THE ROLE OF TNF IN HEPATOTOXICITY

肿瘤坏死因子α(TNFpha)是内毒素休克的主要介质。肿瘤坏死因子诱导的损伤机制之一是通过激活核因子-kB和产生活性氧。我们推测，2，3，7，8-四氯二苯并二恶英(TCDD)诱导的内毒素超敏反应和随后的凋亡诱导可能是通过调节TNFpha信号通路而发生的。我们实验室最近的工作集中在内毒素超敏反应的体内模型以及肿瘤坏死因子α信号与氧化应激之间的关系上。我们通过评估血清酶水平和对凋亡细胞的定量来描述TCDD诱导的肝脏损伤的动力学，并评估了关键时间点的基因表达的变化。我们已经证明，当在内毒素暴露之前用TCDD治疗啮齿动物时，毒性显著增加，并且在这个模型中，放线菌亚胺抑制蛋白质合成阻止了TCDD诱导的对TNFpha的敏感性。在对照组和治疗组动物的肝组织中，用RT-PCR检测了与肿瘤坏死因子和Fas凋亡途径相关的基因的mRNA的表达。TCDD对内毒素调节的Fas早期表达有调节作用，对肿瘤坏死因子α和核因子kappaB(NFKB)的表达有影响。TCDD单独刺激NFKB基因表达，但不影响DNA结合。TCDD治疗不影响IKB-α和-β的表达。其他研究还考察了TCDD对F344大鼠的影响以及肿瘤坏死因子诱导和一氧化氮产生之间的相关性(通过检测5个亚硝基血红素复合体来衡量)。剂量低于5 mg/kg的TCDD不会增加内毒素处理大鼠的一氧化氮水平。然而，在50 mg/kg TCDD剂量下，静脉血中电子顺磁共振波谱检测到的亚硝基血红蛋白显著升高。在肝脏和肾脏中检测到的亚硝酸亚铁血红蛋白的浓度分布与在血液中检测到的相似。该项目先前被报道为Z01 ES 30106 23 LT的一部分-肿瘤坏死因子α，四氯二苯并二恶英，内毒素，细胞凋亡，枯否细胞，肝毒性，B6C3F1小鼠

Tumor necrosis factor alpha (TNFalpha) has been demonstrated to be a primary mediator of endotoxin shock. One mechanism of TNF-induced injury is via the activation of NF-kB and the generation of reactive oxygen species. We have hypothesized that 2,3,7,8- tetrachlorodibenzodioxin (TCDD) -induced endotoxin hypersensitivity and subsequent induction of apoptosis may occur through modulation of TNFalpha signaling pathways. Recent efforts in our laboratory have focused on in vivo models of endotoxin hypersensitivity and the relationship between TNFalpha signaling and oxidative stress. We have characterized the kinetics of TCDD-induced hepatic damage in the liver by evaluating serum enzyme levels and quantitating apoptotic cells, and have evaluated alterations in gene expression at critical time points. We have shown that when rodents are treated with TCDD prior to endotoxin exposure a significant increase in toxicity occurs, and that inhibition of protein synthesis with cycloheximide blocks the TCDD- induced sensitivity to TNFalpha in this model. Expression of mRNA for genes associated with the TNF and Fas apoptotic pathways have been quantitated in liver tissue from control and treated animals using RT- PCR. TCDD modulated endotoxin-regulated early expression of Fas and altered the expression of TNFalpha and nuclear factor kappa B (NFKB). TCDD alone stimulated the expression NFKB gene expression but did not affect DNA binding. Expression of IKB-alpha and -beta was not affected by TCDD treatment. Additional studies have examined the effects of TCDD and correlation between TNF induction and nitric oxide production (as measured by detection of the 5 coordinate nitrosyl heme complexes) in F344 rats. Doses below 5 mg/kg TCDD did not increase nitric oxide levels in endotoxin-treated rats. However, at 50 mg/kg TCDD there was a significant elevation in nitrosyl hemoglobin detected in venous blood by electron paramagnetic resonance spectroscopy. The concentration profile of ferrous nitrosyl hemoproteins detected in both livers and kidneys were similar to that detected in blood. This project was previously reported as part of Z01 ES 30106 23 LT - tumor necrosis factor alpha, tetrachlorodibenzodioxin, endotoxin, apoptosis, Kupffer cells, hepatotoxicity, B6C3F1 mice