Figure 6. Knocking down or inhibition of PARP16 prevents vascular aging in Ang II-infusion mice. (A–D) PARP16 knockdown prevented vascular aging in Ang II-infusion mice. Mice received injection of either 150 μl lentivirus sh PARP16 (shPARP16) or scramble (shMOCK) every 5 days after the Ang II-infusion with mini-osmotic pumps (A); PARP16, p16, COX-2, and VCAM-1 proteins level were assayed by Western blot in arteries from mouse without Ang II infusion (control), Ang II-infused mouse transfected by control vector (Ang II + shMOCK) and Ang II-infused mouse transfected by shRNA of PARP16 (Ang II + shPARP16). GAPDH serves as internal control. (B); Immunofluorescence double staining of PARP16 and p53 in aortic great vessels of control, Ang II + shMOCK and Ang II + shPARP16 mice, the arrowheads indicate the positive endothelial cells staining in the whole blood vessel (C); All data were shown as mean ± S.D; #p < 0.05, ##p < 0.01, ###p < 0.001 vs. control; *p < 0.05, **p < 0.01, ***p < 0.01 vs. Ang II + shMOCK; n=6/group. (D) EGCG attenuated blood pressure in Ang II-infusion mice. The blood pressure was assayed by the standard tail-cuff methods in mouse without Ang II infusion (control), Ang II-infused mouse, and Ang II-infused mouse with EGCG treatment. ###p < 0.001 vs. control; *p < 0.05, **p < 0.01, ***p < 0.001 vs. Ang II-infused mouse; n=7-8/group. (E) Working model for Smyd3-PARP16 axis accelerates unfolded protein response and vascular senescence. Younger cell has lower level of PARP16 protein and ER stress marks. In senescent cells including Ang II-induced cell, Ang II-infused mice, replicative senescence, PARP16 protein level was increased, leading to unfolded protein response and vascular senescence-associated phenotypes. PARP16 is upregulated at least partly through increased histone methyltransferase Smyd3 in senescence cells, leading to higher H3K4me3 mark at the promoter of Parp16 gene and generating more PARP16 expression.