Scribble scrambles parathyroid hormone receptor interactions to regulate phosphate and vitamin D homeostasis.

G protein-coupled receptors, including PTHR, are pivotal for controlling metabolic processes ranging from serum phosphate and vitamin D levels to glucose uptake, and cytoplasmic interactors may modulate their signaling, trafficking, and function. We now show that direct interaction with Scribble, a cell polarity-regulating adaptor protein, modulates PTHR activity. Scribble is a crucial regulator for establishing and developing tissue architecture, and its dysregulation is involved in various disease conditions, including tumor expansion and viral infections. Scribble co-localizes with PTHR at basal and lateral surfaces in polarized cells. Using X-ray crystallography, we show that colocalization is mediated by engaging a short sequence motif at the PTHR C-terminus using Scribble PDZ1 and PDZ3 domain, with binding affinities of 31.7 and 13.4 µM, respectively. Since PTHR controls metabolic functions by actions on renal proximal tubules, we engineered mice to selectively knockout Scribble in proximal tubules. The loss of Scribble impacted serum phosphate and vitamin D levels and caused significant plasma phosphate elevation and increased aggregate vitamin D3 levels, whereas blood glucose levels remained unchanged. Collectively these results identify Scribble as a vital regulator of PTHR-mediated signaling and function. Our findings reveal an unexpected link between renal metabolism and cell polarity signaling.

MCCS: a novel recognition pattern-based method for fast track discovery of anti-SARS-CoV-2 drugs.

Given the scale and rapid spread of the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, or 2019-nCoV), there is an urgent need to identify therapeutics that are effective against COVID-19 before vaccines are available. Since the current rate of SARS-CoV-2 knowledge acquisition via traditional research methods is not sufficient to match the rapid spread of the virus, novel strategies of drug discovery for SARS-CoV-2 infection are required. Structure-based virtual screening for example relies primarily on docking scores and does not take the importance of key residues into consideration, which may lead to a significantly higher incidence rate of false-positive results. Our novel in silico approach, which overcomes these limitations, can be utilized to quickly evaluate FDA-approved drugs for repurposing and combination, as well as designing new chemical agents with therapeutic potential for COVID-19. As a result, anti-HIV or antiviral drugs (lopinavir, tenofovir disoproxil, fosamprenavir and ganciclovir), antiflu drugs (peramivir and zanamivir) and an anti-HCV drug (sofosbuvir) are predicted to bind to 3CLPro in SARS-CoV-2 with therapeutic potential for COVID-19 infection by our new protocol. In addition, we also propose three antidiabetic drugs (acarbose, glyburide and tolazamide) for the potential treatment of COVID-19. Finally, we apply our new virus chemogenomics knowledgebase platform with the integrated machine-learning computing algorithms to identify the potential drug combinations (e.g. remdesivir+chloroquine), which are congruent with ongoing clinical trials. In addition, another 10 compounds from CAS COVID-19 antiviral candidate compounds dataset are also suggested by Molecular Complex Characterizing System with potential treatment for COVID-19. Our work provides a novel strategy for the repurposing and combinations of drugs in the market and for prediction of chemical candidates with anti-COVID-19 potential.

Overcoming pancreatic cancer immune resistance by codelivery of CCR2 antagonist using a STING-activating gemcitabine-based nanocarrier.

STING agonist has recently gained much attention for cancer treatment, but the therapeutic potential of STING agonist is hampered by STING-associated tumor immune resistance. In this work, guided by both bioinformatics and computer modeling, we rationally designed a "one stone hits two birds" nanoparticle-based strategy to simultaneously activate STING innate immune response while eliminating STING-associated immune resistance for the treatment of pancreatic ductal adenocarcinoma (PDAC). We discovered that the ultra-small sized micellar system based on gemcitabine-conjugated polymer (PGEM), which showed superior capacity of penetration in pancreatic tumor spheroid model and orthotopic tumor model, could serve as a novel "STING agonist". The activation of STING signaling in dendritic cells (DCs) by PGEM increased both innate nature killer (NK) and adaptive anti-tumor T cell response. However, activation of STING signaling by PGEM in tumor cells also drove the induction of chemokines CCL2 and CCL7, resulting in immune resistance by recruiting tumor associated macrophage (TAM) and myeloid-derived suppressor cells (MDSCs). Through the combination of computer modeling and experimental screening, we developed a dual delivery modality by incorporating a CCR2 (the receptor shared by both CCL2 and CCL7) antagonist PF-6309 (PF) into PGEM micellar system. Our studies demonstrated that PGEM/PF formulation significantly reduced pancreatic tumor burden and induced potent anti-tumor immunity through reversing the CCL2/CCL7-mediated immunosuppression. Moreover, PGEM/PF sensitized PDAC tumors to anti-PD-1 therapy, leading to complete suppression/eradication of the tumors. Our work has shed light to the multi-faceted role of STING activation and provided a novel immunotherapy regimen to maximize the benefit of STING activation for PDAC treatment. In addition, this work paved a new way for bioinformatics and computer modeling-guided rational design of nanomedicine.

Fexofenadine Plasma Concentrations to Estimate Systemic Exposure in Healthy Adults Using a Limited Sampling Strategy with a Population Pharmacokinetic Approach.

BACKGROUND: Fexofenadine is a recommended in vivo probe drug for phenotyping P-glycoprotein (P-gp) and organic anion transporting polypeptide (OATP) 1B1/3 transporter activities. This study evaluated a limited sampling strategy using a population pharmacokinetic approach to estimate plasma fexofenadine exposure as an index of P-gp and OATP activities. METHODS: In a previous study, a single oral dose of fexofenadine (120 mg) was administered alone or in combination with grapefruit juice, Panax ginseng , or Echinacea purpurea to healthy adult participants. Serial plasma samples were collected up to 72 hours after administration and fexofenadine concentrations were measured. A population pharmacokinetic model was developed using nonlinear mixed-effects modeling. Limited sampling models (LSMs) using single and 2-timepoint fexofenadine concentrations were compared with full profiles from intense sampling using empirical Bayesian post hoc estimations of systemic exposure derived from the population pharmacokinetic model. Predefined criteria for LSM selection and validation included a coefficient of determination (R 2 ) ≥ 0.90, relative percent mean prediction error ≥ -5 to ≤5%, relative percent mean absolute error ≤ 10%, and relative percent root mean square error ≤ 15%. RESULTS: Fexofenadine concentrations (n = 1520) were well described using a 2-compartment model. Grapefruit juice decreased the relative oral bioavailability of fexofenadine by 25%, whereas P. ginseng and E. purpurea had no effect. All the evaluated single timepoint fexofenadine LSMs showed unacceptable percent mean prediction error, percent mean absolute error, and/or percent root mean square error. Although adding a second time point improved precision, the predefined criteria were not met. CONCLUSIONS: Identifying novel fexofenadine LSMs to estimate P-gp and OATP1B1/3 activities in healthy adults for future transporter-mediated drug-drug interaction studies remains elusive.

Limitations of fexofenadine limited sampling strategy using plasma concentrations and partial area under the concentration-time curve to estimate transporter activity in healthy adults.

OBJECTIVE: Fexofenadine is a probe drug used to phenotype P-glycoprotein (P-gp) and organic anion transporting polypeptide (OATP) 1B1/3 activities. This study evaluated a limited sampling strategy using plasma concentrations and/or partial area under the concentration versus time curves (AUCs) to estimate systemic exposure and, potentially, P-gp and OATP1B1/3 activities. MATERIALS AND METHODS: Plasma concentration versus time data were obtained from 53 healthy adult participants (22 females) from four published studies. Participants were administered a single oral dose (120 mg) of fexofenadine during constitutive P-gp and OATP1B1/3 conditions. Concentration-time data were divided into a training (n = 18) and validation (n = 35) set. Backwards stepwise linear regression generated single-, 2-timepoint, and partial AUC limited sampling models (LSMs). Noncompartmental analysis methods were used to determine total AUC (AUC0-lNF) from intensive sampling. Coefficient of determination (r2) and bias and precision were assessed via relative percent mean prediction error (%MPE), relative percent mean absolute error (%MAE), and relative percent root mean square error (%RMSE). RESULTS: The geometric mean observed AUC0-INF was 1,680 ng×h/mL. The 2-, 5-, and 2- plus 5-hour LSMs met backwards stepwise linear regression significance (p < 0.15) to remain in the model but had unacceptable %RMSE (17 - 29%). The majority of partial AUC LSMs had unacceptable r2 (0.21 - 0.83), with all models having unacceptable %MAE (12 - 35%). CONCLUSION: Fexofenadine limited sampling strategy using single-timepoint, 2-timepoint, and partial AUCs were unable to accurately estimate AUC0-lNF and thus constitutive P-gp and OATB1B1/3 activities in healthy adults. Timepoints that were not measured or selected may have improved LSM performance.

Association of Rosuvastatin Use with Risk of Hematuria and Proteinuria.

BACKGROUND: Despite reports of hematuria and proteinuria with rosuvastatin use at the time of its approval by the US Food and Drug Association (FDA), little postmarketing surveillance exists to assess real-world risk. Current labeling suggests dose reduction (maximum daily dose of 10 mg) for patients with severe CKD. METHODS: Using deidentified electronic health record data, we analyzed 152,101 and 795,799 new users of rosuvastatin and atorvastatin, respectively, from 2011 to 2019. We estimated inverse probability of treatment-weighted hazard ratios (HRs) of hematuria, proteinuria, and kidney failure with replacement therapy (KFRT) associated with rosuvastatin. We reported the initial rosuvastatin dose across eGFR categories and evaluated for a dose effect on hematuria and proteinuria. RESULTS: Overall, we identified 2.9% of patients with hematuria and 1.0% with proteinuria during a median follow-up of 3.1 years. Compared with atorvastatin, rosuvastatin was associated with increased risk of hematuria (HR, 1.08; 95% confidence interval [95% CI], 1.04 to 1.11), proteinuria (HR, 1.17; 95% CI, 1.10 to 1.25), and KFRT (HR, 1.15; 95% CI, 1.02 to 1.30). A substantial share (44%) of patients with eGFR <30 ml/min per 1.73 m2 was prescribed high-dose rosuvastatin (20 or 40 mg daily). Risk was higher with higher rosuvastatin dose. CONCLUSIONS: Compared with atorvastatin, rosuvastatin was associated with increased risk of hematuria, proteinuria, and KFRT. Among patients with eGFR <30 ml/min per 1.73 m2, 44% were prescribed a rosuvastatin daily dose exceeding the FDA's recommended 10 mg daily dose. Our findings suggest the need for greater care in prescribing and monitoring rosuvastatin, particularly in patients who receive high doses or who have severe CKD.

Physiologically Based Pharmacokinetic Modeling of Vitamin D3 and Metabolites in Vitamin D-Insufficient Patients.

A physiologically based pharmacokinetic (PBPK) model of vitamin D3 and metabolites [25(OH)D3, 1,25(OH)2D3, and 24,25(OH)2D3] is presented. In this study, patients with 25(OH)D3 plasma concentrations below 30 ng/ml were studied after a single dose of 5000 I.U. (125 µg) cholecalciferol, provided with 5000 I.U. daily cholecalciferol supplementation until vitamin D replete [25(OH)D3 plasma concentrations above 30 ng/ml], and had serial plasma samples were collected at each phase for 14 days. Total concentrations of vitamin D3 and metabolites were measured by ultra-high performance liquid chromatography tandem mass spectrometry. A nine-compartment PBPK model was built using MATLAB to represent the triphasic study nature (insufficient, replenishing, and sufficient). The stimulatory and inhibitory effect of 1,25(OH)2D3 were incorporated by fold-changes in the primary metabolic enzymes CYP27B1 and CYP24A1, respectively. Incorporation of dynamic adipose partition coefficients for vitamin D3 and 25(OH)D3 and variable enzymatic reactions aided in model fitting. Measures of model predictions agreed well with data from metabolites, with 97%, 88%, and 98% of the data for 25(OH)D3, 24,25(OH)2D3, and 1,25(OH)2D3, respectively, within twofold of unity (fold error values between 0.5 and 2.0). Bootstrapping was performed and optimized parameters were reported with 95% confidence intervals. This PBPK model could be a useful tool for understanding the connections between vitamin D and its metabolites under a variety of clinical situations. SIGNIFICANCE STATEMENT: This study developed a physiologically based pharmacokinetic (PBPK) model of vitamin D3 and metabolites for patients moving from an insufficient to a repleted state over a period of 16 weeks.

Effect of removing race from glomerular filtration rate-estimating equations on anticancer drug dosing and eligibility: a retrospective analysis of National Cancer Institute phase 1 clinical trial participants.

BACKGROUND: Kidney function assessment by estimated glomerular filtration rate (eGFR) equations, such as the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation, is important to determine dosing and eligibility for anticancer drugs. Inclusion of race in eGFR equations calculates a higher eGFR at a given serum creatinine concentration for Black patients versus non-Black patients. We aimed to characterise the effect of removing race from the CKD-EPI equation on dosing and eligibility of anticancer drugs with kidney function cutoffs. METHODS: We did a retrospective analysis of patients enrolled in phase 1 studies sponsored by the Cancer Therapy Evaluation Program between January, 1995, and October, 2010. eGFR based on creatinine (eGFRCr) was calculated by the CKD-EPI equation and a version of the CKD-EPI equation without the race term (CKD-EPIwithout race). Estimated creatinine clearance (eClCr) was calculated by the Cockcroft-Gault equation. Dosing simulations based on each assessment of kidney function were done for ten anticancer drugs with kidney function cutoffs for dosing (oxaliplatin, capecitabine, etoposide, topotecan, fludarabine, and bleomycin) or eligibility (cisplatin, pemetrexed, bendamustine, and mitomycin) based on labelling approved by the US Food and Drug Administration or consensus guidelines. The absolute proportion of patients eligible or in each renal dosing range was calculated for each drug. Eligibility and dosing discordance rates were also calculated. FINDINGS: Demographics and laboratory values from 340 Black patients (172 men and 168 women) were used. Median age was 57 years (IQR 47-64), median bodyweight was 78·1 kg (67·0-89·8), median body surface area was 1·91 m2 (1·77-2·09), and median serum creatinine concentration was 0·9 mg/dL (0·8-1·1). Median eGFRCr or eClCr was 103 mL/min (85-122) calculated by CKD-EPI, 89 mL/min (73-105) by CKD-EPIwithout race, and 90 mL/min (72-120) by Cockcroft-Gault. Black patients were recommended to receive dose reductions or were rendered ineligible to receive drug more frequently when using CKD-EPIwithout race than when using CKD-EPI, but at a similar rate as when using Cockcroft-Gault. The number of patients ineligible for therapy or recommended to receive any renal dose adjustment when CKD-EPIwithout race versus CKD-EPI was used increased by 72% (from 25 of 340 to 43 of 340 patients) for cisplatin, by 120% (from five to 11) for pemetrexed, by 67% (from three to five) for bendamustine, by 150% (from ten to 25) for capecitabine, by 150% (from ten to 25) for etoposide, by 67% (from three to five) for topotecan, by 61% (from 74 to 119) for fludarabine, and by 163% (from eight to 21) for bleomycin. Up to 18% of patients had discordant recommendations using CKD-EPIwithout race versus CKD-EPI. INTERPRETATION: Removing race from the CKD-EPI equation will calculate a lower eGFR for Black patients and exclude more patients from receiving anticancer therapy, which could lead to undertreatment of Black patients with cancer and adversely affect their outcomes. FUNDING: National Institutes of Health.

Recommendations from the EXTRIP workgroup on extracorporeal treatment for baclofen poisoning.

Baclofen toxicity results from intentional self-poisoning (acute baclofen poisoning) or accumulation of therapeutic dose in the setting of impaired kidney function. Standard care includes baclofen discontinuation, respiratory support and seizure treatment. Use of extracorporeal treatments (ECTRs) is controversial. To clarify this, a comprehensive review of the literature on the effect of ECTRs in baclofen toxicity was performed and recommendations following EXTRIP methods were formulated based on 43 studies (1 comparative cohort, 1 aggregate results cohort, 1 pharmacokinetic modeling, and 40 patient reports or series). Toxicokinetic data were available for 20 patients. Baclofen's dialyzability is limited by a high endogenous clearance and a short half-life in patients with normal kidney function. The workgroup assessed baclofen as "Moderately dialyzable" by intermittent hemodialysis for patients with normal kidney function (quality of evidence C) and "Dialyzable" for patients with impaired kidney function (quality of evidence C). Clinical data were available for 25 patients with acute baclofen poisoning and 46 patients with toxicity from therapeutic baclofen in kidney impairment. No deaths or sequelae were reported. Mortality in historical controls was rare. No benefit of ECTR was identified in patients with acute baclofen poisoning. Indirect evidence suggests a benefit of ECTR in reducing the duration of toxic encephalopathy from therapeutic baclofen in kidney impairment. These potential benefits were balanced against added costs and harms related to the insertion of a catheter, the procedure itself, and the potential of baclofen withdrawal. Thus, the EXTRIP workgroup suggests against performing ECTR in addition to standard care for acute baclofen poisoning and suggests performing ECTR in toxicity from therapeutic baclofen in kidney impairment, especially in the presence of coma requiring mechanical ventilation.

Extracorporeal treatment for poisoning to beta-adrenergic antagonists: systematic review and recommendations from the EXTRIP workgroup.

BACKGROUND: ß-adrenergic antagonists (BAAs) are used to treat cardiovascular disease such as ischemic heart disease, congestive heart failure, dysrhythmias, and hypertension. Poisoning from BAAs can lead to severe morbidity and mortality. We aimed to determine the utility of extracorporeal treatments (ECTRs) in BAAs poisoning. METHODS: We conducted systematic reviews of the literature, screened studies, extracted data, and summarized findings following published EXTRIP methods. RESULTS: A total of 76 studies (4 in vitro and 2 animal experiments, 1 pharmacokinetic simulation study, 37 pharmacokinetic studies on patients with end-stage kidney disease, and 32 case reports or case series) met inclusion criteria. Toxicokinetic or pharmacokinetic data were available on 334 patients (including 73 for atenolol, 54 for propranolol, and 17 for sotalol). For intermittent hemodialysis, atenolol, nadolol, practolol, and sotalol were assessed as dialyzable; acebutolol, bisoprolol, and metipranolol were assessed as moderately dialyzable; metoprolol and talinolol were considered slightly dialyzable; and betaxolol, carvedilol, labetalol, mepindolol, propranolol, and timolol were considered not dialyzable. Data were available for clinical analysis on 37 BAA poisoned patients (including 9 patients for atenolol, 9 for propranolol, and 9 for sotalol), and no reliable comparison between the ECTR cohort and historical controls treated with standard care alone could be performed. The EXTRIP workgroup recommends against using ECTR for patients severely poisoned with propranolol (strong recommendation, very low quality evidence). The workgroup offered no recommendation for ECTR in patients severely poisoned with atenolol or sotalol because of apparent balance of risks and benefits, except for impaired kidney function in which ECTR is suggested (weak recommendation, very low quality of evidence). Indications for ECTR in patients with impaired kidney function include refractory bradycardia and hypotension for atenolol or sotalol poisoning, and recurrent torsade de pointes for sotalol. Although other BAAs were considered dialyzable, clinical data were too limited to develop recommendations. CONCLUSIONS: BAAs have different properties affecting their removal by ECTR. The EXTRIP workgroup assessed propranolol as non-dialyzable. Atenolol and sotalol were assessed as dialyzable in patients with kidney impairment, and the workgroup suggests ECTR in patients severely poisoned with these drugs when aforementioned indications are present.

Influence of vitamin D treatment on functional expression of drug disposition pathways in human kidney proximal tubule cells during simulated uremia.

Effects of cholecalciferol (VitD3) and calcitriol (1,25-VitD3), on the expression and function of major vitamin D metabolizing enzymes (cytochrome P450 [CYP]2R1, CYP24A1) and select drug transport pathways (ABCB1/P-gp, SLCO4C1/OATP4C1) were evaluated in human kidney proximal tubule epithelial cells (hPTECs) under normal and uraemic serum conditions.hPTECs were incubated with 10% normal or uraemic serum for 24 h followed by treatment with 2% ethanol vehicle, or 100 and 240 nM doses of VitD3, or 1,25-VitD3 for 6 days. The effects of treatment on mRNA and protein expression and functional activity of select CYP enzymes and transporters were assessedUnder uraemic serum, treatment with 1,25-VitD3 resulted in increased mRNA but decreased protein expression of CYP2R1. Activity of CYP2R1 was not influenced by serum or VitD analogues. CYP24A1 expression was increased with 1,25-VitD3 under normal as well as uraemic serum, although to a lesser extent. ABCB1/P-gp mRNA expression increased under normal and uraemic serum, with exposure to 1,25-VitD3. SLCO4C1/OATP4C1 exhibited increased mRNA but decreased protein expression, under uraemic serum + 1,25-VitD3. Functional assessments of transport showed no changes regardless of exposure to serum or 1,25-VitD3.Key findings indicate that uraemic serum and VitD treatment led to differential effects on the functional expression of CYPs and transporters in hPTECs.

Extracorporeal Treatment for Chloroquine, Hydroxychloroquine, and Quinine Poisoning: Systematic Review and Recommendations from the EXTRIP Workgroup.

BACKGROUND: Although chloroquine, hydroxychloroquine, and quinine are used for a range of medical conditions, recent research suggested a potential role in treating COVID-19. The resultant increase in prescribing was accompanied by an increase in adverse events, including severe toxicity and death. The Extracorporeal Treatments in Poisoning (EXTRIP) workgroup sought to determine the effect of and indications for extracorporeal treatments in cases of poisoning with these drugs. METHODS: We conducted systematic reviews of the literature, screened studies, extracted data, and summarized findings following published EXTRIP methods. RESULTS: A total of 44 studies (three in vitro studies, two animal studies, 28 patient reports or patient series, and 11 pharmacokinetic studies) met inclusion criteria regarding the effect of extracorporeal treatments. Toxicokinetic or pharmacokinetic analysis was available for 61 patients (13 chloroquine, three hydroxychloroquine, and 45 quinine). Clinical data were available for analysis from 38 patients, including 12 with chloroquine toxicity, one with hydroxychloroquine toxicity, and 25 with quinine toxicity. All three drugs were classified as non-dialyzable (not amenable to clinically significant removal by extracorporeal treatments). The available data do not support using extracorporeal treatments in addition to standard care for patients severely poisoned with either chloroquine or quinine (strong recommendation, very low quality of evidence). Although hydroxychloroquine was assessed as being non-dialyzable, the clinical evidence was not sufficient to support a formal recommendation regarding the use of extracorporeal treatments for this drug. CONCLUSIONS: On the basis of our systematic review and analysis, the EXTRIP workgroup recommends against using extracorporeal methods to enhance elimination of these drugs in patients with severe chloroquine or quinine poisoning.

Simultaneous Assessment of Hepatic Transport and Metabolism Pathways with a Single Probe Using Individualized PBPK Modeling of 14CO2 Production Rate Data.

Erythromycin is a substrate of cytochrome P4503A4 (CYP3A4) and multiple drug transporters. Although clinical evidence suggests that uptake transport is likely to play a dominant role in erythromycin's disposition, the relative contributions of individual pathways are unclear. Phenotypic evaluation of multiple pathways generally requires a probe drug cocktail. This approach can result in ambiguous conclusions due to imprecision stemming from overlapping specificity of multiple drugs. We hypothesized that an individualized physiologically based pharmacokinetic modeling approach incorporating 14CO2 production rates (iPBPK-R) of the erythromycin breath test (ERMBT) would enable us to differentiate the contribution of metabolic and transporter pathways to erythromycin disposition. A seven-compartmental physiologically based pharmacokinetic (PBPK) model was built for 14C-erythromycin administered intravenously. Transporter clearance and CYP3A4 clearance were embedded in hepatic compartments. 14CO2 production rates were simulated taking the first derivative of by-product 14CO2 concentrations. Parameters related to nonrenal elimination pathways were estimated by model fitting the ERMBT data of 12 healthy subjects individually. Optimized iPBPK-R models fit the individual rate data well. Using one probe, nine PBPK parameters were simultaneously estimated per individual. Maximum velocity of uptake transport, CYP3A4 clearance, total passive diffusion, and others were found to collectively control 14CO2 production rates. The median CYP3A4 clearance was 12.2% of the input clearance. Male subjects had lower CYP3A4 activity than female subjects by 11.3%. We applied iPBPK-R to ERMBT data to distinguish and simultaneously estimate the activity of multiple nonrenal elimination pathways in healthy subjects. The iPBPK-R framework is a novel tool for delineating rate-limiting and non-rate-limiting elimination pathways using a single probe. SIGNIFICANCE STATEMENT: Our developed individualized physiologically based pharmacokinetic modeling approach incorporating rate data (iPBPK-R) enabled us to distinguish and simultaneously estimate the activity of multiple nonrenal elimination pathways of erythromycin in healthy subjects. A new interpretation of erythromycin breath test (ERMBT) data was also obtained via iPBPK-R. We found that rate data have rich information allowing estimation of per-person PBPK parameters. This study serves as proof of principle that the iPBPK-R framework is a novel tool for delineating rate-limiting and non-rate-limiting elimination pathways using a single probe. iPBPK-R can be applied to other rate-derived data beyond ERMBT. Potential areas of application include drug-drug interaction, pathophysiological effects on drug disposition, and the role of biomarkers on hemodialysis efficiency utilizing estimated adjustment factors with correlation analysis.

Activation of Constitutive Androstane Receptor Ameliorates Renal Ischemia-Reperfusion-Induced Kidney and Liver Injury.

Acute kidney injury (AKI) is associate with high mortality. Despite evidence of AKI-induced distant organ injury, a relationship between AKI and liver injury has not been clearly established. The goal of this study is to investigate whether renal ischemia-reperfusion (IR) can affect liver pathophysiology. We showed that renal IR in mice induced fatty liver and compromised liver function through the downregulation of constitutive androstane receptor (CAR; -90.4%) and inhibition of hepatic very-low-density lipoprotein triglyceride (VLDL-TG) secretion (-28.4%). Treatment of mice with the CAR agonist 1,4-bis[2-(3,5 dichloropyridyloxy)] benzene (TCPOBOP) prevented the development of AKI-induced fatty liver and liver injury, which was associated with the attenuation of AKI-induced inhibition of VLDL-TG secretion. The hepatoprotective effect of TCPOBOP was abolished in CAR-/- mice. Interestingly, alleviation of fatty liver by TCPOBOP also improved the kidney function, whereas CAR ablation sensitized mice to AKI-induced kidney injury and lethality. The serum concentrations of interleukin-6 (IL-6) were elevated by 27-fold after renal IR, but were normalized in TCPOBOP-treated AKI mice, suggesting that the increased release of IL-6 from the kidney may have mediated the AKI responsive liver injury. Taken together, our results revealed an interesting kidney-liver organ cross-talk in response to AKI. Given the importance of CAR in the pathogenesis of renal IR-induced fatty liver and impaired kidney function, fatty liver can be considered as an important risk factor for kidney injury, and a timely management of hepatic steatosis by CAR activation may help to restore kidney function in patients with AKI or kidney transplant.

Use of extracorporeal treatments in the management of poisonings.

Historically, the clinical application of extracorporeal treatments (ECTRs), such as hemodialysis or hemoperfusion, was first intended for poisoned patients. With time, ECTRs were used almost indiscriminately to facilitate the elimination of many poisons, albeit with uncertain clinical benefit. To determine the precise role of ECTRs in poisoning situations, multiple variables need to be considered including a careful risk assessment, the poison's characteristics including toxicokinetics, alternative treatments, the patient's clinical status, and intricacies of available ECTRs, all of which are reviewed in this article. Recently, evidence-based and expert opinion-based recommendations from the EXTRIP workgroup were also published to help minimize the knowledge gap in this area.

Decreased Kidney Function Is Associated with Enhanced Hepatic Flavin Monooxygenase Activity and Increased Circulating Trimethylamine N-Oxide Concentrations in Mice.

Circulating trimethylamine N-oxide (TMAO) predicts poor cardiovascular outcomes in patients with chronic kidney disease (CKD). Accumulation of serum TMAO has been observed in CKD patients; however, the mechanisms contributing to this finding have been inadequately explored. The purpose of this study was to investigate the mechanisms responsible for TMAO accumulation in the setting of decreased kidney function using a CKD mouse model. Mice were fed a diet supplemented with 0.2% adenine to induce CKD, which resulted in increased serum TMAO concentrations (females: CKD 29.4 ± 32.1 µM vs. non-CKD 6.9 ± 6.1 µM, P < 0.05; males: CKD 18.5 ± 13.1 µM vs. non-CKD 1.0 ± 0.5 µM, P < 0.001). As anticipated, accumulation of circulating TMAO was accompanied by a decrease in renal clearance (females: CKD 5.2 ± 3.8 µl/min vs. non-CKD 90.4 ± 78.1 µl/min, P < 0.01; males: CKD 10.4 ± 8.1 µl/min vs. non-CKD 260.4 ± 134.5 µl/min; P < 0.001) and fractional excretion of TMAO. Additionally, CKD animals exhibited an increase in hepatic flavin monooxygenase (FMO)-mediated formation of TMAO (females: CKD 125920 ± 2181 pmol/mg per 60 minutes vs. non-CKD 110299 ± 4196 pmol/mg per 60 minutes, P < 0.001; males: CKD 131286 ± 2776 pmol/mg per 60 minutes vs. non-CKD 74269 ± 1558 pmol/mg per 60 minutes, P < 0.001), which likely resulted from increased FMO3 expression in CKD mice. The current study provides evidence that both decreased renal clearance and increased hepatic production of TMAO may contribute to increments in serum TMAO in the setting of CKD. Hepatic FMO activity may represent a novel therapeutic target for lowering circulating TMAO in CKD patients.

Beta-2 microglobulin clearance in high-flux dialysis and convective dialysis modalities: a meta-analysis of published studies.

Background: Recent meta-analyses suggest that higher removal of beta-2 microglobulin (ß2M) with either high-flux (HFD) dialysis or hemodiafiltration (HDF) may be associated with decreased total and cardiovascular mortality in dialysis patients. However, there are limited data about the performance of high flux dialyzers and/or convective therapies in removing ß2M. Methods: This is a random effects meta-analysis and meta-regression of data extracted from randomized controlled trials and observational studies in hemodialysis, hemofiltration and HDF regarding the efficiency of high flux dialyzers to remove ß2M. Studies were searched using ProQuest in SCOPUS, EMBASE and MEDLINE. Results: We included 69 studies from 1 January 2001 to 12 June 2017 on 1879 patients with 6771 available measurements. Average ß2M clearance was 48.75 mL/min [95% confidence interval (CI) 42.50-55.21] for conventional HF dialysis, and 87.06 mL/min (95% CI 75.08-99.03) for convective therapies (hemofiltration and HDF) with substantial heterogeneity among studies [P (Q) ≤ 0.001]. In multivariable meta-regression analyses, we found significantly higher ß2M clearance for polyarylethersulfone dialyzers when used for HFD and polysulfone membranes in convective therapies. However, the mass of ß2M removed into the dialysate did not depend on membrane material. Adjusted dialysate-side (-22.279, 95% CI -9.8 to -34.757, P < 0.001) ß2M clearances were significantly lower than whole blood clearances, suggesting that adsorption contributes substantially to ß2M removal. Higher Kuf, blood flow and substitution fluid rates but not dialysate flow rates were associated with statistically significant and clinically meaningful elevation in ß2M clearance from the body independent of the dialysis modality. Conclusions: Membrane composition and characteristics, modality (convective versus diffusive), blood flow rates and substitution fluid rates in HDF play a significant role in the efficient removal of ß2M from the body in both diffusive and convective dialysis.

Drug Transporters and Na+/H+ Exchange Regulatory Factor PSD-95/Drosophila Discs Large/ZO-1 Proteins.

Drug transporters govern the absorption, distribution, and elimination of pharmacologically active compounds. Members of the solute carrier and ATP binding-cassette drug transporter family mediate cellular drug uptake and efflux processes, thereby coordinating the vectorial movement of drugs across epithelial barriers. To exert their physiologic and pharmacological function in polarized epithelia, drug transporters must be targeted and stabilized to appropriate regions of the cell membrane (i.e., apical versus basolateral). Despite the critical importance of drug transporter membrane targeting, the mechanisms that underlie these processes are largely unknown. Several clinically significant drug transporters possess a recognition sequence that binds to PSD-95/Drosophila discs large/ZO-1 (PDZ) proteins. PDZ proteins, such as the Na(+)/H(+) exchanger regulatory factor (NHERF) family, act to stabilize and organize membrane targeting of multiple transmembrane proteins, including many clinically relevant drug transporters. These PDZ proteins are normally abundant at apical membranes, where they tether membrane-delimited transporters. NHERF expression is particularly high at the apical membrane in polarized tissue such as intestinal, hepatic, and renal epithelia, tissues important to drug disposition. Several recent studies have highlighted NHERF proteins as determinants of drug transporter function secondary to their role in controlling membrane abundance and localization. Mounting evidence strongly suggests that NHERF proteins may have clinically significant roles in pharmacokinetics and pharmacodynamics of several pharmacologically active compounds and may affect drug action in cancer and chronic kidney disease. For these reasons, NHERF proteins represent a novel class of post-translational mediators of drug transport and novel targets for new drug development.

Probenecid, an organic anion transporter 1 and 3 inhibitor, increases plasma and brain exposure of N-acetylcysteine.

1. N-acetylcysteine (NAC) is being investigated as an antioxidant for several conditions including traumatic brain injury, but the mechanism by which it crosses membrane barriers is unknown. We have attempted to understand how the transporter inhibitor, probenecid, affects NAC pharmacokinetics and to evaluate the interaction of NAC with transporters. 2. Juvenile Sprague-Dawley rats were administered NAC alone or in combination with probenecid intraperitoneally. Plasma and brain samples were collected serially and NAC concentrations were measured. Transporter studies were conducted with human embryonic kidney-293 cells that overexpress organic anion transporter (OAT)1 or OAT3 and with human multi-drug resistance-associated protein (MRP)1 or MRP4 membrane vesicles. 3. NAC area under the curve was increased in plasma (1.65-fold) and brain (2.41-fold) by probenecid. The apparent plasma clearance was decreased by 65%. Time- and concentration-dependent NAC uptake that was inhibitable by probenecid was observed with OAT1 and OAT3. No uptake of NAC was observed with MRP1 or MRP4. 4. Our results indicate for the first time that NAC is substrate for OAT1 and OAT3 and that probenecid increases NAC plasma and brain exposure in vivo. These data provide insight regarding how NAC crosses biological barriers and suggest a promising therapeutic strategy to increase NAC exposure.