Different Hydrolases Involved in Bioactivation of Prodrug-Type Angiotensin Receptor Blockers: Carboxymethylenebutenolidase and Carboxylesterase 1
作者:Tomoko Ishizuka、Yasushi Yoshigae、Nobuyuki Murayama、Takashi Izumi
DOI:10.1124/dmd.113.053595
日期:2013.11
Olmesartan medoxomil (OM) is a prodrug-type angiotensin II type 1 receptor blocker (ARB). We recently identified carboxymethylenebutenolidase homolog (CMBL) as the responsible enzyme for OM bioactivation in humans. In the present study, we compared the bioactivating properties of OM with those of other prodrug-type ARBs, candesartan cilexetil (CC) and azilsartan medoxomil (AM), by focusing on interspecies differences and tissue specificity. In in-vitro experiments with pooled tissue subcellular fractions of mice, rats, monkeys, dogs, and humans, substantial OM-hydrolase activities were observed in cytosols of the liver, intestine, and kidney in all the species tested except for dog intestine, which showed negligible activity, whereas lung cytosols showed relatively low activities compared with the other tissues. AM-hydrolase activities were well correlated with the OM-hydrolase activities. In contrast, liver microsomes exhibited the highest CC-hydrolase activity among various tissue subcellular fractions in all the species tested. As a result of Western blot analysis with the tissue subcellular fractions, the band intensities stained with anti-human CMBL and carboxylesterase 1 (CES1) antibodies well reflected OM- and AM-hydrolase activities and CC-hydrolase activity, respectively, in animals and humans. Recombinant human CMBL and CES1 showed significant AM- and CC-hydrolase activities, respectively, whereas CC hydrolysis was hardly catalyzed with recombinant carboxylesterase 2 (CES2). In conclusion, OM is bioactivated mainly via intestinal and additionally hepatic CMBL not only in humans but also in mice, rats, and monkeys, while CC is bioactivated via hepatic CES1 rather than intestinal enzymes, including CES2. AM is a substrate for CMBL.
奥美沙坦酯(OM)是一种前药类型的血管紧张素II 1型受体阻断剂(ARB)。我们最近鉴定出羧甲基烯酮合成酶同源物(CMBL)是人类中负责OM生物活化的酶。在本研究中,我们通过关注种间差异和组织特异性,比较了OM与其他前药类型的ARB,坎地沙坦环己酯(CC)和阿齐沙坦酯(AM)的生物活化特性。在采用小鼠、大鼠、猴、狗和人的组织亚细胞组分的体外实验中,除了狗的肠道(几乎没有活性)外,所有测试物种的肝细胞、肠细胞和肾细胞中都观察到显著的OM水解酶活性,而肺细胞中的活性相对较低。相比之下,肝微粒体表现出所有测试物种中各种组织亚细胞组分中的最高CC水解酶活性。通过Western印迹分析采用组织亚细胞组分,用人CMBL和羧酸酯酶1(CES1)抗体染色的条带强度很好地反映了动物和人类中的OM和AM水解酶活性和CC水解酶活性。人重组的CMBL和CES1表现出显著的AM和CC水解酶活性,而CC水解几乎不能通过重组的羧酸酯酶2(CES2)催化。总之,OM不仅在人类中通过肠道CMBL生物活化,而且在小鼠、大鼠和猴中也是如此,而CC通过肝CES1而非包括CES2在内的肠道酶生物活化。AM是CMBL的底物。