Whole-genome sequencing uncovers two loci for coronary artery calcification and identifies ARSE as a regulator of vascular calcification

Coronary artery calcification (CAC) is a measure of atherosclerosis and a well-established predictor of coronary artery disease (CAD) events. Here we describe a genome-wide association study (GWAS) of CAC in 22,400 participants from multiple ancestral groups. We confirmed associations with four known loci and identified two additional loci associated with CAC (ARSE and MMP16), with evidence of significant associations in replication analyses for both novel loci. Functional assays of ARSE and MMP16 in human vascular smooth muscle cells (VSMCs) demonstrate that ARSE is a promoter of VSMC calcification and VSMC phenotype switching from a contractile to a calcifying or osteogenic phenotype. Furthermore, we show that the association of variants near ARSE with reduced CAC is likely explained by reduced ARSE expression with the G allele of enhancer variant rs5982944. Our study highlights ARSE as an important contributor to atherosclerotic vascular calcification, and a potential drug target for vascular calcific disease.

Development of nitric oxide generators to produce high-dose nitric oxide for inhalation therapy

BACKGROUND

Several nitric oxide (NO) generating devices have been developed to deliver NO between 1 part per million (ppm) and 80 ppm. Although inhalation of high-dose NO may exert antimicrobial effects, the feasibility and safety of producing high-dose (more than 100 ppm) NO remains to be established. In the current study, we designed, developed, and tested three high-dose NO generating devices.

METHODS

We constructed three NO generating devices: a double spark plug NO generator, a high-pressure single spark plug NO generator, and a gliding arc NO generator. The NO and NO2 concentrations were measured at different gas flows and under various atmospheric pressures. The double spark plug NO generator was designed to deliver gas through an oxygenator and mixing with pure oxygen. The high-pressure and gliding arc NO generators were used to deliver gas through a ventilator into artificial lungs to mimic delivering high-dose NO in the clinical settings. The energy consumption was measured and compared among the three NO generators.

RESULTS

The double spark plug NO generator produced 200 ± 2 ppm (mean ± SD) of NO at gas flow of 8 L/min (or 320 ± 3 ppm at gas flow of 5 L/min) with electrode gap of 3 mm. The nitrogen dioxide (NO2) levels were below 3.0 ± 0.1 ppm when mixing with various volumes of pure oxygen. The addition of a second generator increased the delivered NO from 80 (with one spark plug) to 200 ppm. With the high-pressure chamber, the NO concentration reached 407 ± 3 ppm with continuous air flow at 5 L/min when employing the 3 mm electrode gap under 2.0 atmospheric pressure (ATA). When compared to 1 ATA, NO production was increased 22% at 1.5 ATA and 34% at 2 ATA. The NO level was 180 ± 1 ppm when connecting the device to a ventilator with a constant inspiratory airflow of 15 L/min, and NO2 levels were below 1 (0.93 ± 0.02) ppm. The gliding arc NO generator produced up to 180 ± 4 ppm of NO when connecting the device to a ventilator, and the NO2 level was below 1 (0.91 ± 0.02) ppm in all testing conditions. The gliding arc device required more power (in watts) to generate the same concentrations of NO when compared to double spark plug or high-pressure NO generators.

CONCLUSIONS

Our results demonstrated that it is feasible to enhance NO production (more than 100 ppm) while maintaining NO2 level relatively low (less than 3 ppm) with the three recently developed NO generating devices. Future studies might include these novel designs to deliver high doses of inhaled NO as an antimicrobial used to treat upper and lower respiratory tract infections.

Electronic cigarette vaping with aged coils causes acute lung injury in mice

Electronic cigarettes (e-cigarettes) have been used widely as an alternative to conventional cigarettes and have become particularly popular among young adults. A growing body of evidence has shown that e-cigarettes are associated with acute lung injury and adverse effects in multiple other organs. Previous studies showed that high emissions of aldehydes (formaldehyde and acetaldehyde) in aerosols were associated with increased usage of the same e-cigarette coils. However, the impact on lung function of using aged coils has not been reported. We investigated the relationship between coil age and acute lung injury in mice exposed to experimental vaping for 1 h (2 puffs/min, 100 ml/puff). The e-liquid contains propylene glycol and vegetable glycerin (50:50, vol) only. The concentrations of formaldehyde and acetaldehyde in the vaping aerosols increased with age of the nichrome coils starting at 1200 puffs. Mice exposed to e-cigarette aerosols produced from 1800, but not 0 or 900, puff-aged coils caused acute lung injury, increased lung wet/dry weight ratio, and induced lung inflammation (IL-6, TNF-α, IL-1β, MIP-2). Exposure to vaping aerosols from 1800 puff-aged coils decreased heart rate, respiratory rate, and oxygen saturation in mice compared to mice exposed to air or aerosols from new coils. In conclusion, we observed that the concentration of aldehydes (formaldehyde and acetaldehyde) increased with repeated and prolonged usage of e-cigarette coils. Exposure to high levels of aldehyde in vaping aerosol was associated with acute lung injury in mice. These findings show significant risk of lung injury associated with prolonged use of e-cigarette devices.

High-Throughput Assay to Screen Small Molecules for Their Ability to Prevent Sickling of Red Blood Cells

Sickle cell disease (SCD) is an inherited disorder of hemoglobin (Hb); approximately 300,000 babies are born worldwide with SCD each year. In SCD, fibers of polymerized sickle Hb (HbS) form in red blood cells (RBCs), which cause RBCs to develop their characteristic "sickled" shape, resulting in hemolytic anemia and numerous vascular complications including vaso-occlusive crises. The development of novel antisickling compounds will provide new therapeutic options for patients with SCD. We developed a high-throughput "sickling assay" that is based on an automated high-content imaging system to quantify the effects of hypoxia on the shape and size of RBCs from HbSS SCD patients (SS RBCs). We used this assay to screen thousands of compounds for their ability to inhibit sickling. In the assay, voxelotor (an FDA-approved medication used to treat SCD) prevented sickling with a z'-factor > 0.4, suggesting that the assay is capable of identifying compounds that inhibit sickling. We screened the Broad Repurposing Library of 5393 compounds for their ability to prevent sickling in 4% oxygen/96% nitrogen. We identified two compounds, SNS-314 mesylate and voxelotor itself, that successfully prevented sickling. SNS-314 mesylate prevented sickling in the absence of oxygen, while voxelotor did not, suggesting that SNS-314 mesylate acts by a mechanism that is different from that of voxelotor. The sickling assay described in this study will permit the identification of additional, novel antisickling compounds, which will potentially expand the therapeutic options for SCD.

The Antarctic Weddell seal genome reveals evidence of selection on cardiovascular phenotype and lipid handling

The Weddell seal (Leptonychotes weddellii) thrives in its extreme Antarctic environment. We generated the Weddell seal genome assembly and a high-quality annotation to investigate genome-wide evolutionary pressures that underlie its phenotype and to study genes implicated in hypoxia tolerance and a lipid-based metabolism. Genome-wide analyses included gene family expansion/contraction, positive selection, and diverged sequence (acceleration) compared to other placental mammals, identifying selection in coding and non-coding sequence in five pathways that may shape cardiovascular phenotype. Lipid metabolism as well as hypoxia genes contained more accelerated regions in the Weddell seal compared to genomic background. Top-significant genes were SUMO2 and EP300; both regulate hypoxia inducible factor signaling. Liver expression of four genes with the strongest acceleration signals differ between Weddell seals and a terrestrial mammal, sheep. We also report a high-density lipoprotein-like particle in Weddell seal serum not present in other mammals, including the shallow-diving harbor seal.

Matrix Gla Protein Levels Are Associated With Arterial Stiffness and Incident Heart Failure With Preserved Ejection Fraction

OBJECTIVE

Arterial stiffness is a risk factor for cardiovascular disease, including heart failure with preserved ejection fraction (HFpEF). MGP (matrix Gla protein) is implicated in vascular calcification in animal models, and circulating levels of the uncarboxylated, inactive form of MGP (ucMGP) are associated with cardiovascular disease-related and all-cause mortality in human studies. However, the role of MGP in arterial stiffness is uncertain. Approach and Results: We examined the association of ucMGP levels with vascular calcification, arterial stiffness including carotid-femoral pulse wave velocity (PWV), and incident heart failure in community-dwelling adults from the Framingham Heart Study. To further investigate the link between MGP and arterial stiffness, we compared aortic PWV in age- and sex-matched young (4-month-old) and aged (10-month-old) wild-type and Mgp+/- mice. Among 7066 adults, we observed significant associations between higher levels of ucMGP and measures of arterial stiffness, including higher PWV and pulse pressure. Longitudinal analyses demonstrated an association between higher ucMGP levels and future increases in systolic blood pressure and incident HFpEF. Aortic PWV was increased in older, but not young, female Mgp+/- mice compared with wild-type mice, and this augmentation in PWV was associated with increased aortic elastin fiber fragmentation and collagen accumulation.

CONCLUSIONS

This translational study demonstrates an association between ucMGP levels and arterial stiffness and future HFpEF in a large observational study, findings that are substantiated by experimental studies showing that mice with Mgp heterozygosity develop arterial stiffness. Taken together, these complementary study designs suggest a potential role of therapeutically targeting MGP in HFpEF.

High-Dose Nitric Oxide From Pressurized Cylinders and Nitric Oxide Produced by an Electric Generator From Air

BACKGROUND

High-dose (≥ 80 ppm) inhaled nitric oxide (INO) has antimicrobial effects. We designed a trial to test the preventive effects of high-dose NO on coronavirus disease 2019 (COVID-19) in health care providers working with patients with COVID-19. The study was interrupted prematurely due to the introduction of COVID-19 vaccines for health care professionals. We thereby present data on safety and feasibility of breathing 160 ppm NO using 2 different NO sources, namely pressurized nitrogen/NO cylinders (INO) and electric NO (eNO) generators.

METHODS

NO gas was inhaled at 160 ppm in air for 15 min twice daily, before and after each work shift, over 14 d by health care providers (NCT04312243). During NO administration, vital signs were continuously monitored. Safety was assessed by measuring transcutaneous methemoglobinemia (SpMet) and the inhaled nitrogen dioxide (NO₂) concentration.

RESULTS

Twelve healthy health care professionals received a collective total of 185 administrations of high-dose NO (160 ppm) for 15 min twice daily. One-hundred and seventy-one doses were delivered by INO and 14 doses by eNO. During NO administration, SpMet increased similarly in both groups (P = .82). Methemoglobin decreased in all subjects at 5 min after discontinuing NO administration. Inhaled NO₂ concentrations remained between 0.70 ppm (0.63-0.79) and 0.75 ppm (0.67-0.83) in the INO group and between 0.74 ppm (0.68-0.78) and 0.88 ppm (0.70-0.93) in the eNO group. During NO administration, peripheral oxygen saturation and heart rate did not change. No adverse events occurred.

CONCLUSIONS

This pilot study testing high-dose INO (160 ppm) for 15 min twice daily using eNO seems feasible and similarly safe when compared with INO.

Inhaled high dose nitric oxide is a safe and effective respiratory treatment in spontaneous breathing hospitalized patients with COVID-19 pneumonia

BACKGROUND

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator. In-vitro studies report that NO donors can inhibit replication of SARS-CoV-2. This multicenter study evaluated the feasibility and effects of high-dose inhaled NO in non-intubated spontaneously breathing patients with Coronavirus disease-2019 (COVID-19).

METHODS

This is an interventional study to determine whether NO at 160 parts-per-million (ppm) inhaled for 30 min twice daily might be beneficial and safe in non-intubated COVID-19 patients.

RESULTS

Twenty-nine COVID-19 patients received a total of 217 intermittent inhaled NO treatments for 30 min at 160 ppm between March and June 2020. Breathing NO acutely decreased the respiratory rate of tachypneic patients and improved oxygenation in hypoxemic patients. The maximum level of nitrogen dioxide delivered was 1.5 ppm. The maximum level of methemoglobin (MetHb) during the treatments was 4.7%. MetHb decreased in all patients 5 min after discontinuing NO administration. No adverse events during treatment, such as hypoxemia, hypotension, or acute kidney injury during hospitalization occurred. In our NO treated patients, one patient of 29 underwent intubation and mechanical ventilation, and none died. The median hospital length of stay was 6 days [interquartile range 4-8]. No discharged patients required hospital readmission nor developed COVID-19 related long-term sequelae within 28 days of follow-up.

CONCLUSIONS

In spontaneous breathing patients with COVID-19, the administration of inhaled NO at 160 ppm for 30 min twice daily promptly improved the respiratory rate of tachypneic patients and systemic oxygenation of hypoxemic patients. No adverse events were observed. None of the subjects was readmitted or had long-term COVID-19 sequelae.

Hyperbaric phototherapy augments blood carbon monoxide removal

BACKGROUND AND OBJECTIVES

Carbon monoxide (CO) poisoning is responsible for nearly 50,000 emergency department visits and 1200 deaths per year. Compared to oxygen, CO has a 250-fold higher affinity for hemoglobin (Hb), resulting in the displacement of oxygen from Hb and impaired oxygen delivery to tissues. Optimal treatment of CO-poisoned patients involves the administration of hyperbaric 100% oxygen to remove CO from Hb and to restore oxygen delivery. However, hyperbaric chambers are not widely available and this treatment requires transporting a CO-poisoned patient to a specialized center, which can result in delayed treatment. Visible light is known to dissociate CO from carboxyhemoglobin (COHb). In a previous study, we showed that a system composed of six photo-extracorporeal membrane oxygenation (ECMO) devices efficiently removes CO from a large animal with CO poisoning. In this study, we tested the hypothesis that the application of hyperbaric oxygen to the photo-ECMO device would further increase the rate of CO elimination.

STUDY DESIGN/MATERIAL AND METHODS

We developed a hyperbaric photo-ECMO device and assessed the ability of the device to remove CO from CO-poisoned human blood. We combined four devices into a "hyperbaric photo-ECMO system" and compared its ability to remove CO to our previously described photo-ECMO system, which was composed of six devices ventilated with normobaric oxygen.

RESULTS

Under normobaric conditions, an increase in oxygen concentration from 21% to 100% significantly increased CO elimination from CO-poisoned blood after a single pass through the device. Increased oxygen pressure within the photo-ECMO device was associated with higher exiting blood PO₂ levels and increased CO elimination. The system of four hyperbaric photo-ECMO devices removed CO from 1 L of CO-poisoned blood as quickly as the original, normobaric photo-ECMO system composed of six devices.

CONCLUSION

This study demonstrates the feasibility and efficacy of using a hyperbaric photo-ECMO system to increase the rate of CO elimination from CO-poisoned blood. This technology could provide a simple portable emergency device and facilitate immediate treatment of CO-poisoned patients at or near the site of injury.

Veno-venous extracorporeal blood phototherapy increases the rate of carbon monoxide (CO) elimination in CO-poisoned pigs

BACKGROUND AND OBJECTIVES

Carbon monoxide (CO) inhalation is the leading cause of poison-related deaths in the United States. CO binds to hemoglobin (Hb), displaces oxygen, and reduces oxygen delivery to tissues. The optimal treatment for CO poisoning in patients with normal lung function is the administration of hyperbaric oxygen (HBO). However, hyperbaric chambers are only available in medical centers with specialized equipment, resulting in delayed therapy. Visible light dissociates CO from Hb with minimal effect on oxygen binding. In a previous study, we combined a membrane oxygenator with phototherapy at 623 nm to produce a "mini" photo-ECMO (extracorporeal membrane oxygenation) device, which improved CO elimination and survival in CO-poisoned rats. The objective of this study was to develop a larger photo-ECMO device ("maxi" photo-ECMO) and to test its ability to remove CO from a porcine model of CO poisoning.

STUDY DESIGN/MATERIALS AND METHODS

The "maxi" photo-ECMO device and the photo-ECMO system (six maxi photo-ECMO devices assembled in parallel), were tested in an in vitro circuit of CO poisoning. To assess the ability of the photo-ECMO device and the photo-ECMO system to remove CO from CO-poisoned blood in vitro, the half-life of COHb (COHb-t_1/2 ), as well as the percent COHb reduction in a single blood pass through the device, were assessed. In the in vivo studies, we assessed the COHb-t_1/2 in a CO-poisoned pig under three conditions: (1) While the pig breathed 100% oxygen through the endotracheal tube; (2) while the pig was connected to the photo-ECMO system with no light exposure; and (3) while the pig was connected to the photo-ECMO system, which was exposed to red light.

RESULTS

The photo-ECMO device was able to fully oxygenate the blood after a single pass through the device. Compared to ventilation with 100% oxygen alone, illumination with red light together with 100% oxygen was twice as efficient in removing CO from blood. Changes in gas flow rates did not alter CO elimination in one pass through the device. Increases in irradiance up to 214 mW/cm² were associated with an increased rate of CO elimination. The photo-ECMO device was effective over a range of blood flow rates and with higher blood flow rates, more CO was eliminated. A photo-ECMO system composed of six photo-ECMO devices removed CO faster from CO-poisoned blood than a single photo-ECMO device. In a CO-poisoned pig, the photo-ECMO system increased the rate of CO elimination without significantly increasing the animal's body temperature or causing hemodynamic instability.

CONCLUSION

In this study, we developed a photo-ECMO system and demonstrated its ability to remove CO from CO-poisoned 45-kg pigs. Technical modifications of the photo-ECMO system, including the development of a compact, portable device, will permit treatment of patients with CO poisoning at the scene of their poisoning, during transit to a local emergency room, and in hospitals that lack HBO facilities.

UBA6 and NDFIP1 regulate the degradation of ferroportin

Hepcidin regulates iron homeostasis by controlling the level of ferroportin, the only membrane channel that facilitates export of iron from within cells. Binding of hepcidin to ferroportin induces the ubiquitination of ferroportin at multiple lysine residues and subsequently causes the internalization and degradation of the ligand-channel complex within lysosomes. The objective of this study was to identify components of the ubiquitin system that are involved in ferroportin degradation. A HepG2 cell line, which inducibly expresses ferroportingreen fluorescent protein (FPN-GFP), was established to test the ability of small interfering (siRNA) directed against components of the ubiquitin system to prevent BMP6- and exogenous hepcidin-induced ferroportin degradation. Of the 88 siRNA directed against components of the ubiquitin pathway that were tested, siRNA-mediated depletion of the alternative E1 enzyme UBA6 as well as the adaptor protein NDFIP1 prevented BMP6- and hepcidin-induced degradation of ferroportin in vitro. A third component of the ubiquitin pathway, ARIH1, indirectly inhibited ferroportin degradation by impairing BMP6-mediated induction of hepcidin. In mice, the AAV-mediated silencing of Ndfip1 in the murine liver increased the level of hepatic ferroportin and increased circulating iron. The results suggest that the E1 enzyme UBA6 and the adaptor protein NDFIP1 are involved in iron homeostasis by regulating the degradation of ferroportin. These specific components of the ubiquitin system may be promising targets for the treatment of iron-related diseases, including iron overload and anemia of inflammation.

A Novel Inhalation Mask System to Deliver High Concentrations of Nitric Oxide Gas in Spontaneously Breathing Subjects

Nitric Oxide (NO) is administered as gas for inhalation to induce selective pulmonary vasodilation. It is a safe therapy, with few potential risks even if administered at high concentration. Inhaled NO gas is routinely used to increase systemic oxygenation in different disease conditions. The administration of high concentrations of NO also exerts a virucidal effect in vitro. Owing to its favorable pharmacodynamic and safety profiles, the familiarity in its use by critical care providers, and the potential for a direct virucidal effect, NO is clinically used in patients with coronavirus disease-2019 (COVID-19). Nevertheless, no device is currently available to easily administer inhaled NO at concentrations higher than 80 parts per million (ppm) at various inspired oxygen fractions, without the need for dedicated, heavy, and costly equipment. The development of a reliable, safe, inexpensive, lightweight, and ventilator-free solution is crucial, particularly for the early treatment of non-intubated patients outside of the intensive care unit (ICU) and in a limited-resource scenario. To overcome such a barrier, a simple system for the non-invasive NO gas administration up to 250 ppm was developed using standard consumables and a scavenging chamber. The method has been proven safe and reliable in delivering a specified NO concentration while limiting nitrogen dioxide levels. This paper aims to provide clinicians and researchers with the necessary information on how to assemble or adapt such a system for research purposes or clinical use in COVID-19 or other diseases in which NO administration might be beneficial.

Hypoxia ameliorates brain hyperoxia and NAD+ deficiency in a murine model of Leigh syndrome

Leigh syndrome is a severe mitochondrial neurodegenerative disease with no effective treatment. In the Ndufs4-/- mouse model of Leigh syndrome, continuously breathing 11% O2 (hypoxia) prevents neurodegeneration and leads to a dramatic extension (~5-fold) in lifespan. We investigated the effect of hypoxia on the brain metabolism of Ndufs4-/- mice by studying blood gas tensions and metabolite levels in simultaneously sampled arterial and cerebral internal jugular venous (IJV) blood. Relatively healthy Ndufs4-/- and wildtype (WT) mice breathing air until postnatal age ~38 d were compared to Ndufs4-/- and WT mice breathing air until ~38 days old followed by 4-weeks of breathing 11% O2. Compared to WT control mice, Ndufs4-/- mice breathing air have reduced brain O2 consumption as evidenced by an elevated partial pressure of O2 in IJV blood (PijvO2) despite a normal PO2 in arterial blood, and higher lactate/pyruvate (L/P) ratios in IJV plasma revealed by metabolic profiling. In Ndufs4-/- mice, hypoxia treatment normalized the cerebral venous PijvO2 and L/P ratios, and decreased levels of nicotinate in IJV plasma. Brain concentrations of nicotinamide adenine dinucleotide (NAD+) were lower in Ndufs4-/- mice breathing air than in WT mice, but preserved at WT levels with hypoxia treatment. Although mild hypoxia (17% O2) has been shown to be an ineffective therapy for Ndufs4-/- mice, we find that when combined with nicotinic acid supplementation it provides a modest improvement in neurodegeneration and lifespan. Therapies targeting both brain hyperoxia and NAD+ deficiency may hold promise for treating Leigh syndrome.

Antimicrobial effects of nitric oxide in murine models of Klebsiella pneumonia

RATIONALE

Inhalation of nitric oxide (NO) exerts selective pulmonary vasodilation. Nitric oxide also has an antimicrobial effect on a broad spectrum of pathogenic viruses, bacteria and fungi.

OBJECTIVES

The aim of this study was to investigate the effect of inhaled NO on bacterial burden and disease outcome in a murine model of Klebsiella pneumonia.

METHODS

Mice were infected with Klebsiella pneumoniae and inhaled either air alone, air mixed with constant levels of NO (at 80, 160, or 200 parts per million (ppm)) or air intermittently mixed with high dose NO (300 ppm). Forty-eight hours after airway inoculation, the number of viable bacteria in lung, spleen and blood was determined. The extent of infiltration of the lungs by inflammatory cells and the level of myeloperoxidase activity in the lungs were measured. Atomic force microscopy was used to investigate a possible mechanism by which nitric oxide exerts a bactericidal effect.

MEASUREMENTS AND MAIN RESULTS

Compared to control animals infected with K. pneumoniae and breathed air alone, intermittent breathing of NO (300 ppm) reduced viable bacterial counts in lung and spleen tissue. Inhaled NO reduced infection-induced lung inflammation and improved overall survival of mice. NO destroyed the cell wall of K. pneumoniae and killed multiple-drug resistant K. pneumoniae in-vitro.

CONCLUSIONS

Intermittent administration of high dose NO may be an effective approach to the treatment of pneumonia caused by K. pneumoniae.

Airway stem cells sense hypoxia and differentiate into protective solitary neuroendocrine cells

Neuroendocrine (NE) cells are epithelial cells that possess many of the characteristics of neurons, including the presence of secretory vesicles and the ability to sense environmental stimuli. The normal physiologic functions of solitary airway NE cells remain a mystery. We show that mouse and human airway basal stem cells sense hypoxia. Hypoxia triggers the direct differentiation of these stem cells into solitary NE cells. Ablation of these solitary NE cells during hypoxia results in increased epithelial injury, whereas the administration of the NE cell peptide CGRP rescues this excess damage. Thus, we identify stem cells that directly sense hypoxia and respond by differentiating into solitary NE cells that secrete a protective peptide that mitigates hypoxic injury.

Phototherapy and extracorporeal membrane oxygenation facilitate removal of carbon monoxide in rats

Inhaled carbon monoxide (CO) displaces oxygen from hemoglobin, reducing the capacity of blood to carry oxygen. Current treatments for CO-poisoned patients involve administration of 100% oxygen; however, when CO poisoning is associated with acute lung injury secondary to smoke inhalation, burns, or trauma, breathing 100% oxygen may be ineffective. Visible light dissociates CO from hemoglobin. We hypothesized that the exposure of blood to visible light while passing through a membrane oxygenator would increase the rate of CO elimination in vivo. We developed a membrane oxygenator with optimal characteristics to facilitate exposure of blood to visible light and tested the device in a rat model of CO poisoning, with or without concomitant lung injury. Compared to ventilation with 100% oxygen, the addition of extracorporeal removal of CO with phototherapy (ECCOR-P) doubled the rate of CO elimination in CO-poisoned rats with normal lungs. In CO-poisoned rats with acute lung injury, treatment with ECCOR-P increased the rate of CO removal by threefold compared to ventilation with 100% oxygen alone and was associated with improved survival. Further development and adaptation of this extracorporeal CO photo-removal device for clinical use may provide additional benefits for CO-poisoned patients, especially for those with concurrent acute lung injury.

Ideation and assessment of a nitric oxide delivery system for spontaneously breathing subjects

Background

There is an increasing interest in safely delivering high dose of inhaled nitric oxide (NO) as an antimicrobial and antiviral therapeutics for spontaneously breathing patients. A novel NO delivery system is described.

Methods

We developed a gas delivery system that utilizes standard respiratory circuit connectors, a reservoir bag, and a scavenging chamber containing calcium hydroxide. The performance of the system was tested using a mechanical lung, assessing the NO concentration delivered at varying inspiratory flows. Safety was assessed in vitro and in vivo by measuring nitrogen dioxide (NO₂) levels in the delivered NO gas. Lastly, we measured the inspired and expired NO and NO₂ of this system in 5 healthy subjects during a 15-min administration of high dose NO (160 parts-per-million, ppm) using our delivery system.

Results

The system demonstrated stable delivery of prescribed NO levels at various inspiratory flow rates (0–50 L/min). The reservoir bag and a high flow of entering air minimized the oscillation of NO concentrations during inspiration on average 4.6 ppm for each 10 L/min increment in lung inspiratory flow.

The calcium hydroxide scavenger reduced the inhaled NO₂ concentration on average 0.9 ppm (95% CI -1.58, −0.22; p = .01). We performed 49 NO administrations of 160 ppm in 5 subjects. The average concentration of inspired NO was 164.8±10.74 ppm, with inspired NO₂ levels of 0.7±0.13 ppm. The subjects did not experience any adverse events; transcutaneous methemoglobin concentrations increased from 1.05±0.58 to 2.26±0.47%.

Conclusions

The system we developed to administer high-dose NO for inhalation is easy to build, reliable, was well tolerated in healthy subjects.

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We conceived and tested a NO delivery system for spontaneously breathing subjects.

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A scavenger containing calcium hydroxide reduces the inspired NO₂ concentration.

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A reservoir bag reduces variations of NO concentration during breathing.

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In five healthy subjects breathing 164.8±10.74 ppm of NO, inspired NO₂ was 0.7±0.13 ppm.

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In a healthy subject breathing 153 ppm of NO, the exhaled NO₂ was 0.03 ppm.

HDAC9 is implicated in atherosclerotic aortic calcification and affects vascular smooth muscle cell phenotype

Aortic calcification is an important independent predictor of future cardiovascular events. We performed a genome-wide association meta-analysis to determine single nucleotide polymorphisms (SNPs) associated with the extent of abdominal (AAC, n = 9,417) or descending thoracic (TAC, n = 8,422) aortic calcification. Two genetic loci, HDAC9 and RAP1GAP, were associated with AAC at a genome-wide level (P < 5.0 × 10⁻⁸). No SNPs were associated with TAC at the genome-wide threshold. Increased expression of HDAC9 in human aortic smooth muscle cells (HASMCs) promoted calcification and reduced contractility, while inhibition of HDAC9 in HASMCs inhibited calcification and enhanced cell contractility. In matrix Gla protein (MGP)-deficient mice, a model of human vascular calcification, mice lacking HDAC9 had a 40% reduction in aortic calcification and improved survival. This translational genomic study identifies the first genetic risk locus associated with calcification of the abdominal aorta and describes a novel role for HDAC9 in the development of vascular calcification.

Genome-wide analyses identify variants near HDAC9 associated with abdominal aortic calcification and other cardiovascular phenotypes. Functional work shows that HDAC9 promotes an osteogenic vascular smooth muscle cell phenotype, enhancing calcification and reducing contractility.

Leigh Syndrome Mouse Model Can Be Rescued by Interventions that Normalize Brain Hyperoxia, but Not HIF Activation

Leigh syndrome is a devastating mitochondrial disease for which there are no proven therapies. We previously showed that breathing chronic, continuous hypoxia can prevent and even reverse neurological disease in the Ndufs4 knockout (KO) mouse model of complex I (CI) deficiency and Leigh syndrome. Here, we show that genetic activation of the hypoxia-inducible factor transcriptional program via any of four different strategies is insufficient to rescue disease. Rather, we observe an age-dependent decline in whole-body oxygen consumption. These mice exhibit brain tissue hyperoxia, which is normalized by hypoxic breathing. Alternative experimental strategies to reduce oxygen delivery, including breathing carbon monoxide (600 ppm in air) or severe anemia, can reverse neurological disease. Therefore, unused oxygen is the most likely culprit in the pathology of this disease. While pharmacologic activation of the hypoxia response is unlikely to alleviate disease in vivo, interventions that safely normalize brain tissue hyperoxia may hold therapeutic potential.

Low guanylyl cyclase activity in Weddell seals: implications for peripheral vasoconstriction and perfusion of the brain during diving

Nitric oxide (NO) is a potent vasodilator, which improves perfusion and oxygen delivery during tissue hypoxia in terrestrial animals. The vertebrate dive response involves vasoconstriction in select tissues, which persists despite profound hypoxia. Using tissues collected from Weddell seals at necropsy, we investigated whether vasoconstriction is aided by downregulation of local hypoxia signaling mechanisms. We focused on NO-soluble guanylyl cyclase (GC)-cGMP signaling, a well-known vasodilatory transduction pathway. Seals have a lower GC protein abundance, activity, and capacity to respond to NO stimulation than do terrestrial mammals. In seal lung homogenates, GC produced less cGMP (20.1 ± 3.7 pmol·mg protein-1·min-1) than the lungs of dogs (-80 ± 144 pmol·mg protein-1·min-1 less than seals), sheep (-472 ± 96), rats (-664 ± 104) or mice (-1,160 ± 104, P < 0.0001). Amino acid sequences of the GC enzyme α-subunits differed between seals and terrestrial mammals, potentially affecting their structure and function. Vasoconstriction in diving Weddell seals is not consistent across tissues; perfusion is maintained in the brain and heart but decreased in other organs such as the kidney. A NO donor increased median GC activity 49.5-fold in the seal brain but only 27.4-fold in the kidney, consistent with the priority of cerebral perfusion during diving. Nos3 expression was high in the seal brain, which could improve NO production and vasodilatory potential. Conversely, Pde5a expression was high in the seal renal artery, which may increase cGMP breakdown and vasoconstriction in the kidney. Taken together, the results of this study suggest that alterations in the NO-cGMP pathway facilitate the diving response.

Hypoxia Rescues Frataxin Loss by Restoring Iron Sulfur Cluster Biogenesis

Friedreich's ataxia (FRDA) is a devastating, multisystemic disorder caused by recessive mutations in the mitochondrial protein frataxin (FXN). FXN participates in the biosynthesis of Fe-S clusters and is considered to be essential for viability. Here we report that when grown in 1% ambient O2, FXN null yeast, human cells, and nematodes are fully viable. In human cells, hypoxia restores steady-state levels of Fe-S clusters and normalizes ATF4, NRF2, and IRP2 signaling events associated with FRDA. Cellular studies and in vitro reconstitution indicate that hypoxia acts through HIF-independent mechanisms that increase bioavailable iron as well as directly activate Fe-S synthesis. In a mouse model of FRDA, breathing 11% O2 attenuates the progression of ataxia, whereas breathing 55% O2 hastens it. Our work identifies oxygen as a key environmental variable in the pathogenesis associated with FXN depletion, with important mechanistic and therapeutic implications.

Inhaled nitric oxide

Nitric oxide (NO) is a gas that induces relaxation of smooth muscle cells in the vasculature. Because NO reacts with oxyhaemoglobin with high affinity, the gas is rapidly scavenged by oxyhaemoglobin in red blood cells and the vasodilating effects of inhaled NO are limited to ventilated regions in the lung. NO therefore has the unique ability to induce pulmonary vasodilatation specifically in the portions of the lung with adequate ventilation, thereby improving oxygenation of blood and decreasing intrapulmonary right to left shunting. Inhaled NO is used to treat a spectrum of cardiopulmonary conditions, including pulmonary hypertension in children and adults. However, the widespread use of inhaled NO is limited by logistical and financial barriers. We have designed, developed and tested a simple and economic NO generation device, which uses pulsed electrical discharges in air to produce therapeutic levels of NO that can be used for inhalation therapy. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

Impaired hypoxic pulmonary vasoconstriction in a mouse model of Leigh syndrome

Hypoxic pulmonary vasoconstriction (HPV) is a physiological vasomotor response that maintains systemic oxygenation by matching perfusion to ventilation during alveolar hypoxia. Although mitochondria appear to play an essential role in HPV, the impact of mitochondrial dysfunction on HPV remains incompletely defined. Mice lacking the mitochondrial complex I (CI) subunit Ndufs4 ( Ndufs4^-/-) develop a fatal progressive encephalopathy and serve as a model for Leigh syndrome, the most common mitochondrial disease in children. Breathing normobaric 11% O₂ prevents neurological disease and improves survival in Ndufs4^-/- mice. In this study, we found that either genetic Ndufs4 deficiency or pharmacological inhibition of CI using piericidin A impaired the ability of left mainstem bronchus occlusion (LMBO) to induce HPV. In mice breathing air, the partial pressure of arterial oxygen during LMBO was lower in Ndufs4^-/- and in piericidin A-treated Ndufs4^+/+ mice than in respective controls. Impairment of HPV in Ndufs4^-/- mice was not a result of nonspecific dysfunction of the pulmonary vascular contractile apparatus or pulmonary inflammation. In Ndufs4-deficient mice, 3 wk of breathing 11% O₂ restored HPV in response to LMBO. When compared with Ndufs4^-/- mice breathing air, chronic hypoxia improved systemic oxygenation during LMBO. The results of this study show that, when breathing air, mice with a congenital Ndufs4 deficiency or chemically inhibited CI function have impaired HPV. Our study raises the possibility that patients with inborn errors of mitochondrial function may also have defects in HPV.