Antithrombotic properties of water-soluble carbon monoxide-releasing molecules

Plight of CORMs: The unreliability of four commercially available CO-releasing molecules, CORM-2, CORM-3, CORM-A1, and CORM-401, in studying CO biology

Carbon monoxide (CO) is an endogenously produced gaseous signaling molecule with demonstrated pharmacological effects. In studying CO biology, three delivery forms have been used: CO gas, CO in solution, and CO donors of various types. Among the CO donors, four carbonyl complexes with either a transition metal ion or borane (BH3) (termed CO-releasing molecules or CORMs) have played the most prominent roles appearing in over 650 publications. These are CORM-2, CORM-3, CORM-A1, and CORM-401. Intriguingly, there have been unique biology findings that were only observed with these CORMs, but not CO gas; yet these properties were often attributed to CO, raising puzzling questions as to why CO source would make such a fundamental difference in terms of CO biology. Recent years have seen a large number of reports of chemical reactivity (e.g., catalase-like activity, reaction with thiol, and reduction of NAD(P)+) and demonstrated CO-independent biological activity for these four CORMs. Further, CORM-A1 releases CO in an idiosyncratic fashion; CO release from CORM-401 is strongly influenced or even dependent on reaction with an oxidant and/or a nucleophile; CORM-2 mostly releases CO2, not CO, after a water-gas shift reaction except in the presence of a strong nucleophile; and CORM-3 does not release CO except in the presence of a strong nucleophile. All these beg the question as to what constitutes an appropriate CO donor for studying CO biology. This review critically summarizes literature findings related to these aspects, with the aim of helping result interpretation when using these CORMs and development of essential criteria for an appropriate donor for studying CO biology.

High Heme and Low Heme Oxygenase-1 Are Associated with Mast Cell Activation/Degranulation in HIV-Induced Chronic Widespread Pain

An overwhelming number of people with HIV (PWH) experience chronic widespread pain (CWP) throughout their lifetimes. Previously, we demonstrated that PWH with CWP have increased hemolysis and attenuated heme oxygenase 1 (HO-1) levels. HO-1 degrades reactive, cell-free heme into antioxidants like biliverdin and carbon monoxide (CO). We found that high heme or low HO-1 caused hyperalgesia in animals, likely through multiple mechanisms. In this study, we hypothesized that high heme or low HO-1 caused mast cell activation/degranulation, resulting in the release of pain mediators like histamine and bradykinin. PWH who self-report CWP were recruited from the University of Alabama at Birmingham HIV clinic. Animal models included HO-1-/- mice and hemolytic mice, where C57BL/6 mice were injected intraperitoneally with phenylhydrazine hydrochloride (PHZ). Results demonstrated that plasma histamine and bradykinin were elevated in PWH with CWP. These pain mediators were also high in HO-1-/- mice and in hemolytic mice. Both in vivo and in vitro (RBL-2H3 mast cells), heme-induced mast cell degranulation was inhibited by treatment with CORM-A1, a CO donor. CORM-A1 also attenuated mechanical and thermal (cold) allodynia in hemolytic mice. Together, the data suggest that mast cell activation secondary to high heme or low HO-1 seen in cells and animals correlates with elevated plasma levels of heme, histamine, and bradykinin in PWH with CWP.

Emerging role of carbon monoxide in intestinal transplantation

Intestinal transplantation has become an established therapeutic option that provides improved quality of life to patients with end-stage intestinal failure when total parenteral nutrition fails. Whereas this challenging life-saving intervention has shown exceptional growth over the past decade, illustrating the evolution of this complex and technical procedure from its preclinical origin in the mid-20th century to become a routine clinical practice today with several recent innovations, its success is hampered by multiple hurdles including technical challenges such as surgical manipulation during intestinal graft procurement, graft preservation and reperfusion damage, resulting in poor graft quality, graft rejection, post-operative infectious complications, and ultimately negatively impacting long-term recipient survival. Therefore, strategies to improve current intestinal transplantation protocol may have a significant impact on post-transplant outcomes. Carbon monoxide (CO), previously considered solely as a toxic gas, has recently been shown to be a physiological signaling molecule at low physiological concentrations with therapeutic potentials that could overcome some of the challenges in intestinal transplantation. This review discusses recent knowledge about CO in intestinal transplantation, the underlying molecular mechanisms of protection during intestinal graft procurement, preservation, transplantation and post-transplant periods. A section of the review also discusses clinical translation of CO and its challenges in the field of solid organ transplantation.

Distinct Pharmacological Properties of Gaseous CO and CO-Releasing Molecule in Human Platelets

Carbon monoxide (CO)—gaseous or released by CO-RMs—both possess antiplatelet properties; however, it remains uncertain whether the mechanisms involved are the same. Here, we characterise the involvement of soluble guanylate cyclase (sGC) in the effects of CO—delivered by gaseous CO–saturated buffer (CO_G) and generated by CORM-A1—on platelet aggregation and energy metabolism, as well as on vasodilatation in aorta, using light transmission aggregometry, Seahorse XFe technique, and wire myography, respectively. ODQ completely prevented the inhibitory effect of CO_G on platelet aggregation, but did not modify antiplatelet effect of CORM-A1. In turn, CO_G did not affect, whereas CORM-A1 substantially inhibited energy metabolism in platelets. Even though activation of sGC by BAY 41-2272 or BAY 58-2667 inhibited significantly platelet aggregation, their effects on energy metabolism in platelets were absent or weak and could not contribute to antiplatelet effects of sGC activation. In contrast, vasodilatation of murine aortic rings, induced either by CO_G or CORM-A1, was dependent on sGC. We conclude that the source (CO_G vs. CORM-A1) and kinetics (rapid vs. slow) of CO delivery represent key determinants of the mechanism of antiplatelet action of CO, involving either impairment of energy metabolism or activation of sGG.

Antiplatelet Effect of Carbon Monoxide Is Mediated by NAD+ and ATP Depletion

Supplemental Digital Content is available in the text.

Objectives:

Carbon monoxide (CO) produced by haem oxygenases or released by CO-releasing molecules (CORM) affords antiplatelet effects, but the mechanism involved has not been defined. Here, we tested the hypothesis that CO–induced inhibition of human platelet aggregation is mediated by modulation of platelet bioenergetics.

Approach and Results:

To analyze the effects of CORM-A1 on human platelet aggregation and bioenergetics, a light transmission aggregometry, Seahorse XFe technique and liquid chromatography tandem-mass spectrometry–based metabolomics were used. CORM-A1–induced inhibition of platelet aggregation was accompanied by the inhibition of mitochondrial respiration and glycolysis. Interestingly, specific inhibitors of these processes applied individually, in contrast to combined treatment, did not inhibit platelet aggregation considerably. A CORM-A1–induced delay of tricarboxylic acid cycle was associated with oxidized nicotinamide adenine dinucleotide (NAD⁺) depletion, compatible with the inhibition of oxidative phosphorylation. CORM-A1 provoked an increase in concentrations of proximal (before GAPDH [glyceraldehyde 3-phosphate dehydrogenase]), but not distal glycolysis metabolites, suggesting that CO delayed glycolysis at the level of NAD⁺–dependent GAPDH; however, GAPDH activity was directly not inhibited. In the presence of exogenous pyruvate, CORM-A1–induced inhibition of platelet aggregation and glycolysis were lost, but were restored by the inhibition of lactate dehydrogenase, involved in cytosolic NAD⁺ regeneration, pointing out to the key role of NAD⁺ depletion in the inhibition of platelet bioenergetics by CORM-A1.

Conclusions:

The antiplatelet effect of CO is mediated by inhibition of mitochondrial respiration—attributed to the inhibition of cytochrome c oxidase, and inhibition of glycolysis—ascribed to cytosolic NAD⁺ depletion.

Carbon monoxide and its donors - Chemical and biological properties

Carbon monoxide (CO) is an inorganic chemical compound that can bind with hemoglobin with highly toxic effects. In living organisms, it is produced endogenously during the degradation of heme by oxygenase, which occurs in three isoforms: HO-1, HO-2 and HO-3. CO can play an important role in the regulation of many physiological functions. Carbon Oxide Releasing Molecules (CORMs) are a novel group of chemical compounds capable of controlled CO release directly in tissues or organs. This release depends on concentration, pH, solvent type and temperature. The biological role and the therapeutic potential of different CORMs is not always well demonstrated. However, this mini review summarizes the various function of these compounds.

A comparison of multifunctional donors of carbon monoxide: Their anticoagulant, antioxidant, anti-aggregatory and cytotoxicity activities in an in vitro model

The study examines the effect of two water-soluble carbon monoxide (CO) donors, CORM-3 and CORM-A1, on selected parameters of oxidative stress and hemostasis in human plasma and blood platelets in vitro. It also compares their activity with that of the lipid-soluble CORM-2. The oxidation of amino acid residues in plasma proteins was evaluated by measuring the amounts of thiol and carbonyl groups. Plasma lipid peroxidation was measured as thiobarbituric acid reactive substance (TBARS) concentration. In addition, three haemostatic parameters of plasma were studied, viz. activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT), and one haemostatic parameter of platelets (platelet aggregation). Treatment with CORM-3 and CORM-A1 (all concentrations from 0.1 to 100 μM) decreased thiol group oxidation induced by H₂O₂/Fe. Incubation with CORM-3 and CORM-A1 also influenced plasma coagulation activity, e.g. CORM-3 and CORM-A1 significantly prolonged TT at the two highest tested concentrations (50 and 100 μM). Only CORM-2 at the highest tested concentration (100 μM) and CORM-3 (50 and 100 μM) reduced platelet aggregation induced by ADP. None of the tested CORMs caused platelet damage. The treatment of various diseases associated with oxidative stress, including cardiovascular diseases, may be enhanced by the administration of CO donors CORM-2 and CORM-3, these being modulators of oxidative stress and hemostasis.

Carbon monoxide in intensive care medicine-time to start the therapeutic application?!

Carbon monoxide (CO) is not only known as a toxic gas due to its characteristics as an odorless molecule and its rapid binding to haem-containing molecules, thus inhibiting the respiratory chain in cells resulting in hypoxia. For decades, scientists established evidence about its endogenously production in the breakdown of haem via haem-oxygenase (HO-1) and its physiological effects. Among these, the modulation of various systems inside the body are well described (e.g., anti-inflammatory, anti-oxidative, anti-apoptotic, and anti-proliferative). Carbon monoxide is able to modulate several extra- and intra-cellular signaling molecules leading to differentiated response according to the specific stimulus. With our growing understanding in the way CO exerts its effects, especially in the mitochondria and its intracellular pathways, it is tempting to speculate about a clinical application of this substance. Since HO-1 is not easy to induce, research focused on the application of the gaseous molecule CO by itself or the implementation of carbon monoxide releasing molecules (CO-RM) to deliver the molecule at a time- and dose dependently safe way to any target organ. After years of research in cellular systems and animal models, summing up data about safety issues as well as possible target to treat in various diseases, the first feasibility trials in humans were established. Up-to-date, safety issues have been cleared for low-dose carbon monoxide inhalation (up to 500 ppm), while there is no clinical data regarding the injection or intake of any kind of CO-RM so far. Current models of human research include sepsis, acute lung injury, and acute respiratory distress syndrome as well as acute kidney injury. Carbon monoxide is a most promising candidate in terms of a therapeutic agent to improve outbalanced organ conditions. In this paper, we summarized the current understanding of carbon monoxide’s biology and its possible organ targets to treating the critically ill patients in tomorrow’s ICU.

Effect of quinolinic acid - A uremic toxin from tryptophan metabolism - On hemostatic profile in rat and mouse thrombosis models

PURPOSE

We aimed to determine the effect of quinolinic acid (QA) on hemostasis in rat and mouse models of thrombosis.

MATERIAL AND METHODS

Wistar rats (male, n = 72) received QA dissolved in drinking water in doses of 3, 10, 30 mg/kg or pure drinking water (vehicle control group -VEH) for 14 days. On the 14^th day of the experiment the effect of QA on hemostasis was evaluated using electrically induced arterial thrombosis model. The following parameters were measured: thrombus weight, hematology, thromboelastometric (ROTEM) parameters, TXA₂ and 6-keto-PGF_1α concentration, coagulation and fibrinolytic markers activity and concentration. GFP mice (male, n = 30) were assigned to the group receiving QA (30 mg/kg) or VEH for 14 days and to the group receiving: single intravenous dose of QA (30 mg/kg) or VEH or the same dose of QA and anti-CD31 (platelet endothelial cell adhesion molecule-1, PECAM-1) antibody conjugated with Alexa Fluor 647. The effect of QA on hemostasis was evaluated in the model of laser-induced injury of mesentery vein using intravital confocal microscopy.

RESULTS

Administering QA for 14 days resulted in a divergent, depending on dose, increase in concentration of active form of tPA and PAI-1 and concentration of total PAI-1 and PAP complexes in rats' plasma. In turn, administering QA for 14 days in mice revealed its prothrombotic activity, while single-dose IV administration revealed its antithrombotic activity, through the up-regulation of PECAM-1 expression.

CONCLUSIONS

We demonstrated the first evidence for the opposite biological effects of QA on hemostasis in rat and mouse thrombosis models.

Carbon monoxide releasing molecule enhances coagulation and decreases fibrinolysis in canine plasma exposed to Crotalus viridis venom in vitro and in vivo

Carbon monoxide releasing molecule-2 (CORM-2), an emerging therapeutic in human medicine, enhances plasmatic coagulation and attenuates fibrinolysis in vitro in human, rabbit and horse plasma and ameliorates hypocoagulation and hyperfibrinolysis secondary to venom exposure in human plasma in vitro. Fibrinogenases in rattlesnake venom cause decreased clot strength, and in the presence of tissue plasminogen activator (tPA) in vitro, a markedly increased rate of clot lysis. CO interacts with a haem group on fibrinogen, changing its configuration so that the fibrin clot is strengthened and more resistant to fibrinolysis. We hypothesized that CORM-2 enhances coagulation and attenuates fibrinolysis in canine plasma exposed to C viridis venom. We measured the effects of C viridis venom on clot strength, rates of coagulation and fibrinolysis in both pooled canine plasma and plasma from individual naturally envenomed dogs, with and without CORM-2, using thromboelastography (TEG). We tested venom effects on coagulation using tissue factor (TF) activated TEG and on both coagulation and fibrinolysis using TF-activated TEG with added tPA. We found that 17.9 µg/mL of venom causes a mean 26.4% decrease in clot strength, a 61.8% decrease in maximum rate of thrombus generation, 75% faster clot lysis, a 226% increase in maximum rate of lysis and a 92% decrease in total clot life span (CLS). CORM-2 ameliorated these effects, increasing CLS in the presence of venom by 603%. Additionally, we showed that CORM-2 has similar effects in vitro on plasma from naturally envenomed dogs, showing promise as an adjunct therapy for snake envenomation.

Temporal inhibition of mouse mammary gland cancer metastasis by CORM-A1 and DETA/NO combination therapy

Carbon monoxide and nitric oxide are two of the most important vasoprotective mediators. Their downregulation observed during vascular dysfunction, which is associated with cancer progression, leads to uncontrolled platelet activation. Therefore, the aim of our studies was to improve vasoprotection and to decrease platelet activation during progression of mouse mammary gland cancer by concurrent use of CO and NO donors (CORM-A1 and DETA/NO, respectively).

Methods: Mice injected intravenously with 4T1-luc2-tdTomato or orthotopically with 4T1 mouse mammary gland cancer cells were treated with CORM-A1 and DETA/NO. Ex vivo aggregation and activation of platelets were assessed in the blood of healthy donors and breast cancer patients. Moreover, we analyzed the compounds' direct effect on 4T1 mouse and MDA-MB-231 human breast cancer cells proliferation, adhesion and migration in vitro.

Results: We have observed antimetastatic effect of combination therapy, which was only transient in orthotopic model. During early stages of tumor progression concurrent use of CORM-A1 and DETA/NO demonstrated vasoprotective ability (decreased endothelin-1, sICAM and sE-selectin plasma level) and downregulated platelets activation (decreased bound of fibrinogen and vWf to platelets) as well as inhibited EMT process. Combined treatment with CO and NO donors diminished adhesion and migration of breast cancer cells in vitro and inhibited aggregation as well as TGF-β release from breast cancer patients' platelets ex vivo. However, antimetastatic effect was not observed at a later stage of tumor progression which was accompanied by increased platelets activation and endothelial dysfunction related to a decrease of VASP level.

Conclusion: The therapy was shown to have antimetastatic action and resulted in normalization of endothelial metabolism, diminution of platelet activation and inhibition of EMT process. The effect was more prominent during early stages of tumor dissemination. Such treatment could be applied to inhibit metastasis during the first stages of this process.

Heme oxygenase-1-Dependent anti-inflammatory effects of atorvastatin in zymosan-injected subcutaneous air pouch in mice

Statins exert pleiotropic and beneficial anti-inflammatory and antioxidant effects. We have previously reported that macrophages treated with statins increased the expression of heme oxygenase-1 (HO-1), an inducible anti-inflammatory and cytoprotective stress protein, responsible for the degradation of heme. In the present study, we investigated the effects of atorvastatin on inflammation in mice and analyzed its mechanism of action in vivo. Air pouches were established in 8 week-old female C57BL/6J mice. Atorvastatin (5 mg/kg, i.p.) and/or tin protoporphyrin IX (SnPPIX), a heme oxygenase inhibitor (12 mg/kg, i.p.), were administered for 10 days. Zymosan, a cell wall component of Saccharomyces cerevisiae, was injected in the air pouch to trigger inflammation. Cell number and levels of inflammatory markers were determined in exudates collected from the pouch 24 hours post zymosan injection by flow cytometry, ELISA and quantitative PCR. Analysis of the mice treated with atorvastatin alone displayed increased expression of HO-1, arginase-1, C-type lectin domain containing 7A, and mannose receptor C-type 1 in the cells of the exudate of the air pouch. Flow cytometry analysis revealed an increase in monocyte/macrophage cells expressing HO-1 and in leukocytes expressing MRC-1 in response to atorvastatin. Mice treated with atorvastatin showed a significant reduction in cell influx in response to zymosan, and in the expression of proinflammatory cytokines and chemokines such as interleukin-1α, monocyte chemoattractant protein-1 and prostaglandin E₂. Co-treatment of mice with atorvastatin and tin protoporphyrin IX (SnPPIX), an inhibitor of heme oxygenase, reversed the inhibitory effect of statin on cell influx and proinflammatory markers, suggesting a protective role of HO-1. Flow cytometry analysis of air pouch cell contents revealed prevalence of neutrophils and to a lesser extent of monocytes/macrophages with no significant effect of atorvastatin treatment on the modification of their relative proportion. These findings identify HO-1 as a target for the therapeutic actions of atorvastatin and highlight its potential role as an in vivo anti-inflammatory agent.

Carbon monoxide and its donors - their implications for medicine

Inhalation of high concentrations of carbon monoxide (CO) is known to lead to serious systemic complications and neuronal disturbances. However, it has been found that not only is CO produced endogenously, but also that low concentrations can bestow beneficial effects which may be of interest in biology and medicine. As translocation of CO through the human organism is difficult, small molecules known as CO-releasing molecules (CORMs) deliver controlled amounts of CO to biological systems, and these are of great interest from a medical point of view. These actions may prevent vascular dysfunction, regulate blood pressure, inhibit blood platelet aggregation or have anti-inflammatory effects. This review summarizes the functions of various CO-releasing molecules in biology and medicine.

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.

Carbon Monoxide-Releasing Molecule Enhances Coagulation and Decreases Fibrinolysis in Normal Canine Plasma

The dog is an important companion animal and also purpose-bred for research studies. Coagulopathies in dogs are common, although the availability of blood products for therapy is inconsistent throughout the profession. A pro-coagulant therapeutic that is readily available and easily stored would be useful for the treatment of coagulopathies. Tricarbonyldichlororuthenium (II) dimer [Carbon monoxide-releasing molecule-2 (CORM-2)] acts as a prothrombotic agent in plasma by increasing the velocity of clot formation and clot strength, and by decreasing the clot's vulnerability to fibrinolysis. We sought to test CORM-2's effect on coagulation and fibrinolysis in vitro in canine plasma using thromboelastography. Measures of the rate of clot formation and clot strength in plasma without CORM-2 were highly correlated with fibrinogen concentration. We found that CORM-2 significantly enhanced the rate of clot formation and clot strength and significantly reduced the rate of fibrinolysis and the clot lysis time. The per cent change in rate of clot formation and clot strength was not significantly correlated with fibrinogen concentration, indicating that CORM-2's pro-coagulant effect is not dependent on fibrinogen concentration. This study corroborates studies in other species that show that CORM-2 is pro-coagulant in plasma, and lays the groundwork for developing CORM-2 as a therapeutic agent for canine coagulopathies. Future studies will evaluate the effect of CORM-2 on whole blood both in vitro and in vivo.

Modified biovectors for the tuneable activation of anti-platelet carbon monoxide release

This communication describes the anti-platelet effects of a new class of cis-rhenium(ii)-dicarbonyl-vitamin B₁₂ complexes (B₁₂-ReCORMs) with tuneable CO releasing properties.

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

Carbon monoxide (CO), produced by heme oxygenase-1 (HO-1), is an endogenous paracrine factor involved in the regulation of cardiovascular structure and function. We studied the effects of a synthetic CO releasing molecule (CORM-3) on cardiac recovery and myocardial microRNA expression after myocardial infarction (MI). Male Wistar rats with MI (n = 75) or sham-operated controls (n = 75) were treated from day 4 to day 14 after MI either with synthetic CORM-3 or with inactive iCORM and killed 2, 4 or 8 weeks post-MI. Infarct size, vascular and capillary densities, the amount of cardiomyocytes in the infarct area, and cardiomyocyte proliferation and apoptosis were determined. PCR was used for microRNA and mRNA quantification, western blotting to evaluate protein expression and echocardiography to assess cardiac structure and function. CORM-3 treatment increased vascular density (P< 0.05 vs. iCORM) and the proportion of cardiomyocytes (P< 0.05 vs. iCORM) in the infarct area. Ejection fraction improved (P< 0.05) and left ventricular volumes decreased (P< 0.05) in CORM-3 treated MI groups compared to iCORM treatment. CORM-3 treatment decreased the amount of proliferating Ki67 positive cardiomyocytes in the infarct/border area at week 2 after MI compared to iCORM treatment, whereas the amount of apoptotic cardiomyocytes did not differ between CORM-3 and iCORM groups. Compared to iCORM treatment, CORM-3 decreased expression on miR-206 in the remote area at week 2 after MI. The CO releasing molecule CORM-3 improved structural and functional cardiac recovery after MI. Modulation of HO-1-CO axis may prove novel drug targets to facilitate cardiac recovery after myocardial injury.

{Ru(CO)x}-Core complexes with benzimidazole ligands: synthesis, X-ray structure and evaluation of anticancer activity in vivo

fac-[Ru^II(CO)₃Cl₂(MBI)] and -[Ru^II(CO)₃Cl₂(DMBI)] are CO-releasing materials able to link histidines of proteins, and the latter showed antitumor effects in murine colon cancer.

Heparin-binding copolymer reverses effects of unfractionated heparin, enoxaparin, and fondaparinux in rats and mice

The parenteral anticoagulants may cause uncontrolled and life-threatening bleeding. Protamine, the only registered heparin antidote, is partially effective against low-molecular weight heparins, completely ineffective against fondaparinux and may cause unacceptable toxicity. Therefore, we aimed to develop a synthetic compound for safe and efficient neutralization of all parenteral anticoagulants. We synthesized pegylated PMAPTAC block copolymers, and then, we selected a lead heparin-binding copolymer (HBC). We assessed the effectiveness of HBC in the model of arterial thrombosis electrically induced in the carotid artery of rats by measuring thrombus weight, bleeding time, activated partial thromboplastin time, activated clotting time, and anti-factor Xa activity. The intravital tissue distribution, the cardiorespiratory, and organ toxicity were monitored. HBC diminished antithrombotic and anticoagulant effects of unfractionated heparin. Moreover, it stopped bleeding and completely reversed the enhancement of clotting times and anti-factor Xa activity caused by enoxaparin or fondaparinux. We observed slight pulmonary congestion and cell infiltration, but the cardiorespiratory parameters remained unchanged. We found a strong signal of fluorescently-labeled HBC in the urine, and a weaker in the liver and in the kidney. No signs of hepatic or nephrotoxicity were observed in the blood biochemistry or histopathologic examination. We developed a copolymer efficiently neutralizing effects of heparins in the living organism, which shows a very promising efficacy/safety profile and may help in the management of uncontrolled bleeding resulting from an anticoagulant injection. HBC could enable the safe replacement of unfractionated heparin with low-molecular weight heparins in patients undergoing cardiac surgery and complex vascular procedures.

Short-term treatment with nitrate is not sufficient to induce in vivo antithrombotic effects in rats and mice

In humans, short-term supplementation with nitrate is hypotensive and inhibits platelet aggregation via an nitric oxide (NO)-dependent mechanism. In the present work, we analyzed whether short-term treatment with nitrate induces antithrombotic effects in rats and mice. Arterial thrombosis was evoked electrically in a rat model in which renovascular hypertension was induced by partial ligation of the left renal artery. In mice expressing green fluorescent protein, laser-induced thrombosis was analyzed intravitally by using confocal microscope. Sodium nitrate (NaNO₃) or sodium nitrite (NaNO₂) was administered orally at a dose of 0.17 mmol/kg, twice per day for 3 days. Short-term nitrate treatment did not modify thrombus formation in either rats or mice, while nitrite administration led to pronounced antithrombotic activity. In hypertensive rats, nitrite treatment resulted in a significant decrease in thrombus weight (0.50 ± 0.08 mg vs. VEH 0.96 ± 0.09 mg; p < 0.01). In addition, nitrite inhibited ex vivo platelet aggregation and thromboxane B₂ (TxB₂) generation and prolonged prothrombin time. These effects were accompanied by significant increases in blood NOHb concentration and plasma nitrite concentration. In contrast, nitrate did not affect ex vivo platelet aggregation or prothrombin time and led to only slightly elevated nitrite plasma concentration. In mice, nitrate was also ineffective, while nitrite led to decreased platelet accumulation in the area of laser-induced endothelial injury. In conclusion, although nitrite induced profound NO-dependent antithrombotic effects in vivo, conversion of nitrates to nitrite in rats and mice over short-term 3-day treatment was not sufficient to elicit NO-dependent antiplatelet or antithrombotic effects.

Carbon monoxide shifts energetic metabolism from glycolysis to oxidative phosphorylation in endothelial cells

Carbon monoxide (CO) modulates mitochondrial respiration, but the mechanisms involved are not completely understood. The aim of the present study was to investigate the acute effects of CO on bioenergetics and metabolism in intact EA.hy926 endothelial cells using live cell imaging techniques. Our findings indicate that CORM-401, a compound that liberates CO, reduces ATP production from glycolysis, and induces a mild mitochondrial depolarization. In addition, CO from CORM-401 increases mitochondrial calcium and activates complexes I and II. The subsequent increase in mitochondrial respiration leads to ATP production through oxidative phosphorylation. Thus, our results show that nonactivated endothelial cells rely primarily on glycolysis, but in the presence of CO, mitochondrial Ca²⁺ increases and activates respiration that shifts the metabolism of endothelial cells from glycolysis- to oxidative phosphorylation-dependent ATP production.

Heme Oxygenases in Cardiovascular Health and Disease

Heme oxygenases are composed of two isozymes, Hmox1 and Hmox2, that catalyze the degradation of heme to carbon monoxide (CO), ferrous iron, and biliverdin, the latter of which is subsequently converted to bilirubin. While initially considered to be waste products, CO and biliverdin/bilirubin have been shown over the last 20 years to modulate key cellular processes, such as inflammation, cell proliferation, and apoptosis, as well as antioxidant defense. This shift in paradigm has led to the importance of heme oxygenases and their products in cell physiology now being well accepted. The identification of the two human cases thus far of heme oxygenase deficiency and the generation of mice deficient in Hmox1 or Hmox2 have reiterated a role for these enzymes in both normal cell function and disease pathogenesis, especially in the context of cardiovascular disease. This review covers the current knowledge on the function of both Hmox1 and Hmox2 at both a cellular and tissue level in the cardiovascular system. Initially, the roles of heme oxygenases in vascular health and the regulation of processes central to vascular diseases are outlined, followed by an evaluation of the role(s) of Hmox1 and Hmox2 in various diseases such as atherosclerosis, intimal hyperplasia, myocardial infarction, and angiogenesis. Finally, the therapeutic potential of heme oxygenases and their products are examined in a cardiovascular disease context, with a focus on how the knowledge we have gained on these enzymes may be capitalized in future clinical studies.

Carbon monoxide released by CORM-401 uncouples mitochondrial respiration and inhibits glycolysis in endothelial cells: A role for mitoBKCa channels

Carbon monoxide (CO), a product of heme degradation by heme oxygenases, plays an important role in vascular homeostasis. Recent evidence indicates that mitochondria are among a number of molecular targets that mediate the cellular actions of CO. In the present study we characterized the effects of CO released from CORM-401 on mitochondrial respiration and glycolysis in intact human endothelial cells using electron paramagnetic resonance (EPR) oximetry and the Seahorse XF technology. We found that CORM-401 (10-100μM) induced a persistent increase in the oxygen consumption rate (OCR) that was accompanied by inhibition of glycolysis (extracellular acidification rate, ECAR) and a decrease in ATP-turnover. Furthermore, CORM-401 increased proton leak, diminished mitochondrial reserve capacity and enhanced non-mitochondrial respiration. Inactive CORM-401 (iCORM-401) neither induced mitochondrial uncoupling nor inhibited glycolysis, supporting a direct role of CO in the endothelial metabolic response induced by CORM-401. Interestingly, blockade of mitochondrial large-conductance calcium-regulated potassium ion channels (mitoBKCa) with paxilline abolished the increase in OCR promoted by CORM-401 without affecting ECAR; patch-clamp experiments confirmed that CO derived from CORM-401 activated mitoBKCa channels present in mitochondria. Conversely, stabilization of glycolysis by MG132 prevented CORM-401-mediated decrease in ECAR but did not modify the OCR response. In summary, we demonstrated in intact endothelial cells that CO induces a two-component metabolic response: uncoupling of mitochondrial respiration dependent on the activation of mitoBKCa channels and inhibition of glycolysis independent of mitoBKCa channels.

Pharmacological modulation of fibrinolytic response - In vivo and in vitro studies

Fibrinolysis is an action of converting plasminogen by its activators, like tissue- or urokinase-type plasminogen activators (t-PA, u-PA), to plasmin, which in turn cleaves fibrin, thereby causing clot dissolution and restoration of blood flow. Endothelial cells release t-PA, prostacyclin (PGI2) and nitric oxide (NO), the potent factors playing a crucial role in regulation of the fibrinolytic system. Since blood platelets can release not only prothrombotic, but also antifibrinolytic factors, like plasminogen activator inhibitor type-1 (PAI-1), they are involved in fibrynolysis regulation. Therefore agents enhancing fibrinolysis can be preferred pharmacologicals in many cardiovascular diseases. This review describes mechanisms by which major cardiovascular drugs (renin-angiotensin-aldosterone system inhibitors, statins, adrenergic receptors and calcium channel blockers, aspirin and 1-methylnicotinamide) influence fibrinolysis. The presented data indicate, that the influence of these drugs on endothelium-blood platelets interactions via NO/PGI2 pathway is fundamental for its antithrombotic and profibrinolytic action. We also described new approaches for intravital confocal real-time imaging as a tool useful to investigate mechanisms of thrombus formation and the effects of drugs affecting haemostasis and mechanisms of their action in the circulation.

Nonclinical evaluation of novel cationically modified polysaccharide antidotes for unfractionated heparin

Protamine, the only registered antidote of unfractionated heparin (UFH), may produce a number of adverse effects, such as anaphylactic shock or serious hypotension. We aimed to develop an alternative UFH antidote as efficient as protamine, but safer and easier to produce. As a starting material, we have chosen generally non-toxic, biocompatible, widely available, inexpensive, and easy to functionalize polysaccharides. Our approach was to synthesize, purify and characterize cationic derivatives of dextran, hydroxypropylcellulose, pullulan and γ-cyclodextrin, then to screen them for potential heparin-reversal activity using an in vitro assay and finally examine efficacy and safety of the most active polymers in Wistar rat and BALB/c mouse models of experimentally induced arterial and venous thrombosis. Efficacy studies included the measurement of thrombus formation, activated partial thromboplastin time, bleeding time, and anti-factor Xa activity; safety studies included the measurement of hemodynamic, hematologic and immunologic parameters. Linear, high molecular weight dextran substituted with glycidyltrimethylammonium chloride groups at a ratio of 0.65 per glucose unit (Dex40-GTMAC3) is the most potent and the safest UFH inhibitor showing activity comparable to that of protamine while possessing lower immunogenicity. Cationic polysaccharides of various structures neutralize UFH. Dex40-GTMAC3 is a promising and potentially better UFH antidote than protamine.

Heme oxygenase in neonatal lung injury and repair

SIGNIFICANCE

Premature and sick neonates are often exposed to high concentrations of oxygen, which results in lung injury and long-term adverse consequences. Nevertheless, neonates are more tolerant to hyperoxia than are adults. This may be, in part, explained by the high lung content of heme oxygenase-1 (HO-1), the rate-limiting enzyme in the degradation of heme and an important stress protein. The abundance of HO-1 dictates its cytoprotective and deleterious effects. Interestingly, in response to hyperoxia, lung HO-1 mRNA is not further up-regulated in neonates, suggesting that lung HO-1 gene expression is tightly regulated so as to optimize cytoprotection when faced with an oxidative stress such as hyperoxia.

RECENT ADVANCES

In addition to the lack of induction of HO-1 mRNA, neonatal lung HO-1 protein is observed in the nucleus in neonatal mice exposed to hyperoxia but not in adults, which is further evidence for the developmental regulation of HO-1. Nuclear HO-1 had unique properties independent of its enzymatic activity. In addition, there has been increasing evidence that nuclear HO-1 contributes to cellular proliferation and malignant transformation in several human cancers.

CRITICAL ISSUES

Since HO-1 has dual effects in cytoprotection and cellular proliferation, the titration of HO-1 effects is critical to ensure beneficial actions against oxidative stress.

FUTURE DIRECTIONS

Much more has to be understood about the specific roles of HO-1 so as to manipulate its abundance and/or nuclear migration to maximize the therapeutic benefit of this pleiotropic protein in the neonatal lung.

Design and synthesis of new hybrid molecules that activate the transcription factor Nrf2 and simultaneously release carbon monoxide

The transcription factor Nrf2 and its downstream target heme oxygenase-1 (HO-1) are essential protective systems against oxidative stress and inflammation. The products of HO-1 enzymatic activity, biliverdin and carbon monoxide (CO), actively contribute to this protection, suggesting that exploitation of these cellular systems may offer new therapeutic avenues in a variety of diseases. Starting from a CO-releasing compound and a chemical scaffold exhibiting electrophilic characteristics (esters of fumaric acid), we report the synthesis of hybrid molecules that simultaneously activate Nrf2 and liberate CO. These hybrid compounds, which we termed "HYCOs", release CO to myoglobin and activate the CO-sensitive fluorescent probe COP-1, while also potently inducing nuclear accumulation of Nrf2 and HO-1 expression and activity in different cell types. Thus, we provide here the first example of a new class of pharmacologically active molecules that target the HO-1 pathway by combining an Nrf2 activator coordinated to a CO-releasing group.

Eplerenone reduces arterial thrombosis in diabetic rats

INTRODUCTION

Clinical studies demonstrated the benefits of eplerenone (EPL) in reduction of cardiovascular events in diabetic patients. Since acute myocardial infarction (AMI) and stroke are related to acute intravascular thrombosis, we postulate that the beneficial effects of EPL may result from its antithrombotic action.

MATERIALS AND METHODS

Streptozotocin (STZ)-induced diabetic rats were treated with EPL (100 mg/kg/day) for 10 days. Thrombosis in the carotid artery was stimulated electrically.

RESULTS

Thrombosis development was enhanced in STZ-induced diabetic rats as compared to normoglycaemic controls. EPL caused prolongation of the time to artery occlusion, reduction in the incidence of occlusion and decrease in thrombus weight. Changes in the thrombi structure and the inhibition of hypertrophy of the tunica media in the artery wall were also observed. EPL caused reduction in tissue factor, plasminogen activator inhibitor type 1 and interleukin-1β plasma levels.

CONCLUSIONS

Our study demonstrated the antithrombotic effect of EPL manifested by a decrease in the dynamics of thrombus formation and changes in its structure. The changes in thrombosis process were accompanied by antihaemostatic, profibrinolytic and anti-inflammatory effects. The aldosterone blockade with EPL seems to be an additional pharmacological strategy for the prevention and treatment of thrombotic disorders in diabetes.

Antithrombotic effects of pyridinium compounds formed from trigonelline upon coffee roasting

Coffee may exert a preventive effect on arterial thrombosis. Trigonelline is one of the most abundant compounds in coffee that undergoes pyrolysis upon roasting of coffee beans. The aim of the present study was to identify pyridinium compounds formed upon trigonelline pyrolysis and coffee roasting and to investigate the effect of three of them, i.e., 1-methylpyridine and 1,3- and 1,4-dimethylpyridine, on experimentally induced arterial thrombosis in rats. 1,3- and 1,4-dimethylpyridine but not 1-methylpyridine inhibited arterial thrombus formation. 1,3-Dimethylpyridine inhibited platelet aggregation and reduced fibrin formation in platelet-rich plasma, whereas 1,4-dimethylpyridine increased the plasma level of 6-keto-PGF1α. 1,4-Dimethylpyridine slightly increased rat tissue plasminogen activator plasma activity. In summary, we demonstrated that pyridinium compounds display mild antithrombotic properties due to stimulation by prostacyclin release (1,4-dimethylpyridine) and inhibition of platelet aggregation (1,3-dimethylpyridine). Those pyridinium compounds may, to some extent, be responsible for the beneficial effects of coffee drinking.

P21-dependent protective effects of a carbon monoxide-releasing molecule-3 in pulmonary hypertension

OBJECTIVE

Carbon monoxide-releasing molecules (CORMs) represent a pharmacological alternative to CO gas inhalation. Here, we questioned whether CORM-3, a well-characterized water-soluble CORM, could prevent and reverse pulmonary hypertension (PH) in chronically hypoxic mice and in smooth muscle promoter 22 serotonin transporter mice overexpressing the serotonin transporter in smooth muscle cells (SMCs).

APPROACH AND RESULTS

Treatment with CORM-3 (50 mg/kg per day once daily) for 3 weeks prevented PH, right ventricular hypertrophy, and distal pulmonary artery muscularization in mice exposed to chronic hypoxia and partially reversed PH in smooth muscle promoter 22 serotonin transporter mice by reducing Ki67 dividing pulmonary artery SMCs (PA-SMCs). In these models, CORM-3 markedly increased lung p21 mRNA and protein levels and p21-stained PA-SMCs. These effects contrasted with the transient pulmonary vasodilatation and rise in lung cGMP levels induced by a single injection of CORM-3 in mice exposed to acute hypoxia. Studies in cultured rat PA-SMCs revealed that the inhibitory effects of CORM-3 on cell growth were independent of cGMP formation but associated with increased p21 mRNA and protein levels. Protection against PH by CORM-3 required increased lung expression of p21, as indicated by the inability of CORM-3 to prevent chronic hypoxia-induced PH in p21-deficient mice and to alter the growth of PA-SMCs derived from p21-deficient mice. CORM-3-induced p21 overexpression was linked to p53 activation as assessed by the inability of CORM-3 to prevent PH and induce p21 expression in p53-deficient mice and in PA-SMCs derived from p53-deficient mice.

CONCLUSIONS

CORM-3 inhibits pulmonary vascular remodeling via p21, which may represent a useful approach for treating PH.

Carbon monoxide: Anticoagulant or procoagulant?

Within the past decade there have been several investigations attempting to define the impact of exogenous and endogenous carbon monoxide exposure on hemostasis. Critically, two bodies of literature have emerged, with carbon monoxide mediated platelet inhibition cited as a cause of in vitro human and in vitro/in vivo rodent anticoagulation. In contrast, interaction with heme groups associated with fibrinogen, α₂-antiplasmin and plasmin by carbon monoxide has resulted in enhanced coagulation and decreased fibrinolysis in vitro in human and other species, and in vivo in rabbits. Of interest, the ultrastructure of platelet rich plasma thrombi demonstrates an abnormal increase in fine fiber formation and matting that are obtained from humans exposed to carbon monoxide. Further, thrombi obtained from humans and rabbits have very similar ultrastructures, whereas mice and rats have more fine fibers and matting present. In sum, there may be species specific differences with regard to hemostatic response to carbon monoxide. Carbon monoxide may be a Janus-faced molecule, with potential to attenuate or exacerbate thrombophilic disease.

Research of medical gases in Poland

Research of medical gases is well established in Poland and has been marked with the foundation of several professional societies. Numerous academic centers including those dealing with hyperbaric and diving medicine conduct studies of medical gases, in vast majority supported with intramural funds. In general, Polish research of medical gases is very much clinical in nature, covering new applications and safety of medical gases in medicine; on the other hand there are several academic centers pursuing preclinical studies, and elaborating basic theories of gas physiology and mathematical modeling of gas exchange. What dominates is research dealing with oxygen and ozone as well as studies of anesthetic gases and their applications. Finally, several research directions involving noble gas, hydrogen and hydrogen sulfide for cell protection, only begin to gain recognition of basic scientists and clinicians. However, further developments require more monetary spending on research and clinical testing as well as formation of new collective bodies for coordinating efforts in this matter.

Mechanism(s) Involved in Carbon Monoxide-releasing Molecule-2-mediated Cardioprotection During Ischaemia-reperfusion Injury in Isolated Rat Heart

The purpose of the present study was to determine the mechanism(s) involved in carbon monoxide-releasing molecule-2, carbon monoxide-releasing molecule-2-induced cardioprotection. We used the transition metal carbonyl compound carbon monoxide-releasing molecule-2 that can act as carbon monoxide donor in cardiac ischaemia-reperfusion injury model using isolated rat heart preparation. Langendorff's perfused rat hearts when treated with carbon monoxide-releasing molecule-2 (50 μM) for 10 min before global ischaemia exhibited significant reduction in postischaemic levels of myocardial injury markers, creatine kinase and lactate dehydrogenase in coronary effluent. Similarly, pretreatment with carbon monoxide-releasing molecule-2 showed significantly improved postischaemic recovery of heart rate, coronary flow rate, cardiodynamic parameters and reduced infarct size as compared to vehicle control hearts. Perfusion with p38 mitogen-activated protein kinase inhibitor, SB203580, a specific inhibitor of α and β isoform, before and concomitantly with carbon monoxide-releasing molecule-2 treatment abolished carbon monoxide-releasing molecule-2-induced cardioprotection. However, p38 mitogen-activated protein kinase alpha inhibitor, SCIO-469, was unable to inhibit the cardioprotective effect of carbon monoxide-releasing molecule-2. Furthermore, protective effect of carbon monoxide-releasing molecule-2 was significantly inhibited by the protein kinase C inhibitor, chelerythrine, when added before and concomitantly with carbon monoxide-releasing molecule-2. It was also observed that, perfusion with phosphatidylinositol 3-kinase inhibitor, wortmannin, before and concomitantly with carbon monoxide-releasing molecule-2 was not able to inhibit carbon monoxide-releasing molecule-2-induced cardioprotection. Interestingly, we observed that wortmannin perfusion before ischaemia and continued till reperfusion significantly inhibited carbon monoxide-releasing molecule-2-mediated cardioprotection. Our findings suggest that the carbon monoxide-releasing molecule-2 treatment may activate the p38 mitogen-activated protein kinase β and protein kinase C pathways before ischaemia and phosphatidylinositol 3-kinase pathway during reperfusion which may be responsible for the carbon monoxide-releasing molecule-2-mediated cardioprotective effect.

The immunomodulatory role of carbon monoxide during transplantation

The number of organ and tissue transplants has increased worldwide in recent decades. However, graft rejection, infections due to the use of immunosuppressive drugs and a shortage of graft donors remain major concerns. Carbon monoxide (CO) had long been regarded solely as a poisonous gas. Ultimately, physiological studies unveiled the endogenous production of CO, particularly by the heme oxygenase (HO)-1 enzyme, recognizing CO as a beneficial gas when used at therapeutic doses. The protective properties of CO led researchers to develop uses for it, resulting in devices and molecules that can deliver CO in vitro and in vivo. The resulting interest in clinical investigations was immediate. Studies regarding the CO/HO-1 modulation of immune responses and their effects on various immune disorders gave rise to transplantation research, where CO was shown to be essential in the protection against organ rejection in animal models. This review provides a perspective of how CO modulates the immune system to improve transplantation and suggests its use as a therapy in the field.

Vasorelaxing effects and inhibition of nitric oxide in macrophages by new iron-containing carbon monoxide-releasing molecules (CO-RMs)

Carbon monoxide-releasing molecules (CO-RMs) are a class of organometallo carbonyl complexes capable of delivering controlled quantities of CO gas to cells and tissues thus exerting a broad spectrum of pharmacological effects. Here we report on the chemical synthesis, CO releasing properties, cytotoxicity profile and pharmacological activities of four novel structurally related iron-allyl carbonyls. The major difference among the new CO-RMs tested was that three compounds (CORM-307, CORM-308 and CORM-314) were soluble in dimethylsulfoxide (DMSO), whereas a fourth one (CORM-319) was rendered water-soluble by reacting the iron-carbonyl with hydrogen tetrafluoroborate. We found that despite the fact all compounds liberated CO, CO-RMs soluble in DMSO caused a more pronounced toxic effect both in vascular and inflammatory cells as well as in isolated vessels. More specifically, iron carbonyls soluble in DMSO released CO with a fast kinetic and displayed a marked cytotoxic effect in smooth muscle cells and RAW 247.6 macrophages despite exerting a rapid and pronounced vasorelaxation ex vivo. In contrast, CORM-319 that is soluble in water and liberated CO with a slower rate, preserved smooth muscle cell viability, relaxed aortic tissue and exerted a significant anti-inflammatory effect in macrophages challenged with endotoxin. These data suggest that iron carbonyls can be used as scaffolds for the design and synthesis of pharmacologically active CO-RMs and indicate that increasing water solubility and controlling the rate of CO release are important parameters for limiting their potential toxic effects.

Emerging concepts on the anti-inflammatory actions of carbon monoxide-releasing molecules (CO-RMs)

Carbon monoxide-releasing molecules (CO-RMs) are a class of organometallo compounds capable of delivering controlled quantities of CO gas to cells and tissues thus exerting a broad spectrum of pharmacological effects. CO-RMs containing transition metal carbonyls were initially implemented to mimic the function of heme oxygenase-1 (HMOX1), a stress inducible defensive protein that degrades heme to CO and biliverdin leading to anti-oxidant and anti-inflammatory actions. Ten years after their discovery, the research on the chemistry and biological activities of CO-RMs has greatly intensified indicating that their potential use as CO delivering agents for the treatment of several pathological conditions is feasible. Although CO-RMs are a class of compounds that structurally diverge from traditional organic-like pharmaceuticals, their behaviour in the biological environments is progressively being elucidated revealing interesting features of metal-carbonyl chemistry towards cellular targets. Specifically, the presence of carbonyl groups bound to transition metals such as ruthenium, iron or manganese appears to make CO-RMs unique in their ability to transfer CO intracellularly and amplify the mechanisms of signal transduction mediated by CO. In addition to their well-established vasodilatory activities and protective effects against organ ischemic damage, CO-RMs are emerging for their striking anti-inflammatory properties which may be the result of the multiple activities of metal carbonyls in the control of redox signaling, oxidative stress and cellular respiration. Here, we review evidence on the pharmacological effects of CO-RMs in models of acute and chronic inflammation elaborating on some emerging concepts that may help to explain the chemical reactivity and mechanism(s) of action of this distinctive class of compounds in biological systems.