Role of EP3 and EP4 prostaglandin receptors in reorganization of the cytoskeleton in mature human osteoclasts.
OBJECTIVE
Osteoclasts are central to the pathophysiology of several bone diseases. Prostaglandin E2 (PGE2) is well known to influence osteoclasts indirectly, but its direct action on osteoclasts is still controversial and the relevant receptors are unknown. We investigated the distribution and function of EP receptors in human mature osteoclasts.


METHODS
Osteoclasts were extracted from femurs and tibias of human fetuses obtained from legal abortions. In situ hybridization and immunohistochemistry were used to detect the presence of EP1, EP2, EP3, and EP4 receptors on these cells. Actin staining and fluorescent microscopy were used to detect the effects of receptor activation on the cytoskeleton.


RESULTS
Only EP3 and EP4 receptors were detected at the RNA and protein level in osteoclasts. These receptors were functional: PGE2 decreased the number of osteoclasts presenting an actin ring; 11-deoxy-PGE1, an EP2 and EP4 agonist, also decreased the number of tartrate-resistant acid phosphatase-positive cells with an actin ring; sulprostone, an EP3-specific agonist, had no effect on this variable but increased the number of cells with lamellipodia.


CONCLUSIONS
Mature human osteoclasts present 2 subtypes of EP receptors, namely EP3 and EP4, that mediate different actions of PGE2 on these cells: activation of the EP4 receptors inhibits actin ring formation and activation of the EP3 receptors increases the number of lamellipodia. Activation or inhibition of these receptors by specific agents could be used to study and influence osteoclast function.
Division of Rheumatology, Department of Medicine, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada.
Patrice
P
Sarrazin
Josette A
JA
Hackett
Isabelle
I
Fortier
Maxime A
MA
Gallant
Artur
A
de Brum-Fernandes
D000135:Acid Phosphatase / Q000378:metabolism; D000199:Actins / Q000502:physiology; D000527:Alprostadil / Q000031:analogs & derivatives* / Q000494:pharmacology; D016922:Cellular Senescence; D003599:Cytoskeleton / Q000502:physiology*; D015232:Dinoprostone / Q000031:analogs & derivatives* / Q000494:pharmacology; D005333:Fetus; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007527:Isoenzymes / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D018078:Receptors, Prostaglandin E / Q000819:agonists / Q000235:genetics / Q000502:physiology*; D058308:Receptors, Prostaglandin E, EP3 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; D000071681:Tartrate-Resistant Acid Phosphatase
D000199:Actins; D007527:Isoenzymes; C545647:PTGER3 protein, human; C545650:PTGER4 protein, human; D012333:RNA, Messenger; D018078:Receptors, Prostaglandin E; D058308:Receptors, Prostaglandin E, EP3 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; C016767:sulprostone; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D000527:Alprostadil; D015232:Dinoprostone; C034008:11-deoxyprostaglandin E1