Programmed cell death and differential JNK, p38 and ERK response in a prenatal acute hypoxic hypoxia model

We previously found that prenatal hypoxia induces a significant increase in the levels of active Caspase 3 at 60 min post-hypoxia (p-h) and in the number of TUNEL-positive pyknotic cells, which peaks at 6h p-h. The aim of this work was to study alterations in MAPKs pathways and the effect of specific inhibitors of the JNK (SP600125) and p38 (SB203580) pathways following acute hypoxia in chick optic lobe at embryonic day (ED) 12. To this end, JNK, p38 and ERK1-2 protein kinase expression levels were determined by Western blot in both their active and inactive forms, evaluated at successive p-h times. At 10 and 30 min p-h the P-JNK/JNK ratio was 1.912+/-0.341 and 1.920+/-0.304, respectively. Concomitantly, at 0 min p-h the P-p38/p38 ratio was 1.657+/-0.203. Lastly, the P-ERK/ERK ratio proving non-significant throughout. When inhibitors for JNK and p38 were used, we observed a decrease in the values of active Caspase 3 at 60 min p-h, which correlated with the control values in the parameters of TUNEL-positive cells at 6h p-h. Analysis for P-ATF-2 demonstrated an increase in hypoxic embryos compared to control ones which was reverted in a dose-dependent manner with the use of both inhibitors. All these results indicate that at ED 12, acute hypoxia might be differentially activating JNK and p38 pathways, without affecting the ERK pathway, which in turn would be activating Caspase 3, thus leading to cell death by apoptosis. Furthermore, JNK and p38 activation precede in time the programmed cell death induced by hypoxia.