Nitric Oxide Reverses the Position of the Heart during Embryonic Development

S-nitrosylation of EZH2 alters PRC2 assembly, methyltransferase activity, and EZH2 stability to maintain endothelial homeostasis

Nitric oxide (NO), a versatile bio-active molecule modulates cellular functions through diverse mechanisms including S-nitrosylation of proteins. Herein, we report S-nitrosylation of selected cysteine residues of EZH2 in endothelial cells, which interplays with its stability and functions. We detect a significant reduction in H3K27me3 upon S-nitrosylation of EZH2 as contributed by the early dissociation of SUZ12 from the PRC2. Moreover, S-nitrosylation of EZH2 causes its cytosolic translocation, ubiquitination, and degradation. Further analysis reveal S-nitrosylation of cysteine 329 induces EZH2 instability, whereas S-nitrosylation of cysteine 700 abrogates its catalytic activity. We further show that S-nitrosylation-dependent regulation of EZH2 maintains endothelial homeostasis in both physiological and pathological settings. Molecular dynamics simulation reveals the inability of SUZ12 to efficiently bind to the SAL domain of EZH2 upon S-nitrosylation. Taken together, our study reports S-nitrosylation-dependent regulation of EZH2 and its associated PRC2 complex, thereby influencing the epigenetics of endothelial homeostasis.

Mechanical induction in metazoan development and evolution: from earliest multi-cellular organisms to modern animal embryos

The development and origin of animal body forms have long been intensely explored, from the analysis of morphological traits during antiquity to Newtonian mechanical conceptions of morphogenesis. Advent of molecular biology then focused most interests on the biochemical patterning and genetic regulation of embryonic development. Today, a view is arising of development of multicellular living forms as a phenomenon emerging from non-hierarchical, reciprocal mechanical and mechanotransductive interactions between biochemical patterning and biomechanical morphogenesis. Here we discuss the nature of these processes and put forward findings on how early biochemical and biomechanical patterning of metazoans may have emerged from a primitive behavioural mechanotransducive feeding response to marine environment which might have initiated the development of first animal multicellular organisms.

Evaluation of Oxidative and Nitrosative Stress Markers Related To Inflammation in The Cumulus Cells and Follicular Fluid of Women Undergoing Intracytoplasmic Sperm Injection: A Prospective Study

BACKGROUND

Oxidative/nitrosative stress in the oocyte microenvironment could have an impact on intracytoplasmic sperm injection (ICSI) outcomes. The presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) can stimulate the secretion of pro-inflammatory cytokines, leading to chronic inflammation and potentially affecting embryo as well as oocyte quality. This study aimed to examine the relationship of lipid peroxidation [measured by the malondialdehyde (MDA) assay] with protein carbonyl [measured by the 2,4 dinitrophenylhydrazine (DNPH) assay] levels in cumulus cells (CCs), as well as nitric oxide (NO), peroxynitrite (ONOO-), and C-reactive protein (CRP) levels in follicular fluid (FF). The potential relationship of these levels with ICSI outcome was also evaluated.

MATERIALS AND METHODS

In this prospective study, 63 FF samples and their corresponding CCs were collected for ICSI procedures. Spectrophotometry was used to assess levels of DNPH, MDA, NO, and ONOO-. CRP levels were evaluated using an immunoturbidimetric assay.

RESULTS

The patients under 37 years with normal ovarian reserve had significantly lower levels of MDA, DNPH, NO, ONOO-, and CRP compared to those over 37 years. Additionally, we observed higher levels of MDA, DNPH, NO, ONOO-, and CRP in the group with an oocyte maturity rate of less than 60%. No significant difference was observed between the DNPH levels and factors such as infertility duration, embryo quality, pregnancy, or the number of retrieved oocytes. A higher level of MDA, NO, ONOO-, and CRP was found to be significantly related to the lower number of retrieved oocytes, longer periods of infertility, poor embryo quality, and negative pregnancy outcomes.

CONCLUSION

Oxidative/nitrosative stress, linking to inflammation in the oocyte microenvironment, can be considered as a potentially useful biomarker for assessing the development and competence of oocytes and embryos and predicting ICSI outcomes.

Cytoglobin regulates NO-dependent cilia motility and organ laterality during development

Cytoglobin is a heme protein with unresolved physiological function. Genetic deletion of zebrafish cytoglobin (cygb2) causes developmental defects in left-right cardiac determination, which in humans is associated with defects in ciliary function and low airway epithelial nitric oxide production. Here we show that Cygb2 co-localizes with cilia and with the nitric oxide synthase Nos2b in the zebrafish Kupffer's vesicle, and that cilia structure and function are disrupted in cygb2 mutants. Abnormal ciliary function and organ laterality defects are phenocopied by depletion of nos2b and of gucy1a, the soluble guanylate cyclase homolog in fish. The defects are rescued by exposing cygb2 mutant embryos to a nitric oxide donor or a soluble guanylate cyclase stimulator, or with over-expression of nos2b. Cytoglobin knockout mice also show impaired airway epithelial cilia structure and reduced nitric oxide levels. Altogether, our data suggest that cytoglobin is a positive regulator of a signaling axis composed of nitric oxide synthase-soluble guanylate cyclase-cyclic GMP that is necessary for normal cilia motility and left-right patterning.

Teratogenicity and Reactive Oxygen Species after transient embryonic hypoxia: Experimental and clinical evidence with focus on drugs causing failed abortion in humans

Teratogenicity and Reactive Oxygen Species after transient embryonic hypoxia: Experimental and clinical evidence with focus on drugs with human abortive potential. Reactive Oxygen Species (ROS) can be harmful to embryonic tissues. The adverse embryonic effects are dependent on the severity and duration of the hypoxic event and when during organongenesis hypoxia occurs. The vascular endothelium of recently formed arteries in the embryo is highly susceptible to ROS damage. Endothelial damage results in vascular disruption, hemorrhage and maldevelopment of organs, which normally should have been supplied by the artery. ROS can also induce irregular heart rhythm in the embryo resulting in alterations in blood flow and pressure from when the tubular heart starts beating. Such alterations in blood flow and pressure during cardiogenesis can result in a variety of cardiovascular defects, for example transpositions and ventricular septal defects. One aim of this article is to review and compare the pattern of malformations produced by transient embryonic hypoxia of various origins in animal studies with malformations associated with transient embryonic hypoxia in human pregnancy due to a failed abortion process. The results show that transient hypoxia and compounds with potential to cause failed abortion in humans, such as misoprostol and hormone pregnancy tests (HPTs) like Primodos, have been associated with a similar spectrum of teratogenicity. The spectrum includes limb reduction-, cardiovascular- and central nervous system defects. The hypoxia-ROS related teratogenicity of misoprostol and HPTs, is likely to be secondary to uterine contractions and compression of uterinoplacental/embryonic vessels during organogenesis.

Cardiac Hypoxia Tolerance in Fish: From Functional Responses to Cell Signals

Aquatic animals are increasingly challenged by O₂ fluctuations as a result of global warming, as well as eutrophication processes. Teleost fish show important species-specific adaptability to O₂ deprivation, moving from intolerance to a full tolerance of hypoxia and even anoxia. An example is provided by members of Cyprinidae which includes species that are amongst the most tolerant hypoxia/anoxia teleosts. Living at low water O₂ requires the mandatory preservation of the cardiac function to support the metabolic and hemodynamic requirements of organ and tissues which sustain whole organism performance. A number of orchestrated events, from metabolism to behavior, converge to shape the heart response to the restricted availability of the gas, also limiting the potential damages for cells and tissues. In cyprinids, the heart is extraordinarily able to activate peculiar strategies of functional preservation. Accordingly, by using these teleosts as models of tolerance to low O₂, we will synthesize and discuss literature data to describe the functional changes, and the major molecular events that allow the heart of these fish to sustain adaptability to O₂ deprivation. By crossing the boundaries of basic research and environmental physiology, this information may be of interest also in a translational perspective, and in the context of conservative physiology, in which the output of the research is applicable to environmental management and decision making.

Roles of Nitric Oxide in the Regulation of Reproduction: A Review

Nitric oxide (NO) has attracted significant attention as a stellar molecule. Presently, the study of NO has penetrated every field of life science, and NO is widely distributed in various tissues and organs. This review demonstrates the importance of NO in both male and female reproductive processes in numerous ways, such as in neuromodulation, follicular and oocyte maturation, ovulation, corpus luteum degeneration, fertilization, implantation, pregnancy maintenance, labor and menstrual cycle regulation, spermatogenesis, sperm maturation, and reproduction. However, the mechanism of action of some NO is still unknown, and understanding its mechanism may contribute to the clinical treatment of some reproductive diseases.

Recent Advances in the Synthesis and Biomedical Applications of Heterocyclic NO-Donors

Nitric oxide (NO) is a key signaling molecule that acts in various physiological processes such as cellular metabolism, vasodilation and transmission of nerve impulses. A wide number of vascular diseases as well as various immune and neurodegenerative disorders were found to be directly associated with a disruption of NO production in living organisms. These issues justify a constant search of novel NO-donors with improved pharmacokinetic profiles and prolonged action. In a series of known structural classes capable of NO release, heterocyclic NO-donors are of special importance due to their increased hydrolytic stability and low toxicity. It is no wonder that synthetic and biochemical investigations of heterocyclic NO-donors have emerged significantly in recent years. In this review, we summarized recent advances in the synthesis, reactivity and biomedical applications of promising heterocyclic NO-donors (furoxans, sydnone imines, pyridazine dioxides, azasydnones). The synthetic potential of each heterocyclic system along with biochemical mechanisms of action are emphasized.

Ectopic release of nitric oxide modulates the onset of cardiac development in avian model

Heart development is one of the earliest developmental events, and its pumping action is directly linked to the intensity of development of other organs. Heart contractions mediate the circulation of the nutrients and signalling molecules to the focal points of developing embryos. In the present study, we used in vivo, ex vivo, in vitro, and in silico methods for chick embryo model to characterize and identify molecular targets under the influence of ectopic nitric oxide in reference to cardiogenesis. Spermine NONOate (SpNO) treatment of 10 μM increased the percentage of chick embryos having beating heart at 40th h of incubation by 2.2-fold (p < 0.001). In an ex vivo chick embryo culture, SpNO increased the percentage of embryos having beats by 1.56-fold (p < 0.05) compared with control after 2 h of treatment. Total body weight of SpNO-treated chick embryos at the Hamburger and Hamilton (HH) stage 29 was increased by 1.22-fold (p < 0.005). Cardiac field potential (FP) recordings of chick embryo at HH29 showed 2.5-fold (p < 0.001) increased in the amplitude, 3.2-fold (p < 0.001) increased in frequency of SpNO-treated embryos over that of the control group, whereas FP duration was unaffected. In cultured cardiac progenitors cells (CPCs), SpNO treatment decreased apoptosis and cell death by twofold (p < 0.001) and 1.7-fold (p < 0.001), respectively. Transcriptome analysis of chick embryonic heart isolated from HH15 stage pre-treated with SpNO at HH8 stage showed upregulation of genes involved in heart morphogenesis, heart contraction, cardiac cell development, calcium signalling, structure, and development whereas downregulated genes were enriched under the terms extracellular matrix, wnt pathway, and BMP pathway. The key upstream molecules predicted to be activated were p38 MAPK, MEF2C, TBX5, and GATA4 while KDM5α, DNMT3A, and HNF1α were predicted to be inhibited. This study suggests that the ectopic nitric oxide modulates the onset of cardiac development.

Globins and nitric oxide homeostasis in fish embryonic development

Since the discovery of new members of the globin superfamily such as Cytoglobin, Neuroglobin and Globin X, in addition to the most well-known members, Hemoglobin and Myoglobin, different hypotheses have been suggested about their function in vertebrates. Globins are ubiquitously found in living organisms and can carry out different functions based on their ability to bind ligands such as O2, and nitric oxide (NO) and to catalyze reactions scavenging NO or generating NO by reducing nitrite. NO is a highly diffusible molecule with a central role in signaling important for egg maturation, fertilization and early embryonic development. The globins ability to scavenge or generate NO makes these proteins ideal candidates in regulating NO homeostasis depending on the micro environment and tissue NO demands. Different amounts of various globins have been found in zebrafish eggs and developing embryos where it's unlikely that they function as respiratory proteins and instead could play a role in maintaining embryonic NO homeostasis. Here we summarize the current knowledge concerning the role of NO in adult fish in comparison to mammals and we discuss NO function during embryonic development with possible implications for globins in maintaining embryonic NO homeostasis.

Synthesis and Metabolism of Nitric Oxide (NO) in Chicken Embryos and in the Blood of Adult Chicken

In chicken embryos, nitric oxide (NO) is accumulated in the pool of NO donors: S-nitrosothiols, nitrosyl-iron complexes, high-molecular-weight nitro-compounds. Oxidation of NO to nitrate occurs with different intensity in the embryos of different chicken breeds. In some embryos, NO donors accumulate almost without oxidation. Stable concentration of NO donors and nitrate in the blood of adult chicken is a result of dynamic equilibrium between NO synthesis and elimination (oxidation, consumption by other tissues, and excretion). As NO oxidation occurs mainly not in the blood, but in other tissues, decomposition of NO donors and NO oxidation are determined the properties of these tissues, in particular, the presence of physiological targets of NO, rather than spontaneous processes. Hence, evaluation of the intensity of NO metabolism is important for prediction of the efficiency of preparations containing NO donors and stimulators of its synthesis.