Postischemic Brain Injury Is Exacerbated in Mice Lacking the Kinin B2 Receptor

Abstract

Abstract-Kallikrein cleaves low molecular weight kininogen to generate vasoactive kinins, which bind to the kinin B2 receptor, triggering a host of biological effects. Kallikrein gene delivery has been shown previously to reduce ischemia/reperfusioninduced cerebral infarction. In this study, we tested the hypothesis that the kinin B2 receptor plays a protective role in ischemic brain injury using kinin B2 receptor gene knockout (B2R-KO) mice subjected to middle cerebral artery occlusion (MCAO). The mortality rate and neurological deficit scores of B2R-KO mice (nϭ48) after MCAO were significantly increased compared with wild-type (WT) mice (nϭ40) when examined over a 14-day period. In addition, the infarct volume in B2R-KO mice was significantly larger than in WT mice at days 1 and 3 after MCAO. Similarly, apoptotic cells, detected by TUNEL labeling counterstained with propidium iodide, and caspase-3 activity in the ischemic brain increased significantly in B2R-KO mice at days 1 and 3 after MCAO. Furthermore, the accumulation of neutrophils in the ischemic brain of B2R-KO mice after MCAO increased when compared with WT mice and was associated with elevated tumor necrosis factor ␣ expression. These alterations in B2R-KO mice correlated with decreased NO levels, Akt, and glycogen synthase kinase-3␤ phosphorylation and increased nicotinamide-adenine dinucleotide oxidase activity. These results indicate that the kinin B2 receptor promotes survival and protects against brain injury by suppression of apoptosis and inflammation induced by ischemic stroke. The tissue kallikrein-kinin system has been shown previously to exert protective effects in heart after ischemic injury. 6,7 In addition, intracerebroventricular injection of the kallikrein gene has been shown to reduce cerebral infarct size and promote glial cell migration and survival after ischemic stroke. 8 The effects of kallikrein gene delivery were associated with enhanced NO formation, decreased oxidative stress, and activation of cell survival signaling pathways. Our previous studies have shown that the benefits of kallikrein gene delivery in the ischemic heart can be abolished by the administration of a kinin B2 receptor antagonist. 7 Therefore, the kinin B2 receptor may also play an important role in protecting the brain from ischemia/reperfusion (I/R) injury.To determine whether kallikrein/kinin provides neuroprotective effects against ischemic stroke via the kinin B2 receptor, we used wild-type (WT) and kinin B2 receptor knockout (B2R-KO) mice subjected to 90-minute occlusion of the middle cerebral artery followed by reperfusion. We then examined the potential effects of kinin B2 receptor on cell death and inflammatory cell accumulation in the ischemic brain. Our results showed that neurological deficit scores, infarct volume, and mortality rate were significantly elevated in B2R-KO mice in association with increased severity of apoptosis and inflammation in the ischemic brain. Methods Animals and TreatmentsMice (male and female, body weight 25 to 30 g), i...

Blockade of Bradykinin Receptor B1 but Not Bradykinin Receptor B2 Provides Protection From Cerebral Infarction and Brain Edema

“…12 Differences in the time of brain ischemia (45 min vs 60 min) obviously did not account for the divergent results, because we also observed identical infarct volumes after 45 minutes of tMCAO at day 1 in WT and B2R KO mice (not shown). In obvious contrast to Gröger et al, 12 Xia et al 53 postulated that postischemic brain injury is exacerbated in mice lacking the B2R. Numerous studies did not find a detrimental effect of B2R deficiency or blockade on stroke outcome.…”

“…Numerous studies did not find a detrimental effect of B2R deficiency or blockade on stroke outcome. 12,54,55 Infarct size in WT mice after 90 minutes of MCAO was surprisingly small in the study by Xia et al, 53 whereas the B2R KO mice had developed infarcts that were the size that one would usually expect in WT mice after 90 minutes of tMCAO. We and others 27,28,55,56 could demonstrate that 60 minutes of occlusion of the MCA already causes infarct volumes between 50 and 80 mm 3 at day 1 after MCAO, eg, in C57BL/6, SV129, or Swiss mice.…”

Bradykinin B1 and B2 receptors both have protective roles in renal ischemia/reperfusion injury

“…In addition, several studies have suggested that agonism of the B1R and B2R may have different effects on the severity of I/R injury (21)(22)(23). In contrast, lack of the B1R (42) or B2R (43) aggravates the I/R injury in the heart and brain of mice, whereas adenovirus-mediated gene transfer of tissue kallikrein protects against ischemic stroke in rats (44). Transgenic expression of tissue kallikrein in mice attenuates ischemic cardiac damage (45), whereas tissue kallikrein knockout in mice aggravates the damage (24).…”

RNA interference-mediated downregulation of Beclin1 attenuates cerebral ischemic injury in rats

“…Neurological deficit scores were determined at 24 h, 7 days and 14 days after MCAO as previously described [27] : no neurological deficit (value=0); left forelimb flexion when suspended by the tail or failure to extend right forepaw fully (value=1); left shoulder adduction when suspended by the tail (value=2); reduced resistance to lateral push toward the left side (value=3); spontaneous movement in all directions with circling to the left exhibited only if pulled by tail (value=4); circle or walk spontaneously only to the left (value=5); walk only when stimulated (value=6); no response to stimulation (value=7); and stroke-related death (value=8).…”