Chamulitrat W, Wang J F, Spitzer J J
Department of Physiology, Louisiana State University Medical Center, New Orleans 70112-1393, USA.
Life Sci. 1995;57(4):387-95. doi: 10.1016/0024-3205(95)00299-l.
The prior administration of low dose endotoxin induces a state of hyporesponsiveness or tolerance to the lethal effects of endotoxin. It is generally accepted that macrophages are main cellular components in the development of tolerance, hence, nitric oxide (.NO) as one of the macrophage mediators may play a role in host defense mechanisms during tolerance. In this study, we utilized EPR spectroscopy to directly detect nitrosyl complexes as products of .NO in whole blood, livers and intestines of lipopolysaccharide (LPS)-tolerant rats. Male Sprague-Dawley rats were injected with a "low dose" LPS (0.5 mg/kg) 12-168 h prior to a "high dose" LPS (3 mg/kg), then sacrificed 6 h later. EPR signals of nitrosyl hemoprotein complexes were detected in specimens after high dose LPS. The post-LPS EPR signals of nitrosyl complexes from all samples were attenuated by a prior injection of low dose LPS. The signals of dinitrosyl-iron-dithiolate became apparent in samples from tolerant rats as signals of nitrosyl hemoprotein decreased. The maximal tolerance in terms of diminished .NO production was observed when low dose LPS was given 48-96 h prior to high dose LPS. Hemoglobin concentrations in the intestine used as biomarkers of hemorrhagic damage, were concomitantly attenuated in the jejunum of tolerant rats. These results together with our previous studies indicate that suppression of .NO production may contribute to the amelioration of hepatic and intestinal injury during endotoxin tolerance.
预先给予低剂量内毒素可诱导对内毒素致死效应的低反应性或耐受性状态。一般认为巨噬细胞是耐受性发展中的主要细胞成分，因此，一氧化氮（·NO）作为巨噬细胞介质之一可能在耐受性期间的宿主防御机制中发挥作用。在本研究中，我们利用电子顺磁共振波谱直接检测脂多糖（LPS）耐受大鼠全血、肝脏和肠道中作为·NO产物的亚硝酰基复合物。雄性Sprague-Dawley大鼠在给予“高剂量”LPS（3mg/kg）前12 - 168小时注射“低剂量”LPS（0.5mg/kg），然后在6小时后处死。在高剂量LPS处理后的标本中检测到亚硝酰血红蛋白复合物的电子顺磁共振信号。预先注射低剂量LPS可使所有样品中LPS处理后的亚硝酰基复合物的电子顺磁共振信号减弱。随着亚硝酰血红蛋白信号减少，二亚硝酰铁二硫醇盐信号在耐受大鼠的样品中变得明显。当在高剂量LPS前48 - 96小时给予低剂量LPS时，观察到·NO产生减少方面的最大耐受性。用作出血性损伤生物标志物的肠道血红蛋白浓度在耐受大鼠的空肠中也随之降低。这些结果与我们之前的研究共同表明，·NO产生的抑制可能有助于减轻内毒素耐受期间的肝脏和肠道损伤。
