Urinary proteins from patients with nephrotic syndrome alters the signalling proteins regulating epithelial-mesenchymal transition.
SUMMARY AT A GLANCE Patients with MCD and FSGS had significant changes in the expression of several EMT-related urinary proteins through activation ERK1/2 and p38 signaling pathways. Further studies to explore the molecular mechanisms behind the distinct clinical features of different types of nephrotic syndrome are warranted.



OBJECTIVE
Proteinuria plays an important role in the progression of tubulointerstitial fibrosis, but the mechanism for the differential renal damage induced by proteinuria is unknown. This study examined the effects of urinary proteins from patients with idiopathic minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) on several epithelial-mesenchymal transition (EMT)-related marker proteins in cultured proximal tubular HK-2 cells.


METHODS
Urinary proteins from MCD and FSGS patients were extracted by ultrafiltration and incubated with HK-2 cells; the expression of the cytokeratin-18, alpha-smooth muscle actin (alpha-SMA) and vimentin were assessed. p38 and extracellular regulated kinase (ERK) activation were measured by western blotting, and SB203580 (a p38 inhibitor) and PD98059 (an ERK1/2 inhibitor) were used to inhibit their activation.


RESULTS
It was observed that urinary proteins from FSGS patients more significantly induced the expression of alpha-SMA and vimentin and reduced cytokeratin-18 expression than those from MCD patients in HK-2 cells. Both ERK1/2 and p38 were activated by urinary proteins from MCD or FSGS patients. Pretreatment of the cells with SB203580 or PD98059 abolished the effect of urinary proteins from FSGS patients on the expression of alpha-SMA, vimentin and cytokeratin-18, while only SB203580 elicited this effect when cells were treated with urinary proteins from MCD patients.


CONCLUSIONS
The urinary proteins from MCD and FSGS patients induced significant changes of EMT-related proteins through activation of distinct mitogen-activated protein kinase-related signalling pathways. Quality of proteinuria may play an important role in determining the severity and progression of tubular injury associated with different kidney diseases.
Wen
Qiong
Q
Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China.
Huang
Zhao
Z
Zhou
Shu-Feng
SF
Li
Xiao-Yan
XY
Luo
Ning
N
Yu
Xue-Qing
XQ
D000328:Adult; D002478:Cells, Cultured; D004847:Epithelial Cells; D005260:Female; D005923:Glomerulosclerosis, Focal Segmental / Q000652:urine*; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D008297:Male; D008648:Mesoderm / Q000166:cytology; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology; D009402:Nephrosis, Lipoid / Q000652:urine*; D009404:Nephrotic Syndrome / Q000652:urine*; D014176:Protein Biosynthesis; D011506:Proteins / Q000502:physiology*; D015398:Signal Transduction; D055815:Young Adult; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology
D011506:Proteins; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases