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This Article Full Text Full Text (PDF) All Versions of this Article: 297/2/F316    most recent 00089.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Wu, X. Articles by Cunningham, P. N. PubMed PubMed Citation Articles by Wu, X. Articles by Cunningham, P. N.

TNF induces caspase-dependent inflammation in renal endothelial cells through a Rho- and myosin light chain kinase-dependent mechanism

Section of Nephrology, University of Chicago, Chicago, Illinois

Submitted 15 February 2009 ; accepted in final form 4 May 2009

The pathogenesis of LPS-induced acute kidney injury (AKI) requires signaling through tumor necrosis factor- (TNF) receptor 1 (TNFR1), which within the kidney is primarily located in the endothelium. We showed previously that caspase inhibition protected mice against LPS-induced AKI and in parallel significantly inhibited LPS-induced renal inflammation. Therefore we hypothesized that caspase activation amplifies TNF-induced inflammation in renal endothelial cells (ECs). In cultured renal ECs, TNF induced apoptosis through a caspase-8-dependent pathway. TNF caused translocation of the p65 subunit of NF-B to the nucleus, resulting in upregulation of inflammatory markers such as adhesion molecules ICAM-1 and VCAM-1. However, the broad-spectrum caspase inhibitor Boc-D-fmk reduced NF-kB activation as assessed by gel shift assay, reduced phosphorylation of subunit IB, and significantly inhibited TNF-induced expression of ICAM-1 and VCAM-1 as assessed by both real-time PCR and flow cytometry. Broad-spectrum caspase inhibition markedly inhibited neutrophil adherence to the TNF-activated endothelial monolayer, supporting the functional significance of this effect. Specific inhibitors of caspases-8 and -3, but not of caspase-1, reduced TNF-induced NF-B activation. Caspase inhibition also reduced TNF-induced myosin light chain (MLC)-2 phosphorylation, and activation of upstream regulator RhoA. Consistent with this, MLC kinase (MLCK) inhibitor ML-7 reduced TNF-induced NF-B activation. Thus caspase activation influences NF-B signaling via its affect on cytoskeletal changes occurring through RhoA and MLCK pathways. These cell culture experiments support a role for caspase activation in TNF-induced inflammation in the renal endothelium, a key event in LPS-induced AKI.

adhesion molecules; cytokines; sepsis; acute kidney injury; neutrophil