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Transcellular calcium transport in the kidney, pancreas, small intestine, and placenta is partly mediated by transient receptor potential (TRP) channels. The highly selective TRPV6 calcium channel protein is most likely important for the calcium transfer in different specialized epithelial cells. In the human placenta the protein is expressed in trophoblast tissue, where it is implicated in the transepithelial calcium transfer from mother to the fetus. We enriched the TRPV6 channel protein endogenously expressed in placenta together with annexin A2 and cyclophilin B (CypB), which is a member of the huge immunophilin family. In the human placenta TRPV6 and CypB are mainly located intracellularly in the syncytiotrophoblast layer, but a small amount of the mature glycosylated TRPV6 channel protein and CypB is also expressed in microvilli apical membranes, the fetomaternal barrier. To understand the role of CypB on the TRPV6 channel function, we evaluated the effect of CypB co-expression on TRPV6-mediated calcium uptake into Xenopus laevis oocytes expressing TRPV6. A significant increase of TRPV6-mediated calcium uptake was observed after CypB/TRPV6 coexpression. This stimulatory effect of CypB was reversed by the immunosuppressive drug cyclosporin A, which inhibits the enzymatic activity of CypB. Cyclosporin A had no significant effect on TRPV6 and CypB protein expression levels in the oocytes. In summary, our results establish CypB as a new TRPV6 accessory protein with potential involvement in TRPV6 channel activation through its peptidyl-prolyl cis/trans isomerase activity.In the human placenta the epithelial layer of the syncytiotrophoblast separates the fetal blood vessels from the maternal blood. Syncytiotrophoblasts build a multinuclear barrier layer between mother and child, which carries out the maternal metabolite and calcium transfer. This transepithelial calcium transport is a crucial process for the fetal development. Among candidates that function as membrane gates for calcium entry are voltage-dependent L-and T-type channels (1-5), plasma membrane Ca 2ϩ -ATPases, Na ϩ /Ca 2ϩ exchanger, and ion channels of the transient receptor potential subfamilies TRPC and TRPV.2 Transcripts of members of the canonical TRPC family such as TRPC3, -C4, and -C6 have been amplified by reverse transcription-PCR from term placenta. The presence of TRPC channel activity was demonstrated by blocking storeoperated calcium entry with SKF96365 or gadolinium (6). TRPV5 and TRPV6, which belong to the vanilloid receptor-like TRP subfamily, are highly selective calcium channels (PCa 2ϩ / PNa ϩ Ͼ 100) (7), and both genes are expressed in the trophoblast layer of the placenta (6, 8 -11). Reduced calcium uptake in cultured trophoblast cells was detected in the presence of magnesium or Ruthenium Red, which are known to block TRPV5 and TRPV6 channel activity (10). Apparently TRPV5 and/or TRPV6 are involved in the calcium transport mechanism in these cells. In support of such a role of TRPV6 is a recent report that demonstrates that tar...

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Background: Vascular smooth muscle cell (VSMC) proliferation is of importance in the pathogenesis of vascular diseases such as restenosis or atherosclerosis. Endothelial microparticles (EMP) regulate function and phenotype of target endothelial cells (ECs), but their influence on VSMC biology is unknown. Hypothesis: Intercellular communication between ECs and VSMCs via EMPs regulates vascular remodelling. Methods and results: Systemic treatment of mice with EMPs after vascular injury reduced neointima formation in vivo. In vitro, EMP uptake in VSMCs diminished VSMC proliferation and migration, both pivotal steps in neointima formation. To explore the underlying mechanisms, Taqman microRNA-array was performed and microRNA (miR)-126-3p was identified as the predominantly expressed miR in EMP. Confocal microscopy revealed an EMP-mediated miR-126 transfer into recipient VSMCs. Expression of miR-126 target protein LRP6, regulating VSMC proliferation, was reduced in VSMCs after EMP treatment. Importantly, genetic regulation of miR-126 in EMPs showed a miR-126-dependent inhibition of LRP6 expression, VSMC proliferation and neointima formation in vitro and in vivo, suggesting a crucial role of miR-126 in EMP-mediated neointima formation reduction. Exposure of endothelial cells to pathological hyperglycaemic conditions prior to EMP release abrogated EMP-promoted neointima formation reduction. Finally, analysis of miR-126 expression in circulating MPs in 176 patients with coronary artery disease revealed a reduced PCI rate in patients with high miR-126 expression level, supporting a central role for MP-incorporated miR-126 in vascular remodelling. Conclusions: EMPs reduce VSMC proliferation, migration and subsequent neointima formation by delivering functional miR-126 into recipient VSMCs.