The P2X7 nucleotide receptor mediates skeletal mechanotransduction.
The P2X7 nucleotide receptor (P2X7R) is an ATP-gated ion channel expressed in many cell types including osteoblasts and osteocytes. Mice with a null mutation of P2X7R have osteopenia in load bearing bones, suggesting that the P2X7R may be involved in the skeletal response to mechanical loading. We found the skeletal sensitivity to mechanical loading was reduced by up to 73% in P2X7R null (knock-out (KO)) mice. Release of ATP in the primary calvarial osteoblasts occurred within 1 min of onset of fluid shear stress (FSS). After 30 min of FSS, P2X7R-mediated pore formation was observed in wild type (WT) cells but not in KO cells. FSS increased prostaglandin (PG) E2 release in WT cells but did not alter PGE2 release in KO cells. Studies using MC3T3-E1 osteoblasts and MLO-Y4 osteocytes confirmed that PGE2 release was suppressed by P2X7R blockade, whereas the P2X7R agonist BzATP enhanced PGE2 release. We conclude that ATP signaling through P2X7R is necessary for mechanically induced release of prostaglandins by bone cells and subsequent osteogenesis.
Li
Jiliang
J
Department of Anatomy and Cell Biology and Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Liu
Dawei
D
Ke
Hua Zhu
HZ
Duncan
Randall L
RL
Turner
Charles H
CH
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D001851:Bone Diseases, Metabolic / Q000473:pathology; D001861:Bone Regeneration; D001842:Bone and Bones / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D007473:Ion Channels / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008954:Models, Biological; D010006:Osteoblasts / Q000378:metabolism; D010011:Osteocytes / Q000378:metabolism; D011884:Radius / Q000378:metabolism; D018078:Receptors, Prostaglandin E / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism / Q000502:physiology*; D058486:Receptors, Purinergic P2X7; D015398:Signal Transduction; D013314:Stress, Mechanical; D013997:Time Factors; D014457:Ulna / Q000378:metabolism
D007473:Ion Channels; C546469:P2rx7 protein, mouse; D018078:Receptors, Prostaglandin E; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D015232:Dinoprostone