Short peptide motifs for long-lasting anchoring to the cell surface

A rational design strategy has been developed for the construction of stable peptide-based anchors for the efficient modification of cell surfaces. Six types of peptide composed of five residues with divalent hydrophobic groups have been designed using this new strategy. Among them, a peptide with a sequence of NBD-Lys-Lys(X)-Lys-Lys-Lys(X)-NH2 (NBD: fluorophore, Lys(X): N-ε-palmitoyl-l-lysine) was found to show the highest modification efficacy and longevity in culture medium. The good performance of this peptide was attributed to (1) its high aqueous solubility, which allowed it to partition from the medium to the cell surface, and (2) the high binding affinity of the saturated palmitoyl groups to the cell membrane. We found that the distribution of the peptide was affected by recycling endosome, which enabled the representation of the peptide following its endocytotic disappearance from the cell membrane. Biotin was also presented on the cell surface using this peptide-based anchor to examine its recognition by streptavidin. The efficacy of the recognition process increased as the length of the oligoethylene glycol spacer increased, indicating that it was necessary for the biotin tag to move away from the membrane glycoproteins on the cell surface to facilitate its efficient recognition by streptavidin.

Effect of peptide content on the regulation of transgene expression by protein kinase Cα-responsive linear polyethylenimine-peptide conjugates

We examined a series of linear polyethylenimine (LPEI)-based nanocarriers that activate transgene expression in response to cancer-specific protein kinase Cα (PKCα). Eight types of LPEI-peptide conjugate differing in peptide content and number were synthesized using click chemistry. The conjugates could form polyplexes with pDNA through electrostatic interaction, but the degree of pDNA condensation, sizes, and surface charges of the resulting polyplexes depended on the pendant-peptide content and number. None of the polyplexes showed significant cytotoxicity toward human hepatoma cells (HepG2). Furthermore, pendant peptide content and number markedly affected transgene activation in response to PKCα. To achieve an all-or-none response to PKCα, we determined the optimum peptide content and number in LPEI-peptide conjugates as ≈6 mol% and ≈40 peptides/conjugate.

Reply to the letter from Grunze and Walden

Professors Grunze and Walden sent a letter associated with our article. In this letter, we reply to their comments.

Multi-drug-resistant Staphylococcus aureus and future chemotherapy

Staphylococcus (S.) aureus silently stays as our natural flora, and yet sometimes threatens our life as a tenacious pathogen. In addition to its ability to outwit our immune system, its multi-drug resistance phenotype makes it one of the most intractable pathogenic bacteria in the history of antibiotic chemotherapy. It conquered practically all the antibiotics that have been developed since 1940s. In 1961, the first MRSA was found among S. aureus clinical isolates. Then MRSA prevailed throughout the world as a multi-resistant hospital pathogen. In 1997, MRSA strain Mu50 with reduced susceptibility to vancomycin was isolated. Vancomycin-intermediate S. aureus (VISA), so named according to the CLSI criteria, was the product of adaptive mutation of S. aureus against vancomycin that had long been the last resort to MRSA infection. Here, we describe the genetic basis for the remarkable ability of S. aureus to acquire multi-antibiotic resistance, and propose a novel paradigm for future chemotherapy against the multi-resistant pathogens.

Nitroxyl radicals-modified dendritic poly(l-lysine) as a contrast agent for Overhauser-enhanced MRI

Overhauser-enhanced magnetic resonance imaging (OMRI), which is a double resonance technique, creates images of free radical distribution in animals by enhancing the water proton signal intensity by the overhauser effect. In this study, we constructed a contrast agent by combining PROXYL groups that have nitroxyl radicals with PEG-modified dendritic poly(l-lysine) that accumulates in the tumor by enhanced permeability and retention (EPR) effect. Addition of the PROXYL groups at the PEG chains' termini on KG6 was advantageous in OMRI, because the ESR signal of the nitroxyl radical was maintained without decay caused by mobility restriction, even if the PROXYL groups were attached at 25 mol% on one molecule. After intramuscular injection of the molecule modified at 25 mol%, that is, PR25-PEG-KG6, a significant OMRI signal was observed at the injected site. However, no signal was detected in the tumor after intravenous injection of PR25-PEG-KG6 to a tumor-bearing mouse, although PR25-PEG-KG6 itself accumulated in the tumor. The reason was that the nitroxyl radicals were immediately reduced in the blood after the injection, suggesting that use of stable nitroxyl radicals will enable detection of tumors by OMRI after intravenous injection.

Long-term complete remission of multiple extranodal natural killer/T-cell-type posttransplant lymphoproliferative disorder after surgical resection: a case report

BACKGROUND

Posttransplant lymphoproliferative disorder (PTLD) is a life-threatening complication of organ transplantation that results from immunosuppression therapy. Most cases of PTLD derive from the B-cell lineage. T-cell PTLD, particularly natural killer (NK)/T-cell PTLD, is quite rare; only a few cases have been described.

CASE REPORT

A 42-year-old woman received a living-related renal allograft from her father. Sixteen years after transplantation, the patient presented with a 1-week history of low-grade fever and epigastralgia. Computed tomography revealed intestinal masses and a right upper lung lobe mass. Gallium scintigraphy showed uptake in the abdominal mass. Epstein-Barr virus-related antibody was not detected in the patient's serum sample. We performed extirpation of the jejunum and ileum tumors. The pathologic findings showed that these 2 tumors were NK/T-cell lymphoma. After the operation, the lung mass rapidly enlarged, and right upper lobectomy was performed. The right upper lung lobe tumor showed the same histopathologic findings as the small bowel tumor. The final histologic diagnosis was established as multiple extranodal NK/T cell type PTLD of the small bowel and right upper lung lobe.

CONCLUSIONS

After reduction of the immunosuppressive agent, no recurrence of PTLD has been observed for the past 9 years.

In vivo evaluation of lateral lipid chain packing in human stratum corneum

BACKGROUND/AIMS

The matrix of intercellular lipids (ICL) of stratum corneum (SC) plays an important role in the barrier function of SC. It is important to understand the structure of the ICL matrix for dermatology and cosmetic science. Several methods exist for the analysis of the structure; however, it is difficult to conduct these analyses noninvasively.

METHODS

We have developed a method for the analysis of the lateral packing of ICL using Raman spectroscopy. As a proof-of-principle experiment, we prepared a human SC sheet sample and analyzed its structure by the proposed method and by a conventional method involving X-ray diffraction. We compared the results of both methods. In addition, we applied the proposed method to living human skin, and we analyzed the lateral packing of ICL of SC taken from three separate body sites.

RESULTS

The results of our method corresponded to those of the conventional method. We detected regional differences of ICL lateral packing using our method in vivo. The results indicated that the packing of ICL in SC taken from the forearm and upper arm are more ordered than that taken from the cheek.

CONCLUSION

The results verify that our developed method allows the evaluation of the lateral packing of ICL inside the SC layer of the skin in vivo. Using this method, we can detect regional differences of SC samples taken from various body sites.

Valproic acid enhances the effect of bone marrow-derived mononuclear cells in a rat ischemic stroke model

Bone marrow derived mononuclear cell (MNC) transplantation is a potential therapy for ischemic stroke. Here, we hypothesized that valproic acid (VPA) would modulate transplantation effects of MNCs in a rat ischemic stroke model. Male Sprague-Dawley rats were subjected to transient 90min middle cerebral artery occlusion. Infarct volume, neurological outcome, and immunohistological assessments were performed 7 days after ischemia. MNCs injected 6 or 24h but not 48 or 72h after ischemia significantly reduced infarct volume and improved neurological deficits. We then tested whether the therapeutic window of MNC transplantation could be expanded through combination therapy with VPA. MNC transplantation at 48h combined with VPA injection three times at 47, 53, and 72h after ischemia significantly ameliorated infarct volume and neurological deficits compared to a vehicle group. Combination therapy reduced the number of myeloperoxidase-positive cells, ionized calcium binding adapter molecule 1-positive cells, tumor necrosis factor-α-positive cells, and von Willebrand factor-positive cells in the ischemic boundary zone. The number of engrafted MNCs that were fluorescently labeled with PKH 26, on day 7, was significantly higher after combination therapy than after that MNC transplantation alone. Our results demonstrated that combination therapy with VPA enhanced the anti-inflammatory and vasculo-protective effects against endothelial damage following ischemia, and increased the survival of transplanted cells, leading to expansion of the therapeutic time window for MNC transplantation. Together, these findings suggest that VPA may be an appropriate partner for cell-based treatment of ischemic stroke.

Histidinylated poly-L-lysine-based vectors for cancer-specific gene expression via enhancing the endosomal escape

In this work, we synthesized a series of poly-L-lysine (PLL)-based polymers for gene delivery, by modifying the PLL with both cationic peptide and histidine. The peptide moieties serve as cationic centers for polyplex formation, and also as substrates for protein kinase Cα (PKCα), which is specifically activated in many types of cancer cells, to achieve cancer-specific gene expression. The histidine groups serve as buffering moieties to increase the ability of the plasmid DNA (pDNA)-polymer complex (polyplex) to escape the endosome and thus to promote expression of the pDNA in the transfected cells. The facile synthesis of the polymers proceeded by modifying the PLL with side-group-protected peptide and protected histidine, followed by deprotection of the functional groups. The synthesized polymers showed significant buffering capacity over the neutral to acidic pH range and showed less cytotoxicity in vitro compared with histidine-unmodified polymers. The polyplexes successfully showed PKCα-responsive gene expression immediately after their introduction into cancer cells and the gene expression continued for at least 24 h. These PLL-based carriers thus show promise for cancer-targeted gene therapy.

A protein kinase assay based on FRET between quantum dots and fluorescently-labeled peptides

A novel protein kinase assay was developed, based on FRET between QDs and fluorescently-labeled substrate peptides. The negatively charged QDs recognize the change in net charge of the peptide upon phosphorylation. Despite its simple mechanism, this assay is sensitive and robust enough to be applied to the evaluation of protein kinase inhibitors.

Postoperative Clostridium difficile infection with PCR ribotype 078 strain identified at necropsy in five Thoroughbred racehorses

Clostridium difficile is an important cause of acute enterocolitis in horses. We describe five cases of C difficile infection occurring postoperatively in Thoroughbred racehorses. Following diarrhoea or colic accompanied by a marked increase in packed cell volume (to ≥60 per cent) and leucopenia (≤4000 cells/μl) within two to four days after surgery in all five horses, four of them died or were euthanased because of colitis or severe diarrhoea. In these four horses, necrotising entero-typhlo-colitis was revealed by postmortem examination, and C difficile was recovered from the contents of the small and/or large intestine. The remaining horse was euthanased because of marked decline in general condition and the presence of a lung abscess, from which C difficile was isolated. The horse had had severe postoperative diarrhoea before the onset of respiratory disorder; laboratory tests for C difficile were not performed on the faeces. All C difficile isolates were toxin-A-positive, toxin-B-positive and actin-specific ADP-ribosyltransferase (CDT)-positive. The isolates were indistinguishable by pulsed field gel electrophoresis analysis, PCR ribotyping, and slpA sequence typing, and the slpA sequences and PCR ribotype patterns were identical to those of known PCR type 078. This case sequence might have been healthcare-associated infection, although there was about a four-month interval between each disease onset.

CANCER-SPECIFIC GENE CARRIERS RESPONDING TO CANCER MICROENVIRONMENT: ACIDOSIS AND HYPER-ACTIVATED PROTEIN KINASES

Protein kinase (PK)-responsive gene carriers modified with polyethylene glycol (PEG) chains using an acid-labile linker were developed. These carriers were obtained by modifying the PEG chains and substrate peptides for the PKs (PKA or PKCα) on the branched polyethyleneimine main chain. Polyplexes formed from these carriers and plasmid DNA (pDNA) were stably dispersed under neutral pH medium. The polyplexes were also taken up by cells on the release of the PEG chains under the slightly acidic extracellular pH associated with cancer cells. The polyplexes taken up by cells resulted in gene expression when the substrate peptides were phosphorylated by the intracellular PKs to release pDNA from the polyplexes. These novel gene carriers are expected to be promising for cancer-specific gene therapy via intravenous administration.

Branched polyethylenimine-based PKCα-responsive gene carriers

We examined in vitro performance of the branched polyethylenimine (bPEI)-based gene carriers which respond to cancer-specific activation of protein kinase Cα (PKCα) to express plasmid DNA. The carriers were synthesized straightforward by using amide bond formation between a peptide terminal carboxyl and a primary amine group of bPEI. To examine the effect of the peptide contents in the carrier, we prepared several carriers with various peptide contents. The obtained polymers form polyplexes with tighter condensation of plasmid DNA than our previous gene carriers. After internalization of the polyplexes via endocytosis, the polyplexes effectively escaped from the endosome into cytosol. Then, the polyplexes showed a clear-cut response to PKCα to release plasmid DNA for gene expression. We determined the optimum contents of the peptides in carriers as 5 mol% to achieve the clear-cut response to PKCα.

PEG-silica-modified gold nanorods that retain their optical properties in tumor tissues

Gold nanorods modified with polyethylene glycol (PEG) chains via Au-S bonds form aggregates, and their absorption spectra broaden in tumor tissues. In contrast, the gold nanorods modified here via the crosslinking of PEG chains on the silica shell on gold nanorods showed enhanced permeability and retention effects and retained the optical properties of the original gold nanorods in tumor tissues.