The pivotal role of scavenger receptor CD36 and phagocyte-derived oxidants in oxidized low density lipoprotein-induced adhesion to endothelial cells

Oxidized low-density lipoprotein (oxLDL) is known to activate a number of signal transduction pathways in endothelial cells. Among these are the c-Jun NH2-terminal kinase (JNK), also known as stress-activated protein kinase, and extracellular signal-regulated kinase (ERK). These mitogen-activated protein kinases (MAP kinase) determine cell survival in response to environmental stress. Interestingly, JNK signaling involves redox-sensitive mechanisms and is activated by reactive oxygen and nitrogen species derived from both NADPH oxidases, nitric oxide synthases (NOS), peroxides, and oxidized low-density lipoprotein (oxLDL). The role of endothelial NOS (eNOS) in the activation of JNK in response to oxLDL has not been examined. Herein, we show that on exposure of endothelial cells to oxLDL, both ERK and JNK are activated through independent signal transduction pathways. A key role of eNOS activation through a phosphatidylinositol-3-kinase-dependent mechanism leading to phosphorylation of eNOS is demonstrated for oxLDL-dependent activation of JNK. Moreover, we show that activation of ERK by oxLDL is critical in protection against the cytotoxicity of oxLDL.

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Mannose-binding lectin reduces oxidized low-density lipoprotein induced vascular endothelial cells injury by modulating autophagy via LOX1

10.21203/rs.3.rs-238411/v1 ◽

2021 ◽

Author(s):

Xue-lian Zhou ◽

Xue-feng Chen ◽

Li Zhang ◽

Jin-na Yuan ◽

Hu Lin ◽

...

Keyword(s):

Endothelial Cells ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Protective Role ◽

Low Density ◽

Oxidized Low Density Lipoprotein ◽

Over Expression ◽

Mannose Binding ◽

Binding Lectin

Abstract Objective To investigate the role of mannose-binding lectin (MBL) in modulating autophagy and protecting endothelial cells (ECs) from oxidized low-density lipoprotein (ox-LDL) induced injury. Materials and Methods Rapamycin and chloroquine were used to confirm the role of autophagy in ox-LDL induced ECs injury. Dendritic cells (DCs) were co-cultured with ECs, after which inflammatory factors and DCs maturation rate were detected. Autophagy was detected by LC3 and Lamp2a or autophagosomes. Cell viability was analyzed by Cell Counting Kit-8 (CCK-8) assay. Flow cytometry was utilized to analyze cell proliferation and apoptotic rate. ECs transfected with lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1)-siRNA or MBL over-expression plasmid were treated with ox-LDL to explore the mechanism of MBL in ECs injury. HE, Oil Red O, TUNEL staining, and immunofluorescence were used to evaluate the atherosclerotic plaque, ECs injury, and autophagy, respectively. Retro-eyeball injections of MBL over-expression adenovirus were conducted every 4 weeks, after which ECs injury, autophagy, the uptake of ox-LDL, and expression of LOX1 were further analyzed. Results ECs treated with 100 ug/mL ox-LDL for 24 h significantly increased the expression of LC3, Lamp2a, and ET1. Rapamycin aggravated, chloroquine alleviated ox-LDL induced ECs autophagy and injury. LOX1-siRNA transfected ECs inhibited the uptake of ox-LDL and reduced ECs autophagy and injury compared with siRNA group. MBL over-expression in vitro decreased the binding of LOX1 and ox-LDL, ameliorated ECs autophagy and injury compared with the control plasmid group. MBL over-expression in vivo alleviated the formation of atherosclerotic plaque in HFD fed ApoE-/- mice, influenced the maturation of DCs, and down-regulated IL-6, IL-12, and TNF-a level compared with the control group. Also, mannan could reverse the protective role of MBL. Conclusion MBL exerts a protective role in ox-LDL induced ECs injury and HFD induced atherosclerosis model by regulating DCs maturation and modulating ECs autophagy via blocking the binding of LOX1 and ox-LDL.

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