Latest Articles


Free Radical Biology and Medicine (FRBM)

Redox properties of individual quercetin moieties

Publication date: 1 November 2019 Source: Free Radical Biology and Medicine, Volume 143 Author(s): Eva Heřmánková, Martina Zatloukalová, Michal Biler, Romana Sokolová, Martina Bancířová, Andreas G. Tzakos, Vladimír Křen, Marek Kuzma, Patrick Trouillas, Jan Vacek AbstractQuercetin is one of the most prominent and widely studied flavonoids. Its oxidation has been previously investigated only indirectly by comparative analyses of structurally analogous compounds, e.g. dihydroquercetin (taxifolin). To provide direct evidence about the mechanism of quercetin oxidation, we employed selective alkylation procedures for the step-by-step blocking of individual redox active sites, i.e. the catechol, resorcinol and enol C-3 hydroxyls, as represented by newly prepared quercetin derivatives 1–3. Based on the structure-activity relationship (SAR), electrochemical, and computational (density functional theory) studies, we can clearly confirm that quercetin is oxidized in the following steps: the catechol moiety is oxidized first, forming the benzofuranone derivative via intramolecular rearrangement mechanism; therefore the quercetin C-3 hydroxy group cannot be involved in further oxidation reactions or other biochemical processes. The benzofuranone is oxidized subsequently, followed by oxidation of the resorcinol motif to complete the electrochemical cascade of reactions. Derivatization of individual quercetin hydroxyls has a significant effect on its redox behavior, and, importantly, on its antiradical and stability properties, as shown in DPPH/ABTS radical scavenging assays and UV–Vis spectrophotometry, respectively. The SAR data reported here are instrumental for future studies on the oxidation of biologically or technologically important flavonoids and other polyphenols or polyhydroxy substituted aromatics. This is the first complete and direct study mapping redox properties of individual moieties in quercetin structure. Graphical abstract

read article »


Glutathione depletion, lipid peroxidation, and the antecedents of ferroptosis: What about cellular calcium ?

Publication date: 1 November 2019 Source: Free Radical Biology and Medicine, Volume 143 Author(s): Alfonso Pompella, Emilia Maellaro, Angiolo Benedetti, Alessandro F. Casini

read article »


Associations between socioeconomic status, psychosocial stress, and urinary levels of 8-iso-prostaglandin-F2α during pregnancy in Puerto Rico

Publication date: 1 November 2019 Source: Free Radical Biology and Medicine, Volume 143 Author(s): Stephanie M. Eick, John D. Meeker, Phil Brown, Andrea Swartzendruber, Rafael Rios-McConnell, Ye Shen, Ginger L. Milne, Carmen Vélez Vega, Zaira Rosario, Akram Alshawabkeh, José F. Cordero, Kelly K. Ferguson AbstractBackgroundLower socioeconomic status (SES) and psychosocial stress during pregnancy have been associated with adverse birth outcomes. While hypothalamic-pituitary-axis activation is thought to be the primary driver, oxidative stress may also be involved mechanistically. We used data from the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) cohort (N=476) to examine associations between self-reported psychosocial stress measures, SES indicators, and urinary oxidative stress biomarker concentrations, hypothesizing that women with lower SES and increased psychosocial stress would have elevated oxidative stress biomarkers. MethodsMaternal age, education, marital status, insurance status, alcohol use and smoking status were obtained via self-reported questionnaires and were used as indicators of SES. Perceived stress, depression, negative life experiences, neighborhood perceptions, and social support were self-reported in questionnaires administered during pregnancy. Responses were grouped into tertiles for analysis, where the highest tertile corresponded to highest level of psychosocial stress. Urinary concentrations of 8-iso-prostaglandin F2α (8-iso-PGF2α) and its primary metabolite were measured at three study visits (median 18, 24, 28 weeks gestation) and averaged to reflect oxidative stress across pregnancy. Linear models were used to examine associations between SES indicators, tertiles of psychosocial stress and oxidative stress biomarkers. ResultsAverage levels of 8-iso-PGF2α and the 8-iso-PGF2α metabolite were higher among pregnant women who were younger, who had public compared to private insurance, and who were unemployed compared to employed. However, no associations were observed

read article »


Modulation of Caspase-3 activity using a redox active vitamin K3 analogue, plumbagin, as a novel strategy for radioprotection

Publication date: 1 November 2019 Source: Free Radical Biology and Medicine, Volume 143 Author(s): Rahul Checker, Debojyoti Pal, Raghavendra S. Patwardhan, Bhakti Basu, Deepak Sharma, Santosh K. Sandur AbstractRadiation induced damage to normal cells is a major shortcoming of conventional radiotherapy, which necessitates the development of novel radio-protective drugs. An ideal radio-modulator would protect normal cells while having cytotoxic effects on cancer cells. Plumbagin is a potent anti-tumour agent and has been shown to sensitize tumour cells to radiation-induced damage. In the present study, we have evaluated the radio-protective potential of plumbagin and found that it protected normal lymphocytes against radiation-induced apoptosis, but did not protect cancer cells against radiation. Plumbagin offered radioprotection even when it was added to cells after irradiation. The ability of only thiol based antioxidants to abrogate the radio-protective effects of plumbagin suggested a pivotal role of thiol groups in the radio-protective activity of plumbagin. Further, protein interaction network (PIN) analysis was used to predict the molecular targets of plumbagin. Based on the inputs from plumbagin's PIN and in light of its well-documented ability to modulate thiol groups, we proposed that plumbagin may act via modulation of caspase enzyme which harbours a critical catalytic cysteine. Indeed, plumbagin suppressed radiation-induced increase in homogenous caspase and caspase-3 activity in lymphocytes. Plumbagin also inhibited the activity of recombinant caspase-3 and mass spectrometric analysis revealed that plumbagin covalently interacts with caspase-3. Further, the in vivo radioprotective efficacy of plumbagin (single dose of 2mg/kg body weight) was demonstrated by its ability to rescue mice against radiation (7.5 Gy; Whole Body Irradiation) induced mortality. These results indicate that plumbagin prevents radiation induced apoptosis specifically in normal cells by inhibition of caspase-3 activity. Graphical a

read article »


S1QELs suppress mitochondrial superoxide/hydrogen peroxide production from site IQ without inhibiting reverse electron flow through Complex I

Publication date: 1 November 2019 Source: Free Radical Biology and Medicine, Volume 143 Author(s): Hoi-Shan Wong, Pierre-Axel Monternier, Martin D. Brand AbstractMitochondria are important sources of superoxide and hydrogen peroxide in cell signaling and disease. In particular, superoxide/hydrogen peroxide production during reverse electron transport from ubiquinol to NAD+ though Complex I is implicated in several physiological and pathological processes. S1QELs are small molecules that suppress superoxide/hydrogen peroxide production at Complex I without affecting forward electron transport. Their mechanism of action is disputed. To test different mechanistic models, we compared the effects of two inhibitors of Complex I electron transport (piericidin A and rotenone) and two S1QELs from different chemical families on superoxide/hydrogen peroxide production and electron transport by Complex I in isolated mitochondria. Piericidin A and rotenone (and S1QEL1.1 at higher concentrations) prevented superoxide/hydrogen peroxide production from sites IQ and IF in Complex I by inhibiting reverse electron transport into the complex. S1QELs decreased the potency of electron transport inhibition by piericidin A and rotenone, suggesting that S1QELs bind directly to Complex I. S1QEL2.1 (and S1QEL1.1 at lower concentrations) suppressed site IQ without affecting reverse electron transport or site IF, showing that sites IQ and IF are distinct, and that S1QELs do not work simply by decreasing reverse electron transport to site IF (or site IQ). S1QELs did not affect the reduction of NAD+ or the rate of site IF driven by reverse electron transport, therefore they do not alter the driving forces for reverse electron transport and that is not how they suppress site IQ. We conclude that S1QELs bind to Complex I to influence the conformation of the piericidin A and rotenone binding sites and directly suppress superoxide/hydrogen peroxide production at site IQ, which is a separate site from site IF. Graphical abstract

read article »


Redox Biology

Keap1 controls protein S-nitrosation and apoptosis-senescence switch in endothelial cells

Publication date: January 2020 Source: Redox Biology, Volume 28 Author(s): Aleksandra Kopacz, Damian Klóska, Bartosz Proniewski, Dominik Cysewski, Nicolas Personnic, Aleksandra Piechota-Polańczyk, Patrycja Kaczara, Agnieszka Zakrzewska, Henry Jay Forman, Józef Dulak, Alicja Józkowicz, Anna Grochot-Przęczek AbstractPremature senescence, a death escaping pathway for cells experiencing stress, is conducive to aging and cardiovascular diseases. The molecular switch between senescent and apoptotic fate remains, however, poorly recognized. Nrf2 is an important transcription factor orchestrating adaptive response to cellular stress. Here, we show that both human primary endothelial cells (ECs) and murine aortas lacking Nrf2 signaling are senescent but unexpectedly do not encounter damaging oxidative stress. Instead, they exhibit markedly increased S-nitrosation of proteins. A functional role of S-nitrosation is protection of ECs from death by inhibition of NOX4-mediated oxidative damage and redirection of ECs to premature senescence. S-nitrosation and senescence are mediated by Keap1, a direct binding partner of Nrf2, which colocalizes and precipitates with nitric oxide synthase (NOS) and transnitrosating protein GAPDH in ECs devoid of Nrf2. We conclude that the overabundance of this “unrestrained” Keap1 determines the fate of ECs by regulation of S-nitrosation and propose that Keap1/GAPDH/NOS complex may serve as an enzymatic machinery for S-nitrosation in mammalian cells. Graphical abstract

read article »


Advanced oxidation protein products increase TNF-α and IL-1β expression in chondrocytes via NADPH oxidase 4 and accelerate cartilage degeneration in osteoarthritis progression

Publication date: January 2020 Source: Redox Biology, Volume 28 Author(s): Cong-Rui Liao, Sheng-Nan Wang, Si-Yuan Zhu, Yi-Qing Wang, Zong-Ze Li, Zhong-Yuan Liu, Wang-Sheng Jiang, Jian-Ting Chen, Qian Wu AbstractInterleukin (IL)-1β and tumor necrosis factor (TNF)-α, in particular, control the degeneration of articular cartilage, making them prime targets for osteoarthritis (OA) therapeutic strategies. Advanced oxidation protein products (AOPPs) are prevalent in numerous diseases. Our previous work demonstrates that intra-articular injections of AOPPs accelerate regression of cartilage in OA models. Whether AOPPs exist in the course of OA and their effects on TNF-α and IL-1β expression in chondrocytes are still unclear. This study confirmed that AOPPs levels in human synovial fluid were positively associated with severity of OA. We also found AOPPs deposition in articular cartilage in anterior cruciate ligament transection (ACLT) induced rodent OA models. AOPPs increased expression of TNF-α and IL-1β in chondrocytes in vitro, which was inhibited by pre-treatment with SB202190 (p38-MAPK inhibitor) or apocynin (NADPH oxidase inhibitor) or NOX4 knockdown by siRNAs. Subsequently, we further verified in vivo that exogenous injection of AOPPs in OA mice up-regulated expression of TNF-α and IL-1β in cartilage, which was blocked by treatment with apocynin. In parallel, apocynin attenuated articular cartilage degeneration resulting in substantially lower OARSI scores. Specifically, apocynin reduced NOX4, p-P38, TNF-α and IL-1β and increased collagen II and glycosaminoglycan (GAG). This study demonstrated that AOPPs increased expression of TNF-α and IL-1β in chondrocytes via the NADPH oxidase4-dependent and p38-MAPK mediated pathway, and accelerated cartilage degeneration in OA progression. These findings suggest an endogenous pathogenic role of AOPPs in OA progression. Targeting AOPPs-triggered cellular mechanisms might be a promising therapeutic option for patients with OA.

read article »


Blockade of the trans-sulfuration pathway in acute pancreatitis due to nitration of cystathionine β-synthase

Publication date: January 2020 Source: Redox Biology, Volume 28 Author(s): Sergio Rius-Pérez, Salvador Pérez, Isabel Torres-Cuevas, Pablo Martí-Andrés, Raquel Taléns-Visconti, Alberto Paradela, Laura Guerrero, Luis Franco, Gerardo López-Rodas, Luis Torres, Fernando Corrales, Juan Sastre AbstractAcute pancreatitis is an inflammatory process of the pancreatic gland that may lead to dysregulation of the trans-sulfuration pathway. The aims of this work were firstly to study the methionine cycle as well as the trans-sulfuration pathway using metabolomic and proteomic approaches identifying the causes of this dysregulation in an experimental model of acute pancreatitis; and secondly to reveal the effects of S-adenosylmethionine administration on these pathways. Acute pancreatitis was induced by cerulein in mice, and a group of animals received S-adenosylmethionine treatment. Cerulein-induced acute pancreatitis rapidly caused marked depletion of methionine, S-adenosylmethionine, 5′-methylthioadenosine, cystathionine, cysteine, and glutathione levels in pancreas, but S-adenosylhomocysteine and homocysteine remained unchanged. Protein steady-state levels of S-adenosylhomocysteine-hydrolase and cystathionine gamma-lyase diminished but methylthioadenosine phosphorylase levels increased in pancreas with acute pancreatitis. Although cystathionine β-synthase protein levels did not change with acute pancreatitis, Nos2 mRNA and protein levels were markedly up-regulated and caused tyrosine nitration of cystathionine β-synthase in pancreas. S-adenosylmethionine administration enhanced Nos2 mRNA expression and cystathionine β-synthase nitration and triggered homocysteine accumulation in acute pancreatitis. Furthermore, S-adenosylmethionine administration promoted enrichment of the euchromatin marker H3K4me3 in the promoters of Tnf-α, Il-6, and Nos2 and enhanced the mRNA up-regulation of these genes. Accordingly, S-adenosylmethionine administration increased inflammatory infiltrate and edema in pancreas with acute pancreatitis. In c

read article »


The NOTCH1-dependent HIF1α/VGLL4/IRF2BP2 oxygen sensing pathway triggers erythropoiesis terminal differentiation

Publication date: January 2020 Source: Redox Biology, Volume 28 Author(s): Yiqin Wang, Xiaohui Liu, Baoshu Xie, Hao Yuan, Yiyue Zhang, Jun Zhu AbstractHypoxia is widely considered as a limiting factor in vertebrate embryonic development, which requires adequate oxygen delivery for efficient energy metabolism, while nowadays some researches have revealed that hypoxia can induce stem cells so as to improve embryonic development. Erythroid differentiation is the oxygen delivery method employed by vertebrates at the very early step of embryo development, however, the mechanism how erythroid progenitor cell was triggered into mature erythrocyte is still not clear. In this study, after detecting the upregulation of vgll4b in response to oxygen levels, we generated vgll4b mutant zebrafish using CRISPR/Cas9, and verified the resulting impaired heme and dysfunctional erythroid terminal differentiation phenotype. Neither the vgll4b-deficient nor the γ-secretase inhibitor IX (DAPT)-adapted zebrafish were able to mediate HIF1α-induced heme generation. In addition, we showed that vgll4b mutant zebrafish were associated with an impaired erythroid phenotype, induced by the downregulation of alas2, which could be rescued by irf2bp2 depletion. Further mechanistic studies revealed that zebrafish VGLL4 sequesters IRF2BP2, thereby inhibiting its repression of alas2 expression and heme biosynthesis. These processes occur primarily via the VGLL4 TDU1 and IRF2BP2 ring finger domains. Our study also indicates that VGLL4 is a key player in the mediation of NOTCH1-dependent HIF1α-regulated erythropoiesis and can be sensitively regulated by oxygen concentrations. On the other hand, VGLL4 is a pivotal regulator of heme biosynthesis and erythroid terminal differentiation, which collectively improve oxygen metabolism.

read article »


Cysteine oxidation triggers amyloid fibril formation of the tumor suppressor p16INK4A

Publication date: January 2020 Source: Redox Biology, Volume 28 Author(s): Christoph Göbl, Vanessa K. Morris, Loes van Dam, Marieke Visscher, Paulien E. Polderman, Christoph Hartlmüller, Hesther de Ruiter, Manuel Hora, Laura Liesinger, Ruth Birner-Gruenberger, Harmjan R. Vos, Bernd Reif, Tobias Madl, Tobias B. Dansen AbstractThe tumor suppressor p16INK4A induces cell cycle arrest and senescence in response to oncogenic transformation and is therefore frequently lost in cancer. p16INK4A is also known to accumulate under conditions of oxidative stress. Thus, we hypothesized it could potentially be regulated by reversible oxidation of cysteines (redox signaling). Here we report that oxidation of the single cysteine in p16INK4A in human cells occurs under relatively mild oxidizing conditions and leads to disulfide-dependent dimerization. p16INK4A is an all α-helical protein, but we find that upon cysteine-dependent dimerization, p16INK4A undergoes a dramatic structural rearrangement and forms aggregates that have the typical features of amyloid fibrils, including binding of diagnostic dyes, presence of cross-β sheet structure, and typical dimensions found in electron microscopy. p16INK4A amyloid formation abolishes its function as a Cyclin Dependent Kinase 4/6 inhibitor. Collectively, these observations mechanistically link the cellular redox state to the inactivation of p16INK4A through the formation of amyloid fibrils. Graphical abstract

read article »