Autophagic degradation of caveolin-1 promotes liver sinusoidal endothelial cells defenestration

Abstract

Autophagy, interacting with actin cytoskeleton and the NO-dependent pathway, may affect the phenotype and function of endothelial cells. Moreover, caveolin-1 (Cav-1), as a structure protein in liver sinusoidal endothelial cells (LSECs), is closely related to autophagy. Hence, we aim to explore the role of autophagic degradation of Cav-1 in LSECs defenestration. In vivo, we found the increase of autophagy in liver sinusoidal endothelium in human fibrotic liver. Furthermore, autophagy, degradation of Cav-1, and actin filament (F-actin) remodeling were triggered during the process of CCl4-induced LSECs defenestration; in contrast, autophagy inhibitor 3MA diminished the degradation of Cav-1 to maintain fenestrae and relieve CCl4-induced fibrosis. In vitro, during LSECs defenestration, the NO-dependent pathway was down-regulated through the reduction of the PI3K–AKT–MTOR pathway and initiation of autophagic degradation of Cav-1; while, these effects were aggravated by starvation. However, VEGF inhibited autophagic degradation of Cav-1 and F-actin remodeling to maintain LSECs fenestrae via activating the PI3K–AKT–MTOR pathway. Additionally, inhibiting autophagy, such as 3MA, bafilomycin, or ATG5-siRNA, could attenuate the depletion of Cav-1 and F-actin remodeling to maintain LSECs fenestrae and improve the NO-dependent pathway; in turn, eNOS-siRNA and L-NAME, for blocking the NO-dependent pathway, could elevate autophagic degradation of Cav-1 to aggravate defenestration. Finally, overexpressed Cav-1 rescued rapamycin-induced autophagic degradation of Cav-1 to maintain LSECs fenestrae; whereas knockdown of Cav-1 facilitated defenestration due to the activation of the AMPK-dependent autophagy. Consequently, autophagic degradation of Cav-1 promotes LSECs defenestration via inhibiting the NO-dependent pathway and F-actin remodeling.

Exogenous expression of caveolin‐1 is sufficient for hepatic stellate cell activation

“…Moreover, autophagy drives HSC activation by generating metabolic homeostasis. 41,44 In fact, in ours results we demonstrated that GRX EGFP-Cav1 cells endocytosed more FluorSpheres® when compared with GRX. Importantly, Cav-1 and its interactions with actin cytoskeleton and ATP play a pivotal role in the structure, formation, and function of caveolae.…”

“…Cav‐1 has an extensive membrane distribution in all organelles, including lysosomes. Moreover, autophagy drives HSC activation by generating metabolic homeostasis …”

SIRT1 ameliorates premature senescence-induced defenestration in hepatic sinusoidal endothelial cell

“…The contraction and dilatation of fenestrae in HSECs and its differentiation are regulated by actin cytoskeleton (including F-actin) [4]. Our previous studies reveal that oxidative stress facilitates defenestration in HSECs via F-actin remodeling in liver fibrogenesis [5,6]. Novel findings show that lamins and their associated proteins, which regulate nucleoskeleton and cytoskeleton, affect cellular differentiation and senescence [7,8].…”

“…Primary rat HSECs were isolated from normal male SD rats and identified by SEM, based on the modified method [5,6]. Primary rat HSECs were cultured in plates with medium comprising 80% MCDB131 (Gibco, 10372019) and 20% fetal bovine serum (FBS, Biological Industries, 04-007-1A).…”

Complex Cell Type-Specific Roles of Autophagy in Liver Fibrosis and Cirrhosis

“…Conflicting results have been obtained regarding the effects of autophagy on LSEC phenotypes and functions. Luo et al reported that autophagy increases in LSECs in human fibrotic livers [52]. In mouse model of fibrosis, the autophagic degradation of caveolin-1, F-actin remodeling, and the downregulation of the nitric oxide (NO)-dependent pathway occur during the process of CCL 4 -induced LSEC defenestration.…”