Neurologische Klinik und Poliklinik
Refine
Has Fulltext
- yes (19)
Is part of the Bibliography
- yes (19)
Document Type
- Doctoral Thesis (19)
Keywords
- Altern (2)
- Entzündung (2)
- Fibromyalgie (2)
- Parkinson-Krankheit (2)
- Schlaganfall (2)
- deep brain stimulation (2)
- inflammation (2)
- Adaptorproteine (1)
- Affekt (1)
- Agaphelin (1)
Institute
- Graduate School of Life Sciences (19) (remove)
Sonstige beteiligte Institutionen
microRNAs in chronic pain
(2016)
Chronic pain is a common problem in clinical practice, not well understood clinically, and frequently tough to satisfactorily diagnose. Because the pathophysiology is so complex, finding effective treatments for people with chronic pain has been overall less than successful and typically reduced to an unsatisfactory trial-and-error process, all of which translates into a significant burden to society. Knowledge of the mechanisms underlying the development of chronic pain, and moreover why some patients experience pain and others not, may aid in developing specific treatment regimens. Although nerve injuries are major contributors to pain chronification, they cannot explain the entire phenomenon. Considerable research has underscored the importance of the immune system for the development and maintenance of chronic pain, albeit the exact factors regulating inflammatory reactions remain unclear. Understanding the putative molecular and cellular regulator switches of inflammatory reactions will open novel opportunities for immune modulatory analgesics with putatively higher specificity and less adverse effects. It has become clear that small, non- coding RNA molecules known as microRNAs are in fact potent regulators of many thousands of genes and possibly cross-communicate between cellular pathways in multiple systems acting as so-called “master-switches”. Aberrant expression of miRNAs is now implicated in numerous disorders, including nerve injuries as well as in inflammatory processes. Moreover, compelling evidence supports the idea that miRNAs also regulate pain, and in analogy to the oncology field aid in the differential diagnosis of disease subtypes. In fact, first reports describing characteristic miRNA expression profiles in blood or cerebrospinal fluid of patients with distinct pain conditions are starting to emerge, however evidence linking specific miRNA expression profiles to specific pain disorders is still insufficient. The present thesis aimed at first, identifying specific miRNA signatures in two distinct chronic pain conditions, namely peripheral neuropathies of different etiologies and fibromyalgia syndrome. Second, it aimed at identifying miRNA profiles to better understand potential factors that differentiate painful from painless neuropathies and third, study the mechanistic role of miRNAs in the pathophysiology of pain, to pave the way for new druggable targets.
Three studies were conducted in order to identify miRNA expression signatures that are characteristic for the given chronic pain disorder. The first study measured expression of miR-21, miR-146a and miR-155 in white blood cells, skin and nerve biopsies of patients with peripheral neuropathies. It shows that peripheral neuropathies of different etiologies are associated with increased peripheral miR-21 and miR-146a, but decreased miR-155 expression. More importantly, it was shown that painful neuropathies have increased sural nerve miR-21 and miR-155 expression, but reduced miR-146a and miR-155 expression in distal skin of painful neuropathies. These results point towards the potential use of miRNAs profiles to stratify painful neuropathies. The seconds study extends these findings and first analyzed the role of miR-132-3p in patients and subsequently in an animal model of neuropathic pain. Interestingly, miR-132-3p was upregulated in white blood cells and sural nerve biopsies of patients with painful neuropathies and in animals after spared nerve injury. Pharmacologically modulating the expression of miR-132-3p dose-dependently reversed pain behavior and pain aversion, indicating the pro-nociceptive effect of miR-132-3p in chronic pain. This study thus demonstrates the potential analgesic impact by modulating miRNA expression. Fibromyalgia is associated with chronic widespread pain and, at least in a subgroup, impairment in small nerve fiber morphology and function. Interestingly, the disease probably comprises subgroups with different underlying pathomechanisms. In accordance with this notion, the third study shows that fibromyalgia is associated with both aberrant white blood cell and cutaneous miRNA expression. Being the first of its kind, this study identified miR-let-7d and its downstream target IGF-1R as potential culprit for impaired small nerve fiber homeostasis in a subset of patients with decreased intra-epidermal nerve fiber density. The work presented in this thesis is a substantial contribution towards the goal of better characterizing chronic pain based on miRNA expression signatures and thus pave the way for new druggable targets.
Das Schädel-Hirn-Trauma (SHT) entsteht durch äußere Gewalteinwirkung auf den Kopf und verursacht mechanisch eine Schädigung des Hirngewebes. Zusätzlich tragen sekundäre Pathomechanismen, wie Entzündungsprozesse und die Schädigung der Blut-Hirn-Schranke (BHS), dazu bei, dass sich das initial geschädigte Läsionsareal im Laufe der Zeit vergrößert. Vor allem bei jungen Erwachsenen ist das SHT eine der häufigsten Ursachen für bleibende Behinderungen und Todesfälle. Aufgrund der schweren Auswirkungen des SHT und der bislang fehlenden Therapieoptionen ist die Identifizierung neuer Zielstrukturen für eine kausale Therapie von größter Bedeutung. Ausgehend von tierexperimentellen Studien ist das Kallikrein-Kinin-System (KKS) ein besonders erfolgversprechender Angriffspunkt zur Behandlung des SHT. Die Aktivierung des KKS über den Gerinnungsfaktor XII (FXII) und die darauf folgende Bildung von Bradykinin sind mit dem Entstehen von Hirnödemen und Entzündungsreaktionen assoziiert. Vorangegangene Studien haben weiterhin die Frage aufgeworfen, ob und in welchem Maße thrombotische Prozesse einen Einfluss auf die Pathophysiologie und die sekundären Hirnschädigungen nach SHT haben. Da FXII sowohl das KKS als auch die intrinsische plasmatische Gerinnungskaskade initiiert und somit zur Fibrinbildung beiträgt, stand FXII im Mittelpunkt der Untersuchungen dieser Dissertation. Die vorliegende Arbeit beschäftigt sich mit den Fragen, (I) inwiefern FXII eine Rolle bei der sekundären Hirnschädigung nach Trauma spielt und (II) ob thrombotische Prozesse ein pathophysiologisches Merkmal nach Trauma darstellen. In zwei unterschiedlichen Trauma-Modellen wurden FXII-defiziente Tiere und mit einem spezifischen Inhibitor des aktivierten FXII (FXIIa) behandelte Tiere gegen Kontrolltiere nach SHT verglichen. Die Analyse der funktionellen Ausfallerscheinungen und des Ausmaßes an neuronaler Degeneration zeigte, dass FXII-Defizienz und FXIIa-Inhibition vor den Auswirkungen eines SHT schützen. Als zugrundeliegende Mechanismen wurden die Reduktion von thrombotisch verschlossenen Gefäßen in der Mikrovaskulatur des Gehirns sowie der Schutz vor BHS-Störungen und verringerte inflammatorische Prozesse identifiziert. Weiterhin wurde festgestellt, dass eine Blockade der intrinsischen Gerinnungskaskade über FXII keine intrazerebralen Blutungen auslöst. In Gewebeproben von Patienten mit SHT wurde gezeigt, dass Thrombozytenaggregate auch im klinischen Verlauf auftreten und sich somit die tierexperimentellen Befunde auf die humane Situation übertragen lassen. Insgesamt tragen die Ergebnisse dazu bei, die komplexen und vielfältigen Pathomechanismen nach SHT besser zu verstehen und vor allem die Relevanz thrombo-inflammatorischer Prozesse nach SHT aufzuzeigen. Die gezielte Blockade des FXII(a) könnte als therapeutisches Prinzip zur Abschwächung der Sekundärschaden nach SHT geeignet sein.
The role of miR-21 in the pathophysiology of neuropathic pain using the model of B7-H1 knockout mice
(2017)
The impact of microRNA (miRNA) as key players in the regulation of immune and neuronal gene expression and their role as master switches in the pathophysiology of neuropathic pain is increasingly recognized. miR-21 is a promising candidate that could be linked to the immune and the nociceptive system. To further investigate the pathophysiological role of miR-21 in neuropathic pain, we assesed mice deficient of B7 homolog 1 (B7-H1 ko), a protein with suppressive effect on inflammatory responses.
B7-H1 ko mice and wildtype littermates (WT) of three different age-groups, young (8 weeks), middle-aged (6 months), and old (12 months) received a spared nerve injury (SNI). Thermal withdrawal latencies and mechanical withdrawal thresholds were determined. Further, we investigated anxiety-, depression-like and cognitive behavior. Quantitative real time PCR was used to determine miR-21 relative expression in peripheral nerves, dorsal root ganglia and white blood cells (WBC) at distinct time points after SNI.
Naïve B7-H1 ko mice showed mechanical hyposensitivity with increasing age. Young and middle-aged B7-H1 ko mice displayed lower mechanical withdrawal thresholds compared to WT mice. From day three after SNI both genotypes developed mechanical and heat hypersensitivity, without intergroup differences. As supported by the results of three behavioral tests, no relevant differences were found for anxiety-like behavior after SNI in B7-H1 ko and WT mice. Also, there was no indication of depression-like behavior after SNI or any effect of SNI on cognition in both genotypes. The injured nerves of B7-H1 ko and WT mice showed higher miR-21 expression and invasion of macrophages and T cells 7 days after SNI without intergroup differences. Perineurial miR-21 inhibitor injection reversed SNI-induced mechanical and heat hypersensitivity in old B7-H1 ko and WT mice.
This study reveals that reduced mechanical thresholds and heat withdrawal latencies are associated with miR-21 induction in the tibial and common peroneal nerve after SNI, which can be reversed by perineurial injection of a miR-21 inhibitor. Contrary to expectations, miR-21 expression levels were not higher in B7-H1 ko compared to WT mice. Thus, the B7-H1 ko mouse may be of minor importance for the study of miR-21 related pain. However, these results spot the contribution of miR-21 in the pathophysiology of neuropathic pain and emphasize the crucial role of miRNA in the regulation of neuronal and immune circuits that contribute to neuropathic pain.
In addition to bradykinesia and tremor, patients with Parkinson’s disease (PD) are known to exhibit non-motor symptoms such as apathy and hypomimia but also impulsivity in response to dopaminergic replacement therapy. Moreover, a plethora of studies observe differences in electrocortical and autonomic responses to both visual and acoustic affective stimuli in PD subjects compared to healthy controls. This suggests that the basal ganglia (BG), as well as the hyperdirect pathway and BG thalamocortical circuits, are involved in affective processing. Recent studies have shown valence and dopamine-dependent changes in synchronization in the subthalamic nucleus (STN) in PD patients during affective tasks. This thesis investigates the role of dopamine, valence, and laterality in STN electrophysiology by analyzing event-related potentials (ERP), synchronization, and inter-hemispheric STN connectivity. STN recordings were obtained from PD patients with chronically implanted electrodes for deep brain stimulation during a passive affective picture presentation task. The STN exhibited valence-dependent ERP latencies and lateralized ‘high beta’ (28–40 Hz) event-related desynchronization. This thesis also examines the role of dopamine, valence, and laterality on STN functional connectivity with the anterior cingulate cortex (ACC) and the amygdala. The activity of these limbic structures was reconstructed using simultaneously recorded electroencephalographic signals. While the STN was found to establish early coupling with both structures, STN-ACC coupling in the ‘alpha’ range (7–11 Hz) and uncoupling in the ‘low beta’ range (14–21 Hz) were lateralized. Lateralization was also observed at the level of synchrony in both reconstructed sources and for ACC ERP amplitude, whereas dopamine modulated ERP latency in the amygdala. These results may deepen our current understanding of the STN as a limbic node within larger emotional-motor networks in the brain.
Parkinson’s disease (PD) is among the most common neurodegenerative conditions, and it is characterized by the progressive loss of dopaminergic neurons and a great variability in clinical expression. Despite several effective medications, it still causes disability as all patients show treatment-resistant symptoms and complications.
A possible reason for this therapeutic-burden and great clinical variability lies in a probable misconception about its pathophysiology, one that focuses on neurodegeneration, while largely neglecting its functional consequences and the related compensatory changes. In this thesis, I expand on the hypothesis that some PD symptoms have a dysfunctional origin and reflect derangements of neural network dynamics, the means by which brain coordination supports any motor behaviour. In particular, I have investigated resting tremor and freezing of gait, two common symptoms with an enigmatic mechanism and suboptimal management.
In the case of tremor, I predicted a pathological change in response to dopamine loss, which included the activation of noradrenergic (NA) neurons of the locus coeruleus (LC) projecting to the cerebellum. This compensatory LC activation that supports dopaminergic neurons might indeed come at the expense of tremor development. To assess the role of LC-NA in tremor development, I recorded tremor occurrence in the reserpinized rat model of PD, one of very few showing tremor, after selective lesioning (with the neurotoxin DSP-4) of the LC-NA terminal axons. DSP-4 induced a severe reduction of LC-NA terminal axons in the cerebellar cortex and this was associated with a significant reduction in tremor development. Unlike its development, tremor frequency and the akinetic rigid signs did not differ between the groups, thus suggesting a dopaminergic dependency. These findings suggest that the LC-NA innervation of the cerebellum has a critical role for PD tremor, possibly by exerting a network effect, which gates the cerebello-thalamic-cortical circuit into pathological oscillations upon a dopaminergic loss in the basal ganglia.
In contrast, for the study of freezing of gait, I worked with human PD subjects and deep brain stimulation, a therapeutic neuromodulation device that in some prototypes also allows the recording of neural activity in freely-moving subjects. Gait freezing is a disabling PD symptom that suddenly impairs effective stepping, thus causing falls and disability. Also in this study, I hypothesized that the underlying pathophysiology may be represented by dysfunctional neural network dynamics that abruptly impair locomotor control by affecting the communication in the supraspinal locomotor network. To test this hypothesis, I investigated the coupling between the cortex and the subthalamic nucleus, two main nodes of the supraspinal locomotor network, in freely-moving subjects PD patients and also performed molecular brain imaging of striatal dopamine receptor density and kinematic measurements. I found that in PD patients, walking is associated with cortical-subthalamic stable coupling in a low-frequency band (i.e. θ-α rhythms). In contrast, these structures decoupled when gait freezing occurred in the brain hemisphere with less dopaminergic innervation. These findings suggest that freezing of gait is a “circuitopathy”, with dysfunctional cortical-subcortical communication.
Altogether the results of my experiments support the hypothesis that the pathophysiology of PD goes beyond neurodegenerative (loss-of-function) processes and that derangement of neural network dynamics coincides with some disabling PD symptoms, thus suggesting that PD can be interpreted as the combination of multiple circuitopathies.
We examined 143 patients suffering from FMS, a syndrome characterized by chronic widespread pain, sleep disturbances, and fatigue. Etiology and pathophysiology of FMS are scarcely understood. In recent years abnormalities of small Aδ- and C-nerve fibers have been found in subgroups of FMS patients. It is yet unclear how such SFP is caused in FMS patients and how it contributes to FMS symptoms.
We used CCM to analyze corneal small nerve fibers and associated LC, comparing FMS patients’ results to those from 65 healthy controls and 41 disease controls suffering from SFN. We, further, assessed expression levels of mRNA and miRNA in keratinocytes taken from skin punch biopsies of FMS patients and healthy controls kept as monocellular cell cultures. A screening was performed using NGS in a small cohort of 12 FMS patients and 5 healthy controls. Results were validated in larger cohorts by qRT-PCR.
As in previous studies IENFD and CNFD were reduced in a subgroup of FMS patients. We found identical LC densities in FMS patients, healthy controls, and SFN patients. The subpopulation of dLCfiber contact in FMS and SFN patients was lower than in healthy controls. Our RNA expression analysis revealed one mRNA that was expressed higher in FMS patients than in controls: PRSS21.
We conclude that reduced neurotrophic signaling of LC may contribute to SFP in the cornea. Epidermal PRSS21 expression and dLCfiber contact density are promising biomarker candidates for FMS diagnosis.
Effects of dopamine on BDNF / TrkB mediated signaling and plasticity on cortico-striatal synapses
(2021)
Progressive loss of voluntary movement control is the central symptom of Parkinson's disease (PD). Even today, we are not yet able to cure PD. This is mainly due to a lack of understanding the mechanisms of movement control, network activity and plasticity in motor circuits, in particular between the cerebral cortex and the striatum. Brain-derived neurotrophic factor (BDNF) has emerged as one of the most important factors for the development and survival of neurons, as well as for synaptic plasticity. It is thus an important target for the development of new therapeutic strategies against neurodegenerative diseases. Together with its receptor, the Tropomyosin receptor kinase B (TrkB), it is critically involved in development and function of the striatum. Nevertheless, little is known about the localization of BDNF within presynaptic terminals in the striatum, as well as the types of neurons that produce BDNF in the cerebral cortex. Furthermore, the influence of midbrain derived dopamine on the control of BDNF / TrkB interaction in striatal medium spiny neurons (MSNs) remains elusive so far. Dopamine, however, appears to play an important role, as its absence leads to drastic changes in striatal synaptic plasticity. This suggests that dopamine could regulate synaptic activity in the striatum via modulation of BDNF / TrkB function. To answer these questions, we have developed a sensitive and reliable protocol for the immunohistochemical detection of endogenous BDNF. We find that the majority of striatal BDNF is provided by glutamatergic, cortex derived afferents and not dopaminergic inputs from the midbrain. In fact, we found BDNF in cell bodies of neurons in layers II-III and V of the primary and secondary motor cortex as well as layer V of the somatosensory cortex. These are the brain areas that send dense projections to the dorsolateral striatum for control of voluntary movement. Furthermore, we could show that these projection neurons significantly downregulate the expression of BDNF during the juvenile development of mice between 3 and 12 weeks.
In parallel, we found a modulatory effect of dopamine on the translocation of TrkB to the cell surface in postsynaptic striatal Medium Spiny Neurons (MSNs). In MSNs of the direct pathway (dMSNs), which express dopamine receptor 1 (DRD1), we observed the formation of TrkB aggregates in the 6-hydroxydopamine (6-OHDA) model of PD. This suggests that DRD1 activity controls TrkB surface expression in these neurons. In contrast, we found that DRD2 activation has opposite effects in MSNs of the indirect pathway (iMSNs). Activation of DRD2 promotes a rapid decrease in TrkB surface expression which was reversible and depended on cAMP. In parallel, stimulation of DRD2 led to induction of phospho-TrkB (pTrkB). This effect was significantly slower than the effect on TrkB surface expression and indicates that TrkB is transactivated by DRD2. Together, our data provide evidence that dopamine triggers dual modes of plasticity on striatal MSNs by acting on TrkB surface expression in DRD1 and DRD2 expressing MSNs. This surface expression of the receptor is crucial for the binding of BDNF, which is released from corticostriatal afferents. This leads to the induction of TrkB-mediated downstream signal transduction cascades and long-term potentiation (LTP). Therefore, the dopamine-mediated translocation of TrkB could be a mediator that modulates the balance between dopaminergic and glutamatergic signaling to allow synaptic plasticity in a spatiotemporal manner. This information and the fact that TrkB is segregated to persistent aggregates in PD could help to improve our understanding of voluntary movement control and to develop new therapeutic strategies beyond those focusing on dopaminergic supply.
Background: In recent years, health care has increasingly become the focus of public interest, politics, health insurance companies, and research. This includes the development of therapeutic concepts that can respond individually to patients' resources in order to improve coping with chronic diseases. Research into psychosocial and biological resilience factors is very important and the basic objective of the present work. I studied patients with fibromyalgia syndrome (FMS), who suffer among others from chronic pain, fatigue, sleep and gastrointestinal problems. This patient cohort is characterized by a pronounced heterogeneity in terms of clinical outcome, degree in disability and coping. FMS has a prevalence of 3 – 8 % in the Western population and has a significant socio-economic impact. Validated psychosocial resilience factors include optimism, humor, coherence, self-efficacy, awareness with one's own resources and the ability to apply them profitably (coping), and a healthy social environment with positive relationships. Studies in patients with cancer revealed religiosity as positive and negative factor on the health outcome, but there is little data on religious aspects of pain resilience. Various genetic polymorphisms and anti-inflammatory cytokines are known as biological resilience factors. Various microRNA (miRNA) were detected to contribute to resilience in the context of stress and psychiatric disorders. Objective: The underlying research question of this work is to understand the factors that make some FMS patients resilient and others not, even though they suffer from the same disease. The long-term aim was to understand mechanisms and influencing factors of resilience to design preventive and resource-oriented therapies for FMS patients. Material and Methods: Three studies examined religious, physiological, biological, and psychosocial factors which may contribute to resilience in FMS patients. Study one combined data of questionnaires, a psychosocial interview, and regression analyses to investigate the relevance of religiosity for coping and resilience. Study two examined variance explaining factors and defined clusters among FMS patients by their differences in coping, pain phenotype and disability. The factor analysis used variables derived from questionnaires and qPCR of cytokines in white blood samples (WBC) of patients and healthy controls. Study three assessed cluster-wise miRNA signatures which may underly differences in behaviour, emotional and physiological disability, and resilience among patient clusters. A cluster-specific speculative model of a miRNA-mediated regulatory cycle was proposed and its potential targets verified by an online tool. Results: The data from the first study revealed a not very religious patient cohort, which was rather ambivalent towards the institution church, but described itself as a believer. The degree of religiosity played a role in the choice of coping strategy but had no effect on psychological parameters or health outcomes. The coping strategy "reinterpretation", which is closely related iv to the religious coping "reappraisal", had the highest influence on FMS related disability. Cognitive active coping strategies such as reappraisal which belongs to religious coping had the highest effect on FMS related disability (resilience) and could be trained by a therapist. Results from the second study showed high variances of all measured cytokines within the patient group and no difference between patient and control group. The high dispersion indicated cluster among patients. Factor analysis extracted four variance-explaining factors named as affective load, coping, pain, and pro-inflammatory cytokines. Psychological factors such as depression were the most decisive factors of everyday stress in life and represented the greatest influence on the variance of the data. Study two identified four clusters with respective differences in the factors and characterized them as poorly adapted (maladaptive), well adapted (adaptive), vulnerable and resilient. Their naming was based on characteristics of both resilience concepts, indicated by patients who were less stress-sensitive and impaired as a personal characteristic and by patients who emerged as more resilient from a learning and adaptive process. The data from the variance analysis suggests that problem- and emotion-focused coping strategies and a more anti-inflammatory cytokine pattern are associated with low impairment and contribute to resilience. Additional favorable factors include low anxiety, acceptance, and persistence. Some cluster-specific intervention proposals were created that combine existing concepts of behavioral and mindfulness therapies with alternative therapies such as vitamin D supplementation and a healthy intestinal flora. The results of the third study revealed lower relative gene expression of miR103a-3p, miR107, and miR130a-3p in the FMS cohort compared to the healthy controls with a large effect size. The adaptive cluster had the highest gene expression of miR103a-3p and tendentially of miR107, which was correlated with the subscale score "physical abuse" of the trauma questionnaire. Further correlations were found in particular with pain catastrophizing and FMS-related disability. MiR103a-3p and miR107 form a miRNA-family. Based on this, we proposed a miR103a/107 regulated model of an adaptive process to stress, inflammation and pain by targeting genetic factors which are included in different anti-inflammatory and stress-regulating pathways. Conclusion: All three studies provide new insights into resilience in FMS patients. Cognitive coping (reappraisal/reinterpretation) plays a central role and thus offers therapeutic targets (reframing in the context of behavioral therapy). Religosity as a resilience factor was only partially valid for our patient cohort. Basically, the use of resource-oriented therapy in large institutions still requires research and interdisciplinary cooperation to create a consensus between the humanities, natural sciences and humanism.
Beim ischämischen Schlaganfall führt ein thrombotischer Verschluss von gehirnversorgenden Arterien zu einer akuten Durchblutungsstörung, mit der Folge von neurologischen Defiziten. Primäres Therapieziel ist es, diese Blutgerinnsel aufzulösen, um die Sauerstoffversorgung des Gehirns wiederherzustellen und den ischämischen Hirnschaden zu begrenzen. Dazu stehen die intravenösen Thrombolyse mit rt-PA (rekombinanter Gewebe-Plasminogen-Aktivator) sowie die endovaskuläre mechanische Thrombektomie zur Verfügung. Häufig kann ein Schlaganfall, trotz erfolgreicher Rekanalisation der Gefäße, zu einer weiteren Größenzunahme des Infarktes und neurologischen Defiziten bei den Patienten führen. Diese Größenzunahme beruht zum einen auf einem sich entwickelnden Hirnödem und zum anderen auf entzündlichen Prozessen. Zahlreiche Hinweise deuten darauf hin, dass der Schlaganfall ein Zusammenspiel aus thrombotischen und entzündlichen Ereignissen ist, ein Phänomen, das als Thromboinflammation bezeichnet wird. Aufgrund der begrenzten Behandlungsmöglichkeiten ist die Entwicklung neuer Therapieansätze für den ischämischen Schlaganfall besonders wichtig. Agaphelin und Ixolaris sind Proteine aus den Speicheldrüsen von Hämatophagen, für welche in früheren Studien eine starke antithrombotische Wirkung bei gleichzeitig geringem Blutungsrisiko nachgewiesen wurde. Diese möglichen antithrombotischen Effekte wurden in dieser Studie im Hinblick auf ihre Wirksamkeit und Sicherheit im Mausmodell der zerebralen Ischämie untersucht. Die Behandlung der Mäuse mit Agaphelin 1 Stunde nach transienter Okklusion der Arteria cerebri media (tMCAO) führte zu kleineren Schlaganfallvolumina und geringeren neurologischen Defiziten an Tag 1 nach dem Schlaganfall. Die Mortalität der Mäuse war bis Tag 7 deutlich gesunken. Aus klinischer Sicht ist ebenfalls relevant, dass der starke antithrombotische Effekt von Agaphelin im Mausmodell nicht mit einem erhöhten Risiko für intrazerebrale Blutungen einherging. Diesem protektiven Effekt von Agaphelin lagen eine verminderte intrazerebrale Thrombusbildung, eine abgeschwächte Entzündungsantwort und eine Stabilisierung der Blut-Hirn-Schranke sowie eine Reduzierung der Apoptose zugrunde. Nach der Gabe von Ixolaris 1 Stunde nach tMCAO waren zwar signifikant geringere Infarktgrößen messbar, diese führten allerdings nicht zu einer Verbesserung der neurologischen Defizite. Zudem verursachte die Gabe von Ixolaris schon 24 Stunden nach tMCAO erhebliche intrazerebrale Blutungen und auch die Mortalität der Mäuse war zu diesem Zeitpunkt bereits erhöht. Aufgrund dieser massiven Nebenwirkungen scheint Ixolaris kein geeigneter Kandidat für eine humane Anwendung zu sein. Bei Agaphelin hingegen könnte es
sich um einen vielversprechenden Kandidaten für die Behandlung des ischämischen Schlaganfalls handeln. Vor einer möglichen Testung von Agaphelin in klinischen Studien, sind weitere translationale Untersuchungen notwendig, um ein noch präziseres Verständnis für die Wirksamkeit und Sicherheit von Agaphelin zu gewinnen. Insgesamt stellt die Hemmung thromboinflammatorischer Prozesse, ohne eine Erhöhung der Blutungskomplikationen, eine vielversprechende Option zur Behandlung des ischämischen Schlaganfalls dar.
Parkinson’s Disease (PD) constitutes a major healthcare burden in Europe. Accounting for aging alone, ~700,000 PD cases are predicted by 2040. This represents an approximately 56% increase in the PD population between 2005 and 2040, with a consequent rise in annual disease‐related medical costs. Gait and balance disorders are a major problem for patients with PD and their caregivers, mainly because to their correlation with falls. Falls occur as a result of a complex interaction of risk factors. Among them, Freezing of Gait (FoG) is a peculiar gait derangement characterized by a sudden and episodic inability to produce effective stepping, causing falls, mobility restrictions, poor quality of life, and increased morbidity and mortality. Between 50–70% of PD patients have FoG and/or falls after a disease duration of 10 years, only partially and inconsistently improved by dopaminergic treatment and Deep Brain Stimulation (DBS). Treatment-induced worsening has been also observed under certain conditions. Effective treatments for gait disturbances in PD are lacking, probably because of the still poor understanding of the supraspinal locomotor network.
In my thesis, I wanted to expand our knowledge of the supraspinal locomotor network and in particular the contribution of the basal ganglia to the control of locomotion. I believe this is a key step towards new preventive and personalized therapies for postural and gait problems in patients with PD and related disorders. In addition to patients with PD, my studies also included people affected by Progressive Supranuclear Palsy (PSP). PSP is a rare primary progressive parkinsonism characterized at a very early disease stage by poor balance control and frequent backwards falls, thus providing an in vivo model of dysfunctional locomotor control.
I focused my attention on one of the most common motor transitions in daily living, the initiation of gait (GI). GI is an interesting motor task and a relevant paradigm to address balance and gait impairments in patients with movement disorders, as it is associated with FoG and high risk of falls. It combines a preparatory (i.e., the Anticipatory Postural Adjustments [APA]) and execution phase (the stepping) and allows the study of movement scaling and timing as an expression of muscular synergies, which follow precise and online feedback information processing and integration into established feedforward patterns of motor control.
By applying a multimodal approach that combines biomechanical assessments and neuroimaging investigations, my work unveiled the fundamental contribution of striatal dopamine to GI in patients with PD. Results in patients with PSP further supported the fundamental role of the striatum in GI execution, revealing correlations between the metabolic intake of the left caudate nucleus with diverse GI measurements. This study also unveiled the interplay of additional brain areas in the motor control of GI, namely the Thalamus, the Supplementary Motor Area (SMA), and the Cingulate cortex. Involvement of cortical areas was also suggested by the analysis of GI in patients with PD and FoG. Indeed, I found major alterations in the preparatory phase of GI in these patients, possibly resulting from FoG-related deficits of the SMA. Alterations of the weight shifting preceding the stepping phase were also particularly important in PD patients with FoG, thus suggesting specific difficulties in the integration of somatosensory information at a cortical level. Of note, all patients with PD showed preserved movement timing of GI, possibly suggesting preserved and compensatory activity of the cerebellum. Postural abnormalities (i.e., increased trunk and thigh flexion) showed no relationship with GI, ruling out an adaptation of the motor pattern to the altered postural condition. In a group of PD patients implanted with DBS, I further explored the pathophysiological functioning of the locomotor network by analysing the timely activity of the Subthalamic Nucleus (STN) during static and dynamic balance control (i.e., standing and walking). For this study, I used novel DBS devices capable of delivering stimulation and simultaneously recording Local Field Potentials (LFP) of the implanted nucleus months and years after surgery. I showed a gait-related frequency shift in the STN activity of PD patients, possibly conveying cortical (feedforward) and cerebellar (feedback) information to mesencephalic locomotor areas. Based on this result, I identified for each patient a Maximally Informative Frequency (MIF) whose power changes can reliably classify standing and walking conditions. The MIF is a promising input signal for new DBS devices that can monitor LFP power modulations to timely adjust the stimulation delivery based on the ongoing motor task (e.g., gait) performed by the patient (adaptive DBS).
Altogether my achievements allowed to define the role of different cortical and subcortical brain areas in locomotor control, paving the way for a better understanding of the pathophysiological dynamics of the supraspinal locomotor network and the development of tailored therapies for gait disturbances and falls prevention in PD and related disorders.