Blockade of bradykinin receptor B1 but not bradykinin receptor B2 provides protection from cerebral infarction and brain edema.
OBJECTIVE
Brain edema is detrimental in ischemic stroke and its treatment options are limited. Kinins are proinflammatory peptides that are released during tissue injury. The effects of kinins are mediated by 2 different receptors (B1 and B2 receptor [B1R and B2R]) and comprise induction of edema formation and release of proinflammatory mediators.


METHODS
Focal cerebral ischemia was induced in B1R knockout, B2R knockout, and wild-type mice by transient middle cerebral artery occlusion. Infarct volumes were measured by planimetry. Evan's blue tracer was applied to determine the extent of brain edema. Postischemic inflammation was assessed by real-time reverse-transcriptase polymerase chain reaction and immunohistochemistry. To analyze the effect of a pharmacological kinin receptor blockade, B1R and B2R inhibitors were injected.


RESULTS
B1R knockout mice developed significantly smaller brain infarctions and less neurological deficits compared to wild-type controls (16.8+/-4.7 mm(3) vs 50.1+/-9.1 mm(3), respectively; P<0.0001). This was accompanied by a dramatic reduction of brain edema and endothelin-1 expression, as well as less postischemic inflammation. Pharmacological blockade of B1R likewise salvaged ischemic tissue (15.0+/-9.5 mm(3) vs 50.1+/-9.1 mm(3), respectively; P<0.01) in a dose-dependent manner, even when B1R inhibitor was applied 1 hour after transient middle cerebral artery occlusion. In contrast, B2R deficiency did not confer neuroprotection and had no effect on the development of tissue edema.


CONCLUSIONS
These data demonstrate that blocking of B1R can diminish brain infarction and edema formation in mice and may open new avenues for acute stroke treatment in humans.
Austinat
Madeleine
M
Department of Neurology, Julius-Maximilians-University of Würzburg, Josef-Schneider Strasse 11, D-97080 Würzburg, Germany.
Braeuninger
Stefan
S
Pesquero
João B
JB
Brede
Marc
M
Bader
Michael
M
Stoll
Guido
G
Renné
Thomas
T
Kleinschnitz
Christoph
C
D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use; D065169:Bradykinin B1 Receptor Antagonists; D065094:Bradykinin B2 Receptor Antagonists; D001929:Brain Edema / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D002536:Cerebral Arteries / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D002544:Cerebral Infarction / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000235:genetics; D004660:Encephalitis / Q000188:drug therapy / Q000503:physiopathology / Q000517:prevention & control; D019332:Endothelin-1 / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D020244:Infarction, Middle Cerebral Artery / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D043783:Receptor, Bradykinin B1 / Q000235:genetics / Q000378:metabolism; D043782:Receptor, Bradykinin B2 / Q000235:genetics / Q000378:metabolism
D065169:Bradykinin B1 Receptor Antagonists; D065094:Bradykinin B2 Receptor Antagonists; D019332:Endothelin-1; C120984:R 715; D012333:RNA, Messenger; D043783:Receptor, Bradykinin B1; D043782:Receptor, Bradykinin B2; C065679:icatibant; D001920:Bradykinin