Novel functionalization strategies of polymeric nanoparticles as carriers for brain medications.

For targeted brain delivery, nanoparticles (NPs) should bypass the blood-brain barrier (BBB). Novel functionalization strategies, based on low-density lipoprotein receptor (LDLR) binding domain, have been here tested to increase the brain targeting efficacy of poly d,l-lactic-co-glycolic acid (PLGA) NPs, biodegradable and suited for biomedical applications. Custom-made PLGA NPs were functionalized with an apolipoprotein E modified peptide (pep-apoE) responsible for LDLR binding, or with lipocalin-type prostaglandin-d-synthase (L-PGDS), highly expressed in the brain. At the comparison of pep-apoE and L-PGDS sequences, a highly homologs region was here identified, indicating that also L-PGDS could bind LDLR. Non-functionalized and functionalized NPs did not affect the viability of cultured human dendritic cells, protagonists of the immune response, and did not activate them to a proinflammatory profile. At 2 h after intravenous injection in mice, functionalized, but not the non-functionalized ones, fluorescent-tagged NPs were observed in the cerebral cortex parenchyma. The NPs were mostly internalized by neurons and microglia; glial cells showed a weak activation. The findings indicate that the tested functionalization strategies do not elicit adverse immune responses and that the peptidic moieties enable BBB traversal of the NPs, thus providing potential brain drug carriers. These could be especially effective for brain diseases in which LDLR is involved. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 847-858, 2017.

Human Lipocalin-Type Prostaglandin D Synthase-Based Drug Delivery System for Poorly Water-Soluble Anti-Cancer Drug SN-38.

Lipocalin-type prostaglandin D synthase (L-PGDS) is a member of the lipocalin superfamily, which is composed of secretory transporter proteins, and binds a wide variety of small hydrophobic molecules. Using this function, we have reported the feasibility of using L-PGDS as a novel drug delivery vehicle for poorly water-soluble drugs. In this study, we show the development of a drug delivery system using L-PGDS, one that enables the direct clinical use of 7-ethyl-10-hydroxy-camptothecin (SN-38), a poorly water-soluble anti-cancer drug. In the presence of 2 mM L-PGDS, the concentration of SN-38 in PBS increased 1,130-fold as compared with that in PBS. Calorimetric experiments revealed that L-PGDS bound SN-38 at a molecular ratio of 1:3 with a dissociation constant value of 60 µM. The results of an in vitro growth inhibition assay revealed that the SN-38/L-PGDS complexes showed high anti-tumor activity against 3 human cancer cell lines, i.e., Colo201, MDA-MB-231, and PC-3 with a potency similar to that of SN-38 used alone. The intravenous administration of SN-38/L-PGDS complexes to mice bearing Colo201 tumors showed a pronounced anti-tumor effect. Intestinal mucositis, which is one of the side effects of this drug, was not observed in mice administered SN-38/L-PGDS complexes. Taken together, L-PGDS enables the direct usage of SN-38 with reduced side effects.

Pharmacokinetics of recombinant human lipocalin-type prostaglandin D synthase/beta-trace in canine.

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is identical to beta-trace, a major protein in human cerebrospinal fluid (CSF), and acts as both a PGD(2)-producing enzyme and as an extracellular transporter for lipophilic ligands. In this study, we investigated the pharmacokinetics of recombinant human L-PGDS (rh-L-PGDS) in canines. After an intravenous bolus injection of rh-L-PGDS, the serum concentration decreased bi-exponentially with a half-life of the terminal line phase of 0.77h, which was markedly shorter than that of other proteins with the same molecular weight as that of rh-L-PGDS. The distribution volume was 55.4ml/kg, which was close to the volume of canine circulation plasma, indicating that the administrated rh-L-PGDS was distributed mainly in the blood. Only 10.3% of the administered rh-L-PGDS was excreted to the urine, suggesting that rh-L-PGDS was actively degraded within the body. After an intrathecal injection, the peak serum concentration of rh-L-PGDS was observed at 4-5h. The area under the plasma concentration-time curve obtained for 12h after the intrathecal injection was one third of the value for 3h after the intravenous injection, suggesting that at least one third of the intrathecally injected rh-L-PGDS shifted to the blood.

Lipocalin-type prostaglandin D synthase is up-regulated in oligodendrocytes in lysosomal storage diseases and binds gangliosides.

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is a dually functional protein, acting both as a PGD2-synthesizing enzyme and as an extracellular transporter of various lipophilic small molecules. L-PGDS is expressed in oligodendrocytes (OLs) in the central nervous system and is up-regulated in OLs of the twitcher mouse, a model of globoid cell leukodystrophy (Krabbe's disease). We investigated whether up-regulation of L-PGDS is either unique to Krabbe's disease or is a more generalized phenomenon in lysosomal storage disorders (LSDs), using LSD mouse models of Tay-Sachs disease, Sandhoff disease, GM1 gangliosidosis and Niemann-Pick type C1 disease. Quantitative RT-PCR revealed that L-PGDS mRNA was up-regulated in the brains of all these mouse models. In addition, strong L-PGDS immunoreactivity was observed in OLs, but not in either astrocytes or microglia in these models. Thus, up-regulation of L-PGDS appears to be a common response of OLs in LSDs. Moreover, surface plasmon resonance analyses revealed that L-PGDS binds GM1 and GM2 gangliosides, accumulated in neurons in the course of LSD, with high affinities (KD = 65 and 210 nm, respectively). This suggests that L-PGDS may play a role in scavenging harmful lipophilic substrates in LSD.