Targeted Delivery Of BDNF Into The Brain Mediated By Rabies Virus Glycoprotein-derived Peptide

Neurodegenerative disorder, stroke and brain cancer become difficult diseases to treat because most medicines have trouble crossing the blood-brain barrier (BBB) Some macromolecular proteins, such as neurotrophic factors, have been known the exact neuroprotective effect on brain cells, but unfortunately, they can not cross the BBB. Brain-derived neurotrophic factor (BDNF) can rescue the death of cells and have survival and growth-promoting actions on dorsal root ganglion cells, hippocampal and cortical neutrons, peripheral sensory neurons. However, BDNF is owing to the negligible permeability to the brain capillary endothelial wall of the BBB in vivo.To overcome this, we asked whether the strategy used by cell penetrating peptides (CPPs) to enter the central nervous system (CNS) could also be used to enable delivery of macromolecular proteins. We chose the peptides derived from rabies virus glycoprotein (RDP) to test this hypothesis because they show a high degree of neurotropism in vivo. The rabies virus glycoprotein (rabies virus glycoprotein) is proven to carry the siRNA and EGFP, and other macromolecules across the blood-brain barrier ability.Rhodamine B labelled with RDP was intravenous injected into mice. After intravenous injection protein into mice in the same amount of proteins, the mice were sacrificed after 15min and 5h respectively, and then tissues were obtained and sliced. Rhodamine B labeled with RDP was observed by fluorescence microscopy in vivo distribution in the different time points.By molecular cloning method, fusing RDP nucleotide sequence 189/330 with reporter gene firefly Luciferase (Luc) produced recombinant plasmids, pET28a(+)-RDP-Luc, at the same time, constructed recombinant plasmids of Luc without RDP nucleotide sequence, pET28a(+)-Luc which served as control. After positive clones obtained, fusion protein is induced to be expressed on the condition of 16℃,210r/m,6h, IPTG 1.0mM in E. coli. (BL21). The inerest protein was obtained through sonication method and centrifuged. The fusion protein was detected by the SDS-PAGE gel electrophoresis for soluble expression and calculated the expression of target protein.Total protein is measured through Folin-phenol method.luciferase assay kit was applied to detecting the activity of the target protein. Random healthy Kunming mice were divided into four groups:group 1 was the control group, injected with saline; group 2 was injected without RDP, recombinant luciferase; group 3 was injected with recombinant protein containing RDP189-luc; group 4 was injected with recombinant protein RDP330-luc. At time point of 15min,30min, 1h,5h after intravenous injection into mice, central nervous system was taken to detect luciferase activity and protein content in the homogenate.The experimental results show that rhodamine B labeled with RDP fragment issued red tail administered after intravenously 15 min, observed in the central nervous system, distributed in neurons and glial cells, while the distribution of the peripheral tissues with the control groups were similar. It shows that the RDP can quickly enter the brain through the blood-brain-barrier, and is mainly distributed in the central nervous system.In the carrying the luciferase into the brain experiments by the RDP, after 15 min in the central nervous system were detected in higher luciferase activity, indicating that the RDP quickly through the blood-brain barrier, has a strong neurotropic, RDP330 peptides carrying the luciferase activity in the hippocampus is higher than the cortex, RDP 189 the fusion protein activity in the cortex above the hippocampus. After 5 hours, luciferase activity is similar to the control group, which indicates that the fusion protein is able to degraded quickly by organism degradation and it has high biological security. From the experiment results, it can be known that (Ⅰ) the RDP is capable of carrying the luciferase protein macromolecules into the brain and this process is very fast; (Ⅱ) the RDP fusion protein distribution in the brain is different; (III) the RDP330 fusion protein in the hippocampus is more active than the RDP189 fusion protein, which states that the RDP330 is more neurotropic.