A multifunctional and ROS response CO-gas delivery platform for spinal cord regeneration.

Photo-induced eradication of human colorectal adenocarcinoma HT-29 cells by carbon monoxide (CO) delivery from a Mn-based green luminescent photoCORM

Investigating the Combined Toxicity of Cu(II) and Carbon Monoxide (CO); Cellular CO Delivery Using a Cu(II) Flavonolato Complex.

The pathophysiological roles of the endogenous signaling molecule, carbon monoxide (CO), have been extensively studied and validated in cell culture and animal models. Further, evidence supporting the therapeutic effects of CO in various human diseases has been mounting over the last two decades. Along this line, there has been intensive interest in developing various delivery forms including CO gas, CO in solution, metal–carbonyl complexes widely known as CO-releasing molecules (CO-RMs), and organic CO prodrugs. Among them, two ruthenium-based carbonyl complexes, CORM-2 and -3, occupy a very special place because they have been used in over 500 published studies. One of the mechanisms for CO's actions is known to be through attenuation of oxidative stress and regulation of production of reactive oxygen species (ROS). For this reason, it is important that CO delivery forms do not have intrinsic chemical redox properties. Herein, we describe our findings of catalase-like activities of CORM-2 and -3 in a CO-independent fashion, leading to the rapid degradation of hydrogen peroxide (H2O2) in PBS buffer (pH = 7.4) and in cell culture media. Further, we have found that CORM-2 and CORM-3 possess potent radical scavenging abilities. We have also studied two other widely used CO donors: CORM-401 and CORM-A1. Both showed chemical reactivity with ROS, but to a lesser degree than CORM-2 and -3. Because of the central role of ROS in some of the proposed mechanisms of actions for CO biology, the discovery of intrinsic chemical redox properties for these CO-RMs means that additional attention in designing proper controls is needed in future biological experiments using these CO-RMs for their CO-donating functions. Further, much more work is needed to understand the true implications of the chemical reactivity of these CO-RMs in cell-culture and animal-model studies of CO biology.

Carbon monoxide (CO) is widely known for its strong binding affinity to heme proteins and for its potential toxicity. This chapter examines the current landscape of targeted CO delivery using CO donors, including metal-based CORMs, organic CO prodrugs, and others that are sensitive to various stimuli. As a framework to consider targeted CO delivery, it starts with a summary of the endogenous production of CO by heme oxygenase enzymes, focusing on the subcellular and tissue localization of these enzymes. Subsequently described are the structural motifs associated with well-known molecular CO donors that have been used extensively in biological applications as well as emerging structural motifs that offer enhanced control for targeted CO delivery. Nanomaterial-based approaches for the delivery of gasotransmitters, including CO, are a very active field of research, with several recent reviews highlighting advancements in this area. Upconverting nanoparticles offer the possibility of using NIR illumination to trigger CO release in metal carbonyl complexes.

Carbon monoxide (CO) is a gaseous signaling molecule produced in humans via the breakdown of heme in an O2-dependent reaction catalyzed by heme oxygenase enzymes. A long-lived species relative to other signaling molecules (e.g., NO, H2S), CO exerts its physiological effects via binding to low-valent transition metal centers in proteins and enzymes. Studies involving the administration of low doses of CO have shown its potential as a therapeutic agent to produce vasodilation, anti-inflammatory, antiapoptotic, and anticancer effects. In pursuit of developing tools to define better the role and therapeutic potential of CO, carbon monoxide releasing molecules (CORMs) were developed. To date, the vast majority of reported CORMs have been metal carbonyl complexes, with the most well-known being Ru2Cl4(CO)6 (CORM-2), Ru(CO)3Cl(glycinate) (CORM-3), and Mn(CO)4(S2CNMe(CH2CO2H)) (CORM-401). These complexes have been used to probe the effects of CO in hundreds of cell- and animal-based experiments. However, through recent investigations, it has become evident that these reagents exhibit complicated reactivity in biological environments. The interpretation of the effects produced by some of these complexes is obscured by protein binding, such that their formulation is not clear, and by CO leakage and potential redox activity. An additional weakness with regard to CORM-2 and CORM-3 is that these compounds cannot be tracked via fluorescence. Therefore, it is unclear where or when CO release occurs, which confounds the interpretation of experiments using these molecules. To address these weaknesses, our research team has pioneered the development of metal-free CORMs based on structurally tunable extended flavonol or quinolone scaffolds. In addition to being highly controlled, with CO release only occurring upon triggering with visible light (photoCORMs), these CO donors are trackable via fluorescence prior to CO release in cellular environments and can be targeted to specific cellular locations.In the Account, we highlight the development and application of a series of structurally related flavonol photoCORMs that (1) sense characteristics of cellular environments prior to CO release; (2) enable evaluation of the influence of cytosolic versus mitochondrial-localized CO release on cellular bioenergetics; (3) probe the cytotoxicity and anti-inflammatory effects of intracellular versus extracellular CO delivery; and (4) demonstrate that albumin delivery of a photoCORM enables potent anticancer and anti-inflammatory effects. A key advantage of using triggered CO release compounds in these investigations is the ability to examine the effects of the molecular delivery vehicle in the absence and presence of localized CO release, thus providing insight into the independent contributions of CO. Overall, flavonol-based CO delivery molecules offer opportunities for triggerable, trackable, and targetable CO delivery that are unprecedented in terms of previously reported CORMs and, thus, offer significant potential for applications in biological systems.

Carbon monoxide releasing molecule-3 alleviates neuron death after spinal cord injury via inflammasome regulation.

Carbon monoxide (CO) is considered to be an important molecule-gasotransmitter involved in the regulation of the functional activity of plants, including in the processes of adaptation to stress factors. However, the associations of CO with other participants of signaling in the plant cells remain poorly studied. Using an inhibitory method, the role of different calcium pools in realization of the influence of hemin (carbon monoxide donor) on generation and neutralization of reactive oxygen species (ROS) in the root cells of wheat (Triticum aestivum L.) plantlets and their resistance to damaging heating (45°C, 10 min) was studied. The treatment of plantlets with 5 μM hemin caused a transient increase in the activity of extracellular peroxidase in roots and an increase in the generation of ROS with the maximum in 1.5–2 h after the beginning of treatment. The chelator of extracellular calcium EGTA and the inhibitor of inositol-1,4,5-phosphate formation neomycin, which reduces calcium influx into the cytosol from intracellular compartments, almost completely eliminated an increase in the activity of extracellular peroxidase caused by exogenous CO. At the same time, EGTA (completely) and neomycin (partially) leveled an increase in the content of hydrogen peroxide in the roots of plantlets occurring under the influence of CO donor. The treatment of plantlets with hemin also induced an increase in the activity of superoxide dismutase, catalase, and intracellular peroxidase in roots. Both calcium antagonists eliminated these effects. In the presence of EGTA and neomycin, there was also no positive effect of the treatment of hemin on the state of biomembranes and survival of plantlets after the damaging heating. It was concluded that both extracellular calcium and that deposited in intracellular compartments is involved in CO donor-induced increase in the formation of ROS, induction of the antioxidant system, and development of heat resistance of wheat plantlets.

Carbon monoxide (CO) is highly toxic and lethal to humans and animals because of its strong affinity for hemoglobin, while this "silent killer" is constantly generated in the body as a cell-signaling molecule of the gasotransmitter family in various pathological and physiological conditions. Up to now, designing fluorescent probes for real-time imaging of CO in living species is a continuous challenge due to background interference, light scattering, and photoactivation/photobleaching. Herein, a novel type of bioluminescence probe (allyl-luciferin) was synthesized and exploited to realize CO imaging with high signal-to-noise ratios. Based on Pd0-mediated Tsuji-Trost reaction, allyl-luciferin specifically reacted with CO to yield D-luciferin and thus generate a turn-on bioluminescence response, exhibiting high selectivity against bioactive small molecules such as reactive nitrogen, oxygen, and sulfur species. Furthermore, the new probe can be easily employed to detect exogenous CO in Huh7 cells and MDA-MB-231 cells, and CO production was enhanced greatly in these living cells after pretreatment with [Ru(CO)3Cl-(glycinate)] (CORM-3). Through the use of PdCl2-containing liposomes to improve poor membrane permeability of PdCl2, endogenous CO stimulated by heme was also seen clearly. In addition, the probe was successfully used to monitor exogenous and endogenous CO in nude mice. Overall, our data proved that the allyl-luciferin is a promising tool for exogenous and endogenous CO detection and imaging within living species. This is the first demonstration of bioluminescence imaging obtained by a probe for CO. We anticipate that the good imaging properties of allyl-luciferin presented in this study will provide a potentially powerful approach for illuminating CO functions in the future.

Styrene-maleic acid copolymer-encapsulated CORM2, a water-soluble carbon monoxide (CO) donor with a constant CO-releasing property, exhibits therapeutic potential for inflammatory bowel disease

“CO in a pill”: Towards oral delivery of carbon monoxide for therapeutic applications

Carbon monoxide (CO), a gasotransmitter, has gained attention as a potential therapeutic agent in cancer treatment. The precise and sustained release of CO is crucial for minimizing its toxicity and enhancing its therapeutic efficacy. We have developed a light-gated, microenvironment-responsive CO release platform for precise and sustained CO delivery. FeCO was used as the CO donor and integrated into the micelle core containing tertiary amine (TA) residues and a Pd-based photosensitizer (PdTPTBP). In the first stage, the H2O2 generated during light irradiation, in combination with GSH, triggers the release of CO and Fe2+ from FeCO. Subsequently, Fe2+ reacts with H2O2via a Fenton reaction, further promoting sustained CO release under dark conditions in the second stage. Light irradiation acts as a gating mechanism to achieve precise and sustained CO release. This CO delivery platform can be efficiently internalized by 4T1 tumor cells and, upon 630 nm light irradiation, releases CO intracellularly to induce ferroptosis. By synergistically disrupting mitochondrial function, it exhibits effective antitumor activity in 4T1 tumor-bearing mice.

Hemoxygenases play an important role in protecting cells from stressors and provide intracellular catabolism of heme-containing proteins. The activity of hemoxygenase is responsible for the formation of endogenous carbon mon-oxide (CO). In small amounts, CO is known to activate soluble guanylate cyclase, thus performing cytoprotective and anti-apoptotic functions. To date, CO donor compounds, which can be used as anti-inflammatory, anti-apoptotic drugs, are promising for studying their effects on the body. Their effects on the cardiovascular system deserve special attention. The aim of the study was to compare the effects of hemoxygenase inducer-1, gaseous CO and CO donor compound on the metabolism of the isolated heart under ischemia-reperfusion conditions. The effects of hemoxygen-ase inducer hemin, CO donor (CORM-2) and dissolved for 30 min with Krebs-Henseleit perfusion solution was inves-tigated in laboratory mice. Retrograde perfusion of isolated hearts (with perfusion-reperfusion periods) was per-formed to reveal the effect of the studied compounds on the heart. During perfusion we recorded cardiac electrogram, coronary volumetric velocity, determined the content of glucose, calcium, creatinine and aspartate aminotransferase (AST) in the solution drained from the heart, and determined the degree of ischemic damage. Stimulation of hemoxy-genase with hemin did not result in significant fluctuations in myocardial glucose intake during perfusion and early reperfusion, aspartate aminotransferase levels were not elevated during perfusion and early reperfusion, and the R-R interval was stable during perfusion and ischemia. However, at the end of reperfusion, there was myocardial calcium deposition and creatinine level increased. The degree of ischemic damage after reperfusion did not differ from con-trol. Perfusion solution from CO showed vasodilator effect, CORM-2 – vasoconstrictor effect. CO also resulted in Ca2+ deposition at the end of reperfusion. On the contrary, CORM-2 led to its release. CO decreased creatinine level in perfusion solution, while CORM-2 increased its level only at the beginning of reperfusion. CO and CORM-2 did not increase AST release. CO at the beginning of perfusion and during ischemia decreased the amplitude of the R wave-form, although it increased and shortened the R-R interval during reperfusion. CORM-2 lengthened the interval. CO and CORM-2 decreased the area of ischemic myocardial damage.

An ischemic area-targeting, peroxynitrite-responsive, biomimetic carbon monoxide nanogenerator for preventing myocardial ischemia-reperfusion injury

Carbon monoxide (CO) is a bioactive signalling molecule that is produced endogenously via the breakdown of heme. Beneficial health effects associated with the delivery of CO gas have spurred the development of CO-releasing molecules (CORMs) that can be used to provide specific amounts of the gas. In addition to their potential use as therapeutics, CORMs are needed to provide insight into the biological targets of CO. In this regard, light-activated CO-releasing molecules (photoCORMs), are valuable for examining the effects of localized CO release. Herein we examine luminescent CORMs and photoCORMs that have been reported for tracking CO delivery in cells. A variety of motifs are available that exhibit differing luminescence properties and cover a wide range of wavelengths. Trackable CO donors have been successfully applied to targeting CO delivery to mitochondria, thus demonstrating the feasibility of using such molecules in detailed investigations of the biological roles of CO.

Carbon monoxide (CO), previously considered a toxic waste product of heme catabolism, is emerging as an important gaseous molecule. In addition to its important role in neurotransmission, exogenous CO protects against vascular injury, transplant rejection, and acute lung injury. However, little is known regarding the precise signaling mechanisms of CO. We have recently shown that CO attenuates endothelial cell apoptosis during anoxia-reoxygenation injury by activating MKK3/p38alpha mitogen-activated protein kinase (MAPK) pathways. Our current study is the first to demonstrate that CO can differentially modulate STAT1 and STAT3 activation and, specifically, that STAT3 activation by CO is responsible for the anti-apoptotic effect in endothelial cells. In addition, we show that the anti-apoptotic effects of CO depend upon both phosphatidylinositol 3-kinase/Akt and p38 MAPK signaling pathways in endothelial cells, whereas previous reports have implicated only the MKK3/p38 MAPK pathway. Using chemical inhibitors and dominant negative constructs, we show that CO enhances STAT3 activation via phosphatidylinositol 3-kinase/Akt and p38 MAPK pathways with subsequent attenuation of Fas expression and caspase 3 activity. These data highlight the anti-apoptotic signaling mechanisms of CO and, importantly, delineate potential therapeutic strategies to prevent ischemia-reperfusion or anoxia-reoxygenation injury in the vasculature.