Gidday J M, Shah A R, Maceren R G, Wang Q, Pelligrino D A, Holtzman D M, Park T S
Department of Neurosurgery, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Cereb Blood Flow Metab. 1999 Mar;19(3):331-40. doi: 10.1097/00004647-199903000-00011.
Neuroprotection against cerebral ischemia can be realized if the brain is preconditioned by previous exposure to a brief period of sublethal ischemia. The present study was undertaken to test the hypothesis that nitric oxide (NO) produced from the neuronal isoform of NO synthase (NOS) serves as a necessary signal for establishing an ischemia-tolerant state in brain. A newborn rat model of hypoxic preconditioning was used, wherein exposure to sublethal hypoxia (8% oxygen) for 3 hours renders postnatal day (PND) 6 animals completely resistant to a cerebral hypoxic-ischemic insult imposed 24 hours later. Postnatal day 6 animals were treated 0.5 hour before preconditioning hypoxia with the nonselective NOS inhibitor L-nitroarginine (2 mg/kg intraperitoneally). This treatment, which resulted in a 67 to 81% inhibition of calcium-dependent constitutive NOS activity 0.5 to 3.5 hours after its administration, completely blocked preconditioning-induced protection. However, administration of the neuronal NOS inhibitor 7-nitroindazole (40 mg/kg intraperitoneally) before preconditioning hypoxia, which decreased constitutive brain NOS activity by 58 to 81%, was without effect on preconditioning-induced cerebroprotection, as was pretreatment with the inducible NOS inhibitor aminoguanidine (400 mg/kg intraperitoneally). The protective effects of preconditioning were also not blocked by treating animals with competitive [3-(2-carboxypiperazin-4-yl)propyl-1-phosphonate; 5 mg/kg intraperitoneally] or noncompetitive (MK-801; 1 mg/kg intraperitoneally) N-methyl-D-aspartate receptor antagonists prior to preconditioning hypoxia. These findings indicate that NO production and activity are critical to the induction of ischemic tolerance in this model. However, the results argue against the involvement of the neuronal NOS isoform, activated secondary to a hypoxia-induced stimulation of N-methyl-D-aspartate receptors, and against the involvement of the inducible NOS isoform, but rather suggest that NO produced by the endothelial NOS isoform is required to mediate this profound protective effect.
如果大脑预先经历一段短暂的亚致死性缺血，就可以实现对脑缺血的神经保护。本研究旨在验证以下假设：一氧化氮合酶（NOS）的神经元亚型产生的一氧化氮（NO）是在脑中建立缺血耐受状态的必要信号。使用新生大鼠缺氧预处理模型，其中暴露于亚致死性缺氧（8%氧气）3小时可使出生后第6天（PND6）的动物对24小时后施加的脑缺氧缺血性损伤完全耐受。在预处理性缺氧前0.5小时，用非选择性NOS抑制剂L-硝基精氨酸（2mg/kg腹腔注射）处理出生后第6天的动物。该处理在给药后0.5至3.5小时导致钙依赖性组成型NOS活性抑制67%至81%，完全阻断了预处理诱导的保护作用。然而，在预处理性缺氧前给予神经元NOS抑制剂7-硝基吲唑（40mg/kg腹腔注射），可使组成型脑NOS活性降低58%至81%，但对预处理诱导的脑保护作用没有影响，诱导型NOS抑制剂氨基胍（400mg/kg腹腔注射）预处理也是如此。在预处理性缺氧前用竞争性[3-(2-羧基哌嗪-4-基)丙基-1-膦酸酯；5mg/kg腹腔注射]或非竞争性（MK-801；1mg/kg腹腔注射）N-甲基-D-天冬氨酸受体拮抗剂处理动物，预处理的保护作用也未被阻断。这些发现表明，NO的产生和活性对于该模型中缺血耐受的诱导至关重要。然而，结果表明神经元NOS亚型并未参与其中，该亚型是在缺氧诱导的N-甲基-D-天冬氨酸受体刺激后被激活的，诱导型NOS亚型也未参与其中，而是表明内皮型NOS亚型产生的NO是介导这种显著保护作用所必需的。
