Drug-likeness evaluation and inhibitory mechanism of emodin derivative on cardiac fibrosis based on MTA3 pathway
Authors: Liu Heng , Wang Zhixia , Li Runze , Xiao Dan 
Published: July 2024

Background
In our previous research, we demonstrated that emodin inhibits cardiac fibrosis through MTA3. However, the limited bioavailability of emodin has hindered its clinical translation.
Aim
To safely and effectively apply the pharmacology of emodin to disease treatment, a new emodin derivative (emodin succinyl ethyl ester) was synthesized through structural modification at the 3'-OH position. This study primarily focused on the favorable properties of the emodin derivative, including drug-likeness assessment, evaluation of anti-fibrotic abilities, and the molecular mechanism involving the MTA3 pathway.
Methods
Computational-aided drug design (CADD) was applied for drug-likeness evaluations, including the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of the emodin derivative, as well as molecular docking and molecular dynamics simulations. An experimental animal model of transverse aortic constriction (TAC)-induced cardiac fibrosis was established to compare the pharmacological effects of the emodin derivative versus emodin in the progression of cardiac fibrosis. Cardiac collagen deposition, morphological, and functional indices were collected via immunohistochemical staining and animal echocardiography, revealing that the emodin derivative possesses superior capability in inhibiting cardiac fibrosis and restoring MTA3 expression. Primary isolated cardiac fibroblasts were used as in vitro study subjects. The relationships between MTA3 and its upstream transcription factors were predicted through bioinformatics analysis of PROMO database and validated using CADD, chromatin Immunoprecipitation (ChIP), Luciferase reporter assays, and loss-of- and gain-of-function experiments.
Results
The emodin derivative demonstrates superior properties compared to emodin in terms of drug-likeness, anti-cardiac fibrosis effects, inhibition of cardiac fibroblast transdifferentiation, and restoration of MTA3 expression levels. Consistent with emodin, MTA3 mediates the inhibitory effects against cardiac fibroblast transdifferentiation of the emodin derivative. E2F1 was predicted and then verified as the transcriptional regulator and observed that E2F1 positively promoted the expression of α-SMA and COL1A2, negatively regulating its expression. Emodin and its derivatives were found to directly bind to the transcription site of E2F1, with the emodin derivative showing a more robust and stable binding property compared to emodin. The emodin derivative also reduced the expression of E2F1, and conversely, interfering with E2F1 similarly affected the inhibitory action of the emodin derivative on the transdifferentiation of cardiac fibroblasts.
Conclusion
This study demonstrated that emodin derivative exhibits superior drug-likeness properties and more potent inhibition of cardiac fibrosis compared to emodin, by directly targeting the transcriptional regulatory site of E2F1, disrupting its pro-fibrotic function, thereby restoring MTA3 expression and halting cardiac fibrosis progression. These findings advance emodin potential as a clinical therapy for cardiac fibrosis and provide insights into its molecular mechanisms of anti-fibrotic action.