Measuring Myeloperoxidase Activity in Biological Samples
Figure 2
In vivo imaging and in vitro MPO activity assays demonstrate markedly different findings.
(A) MPO-Gd molecular MR imaging reveals MPO inhibition in vivo in mice with experimental autoimmune encephalomyelitis that were treated with ABAH. MPO activity maps are shown in 3D from two angles (left), as well as overlays of MPO activity maps over T1 images (right). (B) Quantification of imaging reveals significant difference in MPO activity in vivo (P = 0.03, n = 8 per group). (C) In vitro assays on whole tissue homogenates using ADHP or TMB do not confirm the in vivo imaging finding (P = 0.68 and 0.88, respectively, n = 4 per group). *: P<0.05, n.s. = not statistically significant. MPO = myeloperoxidase. TMB = 3,3′,5,5′-Tetramethylbenzidine. ADHP = 10-acetyl-3,7-dihydroxyphenoxazine. ABAH = 4-aminobenzoic acid hydrazide. Activation ratio = contrast-to-noise ratio 60 minutes over 15 minutes post MPO-Gd injection.