Figure 8.

ASK1 activation contributes to nigrostriatal neurodegeneration in 6-OHDA-lesioned mice. A, Lentivirus-mediated knockdown of ASK1 expression in mouse SNc. Mouse SNc was infected for 21 d with empty lentiviral vector, Lenti-ASK1t, or Lenti-ASK1sc, and then subjected to immunoblotting against ASK1 and double-label immunofluorescent staining for ASK1 and TH. ***p < 0.001 versus empty vector control; n = 5/group. Scale bars: a–f (low magnification), 50 μm; g–l (high magnification), 20 μm. B, C, ASK1 knockdown attenuates the ASK1 signaling cascade in 6-OHDA-lesioned mice. Mouse SNc was infected for 21 d with the lentiviral vectors described in A, and the mice received striatal infusion of 6-OHDA (3.0 μg) or saline. B, C, Immunoblotting against p-ASK1 and its downstream signaling proteins was performed 7 d after 6-OHDA infusion (B); quantitative data of B are illustrated in C. *p < 0.05, **p < 0.01 versus vehicle control; #p < 0.05, ##p < 0.01 versus empty lentivirus group; n = 5–6/group. D–G, ASK1 knockdown attenuates DA neuron loss and neurological deficits in 6-OHDA-lesioned mice. Mice were treated as described in A; behavioral tests (D, E) and histology (F, G) were performed 21 d after 6-OHDA infusion. Apomorphine-induced circling after 6-OHDA injection is shown as the number of turns in the first 30 min after intraperitoneal injection of apomorphine (D). The corner test shows the mean of the ratio of spontaneous left/right turns of 10 trials/session 21 d after 6-OHDA injection (E). Arrows in F indicate the SNc region lesioned by 6-OHDA. The numbers of TH-positive neurons in the SNc of three experimental groups are illustrated in G. H, Catecholamine levels from the ipsilateral striatum 21 d following the indicated injections. Catecholamines are expressed as picomoles/milligram fresh, wet tissue. *p < 0.05, **p < 0.01 between the groups indicated; n = 10–12 per group for all experiments.