title: Carbon monoxide-releasing molecules (CO-RMs) attenuate the inflammatory response elicited by lipopolysaccharide in RAW264.7 murine macrophages.
abstract: 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 anti-inflammatory 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. 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 microM) 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. 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. CORM-3 also considerably reduced the levels of tumor necrosis factor-alpha, another mediator of the inflammatory response. 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. 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.
authors.affiliation: Department of Surgical Research, Vascular Biology Unit, Northwick Park Institute for Medical Research, Harrow, Middlesex.
authors.forename: Philip
authors.initials: P
authors.lastname: Sawle
authors.forename: Roberta
authors.initials: R
authors.lastname: Foresti
authors.forename: Brian E
authors.initials: BE
authors.lastname: Mann
authors.forename: Tony R
authors.initials: TR
authors.lastname: Johnson
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Green
authors.forename: Roberto
authors.initials: R
authors.lastname: Motterlini
mesh_terms: D000818:Animals; D002248:Carbon Monoxide; D002460:Cell Line; D002470:Cell Survival; D005978:Glutathione / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D051547:Heme Oxygenase-1; D007249:Inflammation / Q000139:chemically induced / Q000517:prevention & control*; D008070:Lipopolysaccharides; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism*; D009942:Organometallic Compounds / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D008565:Membrane Proteins; D009573:Nitrites; D009942:Organometallic Compounds; D014409:Tumor Necrosis Factor-alpha; C476530:tricarbonylchloro(glycinato)ruthenium(II); C447082:tricarbonyldichlororuthenium (II) dimer; D002248:Carbon Monoxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D005978:Glutathione