Catalani Elisabetta, Buonanno Federico, Lupidi Gabriele, Bongiorni Silvia, Belardi Riccardo, Zecchini Silvia, Giovarelli Matteo, Coazzoli Marco, De Palma Clara, Perrotta Cristiana, Clementi Emilio, Prantera Giorgio, Marcantoni Enrico, Ortenzi Claudio, Fausto Anna Maria, Picchietti Simona, Cervia Davide
Department for Innovation in Biological, Agro-Food and Forest Systems, Università degli Studi della Tuscia, Viterbo, Italy.
Laboratory of Protistology and Biology Education, Department of Education, Cultural Heritage and Tourism, Università degli Studi di Macerata, Macerata, Italy.
Front Chem. 2019 Jun 28;7:463. doi: 10.3389/fchem.2019.00463. eCollection 2019.
We synthesized and characterized MOMO as a new small molecule analog of the cytotoxic natural product climacostol efficiently activated in mild extracellular acidosis. The synthesis of MOMO had a key step in the Wittig olefination for the construction of the carbon-carbon double bond in the alkenyl moiety of climacostol. The possibility of obtaining the target ()-alkenyl MOMO derivative in very good yield and without presence of the less active ()-diastereomer was favored from the methoxymethyl ether (MOM)-protecting group of hydroxyl functions in aromatic ring of climacostol aldehyde intermediate. Of interest, the easy removal of MOM-protecting group in a weakly acidic environment allowed us to obtain a great quantity of climacostol in biologically active (Z)-configuration. Results obtained in free-living ciliates that share the same micro-environment of the climacostol natural producer demonstrated that MOMO is well-tolerated in a physiological environment, while its cytotoxicity is rapidly and efficiently triggered at pH 6.3. In addition, the cytostatic vs. cytotoxic effects of acidified-MOMO can be modulated in a dose-dependent manner. In mouse melanoma cells, MOMO displayed a marked pH-sensitivity since its cytotoxic and apoptotic effects become evident only in mild extracellular acidosis. Data also suggested MOMO being preferentially activated in the unique extra-acidic microenvironment that characterizes tumoural cells. Finally, the use of the model organism fed with an acidic diet supported the efficient activity and oral delivery of MOMO molecule . MOMO affected oviposition of mating adults and larvae eclosion. Reduced survival of flies was due to lethality during the larval stages while emerging larvae retained their ability to develop into adults. Interestingly, the gut of eclosed larvae exhibited an extended damage (cell death by apoptosis) and the brain tissue was also affected (reduced mitosis), demonstrating that orally activated MOMO efficiently targets different tissues of the developing fly. These results provided a proof-of-concept study on the pH-dependence of MOMO effects. In this respect, MOM-protection emerges as a potential prodrug strategy which deserves to be further investigated for the generation of efficient pH-sensitive small organic molecules as pharmacologically active cytotoxic compounds.
我们合成并表征了MOMO，它是细胞毒性天然产物climacostol的一种新型小分子类似物，在轻度细胞外酸中毒时能有效激活。MOMO的合成在Wittig烯烃化反应中有一个关键步骤，用于构建climacostol烯基部分的碳 - 碳双键。从climacostol醛中间体芳香环中羟基官能团的甲氧基甲基醚（MOM）保护基团来看，以非常高的产率获得目标（） - 烯基MOMO衍生物且不存在活性较低的（） - 非对映异构体是有可能的。有趣的是，在弱酸性环境中MOM保护基团易于去除，这使我们能够获得大量具有生物活性的（Z） - 构型的climacostol。在与climacostol天然生产者共享相同微环境的自由生活纤毛虫中获得的结果表明，MOMO在生理环境中耐受性良好，而其细胞毒性在pH 6.3时能迅速且有效地触发。此外，酸化MOMO的细胞生长抑制与细胞毒性作用可以呈剂量依赖性调节。在小鼠黑色素瘤细胞中，MOMO表现出明显的pH敏感性，因为其细胞毒性和凋亡作用仅在轻度细胞外酸中毒时才明显。数据还表明MOMO在表征肿瘤细胞的独特超酸性微环境中被优先激活。最后，使用喂食酸性饮食的模式生物支持了MOMO分子的高效活性和口服递送。MOMO影响交配成虫的产卵和幼虫羽化。果蝇存活率降低是由于幼虫阶段的致死率，而羽化后的幼虫保留了发育成成虫的能力。有趣的是，羽化幼虫的肠道表现出广泛的损伤（细胞凋亡导致的细胞死亡），脑组织也受到影响（有丝分裂减少），这表明口服激活的MOMO有效地靶向发育中果蝇的不同组织。这些结果为MOMO效应的pH依赖性提供了概念验证研究。在这方面，MOM保护作为一种潜在的前药策略，值得进一步研究以生成高效的pH敏感型小有机分子作为具有药理活性的细胞毒性化合物。
