IκB Kinase Is Critical for TNF-α-Induced VCAM1 Gene Expression in Renal Tubular Epithelial Cells

Abstract

The expression of VCAM1 is up-regulated in renal proximal tubular epithelial cells (TEC) in a variety of inflammatory renal diseases, a prominent example of which is acute renal allograft rejection. VCAM1 may play an important role in these diseases because it binds to the integrins very late Ag-4 and α4β7 on lymphocytes and monocytes, thereby providing a potential mechanism to recruit these leukocytes to sites of inflammation. The molecular mechanisms underlying VCAM1 regulation in renal TEC are essentially unknown. We now report that VCAM1 mRNA is dramatically up-regulated in C1, a cell line derived from renal TEC, on exposure to TNF-α. Two NF-κB binding sites in the VCAM1 promoter are critical for the TNF-α-induced VCAM1 transcriptional up-regulation, and both sites bind to p65-p50 NF-κB complexes. TNF-α induces activation of inhibitor of NF-κB (IκB) kinase-β (IKK-β), a protein kinase that phosphorylates the NF-κB inhibitor IκB, and thereby targets the latter for degradation via the ubiquitin-proteasome pathway. Moreover, dominant negative versions of IKK inhibit TNF-α activation of a VCAM1 promoter reporter. We conclude that the IKK/NF-κB pathway is critical in the TNF-α-induced up-regulation of VCAM1 mRNA in renal TEC.

Critical Role of Tumor Necrosis Factor-α and NF-κB in Interferon-γ-induced CD40 Expression in Microglia/Macrophages

“…Differences were observed using the two constructs; the IKK-␣ DN partially inhibited CD40 promoter activity, whereas the IKK-␤ DN construct abolished IFN-␥-induced CD40 promoter activation. DN versions of IKK have been shown to inhibit TNF-␣ activation of VCAM-1 promoter activity (29). In this system, similar to ours, DN IKK-␤ was a more potent inhibitor than IKK-␣.…”

Pathogenic Role of NF-κB Activation in Tubulointerstitial Inflammatory Lesions in Human Lupus Nephritis

“…The proinflammatory role of NF-kB activation in renal tubular cells has been implicated in tubulointerstitial injury in the proteinuria-induced rat model through transcriptional activation of NF-kB-dependent inflammatory mediators (Rangan et al 1999;Gomez-Garre et al 2001;Takase et al 2003). NF-kB augments expression of adhesion molecules such as ICAM-1 and VCAM-1 in renal tubular cells (Oertli et al 1998;Tu et al 2001). Proinflammatory cytokines such as TNF-a, IL-1, IL-6, and GM-CSF are also regulated by NF-kB in tubular epithelial cells or glomerular epithelial cells (Guijarro and Egido 2001;de Haij et al 2002;Drumm et al 2002;Greiber et al 2002;Viedt et al 2002).…”

Subdomain VIII Is a Specificity-determining Region in MEKK1

“…Transient transfections were performed using FuGENE 6 (Roche Molecular Biochemicals) as described previously (29). Typically, the cells were split the day prior to transfection so as to achieve 60 -80% confluence, and then transfected using a 2:1 FuGENE/DNA ratio.…”