Recent studies have indicated that HDAC and BRD

Recent studies have indicated that HDAC and BRD4 are associated with similar biological phenotypes related to cancer and combination of the HDAC inhibitor LBH589 and BET inhibitor I-BET151 synergistically induces apoptosis of melanoma cells [20], [21]. Moreover, combination of Panobinostat and (+)-JQ1 synergistically down-regulates the expression of N-Myc and Bcl2 [22]. In addition, combination of Mocetinostat and (+)-JQ1 synergistically inhibits the Ras/MAPK signal pathway [23]. All these conclusions promote us to develop dual HDAC/BRD4 inhibitors. We found the compound (7) bearing indole skeleton as HDAC inhibitor, IC50(HDAC1) = 0.58 μM, IC50(HDAC3) = 0.06 μM. Docking study of compound 7 and HDAC3 demonstrated that the hydroxamic group chelates the zinc ion at the bottom of the HDAC active site and the carbon chain can occupy the hydrophobic tunnel of the HDAC active site. In addition, indole skeleton and the substituent at 3-position can form hydrophobic interactions with the amino 34450 residues at the entrance of the HDAC active site (Fig. 2B). On the other hand, the SAR of BRD4 inhibitors have been carefully studied. Many BRD4 inhibitors consist of a hydrogen bond acceptor group as a mimic of Kac such as 3, 5-dimethylisoxazole, which interact with the conserved asparagine (Asn140), and a hydrophobic group coupled with the hydrogen bond acceptor group via a parent nucleus, which occupies the groove of WPF shelf [24], [25], [26] (Fig. 2A). It is notable that the ZA channel, a hydrophobic tunnel connects BRD4 active pocket and solvent area, is not fully occupied. Coincidently, the linker group of HDAC inhibitor is probably favorable to the ZA channel. Based on these findings, we designed and synthesized a series of compounds as candidate dual HDAC/BRD4 inhibitors. Compound 7 was taken as basic skeleton firstly. The reported BRD4 inhibitors were analysed and compound P-0014 [27] was chosen because of the similar structure to compound 7. Then the active group of BRD4 inhibitor P-0014 was introduced to basic skeleton (compound 7) to obtain the novel molecule (Fig. 2C). We hope the new molecule keeping both HDAC3 inhibitory activity and BRD4 inhibitory power.
Results and discussion
Conclusion We reported herein a series of indole derivatives as HDAC/BRD4 dual inhibition agents. The specific structure-activity relationship of these compounds was summarized in detail simultaneously. The enzymatic assay revealed that the synthesized compounds exhibited an excellent potency of inhibiting HDAC and a good potency of inhibiting BRD4. Compound 19f demonstrated the supreme HDAC inhibitory activity with the IC50 value of 5 nM and BRD4 inhibitory activity with the inhibition rate of 88% at the concentration of 10 µM. All compounds showed preferable anti-proliferation activity against human acute monocytic leukemia THP-1 cell lines with the GI50 value of 7.82 µM to 24.21 µM. Compound 19f as the representative compound was used for further mechanistic studies. The results indicated that the tumor cell growth inhibitory effects were correlated with the decreased protein levels of c-Myc and the increased protein levels of Ac-H3. Molecular docking analysis showed that the hydroxamic acid group could form hydrogen bonds with the residues of not only HDAC but BRD4. The indole ring and the phenyl group are also essential for the key hydrophobic interactions between the compound and the targets. A novel class of HDAC/BRD4 dual inhibitors bearing indole scaffold were provided, and deserved further research.
Experimental
Acknowledgment This work was supported by the National Nature Science Foundation of China (No. 81473086).
Introduction There are approximately 1.5 million new cases of acute myocardial infarction in the United States each year [1]. In the setting of ST-segment elevation myocardial infarction (STEMI), nearly half of cardiomyocyte death occurs as a result of reperfusion injury. As infarct size correlates with untoward clinical outcomes [2,3], there is longstanding interest in targeting reperfusion injury for clinical benefit. However, despite nearly 5 decades of research focusing on mechanisms underlying reperfusion injury, there are currently no clinically meaningful therapies targeting this phase of ischemia/reperfusion (I/R) injury. Rather, all our therapies – drugs, devices, and early reperfusion – target the ischemic component of the process. Despite a history of numerous failures, developing novel therapies for I/R injury remains an opportunity heralding significant clinical benefit.