:
Hypothermia enhances outcomes of patients after
resuscitation after
cardiac arrest (CA). However, the underlying mechanism is not fully understood. In this study, we investigated effects of hypothermic
therapy on neuronal damage/death, microglial activation, and changes of
endogenous antioxidants in the anterior horn in the lumbar spinal cord in a rat model of asphyxial CA (ACA). A total of 77 adult male Sprague-Dawley rats were randomized into five groups: normal,
sham ACA plus (+) normothermia, ACA + normothermia,
sham ACA +
hypothermia, and ACA +
hypothermia. ACA was induced for 5 min by injecting
vecuronium bromide.
Therapeutic hypothermia was applied after return of spontaneous circulation (ROSC) via rapid cooling with
isopropyl alcohol wipes, which was maintained at 33 ± 0.5 °C for 4 h. Normothermia groups were maintained at 37 ± 0.2 °C for 4 h. Neuronal protection, microgliosis, oxidative stress, and changes of
endogenous antioxidants were evaluated at 12 h, 1 day, and 2 days after ROSC following ACA. ACA resulted in neuronal damage from 12 h after ROSC and evoked obvious degeneration/loss of spinal neurons in the ventral horn at 1 day after ACA, showing motor deficit of the hind limb. In addition, ACA resulted in a gradual increase in microgliosis with time after ACA.
Therapeutic hypothermia significantly reduced neuronal loss and attenuated hind limb dysfunction, showing that
hypothermia significantly attenuated microgliosis. Furthermore,
hypothermia significantly suppressed ACA-induced increases of
superoxide anion production and
8-hydroxyguanine expression, and significantly increased
superoxide dismutase 1 (SOD1), SOD2,
catalase, and
glutathione peroxidase. Taken together, hypothermic
therapy was found to have a substantial impact on changes in ACA-induced microglia activation, oxidative stress factors, and
antioxidant enzymes in the ventral horn of the lumbar spinal cord, which closely correlate with neuronal protection and neurological performance after ACA.