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58 p.-16 fig.-5 tab., Complex lipids, phospholipids (PLs) and triacylglycerides (TAGs), are prone to modifications induced by reactive nitrated species and reactive oxygen species, generating a range of nitrated, nitrosated or nitroxidized derivatives, as nitro PLs and nitro TAGs. These modified lipids (epilipids) have been reported in vitro and in vivo using lipidomics approaches. However, their detection in living systems remains a challenge hampered by its complexity, high structural diversity, and low abundance. The advances in high-resolution mass spectrometry combined with the higher sensitivity of the instruments like Orbitrap-based mass spectrometers opened new opportunities for the detection of these modified complex lipids. This review summarizes the challenges and findings behind the identification of nitrated, nitrosated and nitroxidized PLs and TAGs fragmentation fingerprints based on collision-induced dissociation (CID) and higher energy CID (HCD) MS/MS approaches. Following what has already been reported for nitrated fatty acids, these complex lipids are found to act as endogenous mediators with potential electrophilic properties and can express bioactivities such as anti-inflammatory and antioxidant actions. This information can be used to design untargeted and targeted lipidomics strategies for these modified complex lipids in biological samples as well as in pathological, food and industrial settings, further unveiling their biological and signalling roles., The authors would like to thanks to the University of Aveiro and FCT/MCT for the financial support to LAQV/REQUIMTE (UIDP/50006/2020 + UIDB/50006/2020), CESAM (UIDB/50017/2020 + UIDP/50017/2020 + LA/P/0094/2020), CICECO (UIDB/50011/2020+UIDP/50011/2020) and to RNEM, Portuguese Mass Spectrometry Network, (LISBOA-01-0145-FEDER-402-022125) through national founds and, where applicable, co-financed by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. The authors are also thankful to the COST Action EpiLipidNET, CA19105 - Pan-European Network in Lipidomics and EpiLipidomics. Dolores Pérez-Sala thanks to RTI2018-097624-B-I00 from Agencia Estatal de Investigación, MICINN/FEDER, Spain, and Instituto de Salud Carlos III/FEDER, RETIC ARADyAL RD16/0006/002. Ana Moreira thanks the research contract under the project Coccolitho4BioMat - Coccolithophore microalgae biorefinery: an approach for sustainable biomaterials (POCI-01-0145-FEDER-031032), funded by Centro2020, through FEDER and PT2020. Tânia Melo thanks the Junior Researcher contract in the scope of the Individual Call to Scientific Employment Stimulus 2020 [CEECIND/01578/2020]. Bruna Neves (2021.04602.BD), Helena Beatriz Ferreira (2020.04611.BD) and Inês Guerra (2021.04754.BD) thanks FCT for the PhD grant.

23 p.-7 fig., The intermediate filament protein vimentin is involved in essential cellular processes, including cell division and stress responses, as well as in the pathophysiology of cancer, pathogen infection, and autoimmunity. The vimentin network undergoes marked reorganizations in response to oxidative stress, in which modifications of vimentin single cysteine residue, Cys328, play an important role, and is modulated by zinc availability. However, the molecular basis for this regulation is not fully understood. Here, we show that Cys328 displays a low pKa, supporting its reactivity, and is readily alkylated and oxidized in vitro. Moreover, combined oxidation and crosslinking assays and molecular dynamics simulations support that zinc ions interact with Cys328 in its thiolate form, whereas Glu329 and Asp331 stabilize zinc coordination. Vimentin oxidation can induce disulfide crosslinking, implying the close proximity of Cys328 from neighboring dimers in certain vimentin conformations, supported by our computational models. Notably, micromolar zinc concentrations prevent Cys328 alkylation, lipoxidation, and disulfide formation. Moreover, zinc selectively protects vimentin from crosslinking using short-spacer cysteine-reactive but not amine-reactive agents. These effects are not mimicked by magnesium, consistent with a lower number of magnesium ions hosted at the cysteine region, according to molecular dynamics simulations. Importantly, the region surrounding Cys328 is involved in interaction with several drugs targeting vimentin and is conserved in type III intermediate filaments, which include glial fibrillary acidic protein and desmin. Altogether, our results identify this region as a hot spot for zinc binding, which modulates Cys328 reactivity. Moreover, they provide a molecular standpoint for vimentin regulation through the interplay between cysteine modifications and zinc availability., This work was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement No. 675132 “Masstrplan”, Grants SAF2015-68590-R and RTI2018-097624-B-I00 from Agencia Estatal de Investigación, MICINN/FEDER, Spain, and Instituto de Salud Carlos III/FEDER, RETIC ARADyAL RD16/0006/0021 to DPS; Grant CTQ2017-88353-R from MICINN to SMS; Grant BES-2015-071588 from MICINN to JGC.

11 p.-2 fig.-3 tab., The cytoskeleton is a supramolecular structure consisting of interacting protein networks that support cell dynamics in essential processes such as migration and division, as well as in responses to stress. Fast cytoskeletal remodeling is achieved with the participation of regulatory proteins and posttranslational modifications (PTMs).Redox-related PTMs are emerging as critical players in cytoskeletal regulation. Here we used a cellular model of mild nitroxidative stress in which a peroxynitrite donor induced transient changes in the organization of three key cytoskeletal proteins, i.e., vimentin, actin and tubulin. Nitroxidative stress-induced reconfiguration of intermediate filaments, microtubules and actin structures were further correlated with their PTM profiles and dynamics of the PTM landscape. Using high-resolution mass spectrometry, 62 different PTMs were identified and relatively quantified in vimentin, actin and tubulin, including 12 enzymatic, 13 oxidative and 2 nitric oxidederived modifications as well as 35 modifications by carbonylated lipid peroxidation products, thus evidencing the occurrence of a chain reaction with formation of numerous reactive species and activation of multiple signaling pathways. Our results unveil the presence of certain modifications under basal conditions and their modulation in response to stress in a target-, residue- and reactive species-dependent manner. Thus, some modifications accumulated during the experiment whereas others varied transiently. Moreover, we identified protein PTM “hot spots”, such as the single cysteine residue of vimentin, which was detected in seven modified forms, thus, supporting its role in PTM crosstalk and redox sensing. Finally, identification of novel PTMs in these proteins paves the way for unveiling new cytoskeleton regulatory mechanisms., This work was funded by Deutsche Forschungsgemeinschaft (DFG;FE-1236/31 to M.F.), European Regional Development Fund (ERDF,European Union and Free State Saxony; 100146238 and 100121468 to MF), and MASSTRPLAN project funded by the Marie Sklodowska-Curie EU Framework for Research and Innovation Horizon 2020 (Grant Agreement No. 675132, to MF and DPS). EG STSM at CIB-CSIC was supported by COST Action CM1001. DPS work has been supported by Agencia Estatal de Investigación, MINECO/ERDF (grants SAF2015-68590R and RTI2018-097624-B-I00), and ISCIII/ERDF (RETIC ARADYAL RD16/0006/0021).

25 p.-3 fig.-3 tab., Protein lipoxidation is a non-enzymatic post-translational modification that consists of the covalent addition of reactive lipid species to proteins. This occurs under basal conditions but increases in situations associated with oxidative stress. Protein targets for lipoxidation include metabolic and signalling enzymes, cytoskeletal proteins, and transcription factors, among others. There is strong evidence for the involvement of protein lipoxidation in disease, including atherosclerosis, neurodegeneration, and cancer. Nevertheless, the involvement of lipoxidation in cellular regulatory mechanisms is less understood. Here we review basic aspects of protein lipoxidation and discuss several features that could support its role in cell signalling, including its selectivity, reversibility, and possibilities for regulation at the levels of the generation and/or detoxification of reactive lipids. Moreover, given the great structural variety of electrophilic lipid species, protein lipoxidation can contribute to the generation of multiple structurally and functionally diverse protein species. Finally, the nature of the lipoxidised proteins and residues provides a frameshift for a complex interplay with other post-translational modifications, including redox and redox-regulated modifications, such as oxidative modifications and phosphorylation, thus strengthening the importance of detailed knowledge of this process., Work at DPS laboratory is supported by RTI2018-097624-B-I00 from Agencia Estatal de Investigación, MICINN/ERDF, and RETIC ARADYAL RD16/0006/0021 from ISCIII/ERDF, Spain Work at CMS laboratory (including I.C.M. and O.L.) is supported by funding from the European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement No 847419 (MemTrain). Á.V.P. and P.G.J. are the recipients of predoctoral contracts BES-2016-076965 and PRE2019-088194, respectively, from MICINN, Spain.

27 p.-2 fig.-1 tab., Vimentin is an intermediate filament protein that plays key roles in integration of cytoskeletal functions, and therefore in basic cellular processes such as cell division and migration. Consequently, vimentin has complex implications in pathophysiology. Vimentin is required for a proper immune response, but it can also act as an autoantigen in autoimmune diseases or as a damage signal. Although vimentin is a predominantly cytoplasmic protein, it can also appear at extracellular locations, either in a secreted form or at the surface of numerous cell types, often in relation to cell activation, inflammation, injury or senescence. Cell surface targeting of vimentin appears to associate with the occurrence of certain posttranslational modifications, such as phosphorylation and/or oxidative damage. At the cell surface, vimentin can act as a receptor for bacterial and viral pathogens. Indeed, vimentin has been shown to play important roles in virus attachment and entry of severe acute respiratory syndrome-related coronavirus (SARS-CoV), dengue and encephalitis viruses, among others. Moreover, the presence of vimentin in specific virus-targeted cells and its induction by proinflammatory cytokines and tissue damage contribute to its implication in viral infection. Here, we recapitulate some of the pathophysiological implications of vimentin, including the involvement of cell surface vimentin in interaction with pathogens, with a special focus on its role as a cellular receptor or co-receptor for viruses. In addition, we provide a perspective on approaches to target vimentin, including antibodies or chemical agents that could modulate these interactions to potentially interfere with viral pathogenesis, which could be useful when multi-target antiviral strategies are needed., Work in DPS laboratory is supported by Grants from Agencia Estatal de Investigación, MINECO/FEDER,Spain, RTI2018-097624-B-I00, Instituto de Salud Carlos III/FEDER, RETIC Aradyal RD16/0006/0021, and CSIC PTI Global Health (PIE 202020E223/CSIC-COVID-19-100). IR research is partially supported by the NIH/National Institute of Allergy and Infectious Diseases-funded centers PRIME (Program for Research on Immune Modeling and Experimentation, U19AI117873), and DHIPC (Dengue Human Immunology Project Consortium, 1U19AI118610).

16 p.-5 fig., Intermediate filaments (IFs) play key roles in cell mechanics, signaling and homeostasis. Their assembly and dynamics are finely regulated by posttranslational modifications. The type III IFs, vimentin, desmin, peripherin and glial fibrillary acidic protein (GFAP), are targets for diverse modifications by oxidants and electrophiles, for which their conserved cysteine residue emerges as a hot spot. Pathophysiological examples of these modifications include lipoxidation in cell senescence and rheumatoid arthritis, disulfide formation in cataracts and nitrosation in endothelial shear stress, although some oxidative modifications can also be detected under basal conditions. We previously proposed that cysteine residues of vimentin and GFAP act as sensors for oxidative and electrophilic stress, and as hinges influencing filament assembly. Accumulating evidence indicates that the structurally diverse cysteine modifications, either per se or in combination with other posttranslational modifications,elicit specific functional outcomes inducing distinct assemblies or network rearrangements, including filament stabilization, bundling or fragmentation. Cysteine-deficient mutants are protected from these alterations but show compromised cellular performance in network assembly and expansion, organelle positioning and aggresome formation, revealing the importance of this residue. Therefore, the high susceptibility to modification of the conserved cysteine of type III IFs and its cornerstone position in filament architecture sustains their role in redox sensing and integration of cellular responses. This has deep pathophysiological implications and supports the potential of this residue as a drug target., This work was supported by Grants from Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación (MCI, Spain) and European Regional Development Fund, RTI2018-097624-B-I00,Instituto de Salud Carlos III (Spain) RETIC AraDyal RD16/0006/0021,and CSIC PTI Global Health (PIE202020E223/CSIC-COV19-100). AV-P is supported by the FPI program from MCI, reference BES-2016-076965.

11 p.-5 fig.-1 tab., Cells employ multiple defence mechanisms to sustain a wide range of stress conditions associated with accumulation of modified self-biomolecules leading to lipo- and proteotoxicity. One of such mechanisms involves activation of the autophagy-lysosomal pathway for removal and degradation of modified lipids, proteins and even organelles. Biomolecules carbonylation, an irreversible oxidative modification, occurs in a variety of pathological conditions and is generally viewed as a marker of oxidative stress. Here, we used a model of rat primary cardiac cells to elucidate the role of autophagy-lysosomal pathway in the turnover of carbonylated biomolecules. Cells treated with inhibitors of autophagy-lysosomal degradation and primed with a short pulse of mild nitroxidative stress were studied using fluorescent microscopy and accumulation of carbonylated biomolecules in droplets- or vesicle-like structures was observed. Furthermore, systems-wide analysis of proteome regulation using relative label free quantification approach revealed the most significant alterations in cells treated with protease inhibitors. Interestingly, down-regulation of insulin signalling was among the most enriched pathway, as revealed by functional annotation of regulated proteins., The financial support from MASSTRPLAN project funded by the Marie Sklodowska-Curie EU Framework for Research and Innovation Horizon 2020 (Grant Agreement No. 675132; to MF and DPS), German Federal Ministry of Education and Research (BMBF)within the framework of the e: Med research and funding concept for SysMedOS project (to MF), as well as from the Spanish MINECO/FEDER, grant SAF2015-68590-R (to DPS), are gratefully acknowledged.

12 p.-7 fig., Salmonella uses Type 3 secretion systems (T3SSs) to deliver virulence factors, called effectors, into host cells during infection. The T3SS effectors promote invasion into host cells and the generation of a replicative niche. SopB is a T3SS effector that plays an important role in Salmonella pathogenesis through its lipid phosphatase activity. Here, we show that SopB mediates the recruitment of Rho GTPases (RhoB, RhoD, RhoH, and RhoJ) to bacterial invasion sites. RhoJ contributes to Salmonella invasion, and RhoB and RhoH play an important role in Akt activation. R‐Ras1 also contributes to SopB‐dependent Akt activation by promoting the localised production of PI(3,4)P2/PI(3,4,5)P3. Our studies reveal new signalling factors involved in SopB‐dependent Salmonella infection., This work was supported by an operating grant from the Canadian Institutes of Health Research (FDN 154329).

13 p.-6 fig.-1 tab., Endothelial dysfunction has been widely associated with oxidative stress, glucotoxicity and lipotoxicity and underlies the development of cardiovascular diseases (CVDs), atherosclerosis and diabetes. In such pathological conditions, lipids are emerging as mediators of signalling pathways evoking key cellular responses as expression of proinflammatory genes, proliferation and apoptosis. Hence, the assessment of lipid profiles in endothelial cells (EC) can provide valuable information on the molecular alterations underlying CVDs, atherosclerosis and diabetes. We performed a lipidomic approach based on hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) for the analysis of the phospholipidome of bovine aortic EC (BAEC) exposed to oxidative (H2O2), glycative (glucose), or lipoxidative (4-hydroxynonenal, HNE) stress. The phospholipid (PL) profile was evaluated for the classes PC, PE, PS, PG, PI, SM, LPC and CL. H2O2 induced a more acute adaptation of the PL profile than glucose or HNE. Unsaturated PL molecular species were up-regulated after 24h incubation with H2O2, while an opposite trend was observed in glucose- and HNE-treated cells. This study compared, for the first time, the adaptation of the phospholipidome of BAEC upon different induced biochemical stresses. Although further biological studies will be necessary, our results unveil specific lipid signatures in response to characteristic types of stress., This work was supported by funding from European Commission’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement number 675132 (MSCA-ITN-ETN MASSTRPLAN) to University of Aveiro and CSIC. Thanks are due to University of Aveiro, FCT/MEC, European Union, QREN, COMPETE for the financial support to the QOPNA (FCT UID/QUI/00062/2013), through national funds and where applicable co-financed by the FEDER, within the PT2020 Partnership Agreement, to the Portuguese Mass Spectrometry Network (LISBOA-01-0145-FEDER-402-022125). Tânia Melo is grateful for her Post-Doc grant (BPD/UI 51/5388/2017). Work at D.P.S. laboratory is also supported by grants from Spanish MINECO/FEDER, SAF2015-68590-R, and Instituto de Salud Carlos III/FEDER, RETIC Aradyal,RD16/0006/0021. The stay of M.M.L. at University of Aveiro was part of COST Action CM1001.

21 p.-5 fig.-2 tab. (Chapter 3), Homeostasis of the main cellular methyl donor, S-adenosylmethionine, depends on the methionine cycle, which is at the crossroads of metabolic pathways involved in the synthesis and regulation of a large variety of compounds and processes. Impairment of the methionine cycle is detected in a vast majority of liver diseases that concur with oxidative stress. The complex regulation of the pathway is exerted from transcriptional to protein oligomerization and activity levels, subcellular distribution being recently added to the play. Oxidative stress performs a role at all of these regulatory levels either directly (e.g., eliciting protein modifications) or indirectly (e.g., decreasing recycling of vitamin B12). Therefore, the interest in deciphering the mechanisms through which medical interventions could revert methionine cycle impairment, contributing to liver disease treatment. In this line, the control of subcellular distribution has emerged as a putative target for new and existent antioxidants, their evaluation requiring a large research effort., Work carried out in the author’s laboratories was supported by grants of the Ministerio de Economía y Competitividad (BFU2009-08977 to MAP; SAF2012-36519 and SAF2015-68590-R to DPS)

15 p.-8 fig., The intermediate filament protein vimentin constitutes a critical sensor for electrophilic and oxidative stress, which induce extensive reorganization of the vimentin cytoskeletal network. Here, we have investigated the mechanisms underlying these effects. In vitro, electrophilic lipids, including 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) and 4-hydroxynonenal (HNE), directly bind to vimentin, whereas the oxidant diamide induces disulfide bond formation. Mutation of the single vimentin cysteine residue (Cys328) blunts disulfide formation and reduces lipoxidation by 15d-PGJ2, but not HNE. Preincubation with these agents differentially hinders NaClinduced filament formation by wild-type vimentin, with effects ranging from delayed elongation and increased filament diameter to severe impairment of assembly or aggregation. Conversely, the morphology of vimentin Cys328Ser filaments is mildly or not affected. Interestingly, preformed vimentin filaments are more resistant to electrophile-induced disruption, although chemical modification is not diminished, showing that vimentin (lip) oxidation prior to assembly is more deleterious. In cells, electrophiles, particularly diamide, induce a fast and drastic disruption of existing filaments, which requires the presence of Cys328. As the cellular vimentin network is under continuous remodeling, we hypothesized that vimentin exchange on filaments would be necessary for diamide-induced disruption. We confirmed that strategies reducing vimentin dynamics, as monitored by FRAP, including cysteine crosslinking and ATP synthesis inhibition, prevent diamide effect. In turn, phosphorylation may promote vimentin disassembly. Indeed, treatment with the phosphatase inhibitor calyculin A to prevent dephosphorylation intensifies electrophile-induced wild-type vimentin filament disruption. However, whereas a phosphorylation-deficient vimentin mutant is only partially protected from disorganization, Cys328Ser vimentin is virtually resistant, even in the presence of calyculin A. Together, these results indicate that modification of Cys328 and vimentin exchange are critical for electrophile-induced network disruption., This work was supported by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant agreement no. 675132 “Masstrplan”, Grant SAF2015-68590-R from MINECO/FEDER, Spain and Instituto de Salud Carlos III/FEDER,RETIC Aradyal RD16/0006/0021. Feedback from COST Action CA15214 “EuroCellNet” is gratefully acknowledged.

3 p., Work at the authors’ laboratories is supported by grants from “la Caixa” Foundation, Grant Agreement LCF/PR/HR21/52410002, EJP RD COFUND-EJP N° 825575 “Alexander”,Agencia Estatal de Investigación, MICINN and ERDF Grants N°: RTI 2018-097624-B-I00 and PID2021-126827OB-I00 to DPS,and NIH 1R01 GM140108 awarded to MG.

11 p.-7 fig.-1 tab.-1 sch., Cyclopentenone prostaglandins may interfere with cellular functions by multiple mechanisms. The cyclopentenone 15-deoxy-Delta 12,14-prostaglandin J2 (15d-PGJ2) has been reported to inhibit the activity of the transcription factor AP-1 in several experimental settings. We have explored the possibility of a direct interaction of 15d-PGJ2 with AP-1 proteins. Here we show that 15d-PGJ2 covalently modifies c-Jun and directly inhibits the DNA binding activity of AP-1. The modification of c-Jun occurs both in vitro and in intact cells as detected by labeling with biotinylated 15d-PGJ2 and mass spectrometry analysis. Attachment of the cyclopentenone prostaglandin occurs at cysteine 269, which is located in the c-Jun DNA binding domain. In addition, 15d-PGJ2 can promote the oligomerization of a fraction of c-Jun through the formation of intermolecular disulfide bonds or 15d-PGJ2-bonded dimers. Our results identify a novel site of interaction of 15d-PGJ2 with the AP-1 activation pathway that may contribute to the complex effects of cyclopentenone prostaglandins on the cellular response to pro-inflammatory agents. They also show the first evidence for the induction of protein cross-linking by 15d-PGJ2., This work was supported in part by Comunidad Autónoma de Madrid Grants 08.4/0031.1/2000 and 08.4/0025.1/2003 and Ministerio de Ciencia y Tecnología Grant SAF2000-0149, Spain.

7 p.-5 fig., Human mesangial cells express an inducible form of nitric-oxide synthase (iNOS) after treatment with cytokines. Tetrahydrobiopterin (BH4), an essential cofactor for NOS, is required for cytokine-induced NO generation. We report here that BH4 is necessary not only for the activity but also for the expression of iNOS in human mesangial cells. Inhibition of de novo BH4 synthesis with 2,4-diamino-6-hydroxypyrimidine (DAHP) significantly attenuated iNOS activity as well as mRNA and protein expression in response to interleukin 1β plus tumor necrosis factor α (IL-1β/TNF-α). In contrast, sepiapterin, which provides BH4 through the pterin salvage pathway, strongly potentiated IL-1β/TNF-α-induced iNOS expression and abrogated the inhibitory effect of DAHP. Inhibition of the pterin salvage pathway with methotrexate abolished sepiapterin potentiation of iNOS induction but did not alter the effect of IL-1β/TNF-α. Determination of intracellular pteridines confirmed that sepiapterin markedly raised BH4 content, an effect that was blocked by methotrexate. These results suggest that BH4 availability plays an important role in the regulation of iNOS expression. The effect of BH4 appears to be mediated, at least in part, by an increase in mRNA stability, as indicated by the observation that DAHP shortened, whereas sepiapterin prolonged the half-life of IL-1β/TNF-α-induced iNOS mRNA. Taken together, our results suggest that the biosynthesis of BH4 contributes to cytokine induction of iNOS expression in human mesangial cells through the stabilization of iNOS mRNA., This work was supported by Grants PB93-0044 (to S. L.) and PB93-0127 (to F. J. C.) from the Dirección General de Investigación Científica y Técnica (DGICYT).

8 p.-9 fig.-1 tab., Protein isoprenylation is a post-translational modification essential for the biological activity of G-proteins. Inhibition of protein isoprenylation by lovastatin (LOV) induces apoptosis in HL-60 cells, a process of active cell death characterized by the internucleosomal degradation of genomic DNA. In this article we show that LOV-induced apoptosis is associated with intracellular acidification and that activation of the Na+/H+ antiporter induces a raise in pHi which is sufficient to prevent or arrest DNA digestion. First, LOV induced a decrease in pHi which was dose-dependent and correlated with the extent of DNA degradation. Flow cytometry analysis revealed that this acidification was due to the appearance of a subpopulation of cells whose pHi was 0.9 pH units below control values. Cell sorting experiments demonstrated that DNA degradation had occurred only in those cells which had suffered intracellular acidification. LOV-induced apoptosis could be suppressed by mevalonate supplementation, inhibition of protein synthesis, and protein kinase C activation by phorbol myristate acetate. In all three cases, intracellular acidification was abolished. Inhibition of the Na+/H+ antiporter by 5-N-ethyl-N-isopropyl amiloride induced DNA degradation in HL-60 cells per se and suppressed the protective effect of phorbol myristate acetate. LOV-induced intracellular acidification was not due to a complete inhibition of the Na+/H+ antiporter. In fact, LOV-treated cells were able to respond to phorbol myristate acetate stimulation of the Na+/H+ antiporter with a marked increase in pHi. This effect was accompanied by a rapid arrest of DNA digestion. These observations illustrate the strong pH dependence of LOV-induced DNA degradation, thus providing a connection between the activation of the Na+/H+ antiporter and the suppression of apoptosis., This work was supported by Grant PM92-0003 from the Dirección General de Investigación Científica y Técnica (DGICYT).

34 p.-6 fig.-1 graph.abst., Nitrated phospholipids have been recently identified in biological systems and showed to display anti-oxidant and anti-inflammatory potential in models of inflammation in vitro. Here, we have explored the effects of nitrated 1-palmitoyl-2-oleyl-phosphatidyl choline (NO2-POPC) in cellular models. We have observed that NO2-POPC, but not POPC, induces cellular changes consisting in cytoskeletal rearrangement and cell shrinking, and ultimately, loss of cell adhesion or impaired cell attachment. NO2-POPC releases NO in vitro and induces accumulation of NO in cells. Nevertheless, the effects of NO2-POPC are not superimposable with those of NO donors, which points to distinctive mechanisms of action. Notably, they show a stronger parallelism, although not complete overlap, with the effects of nitrated fatty acids. Interestingly, redistribution of vimentin by NO2-POPC is attenuated in a C328S mutant, thus indicating that this residue may be a target for direct or indirect modification in NO2-POPC-treated cells. Additionally, NO2-POPC interacts with several typical lipoxidation targets in vitro, including vimentin and PPARγ constructs, likely through cysteine residues. Therefore, nitrated phospholipids emerge as potential novel electrophilic lipid mediators with selective actions., This work was supported by the H2020 Program, MSCA grant No.: 673152, “Masstrplan” to DPS and MRD, grant SAF2015-68590-R from MINECO/FEDER, and RETIC Aradyal (RD16/0006/0021) from ISCIII/FEDER, Spain to DPS, and grant BFU-2016-77243-P from MINECO/FEDER to JDA. Thanks are due to the University of Aveiro, FCT/MEC, European Union, QREN, COMPETE for the financial support to the QOPNA (FCT UID/QUI/00062/2013) and CESaAM (UID/AMB/50017 - POCI-01-0145-FEDER-007638), through National funds and where applicable co-financed by the FEDER, within the PT2020 Partnership Agreement, to the Portuguese Malaysian Society Nephrology (LISBOA-01-0145-FEDER-402-022125).

4 p.-7 fig., We present evidence which demonstrates that L-cycloserine, structural analog of L-alanine, which is known to be an effective aminotransferase inhibitor, is also a potent inhibitor of cellular pyruvate metabolism. This effect was found to be related to its almost instantaneous action in decreasing pyruvate concentrations in a dose-dependent manner. 1H nuclear magnetic resonance studies clearly demonstrate that the irreversible removal of pyruvate induced by L-cycloserine is caused by the decarboxylating action of the latter. Pyruvate disappearance induced by L-cycloserine can be stoichiometrically accounted for as acetate. The process does not involve any chemically detected transformation of L-cycloserine. These observations lead to two main considerations regarding the known action of L-cycloserine. First, its inhibitory effect on gluconeogenesis from lactate could be explained only on the basis of its ability to reduce pyruvate availability with no apparent need for transaminase inhibition. Second, its ability as a transaminase inhibitor should be reconsidered in view of its potent decarboxylating action on pyruvate and probably other oxoacids., This work has been supported in part by Grants 174 and 1674 from the Spanish Comisión Asesora de Investigación Cientifica y Técnica, and Fondo de Investigaciones Sanitarias Grants 85/839 and 85/1321.