The essential role of protein kinase Cδ in diabetes-induced neural tube defects

Abstract

Background: Maternal diabetes causes neural tube defects (NTDs) in the embryos via activating protein kinase Cs (PKCs), which regulate programmed cell death (apoptosis). The aims of this study are to investigate the role of proapoptotic PKCδ in NTD formation and the underlying mechanisms.

Methods: PKCδ heterozygous (pkcδ(+/-)) female mice were diabetic (DM) induced by intravenous injection of streptozotocin. Occurrence of NTDs was evaluated at embryonic day 11.5 and compared between wild type (WT) and PKCδ homozygous (pkcδ(-/-)) embryos. Changes in oxidative and endoplasmic reticulum (ER) stress-associated factors and stress-response c-Jun N-terminal kinases (JNKs) were assessed using Western blot assay.

Results: Compared to DM/WT, the DM/PKCδ(-/-) embryos had significantly lower NTD rate and lower levels of oxidative and ER stress factors and JNK activation. These values were similar to those in the non-diabetic control group.

Conclusion: PKCδ plays a critical role in diabetes-induced NTDs, potentially through increasing oxidative and ER stress and JNK-associated stress-response pathways.

Figure 1

Neural tube development in the embryos. E11.5 embryos of DM/WT (A), DM/PKCδ^−/− (B), and CON (C). The arrow indicates opened neural tube in the brain region. Scale bars = 200 μm.

Figure 2

Western blot analysis of oxidative stress markers. (A) 3-NT; (B) 4-HNE. The bar charts represent band densities normalized to β-actin (Mean ± SEM; *p < 0.05 vs. CON, #p < 0.05 vs. DM/WT; n = 4).

Figure 3

Alteration of ER stress in PKCδ knockout embryos. ER stress markers (A) CHOP; (B) BiP; and (C) p-eIF2α and eIF2α. The bar charts represent band densities normalized to β-actin (Mean ± SEM; *p < 0.05 vs. CON, #p < 0.05 vs DM/WT; n = 4).

Figure 4

Expression of phosphorylated JNK (p-JNK). The bar charts represent band density normalized to β-actin (Mean ± SEM; *p < 0.05 vs CON, #p < 0.05 vs. DM/WT; n = 4).