A carbon monoxide-releasing molecule (CORM-3) attenuates lipopolysaccharide- and interferon- -induced inflammation in microglia

The development of carbon monoxide-releasing molecules (CO-RMs) in recent years helped to shed more light on the diverse range of anti-inflammatory and cytoprotective activities of CO gas. In this study, we examined the effect of a ruthenium-based water-soluble CO carrier (CORM-3) on lipopolysaccharide (LPS)and interferon(INF)-induced inflammatory responses in BV-2 microglial cells and explored the possible mechanisms of action. BV-2 microglial cells were stimulated with either LPS or INFin the presence of CORM-3 and the inflammatory response evaluated by assessing the effect on nitric oxide production (nitrite levels) and tumor necrosis factor(TNF) release. Similar experiments were also performed in the presence of inhibitors of guanylate cyclase (ODQ), NO synthase (L-NAME), heme oxygenase activity (tin protoporphyrin IX) or various mitogen-activated protein kinase (MAPK) inhibitors. CORM-3 significantly attenuated the inflammatory response to LPS and INFas evidenced by a significant reduction (p < 0.001) in nitrite levels and TNFproduction (P < 0.05). Such effect was maintained in the presence of ODQ, L-NAME or tin protoporphyrin without showing any cytotoxicity. The use of an inactive form of CORM-3 that does not contain carbonyl groups (Ru(DMSO) Cl ) failed to inhibit the increase in inflammatory markers suggesting that liberated CO mediates the observed effects. In addition, inhibition of phosphatidylinositol-3-phosphate kinase (PI3K) and extracellular signal-regulated kinase (ERK) pathways seemed to amplify the anti-inflammatory effect of CORM-3, particularly in cells stimulated with INF. These results suggest that the anti-inflammatory action of CORM-3 could be exploited to mitigate microglia activation in neuro-inflammatory diseases.