Hanjing Peng

A Fluorescent Probe for Fast and Quantitative Detection of Hydrogen Sulfide in Blood

Hydrogen sulfide (H2S), well known for its unpleasant rotten egg smell, was traditionally considered as a toxic gas. However, recent studies have demonstrated that hydrogen sulfide is an endogenously produced gaseous signaling compound (gasotransmitter) with importance on par with that of the other two known endogenous gasotransmitters, nitric oxide (NO)[1] and carbon monoxide (CO).[2] H2S has been recognized for mediating a wide range of physiological effects. Studies have shown that H2S can have an effect on the cardiovascular system[3] by acting as a K-ATP channel opener.[4] Several studies have shown the protective roles of H2S, in situations such as myocardial ischemia, most likely through a combination of antioxidant and anti-apoptotic signaling.[5] Further studies also showed that H2S may be a therapeutic benefit for the treatment of ischemia-induced heart failure.[6-7] It is also a modulator in the central nervous system,[8-10] respiratory system, gastrointestinal system, and endocrine system.[11] It seems that hydrogen sulfide exhibits almost all the beneficial effects of NO without generating the toxic reactive oxygen species (ROS). In contrast, it also acts as an anti-oxidant or scavenger of ROS. Furthermore, research has indicated that hydrogen sulfide level is related to diseases such as Down syndrome[12] and Alzheimer’s disease.[13] Therefore, recent years have seen a steady increase in the interest in understanding hydrogen sulfide ’s physiological and pathological functions.[11, 14-15] One significant limiting factor in studying hydrogen sulfide is the lack of sensors and agents that allow for its rapid and accurate detection. There have been literature methods using colorimetric,[16-18] electrochemical analysis[19-21] and gas chromatography.[22-23] However, hydrogen sulfide catabolism is known to be fast, which could result in continuous fluctuation in its concentration, leading to difficulties in accurate analysis of this important molecule. Current methods do not allow for fast, accurate, and real-time determinations. Literature reported endogenous sulfide concentrations vary substantially among publications with most publications suggesting that sulfide concentration in blood is in the 10-100 μM range.[24-29] There are other studies suggesting sulfide concentration being much lower than this.[30-31] Therefore, there is an urgent need for the development of new methods for the efficient detection of sulfide in biological systems.

Thiol Reactive Probes and Chemosensors

Thiols are important molecules in the environment and in biological processes. Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H2S) play critical roles in a variety of physiological and pathological processes. The selective detection of thiols using reaction-based probes and sensors is very important in basic research and in disease diagnosis. This review focuses on the design of fluorescent and colorimetric probes and sensors for thiol detection. Thiol detection methods include probes and labeling agents based on nucleophilic addition and substitution, Michael addition, disulfide bond or Se-N bond cleavage, metal-sulfur interactions and more. Probes for H2S are based on nucleophilic cyclization, reduction and metal sulfide formation. Thiol probe and chemosensor design strategies and mechanism of action are discussed in this review.

Recent advances in thiol and sulfide reactive probes.

Because of the biological relevance of thiols and sulfides such as cysteine, homocysteine, glutathione and hydrogen sulfide, their detection has attracted a great deal of research interest. Fluorescent probes are emerging as a new strategy for thiol and hydrogen sulfide analysis due to their high sensitivity, low cost, and ability to detect and image thiols in biological samples. In this short review, we have summarized recent advances in the development of thiol and hydrogen sulfide reactive fluorescent probes. These probes are compared and contrasted with regard to their designing strategies, mechanisms, photophysical properties, and/or reaction kinetics. Biological applications of these probes are also discussed. J. Cell. Biochem. 115: 1007–1022, 2014.

Diallyl trisulfide protects against high glucose-induced cardiac apoptosis by stimulating the production of cystathionine gamma-lyase-derived hydrogen sulfide☆

BACKGROUND Cystathionine-γ-lyase (CSE)-derived hydrogen sulfide (H2S) is a potent cardioprotective agent. We investigated the effects of diallyl trisulfide (DATS) on CSE expression and H2S generation in myocardium and examined whether DATS-mediated H2S generation effectively protects rat heart from diabetes-induced cardiac damage. METHODS The correlations between the effects of hyperglycemia and diabetes on CSE expression and the effects of DATS and H2S on hyperglycemia and diabetes were examined in vitro in the cardiomyocyte cell line H9c2 and in vivo in hearts from rats with streptozotocin-induced diabetes mellitus (DM). RESULTS Expression of CSE, a catalyst of H2S production, was suppressed in H9c2 cells treated with high glucose (33 mM) and in DM rat hearts. CSE suppression also correlated with a decrease in the activation of the pro-survival protein kinase Akt. Treatment of H9c2 cells with DATS resulted in increased CSE expression and a reduction in apoptosis via a mechanism involving IGF1R/pAkt signaling and by modulating the expression of reactive oxygen species-related enzymes. The role CSE plays in the cardioprotective effects of DATS was further confirmed by CSE inhibition assays including inhibitors and siRNA. CONCLUSION DATS produces H2S as efficiently as NaSH and DATS-derived H2S provides effective cardioprotection. Further, our data indicate that H2S plays a major role in the protective effect of DATS against apoptosis of cardiomyocytes.

Synthesis and Evaluation of New Antagonists of Bacterial Quorum Sensing in Vibrio harveyi

Bacterial quorum sensing has received much attention in recent years because of its relevance to pathological events such as biofilm formation. Based on the structures of two lead inhibitors (IC50: 35–55 μM) against autoinducer‐2‐mediated quorum sensing identified through virtual screening, we synthesized 39 analogues and examined their inhibitory activities. Twelve of these new analogues showed equal or better inhibitory activities than the lead inhibitors. The best compound showed an IC50 value of ∼6 μM in a whole‐cell assay using Vibrio harveyi as the model organism. The structure–activity relationship is discussed herein.

2,6-Dansyl Azide as a Fluorescent Probe for Hydrogen Sulfide

A second-generation sulfonyl azide-based fluorescent probe, 2,6-DNS-Az, has been developed for the quantitative detection of H2S in aqueous media such as phosphate buffer and bovine serum. Compare to the first-generation 1,5-DNS-Az probe, this probe shows both high sensitivity in phosphate buffer without the need for addition of surfactant and selectivity for sulfide over other anions and biomolecules, and thus can be used as a useful tool for detection of H2S in the biological system.

Carbohydrate biomarkers for future disease detection and treatment

Carbohydrates are considered as one of the most important classes of biomarkers for cell types, disease states, protein functions, and developmental states. Carbohydrate “binders” that can specifically recognize a carbohydrate biomarker can be used for developing novel types of site specific delivery methods and imaging agents. In this review, we present selected examples of important carbohydrate biomarkers and how they can be targeted for the development of therapeutic and diagnostic agents. Examples are arranged based on disease categories including (1) infectious diseases, (2) cancer, (3) inflammation and immune responses, (4) signal transduction, (5) stem cell transformation, (6) embryo development, and (7) cardiovascular diseases, though some issues cross therapeutic boundaries.

Rapid and Specific Post‐Synthesis Modification of DNA through a Biocompatible Condensation of 1,2‐Aminothiols with 2‐Cyanobenzothiazole

Post-synthesis modification of DNA is an important way of functionalizing DNA molecules. Herein, we describe a method that first enzymatically incorporates a cyanobenzothiazole (CBT)-modified thymidine. The side-chain handle CBT can undergo a rapid and site-specific cyclization reaction with 1,2-aminothiols to afford DNA functionalization in aqueous solution. Another key advantage of this method is the formation of a single stereo/regioisomer in the process, which allows for precise control of DNA modification to yield a single component for aptamer selection work and other applications.

Carbohydrate biomarker recognition using synthetic lectin mimics

Carbohydrate biomarkers play very important roles in a wide range of biological and pathological processes. Compounds that can specifically recognize a carbohydrate biomarker are useful for targeted delivery of imaging agents and for development of new diagnostics. Furthermore, such compounds could also be candidates for the development of therapeutic agents. A tremendous amount of active work on synthetic lectin mimics has been reported in recent years. Amongst all the synthetic lectins, boronic-acid-based lectins (boronolectins) have shown great promise. Along this line, four classes of boronolectins including peptide-, nucleic-acid-, polymer-, and small-molecule-based ones are discussed with a focus on the design principles and recent advances. We hope that by presenting the potentials of this field, this review will stimulate more research in this area.

Design, Synthesis, and Polymerase‐Catalyzed Incorporation of Click‐Modified Boronic Acid–TTP Analogues

DNA molecules are known to be important materials in sensing, aptamer selection, nanocomputing, and construction of unique architectures. The incorporation of modified nucleobases affords unique DNA properties for applications in areas that would otherwise be difficult or not possible. Earlier, we demonstrated that the boronic acid moiety can be introduced into DNA through polymerase-catalyzed reactions. In order to study whether such incorporation by polymerase is a general phenomenon, we designed and synthesized four boronic acid-modified thymidine triphosphate (TTP) analogues. The synthesis of certain analogues was through the use of a single dialkyne tether for both the Sonogashira coupling with thymidine and the later Cu-mediated [3+2] cycloaddition for linking the boronic acid moiety. This approach is much more efficient than the previously described method, and paves the way for the preparation of a large number of boronic acid-modified TTPs with a diverse set of structural features. All analogues showed very good stability under polymerase chain reaction (PCR) conditions and were recognized as a substrate by DNA polymerase, and thus incorporated into DNA.