Cellular Reactions and Behavioral Changes in Focal and Diffuse Traumatic Brain Injury : A Study in the Rat and Mouse

Traumatic brain injury (TBI) is a severe condition and a major cause of death and disability. There is no pharmacological treatment available in clinical practice today and knowledge of brain injury mechanisms is of importance for development of neuroprotective drugs. The aims of the thesis were to get a better understanding of astrocyte reactions and immune responses, as well as behavioral changes after focal unilateral cortical contusion injury and diffuse bilateral central fluid percussion injury in rats and mice. In the focal injury models, the astrocyte reactions were generally restricted to the ipsilateral hemisphere. After diffuse TBI, vimentin and glial fibrillary acidic protein (GFAP) positive reactive astrocytes were bilaterally expressed in brain regions even distant from the injury site, including regions where axonal injury was seen. Early after diffuse TBI, there was a robust immune response, including activation of macrophages/microglia (Mac-2+) and infiltration of neutrophils (GR-1+) and T-cells (CD3+). In order to measure functional outcome, the recently established Multivariate Concentric Square Field™ (MCSF) test for complex behaviors, including risk taking and explorative strategies was used. The Morris water maze (MWM) was applied for testing learning and memory. The MCSF test revealed alterations in risk taking, risk assessment and exploratory behavior, in the mice subjected to focal injury whereas mice subjected to the diffuse injury showed a deviant stereotyped behavior. After focal injury mice showed a decreased ability to adapt to the arena in the second trial, when tested repeatedly in the MCSF test. Mice subjected to diffuse injury had an impaired memory but not learning, in the MWM test. Post-injury treatment with the anti-inflammatory anti-interleukin-1β (IgG2 a/k) antibody showed a positive effect on functional outcome in the diffuse injury model. Altogether, the results demonstrate that focal and diffuse TBI models produce differences in cellular reactions and behavioral outcome and that the immune response plays a key role in the pathology after brain injury.

Cellular Reactions and Behavioral Changes in Focal and Diffuse Traumatic Brain Injury : A Study in the Rat and Mouse

Traumatic brain injury (TBI) is a severe condition and a major cause of death and disability. There is no pharmacological treatment available in clinical practice today and knowledge of brain injury mechanisms is of importance for development of neuroprotective drugs. The aims of the thesis were to get a better understanding of astrocyte reactions and immune responses, as well as behavioral changes after focal unilateral cortical contusion injury and diffuse bilateral central fluid percussion injury in rats and mice. In the focal injury models, the astrocyte reactions were generally restricted to the ipsilateral hemisphere. After diffuse TBI, vimentin and glial fibrillary acidic protein (GFAP) positive reactive astrocytes were bilaterally expressed in brain regions even distant from the injury site, including regions where axonal injury was seen. Early after diffuse TBI, there was a robust immune response, including activation of macrophages/microglia (Mac-2+) and infiltration of neutrophils (GR-1+) and T-cells (CD3+). In order to measure functional outcome, the recently established Multivariate Concentric Square Field™ (MCSF) test for complex behaviors, including risk taking and explorative strategies was used. The Morris water maze (MWM) was applied for testing learning and memory. The MCSF test revealed alterations in risk taking, risk assessment and exploratory behavior, in the mice subjected to focal injury whereas mice subjected to the diffuse injury showed a deviant stereotyped behavior. After focal injury mice showed a decreased ability to adapt to the arena in the second trial, when tested repeatedly in the MCSF test. Mice subjected to diffuse injury had an impaired memory but not learning, in the MWM test. Post-injury treatment with the anti-inflammatory anti-interleukin-1β (IgG2 a/k) antibody showed a positive effect on functional outcome in the diffuse injury model. Altogether, the results demonstrate that focal and diffuse TBI models produce differences in cellular reactions and behavioral outcome and that the immune response plays a key role in the pathology after brain injury.

Cellular Reactions and Behavioral Changes in Focal and Diffuse Traumatic Brain Injury : A Study in the Rat and Mouse

Traumatic brain injury (TBI) is a severe condition and a major cause of death and disability. There is no pharmacological treatment available in clinical practice today and knowledge of brain injury mechanisms is of importance for development of neuroprotective drugs. The aims of the thesis were to get a better understanding of astrocyte reactions and immune responses, as well as behavioral changes after focal unilateral cortical contusion injury and diffuse bilateral central fluid percussion injury in rats and mice. In the focal injury models, the astrocyte reactions were generally restricted to the ipsilateral hemisphere. After diffuse TBI, vimentin and glial fibrillary acidic protein (GFAP) positive reactive astrocytes were bilaterally expressed in brain regions even distant from the injury site, including regions where axonal injury was seen. Early after diffuse TBI, there was a robust immune response, including activation of macrophages/microglia (Mac-2+) and infiltration of neutrophils (GR-1+) and T-cells (CD3+). In order to measure functional outcome, the recently established Multivariate Concentric Square Field™ (MCSF) test for complex behaviors, including risk taking and explorative strategies was used. The Morris water maze (MWM) was applied for testing learning and memory. The MCSF test revealed alterations in risk taking, risk assessment and exploratory behavior, in the mice subjected to focal injury whereas mice subjected to the diffuse injury showed a deviant stereotyped behavior. After focal injury mice showed a decreased ability to adapt to the arena in the second trial, when tested repeatedly in the MCSF test. Mice subjected to diffuse injury had an impaired memory but not learning, in the MWM test. Post-injury treatment with the anti-inflammatory anti-interleukin-1β (IgG2 a/k) antibody showed a positive effect on functional outcome in the diffuse injury model. Altogether, the results demonstrate that focal and diffuse TBI models produce differences in cellular reactions and behavioral outcome and that the immune response plays a key role in the pathology after brain injury.

Modeling Parkinson's disease-related symptoms in alpha-synuclein overexpressing mice

Background: Intracellular deposition of alpha-synuclein (alpha-syn) as Lewy bodies and Lewy neurites is a central event in the pathogenesis of Parkinson's disease (PD) and other alpha-synucleinopathies. Transgenic mouse models overexpressing human alpha-syn, are useful research tools in preclinical studies of pathogenetic mechanisms. Such mice develop alpha-syn inclusions as well as neurodegeneration with a topographical distribution that varies depending on the choice of promoter and which form of alpha-syn that is overexpressed. Moreover, they display motor symptoms and cognitive disturbances that to some extent resemble the human conditions. Purpose: One of the main motives for assessing behavior in these mouse models is to evaluate the potential of new treatment strategies, including their impact on motor and cognitive symptoms. However, due to a high within-group variability with respect to such features, the behavioral studies need to be applied with caution. In this review, we discuss how to make appropriate choices in the experimental design and which tests that are most suitable for the evaluation of PD-related symptoms in such studies. Methods: We have evaluated published results on two selected transgenic mouse models overexpressing wild type (L61) and mutated (A30P) alpha-syn in the context of their validity and utility for different types of behavioral studies. Conclusions: By applying appropriate behavioral tests, alpha-syn transgenic mouse models provide an appropriate experimental platform for studies of symptoms related to PD and other alpha-synucleinopathies

Traumatic axonal injury in the mouse is accompanied by a dynamic inflammatory response, astroglial reactivity and complex behavioral changes

Background Diffuse traumatic axonal injury (TAI), a common consequence of traumatic brain injury, is associated with high morbidity and mortality. Inflammatory processes may play an important role in the pathophysiology of TAI. In the murine central fluid percussion injury (cFPI) TAI model, the neuroinflammatory and astroglial response and behavioral changes are unknown. Methods Twenty cFPI-injured and nine sham-injured mice were used, and the neuroinflammatory and astroglial response was evaluated by immunohistochemistry at 1, 3 and 7 days post-injury. The multivariate concentric square field test (MCSF) was used to compare complex behavioral changes in mice subjected to cFPI (n = 16) or sham injury (n = 10). Data was analyzed using non-parametric statistics and principal component analysis (MCSF data). Results At all post-injury time points, beta-amyloid precursor protein (beta-APP) immunoreactivity revealed widespread bilateral axonal injury and IgG immunostaining showed increased blood--brain barrier permeability. Using vimentin and glial fibrillary acidic protein (GFAP) immunohistochemistry, glial cell reactivity was observed in cortical regions and important white matter tracts peaking at three days post-injury. Only vimentin was increased post-injury in the internal capsule and only GFAP in the thalamus. Compared to sham-injured controls, an increased number of activated microglia (MAC-2), infiltrating neutrophils (GR-1) and T-cells (CD3) appearing one day after TAI (P<0.05 for all cell types) was observed in subcortical white matter. In the MCSF, the behavioral patterns including general activity and exploratory behavior differed between cFPI mice and sham-injured controls. Conclusions Traumatic axonal injury in mice resulted in marked bilateral astroglial and neuroinflammatory responses and complex behavioral changes. The cFPI model in mice appears suitable for the study of injury mechanisms, including neuroinflammation, and the development of treatments targeting traumatic axonal injury

Visualization of early oligomeric α‐synuclein pathology and its impact on the dopaminergic system in the (Thy‐1)‐h[A30P]α‐syn transgenic mouse model

Aggregation of alpha-synuclein (alpha-syn) into Lewy bodies and Lewy neurites is a pathological hallmark in the Parkinson ' s disease (PD) brain. The formation of alpha-syn oligomers is believed to be an early pathogenic event and the A30P mutation in the gene encoding alpha-syn, causing familial PD, has been shown to cause an accelerated oligomerization. Due to the problem of preserving antigen conformation on tissue surfaces, alpha-syn oligomers are difficult to detect ex vivo using conventional immunohistochemistry with oligomer-selective antibodies. Herein, we have instead employed the previously reported alpha-syn oligomer proximity ligation assay (ASO-PLA), along with a wide variety of biochemical assays, to discern the pathological progression of alpha-syn oligomers and their impact on the dopaminergic system in male and female (Thy-1)-h[A30P]alpha-syn transgenic (A30P-tg) mice. Our results reveal a previously undetected abundance of alpha-syn oligomers in midbrain of young mice, whereas phosphorylated (pS129) and proteinase k-resistant alpha-syn species were observed to a larger extent in aged mice. Although we did not detect loss of dopaminergic neurons in A30P-tg mice, a dysregulation in the monoaminergic system was recorded in older mice. Taken together, ASO-PLA should be a useful method for the detection of early changes in alpha-syn aggregation on brain tissue, from experimental mouse models in addition to post mortem PD cases

Age-related increase of alpha-synuclein oligomers is associated with motor disturbances in L61 transgenic mice

The pathogenesis of Parkinson's disease involves fibrillization and deposition of alpha-synuclein (alpha-syn) into Lewy bodies. Accumulating evidence suggests that alpha-syn oligomers are particularly neurotoxic. Transgenic (tg) mice overexpressing wild-type human alpha-syn under the Thy-1 promoter (L61) reproduce many Parkinson's disease features, but the pathogenetic relevance of alpha-syn oligomers in this mouse model has not been studied in detail. Here, we report an age progressive increase of alpha-syn oligomers in the brain of L61 tg mice. Interestingly, more profound motor symptoms were observed in animals with higher levels of membrane-bound oligomers. As this tg model is X-linked, we also performed subset analyses, indicating that both sexes display a similar age-related increase in alpha-syn oligomers. However, compared with females, males featured increased brain levels of oligomers from an earlier age, in addition to a more severe behavioral phenotype with hyperactivity and thigmotaxis in the open field test. Taken together, our data indicate that alpha-syn oligomers are central to the development of brain pathology and behavioral deficits in the L61 tg alpha-syn mouse model.Joint first authors: Sahar Roshanbin and Agata Aniszewska</p

Complex behavioral alterations after diffuse traumatic axonal injury in mice are normalized by post-injury neutralization of interleukin-1β

Abstract Wide-spread traumatic axonal injury (TAI), clinically known as diffuse axonal injury, results in brain network dysfunction which commonly leads to persisting cognitive and behavioral impairments following traumatic brain injury (TBI). TBI induces a complex neuroinflammatory response, frequently located at sites of axonal pathology. The role of the pro-inflammatory cytokine interleukin-1β (IL-1β) in TAI has not been established. An IL-1β-neutralizing or a control antibody was administered intraperitoneally at 30 min following central fluid percussion injury (cFPI) in mice, a model of wide-spread TAI. Animals subjected to moderate cFPI (n=41) were compared to sham-injured controls (n=20) and untreated, naive animals (n=9). The anti-IL-1β antibody reached the target brain regions in adequate therapeutic concentrations (up to ~30µg /g brain tissue) at 24h post-injury in both cFPI-injured (n=5) and sham-injured animals (n=3) whereas at 72 h post-injury (n=3 cFPI-injured), the antibody concentration was lower (up to ~18µg /g brain tissue). Functional outcome was analyzed using the multivariate concentric square field™ (MCSF) test at 2 and 9 days post-injury and the Morris water maze (MWM) at 14-21 days post-injury. Following TAI, the IL-1β-neutralizing antibody resulted in an improved behavioral outcome, including normalized behavioral profiles in the MCSF test, and improved performance in the MWM probe (memory) trial, although without influencing MWM learning. The IL1β neutralizing treatment did not influence cerebral ventricle size or the number of activated microglia at 21 days post- injury. These findings support the hypothesis that IL-1β is an important contributor to the processes causing complex cognitive and behavioral disturbances following TAI. Keywords: Interleukin 1β, central fluid percussion injury, mice, multivariate concentric square field test, Morris water maze, microglia, traumatic brain injury, traumatic axonal injury, diffuse axonal injury, behavioral outcom

In vivo imaging of alpha-synuclein with antibody-based PET

The protein alpha-synuclein (alpha SYN) plays a central role in synucleinopathies such as Parkinsons's disease (PD) and multiple system atrophy (MSA). Presently, there are no selective alpha SYN positron emission tomography (PET) radioligands that do not also show affinity to amyloid-beta (A beta). We have previously shown that radiolabeled antibodies, engineered to enter the brain via the transferrin receptor (TfR), is a promising approach for PET imaging of intrabrain targets. In this study, we used this strategy to visualize alpha SYN in the living mouse brain. Five bispecific antibodies, binding to both the murine TfR and alpha SYN were generated and radiolabeled with iodine-125 or iodine-124. All bispecific antibodies bound to alpha SYN and mTfR before and after radiolabelling in an ELISA assay, and bound to brain sections prepared from alpha SYN overexpressing mice as well as human PD- and MSA subjects, but not control tissues in autoradiography. Brain concentrations of the bispecific antibodies were be-tween 26 and 63 times higher than the unmodified IgG format 2 h post-injection, corresponding to about 1.5% of the injected dose per gram brain tissue. Additionally, intrastriatal alpha SYN fibrils were visualized with PET in an alpha SYN deposition mouse model with one of the bispecific antibodies, [I-124]RmAbSynO2-scFv8D3. However, PET images acquired in alpha SYN transgenic mice with verified brain pathology injected with [I-124]RmAbSynO2-scFv8D3 and [I-124]RmAb48-scFv8D3 showed no increase in antibody retention compared to WT mice. Despite successful imaging of deposited extracellular alpha SYN using a brain-penetrating antibody-based radioligand with no cross-specificity towards A beta, this proof-of-concept study demonstrates challenges in imaging intracellular alpha SYN inclusions present in synucleinopathies

Accumulation of alpha-synuclein within the liver, potential role in the clearance of brain pathology associated with Parkinson's disease

Alpha-synuclein (alpha-syn) aggregation is the hallmark pathological lesion in brains of patients with Parkinson's disease (PD) and related neurological disorders characterized as synucleinopathies. Accumulating evidence now indicates that alpha-syn deposition is also present within the gut and other peripheral organs outside the central nervous system (CNS). In the current study, we demonstrate for the first time that alpha-syn pathology also accumulates within the liver, the main organ responsible for substance clearance and detoxification. We further demonstrate that cultured human hepatocytes readily internalize oligomeric alpha-syn assemblies mediated, at least in part, by the gap junction protein connexin-32 (Cx32). Moreover, we identified a time-dependent accumulation of alpha-syn within the liver of three different transgenic (tg) mouse models expressing human alpha-syn under CNS-specific promoters, despite the lack of alpha-syn mRNA expression within the liver. Such a brain-to-liver transmission route could be further corroborated by detection of alpha-syn pathology within the liver of wild type mice one month after a single striatal alpha-syn injection. In contrast to the synucleinopathy models, aged mice modeling AD rarely show any amyloid-beta (Ass) deposition within the liver. In human post-mortem liver tissue, we identified cases with neuropathologically confirmed alpha-syn pathology containing alpha-syn within hepatocellular structures to a higher degree (75%) than control subjects without alpha-syn accumulation in the brain (57%). Our results reveal that alpha-syn accumulates within the liver and may be derived from the brain or other peripheral sources. Collectively, our findings indicate that the liver may play a role in the clearance and detoxification of pathological proteins in PD and related synucleinopathies