Abstract
Normal embryogenesis requires complex regulation and precision, which depends on multiple mechanistic details. Defective embryogenesis can occur by various mechanisms. Maintaining redox homeostasis is of importance during embryogenesis. NADPH, as produced from the action of glucose-6-phosphate dehydrogenase (G6PD), has an important role in redox homeostasis, serving as a cofactor for glutathione reductase in the recycling of glutathione from oxidized glutathione and for NADPH oxidases and nitric oxide synthases in the generation of reactive oxygen (ROS) and nitrogen species (RNS). Oxidative stress differentially influences cell fate and embryogenesis. While low levels of stress (eustress) by ROS and RNS promote cell growth and differentiation, supra-physiological concentrations of ROS and RNS can lead to cell demise and embryonic lethality. G6PD-deficient cells and organisms have been used as models in embryogenesis for determining the role of redox signaling in regulating cell proliferation, differentiation and migration. Embryogenesis is also modulated by anti-oxidant enzymes, transcription factors, microRNAs, growth factors and signaling pathways, which are dependent on redox regulation. Crosstalk among transcription factors, microRNAs and redox signaling is essential for embryogenesis.
Highlights
Introduction published maps and institutional affilThe quality of an embryo and its growth warrant the existence and perpetuation of a species
Transient treatment of tert-butyl hydroperoxide, an inducer of lipid peroxidation decreases brood size and increases germ cell apoptosis [48]. tBHP stimulates malondialdehyde (MDA) generation and up-regulates independent phospholipase A2 (iPLA) activity, thereby interfering with oogenesis and embryogenesis. These findings indicate that glucose-6-phosphate dehydrogenase (G6PD) deficiency-derived lipid peroxidation enhances germ cell demise, leading to embryonic lethality, and demonstrates that G6PD is required for maintaining membrane stability and lipid homeostasis through redox balance during early embryonic stages
nicotinamide adenine dinucleotide phosphate (NADPH) produced from the action of G6PD is important in maintaining redox homeostasis by serving as a cofactor for NADPH-dependent redox enzymes, including GSH reductase, thioredoxin reductase (TrxR), aldo-keto reductase, as well as NADPH oxidase (NOX) and nitric oxide synthase (NOS)
Summary
Different animal models have been used in different redox studies because redox systems in all species are somewhat similar. Human mitochondrial TRXN2 (an ortholog with C. elegans TRX-2) is oxidized by mitochondrial-dependent superoxide, leading to the activation of the apoptosis signal-regulating kinase 1 (ASK-1) signaling pathway [29]. A family of anti-oxidant proteins, peroxiredoxins (Prx), are conserved in all types of organisms, including bacteria, plants, nematodes, and mammals. C. elegans peroxiredoxins-2 (CePrx2), a homolog of human. Fungi, worms and mammals, the disulfide reducing enzymes, GSH reductase and TrxR, are conserved. Glutaredoxins (GLRX) are redox enzymes that use glutathione as a cofactor for reducing protein disulfides. GLRX3 functions as an iron-sulfur protein [28]. Another redox compound, protein disulfide isomerase (PDI), which is found in the endoplasmic reticulum (ER), catalyzes the formation (oxidation), breakage (reduction) and rearrangement (isomerization) of disulfide bonds between cysteine residues within proteins. PDI-1, PDI-2 and PDI-3 are important for embryogenesis, viability and formation of the extracellular matrix in C. elegans [33]
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