title: Protective effect of P188 in the model of acute trauma to human ankle cartilage: the mechanism of action.
abstract: OBJECTIVE
  Because P188 poloxamer is effective in promoting cell survival in models of acute trauma, the objectives were to understand the mechanism of its action focusing on glycogen synthase kinase-3 (GSK3) activation, interleukin-6 (IL-6), and p38 signaling.
  
  
  METHODS
  Sixteen normal human tali were impacted using a 4-mm diameter indenter with an impulse of 1 Ns. Eight-millimeter cartilage plugs containing the 4-mm impacted core and 4-mm adjacent nonimpacted ring were removed and cultured with or without P188. Cell lysates were analyzed using Western blots with antibodies against total and phosphorylated extracellular signal-regulated protein kinase (ERK), c-Jun NH2-terminal kinase (JNK), p38, ATF-2, GSK3, Stat1, and Stat3. Additional tests were performed with the p38 inhibitor (p38i) SB203580.
  
  
  RESULTS
  Studied pathways were activated after impaction with the peak of activity at 1 hour. P188 completely attenuated phosphorylation of Stat1 and ATF-2 and inhibited p38, Stat3, JNK, ERK, and GSK3. The p38i partially offset phosphorylation of Stat3, GSK3, and ERK suggesting a role of p38 in these three pathways. Additionally, the p38i improved cell survival (P = 0.053) and reduced apoptosis (by approximately 20%, P = 0.046, versus almost 40% by P188), thus confirming that P188 acts (at least in part) through the p38 pathway.
  
  
  CONCLUSIONS
  Our results report a novel mechanism through which P188 exerts its protective effects on cartilage in the model of acute injury. In addition to its effect on cellular membrane, P188 affects stress-related p38 signaling, apoptosis-related GSK3, and inflammation-related IL-6 signaling. Taken together, these findings suggest that P188 alone or in combination with proanabolic agents may have a therapeutic potential in preventing progressive cartilage degeneration and the development of posttraumatic osteoarthritis.
authors.affiliation: Department of Biochemistry, Rush University Medical Center, Chicago, IL 60612, USA.
authors.forename: Sarvottam
authors.initials: S
authors.lastname: Bajaj
authors.forename: Thomas
authors.initials: T
authors.lastname: Shoemaker
authors.forename: Arnavaz A
authors.initials: AA
authors.lastname: Hakimiyan
authors.forename: Lev
authors.initials: L
authors.lastname: Rappoport
authors.forename: Cecilia
authors.initials: C
authors.lastname: Pascual-Garrido
authors.forename: Theodore R
authors.initials: TR
authors.lastname: Oegema
authors.forename: Markus A
authors.initials: MA
authors.lastname: Wimmer
authors.forename: Susan
authors.initials: S
authors.lastname: Chubinskaya
mesh_terms: D016512:Ankle Injuries / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D000843:Ankle Joint / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects; D002358:Cartilage, Articular / Q000187:drug effects* / Q000293:injuries / Q000473:pathology; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D050724:Fractures, Cartilage / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism; D020442:Poloxamer / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013501:Surface-Active Agents / Q000494:pharmacology*; D013628:Talus / Q000187:drug effects / Q000293:injuries; D014945:Wound Healing / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; C508600:IL6 protein, human; D007093:Imidazoles; D015850:Interleukin-6; D011725:Pyridines; D013501:Surface-Active Agents; D020442:Poloxamer; D048051:p38 Mitogen-Activated Protein Kinases; D038362:Glycogen Synthase Kinase 3; C093642:SB 203580