Endogenous CSE/H2S regulates ischaemic vascular remodelling mediated during hind limb ischaemia through NO-dependent monocyte recruitment and cytokine induction revealing a previously unknown mechanism of arteriogenesis.

Nitric oxide (NO) and hydrogen sulfide (H2S) are two major gaseous signaling molecules that regulate diverse physiological functions. Recent publications indicate the regulatory role of H2S on NO metabolism. In this chapter, we discuss the latest findings on H2S-NO interactions through formation of novel chemical derivatives, and experimental approaches to study these adducts. This chapter also addresses potential H2S interference on various NO detection techniques, along with precautions for analyzing biological samples from various sources. This information will facilitate critical evaluation and clearer insight into H2S regulation of NO signaling and its influence on various physiological functions.

The gasotransmitter hydrogen sulfide (H2S) is known as an important regulator in several physiological and pathological responses. Among the challenges facing the field is the accurate and reliable measurement of hydrogen sulfide bioavailability. We have reported an approach to discretely measure sulfide and sulfide pools using the monobromobimane (MBB) method coupled with RP-HPLC. The method involves the derivatization of sulfide with excess MBB under precise reaction conditions at room temperature to form sulfide-dibimane. The resultant fluorescent sulfide-dibimane (SDB) is analyzed by RP-HPLC using fluorescence detection with the limit of detection for SDB (2 nM). Care must be taken to avoid conditions that may confound H2S measurement with this method. Overall, RP-HPLC with fluorescence detection of SDB is a useful and powerful tool to measure biological sulfide levels.

Additional studies regarding persulfide and polysulfide formation and molecular reactions are needed in nearly all aspects of biology to better understand how sulfide metabolites contribute to key chemical biology reactions involved in cardiovascular health and immune responses. Antioxid. Redox Signal. 27, 634-653.

(H 2S) are gasotransmitter molecules important in numerous physiological and pathological processes. Although these molecules were first known as environmental toxicants, it is now evident that that they are intricately involved in diverse cellular functions with impact on numerous physiological and pathogenic processes. NO and H 2S share some common characteristics but also have unique chemical properties that suggest potential complementary interactions between the two in affecting cellular biochemistry and metabolism. Central among these is the interactions between NO, H 2S, and thiols that constitute new ways to regulate protein function, signaling, and cellular responses. In this review, we discuss fundamental biochemical principals, molecular functions, measurement methods, and the pathophysiological relevance of NO and H 2S. thiol; oxidation; redox; pulmonary; cardiovascular HISTORICALLY CONSIDERED ONLY as industrial pollutants, nitric oxide (NO) and hydrogen sulfide (H 2 S) are now appreciated as two key physiologically produced signaling molecules that control multiple cellular functions. Appreciation that dysfunction in how these solvated gases affect these functions, through either deficient formation or downstream reactivity, has opened up new therapeutic avenues for a host of diseases in all major organ systems including the lung. Our understanding of NO homeostasis mechanisms are relatively advanced compared with H 2 S, primarily because of the latter's discovery as a biologically relevant entity being postdated by a decade or more compared with NO. Although they are chemically distinct, there are intriguing parallel mechanisms/concepts in NO and H 2 S biology that include overlapping functions, technical challenges in how each of these gases are measured in biological milieu, appreciation of the mechanisms and factors that modulate how metabolism of each of these is regulated, and therapeutic potential for either inhibiting or repleting NO or H 2 S. In this article, and within the framework outlined above, we provide a general overview of NO and H 2 S biology. Nitric Oxide Formation: Enzymatic and Nonenzymatic SourcesEnzymatic sources. Nitric oxide is synthesized by one of three different isoforms of nitric oxide synthase (NOS) that differ in enzymatic activity, in how they are regulated (transcriptional, translational, and posttranslational mechanisms), and in how they are expressed/compartmentalized in tissues as well as the subcellular level. These are called NOS I, II, and III, corresponding to the inducible (iNOS), neuronal (nNOS), and endothelial (eNOS) isoforms, typically with high, mid, and low activities, respectively. In the systemic and pulmonary vasculature, eNOS plays a key role in controlling blood flow and maintaining an antithrombotic and anti-inflammatory luminal surface. On the other hand, iNOS is induced by inflammatory stimuli in leukocytes, airway epithelial cells, and alveolar macrophages to mediate pathogen killing. However, production of NO at higher concentrations in ...

Elucidation of specific molecular targets, characteristics of gasotransmitter molecule heterotypic interactions, and spatiotemporal formation and metabolism are all important to better understand their true pathophysiological importance in various organ systems. Antioxid. Redox Signal. 26, 936-960.

Bone healing is a dynamic process regulated by biochemical signals such as chemokines and growth factors, and biophysical signals such as topographical and mechanical features of extracellular matrix or mechanical stimuli. Hereby, a mechanically tough and bioactive hydrogel based on autologous injectable platelet‐rich fibrin (iPRF) modified with gelatin nanoparticles (GNPs) is developed. This composite hydrogel demonstrates a double network (DN) mechanism, wherein covalent network of fibrin serves to maintain material integrity, and self‐assembled colloidal network of GNPs dissipates force upon loading. A rabbit sinus augmentation model is used to investigate the bioactivity and osteogenesis capacity of the DN hydrogels. The DN hydrogels adapt to the local environmental complexity of bone defects, i.e., accommodate the irregular shape of the defects and withstand the pressure formed in the maxillary sinus during animal's respiration process. The DN hydrogel is also demonstrated to absorb and prolong the release of the bioactive growth factors stemming from iPRF, which could have contributed to the early angiogenesis and osteogenesis observed inside the sinus. This adaptable and bioactive DN hydrogel can achieve enhanced bone regeneration in treating complex bone defects by maintaining long‐term bone mass and withstanding the functional mechanical stimuli.

Hydrogen sulfide (H2S) is an important gaseous signaling molecule in the cardiovascular system. In addition to free H2S, H2S can be oxidized to polysulfide which can be biologically active. Since the impact of H2S on endothelial solute barrier function is not known, we sought to determine whether H2S and its various metabolites affect endothelial permeability. In vitro permeability was evaluated using albumin flux and transendothelial electrical resistance. Different H2S donors were used to examine the effects of exogenous H2S. To evaluate the role of endogenous H2S, mouse aortic endothelial cells (MAECs) were isolated from wild type mice and mice lacking cystathionine γ-lyase (CSE), a predominant source of H2S in endothelial cells. In vivo permeability was evaluated using the Miles assay. We observed that polysulfide donors induced rapid albumin flux across endothelium. Comparatively, free sulfide donors increased permeability only with higher concentrations and at later time points. Increased solute permeability was associated with disruption of endothelial junction proteins claudin 5 and VE-cadherin, along with enhanced actin stress fiber formation. Importantly, sulfide donors that increase permeability elicited a preferential increase in polysulfide levels within endothelium. Similarly, CSE deficient MAECs showed enhanced solute barrier function along with reduced endogenous bound sulfane sulfur. CSE siRNA knockdown also enhanced endothelial junction structures with increased claudin 5 protein expression. In vivo, CSE genetic deficiency significantly blunted VEGF induced hyperpermeability revealing an important role of the enzyme for barrier function. In summary, endothelial solute permeability is critically regulated via exogenous and endogenous sulfide bioavailability with a prominent role of polysulfides.