Abstract
Basic fibroblast growth factor (bFGF) has minimal pharmacological effects in the central nervous system in the absence of blood-brain barrier (BBB) disruption. BBB transport of bFGF occurs via an absorptive-mediated transcytosis mechanism, which is relatively inefficient. To enhance the BBB transport of bFGF, this neurotrophin was reformulated to enable receptor-mediated transport across the BBB via the transferrin receptor. bFGF was monobiotinylated and coupled to a BBB drug-delivery vector comprised of streptavidin (SA) and the OX26 monoclonal antibody to the rat transferrin receptor. The entire conjugate of biotinylated bFGF bound to the OX26-SA is designated bio-bFGF/OX26-SA. The bFGF retains receptor-binding affinity and has increased brain uptake following conjugation to OX26-SA. The bio-bFGF/OX26-SA conjugate protects cortical cell cultures against hypoxia/reoxygenation insult in a dose-dependent manner in vitro. A single intravenous injection of bio-bFGF/OX26-SA, equivalent to a dose of 25 μg/kg bFGF, produces an 80% reduction in infarct volume in the brain of rats subjected to permanent occlusion of the middle cerebral artery in parallel with a significant improvement of neurologic deficit. The neuroprotection is time-dependent, and there is a 67% reduction in stroke volume if the conjugate is administered at 60 min after arterial occlusion, whereas no significant reduction in stroke volume is observed if treatment is delayed 2 h. In conclusion, neuroprotection in regional brain ischemia is possible following the delayed intravenous injection of low doses of bFGF providing the neurotrophin is conjugated to a BBB drug-targeting system.
Footnotes
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Supported by a Scientist Development grant (to D.W.) from the American Heart Association, Western States Affiliate, and by National Institutes of Health Grant NS-34698 (to W.M.P.).
- Abbreviations:
- bFGF
- basic fibroblast growth factor
- bio-bFGF
- biotinylated bFGF
- BBB
- blood-brain barrier
- SA
- streptavidin
- MCAO
- middle cerebral artery occlusion
- BDNF
- brain-derived neurotrophic factor
- MTT
- 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
- FBS
- fetal bovine serum
- DMEM
- Dulbecco's modified Eagle's medium
- ANOVA
- analysis of variance
- Received November 5, 2001.
- Accepted January 9, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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