Okadaic acid induces apoptosis in Down syndrome fibroblasts

Inborn Errors of Adaptive Immunity in Down Syndrome

Down syndrome fits an immunophenotype of combined immunodeficiency with immunodysregulation, manifesting with increased susceptibility to infections, autoimmunity, autoinflammatory diseases, and hematologic malignancies. Qualitative and quantitative alterations in innate and adaptive immunity are found in most individuals with Down syndrome. However, there is substantial heterogeneity and no correlation between immunophenotype and clinical presentation. Previously, it was thought that the immunological changes in Down syndrome were caused by precocious aging. We emphasize in this review that the immune system in Down syndrome is intrinsically different from the very beginning. The overexpression of specific genes located on chromosome 21 contributes to immunodeficiency and immunodysregulation, but gene expression differs between genes located on chromosome 21 and depends on tissue and cell type. In addition, trisomy 21 results in gene dysregulation of the whole genome, reflecting the complex nature of this syndrome in comparison to well-known inborn errors of immunity that result from monogenic germline mutations. In this review, we provide an updated overview focusing on inborn errors of adaptive immunity in Down syndrome.

Protective effects of γ-aminobutyric acid against H2O2-induced oxidative stress in RIN-m5F pancreatic cells

Background

γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the central nervous system and reported to maintain the redox homeostasis and insulin secretion function of pancreatic β cells. This study tested the hypothesis that GABA maintains cellular redox status, and modulates glycogen synthase kinase (GSK)-3β and antioxidant-related nuclear factor erythroid 2-related factor 2 (NRF2) nuclear mass ratio in the H₂O₂-injured RINm5F cells.

Methods

RINm5F cells were treated with/without GABA (50, 100 and 200 μmol/L) for 48 h and then exposed to 100 μmol/L H₂O₂ for 30 min. Viable cells were harvested, and dichloro-dihydro-fluorescein diacetate (DCFH-DA) was used to detect reactive oxygen species (ROS) level; cellular redox status and insulin secretion were measured; cell viability was determined by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay; mitochondrial membrane potential (MMP) was detected by flow cytometry; relative genes levels were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR); western blotting was used to determine protein expression of GSK-3β and p-GSK-3β (Ser9), and nuclear and cytoplasmic NRF2.

Results

H₂O₂ increased ROS production, and induced adverse affects in relation to antioxidant defense systems and insulin secretion. These changes were restored by treatment with 100 and 200 μmol/L GABA. In addition, 100 or 200 μmol/L GABA induced membrane depolarization and increased cell viability. These effects were mediated by Caspase-3, Bcl-2 associated X protein (Bax) and B-cell lymphoma-2 (Bcl-2) expression. Western blotting indicated that GABA inhibited GSK-3β by increasing p-GSK-3β (Ser9) level, and directed the transcription factor NRF2 to the nucleus.

Conclusion

In rat insulin-producing RINm5F cells, GABA exerts its protective effect by regulating GSK-3β and NRF2, which governs redox homeostasis by inhibiting apoptosis and abnormal insulin secretion by exposure to H₂O_2.

Systematic proteome and proteostasis profiling in human Trisomy 21 fibroblast cells

Down syndrome (DS) is mostly caused by a trisomy of the entire Chromosome 21 (Trisomy 21, T21). Here, we use SWATH mass spectrometry to quantify protein abundance and protein turnover in fibroblasts from a monozygotic twin pair discordant for T21, and to profile protein expression in 11 unrelated DS individuals and matched controls. The integration of the steady-state and turnover proteomic data indicates that protein-specific degradation of members of stoichiometric complexes is a major determinant of T21 gene dosage outcome, both within and between individuals. This effect is not apparent from genomic and transcriptomic data. The data also reveal that T21 results in extensive proteome remodeling, affecting proteins encoded by all chromosomes. Finally, we find broad, organelle-specific post-transcriptional effects such as significant downregulation of the mitochondrial proteome contributing to T21 hallmarks. Overall, we provide a valuable proteomic resource to understand the origin of DS phenotypic manifestations.

Trisomy 21 (T21) is a major cause of Down syndrome but little is known about its impact on the cellular proteome. Here, the authors define the proteome of T21 fibroblasts and its turnover and also map proteomic differences in monozygotic T21-discordant twins, revealing extensive, organelle-specific changes caused by T21.

ZYZ-772 Prevents Cardiomyocyte Injury by Suppressing Nox4-Derived ROS Production and Apoptosis

Nox-dependent signaling plays critical roles in the development of heart failure, cardiac hypertrophy, and myocardial infarction. NADPH oxidase 4 (Nox4) as a major source of oxidative stress in the heart offers a new therapeutic target in cardiovascular disease. In the present work, a novel flavonoid was isolated from Zanthoxylum bungeanum. Its structure was elucidated as Quercetin-3-O-(6′′-O-α-l-rhamnopyransoyl)-β-d-glucopyranoside-7-O-β-d-glucopyranoside (ZYZ-772) for the first time. ZYZ-772 exhibited significant cardio-protective property against CoCl₂ induced H9c2 cardiomyocyte cells injury. In CoCl₂ stimulated cardiomyocyte injury, ZYZ-772 inhibited expression of Nox4, and alleviated ROS overproduction. Importantly, ROS triggered MAPKs phosphorylation and P53 signaling mediated apoptosis were restored by ZYZ-772. Our findings present the first piece of evidence for the therapeutic properties of ZYZ-772 in preventing cardiomyocyte injury, which could be attributed to the suppression of Nox4/MAPKs/P53 axis. This will offer a novel therapeutic strategy for the treatment of cardiac ischemia disease.

The discovery of a novel inhibitor of apoptotic protease activating factor-1 (Apaf-1) for ischemic heart: synthesis, activity and target identification

Apaf-1 is a central component in the apoptosis regulatory network for the treatment of apoptosis related diseases. Excessive Apaf-1 activity induced by myocardial ischemia causes cell injury. No drug targeted to Apaf-1 for treating myocardial ischemia has been reported to the best of our knowledge. In the present work, we synthesized a novel compound, ZYZ-488, which exhibited significant cardioprotective property in significantly increasing the viability of hypoxia-induced H9c2 cardiomyocytes and reducing CK and LDH leakage. Further study suggested the protective activity of ZYZ-488 dependent on its anti-apoptosis effect. This anti-apoptotic effect is most probably related to its disturbing the interaction between Apaf-1 and procaspase-9 as the target fishing and molecular docking indicated. The suppression on the activation of procaspase-9 and procaspase-3 with ZYZ-488 strongly suggested that compound ZYZ-488 could be a novel inhibitor of Apaf-1. In conclusion, ZYZ-488 as a novel small molecule competitive inhibitor of Apaf-1, with the great potential for treating cardiac ischemia.

Neurological phenotypes for Down syndrome across the life span

This chapter reviews the neurological phenotype of Down syndrome (DS) in early development, childhood, and aging. Neuroanatomic abnormalities in DS are manifested as aberrations in gross brain structure as well as characteristic microdysgenetic changes. As the result of these morphological abnormalities, brain circuitry is impaired. While an intellectual disability is ubiquitous in DS, there is a wide range of variation in cognitive performance and a growing understanding between aberrant brain circuitry and the cognitive phenotype. Hypotonia is most marked at birth, affecting gait and ligamentous laxity. Seizures are bimodal in presentation with infantile spasms common in infancy and generalized seizures associated with cognitive decline observed in later years. While all individuals have the characteristic neuropathology of Alzheimer's disease (AD) by age 40 years, the prevalence of dementia is not universal. The tendency to develop AD is related, in part, to several genes on chromosome 21 that are overexpressed in DS. Intraneuronal accumulation of β-amyloid appears to trigger a cascade of neurodegeneration resulting in the neuropathological and clinical manifestations of dementia. Functional brain imaging has elucidated the temporal sequence of amyloid deposition and glucose metabolic rate in the development of dementia in DS. Mitochondrial abnormalities contribute to oxidative stress which is part of AD pathogenesis in DS as well as AD in the general population. A variety of medical comorbidities threaten cognitive performance including sleep apnea, abnormalities in thyroid metabolism, and behavioral disturbances. Mouse models for DS are providing a platform for the formulation of clinical trials with intervention targeted to synaptic plasticity, brain biochemistry, and morphological brain alterations.

Antioxidants in Down syndrome

Individuals with Down syndrome (DS) have high levels of oxidative stress throughout the lifespan. Mouse models of DS share some structural and functional abnormalities that parallel findings seen in the human phenotype. Several of the mouse models show evidence of cellular oxidative stress and have provided a platform for antioxidant intervention. Genes that are overexpressed on chromosome 21 are associated with oxidative stress and neuronal apoptosis. The lack of balance in the metabolism of free radicals generated during processes related to oxidative stress may have a direct role in producing the neuropathology of DS including the tendency to Alzheimer disease (AD). Mitochondria are often a target for oxidative stress and are considered to be a trigger for the onset of the AD process in DS. Biomarkers for oxidative stress have been described in DS and in AD in the general population. However, intervention trials using standard antioxidant supplements or diets have failed to produce uniform therapeutic effect. This chapter will examine the biological role of oxidative stress in DS and its relationship to abnormalities in both development and aging within the disorder. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Okadaic acid induces morphological changes, apoptosis and cell cycle alterations in different human cell types

Okadaic acid (OA) is a marine toxin produced by dinoflagellate species which is frequently accumulated in molluscs usual in the human diet. The exact action mechanism of OA has not been described yet and the results of most reported studies are often conflicting. The aim of this work was to evaluate the OA effects on morphology, cell cycle and apoptosis induction by means of light microscopy and flow cytometry, in three different types of human cells (leukocytes, HepG2 cells and SHSY5Y cells). Cells were treated with a range of OA concentrations in the presence and absence of S9 fraction. OA induced morphological changes in all the cell types studied, and cell cycle disruption only in leukocytes and neuronal cells. SHSY5Y cells were the most sensitive to OA assault. Results obtained in the presence and absence of metabolic activation were similar, suggesting that OA acts both directly and indirectly. Furthermore, OA was found to increase the subG(1) region in the flow cytometry cell cycle analysis, suggesting induction of apoptosis. These results were confirmed by the employment of specific methodologies for studying apoptosis such as caspase 3 activation and annexin V staining. Increases in the apoptosis rate were obtained in all the cells treated in the absence of S9 fraction, accompanied by increases in caspase 3 activation, suggesting that apoptosis induced by OA is a caspase 3-dependent process. Nevertheless, in the presence of S9 fraction no apoptosis was detected, indicating a metabolic detoxifying activity, although necrosis was observed in neuroblastoma cells.

Insulin increases H2O2-induced pancreatic beta cell death

Insulin resistance results, in part, from impaired insulin signaling in insulin target tissues. Consequently, increased levels of insulin are necessary to control plasma glucose levels. The effects of elevated insulin levels on pancreatic beta (β) cell function, however, are unclear. In this study, we investigated the possibility that insulin may influence survival of pancreatic β cells. Studies were conducted on RINm, RINm5F and Min-6 pancreatic β-cells. Cell death was induced by treatment with H(2)O(2), and was estimated by measurements of LDH levels, viability assay (Cell-Titer Blue), propidium iodide staining and FACS analysis, and mitochondrial membrane potential (JC-1). In addition, levels of cleaved caspase-3 and caspase activity were determined. Treatment with H(2)O(2) increased cell death; this effect was increased by simultaneous treatment of cells with insulin. Insulin treatment alone caused a slight increase in cell death. Inhibition of caspase-3 reduced the effect of insulin to increase H(2)O(2)-induced cell death. Insulin increased ROS production by pancreatic β cells and increased the effect of H(2)O(2). These effects were increased by inhibition of IR signaling, indicative of an effect independent of the IR cascade. We conclude that elevated levels of insulin may act to exacerbate cell death induced by H(2)O(2) and, perhaps, other inducers of apoptosis.