Rhein, a novel Histone Deacetylase (HDAC) inhibitor with antifibrotic potency in human myocardial fibrosis

Although fibrosis depicts a reparative mechanism, maladaptation of the heart due to excessive production of extracellular matrix accelerates cardiac dysfunction. The anthraquinone Rhein was examined for its anti-fibrotic potency to mitigate cardiac fibroblast-to-myofibroblast transition (FMT). Primary human ventricular cardiac fibroblasts were subjected to hypoxia and characterized with proteomics, transcriptomics and cell functional techniques. Knowledge based analyses of the omics data revealed a modulation of fibrosis-associated pathways and cell cycle due to Rhein administration during hypoxia, whereas p53 and p21 were identified as upstream regulators involved in the manifestation of cardiac fibroblast phenotypes. Mechanistically, Rhein-mediated cellular effects were linked to the histone deacetylase (HDAC)-dependent acetylation status of p53 a posttranslational modification that acts protein stabilizing. Direct enzymatic testing revealed an inhibitory potency of Rhein for HDAC classes I/II. Functionally, Rhein inhibited collagen contraction in response to protein abundance of SMAD7, thus demonstrating its anti-fibrotic property in cardiac remodeling. In conclusion, this study identifies Rhein as a novel potent HDAC inhibitor and provides evidence that Rhein may contribute to the treatment of cardiac fibrosis as anti-fibrotic agent. As readily available drug with approved safety, repurposing of Rhein constitutes a promising potential therapeutic approach in the supplemental and protective intervention of cardiac fibrosis.