The present estimation of the endogenous sulfide release rates,the occurence of SQR in a large majority of the tissues/cellsexplored so far and its high affinity for sulfide make the SQRand mitochondrial respiration the major pathway maintainingintracellular sulfide in an acceptable non toxic low range of con-centrations. Therefore mitochondrial respiration is both the sulfidesink and the target of sulfide toxicity. This paves the way for posi-tive feedback effects making the orientation towards one oranother of the opposite consequences of a given sulfide exposurehighly sensitive to various factors. SQR is thus likely to interferewith any endogenous sulfide signaling and definitely needs to betaken into account when pharmacological intervention involvessulfide donors.

The lumen of the colon hosts a bacterial communautyreleasing sulfide and a value of 60 lM is proposed for theconcentration of free sulfide in the human colon. Accordingly,the epithelial cells (colonocytes) are exposed to toxic sulfideconcentrations. These colonocytes show a high SQR activity andcellular bioenergetics adaptations to increase their tolerance tosulfide.

The mechanisms involved in mitochondrial sulfide bioenergeticsas well as their consequences with regard to the signaling role ofsulfide and to the use of sulfide donors will be explained.

http://dx.doi.org/10.1016/j.niox.2013.06.021

PL12Molecular mechanisms and therapeutic implications ofthe pro-angiogenic effect of hydrogen sulfide

Csaba SzaboDepartment of Anesthesiology, University of Texas Medical Branch andShriners Hospital for Children, Galveston, TX, USA

Introduction: Angiogenesis is a key process in a variety of biologi-cal processes ranging from wound healing to tumor biology. Hydro-gen sulfide (H2S) and nitric oxide (NO) are recognized as essential,interacting, endogenous gaseous signaling molecules. Here wereview the existing data demonstrating the effect of exogenousand endogenous H2S on angiogenesis and overview the molecularpathways involved. We are also presenting a range of therapeuticcontext where these mechanisms can be exploited in the future.

Methods: Murine bEnd.3 endothelial cells were used for in vitrostudies; burn-induced wound healing in rats and mice was usedfor in vivo studies.

Results: Exposure of endothelial cells to a H2S donor increasedintracellular cGMP in a NO-dependent manner, activated proteinkinase G (PKG) and induced the phosphorylation of its downstreamsubstrate, VASP. Inhibition of eNOS or PKG abolished the H2S-stim-ulated angiogenic response. Thus, there is a convergence of the vas-cular actions of H2S and NO to the cGMP/PKG pathway. Silencing ofthe H2S-producing enzyme cystathionine-gamma-lyase (CSE) abol-ished NO-stimulated cGMP accumulation and angiogenesis, indicat-ing the requirement of H2S in the vascular actions of NO. VEGF, apro-angiogenic and vasorelaxant hormone stimulated the produc-tion of both NO and H2S: VEGF-induced angiogenic and vasorelax-ant responses were attenuated either by the inhibition of NO or bythe silencing of CSE. A key site of the cooperative interactionbetween NO and H2S involves the cGMP/PKG pathway: H2S exerteda potent inhibitory effect on phosphodiesterase 5 activity in vitroleading to cGMP elevation and PKG activation. Another site of theinteraction between H2S and NO is Akt: H2S increased the phos-phorylation (activation) of Akt, as well as the phosphorylation ofeNOS at Ser1177. In vivo H2S administration promoted post-burn

wound healing, while reduced H2S production (mice deficient inCSE) delayed it. H2S -mediated and angiogenesis in vivo wassuppressed by pharmacological inhibition (L-NAME) or geneticablation of eNOS (eNOS�/� mice).

Conclusions: H2S is a pro-angiogenic endogenous hormone. Admin-istration of H2S promotes wound healing. NO and H2S are mutuallyrequired for the control of angiogenesis and wound healing. H2S sup-plementation may be beneficial to facilitate post-burn wound heal-ing. Potential modes of delivery may include topical or systemicadministration. However, the angiogenic effect of H2S is not expectedto be optimal in conditions where endogenous NO production isimpaired (i.e. conditions associated with endothelial dysfunctionsyndrome). In such conditions, simultaneous supplementation ofboth gasotransmitters may be possible. In addition to wound healing,the pro-angiogenic effects of H2S may be utilized to improve revascu-larization following ischemic conditions, whereas inhibition of H2Sproduction (and associated angiogenic responses) may be of thera-peutic interest in conditions associated with pathological increasesin angiogenesis (e.g. in the context of tumor angiogenesis or in dia-betic retinopathy).

Acknowledgements

This work was supported by a Grant (#8661) of the Shriners Hos-pitals of North America to C.S.

http://dx.doi.org/10.1016/j.niox.2013.06.022

PL13Saying NO to H2S

Jan Miljkovic a, Mirjam Eberhardt b,c, Martin Herrmann d,Karl Messlinger b, Peter Reeh b, Ivana Ivanovic-Burmazovic a,Milos R. Filipovic a

a Department of Chemistry and Pharmacy, Fridrich-Alexander Univer-sity, Erlangen, Germanyb Institute of Physiology and Pathophysiology, Fridrich-AlexanderUniversity, Erlangen, Germanyc Medical Clinic 3 – Rheumatology and Immunology, Fridrich-AlexanderUniversity, Erlangen, Germanyd Hannover Medical School, Hannover, Germany

Hydrogen sulfide (H2S) emerged recently as an important signal-ing molecule involved in regulation of blood pressure and neuronalactivity. Additionally, H2S and its donors possess huge pharmacolog-ical potential to prevent ischemia–reperfusion injuries and, as it hasbeen speculated, to induce suspended animation-like state in smallanimals. However, the real (bio) chemical events behind all theseobserved phenomena remained elusive. In this talk, physiologicaleffects of H2S in context of its interaction with another physiologicalgassotransmitter, nitric oxide (NO), and its metabolites (peroxyni-trite, S-nitrosothiols, nitrite) will be addressed, providing the evi-dence for the existence of a strong cross-talk of these molecules.Applying state-of-the art analytical techniques, as the products ofthese reactions, we identify thionitric (HSNO2) and thionitrous acid(HSNO) as well as nitroxyl (HNO), and show on cellular level thatthey too serve as important signaling molecules. Finally on the ani-mal level we prove our chemistry and show that H2S-induced vasod-ilatory effects are directly NO dependent, identifying thereforecompletely new signaling cascade for systemic neurovascularcontrol.

http://dx.doi.org/10.1016/j.niox.2013.06.023

S16 Abstracts / Nitric Oxide 31 (2013) S11–S65