title: Effects of xylazine and dexmedetomidine on equine articular chondrocytes in vitro.
abstract: OBJECTIVE
  To assess the effects of xylazine and dexmedetomidine on equine chondrocytes, in vitro.
  
  
  METHODS
  Prospective, experimental study.
  
  
  METHODS
  Equine articular chondrocytes from five male horses.
  
  
  METHODS
  Chondrocytes were isolated from healthy equine articular cartilage of the metacarpo/metatarsophalangeal joints. Cell viability was assessed using the WST-8 assay by exposing chondrocytes to xylazine (0.5, 1, 2, 4, 8, 16.6, 25, 50 mg mL-1) or dexmedetomidine (0.001, 0.005, 0.01, 0.05, 0.175, 0.25 mg mL-1) for 15, 30 and 60 minutes. Based on the results of these tests, cells were treated with xylazine (1, 4, 25 mg mL-1) or dexmedetomidine (0.05, 0.175, 0.25 mg mL-1) for 15 minutes to further evaluate: cell viability by neutral red uptake; cell membrane integrity by lactate dehydrogenase release and by fluorescence microscopy with Hoechst 33342 and propidium iodide (PI), and apoptosis by flow cytometry using double staining with annexin V-fluorescein isothiocyanate/PI and by cell morphology.
  
  
  RESULTS
  Both drugs reduced cell viability in a dose-dependent manner. Specifically, all xylazine concentrations, except 0.5 mg mL-1and 1 mg mL-1, significantly reduced cell viability, whereas the effects of dexmedetomidine were evident only at 0.175 mg mL-1and 0.25 mg mL-1. The highest concentrations of xylazine (25 mg mL-1) and dexmedetomidine (0.25 mg mL-1) caused loss of membrane integrity. Cell morphology and flow cytometry analyses demonstrated signs of late apoptosis in xylazine-treated cells, and signs of late apoptosis and necrosis in dexmedetomidine-treated cells.
  
  
  CONCLUSIONS
  This study offers new insights into the potential chondrotoxicity induced by dexmedetomidine and xylazine. Therefore, the intra-articular administration of α2-agonists should be conducted with care, especially for doses of ≥ 4 mg mL-1of xylazine and 0.175 mg mL-1and 0.25 mg mL-1of dexmedetomidine.
authors.affiliation: Laboratory of Proteomics and Cellular Biochemistry, Department of Veterinary Medicine, University of Perugia, Perugia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Mancini
authors.affiliation: Sport Horse Research Centre, Department of Veterinary Medicine, University of Perugia, Perugia, Italy; Veterinary Teaching Hospital, Department of Veterinary Medicine, University of Perugia, Perugia, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Nannarone
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy.
authors.forename: Sandra
authors.initials: S
authors.lastname: Buratta
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Ferrara
authors.affiliation: Laboratory of Anatomy, Department of Surgery and Biomedical Sciences, University of Perugia, Perugia, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Stabile
authors.affiliation: Veterinary Teaching Hospital, Department of Veterinary Medicine, University of Perugia, Perugia, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Vuerich
authors.affiliation: Veterinary Teaching Hospital, Department of Veterinary Medicine, University of Perugia, Perugia, Italy.
authors.forename: Isabella
authors.initials: I
authors.lastname: Santinelli
authors.affiliation: Laboratory of Anatomy, Department of Surgery and Biomedical Sciences, University of Perugia, Perugia, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pistilli
authors.affiliation: Laboratory of Proteomics and Cellular Biochemistry, Department of Veterinary Medicine, University of Perugia, Perugia, Italy; Sport Horse Research Centre, Department of Veterinary Medicine, University of Perugia, Perugia, Italy. Electronic address: elisabetta.chiaradia@unipg.it.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Chiaradia
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology*; D002462:Cell Membrane / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019902:Chondrocytes / Q000187:drug effects*; D020927:Dexmedetomidine / Q000494:pharmacology*; D006736:Horses; D066298:In Vitro Techniques / Q000662:veterinary; D008297:Male; D011446:Prospective Studies; D013778:Tetrazolium Salts / Q000494:pharmacology; D014991:Xylazine / Q000494:pharmacology*
chemical_list: C476329:2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H tetrazolium monosodium salt; D058647:Adrenergic alpha-2 Receptor Agonists; D013778:Tetrazolium Salts; D014991:Xylazine; D020927:Dexmedetomidine
keywords: apoptosis; chondrotoxicity; dexmedetomidine; xylazine; α(2)-agonists