AMD-like lesions in the rat retina: A latent consequence of perinatal hemorrhage

PURPOSE. Hemorrhaging is a commonplace event in the human retina around the time of birth. This study was conducted to examine the potential long-term sequelae of hemorrhaging in the eyes of rats that exhibited transient spontaneous microhemorrhages a few days after birth. METHODS. Retinas of Dark Agouti rats aged from day of birth to 2 years old were analyzed histologically, histochemically, and by immunocytochemistry. Fetal human retinas were also examined anatomically and histochemically for evidence of hemorrhages. RESULTS. Dark Agouti rats from our colony consistently exhibited spontaneous focal hemorrhages at the vitread surface of the retina between postnatal days 3 and 6. Erythrocytes were subsequently cleared by macrophages, which accumulated hemosiderin. These macrophages remained in focal patches in the inner retina for the duration of the study. For at least 6 months after the initial transient hemorrhages, the retinas exhibited no overt histologic damage. At ~8 to 9 months, photoreceptor degenerative changes were apparent in spatial register with the patches of macrophages in the inner retina. Additional events such as breakdown of Bruch’s membrane, glial remodeling, neovascularization, ingress of RPE cells into the retina and accumulation of drusen-like autofluorescent structures were also observed in topographic register with macrophage-laden patches in aged animals. CONCLUSIONS. Microhemorrhages in the retina may initiate the formation of focal lesions, months or years after the initial insult. The lesions exhibit key features of AMD. These animals may represent a useful model for studying the potential basis of the pathogenesis of AMD

Neuronal migration and glial remodeling in degenerating retinas of aged rats and in nonneovascular AMD

PURPOSE. To demonstrate structural and immunocytochemical changes associated with light-induced degeneration in albino rat retinas and human AMD retinas

Could ethanol-induced alterations in the expression of glutamate transporters in testes contribute to the effect of paternal drinking on the risk of abnormalities in the offspring?

It has been known that a preconception paternal alcoholism impacts adversely on the offspring but the mechanism of the effect is uncertain. Several findings suggest that there are signalling systems in testis that are analogous to those known to be altered by alcoholism in brain. We propose that chronic alcohol affects these systems in a manner similar to that in brain. Specifically, we hypothesise that excessive alcohol may disturb glutamatergic-like signalling in testis by increasing expression of the glutamate transporter GLAST (EAAT1). We discuss ways how to test the hypothesis as well as potential significance of some of the tests as tools in the diagnostics of chronic alcoholism

Phosphorylation of GFAP is associated with injury in the neonatal pig hypoxic-ischemic brain

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein expressed in the astrocyte cytoskeleton that plays an important role in the structure and function of the cell. GFAP can be phosphorylated at six serine (Ser) or threonine (Thr) residues but little is known about the role of GFAP phosphorylation in physiological and pathophysiological states. We have generated antibodies against two phosphorylated GFAP (pGFAP) proteins: p8GFAP, where GFAP is phosphorylated at Ser-8 and p13GFAP, where GFAP is phosphorylated at Ser-13. We examined p8GFAP and p13GFAP expression in the control neonatal pig brain and at 24 and 72 h after an hypoxic-ischemic (HI) insult. Immunohistochemistry demonstrated pGFAP expression in astrocytes with an atypical cytoskeletal morphology, even in control brains. Semi-quantitative western blotting revealed that p8GFAP expression was significantly increased at 24 h post-insult in HI animals with seizures in frontal, parietal, temporal and occipital cortices. At 72 h post-insult, p8GFAP and p13GFAP expression were significantly increased in HI animals with seizures in brain regions that are vulnerable to cellular damage (cortex and basal ganglia), but no changes were observed in brain regions that are relatively spared following an HI insult (brain stem and cerebellum). Increased pGFAP expression was associated with poor neurological outcomes such as abnormal encephalography and neurobehaviour, and increased histological brain damage. Phosphorylation of GFAP may play an important role in astrocyte remodelling during development and disease and could potentially contribute to the plasticity of the central nervous system

Reduction in Phencyclidine Induced Sensorimotor Gating Deficits in the Rat Following Increased System Xc − Activity in the Medial Prefrontal Cortex

Rationale: Aspects of schizophrenia, including deficits in sensorimotor gating, have been linked to glutamate dysfunction and/or oxidative stress in the prefrontal cortex. System xc −, a cystine–glutamate antiporter, is a poorly understood mechanism that contributes to both cellular antioxidant capacity and glutamate homeostasis. Objectives: Our goal was to determine whether increased system xc − activity within the prefrontal cortex would normalize a rodent measure of sensorimotor gating. Methods: In situ hybridization was used to map messenger RNA (mRNA) expression of xCT, the active subunit of system xc −, in the prefrontal cortex. Prepulse inhibition was used to measure sensorimotor gating; deficits in prepulse inhibition were produced using phencyclidine (0.3–3 mg/kg, sc). N-Acetylcysteine (10–100 μM) and the system xc − inhibitor (S)-4-carboxyphenylglycine (CPG, 0.5 μM) were used to increase and decrease system xc − activity, respectively. The uptake of 14C-cystine into tissue punches obtained from the prefrontal cortex was used to assay system xc − activity. Results: The expression of xCT mRNA in the prefrontal cortex was most prominent in a lateral band spanning primarily the prelimbic cortex. Although phencyclidine did not alter the uptake of 14C-cystine in prefrontal cortical tissue punches, intraprefrontal cortical infusion of N-acetylcysteine (10–100 μM) significantly reduced phencyclidine- (1.5 mg/kg, sc) induced deficits in prepulse inhibition. N-Acetylcysteine was without effect when coinfused with CPG (0.5 μM), indicating an involvement of system xc −. Conclusions: These results indicate that phencyclidine disrupts sensorimotor gating through system xc − independent mechanisms, but that increasing cystine–glutamate exchange in the prefrontal cortex is sufficient to reduce behavioral deficits produced by phencyclidine

Cardiac Glycosides Ouabain and Digoxin Interfere with the Regulation of Glutamate Transporter GLAST in Astrocytes Cultured from Neonatal Rat Brain

Glutamate transport (GluT) in brain is mediated chiefly by two transporters GLT and GLAST, both driven by ionic gradients generated by (Na+, K+)-dependent ATPase (Na+/K+-ATPase). GLAST is located in astrocytes and its function is regulated by translocations from cytoplasm to plasma membrane in the presence of GluT substrates. The phenomenon is blocked by a naturally occurring toxin rottlerin. We have recently suggested that rottlerin acts by inhibiting Na+/K+-ATPase. We now report that Na+/K+-ATPase inhibitors digoxin and ouabain also blocked the redistribution of GLAST in cultured astrocytes, however, neither of the compounds caused detectable inhibition of ATPase activity in cell-free astrocyte homogenates (rottlerin inhibited app. 80% of Pi production from ATP in the astrocyte homogenates, IC50 = 25 μM). Therefore, while we may not have established a direct link between GLAST regulation and Na+/K+-ATPase activity we have shown that both ouabain and digoxin can interfere with GluT transport and therefore should be considered potentially neurotoxic

Enhanced tonic GABAA inhibition in typical absence epilepsy

The cellular mechanisms underlying typical absence seizures, which characterize various idiopathic generalized epilepsies, are not fully understood, but impaired GABAergic inhibition remains an attractive hypothesis. In contrast, we show here that extrasynaptic GABAA receptor–dependent ‘tonic’ inhibition is increased in thalamocortical neurons from diverse genetic and pharmacological models of absence seizures. Increased tonic inhibition is due to compromised GABA uptake by the GABA transporter GAT–1 in the genetic models tested, and GAT–1 is critical in governing seizure genesis. Extrasynaptic GABAA receptors are a requirement for seizures in two of the best characterized models of absence epilepsy, and the selective activation of thalamic extrasynaptic GABAA receptors is sufficient to elicit both electrographic and behavioural correlates of seizures in normal animals. These results identify an apparently common cellular pathology in typical absence seizures that may have epileptogenic significance, and highlight novel therapeutic targets for the treatment of absence epilepsy.peer-reviewe

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio

Germline variation at 8q24 and prostate cancer risk in men of European ancestry

Chromosome 8q24 is a susceptibility locus for multiple cancers, including prostate cancer. Here we combine genetic data across the 8q24 susceptibility region from 71,535 prostate cancer cases and 52,935 controls of European ancestry to define the overall contribution of germline variation at 8q24 to prostate cancer risk. We identify 12 independent risk signals for prostate cancer (p < 4.28 × 10−15), including three risk variants that have yet to be reported. From a polygenic risk score (PRS) model, derived to assess the cumulative effect of risk variants at 8q24, men in the top 1% of the PRS have a 4-fold (95%CI = 3.62–4.40) greater risk compared to the population average. These 12 variants account for ~25% of what can be currently explained of the familial risk of prostate cancer by known genetic risk factors. These findings highlight the overwhelming contribution of germline variation at 8q24 on prostate cancer risk which has implications for population risk stratification

Fine-mapping of prostate cancer susceptibility loci in a large meta-analysis identifies candidate causal variants

Prostate cancer is a polygenic disease with a large heritable component. A number of common, low-penetrance prostate cancer risk loci have been identified through GWAS. Here we apply the Bayesian multivariate variable selection algorithm JAM to fine-map 84 prostate cancer susceptibility loci, using summary data from a large European ancestry meta-analysis. We observe evidence for multiple independent signals at 12 regions and 99 risk signals overall. Only 15 original GWAS tag SNPs remain among the catalogue of candidate variants identified; the remainder are replaced by more likely candidates. Biological annotation of our credible set of variants indicates significant enrichment within promoter and enhancer elements, and transcription factor-binding sites, including AR, ERG and FOXA1. In 40 regions at least one variant is colocalised with an eQTL in prostate cancer tissue. The refined set of candidate variants substantially increase the proportion of familial relative risk explained by these known susceptibility regions, which highlights the importance of fine-mapping studies and has implications for clinical risk profiling. © 2018 The Author(s).Prostate cancer is a polygenic disease with a large heritable component. A number of common, low-penetrance prostate cancer risk loci have been identified through GWAS. Here we apply the Bayesian multivariate variable selection algorithm JAM to fine-map 84 prostate cancer susceptibility loci, using summary data from a large European ancestry meta-analysis. We observe evidence for multiple independent signals at 12 regions and 99 risk signals overall. Only 15 original GWAS tag SNPs remain among the catalogue of candidate variants identified; the remainder are replaced by more likely candidates. Biological annotation of our credible set of variants indicates significant enrichment within promoter and enhancer elements, and transcription factor-binding sites, including AR, ERG and FOXA1. In 40 regions at least one variant is colocalised with an eQTL in prostate cancer tissue. The refined set of candidate variants substantially increase the proportion of familial relative risk explained by these known susceptibility regions, which highlights the importance of fine-mapping studies and has implications for clinical risk profiling. © 2018 The Author(s).Peer reviewe