Objective-This study investigates effects of short-term administration of high-density lipoproteins (HDL) and a statin on atherosclerosis in cholesterol-fed rabbits. Effects of HDL apolipoprotein and phospholipid composition have also been investigated. Methods and Results-Aortic atherosclerosis was established over 17 weeks in 46 rabbits by balloon denudation and cholesterol feeding. During the past 5 days of the cholesterol-feeding period, animals received: (1) no treatment; (2)

Objective To develop a new bioactive gas delivery method using echogenic liposomes (ELIP) as the gas carrier. Background Nitric oxide (NO) is a bioactive gas with potent therapeutic effects. Bioavailability of NO by systemic delivery is low with potential systemic effects. Methods Liposomes containing phospholipids and cholesterol were prepared using a new freezing under pressure method. The encapsulation and release profile of NO from NO containing-ELIP (NO-ELIP) or a mixture of NO/Argon (NO/Ar-ELIP was studied. Uptake of NO from NO-ELIP by cultured vascular smooth muscle cells (VSMC) both in the absence and presence of hemoglobin was determined. The effect of NO-ELIP delivery to attenuate intimal hyperplasia in a balloon-injured artery was determined. Results Coencapsulation of NO with argon (Ar) enabled the adjustment the amount of encapsulated NO. A total of 10 µl of gas can be encapsulated into 1 mg liposomes. The release profile of NO from NO-ELIP demonstrated an initial rapid release followed by a slower release over 8 hours. Sixty-eight percent of cells remained viable when incubated with 80 µg/ml of NO/Ar-ELIP for 4 hours. NO delivery to VSMC using NO/Ar-ELIP was 7-fold higher than unencapsulated NO. NO/Ar-ELIP remained effective NO delivery to VSMC even in the presence of hemoglobin. Local NO-ELIP administration to balloon-injured carotid arteries attenuated the development of intimal hyperplasia and reduced arterial wall thickening by 41±9%. Conclusions Liposomes can protect and deliver a bioactive gas to target tissues with the potential for both visualization of gas delivery and controlled therapeutic gas release.

Background-Ischemia-related neurological injury is a primary cause of stroke disability. Studies have demonstrated that xenon (Xe) may have potential as an effective and nontoxic neuroprotectant. Xe delivery is, however, hampered by lack of suitable administration methods. We have developed a pressurization-freeze method to encapsulate Xe into echogenic liposomes (Xe-ELIP) and have modulated local gas release with transvascular ultrasound exposure. Methods and Results-Fifteen microliters of Xe were encapsulated into each 1 mg of liposomes (70% Xe and 30% argon).Xe delivery from Xe-ELIP into cells and consequent neuroprotective effects were evaluated with oxygen/glucosedeprived and control neuronal cells in vitro. Xe-ELIP were administered into Sprague-Dawley rats intravenously or intra-arterially after right middle cerebral artery occlusion. One-megahertz low-amplitude (0.18 MPa) continuous wave ultrasound directed onto the internal carotid artery triggered Xe release from circulating Xe-ELIP. Effects of Xe delivery on ischemia-induced neurological injury and disability were evaluated. Xe-ELIP delivery to oxygen/glucose-deprived neuronal cells improved cell viability in vitro and resulted in a 48% infarct volume decrease in vivo. Intravenous Xe-ELIP administration in combination with the ultrasound directed onto the carotid artery enhanced local Xe release from circulating Xe-ELIP and demonstrated 75% infarct volume reduction. This was comparable to the effect after intra-arterial administration. Behavioral tests on limb placement and grid and beam walking correlated with infarct reduction. Conclusions-This novel methodology may provide a noninvasive strategy for ultrasound-enhanced local therapeutic gas delivery for cerebral ischemia-related injury while minimizing systemic side effects. (Circulation. 2010;122:1578-1587.)

AbbreviationsC-ELIP, calcein-loaded echogenic liposome; ELIP, echogenic liposome; MDI, mean digital intensity; MI, mechanical index; P-ELIP, papaverine-loaded echogenic liposome; ROI, region of interest; rt-PA, recombinant tissue plasminogen activator he clinical need for organ-or tissue-specific drug delivery, also known as targeted drug delivery, arises when systemic delivery of a drug in sufficient doses to achieve a therapeutic effect at the target site results in deleterious systemic effects. Relevant clinical problems include delivery of chemotherapeutic drugs to tumors, delivery of thrombolytic drugs to the cerebral or coronary circulation during ischemic stroke T ArticleObjective. To achieve ultrasound-controlled drug delivery using echogenic liposomes (ELIPs), we assessed ultrasound-triggered release of hydrophilic and lipophilic agents in vitro using color Doppler ultrasound delivered with a clinical 6-MHz compact linear array transducer. Methods. Calcein, a hydrophilic agent, and papaverine, a lipophilic agent, were each separately loaded into ELIPs. Calceinloaded ELIP (C-ELIP) and papaverine-loaded ELIP (P-ELIP) solutions were circulated in a flow model and treated with 6-MHz color Doppler ultrasound or Triton X-100. Treatment with Triton X-100 was used to release the encapsulated calcein or papaverine content completely. The free calcein concentration in the solution was measured directly by spectrofluorimetry. The free papaverine in the solution was separated from liposome-bound papaverine by spin column filtration, and the resulting papaverine concentration was measured directly by absorbance spectrophotometry. Dynamic changes in echogenicity were assessed with low-output B-mode ultrasound (mechanical index, 0.04) as mean digital intensity. Results. Color Doppler ultrasound caused calcein release from C-ELIPs compared with flow alone (P < .05) but did not induce papaverine release from P-ELIPs compared with flow alone (P > .05). Triton X-100 completely released liposome-associated calcein and papaverine. Initial echogenicity was higher for C-ELIPs than P-ELIPs. Color Doppler ultrasound and Triton X-100 treatments reduced echogenicity for both CELIPs and P-ELIPs (P < .05). Conclusions. The differential efficiency of ultrasoundmediated pharmaceutical release from ELIPs for water-and lipid-soluble compounds suggests that water-soluble drugs are better candidates for the design and development of ELIP-based ultrasound-controlled drug delivery systems.