Figure 1.

In vivo imaging of proteases in cutaneous DTHR. Mice were sensitized with 5% TNCB on the abdomen and, after one week, were challenged with 1% TNCB on the right ear to induce acute cutaneous DTHR. As a control, nonsensitized mice were challenged with 1% TNCB on the right ear (irritative-toxic reaction). To induce chronic cutaneous DTHR, mice were repetitively challenged every two days, up to five times. A: ProSense, a probe activatable by several proteases, and ProSense-control, a nonactivatable probe, were injected 12 h after the fifth challenge, and in vivo optical imaging was performed 24 h later. B: The ProSense signal intensity was 4-fold higher in the inflamed right ears than in the control left ears. The nonactivatable control probe displayed almost no signal (n=2; unpaired, two-tailed Student's t-test; mean±SEM). C/D: The signal intensity of CatB680, a probe preferentially activated by cathepsin B, was measured after the first, third and fifth TNCB challenges. After the first challenge, the signal intensity was 4-fold higher than that in untreated control ears. After the third and fifth challenges, the signal intensity increased to 400% and 620% of the control signal intensity (one-way ANOVA; mean±SEM). Unsensitized mice, which developed an irritative-toxic reaction after a single challenge, showed a slightly lower signal than sensitized mice. Untreated naïve mice showed signal intensities similar to those in the untreated left ears.