Where Credit Is Due
Having published on the biology of hydrogen sulfide (H2S) since 1987, we believe that Rui Wang’s “Toxic Gas, Lifesaver” had substantial factual inaccuracies and omissions. Studies by our group from as early as 1987 had already described some of the neurochemical effects of NaHS, an H2S precursor. By 1990 we had reported the presence of detectable endogenous levels of H2S in tissue and discussed the possibility that chronic exposure to sublethal concentrations of NaHS may have biological effects, including the regulation of amino acid neurotransmitter levels. At that time, we had already raised the possibility of neuroprotection by H2S. Wang was certainly aware of this work, because he cited several of these papers in a review he wrote in 2002. At about the time, another group, led by Sheldon Roth of the University of Calgary, was also studying the effects of H2S on the respiratory system.
Samuel B. Kombian
Faculty of Pharmacy, Kuwait University
William F. Colmers
Professor of pharmacology, University of Alberta
Wang suggests that he started the H2S studies based on his own ideas, which is simply not true. In 1996 Kazuho Abe and I had already published the first paper on the positive biological effects of H2S and demonstrated that cystathionine beta-synthase can produce H2S from cysteine in the brain and that H2S facilitates the induction of hippocampal long-term potentiation by enhancing receptor activity.
Wang also claims that “we decided to look at an enzyme called cystathionine gamma-lyase (CSE) ... no one knew whether CSE existed in blood vessels.” In 1997 Rumiko Hosoki, Norio Matsuki and I had already published our second paper on H2S, in which we demonstrated that CSE is expressed in the thoracic aorta, the ileum and the portal vein and produces H2S from cysteine. We also showed that H2S relaxes these smooth muscles. Wang knew about this work, because he cited our papers in 2001—four years after ours.
National Institute of Neuroscience, Tokyo
WANG REPLIES: My article was not intended to be a complete academic chronicle of the discovery of the biological effects of H2S. Many important milestones were not mentioned, but I by no means meant to deny or disregard these contributions, including those of Kimura. Bearing in mind the severe space constraints and general audience of Scientific American, I described how my personal interest in this topic evolved, and the article truthfully reflected that. Nevertheless, some important descriptions were lost during the editing process. For example, shortly before the article went to press, I specifically corrected the text to say [revision in bold], “Some earlier studies by Hideo Kimura in Japan suggested that H2S is a neuromodulator, making neural circuits more or less responsive to stimuli.” Unfortunately, I was told that there was no space for the change to be made.
As to Kimura’s concern about the statement regarding the presence of CSE in blood vessels, in a revision sent to my editor, I wrote, “But no one knew whether the same CSE existed in blood vessels. Sure enough, we found the enzyme there and cloned it.” These words in bold are important for stating our unique contribution, but they were omitted from the text because of a misunderstanding between the editor and me. Indeed, Kimura and his colleagues showed previously that H2S relaxes blood vessels, but that did not prevent us or anyone else from reasoning that H2S might have a similar effect to nitric oxide.