HPLC-MS/MS determination of a hardly soluble drug in human urine through drug-albumin binding assisted dissolution.

ABT-263 is under development for treatment of cancer. In order to support clinical trials, an analytical method for ABT-263 quantification in human urine became necessary. Due to the extremely poor solubility of ABT-263 in aqueous and most common organic solvents, a critical step was to dissolve the drug into urine matrix. Although other potential approaches could be used, addition of powder albumin was found to be the most advantageous. Albumin powder does not significantly alter urine sample volume (< or = 2.8%) and a range of albumin to urine sample volume ratios can be allowed for full recovery of drug and thus accurate quantification. The procedure is fairly simple and can potentially be a universal approach for compounds with low solubility in urine, but strong protein binding. The method has been validated to support clinical trials.

The effect of hepatic insufficiency on the safety and pharmacokinetics of paricalcitol (Zemplar).

BACKGROUND/AIMS: Paricalcitol is highly protein bound, extensively metabolized and eliminated primarily by hepatobiliary excretion. This study was designed to determine if hepatic disease alters the pharmacokinetics or affects the safety of paricalcitol. METHODS: Subjects with mild (n = 5) or moderate (n = 5) hepatic impairment, and subjects with normal hepatic function (n = 10) enrolled in and completed the study. Each subject was administered a single 0.24 microg/kg intravenous dose of paricalcitol, injected within 1 min. RESULTS: For both total and unbound paricalcitol, there were no statistically significant differences in the pairwise comparisons between hepatic function groups in paricalcitol concentration at 5 min postdose (C5) or area under the plasma concentration-time curve from time zero to infinity (AUC(0-infinity), except C5 of total paricalcitol between mild and moderate impairment groups (p = 0.02). Paricalcitol binding to plasma proteins was extensive in all hepatic function groups (mean values >99.7%); unbound fraction was greater in subjects with moderate impairment than either healthy subjects or subjects with mild impairment (p < 0.01). Paricalcitol appeared to be well tolerated both by healthy subjects and subjects with mild to moderate hepatic insufficiency. CONCLUSION: No adjustment of paricalcitol dose is required for subjects with mild to moderate hepatic impairment. However, caution should be exercised in extrapolating the results from this study to subjects with severe hepatic impairment.

Detection and subcellular localization of two 15S-lipoxygenases in human cornea.

PURPOSE: There are two human 15-lipoxygenases (LOX), 15-LOX-1 and -2, which convert arachidonic acid to 15S-hydroxyeicosatetraenoic acid (15S-HETE). The presence of both 15-LOXs in the human cornea prompted this study to delineate their roles in the human corneal epithelium. METHODS: Human corneal epithelia from donor corneas and a human corneal epithelial (HCE) cell line were used in [1-(14)C]arachidonic acid incubations, Western blot analysis, and quantitative real-time RT-PCR. Cell cultures of HCE were treated with 15S-HETE to measure its effect on cell growth. HCE cells were transfected with plasmids to express green fluorescent (GFP) fusion proteins of 15-LOX-1 and -2, and in vivo laser confocal microscopy was performed to determine the subcellular localization of the 15-LOX fusion proteins. RESULTS: [1-(14)C]Arachidonic acid incubations yielded 15S-HETE as the only LOX product. Treatment with 15S-HETE (5-10 microM) reduced growth rate and induced apoptosis in cultured HCE cells in a dose-dependent manner. 15-LOX-2 but not 15-LOX-1 was detected by Western blot analysis, although we were able to detect similar levels of both 15-LOX mRNAs by real-time quantitative RT-PCR. 15-LOX-1 and -2 proteins showed different subcellular expression patterns. 15-LOX-2 GFP was expressed in the cytoplasm and nucleus (actively taken up into the nucleus). 15-LOX-1 GFP fusion protein expression was restricted to the cytoplasm. CONCLUSIONS: These findings indicate that 15-LOX-2 is the predominant 15-LOX protein in human cornea, and its product, 15S-HETE, plays a role in cellular proliferation. Because the two 15-LOXs have different subcellular compartmentalization, the authors hypothesize that their products are also compartmentalized and therefore exert different molecular effects in the human corneal epithelium.

Seeding of corneal wounds by epithelial cell transfer from micropatterned PDMS contact lenses.

Persistent corneal wounds result from numerous eye disorders, and to date, available treatments often fail to accelerate reepithelialization, the key initial step in wound healing. To speed reepithelialization, we explored a cell-transfer transplant method utilizing polydimethylsiloxane (PDMS) contact lenses to deliver epithelial cells derived from limbal explants directly within a corneal wound. Human primary epithelial cells and an immortalized corneal epithelial cell line (HCE-SV40) grew well on PDMS contact lenses and their morphology and growth rates where similar to cells grown on tissue culture polystyrene. To initially study cell transfer from PDMS, HCE-SV40 cells were seeded onto PDMS with or without micropatterned posts. After a day in culture, HCE-SV40 cells attached to the unpatterned PDMS uniformly, whereas on micropatterned PDMS they appeared to attach primarily between posts. The cell-covered PDMS contacts were then placed cell-side down onto tissue culture plastic and, after 1, 2, or 3 days, the PDMS contact was removed and the transferred cells were trypsinized and counted. Micropatterned PDMS contact lenses with 100-microm-diameter posts and a post height of 40 microm transferred three times as many cells as unpatterned PDMS. Cell transfer to a wounded cornea was tested in a pig cornea organ culture model de-epithelialized by alkali treatment. Post micropatterned PDMS contact lenses were seeded with labeled HCE-SV40 cells at a density 50,000 cells/cm2 and applied to the wounded pig corneas. After 24, 48, or 96 h of application, PDMS contact lenses were removed, corneas fixed with formaldehyde, and sectioned. After 48 h, epithelial cells transferred from post micropatterned contact lenses to provide 35% epithelial coverage of denuded pig corneas; after 96 h coverage was 65%. We conclude that cell transfer from epithelial-coated PDMS contact lenses micropatterned with posts provides a promising approach to reepithelialize corneal surfaces.

Bves is expressed in the epithelial components of the retina, lens, and cornea.

PURPOSE: To demonstrate the expression pattern and subcellular localization of Bves/Pop1a protein, a newly identified cell adhesion molecule, during eye development and corneal regeneration. METHODS: Staged embryonic and adult eyes were assayed using fluorescence immunohistochemistry to detect the Bves protein. A human corneal epithelial (HCE) cell line was used as a model to examine Bves localization during corneal growth and regeneration, with and without antisense morpholino treatment. RESULTS: The data detail the expression and localization of Bves protein before, during, and after differentiation of the eye. In these analyses, Bves was localized to an apical-lateral position in the initial epithelial primordia of the eye. Later, Bves became localized to specific cell types and subcellular domains in the retina, lens, and cornea, indicating changes in Bves expression in the differentiated eye. Finally, an in vitro model of corneal wound healing showed that Bves staining was missing at the epithelial surface during cellular migration across the wound, but it reappeared at points of cell contact during the reinitiation of epithelial continuity. When epithelial sheets were treated with Bves antisense morpholinos to inhibit Bves function, disruption of epithelial integrity was observed. After injury, similar treatment resulted in an acceleration of cell movement at the wound surface but regeneration of an intact epithelium was ultimately impeded. CONCLUSIONS: Taken together, these studies suggest that Bves is expressed in epithelial elements of the developing eye and may have a role in corneal epithelial growth and regeneration.

Automated 96-well liquid-liquid back extraction liquid chromatography-tandem mass spectrometry method for the determination of ABT-202 in human plasma.

A high-throughput bioanalytical method using automated sample transferring, automated liquid-liquid back extraction and liquid chromatography-tandem mass spectrometry was developed in a GLP regulated environment for the determination of ABT-202 in human plasma. Samples of 0.30 ml were transferred into 96-well plate using an automatic liquid handler. Automated liquid-liquid extraction (LLE) was carried out on a 96-channel programmable liquid handling workstation using methyl tert-butyl ether as the extraction solvent. A dual-HPLC with single mass spectrometer configuration was utilized to provide a reliable and routine means to increase sample throughput. The standard curve range was 0.38-95.02 ng/ml. There was no interference from endogenous components in the blank plasma tested. The accuracy (% bias) at the lower limit of quantitation (LLOQ) was 7.7% and the precision (% CV) for samples at the LLOQ was 4.7%. The inter-day % CV and % bias of the quality control samples were < or = 6.8 and < or = 7.6%, respectively. Coefficients of determination, a measure of linearity, ranged from 0.994 to 0.997. The method was accurate and reproducible and was successfully applied to generate plasma concentration-time profiles for human subjects after low oral doses of the compound.

Tight junction-associated signaling pathways modulate cell proliferation in uveal melanoma.

PURPOSE: To investigate the role of tight junction (TJ)-associated signaling pathways in the proliferation of uveal melanoma. METHODS: Human uveal melanoma cell lines overexpressing the TJ molecule blood vessel epicardial substance (Bves) were generated. The effects of Bves overexpression on TJ protein expression, cell proliferation, and cell cycle distribution were quantified. In addition, localization and transcription activity of the TJ-associated protein ZO-1-associated nucleic acid binding protein (ZONAB) were evaluated using immunofluorescence and bioluminescence reporter assays to study the involvement of Bves signaling in cell proliferation-associated pathways. RESULTS: Bves overexpression in uveal melanoma cell lines resulted in increased expression of the TJ proteins occludin and ZO-1, reduced cell proliferation, and increased sequestration of ZONAB at TJs and reduced ZONAB transcriptional activity. CONCLUSIONS: TJ proteins are present in uveal melanoma, and TJ-associated signaling pathways modulate cell signaling pathways relevant to proliferation in uveal melanoma.

Bves modulates tight junction associated signaling.

Blood vessel epicardial substance (Bves) is a transmembrane adhesion protein that regulates tight junction (TJ) formation in a variety of epithelia. The role of TJs within epithelium extends beyond the mechanical properties. They have been shown to play a direct role in regulation of RhoA and ZONAB/DbpA, a y-box transcription factor. We hypothesize that Bves can modulate RhoA activation and ZONAB/DbpA activity through its regulatory effect on TJ formation. Immortalized human corneal epithelial (HCE) cells were stably transfected with Flag-tagged full length chicken Bves (w-Bves) or C-terminus truncated Bves (t-Bves). We found that stably transfected w-Bves and t-Bves were interacting with endogenous human Bves. However, interaction with t-Bves appeared to disrupt cell membrane localization of endogenous Bves and interaction with ZO-1. w-Bves cells exhibited increased TJ function reflected by increased trans-epithelial electrical resistance, while t-Bves cells lost TJ protein immunolocalization at cell-cell contacts and exhibited decreased trans-epithelial electrical resistance. In parental HCE and w-Bves cells ZONAB/DbpA and GEF-H1 were seen at cell borders in the same pattern as ZO-1. However, expression of t-Bves led to decreased membrane localization of both ZONAB/DbpA and GEF-H1. t-Bves cells had increased RhoA activity, as indicated by a significant 30% increase in FRET activity compared to parental HCE cells. ZONAB/DbpA transcriptional activity, assessed using a luciferase reporter probe, was increased in t-Bves cells. These studies demonstrate that Bves expression and localization can regulate RhoA and ZONAB/DbpA activity.

BVES regulates EMT in human corneal and colon cancer cells and is silenced via promoter methylation in human colorectal carcinoma.

The acquisition of a mesenchymal phenotype is a critical step in the metastatic progression of epithelial carcinomas. Adherens junctions (AJs) are required for suppressing this epithelial-mesenchymal transition (EMT) but less is known about the role of tight junctions (TJs) in this process. Here, we investigated the functions of blood vessel epicardial substance (BVES, also known as POPDC1 and POP1), an integral membrane protein that regulates TJ formation. BVES was found to be underexpressed in all stages of human colorectal carcinoma (CRC) and in adenomatous polyps, indicating its suppression occurs early in transformation. Similarly, the majority of CRC cell lines tested exhibited decreased BVES expression and promoter DNA hypermethylation, a modification associated with transcriptional silencing. Treatment with a DNA-demethylating agent restored BVES expression in CRC cell lines, indicating that methylation represses BVES expression. Reexpression of BVES in CRC cell lines promoted an epithelial phenotype, featuring decreased proliferation, migration, invasion, and anchorage-independent growth; impaired growth of an orthotopic xenograft; and blocked metastasis. Conversely, interfering with BVES function by expressing a dominant-negative mutant in human corneal epithelial cells induced mesenchymal features. These biological outcomes were associated with changes in AJ and TJ composition and related signaling. Therefore, BVES prevents EMT, and its epigenetic silencing may be an important step in promoting EMT programs during colon carcinogenesis.

Inhibition of RhoA signaling with increased Bves in trabecular meshwork cells.

PURPOSE: Blood vessel epicardial substance (Bves) is a novel adhesion molecule that regulates tight junction (TJ) formation. TJs also modulate RhoA signaling, which has been implicated in outflow regulation. Given that Bves has been reported in multiple ocular tissues, the authors hypothesize that Bves plays a role in the regulation of RhoA signaling in trabecular meshwork (TM) cells. METHODS: Human TM cell lines NTM-5 and NTM-5 transfected to overexpress Bves (NTM-w) were evaluated for TJ formation, and levels of occludin, cingulin, and ZO-1 protein were compared. Assays of TJ function were carried out using diffusion of sodium fluorescein and transcellular electrical resistance (TER). Levels of activated RhoA were measured using FRET probes, and phosphorylation of myosin light chain (MLC-p), a downstream target of RhoA, was assessed by Western blot analysis. RESULTS: Overexpression of Bves led to increased TJ formation in NTM-5 cells. Increased TJ formation was confirmed by increased occludin, cingulin, and ZO-1 protein. Functionally, NTM-w cells showed decreased permeability and increased TER compared with NTM-5 cells, consistent with increased TJ formation. NTM-w cells also exhibited decreased levels of active RhoA and lower levels of MLC-p than did NTM-5 cells. These findings support a TJ role in RhoA signaling. CONCLUSIONS: Increased Bves in TM cells leads to increased TJ formation with decreased RhoA activation and decreased MLC-p. This is the first report of a regulatory pathway upstream of RhoA in TM cells. In TM tissue, RhoA has been implicated in outflow regulation; thus, Bves may be a key regulatory molecule in aqueous outflow.

Identification of a novel intracellular interaction domain essential for Bves function.

While Blood vessel epicardial substance (Bves) confers adhesive properties, the molecular mechanism of regulating this activity is unknown. No predicted functional motifs in this highly conserved integral membrane protein, other than the transmembrane domain, have been identified. Here, we report for the first time that Bves interacts with itself through an intracellular interaction domain that is essential for its intercellular adhesion activity. Glutathione-S-transferase (GST) pull-down and SPOTs analyses mapped this domain to amino acids 268-274 in the intracellular C-terminus. Site-directed mutagenesis revealed that lysines 272 and 273 are essential for homodimerization and cell adhesion. Human corneal cells transfected with wild-type Bves trafficked the protein to the cell surface, assembled junction complexes and formed epithelial sheets. In contrast, cells expressing Bves mutated at these positions did not form continuous epithelial sheets or maintain junctional proteins such as ZO-1 and E-cadherin at the membrane. A dramatic reduction in transepithelial electrical resistance was also observed indicating a functional loss of tight junctions. Importantly, expression of mutated Bves in epithelial cells promoted the transformation of cells from an epithelial to a mesenchymal phenotype. This study is the first to demonstrate the essential nature of any domain within Bves for maintenance of epithelial phenotype and function.

Evaluation of 384-well formatted sample preparation technologies for regulated bioanalysis.

The capabilities and limitations of 384-well formatted sample preparation technologies applied to regulated bioanalysis were evaluated by developing two assays for the simultaneous quantitation of lopinavir and ritonavir, the active ingredients of Kaletra. One method used liquid-liquid extraction (LLE), and the other used solid-phase extraction (SPE). The steps and apparatuses employed by the two methods covered most of those used for bioanalysis. Briefly, the previously validated 96-well formatted assays were adapted to the 384-format with minor modifications. Because the wells of a 384-well plate are clustered together, cross-contamination between adjacent wells was evaluated critically, along with sensitivity, assay throughput, and ruggedness. Samples (35 microL) containing plasma samples (15 microL), internal standard (10 microL), and sodium carbonate (0.5 M, 10 microL to basify the sample) were placed in a 384-well microtiter plate that may contain saquinavir or amprenavir as contamination markers. For LLE preparation, the samples were placed in a deep 384-well plate (300-microL well volume) and extracted with 150 microL of ethyl acetate. Approximately 50 microL of the extracts were removed from each well after phase separation for analysis. For SPE preparation, the fortified samples were transferred to a 384-formatted SPE plate (C18, 5 mg packing). The extracts were eluted from the plate with basified 2-propanol. The LLE or SPE extracts were dried and reconstituted for column-switching high-performance liquid chromatography with tandem mass spectrometric detection (HPLC/MS/MS). The lower limit of quantitation and the assay range were the same as the 96-well formatted assay. If combined with appropriate automation, sample preparation in the 384-well format would be up to five times more efficient than the 96-well format.

Accurate determination of an immunosuppressant in stented swine tissues with LC-MS/MS.

During stent development, accurate monitoring of the drug concentration in animal tissues can provide critical information on how the drug is released into the circulation and the surrounding tissues. To establish the relationship between the drug concentration and the distance from the stent to the target tissue, a comprehensive strategy was developed for sample collection, sample homogenization and sample storage as well as sample analysis. This strategy was developed with the analytical chemists and animal surgical specialists working together as a team. The optimized sampling process was designed to yield a representative sample, appropriately located and of an appropriate size. The sampling process was also designed to eliminate the potential for carryover and cross-contamination. During sample processing, the analyte solution was spiked into blank tissues using a sharp needle and a gas-tight syringe to prepare tissue quality control samples. These tissue quality controls were then used to evaluate the stability of the drug in solid tissue and homogenate, the homogenization carryover, the cross-contamination and the recovery of the drug during method validation and to monitor the overall process of drug analysis of the swine tissues. This thorough strategy has been applied to the accurate determination of zotarolimus in swine tissues for regulated toxicology studies. The entire process was controlled, including precise tissue sampling, compound-based tissue homogenization, method validation, and the application of the method to regulated toxicokinetics studies. The results demonstrate that analytical chemistry concepts can be successfully integrated into toxicokinetics studies in order to collect precise samples and obtain meaningful results. The strategy can be applied to similar toxicokinetics studies of locally administrated drugs in tissues.

A novel approach for in-process monitoring and managing cross-contamination in a high-throughput high-performance liquid chromatography assay with tandem mass spectrometric detection.

Cross-contamination among wells of a high-throughput, high-density assay is a risk that cannot be detected or controlled by the performance of calibration standards and quality control samples. In the current practice, carryover and cross-contamination is detected only when analytes are detected in blank, zero, placebo, pre-dose samples, in a low standard or low quality control sample. There is no mechanism that allows bioanalytical scientists to determine if cross-contamination has occurred among other samples. As a result, erroneous results can be released to clients even though a batch meets the acceptance criteria. We tested a new approach that quantifies the cross-contamination of each sample and allows the scientist to make quality decisions with documentation. The approach will also detect carryover in over 90% of the wells. Briefly, two additional analytes were added as contamination markers. The markers were added to a multi-well plate alternatively creating a pattern of a checkerboard. The spiked multi-well plate was then used to perform the assay. If both markers were detected in a well, the sample was considered contaminated. The amount of the unexpected marker detected in a well measures the degree of contamination and may be used to make deactivation decisions. Depending on the relative impact of the contamination, a scientist can choose to tolerate the bias, reject the sample, reject the batch or raise the lower limit of quantitation for the batch. A guideline for rejection decisions is presented for discussion.

Bves modulates epithelial integrity through an interaction at the tight junction.

We first identified Bves (blood vessel/epicardial substance) as a transmembrane protein that localized to the lateral compartment of the epithelial epicardium. Bves traffics to sites of cell-cell contact in cultured epicardial cells and promotes adhesion following transfection into non-adherent fibroblastic L-cells, reminiscent of a cell adhesion molecule. Currently, no function for Bves in relation to epithelial cell adhesion has been identified. We hypothesize that Bves plays a role at cell junctions to establish and/or modulate cell adhesion or cell-cell interactions in epithelial cell types. In this study, we demonstrate that Bves regulates epithelial integrity and that this function may be associated with a role at the tight junction (TJ). We report that Bves localizes with ZO-1 and occludin, markers of the TJ, in polarized epithelial cell lines and in vivo. We find that the behavior of Bves following low Ca2+ challenge or TPA treatment mimics that observed for ZO-1 and is distinct from adherens junction proteins such as E-cadherin. Furthermore, GST pull-down experiments show an interaction between ZO-1 and the intracellular C-terminal tail of Bves. Finally, we demonstrate that Bves modulates tight junction integrity, as indicated by the loss of transepithelial resistance and junction protein localization at the membrane following Bves knock-down in cultured cells. This study is the first to identify a function for Bves in epithelia and supports the hypothesis that Bves contributes to establishment and/or maintenance of epithelial cell integrity.

Method development for the concentration determination of a protein in human plasma utilizing 96-well solid-phase extraction and liquid chromatography/tandem mass spectrometric detection.

Although liquid chromatography/tandem mass spectrometry (LC/MS/MS) technology has been widely used for quantitative analysis of small organic molecules, it has been a challenging task to quantitatively analyze protein samples utilizing this technology in biological matrices for pre-clinical and clinical studies. Here we present our initial results in method development for the quantitative determination of rK5 protein concentrations in human plasma samples utilizing LC/MS/MS technology. A protein similar in structure to rK5, but with a slightly reduced molecular weight, was used as internal standard. A 96-well solid-phase extraction procedure was developed to effectively extract protein analytes from plasma samples. Quantitative analysis was obtained by a novel approach of protein monitoring that employed selective reaction monitoring (SRM). Even though mass spectrometry of the internal standard protein gave no fragment ions, SRM monitoring greatly reduced background interference. Using samples prepared in human plasma with sodium EDTA as anticoagulant, a correlation coefficient (r(2)) of 0.9940 was obtained by producing a single standard curve with the injection of six rows of standards with a concentration range from 100 ng/mL to 10 microg/mL. The mean analytical recovery for these standards ranged from 91.5 to 103.6%. The CVs for individual standard levels ranged from 3.7 to 20.9%. The experiment was also repeated using samples prepared in human plasma with sodium heparin as anticoagulant, which produced a correlation coefficient (r(2)) of 0.9952 obtained from a single standard curve with the injection of four rows of standards with a concentration range from 50 ng/mL to 10 microg/mL. The mean analytical recovery for the standards ranged from 96.2 to 104.6%. The CVs for individual standard levels ranged from 2.6 to 15.6%.