Plasma Pharmacokinetics and Routes of Excretion of [14C]-Labeled Arruva, a High-Potency Sweetener, Following Oral Administration to Beagle Dogs.

[14C]-Labeled arruva [sodium/potassium (2R,4R)-2-amino-4-carboxy-4-hydroxy-5-(3-indolyl) pentanoate] was administered as a single gavage dose (10 mg/kg bw) to male and female Beagle dogs and 1 bile duct-cannulated male. The mean peak arruva plasma concentration equivalent of 1.2 µg/g occurred at first sampling time point of 1 hour postdosing. The mean area under the concentration versus time curve from 0 hour postdosing to the last time point was approximately 20 µg·h/g and the mean terminal plasma elimination half-life ranged from 15 hours in females to 21 hours in males. Over 168 hours postdosing, 35% to 50% of the administered arruva was eliminated in the urine with 44% to 53% eliminated in feces; 1.3% of the administered dose was recovered in bile. Arruva and its derivatives were identified using tandem mass spectrometry, and the relative percentage of each substance was quantified via radio high-performance liquid chromatography. Over a 168-hour collection period, combined urine and feces extract data from the 6 noncannulated dogs showed that approximately 91% of the dose was excreted as unchanged parent arruva (41% in urine and 50% in feces). In the cannulated male, 95.3% was excreted as unchanged parent arruva; 50.2% in urine, 43.9% in feces, and 1.3% in bile. Lactone and lactam derivatives of arruva and 1 unidentified substance were detected in urine only during the first 24 hours postdosing with the greatest amounts detected during the first 6 hours of collection; up to 1% of lactone or lactam derivatives were detected in bile samples. Plasma pharmacokinetics data indicated rapid absorption of arruva with the majority of radioactivity located in the feces collected in the first 48 hours.

Metabolism and toxicity studies supporting the safety of rebaudioside D.

Rebaudioside D (Reb D) is one of the several glycosides found in the leaves of Stevia rebaudiana (Bertoni) Bertoni (Compositae) which has been identified as a potential sweetener. The metabolism of Reb A and Reb D was evaluated in various in vitro matrices (simulated gastrointestinal fluids, rat liver microsomes, and rat cecal contents) and through analysis of plasma collected from rats in a dietary toxicity study. Reb A and Reb D showed similar stability when exposed to simulated stomach and small intestine fluids, with susceptibility to hydrolytic degradation by enteric bacteria collected from the cecum. Incubations with rat liver microsomes indicated that neither compound is expected to be metabolized by the liver enzymes. Plasma concentrations of Reb D, Reb A, and/or the final hydrolysis product of each compound, free/conjugated steviol, were consistent between animals administered either Reb D or Reb A in the diet. A repeated exposure dietary toxicity study was conducted to compare the safety of Reb D, when administered at target exposure levels of 500, 1000, and 2000 mg/kg body weight (bw)/d to Sprague-Dawley rats for 28 days, to that of Reb A administered at a target exposure level of 2000 mg/kg bw/d. There were no treatment-related effects on the general condition and behavior of the animals and no toxicologically relevant, treatment-related effects on hematology, serum chemistry, or urinalysis. Macroscopic and microscopic findings revealed no treatment-related effects on any organ evaluated. Results were comparable between the group administered 2000 mg/kg/d Reb D and the group administered 2000 mg/kg/d Reb A.

Whole blood or plasma: what is the ideal matrix for pharmacokinetic-driven drug candidate selection?

In the present era of drug development, quantification of drug concentrations following pharmacokinetic studies has preferentially been performed using plasma as a matrix rather than whole blood. However, it is critical to realize the difference between measuring drug concentrations in blood versus plasma and the consequences thereof. Pharmacokinetics using plasma data may be misleading if concentrations differ between plasma and red blood cells (RBCs) because of differential binding in blood. In this review, factors modulating the partitioning of drugs into RBCs are discussed and the importance of determining RBC uptake of drugs for drug candidate selection is explored. In summary, the choice of matrix (plasma vs whole blood) is an important consideration to be factored in during drug discovery.

UV exposure and protection against allergic airways disease.

Asthma is a chronic inflammatory disease of the small and large conducting airway mucosa characterised by Th2 cell immunity. Allergen-specific IgE levels control the immediate response whilst the interplay between airway mucosal antigen presenting cells, Th2 effector cells and CD4+CD25+ regulatory T cells control the late phase, cell-mediated response. Using two experimental systems in mice with ovalbumin and papain, respectively, as the allergens, UV irradiation of skin prior to allergen sensitisation reduced the expression of allergic airways disease, particularly the late phase response. In this review, the reduced Th2-driven, asthma-like responses in respiratory tissues of UV-irradiated mice are detailed. Possible mechanisms of UV regulation are debated. The potential beneficial effects of UV irradiation of skin in controlling allergic airways disease are discussed. This review gives some scientific understanding to century-old anecdotal reports that beach and mountain resort holidays associated with increased UV exposure are beneficial in asthma treatment.

Protein Binding and Stability of Drug Candidates: The Achilles' Heel in In Vitro Potency Assays.

In the present scenario of drug discovery, several screening filters ensure a rigorous nomination of clinical candidates. One of these screens is the determination of IC50, the concentration of drug at half-maximal inhibitory concentration, also known as a potency assay. However, various nuances pertaining to the design, execution, and interpretation of in vitro potency results suggest a sizeable opportunity for the generation of erroneous data. The focus areas of this article include: (1) examining the requirement for the addition of serum albumin in in vitro potency assays, (2) problems encountered with cell lysates, and (3) drug candidate stability concerns during in vitro potency assays/high-throughput screening. Based on this assessment, the interpretation of the data generated using cell-based systems (i.e., lysates with or without the addition of fetal bovine serum) should be carried out with caution for in vitro potency testing, and the inclusion of a correction factor for non-specific protein binding should be considered. The addition of serum albumin to a cell-free system should be restricted to drugs having high protein binding (≥ 90%). Additionally, stability assessment of analytes should be considered to avoid dubious in vitro potency outcomes due to degraded material or active metabolite(s).

Critical Assessment of Pharmacokinetic Drug-Drug Interaction Potential of Tofacitinib, Baricitinib and Upadacitinib, the Three Approved Janus Kinase Inhibitors for Rheumatoid Arthritis Treatment.

The introduction of novel, small-molecule Janus kinase inhibitors namely tofacitinib, baricitinib and upadacitinib has provided an alternative treatment option for patients with rheumatoid arthritis outside of traditional drugs and expensive biologics. This review aimed to critically assess the drug-drug interaction potential of tofacitinib, baricitinib and upadacitinib and provide a balanced perspective for choosing the most appropriate Janus kinase inhibitor based on the needs of patients with rheumatoid arthritis including co-medications and renal/hepatic impairment status. Based on the critical assessment, all three approved Janus kinase inhibitors generally provide a favourable opportunity for co-prescription with a plethora of drugs. While cytochrome P450 3A4-related inhibition or induction altered the exposures (area under the curve) of tofacitinib and upadacitinib, it did not impact the exposure of baricitinib. Transporter drug-drug interaction studies revealed that the disposition of baricitinib was altered with certain transporter inhibitors as compared with either tofacitinib or upadacitinib. Adjustment of tofacitinib or baricitinib dosages but not that of upadacitinib is required with the progression of renal impairment from a mild to a severe condition. While the dosage of tofacitinib needs to be adjusted for patients with moderate hepatic impairment status, it is not the case for either baricitinib or upadacitinib. Assessment of the drug-drug interaction potential suggests that tofacitinib, baricitinib and upadacitinib generally show a favourable disposition with no perpetrator activity; however, as victim drugs, they show subtle pharmacokinetic differences that may be considered during polypharmacy. Moreover, careful choice of the three drugs could be made in patients with rheumatoid arthritis with varying degrees of renal/hepatic impairments.

Pharmacokinetics, excretion balance, and tissue distribution of [14C]-labeled glycolipids and long chain fatty acids from Dacryopinax spathularia in rats.

The pharmacokinetics, excretion balance, and tissue distribution of [14C]-labeled glycolipids from Dacryopinax spathularia (herein referred to as "AM-1") and [14C]-LCFA equivalents following single or repeated administration to Sprague Dawley rats were evaluated to support the safety assessment of these naturally derived jelly mushroom glycolipids for use as a food ingredient. Rats received equimolar doses of either [14C]-AM-1 or [14C]-LCFA via oral or intravenous administration followed by collection of biological samples at specified intervals. Approximately 88%-101% of the administered dose was recovered in expired air, urine, feces, and carcass following single or repeated oral administration of [14C]-AM-1 at 100 mg/kg or equimolar doses of [14C]-LCFA at 46 mg/kg. Cmax and AUClast for [14C]-AM-1- and [14C]-LCFA-equivalents-derived radioactivity detected by quantitative whole body autoradiography was highest in the tissues of the GI tract, as expected following oral administration. The remaining tissues had low concentrations of test article equivalents relative to the administered dose and no target tissues for residence or accumulation were identified. AM-1 and LCFA are poorly absorbed by the oral route and are primarily eliminated in the feces without absorption. Oral bioavailability of both AM-1 and LCFA including their metabolites is low at approximately 11%.

A mutagenesis and screening strategy to generate optimally thermostabilized membrane proteins for structural studies.

The thermostability of an integral membrane protein (MP) in detergent solution is a key parameter that dictates the likelihood of obtaining well-diffracting crystals that are suitable for structure determination. However, many mammalian MPs are too unstable for crystallization. We developed a thermostabilization strategy based on systematic mutagenesis coupled to a radioligand-binding thermostability assay that can be applied to receptors, ion channels and transporters. It takes ∼6-12 months to thermostabilize a G-protein-coupled receptor (GPCR) containing 300 amino acid (aa) residues. The resulting thermostabilized MPs are more easily crystallized and result in high-quality structures. This methodology has facilitated structure-based drug design applied to GPCRs because it is possible to determine multiple structures of the thermostabilized receptors bound to low-affinity ligands. Protocols and advice are given on how to develop thermostability assays for MPs and how to combine mutations to make an optimally stable mutant suitable for structural studies. The steps in the procedure include the generation of ∼300 site-directed mutants by Ala/Leu scanning mutagenesis, the expression of each mutant in mammalian cells by transient transfection and the identification of thermostable mutants using a thermostability assay that is based on binding of an (125)I-labeled radioligand to the unpurified, detergent-solubilized MP. Individual thermostabilizing point mutations are then combined to make an optimally stable MP that is suitable for structural biology and other biophysical studies.

Quality control in eukaryotic membrane protein overproduction.

The overexpression of authentically folded eukaryotic membrane proteins in milligramme quantities is a fundamental prerequisite for structural studies. One of the most commonly used expression systems for the production of mammalian membrane proteins is the baculovirus expression system in insect cells. However, a detailed analysis by radioligand binding and comparative Western blotting of G protein-coupled receptors and a transporter produced in insect cells showed that a considerable proportion of the expressed protein was misfolded and incapable of ligand binding. In contrast, production of the same membrane proteins in stable inducible mammalian cell lines suggested that the majority was folded correctly. It was noted that detergent solubilisation of the misfolded membrane proteins using either digitonin or dodecylmaltoside was considerablyless efficient than using sodium dodecyl sulfate or foscholine-12, whilst these detergents were equally efficient at solubilising correctly folded membrane proteins. This provides a simple and rapid test to suggest whether heterologously expressed mammalian membrane proteins are indeed correctly folded, without requiring radioligand binding assays. This will greatly facilitate the high-throughput production of fully functional membrane proteins for structural studies.

Indiana University Health staffing model for neurotelemetry and epilepsy monitoring unit patient populations: Part 1.

This is part one of a two part series of articles describing the staffing model utilized for neurotelemetry and epilepsy unit monitoring. After peer review, many administrative and technical questions were left unanswered which will be addressed in the second article. Indiana University Health Neuroscience is a facility that provides all levels of care for adult and pediatric patients regarding their specific neurological needs. The facility currently has 24/7 monitoring at Methodist Hospital and Riley Hospital for Children, consisting of adult and pediatric patients for neurotelemetry and epilepsy unit monitoring. Each unit must have staffing models as well as specific protocols in order to adequately monitor each patient's EEG and maintain safety. Specific recommendations, protocols, and requirements have been drafted by administration to maintain a safe patient to neurodiagnostic technologist ratio of 4:1.

Identification and isolation of rodent respiratory tract dendritic cells.

This chapter describes the preparation of respiratory tract tissue from both mice and rats for the isolation of respiratory tract dendritic cells (RTDC). The methods describe in detail the preparation of cells from the respiratory tract tissue of the main conducting airways (representing mucosal populations) and peripheral lung (representing predominantly interstitial populations) in both rodent species. Our research in this area has found that these anatomical sites differ in their composition of antigen-presenting cell (APC) types including RTDC, and that phenotypic and functional differences exist in RTDC isolated from these sites. We predominantly use a flow cytometry-based approach to identify and sort RTDC as this is the most accurate way of isolating RTDC subsets in an environment where many typical dendritic cell surface markers are shared by other APC populations.

Allergic airways disease develops after an increase in allergen capture and processing in the airway mucosa.

Airway mucosal dendritic cells (AMDC) and other airway APCs continuously sample inhaled Ags and regulate the nature of any resulting T cell-mediated immune response. Although immunity develops to harmful pathogens, tolerance arises to nonpathogenic Ags in healthy individuals. This homeostasis is thought to be disrupted in allergic respiratory disorders such as allergic asthma, such that a potentially damaging Th2-biased, CD4(+) T cell-mediated inflammatory response develops against intrinsically nonpathogenic allergens. Using a mouse model of experimental allergic airways disease (EAAD), we have investigated the functional changes occurring in AMDC and other airway APC populations during disease onset. Onset of EAAD was characterized by early and transient activation of airway CD4(+) T cells coinciding with up-regulation of CD40 expression exclusively on CD11b(-) AMDC. Concurrent enhanced allergen uptake and processing occurred within all airway APC populations, including B cells, macrophages, and both CD11b(+) and CD11b(-) AMDC subsets. Immune serum transfer into naive animals recapitulated the enhanced allergen uptake observed in airway APC populations and mediated activation of naive allergen-specific, airway CD4(+) T cells following inhaled allergen challenge. These data suggest that the onset of EAAD is initiated by enhanced allergen capture and processing by a number of airway APC populations and that allergen-specific Igs play a role in the conversion of normally quiescent AMDC subsets into those capable of inducing airway CD4(+) T cell activation.

Influence of mucosal adjuvants on antigen passage and CD4+ T cell activation during the primary response to airborne allergen.

Ag delivery via the nasal route typically induces tolerance or fails to polarize CD4+ T cell responses unless an adjuvant is provided. To better understand this process, we assessed the effects of two mucosal adjuvants, Escherichia coli LPS and cholera toxin (CT), on Ag passage and T cell activation in the draining lymph nodes (DLN) of BALB/c mice following per nasal administration of the model protein allergen, OVA. We found a range of cell types acquired small amounts of fluorescent OVA in the DLN 4 h after per nasal administration. However, this early uptake was eclipsed by a wave of OVA+CD8alpha(low) dendritic cells that accumulated in the DLN over the next 20 h to become the dominant OVA-processing and -presenting population. Both LPS and CT stimulated increases in CD80 and CD86 expression on OVA+CD8alpha(low) DC. LPS also increased the number of OVA+CD8alpha(low) dendritic cells accumulating in the DLN. When the primary T cell response was examined after adoptive transfer of CD4+ T cells from DO11.10 mice, CT and LPS stimulated surprisingly similar effects on T cell activation and proliferation, IL-4 and IFN-gamma priming, and memory T cell production. Despite these similarities, T cell recipients immunized with CT, but not LPS, developed lung eosinophilia upon secondary OVA challenge. Thus, we found no bias within the DLN in Ag handling or the primary T cell response associated with the eventual Th2 polarization induced by CT, and suggest that additional tissue-specific factors influence the development of allergic disease in the airways.

Accelerated antigen sampling and transport by airway mucosal dendritic cells following inhalation of a bacterial stimulus.

An increase in the tempo of local dendritic cell (DC)-mediated immune surveillance is a recognized feature of the response to acute inflammation at airway mucosal surfaces, and transient up-regulation of the APC functions of these DC preceding their emigration to regional lymph nodes has recently been identified as an important trigger for T cell-mediated airway tissue damage in diseases such as asthma. In this study, using a rat model, we demonstrate that the kinetics of the airway mucosal DC (AMDC) response to challenge with heat-killed bacteria is considerably more rapid and as a consequence more effectively compartmentalized than that in recall responses to soluble Ag. Notably, Ag-bearing AMDC expressing full APC activity reach regional lymph nodes within 30 min of cessation of microbial exposure, and in contrast to recall responses to nonpathogenic Ags, there is no evidence of local expression of APC activity within the airway mucosa preceding DC emigration. We additionally demonstrate that, analogous to that reported in the gut, a subset of airway intraepithelial DC extend their processes into the airway lumen. This function is constitutively expressed within the AMDC population, providing a mechanism for continuous immune surveillance of the airway luminal surface in the absence of "danger" signals.

Downregulation of IgE antibody and allergic responses in the lung by epidermal biolistic microparticle delivery.

BACKGROUND: Biolistic injections provide a needle-free delivery of antigen-laden microparticles to the epithelium. The precision of the injection preferentially targets the Langerhans cell network, which, although ideal for vaccination, might not be suitable for the downregulation of immune responses in immunotherapy. OBJECTIVE: We sought to determine the ability of biolistic injection of antigen into the epithelium of sensitized mice to inhibit IgE antibody and lung inflammatory responses produced by further exposure to antigen. METHODS: Mice were sensitized by means of a needle injection of ovalbumin (OVA) in alum and given a series of biolistic injections of OVA or vehicle control, followed by a boost of OVA in alum. Serum IgE and IgG antibodies were measured before and after the boost. The mice were then challenged intranasally, and the infiltration of inflammatory cells was measured by means of bronchoalveolar lavage. Airway reactivity of the challenged mice was measured by examining responses to methacholine with forced oscillatory techniques. RESULTS: Biolistic injection of OVA into the dorsal skin of sensitized mice markedly inhibited IgE and IgG1 antibody responses induced by boosting. IgG2a antibody responses were reduced rather than stimulated. The eosinophilic inflammation in the bronchoalveolar lavage fluid induced by intranasal challenge was also markedly inhibited. Lung hyperreactivity showed an initial increase and then a decrease of responsiveness to methacholine, with elastance returning to the level of unsensitized mice. Biolistic injection into the buccal epithelium was also inhibitory. CONCLUSIONS: Biolistic injection of allergen inhibited the boosting of IgE antibody and eosinophilic lung inflammatory responses without inducing T(H)1 immunity.

Anatomical location determines the distribution and function of dendritic cells and other APCs in the respiratory tract.

APCs, including dendritic cells (DC), are central to Ag surveillance in the respiratory tract (RT). Research in this area is dominated by mouse studies on purportedly representative RT-APC populations derived from whole-lung digests, comprising mainly parenchymal tissue. Our recent rat studies identified major functional differences between DC populations from airway mucosal vs parenchymal tissue, thus seriously questioning the validity of this approach. We addressed this issue for the first time in the mouse by separately characterizing RT-APC populations from these two different RT compartments. CD11c(high) myeloid DC (mDC) and B cells were common to both locations, whereas a short-lived CD11c(neg) mDC was unique to airway mucosa and long-lived CD11c(high) macrophage and rapid-turnover multipotential precursor populations were predominantly confined to the lung parenchyma. Airway mucosal mDC were more endocytic and presented peptide to naive CD4+ T cells more efficiently than their lung counterparts. However, mDC from neither site could present whole protein without further maturation in vitro, or following trafficking to lymph nodes in vivo, indicating a novel mechanism whereby RT-DC function is regulated at the level of protein processing but not peptide loading for naive T cell activation.

Primary defect in UVB-induced systemic immunomodulation does not relate to immature or functionally impaired APCs in regional lymph nodes.

UVB irradiation of the shaved dorsal skin of mice can cause both local and systemic suppression of contact hypersensitivity responses; the former demonstrated by administration of the sensitizing Ag/hapten to the irradiated site and the latter by its administration at least 72 h later to distal unirradiated sites. The immunological basis of systemic immunomodulation is not clear. When haptens (trinitrochlorobenzene, FITC) were administered to the shaved ventral skin 4 days after irradiation (8 kJ/m(2)) to the shaved dorsum of BALB/c mice, CD11c(+)/FITC(+) cells in the skin-draining lymph nodes from control and irradiated mice produced on a per cell basis similar levels of IL-12 and PGE(2) were phenotypically mature and efficient at presenting FITC to lymphocytes from FITC-sensitized mice. Ag presentation by FACS-sorted CD11c(+) lymph node cells isolated 4 days after UVB irradiation was as efficient as were cells from unirradiated mice at presentation in vitro of an OVA peptide (OVA(323-339)) to CD4(+) cells from OVA-TCR-transgenic DO11.10 mice. Further, IFN-gamma levels were increased in the cultures containing CD11c(+) cells from UVB-irradiated mice, suggesting that inflammation may precede downstream immunosuppression. These results suggest that the primary cause of reduced contact hypersensitivity responses in mice in which UV irradiation and the sensitizing Ag are applied to different sites several days apart must originate from cells other than CD11c(+) APCs that directly or by production of soluble mediators (IL-12, PGE(2)) affect cellular responses in the nodes of UVB-irradiated mice.