Flow shear stress differentially regulates endothelial uptake of nanocarriers targeted to distinct epitopes of PECAM-1

Abstract

Targeting nanocarriers (NC to endothelial cell adhesion molecules including Platelet-Endothelial Cell Adhesion Molecule-1 (PECAM-1 or CD31) improves drug delivery and pharmacotherapy of inflammation, oxidative stress, thrombosis and ischemia in animal models. Recent studies unveiled that hydrodynamic conditions modulate endothelial endocytosis of NC targeted to PECAM-1, but the specificity and mechanism of effects of flow remain unknown. Here we studied the effect of flow on endocytosis by human endothelial cells of NC targeted by monoclonal antibodies Ab62 and Ab37 to distinct epitopes on the distal extracellular domain of PECAM. Flow in the range of 1 – 8 dyne/cm2, typical for venous vasculature, stimulated the uptake of spherical Ab/NC (~180 nm diameter) carrying ~50 vs 200 Ab62 and Ab37 per NC, respectively. Effect of flow was inhibited by disruption of cholesterol-rich plasmalemma domains and deletion of PECAM-1 cytosolic tail. Flow stimulated endocytosis of Ab62/NC and Ab37/NC via eliciting distinct signaling pathways mediated by RhoA/ROCK and Src Family Kinases, respectively. Therefore, flow stimulates endothelial endocytosis of Ab/NC in a PECAM-1 epitope specific manner. Using ligands of binding to distinct epitopes on the same target molecule may enable fine-tuning of intracellular delivery based on the hemodynamic conditions in the vascular area of interest.

Nanoparticle targeting to the endothelium during normothermic machine perfusion of human kidneys

“…Collectively, these cell culture data demonstrate both that our CD31-NPs bind ECs with robust specificity and that targeting is occurring under non-saturating kinetics. This finding of nonsaturating kinetics is consistent with previous examples of CD31 targeting to cultured ECs under flow, which showed apparent linear increases in NP accumulation with increasing NP dose, but a direct comparison of our results with previous studies is difficult because the previous studies did not directly examine the time dependence of NP accumulation (30, 31, 34). The critical point raised by the observation that targeting to ECs is a kinetic (time-dependent) process, rather than equilibrium process, is that achieving robust accumulation within human kidneys during a short period of ex vivo NMP will require the optimization of both NP concentration and duration of exposure.…”

“…In addition, a quantification of the number of NPs per cell after 30 min of static incubation suggested that our CD31-NP formulation is capable of accumulating at an amount commensurate with previously validated CD31-targeted NPs evaluated under similar conditions (fig. S1, B and C) (30, 31, 34). Combined treatment of red CD31-NP and green Control-NP for 2 hours demonstrated that simultaneous treatment of CD31-NP and Control-NP did not have an appreciable impact on either specific or non-specific NP accumulation (fig.…”

Vascular‐targeted nanocarriers: design considerations and strategies for successful treatment of atherosclerosis and other vascular diseases

“…Perhaps more interestingly, this same study showed that acute shear stress stimulates the uptake of PECAM‐1 targeted NCs, while chronic shear stress (under which the ECs become elongated) decreases uptake, suggesting that acute shear stress likely stimulates a separate mechanism of NC internalization. A follow‐up study confirmed that this effect involves mechanosensing of shear stress in cholesterol‐rich regions of the plasmalemma, and also suggested the importance of both RhoA/ROCK signaling pathways and Src family kinases …”

ICAM-1 targeting, intracellular trafficking, and functional activity of polymer nanocarriers coated with a fibrinogen-derived peptide for lysosomal enzyme replacement

“…In these studies, however, ICAM-1 targeting was achieved by coating NCs with anti-ICAM antibody molecules and whether similar ERT efficacy can be obtained by using targeting moieties more amenable toward clinical applications (e.g., peptides), remains to be investigated. Although a priori one would expect this to be the case for any ICAM-1-targeting entity, it is not obvious for this particular application because: (a) CAM-mediated signaling and endocytosis has been shown to be highly sensitive to the specific receptor epitope being targeted [27,28], and (b) the presence of specific enzyme cargo capable of targeting the M6P receptor [2] may modulate the targeting ability of peptide-coated NCs. Therefore, the efficacy of a peptide/enzyme NC system must be empirically tested, which constituted the focus on the present study.…”