LY-231617

The role of reactive oxygen species in the pathogenesis of the neurotoxicity associated with ischemia-reperfusion, was investigated in a model of primary rat neuronal cultures and of differentiated PC12 cells, subjected to chemical ischemia by iodoacetic acid (IAA, 2.5 h) followed by a short period of reperfusion (1 h). The injury to the cells was assessed by lactate dehydrogenase (LDH) release into the culture media. The PC12 cells exhibited relative resistance to IAA cytotoxicity. Therefore these cells were studied at a 4-fold higher IAA concentration (400 microM instead of 100 microM for the neurons). The injury to both cell types was significantly greater in the short post-insult reperfusion (PIR) period than during the insult period. The presence, during the combined insult and PIR periods, of alpha-tocopherol (100 microM), melatonin (1 mM) and LY231617 (5 microM), conferred to both cell types considerable protection against the injury occurring during the insult and during the PIR periods (assessed separately). Superoxide dismutase (SOD; 500 IU/ml) conferred protection to the neurons, but not to the PC12 cells. When exposure to the antioxidants was limited to the short (15 min) pre insult period, only LY231617 conferred protection. In the neurons the protection occurred only during the insult period, whereas in the PC12 cells during both the insult and PIR periods. When the exposure to the antioxidants was limited to the PIR period, only SOD conferred protection and only in the neuronal cultures. These findings suggest that neuronal damage caused during ischemia-reperfusion can be diminished markedly by co-presence of antioxidants during the insult period. Certain antioxidants may protect the neurons even when present only before or after the insult.

The potent antioxidant LY231617 (2,6-bis(1,1-dimethylethyl)-4-[[(1-ethyl)amino]methyl]phenol hydrochloride) is cytoprotective in models of focal and global cerebral ischemia. We tested the hypothesis that administration of LY231617, before the insult, would improve recovery of cerebral electrical activity and metabolic function after transient global cerebral ischemia by improving cerebral blood flow (CBF) during the reperfusion period.

Randomized, controlled, prospective study.

Research laboratory at a university teaching hospital.

Twenty-four male beagle dogs.

All experiments were performed under pentobarbital anesthesia and controlled conditions of normoxia, normocarbia, and normothermia. Twelve control dogs received 20 mL/kg saline (vehicle) bolus into the right atrium and 0.01 mL/kg/min i.v., beginning 20 mins before 13 mins of global cerebral ischemia (by aortic occlusion). The dogs in the drug-treated group received LY231617 as a 10-mg/kg bolus 20 mins before ischemia and 5 mg/kg/hr throughout reperfusion (n = 12). CBF was measured using radiolabeled microspheres.

Total CBF, cerebral oxygen consumption, and somatosensory evoked potentials (SEP) were measured during 240 mins of reperfusion. CBF was similar in both vehicle- and LY231617-treated animals at baseline and throughout the experimental period. In all animals, SEP became isoelectric between 60 and 100 secs after cross-clamping of the ascending aorta. SEP amplitude recovery was significantly higher in drug-treated animals compared with controls (73%+/-15% vs. 39%+/-14% [mean+/-SEM] from baseline at 120 mins [p<.05] and 86%+/-12% vs. 49%+/-14% from baseline at 240 mins [p< .05]).

LY231617 improves recovery of cerebral electrical function after complete transient global ischemia via mechanisms unrelated to cerebral circulatory effects.