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The short release half-life of carbon monoxide (CO) is a major obstacle to the effective therapeutic use of carbon monoxide-releasing molecule-2 (CORM-2). The potential of CORM-2-entrapped ultradeformable liposomes (CORM-2-UDLs) to enhance the release half-life of CO and alleviate skin inflammation was investigated in the present study. CORM-2-UDLs were prepared by using soy phosphatidylcholine to form lipid bilayers and Tween 80 as an edge activator. The deformability of CORM-2-UDLs was measured and compared with that of conventional liposomes by passing formulations through a filter device at a constant pressure. The release profile of CO from CORM-2-UDLs was evaluated by myoglobin assay. In vitro and in vivo anti-inflammatory effects of CORM-2-UDLs were assessed in lipopolysaccharide-stimulated macrophages and TPA-induced ear edema model, respectively. The deformability of the optimized CORM-2-UDLs was 2.3 times higher than conventional liposomes. CORM-2-UDLs significantly prolonged the release half-life of CO from 30 s in a CORM-2 solution to 21.6 min. CORM-2-UDLs demonstrated in vitro anti-inflammatory activity by decreasing nitrite production and pro-inflammatory cytokine levels. Furthermore, CORM-2-UDLs successfully ameliorated skin inflammation by reducing ear edema, pathological scores, neutrophil accumulation, and inflammatory cytokines expression. The results demonstrate that CORM-2-UDLs could be used as promising therapeutics against acute skin inflammation.

Toxic carbon monoxide in small concentrations has pro-apoptotic, anti-allergic, vasodilator effects, and stimulates angiogenesis. The problem with the therapeutic use of low doses of carbon monoxide is that it is difficult to dose. To control the amount and gradual release of carbon monoxide, non-toxic preparation is used - CO donor based on carbonyl compound of ruthenium (CORM-2). The aim – is to identify the effect of CORM-2 on the level of immunoglobulins in the blood serum and bone marrow of mice under conditions of inducing an immune response. Materials and methods. 3 groups of 15 white laboratory mice each were formed. Induction of the immune response was due to the intraperitoneal administration of xenogenic red blood cells. The first experimental group on the first day of immunization received CORM-2 (20 mg/kg), group No. 2 – on the 5th day after immunization (period of the productive phase). The control group consisted of immunized animals that did not receive CORM-2. The amount of IgA, IgM, and IgG in blood serum was determined by ELISA on the 2nd and 6th day after immunization. At the end of the experiment, bone marrow cell populations were counted. Results. After the injection of CORM-2 during the induction phase of the immune response, it inhibits the production of immunoglobulins. In comparison with the control, the level of IgA and IgG is reduced, but the amount of IgM remains unchanged. In the bone marrow, the number of monocytes, erythroblasts, and normoblasts, as well as lymphoblasts and plasma cells, increased. At the same time, the number of myeloblasts, myelocytes, basophilic normoblasts, and megakaryocytes decreased. The use of CORM-2 during the productive phase caused a decrease in the level of IgM and IgG with a simultaneous increase in the level of IgA. The number of neutrophils, eosinophils, monocytes, polychromophilic and oxyphilic normoblasts, lymphocytes, and plasma cells in the bone marrow increased. However, the number of myeloblasts, promyelocytes, myelocytes, metamyelocytes, basophilic normoblasts, and megakaryocytes decreased. Conclusions. The impact of the CORM-2 on the inductive phase of the immune response leads to inhibition of the production of immunoglobulins. The injection of CORM-2 during the productive phase of the immune response decreased the level of IgM and IgG, but at the same time, an increase in the level of IgA was observed. After the injection of CORM-2, in the bone marrow, the number of monocytes, lymphocytes, and plasma cells increased. The results indicate that CORM-2 is able to modulate the immune response.

Carbon monoxide (CO)-releasing molecules (CORMs) are used to deliver CO, a biological ‘gasotransmitter’, in biological chemistry and biomedicine. CORMs kill bacteria in culture and in animal models, but are reportedly benign towards mammalian cells. CORM-2 (tricarbonyldichlororuthenium(II) dimer, Ru2Cl4(CO)6), the first widely used and commercially available CORM, displays numerous pharmacological, biochemical and microbiological activities, generally attributed to CO release. Here, we investigate the basis of its potent antibacterial activity against Escherichia coli and demonstrate, using three globin CO sensors, that CORM-2 releases negligible CO (Kd 3 μM; His, Kd 130 μM) as determined by 1H-NMR. Glutathione is proposed to be an important intracellular target of CORM-2, with CORM-2 having a much higher affinity for reduced glutathione (GSH) than oxidised glutathione (GSSG) (GSH, Kd 2 μM; GSSG, Kd 25,000 μM). The toxicity of low, but potent, levels (15 μM) of CORM-2 was accompanied by cell lysis, as judged by the release of cytoplasmic ATP pools. The biological effects of CORM-2 and related CORMs, and the design of biological experiments, must be re-examined in the light of these data.

Background/Aims: Carbon monoxide (CO) interferes with cytochrome-dependent cellular functions and acts as gaseous transmitter. CO is released from CO-releasing molecules (CORM) including tricarbonyl-dichlororuthenium (II) dimer (CORM-2), molecules considered for the treatment of several disorders including vascular dysfunction, inflammation, tissue ischemia and organ rejection. Cytochrome P450-sensitive function include formation of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) by renal 25-hydroxyvitamin D3 1-alpha-hydroxylase (Cyp27b1). The enzyme is regulated by PTH, FGF23 and klotho. 1,25(OH)2D3 regulates Ca2+ and phosphate transport as well as klotho expression. The present study explored, whether CORM-2 influences 1,25(OH)2D3 formation and klotho expression. Methods: Mice were treated with intravenous CORM-2 (20 mg/kg body weight). Plasma 1,25(OH)2D3 and FGF23 concentrations were determined by ELISA, phosphate, calcium and creatinine concentrations by colorimetric methods, transcript levels by quantitative RT-PCR and protein expression by western blotting. Fgf23 mRNA transcript levels were further determined in rat osteosarcoma UMR106 cells without or with prior treatment for 24 hours with 20 µM CORM-2. Results: CORM-2 injection within 24 hours significantly increased FGF23 plasma levels and decreased 1,25(OH)2D3 plasma levels, renal Cyp27b1 gene expression as well as renal klotho protein abundance and transcript levels. Moreover, treatment of UMR106 cells with CORM-2 significantly increased Fgf23 transcript levels. Conclusion: CO-releasing molecule CORM-2 enhances FGF23 expression and release and decreases klotho expression and 1,25(OH)2D3 synthesis.