Figure 2. Time course effect of norrin on
tPA and uPA expression, and on cell survival. RGC-5 cells were left
untreated or treated for 24 h and 48 h with staurosporine (SS) only
(2.0 μM), norrin only (25 ng/ml), or SS and norrin (n=3 experiments).
At the end of the treatment, conditioned medium was collected,
proteolytic activity of tissue plasminogen activator (tPA) and
urokinase plasminogen activator (uPA) was determined by zymography
assays (A,D), and relative amount of proteolytic activity was
determined by densitometric analysis (B,E). Cell viability was
determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium
bromide (MTT) assays (C,F). Compared to low levels of uPA
present in untreated cells or in norrin alone-treated cells (A,B),
uPA levels were increased in SS (B, *p<0.05) or in SS and
norrin-treated cells (B, **p<0.05) at 24 h after treatment.
However, increased levels of uPA alone had no effect on cell survival (C,
not significant, NS). Compared to low levels of uPA present in
untreated cells or in norrin alone-treated cells (D,E), uPA (E,
*p<.0.05, **p<0.05) and tPA (E, %p<0.05, %%p<0.05)
levels were increased significantly in SS or in SS and norrin-treated
cells at 48 h after treatment. Nonetheless, survival of RGC-5 cells
decreased in SS alone-treated cells (F, *p<0.05) but not in
SS and norrin-treated cells (F,**p<0.05).