P2X7-dependent release of interleukin-1beta and nociception in the spinal cord following lipopolysaccharide.
The cytokine interleukin-1beta (IL-1beta) released by spinal microglia in enhanced response states contributes significantly to neuronal mechanisms of chronic pain. Here we examine the involvement of the purinergic P2X7 receptor in the release of IL-1beta following activation of Toll-like receptor-4 (TLR4) in the dorsal horn, which is associated with nociceptive behavior and microglial activation. We observed that lipopolysaccharide (LPS)-induced release of IL-1beta was prevented by pharmacological inhibition of the P2X7 receptor with A-438079, and was absent in spinal cord slices taken from P2X7 knock-out mice. Application of ATP did not evoke release of IL-1beta from the dorsal horn unless preceded by an LPS priming stimulus, and this release was dependent on P2X7 receptor activation. Extensive phosphorylation of p38 MAPK in microglial cells in the dorsal horn was found to correlate with IL-1beta secretion following both LPS and ATP. In behavioral studies, intrathecal injection of LPS in the lumbar spinal cord produced mechanical hyperalgesia in rat hindpaws, which was attenuated by concomitant injections of either a nonspecific (oxidized ATP) or a specific (A-438079) P2X7 antagonist. In addition, LPS-induced hypersensitivity was observed in wild-type but not P2X7 knock-out mice. These data suggest a critical role for the P2X7 receptor in the enhanced nociceptive transmission associated with microglial activation and secretion of IL-1beta in the dorsal horn. We suggest that CNS-penetrant P2X7 receptor antagonists, by targeting microglia in pain-enhanced response states, may be beneficial for the treatment of persistent pain.
Clark
Anna K
AK
Neurorestoration Group, Wolfson Centre for Age-Related Diseases, King's College London, London SE1 1UL, United Kingdom.
Staniland
Amelia A
AA
Marchand
Fabien
F
Kaan
Timothy K Y
TK
McMahon
Stephen B
SB
Malcangio
Marzia
M
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism*; D066298:In Vitro Techniques; D053583:Interleukin-1beta / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D017628:Microglia / Q000187:drug effects / Q000378:metabolism; D048292:Mitogen-Activated Protein Kinase 13 / Q000378:metabolism; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000172:deficiency / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D013116:Spinal Cord / Q000033:anatomy & histology / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013777:Tetrazoles / Q000494:pharmacology; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors
C523668:3-(5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl)methylpyridine; C092431:6-N,N-diethyl-beta,gamma-dibromomethylene-D-ATP; D005904:Glial Fibrillary Acidic Protein; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; C546469:P2rx7 protein, mouse; C546470:P2rx7 protein, rat; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011725:Pyridines; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D013777:Tetrazoles; C031433:8-(4-sulfophenyl)theophylline; D000255:Adenosine Triphosphate; D013806:Theophylline; D048292:Mitogen-Activated Protein Kinase 13; D010751:Phosphopyruvate Hydratase