Imose Motoaki, Nagaki Masahito, Naiki Takafumi, Osawa Yosuke, Brenner David A, Asano Takahiko, Hayashi Hideki, Kato Tomohiro, Moriwaki Hisataka
First Department of Internal Medicine, Gifu University School of Medicine, Gifu, Japan.
Liver Int. 2003 Oct;23(5):386-96. doi: 10.1034/j.1478-3231.2003.00867.x.
BACKGROUND/AIMS: Tumor necrosis factor (TNF)-alpha itself does not induce liver injury in normal mice or hepatocytes. Rather, this event, especially in vitro, is explained by the fact that the TNF-alpha/TNF receptor system not only triggers downstream signals leading to apoptosis but also induces an antiapoptotic pathway through the activation of nuclear factor (NF)-kappaB. The aim of this study was to determine whether inhibition of antiapoptotic pathways influences the susceptibility of mice to TNF-alpha. Here, we focused on the roles of NF-kappaB and phosphatidylinositol 3-kinase (PI3K)-regulated serine/threonine kinase Akt.
TNF-alpha was administered to BALB/c mice after treatment with an adenovirus expressing a mutant form IkappaBalpha (Ad5IkappaB), the PI3K inhibitor wortmannin, or both. Liver injury was assessed biochemically and histologically. The expression of Bcl-2 family members and caspase activity were examined.
In the mice livers, treatment with Ad5IkappaB or the wortmannin suppressed the activation of NF-kappaB or Akt, respectively. Suppression of either NF-kappaB or Akt showed a slight increase in transaminase levels and focal liver cell death after TNF-alpha administration. However, in mice treated with both Ad5IkappaB and wortmannin, TNF-alpha administration resulted in massive hepatocyte apoptosis and hemorrhagic liver destruction in mice. The combination of Ad5IkappaB, wortmannin, and TNF-alpha markedly increased the activation of caspase-3 and -9, and activated caspase-8 to a lesser degree, suggesting that TNF-alpha-induced hepatocyte apoptosis is dependent on type II cell death signaling pathway, probably through the mitochondria. Inhibition of the NF-kappaB and PI3K/Akt pathways had no effect on expression of Bcl-2 families.
The inducible activation of NF-kappaB and constitutive activation of Akt regulate hepatocyte survival against TNF-alpha, which occurs independent of Bcl-2 families.
背景/目的：肿瘤坏死因子（TNF）-α本身不会在正常小鼠或肝细胞中诱导肝损伤。相反，这一现象，尤其是在体外，可由以下事实解释：TNF-α/TNF受体系统不仅触发导致细胞凋亡的下游信号，还通过激活核因子（NF）-κB诱导抗凋亡途径。本研究的目的是确定抗凋亡途径的抑制是否会影响小鼠对TNF-α的易感性。在此，我们重点关注NF-κB和磷脂酰肌醇3激酶（PI3K）调节的丝氨酸/苏氨酸激酶Akt的作用。
在用表达突变型IκBα（Ad5IκB）的腺病毒、PI3K抑制剂渥曼青霉素或两者处理后，将TNF-α给予BALB/c小鼠。通过生化和组织学方法评估肝损伤。检测Bcl-2家族成员的表达和半胱天冬酶活性。
在小鼠肝脏中，用Ad5IκB或渥曼青霉素处理分别抑制了NF-κB或Akt的激活。抑制NF-κB或Akt均显示在给予TNF-α后转氨酶水平略有升高和局灶性肝细胞死亡。然而，在用Ad5IκB和渥曼青霉素两者处理的小鼠中，给予TNF-α导致小鼠出现大量肝细胞凋亡和出血性肝破坏。Ad5IκB、渥曼青霉素和TNF-α的联合使用显著增加了半胱天冬酶-3和-9的激活，并在较小程度上激活了半胱天冬酶-8，这表明TNF-α诱导的肝细胞凋亡依赖于II型细胞死亡信号通路，可能是通过线粒体。抑制NF-κB和PI3K/Akt途径对Bcl-2家族的表达没有影响。
NF-κB的诱导性激活和Akt的组成性激活调节肝细胞对TNF-α的存活能力，这一过程独立于Bcl-2家族发生。
