Bradykinin-induced microglial migration mediated by B1-bradykinin receptors depends on Ca2+ influx via reverse-mode activity of the Na+/Ca2+ exchanger.
Bradykinin (BK) is produced and acts at the site of injury and inflammation. In the CNS, migration of microglia toward the lesion site plays an important role pathologically. In the present study, we investigated the effect of BK on microglial migration. Increased motility of cultured microglia was mimicked by B1 receptor agonists and markedly inhibited by a B1 antagonist but not by a B2 receptor antagonist. BK induced chemotaxis in microglia isolated from wild-type and B2-knock-out mice but not from B1-knock-out mice. BK-induced motility was not blocked by pertussis toxin but was blocked by chelating intracellular Ca2+ or by low extracellular Ca2+, implying that Ca2+ influx is prerequisite. Blocking the reverse mode of Na+/Ca2+ exchanger (NCX) completely inhibited BK-induced migration. The involvement of NCX was further confirmed by using NCX+/- mice; B1-agonist-induced motility and chemotaxis was decreased compared with that in NCX+/+ mice. Activation of NCX seemed to be dependent on protein kinase C and phosphoinositide 3-kinase, and resultant activation of intermediate-conductance (IK-type) Ca2+-dependent K+ currents (I(K(Ca))) was activated. Despite these effects, BK did not activate microglia, as judged from OX6 staining. Using in vivo lesion models and pharmacological injection to the brain, it was shown that microglial accumulation around the lesion was also dependent on B1 receptors and I(K(Ca)). These observations support the view that BK functions as a chemoattractant by using the distinct signal pathways in the brain and, thus, attracts microglia to the lesion site in vivo.
Laboratory of Pathophysiology, Graduate School of Pharmaceutical Science, Kyushu University, Fukuoka 812-8582, Japan.
Masataka
M
Ifuku
Katrin
K
Färber
Yuko
Y
Okuno
Yukiko
Y
Yamakawa
Taiki
T
Miyamoto
Christiane
C
Nolte
Vanessa F
VF
Merrino
Satomi
S
Kita
Takahiro
T
Iwamoto
Issei
I
Komuro
Bing
B
Wang
Giselle
G
Cheung
Eiichi
E
Ishikawa
Hiroaki
H
Ooboshi
Michael
M
Bader
Keiji
K
Wada
Helmut
H
Kettenmann
Mami
M
Noda
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001920:Bradykinin / Q000031:analogs & derivatives / Q000494:pharmacology*; D065169:Bradykinin B1 Receptor Antagonists; D065094:Bradykinin B2 Receptor Antagonists; D002118:Calcium / Q000378:metabolism*; D002465:Cell Movement / Q000187:drug effects*; D002478:Cells, Cultured; D002525:Cerebellar Cortex / Q000166:cytology; D002633:Chemotaxis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D051379:Mice; D018345:Mice, Knockout; D017628:Microglia / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D043783:Receptor, Bradykinin B1 / Q000819:agonists / Q000172:deficiency / Q000502:physiology*; D043782:Receptor, Bradykinin B2 / Q000819:agonists / Q000172:deficiency; D015398:Signal Transduction / Q000187:drug effects; D019831:Sodium-Calcium Exchanger / Q000502:physiology*; D013997:Time Factors
D065169:Bradykinin B1 Receptor Antagonists; D065094:Bradykinin B2 Receptor Antagonists; D043783:Receptor, Bradykinin B1; D043782:Receptor, Bradykinin B2; D019831:Sodium-Calcium Exchanger; C051090:bradykinin, Leu(8)-des-Arg(9)-; D000255:Adenosine Triphosphate; D001920:Bradykinin; D002118:Calcium