title: Sulfite species enhance carbon monoxide release from CO-releasing molecules: implications for the deoxymyoglobin assay of activity.
abstract: Carbon monoxide-releasing molecules (CO-RMs) emulate the beneficial (e.g., anti-inflammatory) effects of CO in biology. CO release from CO-RMs is routinely determined in the presence of reduced deoxy-myoglobin by measuring the formation of carboxy-myoglobin (Mb-CO). Previous studies have highlighted discrepancies between the apparent CO release rates of some CO-RMs established using this assay versus other experimental data where a slower or more complex mechanism of release is suggested. It has been hypothesized that some CO-RMs require a CO acceptor, believed to be reduced myoglobin in Mb-CO assays, in order to facilitate the release of CO. Here, we show, for the first time, that CO is not liberated from the ruthenium (Ru)-based [Ru(CO)(3)Cl(2)](2) (CORM-2) and [Ru(CO)(3)Cl(glycinate)] (CORM-3) at an appreciable rate in the presence of reduced myoglobin alone. Rather, we confirm that it is the reducing agent sodium dithionite that facilitates release of CO from these CO-RMs. Other sulfite compounds, namely sodium sulfite and potassium metabisulfite, also promote the liberation of CO from CORM-3. We describe an alternative oxy-hemoglobin assay that eliminates dithionite and suggest that the efficacy of CO-RMs results from intracellular interactions with anions that facilitate CO delivery to therapeutic targets.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. s.mclean@sheffield.ac.uk
authors.forename: Samantha
authors.initials: S
authors.lastname: McLean
authors.forename: Brian E
authors.initials: BE
authors.lastname: Mann
authors.forename: Robert K
authors.initials: RK
authors.lastname: Poole
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000032:analysis* / Q000737:chemistry; D002384:Catalysis; D002417:Cattle; D004227:Dithionite / Q000737:chemistry; D009211:Myoglobin / Q000097:blood / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry*; D010108:Oxyhemoglobins / Q000737:chemistry*; D013447:Sulfites / Q000737:chemistry
chemical_list: D009211:Myoglobin; D009942:Organometallic Compounds; D010108:Oxyhemoglobins; D013447:Sulfites; C055547:deoxymyoglobin; C476530:tricarbonylchloro(glycinato)ruthenium(II); C447082:tricarbonyldichlororuthenium (II) dimer; D004227:Dithionite; C005199:potassium metabisulfite; D002248:Carbon Monoxide; C025026:sodium sulfite