Tubular NF-kappaB and AP-1 activation in human proteinuric renal disease.
BACKGROUND
Nuclear factor-kappaB (NF-kappaB) and activated protein-1 (AP-1) are transcription factors that regulate many genes involved in the progression of renal disease. Recent data have shown that NF-kappaB is activated in tubules and glomeruli in various experimental models of renal injury. In vitro studies also suggest that proteinuria could be an important NF-kappaB activator. We therefore approached the idea that NF-kappaB may be an indicator of renal damage progression.


METHODS
Paraffin-embedded renal biopsy specimens from 34 patients with intense proteinuria [14 with minimal change disease (MCD) and 20 with idiopathic membranous nephropathy (MN)] and from 7 patients with minimal or no proteinuria (IgA nephropathy) were studied by Southwestern histochemistry for the in situ detection of activated transcription factors NF-kappaB and AP-1. In addition, by immunohistochemistry, we performed staining for the NF-kappaB subunits (p50 and p65) and AP-1 subunits (c-fos, c-jun). By immunohistochemistry and/or in situ hybridization, the expression of some chemokines [monocyte chemoattractant protein-1 (MCP-1), RANTES, osteopontin (OPN)] and profibrogenic cytokines [transforming growth factor-beta (TGF-beta)], whose genes are regulated by NF-kappaB and/or AP-1, were studied further.


RESULTS
NF-kappaB was detected mainly in the tubules of proteinuric patients, but rarely in nonproteinuric IgA nephropathy (IgAN) patients. In addition, there was a significant relationship between the intensity of proteinuria and NF-kappaB activation in MCD (r = 0.64, P = 0.01) and MN patients (r = 0.64, P < 0.01). Unexpectedly, patients with MCD had a significantly higher NF-kappaB tubular activation than those with MN (P < 0.01). To assess whether there was a different composition of NF-kappaB protein components, immunostaining was performed for the NF-kappaB subunits p50 and p65. However, no differences were noted between MCD and MN patients. In those patients, there was a lower tubular activation of AP-1 compared with NF-kappaB. Moreover, a strong correlation in the expression of both transcription factors was observed only in MN (r = 0.7, P = 0.004). Patients with progressive MN had an overexpression of MCP-1, RANTES, OPN, and TGF-beta, mainly in the proximal tubules, while no significant expression was found in MCD patients.


CONCLUSIONS
On the whole, our results show that a tubular overactivation of NF-kappaB and AP-1 and a simultaneous up-regulation of certain proinflammatory and profibrogenic genes are markers of progressive renal disease in humans. Increased activation of solely NF-kappaB and/or AP-1 may merely indicate the response of tubular renal cells to injury.
Mezzano
S A
SA
Division of Nephrology, School of Medicine, Universidad Austral, Valdivia, Chile. smezzano@uach.cl
Barría
M
M
Droguett
M A
MA
Burgos
M E
ME
Ardiles
L G
LG
Flores
C
C
Egido
J
J
D000293:Adolescent; D000328:Adult; D018925:Chemokines / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005260:Female; D015433:Glomerulonephritis, Membranous / Q000503:physiopathology* / Q000652:urine; D006651:Histocytochemistry; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D018836:Inflammation Mediators / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism*; D008297:Male; D016328:NF-kappa B / Q000502:physiology*; D009402:Nephrosis, Lipoid / Q000503:physiopathology* / Q000652:urine; D011507:Proteinuria / Q000209:etiology; D012016:Reference Values; D018808:Transcription Factor AP-1 / Q000502:physiology*
D018925:Chemokines; D018836:Inflammation Mediators; D016328:NF-kappa B; D018808:Transcription Factor AP-1