Cubosomes for topical delivery of the antimicrobial peptide LL-37.

In this study, the use of cubosomes for topical delivery of the antimicrobial peptide (AMP) LL-37 was investigated. Topical delivery of AMPs is of great interest for treatment of skin infections caused by bacteria, such as Staphylococcus aureus. AMP containing cubosomes were produced by three different preparation protocols and compared: (i) pre-loading, where LL-37 was incorporated into a liquid crystalline gel, which thereafter was dispersed into nanoparticles, (ii) post-loading, where LL-37 was let to adsorb onto pre-formed cubosomes, and (iii) hydrotrope-loading, where LL-37 was incorporated during the spontaneously formed cubosomes in an ethanol/glycerol monooleate mixture. Particle size and size distribution were analyzed using dynamic light scattering (DLS), liquid crystalline structure by small angle x-ray scattering (SAXS) and release of LL-37 by a fluorescamine assay. Proteolytic protection of LL-37 as well as bactericidal effect after enzyme exposure was investigated. The skin irritation potential of cubosomes was examined by an in vitro epidermis model. Finally, the bacterial killing property of the cubosomes was examined by an ex vivo pig skin wound infection model with Staphylococcus aureus. Data showed that a high loading of LL-37 induced formation of vesicles in case of cubosomes prepared by sonication (pre-loading). No release of LL-37 was observed from the cubosomes, indicating strong association of the peptide to the particles. Proteolysis studies showed that LL-37 was fully protected against enzymatic attacks while associated with the cubosomes, also denoting strong association of the peptide to the particles. As a consequence, bactericidal effect after enzyme exposure remained, compared to pure LL-37 which was subjected to proteolysis. No skin irritation potential of the cubosomes was found, thus enabling for topical administration. The ex vivo wound infection model showed that LL-37 in pre-loaded cubosomes killed bacteria most efficient.

Antibióticos humanos modulados por calcitriol: nuevos aspectos fisiopatológicos de la hipovitaminosis D / Calcitriol-modulated human antibiotics: New pathophysiological aspects of vitamin D

El calcitriol ha sido considerado durante años exclusivamente como una hormona reguladora del metabolismo fosfocálcico, pero últimamente se ha demostrado que numerosas células implicadas en la inmunidad innata (epitelios de barrera, monocitos/macrófagos, etc.) son capaces de reconocer determinadas moléculas repetitivas características de diversos gérmenes patógenos mediante receptores de membrana o intranucleares. La activación de estos receptores induce la síntesis de la 1α-hidroxilasa, con lo que dichas células son capaces de sintetizar calcitriol a partir de la 25 hidroxivitamina D circulante. El calcitriol, a través del receptor la vitamina D, modula la expresión de determinados péptidos antimicrobianos, como la catelicidina, la β2-defensina o la hepcidina. Estos péptidos representan un mecanismo versátil de la lucha antibacteriana innata y su producción se ve alterada en la hipovitaminosis D. Se realiza un análisis de la literatura sobre sus mecanismos de secreción, las concentraciones en diversos líquidos orgánicos, y los mecanismos de acción y su relación con la vitamina D (AU)

Traditionally, calcitriol has been considered a calcium and phosphate regulating hormone, but has recently been shown to play a pivotal role in innate immunity. Many barrier and immune cells have membrane and intracellular receptors that recognize different microbial antigens. Activation of these receptors induces synthesis of 1α-hydroxylase, which acts on 25 hydroxyvitamin D to generate intracellular calcitriol. Calcitriol activates its receptor and enhances the synthesis of important human antibiotics like cathelicidin and β2-defensin while inhibiting hepcidin. These pluripotent peptides have an important role in innate immunity, and their regulation is abnormal in hypovitaminosis D. The literature on their secretion mechanisms, levels in different organic fluids, mechanism of action, and relationship with vitamin D is reviewed here (AU)