Kidney International, Vol. 62 (2002), pp. 2022–2034 Nitric oxide production in renal cells by immune complexes: Role of kinases and nuclear factor-B CARMEN GO ´ MEZ-GUERRERO,OSCAR LO ´ PEZ-FRANCO,YUSUKE SUZUKI,GUILLERMO SANJUA ´ N, PURIFICACIO ´ N HERNA ´ NDEZ-VARGAS,JULIA BLANCO, and JESU ´ S EGIDO Renal and Vascular Research Laboratory, Fundacio ´n Jime ´nez Dı ´az, Autonoma University, and Hospital Clı ´nico San Carlos, Complutense University, Madrid, Spain Nitric oxide production in renal cells by immune complexes: Nitric oxide (NO) is an important effector molecule Role of kinases and nuclear factor-B. both in physiological conditions and in disease states char- Background. Interaction of deposited immune complexes acterized by inflammation. NO radicals are synthesized (IC) with Fc receptors (FcR) on tissue cells elicits the release from l-arginine by NO synthase, from which three iso- of inflammatory mediators leading to tissue damage. Nitric ox- ide (NO) radicals generated by inducible NO synthase (iNOS) forms can be distinguished: neuronal (nNOS), endothe- are important mediators in inflammatory processes. To analyze lial (eNOS), and inducible (iNOS) nitric oxide synthase the role of NO in IC-mediated glomerular inflammation, we [1]. In the kidney, a constitutive NO release within the studied the in vitro and in vivo expression of iNOS in renal glomerular vasculature may be protective by decreasing cells [resident mesangial cells (MC), and infiltrating monocytes] induced by IC, and the possible intermediate steps between glomerular capillary pressure and autoregulating renal FcR occupancy and iNOS induction. blood flow [2]. However, in pathological conditions, local Methods. MC and monocytes were stimulated with IgG- and generation of high output induced by various stimuli IgA-containing IC, and NO production (nitrite accumulation), through the expression of iNOS may result in damaging iNOS transcription (luciferase assay) and their expression was effects. NO generated by activated cells may amplify the measured by RT-PCR and Western blot. The involvement of FcR, transcription factor nuclear factor-B (NF-B), and injury through the production of peroxynitrite and reac- protein kinases was assessed by using Fc fragments and specific tive oxygen species [3]. In vitro, iNOS expression can inhibitors. Immune glomerulonephritis was induced in rats, be induced in leukocytes and renal cells after exposure and iNOS expression and NF-B activation were analyzed. to cytokines and endotoxin [4–7]. In human and experi- Results. In MC and monocytes, IC enhanced iNOS transcrip- tion/expression and NO generation, which were attenuated by mental nephritis, the glomerular induction of iNOS me- specific inhibitors of NF-B. In addition, mitogen-activated diates renal injury [3, 8–10], suggesting that inhibition protein kinase (MAPK) inhibitors decreased NO production, of high output NO release by blocking iNOS expression but did not interfere with NF-B activity, suggesting that both or activity may be a useful strategy for treatment of pathways may converge downstream in the induction of iNOS. In experimental immune glomerulonephritis, increased iNOS inflammatory disorders. However, conflicting results ex- expression correlated with proteinuria levels, and appeared ist between the published studies of pharmacologic NO colocalized with NF-B in glomerular and infiltrating cells. regulation by unselective or iNOS-specific inhibitors and Treatment of animals and cells with Fc fragments prevented the experimental glomerulonephritis in iNOS deficient iNOS induction and NF-B activation by IC. Conclusions. These results indicate that IC, through activa- mice [3, 11–14]. tion of FcR, induce iNOS expression in renal resident and Inducible NOS gene expression is strictly controlled, recruited cells by mechanisms involving MAPK and NF-B, mostly at the transcriptional level. The promoter region and support the idea of the important role of local NO genera- of iNOS gene has been cloned and sequenced in different tion in IC-mediated glomerular injury. species [4, 15], and contains at least one nuclear factor-B (NF-B) consensus site that has been shown to be impor- tant for iNOS transcription in macrophages and mesan- gial cells (MC) [7, 16]. NF-B is a ubiquitous and rapid Key words: immune complexes, Fc receptors, nitric oxide, glomerulo- nephritis, NF-B, tissue injury, inflammation. transcription factor in several cells in response to cyto- kines and other stimuli, and exerts its effect by regulating Received for publication October 23, 2001 the expression of cytokines, chemokines, cell adhesion and in revised form May 17, 2002 Accepted for publication July 8, 2002 molecules, growth factors, and immunoreceptors [6, 7, 16–20]. In this manner, NF-B contributes to immuno-  2002 by the International Society of Nephrology 2022