Taurine prevents high-glucose-induced human vascular endothelial cell apoptosis

Elevated blood glucose in uncontrolled diabetes is causallycorrelated with diabetic microangiopathy. Hyperglycemia-triggered accelerated endothelial cell apoptosis is a critical event in theprocess of diabetes-associated microvascular disease. The conditionallysemiessential amino acid taurine has been previously shown to protectagainst human endothelial cell apoptosis. Therefore, this study wasdesigned to investigate the role of taurine in the prevention ofhigh-glucose-mediated cell apoptosis in human umbilical veinendothelial cells (HUVEC) and the mechanisms involved. Exposure ofHUVEC to 30 mM glucose for 48 h (short-term) and 14 days (long-term)resulted in a significant increase in apoptosis, compared with normalglucose (5.5 mM; P < 0.05).High-glucose-induced DNA fragmentation preferentially occurred in the Sphase cells. Mannitol (as osmotic control) at 30 mM failed to induceHUVEC apoptosis. Taurine prevented high-glucose-induced HUVECapoptosis, which correlates with taurine attenuation ofhigh-glucose-mediated increased intracellular reactive oxygen species(ROS) formation and elevated intracellularCa²⁺ concentration([Ca²⁺]_i)level. Antioxidants, DMSO, N-acetylcysteine, and glutathione, only partly attenuated high-glucose-inducedHUVEC apoptosis. Glucose at 30 mM did not cause HUVEC necrosis.However, both glucose and mannitol at 60 mM caused HUVEC necrosis asrepresented by increased lactate dehydrogenase release and cell lysis.Taurine failed to prevent hyperosmolarity-induced cell necrosis. Theseresults demonstrate that taurine attenuates hyperglycemia-induced HUVECapoptosis through ROS inhibition and[Ca²⁺]_istabilization and suggest that taurine may exert a beneficial effect inpreventing diabetes-associated microangiopathy.

     

Effect of taurine on ischemia–reperfusion injury

Taurine is an abundant β-amino acid that regulates several events that dramatically influence the development of ischemia–reperfusion injury. One of these events is the extrusion of taurine and Na⁺ from the cell via the taurine/Na⁺ symport. The loss of Na⁺ during the ischemia–reperfusion insult limits the amount of available Na⁺ for Na⁺/Ca²⁺ exchange, an important process in the development of Ca²⁺ overload and the activation of the mitochondrial permeability transition, a key process in ischemia–reperfusion mediated cell death. Taurine also prevents excessive generation of reactive oxygen species by the respiratory chain, an event that also limits the activation of the MPT. Because taurine is an osmoregulator, changes in taurine concentration trigger “osmotic preconditioning,” a process that activates an Akt-dependent cytoprotective signaling pathway that inhibits MPT pore formation. These effects of taurine have clinical implications, as experimental evidence reveals potential promise of taurine therapy in preventing cardiac damage during bypass surgery, heart transplantation and myocardial infarction. Moreover, severe loss of taurine from the heart during an ischemia–reperfusion insult may increase the risk of ventricular remodeling and development of heart failure.     

Mouse recombinant leptin protects human hepatoma HepG2 against apoptosis,TNF-α response and oxidative stress induced by the hepatotoxin–ethanol

Obesity is a risk factor for hepatocellular carcinoma (HCC) complicated with alcoholic liver disease (ALD) and cryptogenic cirrhosis. Leptin is a 16-kDa antiobesity hormone secreted mainly by adipocytes. The role of leptin on alcohol-mediated effects in cell line is yet to be unraveled. Therefore, we investigated the effect of leptin against ethanol-elicited cytoxicity in human hepatoma cell lines (HepG2). HepG2 cells were treated with leptin (31.2 nM), ethanol (500 mM), ethanol + leptin and untreated cells served as control. 48 h after treatment, cell viability, apoptosis, TNF-α secretory response and oxidative damage were analysed. Our results suggest that leptin at a concentration of 31.2 nM prevents ethanol elicited cytotoxicity as evidenced by MTT and trypan blue dye exclusion assay. Leptin also inhibited ethanol-induced apoptosis, which was confirmed by [³H] thymidine uptake and cell cycle analysis using propidium iodide (PI) staining. Further, simultaneous leptin treatment along with ethanol showed protection against ethanol mediated cellular damage as indicated by significantly decreased levels of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) and significantly increased levels of reactive nitrogen species (RNS), reduced glutathione (GSH) and elevated activities of superoxide dismutase (SOD) and catalase (CAT). In addition, leptin downregulated the secretion of tumor necrosis factor-α (TNF-α) by ethanol-induced HepG2 cells. Our results demonstrate that simultaneous leptin treatment along with ethanol could be useful in preventing the damage produced by ethanol, which might be of therapeutic interest.     

Taurine ameliorates alloxan-induced diabetic renal injury, oxidative stress-related signaling pathways and apoptosis in rats

Hyperglycemia-induced oxidative stress plays a vital role in the progression of diabetic nephropathy. The renoprotective nature of taurine has also been reported earlier; but little is known about the mechanism of this beneficial action. The present study has, therefore, been carried out to explore in detail the mechanism of the renoprotective effect of taurine under diabetic conditions. Diabetes was induced in rats by alloxan (single i.p. dose of 120?mg/kg body weight) administration. Taurine was administered orally for 3?weeks (1% w/v in drinking water) either from the day on which alloxan was injected or after the onset of diabetes. Alloxan-induced diabetic rats showed a significant increase in plasma glucose, enhanced the levels of renal damage markers, plasma creatinine, urea nitrogen and urinary albumin. Diabetic renal injury was associated with increased kidney weight to body weight ratio and glomerular hypertrophy. Moreover, it increased the productions of reactive oxygen species, enhanced lipid peroxidation and protein carbonylation in association with decreased intracellular antioxidant defense in the kidney tissue. In addition, hyperglycemia enhanced the levels of proinflammatory cytokins (TNF-α, IL-6, IL-1β) and Na⁺–K⁺-ATPase activity with a concomitant reduction in NO content and eNOS expression in diabetic kidney. Investigation of the oxidative stress-responsive signaling cascades showed the upregulation of PKCα, PKCβ, PKCε and MAPkinases in the renal tissue of the diabetic animals. However, taurine administration decreased the elevated blood glucose and proinflammatory cytokine levels, reduced renal oxidative stress (via decrease in xanthine oxidase activity, AGEs formation and inhibition of p47phox/CYP2E1 pathways), improved renal function and protected renal tissue from alloxan-induced apoptosis via the regulation of Bcl-2 family and caspase-9/3 proteins. Taurine supplementation in regular diet could, therefore, be beneficial to regulate diabetes-associated renal complications.     

Taurine protects cerebellar neurons of the external granular layer against ethanol-induced apoptosis in 7-day-old mice

Acute alcohol administration is harmful especially for the developing nervous system, where it induces massive apoptotic neurodegeneration leading to alcohol-related disorders of newborn infants. Neuroprotection against ethanol-induced apoptosis may save neurons and reduce the consequences of maternal alcohol consumption. Previously we have shown that taurine protects immature cerebellar neurons in the internal granular layer of cerebellum from ethanol-induced apoptosis. Now we describe a similar protective action for taurine in the external layer of cerebellum of 7-day-old mice. The mice were divided into three groups: ethanol-treated, ethanol + taurine-treated and controls. Ethanol (20% solution) was administered subcutaneously at a total dose of 5 g/kg (2.5 g/kg at time 0 h and 2.5 g/kg at 2 h) to the ethanol and ethanol + taurine groups. The ethanol + taurine group also received subcutaneously two injections of taurine (1 g/kg each, 1 h before the first dose of ethanol and 1 h after the second dose of ethanol). To verify apoptosis, immunostaining for activated caspase-3 and TUNEL staining were made in the mid-sagittal sections containing lobules I–X of the cerebellar vermis at 8 h after the first ethanol injection. Ethanol induced apoptosis in the cerebellar external granular layer. Taurine treatment significantly reduced the number of activated caspase-3-immunoreactive and TUNEL-positive cells. Taurine has thus a neuroprotective antiapoptotic action in the external granular layer of the cerebellum, preserving a number of neurons from ethanol-induced apoptosis.     

Taurine modulates kallikrein activity and glucose metabolism in insulin resistant rats

Summary. Taurine, a potent antioxidant has been reported to show an antidiabetic effect in streptozotocin-induced diabetes mellitus in which the development of hyperglycemia results from the damage to β cells of pancreas by reactive oxygen species. In addition, taurine also increases the excretion of nitrite and enhances the formation of kinins and would be expected to improve insulin resistance. The effect of taurine on insulin sensitivity was examined in the high fructose-fed rats, an animal model of insulin resistance. Male Wistar rats of body weight 170–190 g were divided into 4 groups: a control group and taurine-supplemented control group, taurine supplemented and unsupplemented fructose-fed group. An intravenous glucose tolerance test (IVGTT) and a steady state plasma glucose level (SSPG) were performed before the sacrifice. The fructose-fed rats displayed hyperglycemia and insulin resistance and they had a greater accumulation of glycogen than did control rats. Hyperglycemia and insulin resistance were significantly lower in the taurine supplemented fructose-fed group than in the unsupplemented fructose-fed group. Urinary kallikrein activity was higher in taurine-treated animals than in the rats fed only fructose. The activity of membrane bound ATPases were significantly lower in fructose-fed rats than in the control rats and were significantly higher in the taurine supplemented group than in the fructose-fed group. Taurine effectively improves glucose metabolism in fructose-fed rats presumably via improved insulin action and glucose tolerance. Received January 5, 2001 Accepted August 21, 2001     

Mechanisms of Phenytoin‐Induced Toxicity in Freshly Isolated Rat Hepatocytes and the Protective Effects of Taurine and/or Melatonin

Phenytoin is a widely used antiepileptic drug. However, hepatotoxicity is one of its adverse effects reported in some patients. The mechanism(s) by which phenytoin causes hepatotoxicity is not clear yet. This study was designed to evaluate the cytotoxic mechanism(s) of phenytoin toward rat hepatocytes (whose cytochrome P450 enzymes had been induced by Phenobarbital). Furthermore, the effect of taurine and/or melatonin on this toxicity was investigated. Cell death, reactive oxygen species (ROS) formation, lipid peroxidation (LPO), and mitochondrial depolarization were monitored as toxicity markers. Results showed that phenytoin caused an elevation in ROS formation, depletion of intracellular reduced glutathione, increase in cellular oxidized glutathione, enhancement of LPO, and mitochondrial damage. Taurine (1 mM) and/or melatonin (1 mM) administration decreased the intensity of cellular injury caused by phenytoin. This study suggests the protective role of taurine and/or melatonin against phenytoin‐induced cellular damage probably through their reactive radical scavenging properties and their effects on mitochondria.     

Taurine inhibits apoptosis by preventing formation of the Apaf-1/caspase-9 apoptosome

Cardiomyocyte apoptosis contributes to cell death during myocardial infarction. One of the factors that regulate the degree of apoptosis during ischemia is the amino acid taurine. To study the mechanism underlying the beneficial effect of taurine, we examined the interaction between taurine and mitochondria-mediated apoptosis using a simulated ischemia model with cultured rat neonatal cardiomyocytes sealed in closed flasks. Exposure to medium containing 20 mM taurine reduced the degree of apoptosis following periods of ischemia varying from 24 to 72 h. In the untreated group, simulated ischemia for 24 h led to mitochondrial depolarization accompanied by cytochrome c release. The apoptotic cascade was also activated, as evidenced by the activation of caspase-9 and -3. Taurine treatment had no effect on mitochondrial membrane potential and cytochrome c release; however, it inhibited ischemia-induced cleavage of caspase-9 and -3. Taurine loading also suppressed the formation of the Apaf-1/caspase-9 apoptosome and the interaction of caspase-9 with Apaf-1. These findings demonstrate that taurine effectively prevents myocardial ischemia-induced apoptosis by inhibiting the assembly of the Apaf-1/caspase-9 apoptosome. ischemia; cultured cardiomyocytes     

Effects of high salt diets and taurine on the development of hypertension in the stroke-prone spontaneously hypertensive rat

Summary. Taurine is present in high concentrations in mammalian tissues and has been implicated in cardiovascular control mechanisms. The aim of the present study was to evaluate the ability of taurine to attenuate salt-induced elevations in blood pressure and markers of damage to the kidney and cardiovascular system in stroke prone spontaneously hypertensive rats (SPSHR). Male SPSHR (6 weeks old) were placed on high salt diets that contained 1% (w/w) NaCl added to their normal chow for 84 days and then were switched to 3% added NaCl for the remaining 63 days of the study. SPSHR was given 1.5% taurine in the drinking water (n = 8), a taurine free diet (n = 8) or normal chow (n = 8). A final control group (n = 6) was not given high salt diets. High salt diets caused an acceleration in the development of hypertension in all groups. Taurine supplementation reduced ventricular hypertrophy and decreased urinary excretion of protein and creatinine. The taurine free diet did not alter serum or urinary excretion of taurine, but did result in elevated urinary nitrogen excretion, increased serum cholesterol levels, and impaired performance in a spatial learning task. Alterations in dietary taurine intake did not alter urinary or serum electrolytes (Na⁺, K⁺), but taurine supplementation did attenuate a rise in serum calcium seen with the high salt diets. Urinary excretion (μg/24 h) of epinephrine and dopamine was significantly reduced in SPSHR given 1% NaCl in the diet, but this effect was not seen in SPSHR on taurine free or supplemented diets. Taurine supplementation showed cardioprotective and renoprotective effects in SPSHR given high salt diets. Received April 12, 1999/Accepted September 13, 1999     

Mechanisms of Trazodone‐Induced Cytotoxicity and the Protective Effects of Melatonin and/or Taurine toward Freshly Isolated Rat Hepatocytes

It has been reported that the bioactive intermediate metabolites of trazodone might cause hepatotoxicity. This study was designed to investigate the exact mechanism of hepatocellular injury induced by trazodone as well as the protective effects of taurine and/or melatonin against this toxicity. Freshly isolated rat hepatocytes were used. Trazodone was cytotoxic and caused cell death with LC₅₀ of 300 µm within 2 h. Trazodone caused an increase in reactive oxygen species (ROS) formation, malondialdehyde accumulation, depletion of intracellular reduced glutathione (GSH), rise of oxidized glutathione disulfide (GSSG), and a decrease in mitochondrial membrane potential, which confirms the role of oxidative stress in trazodone‐induced cytotoxicity. Preincubation of hepatocytes with taurine prevented ROS formation, lipid peroxidation, depletion of intracellular reduced GSH, and increase of oxidized GSSG. Taurine could also protect mitochondria against trazodone‐induced toxicity. Administration of melatonin reduced the toxic effects of trazodone in isolated rat hepatocytes. © 2013 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:457‐462, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.21509     

Resveratrol ameliorates oxidative DNA damage and protects against acrylamide-induced oxidative stress in rats

Acrylamide (ACR), used in many fields from industrial manufacturing to laboratory personnel work is also formed during the heating process through interactions of amino acids. Therefore ACR poses a significant risk to human health. This study aimed to elucidate whether resveratrol (RVT) treatment could modulate ACR-induced oxidative DNA damage and oxidative changes in rat brain, lung, liver, kidney and testes tissues. Rats were divided into four groups as control (C); RVT (30 mg/kg i.p. dissolved in 0.9% NaCl), ACR (40 mg/kg i.p.) and RVT + ACR groups. After 10 days rats were decapitated and tissues were excised. 8-hydroxydeoxyguanosine (8-OHdG) is a biomarker of oxidative DNA damage. 8-OHdG content in the extracted DNA solution was determined by enzyme-linked immunosorbent assay method. Malondialdehyde (MDA), glutathione (GSH) levels and myeloperoxidase activity (MPO) were determined in tissues, while oxidant-induced tissue fibrosis was determined by collagen contents. Serum enzyme activities, cytokine levels, leukocyte apoptosis were assayed in plasma. As an indicator of oxidative DNA damage, 8-OHdG levels significantly increased in ACR group and this was reversed significantly by RVT treatment. In ACR group, GSH levels decreased significantly while the MDA levels, MPO activity and collagen content increased in the tissues suggesting oxidative organ damage. In RVT-treated ACR group, oxidant responses reversed significantly. Serum enzyme activities, cytokine levels and leukocyte late apoptosis which increased following ACR administration, decreased with RVT treatment. Therefore supplementing with RVT can be useful in individuals at risk of ACR toxicity.     

The effect of taurine on the ion transport system in mitochondria

The effect of taurine on the ATP-dependent mitochondrial swelling that characterizes the activity of mitochondrial ATP-dependent K⁺ channel and the formation of Ca²⁺-dependent pores, different in sensitivity to cyclosporin A, has been studied in rat liver mitochondria. It has been shown that taurine in micromolar concentrations (0.5–125 μM) stimulates the energy-dependent swelling of mitochondria. Taurine in physiological concentrations (0.5–20 mM) has no effect on the ATP-dependent swelling and the formation of cyclosporin A-insensitive Pal/Ca²⁺-activated pore in mitochondria. Taurine in these concentrations increased the rate of cyclosporin A-sensitive swelling of mitochondria induced by Ca²⁺ and P_i and reduced the Ca²⁺ capacity of mitochondria. The different effects of physiological taurine concentrations on the ATP-dependent transport of K⁺ and Ca²⁺ ions in mitochondrial membranes as compared with cell membranes are discussed.     

Taurine attenuates amyloid β 1–42-induced mitochondrial dysfunction by activating of SIRT1 in SK-N-SH cells

Amyloid β (Aβ) plays a critical role in the pathogenesis of Alzheimer disease (AD). Studies indicate that Aβ causes reactive oxygen species (ROS) generation, mitochondrial dysfunction and neurons loss in vivo and in vitro. Taurine, a naturally occurring β-amino acid in the brain, has been demonstrated to have neuroprotective properties. In the present study, the effects of taurine on cell viability and mitochondrial function in Aβ1–42-treated SK-N-SH cells were investigated. Pretreatment of taurine significantly attenuated Aβ1–42-induced neuronal death. Similarly, taurine suppressed the mPTP opening and reversed mitochondrial function in the presence of Aβ1–42. Additionally, taurine attenuated the intracellular Ca²⁺ and ROS generation induced by Aβ1–42. Moreover, the expression of Sirtuin 1 (SIRT1) was obviously recovered by taurine in Aβ1–42-treated SK-N-SH cells. Our results suggest that taurine prevents Aβ1–42-induced mitochondrial dysfunction by activation of SIRT1. This study implies that taurine is a prospective additive for AD patients.     

Anti-inflammatory mechanism of taurine against ischemic stroke is related to down-regulation of PARP and NF-κB

Taurine is reported to reduce tissue damage induced by inflammation and to protect the brain against experimental stroke. The objective of this study was to investigate whether taurine reduced ischemic brain damage through suppressing inflammation related to poly (ADP-ribose) polymerase (PARP) and nuclear factor-kappaB (NF-κB) in a rat model of stroke. Rats received 2 h ischemia by intraluminal filament and were then reperfused. Taurine (50 mg/kg) was administered intravenously 1 h after ischemia. Treatment with taurine markedly reduced neurological deficits, lessened brain swelling, attenuated cell death, and decreased the infarct volume 72 h after ischemia. Our data showed the up-regulation of PARP and NF-κB p65 in cytosolic fractions in the core and nuclear fractions in the penumbra and core, and the increases in the nuclear poly (ADP-ribose) levels and the decreases in the intracellular NAD⁺ levels in the penumbra and core at 22 h of reperfusion; these changes were reversed by taurine. Moreover, taurine significantly reduced the levels of tumor necrosis factor-α, interleukin-1β, inducible nitric oxide synthase, and intracellular adhesion molecule-1, lessened the activities of myeloperoxidase and attenuated the infiltration of neutrophils in the penumbra and core at 22 h of reperfusion. These data demonstrate that suppressing the inflammatory reaction related to PARP and NF-κB-driven expression of inflammatory mediators may be one mechanism of taurine against ischemic stroke.     

N-t-Butyl hydroxylamine regulates ionizing radiation-induced apoptosis in U937 cells

Ionizing radiation induces the production of reactive oxygen species, which play an important causative role in apoptotic cell death. Therefore, compounds that scavenge reactive oxygen species may confer regulatory effects on apoptosis. Recently, it has been shown that the decomposition product of the spin-trapping agent α-phenyl-N-t-butylnitrone, N-t-butyl hydroxylamine (NtBHA), mimics α-phenyl-N-t-butylnitrone and is much more potent in delaying reactive oxygen species-associated senescence. We investigated the effects of NtBHA on ionizing radiation-induced apoptosis. Upon exposure to 2 Gy of γ-irradiation, there was a distinct difference between the control cells and the cells pre-treated with 0.1 mM NtBHA for 2 h in regard to apoptotic parameters, cellular redox status, mitochondria function, and oxidative damage to cells. NtBHA effectively suppressed morphological evidence of apoptosis and DNA fragmentation in U937 cells exposed to ionizing radiation. The generation of intracellular reactive oxygen species was higher and the GSH level was lower in control cells compared to NtBHA-treated cells. The ionizing radiation-induced mitochondrial damage reflected by the altered mitochondrial permeability transition, the increase in the accumulation of reactive oxygen species, and the reduction of ATP production were significantly higher in control cells compared to NtBHA-treated cells. NtBHA pre-treated cells showed significant inhibition of apoptotic features such as activation of caspase-3, up-regulation of Bax and p53, and down-regulation of Bcl-2 compared to control cells upon exposure to ionizing radiation. This study indicates that NtBHA may play an important role in regulating the apoptosis induced by ionizing radiation presumably through scavenging of reactive oxygen species.     

The cytoprotective role of taurine in exercise-induced muscle injury

Summary.  Intense exercise is thought to increase oxidative stress and damage muscle tissue. Taurine is present in high concentration in skeletal muscle and may play a role in cellular defenses against free radical-mediated damage. The aim of this study was to determine if manipulating muscle levels of taurine would alter markers of free radical damage after exercise-induced injury. Adult male Sprague-Dawley rats were supplemented via the drinking water with either 3% (w/v) taurine (n = 10) or the competitive taurine transport inhibitor, β-alanine (n = 10), for one month. Controls (n = 20) drank tap water containing 0.02% taurine and all rats were placed on a taurine free diet. All the rats except one group of sedentary controls (n = 10) were subjected to 90 minutes of downhill treadmill running. Markers of cellular injury and free radical damage were determined along with tissue amino acid content. The 3% taurine treatment raised plasma levels about 2-fold and 3% β-alanine reduced plasma taurine levels about 50%. Taurine supplementation (TS) significantly increased plasma glutamate levels in exercised rats. Exercise reduced plasma methionine levels and taurine prevented its decline. Taurine supplementation increased muscle taurine content significantly in all muscles except the soleus. β-alanine decreased muscle taurine content about 50% in all the muscles examined. Lipid peroxidation (TBARS) was significantly increased by exercise in the extensor digitorium longus (EDL) and gastrocnemius (GAST) muscles. Both taurine and β-alanine completely blocked the increase in TBARs in the EDL, but had no effect in the GAST. Muscle content of the cytosolic enzyme, lactate dehydrogenase (LDH) was significantly decreased by exercise in the GAST muscle and this effect was attenuated by both taurine and β-alanine. Muscle myeloperoxidase (MPO) activity was significantly elevated in the gastrocnemius muscle, but diet had no effect. MPO activity was significantly increased by exercise in the liver and both taurine and β-alanine blocked this effect. There was no effect of either exercise or the diets on MPO activity in the lung or spleen. Running performance as assessed by a subjective rating scale was improved by taurine supplementation and there was a significant loss in body weight in the β-alanine-treated rats 24 hours after exercise. In summary, taurine supplementation or taurine depletion had measurable cytoprotective actions to attenuate exercise-induced injury. Received October 22, 2001 Accepted February 1, 2002     

Mitochondrial DNA-depleted A549 cells are resistant to bleomycin

Alveolar epithelial cells are considered to be the primary target of bleomycin-induced lung injury, leading to interstitial fibrosis. The molecular mechanisms by which bleomycin causes this damage are poorly understood but are suspected to involve generation of reactive oxygen species and DNA damage. We studied the effect of bleomycin on mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) in human alveolar epithelial A549 cells. Bleomycin caused an increase in reactive oxygen species production, DNA damage, and apoptosis in A549 cells; however, bleomycin induced more mtDNA than nDNA damage. DNA damage was associated with activation of caspase-3, cleavage of poly(ADP-ribose) polymerase, and cleavage and activation of protein kinase D1 (PKD1), a newly identified mitochondrial oxidative stress sensor. These effects appear to be mtDNA-dependent, because no caspase-3 or PKD1 activation was observed in mtDNA-depleted (ρ(0)) A549 cells. Survival rate after bleomycin treatment was higher for A549 ρ(0) than A549 cells. These results suggest that A549 ρ(0) cells are more resistant to bleomycin toxicity than are parent A549 cells, likely in part due to the depletion of mtDNA and impairment of mitochondria-dependent apoptotic pathways.     

Effect of methionine dietary supplementation on mitochondrial oxygen radical generation and oxidative DNA damage in rat liver and heart

Methionine restriction without energy restriction increases, like caloric restriction, maximum longevity in rodents. Previous studies have shown that methionine restriction strongly decreases mitochondrial reactive oxygen species (ROS) production and oxidative damage to mitochondrial DNA, lowers membrane unsaturation, and decreases five different markers of protein oxidation in rat heart and liver mitochondria. It is unknown whether methionine supplementation in the diet can induce opposite changes, which is also interesting because excessive dietary methionine is hepatotoxic and induces cardiovascular alterations. Because the detailed mechanisms of methionine-related hepatotoxicity and cardiovascular toxicity are poorly understood and today many Western human populations consume levels of dietary protein (and thus, methionine) 2–3.3 fold higher than the average adult requirement, in the present experiment we analyze the effect of a methionine supplemented diet on mitochondrial ROS production and oxidative damage in the rat liver and heart mitochondria. In this investigation male Wistar rats were fed either a L-methionine-supplemented (2.5 g/100 g) diet without changing any other dietary components or a control (0.86 g/100 g) diet for 7 weeks. It was found that methionine supplementation increased mitochondrial ROS generation and percent free radical leak in rat liver mitochondria but not in rat heart. In agreement with these data oxidative damage to mitochondrial DNA increased only in rat liver, but no changes were observed in five different markers of protein oxidation in both organs. The content of mitochondrial respiratory chain complexes and AIF (apoptosis inducing factor) did not change after the dietary supplementation while fatty acid unsaturation decreased. Methionine, S-AdenosylMethionine and S-AdenosylHomocysteine concentration increased in both organs in the supplemented group. These results show that methionine supplementation in the diet specifically increases mitochondrial ROS production and mitochondrial DNA oxidative damage in rat liver mitochondria offering a plausible mechanism for its hepatotoxicity.     

Activating Nrf-2 Signaling Depresses Unilateral Ureteral Obstruction-Evoked Mitochondrial Stress-Related Autophagy,Apoptosis and Pyroptosis in Kidney

Exacerbated oxidative stress and inflammation may induce three types of programmed cell death, autophagy, apoptosis and pyroptosis in unilateral ureteral obstruction (UUO) kidney. Sulforaphane activating NF-E2-related nuclear factor erythroid-2 (Nrf-2) signaling may ameliorate UUO-induced renal damage. UUO was induced in the left kidney of female Wistar rats. The level of renal blood flow, cortical and medullary oxygen tension and reactive oxygen species (ROS) was evaluated. Fibrosis, ED-1 (macrophage/monocyte) infiltration, oxidative stress, autophagy, apoptosis and pyroptosis were evaluated by immunohistochemistry and Western blot in UUO kidneys. Effects of sulforaphane, an Nrf-2 activator, on Nrf-2- and mitochondrial stress-related proteins and renal injury were examined. UUO decreased renal blood flow and oxygen tension and increased renal ROS, 3-nitrotyrosine stain, ED-1 infiltration and fibrosis. Enhanced renal tubular Beclin-1 expression started at 4 h UUO and further enhanced at 3d UUO, whereas increased Atg-5-Atg12 and LC3-II expression were found at 3d UUO. Increased renal Bax/Bcl-2 ratio, caspase 3 and PARP fragments, apoptosis formation associated with increased caspase 1 and IL-1β expression for pyroptosis formation were started from 3d UUO. UUO reduced nuclear Nrf-2 translocation, increased cytosolic and inhibitory Nrf-2 expression, increased cytosolic Bax translocation to mitochondrial and enhanced mitochondrial Cytochrome c release into cytosol of the UUO kidneys. Sulforaphane significantly increased nuclear Nrf-2 translocation and decreased mitochondrial Bax translocation and Cytochrome c release into cytosol resulting in decreased renal injury. In conclusion, sulforaphane via activating Nrf-2 signaling preserved mitochondrial function and suppressed UUO-induced renal oxidative stress, inflammation, fibrosis, autophagy, apoptosis and pyroptosis.     

Reactive oxygen species, mitochondria, apoptosis and aging

In this paper, we shall review various antioxygen defense systems of the cell paying particular attention to those that prevent superoxide formation rather than scavenge already formed superoxide and its products. The role of uncoupled, decoupled and non-coupled respiration, mitochondrial pore, mitochondrion-linked apoptosis will be considered. Mitochondrial theory of aging will be regarded in context of reactive oxygen species-induced damage of mitochondrial DNA. (Mol Cell Biochem 174: 305–319, 1997)