RESUMO
Objective To evaluate the effect of dexmedetomidine on endoplasmic reticulum stress during intestinal ischemia-reperfusion (I/R) in mice.Methods Thirty SPF healthy male C57BL/6 mice,aged 8 weeks,were divided into 3 groups (n=10 each) using a random number table method:sham operation group (S group),intestinal I/R group (I/R group) and dexmedetomidine group (DEX group).The superior mesenteric artery was only isolated but not clamped in S group.The model of intestinal I/R injury was established by clamping superior mesenteric artery for 20 min followed by 24 h of reperfusion in I/R group and DEX group.Dexmedetomidine 25 μg/kg was intraperitoneally injected at 30 min before ischemia in DEX group,while the equal volume of normal saline was given instead of dexmedetomidine in S group and I/R group.Mice were sacrificed at 24 h of reperfusion,and small intestinal tissues was obtained for examination of the pathological changes and ultrastructure of intestinal epithelial cells and for determination of cell apoptosis,expression of CCAAT-enhancer binding protein homologous protein (CHOP),transcription factors (ATF4),and X-4 box binding protein 1 (XBP1) mRNA (by real-time polymerase chain reaction),and expression of CHOP,Bcl-2,Bax and caspase-3 in intestinal tissues (by Western bolt).The apoptosis index (AI) and ratio of Bcl-2 to Bax were calculated.Intestinal damage was assessed and scored according to Chiu.Results Compared with S group,Chiu's score and AI were significantly increased,the expression of CHOP,ATF4 and XBP-1 mRNA,CHOP,Bax and caspase-3 was up-regulated,and the expression of Bcl-2 was down-regulated,and Bcl-2/Bax ratio was decreased in I/R group and DEX group (P＜0.05).Compared with I/R group,Chiu's score and AI were significantly decreased,the expression of CHOP,ATF4 and XBP-1 mRNA,CHOP,Bax and caspase-3 was down-regulated,and the expression of Bcl-2 was up-regulated,and Bcl-2/Bax ratio was increased in DEX group (P＜0.05).Conclusion The mechanism by which dexmedetomidine reduces intestinal I/R injury may be related to regulating endoplasmic reticulum stress and inhibiting cell apoptosis in mice.
RESUMO
Objective To investigate the effect of esmolol pretreatment on Toll like receptor-4 (TLR4)/nuclear factor-kappa-B (NF-кB) pathway in rats with repeated cerebral ischemia/reperfusion (IR) injury. Methods Forty-eight adult male Sprague-Dawley rats were randomly allocated into sham-operated group, IR group and esmolol group (n=16). Rats in the IR group and esmolol group were injected intravenously with esmolol at a dose of 200 g/(kg?min) or normal saline for one h before surgery, and then, bilateral common carotid arteries were clipped to establish the repeated IR injury models. Bilateral common carotid arteries in rats of sham-operated group were only isolated but not clipped, and injected intravenously with normovolemic normal saline for one h. Learning and memory abilities of rats were measured by Morris water maze test before, and one, 3 and 7 d after surgery. Rats were euthanized and hippocampus tissues were excised. The wet to dry (W/D) ratio of the hippocampus was tested. The permeability of blood-brain barrier was determined by Evans blue (EB) method. The levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6 and IL-1β in the hippocampus were tested by enzyme linked immunosorbent assay (ELISA). The NF-кB p65 and TLR4 mRNA expressions in the hippocampus were determined by reverse transcription-polymerase chain reaction (RT-PCR). The NF-кB p65 and TLR4 protein expressions in hippocampus were detected by Western blotting. Results As compared with those in the sham-operated group, the escape latency was significantly prolonged and swimming distance was signficantly longer in rats of IR group one, 3 and 7 d after surgery (P<0.05), the W/D ratio of the hippocampus and the content of EB in brain tissues were significantly increased in the IR group (P<0.05), the levels of TNF-α, IL-6 and IL-1β in hippocampus were significantly increased in the IR group (P<0.05), and the NF-кB p65 or TLR4 mRNA and protein expressions in the hippocampus of IR group were statistically higher (P<0.05). As compared with IR group, the escape latency and swimming distance of rats in the esmolol group were significantly shortened one, 3 and 7 d after surgery (P<0.05), the W/D ratio of the hippocampus and content of EB in brain tissues of esmolol group were significantly decreased (P<0.05), the levels of TNF-α, IL-6 and IL-1β in the hippocampus of esmolol group were signficantly lower(P<0.05), and the NF-кB p65 or TLR4 mRNA and protein expressions in hippocampus of esmolol group were statistically lower in the esmolol group (P<0.05). Conclusion Esmolol preconditioning can alleviate cerebral injury and improve learning and memory abilities of rats with repeated cerebral IR injury, which may be involved in alleviating inflammation and suppressing TLR4/NF-кB pathway.