一氧化氮補捉物Carboxy-PTIO降低永久性腦梗塞的神經保護作用－－初步報告

Nitric Oxide Scavenger Carboxy-PIlO Reduces Infarct Volume Following Permanent Focal Ischemia

背景：一氧化氮（NO）被報告於大腦缺血時扮演著神經保護與神經毒性的雙重角色。自由離子補捉物則在大腦缺血時據有保護大腦組織的功能。因此我們檢測一氧化氮補捉物2-（4-carbo-xyphenyl）-4, 4, 5, 5-tetramethylimidazoline-l-oxyl-3-oxide （carboxy-PTIO）在大鼠與小鼠永久性中大腦動脈阻塞時的神經保護作用。方法：我們使用中大腦動脈（middle cerebral artery, MCA）永久性梗塞的動物模式。在誘發中大腦 動脈阻塞前一個小時，31隻Sprague-Dawley大鼠分別在腹腔內注射carboxy-PTIO （0.3, 0.6 mg/kg）或生理食鹽水。另一個實驗，則使用49隻C57BL/6NCrj小鼠進行誘發中大腦動脈阻塞之後30分鐘，於腹腔注射carboxyl-PTIO （0.6, 1.2mg/kg）或生理食鹽水。於22～24小時之後，評估神經行為分數，及用2, 3, 5-triphenyltetrazolium （TTC）腦部染色切片定量影像分析梗塞範圍。結果：實驗結果顯示事先於大鼠發生中大腦動脈阻塞前一小時給予0.6mg/kg carboxy-PTIO腹腔內注射，有效的降低梗塞面積的範圍（實驗組19.9 ± 2.9％；n= 10 vs.控制組29.2 ± 2.7％；n = 16），但在0.3 mg/kg劑量則無差異（28.3 ± 8.4%；n = 5）。另一小鼠實驗於發生中大腦動脈阻塞後30分鐘給予0.6 mg/kg carboxy-PTIO （30.3 ± 3.9％；n = 16），亦有效降低梗塞面積的範圍（控制組：46.1 ± 2.8％；n = 18）。結論：初步的研究結論為在中大腦動脈永久性梗塞造成的局部大腦缺血，不管事先於大鼠或事後於小鼠模式給予0.6 mg/kg carboxy-PTIO皆可提供神經保護作用。

Background: Nitric oxide (NO) has been shown to play a dual role as a neuroprotectant and a neurotoxin in cerebral ischemia. Free radical scavengers protect brain tissue from ischemic injury. Consequently, we examined the neuroprotective action of NO scavenger, 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-l-oxyl-3-oxide(carboxy-PTIO), in cerebral ischemia induced by permanent middle cerebral artery occlusion (MCAO) in rats and mice. Methods: All experiments were performed in a randomized fashion. In the first series of experiments, adult Sprague-Dawley rats (n = 31) subjected to permanent MCAO were treated with carboxy-PTIO (0.3, 0.6 mg/kg) or vehicle (normal saline) injected intraperitoneally (IP) 1 hr before permanent MCAO. In the second series of experiments, adult C57BL/6NCrj mice (n = 49) were treated with carboxy-PTIO (0.6, 1.2 mg/kg) or vehicle saline 30 min following MCAO. Neurobehavioral scores were determined 22-24 hr following permanent MCAO and infarct volumes determined by quantitative image analysis of 2, 3, 5-triphenyltetrazolium (TTC)-stained brain sections. Results: Pre-treatment with carboxy-PTIO at 0.6 mg/kg IP in rats significantly attenuated infarct volume (19.9 ± 2.9%; n = 10) as compared with vehicle-treated controls (29.2 ± 2.7%; n = 16), but not at 0.3 mg/kg (28.3 ± 8.4%; n = 5). Post-MCAO treatment in mice with 0.6 mg/kg carboxy-PTIO (30.3 ± 3.9%; n = 16) significantly attenuated infarct volume as compared with vehicle-treated controls (46.1 ± 2.8%; n = 18). Conclusions: These data demonstrate that NO scavenger, carboxy-PTIO, provides significant ischemic neuroprotection when given as a pre-treatment as well as after the onset of permanent focal ischemia in two animal species.