Fig. 3. Plasma fibronectin that undergoes fibrillogenesis is susceptible to MPO-mediated o,o’-dityrosine crosslinking.

(A) Fluorescence spectroscopy measuring the o,o’-dityrosine formation rate of soluble plasma fibronectin treated as indicated. L-tyrosine treatment with MPO and H₂O₂ (L-tyrosine + MPO) was performed as a positive control. Fluorescence was measured at excitation of 320 nm and an emission of 405 nm. ND, not detectable. Data are representative of three independent experiments and show mean ± SD n = 3 independent experiments. (B) Western blot analysis of soluble, pure plasma fibronectin treated as indicated. The positions of molecular weight standards are indicated to the right of the blot. Data are representative of three independent experiments. (C) Western blot analysis of fibronectin from lysates of mouse lung myofibroblasts that were treated as indicated. β-actin is a loading control. Data are representative of three independent experiments.