The Research On The Interaction Between MBL And FGFR4 And Its Role On Human Renal Mesangial Cells

Objective: Ig A nephropathy(Ig AN)is the most common glomerulonephritis in the worldwhile.For the complicated pathogenesis,it is vital to investigate the mechanism of the generation and development and to search the specific therapetic targets.Mannose binding lectin(MBL)has gradually become a research hotspot in recent years,and its participation in the occurrence and progression of various diseases,but its role in Ig AN remains unclear.Our study group confirmed previously that MBL could deposite in glomerular mesangial area,and the high levels of urinary MBL were correlated with the progression and poor prognosis of Ig AN.The experiments in vitro demonstrated that MBL could promote epithelial mesenchymal transition(EMT)in human renal mesangial cells.Bioinformatics forecasted that MBL could interact with fibroblast growth factor receptor 4(FGFR4),and we speculated that this interaction can lead to or promote the damage of mesangial cells and cause severe kidney damage.This study was to further confirm the interaction between MBL and FGFR4 on the basis of the previous studies,and to explore the effects of this interaction on human mesangial cells.Methods: A total of 186 patients with IgA nephropathy confirmed by renal biopsy were collected in this study.Serum MBL level of Ig A nephropathy patients was detected by ELISA.The immunofluorescence of the renal biopsy tissue and the mesangial cells were detected the co-deposition.Immunoprecipitation experiment confirmed the interaction between MBL and FGFR4.The effects of MBL and FGFR4 interaction on the expression of the inflammatory factors in human renal mesangial cells were detected by ELISA..Results: The test of ELISA showed that the levels of serum MBL were significantly higher in patients with Ig AN than those in healthy control group(716.2 ± 23.14 ng/ml vs440.7 ± 40.14 ng/ml,P<0.001).The Immunofluorescence test of renal biopsy revealed that both MBL and FGFR4 could deposited in the glomerular mesangial region,and they could be co-deposited.The immunofluorescence of human renal mesangial cell showed that the three groups of different process factors all existed the expression of MBL and FGFR4 in mesangial cells.MBL and FGFR4 expressed and co-deposited in both nucleus and cytoplasm.The intensity of their expressions was higher in the group treated with the serum of high concentration of MBL(>800ng/ml)plus r MBL(1?g/ml)than that in the group treated with the serum of low concentration(<400ng/ml)of MBL;and that in the group of low concentration of MBL was also higher than that in the group of normal control serum.The results of endogenous immunoprecipitation test showed that MBL and FGFR4 could interact,and the interaction was significant in the group with high serum concentration of MBL plus r MBL(1?g/ml).The levels of IL-6 in the supernatant fluid increased gradually in the groups of normal control serum,low serum concentration of MBL,and high serum concentration of MBL plus r MBL(1?g/ml)(high+r MBL vs.low,162.80 ± 6.45 pg/ml vs.37.16 ± 1.80 pg/m,P < 0.001;low vs.control,37.16 ± 1.80 pg/m vs.28.00 ± 2.67 pg/ml,P < 0.05),The differences between groups was statistically significant.The levels of MCP-1 in the supernatant fluid showed similiar trend(high+r MBL vs.low,195.2±8.23 pg/ml vs.58.23±3.40 pg/ml,P<0.001;low vs.control,58.23±3.40 pg/ml vs.38.03 ± 5.10 pg/ml,P<0.01),The differences between groups was statistically significant.Conclusion: MBL and FGFR4 could co-deposition in glomerular mesangium and human renal mesangial cells.The endogenous MBL and FGFR4 of human renal mesangial cells could interact.The interaction between MBL and FGFR4 could promote the secretions of inflammatory cytokines in mesangial cells,which may cause renal damage.