Stachlewitz R F, Seabra V, Bradford B, Bradham C A, Rusyn I, Germolec D, Thurman R G
Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, University of North Carolina at Chapel Hill, 27599-7365, USA.
Hepatology. 1999 Mar;29(3):737-45. doi: 10.1002/hep.510290335.
Extrahepatic factors, such as increased gut permeability and bacteria from the gut, have been shown to play a role in D-galactosamine toxicity in rats. Because bacterial endotoxin activates Kupffer cells, the purpose of this study was to clarify the role of Kupffer cells in the mechanism of D-galactosamine hepatotoxicity in rats and determine whether uridine, a compound that rescues animals from D-galactosamine toxicity, affects Kupffer cells. Rats were fed control or glycine (5%) containing diets to prevent Kupffer cell activation or treated with gadolinium chloride (GdCl3, 20 mg/kg) to destroy Kupffer cells selectively before injection of D-galactosamine (500 mg/kg, intraperitoneally). D-galactosamine caused panlobular focal hepatocellular necrosis, polymorphonuclear cell infiltration, and increased serum transaminases significantly at 24 hours. Dietary glycine or pretreatment with GdCl3 prevented these effects. D-galactosamine caused a transient increase in circulating endotoxin that was maximal at 1 hour and was blunted significantly by dietary glycine. Additionally, antisera to tumor necrosis factor-alpha (TNF-alpha) prevented hepatotoxicity caused by D-galactosamine. Moreover, apoptosis in hepatocytes caused by D-galactosamine occurred before necrosis (6 hours) and was prevented by glycine, GdCl3, TNF-alpha antiserum, and uridine. Thus, it was hypothesized that TNF-alpha from Kupffer cells causes apoptosis after D-galactosamine administration in the rat. Indeed, increases in TNF-alpha messenger RNA (mRNA) were detected as early as 2.5 hours after D-galactosamine treatment. Previous work proposed that uridine blocks D-galactosamine toxicity by preventing inhibition of mRNA synthesis. In view of these results, the possibility that uridine might affect Kupffer cells was investigated. Uridine significantly blunted the increase in [Ca2+]i and release of TNF-alpha caused by endotoxin in isolated Kupffer cells and prevented apoptosis caused by D-galactosamine treatment in vivo. These data support the hypothesis that uridine prevents D-galactosamine hepatotoxicity not only by rescuing the hepatocyte in the late phases of the injury but also preventing TNF-alpha release from Kupffer cells thereby blocking apoptosis that occurs early after D-galactosamine treatment. Taken together, these data strongly support the role of Kupffer cell activation by endotoxin early after D-galactosamine treatment as an important event in the mechanism of hepatotoxicity in the rat.
肝外因素，如肠道通透性增加和肠道细菌，已被证明在大鼠D - 半乳糖胺毒性中起作用。由于细菌内毒素可激活库普弗细胞，本研究的目的是阐明库普弗细胞在大鼠D - 半乳糖胺肝毒性机制中的作用，并确定尿苷（一种能使动物从D - 半乳糖胺毒性中获救的化合物）是否会影响库普弗细胞。给大鼠喂食对照饮食或含甘氨酸（5%）的饮食以防止库普弗细胞激活，或在注射D - 半乳糖胺（500 mg/kg，腹腔注射）前用氯化钆（GdCl3，20 mg/kg）处理以选择性破坏库普弗细胞。D - 半乳糖胺在24小时时引起全小叶局灶性肝细胞坏死、多形核细胞浸润，并显著增加血清转氨酶。饮食中的甘氨酸或GdCl3预处理可预防这些作用。D - 半乳糖胺导致循环内毒素短暂升高，在1小时时达到峰值，饮食中的甘氨酸可显著减弱这种升高。此外，肿瘤坏死因子 - α（TNF - α）抗血清可预防D - 半乳糖胺引起的肝毒性。而且，D - 半乳糖胺引起的肝细胞凋亡在坏死之前（6小时）就已发生，甘氨酸、GdCl3、TNF - α抗血清和尿苷可预防这种凋亡。因此，推测大鼠给予D - 半乳糖胺后，库普弗细胞产生的TNF - α会导致凋亡。事实上，早在D - 半乳糖胺处理后2.5小时就检测到TNF - α信使核糖核酸（mRNA）增加。先前的研究提出尿苷通过防止mRNA合成受抑制来阻断D - 半乳糖胺毒性。鉴于这些结果，研究了尿苷可能影响库普弗细胞的可能性。尿苷可显著减弱内毒素在分离的库普弗细胞中引起的[Ca2+]i升高和TNF - α释放，并预防体内D - 半乳糖胺处理引起的凋亡。这些数据支持这样的假说，即尿苷预防D - 半乳糖胺肝毒性不仅是通过在损伤后期拯救肝细胞，还通过防止TNF - α从库普弗细胞释放，从而阻断D - 半乳糖胺处理后早期发生的凋亡。综上所述，这些数据有力地支持了D - 半乳糖胺处理后早期内毒素激活库普弗细胞在大鼠肝毒性机制中作为一个重要事件的作用。
