title: Substance P reduces TNF-α-induced apoptosis in human tenocytes through NK-1 receptor stimulation.
abstract: BACKGROUND
  It has been hypothesised that an upregulation of the neuropeptide substance P (SP) and its preferred receptor, the neurokinin-1 receptor (NK-1 R), is a causative factor in inducing tenocyte hypercellularity, a characteristic of tendinosis, through both proliferative and antiapoptotic stimuli. We have demonstrated earlier that SP stimulates proliferation of human tenocytes in culture.
  
  
  OBJECTIVE
  The aim of this study was to investigate whether SP can mediate an antiapoptotic effect in tumour necrosis factor-α (TNF-α)-induced apoptosis of human tenocytes in vitro.
  
  
  RESULTS
  A majority (approximately 75%) of tenocytes in culture were immunopositive for TNF Receptor-1 and TNF Receptor-2. Exposure of the cells to TNF-α significantly decreased cell viability, as shown with crystal violet staining. TNF-α furthermore significantly increased the amount of caspase-10 and caspase-3 mRNA, as well as both BID and cleaved-poly ADP ribosome polymerase (c-PARP) protein. Incubation of SP together with TNF-α resulted in a decreased amount of BID and c-PARP, and in a reduced lactate dehydrogenase release, as compared to incubation with TNF-α alone. The SP effect was blocked with a NK-1 R inhibitor.
  
  
  CONCLUSIONS
  This study shows that SP, through stimulation of the NK-1 R, has the ability to reduce TNF-α-induced apoptosis of human tenocytes. Considering that SP has previously been shown to stimulate tenocyte proliferation, the study confirms SP as a potent regulator of cell-turnover in tendon tissue, capable of stimulating hypercellularity through different mechanisms. This gives further support for the theory that the upregulated amount of SP seen in tendinosis could contribute to hypercellularity.
authors.affiliation: Department of Integrative Medical Biology, Anatomy, Umeå University, Umeå, Sweden Department of Surgical and Perioperative Sciences, Sports Medicine, Umeå University, Umeå, Sweden.
authors.forename: Ludvig J
authors.initials: LJ
authors.lastname: Backman
authors.affiliation: Department of Integrative Medical Biology, Anatomy, Umeå University, Umeå, Sweden.
authors.forename: Daniella E
authors.initials: DE
authors.lastname: Eriksson
authors.affiliation: Department of Integrative Medical Biology, Anatomy, Umeå University, Umeå, Sweden.
authors.forename: Patrik
authors.initials: P
authors.lastname: Danielson
mesh_terms: D000125:Achilles Tendon / Q000166:cytology; D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000187:drug effects; D020169:Caspases / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006801:Humans; D064729:Neurokinin-1 Receptor Antagonists / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000187:drug effects; D012333:RNA, Messenger / Q000187:drug effects; D018040:Receptors, Neurokinin-1 / Q000187:drug effects; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D013373:Substance P / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D064729:Neurokinin-1 Receptor Antagonists; D018377:Neurotransmitter Agents; D012333:RNA, Messenger; D018040:Receptors, Neurokinin-1; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha; D013373:Substance P; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases
keywords: Achilles Tendon; Tendons