Carbon monoxide releasing molecule improves structural and functional cardiac recovery after myocardial injury

Carbon monoxide-releasing molecule-3 ameliorates traumatic brain injury-induced cardiac dysfunctions via inhibition of pyroptosis and apoptosis

Traumatic brain injury (TBI) frequently results in cardiac dysfunction and impacts the quality of survivors' life. It has been reported that carbon monoxide-releasing molecule-3 (CORM-3) administration immediately after hemorrhagic shock and resuscitation (HSR) ameliorated the HSR‑induced cardiac dysfunctions. The purpose of this study was to determine whether the application of CORM-3 on TBI exerted therapeutic effects against TBI-induced cardiac dysfunctions. Rats were randomly divided into four groups (n = 12) including Sham, TBI, TBI/CORM-3 and TBI/inactive CORM-3 (iCORM-3) groups. TBI was established by a weight-drop model. The rats in the TBI/CORM-3 group and TBI/iCORM-3 group were intravenously injected with CORM-3 and iCORM-3 (4 mg/kg) following TBI, respectively. The time of death in the rats that did not survive within 24 h was recorded. 24 h post-trauma, the cardiac function, pathological change, serum troponin T and creatine kinase-MB (CK-MB) levels, pyroptosis, apoptosis and expressions of TUNEL staining, Gasdermin D (GSDMD), IL-1β, IL-18, ratio Bax/Bcl-2 were assessed by echocardiography, hematoxylin-eosin staining, chemiluminescence, immunofluorescence, and western blot assays, respectively. TBI-treated rats exhibited dramatically decreased ejection fraction and aggravated myocardial injury, increased mortality rate, elevated levels of serum troponin T and CK-MB, promoted cardiac pyroptosis and apoptosis, and upregulated expressions of cleaved caspase-3, GSDMD N-terminal fragments, IL-1β, IL-18, and ratio of Bax/Bcl-2, whereas CORM-3 partially reversed these changes. CORM-3 ameliorated TBI-induced cardiac injury and dysfunction. This mechanism may be responsible for the inhibition of pyroptosis and apoptosis in cardiomyocyte.

Inhibitors of NLRP3 Inflammasome Formation: A Cardioprotective Role for the Gasotransmitters Carbon Monoxide, Nitric Oxide, and Hydrogen Sulphide in Acute Myocardial Infarction

Myocardial ischaemia reperfusion injury (IRI) occurring from acute coronary artery disease or cardiac surgical interventions such as bypass surgery can result in myocardial dysfunction, presenting as, myocardial "stunning", arrhythmias, infarction, and adverse cardiac remodelling, and may lead to both a systemic and a localised inflammatory response. This localised cardiac inflammatory response is regulated through the nucleotide-binding oligomerisation domain (NACHT), leucine-rich repeat (LRR)-containing protein family pyrin domain (PYD)-3 (NLRP3) inflammasome, a multimeric structure whose components are present within both cardiomyocytes and in cardiac fibroblasts. The NLRP3 inflammasome is activated via numerous danger signals produced by IRI and is central to the resultant innate immune response. Inhibition of this inherent inflammatory response has been shown to protect the myocardium and stop the occurrence of the systemic inflammatory response syndrome following the re-establishment of cardiac circulation. Therapies to prevent NLRP3 inflammasome formation in the clinic are currently lacking, and therefore, new pharmacotherapies are required. This review will highlight the role of the NLRP3 inflammasome within the myocardium during IRI and will examine the therapeutic value of inflammasome inhibition with particular attention to carbon monoxide, nitric oxide, and hydrogen sulphide as potential pharmacological inhibitors of NLRP3 inflammasome activation.

CORM-3 Inhibits the Inflammatory Response of Human Periodontal Ligament Fibroblasts Stimulated by LPS and High Glucose

Introduction

Diabetes has been recognized as an independent risk factor for periodontitis. Increasing evidences indicate that hyperglycemia aggravates inflammatory response of human periodontal ligament cells (hPDLCs). Carbon monoxide-releasing molecule-3 (CORM-3) is a water-soluble compound that can release carbon monoxide (CO) in a controllable manner. CORM-3 has been shown the anti-inflammatory effect in different cell lineages.

Methods

We stimulated periodontal ligament cells with LPS and high glucose. The expression of inflammatory cytokine was detected by ELISA. RT-qPCR, Western blot and immunofluorescence were used to detect the expression of TLR2, TLR4, RAGE and the activation of NF-κB pathway. We performed silencing and overexpression treatment of RAGE targeting the role of RAGE. We performed the immunostaining of paraffin sections of the periodontitis model in diabetes rats.

Results

The results showed that CORM-3 significantly inhibited the expression of inflammatory cytokine in hPDLCs stimulated with LPS and high glucose. CORM-3 also inhibited LPS and high glucose-induced expression of RAGE/NF-κB pathway and TLR2/TLR4/NF-κB pathway. Silence of RAGE resulted in significantly decreased expression of proteins above. Overexpression of RAGE significantly enhanced the expression of these factors. CORM-3 abrogated the effect of RAGE partially. In animal model, CORM-3 suppressed the inflammatory response of periodontal tissues in experimental periodontitis of diabetic rats.

Discussion

Our research proved CORM-3 reduced the inflammatory response via RAGE/NF-κB pathway and TLR2/TLR4/NF-κB pathway in the process of high glucose exacerbated periodontitis. These findings demonstrated the role of RAGE in the process of high glucose exacerbated periodontitis and suggested that CORM3 be a potential therapeutic strategy for the treatment of diabetes patients with periodontitis.

Deficiency of heme oxygenase 1a causes detrimental effects on cardiac function

Humans lacking heme oxygenase 1 (HMOX1) display growth retardation, haemolytic anaemia, and vulnerability to stress; however, cardiac function remains unclear. We aimed to explore the cardiac function of zebrafish lacking hmox1a at baseline and in response to stress. We generated zebrafish hmox1a mutants using CRISPR/Cas9 genome editing technology. Deletion of hmox1a increases cardiac output and further induces hypertrophy in adults. Adults lacking hmox1a develop myocardial interstitial fibrosis, restrain cardiomyocyte proliferation and downregulate renal haemoglobin and cardiac antioxidative genes. Larvae lacking hmox1a fail to respond to hypoxia, whereas adults are insensitive to isoproterenol stimulation in the heart, suggesting that hmox1a is necessary for cardiac response to stress. Haplodeficiency of hmox1a stimulates non-mitochondrial respiration and cardiac cell proliferation, increases cardiac output in larvae in response to hypoxia, and deteriorates cardiac function and structure in adults upon isoproterenol treatment. Intriguingly, haplodeficiency of hmox1a upregulates cardiac hmox1a and hmox1b in response to isoproterenol. Collectively, deletion of hmox1a results in cardiac remodelling and abrogates cardiac response to hypoxia and isoproterenol. Haplodeficiency of hmox1a aggravates cardiac response to the stress, which could be associated with the upregulation of hmox1a and hmox1b. Our data suggests that HMOX1 homeostasis is essential for maintaining cardiac function and promoting cardioprotective effects.

Tankyrase Inhibition Attenuates Cardiac Dilatation and Dysfunction in Ischemic Heart Failure

Hyperactive poly(ADP-ribose) polymerases (PARP) promote ischemic heart failure (IHF) after myocardial infarction (MI). However, the role of tankyrases (TNKSs), members of the PARP family, in pathogenesis of IHF remains unknown. We investigated the expression and activation of TNKSs in myocardium of IHF patients and MI rats. We explored the cardioprotective effect of TNKS inhibition in an isoproterenol-induced zebrafish HF model. In IHF patients, we observed elevated TNKS2 and DICER and concomitant upregulation of miR-34a-5p and miR-21-5p in non-infarcted myocardium. In a rat MI model, we found augmented TNKS2 and DICER in the border and infarct areas at the early stage of post-MI. We also observed consistently increased TNKS1 in the border and infarct areas and destabilized AXIN in the infarct area from 4 weeks onward, which in turn triggered Wnt/β-catenin signaling. In an isoproterenol-induced HF zebrafish model, inhibition of TNKS activity with XAV939, a TNKSs-specific inhibitor, protected against ventricular dilatation and cardiac dysfunction and abrogated overactivation of Wnt/β-catenin signaling and dysregulation of miR-34a-5p induced by isoproterenol. Our study unravels a potential role of TNKSs in the pathogenesis of IHF by regulating Wnt/β-catenin signaling and possibly modulating miRNAs and highlights the pharmacotherapeutic potential of TNKS inhibition for prevention of IHF.

Carbon Monoxide-Releasing Molecule-3 Enhances Osteogenic Differentiation of Rat Bone Marrow Mesenchymal Stem Cells via miR-195-5p/Wnt3a Pathway

Purpose

Bone marrow-derived mesenchymal stem cells (BMSCs) are hopeful in promoting bone regeneration as their pluripotency in differentiation. Our previous study showed that carbon monoxide-releasing molecule-3 (CORM-3) increased the osteogenic differentiation of rat BMSCs in vitro. However, the mechanism remained unclear. MicroRNAs (miRNAs) play a very important role in modulating the osteogenic differentiation of BMSCs. Therefore, we researched the miRNAs involved in CORM-3-stimulated osteogenic differentiation.

Methods

The CORM-3-stimulated osteogenic differentiation of rat BMSCs was further studied in vivo. Based on the gene sequencing experiment, the rat BMSCs were transfected with miR-195-5p mimics and inhibitor, pcDNA3.1-Wnt3a and Wnt3a siRNA. The osteogenic differentiation of rat BMSCs was measured by quantitative real-time polymerase chain reaction, Western blot and alizarin red staining. Additionally, the targeting relationship between miR-195-5p and Wnt3a was confirmed by the dual-luciferase assay.

Results

MiR-195-5p was down-expressed during the CORM-3-stimulated osteogenic differentiation of rat BMSCs. CORM-3-stimulated osteogenic differentiation of rat BMSCs was inhibited with miR-195-5p overexpression, evidenced by significantly reduced mRNA and protein expressions of runt-related transcription factor 2 and osteopontin, and matrix mineralization demonstrated. On the contrary, the osteogenic differentiation was enhanced with inhibition of miR-195-5p. CORM-3-stimulated osteogenic differentiation of rat BMSCs was increased by overexpression of Wnt3a, while the opposite was observed in the Wnt3a-deficient cells. Moreover, the decreased osteogenic differentiation capacity by increased expression of miR-195-5p was rescued by Wnt3a overexpression, showing miR-195-5p directly targeted Wnt3a.

Conclusion

These results demonstrate that CORM-3 promoted osteogenic differentiation of rat BMSCs via miR-195-5p/Wnt3a, which bodes well for the application of CORM-3 in the treatment of periodontal disease and other bone-defect diseases.

Homocysteine, Vitamins B6 and Folic Acid in Experimental Models of Myocardial Infarction and Heart Failure—How Strong Is That Link?

Cardiovascular diseases are the leading cause of death and the main cause of disability. In the last decade, homocysteine has been found to be a risk factor or a marker for cardiovascular diseases, including myocardial infarction (MI) and heart failure (HF). There are indications that vitamin B6 plays a significant role in the process of transsulfuration in homocysteine metabolism, specifically, in a part of the reaction in which homocysteine transfers a sulfhydryl group to serine to form α-ketobutyrate and cysteine. Therefore, an elevated homocysteine concentration (hyperhomocysteinemia) could be a consequence of vitamin B6 and/or folate deficiency. Hyperhomocysteinemia in turn could damage the endothelium and the blood vessel wall and induce worsening of atherosclerotic process, having a negative impact on the mechanisms underlying MI and HF, such as oxidative stress, inflammation, and altered function of gasotransmitters. Given the importance of the vitamin B6 in homocysteine metabolism, in this paper, we review its role in reducing oxidative stress and inflammation, influencing the functions of gasotransmitters, and improving vasodilatation and coronary flow in animal models of MI and HF.

Carbon Monoxide Releasing Molecule A1 Reduces Myocardial Damage After Acute Myocardial Infarction in a Porcine Model

ABSTRACT

Infarct size is a major determinant of outcomes after acute myocardial infarction (AMI). Carbon monoxide-releasing molecules (CORMs), which deliver nanomolar concentrations of carbon monoxide to tissues, have been shown to reduce infarct size in rodents. We evaluated efficacy and safety of CORM-A1 to reduce infarct size in a clinically relevant porcine model of AMI. We induced AMI in Yorkshire White pigs by inflating a coronary angioplasty balloon to completely occlude the left anterior descending artery for 60 minutes, followed by deflation of the balloon to mimic reperfusion. Fifteen minutes after balloon occlusion, animals were given an infusion of 4.27 mM CORM-A1 (n = 7) or sodium borate control (n = 6) over 60 minutes. Infarct size, cardiac biomarkers, ejection fraction, and hepatic and renal function were compared amongst the groups. Immunohistochemical analyses were performed to compare inflammation, cell proliferation, and apoptosis between the groups. CORM-A1-treated animals had significant reduction in absolute infarct area (158 ± 16 vs. 510 ± 91 mm2, P < 0.001) and infarct area corrected for area at risk (24.8% ± 2.6% vs. 45.2% ± 4.0%, P < 0.0001). Biochemical markers of myocardial injury also tended to be lower and left ventricular function tended to recover better in the CORM-A1 treated group. There was no evidence of hepatic or renal toxicity with the doses used. The cardioprotective effects of CORM-A1 were associated with a significant reduction in cell proliferation and inflammation. CORM-A1 reduces infarct size and improves left ventricular remodeling and function in a porcine model of reperfused MI by a reduction in inflammation. These potential cardioprotective effects of CORMs warrant further translational investigations.

The effects of carbon monoxide releasing molecules on paraquat-induced pulmonary interstitial inflammation and fibrosis

Paraquat, an herbicide used extensively worldwide, can cause severe toxicity in humans and animals, leading to irreversible, lethal lung fibrosis. The potential of CO-releasing molecules (CORMs), substances that release CO (Carbon monoxide) within animal tissues, for treating paraquat-induced ROS generation and inflammation is investigated here. Our results show that the fast CO releaser CORM-3 (4-20 μM) acts as a potential scavenger of free radicals and decreases fibrosis progression by inhibiting paraquat-induced overexpression of connective tissue growth factor and angiotensin II in MRC-5 cells. The slow CO releaser CORM-A1 (5 mg/kg) clearly decreased expression of the lung profibrogenic cytokines COX-2, TNF-α, and α-SMA and serum hydroxyproline, resulting in a lower mortality rate in paraquat-treated mice. Mice treated with higher-dose CORM-A1 (10 mg/kg) had relatively intact lung lobes and fewer fibrotic patches by gross observation, with less collagen deposition, mesangial matrix accumulation, and pulmonary fibrosis resulting from the mitigation of TGF-β overexpression. In conclusion, our data demonstrate for the first time that CORM-A1 alleviated the development of the fibrotic process and improved survival rate in mice exposed to PQ, would be an attractive therapeutic approach to attenuate the progression of pulmonary fibrosis following PQ exposure.

Endogenous Carbon Monoxide Signaling Modulates Mitochondrial Function and Intracellular Glucose Utilization: Impact of the Heme Oxygenase Substrate Hemin

Stress-inducible heme oxygenase-1 (HO-1) catalyzes the oxidative cleavage of heme yielding biliverdin, ferrous iron, and carbon monoxide (CO). Heme oxygenase activity has been attributed to antioxidant defense via the redox cycling system of biliverdin and bilirubin. There is increasing evidence that CO is a gaseous signaling molecule and plays a role in the regulation of energy metabolism. Inhibitory effects of CO on the respiratory chain are well established, but the implication of such a process on the cellular stress response is not well understood. By means of extracellular flux analyses and isotopic tracing, we studied the effects of CO, either released from the CO donor CORM-401 or endogenously produced by heme oxygenases, on the respiratory chain and glucose metabolism. CORM-401 was thereby used as a tool to mimic endogenous CO production by heme oxygenases. In the long term (>60 min), CORM-401-derived CO exposure inhibited mitochondrial respiration, which was compensated by increased glycolysis accompanied by a loss of the ATP production rate and an increase in proton leakage. This effect pattern was likewise observed after endogenous CO production by heme oxygenases. However, in the present setting, these effects were only observed when sufficient substrate for heme oxygenases (hemin) was provided. Modulation of the HO-1 protein level was less important. The long-term influence of CO on glucose metabolism via glycolysis was preceded by a short-term response (<30 min) of the cells to CO. Stable isotope-labeling experiments and metabolic flux analysis revealed a short-term shift of glucose consumption from glycolysis to the pentose phosphate pathway (PPP) along with an increase in reactive oxygen species (ROS) generation. Overall, we suggest that signaling by endogenous CO stimulates the rapid formation of reduction equivalents (NADPH) via the PPP, and plays an additional role in antioxidant defense, e.g., via feed-forward stimulation of the bilirubin/biliverdin redox cycling system.

Carbon Monoxide Inhibits the Expression of Proteins Associated with Intestinal Mucosal Pyroptosis in a Rat Model of Sepsis Induced by Cecal Ligation and Puncture

BACKGROUND Carbon monoxide (CO) has anti-inflammatory effects and protects the intestinal mucosal barrier in sepsis. Pyroptosis, or cell death associated with sepsis, is mediated by caspase-1 activation. This study aimed to investigate the role of CO on the expression of proteins associated with intestinal mucosal pyroptosis in a rat model of sepsis induced by cecal ligation and puncture (CLP). MATERIAL AND METHODS The rat model of sepsis was developed using CLP. Male Sprague-Dawley rats (n=120) were divided into six study groups: the sham group (n=20); the CLP group (n=20); the hemin group (treated with ferric chloride and heme) (n=20); the zinc protoporphyrin IX (ZnPPIX) group (n=20); the CO-releasing molecule 2 (CORM-2) group (n=20); and the inactive CORM-2 (iCORM-2) group (n=20). Hemin and CORM-2 were CO donors, and ZnPPIX was a CO inhibitor. In the six groups, the seven-day survival curves, the fluorescein isothiocyanate (FITC)-labeled dextran 4000 Da (FD-4) permeability assay, levels of intestinal pyroptosis proteins caspase-1, caspase-11, and gasdermin D (GSDMD) were measured by confocal fluorescence microscopy. Proinflammatory cytokines interleukin (IL)-18, IL-1ß, and high mobility group box protein 1 (HMGB1) were measured by Western blot and enzyme-linked immunosorbent assay (ELISA). RESULTS CO reduced the mortality rate in rats with sepsis and reduced intestinal mucosal permeability and mucosal damage. CO also reduced the expression levels of IL-18, IL-1ß, and HMGB1, and reduced pyroptosis by preventing the cleavage of caspase-1 and caspase-11. CONCLUSIONS In a rat model of sepsis induced by CLP, CO had a protective role by inhibiting intestinal mucosal pyroptosis.

CO ameliorates endothelial senescence induced by 5-fluorouracil through SIRT1 activation

Endothelial senescence is the main risk factor that contributes to vascular dysfunction and the progression of vascular disease. Carbon monoxide (CO) plays an important role in preventing vascular dysfunction and in maintaining vascular physiology or homeostasis. The application of exogenous CO has been shown to confer protection in several models of cardiovascular injury or disease, including hypertension, atherosclerosis, balloon-catheter injury, and graft rejection. However, the mechanism by which CO prevents endothelial senescence has been largely unexplored. The aim of this study was to evaluate the effects of CO on endothelial senescence and to investigate the possible mechanisms underlying this process. We measured the levels of senescence-associated-β-galactosidase activity, senescence-associated secretory phenotype, reactive oxygen species (ROS) production, and stress granule in human umbilical vein endothelial cells and the WI-38 human diploid fibroblast cell line. We found that 5-fluorouracil (5FU)-induced ROS generation was inhibited by CO-releasing molecules (CORM)-A1 treatment, and endothelial senescence induced by 5FU was attenuated by CORM-A1 treatment. The SIRT1 inhibitor EX527 reversed the inhibitory effect of CO on the 5FU-induced endothelial senescence. Furthermore, SIRT1 deficiency abolished the stress granule formation by CO. Our results suggest that CO alleviates the endothelial senescence induced by 5FU through SIRT1 activation and may hence have therapeutic potential for the treatment of vascular diseases.

Heme, Heme Oxygenase, and Endoplasmic Reticulum Stress-A New Insight into the Pathophysiology of Vascular Diseases

The prevalence of vascular disorders continues to rise worldwide. Parallel with that, new pathophysiological pathways have been discovered, providing possible remedies for prevention and therapy in vascular diseases. Growing evidence suggests that endoplasmic reticulum (ER) stress is involved in a number of vasculopathies, including atherosclerosis, vascular brain events, and diabetes. Heme, which is released from hemoglobin or other heme proteins, triggers various pathophysiological consequence, including heme stress as well as ER stress. The potentially toxic free heme is converted by heme oxygenases (HOs) into carbon monoxide (CO), iron, and biliverdin (BV), the latter of which is reduced to bilirubin (BR). Redox-active iron is oxidized and stored by ferritin, an iron sequestering protein which exhibits ferroxidase activity. In recent years, CO, BV, and BR have been shown to control cellular processes such as inflammation, apoptosis, and antioxidant defense. This review covers our current knowledge about how heme induced endoplasmic reticulum stress (HIERS) participates in the pathogenesis of vascular disorders and highlights recent discoveries in the molecular mechanisms of HO-mediated cytoprotection in heme stress and ER stress, as well as crosstalk between ER stress and HO-1. Furthermore, we focus on the translational potential of HIERS and heme oxygenase-1 (HO-1) in atherosclerosis, diabetes mellitus, and brain hemorrhage.

[Treatment of carbon monoxide poisoning in Germany : A retrospective single center analysis]

BACKGROUND

The symptoms of acute carbon monoxide (CO) poisoning are unspecific, ranging from headaches to unconsciousness and death. In addition to acute symptoms, delayed severe neurological sequelae may occur. While a total of 440 deaths by CO poisoning were registered in Germany in 1999, a total of 594 patients died (0.73 per 100,000 inhabitants) in 2014 and in 2015 the number even increased to 648 deaths. A national database on clinical symptoms, course of illness or quality of care concerning CO poisoning does not yet exist.

METHODS

The treatment data of patients admitted to the Hyperbaric Emergency Centre Wiesbaden (HEC) from 2013 to 2017 with CO poisoning formed the basis of the study. This was a comparative evaluation of patient demographics, poisoning sources, symptom spectrum, course of treatment and time intervals registered on the preclinical and clinical levels.

RESULTS

From 2013 to 2017 a total of 476 patients (282 men and 194 women) with an average non-invasively measured CO-Hb of 15% (Q_0.25 = 7.6%, Q_0.75 = 22.3%) were treated with hyperbaric oxygen. Heaters (n = 131), charcoal barbecues (n = 93), fires (n = 90), hookahs (n = 78) and combustion engines (n = 37) were the most frequent CO sources identified. Headaches, vertigo, nausea and syncope were the most prevalent symptoms. A median of 91 min (Q_0.25 = 53 min; Q_0.75 = 147 min) passed between first medical contact and BGA-validated diagnosis. In total, 151 patients were transferred directly to the HEC, whereas 325 patients were secondarily transferred. The delay in this subgroup took 183 min (median Q_0.25 = 138 min; Q_0.75 = 248 min). After receiving the first hyperbaric treatment, 80% were free of symptoms. Remaining symptoms included headache (10%), fatigue (8%), vertigo (5%) and nausea (3%) and 45 patients terminated further treatment. Of the patients 417 received a second hyperbaric treatment and 370 patients were treated 3 times. After the third treatment, 89% were free of symptoms and 5% still reported headaches, 3% vertigo and 2% fatigue. In total, 6 patients died and 430 patients were symptom-free after treatment.

CONCLUSION

Commonly known sources (fire, charcoal grills) aside, many poisonings by smoking a hookah were observed. This study highlights the importance of considering CO poisoning as a differential diagnosis when encountering patients, especially of younger age, with non-specific neurological symptoms, as well as the importance of early initiation of treatment. A direct correlation between CO-Hb values (whether measured noninvasively or by invasive BGA) and the initial symptoms could not be demonstrated. In total, substantial time expired between the diagnosis and start of treatment of patients transported to a primary care hospital compared to those transported directly to the HEC. Although analysis showed adequate treatment with oxygen in the preclinical interval, administration of oxygen during primary hospital stay showed room for improvement. Introducing a national CO poisoning register and uniform treatment guidelines could improve in-house clinical processes. Multicenter studies are needed to close the gaps identified in the quality of care in Germany.

Modulation of the monocyte/macrophage system in heart failure by targeting heme oxygenase-1

Upon myocardial infarction (MI) immune system becomes activated by extensive necrosis of cardiomyocytes releasing intracellular molecules called damage-associated molecular patterns. Overactive and prolonged immune responses are likely to be responsible for heart failure development and progression in patients surviving the ischemic episode. Heme oxygenase-1 (HO-1) plays a crucial role in heme degradation and in this way releases carbon monoxide, free iron, and biliverdin. This stress-inducible enzyme is induced by various oxidative and inflammatory signals. Consequently, biological actions of HO-1 are not limited to degradation of a toxic heme released from hemoproteins, but also provide an adaptive cellular response against chronic inflammation and oxidative injury. Indeed, the immunomodulatory and anti-inflammatory properties of HO-1 were demonstrated in several experimental studies, as well as in human cases of genetic HO-1 deficiency. HO-1 was shown to suppress the production, myocardial infiltration and inflammatory properties of monocytes and macrophages what resulted in limitation of post-MI cardiac damage. This review specifically addresses the role of HO-1, heme and its degradation products in macrophage biology and post-ischemic cardiac repair. A more complete understanding of these mechanisms is essential to develop new therapeutic approaches.

An Overview of the Potential Therapeutic Applications of CO-Releasing Molecules

Carbon monoxide (CO) has long been known as the “silent killer” owing to its ability to form carboxyhemoglobin—the main cause of CO poisoning in humans. Its role as an endogenous neurotransmitter, however, was suggested in the early 1990s. Since then, the biological activity of CO has been widely examined via both the direct administration of CO and in the form of so-called “carbon monoxide releasing molecules (CORMs).” This overview will explore the general physiological effects and potential therapeutic applications of CO when delivered in the form of CORMs.