Figure 6. The neuroprotective effect of GPNMB extracellular fragment against SOD1^G93A with serum free-induced cell death was inhibited by NKA α1 siRNA.

(A) Cells were transfected with the empty vector (mock) as a control or with human mutant SOD1^G93A cDNAs and mouse NKA α1 siRNA or negative-control siRNA. Western blotting was used to confirm that NKA α1 levels were knocked down. *p < 0.05 vs. negative-control group (Student’s t-test). Each column and bar represents the mean ± S.E.M. (n = 6). (B) Cells were treated with vehicle or with human recombinant GPNMB (2.5 μg/ml) concomitantly with removing the serum. The number of cells displaying PI or Hoechst 33342 fluorescence was counted, and the cell death rate was expressed as the ratio of PI-positive cells to Hoechst 33342-positive cells. ^##p < 0.01 vs. control group (Student’s t-test). **p < 0.01 vs. vehicle group, ^††p < 0.01 vs GPNMB treated group (Tukey’s test). Each column and bar represents the mean ± S.E.M. (n = 4).