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

Dexmedetomidine improves acute lung injury by activating autophagy in a rat hemorrhagic shock and resuscitation model

Dexmedetomidine (DEX) can reduce lung injury in a hemorrhagic shock (HS) resuscitation (HSR) model in rats by inhibiting inflammation. Here, we aimed to investigate if these effects of DEX are due to autophagy activation. Therefore, we established HSR rat models and divided them into four groups. HS was induced using a blood draw. The rats were then resuscitated by reinjecting the drawn blood and saline. The rats were sacrificed 24 h after resuscitation. Lung tissues were harvested for histopathological examination, determination of wet/dry lung weight ratio, and detection of the levels of autophagy-related marker proteins LC3, P62, Beclin-1, and the ATG12-ATG5 conjugate. The morphological findings of hematoxylin and eosin staining in lung tissues and the pulmonary wet/dry weight ratio showed that lung injury improved in HSR + DEX rats. However, chloroquine (CQ), an autophagy inhibitor, abolished this effect. Detecting the concentration of autophagy-related proteins showed that DEX administration increased LC3, ATG12-ATG5, and Beclin-1 expression and decreased P62 expression. The expression levels of these proteins were similar to those in the HSR group after CQ + DEX administration. In summary, DEX induced autophagic activation in an HSR model. These findings suggest that DEX administration partially ameliorates HSR-induced lung injury via autophagic activation.

Impaired Glucocorticoid Receptor Signaling Aggravates Lung Injury after Hemorrhagic Shock

We previously showed that attenuated lung injury after hemorrhagic shock (HS) coincided with enhanced levels of the glucocorticoid (GC) receptor (GR) in lung tissue of swine. Here, we investigated the effects of impaired GR signaling on the lung during resuscitated HS using a dysfunctional GR mouse model (GR^dim/dim). In a mouse intensive care unit, HS led to impaired lung mechanics and aggravated lung inflammation in GR^dim/dim mice compared to wildtype mice (GR^+/+). After HS, high levels of the pro-inflammatory and pro-apoptotic transcription factor STAT1/pSTAT1 were found in lung samples from GR^dim/dim mice. Lungs of GR^dim/dim mice revealed apoptosis, most likely as consequence of reduced expression of the lung-protective Angpt1 compared to GR^+/+ after HS. RNA-sequencing revealed increased expression of pro-apoptotic and cytokine-signaling associated genes in lung tissue of GR^dim/dim mice. Furthermore, high levels of pro-inflammatory cytokines and iNOS were found in lungs of GR^dim/dim mice. Our results indicate impaired repression of STAT1/pSTAT1 due to dysfunctional GR signaling in GR^dim/dim mice, which leads to increased inflammation and apoptosis in the lungs. These data highlight the crucial role of functional GR signaling to attenuate HS-induced lung damage.

Therapeutic Potential of Carbon Monoxide (CO) and Hydrogen Sulfide (H2S) in Hemolytic and Hemorrhagic Vascular Disorders-Interaction between the Heme Oxygenase and H2S-Producing Systems

Over the past decades, substantial work has established that hemoglobin oxidation and heme release play a pivotal role in hemolytic/hemorrhagic disorders. Recent reports have shown that oxidized hemoglobins, globin-derived peptides, and heme trigger diverse biological responses, such as toll-like receptor 4 activation with inflammatory response, reprogramming of cellular metabolism, differentiation, stress, and even death. Here, we discuss these cellular responses with particular focus on their mechanisms that are linked to the pathological consequences of hemorrhage and hemolysis. In recent years, endogenous gasotransmitters, such as carbon monoxide (CO) and hydrogen sulfide (H₂S), have gained a lot of interest in connection with various human pathologies. Thus, many CO and H₂S-releasing molecules have been developed and applied in various human disorders, including hemolytic and hemorrhagic diseases. Here, we discuss our current understanding of oxidized hemoglobin and heme-induced cell and tissue damage with particular focus on inflammation, cellular metabolism and differentiation, and endoplasmic reticulum stress in hemolytic/hemorrhagic human diseases, and the potential beneficial role of CO and H₂S in these pathologies. More detailed mechanistic insights into the complex pathology of hemolytic/hemorrhagic diseases through heme oxygenase-1/CO as well as H₂S pathways would reveal new therapeutic approaches that can be exploited for clinical benefit.

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.

The Molecular Mechanisms of Iron Metabolism and Its Role in Cardiac Dysfunction and Cardioprotection

Iron is an essential mineral participating in different functions of the organism under physiological conditions. Numerous biological processes, such as oxygen and lipid metabolism, protein production, cellular respiration, and DNA synthesis, require the presence of iron, and mitochondria play an important role in the processes of iron metabolism. In addition to its physiological role, iron may be also involved in the adaptive processes of myocardial "conditioning". On the other hand, disorders of iron metabolism are involved in the pathological mechanisms of the most common human diseases and include a wide range of them, such as type 2 diabetes, obesity, and non-alcoholic fatty liver disease, and accelerate the development of atherosclerosis. Furthermore, iron also exerts potentially deleterious effects that may be manifested under conditions of ischemia/reperfusion (I/R) injury, myocardial infarction, heart failure, coronary artery angioplasty, or heart transplantation, due to its involvement in reactive oxygen species (ROS) production. Moreover, iron has been recently described to participate in the mechanisms of iron-dependent cell death defined as "ferroptosis". Ferroptosis is a form of regulated cell death that is distinct from apoptosis, necroptosis, and other types of cell death. Ferroptosis has been shown to be associated with I/R injury and several other cardiac diseases as a significant form of cell death in cardiomyocytes. In this review, we will discuss the role of iron in cardiovascular diseases, especially in myocardial I/R injury, and protective mechanisms stimulated by different forms of "conditioning" with a special emphasis on the novel targets for cardioprotection.

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.

Carbon Monoxide Attenuates Lipopolysaccharides (LPS)-Induced Acute Lung Injury in Neonatal Rats via Downregulation of Cx43 to Reduce Necroptosis

Background

Acute lung injury (ALI) is one of major causes of death in newborns, making it urgent to improve therapy. Administration of low dose carbon monoxide (CO) plays a protective role in ALI but the mechanisms are not fully understood. This study was designed to test the therapeutic effect of monoxide-releasing molecule 3 (MORM3) in lipopolysaccharide (LPS) induced neonatal ALI and the possibly associated molecular mechanisms.

Material/Methods

For this study, 3- to 8-day old Newborn Sprague-Dawley rats were subjected to intraperitoneal injection of 3 mg/kg LPS to induce ALI. Then animals received intraperitoneal injection of carbon monoxide-releasing molecules 3 (CORM3) (8 mg/kg) or inactive CORM3 (iCORM3) for 7 consecutive days. Lung tissues were collected for histological examination and total cell counts and protein content in bronchoalveolar lavage fluid (BALF) were measured. Expression of Cx43 and necroptosis-related markers were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot.

Results

LPS exposure induced significant lung injury indicated by histological damage, increased lung wet/dry weight ratio (W/D) and increased total cell counts and protein concentration in BALF. These changes were significantly ameliorated by administration of CORM3 but not iCORM3. LPS also increased necroptosis-related markers RIP1, RIP3, and MLKL and their elevation was blocked by CORM3. CORM3 administration ameliorated LPS induced elevation of Cx43 expression and adenoviral overexpression of Cx43 abolished lung protective effect of CORM3. CORM3 administration attenuated LPS induced activation of extracellular-signal-regulated kinase (ERK) and its protection against necroptosis was abolished by ERK inhibitor U0126.

Conclusions

CORM3 attenuates LPS-Induced ALI in neonatal rats and its lung protective effect might be through downregulation of Cx43 to attenuate ERK signaling and ameliorate necroptosis, suggesting CORM3 as a potential therapeutic drug for ALI in neonates.