Plasminogen binding to fibrin and plasmin generation is inhibited by Aβ. Fibrin clots were formed with FITC-plasminogen as described in “Plasminogen binding to fibrin,” and 5 μm z-stacks composed of 11 sections were acquired and projected 2-dimensionally for control (A) and Aβ42-containing (B) clots. Images of 15 random sections from 3 separate clots were also acquired and used for quantification (insets show representative single sections). (A) Control clot has formed with FITC-plasminogen shows plasminogen fluorescence in the pattern of the fibrin network. (B) Clot formed with Aβ has less FITC-plasminogen fluorescence. (C) Fluorescence intensity relative to maximum intensity recorded was significantly lower (P = .02) for Aβ-containing clots. (D) Plasminogen binding to fibrin monolayers exposed to 2μM Aβ42 or vehicle was measured by ELISA and normalized to samples not containing plasminogen. Plasminogen binding was decreased in the presence of Aβ (P = .04). (E) Plasmin generation was measured by overlaying tPA, plasminogen, and chromogenic substrate Pefa-5329 on fibrin monolayers exposed to 2μM Aβ42 or vehicle and recording absorbance at 405 nm. Plasmin generation on fibrin monolayers exposed to Aβ was attenuated.
