Sirtuin 1 ameliorates defenestration in hepatic sinusoidal endothelial cells during liver fibrosis via inhibiting stress-induced premature senescence

Objective: Premature senescence is related to progerin and involves in endothelial dysfunction and liver diseases. Activating Sirtuin 1 (SIRT1) ameliorates liver fibrosis. However, the mechanisms of premature senescence in defenestration of hepatic sinusoidal endothelial cells (HSECs) and how SIRT1 affects HSECs fenestrae remain elusive.

Methods: We employed the CCl₄ -induced liver fibrogenesis rat models and cultured primary HSECs in vitro, administered with the SIRT1-adenovirus vector, the activator of SIRT1 and knockdown NOX2. We measured the activity of senescence-associated β-galactosidase (SA-β-gal) in HSECs. Meanwhile, the protein expression of SIRT1, NOX2, progerin, Lamin A/C, Ac p53 K381 and total p53 was detected by Western blot, co-immunoprecipitation and immunofluorescence.

Results: In vivo, premature senescence was triggered by oxidative stress during CCl₄ -induced HSECs defenestration and liver fibrogenesis, whereas overexpressing SIRT1 with adenovirus vector lessened premature senescence to relieve CCl₄ -induced HSECs defenestration and liver fibrosis. In vitro, HSECs fenestrae disappeared, with emerging progerin-associated premature senescence; these effects were aggravated by H₂ O₂ . Nevertheless, knockdown of NOX2, activation of SIRT1 with resveratrol and SIRT1-adenovirus vector inhibited progerin-associated premature senescence to maintain fenestrae through deacetylating p53. Furthermore, more Ac p53 K381 and progerin co-localized with the abnormal accumulation of actin filament (F-actin) in the nuclear envelope of H₂ O₂ -treated HSECs; in contrast, these effects were rescued by overexpressing SIRT1.

Conclusion: SIRT1-mediated deacetylation maintains HSECs fenestrae and attenuates liver fibrogenesis through inhibiting oxidative stress-induced premature senescence.