Aberrantly glycosylated IgA molecules downregulate the synthesis and secretion of vascular endothelial growth factor in human mesangial cells.
To gain insight into the glomerular capillary repair mechanisms in immunoglobulin A (IgA) nephropathy, we focused on vascular endothelial growth factor (VEGF-A) and nitric oxide (NO). Because abnormal glycosylation of serum IgA has been shown in IgA nephropathy, we examined whether VEGF-A and NO production by mesangial cells (MCs) could be modulated by aberrantly glycosylated (desialylated or degalactosylated) IgA. VEGF-A and NO synthase (NOS) gene expression were examined by reverse-transcriptase polymerase chain reaction (RT-PCR) or Northern blot analysis, and VEGF-A peptide, by capture enzyme-linked immunosorbent assay and NOS activity as production of tritium ([(3)H]) citrulline from [(3)H] arginine. Semiquantitative densitometric analysis of RT-PCR experiments showed a significant downregulation of VEGF-A messenger RNA (mRNA) in MCs incubated with aberrantly glycosylated IgA. This resulted in decreased release of VEGF-A in culture medium (P: < 0. 01). NOS activity and inducible NOS (iNOS) mRNA were enhanced by aberrantly glycosylated IgA (both P: < 0.01). No modulation of constitutive NOS mRNA was found. The depression of the VEGF-A production induced by aberrantly glycosylated IgA was mediated by NO because it was completely reversed by the NOS inhibitor, N:omega-nitro-L-arginine methyl ester. The NO donor, sodium nitroprusside, induced a bimodal modulation of VEGF; although low concentrations (0.0001 nmol/L) increased VEGF-A synthesis, greater concentrations (1,000 nmol/L) depressed it. In conclusion, we report negative control of VEGF-A synthesis in MCs by aberrantly glycosylated IgA, mediated by enhanced iNOS activity. We speculate that both increased iNOS activity and depressed VEGF-A synthesis might have a role in impairing vascular repair and favor sclerosis in IgA nephropathy.
Amore
A
A
Nephrology and Dialysis Department, Regina Margherita Hospital, Torino, Italy.
Conti
G
G
Cirina
P
P
Peruzzi
L
L
Alpa
M
M
Bussolino
F
F
Coppo
R
R
D015536:Down-Regulation; D016228:Endothelial Growth Factors / Q000096:biosynthesis / Q000378:metabolism*; D005920:Glomerular Mesangium / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D005922:Glomerulonephritis, IGA / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A
D016228:Endothelial Growth Factors; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II