Liposomal dexamethasone effectiveness in the treatment of hypersensitivity pneumonitis in mice

Physicochemical properties of extruded and non-extruded liposomes containing the hydrophobic drug dexamethasone

The physicochemical and release properties of non-extruded 'multilamellar' and small sonicated and extruded 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes containing hydrophobic drug dexamethasone were investigated. Non-extruded liposomes had similar diameter, however dexamethasone encapsulation decreased with increase in lipid chain length. Dexamethasone destabilized the liposome membranes as indicated by decrease in enthalpy and increase in the peak width of the main transition. Based on calorimetric analysis, it appeared that dexamethasone and cholesterol were heterogeneously distributed in the non-extruded liposomes. Sonication and extrusion reduced the diameter (DSPC>DPPC>DMPC) and decreased drug encapsulation (approximately 50%). Cholesterol incorporation decreased drug encapsulation in both extruded and non-extruded DMPC liposomes which appeared to be due to structural similarities between cholesterol and dexamethasone. Incorporation of dexamethasone and cholesterol in the same DMPC liposomes caused a marked perturbation in the phase transition. Dexamethasone release from extruded liposomes was fast, while non-extruded liposomes showed slower release. Release was fastest from DMPC liposomes and slowest from liposomes of high phase transition lipid DSPC. Incorporation of cholesterol did not decrease release from DMPC liposomes. These results indicated that change in the physicochemical properties and the phase transition behavior of liposomes, due to processing as well as incorporation of hydrophobic drug dexamethasone, changed their release properties.

Enhanced anti-inflammation of inhaled dexamethasone palmitate using mannosylated liposomes in an endotoxin-induced lung inflammation model

Inhalation of bacterial endotoxin induces pulmonary inflammation by activation of nuclear factor kappaB (NFkappaB), production of cytokines and chemokines, and neutrophil activation. Although glucocorticoids are the drugs of choice, administration of free drugs results in adverse effects as a result of a lack of selectivity for the inflammatory effector cells. Because alveolar macrophages play a key role in the inflammatory response in the lung, selective targeting of glucocorticoids to alveolar macrophages offers efficacious pharmacological intervention with minimal side effects. We have demonstrated previously the selective targeting of mannosylated liposomes to alveolar macrophages via mannose receptor-mediated endocytosis after intratracheal administration. In this study, the anti-inflammatory effects of dexamethasone palmitate incorporated in mannosylated liposomes (DPML) at 0.5 mg/kg via intratracheal administration were investigated in lipopolysaccharide-induced lung inflammation in rats. DPML significantly inhibited tumor necrosis factor alpha, interleukin-1beta, and cytokine-induced neutrophil chemoattractant-1 levels, suppressed neutrophil infiltration and myeloperoxidase activity, and inhibited NFkappaB and p38 mitogen-activated protein kinase activation in the lung. These results prove the value of inhaled mannosylated liposomes as powerful targeting systems for the delivery of anti-inflammatory drugs to alveolar macrophages to improve their efficacy against lung inflammation.

Liposomes in the treatment of inflammatory disorders

This review focuses on the therapeutic utility of liposomes in the treatment of inflammatory disorders, and aims to offer the reader an overview of the in vivo results obtained with liposomally encapsulated anti-inflammatory and immune suppressive drugs. The past 30 years has clearly indicated the added value of liposomes in the search for solutions for the delivery problems encountered. However, only a few liposomal anti-inflammatory therapeutics have entered the clinic. Reasons for the hurdles existing in the translation of promising preclinical findings to clinical studies are discussed.

Liposomal methylprednisolone differentially regulates the expression of TNF and IL-10 in human alveolar macrophages

Glucocorticoids (GC) are frequently used for therapy of various inflammatory lung diseases by either systemic or inhalative application. Because the oral application often has various side effects and because the inhalative application is not as potent, new formulations of GCs are required. We evaluated the effect of a liposomal (Lip) formulation of methylprednisolone (MP) on the expression of lipopolysaccharide (LPS)-induced proinflammatory tumor necrosis factor (TNF) and antiinflammatory interleukin-10 (IL-10) in human alveolar macrophages (AM). AM were obtained from bronchoalveolar lavage fluids of patients with various inflammatory lung diseases and precultured 20 h+/-MP, either liposomal or free, and then stimulated with LPS. Cells were harvested for analysis of mRNA levels by real-time reverse transcriptase polymerase chain reaction (RT-PCR); supernatants were used to measure protein concentrations by ELISA. We confirm the suppression of LPS-induced TNF production by an average of factor 7 at the mRNA level and factor 3 at the protein level. On the other hand, we detected a strong increase of the IL-10 production by MP. At the mRNA level, liposomal MP alone led to an 18-fold increase, and the LPS-induced IL-10 mRNA was enhanced by factor 2. At the protein level, MP alone had no effect, but LPS-induced IL-10 was increased by factor 2.5. Our data show that liposomal MP can consistently induce IL-10 and reduce TNF when macrophages are exposed for a prolonged period of time. In all respects, liposomal MP had similar activities as free MP, but liposomes were selectively taken up by monocytes and macrophages and not by lymphocytes in blood and in the lung. This suggests that liposomal glucocorticoids when applied locally in the lung may act efficiently but with less side effects.

Absorption enhancers in pulmonary protein delivery

Extensive research efforts have been directed towards the systemic administration of therapeutic proteins and poorly absorbed macromolecules via various nontraditional, injection-free administration sites such as the lung. As a portal for noninvasive delivery, pulmonary administration possesses several attractive features including a large surface area for drug absorption. Nevertheless, achieving substantial bioavailability of proteins and macromolecules by this route has remained a challenge, chiefly due to poor absorption across the epithelium. The lungs are relatively impermeable to most drugs when formulated without an absorption enhancer/promoter. In an attempt to circumvent this problem, many novel absorption promoters have been tested for enhancing the systemic availability of drugs from the lungs. Various protease inhibitors, surfactants, lipids, polymers and agents from other classes have been tested for their efficacy in improving the systemic availability of protein and macromolecular drugs after pulmonary administration. The purpose of this article is to provide the reader with a summary of recent advances made in the field of pulmonary protein delivery utilizing absorption enhancers. This report reviews the various agents used to increase the bioavailability of these drugs from the lungs, their mechanisms of action and effectiveness, and their potential for toxicity.

Nebulizer-compatible liquid formulations for aerosol pulmonary delivery of hydrophobic drugs: glucocorticoids and cyclosporine

This review discusses pulmonary delivery of glucocorticoids and cyclosporine in pharmaceutically acceptable organic solvents and liposomes, as well as in micellar solutions and microemulsions, by means of liquid aerosols generated by nebulizers. The review points out the importance of a variety of parameters for successful treatment of immunologically mediated lung diseases by inhalation of drug containing aerosols with particular references to physico-chemical properties of formulations, aerosol parameters, pharmacokinetics, and lung deposition in experimental animals and humans. The prospects for the use of these types of formulations for clinical treatment of asthma, lung transplant rejection processes and other lung diseases are summarized.

Modulation of silica-induced pulmonary toxicity by dexamethasone-containing liposomes

Human exposure to silica (SI) is of great occupational concern because it is marked by pulmonary inflammation and fibrosis. Our objective was to determine if early pharmacological intervention altered the inflammatory and fibrotic responses to silica in rats. Male Fisher-344 rats received intratracheal (IT) instillations of the anti-inflammatory steroid, dexamethasone (DEX), incorporated into a novel liposomal (LIP) delivery system (DEX-LIP), or buffer as control (HBSS) on Day-1 and every fourth day until euthanization. On Day 0, the DEX-LIP group received IT instillations of SI (10 mg/100g body wt, DEX-LIP-SI); half of the HBSS group received SI (10 mg/100g body wt, HBSS-SI) and the other half saline (HBSS-SAL). On Day 10 or 20, bronchoalveolar lavage (BAL) was performed for cellular, biochemical, and functional analyses of inflammation and damage. HBSS-SI rats had significant elevations in the neutrophil cell count over HBSS-SAL rats at both times. DEX-LIP treatment markedly reduced these values, indicating that DEX-LIP protected against SI-induced inflammation. In contrast, DEX-LIP did not protect against biochemical (albumin concentration, and beta-glucuronidase and lactate dehydrogenase activities) and functional (luminol-dependent chemiluminescence) indices of SI-induced damage. At Day 20, the DEX-LIP treatment significantly reduced the SI-induced increase in right lung/total body weight ratio and right lung hydroxyproline content, a biochemical index of fibrosis. This attenuation of fibrosis was confirmed histopathologically on preserved left lungs from these same animals. These results show that administration of liposomes containing dexamethasone attenuated SI-induced pulmonary inflammation and fibrosis in rats, and that this protection is independent of some biochemical and functional parameters of damage.

Pulmonary targeting of liposomal triamcinolone acetonide phosphate

PURPOSE

To explore the use of triamcinolone acetonide phosphate liposomes as a pulmonary targeted drug delivery system.

METHODS

Triamcinolone acetonide phosphate liposomes composed of 1,2-distearoyl phosphatidylcholine and 1,2-distearoyl phosphatidyl glycerol and triamcinolone acetonide 21-phosphate dipotassium salt were prepared by dispersion and extruded through polycarbonate membranes. Encapsulation efficiency and in vitro stability at 37 degrees C were assessed after size exclusion chromatography. TAP liposomes (TAP-lip) or TAP in solution (TAP-sol) were delivered to rats either by intratracheal instillation (IT) or intravenous (IV) administration. Pulmonary targeting was assessed by simultaneous monitoring of glucocorticoid receptor occupancy over time in lung (local organ) and liver (systemic organ) using an ex vivo receptor binding assay as a pharmacodynamic measure of glucocorticoid action.

RESULTS

In vitro studies in different fluids over 24 hours, showed that more than 75% of the TAP remained encapsulated in liposomes. Cumulative pulmonary effects after IT administration of TAP-lip were 1.6 times higher than liver receptor occupancy. In contrast, there was no difference in the pulmonary and hepatic receptor occupancy time profiles when TAP was administered intratracheally as a solution. No preferential lung targeting was observed when TAP-lip was administered IV. As indicated by the mean effect times, lung receptor occupancy was sustained only when TAP-lip was administered IT.

CONCLUSIONS

Intratracheal administration of TAP-lip provided sustained receptor occupancy, and increased pulmonary targeting which was superior to IT administration of TAP-sol or IV administration of TAP-lip. The use of liposomes may represent a valuable approach to optimize sustained delivery of glucocorticoids to the lungs via topical administration.

Liposome-incorporated dexamethasone palmitate inhibits in-vitro lymphocyte response to mitogen

The use of liposomes for the pulmonary delivery of corticosteroid is an area that is under active investigation. We have recently developed a novel liposomal corticosteroid preparation based on the incorporation of dexamethasone palmitate (DMP) within the bilayer of small unilamellar vesicles (SUVs) made of egg yolk phosphatidylcholine (EPC) and cholesterol; molar ratio EPCC:cholesterol: DMP, 4:3:0.3. In the present study, the biological activity of DMP-SUVs was evaluated using the lymphocyte transformation test with peripheral blood mononuclear cells (PBMCs) and a gamma-interferon production assay. Results showed that DMP-SUVs (but not empty SUVs) inhibited [3H]thymidine uptake and gamma-interferon production by concanavalin A-stimulated PBMCs by 94 and 96%, respectively, at a concentration corresponding to 10(-6) M dexamethasone. The inhibition by DMP-SUVs was found to require a 24-h pre-incubation with unstimulated PBMCs, suggesting that interaction of SUVs with lymphocytes may be altered by mitogen stimulation. We conclude that our DMP liposomal preparation is biologically active and may be considered a promising alternative to conventional local glucocorticoid therapy.

PC:PS liposomes induce a recruitment of neutrophils and the release of TNF alpha in the lungs of mice sensitized with Saccharopolyspora rectivirgula

The aim of this study was to verify the effect of nasally instilled liposomes (L) or dexamethasone-containing L (Ldexa) on normal or inflamed lung tissue. Three groups of mice were studied. Group I was given saline instillations for 3 weeks prior to the instillation with liposomes. In groups II and III lung inflammation was induced by repeated instillations of Saccharopolyspora rectivirgula before the instillation of liposomes (group II) or liposomes containing dexamethasone (group III). Animals from all groups were killed at regular time intervals for up to 48 h after the instillation of liposomes. The total cell count in bronchoalveolar lavage fluid did not differ significantly between groups I and II. However, in group III it decreased rapidly from 6.2 to 2.8 x 10(5) cells mL-1 within 2 h. Differential counts did not change in group I, but in group II a transient neutrophilia was observed 180 min after the instillation of liposomes. In group III, the instillation of dexamethasone-containing liposomes depleted all neutrophils and lymphocytes after 4 h. No TNF alpha was found in samples of lavage fluid from any of the groups at time 0. In group I, liposomes induced the production of 0.03 ng mL-1 of TNF alpha in the 1 h sample only. In group II, TNF alpha peaked to 1 ng mL-1 at 1 h and had decreased to 0.35 ng mL-1 by 3 h. In group III, TNF alpha peaked at 1 h, but only reached a level of 0.1 ng mL-1.(ABSTRACT TRUNCATED AT 250 WORDS)