Yuming Yang,†,§ Qiang Zhao,‡,§ Wei Feng,† and Fuyou Li*,† †Department of Chemistry and State Key Laboratory of Molecular Engineering of Polymers and Institutes of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China ‡Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210046, P. R. China.

Luminescent chemodosimeters for bioimaging.

The important life-supporting role of hydrogen sulfide (H2S) has evolved from bacteria to plants, invertebrates, vertebrates, and finally to mammals. Over the centuries, however, H2S had only been known for its toxicity and environmental hazard. Physiological importance of H2S has been appreciated for about a decade. It started by the discovery of endogenous H2S production in mammalian cells and gained momentum by typifying this gasotransmitter with a variety of physiological functions. The H2S-catalyzing enzymes are differentially expressed in cardiovascular, neuronal, immune, renal, respiratory, gastrointestinal, reproductive, liver, and endocrine systems and affect the functions of these systems through the production of H2S. The physiological functions of H2S are mediated by different molecular targets, such as different ion channels and signaling proteins. Alternations of H2S metabolism lead to an array of pathological disturbances in the form of hypertension, atherosclerosis, heart failure, diabetes...

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Physiological Implications of Hydrogen Sulfide: A Whiff Exploration That Blossomed

Hydrogen sulfide (H₂S) is a gaseous mediator synthesized from cysteine by cystathionine γ lyase (CSE) and other naturally occurring enzymes. Pharmacological experiments using H₂S donors and genetic experiments using CSE knockout mice suggest important roles for this vasodilator gas in the regulation of blood vessel caliber, cardiac response to ischemia/reperfusion injury, and inflammation. That H₂S inhibits cytochrome c oxidase and reduces cell energy production has been known for many decades, but more recently, a number of additional pharmacological targets for this gas have been identified. H₂S activates K(ATP) and transient receptor potential (TRP) channels but usually inhibits big conductance Ca²(+)-sensitive K(+) (BK(Ca)) channels, T-type calcium channels, and M-type calcium channels. H₂S may inhibit or activate NF-κB nuclear translocation while affecting the activity of numerous kinases including p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), and Akt. These disparate effects may be secondary to the well-known reducing activity of H₂S and/or its ability to promote sulfhydration of protein cysteine moieties within the cell.

Hydrogen Sulfide and Cell Signaling

This review is intended to stimulate interest in the effect of increased expression of heme oxygenase-1 (HO-1) protein and increased levels of HO activity on normal and pathological states. The HO system includes the heme catabolic pathway, comprising HO and biliverdin reductase, and the products of heme degradation, carbon monoxide (CO), iron, and biliverdin/bilirubin. The role of the HO system in diabetes, inflammation, heart disease, hypertension, neurological disorders, transplantation, endotoxemia and other pathologies is a burgeoning area of research. This review focuses on the clinical potential of increased levels of HO-1 protein and HO activity to ameliorate tissue injury. The use of pharmacological and genetic probes to manipulate HO, leading to new insights into the complex relationship of the HO system with biological and pathological phenomena under investigation, is reviewed. This information is critical in both drug development and the implementation of clinical approaches to moderate and to alleviate the numerous chronic disorders in humans affected by perturbations in the HO system.

Pharmacological and Clinical Aspects of Heme Oxygenase

Hydrogen sulfide (H2S), a messenger molecule generated by cystathionine gamma-lyase, acts as a physiologic vasorelaxant. Mechanisms whereby H2S signals have been elusive. We now show that H2S physiologically modifies cysteines in a large number of proteins by S-sulfhydration. About 10 to 25% of many liver proteins, including actin, tubulin, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), are sulfhydrated under physiological conditions. Sulfhydration augments GAPDH activity and enhances actin polymerization. Sulfhydration thus appears to be a physiologic posttranslational modification for proteins.

H2S Signals Through Protein S-Sulfhydration

Studies of nitric oxide over the past two decades have highlighted the fundamental importance of gaseous signaling molecules in biology and medicine The physiological role of other gases such as carbon monoxide and hydrogen sulfide (H2S) is now receiving increasing attention Here we show that H2S is physiologically generated by cystathionine γ-lyase (CSE) and that genetic deletion of this enzyme in mice markedly reduces H2S levels in the serum, heart, aorta, and other tissues Mutant mice lacking CSE display pronounced hypertension and diminished endothelium-dependent vasorelaxation CSE is physiologically activated by calcium-calmodulin, which is a mechanism for H2S formation in response to vascular activation These findings provide direct evidence that H2S is a physiologic vasodilator and regulator of blood pressure

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H2S as a Physiologic Vasorelaxant: Hypertension in Mice with Deletion of Cystathionine γ-Lyase

Treatment of established hypertension, especially for prolonged control of this pathogenic process, represents a great challenge. To upregulate the expression of heme oxygenase (HO) to lower blood pressure (BP) of spontaneously hypertensive rats (SHRs), we administered hemin to 12-week-old adult SHRs through subcutaneously implanted osmotic minipumps for 3 consecutive weeks (the hemin protocol). Systolic BP of SHRs was normalized 123+/-2 mm Hg (n=20; P<0.001) and this normalization maintained for 9 months after the removal of hemin pumps. At the end of the hemin protocol, HO-1 expression, HO activity, soluble guanylyl cyclase expression, and cGMP content were all increased, but phosphodiesterase-5 expression was downregulated in the mesenteric arteries. The hemin protocol also reversed SHR-featured arterial eutrophic inward remodeling and decreased expression levels of vascular endothelial growth factor. These changes lasted 9 months after the hemin protocol. Our study, thus, formulates a novel hemin protocol that will not only normalize BP in SHRs with established hypertension but, more importantly, will also provide long-lasting antihypertension protection. Sustained upregulation of HO-1-linked signaling pathways and reversal of vascular remodeling in peripheral blood vessels mediate likely the antihypertensive effect of the hemin protocol.

Sustained Normalization of High Blood Pressure in Spontaneously Hypertensive Rats by Implanted Hemin Pump

AIM
α7nAChR agonist GTS-21 is potentially a new treatment for type 2 diabetes (T2D) owing to its ability to stimulate GLP-1 secretion. This study sought to establish if GTS-21 exerts a blood glucose-lowering action in db/db mice, and to test if this action requires coordinate α7nAChR and GLP-1 receptor (GLP-1R) stimulation by GTS-21 and endogenous GLP-1, respectively.


MATERIALS AND METHODS
Blood glucose levels were measured during an oral glucose tolerance test (OGTT) using db/db mice administered intraperitoneal GTS-21. Plasma GLP-1, PYY (1-36), GIP, glucagon, and insulin levels were measured by ELISA. A GLP-1R-mediated action of GTS-21 that is secondary to α7nAChR stimulation was evaluated using α7nAChR and GLP-1R knockout (KO) mice, or by co-administration of GTS-21 with DPP-4 inhibitor sitagliptin, or GLP-1R antagonist Exendin(9-39). Insulin sensitivity was assessed in an insulin tolerance test (ITT).


RESULTS
Single or multiple dose GTS-21 (0.5-8.0 mg/kg) acted in a dose-dependent manner to lower levels of blood glucose in the OGTT using 10-14 week-old male and female db/db mice. This action of GTS-21 was reproduced by α7nAChR agonist PNU-282987, was enhanced by sitagliptin, was counteracted by Exendin(9-39), and was absent in α7nAChR and GLP-1R KO mice. Plasma GLP-1, PYY (1-36), GIP, glucagon, and insulin levels increased in response to GTS-21, but insulin sensitivity, body weight, and food intake were unchanged.


CONCLUSIONS
α7nAChR agonists improve oral glucose tolerance in db/db mice. This action is contingent on coordinate α7nAChR and GLP-1R stimulation. Thus, α7nAChR agonists administered in combination with sitagliptin might serve as a new treatment for T2D. This article is protected by copyright. All rights reserved.

Qinghe Meng

Papers

H2S as a Physiologic Vasorelaxant: Hypertension in Mice with Deletion of Cystathionine γ-Lyase

Sustained Normalization of High Blood Pressure in Spontaneously Hypertensive Rats by Implanted Hemin Pump

α7nAChR agonist GTS-21 engages the GLP-1 incretin hormone axis to lower levels of blood glucose in db/db mice.

Effects of intrauterine and lactational exposure to lanthanum nitrate on BALB/c offspring mice: Developmental immunotoxicity and self-recovery.

Exploration of potential mechanism of interleukin-33 up-regulation caused by 1,4-naphthoquinone black carbon in RAW264.7 cells.