Construction of humanized CYP1A2 rats using CRISPR/Cas9 to promote drug metabolism and pharmacokinetic research

Cytochrome P450 family 1 subfamily A member 2 (CYP1A2), performs an indispensable role in metabolism of both exogenous and endogenous substances. What is more, CYP1A2 functions in human diseases by regulating homeostasis of cholesterol. Despite the emergence of gene-editing animal models, genetically humanized animals that overcome species differences for further exploring the role of CYP1A2 in drug metabolism and human diseases have not yet been constructed. In this study, we inserted human CYP1A2 cDNA into the rat Cyp1a2 gene by using CRISPR/Cas9 technology. Results showed that human CYP1A2 was successfully expressed in humanized rat liver and there were no statistically significant differences of physiological symptoms compared with wild-type (WT) rats. In vitro incubation results indicated the different inhibition of furafylline on CYP1A2 activity in human liver microsomes, humanized CYP1A2 (hCYP1A2) rat liver microsomes, and WT rat liver microsomes, with IC50 values of 7.1 μM, 36.5 μM, and 285.8 μM, respectively. Meanwhile, pharmacokinetic characteristics of clozapine were conducted, and the results suggested that in hCYP1A2 rats, clozapine tended to be metabolized into norclozapine. Both the in vitro and in vivo results demonstrated the different metabolic functions of CYP1A2 in humanized and WT rats. We successfully constructed a novel humanized CYP1A2 rat model using the CRISPR/Cas9 system, providing a powerful tool for better predicting CYP1A2-mediated drug metabolism and pharmacokinetics. Significance Statement Human CYP1A2 takes active part both in the biotransformation of exogenous substances and endogenous substances. Meanwhile, it plays a regulatory role in human diseases, including hypercholesterolemia, hypertension as well as various malignant tumors. This study successfully constructed humanized CYP1A2 rat model by CRISPR/Cas9 technology, providing a powerful model for promoting drug development and safety evaluation, as well as further exploring the role of CYP1A2 in human diseases.

Transgenic animal models to explore and modulate the blood brain and blood retinal barriers of the CNS

The unique environment of the brain and retina is tightly regulated by blood-brain barrier and the blood-retinal barrier, respectively, to ensure proper neuronal function. Endothelial cells within these tissues possess distinct properties that allow for controlled passage of solutes and fluids. Pericytes, glia cells and neurons signal to endothelial cells (ECs) to form and maintain the barriers and control blood flow, helping to create the neurovascular unit. This barrier is lost in a wide range of diseases affecting the central nervous system (CNS) and retina such as brain tumors, stroke, dementia, and in the eye, diabetic retinopathy, retinal vein occlusions and age-related macular degeneration to name prominent examples. Recent studies directly link barrier changes to promotion of disease pathology and degradation of neuronal function. Understanding how these barriers form and how to restore these barriers in disease provides an important point for therapeutic intervention. This review aims to describe the fundamentals of the blood-tissue barriers of the CNS and how the use of transgenic animal models led to our current understanding of the molecular framework of these barriers. The review also highlights examples of targeting barrier properties to protect neuronal function in disease states.

Population Pharmacokinetic Modelling to Support the Evaluation of Preclinical Pharmacokinetic Experiments with Lorlatinib

The effect of transporters and enzymes on drug pharmacokinetics is increasingly evaluated using genetically modified animals that have these proteins either knocked-out or their human orthologues transgenically expressed. Analysis of pharmacokinetic data obtained in such experiments is typically performed using non-compartmental analysis (NCA), which has limitations such as not being able to identify the PK parameter that is affected by the genetic modification of the enzymes or transporters and the requirement of intense and homogeneous sampling of all subjects. Here we used a compartmental population pharmacokinetic modeling approach using PK data from a series of genetically modified mouse experiments with lorlatinib to extend the results and conclusions from previously reported NCA analyses. A compartmental population pharmacokinetic model was built and physiologically plausible covariates were evaluated for the different mouse strains. With the model, similar effects of the strains on the area under the concentration-time curve (AUC) from 0 to 8 hours were found as for the NCA. Additionally, the differences in AUC between the strains were explained by specific effects on clearance and bioavailability for the strain with human expressing CYP3A4. Finally, effects of multidrug efflux transporters ATP-binding cassette (ABC) sub-family B member 1 (ABCB1) and G member 2 (ABCG2) on brain efflux were quantified. Use of compartmental population PK modeling yielded additional insight into the role of drug-metabolizing enzymes and drug transporters in mouse experiments compared to the NCA. Furthermore, these models allowed analysis of heterogeneous pooled datasets and the sparse organ concentration data in contrast to classical NCA analyses.

Conditional Knockout Mouse Models to Study the Roles of Individual NF-κB Transcription Factors in Lymphocytes

The NF-κB signal transduction pathway has crucial functions in cell growth, survival, and the development of lymphocytes and other immune cells. Upon activation of the pathway, five distinct NF-κB transcription factor subunits that occur as homodimers or heterodimers comprise the downstream mediators that transcribe NF-κB target genes. A major quest in NF-κB research is to understand the biology of the separate subunits. However, determining the functions of the individual subunits using constitutional knockout mice is often hampered by the marked cell type and/or developmental stage-specific activation of the NF-κB pathway. To overcome these problems, we and others have generated loxP-flanked alleles of the genes encoding the different NF-κB subunits that upon crossing to suitable Cre-expressing mouse lines can be conditionally deleted in the desired cell type or developmental stage. We here describe the basic characteristics of conditional NF-κB subunit alleles rel (encoding c-REL), rela (RELA), relb (RELB), and nfkb2 (NF-κB2) generated in our laboratory that are available to the research community through a repository, and provide basic methods to study the consequences of tissue-specific ablation of NF-κB transcription factors in lymphocytes.

Astrocytes in Motor Neuron Diseases

Motor neuron disorders are highly debilitating and mostly fatal conditions for which only limited therapeutic options are available. To overcome this limitation and develop more effective therapeutic strategies, it is critical to discover the pathogenic mechanisms that trigger and sustain motor neuron degeneration with the greatest accuracy and detail. In the case of Amyotrophic Lateral Sclerosis (ALS), several genes have been associated with familial forms of the disease, whilst the vast majority of cases develop sporadically and no defined cause can be held responsible. On the contrary, the huge majority of Spinal Muscular Atrophy (SMA) occurrences are caused by loss-of-function mutations in a single gene, SMN1. Although the typical hallmark of both diseases is the loss of motor neurons, there is increasing awareness that pathological lesions are also present in the neighbouring glia, whose dysfunction clearly contributes to generating a toxic environment in the central nervous system. Here, ALS and SMA are sequentially presented, each disease section having a brief introduction, followed by a focussed discussion on the role of the astrocytes in the disease pathogenesis. Such a dissertation is substantiated by the findings that built awareness on the glial involvement and how the glial-neuronal interplay is perturbed, along with the appraisal of this new cellular site for possible therapeutic intervention.

Heart regeneration and the cardiomyocyte cell cycle

Cardiovascular disease and in particular, heart failure are still main causes of death; therefore, novel therapeutic approaches are urgently needed. Loss of contractile substrate in the heart and limited regenerative capacity of cardiomyocytes are mainly responsible for the poor cardiovascular outcome. This is related to the postmitotic state of differentiated cardiomyocytes, which is partly due to their polyploid nature caused by cell cycle variants. As such, the cardiomyocyte cell cycle is a key player, and its manipulation could be a promising strategy for enhancing the plasticity of the heart by inducing cardiomyocyte proliferation. This review focuses on the cardiac cell cycle and its variants during postnatal growth, the different regenerative responses of the heart in dependance of the developmental stage and on manipulations of the cell cycle. Because a therapeutic goal is to induce authentic cell division in cardiomyocytes, recent experimental approaches following this strategy are also discussed.

Apolipoprotein CIII overexpression exacerbates diet-induced obesity due to adipose tissue higher exogenous lipid uptake and retention and lower lipolysis rates

Background

Hypertriglyceridemia is a common type of dyslipidemia found in obesity. However, it is not established whether primary hyperlipidemia can predispose to obesity. Evidences have suggested that proteins primarily related to plasma lipoprotein transport, such as apolipoprotein (apo) CIII and E, may significantly affect the process of body fat accumulation. We have previously observed an increased adiposity in response to a high fat diet (HFD) in mice overexpressing apoCIII. Here, we examined the potential mechanisms involved in this exacerbated response of apoCIII mice to the HFD.

Methods

We measured body energy balance, tissue capacity to store exogenous lipids, lipogenesis and lipolysis rates in non-transgenic and apoCIII overexpressing mice fed a HFD during two months.

Results

Food intake, fat excretion and whole body CO₂ production were similar in both groups. However, the adipose tissue mass (45 %) and leptin plasma levels (2-fold) were significantly greater in apoCIII mice. Lipogenesis rates were similar, while exogenous lipid retention was increased in perigonadal (2-fold) and brown adipose tissues (40 %) of apoCIII mice. In addition, adipocyte basal lipolysis (55 %) and in vivo lipolysis index (30 %) were significantly decreased in apoCIII mice. A fat tolerance test evidenced delayed plasma triglyceride clearance and greater transient availability of non-esterified fatty acids (NEFA) during the post-prandial state in the apoCIII mice plasma. Thus, apoCIII overexpression resulted in increased NEFA availability to adipose uptake and decreased adipocyte lipolysis, favoring lipid enlargement of adipose depots.

Conclusion

We propose that plasma apoCIII levels represent a new risk factor for diet-induced obesity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-015-0058-6) contains supplementary material, which is available to authorized users.

Strategies to Study Desmin in Cardiac Muscle and Culture Systems

Intermediate filament (IF) cytoskeleton comprises the fine-tuning cellular machinery regulating critical homeostatic mechanisms. In skeletal and cardiac muscle, deficiency or disturbance of the IF network leads to severe pathology, particularly in the latter. The three-dimensional scaffold of the muscle-specific IF protein desmin interconnects key features of the cardiac muscle cells, including the Z-disks, intercalated disks, plasma membrane, nucleus, mitochondria, lysosomes, and potentially sarcoplasmic reticulum. This is crucial for the highly organized striated muscle, in which effective energy production and transmission as well as mechanochemical signaling are tightly coordinated among the organelles and the contractile apparatus. The role of desmin and desmin-associated proteins in the biogenesis, trafficking, and organelle function, as well as the development, differentiation, and survival of the cardiac muscle begins to be enlightened, but the precise mechanisms remain elusive. We propose a set of experimental tools that can be used, in vivo and in vitro, to unravel crucial new pathways by which the IF cytoskeleton facilitates proper organelle function, homeostasis, and cytoprotection and further understand how its disturbance and deficiency lead to disease.

Convergent functional genomics in addiction research - a translational approach to study candidate genes and gene networks

Convergent functional genomics (CFG) is a translational methodology that integrates in a Bayesian fashion multiple lines of evidence from studies in human and animal models to get a better understanding of the genetics of a disease or pathological behavior. Here the integration of data sets that derive from forward genetics in animals and genetic association studies including genome wide association studies (GWAS) in humans is described for addictive behavior. The aim of forward genetics in animals and association studies in humans is to identify mutations (e.g. SNPs) that produce a certain phenotype; i.e. "from phenotype to genotype". Most powerful in terms of forward genetics is combined quantitative trait loci (QTL) analysis and gene expression profiling in recombinant inbreed rodent lines or genetically selected animals for a specific phenotype, e.g. high vs. low drug consumption. By Bayesian scoring genomic information from forward genetics in animals is then combined with human GWAS data on a similar addiction-relevant phenotype. This integrative approach generates a robust candidate gene list that has to be functionally validated by means of reverse genetics in animals; i.e. "from genotype to phenotype". It is proposed that studying addiction relevant phenotypes and endophenotypes by this CFG approach will allow a better determination of the genetics of addictive behavior.

C57BL/6J congenic Prp-TDP43A315T mice develop progressive neurodegeneration in the myenteric plexus of the colon without exhibiting key features of ALS

ALS therapy development has been hindered by the lack of rodent animal models. The discovery of TDP-43, a transcription factor that accumulates in the cytoplasm of motor neurons (MNs) in most cases of ALS, prompted attempts to develop TDP-43-based models of the disease. The current study sought to examine, in extensive detail, the emerging disease phenotype of a transgenic mouse model that overexpresses a mutant human TDP-43 (hTDP-43) gene under mouse prion promoter control. Careful attention was given to ALS-like characteristics to determine the appropriateness of this model for testing therapies for ALS. In light of previous reports that gastrointestinal (GI) dysfunction is responsible for early death in these mice, gut immunohistochemistry (IHC) and longitudinal gut motility assays were used to identify the onset and the progression of these defects. IHC studies revealed that site-specific overexpression of the hTDP-43 transgene in colonic myenteric plexes resulted in progressive neurodegeneration in this region. This change was associated with progressively reduced GI motility, culminating in frank stasis that was primarily responsible for decreasing longevity in these mice. The disease phenotype was gender- and genetic background-dependent, with congenic C57BL/6J male mice exhibiting the most aggressive form of the disease. Spinal cord IHC revealed ubiquitin-positive inclusions, but not TDP-43 aggregates, in the cytoplasm of MNs. Neither gender exhibited compelling ALS-like neuromuscular deficits, irrespective of age. While this model may be useful for studying GI tract neurodegeneration, in its present state it does not display a phenotype suitable for testing ALS therapeutics.