57 research outputs found

    Partitioning and Spatial Distribution of Drugs in Ocular Surface Tissues

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    Ocular drug absorption after eye drop instillation has been widely studied, but partitioning phenomena and spatial drug distribution are poorly understood. We investigated partitioning of seven beta-blocking drugs in corneal epithelium, corneal stroma, including endothelium and conjunctiva, using isolated porcine tissues and cultured human corneal epithelial cells. The chosen beta-blocking drugs had a wide range (-1.76-0.79) of n-octanol/buffer solution distribution coefficients at pH 7.4 (Log D-7.4). In addition, the ocular surface distribution of three beta-blocking drugs was determined by matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) after their simultaneous application in an eye drop to the rabbits in vivo. Studies with isolated porcine corneas revealed that the distribution coefficient (K-p) between the corneal epithelium and donor solution showed a positive relationship and good correlation with Log D-7.4 and about a 50-fold range of K-p values (0.1-5). On the contrary, K-p between corneal stroma and epithelium showed an inverse (negative) relationship and correlation with Log D-7.4 based on a seven-fold range of K-p values. In vitro corneal cell uptake showed a high correlation with the ex vivo corneal epithelium/donor K-p values. Partitioning of the drugs into the porcine conjunctiva also showed a positive relationship with lipophilicity, but the range of K-p values was less than with the corneal epithelium. MALDI-IMS allowed simultaneous detection of three compounds in the cornea, showed data in line with other experiments, and revealed uneven spatial drug distribution in the cornea. Our data indicate the importance of lipophilicity in defining the corneal pharmacokinetics and the K-p values are a useful building block in the kinetic simulation models for topical ocular drug administration.Peer reviewe

    Ocular intracameral pharmacokinetics for a cocktail of timolol, betaxolol and atenolol in rabbits

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    The mechanisms of drug clearance from the aqueous humor are poorly defined. In this study, a cocktail approach was used to simultaneously determine the pharmacokinetics of three β-blocker agents after intracameral (ic) injection into the rabbit eyes. Aqueous humor samples were collected and analyzed using LC–MS/MS to determine drug concentrations. Pharmacokinetic parameters were obtained using a compartmental fitting approach, and the estimated clearance, volume of distribution, and half-life values were the following: atenolol (6.44 μL/min, 687 μL, and 73.87 min), timolol (19.30 μL/min, 937 μL, and 33.64 min), and betaxolol (32.20 μL/min, 1421 μL, and 30.58 min). Increased compound lipophilicity (atenolol < timolol < betaxolol) resulted in higher clearance and volume of distributions in the aqueous humor. Clearance of timolol and betaxolol is about 10 times higher than the aqueous humor outflow, demonstrating the importance of other elimination routes (e.g., uptake to iris and ciliary body and subsequent elimination via blood flow)

    Ocular pharmacokinetics of atenolol, timolol and betaxolol cocktail : Tissue exposures in the rabbit eye

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    Quantitative understanding of pharmacokinetics of topically applied ocular drugs requires more research to further understanding and to eventually allow predictive in silico models to be developed. To this end, a topical cocktail of betaxolol, timolol and atenolol was instilled on albino rabbit eyes. Tear fluid, corneal epithelium, corneal stroma with endothelium, bulbar conjunctiva, anterior sclera, iris-ciliary body, lens and vitreous samples were collected and analysed using LC-MS/MS. Iris-ciliary body was also analysed after intracameral cocktail injection. Non-compartmental analysis was utilized to estimate the pharmacokinetics parameters. The most lipophilic drug, betaxolol, presented the highest exposure in all tissues except for tear fluid after topical administration, followed by timolol and atenolol. For all drugs, iris-ciliary body concentrations were higher than that of the aqueous humor. After topical instillation the most hydrophilic drug, atenolol, had 3.7 times higher AUCiris-ciliary body than AUCaqueous humor, whereas the difference was 1.4 and 1.6 times for timolol and betaxolol, respectively. This suggests that the non-corneal route (conjunctival-scleral) was dominating the absorption of atenolol, while the corneal route was more important for timolol and betaxolol. The presented data increase understanding of ocular pharmacokinetics of a cocktail of drugs and provide data that can be used for quantitative modeling and simulation.Peer reviewe

    Methylation status of VTRNA2-1/nc886 is stable across populations, monozygotic twin pairs and in majority of tissues

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    Aims & methods: The aim of this study was to characterize the methylation level of a polymorphically imprinted gene, VTRNA2-1/nc886, in human populations and somatic tissues.48 datasets, consisting of more than 30 tissues and >30,000 individuals, were used. Results: nc886 methylation status is associated with twin status and ethnic background, but the variation between populations is limited. Monozygotic twin pairs present concordant methylation, whereas similar to 30% of dizygotic twin pairs present discordant methylation in the nc886 locus. The methylation levels of nc886 are uniform across somatic tissues, except in cerebellum and skeletal muscle. Conclusion: The nc886 imprint may be established in the oocyte, and, after implantation, the methylation status is stable, excluding a few specific tissues. Tweetable abstract Methylation status of a polymorphically imprinted gene, VTRNA2-1/nc886, is stable in human populations (48 cohorts, n > 30,000) and in somatic tissues, except in cerebellum and skeletal muscle. Twin data suggest it may already be established in the oocyte.Peer reviewe

    Investigating stratospheric changes between 2009 and 2018 with halogenated trace gas data from aircraft, AirCores, and a global model focusing on CFC-11

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    We present new observations of trace gases in the stratosphere based on a cost-effective sampling technique that can access much higher altitudes than aircraft. The further development of this method now provides detection of species with abundances in the parts per trillion (ppt) range and below. We obtain mixing ratios for six gases (CFC-11, CFC-12, HCFC-22, H-1211, H-1301, and SF6), all of which are important for understanding stratospheric ozone depletion and circulation. After demonstrating the quality of the data through comparisons with ground-based records and aircraft-based observations, we combine them with the latter to demonstrate its potential. We first compare the data with results from a global model driven by three widely used meteorological reanalyses. Secondly, we focus on CFC-11 as recent evidence has indicated renewed atmospheric emissions of that species relevant on a global scale. Because the stratosphere represents the main sink region for CFC-11, potential changes in stratospheric circulation and troposphere–stratosphere exchange fluxes have been identified as the largest source of uncertainty for the accurate quantification of such emissions. Our observations span over a decade (up until 2018) and therefore cover the period of the slowdown of CFC-11 global mixing ratio decreases measured at the Earth's surface. The spatial and temporal coverage of the observations is insufficient for a global quantitative analysis, but we do find some trends that are in contrast with expectations, indicating that the stratosphere may have contributed to the slower concentration decline in recent years. Further investigating the reanalysis-driven model data, we find that the dynamical changes in the stratosphere required to explain the apparent change in tropospheric CFC-11 emissions after 2013 are possible but with a very high uncertainty range. This is partly caused by the high variability of mass flux from the stratosphere to the troposphere, especially at timescales of a few years, and partly by large differences between runs driven by different reanalysis products, none of which agree with our observations well enough for such a quantitative analysis

    Pharmacokinetic aspects of retinal drug delivery

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    Drug delivery to the posterior eye segment is an important challenge in ophthalmology, because many diseases affect the retina and choroid leading to impaired vision or blindness. Currently, intravitreal injections are the method of choice to administer drugs to the retina, but this approach is applicable only in selected cases (e.g. anti-VEGF antibodies and soluble receptors). There are two basic approaches that can be adopted to improve retinal drug delivery: prolonged and/or retina targeted delivery of intravitreal drugs and use of other routes of drug administration, such as periocular, suprachoroidal, sub-retinal, systemic, or topical. Properties of the administration route, drug and delivery system determine the efficacy and safety of these approaches. Pharmacokinetic and pharmacodynamic factors determine the required dosing rates and doses that are needed for drug action. In addition, tolerability factors limit the use of many materials in ocular drug delivery. This review article provides a critical discussion of retinal drug delivery, particularly from the pharmacokinetic point of view. This article does not include an extensive review of drug delivery technologies, because they have already been reviewed several times recently. Instead, we aim to provide a systematic and quantitative view on the pharmacokinetic factors in drug delivery to the posterior eye segment. This review is based on the literature and unpublished data from the authors' laboratory.Peer reviewe

    Common breast cancer susceptibility alleles are associated with tumor subtypes in BRCA1 and BRCA2 mutation carriers : results from the Consortium of Investigators of Modifiers of BRCA1/2.

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    Abstract Introduction Previous studies have demonstrated that common breast cancer susceptibility alleles are differentially associated with breast cancer risk for BRCA1 and/or BRCA2 mutation carriers. It is currently unknown how these alleles are associated with different breast cancer subtypes in BRCA1 and BRCA2 mutation carriers defined by estrogen (ER) or progesterone receptor (PR) status of the tumour. Methods We used genotype data on up to 11,421 BRCA1 and 7,080 BRCA2 carriers, of whom 4,310 had been affected with breast cancer and had information on either ER or PR status of the tumour, to assess the associations of 12 loci with breast cancer tumour characteristics. Associations were evaluated using a retrospective cohort approach. Results The results suggested stronger associations with ER-positive breast cancer than ER-negative for 11 loci in both BRCA1 and BRCA2 carriers. Among BRCA1 carriers, single nucleotide polymorphism (SNP) rs2981582 (FGFR2) exhibited the biggest difference based on ER status (per-allele hazard ratio (HR) for ER-positive = 1.35, 95% CI: 1.17 to 1.56 vs HR = 0.91, 95% CI: 0.85 to 0.98 for ER-negative, P-heterogeneity = 6.5 &#215; 10-6). In contrast, SNP rs2046210 at 6q25.1 near ESR1 was primarily associated with ER-negative breast cancer risk for both BRCA1 and BRCA2 carriers. In BRCA2 carriers, SNPs in FGFR2, TOX3, LSP1, SLC4A7/NEK10, 5p12, 2q35, and 1p11.2 were significantly associated with ER-positive but not ER-negative disease. Similar results were observed when differentiating breast cancer cases by PR status. Conclusions The associations of the 12 SNPs with risk for BRCA1 and BRCA2 carriers differ by ER-positive or ER-negative breast cancer status. The apparent differences in SNP associations between BRCA1 and BRCA2 carriers, and non-carriers, may be explicable by differences in the prevalence of tumour subtypes. As more risk modifying variants are identified, incorporating these associations into breast cancer subtype-specific risk models may improve clinical management for mutation carriers
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