Effects of deep hypothermia on nitric oxide‐induced cytotoxicity in primary cultures of cortical neurons

Abstract

Nitric oxide (NO) is thought to play a major role during cerebral ischemia. However, the protective efficacy of hypothermia against NO-induced neurotoxicity remains to be examined. In the present study, the degree of neurotoxicity induced by NO was analyzed in two temperature groups (normothermia, 37 degrees C; deep hypothermia, 22 degrees C) of cultured E16 Wistar rat cortical neurons. Two different NO donors, 1-hydroxy-2-oxo-3-(N-ethyl-2-aminoethyl)-3-ethyl-1-triazene (NOC-12) and 1-hydroxy-2-oxo-3-(3-amynopropyl)-3-isopropyl-1-triazene (NOC-5), that have equal half-lives at 37 degrees C and 22 degrees C, respectively, were used. Cultured neurons in each temperature group were exposed to 30 and 100 micro M NOC for three different time courses, 6 hr, 12 hr, and 24 hr. The survival rates of neurons were evaluated by assessing viable neurons on photomicrographs before and after the experiments. The highest survival rate (approximately 93%) was seen in both temperature groups when neurons were exposed to 30 micro M NOC for 6 hr and 12 hr, and there was no significant difference observed between these two groups (P > 0.05). Almost equal survival rates were observed in both temperature groups following exposure to 30 micro M NOC for 24 hr (at 37 degrees C, 80.4% +/- 2.6%; at 22 degrees C, 83.2% +/- 1.6%; P > 0.05). During exposure to 100 micro M NOC, although the survival rate linearly decreased (approximately from 70% to 5%) in both temperature groups when exposed for 6-24 hr, there were no significant intergroup differences observed (P > 0.05). In conclusion, hypothermia does not provide adequate protection to the neurons by acting on the mechanisms evoked by NO, so we speculate that hypothermia may not confer neuroprotetcion once NO is released during ischemia.

Small temperature variations alter edaravone-induced neuroprotection of cortical cultures exposed to prolonged hypoxic episodes

“…The neuroprotection in the CNS conferred by hypothermia is attributed to a reduction in the cerebral metabolic rate (CMR), decreased release of neurotransmitters, attenuation of N-methyl-D-aspartate (NMDA) receptor activity, reduction in intracellular calcium influx, decreased lipid peroxidation, and reduced production of reactive oxygen species (ROS). 1 We previously reported that mild (328C) and moderate (278C) hypothermia conferred as much neuroprotection as deep (228C) hypothermia in primary cultured neurones when subjected to long-lasting hypoxia. In addition, profound (178C) hypothermia does not offer any greater protection to the neuronal culture compared with that offered by mild, moderate, or deep hypothermia during hypoxic insults for 24 or 48 h. 2 In contrast to hypothermia, hyperthermia has been shown to increase the vulnerability of certain neurones to infarction.…”

Effect of preconditioning on propofol-induced neurotoxicity during the developmental period

“…The suspension was placed in a poly l-lysine-coated film-bottom dish with a diameter of 35 mm (FD10300; Matsunami Glass Ltd, Osaka, Japan) for calcium imaging or in 2 mm-grid tissue culture dishes (Nunc, Naperville, IL, USA) for cytotoxicity measurements. Grid tissue culture dishes were used to observe the same neurons, as previously described [20,21].…”

Neurotoxic Effect of the Complex of the Ovine Prion Protein (OvPrPC) and RNA on the Cultured Rat Cortical Neurons

“…Primary cultures of rat cortical neurons were prepared from 1-day-old newborn rats as described previously [19,20]. The animal were supplied by the Center of Laboratorial Animals in Chinese Academy of Science, Beijing, China.…”