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A classic response to systemic hypoxia is the increased production of red blood cells due to hypoxia-inducible factor (HIF)-mediated induction of erythropoietin (EPO). EPO is a glycoprotein hormone that is essential for normal erythropoiesis and is predominantly synthesized by peritubular renal interstitial fibroblast-like cells, which express cellular markers characteristic of neuronal cells and pericytes. To investigate whether the ability to synthesize EPO is a general functional feature of pericytes, we used conditional gene targeting to examine the von Hippel-Lindau/prolyl-4-hydroxylase domain (PHD)/HIF axis in cell-expressing neural glial antigen 2, a known molecular marker of pericytes in multiple organs. We found that pericytes in the brain synthesized EPO in mice with genetic HIF activation and were capable of responding to systemic hypoxia with the induction of Epo. Using high-resolution multiplex in situ hybridization, we determined that brain pericytes represent an important cellular source of Epo in the hypoxic brain (up to 70% of all Epo-expressing cells). We furthermore determined that Epo transcription in brain pericytes was HIF-2 dependent and cocontrolled by PHD2 and PHD3, oxygen- and 2-oxoglutarate-dependent prolyl-4-hydroxylases that regulate HIF activity. In summary, our studies provide experimental evidence that pericytes in the brain have the ability to function as oxygen sensors and respond to hypoxia with EPO synthesis. Our findings furthermore suggest that the ability to synthesize EPO may represent a functional feature of pericytes in the brain and kidney.

Graphical Abstract Highlights d HIF1a reduces intracellular aspartate levels d HIF1a impairs oxidative and reductive aspartate biosynthesis d The aspartate-generating GOT1 and GOT2 enzymes are repressed by HIF1a d Aspartate supplementation counteracts the antiproliferative influence of HIF1a In Brief Melé ndez-Rodríguez et al. show that HIF1a impairs oxidative and reductive aspartate biogenesis, which consequently drives HIF1a-dependent suppression of tumor cell proliferation. Mechanistically, HIF1a represses the aspartate-producing enzymes GOT1 and GOT2 in several biological settings, including human VHL-deficient renal cell carcinoma, in which HIF1a can act as a tumor suppressor.

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The recreational drug 3,4-methylenedioxymethamphetamine (MDMA; 'ecstasy') produces a neuro-inflammatory response in rats characterized by an increase in microglial activation and IL-1β levels. The integrity of the blood-brain barrier (BBB) is important in preserving the homeostasis of the brain and has been shown to be affected by neuro-inflammatory processes. We aimed to study the effect of a single dose of MDMA on the activity of metalloproteinases (MMPs), expression of extracellular matrix proteins, BBB leakage and the role of the ionotropic purinergic receptor P2X7 (P2X7R) in the changes induced by the drug. Adult male Dark Agouti rats were treated with MDMA (10 mg/kg, i.p.) and killed at several time-points in order to evaluate MMP-9 and MMP-3 activity in the hippocampus and laminin and collagen-IV expression and IgG extravasation in the dentate gyrus. Microglial activation, P2X7R expression and localization were also determined in the dentate gyrus. Separate groups were treated with MDMA and the P2X7R antagonists Brilliant Blue G (BBG; 50 mg/kg, i.p.) or A-438079 (30 mg/kg, i.p.). MDMA increased MMP-3 and MMP-9 activity, reduced laminin and collagen-IV expression and increased IgG immunoreactivity. In addition, MDMA increased microglial activation and P2X7R immunoreactivity in these cells. BBG suppressed the increase in MMP-9 and MMP-3 activity, prevented basal lamina degradation and IgG extravasation into the brain parenchyma. A-438079 also prevented the MDMA-induced reduction in laminin and collagen-IV immunoreactivity. These results indicate that MDMA alters BBB permeability through an early P2X7R-mediated event, which in turn leads to enhancement of MMP-9 and MMP-3 activity and degradation of extracellular matrix.

Background and Purpose-Methamphetamine is a powerful addictive, which has been associated with ischemic stroke and brain hemorrhage in humans. Whether and how methamphetamine influences the expression of tight junctions and adenosine triphosphate-binding cassette transporters, which have previously been shown to be regulated by apolipoprotein-E (ApoE) under conditions of brain ischemia, was unknown. Methods-C57BL/6J mice received intraperitoneal injections of methamphetamine (3 times 4 mg/kg separated by 3 hours) either alone or in combination with the ApoE receptor-2 inhibitor receptor-associated protein (40 g/kg) or the inducible nitric oxide synthase inhibitor 1400W (5 mg/kg). Animals were euthanized 3 or 24 hours after methamphetamine exposure. Tissue responses were evaluated with Western blots, immunoprecipitation, and immunohistochemistry using total brain and cerebral microvessel extracts. Results-Methamphetamine induced a transient activation of stress kinases c-Jun N-terminal kinase 1/2 and p38 in the brain parenchyma and increased intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression on cerebral microvessels without inducing loss of tight junction proteins and without inducing IgG extravasation. Methamphetamine transiently increased the expression of the luminal adenosine triphosphatebinding cassette transporter ABCB1 on cerebral microvessels and reduced the expression of the abluminal transporter ABCC1. Elevated expression of ApoE was noted in the brain parenchyma by methamphetamine, activating ApoE receptor-2 on brain capillaries, deactivating c-Jun N-terminal kinase 1/2 and c-Jun, and regulating ABCB1 and ABCC1 expression. Indeed, ApoE receptor-2 and inducible nitric oxide synthase inhibition prevented the ABCB1 and ABCC1 expression changes. Conclusions-Acute exposure to methamphetamine at doses comparable to those consumed in drug addiction does not induce tight junction breakdown but differentially regulates adenosine triphosphate-binding cassette transporters through the ApoE/ApoE receptor-2/c-Jun N-terminal kinase 1/2 pathway. (Stroke. 2012;43:1647-1653.)Key Words: apolipoprotein-E receptor-2 Ⅲ blood-brain barrier Ⅲ c-Jun N-terminal kinase 1/2 Ⅲ drug abuse Ⅲ endothelium Ⅲ multidrug resistance Ⅲ neuropathology Ⅲ signal transduction Ⅲ tight junction M ethamphetamine (also called crystal meth or meth) is a psychostimulant and addictive that causes severe health problems mainly due to neurotoxicity, cardiac arrhythmia, and hyperthermia. 1,2 In the brain, meth overactivates the dopaminergic system, disrupting synaptic integrity 3 and inducing neuronal injury through oxidative stress. 4,5 Meth may also induce neuroinflammation 6,7 and increase blood-brain barrier (BBB) permeability. 8,9 Possibly related to such vascular actions, meth abuse has been shown to be associated with ischemic stroke and intracerebral and subarachnoid hemorrhage in humans. 10 The BBB is formed by endothelial cell-cell contacts, the tight junctions, 11 which are complemented by transporters on the l...

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