Preventive Anti-inflammatory Effects of Apocynin on Acetic Acid-Induced Colitis in Rats.

Ulcerative colitis is an inflammatory bowel disease with a complex aetiology characterised by abnormal immune responses and oxidative stress-induced tissue injury. Inflammatory cells play an important role in the progression of this pathology through the overproduction of reactive oxygen species (ROS) from various sources including the NADPH oxidases (NOXs). The aim of this study was to investigate the preventive effect of apocynin, a natural antioxidant molecule and a selective inhibitor of NOXs, on acetic acid (AA)-induced ulcerative colitis in rats. Our results first confirmed that apocynin has a high free radical scavenging capacity as well as a potent iron chelating ability. Oral pretreatment of rats with apocynin (200 mg/kg and 400 mg/kg) for 7 days prior to AA-induced colitis suppressed the increase in pro-oxidant markers in colonic homogenates and preserved colonic cytoarchitecture from acetic acid-induced damage. Oral administration of apocynin (200 mg/kg and 400 mg/kg) also reduced several systemic inflammatory markers such as alkaline phosphatase, iron, pro-inflammatory cytokines, C-reactive protein and myeloperoxidase. This study shows that apocynin protects rats from acetic acid-induced colonic inflammation and suggests that apocynin may have a promising beneficial effect in the prevention of ulcerative colitis.

Phytochemical profiling, antioxidant potential and protective effect of leaves extract of tunisian Vitis vinifera autochthonous accessions against acute CCl4-injured hepatotoxicity in mice.

Vitis vinifera leaves (VVL) are agro-industrial waste. In the current study, the phytochemical profile of V. vinifera leaves extracts (VVLE) of two Tunisian autochthonous accessions was determined via LC-UV-ESI/MS, and their antioxidant and hepatoprotective properties were also assessed. Mice were pretreated orally with VVLE (7.5, 15 and 30 mg/kg) for 7 days, and then received acutely and by i.p. a solution CCl4 at 12% in sunflower oil (v/v). Serum levels of hepatic markers, oxidative stress indicators in liver tissue and histological changes were assessed. LC-UV-ESI/MS analysis revealed four phenolic compounds identified in both extracts with quercetin-3-O-glucuronide being the dominant constituent (23.32 ± 1.06 vs. 10.24 ± 0.12 mg/g DM, p < 0.05 for wild and cultivated accessions, respectively). The Antioxidant activity revealed a significant difference between the genotypes. Moreover, the VVLE of the wild "Nefza-I" ecotype was the most active based on antioxidant assays. Furthermore, the results showed that pre-treatment, especially with VVLE, of the wild ecotype "Nefza-I", attenuated CCl4-induced acute liver injury in a dose-dependent manner, as demonstrated by the decrease in the activities of hepatic serum function markers. This was also evidenced by a decrease in the levels of lipoperoxidation and histological damage in the liver, as well as a restoration of antioxidant enzyme activities (SOD and catalase) and an increase in the hepatic glutathione content. Our results demonstrate that VVLE possesses protective effects on CCl4-induced liver injury. Overall, the wild ecotype "Nefza-I" extract could serve as an effective protector against CCl4-induced hepatocellular oxidative stress.

The NADPH Oxidase Inhibitors Apocynin and Diphenyleneiodonium Protect Rats from LPS-Induced Pulmonary Inflammation.

Inflammation is the body's response to insults, for instance, lung inflammation is generally caused by pathogens or by exposure to pollutants, irritants and toxins. This process involves many inflammatory cells such as epithelial cells, monocytes, macrophages and neutrophils. These cells produce and release inflammatory mediators such as pro-inflammatory cytokines, lipids and reactive oxygen species (ROS). Lung epithelial cells and phagocytes (monocytes, macrophages and neutrophils) produce ROS mainly by the NADPH oxidase NOX1 and NOX2, respectively. The aim of this study was to investigate the effects of two NADPH oxidase inhibitors, apocynin and diphenyleneiodonium (DPI), on lipopolysaccharide (LPS)-induced lung inflammation in rats. Our results showed that apocynin and DPI attenuated the LPS-induced morphological and histological alterations of the lung, reduced edema and decreased lung permeability. The evaluation of oxidative stress markers in lung homogenates showed that apocynin and DPI inhibited LPS-induced NADPH oxidase activity, and restored superoxide dismutase (SOD) and catalase activity in the lung resulting in the reduction in LPS-induced protein and lipid oxidation. Additionally, apocynin and DPI decreased LPS-induced MPO activity in bronchoalveolar liquid and lung homogenates, TNF-α and IL-1ß in rat plasma. NADPH oxidase inhibition could be a new therapeutic strategy for the treatment of inflammatory lung diseases.

Change of the litter fall, decomposition, and nutrient release in cork oak forest after anthropogenic disturbances in North West of Tunisia.

In Mediterranean forests, anthropogenic disturbances received little interest in regards to their shrub layer induced enlargement. We studied in the cork oak forest of Beni Métir and in undisturbed and disturbed sites, the relative contribution of the tree (LT, DLT) and shrub (LS, DLS) layers to litter fall, litter decomposition, and nutrients dynamic. Our results showed that disturbance significantly (p < 0.001) reduced (-43%) total litter fall in DS in comparison with S (583 g m-2 year-1); the increased (+ 54%) shrub layer contribution to site litter fall did not counterbalance the decreased input by the tree layer. Leaf litter decomposition was negatively affected (p < 0.001) by disturbance, the remaining mass value being after 2 years, approximately 14 and 33%, respectively, for S and DS. This resulted into a gain of above ground soil organic matter 1.3 higher in DS than it was in S whereas the shrub layer contribution to litter fall increased by 50%. The prevailing driver of decomposition was very probably not related to litter quality but rather site-dependent. Indeed, layers of the same site shared the same remaining mass in spite of significant differences (p < 0.05) in initial content of minerals (N, Ca, and Mn) implicated in biological decomposition. In the disturbed site, the nutrient input by the shrub layer increased by more than double, but its low nutrient quality drastically impaired litter decomposition and mineral return at the site level. In conclusion, this study highlighted the importance of shrub layer which must be taken into account when considering any disturbance assessment and management of Mediterranean forests.

α-TIP aquaporin distribution and size tonoplast variation in storage cells of Vicia faba cotyledons at seed maturation and germination stages.

Vacuoles have been shown to undergo deep modifications in relation to plant developmental stages and in the maintaining the cellular homeostasis. In this context, we studied the variations of the vacuolar membrane size and α-TIP aquaporin distribution at early and advanced seed stages of maturation, germination and embryo growth in Vicia faba cotyledon storage cells.

Effects of seed priming, salinity and methyl jasmonate treatment on bioactive composition of Brassica oleracea var. capitata (white and red varieties) sprouts.

BACKGROUND: Brassica spp. sprouts are rich in nutrients and bioactive compounds, especially glucosinolates and phenolic acid derivatives, and the composition of these young germinating seeds can be altered by several external factors. In this study two cabbage varieties (Brassica oleracea var. capitata, red and white) were studied using seed priming (KCl 50 mmol L-1 ; NaCl 150 mmol L-1 ) and MeJA spraying (25 µmol L-1 ) to elicit the phytochemical content of edible sprouts. RESULTS: The red variety was richer in glucosinolates and phenolic compounds than the white one but not in mineral nutrients. Seed priming enhanced the potassium (K) content and flavonols in both varieties, while the total content of glucosinolates was reduced after seed priming only in the red variety. The white variety responded better than the red one to KCl seed priming, increasing the flavonols (89%). Salinity did not induce any change in the phytochemical content of these two varieties. Elicitation with sprayed MeJA was effective in significantly increasing the content of indolic glucosinolates glucobrassicin (5.7-fold) and neoglucobrassicin (9.7-fold) in the red cultivar. In the white variety, in addition to glucobrassicin (19.4-fold) and neoglucobrassicin (9.4-fold), 4-hydroxyglucobrassicin (2.3-fold) was also enhanced. MeJA also elicited significant amounts of anthocyanins (41%) and chlorogenic acid derivatives (329%) in the white variety. CONCLUSION: KCl seed priming and MeJA elicitation promoted the phytochemical composition of the cabbage varieties, especially in the white variety. The application of NaCl resulted in less efficient elicitation. © 2016 Society of Chemical Industry.

Effects of sodium nitroprusside on mouse erythrocyte catalase activity and malondialdehyde status.

There is controversy about the anti- or pro-oxidative effects of the nitric oxide (NO)-donor sodium nitroprusside (SNP). Hence, the activity of the antioxidant enzyme catalase (CAT) and the status of malondialdehyde (MDA) were investigated after a 2.5 mg/kg dose of SNP had been i.p. administered to different and comparable groups of mice (n = 48). The drug was administered at two different circadian times (1 and 13 h after light onset [HALO]). There were, irrespectively of sampling time, no significant differences in the means of CAT activity and MDA status between control and SNP-treated groups, no matter the treatment time. However, CAT activity was significantly (Student's t-test, p < 0.001) increased 1 h following SNP administration at 1 HALO, whereas the significant (p < 0.001) increase in the enzyme activity was found only 3 h after injection at 13 HALO. The drug dosing either at 1 or 13 HALO resulted in no significant differences of MDA status between control and treated groups regardless to the sampling time. Two-way analysis of variance (ANOVA) detected a significant (F0.05(7,88)= 5.3; p < 0.0006) interaction between sampling time and treatment in mice injected at 1 HALO, suggesting the influence of treatment on sampling-time-related changes in CAT activity. However, ANOVA validated no interaction between the two factors in mice treated at 13 HALO, illustrating that the sampling-time differences in enzyme activity were greater. Furthermore, two-way ANOVA revealed no interaction in the variation of MDA status in animals treated either at 1 or 13 HALO. This study indicates that SNP significantly affected the anti-oxidant system.

Dosing-time dependent effects of sodium nitroprusside on cerebral, renal, and hepatic catalase activity in mice.

To investigate the time dependence of sodium nitroprusside- (NPS-) induced oxidative effects, the authors study the variation of the antioxidant enzyme CAT activity in various tissues after the administration of a single 2.5 mg/kg dose of SNP or sodium chloride (NaCl 0.9%). For each of the two dosing times (1 and 13 hours after light onset, HALO, which correspond to the beginning of diurnal rest span and of nocturnal activity span of mice, resp.), brain, kidney, and liver tissues were excised from animals at 0, 1, 3, 6, 9, 12, 24, and 36 h following the drug administration and CAT activity was assayed. The results suggest that SNP-induced stimulation of CAT activity is greater in all three tissues when the drug is administered at 1 HALO than at 13 HALO. Two-way ANOVA revealed that CAT activity significantly (P < 0.004) varied as a function of the sampling time but not of the treatment in all three tissues. Moreover, a statistically significant (P < 0.004) interaction between the organ sampling-time and the SNP treatment was revealed in kidney regardless of the dosing time, whereas a highly significant (P < 0.0002) interaction was validated in liver only in animals injected at 13 HALO.

Circadian (about 24-hour) variation in malondialdehyde content and catalase activity of mouse erythrocytes.

Lipid peroxidation is a part of normal metabolism that may cause biological molecule damage leading to the formation of several specific metabolites that include aldehydes of variable chains, such as malondialdehyde (MDA). These biological effects are controlled in vivo by a wide spectrum of enzymatic and non-enzymatic defense mechanisms among which catalase (CAT) is considered as an important regulator of oxidative stress. The present study aimed to investigate the possible relationship between the temporal patterns of the formation of MDA and the activity of CAT in the erythrocytes of mice. Twenty-four-hour studies were performed on male Swiss albino mice, 12 weeks old, synchronized to a 12:12 light: dark cycle for 3 weeks. Different and comparable groups of animals (n = 10) were sacrificed at an interval of 4 hours (1, 5, 9, 13, 17, and 21 hours after light onset (HALO)). The levels of erythrocyte MDA concentration and CAT activity both significantly (analysis of variance: F = 6.4, P < 0.002) varied according to the time of sampling under non-stressed conditions. The characteristics of the waveform describing the temporal patterns differed between the two studied variables, e.g. MDA content showing one peak (≅21 HALO) and CAT activity showing three peaks (≅9, 17, and 21 HALO). Cosinor analysis revealed a significant (adjusted Cosinor: P ≤ 0.018) circadian (τ ≅ 24 hours) rhythm in MDA level and no statistically significant rhythmicity in CAT activity. The differences and the absence of correlation between the curve patterns of erythrocyte MDA content and CAT activity under physiological conditions are hypothesized to explain that variation in lipid peroxidation may depend on several factors. Moreover, the identification of peak/trough levels of MDA accumulation in erythrocytes may reflect the degree of oxidative stress in these blood cells. In addition, the observed significant time-of-day effect suggests that, in both clinical and scientific settings, appropriate comparison of MDA production and CAT activity levels can only be achieved on data obtained at the same time of day.

Dosing-time dependent oxidative effects of sodium nitroprusside in brain, kidney, and liver of mice.

UNLABELLED: The purpose of this study was to investigate if the oxidative effects of sodium nitroprusside (SNP) are dosing-time dependent. Therefore, the variation of malondialdehyde (MDA) status was assessed after a single i.p. administration of SNP (2.5mgkg(-1) b.w.) or vehicle (9‰ NaCl) to different and comparable groups of mice (n=48) at two different circadian times (1 and 13h after light onset [HALO]). Brain, kidney, and liver tissues were excised over 36h, and their MDA contents were estimated at 0, 1, 3, 6, 9, 12, 24, and 36h after SNP administration. RESULTS: indicated mean MDA level was not significantly changed in each investigated tissue compared with the control. In contrast, the mean MDA value varied among organs and was comparable in brain and liver but lower than in kidney. The data show SNP significantly (P<0.05) increases MDA status in both tissues and exerts time-dependent oxidative effects with the greatest toxicity coinciding with the beginning of the diurnal rest span (local time: 08:00h, i.e., at 1 HALO). The obtained results reveal SNP-induced oxidative damage (evidenced by MDA accumulation) varies according to both the dosing-time and the target organ.

Study of the heat stability of sunflower oil enriched in natural antioxidants by different analytical techniques and front-face fluorescence spectroscopy combined with Independent Components Analysis.

The aim of this study was to find objective analytical methods to study the degradation of edible oils during heating and thus to suggest solutions to improve their stability. The efficiency of Nigella seed extract as natural antioxidant was compared with butylated hydroxytoluene (BHT) during accelerated oxidation of edible vegetable oils at 120 and 140 °C. The modifications during heating were monitored by 3D-front-face fluorescence spectroscopy along with Independent Components Analysis (ICA), (1)H NMR spectroscopy and classical physico-chemical methods such as anisidine value and viscosity. The results of the study clearly indicate that the natural seed extract at a level of 800 ppm exhibited antioxidant effects similar to those of the synthetic antioxidant BHT at a level of 200 ppm and thus contributes to an increase in the oxidative stability of the oil.

Cardioprotective effect of resveratrol on lipopolysaccharide-induced oxidative stress in rat.

Lipopolysaccharide (LPS) is a glycolipid component of the cell wall of Gram-negative bacteria, which induces a deleterious effect on several organs, including the heart, eventually leading to septic shock and death. Endotoxemia-induced cardiotoxicity is characterized by disturbed intracellular redox balance, excessive reactive oxygen species (ROS) accumulation, inducing DNA, protein, and membrane lipid damage. Resveratrol (trans-3,5,4' trihydroxystilbene; RVT) is a phytoalexin polyphenol that exhibits antioxidant and -inflammatory properties. We investigated the putative effect of a subacute treatment with this natural compound on LPS-induced cardiotoxicity in the rat. We found that resveratrol counteracted LPS-induced lipoperoxidation and decreased superoxide dismutase (SOD) activity, but had no effect on the LPS-induced decrease in catalase (CAT) nor on the increase in peroxidase (POD) activity. Resveratrol also reversed LPS-induced myocardial nitric oxide (NO) elevation. More important, LPS-induced iron depletion from plasma to the myocardial compartment was abolished upon resveratrol treatment. All these data suggest that resveratrol is capable of alleviating LPS-induced cardiotoxicity, and that its mode of action may involve iron-shuttling proteins.

Prevention of lipopolysaccharide-induced mouse lethality by resveratrol.

The present study was undertaken to determine whether subacute treatment with resveratrol (RVT) protects mice against lipopolysaccharide (LPS)-induced oxidative stress and mortality as well as the mechanism involved in such protection. Mice were divided into three groups: control, LPS and LPS+RVT. Animals were pre-treated with RVT during 7 days. The survival rate was monitored over 48 h after LPS administration. Survival animals were sacrificed, their kidney, liver and brain homogenized for malondialdehyde (MDA), catalase (CAT) activity, free iron and nitric oxide (NO) determination. Plasma was also processed for transaminases, creatinine, urea, NO and iron measurement. Pre-treatment with resveratrol greatly improved the survival rate of LPS-treated mice. Resveratrol counteracted LPS-induced tissue lipoperoxidation and catalase activity depletion. The polyphenol abrogated LPS-induced liver and kidney dysfunction as increased creatinine and urea as well as transaminases activities. In addition, pre-treatment with resveratrol abrogated LPS-induced tissues and plasma NO elevation and iron sequestration from plasma to tissue compartment. These data suggest that resveratrol prevents LPS-induced lethality and that its mode of action may involve differential iron deposition via iron shuttling proteins.

NaCl effect on the distribution of wall ingrowth polymers and arabinogalactan proteins in type A transfer cells of Medicago sativa Gabès leaves.

We studied the distribution of wall ingrowth (WI) polymers by probing thin sections of companion cells specialized as transfer cells in minor veins of Medicago sativa cv Gabès blade with affinity probes and antibodies specific to polysaccharides and glycoproteins. The wall polymers in the controls were similar in WIs and in the primary wall but differently distributed. The extent of labeling in these papillate WIs differed for JIM5 and JIM7 homogalacturonans but was in the same range for LM5 and LM6 rhamnogalacturonans and xyloglucans. These data show that WI enhancement probably requires arabinogalactan proteins (JIM8) mainly localized on the outer part of the primary wall and WIs. By comparison, NaCl-treated plants exhibited cell wall polysaccharide modifications indicating (1) an increase in unesterified homogalacturonans (JIM5), probably implicated in Na(+) binding and/or polysaccharide network interaction for limiting turgor variations in mesophyll cells; (2) enhancement of the xyloglucan network with an accumulation of fucosylated xyloglucans (CCRC-M1) known to increase the capacity of cellulose binding; and (3) specific recognition of JIM8 arabinogalactan proteins that could participate in both wall enlargement and cohesion by increasing the number of molecular interactions with the other polymers. In conclusion, the cell wall polysaccharide distribution in enlarged WIs might (1) participate in wall resistance to sequestration of Na(+), allowing a better control of hydric homeostasis in mesophyll cells to maintain metabolic activity in source leaves, and (2) maintain tolerance of M. sativa to NaCl.

Resveratrol, a red wine polyphenol, attenuates lipopolysaccharide-induced oxidative stress in rat liver.

Lipopolysaccharide (LPS) is a glycolipid component of the cell wall of gram-negative bacteria inducing deleterious effects on several organs including the liver and eventually leading to septic shock and death. Endotoxemia-induced hepatotoxicity is characterized by disturbed intracellular redox balance, excessive reactive oxygen species (ROS) accumulation inducing DNA, proteins and membrane lipid damages. Resveratrol (trans-3,5,4' trihydroxystilbene) is a phytoalexin polyphenol exhibiting antioxidant and anti-inflammatory properties. In this study, we investigated the effect of subacute pre-treatment with this natural compound on LPS-induced hepatotoxicity in rat. Resveratrol counteracted LPS-induced lipoperoxidation and depletion of antioxidant enzyme activities as superoxide dismutase (SOD) and catalase (CAT) but slightly glutathione peroxidase (GPx) activity. The polyphenol also abrogated LPS-induced liver and plasma nitric oxide (NO) elevation and attenuated endotoxemia-induced hepatic tissue injury. Importantly resveratrol treatment abolished LPS-induced iron sequestration from plasma to liver compartment. Our data suggest that resveratrol is capable of alleviating LPS-induced hepatotoxicity and that its mode of action may involve differential iron compartmentalization via iron shuttling proteins.

Protective effect of resveratrol against lipopolysaccharide-induced oxidative stress in rat brain.

PRIMARY OBJECTIVE: To study the protective effect of resveratrol on endotoxemia-induced neurotoxicity. METHODS: Rats were pre-treated during 7 days with 20 mg kg(-1) body weight (b.w.) resveratrol and challenged with a single dose of lipopolysaccharide (LPS: 8 mg kg(-1) b.w.) for 24 hours. Brains were harvested to determine LPS-induced lipoperoxidation level, antioxidant enzyme activities, nitric monoxide (NO) and iron distribution as well as the impact of resveratrol on these parameters. RESULTS: Resveratrol counteracted LPS-induced brain malondialdehyde (MDA) level and antioxidant enzyme activities depletion as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Resveratrol also reversed LPS-induced brain and plasma NO elevation as well as iron sequestration from plasma to brain compartment. CONCLUSION: The data suggest that resveratrol is capable of alleviating LPS-induced neurotoxicity by a mechanism that may involve iron shuttling proteins.

Resveratrol opposite effects on rat tissue lipoperoxidation: pro-oxidant during day-time and antioxidant at night.

We investigated the dosing-time dependency of acute resveratrol administration on lipoperoxidation level found in the heart, liver and kidney of male rats synchronized with a 12-h dark-light cycle. Resveratrol was administered by the i.p. route at the middle of the dark (6 h after dark onset, HADO) or light span (18 HADO) and thiobarbituric acid reactive species (TBARS) measured 4 h later at 10 and 22 HADO, respectively. Basal TBARS levels in the three organs were higher during the night span when compared to day span. Resveratrol effect on tissues TBARS was also dosing-time dependent. When administered during the dark phase, resveratrol decreased TBARS levels whereas at the light span, the polyphenol increased TBARS in the three organs. Resveratrol behaved as an antioxidant during the dark span and as a pro-oxidant during the light span. These data suggested a day/night rhythm in basal lipoperoxidation and in resveratrol antioxidant effect.

Protective effect of resveratrol in endotoxemia-induced acute phase response in rats.

Lipopolysaccharide (LPS), a glycolipid component of the cell wall of gram-negative bacteria can elicit a systemic inflammatory process leading to septic shock and death. Acute phase response is characterized by fever, leucocytosis, thrombocytopenia, altered metabolic responses and redox balance by inducing excessive reactive oxygen species (ROS) generation. Resveratrol (trans-3,5,4' trihydroxystilbene) is a natural polyphenol exhibiting antioxidant and anti-inflammatory properties. We investigated the protective effect of resveratrol on endotoxemia-induced acute phase response in rats. When acutely administered by i.p. route, resveratrol (40 mg/kg b.w.) counteracted the effect of a single injection of LPS (4 mg/kg b.w.) which induced fever, a decrease in white blood cells (WBC) and platelets (PLT) counts. When i.p. administered during 7 days at 20 mg/kg per day (subacute treatment), resveratrol abrogated LPS-induced erythrocytes lipoperoxidation and catalase (CAT) activity depression to control levels. In the plasma compartment, LPS increased malondialdehyde (MDA) via nitric monoxide (NO) elevation and decreased iron level. All these deleterious LPS effects were reversed by a subacute resveratrol pre-treatment via a NO independent way. Resveratrol exhibited potent protective effect on LPS-induced acute phase response in rats.

Protective effect of resveratrol on acute endotoxemia-induced nephrotoxicity in rat through nitric oxide independent mechanism.

Lipopolysaccharide (LPS) is a glycolipid component of the cell wall of gram negative bacteria inducing deleterious effects on the kidney. Endotoxemia-induced nephrotoxicity is characterized by disturbed intracellular redox balance and reactive oxygen species (ROS) accumulation leading to DNA, proteins and membrane lipid damages. Resveratrol (trans-3,5,4'-trihydroxystilbene) is a polyphenol displaying antioxidant and anti-inflammatory properties. This study investigated its effects on LPS-induced nephrotoxicity in rats. Resveratrol counteracted all LPS-induced changes in renal haemodynamic parameters. In the kidney resveratrol abrogated LPS-induced lipoperoxidation and antioxidant enzyme activities depletion as superoxide dismutase (SOD) and catalase (CAT) but not peroxidase (POD) activity. LPS increased plasma and urine nitric oxide (NO) level and resveratrol reversed them. More importantly, LPS-induced iron mobilization from plasma to kidney, which was also abolished by resveratrol treatment. All these results suggest that resveratrol exerted strong antioxidant properties against LPS-induced nephrotoxicity and that its mode of action seemed to involve iron shuttling proteins.

Malondialdehyde content and circadian variations in brain, kidney, liver, and plasma of mice.

In aerobic organisms, the use of oxygen (O(2)) to produce energy is associated with the production of Reactive Oxygen Species (ROS), which reacts with biological molecules to produce oxidized metabolites such as malondialdehyde (MDA). This experiment focused on male Swiss mice 12 weeks of age synchronized for 3 weeks by the 12 h light (rest)/12 h dark (activity) span. Different and comparable groups of animals (n=10) were sacrificed at six different circadian stages: 1, 5, 9, 13, 17, and 21 h after light onset (HALO). The 24 h mean MDA level varied among organs of mice in non-stress conditions and was comparable in brain and liver but lower than in kidney. As the MDA 24 h status constitutes only a part of ROS damages in sites differing by their oxygen use, lipid composition, and detoxification capacity, the temporal patterns of their MDA content were comparatively studied in relationship to the animal rest-activity cycle. The results revealed significant circadian rhythms with the peak time located during the rest span (approximately =5 HALO) for both brain and liver, but during the activity span for the kidney ( approximately =21 HALO) and plasma (approximately =13 HALO). This chronobiological study showed that under physiological conditions, lipid peroxidation depends on several factors. The MDA peak/trough might be used as a tool to detect moments of high/low sensitivity of tissues to ROS attack in rodents.