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The Role of Sphingosine 1-phosphate and S1PR1-3 in the Pathophysiology of Meningococcal Meningitis
(2024)
Neisseria meningitidis (N. meningitidis) is an obligate human pathogen which causes live-threatening sepsis and meningitis. The fatality rate after meningococcal infection is high and surviving patients often suffer from severe sequelae. To cause meningitis, N. meningitidis must overcome the endothelium of the blood-brain barrier. The bacterium achieves this through the interaction with endothelial surface receptors leading to alternations of the cellular metabolism and signaling, which lastly results in cellular uptake and barrier traversal of N. meningitidis. Sphingosine 1-phosphate (S1P) is a lipid mediator that belongs to the class of sphingolipids and regulates the integrity of the blood-brain barrier through the interaction with its cognate receptors S1P receptors 1-3 (S1PR1-3).
In this study, high performance liquid chromatography coupled with mass spectrometry (LC-MS/MS) was used to generate a time-resolved picture of the sphingolipid metabolism in a brain endothelial cell line (hCMEC/D3) upon meningococcal infection. Among various changes, S1P was elevated in the cellular compartment as well as in the supernatant of infected hCMEC/D3s. Analysis of mRNA expression in infected hCMEC/D3s with quantitative real-time polymerase chain reaction (RT-qPCR) revealed that the increase in S1P could be attributed to the enhanced expression of the S1P-generating enzyme sphingosine kinase 1 (SphK1). Antibody-based detection of SphK1 protein or phosphorylation at SphK1 residue Serine 225 in hCMEC/D3 plasma membrane fractions via Western Blot revealed that N. meningitidis also induced SphK1 phospho-activation and recruitment to the plasma membrane. Importantly, recruitment of SphK1 to the plasma membrane increases the probability of substrate encounter, thus elevating SphK activity. Enhanced SphK activity was also reflected on a functional level, as detected by a commercially available ATP depletion assay used for measuring the enzymatic activity of SphK. Infection of hCMEC/D3 cells with pilus-deficient mutants resulted in a lower SphK activation compared to the N. meningitidis wild type strain. hCMEC/D3 treatment with pilus-enriched protein fractions showed SphK activation similar to the infection with living bacteria and could be ascribed to pilus interaction with the membrane-proximal domain of cellular surface receptor CD147. Inhibition of SphK1 or SphK2 through pre-treatment with specific inhibitors or RNA interference reduced uptake of N. meningitidis into hCMEC/D3 cells, as measured with Gentamicin protection assays. Released S1P induced the phospho-activation of epidermal growth factor receptor (EGFR) via S1PR2 activation, whose expression was also increasing during infection. Furthermore, S1PR2 blockage had a preventive effect on bacterial invasion into hCMEC/D3 cells. On the contrary, activation of S1PR1+3 also reduced bacterial uptake, indicating an opposing regulatory role of S1PR1+3 and S1PR2 during N. meningitidis uptake. Moreover, SphK2 inhibition prevented inflammatory cytokine expression as well as release of interleukin-8 after N. meningitidis infection. Taken together, this study demonstrates the central role of S1P and its cognate receptors S1PR1-3 in the pathophysiology of meningococcal meningitis.
A highly regulated microenvironment is essential in maintaining normal functioning of the central nervous system (CNS). The existence of a biological barrier, termed as the blood-brain barrier (BBB), at the blood to brain interface effectively allows for selective passage of substances and pathogens into the brain (Kadry, Noorani et al. 2020). The BBB chiefly serves in protecting the brain from extrinsic toxin entry and pathogen invasions. The BBB is formed mainly by brain capillary endothelial cells (BCECs) which are responsible for excluding ∼ 100% of large-molecule neurotherapeutics and more than 98% of all small-molecule drugs from entry into the brain. Minimal BBB transport of major potential CNS drugs allows for attenuated effective treatments for majority of CNS disorders (Appelt-Menzel, Oerter et al. 2020). Animals are generally used as model systems to study neurotherapeutic delivery into the brain, however due to species based disparity, experimental animal models lead to several false positive or false negative drug efficacy predictions thereby being unable to fully predict effects in humans (Ruck, Bittner et al. 2015). An example being that over the last two decades, much of the studies involving animals lead to high failure rates in drug development with ~ 97% failure in cancers and ~ 99% failure for Alzheimer´s disease (Pound 2020). Widespead failures in clinical trials associated with neurological disorders have resulted in questions on whether existing preclinical animal models are genuinely reflective of the human condition (Bhalerao, Sivandzade et al. 2020). Apart from high failure rates in humans, the costs for animal testings is extremely high. According to the Organisation for Economic Co-operation and Development (OECD), responsible for determining animal testing guidelines and methodology for government, industry, and independent laboratories the average cost of a single two-generation reproductive animal toxicity study worldwide is 318,295 € and for Europe alone is ~ 285,842 € (Van Norman 2019). Due to these reasons two separate movements exist within the scientific world, one being to improve animal research and the other to promote new approach methodologies with the European government setting 2025 - 2035 as a deadline for gradually disposing the use of animals in pharmaceutical testing (Pound 2020).
The discovery of human induced pluripotent stem cell (hiPSC) technology in 2006 (Takahashi and Yamanaka 2006, Takahashi, Tanabe et al. 2007) revolutionized the field of drug discovery in-vitro. HiPSCs can be differentiated into various tissue types that mimic disease phenotypes, thereby offering the possibility to deliver humanized in-vitro test systems. With respect to the BBB, several strategies to differentiate hiPSCs to BCECs (iBCECs) are reported over the years (Appelt-Menzel, Oerter et al. 2020). However, iBCECs are said to possess an epithelial or undifferentiated phenotype causing incongruity in BBB lineage specifications (Lippmann,
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Azarin et al. 2020). Therefore, in order to identify a reliable differentiation strategy in deriving iBCECs possessing hallmark BBB characteristics, which can be used for downstream applications, the work in this thesis compared two methods, namely the co-differentiation (CD) and the directed differentiation (DD). Briefly, CD mimics a brain like niche environment for iBCEC specification (Lippmann, Al-Ahmad et al. 2014), while DD focuses on induction of the mesoderm followed by iBCEC specification (Qian, Maguire et al. 2017). The results obtained verified that while iBCECs derived via CD, in comparison to human BCEC cell line hCMEC/D3 showed the presence of epithelial transcripts such as E-Cadherin (CDH1), and gene level downregulation of endothelial specific platelet endothelial cell adhesion molecule-1 (PECAM-1) and VE-cadherin (CDH5) but demonstrated higher barrier integrity. The CD strategy essentially presented iBCECs with a mean trans-endothelial electrical resistance (TEER) of ~ 2000 – 2500 Ω*cm2 and low permeability coefficients (PC) of < 0.50 μm/min for small molecule transport of sodium fluorescein (NaF) and characteristic BCEC tight junction (TJ) protein expression of claudin-5 and occludin. Additionally, iBCECs derived via CD did not form tubes in response to angiogenic stimuli. DD on the other hand resulted in iBCECs with similar down regulations in PECAM-1 and CDH5 gene expression. They were additionally characterized by lower barrier integrity, measured by mean TEER of only ~ 250 – 450 Ω*cm2 and high PC of > 5 μm/min in small molecule transport of NaF. Although iBCECs derived via DD formed tubes in response to angiogenic stimuli, they did not show positive protein expression of characteristic BCEC TJs such as claudin-5 and occludin. These results led to the hypothesis that maturity and lineage specification of iBCECs could be improved by incorporating in-vivo like characteristics in-vitro, such as direct co-culture with neurovascular unit (NVU) cell types via spheroid formation and by induction of shear stress and fluid flow. In comparison to standard iBCEC transwell mono-cultures, BBB spheroids showed enhanced transcript expression of PECAM-1 and reduced expression of epithelial markers such as CDH1 and claudin-6 (CLDN6). BBB spheroids showed classical BCEC-like ultrastructure that was identified by TJ particles on the protoplasmic face (P-face) and exoplasmic face (E-face) of the plasma membrane. TJ strands were organized as particles and particle-free grooves on the E-face, while on the P-face, partly beaded particles and partly continuous strands were identified. BBB spheroids also showed positive protein expression of claudin-5, VE-cadherin, PECAM-1, glucose transporter-1 (GLUT-1), P-glycoprotein (P-gp) and transferrin receptor-1 (Tfr-1). BBB spheroids demonstrated higher relative impedance percentages in comparison to spheroids without an iBCEC barrier. Barrier integrity assessments additionally corresponded with lower permeability to small molecule tracer NaF, with spheroids containing iBCECs showing higher relative fluorescence unit percentages (RFU%) of ~ 90% in apical compartments, compared to ~ 80% in spheroids without iBCECs. In summary, direct cellular contacts in the complex spheroid model resulted in enhanced maturation of iBCECs.
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A bioreactor system was used to further assess the effect of shear stress. This system enabled inclusion of fluidic flow and shear stress conditions in addition to non-invasive barrier integrity measurements (Choi, Mathew et al. 2022). iBCECs were cultured for a total of seven days post differentiation (d17) within the bioreactor and barrier integrity was non-invasively monitored. Until d17 of long-term culture, TEER values of iBCECs steadily dropped from ~ 1800 Ω*cm2 ~ 400 Ω*cm2 under static conditions and from ~ 2500 Ω*cm2 to ~ 250 Ω*cm2 under dynamic conditions. Transcriptomic analyses, morphometric analyses and protein marker expression showed enhanced maturation of iBECs under long-term culture and dynamic flow. Importantly, on d10 claudin-5 was expressed mostly in the cytoplasm with only ~ 5% iBCECs showing continuous staining at the cell borders. With increase in culture duration, iBCECs at d17 of static culture showed ~ 18% of cells having continuous cell border expression, while dynamic conditions showed upto ~ 30% of cells with continuous cell-cell border expression patterns. Similarly, ~ 33% of cells showed cell-cell border expression of occludin on d10 with increases to ~ 55% under d17 static and up to ~ 65% under d17 dynamic conditions, thereby indicating iBCEC maturation.
In conclusion, the data presented within this thesis demonstrates the maturation of iBCECs in BBB spheroids, obtained via direct cellular contacts and by the application of flow and shear stress. Both established novel models need to be further validated for pharmaceutical drug applications together with in-vitro-in-vivo correlations in order to exploit their full potential.
In this work we expanded upon a study from our group where a ligand-based TNF-α mutein was developed to engage specifically TNFR2 and not TNFR1 activating Tregs and expanding them, which in an allo-HCT context conferred protection from GvHD. Fusing TNF trimers to the heavy chain of an Fc-dead and mouse irrelevant antibody, a new generation of this agonist was developed called NewSTAR2. It is believed that other members of the TNFSF can also target Tregs, therefore additional agonists against DR3 and GITR were developed under the same principles as for NewSTAR2. Phenotyping analysis of the expression of these three receptors were done to confirm their specificity for Tregs before in vitro and in vivo testings with mice or murine splenic cells. A potent expansion of Tregs was seen with NewSTAR2 and the other agonists as well as upregulation of activation markers on Tregs. Thorough analyses with NewSTAR2-treated mice showed how Tregs in several immune and non-immune organs were expanded and upregulated immunomodulatory receptors. A miniature suppressive assay and other cocultures with responder cells confirmed their enhanced suppression over unstimulated Tregs through contact dependent and independent mechanisms. Despite other myeloid cells also being increased after treatment, no undesired effects were observed under steady-state and prophylactic administration of a single dose of NewSTAR2 improved survival frequencies and lessened development of clinical symptoms. Prophylactic treatment with the other TNFRSF agonists showed similar protection yet Fc(DANA)-muTL1A was superior in in terms of less death events and lower clinical score. It was found that not all the three TNFSF members have redundant functions as development of skin lesions was observed with GITRL-based agonist Fc(DANA)-muGITRL, although its expansion of Tregs in steady-state was remarkable with no apparent adverse effects. Neither agonist had an impact on donor cell engraftment or allorective T cell response, however NewSTAR2-treatmend proved to reduce inflammation in small intestine and liver. This work is proof of concept of the effectivity of selectively engaging TNFSF to activate Tregs and expand them systemically allowing them to control strong and complex immune interactions like those governing GvHD.
Background
Simulator training is an effective way of acquiring laparoscopic skills but there remains a need to optimize teaching methods to accelerate learning. We evaluated the effect of the mental exercise ‘deconstruction into key steps’ (DIKS) on the time required to acquire laparoscopic skills.
Methods
A randomized controlled trial with undergraduate medical students was implemented into a structured curricular laparoscopic training course. The intervention group (IG) was trained using the DIKS approach, while the control group (CG) underwent the standard course. Laparoscopic performance of all participants was video-recorded at baseline (t0), after the first session (t1) and after the second session (t2) nine days later. Two double-blinded raters assessed the videos. The Impact of potential covariates on performance (gender, age, prior laparoscopic experience, self-assessed motivation and self-assessed dexterity) was evaluated with a self-report questionnaire.
Results
Both the IG (n = 58) and the CG (n = 68) improved their performance after each training session (p < 0.001) but with notable differences between sessions. Whereas the CG significantly improved their performance from t0 –t1 (p < 0.05), DIKS shortened practical exercise time by 58% so that the IG outperformed the CG from t1 -t2, (p < 0.05). High self-assessed motivation and dexterity associated with significantly better performance (p < 0.05). Male participants demonstrated significantly higher overall performance (p < 0.05).
Conclusion
Mental exercises like DIKS can improve laparoscopic performance and shorten practice times. Given the limited exposure of surgical residents to simulator training, implementation of mental exercises like DIKS is highly recommended. Gender, self-assessed dexterity, and motivation all appreciably influence performance in laparoscopic training.
Background
Dislocations of the elbow are the second most common dislocations of humeral joints following the shoulder. Besides numerous possible concomitant injuries of the collateral ligaments or the extensor or flexor apparatus, an accompanying disruption of the brachial artery is a rare occurrence. In the following, such a case is presented and discussed.
Method
A 70-year-old woman sustained a closed posterior elbow dislocation with accompanying disruption of the brachial artery due to a fall in a domestic environment. Pulselessness of the radial artery led to a computed tomography angiography being performed, which confirmed the diagnosis. Direct operative vascular reconstruction with a vein insert was carried out. Due to strong swelling of the soft tissue, other examinations of the elbow could not be performed initially. A redislocation a few days later led to an operative stabilization of the elbow joint.
Results
The final consultation 4 months postoperatively showed a stable, centered elbow joint and a normal perfusion of the affected arm. The elbow function was good with a range of motion of 0/0/110° of extension/flexion.
Conclusion
An elbow dislocation is a complex injury. An accurate clinical examination of possible concomitant injuries is important and should be repeated in the first few days after the occurrence. Vascular reconstruction should be performed immediately. In the case of persistent joint instability, an operative stabilization is indicated and may be supported by a hinged external fixator.
Background
Research on the needs of people with disability is scarce, which promotes inadequate programs. Community Based Inclusive Development interventions aim to promote rights but demand a high level of community participation. This study aimed to identify prioritized needs as well as lessons learned for successful project implementation in different Latin American communities.
Methods
This study was based on a Community Based Inclusive Development project conducted from 2018 to 2021 led by a Columbian team in Columbia, Brazil and Bolivia. Within a sequential mixed methods design, we first retrospectively analyzed the project baseline data and then conducted Focus Group Discussions, together with ratings of community participation levels. Quantitative descriptive and between group analysis of the baseline survey were used to identify and compare sociodemographic characteristics and prioritized needs of participating communities. We conducted qualitative thematic analysis on Focus Group Discussions, using deductive main categories for triangulation: 1) prioritized needs and 2) lessons learned, with subcategories project impact, facilitators, barriers and community participation. Community participation was assessed via spidergrams. Key findings were compared with triangulation protocols.
Results
A total of 348 people with disability from 6 urban settings participated in the baseline survey, with a mean age of 37.6 years (SD 23.8). Out of these, 18 participated within the four Focus Group Discussions. Less than half of the survey participants were able to read and calculate (42.0%) and reported knowledge on health care routes (46.0%). Unemployment (87.9%) and inadequate housing (57.8%) were other prioritized needs across countries. Focus Group Discussions revealed needs within health, education, livelihood, social and empowerment domains.
Participants highlighted positive project impact in work inclusion, self-esteem and ability for self-advocacy. Facilitators included individual leadership, community networks and previous reputation of participating organizations. Barriers against successful project implementation were inadequate contextualization, lack of resources and on-site support, mostly due to the COVID-19 pandemic. The overall level of community participation was high (mean score 4.0/5) with lower levels in Brazil (3.8/5) and Bolivia (3.2/5).
Conclusion
People with disability still face significant needs. Community Based Inclusive Development can initiate positive changes, but adequate contextualization and on-site support should be assured.
Background
Colorectal cancer is a leading cause of cancer-related deaths worldwide. The best method to prevent CRC is a colonoscopy. However, not all colon polyps have the risk of becoming cancerous. Therefore, polyps are classified using different classification systems. After the classification, further treatment and procedures are based on the classification of the polyp. Nevertheless, classification is not easy. Therefore, we suggest two novel automated classifications system assisting gastroenterologists in classifying polyps based on the NICE and Paris classification.
Methods
We build two classification systems. One is classifying polyps based on their shape (Paris). The other classifies polyps based on their texture and surface patterns (NICE). A two-step process for the Paris classification is introduced: First, detecting and cropping the polyp on the image, and secondly, classifying the polyp based on the cropped area with a transformer network. For the NICE classification, we design a few-shot learning algorithm based on the Deep Metric Learning approach. The algorithm creates an embedding space for polyps, which allows classification from a few examples to account for the data scarcity of NICE annotated images in our database.
Results
For the Paris classification, we achieve an accuracy of 89.35 %, surpassing all papers in the literature and establishing a new state-of-the-art and baseline accuracy for other publications on a public data set. For the NICE classification, we achieve a competitive accuracy of 81.13 % and demonstrate thereby the viability of the few-shot learning paradigm in polyp classification in data-scarce environments. Additionally, we show different ablations of the algorithms. Finally, we further elaborate on the explainability of the system by showing heat maps of the neural network explaining neural activations.
Conclusion
Overall we introduce two polyp classification systems to assist gastroenterologists. We achieve state-of-the-art performance in the Paris classification and demonstrate the viability of the few-shot learning paradigm in the NICE classification, addressing the prevalent data scarcity issues faced in medical machine learning.
For the current study the Lazarian stress-coping theory and the appendant model of psychosocial adjustment to chronic illness and disabilities (Pakenham, 1999) has shaped the foundation for identifying determinants of adjustment to ALS. We aimed to investigate the evolution of psychosocial adjustment to ALS and to determine its long-term predictors. A longitudinal study design with four measurement time points was therefore, used to assess patients' quality of life, depression, and stress-coping model related aspects, such as illness characteristics, social support, cognitive appraisals, and coping strategies during a period of 2 years. Regression analyses revealed that 55% of the variance of severity of depressive symptoms and 47% of the variance in quality of life at T2 was accounted for by all the T1 predictor variables taken together. On the level of individual contributions, protective buffering, and appraisal of own coping potential accounted for a significant percentage in the variance in severity of depressive symptoms, whereas problem management coping strategies explained variance in quality of life scores. Illness characteristics at T2 did not explain any variance of both adjustment outcomes. Overall, the pattern of the longitudinal results indicated stable depressive symptoms and quality of life indices reflecting a successful adjustment to the disease across four measurement time points during a period of about two years. Empirical evidence is provided for the predictive value of social support, cognitive appraisals, and coping strategies, but not illness parameters such as severity and duration for adaptation to ALS. The current study contributes to a better conceptualization of adjustment, allowing us to provide evidence-based support beyond medical and physical intervention for people with ALS.
No abstract available.