Targeted Formulation to Treat Spinal Cord Injury and other Neurological Disorders, 01-R8183
Principal Investigators
Gloria Gutierrez
Gianny Rossini
Inclusive Dates: 10/01/10 – Current
Background — There is a great need for effective therapies for spinal cord injury (SCI). Current global estimates indicate that the incidence of SCI ranges from 14.5 to 57.8 cases per million. To date, attempts to overcome some of the destructive neurological effects have resulted in some degree of functional improvement. However, the complexity of SCI obviously demands a multifactorial repair approach. Apart from this, the challenge in treating most brain disorders is surmounting the difficulty of delivering therapeutic agents to the brain by crossing the blood-brain-barrier. Statins, or 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) inhibitors, are front-line therapeutic agents for the prevention of cardiovascular disease and atherosclerotic disorders related to hypercholesterolemia. In addition to their potent anti-atherosclerotic and cardioprotective effects, compelling clinical and preclinical studies delineate the neuroprotective efficacy of statins in various neurological disorders including spinal cord injury, where they have been shown to prevent endothelial dysfunction, facilitate neuroprotection, and promote locomotor recovery following spinal cord injury. The challenge in treating most brain disorders is overcoming the difficulty of delivering therapeutic to the brain by crossing the blood-brain-barrier.
Approach — The goal of this proposal has been to develop a nanoparticle drug delivery system to target the central nervous system using a linear or optimized branched polyethylene glycol (PEG) coating on the liposome surface with glutathione as the targeting ligand to reach the central nervous system. Glutathione is specifically and actively taken up by specialized transporters at the blood-brain barrier and the PEG coating provides prolonged systemic circulation to deliver statin nanocarriers to the spinal cord injury site, exerting controlled release of lovastatin to counteract the reactive oxygen species and suppressing inflammatory response generated by the injury. Thus it is desired that the formulation demonstrates controlled release of lovastatin and accumulation in the site of injury to enable rapid and uniform treatment and avoid unnecessary systemic exposure. SwRI researchers developed and are characterizing in vitro cell binding and permeability across the BBB of ligand-targeted PEG-liposomes and micelles. Researchers have conjugated these linear and branched PEG moieties to glutathione molecules using maleimide chemistry followed by liposome or micelle formulations. They have tested the linear PEGylated formulations in the transcytosis assay with and without targeting and with and without the active drug. They have also established the neurite outgrowth assay in vitro and have been able to quantify neurite formation in response to these formulations. The rate of lovastatin release in vitro was also characterized over time.
Accomplishments — The project team was able to confirm glutathione conjugation to the maleimide moiety in micelles by means of nuclear magnetic resonance spectroscopy. Researchers have completed the major goal of developing and testing targeted and non-targeted liposomes and micelles, using a phospholipid linear PEG2000. The delivery system is able to provide controlled-release of lovastatin (approximately 70% release in 72 hours) improving bioavailability of the drug. They demonstrated cellular uptake and transcytosis of rhodamine-labeled micelles and liposomes in a human brain vascular endothelial cell line, hCMEC/D3 (obtained under license from INSERM, France) (approximately 30% transport across the blood-brain-barrier for targeted micelles and liposomes compared to undetectable levels for non-targeted formulation. They have also been able to prove efficacy of the formulations in the neurite outgrowth assay.
