Theophylline Acetaldehyde as the Initial Product in Doxophylline Metabolism in Human Liver
Theophylline Acetaldehyde as the Initial Product in Doxophylline Metabolism in Human Liver
复制标题
茶碱乙醛作为人肝脏多索茶碱代谢的初始产物
DOI：
10.1124/dmd.119.089565
复制
发表时间：
2020-05-01
影响因子：
3.9
通讯作者：
Yang, Ling
中科院分区：
文献类型：
--
作者：
Zhao, Xiaohua;Ma, Hong;Yang, Ling
Doxophylline (DOXO) and theophylline are widely used as broncho-dilators for treating asthma and chronic obstructive pulmonary disease, and DOXO has a better safety profile than theophylline. How DOXO's metabolism and disposition affect its antiasthmatic efficacy and safety remains to be explored. In this study, the metabolites of DOXO were characterized. A total of nine metabolites of DOXO were identified in vitro using liver microsomes from human and four other animal species. Among them, six metabolites were reported for the first time. The top three metabolites were theophylline acetaldehyde (M1), theophylline-7-acetic acid (M2), and etophylline (M4). A comparative analysis of DOXO metabolismin human using liver microsomes, S9 fraction, and plasma samples demonstrated the following: 1) The metabolism of DOXO began with a cytochrome P450 (P450)-mediated, rate-limiting step at the C ring and produced M1, the most abundant metabolite in human liver microsomes. However, in human plasma, the M1 production was rather low. 2) M1 was further converted to M2 and M4, the end products of DOXO metabolism in vivo, by non-P450 dismutase in the cytosol. This dismutation process also relied on the ratio of NADP1/NADPH in the cell. These findings for the first time elucidated the metabolic sites and routes of DOXO metabolism in human.SIGNIFICANCE STATEMENTWe systematically characterized doxophylline metabolism using in vitro and in vivo assays. Our findings evolved the understandings of metabolic sites and pathways for methylxanthine derivatives with the aldehyde functional group.
