Cell-permeable esters of diazeniumdiolate-based nitric oxide prodrugs

Visible-Light-Triggered Uncaging of Carbonyl Sulfide for Hydrogen Sulfide (H2S) Release

Generation of hydrogen sulfide (H₂S) is challenging and few methods are capable of localized delivery of this gas. Here, a boron dipyrromethene-based carbamothioate (BDP-H₂S) that is uncaged by visible light of 470 nm to generate carbonyl sulfide (COS), which is rapidly hydrolyzed to H₂S in the presence of carbonic anhydrase, a widely prevalent enzyme, is reported.

A highly selective sulfinate ester probe for thiol bioimaging

We describe here hitherto unexplored chemistry of the sulfinate ester functional group as being highly selective towards nucleophilic substitution by thiols at physiological pH. Using this cleavable trigger, an optical thiol probe that is suitable for thiol bioimaging has been developed.

A smart rhodamine–pyridine conjugate for bioimaging of thiocyanate in living cells

A rhodamine–pyridine conjugate, REDA-2PC, can selectively monitor NCS⁻ in human embryonic kidney cells 293. Visible light excitable probe allows fluorescence and naked eye detection of nanomolar NCS⁻.

A phenacrylate scaffold for tunable thiol activation and release

A thiol-selective 2-methyl-3-phenacrylate scaffold with spatiotemporal control over delivery of a cargo is reported. The half-lives of decomposition could be tuned from 30 min to 1 day and the scaffold's utility in thiol-inducible fluorophore release in cell-free as well as within cells is demonstrated.

Site-directed delivery of nitric oxide to cancers

Nitric oxide (NO) is a reactive gaseous free radical which mediates numerous biological processes. At elevated levels, NO is found to be toxic to cancers and hence, a number of strategies for site-directed delivery of NO to cancers are in development during the past two decades. More recently, the focus of research has been to, in conjunction with other cancer drugs deliver NO to cancers for its secondary effects including inhibition of cellular drug efflux pumps. Among the various approaches toward site-selective delivery of exogenous NO sources, enzyme activated nitric oxide donors belonging to the diazeniumdiolate category afford unique advantages including exquisite control of rates of NO generation and selectivity of NO production. For this prodrug approach, enzymes including esterase, glutathione/glutathione S-transferase, DT-diaphorase, and nitroreductase are utilized. Here, we review the design and development of various approaches to enzymatic site-directed delivery of NO to cancers and their potential.

The Nitric Oxide Prodrug V-PROLI/NO Inhibits Cellular Uptake of Proline

V-PYRRO/NO is a well studied nitric oxide (NO) prodrug which has been shown to protect human liver cells from arsenic, acetaminophen, and other toxic assaults in vivo. Its proline-based analogue, V-PROLI/NO, was designed to be a more biocompatible form that decomposes to the naturally occurring metabolites of proline, NO, and glycolaldehyde. Like V-PYRRO/NO, this cytochrome P450-activated prodrug was previously assumed to passively diffuse through the cellular membrane. Using (14)C-labeled proline in a competition assay, we show that V-PROLI/NO is transported through proline transporters into multiple cell lines. A fluorescent NO-sensitive dye (DAF-FM diacetate) and nitrite excretion indicated elevated intracellular NO release after metabolism over V-PYRRO/NO. These results also allowed us to predict and design a more permeable analogue, V-SARCO/NO. We report a proline transporter-based strategy for the selective transport of NO prodrugs that may have enhanced efficacy and aid in development of further NO prodrugs with increased permeability.

Glycosylated PROLI/NO derivatives as nitric oxide prodrugs

GlcNAc-PROLI/NO prodrugs that are activated by N-acetylglucosaminidase to release nitric oxide (NO) are described. A classical acid-amine coupling is used to bifunctionalize these PROLI/NO prodrugs, which on activation generate up to 4 mol of NO, a peptide residue, and an N-acetylglucosamine residue. Many of the prodrugs synthesized are efficient sources of intracellular NO.

Synthesis and evaluation of piperazine and homopiperazine analogues of JS-K, an anti-cancer lead compound

Here we report a number of novel JS-K structural analogues with sub-micromolar anti-proliferative activities against human leukemia cell lines HL-60 and U937; JS-K is the anti-cancer lead compound O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate. The ability of these compounds to generate intracellular nitric oxide correlated well with their observed anti-proliferative effects: analogues that had potent inhibitory activity against leukemia cells formed elevated levels of intracellular nitric oxide.