Fibronectin/integrin system is involved in P2X(4) receptor upregulation in the spinal cord and neuropathic pain after nerve injury.
We have previously shown that activation of the ATP-gated ion channel subtype P2X(4) receptors (P2X(4)Rs) in the spinal cord, the expression of which is upregulated in microglia after nerve injury, is necessary for producing neuropathic pain. The upregulation of P2X(4)Rs in microglia is, therefore, a key process in neuropathic pain, but the mechanism remains unknown. Here, we find a fibronectin/integrin-dependent mechanism in the upregulation of P2X(4)Rs. Microglia cultured on dishes coated with fibronectin, an extracellular matrix molecule, expressed a higher level of P2X(4)R protein when compared with those cultured on control dishes. The increase was suppressed by echistatin, a peptide that selectively blocks beta(1) and beta(3)-containing integrins, and with a function-blocking antibody of beta(1) integrin. In in vivo studies, the upregulation of P2X(4)Rs in the spinal cord after spinal nerve injury was significantly suppressed by intrathecal administration of echistatin. Tactile allodynia in response to nerve injury and intrathecal administration of ATP- and fibronectin-stimulated microglia was inhibited by echistatin. Furthermore, intrathecal administration of fibronectin in normal rats increased the level of P2X(4)R protein in the spinal cord and produced tactile allodynia. Moreover, the fibronectin-induced allodynia was not observed in mice lacking P2X(4)R. Taken together with the results of our previous study showing an increase in the spinal fibronectin level after nerve injury, the present results suggest that the fibronectin/integrin system participates in the upregulation of P2X(4)R expression after nerve injury and subsequent neuropathic pain.
Tsuda
Makoto
M
Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Toyomitsu
Emika
E
Komatsu
Takayuki
T
Masuda
Takahiro
T
Kunifusa
Emiko
E
Nasu-Tada
Kaoru
K
Koizumi
Schuichi
S
Yamamoto
Kimiko
K
Ando
Joji
J
Inoue
Kazuhide
K
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005353:Fibronectins / Q000502:physiology*; D016023:Integrins / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D017628:Microglia / Q000187:drug effects / Q000502:physiology; D009437:Neuralgia / Q000209:etiology / Q000378:metabolism*; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D010455:Peptides / Q000494:pharmacology; D010523:Peripheral Nervous System Diseases / Q000150:complications / Q000473:pathology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058848:Receptors, Purinergic P2X4; D013116:Spinal Cord / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation / Q000502:physiology*
D005353:Fibronectins; D016023:Integrins; D036341:Intercellular Signaling Peptides and Proteins; C548227:P2rx4 protein, mouse; D010455:Peptides; D010975:Platelet Aggregation Inhibitors; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; C057986:echistatin; D000255:Adenosine Triphosphate