Targeting atherosclerosis by using modular, multifunctional micelles

Abstract

Subtle clotting that occurs on the luminal surface of atherosclerotic plaques presents a novel target for nanoparticle-based diagnostics and therapeutics. We have developed modular multifunctional micelles that contain a targeting element, a fluorophore, and, when desired, a drug component in the same particle. Targeting atherosclerotic plaques in ApoE-null mice fed a high-fat diet was accomplished with the pentapeptide cysteine-arginine-glutamic acid-lysine-alanine, which binds to clotted plasma proteins. The fluorescent micelles bind to the entire surface of the plaque, and notably, concentrate at the shoulders of the plaque, a location that is prone to rupture. We also show that the targeted micelles deliver an increased concentration of the anticoagulant drug hirulog to the plaque compared with untargeted micelles.cysteine-arginine-glutamic acid-lysine-alanine ͉ hirulog ͉ plaque ͉ imaging ͉ nanoparicles C ardiovascular disease affects 1 in 3 people in the United States during their lifetime, and accounts for nearly a third of the deaths that occur each year (1). Atherosclerosis is one of the leading causes of cardiovascular disease, and it results in raised plaques in the arterial wall that can occlude the vascular lumen and block blood flow through the vessel. Recently, it has become clear that not all plaques are the same. Those susceptible to rupture, fissuring, and subsequent thrombosis are most frequently the cause of acute coronary syndromes and death (2).Rupture of an atherosclerotic plaque exposes collagen and other plaque components to the bloodstream. This rupture initiates hemostasis in the blood vessel and leads to activation of thrombin and a thrombus to form at the site of rupture. Elevated levels of activated thrombin bound to the vessel wall have been observed up to 72 h after vascular injury (3). These elevated thrombin levels not only induce clot formation but also have been implicated in the progression of atherosclerosis by causing smooth muscle cells to bind circulating low density lipoprotein (4). Subtle clotting in plaques is also indicated by deposition of fibrin(ogen) both inside and on the surface of atherosclerotic plaques, which has been well documented since the 1940s (5-7).Fibrin-containing blood clots have been extensively used as a target for site-specific delivery of imaging agents and anticlotting agents to thrombi (8-10). Delivering anticoagulants into vessels where clotting is taking place has been shown to be effective at reducing the formation and expansion of clots, and it also decreases the risk of systemic side effects (11,12). Antibodies and peptides that bind to molecular markers specifically expressed on atherosclerotic plaques have shown promise for plaque imaging in vivo (13-16), but clotting on the plaque has not been used as a target. We reasoned that the fibrin deposited on plaques could serve as a target for delivering diagnostic and therapeutic compounds to plaques.We chose the clot-binding peptide cysteine-arginine-glutamic acid-lysine-alanine (CREKA) to te...

Specific penetration and accumulation of a homing peptide within atherosclerotic plaques of apolipoprotein E-deficient mice

“…In comparison, the accumulation of untargeted NWs was low and limited to the luminal surface of plaques. CREKA-targeted NWs showed greater accumulation on the surface of the plaques, and minimally penetrated into the plaques, confirming reported results (10). Ex vivo MRI of aortas from mice injected with LyP-1-NWs revealed decreased T2*-weighted signal in areas that contained plaque (Fig.…”

“…Staining with an antifluorescein antibody confirmed the presence of LyP-1 in the plaques. For comparison, we also injected mice with a peptide previously shown to home to plaques, CREKA (10). In agreement with the reported results, FAM-CREKA homed to the plaques in a pattern distinct from LyP-1 in that CREKA was essentially confined to the surface of the plaques (Fig.…”

“…In vivo phage display (4) has been used with some success to identify reagents with improved specificity for plaque targeting (5)(6)(7)(8)(9)(10)(11). We have shown that the pentapeptide CREKA, which binds to fibrin-fibronectin complexes in clotted plasma (12), homes to plaques (10).…”

“…We have shown that the pentapeptide CREKA, which binds to fibrin-fibronectin complexes in clotted plasma (12), homes to plaques (10). Following intravenous injection, CREKAconjugated micelles bound to the surface of plaques and predominantly concentrated at the shoulders of the plaque, which is a location that is prone to rupture (10).…”

Peptide Amphiphile Micelles Self-Adjuvant Group A Streptococcal Vaccination

“…They have been shown capable of delivering biologically active peptides for a variety of applications including angiogenesis (19,20), osteogenesis (21,22), neurogenesis (23,24), atherosclerosis treatment (25), cancer therapy (26,27), and islet transplantation (28,29). Also, peptide amphiphile micelles are comprised of a high concentration of peptide (30), inhibit peptide degradation (31), and can greatly increase peptide intracellular delivery (32).…”