ATP-loaded liposomes effectively protect mechanical functions of the myocardium from global ischemia in an isolated rat heart model.

ATP-loaded liposomes (ATP-L) infused into Langendorff-instrumented isolated rat hearts protect the mechanical functions of the myocardium during ischemia/reperfusion. The left ventricular developed pressure (LVDP) at the end of the reperfusion in the ATP-L group recovered to 72% of the baseline (preservation of the systolic function) compared to 26%, 40%, and 51% in the groups treated with Krebs-Henseleit (KH) buffer, empty liposomes (EL), and free ATP (F-ATP), respectively. The ATP-L-treated group also showed a significantly lower left ventricular end diastolic pressure (LVEDP; better preservation of the diastolic function) after ischemia/reperfusion than controls. After incubating the F-ATP and ATP-L with ATPase, the protective effect of the F-ATP was completely eliminated because of ATP degradation, while the protective effect of the ATP-L remained unchanged. Fluorescence microscopy confirmed the accumulation of liposomes in ischemic areas, and the net ATP in the ischemic heart increased with ATP-L. Our results suggest that ATP-L can effectively protect myocardium from ischemic/reperfusion damage.

Treatment of alopecia areata in the DEBR model using Cyclosporin A lipid vesicles.

Alopecia areata (AA) is a chronic cutaneous disease with a suspected autoimmune origin. We evaluated the efficacy of 0.5% Cyclosporin A (CyA) in a topically applied liposomal formulation as a potential treatment for AA using the Dundee Experimental Bald Rat (DEBR) model. The vehicle consisted of liposomes (75% phosphatidylcholine, 5% lysophosphatidylcholine, 5% sterol, natural oils) of 10% wt. in ethanol with and without 2% wt. terpenes (d-limonene: citral: cineole, 10:45:45) as a penetration enhancer (PE). Fifteen DEBR were allocated to 3 groups of 5. Groups I, II and III received CyA vesicles with PE, CyA vesicles without PE, and CyA in ethanol respectively. All rats were treated twice a day for 6 weeks within a 4 cm2 area on one bald flank with CyA while the contralateral flank received an equivalent control formulation. Rats in group I exhibited visible hair regrowth on the drug treated site after one week of drug application. Group II rats had visible hair regrowth by the end of the second week. The hair growth was progressive and reached a maximum density at the site of application after six weeks in both groups. Histological examination revealed a reduced inflammatory infiltrate and improved hair follicle morphology within the drug treated area as compared to the contralateral vehicle treated skin. Group III rats showed neither visible signs of hair growth nor reduction of hair follicle inflammation. The results of this proof of concept preliminary study suggest that CyA vesicle formulations with and without PE have promising potential as a topical treatment for AA in humans.

Synergistic penetration enhancement effect of ethanol and phospholipids on the topical delivery of cyclosporin A.

In the present study, ethanol was used with a commercially available lipid mixture, NAT 8539, to improve the topical delivery of cyclosporin A (CyA). The vesicles formed from this solution ranged from 56.6 to 100.6 nm in diameter, depending on the amount of ethanol added in the formulation. In-vitro skin penetration studies were carried out with Franz diffusion cell using human abdominal skin. There was a decrease in average size of vesicles, as the amount of ethanol in formulation increased from 0% to 3.3% and a further addition of ethanol resulted in an increase in average diameter of vesicles. CyA vesicles containing 10% and 20% ethanol showed statistically enhanced deposition of CyA into the stratum corneum (SC), as compared to vesicles prepared without ethanol. CyA vesicles prepared with NAT 8539/ethanol (10/3.3) showed a 2.1-fold, CyA vesicles with NAT 8539/ethanol (10/10) showed a 4.4-fold, and CyA vesicles with NAT 8539/ethanol (10/20) showed a 2.2-fold higher deposition of CyA into SC, as compared to vesicles made of NAT 8539 without ethanol [NAT 8539/ethanol (10/0)]. The efficiency of the formulations was sequenced in the order of: NAT 8539/ethanol (10/10)>NAT 8539/ethanol (10/20)>NAT 8539/ethanol (10/3.3)>ethanol>NAT 8539/ethanol (10/0). These results can be considered a step forward for the topical delivery of problematic molecules like CyA using liposomes as a tool for the treatment of inflammatory skin diseases like psoriasis, atopic dermatitis, and diseases of the hair follicle like alopecia areata, etc.

Particle size of liposomes influences dermal delivery of substances into skin.

In the present study, the influence of vesicle size on the penetration of two fluorescently labeled substances into the human skin was investigated. For the measurements either a hydrophilic fluorescent compound [carboxyfluorescein (CF)] or a lipophilic one [1,1'-dioctadecyl-3,3,3',3'-tertramethylindocarbo-cyanine perchlorate (DiI)] were encapsulated into vesicles. Liposomal formulations were prepared by extruding the vesicles through polycarbonate membrane filters with pores of different sizes. In vitro penetration studies into human abdominal skin were performed by using the Franz diffusion cell and a standardized skin stripping technique in attempt to find an optimum size for topical drug delivery by liposomes. Confocal laser scanning microscopy (CLSM) was used to visualize the effect of penetration ability of liposomal DiI. The maximum DiI fluorescence in the skin was observed with smaller liposomes of 71 nm diameter. The liposomes with a size of 120 nm diameter showed statistically enhanced penetration of CF into the skin as compared to larger ones. The results indicated that the CF penetration was inversely related to the size of the liposomes, which was confirmed by the data of the confocal laser scanning microscopy studies.

Liposomes increase skin penetration of entrapped and non-entrapped hydrophilic substances into human skin: a skin penetration and confocal laser scanning microscopy study.

Liposomes have been extensively studied and suggested as a vehicle for topical drug delivery systems. However, the mechanism by which liposomes deliver drugs into intact skin is not fully understood. In the present study, we have tried to understand the mechanism of transport of hydrophilic drugs into the skin using liposomes. The effect of separation of the non-entrapped, hydrophilic fluorescent compound, carboxyfluorescein (CF), from liposomally entrapped CF was investigated by measuring the penetration of CF across human skin under non-occlusive conditions in vitro using Franz diffusion cells. The fluorescent dye, CF, was incorporated into the liposomes and applied onto the skin. After a 6 and 12h incubation period, the amount of CF in the epidermal membrane and the full thickness skin was determined by fluorescence spectroscopy or by confocal laser scanning microscopy (CLSM). The liposomal formulation containing CF both inside and outside the vesicles showed statistically enhanced penetration of CF into the human stratum corneum (SC) as compared to the formulations containing CF only outside of the liposomes and CF in Tris buffer. The CLSM results revealed that the formulation in which CF was present outside the liposomes showed bright fluorescence intensity in the SC and very weak fluorescence in the viable epidermis. However, the CF in Tris buffer failed to show any fluorescence in the viable epidermis. The results indicated that phospholipid vesicles not only carry the entrapped hydrophilic substance, but also the non-entrapped hydrophilic substance into the SC and possibly into the deeper layers of the skin.

Streptogramins: a new class of antibiotics.

Streptogramin antibiotics represent a unique class of antibacterials in the each member of the class consists of at least 2 structurally unrelated molecules: group a streptogramins (macrolactones) and group B streptogramins (cyclic hexadepsipeptides). Both group A and group B streptogramins inhibit protein synthesis at the ribosomal level, and they act synergistically against many isolates their combination generating bactericidal activities and reducing the possibility of emergencies of resistant strains. The mechanisms of acquired resistance to group B streptogramins remain unaffected by target modifications and active efflux. The pharmacokinetic parameters of group A and group B streptogramins in blood are quite similar. In addition, both the A and B group penetrate and accumulate in macrophages and in the bacterial gegetations of experimental endocarditis. Until recently, the complex and irregular composition of naturally occurring pristinamycin and virginiamycin, as well as the unavailability of soluble forms, have limited the clinical development of streptogramins. The synthesis of water soluble derivatives of pristinamycin IA and IIB has now allowed the development of injectable streptogramins with fixed compositions. This unique class of antibacterials will have a significant clinical impact in a world of increasing multidrug resistance affecting the Gram-positive cocci, especially staphylococci and pneumococci. The absence of cross-resistance to macrolides in many of these isolates and the rapid antibacterial killing against these species bright future for this class of antibiotics.