Homocysteine-induced cardiomyocyte apoptosis and plasma membrane flip-flop are independent of S-adenosylhomocysteine: a crucial role for nuclear p47(phox).

Item does not contain fulltextWe previously found that homocysteine (Hcy) induced plasma membrane flip-flop, apoptosis, and necrosis in cardiomyocytes. Inactivation of flippase by Hcy induced membrane flip-flop, while apoptosis was induced via a NOX2-dependent mechanism. It has been suggested that S-adenosylhomocysteine (SAH) is the main causative factor in hyperhomocysteinemia (HHC)-induced pathogenesis of cardiovascular disease. Therefore, we evaluated whether the observed cytotoxic effect of Hcy in cardiomyocytes is SAH dependent. Rat cardiomyoblasts (H9c2 cells) were treated under different conditions: (1) non-treated control (1.5 nM intracellular SAH with 2.8 muM extracellular L -Hcy), (2) incubation with 50 muM adenosine-2,3-dialdehyde (ADA resulting in 83.5 nM intracellular SAH, and 1.6 muM extracellular L -Hcy), (3) incubation with 2.5 mM D, L -Hcy (resulting in 68 nM intracellular SAH and 1513 muM extracellular L -Hcy) with or without 10 muM reactive oxygen species (ROS)-inhibitor apocynin, and (4) incubation with 100 nM, 10 muM, and 100 muM SAH. We then determined the effect on annexin V/propodium iodide positivity, flippase activity, caspase-3 activity, intracellular NOX2 and p47(phox) expression and localization, and nuclear ROS production. In contrast to Hcy, ADA did not induce apoptosis, necrosis, or membrane flip-flop. Remarkably, both ADA and Hcy induced a significant increase in nuclear NOX2 expression. However, in contrast to ADA, Hcy additionally induced nuclear p47(phox) expression, increased nuclear ROS production, and inactivated flippase. Incubation with SAH did not have an effect on cell viability, nor on flippase activity, nor on nuclear NOX2-, p47phox expression or nuclear ROS production. HHC-induced membrane flip-flop and apoptosis in cardiomyocytes is due to increased Hcy levels and not primarily related to increased intracellular SAH, which plays a crucial role in nuclear p47(phox) translocation and subsequent ROS production.1 december 201

Author Correction: Loss of NARS1 impairs progenitor proliferation in cortical brain organoids and leads to microcephaly (Nature Communications, (2020), 11, 1, (4038), 10.1038/s41467-020-17454-4)

The original version of this Article omitted a reference to another publication which included overlapping genetic and MRI data for a research participant. This has been added as reference 59 at the end of the Discussion: ‘While this paper was under review, a separate paper appeared reporting that mutations in NARS1 associate with neurodevelopmental delay through either biallelic loss or dominant negative effects, impairing NARS1 enzyme activity. This article contained genetic data on family MIC-1433 which overlaps this study59.’ Accordingly, reference 59 has now been included in the References section as ‘Manole, A. et al. De novo and bi-allelic pathogenic variants in NARS1 cause neurodevelopmental delay due to toxic gain-of-function and partial loss-of-function effects. Am. J. Hum. Genet. 107(2), 311–324 (2020).’ In addition, the original version of this Article contained an error in Fig. 1A, where there was an error in the family depiction in generation 1 of pedigree MIC-1433; this has been revised to correctly depict the family. Figure 1D also contained MRI scans that had been previously published in Ref 59; this has been revised to include different and unpublished MRI scans from the same individual. (Figure presented.)

Megalobastic anemia, infantile leukemia, and immunodeficiency caused by a novel homozygous mutation in the DHFR gene

Dihydrofolate reductase (DHFR) is a critical enzyme in folate metabolism that reduces folic acid to dihydrofolic and tetrahydrofolic acid and provides an important target for antineoplastic, antimicrobial, and anti-inflammatory drugs. Defective DHFR activity leads to megaloblastic anemia syndrome combined with severe cerebral folate deficiency, and cerebral tetrahydrobiopterin deficiency due to a germ line missense mutation in DHFR has been reported.1,2 Folate represents a large family of water-soluble vitamins that play an important role in DNA synthesis, repair, and transmethylation pathways.3 Folate is also a substrate for purine and thymidine synthesis and a methyl donor for homocysteine to methionine conversion, with low folate status being reflected by elevated plasma homocysteine concentrations.4 Cerebral tetrahydrobiopterin is required for the formation of dopamine, serotonin, and norepinephrine and the hydroxylation of aromatic amino acids as a link to neurodevelopmental symptoms

Homocysteine affects cardiomyocyte viability: concentration-dependent effects on reversible flip-flop, apoptosis and necrosis

BACKGROUND: Hyperhomocysteinaemia (HHC) is thought to be a risk factor for cardiovascular disease including heart failure. While numerous studies have analyzed the role of homocysteine (Hcy) in the vasculature, only a few studies investigated the role of Hcy in the heart. Therefore we have analyzed the effects of Hcy on isolated cardiomyocytes. METHODS: H9c2 cells (rat cardiomyoblast cells) and adult rat cardiomyocytes were incubated with Hcy and were analyzed for cell viability. Furthermore, we determined the effects of Hcy on intracellular mediators related to cell viability in cardiomyocytes, namely NOX2, reactive oxygen species (ROS), mitochondrial membrane potential (DeltaPsi (m)) and ATP concentrations. RESULTS: We found that incubation of H9c2 cells with 0.1 mM D,L-Hcy (= 60 microM L-Hcy) resulted in an increase of DeltaPsi (m) as well as ATP concentrations. 1.1 mM D,L-Hcy (= 460 microM L-Hcy) induced reversible flip-flop of the plasma membrane phospholipids, but not apoptosis. Incubation with 2.73 mM D,L-Hcy (= 1.18 mM L-Hcy) induced apoptosis and necrosis. This loss of cell viability was accompanied by a thread-to-grain transition of the mitochondrial reticulum, ATP depletion and nuclear NOX2 expression coinciding with ROS production as evident from the presence of nitrotyrosin residues. Notably, only at this concentration we found a significant increase in S-adenosylhomocysteine which is considered the primary culprit in HHC. CONCLUSION: We found concentration-dependent effects of Hcy in cardiomyocytes, varying from induction of reversible flip-flop of the plasma membrane phospholipids, to apoptosis and necrosis

’Let’s Call Ourselves the Super Elite’: Using the Collective Behavior Tradition to Analyze Trump’s America

The mid‐twentieth century “collective behavior” school asserted that (1) collective behavior—the actions of crowds, movements, and other gatherings—had distinct dynamics; (2) such action was often “nonrational,” or not governed by cost‐benefit calculation; and (3) collective behavior could pose a threat to liberal democracy because of these features. While this tradition fell out of scholarly favor, the 2016 election has given us empirical reasons to revisit some elements of collective behavior approaches. We argue for three key orienting concerns, drawn from this tradition, to understand the current political era. First is a focus on authoritarianism and populism, particularly among those who feel disaffected and isolated from political institutions, pared of psychologistic determinism and geared more sensitively to their manifestations as a political style. Second is a focus on racialized resentment, strain, and perceptions of status decline, especially in how such feelings are activated when people are confronted with disruptions to their lives. Third is an analysis of “emergent norms” and the extent to which political actors produce normative understandings of contextually appropriate action that are distinct from traditional political behavior. We elaborate on these themes, apply them to examples from current politics, and suggest ways to incorporate them into contemporary sociological research