Albumin stimulates interleukin-8 expression in proximal tubular epithelial cells in vitro and in vivo
Sydney Tang, … , Tak Mao Chan, Kar Neng Lai
Sydney Tang, … , Tak Mao Chan, Kar Neng Lai
Published February 15, 2003
Citation Information: J Clin Invest. 2003;111(4):515-527. https://doi.org/10.1172/JCI16079.
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Article Nephrology

Albumin stimulates interleukin-8 expression in proximal tubular epithelial cells in vitro and in vivo

Abstract

Renal tubulointerstitial injury is characterized by inflammatory cell infiltrate; however, the stimuli for leukocyte recruitment are not fully understood. IL-8 is a potent chemokine produced by proximal tubular epithelial cells (PTECs). Whether nephrotic proteins stimulate tubular IL-8 expression remains unknown. Acute exposure of human PTECs to albumin induced IL-8 gene and protein expression time- and dose-dependently. Apical albumin predominantly stimulated basolateral IL-8 secretion. Electrophoretic mobility shift assay demonstrated nuclear translocation of NF-κB, and the p65/p50 subunits were activated. NF-κB activation and IL-8 secretion were attenuated by the NF-κB inhibitors pyrrolidine dithiocarbamate and cell-permeable peptide. Albumin upregulated intracellular reactive oxygen species (ROS) generation, while exogenous H2O2 stimulated NF-κB translocation and IL-8 secretion. Albumin-induced ROS generation, NF-κB activation, and IL-8 secretion were endocytosis- and PKC-dependent as these downstream events were abrogated by the PI3K inhibitors LY294002 and wortmannin, and the PKC inhibitors GF109203X and staurosporin, respectively. In vivo, IL-8 mRNA expression was localized by in situ hybridization to the proximal tubules in nephrotic kidney tissues. The intensity of IL-8 immunostaining was higher in nephrotic than non-nephrotic subjects. In conclusion, albumin is a strong stimulus for tubular IL-8 expression, which occurs via NF-κB–dependent pathways through PKC activation and ROS generation.

Authors

Sydney Tang, Joseph C.K. Leung, Katsushige Abe, Kwok Wah Chan, Loretta Y.Y. Chan, Tak Mao Chan, Kar Neng Lai

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Effect of albumin from different suppliers, heat or protease pretreatmen...
Effect of albumin from different suppliers, heat or protease pretreatment, and nonalbumin serum proteins. Confluent, growth-arrested PTECs were cultured for 24 h with 10 mg/ml of HSA from different suppliers (shown in parentheses), human transferrin, human IgG, boiled HSA (HSA boiled for 10 min), or trypsin-digested HSA (HSA digested with trypsin-conjugated agarose for 2 h). IL-8 protein secretion was measured in cell culture supernatants by ELISA. Results are means ± SD of triplicate experiments. *P < 0.0001, †P = 0.001 versus cells incubated in serum-free medium alone; #P < 0.0001 versus cells treated with HSA 1, HSA 2, or HSA 3.