Polyamine Modification Increases the Permeability of Proteins at the Blood‐Nerve and Blood‐Brain Barriers

Abstract

The permeability of the blood‐nerve barrier (BNB) and the blood‐brain barrier (BBB) to superoxide dismutase (SOD), insulin, albumin, and IgG in normal adult rats was quantified by measuring the permeability coefficient‐surface area product (PS) with the intravenous bolus injection technique before and after covalent protein modification with the naturally occurring polyamines—putrescine (PUT), spermidine (SPD), and spermine (SPM). The PS value of the BNB for PUT‐SOD was 21.1‐fold greater than the native SOD, and the PS values of the BBB for PUT‐SOD ranged from 17.6‐fold greater for the thalamus to 23.6‐fold greater for the caudate‐putamen compared with native SOD. In a similar manner, polyamine‐modified insulin showed a 1.7–2.0‐fold increase in PS of the BNB and BBB compared with the high values of native insulin. Polyamine‐modified albumin showed a remarkable 54–165‐fold increase in PS of the BNB and BBB compared with native albumin, whereas PUT‐IgG resulted in an even higher increase in the PS that ranged from 111‐ to 349‐fold for nerve and different brain regions compared with native IgG. Polyamine modification of proteins, therefore, can dramatically increase the permeability at the BNB and BBB of a variety of proteins with widely differing Mr and function. It is surprising that the PS values of the BNB and BBB decreased with the increasing number of positive charges of the protonated amino groups on the polyamines (PUT > SPD > SPM). Although cationic proteins are known to interact with fixed anionic charges on the lumen of the microvascular endothelium, this observation of decreased permeability with increased positive charge distribution along the aliphatic carbon chain of the polyamines implies mechanisms other than simple electrostatic interaction involving charge density. It is suggested that the polyamine transporter may be responsible for the transport of these polyamine‐modified proteins. Systemic administration of polyamine‐modified peptides and proteins might prove to be an efficient approach to deliver therapeutic agents into the CNS and PNS for the treatment of a variety of neurological diseases.

CNS Delivery Via Adsorptive Transcytosis

“…In vivo: rat, iv injection (10) Combinations of enzymatic treatments and cationic tracers, however, demonstrated distinct differences between these two surfaces (12). A more intense labeling of the luminal surface with cationic colloidal gold was reached, indicating a polar distribution of anionic components of the plasma membrane (Fig.…”

“…Moreover, mixing protamine, poly-L-lysine or other cationic molecules with proteins (e.g. albumin and horseradish peroxidase) greatly increased the permeability of these proteins across cerebral microvessels (9,10). This could probably be due to their binding affinity for polycations.…”

Developing Therapeutic Antibodies for Neurodegenerative Disease

“…Drug targeting using absorptive-mediated endocytosis utilizes chemical modifications, such as cationization of carboxyl groups, to nonspecifically increase cellular uptake through binding of the positively charged modified antibody to the negatively charged plasma membrane [97][98][99]. This type of drug targeting is nonselective in that it does not require binding of the drug to receptors; rather, endocytosis of cationic-bound membrane results in the internalization of compounds into intracellular endosomes.…”

“…This type of drug targeting is nonselective in that it does not require binding of the drug to receptors; rather, endocytosis of cationic-bound membrane results in the internalization of compounds into intracellular endosomes. Polyamination and glycation of antibodies and proteins have shown increased BBB penetration [21,98]. However, the nonspecific nature of absorptive-mediated transport greatly limits its therapeutic potential, as indiscriminate cellular uptake is not only a major disadvantage in terms of off-target effects, but also for their reduced pharmacokinetic properties.…”

Design and Chemical Synthesis of a Magnetic Resonance Contrast Agent with Enhancedin VitroBinding, High Blood−Brain Barrier Permeability, andin VivoTargeting to Alzheimer's Disease Amyloid Plaques

“…In particular, covalent modification with the naturally occurring polyamines, such as putrescine, spermidine, or spermine, has resulted in dramatic increases in the BBB permeability of a number of proteins (6)(7)(8)(9)(10)(11). Indeed, polyamine modification of human Aβ40 as described above not only resulted in a significant increase in the BBB permeability but also resulted in enhanced binding to amyloid plaques in AD brain sections (1,2).…”