Escherichia coli-induced expression of IL-1 alpha, IL-1 beta, IL-6 and IL-8 in normal human renal tubular epithelial cells

The aim of the present study was to investigate whether the IL-1 family cyt okines, in addition to IL-6 and IL-8, could be induced in normal human cort ical epithelial cells in response to bacterial stimuli. Human renal tissue was obtained from 9 patients undergoing elective tumour nephrectomy. Renal cortical epithelial cells of tubular origin were prepared from the unaffect ed tissue. The proximal tubular cells were stimulated for 2, 6 and 24 h wit h a heat-inactivated pyelonephritogenic Escherichia coli strain DS-17. Cult ured unstimulated tubular cells served as controls. IL-1 alpha, IL-1 beta, IL-1 receptor antagonist, IL-6, IL-8, IL-10, TNF-alpha, G-CSF and GM-CSF we re analysed using immunohistochemistry at the single cell level. The nonsti mulated cells were found to express low levels of IL-6 and IL-8 (mean value < 3% of total cells). In contrast, E. coli exposure resulted in significan tly increased incidences of IL-6 and IL-8 expressing cells (mean values <ap proximate to>18% of total cells) peaking within two hours of stimulation (P < 0.008 and P < 0.02 versus non-stimulated cells, respectively). A gradual decrease was thereafter observed at 6 and 24 h, respectively, although per sistently higher compared to controls. A different kinetic response was fou nd for IL-1 alpha, IL-1 beta and IL-1 receptor antagonist-expressing cells, which peaked 24 h after E. coli stimulation (mean values 3-10%) (P < 0.008 , P < 0.02, P < 0.02 versus non-stimulated cells, respectively). Low levels of TNF-<alpha> and GM-CSF were found in 3 of the 9 donated epithelial cell s, peaking at 2 h, and IL-10 and G-CSF producing cells in 1 patient each. I n conclusion we found that heat-inactivated pyelonephritic E. coli induced a proinflammatory cytokine response in the normal human proximal tubular ce lls including the IL-1 family, IL-6 and IL-8.