title: Liposomal encapsulation enhances and prolongs the anti-inflammatory effects of water-soluble dexamethasone phosphate in experimental adjuvant arthritis.
abstract: BACKGROUND
  The objective of this study was to evaluate the efficacy of intravenous (i.v.) injection of liposomally encapsulated dexamethasone phosphate (DxM-P) in comparison to free DxM-P in rats with established adjuvant arthritis (AA). This study focused on polyethylene glycol (PEG)-free liposomes, to minimize known allergic reactions caused by neutral PEG-modified (PEG-ylated) liposomes.
  
  
  METHODS
  Efficacy was assessed clinically and histologically using standard scores. Non-specific and specific immune parameters were monitored. Activation of peritoneal macrophages was analyzed via cytokine profiling. Pharmacokinetics/biodistribution of DxM in plasma, synovial membrane, spleen and liver were assessed via mass spectrometry.
  
  
  RESULTS
  Liposomal DxM-P (3 × 1 mg/kg body weight; administered intravenously (i.v.) on Days 14, 15 and 16 of AA) suppressed established AA, including histological signs, erythrocyte sedimentation rate, white blood cell count, circulating anti-mycobacterial IgG, and production of interleukin-1beta (IL-1β) and IL-6 by peritoneal macrophages. The suppression was strong and long-lasting. The clinical effects of liposomal DxM-P were dose-dependent for dosages between 0.01 and 1.0 mg/kg. Single administration of 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.
authors.affiliation: Department of Orthopedics, University Hospital Jena, Eisenberg, Germany. rebecca.anderso@web.de
authors.forename: Rebecca
authors.initials: R
authors.lastname: Anderson
authors.forename: Angels
authors.initials: A
authors.lastname: Franch
authors.forename: Margarida
authors.initials: M
authors.lastname: Castell
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Perez-Cano
authors.forename: Rolf
authors.initials: R
authors.lastname: Bräuer
authors.forename: Dirk
authors.initials: D
authors.lastname: Pohlers
authors.forename: Mieczyslaw
authors.initials: M
authors.lastname: Gajda
authors.forename: Alexandros P
authors.initials: AP
authors.lastname: Siskos
authors.forename: Theodora
authors.initials: T
authors.lastname: Katsila
authors.forename: Constantin
authors.initials: C
authors.lastname: Tamvakopoulos
authors.forename: Una
authors.initials: U
authors.lastname: Rauchhaus
authors.forename: Steffen
authors.initials: S
authors.lastname: Panzner
authors.forename: Raimund W
authors.initials: RW
authors.lastname: Kinne
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D002626:Chemistry, Pharmaceutical; D016207:Cytokines / Q000378:metabolism; D003907:Dexamethasone / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers / Q000493:pharmacokinetics*; D005260:Female; D005938:Glucocorticoids / Q000493:pharmacokinetics*; D006968:Hypersensitivity, Delayed / Q000139:chemically induced; D007074:Immunoglobulin G / Q000097:blood; D007275:Injections, Intravenous; D007958:Leukocyte Count; D008081:Liposomes / Q000493:pharmacokinetics*; D008214:Lymphocytes / Q000187:drug effects / Q000473:pathology; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000473:pathology; D051381:Rats; D011917:Rats, Inbred Lew; D012995:Solubility; D014018:Tissue Distribution
chemical_list: D016207:Cytokines; D004337:Drug Carriers; D005938:Glucocorticoids; D007074:Immunoglobulin G; D008081:Liposomes; C004180:dexamethasone 21-phosphate; D003907:Dexamethasone