Vela Jennifer E, Miller Michael D, Rhodes Gerald R, Ray Adrian S
Department of Preclinical Drug Metabolism, Gilead Sciences, Inc., Foster City, CA, USA.
Antivir Ther. 2008;13(6):789-97.
Alterations in endogenous nucleotide pools as a result of HIV therapy with nucleoside and nucleotide reverse transcriptase inhibitors (N[t]RTIs) is a proposed mechanism for therapy-related adverse events and drug interactions resulting in treatment failure. In vitro studies were performed in order to understand the effect of N(t)RTIs on endogenous nucleotide pools.
The T-cell line CEM-CCRF was treated with control antimetabolites or the N(t)RTIs abacavir, didanosine, lamivudine, tenofovir (TFV) and zidovudine (AZT), either alone or in combination. The levels of natural 2'-deoxynucleoside triphosphates (dNTP) and ribonucleoside triphophosphates were determined by liquid chromatography coupled with triple quadrupole mass spectrometry.
Antimetabolites altered nucleotide pools in a manner consistent with their known mechanisms of action. AZT was the only N(t)RTI that significantly altered dNTP pools. incubation of 10 microM AZT, either alone or in combination with other N(t)RTIs, increased 2'-deoxyadenosine triphosphate, 2'-deoxyguanosine triphosphate and thymidine triphosphate levels by up to 1.44-fold the concentrations observed in untreated cells. At higher than pharmacological concentrations of AZT, evidence for inhibition of 2'-deoxycytidylate deaminase and enzymes involved in the salvage of thymidine was also observed. Phosphorylated metabolites of TFV are known to inhibit purine nucleoside phosphorylase (PNP). However, in contrast to a potent PNP inhibitor, TFV was unable to alter intracellular dNTP pools upon addition of exogenous 2'-deoxyguanosine.
N(t)RTIs have the potential to alter nucleotide pools; however, at the pharmacologically relevant concentrations, tested N(t)RTI or their combinations did not have an effect on nucleotide pools with the notable exception of AZT.
核苷及核苷酸类逆转录酶抑制剂（N[t]RTIs）用于治疗HIV时，内源性核苷酸池的改变是治疗相关不良事件及导致治疗失败的药物相互作用的一种推测机制。为了解N(t)RTIs对内源性核苷酸池的影响，进行了体外研究。
T细胞系CEM-CCRF单独或联合使用对照抗代谢物或N(t)RTIs阿巴卡韦、去羟肌苷、拉米夫定、替诺福韦（TFV）和齐多夫定（AZT）进行处理。通过液相色谱-三重四极杆质谱联用测定天然2'-脱氧核苷三磷酸（dNTP）和核糖核苷三磷酸的水平。
抗代谢物以与其已知作用机制一致的方式改变核苷酸池。AZT是唯一能显著改变dNTP池的N(t)RTI。单独或与其他N(t)RTIs联合使用10 microM AZT孵育，可使2'-脱氧腺苷三磷酸、2'-脱氧鸟苷三磷酸和胸苷三磷酸水平增加至未处理细胞中观察到的浓度的1.44倍。在高于AZT药理浓度时，还观察到抑制2'-脱氧胞苷酸脱氨酶和参与胸苷补救的酶的证据。已知TFV磷酸化代谢物可抑制嘌呤核苷磷酸化酶（PNP）。然而，与强效PNP抑制剂相比，加入外源性2'-脱氧鸟苷后，TFV无法改变细胞内dNTP池。
N(t)RTIs有改变核苷酸池的潜力；然而，在药理相关浓度下，除AZT外，所测试的N(t)RTI或其组合对核苷酸池没有影响。
