Complement Inhibition Promotes Endogenous Neurogenesis and Sustained Anti-Inflammatory Neuroprotection following Reperfused Stroke

The restoration of blood-flow following cerebral ischemia incites a series of deleterious cascades that exacerbate neuronal injury. Pharmacologic inhibition of the C3a-receptor ameliorates cerebral injury by attenuating post-ischemic inflammation. Recent reports also implicate C3a in the modulation of tissue repair, suggesting that complement may influence both injury and recovery at later post-ischemic time-points.To evaluate the effect of C3a-receptor antagonism on post-ischemic neurogenesis and neurological outcome in the subacute period of stroke, transient focal cerebral ischemia was induced in adult male C57BL/6 mice treated with multiple regimens of a C3a receptor antagonist (C3aRA).Low-dose C3aRA administration during the acute phase of stroke promotes neuroblast proliferation in the subventricular zone at 7 days. Additionally, the C3a receptor is expressed on T-lymphocytes within the ischemic territory at 7 days, and this cellular infiltrate is abrogated by C3aRA administration. Finally, C3aRA treatment confers robust histologic and functional neuroprotection at this delayed time-point.Targeted complement inhibition through low-dose antagonism of the C3a receptor promotes post-ischemic neuroblast proliferation in the SVZ. Furthermore, C3aRA administration suppresses T-lymphocyte infiltration and improves delayed functional and histologic outcome following reperfused stroke. Post-ischemic complement activation may be pharmacologically manipulated to yield an effective therapy for stroke

Downregulation of Homologous Recombination DNA Repair Genes by HDAC Inhibition in Prostate Cancer Is Mediated through the E2F1 Transcription Factor

Histone deacetylase inhibitors (HDACis) re-express silenced tumor suppressor genes and are currently undergoing clinical trials. Although HDACis have been known to induce gene expression, an equal number of genes are downregulated upon HDAC inhibition. The mechanism behind this downregulation remains unclear. Here we provide evidence that several DNA repair genes are downregulated by HDAC inhibition and provide a mechanism involving the E2F1 transcription factor in the process.Applying Analysis of Functional Annotation (AFA) on microarray data of prostate cancer cells treated with HDACis, we found a number of genes of the DNA damage response and repair pathways are downregulated by HDACis. AFA revealed enrichment of homologous recombination (HR) DNA repair genes of the BRCA1 pathway, as well as genes regulated by the E2F1 transcription factor. Prostate cancer cells demonstrated a decreased DNA repair capacity and an increased sensitization to chemical- and radio-DNA damaging agents upon HDAC inhibition. Recruitment of key HR repair proteins to the site of DNA damage, as well as HR repair capacity was compromised upon HDACi treatment. Based on our AFA data, we hypothesized that the E2F transcription factors may play a role in the downregulation of key repair genes upon HDAC inhibition in prostate cancer cells. ChIP analysis and luciferase assays reveal that the downregulation of key repair genes is mediated through decreased recruitment of the E2F1 transcription factor and not through active repression by repressive E2Fs.Our study indicates that several genes in the DNA repair pathway are affected upon HDAC inhibition. Downregulation of the repair genes is on account of a decrease in amount and promoter recruitment of the E2F1 transcription factor. Since HDAC inhibition affects several pathways that could potentially have an impact on DNA repair, compromised DNA repair upon HDAC inhibition could also be attributed to several other pathways besides the ones investigated in this study. However, our study does provide insights into the mechanism that governs downregulation of HR DNA repair genes upon HDAC inhibition, which can lead to rationale usage of HDACis in the clinics

The Time Course of Segmentation and Cue-Selectivity in the Human Visual Cortex

Texture discontinuities are a fundamental cue by which the visual system segments objects from their background. The neural mechanisms supporting texture-based segmentation are therefore critical to visual perception and cognition. In the present experiment we employ an EEG source-imaging approach in order to study the time course of texture-based segmentation in the human brain. Visual Evoked Potentials were recorded to four types of stimuli in which periodic temporal modulation of a central 3° figure region could either support figure-ground segmentation, or have identical local texture modulations but not produce changes in global image segmentation. The image discontinuities were defined either by orientation or phase differences across image regions. Evoked responses to these four stimuli were analyzed both at the scalp and on the cortical surface in retinotopic and functional regions-of-interest (ROIs) defined separately using fMRI on a subject-by-subject basis. Texture segmentation (tsVEP: segmenting versus non-segmenting) and cue-specific (csVEP: orientation versus phase) responses exhibited distinctive patterns of activity. Alternations between uniform and segmented images produced highly asymmetric responses that were larger after transitions from the uniform to the segmented state. Texture modulations that signaled the appearance of a figure evoked a pattern of increased activity starting at ∼143 ms that was larger in V1 and LOC ROIs, relative to identical modulations that didn't signal figure-ground segmentation. This segmentation-related activity occurred after an initial response phase that did not depend on the global segmentation structure of the image. The two cue types evoked similar tsVEPs up to 230 ms when they differed in the V4 and LOC ROIs. The evolution of the response proceeded largely in the feed-forward direction, with only weak evidence for feedback-related activity

Abstract 1498: Feasibility of 2-hydroxyglutarate 1H-MR spectroscopy for routine clinical glioma imaging

Abstract The metabolic genes isocitrate dehydrogenase 1 (IDH1) or IDH2 are mutated in 70-80% of WHO grade II and III glioma. The mutant IDH enzyme gains a new function producing D-2-hydroxyglutarate (2-HG). 2-HG is a small molecule that accumulates in IDH mutant gliomas as high as 5 to 35 mM and is considered the principal effector of IDH mutation in cancers. Proton magnetic resonance spectroscopy (MRS) is an approved method in brain tumors to identify and quantify metabolites within brain lesions by using signals emitted by proton nuclei (1H). The 2-HG molecule has five nonexchangeable scalar-coupled protons that give rise to multiplet resonances in MR spectra. First attempts to measure 2-HG in IDH mutant glioma have been promising but were limited to scanners dedicated to research MRIs, long scanning times, and large tumors. The goal of this study was to explore the feasibility of performing 2HG-MRS as part of standard glioma imaging. We developed single and multivoxel spectroscopy techniques using unique alterations of pulse sequence parameters and software routines on clinical 3Tesla MRI scanners. We added those sequences to our clinical MRI protocol. All metabolites, including 2-HG, were estimated by linear combination of model (LC Model). 107 consecutive glioma patients were evaluated, including 48 (45%) WHO grade II glioma, 40 (37%) grade III glioma and 19(18%) grade IV glioma. 80/107 (75%) patients had IDH mutant gliomas. At the time of MRS, 42(39%) patients were on active treatment with radiation or chemotherapy, 19(18%) had received such treatment in the past, and 46(43%) had never received radiation or chemotherapy. MRI tumor volume was &amp;lt;8cc in 38 (36%) patients and ≥8cc in 69 (64%) patients. 2-HG MRS was negative in all patients with IDH-wild type tumors and in all IDH-mutant gliomas with a tumor volume &amp;lt;8cc. In the group of IDH-mutant tumors with a tumor volume ≥8cc, 2-HG MRS was positive in approximately 35% of the untreated patients and in approximately 30% of the treated patients. For a subset of patients we measured dynamic changes in 2-HG over time (multiple times MRS). A drop in 2HG-MRS signal was associated with treatment response. 2-HG MRS in the clinical setting is feasible. Specificity was 100%. Sensitivity appears, at least in part, dependent on tumor volume with higher sensitivity in larger tumors. In patients with a detectable 2-HG peak, 2HG-MRS represents a promising non-invasive biomarker to monitor tumor growth and treatment response. Final results for the entire cohort will be presented at the meeting. Citation Format: Macarena I. de la Fuente, Robert Young, Jennifer Rubel, Jamie Tisnado, Samuel Briggs, Andrei I. Holodny, Joseph Deasy, Lisa M. DeAngelis, Justin Cross, Ingo K. Mellinghoff, Sunitha Thakur. Feasibility of 2-hydroxyglutarate 1H-MR spectroscopy for routine clinical glioma imaging. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1498. doi:10.1158/1538-7445.AM2015-1498</jats:p