Nullifying epigenetic writer DOT1L attenuates neointimal hyperplasia

Background and aims Histone methyltransferases are emerging targets for epigenetic therapy. DOT1L (disruptor of telomeric silencing 1-like) is the only known methylation writer at histone 3 lysine 79 (H3K79). It is little explored for intervention of cardiovascular disease. We investigated the role of DOT1L in neointimal hyperplasia (IH), a basic etiology of occlusive vascular diseases. Methods and results IH was induced via balloon angioplasty in rat carotid arteries. DOT1L and its catalytic products H3K79me2 and H3K79me3 (immunostaining) increased by 4.69 ± 0.34, 2.38 ± 0.052, and 3.07 ± 0.27 fold, respectively, in injured (versus uninjured) carotid arteries at post-injury day 7. Dot1l silencing via shRNA-lentivirus infusion in injured arteries reduced DOT1L, H3K79me2, and IH at day 14 by 54.5%, 37.1%, and 76.5%, respectively. Moreover, perivascular administration of a DOT1L-selective inhibitor (EPZ5676) reduced H3K79me2, H3K79me3, and IH by 56.1%, 58.6%, and 39.9%, respectively. In addition, Dot1l silencing and its inhibition (with EPZ5676) in vivo in injured arteries boosted smooth muscle α-actin immunostaining; pretreatment of smooth muscle cells with EPZ5676 in vitro reduced pro-proliferative marker proteins, including proliferating cell nuclear antigen (PCNA) and cyclin-D1. Conclusions While DOT1L is upregulated in angioplasty-injured rat carotid arteries, either its genetic silencing or pharmacological inhibition diminishes injury-induced IH. As such, this study presents a strong rationale for continued mechanistic and translational investigation into DOT1L targeting for treatment of (re)stenotic vascular conditions.