Relevance of systemic lupus erythematosus nephritis animal models to human disease

Systemic lupus erythematosus (SLE) is characterized by spontaneous B and T cell autoreactivity and multiorgan immune injury including severe glomerulonephritis. This autoimmune syndrome results from a global derangement in immune regulation dependent on the interaction of complex genetic and environmental susceptibility factors. Animal models have provided a powerful tool to study disease mechanisms and novel therapeutic interventions under well-defined conditions, and bypass the barriers inherent in the study of human lupus. Classical models of spontaneous and investigator-induced murine lupus, their mutant variants, and novel transgenic and gene-targeted mutant lineages have been particularly useful. Extensive genome typing in inbred and recombinant lupus-prone strains permits mapping and characterization of multiple lupus susceptibility loci and genes and their contribution to various disease phenotypes. Murine models provide important insight into the identity of targeted self-antigens, the molecules and pathways that maintain tolerance, immune cell and cytokine interactions that promote autoimmunity, and mechanisms of renal localization and injury by immune effectors. These models reveal that multiple and independent mechanisms contribute to disease pathogenesis and provide a better understanding of the remarkable phenotypic and histopathologic heterogeneity that characterizes human SLE.     

Unravelling high density lipoprotein-apolipoprotein metabolism in human mutants and animal models

Apolipoprotein A-I plays an essential structural and functional role in HDL metabolism and apolipoprotein A-II has important effects on HDL metabolism and function. Kinetic studies in humans have established that variation in plasma HDL-cholesterol and apolipoprotein A-I concentrations is primarily determined by variation in the rate of apolipoprotein A-I catabolism. In contrast, plasma apolipoprotein A-II levels are primarily determined by the rate of apolipoprotein A-II production. Genetic factors play an important role in modulating the plasma levels of HDL-cholesterol and apolipoproteins A-I and A-II. Studies in humans have established that mutations in genes encoding enzymes that esterify cholesterol (lecithin : cholesterol acyltransferase), transfer cholesterol (cholesteryl ester transfer protein) and hydrolyze lipids (hepatic lipase, lipoprotein lipase) regulate HDL-cholesterol and apolipoprotein A-I levels by modifying the lipid content (and therefore the size) of HDL particles. Recent studies in transgenic and knockout animals have confirmed the key role of HDL lipid-modifying proteins in HDL, apolipoprotein A-I and apolipoprotein A-II metabolism and have expanded our understanding of the role of lipid modification in determining plasma concentrations of HDL-cholesterol and apolipoprotein A-I, as well as the potential functional roles of apolipoprotein A-II.     

Immunoconjugates: lessons from animal models

Monoclonal antibody-mediated cancer therapy has evolved through a challenging chain of problems and solutions. The very limited therapeutic success obtained with unarmed monoclonal antibodies has increased the interest in different antibody-based targeting strategies, and numerous preclinical and even clinical studies with immunoconjugates have now been conducted. We comment here on the messages implicit in a recent report on a doxorubicin-anti-carcinoma antibody conjugate and from several other studies.     

Experimental animal models in cerebral ischemia

This paper describes the potential markers of cell death and connective tissue degradation which might serve as markers of periodontal disease activity. The first section deals with enzymes released by dead and degenerating cells. Firstly, it describes how these pass from the periodontal tissues into gingival crevicular fluid (GCF) and explains that these enzymes have been used as markers of cell death in medicine for several decades. It then discusses the main enzymes in this group, aspartate amino transferase (AST) and lactate dehydrogenase (LDH) and reviews those studies which have attempted to relate these enzymes to periodontal disease severity and activity. Secondly, it describes the potential markers of connective tissue degradation, fibronectin, hydroxyproline-containing peptides and glycosaminoglycans (GAGs) and explains how these are produced. Finally, it describes the only commercial test kit for markers in this group (GCF-AST).     

Lessons from animal models of atrial arrhythmias

This article presents selected lessons from experimental studies of atrial fibrillation and atrial flutter that pertain to the mechanisms and predisposing factors for flutter and fibrillation and approaches to treatment by antiarrhythmic drugs. Experimental studies also provide lessons for the effects of ablation and surgical lesions on prevention or facilitation of atrial fibrillation and flutter.     

Genital anomalies in human and animal models reveal the mechanisms and hormones governing testicular descent

A systematic examination of the conditions characterized by the presence of genital anomalies in humans, noting in each condition the position of the gonad, the nature of the gubernaculum and cranial suspensory ligament can provide valuable information regarding the mechanisms controlling the final position of the gonads. In conditions where MIS is absent, the gubernaculum is "feminized', resulting in a testis in the position normally occupied by an ovary or an abnormally mobile testis that can prolapse to the inguinal region. In conditions of androgen insensitivity the testis is located in the inguinal region, indicating that the first phase of descent is normal but that inguinoscrotal descent has failed to occur. Ovarian descent fails to occur in congenital adrenal hyperplasia, despite exposure of the developing fetus to high levels of androgens, indicating that androgen alone does not control gonadal descent. Moreover, ovarian descent fails to occur despite androgen-dependent regression of the cranial suspensory ligament. The correlation between the degree of Müllerian duct retention and scrotal position in mixed gonadal dysgenesis further strengthens the hypothesis that the first stage of testicular descent is controlled by MIS. The study of genital anomalies suggests that MIS controls the swelling reaction in the male gubernaculum, which is responsible for the first phase of testicular descent to the inguinal region. The second or inguinoscrotal phase of descent is androgen-dependent. Regression of the cranial suspensory ligament is also androgen-dependent: however, it is the gubernaculum and not the presence or absence of the cranial suspensory ligament which controls testicular descent. A combined knowledge of the hormonal basis controlling sexual differentiation and the biphasic model of testicular descent enables the clinician to accurately predict the internal anatomy of these complex sexual anomalies.     

Introducing Critical Appraisal to studies of animal models investigating novel therapies in sepsis

OBJECTIVES: To discuss theoretical and practical aspects relating to the design of animal studies investigating the efficacy of novel therapeutic agents for the treatment of sepsis, and to make explicit the process whereby these studies can be evaluated for the purpose of designing clinical trials in humans. DATA SOURCES: Relevant articles from the pertinent literature were reviewed. STUDY SELECTION: Studies relevant to an evidence-based assessment of clinical studies on therapeutic efficacy, and studies relevant to the design of animal models of sepsis were selected. DATA EXTRACTION: Concepts relevant to an evidence-based assessment of the animal literature were extracted. DATA SYNTHESIS: Articles were reviewed and an evidence-based framework for the assessment of animal studies was developed. In this process, we discuss the steps that are necessary to assess the internal validity of an individual study and review topics relevant to the application of animal data to the design of clinical trials. CONCLUSIONS: The success of clinical trials of sepsis therapies is predicated on the generation and interpretation of sound preclinical data. In this review, we have attempted to outline an evidence-based approach to the assessment of preclinical animal studies evaluating novel therapeutic interventions in sepsis.     

Genetic dissection of obesity in polygenic animal models

In contrast to diseases caused by single-gene defects, many of the most common human maladies such as obesity, atherosclerosis, diabetes, and hypertension exhibit continuous phenotypic variation and a predominantly multifactorial and polygenic basis. Genes with roles in energy balance, nutrient partitioning, lipid and insulin metabolism, and a variety of behavioral traits are likely interacting with environmental stimuli to regulate obesity phenotypes. With the current proliferation of highly polymorphic genetic markers and the refinement of experimental approaches, it is now possible to screen thoroughly the genomes of model organisms for the individual genes or quantitative trait loci (QTL) that control measurable polygenic traits such as obesity. With the growing wealth of comparative mapping, it will be possible to predict the location of a homologous locus in the human after first mapping it in the mouse. Many experiments have been conducted in mice, rats, and pigs to estimate the number, location, and effect of QTL controlling obesity and related traits. This review describes the design and strategies of such studies and summarizes the results and their implications toward understanding the complex nature of obesity in humans.     

Aromatic hydroxylation in animal models of diabetes mellitus

Although the involvement of oxidative stress is well documented in the diabetic state, the individual active oxygen species generated have not been demonstrated in animal models of diabetes currently used. Since streptozotocin-induced diabetes mellitus in animals still serves as an animal model of diabetes mellitus, but streptozotocin induces diabetes and generates oxidative stress per se, we decided to study whether aromatic hydroxylation reflecting hydroxyl radical attack was found in three animal models of diabetes mellitus without streptozotocin induction or in streptozotocin-induced diabetes only. For this purpose, we compared lipid peroxidation, aromatic hydroxylation of phenylalanine, glycoxidation in genetically determined diabetic mouse strains db/db and kk, and the diabetic BB rat to these parameters in the streptozotocin-treated rat. Kidney malondialdehyde concentrations, reflecting lipid peroxidation, pentosidine, and Nepsilon-caboxymethyllysine concentrations, reflecting glycoxidation, were significantly elevated in all diabetic groups as compared to their nondiabetic mates. Aromatic hydroxylation was significantly elevated in the streptozotocin-induced diabetic state exclusively. We conclude that biochemical, pathophysiological, and treatment studies in the streptozotocin model of diabetes mellitus may be confounded by the presence of products, reactions, and tissue damage generated by aromatic hydroxylation reflecting hydroxyl radical attack. We suggest it is not the diabetic state but streptozotocin that generates the hydroxyl radical, as reflected by aromatic hydroxylation in this model.     

Quantitative models of animal learning and cognition.

This article reviews the prerequisites for quantitative models of animal learning and cognition, describes the types of models, provides a rationale for the development of such quantitative models, describes criteria for their evaluation, and makes recommendations for the next generation of quantitative models. A modular approach to the development of models is described in which a procedure is considered as a generator of stimuli and a model is considered as a generator of responses. The goal is to develop models that, in combination with many different procedures, produce sequences of times of occurrence of events (stimuli and responses) that are indistinguishable from those produced by the animal under many experimental procedures and data analysis techniques. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Glycosphingolipid degradation and animal models of GM2-gangliosidoses

Glycosphingolipids form cell type-specific patterns on the surface of eukaryotic cells. Degradation of glycosphingolipids requires endocytic membrane flow of plasma membrane-derived glycosphingolipids into the lysosomes as the digesting organelles. The inherited deficiencies of lysosomal hydrolases and of sphingolipid activator proteins both give rise to sphingolipid storage diseases. Recent research has focused on the mechanisms leading to selective membrane degradation in the lysosomes and on the mechanism and physiological function of sphingolipid activator proteins. The GM2-degrading system is a paradigm for activator protein-dependent lysosomal degradation. Three polypeptide chains contribute to the in vivo degradation of ganglioside GM2: the alpha- and beta-chains of the beta-hexosaminidases and the GM2 activator. Mouse models of Tay-Sachs disease (alpha-chain deficiency), Sandhoff disease (beta-chain deficiency) and GM2 activator deficiency have been described. While the phenotypes of these variants of GM2-gangliosidoses are only slightly different in humans, the animal models show drastic differences in severity and course of the diseases. The reason for this is the specificity of sialidase, which is different between mouse and human. A double-knockout mouse lacking beta-hexosaminidases A, B and S shows a phenotype of mucopolysaccharidosis and gangliosidosis. A substrate deprivation approach to therapy is discussed with respect to animal models of the GM2-gangliosidoses.     

Anxiogenic-like consequences in animal models of complex partial seizures

Extracellular adenosine triphosphate (ATP) plays an important role in the regulation of endothelial function. However, its receptors and their signal-transduction pathways in major cerebral arterial endothelial cells are largely unknown. This study was undertaken functionally to classify the P2 purinoceptors in cultured bovine middle cerebral artery endothelial cells by using [Ca2+]i microfluorimetry. The rank order of potency to increase [Ca2+]i was 2-methylthio-ATP approximately ATP approximately uridine triphosphate (UTP) > adenosine diphosphate (ADP) > adenosine monophosphate (AMP) > alpha,beta-methylene-ATP > adenosine, suggesting that the effect was mediated by both P2y and P2u receptors. ATP, 2-methylthio-ATP, and UTP mobilized Ca2+ from intracellular stores and triggered Ca2+ entry. The effects of ATP, 2-methylthio-ATP, and UTP were reduced by phospholipase C inhibitor 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate (NCDC), but only the effects of ATP and UTP were attenuated by pertussis toxin, indicating that P2y and P2u receptors may activate the same effector mechanisms by coupling to different G proteins. The [Ca2+]i entry caused by UTP was significantly reduced by the receptor-regulated Ca2+ channel blocker SK&F 96365, by P-450 inhibitor econazole and by inorganic Ca2+ entry blocker lanthanum. P2-receptor antagonists suramin, pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), and reactive blue 2 reduced the effects of ATP and 2-methylthio-ATP, but not those of UTP, in a concentration-dependent manner. These studies suggest a coexistence of P2y and P2u receptors in cultured bovine middle cerebral artery endothelial cells.     

Development of animal models for adeno-associated virus site-specific integration

The adeno-associated virus (AAV) is unique in its ability to target viral DNA integration to a defined region of human chromosome 19 (AAVS1). Since AAVS1 sequences are not conserved in a rodent's genome, no animal model is currently available to study AAV-mediated site-specific integration. We describe here the generation of transgenic rats and mice that carry the AAVS1 3.5-kb DNA fragment. To test the response of the transgenic animals to Rep-mediated targeting, primary cultures of mouse fibroblasts, rat hepatocytes, and fibroblasts were infected with wild-type wt AAV. PCR amplification of the inverted terminal repeat (ITR)-AAVS1 junction revealed that the AAV genome integrated into the AAVS1 site in fibroblasts and hepatocytes. Integration in rat fibroblasts was also observed upon transfection of a plasmid containing the rep gene under the control of the p5 and p19 promoters and a dicistronic cassette carrying the green fluorescent protein (GFP) and neomycin (neo) resistance gene between the ITRs of AAV. The localization of the GFP-Neo sequence in the AAVS1 region was determined by Southern blot and FISH analysis. Lastly, AAV genomic DNA integration into the AAVS1 site in vivo was assessed by virus injection into the quadriceps muscle of transgenic rats and mice. Rep-mediated targeting to the AAVS1 site was detected in several injected animals. These results indicate that the transgenic lines are proficient for Rep-mediated targeting. These animals should allow further characterization of the molecular aspects of site-specific integration and testing of the efficacy of targeted integration of AAV recombinant vectors designed for human gene therapy.     

Experimental animal models and complications of transluminal coronary angioplasty

Serial changes in the endometrial levels of estrogen and progesterone receptors (ER and PR) were measured in 50 women from days 2 to 14 of missed menses and correlated with the plasma concentrations of hCG, progesterone and 17 beta-estradiol. Both ER and PR of nuclei were higher than cytosolic proteins, with a shift in the ratio of nER/nPR to nPR from 4th day after missed menses. On Scatchard analysis of the cytosolic and nuclear binding proteins, two classes of proteins, corresponding to Type I and II, were found. While the increasing levels of hCG maintained luteal secretion of progesterone and 17 beta-estradiol at normal mid-luteal phase levels, a gradual increase in 17 beta estradiol from 9th day of missed menses was noted. This delicate balance between circulating levels of progesterone and 17 beta-estradiol and their nuclear receptors at early stages of pregnancy may be of significance.     

Anti-phospholipid syndrome: from patient's bedside to experimental animal models and back to the patient's bedside

The availability of animal models of the APS has provided a lot of experimental data which might be considered in trying to unravel several questions concerning this complicated disease. The main clinical manifestations associated with this disorder are repeated pregnancy loss, thrombocytopenia and thrombotic events. Other manifestations have been reported in relation to APS. However, the association with anti-phospholipid antibodies (aPL) are still uncertain. In the APS murine models presented here, both the Lupus-prone mice and the naive mice with induced APS, fetal resorption (parallels to embryo loss) and reduced fecundity rate were prominent features strongly associated with pathogenic aCL antibodies, making these models appropriate for investigating the human disease. Utilizing these models for APS have enabled to show the pathogenicity of aPL in pregnancy loss, neurological and behavioral changes, renal involvement and thrombus formation. Antiphospholipid antibodies from patients with APS, as well as natural aCL antibodies exerted pathogenic effects in naive mice, and in an in vivo thrombosis model. Several therapeutic modalities were found promising for application in the clinics. These include the antithrombotic and anticoagulant treatments using aspirin or LMWH, IL-3, or immunomodulation by high dose IVIG, specific anti-idiotypic or anti-CD4 antibodies, cyprofloxacin or bromocriptin administration.