Maternal Undernutrition Dysregulates Apoptosis in Offspring Fetal Kidneys
CC Nast, MG Ross, M Desai, TR Magee. Cedars-Sinai Medical Center, Los Angeles, CA; Harbor-UCLA Medical Center, Torrance, CA
Background: Maternal undernutrition (MUN) results in offspring kidney nephron deficits but the mechanisms of this phenotypic change are unknown. We sought to evaluate alterations in MUN-induced fetal kidney RNA and protein expression to assess dysregulation of apoptosis in this model.
Design: Pregnant rat dams were 50% food restricted from embryonic day (E)10. Male offspring E20 and postpartum day (P) 1 kidneys were removed. E20 whole kidney RNA was hybridized using rat Agilent DNA microarrays. E20 and P1 kidneys were frozen for Western blot analysis. P1 kidneys were fixed in paraformaldehyde for TUNEL staining and assessed semiquantitatively (0-4+ scale).
Results: E20 kidney microarray assessment showed 198 known genes with ≥ 1.5 fold change, which were analyzed for placement into ontological groups and signaling pathways. Four significantly upregulated genes were detected in apoptotic signaling pathways; Fas ligand (7.0 fold), TNFα1 (3.5 fold), PI kinase (6.2 fold), and AKT2 (1.5 fold). To further assess apoptosis, Western blots were performed for these proteins as well as down-stream effector genes. E20 kidneys had upregulation of Fas (2.2 fold, p < 0.002) and Bcl-2 (1.8 fold, p < 0.003) relative to controls (C). P1 kidneys demonstrated augmented Fas (1.9 fold, p < 0.05), BAX (4.5 fold, p < 0.01) and caspase 3 (1.6 fold, p < 0.03) with significant decrease in Bcl-2 (0.6 fold, p < 0.01). Fas ligand protein was not significantly altered at E20 (1.4 fold) or P1 (1.3 fold). TUNEL stain in P1 kidneys revealed apoptosis predominantly in the nephrogenic zone and the deep medulla/papillae. MUN P1 kidneys had significant increase in nephrogenic zone TUNEL staining (MUN 2.2 ± .3 vs C 1.6 ± .5, p < 0.05); deep medullary TUNEL was not significantly different.
Conclusions: This study demonstrates upregulation of apoptosis in MUN offspring kidneys prominently in the nephrogenic zone, with differences in apoptosis signaling before and after birth. Pro-apoptotic proteins were augmented, while anti-apoptotic Bcl-2 was increased at E20 but reduced at P1 suggesting an effect of parturition on cell survival. Previously, we have demonstrated downregulation of Notch in MUN E20 kidneys; Notch determines cell fate and impacts apoptosis. Therefore, in the late fetal period altered apoptosis may be, in part, a downstream effect of Notch dysregulation and/or a direct effect of MUN. Increased apoptosis likely is an important mechanism inducing nephropenia in MUN progeny.
Category: Kidney (does not include tumors)
Monday, March 22, 2010 1:00 PM
Platform Session: Section H, Monday Afternoon