ABSTRACT
Neuregulin-1 (Nrg1)/erbB signaling regulates neuronal development, migration, myelination, and synaptic maintenance. The Nrg1 gene is a schizophrenia susceptibility gene. To understand the contribution of Nrg1 signaling to adult brain structure and behaviors, we studied the regulation of type III Nrg1 expression and evaluated the effect of decreased expression of the type III Nrg1 isoforms. Type III Nrg1 is transcribed by a promoter distinct from those for other Nrg1 isoforms and, in the adult brain, is expressed in the medial prefrontal cortex, ventral hippocampus, and ventral subiculum, regions involved in the regulation of sensorimotor gating and short-term memory. Adult heterozygous mutant mice with a targeted disruption for type III Nrg1 (Nrg1(tm1.1Lwr+/-)) have enlarged lateral ventricles and decreased dendritic spine density on subicular pyramidal neurons. Magnetic resonance imaging of type III Nrg1 heterozygous mice revealed hypofunction in the medial prefrontal cortex and the hippocampal CA1 and subiculum regions. Type III Nrg1 heterozygous mice also have impaired performance on delayed alternation memory tasks, and deficits in prepulse inhibition (PPI). Chronic nicotine treatment eliminated differences in PPI between type III Nrg1 heterozygous mice and their wild-type littermates. Our findings demonstrate a role of type III Nrg1 signaling in the maintenance of corticostriatal components and in the neural circuits involved in sensorimotor gating and short-term memory.
Subject(s)
Corpus Striatum/abnormalities , Hippocampus/abnormalities , Memory Disorders/genetics , Nerve Tissue Proteins/genetics , Prefrontal Cortex/abnormalities , Sensation Disorders/genetics , Animals , Atrophy/genetics , Atrophy/metabolism , Atrophy/physiopathology , Corpus Striatum/metabolism , Corpus Striatum/physiopathology , Disease Models, Animal , Gene Expression Regulation, Developmental/genetics , Heterozygote , Hippocampus/metabolism , Hippocampus/physiopathology , Lateral Ventricles/abnormalities , Memory Disorders/metabolism , Memory Disorders/physiopathology , Memory, Short-Term/physiology , Mice , Mice, Knockout , Mice, Transgenic , Nervous System Malformations/genetics , Nervous System Malformations/metabolism , Nervous System Malformations/physiopathology , Neural Inhibition/genetics , Neural Pathways/abnormalities , Neural Pathways/metabolism , Neural Pathways/physiopathology , Neuregulin-1 , Nicotinic Agonists/pharmacology , Prefrontal Cortex/metabolism , Prefrontal Cortex/physiopathology , Promoter Regions, Genetic/genetics , Protein Isoforms/genetics , Protein Isoforms/metabolism , Sensation Disorders/metabolism , Sensation Disorders/physiopathologyABSTRACT
INTRODUCTION: Prediction of the propensity of a compound to induce Torsades de Pointes continues to be a formidable challenge to the pharmaceutical industry. Development of an in vitro model for assessment of proarrhythmic potential offers the advantage of higher throughput and reduced compound quantity requirements when compared to in vivo studies. A rabbit isolated heart model (SCREENIT) has been reported to identify compounds with proarrhythmic potential based on the observance of compound-induced triangulation and instability of the monophasic action potential (MAP), ectopic beats, and reverse-use dependence of prolongation of the MAP duration. Previous reports have indicated that this model qualitatively identifies proarrhythmic compounds and suggest the use of this model to assign safety margins for human clinical use. The intent of this series of studies was to evaluate the impact of study design on the proarrhythmic concentration predicted by this model. METHODS: Nine compounds of varying proarrhythmic potential and a negative control were tested in a blinded fashion using a series of different experimental protocols: Compounds were tested at multiple concentration ranges and extended perfusion times were also evaluated. RESULTS: In general when the dataset is viewed as a whole, the model did identify proarrhythmic compounds, however the concentration at which action potential prolongation, triangulation, instability, reverse-use dependence and ectopic beats occurred often varied based on the concentration range selected. Further analysis using extended compound perfusion times demonstrated that variability may be due in part to lack of adequate equilibration of compound with the cardiac tissue. DISCUSSION: We report that the model correctly identified proarrhythmic agents in a qualitative manner, but that study design impacts the proarrhythmic concentration derived from the model.
Subject(s)
Arrhythmias, Cardiac/chemically induced , Cardiovascular Agents/adverse effects , Action Potentials/drug effects , Animals , Computer Simulation , Dose-Response Relationship, Drug , Drug Evaluation, Preclinical , Drug-Related Side Effects and Adverse Reactions , Electrophysiologic Techniques, Cardiac , Heart Conduction System/drug effects , Models, Biological , Predictive Value of Tests , RabbitsABSTRACT
BACKGROUND AND AIMS: The significance of normal alanine aminotransferase (ALT) levels in patients with HIV/hepatitis C virus (HCV) coinfection is not well understood. METHODS: We performed a cross-sectional retrospective analysis on consecutive HIV/HCV-coinfected patients (n = 89) who underwent a liver biopsy during a 2-year period. Similar data were also collected on HCV-monoinfected patients (n = 117). RESULTS: Mean ALT levels and the percentage of patients with normal ALT (< or =40 U/L) levels were similar in HIV/HCV-coinfected (mean +/- SD, 81.7 +/- 56.1 U/L; 21%) and HCV-monoinfected patients (97.3 +/- 100.7 U/L; 18%; P = 0.19 and 0.54, respectively). Coinfected patients, however, had significantly advanced necroinflammation (P= 0.001) and fibrosis (P = 0.02) compared with monoinfected patients. The percentage of patients with advanced necroinflammation (grades 3 or 4) was lower in HCV-monoinfected patients with normal ALT levels compared with those with elevated ALT (5% vs 20%, respectively). In contrast, the percentage of coinfected patients with advanced necroinflammation was similar whether the patient had normal or elevated ALT levels (32% vs 37%, respectively). CONCLUSIONS: In coinfected patients, normal ALT levels are not an indicator of mild necroinflammation and may not portend a more benign disease course.
Subject(s)
Alanine Transaminase/blood , HIV Infections/complications , Hepatitis C/complications , Adult , Aspartate Aminotransferases/blood , Female , Genotype , HIV Infections/blood , HIV-1/genetics , Hepacivirus/genetics , Hepatitis C/blood , Hepatitis C/epidemiology , Humans , Inflammation/virology , Liver Function Tests , Male , Middle Aged , Racial Groups , Reference Values , Risk Factors , Viral LoadABSTRACT
Coinfection with HIV and hepatitis C virus (HCV)-specific immune responses, increases hepatic inflammation, accelerates hepatic fibrosis, and is associated with deceased treatment responses. We quantified intrahepatic lymphocyte and hepatocyte phenotypes in HCV-infected patients with (n = 38) and without (n = 41) HIV infection. A single pathologist counted positive cells in 5 portal and 5 lobular areas. Coinfected patients had 6.81 +/- 1.9 fewer CD4 cells per portal field (10.58 +/- 1.12 vs. 4.97 +/- 1.09 cells/high-power field [HPF]; P < 0.001) and 0.48 +/- 0.15 more apoptotic lymphocytes per lobular field (0.16 +/- 0.06 vs. 0.64 +/- 0.15 cell/HPF; P = 0.002) than monoinfected patients. The number of portal CD4 cells was not associated with the peripheral CD4 cell number. Portal and lobular CD8 cells did not differ between the 2 groups. Portal proliferative hepatocytes were increased in coinfected patients with HIV RNA levels of >400 copies/mL (1.13 +/- 0.32 cells/HPF; P = 0.01) compared with those with undetectable HIV RNA (0.46 +/- 0.09 cell/HPF) and monoinfected patients (0.45 +/- 0.08 cell/HPF). In conclusion, HIV coinfection is associated with fewer portal CD4 cells and increased lobular lymphocyte apoptosis that may impact on the natural history of HCV infection.
