Search

Bioconjugation with polyethylene glycol (PEG) is important for protein drug development as it has improved biological stability. In contrast, proteins including PEGylated ones are susceptible to physicochemical stresses. Particularly, protein drugs in solution may form aggregates or subvisible particles if they are exposed to dropping stress during transportation. However, many PEGylation studies have focused on its usefulness, such as the extension of half-life in blood, and changes in the physical properties or biological responses of PEGylated proteins under dropping stress remain unexplored. Here, we prepared four PEGylated ovalbumin (PEG-OVA) molecules conjugated with different lengths (5 or 20 kDa) and numbers (large [L] or small [S]) of PEG, analyzed the formation of subvisible particles under dropping stress, and examined their impact on antibody production and clearance. Under dropping stress, the aggregated particle concentration of 20 kDa PEG-OVA (S) and (L) solutions was approximately 3-fold that of the OVA solution. Moreover, administration of 20 kDa PEG-OVA with dropping stress induced anti-PEG antibody production and clearance of PEG-OVA. As a mechanism, dropping stress could enhance the uptake of 20 kDa PEG-OVA (L) by macrophages. These findings could provide insights into proper transportation conditions to ensure the quality of PEGylated protein drugs.

Nanosize plasma proteins could be used as a biomimetic drug delivery system (DDS) for cancer treatment when loaded with anticancer drugs based on the fact that plasma proteins can serve as a source of nutrients for cancer cells. This prompted us to investigate the potential of α1-acid glycoprotein (AGP) for this role because it is a nanosize plasma protein and binds a variety of anticancer agents. Pharmacokinetic analyses indicated that AGP is distributed more extensively in tumor tissue than human serum albumin, which was already established as a cancer DDS carrier. AGP is possibly being incorporated into tumor cells via endocytosis pathways. Moreover, a synthetic AGP-derived peptide which possesses a high ability to form an α-helix, as deduced from the primary structure of AGP, was also taken up by the tumor cells. AGP loaded with anticancer agents, such as paclitaxel or nitric oxide, efficiently induced tumor cell death. These results suggest that AGP has the potential to be a novel DDS carrier for anticancer agents.

Nanosize plasma proteins could be used as a biomimetic drug delivery system (DDS) for cancer treatment when loaded with anticancer drugs based on the fact that plasma proteins can serve as a source of nutrients for cancer cells. This prompted us to investigate the potential of α

Red blood cell (RBC) transfusions are the gold standard in cases of massive hemorrhage, but induce hepatic ischemia-reperfusion injury, a serious complication associated with hemorrhage and RBC resuscitation. Thus, the development of a novel resuscitable fluid that is not associated with hepatic ischemia-reperfusion injury would be desirable. It was reported that exogenous carbon monoxide (CO) treatment ameliorated hepatic ischemia-reperfusion injury accompanying liver transplantation. This suggests that transfusions with CO-bound RBC (CO-RBC) might protect against hepatic ischemia-reperfusion injury following massive hemorrhage and resuscitation compared with RBC resuscitation. To investigate this, we created a hemorrhagic shock model rat, followed by resuscitation with RBC and CO-RBC. Hepatic ischemia-reperfusion injury and the destruction of hepatic cytochrome P450 (CYP) were significantly ameliorated in the CO-RBC resuscitation group compared with the RBC resuscitation group. The free heme derived from the destruction of hepatic CYP was correlated with hepatic oxidation and injury, suggesting that CO-RBC was a major factor in the amelioration of hepatic ischemia-reperfusion injury induced by hemorrhage and resuscitation via hepatic CYP protection. These results indicate that CO-RBC has potential for use as a resuscitative fluid in blood transfusion and does not suffer from the limitations associated with the RBC transfusions that are currently in use.

Macromolecules have been developed as carriers of low-molecular-weight drugs in drug delivery systems (DDS) to improve their pharmacokinetic profile or to promote their uptake in tumor tissue via enhanced permeability and retention (EPR) effects. We have previously demonstrated that poly-nitric oxide (NO) conjugated human serum albumin (Poly-SNO-HSA) has the potential to be a DDS carrier capable of accumulating NO in tumors. However, the stability of Poly-SNO-HSA in the circulation has to be improved, and its optimal molecular size for using the EPR effects has to be evaluated. In the present study, we performed two tuning methods for refining Poly-SNO-HSA, namely, pegylation and dimerization. We observed that pegylation enhanced the stability of Poly-SNO-HSA both in vitro and in vivo, and that dimerization of Poly-SNO-HSA enhanced the antitumor activity via more efficient delivery of NO in Colon 26 tumor-bearing mice. Intriguingly, dimerization resulted in a 10 times higher antitumor activity. These data suggest that pegylation and dimerization of Poly-SNO-HSA are very important tuners to optimize NO stability and accumulation, and thereby effect, in tumors. Thus, polyethylene glycol-Poly-SNO-HSA dimer seems to be a very appealing and safe NO carrier and thereby a strong candidate as an antitumor drug in future development of cancer therapeutics.

8-Nitroguanosine 3′,5′-cyclic monophosphate (8-nitro-cGMP) is a nitric oxide metabolite and an important second messenger. 8-Nitro-cGMP reacts with sulfhydryl groups forming a novel posttranslational modification, namely, S -guanylation. In this work, we found, by using a quantitative competition enzyme-linked immunosorbent assay procedure, that S -guanylated human serum albumin ( S -cGMP-HSA) is a component of normal plasma, and that hemodialysis patients decrease its concentration, on an average, from 68 to 34nM. End-stage renal disease is often accompanied by septicemia, and we found that S -cGMP-HSA possesses an in vitro antibacterial effect with half maximal inhibitory concentration of approximately 2μM against Escherichia coli American Type Culture Collection. Our findings indicate that S -cGMP-HSA can be regarded as an endogenous antibacterial agent in healthy conditions and as a useful new class of antibacterial agents with a circulation time sufficient for in vivo biological activity. The clinical development of S -cGMP-HSA as a safe and strong antibacterial agent arisen from endogenous posttranslational modification would be expected. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association.