Albumin stimulates interleukin-8 expression in proximal tubular epithelial cells in vitro and in vivo.
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.
Tang
Sydney
S
Division of Nephrology, Department of Medicine, The University of Hong Kong, Hong Kong, People's Republic of China.
Leung
Joseph C K
JC
Abe
Katsushige
K
Chan
Kwok Wah
KW
Chan
Loretta Y Y
LY
Chan
Tak Mao
TM
Lai
Kar Neng
KN
D002460:Cell Line; D004705:Endocytosis; D004847:Epithelial Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics*; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000276:immunology* / Q000293:injuries / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012709:Serum Albumin / Q000378:metabolism / Q000494:pharmacology*
D016209:Interleukin-8; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D017382:Reactive Oxygen Species; D012709:Serum Albumin