Increased copper (Cu) and iron (Fe) levels in liver and brain are associated to oxidative stress and damage with increased phospholipid oxidation process. The aim of this work was to assess the toxic ...effects of Cu2+ and Fe3+ addition to rat liver mitochondria by determining mitochondrial respiration in states 3 (active respiration) and 4 (resting respiration), and phospholipid peroxidation. Both, Cu2+ and Fe3+ produced decreases in O2 consumption in a concentration-dependent manner in active state 3: both ions by 42% with malate-glutamate as complex I substrate (concentration for half maximal response (C50) 60μM Cu2+ and 1.25mM Fe3+), and with succinate as complex II substrate: 64–69% with C50 of 50μM Cu2+ and with C50 of 1.25mM of Fe3+. Respiratory control decreased with Cu2+ (C50 50μM) and Fe3+ (C50 1.25-1-75mM) with both substrates. Cu2+ produced a 2-fold increase and Fe3+ a 5-fold increase of thiobarbituric acid-reactive substances (TBARS) content from 25μM Cu2+ (C50 40μM) and from 100μM Fe3+ (C50 1.75mM). Supplementations with Cu2+ and Fe3+ ions induce mitochondrial dysfunction with phospholipid peroxidation in rat liver mitochondria. Although is proved that a Fenton/Haber Weiss mechanism of oxidative damage occurs in metal-ion induced mitochondrial toxicity, slightly different responses to the metal ions suggest some differences in the mechanism of intracellular toxicity. The decreased rates of mitochondrial respiration and the alteration of mitochondrial function by phospholipid and protein oxidations lead to mitochondrial dysfunction, cellular dyshomeostasis and cell death.
The Copper(II) and Iron(III) addition to isolated rat liver mitochondria produced decreased rates of mitochondrial respiration and oxygen consumption in active state 3 and phospholipid peroxidation by a Fenton/Haber Weiss mechanism of oxidative damage. Slightly different responses to the metal ions suggest some differences in the mechanism of intracellular toxicity. Display omitted
•Cu(II) and Fe(III) addition to isolated rat liver mitochondria produced inhibition of mitochondrial respiration.•Decreased mitochondrial respiration is maximal in O2 consumption in active state 3.•Mitochondrial respiratory dysfunction is related to phospholipid peroxidation in mitochondria supplemented with Cu(II) and Fe(III).•Different response to metal addition indicates different intracellular toxicity mechanisms.•The direct impact on the organelle functionality of far lower concentrations of Cu than Fe suggests a dissociating event in the mechanism of toxicity of both metals.
The metals iron (Fe) and copper (Cu) are considered trace elements, and the metals cobalt (Co) and nickel (Ni) are known as ultra-trace elements, considering their presence in low to very low ...quantity in humans. The biologic activity of these transition metals is associated with the presence of unpaired electrons that favor their participation in redox reactions. They are part of important enzymes involved in vital biologic processes. However, these transition metals become toxic to cells when they reach elevated tissue concentrations and produce cellular oxidative damage. Phospholipid liposomes (0.5 mg/ml, phosphatidylcholine (PC)/phosphatidylserine (PS), 60/40) were incubated for 60 min at 37°C with 25 μM of Fe²⁺ in the absence and in the presence of Cu²⁺, Co²⁺, and Ni²⁺ (0-100 μM) with and without the addition of hydrogen peroxide (H₂O₂, 5-50 μM). Iron-dependent lipid peroxidation in PC/PS liposomes was assessed by thiobarbituric acid-reactive substances (TBARS) production. Metal transition ions promoted lipid peroxidation by H₂O₂ decomposition and direct homolysis of endogenous hydroperoxides. The Fe²⁺-H₂O₂-mediated lipid peroxidation takes place by a pseudo-second order process, and the Cu²⁺-mediated process by a pseudo-first order reaction. Co²⁺ and Ni²⁺ alone do not induce lipid peroxidation. Nevertheless, when they are combined with Fe²⁺, Fe²⁺-H₂O₂-mediated lipid peroxidation was stimulated in the presence of Ni²⁺ and was inhibited in the presence of Co²⁺. The understanding of the effects of transition metal ions on phospholipids is relevant to the prevention of oxidative damage in biologic systems.
Rat liver mitochondria (1.5–2.1mg protein·mL−1) supplemented with either 25 and 100μM Cu2+ or 100 and 500μM Fe3+ show inhibition of active respiration (O2 consumption in state 3) and increased ...phospholipid peroxidation . Liver mitochondria were supplemented with the antioxidants reduced glutathione, N-acetylcysteine or butylated hydroxitoluene, to evaluate their effects on the above-mentioned alterations. Although the mitochondrial dysfunction is clearly associated to phospholipid peroxidation, the different responses to antioxidant supplementation indicate that the metal ions have differences in their mechanisms of toxicity. Mitochondrial phospholipid peroxidation through the formation of hydroxyl radical by a Fenton/Haber-Weiss mechanism seems to precede the respiratory inhibition and to be the main fact in Fe-induced mitochondrial dysfunction. In the case of Cu2+, it seems that the ion oxidizes glutathione, and low molecular weight protein thiol groups in a direct reaction, as part of its intracellular redox cycling. The processes involving phospholipid peroxidation, protein oxidation and mitochondrial respiratory inhibition characterize a redox dyshomeostatic situation that ultimately leads to cell death. However, Cu2+ exposure involves an additional, yet unidentified, toxic event as previous reduction of the metal with N-acetylcysteine has only a minor effect in preventing the mitochondrial damage.
Cu2+ and Fe3+ overloads produce respiratory inhibition and phospholipid peroxidation in mitochondria. While the HO• formation by a Fenton/Haber-Weiss reaction is the responsible mechanism for Fe3+ cytotoxicity, Cu2+ also reacts with thiol groups and glutathione (GSH) since supplementation with GSH leads to full protection probably through formation of Cu(I)-(GSH)2 complexes. Display omitted
•Cu and Fe yield phospholipid oxidation and unpaired respiration in isolated mitochondria.•Fe and Cu showed differences in the mechanism of intracellular toxicity.•Lipid oxidation by hydroxyl radical is the main factor in Fe toxicity to mitochondria.•Cu may be oxidizing thiol groups in a direct reaction as part of its redox cycling.
The transition metals iron (Fe) and copper (Cu) are needed at low levels for normal health and at higher levels they become toxic for humans and animals. The acute liver toxicity of Fe and Cu was ...studied in Sprague Dawley male rats (200g) that received ip 0–60mg/kg FeCl2 or 0–30mg/kg CuSO4. Dose and time-responses were determined for spontaneous in situ liver chemiluminescence, phospholipid lipoperoxidation, protein oxidation and lipid soluble antioxidants. The doses linearly defined the tissue content of both metals. Liver chemiluminescence increased 4 times and 2 times after Fe and Cu overloads, with half maximal responses at contents (C50%) of 110μgFe/g and 42μgCu/g liver, and with half maximal time responses (t1/2) of 4h for both metals. Phospholipid peroxidation increased 4 and 1.8 times with C50% of 118μg Fe/g and 45μg Cu/g and with t1/2 of 7h and 8h. Protein oxidation increased 1.6 times for Fe with C50% at 113μg Fe/g and 1.2 times for Cu with 50μg Cu/g and t1/2 of 4h and 5h respectively. The accumulation of Fe and Cu in liver enhanced the rate of free radical reactions and produced oxidative damage. A similar free radical‐mediated process, through the formation HO• and RO• by a Fenton-like homolytic scission of H2O2 and ROOH, seems to operate as the chemical mechanism for the liver toxicity of both metals.
The acute liver toxicity of Fe and Cu overloads, evaluated from dose and time-responses, indicate that a similar chemical mechanism of a free radical‐mediated process seems to operate for the biochemical effects through the formation HO• and RO• by a Fenton-like homolytic scission of H2O2 and ROOH. Display omitted
► Liver oxidative damage is produced by higher than normal Fe and Cu liver contents. ► Metal concentration in liver is linearly related to metal intakes. ► Increased liver Fe and Cu contents similarly produced increased oxidative damage. ► This damage is simultaneous and generated for a common biochemical mechanism. ► Free radical process operate by HO• and RO• generated from H2O2 and ROOH scission.
Oxidative stress and damage are characterized by decreased tissue antioxidant levels, consumption of tissue α-tocopherol, and increased lipid peroxidation. These processes occur earlier than necrosis ...in the liver, heart, kidney, and brain of weanling rats fed a choline deficient (CD) diet. In tissues, water-soluble antioxidants were analyzed as total reactive antioxidant potential (TRAP), α-tocopherol content was estimated from homogenate chemiluminescence (homogenate-CL), and lipid peroxidation was evaluated by thiobarbituric acid reactive substances (TBARS). Histopathology showed hepatic steatosis at days 1–7, tubular and glomerular necrosis in kidney at days 6 and 7, and inflammation and necrosis in heart at days 6 and 7. TRAP levels decreased by 18%, 48%, 56%, and 66% at day 7, with
t
1/2 (times for half maximal change) of 2.0, 1.8, 2.5, and 3.0 days in liver, kidney, heart, and brain, respectively. Homogenate-CL increased by 97%, 113%, 18%, and 297% at day 7, with
t
1/2 of 2.5, 2.6, 2.8, and 3.2 days in the four organs, respectively. TBARS contents increased by 98%, 157%, 104%, and 347% at day 7, with
t
1/2 of 2.6, 2.8, 3.0, and 5.0 days in the four organs, respectively. Plasma showed a 33% decrease in TRAP and a 5-fold increase in TBARS at day 5. Oxidative stress and damage are processes occurring earlier than necrosis in the kidney and heart. In case of steatosis prior to antioxidant consumption and increased lipid peroxidation, no necrosis is observed in the liver.
The rat liver antioxidant response to Fe and Cu overloads (0–60mg/kg) was studied. Dose- and time-responses were determined and summarized by t1/2 and C50, the time and the liver metal content for ...half maximal oxidative responses. Liver GSH (reduced glutathione) and GSSG (glutathione disulfide) were determined. The GSH content and the GSH/GSSG ratio markedly decreased after Fe (58–66%) and Cu (79–81%) loads, with t1/2 of 4.0 and 2.0h. The C50 were in a similar range for all the indicators (110–124μgFe/g and 40–50μgCu/g) and suggest a unique free-radical mediated process. Hydrophilic antioxidants markedly decreased after Fe and Cu (60–75%; t1/2: 4.5 and 4.0h). Lipophilic antioxidants were also decreased (30–92%; t1/2: 7.0 and 5.5h) after Fe and Cu. Superoxide dismutase (SOD) activities (Cu,Zn-SOD and Mn-SOD) and protein expression were adaptively increased after metal overloads (Cu,Zn-SOD: t1/2: 8–8.5h and Mn-SOD: t1/2: 8.5–8.0h). Catalase activity was increased after Fe (65%; t1/2: 8.5h) and decreased after Cu (26%; t1/2: 8.0h), whereas catalase expression was increased after Fe and decreased after Cu overloads. Glutathione peroxidase activity decreased after metal loads by 22–39% with a t1/2 of 4.5h and with unchanged protein expression. GSH is the main and fastest responder antioxidant in Fe and Cu overloads. The results indicate that thiol (SH) content and antioxidant enzyme activities are central to the antioxidant defense in the oxidative stress and damage after Fe and Cu overloads.
The antioxidant protection in liver is highly affected after Fe and Cu acute overloads. GSH is the main and fastest-responder antioxidant. An adaptive response of increased expression and activity of SOD1, SOD2 and catalase follows to Fe and Cu overloads. Increased cytosolic levels of Fe2+ and Cu+ and of H2O2 are central to the hypothesis that Fe and Cu toxicities are mediated by increased rates of HO and RO formation. Display omitted
Abstract Aim To evaluate the cognitive performance of a homogeneous population of Alzheimer's disease (AD), non-demented Type 2 Diabetes Mellitus (DIAB), demented with concomitant diseases (AD+DIAB) ...and healthy control subjects. AD is a progressive dementia disorder characterized clinically by impairment of memory, cognition and behavior. Recently, a major research interest in AD has been placed on early evaluation. Diabetes is one of the clinical conditions that represent the greatest risk of developing oxidative stress and dementia. Glucose overload, leading to the development of impaired-induced insulin secretion in DIAB and has been suggested to slow or deter AD pathogenesis. Methods The degree of cognitive impairment was determined on the Alzheimer Disease Assessment Scale-Cognitive (ADAS-Cog) and the Folstein's Mini Mental State Examination (MMSE); the severity of dementia was quantified applying the Clinical Dementia Rating (CDR) test; the Hamilton test was employed to evaluate depressive conditions; the final population studied was 101 subjects. Results The cognitive deterioration is statistically significantly lower ( p < 0.05) in AD+DIAB patients as compared with AD patients. Conclusions In this longitudinal study the superimposed diabetic condition was associated with a lower rate of cognitive decline, while diabetic non-demented patients and controls present normal scores.
Long-term lithium treatment was associated with chronic kidney disease and renal failure although the underlying pathogenic mechanisms are not certainty known. The aim of this study was to evaluate ...changes in oxidative stress measures as well as renal functional and structural alterations associated with chronic use of lithium in rats. Forty Wistar male rats were randomized into four groups: control groups fed ad libitum powered standard diet for 1 and 3 months and experimental groups fed ad libitum the same diet supplemented with 60 mmol/kg diet for 1 and 3 months. Histopathological changes, laboratory parameters, and oxidative stress measurements were assessed at months 1 and 3. The experimental animals showed alteration of the cortical tubules from the first month of lithium-treatment and a decrease in the glomerular filtration rate and in the glomerular area at the third month. There was an increase in thiobarbituric acid reactive substances and carbonyls, as well as an increase in reduced glutathione, in the kidney of rats exposed to lithium. These changes were evident from the first month of treatment and remained throughout the experiment. Our results suggest that, oxidative stress could be one of the pathogenic mechanisms involved in the structural and functional alterations of the kidney associated with prolonged use of lithium. The study of the pathogenic mechanisms involved in lithium-induced nephropathy is a critical issue for the development of new strategies for prevention and/or early detection.
This study reports on the acute brain toxicity of Fe and Cu in male Sprague-Dawley rats (200 g) that received 0 to 60 mg kg(-1) (ip) FeCl2 or CuSO4. Brain metal contents and time-responses were ...determined for rat survival, in situ brain chemiluminescence and phospholipid and protein oxidation products. Metal doses hyperbolically defined brain metal content. Rat survival was 91% and 60% after Fe and Cu overloads. Brain metal content increased from 35 to 114 μg of Fe per g and from 3.6 to 34 μg of Cu per g. Brain chemiluminescence (10 cps cm(-2)) increased 3 and 2 times after Fe and Cu overloads, with half maximal responses (C50) of 38 μg of Fe per g of brain and 15 μg of Cu per g of brain, and with half time responses (t1/2) of 12 h for Fe and 20 h for Cu. Phospholipid peroxidation increased by 56% and 31% with C50 of 40 μg of Fe per g and 20 μg of Cu per g and with t1/2 of 9 h and 14 h. Protein oxidation increased by 45% for Fe with a C50 of 40 μg of Fe per g and 18% for Cu with a C50 of 10 μg of Cu per g and a t1/2 of 12 h for both metals. Fe and Cu brain toxicities are likely mediated by Haber-Weiss type HO˙ formation with subsequent oxidative damage.
Rotenone and pyridaben were tested on activities and properties of rat brain mitochondria determining Ki (inhibitor concentration at half maximal inhibition) and Imax (% of inhibition at maximal ...inhibitor concentration). The assayed activities were complexes I, II and IV, respiration in states 3, 3u (uncoupled) and 4, biochemical and functional activities of mitochondrial nitric oxide synthase (mtNOS), and inner membrane potential. Selective inhibitions of complex I activity, mitochondrial respiration and membrane potential with malate-glutamate as substrate were observed, with a Ki of 0.28–0.36 nmol inhibitor/mg of mitochondrial protein. Functional mtNOS activity was half-inhibited at 0.70–0.74 nmol inhibitor/mg protein in state 3 mitochondria and at 2.52–2.98 nmol inhibitor/mg protein in state 3u mitochondria. This fact is interpreted as an indication of mtNOS being structurally adjacent to complex I with an intermolecular mtNOS-complex I hydrophobic bonding that is stronger at high Δψ and weaker at low Δψ.
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