Fine-tuned ATP signals are acute mediators in osteocyte mechanotransduction.
Osteocytes are considered the primary mechanosensors of bone, but the signaling pathways they apply in mechanotransduction are still incompletely investigated and characterized. A growing body of data strongly indicates that P2 receptor signaling among osteoblasts and osteoclasts has regulatory effects on bone remodeling. Therefore, we hypothesized that ATP signaling is also applied by osteocytes in mechanotransduction. We applied a short fluid pulse on MLO-Y4 osteocyte-like cells during real-time detection of ATP and demonstrated that mechanical stimulation activates the acute release of ATP and that these acute ATP signals are fine-tuned according to the magnitude of loading. ATP release was then challenged by pharmacological inhibitors, which indicated a vesicular release pathway for acute ATP signals. Finally, we showed that osteocytes express functional P2X2 and P2X7 receptors and respond to even low concentrations of nucleotides by increasing intracellular calcium concentration. These results indicate that in osteocytes, vesicular ATP release is an acute mediator of mechanical signals and the magnitude of loading. These and previous results, therefore, implicate purinergic signaling as an early signaling pathway in osteocyte mechanotransduction.
Research Center for Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark; Research Center for Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark; The Osteoporosis and Bone Metabolic Unit, Dept. of Endocrinology, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; The Osteoporosis and Bone Metabolic Unit, Dept. of Clinical Biochemistry, Copenhagen, University Hospital Hvidovre, Hvidovre, Denmark.
Tina M
TM
Kringelbach
Research Center for Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark; Research Center for Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark.
Derya
D
Aslan
Department of Biology, University of Copenhagen, Copenhagen Ø, Denmark.
Ivana
I
Novak
Research Center for Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark; Research Center for Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark.
Maria
M
Ellegaard
Research Center for Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark; Research Center for Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark.
Susanne
S
Syberg
Research Center for Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark; Research Center for Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark.
Christina K B
CK
Andersen
Department of Clinical Research, Copenhagen University Hospital Glostrup, Glostrup, Denmark.
Kim A
KA
Kristiansen
Department of Science, Systems and Models, Roskilde University, Roskilde, Denmark.
Ole
O
Vang
Research Center for Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark; Research Center for Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark; Faculty of Health Science, University of Copenhagen, Copenhagen, Denmark.
Peter
P
Schwarz
Research Center for Ageing and Osteoporosis, Department of Diagnostics, Copenhagen University Hospital Glostrup, Glostrup, Denmark; Research Center for Ageing and Osteoporosis, Department of Medicine, Copenhagen University Hospital Glostrup, Glostrup, Denmark; The Osteoporosis and Bone Metabolic Unit, Dept. of Endocrinology, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark; The Osteoporosis and Bone Metabolic Unit, Dept. of Clinical Biochemistry, Copenhagen, University Hospital Hvidovre, Hvidovre, Denmark. Electronic address: Niklas@dadlnet.dk.
Niklas R
NR
Jørgensen
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D016723:Bone Remodeling; D020013:Calcium Signaling; D002460:Cell Line; D018031:Connexin 43 / Q000378:metabolism; D017630:Connexins / Q000378:metabolism; D015870:Gene Expression; D040542:Mechanotransduction, Cellular; D008807:Mice, Inbred BALB C; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010011:Osteocytes / Q000378:metabolism* / Q000502:physiology; D058469:Receptors, Purinergic P2X / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems
D018031:Connexin 43; D017630:Connexins; C543076:GJA1 protein, mouse; D009419:Nerve Tissue Proteins; C503631:Panx1 protein, mouse; D058469:Receptors, Purinergic P2X; D000255:Adenosine Triphosphate
ATP release; Mechanotransduction; Osteocyte; P2 receptors; Vesicles