Hydrogen sulfide and nitric oxide are mutually dependent in the regulation of angiogenesis and endothelium-dependent vasorelaxation

Abstract

Hydrogen sulfide (H 2 S) is a unique gasotransmitter, with regulatory roles in the cardiovascular, nervous, and immune systems. Some of the vascular actions of H 2 S (stimulation of angiogenesis, relaxation of vascular smooth muscle) resemble those of nitric oxide (NO). Although it was generally assumed that H 2 S and NO exert their effects via separate pathways, the results of the current study show that H 2 S and NO are mutually required to elicit angiogenesis and vasodilatation. Exposure of endothelial cells to H 2 S increases intracellular cyclic guanosine 5′-monophosphate (cGMP) in a NO-dependent manner, and activated protein kinase G (PKG) and its downstream effector, the vasodilator-stimulated phosphoprotein (VASP). Inhibition of endothelial isoform of NO synthase (eNOS) or PKG-I abolishes the H 2 S-stimulated angiogenic response, and attenuated H 2 S-stimulated vasorelaxation, demonstrating the requirement of NO in vascular H 2 S signaling. Conversely, silencing of the H 2 S-producing enzyme cystathionine-γ-lyase abolishes NO-stimulated cGMP accumulation and angiogenesis and attenuates the acetylcholine-induced vasorelaxation, indicating a partial requirement of H 2 S in the vascular activity of NO. The actions of H 2 S and NO converge at cGMP; though H 2 S does not directly activate soluble guanylyl cyclase, it maintains a tonic inhibitory effect on PDE5, thereby delaying the degradation of cGMP. H 2 S also activates PI3K/Akt, and increases eNOS phosphorylation at its activating site S1177. The cooperative action of the two gasotransmitters on increasing and maintaining intracellular cGMP is essential for PKG activation and angiogenesis and vasorelaxation. H 2 S-induced wound healing and microvessel growth in matrigel plugs is suppressed by pharmacological inhibition or genetic ablation of eNOS. Thus, NO and H 2 S are mutually required for the physiological control of vascular function. N itric oxide (NO) and hydrogen sulfide (H 2 S) are two endogenous gasotransmitters whose regulatory roles in the cardiovascular system include vasorelaxation and stimulation of angiogenesis (1, 2). In endothelial cells, NO is synthesized by the endothelial isoform of NO synthase (eNOS). The principal pathway of NO signaling involves binding to the heme moiety of the soluble guanylyl cyclase (sGC) and production of the second messenger cyclic guanosine 5′-monophosphate (cGMP), followed by the activation of protein kinase G (PKG) (3, 4). However, vascular H 2 S is generated from L-cysteine by two pyridoxal 5′-phosphate-dependent enzymes, cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), and by the combined action of cysteine aminotransferase (CAT) and 3-mercaptopyruvate sulfurtransferase (3-MST); activation of the ATP-dependent potassium channel (K ATP channel), modulation of cell metabolism, and posttranslational protein modifications via sulfhydration have been identified as some of its key signaling pathways (5-7).It is generally assumed that the signaling pathways of NO and H 2 S are independent. In the ...

Highly sensitive sulphide mapping in live cells by kinetic spectral analysis of single Au-Ag core-shell nanoparticles

“…H ydrogen sulphide (H 2 S), traditionally considered a toxic gas with a rotten egg smell, has been recognized as an endogenous gasotransmitter with importance comparable to nitric oxide (NO) and carbon monoxide (CO), and has attracted increasing attention in recent years [1][2][3][4] . H 2 S equilibrates with aqueous sulphides (HS À and S 2 À ) in biological environments and has vital roles in various physiological and pathological processes, including vasorelaxation 5 , angiogenesis 6 , cerebral microcirculation 7 , neurotransmission 8,9 , inflammation 10 , apoptosis 11 , insulin signalling inhibition 12 , oxygen sensing 13 and energy production in mitochondria 14 .…”

Shared signaling pathways among gasotransmitters

“…Coletta et al found that the proangiogenic effect of H 2 S on angiogenesis and wound healing was completely absent in endothelial NO synthase KO mice, and that eliminating H 2 S production by silencing cystathionine-γ-lyase (CSE) abolished NO-stimulated angiogenesis (2). This mutually dependent relationship between H 2 S and NO in vascular endothelial cells is rooted in the regulation of the cellular levels of cGMP.…”

“…After being synthesized in, and released from, the endothelium, NO activates sGC in vascular SMCs to induce vasorelaxation (3), whereas H 2 S opens intermediate-and small-conductance calcium-sensitive K channels in the endothelium as an endothelium-derived hyperpolarizing factor (7), and stimulates K ATP channels in vascular SMCs to relax blood vessels (8). A mechanism was introduced by Coletta et al, who ascribed endothelium-dependent and H 2 S-induced vasorelaxation partially to the inhibition of PDE5 in vascular SMCs (2). This proposed mechanism is not undisputed, as, under resting conditions, total cGMP content in rat aortic rings was not significantly decreased by silencing CSE, or increased by addition of NaHS (a H 2 S donor) (2).…”

“…by Coletta et al (2) presents an interesting example of how the interaction of gasotransmitters converges at the same downstream molecular target. Coletta et al found that the proangiogenic effect of H 2 S on angiogenesis and wound healing was completely absent in endothelial NO synthase KO mice, and that eliminating H 2 S production by silencing cystathionine-γ-lyase (CSE) abolished NO-stimulated angiogenesis (2).…”

“…This mutually dependent relationship between H 2 S and NO in vascular endothelial cells is rooted in the regulation of the cellular levels of cGMP. NO activates soluble guanylyl cyclase (sGC) to generate cGMP, whereas H 2 S inhibits phosphodiesterase-5 (PDE5) to slow down the degradation of the existing cGMP (2). A net increase in cGMP level leads to the activation of protein kinase G (PKG) and its downstream effector, vasodilator-stimulated phosphoprotein.…”