388-P: GLP-1 Receptor Agonists Attenuates Secretion of Extracellular Matrix via Inhibiting HMGB1 Signaling in Rat Mesangial Cells

Abstract

Background: GLP-1R agonists can exhibit a direct renoprotective effect in patients with diabetic nephropathy (DN) beyond the hypoglycemic effect, but the underlying mechanisms remain unknown. Recent studies have suggested that high mobility group box 1 (HMGB1) contributes to the development and progression of DN. In this study, we assessed whether GLP-1R agonists acts through HMGB1 and explored its downstream signaling pathways in DN. Methods: Rat glomerular mesangial cells (GMCs) were divided into four groups: normal control (NG), normal control with 10 nmol/L exendin-4 treatment (GLP-1 analog) (NGE), high glucose (HG), and high glucose with 10 nmol/L exendin-4 treatment (HGE) groups. GMCs were transfected with GLP-1R-siRNA using Lipofectamine TM2000 and divided as HG, HGE, HGE + GLP-1R-siRNA, or HGE + scrambled siRNA. FN and type IV collagen (COL-IV) were evaluated by enzyme-linked immunosorbent assay (ELISA). GLP-1R, HMGB1, TGF-β1, phosphorylated and total extracellular signal-regulated kinases (ERK), c-Jun NH2-terminal kinases (JNK), p38 mitogen-activated protein kinases (p38MAPK), and NF-κB p65 were measured by western blot analysis. Results: FN and COL-IV were higher in the HG group than NG group (P<0.05). Compared with NG group, the level of GLP-1R was decreased, HMGB1 and TGF-β1 were increased in the HG group (P<0.05). Additionally, NF-κB p65, the phosphorylation levels of ERK, JNK, and p38MAPK were all significantly elevated in the HG group (P<0.05). However, all these effects were reversed by Exendin-4 treatment (P<0.05), except phosphorylated p38MAPK (P>0.05). Moreover, the protective effects of Exendin-4 were abolished by GLP-1R knockdown (P<0.05). Conclusion: These results suggest that GLP-1 receptor agonists attenuates the ECM secretion of GMCs induced by high glucose. The potential mechanism involves it binding to and activating GLP-1R, which prevents ECM production by inhibiting HMGB1 and its signaling pathways. Disclosure W. Gu: None. M. Shi: None. H. Zhang: None. Funding National Natural Science Foundation of China (81200595, 81400807, 81700723)