Effects of LF 16-0687 Ms, a bradykinin B(2) receptor antagonist, on brain edema formation and tissue damage in a rat model of temporary focal cerebral ischemia.

Bradykinin, an endogenous nonapeptide produced by activation of the kallikrein-kinin system, promotes neuronal tissue damage as well as disturbances in blood-brain barrier function through activation of B(2) receptors. LF 16-0687 Ms, a non-peptide competitive bradykinin B(2) receptor antagonist, was recently found to decrease brain swelling in various models of traumatic brain injury. We have investigated the influence of LF 16-0687 Ms on the edema formation, neurological outcome, and infarct size in temporary focal cerebral ischemia in rats. Sprague-Dawley rats were subjected to MCA occlusion for 90 min by an intraluminal filament. Local CBF was bilaterally recorded by laser Doppler flowmetry. Study I: animals were assigned to one of three treatment arms (n=11 each): (a) vehicle, (b) LF 16-0687 Ms (12.0 mg/kg per day), or (c) LF 16-0687 Ms (36.0 mg/kg per day) given repetitively s.c. over 3 days. The neurological recovery was examined daily. The infarct volume was assessed histologically 7 days after ischemia. Study II: brain swelling and bilateral hemispheric water content were determined at 48 h post ischemia in eight rats, subjected to the low dose regimen as described above, and in eight vehicle-treated control animals. All treated animals showed tendency to exhibit improved neurological recovery throughout the observation period as compared to the vehicle-treated controls, while this improvement was only significant within the low dose group from postischemic days 3 to 4. Low dose LF 16-0687 Ms significantly attenuated the total and cortical infarct volume by 50 and 80%, respectively. Furthermore, postischemic swelling (-62%) and increase in water content of the infarcted brain hemisphere (-60.5%) was significantly inhibited. The present findings provide strong evidence for an involvement of bradykinin-mediated secondary brain damage following from focal cerebral ischemia. Accordingly, specific inhibition of bradykinin B(2) receptors by LF 16-0687 Ms attenuated postischemic brain swelling, improved the functional neurological recovery, and limited ischemic tissue damage, raising its potential for clinical evaluation in patients with acute stroke.