Hydrogen sulphide induces angiogenesis

Hydrogen sulphide (H₂S) is emerging as an important signalling molecule in the cardiovascular and neuronal systems. Although H₂S is known to relax vascular smooth muscle leading to a reduction in blood pressure, the role of this gaseous mediator in other aspects of the biology of vascular cells remains largely unexplored. In order to study the effects of H₂S on neovascularisation, we have utilised an aqueous formulation of H₂S. Incubation of endothelial cells (EC) with H₂S enhanced their angiogenic potential as it promoted cell growth, migration and capillary morphogenesis on matrigel. In line with the in vitro observations, treatment of chicken chorioallantoic membranes (CAM) with H₂S increased vascular length. Morever, exposure of EC to H₂S resulted in increased phosphorylation of kinases linked to angiogenic responses, namely Akt, ERK and p38. Pretreatment of cells with the K_ATP channel blocker glibenclamide or the p38 inhibitor SB203580 abolished H₂S-induced motility. Since glibenclamide inhibited H₂S-triggered p38 phosphorylation, we propose that K_ATP channels lay upstream of p38. Once activated, p38 phosphorylates the actin-binding protein hsp27 to promote cell motility, as hsp27 silencing reduced H₂S-driven migration. To determine whether endogenously produced H₂S, similarly to exogensouly applied H₂S drives the angiogenic response, CAMs were treated with PAG, an inhibitor of H₂S biosynthesis; indeed, PAG-treated membranes displayed reduced vessel length and branching. Finally, pre-treatment of cells with PAG or glibenclamide blocked vascular-endothelial growth factor-induced migration. In conclusion, we provide evidence that endogenously produced or exogenously administered H₂S stimulates EC properties associated with angiogenesis through a K_ATP channel/MAPK pathway.