WFU Physics Colloquium

TITLE: Interaction between RSNO and H₂S: The formation, stability, and NO-donating capacity of SSNO* and the effects of SSNO* on platelet activation

SPEAKER: Crystal Bolden

TIME: Thursday April 27, 2017 at 9:00 AM

PLACE: Olin 103

H₂S is an gaseous mediator that has its own beneficial effects on vascular physiology. It has been implicated in the modulation of cellular processes including vessel tone/constriction, blood pressure, and tissue reperfusion. When S-nitrosothiols (RSNOs) react with excess H₂S, they form several intermediates including the soluble guanylate cyclase (sGC) activating nitrosopersulfide (SSNO^-). However, the stability and reactivity of this intermediate remained under debate, and hence, the relevance of nitric oxide (NO) and HS^- reactions had not been established. With novel and confirmatory data, my work has demonstrated the capacity of SSNO^- to donate NO and the mechanism by which it does so. I have shown that SSNO^- has a half-life in anaerobic and aqueous conditions of 40 minutes. I employed UV/visible spectroscopy, electron paramagnetic resonance (EPR), and took advantage of the redox reactivity of liganded hemoglobin under aerobic and anaerobic conditions, to determine that SSNO^- spontaneously releases very little NO upon decomposition. Using the selectivity of ferricatalase, I have also shown that nitroxyl (HNO) release from SSNO^- decomposition is unlikely. However, I have determined that NO is acquired from SSNO^- in the presence of vacant heme. Indeed, our data shows that a vacant heme is necessary to acquire NO from SSNO^-, which indicates a direct heme-SSNO^- reaction. SSNO^- reacts with ferrous and ferri-hemes, but more efficiently with ferrihemoglobin (metHb). I have further demonstrated the stability of SSNO- in platelet-rich plasma, in which, the inhibition of platelet activation in platelets treated with SSNO^- is comparable to those treated with S-nitrosoglutathione (GSNO). Lastly, I have also employed chemiluminescence to quantify nitrite in the evaluation of the relationship between basal oral and plasma NO₂^- and NO₃^- as well as ex vivo NO₃^- reduction in saliva with in vivo changes in plasma NO₂^-. We found that salivary NO₂^- and NO₃^- are correlated, while plasma NO₂^- and salivary NO₂^- are not correlated. Plasma NO₃- was correlated with salivary NO₂^- and NO₃^-. Finally, there was no correlation between ex vivo NO₃^- reduction and in vivo changes in plasma NO₂^-.