Mediation of inflammatory activation of renal tubular epithelial cells by high mobility group protein box 1 interacting with Toll- like receptor 4

Abstract

Objective To observe functional changes of renal tubular epithelial cells stimulated by high mobility group protein box 1 (HMGB1) and associated mechanism. Methods Renal tubular epithelial cells (NRK52E) were divided into control group, HMGB1 group and HMGB1+ lipopolysaccharide from Rhodobactersphaeroides (LPS RS) group. Toll-like receptor 4 (TLR4) expression was detected by immunofluorescence and Western blotting. Apoptosis rate and cell cycle arrest were identified with flow cytometry. The activation of MAPK signaling pathway and NF-κB were detected by Western blotting. The IL- 1, IL- 6 and tissue inhibitor of metalloproteinases 2 (TIMP2) mRNA levels were measured by real- time PCR. The secretion levels of IL- 1, IL- 6 and TIMP2 were measured by protein chips assay. Results TLR4 was expressed by NRK52E cells. Compared with the control group, there were increased cell cycle G1 arrest, MAPK signaling pathway and NF - κB activation in HMGB1 group. Furthermore, IL- 1, IL- 6 and TIMP2 mRNA levels were increased and IL- 1, IL- 6 and TIMP2 were secreted by NRK52E when stimulated with HMGB1 (all P<0.05). However, effects mediated by HMGB1 stimulation could be inhibited by LPS RS (all P<0.05). Conclusions Inflammatory activation of NRK52E cells can be mediated by the interaction of HMGB1 and TLR4. Key words: Inflammation; Toll - like receptor 4; HMGB1 protein; Renal tubular epithelial cells