Nitration of cytoskeletal proteins in the chicken embryo chorioallantoic membrane

Effects of the Dietary Inclusion of Partially Defatted Black Soldier Fly (Hermetia illucens) Meal on the Blood Chemistry and Tissue (Spleen, Liver, Thymus, and Bursa of Fabricius) Histology of Muscovy Ducks (Cairina moschata domestica)

Simple Summary

Insects represent a promising feed ingredient for poultry diets, as an alternative to conventional feedstuffs. Black soldier fly (BSF; Hermetia illucens) larvae are processed to obtain two main products: the protein and fat fractions. The possible utilization of BSF defatted meal in Muscovy duck (Cairina moschata domestica) diets has been poorly investigated. However, its effect on in vivo and post-mortem traits, which are extremely important for animal welfare, has not yet been investigated. Therefore, the present study has evaluated the effect of 0%, 3%, 6%, and 9% dietary BSF meal replacement on the in vivo haematological parameters and on the post-mortem organ traits. Overall, the obtained results are encouraging as increasing dietary BSF meal did not impair the growth performance or the haematological traits. Furthermore, both the liver and renal function were unaffected or even improved. The antioxidant picture appeared improved and the histological traits were not influenced by the dietary inclusion of BSF meal. From a productive and biological point of view, the dietary replacement up to 9% of BSF meal in Muscovy duck diet is feasible and BSF meal could represent a promising feed ingredient.

Abstract

The present study has evaluated the effects of dietary partially-defatted black soldier fly (BSF; Hermetia illucens L.) larva meal on the blood parameters, antioxidant status, and histological features of the organs of broiler ducks. A total of 192 female 3-days of age Muscovy ducklings (Cairina moschata domestica) were divided into four dietary treatments (0%, 3%, 6%, and 9% BSF meal inclusion; 6 pens/treatment, 8 birds/pen). A total of 12 ducks/treatment (2 birds/pen) were slaughtered at 51 days of age and blood samples were collected to evaluate the haematological traits, serum protein, lipid and minerals, liver and renal function serum enzymes, plasma oxidative enzymes, and metabolites. Liver, spleen, thymus, and bursa of Fabricius samples were submitted to histopathological investigations. Between the serum and plasma traits, triglycerides, cholesterol, creatinine, alkaline phosphatase, magnesium, malondialdehyde, and nitrotyrosine showed a linear decrease for increasing amounts of dietary BSF meal (p <0.01); in contrast, the serum iron concentration showed a linear increase (p <0.01). Moreover, the histopathological findings were not significantly affected by the dietary BSF larva meal inclusion. The results showed that the inclusion of up to 9% BSF larva meal represents a promising feed ingredient for Muscovy duck nutrition, and improved blood traits were observed.

Temporal patterns of tyrosine nitration in embryo heart development

Tyrosine nitration is a biomarker for the production of peroxynitrite and other reactive nitrogen species. Nitrotyrosine immunoreactivity is present in many pathological conditions including several cardiac diseases. Because the events observed during heart failure may recapitulate some aspects of development, we tested whether nitrotyrosine is present during normal development of the rat embryo heart and its potential relationship in cardiac remodeling through apoptosis. Nitric oxide production is highly dynamic during development, but whether peroxynitrite and nitrotyrosine are formed during normal embryonic development has received little attention. Rat embryo hearts exhibited strong nitrotyrosine immunoreactivity in endocardial and myocardial cells of the atria and ventricles from E12 to E18. After E18, nitrotyrosine staining faded and disappeared entirely by birth. Tyrosine nitration in the myocardial tissue coincided with elevated protein expression of nitric oxide synthases (eNOS and iNOS). The immunoreactivity for these NOS isoforms remained elevated even after nitrotyrosine had disappeared. Tyrosine nitration did not correlate with cell death or proliferation of cardiac cells. Analysis of tryptic peptides by MALDI-TOF showed that nitration occurs in actin, myosin, and the mitochondrial ATP synthase α chain. These results suggest that reactive nitrogen species are not restricted to pathological conditions but may play a role during normal embryonic development.

Tubulin tyrosine nitration regulates microtubule organization in plant cells

During last years, selective tyrosine nitration of plant proteins gains importance as well-recognized pathway of direct nitric oxide (NO) signal transduction. Plant microtubules are one of the intracellular signaling targets for NO, however, the molecular mechanisms of NO signal transduction with the involvement of cytoskeletal proteins remain to be elucidated. Since biochemical evidence of plant α-tubulin tyrosine nitration has been obtained recently, potential role of this posttranslational modification in regulation of microtubules organization in plant cell is estimated in current paper. It was shown that 3-nitrotyrosine (3-NO2-Tyr) induced partially reversible Arabidopsis primary root growth inhibition, alterations of root hairs morphology and organization of microtubules in root cells. It was also revealed that 3-NO2-Tyr intensively decorates such highly dynamic microtubular arrays as preprophase bands, mitotic spindles and phragmoplasts of Nicotiana tabacum Bright Yellow-2 (BY-2) cells under physiological conditions. Moreover, 3D models of the mitotic kinesin-8 complexes with the tail of detyrosinated, tyrosinated and tyrosine nitrated α-tubulin (on C-terminal Tyr 450 residue) from Arabidopsis were reconstructed in silico to investigate the potential influence of tubulin nitrotyrosination on the molecular dynamics of α-tubulin and kinesin-8 interaction. Generally, presented data suggest that plant α-tubulin tyrosine nitration can be considered as its common posttranslational modification, the direct mechanism of NO signal transduction with the participation of microtubules under physiological conditions and one of the hallmarks of the increased microtubule dynamics.

Protein nitration as footprint of oxidative stress-related nitric oxide signaling pathways in developing Ciona intestinalis

Developmental processes in the ascidian Ciona intestinalis depend on a complex interplay of events including, during metamorphosis, a caspase-dependent apoptosis which is regulated by the nitric oxide (NO)-cGMP signaling pathway. Herein we disclose an alternate NO-mediated signaling pathway during Ciona development which appears to be critically dependent on local redox control. Evidence in support of this conclusion includes: (a) inhibitors of NO synthase (NOS) and scavengers of NO-derived nitrating agents markedly decrease the rate of Ciona metamorphosis; (b) an NO donor or peroxynitrite caused an opposite effect; (c) increased protein nitration is observed at larva stage. Integrated proteomic and immunochemical methodologies identified nitrated tyrosine residues in ERK and snail. Overall, these results point to protein nitration as a hitherto overlooked NO-dependent regulatory mechanism in Ciona which is specifically triggered by elevated ROS production during developmental processes.

Nitric oxide signalling via cytoskeleton in plants

Nitric oxide (NO) in plant cell mediates processes of growth and development starting from seed germination to pollination, as well as biotic and abiotic stress tolerance. However, proper understanding of the molecular mechanisms of NO signalling in plants has just begun to emerge. Accumulated evidence suggests that in eukaryotic cells NO regulates functions of proteins by their post-translational modifications, namely tyrosine nitration and S-nitrosylation. Among the candidates for NO-downstream effectors are cytoskeletal proteins because of their involvement in many processes regulated by NO. This review discusses new insights in plant NO signalling focused mainly on the involvement of cytoskeleton components into NO-cascades. Herein, examples of NO-related post-translational modifications of cytoskeletal proteins, and also indirect NO impact, are discussed. Special attention is paid to plant α-tubulin tyrosine nitration as an emerging topic in plant NO research.

Tyrosine nitration within the proline-rich region of Tau in Alzheimer's disease

A substantial body of evidence suggests that nitrative injury contributes to neurodegeneration in Alzheimer's disease (AD) and other neurodegenerative disorders. Previously, we showed in vitro that within the tau protein the N-terminal tyrosine residues (Y18 and Y29) are more susceptible to nitrative modifications than other tyrosine sites (Y197 and Y394). Using site-specific antibodies to nitrated tau at Y18 and Y29, we identified tau nitrated in both glial (Y18) and neuronal (Y29) tau pathologies. In this study, we report the characterization of two novel monoclonal antibodies, Tau-nY197 and Tau-nY394, recognizing tau nitrated at Y197 and Y394, respectively. By Western blot analysis, Tau-nY197 labeled soluble tau and insoluble paired helical filament proteins (PHF-tau) nitrated at Y197 from control and AD brain samples. Tau-nY394 failed to label soluble tau isolated from control or severe AD samples, but labeled insoluble PHF-tau to a limited extent. Immunohistochemical analysis using Tau-nY197 revealed the hallmark tau pathology associated with AD; Tau-nY394 did not detect any pathological lesions characteristic of the disorder. These data suggest that a subset of the hallmark pathological inclusions of AD contain tau nitrated at Y197. However, nitration at Y197 was also identified in soluble tau from all control samples, including those at Braak stage 0, suggesting that nitration at this site in the proline-rich region of tau may have normal biological functions in the human brain.

Peroxynitrite-induced nitrative and oxidative modifications alter tau filament formation

Tau undergoes numerous posttranslational modifications during the progression of Alzheimer's disease (AD). Some of these changes accelerate tau aggregation, while others are inhibitory. AD-associated inflammation is thought to create oxygen and nitrogen radicals such as peroxynitrite (PN). In vitro, PN can nitrate many proteins, including tau. We have previously demonstrated that tau's ability to form filaments is profoundly affected by treatment with PN and have attributed this inhibition to tyrosine nitration. However, PN is highly reactive and unstable leading to oxidative amino acid modifications through its free radical byproducts. To test whether PN can modify other amino acids in tau via oxidative modifications, a mutant form of the tau protein lacking all tyrosines (5XY → F) was constructed. 5XY → F tau readily forms filaments; however, like wild-type tau the extent of polymerization was greatly reduced following PN treatment. Since 5XY → F tau cannot be nitrated, it was clear that nonnitrative modifications are generated by PN treatment and that these modifications change tau filament formation. Mass spectrometry was used to identify these oxidative alterations in wild-type tau and 5XY → F tau. PN-treated wild-type tau and 5XY → F tau consistently displayed lysine formylation throughout tau in a nonsequence-specific distribution. Lysine formylation likely results from reactive free radical exposure caused by PN treatment. Therefore, our results indicate that PN treatment of proteins in vitro cannot be used to study protein nitration as it likely induces numerous other random oxidative modifications clouding the interpretations of any functional consequences of tyrosine nitration.

Tau is Endogenously Nitrated in Mouse Brain: Identification of a Tyrosine Residue Modified In vivo by NO

Nitration of tau protein is normally linked to neurodegeneration but, until now, no comprehensive information is available regarding tau nitration in healthy subjects. It has been previously reported that in differentiated PC12 cells, tau co-immunoprecipitated with alpha-tubulin is nitrated at tyrosine residues and that this post-translation modification doesn't impair the association of tau with the cytoskeleton. The present paper is focused on the identification of tyrosine residues endogenously modified in tau from PC12 cells and reports for the first time that tau is also nitrated in vivo in normal mouse brain and that one tyrosine is endogenously modified.

Peroxynitrite diminishes myogenic tone in cerebral arteries: role of nitrotyrosine and F-actin

This study investigated the effect of peroxynitrite (OONO(-))-induced nitrosylation of filamentous (F)-actin on myogenic tone in isolated and pressurized posterior cerebral arteries (PCAs). Immunohistochemical staining was used to determine 3-nitrotyrosine (NT) and F-actin content in vascular smooth muscle after exposure to 10(-7) M or 10(-4) M OONO(-) for 5 or 60 min in isolated third-order PCAs (n = 37) from male Wistar rats pressurized to 75 mmHg in an arteriograph chamber, quantified with confocal microscopy. Additionally, the role of K(+) channels in OONO(-)-induced dilation was investigated with 3 microM glibenclamide or 10 mM tetraethylammonium chloride before OONO(-) exposure. OONO(-) (10(-4) M) induced a 40% dilation of tone (P < 0.05) while diminishing F-actin content by half (P < 0.05) and causing a 60-fold increase in NT (P < 0.05) in the vascular smooth muscle of PCAs. Additionally, F-actin was inversely correlated with both diameter and NT content (P < 0.05) and was significantly colocalized in the vascular smooth muscle with NT (overlap coefficient = 0.8). The dilation to ONOO(-) was independent of K(+) channel activity and thiol oxidation as glibenclamide, tetraethylammonium chloride, and dithiothreitol had no effect on OONO(-)-induced dilation or F-actin or NT content in PCAs. Because NT was colocalized with F-actin, we hypothesize that OONO(-) induces nitrosylation of F-actin in vascular smooth muscle leading to depolymerization and the subsequent loss of myogenic tone, which may promote vascular damage during oxidative stress such as in ischemia and reperfusion injury.

Tubulin nitration in human gliomas

Immunohistochemical and biochemical investigations showed that significant protein nitration occurs in human gliomas, especially in grade IV glioblastomas at the level of astrocytes and oligodendrocytes and neurones. Enhanced alpha-tubulin immunoreactivity was co-present in the same elements in the glioblastomas. Proteomic methodologies were employed to identify a nitrated protein band at 55 kDa as alpha-tubulin. Peptide mass fingerprinting procedures demonstrated that tubulin is nitrated at Tyr224 in grade IV tumour samples but is unmodified in grade I samples and in non-cancerous brain tissue. These results provide the first characterisation of endogenously nitrated tubulin from human tumour samples.

Methods for proteomics in neuroscience

Proteomics reveals complex protein expression, function, interactions and localization in different phenotypes of neuron. As proteomics, regarded as a highly complex screening technology, moves from a theoretical approach to practical reality, neuroscientists have to determine the most-appropriate applications for this technology. Even though proteomics compliments genomics, it is in sheer contrast to the basically constant genome due to its dynamic nature. Neuroscientists have to surmount difficulties particular to the research in neuroscience; such as limited sample amounts, heterogeneous cellular compositions in samples and the fact that many proteins of interest are hydrophobic proteins. The necessity of exclusive technology, sophisticated software and skilled manpower tops the challenge. This review examines subcellular organelle isolation, protein fractionation and separation using two-dimensional gel electrophoresis (2-DGE) as well as multi-dimensional liquid chromatography (LC) followed by mass spectrometry (MS). The methods for quantifying relative gene product expression between samples (e.g., two-dimensional difference in gel electrophoresis (2D-DIGE), isotope-coded affinity tag (ICAT) and iTRAQ) are elaborated. An overview of the techniques used currently to assign post-translational modification status on a proteomics scale is also evaluated. The feasible coverage of the proteome, ability to detect unique cell components such as post-synaptic densities and membrane proteins, resource requirements and quantitative as well as qualitative reliability of different approaches is also discussed. While there are many challenges in neuroproteomics, this field promises many returns in the future.

Nitrative stress through formation of 8-nitroguanosine: insights into microbial pathogenesis

Reactive oxygen and nitrogen species, respectively, mediate oxidative and nitrative stresses by means of oxidation and nitration of various biomolecules including proteins, lipids, and nucleic acids. We have observed nitric oxide (NO)-dependent formation of 8-nitroguanosine and 3-nitrotyrosine during microbial infection, and we determined that both 8-nitroguanosine and 3-nitrotyrosine are useful biomarkers of nitrative stress. Of importance, however, is the great difference in biological characteristics of these two nitrated compounds. 8-Nitroguanosine has unique biochemical and pharmacological properties such as redox activity and mutagenic potential, which 3-nitrotyrosine does not. In this review, we discuss the mechanism of nitrative stress occurring during microbial infections, with special emphasis on biological functions of 8-nitroguanosine formed via NO during the host response to pathogens. These findings provide insights into NO-mediated pathogenesis not only of viral infections but also of many other diseases.

Characterization of nitroproteome in neuron-like PC12 cells differentiated with nerve growth factor: Identification of two nitration sites in α-tubulin

Nitric oxide (NO) is a precursor of reactive nitrating species, peroxynitrite and nitrogen dioxide, which modify proteins to generate oxidized species such as 3-nitrotyrosine that has been used as a hallmark of peroxynitrite-mediated oxidative stress on proteins. In the last few years however, a growing body of evidence indicates that NO also regulates a myriad of physiologic responses by modifying tyrosine residues. Looking for the molecular event triggered by NO in nerve growth factor (NGF)-induced neuronal differentiation, we recently reported that in differentiating PC12 cells, the cytoskeleton becomes the main cellular fraction containing nitrotyrosinated proteins, and alpha-tubulin is the major target. In the present work, we focus on the investigation of the sites of tyrosine nitration in alpha-tubulin purified by two-dimensional gel electrophoresis following anti-alpha-tubulin immunoprecipitation of protein extract from NGF-treated PC12 cells. Using Western blotting and matrix-assisted laser desorption/ionization-time of flight analysis, we show for the first time, both in vivo and in vitro, that nitration can occur on alpha-tubulin at sites other than the C-terminus and we positively identify Tyr 161 and Tyr 357 as two specific amino acids endogenously nitrated.

Protein tyrosine nitration in rat brain is associated with raft proteins, flotillin-1 and α-tubulin: effect of biological aging

Protein 3-nitrotyrosine (3-NY) immunoreactivity of rat brain homogenate was localized to a ca. 50 kDa protein band by western blot (WB) analysis. The nitrated proteins were localized to the raft fraction obtained by centrifugation of the homogenate in a sucrose density gradient, which contained specific raft markers such as flotillin-1 and caveolin-1. Purification of the nitrated raft proteins either by a combination of reversed-phase high-performance liquid chromatography (HPLC) and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) or by immunoprecipitation (IP) with protein- and modification-specific antibodies coupled to WB and HPLC-electrospray ionization-tandem mass spectrometry (ESI--MS/MS) analysis allowed us to identify two proteins modified by 3-NY: flotillin-1 and alpha-tubulin. Both alpha- and beta-tubulin were detected in the rat brain raft fraction as abundant proteins, which co-immunoprecipitate with flotillin-1 and caveolin-1. Importantly, some protein-protein interactions in rafts were disrupted in 3-NY-containing proteins, e.g. caveolin-1 was dissociated from a complex with flotillin-1 and alpha-tubulin. The analysis of age dependencies did not show any significant change in protein nitration and expression of flotillin-1 and alpha-tubulin, but a decrease in the brain caveolin-1 level for old (34 months) versus young (6 months) rats. The putative mechanism of nitric oxide synthase (NOS) activity regulation by the level of caveolin expression and raft protein-protein interactions is discussed.

Antioxidants inhibit angiogenesis in vivo through down-regulation of nitric oxide synthase expression and activity

Although reactive oxygen species (ROS) participate in many cellular mechanisms, only few data exist concerning their involvement in physiological angiogenesis. The aim of the present work was to elucidate possible mechanisms through which ROS affect angiogenesis in vivo, using the model of the chicken embryo chorioallantoic membrane (CAM). Superoxide dismutase (SOD) and its membrane permeable mimetic tempol, dose dependently decreased angiogenesis and down-regulated inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production. The NADPH oxidase inhibitors, 4-(2-aminoethyl)-benzenesulfonyl fluoride (AEBSF) and apocynin, but not allopurinol, also had a dose dependent inhibitory effect on angiogenesis and NO production in vivo. Catalase and the intracellular hydrogen peroxide (H2O2) scavenger sodium pyruvate decreased, while H2O2 increased in a dose-dependent manner the number of CAM blood vessels, as well as the expression and activity of iNOS. Dexamethasone, which down-regulated NO production by iNOS and L-NAME, but not D-NAME, dose dependently decreased angiogenesis in vivo. These data suggest that antioxidants affect physiological angiogenesis in vivo, through regulation of NOS expression and activity.

Amifostine has antiangiogenic properties in vitro by changing the redox status of human endothelial cells

Amifostine is a broad-spectrum cytoprotective agent, selective for normal tissues. It is a pro-drug metabolised to the free thiol WR-1065 that may act as a scavenger of free radicals, generated in tissues exposed to chemotherapeutic agents or radiation. WR-1065 can be further oxidized to its symmetric disulfide WR-33278 or degraded to hydrogen peroxide (H2O2). Both WR-1065 and WR-33278 resemble endogenous polyamines. Although amifostine is used in some cases in the clinic, there are only few studies concerning its actions at the cellular level. We have previously shown that amifostine inhibits angiogenesis in vivo, affecting the expression of several angiogenic genes. In the present work, we studied the effect of amifostine on human umbilical vein endothelial cell (HUVEC) functions in vitro, in order to further clarify its mechanism(s) of action. Amifostine increased HUVEC proliferation, an effect that was reversed by the intracellular H2O2 scavenger sodium pyruvate, agents that increase intracellular cAMP levels and L-valine. On the other hand, amifostine decreased HUVEC migration, an effect that was reversed by L-valine or L-arginine but not sodium pyrouvate. The decrease in migration was in line with decreased tube formation on matrigel and decreased amounts of metalloproteinase-2 released into the culture medium of HUVEC. Finally, amifostine reduced tyrosine nitration of the cytoskeletal proteins actin and alpha-tubulin in a time dependent manner. This last action could be due to the reduced production of nitric oxide (NO) or to other not yet identified mechanisms. Collectively, our results suggest that amifostine acts on endothelial cells through pathways that affect the redox status of the cells, either by producing H2O2 or by modulating NO production.

The nitration of tau protein in neurone-like PC12 cells

Tyrosine nitration of proteins is emerging as a post-translational modification playing a role in physiological conditions. Looking for the molecular events triggered by nitric oxide in nerve growth factor-induced neuronal differentiation, we now find that nitration occurs on the microtubule-associated protein tau. In differentiated PC12 cells, we have identified as tau a nitrated protein that co-immunoprecipitates with alpha-tubulin and indicated that the modified protein is associated with the cytoskeleton but it is confined to a restricted cell region. This paper supplies the first evidence that nitration of tau occurs in a physiological process and suggests that it could play a role in neuronal differentiation.

Amifostine inhibits angiogenesis in vivo

Amifostine (WR-2721) is an inorganic thiophosphate-cytoprotective agent developed to selectively protect normal tissues against the toxicity of chemotherapy and radiation. We have previously shown that amifostine protects both chicken embryo chorioallantoic membrane (CAM) vessels and cells from the effects of X-rays. In the present work, we studied the effect of amifostine on angiogenesis in vivo, using the CAM model. Amifostine decreased the number of CAM vessels in a dose-dependent manner, without being toxic for the tissue. It also decreased the mRNA levels of both vascular endothelial growth factor (VEGF) isoforms VEGF(165) and VEGF(190), 6 and up to 48 h after its application onto the CAM. Similarly, it decreased the mRNA levels of inducible nitric-oxide synthase, 24 and 48 h after drug application. Furthermore, amifostine decreased the deposited amounts of laminin and collagen I 24 h after its application, without affecting the expression of the corresponding genes. The protein amounts and activity of matrix metalloproteinase-2 were not affected, whereas the expression of the corresponding gene was decreased up to 48 h after drug application. Finally, the activity of plasmin was increased 6 h after amifostine application and remained increased at later time points. These findings suggest that amifostine alters the expression of several molecules implicated in the angiogenesis process and affects the composition of the extracellular matrix in a way that leads to inhibition of angiogenesis. Such an antiangiogenic action of amifostine, together with its radioprotective effects, further supports its use in combination with radiotherapy for increased therapeutic efficacy.

Different inhibitors of plasmin differentially affect angiostatin production and angiogenesis

Plasmin is a broad-spectrum serine proteinase, which is presumed to cleave many extracellular proteins and affect angiogenesis. In the present work, we studied the effect of two different inhibitors of plasmin (epsilon-aminocaproic and alpha(2)-antiplasmin) on angiogenesis in vivo using the chicken embryo chorioallantoic membrane assay, and in vitro using human umbilical vein endothelial cells. Epsilon-aminocaproic acid inhibited, while alpha(2)-antiplasmin induced, angiogenesis, as well as human umbilical vein endothelial cell proliferation, migration and tube formation on matrigel in a dose-dependent manner. Since plasmin has been implicated in the production of angiostatin, we studied the effect of the two plasmin inhibitors on angiostatin protein amounts in the chicken embryo chorioallantoic membrane. In this tissue, the 38- and 45-kDa isoforms of angiostatin are differentially affected by the two inhibitors: epsilon-aminocaproic acid increased, while alpha(2)-antiplasmin decreased the amounts of both isoforms. These data suggest that plasmin may have an antiangiogenic role in vivo through generation of angiostatin. Moreover, plasmin inhibitors differentially affect in vivo angiogenesis, depending on the mechanism by which they inhibit plasmin activity.