Korean J Nephrol.  2003 Sep;22(5):483-493.

The Effect of High Glucose on p38 MAPK Pathway and Fibronectin Synthesis in Cultured Rat Mesangial Cells

• Yoo TH
• Xu ZG
• Ryu DR
• Kim HW
• Lee SH
• Kim JJ
• Jung DS
• Choi KH
• Lee HY
• Han DS
• Kang SW

Abstract

BACKGROUND
The p38 mitogen-activated protein kinase (MAPK) pathway is activated by several stress factors, potentially leading to cellular apoptosis and growth. Little is known about the pattern of p38 MAPK pathway activation in mesangial cells under high glucose conditions. We examined the activity and expression of p38 MAPK members, p38 MAPK, MAPK kinase 3/6 (MKK3/6), c-AMP responsive element binding protein (CREB), and MAPK phosphatase-1 (MKP-1) in cultured mesangial cells exposed to high glucose. METHODS: Mesangial cells were subcultured from rat glomeruli isolated by sieving technique. After serum restriction for 48 hours mesangial cells were exposed to 5.6 mM glucose (low glucose, LG), 5.6 mM glucose+24.4 mM mannitol (LG+M), or 30 mM glucose (high glucose, HG) for 3 minutes to 48 hours with or without SB203580. Western blot was performed to determine the activity and protein expression of p38 MAPK members. RT-PCR and ELISA were performed for fibronectin mRNA expression and fibronectin synthesis, respectively. RESULTS: p38 MAPK and CREB activities were significantly increased in mesangial cells exposed to HG compared with LG or LG+M after 10 minutes and was sustained at higher levels to 48 hours (p<0.05), but total p38 MAPK and CREB protein expressions did not differ. MKP-1 showed a similar pattern as p38 MAPK and CREB (p<0.05). MKK3/6 acitvity was significantly higher in HG cells after 3 minutes and remained at higher levels throught the study period (p<0.05). Fibronectin mRNA expression and fibronectin synthesis were significantly increased in mesangial cells exposed to HG after 48 hours (p< 0.05). SB203580 (1 micrometer) pretreatment for 1 hour significantly reduced HG-induced fibronectin mRNA expression and fibronectin synthesis by 73% and 69%, respectively (p<0.05). CONCLUSION: p38 MAPK activity was increased in mesangial cells exposed to HG in parallel with increased MKK3/6 activity, resulting in CREB activation and increased fibronectin synthesis. This activated p38 MAPK may play a role in the pathogenesis of diabetic nephropathy.

Keyword

p38 MAPK; MKK3/6; CREB; High glucose; Mesangial cell; Diabetic nephropathy

MeSH Terms

Animals
Apoptosis
Blotting, Western
Carrier Proteins
Cyclic AMP Response Element-Binding Protein
Diabetic Nephropathies
Enzyme-Linked Immunosorbent Assay
Fibronectins*
Glucose*
Mannitol
Mesangial Cells*
p38 Mitogen-Activated Protein Kinases*
Phosphotransferases
Protein Kinases
Rats*
RNA, Messenger
Carrier Proteins
Cyclic AMP Response Element-Binding Protein
Fibronectins
Glucose
Mannitol
Phosphotransferases
Protein Kinases
RNA, Messenger
p38 Mitogen-Activated Protein Kinases