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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

Ph.D. Defense

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

PLACE: Olin 103

All interested persons are cordially invited to attend.


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-.

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