Clinical utility of therapeutic drug monitoring in biological disease modifying anti-rheumatic drug treatment of rheumatic disorders: a systematic narrative review

Introduction: Biological Disease Modifying Anti-Rheumatic Drugs (bDMARDs) have improved the treatment outcomes of inflammatory rheumatic diseases including Rheumatoid Arthritis and spondyloarthropathies. Inter-individual variation exists in (maintenance of) response to bDMARDs. Therapeutic Drug Monitoring (TDM) of bDMARDs could potentially help in optimizing treatment for the individual patient.

Areas covered: Evidence of clinical utility of TDM in bDMARD treatment is reviewed. Different clinical scenarios will be discussed, including: prediction of response after start of treatment, prediction of response to a next bDMARD in case of treatment failure of the first, prediction of successful dose reduction or discontinuation in case of low disease activity, prediction of response to dose-escalation in case of active disease and prediction of response to bDMARD in case of flare in disease activity.

Expert opinion: The limited available evidence does often not report important outcomes for diagnostic studies, such as sensitivity and specificity. In most clinical relevant scenarios, predictive value of serum (anti-) drug levels is absent, therefore the use of TDM of bDMARDs cannot be advocated. Well-designed prospective studies should be done to further investigate the promising scenarios to determine the place of TDM in clinical practice.     

Impaired longitudinal deformation measured by speckle-tracking echocardiography in children with end-stage renal disease

Background

Left ventricular dysfunction is an important co-morbidity of end-stage renal disease (ESRD) and is associated with a poor prognosis in the adult population. In pediatric ESRD, left ventricular function is generally well preserved, but limited information is available on early changes in myocardial function. The aim of this study was to investigate myocardial mechanics in pediatric patients with ESRD using speckle-tracking echocardiography (STE).

Methods

Echocardiographic studies, including M-mode, tissue Doppler imaging (TDI) and STE, were performed in 19 children on dialysis, 17 transplant patients and 33 age-matched controls. Strain measurements were performed from the apical four-chamber and the short axis view, respectively.

Results

The interventricular and left ventricular posterior wall thickness was significantly increased in dialysis and transplant patients compared to healthy controls. No significant differences were found in shortening fraction, ejection fraction and systolic tissue Doppler velocities. Dialysis and transplant patients had a decreased mean longitudinal strain compared to healthy controls, with a mean difference of 3.1 [95 % confidence interval (CI) 2.0–4.4] and 2.7 (95 % CI 1.2–4.2), respectively. No differences were found for radial and circumferential strain.

Conclusions

Speckle-tracking echocardiography may reveal early myocardial dysfunction in the absence of systolic dysfunction measured by conventional ultrasound or TDI in children with ESRD.

     

Molecular diagnosis of kidney transplant failure based on urine

In light of the organ shortage, there is a great responsibility to assess postmortal organs for which procurement has been consented and to increase the life span of transplanted organs. The former responsibility has moved many centers to accept extended criteria organs. The latter responsibility requires an exact diagnosis and, if possible, omission of the harmful influence on the transplant. We report the course of a kidney transplant that showed a steady decline of function over a decade, displaying numerous cysts of different sizes. Clinical workup excluded the most frequent causes of chronic transplant failure. The filed allocation documents mentioned the donor’s disease of oral‐facial‐digital syndrome, a rare ciliopathy, which can also affect the kidney. Molecular diagnosis was performed by culturing donor tubular cells from the recipient´s urine more than 10 years after transplantation. Next‐generation panel sequencing with DNA from tubular urinary cells revealed a novel truncating mutation in OFD1, which sufficiently explains the features of the kidney transplants, also found in the second kidney allograft. Despite this severe donor disease, lifesaving transplantation with good long‐term outcome was enabled for 5 recipients.     

Reweighting of Binaural Localization Cues Induced by Lateralization Training

Journal of the Association for Research in Otolaryngology - Normal-hearing listeners adapt to alterations in sound localization cues. This adaptation can result from the establishment of a new...     

First do no harm: iron loss in whole blood donors

Frequent whole blood donations are known to be related to iron deficiency, potentially leading to donor deferral and iron deficiency‐related symptoms. To ensure that blood donation causes no harm to the donor, it is of importance for blood collection centres to gain insight in whole blood donors’ iron status, how that affects donor health and by what means low iron stores in blood donors should be managed. Since haemoglobin levels do not reflect donors’ true iron status, measuring ferritin might be a better way to detect low iron stores. International consensus on an appropriate strategy for iron monitoring is currently lacking. Multiple strategies for iron monitoring of whole blood donors are available, including haemoglobin‐ or ferritin‐guided donation intervals and iron supplementation. Studies from the USA and Denmark showed that on the introduction of ferritin‐guided donation intervals or iron supplementation, deferral percentages for low haemoglobin declined in both male and female donors. However, implementing an iron monitoring strategy may introduce its own challenges in donor management and donor availability. Here, we present the prevalence and determinants of iron deficiency in blood donors and describe subgroups of donors who may be more prone to iron deficiency. Furthermore, we provide an overview of possible strategies for iron monitoring and describe challenges and implications. Possible adverse events associated with iron deficiency in whole blood donors should be further investigated to evaluate the potential harm to the donor. Evidence‐based insight in measures to prevent iron deficiency could help to develop an appropriate iron monitoring strategy.     

Easy performance of 6-color confocal immunofluorescence with 4-laser line microscopes

Confocal laser scanning microscopy is an advanced technique for imaging tissue samples in vitro and in vivo at high optical resolution. The development of new fluorochrome variants do not only make it possible to perform multicolor flow cytometry of single cells, but in combination with high resolution laser scanning systems also to investigate the distribution of cells in lymphoid tissues by confocal immunofluorescence analyses, thus allowing the distinction of various cell populations directly in the tissue. Here, we provide a protocol for the visualization of at least six differently fluorochrome-labeled antibodies at the same time using a conventional confocal laser scanning microscope with four laser lines (405 nm, 488 nm, 555 nm, and 639 nm laser wavelength) in both murine and human tissue samples. We further demonstrate that compensation correction algorithms are not necessary to reduce spillover of fluorochromes into other channels when the used fluorochromes are combined according to their specific emission bands and the varying Stokes shift for co-excited fluorochromes with the same laser line.     

First Epileptic Seizure and Initial Diagnosis of Juvenile Myoclonus Epilepsy (JME) in a Transcranial Direct Current Stimulation (tDCS) Study– Ethical Analysis of a Clinical case

We discuss an epileptic incident in an undiagnosed 13-year old girl participating in a clinical study investigating the effects of transcranial direct current stimulation (tDCS) in healthy children and adolescents. This incident poses important research ethics questions with regard to study design, especially pertaining to screening and gaining informed consent. Potential benefits and problems of the incident also need to be considered. The ethical analysis of the case presented in this paper has been informed by an in-depth interview conducted after the incident with the child and the accompanying parent. We discuss the ethical implications of the epileptic incident, the need for improving screening procedures for studies with minors and for providing more effective communication. This case also underscores the problem of undetected teenage epilepsy in neuropsychological clinical studies and the necessity of raising more awareness of this issue. Since research in tDCS is an active and expanding field, we conclude with providing some recommendation that could ensure that future research on tDCS, or other therapies and neuro-interventions where there is a risk of triggering an epileptic seizure, take into account the specifics of teenage epilepsy and the need for more thorough provision of information during the process of gaining informed consent.

     

In vivo synaptic recovery following optogenetic hyperstimulation

Local recycling of synaptic vesicles (SVs) allows neurons to sustain transmitter release. Extreme activity (e.g., during seizure) may exhaust synaptic transmission and, in vitro, induces bulk endocytosis to recover SV membrane and proteins; how this occurs in animals is unknown. Following optogenetic hyperstimulation of Caenorhabditis elegans motoneurons, we analyzed synaptic recovery by time-resolved behavioral, electrophysiological, and ultrastructural assays. Recovery of docked SVs and of evoked-release amplitudes (indicating readily-releasable pool refilling) occurred within ∼8–20 s (τ = 9.2 s and τ = 11.9 s), whereas locomotion recovered only after ∼60 s (τ = 20 s). During ∼11-s stimulation, 50- to 200-nm noncoated vesicles (“100nm vesicles”) formed, which disappeared ∼8 s poststimulation, likely representing endocytic intermediates from which SVs may regenerate. In endophilin, synaptojanin, and dynamin mutants, affecting endocytosis and vesicle scission, resolving 100nm vesicles was delayed (>20 s). In dynamin mutants, 100nm vesicles were abundant and persistent, sometimes continuous with the plasma membrane; incomplete budding of smaller vesicles from 100nm vesicles further implicates dynamin in regenerating SVs from bulk-endocytosed vesicles. Synaptic recovery after exhaustive activity is slow, and different time scales of recovery at ultrastructural, physiological, and behavioral levels indicate multiple contributing processes. Similar processes may jointly account for slow recovery from acute seizures also in higher animals.Efficient chemical synaptic neurotransmission requires synaptic vesicle (SV) biogenesis, transmitter loading, membrane approximation and docking, priming, fusion, and release of transmitter (1–3). These processes are followed by retrieval of membrane and proteins from the plasma membrane (PM) via endocytosis (4, 5). Particularly, sustained SV release relies on a tight coupling of exocytosis and endocytosis (5–8). During high-frequency or long-term neuronal activity, SVs need to be efficiently recycled, because, otherwise, the readily releasable pool and the (mobilized) resting pool of SVs would be depleted and transmission would seize (9, 10). After fusion, SV membranes and proteins are recycled (11). Coupling SV exocytosis with local recycling largely eliminates the dependence of chemical transmission on somatic de novo SV synthesis and transport. Thus far, these processes have been studied in dissected preparations or cultured cells and tissues; how and at which time scales this occurs within a live, nondissected animal (e.g., during seizures) is currently unclear. For example, patients suffering from a seizure often remain unconscious for minutes to hours (12, 13). Although fatigue at different levels of circuits and brain systems is likely to contribute, also physiological changes in chemical synapses may play a role in this slow recovery.Depending on the SV fusion rate, endocytosis occurs via different pathways: (i) clathrin-mediated endocytosis (14), supposedly accounting for most recycled SVs; (ii) fast “kiss-and-run” recycling, where SVs do not fully fuse but open a transient pore for transmitter release (15, 16); and (iii) clathrin-independent bulk-phase endocytosis, going along with high neuronal activity (17–20). Following membrane invagination, or to close the fusion pore, the GTPase dynamin finalizes, or at least speeds up, the process of membrane severing (21–25). Before scission by dynamin, the phospholipid phosphatase synaptojanin, via the membrane-binding Bin–amphiphysin–Rvs (BAR) domain protein endophilin, binds to the phospholipid enriched PM at endocytic sites and modifies lipids to promote scission (6, 26–28). Synaptojanin is also required after scission, particularly to uncoat endocytosed vesicles: by dephosphorylating the lipid head groups, synaptojanin releases the interaction of clathrin adaptors with the endocytosed membranes (27, 29). By recruiting clathrin adaptors, synaptotagmin/SNT-1 is also involved in SV recycling (30, 31).Across systems, different modes of endocytosis appear to be in effect: for example, in dynamin knockout mice, spontaneous activity induced endocytosed synaptic membrane, which appeared trapped as invaginations, tubulated and capped by clathrin-coated pits (21). Upon excessive stimulation, in inhibitory neurons, bulk-endocytosed, endosome-like structures resulted, which were severed from the PM despite the absence of dynamin (25). In neuron terminals of Drosophila in which clathrin function was acutely inhibited, SV recycling was impaired, whereas bulk endocytosis was still observed (22), and inhibition of dynamin uncovered different modes of SV recycling (32). Furthermore, when dynamin dephosphorylation was stalled, clathrin-mediated SV endocytosis was functional, but bulk endocytosis was affected (23). Thus, during moderate activity, SV recycling may occur by clathrin-mediated endocytosis (CME), to allow SV proteins to be retrieved and release sites to be “cleared” from integral membrane proteins. Upon prolonged or high-frequency activation, bulk endocytosis may follow in a clathrin-independent and, depending on synapse type, dynamin-dependent or -independent fashion, whereas resolution of the invaginated membrane structures may again be clathrin-dependent. However, in retinal bipolar cells, clathrin was required for a slow (τ ≈ 10–20 s) but not a fast (τ ≈ 1–2 s) phase of endocytosis (33), the latter of which was shown to depend on endophilin (34). In Caenorhabditis elegans, clathrin inactivation, surprisingly, had no effect on normal chemical transmission, and yet SV size was altered (35). Thus, it is unclear whether CME is required for SV endocytosis in C. elegans or is needed at a later step (e.g., following a different endocytic pathway) to shape new SVs. Bulk endocytosis can rapidly remove membrane material from the PM after excessive fusion of many SVs in vitro and was observed in experimental paradigms involving long-term electrical or chemical stimulation and pharmacological treatment (36–42), and yet it has not been studied in an intact animal.How the diverse endocytic events differentially contribute to the dynamic refilling of different SV pools is only partially understood. Because virtually all processes at active zones (AZs) occur at scales below the diffraction limit of light microscopy, it is difficult to study their dynamic behavior during and after stimulation. Therefore, electron microscopy (EM) has been the method of choice to analyze SV pools and AZ morphology at high resolution. Although previous work could visualize triggered SV exocytosis and endocytosis, these dynamic processes are difficult to analyze at high temporal resolution using classical EM (36–39). The dependence on slow chemical-fixation techniques precluded the capture of precise time points during dynamic events and limited the preservation of synaptic structures. Both problems may be overcome using cryofixation by high-pressure freeze (HPF)-EM (43, 44). The requirement of endophilin, synaptojanin, clathrin, and other proteins for SV endocytosis has been studied to some extent in C. elegans, also by EM (27, 28, 35, 43, 45–47). However, this was not done in a temporally resolved fashion relative to a stimulus (i.e., only steady-state “snapshots” were analyzed), and also HPF-EM has not yet been used in this context. How C. elegans synapses regulate endocytosis during and following periods of extreme activity, possibly by different modes of endocytosis, and which proteins are required for this, is unknown.Using a combination of channelrhodopsin-2 (ChR2)-mediated photostimulation of neurons and electrophysiological analysis in dissected animals (48, 49), as well as photostimulation followed by HPF-EM in intact animals, we monitored dynamic processes at AZs in three dimensions at EM resolution, and in a time-dependent manner. We studied the kinetics of docked SV depletion and recovery, as well as the generation and decomposition of bulk-endocytosed vesicles, during and following prolonged photostimulation. Whereas behavioral recovery required 60 s, synapses became fully competent to release transmitter only after ∼20 s, in line with morphological recovery of most docked SVs, whereas spontaneous release occurred at normal rates right after the stimulus. In addition, we found formation and disintegration of large (50–200 nm) bulk-endocytosed vesicles, within 11 and 8 s, respectively, the disassembly of which was largely delayed in animals expressing mutant endophilin, synaptojanin, and dynamin proteins.