RESUMO
Objective:To evaluate the role of transient receptor potential vanillic acid 4 (TRPV4) in dexmedetomidine-induced improvement in cognitive function in mice with mechanical ventilator-caused brain injury.Methods:Ninety clean-grade healthy male C57BL6 mice, weighing 20-25 g, aged 8-12 weeks, were divided into 5 groups ( n=18 each) using a random number table method: control group (group C), mechanical ventilation group (group V), HC-067047 group (group H), dexmedetomidine group (group D), and dexmedetomidine+ GSK1016790A group (group DG). In group C, the animals breathed air spontaneously for 6 h without mechanical ventilation. In group V, the animals were mechanically ventilated for 6 h. In group H, TRPV4 blocker HC-067047 10 mmol was injected into the cerebral ventricle at 3 and 6 h of mechanical ventilation. In D and DG groups, dexmedetomidine 50 μg/kg was intraperitoneally injected at 30 min before mechanical ventilation. In group DG, TRPV4 agonist GSK1016790A 5 μmol was injected into the cerebral ventricle at 60 min before mechanical ventilation. Morris water maze test was performed on 6 mice in each group at 1 day before mechanical ventilation and 3 and 7 days after mechanical ventilation. Six mice in each group were randomly selected and sacrificed at 1 day after mechanical ventilation, and the brain tissue was taken for determination of the neuronal apoptosis in hippocampal CA1 area by TUNEL method, and the apoptosis index was calculated. Six mice in each group were randomly selected and sacrificed at 1 day after mechanical ventilation, and the hippocampal tissues were taken for determination of the expression of TRPV4, serine-threonine protein kinase (Akt), phosphorylated Akt (p-Akt), Bcl-2, Bax and caspase-3 by Western blot. Results:Compared with group C, the escape latency was significantly prolonged and the number of crossing the original platform was reduced at 3 and 7 days after mechanical ventilation, the expression of TRPV4 and caspase-3 was up-regulated, the ratio of Bcl-2/Bax was decreased, and the apoptosis index of neurons was increased in group V and group DG ( P<0.05). Compared with group V, the escape latency was significantly shortened and the number of crossing the original platform was increased at 3 and 7 days after mechanical ventilation, the expression of TRPV4 and caspase-3 was down-regulated, the expression of p-Akt was up-regulated, the ratio of Bcl-2/Bax was increased, and the apoptosis index of neurons was decreased in group D and group H ( P<0.05). Compared with group D, the escape latency was significantly prolonged at 3 and 7 days after mechanical ventilation, the number of crossing the original platform was reduced, the expression of TRPV4 and caspase-3 was up-regulated, the expression of p-Akt was down-regulated, the ratio of Bcl-2/Bax was decreased, and the apoptosis index of neurons was increased in group DG ( P<0.05). Conclusions:TRPV 4 is involved in dexmedetomidine-induced improvement in cognitive function, which is related to up-regulation of p-Akt expression and inhibition of apoptosis in hippocampal neurons in mice with mechanical ventilation-caused brain injury.
RESUMO
Objective:To investigate the effect of baicalin on cognitive function of mice with brain injury induced by mechanical ventilation and its mechanism.Methods:Seventy two C57BL6 mice, weighing 20-25 g, aged 8-12 weeks, were randomly divided into control group (group C), mechanical ventilation group (group V), baicalin group (group B), baicalin+ Akt inhibitor MK-2206 group (group BM) according to random number table method, with 18 in each group.Mice in group C did not have mechanical ventilation and breathed air independently for 6 hours.Mice in group V received mechanical ventilation for 6 hours.Mice in group B and group BM were intraperitoneally injected with baicalin 100 mg/kg 30 minutes before mechanical ventilation, and mice in group BM were injected intraventricular with Akt inhibitor MK-2206 300 μg/kg 60 minutes before mechanical ventilation.Six mice in each group were randomly selected to test their learning and memory abilities by Morris water maze test 1st day before mechanical ventilation and 3rd day and 7th day after mechanical ventilation.One day after mechanical ventilation, six mice in each group were killed, and the brain tissue was taken.TUNEL method was used to detect the neuronal apoptosis in hippocampal CA1 area, and the apoptosis index was calculated.One day after mechanical ventilation, six mice in each group were killed, and the hippocampus was taken, Western blot was used to detect the protein expressions of caspase-3, caspase-9, Akt, p-Akt, GSK-3β and p-GSK-3β.SPSS 22.0 software was used for statistical analysis of data, repeated measure ANOVA and one-way ANOVA were used for comparison between multiple groups.LSD- t test was used for further pairwise comparison. Results:The results of water maze test showed that the time and group interaction of the four groups were not significant ( F=1.14, P>0.05), the main effect of time and group were both significant ( F=47.36, 59.65, both P<0.05). At 3rd day and 7th day after mechanical ventilation, the escape latencies of mice in group V were higher than those in group C (both P<0.05), and the numbers of platform crossing were lower than those in group C (both P<0.05). And 3 days and 7 days after mechanical ventilation, the escape latencies of mice in group B were lower than those in group V (both P<0.05) and the numbers of platform crossing were higher than those in group V (both P<0.05). The escape latenies of mice in BM group on the 3rd and 7th day were higher than those in group B (both P<0.05), and the numbers of platform crossing were lower than those in group B on the 3rd day and 7th day after mechanical ventilation(both P<0.05). TUNEL and Western blot results showed that apoptosis index of hippocampal neurons and expression levels of apoptosis-related proteins caspase-3 and caspase-9 were significant different in the four groups ( F=51.42, 41.21, 40.19, all P<0.05). The apoptosis index of hippocampal neurons ((40.6±3.9)%), the expression levels of caspase-3 (4.93±0.92) and caspase-9 (4.81±0.88) in the hippocampus of mice in group V were higher than those in group C ((13.7±1.4)%, (1.87±0.27), (1.71±0.25), all P<0.05), the apoptosis index of hippocampal neurons ((15.6±1.6)%), the expression levels of caspase-3 (1.95±0.30) and caspase-9 (1.76±0.28) in group B were lower than those in group V ((40.6±3.9)%, (4.93±0.92), (4.81±0.88), all P<0.05), the apoptosis index of hippocampal neurons ((27.8±2.7)%), the expression levels of caspase-3 (3.58±0.61) and caspase-9 (3.49±0.57) in BM group were higher than those in group B ((15.6±1.6)%, (1.95±0.30), (1.76±0.28), all P<0.05). Expression level of p-Akt, p-GSK-3β in hippocampal tissues of the four group of mice were significantly different ( F=37.54, 43.23, both P<0.05). The expression level of p-Akt (0.51±0.06) and p-GSK-3β (0.47±0.05) of hippocampal tissues of mice in group V were lower than those of group C ((1.07±0.10), (1.11±0.12), both P<0.05), the expression level of p-Akt (0.99±0.10) and p-GSK-3β (1.08±0.09) of hippocampal tissues of mice in group B were higher than those of group V (both P<0.05), the expression level of p-Akt (0.83±0.08) and p-GSK-3β (0.81±0.07) of hippocampal tissues of mice in group BM were lower than those in group B (both P<0.05). Conclusion:Baicalin can improve the cognitive function of mice with brain injury induced by mechanical ventilation, which is related with activation of Akt/GSK-3β signaling pathway and inhibition of hippocampal neuron apoptosis.
RESUMO
Objective:To evaluate the effect of dexmedetomidine on the extracellular signal-regulated kinase(ERK)/sodium-potassium ATPase(Na + -K + -ATPase)signaing pathway in lung tissues of rats with mechanical ventilation-induced lung injury (VILI). Methods:Forty-eighty clean-grade male Sprague-Dawley rats, weighing 270-320 g, aged 4-5 months, were divided into 4 groups ( n=12 each) using a random number table method: control group (group C), VILI (alpha2-adrenergic receptor antagonist) group (group V), dexmedetomidine group (group D), and dexmedetomidine plus yohimbine group (group DY). Group C underwent no mechanical ventilation and breathed air spontaneously for 4 h. Mechanical ventilation (respiratory rate 40 breaths/min, tidal volume 40 ml/kg, inspiratory/expiratory ratio 1∶1, PEEP 0, fraction of inspired oxygen 21%) lasted 4 h in group V. Dexmedetomidine was infused intravenously in a dose of 5.0 μg/kg at 20 min before ventilation followed by an infusion of 5.0 μg·kg -1· h -1 throughout ventilation in group D. In group DY, yohimbine 0.1 mg/kg was injected intravenously at 10 min before dexmedetomidine, and the other treatments were similar to these previously described in group D. Blood samples and lung tissues were taken at 4 h of mechanical ventilation to determine the wet/dry weight ratio (W/D ratio), lung permeability index (LPI), alveolar fluid clearance rate (AFC), and expression of extracellular signal-regulated kinase (ERK), phosphorylated extracellular signal-regulated kinase (p-ERK), and Na + -K + -ATPase in lung tissues (by Western blot) and to observe pathological changes of lung tissues. Results:Compared with group C, LPI and W/D ratio were significantly increased, AFC was decreased, p-ERK expression was up-regulated, and Na + -K + -ATPase expression was down-regulated in group V and group DY ( P<0.05), and no significant change was found in the incidence of the parameters mentioned above in group D ( P>0.05). Compared with group V, LPI and W/D ratio were significantly decreased, AFC was increased, p-ERK expression was down-regulated, Na + -K + -ATPase expression was up-regulated ( P<0.05), and the pathological changes of lung tissues were significantly attenuated in group D, and no significant change was found in the incidence of the parameters mentioned above in group DY ( P>0.05). Compared with group D, LPI and W/D ratio were significantly increased, AFC was decreased, p-ERK expression was up-regulated, Na + -K + -ATPase expression was down-regulated ( P<0.05), and the pathological changes of lung tissues were accentuated in group DY. Conclusion:The mechanism by which dexmedetomidine alleviates VILI may be related to activating alpha2-adrenergic receptors and inhibiting ERK/Na + -K + -ATPase signaling pathway in rats.