Experimental evidence suggests that nitric oxide (NO) and hydrogen sulfide (H 2 S) signaling pathways are intimately intertwined, with mutual attenuation or potentiation of biological responses in the cardiovascular system and elsewhere. The chemical basis of this interaction is elusive. Moreover, polysulfides recently emerged as potential mediators of H 2 S/sulfide signaling, but their biosynthesis and relationship to NO remain enigmatic. We sought to characterize the nature, chemical biology, and bioactivity of key reaction products formed in the NO/sulfide system. At physiological pH, we find that NO and sulfide form a network of cascading chemical reactions that generate radical intermediates as well as anionic and uncharged solutes, with accumulation of three major products: nitrosopersulfide (SSNO − ), polysulfides, and dinitrososulfite [N-nitrosohydroxylamine-N-sulfonate (SULFI/NO)], each with a distinct chemical biology and in vitro and in vivo bioactivity. SSNO − is resistant to thiols and cyanolysis, efficiently donates both sulfane sulfur and NO, and potently lowers blood pressure. Polysulfides are both intermediates and products of SSNO − synthesis/decomposition, and they also decrease blood pressure and enhance arterial compliance. SULFI/NO is a weak combined NO/nitroxyl donor that releases mainly N 2 O on decomposition; although it affects blood pressure only mildly, it markedly increases cardiac contractility, and formation of its precursor sulfite likely contributes to NO scavenging. Our results unveil an unexpectedly rich network of coupled chemical reactions between NO and H 2 S/sulfide, suggesting that the bioactivity of either transmitter is governed by concomitant formation of polysulfides and anionic S/N-hybrid species. This conceptual framework would seem to offer ample opportunities for the modulation of fundamental biological processes governed by redox switching and sulfur trafficking.sulfide | nitric oxide | nitroxyl | redox | gasotransmitter N itrogen and sulfur are essential for all known forms of life on Earth. Our planet's earliest atmosphere is likely to have contained only traces of O 2 but rather large amounts of hydrogen sulfide (H 2 S) (1). Indeed, sulfide may have supported life long before the emergence of O 2 and NO (2, 3).* This notion is consistent with a number of observations: H 2 S is essential for efficient abiotic amino acid generation as evidenced by the recent reanalysis of samples of Stanley Miller's original spark discharge experiments (4), sulfide is an efficient reductant in protometabolic reactions forming RNA, protein, and lipid precursors (5), and sulfide is both a bacterial and mitochondrial substrate (6), enabling even multicellular lifeforms to exist and reproduce under conditions of permanent anoxia (7). Thus, although eukaryotic cells may have originated from the symbiosis of sulfurreducing and -oxidizing lifeforms within a self-contained sulfur redox metabolome (8), sulfide may have been essential even earlier by providing the basic building blocks of ...

Lysine specific demethylase 1 (LSD1) plays a key role in the regulation of gene expression by removing the methyl groups from methylated Lys4 of histone H3 (H3K4). Here we report the identification of the first small-molecule LSD1-selective inhibitors. These inhibitors show in vivo H3K4-methylating activity and antiproliferative activity and should be useful as lead structures for anticancer drugs and as tools for studying the biological roles of LSD1.

Selective inhibitors of Jumonji domain-containing protein (JMJD) histone demethylases are candidate anticancer agents as well as potential tools for elucidating the biological functions of JMJDs. On the basis of the crystal structure of JMJD2A and a homology model of JMJD2C, we designed and prepared a series of hydroxamate analogues bearing a tertiary amine. Enzyme assays using JMJD2C, JMJD2A, and prolyl hydroxylases revealed that hydroxamate analogue 8 is a potent and selective JMJD2 inhibitor, showing 500-fold greater JMJD2C-inhibitory activity and more than 9100-fold greater JMJD2C-selectivity compared with the lead compound N-oxalylglycine 2. Compounds 17 and 18, prodrugs of compound 8, each showed synergistic growth inhibition of cancer cells in combination with an inhibitor of lysine-specific demethylase 1 (LSD1). These findings suggest that combination treatment with JMJD2 inhibitors and LSD1 inhibitors may represent a novel strategy for anticancer chemotherapy.

To find novel non-hydroxamate histone deacetylase (HDAC) inhibitors, a series of compounds modeled after suberoylanilide hydroxamic acid (SAHA) was designed and synthesized. In this series, compound 7, in which the hydroxamic acid of SAHA is replaced by a thiol, was found to be as potent as SAHA, and optimization of this series led to the identification of HDAC inhibitors more potent than SAHA. In cancer cell growth inhibition assay, S-isobutyryl derivative 51 showed strong activity, and its potency was comparable to that of SAHA. The cancer cell growth inhibitory activity was verified to be the result of histone hyperacetylation and subsequent induction of p21(WAF1/CIP1) by Western blot analysis. Kinetical enzyme assay and molecular modeling suggest the thiol formed by enzymatic hydrolysis within the cell interacts with the zinc ion in the active site of HDACs.

Selective inhibitors of human sirtuin 2 (SIRT2), a deacetylase, are candidate therapeutic agents for neurodegenerative diseases such as Parkinson's disease and Huntington's disease as well as potential tools for elucidating the biological functions of SIRT2. On the basis of homology models of SIRT1 and SIRT2, we designed and prepared a series of 2-anilinobenzamide analogues. Enzyme assays using recombinant SIRT1 and SIRT2 revealed that 3'-phenethyloxy-2-anilinobenzamide analogues such as 33a and 33i are potent and selective SIRT2 inhibitors, showing more than 3.5-fold greater SIRT2-inhibitory activity and more than 35-fold greater SIRT2-selectivity compared with AGK2 (3), a previously reported SIRT2-selective inhibitor. Compound 33a also induced a dose-dependent selective increase of α-tubulin acetylation in human colon cancer HCT116 cells, indicating selective inhibition of SIRT2 in the cells. These 3'-phenethyloxy-2-anilinobenzamide derivatives represent an entry into a new class of SIRT2-selective inhibitors.

No abstract

Spatiotemporally controllable nitric oxide (NO)-releasers allow us to analyze the physiological effects of NO, a gaseous mediator that modulates many biological signaling networks, and are also candidate chemotherapeutic agents. We designed and synthesized a blue-light-controllable NO releaser, named NOBL-1, which bears an N-nitrosoaminophenol moiety for NO release tethered to a BODIPY dye moiety for harvesting blue light. Photoinduced electron transfer from N-nitrosoaniline to the antenna moiety upon irradiation with relatively noncytotoxic blue light (470-500 nm) should result in NO release with formation of a stable quinone moiety. NO release from NOBL-1 was confirmed by ESR spin trapping and fluorescence detection. Spatially controlled NO release in cells was observed with DAR-4M AM, a fluorogenic NO probe. We also demonstrated temporally controlled vasodilation of rat aorta ex vivo by blue-light-induced NO release from NOBL-1. This compound should be useful for precise examination of the functions of NO with excellent spatiotemporal control.

Nitroxyl (HNO) is a one-electron reduced and protonated derivative of nitric oxide (NO) and has characteristic biological and pharmacological effects distinct from those of NO. However, studies of its biosynthesis and activities are restricted by the lack of versatile HNO detection methods applicable to living cells. Here, we report the first metal-free and reductant-resistant HNO imaging probe available for use in living cells, P-Rhod. It consists of a rhodol derivative moiety as the fluorophore, linked via an ester moiety to a diphenylphosphinobenzoyl group, which forms an aza-ylide upon reaction with HNO. Intramolecular attack of the aza-ylide on the ester carbonyl group releases a fluorescent rhodol derivative. P-Rhod showed high selectivity for HNO in the presence of various biologically relevant reductants, such as glutathione and ascorbate, in comparison with previous HNO probes. We show that P-Rhod can detect not only HNO enzymatically generated in the horseradish peroxidase-hydroxylamine system in vitro but also intracellular HNO release from Angeli's salt in living cells. These results suggest that P-Rhod is suitable for detection of HNO in living cells.