A plant sesquiterpene lactone and its derivative reduce cutaneous side effect of vemurafenib,a BRAF inhibitor drug to treat late stage melanoma

OBJECTIVE To investigate the pharmacological effect of a plant sesquiterpene lactone(designated D)and its semi-organically synthesized novel derivative(designated S)and the role of lipid mediators,viz.,oxylipins in attenuating vemurafenib-induced cutaneous side effects.METHODS A DMBA/TPAinduced skin carcinogenesis mouse model mimicking cutaneous side effect caused by vemurafenib was established to evaluate the efficacy of compound D and S in reversal of vemurafenib side effect.Comparative oxylipin metabolomics platform using UPLC-TQD mass spectrometry coupled with partial least squares-discriminant analysis(PLS-DA)analysis,cell-based assays,and immunochemistry analysis were performed to elucidate the mechanism insights of DET and S compounds and the role of specific oxylipins in skin cancer carcinogenesis.RESULTS Vemurafenib treatment expedited the skin papillomas formation in DMBA-TPA treated mouse from week 6 to week 3.Both D and S compounds could suppress the vemurafenib side effect and also decrease total papillomas numbers(55% to 72%)and average sizes(66% to 89%).Oxylipins metabolome analysis shows that specific arachidonic acid metabolites may play a role in vemurafenib-induced squamous cell carcinoma or keratoacanthomas formation in mouse skin that can be deregulated by D or S compound treatment.Notably,S compound can inhibit vemurafenib-induced paradoxical activation of MAP kinases in mouse skin or in NRAS mutant melanoma cells.CONCLUSION Our results indicate that plant sesquiterpene lactone D and its novel analog can reduce cutaneous side effect of vemurafenib through novel modes of action by inhibiting paradoxical activation of MAP kinases and de-regulating pro-inflammation mediators COX-2 and specific ecosanoid-type of oxylipins.This study may suggest a novel adjuvant therapy approach in treatment of BRAFV600 Emutant melanoma.

单叶细辛中一个新的马兜铃酸类化合物

为了研究单叶细辛(Asarum himalaicum)的化学成分,利用溶剂提取、硅胶柱色谱、凝胶(SephadexLH-20)柱色谱和半制备型高效液相色谱(semi-preparative high performance liquid chromatography,HPLC)等手段进行分离、纯化,从单叶细辛全草中共分离鉴定了15个化合物。其结构经1H NMR、13C NMR、HR-ESI-MS等谱学方法分别鉴定为4-去甲氧基马兜铃酸BII(4-demethoxyaristolochic acid BII,1)、马兜铃酸I(aristolochicacid I,2)、马兜铃酸Ia(aristolochic acid Ia,3)、7-羟基马兜铃酸I(7-hydroxyaristolochic acid I,4)、马兜铃酸IV(aristolochic acid IV,5)、马兜铃次酸II(aristolic acid II,6)、青木香酸(debilic acid,7)、马兜铃内酰胺I(aristololactam I,8)、9-羟基马兜铃内酰胺I(9-hydroxyaristololactam I,9)、7-甲氧基马兜铃内酰胺IV(7-methoxyaristololactam IV,10)、(2S)-柚皮素-5,7-二-O-β-D-吡喃葡萄糖苷((2S)-naringenin 5,7-di-O-β-D-pyranosylglucoside,11)、4-羟基苯甲酸(4-hydroxybenzoic acid,12)、3,4-二羟基苯甲酸(3,4-dihydroxybenzoic acid,13)、4-羟基肉桂酸(4-hydroxycinnamic acid,14)和β-谷甾醇(β-sitosterol,15)。其中,化合物1为新化合物,化合物3～6、9、12～14为首次从细辛属植物中分离得到,所有化合物均为首次从单叶细辛中分离得到。据文献报道,马兜铃酸和马兜铃内酰胺类成分具肾毒性,本研究提示单叶细辛药用的安全问题值得关注。