Dominik Michalski

Blood-Brain Barrier Breakdown after Embolic Stroke in Rats Occurs without Ultrastructural Evidence for Disrupting Tight Junctions

The term blood-brain barrier (BBB) relates to the ability of cerebral vessels to hold back hydrophilic and large molecules from entering the brain, thereby crucially contributing to brain homeostasis. In fact, experimental opening of endothelial tight junctions causes a breakdown of the BBB evidenced as for instance by albumin leakage. This and similar observations led to the conclusion that BBB breakdown is predominantly mediated by damage to tight junction complexes, but evidentiary ultrastructural data are rare. Since functional deficits of the BBB contribute to an increased risk of hemorrhagic transformation and brain edema after stroke, which both critically impact on the clinical outcome, we studied the mechanism of BBB breakdown using an embolic model of focal cerebral ischemia in Wistar rats to closely mimic the essential human pathophysiology. Ischemia-induced BBB breakdown was detected using intravenous injection of FITC-albumin and tight junctions in areas of FITC-albumin extravasation were subsequently studied using fluorescence and electron microscopy. Against our expectation, 25 hours after ischemia induction the morphology of tight junction complexes (identified ultrastructurally and using antibodies against the transcellular proteins occludin and claudin-5) appeared to be regularly maintained in regions where FITC-albumin massively leaked into the neuropil. Furthermore, occludin signals along pan-laminin-labeled vessels in the affected hemisphere equaled the non-affected contralateral side (ratio: 0.966 vs. 0.963; P = 0.500). Additional ultrastructural analyses at 5 and 25 h after ischemia induction clearly indicated FITC-albumin extravasation around vessels with intact tight junctions, while the endothelium exhibited enhanced transendothelial vesicle trafficking and signs of degeneration. Thus, BBB breakdown and leakage of FITC-albumin cannot be correlated with staining patterns for common tight junction proteins alone. Understanding the mechanisms causing functional endothelial alterations and endothelial damage is likely to provide novel protective targets in stroke.

Blood–brain barrier breakdown involves four distinct stages of vascular damage in various models of experimental focal cerebral ischemia

Ischemic stroke not only impairs neuronal function but also affects the cerebral vasculature as indicated by loss of blood—brain barrier (BBB) integrity. Therefore, therapeutical recanalization includes an enhanced risk for hemorrhagic transformation and bleeding, traditionally attributed to a ‘reperfusion injury’. To investigate the mechanisms underlying ischemia-/reperfusion-related BBB opening, we applied multiple immunofluorescence labeling and electron microscopy in a rat model of thromboembolic stroke as well as mouse models of permanent and transient focal cerebral ischemia. In these models, areas exhibiting BBB breakdown were identified by extravasation of intravenously administered fluorescein isothiocyanate (FITC)-albumin. After 24 hours, expression of markers for tight and adherens junctions in areas of FITC-albumin leakage consistently remained unaltered in the applied models. However, lectin staining with isolectin B4 indicated structural alterations in the endothelium, which were confirmed by electron microscopy. While ultrastructural alterations in endothelial cells did not differ between the applied models including the reperfusion scenario, we regularly identified vascular alterations, which we propose to reflect four distinct stages of BBB breakdown with ultimate loss of endothelial cells. Therefore, our data strongly suggest that ischemia-related BBB failure is predominantly caused by endothelial degeneration. Thus, protecting endothelial cells may represent a promising therapeutical approach in addition to the established recanalizing strategies.

Use of normobaric and hyperbaric oxygen in acute focal cerebral ischemia - a preclinical and clinical review

Michalski D, Härtig W, Schneider D, Hobohm C. Use of normobaric and hyperbaric oxygen in acute focal cerebral ischemia – a preclinical and clinical review.
Acta Neurol Scand: 2011: 123: 85–97.
© 2010 The Authors Journal compilation

A novel quantification of blood-brain barrier damage and histochemical typing after embolic stroke in rats.

Treatment strategies in acute ischemic stroke are still limited. Considering numerous translation failures, research is tending to a preferred use of human-like animal models, and a more-complex perspective of tissue salvaging involving endothelial, glial and neuronal components according to the neurovascular unit (NVU) concept. During ischemia, blood-brain barrier (BBB) alterations lead to brain edema and hemorrhagic transformation affecting NVU components. The present study aims on a novel quantification method of BBB damage and affected tissue following experimental cerebral ischemia, closely to the human condition. Wistar rats underwent embolic middle cerebral artery occlusion, followed by an intravenous application of fluorescein isothiocyanate (FITC)-tagged albumin (≈70kDa) and/or biotinylated rat IgG (≈150kDa) as BBB permeability markers. Both fluorescent agents revealed similar leakage and allow quantification of BBB permeability by fluorescence microscopy, and after immunohistochemical conversion into a permanent diaminobenzidine label at light-microscopical level. The following markers were identified for sufficient detection of NVU components: Rat endothelial cell antigen-1 (RECA) and laminin for vessels, Lycopersicon esculentum and Griffonia simplicifolia agglutinin for vessels and microglial subpopulations, ionized calcium binding adaptor molecule 1 (Iba1), CD68 and CD11b for macrophages, activated microglia, monocytes and neutrophils, S100β for astroglia, as well as NeuN and HuC/D for neurons. This is the first report confirming the usefulness of simultaneously applied FITC-albumin and biotinylated rat IgG as BBB permeability markers in experimental stroke, and, specifying antibodies and lectins for multiple fluorescence labeling of NVU components. Newly elaborated protocols might facilitate a more-complex outcome measurement in drug development for cerebral ischemia.

Anxiety and depression in patients with prostate cancer and other urogenital cancer: A longitudinal study

OBJECTIVE The aim of this study was to assess the degree and the course of psychological distress (anxiety and depression) in cancer patients and to detect sociodemographic determinants of the scores. METHODS AND MATERIALS Patients with prostate cancer (n = 287) and other urogenital cancer (n = 126) were tested with the Hospital Anxiety and Depression Scale (HADS) at the following time points: at the beginning (T1) and the end (T2) of the treatment in the hospital, 6 months later (T3), and 1 year later (T4). RESULTS Anxiety mean scores were highest at the start of the stay in the hospital. About 36% of the patients were at least doubtful cases at T1. However, the anxiety mean scores from T2 to T4 were similar to those of the general population and lower than those of cardiac patients. Depression mean scores were even lower than those of the general population. Young age and receiving radio- and/or chemotherapy were predictive of higher psychological distress. CONCLUSIONS The low mean scores of anxiety and depression from T2 to T4 indicate that most of the prostate cancer patients do not need help from mental health professionals. Nevertheless, some patients may profit from mental health support, especially at the beginning of the stay in the hospital.

Cracking Down on Inhibition: Selective Removal of GABAergic Interneurons from Hippocampal Networks

Inhibitory (GABAergic) interneurons entrain assemblies of excitatory principal neurons to orchestrate information processing in the hippocampus. Disrupting the dynamic recruitment as well as the temporally precise activity of interneurons in hippocampal circuitries can manifest in epileptiform seizures, and impact specific behavioral traits. Despite the importance of GABAergic interneurons during information encoding in the brain, experimental tools to selectively manipulate GABAergic neurotransmission are limited. Here, we report the selective elimination of GABAergic interneurons by a ribosome inactivation approach through delivery of saporin-conjugated anti-vesicular GABA transporter antibodies (SAVAs) in vitro as well as in the mouse and rat hippocampus in vivo. We demonstrate the selective loss of GABAergic—but not glutamatergic—synapses, reduced GABA release, and a shift in excitation/inhibition balance in mixed cultures of hippocampal neurons exposed to SAVAs. We also show the focal and indiscriminate loss of calbindin+, calretinin+, parvalbumin/system A transporter 1+, somatostatin+, vesicular glutamate transporter 3 (VGLUT3)/cholecystokinin/CB1 cannabinoid receptor+ and neuropeptide Y+ local-circuit interneurons upon SAVA microlesions to the CA1 subfield of the rodent hippocampus, with interneuron debris phagocytosed by infiltrating microglia. SAVA microlesions did not affect VGLUT1+ excitatory afferents. Yet SAVA-induced rearrangement of the hippocampal circuitry triggered network hyperexcitability associated with the progressive loss of CA1 pyramidal cells and the dispersion of dentate granule cells. Overall, our data identify SAVAs as an effective tool to eliminate GABAergic neurons from neuronal circuits underpinning high-order behaviors and cognition, and whose manipulation can recapitulate pathogenic cascades of epilepsy and other neuropsychiatric illnesses.

Pain in patients with multiple sclerosis: a complex assessment including quantitative and qualitative measurements provides for a disease-related biopsychosocial pain model.

Background: Pain of various causes is a common phenomenon in patients with Multiple Sclerosis (MS). A biopsychosocial perspective has proven a useful theoretical construct in other chronic pain conditions and was also started in MS. To support such an approach, we aimed to investigate pain in MS with special emphasis on separating quantitative and qualitative aspects, and its interrelation to behavioral and physical aspects. Materials and methods: Pain intensity (NRS) and quality (SES) were measured in 38 consecutive outpatients with MS (mean age, 42.0 ± 11.5 years, 82% women). Pain-related behavior (FSR), health care utilization, bodily complaints (GBB-24) and fatigue (WEIMuS) were assessed by questionnaires, and MS-related neurological impairment by a standardized neurological examination (EDSS). Results: Mean pain intensity was 4.0 (range, 0–10) and mean EDSS 3.7 (range, 0–8) in the overall sample. Currently present pain was reported by 81.6% of all patients. Disease duration and EDSS did not differ between patients with and without pain and were not correlated to quality or intensity of pain. Patients with pain had significantly higher scores of musculoskeletal complaints, but equal scores of exhaustion, gastrointestinal and cardiovascular complaints. Pain intensity correlated only with physical aspects, whereas quality of pain was additionally associated with increased avoidance, resignation and cognitive fatigue. Conclusion: As in other conditions, pain in MS must be assessed in a multidimensional way. Further research should be devoted to adapt existing models to a MS-specific model of pain.

Region-specific expression of vesicular glutamate and GABA transporters under various ischaemic conditions in mouse forebrain and retina

There is accumulating evidence that glutamate and GABA release are key mechanisms of ischaemic events in the CNS. However, data on the expression of involved transporters for these mediators are inconsistent, potentially impeding further neuroprotective approaches. Here, we applied immunofluorescence labelling to characterise the expression pattern of vesicular glutamate (VGLUT) and GABA transporters (VGAT) after acute focal cerebral ischaemia and in two models of retinal ischaemia. Mice were subjected to filament-based focal cerebral ischaemia predominantly involving the middle cerebral artery territory, also leading to retinal ischaemia due to central retinal artery occlusion (CRAO). Alternatively, retinal ischaemia was induced by a transient increase of the intraocular pressure (HIOP). One day after ischaemia onset, diminished immunolabelling of neuronal nuclei and microtubule-associated protein 2-positive structures were found in the ipsilateral neocortex, subcortex and the retina, indicating neuronal degeneration. VGLUT1 expression did not change significantly in ischaemic tissues whereas VGLUT2 was down-regulated in specific areas of the brain. VGLUT3 expression was only slightly down-regulated in the ischaemia-affected neocortex, and was found to form clusters on fibrils of unknown origin in the ischaemic lateral hypothalamus. In contrast, retinae subjected to CRAO or HIOP displayed a rapid loss of VGLUT3-immunoreactivity. The expression of VGAT appears resistant to ischaemia as there was no significant alteration in all the regions analysed. In summary, these data indicate a region- and subtype-specific change of VGLUT expression in the ischaemia-affected CNS, whose consideration might help to generate specific neuroprotective strategies.

Stroke-induced opposite and age-dependent changes of vessel-associated markers in co-morbid transgenic mice with Alzheimer-like alterations

The pathophysiological concept of ischaemic stroke was recently expanded to a more comprehensive perspective, focussing on the vasculature as well as peri- and juxtavascular cells including astrocytes. Increasing evidence also supports a role of the vasculature in Alzheimers disease (AD), but causal relationships are poorly understood. The purpose of this study was to examine vascular alterations due to cerebral ischaemia in aged wildtype (WT) mice and in the triple-transgenic (3xTg) mouse model of AD. Three- and 12-month-old WT and 3xTg mice underwent permanent middle cerebral artery occlusion. One day after ischaemia onset, expression of collagen IV and laminin as basement membrane constituents, and Solanum tuberosum lectin (STL) as endothelial marker was quantified in the ischaemic neocortex, striatum and hippocampus. Further, CD31- and aquaporin-4-immunoreactivity served for coverage of endothelium and astrocyte endfeet. Ischaemia resulted in strong upregulation of collagen IV and laminin in the neocortex of 3-month-old WT and 3xTg mice, while STL appeared unaffected. Quantification confirmed collagen IV upregulation in the ischaemic neocortex of 3- and 12-month-old WT and 3xTg mice, whereas striatal changes were limited to young WT mice. However, collagen IV expression in the hippocampus appeared nearly unaltered. Qualitative and quantitative data evidenced more severe degeneration of endothelial cells and astrocyte endfeet in 3xTg mice. In conclusion, this study supports the critical impact of the vasculature in the aged and AD brain by showing an age- and genetic background-dependent response of basement membranes to cerebral ischaemia, and a pronounced endothelial and astrocytic degeneration in the AD-like brain.

Long-term functional and neurological outcome after simultaneous treatment with tissue-plasminogen activator and hyperbaric oxygen in early phase of embolic stroke in rats

The combination of hyperbaric oxygen therapy (HBO) and recombinant tissue-plasminogen activator (tPA) is of interest in the treatment of acute ischemic stroke with a view to combine positive effects of both strategies. We investigated neurological and functional outcome after early treatment with HBO additional to tPA in ischemic stroke. Focal cerebral ischemia was induced using an embolic stroke model in 87 male Wistar rats. Animals were randomized to therapy with tPA+HBO, tPA alone, or control. Menzies score, Beam walk, and the Corner test were assessed for a period of 4 weeks following ischemia. Within the first 24 h neurological deficits improved in all groups but most pronounced in animals treated with tPA+HBO. Thereafter, a deterioration of neurological deficits occurred in the tPA+HBO group with significant differences at day 7, 8, 18, and 24 (P<0.05). Surprisingly, Beam walk and Corner test results did not differ significantly between all groups. This first report of early simultaneous treatment with tPA and HBO in experimental embolic stroke with 4-week follow-up confirms previous studies reporting positive effects of HBO shortly after the ischemia. Following the acute phase, combined tPA and HBO resulted in deterioration of neurological deficits without affecting functional recovery. Future studies should focus on interactions of tPA and HBO on molecular level leading to delayed damage to brain tissue at risk.