Effects of mild hypothermia on calmodulin expression and brain edema in the brain tissue of rats with traumatic brain injury / 医学研究生学报

ABSTRACT

Objective Mild hypothermia (MHT) can effectively protect the brain in traumatic brain injury (TBI). This study was to investigate the effects of MHT on the calmodulin (CAM) expression and brain edema in the rat model of TBI. Methods Ninety adult SD rats were randomly divided into a sham operation, a normal temperature and an MHT group of equal number. Immediately after TBI, the rats of the MHT group maintained at a rectal temperature of (32 ± 0.5) °C for 6 hours. Modified neurological severity scores (mNSS) were obtained from 6 rats in each group at 1, 3, 5 and 7 days after modeling, and the rest of the animals subjected to brain MRI at 6, 12, 24 and 48 hours and then killed for determination of the CAM gene transcription and protein expression in the brain tissue by real-time PCR, immunohistochemistry and Western blot. Results The mNSSs were significantly higher in the MHT and normal temperature groups than in the sham operation control (P < 0.05) at all time points, neurological severity markedly decreased in the MHT group compared with the normal temperature group (P < 0.05). At 6, 12, 24 and 48 hours, the expression of CAM mRNA was remarkably down-regulated in the MHT group (1.83 ± 0.19, 1.72 ± 0.12, 1.59 ± 0.06 and 1.60 ± 0.07) in comparison with the normal temperature group (2.76 ± 0.25, 2.49 ± 0.18, 2.04 ± 0.14 and 1.65 ± 0.09) (P < 0.05), even lower in the MHT than in the normal temperature group (P < 0.05), but higher in both of the two groups than in the sham operation group (P < 0.05). At 6, 12, 24 and 48 hours, the volume of brain edema was significantly reduced in the MHT group ([32.14 ± 4.52], [36.52 ± 4.10], [42.10 ± 4.38] and [46.25 ± 5.02] mm3) as compared with the normal temperature group ([48.56 ± 5.35], [53.13 ± 6.31], [59.23 ± 6.82] and [62.35 ± 7.25] mm3) (P < 0.05). Conclusion Mild hypothermia can improve the neurological function and reduce the CAM expression and brain edema in the brain tissue of rats with traumatic brain injury, which may be related to the neuroprotective effect of mild hypothermia.