Efficacy of liposome-encapsulated hemoglobin in a rat model of cerebral ischemia.

Use of liposome-encapsulated hemoglobin (LEH) for oxygen delivery in the treatment of cerebral ischemia has been studied previously and its expected benefits confirmed. However, the relationship between the timing of administration and the efficacy of LEH in cerebral ischemia has not been studied in detail. We therefore investigated the therapeutic time window of LEH by using a rat model of cerebral ischemia, as well as evaluating the contribution of oxygen delivery to the efficacy of LEH. Dose-dependent effects and the therapeutic time window of LEH were studied using models of transient and permanent middle cerebral artery occlusion (MCAO), respectively, in SD rats. LEH was intravenously administered at 0.5 h after the onset of ischemia in the transient MCAO model and at 0.5, 2, 4, or 6 h in the permanent MCAO model. Efficacy of LEH treatment was evaluated using the infarct volume, which was examined with 2,3,5-triphenyltetrazolium chloride staining and estimated by integrating the unstained areas in serial sections of cerebral tissue. Effects of oxygen delivery by LEH were examined immunohistochemically with pimonidazole to stain for areas of low oxygen tension in the tissue. LEH treatment dose-dependently reduced the cerebral infarct volume, which was especially significant in the cortical region at doses of over 60 mg hemoglobin (Hb)/kg. In rats with permanent MCAO, LEH administration at a dose of 300 mg Hb/kg at 0.5 h and 2 h after the onset of cerebral ischemia significantly reduced cerebral infarct volume. Furthermore, immunohistochemical staining with pimonidazole showed that the areas of cerebral tissue that were hypoxic and had abnormal histological structure were reduced after LEH treatment. These results indicated that LEH is efficacious in the treatment of cerebral infarction secondary to MCAO and that oxygen delivery to ischemic cerebral tissues by LEH administered early after the onset of cerebral ischemia contributes to this effect.

Site-specific targeting of nanoparticle prednisolone reduces in-stent restenosis in a rabbit model of established atheroma.

OBJECTIVE: TRM-484 is a novel drug consisting of nanoparticles of prednisolone with high affinity to chondroitin sulfate proteoglycans (CSPGs). This may allow for neointimal suppression via directed targeting to areas of injury at systemic concentrations low enough to avoid adverse side effects known to occur with oral delivery of steroids. METHODS AND RESULTS: Atherosclerotic New Zealand white Rabbits were implanted with bare metal stents and randomized to receive intravenous TRM-484 at doses of 1 mg/kg or 0.32 mg/kg starting at the day of stenting and continuing 3 times a week for the duration of the study. Control animals received empty liposomes (placebo) or saline infusion. Stented arterial segments were harvested at 42 days and processed for histomorphometry and immunohistochemistry. Tissue and plasma levels were determined along with confocal microscopic analysis to determine distribution of rhodamine-labeled TRM-484 at various time points. TRM-484 was exclusively observed at sites of stent-induced injury, with absence of drug in contralateral nonstented arteries. Tissue concentration of stented arteries exceeded that of contralateral nonstented arteries by 100-fold 24 hours after administration of 1 mg/kg TRM-484 and resulted in significant reduction of percent stenosis compared to saline and placebo treated rabbits (22.5+/-4.4 versus 31.0+/-8.4 and 29.5+/-8.1%, P<0.03). CONCLUSIONS: TRM-484 at doses of 1 mg/kg resulted in significant suppression of in-stent neointimal growth in atherosclerotic rabbits. Site-specific targeting by this nanoparticle steroid in injured atherosclerotic areas might be a valuable and cost-effective approach for the prevention of in-stent restenosis.

Advances in targeting drug delivery to glomerular mesangial cells by long circulating cationic liposomes for the treatment of glomerulonephritis.

PURPOSE: Newly designed polyethylene glycol (PEG)-modified cationic liposomes, containing a novel cationic lipid TRX-20 (3,5-dipentadecyloxybenzamidine hydrochloride), bind specifically to cultured human mesangial cells, and not to endothelial cells. In this study, we investigated targeting the delivery of PEG-modified liposomes containing TRX-20 (TRX-liposomes) to mesangial cells and evaluated their pharmacokinetic behavior in a rat experimental glomerulonephritis model, using prednisolone phosphate (PSLP) as a model drug. MATERIAL AND METHODS: TRX-liposomes were injected intravenously into experimental glomerulonephritic rats and normal rats to compare its pharmacokinetic behavior with that of non-cationic liposomes (PEG-liposomes). Rhodamine-labeled liposomes were used to evaluate the accumulation in inflamed kidneys. Pharmacological effects of three formulations of PSLP (i.e., a single injection of two liposomal formulations and daily injections of PSLP in saline solution) were estimated in terms of suppressing glomerular cell proliferation in the rat nephritis model. RESULTS: TRX-liposomes markedly accumulated in the glomeruli of inflamed kidneys, but did not accumulate in the glomeruli of normal kidneys. Although the PEG-liposomes also accumulated in the glomeruli of the inflamed kidneys, their pharmacological behavior was quite different from that of the TRX-liposomes, which were internalized by the target cells. In a comparison among the three formulations of PSLP, the dose of TRX-liposomes required for significant suppression of glomerular cell proliferation was much less (dose of 0.032 mg/kg and above) than that required for the same effect by the PSLP saline solution (3.2 mg/kg daily; 12.8 mg/kg total) and PEG-liposomes (0.32 mg/kg). Interestingly, significant suppression of mesangial cell activation, as assessed by the expression of alpha-smooth muscle actin, was observed in nephritic rats treated with TRX-liposomes, but not in the other two treatment groups. CONCLUSIONS: The pharmaceutical properties of TRX-liposomes due to their preferential binding to mesangial cells and long circulation time make this a likely candidate system for targeted drug delivery to the inflamed glomeruli of glomerulonephritis.