An assessment of mutagenicity, genotoxicity, acute-, subacute and subchronic oral toxicity of paraxanthine (1,7-dimethylxanthine).

Paraxanthine or 1,7-dimethylxanthine is a natural dietary component and the main metabolite of caffeine in humans. A battery of toxicological studies was conducted in accordance with international guidelines to investigate mutagenicity, genotoxicity and acute and repeated-dose oral toxicity in rats of synthetic paraxanthine (ENFINITY™, Ingenious Ingredients, L.P., >99% purity). There was no evidence of mutagenicity in a bacterial reverse mutation as well as in an in vitro mammalian chromosomal aberration test. There was no evidence of genotoxicity in an in vivo mammalian erythrocyte micronucleus test as well as in an in vitro mammalian cell gene mutation test. An acute oral toxicity test resulted in a LD50 value of 1601 mg/kg bw/d. Paraxanthine did not cause mortality or toxic effects in a subacute 28-day repeated-dose oral toxicity study at daily doses of 75, 150, or 300 mg/kg bw/d (each group n = 10 per sex), administered by gavage. Paraxanthine also did not cause mortality or toxic effects in a subchronic 90-day repeated-dose oral toxicity study at daily doses of 75, 150, or 300 mg/kg bw/d (each group n = 10 per sex), administered by gavage. The no observed adverse effect level (NOAEL) determined from the 90-day study was greater than or equal to 300 mg/kg bw/d, the highest dose tested, for both male and female Wistar rats.

Food-Drug Interaction between the Adlay Bran Oil and Drugs in Rats.

Adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) contains various phytonutrients for treating many diseases in Asia. To investigate whether orally administered adlay bran oil (ABO) can cause drug interactions, the effects of ABO on the pharmacokinetics of five cytochrome P450 (CYP) probe drugs were evaluated. Rats were given a single oral dose (2.5 mL/kg BW) of ABO 1 h before administration of a drug cocktail either orally or intravenously, and blood was collected at various time points. A single oral dose of ABO administration did not affect the pharmacokinetics of five probe drugs when given as a drug cocktail intravenously. However, ABO increased plasma theophylline (+28.4%), dextromethorphan (+48.7%), and diltiazem (+46.7%) when co-administered an oral drug cocktail. After 7 days of feeding with an ABO-containing diet, plasma concentrations of theophylline (+45.4%) and chlorzoxazone (+53.6%) were increased after the oral administration of the drug cocktail. The major CYP enzyme activities in the liver and intestinal tract were not affected by ABO treatment. Results from this study indicate that a single oral dose or short-term administration of ABO may increase plasma drug concentrations when ABO is given concomitantly with drugs. ABO is likely to enhance intestinal drug absorption. Therefore, caution is needed to avoid food-drug interactions between ABO and co-administered drugs.

Placentation-related processes in a human first-trimester extravillous trophoblast cell line (HTR-8/SVneo cells) are affected by several xenobiotics.

Our aim was to investigate the effect of some xenobiotics on placentation-related processes in an extravillous trophoblastic cell line (HTR-8/SVneo cells). Amphetamine, MDMA, theophylline, and fluoxetine, but not nicotine, cocaine, and caffeine, had a negative effect on cell proliferation rates, culture growth, viability, or migratory capacity. These compounds have a detrimental effect in placentation-related processes of HTR-8/SVneo cells.

Small Heterodimer Partner Regulates Circadian Cytochromes p450 and Drug-Induced Hepatotoxicity.

The role of small heterodimer partner (SHP) in regulation of xenobiotic detoxification remains elusive. Here, we uncover a critical role for SHP in circadian regulation of cytochromes P450 (CYPs) and drug-induced hepatotoxicity. Methods: The mRNA and protein levels of CYPs in the livers of wild-type and SHP-/- mice were measured by quantitative real-time polymerase chain reaction and Western blotting, respectively. Regulation of CYP by SHP was investigated using luciferase reporter, mobility shift, chromatin immunoprecipitation, and/or co-immunoprecipitation assays. Results: The circadian rhythmicities of xenobiotic-detoxifying CYP mRNAs and proteins were disrupted in SHP-deficient mice. Of note, SHP ablation up-regulated Cyp2c38 and Cyp2c39, whereas it down-regulated all other CYP genes. Moreover, SHP regulated the expression of CYP genes through different mechanisms. SHP repressed Lrh-1/Hnf4α to down-regulate Cyp2c38, E4bp4 to up-regulate Cyp2a5, Dec2/HNF1α axis to up-regulate Cyp1a2, Cyp2e1 and Cyp3a11, and Rev-erbα to up-regulate Cyp2b10, Cyp4a10 and Cyp4a14. Furthermore, SHP ablation sensitized mice to theophylline (or mitoxantrone)-induced toxicity. Higher level of toxicity was correlated with down-regulated metabolism and clearance of theophylline (or mitoxantrone). In contrast, SHP ablation blunted the circadian rhythmicity of acetaminophen-induced hepatotoxicity and alleviated the toxicity by down-regulating Cyp2e1-mediated metabolism and reducing formation of the toxic metabolite. Toxicity alleviation by SHP ablation was also observed for aflatoxin B1 due to reduced formation of the toxic epoxide metabolite. Conclusion: SHP participates in circadian regulation of CYP enzymes, thereby impacting xenobiotic metabolism and drug-induced hepatotoxicity.

Engineering riboswitch in L. major: From prediction to conceptualization.

Post-transcriptional gene regulation is a vital process to regulate expression of the key genes in the eukaryotic cell. Such processes are essential for pathogens which reside inside the host cell. One such pathogen is Leishmania major, which causes cutaneous leishmaniasis. The parasite lives inside the macrophages of mammalian host (mostly human). Inside the macrophage, Leishmania genes show complex host-pathogen interaction regulating a plethora of gene expression. Till date, most of the studies have shown this kind of regulation with respect to the host macrophages. Here, based on an extensive in silico analysis, we have hypothesized a novel Theophylline binding riboswitch mediated post-transcriptional regulation of a gene i.e. RNA Polymerase III subunit1 (Lmjf_09_1060), an essential gene for the parasite's survival both in its promastigote as well as in its amastigote form. Later, we have conceptualized the working of the identified putative Theophylline binding riboswitch cassette in in vitro using E. coli based reporter assay, wherein, a reporter gene (eGFP) is used instead of RNA Polymerase III subunit1 gene and apparently have shown the downregulation of the reporter gene (eGFP) expression under the influence of in silico identified Theophylline binding riboswitch.

Regulatory respiratory data refinement with reduced animal usage.

INTRODUCTION: Assessment of effects of potential drug candidates on the respiratory system is part of the regulatory preclinical safety assessment conducted prior to first in human trials (FTIH). Commonly, this is carried out utilizing head out plethysmography (HOP) or whole body plethysmography (WBP) which record only ventilatory parameters. When dosing via the inhaled route a more thorough respiratory assessment, including a direct measure of airway mechanics, is desirable. The aim of the present work was to improve the strategy for respiratory safety testing by a) evaluating a telemetered pleural pressure - HOP (PP-HOP) model and b) evaluating a crossover study design protocol in the WBP model to reduce variability and animal usage. METHODS: For the PP- HOP model, rats were surgically implanted with a telemetry device for measurement of pleural pressure. Animals were placed in HOP tubes and respiratory function assessed when exposed to methacholine at doses of 0 (saline only), 0.42, 1.6 and 3.8 mg/kg. WBP assessment was performed in rats in a crossover study design when treated with theophylline at doses of 0 (saline only), 3, 10 and 30 mg/kg. RESULTS: Data from the PP-HOP study confirmed the expected changes in ventilatory parameters and airway mechanics in response to inhaled methacholine, including an increase in pulmonary resistance and decrease in tidal volume. Data from the WBP crossover study demonstrated similar sensitivity and statistical power to detect changes in respiratory rate and tidal volume to a standard parallel group design. CONCLUSION: Measurement of PP-HOP in a stand-alone safety pharmacology study in conjunction with HOP assessment conducted as part of a toxicology study, represents an improved respiratory testing strategy for inhaled drugs. For compounds administered by other routes, we conclude that use of WBP using a crossover dosing design is a suitable alternative to parallel dosing groups, with a significant reduction in animal numbers and no loss of statistical power.

Human Umbilical Cord Blood-Derived Neural Stem Cell Line as a Screening Model for Toxicity.

The aim was to investigate whether a human neural stem cell (NSC) line derived from human umbilical cord blood (hUCB) can be used for toxicity study. Toxicity of both neurotoxic environmental xenobiotics, methyl mercury chloride (CH3HgCl), lead acetate (CH3COOPb), and chlorpyrifos (CP), and non-neurotoxic insecticide, dichlorvos, as well as non-neurotoxic drugs, theophylline and acetaminophen were assessed. Additionally, differentiation of neuronal and glial cell lines derived from hUCB was elucidated. It was observed that CH3HgCl was more toxic to human NSCs in comparison to CH3COOPb and CP. The minimum inhibitory concentration (MIC) value against NSCs was 3, 10, and 300 mg/L, in each staining process, acridine orange/ethidium bromide (AO/EB) staining, 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide (MTT) assay, and Hoechst staining, for CH3HgCl, CP, and CH3COOPb, respectively. CH3HgCl had the LC25 value as 10.0, 14.4, and 12.7 mg/L, by staining method mentioned in succession. CP had the LC25 value as 21.9, 23.7, and 18.4 mg/L; similarly, CH3COOPb had LC25 values, successively as 616.9, 719.2, and 890.3 mg/L. LC50 values ranged from 18.2 to 21.7 mg/L for CH3HgCl, 56.4 to 60.2 mg/L for CP, and 1000 to 1460.1 for CH3COOPb. Theophylline, acetaminophen, and dichlorvos had no impact on the viability of NSCs. This work justified that hUCB-NSC model can be used for toxicity study.

Potential risks of maternal administration of Mucophylline on the pups of albino rats during lactation.

The present study was undertaken to evaluate the potential risks of the mucolytic and broncholytic drug, Theophylline derivatives (Mucophylline) maternally administered on the pups. The nursing rats orally administered from 1st postpartum day (PPD) to 21th PPD with two different doses 30.83mg/kg (low dose) and 66.61mg/kg (Human equivalent dose (HED)). On the 21th PPD, the postnatal developmental signs, skeletal malformation and the histopathology of neonatal liver, kidney and brain were examined. Our results showed that Mucophylline induced a significant reduction in the neonatal weight and length, delayed, weak and incomplete ossification, wavy ribs and the neonatal liver revealed histopathological changes, pyknotic hepatocytes, cytoplasmic vacuolization, dilated sinusoid and necrotic area. Kidney revealed alternation changes, enlargement of the glomerulus, renal tubules degeneration and lymphatic infiltration. Brain (cerebral cortex and cerebellum) showed neurodegenerative changes, vacuolization of neuropil, congested and dilated blood vessel and dark stain neurons. Our results showed that the activities of non-enzymatic (GSH) and enzymatic (GST, CAT) antioxidants were insignificantly decrease in both neonatal brain and liver tissues of rats administered with 30.83mg/kg and 61.66mg/kg of Mucophylline and insignificant increase in MDA levels in both neonatal brain and liver tissues. However, significant reduction (P≤0.05) in the content of GR was recorded in neonatal brain tissue of rats administered with 30.83mg/kg and 61.66mg/kg of Mucophylline during lactation period in comparison with control. These support and proof the potential risks of the maternal administration of Mucophylline on pups.

Uso crónico de teofilina y mortalidad en la enfermedad pulmonar obstructiva crónica: un metaanálisis / Chronic Use of Theophylline and Mortality in Chronic Obstructive Pulmonary Disease: A Meta-analysis

Antecedentes: Se ha demostrado que la teofilina mejora la función respiratoria y la oxigenación en pacientes con enfermedad pulmonar obstructiva crónica (EPOC). Sin embargo, no está suficientemente evaluado el impacto de la teofilina sobre la mortalidad de los pacientes con EPOC. Método: Dos investigadores buscaron de forma independiente artículos elegibles en 4 bases de datos. Los artículos seleccionados para el presente metaanálisis debían ser artículos de investigación originales que proporcionaran el cociente de riesgos instantáneos (HR) de la mortalidad por cualquier causa en pacientes con EPOC tratados con teofilina. Se permitió incluir tanto ensayos controlados aleatorizados como estudios observacionales. Después de confirmar que la heterogeneidad no era significativa (I2<50%), para estimar el cociente de riesgos instantáneos del metaanálisis se empleó un modelo fijo con un método de varianza inversa genérica. Resultados: Se seleccionaron 364 artículos potencialmente elegibles. De los 364 artículos, 259 fueron excluidos basándose en el título y el resumen, y 99 fueron excluidos después de considerar sus textos completos. Finalmente, nuestro análisis incluyó 6 estudios observacionales y ningún ensayo controlado aleatorizado. Un estudio estaba realizado con 2 cohortes. El número de pacientes en cada cohorte varió de 47 a 46.403. La heterogeneidad (I2 = 42%, p = 0,11) y el sesgo de publicación (r = 0,21, p = 0,662 en la prueba de Begg) no fueron significativos. El metaanálisis del modelo fijo arrojó un cociente de riesgos instantáneos combinado de mortalidad por cualquier causa con teofilina de 1,07 (intervalo de confianza del 95%: 1,2-1,13, p = 0,003). Conclusión: El presente metaanálisis de 7 cohortes observacionales sugiere que la teofilina aumenta ligeramente la mortalidad por cualquier causa de los pacientes con EPOC

Background: Theophylline has been shown to improve respiratory function and oxygenation in patients with chronic obstruction pulmonary disease (COPD). However, the impact of theophylline on mortality in COPD patients has not been not sufficiently evaluated. Method: Two investigators independently searched for eligible articles in 4 databases. The eligibility criterion for this meta-analysis was an original research article that provided a hazard ratio for theophylline for all-cause mortality of COPD patients. Both randomized controlled trials and observational studies were accepted. After we confirmed no substantial heterogeneity (I2 < 50%), the fixed-model method with generic inverse variance was used for meta-analysis to estimate the pooled hazard ratio. Results: We screened 364 potentially eligible articles. Of the 364 articles, 259 were excluded on the basis of title and abstract, and 99 were excluded after examination of the full text. Our final analysis included 6 observational studies and no randomized controlled trials. One study reported 2 cohorts. The number of patients in each cohort ranged from 47 to 46,403. Heterogeneity (I2 = 42%, P = .11) and publication bias (Begg's test r = 0.21, P = .662) were not substantial. Fixed-model meta-analysis yielded a pooled hazard ratio for theophylline for all-cause death of 1.07 (95% confidence interval: 1.02-1.13, P = .003). Conclusion: This meta-analysis of 7 observational cohorts suggests that theophylline slightly increases all-cause death in COPD patients

Fenethylline (Captagon) Abuse - Local Problems from an Old Drug Become Universal.

Fenethylline is a theophylline derivative of amphetamine having stimulant effects similar to those of other amphetamine-type derivatives. Fenethylline was used as medicament for hyperactivity disorders in children, narcolepsy and depression, but it has also been used as a drug of abuse under the common name of 'captagon'. Unlike other drugs of abuse, the clandestine synthesis of fenethylline is simple, using inexpensive laboratory instrumentation and raw materials legal to obtain. A review of all the existing knowledge of fenethylline is reported, concerning its chemistry, synthesis, pharmacology and toxicology, legislation, its prevalence and use as drug of abuse, as well as its analysis in biological or seized samples. Published or reported captagon-related cases and seizures are also presented. All the reviewed information was gathered through a detailed search of PubMed and the Internet. The primary drug market for fenethylline (as captagon) has traditionally been countries located on the Arabian Peninsula but also North Africa since 2013. In Arab countries, millions of captagon tablets are seized every year which represents one-third of global amphetamines seizures within a year. Furthermore, three of four patients treated for drug problems in Saudi Arabia are addicted to amphetamines, almost exclusively in the form of captagon. Significant information on fenethylline is provided for pharmacologists, toxicologists and forensic pathologists. Fenethylline, although old, has recently been introduced to the drug market, especially in Arab countries. Continuous community alertness is needed to tackle this current growing phenomenon.

Theophylline Pharmacokinetics in Foetal Sheep: Maternal Metabolic Capacity is the Principal Driver.

Understanding theophylline pharmacokinetics (PK) in the foetus is essential to prevent in utero toxicity and optimize prophylactic therapies. Previous studies in pregnancy have been obfuscated by maternal dosing and inadequate sampling in the foetus; both render modelling of foetal PK difficult. Six ewes carrying singleton foetuses received theophylline (60 mg) into the foetal jugular vein. Blood samples were drawn from the foetus and ewe over 36 hr. Serum concentrations were measured. Maternal and foetal pharmacokinetic parameters were estimated. Foetal non-compartmental pharmacokinetic parameters were as follows: half-life 7.37 ± 1.22 hr; volume of distribution 44.62 ± 11.45 L; area under the curve 14.82 ± 2.71 hr/(µg/mL); and clearance 4.15 ± 0.70 L/hr. Rapid theophylline distribution across the placenta was observed. Maternal non-compartmental pharmacokinetic parameters were as follows: half-life 6.54 ± 2.44 hr; volume of distribution 32.48 ± 9.99 L; area under the curve 16.28 ± 4.53 hr/(µg/mL); and clearance 3.69 ± 1.47 L/hr. Foetal and ewe serum concentration-time profiles were fit together into a 3-compartment population pharmacokinetic model, and parameters were as follows: central volume 1.38 ± 0.11 L; 2nd peripheral compartment volume 3.11 ± 0.29 L; 3rd peripheral compartment volume 60.14 ± 6.02 L; elimination clearance 9.89 ± 0.90 L/hr; distribution clearance between central and 2nd compartment 30.87 ± 2.31 L/hr; and distribution clearance between 2nd and 3rd compartments 13.89 ± 1.11 L/hr. Cytochrome P4501A expression was robust in maternal liver; negligible activities were observed in placenta, foetal liver and foetal kidney. In vitro protein binding of theophylline was 30% lower in foetal serum compared to maternal serum (29.7 ± 4.4 versus 42.0 ± 3.6%-bound). Free concentrations were lower in the foetus than in the ewe, suggesting active transport across placenta. In summary, foetal clearance of theophylline is attributable to rapid distribution into the maternal circulation across the placenta followed by greater maternal protein binding and metabolic activity.

Evaluation of pro-convulsant risk in the rat: spontaneous and provoked convulsions.

INTRODUCTION: The aim of the present study was to evaluate the utility of different tests performed in the absence or presence of factors promoting seizures in order to evaluate the pro-convulsant effects of drugs. We studied the effects of theophylline in the rat since this is a well-known pro-convulsant substance in humans. METHODS: The occurrence of spontaneous convulsions following administration of theophylline was evaluated by observation in the Irwin Test and by measuring brain activity using video-EEG recording in conscious telemetered animals. Theophylline was also tested in the electroconvulsive shock (ECS) threshold and pentylenetetrazole (PTZ)-induced convulsions tests, two commonly used models of provoked convulsions. RESULTS: In the Irwin test, theophylline induced convulsions in 1 out of 6 rats at 128 mg/kg. Paroxysmal/seizure activity was also observed by video-EEG recording in 4 out of the 12 animals tested at 128 mg/kg, in presence of clonic convulsions in 3 out of the 4 rats. Paroxysmal activity was observed in two rats in the absence of clear behavioral symptoms, indicating that some precursor signs can be detected using video-EEG. Clear pro-convulsant activity was shown over the dose-range 32-128 mg/kg in the ECS threshold and PTZ-induced convulsions tests. DISCUSSION: Evaluation of spontaneous convulsions provides information on the therapeutic window of a drug and the translational value of the approach is increased by the use of video-EEG. Tests based on provoked convulsions further complement the evaluation since they try to mimic high risk situations. Measurement of both spontaneous and provoked convulsions improves the evaluation of the pro-convulsant risk of novel pharmacological substances.

A panel of biological tests reveals developmental effects of pharmaceutical pollutants on late stage zebrafish embryos.

Standard toxicological assays using the zebrafish model system evaluate lethality and teratogenicity upon exposure during the first 2 days after fertilization. We tested the biological effects of several widely used drugs on zebrafish by acute treatment for 24 h starting at late embryonic stages, between 48 and 72 h post-fertilization. For 4 out of 6 compounds, we observed a higher sensitivity of late stage zebrafish embryos for general toxicity (lethality) compared to younger embryos. Morphological defects such as edema, body curvature, delayed growth, decreased heart rate and locomotion were observed for each of the compounds tested, often at sublethal concentrations. Gene expression studies on a set of four selected genes revealed a specific regulatory pattern for the different compounds tested. Our results allow us to compare various toxicological endpoints and may contribute to the design of a rational high throughput approach using the zebrafish model.

Efecto del adyuvante vacunal AFCo1 intranasal sobre la concentración plasmática de teofilina en ratas / Effect of intranasal vaccine adjuvant AFCo1 on plasma concentration of theophylline in rats

En este estudio se evaluó el efecto del adyuvante Finlay cocleato 1 (AFCo1), aplicado 4 veces por vía intranasal en 2 niveles de dosis (50 µg y 100 µg) sobre la concentración plasmática de teofilina, administrada a las 24 horas de la última aplicación (5 mg/kg, por vía intraperitoneal) en ratas Sprague-Dawley. Se empleó como control positivo de inflamación la aplicación de 2 dosis por vía subcutánea de adyuvante completo de Freund (ACF). Las ratas que recibieron AFCo1 no mostraron cambios significativos en la concentración sérica de teofilina; mientras que las tratadas con ACF desarrollaron inflamación local asociadas a signos de toxicidad a la teofilina y elevación de las cifras de inmunoglobulina G específica, de las concentraciones plasmáticas y el tiempo de vida media de teofilina en suero, en comparación con los grupos restantes. Estos resultados indican que la inmunoestimulación inducida por AFCo1 intranasal no incrementa los parámetros farmacocinéticos ni la toxicidad de la teofilina en el modelo empleado(AU)

The effect of the adjuvant Finlay cochleate1 (AFCo1), applied intranasally 4 times in 2 dose levels (50 µg and 100 µg) on plasma concentration of theophylline administered 24 hours after the last application (5 mg/kg intraperitoneally) in Sprague-Dawley rats was evaluated in this study. Application subcutaneously of 2 doses of Freund's complete adjuvant (FCA) was used as positive control of inflammation. Rats receiving AFCo1 had no significant changes in serum theophylline concentration, while those treated with FCA developed local inflammation associated with signs of theophylline toxicity and increased specific G immunoglobulin, plasma concentrations and serum theophylline half-life as compared with the remaining groups. These results show that intranasal AFCo1-induced immunostimulation does not increase pharmacokinetic parameters and theophylline toxicity in the model used(AU)

Methylxanthines, seizures, and excitotoxicity.

Clinical evidence, in particular the wide use of theophylline as a bronchodilator, suggests that methylxanthines can cause seizures in patients without known underlying epilepsy. Theophylline is also known to be an added risk factor for seizure exacerbation in patients with epilepsy. The proconvulsant activity of methylxanthines can best be explained by their antagonizing the brain's own anticonvulsant adenosine. Recent evidence suggests that adenosine dysfunction is a pathological hallmark of epilepsy contributing to seizure generation and seizure spread. Conversely, adenosine augmentation therapies are effective in seizure suppression and prevention, whereas adenosine receptor antagonists such as methylxanthines generally exacerbate seizures. The impact of the methylxanthines caffeine and theophylline on seizures and excitotoxicity depends on timing, dose, and acute versus chronic use. New findings suggest a role of free radicals in theophylline-induced seizures, and adenosine-independent mechanisms for seizure generation have been proposed.

Performance-based quality specifications: the relationship between process critical control parameters, critical quality attributes, and clinical performance.

The quality of pharmaceutical products is currently evaluated through a series of tests that do not explicitly communicate the clinical consequences of product variability. A previously published risk simulation platform was used to generate quantitative estimates of inefficacy and toxicity for 288 uniform lots of extended-release theophylline tablets displaying various levels of content uniformity and dissolution variability. These data were used to evaluate the univariate specifications utilized in the United States Pharmacopeia (USP) <711> and <905>. Simulation revealed that the specifications are too lenient for content uniformity, both in terms of inefficacy and toxicity, whereas the criteria for dissolution testing are too strict for inefficacy and inaccurate for toxicity. The USP tests also failed to pinpoint the clinical interaction between content uniformity and dissolution variability. Additionally, the simulation platform was used to define the underlying relationship between product quality attributes and clinical performance. Here, content uniformity and Weibull dissolution time constants were used as inputs to the design spaces, which were conditioned on quantitative estimates of inefficacy and toxicity. This methodology enhances the information content of the design space by omitting quality surrogates (e.g., dissolution, moisture content) that are utilized in current design space practices.

Theophylline-induced changes in mouse electroencephalograms.

Theophylline can induce life-threatening seizures in humans, especially in infants, but the mechanism of induction remains unknown. We investigated the effects of orally administered theophylline on mouse electroencephalograms (EEGs). ddY mice, which are generally completely free of seizures, were used for the experiments. While EEGs, used as controls, showed no paroxysmal spike discharges, theophylline induced clear spike discharges. This study demonstrated that theophylline administered at doses that achieve low serum concentrations can cause spike discharges in mouse EEGs even without causing clinical seizures, indicating that theophylline plays a potent role in subclinical epileptogenicity.

Free radicals and theophylline neurotoxicity : an experimental study.

Free radicals play a crucial role in health and disease and both reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been implicated in CNS effects like excitotoxicity. Theophylline, a re-emerging drug for the treatment of obstructive airway disease, has a narrow therapeutic index which precludes its safe use. The present study evaluated the possible involvement of free radicals in theophylline induced seizures in mice. Aminophylline (100-250 mg/kg) consistently induced seizures and post-ictal mortality, and conventional anticonvulsants and adenosine agonists were ineffective in antagonizing them. Further, phosphodiesterase inhibitors, per se, also did not show any significant seizurogenic potential. Pretreatments with antioxidants, ascorbic acid, alpha-tocopherol and melatonin, all dose dependently reduced seizure incidence and mortality after aminophylline, whereas, antioxidant depletion potentiated such excitotoxicity. Pretreatments with the NO synthase inhibitors, L-NAME and 7-NI blocked aminophylline seizures, whereas, the NO mimetics, L-arginine and glyceryl trinitrate, tended to potentiate this phenomenon. Sub-effective doses of aminophylline (100 mg/kg) also induced seizures when combined with subthreshold intensity of electroshock, and such seizures were similarly antagonized by the antioxidants and NO synthase inhibitors. Biochemical assay of brain homogenates showed that aminophylline seizures were associated with enhancements in brain MDA and NOx (NO metabolites) levels, whereas, SOD activity was reduced, and these changes were attenuated after melatonin and L-NAME pretreatments. The pharmacological and biochemical data are strongly suggestive of the involvement of both ROS and RNS during theophylline-induced seizures.

Differential expression of genes encoding constitutive and inducible 20S proteasomal core subunits in the testis and epididymis of theophylline- or 1,3-dinitrobenzene-exposed rats.

Theophylline (THP) and 1,3-dinitrobenzene (DNB) are thought to induce infertility by incapacitating the nurturing Sertoli cells and causing germ cell apoptosis in the testicular seminiferous epithelium, respectively. We hypothesized that THP and DNB exposure would alter the expression of the genes within the ubiquitin-proteasome pathway (UPP), implicated in spermatogenesis and epididymal sperm quality control. Rats were fed 0 or 8000 ppm of THP and necropsied on Days 18, 30, and 42 or administered 0, 2, or 6 mg/kg DNB via oral gavage and necropsied on Day 7. Tissues were collected from the testis and the caput, corpus, and cauda regions of the epididymis for transcriptional profiling by semiquantitative RT-PCR, real-time RT-PCR, and histopathology. Target UPP genes included those encoding for constitutive the 20S proteasomal core subunits Psmb1 (beta1), Psmb2 (beta2), and Psmb5 (beta5); the inducible 20S core subunits Psmb9 (LMP2), Psmb8 (LMP7), and Psmb10 (LMP10); and Ube1 (ubiquitin-activating enzyme E1), Ube2d3 (ubiquitin-conjugating enzyme E2), and Uchl1 (ubiquitin C-terminal hydrolase PGP9.5). Spermatozoa were collected from the cauda epididymis for analysis by light microscopy and flow cytometric evaluation of sperm surface ubiquitin. These data show that reprotoxic exposure alters the tissue-specific expression of UPP genes in the testis and epididymis, which may contribute to the aberrant spermatogenesis and epididymal processing of both normal and defective spermatozoa. Transcriptional profiling and flow cytometric analysis of the UPP thus captures the prodromal effects of reproductive toxicity not captured by conventional histology and functional cytology. Complementing seminal analysis with these measures may be useful in screening drug-induced toxicity or environmental infertility.

Reproductive cytotoxicity is predicted by magnetic resonance microscopy and confirmed by ubiquitin-proteasome immunohistochemistry in a theophylline-induced model of rat testicular and epididymal toxicity.

This study investigated the testicular changes in the rat induced by the nonspecific phosphodiesterase inhibitor, theophylline using magnetic resonance microscopy (MRM) and ubiquitin immunostaining techniques. In vivo T1- and T2-weighted images were acquired at 2 T under anesthesia. Increased signal observed in the theophylline-treated rats suggests that leakage of MRM contrast was occurring. In vivo MRM results indicate that day 16 testis displayed an increased T1-weighted water signal in the area of the seminiferous tubule that decreased by day 32. These findings were validated by histopathology, suggesting that in vivo MRM has the sensitivity to predict changes in testis and epididymal tissues. The participation of the ubiquitin system was investigated, using probes for various markers of the ubiquitin-proteasome pathway. MRM can be used to detect subtle changes in the vascular perfusion of organ systems, and the up-regulation/mobilization of ubiquitin-proteasome pathway may be one of the mechanisms used in theophylline-treated epididymis to remove damaged cells before storage in the cauda epididymis. The combined use of in vivo MRM and subsequent tissue or seminal analysis for the presence of ubiquitin in longitudinal studies may become an important biomarker for assessing testis toxicities drug studies.