhaled RSH increased from 1.42+/-1.69microM (0min) to 2.49+/-2.00microM (30min), and 1.71+/-1.83microM (180min) (p=0.009 and 0.03, respectively, compared with 0min).

CONCLUSIONS

These data demonstrate that nebulized NAC transiently increases exhaled H(2)O(2) level, whereas it has no effect on other oxidative parameters.

Fulminant Hepatic Failure in Rats Induces Oxidative Stress Differentially in Cerebral Cortex, Cerebellum and Pons Medulla

Hepatic Encephalopathy (HE) is one of the most common complications of acute liver diseases and is known to have profound influence on the brain. Most of the studies, available from the literature are pertaining to whole brain homogenates or mitochondria. Since brain is highly heterogeneous with functions localized in specific areas, the present study was aimed to assess the oxidative stress in different regions of brain-cerebral cortex, cerebellum and pons medulla during acute HE. Acute liver failure was induced in 3-month old adult male Wistar rats by intraperitoneal injection of thioacetamide (300 mg/kg body weight for two days), a well known hepatotoxin. Oxidative stress conditions were assessed by free radical production, lipid peroxidation, nitric oxide levels, GSH/GSSG ratio and antioxidant enzyme machinery in three distinct structures of rat braincerebral cortex, cerebellum and pons medulla. Results of the present study indicate a significant increase in malondialdehyde (MDA) levels, reactive oxygen species (ROS), total nitric oxide levels [(NO) estimated by measuring (nitrites + nitrates)] and a decrease in GSH/GSSG ratio in all the regions of brain. There was also a marked decrease in the activity of the antioxidant enzymes-glutathione peroxidase, glutathione reductase and catalase while the super oxide dismutase activity (SOD) increased. However, the present study also revealed that pons medulla and cerebral cortex were more susceptible to oxidative stress than cerebellum. The increased vulnerability to oxidative stress in pons medulla could be due to the increased NO levels and increased activity of SOD and decreased glutathione peroxidase and glutathione reductase activities. In summary, the present study revealed that oxidative stress prevails in different cerebral regions analyzed during thioacetamide-induced acute liver failure with more pronounced effects on pons medulla and cerebral cortex.