ABSTRACT
Endosomolytic peptides are often coupled to drug delivery systems to enhance endosomal escape, which is crucial for the delivery of macromolecular drugs that are vulnerable to degradation in the endolysosomal pathway. Melittin is a 26 amino acid peptide derived from bee venom that has a very high membranolytic activity. However, such lytic peptides also impose a significant safety risk when applied in vivo as they often have similar activity against red blood cells and other nontarget cell membranes. Our aim is to control the membrane-disrupting capacity of these peptides in time and space by physically constraining them to a nanocarrier surface in such a way that they only become activated when delivered inside acidic endosomes. To this end, a variety of chemical approaches for the coupling of lytic peptides to liposomes via functionalized PEG-lipids were explored, including maleimide-thiol chemistry, click-chemistry, and aldehyde-hydrazide chemistry. The latter enables reversible conjugation via a hydrazone bond, allowing for release of the peptide under endosomal conditions. By carefully choosing the conjugation site and by using a pH activated analog of the melittin peptide, lytic activity toward a model membrane is completely inhibited at physiological pH. At endosomal pH the activity is restored by hydrolysis of the acid-labile hydrazone bond, releasing the peptide in its most active, free form. Furthermore, using an analogue containing a nonhydrolyzable bond as a control, it was shown that the activity observed can be completely attributed to release of the peptide, validating dynamic covalent conjugation as a suitable strategy to maintain safety during circulation.
Subject(s)
Delayed-Action Preparations/metabolism , Endosomes/metabolism , Liposomes/metabolism , Melitten/metabolism , Amino Acid Sequence , Click Chemistry , Delayed-Action Preparations/chemistry , Hydrazones/chemistry , Hydrazones/metabolism , Hydrogen-Ion Concentration , Liposomes/chemistry , Maleimides/chemistry , Maleimides/metabolism , Melitten/chemistry , Phosphatidylethanolamines/chemistry , Phosphatidylethanolamines/metabolism , Polyethylene Glycols/chemistry , Polyethylene Glycols/metabolism , Sulfhydryl Compounds/chemistry , Sulfhydryl Compounds/metabolismABSTRACT
OBJECTIVE: Shock is defined as a change of circulation which results in hypoxia at the tissue level. Lactate and base deficit (BD) are associated with a high risk of multiple organ dysfunction in trauma patients. In this study we evaluated the influence of early recognition of shock in trauma patients. METHODS: In a retrospective study, relevant data were collected from the Radboud University Nijmegen Medical Centre (RUNMC) database between January 2009 and December 2010. Vital parameters were taken at the accident scene, and patients were divided into four shock classes. Arterial blood gas analysis was performed on arrival in the emergency department. Statistical analysis was performed with SPSS version 17.0. Statistical significance was assumed at p ≤ 0.05. RESULTS: A total of 255 patients were included. Patients who suffered from prehospital shock, and those who were intubated prior to hospital admittance showed a bad outcome, presenting with a more severe metabolic acidosis, higher ISS and higher mortality. There was a significant difference for bicarbonate and BD between shockclass I + II and shockclass III + IV, respectively 22.7 vs. 19.7 and -3.4 vs. -6.9. Intubated patients had a decreased bicarbonate and BD compared to not intubated patients, respectively 21.81 vs. 23.24 and -5.08 vs. -2.38. Mortality and ISS were higher in patients in shock class III and IV. Significant differences in serum lactate levels were not found. CONCLUSIONS: Prehospital shock influences patient outcome; outcome of patients is related to initial shock classification. Further validation of our shock classification, however, is necessary.
