The miR-322-TRAF3 circuit mediates the pro-apoptotic effect of high glucose on neural stem cells

Diabetes and Early Development: Epigenetics, Biological Stress, and Aging

Pregestational diabetes, either type 1 or type 2 diabetes, induces structural birth defects including neural tube defects and congenital heart defects in human fetuses. Rodent models of type 1 and type 2 diabetic embryopathy have been established and faithfully mimic human conditions. Hyperglycemia of maternal diabetes triggers oxidative stress in the developing neuroepithelium and the embryonic heart leading to the activation of proapoptotic kinases and excessive cell death. Oxidative stress also activates the unfolded protein response and endoplasmic reticulum stress. Hyperglycemia alters epigenetic landscapes by suppressing histone deacetylation, perturbing microRNA (miRNA) expression, and increasing DNA methylation. At cellular levels, besides the induction of cell apoptosis, hyperglycemia suppresses cell proliferation and induces premature senescence. Stress signaling elicited by maternal diabetes disrupts cellular organelle homeostasis leading to mitochondrial dysfunction, mitochondrial dynamic alteration, and autophagy impairment. Blocking oxidative stress, kinase activation, and cellular senescence ameliorates diabetic embryopathy. Deleting the mir200c gene or restoring mir322 expression abolishes maternal diabetes hyperglycemia-induced senescence and cellular stress, respectively. Both the autophagy activator trehalose and the senomorphic rapamycin can alleviate diabetic embryopathy. Thus, targeting cellular stress, miRNAs, senescence, or restoring autophagy or mitochondrial fusion is a promising approach to prevent poorly controlled maternal diabetes-induced structural birth defects. In this review, we summarize the causal events in diabetic embryopathy and propose preventions for this pathological condition. KEY POINTS: · Maternal diabetes induces structural birth defects.. · Kinase signaling and cellular organelle stress are critically involved in neural tube defects.. · Maternal diabetes increases DNA methylation and suppresses developmental gene expression.. · Cellular apoptosis and senescence are induced by maternal diabetes in the neuroepithelium.. · microRNAs disrupt mitochondrial fusion leading to congenital heart diseases in diabetic pregnancy..

MiR-322-5p is involved in regulating chondrocyte proliferation and differentiation in offspring's growth plate of maternal gestational diabetes

Pregestational diabetes mellitus (PGDM) has an impact on fetal bone formation, but the underlying mechanism is still obscure. Although miRNAs have been extensively investigated throughout bone formation, their effects on fetal bone development caused by PGDM still need clarification. This study intends to examine the mechanism by which hyperglycemia impairs the bone formation of offspring via miR-322-5p (miR-322). In this study, miR-322 was selected by systemically screening utilizing bioinformatics and subsequent validation experiments. Using streptozotocin (STZ)-induced diabetic mice and ATDC5 cell lines, we found that miR-322 was abundantly expressed in the proliferative and hypertrophic zones of the growth plate, and its expression pattern was disturbed in the presence of hyperglycemia, suggesting that miR-322 is involved in the chondrocyte proliferation and differentiation in absence/presence of hyperglycemia. This observation was proved by manipulating miR-322 expression in ATDC5 cells by transfecting mimic and inhibitor of miR-322. Furthermore, Adamts5, Col12a1, and Cbx6 were identified as the potential target genes of miR-322, verified by the co-transfection of miR-322 inhibitor and the siRNAs, respectively. The evaluation criteria are the chondrocyte proliferation and differentiation and their relevant key gene expressions (proliferation: Sox9 and PthIh; differentiation: Runx2 and Col10a1) after manipulating the gene expressions in ATDC5 cells. This study revealed the regulative role miR-322 on chondrocyte proliferation and differentiation of growth plate by targeting Adamts5, Col12a1, and Cbx6 in hyperglycemia during pregnancy. This translational potential represents a promising avenue for advancing our understanding of bone-related complications in diabetic pregnancy and mitigating bone deficiencies in diabetic pregnant individuals, improving maternal and fetal outcomes.

MicroRNA-322 overexpression reduces neural tube defects in diabetic pregnancies

BACKGROUND

Hyperglycemia from pregestational diabetes mellitus induces neural tube defects in the developing fetus. Folate supplementation is the only effective way to prevent neural tube defects; however, some cases of neural tube defects are resistant to folate. Excess folate has been linked to higher maternal cancer risk and infant allergy. Therefore, additional interventions are needed. Understanding the mechanisms underlying maternal diabetes mellitus-induced neural tube defects can identify potential targets for preventing such defects. Despite not yet being in clinical use, growing evidence suggests that microRNAs are important intermediates in embryonic development and can serve as both biomarkers and drug targets for disease intervention. Our previous studies showed that maternal diabetes mellitus in vivo activates the inositol-requiring transmembrane kinase/endoribonuclease 1α (IRE1α) in the developing embryo and that a high glucose condition in vitro reduces microRNA-322 (miR-322) levels. IRE1α is an RNA endonuclease; however, it is unknown whether IRE1α targets and degrades miR-322 specifically or whether miR-322 degradation leads to neural tube defects via apoptosis. We hypothesize that IRE1α can inhibit miR-322 in maternal diabetes mellitus-induced neural tube defects and that restoring miR-322 expression in developing neuroepithelium ameliorates neural tube defects.

OBJECTIVE

This study aimed to identify potential targets for preventing maternal diabetes mellitus-induced neural tube defects and to investigate the roles and relationship of a microRNA and an RNA endonuclease in mouse embryos exposed to maternal diabetes mellitus.

STUDY DESIGN

To determine whether miR-322 reduction is necessary for neural tube defect formation in pregnancies complicated by diabetes mellitus, male mice carrying a transgene expressing miR-322 were mated with nondiabetic or diabetic wide-type female mice to generate embryos with or without miR-322 overexpression. At embryonic day 8.5 when the neural tube is not yet closed, embryos were harvested for the assessment of 3 miR-322 transcripts (primary, precursor, and mature miR-322), tumor necrosis factor receptor-associated factor 3 (TRAF3), and neuroepithelium cell survival. Neural tube defect incidences were determined in embryonic day 10.5 embryos when the neural tube should be closed if there is no neural tube defect formation. To identify which miR-322 transcript is affected by maternal diabetes mellitus and high glucose conditions, 3 miR-322 transcripts were assessed in embryos from dams with or without diabetes mellitus and in C17.2 mouse neural stem cells treated with different concentrations of glucose and at different time points. To determine whether the endonuclease IRE1α targets miR-322, small interfering RNA knockdown of IRE1α or overexpression of inositol-requiring transmembrane kinase/endoribonuclease 1α by DNA plasmid transfection was used to determine the effect of IRE1α deficiency or overexpression on miR-322 expression. RNA immunoprecipitation was performed to reveal the direct targets of inositol-requiring transmembrane kinase/endoribonuclease 1α.

RESULTS

Maternal diabetes mellitus suppressed miR-322 expression in the developing neuroepithelium. Restoring miR-322 expression in the neuroepithelium blocked maternal diabetes mellitus-induced caspase-3 and caspase-8 cleavage and cell apoptosis, leading to a neural tube defect reduction. Reversal of maternal diabetes mellitus-inhibited miR-322 via transgenic overexpression prevented TRAF3 up-regulation in embryos exposed to maternal diabetes mellitus. Activated IRE1α acted as an endonuclease and degraded precursor miR-322, resulting in mature miR-322 reduction.

CONCLUSION

This study supports the crucial role of the IRE1α-microRNA-TRAF3 circuit in the induction of neuroepithelial cell apoptosis and neural tube defect formation in pregnancies complicated by diabetes mellitus and identifies IRE1α and miR-322 as potential targets for preventing maternal diabetes mellitus-induced neural tube defects.

High glucose-increased miR-200c contributes to cellular senescence and DNA damage in neural stem cells

BACKGROUND

Maternal diabetes increases the risk for neural tube defects (NTDs). It is unclear if miRNAs, senescence, and DNA damage are involved in this process. In this study, we used neural stem cells as an in vitro proxy of embryonic neuroepithelium to investigate whether high glucose triggers neural stem cell senescence and DNA damage by upregulating miR-200c, which may be responsible for NTDs.

METHODS

C17.2 neural stem cells were cultured with normal glucose (5 mM) or high glucose (≥16.7 mM) at different doses and time points for detecting miR-200c levels, markers of senescence and DNA damage. Neural stem cells were exposed to antioxidant SOD1 mimetic Tempol and high glucose for 48 h to test roles of oxidative stress on the miR-200c, senescence, and DNA damage levels. An miR-200c mimic and an inhibitor were transfected into neural stem cells to increase or decrease miR-200c activities.

RESULTS

High glucose upregulated miR-200c in neural stem cells. A time course study of the effect of high glucose revealed that miR-200c initially increased at 12 h and reached its zenith at 18 h. Tempol reduced miR-200c levels caused by high glucose. High glucose induced markers of senescence and DNA damage in neural stem cells. Tempol abolished high glucose-induced markers of senescence and DNA damage. The miR-200c inhibitor suppressed high glucose-induced markers of senescence and DNA damage. Treatment with miR-200c mimic imitates high glucose-induced markers of senescence and DNA damage.

CONCLUSIONS

We show that high glucose increases miR-200c, which contributes to cellular senescence and DNA damage in neural stem cells and provides a potential pathway for maternal diabetes-induced neural tube defects.

Adipocyte-Derived Exosomal LINC00968 Promotes Mouse Retina Microvascular Endothelial Cell Dysfunction in a High-Glucose Environment by Modulating the miR-361-5p/TRAF3 Axis

As a major cause of mortality, cardiovascular disease is associated with obesity and diabetes. However, the molecular mechanism by which diabetes-obesity causes cardiovascular complications is largely unknown. In this study, the crosstalk mediated by 3T3-L1 preadipocytes and mouse retina microvascular endothelial cells (mRMECs) was determined after co-culturing performed with a Transwell system or measuring exosome uptake by mRMECs. CCK-8 assays, EdU incorporation assays, TUNEL staining, and ELISAs were used to evaluate the functions of mRMECs. Related protein markers were analyzed by western blotting. Our results showed that LINC00968 levels were significantly elevated in the exosomes derived from H-Glu-induced 3T3-L1 preadipocytes. Both H-Glu treatment and co-culture with 3T3-L1 cells damaged mRMECs, as indicated by lower rates of proliferation and higher rates of apoptosis and cell adhesion molecule expression, as well as by induced inflammation and oxidative stress, which were enhanced by combined H-Glu and co-culture treatment. Furthermore, H-Glu and co-culture treatment increased LINC00968 expression in mRMECs, and the exosomes collected from 3T3-L1 cells had a similar effect. Functionally, LINC00968 inhibition protected mRMECs against the effects of H-Glu and co-culture treatment, while LINC00968 played the opposite role. LINC00968 was found to target miR-361-5p, and TRAF3 was identified as a target gene of miR-361-5p. Finally, miR-361-5p overexpression alleviated the effects of LINC00968 on H-Glu-induced mRMEC dysfunction in vitro. In conclusion, our results indicated that in an H-glu environment, adipocyte exosomes damage microvascular endothelial cells via a LINC00968/miR-361-5p/TRAF3 signaling pathway, which could possibly serve as a target for treating diabetes-obesity-triggered microvascular complications.

MicroRNA 322-5p reduced neuronal inflammation via the TLR4/TRAF6/NF-κB axis in a rat epilepsy model

This study aimed to determine whether microRNA-322-5p regulates seizure and seizure damage by targeting the TLR4/TRAF6/NF-κB-associated inflammatory signaling pathway. In a pilocarpine-induced epileptic rat model, the expressions of miR-322-5p, TLR4, NF-κB, TRAF6, IRF5, IL-1β, and GABA were assessed by a quantitative polymerase chain reaction and western blotting. Tunel detects hippocampal neuron apoptosis. The results showed that the expression of miR-322-5p significantly decreased in status epilepticus (SE) rats. The reduction of miR-322-5p was accompanied by increased levels of pro-inflammatory cytokines, an increased NF-κB expression, and reduced γ-aminobutyric acid (GABA) levels. Exogenous miR-322-5p reduced the expression of inflammatory molecules and increased the GABA levels in SE rats, and also reduced hippocampal neuronal cell apoptosis caused by epilepsy. In conclusion, the miR-322-5p significantly inhibited the TLR4/TRAF6/NF-κB-associated inflammation and reduced neuronal apoptosis, suggesting that its induction may be of potential interest for novel antiseizure medications.

TNF Signaling Acts Downstream of MiR-322/-503 in Regulating DM1 Myogenesis

Myotonic dystrophy type 1 (DM1) is caused by the expanded CUG repeats and usually displays defective myogenesis. Although we previously reported that ectopic miR-322/-503 expression improved myogenesis in DM1 by targeting the toxic RNA, the underlying pathways regulating myogenesis that were aberrantly altered in DM1 and rescued by miR-322/-503 were still unknown. Here, we constructed DM1 and miR-322/-503 overexpressing DM1 myoblast models, which were subjected to in vitro myoblast differentiation along with their corresponding controls. Agreeing with previous findings, DM1 myoblast showed remarkable myogenesis defects, while miR-322/-503 overexpression successfully rescued the defects. By RNA sequencing, we noticed that Tumor necrosis factor (TNF) signaling was the only pathway that was significantly and oppositely altered in these two experimental sets, with it upregulated in DM1 and inhibited by miR-322/-503 overexpression. Consistently, hyperactivity of TNF signaling was detected in two DM1 mouse models. Blocking TNF signaling significantly rescued the myogenesis defects in DM1. On the contrary, TNF-α treatment abolished the rescue effect of miR-322/-503 on DM1 myogenesis. Taking together, these results implied that TNF signaling mediated the myogenesis defects in DM1 and might act downstream of miR-322/-503 in regulating the myogenesis in DM1. Moreover, the inhibition of TNF signaling benefiting myogenesis in DM1 provided us with a novel therapeutic strategy for DM1.

Nuclear factor I-C disrupts cellular homeostasis between autophagy and apoptosis via miR-200b-Ambra1 in neural tube defects

Impaired autophagy and excessive apoptosis disrupt cellular homeostasis and contribute to neural tube defects (NTDs), which are a group of fatal and disabling birth defects caused by the failure of neural tube closure during early embryonic development. However, the regulatory mechanisms underlying NTDs and outcomes remain elusive. Here, we report the role of the transcription factor nuclear factor I-C (NFIC) in maintaining cellular homeostasis in NTDs. We demonstrated that abnormally elevated levels of NFIC in a mouse model of NTDs can interact with the miR-200b promoter, leading to the activation of the transcription of miR-200b, which plays a critical role in NTD formation, as reported in our previous study. Furthermore, miR-200b represses autophagy and triggers apoptosis by directly targeting the autophagy-related gene Ambra1 (Autophagy/Beclin1 regulator 1). Notably, miR-200b inhibitors mitigate the unexpected effects of NFIC on autophagy and apoptosis. Collectively, these results indicate that the NFIC-miR-200b-Ambra1 axis, which integrates transcription- and epigenome-regulated miRNAs and an autophagy regulator, disrupts cellular homeostasis during the closure of the neural tube, and may provide new insight into NTD pathogenesis.

Micronutrient imbalance and common phenotypes in neural tube defects

Neural tube defects (NTDs) are among the most common birth defects, with a prevalence of close to 19 per 10,000 births worldwide. The etiology of NTDs is complex involving the interplay of genetic and environmental factors. Since nutrient deficiency is a risk factor and dietary changes are the major preventative measure to reduce the risk of NTDs, a more detailed understanding of how common micronutrient imbalances contribute to NTDs is crucial. While folic acid has been the most discussed environmental factor due to the success that population-wide fortification has had on prevention of NTDs, folic acid supplementation does not prevent all NTDs. The imbalance of several other micronutrients has been implicated as risks for NTDs by epidemiological studies and in vivo studies in animal models. In this review, we highlight recent literature deciphering the multifactorial mechanisms underlying NTDs with an emphasis on mouse and human data. Specifically, we focus on advances in our understanding of how too much or too little retinoic acid, zinc, and iron alter gene expression and cellular processes contributing to the pathobiology of NTDs. Synthesis of the discussed literature reveals common cellular phenotypes found in embryos with NTDs resulting from several micronutrient imbalances. The goal is to combine knowledge of these common cellular phenotypes with mechanisms underlying micronutrient imbalances to provide insights into possible new targets for preventative measures against NTDs.

Maternal diabetes induces senescence and neural tube defects sensitive to the senomorphic rapamycin

Neural tube defects (NTDs) are the second most common structural birth defect. Senescence, a state of permanent cell cycle arrest, occurs only after neural tube closure. Maternal diabetes-induced NTDs are severe diabetic complications that lead to infant mortality or lifelong morbidity and may be linked to premature senescence. Here, we report that premature senescence occurs in the mouse neuroepithelium and disrupts neurulation, leading to NTDs in diabetic pregnancy. Premature senescence and NTDs were abolished by knockout of the transcription factor Foxo3a, the miR-200c gene, and the cell cycle inhibitors p21 and p27; transgenic expression of the dominant-negative FoxO3a mutant; or the senomorphic rapamycin. Double transgenic expression of p21 and p27 mimicked maternal diabetes in inducing premature neuroepithelium senescence and NTDs. These findings integrate transcription- and epigenome-regulated miRNAs and cell cycle regulators in premature neuroepithelium senescence and provide a mechanistic basis for targeting premature senescence and NTDs using senomorphics.

miR-339-3p regulated acute pancreatitis induced by caerulein through targeting TNF receptor-associated factor 3 in AR42J cells

Acute pancreatitis (AP) is an inflammatory disease with high morbidity and mortality. The regulation mechanism of miRNA is involved in the production and development of various diseases, but the regulation mechanism of miRNA in AP is still not fully elucidated. The expression of miR-339-3p was detected using quantitative real-time PCR. The levels of TNF-α, IL-1β, and IL-6 were detected using enzyme-linked immunosorbent assay. Cell apoptosis was measured using flow cytometry. The protein expressions of TNF receptor-associated factor 3 (TRAF3), Bcl-2, C-caspase 3, Bax, p-p38, and p38 were measured using western blot. Luciferase reporter assay and RNA immunoprecipitation assay were applied to ensure that miR-399-3p targeted TRAF3. Caerulein promoted the expression of TNF-α, IL-1β, and IL-6, enhanced the expression of C-caspase 3 and Bax while inhibited Bcl-2 protein expression. Meanwhile, caerulein also reduced the expression of miR-339-3p and induced the expression of TRAF3 in rat pancreatic acinar cells. miR-399-3p transfection inhibited the levels of TNF-α, IL-1β, and IL-6 and C-caspase 3 and Bax protein expression as well as suppressed cell apoptosis, while increased Bcl-2 protein expression in caerulein-induced AP. TRAF3 has been verified as a target of miR-339-3p. Interestingly, the reduction of miR-399-3p inhibited the p38 pathway, which was impaired by the upregulation of TRAF3. In addition, the suppression effects of miR-339-3p on cell inflammation and apoptosis in caerulein-induced AP were reversed by enhancing TRAF3 expression. In this study, in vitro model of AP was characterized by strong inflammation and cell apoptosis. We have first demonstrated the regulatory network of miR-339-3p and TRAF3. Overexpression of miR-339-3p inhibited cell inflammation and cell apoptosis in caerulein-induced AP through modulating TRAF3 expression via the p38 pathway, providing a new therapeutic target in the treatment of AP.

microRNA-322/424 promotes liver fibrosis by regulating angiogenesis through targeting CUL2/HIF-1α pathway

AIMS

To investigate the effects and mechanism of miR-322/424 in liver fibrosis.

MAIN METHODS

miR-322/424 expression in liver cirrhosis patients, mouse and rat liver fibrosis was determined by qPCR. Mice liver fibrosis was established by CCl₄, and intervened by miR-322/424 agomir or antagomir. Liver hydroxyproline content and Sirius red staining were used to evaluate collagen deposition. CD31 expression was used to evaluate liver microvessel density. In vitro, the effects of miR-322/424 mimic or inhibitor on human hepatic sinusoidal endothelial cells (HHSECs) migration and tube formation were investigated. A dual luciferase reporter assay was performed to confirm the direct interaction between miR-322/424 and Cullin2. mRNA expression of elongin B/C, Cullin2, and RBX1 was determined by qPCR. HIF-1α protein expression was determined by Western blotting.

KEY FINDINGS

miR-322/424 level in liver cirrhosis patients, mouse liver fibrosis induced by CCl₄ and BDL, and rat liver fibrosis induced by CCl₄ and dimethylnitrosamine was increased. miR-322/424 agomir exacerbated CCl₄-induced mouse liver fibrosis, whereas the opposite effect was observed for miR-322/424 antagomir. miR-322/424 agomir significantly upregulated liver CD31 expression; opposite effects occurred with miR-322/424 antagomir. In vitro, miR-322/424 mimic significantly promoted tube formation and cell migration, and increased von Willebrand factor expression, whereas miR-322/424 inhibitor had the opposite effect. Dual-Luciferase Reporter Assay identified Cullin2 as miR-322/424 target. miR-322/424 decreased the mRNA expression of elongin B/C, Cullin2, and RBX1 and increased HIF-1α protein expression in HHSECs.

SIGNIFICANCE

miR-322/424 plays a central role in the pathogenesis of liver fibrosis by targeting Cullin2, and enhancing HIF-1α-mediated hepatic angiogenesis.

Emerging roles of microRNAs in intestinal ischemia/reperfusion-induced injury: a review

Intestinal ischemia/reperfusion (II/R) injury is a serious pathological phenomenon in underlying hemorrhagic shock, trauma, strangulated intestinal obstruction, and acute mesenteric ischemia which associated with high morbidity and mortality. MicroRNAs (miRNAs, miRs) are endogenous non-coding RNAs that regulate post-transcriptionally target mRNA translation via degrading it and/or suppressing protein synthesis. This review discusses on the role of some miRNAs in underlying II/R injury. Some of these miRNAs can have protective action through agomiR or specific antagomiR, and others can have destructive effects in the basal level of II/R insult. Based on these literature reviews, II/R injury affects several miRNAs and their specific target genes. Some miRNAs upregulate under condition of II/R injury, and multiple miRNAs downregulate following II/R damage. Data of this review have been collected from the scientific articles published in databases such as Science Direct, Scopus, PubMed, Web of Science, and Scientific Information Database from 2000 to 2020. It is shown a correlation between changes in the expression of miRNAs and autophagy, inflammation, oxidative stress, apoptosis, and epithelial barrier function. Taken together, agomiR or antagomiR of some miRNAs can be considered as one new target for the research and development of innovative drugs to the prevention or treatment of II/R damage.

Deficiency of the oxidative stress-responsive kinase p70S6K1 restores autophagy and ameliorates neural tube defects in diabetic embryopathy

BACKGROUND

Autophagy is highly active in neuroepithelial cells of the developing neuroepithelium, and impairment of autophagy leads to neural tube defects. In this study, we have found that maternal diabetes suppresses autophagy that leads to neural tube defects and consequent cellular imbalance in the endoplasmic reticulum where critical events occur, leading to the induction of diabetic embryopathy. Because the mammalian target of rapamycin pathway suppresses autophagy, we hypothesized that 70 kDa ribosomal protein S6 kinase 1 (p70S6K1), a major downstream effector of mammalian target of rapamycin, mediates the inhibitory effect of maternal diabetes on autophagy in the developing neuroepithelium.

OBJECTIVE

We investigated whether p70S6K1 mediates the inhibitory effect of maternal diabetes on autophagy during neurulation. We also examined whether p70S6K1 deficiency restores autophagy and therefore relieves endoplasmic reticulum stress and inhibits maternal diabetes-induced apoptosis, which leads to reduction in neural tube defect incidence in diabetic embryopathy.

STUDY DESIGN

Female p70S6K1 heterogeneous knockout (p70S6K1+/-) mice were bred with male p70S6K1 heterogeneous knockout (p70S6K1+/-) mice to generate wild-type (WT), p70S6K1+/- and p70S6K1 knockout (p70S6K1-/-) embryos. Embryos at embryonic day 8.5 were harvested for the assessment of indices of autophagy, endoplasmic reticulum stress, and apoptosis. Neural tube defect incidence in embryos was determined at embryonic day 10.5. For in vitro studies, small interfering RNA knockdown of p70S6K1 in C17.2 mouse neural stem cells was used to determine the effect of p70S6K1 deficiency on autophagy impairment and endoplasmic reticulum stress under high glucose conditions.

RESULTS

Knockout of the Rps6kb1 gene, which encodes for p70S6K1, ameliorated maternal diabetes-induced NTDs and restored autophagosome formation in neuroepithelial cells suppressed by maternal diabetes. Maternal diabetes-suppressed conversion of LC3-I (microtubule-associated protein 1A/1B-light chain 3) to LC3-II, an index of autophagic activity, in neurulation stage embryos was abrogated in the absence of p70S6K1. p70S6K1 knockdown in neural stem cells also restored autophagosome formation and the conversion of LC3-I to LC3-II. The activation of the major unfolded protein response, indicated by phosphorylation of inositol-requiring enzyme 1 alpha, and protein kinase R-like endoplasmic reticulum kinase, and eukaryotic translation initiation factor 2α, and the increase of the endoplasmic reticulum stress marker, C/EBP homologous protein, were induced by maternal diabetes in vivo and high glucose in vitro. Unfolded protein response and endoplasmic reticulum stress induced by maternal diabetes or high glucose were reduced by Rps6kb1 deletion or p70S6K1 knockdown, respectively. Rps6kb1 knockout blocked maternal diabetes-induced caspase cleavage and neuroepithelial cell apoptosis. The superoxide dismutase mimetic Tempol abolished high glucose-induced p70S6K1 activation.

CONCLUSION

The study revealed the critical involvement of p70S6K1 in the pathogenesis of diabetic embryopathy.

Downregulation of circular RNA HECTD1 induces neuroprotection against ischemic stroke through the microRNA-133b/TRAF3 pathway

AIMS

Circular RNAs (circRNAs) have been shown to play crucial roles in various biological processes and human diseases. However, their exact functions in ischemic stroke remain largely unknown. In this study, we explored the functional role of circRNA HECTD1 (circ-HECTD1) and its underlying mechanism in cerebral ischemia/reperfusion injury.

METHODS

Mouse middle cerebral artery occlusion (MCAO) model and oxygen-glucose deprivation (OGD) model in HT22 cells were used to mimic the cerebral ischemia/reperfusion injury. Brain infarct volume, flow cytometry, caspase 3 activity, NF-κB activity, and TUNEL staining were performed to evaluate the function of circ-HECTD1. Luciferase report assay was used to explore the regulatory mechanism.

FINDINGS

The results showed that the expression of circ-HECTD1 and tumor necrosis factor receptor-associated factor 3 (TRAF3) was remarkably up-regulated, while miR-133b was down-regulated in oxygen-glucose deprivation (OGD)-induced HT22 cells and mouse middle cerebral artery occlusion (MCAO) model. circ-HECTD1 knockdown relieved OGD-caused neuronal cell death in vitro. Simultaneously, circ-HECTD1 knockdown improved cerebral infarction volume and neuronal apoptosis in MCAO mice. circ-HECTD1 was able to negatively regulate the expression of miR-133b, and TRAF3 is one of the targets of miR-133b. Upregulation of miR-133b inhibited the expression of TRAF3 in OGD-stimulated cells, whereas circ-HECTD1 upregulation reversed this effect. Furthermore, upregulation of miR-133 was able to inhibit OGD-caused cell apoptosis and NF-κB activation, whereas upregulation of circ-HECTD1 attenuated these effects of miR-133b mimics.

SIGNIFICANCE

Taken together, circ-HECTD1 knockdown inhibited the expression of TRAF3 by targeting miR-133b, thereby attenuating neuronal injury caused by cerebral ischemia.

miR-322 treatment rescues cell apoptosis and neural tube defect formation through silencing NADPH oxidase 4

AIMS

Failure of neural tube closure resulting from excessive apoptosis leads to neural tube defects (NTDs). NADPH oxidase 4 (NOX4) is a critical mediator of cell growth and death, yet its role in NTDs has never been characterized. NOX4 is a potential target of miR-322, and we have previously demonstrated that miR-322 was involved in high glucose-induced NTDs. In this study, we investigated the effect of NOX4 on the embryonic neuroepithelium in NTDs and reveal a new regulatory mechanism for miR-322 that disrupts neurulation by ameliorating cell apoptosis.

METHODS

All-trans-retinoic acid (ATRA)-induced mouse model was utilized to study NTDs. RNA pull-down and dual-luciferase reporter assays were used to confirm the interaction between NOX4 and miR-322. In mouse neural stem cells and whole-embryo culture, Western blot and TUNEL were carried out to investigate the effects of miR-322 and NOX4 on neuroepithelium apoptosis in NTD formation.

RESULTS

NOX4, as a novel target of miR-322, was upregulated in ATRA-induced mouse model of NTDs. In mouse neural stem cells, the expression of NOX4 was inhibited by miR-322; still further, NOX4-triggered apoptosis was also suppressed by miR-322. Moreover, in whole-embryo culture, injection of the miR-322 mimic into the amniotic cavity attenuated cell apoptosis in NTD formation by silencing NOX4.

CONCLUSION

miR-322/NOX4 plays a crucial role in apoptosis-induced NTD formation, which may provide a new understanding of the mechanism of embryonic NTDs and a basis for potential therapeutic target against NTDs.

MiR-92b-3p regulates oxygen and glucose deprivation-reperfusion-mediated apoptosis and inflammation by targeting TRAF3 in PC12 cells

NEW FINDINGS

What is the central question of this study? MiR-92b-3p was found to be reduced in a rat model of middle cerebral artery occlusion: what are the functions of miR-92b-3p in oxygen and glucose deprivation-reperfusion (OGD/R)? What is the main finding and its importance? MiR-92b-3p abated apoptosis, mitochondrial dysfunction and inflammation caused by OGD/R via targeting TRAF3, suggesting that miR-92b-3p may serve as a potential therapeutic target in ischaemic stroke treatment.

ABSTRACT

Stroke is the most common cause of human neurological disability. MiR-92b-3p has been shown to be decreased in a rat model of middle cerebral artery occlusion, but its effects in cerebral ischaemic insult are unknown. In this study, PC12 cells were exposed to oxygen and glucose deprivation-reperfusion (OGD/R) to establish cerebral ischaemic injury in vitro. Quantitative real time-PCR analysis demonstrated that OGD/R exposure led to down-regulation of miR-92b-3p and increased mRNA and protein levels of tumour necrosis factor receptor-associated factor 3 (TRAF3). Gain of miR-92b-3p expression facilitated cell survival; attenuated lactate dehydrogenase leakage, cell apoptosis, caspase 3 activity and cleaved-caspase 3 (c-caspase 3) expression; and decreased the Bax/Bcl-2 ratio. Furthermore, miR-92b-3p repressed mitochondrial membrane potential depolarization, reactive oxygen species production, cytochrome c protein expression, inflammatory cytokine production and the reduction of ATP content. MiR-92b-3p directly targeted the 3'-untranslated region of TRAF3 and decreased TRAF3 expression. Reinforced expression of TRAF3 partly abrogated the biological activity of miR-92b-3p during OGD/R. Hence, miR-92b-3p abated apoptosis, mitochondrial dysfunction and inflammatory responses induced by OGD/R by targeting TRAF3.

The Role of MicroRNAs in Diabetes-Related Oxidative Stress

Cellular stress, combined with dysfunctional, inadequate mitochondrial phosphorylation, produces an excessive amount of reactive oxygen species (ROS) and an increased level of ROS in cells, which leads to oxidation and subsequent cellular damage. Because of its cell damaging action, an association between anomalous ROS production and disease such as Type 1 (T1D) and Type 2 (T2D) diabetes, as well as their complications, has been well established. However, there is a lack of understanding about genome-driven responses to ROS-mediated cellular stress. Over the last decade, multiple studies have suggested a link between oxidative stress and microRNAs (miRNAs). The miRNAs are small non-coding RNAs that mostly suppress expression of the target gene by interaction with its 3'untranslated region (3'UTR). In this paper, we review the recent progress in the field, focusing on the association between miRNAs and oxidative stress during the progression of diabetes.

High Glucose Inhibits Neural Stem Cell Differentiation Through Oxidative Stress and Endoplasmic Reticulum Stress

Maternal diabetes induces neural tube defects by suppressing neurogenesis in the developing neuroepithelium. Our recent study further revealed that high glucose inhibited embryonic stem cell differentiation into neural lineage cells. However, the mechanism whereby high glucose suppresses neural differentiation is unclear. To investigate whether high glucose-induced oxidative stress and endoplasmic reticulum (ER) stress lead to the inhibition of neural differentiation, the effect of high glucose on neural stem cell (the C17.2 cell line) differentiation was examined. Neural stem cells were cultured in normal glucose (5 mM) or high glucose (25 mM) differentiation medium for 3, 5, and 7 days. High glucose suppressed neural stem cell differentiation by significantly decreasing the expression of the neuron marker Tuj1 and the glial cell marker GFAP and the numbers of Tuj1⁺ and GFAP⁺ cells. The antioxidant enzyme superoxide dismutase mimetic Tempol reversed high glucose-decreased Tuj1 and GFAP expression and restored the numbers of neurons and glial cells differentiated from neural stem cells. Hydrogen peroxide treatment imitated the inhibitory effect of high glucose on neural stem cell differentiation. Both high glucose and hydrogen peroxide triggered ER stress, whereas Tempol blocked high glucose-induced ER stress. The ER stress inhibitor, 4-phenylbutyrate, abolished the inhibition of high glucose or hydrogen peroxide on neural stem cell differentiation. Thus, oxidative stress and its resultant ER stress mediate the inhibitory effect of high glucose on neural stem cell differentiation.

Downregulation of miR-322 promotes apoptosis of GC-2 cell by targeting Ddx3x

BACKGROUND

Aberrant DNA damage of germ cells, which impairs spermatogenesis and lowers fertility, is an important factor contributing to male infertility. MicroRNAs (miRNAs) play a significant role in the expression and regulation of multiple genes during spermatogenesis. Our previous study found much lower miR-424 (murine homologue miR-322) levels in the seminal plasma of infertile patients with high DFI(DNA Fragmentation Index)than in the fertile group. However, the mechanism by which miR-322 regulates germ cells during spermatogenesis remains unknown.

METHODS

In this study, we successfully established a GC-2 cell model of miR-322 downregulation resulting in impaired spermatogenesis. And the cell viability were measured using Cell Counting Kit-8 (CCK-8; Dojindo, Japan) and MTT (Sigma Aldrich, USA). Immunofluorescence assay was used to detect cell damage and the expression of apoptosis-related proteins were measured using real-time quantitative PCR and Western blot analysis. Target genes were predicted and verified by online database retrieval and Dual-luciferase reporter gene assay.

RESULTS

We observed evident decreases in the cell viability of GC-2 cells along with remarkable increases in apoptosis after miR-322 inhibition. While the expression of apoptosis-related genes, including Bax and caspases 3, 9, and 8 greatly increased in GC-2 cells after miR-322 downregulation, that of the anti-apoptotic Bcl-2 gene decreased. Ddx3x was found to be the direct target of miR-322. MiR-424 was then detected in the seminal plasma of infertile patients with high DFI(DNA Fragmentation Index); this miRNA was down-regulated but Ddx3x was upregulated in the infertile group.

CONCLUSION

MiR-322 plays a key role in promoting GC-2 cell apoptosis by directly regulating Ddx3x expression. MiR-424 downregulation in infertile men may induce spermatogenic cell apoptosis and sperm DNA damage by directly acting on the target gene locus Ddx3x, resulting in male infertility.

MicroRNA-29b-3p reduces intestinal ischaemia/reperfusion injury via targeting of TNF receptor-associated factor 3

BACKGROUND AND PURPOSE

The microRNA miR-29b-3p shows important roles in regulating apoptosis and inflammation. However, its effects on intestinal ischaemia/reperfusion (II/R) injury have not been reported. Here we have investigated the functions of miR-29b-3p on II/R injury on order to find drug targets to treat the injury.

EXPERIMENTAL APPROACH

Two models - in vitro hypoxia/reoxygenation (H/R) of IEC-6 cells; in vivo, II/R injury in C57BL/6 mice were used. Western blotting and dual-luciferase reporter assays were used and mimic and siRNA transfection tests were applied to assess the effects of miR-29b-3p on II/R injury via targeting TNF receptor-associated factor 3 (TRAF3).

KEY RESULTS

The H/R procedure decreased cell viability and promoted inflammation and apoptosis in IEC-6 cells, and the II/R procedure also promoted intestinal inflammation and apoptosis in mice. Expression levels of miR-29b-3p were decreased in H/R-induced cells and II/R-induced intestinal tissues of mice compared with control group or sham group, which directly targeted TRAF3. Decreased miR-29b-3p level markedly increased TRAF3 expression via activating TGF-α-activated kinase 1 phosphorylation, increasing NF-κB (p65) levels to promote inflammation, up-regulating Bcl2-associated X expression, and down-regulating Bcl-2 expression to trigger apoptosis. In addition, the miR-29b-3p mimetic and TRAF3 siRNA in IEC-6 cells markedly suppressed apoptosis and inflammation to alleviate II/R injury via inhibiting TRAF3 signallimg.

CONCLUSIONS AND IMPLICATIONS

The miR-29b-3p played a critical role in II/R injury, via targeting TRAF3, which should be considered as a significant drug target to treat the disease.

MiR322 mediates cardioprotection against ischemia/reperfusion injury via FBXW7/notch pathway

Myocardial ischemia/reperfusion (MI/R) causes loss of cardiomyocytes via oxidative stress-induced cardiomyocyte apoptosis. miR322, orthologous to human miR-424, was identified as an ischemia-induced angiogenic miRNA, but its cellular source and function in the setting of acute MI/R remains largely unknown. Using LacZ-tagged miR322 cluster reporter mice, we observed that vascular endothelial cells are the major cellular source of the miR322 cluster in adult hearts. Moreover, miR322 levels were significantly reduced in the heart at 24 h after MI/R injury. Intramyocardial injection of mimic-miR322 significantly diminished cardiac apoptosis (as determined by expression levels of active caspase 3 by Western blot analysis and immunostaining for TUNEL) and reduced infarct size by about 40%, in association with reduced FBXW7 and increased active Notch 1 levels in the ischemic hearts. FBXW7, which is an ubiquitin ligase that is crucial for activated Notch1 turnover, was identified as a direct target of miR322 via FBXW7 3'UTR reporter assay. Co-injection of FBXW7 plasmid with mimic-miR322 in ischemic hearts abolished the effect of mimic-miR322 to reduce apoptosis and infarct size in MI/R hearts. These data identify FBXW7 as a direct target of miR322 and suggest that miR322 could have potential therapeutic application for cardioprotection against ischemia/reperfusion-induced injury.

MicroRNA-322 Regulates Self-renewal of Mouse Spermatogonial Stem Cells through Rassf8

Spermatogonial stem cells (SSCs) are essential for spermatogenesis and male fertility. MicroRNAs (miRs) are key regulators of gene expression involved in self-renewal, differentiation, and apoptosis. However, the function and mechanisms of individual miR in regulating self-renewal and differentiation of SSCs remain unclear. Here, we report for the first time that miR-322 regulates self-renewal of SSCs. Functional assays revealed that miR-322 was essential for SSC self-renewal. Mechanistically, miR-322 promoted SSC self-renewal by targeting RASSF8 (ras association domain family 8). Moreover, the WNT/β-catenin signaling pathway was involved in the miR-322-mediated regulation. Furthermore, miR-322 overexpression increased GFRα1, ETV5 and PLZF expression but decreased STRA8, C-KIT and BCL6 expression. Our study provides not only a novel insight into molecular mechanisms regulating SSC self-renewal but also a basis for the diagnosis, treatment, and prevention of male infertility.

Comparison of Cardiac miRNA Transcriptomes Induced by Diabetes and Rapamycin Treatment and Identification of a Rapamycin-Associated Cardiac MicroRNA Signature

Rapamycin (Rap), an inhibitor of mTORC1, reduces obesity and improves lifespan in mice. However, hyperglycemia and lipid disorders are adverse side effects in patients receiving Rap treatment. We previously reported that diabetes induces pansuppression of cardiac cytokines in Zucker obese rats (ZO-C). Rap treatment (750 μg/kg/day for 12 weeks) reduced their obesity and cardiac fibrosis significantly; however, it increased their hyperglycemia and did not improve their cardiac diastolic parameters. Moreover, Rap treatment of healthy Zucker lean rats (ZL-C) induced cardiac fibrosis. Rap-induced changes in ZL-C's cardiac cytokine profile shared similarities with that of diabetes-induced ZO-C. Therefore, we hypothesized that the cardiac microRNA transcriptome induced by diabetes and Rap treatment could share similarities. Here, we compared the cardiac miRNA transcriptome of ZL-C to ZO-C, Rap-treated ZL (ZL-Rap), and ZO (ZO-Rap). We report that 80% of diabetes-induced miRNA transcriptome (40 differentially expressed miRNAs by minimum 1.5-fold in ZO-C versus ZL-C; p ≤ 0.05) is similar to 47% of Rap-induced miRNA transcriptome in ZL (68 differentially expressed miRNAs by minimum 1.5-fold in ZL-Rap versus ZL-C; p ≤ 0.05). This remarkable similarity between diabetes-induced and Rap-induced cardiac microRNA transcriptome underscores the role of miRNAs in Rap-induced insulin resistance. We also show that Rap treatment altered the expression of the same 17 miRNAs in ZL and ZO hearts indicating that these 17 miRNAs comprise a unique Rap-induced cardiac miRNA signature. Interestingly, only four miRNAs were significantly differentially expressed between ZO-C and ZO-Rap, indicating that, unlike the nondiabetic heart, Rap did not substantially change the miRNA transcriptome in the diabetic heart. In silico analyses showed that (a) mRNA-miRNA interactions exist between differentially expressed cardiac cytokines and miRNAs, (b) human orthologs of rat miRNAs that are strongly correlated with cardiac fibrosis may modulate profibrotic TGF-β signaling, and (c) changes in miRNA transcriptome caused by diabetes or Rap treatment include cardioprotective miRNAs indicating a concurrent activation of an adaptive mechanism to protect the heart in conditions that exacerbate diabetes.

IL-17A modulates osteoclast precursors' apoptosis through autophagy-TRAF3 signaling during osteoclastogenesis

Osteoclasts play an important role in bone remodeling. The inflammatory cytokine IL-17A could modulate the RANKL-induced osteoclastogenesis by regulating the autophagic activity. It is well accepted that protective autophagy has an anti-apoptotic effect. It is necessary to elucidate whether IL-17A can influence the apoptosis of osteoclast precursors (OCPs) through autophagy responses during osteoclastogenesis. The results showed that apoptosis of RAW264.7-derived OCPs was promoted by high levels of IL-17A, but the opposite anti-apoptotic function was shown by low levels of IL-17A. Furthermore, the enhanced apoptosis by high levels of IL-17A was reversed by overexpression of autophagy protein Beclin1; conversely, the inhibited apoptosis by low levels of IL-17A was restored by knockdown of Beclin1. It was also found that Beclin1 suppression with Beclin1 inhibitor (spautin1) could block the reduced apoptosis by low levels of IL-17A, which was recovered by TRAF3 knockdown. Moreover, the enhanced apoptosis by high levels of IL-17A decreased following the downregulation of TRAF3. Importantly, overexpression of caspase3 further attenuated osteoclastogenesis treated by high levels of IL-17A, without significantly affecting osteoclastogenesis stimulated by low levels of IL-17A. In conclusion, IL-17A modulates apoptosis of OCPs through Beclin1-autophagy-TRAF3 signaling pathway, thereby influencing osteoclastogenesis. Therefore, our study sheds lights on the improvement of clinical strategies of dental implantation or orthodontic treatment by revealing the novel targets in the bone remodeling.

Inhibition of TRAF3 expression alleviates cardiac ischemia reperfusion (IR) injury: A mechanism involving in apoptosis, inflammation and oxidative stress

Ischemia reperfusion (IR) injury is known as a major issue in cardiac transplantation and various pathogenesis are involved in myocardial IR injury. Here, we show that tumor necrosis factor receptor-associated factor 3 (TRAF3) was increased in hearts of mice with cardiac IR injury and in cardiomyocytes incubated with lipopolysaccharide (LPS) and H₂O₂. Reducing TRAF3 expression in vivo markedly reduced the infacrted area, attenuated the histological changes, improved cardiac dysfunction and injury in mice subjected to IR injury. Functional study further indicated that TRAF3 knockdown inhibited apoptosis in murine hearts of mice with cardiac IR injury and in LPS and H₂O₂-cotreated cardiomyocytes, as evidenced by the decreased expression of cleaved Caspase-3 and poly (ADP-ribose) polymerases (PARP). In addition, inflammatory response and oxidative stress observed in hearts of mice with IR operation were significantly alleviated by TRAF3 knockdown through inhibiting nuclear factor-κB (NF-κB) and xanthine oxidase (XO) signaling pathways, and similar results were detected in LPS and H₂O₂-cotreated cardiomyocytes in vitro. Moreover, the loss of TRAF3 also restrained the phosphorylated c-Jun N-terminal protein kinase (JNK) activation following cardiac IR injury. Importantly, blocking JNK activation, as TRAF3 knockdown, greatly reduced apoptosis, inflammation and reactive oxygen species (ROS) production in LPS and H₂O₂-cotreated cardiomyocytes. In contrast, TRAF3 knockdown-reduced apoptosis, inflammatory response and oxidative stress were significantly rescued by promoting JNK activity in LPS and H₂O₂-cotreated cardiomyocytes. In summary, the results of our study indicated that repressing TRAF3 expression could be served as essential therapeutic target for protection against cardiac IR injury through restraining JNK-meditated apoptosis, inflammation and the production of ROS.

TRAF3 as a Multifaceted Regulator of B Lymphocyte Survival and Activation

The adaptor protein TNF receptor-associated factor 3 (TRAF3) serves as a powerful negative regulator in multiple aspects of B cell biology. Early in vitro studies in transformed cell lines suggested the potential of TRAF3 to inhibit signaling by its first identified binding receptor, CD40. However, because the canonical TRAF3 binding site on many receptors also mediates binding of other TRAFs, and whole-mouse TRAF3 deficiency is neonatally lethal, an accurate understanding of TRAF3's specific functions was delayed until conditional TRAF3-deficient mice were produced. Studies of B cell-specific TRAF3-deficient mice, complemented by investigations in normal and malignant mouse and human B cells, reveal that TRAF3 has powerful regulatory roles that are unique to this TRAF, as well as functions context-specific to the B cell. This review summarizes the current state of knowledge of these roles and functions. These include inhibition of signaling by plasma membrane receptors, negative regulation of intracellular receptors, and restraint of cytoplasmic NF- κB pathways. TRAF3 is also now known to function as a resident nuclear protein, and to impact B cell metabolism. Through these and additional mechanisms TRAF3 exerts powerful restraint upon B cell survival and activation. It is thus perhaps not surprising that TRAF3 has been revealed as an important tumor suppressor in B cells. The many and varied functions of TRAF3 in B cells, and new directions to pursue in future studies, are summarized and discussed here.

miR-17-92 functions as an oncogene and modulates NF-κB signaling by targeting TRAF3 in MGC-803 human gastric cancer cells

The miR-17-92 cluster plays either an oncogenic or anti-oncogenic role in cancer progression in diverse human cancers. However, the underlying mechanisms of the miR-17-92 cluster in gastric cancer have not yet been fully elucidated. In this study, the function of the miR-17-92 cluster in diverse aspects of MGC-803 gastric cancer cells was systematically elucidated. The enforced introduction of the miR-17-92 cluster into the MGC-803 cells significantly promoted cell growth due to the increased cellular proliferation and decreased cellular apoptosis, which were detected by CCK-8, cell viability and TUNEL assays. Moreover, the results of western blot analyses revealed that the activated protein kinase B (AKT), extracellular-signal-regulated kinase (ERK) and nuclear factor (NF-κB) signaling pathways were activated in these processes. Moreover, the overexpression of the miR-17-92 cluster markedly enhanced the migratory and invasive abilities of the MGC-803 cells, which was associated with the occurrence of epithelial-mesenchymal transition (EMT). Tumor necrosis factor receptor associated factor 3 (TRAF3), which negatively regulates the NF-κB signaling pathway, was identified as a direct target of miR-17-92. Furthermore, TRAF3 silencing enhanced the oncogenic functions of the miR-17-92 cluster in the MGC-803 cells, including the increased cellular proliferation, migration and invasion. Moreover, immunohistochemical staining and survival analyses of a gastric cancer tissue microarray revealed that TRAF3 functioned as a tumor suppressor in gastric cancer. Taken together, the findings of this study provide new insight into the specific biological functions of the miR-17-92 cluster in gastric cancer progression by directly targeting TRAF3.

Endoplasmic Reticulum Stress-Induced CHOP Inhibits PGC-1α and Causes Mitochondrial Dysfunction in Diabetic Embryopathy

Endoplasmic reticulum (ER) stress has been implicated in the development of maternal diabetes-induced neural tube defects (NTDs). ER stress-induced C/EBP homologous protein (CHOP) plays an important role in the pro-apoptotic execution pathways. However, the molecular mechanism underlying ER stress- and CHOP-induced neuroepithelium cell apoptosis in diabetic embryopathy is still unclear. Deletion of the Chop gene significantly reduced maternal diabetes-induced NTDs. CHOP deficiency abrogated maternal diabetes-induced mitochondrial dysfunction and neuroepithelium cell apoptosis. Further analysis demonstrated that CHOP repressed the expression of peroxisome-proliferator-activated receptor-γ coactivator-1α (PGC-1α), an essential regulator for mitochondrial biogenesis and function. Both CHOP deficiency in vivo and knockdown in vitro restore high glucose-suppressed PGC-1α expression. In contrast, CHOP overexpression mimicked inhibition of PGC-1α by high glucose. In response to the ER stress inducer tunicamycin, PGC-1α expression was decreased, whereas the ER stress inhibitor 4-phenylbutyric acid blocked high glucose-suppressed PGC-1α expression. Moreover, maternal diabetes in vivo and high glucose in vitro promoted the interaction between CHOP and the PGC-1α transcriptional regulator CCAAT/enhancer binding protein-β (C/EBPβ), and reduced C/EBPβ binding to the PGC-1α promoter leading to markedly decrease in PGC-1α expression. Together, our findings support the hypothesis that maternal diabetes-induced ER stress increases CHOP expression which represses PGC-1α through suppressing the C/EBPβ transcriptional activity, subsequently induces mitochondrial dysfunction and ultimately results in NTDs.

Role of TRAF3 in neurological and cardiovascular diseases: an overview of recent studies

Tumour necrosis factor receptor-associated factor 3 (TRAF3) is a member of the TRAF adaptor protein family, which exerts different effects on the cell depending on the receptor to which it binds and the cell type in which it is expressed. TRAF3 is a major regulator of the innate immune response. To perform its functions properly, TRAF3 is transcriptionally and epigenetically regulated. At the transcriptional level, TRAF3 expression has been associated with neurological and cardiovascular diseases including stroke, among other pathologies. Epigenetic modifications of TRAF3 have been observed at the histone and DNA levels. It has been observed that acetylation of TRAF3, as well as other NF-κβ target genes, is associated with cardiac hypertrophy. Furthermore, TRAF3 methylation has been associated with vascular recurrence after ischemic stroke in patients treated with clopidogrel. In this overview, we summarise the most interesting studies related to transcriptional and epigenetic regulation of TRAF3 focusing on those studies performed in neurological and cardiovascular diseases.

Oxidative stress-induced miR-27a targets the redox gene nuclear factor erythroid 2-related factor 2 in diabetic embryopathy

BACKGROUND

Maternal diabetes induces neural tube defects, and oxidative stress is a causal factor for maternal diabetes-induced neural tube defects. The redox gene nuclear factor erythroid 2-related factor 2 is the master regulator of the cellular antioxidant system.

OBJECTIVE

In this study, we aimed to determine whether maternal diabetes inhibits nuclear factor erythroid 2-related factor 2 expression and nuclear factor erythroid 2-related factor 2-controlled antioxidant genes through the redox-sensitive miR-27a.

STUDY DESIGN

We used a well-established type 1 diabetic embryopathy mouse model induced by streptozotocin for our in vivo studies. Embryos at embryonic day 8.5 were harvested for analysis of nuclear factor erythroid 2-related factor 2, nuclear factor erythroid 2-related factor 2-controlled antioxidant genes, and miR-27a expression. To determine if mitigating oxidative stress inhibits the increase of miR-27a and the decrease of nuclear factor erythroid 2-related factor 2 expression, we induced diabetic embryopathy in superoxide dismutase 2 (mitochondrial-associated antioxidant gene)-overexpressing mice. This model exhibits reduced mitochondria reactive oxygen species even in the presence of hyperglycemia. To investigate the causal relationship between miR-27a and nuclear factor erythroid 2-related factor 2 in vitro, we examined C17.2 neural stem cells under normal and high-glucose conditions.

RESULTS

We observed that the messenger RNA and protein levels of nuclear factor erythroid 2-related factor 2 were significantly decreased in embryos on embryonic day 8.5 from diabetic dams compared to those from nondiabetic dams. High-glucose also significantly decreased nuclear factor erythroid 2-related factor 2 expression in a dose- and time-dependent manner in cultured neural stem cells. Our data revealed that miR-27a was up-regulated in embryos on embryonic day 8.5 exposed to diabetes, and that high glucose increased miR-27a levels in a dose- and time-dependent manner in cultured neural stem cells. In addition, we found that a miR-27a inhibitor abrogated the inhibitory effect of high glucose on nuclear factor erythroid 2-related factor 2 expression, and a miR-27a mimic suppressed nuclear factor erythroid 2-related factor 2 expression in cultured neural stem cells. Furthermore, our data indicated that the nuclear factor erythroid 2-related factor 2-controlled antioxidant enzymes glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, and glutathione S-transferase A1 were down-regulated by maternal diabetes in embryos on embryonic day 8.5 and high glucose in cultured neural stem cells. Inhibiting miR-27a restored expression of glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, and glutathione S-transferase A1. Overexpressing superoxide dismutase 2 reversed the maternal diabetes-induced increase of miR-27a and suppression of nuclear factor erythroid 2-related factor 2 and nuclear factor erythroid 2-related factor 2-controlled antioxidant enzymes.

CONCLUSION

Our study demonstrates that maternal diabetes-induced oxidative stress increases miR-27a, which, in turn, suppresses nuclear factor erythroid 2-related factor 2 and its responsive antioxidant enzymes, resulting in diabetic embryopathy.

The current status and future of cardiac stem/progenitor cell therapy for congenital heart defects from diabetic pregnancy

Pregestational maternal diabetes induces congenital heart defects (CHDs). Cardiac dysfunction after palliative surgical procedures contributes to the high mortality of CHD patients. Autologous or allogeneic stem cell therapies are effective for improving cardiac function in animal models and clinical trials. c-kit+ cardiac progenitor cells (CPCs), the most recognized CPCs, have the following basic properties of stem cells: self-renewal, multicellular clone formation, and differentiation into multiple cardiac lineages. However, there is ongoing debate regarding whether c-kit+ CPCs can give rise to sufficient cardiomyocytes. A new hypothesis to address the beneficial effect of c-kit+ CPCs is that these cells stimulate endogenous cardiac cells through a paracrine function in producing a robust secretome and exosomes. The values of other cardiac CPCs, including Sca1+ CPCs and cardiosphere-derived cells, are beginning to be revealed. These cells may be better choices than c-kit+ CPCs for generating cardiomyocytes. Adult mesenchymal stem cells are considered immune-incompetent and effective for improving cardiac function. Autologous CPC therapy may be limited by the observation that maternal diabetes adversely affects the biological function of embryonic stem cells and CPCs. Future studies should focus on determining the mechanistic action of these cells, identifying new CPC markers, selecting highly effective CPCs, and engineering cell-free products.

MicroRNA-322 attenuates aluminum maltolate-induced apoptosis in the human SH-SY5Y neuroblastoma cell line

Aluminum-maltolate (Al‑Malt) is a potent apoptosis inductor, which has been widely reported as an etiologic factor in Alzheimer's disease (AD). MicroRNA-322 (miR‑322) is a vital regulator in various biological processes. The aim of the current study was to identify the role and possible underlying mechanism of miR‑322 in Al‑Malt‑induced apoptosis. Eight concentrations of Al‑Malt were prepared and used for treating the human neuroblastoma cell line, SH‑SY5Y. Subsequent to treatment with Al‑Malt for 3 days, cell viability, apoptosis and the expression levels of apoptosis‑associated factors were measured. In addition, the mRNA expression level of miR‑322 was monitored. Furthermore, cells were transfected with an miR‑322 mimic and/or treated with Al‑Malt, and cell viability, apoptosis and the expression levels of apoptosis‑associated factors were measured again. Al‑Malt significantly inhibited cell viability, but promoted apoptosis. The apoptosis‑associated factors, V‑Myc avian myelocytomatosis viral oncogene homolog (c‑Myc), Bcl-2-associated X protein, caspase‑3 and cleaved caspase‑3 were markedly upregulated by Al‑Malt. The mRNA expression level of miR‑322 was negatively regulated by Al‑Malt. Furthermore, miR‑322 attenuated the apoptosis induced by Al‑Malt and recovered the expression changes of these four factors. Thus, miR‑322 may attenuate Al‑Malt‑induced apoptosis by recovering the expression change of c‑Myc. Furthermore, miR‑322 may be involved in the pathogenesis of Al‑Malt‑associated AD.

The p90 ribosomal S6 kinase-UBR5 pathway controls Toll-like receptor signaling via miRNA-induced translational inhibition of tumor necrosis factor receptor-associated factor 3

MicroRNAs (miRNAs) are small, noncoding RNAs that post-transcriptionally regulate gene expression. For example, miRNAs repress gene expression by recruiting the miRNA-induced silencing complex (miRISC), a ribonucleoprotein complex that contains miRNA-engaged Argonaute (Ago) and the scaffold protein GW182. Recently, ubiquitin-protein ligase E3 component N-recognin 5 (UBR5) has been identified as a component of miRISC. UBR5 directly interacts with GW182 proteins and participates in miRNA silencing by recruiting downstream effectors, such as the translation regulator DEAD-box helicase 6 (DDX6) and transducer of ERBB2,1/2,2 (Tob1/2), to the Ago-GW182 complex. However, the regulation of miRISC-associated UBR5 remains largely elusive. In the present study, we showed that UBR5 down-regulates the levels of TNF receptor-associated factor 3 (TRAF3), a key component of Toll-like receptor signaling, via the miRNA pathway. We further demonstrated that p90 ribosomal S6 kinase (p90RSK) is an upstream regulator of UBR5. p90RSK phosphorylates UBR5 at Thr⁶³⁷, Ser¹²²⁷, and Ser²⁴⁸³, and this phosphorylation is required for the translational repression of TRAF3 mRNA. Phosphorylated UBR5 co-localized with GW182 and Ago2 in cytoplasmic speckles, which implies that miRISC is affected by phospho-UBR5. Collectively, these results indicated that the p90RSK-UBR5 pathway stimulates miRNA-mediated translational repression of TRAF3. Our work has added another layer to the regulation of miRISC.

FAM3B mediates high glucose-induced vascular smooth muscle cell proliferation and migration via inhibition of miR-322-5p

The proliferation and migration of vascular smooth muscle cells (VSMCs) play an essential role during the development of cardiovascular diseases (CVDs). While many factors potentially contribute to the abnormal activation of VSMCs, hyperglycemia is generally believed to be a major causative factor. On the other hand, FAM3B (named PANDER for its secretory form) is a uniquely structured protein strongly expressed within and secreted from the endocrine pancreas. FAM3B is co-secreted with insulin from the β-cell upon glucose stimulation and regulates glucose homeostasis. In the present study, we sought to determine the roles of FAM3B in the regulation of VSMC physiology, especially under the hyperglycemic condition. We found that FAM3B expression was induced by hyperglycemia both in vivo and in vitro. FAM3B knockdown inhibited, whereas FAM3B overexpression accelerated VSMC proliferation and migration. At the molecular level, FAM3B inhibited miR-322-5p expression, and enforced expression of miR-322-5p antagonized FAM3B-induced VSMC proliferation and migration, suggesting that FAM3B facilitated VSMC pathological activation via miR-322-5p. Taken together, FAM3B mediates high glucose-induced VSMC proliferation and migration via inhibition of miR-322-5p. Thus, FAM3B may therefore serve as a novel therapeutic target for diabetes-related CVDs.

Protein kinase C-alpha suppresses autophagy and induces neural tube defects via miR-129-2 in diabetic pregnancy

Gene deletion-induced autophagy deficiency leads to neural tube defects (NTDs), similar to those in diabetic pregnancy. Here we report the key autophagy regulators modulated by diabetes in the murine developing neuroepithelium. Diabetes predominantly leads to exencephaly, induces neuroepithelial cell apoptosis and suppresses autophagy in the forebrain and midbrain of NTD embryos. Deleting the Prkca gene, which encodes PKCα, reverses diabetes-induced autophagy impairment, cellular organelle stress and apoptosis, leading to an NTD reduction. PKCα increases the expression of miR-129-2, which is a negative regulator of autophagy. miR-129-2 represses autophagy by directly targeting PGC-1α, a positive regulator for mitochondrial function, which is disturbed by maternal diabetes. PGC-1α supports neurulation by stimulating autophagy in neuroepithelial cells. These findings identify two negative autophagy regulators, PKCα and miR-129-2, which mediate the teratogenicity of hyperglycaemia leading to NTDs. We also reveal a function for PGC-1α in embryonic development through promoting autophagy and ameliorating hyperglycaemia-induced NTDs.

MicroRNA-322 inhibits inflammatory cytokine expression and promotes cell proliferation in LPS-stimulated murine macrophages by targeting NF-κB1 (p50)

Inflammation is the body’s normal self-protection mechanism to eliminate pathogens and resist pathogen invasion. The excessive inflammatory response may lead to inflammatory lesions. The mechanisms accounting for inflammation remain hazy. miRNAs have been proposed to have crucial effects on inflammation. In the present study, we reported that lipopolysaccharide (LPS)-stimulation increased the expression levels of inflammatory cytokines and the cell-cycle progression was suppressed in RAW264.7 cells. Meanwhile, the expression of miR-322 was significantly down-regulated after LPS treatment. Bioinformatics predictions revealed a potential binding site of miR-322 in 3′-UTR of NF-κB1 (p50) and it was further confirmed by luciferase assay. Moreover, both the mRNA and protein levels of NF-κB1 (p50) were down-regulated by miR-322 in RAW264.7 cells. Subsequently, we demonstrated that miR-322 mimics decrease in the expression levels of inflammatory cytokines and cell-cycle repression can be rescued following LPS treatment in RAW264.7 cells. The anti-inflammatory cytokines expression including IL-4 and IL-10 were significantly up-regulated. Furthermore, miR-322 could also promote RAW264.7 cells proliferation. These results demonstrate that miR-322 is a negative regulator of inflammatory response by targeting NF-κB1 (p50).

microRNA expression profiling and functional annotation analysis of their targets modulated by oxidative stress during embryonic heart development in diabetic mice

Maternal pregestational diabetes mellitus (PGDM) induces congenital heart defects (CHDs). The molecular mechanism underlying PGDM-induced CHDs is unknown. microRNAs (miRNAs), small non-coding RNAs, repress gene expression at the posttranscriptional level and play important roles in heart development. We performed a global miRNA profiling study to assist in revealing potential miRNAs modulated by PGDM and possible developmental pathways regulated by miRNAs during heart development. A total of 149 mapped miRNAs in the developing heart were significantly altered by PGDM. Bioinformatics analysis showed that the majority of the 2111 potential miRNA target genes were associated with cardiac development-related pathways including STAT3 and IGF-1 and transcription factors (Cited2, Zeb2, Mef2c, Smad4 and Ets1). Overexpression of the antioxidant enzyme, superoxide dismutase 1, reversed PGDM-altered miRNAs, suggesting that oxidative stress is responsible for dysregulation of miRNAs. Thus, our study provides the foundation for further investigation of a miRNA-dependent mechanism underlying PGDM-induced CHDs.

The green tea polyphenol EGCG alleviates maternal diabetes-induced neural tube defects by inhibiting DNA hypermethylation

BACKGROUND

Maternal diabetes increases the risk of neural tube defects in offspring. Our previous study demonstrated that the green tea polyphenol, Epigallocatechin gallate, inhibits high glucose-induced neural tube defects in cultured embryos. However, the therapeutic effect of Epigallocatechin gallate on maternal diabetes-induced neural tube defects is still unclear.

OBJECTIVE

We aimed to examine whether Epigallocatechin gallate treatment can reduce maternal diabetes-induced DNA methylation and neural tube defects.

STUDY DESIGN

Nondiabetic and diabetic pregnant mice at embryonic day 5.5 were given drinking water with or without 1 or 10 μM Epigallocatechin gallate. At embryonic day 8.75, embryos were dissected from the visceral yolk sac for the measurement of the levels and activity of DNA methyltransferases, the levels of global DNA methylation, and methylation in the CpG islands of neural tube closure essential gene promoters. embryonic day 10.5 embryos were examined for neural tube defect incidence.

RESULTS

Epigallocatechin gallate treatment did not affect embryonic development because embryos from nondiabetic dams treated with Epigallocatechin gallate did not exhibit any neural tube defects. Treatment with 1 μM Epigallocatechin gallate did not reduce maternal diabetes-induced neural tube defects significantly. Embryos from diabetic dams treated with 10 μM Epigallocatechin gallate had a significantly lower neural tube defect incidence compared with that of embryos without Epigallocatechin gallate treatment. Epigallocatechin gallate reduced neural tube defect rates from 29.5% to 2%, an incidence that is comparable with that of embryos from nondiabetic dams. Ten micromoles of Epigallocatechin gallate treatment blocked maternal diabetes-increased DNA methyltransferases 3a and 3b expression and their activities, leading to the suppression of global DNA hypermethylation. Additionally, 10 μM Epigallocatechin gallate abrogated maternal diabetes-increased DNA methylation in the CpG islands of neural tube closure essential genes, including Grhl3, Pax3, and Tulp3.

CONCLUSION

Epigallocatechin gallate reduces maternal diabetes-induced neural tube defects formation and blocks the enhanced expression and activity of DNA methyltransferases, leading to the suppression of DNA hypermethylation and the restoration of neural tube closure essential gene expression. These observations suggest that Epigallocatechin gallate supplements could mitigate the teratogenic effects of hyperglycemia on the developing embryo and prevent diabetes-induced neural tube defects.

Type 2 diabetes mellitus induces congenital heart defects in murine embryos by increasing oxidative stress, endoplasmic reticulum stress, and apoptosis

BACKGROUND

Maternal type 1 and 2 diabetes mellitus are strongly associated with high rates of severe structural birth defects, including congenital heart defects. Studies in type 1 diabetic embryopathy animal models have demonstrated that cellular stress-induced apoptosis mediates the teratogenicity of maternal diabetes leading to congenital heart defect formation. However, the mechanisms underlying maternal type 2 diabetes mellitus-induced congenital heart defects remain largely unknown.

OBJECTIVE

We aim to determine whether oxidative stress, endoplasmic reticulum stress, and excessive apoptosis are the intracellular molecular mechanisms underlying maternal type 2 diabetes mellitus-induced congenital heart defects.

STUDY DESIGN

A mouse model of maternal type 2 diabetes mellitus was established by feeding female mice a high-fat diet (60% fat). After 15 weeks on the high-fat diet, the mice showed characteristics of maternal type 2 diabetes mellitus. Control dams were either fed a normal diet (10% fat) or the high-fat diet during pregnancy only. Female mice from the high-fat diet group and the 2 control groups were mated with male mice that were fed a normal diet. At E12.5, embryonic hearts were harvested to determine the levels of lipid peroxides and superoxide, endoplasmic reticulum stress markers, cleaved caspase 3 and 8, and apoptosis. E17.5 embryonic hearts were harvested for the detection of congenital heart defect formation using India ink vessel patterning and histological examination.

RESULTS

Maternal type 2 diabetes mellitus significantly induced ventricular septal defects and persistent truncus arteriosus in the developing heart, along with increasing oxidative stress markers, including superoxide and lipid peroxidation; endoplasmic reticulum stress markers, including protein levels of phosphorylated-protein kinase RNA-like endoplasmic reticulum kinase, phosphorylated-IRE1α, phosphorylated-eIF2α, C/EBP homologous protein, and binding immunoglobulin protein; endoplasmic reticulum chaperone gene expression; and XBP1 messenger RNA splicing, as well as increased cleaved caspase 3 and 8 in embryonic hearts. Furthermore, maternal type 2 diabetes mellitus triggered excessive apoptosis in ventricular myocardium, endocardial cushion, and outflow tract of the embryonic heart.

CONCLUSION

Similar to those observations in type 1 diabetic embryopathy, maternal type 2 diabetes mellitus causes heart defects in the developing embryo manifested with oxidative stress, endoplasmic reticulum stress, and excessive apoptosis in heart cells.

Superoxide dismutase 2 overexpression alleviates maternal diabetes-induced neural tube defects, restores mitochondrial function and suppresses cellular stress in diabetic embryopathy

Pregestational diabetes disrupts neurulation leading to neural tube defects (NTDs). Oxidative stress resulting from reactive oxygen species (ROS) plays a central role in the induction of NTD formation in diabetic pregnancies. We aimed to determine whether mitochondrial dysfunction increases ROS production leading to oxidative stress and diabetic embryopathy. Overexpression of the mitochondrion-specific antioxidant enzyme superoxide dismutase 2 (SOD2) in a transgenic (Tg) mouse model significantly reduced maternal diabetes-induced NTDs. SOD2 overexpression abrogated maternal diabetes-induced mitochondrial dysfunction by inhibiting mitochondrial translocation of the pro-apoptotic Bcl-2 family members, reducing the number of defective mitochondria in neuroepithelial cells, and decreasing mitochondrial membrane potential. Furthermore, SOD2 overexpression blocked maternal diabetes-increased ROS production by diminishing dihydroethidium staining signals in the developing neuroepithelium, and reducing the levels of nitrotyrosine-modified proteins and lipid hydroperoxide level in neurulation stage embryos. SOD2 overexpression also abolished maternal diabetes-induced endoplasmic reticulum stress. Finally, caspase-dependent neuroepithelial cell apoptosis enhanced by oxidative stress was significantly reduced by SOD2 overexpression. Thus, our findings support the hypothesis that mitochondrial dysfunction in the developing neuroepithelium enhances ROS production, which leads to oxidative stress and endoplasmic reticulum (ER) stress. SOD2 overexpression blocks maternal diabetes-induced oxidative stress and ER stress, and reduces the incidence of NTDs in embryos exposed to maternal diabetes.

High glucose-induced oxidative stress represses sirtuin deacetylase expression and increases histone acetylation leading to neural tube defects

Aberrant epigenetic modifications are implicated in maternal diabetes-induced neural tube defects (NTDs). Because cellular stress plays a causal role in diabetic embryopathy, we investigated the possible role of the stress-resistant sirtuin (SIRT) family histone deacetylases. Among the seven sirtuins (SIRT1-7), pre-gestational maternal diabetes in vivo or high glucose in vitro significantly reduced the expression of SIRT 2 and SIRT6 in the embryo or neural stem cells, respectively. The down-regulation of SIRT2 and SIRT6 was reversed by superoxide dismutase 1 (SOD1) over-expression in the in vivo mouse model of diabetic embryopathy and the SOD mimetic, tempol and cell permeable SOD, PEGSOD in neural stem cell cultures. 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), a superoxide generating agent, mimicked high glucose-suppressed SIRT2 and SIRT6 expression. The acetylation of histone 3 at lysine residues 56 (H3K56), H3K14, H3K9, and H3K27, putative substrates of SIRT2 and SIRT6, was increased by maternal diabetes in vivo or high glucose in vitro, and these increases were blocked by SOD1 over-expression or tempol treatment. SIRT2 or SIRT6 over-expression abrogated high glucose-suppressed SIRT2 or SIRT6 expression, and prevented the increase in acetylation of their histone substrates. The potent sirtuin activator (SRT1720) blocked high glucose-increased histone acetylation and NTD formation, whereas the combination of a pharmacological SIRT2 inhibitor and a pan SIRT inhibitor mimicked the effect of high glucose on increased histone acetylation and NTD induction. Thus, diabetes in vivo or high glucose in vitro suppresses SIRT2 and SIRT6 expression through oxidative stress, and sirtuin down-regulation-induced histone acetylation may be involved in diabetes-induced NTDs. The mechanism underlying pre-gestational diabetes-induced neural tube defects (NTDs) is still elusive. Our study unravels a new epigenetic mechanism in which maternal diabetes-induced oxidative stress represses sirtuin deacetylase 2 (SIRT2) and 6 (SIRT6) expression leading to histone acetylation and gene expression. SIRT down-regulation mediates the teratogenicity of diabetes leading to (NTD) formation. The study provides a mechanistic basis for the development of natural antioxidants and SIRT activators as therapeutics for diabetic embryopathy.

New development of the yolk sac theory in diabetic embryopathy: molecular mechanism and link to structural birth defects

Maternal diabetes mellitus is a significant risk factor for structural birth defects, including congenital heart defects and neural tube defects. With the rising prevalence of type 2 diabetes mellitus and obesity in women of childbearing age, diabetes mellitus-induced birth defects have become an increasingly significant public health problem. Maternal diabetes mellitus in vivo and high glucose in vitro induce yolk sac injuries by damaging the morphologic condition of cells and altering the dynamics of organelles. The yolk sac vascular system is the first system to develop during embryogenesis; therefore, it is the most sensitive to hyperglycemia. The consequences of yolk sac injuries include impairment of nutrient transportation because of vasculopathy. Although the functional relationship between yolk sac vasculopathy and structural birth defects has not yet been established, a recent study reveals that the quality of yolk sac vasculature is related inversely to embryonic malformation rates. Studies in animal models have uncovered key molecular intermediates of diabetic yolk sac vasculopathy, which include hypoxia-inducible factor-1α, apoptosis signal-regulating kinase 1, and its inhibitor thioredoxin-1, c-Jun-N-terminal kinases, nitric oxide, and nitric oxide synthase. Yolk sac vasculopathy is also associated with abnormalities in arachidonic acid and myo-inositol. Dietary supplementation with fatty acids that restore lipid levels in the yolk sac lead to a reduction in diabetes mellitus-induced malformations. Although the role of the human yolk in embryogenesis is less extensive than in rodents, nevertheless, human embryonic vasculogenesis is affected negatively by maternal diabetes mellitus. Mechanistic studies have identified potential therapeutic targets for future intervention against yolk sac vasculopathy, birth defects, and other complications associated with diabetic pregnancies.

The Nrf2 Activator Vinylsulfone Reduces High Glucose-Induced Neural Tube Defects by Suppressing Cellular Stress and Apoptosis

The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway is one of the primary pathways responsible for the cellular defense system against oxidative stress. Oxidative stress-induced apoptosis is a causal event in diabetic embryopathy. Thus, the Nrf2 pathway may play an important role in the induction of diabetic embryopathy. In the present study, we investigated the potentially protective effect of the Nrf2 activator, vinylsulfone, on high glucose-induced cellular stress, apoptosis, and neural tube defects (NTDs). Embryonic day 8.5 (E8.5) whole mouse embryos were cultured in normal (5 mmol/L) or high (16.7 mmol/L) glucose conditions, with or without vinylsulfone. At a concentration of 10 μmol/L, vinylsulfone had an inhibitory effect on high glucose-induced NTD formation, but it was not significant. At a concentration of 20 μmol/L, vinylsulfone significantly reduced high glucose-induced NTDs. In addition, 20 μmol/L vinylsulfone abrogated the high glucose-induced oxidative stress markers lipid hydroperoxide (LPO), 4-hydroxynonenal (4-HNE), and nitrotyrosine-modified proteins. The high glucose-induced endoplasmic reticulum (ER) stress biomarkers were also suppressed by 20 μmol/L vinylsulfone through the inhibition of phosphorylated protein kinase RNA-like ER kinase (PERK), inositol requiring protein 1α (IRE1a), eukaryotic initiation factor 2α (eIF2a), upregulated C/EBP-homologous protein (CHOP), binding immunoglobulin protein (BiP), and x-box binding protein 1 (XBP1) messenger RNA splicing. Furthermore, 20 μmol/L vinylsulfone abolished caspase 3 and caspase 8 cleavage, markers of apoptosis, in embryos cultured under high glucose conditions. The Nrf2 activator, vinylsulfone, is protective against high glucose-induced cellular stress, caspase activation, and subsequent NTD formation. Our data suggest that vinylsulfone supplementation is a potential therapy for diabetes-associated neurodevelopmental defects.

High Glucose-Repressed CITED2 Expression Through miR-200b Triggers the Unfolded Protein Response and Endoplasmic Reticulum Stress

High glucose in vivo and in vitro induces neural tube defects (NTDs). CITED2 (CBP/p300-interacting transactivator with ED-rich tail 2) is essential for neural tube closure. We explored the regulatory mechanism underlying CITED2 expression and its relationship with miRNA and endoplasmic reticulum (ER) stress. miR-200b levels were increased by maternal diabetes or high glucose in vitro, and this increase was abrogated by transgenic overexpression of superoxide dismutase 1 (SOD1) or an SOD1 mimetic. CITED2 was the target of miR-200b and was downregulated by high glucose. Two miR-200b binding sites in the 3'-untranslated region of the CITED2 mRNA were required for inhibiting CITED2 expression. The miR-200b mimic and a CITED2 knockdown mimicked the stimulative effect of high glucose on unfolded protein response (UPR) and ER stress, whereas the miR-200b inhibitor and CITED2 overexpression abolished high glucose-induced UPR signaling, ER stress, and apoptosis. The ER stress inhibitor, 4-phenylbutyrate, blocked CITED2 knockdown-induced apoptosis. Furthermore, the miR-200b inhibitor reversed high glucose-induced CITED2 downregulation, ER stress, and NTDs in cultured embryos. Thus, we showed a novel function of miR-200b and CITED2 in high glucose-induced UPR and ER stress, suggesting that miR-200b and CITED2 are critical for ER homeostasis and NTD formation in the developing embryo.