Methyl Substitution of a Rexinoid Agonist Improves Potency and Reveals Site of Lipid Toxicity
作者:Venkatram R. Atigadda、Gang Xia、Anil Desphande、LeeAnn J. Boerma、Susan Lobo-Ruppert、Clinton J. Grubbs、Craig D. Smith、Wayne J. Brouillette、Donald D. Muccio
DOI:10.1021/jm5004792
日期:2014.6.26
(2E,4E,6Z,8E)-8- (3',4'-Dihydro-1'(2'H)-naphthalen-1'-ylidene)-3,7-dimethyl-2,4,6-octatrienoic acid, 9cUAB30, is a selective rexinoid that displays substantial chemopreventive capacity with little toxicity. 4-Methyl-UAB30, an analogue of 9cUAB30, is a potent RXR agonist but caused increased lipid biosynthesis unlike 9cUAB30. To evaluate how methyl substitution influenced potency and lipid biosynthesis, we synthesized four 9cUAB30 homologues with methyl substitutions at the 5-, 6-, 7-, or 8-position of the tetralone ring. The syntheses and biological evaluations of these new analogues are reported here along with the X-ray crystal structures of each homologue bound to the ligand binding domain of hRXR alpha. We demonstrate that each homologue of 9cUAB30 is a more potent agonist, but only the 7-methyl-9cUAB30 caused severe hyperlipidemia in rats. On the basis of the X-ray crystal structures of these new rexinoids and bexarotene (Targretin) bound to hRXR alpha-LBD, we reveal that each rexinoid, which induced hyperlipidemia, had methyl groups that interacted with helix 7 residues of the LBD.
(2E,4E,6Z,8E)-8-(3',4'-二氢-1'(2'H)-萘烷-1'-基亚基)-3,7-二甲基-2,4,6-辛三烯酸(9cUAB30)是一种选择性Rexinoid,具有显著的化学预防能力且毒性较小。4-甲基-UAB30作为9cUAB30的类似物,是一种强力的RXR激动剂,但与9cUAB30不同,它导致了脂质生物合成增加。为了评估甲基取代对活性和脂质生物合成的影响,我们合成了四个9cUAB30的同系物,在四元环的5-,6-,7-或8-位分别引入甲基取代基。本文报告了这些新类似物的合成及其生物活性评估,并提供了每个同系物与其结合到人RXRα受体配体结合域的X射线衍射晶体结构。我们证明,每个9cUAB30的同系物都是一种更有效的激动剂,但只有7-甲基-9cUAB30在大鼠中引起了严重的高脂血症。基于这些新型Rexinoid以及贝沙罗汀(Targretin)与人RXRα-LBD结合的X射线衍射晶体结构,我们揭示,每种诱导高脂血症的Rexinoid具有与LBD的螺旋7残基相互作用的甲基基团。