5-Aminolevulinic acid and the blood-brain barrier - A review

Until recently little has been known about the movement of 5-aminolevulinic acid (5-ALA) between blood and brain. In the last several years 5-ALA experienced a renaissance after its ability to induce porphyrin fluorescence in malignant tissues was discovered and this observation was extended to malignant brain tumors. Presently, 5-ALA is routinely used in certain centers for highlighting malignant glioma tissue intraoperatively and thereby aiding resection of this tumor entity. However, in order to understand the apparent tumor selectivity of 5-ALA induced porphyrins, insight into the mechanisms governing 5-ALA movement across the blood-brain barrier (BBB) in healthy and malignant brain tissue is crucial. This especially bears weight in view of the potential use of 5-ALA-induced porphyrins, which are phototoxic, for augmental phototherapy of the resection cavity. This article reviews the available literature dealing with 5-ALA blood-brain barrier transport.