Prominent corticosteroid disturbance in experimental prion disease

Fatal familial insomnia: A new case description with early response to immunotherapy

Fatal Familial Insomnia (FFI) is a rare prionopathy with autosomal dominant inheritance. Although it owes its name because insomnia is one of the most frequent and core symptoms, its clinical phenotype can be wide and heterogeneous. This usually makes it necessary to rule out other clinical processes, such as limbic encephalitis or Creutzfeldt Jakob disease, whose symptoms can sometimes overlap. We present the case of a 46-year-old male with a rapidly progressive multidomain cognitive impairment, associated with instability in gait, myoclonus and persistent and progressive insomnia. His mother had died from a genetically determined FFI (D178N mutation). Due to clinical course, an immunomediated encephalopathy was suspected, and immunosuppressive treatment with steroids and immunoglobulins was initiated. The patient showed initial improvement, but later rapidly progressive deterioration until his death 7 months after clinical onset. Cranial magnetic resonance, electroencephalogram and cerebrospinal fluid (CSF) did not show any findings. The antiTPO and antineuronal antibodies were negative. The genetiic study demonstrated the missense mutation c.532G > A (p.Asp178Asn) compatible with FFI. Postmortem study showed synaptic deposits of PrPsc in the entorhinal cortex and in thalamus, which confirmed FFI diagnosis.

Case of fatal familial insomnia caused by a d178n mutation with phenotypic similarity to Hashimoto's encephalopathy

Fatal familial insomnia (FFI) is a rare prion disease commonly inherited in an autosomal dominant pattern from a mutation in the PRioN Protein (PRNP) gene. Hashimoto's encephalopathy (HE) is characterised by encephalopathy associated with antithyroid peroxidase (TPO) or antithyroglobulin (Tg) antibodies. These two conditions characteristically have differing clinical presentations with dramatically different clinical course and outcomes. Here, we present a case of FFI mimicking HE. A woman in her 50s presented with worsening confusion, hallucinations, tremor and leg jerks. Several maternal relatives had been diagnosed with FFI, but the patient had had negative genetic testing for PRNP. MRI of brain, cervical and thoracic spine were unremarkable except for evidence of prior cervical transverse myelitis. Cerebrospinal fluid analysis was normal. Anti-TPO and anti-Tg antibodies were elevated. She was started on steroids for possible HE and showed improvement in symptoms. Following discharge, the results of her PRNP gene test returned positive for variant p.Asp178Asn.

Impact of male presence on female sociality and stress endocrinology in wild house mice (Mus musculus domesticus)

In group living animals, reproductive competition plays an important role in shaping social relationships and associations among female group members. In this study, we investigated the impact of male presence on the development of female-female competition and female sociality in groups of female wild house mice, using physiological and behavioral parameters. We predicted that, by eliciting intra-sexual competition, males influence social relationships among female group members and thus affect female associations to potential cooperation partners. To test this hypothesis we compared stress hormone production, the frequency of agonistic interactions, social hierarchies and social partner preferences in groups of unrelated, unfamiliar females in the absence and presence of males. Our results revealed no indication that the introduction of males into all-female groups of wild house mice elicited increased competition among female group members, neither on the physiological nor on the behavioral level. We found no effect of male presence on female glucocorticoid secretion, aggression, dominance hierarchies or on the females' sociability. Females thus seem not to intensely compete over access to males. This female ability to behaviorally and physiologically deal with even previously unfamiliar same-sex group members may be an important feature of female house mouse societies. In fact, it could be a necessary prerequisite to establish cooperative relationships between females in the context of reproduction, such as communal nursing of young.

Lifetime Dependent Variation of Stress Hormone Metabolites in Feces of Two Laboratory Mouse Strains

Non-invasive measurement of stress hormone metabolites in feces has become routine practice for the evaluation of distress and pain in animal experiments. Since metabolism and excretion of glucocorticoids may be variable, awareness and adequate consideration of influencing factors are essential for accurate monitoring of adrenocortical activity. Reference values are usually provided by baselines compiled prior to the experiment and by age matched controls. The comparison of stress hormone levels between animals of different ages or between studies looking at hormone levels at the beginning and at the end of a long term study might be biased by age-related effects. In this study we analyzed fecal corticosterone metabolites (FCM) during the lifetime of untreated female mice of the strains C57BL/6NCrl and Crl:CD1. For this purpose feces for each individual mouse were collected every two months over a period of 24 hours, at intervals of four hours, until the age of 26 months. Results of the study revealed that age of the animals had a significant impact on the level and circadian rhythm of stress hormone metabolites. Furthermore, long-term observation of mice revealed a strain specific excretion profile of FCM influenced by strong seasonal variability.

Membrane toxicity of abnormal prion protein in adrenal chromaffin cells of scrapie infected sheep

Transmissible spongiform encephalopathies (TSEs) or prion diseases are associated with accumulations of disease specific PrP (PrP(d)) in the central nervous system (CNS) and often the lymphoreticular system (LRS). Accumulations have additionally been recorded in other tissues including the peripheral nervous system and adrenal gland. Here we investigate the effect of sheep scrapie on the morphology and the accumulation of PrP(d) in the adrenal medulla of scrapie affected sheep using light and electron microscopy. Using immunogold electron microscopy, non-fibrillar forms of PrP(d) were shown to accumulate mainly in association with chromaffin cells, occasional nerve endings and macrophages. PrP(d) accumulation was associated with distinctive membrane changes of chromaffin cells including increased electron density, abnormal linearity and invaginations. Internalisation of PrP(d) from the chromaffin cell plasma membrane occurred in association with granule recycling following hormone exocytosis. PrP(d) accumulation and internalisation from membranes is similarly associated with perturbations of membrane structure and trafficking in CNS neurons and tingible body macrophages of the LRS. These data suggest that a major toxic effect of PrP(d) is at the level of plasma membranes. However, the precise nature of PrP(d)-membrane toxicity is tissue and cell specific suggesting that the normal protein may act as a multi-functional scaffolding molecule. We further suggest that the co-localisation of PrP(d) with exocytic granules of the hormone trafficking system may provide an additional source of infectivity in blood.

Non-invasive monitoring of glucocorticoid metabolites in banded mongooses (Mungos mungo) in response to physiological and biological challenges

Free-ranging banded mongooses are infected by the novel pathogen, Mycobacterium mungi in northern Botswana. A reliable method for determining stress-related physiological responses in banded mongooses will increase our understanding of the stress response in M. mungi infection. Therefore, our aim was to examine the suitability of four enzyme immunoassays (EIAs) for monitoring adrenocortical endocrine function in captive and free-ranging banded mongooses based on fecal glucocorticoid metabolite (FGM) analysis. A conducted adrenocorticotropic hormone challenge revealed suitability of a valid measurement of FGM levels in banded mongoose feces for all four tested EIAs, with an 11-oxoetiocholanolone assay detecting 11,17-dioxoandrostanes (11,17-DOA) performing best. Subsequent analyses using only this EIA showed the expected decrease in FGM concentrations 48 h after administering dexamethasone sodium phosphate. Furthermore, captive mongooses showed higher FGM concentrations during reproductive activity, agonistic encounters and depredation events. Finally, a late-stage, tuberculosis-infected moribund mongoose in a free-ranging troop had a 54-fold elevation in FGM levels relative to the rest of the troop. Measurements of gastrointestinal transit times and FGM metabolism post-defecation indicate that the time delay of FGM excretion approximately corresponded with food transit time and that FGM metabolism is minimal up to 8h post-defecation. The ability to reliably assess adrenocortical endocrine function in banded mongoose now provides a solid basis for advancing our understanding of infectious disease and endocrinology in this species.

[Mice cope with parabiosis − assessment of their physiological changes of life]

The purpose of this study was to establish a parabiotic mice model and assess the physiological changes of the mice under the parabiotic state. Thirteen pairs of isogenic partners were studied. The model was created by preparing a bridge of skin and subcutaneous tissues between the two mice starting distal of the elbow joint along the humerus along the lateral costal region until the end of the waist line. Physiological, social and affective qualities of life were studied in the mice through behavioural observations for 120 days following the parabiotic surgery. During the first 2-3 days following the operation, the animals suffered from severe pain and distress. During the following days and weeks, the physiological system began to recover and the animals displayed behavioral adaptations to the parabiotic condition. All animals survived at day 120. At three days post operation, the body weight began to decrease. Following this, the animals experienced a continual body weight recovery and reached pre-surgical measures at about 30 days post op. Forty-eight h post op., faecal corticosterone-metabolites were extremely elevated, but their levels returned to two to four times of levels in control females within 72 hours post op. The faecal corticosterone-metabolite levels decreased near to control values on day 75. Out of the 13 pairs, the blood exchange rate of three parabiotic partners was tested, with the result being normal post op. After 12 weeks, the total blood exchange between both partners needed 63 or 46 or 107 min, respectively. These results demonstrated that the animals could adapt behaviourally to the parabiotic situation. Therefore, this parabiosis mouse model may provide useful insights in many research areas, such as transplantation immunity, hematological system and metabolism, etc.

Repeated use of surrogate mothers for embryo transfer in the mouse

Embryo transfer in mice is a crucial technique for generation of transgenic animals, rederivation of contaminated lines, and revitalization of cryopreserved strains, and it is a key component of assisted reproduction techniques. It is common practice to use females only once as surrogate mothers. However, their reuse for a second embryo transfer could provide hygienic and economic advantages and conform to the concept of the 3Rs (replace, reduce, refine). This investigation evaluated the potential for a second embryo transfer in terms of feasibility, reproductive results, and experimental burden for the animal. Virgin female ICR mice (age 8-16 wk) were used as recipients for the first embryo transfer. Immediately after weaning of the first litter, a second surgical embryo transfer was performed into the same oviduct. Virgin females of comparable age to the reused mothers served as controls and underwent the same procedure. The first surgery did not affect the success of the second embryo transfer. Histological sections showed excellent wound healing without relevant impairment of involved tissues. We observed no differences in pregnancy rates or litter sizes between the transfer groups. Most importantly, we found no change in behavior indicating reduced well-being and no increase of corticosterone metabolites in the feces of surrogate mothers reused for a second embryo transfer. We conclude that a second embryo transfer in mice is feasible with regard to reproductive and animal welfare aspects.

Faecal glucocorticoid metabolites: How to express yourself – comparison of absolute amounts versus concentrations in samples from a study in laboratory rats

During the last two decades, measurement of faecal Cortisol or corticosterone metabolites (FCM) has become one of the most important tools to non-invasively monitor stress in animals. However, to reliably assess an animal's adrenocortical activity, a careful validation of this technique for each species and sex investigated is obligatory. Usually results in these validation studies and in subsequent applications are expressed as concentration (FCMconc). Nevertheless, some authors express their results as absolute amounts (FCMabs) and claim this to be more accurate. A physiological validation to prove this assumption, however, is still missing as well as information about the influence of the intervals set for faecal sampling, although the chosen intervals might play an important role. Since FCMconc and FCMabs may differ and therefore lead to different conclusions, our study aimed to gain fundamental and scientifically valid information about these parameters by re-analysing a set of data obtained in a study on laboratory rats. The data basis used was derived from four validation experiments performed in male and female rats: an adrenocorticotrophic hormone challenge test, a dexamethasone (Dex) suppression test, an investigation of the diurnal variation (DV) of glucocorticoids and the stress response in reaction to the injection procedure itself (for details see Lepschy et al. Non-invasive measurement of adrenocortical activity in male and female rats. Lab Anim 2007;41:372–87). Faecal samples were collected in short time intervals and the exact amount of faeces voided during each sampling interval was documented. Throughout all performed tests strong positive correlations between FCMconc and FCMabs were found (median of rs > 0.72). In males, for all calculated sampling intervals (4, 8 and 12 h) pharmacological stimulation, suppression and the DV of adrenocortical activity were reflected accurately using both FCMconc and FCMabs. In females, suppression of FCM by Dex was also clearly reflected in both systems. However, pharmacological stimulation was only reflected accurately by means of FCMconc, which clearly limits the usability of FCMabs. Thus, using the data of physiological validation experiments, we clearly demonstrate for the first time advantages and disadvantages of presenting results as FCMconc or FCMabs. Based on our findings in laboratory animals such as rats, giving results as FCMconc seems to be more appropriate and FCMabs - if at all - might only be used as an addition.

Neurodevelopmental expression and localization of the cellular prion protein in the central nervous system of the mouse

Transmissible spongiform encephalopathies (TSEs) are neurodegenerative disorders caused by PrP(Sc), or prion, an abnormally folded form of the cellular prion protein (PrP(C)). The abundant expression of PrP(C) in the central nervous system (CNS) is a requirement for prion replication, yet despite years of intensive research the physiological function of PrP(C) still remains unclear. Several routes of investigation point out a potential role for PrP(C) in axon growth and neuronal development. Thus, we undertook a detailed analysis of the spatial and temporal expression of PrP(C) during mouse CNS development. Our findings show regional differences of the expression of PrP, with some specific white matter structures showing the earliest and highest expression of PrP(C). Indeed, all these regions are part of the thalamolimbic neurocircuitry, suggesting a potential role of PrP(C) in the development and functioning of this specific brain system.

Systemic inflammation induces acute working memory deficits in the primed brain: relevance for delirium

Delirium is an acute, severe neuropsychiatric syndrome, characterized by cognitive deficits, that is highly prevalent in aging and dementia and is frequently precipitated by peripheral infections. Delirium is poorly understood and the lack of biologically relevant animal models has limited basic research. Here we hypothesized that synaptic loss and accompanying microglial priming during chronic neurodegeneration in the ME7 mouse model of prion disease predisposes these animals to acute dysfunction in the region of prior pathology upon systemic inflammatory activation. Lipopolysaccharide (LPS; 100 μg/kg) induced acute and transient working memory deficits in ME7 animals on a novel T-maze task, but did not do so in normal animals. LPS-treated ME7 animals showed heightened and prolonged transcription of inflammatory mediators in the central nervous system (CNS), compared with LPS-treated normal animals, despite having equivalent levels of circulating cytokines. The demonstration that prior synaptic loss and microglial priming are predisposing factors for acute cognitive impairments induced by systemic inflammation suggests an important animal model with which to study aspects of delirium during dementia.

Morphological, physiological and behavioural evaluation of a 'Mice in Space' housing system

Environmental conditions likely affect physiology and behaviour of mice used for life sciences research on Earth or in Space. Here, we analysed the effects of cage confinement on the weightbearing musculoskeletal system, behaviour and stress of wild-type mice (C57BL/6JRj, 30 g b.wt., total n = 24) housed for 25 days in a prototypical ground-based and fully automated life support habitat device called "Mice in Space" (MIS). Compared with control housing (individually ventilated cages) the MIS mice revealed no significant changes in soleus muscle size and myofiber distribution (type I vs. II) and quality of bone (3-D microarchitecture and mineralisation of calvaria, spine and femur) determined by confocal and micro-computed tomography. Corticosterone metabolism measured non-invasively (faeces) monitored elevated adrenocortical activity at only start of the MIS cage confinement (day 1). Behavioural tests (i.e., grip strength, rotarod, L/D box, elevated plus-maze, open field, aggressiveness) performed subsequently revealed only minor changes in motor performance (MIS vs. controls). The MIS habitat will not, on its own, produce major effects that could confound interpretation of data induced by microgravity exposure during spaceflight. Our results may be even more helpful in developing multidisciplinary protocols with adequate scenarios addressing molecular to systems levels using mice of various genetic phenotypes in many laboratories.

Rhythmicity in mice selected for extremes in stress reactivity: behavioural, endocrine and sleep changes resembling endophenotypes of major depression

BACKGROUND

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, including hyper- or hypo-activity of the stress hormone system, plays a critical role in the pathophysiology of mood disorders such as major depression (MD). Further biological hallmarks of MD are disturbances in circadian rhythms and sleep architecture. Applying a translational approach, an animal model has recently been developed, focusing on the deviation in sensitivity to stressful encounters. This so-called 'stress reactivity' (SR) mouse model consists of three separate breeding lines selected for either high (HR), intermediate (IR), or low (LR) corticosterone increase in response to stressors.

METHODOLOGY/PRINCIPLE FINDINGS

In order to contribute to the validation of the SR mouse model, our study combined the analysis of behavioural and HPA axis rhythmicity with sleep-EEG recordings in the HR/IR/LR mouse lines. We found that hyper-responsiveness to stressors was associated with psychomotor alterations (increased locomotor activity and exploration towards the end of the resting period), resembling symptoms like restlessness, sleep continuity disturbances and early awakenings that are commonly observed in melancholic depression. Additionally, HR mice also showed neuroendocrine abnormalities similar to symptoms of MD patients such as reduced amplitude of the circadian glucocorticoid rhythm and elevated trough levels. The sleep-EEG analyses, furthermore, revealed changes in rapid eye movement (REM) and non-REM sleep as well as slow wave activity, indicative of reduced sleep efficacy and REM sleep disinhibition in HR mice.

CONCLUSION/SIGNIFICANCE

Thus, we could show that by selectively breeding mice for extremes in stress reactivity, clinically relevant endophenotypes of MD can be modelled. Given the importance of rhythmicity and sleep disturbances as biomarkers of MD, both animal and clinical studies on the interaction of behavioural, neuroendocrine and sleep parameters may reveal molecular pathways that ultimately lead to the discovery of new targets for antidepressant drugs tailored to match specific pathologies within MD.

Hypothalamic-pituitary-adrenal axis disregulation in PrPC-null mice

As manifestations of prion diseases include disturbances of hypothalamic and pituitary functions, we tested the hypothesis that the cellular prion protein (PrPC) has a role as modulator of the hypothalamic-pituitary-adrenal axis. The level of corticosterone and adrenocorticotropic hormone were compared in PrPC null (PrP 0/0) and wild-type (PrP+/+) mice. PrP 0/0 showed hypercorticism during the dark part of day. After acute stress, corticosterone and adrenocorticotropic hormone increased similarly in PrP+/+ and PrP 0/0 mice. Adrenocorticotropic hormone, however, remained elevated in PrP+/+ 0/0 mice at corticosterone levels that are inhibitory in PrP mice. Pretreatment with corticosterone or dexamethasone inhibited stress-induced elevation of adrenocorticotropic hormone in PrP+/+ but not in PrP 0/0 mice. Thus, PrPC may play a role in the negative feedback regulation of axis.

Mice selected for high versus low stress reactivity: a new animal model for affective disorders

Affective disorders such as major depression are among the most prevalent and costly diseases of the central nervous system, but the underlying mechanisms are still poorly understood. In recent years, it has become evident that alterations of the stress hormone system, in particular dysfunctions (hyper- or hypo-activity) of the hypothalamic-pituitary-adrenal (HPA) axis, play a prominent role in the development of major depressive disorders. Therefore, we aimed to generate a new animal model comprising these neuroendocrine core symptoms in order to unravel parameters underlying increased or decreased stress reactivity. Starting from a population of outbred mice (parental generation: 100 males and 100 females of the CD-1 strain), two breeding lines were established according to the outcome of a 'stress reactivity test' (SRT), consisting of a 15-min restraint period and tail blood samplings immediately before and after exposure to the stressor. Mice showing a very high or a very low secretion of corticosterone in the SRT, i.e. animals expressing a hyper- or a hypo-reactivity of the HPA axis, were selected for the 'high reactivity' (HR) and the 'low reactivity' (LR) breeding line, respectively. Additionally, a third breeding line was established consisting of animals with an 'intermediate reactivity' (IR) in the SRT. Already in the first generation, i.e. animals derived from breeding pairs selected from the parental generation, significant differences in the reactivity of the HPA axis between HR, IR, and LR mice were observed. Moreover, these differences were found across all subsequent generations and could be increased by selective breeding, which indicates a genetic basis of the respective phenotype. Repeated testing of individuals in the SRT furthermore proved that the observed differences in stress responsiveness are present already early in life and can be regarded as a robust genetic predisposition. Tests investigating the animal's emotionality including anxiety-related behavior, exploratory drive, locomotor activity, and depression-like behavior point to phenotypic similarities with behavioral changes observed in depressive patients. In general, HR males and females were 'hyperactive' in some behavioral paradigms, resembling symptoms of restlessness and agitation often seen in melancholic depression. LR mice, on the other hand, showed more passive-aggressive coping styles, corresponding to signs of retardation and retreat observed in atypical depression. Several morphometric and neuroendocrine findings further support this view. For example, monitoring the circadian rhythm of glucocorticoid secretion revealed clearly increased trough levels in HR mice, resulting in a flattened diurnal rhythm, again adding to the neuroendocrine similarities to patients suffering from melancholic depression. Taken together, our results suggest that distinct mechanisms influencing the function and regulation of the HPA axis are involved in the respective behavioral and neurobiological endophenotypes. Thus, the generated HR/IR/LR mouse lines can be a valuable model to elucidate molecular genetic, neuroendocrine, and behavioral parameters associated with altered stress reactivity, thereby improving our understanding of affective disorders, presumably including the symptomatology and pathophysiology of specific subtypes of major depression.

Prion diseases: from protein to cell pathology

Prion diseases or transmissible spongiform encephalopathies are fatal neurodegenerative conditions in humans and animals that originate spontaneously, genetically or by infection. Conformational change of the normal (cellular) form of prion protein (PrP c) to a pathological, disease-associated form (PrP TSE) is considered central to pathogenesis and formation of the infectious agent or prion. Neuronal damage is central to clinical manifestation of prion diseases but poorly understood. In this review, we analyze the major pathogenetic pathways that lead to tissue pathology in different forms of disease. Neuropathogenesis of prion diseases evolves in complex ways on several front lines, most but not all of which exist also in other neurodegenerative as well as infectious diseases. Whereas intracellular accumulation of PrP forms might significantly impair cell function and lead to cytopathology, mere extracellular deposition of PrP TSE is questionable as a direct cytotoxic factor. Tissue damage may result from several parallel, interacting, or subsequent pathways. Future studies should clarify the trigger(s) and sequence of these processes and whether, and which, one is dominating or decisive.

The role of parvalbumin and calbindin D28k in experimental scrapie

AIMS

Prion diseases are generally characterized by pronounced neuronal loss. In particular, a subpopulation of inhibitory neurones, characterized by the expression of the calcium-binding protein parvalbumin (PV), is selectively destroyed early in the course of human and experimental prion diseases. By contrast, nerve cells expressing calbindin D28 k (CB), another calcium-binding protein, as well as PV/CB coexpressing Purkinje cells, are well preserved.

METHODS

To evaluate, if PV and CB may directly contribute to neuronal vulnerability or resistance against nerve cell death, respectively, we inoculated PV- and CB-deficient mice, and corresponding controls, with 139A scrapie and compared them with regard to incubation times and histological lesion profiles.

RESULTS

While survival times were slightly but significantly diminished in CB-/-, but not PV-/- mice, scrapie lesion profiles did not differ between knockout mice and controls. There was a highly significant and selective loss of isolectin B(4)-decorated perineuronal nets (which specifically demarcate the extracellular matrix surrounding the 'PV-expressing' subpopulation of cortical interneurones) in scrapie inoculated PV+/+, as well as PV-/- mice. Purkinje cell numbers were not different in CB+/+ and CB-/- mice.

CONCLUSIONS

Our results suggest that PV expression is a surrogate marker for neurones highly vulnerable in prion diseases, but that the death of these neurones is unrelated to PV expression and thus based on a still unknown pathomechanism. Further studies including the inoculation of mice ectopically (over)expressing CB are necessary to determine whether the shortened survival of CB-/- mice is indeed due to a neuroprotective effect of this molecule.