AA/DxM-P 1 mg/kg; all Mann Whitney U-test

AA/DxM-P 1 mg/kg; all Mann Whitney U-test. between 0.01 and 1.0 mg/kg. Single ATN-161 trifluoroacetate salt administration of 1 1 mg/kg liposomal DxM-P and 3 1 mg/kg of free DxM-P showed comparable effects consisting of a partial and transient suppression. Moreover, the effects of medium-dose liposomal DxM-P (3 0.1 mg/kg) were equal (in the short term) or superior (in the long term) to those of high-dose free DxM-P (3 1 mg/kg), suggesting a potential dose reduction by a factor between 3 and 10 by liposomal encapsulation. For at least 48 hours after the last injection, the liposomal drug achieved significantly higher levels in plasma, synovial membrane, spleen and liver than the free drug. Conclusions This new PEG-free formulation of macrophage-targeting liposomal DxM-P considerably reduces the dose and/or frequency required to treat AA, with a potential to enhance or prolong therapeutic efficacy and limit side-effects also in the therapy of rheumatoid arthritis. Depot and/or recirculation effects in plasma, inflamed joint, liver, and spleen may contribute to this superiority of liposomally encapsulated DxM-P. Introduction Rheumatoid arthritis (RA) is usually a systemic disorder of unknown etiology characterized by chronic inflammation and symmetric, progressive destruction of arthritic joints. The abundance and activation of macrophages (M) in the inflamed synovial membrane significantly correlates with ATN-161 trifluoroacetate salt the severity of RA [1,2]. In addition, activation of the monocytic lineage extends to systemic parts of the mononuclear phagocyte system [3-7]. Thus, selective counteraction of M activation is usually a promising approach to diminish local and systemic inflammation or to prevent irreversible joint damage. In addition to disease-modifying anti-rheumatic drugs (DMARDs) and to recently introduced biologicals (for example, antibodies against tumor necrosis factor- (TNF)- or soluble TNF–receptors, [8-14]), anti-inflammatory glucocorticoids are still frequently employed to bridge the gap before the onset of action of DMARDs [15-17] and to improve the therapeutic control of RA. Due ATN-161 trifluoroacetate salt to their unequalled efficacy, bridging application and wide indication range (for example, renal failure, pregnancy), glucocorticoids remain valuable therapeutic tools. However, concerns about long-term side effects, such as Cushing syndrome or bone demineralization, strongly emphasize the need for safer treatment modalities. Specific targeting of glucocorticoids to phagocytic cells by liposomal encapsulation potentially increases drug efficacy and longevity while minimizing side-effects [18,19]. Previous studies have exhibited good therapeutic efficacy of water-soluble prednisolone in neutral polyethylene glycol-modified (PEGylated) liposomes in animal models of arthritis and multiple sclerosis [20-23]. However, evidence has emerged that repeated injections can result in the generation of anti-PEG antibodies, emphasizing the need for a PEG-free liposomal formulation [24-27]. In this study, water-soluble dexamethasone phosphate (DxM-P) was encapsulated in a novel, non-PEGylated liposome formulation (Micromethason). All lipids in this formulation have market approval, thereby minimizing the risk of lipid-associated toxicity. The efficacy of liposomal DxM-P was evaluated in rat adjuvant arthritis (AA), a severe animal model characterized by histopathological similarities to RA, including both systemic and local features of inflammation [28]. The effects of treatment with free DxM-P or different doses of liposomally-encapsulated DxM-P were also evaluated, in order to assess the increase of therapeutic potency by encapsulation. ICAM2 In addition, a pharmacokinetics and biodistribution study of DxM was carried out following administration of liposomal DxM-P or free DxM-P. ATN-161 trifluoroacetate salt Materials and methods Micromethason preparation Micromethason liposomes were prepared by Novosom AG (Halle, Germany) from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-(phosphor-rac-(1-glycerol))(sodium salt) (DPPG) and cholesterol (50:10:40 mol %; all lipids with market approval) using the lipid film extrusion method [29]. The lipid film was hydrated with DxM-P (25 mg/ml in phosphate-buffered saline (PBS), pH 7.5) and the resulting vesicles were extruded through 400 nm membranes. Non-encapsulated DxM-P was removed by gel filtration. Particle size (283 to 310 nm) and polydispersity (0.3) were determined by dynamic light scattering. The drug/lipid ratio was 40 g/mol (decided as in [30]) and the concentration was adjusted to 500 g DxM-P/ml. The liposomes were selected for tolerability in ATN-161 trifluoroacetate salt vivo and their ability to target cells of the macrophage-phagocyte system while avoiding unwanted sites such as the liver parenchyme. The latter was achieved by using rather large particles, which cannot penetrate across the 150 nm fenestrations of liver endothelium [31]. The cellular targeting to cells of the macrophage-phagocyte system relates to the unfavorable surface charge of the liposomes [32]. Adjuvant arthritis AnimalsFemale Lewis rats (seven to eight weeks of age) were obtained from Harlan (Barcelona, Spain) and housed three to four per cage under standard conditions, with food and water ad libitum and a 12-hour-light/12-hour-dark cycle. The animals were allowed two weeks to adjust to the housing conditions prior to the initiation of studies. The experiments.