Fig. 5.

Lipocalin 2 mediates inflammation-induced FGF23 elevation. Levels of serum total FGF23 (cFGF23) and serum intact FGF23 (iFGF23) inWT and Lcn2^KO mice fed (a), (b) a 0.8% (Ctr) or a 2% high phosphate (HP) diet from 6 to 12 weeks, (c), (d) a 48 ppm (Ctr) or a 3 ppm iron deficient (ID) diet from 3 to 6 weeks, and (e), (f) 6 h post-injection of a single dose of saline (Ctr) or interleukin 1β (IL-1β, 250 ng·g⁻¹) in 6-week old mice. (g) Serum levels of LCN2 in WT mice submitted to the same challenges. Data are presented as mean ± SE, n ≥ 5 per group, P < 0.05 vs.*Ctr-WT, ^$Ctr-Lcn2^KO, ^&IL-1β-WT. Levels of (h), (k) bone Fgf23 mRNA, (i), (l) serum total FGF23 (cFGF23) and (j), (m) serum intact FGF23 (iFGF23) in WT mice treated continuously for 4 weeks with 0 (0.9%NaCl), 5 and 50 ng·g⁻¹ of mouse recombinant LCN2 (mrLCN2) (h)–(j) or injected daily for 4 d with 0 (0.9%NaCl) and 50 ng·g⁻¹ of mrLCN2 (k)–(m). Data are presented as mean ± SE, n ≥ 5 per group, P < 0.05 vs. *non treated, ^&5 ng·g⁻¹ mrLCN2. Fgf23 mRNA levels (n) in primary osteoblast and (o) in MC3T3-E1 osteoblasts cultures treated with 0–50 osteoblasts cultures treated with 0–50 ng·mL^–1 of mrLCN2. (p) Fgf23 promoter activity in Fgf23 promoter-reporter MC3T3-E1 osteoblast cultures treated with 0–50 ng·mL⁻¹ of mrLCN2. Data are presented as mean ± SE, n ≥ 3 per group, P < 0.05 vs. *non treated, ^&5 ng·mL⁻¹, ^#25 ng·mL⁻¹ mrLCN2