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A Case of Mistaken Identity: Are Reactive Oxygen Species Actually Reactive Sulfide Species?
Author(s) -
Olson Kenneth R,
Gao Yan,
Huang Evelyn,
Arif Maaz,
Arora Nitin,
Divietro Alexander,
Patel Shivali,
Deleon Eric R
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.742.13
Subject(s) - reactive oxygen species , chemistry , hydrogen peroxide , superoxide , oxygen , photochemistry , redox , rss , biochemistry , enzyme , inorganic chemistry , organic chemistry , computer science , operating system
Stepwise one‐electron reduction of oxygen to water produces reactive oxygen species (ROS), namely peroxide (H 2 O 2 ), superoxide (O 2 .− ) and the hydroxyl radical (HO .− ). These are chemically and biochemically similar to reactive sulfide species (RSS) that are derived from one‐electron oxidation of hydrogen sulfide (H 2 S) to elemental sulfur, namely persulfide (H 2 S 2 ), “supersulfide” (S 2 .− ) and the thiyl radical (HS .− ). H 2 S is also reactive and can act as a RSS. Both ROS and RSS are endogenously generated, signal via reactive protein thiols and have common effector targets. Given these similarities, we hypothesized that extant methods for measuring the former would also detect the latter. Here we compared the sensitivity of five methods commonly employed for measuring ROS to both ROS (H 2 O 2 and superoxide as KO 2 ), and to RSS (H 2 S, H 2 S n where n=2–8, H 2 S 2 , H 2 S 3 and H 2 S 4 . The methods examined were redox‐sensitive green fluorescent protein (roGFP), 2′, 7′‐dihydrodichlorofluorescein (DCF), MitoSox Red, Amplex Red and H 2 O 2 amperometric electrodes. All methods detected RSS and were as or more sensitive to RSS than they were to ROS. roGFP, arguably the “gold standard” for ROS measurement, was over two‐hundred fold more sensitive to H 2 S n (n=2–8) than H 2 O 2 . Likewise, ROS and RSS produced dose‐dependent increases in 10 ìM DCF fluorescence, with high (1, 3 mM) H 2 S giving the most rapid increase in DCF fluorescence. H 2 O 2 and H 2 S were essentially equipotent, whereas KO 2 was considerably less efficacious. Lastly, amperometric H 2 O 2 sensors were nearly 30 times more sensitive to H 2 S than to H 2 O 2 and two or three times more sensitive to H 2 S 2 , H 2 S 3 and H 2 S 4 than to H 2 O 2 . The responses of roGFP and DCF to RSS were not diminished by hypoxia (Po 2 <4 mmHg) which indicates that they did not involve ROS generation from RSS. The estimated daily production of RSS by cysteine catabolism is similar to estimated ROS production from oxygen consumption, but may exceed it if ROS production is overestimated due to RSS interference. These findings suggest that RSS are far more prevalent in intracellular signaling than previously appreciated and that the contribution of ROS may be overestimated. This conclusion is further supported by the fact that both RSS and antioxidant mechanisms have been present since the origin of life nearly 4 billion years ago, long before the rise in environmental oxygen 600 million years ago. Although ROS are assumed to be the most biologically relevant oxidants, our results question this paradigm. We also anticipate our findings will direct attention toward development of novel and clinically relevant anti‐(RSS)‐oxidants. Support or Funding Information NSF IOS‐144‐6310 (KRO), NSF GRFP DGE‐131‐3583 (ERD)