Plasminogen activator inhibitor type 1 (PAI-1) promoted microglial migration through low-density lipoprotein receptor-related protein (LRP)1. (A, B) BV-2 microglial cells were transiently transfected with control small interfering (si)RNA or LRP1-specific siRNA. After 48 hours, a scratch wound was made. Cells were treated with or without mouse PAI-1 protein (100 ng/ml), followed by (A) the wound-healing assay and (B) the Boyden chamber assay, as described in Figure 2. Results are given as mean ± SD (n = 3). *P < 0.05, **P < 0.01, NS = not significant (lower panel). (Upper panels) Representative images of each assay. (C, D) Knockdown of LRP1 gene expression by siRNA was confirmed by using (C) reverse transcriptase PCR, (D) dot blotting (upper panel), and western blotting (lower panel). β-actin and the α-tubulin were used as internal controls. (E) BV-2 microglial cells were treated with mouse PAI-1 protein (100 ng/ml) and RAP protein (5 μg/ml) as indicated. The fold increase in migration distance was measured using the wound-healing assay. Results are given as mean ± SD (n = 3). *P < 0.05, NS = not significant, compared with the untreated control (lower panel). (Upper panel) Representative images also shown.