Increased Protein Oxidation Research Articles

Comparison of microbiological loads and physicochemical properties of raw milk treated with single-/multiple-cycle high hydrostatic pressure and ultraviolet-C light

The effects of ultraviolet-C radiation (UV-C, 11.8 W/m2), single-cycle and multiple-cycle high hydrostatic pressure (HHP at 200, 400 or 600 MPa) on microbial load and physicochemical quality of raw milk were evaluated. Reductions of aerobic plate count (APC) and coliform count (CC) by HHP were more than 99.9% and 98.7%, respectively. Inactivation efficiency of microorganisms increased with pressure level. At the same pressure level, two-cycle treatments caused lower APC, but did not show CC differences compared with single-cycle treatments. Reductions of APC and CC by UV-C were somewhere between 200 MPa and 400/600 MPa. Both HHP and UV-C significantly decreased lightness and increased pH, but did not change soluble solids content and thiobarbituric acid-reactive substances’ values. Two 2.5 min cycles of HHP at 600 MPa caused minimum APC and CC, and maximum conductivity. Compared with HHP, UV-C markedly increased protein oxidation and reduced darkening.

Arsenic induced oxidative stress and mitochondrial dysfunction in rat brain

The present study was undertaken to reveal the effects of chronic arsenic exposure (25ppm intragastrically for 12 weeks) on mitochondrial functions and oxidative stress in male Wister rats. Chronic arsenic exposure resulted in decrease in the activities of the mitochondrial complexes. There was increased generation of ROS followed by decrease in MnSOD activity. The generation of oxidative stress was associated with increased protein oxidation and lipid peroxidation in rat brain as evident by FTIR spectra. The RT-PCR analysis of NRF 1, NRF 2 and PGC 1α revealed decrease in gene expression suggesting decreased biogenesis following chronic exposure in rat brain. Thus, the findings of the present study reveal that arsenic induced decrease in mitochondrial biogenesis may be responsible for the decreased metabolic response that may be further involved in the generation of oxidative stress and neurodegeneration in rat brain.

Association between hyperleptinemia and oxidative stress in obese diabetic subjects.

BackgroundObesity is a worldwide metabolic disorder affecting all types of people. The mechanism by which increased body fat mass that leads to insulin resistance and type 2 diabetes is not yet clearly known. There is a possible crosstalk between leptin, an adipokine and insulin signaling. Leptin mediates insulin sensitivity in hepatocytes; however, its concentration has found to be increased in obese and diabetic subjects. These subjects also have high incidence of oxidative stress status. Therefore, knowing the level of leptin present in obese diabetic subjects will be informative along with its relation to oxidative stress.MethodsA small population study was performed to explore the association between leptin concentration and oxidative stress status in control and obese type 2 diabetic subjects. Oxidative stress status parameters like malondialdehyde (MDA), superoxide dismutase activity (SOD), glutathione peroxidase activity (GSH-Px), and protein carbonyl (PCO) groups content was measured spectrophotometrically in serum of 43 subjects. Serum Leptin concentration was measured by quantikine sandwich ELISA assay.ResultsThe strong positive correlation between MDA (malondialdehyde) and leptin in obese diabetic patients (ρ = 0.787, P < 0.05) suggests close association between lipid peroxidation and hyperleptinemia. In addition, observed positive correlation between protein carbonyl groups and leptin level in obese diabetic subjects (ρ = 0.599, P = 0.001) suggest that hyperleptinemia might also be associated with increased protein oxidation. In multiple logistic regression analysis, leptin has shown a significant association with obese type 2 diabetes [odds ratio (OR): 1.161, 95% confidence interval (Cl): 1.027-1.312, P < 0.05], but the significance is lost after adjusting for Age, BMI, MDA and anti-oxidant parameters.ConclusionsIn the subjects with both obesity and diabetes, there is a significant degree of association between hyperleptinemia and oxidative stress. This association reinforces the existing understanding that obese subjects who also have diabetes are vulnerable to cardiovascular complications driven by increased oxidative stress and hyperleptinemia.

Implications of Dietary Leucine on Muscle mTOR Gene Expression and Redox Status in Rats Following High Intensity Effort

Leucine supplementation exerts a positive effect on mTOR pathway that is involved in the synthesis of skeletal muscle protein. In the present study, the capability of a 15-day dietary leucine supplementation (310 mg/kg) to improve the performance in acute high intensity effort and the inductive capacity on skeletal muscle protein anabolism in rats submitted to swimming exercise with a 10% bodyweight load attached to the tail, were studied. A 1.83-fold increase in mTOR gene expression in the treated group was found, while no changes in muscle protein content and rats body weight were observed. An increase in protein oxidation and a significant decrease in catalase were found in treated rats, while no changes in DNA damage, GSH and SOD levels were reported. We found an increase of superoxide anion and hydrogen peroxide/myeloperoxidase system in polymorphonuclear neutrophils obtained by treated group. These outcomes suggest slight enhancement in basal inflammation due to exercise activity via mTOR activation during treatment, without serious impairment of the antioxidant system and cell status. In conclusion, the 15-day leucine supplementation at the given dose, enhanced mTOR gene expression in the presence of acute effort which was also well tolerated by skeletal muscle, but probably too short to improve its anabolic activity. Keywords: Antioxidant enzymes, comet assay, leucine, mTOR gene expression, respiratory burst.

Increased protein oxidation and decreased expression of nuclear factor E2-related factor 2 protein in skin tissue of patients with diabetes.

Reactive oxygen species (ROS) contribute to the cell dysfunction and tissue damage that result from glucolipotoxicity in diabetes. ROS formation in cells causes oxidative stress, thereby activating oxidative damage-inducing genes. Nuclear factor erythroid 2-related factor 2 (Nrf2) has been shown to play an essential role in the vital defence mechanisms that help cells cope with oxidative stress. To compare Nrf2 protein expression in nondiabetic skin tissue with that in diabetic skin tissue. Nrf2 expression was evaluated by Western blotting, reverse transcription (RT)-PCR, and immunohistochemical staining in diabetic and nondiabetic skin tissues. Dinitrophenylhydrazone derivatives of protein carbonyls in the oxidized proteins were measured by oxyblotting analysis. Cytoplasmic and nuclear Nrf2 protein expression was determined to identify the activity and level of Nrf2. Protein oxidation, a marker of oxidative stress, was found to be increased in diabetic skin tissue. In subcellular fraction analysis, Nrf2 protein was detected in the nuclei and cytoplasm of nondiabetic skin tissues, and the Nrf2 protein band was identified from among the multiple bands detected, using small interfering RNA-mediated Nrf2 gene silencing. Compared with nondiabetic tissue, diabetic skin tissue showed simultaneous downregulation of Nrf2 at both the mRNA and protein levels. Nuclear condensation, loss of nuclei, and vacuolization were seen in some parts of the specimen by haematoxylin and eosin staining of diabetic skin tissue. Immunohistochemical staining of Nrf2 confirmed the RT-PCR and Western blotting results. Collectively, our data show that expression of Nrf2 is clearly downregulated in diabetic skin tissue, and suggest that Nrf2 may be necessary for protection against glucose-induced oxidative stress.

Role of Phenolics Extracting from Rosa canina L. on Meat Protein Oxidation During Frozen Storage and Beef Patties Processing

Recent findings suggested that using frozen material for meat processing leads to products with increased protein oxidation rates and impaired quality traits. Therefore, the effects of frozen storage and the addition of a phenolic-rich dog rose extract (Rosa canina L.; RC), on lipid and protein oxidation, moisture losses, color stability, and hardness of beef patties were investigated. Protein oxidation was assessed by means of tryptophan loss and the formation of specific lysine oxidation products: α-aminoadipic semialdehyde (AAS), α-aminoadipic acid (AAA), and Schiff bases. Frozen storage increased proteins susceptibility towards oxidation during successive technological processes. The addition of the RC extract inhibited the formation of AAS, AAA, and had an antioxidant effect towards tryptophan oxidation, but promoted the formation of Schiff bases and incremented the hardness of beef patties. The antioxidant effect may be attributed to the phenolic compounds, mainly procyanidins, found on the RC extract. Further knowledge on the interactions between phenolics and proteins is needed to optimize the application of these antioxidants against meat protein oxidation.

Interplay between pro-inflammatory cytokines and brain oxidative stress biomarkers: Evidence of parallels between butyl paraben intoxication and the valproic acid brain physiopathology in autism rat model

Butyl paraben is a preservative used in food, drugs and cosmetics. Neurotoxic effect was reported recently beside the potential estrogenic activity of parabens. There is controversy as to the potential harmful effects of butyl parabens, which are suspected to contribute to autism and learning disabilities. The purpose of this study was to examine the similarities between paraben intoxication signs in the rat brain and brain markers in an autistic like rat model. This study provides evidence of many parallels between the two, including (1) oxidative stress, (2) decreased reduced glutathione levels and elevated oxidised glutathione, (3) mitochondrial dysfunction, and (4) neuroinflammation and increased pro-inflammatory cytokine levels in the brain (tumour necrosis factor-alpha, interleukin-1-beta, and interleukin-6). (5) Increased protein oxidation reported by a significant increase in 3-nitrotyrosine (3-NT)/tyrosine ratio. (6) A marked disturbance was found in the production of energy carriers (AMP, ATP and AMP/ATP ratio) in comparison with the control. The evidence suggests that paraben may, to some extent, either cause or contribute to the brain physiopathology in ASDs or pathogens that produce the brain pathology observed in the diagnosed rat model of ASD.

Copper-induced tight junction mRNA expression changes, apoptosis and antioxidant responses via NF-κB, TOR and Nrf2 signaling molecules in the gills of fish: Preventive role of arginine

This study explored the possible preventive effects of dietary arginine on copper (Cu)-induced tight junction mRNA expression changes, apoptosis and antioxidant responses in the gills of young grass carp (Ctenopharyngodon idella). The results indicated that exposure to 0.7mg/L (11.01μmol/L) Cu for 96h induced the production of reactive oxygen species (ROS), thereby increasing protein oxidation, lipid peroxidation and DNA damage in the gills of fish. However, these oxidative effects were prevented by arginine supplementation. Arginine also prevented the toxic effects of Cu on the activities of copper/zinc superoxide dismutase (SOD1), glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR) and the glutathione (GSH) content (P<0.05). However, Cu induced an adaptive increase in the activity of catalase (CAT), and arginine supplementation further increased CAT activity (P<0.05). Moreover, Cu induced increases in the relative mRNA expressions of SOD1, CAT, GPx, GST, caspase-3, caspase-9, NF-E2-related factor 2 (Nrf2), Kelch-like-ECH-associated protein 1a (Keap1a), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-8 (IL-8), transforming growth factor-β (TGF-β) and nuclear transcription factor-κB p65 (NF-κB p65) in the gills of grass carp (P<0.05). In contrast, the relative mRNA expression levels of occludin, zonula occludens-1 (ZO-1), claudin b, claudin 3, claudin 12, target of rapamycin (TOR) and inhibitor factor κBα (IκBα) in the gills were decreased by Cu (P<0.05). However, pre-treatment of fish with arginine prevented Cu-induced relative mRNA expression decrease. Interestingly, Cu exposure resulted in increases in claudin 15a mRNA expression (P<0.05) but could not induce claudin c, caspase-8 and interleukin-10 (IL-10) mRNA expression changes in the gill of fish (P>0.05). These results indicated that Cu exposure induced apoptosis and antioxidant system and tight junction mRNA changes in the fish gills, which could be completely blocked by dietary arginine pre-supplementation.

Protein carbonylation associated to high-fat, high-sucrose diet and its metabolic effects

The present research draws a map of the characteristic carbonylation of proteins in rats fed high-caloric diets with the aim of providing a new insight of the pathogenesis of metabolic diseases derived from the high consumption of fat and refined carbohydrates. Protein carbonylation was analyzed in plasma, liver and skeletal muscle of Sprague–Dawley rats fed a high-fat, high-sucrose (HFHS) diet by a proteomics approach based on carbonyl-specific fluorescence-labeling, gel electrophoresis and mass spectrometry. Oxidized proteins along with specific sites of oxidative damage were identified and discussed to illustrate the consequences of protein oxidation. The results indicated that long-term HFHS consumption increased protein oxidation in plasma and liver; meanwhile, protein carbonyls from skeletal muscle did not change. The increment of carbonylation by HFHS diet was singularly selective on specific target proteins: albumin from plasma and liver, and hepatic proteins such as mitochondrial carbamoyl-phosphate synthase (ammonia), mitochondrial aldehyde dehydrogenase, argininosuccinate synthetase, regucalcin, mitochondrial adenosine triphosphate synthase subunit beta, actin cytoplasmic 1 and mitochondrial glutamate dehydrogenase 1. The possible consequences that these specific protein carbonylations have on the excessive weight gain, insulin resistance and nonalcoholic fatty liver disease resulting from HFHS diet consumption are discussed.

Differential expression of heat shock transcription factors and heat shock proteins after acute and chronic heat stress in laying chickens (Gallus gallus).

Heat stress due to high environmental temperature negatively influences animal performances. To better understand the biological impact of heat stress, laying broiler breeder chickens were subjected either to acute (step-wisely increasing temperature from 21 to 35°C within 24 hours) or chronic (32°C for 8 weeks) high temperature exposure. High temperature challenges significantly elevated body temperature of experimental birds (P<0.05). However, oxidation status of lipid and protein and expression of heat shock transcription factors (HSFs) and heat shock proteins (HSPs) 70 and 90 were differently affected by acute and chronic treatment. Tissue-specific responses to thermal challenge were also found among heart, liver and muscle. In the heart, acute heat challenge affected lipid oxidation (P = 0.05) and gene expression of all 4 HSF gene expression was upregulated (P<0.05). During chronic heat treatment, the HSP 70 mRNA level was increased (P<0.05) and HSP 90 mRNA (P<0.05) was decreased. In the liver, oxidation of protein was alleviated during acute heat challenge (P<0.05), however, gene expression HSF2, 3 and 4 and HSP 70 were highly induced (P<0.05). HSP90 expression was increased by chronic thermal treatment (P<0.05). In the muscle, both types of heat stress increased protein oxidation, but HSFs and HSPs gene expression remained unaltered. Only tendencies to increase were observed in HSP 70 (P = 0.052) and 90 (P = 0.054) gene expression after acute heat stress. The differential expressions of HSF and HSP genes in different tissues of laying broiler breeder chickens suggested that anti-heat stress mechanisms might be provoked more profoundly in the heart, by which the muscle was least protected during heat stress. In addition to HSP, HSFs gene expression could be used as a marker during acute heat stress.

Increased DNA oxidation (8-OHdG) and protein oxidation (AOPP) by low level electromagnetic field (2.45 GHz) in rat brain and protective effect of garlic

Purpose: To investigate the oxidative damage and protective effect of garlic on rats exposed to low level of electromagnetic fields (EMF) at 2.45 GHz Microwave radiation (MWR).Methods: Thirty-six Wistar rats were divided into three groups. Group I was the control group and not exposed to EMF. Group II and III were exposed to low level EMF (3.68 ± 0.36 V/m) at 2.45 GHz MWR for 1 hour/day for 30 consecutive days. Daily 500 mg/kg garlic was given to Group III during the study period. At the end of the study, thiobarbituric acid reactive substances (TBARS), advanced oxidation protein products (AOPP) and 8-hydroxydeoxyguanosine (8-OHdG) levels were investigated in brain tissue and blood samples.Results: Exposure to low level of EMF increased 8-OHdG level in both plasma and brain tissue whereas it increased AOPP level only in plasma. Garlic prevented the increase of 8-OHdG level in brain tissue and plasma AOPP levels.Conclusions: It may be concluded that low level EMF at 2.45 GHz MWR increases the DNA damage in both brain tissues and plasma of the rats whereas it increases protein oxidation only in plasma. It may also be argued that the use of garlic decreases these effects.

P62 provides dual cytoprotection against oxidative stress in the retinal pigment epithelium

As a signaling hub, p62/sequestosome plays important roles in cell signaling and degradation of misfolded proteins. p62 has been implicated as an adaptor protein to mediate autophagic clearance of insoluble protein aggregates in age-related diseases, including age-related macular degeneration (AMD), which is characterized by dysfunction of the retinal pigment epithelium (RPE). Our previous studies have shown that cigarette smoke (CS) induces oxidative stress and inhibits the proteasome pathway in cultured human RPE cells, suggesting that p62-mediated autophagy may become the major route to remove impaired proteins under such circumstances. In the present studies, we found that all p62 mRNA variants are abundantly expressed and upregulated by CS induced stress in cultured human RPE cells, yet isoform1 is the major translated form. We also show that p62 silencing exacerbated the CS induced accumulation of damaged proteins, both by suppressing autophagy and by inhibiting the Nrf2 antioxidant response, which in turn, increased protein oxidation. These effects of CS and p62 reduction were further confirmed in mice exposed to CS. We found that over-expression of p62 isoform1, but not its S403A mutant, which lacks affinity for ubiquitinated proteins, reduced misfolded proteins, yet simultaneously promoted an Nrf2-mediated antioxidant response. Thus, p62 provides dual, reciprocal enhancing protection to RPE cells from environmental stress induced protein misfolding and aggregation, by facilitating autophagy and the Nrf2 mediated antioxidant response, which might be a potential therapeutic target against AMD.

SIRT1 protects against cigarette smoke-induced lung oxidative stress via a FOXO3-dependent mechanism

Oxidative and carbonyl stress is increased in lungs of smokers and patients with chronic obstructive pulmonary disease (COPD), as well as in cigarette smoke (CS)-exposed rodent lungs. We previously showed that sirtuin1 (SIRT1), an antiaging protein, is reduced in lungs of CS-exposed mice and patients with COPD and that SIRT1 attenuates CS-induced lung inflammation and injury. It is not clear whether SIRT1 protects against CS-induced lung oxidative stress. Therefore, we determined the effect of SIRT1 on lung oxidative stress and antioxidants in response to CS exposure using loss- and gain-of-function approaches, as well as a pharmacological SIRT1 activation by SRT1720. We found that CS exposure increased protein oxidation and lipid peroxidation in lungs of wild-type (WT) mice, which was further augmented in SIRT1-deficient mice. Furthermore, both SIRT1 genetic overexpression and SRT1720 treatment significantly decreased oxidative stress induced by CS exposure. FOXO3 deletion augmented lipid peroxidation products but reduced antioxidants in response to CS exposure, which was not affected by SRT1720. Interestingly, SRT1720 treatment exhibited a similar effect on lipid peroxidation and antioxidants (i.e., manganese superoxide dismutase, heme oxygenase-1, and NADPH quinone oxidoreductase-1) in WT and nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-deficient mice in response to CS exposure. This indicates that SIRT1 protects against CS-induced oxidative stress, which is mediated by FOXO3, but is independent of Nrf2. Overall, these findings reveal a novel function of SIRT1, which is to reduce CS-induced oxidative stress, and this may contribute to its protective effects against lung inflammation and subsequent development of COPD.

Cardiopulmonary Bypass Is Associated With Hemolysis and Acute Kidney Injury in Neonates, Infants, and Children*

This pilot study assesses the degree of hemolysis induced by cardiopulmonary bypass and determines its association with acute kidney injury in pediatric patients. Further, it evaluates the degree to which the use of urinary biomarkers neutrophil gelatinase-associated lipocalin and cystatin C correlate with the presence of acute kidney injury and hemolysis following cardiopulmonary bypass. Prospective observational study. A 13-bed pediatric cardiac ICU in a university hospital. Children undergoing cardiac surgery with the use of cardiopulmonary bypass. None. Blood and urine samples were obtained at multiple time points before and after cardiopulmonary bypass. Hemolysis was assessed by measuring levels of plasma hemoglobin and haptoglobin. Acute kidney injury was defined as a doubling in serum creatinine from preoperative baseline and by using the pediatric-modified RIFLE criteria. Urinary neutrophil gelatinase-associated lipocalin and cystatin C levels were measured. A total of 40 patients (range, 3 d to 4.8 yr) were enrolled. Plasma hemoglobin levels increased markedly on separation from cardiopulmonary bypass with a concurrent decrease in haptoglobin. This was associated with an increase in protein oxidation in the plasma. Hemolysis was more evident in younger patients with a longer duration of bypass and in those requiring a blood-primed circuit. Forty percent of patients had a doubling in serum creatinine and acute kidney injury was developed in 88% of patients when defined by the pediatric-modified RIFLE criteria. Controlling for cardiopulmonary bypass time, persistently elevated levels of plasma hemoglobin were associated with a five-fold increase in acute kidney injury. Further, urinary neutrophil gelatinase-associated lipocalin measured 2 hours after separation from cardiopulmonary bypass was associated with acute kidney injury and with elevations in plasma hemoglobin. Cardiopulmonary bypass in pediatric patients results in significant hemolysis, which is associated with the development of acute kidney injury. The biomarker neutrophil gelatinase-associated lipocalin correlates with both acute kidney injury and hemolysis in this population.

PGC-1α regulation of mitochondrial degeneration in experimental diabetic neuropathy

Mitochondrial degeneration is considered to play an important role in the development of diabetic peripheral neuropathy in humans. Mitochondrial degeneration and the corresponding protein regulation associated with the degeneration were studied in an animal model of diabetic neuropathy. PGC-1α and its-regulated transcription factors including TFAM and NRF1, which are master regulators of mitochondrial biogenesis, are significantly downregulated in streptozotocin diabetic dorsal root ganglion (DRG) neurons. Diabetic mice develop peripheral neuropathy, loss of mitochondria, decreased mitochondrial DNA content and increased protein oxidation. Importantly, this phenotype is exacerbated in PGC-1α (−/−) diabetic mice, which develop a more severe neuropathy with reduced mitochondrial DNA and a further increase in protein oxidation. PGC-1α (−/−) diabetic mice develop an increase in total cholesterol and triglycerides, and a decrease in TFAM and NRF1 protein levels. Loss of PGC-1α causes severe mitochondrial degeneration with vacuolization in DRG neurons, coupled with reduced state 3 and 4 respiration, reduced expression of oxidative stress response genes and an increase in protein oxidation. In contrast, overexpression of PGC-1α in cultured adult mouse neurons prevents oxidative stress associated with increased glucose levels. The study provides new insights into the role of PGC-1α in mitochondrial regeneration in peripheral neurons and suggests that therapeutic modulation of PGC-1α function may be an attractive approach for treatment of diabetic neuropathy.

Bixin and Norbixin Have Opposite Effects on Glycemia, Lipidemia, and Oxidative Stress in Streptozotocin-Induced Diabetic Rats

The present study investigated the effects of oral administration of annatto carotenoids (bixin (BIX) and norbixin (NBIX)) on glucose levels, lipid profiles, and oxidative stress parameters in streptozotocin (STZ)-induced diabetic rats. Animals were treated for 30 days in the following groups: nondiabetic control, diabetic vehicle, diabetic 10 mg/kg BIX, diabetic 100 mg/kg BIX, diabetic 10 mg/kg NBIX, diabetic 100 mg/kg NBIX, diabetic metformin, and diabetic insulin. Blood glucose, LDL cholesterol, and triglyceride levels were reduced in the diabetic rats treated with BIX. BIX treatment prevented protein oxidation and nitric oxide production and restored superoxide dismutase activity. NBIX treatment did not change most parameters assessed, and at the highest dose, it increased LDL cholesterol and triglycerides levels and showed prooxidant action (increased protein oxidation and nitric oxide levels). These findings suggested that BIX could have an antihyperglycemic effect, improve lipid profiles, and protect against damage induced by oxidative stress in the diabetic state. Because NBIX is a water-soluble analog of BIX, we propose that lipophilicity is crucial for the protective effect of annatto carotenoids against streptozotocin-induced diabetes.

Identification of the Immunoproteasome as a Novel Regulator of Skeletal Muscle Differentiation

While many of the molecular details of myogenesis have been investigated extensively, the function of immunoproteasomes (i-proteasomes) in myogenic differentiation remains unknown. We show here that the mRNA of i-proteasome subunits, the protein levels of constitutive and inducible proteasome subunits, and the proteolytic activities of the 20S and 26S proteasomes were significantly upregulated during differentiation of skeletal muscle C2C12 cells. Knockdown of the i-proteasome catalytic subunit PSMB9 by short hairpin RNA (shRNA) decreased the expression of both PSMB9 and PSMB8 without affecting other catalytic subunits of the proteasome. PSMB9 knockdown and the use of i-proteasome-specific inhibitors both decreased 26S proteasome activities and prevented C2C12 differentiation. Inhibition of the i-proteasome also impaired human skeletal myoblast differentiation. Suppression of the i-proteasome increased protein oxidation, and these oxidized proteins were found to be more susceptible to degradation by exogenous i-proteasomes. Downregulation of the i-proteasome also increased proapoptotic proteins, including Bax, as well as cleaved caspase 3, cleaved caspase 9, and cleaved poly(ADP-ribose) polymerase (PARP), suggesting that impaired differentiation is likely to occur because of significantly increased apoptosis. These results demonstrate for the first time that i-proteasomes, independent of constitutive proteasomes, are critical for skeletal muscle differentiation of mouse C2C12 cells.

Intense exercise increases protein oxidation in spleen and liver of mice.

Studies have indicated that sports anemia is mainly associated with intravascular hemolysis induced by exercise. We hypothesized that such exercise-induced hemolysis leads to oxidative damage due to an increase in free iron caused by hematocyte destruction. Thirty-one male ICR mice were randomly divided into 3 groups: a rested control group, an intense-exercise group, and a group rested for 24 hours after intense exercise. The serum haptoglobin level of the intense-exercise group decreased compared with that of the rested control group, suggesting hemolysis. Tissue iron and protein carbonyl levels in the liver were increased after exercise, and the protein carbonyl level in the spleen on the day after exercise was significantly increased compared with that of the resting state. These results suggest that the spleen and liver, where extravascular hemolysis occurs, were subjected to oxidative modification by the free iron, which was released from large numbers of hemocytes that were destroyed due to the intense exercise.

Time course of systemic oxidative stress and inflammatory response induced by an acute exposure to Residual Oil Fly Ash

It is suggested that systemic oxidative stress and inflammation play a central role in the onset and progression of cardiovascular diseases associated with the exposure to particulate matter (PM). The aim of this work was to evaluate the time changes of systemic markers of oxidative stress and inflammation, after an acute exposure to Residual Oil Fly Ash (ROFA). Female Swiss mice were intranasally instilled with a ROFA suspension (1.0mg/kg body weight) or saline solution, and plasma levels of oxidative damage markers [thiobarbituric acid reactive substances (TBARSs) and protein carbonyls], antioxidant status [reduced (GSH) and oxidized (GSSG) glutathione, ascorbic acid levels, and superoxide dismutase (SOD) activity], cytokines levels, and intravascular leukocyte activation were evaluated after 1, 3 or 5h of exposure. Oxidative damage to lipids and decreased GSH/GSSG ratio were observed in ROFA-exposed mice as early as 1h. Afterwards, increased protein oxidation, decreased ascorbic acid content and SOD activity were found in this group at 3h. The onset of an adaptive response was observed at 5h after the ROFA exposure, as indicated by decreased TBARS plasma content and increased SOD activity. The observed increase in oxidative damage to plasma macromolecules, together with systemic antioxidants depletion, may be a consequence of a systemic inflammatory response triggered by the ROFA exposure, since increased TNF-α and IL-6 plasma levels and polymorphonuclear leukocytes activation was found at every evaluated time point. These findings contribute to the understanding of the increase in cardiovascular morbidity and mortality, in association with environmental PM inhalation.

Whole-body protein turnover response to short-term high-protein diets during weight loss: a randomized controlled trial

To determine whole-body protein turnover responses to high-protein diets during weight loss, 39 adults (age, 21±1 years; VO2peak, 48±1 ml kg(-1) min(-1); body mass index, 25±1 kg m(2)) were randomized to diets providing protein at the recommend dietary allowance (RDA), 2 × -RDA or 3 × -RDA. A 10-day weight maintenance period preceded a 21-day, 40% energy deficit. Postabsorptive (FASTED) and postprandial (FED) whole-body protein turnover was determined during weight maintenance (day 10) and energy deficit (day 31) using [1-(13)C]leucine. FASTED flux, synthesis and breakdown were lower (P<0.05) for energy deficit than weight maintenance. Protein flux and synthesis were higher (P<0.05) for FED than FASTED. Feeding attenuated (P<0.05) breakdown during weight maintenance but not energy deficit. Oxidation increased (P<0.05) between dietary protein levels and feeding stimulated oxidation, although oxidative responses to feeding were higher (P<0.05) for energy deficit than weight maintenance. FASTED net balance decreased between dietary protein levels, but in the FED state, net balance was lower for 3 × -RDA as compared with RDA and 2 × -RDA (diet-by-state, P<0.05). Consuming dietary protein at levels above the RDA, particularly 3 × -RDA, during short-term weight loss increases protein oxidation with concomitant reductions in net protein balance.