Clomiphene citrate administered in peri-conception phase causes fetal loss and developmental impairment in mice

Clomiphene citrate is a common treatment for ovulation induction in subfertile women, but its use is associated with elevated risk of adverse perinatal outcomes and birth defects. To investigate the biological plausibility of a causal relationship, this study investigated in mice the consequences for fetal development and pregnancy outcome of peri-conception clomiphene citrate administration at doses approximating human exposures. A dose-dependent adverse effect of clomiphene citrate given twice in the 36 h after mating was seen, with a moderate dose of 0.75 mg/kg sufficient to cause altered reproductive outcomes in three independent cohorts. Viable pregnancy was reduced by 30%, late gestation fetal weight was reduced by 16%, and ∼30% of fetuses exhibited delayed development and/or congenital abnormalities not seen in control dams, including defects of the lung, kidney, liver, eye, skin, limbs, and umbilicus. Clomiphene citrate also caused a 30 h average delay in time of birth, and elevated rate of pup death in the early postnatal phase. In surviving offspring, growth trajectory tracking and body morphometry analysis at 20 weeks of age showed post-weaning growth and development comparable to controls. A dysregulated inflammatory response in the endometrium was observed and may contribute to the underlying pathophysiological mechanism. These results demonstrate that in utero exposure to clomiphene citrate during early pregnancy can inhibit implantation and impact fetal growth and development, causing adverse perinatal outcomes. The findings raise the prospect of similar iatrogenic effects in women where clomiphene citrate may be present in the peri-conception phase unless its use is well-supervised.

Impact of weight loss and weight gain trajectories on body composition in a population at high risk of type 2 diabetes: A prospective cohort analysis

AIM

In a primary care population at high risk of type 2 diabetes, 24-month weight change trajectories were used to investigate the impact of weight cycling on fat mass (FM) and fat-free mass (FFM).

MATERIALS AND METHODS

Cohort data from the Walking Away from Type 2 Diabetes trial was used, which recruited adults at-risk of type 2 diabetes from primary care in 2009/10. Annual weight change trajectories based on weight loss/gain of ≥5% were assessed over two 24-month periods. Body composition was measured by bioelectrical impedance analysis. Repeated measures were analysed using generalized estimating equations with participants contributing up to two 24-month observation periods.

RESULTS

In total, 622 participants were included (average age = 63.6 years, body mass index = 32.0 kg/m2 , 35.4% women), contributing 1163 observations. Most observations (69.2%) were from those that maintained their body weight, with no change to FM or FFM. A minority (4.6% of observations) lost over 5% of body weight between baseline and 12 months, which was then regained between 12 and 24 months. These individuals regained FM to baseline levels, but lost 1.50 (0.66, 2.35) kg FFM, adjusted for confounders. In contrast, those that gained weight between baseline and 12 months but lost weight between 12 and 24 months (5.5% of observations) had a net gain in FM of 1.70 (0.27, 3.12) kg with no change to FFM.

CONCLUSION

Weight cycling may be associated with a progressive loss in FFM and/or gain in FM in those with overweight and obesity at-risk of type 2 diabetes.

Oxidation of the active site cysteine residue of glyceraldehyde-3-phosphate dehydrogenase to the hyper-oxidized sulfonic acid form is favored under crowded conditions

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key cellular enzyme, with major roles in both glycolysis, and 'moonlighting' activities in the nucleus (uracil DNA glycosylase activity, nuclear protein nitrosylation), as a regulator of mRNA stability, a transferrin receptor, and as an antimicrobial agent. These activities are dependent, at least in part, on the integrity of an active site Cys residue, and a second neighboring Cys. These residues are differentially sensitive to oxidation, and determine both its catalytic activity and the redox signaling capacity of the protein. Such Cys modification is critical to cellular adaptation to oxidative environments by re-routing metabolic pathways to favor NADPH generation and antioxidant defenses. Despite the susceptibility of GAPDH to oxidation, it remains a puzzle as to how this enzyme acts as a redox signaling hub for oxidants such as hydrogen peroxide (H2O2) in the presence of high concentrations of specialized high-efficiency peroxide-removing enzymes. One possibility is that crowded environments, such as the cell cytosol, alter the oxidation pathways of GAPDH. In this study, we investigated the role of crowding (induced by dextran) on H2O2- and SIN-1-induced GAPDH oxidation, with data for crowded and dilute conditions compared. LC-MS/MS data revealed a lower extent of modification of the catalytic Cys under crowded conditions (i.e. less monomer units modified), but enhanced formation of the sulfonic acid resulting from hyper-oxidation. This effect was not observed with SIN-1. These data indicate that molecular crowding can modulate the oxidation pathways of GAPDH and its extent of oxidation and inactivation.

Proteomic analysis of the extracellular matrix of human atherosclerotic plaques shows marked changes between plaque types

Cardiovascular disease is the leading cause of death, with atherosclerosis the major underlying cause. While often asymptomatic for decades, atherosclerotic plaque destabilization and rupture can arise suddenly and cause acute arterial occlusion or peripheral embolization resulting in myocardial infarction, stroke and lower limb ischaemia. As extracellular matrix (ECM) remodelling is associated with plaque instability, we hypothesized that the ECM composition would differ between plaques. We analyzed atherosclerotic plaques obtained from 21 patients who underwent carotid surgery following recent symptomatic carotid artery stenosis. Plaques were solubilized using a new efficient, single-step approach. Solubilized proteins were digested to peptides, and analyzed by liquid chromatography-mass spectrometry using data-independent acquisition. Identification and quantification of 4498 plaque proteins was achieved, including 354 ECM proteins, with unprecedented coverage and high reproducibility. Multidimensional scaling analysis and hierarchical clustering indicate two distinct clusters, which correlate with macroscopic plaque morphology (soft/unstable versus hard/stable), ultrasound classification (echolucent versus echogenic) and the presence of hemorrhage/ulceration. We identified 714 proteins with differential abundances between these groups. Soft/unstable plaques were enriched in proteins involved in inflammation, ECM remodelling, and protein degradation (e.g. matrix metalloproteinases, cathepsins). In contrast, hard/stable plaques contained higher levels of ECM structural proteins (e.g. collagens, versican, nidogens, biglycan, lumican, proteoglycan 4, mineralization proteins). These data indicate that a single-step proteomics method can provide unique mechanistic insights into ECM remodelling and inflammatory mechanisms within plaques that correlate with clinical parameters, and help rationalize plaque destabilization. These data also provide an approach towards identifying biomarkers for individualized risk profiling of atherosclerosis.

Sotagliflozin and Kidney Outcomes, Kidney Function, and Albuminuria in T2DM and CKD: A Secondary Analysis of the SCORED Trial

INTRODUCTION

In the initial analysis of SCORED, due to early trial termination and suspension of adjudication, reconciliation of eGFR laboratory data and case report forms had not been completed. This resulted in a small number of kidney composite events and a nominal effect of sotagliflozin versus placebo on this outcome. This exploratory analysis uses laboratory eGFR data, regardless of case report form completion, to assess the effects of sotagliflozin on the predefined kidney composite endpoint in SCORED and additional cardiorenal composite endpoints.

METHODS

SCORED was a multicenter, randomized trial evaluating cardiorenal outcomes with sotagliflozin versus placebo in 10,584 patients with type 2 diabetes and chronic kidney disease (CKD). The present exploratory analyses used laboratory data to derive the eGFR components and case report form data for the non-laboratory defined components that together made up the kidney and cardiorenal composites. Acute kidney injury (AKI) was also assessed in this dataset.

RESULTS

Using laboratory data, 223 events were identified and sotagliflozin reduced the risk of the composite of first event of sustained ≥50% decline in eGFR, eGFR<15 mL/min/1.73m2, dialysis, or kidney transplant with 87 events (1.6%) in the sotagliflozin group and 136 events (2.6%) in the placebo group (HR [95% CI] = 0.62 [0.48, 0.82]), p<0.001). Sotagliflozin reduced the risk of a cardiorenal composite endpoint defined as the above composite plus cardiovascular or kidney death with 239 events (4.5%) in the sotagliflozin group and 306 events (5.7%) in the placebo group (HR [95% CI] = 0.77 [0.65, 0.91], p=0.0023). Results were consistent when using different eGFR decline thresholds and when only including kidney death in composites (all p<0.01). The incidence of AKI was similar between treatment groups.

CONCLUSIONS

In this exploratory analysis using the complete laboratory dataset, sotagliflozin reduced the risk of kidney and cardiorenal composite endpoints in patients with type 2 diabetes and CKD.

The enzymes of the oxidative phase of the pentose phosphate pathway as targets of reactive species: consequences for NADPH production

The pentose phosphate pathway (PPP) is a key metabolic pathway. The oxidative phase of this process involves three reactions catalyzed by glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconolactonase (6PGL) and 6-phosphogluconate dehydrogenase (6PGDH) enzymes. The first and third steps (catalyzed by G6PDH and 6PGDH, respectively) are responsible for generating reduced nicotinamide adenine dinucleotide phosphate (NAPDH), a key cofactor for maintaining the reducing power of cells and detoxification of both endogenous and exogenous oxidants and electrophiles. Despite the importance of these enzymes, little attention has been paid to the fact that these proteins are targets of oxidants. In response to oxidative stimuli metabolic pathways are modulated, with the PPP often up-regulated in order to enhance or maintain the reductive capacity of cells. Under such circumstances, oxidation and inactivation of the PPP enzymes could be detrimental. Damage to the PPP enzymes may result in a downward spiral, as depending on the extent and sites of modification, these alterations may result in a loss of enzymatic activity and therefore increased oxidative damage due to NADPH depletion. In recent years, it has become evident that the three enzymes of the oxidative phase of the PPP have different susceptibilities to inactivation on exposure to different oxidants. In this review, we discuss existing knowledge on the role that these enzymes play in the metabolism of cells, and their susceptibility to oxidation and inactivation with special emphasis on NADPH production. Perspectives on achieving a better understanding of the molecular basis of the oxidation these enzymes within cellular environments are given.

Efficacy of Sotagliflozin in Adults With Type 2 Diabetes in Relation to Baseline Hemoglobin A1c

BACKGROUND

The SCORED (Effect of Sotagliflozin on Cardiovascular and Renal Events in Patients with Type 2 Diabetes and Moderate Renal Impairment Who Are at Cardiovascular Risk) and SOLOIST-WHF (Effect of Sotagliflozin on Cardiovascular Events in Patients with Type 2 Diabetes Post Worsening Heart Failure) trials demonstrated that sotagliflozin, an SGLT1 and SGLT2 inhibitor, improves outcomes in individuals with type 2 diabetes who have heart failure (HF) or kidney disease.

OBJECTIVES

We assessed the efficacy of sotagliflozin on HF clinical outcomes in individuals with differing baseline glycosylated hemoglobin (HbA1c) levels.

METHODS

We included all adults from SCORED and SOLOIST-WHF. The primary outcome was a composite of cardiovascular death, hospitalizations for HF, and urgent visits for HF. The efficacy of sotagliflozin compared with placebo was evaluated by baseline HbA1c using competing-risk marginal proportional hazards models.

RESULTS

We identified 11,744 adults. Individuals with HbA1c ≤7.5% experienced the primary outcome at a lower rate in the sotagliflozin group (11.2 per 100 person-years) than the placebo group (15.5 per 100 person-years) (HR: 0.73; 95% CI: 0.57-0.93). Similarly, individuals with HbA1c of 7.6% to 9.0% experienced the primary outcome at a lower rate in the sotagliflozin group (7.3 per 100 person-years) than the placebo group (9.4 per 100 person-years) (HR: 0.77; 95% CI: 0.63-0.96). These findings were also consistent among individuals with HbA1c >9.0%, with a primary outcome rate in the sotagliflozin group (7.8 per 100 person-years) that was lower than the placebo group (11.6 per 100 person-years) (HR: 0.65; 95% CI: 0.50-0.84). The efficacy of sotagliflozin was consistent by baseline HbA1c level (P for interaction = 0.58).

CONCLUSIONS

In individuals with type 2 diabetes and either HF or kidney disease, sotagliflozin reduced HF outcomes irrespective of baseline HbA1c.

Genotoxicity assessment of 1,4-anhydro-4-seleno-D-talitol (SeTal) in human liver HepG2 and HepaRG cells

1,4-Anhydro-4-seleno-D-talitol (SeTal) is a highly water-soluble selenosugar with interesting antioxidant and skin-tissue-repair properties; it is highly stable in simulated gastric and gastrointestinal fluids and is a potential pharmaceutical ingredient that may be administered orally. Hepatic toxicity is often a major problem with novel drugs and can result in drug withdrawal from the market. Predicting hepatotoxicity is therefore essential to minimize late failure in the drug-discovery process. Herein, we report in vitro studies to evaluate the cytotoxic and genotoxic potential of SeTal in HepG2 and hepatocyte-like differentiated HepaRG cells. Except for extremely high concentrations (10 mM, 68 h-treatment in HepG2), SeTal did not affect the viability of each cell type. While the highest examined concentrations (0.75 and 1 mM in HepG2; 1 mM in HepaRG) were observed to induce primary DNA damage, SeTal did not exhibit clastogenic or aneugenic activity toward either HepG2 or HepaRG cells. Moreover, no significant cytostasis variations were observed in any experiment. The clearly negative results observed in the CBMN test suggest that SeTal might be used as a potential active pharmaceutical ingredient. The present study will be useful for the selection of non-toxic concentrations of SeTal in future investigations.

Recent Advances in the Synthesis and Antioxidant Activity of Low Molecular Mass Organoselenium Molecules

Selenium is an essential trace element in living organisms, and is present in selenoenzymes with antioxidant activity, like glutathione peroxidase (GPx) and thioredoxin reductase (TrxR). The search for small selenium-containing molecules that mimic selenoenzymes is a strong field of research in organic and medicinal chemistry. In this review, we review the synthesis and bioassays of new and known organoselenium compounds with antioxidant activity, covering the last five years. A detailed description of the synthetic procedures and the performed in vitro and in vivo bioassays is presented, highlighting the most active compounds in each series.

The structure of model and peptide disulfides markedly affects their reactivity and products formed with singlet oxygen

Disulfide bonds are critical structural elements in proteins and stabilize folded structures. Modification of these linkages is associated with a loss of structure and function. Previous studies have reported large variations in the rate of disulfide oxidation by hypohalous acids, due to stabilization of reaction intermediates. In this study we hypothesized that considerable variation (and hence selective oxidation) would occur with singlet oxygen (1O2), a key intermediate in photo-oxidation reactions. The kinetics of disulfide-mediated 1O2 removal were monitored using the time-resolved 1270 nm phosphorescence of 1O2. Stern-Volmer plots of these data showed a large variation (∼103) in the quenching rate constants kq (from 2 × 107 for α-lipoic acid to 3.6 × 104 M-1s-1 for cystamine). The time course of disulfide loss and product formation (determined by LC-MS) support a role for 1O2, with mono- and di-oxygenated products detected. Elevated levels of these latter species were generated in D2O- compared to H2O buffers, which is consistent with solvent effects on the 1O2 lifetime. These data are interpreted in terms of the intermediacy of a zwitterion [-S+(OO-)-S-], which either isomerizes to a thiosulfonate [-S(O)2-S-] or reacts with another parent molecule to give two thiosulfinates [-S(O)-S-]. The variation in quenching rates and product formation are ascribed to zwitterion stabilization by neighboring, or remote, lone pairs of electrons. These data suggest that some disulfides, including some present within or attached to proteins (e.g., α-lipoic acid), may be selectively modified, and undergo subsequent cleavage, with adverse effects on protein structure and function.

Detrimental Actions of Chlorinated Nucleosides on the Function and Viability of Insulin-Producing Cells

Neutrophils are innate immune cells that play a key role in pathogen clearance. They contribute to inflammatory diseases, including diabetes, by releasing pro-inflammatory cytokines, reactive oxygen species, and extracellular traps (NETs). NETs contain a DNA backbone and catalytically active myeloperoxidase (MPO), which produces hypochlorous acid (HOCl). Chlorination of the DNA nucleoside 8-chloro-deoxyguanosine has been reported as an early marker of inflammation in diabetes. In this study, we examined the reactivity of different chlorinated nucleosides, including 5-chloro-(deoxy)cytidine (5ClC, 5CldC), 8-chloro-(deoxy)adenosine (8ClA, 8CldA) and 8-chloro-(deoxy)guanosine (8ClG, 8CldG), with the INS-1E β-cell line. Exposure of INS-1E cells to 5CldC, 8CldA, 8ClA, and 8CldG decreased metabolic activity and intracellular ATP, and, together with 8ClG, induced apoptotic cell death. Exposure to 8ClA, but not the other nucleosides, resulted in sustained endoplasmic reticulum stress, activation of the unfolded protein response, and increased expression of thioredoxin-interacting protein (TXNIP) and heme oxygenase 1 (HO-1). Exposure of INS-1E cells to 5CldC also increased TXNIP and NAD(P)H dehydrogenase quinone 1 (NQO1) expression. In addition, a significant increase in the mRNA expression of NQO1 and GPx4 was seen in INS-1E cells exposed to 8ClG and 8CldA, respectively. However, a significant decrease in intracellular thiols was only observed in INS-1E cells exposed to 8ClG and 8CldG. Finally, a significant decrease in the insulin stimulation index was observed in experiments with all the chlorinated nucleosides, except for 8ClA and 8ClG. Together, these results suggest that increased formation of chlorinated nucleosides during inflammation in diabetes could influence β-cell function and may contribute to disease progression.

Oxygen Exposure and Tolerance Shapes the Cell Wall-Associated Lipids of the Skin Commensal Cutibacterium acnes

Cutibacterium acnes is one of the most abundant bacteria on the skin. Being exposed to oxygen and oxic stress, the secretion of the bacterial antioxidant protein RoxP ensures an endogenous antioxidant system for the preservation of skin health. To investigate the impact of the antioxidant RoxP on oxidation of the bacteria, wildtype and an isogenic roxp mutant were cultured in anaerobic and oxic conditions. The carbonylated status of proteins were recorded, as were the most significant modifications in a relative intensity of free fatty acids (FFA) and lipids containing fatty acids (FA), such as di- (DG) and triglycerides (TG), di- (DGDG) and sulfoquinozyldiacylglycerol (SQDG) and ceramides. Concerning the fatty acid types, it was observed that the free fatty acids contained mainly C12:0-C26:0 in hydroxy and acylated forms, the DG contained mainly C29:0-C37:0, the TG contained mainly C19:0-C33:0, and the DGDG/SQDGs contained very long fatty acids (C29:0-C37:0) demonstrating the interdependence of de novo synthesis of lipids and RoxP. The area of DGDG peaks (924.52, 929.56 and 930.58) were affected by bacterial growth conditions, with the exception of m/z 910.61. Moreover, the FFA unsaturation is wider in the SQDG species (C30:0 to C36:6) than in DG, TG or free FFA species. It could be concluded that both environmental oxidative statuses, as well as the prevalence of bacterial antioxidant systems, significantly shape the lipidome of C. acnes.

Exposure to peroxynitrite impacts the ability of anastellin to modulate the structure of extracellular matrix

The extracellular matrix (ECM) of tissues consists of multiple proteins, proteoglycans and glycosaminoglycans that form a 3-dimensional meshwork structure. This ECM is exposed to oxidants including peroxynitrite (ONOO-/ONOOH) generated by activated leukocytes at sites of inflammation. Fibronectin, a major ECM protein targeted by peroxynitrite, self-assembles into fibrils in a cell-dependent process. Fibrillation of fibronectin can also be initiated in a cell-independent process in vitro by anastellin, a recombinant fragment of the first type-III module in fibronectin. Previous studies demonstrated that modification of anastellin by peroxynitrite impairs its fibronectin polymerization activity. We hypothesized that exposure of anastellin to peroxynitrite would also impact on the structure of ECM from cells co-incubated with anastellin, and influence interactions with cell surface receptors. Fibronectin fibrils in the ECM of primary human coronary artery smooth muscle cells exposed to native anastellin are diminished, an effect which is reversed to a significant extent by pre-incubation of anastellin with high (200-fold molar excess) concentrations of peroxynitrite. Treatment with low or moderate levels of peroxynitrite (2-20 fold molar excess) influences interactions between anastellin and heparin polysaccharides, as a model of cell-surface proteoglycan receptors, and modulates anastellin-mediated alterations in fibronectin cell adhesiveness. Based on these observations it is concluded that peroxynitrite has a dose-dependent influence on the ability of anastellin to modulate ECM structure via interactions with fibronectin and other cellular components. These observations may have pathological implications since alterations in fibronectin processing and deposition have been associated with several pathologies, including atherosclerosis.

Oxidant-modified amylin fibrils and aggregates alter the inflammatory profile of multiple myeloid cell types, but are non-toxic to islet β cells

Diabetes mellitus currently affects ∼10% of the population worldwide, with Type 2 predominating, and this incidence is increasing steadily. Both Type 1 and 2 are complex diseases, involving β-cell death and chronic inflammation, but the pathways involved are unresolved. Chronic inflammation is characterized by increased oxidant formation, with this inducing protein modification, altered function and immunogenicity. Amylin, a peptide hormone co-secreted with insulin by β-cells, has attracted considerable interest for its amyloidogenic properties, however, the effects that oxidants have on amylin aggregation and function are poorly understood. Amylin was exposed in vitro to hypochlorous acid, hydrogen peroxide and peroxynitrous acid/peroxynitrite to investigate the formation of post-translational oxidative modifications (oxPTMs, via mass spectrometry) and fibril formation (via transmission electron microscopy). Amylin free acid (AFA) was also examined to investigate the role of the C-terminal amide in amylin. Oxidant exposure led to changes in aggregate morphology and abundance of oxPTMs in a concentration-dependent manner. The toxicity and immunogenic potential of oxidant-modified amylin or AFA on pancreatic islet cells (INS-1E), human monocyte cell line (THP-1) and monocyte-derived dendritic cells (moDCs) were examined using metabolic activity and cytokine assays, and flow cytometry. No significant changes in vitality or viability were detected, but exposure to oxidant-modified amylin or AFA resulted in altered immunogenicity when compared to the native proteins. THP-1 and moDCs show altered expression of activation markers and changes in cytokine secretion. Furthermore, oxidant-treated amylin and AFA promoted maturation of THP-1 and pre-mature moDCs, as determined by changes in size, and maturation markers.

Identification of bile acid-CoA:amino acid N-acyltransferase as the hepatic N-acyl taurine synthase for polyunsaturated fatty acids

N-acyl taurines (NATs) are bioactive lipids with emerging roles in glucose homeostasis and lipid metabolism. The acyl chains of hepatic and biliary NATs are enriched in polyunsaturated fatty acids (PUFAs). Dietary supplementation with a class of PUFAs, the omega-3 fatty acids, increases their cognate NATs in mice and humans. However, the synthesis pathway of the PUFA-containing NATs remains undiscovered. Here, we report that human livers synthesize NATs and that the acyl-chain preference is similar in murine liver homogenates. In the mouse, we found that hepatic NAT synthase activity localizes to the peroxisome and depends upon an active-site cysteine. Using unbiased metabolomics and proteomics, we identified bile acid-CoA:amino acid N-acyltransferase (BAAT) as the likely hepatic NAT synthase in vitro. Subsequently, we confirmed that BAAT knockout livers lack up to 90% of NAT synthase activity and that biliary PUFA-containing NATs are significantly reduced compared with wildtype. In conclusion, we identified the in vivo PUFA-NAT synthase in the murine liver and expanded the known substrates of the bile acid-conjugating enzyme, BAAT, beyond classic bile acids to the synthesis of a novel class of bioactive lipids.

Myeloperoxidase Alters Lung Cancer Cell Function to Benefit Their Survival

Myeloperoxidase (MPO) is a neutrophil-derived enzyme that has been recently associated with tumour development. However, the mechanisms by which this enzyme exerts its functions remain unclear. In this study, we investigated whether myeloperoxidase can alter the function of A549 human lung cancer cells. We observed that MPO promoted the proliferation of cancer cells and inhibited their apoptosis. Additionally, it increased the phosphorylation of AKT and ERK. MPO was rapidly bound to and internalized by A549 cells, retaining its enzymatic activity. Furthermore, MPO partially translocated into the nucleus and was detected in the chromatin-enriched fraction. Effects of MPO on cancer cell function could be reduced when MPO uptake was blocked with heparin or upon inhibition of the enzymatic activity with the MPO inhibitor 4-aminobenzoic acid hydrazide (4-ABAH). Lastly, we have shown that tumour-bearing mice treated with 4-ABAH had reduced tumour burden when compared to control mice. Our results highlight the role of MPO as a neutrophil-derived enzyme that can alter the function of lung cancer cells.

Effect of Sotagliflozin on Early Mortality and Heart Failure-Related Events: A Post Hoc Analysis of SOLOIST-WHF

BACKGROUND

Approximately 25% of patients admitted to hospitals for worsening heart failure (WHF) are readmitted within 30 days.

OBJECTIVES

The authors conducted a post hoc analysis of the SOLOIST-WHF (Effect of Sotagliflozin on Cardiovascular Events in Patients With Type 2 Diabetes Post-WHF) trial to evaluate the efficacy of sotagliflozin versus placebo to decrease mortality and HF-related events among patients who began study treatment on or before discharge from their index hospitalization.

METHODS

The main endpoint of interest was cardiovascular death or HF-related event (HF hospitalization or urgent care visit) occurring within 90 and 30 days after discharge for the index WHF hospitalization. Treatment comparisons were by proportional hazards models, generating HRs, 95% CIs, and P values.

RESULTS

Of 1,222 randomized patients, 596 received study drug on or before their date of discharge. Sotagliflozin reduced the main endpoint at 90 days after discharge (HR: 0.54 [95% CI: 0.35-0.82]; P = 0.004) and at 30 days (HR: 0.49 [95% CI: 0.27-0.91]; P = 0.023) and all-cause mortality at 90 days (HR: 0.39 [95% CI: 0.17-0.88]; P = 0.024). In subgroup analyses, sotagliflozin reduced the 90-day main endpoint regardless of sex, age, estimated glomerular filtration rate, N-terminal pro-B-type natriuretic peptide, left ventricular ejection fraction, or mineralocorticoid receptor agonist use. Sotagliflozin was well-tolerated but with slightly higher rates of diarrhea and volume-related events than placebo.

CONCLUSIONS

Starting sotagliflozin before discharge in patients with type 2 diabetes hospitalized for WHF significantly decreased cardiovascular deaths and HF events through 30 and 90 days after discharge, emphasizing the importance of beginning sodium glucose cotransporter treatment before discharge.

The inflammatory oxidant peroxynitrous acid modulates the structure and function of the recombinant human V3 isoform of the extracellular matrix proteoglycan versican

Continued oxidant production during chronic inflammation generates host tissue damage, with this being associated with pathologies including atherosclerosis. Atherosclerotic plaques contain modified proteins that may contribute to disease development, including plaque rupture, the major cause of heart attacks and strokes. Versican, a large extracellular matrix (ECM) chondroitin-sulfate proteoglycan, accumulates during atherogenesis, where it interacts with other ECM proteins, receptors and hyaluronan, and promotes inflammation. As activated leukocytes produce oxidants including peroxynitrite/peroxynitrous acid (ONOO^-/ONOOH) at sites of inflammation, we hypothesized that versican is an oxidant target, with this resulting in structural and functional changes that may exacerbate plaque development. The recombinant human V3 isoform of versican becomes aggregated on exposure to ONOO^-/ONOOH. Both reagent ONOO^-/ONOOH and SIN-1 (a thermal source of ONOO^-/ONOOH) modified Tyr, Trp and Met residues. ONOO^-/ONOOH mainly favors nitration of Tyr, whereas SIN-1 mostly induced hydroxylation of Tyr, and oxidation of Trp and Met. Peptide mass mapping indicated 26 sites with modifications (15 Tyr, 5 Trp, 6 Met), with the extent of modification quantified at 16. Multiple modifications, including the most extensively nitrated residue (Tyr¹⁶¹), are within the hyaluronan-binding region, and associated with decreased hyaluronan binding. ONOO^-/ONOOH modification also resulted in decreased cell adhesion and increased proliferation of human coronary artery smooth muscle cells. Evidence is also presented for colocalization of versican and 3-nitrotyrosine epitopes in advanced (type II-III) human atherosclerotic plaques. In conclusion, versican is readily modified by ONOO^-/ONOOH, resulting in chemical and structural modifications that affect protein function, including hyaluronan binding and cell interactions.

Identification and quantification of protein nitration sites in human coronary artery smooth muscle cells in the absence and presence of peroxynitrous acid/peroxynitrite

Peroxynitrous acid/peroxynitrite (ONOOH/ONOO^-) is a powerful oxidizing/nitrating system formed at sites of inflammation, which can modify biological targets, and particularly proteins. Here, we show that multiple proteins from primary human coronary artery smooth muscle cells are nitrated, with LC-MS peptide mass mapping providing data on the sites and extents of changes on cellular and extracellular matrix (ECM) proteins. Evidence is presented for selective and specific nitrations at Tyr and Trp on 11 cellular proteins (out of 3668, including 205 ECM species) in the absence of added reagent ONOOH/ONOO^-, with this being consistent with low-level endogenous nitration. A number of these have key roles in cell signaling/sensing and protein turnover. With added ONOOH/ONOO^-, more proteins were modified (84 total; with 129 nitrated Tyr and 23 nitrated Trp, with multiple modifications on some proteins), with this occurring at the same and additional sites to endogenous modification. With low concentrations of ONOOH/ONOO^- (50 μM) nitration occurs on specific proteins at particular sites, and is not driven by protein or Tyr/Trp abundance, with modifications detected on some low abundance proteins. However, with higher ONOOH/ONOO^- concentrations (500 μM), modification is primarily driven by protein abundance. ECM species are major targets and over-represented in the pool of modified proteins, with fibronectin and thrombospondin-1 being particularly heavily modified (12 sites in each case). Both endogenous and exogenous nitration of cell- and ECM-derived species may have significant effects on cell and protein function, and potentially be involved in the development and exacerbation of diseases such as atherosclerosis.

Treating atopic-dermatitis-like skin lesions in mice with gelatin-alginate films containing 1,4-anhydro-4-seleno-d-talitol (SeTal)

New compounds and pharmacological strategies offer alternatives for treating chronic skin diseases, such as atopic dermatitis (AD). Here, we investigated the incorporation of 1,4-anhydro-4-seleno-d-talitol (SeTal), a bioactive seleno-organic compound, in gelatin and alginate (Gel-Alg) polymeric films as a strategy for improving the treatment and attenuation of AD-like symptoms in a mice model. Hydrocortisone (HC) or vitamin C (VitC) were incorporated with SeTal in the Gel-Alg films, and their synergy was investigated. All the prepared film samples were able to retain and release SeTal in a controlled manner. In addition, appreciable film handling facilitates SeTal administration. A series of in-vivo/ex-vivo experiments were performed using mice sensitized with dinitrochlorobenzene (DNCB), which induces AD-like symptoms. Long-term topical application of the loaded Gel-Alg films attenuated disease symptoms and pruritus, with suppression of the levels of inflammatory markers, oxidative damage, and the skin lesions associated with AD. Moreover, the loaded films showed superior efficiency in attenuating the analyzed symptoms when compared to hydrocortisone (HC) cream, a traditional AD-treatment, and decreased the inherent drawbacks of this compound. In short, incorporating SeTal (by itself or with HC or VitC) in biopolymeric films provides a promising alternative for the long-term treatment of AD-type skin diseases.

Peroxyl radicals modify 6-phosphogluconolactonase from Escherichia coli via oxidation of specific amino acids and aggregation which inhibits enzyme activity

6-phosphogluconolactonase (6PGL) catalyzes the second reaction of the pentose phosphate pathway (PPP) converting 6-phosphogluconolactone to 6-phosphogluconate. The PPP is critical to the generation of NADPH and metabolic intermediates, but some of its components are susceptible to oxidative inactivation. Previous studies have characterized damage to the first (glucose-6-phosphate dehydrogenase) and third (6-phosphogluconate dehydrogenase) enzymes of the pathway, but no data are available for 6PGL. This knowledge gap is addressed here. Oxidation of Escherichia coli 6PGL by peroxyl radicals (ROO^•, from AAPH (2,2'-azobis(2-methylpropionamidine) dihydrochloride) was examined using SDS-PAGE, amino acid consumption, liquid chromatography with mass detection (LC-MS), protein carbonyl formation and computational methods. NADPH generation was assessed using mixtures all three enzymes of the oxidative phase of the PPP. Incubation of 6PGL with 10 or 100 mM AAPH resulted in protein aggregation mostly due to reducible (disulfide) bonds. High fluxes of ROO^• induced consumption of Cys, Met and Trp, with the Cys oxidation rationalizing the aggregate formation. Low levels of carbonyls were detected, while LC-MS analyses provided evidence for oxidation of selected Trp and Met residues (Met1, Trp18, Met41, Trp203, Met220 and Met221). ROO^• elicited little loss of enzymatic activity of monomeric 6PGL, but the aggregates showed diminished NADPH generation. This is consistent with in silico analyses that indicate that the modified Trp and Met are far from the 6-phosphogluconolactone binding site and the catalytic dyad (His130 and Arg179). Together these data indicate that monomeric 6PGL is a robust enzyme towards oxidative inactivation by ROO^• and when compared to other PPP enzymes.

Moderate-intensity stepping in older adults: insights from treadmill walking and daily living

BACKGROUND

A step cadence of 100 steps/minute is widely used to define moderate-intensity walking. However, the generalizability of this threshold to different populations needs further research. We investigate moderate-intensity step cadence values during treadmill walking and daily living in older adults.

METHODS

Older adults (≥ 60 years) were recruited from urban community venues. Data collection included 7 days of physical activity measured by an activPAL3™ thigh worn device, followed by a laboratory visit involving a 60-min assessment of resting metabolic rate, then a treadmill assessment with expired gas measured using a breath-by-breath analyser and steps measured by an activPAL3™. Treadmill stages were undertaken in a random order and lasted 5 min each at speeds of 1, 2, 3, 4 and 5 km/h. Metabolic equivalent values were determined for each stage as standardised values (METS_standard) and as multiples of resting metabolic rate (METS_relative). A value of 3 METS_standard defined moderate-intensity stepping. Segmented generalised estimating equations modelled the association between step cadence and MET values.

RESULTS

The study included 53 participants (median age = 75, years, BMI = 28.0 kg/m², 45.3% women). At 2 km/h, the median METS_standard and METS_relative values were above 3 with a median cadence of 81.00 (IQR 72.00, 88.67) steps/minute. The predicted cadence at 3 METS_standard was 70.3 (95% CI 61.4, 75.8) steps/minute. During free-living, participants undertook median (IQR) of 6988 (5933, 9211) steps/day, of which 2554 (1297, 4456) steps/day were undertaken in continuous stepping bouts lasting ≥ 1 min. For bouted daily steps, 96.4% (90.7%, 98.9%) were undertaken at ≥ 70 steps/minute.

CONCLUSION

A threshold as low as 70 steps/minute may be reflective of moderate-intensity stepping in older adults, with the vast majority of all bouted free-living stepping occurring above this threshold.

Sotagliflozin, a dual sodium-glucose co-transporter-1 and sodium-glucose co-transporter-2 inhibitor, reduces the risk of cardiovascular and kidney disease, as assessed by the Steno T1 Risk Engine in adults with type 1 diabetes

AIMS

Sotagliflozin (SOTA) as adjunct to insulin therapy improves glycemic control, reduces body weight and blood pressure, and increases time in range in adults with type 1 diabetes (T1D). SOTA demonstrated CV and kidney benefits in high-risk adults with type 2 diabetes. These potential benefits using SOTA for T1D may collectively outweigh the risk of diabetic ketoacidosis. The present analysis estimated the risk of CVD and kidney failure in adults with T1D treated with SOTA.

MATERIALS AND METHODS

Participant-level data were used from the inTandem trials evaluating 2980 adults with T1D randomized to once-daily placebo, SOTA 200 mg, or SOTA 400 mg for 24 weeks. For each participant, the cumulative risks of developing CVD and kidney failure were estimated using the Steno T1 Risk Engine. A subgroup analysis was performed in participants with BMI ≥ 27 kg/m² .

RESULTS

SOTA significantly reduced the predicted 5- and 10-year CVD risk in the SOTA 200 and 400 mg pooled group with a relative change in the SOTA group compared to the relative change in the placebo group of (mean [95%-confidence interval (CI)]) -6.6 (-7.9, -5.3) % and -6.4 (-7.6, -5.1) % (p < 0.0001 for both) respectively. For the 5-year ESKD risk there was a significant reduction with a relative change of -5.0 (-7.6, -2.3) % (p = 0.0003). Similar results were observed with the individual doses and in participants with BMI ≥ 27 kg/m² .

CONCLUSION

This analysis provides additional clinical results that may positively balance the benefit/risk assessment of SGLT inhibition use in T1D.

Effect of crowding, compartmentalization and nanodomains on protein modification and redox signaling - current state and future challenges

Biological milieus are highly crowded and heterogeneous systems where organization of macromolecules within nanodomains (e.g. membraneless compartments) is vital to the regulation of metabolic processes. There is an increasing interest in understanding the effects that such packed environments have on different biochemical and biological processes. In this context, the redox biochemistry and redox signaling fields are moving towards investigating oxidative processes under conditions that exhibit these key features of biological systems in order to solve existing paradigms including those related to the generation and transmission of specific redox signals within and between cells in both normal physiology and under conditions of oxidative stress. This review outlines the effects that crowding, nanodomain formation and altered local viscosities can have on biochemical processes involving proteins, and then discusses some of the reactions and pathways involving proteins and oxidants that may, or are known to, be modulated by these factors. We postulate that knowledge of protein modification processes (e.g. kinetics, pathways and product formation) under conditions that mimic biological milieus, will provide a better understanding of the response of cells to endogenous and exogenous stressors, and their role in ageing, signaling, health and disease.

Efficacy and safety of sotagliflozin in patients with type 2 diabetes and stage 3 chronic kidney disease

AIM

To assess the efficacy and safety of sotagliflozin, a dual inhibitor of sodium-glucose co-transporters 1 and 2, in adults with type 2 diabetes (T2D) and stage 3 chronic kidney disease (CKD3).

MATERIALS AND METHODS

This phase 3, randomized, placebo-controlled trial evaluated sotagliflozin 200 and 400 mg in 787 patients with T2D and an estimated glomerular filtration rate of 30-59 ml/min/1.73m² . The primary objective was superiority of week 26 HbA1c reductions with sotagliflozin versus placebo. Secondary endpoints included changes in other glycaemic and renal endpoints overall and in CKD3 subgroups.

RESULTS

At 26 weeks, the placebo-adjusted mean change in HbA1c (from a baseline of 8.3% ± 1.0%) was -0.1% (95% CI: -0.2% to 0.05%; P = .2095) and -0.2% (-0.4% to -0.09%; P = .0021) in the sotagliflozin 200 and 400 mg groups, respectively. Significant reductions in fasting plasma glucose and body weight, but not systolic blood pressure, were observed. Among patients with at least A2 albuminuria at week 26, the urine albumin-creatinine ratio (UACR) was reduced with both sotagliflozin doses relative to placebo. At week 52, UACR was reduced with sotagliflozin 200 mg in the CKD3B group. Adverse events (AEs), including serious AEs, were similar between the treatment groups.

CONCLUSIONS

After 26 weeks, HbA1c was significantly reduced with sotagliflozin 400 but not 200 mg compared with placebo in this CKD3 cohort. UACR in patients with at least A2 albuminuria was reduced with each of the two doses at 26 weeks, but changes were not sustained at week 52. The safety findings were consistent with previous reports (NCT03242252).

Hypochlorous Acid and Chloramines Induce Specific Fragmentation and Cross-Linking of the G1-IGD-G2 Domains of Recombinant Human Aggrecan, and Inhibit ADAMTS1 Activity

Atherosclerosis is a chronic inflammatory disease and a leading cause of mortality. It is characterized by arterial wall plaques that contain high levels of cholesterol and other lipids and activated leukocytes covered by a fibrous cap of extracellular matrix (ECM). The ECM undergoes remodelling during atherogenesis, with increased expression of aggrecan, a proteoglycan that binds low-density-lipoproteins (LDL). Aggrecan levels are regulated by proteases, including a disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1). Activated leukocytes release myeloperoxidase (MPO) extracellularly, where it binds to proteins and proteoglycans. Aggrecan may therefore mediate colocalization of MPO and LDL. MPO generates hypochlorous acid (HOCl) and chloramines (RNHCl species, from reaction of HOCl with amines on amino acids and proteins) that damage LDL and proteins, but effects on aggrecan have not been examined. The present study demonstrates that HOCl cleaves truncated (G1-IGD-G2) recombinant human aggrecan at specific sites within the IGD domain, with these being different from those induced by ADAMTS1 which also cleaves within this region. Irreversible protein cross-links are also formed dose-dependently. These effects are limited by the HOCl scavenger methionine. Chloramines including those formed on amino acids, proteins, and ECM materials induce similar damage. HOCl and taurine chloramines inactivate ADAMTS1 consistent with a switch from proteolytic to oxidative aggrecan fragmentation. Evidence is also presented for colocalization of aggrecan and HOCl-generated epitopes in advanced human atherosclerotic plaques. Overall, these data show that HOCl and chloramines can induce specific modifications on aggrecan, and that these effects are distinct from those of ADAMTS1.

Multiple oxidative post-translational modifications of human glutamine synthetase mediate peroxynitrite-dependent enzyme inactivation and aggregation

Glutamine synthetase (GS), which catalyzes the ATP-dependent synthesis of L-glutamine from L-glutamate and ammonia, is a ubiquitous and conserved enzyme that plays a pivotal role in nitrogen metabolism across all life domains. In vertebrates, GS is highly expressed in astrocytes, where its activity sustains the glutamate-glutamine cycle at glutamatergic synapses and is thus essential for maintaining brain homeostasis. In fact, decreased GS levels or activity have been associated with neurodegenerative diseases, with these alterations attributed to oxidative post-translational modifications of the protein, in particular tyrosine nitration. In this study, we expressed and purified human GS (HsGS) and performed an in-depth analysis of its oxidative inactivation by peroxynitrite (ONOO^-) in vitro. We found that ONOO^- exposure led to a dose-dependent loss of HsGS activity, the oxidation of cysteine, methionine, and tyrosine residues and also the nitration of tryptophan and tyrosine residues. Peptide mapping by LC-MS/MS through combined H₂¹⁶O/H₂¹⁸O trypsin digestion identified up to 10 tyrosine nitration sites and five types of dityrosine cross-links; these modifications were further scrutinized by structural analysis. Tyrosine residues 171, 185, 269, 283, and 336 were the main nitration targets; however, tyrosine-to-phenylalanine HsGS mutants revealed that their sole nitration was not responsible for enzyme inactivation. In addition, we observed that ONOO^- induced HsGS aggregation and activity loss. Thiol oxidation was a key modification to elicit aggregation, as it was also induced by hydrogen peroxide treatment. Taken together, our results indicate that multiple oxidative events at various sites are responsible for the inactivation and aggregation of human GS.

The cysteine residue in beta-lactoglobulin reacts with oxidized tyrosine residues in beta-casein to give casein-lactoglobulin dimers

Proteins are modified during milk processing and storage, with sidechain oxidation and crosslinking being major consequences. Despite the prevalence and importance of proteins in milk, and particularly caseins (∼80% of total content), the nature of the cross-links formed by oxidation, and their mechanisms of formation, are poorly characterized. In this study, we investigated the formation and stability of cross-links generated by the nucleophilic addition of Cys residues to quinones generated on oxidation of Tyr residues. The mechanisms and stability of these adducts was explored using ubiquitin as a model protein, and β-casein. Ubiquitin and β-casein were oxidized using a rose Bengal/visible light/O₂ system, or by the enzyme tyrosinase. The oxidized proteins were incubated with glutathione or β-lactoglobulin (non-oxidized, but unfolded by treatment at 70 °C), before analysis by SDS-PAGE, immunoblotting and LC-MS. Our data indicate that Cys-quinone adducts are readily-formed, and are stable for >48 h. Thus, oxidized β-casein reacts efficiently with the thermally unfolded β-lactoglobulin, likely via Michael addition of the exposed Cys to a Tyr-derived quinone. These data provide a novel, and possibly general, mechanism of protein cross-link formation, and provides information of the stability of these species that have potential as markers of protein quality.

The feasibility of a self-management programme (My Life After Stroke; MLAS) for stroke survivors

PURPOSE

An evidence-based, theory-driven self-management programme "My Life After Stroke" (MLAS) was developed to address the longer-term unmet needs of stroke survivors.This study's aim was to test the acceptability and feasibility of MLAS as well as exploring what outcomes measures to include as part of further testing.

METHODS

Stroke registers in four GP practices across Leicester and Cambridge were screened, invite letters sent to eligible stroke survivors and written, informed consent gained. Questionnaires including Southampton Stroke Self-Management Questionnaire (SSSMQ) were completed before and after MLAS.Participants (and carers) attended MLAS (consisting of two individual appointments and four group sessions) over nine weeks, delivered by two trained facilitators. Feedback was gained from participants (after the final group session and final individual appointment) and facilitators.

RESULTS

Seventeen of 36 interested stroke survivors participated alongside seven associated carers. 15/17 completed the programme and attendance ranged from 13-17 per session. A positive change of 3.5 of the SSSMQ was observed. Positive feedback was gained from facilitators and 14/15 participants recommended MLAS (one did not respond).

CONCLUSIONS

MLAS was a feasible self-management programme for stroke survivors and warrants further testing as part of the Improving Primary Care After Stroke (IPCAS) cluster randomised controlled trial.IMPLICATIONS FOR REHABILITATIONMy Life After Stroke is a self-management programme developed for stroke survivors living in the community.MLAS is feasible and acceptable to stroke survivors.MLAS could be considered to help address the unmet educational and psychological needs of stroke survivors.

Anastellin impacts on the processing of extracellular matrix fibronectin and stimulates release of cytokines from coronary artery smooth muscle cells

Anastellin, a recombinant protein fragment from the first type III module of fibronectin, mimics a partially unfolded intermediate implicated in the assembly of fibronectin fibrils. Anastellin influences the structure of fibronectin and initiates in vitro fibrillation, yielding "superfibronectin", a polymer with enhanced cell-adhesive properties. This ability is absent in an anastellin double mutant, L37AY40A. Here we demonstrate that both wild-type and L37AY40A anastellin affect fibronectin processing within the extracellular matrix (ECM) of smooth muscle cells. Fibronectin fibrils are diminished in the ECM from cells treated with anastellin, but are partially rescued by supplementation with plasma fibronectin in cell media. Proteomic analyses reveal that anastellin also impacts on the processing of other ECM proteins, with increased collagen and decreased laminin detected in media from cells exposed to wild-type anastellin. Moreover, both anastellin forms stimulate release of inflammatory cytokines, including interleukin 6. At the molecular level, L37AY40A does not exhibit major perturbations of structural features relative to wild-type anastellin, though the mutant showed differences in heparin binding characteristics. These findings indicate that wild-type and L37AY40A anastellin share similar molecular features but elicit slightly different, but partially overlapping, responses in smooth muscle cells resulting in altered secretion of cytokines and proteins involved in ECM processing.

Identification of galectin-1 and other cellular targets of alpha,beta-unsaturated carbonyl compounds, including dimethylfumarate, by use of click-chemistry probes

α,β-Unsaturated carbonyls are a common motif in environmental toxins (e.g. acrolein) as well as therapeutic drugs, including dimethylfumarate (DMFU) and monomethylfumarate (MMFU), which are used to treat multiple sclerosis and psoriasis. These compounds form adducts with protein Cys residues as well as other nucleophiles. The specific targets ('adductome') that give rise to their therapeutic or toxic activities are poorly understood. This is due, at least in part, to the absence of antigens or chromophores/fluorophores in these compounds. We have recently reported click-chemistry probes of DMFU and MMFU (Redox Biol., 2022, 52, 102299) that allow adducted proteins to be visualized and enriched for further characterization. In the current study, we hypothesized that adducted proteins could be 'clicked' to agarose beads and thereby isolated for LC-MS analysis of DMFU/MMFU targets in primary human coronary artery smooth muscle cells. We show that the probes react with thiols with similar rate constants to the parent drugs, and give rise to comparable patterns of gene induction, confirming similar biological actions. LC-MS proteomic analysis identified ∼2970 cellular targets of DMFU, ∼1440 for MMFU, and ∼140 for the control (succinate-probe) treated samples. The most extensively modified proteins were galectin-1, annexin-A2, voltage dependent anion channel-2 and vimentin. Other previously postulated DMFU targets, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH), cofilin, p65 (RELA) and Keap1 were also identified as adducted species, though at lower levels with the exception of GAPDH. These data demonstrate the utility of the click-chemistry approach to the identification of cellular protein targets of both exogenous and endogenous compounds.

Aryl Fluorosulfate Based Inhibitors That Covalently Target the SIRT5 Lysine Deacylase

The sirtuin enzymes are a family of lysine deacylases that regulate gene transcription and metabolism. Sirtuin 5 (SIRT5) hydrolyzes malonyl, succinyl, and glutaryl ϵ-N-carboxyacyllysine posttranslational modifications and has recently emerged as a vulnerability in certain cancers. However, chemical probes to illuminate its potential as a pharmacological target have been lacking. Here we report the harnessing of aryl fluorosulfate-based electrophiles as an avenue to furnish covalent inhibitors that target SIRT5. Alkyne-tagged affinity-labeling agents recognize and capture overexpressed SIRT5 in cultured HEK293T cells and can label SIRT5 in the hearts of mice upon intravenous injection of the compound. This work demonstrates the utility of aryl fluorosulfate electrophiles for targeting of SIRT5 and suggests this as a means for the development of potential covalent drug candidates. It is our hope that these results will serve as inspiration for future studies investigating SIRT5 and general sirtuin biology in the mitochondria.

Crowding modulates the glycation of plasma proteins: In vitro analysis of structural modifications to albumin and transferrin and identification of sites of modification

Protein modification occurs in biological milieus that are characterized by high concentrations of (macro)molecules (i.e. heterogeneous and packed environments). Recent data indicate that crowding can modulate the extent and rate of protein oxidation, however its effect on other post-translational modifications remains to be explored. In this work we hypothesized that crowding would affect the glycation of plasma proteins. Physiologically-relevant concentrations of albumin (35 mg mL^-1) and transferrin (2 mg mL^-1) were incubated with methylglyoxal and glyoxal (5 μM-5 mM), two α-oxoaldehyde metabolites that are elevated in the plasma of people with diabetes. Crowding was induced by adding dextran or ficoll polymers. Electrophoresis, electron microscopy, fluorescence spectroscopy and mass spectrometry were employed to investigate the structural consequences of glycation under crowded conditions. Our data demonstrate that crowding modulates the extent of formation of transferrin cross-links, and also the modification pathways in both albumin and transferrin. Arginine was the most susceptible residue to modification, with lysine and cysteine also affected. Loss of 0.48 and 7.28 arginine residues per protein molecule were determined on incubation with 500 μM methylglyoxal for albumin and transferrin, respectively. Crowding did not influence the extent of loss of arginine and lysine for either protein, but the sites of modification, detected by LC-MS, were different between dilute and crowded conditions. These data confirm the relevance of studying modification processes under conditions that closely mimic biological milieus. These data unveil additional factors that influence the pattern and extent of protein modification, and their structural consequences, in biological systems.

Self-reported walking pace, polygenic risk scores and risk of coronary artery disease in UK biobank

BACKGROUND AND AIMS

Both polygenic risk scores (PGS) and self-reported walking pace have been shown to predict cardiovascular disease; whether combining both factors produces greater risk differentiation is, however, unknown.

METHODS AND RESULTS

We estimated the 10-year absolute risk of coronary artery disease (CAD), adjusted for traditional risk factors, and the C-index across nine PGS and self-reported walking pace in UK Biobank study participants between Mar/2006-Feb/2021. In 380,693 individuals (54.8% women), over a median (5th, 95th percentile) of 11.9 (8.3, 13.4) years, 2,603 (1.2%) CAD events occurred in women and 8,259 (4.8%) in men. Both walking pace and genetic risk were strongly associated with CAD. The absolute 10-year risk of CAD was highest in slow walkers at high genetic risk (top 20% of PGS): 2.72% (95% CI: 2.30-3.13) in women; 9.60% (8.62-10.57) in men. The risk difference between slow and brisk walkers was greater at higher [1.26% (0.81-1.71) in women; 3.63% (2.58-4.67) in men] than lower [0.76% (0.59-0.93) and 2.37% (1.96-2.78), respectively] genetic risk. Brisk walkers at high genetic risk had equivalent (women) or higher (men) risk than slow walkers at moderate-to-low genetic risk (bottom 80% of PGS). When added to a model containing traditional risk factors, both factors separately improved risk discrimination; combining them resulted in the greatest discrimination: C-index of 0.801 (0.793-0.808) in women; 0.732 (0.728-0.737) in men.

CONCLUSION

Self-reported slow walkers at high genetic risk had the greatest risk of CAD, identifying a potentially important population for intervention. Both PGS and walking pace contributed to risk discrimination.

Electrophile versus oxidant modification of cysteine residues: Kinetics as a key driver of protein modification

Humans have widespread exposure to both oxidants, and soft electrophilic compounds such as alpha,beta-unsaturated aldehydes and quinones. Electrophilic motifs are commonly found in a drugs, industrial chemicals, pollutants and are also generated via oxidant-mediated degradation of biomolecules including lipids (e.g. formation of 4-hydroxynonenal, 4-hydroxyhexenal, prostaglandin J2). All of these classes of compounds react efficiently with Cys residues, and the particularly the thiolate anion, with this resulting in Cys modification via either oxidation or adduct formation. This can result in deleterious or beneficial effects, that are either reversible (e.g. in cell signalling) or irreversible (damaging). For example, acrolein is a well-established toxin, whereas dimethylfumarate is used in the treatment of multiple sclerosis and psoriasis. This short review discusses the targets of alpha,beta-unsaturated aldehydes, and particularly two prototypic cases, acrolein and dimethylfumarate, and the factors that control the selectivity and kinetics of reaction of these species. Comparison is made between the reactivity of oxidants versus soft electrophiles. These rate constants indicate that electrophiles can be significant thiol modifying agents in some situations, as they have rate constants similar to or greater than species such as H₂O₂, can be present at higher concentrations, and are less efficiently removed by protective systems when compared to H₂O₂. They may also induce similar or higher levels of modification than highly reactive oxidants, due to the very low concentrations of oxidants formed in most in vivo situations.

Loss of Nuclear Envelope Integrity and Increased Oxidant Production Cause DNA Damage in Adult Hearts Deficient in PKP2: A Molecular Substrate of ARVC

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by high propensity to life-threatening arrhythmias and progressive loss of heart muscle. More than 40% of reported genetic variants linked to ARVC reside in the PKP2 gene, which encodes the PKP2 protein (plakophilin-2).

METHODS

We describe a comprehensive characterization of the ARVC molecular landscape as determined by high-resolution mass spectrometry, RNA sequencing, and transmission electron microscopy of right ventricular biopsy samples obtained from patients with ARVC with PKP2 mutations and left ventricular ejection fraction >45%. Samples from healthy relatives served as controls. The observations led to experimental work using multiple imaging and biochemical techniques in mice with a cardiac-specific deletion of Pkp2 studied at a time of preserved left ventricular ejection fraction and in human induced pluripotent stem cell-derived PKP2-deficient myocytes.

RESULTS

Samples from patients with ARVC present a loss of nuclear envelope integrity, molecular signatures indicative of increased DNA damage, and a deficit in transcripts coding for proteins in the electron transport chain. Mice with a cardiac-specific deletion of Pkp2 also present a loss of nuclear envelope integrity, which leads to DNA damage and subsequent excess oxidant production (O2.- and H2O2), the latter increased further under mechanical stress (isoproterenol or exercise). Increased oxidant production and DNA damage is recapitulated in human induced pluripotent stem cell-derived PKP2-deficient myocytes. Furthermore, PKP2-deficient cells release H2O2 into the extracellular environment, causing DNA damage and increased oxidant production in neighboring myocytes in a paracrine manner. Treatment with honokiol increases SIRT3 (mitochondrial nicotinamide adenine dinucleotide-dependent protein deacetylase sirtuin-3) activity, reduces oxidant levels and DNA damage in vitro and in vivo, reduces collagen abundance in the right ventricular free wall, and has a protective effect on right ventricular function.

CONCLUSIONS

Loss of nuclear envelope integrity and subsequent DNA damage is a key substrate in the molecular pathology of ARVC. We show transcriptional downregulation of proteins of the electron transcript chain as an early event in the molecular pathophysiology of the disease (before loss of left ventricular ejection fraction <45%), which associates with increased oxidant production (O2.- and H2O2). We propose therapies that limit oxidant formation as a possible intervention to restrict DNA damage in ARVC.

Role of amino acid oxidation and protein unfolding in peroxyl radical and peroxynitrite-induced inactivation of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides

The mechanisms underlying the inactivation of Leuconostoc mesenteroides glucose 6-phosphate dehydrogenase (G6PDH) induced by peroxyl radicals (ROO^●) and peroxynitrite (ONOO^-), were explored. G6PDH was incubated with AAPH (2,2' -azobis(2-methylpropionamidine)dihydrochloride), used as ROO^● source, and ONOO^-. Enzymatic activity was assessed by NADPH generation, while oxidative modifications were analyzed by gel electrophoresis and liquid chromatography (LC) with fluorescence and mass detection. Changes in protein conformation were studied by circular dichroism (CD) and binding of the fluorescent dye ANS (1-anilinonaphthalene-8-sulfonic acid). Incubation of G6PDH (54.4 μM) with 60 mM AAPH showed an initial phase without significant changes in enzymatic activity, followed by a secondary time-dependent continuous decrease in activity to ∼59% of the initial level after 90 min. ONOO^- induced a significant and concentration-dependent loss of G6PDH activity with ∼46% of the initial activity lost on treatment with 1.5 mM ONOO^-. CD and ANS fluorescence indicated changes in G6PDH secondary structure with exposure of hydrophobic sites on exposure to ROO^●, but not ONOO^-. LC-MS analysis provided evidence for ONOO^--mediated oxidation of Tyr, Met and Trp residues, with damage to critical Met and Tyr residues underlying enzyme inactivation, but without effects on the native (dimeric) state of the protein. In contrast, studies using chloramine T, a specific oxidant of Met, provided evidence that oxidation of specific Met and Trp residues and concomitant protein unfolding, loss of dimer structure and protein aggregation are involved in G6PDH inactivation by ROO^●. These two oxidant systems therefore have markedly different effects on G6PDH structure and activity.

Activation and Inhibition of Human Matrix Metalloproteinase-9 (MMP9) by HOCl, Myeloperoxidase and Chloramines

Matrix metalloproteinase-9 (MMP9, gelatinase B) plays a key role in the degradation of extracellular-matrix (ECM) proteins in both normal physiology and multiple pathologies, including those linked with inflammation. MMP9 is excreted as an inactive proform (proMMP9) by multiple cells, and particularly neutrophils. The proenzyme undergoes subsequent processing to active forms, either enzymatically (e.g., via plasmin and stromelysin-1/MMP3), or via the oxidation of a cysteine residue in the prodomain (the “cysteine-switch”). Activated leukocytes, including neutrophils, generate O₂⁻ and H₂O₂ and release myeloperoxidase (MPO), which catalyzes hypochlorous acid (HOCl) formation. Here, we examine the reactivity of HOCl and a range of low-molecular-mass and protein chloramines with the pro- and activated forms of MMP9. HOCl and an enzymatic MPO/H₂O₂/Cl⁻ system were able to generate active MMP9, as determined by fluorescence-activity assays and gel zymography. The inactivation of active MMP9 also occurred at high HOCl concentrations. Low (nM—low μM) concentrations of chloramines formed by the reaction of HOCl with amino acids (taurine, lysine, histidine), serum albumin, ECM proteins (laminin and fibronectin) and basement membrane extracts (but not HEPES chloramines) also activate proMMP9. This activation is diminished by the competitive HOCl-reactive species, methionine. These data indicate that HOCl-mediated oxidation and MMP-mediated ECM degradation are synergistic and interdependent. As previous studies have shown that modified ECM proteins can also stimulate the cellular expression of MMP proteins, these processes may contribute to a vicious cycle of increasing ECM degradation during disease development.

Influence of plasma halide, pseudohalide and nitrite ions on myeloperoxidase-mediated protein and extracellular matrix damage

Myeloperoxidase (MPO) mediates pathogen destruction by generating the bactericidal oxidant hypochlorous acid (HOCl). Formation of this oxidant is however associated with host tissue damage and disease. MPO also utilizes H₂O₂ to oxidize other substrates, and we hypothesized that mixtures of other plasma anions, including bromide (Br^-), iodide (I^-), thiocyanate (SCN^-) and nitrite (NO₂^-), at normal or supplemented concentrations, might modulate MPO-mediated HOCl damage. For the (pseudo)halide anions, only SCN^- significantly modulated HOCl formation (IC₅₀ ∼33 μM), which is within the normal physiological range, as judged by damage to human plasma fibronectin or extracellular matrix preparations detected by ELISA and LC-MS. NO₂^- modulated HOCl-mediated damage, in a dose-dependent manner, at physiologically-attainable anion concentrations. However, this was accompanied by increased tyrosine and tryptophan nitration (detected by ELISA and LC-MS), and the overall extent of damage remained approximately constant. Increasing NO₂^- concentrations (0.5-20 μM) diminished HOCl-mediated modification of tyrosine and methionine, whereas tryptophan loss was enhanced. At higher NO₂^- concentrations, enhanced tyrosine and methionine loss was detected. These analytical data were confirmed in studies of cell adhesion and metabolic activity. Together, these data indicate that endogenous plasma levels of SCN^- (but not Br^- or I^-) can modulate protein modification induced by MPO, including the extent of chlorination. In contrast, NO₂^- alters the type of modification, but does not markedly decrease its extent, with chlorination replaced by nitration. These data also indicate that MPO could be a major source of nitration in vivo, and particularly at inflammatory sites where NO₂^- levels are often elevated.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Oxidant-mediated modification and cross-linking of beta-2-microglobulin

Beta-2-microglobulin (B2M) is synthesized by all nucleated cells and forms part of the major histocompatibility complex (MHC) class-1 present on cell surfaces, which presents peptide fragments to cytotoxic CD8⁺ T-lymphocytes, or by association with CD1, antigenic lipids to natural killer T-cells. Knockout of B2M results in loss of these functions and severe combined immunodeficiency. Plasma levels of this protein are low in healthy serum, but are elevated up to 50-fold in some pathologies including chronic kidney disease and multiple myeloma, where it has both diagnostic and prognostic value. High levels of the protein are associated with amyloid formation, with such deposits containing significant levels of modified or truncated protein. In the current study we examine the chemical and structural changes induced of B2M generated by both inflammatory oxidants (HOCl and ONOOH), and photo-oxidation (¹O₂) which is linked with immunosuppression. Oxidation results in oligomer formation, with this occurring most readily with HOCl and ¹O₂, and a loss of native protein conformation. LC-MS analysis provided evidence for nitrated (from ONOOH), chlorinated (from HOCl) and oxidized residues (all oxidants) with damage detected at Tyr, Trp, and Met residues, together with cleavage of the disulfide (cystine) bond. An intermolecular di-tyrosine crosslink is also formed between Tyr10 and Tyr63. The pattern of these modifications is oxidant specific, with ONOOH inducing a greater range of modifications than HOCl. Comparison of the sites of modification with regions identified as amyloidogenic indicate significant co-localization, consistent with the hypothesis that oxidation may contribute, and predispose B2M, to amyloid formation.

Proteomic Characterization of Atherosclerotic Lesions In Situ Using Percutaneous Coronary Intervention Angioplasty Balloons-Brief Report

BACKGROUND

Materials extracted from atherosclerotic arteries can disclose data about the molecular pathology of cardiovascular disease, but obtaining such samples is complex and requires invasive surgery. To overcome this barrier, this study investigated whether angioplasty balloons inflated during standard percutaneous coronary interventions retain proteins from treated (dilated) atherosclerotic lesions and whether proteomic analysis of this material could provide data on lesion protein profiles and distinguish between patients with stable and unstable coronary artery disease.

METHODS

Patients with ST-segment-elevation myocardial infarction and stable angina pectoris were subjected to routine percutaneous coronary interventions. All angioplasty balloons inflated in a coronary artery were collected. Proteins retained on the balloons were extracted and analyzed using shotgun proteomic analysis.

RESULTS

Proteomics identified and quantified 1365 unique proteins captured on percutaneous coronary intervention balloons. Control balloons inflated in the ascending aorta showed minimal nonspecific protein binding, indicating specificity to the luminal region of atherosclerotic lesions of the diseased artery wall. Clustering and principal component analyses showed that ST-segment-elevation myocardial infarction and stable angina pectoris subjects could be separated by variations in protein content and abundance. We identified 206 proteins as differentially abundant between ST-segment-elevation myocardial infarction and stable angina pectoris subjects. Pathway analysis indicated several enriched processes in the ST-segment-elevation myocardial infarction group involved in neutrophil-mediated immunity and platelet activation.

CONCLUSIONS

Disease-related proteins from coronary artery lesions adhere to angioplasty balloons and constitute a source of material for proteomic analysis. This approach can identify proteins and processes occurring in unstable coronary atherosclerotic lesions and suggest novel therapeutic approaches.

Defining roles of specific reactive oxygen species (ROS) in cell biology and physiology

'Reactive oxygen species' (ROS) is a generic term that defines a wide variety of oxidant molecules with vastly different properties and biological functions that range from signalling to causing cell damage. Consequently, the description of oxidants needs to be chemically precise to translate research on their biological effects into therapeutic benefit in redox medicine. This Expert Recommendation article pinpoints key issues associated with identifying the physiological roles of oxidants, focusing on H₂O₂ and O₂^.-. The generic term ROS should not be used to describe specific molecular agents. We also advocate for greater precision in measurement of H₂O₂, O₂^.- and other oxidants, along with more specific identification of their signalling targets. Future work should also consider inter-organellar communication and the interactions of redox-sensitive signalling targets within organs and whole organisms, including the contribution of environmental exposures. To achieve these goals, development of tools that enable site-specific and real-time detection and quantification of individual oxidants in cells and model organisms are needed. We also stress that physiological O₂ levels should be maintained in cell culture to better mimic in vivo redox reactions associated with specific cell types. Use of precise definitions and analytical tools will help harmonize research among the many scientific disciplines working on the common goal of understanding redox biology.

Structural Basis for Dityrosine-Mediated Inhibition of α-Synuclein Fibrillization

α-Synuclein (α-Syn) is an intrinsically disordered protein which self-assembles into highly organized β-sheet structures that accumulate in plaques in brains of Parkinson’s disease patients. Oxidative stress influences α-Syn structure and self-assembly; however, the basis for this remains unclear. Here we characterize the chemical and physical effects of mild oxidation on monomeric α-Syn and its aggregation. Using a combination of biophysical methods, small-angle X-ray scattering, and native ion mobility mass spectrometry, we find that oxidation leads to formation of intramolecular dityrosine cross-linkages and a compaction of the α-Syn monomer by a factor of √2. Oxidation-induced compaction is shown to inhibit ordered self-assembly and amyloid formation by steric hindrance, suggesting an important role of mild oxidation in preventing amyloid formation.

Peroxynitrous acid-modified extracellular matrix alters gene and protein expression in human coronary artery smooth muscle cells and induces a pro-inflammatory phenotype

Leukocytes produce oxidants at inflammatory sites, including within the artery wall during the development of atherosclerosis. Developing lesions contain high numbers of activated leukocytes that generate reactive nitrogen species, including peroxynitrite/peroxynitrous acid (ONOO^-/ONOOH), as evidenced by the presence of oxidized/nitrated molecules including extracellular matrix (ECM) proteins. ECM materials are critical for arterial wall integrity, function, and determine cell phenotype, with smooth muscle cells undergoing a phenotypic switch from quiescent/contractile to proliferative/synthetic during disease development. We hypothesized that ECM modification by ONOO^-/ONOOH might drive this switch, and thereby potentially contribute to atherogenesis. ECM generated by primary human coronary artery smooth muscle cells (HCASMCs) was treated with increasing ONOO^-/ONOOH concentrations (1-1000 μM). This generated significant damage on laminin, fibronectin and versican, and lower levels on collagens and glycosaminoglycans, together with the increasing concentrations of the damage biomarker 3-nitrotyrosine. Adhesion of naïve HCASMC to ECM modified by 1 μM ONOO^-/ONOOH was enhanced, but significantly diminished by higher ONOO^-/ONOOH treatment. Cell proliferation and metabolic activity were significantly enhanced by 100 μM ONOO^-/ONOOH pre-treatment. These changes were accompanied by increased expression of genes involved in mitosis (PCNA, CCNA1, CCNB1), ECM (LAMA4, LAMB1, VCAN, FN1) and inflammation (IL-1B, IL-6, VCAM-1), and corresponding protein secretion (except VCAM-1) into the medium. These changes induced by modified ECM are consistent with HCASMC switching to a synthetic/proliferative/pro-inflammatory phenotype, together with ECM remodelling. These changes model those in atherosclerosis, suggesting a link between oxidant-modified ECM and disease progression, and highlight the potential of targeting oxidant generation as a therapeutic strategy.

Guidelines for measuring reactive oxygen species and oxidative damage in cells and in vivo

Multiple roles of reactive oxygen species (ROS) and their consequences for health and disease are emerging throughout biological sciences. This development has led researchers unfamiliar with the complexities of ROS and their reactions to employ commercial kits and probes to measure ROS and oxidative damage inappropriately, treating ROS (a generic abbreviation) as if it were a discrete molecular entity. Unfortunately, the application and interpretation of these measurements are fraught with challenges and limitations. This can lead to misleading claims entering the literature and impeding progress, despite a well-established body of knowledge on how best to assess individual ROS, their reactions, role as signalling molecules and the oxidative damage that they can cause. In this consensus statement we illuminate problems that can arise with many commonly used approaches for measurement of ROS and oxidative damage, and propose guidelines for best practice. We hope that these strategies will be useful to those who find their research requiring assessment of ROS, oxidative damage and redox signalling in cells and in vivo.

Synthesis and cellular evaluation of click-chemistry probes to study the biological effects of alpha, beta-unsaturated carbonyls

Humans are commonly exposed to α,β-unsaturated carbonyls as both environmental toxins (e.g. acrolein) and therapeutic drugs (e.g. dimethylfumarate, DMFU, a front-line drug for the treatment of multiple sclerosis and psoriasis). These compounds undergo rapid Michael addition reactions with amine, imidazole and thiol groups on biological targets, with reaction at protein Cys residues being a major reaction pathway. However, the cellular targets of these species (the ‘adductome’) are poorly understood due to the absence of readily identifiable tags or reporter groups (chromophores/fluorophores or antigens) on many α,β-unsaturated carbonyls. Here we report a ‘proof of concept’ study in which we synthesize novel α,β-unsaturated carbonyls containing an alkyne function introduced at remote sites on the α,β-unsaturated carbonyl compounds (e.g. one of the methyl groups of dimethylfumarate). The presence of this tag allows ‘click-chemistry’ to be used to visualize, isolate, enrich and characterize the cellular targets of such compounds. The probes show similar selectivity and reactivity to the parent compounds, and compete for cellular targets, yielding long-lived (stable) adducts that can be visualized in intact cells (such as primary human coronary artery smooth muscle cells), and extracted and enriched for subsequent target analysis. It is shown using this approach that dimethylfumarate forms adducts with multiple intracellular targets including cytoskeletal, organelle and nuclear species, with these including the rate-limiting glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). This approach should be amenable to use with multiple α,β-unsaturated carbonyls and a wide variety of targets containing nucleophilic sites.

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Humans are widely exposed to α,β-unsaturated carbonyls via drugs and environmental toxins.

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These compounds react with cellular targets, and particularly Cys residues, via Michael addition.

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Alkyne tagged derivatives have been synthesized to allow click chemistry detection.

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These tags allow visualization, extraction, enrichment and identification of adducted proteins.

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GAPDH reacts with dimethylfumarate, with adducts detected in both the cytosol and nucleus.