CO-RMs

"""Carbon monoxide (CO) is increasingly being accepted as a cytoprotective and homeostatic molecule with important signalling capabilities in physiological and pathophysiological situations. The endogenous production of CO occurs through the
activity of constitutive (haem oxygenase 2) and inducible (haem oxygenase 1) haem oxygenases, enzymes that are responsible for the catabolism of haem. Through the generation of its products, which in addition to CO includes the bile pigments biliverdin, bilirubin and ferrous iron, the haem oxygenase 1 system also has an obligatory role in the regulation of the stress response and in cell adaptation to injury. This Review provides an
overview of the physiology of CO, summarizes the effects of CO gas and CO-releasing molecules in preclinical animal models of cardiovascular disease, inflammatory disorders and organ transplantation, and discusses the development and therapeutic options for the exploitation of this simple gaseous molecule."""

It is now established that NO is a messenger molecule in mammals despite its high toxicity. As NO+ and CO are isoelectronic, it should not be unexpected that CO could also have a role as a messenger. CO is produced naturally in humans at a rate of between 3 and 6 cm3 per day, and this rate is increased markedly by certain inflammatory states and pathological conditions associated with red blood cell hemolysis. Over the last 10 years, the interest in the biological effects of CO has greatly increased, and it is now established in the medical literature that CO does have a major role as a signaling molecule in mammals. It is particularly active within the cardiovascular system, for example, in suppressing organ graft rejection and protecting tissues from ischemic injury and apoptosis. Recently it has been shown that metal carbonyls can also function as CO-releasing molecules and provide similar biological activities. This opens the possibility to develop pharmaceutically important metal carbonyls.

[Mn(CO)(4){S(2)CNMe(CH(2)CO(2)H)}] is shown to be a CO releasing molecule providing at least three moles CO per mole of compound. The mechanism of CO loss is dissociative and reversible and was investigated using Gaussian 09 calculations. The reversible binding of CO results in a relatively stable solution of the compound, while in the presence of a CO receptor or a ligand to prevent the rebinding of CO, the CO is lost rapidly. The X-ray structure was determined.

""Carbon monoxide (CO) is emerging as an important and versatile mediator of physiological
processes to the extent that treatment of animals with exogenous CO gas has beneficial effects in a range of vascular- and inflammatory-related disease models. The recent discovery that certain transition metal carbonyls function as CO-releasing molecules (CO-RMs) in biological systems highlighted the potential of exploiting this and similar classes of compounds as a stratagem to deliver CO for therapeutic purposes. Here we describe the biochemical features and pharmacological actions of a newly identified water-soluble CO releaser (CORM-A1) that, unlike the first prototypic molecule recently described (CORM-3), does not contain a transition metal and liberates CO at a much slower rate under physiological conditions. Using a myoglobin assay and an amperometric CO electrode, we demonstrated that the release of CO from CORMA1 is both pH- and temperature-dependent with a half-life of ~21 min at 37°C and pH 7.4. In isolated aortic rings, CORM-A1 promoted a gradual but profound concentration-dependent vasorelaxation over time, which was highly amplified by YC-1 (1 μM) and attenuated by ODQ, a stimulator and inhibitor of guanylate cyclase, respectively. Similarly, administration of CORM-A1 (30 μmol/kg i.v.) in vivo produced a mild decrease in mean arterial pressure, which was markedly potentiated by pretreatment with YC-1 (1.2 μmol/kg i.v.). Interestingly, an inactive form of CORM-A1 that is incapable of releasing CO failed to promote both vasorelaxation and hypotension, thus directly implicating CO as the mediator of the observed pharmacological effects. Our results reveal that the bioactivities exerted by CORM-A1 reflect its intrinsic biochemical behavior of a slow CO releaser, which may be advantageous in the treatment of chronic conditions that require CO to be delivered in a carefully controlled manner.""

"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.

As a by-product of heme catabolism by the heme oxygenase system, carbon monoxide (CO) has been neglected for many years, and only recently has its role as an essential signaling molecule been appreciated. In the past decade, the use of CO gas in pre-clinical experimental models of disease has produced some remarkable data indicating that its therapeutic delivery to mammals could alleviate inflammatory processes and cardiovascular disorders. However, the inherent toxic nature of CO cannot be ignored, knowing that inhalation of uncontrolled amounts of this gas can ultimately lead to serious systemic complications and neuronal derangements. From a clinical perspective, a key question is whether a safe and therapeutically effective threshold of CO can be reached locally in organs and tissues without delivering potentially toxic amounts through the lung. The advent of CO-releasing molecules (CO-RMs), a group of compounds capable of carrying and liberating controlled quantities of CO in cellular systems, appears a plausible alternative in the attempt to overcome the limitations of CO gas. Although in its infancy and far from being used for clinical applications, the CO-RMs technology is supported by very encouraging biological results and reflected by the chemical versatility of these compounds and their endless potential to be transformed into CO-based pharmaceuticals.

The perception that carbon monoxide (CO) is poisonous and life-threatening for mammalian organisms stems from its intrinsic propensity to bind iron in hemoglobin, a reaction that ultimately leads to impaired oxygen delivery to tissues. From evolutionary and chemical perspectives, however, CO is one of the most essential molecules in the formation of biological components and its interaction with transition metals is at the origin of primordial cell signaling. Not surprisingly, mammals have gradually evolved systems to finely control the synthesis and the sensing of this gaseous molecule. Cells are indeed continuously exposed to small quantities of CO produced endogenously during the degradation of heme by constitutive and inducible heme oxygenase enzymes. We have gradually learnt that heme oxygenase-derived carbon monoxide (CO) serves as a ubiquitous signaling mediator which could be exploited for therapeutic purposes. The development of transition metal carbonyls as prototypic carbon monoxide-releasing molecules (CO-RMs) represents a novel stratagem for a safer delivery of CO-based pharmaceuticals in the treatment of various pathological disorders. This review looks back at evolution to analyze and argue that a dynamic interaction of CO with specific intracellular metal centers is the common denominator for the diversified beneficial effects mediated by this gaseous molecule.

Carbon monoxide (CO) is generated in living organisms during the degradation of heme by the enzyme heme oxygenase, which exists in constitutive (HO-2 and HO-3) and inducible (HO-1) isoforms. Carbon monoxide gas is known to dilate blood vessels in a manner similar to nitric oxide and has been recently shown to possess antiinflammatory and antiapoptotic properties. We report that a series of transition metal carbonyls, termed here carbon monoxide–releasing molecules (CO-RMs), liberate CO to elicit direct biological activities. Specifically, spectrophotometric and NMR analysis revealed that dimanganese decacarbonyl and tricarbonyldichlororuthenium (II) dimer release CO in a concentration-dependent manner. Moreover, CO-RMs caused sustained vasodilation in precontracted rat aortic rings, attenuated coronary vasoconstriction in hearts ex vivo, and significantly reduced acute hypertension in vivo. These vascular effects were mimicked by induction of HO-1 after treatment of animals with hemin, which increases endogenously generated CO. Thus, we have identified a novel class of compounds that are useful as prototypes for studying the bioactivity of CO. In the long term, transition metal carbonyls could be utilized for the therapeutic delivery of CO to alleviate vascular- and immuno-related dysfunctions. The full text of this article is available at http://www.circresaha.org. (Circ Res. 2002;90:e17-e24.)

"Significance: Heme oxygenase enzymes, which exist as constitutive (HO-2) and inducible (HO-1) isoforms, degrade heme to carbon monoxide (CO) and the bile pigment biliverdin. In the last two decades substantial scientific evidence has been collected on the function of HO-1 in cell homeostasis emphasizing these two important features: 1) HO-1 is a fundamental ‘sensor’ of cellular stress and directly contributes to limit or prevent tissue damage; 2) the products of HO-1 activity
dynamically participate in cellular adaptation to stress and are inherently involved in the mechanisms of defence.
Recent advances: On the bases of its promising cytoprotective features, scientists have pursued the targeting of HO-1 as an attractive cellular pathway for drug discovery. Three different pharmacological approaches are currently being investigated in relation to HO-1, namely the use of CO gas, the development of CO-releasing molecules (CO-RMs) and small molecules possessing the ability to up-regulate HO-1 in cells and tissues.
Critical issue: Studies on the regulation and amplification of the HO-1/CO pathway by selective pharmacological approaches may lead to the discovery of novel drugs for the treatment of a variety of diseases.
Future directions: In this review we will discuss in detail the importance of
pharmacologically manipulating the HO-1 pathway and its products for conferring
protection against a variety of conditions characterized by oxidative stress and
inflammation. We will also evaluate each of the strategic approach being developed
by considering the intrinsic advantages and disadvantages, which may have
implications for their use as therapeutics in specific pathological conditions."

Carbon monoxide is continuously produced in small quantities in tissues and is an important signaling mediator in mammalian cells. We previously demonstrated that CO delivered to isolated rat heart mitochondria using a water-soluble CO-releasing molecule (CORM-3) is able to uncouple mitochondrial respiration. The aim of this study was to explore more in depth the mechanism(s) of this uncoupling effect. We found that acceleration of mitochondrial O2 consumption and decrease in membrane potential induced by CORM-3 were associated with an increase in mitochondrial swelling. This effect was independent of the opening of the mitochondrial transition pore as cyclosporine A was unable to prevent it. Interestingly, removal of phosphate from the incubation medium suppressed the effects mediated by CORM-3. Blockade of the dicarboxylate carrier, which exchanges dicarboxylate for phosphate, decreased the effects induced by CORM-3 while direct inhibition of the phosphate carrier with N-ethylmaleimide completely abolished the effects of CORM-3. In addition, CORM-3 was able to enhance the transport of phosphate into mitochondria as evidenced by changes in mitochondrial phosphate concentration and mitochondrial swelling that evaluates the activity of the phosphate carrier in de-energized conditions. These results indicate that CORM-3 activates the phosphate carrier leading to an increase in phosphate and proton transport inside mitochondria, both of which could contribute to the non-classical uncoupling effect mediated by CORM-3. The dicarboxylate carrier amplifies this effect by increasing intra-mitochondrial phosphate concentration.

Carbon monoxide (CO) is a resourceful gas as recent advances in the area of cell signaling are revealing an unexpected physiological role for CO in the cardiovascular, immune and nervous systems. Transition metal carbonyls have been lately discovered to function as CO releasing molecules (CO-RMs) and elicit distinct pharmacological activities in biological systems. Studies currently ongoing in our laboratories are investigating both the chemical and bioactive features of a series of water-soluble CO-RMs and their specific utilization as vasoactive mediators, anti-inflammatory agents and inhibitors of cellular and tissue damage. The data presented in this review corroborate the notion that transition metal carbonyls could be used as carriers to deliver CO in mammals and highlight the bioactivity and potential therapeutic features of CO-RMs in the mitigation of cellular and organ dysfunction.

The well-known adverse effects of CO (carbon monoxide) intoxication are counterbalanced by its positive actions when small amounts are produced intracellularly by the cytoprotective enzyme HO-1 (haem oxygenase-1). As compelling scientific evidence accumulated to sustain that HO-1 plays a fundamental role in counteracting vascular and inflammatory disorders, we began to appreciate that a controlled delivery of CO to mammals may provide therapeutic benefits in a number of pathological states. This is the rationale for the recent development of CO-RMs (CO-releasing molecules), a group of compounds capable of carrying and liberating controlled quantities of CO in cellular systems, which offer a plausible tool for studying the pharmacological effects of this gas and identifying its mechanism(s) of action. The present review will highlight the encouraging results obtained so far on the vasodilatory, anti-ischaemic and anti-inflammatory effects elicited by CO-RMs in in vitro and in vivo models with an emphasis on the prospect of converting chemical CO carriers into CO-based pharmaceuticals.

Nephrotoxicity is one of the main side effects caused by cisplatin (CP), a widely used antineoplastic agent. Here, we examined the effect of a novel water soluble carbon monoxide-releasing molecule (CORM-3) on CP-mediated cytotoxicity in renal epithelial cells and explored the potential therapeutic benefits of carbon monoxide in CP-induced nephrotoxicity in vivo. Exposure of LLC-PK1 cells to CP (50 µM) caused significant apoptosis as evidenced by caspase-3 activation and an increased number of floating cells. Treatment with CORM-3 (1–50 µM) resulted in a remarkable and concentration-dependent decrease in CP-induced caspase-3 activity and cell detachment. This effect involved activation of the cGMP pathway as 1H-oxadiazole [4, 3-a] quinoxaline-1-ore (ODQ), a guanylate cyclase inhibitor, completely abolished the protection elicited by CORM-3. Using a rat model of CP-induced renal failure, we found that treatment with CP (7.5 mg/kg) caused a significant elevation in plasma urea (6.6-fold) and creatinine (3.1-fold) levels, which was accompanied by severe morphological changes and marked apoptosis in tubules at the corticomedullary junction. A daily administration of CORM-3 (10 mg/kg ip), starting 1 day before CP treatment and continuing for 3 days thereafter, resulted in amelioration of renal function as shown by reduction of urea and creatinine levels to basal values, a decreased number of apoptotic tubular cells, and an improved histological profile. A negative control (iCORM-3) that is incapable of liberating CO failed to prevent renal dysfunction mediated by CP, indicating that CO is directly involved in renoprotection. Our data demonstrate that CORM-3 can be used as an effective therapeutic adjuvant in the treatment of CP-induced nephrotoxicity.

Carbon monoxide (CO), which is formed in mammalian cells through the oxidation of haem by the enzyme haem oxygenase, actively participates in the regulation of key intracellular functions. Emerging evidence reveals that an increased generation of haem oxygenase-derived CO plays a critical role in the resolution of inflammatory processes and alleviation of cardiovascular disorders. The authors have identified a novel class of substances, CO-releasing molecules (CO-RMs), which are capable of exerting a variety of pharmacological activities via the liberation of controlled amounts of CO in biological systems. A wide range of CO carriers containing manganese (CORM-1), ruthenium (CORM-2 and -3), boron (CORM-A1) and iron (CORM-F3) are currently being investigated to tailor therapeutic approaches for the prevention of vascular dysfunction, inflammation, tissue ischaemia and organ rejection.

""Carbon monoxide (CO), one of the end products of heme oxygenase activity, inhibits smooth muscle proliferation by decreasing ERK1/2 phosphorylation and cyclin D1 expression, a signaling pathway that is known to be modulated by reactive oxygen species (ROS) in airway smooth muscle cells (ASMCs). Two important sources of ROS involved in cell signalling are the membrane NAD(P)H oxidase and the mitochondrial respiratory chain. Thus, that CO could modulate redox signalling in ASMCs by interacting with the heme moiety of NAD(P)H oxidase and/or the respiratory chain is a plausible hypothesis. Here we show that a recently identified carbon monoxide-releasing molecule, [Ru(CO)3Cl2]2 (or CORM-2) 1) inhibits NAD(P)H oxidase cytochrome b558 activity, 2) increases oxidant production by the mitochondria, and 3) inhibits ASMC proliferation and phosphorylation of the ERK1/2 mitogen-activated protein kinase and expression of cyclin D1, two critical pathways involved in muscle proliferation. No such effects were observed with the negative control (Ru(Me2SO)4Cl2), which does not contain CO groups. Because both diphenylene iodinium or apocynin (inhibitors of NAD(P)H oxidase) and rotenone (a molecule that increases mitochondrial ROS production by blocking the respiratory
chain) mimicked the effect of CORM-2 on cyclin D1 expression and ASMC proliferation, the antiproliferative effect of CORM-2 is probably related to inhibition of cytochromes on both NAD(P)H oxidase and the respiratory chain. The involvement of increased mitochondriaderived oxidants is substantiated by the findings showing that the antioxidant N-acetylcysteine partially inhibited the effects of CORM-2. This study provides a new mechanism to explain redox signaling by CO.""

Carbon monoxide, which is generated in mammals during the degradation of heme by the enzyme heme oxygenase, is an important signaling mediator. Transition metal carbonyls have been recently shown to function as carbon monoxide–releasing molecules (CO-RMs) and to elicit distinct pharmacological activities in biological systems. In the present study, we report that a water-soluble form of CO-RM promotes cardioprotection in vitro and in vivo. Specifically, we found that tricarbonylchloro(glycinato)ruthenium(II) (CORM-3) is stable in water at acidic pH but in physiological buffers rapidly liberates CO in solution. Cardiac cells pretreated with CORM-3 (10 to 50 mol/L) become more resistant to the damage caused by hypoxia-reoxygenation and oxidative stress. In addition, isolated hearts reperfused in the presence of CORM-3 (10
mol/L) after an ischemic event displayed a significant recovery in myocardial performance and a marked and significant reduction in cardiac muscle damage and infarct size. The cardioprotective effects mediated by CORM-3 in cardiac cells and isolated hearts were totally abolished by 5-hydroxydecanoic acid, an inhibitor of mitochondrial ATP-dependent potassium channels. Predictably, cardioprotection is lost when CORM-3 is replaced by an inactive form (iCORM-3) that is incapable of liberating CO. Using a model of cardiac allograft rejection in mice, we also found that treatment of recipients with CORM-3 but not iCORM-3 considerably prolonged the survival rate of transplanted hearts. These data corroborate the notion that transition metal carbonyls could be used as carriers to deliver CO and highlight the bioactivity and potential therapeutic features of CO-RMs in the mitigation of cardiac dysfunction. The full text of this article is available online at http://www.circresaha.org. (Circ Res. 2003;93:e2-e8.)

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.

"BACKGROUND and AIMS: Treatment with carbon monoxide (CO) inhalation has been shown to ameliorate postoperative ileus (POI) in rodents and swine. The aim of this study was to investigate whether CO liberated from water-soluble CO-releasing molecules (CO-RMs) can protect against POI in mice and to elucidate the mechanisms involved.
METHODS: Ileus was induced by surgical manipulation of the small intestine (IM). Intestinal contractility-transit was evaluated by video-fluorescence imaging. Leucocyte infiltration (myeloperoxidase), inflammatory parameters (ELISA), oxidative stress (lipid peroxidation), and haem oxygenase (HO)/inducible nitric oxide synthase (iNOS) enzyme activity were measured in the intestinal mucosa and muscularis propria.
RESULTS: Intestinal contractility and transit were markedly restored when manipulated mice were pre-treated with CO-RMs. Intestinal leucocyte infiltration, expression levels of interleukin 6 (IL6), monocyte chemoattractant protein-1 and intercellular adhesion molecule-1, as well as iNOS activity were reduced by treatment with CORM-3 (a transition metal carbonyl that releases CO very rapidly); whereas expression of IL10/HO-1 was further increased when compared to nontreated manipulated mice. Moreover, treatment with CORM-3 markedly reduced oxidative stress and extracellular signal-related kinase (ERK)1/2 activation in both mucosa (early response) and muscularis (biphasic response). The p38 mitogen-activated protein kinase inhibitor SB203580 abolished CORM-3-mediated HO-1 induction. The HO inhibitor chromium mesoporphyrin only partially reversed the protective effects of CORM-3 on inflammation/oxidative stress in the muscularis, but completely abrogated CORM-3-mediated inhibition of the early "oxidative burst" in the mucosa.
CONCLUSIONS: Pre-treatment with CO-RMs markedly reduced IM-induced intestinal muscularis inflammation. These protective effects are, at least in part, mediated through induction of HO-1, in a p38-dependent manner, as well as reduction of ERK1/2 activation. In addition, CORM-induced HO-1 induction reduces the early "oxidative burst" in the mucosa following IM."

"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."

Nephrotoxicity is one of the main side effects caused by cisplatin (CP), a widely used antineoplastic agent. Here, we examined the effect of a novel water-soluble carbon monoxide-releasing molecule (CORM-3) on CP-mediated cytotoxicity in renal epithelial cells and explored the potential therapeutic benefits of carbon monoxide in CP-induced nephrotoxicity in vivo. Exposure of LLC-PK1 cells to CP (50 μM) caused significant apoptosis as evidenced by caspase-3 activation and an increased number of floating cells. Treatment with CORM-3 (1–50 μM) resulted in a remarkable and concentration-dependent decrease in CP-induced caspase-3 activity and cell detachment. This effect involved activation of the cGMP pathway as 1H-oxadiazole [4, 3-a] quinoxaline-1-ore (ODQ), a guanylate cyclase inhibitor, completely abolished the protection elicited by CORM-3. Using a rat model of CP-induced renal failure, we found that treatment with CP (7.5 mg/kg) caused a significant elevation in plasma urea (6.6-fo...

Purpose: Cisplatin (CP)-induced nephrotoxicity is associated with the increased generation of reactive oxygen metabolites and lipid peroxidation in kidney, caused by the decreased levels of antioxidants and antioxidant enzymes. The purpose of this study was to evaluate the role of Spirulina, blue–green alga with antioxidant properties, in the protection of cisplatin-induced nephrotoxicity in rat. Methods: Rats were treated with CP (6 mg/kg bw, single dose, intraperitoneally). Spirulina (1,000 mg/kg) was administered orally for 8 days and CP treatment was given on day 4. Nephrotoxicity was assessed, 6 days after the CP treatment, by measuring plasma urea, creatinine, urinary N-acetyl-(d-glucose-aminidase) (β-NAG) and histopathology of kidney. Results: Rats treated with CP showed marked nephrotoxicity as evidenced from the significant elevation in plasma urea, creatinine and urinary β-NAG. Histological assessment revealed marked proximal tubular necrosis and extensive epithelial vacuolization in the kidney of CP-treated rats. Superoxide dismutase, catalase and glutathione peroxidase were decreased and lipid peroxidation was increased in kidney tissue. Pretreatment with Spirulina protected the rats from CP-induced nephrotoxicity. The rise in plasma urea, creatinine, urinary β-NAG, plasma and kidney tissue MDA and histomorphological changes were significantly attenuated by Spirulina. In vitro studies using human ovarian cancer cells revealed that Spirulina did not interfere with the cytotoxic effects of CP on tumor cells. Conclusions: In summary, Spirulina significantly protected the CP-induced nephrotoxicity through its antioxidant properties.

The Nrf2/heme oxygenase-1 (HO-1) axis affords significant protection against oxidative stress and cellular damage. We synthesized a series of cobalt-based hybrid molecules (HYCOs) that combine an Nrf2 inducer with a releaser of carbon monoxide (CO), an anti-inflammatory product of HO-1. Two HYCOs markedly increased Nrf2/HO-1 expression, liberated CO and exerted anti-inflammatory activity in vitro. HYCOs also up-regulated tissue HO-1 and delivered CO in blood after administration in vivo, supporting their potential use against inflammatory conditions.

The inducible stress protein heme oxygenase-1 (HO-1) has been linked to tissue and organ protection against the deleterious actions of many pathological conditions, including endotoxin challenge. Similar protection can be achieved by the main products of heme oxygenase ...

Aims: Carbon monoxide (CO) delivered in a controlled manner to cells and organisms mediates a variety of pharmacological effects to the extent that CO-releasing molecules (CO-RMs) are being developed for  therapeutic purposes. Recently, ruthenium-based CO-RMs have been shown to posses important bactericidal activity. Here we assessed the effect of fast CO releasers containing ruthenium (Ru(CO)3Cl(glycinate) [CORM-3] and tricarbonyldichloro ruthenium(II) dimer [CORM-2]) and a novel slow manganese-based CO releaser ([Me4N] [Mn(CO)4(thioacetate)2] [CORM-371]) on O2 consumption and growth of Pseudomonas aeruginosa (PAO1). We then compared these effects with the action elicited by sodium boranocarbonate (CORM-A1), which lacks a transition metal but liberates CO with a rate similar to CORM-371. Results: CORM-2, CORM-3, and, to a lesser extent, CORM-371 exerted a significant bactericidal effect and decreased O2 consumption in PAO1 in vitro. The effect appeared to be independent of reactive oxygen species production, but in the case of metal-containing compounds it is prevented by the thiol donor N-acetylcysteine. In contrast, CORM-A1 was bacteriostatic rather than bactericidal in vitro eliciting only a moderate and transient decrease in O2 consumption. Innovation: None of the tested CO-RMs was toxic to murine macrophages or human fibroblasts at the concentration impairing PA01 growth but only ruthenium-containing CO-RMs showed potential therapeutic properties by increasing the survival of mice infected with PA01. Conclusion: CO carriers inhibit bacterial growth and O2 consumption in vitro, but transition metal carbonyls appear more powerful than compounds spontaneously liberating CO. The nature of the metal in CO-RMs also modulates the anti-bacterial effect, with ruthenium-based CO-RMs being efficacious both in vitro and in vivo.

Use of metal carbonyl-based compounds capable of releasing carbon monoxide (CO) in biological systems have emerged as a potential adjunctive therapy for sepsis via their antioxidant, anti-inflammatory, and antiapoptotic effects. The role of CO in regulation of mitochondrial dysfunction and biogenesis associated with sepsis has not been investigated. In the present study, we employed a ruthenium-based water-soluble CO carrier, tricarbonylchoro(glycinato)ruthenium (II) (CORM-3), one of the novel CO-releasing molecules (CO-RMs), to test whether CO can improve cardiac mitochondrial dysfunction and survival in peritonitis-induced sepsis. Peritonitis was performed in mice by cecal ligation and perforation. Tumor necrosis factor-alpha, interleukin-10, and nitrite/nitrate plasma levels were tested to evaluate the systemic inflammatory response. Functional mitochondrial studies included determination of membrane potential, respiration, and redox status. Oxidative stress was evaluated by measurements of mitochondrial hydrogen peroxide, carbonyl protein and GSH levels. Mitochondrial biogenesis was assessed by peroxisome proliferator-activated receptor gamma coactivator (PGC)-1alpha protein expression and mitochondrial DNA (mtDNA) copy number. The systemic inflammatory response elicited by peritonitis was accompanied by mitochondrial energetic metabolism deterioration and reduced PGC-1alpha protein expression. CORM-3 treatment in septic mice restored the deleterious effects of sepsis on mitochondrial membrane potential, respiratory control ratio, and energetics. It is interesting that administration of CORM-3 during sepsis elicited a mild oxidative stress response that stimulated mitochondrial biogenesis with PGC-1alpha protein expression and mtDNA copy number increases. Our results reveal that delivery of controlled amounts of CO dramatically reduced mortality in septic mice, indicating that CO-RMs could be used therapeutically to prevent organ dysfunction and death in sepsis.

Carbon monoxide-releasing molecules can counteract inflammatory responses. The aim of this study was to investigate whether tricarbonylchloro(glycinate)ruthenium (II) (CORM-3) is able to control the effector phase of experimental arthritis. Arthritis was induced in C57Black-6 mice by an intraperitoneal injection of serum from arthritic K/BxN mice. CORM-3 was administered intraperitoneally at 10 mg/kg/day (5 mg/kg twice a day) from days 0 to 10 and animals were sacrificed on day 11. Serum levels of osteocalcin and prostanoids were measured by enzyme-linked immunosorbent assay and radioimmunoassay. Gene expression was determined by real-time PCR. Histological analysis was performed and protein expression was examined by immunohistochemistry. Treatment with CORM-3 reduced the macroscopic score in hind paws, the migration of inflammatory cells and erosion of cartilage and bone. CORM-3 increased the levels of osteocalcin in the serum and reduced PGD2 levels, whereas PGE2 and 6-ketoPGF1alpha were not affected. In synovial tissues, we also observed a significant reduction in gene expression of interleukin-1beta, receptor activator of nuclear factor kappaB ligand (RANKL), matrix metalloproteinase (MMP)-9 and MMP-13. CORM-3 induced HO-1 expression in joint tissues but inhibited high mobility group box 1 (HMGB1), hematopoietic-prostaglandin D2 synthase (H-PGDS) and lipocalin-type prostaglandin D2 synthase (L-PGDS), as well as RANKL and intercellular adhesion molecule-1. COX-2 expression was not affected by CORM-3 treatment. We have shown that CORM-3 decreases the inflammatory response and protects against the degradation of cartilage and bone in the arthritic mice. Pharmacological CO delivery represents a novel strategy to regulate the effector phase of arthritis.

Carbon monoxide (CO) generated by the enzyme heme oxygenase during the breakdown of heme is known to mediate a number of biological effects. Here, we investigated whether CO liberated from a water-soluble CO-releasing molecule (CO-RM) is capable of modulating leukocyte-endothelial interactions. Tricarbonylchoro(glycinato)ruthenium (II) (CORM-3), a fast CO releaser, proved to be anti-inflammatory in two distinct models of acute inflammation in vivo. In both cases, a significant reduction in neutrophil extravasation was observed. Subsequent in vitro static experiments showed that CORM-3 produced a direct effect on neutrophil (polymorphonuclear neutrophil; PMN) adhesion molecule expression; dose-dependently inhibiting platelet-activating factor stimulated CD11b up-regulation and L-selectin shedding, whereas no effect was observed on up-regulation of human umbilical vein endothelial cell (HUVEC) adhesion molecules intercellular adhesion molecule-1 or E-selectin nor on interleukin-8 chemokine production. In addition, when PMN interaction with HUVECs was studied, an inhibitory effect of CORM-3 on cell capture and rolling was observed. The effect of CORM-3 on PMN CD11b expression was mimicked by the incubation of PMN with the selective large potassium channel opener 1,3-dihydro-1-(2-hydroxy-5-(trifluoromethyl)-phenyl)-5-(trifluoromethyl)-2H-benzimidazol-2-one (NS-1619), which suggests that CORM-3 actions in this instance are mediated, at least in part, via opening of this channel. In conclusion, we have reported that CORM-3 possesses acute anti-inflammatory effects in vivo and that these are probably the result of targeting PMN activation and rolling upon the endothelium.

Carbon monoxide-releasing molecules are emerging as a new class of pharmacological agents that regulate important cellular function by liberating CO in biological systems. Here, we examined the role of carbon monoxide-releasing molecule 3 (CORM-3) in modulating neuroinflammatory responses in BV-2 microglial cells, considering its practical application as a novel therapeutic alternative in the treatment of stroke. BV-2 microglia cells were incubated for 24 h in normoxic conditions with thrombin alone or in combination with interferon- to simulate the inflammatory response. Cells were also subjected to 12 h of hypoxia and reoxygenated for 24 h in the presence of thrombin and interferon-. In both set of experiments, the anti-inflammatory action of CORM-3 was evaluated by assessing its effect on nitric oxide production (nitrite levels) and tumor necrosis factor (TNF)-α release. CORM-3 (75 µM) did not show any cytotoxicity and markedly attenuated the inflammatory response to thrombin and interferon- in normoxia and to a lesser extent in hypoxia as evidenced by a reduction in nitrite levels and TNF-α production. Inactive CORM-3, which does not liberate CO and is used as a negative control, failed to prevent the increase in inflammatory mediators. Blockade of endogenous CO production by tin protoporphyrin-IX did not change the anti-inflammatory activity of CORM-3, suggesting that CO liberated from the compound is responsible for the observed effects. In addition, inhibition of the mitogen-activated protein kinases phosphatidyl inositol 3 kinase and extracellular signal-regulated kinase amplified the anti-inflammatory effect of CORM-3. These results suggest that the anti-inflammatory activity of CORM-3 could be exploited to mitigate microglia activity in stroke and other neuroinflammatory diseases.