[High glucose stimulates synthesis of fibronectin in human mesangial cells via serum and glucocorticoid induced protein kinase-1 signaling pathway].
OBJECTIVE
To investigate the role of serum and glucocorticoid induced kinase-1 (SGK(1)) pathways in fibronectin (FN) synthesis in human mesangial cell (HMC) under high glucose condition and the mechanism by which SGK(1) contributes to glomerulosclerosis in diabetic nephropathy (DN).


METHODS
HMCs were cultured and transfected with (P)IRES2-EGFP-(S422D) SGK(1) mutant (SD), plasmid containing SGK(1) dominant activation mutant, or blank plasmid. Non-transfected HMCs were used as control group. Then the HMCs were divided into 6 groups: transfected with SD + high glucose (SD-HG, 25 mmol/L D-glucose), transfected with FP + high glues (FP + HG), non-transfected + high glucose (NT-HG), transfeted with SD + normal glucose (SD-NG, 5.5 mmol/L D-glucose), transfected with FP + normal glues (FP + NG), and non-transfected + normal glucose (NT-NG). Eight hours after the glucose stimulation, RT-PCR was used to examine the SGK(1) mRNA expression and fibronectin (FN). Western blotting was used to detect the fibronectin (FN) protein expression.


RESULTS
The SGK(1) mRNA expression of the SD + HG group was 0.709, significantly higher than those of the FP + HG and NT + HP groups (0.497 and 0.491, both P < 0.01). The SGK(1) protein expression of the SD + HG group was 1,178,497, significantly higher than those of the FP + HG and NT + HP groups (193,875 and 195,597 respectively, both P < 0.01). The FN mRNA expression of the SD + HG group was 0.749, significantly higher than those of the FP + HG and NT + HP groups (0.463 and 0.475 respectively, both P < 0.01). The FN protein expression of the SD + HG group was 659,550, significantly higher than those of the FP + HG and NT + HG groups (342,354 and 340,428 respectively, both P < 0.01). There were not significant differences in the expressions of FN mRNA and protein among different NG groups.


CONCLUSIONS
SGK(1) may be involved in the signal transduction leading to the increase of fibronectin production in DN and therefore may play an active part in glomerulosclerosis in DN.
Wang
Quan-sheng
QS
Renal Division, Union Hospital, Tongji Medical College, Huazhong Science and Technology University, Wuhan 430022, China.
Zhang
Xiao-li
XL
Wang
Yu-mei
YM
Zhang
A-li
AL
Deng
An-guo
AG
Zhu
Zhong-hua
ZH
Feng
Yu-xi
YX
D002478:Cells, Cultured; D005353:Fibronectins / Q000096:biosynthesis* / Q000235:genetics; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D005938:Glucocorticoids / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D011494:Protein Kinases / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D044967:Serum; D015398:Signal Transduction
D005353:Fibronectins; D005938:Glucocorticoids; D012333:RNA, Messenger; D011494:Protein Kinases; D005947:Glucose