Blood-brain barrier dysfunction in L-ornithine induced acute pancreatitis in rats and the direct effect of L-ornithine on cultured brain endothelial cells

Background

In severe acute pancreatitis (AP) the CNS is affected manifesting in neurological symptoms. Earlier research from our laboratory showed blood–brain barrier (BBB) permeability elevation in a taurocholate-induced AP model. Here we aimed to further explore BBB changes in AP using a different, non-invasive in vivo model induced by l-ornithine. Our goal was also to identify whether l-ornithine, a cationic amino acid, has a direct effect on brain endothelial cells in vitro contributing to the observed BBB changes.

Methods

AP was induced in rats by the intraperitoneal administration of l-ornithine-HCl. Vessel permeability and the gene expression of the primary transporter of l-ornithine, cationic amino acid transporter-1 (Cat-1) in the brain cortex, pancreas, liver and lung were determined. Ultrastructural changes were followed by transmission electron microscopy. The direct effect of l-ornithine was tested on primary rat brain endothelial cells and a triple co-culture model of the BBB. Viability and barrier integrity, including permeability and TEER, nitrogen monoxide (NO) and reactive oxygen species (ROS) production and NF-κB translocation were measured. Fluorescent staining for claudin-5, occludin, ZO-1, β-catenin, cell adhesion molecules Icam-1 and Vcam-1 and mitochondria was performed. Cell surface charge was measured by laser Doppler velocimetry.

Results

In the l-ornithine-induced AP model vessel permeability for fluorescein and Cat-1 expression levels were elevated in the brain cortex and pancreas. On the ultrastructural level surface glycocalyx and mitochondrial damage, tight junction and basal membrane alterations, and glial edema were observed. l-ornithine decreased cell impedance and elevated the BBB model permeability in vitro. Discontinuity in the surface glycocalyx labeling and immunostaining of junctional proteins, cytoplasmic redistribution of ZO-1 and β-catenin, and elevation of Vcam-1 expression were measured. ROS production was increased and mitochondrial network was damaged without NF-κB, NO production or mitochondrial membrane potential alterations. Similar ultrastructural changes were seen in l-ornithine treated brain endothelial cells as in vivo. The basal negative zeta potential of brain endothelial cells became more positive after l-ornithine treatment.

Conclusion

We demonstrated BBB damage in the l-ornithine-induced rat AP model suggesting a general, AP model independent effect. l-ornithine induced oxidative stress, decreased barrier integrity and altered BBB morphology in a culture BBB model. These data suggest a direct effect of the cationic l-ornithine on brain endothelium. Endothelial surface glycocalyx injury was revealed both in vivo and in vitro, as an additional novel component of the BBB-related pathological changes in AP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-022-00308-0.

Effective capture of circulating tumor cells from an S180-bearing mouse model using electrically charged magnetic nanoparticles

Background

Technology enabling the separation of rare circulating tumor cells (CTCs) provides the potential to enhance our knowledge of cancer metastasis and improve the care of cancer patients. Modern detection approaches commonly depend on tumor antigens or the physical size of CTCs. However, few studies report the detection of CTCs by the electrical differences between cancer cells and normal cells.

Results

In this study, we report a procedure for capturing CTCs from blood samples using electrically charged superparamagnetic nanoparticles (NPs). We found that only positively charged NPs attached to cancer cells, while negatively charged NPs did not. The capture method with positively charged NPs offered a sensitivity of down to 4 CTCs in 1 mL blood samples and achieved a superior capture yield (> 70%) for a high number of CTCs in blood samples (10³–10⁶ cells/mL). Following an in vitro evaluation, S180-bearing mice were employed as an in vivo model to assess the specificity and sensitivity of the capture procedure. The number of CTCs in blood from tumor-bearing mice was significantly higher than that in blood from healthy controls (on average, 75.8 ± 16.4 vs. zero CTCs/100 μL of blood, p < 0.0001), suggesting the high sensitivity and specificity of our method.

Conclusions

Positively charged NPs combined with an in vivo tumor model demonstrated that CTCs can be distinguished and isolated from other blood cells based on their electrical properties.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0491-1) contains supplementary material, which is available to authorized users.

Surfactin restores and enhances swarming motility under heavy metal stress

The present work reports the importance of lipopeptide biosurfactant on swarming motility of multi-metal resistant (MMR) bacterium under heavy metal stress. The MMR bacteria strain CM100B, identified as Bacillus cereus, was isolated from the coal mine sample. The strain was able to grow and reduce several metals namely Cd(2+), Co(2+), Cu(2+), Ni(2+), Mn(2+) and Pb(2+) ions which are common environmental pollutants. Presence of toxic heavy metal ions in the swarming medium significantly altered the motility of CM100B. Presence of Cd(2+) and Pb(2+) ions inhibited development of peritrichous flagella, thus inhibiting swarming motility. However, the addition of anionic biosurfactant surfactin restored (in case of Cd(2+) and Pb(2+) ions) or enhanced (in case of Co(2+), Cu(2+), Ni(2+) and Mn(2+)) the swarming ability of CM100B. Zeta potential studies for determining bacterial cell surface charge indicated that surfactin provided a suitable swarming environment to bacteria even under metal stress by chelating to cationic metal ions. Non-ionic surfactant Triton X-100 was unable to restore swarming under Cd(2+) and Pb(2+) ion stress. Thus, suggesting that surfactin can aid in motility not only by reducing the surface tension of swarming medium but also by binding to metal ions in the presence of metal ions stress.