Lechner A J, Johanns C A, Matuschak G M
Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, MO 63104-1028, USA.
J Crit Care. 1997 Mar;12(1):28-38. doi: 10.1016/s0883-9441(97)90023-x.
During gram-negative bacteremia (GNB), tumor necrosis factor-alpha (TNF-alpha) is a critical early mediator of host defense, whose overexpression can initiate acute lung injury, multiple organ failure, and death. In this study we evaluated the ability of a chimeric fusion protein containing two extracellular domains of the human p80 TNF-alpha receptor and the Fc region of human IgG1 (TNFR:Fc) to reduce circulating TNF-alpha, and to ameliorate organ injury and improve survival in a rodent model of GNB during immunosuppression-related neutropenia.
Conscious catheterized male rats (n = 37) with stable cyclophosphamide-induced neutropenia were infected intravenously (i.v.) with 5 x 10(9) live Escherichia coli (EC, serotype O55:B5) ending at t = 0. All animals received antibiotics (penicillin/ amikacin sulfate) at t = 0.5 and t = 8 hours, and 0.9% sodium chloride (normal saline solution (NS), 1 mL/h) from t = 0 to 8 hours. Subgroups were post-treated at t = 0.5 hours with a 1.0 mL i.v. dose of TNFR:Fc (60, 600, or 1,200 micrograms; Immunex), 600 micrograms of human IgG1-kappa or IgG1-lambda (Sigma), or NS alone (controls). A separate TNFR:Fc pretreatment subgroup received 600 micrograms/rat of the fusion protein 5 minutes before starting EC infusion. Hemodynamics were monitored continuously through t = 24 hours, and arterial samples were collected at baseline and at t = 1.5, 4.5, 8, and 24 hours after EC were analyzed for blood gases, quantitative culture, serum endotoxin, bioactive and antigenic TNF-alpha, and formed elements. Postmortem tissues were examined for histopathologic changes.
Compared with antibiotic-treated and fluid-supported controls, TNFR:Fc dose-dependently reduced bioactive but not antigenic TNF-alpha without altering bacterial clearance, serum endotoxin, or 24-hour survival. Of note, 600 micrograms of IgG1-kappa or IgG1-lambda attenuated peak bioactive TNF-alpha to a similar degree as 1,200 micrograms TNFR:Fc, and also significantly reduced serum endotoxin levels. Nevertheless, by t = 8 hours all bacteremic rats were hypothermic with tachypnea-related hypocarbia and hyperoxemia and were thrombocytopenic. At death, all subgroups showed similar hepatic glycogen depletion and pulmonary congestion with perivascular edema and alveolar hemorrhage.
Although TNFR:Fc and its idiotypic control IgG1 reduced circulating bioactive TNF-alpha, neither treatment prevented progression of lethal shock with attendant organ injury in this conscious, antibiotic-treated and fluid-resuscitated model of immunosuppression-related GNB.
在革兰氏阴性菌血症（GNB）期间，肿瘤坏死因子-α（TNF-α）是宿主防御的关键早期介质，其过度表达可引发急性肺损伤、多器官功能衰竭和死亡。在本研究中，我们评估了一种嵌合融合蛋白的能力，该蛋白包含人p80 TNF-α受体的两个细胞外结构域和人IgG1的Fc区域（TNFR:Fc），以降低循环中的TNF-α，并改善免疫抑制相关中性粒细胞减少症的啮齿动物GNB模型中的器官损伤并提高生存率。
对37只经环磷酰胺诱导的中性粒细胞减少稳定的清醒雄性大鼠进行插管，于t = 0时静脉内（i.v.）注射5×10⁹活的大肠杆菌（EC，血清型O55:B5）。所有动物在t = 0.5小时和t = 8小时接受抗生素（青霉素/硫酸阿米卡星），并在t = 0至8小时接受0.9%氯化钠（生理盐水溶液（NS），1 mL/h）。亚组在t = 0.5小时接受1.0 mL静脉注射剂量的TNFR:Fc（60、600或1200微克；Immunex）、600微克人IgG1-κ或IgG1-λ（Sigma）或仅NS（对照组）进行后处理。一个单独的TNFR:Fc预处理亚组在开始输注EC前5分钟接受600微克/大鼠的融合蛋白。持续监测血流动力学直至t = 24小时，并在基线以及EC后t = 1.5、4.5、8和24小时采集动脉样本，分析血气、定量培养、血清内毒素、生物活性和抗原性TNF-α以及血细胞成分。对死后组织进行组织病理学变化检查。
与抗生素治疗和液体支持的对照组相比，TNFR:Fc剂量依赖性地降低了生物活性但未降低抗原性TNF-α，且未改变细菌清除、血清内毒素或24小时生存率。值得注意的是，600微克的IgG1-κ或IgG1-λ将生物活性TNF-α峰值降低到与1200微克TNFR:Fc相似的程度，并且还显著降低了血清内毒素水平。然而，到t = 8小时，所有菌血症大鼠均出现体温过低、与呼吸急促相关的低碳酸血症和高氧血症以及血小板减少。死亡时，所有亚组均表现出相似的肝糖原消耗以及伴有血管周围水肿和肺泡出血的肺充血。
尽管TNFR:Fc及其独特型对照IgG1降低了循环中的生物活性TNF-α，但在这个清醒、接受抗生素治疗和液体复苏的免疫抑制相关GNB模型中，两种治疗均未能阻止致命性休克的进展以及随之而来的器官损伤。
