Attenuation of stroke damage by angiotensin II type 2 receptor stimulation via peroxisome proliferator-activated receptor-gamma activation.

ABSTRACT

The brain renin-angiotensin system plays a crucial role in ischemic stroke. It is known that stimulation of the angiotensin II type 2 (AT2) receptor protects against ischemic brain injury. We recently demonstrated that AT2 receptor stimulation by compound 21 (C21), a direct AT2 receptor agonist, inhibited vascular intimal proliferation with activation of peroxisome proliferator-activated receptor-gamma (PPAR-γ). However, whether direct AT2 receptor stimulation protects against ischemic brain injury via PPAR-γ activation is still unknown. 8-week-old male C57BL/6 J mice were subjected to middle cerebral artery (MCA) occlusion. 2 weeks before MCA occlusion, they were administered C21 with or without GW9662, a PPAR-γ antagonist. Neurologic deficit, ischemic size, superoxide anion, superoxide dismutase (SOD) activity, expression of NADPH subunits and blood brain barrier (BBB) stabilization were assessed 24 h after MCA occlusion. Cerebral blood flow (CBF) was measured in the core and periphery of the MCA territory before, immediately after, 1 h and 24 h after MCA occlusion. Treatment with C21 markedly decreased the neurologic deficit and ischemic size with an increase in CBF, SOD activity and BBB stabilization genes compared with the non-treated group. Co-administration of GW9662 partially attenuated this protective effect of C21 on neurologic deficit and ischemic size via an increase in superoxide anion production and a decrease of SOD activity and BBB stabilization genes, while GW9662 treatment alone had no significant effect on neurologic deficit and ischemic size. These results suggest that direct AT2 receptor stimulation has a preventive effect on stroke-induced brain injury partly due to activation of PPAR-γ.