Browsing by Subject "hydrogen sulfide"
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Item A hydrogen-sulfide derivative of mesalamine reduces the severity of intestinal and lung injury in necrotizing enterocolitis through endothelial nitric oxide synthase(American Physiological Society, 2022-10-01) Hosfield, Brian D.; Hunter, Chelsea E.; Li, Hongge; Drucker, Natalie A.; Pecoraro, Anthony R.; Manohar, Krishna; Shelley, W. Christopher; Markel, Troy A.; Surgery, School of MedicineNecrotizing enterocolitis (NEC) remains a devastating disease that affects preterm infants. Hydrogen sulfide (H2S) donors have been shown to reduce the severity of NEC, but the optimal compound has yet to be identified. We hypothesized that oral H2S-Mesalamine (ATB-429) would improve outcomes in experimental NEC, and its benefits would be dependent on endothelial nitric oxide synthase (eNOS) pathways. NEC was induced in 5-day-old wild-type (WT) and eNOS knockout (eNOSKO) pups by formula feeding and stress. Four groups were studied in both WT and eNOSKO mice: 1) breastfed controls, 2) NEC, 3) NEC + 50 mg/kg mesalamine, and 4) NEC + 130 mg/kg ATB-429. Mesalamine and ATB-429 doses were equimolar. Pups were monitored for sickness scores and perfusion to the gut was measured by Laser Doppler Imaging (LDI). After euthanasia of the pups, intestine and lung were hematoxylin and eosin-stained and scored for injury in a blind fashion. TLR4 expression was quantified by Western blot and IL-6 expression by ELISA. P < 0.05 was significant. Both WT and eNOSKO breastfed controls underwent normal development and demonstrated milder intestinal and pulmonary injury compared with NEC groups. For the WT groups, ATB-429 significantly improved weight gain, reduced clinical sickness score, and improved perfusion compared with the NEC group. In addition, WT ATB-429 pups had a significantly milder intestinal and pulmonary histologic injury when compared with NEC. ATB-429 attenuated the increase in TLR4 and IL-6 expression in the intestine. When the experiment was repeated in eNOSKO pups, ATB-429 offered no benefit in weight gain, sickness scores, perfusion, intestinal injury, pulmonary injury, or decreasing intestinal inflammatory markers. An H2S derivative of mesalamine improves outcomes in experimental NEC. Protective effects appear to be mediated through eNOS. Further research is warranted to explore whether ATB-429 may be an effective oral therapy to combat NEC.Item Hydrogen sulfide provides intestinal protection during a murine model of experimental necrotizing enterocolitis(Elsevier, 2018) Drucker, Natalie A.; Jensen, Amanda R.; Ferkowicz, Michael; Markel, Troy A.; Surgery, School of MedicineBackground Necrotizing enterocolitis (NEC) continues to be a morbid surgical condition among preterm infants. Novel therapies for this condition are desperately needed. Hydrogen sulfide (H2S) is an endogenous gasotransmitter that has been found to have beneficial properties. We therefore hypothesized that intraperitoneal injection of various H2S donors would improve clinical outcomes, increase intestinal perfusion, and reduce intestinal injury in an experimental mouse model of necrotizing enterocolitis. Methods NEC was induced in five-day-old mouse C57BL/6 mouse pups through maternal separation, formula feeding, and intermittent hypoxic and hypothermic stress. The control group (n = 10) remained with their mother and breastfed ad lib. Experimental groups (n = 10/group) received intraperitoneal injections of phosphate buffered saline (PBS) vehicle or one of the following H2S donors: (1) GYY4137, 50 mg/kg daily; (2) Sodium sulfide (Na2S), 20 mg/kg three times daily; (3) AP39, 0.16 mg/kg daily. Pups were monitored for weight gain, clinical status, and intestinal perfusion via transcutaneous Laser Doppler Imaging (LDI). After sacrifice on day nine, intestinal appearance and histology were scored and cytokines were measured in tissue homogenates of intestine, liver, and lung. Data were compared with Mann–Whitney and p < 0.05 was considered significant. Results Clinical score and weight gain were significantly improved in all three H2S-treated groups as compared to vehicle (p < 0.05 for all groups). Intestinal perfusion of the vehicle group was 22% of baseline while the GYY4137 group was 38.7% (p = 0.0103), Na2S was 47.0% (p = 0.0040), and AP39 was 43.0% (p = 0.0018). The vehicle group had a median histology score of 2.5, while the GYY4137 group's was 1 (p = 0.0013), Na2S was 0.5 (p = 0.0004), and AP39 was 0.5 (p = 0.0001). Cytokine analysis of the intestine of the H2S-treated groups revealed levels closer to breastfed pups as compared to vehicle (p < 0.05 for all groups). Conclusion Intraperitoneal administration of H2S protects against development of NEC by improving mesenteric perfusion, and by limiting mucosal injury and altering the tissue inflammatory response. Further experimentation is necessary to elucidate downstream mechanisms prior to clinical implementation.Item Hydrogen Sulfide: A Potential Novel Therapy for the Treatment of Ischemia(Wolters Kluwer, 2017-11) Jensen, Amanda R.; Drucker, Natalie A.; Khaneki, Sina; Surgery, School of MedicineHydrogen 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. Recent studies have discovered a multitude of different targets for H2S therapy, including those related to protein modification, intracellular signaling, and ion channel depolarization. The most difficult part of studying hydrogen sulfide has been finding a way to accurately and reproducibly measure it. The purpose of this review is to: elaborate on the biosynthesis and catabolism of H2S in the human body, review current knowledge of the mechanisms of action of this gas in relation to ischemic injury, define strategies for physiological measurement of H2S in biological systems, and review potential novel therapies that use H2S for treatment.Item Inhibiting hydrogen sulfide production in umbilical stem cells reduces their protective effects during experimental necrotizing enterocolitis(Elsevier, 2019) Drucker, Natalie A.; te Winkel, Jan P.; Shelley, W. Christopher; Olson, Kenneth R.; Markel, Troy A.; Surgery, School of MedicineIntroduction Umbilical mesenchymal stem cells (USC) have been shown to reduce illness in animal models of necrotizing enterocolitis (NEC), possibly through the paracrine release of hydrogen sulfide (H2S). We hypothesized that animals treated with USCs with inhibited H2S synthesis would exhibit more severe disease. Methods NEC was induced in five-day-old mouse pups by formula feeding and hypoxic and hypothermic stress. Experimental groups received intraperitoneal injection of either saline vehicle or 80,000cells/gram of one of the following cell types: USC, USCs with negative-control siRNA, or USCs with targeted siRNA inhibition of the H2S-producing enzymes. Pups were monitored by clinical assessment and after euthanasia, intestine and lung histologic injury were scored. Tissue was homogenized, and concentrations of IL-6, IL-10, and VEGF were determined by ELISA. For statistical analysis, p < 0.05 was considered significant. Results Animals treated with negative-control siRNA USCs were significantly improved compared to vehicle. Clinical sickness scores as well as intestinal and lung histologic injury scores in the targeted siRNA groups were significantly worse when compared to the negative-control siRNA group. IL-6, IL-10, and VEGF had varying patterns of expression in the different groups. Conclusion Inhibition of H2S production in USCs reduces the beneficial effects of these cells during therapy in experimental NEC.Item Mesenchymal stem cells promote mesenteric vasodilation through hydrogen sulfide and endothelial nitric oxide(American Physiological Society, 2019-09-24) Te Winkel, Jan; John, Quincy E.; Hosfield, Brian D.; Drucker, Natalie A.; Das, Amitava; Olson, Ken R.; Markel, Troy A.; Surgery, School of MedicineMesenteric ischemia is a devastating process that can result in intestinal necrosis. Mesenchymal stem cells (MSCs) are becoming a promising treatment modality. We hypothesized that 1) MSCs would promote vasodilation of mesenteric arterioles, 2) hydrogen sulfide (H2S) would be a critical paracrine factor of stem cell-mediated vasodilation, 3) mesenteric vasodilation would be impaired in the absence of endothelial nitric oxide synthase (eNOS) within the host tissue, and 4) MSCs would improve the resistin-to-adiponectin ratio in mesenteric vessels. H2S was measured with a specific fluorophore (7-azido-3-methylcoumarin) in intact MSCs and in cells with the H2S-producing enzyme cystathionine β synthase (CBS) knocked down with siRNA. Mechanical responses of isolated second- and third-order mesenteric arteries (MAs) from wild-type and eNOS knockout (eNOSKO) mice were monitored with pressure myography, after which the vessels were snap frozen and later analyzed for resistin and adiponectin via multiplex beaded assay. Addition of MSCs to the myograph bath significantly increased vasodilation of norepinephrine-precontracted MAs. Knockdown of CBS in MSCs decreased H2S production by MSCs and also decreased MSC-initiated MA dilation. MSC-initiated vasodilation was further reduced in eNOSKO vessels. The MA resistin-to-adiponectin ratio was higher in eNOSKO vessels compared with wild-type. These results show that MSC treatment promotes dilation of MAs by an H2S-dependent mechanism. Furthermore, functional eNOS within the host mesenteric bed appears to be essential for maximum stem cell therapeutic benefit, which may be attributable, in part, to modifications in the resistin-to-adiponectin ratio. NEW & NOTEWORTHY Stem cells have been shown to improve survival, mesenteric perfusion, and histological injury scores following intestinal ischemia. These benefits may be due to the paracrine release of hydrogen sulfide. In an ex vivo pressure myography model, we observed that mesenteric arterial dilation improved with stem cell treatment. Hydrogen sulfide release from stem cells and endothelial nitric oxide synthase within the vessels were critical components of optimizing stem cell-mediated mesenteric artery dilation.Item Spatially resolved capture of hydrogen sulfide from the water column and sedimentary pore waters for abundance and stable isotopic analysis(Elsevier, 2017) Fike, D. A.; Houghton, J. L.; Moore, S. E.; Gilhooly, William P., III; Dawson, K. S.; Druschel, Gregory K.; Amend, J. P.; Orphan, V. J.; Department of Earth Sciences, School of ScienceSulfur cycling is ubiquitous in sedimentary environments, where it plays a major role in mediating carbon remineralization and impacts both local and global redox budgets. Microbial sulfur cycling is dominated by metabolic activity that either produces (e.g., sulfate reduction, disproportionation) or consumes (sulfide oxidation) hydrogen sulfide (H2S). As such, improved constraints on the production, distribution, and consumption of H2S in the natural environment will increase our understanding of microbial sulfur cycling. These different microbial sulfur metabolisms are additionally associated with particular stable isotopic fractionations. Coupling measurements of the isotopic composition of the sulfide with its distribution can provide additional information about environmental conditions and microbial ecology. Here we investigate the kinetics of sulfide capture on photographic films as a way to document the spatial distribution of sulfide in complex natural environments as well as for in situ capture of H2S for subsequent stable isotopic analysis. Laboratory experiments and timed field deployments demonstrate the ability to infer ambient sulfide abundances from the yield of sulfide on the films. This captured sulfide preserves the isotopic composition of the ambient sulfide, offset to slightly lower δ34S values by ~ 1.2 ± 0.5‰ associated with the diffusion of sulfide into the film and subsequent reaction with silver to form Ag2S precipitates. The resulting data enable the exploration of cm-scale lateral heterogeneity that complement most geochemical profiles using traditional techniques in natural environments. Because these films can easily be deployed over a large spatial area, they are also ideal for real-time assessment of the spatial and temporal dynamics of a site during initial reconnaissance and for integration over long timescales to capture ephemeral processes.Item Stem Cell Therapy and Hydrogen Sulfide: Conventional or Nonconventional Mechanisms of Action?(Wolters Kluwer, 2019) Jensen, Amanda R.; Drucker, Natalie A.; Olson, Ken R.; Markel, Troy A.; Surgery, School of MedicinePurpose: Hydrogen sulfide (H2S) has many beneficial biological properties, including the ability to promote vasodilation. It has been shown to be released from stem cells and increased by hypoxia. Therefore, H2S may be an important paracrine factor in stem cell mediated intestinal protection. We hypothesized that hydrogen sulfide created through conventional pathways would be a critical component of stem cell mediated intestinal protection following ischemic injury. Methods: Human bone marrow derived mesenchymal stem cells (BMSCs) were transfected with negative control siRNA (Scramble), or with siRNA to CBS, MPST, or CTH. Knockdown was confirmed with PCR and hydrogen sulfide gas assessed with AzMC fluorophore. Eight week old male mice then underwent intestinal ischemia for 60 mins, after which time, perfusion was restored. BMSCs from each of the above groups were then placed into the mouse abdominal cavity prior to final closure. After 24 hours, mice were reanesthetized and mesenteric perfusion was assessed by Laser Doppler Imaging (LDI). Animals were then sacrificed and intestines excised, placed in formalin, paraffin embedded, and stained with H & E. Intestines were then scored with a common mucosal injury grading scale. Results: PCR confirmed knockdown of conventional H2S producing enzymes (CBS, MPST, CTH). Hydrogen sulfide gas was decreased in MPST and CTH transfected cells in normoxic conditions but was not decreased compared to scramble in any of the transfected groups in hypoxic conditions. BMSCs promoted increased mesenteric perfusion at 24 hours post-ischemia compared to vehicle. Transfected stem cells provided equivalent protection. Histologic injury was improved with BMSCs compared to vehicle. CBS, MPST, and CTH knockdown cell lines did not have any worse histological injury compared to Scramble. Conclusion: Knocking down conventional H2S producing enzymes only impacted gas production in normoxic conditions. When cells were transfected in hypoxic conditions, as would be expected in the ischemic intestines, hydrogen sulfide gas was not depressed. These data, along with unchanged perfusion and histological injury parameters with conventional enzyme knockdown would indicate that alternative H2S production pathways may be initiated during hypoxic and/or ischemic events.