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Inorganic Reactive Sulfur-Nitrogen Species: Intricate Release Mechanisms or Cacophony in Yellow, Blue and Red?

View Article: PubMed Central - PubMed

ABSTRACT

Since the heydays of Reactive Sulfur Species (RSS) research during the first decade of the Millennium, numerous sulfur species involved in cellular regulation and signalling have been discovered. Yet despite the general predominance of organic species in organisms, recent years have also seen the emergence of inorganic reactive sulfur species, ranging from inorganic polysulfides (HSx−/Sx2−) to thionitrous acid (HSNO) and nitrosopersulfide (SSNO−). These inorganic species engage in a complex interplay of reactions in vitro and possibly also in vivo. Employing a combination of spectrophotometry and sulfide assays, we have investigated the role of polysulfanes from garlic during the release of nitric oxide (•NO) from S-nitrosoglutathione (GSNO) in the absence and presence of thiol reducing agents. Our studies reveal a distinct enhancement of GSNO decomposition by compounds such as diallyltrisulfane, which is most pronounced in the presence of cysteine and glutathione and presumably proceeds via the initial release of an inorganic mono- or polysulfides, i.e., hydrogen sulfide (H2S) or HSx−, from the organic polysulfane. Albeit being of a preliminary nature, our spectrophotometric data also reveals a complicated underlying mechanism which appears to involve transient species such as SSNO−. Eventually, more in depth studies are required to further explore the underlying chemistry and wider biological and nutritional implications of this interplay between edible garlic compounds, reductive activation, inorganic polysulfides and their interplay with •NO storage and release.

No MeSH data available.


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(A) Time resolved absorption spectra of 200 µM GSNO (dashed line) and after addition of 200 µM DATS and 800 µM Cys (spectra were recorded every 30 s); (B) Absorption spectrum of 200 µM GSNO (solid line); 2 mM H2S (prepared from Na2S·9 H2O, long-dashed line); 2 mM DTT (short-dashed line); spectrum of the mixture of 200 µM GSNO with 2 mM H2S after 5 min of their interaction (dash-dotted line) and spectrum of the same mixture treated 10 min with 2 mM DTT (dotted line).
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antioxidants-06-00014-f002: (A) Time resolved absorption spectra of 200 µM GSNO (dashed line) and after addition of 200 µM DATS and 800 µM Cys (spectra were recorded every 30 s); (B) Absorption spectrum of 200 µM GSNO (solid line); 2 mM H2S (prepared from Na2S·9 H2O, long-dashed line); 2 mM DTT (short-dashed line); spectrum of the mixture of 200 µM GSNO with 2 mM H2S after 5 min of their interaction (dash-dotted line) and spectrum of the same mixture treated 10 min with 2 mM DTT (dotted line).

Mentions: Figure 2A represents time-resolved absorption spectra indicative of the interaction of diallyltrisulfane (DATS) with GSNO and Cys. Based on the typical spectra of GSNO itself or its interaction with excess of sulfide (Figure 2B), we decided to investigate the spectral changes at 270, 334 and 412 nm, which were assigned to the formation of inorganic polysulfides or organic hydroper- and polysulfides (270 nm), decomposition of GSNO (334 nm, ʎmax(GSNO)) and formation of the nitrosopersulfide (perthionitrite, SSNO−) anion (a rather colourful yellow species with ʎmax at 412 nm) [10,13,14]. It should be mentioned that inorganic per- and polysulfides, as sulfane-sulfur species, show a typical broad absorption spectrum in the range of 260–420 nm (as reported in the literature, e.g., [15]). We intentionally chose 270 nm due to an absorption minimum of GSNO at that wavelength. It should also be noted that also other possible interaction products may contribute to this absorption signal, still we presume that changes at this specific wavelength primarily reflect the formation of inorganic polysulfides or organic hydroper- and polysulfides. Here, our assumption is based on a comparable absorbance of SSNO− at 270 nm and 412 nm (Figure 2B—dotted line, experiment with dithiothreitol (DTT)) and on the fact that in our experiments the absorbance at 412 nm is significantly smaller when compared to the absorbance at 270 nm (~0.01 vs. ~0.06). We have also performed spectral corrections to the light scattering of the DATS sample (A510 nm), the contribution of absorbance of polysulfides at 334 nm and the GSNO absorbance at 412 nm. Eventually, kinetic traces at 270 nm reflect the changes of absorbance at this wavelength after addition of Cys to the mixture of GSNO plus organic polysulfanes, kinetic traces at 334 nm reflect changes due to GSNO decomposition and kinetic traces at 412 nm indicate the predicted absorbance of SSNO− formed during the reaction.


Inorganic Reactive Sulfur-Nitrogen Species: Intricate Release Mechanisms or Cacophony in Yellow, Blue and Red?
(A) Time resolved absorption spectra of 200 µM GSNO (dashed line) and after addition of 200 µM DATS and 800 µM Cys (spectra were recorded every 30 s); (B) Absorption spectrum of 200 µM GSNO (solid line); 2 mM H2S (prepared from Na2S·9 H2O, long-dashed line); 2 mM DTT (short-dashed line); spectrum of the mixture of 200 µM GSNO with 2 mM H2S after 5 min of their interaction (dash-dotted line) and spectrum of the same mixture treated 10 min with 2 mM DTT (dotted line).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384177&req=5

antioxidants-06-00014-f002: (A) Time resolved absorption spectra of 200 µM GSNO (dashed line) and after addition of 200 µM DATS and 800 µM Cys (spectra were recorded every 30 s); (B) Absorption spectrum of 200 µM GSNO (solid line); 2 mM H2S (prepared from Na2S·9 H2O, long-dashed line); 2 mM DTT (short-dashed line); spectrum of the mixture of 200 µM GSNO with 2 mM H2S after 5 min of their interaction (dash-dotted line) and spectrum of the same mixture treated 10 min with 2 mM DTT (dotted line).
Mentions: Figure 2A represents time-resolved absorption spectra indicative of the interaction of diallyltrisulfane (DATS) with GSNO and Cys. Based on the typical spectra of GSNO itself or its interaction with excess of sulfide (Figure 2B), we decided to investigate the spectral changes at 270, 334 and 412 nm, which were assigned to the formation of inorganic polysulfides or organic hydroper- and polysulfides (270 nm), decomposition of GSNO (334 nm, ʎmax(GSNO)) and formation of the nitrosopersulfide (perthionitrite, SSNO−) anion (a rather colourful yellow species with ʎmax at 412 nm) [10,13,14]. It should be mentioned that inorganic per- and polysulfides, as sulfane-sulfur species, show a typical broad absorption spectrum in the range of 260–420 nm (as reported in the literature, e.g., [15]). We intentionally chose 270 nm due to an absorption minimum of GSNO at that wavelength. It should also be noted that also other possible interaction products may contribute to this absorption signal, still we presume that changes at this specific wavelength primarily reflect the formation of inorganic polysulfides or organic hydroper- and polysulfides. Here, our assumption is based on a comparable absorbance of SSNO− at 270 nm and 412 nm (Figure 2B—dotted line, experiment with dithiothreitol (DTT)) and on the fact that in our experiments the absorbance at 412 nm is significantly smaller when compared to the absorbance at 270 nm (~0.01 vs. ~0.06). We have also performed spectral corrections to the light scattering of the DATS sample (A510 nm), the contribution of absorbance of polysulfides at 334 nm and the GSNO absorbance at 412 nm. Eventually, kinetic traces at 270 nm reflect the changes of absorbance at this wavelength after addition of Cys to the mixture of GSNO plus organic polysulfanes, kinetic traces at 334 nm reflect changes due to GSNO decomposition and kinetic traces at 412 nm indicate the predicted absorbance of SSNO− formed during the reaction.

View Article: PubMed Central - PubMed

ABSTRACT

Since the heydays of Reactive Sulfur Species (RSS) research during the first decade of the Millennium, numerous sulfur species involved in cellular regulation and signalling have been discovered. Yet despite the general predominance of organic species in organisms, recent years have also seen the emergence of inorganic reactive sulfur species, ranging from inorganic polysulfides (HSx−/Sx2−) to thionitrous acid (HSNO) and nitrosopersulfide (SSNO−). These inorganic species engage in a complex interplay of reactions in vitro and possibly also in vivo. Employing a combination of spectrophotometry and sulfide assays, we have investigated the role of polysulfanes from garlic during the release of nitric oxide (•NO) from S-nitrosoglutathione (GSNO) in the absence and presence of thiol reducing agents. Our studies reveal a distinct enhancement of GSNO decomposition by compounds such as diallyltrisulfane, which is most pronounced in the presence of cysteine and glutathione and presumably proceeds via the initial release of an inorganic mono- or polysulfides, i.e., hydrogen sulfide (H2S) or HSx−, from the organic polysulfane. Albeit being of a preliminary nature, our spectrophotometric data also reveals a complicated underlying mechanism which appears to involve transient species such as SSNO−. Eventually, more in depth studies are required to further explore the underlying chemistry and wider biological and nutritional implications of this interplay between edible garlic compounds, reductive activation, inorganic polysulfides and their interplay with •NO storage and release.

No MeSH data available.


Related in: MedlinePlus