Abstract
Background and PurposeThe Sigma-1 receptor (Sig1R) impacts on calcium ion signalling and has a plethora of ligands. This study investigated Sig1R and its ligands in relation to endogenous calcium events of endothelial cells and transient receptor potential (TRP) channels.Experimental ApproachIntracellular calcium and patch clamp measurements were made from human saphenous vein endothelial cells and HEK 293 cells expressing exogenous human TRPC5, TRPM2 or TRPM3. Sig1R ligands were applied and short interfering RNA was used to deplete Sig1R. TRP channels tagged with fluorescent proteins were used for subcellular localization studies.Key ResultsIn endothelial cells, 10–100 μM of the Sig1R antagonist BD1063 inhibited sustained but not transient calcium responses evoked by histamine. The Sig1R agonist 4-IBP and related antagonist BD1047 were also inhibitory. The Sig1R agonist SKF10047 had no effect. Sustained calcium entry evoked by VEGF or hydrogen peroxide was also inhibited by BD1063, BD1047 or 4-IBP, but not SKF10047. 4-IBP, BD1047 and BD1063 inhibited TRPC5 or TRPM3, but not TRPM2. Inhibitory effects of BD1047 were rapid in onset and readily reversed on washout. SKF10047 inhibited TRPC5 but not TRPM3 or TRPM2. Depletion of Sig1R did not prevent the inhibitory actions of BD1063 or BD1047 and Sig1R did not co-localize with TRPC5 or TRPM3.Conclusions and ImplicationsThe data suggest that two types of Sig1R ligand (BD1047/BD1063 and 4-IBP) are inhibitors of receptor- or chemically activated calcium entry channels, acting relatively directly and independently of the Sig1R. Chemical foundations for TRP channel inhibitors are suggested.
Highlights
Endothelial cells line the inner walls of blood vessels to provide physiological regulation of blood pressure (Aird, 2007)
We investigated whether Sigma-1 receptor (Sig1R) might have importance for endothelial cell Ca2+ signalling by exploring whether there are effects of Sig1R ligands and short inferring RNA targeted to Sig1R expression
In the presence of the Sig1R antagonist BD1047 or BD1063 at 100 mM, the initial response to histamine was similar to the control but the plateau phases were strongly inhibited (Figure 1B–D; Supporting Information Fig. S1a)
Summary
Endothelial cells line the inner walls of blood vessels to provide physiological regulation of blood pressure (Aird, 2007). Endothelial cells provide the basis for new vessel growth during development or in adult life (Carmeliet, 2005; Aird, 2007; Folkman, 2007). New growth from preexisting blood vessels (angiogenesis) has pivotal roles in physiology and enables tumour expansion, driving research efforts to develop novel anticancer agents through inhibition of angiogenesis (Carmeliet, 2005; Folkman, 2007). AND PURPOSE The Sigma-1 receptor (Sig1R) impacts on calcium ion signalling and has a plethora of ligands. This study investigated Sig1R and its ligands in relation to endogenous calcium events of endothelial cells and transient receptor potential (TRP) channels. TRP channels tagged with fluorescent proteins were used for subcellular localization studies
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