Extended hypoxia-mediated H S production provides for long-term oxygen sensing.

Aim: Numerous studies have shown that H S serves as an acute oxygen sensor in a variety of cells. We hypothesize that H S also serves in extended oxygen sensing.

Methods: Here, we compare the effects of extended exposure (24-48 hours) to varying O tensions on H S and polysulphide metabolism in human embryonic kidney (HEK 293), human adenocarcinomic alveolar basal epithelial (A549), human colon cancer (HTC116), bovine pulmonary artery smooth muscle, human umbilical-derived mesenchymal stromal (stem) cells and porcine tracheal epithelium (PTE) using sulphur-specific fluorophores and fluorometry or confocal microscopy.

Metabolism of hydrogen sulfide (HS) and Production of Reactive Sulfur Species (RSS) by superoxide dismutase.

Reactive sulfur species (RSS) such as HS, HS, HS, (n = 2-7) and HS are chemically similar to HO and the reactive oxygen species (ROS) HO, HO, O and act on common biological effectors. RSS were present in evolution long before ROS, and because both are metabolized by catalase it has been suggested that "antioxidant" enzymes originally evolved to regulate RSS and may continue to do so today. Here we examined RSS metabolism by Cu/Zn superoxide dismutase (SOD) using amperometric electrodes for dissolved HS, a polysulfide-specific fluorescent probe (SSP4), and mass spectrometry to identify specific polysulfides (HS-HS).

Hydrogen Sulfide: A Potential Novel Therapy for the Treatment of Ischemia.

Hydrogen sulfide (H2S) is a novel signaling molecule most recently found to be of fundamental importance in cellular function as a regulator of apoptosis, inflammation, and perfusion. Mechanisms of endogenous H2S signaling are poorly understood; however, signal transmission is thought to occur via persulfidation at reactive cysteine residues on proteins. Although much has been discovered about how H2S is synthesized in the body, less is known about how it is metabolized.

Catalase as a sulfide-sulfur oxido-reductase: An ancient (and modern?) regulator of reactive sulfur species (RSS).

Catalase is well-known as an antioxidant dismutating HO to O and HO. However, catalases evolved when metabolism was largely sulfur-based, long before O and reactive oxygen species (ROS) became abundant, suggesting catalase metabolizes reactive sulfide species (RSS). Here we examine catalase metabolism of HS, the sulfur analog of HO, hydrogen sulfide (HS) and other sulfur-bearing molecules using HS-specific amperometric electrodes and fluorophores to measure polysulfides (HS; SSP4) and ROS (dichlorofluorescein, DCF).

Hydrogen sulfide contributes to hypoxic inhibition of airway transepithelial sodium absorption.

In lung epithelial cells, hypoxia decreases the expression and activity of sodium-transporting molecules, thereby reducing the rate of transepithelial sodium absorption. The mechanisms underlying the sensing of hypoxia and subsequent coupling to sodium-transporting molecules remain unclear. Hydrogen sulfide (H2S) has recently been recognized as a cellular signaling molecule whose intracellular concentrations critically depend on oxygen levels.

Garlic oil polysulfides: H2S- and O2-independent prooxidants in buffer and antioxidants in cells.

The health benefits of garlic and other organosulfur-containing foods are well recognized and have been attributed to both prooxidant and antioxidant activities. The effects of garlic are surprisingly similar to those of hydrogen sulfide (H2S), which is also known to be released from garlic under certain conditions. However, recent evidence suggests that polysulfides, not H2S, may be the actual mediator of physiological signaling.

A case of mistaken identity: are reactive oxygen species actually reactive sulfide species?

Stepwise one-electron reduction of oxygen to water produces reactive oxygen species (ROS) that are chemically and biochemically similar to reactive sulfide species (RSS) derived from one-electron oxidations of hydrogen sulfide to elemental sulfur. Both ROS and RSS are endogenously generated and signal via protein thiols. Given the similarities between ROS and RSS, we wondered whether extant methods for measuring the former would also detect the latter.

Controversies and conundrums in hydrogen sulfide biology.

Hydrogen sulfide (H2S) signaling has been implicated in physiological processes in practically all organ systems studied to date. At times the excitement of this new field has outpaced the technical expertise or practical knowledge with which to accurately assess these advancements. Recently, the myriad of proposed H2S actions has spawned interest in using indicators of H2S metabolism, especially plasma H2S concentrations, as a means of identifying a variety of pathophysiological conditions or to predict clinical outcomes.

Thiosulfate: a readily accessible source of hydrogen sulfide in oxygen sensing.

H2S derived from organic thiol metabolism has been proposed serve as an oxygen sensor in a variety of systems because of its susceptibility to oxidation and its ability to mimic hypoxic responses in numerous oxygen-sensing tissues. Thiosulfate, an intermediate in oxidative H2S metabolism can alternatively be reduced and regenerate H2S. We propose that this contributes to the H2S-mediated oxygen-sensing mechanism.

Hydrogen sulfide (H₂S) and hypoxia inhibit salmonid gastrointestinal motility: evidence for H₂S as an oxygen sensor.

Hydrogen sulfide (H(2)S) has been shown to affect gastrointestinal (GI) motility and signaling in mammals and O(2)-dependent H(2)S metabolism has been proposed to serve as an O(2) 'sensor' that couples hypoxic stimuli to effector responses in a variety of other O(2)-sensing tissues. The low P(O2) values and high H(2)S concentrations routinely encountered in the GI tract suggest that H(2)S might also be involved in hypoxic responses in these tissues. In the present study we examined the effect of H(2)S on stomach, esophagus, gallbladder and intestinal motility in the rainbow trout (Oncorhynchus mykiss) and coho salmon (Oncorhynchus kisutch) and we evaluated the potential for H(2)S in oxygen sensing by examining GI responses to hypoxia in the presence of known inhibitors of H(2)S biosynthesis and by adding the sulfide donor cysteine (Cys).

Passive loss of hydrogen sulfide in biological experiments.

Hydrogen sulfide (H(2)S) is a volatile gas of considerable interest as a physiologically relevant signaling molecule, but this volatility has typically been overlooked in the context of biological experiments. We examined volatility of 10 and 100 μM H(2)S (Na(2)S·9H(2)O) in real time with polarographic electrodes in three commonly employed experimental apparatuses: 24-well tissue culture plates (WP), muscle myograph baths (MB), and the Langendorff perfused heart apparatus (LPH). H(2)S loss from all apparatuses was rapid and exponential, with half-times (t(1/2)) of 5 min (WP), less than 4 min (MB), and less than 0.