A general method for the introduction of enzymes, by means of immunoglobulin-coated liposomes, into lysosomes of deficient cells.

Abstract

Phagocytes of the smooth dogfish (Mustelus canis) contain no endogenous peroxidase within their lysosomes and constitute models for cells genetically deficient in lysosomal enzymes such as myeloperoxidase. We have obtained uptake of over 50% of exogenous horseradish peroxidase, provided the enzyme is exhibited to cells after incorporation into liposomes coated with heat-aggregated (620, 10 min), isologous IgM. Trapping of horseradish peroxidase (EC 1.11.1.7) by liposomes was established by chromatographic resolution (Sephadex G-200; Sepharose 2B and 4B) of free enzyme from that associated with liposomes; liposome-associated horseradish peroxidase, together with trapped markers of the aqueous compartment (glucose, CrO4=), were excluded, and free enzyme and markers were retained. Enzyme and marker trapping was not electrostatic, varied with the molar ratio of charged membrane components, and was reversed by detergent lysis (Triton X-100) of liposomes. Uptake at 300 of aggregated IgM-coated liposomes containing trapped horseradish peroxidase exceeded that of free enzyme by 100-fold, and was more efficient than uptake of horseradish peroxidase presented in uncoated liposomes or in liposomes coated with native IgM. After phagocytosis, peroxidaserich liposomes were localized exclusively in lysosomes of the phagocytes by ultrastructural histochemistry; the enzyme displayed over 50% latency to osmotic lysis. This method may prove to be of general use in the provision of exogenous enzymes to phagocytic cells genetically deficient in lysosomal hydrolases.

Lipossomas: a bala mágica acertou?

“…Tendo em conta que a principal limitação dos lipossomas convencionais é a sua eliminação de circulação pelo sistema retículo-endotelial, Lasic e Needham 50 definem arbitrariamente lipossomas furtivos como sistemas lipídicos modificados com um tempo de meia vida em circulação (tempo necessário para que a sua concentração seja reduzida a metade) superior a 2 h. Contudo, podem-se obter com lipossomas furtivos tempos de meia vida em circulação 100 vezes superiores aos dos lipossomas convencionais 65 . Os métodos de modificação experimentados na alteração dos lipossomas convencionais de modo a reduzir a sua eliminação incluíram a sua associação com anticorpos específicos para determinadas células 66 , revestimento com imunoglobinas M (IgM) agregadas por aquecimento 67 , ligação covalente de anticorpos 68 , ou por incorporação de lípidos imunogénicos 69 , glicoproteínas 70 , glicolípidos naturais 71 e glicolípidos sintéticos 72 . Alguns destes métodos de modificação já se mostraram úteis na preparação de transportadores para aplicações biomédicas, nomeadamente terapia génica, quimioterapia e direccionamento de lipossomas para células, orgãos ou tecidos específicos 65 .…”

The interaction of Bacillus protoplasts with sonicated phosphatidylcholine liposomes

“…However, in our system, none of these inhibitors was effective in reducing the incorporation of phosphatidylcholine into Bacillus protoplasts (table 1). In any case, endocytosis is more commonly found with large multilamellar liposomes than with sonicated vesicles [16,17].…”

Nanomedicine and Drug Delivery Strategies for Treatment of Genetic Diseases

“…Encapsulation within or coupling to liposomes and polymer carriers, as well as the incorporation of active targeting moieties, may help these aspects. Some examples of these applications were explored in the late 70's, such as in the case of enhanced delivery of glucocerebrosidase deficient in Gaucher disease upon encapsulation within liposomes (Dale, et al, 1979), or liposomes coupled to aggregated immunoglobulins or apolipoproteins for enhanced enzyme targeting to polymorphonucleocytes for treatment of Batten disease (Weissmann, et al, 1975, Steger & Desnick, 1977). Yet, not many subsequent works have risen from these seminal studies, adapting the rapid evolving arena of nanomedicine to formulations for treatment of genetic conditions, and both fields have developed independently.…”