Factors affecting the thiobarbituric acid test as index of red blood cell susceptibility to lipid peroxidation: a multivariate analysis

Protection by sildenafil and theophylline of lead acetate-induced oxidative stress in rat submandibular gland and saliva

The role of oxidative stress in lead toxicity has been proposed in many organs, however, no study has been performed in the salivary glands, which are important parts of the gastrointestinal tract with a high implication in health of the whole body. Recently, it has been proposed that increasing the levels of cGMP and cAMP in the cells may protect from the neurotoxicity of lead. The objective of this study was to determine the ability of lead acetate to produce oxidative stress in rat submandibular as the main salivary gland of the body and to study the role of pretreatment by specific phosphodiesterase inhibitors in the prevention of oxidative stress. Lead acetate (100 mg/kg), alone or in combination with theophylline (25 mg/kg) and sildenafil (5 mg/kg), was administered intraperitoneally to rats. After 2 hours and under general anaesthesia, the submandibular gland ducts were cannulated intraorally using microcannula, and pure saliva was collected for 30 min using pilocarpine (8 mg/kg) as a secretagogue. The submandibular glands were then isolated free under surgery. Oxidative stress in the gland and pure saliva were evaluated measuring lipid peroxidation (thiobarbituric acid reactive substances assay), total thiol groups content and total antioxidant capacity (the ferric reducing ability assay). Results showed significant oxidative stress in the gland and secretions as indicated by increased lipid peroxidation, decreased total antioxidant capacity and thiol group levels. The use of cAMP and cGMP phosodiesterase inhibitors, theophylline and sildenafil, prevented leadinduced increased lipid peroxidation and also protected from decreased thiol groups content and total antioxidant power of the gland and secretions. The same trend of effects was observed in gland and saliva. It is concluded that lead toxicity is mediated through oxidative stress in salivary glands, while increasing intracellular cAMP and cGMP levels may prevent lead-induced oxidative stress.

Evaluation of oxidative stress and genotoxicity in organophosphorus insecticide formulators

The aim of this study was to evaluate genotoxicity and oxidative stress in workers who formulate organophosphorus (OP) pesticides. In this survey, blood leukocytes and erythrocytes of a group of 21 pesticide formulating workers and an equal number of control subjects were examined for genotoxicity and oxidative stress parameters. The mean comet tail length and mean comet length were used to measure DNA damage. Lipid peroxidation level, catalase, superoxide dismutase (SOD) and glutathione peroxidase activities in erythrocytes were analysed as biomarkers of oxidative stress. In addition, the acetylcholinesterase activity was measured as a biomarker of toxicity. The average duration of employment of workers in the factory was 97 months. Results indicated that chronic exposure (multiple5dose, greater than or equal to 6 months duration) to OP pesticides was associated with increased activities of catalase, SOD and glutathione peroxidase in erythrocytes. The level of lipid peroxidation and acetylcholinesterase activity did not show any significant differences between the two groups. The results also indicated that chronic exposure to OP pesticides was associated with increased DNA damage. It is concluded that human chronic exposure to OP pesticides may result in stimulated antioxidant enzymes and increased DNA damage in the absence of depressed acetylcholinesterase levels. Routine genotoxicity monitoring concomitant to acetylcholinesterase activity in workers occupationally exposed to OP insecticides is suggested.

Biochemical evidence for free radicalinduced lipid peroxidation as a mechanism for subchronic toxicity of malathion in blood and liver of rats

Organophosphorus compounds may induce oxidative stress leading to generation of free radicals and alterations in antioxidant and scavengers of oxygen free radicals (OFRs). The effect of subchronic exposure to malathion in the production of oxidative stress was evaluated in male Wistar rats. Administration of malathion (100, 316, 1000, 1500 ppm) for 4 weeks increased catalase (CAT), superoxide dismutase (SOD) activities as well as malondialdehyde (MDA) concentration in red blood cells (RBC) and liver. However, acetylcholinesterase (AChE) and cholinesterase (ChE) activities were decreased in these samples. The increase in RBC and liver lipid peroxidation correlated well with the inhibition in RBC AChE and liver ChE activities. Elevation of MDA concentrations and increased activities of CAT and SOD showed significant correlations in both RBC and liver samples when different doses of malathion were used. The results of the present study suggest the usefulness of RBC AChE measurement as a good biomarker in the estimation of malathion-induced oxidative stress affecting blood and liver.

Biochemical evidence for free radical-induced lipid peroxidation as a mechanism for subchronic toxicity of malathion in blood and liver of rats

Organophosphorus compounds may induce oxidative stress leading to generation of free radicals and alterations in antioxidant and scavengers of oxygen free radicals (OFRs). The effect of subchronic exposure to malathion in the production of oxidative stress was evaluated in male Wistar rats. Administration of malathion (100, 316, 1000, 1500 ppm) for 4 weeks increased catalase (CAT), superoxide dismutase (SOD) activities as well as malondialdehyde (MDA) concentration in red blood cells (RBC) and liver. However, acetylcholinesterase (AChE) and cholinesterase (ChE) activities were decreased in these samples. The increase in RBC and liver lipid peroxidation correlated well with the inhibition in RBC AChE and liver ChE activities. Elevation of MDA concentrations and increased activities of CAT and SOD showed significant correlations in both RBC and liver samples when different doses of malathion were used. The results of the present study suggest the usefulness of RBC AChE measurement as a good biomarker in the estimation of malathion-induced oxidative stress affecting blood and liver.

Effects of duodenal seal oil administration in patients with inflammatory bowel disease

Long-chain n-3 PUFA in fish oil have modulating effects on inflammatory responses. The aim of this open pilot study was to investigate whether duodenal seal oil administration would benefit patients with inflammatory bowel disease (IBD). Seal oil (10 mL) was administered three times a day directly into the distal part of the duodenum via a nasoduodenal feeding tube for 10 d in 10 patients, 5 of whom had Crohn's disease and 5 ulcerative colitis. Nine of the 10 patients suffered from IBD-associated joint pain. Various parameters of disease activity and FA incorporation in tissues were analyzed before and after treatment. Following seal oil therapy, joint pain index, disease activity, and serum cholesterol level were significantly decreased, whereas the n-3 to n-6 ratio both in intestinal biopsies and blood was significantly increased. Measures of calprotectin concentration in gut lavage fluid, intestinal permeability, and lipid peroxidation were not significantly changed. The results suggest positive effects of seal oil in patients with IBD, especially on IBD-associated joint pain. Further controlled studies are warranted.

Mixed tocopherols have a stronger inhibitory effect on lipid peroxidation than alpha-tocopherol alone

Intake of vitamin E with food (mixed tocopherols) has been found to counteract the development of atherosclerotic cardiovascular disease, whereas intake of large amounts of pure alpha-tocopherol has shown only a slight or no effect in clinical studies. This study was designed to investigate the effects of alpha-tocopherol alone and a mixed tocopherol preparation (gamma-, delta-, and alpha-tocopherol) on hydrogen peroxide-induced lipid peroxidation in human erythrocytes. Erythrocytes were incubated with different concentrations of alpha-tocopherol or mixed tocopherols and then exposed to hydrogen peroxide. Tocopherol levels and malondialdehyde-thiobarbituric acid-reactive substances were determined by high-performance liquid chromatography and fatty acids by gas chromatography. Incubation of erythrocytes with tocopherols (30-120 microM) increased the tocopherol level in a concentration-dependent manner. The uptake of gamma- and delta-tocopherols was much higher than that of alpha-tocopherol. Hydrogen peroxide strongly increased lipid peroxidation and decreased polyunsaturated fatty acids in erythrocytes. Both alpha-tocopherol and the tocopherol mixture protected the cells from lipid peroxidation, the mixture being much more potent than alpha-tocopherol alone. This study indicates that a mixture of tocopherols has a stronger inhibitory effect on lipid peroxidation induced in human erythrocytes than alpha-tocopherol alone, due to higher uptake of gamma- and delta-tocopherol in the cells.

Evidence for alterations in circulating low-molecular-weight antioxidants and increased lipid peroxidation in smokers on hemodialysis

BACKGROUND/AIM

Cardiovascular disease is the major cause of mortality in dialysis patients, accounting for about 40% of deaths in most large registries. Oxidative stress has been strongly implicated in the pathogenesis of these events. As end-stage renal disease is a state of elevated free radical activity, the aim of the present study was to investigate the negative impact of smoking in 57 male hemodialysis patients.

METHODS

The patients, who were 20-85 years of age (mean age 51.0 +/- 14 years), had been on hemodialysis for at least 6 months before participating in this study. Fasting blood sampling for serum lipid, albumin, urate and lipophilic antioxidants such as tocopherols, carotenes, ascorbate and lipid peroxides was performed.

RESULTS

The plasma malondialdehyde (MDA) concentration was significantly higher in hemodialysis patients who smoked compared to hemodialysis patients who were nonsmokers (1.92 +/- 0.52 vs. 1.59 +/- 0.42 nmol/ml, p = 0.006). No association was found between levels of MDA in smokers and parameters such as body mass index, serum cholesterol, serum triglycerides and smoking index. There were no significant differences in the plasma levels of uric acid, alpha-tocopherol, gamma-tocopherol, delta-tocopherol, alpha-carotene, beta-carotene and retinol between the two groups. A significantly lower level of plasma ascorbate was observed in hemodialysis patients who smoked compared to the nonsmoking hemodialysis patients or healthy controls (4.59 +/- 4.0 vs. 9.57 +/- 4.0 and 10.16 +/- 4.6 microg/ml, p < 0.05). Moreover, in smokers, the plasma levels of ascorbate were negatively correlated with the levels of plasma MDA (r = -0.43, p < 0.001) of each patient. Partial correlation analysis of the plasma levels of the measured antioxidants and the smoking index revealed a negative correlation between the plasma levels of lipid-normalized lycopene and the smoking index (r = -0.53, p < 0.05).

CONCLUSION

Our data suggest that cigarette smoking further increases plasma-circulating products of lipid peroxidation, which are already increased in nonsmoking hemodialysis patients as compared to matched healthy controls. The lower plasma levels of ascorbate in hemodialysis patients who smoke suggest that these patients may be more susceptible to oxidative tissue damage caused by smoking.

Nutritional supplementation with N-3 fatty acids and antioxidants in patients with Crohn's disease in remission: effects on antioxidant status and fatty acid profile

In patients with Crohn's disease (CD), malnutrition is frequently observed and is generally accepted to be an important issue. The aim of this study was to investigate the effects of 3 months of supplementation with a liquid formula containing either antioxidants (AO) or n-3 fatty acids plus AO on the antioxidant status and fatty acid profile of plasma phospholipids and adipose tissue, respectively, in patients with long-standing CD currently in remission. In a randomized, double-blind placebo-controlled study, CD patients received either placebo, AO, or n-3 fatty acids plus AO for 3 months in addition to their regular diet. In all, 25/37 CD patients completed the study. AO status was assessed by blood biochemical parameters. A statistical per-protocol analysis was performed. Serum concentrations of selenium, vitamin C, and vitamin E, the activity of superoxide dismutase and total antioxidant status were significantly (p < 0.05) increased after AO supplementation. Furthermore, compared with controls, serum concentrations of beta-carotene, selenium, and vitamin C and the activity of glutathione peroxidase (GPx) were significantly (p < 0.05) lower before supplementation; however, after AO supplementation these levels were not significantly different from controls (except for GPx). N-3 fatty acids plus AO supplementation significantly (p < 0.05) decreased the proportion of arachidonic acid, and increased the proportion of eicosapentanoic acid and docosahexanoic acid in both plasma phospholipids and adipose tissue. Supplementation with antioxidants improved antioxidant status in patients with CD in remission. In addition, supplementation with n-3 fatty acids plus antioxidants significantly changed the eicosanoid precursor profile, which may lead to the production of eicosanoids with attenuated proinflammatory activity. This study indicates that an immunomodulating formula containing n-3 fatty acids and/or AO may have the potential to play a role in the treatment of CD.

Nutrition and inflammatory bowel disease: an update

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic inflammatory process, the aetiology of which remains unknown. Nutrition may play an important role in the pathogenesis and treatment of IBD. The evidence regarding the role of specific dietary components in the pathogenesis of IBD is still inconclusive. Many studies have been subject to methodological limitations; studies of better design are necessary to confirm the hypothesis that nutritional factors may indeed play a role in the development of IBD. Several studies have reported nutritional and functional deficiencies in IBD patients, especially in Crohn's disease. It is, however, hard to discriminate between disease-induced and malnutrition-induced changes in nutritional parameters. Maintaining adequate nutritional status has been suggested to be beneficial to the course of the disease in IBD. Studies have provided further insight into the possible beneficial effects of nutritional supplementation as primary and adjunctive therapy in IBD. The effects of specific nutritional therapy may be caused by alterations in intestinal flora and hence in the production of intraluminal proinflammatory substances. Immunonutrients such as n-3 fatty acids and antioxidants may also play a role in the treatment of IBD. In this paper, the relation between nutritional aetiological factors, nutritional status and nutritional therapy is discussed in detail.

Lipid peroxidation in proliferative vitreoretinopathies

PURPOSE

To study the lipid hydroperoxide activity in vasoproliferative and fibroproliferative retinal disorders.

METHODS

Vitreous body samples from patients undergoing vitrectomy because of proliferative vitreoretinopathy (PVR; n = 12) or proliferative diabetic retinopathy (PDR; n = 15), and rhegmatogenous retinal detachment/macular hole/epiretinal membranes as the comparison group (CG; n = 14), were analysed for protein content and basal and induced lipid peroxidation (LPO), as determined by the thiobarbituric acid reactive substances (TBARS) test and LPO 586 commercial kit. The antioxidant activity for superoxide dismutase (SOD) and catalase (CAT) was also assayed.

RESULTS

Malondialdehyde (MDA)-like metabolites and 4-hydroxynonenal (4-HNE) mean values were first measured to assess basal LPO, and found to be significantly higher in the PVR and PDR cases than in the CG (p < or = 0.0001). LPO induced by nicotine adenine dinucleotide phosphate iron (NADPH-Fe) was then assayed and the data showed that MDA mean values were 5-fold greater for the PVR and PDR eyes than in the case of basal LPO (p < or = 0.0001). SOD activity was significantly smaller in the PVR (p = 0.0010) and PDR (p < or = 0.0001) groups than in the CG. CAT levels displayed significantly lower values in the PVR and PDR cases than in the CG (p < or = 0.0001). No significant differences in free radical (FR) formation and antioxidant status between PVR and PDR patients were observed.

CONCLUSIONS

Fibrovascular proliferative vitreoretinopathies correlate with increased FR formation and decreased antioxidant activity in the human vitreous body.

Anti-oxidant status and lipid peroxidation in patients with essential hypertension

BACKGROUND

Lipid peroxidation and derived oxidized products are being intensively investigated, because of their potential to cause injury and their pathogenetic role in several clinically significant diseases. The view that an excess of lipid peroxidation products is present and relevant in the pathogenesis of human essential hypertension or in hypertension-induced damage has still not received definitive support.

OBJECTIVE

To evaluate both the extent of lipoperoxidation in essential hypertensive patients and the status of enzymatic and non-enzymatic antioxidants that potentially are able to modulate it

METHODS

We selected 105 newly diagnosed essential hypertensives among those referred to our hypertension outpatient clinic and compared them with 100 normotensive controls matched for age. Plasma malondialdehyde was measured by high-performance liquid chromatography after reaction with thiobarbituric acid, as an end product of lipid peroxidation; serum selenium (Se), plasma copper (Cu) and zinc (Zn), vitamins A and E, erythrocyte superoxide dismutase and glutathione peroxidase levels were evaluated as indices of oxidant balance. Differences between the groups were tested by Student's t test and chi2 test.

RESULTS

Compared with controls, essential hypertension patients had higher malondialdehyde and glutathione peroxidase activities (P<0.05 for both) and Zn concentrations (P<0.001) and lower superoxide dismutase activities (P<0.005), vitamin A (P<0.05) and E (P<0.001) levels and Cu concentrations (P<0.005). We found no difference between Se levels of essential hypertensive and control subjects.

CONCLUSIONS

Essential hypertension is associated with greater than normal lipoperoxidation and an imbalance in anti-oxidant status, suggesting that oxidative stress is important in the pathogenesis of essential hypertension or in arterial damage related to essential hypertension.

Vitamin E status in preterm infants: assessment by plasma and erythrocyte vitamin E-lipid ratios and hemolysis tests

BACKGROUND

Vitamin E is an essential component of the antioxidant defenses, but supplementation can have side effects in the preterm infant. Careful monitoring of vitamin E status is thus essential, however no consensus has been reached on the best clinical method.

METHODS

In 47 healthy preterm infants, several methods for assessment of vitamin E status were evaluated: plasma and erythrocyte vitamin E levels were measured, vitamin E lipid ratios were calculated, and two variations of the hydrogen peroxide hemolysis test were conducted.

RESULTS

At birth, the plasma and erythrocyte vitamin E levels were low. After birth, the plasma levels rose gradually, whereas the erythrocyte levels remained low. In contrast, the vitamin E-total-lipid ratio was in the low normal range from birth onwards. Vitamin E-lipid ratios using two lipid components (cholesterol with triglycerides, or cholesterol with phospholipids) or one lipid component (cholesterol) correlated with the vitamin E-total-lipid ratio with a good sensitivity and specificity. The susceptibility of erythrocytes to hydrogen peroxide-induced damage (measured as potassium release or malondialdehyde production) was high at birth and declined after birth. However, this susceptibility did not correlate with plasma or erythrocyte vitamin E levels or vitamin E-total-lipid ratio, and the hydrogen peroxide hemolysis test is not a reliable indicator of vitamin E status in preterm infants.

CONCLUSIONS

Our study indicated that a gold standard for clinical assessment of vitamin E status in preterm infants is yet to be found.

Association between cigarette smoking and lipid peroxidation in a controlled feeding study

BACKGROUND

Cigarette smoke may promote atherogenesis by producing oxygen-derived free radicals that damage lipids. However, evidence in support of this hypothesis is inconsistent because most studies did not control for aspects of diet (antioxidants and lipid substrate) that may confound the association between smoking and measures of lipid peroxidation.

METHODS AND RESULTS

The relationships between cigarette smoking and two measures of lipid peroxidation, breath ethane (an in vivo assay) and thiobarbituric acid-reactive substances (TBARS, an in vitro assay), were examined in 123 adults (11% of whom were smokers) participating in a controlled feeding study. After 3 weeks of controlled feeding on a common diet (36% total fat, 14% saturated fats, 6% polyunsaturated fats, and 12% monounsaturated fats), breath and fasting serum samples were collected for measurement of ethane and TBARS, respectively. Baseline characteristics of smokers and nonsmokers were similar, including several indices related to diet and nutritional status (albumin, cholesterol, body mass index, and oxygen radical-absorbing capacity). Cigarette smokers had significantly higher breath ethane (8.88 versus 1.71 pmol/L; P<.0001) and TBARS (24.0 versus 20.7 micromol/mL; P=.008) than nonsmokers. The interval between breath collection and the time the last cigarette was smoked was significantly and inversely correlated with breath ethane. Neither measure of lipid peroxidation was associated with measures of serum cholesterol or albumin, body mass index, or serum oxygen radical-absorbing capacity.

CONCLUSIONS

Cigarette smokers have higher rates of in vivo and in vitro lipid peroxidation. These results support the hypothesis that the atherogenic effects of smoking are mediated in part by free radical damage to lipids.