The Role of Cytoplasmic Deacetylase, SIRT2, in Stabilizing Lung Endothelial Barrier Function

Abstract

Lung microvascular endothelial functional and structural integrity is essential for maintenance of tissue‐fluid homeostasis and normal function of the respiratory system. Disruption of the pulmonary endothelial barrier leads to pulmonary edema, acute lung injury, and respiratory failure. Adherens junction (AJ) proteins, actin cytoskeleton, and microtubules are major components required for maintenance of barrier integrity. Post‐translational protein modifications of AJ constituents, such as phosphorylation, nitration, and nitrosylation, have been well known to regulate endothelial barrier function. More recently, lysine acetylation/deacetylation has emerged as an important and physiologically significant posttranslational protein modification in physiological and pathological conditions. However, its role in endothelial barrier function remains largely unknown. Sirtuins (SIRTs) are NAD+‐dependent deacetylases, and critical regulators of energy metabolism and oxidative stress response in different cell types. We studied the function of SIRT2, the only cytosolic sirtuin family member, in regulating pulmonary endothelial barrier function during inflammatory response. We showed that SIRT2 is the most abundant sirtuin in human lung endothelial cells. Importantly, SIRT2 protein level is significantly increased in lung endothelial cells upon challenging mice with a sublethal dose of lipopolysaccharides, a gram‐negative bacteria endotoxin which causes systemic inflammatory responses resulting in acute lung injury. Increase in SIRT2 protein level was also observed in human lung microvascular endothelial cells (HLMVEC) upon challenge with permeability‐increasing agents such as human α‐thrombin and TNF‐α, further emphasizing the potentially important role of SIRT2 in regulating adaptation of endothelial cells to inflammatory responses. To determine the role of SIRT2 activity in the maintenance of lung endothelial barrier function, we knocked down SIRT2 in HLMVECs and assessed changes in endothelial permeability upon challenge with α‐thrombin. We found that SIRT2 knock down significantly augmented α‐thrombin‐induced permeability increases as compared to control siRNA‐treated cells, suggesting that SIRT2 activity may play a critical role in regulating endothelial barrier integrity. Furthermore, treatment of endothelial cells with AGK2, a SIRT2‐selective inhibitor, significantly decreased assembly of endothelial junctions due to increased accumulation of VE‐cadherin in the cytoplasm. Our data suggest that SIRT2 plays a critical role in the maintenance of endothelial barrier function under basal conditions and upon inflammatory response.Support or Funding InformationXiaoyan Yang : T32HL007829‐23, AHA 17SDG33410608.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.