Biochemistry and pathology of radical-mediated protein oxidation

Transglutaminase crosslinking promotes physical and oxidative stability of filled hydrogel particles based on biopolymer phase separation

In the present study, the effect of transglutaminase (TGase) concentration on the physical and oxidative stabilities of filled hydrogel particles created by biopolymer phase separation was investigated. The results showed that filled hydrogels had relatively smaller particle sizes, higher absolute zeta-potentials, higher interfacial layer thicknesses and lightness values with the increasing of TGase concentration (P < 0.05), as evidenced by the apparent viscosity and viscoelasticity behavior. However, the relatively higher TGase concentration promoted the protein aggregation, which weakens the protection of the surface protein layer, having the negatively impacted the physical stability of filled hydrogels. Microstructural images which obtained via cryo-scanning electron microscopy also verified the above results. In particular, it is noted that filled hydrogels displayed the lowest degrees of lipid and protein oxidation during 10 days of storage (P < 0.05) at TGase concentration of 10 U/g. Prevention against oxidation was attributed mainly to TGase crosslinking of protein molecules on the surface of droplets, which likely provided a denser interface around lipid droplets. Our results indicated that TGase was a favourable agent to crosslink protein on the surface of lipid and improve the physical and oxidative stability of filled hydrogel particles.

Oxidative Stress in the Pathogenesis of Crohn's Disease and the Interconnection with Immunological Response, Microbiota, External Environmental Factors, and Epigenetics

Inflammatory bowel disease (IBD) is a complex multifactorial disorder in which external and environmental factors have a large influence on its onset and development, especially in genetically susceptible individuals. Crohn’s disease (CD), one of the two types of IBD, is characterized by transmural inflammation, which is most frequently located in the region of the terminal ileum. Oxidative stress, caused by an overabundance of reactive oxygen species, is present locally and systemically in patients with CD and appears to be associated with the well-described imbalanced immune response and dysbiosis in the disease. Oxidative stress could also underlie some of the environmental risk factors proposed for CD. Although the exact etiopathology of CD remains unknown, the key role of oxidative stress in the pathogenesis of CD is extensively recognized. Epigenetics can provide a link between environmental factors and genetics, and numerous epigenetic changes associated with certain environmental risk factors, microbiota, and inflammation are reported in CD. Further attention needs to be focused on whether these epigenetic changes also have a primary role in the pathogenesis of CD, along with oxidative stress.

Stress-sensing in the human greying hair follicle: Ataxia Telangiectasia Mutated (ATM) depletion in hair bulb melanocytes in canities-prone scalp

Canities (or hair greying) is an age-linked loss of the natural pigment called melanin from hair. While the specific cause(s) underlying the loss of melanogenically-active melanocytes from the anagen hair bulbs of affected human scalp remains unclear, oxidative stress sensing appears to be a key factor involved. In this study, we examined the follicular melanin unit in variably pigmented follicles from the aging human scalp of healthy individuals (22-70 years). Over 20 markers were selected within the following categories: melanocyte-specific, apoptosis, cell cycle, DNA repair/damage, senescence and oxidative stress. As expected, a reduction in melanocyte-specific markers in proportion to the extent of canities was observed. A major finding of our study was the intense and highly specific nuclear expression of Ataxia Telangiectasia Mutated (ATM) protein within melanocytes in anagen hair follicle bulbs. ATM is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks and functions as an important sensor of reactive oxygen species (ROS) in human cells. The incidence and expression level of ATM correlated with pigmentary status in canities-affected hair follicles. Moreover, increased staining of the redox-associated markers 8-OHdG, GADD45 and GP-1 were also detected within isolated bulbar melanocytes, although this change was not clearly associated with donor age or canities extent. Surprisingly, we were unable to detect any specific change in the expression of other markers of oxidative stress, senescence or DNA damage/repair in the canities-affected melanocytes compared to surrounding bulbar keratinocytes. By contrast, several markers showed distinct expression of markers for oxidative stress and apoptosis/differentiation in the inner root sheath (IRS) as well as other parts of the hair follicle. Using our in vitro model of primary human scalp hair follicle melanocytes, we showed that ATM expression increased after incubation with the pro-oxidant hydrogen peroxide (H₂O₂). In addition, this ATM increase was prevented by pre-incubation of cells with antioxidants. The relationship between ATM and redox stress sensing was further evidenced as we observed that the inhibition of ATM expression by chemical inhibition promoted the loss of melanocyte viability induced by oxidative stress. Taken together these new findings illustrate the key role of ATM in the protection of human hair follicle melanocytes from oxidative stress/damage within the human scalp hair bulb. In conclusion, these results highlight the remarkable complexity and role of redox sensing in the status of human hair follicle growth, differentiation and pigmentation.

Sleeve Gastrectomy Ameliorates Diabetes-Related Spleen Damage by Improving Oxidative Stress Status in Diabetic Obese Rats

PURPOSE

Oxidative stress and inflammation are important pathogenic mediators in diabetes-related organ damage. Accumulating evidence suggests that immunodeficiency in diabetes is associated with diabetes-induced spleen damage. Sleeve gastrectomy (SG) has been proved to improve diabetes and its multiple associated complications. However, the ameliorative role of SG against spleen damage in diabetes has not been investigated.

MATERIALS AND METHODS

Animal model of diabetic obese rats induced by high-fat diet (HFD) combined with streptozotocin (STZ) was treated with sham operation, caloric restriction, and SG. Metabolic parameters were measured, and the morphological and histopathological changes, status of oxidative stress, and levels of inflammatory factors were evaluated.

RESULTS

SG reduced body weight and improved glucose tolerance and insulin sensitivity in diabetic obese rats. SG significantly reversed splenic atrophy and alleviated abnormalities of white and red pulp. Additionally, SG also reversed the increased splenocyte apoptosis (P < 0.001). Meanwhile, indicators of oxidative stress including reactive oxygen species (ROS), nitric oxide (NO), malondialdehyde (MDA), and protein carbonylation were reduced, and the activity and expression of antioxidant enzymes including SOD and CAT were improved after SG. The mRNA expression of inflammatory factors in SG groups such as TNF-α (P < 0.001), IL-6 (P < 0.001), MCP-1 (P < 0.01), and ICAM-1 (P < 0.001) was also significantly reduced.

CONCLUSION

SG ameliorates diabetes-related splenic injury by restoring the balance between oxidative stress process and antioxidant defense systems as well as reducing inflammation in the spleen. These findings indicate that SG is an appropriate therapeutic strategy for diabetes-related spleen damage.

Studies on the synthesis and stability of α-ketoacyl peptides

Oxidative stress, an excess of reactive oxygen species (ROS), may lead to oxidative post-translational modifications of proteins resulting in the cleavage of the peptide backbone, known as α-amidation, and formation of fragments such as peptide amides and α-ketoacyl peptides (α-KaP). In this study, we first compared different approaches for the synthesis of different model α-KaP and then investigated their stability compared to the corresponding unmodified peptides. The stability of peptides was studied at room temperature or at temperatures relevant for food processing (100 °C for cooking and 150 °C as a simulation of roasting) in water, in 1% (m/v) acetic acid or as the dry substance (to simulate the thermal treatment of dehydration processes) by HPLC analysis. Oxidation of peptides by 2,5-di-tert-butyl-1,4-benzoquinone (DTBBQ) proved to be the most suited method for synthesis of α-KaPs. The acyl side chain of the carbonyl-terminal α-keto acid has a crucial impact on the stability of α-KaPs. This carbonyl group has a catalytic effect on the hydrolysis of the neighboring peptide bond, leading to the release of α-keto acids. Unmodified peptides were significantly more stable than the corresponding α-KaPs. The possibility of further degradation reactions was shown by the formation of Schiff bases from glyoxylic or pyruvic acids with glycine and proven through detection of transamination products and Strecker aldehydes of α-keto acids by HPLC–MS/MS. We propose here a mechanism for the decomposition of α-ketoacyl peptides.

Alcohol as an early life stressor: Epigenetics, metabolic, neuroendocrine and neurobehavioral implications

Ethanol exposure during gestation is an early life stressor that profoundly dysregulates structure and functions of the embryonal nervous system, altering the cognitive and behavioral development. Such dysregulation is also achieved by epigenetic mechanisms, which, altering the chromatin structure, redraw the entire pattern of gene expression. In parallel, an oxidative stress response at the cellular level and a global upregulation of neuroendocrine stress response, regulated by the HPA axis, exist and persist in adulthood. This neurobehavioral framework matches those observed in other psychiatric diseases such as mood diseases, depression, autism; those early life stressing events, although probably triggered by specific and different epigenetic mechanisms, give rise to largely overlapping neurobehavioral phenotypes. An early diagnosis of prenatal alcohol exposure, using reliable markers of ethanol intake, together with a deeper understanding of the pathogenic mechanisms, some of them reversible by their nature, can offer a temporal "window" of intervention. Supplementing a mother's diet with protective and antioxidant substances in addition to supportive psychological therapies can protect newborns from being affected.

Redox Post-translational Modifications of Protein Thiols in Brain Aging and Neurodegenerative Conditions-Focus on S-Nitrosation

Reactive oxygen species and reactive nitrogen species (RONS) are by-products of aerobic metabolism. RONS trigger a signaling cascade that can be transduced through oxidation-reduction (redox)-based post-translational modifications (redox PTMs) of protein thiols. This redox signaling is essential for normal cellular physiology and coordinately regulates the function of redox-sensitive proteins. It plays a particularly important role in the brain, which is a major producer of RONS. Aberrant redox PTMs of protein thiols can impair protein function and are associated with several diseases. This mini review article aims to evaluate the role of redox PTMs of protein thiols, in particular S-nitrosation, in brain aging, and in neurodegenerative diseases. It also discusses the potential of using redox-based therapeutic approaches for neurodegenerative conditions.

Targeting glutathione with the triterpenoid CDDO-Im protects against benzo-a-pyrene-1,6-quinone-induced cytotoxicity in endothelial cells

Epidemiological studies have exhibited a strong correlation between exposure to air pollution and deaths due to vascular diseases such as atherosclerosis. Benzo-a-pyrene-1,6-quinone (BP-1,6-Q) is one of the components of air pollution_. This study was to examine the role of GSH in BP-1,6-Q mediated cytotoxicity in human EA.hy96 endothelial cells and demonstrated that induction of cellular glutathione by a potent triterpenoid, CDDO-Im (1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole), protects cells against BP-1,6-Q induced protein and lipid damage. Incubation of EA.hy926 endothelial cells with BP-1,6-Q caused a significant increase in dose-dependent cytotoxicity as measured by LDH release assay and both apoptotic and necrotic cell deaths as measured by flow cytometric analysis. Incubation of EA.hy926 endothelial cells with BP-1,6-Q also caused a significant decrease in cellular GSH levels. The diminishment of cellular GSH by buthionine sulfoximine (BSO) potentiated BP-1,6-Q-induced toxicity significantly suggesting a critical involvement of GSH in BP-1,6-Q induced cellular toxicity. GSH-induction by CDDO-Im significantly protects cells against BP-1,6-Q induced protein and lipid damage as measured by protein carbonyl (PC) assay and thiobarbituric acid reactive substances (TBARS) assay, respectively. However, the co-treatment of cells with CDDO-Im and BSO reversed the cytoprotective effect of CDDO-Im on BP-1,6-Q-mediated lipid peroxidation and protein oxidation. These results suggest that induction of GSH by CDDO-Im might be the important cellular defense against BP-1,6-Q induced protein and lipid damage. These findings would contribute to better understand the action of BP-1,6-Q and may help to develop novel therapies to protect against BP-1,6-Q-induced atherogenesis.

Carbonylation of proteins-an element of plant ageing

Carbonylation-ROS-dependent posttranslational modification of proteins-may be regarded as one of the important events in the process of ageing or senescence in plants. Ageing is the progressive process starting from seed development (plants) and birth (animals). The life-span of living organisms depends on many factors and stresses, which influence reactive oxygen species (ROS) level. The imbalance of their production and scavenging causes pathophysiological conditions that accelerate ageing. ROS modify nucleic acids, lipids, sugars and proteins. The level of carbonylated proteins can serve as an indicator of an oxidative cellular status. Several pathways of protein carbonylation, e.g. the conjugation with reactive carbonyl species, and/or a direct metal-catalysed oxidative attack on amino acids residues are known. Dysfunctional carbonylated proteins are more prone to degradation or form aggregates when the proteolytic machinery is inhibited, as observed in ageing. Protein carbonylation may contribute to formation of organelle-specific signal and to the control of protein quality. Carbonylated proteins are formed during the whole plant life; nevertheless, accelerated ageing stimulates the accumulation of carbonyl derivatives. In the medicine-related literature, concerned ageing and ROS-mediated protein modifications, this topic is extensively analysed, in comparison to the plant science. In plant science, ageing and senescence are considered to describe slightly different processes (physiological events). However, senescence (Latin: senēscere) means "to grow old". This review describes the correlation of protein carbonylation level to ageing or/and senescence in plants. Comparing data from the area of plant and animal research, it is assumed that some basic mechanism of time-dependent alterations in the cellular biochemical processes are common and the protein carbonylation is one of the important causes of ageing.

Increased oxidative stress is associated with thiol/disulphide homeostasis in clomiphene citrate resistant polycystic ovary syndrome

The purpose of this study was to evaluate the relation CC resistant PCOS and the thiol/disulphide homeostasis, used as a marker of OS, by measuring that exchange using a novel technique. Sixty women patients admitted to the infertility clinic were evaluated. The patients were divided into two groups. Group 1 comprised 30 infertile PCOS patients with CC resistance; Group 2 was the control group comprising 30 infertile PCOS patients with CC sensitivity. Serum total thiol (p = .024), native thiol (p = .0052), disulphide (p = .003), index 1 (p = .001), index 2 (p = .001) and index 3 (p = .001), HOMA-IR (p < .001) and free testosterone (p < .001) were statistically significant. The independent variables BMI and age effects were adjusted according to the logistic regression method with groups. Significant differences were observed between the two groups in the levels of native thiol (p* = .0042), total thiol (p* = .024), disulphide (p* = .0003), index 1 (p* = .0001) index 2 (p*= .0001), index 3 (p* = .0001), HOMA-IR (p* = .0044), insulin (p*= .032) and free testosterone (p* = .0001) values. The thiol/disulphide homeostasis viewed in favour of OS. Like a reflection of OS in the follicular endocrine microenvironment may be linked with increased thiol/disulphide homeostasis, free testosterone, insulin and HOMA-IR levels.Impact statementWhat is already known about this subject? In previous studies, thiol/disulphide homeostasis was compared between PCOS and control groups. In this study, serum thiol/disulphide homeostasis was measured in infertile PCOS patients resistant to CC for the first time.What do the results of this study add? Disulphide concentrations were significantly higher in patients with CC resistant patients thanthe control group. This shows us that more OS occurs in the CC-resistant group.What are the implications of these findings for clinical practice and further research? Thiol/disulphide homeostasis will be a guide for PCOS management in patients with CC-resistant PCOS.

Discrimination of Dental Pulp Stem Cell Regenerative Heterogeneity by Single-Cell Raman Spectroscopy

IMPACT STATEMENT

This study is the first to investigate and confirm the effectiveness of single-cell Raman spectroscopy (SCRM), in its ability to discriminate between dental pulp stem cells (DPSCs) with contrasting proliferative and differentiation capabilities. The findings show that SCRM can rapidly and noninvasively distinguish and identify DPSC subpopulations in vitro with superior proliferative and multipotency properties, versus lesser quality DPSCs, thereby overcoming the significant heterogeneity issues surrounding DPSC ex vivo expansion and differentiation capabilities. Such findings support further SCRM assessment for the selective screening/isolation of superior quality DPSCs from whole dental pulp tissues, for more effective in vitro evaluation and therapy development.

Oxidative Stress and Photodynamic Therapy of Skin Cancers: Mechanisms, Challenges and Promising Developments

Ultraviolet radiation is one of the most pervasive environmental interactions with humans. Chronic ultraviolet irradiation increases the danger of skin carcinogenesis. Probably, oxidative stress is the most important mechanism by which ultraviolet radiation implements its damaging effects on normal cells. However, notwithstanding the data referring to the negative effects exerted by light radiation and oxidative stress on carcinogenesis, both factors are used in the treatment of skin cancer. Photodynamic therapy (PDT) consists of the administration of a photosensitiser, which undergoes excitation after suitable irradiation emitted from a light source and generates reactive oxygen species. Oxidative stress causes a condition in which cellular components, including DNA, proteins, and lipids, are oxidised and injured. Antitumor effects result from the combination of direct tumour cell photodamage, the destruction of tumour vasculature and the activation of an immune response. In this review, we report the data present in literature dealing with the main signalling molecular pathways modified by oxidative stress after photodynamic therapy to target skin cancer cells. Moreover, we describe the progress made in the design of anti-skin cancer photosensitisers, and the new possibilities of increasing the efficacy of PDT via the use of molecules capable of developing a synergistic antineoplastic action.

Top-Down ETD-MS Provides Unreliable Quantitation of Methionine Oxidation

Methionine oxidation plays a critical role in many processes of biologic and biomedical importance, including cellular redox responses and stability of protein pharmaceuticals. Bottom-up methods for analysis of methionine oxidation can suffer from incomplete sequence coverage, as well as an inability to readily detect correlated oxidation between 2 or more methionines. However, the methodology for quantifying protein oxidation in top-down analyses is lacking. Previous work has shown that electron transfer dissociation (ETD)-based tandem mass spectrometry (MS/MS) fragmentation offers accurate and precise quantification of amino acid oxidation in peptides, even in complex samples. However, the ability of ETD-based MS/MS fragmentation to accurately quantify amino acid oxidation of proteins in a top-down manner has not been reported. Using apomyoglobin and calmodulin as model proteins, we partially converted methionines into methionine sulfoxide by incubation in H₂O₂. Using top-down ETD-based fragmentation, we quantified the amount of oxidation of various ETD product ions and compared the quantified values with those from traditional bottom-up analysis. We find that overall quantification of methionine oxidation by top-down MS/MS ranges from good agreement with traditional bottom-up methods to vast differences between the 2 techniques, including missing oxidized product ions and large differences in measured oxidation quantities. Care must be taken in transitioning ETD-based quantitation of oxidation from the peptide level to the intact protein level.

Redox regulation of tumor suppressor PTEN in cell signaling

Phosphatase and tensin homologs deleted on chromosome 10 (PTEN) is a potent tumor suppressor and often dysregulated in cancers. Cellular PTEN activity is restrained by the oxidation of active-site cysteine by reactive oxygen species (ROS). Recovery of its enzymatic activity predominantly depends on the availability of cellular thioredoxin (Trx) and peroxiredoxins (Prx), both are important players in cell signaling. Trx and Prx undergo redox-dependent conformational changes through the oxidation of cysteine residues at their active sites. Their dynamics are essential for protein functionality and regulation. In this review, we summarized the recent advances regarding the redox regulation of PTEN, with a specific focus on our current state-of-the-art understanding of the redox regulation of PTEN. We also proposed a tight association of the redox regulation of PTEN with Trx dimerization and Prx hyperoxidation, providing guidance for the identification of novel therapeutic targets.

Influence of ultrasound pretreatment on the subsequent glycation of dietary proteins

The influence of ultrasound treatment on the subsequent glycation process of proteins is controversial. Glycation behaviors of bovine serum albumin (BSA), β-lactoglobulin (β-Lg) and β-casein (β-CN) after ultrasound pretreatment (UP) were compared by both evaluating glycation kinetics and analyzing structural changes of proteins. UP resulted in both unfolding and aggregation behavior in protein samples, which altered the accessibility of the Lys and Arg. Five cycles of UP up-regulated the glycation degree of BSA and β-Lg, possibly due to the unfolding behavior induced by UP, which exposed additional glycation sites. In contrast, 30 cycles of UP induced a dramatic increase (by 97.9 nm) in particle size of BSA, thus burying portions of glycation sites and suppressing the glycation process. Notably, UP had minimal influence on glycation kinetics of β-CN, due to its intrinsic disordered structure. Based on proteomics analysis, the preference of Lys and Arg during glycation was found to be changed by UP in BSA and β-Lg. Four, 3 and 3 unique carboxyethylated lysine residues were identified in glycated BSA after 0, 5 and 30 cycles of UP, respectively. This study suggests that the protein glycation can be affected by UP, depending on the ultrasonication duration and native structure of the protein.

Role of 904 nm superpulsed laser-mediated photobiomodulation on nitroxidative stress and redox homeostasis in burn wound healing

BACKGROUND

Burn wound healing is delayed due to several critical factors such as sustained inflammation, vascular disorder, neuropathy, enhanced proteolysis, infection, and oxidative stress. Burn wounds have limited oxygen supply owing to compromised blood circulation. Hypoxic burn milieu leads to free radicals overproduction incurring oxidative injury, which impedes repair process causing damage to cell membranes, proteins, lipids, and DNA. Photobiomodulation (PBM) with 904 nm superpulsed laser had shown potent healing efficacy via attenuating inflammation while enhancing proliferation, angiogenesis, collagen accumulation, and bioenergetic activation in burn wounds.

METHODS

This study investigated the effects of 904 nm superpulsed laser at 0.4 mW/cm² average power density, 0.2 J/cm² total energy density, 100 Hz frequency, and 200 ns pulse width for 10 min daily for seven days postburn injury on nitroxidative stress, endogenous antioxidants status, and redox homeostasis.

RESULTS

Photobiomodulation treatment significantly decreased reactive oxygen species, nitric oxide, and lipid peroxidation levels as compared to non-irradiated control. Further, protective action of PBM against protein oxidative damage was evidenced by reduced protein carbonylation and advanced oxidation protein product levels along with significantly enhanced endogenous antioxidants levels of SOD, catalase, GPx, GST, reduced glutathione, and thiol (T-SH, Np-SH, P-SH). Biochemical changes aid in reduction of oxidative stress and maintenance of redox homeostasis, which further well corroborated by significantly up-regulated protein expression of Nrf 2, hemeoxygenase (HO-1), and thioredoxin reductase 2 (Txnrd2).

CONCLUSION

Photobiomodulation with 904 nm superpulsed laser led to reduction of nitroxidative stress, induction of endogenous antioxidants, and maintenance of redox homeostasis that could play a vital role in augmentation of burn wound healing.

Observation of peroxynitrite overproduction in cells during 5-fluorouracil treatment via a ratiometric fluorescent probe

We describe a colorimetric and fluorescent probe 3a to detect cellular peroxynitrite with high selectivity and sensitivity. 3a was successfully applied in the bioimaging of exogenous and endogenous peroxynitrite in living cells. The up-regulation of peroxynitrite in cancer cells and normal cells during 5-fluorouracil treatment was finally monitored.

Comparative proteomic analysis reveals that exogenous 6-benzyladenine (6-BA) improves the defense system activity of waterlogged summer maize

BACKGROUND

Exogenous 6-benzyladenine (6-BA) could improve leaf defense system activity. In order to better understand the regulation mechanism of exogenous 6-benzyladenine (6-BA) on waterlogged summer maize, three treatments including control (CK), waterlogging at the third leaf stage for 6 days (V3-6), and application of 100 mg dm- 3 6-BA after waterlogging for 6 days (V3-6-B), were employed using summer maize hybrid DengHai 605 (DH605) as the experimental material. We used a labeling liquid chromatography-based quantitative proteomics approach with tandem mass tags to determine the changes in leaf protein abundance level at the tasseling stage.

RESULTS

Waterlogging significantly hindered plant growth and decreased the activities of SOD, POD and CAT. In addition, the activity of LOX was significantly increased after waterlogging. As a result, the content of MDA and H2O2 was significantly increased which incurred serious damages on cell membrane and cellular metabolism of summer maize. And, the leaf emergence rate, plant height and grain yield were significantly decreased by waterlogging. However, application of 6-BA effectively mitigated these adverse effects induced by waterlogging. Compared with V3-6, SOD, POD and CAT activity of V3-6-B were increased by 6.9, 12.4, and 18.5%, LOX were decreased by 13.6%. As a consequence, the contents of MDA and H2O2 in V3-6-B were decreased by 22.1 and 17.2%, respectively, compared to that of V3-6. In addition, the leaf emergence rate, plant height and grain yield were significantly increased by application of 6-BA. Based on proteomics profiling, the proteins involved in protein metabolism, ROS scavenging and fatty acid metabolism were significantly regulated by 6-BA, which suggested that application of 6-BA exaggerated the defensive response of summer maize at proteomic level.

CONCLUSIONS

These results demonstrated that 6-BA had contrastive effects on waterlogged summer maize. By regulating key proteins related to ROS scavenging and fatty acid metabolism, 6-BA effectively increased the defense system activity of waterlogged summer maize, then balanced the protein metabolism and improved the plant physiological traits and grain yield.

Discovery of a Small-Molecule-Dependent Photolytic Peptide

We accidentally found that YM-53601, a known small-molecule inhibitor of squalene synthase (SQS), selectively depletes SQS from mammalian cells upon UV irradiation. Further analyses indicated that the photodepletion of SQS requires its short peptide segment located at the COOH terminus. Remarkably, when the 27 amino acid peptide was fused to green fluorescent protein or unrelated proteins at either the NH₂ or COOH terminus, such fusion proteins were selectively depleted when the cells were treated with both YM-53601 and UV exposure. Product analysis and electron spin resonance experiments suggested that the UV irradiation promotes homolytic C-O bond cleavage of the aryl ether group in YM-53601. It is likely that the radical species generated from UV-activated YM-53601 abstract hydrogen atoms from the SQS peptide, leading to the photolysis of the entire protein. The pair of the SQS peptide and YM-53601 discovered in the present study paves the way for the design of a new small-molecule-controlled optogenetic tool.

A second intracellular copper/zinc superoxide dismutase and a manganese superoxide dismutase in Oxya chinensis: Molecular and biochemical characteristics and roles in chlorpyrifos stress

A second intracellular copper/zinc superoxide dismutase (icCuZnSOD2) and manganese SOD (MnSOD) were cloned and characterized in Oxya chinensis. The open reading frame (ORF) of OcicCuZnSOD2 and OcMnSOD are 462 and 672 bp encoding 153 and 223 amino acids, respectively. OcicCuZnSOD2 contains two signature sequences, one potential N-glycosylation site, and seven copper/zinc binding sites. OcMnSOD includes a mitochondria targeting sequence of 7 amino acids at N-terminal, one signature sequence, two N-glycosylation sites, and four manganese binding sites. The secondary structure and homology model of OcicCuZnSOD2 include nine β sheets, two Greek-key motifs, and one electrostatic loop. OcMnSOD contains nine α-helices and three β-sheets. Phylogenetic analysis shows that OcMnSOD is evolutionarily conserved while OcicCuZnSOD2 may be gene duplication and is paralogous to OcicCuZnSOD1. OcMnSOD expressed widely in all tissues and developmental stages. OcicCuZnSOD2 showed testis-specific expression and expressed highest in the 5th-instar nymph and the adult. The optimum temperatures and pH values of the recombinant OcicCuZnSOD2 and OcMnSOD were 40 °C and 8.0. They were stable at 25-55 °C and at pH 5.0-12.0 and pH 6.0-12.0, respectively. The activity and mRNA expression of each OcSOD were assayed after chlorpyrifos treatments. Total SOD and CuZnSOD activities first increased then declined under chlorpyrifos stress. Chlorpyrifos induced the mRNA expression and activity of OcMnSOD as a dose-dependent manner and inhibited OcicCuZnSOD2 transcription. The role of each OcSOD gene in chlorpyrifos stress was investigated using RNAi and disc diffusion assay with Escherichia coli overexpressing OcSOD proteins. Silencing of OcMnSOD significantly increased ROS content in chlorpyrifos-exposed grasshoppers. Disc diffusion assay showed that the plates with E. coli overexpressing OcMnSOD had the smaller inhibition zones around the chlorpyrifos-soaked filter discs. These results implied that OcMnSOD played a significant role in defense chlorpyrifos-induced oxidative stress.

A new dendrimer series: synthesis, free radical scavenging and protein binding studies

Tri-o-tolyl benzene-1,3,5-tricarboxylate (TOBT (T0)), tri-4-hydroxyphenyl benzene-1,3,5-tricarboxylate (THBT (T1)), and tri-3,5-dihydroxyphenyl benzene-1,3,5-tricarboxylate (TDBT (T2)), a series of 1^st tier dendrimers with a common 1,3,5-benzenetricarbonyl trichloride/trimesoyl chloride (TMC) core, are reported. T0 does not have any replaceable H⁺ on its terminal phenyl group, acting as a branch. T1 has one phenolic –OH at the para position and T2 has two phenolic –OH groups at the 3 and 5 positions of each terminal phenyl group. During synthesis, these –OH groups at the terminal phenyl groups were protected through tert-butyldimethylsilyl chloride (TBDMSCl) assisted with t-BuOK in DCM, THF, indazole, 4-dimethylaminopyridine (DMAP), and tertiary-n-butyl ammonium fluoride (TBAF). MTBDMSP (mono-tertiary butyl dimethylsilane phloroglucinol), DTBDMSP (di-tertiary butyl dimethylsilane phloroglucinol), and TTBDMSP (tri-tertiary butyl dimethylsilane phloroglucinol) were obtained with >90% yield, and TTBDMSP phenolic derivatives (PDs) were developed to synthesize T0, T1, and T2 dendrimers by deprotecting with TBAF. T0 showed superhydrophobic properties as it did not dissolve in methanol, contrary to T1 and T2, but dissolved in acetone. Their structures were determined using ¹H and ¹³C NMR spectroscopies, and mass spectrometry. Their scavenging activities were studied using UV-Vis spectrophotometry compared with ascorbic acid and protein binding was studied with bovine serum albumin (BSA) and lysozyme (lyso). T0 exhibited exceptional optical activity contrary to T1 and T2, which acted as antioxidants to scavenge free radicals.

Superhydrophobic dendrimers with excellent antioxidant properties, and the ability to bind proteins and enzymes in their functional void spaces.

A systematic review of the interaction and effects generated by antimicrobial metallic substituents in bone tissue engineering

Changes brought about by metal ions and metal nanoparticles within bacterial cells and the damage caused to the cellular membrane upon contact with negatively charged surface components.

The Role of Meat Protein in Generation of Oxidative Stress and Pathophysiology of Metabolic Syndromes

Various processing methods have a great impact on the physiochemical and nutritional properties of meat that are of health concern. Hence, the postmortem processing of meat by different methods is likely to intensify the potential effects on protein oxidation. The influence of meat protein oxidation on the modulation of the systemic redox status and underlying mechanism is well known. However, the effects of processed meat proteins isolated from different sources on gut microbiota, oxidative stress biomarkers, and metabolomic markers associated with metabolic syndromes are of growing interest. The application of advanced methodological approaches based on OMICS, and mass spectrometric technologies has enabled to better understand the molecular basis of the effect of processed meat oxidation on human health and the aging process. Animal studies indicate the involvement of dietary proteins isolated from different sources on health disorders, which emphasizes the impact of processed meat protein on the richness of bacterial taxa such as (Mucispirillum, Oscillibacter), accompanied by increased expression of lipogenic genes. This review explores the most recent evidences on meat processing techniques, meat protein oxidation, underlying mechanisms, and their potential effects on nutritional value, gut microbiota composition and possible implications on human health.

A new long-wavelength fluorescent probe for tracking peroxynitrite in live cells and inflammatory sites of zebrafish

Design of a long-wavelength fluorescent probe for tracking peroxynitrite in live cells and inflammatory sites of zebrafish.

Oxidized Pork Induces Oxidative Stress and Inflammation by Altering Gut Microbiota in Mice

SCOPE

Reduced digestibility of foods containing oxidized proteins and the subsequent excessive accumulation of undigested components in the colon may cause changes in the intestinal flora composition. This study evaluates the characteristics of this change and the potential adverse effects on organisms.

METHODS AND RESULTS

Pork is cooked using sous-vide or at high temperature and pressure (HTP), then freeze-dried, resulting in different levels of oxidized damage. Mice are fed diets containing low- (LOP), medium- (MOP), or high-oxidative damage pork (HOP) for 12 weeks. HOP intake increases mice body weight, induces inflammatory response, and causes oxidative stress, as indicated by the accumulation of oxidative products. Increased serum LPS levels and downregulation of tight junction-related genes in the mucosa suggest mucosal barrier damage. Alterations in the cecal microbiota include reduced relative abundance of the mucin-degrading bacteria Akkermansia, beneficial bacteria Lactobacillus and Bifidobacterium, and H₂ S-producing bacteria Desulfovibrio and increased relative abundance of the pro-inflammatory bacteria Escherichia-Shigella and pathobiont Mucispirillum.

CONCLUSION

HOP intake causes the accumulation of oxidative products, increases body weight, damages the intestinal barrier, and induces oxidative stress and inflammatory response, likely by altering gut microbiota through protein oxidation (POX).

Azulene-Derived Fluorescent Probe for Bioimaging: Detection of Reactive Oxygen and Nitrogen Species by Two-Photon Microscopy

Two-photon fluorescence microscopy has become an indispensable technique for cellular imaging. Whereas most two-photon fluorescent probes rely on well-known fluorophores, here we report a new fluorophore for bioimaging, namely azulene. A chemodosimeter, comprising a boronate ester receptor motif conjugated to an appropriately substituted azulene, is shown to be an effective two-photon fluorescent probe for reactive oxygen species, showing good cell penetration, high selectivity for peroxynitrite, no cytotoxicity, and excellent photostability.

Nitroxidized-Albumin Advanced Glycation End Product and Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease whose major clinical consequence is inflammation of small joints and contiguous structures. Oxidative and nitrosative stress along with increased formation of advanced glycation end products (AGEs) play an important role in the disease process. Generation of reactive species during glycation of proteins further adds to the oxidative and nitrosative stress. Albumin, being the most abundant plasma protein, is frequently targeted by different oxidizing and nitrating agents, including peroxynitrite (OONO-) anion. Albumin is also targeted and modified by dicarbonyl metabolites (glyoxal and methylglyoxal) which are formed in oxidative and non-oxidative processes during the synthesis of AGEs. The endogenously formed OONO- and dicarbonyls may modify plasma albumin including those albumin that have travelled or migrated to synovial cells and caused nitration, oxidation, and glycation. These modifications may produce crosslinks, aggregate in albumin and confer immunogenicity. Simultaneous modification of albumin by OONO- and dicarbonyls may generate nitroxidized-AGE-albumin which may persist in circulation for a longer duration compared to native albumin. Nitroxidized-AGE-albumin level (or serum autoantibodies against nitroxidized- AGE-albumin) along with other pre-clinical features may help predict the likely onset of RA.

Structural and Functional Characterization of Laccase-Induced β-Lactoglobulin-Ferulic Acid-Chitosan Ternary Conjugates

The purpose of current research is to design and acquire novel biological macromolecule materials with enhanced functional properties. Chitosan-ferulic acid binary conjugate (CFC) was synthesized based on the carbodiimide-mediated coupling reaction, and then β-lactoglobulin-ferulic acid-chitosan ternary conjugate (BFCC) was fabricated by laccase induction. Furthermore, the impact of laccase concentration on the formation mechanism of BFCC was investigated by the analyses of reaction group content, ultraviolet-visible (UV-vis) absorption, circular dichroism (CD), and fluorescence spectroscopy. Results showed that hetero- and homo-conjugates between CFC and β-lactoglobulin (β-LG) were achievable at the low concentration (≤4 U/mL) and high concentration (≥6 U/mL) of laccase, respectively. The CD spectrum indicated that the interaction with CFC made β-LG more disorderly. Functional evaluation results revealed that the antioxidant activity and thermal stability of BFCC were improved compared with β-LG. The knowledge obtained in the present study provided an effective method to acquire innovative biological macromolecule materials with desirable functional characteristics.

The effect of thiol-disulfide homeostasis in patients undergoing on-pump coronary artery bypass grafting

Background

In this study, we aimed to investigate the effects of thiol-disulfide homeostasis in patients undergoing on-pump coronary artery bypass grafting.

Methods

Between January 2018 and October 2018, a total of 51 patients (43 males, 8 females; mean age 61.8±8.7 years; range, 38 to 78 years) who underwent isolated on-pump coronary artery bypass grafting were included. Thiol-disulfide homeostasis parameters were studied in the preoperative period (T1), 30 min after the removal of cross-clamp (T2), and postoperative sixth h (T3). Hemodynamic parameters such as atrial fibrillation and inotropic support requirement of the patients were evaluated in the postoperative period.

Results

There were significant differences in the measured thiol-disulfide homeostasis parameters at different time points of surgery (p<0.001). Binary logistic regression analysis showed that T2-disulfide/native thiol ratio was an independent predictor of the development of postoperative atrial fibrillation (p=0.042). There were positive and significant correlations between the T2-disulfide levels and cross-clamp time (r:0.307, p=0.029).

Conclusion

Thiol-disulfide homeostasis in patients undergoing on-pump coronary artery bypass grafting changes toward to disulfide. Disulfide levels increase in parallel with prolonged ischemia time. Decreased native thiol and increased disulfide levels during ischemic period may be predictive of postoperative atrial fibrillation.

Pd-catalyzed site-selective C(sp2)-H radical acylation of phenylalanine containing peptides with aldehydes

The site-selective functionalization of C-H bonds within a peptide framework remains a challenging task of prime synthetic importance. Herein, the first Pd-catalyzed δ-C(sp2)-H acylation of Phe containing peptides with aldehydes is described. This oxidative coupling is distinguished by its site-specificity, tolerance of sensitive functional groups, scalability, and enantiospecificity and exhibits entire chemoselectivity for Phe motifs over other amino acid units. The compatibility of this dehydrogenative acylation platform with a number of oligopeptides of high structural complexity illustrates its ample opportunities for the late-stage peptide modification and bioconjugation.

CNS function and dysfunction during exposure to hyperbaric oxygen in operational and clinical settings

Hyperbaric oxygen (HBO2) is breathed during hyperbaric oxygen therapy and during certain undersea pursuits in diving and submarine operations. What limits exposure to HBO2 in these situations is the acute onset of central nervous system oxygen toxicity (CNS-OT) following a latent period of safe oxygen breathing. CNS-OT presents as various non-convulsive signs and symptoms, many of which appear to be of brainstem origin involving cranial nerve nuclei and autonomic and cardiorespiratory centers, which ultimately spread to higher cortical centers and terminate as generalized tonic-clonic seizures. The initial safe latent period makes the use of HBO2 practical in hyperbaric and undersea medicine; however, the latent period is highly variable between individuals and within the same individual on different days, making it difficult to predict onset of toxic indications. Consequently, currently accepted guidelines for safe HBO2 exposure are highly conservative. This review examines the disorder of CNS-OT and summarizes current ideas on its underlying pathophysiology, including specific areas of the CNS and fundamental neural and redox signaling mechanisms that are thought to be involved in seizure genesis and propagation. In addition, conditions that accelerate the onset of seizures are discussed, as are current mitigation strategies under investigation for neuroprotection against redox stress while breathing HBO2 that extend the latent period, thus enabling safer and longer exposures for diving and medical therapies.

Thiol-disulphide Homeostasis in Essential Thrombocythemia Patients

Background

This study aimed to show the status of thioldisulphide homeostasis in essential thrombocytosis patients, which is known to play a role in platelet function.

Methods

The study included 27 ET patients and a control group of 36 healthy subjects. Serum total (-SH + -S-S-) and native (-SH) thiol levels were measured in all subjects using an automatic method.

Results

Age and gender distribution were similar in both groups. Compared with the control group, in the ET group, there were increased native thiol and total thiol levels (p = 0.001, p = 0.046). There was no correlation between thiol, total thiol and disulphide ratios with Jak2 mutation, hemorrhage and thrombosis. A positive correlation was determined between thrombosis and thiol disulphide homeostasis (p = 0.058). The study results showed that thiol-disulphide homeostasis shifted to the proliferative side in ET, in which ineffective erythropoiesis was predominant. It is also known that platelets are more active in ET cases and thiol disulphide balance is important in platelet function.

Conclusions

This result suggests that thrombotic complications may be reduced if the formation is achieved of mechanisms (oxidation mechanisms) that will trigger the increase of disulphide groups. However, more extensive research is needed on this subject.

Influence of malondialdehyde-induced modifications on physicochemical and digestibility characteristics of whey protein isolate

Impacts of lipid oxidation product malondialdehyde (MDA) on the properties of whey protein isolate (WPI) were investigated in this study. The incorporation of MDA into WPI promoted the formation of protein carbonyls, with the significant loss of protein sulfhydryls, impaired intrinsic fluorescence, and increased protein surface hydrophobicity. The visualized band profiles revealed by gel electrophoresis and immunoblotting suggested that WPI's main components β-lactoglobulin and α-lactalbumin were the targets of MDA, and the derivatives of MDA were involved in protein cross-linking and aggregation at higher molecular weights. Abnormal protein aggregation was further confirmed by scanning electron microscopy analysis of the surface microstructure of MDA-modified WPI. Finally, in vitro digestibility assay indicated that the modification of MDA reduced WPI's susceptibility to digestive enzymes. The present study demonstrated that the contribution of MDA to protein modification in dairy products can be substantial in complex foodstuffs composed of lipids and proteins. PRACTICAL APPLICATIONS: The present work enhanced our knowledge on the remarkable susceptibility of dairy product WPI to lipid oxidation product MDA. With the trend of application of highly unsaturated fatty acids such as fish oil or alga oils as functional ingredients in dairy products, it is obvious that apart from monitoring lipid oxidation products, the resultant changes in dietary proteins deserve more attention. The food industry must be aware of the importance of appropriate preventive measures in minimizing the negative effects of lipid oxidation products on dairy products.

Malondialdehyde interferes with the formation and detection of primary carbonyls in oxidized proteins

Carbonylation is one of the most remarkable expressions of the oxidative damage to proteins and the DNPH method the most common procedure to assess protein oxidation in biological samples. The present study was elicited by two hypotheses: i) is malondialdehyde, as a reactive dicarbonyl, able to induce the formation of allysine through a Maillard-type reaction? and ii) to which extent does the attachment of MDA to proteins interfere in the assessment of protein carbonyls using the DNPH method? Human serum albumin (HSA), human hemoglobin (HEM) and β-lactoglobulin (LAC) (5 mg/mL) were incubated with MDA (0.25 mM) for 24 h at 37 °C (HSA and HEM) or 80 °C (LAC). Results showed that MDA was unable to induce oxidative deamination of lysine residues and instead, formed stable and fluorescent adducts with proteins. Such adducts were tagged by the DNPH method, accounting for most of the protein hydrazones quantified. This interfering effect was observed in a wide range of MDA concentrations (0.05-1 mM). Being aware of its limitations, protein scientists should accurately interpret results from the DNPH method, and apply, when required, other methodologies such as chromatographic methods to detect specific primary oxidation products such as allysine.

Negative effects of ROS generated during linear sperm motility on gene expression and ATP generation in boar sperm mitochondria

Mitochondrial oxidative phosphorylation (OXPHOS) is essential for ATP production to maintain sperm linear motility during migration from the uterus to the oviduct. However, ROS are generated as by-products of OXPHOS, causing stress and damaging the sperm quality. This study aimed to clarify the ROS targets in sperm mitochondria that decrease linear motility and to investigate whether mitochondria-target antioxidants (PQQ and CoQ10) affect mitochondrial activity and sperm motility. Sperm linear motility pattern, ATP production, and mitochondrial activity were decreased with increasing ROS levels during incubation in the low-glucose medium. However, sperm motility patterns and ROS levels were not significantly changed in the high-glucose medium. Moreover, the gene expression system (mt-DNA, mitochondrial transcription factor-A (TFAM) and RNA polymerase (POLRMT)) in sperm mitochondria was damaged during incubation in the low-glucose medium. Interestingly, PQQ treatment increased the mt-DNA stability and decreased the damage to TFAM and POLRMT, which resulted in high expression of mitochondrial genes. Furthermore, the antioxidants increased mitochondrial activity and maintained sperm linear motility under the low glucose condition. These results revealed that both ATP production and the mitochondrial transcription system are damaged with increasing ROS levels in sperm that show a linear motility pattern. Treatment with antioxidants, such as PQQ and CoQ10, is beneficial tool to maintain sperm linear motility.

Variation in the structure and emulsification of egg yolk high-density lipoprotein by lipid peroxide

To further clarify the effect of the oxidation of egg yolk high-density lipoprotein (EYHDL) on the protein structure and emulsification, 2,2'-azobis (2-methylpropionamidine) dihydrochloride (AAPH) was selected as a representative lipid peroxidation-derived peroxyl radical. The results of Raman spectroscopy indicated that, with the increase in the concentration of AAPH, the EYHDL carbonyl content increased significantly and the free sulfhydryl content declined sharply. Circular dichroism spectroscopy and intrinsic fluorescence indicated that exposure of EYHDL to AAPH led to destruction of the orderly structure and reduction of the structural stability. The particle size distribution and zeta potential indicated that the peroxyl radical caused molecular aggregation. Moderate oxidizing conditions can enhance the emulsification of EYHDL, and high-intensity oxidation decreased emulsification. The research results indicated that EYHDL made a significant change in the oxidation system and led to a change in its structure and emulsification, providing a theoretical basis to clarify the EYHDL oxidation mechanism. PRACTICAL APPLICATIONS: Egg yolk powder is prone to emulsification degradation during storage. The emulsification of egg yolk powder is mainly derived from high-density lipoprotein in egg yolk. Moreover, egg yolk powder contains a large amount of lipids, and, during the processing and storage of egg yolk powder, many lipid peroxyl radicals are inevitably generated. Therefore, it is desired to combine the lipid peroxyl radicals generated during the storage of egg yolk powder with the decrease in emulsifiability. In this paper, we first investigated the effects of peroxyl radicals on the structure and emulsifying properties of high-density lipoproteins and provided a theoretical basis to solve the problem that the emulsifiability of egg yolk powder is significantly reduced during storage.

The Chemistry of Protein Oxidation in Food

Oxidation is one of the deterioration reactions of proteins in food, the importance of which is comparable to others such as Maillard, lipation, or protein-phenol reactions. While research on protein oxidation has led to a precise understanding of the processes and consequences in physiological systems, knowledge about the specific effects of protein oxidation in food or the role of "oxidized" dietary protein for the human body is comparatively scarce. Food protein oxidation can occur during the whole processing axis, from primary production to intestinal digestion. The present review summarizes the current knowledge and mechanisms of food protein oxidation from a chemical, technological, and nutritional-physiological viewpoint and gives a comprehensive classification of the individual reactions. Different analytical approaches are compared, and the relationship between oxidation of food proteins and oxidative stress in vivo is critically evaluated.

Investigation of Dynamic Thiol/Disulfide Homeostasis in Children With Acute Immune Thrombocytopenia

Oxidative stress may play a role in the pathogenesis of immune thrombocytopenia (ITP), but the role of dynamic thiol/disulfide homeostasis has not been studied. The objective of this study was to assess whether there is a change in thiol/disulfide homeostasis in children with acute ITP. A total of 40 children with acute ITP and 50 healthy age-matched and sex-matched controls were included in this study. Serum total thiol and native thiol levels have been measured with a novel automatic spectrophotometric method. The amount of dynamic disulfide bonds and related ratios were calculated from these values. The average total thiol and native thiol levels of the patient group were found to be significantly lower than those levels of controls (P<0.01). However, intravenous immunoglobulin (IVIG) treatment with 1 g/kg/d prevented these reductions. disulfide level was slightly, but not significantly, depressed in ITP patients, but it recovered following IVIG treatment. We detected no marked changes in disulfide/total thiol, disulfide/native thiol, and native thiol/total thiol ratios between groups. These results are the first to demonstrate that thiol/disulfide homeostasis plays a role in ITP pathogenesis, and IVIG treatment can prevent the reduced thiol levels in children.