Nakahira Kiichi, Takahashi Toru, Shimizu Hiroko, Maeshima Kyoichiro, Uehara Kenji, Fujii Hiromi, Nakatsuka Hideki, Yokoyama Masataka, Akagi Reiko, Morita Kiyoshi
Department of Anesthesiology and Resuscitology, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700-8558, Japan.
Biochem Pharmacol. 2003 Sep 15;66(6):1091-105. doi: 10.1016/s0006-2952(03)00444-1.
Reductive metabolism of carbon tetrachloride (CCl(4)) is thought to cause lipid peroxidation which results in hepatic injury. Heme oxygenase-1 (HO-1) (EC 1.14.99.3), the rate-limiting enzyme in heme catabolism, is known to be induced by oxidative stress and to confer protection against oxidative tissue injuries. In this study, we examined the role of HO-1 induction in a rat model of CCl(4)-induced acute liver injury. CCl(4) treatment (1 mL/kg, intraperitoneally) produced severe hepatic injury in rats as revealed by significant increases in serum alanine transaminase (ALT) (EC 2.6.1.2) activity and hepatic malondialdehyde (MDA) content, severe liver cell injury, and increases in hepatic tumor necrosis factor-alpha (TNF-alpha) mRNA expression and DNA binding activity of nuclear factor-kappa B (NF-kappa B). Following CCl(4) treatment, hepatic HO-1 expression was markedly increased both at transcriptional and protein levels in hepatocytes, especially around the central vein. HO-1 induction was mediated in part through a rapid increase in microsomal free heme concentration presumably derived from hepatic cytochrome P450. Inhibition of HO activity by tin-mesoporphyrin (Sn-MP), which resulted in a sustained increase in microsomal free heme concentration, exacerbated liver injury, as judged by the sustained increase in serum ALT activity, extensive hepatocytes injuries, a more pronounced expression of hepatic TNF-alpha mRNA and an enhanced NF-kappa B activation. These findings indicate that induction of HO-1 is an adaptive response to CCl(4) treatment, and it may be critical in the recovery of hepatocytes from injury. Our findings also suggest that HO-1 induction may play an important role in conferring protection on hepatocytes from oxidative damage caused by free heme.
四氯化碳（CCl₄）的还原代谢被认为会导致脂质过氧化，进而引发肝损伤。血红素加氧酶-1（HO-1）（EC 1.14.99.3）是血红素分解代谢中的限速酶，已知其可被氧化应激诱导，并对氧化组织损伤具有保护作用。在本研究中，我们检测了HO-1诱导在CCl₄诱导的大鼠急性肝损伤模型中的作用。CCl₄处理（1 mL/kg，腹腔注射）在大鼠中导致了严重的肝损伤，血清丙氨酸转氨酶（ALT）（EC 2.6.1.2）活性和肝丙二醛（MDA）含量显著增加、严重的肝细胞损伤以及肝肿瘤坏死因子-α（TNF-α）mRNA表达和核因子-κB（NF-κB）的DNA结合活性增加均表明了这一点。CCl₄处理后，肝细胞中HO-1的表达在转录和蛋白质水平均显著增加，尤其是在中央静脉周围。HO-1的诱导部分是通过微粒体游离血红素浓度的快速增加介导的，推测该游离血红素源自肝细胞色素P450。用锡-中卟啉（Sn-MP）抑制HO活性，导致微粒体游离血红素浓度持续增加，加重了肝损伤，这可通过血清ALT活性的持续增加、广泛的肝细胞损伤、肝TNF-α mRNA更明显的表达以及增强的NF-κB激活来判断。这些发现表明，HO-1的诱导是对CCl₄处理的一种适应性反应，并且它可能对肝细胞从损伤中恢复至关重要。我们的发现还表明，HO-1的诱导可能在保护肝细胞免受游离血红素引起的氧化损伤方面发挥重要作用。
