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

The effects of CORM3 or NaHS on the oxidative stress caused by chronic kidney disease in rats: potential interaction between CO and H2S signaling pathway

Neurotoxicity is implicated as a severe complication of chronic kidney disease (CKD). Accumulation of urea and other toxic compounds leads to oxidative stress, inflammation and destruction of the blood-brain barrier. Carbon monoxide (CO) and hydrogen sulfide (H2S) have been shown to have anti-inflammatory, anti-apoptotic, and anti-proliferative properties. The aims of the present study were evaluated the protective effects of CO-releasing molecule (CORM3) and H2S donor (NaHS) on oxidative stress and neuronal death induced by CKD in the hippocampus and prefrontal cortex by considering interaction between CO and H2S on CBS expression. CORM3 or NaHS significantly compensated deficits in the antioxidant defense mechanisms, suppressed lipid peroxidation and reduced neuronal death in hippocampus and prefrontal cortex and improvement the markers of renal injury that induced by CKD. In addition, CORM3 or NaHS significantly improved CBS expression which were reduced by CKD. However, improving effects of CORM3 on antioxidant defense mechanisms, lipid peroxidation, neuronal death, renal injury and CBS expression were prevented by amino-oxy acetic acid (AOAA) (CBS inhibitor) and reciprocally improving effects of NaHS on all above indices were prevented by zinc protoporphyrin IX (Znpp) (HO-1 inhibitor). In conclusion, this study demonstrated that formation of CO and H2S were interdependently improved CKD-induced oxidative stress and neuronal death, which is may be through increased expression of CBS.

Carbon Monoxide-Loaded Red Blood Cell Prevents the Onset of Cisplatin-Induced Acute Kidney Injury

Cisplatin-induced acute kidney injury (AKI) is an important factor that limits the clinical use of this drug for the treatment of malignancies. Oxidative stress and inflammation are considered to be the main causes of not only cisplatin-induced death of cancer cells but also cisplatin-induced AKI. Therefore, developing agents that exert antioxidant and anti-inflammatory effects without weakening the anti-tumor effects of cisplatin is highly desirable. Carbon monoxide (CO) has recently attracted interest due to its antioxidant, anti-inflammatory, and anti-tumor properties. Herein, we report that CO-loaded red blood cell (CO-RBC) exerts renoprotective effects on cisplatin-induced AKI. Cisplatin treatment was found to reduce cell viability in proximal tubular cells via oxidative stress and inflammation. Cisplatin-induced cytotoxicity, however, was suppressed by the CO-RBC treatment. The intraperitoneal administration of cisplatin caused an elevation in the blood urea nitrogen and serum creatinine levels. The administration of CO-RBC significantly suppressed these elevations. Furthermore, the administration of CO-RBC also reduced the deterioration of renal histology and tubular cell injury through its antioxidant and anti-inflammatory effects in cisplatin-induced AKI mice. Thus, our data suggest that CO-RBC has the potential to substantially prevent the onset of cisplatin-induced AKI, which, in turn, may improve the usefulness of cisplatin-based chemotherapy.

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.

Prolonged hypothermic storage of oocytes of the European common frog Rana temporaria in a gas mixture of oxygen and carbon monoxide

The maximum hypothermic storage time of amphibian oocytes is several hours, which is due to the peculiarities of the structure of the cell envelope. The authors of this paper have already demonstrated the possibility of increasing the storage period of unfertilized oocytes of the common frog (Rana temporaria) up to 5-7 days. The aim of the current study was to determine the possibility of using a 6.5 atm gaseous mixture of carbon monoxide and oxygen, for prolonged hypothermic preservation of unfertilized oocytes for 4 to 12 days. After four days, oocytes stored under CO+O2 conditions exhibited fertilization and hatching rates that were 1.6 and 2.2-fold higher than control, respectively. While no oocytes in the control group survived to day twelve, oocytes held under CO +O2 gas exhibited a 39±14% (38 out of 99 oocytes in total) fertilization rate, however only 1±2% (1/99) of those hatched. This approach is promising for the storage of genetic material from female amphibians, particularly in respect to managing and restoring endangered species, but may also be applicable to oocytes of other classes of vertebrates.

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.

Precise Identification of the Dimethyl Sulfoxide Triggered Tricarbonyldichlororuthenium(II) Dimer for Releasing CO

Low concentrations of carbon monoxide (CO) can play vital roles in pharmacological and physiological functions in the human body. The transition-metal carbonyl complexes of the tricarbonyldichlororuthenium(II) dimer [Ru₂(CO)₆Cl₄ (CORM-2)] were proposed as CO-releasing molecules (CORMs) to improve the delivery efficiency of CO for therapeutic effects. The accurate identification of final products for CORMs in solution and the detailed mechanisms of the release of CO were the essential prerequisite for its effective physiological application, which have been deficient. In this study, utilizing the cutting-edge two-dimensional (2D) IR spectroscopy, with the intrinsic vibrational modes and the coupling information on dynamics of intramolecular vibrational energy redistribution (IVR), the final products of A, B, C, and E are accurately identified when CORM-2 is dissolved in dimethyl sulfoxide (DMSO). Furthermore, with the clues on intermolecular interaction and chemical exchange dynamics between different products, the transformations between different products are also directly characterized for the first time. These findings challenge the results from the classic 1D spectroscopic pattern, and they evidently demonstrated that the release of CO from CORM-2 in DMSO was slow and complicated with multiple reaction pathways. Combining with DFT simulations, the detailed mechanisms of release of CO for CORM-2 dissolved in DMSO are schematically proposed, which can significantly contribute to its drug optimization and pharmacological as well as physiological applications.

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

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

Dual Acting Carbon Monoxide Releasing Molecules and Carbonic Anhydrase Inhibitors Differentially Modulate Inflammation in Human Tenocytes

Sustained oxidative stress and inflammation have been reported as the major factors responsible for the failure of tendon healing during rotator cuff tears (RCTs) and rotator cuff disease (RCD). Although, their therapeutic management remains still challenging. Carbonic anhydrases (CAs) are involved in many pathological conditions, and the overexpression of both CA9 and 12 in inflamed joints has been recently reported. Consequently, a selective CA9/12 inhibition could be a feasible strategy for improving tendon recovery after injury. In addition, since carbon monoxide (CO) has been proven to have an important role in modulating inflammation, CO releasing molecules (CORMs) can be also potentially suitable compounds. The present study aims at evaluating five newly synthesized dual-mode acting CA inhibitors (CAIs)-CORMs compounds, belonging to two chemical scaffolds, on tendon-derived human primary cells under H₂O₂ stimulation in comparison with Meloxicam. Our results show that compounds 2 and 7 are the most promising of the series in counteracting oxidative stress-induced cytotoxicity and display a better profile in terms of enhanced viability, decreased LDH release, and augmented tenocyte proliferation compared to Meloxicam. Moreover, compound 7, as a potent superoxide scavenger, exerts its action inhibiting NF-ĸB translocation and downregulating iNOS, whereas compound 2 is more effective in increasing collagen I deposition. Taken together, our data highlight a potential role of CA in RCTs and RCD and the prospective effectiveness of compounds acting as CAI-CORM during inflammation.