A mouse model to assess endothelial activation in vivo by targeted insertion of alkaline phosphatase into the E-selectin gene

We have developed a novel and noninvasive animal model in which the activity of a marker enzyme in plasma is used to measure endothelial cell activation. Secreted heat‐stable human placental alkaline phosphatase (SeAP) was placed under the transcriptional control of the E‐selectin promoter by targeted integration into the mouse E‐selectin locus. Two transgenic mouse lines were generated: (1) ESAP‐1, coding for an extended mRNA containing SeAP and part of the 3′ E‐selectin mRNA and (2) ESAP‐2, coding for a short mRNA containing SeAP followed by the SV40 late mRNA polyadenylation site. Wild‐type mice did not express SeAP mRNA or detectable enzyme activity in plasma. Baseline SeAP activity was 8.1±0.4 ng/mL for ESAP‐1 mice and 12.3±0.4 µg/mL for ESAP‐2 mice. Upon treatment with lipopolysaccharide or tumor necrosis factor TNF‐α (but not interferon‐γ), SeAP activity increased 7–11‐fold in plasma obtained from both mouse lines, with 500‐fold higher levels and prolonged expression kinetics in the ESAP‐2 mice compared to ESAP‐1 mice. Enzyme histochemistry indicated endothelial origin of the alkaline phosphatase activity. Administration of dexamethasone, an antiinflammatory steroid, inhibited TNFα‐induced SeAP expression in mice from both lines. The model described here allows monitoring of the E‐selectin expression in vivo, offering a noninvasive means to quantitate inflammatory endothelial cell activation and to evaluate therapeutic approaches designed to inhibit endothelial cell activation. Drug Dev. Res. 63:54–65, 2004. © 2004 Wiley‐Liss, Inc.