No abstract

1 The enzyme heme oxygenase-1 (HO-1) is a cytoprotective and anti-inflammatory protein that degrades heme to produce biliverdin/bilirubin, ferrous iron and carbon monoxide (CO). The antiinflammatory properties of HO-1 are related to inhibition of adhesion molecule expression and reduction of oxidative stress, while exogenous CO gas treatment decreases the production of inflammatory mediators such as cytokines and nitric oxide (NO). CO-releasing molecules (CO-RMs) are a novel group of substances identified by our group that are capable of modulating physiological functions via the liberation of CO. We aimed in this study to examine the potential anti-inflammatory characteristics of CORM-2 and CORM-3 in an in vitro model of lipopolysaccharide (LPS)-stimulated murine macrophages. 2 Stimulation of RAW264.7 macrophages with LPS resulted in increased expression of inducible NO synthase (iNOS) and production of nitrite. CORM-2 or CORM-3 (10-100 mM) reduced nitrite generation in a concentration-dependent manner but did not affect the protein levels of iNOS. CORM-3 also decreased nitrite levels when added 3 or 6 h after LPS exposure. 3 CORM-2 or CORM-3 did not cause any evident cytotoxicity and produced an increase in HO-1 expression and heme oxygenase activity; this effect was completely prevented by the thiol donor N-acetylcysteine. 4 CORM-3 also considerably reduced the levels of tumor necrosis factor-a, another mediator of the inflammatory response. 5 The inhibitory effects of CORM-2 and CORM-3 were not observed when the inactive compounds, which do not release CO, were coincubated with LPS. 6 These results indicate that CO liberated by CORM-2 and CORM-3 significantly suppresses the inflammatory response elicited by LPS in cultured macrophages and suggest that CO carriers can be used as an effective strategy to modulate inflammation.

The deoxy-myoglobin (deoxy-Mb)/carbonmonoxy-myoglobin (Mb-CO) UV-vis assay is the principal method used for quantifying the rates of CO release from CO-releasing molecules (CO-RMs) that might possess therapeutic benefits. Some issues emerge when the Mb-CO assay is utilized for testing CO-RMs with novel structures, which are comprehensively discussed here for the first time. Two methods for processing raw UV-vis spectroscopic data generated from the assay are presented in this paper.

[Mn(CO)(4){S(2)CNMe(CH(2)CO(2)H)}], 1, 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.

CORM-3 promotes neuroprotection or neurotoxicity after intracerebral hemorrhage depending on the time of administration. Beneficial effects are achieved when CORM-3 is given either before or 3 days after intracerebral hemorrhage, namely, as a prophylactic agent or during the postacute inflammatory phase.