Oxidative stress is responsible for maternal diabetes-impaired transforming growth factor beta signaling in the developing mouse heart

OBJECTIVE: Oxidative stress plays a causal role in diabetic embryopathy. Maternal diabetes induces heart defects and impaired transforming growth factor beta (TGF beta) signaling, which is essential for cardiogenesis. We hypothesize that mitigating oxidative stress through superoxide dismutase 1 (SOD1) overexpression in transgenic (Tg) mice reverses maternal hyperglycemia-impaired TGF beta signaling and its downstream effectors. STUDY DESIGN: Day 12.5 embryonic hearts from wild-type (WT) and SOD1 overexpressing embryos of nondiabetic (ND) and diabetic mellitus (DM) dams were used for the detection of oxidative stress markers: 4-hydroxynonenal (4-HNE) and malondlaldehyde (MDA), and TGF beta 1, 2, and 3, phosphor (p)-TGF beta receptor II (T beta RII), p-phosphorylated mothers against decapentaplegic (Smad) 2, and p-Smad3. The expression of 3 TGF beta-responsive genes was also assessed. Day 11.5 embryonic hearts were explanted and cultured ex vivo, with or without treatments of a SOD1 mimetic (Tempol; Enzo Life Science, Farmingdale, NY) or a TGF beta recombinant protein for the detection of TGF beta signaling intermediates. RESULTS: Levels of 4-HNE and MDA were significantly increased by maternal diabetes, and SOD1 overexpression blocked the increase of these 2 oxidative stress markers. Maternal diabetes suppresses the TGF beta signaling pathway by down-regulating TGF beta 1 and TGF beta 3 expression. Consequently, phosphorylation of TbRII, Smad2, and Smad3, downstream effectors of TGF beta, and expression of 3 TGF beta-responsive genes were reduced by maternal diabetes, and these reductions were prevented by SOD1 overexpression. Treatment with Tempol or TGF beta recombinant protein restored high-glucosee-suppressed TGF beta signaling intermediates and responsive gene expression. CONCLUSION: Oxidative stress mediates the inhibitory effect of hyperglycemia in the developing heart. Antioxidants, TGF beta recombinant proteins, or TGF beta agonists may have potential therapeutic values in the prevention of heart defects in diabetic pregnancies.