Biological variability hampers the use of skeletal staining methods in zebrafish embryo developmental toxicity assays.

Zebrafish embryo assays are used by pharmaceutical and chemical companies as new approach methodologies (NAMs) in developmental toxicity screening. Despite an overall high concordance of zebrafish embryo assays with in vivo mammalian studies, false negative and false positive results have been reported. False negative results in risk assessment models are of particular concern for human safety, as developmental anomalies may be missed. Interestingly, for several chemicals and drugs that were reported to be false negative in zebrafish, skeletal findings were noted in the in vivo studies. As the number of skeletal endpoints assessed in zebrafish is very limited compared to the in vivo mammalian studies, the aim of this study was to investigate whether the sensitivity could be increased by including a skeletal staining method. Three staining methods were tested on zebrafish embryos that were exposed to four teratogens that caused skeletal anomalies in rats and/or rabbits and were false negative in zebrafish embryo assays. These methods included a fixed alizarin red-alcian blue staining, a calcein staining, and a live alizarin red staining. The results showed a high variability in staining intensity of larvae exposed to mammalian skeletal teratogens, as well as variability between control larvae originating from the same clutch of zebrafish. Hence, biological variability in (onset of) bone development in zebrafish hampers the detection of (subtle) treatment-related bone effects that are not picked-up by gross morphology. In conclusion, the used skeletal staining methods did not increase the sensitivity of zebrafish embryo developmental toxicity assays.

From the Cover: MechanisticInsights in Cytotoxic and Cholestatic Potential of the Endothelial Receptor Antagonists Using HepaRG Cells.

Several endothelin receptor antagonists (ERAs) have been developed for the treatment of pulmonary arterial hypertension (PAH). Some of them have been related to clinical cases of hepatocellular injury (sitaxentan [SIT]) and/or cholestasis (bosentan [BOS]). We aimed to determine if ambrisentan (AMB) and macitentan (MAC), in addition to BOS and SIT, could potentially cause liver damage in man by use of human HepaRG cells. Our results showed that like BOS, MAC-induced cytotoxicity and cholestatic disorders characterized by bile canaliculi dilatation and impairment of myosin light chain kinase signaling. Macitentan also strongly inhibited taurocholic acid and carboxy-2',7'-dichlorofluorescein efflux while it had a much lower inhibitory effect on influx activity compared to BOS and SIT. Moreover, these three drugs caused decreased intracellular accumulation and parallel increased levels of total bile acids (BAs) in serum-free culture media. In addition, all drugs except AMB variably deregulated gene expression of BA transporters. In contrast, SIT was hepatotoxic without causing cholestatic damage, likely via the formation of reactive metabolites and AMB was not hepatotoxic. Together, our results show that some ERAs can be hepatotoxic and that the recently marketed MAC, structurally similar to BOS, can also cause cholestatic alterations in HepaRG cells. The absence of currently known or suspected cases of cholestasis in patients suffering from PAH treated with MAC is rationalized by the lower therapeutic doses and Cmax, and longer receptor residence time compared to BOS.

Early Alterations of Bile Canaliculi Dynamics and the Rho Kinase/Myosin Light Chain Kinase Pathway Are Characteristics of Drug-Induced Intrahepatic Cholestasis.

Intrahepatic cholestasis represents 20%-40% of drug-induced injuries from which a large proportion remains unpredictable. We aimed to investigate mechanisms underlying drug-induced cholestasis and improve its early detection using human HepaRG cells and a set of 12 cholestatic drugs and six noncholestatic drugs. In this study, we analyzed bile canaliculi dynamics, Rho kinase (ROCK)/myosin light chain kinase (MLCK) pathway implication, efflux inhibition of taurocholate [a predominant bile salt export pump (BSEP) substrate], and expression of the major canalicular and basolateral bile acid transporters. We demonstrated that 12 cholestatic drugs classified on the basis of reported clinical findings caused disturbances of both bile canaliculi dynamics, characterized by either dilatation or constriction, and alteration of the ROCK/MLCK signaling pathway, whereas noncholestatic compounds, by contrast, had no effect. Cotreatment with ROCK inhibitor Y-27632 [4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride] and MLCK activator calmodulin reduced bile canaliculi constriction and dilatation, respectively, confirming the role of these pathways in drug-induced intrahepatic cholestasis. By contrast, inhibition of taurocholate efflux and/or human BSEP overexpressed in membrane vesicles was not observed with all cholestatic drugs; moreover, examples of noncholestatic compounds were reportedly found to inhibit BSEP. Transcripts levels of major bile acid transporters were determined after 24-hour treatment. BSEP, Na+-taurocholate cotransporting polypeptide, and organic anion transporting polypeptide B were downregulated with most cholestatic and some noncholestatic drugs, whereas deregulation of multidrug resistance-associated proteins was more variable, probably mainly reflecting secondary effects. Together, our results show that cholestatic drugs consistently cause an early alteration of bile canaliculi dynamics associated with modulation of ROCK/MLCK and these changes are more specific than efflux inhibition measurements alone as predictive nonclinical markers of drug-induced cholestasis.

Differential sensitivity of metabolically competent and non-competent HepaRG cells to apoptosis induced by diclofenac combined or not with TNF-α.

The role of reactive metabolites and inflammatory stress has been largely evoked in idiosyncratic hepatotoxicity of diclofenac (DCF); however mechanisms remain poorly understood. We aimed to evaluate the influence of liver cell phenotype on the hepatotoxicity of DCF combined or not with TNF-α using differentiated and undifferentiated HepaRG cells, and for comparison, HepG2 cells. Our results demonstrate that after a 24h-treatment metabolizing HepaRG cells were less sensitive to DCF than their undifferentiated non-metabolizing counterparts as shown by lower oxidative and endoplasmic reticulum stress responses and lower activation of caspase 9. Differentiated HepaRG cells were also less sensitive than HepG2 cells. Their lower sensitivity to DCF was related to their high content in glutathione transferases. DCF-induced apoptotic effects were potentiated by TNF-α only in death receptor-expressing differentiated HepaRG and HepG2 cells and were associated with marked activation of caspase 8. TNF-α co-treatment did not aggravate DCF-induced cholestatic features. Altogether, our results demonstrate that (i) lower sensitivity to DCF of differentiated HepaRG cells compared to their non-metabolically active counterparts was related to their high detoxifying capacity, giving support to the higher sensitivity of nonhepatic tissues than liver to this drug; (ii) TNF-α-potentiation of DCF cytotoxicity occurred only in death receptor-expressing cells.

Rho-kinase/myosin light chain kinase pathway plays a key role in the impairment of bile canaliculi dynamics induced by cholestatic drugs.

Intrahepatic cholestasis represents a frequent manifestation of drug-induced liver injury; however, the mechanisms underlying such injuries are poorly understood. In this study of human HepaRG and primary hepatocytes, we found that bile canaliculi (BC) underwent spontaneous contractions, which are essential for bile acid (BA) efflux and require alternations in myosin light chain (MLC2) phosphorylation/dephosphorylation. Short exposure to 6 cholestatic compounds revealed that BC constriction and dilation were associated with disruptions in the ROCK/MLCK/myosin pathway. At the studied concentrations, cyclosporine A and chlorpromazine induced early ROCK activity, resulting in permanent MLC2 phosphorylation and BC constriction. However, fasudil reduced ROCK activity and caused rapid, substantial and permanent MLC2 dephosphorylation, leading to BC dilation. The remaining compounds (1-naphthyl isothiocyanate, deoxycholic acid and bosentan) caused BC dilation without modulating ROCK activity, although they were associated with a steady decrease in MLC2 phosphorylation via MLCK. These changes were associated with a common loss of BC contractions and failure of BA clearance. These results provide the first demonstration that cholestatic drugs alter BC dynamics by targeting the ROCK/MLCK pathway; in addition, they highlight new insights into the mechanisms underlying bile flow failure and can be used to identify new predictive biomarkers of drug-induced cholestasis.

Assessing public attitudes on the retention and use of residual newborn screening blood samples: a focus group study.

This paper discusses attitudes and opinions of a diverse group of participants toward the retention and use of residual newborn blood samples for research. Data were drawn from focus groups based in six states in the USA, and results provide support for the retention and use of residual newborn blood samples for research when parental permission is asked beforehand. However, there were a number of concerns that also warrant attention for the development of policy and maintaining trust with the public, such as timing of permission, use of samples already stored, level of personal control of sample use and education. The results demonstrate the complexity of the topic and the ethical ambiguities associated with the retention and use of residual newborn blood samples.

Public attitudes regarding the use of residual newborn screening specimens for research.

BACKGROUND AND OBJECTIVES: Many state newborn screening (NBS) programs retain residual NBS bloodspots after the completion of screening. Potential uses for residual specimens include laboratory quality assurance, biomedical research, and, rarely, forensic applications. Our objective was to evaluate public opinion about the policies and practices relevant to the retention and use of residual bloodspots for biomedical research. METHODS: A total of 3855 respondents were recruited using 3 methods: focus groups (n = 157), paper or telephone surveys (n = 1418), and a Knowledge Networks panel (n = 2280). Some participants (n = 1769) viewed a 22-minute movie about the retention and use of residual specimens while other participants were provided only written information about this practice. All participants were surveyed using a 38-item questionnaire. RESULTS: A diverse set of participants was recruited. Respondents were very supportive of NBS in general and accepting of the use of residual bloodspots for important research activities. Respondents were evenly divided on the acceptability of NBS without parental permission, but the majority of respondents supported the use of an "opt-in" process for parental permission for residual bloodspot retention and use. Viewing the educational movie was associated with greater support for bloodspot retention and use. CONCLUSIONS: Our results show that the general public surveyed here was supportive of NBS and residual sample retention and research use. However, there was a clear preference for an informed permission process for parents regarding these activities. Education about NBS was associated with a higher level of support and may be important to maintain public trust in these important programs.

Concerns of newborn blood screening advisory committee members regarding storage and use of residual newborn screening blood spots.

OBJECTIVES: We assessed attitudes and opinions of members of newborn blood screening (NBS) advisory committees regarding the storage and secondary research use of residual specimens from NBS. METHODS: We conducted focus groups in 2008 and 2009 with NBS advisory committees (4 focus groups; n = 39 participants) in the Mountain States region (i.e., AZ, CO, MT, NM, NV, TX, UT, and WY). RESULTS: Participants identified several challenges to implementing policies for storage of and research on residual newborn blood specimens. Themes that emerged from the data were public health relevancy; improvement of parental knowledge; impact of enhanced parental involvement; concerns over ownership, privacy, and confidentiality; identification of secondary research uses; and role of advisory committees. CONCLUSIONS: Participants indicated that secondary uses of residual specimens entailed opportunities for improvements in NBS programs but also carried significant risks for their programs. Addressing concerns from stakeholders will be necessary for state-level adoption of national recommendations.