title: Plasma kallikrein mediates retinal vascular dysfunction and induces retinal thickening in diabetic rats.
abstract: OBJECTIVE
  Plasma kallikrein (PK) has been identified in vitreous fluid obtained from individuals with diabetic retinopathy and has been implicated in contributing to retinal vascular dysfunction. In this report, we examined the effects of PK on retinal vascular functions and thickness in diabetic rats.
  
  
  METHODS
  We investigated the effects of a selective PK inhibitor, ASP-440, and C1 inhibitor (C1-INH), the primary physiological inhibitor of PK, on retinal vascular permeability (RVP) and hemodynamics in rats with streptozotocin-induced diabetes. The effect of intravitreal PK injection on retinal thickness was examined by spectral domain optical coherence tomography.
  
  
  RESULTS
  Systemic continuous administration of ASP-440 for 4 weeks initiated at the time of diabetes onset inhibited RVP by 42% (P = 0.013) and 83% (P < 0.001) at doses of 0.25 and 0.6 mg/kg per day, respectively. Administration of ASP-440 initiated 2 weeks after the onset of diabetes ameliorated both RVP and retinal blood flow abnormalities in diabetic rats measured at 4 weeks' diabetes duration. Intravitreal injection of C1-INH similarly decreased impaired RVP in rats with 2 weeks' diabetes duration. Intravitreal injection of PK increased both acute RVP and sustained focal RVP (24 h postinjection) to a greater extent in diabetic rats compared with nondiabetic control rats. Intravitreal injection of PK increased retinal thickness compared with baseline to a greater extent (P = 0.017) in diabetic rats (from 193 ± 10 μm to 223 ± 13 μm) compared with nondiabetic rats (from 182 ± 8 μm to 193 ± 9 μm).
  
  
  CONCLUSIONS
  These results show that PK contributes to retinal vascular dysfunctions in diabetic rats and that the combination of diabetes and intravitreal injection of PK in rats induces retinal thickening.
authors: Research Division, Joslin Diabetes Center, Boston, Massachusetts, USA.
authors: Allen
authors: A
authors: Clermont
authors: Tamie J
authors: TJ
authors: Chilcote
authors: Takeshi
authors: T
authors: Kita
authors: Jia
authors: J
authors: Liu
authors: Priscilla
authors: P
authors: Riva
authors: Sukanto
authors: S
authors: Sinha
authors: Edward P
authors: EP
authors: Feener
mesh_terms: D000818:Animals; D050718:Complement C1 Inhibitor Protein / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005451:Fluorescein Angiography; D015590:Fluorophotometry; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008297:Male; D020842:Plasma Kallikrein / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*
chemical_list: D050718:Complement C1 Inhibitor Protein; D004791:Enzyme Inhibitors; D020842:Plasma Kallikrein