Webster C R, Anwer M S
Tufts University School of Veterinary Medicine, North Grafton, MA, USA.
Hepatology. 1998 May;27(5):1324-31. doi: 10.1002/hep.510270519.
Cyclic adenosine monophosphate (cAMP) has been shown to modulate apoptosis. To evaluate the role of cAMP in bile acid-induced hepatocyte apoptosis, we studied the effect of agents that increase cAMP on the induction of apoptosis by glycochenodeoxycholate (GCDC) in cultured rat hepatocytes. GCDC induced apoptosis in 26.5%+/-1.1% of hepatocytes within 2 hours. Twenty-minute pretreatment of hepatocytes with 100 micromol/L 8-(4-chlorothiophenyl) cAMP (CP-cAMP) resulted in a reduction in the amount of apoptosis to 35.2%+/-3.8% of that seen in hepatocytes treated with GCDC alone. Other agents that increase intracellular cAMP, including dibutyryl cAMP (100 micromol/L), glucagon (200 nmol/L), and a combination of forskolin (20 micromol/L) and 3-isobutyl-1-methylxanthine (20 micromol/L), also inhibited GCDC-induced apoptosis to a similar extent. Pretreatment with the protein kinase A (PKA) inhibitor, KT5720, prevented the protective effect of CP-cAMP and inhibited CP-cAMP-induced activation of PKA activity. Inhibitors of phosphatidylinositol 3-kinase (PI3K), wortmannin (50 nmol/L), or Ly 294002 (20 micromol/L) also prevented the cytoprotective effect of cAMP. PI3K assays confirmed that wortmannin (50 nmol/L) inhibited PI3K activity, while CP-cAMP had no effect on the activity of this lipid kinase. GCDC increased mitogen-activated protein kinase (MAPK) activity, but had no effect on stress-activated protein kinase (SAPK) activity in hepatocytes. cAMP decreased basal and GCDC-induced MAPK activity and increased SAPK activity. The MAPK kinase inhibitor, PD 98059, inhibited both GCDC-mediated MAPK activation and GCDC-induced apoptosis.
环磷酸腺苷（cAMP）已被证明可调节细胞凋亡。为评估cAMP在胆汁酸诱导的肝细胞凋亡中的作用，我们研究了能增加cAMP的药物对培养的大鼠肝细胞中甘氨鹅脱氧胆酸（GCDC）诱导凋亡的影响。GCDC在2小时内诱导26.5%±1.1%的肝细胞发生凋亡。用100μmol/L 8-（4-氯硫苯基）cAMP（CP-cAMP）对肝细胞进行20分钟预处理后，凋亡细胞数量减少至单独用GCDC处理的肝细胞的35.2%±3.8%。其他能增加细胞内cAMP的药物，包括二丁酰cAMP（100μmol/L）、胰高血糖素（200nmol/L）以及福斯可林（20μmol/L）和3-异丁基-1-甲基黄嘌呤（20μmol/L）的组合，也能在相似程度上抑制GCDC诱导的凋亡。用蛋白激酶A（PKA）抑制剂KT5720预处理可阻止CP-cAMP的保护作用，并抑制CP-cAMP诱导的PKA活性激活。磷脂酰肌醇3激酶（PI3K）抑制剂渥曼青霉素（50nmol/L）或LY294002（20μmol/L）也可阻止cAMP的细胞保护作用。PI3K检测证实渥曼青霉素（50nmol/L）可抑制PI3K活性，而CP-cAMP对这种脂质激酶的活性无影响。GCDC可增加丝裂原活化蛋白激酶（MAPK）活性，但对肝细胞中的应激激活蛋白激酶（SAPK）活性无影响。cAMP可降低基础和GCDC诱导的MAPK活性，并增加SAPK活性。MAPK激酶抑制剂PD 98059可抑制GCDC介导的MAPK激活及GCDC诱导的凋亡。
1）能增加细胞内cAMP的药物可保护肝细胞免受疏水性胆汁酸诱导的凋亡；2）GCDC激活MAPK可能参与胆汁酸诱导的凋亡；3）cAMP介导的针对胆汁酸诱导凋亡的细胞保护作用似乎涉及PKA、MAPK和PI3K。
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