Maternal nano-titanium dioxide inhalation exposure alters placental cyclooxygenase and oxidant balance in a sexually dimorphic manner

The placenta plays a critical role in nutrient-waste exchange between the maternal and fetal circulation, and thus impacts fetal growth and development. We have previously shown that nano-titanium dioxide (nano-TiO2) inhalation exposure during gestation decreased fetal female pup and placenta mass [1], which persists in the following generation [2]. In utero exposed females, once mated, their offspring's placentas had increased capacity for H2O2 production. Generation of oxidants such as hydrogen peroxide (H2O2), have been shown to impact cyclooxygenase activity, specifically metabolites such as prostacyclin (PGI2) or thromboxane (TXA2). Therefore, we hypothesized that maternal nano-TiO2 inhalation exposure during gestation results in alterations in placental production of prostacyclin and thromboxane mediated by enhanced H2O2 production in a sexually dimorphic manner. Pregnant Sprague-Dawley rats were exposed to nano-TiO2 aerosols or filtered air (sham--control) from gestational day (GD) 10-19. Dams were euthanized on GD 20, and fetal serum and placental tissue were collected based on fetal sex. Fetal placental zones (junctional zone (JZ) and labyrinth zone (LZ)) were assessed for xanthine oxidoreductase (XOR) activity, H2O2, and catalase activity, as well as 6-keto-PGF1α and TXB2 levels. Nano-TiO2 exposed fetal female LZ demonstrated significantly greater XOR activity compared to exposed males. Exposed fetal female LZ also demonstrated significantly diminished catalase activity compared to sham-control females. Exposed fetal female LZ had significantly increased abundance of 6-keto-PGF1α compared to sham-control females and increased TXB2 compared to exposed males. In the aggregate these data indicate that maternal nano-TiO2 inhalation exposure has a greater impact on redox homeostasis and PGI2/TXA2 balance in the fetal female LZ. Future studies need to address if treatment with an XO inhibitor during gestation can prevent diminished fetal female growth during maternal nano-TiO2 inhalation exposure.

Hemin and iron increase synthesis and trigger export of xanthine oxidoreductase from hepatocytes to the circulation

We recently reported a previously unknown salutary role for xanthine oxidoreductase (XOR) in intravascular heme overload whereby hepatocellular export of XOR to the circulation was identified as a seminal step in affording protection. However, the cellular signaling and export mechanisms underpinning this process were not identified. Here, we present novel data showing hepatocytes upregulate XOR expression/protein abundance and actively release it to the extracellular compartment following exposure to hemopexin-bound hemin, hemin or free iron. For example, murine (AML-12 cells) hepatocytes treated with hemin (10 μM) exported XOR to the medium in the absence of cell death or loss of membrane integrity (2.0 ± 1.0 vs 16 ± 9 μU/mL p < 0.0001). The path of exocytosis was found to be noncanonical as pretreatment of the hepatocytes with Vaculin-1, a lysosomal trafficking inhibitor, and not Brefeldin A inhibited XOR release and promoted intracellular XOR accumulation (84 ± 17 vs 24 ± 8 hemin vs 5 ± 3 control μU/mg). Interestingly, free iron (Fe2+ and Fe3+) induced similar upregulation and release of XOR compared to hemin. Conversely, concomitant treatment with hemin and the classic transition metal chelator DTPA (20 μM) or uric acid completely blocked XOR release (p < 0.01). Our previously published time course showed XOR release from hepatocytes likely required transcriptional upregulation. As such, we determined that both Sp1 and NF-kB were acutely activated by hemin treatment (∼2-fold > controls for both, p < 0.05) and that silencing either or TLR4 with siRNA prevented hemin-induced XOR upregulation (p < 0.01). Finally, to confirm direct action of these transcription factors on the Xdh gene, chromatin immunoprecipitation was performed indicating that hemin significantly enriched (∼5-fold) both Sp1 and NF-kB near the transcription start site. In summary, our study identified a previously unknown pathway by which XOR is upregulated via SP1/NF-kB and subsequently exported to the extracellular environment. This is, to our knowledge, the very first study to demonstrate mechanistically that XOR can be specifically targeted for export as the seminal step in a compensatory response to heme/Fe overload.

A nitroalkene derivative of salicylate alleviates diet-induced obesity by activating creatine metabolism and non-shivering thermogenesis

Obesity-related type II diabetes (diabesity) has increased global morbidity and mortality dramatically. Previously, the ancient drug salicylate demonstrated promise for the treatment of type II diabetes, but its clinical use was precluded due to high dose requirements. In this study, we present a nitroalkene derivative of salicylate, 5-(2-nitroethenyl)salicylic acid (SANA), a molecule with unprecedented beneficial effects in diet-induced obesity (DIO). SANA reduces DIO, liver steatosis and insulin resistance at doses up to 40 times lower than salicylate. Mechanistically, SANA stimulated mitochondrial respiration and increased creatine-dependent energy expenditure in adipose tissue. Indeed, depletion of creatine resulted in the loss of SANA action. Moreover, we found that SANA binds to creatine kinases CKMT1/2, and downregulation CKMT1 interferes with the effect of SANA in vivo. Together, these data demonstrate that SANA is a first-in-class activator of creatine-dependent energy expenditure and thermogenesis in adipose tissue and emerges as a candidate for the treatment of diabesity.

Release of hepatic xanthine oxidase (XO) to the circulation is protective in intravascular hemolytic crisis

Xanthine oxidase (XO) catalyzes the catabolism of hypoxanthine to xanthine and xanthine to uric acid, generating oxidants as a byproduct. Importantly, XO activity is elevated in numerous hemolytic conditions including sickle cell disease (SCD); however, the role of XO in this context has not been elucidated. Whereas long-standing dogma suggests elevated levels of XO in the vascular compartment contribute to vascular pathology via increased oxidant production, herein, we demonstrate, for the first time, that XO has an unexpected protective role during hemolysis. Using an established hemolysis model, we found that intravascular hemin challenge (40 μmol/kg) resulted in a significant increase in hemolysis and an immense (20-fold) elevation in plasma XO activity in Townes sickle cell phenotype (SS) sickle mice compared to controls. Repeating the hemin challenge model in hepatocyte-specific XO knockout mice transplanted with SS bone marrow confirmed the liver as the source of enhanced circulating XO as these mice demonstrated 100% lethality compared to 40% survival in controls. In addition, studies in murine hepatocytes (AML12) revealed hemin mediates upregulation and release of XO to the medium in a toll like receptor 4 (TLR4)-dependent manner. Furthermore, we demonstrate that XO degrades oxyhemoglobin and releases free hemin and iron in a hydrogen peroxide-dependent manner. Additional biochemical studies revealed purified XO binds free hemin to diminish the potential for deleterious hemin-related redox reactions as well as prevents platelet aggregation. In the aggregate, data herein reveals that intravascular hemin challenge induces XO release by hepatocytes through hemin-TLR4 signaling, resulting in an immense elevation of circulating XO. This increased XO activity in the vascular compartment mediates protection from intravascular hemin crisis by binding and potentially degrading hemin at the apical surface of the endothelium where XO is known to be bound and sequestered by endothelial glycosaminoglycans (GAGs).

Xanthine oxidase mediates chronic stress-induced cerebrovascular dysfunction and cognitive impairment

Xanthine oxidase (XO) mediates vascular function. Chronic stress impairs cerebrovascular function and increases the risk of stroke and cognitive decline. Our study determined the role of XO on stress-induced cerebrovascular dysfunction and cognitive decline. We measured middle cerebral artery (MCA) function, free radical formation, and working memory in 6-month-old C57BL/6 mice who underwent 8 weeks of control conditions or unpredictable chronic mild stress (UCMS) with or without febuxostat (50 mg/L), a XO inhibitor. UCMS mice had an impaired MCA dilation to acetylcholine vs. controls (p < 0.0001), and increased total free radical formation, XOR protein levels, and hydrogen peroxide production in the liver compared to controls. UCMS increased hydrogen peroxide production in the brain and cerebrovasculature compared to controls. Working memory, using the y-maze test, was impaired (p < 0.05) in UCMS mice compared to control mice. However, blocking XO using febuxostat prevented the UCMS-induced impaired MCA response, while free radical production and hydrogen peroxide levels were similar to controls in the liver and brain of UCMS mice treated with febuxostat. Further, UCMS + Feb mice did not have a significant reduction in working memory. These data suggest that the cerebrovascular dysfunction associated with chronic stress may be driven by XO, which leads to a reduction in working memory.

Lung-gut axis of microbiome alterations following co-exposure to ultrafine carbon black and ozone

BACKGROUND

Microbial dysbiosis is a potential mediator of air pollution-induced adverse outcomes. However, a systemic comparison of the lung and gut microbiome alterations and lung-gut axis following air pollution exposure is scant. In this study, we exposed male C57BL/6J mice to inhaled air, CB (10 mg/m3), O3 (2 ppm) or CB + O3 mixture for 3 h/day for either one day or four consecutive days and were euthanized 24 h post last exposure. The lung and gut microbiome were quantified by 16 s sequencing.

RESULTS

Multiple CB + O3 exposures induced an increase in the lung inflammatory cells (neutrophils, eosinophils and B lymphocytes), reduced absolute bacterial load in the lungs and increased load in the gut. CB + O3 exposure was more potent as it decreased lung microbiome alpha diversity just after a single exposure. CB + O3 co-exposure uniquely increased Clostridiaceae and Prevotellaceae in the lungs. Serum short chain fatty acids (SCFA) (acetate and propionate) were increased significantly only after CB + O3 co-exposure. A significant increase in SCFA producing bacterial families (Ruminococcaceae, Lachnospiraceae, and Eubacterium) were also observed in the gut after multiple exposures. Co-exposure induced significant alterations in the gut derived metabolite receptors/mediator (Gcg, Glp-1r, Cck) mRNA expression. Oxidative stress related mRNA expression in lungs, and oxidant levels in the BALF, serum and gut significantly increased after CB + O3 exposures.

CONCLUSION

Our study confirms distinct gut and lung microbiome alterations after CB + O3 inhalation co-exposure and indicate a potential homeostatic shift in the gut microbiome to counter deleterious impacts of environmental exposures on metabolic system.

Loss of DNA repair mechanisms in cardiac myocytes induce dilated cardiomyopathy

Cardiomyopathy is a progressive disease of the myocardium leading to impaired contractility. Genotoxic cancer therapies are known to be potent drivers of cardiomyopathy, whereas causes of spontaneous disease remain unclear. To test the hypothesis that endogenous genotoxic stress contributes to cardiomyopathy, we deleted the DNA repair gene Ercc1 specifically in striated muscle using a floxed allele of Ercc1 and mice expressing Cre under control of the muscle-specific creatinine kinase (Ckmm) promoter or depleted systemically (Ercc1-/D mice). Ckmm-Cre+/- ;Ercc1-/fl mice expired suddenly of heart disease by 7 months of age. As young adults, the hearts of Ckmm-Cre+/- ;Ercc1-/fl mice were structurally and functionally normal, but by 6-months-of-age, there was significant ventricular dilation, wall thinning, interstitial fibrosis, and systolic dysfunction indicative of dilated cardiomyopathy. Cardiac tissue from the tissue-specific or systemic model showed increased apoptosis and cardiac myocytes from Ckmm-Cre+/- ;Ercc1-/fl mice were hypersensitive to genotoxins, resulting in apoptosis. p53 levels and target gene expression, including several antioxidants, were increased in cardiac tissue from Ckmm-Cre+/- ;Ercc1-/fl and Ercc1-/D mice. Despite this, cardiac tissue from older mutant mice showed evidence of increased oxidative stress. Genetic or pharmacologic inhibition of p53 attenuated apoptosis and improved disease markers. Similarly, overexpression of mitochondrial-targeted catalase improved disease markers. Together, these data support the conclusion that DNA damage produced endogenously can drive cardiac disease and does so mechanistically via chronic activation of p53 and increased oxidative stress, driving cardiac myocyte apoptosis, dilated cardiomyopathy, and sudden death.

Aerosol physicochemical determinants of carbon black and ozone inhalation co-exposure induced pulmonary toxicity

Air pollution accounts for more than 7 million premature deaths worldwide. Using ultrafine carbon black (CB) and ozone (O3) as a model for an environmental co-exposure scenario, the dose response relationships in acute pulmonary injury and inflammation were determined by generating, characterizing, and comparing stable concentrations of CB aerosols (2.5, 5.0, 10.0 mg/m3), O3 (0.5, 1.0, 2.0 ppm) with mixture CB + O3 (2.5 + 0.5, 5.0 + 1.0, 10.0 + 2.0). C57BL6 male mice were exposed for 3 h by whole body inhalation and acute toxicity determined after 24 h. CB itself did not cause any alteration, however, a dose response in pulmonary injury/inflammation was observed with O3 and CB + O3. This increase in response with mixtures was not dependent on the uptake but was due to enhanced reactivity of the particles. Benchmark dose modeling showed several-fold increase in potency with CB + O3 compared with CB or O3 alone. Principal component analysis provided insight into response relationships between various doses and treatments. There was a significant correlation in lung responses with charge-based size distribution, total/alveolar deposition, oxidant generation, and antioxidant depletion potential. Lung tissue gene/protein response demonstrated distinct patterns that are better predicted by either particle dose/aerosol responses (interleukin-1β, keratinocyte chemoattractant, transforming growth factor beta) or particle reactivity (thymic stromal lymphopoietin, interleukin-13, interleukin-6). Hierarchical clustering showed a distinct signature with high dose and a similarity in mRNA expression pattern of low and medium doses of CB + O3. In conclusion, we demonstrate that the biological outcomes from CB + O3 co-exposure are significantly greater than individual exposures over a range of aerosol concentrations and aerosol characteristics can predict biological outcome.

Obese female mice do not exhibit overt hyperuricemia despite hepatic steatosis and impaired glucose tolerance

Recent reports have clearly demonstrated a tight correlation between obesity and elevated circulating uric acid levels (hyperuricemia). However, nearly all preclinical work in this area has been completed with male mice, leaving the field with a considerable gap in knowledge regarding female responses to obesity and hyperuricemia. This deficiency in sex as a biological variable extends beyond unknowns regarding uric acid (UA) to several important comorbidities associated with obesity including nonalcoholic fatty liver disease (NAFLD). To attempt to address this issue, herein we describe both phenotypic and metabolic responses to diet-induced obesity (DIO) in female mice. Six-week-old female C57BL/6J mice were fed a high-fat diet (60% calories derived from fat) for 32 weeks. The DIO female mice had significant weight gain over the course of the study, higher fasting blood glucose, impaired glucose tolerance, and elevated plasma insulin levels compared to age-matched on normal chow. While these classic indices of DIO and NAFLD were observed such as increased circulating levels of ALT and AST, there was no difference in circulating UA levels. Obese female mice also demonstrated increased hepatic triglyceride (TG), cholesterol, and cholesteryl ester. In addition, several markers of hepatic inflammation were significantly increased. Also, alterations in the expression of redox-related enzymes were observed in obese mice compared to lean controls including increases in extracellular superoxide dismutase (Sod3), heme oxygenase (Ho)-1, and xanthine dehydrogenase (Xdh). Interestingly, hepatic UA levels were significantly elevated (~2-fold) in obese mice compared to their lean counterparts. These data demonstrate female mice assume a similar metabolic profile to that reported in several male models of obesity in the context of alterations in glucose tolerance, hepatic steatosis, and elevated transaminases (ALT and AST) in the absence of hyperuricemia affirming the need for further study.

Indirect Antioxidant Effects of the Nitrite Anion: Focus on Xanthine Oxidase

One electron reduction of nitrite (NO₂ ^-) has been determined to be a significant, noncanonical source of nitric oxide (NO) with molybdopterin enzymes being identified as critical to this process. Of the molybdopterin enzymes identified as NO₂ ^- reductases, xanthine oxidoreductase (XOR) is the most extensively studied. Paradoxically, XOR generates oxidants and thus can contribute to oxidative stress under inflammatory conditions when the oxidase form (XO) of XOR is abundant. However, under similar inflammatory conditions XO has been associated with NO generation, especially when NO₂ ^- levels are elevated which begs the question: if reaction of nitrite with XO consumes electrons, then does it subsequently reduce oxidant generation? To address this question, electron paramagnetic resonance (EPR) was used, under controlled O₂ tensions, to assess superoxide (O₂ ^•-) generation by endothelial-bound XO plus xanthine and the resultant impact of introducing NO₂ ^-. Nitrite diminished XO-derived O₂ ^•- under hypoxia (1% O₂) whereas at 21% O₂, it had no impact. To confirm these results and discount contributions from the reaction of NO with O₂ ^•-, molecular O₂ consumption was assessed. The presence of NO₂ ^- decreased the rate of XO/xanthine-dependent O₂ consumption in a concentration-dependent manner with greater impact under hypoxic conditions (1% O₂) compared to 21% O₂. In a more biologic setting, NO₂ ^- also diminished XO-dependent H₂O₂ formation in murine liver homogenates supplemented with xanthine. Interestingly, nitrate (NO₃ ^-) did not alter XO-dependent O₂ consumption at either 21% or 1% O₂; yet it did slightly impact nitrite-mediated effects when present at 2:1 ratio vs. NO₂ ^-. When combined, these data: 1) show a significant indirect antioxidant function for NO₂ ^- by decreasing oxidant generation from XO, 2) demonstrate that both XO-derived H₂O₂ and O₂ ^•- production are diminished by the presence of NO₂ ^- and 3) incentivize further exploration of the difference between XO reaction with NO₂ ^- vs. NO₃ ^-.

Left Ventricular Segmental Strain Identifies Unique Myocardial Deformation Patterns After Intrinsic and Extrinsic Stressors in Mice

We used segmental strain analysis to evaluate whether intrinsic (diet-induced obesity [DIO]) and extrinsic (unpredictable chronic mild stress [UCMS]) stressors can alter deformational patterns of the left ventricle. Six-week-old male C57BL/6J mice were randomized into the lean or obese group (n = 24/group). Mice underwent 12 wk of DIO with a high-fat diet (HFD). At 18 wk, lean and obese mice were further randomized into UCMS and non-UCMS groups (UCMS, 7 h/d, 5 d/wk, for 8 wk). Echocardiography was performed at baseline (6 wk), post-HFD (18 wk) and post-UCMS (26 wk). Machine learning was applied to the DIO and UCMS groups. There was robust predictive accuracy (area under the receiver operating characteristic curve [AUC] = 0.921) when comparing obese with lean mice, with radial strain changes in the lateral (-64%, p ≤ 0.001) and anterior free (-53%, p < 0.001) walls being most informative. The ability to predict mice that underwent UCMS, irrespective of diet, was assessed (AUC = 0.886), revealing longitudinal strain rate of the anterior midwall and radial strain of the posterior septal wall as the top features. The wall segments indicate a predilection for changes in deformation patterns to the free wall (DIO) and septal wall (UCMS), indicating disease-specific alterations to the myocardium.

Redox imbalance in COVID-19 pathophysiology

Background

The pathophysiologic significance of redox imbalance is unquestionable as numerous reports and topic reviews indicate alterations in redox parameters during corona virus disease 2019 (COVID-19). However, a more comprehensive understanding of redox-related parameters in the context of COVID-19-mediated inflammation and pathophysiology is required.

Methods

COVID-19 subjects (n = 64) and control subjects (n = 19) were enrolled, and blood was drawn within 72 h of diagnosis. Serum multiplex assays and peripheral blood mRNA sequencing was performed. Oxidant/free radical (electron paramagnetic resonance (EPR) spectroscopy, nitrite-nitrate assay) and antioxidant (ferrous reducing ability of serum assay and high-performance liquid chromatography) were performed. Multivariate analyses were performed to evaluate potential of indicated parameters to predict clinical outcome.

Results

Significantly greater levels of multiple inflammatory and vascular markers were quantified in the subjects admitted to the ICU compared to non-ICU subjects. Gene set enrichment analyses indicated significant enhancement of oxidant related pathways and biochemical assays confirmed a significant increase in free radical production and uric acid reduction in COVID-19 subjects. Multivariate analyses confirmed a positive association between serum levels of VCAM-1, ICAM-1 and a negative association between the abundance of one electron oxidants (detected by ascorbate radical formation) and mortality in COVID subjects while IL-17c and TSLP levels predicted need for intensive care in COVID-19 subjects.

Conclusion

Herein we demonstrate a significant redox imbalance during COVID-19 infection affirming the potential for manipulation of oxidative stress pathways as a new therapeutic strategy COVID-19. However, further work is requisite for detailed identification of oxidants (O₂^•-, H₂O₂ and/or circulating transition metals such as Fe or Cu) contributing to this imbalance to avoid the repetition of failures using non-specific antioxidant supplementation.

Interstitial Collagen Loss, Myocardial Remodeling, and Function in Primary Mitral Regurgitation

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The stretch of volume overload in PMR initiates interstitial collagen loss and decrease in LV sphericity index.

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LV chamber diastolic function is normal whereas LA function, LV twist/volume slope, early LV untwist, and myocardial circumferential strain are impaired.

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There is increased oxidative stress in the cardiomyocyte with cytoskeletal breakdown and myofibrillar loss in PMR.

Interstitial collagen loss and cardiomyocyte ultrastructural damage accounts for left ventricular (LV) sphericity and decrease in LV twist and circumferential strain. Normal LV diastolic function belies significantly abnormal left atrial (LA) function and early LV diastolic untwist rate. This underscores the complex interplay of LV and LA myocardial remodeling and function in the pathophysiology of primary mitral regurgitation. In this study, we connect LA function with LV systolic and diastolic myocardial remodeling and function using cardiac magnetic resonance tissue tagging in primary mitral regurgitation.

Extracellular biomolecular free radical formation during injury

Determine if oxidative damage increases in articular cartilage as a result of injury and matrix failure and whether modulation of the local redox environment influences this damage. Osteoarthritis is an age associated disease with no current disease modifying approaches available. Mechanisms of cartilage damage in vitro suggest tissue free radical production could be critical to early degeneration, but these mechanisms have not been described in intact tissue. To assess free radical production as a result of traumatic injury, we measured biomolecular free radical generation via immuno-spin trapping (IST) of protein/proteoglycan/lipid free radicals after a 2 J/cm² impact to swine articular cartilage explants. This technique allows visualization of free radical formation upon a wide variety of molecules using formalin-fixed, paraffin-embedded approaches. Scoring of extracellular staining by trained, blinded scorers demonstrated significant increases with impact injury, particularly at sites of cartilage cracking. Increases remain in the absence of live chondrocytes but are diminished; thus, they appear to be a cell-dependent and -independent feature of injury. We then modulated the extracellular environment with a pulse of heparin to demonstrate the responsiveness of the IST signal to changes in cartilage biology. Addition of heparin caused a distinct change in the distribution of protein/lipid free radicals at sites of failure alongside a variety of pertinent redox changes related to osteoarthritis. This study directly confirms the production of biomolecular free radicals from articular trauma, providing a rigorous characterization of their formation by injury.

Racial Differences in XO (Xanthine Oxidase) and Mitochondrial DNA Damage-Associated Molecular Patterns in Resistant Hypertension

BACKGROUND

We previously reported increased plasma XO (xanthine oxidase) activity in patients with resistant hypertension. Increased XO can cause mitochondrial DNA damage and promote release of fragments called mitochondrial DNA damage-associated molecular patterns (mtDNA DAMPs). Here, we report racial differences in XO activity and mtDNA DAMPs in Black and White adults with resistant hypertension.

METHODS

This retrospective study includes 91 resistant hypertension patients (44% Black, 47% female) with blood pressure >140/90 mm Hg on ≥4 medications and 37 normotensive controls (30% Black, 54% female) with plasma XO activity, mtDNA DAMPs, and magnetic resonance imaging of left ventricular morphology and function.

RESULTS

Black-resistant hypertension patients were younger (mean age 52±10 versus 59±10 years; P=0.001), with higher XO activity and left ventricular wall thickness, and worse diastolic dysfunction than White resistant hypertension patients. Urinary sodium excretion (mg/24 hour per kg) was positively related to left ventricular end-diastolic volume (r=0.527, P=0.001) and left ventricular mass (r=0.394, P=0.02) among Black but not White resistant hypertension patients. Patients with resistant hypertension had increased mtDNA DAMPs versus controls (P<0.001), with Black mtDNA DAMPS greater than Whites (P<0.001). Transmission electron microscopy of skeletal muscle biopsies in resistant hypertension patients demonstrates mitochondria cristae lysis, myofibrillar loss, large lipid droplets, and glycogen accumulation.

CONCLUSIONS

These data warrant a large study to examine the role of XO and mitochondrial mtDNA DAMPs in cardiac remodeling and heart failure in Black adults with resistant hypertension.

Oxidized carbon black nanoparticles induce endothelial damage through C-X-C chemokine receptor 3-mediated pathway

Oxidation of engineered nanomaterials during application in various industrial sectors can alter their toxicity. Oxidized nanomaterials also have widespread industrial and biomedical applications. In this study, we evaluated the cardiopulmonary hazard posed by these nanomaterials using oxidized carbon black (CB) nanoparticles (CBox) as a model particle. Particle surface chemistry was characterized by X-ray photo electron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). Colloidal characterization and in vitro dosimetry modeling (particle kinetics, fate and transport modeling) were performed. Lung inflammation was assessed following oropharyngeal aspiration of CB or oxidized CBox particles (20 μg per mouse) in C57BL/6J mice. Toxicity and functional assays were also performed on murine macrophage (RAW 264.7) and endothelial cell lines (C166) with and without pharmacological inhibitors. Oxidant generation was assessed by electron paramagnetic resonance spectroscopy (EPR) and via flow cytometry. Endothelial toxicity was evaluated by quantifying pro-inflammatory mRNA expression, monolayer permeability, and wound closure. XPS and FTIR spectra indicated surface modifications, the appearance of new functionalities, and greater oxidative potential (both acellular and in vitro) of CBox particles. Treatment with CBox demonstrated greater in vivo inflammatory potentials (lavage neutrophil counts, secreted cytokine, and lung tissue mRNA expression) and air-blood barrier disruption (lavage proteins). Oxidant-dependent pro-inflammatory signaling in macrophages led to the production of CXCR3 ligands (CXCL9,10,11). Conditioned medium from CBox-treated macrophages induced significant elevation in endothelial cell pro-inflammatory mRNA expression, enhanced monolayer permeability and impairment of scratch healing in CXCR3 dependent manner. In summary, this study mechanistically demonstrated an increased biological potency of CBox particles and established the role of macrophage-released chemical mediators in endothelial damage.

Human and rodent red blood cells do not demonstrate xanthine oxidase activity or XO-catalyzed nitrite reduction to NO

A number of molybdopterin enzymes, including xanthine oxidoreductase (XOR), aldehyde oxidase (AO), sulfite oxidase (SO), and mitochondrial amidoxime reducing component (mARC), have been identified as nitrate and nitrite reductases. Of these enzymes, XOR has been the most extensively studied and reported to be a substantive source of nitric oxide (NO) under inflammatory/hypoxic conditions that limit the catalytic activity of the canonical NOS pathway. It has also been postulated that XOR nitrite reductase activity extends to red blood cell (RBCs) membranes where it has been immunohistochemically identified. These findings, when combined with countervailing reports of XOR activity in RBCs, incentivized our current study to critically evaluate XOR protein abundance/enzymatic activity in/on RBCs from human, mouse, and rat sources. Using various protein concentrations of RBC homogenates for both human and rodent samples, neither XOR protein nor enzymatic activity (xanthine → uric acid) was detectable. In addition, potential loading of RBC-associated glycosaminoglycans (GAGs) by exposing RBC preparations to purified XO before washing did not solicit detectable enzymatic activity (xanthine → uric acid) or alter NO generation profiles. To ensure these observations extended to absence of XOR-mediated contributions to overall RBC-associated nitrite reduction, we examined the nitrite reductase activity of washed and lysed RBC preparations via enhanced chemiluminescence in the presence or absence of the XOR-specific inhibitor febuxostat (Uloric®). Neither addition of inhibitor nor the presence of the XOR substrate xanthine significantly altered the rates of nitrite reduction to NO by RBC preparations from either human or rodent sources confirming the absence of XO enzymatic activity. Furthermore, examination of the influence of the age (young cells vs. old cells) of human RBCs on XO activity also failed to demonstrate detectable XO protein. Combined, these data suggest: 1) that XO does not contribute to nitrite reduction in/on human and rodent erythrocytes, 2) care should be taken to validate immuno-detectable XO by demonstrating enzymatic activity, and 3) XO does not associate with human erythrocytic glycosaminoglycans or participate in nonspecific binding.

Oxidant-induced epithelial alarmin pathway mediates lung inflammation and functional decline following ultrafine carbon and ozone inhalation co-exposure

Environmental inhalation exposures are inherently mixed (gases and particles), yet regulations are still based on single toxicant exposures. While the impacts of individual components of environmental pollution have received substantial attention, the impact of inhalation co-exposures is poorly understood. Here, we mechanistically investigated pulmonary inflammation and lung function decline after inhalation co-exposure and individual exposures to ozone (O₃) and ultrafine carbon black (CB). Environmentally/occupationally relevant lung deposition levels in mice were achieved after inhalation of stable aerosols with similar aerodynamic and mass median distributions. X-ray photoemission spectroscopy detected increased surface oxygen contents on particles in co-exposure aerosols. Compared with individual exposures, co-exposure aerosols produced greater acellular and cellular oxidants detected by electron paramagnetic resonance (EPR) spectroscopy, and in vivo immune-spin trapping (IST), as well as synergistically increased lavage neutrophils, lavage proteins and inflammation related gene/protein expression. Co-exposure induced a significantly greater respiratory function decline compared to individual exposure. A synthetic catalase-superoxide dismutase mimetic (EUK-134) significantly blunted lung inflammation and respiratory function decline confirming the role of oxidant imbalance. We identified a significant induction of epithelial alarmin (thymic stromal lymphopoietin-TSLP)-dependent interleukin-13 pathway after co-exposure, associated with increased mucin and interferon gene expression. We provided evidence of interactive outcomes after air pollution constituent co-exposure and identified a key mechanistic pathway that can potentially explain epidemiological observation of lung function decline after an acute peak of air pollution. Developing and studying the co-exposure scenario in a standardized and controlled fashion will enable a better mechanistic understanding of how environmental exposures result in adverse outcomes.

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Interaction with O₃ mediates free radical production on the surface of carbon black (CB) particles.

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Oxidants mediate co-exposure (CB + O₃)-induced lung function decline.

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EUK-134 (a synthetic superoxide-catalase mimetic) abrogates CB + O₃-induced lung inflammation.

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CB + O₃ co-exposure induces greater lung inflammation than individual exposures.

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Epithelial alarmin (TSLP) contributes significantly to the CB + O₃ toxicity.

Olive oil-derived nitro-fatty acids: protection of mitochondrial function in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive liver fat deposition in the absence of significant alcohol intake. Since extra virgin olive oil (EVOO) reduces fat accumulation, we analyzed the involvement of nitro-fatty acids (NO2-FA) on the beneficial effects of EVOO consumption on NAFLD. Nitro-fatty acids formation was observed during digestion in mice supplemented with EVOO and nitrite. Mice fed with a high-fat diet (HF) presented lower plasma NO2-FA levels than normal chow, and circulating concentrations recovered when the HF diet was supplemented with 10% EVOO plus nitrite. Under NO2-FA formation conditions, liver hemoxygenase-1 expression significantly increased while decreased body weight and fat liver accumulation. Mitochondrial dysfunction plays a central role in the pathogenesis of NAFLD while NO2-FA has been shown to protect from mitochondrial oxidative damage. Accordingly, an improvement of respiratory indexes was observed when mice were supplemented with both EVOO plus nitrite. Liver mitochondrial complexes II and V activities were greater in mice with EVOO supplementation and further improved in the presence of nitrite. Overall, our results strongly suggest a positive correlation between NO2-OA formation from EVOO and the observed improvement of mitochondrial function in NAFLD. The formation of NO2-FA can account for the health benefits associated with EVOO consumption.

Long-term cerebrovascular dysfunction in the offspring from maternal electronic cigarette use during pregnancy

Electronic cigarettes (E-cigs) have been promoted as harm-free or less risky than smoking, even for women during pregnancy. These claims are made largely on E-cig aerosol having fewer number of toxic chemicals compared with cigarette smoke. Given that even low levels of smoking are found to produce adverse birth outcomes, we sought to test the hypothesis that vaping during pregnancy (with or without nicotine) would not be harm-free and would result in vascular dysfunction that would be evident in offspring during adolescent and/or adult life. Pregnant female Sprague Dawley rats were exposed to E-cig aerosol (1 h/day, 5 days/wk, starting on gestational day 2 until pups were weaned) using e-liquid with 0 mg/mL (E-cig0) or 18 mg/mL nicotine (E-cig18) and compared with ambient air-exposed controls. Body mass at birth and at weaning were not different between groups. Assessment of middle cerebral artery (MCA) reactivity revealed a 51%-56% reduction in endothelial-dependent dilation response to acetylcholine (ACh) for both E-cig0 and E-cig18 in 1-mo, 3-mo (adolescent), and 7-mo-old (adult) offspring (P < 0.05 compared with air, all time points). MCA responses to sodium nitroprusside (SNP) and myogenic tone were not different across groups, suggesting that endothelial-independent responses were not altered. The MCA vasoconstrictor response (5-hydroxytryptamine, 5-HT) was also not different across treatment and age groups. These data demonstrate that maternal vaping during pregnancy is not harm-free and confers significant cerebrovascular health risk/dysfunction to offspring that persists into adult life. NEW & NOTEWORTHY These data established that vaping electronic cigarettes during pregnancy, with or without nicotine, is not safe and confers significant risk potential to the cerebrovascular health of offspring in early and adult life. A key finding is that vaping without nicotine does not protect offspring from cerebrovascular dysfunction and results in the same level of cerebrovascular dysfunction (compared with maternal vaping with nicotine), indicating that the physical and/or chemical properties from the base solution (other than nicotine) are responsible for the cerebrovascular dysfunction that we observed. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/maternal-vaping-impairs-vascular-function-in-theoffspring/.

An aged immune system drives senescence and ageing of solid organs

Ageing of the immune system, or immunosenescence, contributes to the morbidity and mortality of the elderly1,2. To define the contribution of immune system ageing to organism ageing, here we selectively deleted Ercc1, which encodes a crucial DNA repair protein3,4, in mouse haematopoietic cells to increase the burden of endogenous DNA damage and thereby senescence5-7 in the immune system only. We show that Vav-iCre+/-;Ercc1-/fl mice were healthy into adulthood, then displayed premature onset of immunosenescence characterized by attrition and senescence of specific immune cell populations and impaired immune function, similar to changes that occur during ageing in wild-type mice8-10. Notably, non-lymphoid organs also showed increased senescence and damage, which suggests that senescent, aged immune cells can promote systemic ageing. The transplantation of splenocytes from Vav-iCre+/-;Ercc1-/fl or aged wild-type mice into young mice induced senescence in trans, whereas the transplantation of young immune cells attenuated senescence. The treatment of Vav-iCre+/-;Ercc1-/fl mice with rapamycin reduced markers of senescence in immune cells and improved immune function11,12. These data demonstrate that an aged, senescent immune system has a causal role in driving systemic ageing and therefore represents a key therapeutic target to extend healthy ageing.

Chronic stress induced perivascular adipose tissue impairment of aortic function and the therapeutic effect of exercise

NEW FINDINGS

What is the central question of this study? Thoracic perivascular adipose tissue (tPVAT) is known to, in part, regulate aortic function: what are the effects of unpredictable chronic mild stress (UCMS) on the tPVAT regulation of aortic function and what is the role of exercise training in alleviating the potential negative actions of UCMS on tPVAT? What is the main finding and its importance? UCMS causes tPVAT to disrupt endothelium-dependent dilatation, increases inflammatory cytokine production and diminishes tPVAT-adiponectin. Exercise training proved efficacious in preventing tPVAT-mediated disruption of aortic function. The data support a tPVAT mechanism through which chronic stress negatively impacts vascular health, which adds to our knowledge of how psychological disorders might increase the risk of cardiovascular disease.

ABSTRACT

Chronic stress is a major risk for cardiovascular disease. Perivascular adipose tissue (PVAT) has been shown to regulate vascular function; however, the impact of chronic stress and the comorbidity of metabolic syndrome (MetS) on thoracic (t)PVAT is unknown. Additionally, aerobic exercise training (AET) is known to combat the pathology of MetS and chronic stress, but the role of tPVAT in these actions is also unknown. Therefore, the purpose of this study was to examine the effects of unpredictable chronic mild stress (UCMS) on the tPVAT regulation of aortic function and the preventative effect of AET. Lean (LZR) and obese (OZR) Zucker rats (16-17 weeks old) were exposed to 8 weeks of UCMS with and without treadmill exercise (AET). In LZR, UCMS impaired aortic endothelium-dependent dilatation (EDD) (assessed ex vivo by wire myography) and aortic stiffness (assessed by elastic modulus) with no change in OZR subject to UCMS. However, both LZR and OZR UCMS tPVAT impaired EDD compared to respective controls. LZR and OZR subject to UCMS had higher oxidative stress production, diminished adiponectin and impaired aortic nitric oxide levels. Divergently, UCMS induced greater inflammatory cytokine production in LZR UCMS tPVAT, but not in OZR UCMS tPVAT. AET prevented the tPVAT impairment of aortic relaxation with UCMS in LZR and OZR. Additionally, AET reduced aortic stiffness in both LZR and OZR. These beneficial effects on tPVAT regulation of the aorta are likely due to AET preservation of adiponectin, reduced oxidative stress and inflammation, and enhanced nitric oxide. UCMS impaired tPVAT-regulated aortic function in LZR, and augmented MetS-induced EDD in OZR. Conversely, AET in combination with UCMS largely preserved aortic function and the tPVAT environment, in both groups.

The Mitochondrial mitoNEET Ligand NL-1 Is Protective in a Murine Model of Transient Cerebral Ischemic Stroke

PURPOSE

Therapeutic strategies to treat ischemic stroke are limited due to the heterogeneity of cerebral ischemic injury and the mechanisms that contribute to the cell death. Since oxidative stress is one of the primary mechanisms that cause brain injury post-stroke, we hypothesized that therapeutic targets that modulate mitochondrial function could protect against reperfusion-injury after cerebral ischemia, with the focus here on a mitochondrial protein, mitoNEET, that modulates cellular bioenergetics.

METHOD

In this study, we evaluated the pharmacology of the mitoNEET ligand NL-1 in an in vivo therapeutic role for NL-1 in a C57Bl/6 murine model of ischemic stroke.

RESULTS

NL-1 decreased hydrogen peroxide production with an IC50 of 5.95 μM in neuronal cells (N2A). The in vivo activity of NL-1 was evaluated in a murine 1 h transient middle cerebral artery occlusion (t-MCAO) model of ischemic stroke. We found that mice treated with NL-1 (10 mg/kg, i.p.) at time of reperfusion and allowed to recover for 24 h showed a 43% reduction in infarct volume and 68% reduction in edema compared to sham-injured mice. Additionally, we found that when NL-1 was administered 15 min post-t-MCAO, the ischemia volume was reduced by 41%, and stroke-associated edema by 63%.

CONCLUSION

As support of our hypothesis, as expected, NL-1 failed to reduce stroke infarct in a permanent photothrombotic occlusion model of stroke. This report demonstrates the potential therapeutic benefits of using mitoNEET ligands like NL-1 as novel mitoceuticals for treating reperfusion-injury with cerebral stroke.

Xanthine Oxidase Drives Hemolysis and Vascular Malfunction in Sickle Cell Disease

OBJECTIVE

Chronic hemolysis is a hallmark of sickle cell disease (SCD) and a driver of vasculopathy; however, the mechanisms contributing to hemolysis remain incompletely understood. Although XO (xanthine oxidase) activity has been shown to be elevated in SCD, its role remains unknown. XO binds endothelium and generates oxidants as a byproduct of hypoxanthine and xanthine catabolism. We hypothesized that XO inhibition decreases oxidant production leading to less hemolysis. Approach and Results: Wild-type mice were bone marrow transplanted with control (AA) or sickle (SS) Townes bone marrow. After 12 weeks, mice were treated with 10 mg/kg per day of febuxostat (Uloric), Food and Drug Administration-approved XO inhibitor, for 10 weeks. Hematologic analysis demonstrated increased hematocrit, cellular hemoglobin, and red blood cells, with no change in reticulocyte percentage. Significant decreases in cell-free hemoglobin and increases in haptoglobin suggest XO inhibition decreased hemolysis. Myographic studies demonstrated improved pulmonary vascular dilation and blunted constriction, indicating improved pulmonary vasoreactivity, whereas pulmonary pressure and cardiac function were unaffected. The role of hepatic XO in SCD was evaluated by bone marrow transplanting hepatocyte-specific XO knockout mice with SS Townes bone marrow. However, hepatocyte-specific XO knockout, which results in >50% diminution in circulating XO, did not affect hemolysis levels or vascular function, suggesting hepatocyte-derived elevation of circulating XO is not the driver of hemolysis in SCD.

CONCLUSIONS

Ten weeks of febuxostat treatment significantly decreased hemolysis and improved pulmonary vasoreactivity in a mouse model of SCD. Although hepatic XO accounts for >50% of circulating XO, it is not the source of XO driving hemolysis in SCD.

Uric Acid and Hypertension: An Update With Recommendations

The association between increased serum urate and hypertension has been a subject of intense controversy. Extracellular uric acid drives uric acid deposition in gout, kidney stones, and possibly vascular calcification. Mendelian randomization studies, however, indicate that serum urate is likely not the causal factor in hypertension although it does increase the risk for sudden cardiac death and diabetic vascular disease. Nevertheless, experimental evidence strongly suggests that an increase in intracellular urate is a key factor in the pathogenesis of primary hypertension. Pilot clinical trials show beneficial effect of lowering serum urate in hyperuricemic individuals who are young, hypertensive, and have preserved kidney function. Some evidence suggest that activation of the renin-angiotensin system (RAS) occurs in hyperuricemia and blocking the RAS may mimic the effects of xanthine oxidase inhibitors. A reduction in intracellular urate may be achieved by lowering serum urate concentration or by suppressing intracellular urate production with dietary measures that include reducing sugar, fructose, and salt intake. We suggest that these elements in the western diet may play a major role in the pathogenesis of primary hypertension. Studies are necessary to better define the interrelation between uric acid concentrations inside and outside the cell. In addition, large-scale clinical trials are needed to determine if extracellular and intracellular urate reduction can provide benefit hypertension and cardiometabolic disease.

Hydrogen sulfide stimulates xanthine oxidoreductase conversion to nitrite reductase and formation of NO

Cardiovascular disease is the leading cause of death and disability worldwide with increased oxidative stress and reduced NO bioavailability serving as key risk factors. For decades, elevation in protein abundance and enzymatic activity of xanthine oxidoreductase (XOR) under hypoxic/inflammatory conditions has been associated with organ damage and vascular dysfunction. Recent reports have challenged this dogma by identifying a beneficial function for XOR, under similar hypoxic/acidic conditions, whereby XOR catalyzes the reduction of nitrite (NO2-) to nitric oxide (NO) through poorly defined mechanisms. We previously reported that hydrogen sulfide (H2S/sulfide) confers significant vascular benefit under these same conditions via NO2- mediated mechanisms independent of nitric oxide synthase (NOS). Here we report for the first time the convergence of H2S, XOR, and nitrite to form a concerted triad for NO generation. Specifically, hypoxic endothelial cells show a dose-dependent, sulfide and polysulfide (diallyl trisulfide (DATS)-induced, NOS-independent NO2- reduction to NO that is dependent upon the enzymatic activity of XOR. Interestingly, nitrite reduction to NO was found to be slower and more sustained with DATS compared to H2S. Capacity for sulfide/polysulfide to produce an XOR-dependent impact on NO generation translates to salutary actions in vivo as DATS administration in cystathionine-γ-lyase (CSE) knockout mice significantly improved hindlimb ischemia blood flow post ligation, while the XOR-specific inhibitor, febuxostat (Febx), abrogated this benefit. Moreover, flow-mediated vasodilation (FMD) in CSE knockout mice following administration of DATS resulted in greater than 4-fold enhancement in femoral artery dilation while co-treatment with Febx completely completely abrogated this effect. Together, these results identify XOR as a focal point of convergence between sulfide- and nitrite-mediated signaling, as well as affirm the critical need to reexamine current dogma regarding inhibition of XOR in the context of vascular dysfunction.

Exercise training prevents the perivascular adipose tissue-induced aortic dysfunction with metabolic syndrome

The aim of the study was to determine the effects of exercise training on improving the thoracic perivascular adipose tissue (tPVAT) phenotype (inflammation, oxidative stress, and proteasome function) in metabolic syndrome and its subsequent actions on aortic function.

Methods

Lean and obese (model of metabolic syndrome) Zucker rats (n=8/group) underwent 8-weeks of control conditions or treadmill exercise (70% of max speed, 1 h/day, 5 days/week). At the end of the intervention, the tPVAT was removed and conditioned media was made. The cleaned aorta was attached to a force transducer to assess endothelium-dependent and independent dilation in the presence or absence of tPVAT-conditioned media. tPVAT gene expression, inflammatory /oxidative phenotype, and proteasome function were assessed.

Results

The main findings were that Ex induced: (1) a beige-like, anti-inflammatory tPVAT phenotype; (2) a greater abundance of ^•NO in tPVAT; (3) a reduction in tPVAT oxidant production; and (4) an improved tPVAT proteasome function. Regarding aortic function, endothelium-dependent dilation was greater in exercised lean and obese groups vs. controls (p < 0.05). Lean control tPVAT improved aortic relaxation, whereas obese control tPVAT decreased aortic relaxation. In contrast, the obese Ex-tPVAT increased aortic dilation, whereas the lean Ex-tPVAT did not affect aortic dilation.

Conclusion

Overall, exercise had the most dramatic impact on the obese tPVAT reflecting a change towards an environment with less oxidant load, less inflammation and improved proteasome function. Such beneficial changes to the tPVAT micro-environment with exercise likely played a significant role in mediating the improvement in aortic function in metabolic syndrome following 8 weeks of exercise.

Hepatocyte-Specific Ablation or Whole-Body Inhibition of Xanthine Oxidoreductase in Mice Corrects Obesity-Induced Systemic Hyperuricemia Without Improving Metabolic Abnormalities

Systemic hyperuricemia (HyUA) in obesity/type 2 diabetes facilitated by elevated activity of xanthine oxidoreductase (XOR), which is the sole source of uric acid (UA) in mammals, has been proposed to contribute to the pathogenesis of insulin resistance/dyslipidemia in obesity. Here, the effects of hepatocyte-specific ablation of Xdh, the gene encoding XOR (HXO), and whole-body pharmacologic inhibition of XOR (febuxostat) on obesity-induced insulin resistance/dyslipidemia were assessed. Deletion of hepatocyte Xdh substantially lowered liver and plasma UA concentration. When exposed to an obesogenic diet, HXO and control floxed (FLX) mice became equally obese, but systemic HyUA was absent in HXO mice. Despite this, obese HXO mice became as insulin resistant and dyslipidemic as obese FLX mice. Similarly, febuxostat dramatically lowered plasma and tissue UA and XOR activity in obese wild-type mice without altering obesity-associated insulin resistance/dyslipidemia. These data demonstrate that hepatocyte XOR activity is a critical determinant of systemic UA homeostasis, that deletion of hepatocyte Xdh is sufficient to prevent systemic HyUA of obesity, and that neither prevention nor correction of HyUA improves insulin resistance/dyslipidemia in obesity. Thus, systemic HyUA, although clearly a biomarker of the metabolic abnormalities of obesity, does not appear to be causative.

Role of Chronic Stress and Exercise on Microvascular Function in Metabolic Syndrome

PURPOSE

The present study examined the effect of unpredictable chronic mild stress (UCMS) on peripheral microvessel function in healthy and metabolic syndrome (MetS) rodents and whether exercise training could prevent the vascular dysfunction associated with UCMS.

METHODS

Lean and obese (model of MetS) Zucker rats (LZR and OZR) were exposed to 8 wk of UCMS, exercise (Ex), UCMS + Ex, or control conditions. At the end of the intervention, gracilis arterioles (GA) were isolated and hung in a pressurized myobath to assess endothelium-dependent (EDD) and endothelium-independent (EID) dilation. Levels of nitric oxide (NO) and reactive oxygen species (ROS) were measured through 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate and dihydroethidium staining, respectively.

RESULTS

Compared with LZR controls, EDD and EID were lower (P = 0.0001) in LZR-UCMS. The OZR-Ex group had a higher EDD (P = 0.0001) and EID (P = 0.003) compared with OZR controls, whereas only a difference in EDD (P = 0.01) was noted between the LZR-control and LZR-Ex groups. Importantly, EDD and EID were higher in the LZR (P = 0.0001; P = 0.02) and OZR (P = 0.0001; P = 0.02) UCMS + Ex groups compared with UCMS alone. Lower NO bioavailability and higher ROS were noted in the LZR-UCMS group (P = 0.0001), but not OZR-UCMS, compared with controls. The Ex and UCMS-Ex groups had higher NO bioavailability (P = 0.0001) compared with the control and UCMS groups, but ROS levels remained high.

CONCLUSIONS

The comorbidity between UCMS and MetS does not exacerbate the effects of one another on GA EDD responses, but does lead to the development of other vasculopathy adaptations, which can be partially explained by alterations in NO and ROS production. Importantly, exercise training alleviates most of the negative effects of UCMS on GA function.

Diminishing Inflammation by Reducing Oxidant Generation: Nitrated Fatty Acid-Mediated Inactivation of Xanthine Oxidoreductase

Inhibition of xanthine oxidoreductase (XOR) has proven beneficial in a plethora of inflammatory disease processes due to a net reduction in pro-inflammatory oxidants and secondary nitrating species. Electrophilic nitrated fatty acid derivatives, such as nitro-oleic acid (OA-NO₂) are also noted to display a broad spectrum of anti-inflammatory effects via interaction with critical signaling pathways. An alternative process in which nitrated fatty acids may extend anti-inflammatory actions is via inactivation of XOR, a process that is more effective than allo/oxypurinol-mediated inhibition. Herein, we describe the molecular aspects of nitrated fatty acid-associated inactivation of XOR, identify specificity via structure function relationships and discuss XOR as a crucial component of the anti-inflammatory portfolio of nitrated fatty acids.

Adipose tissue-derived free fatty acids initiate myeloid cell accumulation in mouse liver in states of lipid oversupply

Accumulation of myeloid cells in the liver, notably dendritic cells (DCs) and monocytes/macrophages (MCs), is a major component of the metainflammation of obesity. However, the mechanism(s) stimulating hepatic DC/MC infiltration remain ill defined. Herein, we addressed the hypothesis that adipose tissue (AT) free fatty acids (FFAs) play a central role in the initiation of hepatic DC/MC accumulation, using a number of mouse models of altered FFA supply to the liver. In two models of acute FFA elevation (lipid infusion and fasting) hepatic DC/MC and triglycerides (TGs) but not AT DC/MC were increased without altering plasma cytokines (PCs; TNFα and monocyte chemoattractant protein 1) and with variable effects on oxidative stress (OxS) markers. However, fasting in mice with profoundly reduced AT lipolysis (AT-specific deletion of adipose TG lipase; AAKO) failed to elevate liver DC/MC, TG, or PC, but liver OxS increased. Livers of obese AAKO mice that are known to be resistant to steatosis were similarly protected from inflammation. In high-fat feeding studies of 1, 3, 6, or 20-wk duration, liver DC/MC accumulation dissociated from PC and OxS but tracked with liver TGs. Furthermore, decreasing OxS by ~80% in obese mice failed to decrease liver DC/MC. Therefore, FFA and more specifically AT-derived FFA stimulate hepatic DC/MC accumulation, thus recapitulating the pathology of the obese liver. In a number of cases the effects of FFA can be dissociated from OxS and PC but match well with liver TG, a marker of FFA oversupply.

Microvascular Dysfunction Following Multiwalled Carbon Nanotube Exposure Is Mediated by Thrombospondin-1 Receptor CD47

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) disrupts peripheral microvascular function. Thrombospondin-1 (TSP-1) is highly expressed during lung injury and has been shown to alter microvascular reactivity. It is unclear exactly how TSP-1 exerts effects on vascular function, but we hypothesized that the TSP-1 receptor CD47 may mediate changes in vasodilation. Wildtype (WT) or CD47 knockout (CD47 KO) C57B6/J-background animals were exposed to 50 µg of MWCNT or saline control via pharyngeal aspiration. Twenty-four hours postexposure, intravital microscopy was performed to assess arteriolar dilation and venular leukocyte adhesion and rolling. To assess tissue redox status, electron paramagnetic resonance and NOx measurements were performed, while inflammatory biomarkers were measured via multiplex assay.Vasodilation was impaired in the WT + MWCNT group compared with control (57 ± 9 vs 90 ± 2% relaxation), while CD47 KO animals showed no impairment (108 ± 8% relaxation). Venular leukocyte adhesion and rolling increased by >2-fold, while the CD47 KO group showed no change. Application of the antioxidant apocynin rescued normal leukocyte activity in the WT + MWCNT group. Lung and plasma NOx were reduced in the WT + MWCNT group by 47% and 32%, respectively, while the CD47 KO groups were unchanged from control. Some inflammatory cytokines were increased in the CD47 + MWCNT group only. In conclusion, TSP-1 is an important ligand mediating MWCNT-induced microvascular dysfunction, and CD47 is a component of this dysregulation. CD47 activation likely disrupts nitric oxide (•NO) signaling and promotes leukocyte-endothelial interactions. Impaired •NO production, signaling, and bioavailability is linked to a variety of cardiovascular diseases in which TSP-1/CD47 may play an important role.

Experimental intravascular hemolysis induces hemodynamic and pathological pulmonary hypertension: association with accelerated purine metabolism

Pulmonary hypertension (PH) is emerging as a serious complication associated with hemolytic disorders, and plexiform lesions (PXL) have been reported in patients with sickle cell disease (SCD). We hypothesized that repetitive hemolysis per se induces PH and angioproliferative vasculopathy and evaluated a new mechanism for hemolysis-associated PH (HA-PH) that involves the release of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) from erythrocytes. In healthy rats, repetitive administration of hemolyzed autologous blood (HAB) for 10 days produced reversible pulmonary parenchymal injury and vascular remodeling and PH. Moreover, the combination of a single dose of Sugen-5416 (SU, 200 mg/kg) and 10-day HAB treatment resulted in severe and progressive obliterative PH and formation of PXL (Day 26, right ventricular peak systolic pressure (mmHg): 26.1 ± 1.1, 41.5 ± 0.5 and 85.1 ± 5.9 in untreated, HAB treated and SU+HAB treated rats, respectively). In rats, repetitive administration of HAB increased plasma ADA activity and reduced urinary adenosine levels. Similarly, SCD patients had higher plasma ADA and PNP activity and accelerated adenosine, inosine, and guanosine metabolism than healthy controls. Our study provides evidence that hemolysis per se leads to the development of angioproliferative PH. We also report the development of a rat model of HA-PH that closely mimics pulmonary vasculopathy seen in patients with HA-PH. Finally, this study suggests that in hemolytic diseases released ADA and PNP may increase the risk of PH, likely by abolishing the vasoprotective effects of adenosine, inosine and guanosine. Further characterization of this new rat model of hemolysis-induced angioproliferative PH and additional studies of the role of purines metabolism in HA-PH are warranted.

Spontaneous DNA damage to the nuclear genome promotes senescence, redox imbalance and aging

Accumulation of senescent cells over time contributes to aging and age-related diseases. However, what drives senescence in vivo is not clear. Here we used a genetic approach to determine if spontaneous nuclear DNA damage is sufficient to initiate senescence in mammals. Ercc1-/∆ mice with reduced expression of ERCC1-XPF endonuclease have impaired capacity to repair the nuclear genome. Ercc1-/∆ mice accumulated spontaneous, oxidative DNA damage more rapidly than wild-type (WT) mice. As a consequence, senescent cells accumulated more rapidly in Ercc1-/∆ mice compared to repair-competent animals. However, the levels of DNA damage and senescent cells in Ercc1-/∆ mice never exceeded that observed in old WT mice. Surprisingly, levels of reactive oxygen species (ROS) were increased in tissues of Ercc1-/∆ mice to an extent identical to naturally-aged WT mice. Increased enzymatic production of ROS and decreased antioxidants contributed to the elevation in oxidative stress in both Ercc1-/∆ and aged WT mice. Chronic treatment of Ercc1-/∆ mice with the mitochondrial-targeted radical scavenger XJB-5-131 attenuated oxidative DNA damage, senescence and age-related pathology. Our findings indicate that nuclear genotoxic stress arises, at least in part, due to mitochondrial-derived ROS, and this spontaneous DNA damage is sufficient to drive increased levels of ROS, cellular senescence, and the consequent age-related physiological decline.

Dysregulation of DAF-16/FOXO3A-mediated stress responses accelerates oxidative DNA damage induced aging

DNA damage is presumed to be one type of stochastic macromolecular damage that contributes to aging, yet little is known about the precise mechanism by which DNA damage drives aging. Here, we attempt to address this gap in knowledge using DNA repair-deficient C. elegans and mice. ERCC1-XPF is a nuclear endonuclease required for genomic stability and loss of ERCC1 in humans and mice accelerates the incidence of age-related pathologies. Like mice, ercc-1 worms are UV sensitive, shorter lived, display premature functional decline and they accumulate spontaneous oxidative DNA lesions (cyclopurines) more rapidly than wild-type worms. We found that ercc-1 worms displayed early activation of DAF-16 relative to wild-type worms, which conferred resistance to multiple stressors and was important for maximal longevity of the mutant worms. However, DAF-16 activity was not maintained over the lifespan of ercc-1 animals and this decline in DAF-16 activation corresponded with a loss of stress resistance, a rise in oxidant levels and increased morbidity, all of which were cep-1/ p53 dependent. A similar early activation of FOXO3A (the mammalian homolog of DAF-16), with increased resistance to oxidative stress, followed by a decline in FOXO3A activity and an increase in oxidant abundance was observed in Ercc1^-/- primary mouse embryonic fibroblasts. Likewise, in vivo, ERCC1-deficient mice had transient activation of FOXO3A in early adulthood as did middle-aged wild-type mice, followed by a late life decline. The healthspan and mean lifespan of ERCC1 deficient mice was rescued by inactivation of p53. These data indicate that activation of DAF-16/FOXO3A is a highly conserved response to genotoxic stress that is important for suppressing consequent oxidative stress. Correspondingly, dysregulation of DAF-16/FOXO3A appears to underpin shortened healthspan and lifespan, rather than the increased DNA damage burden itself.

Cytochrome b5 Reductase 3 Modulates Soluble Guanylate Cyclase Redox State and cGMP Signaling

RATIONALE

Soluble guanylate cyclase (sGC) heme iron, in its oxidized state (Fe³⁺), is desensitized to NO and limits cGMP production needed for downstream activation of protein kinase G-dependent signaling and blood vessel dilation.

OBJECTIVE

Although reactive oxygen species are known to oxidize the sGC heme iron, the basic mechanism(s) governing sGC heme iron recycling to its NO-sensitive, reduced state remain poorly understood.

METHODS AND RESULTS

Oxidant challenge studies show that vascular smooth muscle cells have an intrinsic ability to reduce oxidized sGC heme iron and form protein-protein complexes between cytochrome b5 reductase 3, also known as methemoglobin reductase, and oxidized sGC. Genetic knockdown and pharmacological inhibition in vascular smooth muscle cells reveal that cytochrome b5 reductase 3 expression and activity is critical for NO-stimulated cGMP production and vasodilation. Mechanistically, we show that cytochrome b5 reductase 3 directly reduces oxidized sGC required for NO sensitization as assessed by biochemical, cellular, and ex vivo assays.

CONCLUSIONS

Together, these findings identify new insights into NO-sGC-cGMP signaling and reveal cytochrome b5 reductase 3 as the first identified physiological sGC heme iron reductase in vascular smooth muscle cells, serving as a critical regulator of cGMP production and protein kinase G-dependent signaling.

Nox2-Mediated PI3K and Cofilin Activation Confers Alternate Redox Control of Macrophage Pinocytosis

AIMS

Internalization of extracellular fluid and its solute by macropinocytosis requires dynamic reorganization of actin cytoskeleton, membrane ruffling, and formation of large endocytic vacuolar compartments, called macropinosomes, inside the cell. Although instigators of macropinocytosis, such as growth factors and phorbol esters, stimulate NADPH oxidase (Nox) activation and signal transduction mediators upstream of Nox assembly, including Rac1 and protein kinase C (PKC), are involved in macropinocytosis, the role of Nox enzymes in macropinocytosis has never been investigated. This study was designed to examine the role of Nox2 and the potential downstream redox signaling involved in macropinocytosis.

RESULTS

Phorbol myristate acetate activation of human and murine macrophages stimulated membrane ruffling, macropinosome formation, and subsequent uptake of macromolecules by macropinocytosis. Mechanistically, we found that pharmacological blockade of PKC, transcriptional knockdown of Nox2, and scavenging of intracellular superoxide anion abolished phorbol ester-induced macropinocytosis. We observed that Nox2-derived reactive oxygen species via inhibition of phosphatase and tensin homolog and activation of the phosphoinositide-3-kinase (PI3K)/Akt pathway lead to activation of actin-binding protein cofilin, membrane ruffling, and macropinocytosis. Similarly, activation of macropinocytosis by macrophage colony-stimulating factor involves Nox2-mediated cofilin activation. Furthermore, peritoneal chimera experiments indicate that macropinocytotic uptake of lipids in hypercholesterolemic ApoE^-/- mice was attenuated in Nox2^y/- macrophages compared with wild-type controls. Innovation and Conclusion: In summary, these findings demonstrate a novel Nox2-mediated mechanism of solute uptake via macropinocytosis, with broad implications for both general cellular physiology and pathological processes. The redox mechanism described here may also identify new targets in atherosclerosis and other disease conditions involving macropinocytosis. Antioxid. Redox Signal. 26, 902-916.

CD47 and Nox1 Mediate Dynamic Fluid-Phase Macropinocytosis of Native LDL

AIMS

Macropinocytosis has been implicated in cardiovascular and other disorders, yet physiological factors that initiate fluid-phase internalization and the signaling mechanisms involved remain poorly identified. The present study was designed to examine whether matrix protein thrombospondin-1 (TSP1) stimulates macrophage macropinocytosis and, if so, to investigate the potential signaling mechanism involved.

RESULTS

TSP1 treatment of human and murine macrophages stimulated membrane ruffle formation and pericellular solute internalization by macropinocytosis. Blockade of TSP1 cognate receptor CD47 and NADPH oxidase 1 (Nox1) signaling, inhibition of phosphoinositide 3-kinase, and transcriptional knockdown of myotubularin-related protein 6 abolished TSP1-induced macropinocytosis. Our results demonstrate that Nox1 signaling leads to dephosphorylation of actin-binding protein cofilin at Ser-3, actin remodeling, and macropinocytotic uptake of unmodified native low-density lipoprotein (nLDL), leading to foam cell formation. Finally, peritoneal chimera studies suggest the role of CD47 in macrophage lipid macropinocytosis in hypercholesterolemic ApoE^-/- mice in vivo.

INNOVATION

Activation of a previously unidentified TSP1-CD47 signaling pathway in macrophages stimulates direct receptor-independent internalization of nLDL, leading to significant lipid accumulation and foam cell formation. These findings reveal a new paradigm in which delimited Nox1-mediated redox signaling, independent of classical lipid oxidation, contributes to early propagation of vascular inflammatory disease.

CONCLUSIONS

The findings of the present study demonstrate a new mechanism of solute uptake with implications for a wide array of cell types, including macrophages, dendritic cells, and cancer cells, and multiple pathological conditions in which matrix proteins are upregulated. Antioxid. Redox Signal. 26, 886-901.

Elevated oxidative stress in the aortic media of patients with bicuspid aortic valve

OBJECTIVE

Congenital bicuspid aortic valve (BAV) is distinctly associated with the development of ascending aortopathy in adulthood, portending risk of both ascending aortic aneurysm and dissection. Our previous work implicated deficiency in oxidative stress response as a mediator of the BAV-associated aortopathy. We hypothesize that reactive oxygen species generation invokes elevated local oxidative tissue damage in ascending aorta of patients with BAV.

METHODS

Ascending aortic specimens were obtained from patients undergoing elective aortic replacement and/or aortic valve replacement and during heart transplant operations. Levels of superoxide anion were measured via high-pressure liquid chromatography-based detection of 2-hydroxyethidium in aortic specimens. Lipid peroxidation and enzymatic activity of superoxide dismutase and peroxidase were quantified in aortic specimens.

RESULTS

Superoxide anion production was elevated in aortic specimens from patients with nonaneurysmal BAV (n = 59) compared with specimens from patients with the morphologically normal tricuspid aortic valve (TAV, n = 38). Total superoxide dismutase activity was similar among aortic specimens from patients with TAV versus BAV (n = 27 and 26, respectively), whereas peroxidase activity was increased in aortic specimens from patients with BAV compared with specimens from patients with TAV (n = 14 for both groups). Lipid peroxidation was elevated in aortic specimens from BAV patients compared with TAV patients (n = 14 and 11, respectively).

CONCLUSIONS

Superoxide anion accumulation and increased lipid peroxidation demonstrate that, despite increased peroxidase activity, the ascending aortopathy of patients with BAV involves oxidative stress. In addition, the absence of increased superoxide dismutase activity in BAV specimens indicates a deficiency in antioxidant defense. This suggests that the characteristic smooth muscle cell loss observed in BAV aortopathy may be a consequence of superoxide-mediated cell damage.

Abstract TMP115: Nox-2 and Cerebrovascular Function in Metabolic Syndrome After a Stroke

Introduction: The aim here is to elucidate the mechanisms involved in post-stroke cerebrovascular impairments in metabolic syndrome (MetS) that pre-dispose obese patients to more severe post-stroke deficits.

Methods: 1 hr middle cerebral artery occlusion was performed in 17 week old lean (LZR) and obese Zucker (OZR: MetS model) rats. At 24 hr or 15 days post-stroke, the ipsilateral middle cerebral artery (MCA) was cannulated in an ex-vivo microvessel preparation to examine MCA reactivity. Cerebrovascular microvessel density (MVD) was examined 15 days post-stroke via IHC. To examine a potential role of Nox2 and oxidative stress, a specific inhibitor of Nox2 oxidase Nox2-dstat (i.p 10mg/kg) was given during the stroke procedure in OZR.

Results: In LZR, MCA reactivity was impaired vs. non-stroke control at 24hr post-stroke and remained stable at 15 days post-stroke. In LZR, NO bioavailability was reduced at 24hrs vs. controls, which remained stable at 15 days. In OZR, the MCA impairment was greater at 24 hr vs. LZR, and worsened significantly at 15 days post stroke. NO bioavailability for OZR at 24 hr was similar to LZR stroke, but by 15 days had fallen. MVD was reduced 15 days post-stroke, with a larger loss in OZR vs. LZR. Stroke mortality and infarct size were higher for OZR. Nox2 inhibition restored MCA reactivity, improved MVD and NO levels, and limited stroke infarct size in OZR post-stroke.

Discussion: Our data suggest that the MetS increases stroke severity and drives a progressive decline in cerebrovascular dysfunction following ischemic stroke. Inhibiting Nox2 production improved stroke outcome in MetS.

Mechanistic characterization of nitrite-mediated neuroprotection after experimental cardiac arrest

Nitrite acts as an ischemic reservoir of nitric oxide (NO) and a potent S-nitrosating agent which reduced histologic brain injury after rat asphyxial cardiac arrest (ACA). The mechanism(s) of nitrite-mediated neuroprotection remain to be defined. We hypothesized that nitrite-mediated brain mitochondrial S-nitrosation accounts for neuroprotection by reducing reperfusion reactive oxygen species (ROS) generation. Nitrite (4 μmol) or placebo was infused IV after normothermic (37°C) ACA in randomized, blinded fashion with evaluation of neurologic function, survival, brain mitochondrial function, and ROS. Blood and CSF nitrite were quantified using reductive chemiluminescence and S-nitrosation by biotin switch. Direct neuroprotection was verified in vitro after 1 and 4 h neuronal oxygen glucose deprivation measuring neuronal death with inhibition studies to examine mechanism. Mitochondrial ROS generation was quantified by live neuronal imaging using mitoSOX. Nitrite significantly reduced neurologic disability after ACA. ROS generation was reduced in brain mitochondria from nitrite- versus placebo-treated rats after ACA with congruent preservation of brain ascorbate and reduction of ROS in brain sections using immuno-spin trapping. ATP generation was maintained with nitrite up to 24 h after ACA. Nitrite rapidly entered CSF and increased brain mitochondrial S-nitrosation. Nitrite reduced in vitro mitochondrial superoxide generation and improved survival of neurons after oxygen glucose deprivation. Protection was maintained with inhibition of soluble guanylate cyclase but lost with NO scavenging and ultraviolet irradiation. Nitrite therapy results in direct neuroprotection from ACA mediated by reductions in brain mitochondrial ROS in association with protein S-nitrosation. Neuroprotection is dependent on NO and S-nitrosothiol generation, not soluble guanylate cyclase.

Regional Disruptions in Endothelial Nitric Oxide Pathway Associated With Bicuspid Aortic Valve

BACKGROUND

Endothelial nitric oxide (NO) synthase (eNOS) has been implicated in the development of bicuspid aortic valve (BAV) and with differential expression in the ascending aorta of BAV patients. However, little is known about functional disruptions in the eNOS pathway and the effect on BAV-associated aortic dilatation. We tested the hypothesis that eNOS function is regionally diminished in ascending thoracic aortic aneurysms associated with BAV.

METHODS

Thoracic aortic aneurysms specimens were collected from patients with BAV (n = 21) or tricuspid aortic valve (n = 12). Tissue samples were harvested from three circumferential regions corresponding to locations above the right, left, and noncoronary sinuses. Adventitial-stripped specimens containing media and intima only were analyzed for NO synthase 3 gene expression and total eNOS protein. Indicators of eNOS activity (pSer1177-eNOS) and NO bioavailability (phosphorylation of vasodilator-stimulated phosphoprotein at Ser239) were also measured.

RESULTS

NO synthase 3 and eNOS protein were elevated in the right aortic region of BAV specimens compared with tricuspid aortic valve specimens. Activation of eNOS, as indicated by pSer1177-eNOS, was higher in BAV specimens across all regions. Despite increases in eNOS and pSer1177-eNOS, BAV specimens displayed no change in pSer239-vasodilator-stimulated phosphoprotein compared with tricuspid aortic valve specimens.

CONCLUSIONS

BAV is associated with regional disruptions in the eNOS pathway, most markedly in the right aortic region. The discrepancy between increased eNOS activity and the absence of increased NO bioavailability in this region provides insight into physiologic mechanisms potentially underlying the asymmetric dilatation pattern observed in BAV.

Fatty acid nitroalkenes induce resistance to ischemic cardiac injury by modulating mitochondrial respiration at complex II

Nitro-fatty acids (NO₂-FA) are metabolic and inflammatory-derived electrophiles that mediate pleiotropic signaling actions. It was hypothesized that NO₂-FA would impact mitochondrial redox reactions to induce tissue-protective metabolic shifts in cells. Nitro-oleic acid (OA-NO₂) reversibly inhibited complex II-linked respiration in isolated rat heart mitochondria in a pH-dependent manner and suppressed superoxide formation. Nitroalkylation of Fp subunit was determined by BME capture and the site of modification by OA-NO₂ defined by mass spectrometric analysis. These effects translated into reduced basal and maximal respiration and favored glycolytic metabolism in H9C2 cardiomyoblasts as assessed by extracellular H⁺ and O₂ flux analysis. The perfusion of NO₂-FA induced acute cardioprotection in an isolated perfused heart ischemia/reperfusion (IR) model as evidenced by significantly higher rate-pressure products. Together these findings indicate that NO₂-FA can promote cardioprotection by inducing a shift from respiration to glycolysis and suppressing reactive species formation in the post-ischemic interval.

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Nitro-oleic acid (OA-NO₂) reversibly inhibits complex II-linked respiration.

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Nitrated fatty acid favor a switch from beta oxidation to glycolysis in cardiomyoblasts.

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Nitrated fatty acid induce cardioprotection in a heart ischemia/reperfusion model.

In Vivo Immuno-Spin Trapping: Imaging the Footprints of Oxidative Stress

A plethora of disease processes are associated with elevated reactive species formation and allied reactions with biomolecules that alter cell signaling, induce overt damage, and promote dysfunction of tissues. Unfortunately, effective detection of reactive species in tissues is wrought with issues that significantly limit capacity for validating species identity, establishing accurate concentrations, and identifying anatomic sites of production. These shortcomings reveal the pressing need for new approaches to more precisely assess reactive species generation in vivo. Herein, we describe an in vivo immuno-spin trapping method for indirectly assessing oxidant levels by detecting free radicals resulting from reaction of oxidants with biomolecules to form stable, immunologically detectable nitrone-biomolecular adducts. This process couples the reactivity and sensitivity of an electron paramagnetic resonance spin trap with the resolution of confocal imaging to visualize the extent of cell and tissue oxidation and anatomic sites of production by detecting resultant free radical formation.