Carbon monoxide inhibition of apoptosis during ischemia-reperfusion lung injury is dependent on the p38 mitogen-activated protein kinase pathway and involves caspase 3

Carbon Monoxide Poisoning: From Occupational Health to Emergency Medicine

Carbon monoxide poisoning remains a leading cause of accidental poisoning worldwide (both at home and at work), and it is also a cause of suicidal poisoning. Such poisoning can arise following prolonged exposure to low levels of CO or following brief exposure to high concentrations of the gas. In fact, despite exposure limits, high safety standards, and the availability of CO alarms, nearly 50,000 people in the United States visit the emergency department each year due to poisoning. Additionally, CO poisoning in the United States causes up to 500 deaths each year. Despite the widespread nature of this form of poisoning, known about for centuries and whose damage mechanisms have been recognized (or rather hypothesized about) since the 1800s, early recognition, especially of late complications, and treatment remain a medical challenge. A well-designed therapeutic diagnostic process is necessary so that indication for hyperbaric or normobaric therapy is correctly made and so that patients are followed up even after acute exposure to diagnose late complications early. Furthermore, it is necessary to consider that in the setting of emergency medicine, CO poisoning can be part of a differential diagnosis along with other more frequent conditions, making its recognition difficult. The last thirty years have been marked by a significant increase in knowledge regarding the toxicity of CO, as well as its functioning and its importance at physiological concentrations in mammalian systems. This review, taking into account the significant progress made in recent years, aims to reconsider the pathogenicity of CO, which is not trivially just poisonous to tissues. A revision of the paradigm, especially as regards treatment and sequelae, appears necessary, and new studies should focus on this new point of view.

Pyrogallol protects against influenza A virus-triggered lethal lung injury by activating the Nrf2-PPAR-γ-HO-1 signaling axis

Pyrogallol, a natural polyphenol compound (1,2,3-trihydroxybenzene), has shown efficacy in the therapeutic treatment of disorders associated with inflammation. Nevertheless, the mechanisms underlying the protective properties of pyrogallol against influenza A virus infection are not yet established. We established in this study that pyrogallol effectively alleviated H1N1 influenza A virus-induced lung injury and reduced mortality. Treatment with pyrogallol was found to promote the expression and nuclear translocation of nuclear factor erythroid-2-related factor 2 (Nrf2) and peroxisome proliferator-activated receptor gamma (PPAR-γ). Notably, the activation of Nrf2 by pyrogallol was involved in elevating the expression of PPAR-γ, both of which act synergistically to enhance heme oxygenase-1 (HO-1) synthesis. Blocking HO-1 by zinc protoporphyrin (ZnPP) reduced the suppressive impact of pyrogallol on H1N1 virus-mediated aberrant retinoic acid-inducible gene-I-nuclear factor kappa B (RIG-I-NF-κB) signaling, which thus abolished the dampening effects of pyrogallol on excessive proinflammatory mediators and cell death (including apoptosis, necrosis, and ferroptosis). Furthermore, the HO-1-independent inactivation of janus kinase 1/signal transducers and activators of transcription (JAK1/STATs) and the HO-1-dependent RIG-I-augmented STAT1/2 activation were both abrogated by pyrogallol, resulting in suppression of the enhanced transcriptional activity of interferon-stimulated gene factor 3 (ISGF3) complexes, thus prominently inhibiting the amplification of the H1N1 virus-induced proinflammatory reaction and apoptosis in interferon-beta (IFN-β)-sensitized cells. The study provides evidence that pyrogallol alleviates excessive proinflammatory responses and abnormal cell death via HO-1 induction, suggesting it could be a potential agent for treating influenza.

Clinical Applications for Gasotransmitters in the Cardiovascular System: Are We There Yet?

Ischemia is the underlying mechanism in a wide variety of acute and persistent pathologies. As such, understanding the fine intracellular events occurring during (and after) the restriction of blood supply is pivotal to improving the outcomes in clinical settings. Among others, gaseous signaling molecules constitutively produced by mammalian cells (gasotransmitters) have been shown to be of potential interest for clinical treatment of ischemia/reperfusion injury. Nitric oxide (NO and its sibling, HNO), hydrogen sulfide (H2S), and carbon monoxide (CO) have long been proven to be cytoprotective in basic science experiments, and they are now awaiting confirmation with clinical trials. The aim of this work is to review the literature and the clinical trials database to address the state of development of potential therapeutic applications for NO, H2S, and CO and the clinical scenarios where they are more promising.

Prenatal Exposure to Air Pollution and Immune Thrombocytopenia: A Nationwide Population-Based Cohort Study

INTRODUCTION

Immune thrombocytopenia (ITP) is one of the most common hematologic disorders in children. However, its etiology is still unclear. Epidemiological studies have shown that air pollution is a plausible risk factor in stimulation of oxidative stress, induction of inflammation, and onset of autoimmune diseases. The objective of this article is to examine the effects of prenatal exposure to air pollution on the occurrence of immune thrombocytopenia (ITP) in children.

MATERIALS AND METHODS

This is a nationwide, population-based, matched case-control study. Using data from Taiwan's Maternal and Child Health Database (MCHD), we identified 427 children with ITP less than 6 years of age and age-matched controls without ITP between 2004 and 2016. Levels of prenatal exposure to air pollutants were obtained from 71 Environmental Protection Administration monitoring stations across Taiwan according to the maternal residence during pregnancy. Patients who had outpatient visits or admission with diagnosis of ITP and subsequently received first-line treatment of intravenous immunoglobulin or oral glucocorticoids were defined as incidence cases.

RESULTS

Prenatal exposure to particulate matter <10 μm (PM10) in diameter and the pollutant standard index (PSI) increased the risk of childhood ITP. Conversely, carbon monoxide (CO) exposure during pregnancy was negatively associated with the development of ITP.

CONCLUSION

Certain prenatal air pollutant exposure may increase the incidence of ITP in children.

Carbon Monoxide Releasing Molecule-3 Enhances Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Carbon Monoxide Release

Purpose

Limited intrinsic regeneration capacity following bone destruction remains a significant medical problem. Multiple regulatory effects of carbon monoxide releasing molecule-3 (CORM-3) have been reported. The aim of this study was to investigate the effect of CORM-3 on the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) during osteogenesis.

Patients and Methods

hPDLSCs obtained from healthy periodontal ligament tissues were cultured and identified with specific surface antigens by flow cytometry. Effect of CORM-3 on the proliferation of hPDLSCs was determined by CCK-8 assay. Alizarin red staining and alkaline phosphatase (ALP) activity were used to assess the osteogenic differentiation of hPDLSCs. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis were used to detect the expression of the indicated genes. Critical-sized skull defect was made in Balb/c-nude mice, microcomputed tomography (Micro-CT) and Masson trichrome staining were used to assess the new bone regeneration in mice.

Results

CORM-3 (400 μmol/l) significantly promoted the proliferation of hPDLSCs. CORM-3 pretreatment not only notably enhanced the mRNA and protein expression of osteo-specific marker OPN, Runx2 and ALP, but also increased mineral deposition and ALP activity by the release of CO on day 3, 7 and 14 (P<0.05). Degassed CORM-3 did not show the same effect as CORM-3. In animal model, application of CORM-3 with hPDLSCs transplantation highly increased new bone formation in skull defect region.

Conclusion

CORM-3 promoted osteogenic differentiation of hPDLSCs, and increased hPDLSCs-induced new bone formation in mice with critical-sized skull defect, which suggests an efficient and promising strategy in the treatment of disease with bone defect.

Heme Oxgenase-1, a Cardinal Modulator of Regulated Cell Death and Inflammation

Heme oxygenase catalyzes the rate-limiting step in heme degradation in order to generate biliverdin, carbon monoxide (CO), and iron. The inducible form of the enzyme, heme oxygenase-1 (HO-1), exerts a central role in cellular protection. The substrate, heme, is a potent pro-oxidant that can accelerate inflammatory injury and promote cell death. HO-1 has been implicated as a key mediator of inflammatory cell and tissue injury, as validated in preclinical models of acute lung injury and sepsis. A large body of work has also implicated HO-1 as a cytoprotective molecule against various forms of cell death, including necrosis, apoptosis and newly recognized regulated cell death (RCD) programs such as necroptosis, pyroptosis, and ferroptosis. While the antiapoptotic potential of HO-1 and its reaction product CO in apoptosis regulation has been extensively characterized, relatively fewer studies have explored the regulatory role of HO-1 in other forms of necrotic and inflammatory RCD (i.e., pyroptosis, necroptosis and ferroptosis). HO-1 may provide anti-inflammatory protection in necroptosis or pyroptosis. In contrast, in ferroptosis, HO-1 may play a pro-death role via enhancing iron release. HO-1 has also been implicated in co-regulation of autophagy, a cellular homeostatic program for catabolic recycling of proteins and organelles. While autophagy is primarily associated with cell survival, its occurrence can coincide with RCD programs. This review will summarize the roles of HO-1 and its reaction products in co-regulating RCD and autophagy programs, with its implication for both protective and detrimental tissue responses, with emphasis on how these impact HO-1 as a candidate therapeutic target in disease.

Ischemia-reperfusion Injury in the Transplanted Lung: A Literature Review

Lung ischemia-reperfusion injury (LIRI) and primary graft dysfunction are leading causes of morbidity and mortality among lung transplant recipients. Although extensive research endeavors have been undertaken, few preventative and therapeutic treatments have emerged for clinical use. Novel strategies are still needed to improve outcomes after lung transplantation. In this review, we discuss the underlying mechanisms of transplanted LIRI, potential modifiable targets, current practices, and areas of ongoing investigation to reduce LIRI and primary graft dysfunction in lung transplant recipients.

Multicomponent design of chromeno[2,3-b]pyridine systems

The review summarizes and systematizes data on the methods for the preparation of chromeno[2,3-b]pyridines. Both multicomponent and pseudo-multicomponent synthetic approaches and one-pot transformations based on the reactions of carbonyl compounds, malononitrile or its derivatives, and CH-acids are considered. Examples of the use of various catalysts, microwave and ultrasonic radiation, as well as electric current for the implementation of multicomponent transformations of this type are given. Characteristic features of the course and mechanisms of reactions are discussed. Data on the biological activity of the obtained compounds and on other fields of application of such heterocyclic systems are presented.

The bibliography includes 109 references.

The Effects of Volatile Anesthetics on Lung Ischemia-Reperfusion Injury: Basic to Clinical Studies

Case reports from as early as the 1970s have shown that intravenous injection of even a small dose of volatile anesthetics result in fatal lung injury. Direct contact between volatile anesthetics and pulmonary vasculature triggers chemical damage in the vessel walls. A wide variety of factors are involved in lung ischemia-reperfusion injury (LIRI), such as pulmonary endothelial cells, alveolar epithelial cells, alveolar macrophages, neutrophils, mast cells, platelets, proinflammatory cytokines, and surfactant. With a constellation of factors involved, the assessment of the protective effect of volatile anesthetics in LIRI is difficult. Multiple animal studies have reported that with regards to LIRI, sevoflurane demonstrates an anti-inflammatory effect in immunocompetent cells and an anti-apoptotic effect on lung tissue. Scattered studies have dismissed a protective effect of desflurane against LIRI. While a single-center randomized controlled trial (RCT) found that volatile anesthetics including desflurane demonstrated a lung-protective effect in thoracic surgery, a multicenter RCT did not demonstrate a lung-protective effect of desflurane. LIRI is common in lung transplantation. One study, although limited due to its small sample size, found that the use of volatile anesthetics in organ procurement surgery involving "death by neurologic criteria" donors did not improve lung graft survival. Future studies on the protective effect of volatile anesthetics against LIRI must examine not only the mechanism of the protective effect but also differences in the effects of different types of volatile anesthetics, their optimal dosage, and the appropriateness of their use in the event of marked alveolar capillary barrier damage.

Tat-indoleamine 2,3-dioxygenase 1 elicits neuroprotective effects on ischemic injury

It is well known that oxidative stress participates in neuronal cell death caused production of reactive oxygen species (ROS). The increased ROS is a major contributor to the development of ischemic injury. Indoleamine 2,3-dioxygenase 1 (IDO-1) is involved in the kynurenine pathway in tryptophan metabolism and plays a role as an anti-oxidant. However, whether IDO-1 would inhibit hippocampal cell death is poorly known. Therefore, we explored the effects of cell permeable Tat-IDO-1 protein against oxidative stress-induced HT-22 cells and in a cerebral ischemia/reperfusion injury model. Transduced Tat-IDO-1 reduced cell death, ROS production, and DNA fragmentation and inhibited mitogen-activated protein kinases (MAPKs) activation in H₂O₂ exposed HT-22 cells. In the cerebral ischemia/reperfusion injury model, Tat-IDO-1 transduced into the brain and passing by means of the blood-brain barrier (BBB) significantly prevented hippocampal neuronal cell death. These results suggest that Tat-IDO-1 may present an alternative strategy to improve from the ischemic injury.

Therapeutic Potential of Heme Oxygenase-1 and Carbon Monoxide in Acute Organ Injury, Critical Illness, and Inflammatory Disorders

Heme oxygenase-1 (HO-1) is an inducible stress protein that catalyzes the oxidative conversion of heme to carbon monoxide (CO), iron, and biliverdin (BV), the latter of which is converted to bilirubin (BR) by biliverdin reductase. HO-1 has been implicated as a cytoprotectant in various models of acute organ injury and disease (i.e., lung, kidney, heart, liver). Thus, HO-1 may serve as a general therapeutic target in inflammatory diseases. HO-1 may function as a pleiotropic modulator of inflammatory signaling, via the removal of heme, and generation of its enzymatic degradation-products. Iron release from HO activity may exert pro-inflammatory effects unless sequestered, whereas BV/BR have well-established antioxidant properties. CO, derived from HO activity, has been identified as an endogenous mediator that can influence mitochondrial function and/or cellular signal transduction programs which culminate in the regulation of apoptosis, cellular proliferation, and inflammation. Much research has focused on the application of low concentration CO, whether administered in gaseous form by inhalation, or via the use of CO-releasing molecules (CORMs), for therapeutic benefit in disease. The development of novel CORMs for their translational potential remains an active area of investigation. Evidence has accumulated for therapeutic effects of both CO and CORMs in diseases associated with critical care, including acute lung injury/acute respiratory distress syndrome (ALI/ARDS), mechanical ventilation-induced lung injury, pneumonias, and sepsis. The therapeutic benefits of CO may extend to other diseases involving aberrant inflammatory processes such as transplant-associated ischemia/reperfusion injury and chronic graft rejection, and metabolic diseases. Current and planned clinical trials explore the therapeutic benefit of CO in ARDS and other lung diseases.

Two Faces of Heme Catabolic Pathway in Newborns: A Potential Role of Bilirubin and Carbon Monoxide in Neonatal Inflammatory Diseases

In an infant's body, all the systems undergo significant changes in order to adapt to the new, extrauterine environment and challenges which it poses. Fragile homeostasis can be easily disrupted as the defensive mechanisms are yet imperfect. The activity of antioxidant enzymes, i.e., superoxide dismutase, catalase, and glutathione peroxidase, is low; therefore, neonates are especially vulnerable to oxidative stress. Free radical burden significantly contributes to neonatal illnesses such as sepsis, retinopathy of premature, necrotizing enterocolitis, bronchopulmonary dysplasia, or leukomalacia. However, newborns have an important ally-an inducible heme oxygenase-1 (HO-1) which expression rises rapidly in response to stress stimuli. HO-1 activity leads to production of carbon monoxide (CO), free iron ion, and biliverdin; the latter is promptly reduced to bilirubin. Although CO and bilirubin used to be considered noxious by-products, new interesting properties of those compounds are being revealed. Bilirubin proved to be an efficient free radicals scavenger and modulator of immune responses. CO affects a vast range of processes such as vasodilatation, platelet aggregation, and inflammatory reactions. Recently, developed nanoparticles consisting of PEGylated bilirubin as well as several kinds of molecules releasing CO have been successfully tested on animal models of inflammatory diseases. This paper focuses on the role of heme metabolites and their potential utility in prevention and treatment of neonatal diseases.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

Estrogen Receptors and Estrogen-Induced Uterine Vasodilation in Pregnancy

Normal pregnancy is associated with dramatic increases in uterine blood flow to facilitate the bidirectional maternal–fetal exchanges of respiratory gases and to provide sole nutrient support for fetal growth and survival. The mechanism(s) underlying pregnancy-associated uterine vasodilation remain incompletely understood, but this is associated with elevated estrogens, which stimulate specific estrogen receptor (ER)-dependent vasodilator production in the uterine artery (UA). The classical ERs (ERα and ERβ) and the plasma-bound G protein-coupled ER (GPR30/GPER) are expressed in UA endothelial cells and smooth muscle cells, mediating the vasodilatory effects of estrogens through genomic and/or nongenomic pathways that are likely epigenetically modified. The activation of these three ERs by estrogens enhances the endothelial production of nitric oxide (NO), which has been shown to play a key role in uterine vasodilation during pregnancy. However, the local blockade of NO biosynthesis only partially attenuates estrogen-induced and pregnancy-associated uterine vasodilation, suggesting that mechanisms other than NO exist to mediate uterine vasodilation. In this review, we summarize the literature on the role of NO in ER-mediated mechanisms controlling estrogen-induced and pregnancy-associated uterine vasodilation and our recent work on a “new” UA vasodilator hydrogen sulfide (H₂S) that has dramatically changed our view of how estrogens regulate uterine vasodilation in pregnancy.

Carbon Monoxide-Releasing Molecule-3 Suppresses Tumor Necrosis Factor-α- and Interleukin-1β-Induced Expression of Junctional Molecules on Human Gingival Fibroblasts via the Heme Oxygenase-1 Pathway

Human gingival fibroblast barrier dysfunction caused by inflammation contributes to gingivitis and can lead to inflammatory periodontal disease. The disease features include upregulated epithelial permeability, increased inflammatory mediators, and downregulated junctional complex molecules. Carbon monoxide- (CO-) releasing molecule-3 (CORM-3) is a water-soluble compound that has demonstrated anti-inflammatory effects in in vitro and in vivo studies. In this study, we aimed to investigate the effects of CORM-3 on the expression of tight and adherens junction molecules on human gingival fibroblasts (HGFs) stimulated with tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). HGFs were cultured from the explants of normal human gingival tissues, which were stimulated in the presence or absence of CORM-3. Epithelial barrier function was evaluated by paracellular permeability and junctional complex molecule expression analyses. The protein and mRNA expression levels of adherens junction molecules (VE-cadherin and β-catenin) and tight junction molecules (zona occludens-1, ZO-1) were studied using western blot analysis and reverse transcription-quantitative polymerase chain reaction (RT-PCR). The mRNA and protein expression levels of these cytokines were also analyzed in HGFs transiently transfected with HO-1 small interfering RNA (siRNA) in response to TNF-α and IL-1β stimulation. CORM-3 reduced permeability and enhanced the expression of junctional complex molecules (ZO-1, VE-cadherin, and β-catenin) in TNF-α- and IL-1β-induced HGFs. However, these effects of CORM-3 were attenuated when HO-1 siRNA was transiently transfected in HGFs. These findings indicate that CORM-3 exerts anti-inflammatory effects on TNF-α- and IL-1β-stimulated HGFs via the HO-1 pathway, which suggests the promising potential of CORM-3 in the treatment of inflammatory periodontal disease.

The CO-releasing molecule CORM-3 protects adult cardiomyocytes against hypoxia-reoxygenation by modulating pH restoration

Several studies have reported that CORM-3, a water-soluble carbon monoxide releasing molecule, elicits cardioprotection against myocardial infarction but the mechanism remains to be investigated. Numerous reports indicate that inhibition of pH regulators, the Na⁺/H⁺ exchanger (NHE) and Na⁺/HCO₃^- symporter (NBC), protect cardiomyocytes from hypoxia/reoxygenation injury by delaying the intracellular pH (pHi) recovery at reperfusion. Our goal was to explore whether CORM-3-mediated cytoprotection involves the modulation of pH regulation. When added at reoxygenation, CORM-3 (50 μM) reduced the mortality of cardiomyocytes exposed to 3 h of hypoxia and 2 h of reoxygenation in HCO₃^--buffered solution. This effect was lost when using inactive iCORM-3, which is depleted of CO and used as control, thus implicating CO as the mediator of this cardioprotection. Interestingly, the cardioprotective effect of CORM-3 was abolished by switching to a bicarbonate-free medium. This effect of CORM-3 was also inhibited by 5-hydroxydecanoate, a mitochondrial ATP-dependent K⁺ (mK_ATP) channel inhibitor (500 μM) or PD098059, a MEK1/2 inhibitor (10 μM). In additional experiments and in the absence of hypoxia-reoxygenation, intracellular pH was monitored in cardiomyocytes exposed to cariporide to block NHE activity. CORM-3 inhibited alkalinisation and this effect was blocked by PD098059 and 5-HD. In conclusion, CORM-3 protects the cardiomyocyte against hypoxia-reoxygenation injury by inhibiting a bicarbonate transporter at reoxygenation, probably the Na⁺/HCO₃^- symporter. This cardioprotective effect of CORM-3 requires the activation of mK_ATP channels and the activation of MEK1/2.

Metabolic Resuscitation Strategies to Prevent Organ Dysfunction in Sepsis

Significance: Sepsis is the main cause of death among patients admitted to the intensive care unit. As current treatment is limited to antimicrobial therapy and supportive care, mortality remains high, which warrants efforts to find novel therapies. Recent Advances: Mitochondrial dysfunction is emerging as a key process in the induction of organ dysfunction during sepsis, and metabolic resuscitation might reveal to be a novel cornerstone in the treatment of sepsis. Critical Issues: Here, we review novel strategies to maintain organ function in sepsis by precluding mitochondrial dysfunction by lowering energetic demand to allow preservation of adenosine triphosphate-levels, while reducing free radical generation. As the most common strategy to suppress metabolism, that is, cooling, does not reveal unequivocal beneficial effects and may even increase mortality, caloric restriction or modulation of energy-sensing pathways (i.e., sirtuins and AMP-activated protein kinase) may offer safe alternatives. Similar effects may be offered when mimicking hibernation by hydrogen sulfide (H₂S). In addition H₂S may also confer beneficial effects through upregulation of antioxidant mechanisms, similar to the other gasotransmitters nitric oxide and carbon monoxide, which display antioxidant and anti-inflammatory effects in sepsis. In addition, oxidative stress may be averted by systemic or mitochondria-targeted antioxidants, of which a wide range are able to lower inflammation, as well as reduce organ dysfunction and mortality from sepsis. Future Directions: Mitochondrial dysfunction plays a key role in the pathophysiology of sepsis. As a consequence, metabolic resuscitation might reveal to be a novel cornerstone in the treatment of sepsis.

High-Pressure Carbon Monoxide and Oxygen Mixture is Effective for Lung Preservation

(1) Background: Heme oxygenase-1 (HO-1) degrades heme and generates carbon monoxide (CO), producing various anti-inflammatory, anti-oxidative, and anti-apoptotic effects. This study aimed to confirm the effects of CO on the ischemia–reperfusion injury (IRI) of donor lungs using a high-pressure gas (HPG) preservation method. (2) Methods: Donor rat and canine lungs were preserved in a chamber filled with CO (1.5 atm) and oxygen (O₂; 2 atm) and were ventilated with either CO and O₂ mixture (CO/O₂ group) or air (air group) immediately before storage. Rat lungs were subjected to heterotopic cervical transplantation and evaluated after reperfusion, whereas canine lungs were subjected to allogeneic transplantation and evaluated. (3) Results: Alveolar hemorrhage in the CO/O₂ group was significantly milder than that in the air group. mRNA expression levels of HO-1 remained unchanged in both the groups; however, inflammatory mediator levels were significantly lower in the CO/O₂ group than in the air group. The oxygenation of graft lungs was comparable between the two groups, but lactic acid level tended to be higher in the air group. (4) Conclusions: The HO-1/CO system in the HPG preservation method is effective in suppressing IRI and preserving donor lungs.

Therapeutic effect of carbon monoxide-releasing molecule-3 on acute lung injury after hemorrhagic shock and resuscitation

Hemorrhagic shock and resuscitation (HSR) induces a pulmonary inflammatory response and frequently causes acute lung injury. Carbon monoxide-releasing molecule-3 (CORM-3) has been reported to liberate and deliver CO under physiological conditions, which exerts organ-protective effects during systemic insults. The present study aimed to determine whether the administration of CORM-3 following HSR exerts a therapeutic effect against HSR-induced lung injury without any detrimental effects on oxygenation and hemodynamics. To induce hemorrhagic shock, rats were bled to a mean arterial blood pressure of 30 mmHg for 45 min and then resuscitated with the shed blood. CORM-3 or a vehicle was intravenously administered immediately following the completion of resuscitation. The rats were divided into four groups, including sham, HSR, HSR/CORM-3 and HSR/inactive CORM-3 groups. Arterial blood gas parameters and vital signs were recorded during HSR. The histopathological changes to the lungs were evaluated using a lung injury score, while pulmonary edema was evaluated on the basis of the protein concentration in bronchoalveolar lavage fluid and the lung wet/dry ratio. We also investigated the pulmonary expression levels of inflammatory mediators and apoptotic markers such as cleaved caspase-3 and transferase-mediated dUTP-fluorescein isothiocyanate nick-end labeling (TUNEL) staining. Although HSR caused significant lung histopathological damage and pulmonary edema, CORM-3 significantly ameliorated this damage. CORM-3 also attenuated the HSR-induced upregulation of tumor necrosis factor-α, inducible nitric oxide synthase and interleukin-1β genes, and the expression of interleukin-1β and macrophage inflammatory protein-2. In addition, the expression of interleukin-10, an anti-inflammatory cytokine, was inversely enhanced by CORM-3, which also reduced the number of TUNEL-positive cells and the expression of cleaved caspase-3 following HSR. Although CORM-3 was administered during the acute phase of HSR, it did not exert any influence on arterial blood gas analysis data and vital signs during HSR. Therefore, treatment with CORM-3 ameliorated HSR-induced lung injury, at least partially, through anti-inflammatory and anti-apoptotic effects, without any detrimental effects on oxygenation and hemodynamics.

Carbon monoxide releasing molecule-2 protects mice against acute kidney injury through inhibition of ER stress

Acute kidney injury (AKI), which is defined as a rapid decline of renal function, becomes common and recently recognized to be closely intertwined with chronic kidney diseases. Current treatment for AKI is largely supportive, and endoplasmic reticulum (ER) stress has emerged as a novel mediator of AKI. Since carbon monoxide attenuates ER stress, the objective of the present study aimed to determine the protective effect of carbon monoxide releasing molecule-2 (CORM2) on AKI associated with ER stress. Kidney injury was induced after LPS (15 mg/kg) treatment at 12 to 24 h in C57BL/6J mice. Pretreatment of CORM2 (30 mg/kg) effectively prevented LPS-induced oxidative stress and inflammation during AKI in mice. CORM2 treatment also effectively inhibited LPS-induced ER stress in AKI mice. In order to confirm effect of CO on the pathophysiological role of tubular epithelial cells in AKI, we used mProx24 cells. Pretreatment of CORM2 attenuated LPS-induced ER stress, oxidative stress, and inflammation in mProx24 cells. These data suggest that CO therapy may prevent ER stress-mediated AKI.

SPRED2 deficiency may lead to lung ischemia-reperfusion injury via ERK1/2 signaling pathway activation

PURPOSE

Inflammatory changes during lung ischemia-reperfusion injury (IRI) are related to the activation of the extracellular signal-regulated kinase (ERK)1/2 signaling pathway. Sprouty-related EVH1 (enabled/vasodilator-stimulated phosphoprotein homology 1)-domain-containing proteins (SPREDs) are known inhibitors of ERK1/2 signaling. The role of SPRED2 in lung IRI was examined in a left hilar clamp mouse model.

METHODS

C57BL/6 wild-type (WT) and Spred2^-/- mice were used in the left hilar clamp model. Experimental groups underwent 30 min of left hilar clamping followed by 1 h of reperfusion. U0126, an ERK1/2 inhibitor, was administered to Spred2^-/- mice with reperfused lungs.

RESULTS

The partial pressures of oxygen of the Spred2^-/- mice after reperfusion were significantly worse than those of WT mice (p < 0.01). Spred2^-/- mice displayed more severe injuries than WT mice with increased neutrophil infiltration observed by a histological evaluation and flow cytometry (p < 0.001). This severe inflammation was inhibited by U0126. In addition, the rate of ERK1 activation was significantly higher in the lungs of Spred2^-/- mice after reperfusion than in WT mice according to a Western blot analysis (p < 0.05).

CONCLUSION

The activation of the ERK1/2 signaling pathway influences the severity of lung IRI, causing inflammation with neutrophil infiltration. SPRED2 may be a promising target for the suppression of lung IRI.

BTP2, a Store-Operated Calcium Channel Inhibitor, Attenuates Lung Ischemia-Reperfusion Injury in Rats

Lung ischemia-reperfusion (I/R) injury is a critical complication following a lung transplant, cardiopulmonary bypass, pulmonary embolism, and trauma. Immune cells and their effector functions are involved in the lung I/R injury. Store-operated calcium channels (SOCC) are highly Ca²⁺-selective cation channels and have crucial effects on the immune system. It has been indicated that BTP2, a potent SOCC blocker, could inhibit pro-inflammatory cytokine production from immune cells both in vitro and in vivo. Therefore, this study was conducted to investigate the beneficial effects of BTP2 on lung I/R injury in Sprague-Dawley (SD) rats. The left lungs of male SD rats underwent ischemia for 60 min and reperfusion for 2 h. Treated animals received BTP2 4 mg/kg or 10 mg/kg intraperitoneally 30 min before the ischemia. The results revealed that pretreatment with BTP2 markedly attenuated I/R injury-induced pulmonary edema, microvascular protein leakage, neutrophil infiltration, adhesion molecules, cytokine production (e.g., ICAM-1, TNF-α, IL-1β, and IL-2), and the transcription factor nuclear factor of activated T cells c1 nuclear translocation in the lung tissue. These findings indicate that BTP2 can be a potential therapeutic drug for lung I/R injury and suggest that SOCC may play a critical role in lung I/R injury.

Carbon monoxide releasing molecule‑3 promotes the osteogenic differentiation of rat bone marrow mesenchymal stem cells by releasing carbon monoxide

Stem cell‑based therapies are promising strategies to stimulate bone regeneration. Carbon monoxide releasing molecule‑3 (CORM‑3) exhibits multiple regulatory effects in a number of cells by releasing carbon monoxide (CO). The present study aimed to investigate the influence of CORM‑3 on the osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs). BMSCs were divided into five groups: A CORM‑3‑osteogenic group, in which cells were pretreated with CORM‑3 and subjected to osteogenic differentiation induction using osteogenic medium; an osteogenic group, in which cells were cultured in osteogenic medium; a degassed CORM‑3‑osteogenic group, in which cells were pretreated with degassed CORM‑3 and subjected to osteogenic differentiation induction; a CORM‑3 group, in which cells were cultured in control medium containing CORM‑3; and a control group, in which cells were cultured in control medium alone. The osteo‑specific mRNA and protein expression of runt‑related transcription factor 2 (Runx2), osteocalcin (OCN) and osteopontin (OPN) were assessed using reverse transcription‑quantitative polymerase chain reaction and western blot analysis. Alkaline phosphatase (ALP) activity was also examined and mineralization was detected using alizarin red staining. Levels of Runx2, OCN and OPN mRNA and protein in the CORM‑3‑osteogenic group were significantly increased compared with the osteogenic group (P<0.05), with the exception of OCN protein levels on day 3. The mRNA and protein expression of Runx2, OCN and OPN in the degassed CORM‑3‑osteogenic and osteogenic groups were similar. In addition, the mRNA and protein expression of Runx2, OCN and OPN in the CORM‑3 and control group were similar. ALP activity in the CORM‑3‑osteogenic group was increased from day 3 and remained significantly higher compared with all other groups on days 3, 5 and 7 (P<0.05). Additionally, the results indicated that the optical density value of alizarin red staining in the CORM‑3‑osteogenic group was significantly increased compared with the other groups (P<0.05). Therefore, the present study demonstrated that CORM‑3 may promote the osteogenic differentiation of BMSCs by releasing CO.

Rosmarinic acid elicits neuroprotection in ischemic stroke via Nrf2 and heme oxygenase 1 signaling

Rosmarinic acid (RA) can elicit a neuroprotective effect against ischemic stroke, but the precise molecular mechanism remains poorly understood. In this study, an experimental ischemic stroke model was established in CD-1 mice (Beijing Vital River Laboratory Animal Technology, Beijing, China) by occluding the right middle cerebral artery for 1 hour and allowing reperfusion for 24 hours. After intraperitoneally injecting model mice with 10, 20, or 40 mg/kg RA, functional neurological deficits were evaluated using modified Longa scores. Subsequently, cerebral infarct volume was measured using TTC staining and ischemic brain tissue was examined for cell apoptosis with TUNEL staining. Superoxide dismutase activity and malondialdehyde levels were measured by spectrophometry. Expression of heme oxygenase-1 (HO-1), nuclear factor erythroid 2-related factor 2 (Nrf2), Bcl-2, Bax, Akt, and phospho-Ser473 Akt proteins in ischemic brain tissue was detected by western blot, while mRNA levels of Nrf2, HO-1, Bcl-2, and Bax were analyzed using real time quantitative PCR. In addition, HO-1 enzyme activity was measured spectrophotometrically. RA (20 and 40 mg/kg) greatly improved neurological function, reduced infarct volume, decreased cell apoptosis, upregulated Bcl-2 protein and mRNA expression, downregulated Bax protein and mRNA expression, increased HO-1 and Nrf2 protein and mRNA expression, increased superoxide dismutase activity, and decreased malondialdehyde levels in ischemic brain tissue of model mice. However, intraperitoneal injection of a HO-1 inhibitor (10 mg/kg zinc protoporphyrin IX) reversed the neuroprotective effects of RA on HO-1 enzyme activity and Bcl-2 and Bax protein expression. The PI3K/Akt signaling pathway inhibitor LY294002 (10 mM) inhibited Akt phosphorylation, as well as Nrf2 and HO-1 expression. Our findings suggest that RA has anti-oxidative and anti-apoptotic properties that protect against ischemic stroke by a mechanism involving upregulation of Nrf2 and HO-1 expression via the PI3K/Akt signaling pathway.

Carbon monoxide in lung cell physiology and disease

Carbon monoxide (CO) is an endogenously produced gas that has gained recognition as a biological signal transduction effector with properties similar, but not identical, to that of nitric oxide (NO). CO, which binds primarily to heme iron, may activate the hemoprotein guanylate cyclase, although with lower potency than NO. Furthermore, CO can modulate the activities of several cellular signaling molecules such as p38 MAPK, ERK1/2, JNK, Akt, NF-κB, and others. Emerging studies suggest that mitochondria, the energy-generating organelle of cells, represent a key target of CO action in eukaryotes. Dose-dependent modulation of mitochondrial function by CO can result in alteration of mitochondrial membrane potential, mitochondrial reactive oxygen species production, release of proapoptotic and proinflammatory mediators, as well as the inhibition of respiration at high concentration. CO, through modulation of signaling pathways, can impact key biological processes including autophagy, mitochondrial biogenesis, programmed cell death (apoptosis), cellular proliferation, inflammation, and innate immune responses. Inhaled CO is widely known as an inhalation hazard due to its rapid complexation with hemoglobin, resulting in impaired oxygen delivery to tissues and hypoxemia. Despite systemic and cellular toxicity at high concentrations, CO has demonstrated cyto- and tissue-protective effects at low concentration in animal models of organ injury and disease. These include models of acute lung injury (e.g., hyperoxia, hypoxia, ischemia-reperfusion, mechanical ventilation, bleomycin) and sepsis. The success of CO as a candidate therapeutic in preclinical models suggests potential clinical application in inflammatory and proliferative disorders, which is currently under evaluation in clinical trials.

Carbon monoxide and hydrogen sulphide reduce reperfusion injury in abdominal compartment syndrome

BACKGROUND

Carbon monoxide (CO)- and hydrogen sulphide-releasing molecules (CORM-3 and GYY4137, respectively) have been shown to be potent antioxidant and antiinflammatory agents at the tissue and systemic level. We hypothesized that both CORM-3 and GYY4137 would reduce the significant organ dysfunction associated with abdominal compartment syndrome (ACS).

MATERIAL AND METHODS

Randomized trial was conducted where ACS was maintained for 2 hours in 27 rats using an abdominal plaster cast and intraperitoneal CO₂ insufflation at 20 mmHg. Three experimental groups underwent ACS and received an experimental molecule at the time of decompression: inactive CORM-3, active CORM-3, and GYY4137, whereas three groups underwent no ACS to serve as a sham. Sinusoidal perfusion, inflammatory response and cell death were quantified in exteriorized livers. Respiratory, liver, and renal dysfunction was assessed biochemically.

RESULTS

Hepatocellular death and the number of activated leukocytes within postsinusoidal venules were significantly increased in rats with ACS (16-fold increase, 17-fold leukocyte activation, respectively, P < 0.05). Administration of CORM-3 or GYY4137 resulted in a significant decrease of both parameters (P = 0.03 and P = 0.009). ACS resulted in an increase in markers of renal and liver injury; CORM-3 or GYY4137 partially restored levels to those seen in sham animals. Myeloperoxidase was significantly elevated in the ACS group in lung, liver, and small intestine (P = 0.0002, P = 0.01, and P = 0.08, respectively). CORM-3 treatment, but not GYY4137, was able to completely block the response (65 ± 11 U/ml and 92 ± 18 U/ml, respectively versus 110 ± 10U/ml in the ACS group, lung tissue).

CONCLUSIONS

We have demonstrated the effect of two molecules, CO and hydrogen sulphide, on tempering the reperfusion-associated metabolic and organ derangements in ACS. CORM-3 demonstrated a greater effect than GYY4137 and was able to restore most of the measured parameters to levels comparable to sham.

Anti-apoptotic properties of carbon monoxide in porcine oocyte during in vitro aging

If fertilization of matured oocyte does not occur, unfertilized oocyte undergoes aging, resulting in a time-dependent reduction of the oocyte’s quality. The aging of porcine oocytes can lead to apoptosis. Carbon monoxide (CO), a signal molecule produced by the heme oxygenase (HO), possesses cytoprotective and anti-apoptotic effects that have been described in somatic cells. However, the effects of CO in oocytes have yet to be investigated. By immunocytochemistry method we detected that both isoforms of heme oxygenase (HO-1 and HO-2) are present in the porcine oocytes. Based on the morphological signs of oocyte aging, it was found that the inhibition of both HO isoforms by Zn-protoporphyrin IX (Zn-PP IX) leads to an increase in the number of apoptotic oocytes and decrease in the number of intact oocytes during aging. Contrarily, the presence of CO donors (CORM-2 or CORM-A1) significantly decrease the number of apoptotic oocytes while increasing the number of intact oocytes. We also determined that CO donors significantly decrease the caspase-3 (CAS-3) activity. Our results suggest that HO/CO contributes to the sustaining viability through regulation of apoptosis during in vitro aging of porcine oocytes.

Carbon monoxide ameliorates hepatic ischemia/reperfusion injury via sirtuin 1-mediated deacetylation of high-mobility group box 1 in rats

Carbon monoxide (CO) exerts protective effects on hepatic ischemia/reperfusion injury (IRI), but the underlying molecular mechanisms are not fully understood. High-mobility group box 1 (HMGB1) is an important mediator of injury and inflammation in hepatic IRI. Here, we investigated whether CO could attenuate hepatic IRI via inhibition of HMGB1 release, particularly through sirtuin 1 (SIRT1). CO was released by treatment with carbon monoxide-releasing molecule (CORM)-2. CORM-2-delivered CO ameliorated hepatic IRI, as indicated by lower serum aminotransferase levels, lower hepatic inflammatory responses, and less severe ischemia/reperfusion-associated histopathologic changes. Treatment with CORM-2 significantly inhibited IRI-induced HMGB1 translocation and release. SIRT1 expression was increased by CORM-2 pretreatment. When CORM-2-induced SIRT1 expression was inhibited using EX527, HMGB1 translocation and release were increased and hepatic IRI was worsened, whereas SIRT1 activation by resveratrol reversed this trend. In vitro, CORM-2 reduced hypoxia/reoxygenation-induced HMGB1 translocation and release, these inhibitions were blocked by SIRT1 inhibition using EX527 or SIRT1 small interfering RNA both in alpha mouse liver 12 cells and RAW264.7 macrophages. Moreover, SIRT1 directly interacted with and deacetylated HMGB1. IRI increased HMGB1 acetylation, which was abolished by CORM-2 treatment via SIRT1. In conclusion, these results suggest that CO may increase SIRT1 expression, which may decrease HMGB1 acetylation and subsequently reduce its translocation and release, thereby protecting against hepatic IRI. Liver Transplantation 23 510-526 2017 AASLD.

Effects of p38 mitogen-activated protein kinase on lung ischemia-reperfusion injury in diabetic rats

BACKGROUND

Lung ischemia-reperfusion injury (LIRI) is a pathologic process that is observed in several clinical conditions, and p38 mitogen-activated protein kinase (MAPK) is involved. Diabetes mellitus (DM) results in an increased incidence of ischemia-induced organ damage. The aims of this study were to examine the effects of DM on LIRI in a rat model of DM and to explore the possible mechanisms in relation to the p38 MAPK pathway.

METHODS

Forty rats were randomly divided into the following five groups (n = 8 each): a control + sham group, a control + IR group (CIR), a DM + sham group, a DM + IR group (DIR), and a DM + IR + SB203580 group. The control and streptozotocin-induced diabetic rats underwent a sham operation or left hilum occlusion for 90 min followed by reperfusion for 4 h. SB203580 was used to inhibit the p38 MAPK pathway. The pulmonary oxygenation index, inflammatory cytokines in the serum, lung edema, histopathology, oxidant stress, apoptosis, and phosphorylated/total-p38 MAPK protein levels were measured.

RESULTS

The DIR group displayed greater concentrations of tumor necrosis factor-α, interleukin-6, and intercellular adhesion molecule-1 and increases in the wet weight-to-dry weight ratio, lung injury scores, malondialdehyde levels, and cellular apoptosis, and these effects were accompanied by lower pulmonary oxygenation compared with the CIR group (P < 0.05). In the DIR group, the expression levels of p38 MAPK protein were significantly upregulated compared with those of the CIR group. Additionally, all of these alterations were attenuated in the DM + IR + SB203580 group compared with the DIR group.

CONCLUSIONS

Diabetes exacerbates LIRI by activating the p38 MAPK pathway.

Suppression of human alloreactive T cells by linear tetrapyrroles; relevance for transplantation

The main limitation to successful transplantation is the antigraft response developed by the recipient immune system, and the adverse side effects of immunosuppressive agents which are associated with significant toxicity and counter indications such as infection and cancer. Furthermore, immunosuppressants do little to prevent ischemia-reperfusion injury during the transplantation procedure itself hence there is a growing need to develop novel immunosuppressive drugs specifically aimed at prolonging graft survival. Linear tetrapyrroles derived from the breakdown of mammalian heme have been shown in numerous studies to play a protective role in allograft transplantation and ischemia-reperfusion injury; however, commercial sources of these products have not been approved for use in humans. Plants and algae produce equivalent linear tetrapyrroles called bilins that serve as chromophores in light-sensing. One such marine-derived tetrapyrrole, phycocyanobilin (PCB), shows significant structural similarity to mammalian biliverdin (BV) and may prove to be a safer alternative for use in the clinic if it can exert direct effects on human immune cells. Using a mixed lymphocyte reaction, we quantified the allogeneic responses of recipient cells to donor cells and found that PCB, like BV, effectively suppressed proliferation and proinflammatory cytokine production. In addition, we found that BV and PCB can directly downregulate the proinflammatory responses of both innate dendritic cells and adaptive T cells. We therefore propose that PCB may be an effective therapeutic drug in the clinical setting of transplantation and may also have wider applications in regulating inappropriate inflammation.

MKK3 influences mitophagy and is involved in cigarette smoke-induced inflammation

Cigarette smoking is the primary risk factor for COPD which is characterized by excessive inflammation and airflow obstruction of the lung. While inflammation is causally related to initiation and progression of COPD, the mitochondrial mechanisms that underlie the associated inflammatory responses are poorly understood. In this context, we have studied the role played by Mitogen activated protein (MAP) kinase kinase 3 (MKK3), a dual-specificity protein kinase, in cigarette smoke induced-inflammation and mitochondrial dysfunction. Serum pro-inflammatory cytokines were significantly elevated in WT but not in MKK3-/- mice exposed to Cigarette smoke (CS) for 2 months. To study the cellular mechanisms of inflammation, bone marrow derived macrophages (BMDMs), wild type (WT) and MKK3-/-, were exposed to cigarette smoke extract (CSE) and inflammatory cytokine production and mitochondrial function assessed. The levels of IL-1β, IL-6, and TNFα were increased along with higher reactive oxygen species (ROS) and P-NFκB after CSE treatment in WT but not in MKK3-/- BMDMs. CSE treatment adversely affected basal mitochondrial respiration, ATP production, maximum respiratory capacity, and spare respiratory capacity in WT BMDMs only. Mitophagy, clearance of dysfunctional mitochondria, was up regulated in CS exposed WT mice lung tissue and CSE exposed WT BMDMs, respectively. The proteomic analysis of BMDMs by iTRAQ (isobaric tags for relative and absolute quantitation) showed up regulation of mitochondrial dysfunction associated proteins in WT and higher OXPHOS (Oxidative phosphorylation) and IL-10 signaling proteins in MKK3-/- BMDMs after CSE exposure, confirming the critical role of mitochondrial homeostasis. Interestingly, we found increased levels of p-MKK3 by immunohistochemistry in COPD patient lung tissues that could be responsible for insufficient mitophagy and disease progression. This study identifies MKK3 as a negative regulator of mitochondrial function and inflammatory responses to CS and suggests that MKK3 could be a therapeutic target.

Development of Vascular Biology over the past 10 Years: Heme Oxygenase-1 in Cardiovascular Homeostasis

The study of vascular biology has provided strong evidence for the role that free radical attack plays in the pathogenesis of cardiovascular diseases. The endothelial cell (EC) dysfunction that results from exposure to oxidative stresses, such as oxidized LDL, influences vascular cell gene expression, promoting smooth muscle cell (SMC) mitogenesis and apoptosis. These factors also play an important role in atherogenesis, which is attenuated by antioxidants. Thus, antioxidants are important to understanding the pathophysiology of cardiovascular diseases and to constructing an effective treatment strategy for these patients. Over the last decade, there has been a tremendous interest in the biology of heme oxygenase-1 (HO-1), which exhibits antioxidant effects in various forms of tissue injury. Moreover, the reaction is also the major source of carbon dioxide (CO) in the body, which is a physiologically important gaseous vasodilator that inhibits SMC proliferation. Thus, HO-1–derived products provide various mechanisms to maintain cardiovascular homeostasis. We review recent work on the cellular and molecular biological aspects of the HO/CO system in vascular pathophysiology.

Pretreatment with Rho-kinase inhibitor ameliorates lethal endotoxemia-induced liver injury by improving mitochondrial function

Rho kinase (ROCK) inhibition has been reported to improve various inflammatory diseases including endotoxemia. Mitochondrial dysfunction might be the key to the pathophysiology of sepsis-induced organ failure. Therefore, this study aimed to explore whether ROCK inhibition protects against the liver injury by regulating mitochondrial function in endotoxemia model mice. The mice were randomly divided into four groups (N=6-8 per group): control, LPS, LPS+Y-27632 (LPS+Y), and LPS+Mito-TEMPO (LPS+M). For induction of endotoxin-induced acute liver injury, the mice were intraperitoneally administered lipopolysaccharide (LPS, 20mg/kg). The ROCK inhibitor Y-27632 (or mitochondrial antioxidant Mito-TEMPO) was intraperitoneally administered at 18 and 1h before injection of LPS. The mice were euthanized 8h after LPS administration. The liver and blood samples were taken and preserved for analysis. Results of this study showed that pretreatment with Y-27632 or Mito-TEMPO significantly attenuated the liver injury as compared to the LPS group. This was confirmed by decreased plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, and by reduced hepatocellular apoptosis and histologic damage. Pretreatment with Y-27632 or Mito-TEMPO markedly reduced the LPS-induced inflammatory response and oxidative stress the in liver. Furthermore, it showed similar protective effects on the hepatic mitochondrial function, including an increased activity of complexes I and IV and mitochondrial superoxide dismutase (MnSOD), and an upregulated expression of mtDNA-encoded genes. Taken together, these data demonstrate that Mito-TEMPO can potently inhibit the endotoxin-induced mitochondrial and hepatic abnormalities and indicate that mitochondrial dysfunction might play a key role in the endotoxemia-induced acute liver injury. Moreover, our study shows that ROCK inhibition protects against the endotoxemia-induced liver injury by improving the mitochondrial function.

Protection of donor lung inflation in the setting of cold ischemia against ischemia-reperfusion injury with carbon monoxide, hydrogen, or both in rats

AIMS

Lung ischemia-reperfusion injury (IRI) may be attenuated through carbon monoxide (CO)'s anti-inflammatory effect or hydrogen (H2)'s anti-oxidant effect. In this study, the effects of lung inflation with CO, H2, or both during the cold ischemia phase on graft function were observed.

MATERIALS AND METHODS

Rat donor lungs, inflated with 40% oxygen (control group), 500ppm CO (CO group), 3% H2 (H2 group) or 500ppm CO+3% H2 (COH group), were kept at 4°C for 180min. After transplantation, the recipients' artery blood gas and pressure-volume (P-V) curves were analyzed. The inflammatory response, oxidative stress and apoptosis in the recipients were assessed at 180min after reperfusion.

KEY FINDINGS

Oxygenation in the CO and H2 groups were improved compared with the control group. The CO and H2 groups also exhibited significantly improved P-V curves, reduced lung injury, and decreased inflammatory response, malonaldehyde content, and cell apoptosis in the grafts. Furthermore, the COH group experienced enhanced improvements in oxygenation, P-V curves, inflammatory response, lipid peroxidation, and graft apoptosis compared to the CO and H2 groups.

SIGNIFICANCE

Lung inflation with CO or H2 protected against IRI via anti-inflammatory, anti-oxidant and anti-apoptotic mechanisms in a model of lung transplantation in rats, which was enhanced by combined treatment with CO and H2.

Targeting heme oxygenase-1 and carbon monoxide for therapeutic modulation of inflammation

The heme oxygenase-1 (HO-1) enzyme system remains an attractive therapeutic target for the treatment of inflammatory conditions. HO-1, a cellular stress protein, serves a vital metabolic function as the rate-limiting step in the degradation of heme to generate carbon monoxide (CO), iron, and biliverdin-IXα (BV), the latter which is converted to bilirubin-IXα (BR). HO-1 may function as a pleiotropic regulator of inflammatory signaling programs through the generation of its biologically active end products, namely CO, BV and BR. CO, when applied exogenously, can affect apoptotic, proliferative, and inflammatory cellular programs. Specifically, CO can modulate the production of proinflammatory or anti-inflammatory cytokines and mediators. HO-1 and CO may also have immunomodulatory effects with respect to regulating the functions of antigen-presenting cells, dendritic cells, and regulatory T cells. Therapeutic strategies to modulate HO-1 in disease include the application of natural-inducing compounds and gene therapy approaches for the targeted genetic overexpression or knockdown of HO-1. Several compounds have been used therapeutically to inhibit HO activity, including competitive inhibitors of the metalloporphyrin series or noncompetitive isoform-selective derivatives of imidazole-dioxolanes. The end products of HO activity, CO, BV and BR may be used therapeutically as pharmacologic treatments. CO may be applied by inhalation or through the use of CO-releasing molecules. This review will discuss HO-1 as a therapeutic target in diseases involving inflammation, including lung and vascular injury, sepsis, ischemia-reperfusion injury, and transplant rejection.

Controlled therapeutic gas delivery systems for quality-improved transplants

Therapeutic gases enriched into perfusion solutions have been effectively used for the improvement of organ transplant quality. At present, the enrichment of perfusion solutions with gases requires complex machinery/containers and handling precautions. Alternatively, the gas is generated within the perfusion solution by supplemented carbonylated transition metal complexes with associated toxicological concerns when these metals contact the transplant. Therefore, we developed therapeutic gas releasing systems (TGRSs) allowing for the controlled generation and release of therapeutic gases (carbon monoxide and hydrogen sulfide) from otherwise hermetically sealed containers, such that the perfusion solution for the transplant is saturated with the gas but no other components from the TGRS are liberated in the solution. The release from the TGRS into the perfusion solution can be tailored as a function of the number and thickness of gas permeable membranes leading to release patterns having been linked to therapeutic success in previous trials. Furthermore, the surrogate biomarker HMGB1 was significantly downregulated in ischemic rat liver transplants perfused with enriched CO solution as compared to control. In conclusion, the TGRS allows for easy, reliable, and controlled generation and release of therapeutic gases while removing safety concerns of current approaches, thereby positively impacting the risk benefit profile of using therapeutic gases for transplant quality improvement in the future.

The therapeutic potential of carbon monoxide for inflammatory bowel disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis and Crohn's disease, are chronic, relapsing and remitting inflammatory disorders of the intestinal tract. Because the precise pathogenesis of IBD remains unclear, it is important to investigate the pathogenesis of IBD and to evaluate new anti-inflammatory strategies. Recent accumulating evidence has suggested that carbon monoxide (CO) may act as an endogenous defensive gaseous molecule to reduce inflammation and tissue injury in various organ injury models, including intestinal inflammation. Furthermore, exogenous CO administration at low concentrations is protective against intestinal inflammation. These data suggest that CO may be a novel therapeutic molecule in patients with IBD. In this review, we present what is currently known regarding the therapeutic potential of CO in intestinal inflammation.

BMP9-Induced Survival Effect in Liver Tumor Cells Requires p38MAPK Activation

The study of bone morphogenetic proteins (BMPs) role in tumorigenic processes, and specifically in the liver, has gathered importance in the last few years. Previous studies have shown that BMP9 is overexpressed in about 40% of hepatocellular carcinoma (HCC) patients. In vitro data have also shown evidence that BMP9 has a pro-tumorigenic action, not only by inducing epithelial to mesenchymal transition (EMT) and migration, but also by promoting proliferation and survival in liver cancer cells. However, the precise mechanisms driving these effects have not yet been established. In the present work, we deepened our studies into the intracellular mechanisms implicated in the BMP9 proliferative and pro-survival effect on liver tumor cells. In HepG2 cells, BMP9 induces both Smad and non-Smad signaling cascades, specifically PI3K/AKT and p38MAPK. However, only the p38MAPK pathway contributes to the BMP9 growth-promoting effect on these cells. Using genetic and pharmacological approaches, we demonstrate that p38MAPK activation, although dispensable for the BMP9 proliferative activity, is required for the BMP9 protective effect on serum withdrawal-induced apoptosis. These findings contribute to a better understanding of the signaling pathways involved in the BMP9 pro-tumorigenic role in liver tumor cells.

Inflation with carbon monoxide in rat donor lung during cold ischemia phase ameliorates graft injury

Carbon monoxide (CO) attenuates lung ischemia reperfusion injury (IRI) via inhalation, and as an additive dissolved in flush/preservation solution. This study observed the effects of lung inflation with CO on lung graft function in the setting of cold ischemia. Donor lungs were inflated with 40% oxygen + 60% nitrogen (control group) or with 500 ppm CO + 40% oxygen + nitrogen (CO group) during the cold ischemia phase and were kept at 4℃ for 180 min. Recipients were sacrificed by exsanguinations at 180 min after reperfusion. Rats in the sham group had no transplantation and were performed as the recipients. Compared with the sham group, the oxygenation determined by blood gas analysis and the pressure-volume curves of the lung grafts decreased significantly, while the wet weight/dry weight (W/D) ratio, inflammatory reaction, oxidative stress, and cell apoptosis increased markedly (P < 0.05). However, compared to the control group, CO treatment improved the oxygenation (381 ± 58 vs. 308 ± 78 mm Hg) and the pressure-volume curves (15.8 ± 2.4 vs. 11.6 ± 1.7 mL/kg) (P < 0.05). The W/D ratio (4.6 ± 0.6) and the serum levels of interleukin-8 (279 ± 46 pg/mL) and tumor necrosis factor-α (377 ± 59 pg/mL) in the CO group decreased significantly compared to the control group (5.8 ± 0.8, 456 ± 63 pg/mL, and 520 ± 91 pg/mL) (P < 0.05). In addition, CO inflation also significantly decreased malondialdehyde activity and apoptotic cells in grafts, and increased the superoxide dismutase content. Briefly, CO inflation in donor lungs in the setting of cold ischemia attenuated lung IRI and improved the graft function compared with oxygen.

Carbon monoxide protects against hepatic ischemia/reperfusion injury by modulating the miR-34a/SIRT1 pathway

Hepatic ischemia/reperfusion (I/R) injury can arise as a complication of liver surgery and transplantation. Sirtuin 1 (SIRT1), an NAD+-dependent deacetylase, modulates inflammation and apoptosis in response to oxidative stress. SIRT1, which is regulated by p53 and microRNA-34a (miR-34a), can modulate non-alcoholic fatty liver disease, fibrosis and cirrhosis. Since carbon monoxide (CO) inhalation can protect against hepatic I/R, we hypothesized that CO could ameliorate hepatic I/R injury by regulating the miR-34a/SIRT1 pathway. Livers from mice pretreated with CO, or PFT, a p53 inhibitor, displayed reduced production of pro-inflammatory mediators, including TNF-α, iNOS, interleukin (IL)-6, and IL-1β after hepatic I/R injury. SIRT1 expression was increased by CO or PFT in the liver after I/R, whereas acetylated p65, p53 levels, and miR-34a expression were decreased. CO increased SIRT1 expression by inhibiting miR-34a. Both CO and PFT diminished pro-inflammatory cytokines production in vitro. Knockdown of SIRT1 in LPS-stimulated macrophages increased NF-κB acetylation, and increased pro-inflammatory cytokines. CO treatment reduced miR-34a expression and increased SIRT1 expression in oxidant-challenged hepatocytes; and rescued SIRT1 expression in p53-expressing or miR-34a transfected cells. In response to CO, enhanced SIRT1 expression mediated by miR-34a inhibition protects against liver damage through p65/p53 deacetylation, which may mediate inflammatory responses and hepatocellular apoptosis. The miR-34a/SIRT1 pathway may represent a therapeutic target for hepatic injury.

Carbon monoxide: a critical quantitative analysis and review of the extent and limitations of its second messenger function

Endogenously produced carbon monoxide (CO) is commonly believed to be a ubiquitous second messenger involved in a wide range of physiological and pathological responses. The major evidence supporting this concept is that CO is produced endogenously via heme oxygenase-catalyzed breakdown of heme and that experimental exposure to CO alters tissue function. However, it remains to be conclusively demonstrated that there are specific receptors for CO and that endogenous CO production is sufficient to alter tissue function. Unlike other signaling molecules, CO is not significantly metabolized, and it is removed from cells solely via rapid diffusion into blood, which serves as a near infinite sink. This non-metabolizable nature of CO renders the physiology of this gas uniquely susceptible to quantitative modeling. This review analyzes each of the steps involved in CO signaling: 1) the background CO partial pressure (PCO) and the blood and tissue CO binding; 2) the affinity of the putative CO receptors; 3) the rate of endogenous tissue CO production; and 4) the tissue PCO that results from the balance between this endogenous CO production and diffusion to the blood sink. Because existing data demonstrate that virtually all endogenous CO production results from the routine "housekeeping" turnover of heme, only a small fraction can play a signaling role. The novel aspect of the present report is to demonstrate via physiological modeling that this small fraction of CO production is seemingly insufficient to raise intracellular PCO to the levels required for the conventional, specific messenger receptor activation. It is concluded that the many physiological alterations observed with exogenous CO administration are probably produced by the non-specific CO inhibition of cytochrome C oxidase activity, with release of reactive oxygen species (ROS) and that this ROS signaling pathway is a potential effector mechanism for endogenously produced CO.

CO and CO-releasing molecules (CO-RMs) in acute gastrointestinal inflammation

Carbon monoxide (CO) is enzymatically generated in mammalian cells alongside the liberation of iron and the production of biliverdin and bilirubin. This occurs during the degradation of haem by haem oxygenase (HO) enzymes, a class of ubiquitous proteins consisting of constitutive and inducible isoforms. The constitutive HO2 is present in the gastrointestinal tract in neurons and interstitial cells of Cajal and CO released from these cells might contribute to intestinal inhibitory neurotransmission and/or to the control of intestinal smooth muscle cell membrane potential. On the other hand, increased expression of the inducible HO1 is now recognized as a beneficial response to oxidative stress and inflammation. Among the products of haem metabolism, CO appears to contribute primarily to the antioxidant and anti-inflammatory effects of the HO1 pathway explaining the studies conducted to exploit CO as a possible therapeutic agent. This article reviews the effects and, as far as known today, the mechanism(s) of action of CO administered either as CO gas or via CO-releasing molecules in acute gastrointestinal inflammation. We provide here a comprehensive overview on the effect of CO in experimental in vivo models of post-operative ileus, intestinal injury during sepsis and necrotizing enterocolitis. In addition, we will analyse the in vitro data obtained so far on the effect of CO on intestinal epithelial cell lines exposed to cytokines, considering the important role of the intestinal mucosa in the pathology of gastrointestinal inflammation.

Application of carbon monoxide for treatment of acute kidney injury

Acute kidney injury in critically ill patients is common and associated with a substantial increase in morbidity and mortality. Even with aggressive medical care and renal replacement therapy, acute kidney injury remains a significant health care concern. Recent published reports offer new strategies for the prevention and amelioration of acute kidney injury using carbon monoxide. Although considered a toxic environmental gas, carbon monoxide has recently aroused scientific and clinical interest, as its beneficial effects and mechanisms of action have been substantially defined in various in vitro and in vivo experiments. The exogenous application of carbon monoxide can confer cytoprotection by modulating intracellular signaling pathways through its anti-inflammatory, anti-apoptotic, vasodilative, antithrombotic and antiproliferative properties. Thus, evidence is accumulating to support the notion of carbon monoxide treatment for acute kidney disease. In this review, we focus on the extensively analyzed advantageous value of treatment with inhaled/soluble carbon monoxide in the context of kidney injury. Mechanisms such as signaling pathways, as well as an expanded view regarding toxicity and side-effects, are described broadly. In addition, we discuss the clinical applicability of carbon monoxide as a promising therapeutic strategy for the treatment of patients with acute kidney disease based on translating basic experimental findings into clinical application.

The multifunctional role and therapeutic potential of HO-1 in the vascular endothelium

SIGNIFICANCE

Heme oxygenases (HO-1 and HO-2) catalyze the degradation of the pro-oxidant heme into carbon monoxide (CO), iron, and biliverdin, which is subsequently converted to bilirubin. In the vasculature, particular interest has focused on antioxidant and anti-inflammatory properties of the inducible HO-1 isoform in the vascular endothelium. This review will present evidence that illustrates the potential therapeutic significance of HO-1 and its products, with special emphasis placed on their beneficial effects on the endothelium in vascular diseases.

RECENT ADVANCES

The understanding of the molecular basis for the regulation and functions of HO-1 has led to the identification of a variety of drugs that increase HO-1 activity in the vascular endothelium. Moreover, therapeutic delivery of HO-1 products CO, biliverdin, and bilirubin has been shown to have favorable effects, notably on endothelial cells and in animal models of vascular disease.

CRITICAL ISSUES

To date, mechanistic data identifying the downstream target genes utilized by HO-1 and its products to exert their actions remain relatively sparse. Likewise, studies in man to investigate the efficacy of therapeutics known to induce HO-1 or the consequences of the tissue-specific delivery of CO or biliverdin/bilirubin are rarely performed.

FUTURE DIRECTIONS

Based on the promising in vivo data from animal models, clinical trials to explore the safety and efficacy of the therapeutic induction of HO-1 and the delivery of its products should now be pursued further, targeting, for example, patients with severe atherosclerotic disease, ischemic limbs, restenosis injury, or at high risk of organ rejection.

Carbon monoxide potently prevents ischemia-induced high-mobility group box 1 translocation and release and protects against lethal renal ischemia-reperfusion injury

High-mobility group box 1 (HMGB1) is a chromatin-binding nuclear molecule that has potent proinflammatory effects once released by damaged cells. In some disease models, carbon monoxide (CO) exhibits anti-inflammatory and protective properties. Here, we investigated whether the protective effect of CO on renal ischemia-reperfusion injury is associated with the inhibition of HMGB1 translocation and release. A renal ischemia-reperfusion injury model was established with a 100% mortality rate in untreated mice. Pretreatment with the CO-releasing molecule-2 (CORM-2) resulted in 100% survival, maximal preservation of renal function, a marked reduction in pathological damage, and blunted upregulation of TLR4, RAGE, TNF-α, IL-1β, IL-6, and MCP1 mRNA. Interestingly, CORM-2 pretreatment almost completely inhibited ischemia-induced HMGB1 nucleocytoplasmic shuttling and release. This inhibition was associated with a decrease in nuclear histone acetyltransferase activity. Indeed, CORM-2 pretreatment inhibited the acetylation and release of HMGB1 during hypoxic culture of primary mouse renal tubular epithelia cells in vitro. Using the same renal ischemia-reperfusion injury model, neutralization of HMGB1 was protective, and administration of exogenous HMGB1 largely reversed the protective effect of CORM-2 on kidney ischemia-reperfusion injury. Thus, CORM-2-delivered CO protects against lethal renal ischemia-reperfusion injury. This protection is correlated with the prevention of HMGB1 nuclear-cytoplasmic translocation and release.

Circulating histones exacerbate inflammation in mice with acute liver failure

Circulating histones are a newly recognized mediator implicated in various inflammatory diseases. It is likely that the release of histones, from dying hepatocytes or inflammatory leukocytes, into the circulation initiates and amplifies inflammation during the course of acute liver failure (ALF). In this study, we investigated a putative pathogenic role of circulating histones in a murine model of ALF induced by D-galactosamine (GalN) plus lipopolysaccharide (LPS). Hepatic function and histological indexes, myeloperoxidase (MPO) activity, hepatocyte apoptosis and the levels of circulating histone were measured in GalN/LPS-treated mice. GalN/LPS caused severe liver damage and a notable increase in plasma concentration of circulating histones. To further assess the role of circulating histones in our model, we administered exogenous histones and anti-histone H4 antibody. Notably, exogenous histones aggravated GalN/LPS-induced hepatotoxicity, whereas anti-histone antibody significantly protected mice. Circulating histones may serve as both a functional marker of ALF activity and as an inflammatory mediator contributing to the progression of ALF. Blockade of circulating histones shows potent protective effects, suggesting a potential therapeutic strategy for ALF.

Carbon monoxide confers protection in sepsis by enhancing beclin 1-dependent autophagy and phagocytosis

AIMS

Sepsis, a systemic inflammatory response to infection, represents the leading cause of death in critically ill patients. However, the pathogenesis of sepsis remains incompletely understood. Carbon monoxide (CO), when administered at low physiologic doses, can modulate cell proliferation, apoptosis, and inflammation in pre-clinical tissue injury models, though its mechanism of action in sepsis remains unclear.

RESULTS

CO (250 ppm) inhalation increased the survival of C57BL/6J mice injured by cecal ligation and puncture (CLP) through the induction of autophagy, the down-regulation of pro-inflammatory cytokines, and by decreasing the levels of bacteria in blood and vital organs, such as the lung and liver. Mice deficient in the autophagic protein, Beclin 1 (Becn1(+/-)) were more susceptible to CLP-induced sepsis, and unresponsive to CO therapy, relative to their corresponding wild-type (Becn1(+/+)) littermate mice. In contrast, mice deficient in autophagic protein microtubule-associated protein-1 light chain 3B (LC3B) (Map1lc3b(-/-)) and their corresponding wild-type (Map1lc3b(+/+)) mice showed no differences in survival or response to CO, during CLP-induced sepsis. CO enhanced bacterial phagocytosis in Becn1(+/+) but not Becn1(+/-) mice in vivo and in corresponding cultured macrophages. CO also enhanced Beclin 1-dependent induction of macrophage protein signaling lymphocyte-activation molecule, a regulator of phagocytosis.

INNOVATION

Our findings demonstrate a novel protective effect of CO in sepsis, dependent on autophagy protein Beclin 1, in a murine model of CLP-induced polymicrobial sepsis.

CONCLUSION

CO increases the survival of mice injured by CLP through systemic enhancement of autophagy and phagocytosis. Taken together, we suggest that CO gas may represent a novel therapy for patients with sepsis.