Immunomodulatory effects of HYCO-3, a dual action CO-releaser/Nrf2 activator

HYCOs are hybrid molecules consisting of activators of the transcription factor Nrf2 conjugated to carbon monoxide (CO)-releasing moieties. These 'dual action' compounds (HYCOs) have been designed to mimic the activity of heme oxygenase-1 (HO-1), a stress inducible cytoprotective enzyme that degrades heme to CO which expression is regulated by Nrf2. HYCOs have recently shown efficacy in ameliorating experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. However, the mechanism(s) of action of HYCOs still remains to be fully investigated. Here, we assessed the effects of HYCO-3, a prototype of these hybrids, on myeloid-derived cells, microglial cells and T lymphocytes obtained from EAE-immunized mice. HYCO-3 exerted immunomodulatory effects on all the examined cell populations by inhibiting the generation of pro-inflammatory cytokines and nitric oxide, and downregulating antigen-presenting capacity of these cells. The observed effects support the view that HYCOs are promising candidates to be developed for the treatment of autoimmune and chronic inflammatory disorders.