AN EVALUATION OF THE CENTRAL NEUROTOXIC EFFECTS OF AROCLOR 1254, A COMMERCIAL MIXTURE OF POLYCHLORINATED BIPHENYLS, IN MICE

Polychlorinated biphenyls (PCBs) are industrial compounds whose ubiquitous environmental contamination has been known since the late 1960\u27s. Incidents of human intoxication have been reported, most notably, the Yusho incident that affected over 1600 people in Japan in 1968. A broad spectrum of adverse effects are produced by PCBs, including some neurological symptoms. While examination of the toxic effects of PCBs has received much attention, there has been little work on the neurotoxicity of PCBs. The intent of the experiments presented in this thesis is to provide further information on the central neurotoxicity of PCBs in mice. A commercial mixture of PCBS (Aroclor 1254) was used in these experiments. The first set of experiments was initiated to evaluate the behavioral effects of orally administered Aroclor 1254 in mice. A dose of 500 mg/kg depressed spontaneous motor activity at times of 15 min to 3 hr after gavage, with the peak effect observed at 45 min. A dose-response curve generated at 45 min revealed statistically significant effects only at the highest dose, 500 mg/kg. Aroclor 1254 had no effect on the other behavioral measures evaluated - performance on the rotor rod and inverted screen and effect on pentylenetetrazol-induced convulsions. These results suggest that Aroclor 1254 may be exerting a CNS depressant effect as evidenced by a suppression of spontaneous activity in the absence of impaired motor coordination. In order to examine further the suggested CNS depressant effect, the interaction of Aroclor 1254 with a known CNS depressant, pentobarbital, was investigated. Pretreatment with a single dose of Aroclor 1254 (500 mg/kg) significantly enhanced pentobarbital-induced sleep time at pretreatment times of 0, 0.75, 2, 4 and 8 hr. A dose-response relationship was demonstrated with doses of 5 to 500 mg/kg of Aroclor‘ 1254 given at the pretreatment time of peak effect, 2 hr. By contrast, subchronic (14 day) administration of Aroclor 1254 (30 or 100 mg/kg) reduced pentobarbital induced sleep time in a dose-dependent fashion when pentobarbital was given 45 min after the last dose of Aroclor 1254 with a further reduction when given 24 hr after Aroclor 1254. Results of studies of the disposition of 14C-pentobarbital following Aroclor 1254-pretreatment suggested that acute Aroclor 1254-pretreatment inhibits pentobarbital metabolism while subchronic PCB-pretreatment enhances pentobarbital metabolism as evidenced by tissue levels of pentobarbital and metabolites. Therefore, it appears that the observed increase in pentobarbital-induced sleep time is not a result of altered CNS sensitivity or combined depressant effects of the two compounds, but rather is due to Aroclor 1254-induced alterations in the pharmacokinetics of pentobarbital. The next series of experiments was aimed at evaluating the effects of Aroclor 1254 on neurochemistry. Aroclor 1254 produced concentration-dependent alterations in the following parameters measured in vitro: inhibition of neurotransmitter and precursor uptake, enhancement of neurotransmitter release, enhancement of synaptosomal 45Ca++ uptake, stimulation of ATP-supported mitochondrial 45Ca++ uptake, inhibition of synaptosomal Na+ /K+ - and Mg++- ATPases, and inhibition of mitochondrial Mg++ -ATPases. Effective concentrations of Aroclor 1254 in these in vitro systems ranged from 10-6 to 10-4 M. Acute (up to 500 mg/kg) and subchronic (90 day) administration of Aroclor 1254 had no effect on\u27 uptake of neurotransmitters or precursors by synaptosomes isolated from Aroclor 1254-treated mice. Nor was there any effect on ATPase activities in synaptosomes or mitochondria isolated from mice exposed to acute or subchronic (14 day) Aroclor 1254 regimens. This disparity between the results of in vitro and in vivo exposure to Aroclor 1254 prompted studies of the disposition of 14C-PCBs. A time course of radioactivity in plasma and brain following a 500 mg/kg dose of 14C-PCBS (a mixture of PCBs with 50% Cl by weight and uniformly labeled with 14C)compared favorably with that of the behavioral activity of Aroclor 1254. No differences in brain regional distribution of 14C-PCBs was observed. Most importantly, levels of radioactivity in synaptosomes and mitochondria of sub fractionated brains of mice that had been exposed to a behaviorally active dose of 14C-PCBS (500 mg/kg) were comparable to tissue levels in isolated synaptosomes and mitochondria that had been incubated with concentrations of 14C-PCBs (10-5 to 10-4M) that altered neurochemistry in vitro. Thus, effective concentrations of 14C-PCBS are apparently achieved in subcellular organelles of brain following oral administration of a behaviorally active dose. The lack of observable neurochemical effects in Aroclor 1254-treated mice may be due to compensatory mechanisms that maintain homeostasis in the intact brain. In summary, Aroclor 1254 has been shown to produce a depression of spontaneous motor activity in mice, changes in pentobarbital-induced sleep time (an effect that is probably a manifestation of changes in the pharmacokinetic behavior of pentobarbital rather than a direct effect of Aroclor 1254 on brain), and alterations in a number of neurochemical events in vitro. These results may help to expand the limited data base on the neurotoxicity of PCBs

Activity Patterns Govern Synapse-Specific AMPA Receptor Trafficking between Deliverable and Synaptic Pools

SummaryIn single neurons, glutamatergic synapses receiving distinct afferent inputs may contain AMPA receptors (-Rs) with unique subunit compositions. However, the cellular mechanisms by which differential receptor transport achieves this synaptic diversity remain poorly understood. In lateral geniculate neurons, we show that retinogeniculate and corticogeniculate synapses have distinct AMPA-R subunit compositions. Under basal conditions at both synapses, GluR1-containing AMPA-Rs are transported from an anatomically defined reserve pool to a deliverable pool near the postsynaptic density (PSD), but further incorporate into the PSD or functional synaptic pool only at retinogeniculate synapses. Vision-dependent activity, stimulation mimicking retinal input, or activation of CaMKII or Ras signaling regulated forward GluR1 trafficking from the deliverable pool to the synaptic pool at both synapses, whereas Rap2 signals reverse GluR1 transport at retinogeniculate synapses. These findings suggest that synapse-specific AMPA-R delivery involves constitutive and activity-regulated transport steps between morphological pools, a mechanism that may extend to the site-specific delivery of other membrane protein complexes

Key Modulatory Role of Presynaptic Adenosine A 2A

Basal ganglia processing results from a balanced activation of direct and indirect striatal efferent pathways, which are controlled by dopamine D1 and D2 receptors, respectively. Adenosine A2A receptors are considered novel antiparkinsonian targets, based on their selective postsynaptic localization in the indirect pathway, where they modulate D2 receptor function. The present study provides evidence for the existence of an additional, functionally significant, segregation of A2A receptors at the presynaptic level. Using integrated anatomical, electrophysiological, and biochemical approaches, we demonstrate that presynaptic A2A receptors are preferentially localized in cortical glutamatergic terminals that contact striatal neurons of the direct pathway, where they exert a selective modulation of corticostriatal neurotransmission. Presynaptic striatal A2A receptors could provide a new target for the treatment of neuropsychiatric disorders

Human Recombinant Alkaline Phosphatase (Ilofotase Alfa) Protects Against Kidney Ischemia-Reperfusion Injury in Mice and Rats Through Adenosine Receptors

Adenosine triphosphate (ATP) released from injured or dying cells is a potent pro-inflammatory “danger” signal. Alkaline phosphatase (AP), an endogenous enzyme that de-phosphorylates extracellular ATP, likely plays an anti-inflammatory role in immune responses. We hypothesized that ilofotase alfa, a human recombinant AP, protects kidneys from ischemia-reperfusion injury (IRI), a model of acute kidney injury (AKI), by metabolizing extracellular ATP to adenosine, which is known to activate adenosine receptors. Ilofotase alfa (iv) with or without ZM241,385 (sc), a selective adenosine A2A receptor (A2AR) antagonist, was administered 1 h before bilateral IRI in WT, A2AR KO (Adora2a–/–) or CD73–/– mice. In additional studies recombinant alkaline phosphatase was given after IRI. In an AKI-on-chronic kidney disease (CKD) ischemic rat model, ilofotase alfa was given after the three instances of IRI and rats were followed for 56 days. Ilofotase alfa in a dose dependent manner decreased IRI in WT mice, an effect prevented by ZM241,385 and partially prevented in Adora2a–/– mice. Enzymatically inactive ilofotase alfa was not protective. Ilofotase alfa rescued CD73–/– mice, which lack a 5′-ectonucleotidase that dephosphorylates AMP to adenosine; ZM241,385 inhibited that protection. In both rats and mice ilofotase alfa ameliorated IRI when administered after injury, thus providing relevance for therapeutic dosing of ilofotase alfa following established AKI. In an AKI-on-CKD ischemic rat model, ilofotase alfa given after the third instance of IRI reduced injury. These results suggest that ilofotase alfa promotes production of adenosine from liberated ATP in injured kidney tissue, thereby amplifying endogenous mechanisms that can reverse tissue injury, in part through A2AR-and non-A2AR-dependent signaling pathways

Bone marrow stromal cell antigen-1 (CD157) regulated by sphingosine kinase 2 mediates kidney fibrosis

Chronic kidney disease is a progressive disease that may lead to end-stage renal disease. Interstitial fibrosis develops as the disease progresses. Therapies that focus on fibrosis to delay or reverse progressive renal failure are limited. We and others showed that sphingosine kinase 2-deficient mice (Sphk2−/−) develop less fibrosis in mouse models of kidney fibrosis. Sphingosine kinase2 (SphK2), one of two sphingosine kinases that produce sphingosine 1- phosphate (S1P), is primarily located in the nucleus. S1P produced by SphK2 inhibits histone deacetylase (HDAC) and changes histone acetylation status, which can lead to altered target gene expression. We hypothesized that Sphk2 epigenetically regulates downstream genes to induce fibrosis, and we performed a comprehensive analysis using the combination of RNA-seq and ChIP-seq. Bst1/CD157 was identified as a gene that is regulated by SphK2 through a change in histone acetylation level, and Bst1−/− mice were found to develop less renal fibrosis after unilateral ischemia-reperfusion injury, a mouse model of kidney fibrosis. Although Bst1 is a cell-surface molecule that has a wide variety of functions through its varied enzymatic activities and downstream intracellular signaling pathways, no studies on the role of Bst1 in kidney diseases have been reported previously. In the current study, we demonstrated that Bst1 is a gene that is regulated by SphK2 through epigenetic change and is critical in kidney fibrosis

Measurement of the inclusive isolated-photon cross section in pp collisions at √s = 13 TeV using 36 fb−1 of ATLAS data

The differential cross section for isolated-photon production in pp collisions is measured at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC using an integrated luminosity of 36.1 fb. The differential cross section is presented as a function of the photon transverse energy in different regions of photon pseudorapidity. The differential cross section as a function of the absolute value of the photon pseudorapidity is also presented in different regions of photon transverse energy. Next-to-leading-order QCD calculations from Jetphox and Sherpa as well as next-to-next-to-leading-order QCD calculations from Nnlojet are compared with the measurement, using several parameterisations of the proton parton distribution functions. The predictions provide a good description of the data within the experimental and theoretical uncertainties. [Figure not available: see fulltext.

Clinical features of idiopathic inflammatory polymyopathy in the Hungarian Vizsla

Background A retrospective study of the clinicopathological features of presumed and confirmed cases of idiopathic inflammatory polymyopathy in the Hungarian Vizsla dog and guidelines for breeding. Results 369 medical records were reviewed (1992–2013) and 77 Hungarian Vizslas were identified with a case history consistent with idiopathic inflammatory polymyopathy. Inclusion criteria were: group 1 (confirmed diagnosis); histopathology and clinical findings compatible with an inflammatory polymyopathy and group 2 (probable diagnosis); clinical findings compatible with a polymyopathy including dysphagia, sialorrhea, temporal muscle atrophy, elevated serum creatine kinase (CK) activity, and sufficient clinical history to suggest that other neuromuscular disorders could be ruled out. Some group 2 dogs had muscle biopsy, which suggested muscle disease but did not reveal an inflammatory process. The mean age of onset was 2.4 years; male dogs were slightly overrepresented. Common presenting signs were dysphagia, sialorrhea, masticatory muscle atrophy, and regurgitation. Common muscle histopathological findings included degenerative and regenerative changes, with multifocal mononuclear cell infiltration with lymphoplasmacytic myositis of variable severity. A positive response to immunosuppressive treatment supported an immune-mediated aetiology. The mean age at death and survival time were 6.4 and 3.9 years, respectively. Recurrence of clinical signs and aspiration pneumonia were common reasons for euthanasia. Conclusions Diagnosis of Vizsla idiopathic inflammatory polymyopathy can be challenging due to lack of specific tests, however the presence of dysphagia, regurgitation and masticatory muscle atrophy in this breed with negative serological tests for masticatory muscle myositis and myasthenia gravis, along with muscle biopsies suggesting an inflammatory process, support the diagnosis. However, there is an urgent need for a more specific diagnostic test. The average of inbreeding coefficient (CoI) of 16.3% suggests an increased expression of a Dog Leukocyte Antigen Class II haplotype, leading to an increased disease risk. The prognosis remains guarded, as treatment can only manage the disease. Recurrence of clinical signs and perceived poor quality of life are the most common reasons for humane euthanasia.</p

Serotonergic neurons activate chemosensitive retrotrapezoid nucleus neurons by a pH-independent mechanism

Serotonin activates respiration and enhances the stimulatory effect of CO2 on breathing. the present study tests whether the mechanism involves the retrotrapezoid nucleus (RTN), a group of medullary glutamatergic neurons activated by extracellular brain pH and presumed to regulate breathing. We show that the RTN is innervated by both medullary and pontine raphe and receives inputs from thyrotropin-releasing hormone (TRH) and substance P-expressing neurons. Coexistence of serotonin and substance P in terminals within RTN confirmed that lower medullary serotonergic neurons innervate RTN. in vivo, unilateral injection of serotonin into RTN stimulated inspiratory motor activity, and pH-sensitive RTN neurons were activated by iontophoretic application of serotonin or substance P. in brain slices, pH-sensitive RTN neurons were activated by serotonin, substance P, and TRH. the effect of serotonin in slices was ketanserin sensitive and persisted in the presence of glutamate, GABA, glycine, and purinergic ionotropic receptor antagonists. Serotonin and pH had approximately additive effects on the discharge rate of RTN neurons, both in slices and in vivo. in slices, serotonin produced an inward current with little effect on conductance and had no effect on the pH-induced current. We conclude that (1) RTN receives input from multiple raphe nuclei, (2) serotonin, substance P, and TRH activate RTN chemoreceptors, and (3) excitatory effects of serotonin and pH are mediated by distinct ionic conductances. Thus, RTN neurons presumably contribute to the respiratory stimulation caused by serotonergic neurons, but serotonin seems without effect on the cellular mechanism by which RTN neurons detect pH.Univ Virginia, Dept Pharmacol, Charlottesville, VA 22908 USAUniversidade Federal de São Paulo, Dept Physiol, Escola Paulista Med, BR-04023060 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Physiol, Escola Paulista Med, BR-04023060 São Paulo, BrazilWeb of Scienc