Inflammation-induced brain endothelial activation leads to uptake of electrostatically stabilized iron oxide nanoparticles via sulfated glycosaminoglycans

Abstract

Based on our previous data on the presence of very small superparamagnetic iron oxide nanoparticles (VSOP) on brain endothelial structures during experimental autoimmune encephalomyelitis (EAE), we investigated the mechanisms of VSOP binding on inflamed brain endothelial cells in vivo and in vitro. After intravenous application, VSOP were detected in brain endothelial cells of EAE animals at peak disease and prior to clinical onset. In vitro, inflammatory stimuli increased VSOP uptake by brain endothelial bEnd.3 cells, which we confirmed in primary endothelial cells and in bEnd.3 cells cultured under shear stress. Transmission electron microscopy and blocking experiments revealed that during inflammation VSOP were endocytosed by bEnd.3. Modified sulfated glycosaminoglycans (GAG) on inflamed brain endothelial cells were the primary binding site for VSOP, as GAG degradation and inhibition of GAG sulfation reduced VSOP uptake. Thus, VSOP-based MRI is sensitive to visualize early neuroinflammatory processes such as GAG modifications on brain endothelial cells.

Contribution of Tissue Inflammation and Blood-Brain Barrier Disruption to Brain Softening in a Mouse Model of Multiple Sclerosis

“…Previous studies have shown that Gd-enhancing lesions are present before disease signs become apparent ( Wuerfel et al, 2007 ) but rarely correlate with the presence of characteristic immune infiltrate-derived lesions, a hallmark of EAE and MS ( Nessler et al, 2007 ; Nathoo et al, 2014 ). In contrast, we show that Eu-VSOPs also accumulate in areas that are not enhanced by GBCA and are present at sites of immune cell infiltration, which is in alignment with the literature ( Tysiak et al, 2009 ; Millward et al, 2019 ; Berndt et al, 2017 ). More precisely, we found Eu-VSOPs to be dispersed and mostly located in the vicinity of vessels and ventricles, as indicated in the incidence maps.…”

“…Eu-VSOPs were imaged 24 h after injection when they have been shown to be cleared from the blood ( Wuerfel et al, 2007 ). Therefore, we propose that hypointense signals seen in T2 ∗ images originate primarily from VSOP bound to altered ECM components ( Berndt et al, 2017 ) or from particles phagocytosed by peripheral macrophages or/and activated microglia present at sites of inflammation ( Tysiak et al, 2009 ; Millward et al, 2013 , 2019 ). However, it cannot be excluded that these hypointense signals originate from particles phagocytosed by intravascular immune cells patrolling the endothelium and ready to cross upon inflammatory signals as reported in Masthoff et al, 2018 ( Masthoff et al, 2018 ).…”

“…We hypothesize that novel tomoelastography sensitively detects mechanical changes in sites of intense neuroinflammation that are revealed by VSOP-deposits. Those sites are known to be characterized by enhanced myeloid cell activity ( Millward et al, 2013 ), alterations of the glycocalyx on barrier cells ( Berndt et al, 2017 ) and ECM remodeling ( Wang et al, 2020 ). To test our hypothesis, we combined in vivo viscoelasticity measured by multifrequency MRE with both, GBCA- and VSOP- MRI, in the adoptive transfer EAE model.…”

Cellular interactions of functionalized superparamagnetic iron oxide nanoparticles on oligodendrocytes without detrimental side effects: Cell death induction, oxidative stress and inflammation

“…However, the cells exhibited a dose dependent response with regard to fluorescence property. These results agree with the study of M. Abdollah et al[38] and D. Berndt et al[39] who found that cellular uptake of iron oxide increases in a dose-dependent manner. Cell morphology was not altered in any of the fSPIONs concentration used in the present study.…”

Labeling of cell therapies: How can we get it right?

“…Electron microscopy is the gold standard for definitive confirmation of intracellular localization of nanoparticle labels, and is the method of choice. [7][8][9] With its high resolution, electron microscopy can clearly visualize the intracellular compartments with high definition, and visualization of the nanoparticles with this method provides the best assurance of successful cell labeling. Confocal microscopy is commonly used to assess uptake of fluorescently-labeled nanoparticles, and while this is a useful tool most researchers often omit the necessary additional staining steps to detail the plasma membrane, intracellular compartments and cytoskeleton.…”