Posttranslational nitrotyrosination of α-tubulin induces cell cycle arrest and inhibits proliferation of vascular smooth muscle cells

Investigation into the role of Stmn2 in vascular smooth muscle phenotype transformation during vascular injury via RNA sequencing and experimental validation

This study examined the effects of Stmn2 on phenotype transformation of vascular smooth muscle in vascular injury via RNA sequencing and experimental validation. Total RNA was extracted for RNA sequencing after 1, 3 and 5 days of injury to screen the differentially expressed genes (DEGs). Western blot was used to detect the protein expression of Stmn2 and its associated targets. The morphological changes of carotid arteries in rats were examined by hematoxylin and eosin (H&E) staining. The expression of vascular smooth muscle cell (VSMC) phenotype markers smooth muscle alpha-actin (α-SMA), vimentin and OPN were detected by immunohistochemistry. DEGs were related to the extracellular matrix and other cell components outside the plasma membrane. They were associated with protein binding, cytoskeleton protein binding, signal receptor binding and other molecular functions, actin cytoskeleton regulation and other Kyoto Encyclopedia of Genes and Genomes pathways. Stmn2 was identified as the hub gene of actin cytoskeleton pathway and vascular disease, and its expression followed the trend of decreasing initially and increasing afterwards during the progress of vascular injury. Western blot assay showed that the expression of Stmn2 and Tubulin decreased immediately after vascular injury; Stmn2 overexpression significantly up-regulated the expression of osteopontin and α-SMA and vimentin in VSMCs. The results of morphology analysis and immunostaining also showed that Stmn2 overexpression promoted the intima thickening and enhanced the proliferating cell nuclear antigen expression in the injured vascular tissues. In conclusion, our results implied that Stmn2 may play a potential role in vascular injury, which may be associated with VSMC phenotype transformation. Further studies are warranted to determine detailed molecular mechanisms of Stmn2 in vascular injury.

Simultaneous LC-MS/MS-Based Quantification of Free 3-Nitro-l-tyrosine, 3-Chloro-l-tyrosine, and 3-Bromo-l-tyrosine in Plasma of Colorectal Cancer Patients during Early Postoperative Period

Quantification with satisfactory specificity and sensitivity of free 3-Nitro-l-tyrosine (3-NT), 3-Chloro-l-tyrosine (3-CT), and 3-Bromo-l-tyrosine (3-BT) in biological samples as potential inflammation, oxidative stress, and cancer biomarkers is analytically challenging. We aimed at developing a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method for their simultaneous analysis without an extract purification step by solid-phase extraction. Validation of the developed method yielded the following limits of detection (LOD) and quantification (LOQ) for 3-NT, 3-BT, and 3-CT: 0.030, 0.026, 0.030 ng/mL (LODs) and 0.100, 0.096, 0.098 ng/mL (LOQs). Coefficients of variation for all metabolites and tested concentrations were <10% and accuracy was within 95-105%. Method applicability was tested on colorectal cancer patients during the perioperative period. All metabolites were significantly higher in cancer patients than healthy controls. The 3-NT was significantly lower in advanced cancer and 3-BT showed a similar tendency. Dynamics of 3-BT in the early postoperative period were affected by type of surgery and presence of surgical site infections. In conclusion, a sensitive and specific LC-MS/MS method for simultaneous quantification of free 3-NT, 3-BT, and 3-CT in human plasma has been developed.

Identification of putative biomarkers for Infantile Hemangiomas and Propranolol treatment via data integration

Infantile hemangiomas (IHs) are the most common benign tumors in early childhood. They show a distinctive mechanism of tumor growth in which a rapid proliferative phase is followed by a regression phase (involution). Propranolol is an approved treatment for IHs, but its mechanism of action remains unclear. We integrated and harmonized microRNA and mRNA transcriptome data from newly generated microarray data on IHs with publicly available data on toxicological transcriptomics from propranolol exposure, and with microRNA data from IHs and propranolol exposure. We identified subsets of putative biomarkers for proliferation and involution as well as a small set of putative biomarkers for propranolol's mechanism of action for IHs, namely EPAS1, LASP1, SLC25A23, MYO1B, and ALDH1A1. Based on our integrative data approach and confirmatory experiments, we concluded that hypoxia in IHs is regulated by EPAS1 (HIF-2α) instead of HIF-1α, and also that propranolol-induced apoptosis in endothelial cells may occur via mitochondrial stress.

Highly variable contractile performance correlates with myocyte content in trabeculae from failing human hearts

Heart failure (HF) is defined by compromised contractile function and is associated with changes in excitation-contraction (EC) coupling and cardiomyocyte organisation. Tissue level changes often include fibrosis, while changes within cardiomyocytes often affect structures critical to EC coupling, including the ryanodine receptor (RyR), the associated protein junctophilin-2 (JPH2) and the transverse tubular system architecture. Using a novel approach, we aimed to directly correlate the influence of structural alterations with force development in ventricular trabeculae from failing human hearts. Trabeculae were excised from explanted human hearts in end-stage failure and immediately subjected to force measurements. Following functional experiments, each trabecula was fixed, sectioned and immuno-stained for structural investigations. Peak stress was highly variable between trabeculae from both within and between failing hearts and was strongly correlated with the cross-sectional area occupied by myocytes (MCSA), rather than total trabecula cross-sectional area. At the cellular level, myocytes exhibited extensive microtubule densification which was linked via JPH2 to time-to-peak stress. Trabeculae fractional MCSA variability was much higher than that in adjacent free wall samples. Together, these findings identify several structural parameters implicated in functional impairment in human HF and highlight the structural variability of ventricular trabeculae which should be considered when interpreting functional data.

iNOS-derived peroxynitrite mediates high glucose-induced inflammatory gene expression in vascular smooth muscle cells through promoting KLF5 expression and nitration

Inducible NO synthase (iNOS) expression and peroxynitrite formation are significantly increased in diabetic vascular tissues. Transcription factor KLF5 activates iNOS gene transcription and is involved in vascular inflammatory injury and remodeling. However, mutual regulation between KLF5, iNOS and peroxynitrite in diabetic vascular inflammation, as well as the underlying mechanisms, remain largely unknown. In this study, we found a marked increase in KLF5 and iNOS expression in vascular smooth muscle cells (VSMC) of diabetic patients. High glucose-induced expression of KLF5 and iNOS was also observed in cultured mouse VSMCs. Further investigation showed that high glucose induced KLF5 nitration by iNOS-mediated peroxynitrite generation, and nitrated KLF5 increased its interaction with NF-κB p50 and thus cooperatively activated the expression of inflammatory cytokines TNF-α and IL-1β. Furthermore, we showed that the VSMC-specific knockout of KLF5 dramatically reduced inflammatory cytokine expression in the vascular tissues of diabetic mice. Moreover, 17β-estradiol (E2) inhibited high glucose-mediated effects in VSMCs, and in the response to E2, estrogen receptor (ER) α competed with KLF5 for binding to NF-κB p50, which in turn leads to the suppression of inflammatory gene expression in VSMCs. Together, the present findings were the first to show that KLF5 expression and nitration by iNOS-mediated peroxynitrite are necessary for the induction of TNF-α and IL-1β expression in VSMCs of diabetic vascular tissues.

Nitric Oxide Modulates Postnatal Bone Marrow-Derived Mesenchymal Stem Cell Migration

Nitric oxide (NO) is a small free-radical gas molecule, which is highly diffusible and can activate a wide range of downstream effectors, with rapid and widespread cellular effects. NO is a versatile signaling mediator with a plethora of cellular functions. For example, NO has been shown to regulate actin, the microfilament, dependent cellular functions, and also acts as a putative stem cell differentiation-inducing agent. In this study, using a wound-healing model of cellular migration, we have explored the effect of exogenous NO on the kinetics of movement and morphological changes in postnatal bone marrow-derived mesenchymal stem cells (MSCs). Cellular migration kinetics and morphological changes of the migrating MSCs were measured in the presence of an NO donor (S-Nitroso-N-Acetyl-D,L-Penicillamine, SNAP), especially, to track the dynamics of single-cell responses. Two experimental conditions were assessed, in which SNAP (200 μM) was applied to the MSCs. In the first experimental group (SN-1), SNAP was applied immediately following wound formation, and migration kinetics were determined for 24 h. In the second experimental group (SN-2), MSCs were pretreated for 7 days with SNAP prior to wound formation and the determination of migration kinetics. The generated displacement curves were further analyzed by non-linear regression analysis. The migration displacement of the controls and NO treated MSCs (SN-1 and SN-2) was best described by a two parameter exponential functions expressing difference constant coefficients. Additionally, changes in the fractal dimension (D) of migrating MSCs were correlated with their displacement kinetics for all the three groups. Overall, these data suggest that NO may evidently function as a stop migration signal by disordering the cytoskeletal elements required for cell movement and proliferation of MSCs.

Long-term effect of PROLI/NO on cellular proliferation and phenotype after arterial injury

Vascular interventions are associated with high failure rates from restenosis secondary to negative remodeling and neointimal hyperplasia. Periadventitial delivery of nitric oxide (NO) inhibits neointimal hyperplasia, preserving lumen patency. With the development of new localized delivery vehicles, NO-based therapies remain a promising therapeutic avenue for the prevention of restenosis. While the time course of events during neointimal development has been well established, a full characterization of the impact of NO donors on the cells that comprise the arterial wall has not been performed. Thus, the aim of our study was to perform a detailed assessment of proliferation, cellularity, inflammation, and phenotypic cellular modulation in injured arteries treated with the short-lived NO donor, PROLI/NO. PROLI/NO provided durable inhibition of neointimal hyperplasia for 6 months after arterial injury. PROLI/NO inhibited proliferation and cellularity in the media and intima at all of the time points studied. However, PROLI/NO caused an increase in adventitial proliferation at 2 weeks, resulting in increased cellularity at 2 and 8 weeks compared to injury alone. PROLI/NO promoted local protein S-nitrosation and increased local tyrosine nitration, without measurable systemic effects. PROLI/NO predominantly inhibited contractile smooth muscle cells in the intima and media, and had little to no effect on vascular smooth muscle cells or myofibroblasts in the adventitia. Finally, PROLI/NO caused a delayed and decreased leukocyte infiltration response after injury. Our results show that a short-lived NO donor exerts durable effects on proliferation, phenotype modulation, and inflammation that result in long-term inhibition of neointimal hyperplasia.

Nitroproteins in Human Astrocytomas Discovered by Gel Electrophoresis and Tandem Mass Spectrometry

Protein tyrosine nitration is involved in the pathogenesis of highly fatal astrocytomas, a type of brain cancer. To understand the molecular mechanisms of astrocytomas and to discover new biomarkers/therapeutic targets, we sought to identify nitroproteins in human astrocytoma tissue. Anti-nitrotyrosine immunoreaction-positive proteins from a high-grade astrocytoma tissue were detected with two-dimensional gel electrophoresis (2DGE)-based nitrotyrosine immunoblots, and identified with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Fifty-seven nitrotyrosine immunopositive protein spots were detected. A total of 870 proteins (nitrated and non-nitrated) in nitrotyrosine-immunopositive 2D gel spots were identified, and 18 nitroproteins and their 20 nitrotyrosine sites were identified with MS/MS analysis. These nitroproteins participate in multiple processes, including drug-resistance, signal transduction, cytoskeleton, transcription and translation, cell proliferation and apoptosis, immune response, phenotypic dedifferentiation, cell migration, and metastasis. Among those nitroproteins that might play a role in astrocytomas was nitro-sorcin, which is involved in drug resistance and metastasis and might play a role in the spread and treatment of an astrocytoma. Semiquantitative immune-based measurements of different sorcin expressions were found among different grades of astrocytomas relative to controls, and a semiquantitative increased nitration level in high-grade astrocytoma relative to control. Nitro-β-tubulin functions in cytoskeleton and cell migration. Semiquantitative immunoreactivity of β-tubulin showed increased expression among different grades of astrocytomas relative to controls and semiquantitatively increased nitration level in high-grade astrocytoma relative to control. Each nitroprotein was rationalized and related to the corresponding functional system to provide new insights into tyrosine nitration and its potential role in the pathogenesis of astrocytoma formation. Graphical Abstract ᅟ.

Parthenolide and costunolide reduce microtentacles and tumor cell attachment by selectively targeting detyrosinated tubulin independent from NF-κB inhibition

Introduction

Detyrosinated tubulin, a post-translational modification of α-tubulin and a hallmark of stable microtubules, has gained recent attention given its association with tumor progression, invasiveness, and chemoresistance. We also recently reported that epithelial-to-mesenchymal transition (EMT) promotes tubulin detyrosination through tubulin tyrosine ligase (TTL) suppression. Furthermore, detyrosinated tubulin-enriched membrane protrusions, termed microtentacles (McTN), facilitate tumor cell reattachment to endothelial layers. Given the induction of EMT associated with inflammation and cancer progression, we tested anti-inflammatory nuclear factor-kappaB (NF-κB) inhibitors on a panel of human breast carcinoma cells to examine their effects on detyrosinated tubulin to identify more specific tubulin-directed anti-cancer treatments.

Methods

Using metastatic human breast carcinoma cells MDA-MB-157, MDA-MB-436, and Bt-549, we measured the impact of NF-κB inhibitors parthenolide, costunolide, and resveratrol on detyrosinated tubulin using protein expression analysis and immunofluorescence. A luciferase reporter assay and a viability screen were performed to determine if the effects were associated with their NF-κB inhibitory properties or were a result of apoptosis. Real-time monitoring of cell-substratum attachment was measured utilizing electrical impedance across microelectronic sensor arrays. We compared the selectivity of the NF-κB inhibitors to specifically target detyrosinated tubulin with traditional tubulin-targeted therapeutics, paclitaxel and colchicine, throughout the study.

Results

Sesquiterpene lactones, parthenolide and costunolide, selectively decrease detyrosinated tubulin independent of their inhibition of NF-κB. Live-cell scoring of suspended cells treated with parthenolide and costunolide show reduction in the frequency of microtentacles and inhibition of reattachment. Structural analysis shows that parthenolide and costunolide can decrease detyrosinated microtubules without significantly disrupting the overall microtubule network or cell viability. Paclitaxel and colchicine display indiscriminate disruption of the microtubule network.

Conclusions

Our data demonstrate that selective targeting of detyrosinated tubulin with parthenolide and costunolide can reduce McTN frequency and inhibit tumor cell reattachment. These actions are independent of their effects on NF-κB inhibition presenting a novel anti-cancer property and therapeutic opportunity to selectively target a stable subset of microtubules in circulating tumor cells to reduce metastatic potential with less toxicity in breast cancer patients.

Anti-migratory effect of vinflunine in endothelial and glioblastoma cells is associated with changes in EB1 C-terminal detyrosinated/tyrosinated status

We previously showed that vinflunine, a microtubule-targeting drug of the Vinca-alkaloid family exerted its anti-angiogenic/anti-migratory activities through an increase in microtubule dynamics and an inhibition of microtubule targeting to adhesion sites. Such effect was associated with a reduction of EB1 comet length at microtubule (+) ends. In this work we first showed that the pro-angiogenic vascular endothelial growth factor VEGF suppressed microtubule dynamics in living Human Umbilical Vein Endothelial Cells (HUVECs), increased EB1 comet length by 40%, and induced EB1 to bind all along the microtubules, without modifying its expression level. Such microtubule (+) end stabilization occurred close to the plasma membrane in the vicinity of focal adhesion as shown by TIRF microscopy experiments. Vinflunine completely abolished the effect of VEGF on EB1 comets. Interestingly, we found a correlation between the reduction of EB1 comet length by vinflunine and the inhibition of cell migration. By using 2D gel electrophoresis we demonstrated for the first time that EB1 underwent several post-translational modifications in endothelial and tumor cells. Particularly, the C-terminal EEY sequence was poorly detectable in control and VEGF-treated HUVECs suggesting the existence of a non-tyrosinated form of EB1. By using specific antibodies that specifically recognized and discriminated the native tyrosinated form of EB1 and a putative C-terminal detyrosinated form, we showed that a detyrosinated form of EB1 exists in HUVECs and tumor cells. Interestingly, vinflunine decreased the level of the detyrosinated form and increased the native tyrosinated form of EB1. Using 3-L-Nitrotyrosine incorporation experiments, we concluded that the EB1 C-terminal modifications result from a detyrosination/retyrosination cycle as described for tubulin.

Altogether, our results show that vinflunine inhibits endothelial cell migration through an alteration of EB1 comet length and EB1 detyrosination/retyrosination cycle.

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.

Differentiating vitreous proteomes in proliferative diabetic retinopathy using high-performance liquid chromatography coupled to tandem mass spectrometry

Proliferative diabetic retinopathy (PDR) is a serious microangiopathic complication of diabetes mellitus and a major cause of blindness in working-age adults. Diabetes-induced alterations in the vitreous protein composition in diabetic patients with PDR may be responsible for the presence of PDR. Therefore, we performed a comprehensive proteomic analysis and compared the protein profiles of vitreous humor from type 2 diabetic patients with PDR (n = 8) and that from normal human eyes donated for corneal transplant (n = 8). Using reversed phase high-performance liquid chromatography (RP-HPLC) coupled to electrospray Ionization tandem mass spectrometry (ESI-MS/MS), we identified 96 significant differentially expressed proteins (abundance ratio > 1.5, p < 0.05), including 37 and 59 proteins up- and downregulated in PDR vitreous compared with the control, respectively. Biological pathway analysis revealed 44 proteins involved in 56 biological pathways; among them, the most remarkable pathways differentially represented between PDR and normal vitreous were the glycolysis/gluconeogenesis, complement and coagulation cascades, gap junction, and phagosome pathways. The differential expressions of angiopoietin-related protein 6, apolipoprotein A-I, estrogen receptor alpha, and tubulin were confirmed by western blot analysis. These data provide insight into the molecular events possibly involved in the pathogenesis of PDR and widen the scope of potential avenues for new therapies for PDR.

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.

Nitrotyrosine impairs angiogenesis and uncouples eNOS activity of pulmonary artery endothelial cells isolated from developing sheep lungs

Infection is known to impair the growth of developing lungs. It is known that plasma free nitrotyrosine (NT) levels can reach 150 μM during sepsis. Free NT incorporates into microtubules and impairs cell function. We hypothesize that free NT perturbs the angiogenic activity of pulmonary artery endothelial cells (PAEC) in developing lungs. PAEC from fetal lamb lungs were incubated with NT (1-100 μM). We examined the effects of NT on tube formation, cell proliferation, apoptosis, and α-tubulin assembly in PAEC. We assessed superoxide anion (O2) and NO levels in PAEC during NT exposure. Effects of NT on endothelial NO synthase (eNOS) were examined with respect to eNOS-dimer formation and the association of eNOS chaperone, heat-shock-protein-90 (hsp90). NT decreased tube formation and increased apoptosis in PAEC. NT also decreased NO levels, increased NOS-dependent O2 generation, and promoted α-tubulin depolymerization. Although NT increased eNOS homodimer formation, it decreased the hsp90 association with eNOS. Our data suggest that increased NT formation during sepsis may uncouple eNOS activity and increase oxidative stress. Because NO plays an important role in angiogenesis and vasodilation, these observations suggest a mechanism for the impaired vasodilation and angiogenesis during sepsis in the developing lung.

Microtubule plus-end binding protein EB1 is necessary for muscle cell differentiation, elongation and fusion

During muscle differentiation, microtubule stability, nucleation and orientation all undergo profound changes, which are simultaneous with and possibly necessary for the elongation and fusion of muscle cells. We do not yet understand these events, but they present similarities with the polarized migration of fibroblasts, in which EB1 is necessary for microtubule stabilization. However, it was recently reported that EB3, not EB1, is involved in muscle cell elongation and fusion, and that neither of these two proteins influences microtubule stabilization. To re-examine the role of EB1, we have generated C2 cell lines permanently expressing EB1-targeted shRNAs. In these lines, EB1 is specifically knocked down by more than 90% before any differentiation-related changes can take place. We find that differentiation (assessed by myogenin expression), elongation and fusion are prevented. In addition, two early events that normally precede differentiation - microtubule stabilization and the accumulation of cadherin and beta-catenin on the plasma membrane - are inhibited. Re-expression of EB1 as EB1-GFP restores all aspects of normal differentiation, whereas overexpression of EB3-GFP restores elongation but not fusion. We conclude that EB1 is necessary for the early stages of muscle differentiation.

Overexpression of PwTUA1, a pollen-specific tubulin gene, increases pollen tube elongation by altering the distribution of alpha-tubulin and promoting vesicle transport

Tubulin genes are intimately associated with cell division and cell elongation, which are central to plant secondary cell wall development. However, their roles in pollen tube polar growth remain elusive. Here, a TUA1 gene from Picea wilsonii, which is specifically expressed in pollen, was isolated. Semi-quantitative RT-PCR analysis showed that the amount of PwTUA1 transcript varied at each stage of growth of the pollen tube and was induced by calcium ions and boron. Transient expression analysis in P. wilsonii pollen indicated that PwTUA1 improved pollen germination and pollen tube growth. The pollen of transgenic Arabidopsis overexpressing PwTUA1 also showed a higher percentage of germination and faster growth than wild-type plants not only in optimal germination medium, but also in medium supplemented with elevated levels of exogenous calcium ions or boron. Immunofluorescence and electron microscopy showed alpha-tubulin to be enriched and more vesicles accumulated in the apex region in germinating transgenic Arabidopsis pollen compared with wild-type plants. These results demonstrate that PwTUA1 up-regulated by calcium ions and boron contributes to pollen tube elongation by altering the distribution of alpha-tubulin and regulating the deposition of pollen cell wall components during the process of tube growth. The possible role of PwTUA1 in microtubule dynamics and organization was discussed.

The cloning and expression of alpha-tubulin in Monochamus alternatus

The Japanese pine sawyer Monochamus alternatus is one of the major forest pests. It damages pine directly and transfers the nematode Bursaphelenchus xylophilus to pine wood; resulting in serious economic losses around the world every year. Alpha-tubulin is one of most important proteins in most species. We cloned a ubiquitously expressed M. alternatus alpha-tubulin gene and analysed its nucleotides and protein structure; its sequence characters are consistent with what have been reported in other insects. The alignment of proteins showed that there is high homology of alpha-tubulin between M. alternatus and other species. Western blot and immunocytochemistry analyses suggested a common epitope of alpha-tubulin between M. alternatus and Strongylcentrotus purpuratus. We also expressed the protein in Escherichia coli for further functional studies.

Nitrotyrosine promotes human aortic smooth muscle cell migration through oxidative stress and ERK1/2 activation

Nitrotyrosine is a new biomarker of atherosclerosis and inflammation. The objective of this study was to determine the direct effects of free nitrotyrosine on human aortic smooth muscle cell (AoSMC) migration and molecular mechanisms. By a modified Boyden chamber assay, nitrotyrosine significantly increased AoSMC migration in a concentration-dependent manner. For example, nitrotyrosine at 300 nM increased AoSMC migration up to 152% compared with l-tyrosine-treated control cells (P<0.01). Cell wound healing assay confirmed this effect. Nitrotyrosine significantly increased the expression of some key cell migration-related molecules including PDGF receptor-B, matrix metalloproteinase 2 (MMP2) and integrins alphaV and beta3 at both mRNA and protein levels in AoSMC (P<0.01). In addition, nitrotyrosine increased reactive oxygen species (ROS) production in AoSMC by staining with fluorescent dye DCFHDA. Furthermore, nitrotyrosine induced transient phosphorylation of ERK2 by Bio-Plex luminex immunoassay and western blot analysis. AoSMC were able to uptake nitrotyrosine. Antioxidants including seleno-l-methionine and superoxide dismutase mimetic (MnTBAP) as well as ERK1/2 inhibitor PD98059 effectively blocked the promoting effect of nitrotyrosine on AoSMC migration and the mRNA expression of above cell migration-related molecules. Thus, nitrotyrosine directly increases AoSMC migration in vitro and the expression of migration-related molecules through overproduction of ROS and activation of ERK1/2 pathway. Nitrotyrosine may contribute to cardiovascular pathogenesis.