Alveolar Mitochondrial Quality Control During Acute Respiratory Distress Syndrome.

Acute respiratory distress syndrome (ARDS) is a leading cause of respiratory failure and death in patients in the intensive care unit. Experimentally, acute lung injury resolution depends on the repair of mitochondrial oxidant damage by the mitochondrial quality control (MQC) pathways, mitochondrial biogenesis, and mitophagy, but nothing is known about this in the human lung. In a case-control autopsy study, we compared the lungs of subjects dying of ARDS (n = 8; cases) and age-/gender-matched subjects dying of nonpulmonary causes (n = 7; controls).

GAT inhibition preserves cerebral blood flow and reduces oxidant damage to mitochondria in rodents exposed to extreme hyperbaric oxygen.

Oxygen breathing at elevated partial pressures (PO's) at or more than 3 atmospheres absolute (ATA) causes a reduction in brain γ-aminobutyric acid (GABA) levels that impacts the development of central nervous system oxygen toxicity (CNS-OT). Drugs that increase brain GABA content delay the onset of CNS-OT, but it is unknown if oxidant damage is lessened because brain tissue PO remains elevated during hyperbaric oxygen (HBO) exposures. Experiments were performed in rats and mice to measure brain GABA levels with or without GABA transporter inhibitors (GATs) and its influence on cerebral blood flow, oxidant damage, and aspects of mitochondrial quality control signaling (mitophagy and biogenesis).

Nuclear respiratory factor-1 negatively regulates TGF-β1 and attenuates pulmonary fibrosis.

The preclinical model of bleomycin-induced lung fibrosis is useful to study mechanisms related to human pulmonary fibrosis. Using BLM in mice, we find low HO-1 expression. Although a unique Rhenium-CO-releasing molecule (ReCORM) up-regulates HO-1, NRF-1, CCN5, and SMAD7, it reduces TGFβ1, TGFβr1, collagen, α-SMA, and phosphorylated Smad2/3 levels in mouse lung and in human lung fibroblasts.

The HO-1/CO System and Mitochondrial Quality Control in Skeletal Muscle.

Inducible heme oxygenase (HO)-1 catalyzes the breakdown of heme to biliverdin, iron, and carbon monoxide (CO). CO binds to cytochrome c oxidase and alters mitochondrial redox balance and coordinately regulates mitochondrial quality control (MQC) during oxidant stress and inflammation. The hypothesis presented is that the skeletal muscle HO-1/CO system helps modulate components in the MQC cycle during metabolic stress.

Heparin-based blood purification attenuates organ injury in baboons with pneumonia.

Bacterial pneumonia is a major cause of morbidity and mortality worldwide despite the use of antibiotics, and novel therapies are urgently needed. Building on previous work, we aimed to ) develop a baboon model of severe pneumococcal pneumonia and sepsis with organ dysfunction and ) test the safety and efficacy of a novel extracorporeal blood filter to remove proinflammatory molecules and improve organ function. After a dose-finding pilot study, 12 animals were inoculated with [5 × 10 colony-forming units (CFU)], given ceftriaxone at 24 h after inoculation, and randomized to extracorporeal blood purification using a filter coated with surface-immobilized heparin sulfate ( = 6) or sham treatment ( = 6) for 4 h at 30 h after inoculation.

Skeletal muscle mitochondrial fragmentation and impaired bioenergetics from nutrient overload are prevented by carbon monoxide.

Nutrient excess increases skeletal muscle oxidant production and mitochondrial fragmentation that may result in impaired mitochondrial function, a hallmark of skeletal muscle insulin resistance. This led us to explore whether an endogenous gas molecule, carbon monoxide (CO), which is thought to prevent weight gain and metabolic dysfunction in mice consuming high-fat diets, alters mitochondrial morphology and respiration in C2C12 myoblasts exposed to high glucose (15.6 mM) and high fat (250 µM BSA-palmitate) (HGHF).

Carbon Monoxide and Exercise Prevents Diet-Induced Obesity and Metabolic Dysregulation Without Affecting Bone.

Objective: Carbon monoxide (CO) may counteract obesity and metabolic dysfunction in rodents consuming high-fat diets, but the skeletal effects are not understood. This study investigated whether low-dose inhaled CO (250 ppm) with or without moderate intensity aerobic exercise (3 h/wk) would limit diet-induced obesity and metabolic dysregulation and preserve bone health.

Methods: Obesity-resistant (OR) rats served as controls, and obesity-prone (OP) rats were randomized to sedentary, sedentary plus CO, exercise, or CO plus exercise.

Nonclassical Monocytes Sense Hypoxia, Regulate Pulmonary Vascular Remodeling, and Promote Pulmonary Hypertension.

An increasing body of evidence suggests that bone marrow-derived myeloid cells play a critical role in the pathophysiology of pulmonary hypertension (PH). However, the true requirement for myeloid cells in PH development has not been demonstrated, and a specific disease-promoting myeloid cell population has not been identified. Using bone marrow chimeras, lineage labeling, and proliferation studies, we determined that, in murine hypoxia-induced PH, Ly6C nonclassical monocytes are recruited to small pulmonary arteries and differentiate into pulmonary interstitial macrophages.

Mitochondrial DNA, oxidants, and innate immunity.

Mitochondrial oxidant damage, including damage to mitochondrial DNA (mtDNA) is a feature of both severe microbial infections and inflammation arising from sterile (non-infectious) sources such as tissue trauma. Damaged mitochondria release intact or oxidized fragments of mtDNA into the cytoplasm, which represent oxidant injury, and the fragments promote a spontaneous innate immune response, exemplifying a modern frontier of immunological research. MtDNA and mitochondrial-derived oxidants are central factors in activating at least three innate immune pathways involving the TLR9 (Toll-like receptor 9), the NLRP3 (NACHT, LRR and PYD domains-containing protein-3) inflammasome, and the cGAS (cyclic AMP-GMP synthase) pathway.

Increased Antiseizure Effectiveness with Tiagabine Combined with Sodium Channel Antagonists in Mice Exposed to Hyperbaric Oxygen.

Hyperbaric oxygen (HBO) is acutely toxic to the central nervous system, culminating in EEG spikes and tonic-clonic convulsions. GABA enhancers and sodium channel antagonists improve seizure latencies in HBO when administered individually, while combining antiepileptic drugs from different functional classes can provide greater seizure latency. We examined the combined effectiveness of GABA enhancers (tiagabine and gabapentin) with sodium channel antagonists (carbamazepine and lamotrigine) in delaying HBO-induced seizures.

Peripheral Blood Mononuclear Cells Demonstrate Mitochondrial Damage Clearance During Sepsis.

Objectives: Metabolic derangements in sepsis stem from mitochondrial injury and contribute significantly to organ failure and mortality; however, little is known about mitochondrial recovery in human sepsis. We sought to test markers of mitochondrial injury and recovery (mitochondrial biogenesis) noninvasively in peripheral blood mononuclear cells from patients with sepsis and correlate serial measurements with clinical outcomes.

Design: Prospective case-control study.

ABL kinase inhibition promotes lung regeneration through expansion of an SCGB1A1+ SPC+ cell population following bacterial pneumonia.

Current therapeutic interventions for the treatment of respiratory infections are hampered by the evolution of multidrug resistance in pathogens as well as the lack of effective cellular targets. Despite the identification of multiple region-specific lung progenitor cells, the identity of molecules that might be therapeutically targeted in response to infections to promote activation of progenitor cell types remains elusive. Here, we report that loss of specifically in SCGB1A1-expressing cells leads to a significant increase in the proliferation and differentiation of bronchiolar epithelial cells, resulting in dramatic expansion of an SCGB1A1+ airway cell population that coexpresses SPC, a marker for type II alveolar cells that promotes alveolar regeneration following bacterial pneumonia.

Vascular Endothelial Growth Factor Receptor 3 Regulates Endothelial Function Through β-Arrestin 1.

Background: Receptor signaling is central to vascular endothelial function and is dysregulated in vascular diseases such as atherosclerosis and pulmonary arterial hypertension (PAH). Signaling pathways involved in endothelial function include vascular endothelial growth factor receptors (VEGFRs) and G protein-coupled receptors, which classically activate distinct intracellular signaling pathways and responses. The mechanisms that regulate these signaling pathways have not been fully elucidated and it is unclear what nodes for cross talk exist between these diverse signaling pathways.

A phase I trial of low-dose inhaled carbon monoxide in sepsis-induced ARDS.

Background: Acute respiratory distress syndrome (ARDS) is a prevalent disease with significant mortality for which no effective pharmacologic therapy exists. Low-dose inhaled carbon monoxide (iCO) confers cytoprotection in preclinical models of sepsis and ARDS.

Methods: We conducted a phase I dose escalation trial to assess feasibility and safety of low-dose iCO administration in patients with sepsis-induced ARDS.

Adrenoceptor blockade modifies regional cerebral blood flow responses to hyperbaric hyperoxia: protection against CNS oxygen toxicity.

Exposure to extreme hyperbaric oxygen (HBO) >5-6 atmospheres absolute (ATA) produces baroreflex impairment, sympathetic hyperactivation, hypertension, tachycardia, and cerebral hyperemia, known as phase II, culminating in seizures. We hypothesized that attenuation of the effects of high sympathetic outflow would preserve regional cerebral blood flow (rCBF) and protect against HBO-induced seizures. To explore this possibility, we tested four adrenoceptor antagonists in conscious and anesthetized rats exposed to HBO at 5 and 6 ATA, respectively: phentolamine (nonselective α and α), prazosin (selective α), propranolol (nonselective β and β), and atenolol (selective β).

RhoA inactivation by S-nitrosylation regulates vascular smooth muscle contractive signaling.

S-nitrosothiols derived from nitric oxide are known to regulate cell signaling through thiol modification. Since small G protein RhoA contains cysteine residues in the GTP-binding domain which is critical for its function, modification these thiols may alter RhoA activity and lead to changes in the downstream signaling such as myosin light chain phosphorylation. However, it is still unclear that if RhoA activity and its downstream signals might be modulated by S-nitrosothiols and if the two cysteine residues located in the GTP-binding domain are critical for the regulation.

The release of microparticles and mitochondria from RAW 264.7 murine macrophage cells undergoing necroptotic cell death in vitro.

Microparticles (MPs) are small membrane-bound vesicles released from activated or dying cells. As shown previously, LPS stimulation of the RAW 264.7 macrophage cell line can induce MP release, with the caspase inhibitor Z-VAD increasing the extent of this process.

Pharmacologic Targeting of Red Blood Cells to Improve Tissue Oxygenation.

Disruption of microvascular blood flow is a common cause of tissue hypoxia in disease, yet no therapies are available that directly target the microvasculature to improve tissue oxygenation. Red blood cells (RBCs) autoregulate blood flow through S-nitroso-hemoglobin (SNO-Hb)-mediated export of nitric oxide (NO) bioactivity. We therefore tested the idea that pharmacological enhancement of RBCs using the S-nitrosylating agent ethyl nitrite (ENO) may provide a novel approach to improve tissue oxygenation.

Safety and Ergogenic Properties of Combined Aminophylline and Ambrisentan in Hypoxia.

We hypothesized that concomitant pharmacological inhibition of the endothelin and adenosine pathway is safe and improves exercise performance in hypoxic humans, via a mechanism that does not involve augmentation of blood oxygenation. To test this hypothesis, we established safety and drug interactions for aminophylline (500 mg) plus ambrisentan (5 mg) in normoxic volunteers. Subsequently, a placebo-controlled study was employed to test the combination in healthy resting and exercising volunteers at simulated altitude (4,267 m).

Mitochondrial quality control in alveolar epithelial cells damaged by pneumonia in mice.

Mitochondrial damage is often overlooked in acute lung injury (ALI), yet most of the lung's physiological processes, such as airway tone, mucociliary clearance, ventilation-perfusion (Va/Q) matching, and immune surveillance require aerobic energy provision. Because the cell's mitochondrial quality control (QC) process regulates the elimination and replacement of damaged mitochondria to maintain cell survival, we serially evaluated mitochondrial biogenesis and mitophagy in the alveolar regions of mice in a validated pneumonia model. We report that apart from cell lysis by direct contact with microbes, modest epithelial cell death was detected despite significant mitochondrial damage.

S-nitrosylation of GAD65 is implicated in decreased GAD activity and oxygen-induced seizures.

Breathing oxygen at partial pressures ≥2.5 atmospheres absolute, which can occur in diving and hyperbaric oxygen (HBO) therapy, can rapidly become toxic to the central nervous system (CNS). This neurotoxicity culminates in generalized EEG epileptiform discharges, tonic-clonic convulsions and ultimately death.

The novel combination of theophylline and bambuterol as a potential treatment of hypoxemia in humans.

Hypoxemia can be life-threatening, both acutely and chronically. Because hypoxemia causes vascular dysregulation that further restricts oxygen availability to tissue, it can be pharmacologically addressed. We hypothesized that theophylline can be safely combined with the β2-adrenergic vasodilator bambuterol to improve oxygen availability in hypoxemic patients.

Mitochondrial quality-control dysregulation in conditional HO-1 mice.

The heme oxygenase-1 (; HO-1) pathway was tested for defense of mitochondrial quality control in cardiomyocyte-specific KO mice (HO-1[CM]) exposed to oxidative stress (100% O). After 48 hours of exposure, these mice showed persistent cardiac inflammation and oxidative tissue damage that caused sarcomeric disruption, cardiomyocyte death, left ventricular dysfunction, and cardiomyopathy, while control hearts showed minimal damage. After hyperoxia, HO-1(CM) hearts showed suppression of the Pgc-1α/nuclear respiratory factor-1 (NRF-1) axis, swelling, low electron density mitochondria by electron microscopy (EM), increased cell death, and extensive collagen deposition.

Antiepileptic drugs prevent seizures in hyperbaric oxygen: A novel model of epileptiform activity.

Breathing oxygen at sufficiently elevated pressures can trigger epileptiform seizures. Therefore, we tested the hypothesis that pre-treatment with FDA-approved antiepileptic drugs could prevent seizure onset in hyperoxia at 5 atmospheres absolute. We selected drugs from two putative functional categories, Na-channel antagonists and GABA enhancers, each administered intraperitoneally at four doses in separate groups of C57BL/6 mice.

Mitochondrial Dysfunction in Lung Pathogenesis.

Remarkable new roles for mitochondria in calcium handling, apoptosis, heme turnover, inflammation, and oxygen and nutrient sensing have been discovered for organelles that were once thought to be simple energy converters. Although deficits in mitochondrial function are often associated with energy failure and apoptosis, working cells maintain a mitochondrial reserve that affords the organelles distinct homeostatic sensing and regulatory abilities in lung cells. As primary intracellular sources of oxidants, mitochondria serve as critical monitors and modulators of vital oxidation-reduction processes, including mitochondrial biogenesis, mitophagy, inflammasome activation, cell proliferation, and prevention of fibrosis.