title: Development of a macromolecular prodrug for the treatment of inflammatory arthritis: mechanisms involved in arthrotropism and sustained therapeutic efficacy.
abstract: BACKGROUND
  The purpose of the present manuscript is to test the hypothesis that arthrotropic localization and synovial cell internalization account for the unique capacity of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-dexamethasone conjugate (P-Dex, a macromolecular prodrug of dexamethasone) to induce sustained amelioration of joint inflammation and inhibition of tissue damage in an animal model of inflammatory arthritis.
  
  
  METHODS
  Rats with adjuvant-induced arthritis (AA) were treated with P-Dex, free dexamethasone, saline or HPMA homopolymer. To define the biodistribution of P-Dex, conjugates with different imaging labels were given to AA rats and analyzed. Isolated joint tissues were evaluated by fluorescence-activated cell sorting (FACS) and immunohistochemical staining. Cellular uptake of P-Dex and its effects on apoptosis and production of proinflammatory cytokines were examined using human monocyte-macrophages and fibroblasts.
  
  
  RESULTS
  A single systemic administration of P-Dex completely suppressed AA for >20 days. Magnetic resonance imaging demonstrated higher HPMA copolymer influx into the inflamed joints than the normal joints. Immunohistochemistry and FACS analyses of arthritic joints revealed extensive uptake of the polymer conjugate by synovial fibroblasts and myeloid lineage cells. The capacity of P-Dex to suppress inflammation was confirmed in monocyte-macrophage cultures in which P-Dex treatment resulted in suppression of lipopolysaccharide-induced IL-6 and TNFα release. Similarly, TNFα-induced expression of matrix metalloproteinases (MMP1 and MMP3) in synovial fibroblasts from a rheumatoid arthritis patient was suppressed by P-Dex. P-Dex showed no detectable effect on monocyte apoptosis.
  
  
  CONCLUSIONS
  P-Dex provides superior and sustained amelioration of AA compared with an equivalent dose of free dexamethasone. The arthrotropism and local retention of P-Dex is attributed to the enhanced vascular permeability in arthritic joints and the internalization of P-Dex by synovial cells. The uptake and processing of P-Dex by macrophages and fibroblasts, and downregulation of proinflammatory mediators, provides an explanation for the sustained anti-inflammatory efficacy of P-Dex in this model of inflammatory arthritis.
authors.affiliation: Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE 68198-6025, USA. lquan@unmc.edu
authors.forename: Ling-dong
authors.initials: LD
authors.lastname: Quan
authors.forename: P Edward
authors.initials: PE
authors.lastname: Purdue
authors.forename: Xin-ming
authors.initials: XM
authors.lastname: Liu
authors.forename: Michael D
authors.initials: MD
authors.lastname: Boska
authors.forename: Subodh M
authors.initials: SM
authors.lastname: Lele
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Thiele
authors.forename: Ted R
authors.initials: TR
authors.lastname: Mikuls
authors.forename: Huanyu
authors.initials: H
authors.lastname: Dou
authors.forename: Steven R
authors.initials: SR
authors.lastname: Goldring
authors.forename: Dong
authors.initials: D
authors.lastname: Wang
mesh_terms: D000276:Adjuvants, Immunologic / Q000633:toxicity; D000818:Animals; D018501:Antirheumatic Agents / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology; D001169:Arthritis, Experimental / Q000139:chemically induced / Q000188:drug therapy* / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000139:chemically induced / Q000188:drug therapy* / Q000276:immunology; D002199:Capillary Permeability / Q000187:drug effects; D002469:Cell Separation; D003907:Dexamethasone / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000276:immunology; D005434:Flow Cytometry; D005620:Freund's Adjuvant / Q000633:toxicity; D006801:Humans; D007150:Immunohistochemistry; D008689:Methacrylates / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D018613:Microscopy, Confocal; D022423:Myeloid Cells / Q000187:drug effects / Q000276:immunology; D011355:Prodrugs / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D051381:Rats; D013583:Synovial Membrane / Q000187:drug effects / Q000276:immunology; D014018:Tissue Distribution
chemical_list: D000276:Adjuvants, Immunologic; D018501:Antirheumatic Agents; D008689:Methacrylates; D011355:Prodrugs; D003907:Dexamethasone; D005620:Freund's Adjuvant; C032802:hydroxypropyl methacrylate