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Activation of oxidative stress signaling that is implicated in apoptosis with a mouse model of diabetic embryopathy
Peixin Yang1, Zhiyong Zhao, E Albert Reece
1Department of Obstetrics, Gynecology & Reproductive Sciences, University of Maryland School of Medicine, Baltimore, MD, USA.
Objective:
A mouse model of diabetic embryopathy in C57BL/6J background was established to use the resources of genetically engineered mice in which a specific gene is deleted or overexpressed. To test whether our previous fundamental findings in the rat model of diabetic embryopathy are transferable to this mouse model of diabetic embryopathy, levels of phosphorylated-JNK1/2 (c-Jun N-terminal kinase 1 and 2) and apoptotic markers (cleaved caspase 3) were determined. To establish a link between oxidative stress signaling and diabetic embryopathy, levels of phosphorylated-p66Shc (which is a key signaling molecule that mediates oxidative stress-induced apoptosis) were evaluated.
Study Design:
Diabetes mellitus was induced in female C57BL/6J mice by an intravenous injection of streptozotocin (75 mg/kg). Glucose levels were controlled by the subcutaneous implantation of insulin pellets. The female mice were mated with normal male mice. At gestation day 5 or embryonic day 5 (E5), the insulin pellets were removed from a group of animals, which made them hyperglycemic (> 250 mg/dL glucose). The animals with retained insulin pellets served as controls. On embryonic day 11, mice were killed, and embryos were dissected from the uteri for examination. Embryos and yolk sacs from individual conceptus were collected. Levels of phosphorylated-JNK1/2, phosphorylated-p66Shc, and cleaved caspase 3 were determined in the embryos and yolk sacs.
Results:
Malformation rates in embryos from diabetic mice were 3-fold higher than those in embryos from nondiabetic or diabetic/euglycemic control groups. JNK1/2, especially p54 JNK isoform, which is predominantly expressed by jnk2 gene, was activated in malformed embryos and their respective yolk sacs from diabetic mice and was significantly higher than those in normally developed embryos and their respective yolk sacs from nondiabetic and diabetic mice. Correlating to JNK1/2 activation, phosphorylated-p66Shc was also significantly increased in malformed embryos and their respective yolk sacs from diabetic mice than in normally developed embryos and their respective yolk sacs from nondiabetic and diabetic mice. Cleaved caspase 3 was observed in malformed embryos from diabetic mice.
Conclusion:
The present study shows that maternal hyperglycemia is able to induce embryonic dysmorphogenesis in C57BL/6J mice that is comparable with that seen in the rat model of diabetic embryopathy. Like the well-studied rat model of diabetic embryopathy, activation of JNK1/2 and p66Shc and the increase of apoptotic markers are manifested in this mouse model of diabetic embryopathy. These findings suggest that the activation of oxidative stress signaling in diabetic embryopathy leads to excessive embryonic cell apoptosis and ultimately embryonic dysmorphogenesis. To apply the powerful genetic approach to the research of diabetic embryopathy, a mouse is a better animal model than a rat because all gene knockout (deletion) and gene transgenic (gene overexpression) animals are made in the mouse. The mouse model of diabetic embryopathy that was established in the present study may serve as a suitable substitute for the rat model of diabetic embryopathy, thus enabling us and other investigators to use genetically engineered technologies in the study of diabetic embryopathy.
Insights
Maternal hyperglycemia in mice induces embryonic malformations by activating oxidative stress pathways, specifically JNK1/2 and p66Shc, leading to apoptosis. This mouse model is crucial for studying diabetic embryopathy using genetic engineering.
Area of Science:
- Developmental Biology
- Reproductive Medicine
- Genetics
Background:
- Diabetic embryopathy, a complication of maternal diabetes, causes birth defects.
- Previous studies in rat models identified key molecular pathways involved.
- A need exists for a mouse model to leverage genetic engineering tools.
Purpose of the Study:
- Establish a mouse model of diabetic embryopathy in C57BL/6J mice.
- Validate the transferability of findings from rat models.
- Investigate the roles of phosphorylated-JNK1/2, cleaved caspase 3, and phosphorylated-p66Shc.
Main Methods:
- Induction of diabetes in female mice using streptozotocin.
- Hyperglycemia achieved by insulin pellet removal during gestation.
- Quantification of phosphorylated-JNK1/2, phosphorylated-p66Shc, and cleaved caspase 3 in embryos and yolk sacs.
Main Results:
- Diabetic mice exhibited a 3-fold increase in embryonic malformations.
- Activated JNK1/2 and increased phosphorylated-p66Shc were observed in malformed embryos.
- Cleaved caspase 3, an apoptotic marker, was present in malformed embryos.
Conclusions:
- Maternal hyperglycemia induces dysmorphogenesis in mice, mirroring rat models.
- Activation of oxidative stress signaling (JNK1/2, p66Shc) contributes to apoptosis and malformations.
- This mouse model facilitates genetic studies of diabetic embryopathy.
