Blocking P2RX7 Attenuates Ferroptosis in Endothelium and Reduces HG-induced Hemorrhagic Transformation After MCAO by Inhibiting ERK1/2 and P53 Signaling Pathways

Hyperglycemia is a risk factor for poor prognosis after acute ischemic stroke and promote the occurrence of hemorrhagic transformation (HT). The activation of P2RX7 play an important role in endotheliocyte damage and BBB disruption. Ferroptosis is a novel pattern of programmed cell death caused by the accumulation of intracellular iron and lipid peroxidation, resulting in ROS production and cell death. This study is to explore the mechanism of P2RX7 in reducing HT pathogenesis after acute ischemic stroke through regulating endotheliocyte ferroptosis. Male SD rats were performed to establish middle cerebral artery occlusion (MCAO) model injected with 50% high glucose (HG) and HUVECs were subjected to OGD/R treated with high glucose (30 mM) for establishing HT model in vivo and in vitro. P2RX7 inhibitor (BBG), and P2RX7 small interfering RNAs (siRNA) were used to investigate the role of P2RX7 in BBB after MCAO in vivo and OGD/R in vitro, respectively. The neurological deficits, infarct volume, degree of intracranial hemorrhage, integrity of the BBB, immunoblotting, and immunofluorescence were evaluated at 24 h after MCAO. Our study found that the level of P2RX7 was gradually increased after MCAO and/or treated with HG. Our results showed that treatment with HG after MCAO can aggravate neurological deficits, infarct volume, oxidative stress, iron accumulation, and BBB injury in HT model, and HG-induced HUVECs damage. The inhibition of P2RX7 reversed the damage effect of HG, significantly downregulated the expression level of P53, HO-1, and p-ERK1/2 and upregulated the level of SLC7A11 and GPX4, which implicated that P2RX7 inhibition could attenuate oxidative stress and ferroptosis of endothelium in vivo and in vitro. Our data provided evidence that the P2RX7 play an important role in HG-associated oxidative stress, endothelial damage, and BBB disruption, which regulates HG-induced HT by ERK1/2 and P53 signaling pathways after MCAO.

Impact of the Cellular Zinc Status on PARP-1 Activity and Genomic Stability in HeLa S3 Cells

Poly(ADP-ribose) polymerase 1 (PARP-1) is actively involved in several DNA repair pathways, especially in the detection of DNA lesions and DNA damage signaling. However, the mechanisms of PARP-1 activation are not fully understood. PARP-1 contains three zinc finger structures, among which the first zinc finger has a remarkably low affinity toward zinc ions. Within the present study, we investigated the impact of the cellular zinc status on PARP-1 activity and on genomic stability in HeLa S3 cells. Significant impairment of H₂O₂-induced poly(ADP-ribosyl)ation and an increase in DNA strand breaks were detected in the case of zinc depletion by the zinc chelator N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN) which reduced the total and labile zinc concentrations. On the contrary, preincubation of cells with ZnCl₂ led to an overload of total as well as labile zinc and resulted in an increased poly(ADP-ribosyl)ation response upon H₂O₂ treatment. Furthermore, the impact of the cellular zinc status on gene expression profiles was investigated via high-throughput RT-qPCR, analyzing 95 genes related to metal homeostasis, DNA damage and oxidative stress response, cell cycle regulation and proliferation. Genes encoding metallothioneins responded most sensitively on conditions of mild zinc depletion or moderate zinc overload. Zinc depletion induced by higher concentrations of TPEN led to a significant induction of genes encoding DNA repair factors and cell cycle arrest, indicating the induction of DNA damage and genomic instability. Zinc overload provoked an up-regulation of the oxidative stress response. Altogether, the results highlight the potential role of zinc signaling for PARP-1 activation and the maintenance of genomic stability.

Lower Cardiac Output Relates to Longitudinal Cognitive Decline in Aging Adults

Background

Subclinical reductions in cardiac output correspond to lower cerebral blood flow (CBF), placing the brain at risk for functional changes.

Objectives

This study aims to establish the consequences of reduced cardiac output on longitudinal cognitive outcomes in aging adults.

Methods

Vanderbilt Memory and Aging Project participants free of clinical dementia and heart failure (n = 306, 73 ± 7, 58% male) underwent baseline echocardiography to assess cardiac output (L/min) and longitudinal neuropsychological assessment at baseline, 18 months, 3 and 5 years. Linear mixed-effects regressions related cardiac output to trajectory for each longitudinal neuropsychological outcome, adjusting for age, sex, race/ethnicity, education, body surface area, Framingham Stroke Risk Profile score, apolipoprotein E (APOE) ε4 status and follow-up time. Models were repeated, testing interactions with cognitive diagnosis and APOE-ε4 status.

Results

Lower baseline cardiac output related to faster declines in language (β = 0.11, p = 0.01), information processing speed (β = 0.31, p = 0.006), visuospatial skills (β = 0.09, p = 0.03), and episodic memory (β = 0.02, p = 0.001). No cardiac output x cognitive diagnosis interactions were observed (p > 0.26). APOE-ε4 status modified the association between cardiac output and longitudinal episodic memory (β = 0.03, p = 0.047) and information processing speed outcomes (β = 0.55, p = 0.02) with associations stronger in APOE-ε4 carriers.

Conclusion

The present study provides evidence that even subtle reductions in cardiac output may be associated with more adverse longitudinal cognitive health, including worse language, information processing speed, visuospatial skills, and episodic memory performances. Preservation of healthy cardiac functioning is important for maintaining optimal brain aging among older adults.

Zinc-aggravated M1 microglia regulate astrocytic engulfment via P2×7 receptors

BACKGROUND

Glial cells such as astrocytes and microglia play an important role in the central nervous system via communication between these glial cells. Activated microglia can exhibit either the inflammatory M1 phenotype or the anti-inflammatory M2 phenotype, which influences astrocytic neuroprotective functions, including engulfment of cell debris. Recently, extracellular zinc has been shown to promote the inflammatory M1 phenotype in microglia through intracellular zinc accumulation and reactive oxygen species (ROS) generation.

PURPOSE

Here, we investigated whether the zinc-enhanced inflammatory M1 phenotype of microglia affects the astrocytic engulfing activity.

METHODS

Engulfing activity was assessed in astrocytes treated with microglial-conditioned medium (MCM) from lipopolysaccharide (LPS)-activated or from ZnCl2-pretreated LPS-activated M1 microglia. The effect of zinc on microglia phenotype was also validated using the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) and the ROS scavenger Trolox.

RESULTS

Although treatment of astrocytes with LPS showed no significant effect on the engulfing activity, MCM from LPS-induced M1 microglia increased the beads uptake by astrocytes. This increased uptake activity was suppressed when MCM from LPS-induced M1 microglia pretreated with ZnCl2 was applied to astrocytes, which was further abolished by the intracellular zinc chelator TPEN and the ROS scavenger Trolox. In addition, expression of P2×7 receptors (P2×7R) was increased in astrocytes treated with MCM derived from M1 microglia but not in the M1 microglia pretreated with ZnCl2.

CONCLUSION

These findings suggest that zinc pre-treatment abolishes the ability of LPS-induced M1 microglia to increase the engulfing activity in astrocytes via alteration of astrocytic P2×7R.

Towards a comprehensive etiopathogenetic and pathophysiological theory of multiple sclerosis

Background: Multiple sclerosis (MS) is a neurodegenerative disease caused by dysfunction of the immune system that affects the central nervous system (CNS). It is characterized by demyelination, chronic inflammation, neuronal and oligodendrocyte loss and reactive astrogliosis. It can result in physical disability and acute neurological and cognitive problems. Despite the gains in knowledge of immunology, cell biology, and genetics in the last five decades, the ultimate etiology or specific elements that trigger MS remain unknown. The objective of this review is to propose a theoretical basis for MS etiopathogenesis.Methods: Search was done by accessing PubMed/Medline, EBSCO, and PsycINFO databases. The search string used was "(multiple sclerosis* OR EAE) AND (pathophysiology* OR etiopathogenesis)". The electronic databases were searched for titles or abstracts containing these terms in all published articles between January 1, 1960, and June 30, 2019. The search was filtered down to 362 articles which were included in this review.Results: A framework to better understand the etiopathogenesis and pathophysiology of MS can be derived from four essential factors; mitochondria dysfunction (MtD) & oxidative stress (OS), vitamin D (VD), sex hormones and thyroid hormones. These factors play a direct role in MS etiopathogenesis and have a modulatory effect on many other factors involved in the disease.Conclusions: For better MS prevention and treatment outcomes, efforts should be geared towards treating thyroid problems, sex hormone alterations, VD deficiency, sleep problems and melatonin alterations. MS patients should be encouraged to engage in activities that boost total antioxidant capacity (TAC) including diet and regular exercise and discouraged from activities that promote OS including smoking and alcohol consumption.

[Brain zinc dyshomeostasis and glial cells in ischemic stroke]

Zinc, an essential trace element, plays an important role in a large number of biological functions. In mammalian brain, whereas the majority of brain zinc is bound to proteins including metallothionein, about 5-15% is stored in presynaptic vesicles of glutamatergic neurons throughout the forebrain, especially in the hippocampus, in a relatively free state. Thus, free zinc (Zn²⁺) concentration in the brain is considered to be regulated in order to maintain normal brain functions such as learning and memory. On the other hand, brain Zn²⁺ dyshomeostasis has been recognized as a mechanism for neuronal injury in brain disorders including Alzheimer's disease and brain ischemia. In particular, after transient brain ischemia, Zn²⁺ accumulates in hippocampal neurons via a zinc transport system, or via release from cytosolic zinc-binding proteins, which results in neuronal cell death. Recently, it has been demonstrated that Zn²⁺ dyshomeostasis also occurs in glial cells such as microglia, astrocytes and oligodendrocytes after brain ischemia. In oligodendrocytes, ischemic insult triggers intracellular Zn²⁺ accumulation, resulting in cell death via mitochondrial dysfunction. Increased extracellular Zn²⁺ inhibits astrocytic glutamate uptake. In addition, extracellular Zn²⁺ massively released from ischemic neurons primes microglia to enhance production of pro-inflammatory cytokines in response to stimuli that trigger M1 activation. This review aims to describe the impact of brain Zn²⁺ dyshomeostasis on alterations in glial cell survival and functions in post-ischemic brains.

Intracellular labile zinc is a determinant of vulnerability of cultured astrocytes to oxidative stress

Recently, we found that treatment of cultured mouse astrocytes of ddY-strain mice (ddY-astrocytes) with 400 μM H₂O₂ for 24 h increased the intracellular labile zinc level without cell toxicity. In contrast, 170 μM H₂O₂ for 12 h is reported to kill mouse astrocytes obtained from C57BL/6-strain mice (C57BL/6-astrocytes) with an increase in intracellular labile zinc. To clarify this discrepancy, we compared the intracellular zinc levels and cell toxicity in H₂O₂-treated ddY- and C57BL/6-astrocytes. Exposure of C57BL/6-astrocytes to 170 or 400 μM H₂O₂ for 12 h dose-dependently decreased the cell viability and administration of plasma membrane-permeable zinc chelator TPEN prevented the 170 μM H₂O₂-induced astrocyte death, while neither concentration of H₂O₂ killed ddY-astrocytes. The intracellular zinc level in H₂O₂-treated C57BL/6-astrocytes was higher than that in H₂O₂-treated ddY-astrocytes, and this increase was suppressed by TPEN. There was no apparent difference in the expression levels of zinc transporters ZIPs and ZnTs between the two types of astrocytes, while expression of zinc releasable channel TRPM7 was found on the plasma membrane in ddY-astrocytes, but not in C57BL/6-astrocytes, although the total cellular expression levels were almost the same. In addition, a TRPM7 blocker, 2-aminoethoxydiphenyl borate, increased the intracellular zinc level in H₂O₂-treated ddY-, but not C57BL/6-astrocytes. Collectively, it is suggested that vulnerability of astrocytes to oxidative stress depends on an increased level of intracellular labile zinc, and TRPM7 localized on the plasma membrane contributes, at least in part, to ameliorate the cell injury by decreasing the zinc level.

Supraphysiologic-dose anabolic-androgenic steroid use: A risk factor for dementia?

Supraphysiologic-dose anabolic-androgenic steroid (AAS) use is associated with physiologic, cognitive, and brain abnormalities similar to those found in people at risk for developing Alzheimer's Disease and its related dementias (AD/ADRD), which are associated with high brain β-amyloid (Aβ) and hyperphosphorylated tau (tau-P) protein levels. Supraphysiologic-dose AAS induces androgen abnormalities and excess oxidative stress, which have been linked to increased and decreased expression or activity of proteins that synthesize and eliminate, respectively, Aβ and tau-P. Aβ and tau-P accumulation may begin soon after initiating supraphysiologic-dose AAS use, which typically occurs in the early 20s, and their accumulation may be accelerated by other psychoactive substance use, which is common among non-medical AAS users. Accordingly, the widespread use of supraphysiologic-dose AAS may increase the numbers of people who develop dementia. Early diagnosis and correction of sex-steroid level abnormalities and excess oxidative stress could attenuate risk for developing AD/ADRD in supraphysiologic-dose AAS users, in people with other substance use disorders, and in people with low sex-steroid levels or excess oxidative stress associated with aging.

Captan-induced increase in the concentrations of intracellular Ca2+ and Zn2+ and its correlation with oxidative stress in rat thymic lymphocytes

Captan, a phthalimide fungicide, is considered to be relatively nontoxic to mammals. There is a possibility that captan affects membrane and cellular parameters of mammalian cells, resulting in adverse effects, because of high residue levels. To test the possibility, we examined the effects of captan on rat thymic lymphocytes using flow-cytometry with appropriate fluorescent probes. Treatment with 10 and 30 μM captan induced apoptotic and necrotic cell death. Before cell death occurred, captan elevated the intracellular concentrations of Ca²⁺ and Zn²⁺ and decreased the concentration of cellular thiol compounds. These captan-induced phenomena are shown to cause cell death and are similar to those caused by oxidative stress. Captan also elevated the cytotoxicity of hydrogen peroxide. Results indicate that 10 and 30 μM captan cause cytotoxic effects on mammalian cells. Despite no report on the significant environmental toxicity hazard of captan in humans, it may exhibit adverse effects, described above, on wild organisms.