Gilmore W James, Hartmann Georgy, Piquette-Miller Micheline, Marriott Jason, Kirby Gordon M
Department of Biomedical Sciences, University of Guelph, Ont., Canada.
Toxicology. 2003 Mar 3;184(2-3):211-26. doi: 10.1016/s0300-483x(02)00581-4.
Murine hepatic cytochrome P450 2a5 (Cyp2a5) is induced during hepatotoxicity and hepatitis, however, the specific regulatory mechanisms have not been determined. We compared the influence of acute inflammation elicited in vivo by bacterial endotoxin lipopolysaccharide (LPS) and liver injury caused by the hepatotoxin pyrazole on hepatic Cyp2a5 expression in mice. Pyrazole treatment resulted in statistically significant increases in levels of Cyp2a5 mRNA, protein and catalytic activity by 540, 273 and 711%, respectively (P<0.05). In LPS-treated livers Cyp2a5 expression was significantly reduced compared to controls at the mRNA (46%) protein (35%), and activity (23%) levels (P<0.05). Treatment of mice with recombinant murine interleukin-1 beta and interleukin-6 had no significant effect on Cyp2a5 mRNA and protein levels. Liver injury, as assessed by serum alanine aminotransferase, was greater with pyrazole than with LPS treatment (609 vs 354% of control levels respectively). ER stress, determined by hepatic glucose regulated protein 78 (grp78) levels, was greater with pyrazole (185% of controls) than with LPS (128% of controls). In pyrazole-treated liver, overexpression of immunoreactive grp78 protein revealed that ER stress was localized to pericentral hepatocytes in which Cyp2a5 was induced. Evidence of glycogen loss and membrane damage in these cells was suggestive of oxidative damage. Moreover, vitamin E attenuated Cyp2a5 induction by pyrazole in vivo. These results suggest that induction of Cyp2a5 that has been observed in mouse models of hepatitis and hepatoxicity may be related to oxidative injury to the endoplasmic reticulum of pericentral hepatocytes rather than exposure to pro-inflammatory cytokines.
小鼠肝细胞色素P450 2a5（Cyp2a5）在肝毒性和肝炎期间会被诱导，然而，具体的调控机制尚未确定。我们比较了细菌内毒素脂多糖（LPS）在体内引发的急性炎症和肝毒素吡唑引起的肝损伤对小鼠肝脏Cyp2a5表达的影响。吡唑处理导致Cyp2a5 mRNA、蛋白质和催化活性水平分别在统计学上显著增加540%、273%和711%（P<0.05）。在LPS处理的肝脏中，与对照组相比，Cyp2a5在mRNA（46%）、蛋白质（35%）和活性（23%）水平上显著降低（P<0.05）。用重组小鼠白细胞介素-1β和白细胞介素-6处理小鼠对Cyp2a5 mRNA和蛋白质水平没有显著影响。通过血清丙氨酸转氨酶评估的肝损伤，吡唑处理比LPS处理更严重（分别为对照水平的609%和354%）。通过肝脏葡萄糖调节蛋白78（grp78）水平确定的内质网应激，吡唑处理（对照组的185%）比LPS处理（对照组的128%）更严重。在吡唑处理的肝脏中，免疫反应性grp78蛋白的过表达表明内质网应激定位于诱导Cyp2a5的中央周围肝细胞。这些细胞中糖原损失和膜损伤的证据提示氧化损伤。此外，维生素E在体内减弱了吡唑对Cyp2a5的诱导。这些结果表明，在肝炎和肝毒性小鼠模型中观察到的Cyp2a5诱导可能与中央周围肝细胞内质网的氧化损伤有关，而不是与接触促炎细胞因子有关。
