Angiotensin-2-mediated Ca2+ signaling in the retinal pigment epithelium: role of angiotensin-receptor-associated-protein and TRPV2 channel

PLoS One. 2012;7(11):e49624. doi: 10.1371/journal.pone.0049624. Epub 2012 Nov 20.

Abstract

Angiotensin II (AngII) receptor (ATR) is involved in pathologic local events such as neovascularisation and inflammation including in the brain and retina. The retinal pigment epithelium (RPE) expresses ATR in its AT1R form, angiotensin-receptor-associated protein (Atrap), and transient-receptor-potential channel-V2 (TRPV2). AT1R and Atrap co-localize to the basolateral membrane of the RPE, as shown by immunostaining. Stimulation of porcine RPE (pRPE) cells by AngII results in biphasic increases in intracellular free Ca(2+)inhibited by losartan. Xestospongin C (xest C) and U-73122, blockers of IP3R and PLC respectively, reduced AngII-evoked Ca(2+)response. RPE cells from Atrap(-/-) mice showed smaller AngII-evoked Ca(2+)peak (by 22%) and loss of sustained Ca(2+)elevation compared to wild-type. The TRPV channel activator cannabidiol (CBD) at 15 µM stimulates intracellular Ca(2+)-rise suggesting that porcine RPE cells express TRPV2 channels. Further evidence supporting the functional expression of TRPV2 channels comes from experiments in which 100 µM SKF96365 (a TRPV channel inhibitor) reduced the cannabidiol-induced Ca(2+)-rise. Application of SKF96365 or reduction of TRPV2 expression by siRNA reduced the sustained phase of AngII-mediated Ca(2+)transients by 53%. Thus systemic AngII, an effector of the local renin-angiotensin system stimulates biphasic Ca(2+)transients in the RPE by releasing Ca(2+)from cytosolic IP3-dependent stores and activating ATR/Atrap and TRPV2 channels to generate a sustained Ca(2+)elevation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Angiotensin II / metabolism*
  • Animals
  • Calcium / chemistry
  • Calcium / metabolism*
  • Estrenes / pharmacology
  • Imidazoles / pharmacology
  • Immunohistochemistry / methods
  • Losartan / pharmacology
  • Macrocyclic Compounds / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Oxazoles / metabolism
  • Pyrrolidinones / pharmacology
  • RNA, Small Interfering / metabolism
  • Retinal Pigment Epithelium / metabolism
  • Retinal Pigment Epithelium / physiology*
  • Signal Transduction
  • Swine
  • TRPV Cation Channels / metabolism*

Substances

  • AGTRAP protein, human
  • Adaptor Proteins, Signal Transducing
  • Estrenes
  • Imidazoles
  • Macrocyclic Compounds
  • Oxazoles
  • Pyrrolidinones
  • RNA, Small Interfering
  • TRPV Cation Channels
  • TRPV2 protein, human
  • xestospongin C
  • Angiotensin II
  • 1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
  • 1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole
  • Losartan
  • Calcium

Grants and funding

Deutsche Forschungsgemeinschaft SFB 699, TPB8 ProRetina PhD grant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.”