ABSTRACT
Adrenomedullin (AM) is a vasodilator peptide with pleiotropic effects, including cardiovascular protection and anti-inflammation. Because of these beneficial effects, AM appears to be a promising therapeutic tool for human diseases, while intravenous injection of AM stimulates sympathetic nerve activity due to short-acting potent vasodilation, resulting in increased heart rate and renin secretion. To lessen these acute reactions, we conjugated the N-terminal of human AM peptide with polyethylene glycol (PEG), and examined the biological properties of PEGylated AM in the present study. PEGylated AM stimulated cAMP production, an intracellular second messenger of AM, in cultured human embryonic kidney cells expressing a specific AM receptor in a dose-dependent manner, as did native human AM. The pEC50 value of PEGylated AM was lower than human AM, but no difference was noted in maximum response (Emax) between the PEGylated and native peptides. Intravenous bolus injection of 10nmol/kg PEGylated AM lowered blood pressure in anesthetized rats, but the acute reduction became significantly smaller by PEGylation as compared with native AM. Plasma half-life of PEGylated AM was significantly longer than native AM both in the first and second phases in rats. In summary, N-terminal PEGylated AM stimulated cAMP production in vitro, showing lessened acute hypotensive action and a prolonged plasma half-life in comparison with native AM peptide in vivo.
Subject(s)
Adrenomedullin/administration & dosage , Cyclic AMP/biosynthesis , Peptides/administration & dosage , Polyethylene Glycols/administration & dosage , Adrenomedullin/chemistry , Adrenomedullin/pharmacokinetics , Animals , Blood Pressure/drug effects , Humans , Hypertension/metabolism , Kidney/metabolism , Peptides/chemistry , Polyethylene Glycols/chemistry , Polyethylene Glycols/pharmacokinetics , Rats , Receptors, Adrenomedullin/biosynthesisABSTRACT
The use of N(alpha)-tert.-butyloxycarbonyl-N(pi)-benzyloxymethylhistidine [Boc-His(Bom)] in peptide synthesis results in a serious level of side products arising from the generation of formaldehyde during the HF cleavage reaction. In particular, when treating a His(Bom)-containing peptide having Cys at the N-terminus by HF, this leads to almost complete conversion of the Cys-peptide to thiazolidyl (Thz)-peptide unless precautions are taken. Also, the reaction of formaldehyde with the N-terminal Trp and the N-methylanthranyl (Nma) group was found to produce tetrahydro-beta-carboline and dihydroquinazolin derivatives, respectively, upon isolation from HF mixtures. The addition of cysteine as a scavenger in HF proved to be effective for suppressing modification arising from the generation of formaldehyde.
