GSH transporters: molecular characterization and role in GSH homeostasis

Serum Protein Biomarker Findings Reflective of Oxidative Stress and Vascular Abnormalities in Male, but Not Female, Collision Sport Athletes

Studies have indicated that concussive and sub-concussive brain injuries that are frequent during collision sports may lead to long-term neurological abnormalities, however there is a knowledge gap on how biological sex modifies outcomes. Blood-based biomarkers can help to identify the molecular pathology induced by brain injuries and to better understand how biological sex affects the molecular changes. We therefore analyzed serum protein biomarkers in male (n = 50) and female (n = 33) amateur Australian rules footballers (i.e., Australia's most participated collision sport), both with a history of concussion (HoC) and without a history of concussion (NoHoC). These profiles were compared to those of age-matched control male (n = 24) and female (n = 20) athletes with no history of neurotrauma or participation in collision sports. Serum levels of protein markers indicative of neuronal, axonal and glial injury (UCH-L1, NfL, tau, p-tau, GFAP, BLBP, PEA15), metabolic (4-HNE) and vascular changes (VEGF-A, vWF, CLDN5), and inflammation (HMGB1) were assessed using reverse phase protein microarrays. Male, but not female, footballers had increased serum levels of VEGF-A compared to controls regardless of concussion history. In addition, only male footballers who had HoC had increased serum levels of 4-HNE. These findings being restricted to males may be related to shorter collision sport career lengths for females compared to males. In summary, these findings show that male Australian rules footballers have elevated levels of serum biomarkers indicative of vascular abnormalities (VEGF-A) and oxidative stress (4-HNE) in comparison to non-collision control athletes. While future studies are required to determine how these findings relate to neurological function, serum levels of VEGF-A and 4-HNE may be useful to monitor subclinical neurological injury in males participating in collision sports.

Lens glutathione homeostasis: Discrepancies and gaps in knowledge standing in the way of novel therapeutic approaches

Cataract is the major cause of blindness worldwide. The WHO has estimated around 20 million people have bilateral blindness from cataract, and that number is expected to reach 50 million in 2050. The cataract surgery is currently the main treatment approach, though often associated with complications, such as Posterior Capsule Opacification (PCO)-also known as secondary cataract. The lens is an avascular ocular structure equipped with an unusually high level of glutathione (GSH), which plays a vital role in maintaining lens transparency by regulating lenticular redox state. The lens epithelium and outer cortex are thought to be responsible for providing the majority of lens GSH via GSH de novo synthesis, assisted by a continuous supply of constituent amino acids from the aqueous humor, as well as extracellular GSH recycling from the gamma-glutamyl cycle. However, when de novo synthesis is impaired, in the presence of low GSH levels, as in the aging human lens, compensatory mechanisms exist, suggesting that the lens is able to uptake GSH from the surrounding ocular tissues. However, these uptake mechanisms, and the GSH source and its origin, are largely unknown. The lens nucleus does not have the ability to synthesize its own GSH and fully relies on transport from the outer cortex by yet unknown mechanisms. Understanding how aging reduces GSH levels, particularly in the lens nucleus, how it is associated with age-related nuclear cataract (ARNC), and how the lens compensates for GSH loss via external uptake should be a major research priority. The intent of this review, which is dedicated to the memory of David C. Beebe, is to summarize our current understanding of lens GSH homeostasis and highlight discrepancies and gaps in knowledge that stand in the way of pharmacologically minimizing the impact of declining GSH content in the prevention of age-related cataract.

Clinical Relevance of Biomarkers of Oxidative Stress

SIGNIFICANCE

Oxidative stress is considered to be an important component of various diseases. A vast number of methods have been developed and used in virtually all diseases to measure the extent and nature of oxidative stress, ranging from oxidation of DNA to proteins, lipids, and free amino acids.

RECENT ADVANCES

An increased understanding of the biology behind diseases and redox biology has led to more specific and sensitive tools to measure oxidative stress markers, which are very diverse and sometimes very low in abundance.

CRITICAL ISSUES

The literature is very heterogeneous. It is often difficult to draw general conclusions on the significance of oxidative stress biomarkers, as only in a limited proportion of diseases have a range of different biomarkers been used, and different biomarkers have been used to study different diseases. In addition, biomarkers are often measured using nonspecific methods, while specific methodologies are often too sophisticated or laborious for routine clinical use.

FUTURE DIRECTIONS

Several markers of oxidative stress still represent a viable biomarker opportunity for clinical use. However, positive findings with currently used biomarkers still need to be validated in larger sample sizes and compared with current clinical standards to establish them as clinical diagnostics. It is important to realize that oxidative stress is a nuanced phenomenon that is difficult to characterize, and one biomarker is not necessarily better than others. The vast diversity in oxidative stress between diseases and conditions has to be taken into account when selecting the most appropriate biomarker.

Biochemical responses and mitochondrial mediated activation of apoptosis on long-term effect of aspartame in rat brain

Aspartame, an artificial sweetener, is very widely used in many foods and beverages. But there are controversies about its metabolite which is marked for its toxicity. Hence it is believed to be unsafe for human use. Previous studies have reported on methanol exposure with involvements of free radicals on excitotoxicity of neuronal apoptosis. Hence, this present study is proposed to investigate whether or not chronic aspartame (FDA approved Daily Acceptable Intake (ADI),40 mg/kg bwt) administration could release methanol, and whether or not it can induce changes in brain oxidative stress status and gene and protein expression of anti-apoptotic Bcl-2 and pro-apoptotic Bax and caspase-3 in the rat brain region. To mimic the human methanol metabolism, Methotrexate (MTX)-treated Wistar strain male albino rats were used and after the oral administration of aspartame, the effects were studied along with controls and MTX-treated controls. Aspartame exposure resulted with a significant increase in the enzymatic activity in protein carbonyl, lipid peroxidation levels, superoxide dismutase, glutathione-S-transferase, glutathione peroxidase and catalase activity in (aspartame MTX)-treated animals and with a significant decrease in reduced glutathione, glutathione reductase and protein thiol, pointing out the generation of free radicals. The gene and protein expression of pro apoptotic marker Bax showed a marked increase whereas the anti-apoptotic marker Bcl-2 decreased markedly indicating the aspartame is harmful at cellular level. It is clear that long term aspartame exposure could alter the brain antioxidant status, and can induce apoptotic changes in brain.

Nitro-fatty acids reduce atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

Inflammatory processes and foam cell formation are key determinants in the initiation and progression of atherosclerosis. Electrophilic nitro-fatty acids, byproducts of nitric oxide- and nitrite-dependent redox reactions of unsaturated fatty acids, exhibit antiinflammatory signaling actions in inflammatory and vascular cell model systems. The in vivo action of nitro-fatty acids in chronic inflammatory processes such as atherosclerosis remains to be elucidated.

METHODS AND RESULTS

Herein, we demonstrate that subcutaneously administered 9- and 10-nitro-octadecenoic acid (nitro-oleic acid) potently reduced atherosclerotic lesion formation in apolipoprotein E-deficient mice. Nitro-fatty acids did not modulate serum lipoprotein profiles. Immunostaining and gene expression analyses revealed that nitro-oleic acid attenuated lesion formation by suppressing tissue oxidant generation, inhibiting adhesion molecule expression, and decreasing vessel wall infiltration of inflammatory cells. In addition, nitro-oleic acid reduced foam cell formation by attenuating oxidized low-density lipoprotein-induced phosphorylation of signal transducer and activator of transcription-1, a transcription factor linked to foam cell formation in atherosclerotic plaques. Atherosclerotic lesions of nitro-oleic acid-treated animals also showed an increased content of collagen and alpha-smooth muscle actin, suggesting conferral of higher plaque stability.

CONCLUSION

These results reveal the antiatherogenic actions of electrophilic nitro-fatty acids in a murine model of atherosclerosis.

Transduction of redox signaling by electrophile-protein reactions

Over the last 50 years, the posttranslational modification (PTM) of proteins has emerged as a central mechanism for cells to regulate metabolism, growth, differentiation, cell-cell interactions, and immune responses. By influencing protein structure and function, PTM leads to a multiplication of proteome diversity. Redox-dependent PTMs, mediated by environmental and endogenously generated reactive species, induce cell signaling responses and can have toxic effects in organisms. PTMs induced by the electrophilic by-products of redox reactions most frequently occur at protein thiols; other nucleophilic amino acids serve as less favorable targets. Advances in mass spectrometry and affinity-chemistry strategies have improved the detection of electrophile-induced protein modifications both in vitro and in vivo and have revealed a high degree of amino acid and protein selectivity of electrophilic PTM. The identification of biological targets of electrophiles has motivated further study of the functional impact of various PTM reactions on specific signaling pathways and how this might affect organisms.

Nutrition intervention: a strategy against systemic inflammatory syndrome

BACKGROUND

Sepsis and septic shock syndrome are the leading causes of death in critically ill patients. Lipopolysaccharide (LPS) released by the colonic microorganisms may translocate across a compromised lumen, leading to upregulated reactive oxidative stress, inflammation, and sepsis. The authors examined an enteral formula high in cysteine (antioxidant precursor), omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and prebiotic fructooligosaccharides (FOS) against systemic inflammatory syndrome.

METHODS

Rats were allocated to (1) standard soy-based diet high in cysteine and crude fiber and devoid of EPA-DHA (CHOW); (2) whey-peptide-based liquid diet high in cysteine, EPA-DHA, and FOS (CYSPUFA); or (3) casein-based liquid isonitrogenous diet, low in cysteine and devoid of EPA-DHA-FOS (CASN). Liquid diets provided 25% and CHOW, 23% of calories as protein. After 6 days on diets, rats received an intraperitoneal injection of LPS or saline. Animals gained weight on their respective diets and lost weight after LPS administration. The CYSPUFA group lost considerably less weight (vs CASN or CHOW, P < .05). Inflammatory cytokines significantly increased by 4 hours and subsided 18 hours after assault. The CASN group showed elevated liver enzyme alanine aminotransferase release from damaged hepatocytes and developed severe hepatic pathology with low hematocrit. The CHOW group developed more severe hepatic lesions compared with those on liquid diets. Concentration of liver enzyme and pathology were improved in rats receiving CYSPUFA.

CONCLUSIONS

Data indicate that CYSPUFA, a diet rich in EPA-DHA-FOS, protects against LPS-induced systemic inflammatory responses and warrants clinical studies in critically ill patients.

The gamma-glutamyl transpeptidase inhibitor acivicin preserves glutathione released by astroglial cells in culture

The release of glutathione from astroglial cells was investigated using astroglia-rich primary cultures prepared from the brains of newborn rats. These cells release glutathione after onset of an incubation in a glucose-containing minimal medium. The amount of extracellular glutathione increased with the time of incubation, although the accumulation slowed down gradually. An elevated rate of increase of the glutathione concentration in the incubation medium was found if the astroglial ectoenzyme gamma-glutamyl transpeptidase was inhibited by acivicin. The activity of gamma-glutamyl transpeptidase in astroglia-rich primary cultures, which was found to be 1.9 +/- 0.3 nmol/(min x mg protein), was markedly reduced if the cells had been incubated in the presence of acivicin. After 2 h of incubation with acivicin half-maximal and maximal inhibition of gamma-glutamyl transpeptidase activity was found at concentrations of about 5 microM and 50 microM, respectively. In the presence of acivicin at a concentration above 10 microM the glutathione content found released from astroglial cells apparently increased almost proportional to time for up to 10 h. Under these conditions the average rate of release was 2.1 +/- 0.3 nmol/(h x mg protein) yielding after a 10 h incubation an extracellular glutathione content three times that of the medium of cells incubated without inhibitor. Half-maximal and maximal effects on the level of extracellular glutathione were found at 4 microM and 50 microM acivicin, respectively. After a 10 h incubation with acivicin the intracellular content of glutathione was reduced to 75% of the level of untreated astroglial cultures. These results suggest that glutathione released from astroglial cells can serve as substrate for the ectoenzyme gamma-glutamyl transpeptidase of these cells.