Nitric oxide production in renal cells by immune complexes: Role of kinases and nuclear factor-kappaB.
BACKGROUND
Interaction of deposited immune complexes (IC) with Fc receptors (FcR) on tissue cells elicits the release of inflammatory mediators leading to tissue damage. Nitric oxide (NO) radicals generated by inducible NO synthase (iNOS) are important mediators in inflammatory processes. To analyze the role of NO in IC-mediated glomerular inflammation, we studied the in vitro and in vivo expression of iNOS in renal cells [resident mesangial cells (MC), and infiltrating monocytes] induced by IC, and the possible intermediate steps between FcR occupancy and iNOS induction.


METHODS
MC and monocytes were stimulated with IgG- and IgA-containing IC, and NO production (nitrite accumulation), iNOS transcription (luciferase assay) and their expression was measured by RT-PCR and Western blot. The involvement of FcR, transcription factor nuclear factor-kappaB (NF-kappaB), and protein kinases was assessed by using Fc fragments and specific inhibitors. Immune glomerulonephritis was induced in rats, and iNOS expression and NF-kappaB activation were analyzed.


RESULTS
In MC and monocytes, IC enhanced iNOS transcription/expression and NO generation, which were attenuated by specific inhibitors of NF-kappaB. In addition, mitogen-activated protein kinase (MAPK) inhibitors decreased NO production, but did not interfere with NF-kappaB activity, suggesting that both pathways may converge downstream in the induction of iNOS. In experimental immune glomerulonephritis, increased iNOS expression correlated with proteinuria levels, and appeared colocalized with NF-kappaB in glomerular and infiltrating cells. Treatment of animals and cells with Fc fragments prevented iNOS induction and NF-kappaB activation by IC.


CONCLUSIONS
These results indicate that IC, through activation of FcR, induce iNOS expression in renal resident and recruited cells by mechanisms involving MAPK and NF-kappaB, and support the idea of the important role of local NO generation in IC-mediated glomerular injury.
Gómez-Guerrero
Carmen
C
Renal and Vascular Research Laboratory, Fundación Jiménez Díaz, Autonoma University, and Hospital Clínico San Carlos, Complutense University, Madrid, Spain. cgomez@fjd.es
López-Franco
Oscar
O
Suzuki
Yusuke
Y
Sanjuán
Guillermo
G
Hernández-Vargas
Purificación
P
Blanco
Julia
J
Egido
Jesús
J
D000818:Animals; D000936:Antigen-Antibody Complex / Q000276:immunology*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000276:immunology; D005920:Glomerular Mesangium / Q000166:cytology / Q000201:enzymology / Q000276:immunology*; D005921:Glomerulonephritis / Q000276:immunology / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology*; D009000:Monocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000276:immunology; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D015533:Transcriptional Activation / Q000276:immunology
D000936:Antigen-Antibody Complex; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat