Improving combination therapies: targeting A2B-adenosine receptor to modulate metabolic tumor microenvironment and immunosuppression

BACKGROUND

We investigated the role of A2B-adenosine receptor in regulating immunosuppressive metabolic stress in the tumor microenvironment. Novel A2B-adenosine receptor antagonist PBF-1129 was tested for antitumor activity in mice and evaluated for safety and immunologic efficacy in a phase I clinical trial of patients with non-small cell lung cancer.

METHODS

The antitumor efficacy of A2B-adenosine receptor antagonists and their impact on the metabolic and immune tumor microenvironment were evaluated in lung, melanoma, colon, breast, and epidermal growth factor receptor-inducible transgenic cancer models. Employing electron paramagnetic resonance, we assessed changes in tumor microenvironment metabolic parameters, including pO2, pH, and inorganic phosphate, during tumor growth and evaluated the immunologic effects of PBF-1129, including its pharmacokinetics, safety, and toxicity, in patients with non-small cell lung cancer.

RESULTS

Levels of metabolic stress correlated with tumor growth, metastasis, and immunosuppression. Tumor interstitial inorganic phosphate emerged as a correlative and cumulative measure of tumor microenvironment stress and immunosuppression. A2B-adenosine receptor inhibition alleviated metabolic stress, downregulated expression of adenosine-generating ectonucleotidases, increased expression of adenosine deaminase, decreased tumor growth and metastasis, increased interferon γ production, and enhanced the efficacy of antitumor therapies following combination regimens in animal models (anti-programmed cell death 1 protein vs anti-programmed cell death 1 protein plus PBF-1129 treatment hazard ratio = 11.74 [95% confidence interval = 3.35 to 41.13], n = 10, P < .001, 2-sided F test). In patients with non-small cell lung cancer, PBF-1129 was well tolerated, with no dose-limiting toxicities; demonstrated pharmacologic efficacy; modulated the adenosine generation system; and improved antitumor immunity.

CONCLUSIONS

Data identify A2B-adenosine receptor as a valuable therapeutic target to modify metabolic and immune tumor microenvironment to reduce immunosuppression, enhance the efficacy of immunotherapies, and support clinical application of PBF-1129 in combination therapies.

Bacterial Pyocyanin Inducible Keratin 6A Accelerates Closure of Epithelial Defect under Conditions of Mitochondrial Dysfunction

Repair of epithelial defect is complicated by infection and related metabolites. Pyocyanin (PYO) is one such metabolite that is secreted during Pseudomonas aeruginosa infection. Keratinocyte (KC) migration is required for the closure of skin epithelial defects. This work sought to understand PYO-KC interaction and its significance in tissue repair. Stable Isotope Labeling by Amino acids in Cell culture proteomics identified mitochondrial dysfunction as the top pathway responsive to PYO exposure in human KCs. Consistently, functional studies showed mitochondrial stress, depletion of reducing equivalents, and adenosine triphosphate. Strikingly, despite all stated earlier, PYO markedly accelerated KC migration. Investigation of underlying mechanisms revealed, to our knowledge, a previously unreported function of keratin 6A in KCs. Keratin 6A was PYO inducible and accelerated closure of epithelial defect. Acceleration of closure was associated with poor quality healing, including compromised expression of apical junction proteins. This work recognizes keratin 6A for its role in enhancing KC migration under conditions of threat posed by PYO. Qualitatively deficient junctional proteins under conditions of defensive acceleration of KC migration explain why an infected wound close with deficient skin barrier function as previously reported.

Abstract TMP32: Genetic Knockout Of CD38 Is Associated With Improved Cognitive Performance And Protection Against Oxidative Stress In Aged Mice

Introduction: CD38 enzymatic activity is the main determinant of the age-dependent decline in nicotinamide adenine dinucleotide (NAD + ) levels and the loss of CD38 function has been associated with increased longevity in rodents. Therefore, we hypothesize that the loss of CD38 and its enzymatic function will improve cognitive performance in advanced age through the preservation of NAD + levels and the protection against oxidative stress.

Methods: CD38 Knockout (CD38KO) and C57BL/6J (wild type WT) male mice were aged for at least 24 months. The cognitive performance was compared through Barnes maze, Fear conditioning and Y-maze tests. Dihydroethidium (DHE), Diaminofluorescein-2 diacetate (DAF) and nicotinamide adenine dinucleotide phosphate NAD(P)H staining were used to assess the levels of superoxide, nitric oxide (NO) and NAD(P)H in the brain, respectively.

Results: 5 WT and 5 CD38KO mice aged (24-30) months were included. While there were no significant differences in fear conditioning and Y-maze tests, CD38KO mice showed better memory performance in Barnes maze test including shorter distance travelled (CD38KO: 2±0.06 vs WT: 3.7±1.1 m, p=0.008), longer time in proximity of the holes (CD38KO: 51.2±11.1 vs WT: 34.6±8.4 s, p=0.027), and shorter distance from the hole (CD38KO: 0.17±0.025 vs WT: 0.23±0.04 m, p=0.038) and less errors (CD38KO: 3.5±2.3 vs WKY: 6±0.7, p=0.04). Brain tissue analysis showed 58% lower superoxide (p<0.0001), 129% higher NO (p=0.009), and 141% higher NAD(P)H levels (p<0.0001) in CD38KO compared to WT mice.

Conclusions: The loss of CD38 and its enzymatic function is associated with better memory performance, less oxidative stress, and higher NAD(P)H in older mice suggesting its potential role as a future therapeutic target against age-related dementias.

Trityl Quinodimethane Derivatives as Unimolecular Triple-Function Extracellular EPR Probes for Redox, pH, and Oxygen

Electron paramagnetic resonance (EPR) spectroscopy and imaging coupled with the use of suitable probes is a promising tool for assessment of the tumor microenvironment (TME). Measurement of multiple TME parameters by EPR is very desirable but challenging. Herein, we designed and synthesized a class of negative-charged trityl quinodimethane MTPs as unimolecular triple-function extracellular probes for redox, pH, and oxygen (O2) levels. Using the deuterated analogue, dMTP5, which has an optimal pKa as well as high sensitivity to bioreduction and O2, we reasonably evaluated pH effects on efflux of reducing agents from HepG2 cells and cellular O2 consumption.

Characterizing CD38 Expression and Enzymatic Activity in the Brain of Spontaneously Hypertensive Stroke-Prone Rats

Background: CD38 is a transmembrane glycoprotein that catabolizes nicotinamide adenine dinucleotide (NAD+) and is the main source for the age-dependent decrease in NAD+ levels. Increased CD38 enzymatic activity has been implicated in several neurological diseases. However, its role in the pathogenesis of cerebral small vessel disease (CSVD) remains unknown. We aimed to characterize CD38 expression and enzymatic activity in the brain of spontaneously hypertensive stroke-prone rats (SHRSP), a genetic model for hypertension and human CSVD, in comparison to age-matched normotensive Wistar Kyoto rats (WKY). Materials and Methods: Age-matched male 7- and 24-week-old WKY and SHRSP were studied. CD38 enzymatic activity was determined in the brain homogenate. Immunohistochemistry and Western Blotting (WB) were used to characterize CD38 expression and localize it in the different cell types within the brain. In addition, expression of nitric oxide synthase (NOS) isoforms and the levels of nitric oxide (NO), superoxide, nicotinamide dinucleotide (phosphate) NAD(P)H were measured the brain of in WKY and SHRSP. Results: CD38 expression and enzymatic activity were increased in SHRSP brains compared to age matched WKY starting at 7 weeks of age. CD38 expression was localized to the endothelial cells, astrocytes, and microglia. We also identified increased CD38 expression using WB with age in SHRSP and WKY. CD38 enzymatic activity was also increased in 24-week SHRSP compared to 7-week SHRSP. In association, we identified evidence of oxidative stress, reduced NO level, reduced NAD(P)H level and endothelial NOS expression in SHRSP compared to age matched WKY. NAD(P)H also decreased with age in WKY and SHRSP. Additionally, activation of astrocytes and microglia were present in SHRSP compared to WKY. Conclusions: CD38 is overexpressed, and its enzymatic activity is increased in SHRSP, a genetic model for marked hypertension and human CSVD. Our results suggest a potential role for CD38 enzymatic activation in the pathogenesis of CSVD and points to the need for future mechanistic and pharmacological studies.

In Situ EPR Spin Trapping and Competition Kinetics Demonstrate Temperature-Dependent Mechanisms of Synergistic Radical Production by Ultrasonically Activated Persulfate

Ultrasound coupled with activated persulfate can synergistically degrade aqueous organic contaminants. Here, in situ electron paramagnetic resonance spin trapping was used to compare radicals produced by ultrasonically activated persulfate (US-PS) and its individual technologies, ultrasound alone (US) and heat-activated persulfate (PS), with respect to temperature. Radicals were trapped using 5,5-dimethyl-1-pyrroline-N-oxide, DMPO, to form detectable nitroxide adducts. Using initial rates of radical adduct formation, and compared to US and PS, US-PS at 40 and 50 °C resulted in the largest synergistic production of radicals. Radicals generated from US were reasonably consistent from 40 to 70 °C, indicating that temperature had little effect on cavitational bubble collapse over this range. However, synergy indexes calculated from initial rates showed that ultrasonic activation of persulfate at the bubble interface changes with temperature. From these results, we speculate that higher temperatures enhance persulfate uptake into cavitation bubbles via nanodroplet injection. DMPO-OH was the predominant adduct detected for all conditions. However, competition modeling and spin trapping in the presence of nitrobenzene and atrazine probes showed that SO₄^•- predominated. Therefore, the DMPO-OH signal is derived from SO₄^•- trapping with subsequent DMPO-SO₄^- hydrolysis to DMPO-OH. Spin trapping is effective in quantifying total radical adduct formation but limited in measuring primary radical speciation in this case.

Abstract WP16: Characterizing Cd38 Expression And Activity In The Brain Of Spontaneously Hypertensive Stroke Prone Rats

Introduction: CD38 is an ectoenzyme that is the main source of age dependent decrease in NAD + levels. Its role in cerebral small vessel disease (cSVD) is unknown. We hypothesize that CD38 is over-expressed and activated in spontaneously hypertensive stroke-prone rat (SHRSP), a model of human cSVD.

Methods: 20 SHRSP and 20 age matched male Wistar Kyoto control rats (WKY) were studied. Systolic blood pressure (SBP) was measured weekly using tail-cuff plethysmography. Half of the groups were euthanized at 7 weeks of age (Wks) and the remaining rats were followed until 24 Wks. Routine histology and immunohistochemistry (IHC) were performed for nitric oxide synthase (NOS) subtypes, superoxides (DHE), NO (DAF), and NADPH. IHC was used to detect CD38 expression and co-staining determined expression on endothelial cells (eNOS), astrocytes (GFAP), microglia (Iba1), T cells (CD3), macrophages (CD68), neutrophils (MPO) and neurons (Neuon). CD38 activity was detected in the brain homogenate by using a substrate analog of NAD + with measurement of its conversion to the strongly fluorescent product (ε-ADPR).

Results: Compared to WKY, SHRSP developed hypertension between (9 -12) Wks and sustained it afterwards (SBP: 19 Wks: WKY 142.5±11.8 mmHg vs SHRSP 180.3±12.8 mmHg, P<0.0001). At 24 Wks, SHRSP showed histological evidence of cSVD including microbleed, enlarged perivascular spaces, and lipohyalinosis. Compared to WKY, CD38 expression was increased in SHRSP brain (7 Wks: 102.6%, P=0.011, 24 Wks: 83.2%, p=0.0077). CD38 activity was also significantly higher in SHRSP (7 Wks: 11.8%, p=0.012, 24 Wks: 20.2%, p=0.0065). We identified CD38 expression on endothelial cells, astrocytes and microglia. In comparison to WKY, SHRSP showed lower levels of NADPH (7 Wks: 22.3%, p=0.029, 24 Wks: 65.5%, p=0.0065), NO (7 Wks: 39.3% p=0.0008, 24 Wks: 36%, p=0.04), endothelial NOS (7 Wks: 57.5%, p=0.02, 24 Wks: 50.6%, p=0.01) and higher superoxide (7 Wks: 131%, p<0.0001, 24 Wks: 163%, p<0.0001).

Conclusions: The brain of SHRSP shows evidence for elevated CD38 activity and expression with associated oxidative stress, depletion of NADPH and eNOS dysfunction compared to normotensive WKY. These results suggest the potential role of CD38 based therapeutics in future management of human cSVD.

Role of cytoglobin in cigarette smoke constituent-induced loss of nitric oxide bioavailability in vascular smooth muscle cells

Cytoglobin (Cygb) has been identified as the major nitric oxide (NO) metabolizing protein in vascular smooth muscle cells (VSMCs) and is crucial for the regulation of vascular tone. In the presence of its requisite cytochrome B5a (B5)/B5 reductase-isoform-3 (B5R) reducing system, Cygb controls NO metabolism through the oxygen-dependent process of NO dioxygenation. Tobacco cigarette smoking (TCS) induces vascular dysfunction; however, the role of Cygb in the pathophysiology of TCS-induced cardiovascular disease has not been previously investigated. While TCS impairs NO biosynthesis, its effect on NO metabolism remains unclear. Therefore, we performed studies in aortic VSMCs with tobacco smoke extract (TSE) exposure to investigate the effects of cigarette smoke constituents on the rates of NO decay, with focus on the alterations that occur in the process of Cygb-mediated NO metabolism. TSE greatly enhanced the rates of NO metabolism by VSMCs. An initial increase in superoxide-mediated NO degradation was seen at 4 h of exposure. This was followed by much larger progressive increases at 24 and 48 h, accompanied by parallel increases in the expression of Cygb and B5/B5R. siRNA-mediated Cygb knockdown greatly decreased these TSE-induced elevations in NO decay rates. Therefore, upregulation of the levels of Cygb and its reducing system accounted for the large increase in NO metabolism rate seen after 24 h of TSE exposure. Thus, increased Cygb-mediated NO degradation would contribute to TCS-induced vascular dysfunction and partial inhibition of Cygb expression or its NO dioxygenase function could be a promising therapeutic target to prevent secondary cardiovascular disease.

Electronic Cigarette Exposure Causes Vascular Endothelial Dysfunction Due to NADPH Oxidase Activation and eNOS Uncoupling

We recently reported a mouse model of chronic electronic cigarette (e-cig) exposure-induced cardiovascular pathology, where long-term exposure to e-cig vape (ECV) induces cardiac abnormalities, impairment of endothelial function, and systemic hypertension. Here, we delineate the underlying mechanisms of ECV-induced vascular endothelial dysfunction (VED), a central trigger of cardiovascular disease. C57/BL6 male mice were exposed to ECV generated from e-cig liquid containing 0, 6, or 24 mg/ml nicotine for 16 and 60 weeks. Time-dependent elevation in blood pressure and systemic vascular resistance were observed, along with an impairment of acetylcholine-induced aortic relaxation in ECV-exposed mice, compared to air-exposed control. Decreased intravascular nitric oxide (NO) levels and increased superoxide generation with elevated 3-nitrotyrosine levels in the aorta of ECV-exposed mice were observed, indicating that ECV-induced superoxide reacts with NO to generate cytotoxic peroxynitrite. Exposure increased NADPH oxidase expression, supporting its role in ECV-induced superoxide generation. Downregulation of endothelial nitric oxide synthase (eNOS) expression and Akt-dependent eNOS phosphorylation occurred in the aorta of ECV-exposed mice, indicating that exposure inhibited de novo NO synthesis. Following ECV exposure, the critical NOS cofactor tetrahydrobiopterin was decreased, with a concomitant loss of its salvage enzyme, dihydrofolate reductase. NADPH oxidase and NOS inhibitors abrogated ECV-induced superoxide generation in the aorta of ECV exposed mice. Together, our data demonstrate that ECV exposure activates NADPH oxidase and uncouples eNOS, causing a vicious cycle of superoxide generation and vascular oxidant stress that triggers VED and hypertension with predisposition to other cardiovascular disease.

Cytoglobin has potent superoxide dismutase function

Cytoglobin (Cygb) was discovered as a novel type of globin that is expressed in mammals; however, its functions remain uncertain. While Cygb protects against oxidant stress, the basis for this is unclear, and the effect of Cygb on superoxide metabolism is unknown. From dose-dependent studies of the effect of Cygb on superoxide catabolism, we identify that Cygb has potent superoxide dismutase (SOD) function. Initial assays using cytochrome c showed that Cygb exhibits a high rate of superoxide dismutation on the order of 108 M-1 ⋅ s-1 Spin-trapping studies also demonstrated that the rate of Cygb-mediated superoxide dismutation (1.6 × 108 M-1 ⋅ s-1) was only ∼10-fold less than Cu,Zn-SOD. Stopped-flow experiments confirmed that Cygb rapidly dismutates superoxide with rates within an order of magnitude of Cu,Zn-SOD or Mn-SOD. The SOD function of Cygb was inhibited by cyanide and CO that coordinate to Fe3+-Cygb and Fe2+-Cygb, respectively, suggesting that dismutation involves iron redox cycling, and this was confirmed by spectrophotometric titrations. In control smooth-muscle cells and cells with siRNA-mediated Cygb knockdown subjected to extracellular superoxide stress from xanthine/xanthine oxidase or intracellular superoxide stress triggered by the uncoupler, menadione, Cygb had a prominent role in superoxide metabolism and protected against superoxide-mediated death. Similar experiments in vessels showed higher levels of superoxide in Cygb-/- mice than wild type. Thus, Cygb has potent SOD function and can rapidly dismutate superoxide in cells, conferring protection against oxidant injury. In view of its ubiquitous cellular expression at micromolar concentrations in smooth-muscle and other cells, Cygb can play an important role in cellular superoxide metabolism.

Reperfusion mediates heme impairment with increased protein cysteine sulfonation of mitochondrial complex III in the post-ischemic heart

A serious consequence of myocardial ischemia-reperfusion injury (I/R) is oxidative damage, which causes mitochondrial dysfunction. The cascading ROS can propagate and potentially induce heme bleaching and protein cysteine sulfonation (PrSO3H) of the mitochondrial electron transport chain. Herein we studied the mechanism of I/R-mediated irreversible oxidative injury of complex III in mitochondria from rat hearts subjected to 30-min of ischemia and 24-h of reperfusion in vivo. In the I/R region, the catalytic activity of complex III was significantly impaired. Spectroscopic analysis indicated that I/R mediated the destruction of hemes b and c + c1 in the mitochondria, supporting I/R-mediated complex III impairment. However, no significant impairment of complex III activity and heme damage were observed in mitochondria from the risk region of rat hearts subjected only to 30-min ischemia, despite a decreased state 3 respiration. In the I/R mitochondria, carbamidomethylated C122/C125 of cytochrome c1 via alkylating complex III with a down regulation of HCCS was exclusively detected, supporting I/R-mediated thioether defect of heme c1. LC-MS/MS analysis showed that I/R mitochondria had intensely increased complex III PrSO3H levels at the C236 ligand of the [2Fe2S] cluster of the Rieske iron‑sulfur protein (uqcrfs1), thus impairing the electron transport activity. MS analysis also indicated increased PrSO3H of the hinge protein at C65 and of cytochrome c1 at C140 and C220, which are confined in the intermembrane space. MS analysis also showed that I/R extensively enhanced the PrSO3H of the core 1 (uqcrc1) and core 2 (uqcrc2) subunits in the matrix compartment, thus supporting the conclusion that complex III releases ROS to both sides of the inner membrane during reperfusion. Analysis of ischemic mitochondria indicated a modest reduction from the basal level of complex III PrSO3H detected in the mitochondria of sham control hearts, suggesting that the physiologic hyperoxygenation and ROS overproduction during reperfusion mediated the enhancement of complex III PrSO3H. In conclusion, reperfusion-mediated heme damage with increased PrSO3H controls oxidative injury to complex III and aggravates mitochondrial dysfunction in the post-ischemic heart.

Characterizing the Neuroimaging and Histopathological Correlates of Cerebral Small Vessel Disease in Spontaneously Hypertensive Stroke-Prone Rats

Introduction: Spontaneously hypertensive stroke-prone rats (SHRSP) are used to model clinically relevant aspects of human cerebral small vessel disease (CSVD). To decipher and understand the underlying disease dynamics, assessment of the temporal progression of CSVD histopathological and neuroimaging correlates is essential. Materials and Methods: Eighty age-matched male SHRSP and control Wistar Kyoto rats (WKY) were randomly divided into four groups that were aged until 7, 16, 24 and 32 weeks. Sensorimotor testing was performed weekly. Brain MRI was acquired at each study time point followed by histological analyses of the brain. Results: Compared to WKY controls, the SHRSP showed significantly higher prevalence of small subcortical hyperintensities on T2w imaging that progressed in size and frequency with aging. Volumetric analysis revealed smaller intracranial and white matter volumes on brain MRI in SHRSP compared to age-matched WKY. Diffusion tensor imaging (DTI) showed significantly higher mean diffusivity in the corpus callosum and external capsule in WKY compared to SHRSP. The SHRSP displayed signs of motor restlessness compared to WKY represented by hyperactivity in sensorimotor testing at the beginning of the experiment which decreased with age. Distinct pathological hallmarks of CSVD, such as enlarged perivascular spaces, microbleeds/red blood cell extravasation, hemosiderin deposits, and lipohyalinosis/vascular wall thickening progressively accumulated with age in SHRSP. Conclusions: Four stages of CSVD severity in SHRSP are described at the study time points. In addition, we find that quantitative analyses of brain MRI enable identification of in vivo markers of CSVD that can serve as endpoints for interventional testing in therapeutic studies.

Serine mutations in overexpressed Hsp27 abrogate the protection against doxorubicin-induced p53-dependent cardiac apoptosis in mice

Small heat shock proteins (sHsps) protect the heart from chemotherapeutics-induced heart failure by inhibiting p53-dependent apoptosis. However, mechanism of such protection has not been elucidated yet. Here we test a hypothesis that serine phosphorylation of sHsps is essential to inhibit the doxorubicin-induced and p53-dependent apoptotic pathway. Three transgenic mice (TG) lines with cardiomyocyte-specific overexpression of human heat shock protein 27 (hHsp27), namely, wild-type [myosin heavy chain (MHC)-hHsp27], S82A single mutant [MHC-mut-hHsp27(S82A)], and trimutant [MHC-mut-hHsp27(S15A/S78A/S82A)] were generated. TG mice were treated with Dox (6 mg/kg body wt; once in a week; 4 wk) along with age-matched nontransgenic (non-TG) controls. The Dox-treated MHC-hHsp27 mice showed improved survival and cardiac function (both MRI and echocardiography) in terms of contractility [ejection fraction (%EF)] and left ventricular inner diameter (LVID) compared with the Dox-treated non-TG mice. However, both MHC-mut-hHsp27(S82A) and MHC-mut-hHsp27(S15A/S78A/S82A) mutants overexpressing TG mice did not show such a cardioprotection. Furthermore, transactivation of p53 was found to be attenuated only in Dox-treated MHC-hHsp27 mice-derived cardiomyocytes in vitro, as low p53 was detected in the nuclei, not in mutant hHsp27 overexpressing cardiomyocytes. Similarly, only in MHC-hHsp27 overexpressing cardiomyocytes, low Bax, higher mechanistic target of rapamycin (mTOR) phosphorylation, and low apoptotic poly(ADP-ribose) polymerase-1 (PARP-1) cleavage (89 kDa fragment) were detected. Pharmacological inhibition of p53 was more effective in mutant TG mice compared with MHC-hHsp27 mice. We conclude that phosphorylation of overexpressed Hsp27 at S82 and its association with p53 are essential for the cardioprotective effect of overexpressed Hsp27 against Dox-induced dilated cardiomyopathy. Only phosphorylated Hsp27 protects the heart by inhibiting p53 transactivation.NEW & NOTEWORTHY Requirement of serine phosphorylation in Hsp27 for cardioprotective effect against Dox is tested in various mutants overexpressing mice. Cardioprotective effect was found to be compromised in Hsp27 serine mutants overexpressed mice compared with wild-type overexpressing mice. These results indicate that cancer patients, who carry these mutations, may have higher risk of aggravated cardiomyopathy on treated with cardiotoxic chemotherapeutics such as doxorubicin.

Development of an L-band resonator optimized for fast scan EPR imaging of the mouse head

PURPOSE

To develop a novel resonator for high-quality fast scan electron paramagnetic resonance (EPR) and EPR/NMR co-imaging of the head and brain of mice at 1.25 GHz.

METHODS

Resonator dimensions were scaled to fit the mouse head with maximum filling factor. A single-loop 6-gap resonator of 20 mm diameter and 20 mm length was constructed. High resonator stability was achieved utilizing a fixed position double coupling loop. Symmetrical mutually inverted connections rendered it insensitive to field modulation and fast scan. Coupling adjustment was provided by a parallel-connected variable capacitor located at the feeding line at λ/4 distance. To minimize radiation loss, the shield around the resonator was supplemented with a planar conductive disc that focuses return magnetic flux.

RESULTS

Coupling of the resonator loaded with the mouse head was efficient and easy. This resonator enabled high-quality in vivo 3D EPR imaging of the mouse head following intravenous infusion of nitroxide probes. With this resonator and rapid scan EPR system, 4 ms scans were acquired in forward and reverse directions so that images with 2-scan 3,136 projections were acquired in 25 s. Head images were achieved with resolutions of 0.4 mm, enabling visualization of probe localization and uptake across the blood-brain barrier.

CONCLUSIONS

This resonator design provides good sensitivity, high stability, and B1 field homogeneity for in vivo fast scan EPR of the mouse head and brain, enabling faster measurements and higher resolution imaging of probe uptake, localization, and metabolism than previously possible.

High fidelity triangular sweep of the magnetic field for millisecond scan EPR imaging

Linearity of the magnetic field sweep is important for high resolution continuous wave EPR imaging. Driving the field with triangular wave function is the most efficient way to scan EPR projections. However, the magnetic field sweep profile can be significantly distorted during fast millisecond projection scan. In this work, we introduce a method to generate highly linear and properly symmetrical triangular sweeps of the magnetic field using calibrated harmonics of the triangular wave function. First, the frequency response function of the EPR magnet and its power circuitry was obtained. For this, the field sweeping coil was driven with sinusoidal signals of different frequencies and the actual magnetic field inside the magnet was recorded. To cover wide range of frequencies, the measurements were carried out independently using gaussmeter, Hall-effect linear sensor integrated circuit, and an inductance coil. For each frequency, the system gain and the phase delay were determined. These data were used to adjust the amplitudes and the phases of individual harmonics of the triangular wave function. After the calibration, the maximum deviation of the magnetic field from the linear function was 0.05% of sweep width for 4 ms scan. The maximum discrepancy between the forward and the reverse scan was less than 0.04%. Sweep overhead time for changing the scan direction was 5%. The proposed approach allows generation of high fidelity triangular magnetic field sweeps with accuracy better than 0.1% for the range of the magnetic field sweep widths up to 48 G and scan duration from 10 s down to 1 ms.

Abstract P52: Temporal Progression of Cerebral Small Vessel Disease Lesions on Brain Magnetic Resonance Imaging in Spontaneously Hypertensive Stroke Prone Rats

Introduction: Spontaneously Hypertensive Rats- Stroke Prone (SHRSP) are a relevant model for human cerebral small vessel disease (cSVD). However, data are still lacking regarding the neuroimaging correlates of cSVD lesions in SHRSP and their temporal evolution in relationship to histological findings.

Methods: 40 SHRSP and 40 Wistar Kyoto control (WKY) male rats were divided into 4 groups (10 WKY and 10 SHRSP) per group. Systolic blood pressure (SBP) was measured using tail-cuff device, weekly. Select animals of each group had brain MRI at 9.4T machine at 7, 16, 24, and 32 weeks of age. Volumetric analysis was completed using manual segmentation of the total brain, ventricles and bilateral hippocampi. Following MRI, brain histology was completed at the same time points.

Results: At 6 weeks, SBP was similar (WKY 123.8±0.1 vs SHRSP 130.7±3.2, P=0.09). SHRSP developed hypertension between 9-11 weeks of age and maintained it throughout the experiment (SBP at 31 weeks: WKY 138.1±6 vs SHRSP 169.1±6.7, p=0.0006). At 7 weeks, brain MRI was normal in SHRSP and WKY. Histology was largely unremarkable except for few areas of red blood cell extravasation in couple of SHRSP. At 16 weeks, MRI was normal in WKY and it showed small subcortical hyperintensity on T2 sequences in one SHRSP while histology showed microbleeds (MBs) in 85% of SHRSP. At 24 weeks, brain MRI consistently identified subcortical hyperintensities in SHRSP and H&E showed MBs in all SHRSP in addition to hemosiderin deposition and arteriosclerosis. LFB staining showed areas of demyelination in the corpus callosum. At 32 weeks, SHRSP had hydrocephalus and H&E showed widespread hemosiderin deposition. Volumetric analysis showed larger ventricles in SHRSP (SHRSP 42.3±18.1 ml vs WKY 28.4±7.2 ml, p=0.013) and ventricle size significantly increased with age in SHRSP. Hippocampal and brain volumes were similar in both groups (hippocampal volume: WKY 84.5±8.1 ml vs SHRSP 81.6±2.6 ml, p=0.39; brain volume WKY 2103.4±100.4 ml vs SHRSP 2169.6 ±164.2 ml, p=0.2).

Conclusions: SHRSP develop cSVD histological changes early in life and brain MRI showed consistent abnormalities at a later time point. These results have implications in defining cSVD phenotypes in SHRSP in future mechanistic studies.

Abstract P731: Genetic Knockout of Cd38 Protects Mice Against Ischemic Brain Injury

Introduction: CD38 is an ectoenzyme that is present on the cellular membranes of endothelial cells and subtypes of inflammatory cells. We have shown that ischemia/reperfusion (I/R) in the heart triggers CD38 activation that in turns leads to NADPH depletion and endothelial nitric oxide synthase (eNOS) impairment. This cascade results in worsening of ischemic injury secondary to endothelial dysfunction. We hypothesize that a similar paradigm exists in acute ischemic stroke and that loss of CD38 function is protective against cerebral I/R injury.

Methods: Middle cerebral artery occlusion (MCAO) was performed for 60 minutes in 15 week-old CD38 knockout mice (KO) n=12 and wild type (WT) mice n=12. Stroke volume was calculated using T2 MRI sequences obtained at 48 hours post MCAO. Percentage of brain infarction volume compensated for swelling (IFV) was calculated by manual segmentation of the stroke area and non-affected cerebral hemisphere. Following brain MRI, H&E staining and immunohistochemistry assessment of superoxide radicals (DHE fluorescence) nitric oxide (NO) (DAF fluorescence), eNOS expression, CD38 expression and microglia activation (Iba1) were performed. (P<0.05) was considered significant in statistical testing.

Results: CD38 KO mice had a smaller IFV as % of the normal contralateral hemisphere volume compared to WT (19.6±3 vs 33.5±9, P=0.001). Both western blotting and immunohistology confirmed lack of CD38 expression in CD38 KO mice. CD38 expression was 55% higher in the ipsilateral stroke side compared to the contralateral stroke side in WT mice (P=0.0105). Compared to WT mice, CD38 KO had 45% lower superoxide levels (P<0.001), 50% higher NO levels (P<0.05) and 46% lower Iba-1 expression with more significance in ipsilateral side (P<0.01) than contralateral side (P<0.05). While eNOS expression was 40% lower in WT vs CD38 KO, this did not reach statistical significance.

Conclusions: Thus, genetic deletion of CD38 is protective against cerebral ischemia with reduced superoxide production and preserved NO production, likely through the protection conferred against NADPH depletion. These results suggest that inhibition of CD38 could serve as a potent therapeutic approach to protect against acute ischemic stroke and related brain I/R injury.

Abstract P51: Temporal Changes In Nitric Oxide Synthase Isoform Expression And Function In Spontaneously Hypertensive Stroke Prone Rats

Introduction: Nitric oxide (NO) has been implicated in the pathogenesis of cerebral small vessel disease (cSVD). NO is produced by three NO synthase (NOS) isoforms including endothelial (eNOS), neuronal (nNOS), and inducible (iNOS). While eNOS has been implicated in cSVD pathologies that occur in Spontaneously Hypertensive Stroke Prone Rats (SHRSP), cSVD model, the mechanistic role and temporal changes of NOS isoform expression including eNOS in relation to cSVD development in SHRSP remains unknown. We aimed to characterize the temporal changes of NOS isoforms expression in SHRSP from the asymptomatic stage until the development of cSVD lesions.

Methods: 20 SHRSP and 20 Wistar Kyoto (WKY) male rats were studied. Systolic blood pressure (SBP) was measured weekly using tail-cuff plethysmography. Half of the groups were euthanized at 7 weeks of age and the remaining rats were followed until 24 weeks of age. Routine histology and immunohistochemistry were performed for eNOS, nNOS, iNOS, superoxide radicals (DHE), NO (DAF) and Iba1 for microglia activation.

Results: At 7 weeks, SBP was not significantly different between the groups (WKY 106.6±5.4 vs SHRSP 120.8±5.4, P=0.06). SHRSP developed hypertension between 9-11 weeks and maintained it throughout the experiment (SBP (21 weeks): WKY 134.8±5.4 vs 168.9±5.4, P<0.0001). Brain histology was largely negative for cSVD lesions at 7 weeks. At 24 weeks, histology showed areas of demyelination, microbleed formation, arteriosclerosis and hemosiderin deposits in SHRSP. At 7 weeks, compared to WKY, eNOS and nNOS expression were 50% and 30% lower in SHRSP (P=0.0038 and 0.0211, respectively). iNOS expression was 93% higher in SHRSP (P=0.0068). Superoxide levels were 133% higher in SHRSP (P<0.0001) and NO was 40% lower in SHRSP (P<0.0008). At 24 weeks, all of these differences became larger. Iba-1 expression was 25% higher at 7 weeks and became 97% higher in SHRSP at 24 weeks (P<0.0001).

Conclusions: SHRSP show significant differences in NOS isoform expression with loss of NO and gain of superoxide production early in life prior to development of cSVD lesions. Superoxide overproduction and related oxidant stress may lead to NOS dysfunction and uncoupling which may trigger cSVD onset and point towards potential future therapies.

Long-term electronic cigarette exposure induces cardiovascular dysfunction similar to tobacco cigarettes: role of nicotine and exposure duration

Electronic cigarette (e-cig) vaping (ECV) has been proposed as a safer alternative to tobacco cigarette smoking (TCS); however, this remains controversial due to a lack of long-term comparative studies. Therefore, we developed a chronic mouse exposure model that mimics human vaping and allows comparison with TCS. Longitudinal studies were performed to evaluate alterations in cardiovascular function with TCS and ECV exposure durations of up to 60 wk. For ECV, e-cig liquid with box-mod were used and for TCS, 3R4F-cigarettes. C57/BL6 male mice were exposed 2 h/day, 5 days/wk to TCS, ECV, or air control. The role of vape nicotine levels was evaluated using e-cig-liquids with 0, 6, or 24 mg/mL nicotine. Following 16-wk exposure, increased constriction to phenylephrine and impaired endothelium-dependent and endothelium-independent vasodilation were observed in aortic segents, paralleling the onset of systemic hypertension, with elevations in systemic vascular resistance. Following 32 wk, TCS and ECV induced cardiac hypertrophy. All of these abnormalities further increased out to 60 wk of exposure, with elevated heart weight and aortic thickness along with increased superoxide production in vessels and cardiac tissues of both ECV and TCS mice. While ECV-induced abnormalities were seen in the absence of nicotine, these occurred earlier and were more severe with higher nicotine exposure. Thus, long-term vaping of e-cig can induce cardiovascular disease similar to TCS, and the severity of this toxicity increases with exposure duration and vape nicotine content.NEW & NOTEWORTHY A chronic mouse exposure model that mimics human e-cigarette vaping and allows comparison with tobacco cigarette smoking was developed and utilized to perform longitudinal studies of alterations in cardiovascular function. E-cigarette exposure led to the onset of cardiovascular disease similar to that with tobacco cigarette smoking. Impaired endothelium-dependent and endothelium-independent vasodilation with increased adrenergic vasoconstriction were observed, paralleling the onset of systemic hypertension and subsequent cardiac hypertrophy. This cardiovascular toxicity was dependent on exposure duration and nicotine dose.

Defining the reducing system of the NO dioxygenase cytoglobin in vascular smooth muscle cells and its critical role in regulating cellular NO decay

In smooth muscle, cytoglobin (Cygb) functions as a potent nitric oxide (NO) dioxygenase and regulates NO metabolism and vascular tone. Major questions remain regarding which cellular reducing systems regulate Cygb-mediated NO metabolism. To better define the Cygb-mediated NO dioxygenation process in vascular smooth muscle cells (SMCs), and the requisite reducing systems that regulate cellular NO decay, we assessed the intracellular concentrations of Cygb and its putative reducing systems and examined their roles in the process of NO decay. Cygb and the reducing systems, cytochrome b5 (B5)/cytochrome b5 reductase (B5R) and cytochrome P450 reductase (CPR) were measured in aortic SMCs. Intracellular Cygb concentration was estimated as 3.5 μM, while B5R, B5, and CPR were 0.88, 0.38, and 0.15 μM, respectively. NO decay in SMCs was measured following bolus addition of NO to air-equilibrated cells. siRNA-mediated knockdown experiments indicated that ∼78% of NO metabolism in SMCs is Cygb-dependent. Of this, ∼87% was B5R- and B5-dependent. CPR knockdown resulted in a small decrease in the NO dioxygenation rate (V_NO), while depletion of ascorbate had no effect. Kinetic analysis of V_NO for the B5/B5R/Cygb system with variation of B5 or B5R concentrations from their SMC levels showed that V_NO exhibits apparent Michaelis–Menten behavior for B5 and B5R. In contrast, linear variation was seen with change in Cygb concentration. Overall, B5/B5R was demonstrated to be the major reducing system supporting Cygb-mediated NO metabolism in SMCs with changes in cellular B5/B5R levels modulating the process of NO decay.

Whole body electronic cigarette exposure system for efficient evaluation of diverse inhalation conditions and products

Objectives: To develop and test a new system for whole body exposure of small animals to support investigation of the biological effects of aerosol generated by electronic cigarette (e-cig) products under diverse inhalation conditions with improved control and monitoring of the e-cig vape exposure and nicotine delivered to the animal's systemic circulation. Methods: A computer-controlled design, with built-in sensors for real time monitoring of O₂, CO₂, relative humidity, and temperature within the exposure chambers and port for measuring total particulate matter (TPM) was developed, constructed and tested. This design accommodates a variety of commercial vaping devices, offers software flexibility to adjust exposure protocols to mimic different users' puffing patterns, enables variable nicotine delivery to the animal's systemic circulation; minimizes travel time and alterations of aerosol quality or quantity by delivering aerosol directly to the exposure chamber, offers local or remote operation of up to six distinct exposure chambers from a single control unit, and can simultaneously test different exposure conditions or products in diverse animal groups, which reduces inter-run variability, saves time, and increases productivity. Results: The time course pattern of TPM concentration during different phases of the exposure cycle was measured. With increased puffing duration or number of exposure cycles, higher TPM exposure and plasma cotinine levels were observed with plasma cotinine levels in the range reported in light or heavy smokers. Conclusion: Overall, this novel, versatile, and durable exposure system facilitates high-throughput evaluation of the relative safety and potential toxicity of a variety of e-cig devices and liquids.

The novel SOD mimetic GC4419 increases cancer cell killing with sensitization to ionizing radiation while protecting normal cells

While radiotherapy is a widely used treatment for many types of human cancer, problems of radio-resistance and side effects remain. Side effects induced by ionizing radiation (IR) arise primarily from its propensity to trigger inflammation and oxidative stress with damage of normal cells and tissues near the treatment area. The highly potent superoxide dismutase mimetic, GC4419 (Galera Therapeutics), rapidly enters cells and is highly effective in dismutating superoxide (O₂^•-). We performed studies to assess the potency of GC4419 in cancer killing and radio-sensitization in human lung cancer cells and normal immortalized lung cells. Treatment with GC4419 did not alter the radical generation during IR, primarily hydroxyl radical (^.OH); however, it quenched the increased levels of O₂^•- detected in the cancer cells before and following IR. GC4419 triggered cancer cell death and inhibited cancer cell proliferation with no adverse effect on normal cells. Combination of GC4419 with IR augmented the cytotoxic effects of IR on cancer cells compared to monotherapy, while protecting normal cells from IR-induced cell death. DNA fragmentation and caspase-3 activity assays showed that combination of GC4419 with IR enhances cancer cell apoptosis. Moreover, GC4419 increased IR-induced Bax levels with decreased Bcl-2 and elevated Bax/Bcl-2 ratio following treatment. GC4419 increased TrxR activity in the normal cells but decreased activity in cancer cells, conferring increased cancer cell sensitivity to oxidative stress. In conclusion, GC4419 increases the cytotoxic and pro-apoptotic activity of IR in lung cancer cells while decreasing injury in normal cells.

Algebraic reconstruction of 3D spatial EPR images from high numbers of noisy projections: An improved image reconstruction technique for high resolution fast scan EPR imaging

A novel method for reconstructing 3D spatial EPR images from large numbers of noisy projections was developed that minimizes mean square error between the experimental projections and those from the reconstructed image. The method utilizes raw projection data and zero gradient spectrum to account for EPR line shape and hyperfine structure of the paramagnetic probe without the need for deconvolution techniques that are poorly suited for processing of high noise projections. A numerical phantom was reconstructed for method validation. Reconstruction time for the matrix of 128³ voxels and 16,384 noiseless projections was 4.6 min for a single iteration. The algorithm converged quickly, reaching R² ~ 0.99975 after the very first iteration. An experimental phantom sample with nitroxyl radical was measured. With 16,384 projections and a field gradient of 8 G/cm, resolutions of 0.4 mm were achieved for a cubical area of 25 × 25 × 25 mm³. Reconstruction was sufficiently fast and memory efficient making it suitable for applications with large 3D matrices and fully determined system of equations. The developed algorithm can be used with any gradient distribution and does not require adjustable filter parameters that makes for simple application. A thorough analysis of the strengths and limitations of this method for 3D spatial EPR imaging is provided.

Synergistic, aqueous PAH degradation by ultrasonically-activated persulfate depends on bulk temperature and physicochemical parameters

Coupling ultrasound with other remediation technologies has potential to result in synergistic degradation of contaminants. In this work, we evaluated synergisms from adding high-power ultrasound (20 kHz; 250 W) to activated persulfate over a range of bulk temperatures (20-60 °C). We studied the aqueous degradation kinetics of three polycyclic aromatic hydrocarbons (PAHs: naphthalene, phenanthrene, and fluoranthene) treated by ultrasound-alone, heat-activated persulfate, and combined ultrasonically-activated persulfate (US-PS). At 20 °C, observed US-PS rate constants strongly correlated with Wilke-Chang diffusion coefficients. This correlation indicates PAH molecules diffuse to the bubble-water interface prior to reaction with sulfate radicals (SO₄^-) generated at the interface. At higher temperatures, observed US-PS rate constants appear to be a more complicated function of temperature and diffusion coefficients. Synergy indexes for PAHs with fast diffusion coefficients were greatest at 20 °C. Fluoranthene, the largest and most hydrophobic PAH, had a maximum synergy index at 30 °C; it benefited from additional thermal persulfate activation in bulk solution. Fluoranthene synergy indexes, however, decreased above 30 °C and became antagonistic at 60 °C. Electron paramagnetic resonance (EPR) spin trapping was used to quantify hydroxyl radical (OH) produced from acoustic cavitation in the absence of persulfate. These data showed consistent OH production from 20 to 60 °C, indicating PAH antagonisms at 60 °C were not due to lower bubble collapse temperatures. Instead, the results suggest that PAH antagonisms are caused by increased radical-radical recombination as bulk temperature increases. In effort to develop an efficient, combined remediation technology, this work suggests bulk temperatures between 20 and 40 °C maximize US-PS synergisms.

Imbalance in zinc homeostasis enhances lung Tissue Loss following cigarette smoke exposure

Cigarette smoke exposure is a major cause of chronic obstructive pulmonary disease. Cadmium is a leading toxic component of cigarette smoke. Cadmium and zinc are highly related metals. Whereas, zinc is an essential metal required for normal health, cadmium is highly toxic. Zrt- and Irt-like protein 8 (ZIP8) is an avid transporter of both zinc and cadmium into cells and is abundantly expressed in the lung of smokers compared to nonsmokers. Our objective was to determine whether disturbed zinc homeostasis through diet or the zinc transporter ZIP8 increase susceptibility to lung damage following prolonged cigarette smoke exposure.

METHODS

Cigarette smoke exposure was evaluated in the lungs of mice subject to insufficient and sufficient zinc intakes, in transgenic ZIP8 overexpressing mice, and a novel myeloid-specific ZIP8 knockout strain.

RESULTS

Moderate depletion of zinc intakes in adult mice resulted in a significant increase in lung cadmium burden and permanent lung tissue loss following prolonged smoke exposure. Overexpression of ZIP8 resulted in increased lung cadmium burden and more extensive lung damage, whereas cigarette smoke exposure in ZIP8 knockout mice resulted in increased lung tissue loss without a change in lung cadmium content, but a decrease in zinc.

CONCLUSIONS

Overall, findings were consistent with past human studies. Imbalance in Zn homeostasis increases susceptibility to permanent lung injury following prolonged cigarette smoke exposure. Based on animal studies, both increased and decreased ZIP8 expression enhanced irreversible tissue damage in response to prolonged tobacco smoke exposure. We believe these findings represent an important advancement in our understanding of how imbalance in zinc homeostasis and cadmium exposure via tobacco smoke may increase susceptibility to smoking-induced lung disease.

Regulation of Nitric Oxide Metabolism and Vascular Tone by Cytoglobin

Significance: Cytoglobin (Cygb) was discovered as a new addition to the globin superfamily and subsequently identified to have potent nitric oxide (NO) dioxygenase function. Cygb plays a critical role in the oxygen-dependent regulation of NO levels and vascular tone. Recent Advances: In recent years, the mechanism of the Cygb-mediated NO dioxygenation has been studied in isolated protein, smooth muscle cell, isolated blood vessel, and in vivo animal model systems. Studies in Cygb^-/- mice have demonstrated that Cygb plays a critical role in regulating blood pressure and vascular tone. This review summarizes advances in the knowledge of NO dioxygenation/metabolism regulated by Cygb. Advances in measurement of NO diffusion dynamics across blood vessels and kinetic modeling of Cygb-mediated NO dioxygenation are summarized. The oxygen-dependent regulation of NO degradation by Cygb is also reviewed along with how Cygb paradoxically generates NO from nitrite under anaerobic conditions. The important role of Cygb in the regulation of vascular function and disease is reviewed. Critical Issues: Cygb is a more potent NO dioxygenase (NOD) than previously known globins with structural differences in heme coordination and environment, conferring it with a higher rate of reduction and more rapid process of NO dioxygenation with unique oxygen dependence. Various cellular reducing systems regenerate the catalytic oxyferrous Cygb species, supporting a high rate of NO dioxygenation. Future Directions: There remains a critical need to further characterize the factors and processes that modulate Cygb-mediated NOD function, and to develop pharmacological or other approaches to modulate Cygb function and expression.

Dioxygen Binding and Sensing Proteins

Oxygen binding proteins (O₂BIP) have been actively investigated for the past five decades due to their rich redox chemistry and function as O₂ carriers in blood cells, as well as their function as gasotransmitters and sensors that modulate cellular signaling. A series of meetings on the periodic advances in the knowledge gained in the field of globin structure and function are conducted typically on a biannual basis. In the fall of 2018, the XXth International Conference was conducted, and very important articles with breakthrough discoveries were presented and very enthusiastically discussed. This was yet another highly successful meeting in the series. Select articles from this meeting were recently reviewed, updated, and published over several issues of Antioxidants and Redox Signaling, as Forum articles communicating the latest advances in this important area of redox biology. This Forum editorial introduces these articles and highlights their scientific significance in advancing the field. Each of these articles grew out of lectures presented in the meeting, and appears either as an original contribution or a comprehensive review in the journal. Overall, the articles published in the Forum provide in-depth details on the recent developments in the field as well as point the way to future directions. These Forum articles thus serve as an important summary of progress and the ongoing direction of this field, and serve to highlight recent advances in our understanding of O₂BIP.

Chronic cigarette smoke exposure triggers a vicious cycle of leukocyte and endothelial-mediated oxidant stress that results in vascular dysfunction

Although there is a strong association between cigarette smoking exposure (CSE) and vascular endothelial dysfunction (VED), the underlying mechanisms by which CSE triggers VED remain unclear. Therefore, studies were performed to define these mechanisms using a chronic mouse model of cigarette smoking (CS)-induced cardiovascular disease mirroring that in humans. C57BL/6 male mice were subjected to CSE for up to 48 wk. CSE impaired acetylcholine (ACh)-induced relaxation of aortic and mesenteric segments and triggered hypertension, with mean arterial blood pressure at 32 and 48 wk of exposure of 122 ± 6 and 135 ± 5 mmHg compared with 99 ± 4 and 102 ± 6 mmHg, respectively, in air-exposed mice. CSE led to monocyte activation with superoxide generation in blood exiting the pulmonary circulation. Macrophage infiltration with concomitant increase in NADPH oxidase subunits p22^phox and gp91^phox was seen in aortas of CS-exposed mice at 16 wk, with further increase out to 48 wk. Associated with this, increased superoxide production was detected that decreased with Nox inhibition. Tetrahydrobiopterin was progressively depleted in CS-exposed mice but not in air-exposed controls, resulting in endothelial nitric oxide synthase (eNOS) uncoupling and secondary superoxide generation. CSE led to a time-dependent decrease in eNOS and Akt expression and phosphorylation. Overall, CSE induces vascular monocyte infiltration with increased NADPH oxidase-mediated reactive oxygen species generation and depletes the eNOS cofactor tetrahydrobiopterin, uncoupling eNOS and triggering a vicious cycle of oxidative stress with VED and hypertension. Our study provides important insights toward understanding the process by which smoking contributes to the genesis of cardiovascular disease and identifies biomarkers predictive of disease.NEW & NOTEWORTHY In a chronic model of smoking-induced cardiovascular disease, we define underlying mechanisms of smoking-induced vascular endothelial dysfunction (VED). Smoking exposure triggered VED and hypertension and led to vascular macrophage infiltration with concomitant increase in superoxide and NADPH oxidase levels as early as 16 wk of exposure. This oxidative stress was accompanied by tetrahydrobiopterin depletion, resulting in endothelial nitric oxide synthase uncoupling with further superoxide generation triggering a vicious cycle of oxidative stress and VED.

Abstract 40: Time Course of Cerebral Small Vessel Disease Lesions and Sensory Motor Changes in Spontaneously Hypertensive Stroke Prone Rats

Introduction: Animal models of human cerebral small vessel disease (CSVD) are important for the study of the disease underlying mechanisms and testing therapeutic interventions. Spontaneusly Hypertensive Rats - Stroke Prone (SHRSP) are used as an animal model of human CSVD. However, there is a lack of data regarding the time course of cognitive and motor impairment.

Methods: Male age-matched SHRSP and Wistar Kyoto rats (WKY) were studied. Sensorimotor testing (open field test) and tail-cuff systolic blood pressure (SBP) measurements (Visitech Systems, Inc.) were performed weekly starting from 6 until 24 weeks of age. Brain MRI at 7 and 24 weeks was acquired using a 9.4T MRI system. Brain histology was completed at the same time points. Statistical analysis was performed using a linear mixed model with repeated measurements. P< 0.05 was considered significant.

Results: 20 SHRSP and 20 WKY male rats were studied. 10 per group were euthanized following brain MRI at 7 weeks and the rest were followed until 24 weeks. SHRSP weighed on average 30 grams less than WKY throughout the study (P=0.0003). At 7 weeks SBP was not different (WKY 106.6±5.4 vs SHRSP 120.8±5.4, P=0.06). SHRSP started to develop hypertension at 9-12 weeks and maintained hypertension until 24 weeks (average group difference across time P<0.0001; SBP at 21 weeks WKY 134.8±5.4 vs SHRSP 168.9±5.4, P<0.0001). Sensorimotor testing showed higher total distance travelled (TDT) at 7 weeks in SHRSP that trended down with ageing. Both groups became similar at 21 weeks (TDT: at 7 weeks WKY 3.78±1.3 vs SHRSP 7.8±1.3, P =0.037; at 21 weeks: WKY 4±1.3 vs SHRSP 4.4±1.3, P=0.83; average group difference across time P=0.014). Brain MRI was normal at 7 weeks, but small white matter hyperintensities were seen at 24 weeks. Brain Histology showed normal histology on hematoxylin & eosin staining at 7 weeks in both groups, while at 24 weeks SHRSP showed CSVD histopathological changes including microbleed formation, homeostasis and vascular hyalinosis.

Conclusions: SHRSP develops hypertension, sensorimotor deficits and CSVD pathology as they age suggesting their utility as human CSVD model. Intervention time points should be selected carefully in future therapeutic drug interventions.

Abstract WP323: Genetic Knockout of CD38 in Mice Protects Against Ischemic Stroke With Smaller Infarct Volumes and Decreased Motor Impairment

Introduction: Endothelial dysfunction is an important mediator of post ischemic injury of the heart and brain following ischemia/reperfusion (I/R). We have reported that CD38 activation in heart I/R models leads to NADPH depletion with endothelial nitric oxide synthase (eNOS) impairment, loss of endothelial-mediated coronary dilatation and increased myocardial infarction. While CD38 knockout or inhibition prevents this dysfunction and decreases myocardial infarction, the role of CD38 in ischemic stroke remains uncertain.

Hypothesis: We hypothesize that loss of CD38 expression and activity through gene knockout is protective with smaller infarct volume.

Methods: 15 week-old male CD38 knock out (KO) n=12 and wild type (WT) mice n=12 underwent middle cerebral artery occlusion (MCAO) for 60 minutes. Stroke volume was calculated using T2 MRI sequences on a 9.4 T MRI system acquired 48 hours post stroke with images analyzed using Osirix software. The ratios of the stroke volume to the affected hemisphere volume and the compensated swelling infarction volume percentage of normal hemisphere were calculated using established methods. Open field test to measure motor impairment was performed at baseline and 48 hours post stroke (KO, n=12, WT n=6). Statistical analysis was completed in STATA using Man-Whitney U test and T-test to compare infarct volumes and cognitive parameters. Values are shown as mean ± SD. P value < 0.05 was considered significant.

Results: At 48 hours, brain MRI showed a smaller percentage of cerebral hemisphere affected by stroke in CD38 KO compared to WT (25.9±3.7 vs 41.1±9.4, respectively P=0.0001) and a smaller percentage of compensated swelling infarction volume of normal hemisphere in KO mice compared to WT (19.6±3 vs 33.5±9, respectively P=0.0001). Open field test showed significant post stroke motor impairment in WT compared to CD38KO mice (distance travelled 1.8±1 m vs 4.7±3 m, P=0.04, respectively and average speed 0.006±0.003 m/s vs 0.016±0.01m/s, P=0.04, respectively).

Conclusions: Infarct volumes are smaller and motor impairment is decreased in CD38 KO mice compared to WT demonstrating that gene knockout of CD38 confers neuroprotection against acute ischemic brain injury.

Discriminative Detection of Biothiols by Electron Paramagnetic Resonance Spectroscopy using a Methanethiosulfonate Trityl Probe

Biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), coexist in biological systems with diverse biological roles. Thus, analytical techniques that can detect, quantify, and distinguish between multiple biothiols are desirable but challenging. Herein, we demonstrate the simultaneous detection and quantitation of multiple biothiols, including up to three different biothiols in a single sample, using electron paramagnetic resonance (EPR) spectroscopy and a trityl-radical-based probe (MTST). We term this technique EPR thiol-trapping. MTST could trap thiols through its methanethiosulfonate group to form the corresponding disulfide conjugate with an EPR spectrum characteristic of the trapped thiol. MTST was used to investigate effects of l-buthionine sulfoximine (BSO) and pyrrolidine dithiocarbamate (PDTC) on the efflux of GSH and Cys from HepG2 cells.

Membrane-specific spin trap, 5-dodecylcarbamoyl-5-N-dodecylacetamide-1-pyroline-N-oxide (diC12PO): theoretical, bioorthogonal fluorescence imaging and EPR studies

Membranous organelles are major endogenous sources of reactive oxygen and nitrogen species. When present at high levels, these species can cause macromolecular damage and disease. To better detect and scavenge free radical forms of the reactive species at their sources, we investigated whether nitrone spin traps could be selectively targeted to intracellular membranes using a bioorthogonal imaging approach. Electron paramagnetic resonance imaging demonstrated that the novel cyclic nitrone 5-dodecylcarbamoyl-5-N-dodecylacetamide-1-pyroline-N-oxide (diC₁₂PO) could be used to target the nitrone moiety to liposomes composed of phosphatidyl choline. To test localization with authentic membranes in living cells, fluorophores were introduced via strain-promoted alkyne-nitrone cycloaddition (SPANC). Two fluorophore-conjugated alkynes were investigated: hexynamide-fluoresceine (HYA-FL) and dibenzylcyclooctyne-PEG4-5/6-sulforhodamine B (DBCO-Rhod). Computational and mass spectrometry experiments confirmed the cycloadduct formation of DBCO-Rhod (but not HYA-FL) with diC₁₂PO in cell-free solution. Confocal microscopy of bovine aortic endothelial cells treated sequentially with diC₁₂PO and DBCO-Rhod demonstrated clear localization of fluorescence with intracellular membranes. These results indicate that targeting of nitrone spin traps to cellular membranes is feasible, and that a bioorthogonal approach can aid the interrogation of their intracellular compartmentalization properties.

[D-Ala2, D-Leu5] Enkephalin Improves Liver Preservation During Normothermic Ex Vivo Perfusion

BACKGROUND

Meeting the metabolic demands of donor livers using normothermic ex vivo liver perfusion (NEVLP) preservation technology is challenging. The delta opioid agonist [D-Ala2, D-Leu5] enkephalin (DADLE) has been reported to decrease the metabolic demand in models of ischemia and cold preservation. We evaluated the therapeutic potential of DADLE by investigating its ability to protect against oxidative stress and hepatic injury during normothermic perfusion.

MATERIALS AND METHODS

Primary rat hepatocytes were used in an in vitro model of oxidative stress to determine the minimum dose of DADLE needed to induce protection and the mechanisms associated with protection. NEVLP was then used to induce injury in rat livers and determine the effectiveness of DADLE in preventing liver injury.

RESULTS

In hepatocytes, DADLE was protective against oxidative stress and led to a decrease in phosphorylation of JNK and p38. Naltrindole, a δ-opioid receptor antagonist, blocked this effect. DADLE also activated the PI3K/Akt signaling pathway, and PI3K/Akt inhibition decreased the protective effects of DADLE treatment. In addition, DADLE treatment during NEVLP resulted in lower perfusate alanine aminotransferase and tissue malondialdehyde and better tissue adenosine triphosphate and glutathione. Furthermore, perfusion with DADLE compared with perfusate alone preserved tissue architecture.

CONCLUSIONS

DADLE confers protection against oxidative stress in hepatocytes and during NEVLP. These data suggest that the mechanism of protection involved the prevention of mitochondrial dysfunction by opioid receptor signaling and subsequent increased expression of prosurvival/antiapoptotic signaling pathways. Altogether, data suggest that opioid receptor agonism may serve as therapeutic target for improved liver protection during NEVLP.

Development of a fast-scan EPR imaging system for highly accelerated free radical imaging

PURPOSE

In continuous wave EPR imaging, the acquisition of high-quality images was previously limited by the requisite long acquisition times of each image projection that was typically greater than 1 second. To accelerate the process of image acquisition facilitating greater numbers of projections and higher image resolution, instrumentation was developed to greatly accelerate the magnetic field scan that is used to obtain each EPR image projection.

METHODS

A low-inductance solenoidal coil for field scanning was used along with a spherical solenoid air core magnet, and scans were driven by triangular symmetric waves, allowing forward and reverse spectrum acquisition as rapid as 3.8 ms. The uniform distribution of projections was used to optimize the contribution of projections for 3D image reconstruction.

RESULTS

Using this fast-scan EPR system, high-quality EPR images of phantoms and perfused rat hearts were performed using trityl or nanoparticulate LiNcBuO (lithium octa-n-butoxy-substituted naphthalocyanine) probes with fast-scan EPR imaging at L-band, achieving spatial resolutions of up to 250 micrometers in 1 minute.

CONCLUSION

Fast-scan EPR imaging can greatly facilitate the efficient and precise mapping of the spatial distribution of free radical and other paramagnetic probes in living systems.

Inhibition of CD38 with the Thiazoloquin(az)olin(on)e 78c Protects the Heart against Postischemic Injury

Inhibition of and genetic deletion of the NAD(P)+ hydrolase [NAD(P)ase] CD38 have been shown to protect against ischemia/reperfusion (I/R) injury in rat and mouse hearts. CD38 has been shown to enhance salvage of NADP(H), which in turn prevents impairment of endothelial nitric oxide synthase function, a hallmark of endothelial dysfunction. Despite growing evidence for a role of CD38 in postischemic injury, until recently there had been a lack of potent CD38 inhibitors. Recently, a new class of thiazoloquin(az)olin(on)e compounds were identified as highly potent and specific CD38 inhibitors. Herein, we investigate the ability of one of these compounds, 78c, to inhibit CD38 and protect the heart in an ex vivo model of myocardial I/R injury. The potency and mechanism of CD38 inhibition by 78c was assessed in vitro using recombinant CD38. The dose-dependent tissue uptake of 78c in isolated mouse hearts was determined, and high tissue permeability of 78c was observed when delivered in perfusate. Treatment of hearts with 78c was protective against both postischemic endothelial and cardiac myocyte injury, with preserved nitric oxide synthase-dependent vasodilatory and contractile function, respectively. Myocardial infarction was also significantly decreased in 78c-treated hearts, with preserved levels of high-energy phosphates. Protective effects peaked at 10 μM treatment, and similar protection without toxicity was seen at 5-fold higher doses. Overall, 78c was shown to be a potent and biologically active CD38 inhibitor with favorable tissue uptake and marked protective effects against I/R injury with enhanced preservation of contractile function, coronary flow, and decreased infarction.

Preclinical Development of a vWF Aptamer to Limit Thrombosis and Engender Arterial Recanalization of Occluded Vessels

Endothelial surface and circulating glycoprotein von Willebrand factor (vWF) regulates platelet adhesion and is associated with thrombotic diseases, including ischemic stroke, myocardial infarction, and peripheral vascular disease. Thrombosis, as manifested in these diseases, is the leading cause of disability and death in the western world. Current parenteral antithrombotic and thrombolytic agents used to treat these conditions are limited by a short therapeutic window, irreversibility, and major risk of hemorrhage. To overcome these limitations, we developed a novel anti-vWF aptamer, called DTRI-031, that selectively binds and inhibits vWF-mediated platelet adhesion and arterial thrombosis while enabling rapid reversal of this antiplatelet activity by an antidote oligonucleotide (AO). Aptamer DTRI-031 exerts dose-dependent inhibition of platelet aggregation and thrombosis in whole blood and mice, respectively. Moreover, DTRI-031 can achieve potent vascular recanalization of platelet-rich thrombotic occlusions in murine and canine carotid arteries. Finally, DTRI-031 activity is rapidly (<5 min) and completely reversed by AO administration in a murine saphenous vein hemorrhage model, and murine toxicology studies indicate the aptamer is well tolerated. These findings suggest that targeting vWF with an antidote-controllable aptamer potentially represents an effective and safer treatment for thrombosis patients having platelet-rich arterial occlusions in the brain, heart, or periphery.

Intrahepatic Delivery of Pegylated Catalase Is Protective in a Rat Ischemia/Reperfusion Injury Model

BACKGROUND

Ischemia/reperfusion injury (IRI) can occur during liver surgery. Endogenous catalase is important to cellular antioxidant defenses and is critical to IRI prevention. Pegylation of catalase (PEG-CAT) improves its therapeutic potential by extending plasma half-life, but systemic administration of exogenous PEG-CAT has been only mildly therapeutic for hepatic IRI. Here, we investigated the protective effects of direct intrahepatic delivery of PEG-CAT during IRI using a rat hilar clamp model.

MATERIALS AND METHODS

PEG-CAT was tested in vitro and in vivo. In vitro, enriched rat liver cell populations were subjected to oxidative stress injury (H₂O₂), and measures of cell health and viability were assessed. In vivo, rats underwent segmental (70%) hepatic warm ischemia for 1 h, followed by 6 h of reperfusion, and plasma alanine aminotransferase and aspartate aminotransferase, tissue malondialdehyde, adenosine triphosphate, and GSH, and histology were assessed.

RESULTS

In vitro, PEG-CAT pretreatment of liver cells showed substantial uptake and protection against oxidative stress injury. In vivo, direct intrahepatic, but not systemic, delivery of PEG-CAT during IRI significantly reduced alanine aminotransferase and aspartate aminotransferase in a time-dependent manner (P < 0.01, P < 0.0001, respectively, for all time points) compared to control. Similarly, tissue malondialdehyde (P = 0.0048), adenosine triphosphate (P = 0.019), and GSH (P = 0.0015), and the degree of centrilobular necrosis, were improved by intrahepatic compared to systemic PEG-CAT delivery.

CONCLUSIONS

Direct intrahepatic administration of PEG-CAT achieved significant protection against IRI by reducing the volume distribution and taking advantage of the substantial hepatic first-pass uptake of this molecule. The mode of delivery was an important factor for protection against hepatic IRI by PEG-CAT.

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, normothermic ex vivo liver perfusion (NEVLP) has been introduced as a method to evaluate and modify organ function. NEVLP has many advantages in comparison to hypothermic and subnormothermic perfusion including reduced preservation injury, restoration of normal organ function under physiologic conditions, assessment of organ performance, and as a platform for organ repair, remodeling, and modification. Both murine and porcine NEVLP models have been described. We demonstrate a rat model of NEVLP and use this model to show one of its important applications - the use of a therapeutic molecule added to liver perfusate. Catalase is an endogenous reactive oxygen species (ROS) scavenger and has been demonstrated to decrease ischemia-reperfusion in the eye, brain, and lung. Pegylation has been shown to target catalase to the endothelium. Here, we added pegylated-catalase (PEG-CAT) to the base perfusate and demonstrated its ability to mitigate liver preservation injury. An advantage of our rodent NEVLP model is that it is inexpensive in comparison to larger animal models. A limitation of this study is that it does not currently include post-perfusion liver transplantation. Therefore, prediction of the function of the organ post-transplantation cannot be made with certainty. However, the rat liver transplant model is well established and certainly could be used in conjunction with this model. In conclusion, we have demonstrated an inexpensive, simple, easily replicable NEVLP model using rats. Applications of this model can include testing novel perfusates and perfusate additives, testing software designed for organ evaluation, and experiments designed to repair organs.

Cigarette smoke constituents cause endothelial nitric oxide synthase dysfunction and uncoupling due to depletion of tetrahydrobiopterin with degradation of GTP cyclohydrolase

Cigarette smoking (CS) is a well-established risk factor for cardiovascular disease (CVD). Endothelial dysfunction (ED) with loss of nitric oxide (NO) production is a central mechanism leading to the advent of CVD. Despite many prior studies of this major health problem, the exact mechanism by which CS induces ED is not well understood. This study examines the mechanism by which CS induces ED with altered endothelial NO synthase (eNOS) function in aortic endothelial cells (AECs). Exposure of AECs to cigarette smoke extract (CSE) resulted in a marked decrease in NO production with concomitant increase in superoxide (O2.-) generation and accumulation of 4-hydroxy-2-nonenal protein adducts. CSE exposure led to depletion of the essential eNOS cofactor tetrahydrobiopterin (BH4) as well as total biopterin levels and decreased the expression level of guanosine triphosphate cyclohydrolase (GTPCH), the rate limiting enzyme in BH4 biosynthesis. Moreover, exposure of AECs to CSE increased the level of ubiquitinated proteins and increased 26 S proteasomal activity in a concentration-dependent manner. Pre-treatment with MG132, a 26 S proteasome inhibitor, partially prevented CSE-induced loss of BH4, total biopterin, GTPCH, and increased NO production following CSE exposure, indicating a role of the ubiquitin-proteasome system in CSE-induced eNOS dysfunction. In conclusion, CSE-induced eNOS dysfunction and uncoupling occurs due to BH4 depletion with BH4de novo synthesis limited by diminished GTPCH expression.

Genetic deletion of CD38 confers post-ischemic myocardial protection through preserved pyridine nucleotides

Following the onset of ischemia/reperfusion (I/R), CD38 activation occurs and is associated with depletion of NAD(P)(H) in the heart as well as myocardial injury and endothelial dysfunction. Studies with pharmacological inhibitors suggest that the NADP+-hydrolyzing ability of CD38 can deplete the NAD(P)(H) pools. However, there is a need for more specific studies on the importance of CD38 and its role in the process of endothelial dysfunction and myocardial injury in the post-ischemic heart. Therefore, experiments were performed in hearts of mice with global gene knockout of CD38. Isolated perfused CD38-/- and wild type (WT) mouse hearts were studied to determine the link between CD38 activation, the levels of NADP(H), endothelial dysfunction, and myocardial injury after I/R. Genetic deletion of CD38 preserves the myocardial and endothelial NADP(H) pools compared to WT. Whole heart BH4 levels in CD38-/- hearts were also preserved. Post-ischemic levels of cGMP were greatly depleted in WT hearts, but preserved to near baseline levels in CD38-/- hearts. The preservation of these metabolite pools in CD38-/- hearts was accompanied by near full recovery of NOS-dependent coronary flow, while in WT hearts, severe impairment of endothelial function and NOS uncoupling occurred with decreased NO and enhanced superoxide generation. CD38-/- hearts also exhibited marked protection against I/R with preserved glutathione levels, increased recovery of left ventricular contractile function, decreased myocyte enzyme release, and decreased infarct size. Thus, CD38 activation causes post-ischemic depletion of NADP(H) within the heart, with severe depletion from the endothelium, resulting in endothelial dysfunction and myocardial injury.

Angiotensin Receptor Expression and Vascular Endothelial Dysfunction in Obstructive Sleep Apnea

BACKGROUND

Obstructive sleep apnea (OSA) is associated with vascular endothelial dysfunction (VED) in otherwise healthy patients. The role of renin-angiotensin system (RAS) in the OSA induced VED is not well understood.

METHODS

Recently diagnosed OSA patients with very low cardiovascular disease (CVD) risk (Framingham score <5%) were studied at diagnosis and after 12 weeks of verified continuous positive airway pressure (CPAP) therapy. Participants underwent biopsy of gluteal subcutaneous tissue at baseline and after CPAP. Microcirculatory endothelial expression of angiotensin receptors type-1 (AT-1) and type-2 (AT-2) was measured in the subcutaneous tissue using quantitative confocal microscopy techniques. The ex-vivo effect of AT-1 receptor blockade (ARB) on endothelial superoxide production was also measured before and after CPAP treatment.

RESULTS

In OSA patients (n = 11), microcirculatory endothelial AT1 expression decreased from 873 (200) (fluorescence units) at baseline to 393 (59) units after 12 weeks of CPAP (P = 0.02). AT2 expression did not decrease significantly in these patients (479 (75) to 329 (58) post CPAP (P = 0.08)). The ex-vivo addition of the losartan to the microcirculatory endothelium resulted in decreased superoxide expression in the vascular walls from 14.2 (2.2) units to 4.2 (0.8) P < 0.001; while it had no effect on post-CPAP patient tissue (P = 0.64).

CONCLUSIONS

In OSA patients with no to minimal CVD risk, VED is associated with upregulation of AT-1 expression that is reversible with CPAP. Endothelial oxidative stress was reversible with ARB. RAS activation may play an important role in the development of early CVD risk in OSA patients.

Abstract WP70: Aptamer Inhibition of Von Willebrand Factor Ameliorates Ischemic Stroke Burden in a Murine Model of Thromboembolic Stroke

Introduction: While recombinant tissue plasminogen activator (rTPA) is the mainstay of ischemic stroke treatment, recanalization is only achieved in 25-50% of patients. With a significant risk of intracranial hemorrhage, its use has been limited to within 4.5 hours of symptom onset. Previous work has demonstrated that aptamer inhibition of Von Willebrand Factor (VWF) effectively restores reperfusion following murine carotid artery occlusion.

Hypothesis: We tested the hypothesis that VWF aptamer would promote recanalization following thrombotic middle cerebral artery (MCA) occlusion, ameliorating stroke burden with greater efficacy than rTPA.

Methods: Adult wild-type (C57BL/6J) mice were anesthetized, and the right carotid artery was exposed. A 32-gauge intracranial catheter was advanced within the carotid artery. Murine autologous blood was then mixed with 10 μL 0.9% normal saline and 1 μL murine thrombin and was allowed to stabilize at 37 °C for 15 minutes, after which it was injected through the catheter into the MCA. Laser-doppler flowmetry monitoring measured decreased flow following injection of the embolus. Treatment (vehicle, platelet binding buffer, n=5; VWF aptamer, n=6; rTPA, n=7) was initiated 20 minutes after thrombus injection. An MRI was obtained at 24 hours to assess ischemic stroke volumes.

Results: None of the mice receiving rTPA survived to 24 hours, while all mice treated with VWF aptamer and vehicle survived to 24 hours and received an MRI. Ischemic stroke volume was significantly decreased in mice treated with VWF aptamer (5.49 ± 5.01 mm 3 ) compared to vehicle (35.34 ± 9.57 mm 3 , p<0.05)(Figure 1). No evidence of intracranial hemorrhage was identified in either cohort.

Conclusions: Treatment with VWF aptamer decreases stroke volume on MRI in a murine model of embolic stroke without the risk of hemorrhagic conversion seen in patients treated rTPA. VWF inhibition represents a promising therapy in stroke treatment.