Nucleoside Analogue Reverse Transcriptase Inhibitors Differentially Inhibit Human LINE-1 Retrotransposition

Intact LINE-1 elements are the only retrotransposons encoded by the human genome known to be capable of autonomous replication. Numerous cases of genetic disease have been traced to gene disruptions caused by LINE-1 retrotransposition events in germ-line cells. In addition, genomic instability resulting from LINE-1 retrotransposition in somatic cells has been proposed as a contributing factor to oncogenesis and to cancer progression. LINE-1 element activity may also play a role in normal physiology. LINE-1 retrotransposition reporter assay, we evaluated the abilities of several antiretroviral compounds to inhibit LINE-1 retrotransposition. The nucleoside analogue reverse transcriptase inhibitors (nRTIs): stavudine, zidovudine, tenofovir disoproxil fumarate, and lamivudine all inhibited LINE-1 retrotransposition with varying degrees of potencies, while the non-nucleoside HIV-1 reverse transcriptase inhibitor nevirapine showed no effect.Our data demonstrates the ability for nRTIs to suppress LINE-1 retrotransposition. This is immediately applicable to studies aimed at examining potential roles for LINE-1 retrotransposition in physiological processes. In addition, our data raises novel safety considerations for nRTIs based on their potential to disrupt physiological processes involving LINE-1 retrotransposition

The effects of acrylamide treatment upon the dopamine receptor.

The binding of tritiated spiroperidol to striatal membranes prepared from acrylamide-treated male 6-week-old rats and matched controls has been studied. This binding has high-affinity characteristics and is stereospecific and reversible. Equilibrium was attained within 15 min at 37°C. The extent of binding was much more pronounced in the striatum than in any other brain region and was not detectable within the cerebellum or spinal cord. Regional distribution of binding and competition studies with other pharmacologic agents suggested a correspondence between the location of ligand-membrane complex formation and the dopamine receptor. Twenty-four hours after a single oral administration of acrylamide there was a significant increase in [3H]spiroperidol binding at all acrylamide doses tested (50, 100, and 200 mg/kg body weight). However, there was no significant change in striatal dopamine levels of treated animals. Kinetic analysis of animals treated with 100 mg acrylamide/kg suggested increased affinity of receptors of treated animals toward the labeled ligand. Receptor density was only slightly elevated in experimental animals. Effects were also studied in rats that had received 10, 20, or 30 mg/kg acrylamide daily for 10 days. Twenty-four hours after the last dose there was a major increase in spiroperidol binding in treated animals. Scatchard plot analysis again revealed that this change was largely attributable to a change in the dissociation constant of the binding interaction but also there was an increase in the overall number of receptor sites. Normal values were restored within 8 days after cessation of dosing. This illustrates that, under the conditions of this experiment, the effect of acrylamide on a central neurotransmitter system is reversible. © 1981

The effects of acrylamide treatment upon the dopamine receptor.

The binding of tritiated spiroperidol to striatal membranes prepared from acrylamide-treated male 6-week-old rats and matched controls has been studied. This binding has high-affinity characteristics and is stereospecific and reversible. Equilibrium was attained within 15 min at 37°C. The extent of binding was much more pronounced in the striatum than in any other brain region and was not detectable within the cerebellum or spinal cord. Regional distribution of binding and competition studies with other pharmacologic agents suggested a correspondence between the location of ligand-membrane complex formation and the dopamine receptor. Twenty-four hours after a single oral administration of acrylamide there was a significant increase in [3H]spiroperidol binding at all acrylamide doses tested (50, 100, and 200 mg/kg body weight). However, there was no significant change in striatal dopamine levels of treated animals. Kinetic analysis of animals treated with 100 mg acrylamide/kg suggested increased affinity of receptors of treated animals toward the labeled ligand. Receptor density was only slightly elevated in experimental animals. Effects were also studied in rats that had received 10, 20, or 30 mg/kg acrylamide daily for 10 days. Twenty-four hours after the last dose there was a major increase in spiroperidol binding in treated animals. Scatchard plot analysis again revealed that this change was largely attributable to a change in the dissociation constant of the binding interaction but also there was an increase in the overall number of receptor sites. Normal values were restored within 8 days after cessation of dosing. This illustrates that, under the conditions of this experiment, the effect of acrylamide on a central neurotransmitter system is reversible. © 1981

Neurotransmitter receptors in brain regions of acrylamide- treated rats. I: Effects of a single exposure to acrylamide.

A single oral dose of acrylamide (25 or 50 mg/kg) increased the level of striatal 3H-spiroperidol binding in six week old male rats. This enhanced dopamine receptor activity was specific since treatment caused no significant changes in glycine, serotonin, and muscarinic cholinergic binding. At the highest acrylamide dose tested (100 mg/kg), elevations of the medullary glycine and frontal cortical serotonin receptors were also found. Pretreatment of animals with a blocker of hepatic mixed function oxidase (SKF 525a) or a thiol blocker (methylmercuric chloride) prevented the acrylamide-induced elevation of striatal spiroperidol binding, indicating that the causative agent was a secondary metabolite of acrylamide. Apomorphine-induced motility was significantly attenuated by 24 hr predosing with acrylamide, suggesting a change in the sensitivity of the dopamine receptor. The behavioral relevance of observed biochemical changes was thus shown by the altered response of treated animals to apomorphine

Marked reduction in gonadal steroid hormone levels in rats treated neonatally with monosodium L-glutamate: further evidence for disruption of hypothalamic-pituitary-gonadal axis regulation.

Serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin, estradiol-17 beta and testosterone were determined in adult rats that were treated in the neonatal period with monosodium L-glutamate (MSG) which has previously been shown to reliably produce destruction of arcuate nucleus perikarya. MSG-treated males had significantly smaller accessory sexual organs (seminal vesicles and ventral prostate) and tests and had significantly lower serum concentrations of FSH and testosterone than sex-matched controls. MSG-treated females had significantly lower serum concentrations of LH, FSH and estradiol-17 beta. Prolactin levels of MSG-treated rats were no different than sex-matched controls. This marked reduction in gonadal steroid levels (decreases 68%) and inappropriately low gonadotropin levels further characterizes the deficit of feedback regulation in the hypothalamic-pituitary-gonadal axis in MSG-treated rats

Neurotransmitter receptors in brain regions of acrylamide- treated rats. I: Effects of a single exposure to acrylamide.

A single oral dose of acrylamide (25 or 50 mg/kg) increased the level of striatal 3H-spiroperidol binding in six week old male rats. This enhanced dopamine receptor activity was specific since treatment caused no significant changes in glycine, serotonin, and muscarinic cholinergic binding. At the highest acrylamide dose tested (100 mg/kg), elevations of the medullary glycine and frontal cortical serotonin receptors were also found. Pretreatment of animals with a blocker of hepatic mixed function oxidase (SKF 525a) or a thiol blocker (methylmercuric chloride) prevented the acrylamide-induced elevation of striatal spiroperidol binding, indicating that the causative agent was a secondary metabolite of acrylamide. Apomorphine-induced motility was significantly attenuated by 24 hr predosing with acrylamide, suggesting a change in the sensitivity of the dopamine receptor. The behavioral relevance of observed biochemical changes was thus shown by the altered response of treated animals to apomorphine

Pharmacokinetic Modelling of Efavirenz, Atazanavir, Lamivudine and Tenofovir in the Female Genital Tract of HIV-Infected Pre-Menopausal Women

BACKGROUND AND OBJECTIVES: A previously published study of antiretroviral pharmacokinetics in the female genital tract of HIV-infected women demonstrated differing degrees of female genital tract penetration among antiretrovirals. These blood plasma (BP) and cervicovaginal fluid (CVF) data were co-modelled for four antiretrovirals with varying CVF exposures. METHODS: Six paired BP and CVF samples were collected over 24 h, and antiretroviral concentrations determined using validated liquid chromatography (LC) with UV detection or LC-mass spectrometry analytical methods. For each antiretroviral, a BP model was fit using Bayesian estimation (ADAPT5), followed by addition of a CVF model. The final model was chosen based on graphical and statistical output, and then non-linear mixed-effects modelling using S-ADAPT was performed. Population mean parameters and their variability are reported. Model-predicated area under the concentration-time curve during the dosing interval (AUC(τ)) and exposure ratios of CVF AUC(τ):BP AUC(τ) were calculated for each drug. RESULTS: The base model uses first-order absorption with a lag time, a two-compartment model, and a series of transit compartments that transfer the drug from BP to CVF. Protein-unbound drug transfers into CVF for efavirenz and atazanavir; total drug transfers for lamivudine and tenofovir. CVF follows a one-compartment model for efavirenz and atazanavir, and a two-compartment model for lamivudine and tenofovir. As expected, inter-individual variability was high. Model-predicted CVF AUC(τ):BP AUC(τ) ratios are consistent with published results. CONCLUSIONS: This is the first pharmacokinetic modelling of antiretroviral disposition in BP and CVF. These models will be further refined with tissue data, and used in clinical trials simulations to inform future studies of HIV pre-exposure prophylaxis in women