Nihayet Mehmet

The role of oxidative stress in bronchoconstriction due to occupational sulfur dioxide exposure

BACKGROUND We previously showed that apricot sulfurization workers (ASW) are exposed to high concentrations of SO(2), resulting in an asthma-like syndrome. The aim of this study was to evaluate whether oxidative stress plays a role in the pathogenesis of asthma-like syndrome due to the high concentrations of SO(2) exposure in agricultural environment. METHODS Serum antioxidant enzyme activities and malondialdehyde (MDA) concentrations, which are markers of lipid peroxidation, and pulmonary function tests (PFT) were measured in 40 volunteer ASW and compared to 20 healthy control subjects. RESULTS The superoxide dismutase (SOD, 2.2+/-0.6 vs. 3.2+/-0.7 U/ml), glutathione peroxidase (GSH-Px, 0.6+/-0.3 vs. 1.1+/-0.3 U/ml) and catalase (107.6+/-27.4 vs. 152.6+/-14.3 k/l) activities in ASW were significantly (p<0.0001) lower than controls, whereas the malondialdehyde concentration (4.1+/-0.9 vs. 1.9+/-5.3 nmol/l) was higher in ASW (p<0.0001). ASW had significant decreases in pulmonary function parameters after exposure. CONCLUSION These results show that occupational exposure to high concentrations of SO(2) enhances oxidative stress and lipid peroxidation may be considered as a new mechanism of SO(2)-induced bronchoconstriction.

Serum nitrite and nitrate levels in epileptic children using valproic acid or carbamazepine

In experimental epilepsy studies, nitric oxide was found to act as both proconvulsant and anticonvulsant. The objective of this study was to investigate the effects of valproic acid and carbamazepine on serum levels of nitrite and nitrate, which are the metabolites of nitric oxide. To achieve this goal, serum nitrite and nitrate levels were determined in active epileptic 34 children using valproic acid and 23 children using carbamazepine and in non-active epileptic 38 children (control group) not using any antiepileptic drug. In the valproic acid group serum nitrite and nitrate levels were 2.66 +/- 2.11 micromol/l and 69.35 +/- 23.20 micromol/l, 1.89 +/- 1.01 micromol/l and 49.39 +/- 10.61 micromol/l in the carbamazepine group, and 1.22 +/- 0.55 micromol/l, 29.53 +/- 10.05 micromol in the control group, respectively. Nitrite and nitrate levels were significantly high in both valproic acid and carbamazepine groups compared to the control group (P < 0.01). When valproic acid and carbamazepine groups were compared to each other, level of nitrate was found statistically higher in the valproic acid group in relation to the carbamazepine group (P < 0.01), however, there was no statistically significant difference in the levels of nitrite (P > 0.05). No relation could be found between serum drug levels and nitrite and nitrate levels. According to these results, it can be suggested that valproic acid and carbamazepine might have antiepileptic effects through nitric oxide.

Urinary nitric oxide levels are increased and correlated with plasma concentrations in patients with Behçet's disease: is it a new urinary activity marker?

SUMMARY:  Nitric oxide (NO) is a free radical and serves many functions within the kidney. Excess NO causes glomerular injury. Behçets disease (BD) is a systemic immunoinflammatory vasculitis, affecting every organ in the body including the kidneys (subclinic glomerulonephritis). We investigated the role of urinary total nitrite levels (end product of NO) in BD and evaluated whether urinary concentrations were correlated with its plasma levels or disease activity. Thirty‐six consecutive Behçets patients (19 men, 17 women; 35.9 years), and 20 age‐ and sex‐matched healthy control volunteers (12 men, eight women; 33.2 years) were divided into an active (n = 16) and inactive (n = 20) period. Urinary and serum NO levels (µmol/mg urinary creatinine) were higher in BD patients (4.1 ± 0.3) than control subjects (1.7 ± 0.2; P < 0.001). Serum NO levels in Behçets patients and control subjects were 51.3 ± 9.8 and 21.7 ± 7.3 µmol/L, respectively (P < 0.001). Active patients had higher urinary NO excretion (4.9 ± 0.3) than inactive patients (3.3 ± 0.3; P < 0.01). Urinary NO levels were correlated with its serum levels (r2 = 0.69, P < 0.001). Higher urinary NO levels found in BD may be produced by the kidney as a result of an inflammatory stimulation. As excess NO is toxic to the tissues, increased NO levels may play a role in mediating subclinic glomerular injury of such patients. However, we could not determine the exact site(s) of NO synthesis by the kidney, such as the glomeruli, blood vessels and/or the tubular cells. Whatever the source, urinary NO levels may be used as a new activity marker in the diagnosis and follow up of BD by serial measurements.

The role of nitric oxide and cytokines in asthma-like syndrome induced by sulfur dioxide exposure in agricultural environment

BACKGROUND We previously demonstrated that apricot sulfurization workers are exposed to high concentrations of SO(2), subsequently causing asthma-like syndrome. This study investigated the effects of SO(2) exposure on serum TNF-alpha, IL-1beta, IL-6, IL-8, nitrite and nitrate levels to understand the mechanism of SO(2)-induced bronchoconstriction in asthma-like syndrome. METHODS We measured the serum levels of the cytokines, direct nitrite, total nitrite and nitrate obtained from 40 volunteer workers after an hour of exposure to SO(2) and 23 healthy controls. RESULTS The concentrations of the cytokines, direct nitrite, total nitrite and nitrate were significantly (p<0.0001) higher in the workers than in the controls. The mean serum concentrations of TNF-alpha, IL-1beta, IL-6, IL-8, direct nitrite, total nitrite and nitrate were 430.60+/-397.03 pg/ml, 436.67+/-316.31 pg/ml, 752.11+/-394.95 pg/ml, 262.12+/-287.99 pg/ml, 7.75+/-3.34 micromol/l, 115.72+/-48.78 micromol/l and 107.97+/-46.19 micromol/l in the workers, while they were 9.83+/-3.12 pg/ml, <5 pg/ml, 7.49+/-1.27 pg/ml, 9.38+/-1.99 pg/ml, 2.17+/-0.77 micromol/l, 59.91+/-7.56 micromol/l and 57.74+/-7.20 micromol/l in the controls, respectively. CONCLUSION These results show that TNF-alpha, IL-1beta, IL-6, IL-8 and nitric oxide may play a role in the pathogenesis of bronchoconstriction in asthma-like syndrome due to the SO(2) exposure.