Albumin Stimulates interleukin-8 Expression in Proximal Tubular Epithelial Cells in Vitro and in Vivo

J Clin Invest. 2003 Feb;111(4):515-27. doi: 10.1172/JCI16079.

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-kappaB, and the p65/p50 subunits were activated. NF-kappaB activation and IL-8 secretion were attenuated by the NF-kappaB inhibitors pyrrolidine dithiocarbamate and cell-permeable peptide. Albumin upregulated intracellular reactive oxygen species (ROS) generation, while exogenous H2O2 stimulated NF-kappaB translocation and IL-8 secretion. Albumin-induced ROS generation, NF-kappaB 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-kappaB-dependent pathways through PKC activation and ROS generation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Endocytosis
  • Epithelial Cells / drug effects
  • Epithelial Cells / immunology
  • Epithelial Cells / metabolism
  • Gene Expression / drug effects
  • Humans
  • In Vitro Techniques
  • Interleukin-8 / biosynthesis*
  • Interleukin-8 / genetics*
  • Kidney Tubules, Proximal / drug effects*
  • Kidney Tubules, Proximal / immunology*
  • Kidney Tubules, Proximal / injuries
  • Kidney Tubules, Proximal / metabolism
  • NF-kappa B / antagonists & inhibitors
  • NF-kappa B / metabolism
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism
  • Reactive Oxygen Species / metabolism
  • Serum Albumin / metabolism
  • Serum Albumin / pharmacology*

Substances

  • Interleukin-8
  • NF-kappa B
  • Phosphoinositide-3 Kinase Inhibitors
  • Reactive Oxygen Species
  • Serum Albumin
  • Protein Kinase C