Molecular interactions of polyvinyl chloride microplastics and beta-blockers (Diltiazem and Bisoprolol) and their effects on marine meiofauna: Combined in vivo and modeling study.

The ecotoxicological effects of beta-blockers (i.e. Diltiazem and Bisoprolol) and their interactions with the microplastic polyvinyl chloride on marine meiofauna were tested in laboratory microcosms. An experimental factorial design was applied, using meiobenthic fauna collected from the Old Harbor of Bizerte (NE Tunisia), but with a main focus on the nematode communities. The meiobenthic invertebrates were exposed to two concentrations of Diltiazem and Bisoprolol, of 1.8 µg.L-1 and 1.8 mg.L-1, respectively, and one concentration of polyvinyl chloride (i.e. 20 mg.kg-1), separately and mixed. The overall meiofauna abundance was significantly reduced in all treatments, mainly that of polychaetes and amphipods. Moreover, the juveniles-gravid female ratios of the nematode communities were the lowest in the 1.8 µg.L-1 Bisoprolol treatment and for the 1.8 mg.L-1 mixture of Diltiazem and microplastics, suggesting that different dosages influence the maturity status of the examined species. The demographic results were also supported by in silico approach. The simulation of molecular interactions revealed acceptable binding affinities (up to -8.1 kcal/mol) and interactions with key residues in the germ line development protein 3 and sex-determining protein from Coenorhabditis elegans. Overall, the experimental outcome strongly indicates synergistic interactions among the beta-blockers Diltiazem and Bisoprolol and the microplastic polyvinyl chloride on marine nematode communities.

Evaluation of ß-adrenergic ligands for development of pharmacological heart failure and transparency models in zebrafish.

Cardiovascular toxicity represents one of the most common reasons for clinical trial failure. Consequently, early identification of novel cardioprotective strategies could prevent the later-stage drug-induced cardiac side effects. The use of zebrafish (Danio rerio) in preclinical studies has greatly increased. High-throughput and low-cost of assays make zebrafish model ideal for initial drug discovery. A common strategy to induce heart failure is a chronic ß-adrenergic (ßAR) stimulation. Herein, we set out to test a panel of ßAR agonists to develop a pharmacological heart failure model in zebrafish. We assessed ßAR agonists with respect to the elicited mortality, changes in heart rate, and morphological alterations in zebrafish larvae according to Fish Embryo Acute Toxicity Test. Among the tested ßAR agonists, epinephrine elicited the most potent onset of heart stimulation (EC50 = 0.05 mM), which corresponds with its physiological role as catecholamine. However, when used at ten-fold higher dose (0.5 mM), the same compound caused severe heart rate inhibition (-28.70 beats/min), which can be attributed to its cardiotoxicity. Further studies revealed that isoetharine abolished body pigmentation at the sublethal dose of 7.50 mM. Additionally, as a proof of concept that zebrafish can mimic human cardiac physiology, we tested ßAR antagonists (propranolol, carvedilol, metoprolol, and labetalol) and verified that they inhibited fish heart rate in a similar fashion as in humans. In conclusion, we proposed two novel pharmacological models in zebrafish; i.e., epinephrine-dependent heart failure and isoetharine-dependent transparent zebrafish. We provided strong evidence that the zebrafish model constitutes a valuable tool for cardiovascular research.

Is hypoglycemia really observed in pediatric beta-blocker intoxications? A case-control study.

BACKGROUND: Beta-blocker (BB) intoxications are common in both childhood and adulthood. In the case of poisoning, bradycardia, hypotension, ventricular dysrhythmias, mental status changes, seizures, hypoglycemia, and bronchospasm may occur. Effects on the cardiovascular system are commonly seen, but hypoglycemia is not frequently observed in clinical practice. In this study, we aimed to answer the question, "Is hypoglycemia more commonly observed in BB intoxications than in other intoxications?" METHOD: This was a case-control study conducted in a pediatric emergency department of a university hospital. The case group (Group 1) consisted of cases with BB poisonings and the control group (Group 2) consisted of cases with selective serotonin receptor inhibitor (SSRI) poisonings. Data were obtained from patient files. We recorded the blood glucose levels (BGLs) of all patients on admission to the emergency department and at the 1-, 6-, and 24-h follow-up. The amounts of BBs received by the cases were compared with the specific toxic doses of each drug. The data obtained were analyzed using the Statistical Package for the Social Sciences 22 (SPSS.22) program. Mean and standard deviation for numerical values and frequency for categorical data are reported; at test, chi-square test, and ANOVA tests were used for the analysis. RESULTS: The study comprised 40 patients (Group 1) and 40 controls (Group 2). The mean serum BGLs of patients in Group 1 at admission and at the 1-, 6-, and 24-h follow-up were 107.2 ± 46.3 mg/dl, 86.3 ± 20.1 mg/dl, 88.6 ± 28.4 mg/dl, and 86.5 ± 23.7 mg/dl, respectively. The mean values of Group 2 cases were 100 ± 39.5 mg/dl, 92.1 ± 30 mg/dl, 91±28 mg/dl, and 127.8 ± 60.7 mg/dl, respectively, at admission and at the 1-, 6-, and 24-h follow-up (p = 0.4, p < 0.001, p = 0.7, and p < 0.001, respectively). The mean BGLs of patients who were exposed to propranolol at admission and at the 1-, 6-, and 24-h follow-up were significantly lower than those of the patients who had taken different BBs in Group 1. No linear correlation was found between the percentage of exposure to BB toxic doses and BGLs. CONCLUSION: Our study showed that the BGLs of patients receiving BBs could be lower, but they were not at a level that would have serious consequences. Nevertheless, the BGLs of all cases of intoxication should be monitored closely.

The cytotoxic and apoptotic effects of beta-blockers with different selectivity on cancerous and healthy lung cell lines.

ß-blockers having specific affinities to ß-adrenergic receptors are routinely used to treat cardiovascular problems. Additionally, it has been demonstrated that these drugs can be effective in treating apoptosis-related diseases. The current study was conducted to investigate the cytotoxic and apoptotic effects of ß-1 selective esmolol, ß-2 selective ICI-118,551, and non-selective nadolol blockers on the cancerous and healthy lung cells. MTT test was used to evaluate cytotoxicity. Apoptotic actions were examined by using Annexin V-FITC/PI assay, JC-1 staining, ROS test, and the determination of the caspase-4 and -9, Bcl-2, Bax, Bax/Bcl-2, and JNK levels. Although the MRC-5 showed greater resistance than A549 cells, the ß-blockers at 150-250 µM exhibited different levels of cytotoxic effect on both lung cell lines. Esmolol was found to be the most ineffective blocker and the increases in Bcl-2 protein levels were appeared to be effective in resistance to this drug. The increases in reactive oxygen species (ROS) together with the increase in caspase-4 and Bax protein levels have been shown to play a role in ICI-118,551 induced lung cell death. Nadolol was the most effective blocker increasing the total apoptotic cell population in both lung cells, which was based on both mitochondrial and endoplasmic reticulum stress. When the selectivities of the ß-blockers are considered, it seems that ß-2 specific antagonism predominantly mediated the death of lung cells, and the overwhelming factors causing apoptosis mainly varied depending on the selectivity of the blockers.

Intoxicación por beta bloqueadores / Beta Blockers Intoxication

La intoxicación por betabloqueadores es una situación clínica de poca frecuencia, estrechamente relacionada con trastornos depresivos mayores, con una prevalencia mayor en mujeres. Los episodios de gravedad relacio- nados a toxicidad por betabloqueadores son clasificados como episodios de moderados a severos. En el caso del carvedilol con un umbral tóxico de 50mg. Caso Clínico: Paciente de 16 años con historia de ingesta de carvedilol en niveles tóxicos y único antecedente depresión ma- yor. Discusión: Los betabloqueadores antagonizan los receptores betaadrenérgicos, la sintomatología relacio- nada con bradicardia e hipotensión es frecuente y puede generar afección a nivel del sistema nervioso central. El tratamiento de emergencia sí se capta al paciente en la primera hora consiste en realizar un lavado gástrico y aplicar carbón activado. Se propone el uso de crista- loides y el uso de epinefrina o norepinefrina como ma- nejo de primera línea, en caso de bradicardias sosteni- das debe considerarse el uso de atropina. Los pacientes asintomáticos deben ser vigilados durante seis horas...(AU)

Dynamic features of cardiac vector as alternative markers of drug-induced spatial dispersion.

INTRODUCTION: The abnormal amplification of ventricular repolarization dispersion (VRD) has long been linked to proarrhythmia risk. Recently, the measure of VRD through electrocardiogram intervals has been strongly questioned. The search for an efficient and non-invasive surrogate marker of drug-induced dispersion effects constitute an urgent research challenge. METHODS: Herein, drug-induced ventricular dispersion is generated by d-Sotalol supply in an In-vitro rabbit heart model. A cilindrical chamber simulates the thorax and a multi-electrode net is used to obtain spatial electrocardiographic signals. Cardiac vector dynamics is captured by novel velocity cardiomarkers obtained by quaternion methods. Through statistical analysis and machine learning technics, we compute potential dispersion markers that could define proarrhythmic risk. RESULTS: The cardiomarkers with the greatest statistical significance, both obtained from the electrical cardiac vector, were: the QTω, which is the difference between first and last maxima of angular velocity and λ21vT, the roundness of linear velocity. When comparing with the performance of the current standards (89%), this pair was able to correctly separate 21 out of 22 experiments achieving a performance of 95%. Moreover, the QTω computes in a much more robust basis the QT interval, the current index for drug regulation. DISCUSSION: These velocity markers circumvent the problems of accuratelly finding the fiducial points such as the always tricky T-wave end. Given the high performance they achieved, it is provided a promising outcome for future applications to the detection of anomalous changes of heterogeneity that may be useful for the purposes of torsadogenic toxicity studies.

Toxin-induced cardiac arrest: frequency, causative agents, management and hospital outcome.

BACKGROUND: Cardiac arrest (CA) is a public health problem, with various etiologies and a fatal issue in 90-95% of cases. Toxin-induced cardiac arrests (TICA) are poorly described. Scarcity of national data prompted us to carry-out this study. AIM: To determine TICA frequency in a Tunisian reference center in toxicology and its hospital prognosis, and to describe its clinical and therapeutic aspects Methods : Data were collected retrospectively over an 8-years period. We included patients admitted for post-CA care with highly suspected or confirmed TICA. Clinical and toxicological data were recorded. RESULTS: We recorded 21 cases of TICA, which represented 48.8% of CA. A single toxic agent was incriminated in 90% of cases. Main causative agents identified in our series were pesticides and betablockers: chloralosed (n = 6), carbamate inhibitor of cholinesterase (n = 5), acebutolol (n = 4) and organophosphate (n = 2). One case of opiates and cocaine poisoning was reported. Median duration of "no flow" was 0 minutes. Mean duration of "low flow" was 13.74±9.15 minutes. An initial shockable rhythm was noted only in three patients. Mortality rate was 76% (16/21). Four of the five survivors had a Cerebral Performance Category Scale (CPC) 1, only one patient survived with a CPC 3. Factors associated with mortality were : the duration of "low flow" (p=0.02) and APACHE II score (p=0.014). APACHE II≥29 was the only independent factor (OR=2.0, 95%CI [1.07;3.71]). CONCLUSION: TICA were most frequently provoked by pesticides, mortality was high and was independently predicted by APACHE II score.

Toxicity of Atenolol and Propranolol on Rat Heart Mitochondria.

Propranolol and atenolol are known as ß receptor blocker drugs. These drugs are used to treat some heart diseases. There are controversies in the relationship between the use of beta-blocker drugs and the level of reactive oxygen species (ROS). Mitochondria as one of the most important sources of ROS are considered as one of the targets of drug-induced cardiotoxicity. The aim of this study was to evaluate the effects of propranolol and atenolol on mitochondria isolated from the heart. To achieve this aim, several markers of mitochondrial and cellular toxicity were evaluated. The key results of this study are the increased ROS level, collapse in mitochondrial membrane potential (MMP), mitochondrial swelling and cytochrome c release as well as disruption of respiratory chain complex II in mitochondria in isolated heart mitochondria after exposure to propranolol and atenolol. The results indicate an increase in caspase-3 activity and a decrease in the ATP level in cardiomyocytes after exposure to propranolol and atenolol. The underlying mechanisms of propranolol and atenolol induced cardiotoxicity may be associated with alterations in mitochondrial function, oxidative stress, and changes in the mitochondrial membrane.

Experiencia en el manejo de intoxicaciones por Betabloqueadores y Calcioantagonistas: serie de casos y revisión de la literatura / Experience in the management of intoxications by Beta-blockers and Calcium-antagonists: case series and review

La intoxicación por betabloqueantes y calcio antagonistas suele generar una gran morbilidad y mortalidad secundaria a sus efectos tóxicos cardiovasculares, como son los trastornos de la conducción cardíaca y la caída en la resistencia vascular periférica. En sobredosis, los beta bloqueantes y calcio antagonistas tienen similar presentación clínica y su tratamiento suele ser común entre ellos, en varios puntos del manejo. Estas intoxicaciones, a menudo, son refractarias al manejo médico estándar, por lo que las intervenciones a realizar deben ser ordenadas y estandarizadas con conocimiento profundo de la farmacología. Las emulsiones lipídicas no son el tratamiento de primera línea para las intoxicaciones por calcio antagoistas y betabloqueantes y se usan solamente cuando se han agotado las otras opciones terapeúticas descritas, siendo una alternativa eficaz para el manejo de este tipo de intoxicaciones. En este trabajo se pretende, con una serie de casos y revisión de la literatura, analizar la evidencia disponible en el paso a paso del abordaje y tratamiento de los pacientes intoxicados por calcio antagonistas y betabloqueantes planteando un algoritmo de manejo

The poisoning by beta blockers and calcium antagonists usually generates great morbidity and mortality secondary to its cardiovascular toxic effects such as cardiac conduction disorders and the decrease in peripheral vascular resistance. In overdose beta blockers and calcium antagonists have a similar clinical presentation and their treatment usually overcomes, these poisonings are often refractory to standard medical management so the interventions to be performed must be ordered and standardized with deep knowledge of pharmacology. Lipid emulsions are not the first-line treatment for antagonistic calcium blockers and beta blockers, they are used only when the other therapeutic options described have been exhausted but they are an effective alternative for the management of this type of poisoning. It is intended with this series of cases and review of the literature to analyze the evidence available in the step-by-step approach and treatment of calcium-poisoning patients antagonists and beta blockers posing a management algorithm

Analysis of beta-blocker bioconcentration in brown planaria (Girardia dorotocephala) and its effects on regeneration.

Production, distribution, and disposal of pharmaceutical products, including beta-blockers, have become a global issue. Beta-blockers are known to persist in the environment months after their release and may result in the disruption of the homeostatic system in non-target organisms. Here, we study the bioconcentration of three of the most commonly used beta-blockers and their effect on the regeneration of Girardia dorotocephala, a freshwater brown planarian. Acute toxicity tests determined LC50s for acebutolol, metoprolol, and propranolol to be 778 mg/L, 711 mg/L, and 111 mg/L, respectively. The quantification and analysis of beta-blocker bioconcentration during acute exposure were performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). After 4 days of exposure to beta-blockers, the bioconcentration drastically decreased for all three beta-blockers at all exposure levels, suggesting that an effective mechanism to reduce uptake or excrete beta-blockers could be present. Additionally, Girardia dorotocephala were cut proximal to the head and the quality of regeneration was documented from each fragment daily. No significant difference was visually observed after 2 weeks of regeneration between the brown planarians placed in beta-blocker solution and those placed in control solution.

A rapid zebrafish embryo behavioral biosensor that is capable of detecting environmental ß-blockers.

ß-Blockers (BB) are one of the most commonly prescribed pharmaceuticals used for treating cardiovascular and acute anxiety-related disorders. This class of drugs inhibit ß-adrenoceptor signalling and given their growing, widespread use, BB are routinely detected in surface waters at nM concentrations. This is concerning as trace levels of BB impart developmental and reproductive dysfunction in non-target aquatic organisms, with potential for ecological risks. To date, environmental pharmaceutical risks to non-target animals are not part of the monitoring framework due to the lack of bioassays for assessing their biological effects. Behavioral endpoints have the advantage of a systems-level integration of multiple sensory signals and motor responses for toxicity screening; however, they are not currently used for risk assessment of environmental contaminants. The zebrafish (Danio rerio) embryo photomotor response (zfPMR) has been used in high-throughput behavioral screenings for neuroactive drug effects at high, therapeutic concentrations. Our objective here was to examine if we could utilize the zfPMR for screening environmental levels of BB. Embryos were placed into 96-well plates, exposed to chemicals and/or municipal wastewater effluent (MWWE), and their zfPMRs were measured with video-analysis. To specifically target BB, embryos were co-treated with isoproterenol, a ß-adrenergic agonist that stimulates the zfPMR, and the inhibition of isoproterenol-induced response was used as a biomarker of BB exposure. Our results reveal that the inhibition of isoproterenol-stimulated zfPMRs can be used as a biosensor capable of detecting BB in the parts-per-billion to parts-per-trillion in water samples, including diluted MWWE. The method developed detects BB in spite of the presence of other neuroactive compounds in water samples. This systems level approach of rapid screening for BB effects provides the most promising evidence to date that behavioral neuromodulation can be potentially applied for environmental effects monitoring of pharmaceuticals.

Measurement of J-Tpeakc along with QT-Interval Prolongation May Increase the Assay Sensitivity and Specificity for Predicting the Onset of Drug-Induced Torsade de Pointes: Experimental Evidences Based on Proarrhythmia Model Animals.

dl-Sotalol which can block both K+ channel and ß-adrenoceptor has been shown to prolong the J-Tpeakc of electrocardiogram in beagle dogs but tended to shorten it in microminipigs, although the drug prolonged the QT interval in both animals under physiologically maintained experimental condition. In order to estimate how the changes in the J-Tpeakc in the normal hearts would be reflected in the pathologic hearts, we compared proarrhythmic effects of dl-sotalol by using proarrhythmia models of beagle dogs and microminipigs, of which atrioventricular node had been ablated > 2 months and 8-9 weeks before, respectively (n = 4 for each species). dl-Sotalol in an oral dose of 10 mg/kg induced torsade de pointes in three out of four beagle dogs, which degenerated into ventricular fibrillation. In microminipigs, the same dose did not trigger torsade de pointes at all, whereas intermittent ventricular pauses were observed in each animal after the drug treatment. These results indicate that assessment of the J-Tpeakc along with the QT-interval prolongation in healthy subjects may provide reliable information of risk prediction for patients susceptible to the drug-induced torsade de pointes.

Gelatinized core liposomes: A new Trojan horse for the development of a novel timolol maleate glaucoma medication.

Glaucoma treatment with ocular medications requires overcoming the corneal barrier to drug penetration. Liposomes have a great corneal penetration ability and affinity while suffering from poor stability and low entrapment of hydrophilic drugs accompanied by rapid drug release. This work aims to develop a new, effective and stable glaucoma medication with sustained drug release properties; Timolol maleate gelatinized core liposomes. A full factorial design was utilized to study the effects of three formulation variables on drug loading and vesicle particle size. Vesicles were prepared by the thin-film hydration method, and characterized for in-vitro drug release and stability. Intra-ocular pressure (IOP) reduction was evaluated in-vivo on glaucomatous rabbit's eyes. The safety profile was assessed using histopathological examinations. Gelatin significantly increased the drug entrapment percentage reaching 50% with a particle size of 38.81 µm. Sustained drug release was recorded compared to a marketed product and to a conventional liposomal formulation. The prepared vesicles caused the highest reduction in IOP accompanied by safe histological findings. This work provided a new, safe and effective ocular glaucoma medication; Timolol maleate gelatinized core liposomes, solving the main problems of ocular liposomal formulations of hydrophilic drugs, suitable for the pharmaceutical industry and comprising abundant and relatively cheap components.

Influence of pH on the uptake and toxicity of ß-blockers in embryos of zebrafish, Danio rerio.

ß-Blockers are weak bases with acidity constants related to their secondary amine group. At environmental pH they are protonated with the tendency to shift to their neutral species at more alkaline pH. Here we studied the influence of pH from 5.5 to 8.6 on the toxicity of the four ß-blockers atenolol, metoprolol, labetalol and propranolol in zebrafish embryos, relating toxicity not only in a conventional way to external aqueous concentrations but also to measured internal concentrations. Besides lethality, we evaluated changes in swimming activity and heartbeat, using the Locomotor Response (LMR) method and the Vertebrate Automated Screening Technology (VAST) for high throughput imaging. Effects of metoprolol, labetalol and propranolol were detected on phenotype, heart rate and swimming activity. External effect concentrations decreased with increasing neutral fraction for all three pharmaceuticals, attributed by an enhanced uptake of the neutral species in comparison to the corresponding charged form. The LC50 of metoprolol decreased by a factor of 35 from 1.91 mM with almost complete cationic state at pH 7.0 to 0.054 mM with 8% neutral fraction at pH 8.6. For propranolol the LC50 of 2.42 mM at pH 5.5 was even 100 fold higher than the LC50 at pH 8 with 0.023 mM where 3% were neutral fraction. No effects were detected in the zebrafish embryo exposed to atenolol. The internal concentrations for metoprolol and propranolol were quantified at non-toxic concentrations and at the LC10. Apparent bioconcentration factors (BCF) ranged from 1.96 at pH 7.0 to 32.0 at pH 8.6 for metoprolol and from 1.86 at pH 5.5 to 169 at pH 8.0 for propranolol. The BCFs served to predict the internal effect concentrations from the measured external effect concentrations. Internal effect concentrations of metoprolol and propranolol were in a similar range for all pH-values and for all endpoints. Interestingly, the internal effect concentrations were in the internal concentration range of baseline toxicity, which suggests that the effects of the ß-blockers are rather unspecific, even for sublethal effects on heart rate. In summary, our data confirm that the pH-dependent toxicity related to external concentrations can be explained by toxicokinetic effects and that the internal effect concentrations are pH-independent.

Effect of ß-adrenergic receptor agents on cardiac structure and function and whole-body gene expression in Daphnia magna.

Propranolol (PRO), a human ß-AR (ß-adrenergic receptor) antagonist, is considered to result in specific effects in a non-target species, D. magna, based on our previous studies. The present study investigated the effects of ß-AR agents, including an antagonist and agonist using pharmacologically relevant endpoints as well as a more holistic gene expression approach to reveal the impacts and potential mode of actions (MOAs) in the model non-target species. Results show that the responses in cardiac endpoints and gene expression in D. magna are partially similar but distinguishable from the observations in different organisms. No effect was observed on heart size growth in PRO and isoprenaline (ISO) exposure. The contraction capacity of the heart was decreased in ISO exposure, and the heart rate was decreased in PRO exposure. Time-series exposures showed different magnitudes of effect on heart rate and gene expression dependent on the type of chemical exposure. Significant enrichment of gene families involved in protein metabolism and biotransformation was observed within the differentially expressed genes, and we also observed differential expression in juvenile hormone-inducible proteins in ISO and PRO exposure, which is suspected of having endocrine disruption potential. Taken together, deviation between the effects of PRO and ISO in D. magna and other organisms suggests dissimilarity in MOAs or attributes of target bio-molecules between species. Additionally, PRO and ISO may act as endocrine disruptors based on the gene expression observation. Results in the present study confirm that it is challenging to predict ecological impact of active pharmaceutical ingredients (APIs) based on the available data acquired through human-focused studies. Furthermore, the present study provided unique data and a case study on the impact of APIs in a non-target organism.

Proposal of degradation pathway with toxicity prediction for hydrolytic and photolytic degradation products of timolol.

Timolol (TIM) is a potent ß-adrenergic blocker, useful in treatment of ocular hypertension or open-angle glaucoma. Development and validation of stability indicating LCMS assay method for TIM was accomplished coherent with ICH guideline. Successful chromatographic separation of TIM with its four degradation products was attained by using gradient elution mode on reverse phase column using ammonium acetate buffer, pH 4.6 as mobile phase A and organic solvent as the mobile phase B. Chromatographic conditions were set such as 1.0 mL min-1 flow rate, 20 µL injection volume, 30 °C column temperature and 320 nm detection wavelength. Four major degradation products obtained from hydrolysis and photolysis, were identified and characterized with the combination of liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS/MS) and accurate mass measurements. Degradation pathways were identified based on a comparison of the fragmentation pattern of the [M+H]+ ions of TIM and its degradation products. The method validation was performed as per ICH guideline Q2 (R1).

Antiarrhythmic effect of antazoline in experimental models of acquired short- and long-QT-syndromes.

Aims: Antazoline is a first-generation antihistamine with antiarrhythmic properties. This study examines potential electrophysiological effects of antazoline in short-QT-syndrome (SQTS) and long-QT-syndrome (LQTS). Methods and results: Sixty-five rabbit hearts were Langendorff-perfused. Action potential duration at 90% of repolarization (APD90), QT-interval, spatial dispersion (DISP), and effective refractory period (ERP) were measured. The IK, ATP-opener pinacidil (1 µM, n = 14) reduced APD90 (-14 ms, P < 0.01), QT-interval (-14 ms, P < 0.01), and ERP (-11 ms, P < 0.01), thus simulating acquired SQTS. Additional infusion of 20 µM antazoline prolonged repolarization. Under baseline conditions, ventricular fibrillation (VF) was inducible in 5 of 14 hearts (10 episodes) and in 5 of 14 pinacidil-treated hearts (21 episodes, P = ns). Antazoline significantly reduced induction of VF (0 episodes, P < 0.05 each). Further 17 hearts were perfused with 100 µM sotalol and 17 hearts with 300 µM erythromycin to induce acquired LQTS2. In both groups, prolongation of APD90, QT-interval, and ERP was observed. Spatial dispersion was increased (sotalol: +26 ms, P < 0.01; erythromycin: +31 ms, P < 0.01). Additional infusion of antazoline reduced DISP (sotalol: -22 ms, P < 0.01; erythromycin: -26 ms, P < 0.01). Torsade de pointes (TdP) occurred in 6 of 17 sotalol-treated (22 episodes, P < 0.05 each) and in 8 of 17 erythromycin-treated hearts (96 episodes P < 0.05 each). Additional infusion of antazoline completely suppressed TdP in both groups (P < 0.05 each). Acquired LQTS3 was induced by veratridine (0.5 µM, n = 17) and similar results were obtained (APD90: +24 ms, P < 0.01, QT-interval: +58 ms, P < 0.01, DISP: +38 ms, P < 0.01). Torsade de pointes occurred in 10 of 17 hearts (41 episodes, P < 0.05 each). Antazoline significantly reduced TdP (2 of 17 hearts, 4 episodes, P < 0.05 each). Conclusion: Antazoline significantly reduced induction of VF in an experimental model of acquired SQTS. In three experimental models of acquired LQTS, antazoline effectively suppressed TdP.

Microbial detoxification of carvedilol, a ß-adrenergic antagonist, by the filamentous fungus Cunninghamella echinulata.

Beta adrenergic antagonists like carvedilol are typical environmental pollutants detected in wastewater and surface water. Human metabolism of carvedilol is well investigated, while its environmental fates are still unknown. In recent years, there have been appearing reports on high toxicity of ß-blockers toward aquatic organisms. In this paper the ability of the filamentous fungus C. echinulata to eliminate the ß-blocker has been described for the first time. An 83% loss of carvedilol was observed after 120 h incubation of the tested fungus with the compound, where hydroxylated carvedilol metabolites were identified as the major biotransformation products. Carvedilol degradation by C. echinulata was proceeded by hydroxylation and conjugation reactions similar to its mammalian metabolism. Glucose conjugate was found in the fungi cultures, whereas glucuronide conjugates were detected in mammals. The impact of carvedilol on the functionality of fungal cells was also evaluated. A 2-fold decrease in the PC/PE ratio was noticed in the C. echinulata cell membrane after the exposition to carvedilol compared to control mycelium incubated without the ß-blocker. The change can denote perturbation of fungal cell membrane integration by carvedilol. Moreover, 2.8-fold lower toxicity of postcultures supernatants toward D. magna were shown in contrast to abiotic control.

Influence of Pilocarpine and Timolol on Human Meibomian Gland Epithelial Cells.

PURPOSE: Investigators have discovered that topical antiglaucoma drugs may induce meibomian gland dysfunction. This response may contribute to the dry eye disease commonly found in patients with glaucoma taking such medications. We hypothesize that drug action involves a direct effect on human meibomian gland epithelial cells (HMGECs). To test this hypothesis, we examined the influence of the antiglaucoma drugs, pilocarpine and timolol, on the morphology, survival, proliferation, and differentiation of HMGECs. METHODS: Immortalized (I) HMGECs (n = 2-3 wells/treatment/experiment) were cultured with multiple concentrations of pilocarpine or timolol for up to 7 days. Experiments included positive controls for proliferation (epidermal growth factor and bovine pituitary extract) and differentiation (azithromycin). Cells were enumerated using a hemocytometer and evaluated for morphology, neutral lipid staining, and lysosome accumulation. RESULTS: Our results demonstrate that pilocarpine and timolol cause a dose-dependent decrease in the survival of IHMGECs. The clinically used concentrations are toxic and lead to cell atrophy, poor adherence, or death. By contrast, drug levels that are known to accumulate within the conjunctiva, adjacent to the meibomian glands, do not influence IHMGEC survival. These latter concentrations also have no effect on IHMGEC proliferation or differentiation, and they do not interfere with the ability of azithromycin to stimulate cellular neutral lipid and lysosome accumulation. This dose of pilocarpine, though, did suppress the epidermal growth factor+bovine pituitary extract-induced proliferation of IHMGECs. CONCLUSIONS: Our results support our hypothesis and demonstrate that these antiglaucoma drugs, pilocarpine and timolol, have direct effects on HMGECs that may influence their morphology, survival, and proliferative capacity.

Assessing the environmental hazard of individual and combined pharmaceuticals: acute and chronic toxicity of fluoxetine and propranolol in the crustacean Daphnia magna.

Pharmaceuticals are widespread emerging contaminants and, like all pollutants, are present in combination with others in the ecosystems. The aim of the present work was to evaluate the toxic response of the crustacean Daphnia magna exposed to individual and combined pharmaceuticals. Fluoxetine, a selective serotonin re-uptake inhibitor widely prescribed as antidepressant, and propranolol, a non-selective ß-adrenergic receptor-blocking agent used to treat hypertension, were tested. Several experimental trials of an acute immobilization test and a chronic reproduction test were performed. Single chemicals were first tested separately. Toxicity of binary mixtures was then assessed using a fixed ratio experimental design. Five concentrations and 5 percentages of each substance in the mixture (0, 25, 50, 75, and 100%) were tested. The MIXTOX model was applied to analyze the experimental results. This tool is a stepwise statistical procedure that evaluates if and how observed data deviate from a reference model, either concentration addition (CA) or independent action (IA), and provides significance testing for synergism, antagonism, or more complex interactions. Acute EC50 values ranged from 6.4 to 7.8 mg/L for propranolol and from 6.4 to 9.1 mg/L for fluoxetine. Chronic EC50 values ranged from 0.59 to 1.00 mg/L for propranolol and from 0.23 to 0.24 mg/L for fluoxetine. Results showed a significant antagonism between chemicals in both the acute and the chronic mixture tests when CA was adopted as the reference model, while absence of interactive effects when IA was used.