Kishikawa Hiroaki, Kobayashi Katsuya, Takemori Ken, Okabe Tadashi, Ito Kimiaki, Sakamoto Atsuhiro
Department of Anesthesiology, Nippon Medical School, Tokyo, Japan.
Biomed Res. 2008 Aug;29(4):189-94. doi: 10.2220/biomedres.29.189.
The purpose of the present study was to evaluate the effect of dexmedetomidine, used as a sedative in the intensive care unit, on human neutrophil apoptosis and superoxide production in vitro. Neutrophils from healthy volunteers were incubated in different concentrations of dexmedetomidine (1, 10 and 100 ng/mL). Apoptosis was assessed by Hoechst 33342 staining, caspase activities and loss of mitochondrial transmembrane potential (MTP). Superoxide production was determined by the WST-1 assay. After 24 h of incubation, dexmedetomidine accelerated neutrophil apoptosis in a dose-dependent manner and 100 microM yohimbine did not inhibit the apoptosis. Treatment with 100 ng/mL of dexmedetomidine significantly enhanced the activation of caspases-3/7, -8 and -9, and also markedly increased the number of neutrophils with decreased MTP. At 24 h, the suppression of superoxide production was dependent on dexmedetomidine concentrations. However, a clinically relevant concentration (1 ng/mL) of dexmedetomidine did not affect neutrophil apoptosis and superoxide production. These results suggest that high doses of dexmedetomidine induce apoptosis without alpha(2)-adrenoceptors stimulus and inhibit superoxide production after long-term incubation. The mechanisms of dexmedetomidine-induced apoptosis are associated with the caspase cascade and loss of MTP.
本研究的目的是评估重症监护病房中用作镇静剂的右美托咪定对人中性粒细胞凋亡及体外超氧化物生成的影响。将健康志愿者的中性粒细胞在不同浓度的右美托咪定（1、10和100 ng/mL）中孵育。通过Hoechst 33342染色、半胱天冬酶活性及线粒体跨膜电位（MTP）丧失来评估凋亡。通过WST-1测定法测定超氧化物生成。孵育24小时后，右美托咪定以剂量依赖性方式加速中性粒细胞凋亡，且100 microM育亨宾未抑制凋亡。用100 ng/mL右美托咪定处理显著增强了半胱天冬酶-3/7、-8和-9的活化，并且还显著增加了MTP降低的中性粒细胞数量。在24小时时，超氧化物生成的抑制取决于右美托咪定浓度。然而，临床相关浓度（1 ng/mL）的右美托咪定不影响中性粒细胞凋亡和超氧化物生成。这些结果表明，高剂量右美托咪定在无α2肾上腺素能受体刺激的情况下诱导凋亡，并在长期孵育后抑制超氧化物生成。右美托咪定诱导凋亡的机制与半胱天冬酶级联反应及MTP丧失有关。
