Secretion of extracellular matrix were inhibited by Exendin-4 treatment through MAPK-NF-κB related inflammation in high glucose-induced glomerular mesangial cells

Objective To explore the effects and related mechanism of Exendin-4 on secretion of extracellular matrix in high glucose-induced glomerular mesangial cells(GMCs). Methods GMCs were incubated in medium with glucose or Exendin-4 for the four groups: normal glucose group(NG group): cells were treated in medium with 5.6 mmol/L glucose; NG with Exendin-4 treatment group(NGE group): cells were treated with 5.6 mmol/L glucose and Exendin-4; high glucose group(HG group): cells were cultured with 30 mmol/L glucose; HG with Exendin-4 treatment group(HGE group): cells were treated with 30 mmol/L glucose and Exendin-4 at concentration of 3, 5, 10, 15, 30 nmol/L separately, which were cultured for 12, 24, 48 hours. GMCs treated with Exendin-4 were determined by assessing proliferation using a CCK8 method. The levels of fibronectin(FN), collagen type Ⅳ(Col-Ⅳ)in the cell supernatant were measured using enzyme-linked immunosorbent assay(ELISA). The gene levels of Col-Ⅳ, FN, and expression of inflammatory mediators including monocyte chemotactic protein 1(MCP-1), tumor necrosis factor-α(TNF-α), intercellular cell adhesion molecule-1(ICAM-1), transforming growth factor-β1(TGF-β1)were evaluated using reverse transcription PCR(RT-PCR); The expression of nuclear transcription factor-κB(NF-κB), glucagon-like peptide-l receptor(GLP-1R), and phosphorylation levels of mitogen-activated protein kinases(MAPKs)were evaluated by Western blot. Results (1)After treatment with 10 nmol/L Exendin-4 for 24 hour, the proliferation rate of GMCs was significantly decreased compared with 3 nmol/L, 5 nmol/L Exendin-4 treatment(P 0.05). (2)The gene expression of FN, Col-Ⅳ and the inflammatory mediators, MCP-1, TNF-α, ICAM-1, TGF-β1 in HG group were significantly increased compared with the NG group, (all P<0.05). After treatment with Exendin-4, the levels of FN, Col-Ⅳ and the gene expression of TNF-α, MCP-1, ICAM-1, TGF-β1 were decreased(all P<0.05). (3)Compared with NG group, the expression of NF-κB and the phosphorylation of extracellular regulated protein kinases(p-Erk1/2), Jun N-terminal kinase(p-JNK)and, p38MAPK(p-p38MAPK)in the group of HG group were increased significantly, accompanied by the decrease of GLP-1R protein level(all P<0.05). Importantly, Exendin-4 treatment significantly reduced protein expression of p-Erk1/2, p-JNK, and NF-κB(all P<0.05), and the level of GLP-1R protein increased(P<0.05). Furthermore, specific Erk1/2, JNK or NF-κB inhibitors markedly blocked Exendin-4-mediated decrease in the levels of FN, Col-Ⅳ. Conclusion Exendin-4 treatment inhibits the secretion of extracellular matrix potentially through Erk1/2, JNK/NF-κB signaling in higher glucose induced GMCs. (Chin J Endocrinol Metab, 2017, 33: 220-227) Key words: Exendin-4; Glomerular mesangial cells; Mitogen-activated protein kinase; Nuclear transcription factor-κB; Extracellular matrix