1491-P: ER Stress Drives the VEGF Expression in Monocytic Cells by Mechanisms Involving CHOP/ROS/HIF-1alpha/NRF2 and NF-kappaB/p38 MAPK Pathways

Obesity is marked by metabolic inflammation and by metabolic impairment caused by increased endotoxin, free fatty acids, and vascular endothelial growth factor (VEGF) levels; and involves the endoplasmic reticulum (ER) stress as well. However, it remains unclear whether the ER stress can induce/amplify VEGF expression in metabolically-stressed monocytic cells; and if so, by which mechanism(s). To test this, metabolic stress was induced in THP-1 monocytic cells by treating cells separately with lipopolysaccharide (LPS), palmitic acid (PA), and oleic acid (OA), in presence/absence of ER stressor thapsigargin (TG). Gene expression of VEGF/ER stress markers was assessed by qRT-PCR, protein expression by ELISA, ROS by DCFH-DA assay, phosphorylation of HIF-1α, NF-κB, ERK1/2, and p38 MAPK by immunoblotting, and the insulin response in stressed cells by glucose-uptake assay. Regarding clinical analyses, adipose VEGF gene and protein expression was detected using qRT-PCR and IHC, respectively, while plasma hs-CRP, TNF-α, MDA, and OX-LDL levels were measured by ELISA. The experimental data show that a cooperative interaction between the metabolic and ER stresses led to the expression of VEGF, ROS, CHOP, ATF6, SOD2, and NRF2 (P˂0.05), as well as stimulated the CHOP and NRF2 promoter activities in reporter cells (P˂0.05). However, the glucose uptake was not impaired. The VEGF expression was dependent on phosphorylation of HIF-1α, NF-κB, and p38 MAPK; and the inhibitors of NF-κB/MAPK pathways as well as antioxidants or ROS scavengers suppressed the VEGF production. Further, individuals with obesity showed increased VEGF expression which associated positively with plasma levels of hs-CRP, TNF-α, MDA, and OX-LDL (P≤0.05). Overall, our findings support a cooperativity model in which the ER and metabolic stresses interact to augment VEGF expression in monocytic cells via the mechanisms involving CHOP/ROS/HIF-1α/NRF2 and NF-κB/p38 MAPK pathways.