Design of an Anti-HMGB1 Synthetic Antibody for In Vivo Ischemic/Reperfusion Injury Therapy.

High-mobility group box 1 (HMGB1) is a multifunctional protein. Upon injury or infection, HMGB1 is passively released from necrotic and activated dendritic cells and macrophages, where it functions as a cytokine, acting as a ligand for RAGE, a major receptor of innate immunity stimulating inflammation responses including the pathogenesis of cerebral ischemia/reperfusion (I/R) injury. Blocking the HMGB1/RAGE axis offers a therapeutic approach to treating these inflammatory conditions. Here, we describe a synthetic antibody (SA), a copolymer nanoparticle (NP) that binds HMGB1. A lightly cross-linked N-isopropylacrylamide (NIPAm) hydrogel copolymer with nanomolar affinity for HMGB1 was selected from a small library containing trisulfated 3,4,6S-GlcNAc and hydrophobic N-tert-butylacrylamide (TBAm) monomers. Competition binding experiments with heparin established that the dominant interaction between SA and HMGB1 occurs at the heparin-binding domain. In vitro studies established that anti-HMGB1-SA inhibits HMGB1-dependent ICAM-1 expression and ERK phosphorylation of HUVECs, confirming that SA binding to HMGB1 inhibits the proteins' interaction with the RAGE receptor. Using temporary middle cerebral artery occlusion (t-MCAO) model rats, anti-HMGB1-SA was found to accumulate in the ischemic brain by crossing the blood-brain barrier. Significantly, administration of anti-HMGB1-SA to t-MCAO rats dramatically reduced brain damage caused by cerebral ischemia/reperfusion. These results establish that a statistical copolymer, selected from a small library of candidates synthesized using an "informed" selection of functional monomers, can yield a functional synthetic antibody. The knowledge gained from these experiments can facilitate the discovery, design, and development of a new category of drug.

Engineering the Binding Kinetics of Synthetic Polymer Nanoparticles for siRNA Delivery.

The affinity of a synthetic polymer nanoparticle (NP) to a target biomacromolecule is determined by the association and dissociation rate constants (kon, koff) of the interaction. The individual rates and their sensitivity to local environmental influences are important factors for the on-demand capture and release a target biomacromolecule. Positively charged NPs for small interfering RNA (siRNA) delivery is a case in point. The knockdown efficacy of siRNA can be strongly influenced by the binding kinetics to the NP. Here, we show that kon and koff of siRNA to NPs can be individually engineered by tuning the chemical structure and composition of the NP. N-Isopropylacrylamide-based NPs functionalized with hydrophobic and amine monomers were used. koff decreased by increasing the amount of amine groups in the NP, whereas kon did not change. Importantly, NPs showing a low koff at pH 5.5 together with a high koff at pH 7.4 showed high knockdown efficiency when NP/siRNA complexes were packaged in lipid nanoparticles. These results provide direct evidence for the premise that the efficacy of an siRNA delivery vector is linked with the strong affinity to the siRNA in the endosome and low affinity in the cytoplasm.

Rational designing of an antidote nanoparticle decorated with abiotic polymer ligands for capturing and neutralizing target toxins.

Many of macromolecular toxins induce cell death by directly interacting with cells or induction of inflammatory cytokines. Abiotic polymer ligands (PLs) composed of functional monomers are able to bind and neutralize toxins in vivo and are of great interest for efficient antidotes. However, little has been reported about recognition and neutralization of target molecules in the bloodstream because of readily elimination from the bloodstream. Here, we report a rational design of PLs-decorated lipid nanoparticles (PL-NPs) for neutralizing a target toxin in vivo. PL that decorated on the NPs would cooperatively interacts with target biomacromolecules since the lipid molecules in NPs have a high degree of freedom. In the present study, N-isopropylacrylamide based PLs interacting with histones, major mediators of sepsis, were synthesized. Affinity between PL-NPs and histones depends on monomer composition and polymer length. The optimized PL-NP showed little affinity for plasma proteins. The PL-NPs inhibited the toxicity of histones both in vitro and in vivo, suggesting that PLs on the NPs cooperatively bound to histones and neutralized their toxicity. In addition, circulation time of optimized PL was significantly prolonged by the modification onto NPs. These results provide a platform for designing antidote nanoparticles neutralizing toxic biomacromolecules.

Non-invasive evaluation of neuroprotective drug candidates for cerebral infarction by PET imaging of mitochondrial complex-I activity.

The development of a diagnostic technology that can accurately determine the pathological progression of ischemic stroke and evaluate the therapeutic effects of cerebroprotective agents has been desired. We previously developed a novel PET probe, 2-tert-butyl-4-chloro-5-{6-[2-(2-(18)F-fluoroethoxy)-ethoxy]-pyridin-3-ylmethoxy}-2H-pyridazin-3-one ([(18)F]BCPP-EF) for detecting activity of mitochondrial complex I (MC-I). This probe was shown to visualize neuronal damage in the living brain of rodent and primate models of neurodegenerative diseases. In the present study, [(18)F]BCPP-EF was applied to evaluate the therapeutic effects of a neuroprotectant, liposomal FK506 (FK506-liposomes), on cerebral ischemia/reperfusion (I/R) injury in transient middle cerebral artery occlusion rats. The PET imaging using [(18)F]BCPP-EF showed a prominent reduction in the MC-I activity in the ischemic brain hemisphere. Treatment with FK506-liposomes remarkably increased the uptake of [(18)F]BCPP-EF in the ischemic side corresponding to the improvement of blood flow disorders and motor function deficits throughout the 7 days after I/R. Additionally, the PET scan could diagnose the extent of the brain damage accurately and showed the neuroprotective effect of FK506-liposomes at Day 7, at which 2, 3, 5-triphenyltetrazolium chloride staining couldn't visualize them. Our study demonstrated that the PET technology using [(18)F]BCPP-EF has a potent capacity to evaluate the therapeutic effect of drug candidates in living brain.

One-step encapsulation of siRNA between lipid-layers of multi-layer polycation liposomes by lipoplex freeze-thawing.

Small interfering RNA (siRNA) has the potential to be a candidate as a cure for intractable diseases. However, an appropriate vector is required for siRNA delivery because of the low transfection efficiency of siRNA without a vector and its easy degradation in vivo. Here, we report a simple, only one step, and efficient method for siRNA encapsulation into a lipidic nanocarrier by freeze-thawing: siRNA was entrapped between the lipid layers of multi-layer liposomes by freeze-thawing of lipoplexes composed of polycation liposomes (PCLs) and siRNA. siRNA-holding capacity to the PCL was increased by repeating freeze-thaw of the lipoplex up to 5cycles. Although siRNA in the conventional lipoplex was degraded after incubation in 90% fetal bovine serum for 72h, siRNA in the frozen and thawed lipoplex was not degraded. Interestingly, we found that the lipoplex formed a "packed multi-layer" structure after the freeze-thawing of "single-layer" PCL and siRNA complex, suggesting that siRNA exists between the lipid layers working as a binder. The frozen and thawed lipoplex showed significantly higher knockdown efficacy compared with the conventional lipoplex. In addition, PEGylated freeze-thawed lipoplexes delivered a higher amount of siRNA to a tumor in vivo compared with the PEGylated conventional ones. These results provide an attractive strategy for "one-step" encapsulation of siRNA into liposomes by freeze-thawing.

Complete genome structure of Gloeobacter violaceus PCC 7421, a cyanobacterium that lacks thylakoids.

The nucleotide sequence of the entire genome of a cyanobacterium Gloeobacter violaceus PCC 7421 was determined. The genome of G. violaceus was a single circular chromosome 4,659,019 bp long with an average GC content of 62%. No plasmid was detected. The chromosome comprises 4430 potential protein-encoding genes, one set of rRNA genes, 45 tRNA genes representing 44 tRNA species and genes for tmRNA, B subunit of RNase P, SRP RNA and 6Sa RNA. Forty-one percent of the potential protein-encoding genes showed sequence similarity to genes of known function, 37% to hypothetical genes, and the remaining 22% had no apparent similarity to reported genes. Comparison of the assigned gene components with those of other cyanobacteria has unveiled distinctive features of the G. violaceus genome. Genes for PsaI, PsaJ, PsaK, and PsaX for Photosystem I and PsbY, PsbZ and Psb27 for Photosystem II were missing, and those for PsaF, PsbO, PsbU, and PsbV were poorly conserved. cpcG for a rod core linker peptide for phycobilisomes and nblA related to the degradation of phycobilisomes were also missing. Potential signal peptides of the presumptive products of petJ and petE for soluble electron transfer catalysts were less conserved than the remaining portions. These observations may be related to the fact that photosynthesis in G. violaceus takes place not in thylakoid membranes but in the cytoplasmic membrane. A large number of genes for sigma factors and transcription factors in the LuxR, LysR, PadR, TetR, and MarR families could be identified, while those for major elements for circadian clock, kaiABC were not found. These differences may reflect the phylogenetic distance between G. violaceus and other cyanobacteria.

Complete genome structure of the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1.

The entire genome of a thermophilic unicellular cyanobacterium, Thermosynechococcus elongatus BP-1, was sequenced. The genome consisted of a circular chromosome 2,593,857 bp long, and no plasmid was detected. A total of 2475 potential protein-encoding genes, one set of rRNA genes, 42 tRNA genes representing 42 tRNA species and 4 genes for small structural RNAs were assigned to the chromosome by similarity search and computer prediction. The translated products of 56% of the potential protein-encoding genes showed sequence similarity to experimentally identified and predicted proteins of known function, and the products of 34% of these genes showed sequence similarity to the translated products of hypothetical genes. The remaining 10% lacked significant similarity to genes for predicted proteins in the public DNA databases. Sixty-three percent of the T. elongatus genes showed significant sequence similarity to those of both Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120, while 22% of the genes were unique to this species, indicating a high degree of divergence of the gene information among cyanobacterial strains. The lack of genes for typical fatty acid desaturases and the presence of more genes for heat-shock proteins in comparison with other mesophilic cyanobacteria may be genomic features of thermophilic strains. A remarkable feature of the genome is the presence of 28 copies of group II introns, 8 of which contained a presumptive gene for maturase/reverse transcriptase. A trace of genome rearrangement mediated by the group II introns was also observed.