title: Renin inhibitor VTP-27999 differs from aliskiren: focus on their intracellular accumulation and the (pro)renin receptor.
abstract: BACKGROUND
  VTP-27999 is a renin inhibitor with an IC50 that is comparable to that of aliskiren, but with a higher bioavailability. Unexpectedly, VTP-27999, unlike aliskiren, did not unfold renin's precursor, prorenin, and increased the affinity of the antibodies applied in renin immunoassays.
  
  
  METHODS
  Here we verified to what degree these differences affect intracellular renin inhibitor accumulation in renin-synthesizing human mast cells (HMC-1), and (pro)renin's signaling via the (pro)renin receptor ((P)RR) in rat vascular smooth muscle cells. We also addressed the consequences of (P)RR knockdown by small-interfering (si) RNA on (pro)renin release. Finally, making use of FRET(Bodipy-FL)-labeled aliskiren, we studied, by subcellular fractionation, the cellular distribution pattern of this renin inhibitor.
  
  
  RESULTS
  VTP-27999 accumulated at higher levels in HMC-1 cells than aliskiren, allowing this inhibitor to block intracellular renin at approximately five-fold lower medium levels. Labeled aliskiren accumulated in mitochondria and lysosomes, and its distribution pattern was different from that of renin. Moreover, the intracellular accumulation of both inhibitors in nonrenin-synthesizing HEK293 cells was not different from that in HMC-1 cells, suggesting that it is renin synthesis-independent. VTP-27999, but not aliskiren, blocked renin's capacity to stimulate extracellular signal-regulated kinase 1/2 phosphorylation in vascular smooth muscle cells, whereas neither inhibitor interfered with prorenin-induced signaling. (P)RR knockdown greatly increased renin (and to a lesser degree, prorenin) release, without affecting the capacity of forskolin or cAMP to stimulate renin release.
  
  
  CONCLUSIONS
  VTP-27999 differs from aliskiren regarding its level of intracellular accumulation and its capacity to interfere with renin signaling via the (P)RR, and the (P)RR determines prorenin-renin conversion and constitutive (but not regulated) (pro)renin release.
authors.affiliation: Division of Pharmacology and Vascular Medicine, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Xifeng
authors.initials: X
authors.lastname: Lu
authors.forename: Manne
authors.initials: M
authors.lastname: Krop
authors.forename: Wendy W
authors.initials: WW
authors.lastname: Batenburg
authors.forename: Usha M
authors.initials: UM
authors.lastname: Musterd-Bhaggoe
authors.forename: Ingrid M
authors.initials: IM
authors.lastname: Garrelds
authors.forename: A H Jan
authors.initials: AH
authors.lastname: Danser
mesh_terms: D000577:Amides / Q000627:therapeutic use*; D000818:Animals; D000959:Antihypertensive Agents / Q000627:therapeutic use; D002219:Carbamates / Q000627:therapeutic use*; D031541:Fluorescence Resonance Energy Transfer; D005650:Fumarates / Q000627:therapeutic use*; D057809:HEK293 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D008247:Lysosomes / Q000187:drug effects; D008407:Mast Cells / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects; D010880:Piperidines / Q000627:therapeutic use*; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012083:Renin / Q000737:chemistry / Q000378:metabolism; D000093342:Prorenin Receptor; D000092502:Renin Inhibitors
chemical_list: D000577:Amides; D000959:Antihypertensive Agents; D002219:Carbamates; D005650:Fumarates; D010880:Piperidines; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D012083:Renin; D000093342:Prorenin Receptor; D000092502:Renin Inhibitors; C582069:methyl (2-((3-chlorophenyl)(1-((2-(methylamino)-3-(tetrahydro-2H-pyran-3-yl)propyl)carbamoyl)piperidin-3-yl)methoxy)ethyl)carbamate; C446481:aliskiren