title: Activation of stress-activated protein kinases (SAPK) in tendon cells following cyclic strain: the effects of strain frequency, strain magnitude, and cytosolic calcium.
abstract: Cyclic strain has been shown to benefit tendon health. However, repetitive loading has also been implicated in the etiology of tendon overuse injuries. Recent studies demonstrated that in several cell lines cyclic strain was associated with an activation of stress-activated protein kinases (SAPKs). These SAPKs, in turn, were shown to be important upstream regulators of a variety of cell processes including apoptosis. To examine the effect of repetitive loading on SAPK activation in tendon cells in vitro, canine patellar tendon cells were cyclically strained, and the cellular stress response evaluated by measuring c-Jun N-terminal kinase (JNK) activation. The effects of strain frequency and strain magnitude as well as the role of calcium signaling in this mechanotransduction mechanism were also examined. Cyclic strain resulted in an immediate activation of JNK, which peaked at 30 min and returned to resting levels by 2 h. This activation was regulated by a magnitude-dependent but not frequency-dependent response and appeared to be mediated through a calcium-dependent mechanotransduction pathway. While transient JNK activation is associated with normal cell processes. persistent JNK activation has been linked to the initiation of the apoptotic cascade. A similar mechanism could be responsible for initiating the pathological events (localized cell death) seen in tendon overuse injury.
authors.affiliation: Laboratory for Comparative Orthopaedic Research, College of Veterinary Medicine, Michigan State University, East Lansing 48824, USA. arnoczky@cvm.msu.edu
authors.forename: Steven P
authors.initials: SP
authors.lastname: Arnoczky
authors.forename: Tao
authors.initials: T
authors.lastname: Tian
authors.forename: Michael
authors.initials: M
authors.lastname: Lavagnino
authors.forename: Keri
authors.initials: K
authors.lastname: Gardner
authors.forename: Paul
authors.initials: P
authors.lastname: Schuler
authors.forename: Patrick
authors.initials: P
authors.lastname: Morse
mesh_terms: D000818:Animals; D015153:Blotting, Western; D000001:Calcimycin / Q000494:pharmacology; D020013:Calcium Signaling; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004285:Dogs; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D008660:Metabolism / Q000187:drug effects; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis*; D010329:Patella; D013314:Stress, Mechanical; D013710:Tendons / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D016474:Weight-Bearing; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D000001:Calcimycin; D004533:Egtazic Acid; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases