Combined expression of A1 and A20 achieves optimal protection of renal proximal tubular epithelial cells
BACKGROUND: Apoptotic death of renal proximal tubular epithelial cells (RPTECs) is a feature of acute and chronic renal failure. RPTECs are directly damaged by ischemia, inflammatory, and cytotoxic mediators but also contribute to their own demise by up-regulating proinflammatory nuclear factor-kappaB (NF-kappaB)-dependent proteins. In endothelial cells, the Bcl family member A1 and the zinc finger protein A20 have redundant and dual antiapoptotic and anti-inflammatory effects. We studied the function(s) of A1 and A20 in human RPTECs in vitro. METHODS: Expression of A1 [reverse transcription-polymerase chain reaction (RT-PCR) and A20 (Northern and Western blot analysis)] in RPTECs was evaluated. A1 and A20 were overexpressed in RPTECs by recombinant adenoviral-mediated gene transfer. Their effect upon inhibitor of NFkappaB alpha (IkappaBalpha) degradation (Western blot), NF-kappaB nuclear translocation [electrophoretic mobility shift assay (EMSA)], up-regulation of intercellular adhesion molecule-1 (ICAM-1) [fluorescence-activated cell sorter (FACS)] and monocyte chemoattractant protein-1 (MCP-1) (Northern blot) and apoptosis [terminal deoxynucleotiddyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL)] and FACS analysis of DNA content) was determined. RESULTS: A1 and A20 were induced in RPTECs as part of the physiologic response to tumor necrosis factor (TNF). A20, but not A1, inhibited TNF-induced NF-kappaB activation by preventing IkappaBalpha degradation, hence subsequent up-regulation of the proinflammatory molecules ICAM-1 and MCP-1. Unexpectedly, A20 did not protect RPTECs from TNF and Fas-mediated apoptosis while A1 protected against both stimuli. Coexpression of A1 and A20 in RPTECs achieved additive anti-inflammatory and antiapoptotic cytoprotection. CONCLUSION: A1 and A20 exert differential cytoprotective effects in RPTECs. A1 is antiapoptotic. A20 is anti-inflammatory via blockade of NF-kappaB. We propose that A1 and A20 are both required for optimal protection of RPTECs from apoptosis (A1) and inflammation (A20) in conditions leading to renal damage.
|Authors||Kunter, U.;Daniel, S.;Arvelo, M. B.;Choi, J.;Shukri, T.;Patel, V. I.;Longo, C. R.;Scali, S. T.;Shrikhande, G.;Rocha, E.;Czismadia, E.;Mottley, C.;Grey, S. T.;Floege, J.;Ferran, C. :|
|Publisher Name||KIDNEY INT|
|Published Date||2005-01-01 00:00:00|