In vivo and in vitro sevoflurane-induced lipid peroxidation in guinea-pig liver microsomes

Dynamic thiol disulphide homeostasis in operating theater personnel exposed to anesthetic gases

BACKGROUND

The purpose of this study was to investigate the association between dynamic thiol/disulphide homeostasis and occupational exposure to volatile anesthetic gases in operating theater personnel. Decreased blood thiol levels and raised blood disulphide levels serve as biomarkers of oxidative stress.

METHODS

We included 65 subjects occupationally exposed and 55 unexposed healthy medical professionals into the study. A novel method enabled separate measurements of components involved in dynamic thiol/disulphide homeostasis (native thiol, disulphide, and total thiol). To control for the potential confounding effect on oxidative stress of psychological symptoms potentially caused by occupational stress, we used scores obtained from four different anxiety and depression inventories.

RESULTS

Mean ± standard deviation native thiol was found to be 433.35 ± 30.68 in the exposed group, lower than among controls, 446.61 ± 27.8 (P = 0.02). Disulphide in the exposed group was 15.78 ± 5.12, higher than among controls, 12.14 ± 5.33 (P < 0.001). After adjusting for anxiety and depression scores, age and gender, native thiol remained lower and disulphide higher in the exposed group (P = 0.008 and P < 0.001).

CONCLUSION

Dynamic thiol/disulphide homeostasis in workers exposed to anesthetic gases was found to be disturbed after adjusting for the possible contribution of anxiety. We infer that this is due to the oxidative effect of exposure to anesthetic gases.

Urinary lipid and protein oxidation products upon halothane, isoflurane, or sevoflurane anesthesia in humans: potential biomarkers for a subclinical nephrotoxicity

OBJECTIVE

To investigate whether lipid and protein oxidation products are elevated and correlated with routine clinical markers of hepatic and renal function in patients anesthetized with halothane, isoflurane, or sevoflurane.

METHODS

Urine and blood samples were collected from patient groups. Excretion of aldehydes, acetone, and o,o'-dityrosine was measured before and after anesthesia. Blood samples were analysed for clinical markers.

RESULTS

Urinary concentrations of aldehydes, acetone, o,o'-dityrosine and glucose were significantly increased after anesthesia in halothane and sevoflurane groups earlier than clinical markers. Significant correlations were found in sevoflurane group.

CONCLUSION

Lipid and protein oxidation contributes to subclinical sevoflurane nephrotoxicity. Oxidation products may serve as early biomarkers.

Oxidative and antioxidative effects of desflurane and sevoflurane on rat tissue in vivo

General anaesthetics are often used in patients who are under oxidative stress due to a critical illness or surgical trauma. Some anaesthetics may worsen oxidative stress and some may act as antioxidants. The aim of this study was to evaluate liver, brain, kidney, and lung tissue oxidative stress in rats exposed to desflurane and sevoflurane and in unexposed rats. The animals were divided in three groups: control (received only air); sevoflurane (8 %), and desflurane (4 %). After four hours of exposure, we evaluated the levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), Cu, and Zn. Exposure to either of the anaesthetics significantly increased lung MDA levels compared to control (Mann-Whitney U test; P<0.05), probably because it is the tissue directly exposed to anaesthetic gases. Oxidative stress and antioxidant activity in other tissues varied between the desflurane and sevoflurane groups. Our results suggest that anaesthesiologist should not only be aware of the oxidative or antioxidative potential of anaesthetics they use, but should also base their choices on organs which are the most affected by their oxidative action.

Evaluation of antioxidant parameters in rats treated with sevoflurane

BACKGROUND AND OBJECTIVES

Sevoflurane is a halogenated fluorinated ether that undergoes hepatic biotransformation through cytochrome P4502E1. Halogenated ethers undergoing biotransformation by P4502E1 can produce reactive oxygen species (ROS), weakening the antioxidant defense mechanism. The objective of this study was to investigate the relationship between the activity of erythrocyte antioxidant enzymes and sevoflurane.

METHODS

Animals were divided in four groups: Group 1 - control: 100% oxygen (1 L.min(-1) for 60 min during five consecutive days); Group 2 - 4.0% sevoflurane in 100% oxygen (1 L.min(-1) for 60 minutes during five consecutive days); Group 3 - isoniazid (i.p.), 50 mg.kg(-1)/ day for four consecutive days, followed by 100% oxygen (1 L.min(-1) for 60 minutes during four consecutive days); Group 4 - intraperitoneal isoniazid, 50 mg.kg(-1) daily for four days, followed by 4.0% sevoflurane in 100% oxygen (1 L.min(-1) for 60 minutes during five days). Twelve hours after the last exposure to sevoflurane, animals were sacrificed and their blood was collected through the portal vein for analysis of antioxidant enzymes.

RESULTS

An increase in the activity of glucose-6-phosphate dehydrogenase and a decrease in the activity of catalase were observed, especially in the group of animals pre-treated with isoniazid. Changes in the activity of glutathione peroxidase were not observed.

CONCLUSIONS

The interaction between sevoflurane and cytochrome P450 2E1 with enzymatic inducers can lead to oxidative stress with prolonged and repetitive exposure.

Isoflurane reduces the synthesis of surfactant-related protein a of alveolar type II cells injured by H2O2

The influence of isoflurane (Iso) on the synthesis of surfactant-related protein A (SP-A) of alveolar type II (AT II) cells in primary culture and after injury by H2O2 was investigated. AT II cells were isolated and purified from adult Sprague-Dawley rats and used for experiments after 32 h in primary culture. The cell cultures were randomized to six groups (n = 8 in each group): control group (no treatment), 0.28 mM Iso group, 2.8 mM Iso group, 75 microM H2O2 group, 75 microM H2O2 + 0.28 mM Iso group, and 75 microM H2O2 + 2.8 mM Iso group. Each group was continuously incubated for 3 h after administration of Iso and/or H2O2. The intracellular SP-A and the SP-A of the culture medium were measured with an enzyme-linked immunosorbent assay (ELISA). Iso significantly decreased the intracellular SP-A content and that of the culture medium, and aggravated the decrease of SP-A content induced by H2O2. These findings suggest that Iso itself may decrease SP-A synthesis of AT II cells in vitro, and aggravate the damage to AT II cells under peroxidation conditions.

Analyses of representative biomarkers of exposure and effect by chromatographic, mass spectrometric, and nuclear magnetic resonance techniques: method development and application in life sciences

Biomarkers are essential tools in monitoring studies, which include environmental monitoring, biological monitoring, biological effect monitoring, and health surveillance, as well as drug development processes. Their discovery, validation, and analysis require highly sensitive and selective analytical technologies. In this regard, gas and liquid chromatography, mass spectrometry, and nuclear magnetic resonance spectroscopy have facilitated great achievements in all these areas. In addition and closely related to biomarkers, the ongoing developments in these techniques promise a better understanding of the nature and mechanisms of toxic effects originating from various chemical, biological, or physical sources. This Review compiles studies performed on selected biomarkers with respect to both method development and application. Section 1 summarizes the concept of biomarkers; their application in various industrial/occupational, agricultural, drug developmental, and medical/clinical platforms. This section also focuses on biotransformation studies in close relation to biomarker discovery and validation, and on major techniques utilized in this area. In Section 2, biotransformation of volatile anesthetics in humans with a focus on mercapturic acid derivatives as potential biomarkers of effect is reviewed. The use of GC-ECD, GC/MS, and 19F-NMR in these studies is described. Section 3 focuses on the analysis of aldehydic lipid peroxidation degradation products by GC-ECD in mammalian cells in which oxidative stress induced chemically, and in humans after various challenges; anesthetic exposure, ischemia-reperfusion, and controlled endurance exercise. In Section 4, method development for protein and DNA oxidation products by LC-tandem MS and its application in mammalian cells and in humans are summarized. Possibilities, limitations, and future perspectives are discussed in Section 5.

Effect of isoflurane on proliferation and Na+,K+-ATPase activity of alveolar type II cells injured by hydrogen peroxide

The influence of isoflurane (Iso) on proliferation and Na+,K+-ATPase activity of alveolar type II cells (ATII cells) injured by hydrogen peroxide (H2O2) was investigated. ATII cells isolated and purified from adult Sprague-Dawley rats were randomly divided into six groups: control group, 0.28 mM Iso group, 2.8 mM Iso group, 75 microM H2O2 group, 75 microM H2O2 + 0.28 mM Iso group, and 75 microM H2O2 + 2.8 mM Iso group. After primary culture for 32 hours, the proliferation of ATII cells was detected by MTT assay, and after culture for 24 hours the activity of Na+,K+-ATPase and lactate dehydrogenase (LDH) in the cells, and malonaldehyde (MDA) content of the culture medium, were measured by colorimetry. It was found that 0.28 mM and 2.8 mM Iso had no effect on the proliferation of ATII cells (p > 0.05), but 75 microM H2O2 inhibited their proliferation (p < 0.05) compared with untreated controls; 0.28 mM and 2.8 mM Iso significantly decreased Na+,K+-ATPase activity of ATII cells compared with untreated control cells (p < 0.05), and 75 microM H2O2 markedly decreased Na+,K+-ATPase activity of ATII cells (p < 0.01) with untreated control cells. 0.28 mM and 2.8 mM Iso aggravated the decrease of Na+,K+-ATPase activity induced by H2O2. Iso had no effect on LDH activity and MDA content of the culture medium of normal ATII cells, but significantly increased LDH activity and MDA content of the culture medium of ATII cells injured by H2O2. These findings suggest that Iso itself may decrease the activity of Na+,K+-ATPase of ATII cells in vitro and further damage the cells' function under peroxidation conditions, but has no effect on the proliferation of ATII cells.

Hepatic effects of halothane, isoflurane or sevoflurane anaesthesia in dogs

The effects of halothane, isoflurane and sevoflurane anaesthesia on hepatic function and hepatocellular damage were investigated in dogs, comparing the activity of hepatic enzymes and bilirubin concentration in serum. An experimental study was designed. Twenty-one clinically normal mongrel dogs were divided into three groups and accordingly anaesthetized with halothane (n = 7), isoflurane (n = 7) and sevoflurane (n = 7). The dogs were 1-4 years old, and weighed between 13.5 and 27 kg (18.4 +/- 3.9). Xylazine HCI (1-2 mg/kg) i.m. was used as pre-anaesthetic medication. Anaesthesia was induced with propofol 2 mg/kg i.v. The trachea was intubated and anaesthesia maintained with halothane, isoflurane or sevoflurane in oxygen at concentrations of 1.35, 2 and 3%, respectively. Intermittent positive pressure ventilation (tidal volume, 15 ml/kg; respiration rate, 12-14/min) was started immediately after intubation and the anaesthesia lasted for 60 min. Venous blood samples were collected before pre-medication, 24 and 48 h, and 7 and 14 days after anaesthesia. Serum level of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT), lactate dehydrogenase (LDH GGT) activities and bilirubin concentration were measured. Serum AST, ALT and GGT activities increased after anaesthesia in all groups. In the halothane group, serum AST and ALT activities significantly increased all the time after anaesthesia compared with baseline activities. But in the isoflurane group AST and ALT activities increased only between 2 and 7 days, and in the sevoflurane group 7 days after anaesthesia. GGT activity was increased in the halothane group between 2 and 7 days, and in the isoflurane and sevoflurane groups 7 days after anaesthesia. All dogs recovered from anaesthesia without complications and none developed clinical signs of hepatic damage within 14 days. The results suggest that the use of halothane anaesthesia induces an elevation of serum activities of liver enzymes more frequently than isoflurane or sevoflurane from 2 to 14 days after anaesthesia in dogs. The effects of isoflurane or sevoflurane anaesthesia on the liver in dogs is safer than halothane anaesthesia in dogs.

Free radicals, antioxidants, and neurologic injury: possible relationship to cerebral protection by anesthetics

Oxygen-centered free radicals cause brain injury associated with trauma and stroke. These reactive oxygen species may be detoxified by endogenous antioxidants, but cell death occurs after antioxidants become depleted. General anesthetics penetrate into brain parenchyma, where they may abrogate oxidative injury to neurons by several mechanisms that prevent the initiation of free radical chain reactions or terminate the propagation of highly reactive radicals. First, general anesthetics may inhibit free radical generation because these drugs slow cerebral utilization of oxygen and glucose, inhibit oxidative metabolism in neutrophils, and prevent redox changes in hemoglobin. Second, antioxidant anesthetics, such as thiopental and propofol, directly scavenge reactive oxygen species and inhibit lipid peroxidation. Finally, anesthetics may prevent the elevation of extracellular glutamate concentration and inhibit the activation of excitatory glutamatergic receptors that augment oxidative stress after ischemia.

Prostaglandin F2-like compounds, F2-isoprostanes, are present in increased amounts in human atherosclerotic lesions

Oxidative modification of LDL is believed to play a major role in atherogenesis. As major lipid peroxidation products oxygenated linoleic acid derivatives and oxysterols have been described in human atherosclerotic lesions. Here we report that human lesions contain isoprostanes as peroxidation products of arachidonic acid at a level of 27.1 +/- 21.2 pg/mg wet weight (n = 10), which corresponds to 75.9 +/- 59.3 pg/mg dry weight, n contrast, human umbilical veins (n = 10), which were used as nonatherosclerotic control vessels, contain much smaller amounts of isoprostanes (1.4 +/- 0.7 pg/mg wet weight, which corresponds to 11.7 +/- 6.2 pg/mg dry weight), and there are significant differences between the two types of vessels. As major products of linoleic acid oxidation, racemic hydroxy linoleate isomers were detected in the lesional ester lipids. In human lesions, the hydroxy linoleic acid/linoleic acid ratio was about 0.5%, a result indicating that 5 out of 1000 linoleate residues are present as hydroxylated derivatives. In umbilical veins, no hydroxy linoleic acid could be detected. These data show that human atherosclerotic lesions contain increased amounts of hydroxy linoleic acid isomers and isoprostanes when compared with nonatherosclerotic vessel wall and suggest a link between local lipid peroxidation and progression of atherosclerosis. For evaluation of the degree of lipid peroxidation, the determination of the hydroxy linoleic acid/linoleic acid ratio appears to be more suitable than the isoprostane content.