ATTENUATION OF ISCHEMIC INFLAMMATORY RESPONSE IN MOUSE-BRAIN USING ANADENOVIRAL VECTOR TO INDUCE OVEREXPRESSION OF INTERLEUKIN-1 RECEPTOR ANTAGONIST

It has been demonstrated that administration of an interleukin-1 recep tor antagonist protein (IL-1ra) reduces ischemic brain injury; however , the detrimental mechanism initialed by interleukin-1 (IL-1) in ische mic brain injury is unclear. In this study, we used mice that were tra nsfected to overexpress human IL-1ra to elucidate the role of IL-1 in the activation of the inflammatory response after middle cerebral arte ry occlusion (MCAO). Myeloperoxidase (MPO) activity and immunohistosta ining were used as a marker of polymorphonuclear leukocytes (PMNL) inf iltration. Adenoviral vector (1 x 10(9) particles) was administered by injection into the right lateral ventricle in mice. Five days later, MCAO was performed on the mice using a suture technique. Permanent MCA O was achieved for 24 hours in the Ad.RSVIL-1ra-transfected, Ad.RSVlac Z-transfected, and saline (control) mice. Myeloperoxidase activity was quantified in each region and localization of MPO was determined by i mmunohistochemistry. After 2 hours of MCAO, the surface cerebral blood flow was reduced to 13.5% +/- 3.4%, 10.75% +/- 2.6%, and 10.9% +/- 2. 6% of baseline in the ischemic hemisphere in Ad.RSVIL-1ra-transfected, Ad.RSV-lacZ-transfected, and saline-treated mice, respectively. The M PO activity in the ischemic hemisphere in the Ad.RSVlacZ group was sim ilar to that in the saline control group (cortex: 0.40 +/- 0.22 versus 0.33 +/- 0.11; basal ganglia: 0.46 +/- 0.23 versus 0.49 +/- 0.17; P > 0.05); however, it was significantly reduced in the Ad.RSVIL-1ra grou p (cortex: 0.18 +/- 0.07; basal ganglia: 0.26 +/- 0.15; P < 0.05). Mye loperoxidase immunohis tochemistry showed that the massive accumulatio n of MPO-positive cells in the ischemic cortex, striatum, and corpus c allosum regions was greatly attenuated in Ad.RSVIL-1ra-transfected mic e. Our results indicate that Ad.RSVIL-1ra transfected mice provide a u seful tool to study the mechanism of action of IL-1. The MPO activity assay and immunostaining after 24 hours of focal ischemia were signifi cantly reduced in IL-1ra gene-transfected mice, suggesting that IL-1 m ay play an important role in the activation of inflammatory cells duri ng focal cerebral ischemia.