Self-Reported Medication Use and Urinary Drug Metabolites in the German Chronic Kidney Disease (GCKD) Study

BACKGROUND

Polypharmacy is common among patients with CKD, but little is known about the urinary excretion of many drugs and their metabolites among patients with CKD.

METHODS

To evaluate self-reported medication use in relation to urine drug metabolite levels in a large cohort of patients with CKD, the German Chronic Kidney Disease study, we ascertained self-reported use of 158 substances and 41 medication groups, and coded active ingredients according to the Anatomical Therapeutic Chemical Classification System. We used a nontargeted mass spectrometry-based approach to quantify metabolites in urine; calculated specificity, sensitivity, and accuracy of medication use and corresponding metabolite measurements; and used multivariable regression models to evaluate associations and prescription patterns.

RESULTS

Among 4885 participants, there were 108 medication-drug metabolite pairs on the basis of reported medication use and 78 drug metabolites. Accuracy was excellent for measurements of 36 individual substances in which the unchanged drug was measured in urine (median, 98.5%; range, 61.1%-100%). For 66 pairs of substances and their related drug metabolites, median measurement-based specificity and sensitivity were 99.2% (range, 84.0%-100%) and 71.7% (range, 1.2%-100%), respectively. Commonly prescribed medications for hypertension and cardiovascular risk reduction-including angiotensin II receptor blockers, calcium channel blockers, and metoprolol-showed high sensitivity and specificity. Although self-reported use of prescribed analgesics (acetaminophen, ibuprofen) was <3% each, drug metabolite levels indicated higher usage (acetaminophen, 10%-26%; ibuprofen, 10%-18%).

CONCLUSIONS

This comprehensive screen of associations between urine drug metabolite levels and self-reported medication use supports the use of pharmacometabolomics to assess medication adherence and prescription patterns in persons with CKD, and indicates under-reported use of medications available over the counter, such as analgesics.

Establishment of a novel, cell-based autotaxin assay

Autotaxin (ATX) plays an important role in (patho-)physiological lysophosphatidic acid (LPA) signaling. Here we describe the establishment of novel cell-based ATX assay formats. ATX-mediated LPA generation is detected by using a stable LPA receptor reporter cell line. In a first assay variant, ATX-mediated LPA generation is started in the absence of cells and the reaction mix is transferred to the reporter cells after stopping the reaction (two-tube assay). In a second assay variant, ATX is added to the reporter cells expressing the known autotaxin binding partners integrin β1, integrin β3 and the LPA receptor 1. LPA generation is started in the presence of cells and is detected in real-time (one-tube assay). Structurally diverse ATX inhibitors with different binding modes were characterized in both cell-based assay variants and were also tested in the well-established biochemical choline release assay. ATX inhibitors displayed similar potencies, regardless if the assay was performed in the absence or presence of cells, and comparable results were obtained in all three assay formats. In summary, our novel cell-based ATX assay formats are well-suited for sensitive detection of enzyme activity as well as for the characterization of ATX inhibitors in the presence and absence of cells.

A flow cytometry approach reveals heterogeneity in conventional subsets of murine renal mononuclear phagocytes

Mononuclear phagocytes (MNPs) participate in inflammation and repair after kidney injury, reflecting their complex nature. Dissection into refined functional subunits has been challenging and would benefit understanding of renal pathologies. Flow cytometric approaches are limited to classifications of either different MNP subsets or functional state. We sought to combine these two dimensions in one protocol that considers functional heterogeneity in each MNP subset. We identified five distinct renal MNP subsets based on a previously described strategy. In vitro polarization of bone marrow-derived macrophages (BMDM) into M1- and M2-like cells suggested functional distinction of CD86 + MHCII + CD206- and CD206 + cells. Combination of both distinction methods identified CD86 + MHCII + CD206- and CD206 + cells in all five MNP subsets, revealing their heterologous nature. Our approach revealed that MNP composition and their functional segmentation varied between different mouse models of kidney injury and, moreover, was dynamically regulated in a time-dependent manner. CD206 + cells from three analyzed MNP subsets had a higher ex vivo phagocytic capacity than CD86 + MHCII + CD206- counterparts, indicating functional uniqueness of each subset. In conclusion, our novel flow cytometric approach refines insights into renal MNP heterogeneity and therefore could benefit mechanistic understanding of renal pathology.

The Importance of Incorporating Landscape Change for Predictions of Climate-Induced Plant Phenological Shifts

Warming in the high Arctic is occurring at the fastest rate on the planet, raising concerns over how this global change driver will influence plant community composition, the timing of vegetation phenological events, and the wildlife that rely on them. In this region, as much as 50% of near-surface permafrost is composed of thermally sensitive ground ice that when melted produces substantial changes in topography and microbiome conditions. We take advantage of natural variations in permafrost melt to conduct a space-for-time study on Ellesmere Island in northern Canada. We demonstrate that phenological timing can be delayed in thermokarst areas when compared to stable ground, and that this change is a function of shifting species composition in these vegetation communities as well as delayed timing within species. These findings suggest that a warming climate could result in an overall broadening of blooming and leafing windows at the landscape level when these delayed timings are taken into consideration with the projected advance of phenological timings in ice-poor areas. We emphasize that the impacts of geomorphic processes on key phenological drivers are essential for enhancing our understanding of community response to climate warming in the high Arctic, with implications for ecosystem functioning and trophic interactions.

The anticancer phytochemical rocaglamide inhibits Rho GTPase activity and cancer cell migration

Chemotherapy is one of the pillars of anti-cancer therapy. Although chemotherapeutics cause regression of the primary tumor, many chemotherapeutics are often shown to induce or accelerate metastasis formation. Moreover, metastatic tumors are largely resistant against chemotherapy. As more than 90% of cancer patients die due to metastases and not due to primary tumor formation, novel drugs are needed to overcome these shortcomings. In this study, we identified the anticancer phytochemical Rocaglamide (Roc-A) to be an inhibitor of cancer cell migration, a crucial event in metastasis formation. We show that Roc-A inhibits cellular migration and invasion independently of its anti-proliferative and cytotoxic effects in different types of human cancer cells. Mechanistically, Roc-A treatment induces F-actin-based morphological changes in membrane protrusions. Further investigation of the molecular mechanisms revealed that Roc-A inhibits the activities of the small GTPases RhoA, Rac1 and Cdc42, the master regulators of cellular migration. Taken together, our results provide evidence that Roc-A may be a lead candidate for a new class of anticancer drugs that inhibit metastasis formation.

The protein phosphatase 2A regulatory subunit B56γ mediates suppression of T cell receptor (TCR)-induced nuclear factor-κB (NF-κB) activity

NF-κB is an important transcription factor in the immune system, and aberrant NF-κB activity contributes to malignant diseases and autoimmunity. In T cells, NF-κB is activated upon TCR stimulation, and signal transduction to NF-κB activation is triggered by a cascade of phosphorylation events. However, fine-tuning and termination of TCR signaling are only partially understood. Phosphatases oppose the role of kinases by removing phosphate moieties. The catalytic activity of the protein phosphatase PP2A has been implicated in the regulation of NF-κB. PP2A acts in trimeric complexes in which the catalytic subunit is promiscuous and the regulatory subunit confers substrate specificity. To understand and eventually target NF-κB-specific PP2A functions it is essential to define the regulatory PP2A subunit involved. So far, the regulatory PP2A subunit that mediates NF-κB suppression in T cells remained undefined. By performing a siRNA screen in Jurkat T cells harboring a NF-κB-responsive luciferase reporter, we identified the PP2A regulatory subunit B56γ as negative regulator of NF-κB in TCR signaling. B56γ was strongly up-regulated upon primary human T cell activation, and B56γ silencing induced increased IκB kinase (IKK) and IκBα phosphorylation upon TCR stimulation. B56γ silencing enhanced NF-κB activity, resulting in increased NF-κB target gene expression including the T cell cytokine IL-2. In addition, T cell proliferation was increased upon B56γ silencing. These data help to understand the physiology of PP2A function in T cells and the pathophysiology of diseases involving PP2A and NF-κB.

The traditional Chinese medical compound Rocaglamide protects nonmalignant primary cells from DNA damage-induced toxicity by inhibition of p53 expression

One of the main obstacles of conventional anticancer therapy is the toxicity of chemotherapeutics to normal tissues. So far, clinical approaches that aim to specifically reduce chemotherapy-mediated toxicities are rare. Recently, a number of studies have demonstrated that herbal extracts derived from traditional Chinese medicine (TCM) may reduce chemotherapy-induced side effects. Thus, we screened a panel of published cancer-inhibiting TCM compounds for their chemoprotective potential and identified the phytochemical Rocaglamide (Roc-A) as a candidate. We show that Roc-A significantly reduces apoptotic cell death induced by DNA-damaging anticancer drugs in primary human and murine cells. Investigation of the molecular mechanism of Roc-A-mediated protection revealed that Roc-A specifically blocks DNA damage-induced upregulation of the transcription factor p53 by inhibiting its protein synthesis. The essential role of p53 in Roc-A-mediated protection was confirmed by siRNA knockdown of p53 and by comparison of the effects of Roc-A on chemoprotection of splenocytes isolated from wild-type and p53-deficient mice. Importantly, Roc-A did not protect p53-deficient or -mutated cancer cells. Our data suggest that Roc-A may be used as an adjuvant to reduce the side effects of chemotherapy in patients with p53-deficient or -mutated tumors.

LORD-Q: a long-run real-time PCR-based DNA-damage quantification method for nuclear and mitochondrial genome analysis

DNA damage is tightly associated with various biological and pathological processes, such as aging and tumorigenesis. Although detection of DNA damage is attracting increasing attention, only a limited number of methods are available to quantify DNA lesions, and these techniques are tedious or only detect global DNA damage. In this study, we present a high-sensitivity long-run real-time PCR technique for DNA-damage quantification (LORD-Q) in both the mitochondrial and nuclear genome. While most conventional methods are of low-sensitivity or restricted to abundant mitochondrial DNA samples, we established a protocol that enables the accurate sequence-specific quantification of DNA damage in >3-kb probes for any mitochondrial or nuclear DNA sequence. In order to validate the sensitivity of this method, we compared LORD-Q with a previously published qPCR-based method and the standard single-cell gel electrophoresis assay, demonstrating a superior performance of LORD-Q. Exemplarily, we monitored induction of DNA damage and repair processes in human induced pluripotent stem cells and isogenic fibroblasts. Our results suggest that LORD-Q provides a sequence-specific and precise method to quantify DNA damage, thereby allowing the high-throughput assessment of DNA repair, genotoxicity screening and various other processes for a wide range of life science applications.

TNF-α mediates mitochondrial uncoupling and enhances ROS-dependent cell migration via NF-κB activation in liver cells

Development of hepatocellular carcinoma (HCC) is accompanied by a continuous increase in reactive oxygen species (ROS) levels. To investigate the primary source of ROS in liver cells, we used tumor necrosis factor-alpha (TNF-α) as stimulus. Applying inhibitors against the respiratory chain complexes, we identified mitochondria as primary source of ROS production. TNF-α altered mitochondrial integrity by mimicking a mild uncoupling effect in liver cells, as indicated by a 40% reduction in membrane potential and ATP depletion (35%). TNF-α-induced ROS production activated NF-κB 3.5-fold and subsequently enhanced migration up to 12.7-fold. This study identifies complex I and complex III of the mitochondrial respiratory chain as point of release of ROS upon TNF-α stimulation of liver cells, which enhances cell migration by activating NF-κB signalling.

Spatial organization of the mouse genome and its role in recurrent chromosomal translocations

The extent to which the three-dimensional organization of the genome contributes to chromosomal translocations is an important question in cancer genomics. We generated a high-resolution Hi-C spatial organization map of the G1-arrested mouse pro-B cell genome and used high-throughput genome-wide translocation sequencing to map translocations from target DNA double-strand breaks (DSBs) within it. RAG endonuclease-cleaved antigen-receptor loci are dominant translocation partners for target DSBs regardless of genomic position, reflecting high-frequency DSBs at these loci and their colocalization in a fraction of cells. To directly assess spatial proximity contributions, we normalized genomic DSBs via ionizing radiation. Under these conditions, translocations were highly enriched in cis along single chromosomes containing target DSBs and within other chromosomes and subchromosomal domains in a manner directly related to pre-existing spatial proximity. By combining two high-throughput genomic methods in a genetically tractable system, we provide a new lens for viewing cancer genomes.

Beta1 integrin establishes endothelial cell polarity and arteriolar lumen formation via a Par3-dependent mechanism

Maintenance of single-layered endothelium, squamous endothelial cell shape, and formation of a patent vascular lumen all require defined endothelial cell polarity. Loss of beta1 integrin (Itgb1) in nascent endothelium leads to disruption of arterial endothelial cell polarity and lumen formation. The loss of polarity is manifested as cuboidal-shaped endothelial cells with dysregulated levels and mislocalization of normally polarized cell-cell adhesion molecules, as well as decreased expression of the polarity gene Par3 (pard3). beta1 integrin and Par3 are both localized to the endothelial layer, with preferential expression of Par3 in arterial endothelium. Luminal occlusion is also exclusively noted in arteries, and is partially rescued by replacement of Par3 protein in beta1-deficient vessels. Combined, our findings demonstrate that beta1 integrin functions upstream of Par3 as part of a molecular cascade required for endothelial cell polarity and lumen formation.

Fate tracing reveals the endothelial origin of hematopoietic stem cells

Hematopoietic stem cells (HSCs) originate within the aortic-gonado-mesonephros (AGM) region of the midgestation embryo, but the cell type responsible for their emergence is unknown since critical hematopoietic factors are expressed in both the AGM endothelium and its underlying mesenchyme. Here we employ a temporally restricted genetic tracing strategy to selectively label the endothelium, and separately its underlying mesenchyme, during AGM development. Lineage tracing endothelium, via an inducible VE-cadherin Cre line, reveals that the endothelium is capable of HSC emergence. The endothelial progeny migrate to the fetal liver, and later to the bone marrow, and are capable of expansion, self-renewal, and multilineage hematopoietic differentiation. HSC capacity is exclusively endothelial, as ex vivo analyses demonstrate lack of VE-cadherin Cre induction in circulating and fetal liver hematopoietic populations. Moreover, AGM mesenchyme, as selectively traced via a myocardin Cre line, is incapable of hematopoiesis. Our genetic tracing strategy therefore reveals an endothelial origin of HSCs.

Primary total knee arthroplasty in stiff and ankylosed knees

This study reviewed 71 patients who underwent 82 total knee arthroplasties between 1974 and 1987. All patients had severe limitations of motion preoperatively with a total preoperative arc of motion of < or = 50 degrees. Follow-up ranged from 2 to 12 years (average: 5.3 years). The average preoperative knee score was 38 (range: 14 to 54). The average preoperative arc of motion was 36 degrees (range: 0 degree to 50 degrees), with an average flexion contracture of 22 degrees average maximum flexion of 58 degrees. Postoperatively, the average knee score was 80 (range: 0 to 98). The average postoperative arc of motion was 93 degrees (range: 35 degrees to 130 degrees), with an average maximum flexion of 94 degrees. Nine knees had 5 degrees flexion contractures, while 5 knees had 10 degrees flexion contractures. Postoperatively, no knee had a flexion contracture > 10 degrees. Two knees had a decreased range of motion postoperatively. Two knees with severe flexion-valgus deformities developed peroneal nerve palsies that both resolved. Total knee arthroplasty in stiff or ankylosed knees can produce good or excellent results and can lead to significant improvement in range of motion and pain.