Abstract
Targeting of diagnostic and therapeutic agents to endothelial cells (ECs) provides an avenue to improve treatment of many maladies. For example, intercellular adhesion molecule 1 (ICAM-1), a constitutive endothelial cell adhesion molecule up-regulated in many diseases, is a good determinant for endothelial targeting of therapeutic enzymes and polymer nanocarriers (PNCs) conjugated with anti-ICAM (anti-ICAM/PNCs). However, intrinsic and extrinsic factors that control targeting of anti-ICAM/PNCs to ECs (e.g., anti-ICAM affinity and PNC valency and flow) have not been defined. In this study we tested in vitro and in vivo parameters of targeting to ECs of anti-ICAM/PNCs consisting of either prototype polystyrene or biodegradable poly(lactic-coglycolic) acid polymers (∼200 nm diameter spheres carrying ∼200 anti-ICAM molecules). Anti-ICAM/PNCs, but not control IgG/PNCs 1) rapidly (t1/2 ∼5 min) and specifically bound to tumor necrosis factor-activated ECs in a dose-dependent manner (Bmax ∼350 PNC/cell) at both static and physiological shear stress conditions and 2) bound to ECs and accumulated in the pulmonary vasculature after i.v. injection in mice. Anti-ICAM/PNCs displayed markedly higher EC affinity versus naked anti-ICAM (Kd ∼80 pM versus ∼8 nM) in cell culture and, probably because of this factor, higher value (185.3 ± 24.2 versus 50.5 ± 1.5% injected dose/g) and selectivity (lung/blood ratio 81.0 ± 10.9 versus 2.1 ± 0.02, in part due to faster blood clearance) of pulmonary targeting. These results 1) show that reformatting monomolecular anti-ICAM into high-affinity multivalent PNCs boosts their vascular immuno-targeting, which withstands physiological hydrodynamics and 2) support potential anti-ICAM/PNCs utility for medical applications.
Footnotes
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This work was supported by American Heart Association Grant 0435181N (to S.M.), National Institutes of Health Grants HL/GM 71175-01 and P01 HL0790063, and Department of Defense Grant PR 012262 (to V.M.).
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doi:10.1124/jpet.105.098970.
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ABBREVIATIONS: EC, endothelial cell; ICAM, intercellular adhesion molecule(s); PNC, polymer nanocarrier; PLGA, poly(lactic-coglycolic) acid; PBS, phosphate-buffered saline; PEG, polyethylene glycol; HUVEC, human umbilical vein endothelial cell; TNF, tumor necrosis factor; ID, injected dose; LR, localization ratio; ISI, immunospecificity index.
- Received November 23, 2005.
- Accepted February 23, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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