Lipids modulate H(2)S/HS(-) induced NO release from S-nitrosoglutathione

Hydrogen Sulfide and the Immune System

Hydrogen sulfide (H₂S) is the "third gasotransmitter" recognized alongside nitric oxide (NO) and carbon monoxide (CO). H₂S exhibits an array of biological effects in mammalian cells as revealed by studies showing important roles in the cardiovascular system, in cell signalling processes, post-translational modifications and in the immune system. Regarding the latter, using pharmacological and genetic approaches scientists have shown this molecule to have both pro- and anti-inflammatory effects in mammalian systems. The anti-inflammatory effects of H₂S appeared to be due to its inhibitory action on the nuclear factor kappa beta signalling pathway; NF-kB representing a transcription factor involved in the regulation pro-inflammatory mediators like nitric oxide, prostaglandins, and cytokines. In contrast, results from several animal model describe a more complicated picture and report on pro-inflammatory effects linked to exposure to this molecule; linked to dosage used and point of administration of this molecule. Overall, roles for H₂S in several inflammatory diseases spanning arthritis, atherosclerosis, sepsis, and asthma have been described by researchers. In light this work fascinating research, this chapter will cover H₂S biology and its many roles in the immune system.

Inhibition of endogenous hydrogen sulfide production improves viral elimination in CVB3-infected myocardium in mice

BACKGROUND

To find whether administration of hydrogen sulfide has interaction with coxsackie virus B3 (CVB3) replication and spread.

METHODS

Six-week-old inbred male Balb/c mice were injected intraperitoneally with CVB3. Mice were randomized to four groups (n = 10 for each group): group N (sham infection + vehicle), group C (virus + vehicle), group P (virus + DL-proparglygylcine (PAG)), and group S (virus + sodium hydrogen sulfide (NaHS)). PAG and NaHS were administered intraperitoneally daily and mice were killed on day 4 after viral inoculation. Serum specimens were obtained to assay tumor necrosis factor-α (TNFα) level, and heart specimens were harvested for histological examination, 50% tissue culture infection dose (TCID50) assay, reverse transcription-polymerase chain reaction and Western blot analysis.

RESULTS

The ratio of heart-weight to body-weight and inflammatory scores showed no significant difference between infected groups. The circulatory and local concentrations of TNFα, nitric oxide synthase 2 messenger RNA, and protein were higher in group P, and were lower in group S compared to those in group C. Mice treated with PAG and NaHS had significantly lower and higher viral stocks than those inoculated with CVB3 only, respectively.

CONCLUSION

Inhibition of endogenous hydrogen sulfide production contributed to viral clearance in acute viremia of CVB3-induced myocarditis.

In Vitro Measurement of H2S-Mediated Vasoactive Responses

Isolated tissue chamber bath system and wire myograph were developed for "in vitro" investigation of vasoactive responses on isolated arteries from a variety of animal species and vascular beds. The chapter characterizes the main principles of mechanical measurement of the changes in isometric tension of vascular smooth muscles in isolated rat thoracic aorta and superior mesenteric artery and describes several protocols on how to investigate vasoactive properties of hydrogen sulfide (H₂S) from the point of view of its mutual interaction with NO. Several methodological advances, results, and their interpretations in the context of the general knowledge are described. In the protocols the approach on how to study the vasoactive modulatory as well as direct action of H₂S and mutual interaction of H₂S with nitroso compounds, lipids, and endogenously produced NO is described.

The role of hydrogen sulphide in blood pressure regulation

Cardiovascular studies have confirmed that hydrogen sulphide (H(2)S) is involved in various signaling pathways in both physiological and pathological conditions, including hypertension. In contrast to nitric oxide (NO), which has a clear vasorelaxant action, H(2)S has both vasorelaxing and vasoconstricting effects on the cardiovascular system. H(2)S is an important antihypertensive agent, and the reduced production of H(2)S and the alterations in its functions are involved in the initiation of spontaneous hypertension. Moreover, cross-talk between H(2)S and NO has been reported. NO-H(2)S interactions include reactions between the molecules themselves, and each has been shown to regulate the endogenous production of the other. In addition, NO and H(2)S can interact to form a nitrosothiol/s complex, which has original properties and represents a novel nitroso-sulphide signaling pathway. Furthermore, recent results have shown that the interaction between H(2)S and NO could be involved in the endothelium-regulated compensatory mechanisms that are observed in juvenile spontaneously hypertensive rats. The present review is devoted to role of H(2)S in vascular tone regulation. We primarily focus on the mechanisms of H(2)S-NO interactions and on the role of H(2)S in blood pressure regulation in normotensive and spontaneously hypertensive rats.

Effects of AP39, a novel triphenylphosphonium derivatised anethole dithiolethione hydrogen sulfide donor, on rat haemodynamic parameters and chloride and calcium Cav3 and RyR2 channels

H2S donor molecules have the potential to be viable therapeutic agents. The aim of this current study was (i) to investigate the effects of a novel triphenylphosphonium derivatised dithiolethione (AP39), in the presence and absence of reduced nitric oxide bioavailability and (ii) to determine the effects of AP39 on myocardial membrane channels; CaV3, RyR2 and Cl(-). Normotensive, L-NAME- or phenylephrine-treated rats were administered Na2S, AP39 or control compounds (AP219 and ADT-OH) (0.25-1 µmol kg(-1)i.v.) and haemodynamic parameters measured. The involvement of membrane channels T-type Ca(2+) channels CaV3.1, CaV3.2 and CaV3.3 as well as Ca(2+) ryanodine (RyR2) and Cl(-) single channels derived from rat heart sarcoplasmic reticulum were also investigated. In anaesthetised Wistar rats, AP39 (0.25-1 µmol kg(-1) i.v) transiently decreased blood pressure, heart rate and pulse wave velocity, whereas AP219 and ADT-OH and Na2S had no significant effect. In L-NAME treated rats, AP39 significantly lowered systolic blood pressure for a prolonged period, decreased heart rate and arterial stiffness. In electrophysiological studies, AP39 significantly inhibited Ca(2+) current through all three CaV3 channels. AP39 decreased RyR2 channels activity and increased conductance and mean open time of Cl(-) channels. This study suggests that AP39 may offer a novel therapeutic opportunity in conditions whereby (•)NO and H2S bioavailability are deficient such as hypertension, and that CaV3, RyR2 and Cl(-) cardiac membrane channels might be involved in its biological actions.

Regulation of mitochondrial bioenergetic function by hydrogen sulfide. Part II. Pathophysiological and therapeutic aspects

Emerging work demonstrates the dual regulation of mitochondrial function by hydrogen sulfide (H2 S), including, at lower concentrations, a stimulatory effect as an electron donor, and, at higher concentrations, an inhibitory effect on cytochrome C oxidase. In the current article, we overview the pathophysiological and therapeutic aspects of these processes. During cellular hypoxia/acidosis, the inhibitory effect of H2 S on complex IV is enhanced, which may shift the balance of H2 S from protective to deleterious. Several pathophysiological conditions are associated with an overproduction of H2 S (e.g. sepsis), while in other disease states H2 S levels and H2 S bioavailability are reduced and its therapeutic replacement is warranted (e.g. diabetic vascular complications). Moreover, recent studies demonstrate that colorectal cancer cells up-regulate the H2 S-producing enzyme cystathionine β-synthase (CBS), and utilize its product, H2 S, as a metabolic fuel and tumour-cell survival factor; pharmacological CBS inhibition or genetic CBS silencing suppresses cancer cell bioenergetics and suppresses cell proliferation and cell chemotaxis. In the last chapter of the current article, we overview the field of H2 S-induced therapeutic 'suspended animation', a concept in which a temporary pharmacological reduction in cell metabolism is achieved, producing a decreased oxygen demand for the experimental therapy of critical illness and/or organ transplantation.

Chemical foundations of hydrogen sulfide biology

Following nitric oxide (nitrogen monoxide) and carbon monoxide, hydrogen sulfide (or its newer systematic name sulfane, H2S) became the third small molecule that can be both toxic and beneficial depending on the concentration. In spite of its impressive therapeutic potential, the underlying mechanisms for its beneficial effects remain unclear. Any novel mechanism has to obey fundamental chemical principles. H2S chemistry was studied long before its biological relevance was discovered, however, with a few exceptions, these past works have received relatively little attention in the path of exploring the mechanistic conundrum of H2S biological functions. This review calls attention to the basic physical and chemical properties of H2S, focuses on the chemistry between H2S and its three potential biological targets: oxidants, metals and thiol derivatives, discusses the applications of these basics into H2S biology and methodology, and introduces the standard terminology to this youthful field.

Hydrogen sulfide in biochemistry and medicine

SIGNIFICANCE

An abundance of experimental evidence suggests that hydrogen sulfide (H(2)S) plays a prominent role in physiology and pathophysiology. Many targets exist for H(2)S therapy. The molecular targets of H(2)S include proteins, enzymes, transcription factors, and membrane ion channels.

RECENT ADVANCES

Novel H(2)S precursors are being synthesized and discovered that are capable of releasing H(2)S in a slow and sustained manner. This presents a novel and advantageous approach to H(2)S therapy for treatment of chronic conditions associated with a decline in endogenous H(2)S, such as diabetes and cardiovascular disease.

CRITICAL ISSUES

While H(2)S is cytoprotective at physiological concentrations, it is not universally cytoprotective, as it appears to have pro-apoptotic actions in cancer cells and is well known to be toxic at supraphysiological concentrations. Many of the pleiotropic effects of H(2)S on health are associated with the inhibition of inflammation and upregulation of prosurvival pathways. The powerful anti-inflammatory, cytoprotective, immunomodulating, and trophic effects of H(2)S on the vast majority of normal cells seem to be mediated mainly by its actions as an extremely versatile direct and indirect antioxidant and free radical scavenger. While the overall effects of H(2)S on transformed (i.e., malignant) cells can be characterized as pro-oxidant and pro-apoptotic, they contrast sharply with the cytoprotective effects on most normal cells.

FUTURE DIRECTIONS

H(2)S has become a molecule of great interest, and several slow-releasing H(2)S prodrugs are currently under development. We believe that additional agents regulating H(2)S bioavailability will be developed during the next 10 years.

Hydrogen sulphide and angiogenesis: mechanisms and applications

In vascular tissues, hydrogen sulphide (H(2)S) is mainly produced from L-cysteine by the cystathionine gamma-lyase (CSE) enzyme. Recent studies show that administration of H(2)S to endothelial cells in culture stimulates cell proliferation, migration and tube formation. In addition, administration of H(2)S to chicken chorioallantoic membranes stimulates blood vessel growth and branching. Furthermore, in vivo administration of H(2)S to mice stimulates angiogenesis, as demonstrated in the Matrigel plug assay. Pathways involved in the angiogenic response of H(2)S include the PI-3K/Akt pathway, the mitogen activated protein kinase pathway, as well as ATP-sensitive potassium channels. Indirect evidence also suggests that the recently demonstrated role of H(2)S as an inhibitor of phosphodiesterases may play an additional role in its pro-angiogenic effect. The endogenous role of H(2)S in the angiogenic response has been demonstrated in the chicken chorioallantoic membranes, in endothelial cells in vitro and ex vivo. Importantly, the pro-angiogenic effect of vascular endothelial growth factor (but not of fibroblast growth factor) involves the endogenous production of H(2)S. The pro-angiogenic effects of H(2)S are also apparent in vivo: in a model of hindlimb ischaemia-induced angiogenesis, H(2)S induces a marked pro-angiogenic response; similarly, in a model of coronary ischaemia, H(2)S exerts angiogenic effects. Angiogenesis is crucial in the early stage of wound healing. Accordingly, topical administration of H(2)S promotes wound healing, whereas genetic ablation of CSE attenuates it. Pharmacological modulation of H(2)S-mediated angiogenic pathways may open the door for novel therapeutic approaches.