REGULATION AND PRODUCTION OF IL-8 BY HUMAN PROXIMAL TUBULAR EPITHELIAL-CELLS IN-VITRO

A number of inflammatory kidney diseases are associated with interstit ial nephritis and influx of leucocytes in the renal interstitium. Pote ntially the influx of neutrophils in the interstitium may be induced b y the chemotactic cytokine IL-8. In the present study we have analysed the production of IL-8 by cultured human proximal tubular epithelial cells (PTEC) in response to a number of proinflammatory cytokines. Pri mary cell lines of proximal tubular epithelium obtained from ten diffe rent kidneys, and cultured under serum-free conditions, were found to produce IL-8 to different degrees from not detectable levels up to 10. 8 +/- 1.5 ng IL-8 per 1 x 10(5) cells in 72 h. Gel filtration chromato graphy of PTEC supernatant indicated that the size of IL-8 of PTEC is 15.1 and 8.1 kD, and is chemotactically active for polymorphonuclear n eutrophils (PMN). Addition of 0.5 ng/ml rIL-1 alpha or 1000 U/ml recom binant tumour necrosis factor-alpha (rTNF-alpha) to the culture media of PTEC induced an up-regulation of IL-8 production up to 6.3-fold and 3.0-fold, respectively. The up-regulation by IL-1 alpha and TNF-alpha was dose- and time-dependent. In contrast, 500 U/ml recombinant inter feron-gamma (rIFN-gamma) down-regulated the production of IL-8 3.4-fol d. Northern blot analysis showed that IL-1 alpha and TNF-alpha increas ed the expression of IL-8 mRNA, whereas IFN-gamma reduced IL-8 mRNA ex pression. Taken together, these experiments indicate that human PTEC a re a potential source of IL-8 in the kidney, and that IL-8 produced in the proximal tubule can be induced by various proinflammatory cytokin es.