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During stroke the blood–brain barrier (BBB) is damaged which can result in vasogenic brain edema and inflammation. The reduced blood supply leads to decreased delivery of oxygen and glucose to affected areas of the brain. Oxygen and glucose deprivation (OGD) can cause upregulation of glucose uptake of brain endothelial cells. In this letter, we investigated the influence of MK801, a non-competitive inhibitor of the NMDA-receptor, on the regulation of the glucose uptake and of the main glucose transporters glut1 and sglt1 in murine BBB cell line cerebEND during OGD. mRNA expression of glut1 was upregulated 68.7- fold after 6 h OGD, which was significantly reduced by 10 μM MK801 to 28.9-fold. Sglt1 mRNA expression decreased during OGD which was further reduced by MK801. Glucose uptake was significantly increased up to 907% after 6 h OGD and was still higher (210%) after the 20 h reoxygenation phase compared to normoxia. Ten micromolar MK801 during OGD was able to reduce upregulated glucose uptake after OGD and reoxygenation significantly. Presence of several NMDAR subunits was proven on the mRNA level in cerebEND cells. Furthermore, it was shown that NMDAR subunit NR1 was upregulated during OGD and that this was inhibitable by MK801. In conclusion, the addition of MK801 during the OGD phase reduced significantly the glucose uptake after the subsequent reoxygenation phase in brain endothelial cells.
Balanced hydroxyethylstarch (HES 130/0.4) impairs kidney function in-vivo without inflammation
(2015)
Volume therapy is a standard procedure in daily perioperative care, and there is an ongoing discussion about the benefits of colloid resuscitation with hydroxyethylstarch (HES). In sepsis HES should be avoided due to a higher risk for acute kidney injury (AKI). Results of the usage of HES in patients without sepsis are controversial. Therefore we conducted an animal study to evaluate the impact of 6% HES 130/0.4 on kidney integrity with sepsis or under healthy conditions Sepsis was induced by standardized Colon Ascendens Stent Peritonitis (sCASP). sCASP-group as well as control group (C) remained untreated for 24 h. After 18 h sCASP+HES group (sCASP+VOL) and control+HES (C+VOL) received 50 ml/KG balanced 6% HES (VOL) 130/0.4 over 6h. After 24h kidney function was measured via Inulin- and PAH-Clearance in re-anesthetized rats, and serum urea, creatinine (crea), cystatin C and Neutrophil gelatinase-associated lipocalin (NGAL) as well as histopathology were analysed. In vitro human proximal tubule cells (PTC) were cultured +/- lipopolysaccharid (LPS) and with 0.1–4.0% VOL. Cell viability was measured with XTT-, cell toxicity with LDH-test. sCASP induced severe septic AKI demonstrated divergent results regarding renal function by clearance or creatinine measure focusing on VOL. Soleley HES (C+VOL) deteriorated renal function without sCASP. Histopathology revealed significantly derangements in all HES groups compared to control. In vitro LPS did not worsen the HES induced reduction of cell viability in PTC cells. For the first time, we demonstrated, that application of 50 ml/KG 6% HES 130/0.4 over 6 hours induced AKI without inflammation in vivo. Severity of sCASP induced septic AKI might be no longer susceptible to the way of volume expansion
Multiple Antenatal Dexamethasone Treatment Alters Brain Vessel Differentiation in Newborn Mouse Pups
(2015)
Antenatal steroid treatment decreases morbidity and mortality in premature infants through the maturation of lung tissue, which enables sufficient breathing performance. However, clinical and animal studies have shown that repeated doses of glucocorticoids such as dexamethasone and betamethasone lead to long-term adverse effects on brain development. Therefore, we established a mouse model for antenatal dexamethasone treatment to investigate the effects of dexamethasone on brain vessel differentiation towards the blood-brain barrier (BBB) phenotype, focusing on molecular marker analysis. The major findings were that in total brains on postnatal day (PN) 4 triple antenatal dexamethasone treatment significantly downregulated the tight junction protein claudin-5, the endothelial marker Pecam-1/CD31, the glucocorticoid receptor, the NR1 subunit of the N-methyl-D-aspartate receptor, and Abc transporters (Abcb1a, Abcg2 Abcc4). Less pronounced effects were found after single antenatal dexamethasone treatment and in PN10 samples. Comparisons of total brain samples with isolated brain endothelial cells together with the stainings for Pecam-1/CD31 and claudin-5 led to the assumption that the morphology of brain vessels is affected by antenatal dexamethasone treatment at PN4. On the mRNA level markers for angiogenesis, the sonic hedgehog and the Wnt pathway were downregulated in PN4 samples, suggesting fundamental changes in brain vascularization and/or differentiation. In conclusion, we provided a first comprehensive molecular basis for the adverse effects of multiple antenatal dexamethasone treatment on brain vessel differentiation.
Stabilization of the blood-brain barrier during and after stroke can lead to less adverse outcome. For elucidation of underlying mechanisms and development of novel therapeutic strategies validated in vitro disease models of the blood-brain barrier could be very helpful. To mimic in vitro stroke conditions we have established a blood-brain barrier in vitro model based on mouse cell line cerebEND and applied oxygen/glucose deprivation (OGD). The role of astrocytes in this disease model was investigated by using cell line C6. Transwell studies pointed out that addition of astrocytes during OGD increased the barrier damage significantly in comparison to the endothelial monoculture shown by changes of transendothelial electrical resistance as well as fluorescein permeability data. Analysis on mRNA and protein levels by qPCR, western blotting and immunofluorescence microscopy of tight junction molecules claudin-3,-5,-12, occludin and ZO-1 revealed that their regulation and localisation is associated with the functional barrier breakdown. Furthermore, soluble factors of astrocytes, OGD and their combination were able to induce changes of functionality and expression of ABC-transporters Abcb1a (P-gp), Abcg2 (bcrp), and Abcc4 (mrp4). Moreover, the expression of proteases (matrixmetalloproteinases MMP-2, MMP-3, MMP-9, and t-PA) as well as of their endogenous inhibitors (TIMP-1, TIMP-3, PAI-1) was altered by astrocyte factors and OGD which resulted in significant changes of total MMP and t-PA activity. Morphological rearrangements induced by OGD and treatment with astrocyte factors were confirmed at a nanometer scale using atomic force microscopy. In conclusion, astrocytes play a major role in blood-brain barrier breakdown during OGD in vitro.
The aim of this work was to conduct a comprehensive study about the transport properties of NSAIDs across the blood-brain barrier (BBB) in vitro. Transport studies with celecoxib, diclofenac, ibuprofen, meloxicam, piroxicam and tenoxicam were accomplished across Transwell models based on cell line PBMEC/C1-2, ECV304 or primary rat brain endothelial cells. Single as well as group substance studies were carried out. In group studies substance group compositions, transport medium and serum content were varied, transport inhibitors verapamil and probenecid were added. Resulted permeability coefficients were compared and normalized to internal standards diazepam and carboxyfluorescein. Transport rankings of NSAIDs across each model were obtained. Single substance studies showed similar rankings as corresponding group studies across PBMEC/C1-2 or ECV304 cell layers. Serum content, glioma conditioned medium and inhibitors probenecid and verapamil influenced resulted permeability significantly. Basic differences of transport properties of the investigated NSAIDs were similar comparing all three in vitro BBB models. Different substance combinations in the group studies and addition of probenecid and verapamil suggested that transporter proteins are involved in the transport of every tested NSAID. Results especially underlined the importance of same experimental conditions (transport medium, serum content, species origin, cell line) for proper data comparison.
The blood-air barrier in the lung consists of the alveolar epithelium, the underlying capillary endothelium, their basement membranes and the interstitial space between the cell layers. Little is known about the interactions between the alveolar and the blood compartment. The aim of the present study was to gain first insights into the possible interplay between these two neighboured cell layers. We established an in vitro Transwell model of the alveolar epithelium based on human cell line H441 and investigated the influence of conditioned medium obtained from human lung endothelial cell line HPMEC-ST1.6R on the barrier properties of the H441 layers. As control for tissue specificity H441 layers were exposed to conditioned medium from human brain endothelial cell line hCMEC/D3. Addition of dexamethasone was necessary to obtain stable H441 cell layers. Moreover, dexamethasone increased expression of cell type I markers (caveolin-1, RAGE) and cell type II marker SP-B, whereas decreased the transepithelial electrical resistance (TEER) in a concentration dependent manner. Soluble factors obtained from the lung endothelial cell line increased the barrier significantly proven by TEER values and fluorescein permeability on the functional level and by the differential expression of tight junctional proteins on the molecular level. In contrast to this, soluble factors derived from brain endothelial cells weakened the barrier significantly. In conclusion, soluble factors from lung endothelial cells can strengthen the alveolar epithelium barrier in vitro, which suggests communication between endothelial and epithelial cells regulating the integrity of the blood-air barrier.
Multiple antenatal dexamethasone treatment alters brain vessel differentiation in newborn mouse pups
(2015)
Antenatal steroid treatment decreases morbidity and mortality in premature infants through the maturation of lung tissue, which enables sufficient breathing performance. However, clinical and animal studies have shown that repeated doses of glucocorticoids such as dexamethasone and betamethasone lead to long-term adverse effects on brain development. Therefore, we established a mouse model for antenatal dexamethasone treatment to investigate the effects of dexamethasone on brain vessel differentiation towards the blood-brain barrier (BBB) phenotype, focusing on molecular marker analysis. The major findings were that in total brains on postnatal day (PN) 4 triple antenatal dexamethasone treatment significantly downregulated the tight junction protein claudin-5, the endothelial marker Pecam-1/CD31, the glucocorticoid receptor, the NR1 subunit of the N-methyl-D-aspartate receptor, and Abc transporters (Abcb1a, Abcg2 Abcc4). Less pronounced effects were found after single antenatal dexamethasone treatment and in PN10 samples. Comparisons of total brain samples with isolated brain endothelial cells together with the stainings for Pecam-1/CD31 and claudin-5 led to the assumption that the morphology of brain vessels is affected by antenatal dexamethasone treatment at PN4. On the mRNA level markers for angiogenesis, the sonic hedgehog and the Wnt pathway were downregulated in PN4 samples, suggesting fundamental changes in brain vascularization and/or differentiation. In conclusion, we provided a first comprehensive molecular basis for the adverse effects of multiple antenatal dexamethasone treatment on brain vessel differentiation.
Infection research largely relies on classical cell culture or mouse models. Despite having delivered invaluable insights into host-pathogen interactions, both have limitations in translating mechanistic principles to human pathologies. Alternatives can be derived from modern Tissue Engineering approaches, allowing the reconstruction of functional tissue models in vitro. Here, we combined a biological extracellular matrix with primary tissue-derived enteroids to establish an in vitro model of the human small intestinal epithelium exhibiting in vivo-like characteristics. Using the foodborne pathogen Salmonella enterica serovar Typhimurium, we demonstrated the applicability of our model to enteric infection research in the human context. Infection assays coupled to spatio-temporal readouts recapitulated the established key steps of epithelial infection by this pathogen in our model. Besides, we detected the upregulation of olfactomedin 4 in infected cells, a hitherto unrecognized aspect of the host response to Salmonella infection. Together, this primary human small intestinal tissue model fills the gap between simplistic cell culture and animal models of infection, and shall prove valuable in uncovering human-specific features of host-pathogen interplay.
Translating basic biological knowledge into applications remains a key issue for effectively tackling neurodegenerative, neuroinflammatory, or neuroendocrine disorders. Efficient delivery of therapeutics across the neuroprotective blood‐brain barrier (BBB) still poses a demanding challenge for drug development targeting central nervous system diseases. Validated in vitro models of the BBB could facilitate effective testing of drug candidates targeting the brain early in the drug discovery process during lead generation. We here review the potential of mono‐ or (isogenic) co‐culture BBB models based on brain capillary endothelial cells (BCECs) derived from human‐induced pluripotent stem cells (hiPSCs), and compare them to several available BBB in vitro models from primary human or non‐human cells and to rodent in vivo models, as well as to classical and widely used barrier models [Caco‐2, parallel artificial membrane permeability assay (PAMPA)]. In particular, we are discussing the features and predictivity of these models and how hiPSC‐derived BBB models could impact future discovery and development of novel CNS‐targeting therapeutics.
Significant advancements in the field of preclinical in vitro blood-brain barrier (BBB) models have been achieved in recent years, by developing monolayer-based culture systems towards complex multi-cellular assays. The coupling of those models with other relevant organoid systems to integrate the investigation of blood-brain barrier permeation in the larger picture of drug distribution and metabolization is still missing. Here, we report for the first time the combination of a human induced pluripotent stem cell (hiPSC)-derived blood-brain barrier model with a cortical brain and a liver spheroid model from the same donor in a closed microfluidic system (MPS). The two model compounds atenolol and propranolol were used to measure permeation at the blood–brain barrier and to assess metabolization. Both substances showed an in vivo-like permeation behavior and were metabolized in vitro. Therefore, the novel multi-organ system enabled not only the measurement of parent compound concentrations but also of metabolite distribution at the blood-brain barrier.