Concentration-effect Relationship Research Articles

On the relationship between inhibition and receptor occupancy by nondepolarizing neuromuscular blocking drugs

BackgroundNondepolarizing neuromuscular blocking drugs (NDNBs) are clinically used to produce muscle relaxation during general anesthesia. To better understand clinical properties of NDNBs, comparative in vitro pharmacologic studies have been performed. In these studies, a receptor binding model, which relies on the assumption that the inhibition, i.e., the effect of an NDNB, is proportional to the receptor occupancy by the drug, has been effectively used to describe obtained experimental data. However, it has not been studied in literature under which conditions the above assumption can be justified nor the assumption still holds in vivo. The purpose of this study is to explore the in vivo relationship between the inhibition and the receptor occupancy by an NDNB and to draw implications on how in vitro experimental results can be used to discuss the in vivo properties of NDNBs.MethodsAn ordinary differential equation model is employed to simulate physiologic processes of the activation of receptors by acetylcholine (ACh) as well as inhibition by an NDNB. With this model, the degree of inhibition is quantified by the fractional amount of receptors that are not activated by ACh due to the presence of an NDNB. The results are visualized by plotting the fractional amounts of the activated receptors as a function of the receptor occupancy.ResultsNumerical investigations reflecting in vivo conditions show that the degree of inhibition is not proportional to the receptor occupancy, i.e., there is a nonlinear relationship between the inhibition and the receptor occupancy. However, under a setting of high concentration of ACh reflecting a typical situation of in vitro experiments, the relationship between the inhibition and the receptor occupancy becomes linear, suggesting the validity of the receptor binding model. Also, it is found that the extent of nonlinearity depends on the selectivity of NDNBs for the two binding sites of the receptors.ConclusionsWhile the receptor binding model may be effective for estimating affinity of an NDNB through in vitro experiments, these models do not directly describe in vivo properties of NDNBs, because the nonlinearity between the inhibition and the receptor occupancy causes the modulation of the resultant concentration-effect relationships of NDNBs.

Biperiden Challenge Model in Healthy Elderly as Proof-of-Pharmacology Tool: A Randomized, Placebo-Controlled Trial.

Selective M1 muscarinic acetylcholine receptor (mAChR) agonists are being developed as symptomatic treatment for neurodegenerative and neuropsychiatric disorders that lead to cognitive dysfunction. Demonstrating cognition‐enhancing effects in early‐phase clinical development in healthy subjects is difficult. A challenge with the M1 mAChR antagonist biperiden could be used to demonstrate procognitive and pharmacological effects of selective M1 mAChR agonists. The aim of this study was to develop such a model. To this end, 12 healthy elderly subjects participated in a randomized, placebo‐controlled, 3‐way crossover study investigating tolerability, pharmacokinetic (PK) and pharmacodynamic (PD) effects of 2 and 4 mg biperiden. Repeated PD assessments were performed using neurocognitive tasks and electrophysiological measurements. A population PK‐PD model was developed. Four milligrams of biperiden showed significant impairment of sustained attention (−2.1 percentage point in adaptive tracking [95%CI, −3.043 to −1.148], verbal memory (2‐3 fewer words recalled [95%CI, −5.9 to −0.2]) and working memory (up to a 50‐millisecond increase in the n‐back task reaction time [95%CI, 21.854‐77.882]) compared with placebo. The PK data were best fitted by a 2‐compartment model and showed high interoccasion and intersubject variability. Population PK‐PD analysis quantified significant concentration‐effect relationships for the n‐back reaction time, n‐back accuracy, and adaptive tracking. In conclusion, biperiden caused M1 mAChR‐related dose‐ and concentration‐dependent temporary declines in cognitive functioning. Therefore a biperiden pharmacological challenge model can be used for proof‐of‐pharmacology studies and to demonstrate cognition‐enhancing effects of new cholinergic compounds that are being developed.

Prednisolone in Dogs-Plasma Exposure and White Blood Cell Response.

Glucocorticoids such as prednisolone are commonly used in dogs but there is sparse quantitative pharmacokinetic and pharmacodynamic information of this drug in this species. The objective of this study was to quantitatively characterize the concentration-effect relationship for prednisolone in dogs on neutrophil and lymphocyte trafficking and cortisol suppression. Nine beagles, 2–12 years old and part of a group for teaching/research were used in a 4-way crossover experiment including two treatments, active or placebo, administered either per os (PO) or intravenously (IV). Plasma was analyzed for prednisolone and cortisol using ultra-high performance liquid chromatography – tandem mass spectrometry. Leucocyte counts were performed in whole blood. Data was then analyzed by non-linear mixed effect modeling to estimate pharmacokinetic and pharmacodynamic parameters. After administration of prednisolone sodium succinate IV, the typical value (between subject variation) for total body prednisolone clearance was 1,370 ml/h·kg (13.4%). The volumes of the central and peripheral compartment were 2,300 ml/kg (10.7%) and 600 ml/kg (16.0%), respectively. The terminal plasma half-life was 1.7 h. The prednisolone plasma concentration producing 50% of the maximum response was 10 ng/mL (90.3%), 22.5 ng/ml (52.3%) and 0.04 ng/mL (197.3%) for neutrophil, lymphocyte and cortisol response, respectively. The administered dose (1 mg/kg) increased neutrophil and decreased lymphocyte numbers but not over the entire dosage interval of 24 h, due to the short half-life. However, glucocorticoids have a wide range of responses. An anti-inflammatory response due to altered gene transcription might have a longer duration. Future studies on the anti-inflammatory potency together with data presented are needed to optimize future dosage recommendations in dogs.

Effects of Two PPCPs on Nitrification in Sediments in the Yarlung Zangbo River

To understand the effects of pharmaceuticals and personal care products (PPCPs) on nitrogen transformation in high-altitude rivers, we investigated the influence of the single and combined exposure of sulfamethoxazole (SMX) and 2-ethylhexyl-4-methoxycinnamate (EHMC) at different concentrations (0.01, 0.1, 1.0, 10, and 100 μg·L-1) on nitrification in the sediments of the Yarlung Zangbo River in sediment slurry experiments. All treatments significantly reduced nitrification rates, and the maximum inhibition rates induced by SMX and EHMC (alone and in combination) were 47%, 50%, and 66%, respectively. SMX significantly inhibited ammonia monooxygenase (AMO) activity in a concentration-dependent manner, with the inhibition rates ranging from 51% to 78%. The inhibitory effect of SMX combined with EHMC on AMO activity was similar to or stronger than that of SMX alone, and the inhibition rates ranged from 55% to 84%. All EHMC exposures also significantly inhibited AMO activity, but the inhibition rates decreased with an increase in EHMC concentrations. The amoA gene abundance was significantly reduced in all the treatments, and SMX alone and in combination with EHMC induced stronger inhibitory effects than EHMC alone. SMX alone and in combination with EHMC significantly inhibited HAO activity, showing a similar concentration-effect relationship, but their combined exposure produced a stronger effect. SMX alone and in combination with EHMC also significantly decreased hao gene abundance in the sediments, and the maximum inhibition rates were 76% and 68%, respectively. Although exposure to higher concentrations of EHMC increased hao gene abundance and HAO activity, the notable decrease in nitrification rates in the sediments suggested that oxidation of ammonia to hydroxylamine catalyzed by AMO was the rate-limiting step in the nitrification process. The results also showed that PPCPs influence the activities of nitrifying communities in the sediments of high-altitude rivers and inhibit nitrification, and their coexistence further increases the pressure of nitrogen loading in aquatic ecosystems.

Development and Validation of an Up-to-Date Highly Sensitive UHPLC-MS/MS Method for the Simultaneous Quantification of Current Anti-HIV Nucleoside Analogues in Human Plasma.

Therapeutic options to treat HIV infection have widened in the past years, improving both effectiveness and tolerability, but nucleoside reverse transcriptase inhibitors (NRTIs) are still considered the standard backbone of the combination regimens. Therapeutic drug monitoring (TDM) can be useful for these drugs, due to concentration–effect relationship, with risk of ineffectiveness, toxicity or adherence concerns: in this scenario, robust and multiplexed methods are needed for an effective TDM activity. In this work, the first validated ultra-high spectrometry liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) method is described for the high-sensitive simultaneous quantification of all the currently used NRTIs in human plasma, including tenofovir alafenamide (TAF), following FDA and EMA guidelines. The automated sample preparation consisted in the addition of an internal standard (IS) working solution, containing stable-isotope-linked drugs, protein precipitation and drying. Dry extracts were reconstituted with water, then, these underwent reversed phase chromatographic separation: compounds were detected through electrospray ionization and multiple reaction monitoring. Accuracy, precision, recovery and IS-normalized matrix effect fulfilled guidelines’ requirements. The application of this method on samples from people living with HIV (PLWH) showed satisfactory performance, being capable of quantifying the very low concentrations of tenofovir (TFV) in patients treated with TAF.

501 Clinical PK of XW10172 for Once Nightly Therapy in Patients with Narcolepsy or Sleep Disorders in Neurodegenerative Diseases

Abstract Introduction Patients with narcolepsy and patients with sleep disorders secondary to neurodegenerative diseases have been shown to respond to oxybate. To overcome the limitations of current oxybate therapies, we designed XW10172, a new chemical entity and GABA-B agonist with no sodium or other cation content and for once nightly dosing. The objectives of two clinical studies were to assess the XW10172 pharmacokinetics (PK), pharmacodynamics (PD) and safety/tolerability in normal study participants. Methods Two XW10172 studies in healthy participants assessed ascending single and multiple doses, comparison to sodium oxybate in immediate release (IR) and extended release (ER) formulations. PK parameters were calculated from concentration vs. time data. Safety and tolerability were assessed by monitoring adverse events, laboratory tests, and vital signs. Results To date, 84 study participants received XW10172 and the PK from single and multiple dose administration showed doses of 0.1 to 7.25 g had a mean oxybate half-life range of 0.5 to 1.3 hours. Oxybate levels from the drug were about 6-fold higher than XW10172 levels. Oxybate PK from XW10172 (IR) was the same as from equal molar doses of sodium oxybate. XW10172 (ER) formulations showed delayed Tmax with extended oxybate exposure compatible with single nightly dose therapy. PK-PD assessment of somnolence, the desired pharmacologic effect, showed a concentration-effect relationship (Cmax p=0.0004, AUC p<0.0001). XW10172 was generally well tolerated and adverse events were those known to be associated with oxybate. Conclusion These data support progression of XW10172 (ER) in further clinical development studies to assess this once nightly GABA-B agonist therapy for the treatment of patients with various sleep disorders. Support (if any) XWPharma

Evaluation of Hydroxychloroquine Blood Concentrations and Effects in Childhood-Onset Systemic Lupus Erythematosus.

Background: Hydroxychloroquine (HCQ) is an antimalarial agent given to patients with systemic lupus erythematosus (SLE) as first-line therapy. It alleviates childhood-onset systemic lupus erythematosus cSLE skin and musculoskeletal disease, decreasing disease activity and flares. HCQ concentration–effect relationships in children remains unknown. This study aimed to investigate the pharmacokinetics of HCQ and possible concentration–effect relationships. Methods: HCQ blood concentrations and effects were obtained during clinical follow-up on different occasions. cSLE flares were defined using the SLE Disease Activity Index (SLEDAI); flare was denoted by a SLEDAI score > 6. Blood concentration was measured using high-performance liquid chromatography with fluorometric detection. Statistical analysis was performed using a nonlinear mixed-effect approach with the Monolix software. Results: A total of 168 blood samples were obtained from 55 pediatric patients. HCQ apparent blood clearance (CL/F) was dependent on patients’ bodyweight and platelet count. Patients with active cSLE had a lower mean blood HCQ concentration compared with inactive cSLE patients (536 ± 294 vs. 758 ± 490 ng/mL, p = 5 × 10−6). Among patients with HCQ blood concentration ≥750 ng/mL, 87.6% had inactive cSLE. Moreover, HCQ blood concentration was a significant predictor of disease status. Conclusion: We developed the first HCQ blood concentration–effect relationship for cSLE associated with active or non-active disease status. A prospective randomized study is necessary to confirm these results.

Population Pharmacodynamic Modeling Using the Sigmoid Emax Model: Influence of Inter-individual Variability on the Steepness of the Concentration\u2013Effect Relationship. a Simulation Study

The relationship between the concentration of a drug and its pharmacological effect is often described by empirical mathematical models. We investigated the relationship between the steepness of the concentration–effect relationship and inter-individual variability (IIV) of the parameters of the sigmoid Emax model, using the similarity between the sigmoid Emax model and the cumulative log-normal distribution. In addition, it is investigated whether IIV in the model parameters can be estimated accurately by population modeling. Multiple data sets, consisting of 40 individuals with 4 binary observations in each individual, were simulated with varying values for the model parameters and their IIV. The data sets were analyzed using Excel Solver and NONMEM. An empirical equation (Eq. (11)) was derived describing the steepness of the population-predicted concentration–effect profile (γ*) as a function of γ and IIV in C50 and γ, and was validated for both binary and continuous data. The tested study design is not suited to estimate the IIV in C50 and γ with reasonable precision. Using a naive pooling procedure, the population estimates γ* are significantly lower than the value of γ used for simulation. The steepness of the population-predicted concentration–effect relationship (γ*) is less than that of the individuals (γ). Using γ*, the population-predicted drug effect represents the drug effect, for binary data the probability of drug effect, at a given concentration for an arbitrary individual.

Clinical phenotype and risk factors for severe efavirenz-associated neurotoxicity amongst inpatients in Cape Town, South Africa

Background: Efavirenz, widely used as first line antiretroviral therapy (ART), is frequently associated with mild transient neuropsychiatric symptoms, usually occurring early in therapy. More severe neurotoxicity has been reported, but the clinical phenotype and risk factors are poorly defined. Methods and materials: We identified adult patients with an efavirenz concentration >4 mg/L (target 1–4 mg/L) at four hospitals in Cape Town, South Africa. Data were extracted from medical records, including clinical symptoms and signs and laboratory abnormalities at the time of efavirenz quantification; severe neurotoxicity was defined as Division of AIDS score > 3. We performed logistic regression to identify associations with neuropsychiatric symptoms and severe neurotoxicity. Results: Data were included from 82 patients: 62 had neuropsychiatric symptoms, 19 had hepatitis, and 1 had no apparent indication for efavirenz quantification. Median age was 38 years (interquartile range (IQR) 29–45), median weight 53 kg (IQR 44–63), 29 (34%) were male, and 49 (63%) patients had concomitant isoniazid exposure. Median efavirenz concentration was 12.1 mg/L (IQR 6.6–20.0). Neuropsychiatric manifestations included ataxia (n = 20) and other cerebellar signs (n = 13), psychomotor slowing (n = 24), psychosis (n = 17), mood disturbance (n = 11), and insomnia/sleep disturbance (n = 4). Compared with hepatitis, neurotoxicity was associated with male sex (adjusted odds ratio (aOR) 20.0, 95% CI 2.0–199.9), higher efavirenz concentrations (aOR 1.2 per 1 mg/L increase, 95% CI 1.0–1.4) and isoniazid exposure (aOR 5.1, 95% CI 1.1–23.5). Severe neuropsychiatric symptoms occurred in 47 (75%) patients with neurotoxicity, after a median of 25 weeks (IQR 9–175) on efavirenz-based ART. Median efavirenz concentration was 20.0 mg/L (the upper limit of assay detection, IQR 13.0–20.0) in those with severe versus 7.0 mg/L (4.5–11.8) in those with mild neurotoxicity (p < 0.01). Amongst patients with severe neurotoxicity, there was complete resolution of symptoms within 1 month in 29/31 (94%) who discontinued efavirenz and in 2/5 (40%) who underwent dose-reduction. 3-month mortality was 11% (n = 45) for patients with severe neurotoxicity. Conclusion: Cerebellar signs were the most frequent clinical manifestation of efavirenz-associated neurotoxicity. There was a concentration-effect relationship for severe neurotoxicity, which occurred late and resolved in most patients after efavirenz discontinuation.

Anti-tuberculosis effect of isoniazid scales accurately from zebrafish to humans.

Background and PurposeThere is a clear need for innovation in anti‐tuberculosis drug development. The zebrafish larva is an attractive disease model in tuberculosis research. To translate pharmacological findings to higher vertebrates, including humans, the internal exposure of drugs needs to be quantified and linked to observed response.Experimental ApproachIn zebrafish studies, drugs are usually dissolved in the external water, posing a challenge to quantify internal exposure. We developed experimental methods to quantify internal exposure, including nanoscale blood sampling, and to quantify the bacterial burden, using automated fluorescence imaging analysis, with isoniazid as the test compound. We used pharmacokinetic–pharmacodynamic modelling to quantify the exposure–response relationship responsible for the antibiotic response. To translate isoniazid response to humans, quantitative exposure–response relationships in zebrafish were linked to simulated concentration–time profiles in humans, and two quantitative translational factors on sensitivity to isoniazid and stage of infection were included.Key ResultsBlood concentration was only 20% of the external drug concentration. The bacterial burden increased exponentially, and an isoniazid dose corresponding to 15 mg·L−1 internal concentration (minimum inhibitory concentration) leads to bacteriostasis of the mycobacterial infection in the zebrafish. The concentration–effect relationship was quantified, and based on that relationship and the translational factors, the isoniazid response was translated to humans, which correlated well with observed data.Conclusions and ImplicationsThis proof of concept study confirmed the potential of zebrafish larvae as tuberculosis disease models in translational pharmacology and contributes to innovative anti‐tuberculosis drug development, which is very clearly needed.

Incorporating Pharmacometrics into Pharmacoeconomic Models: Applications from Drug Development.

Pharmacometrics is the science of quantifying the relationship between the pharmacokinetics and pharmacodynamics of drugs in combination with disease models and trial information to aid in drug development and dosing optimization for clinical practice. Considering the variability in the dose–concentration–effect relationship of drugs, an opportunity exists in linking pharmacokinetic and pharmacodynamic model-based estimates with pharmacoeconomic models. This link may provide early estimates of the cost effectiveness of drug therapies, thus informing late-stage drug development, pricing, and reimbursement decisions. Published case studies have demonstrated how integrated pharmacokinetic–pharmacodynamic–pharmacoeconomic models can complement traditional pharmacoeconomic analyses by identifying the impact of specific patient sub-groups, dose, dosing schedules, and adherence on the cost effectiveness of drugs, thus providing a mechanistic basis to predict the economic value of new drugs. Greater collaboration between the pharmacoeconomics and pharmacometrics community can enable methodological improvements in pharmacokinetic–pharmacodynamic–pharmacoeconomic models to support drug development.

Antimicrobial and time-kill kinetics of the aqueous extract of Citrullus lanatus (Thunb.) seeds

This study evaluated the antimicrobial property of the aqueous extract of Citrullus lanatus (watermelon) seeds and its concentration-effect relationship (time-kill studies) on typed bacterial and fungal strains. Crude powdered seeds of Citrullus lanatus were extracted by maceration with water. Antimicrobial assay of the aqueous extracts was determined against Bacillus subtilis (NCTC 8236), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 10145), Staphylococcus aureus (ATCC 25923), and Candida albicans (ATCC 24433) using standard microbiological methods. A total of 106 CFU/mL of each test strain was used as a baseline to carry out the time-kill studies. Extract concentration at minimum inhibitory concentration (MIC), 2MIC and 4MIC were used over a period of 24 hours. Aqueous extract had an intermediate antibacterial activity with inhibition zone diameters (IZD) of 15 - 18 mm and MIC range of 2.5 - 20 mg/mL. Time-kill studies showed a bacteriostatic, non-concentration dependent mode of antimicrobial activity with characteristic regrowth for all test strains. Citrullus lanatus seeds aqueous extract exhibited antimicrobial activity with a bacteriostatic, non-concentration dependent mode of action against test bacterial strains. Further studies aimed at isolating and purifying the antimicrobial principle in the aqueous extract of C. lanatus seed is warranted as this could serve as a potential new antibiotic for treating microbial infections.

Development and application of an LC-MS/MS method for determining methylsulfonylmethane (MSM) levels in human plasma

Methylsulfonylmethane (MSM) isan organosulfur phytochemical widely used as a dietary supplement carrying structure/function claims that includethe promotion of joint health. Untargeted metabolomics studies using nuclear magnetic resonance (NMR) have identified MSM in plasma and urine. However, MS-based methodology is more suitable for pharmacokinetic studies designed to explore MSM’s concentration-effect relationship for purposes of establishing dosing guidelines. To address this deficiency, an LC-MS/MS method using MSM, deuterated MSM (MSM-d6, internal standard), and liquid-liquid extraction was developed and validated in accordance with international guidelines. The method proved well-suited for determining MSM levels in human plasma following chronic oral administration (1, 2, or 3 grams daily) for four weeks. The availability of a robust LC-MS/MS method and MSM dose linearity data provides a framework for exploring MSM’s concentration-effect relationship to support various structure/function claims.

Inducibility of cytochrome P450-mediated 7-methoxycoumarin-O-demethylase activity in zebrafish (Danio rerio) embryos

The zebrafish (Danio rerio) embryo has increasingly been used as an alternative model in human and environmental toxicology. Since the cytochrome P450 (CYP) system is of fundamental importance for the understanding and correct interpretation of the outcome of toxicological studies, constitutive and xenobiotic-induced 7-methoxycoumarin-O-demethylase (MCOD), i.e. ‘mammalian CYP2-like’, activities were monitored in vivo in zebrafish embryos via confocal laser scanning microscopy. In order to elucidate molecular mechanisms underlying the MCOD induction, dose-dependent effects of the prototypical CYP inducers β-naphthoflavone (aryl hydrocarbon receptor (AhR) agonist), rifampicin (pregnane X receptor (PXR) agonist), carbamazepine and phenobarbital (constitutive androstane receptor (CAR) agonists) were analyzed in zebrafish embryos of varying age.Starting from 36 h of age, all embryonic stages of zebrafish could be shown to have constitutive MCOD activity, albeit with spatial variation and at distinct levels. Whereas carbamazepine, phenobarbital and rifampicin had no effect on in vivo MCOD activity in 96 h old zebrafish embryos, the model aryl hydrocarbon receptor agonist β-naphthoflavone significantly induced MCOD activity in 96 h old zebrafish embryos at 46–734 nM, however, without a clear concentration-effect relationship. Induction of MCOD activity by β-naphthoflavone gradually decreased with progression of embryonic development. By in vivo characterization of constitutive and xenobiotic-induced MCOD activity patterns in 36, 60, 84 and 108 h old zebrafish embryos, this decrease could primarily be attributed to an age-related decline in the induction of MCOD activity in the cardiovascular system. Results of this study provide novel insights into the mechanism and extent, by which specific CYP activities in early life-stages of zebrafish can be influenced by exposure to xenobiotics. The study thus lends further support to the view that zebrafish embryos– at least from an age of 36 h – have an elaborate and inducible biotransformation system.

In Vitro and In Vivo Efficacy of AZD3965 and Alpha-Cyano-4-Hydroxycinnamic Acid in the Murine 4T1 Breast Tumor Model

Monocarboxylate transporter 1 (MCT1) represents a potential therapeutic target in cancer. The objective of this study was to determine the efficacy of AZD3965 (a specific inhibitor of MCT1) and α-cyano-4-hydroxycinnamic acid (CHC, a nonspecific inhibitor of MCTs) in the murine 4T1 tumor model of triple-negative breast cancer (TNBC). Expression of MCT1 and MCT4 in 4T1 and mouse mammary epithelial cells were determined by Western blot. Inhibition of MCT1-mediated L-lactate uptake and cellular proliferation by AZD3965 and CHC was determined. Mice bearing 4T1 breast tumors were treated with AZD3965 100mg/kg i.p. twice-daily or CHC 200mg/kg i.p. once-daily. Tumor growth, metastasis, intra-tumor lactate concentration, immune function, tumor MCT expression, and concentration-effect relationships were determined. AZD3965 and CHC inhibited cell growth and L-lactate uptake in 4T1 cells. AZD3965 treatment resulted in trough plasma and tumor concentrations of 29.1 ± 13.9 and 1670 ± 946nM, respectively. AZD3965 decreased the tumor proliferation biomarker Ki67 expression, increased intra-tumor lactate concentration, and decreased tumor volume, although tumor weight was not different from untreated controls. CHC had no effect on tumor volume and weight, or intra-tumor lactate concentration. AZD3965 treatment reduced the blood leukocyte count and spleen weight and increased lung metastasis, while CHC did not. These findings indicate AZD3965 is a potent MCT1 inhibitor that accumulates to high concentrations in 4T1 xenograft tumors, where it increases tumor lactate concentrations and produces beneficial effects on markers of TNBC; however, overall effects on tumor growth were minimal and lung metastases increased.

An in vivo study of nanorod, nanosphere, and nanowire forms of titanium dioxide using Drosophila melanogaster: toxicity, cellular uptake, oxidative stress, and DNA damage

ABSTRACT The biological impact of nanomaterials (NMs) is determined by several factors such as size and shape, which need to be taken into consideration in any type of analysis. While investigators often prefer to conduct in vitro studies for detection of any possible adverse effects of NMs, in vivo approaches yield more relevant data for risk assessment. For this reason, Drosophila melanogaster was selected as a suitable in vivo model to characterize the potential risks associated with exposure nanorods (NRs), nanospheres (NSs), nanowires (NWs) forms of titanium dioxide (TiO2), and their microparticulated (or bulk) form, as TiO2. Third instar larvae (72 hr old larvae) were fed with TiO2 (NRs, NSs, or NWs) and TiO2 at concentrations ranging from 0.01 to 10 mM. Viability (toxicity), internalization (cellular uptake), intracellular reactive oxygen species (ROS) production, and genotoxicity (Comet assay) were the end-points evaluated in hemocyte D. melanogaster larvae. Significant intracellular oxidative stress and genotoxicity were noted at the highest exposure concentration (10 mM) of TiO2 (NRs, NSs, or NWs), as determined by the Comet assay and ROS analysis, respectively. A concentration–effect relationship was observed in hemocytes exposed to the NMs. Data demonstrated that selected forms of TiO2.-induced genotoxicity in D. melanogaster larvae hemocytes indicating this organism is susceptible for use as a model to examine in vivo NMs-mediated effects.

Exploring the Relationship Between Morphine Concentration and Oversedation in Children After Cardiac Surgery.

Titrating analgesic and sedative drugs in pediatric intensive care remains a challenge for caregivers due to the lack of pharmacodynamic knowledge in this population. The aim of the current study is to explore the concentration‐effect relationship for morphine‐associated oversedation after cardiac surgery in children aged 3 months to 3 years. Data on morphine dosing, as well as morphine plasma concentrations, were available from a previous study on the pharmacokinetics of morphine after cardiac surgery in children. Oversedation was defined as scores below 11 on the validated COMFORT–behavioral scale. Population pharmacokinetic‐pharmacodynamic modeling was performed in NONMEM 7.3. The probability of oversedation as a function of morphine concentration was best described using a step function in which the EC50 was 46.3 ng/mL. At morphine concentrations below the EC50, the probability of oversedation was 2.9% (0.4& to 18%), whereas above the EC50 percentages were 13% (1.9% to 52%) (median value [95% prediction interval from interindividual variability]). Additionally, the risk of oversedation was found to be increased during the first hours after surgery (P < .001) and was significantly lower during mechanical ventilation (P < .005). We conclude that morphine concentrations above approximately 45 ng/mL may increase the probability of oversedation in children after cardiac surgery. The clinician must evaluate, on a case‐by‐case basis, whether the analgesic benefits arising from dosing regimen associated with such concentrations outweigh the risks.

The FcγRIIIA-158 VV genotype increased the risk of post-transplant lymphoproliferative disorder in T-cell-depleted kidney transplant recipients - a retrospective study.

Post-transplantation lymphoproliferative disorder (PTLD) is a severe complication in organ transplant recipients. The use of T lymphocyte-depleting antibodies (TLDAb), especially rabbit TLDAb, contributes to PTLD, and the V158F polymorphism of Fc gamma receptor IIIA (FcγRIIIA) also named CD16A could affect the concentration-effect relationship of TLDAb. We therefore investigated the association of this polymorphism with PTLD in kidney transplant recipients. We characterized the V158F polymorphism in two case-control cohorts (discovery, n=196; validation, n=222). Then, we evaluated the binding of rabbit IgG to human FcγRIIIA-158V and FcγRIIIA-158F. The V158F polymorphism was not linked to PTLD in the overall cohorts, but risk of PTLD was increased in VV homozygous recipients receiving TLDAb compared with F carriers in both cohorts, especially in recipients receiving TLDAb without muromonab (discovery: HR=2.22 [1.03-4.76], P=0.043, validation: HR=1.75 [1.01-3.13], P=0.049). In vitro, we found that the binding of rabbit IgG to human NK-cell FcγRIIIA was increased when cells expressed the 158-V versus the 158-F allotype. While the 158-V allotype of human FcγRIIIA binds rabbit immunoglobulin-G with higher affinity, the risk of PTLD was increased in homozygous VV kidney transplant recipients receiving polyclonal TLDAb.

Quantification of the endogenous growth hormone and prolactin lowering effects of a somatostatin-dopamine chimera using population PK/PD modeling

A phase 1 clinical trial in healthy male volunteers was conducted with a somatostatin-dopamine chimera (BIM23B065), from which information could be obtained on the concentration-effect relationship of the inhibition of pulsatile endogenous growth hormone and prolactin secretion. Endogenous growth hormone profiles were analyzed using a two-step deconvolution-analysis-informed population pharmacodynamic modeling approach, which was developed for the analyses of pulsatile profiles. Prolactin concentrations were modelled using a population pool model with a circadian component on the prolactin release. During treatment with BIM23B065, growth hormone secretion was significantly reduced (maximal effect [EMAX] = − 64.8%) with significant reductions in the pulse frequency in two out of three multiple ascending dose cohorts. A circadian component in prolactin secretion was identified, modelled using a combination of two cosine functions with 24 h and 12 h periods. Dosing of BIM23B065 strongly inhibited (EMAX = − 91%) the prolactin release and demonstrated further reduction of prolactin secretion after multiple days of dosing. This study quantified the concentration-effect relationship of BIM23B065 on the release of two pituitary hormones, providing proof of pharmacology of the chimeric actions of BIM23B065.

Mathematical modeling and parameter estimation of levodopa motor response in patients with parkinson disease

Parkinson disease (PD) is characterized by a clear beneficial motor response to levodopa (LD) treatment. However, with disease progression and longer LD exposure, drug-related motor fluctuations usually occur. Recognition of the individual relationship between LD concentration and its effect may be difficult, due to the complexity and variability of the mechanisms involved. This work proposes an innovative procedure for the automatic estimation of LD pharmacokinetics and pharmacodynamics parameters, by a biologically-inspired mathematical model. An original issue, compared with previous similar studies, is that the model comprises not only a compartmental description of LD pharmacokinetics in plasma and its effect on the striatal neurons, but also a neurocomputational model of basal ganglia action selection. Parameter estimation was achieved on 26 patients (13 with stable and 13 with fluctuating LD response) to mimic plasma LD concentration and alternate finger tapping frequency along four hours after LD administration, automatically minimizing a cost function of the difference between simulated and clinical data points. Results show that individual data can be satisfactorily simulated in all patients and that significant differences exist in the estimated parameters between the two groups. Specifically, the drug removal rate from the effect compartment, and the Hill coefficient of the concentration-effect relationship were significantly higher in the fluctuating than in the stable group. The model, with individualized parameters, may be used to reach a deeper comprehension of the PD mechanisms, mimic the effect of medication, and, based on the predicted neural responses, plan the correct management and design innovative therapeutic procedures.