The Prescription of Drugs That Inhibit Organic Anion Transporters 1 or 3 Is Associated with the Plasma Accumulation of Uremic Toxins in Kidney Transplant Recipients

The renal elimination of uremic toxins (UTs) can be potentially altered by drugs that inhibit organic anion transporters 1/3 (OAT1/OAT3). The objective of the present study was to determine whether the prescription of at least one OAT1/OAT3 inhibitor was associated with the plasma accumulation of certain UTs in kidney transplant recipients. We included 403 kidney transplant recipients. For each patient, we recorded all prescription drugs known to inhibit OAT1/OAT3. Plasma levels of four UTs (trimethylamine N-oxide (TMAO), indole acetic acid (IAA), para-cresylsulfate (pCS), and indoxylsulfate (IxS) were assayed using liquid chromatography-tandem mass spectrometry. Plasma UT levels were significantly higher among patients prescribed at least one OAT inhibitor (n = 311) than among patients not prescribed any OAT inhibitors (n = 92). Multivariate analysis revealed that after adjustment for age, estimated glomerular filtration rate (eGFR), plasma level of albumin and time since transplantation, prescription of an OAT1/OAT3 inhibitor was independently associated with the plasma accumulation of pCS (adjusted odds ratio (95% confidence interval): 2.11 (1.26; 3.61]). Our results emphasize the importance of understanding the interactions between drugs and UTs and those involving UT transporters in particular.

HeGRI: A Novel Index of Serum Hepcidin Suppression in Relation to the Degree of Renal Dysfunction among β-Thalassemia Major Patients

Background: The progressive renal function inadequacy results in altered hepcidin metabolism due to a shifting of its renal elimination, which consequently affects enteric iron absorption and iron stores’ availability. This study aimed to investigate and correlate renal function, iron status, and hepcidin in patients with β-thalassemia major through a novel index. Methods: In this 1:1 case–control study, serum hepcidin, serum ferritin, iron study, hematological and renal function parameters were compared between 60 β-thalassemia major patients with iron overload and 61 healthy individuals (2–30 years old). Results: The concentrations of serum hepcidin (21.898 vs. 9.941 ng/mL; p < 0.001) and eGFR (179.71 vs. 132.95; p < 0.001) were significantly higher in β-thalassemia major patients compared to the controls. The serum hepcidin levels decreased with increasing levels of total iron-binding capacity (TIBC; β = −0.442; p = 0.024), transferrin saturation (β = −0.343; p = 0.023), serum creatinine (β = −0.625; p = 0.0030), and eGFR (β = −0.496; p = 0.011). The mean hepcidin/ferritin ratio was significantly lower in the β-thalassemia major cases (0.0069 vs. 0.3970; p < 0.001). The novel hepcidin/eGFR ratio index (HeGRI) was significantly higher in the patient group compared to controls (0.12 vs. 0.09; p = 0.031), respectively. Conclusions: These results suggest that HeGRI could be a potential index of the appropriateness of serum hepcidin suppression associated with the degree of renal dysfunction among β-thalassemia major patients.

Towards Optimized Bioavailability of 99mTc-Labeled Barbiturates for Non-invasive Imaging of Matrix Metalloproteinase Activity

Introduction Dysregulated activity of matrix metalloproteinases (MMPs) drives a variety of pathophysiological conditions. Non-invasive imaging of MMP activity in vivo promises diagnostic and prognostic value. However, current targeting strategies by small molecules are typically limited with respect to the bioavailability of the labeled MMP binders in vivo. To this end, we here introduce and compare three chemical modifications of a recently developed barbiturate-based radiotracer with respect to bioavailability and potential to image MMP activity in vivo. Methods Barbiturate-based MMP inhibitors with an identical targeting unit but varying hydrophilicity were synthesized, labeled with technetium-99m, and evaluated in vitro and in vivo. Biodistribution and radiotracer elimination were determined in C57/BL6 mice by serial SPECT imaging. MMP activity was imaged in a MMP-positive subcutaneous xenograft model of human K1 papillary thyroid tumors. In vivo data were validated by scintillation counting, autoradiography, and MMP immunohistochemistry. Results We prepared three new 99mTc‐labeled MMP inhibitors, bearing either a glycine ([99mTc]MEA39), lysine ([99mTc]MEA61), or the ligand HYNIC with the ionic co-ligand TPPTS ([99mTc]MEA223) yielding gradually increasing hydrophilicity. [99mTc]MEA39 and [99mTc]MEA61 were rapidly eliminated via hepatobiliary pathways. In contrast, [99mTc]MEA223 showed delayed in vivo clearance and primary renal elimination. In a thyroid tumor xenograft model, only [99mTc]MEA223 exhibited a high tumor-to-blood ratio that could easily be delineated in SPECT images. Conclusion Introduction of HYNIC/TPPTS into the barbiturate lead structure ([99mTc]MEA223) results in delayed renal elimination and allows non-invasive MMP imaging with high signal-to-noise ratios in a papillary thyroid tumor xenograft model.

Molecular Properties of Drugs Handled by Kidney OATs and Liver OATPs Revealed by Chemoinformatics and Machine Learning: Implications for Kidney and Liver Disease

In patients with liver or kidney disease, it is especially important to consider the routes of metabolism and elimination of small-molecule pharmaceuticals. Once in the blood, numerous drugs are taken up by the liver for metabolism and/or biliary elimination, or by the kidney for renal elimination. Many common drugs are organic anions. The major liver uptake transporters for organic anion drugs are organic anion transporter polypeptides (OATP1B1 or SLCO1B1; OATP1B3 or SLCO1B3), whereas in the kidney they are organic anion transporters (OAT1 or SLC22A6; OAT3 or SLC22A8). Since these particular OATPs are overwhelmingly found in the liver but not the kidney, and these OATs are overwhelmingly found in the kidney but not liver, it is possible to use chemoinformatics, machine learning (ML) and deep learning to analyze liver OATP-transported drugs versus kidney OAT-transported drugs. Our analysis of >30 quantitative physicochemical properties of OATP- and OAT-interacting drugs revealed eight properties that in combination, indicate a high propensity for interaction with “liver” transporters versus “kidney” ones based on machine learning (e.g., random forest, k-nearest neighbors) and deep-learning classification algorithms. Liver OATPs preferred drugs with greater hydrophobicity, higher complexity, and more ringed structures whereas kidney OATs preferred more polar drugs with more carboxyl groups. The results provide a strong molecular basis for tissue-specific targeting strategies, understanding drug–drug interactions as well as drug–metabolite interactions, and suggest a strategy for how drugs with comparable efficacy might be chosen in chronic liver or kidney disease (CKD) to minimize toxicity.

Tumor-Targeted ZW800-1 Analog for Enhanced Tumor Imaging and Photothermal Therapy

ZW800-1, a representative zwitterionic near-infrared (NIR) fluorophore, can minimize background tissue uptake owing to its balanced surface charges, and therefore, is widely used for improved NIR fluorescence imaging. As ZW800-1 has no tumor targetability, tumor imaging is highly dependent on the ability of the molecules conjugated to the ZW800-1. To enable tumor targeting using ZW800-1 without additional conjugation, we developed a tumor-targetable and renal-clearable ZW800-1 analog (ZW800-AM) based on the structural modification of ZW800-1. Specifically, an amine group on the center linker of the ZW800-1 indocyanine backbone was modified by replacing phenoxypropionic acid with tyramine linkage on the meso-chlorine atom. This modification improved the tumor targeting ability, which is known as the structure-inherent targeting strategy. More importantly, ZW800-AM not only showed sufficient tumor accumulation without nonspecific uptake but also produced a photothermal effect, killing tumor cells under 808 nm NIR laser irradiation. In addition, ZW800-AM exhibited rapid renal elimination from the body within 4 h of injection, similar to ZW800-1. Overall, the discovery of ZW800-AM as a bifunctional phototherapeutic agent may provide an ideal alternative for tumor-targeted imaging and phototherapy.

Role of Hepcidin as a biomarker for iron status in patients on regular hemodialysis after treatment of hepatitis C virus

Background Hepcidin, an acute phase reactant protein produced in the liver, is a key regulator of iron homeostasis. Because of its renal elimination and regulation by inflammation, it is possible that progressive renal insufficiency leads to altered hepcidin metabolism. Aim of the work to assess effect of HCV treatment on hepcidin levels in regular heamodialysis patients and its relation to iron status. Patients and Methods This cross sectional study was conducted on 45 ESRD patients on regular hemodialysis. All candidates included in this study subjected to careful history taking, full clinical examination and investigations (including complete blood count, HCVAb, HBVsAg and HIVAb). All patients had positive antibodies for hepatitis C; however, all of them had negative PCR and negative HIV, HBV antibodies. Results In our study, dry weight ranged from 46 to 117 kg with mean 77.36. Weight gain ranged from 2 to 5 kg with mean 3.09.About 87% of patients had LTAVF access. About 12 patients (27%) received blood transfusion once. Timing of transfusion ranged from 4 to 60 month with median of 24 months. Regarding frequency of epoetin dose, 11 patients (24.4%) did not receive epoetin, 16 patients (35.6%) received it twice/week. Only 3 patients (6.7%) received iron therapy for time ranging from 3 to 5 months with mean of 4 months. Mean Hb concentration in our study population was 10.11 ±1.64 gm/dl. The mean of iron was 64.22 ±19.52, TIBC was 409.96 ± 67.85, ferritin was 394.56 ± 239.22 and TSAT% was 22.6 ±7.36. The mean serum hepcidin was 218.51 ±127. Our study demonstrated that increase in serum hepcidin is associated with lower serum Hb and iron levels. On the other hand, there is statistically significant positive correlation between serum hepcidin and both serum ferritin and transferrin saturation. Conclusion Median hepcidin value is elevated in dialysis ESRD patients due to increased inflammation and decreased clearance of hepcidin. Also serum hepcidin levels were lowered in HCV patients. Therefore ESRD patients on maintenance HD after treatment of HCV infection showed elevated levels of serum hepcidin.

Atrial fibrillation in advanced renal failure: are there alternative solutions to warfarin-dicumarol?

Patients with atrial fibrillation (AF) and chronic renal failure (CRF) represent a growing population in epidemiological terms since both conditions increase with advancing age. The association of AF and CRF is burdened with a poor prognosis and with a high risk of adverse events, both ischaemic and haemorrhagic. Oral anticoagulant therapy, in these patients, is more problematic, especially due to the concomitant increased risk of bleeding. The use of direct oral anticoagulants (DOACs) in patients with non-severe renal insufficiency appears to be safe and effective. Since all currently available DOACs are at least partially eliminated by the kidney (dabigatran is the direct anticoagulant with the highest rate of renal elimination, approximately 80%), periodic monitoring of renal function is recommended to evaluate possible need for dosage adjustment. In patients with advanced renal insufficiency, the use of DOAC appears controversial, given the small number of clinical studies that have tested its efficacy and safety. It is known, however, that oral anticoagulation therapy with vitamin K antagonists (VKAs) is associated with an increase in nephropathy and renal-vascular calcification. From this point of view, therapy with DOAC could be more advantageous than VKAs. Data from clinical studies would seem to show that the use of dabigatran and rivaroxaban in these patients may lead to a reduction in the inevitable deterioration of renal function.

Lactic acidosis and hyperlactatemia associated with lamivudine accumulation and sepsis in a kidney transplant recipient—a case report and review of the literature

Background We report a case of sudden, lethal metabolic acidosis in a 70-year-old man on long-term nucleoside reverse transcriptase inhibitor (NRTI) -based antiretroviral therapy (ART) who had developed atypical necrotizing fasciitis 1 month after kidney transplantation. Case presentation The HIV infection of the patient was treated for the last four months with an integrase strand inhibitor (dolutegravir 50 mg/d) plus a NRTI backbone including lamivudine (150 mg/d) and abacavir (600 mg/d). In this renal transplant patient we hypothesize that the co-existence of sepsis, renal failure and an accumulation of lamivudine led to the development of fatal metabolic acidosis and hyperlactatemia. Although lamivudine is only rarely associated with hyperlactatemia, there is evidence that overdose may be a risk factor for developing it. In our patient the lamivudine concentration two days after stopping and during hemodiafiltration was more than 50 times higher than therapeutic target trough concentrations. Likely reasons for this were renal impairment and concurrent treatment with trimethoprim, known to inhibit the renal elimination of lamivudine. Conclusions NRTIs could trigger the development of hyperlactatemia in septic patients. The use of NRTI sparing regimens might be considered in the presence of this critical condition.

The Impact of Functional and Structural Maturation of the Kidney on Susceptibility to Drug and Chemical Toxicity in Neonatal Rodents

Drug responses are often unpredictable in juvenile animal toxicity studies; hence, optimizing dosages is challenging. Renal functional differences based on age of development will often result in vastly different toxicologic responses. Developmental changes in renal function can alter plasma clearance of compounds with extensive renal elimination. Absorption, distribution, metabolism, and excretion of drugs vary depending on animal age and kidney maturation. Toxicity can result in malformations or renal degeneration. Although renal morphologic development in humans generally occurs in utero, maximal levels of tubular secretion, acid–base equilibrium, concentrating ability, or glomerular filtration rate (GFR) are reached postnatally in humans and animals and subject to drug effects. Maturation of renal metabolism and transporters occurs postnatally and plays a critical role in detoxification and excretion. Maturation times must be considered when designing juvenile toxicity studies and may require cohorts of animals of specific ages to achieve optimal dosing schemes and toxicokinetics. In recent years, critical end points and windows of susceptibility have been established comparatively between species to better model pharmacokinetics and understand pediatric nephrotoxicity. There are examples of agents where toxicity is enhanced in neonates, others where it is diminished, and others where rat nephrotoxicity is expressed as juvenile toxicity, but in humans as gestational toxicity.

Human metabolism and kinetics of the UV absorber 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV 328) after oral administration

Abstract2-(2H-Benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV 328; CAS: 25973-55-1) is an ultraviolet light (UV) absorber which belongs to the class of hydroxy phenol benzotriazoles. Therefore, UV 328 is added to plastics and other polymers due to its photostability to prevent discoloration and prolong product stability which may result in an exposure of consumers. However, information about the toxic effects on humans and the human metabolism are still lacking. In the present study, human metabolism pathways of UV 328 and its elimination kinetics were explored. For that purpose, three healthy volunteers were orally exposed to a single dose of 0.3 mg UV 328/kg bodyweight. UV 328 and its metabolites were investigated in blood and urine samples collected until 48 and 72 h after exposure, respectively. Thereby, previously published analytical procedures were applied for the sample analysis using dispersive liquid–liquid microextraction and subsequent measurement via gas chromatography coupled to tandem mass spectrometry with advanced electron ionization. UV 328 was found to be oxidized at its alkyl side chains leading to the formation of hydroxy and/or oxo function with maximum blood concentrations at 8–10 h after exposure for UV 328-6/3-OH, UV 328-4/3-OH and UV 328-4/3-CO. In contrast, a plateau for UV 328-4/3-CO-6/3-OH levels was reached around 10 h post-dosage. The highest blood levels were found for native UV 328 at 8 h after ingestion. Furthermore, biphasic elimination kinetics in blood were revealed for almost all detected metabolites. UV 328 and its metabolites did not occur in blood as conjugates. The renal elimination kinetics were very similar with the kinetics in blood. However, the prominence of the metabolites in urine was somewhat different compared to blood. In contrast, mostly conjugated metabolites occurred for renal elimination. In urine, UV 328-4/3-CO-6/3-OH was found to be the most dominant urinary biomarker followed by UV 328-6/3-OH and UV 328-4/3-OH. In total, approximately 0.1% of the orally administered dose was recovered in urine within 72 h. Although high levels of UV 328 in blood proved good resorption and high systemic availability of the substance in the human body, the urine results revealed a rather low quantitative metabolism and urinary excretion rate. Consequently, biliary excretion as part of the enterohepatic cycle and elimination via feces are assumed to be the preferred pathways instead of renal elimination.