Thiol catalyzed NO-ferro-heme signaling

Nitric oxide (NO) is an endogenously produced signaling molecule that regulates blood flow and platelet activation. However, intracellular and intravascular diffusion of NO are severely limited by scavenging reactions with hemoglobin, myoglobin, and other hemoproteins, raising unanswered questions as to how free NO can signal in hemoprotein-rich environments. We explored the hypothesis that NO could be stabilized as a ferrous heme-nitrosyl complex (Fe2+-NO, NO-ferroheme. Unexpectedly, we observed a rapid reaction of NO with labile ferric heme (Fe3+) and a reduced thiol to yield NO-ferroheme and a thiyl radical. This thiol-catalyzed reductive nitrosylation reaction occurs readily when hemin is solubilized in lipophilic environments, such as red blood cell membranes or bound to serum albumin. The resulting NO-ferroheme is stable, even in the presence of oxyhemoglobin, and potently inhibits platelet activation. NO-ferroheme albumin administered intravenously to mice results in dose-dependent vasodilation at low- to mid-nanomolar concentrations. In conclusion, we report the fastest rate of reductive nitrosylation observed to date to generate a NO-ferroheme molecule that resists oxidative inactivation, is soluble in cell membranes, and is transported intravascularly by albumin to promote potent vasodilation.Almost all data is in Excel and can also be opened with Google Sheets. There are a few JPEG image files.Funding provided by: National Heart, Lung, and Blood InstituteCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000050Award Number: R01 HL125886Funding provided by: National Heart, Lung, and Blood InstituteCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000050Award Number: R01 HL098032Funding provided by: National Heart, Lung, and Blood InstituteCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000050Award Number: K08 HL136857Funding provided by: U.S. Department of DefenseCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000005Award Number: W81XWH2210198Methods are described in the paper and preprint