Abstract: Objective To observe the expression of histone H3 lysine residue 9 acetylation(H3K9Ac)in macrophage apoptosis model induced by oxidized low density lipoprotein(oxLDL), and to explore the controlling mechanism of histone deacetylase-inflammatory factor silencing information regulating protein1(SIRT1)on macrophage apoptosis by gene epigenetics, which was realized by peroxisome proliferator activated receptor γ(PPARγ)signaling pathway. Methods Mouse BALB/c macrophage cell line RAW264.7 was cultured with 50 μg/mL oxLDL. The cells were divided into control group(treated with double distilled water)and experimental group(treated with 50 μg/mL oxLDL). The number of apoptotic cells and protein expressions of interleukin(IL-6), SIRT1, H3K9Ac and PPARγ were detected. In addition, the experimental group was treated with SIRT1 stimulant(resveratrol, final concentration 50 nmoL/L)and SIRT1 inhibitor(nicotinamide, final concentration 50 nmoL/L). The apoptosis and protein expressions of SIRT1, H3K9Ac, PPARγ and phosphorylated peroxisome proliferator-activated receptor γ(Ser112 site)［pPPARγ(S112)］ after SIRT1 overexpression or inhibition were detected. The cell apoptosis was detected with Hoechst fluorescence apoptosis staining. The protein expressions of IL-6, SIRT1, H3K9Ac, PPARγ and pPPARγ(S112)were detected with Western blotting. Results The number of apoptotic cells in the experimental group was higher than that in the control group ［(84.88±5.89)vs(7.13±3.31), P<0.01］. The relative protein expressions of IL-6 and H3K9Ac in the experimental group were higher than those in the control group ［(0.50±0.01)vs(0.20±0.02),(0.32±0.02)vs(0.20±0.03), P<0.01］, while the relative protein expressions of SIRT1 and PPARγ in the experimental group were lower than those in the control group ［(0.20±0.01)vs(0.30±0.02),(0.11±0.02)vs(0.20±0.03), P<0.01］. The number of apoptotic cells in the SIRT1 stimulant group was lower than that in the experimental group ［(28.63±6.44)vs(84.88±5.89), P<0.01］, while the number of apoptotic cells in the SIRT1 inhibitor group was higher than that in the experimental group ［(266.88±35.10)vs(84.88±5.89), P<0.01］. In the SIRT1 stimulant group, the relative protein expressions of SIRT1 and PPARγ were higher than those in the experimental group ［(0.27±0.03)vs(0.20±0.01),(0.20±0.02)vs.(0.11±0.02), P<0.01］, while the expressions of H3K9Ac and pPPARγ(S112)were lower ［(0.21±0.02)vs(0.32±0.02),(0.04±0.00)vs(0.12±0.02), P<0.01］. In the SIRT1 inhibitor group, the relative expressions of SIRT1 and PPARγ were lower than those in the experimental group ［(0.10±0.01)vs(0.20±0.01),(0.06±0.01)vs(0.11±0.02), P<0.01］, while the expressions of H3K9Ac and pPPARγ(S112)were higher ［(0.56±0.01)vs(0.32±0.02),(0.18±0.03)vs(0.12±0.02), P<0.01］. Conclusion The gene epigenetics with abnormal histone acetylation modification is involved in the occurrence and development of macrophages apoptosis exposed to oxLDL. In oxLDL-induced macrophage apoptosis model, the expression of histone deacetylase SIRT1 decreases, resulting in a high expression of H3K9Ac, while the downstream PPARγ expressed at a low level and the expression of PPARγ phosphorylation increases. Up-regulation of SIRT1 can reverse the expression of those factors, and improve macrophage apoptosis. SIRT1 has positive regulation on PPARγ signal channel with the anti-inflammatory and anti-apoptosis effects, which are not only related to histone regulating PPARγ expression at gene transcription level, but also to the effects on PPARγ phosphorylation modification after post-translational.

Key words: Gene epigenetics, Histone, Histone deacetylation, Acetylation modification, Peroxisome proliferator activated receptor γ, Apoptosis