title: Mycophenolic acid increases apoptosis, lysosomes and lipid droplets in human lymphoid and monocytic cell lines.
abstract: BACKGROUND
  Mycophenolic acid (MPA), a selective inhibitor of inosine monophosphate dehydrogenase, is the active agent of the immunosuppressive drug, mycophenolate mofetil (MMF). Previous studies have shown that MPA inhibits DNA synthesis in T and B lymphocytes by blocking de novo guanosine synthesis, and that MPA induces monocyte differentiation. MMF is being used for prevention of organ graft rejection and has also shown efficacy in rheumatoid arthritis trials. This study was designed to determine if apoptosis also plays a role in the immunosuppressive and anti-inflammatory effects of MMF.
  
  
  METHODS
  Cultured human T lymphocytic (MOLT-4) and monocytic (THP-1 and U937) cell lines were treated with MPA. Apoptosis, cell viability, DNA content, lipid content, cell volume, and lysosomes were measured by a variety of microscopic, flow cytometric, and biochemical techniques.
  
  
  RESULTS
  MPA inhibits proliferation, arrests cell cycle in S phase, and increases apoptosis in all three cell lines. Exogenous guanosine added within 24 hr of MPA treatment, but not later, partially reversed MPA-induced apoptosis in MOLT-4 cells. MPA increased lipid droplets in all three cell lines and increased both cell volumes and numbers of lysosomes in the monocytic cell lines. In both monocytic cell lines, MPA also reduced the number of nuclei containing nucleoli and greatly increased neutral lipids, primarily triacylglycerols, suggesting that these cells were differentiating.
  
  
  CONCLUSIONS
  Increased apoptosis and terminal differentiation of both lymphocytes and monocytes may promote the antiproliferative, immunosuppressive, and anti-inflammatory effects of MMF seen clinically in transplantation and rheumatoid arthritis.
authors.affiliation: Department of Biomathematics, Central Research and Development, Roche Bioscience, Palo Alto, California 94304, USA.
authors.forename: R G
authors.initials: RG
authors.lastname: Cohn
authors.forename: A
authors.initials: A
authors.lastname: Mirkovich
authors.forename: B
authors.initials: B
authors.lastname: Dunlap
authors.forename: P
authors.initials: P
authors.lastname: Burton
authors.forename: S H
authors.initials: SH
authors.lastname: Chiu
authors.forename: E
authors.initials: E
authors.lastname: Eugui
authors.forename: J P
authors.initials: JP
authors.lastname: Caulfield
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D048429:Cell Size; D004305:Dose-Response Relationship, Drug; D006151:Guanosine / Q000494:pharmacology; D006801:Humans; D008055:Lipids / Q000032:analysis; D008214:Lymphocytes / Q000166:cytology*; D008247:Lysosomes / Q000187:drug effects; D009000:Monocytes / Q000166:cytology*; D009173:Mycophenolic Acid / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000166:cytology; D020298:U937 Cells / Q000737:chemistry / Q000166:cytology
chemical_list: D008055:Lipids; D006151:Guanosine; D009173:Mycophenolic Acid