Targeting the Histone Methyltransferase SETD7 Rescues Diabetes-induced Impairment of Angiogenic Response by Transcriptional Repression of Semaphorin 3G

BackgroundPeripheral artery disease (PAD) is highly prevalent in patients with diabetes (DM) and associates with a poor prognosis. Revascularization strategies failed to improve outcome, suggesting that new strategies to promote blood vessel growth are needed. Histone modifications have emerged as key modulators of gene expression, however their role in angiogenic response in DM remains poorly understood. Here we investigate the role of chromatin remodelling in DM-related impairment of angiogenic response. MethodologyPrimary human aortic endothelial cells (HAECs) were exposed to normal glucose (NG, 5 mM) or high glucose (HG, 25 mM) for 48 hours. Gene expression profiling was performed by RNA sequencing (RNA-seq). Cell migration and tube formation were employed to study angiogenic properties in HAECs. Levels of the histone methyltransferase SETD7 and its chromatin signature at histone 3 on lysine 4 (H3K4me1) were investigated by Western blot and chromatin immunoprecipitation (ChIP). Pharmacological blockade of SETD7 was achieved by using the selective inhibitor (R)-PFI-2 while the inactive enantiomer (S)-PFI-2 was used as a control. Mice with streptozotocin-induced DM were orally treated with (R)-PFI-2 or vehicle and underwent hindlimb ischemia by femoral artery ligation. Our experimental findings were translated in endothelial cells and gastrocnemius muscle samples obtained from DM patients with PAD. ResultsRNA-seq in HG-treated HAECs unveiled the histone methyltransferase SETD7 as the top-ranking transcript. SETD7 upregulation was associated with increased H3K4me1 levels as well as with impaired HAECs migration and tube formation. Both SETD7 silencing and inhibition by (R)PFI-2 rescued hyperglycemia-induced impairment of HAECs migration and tube formation, while SETD7 overexpression blunted the angiogenic response. RNA-seq and ChIP assays showed that SETD7-induced H3K4me1 enables the transcription of the angiogenesis inhibitor semaphorin-3G (SEMA3G) by increasing chromatin accessibility to PPAR{gamma}. Moreover, SEMA3G overexpression mimicked the impairment of angiogenic response observed during hyperglycemia. In DM mice with hindlimb ischemia, (R)-PFI-2 improved limb perfusion by suppressing SEMA3G. Finally, RNAseq and immunofluorescence in vascular specimens from two cohorts of DM patients with PAD confirmed the upregulation of SETD7/SEMA3G signalling. Of note, (R)-PFI-2 restored angiogenic properties in HAECs collected from DM patients. ConclusionSETD7 is a druggable epigenetic target to promote neovascularization in DM.