Interleukin-8 Secretion of Cortical Tubular Epithelial Cells Is Directed to the Basolateral Environment and Is Not Enhanced by Apical Exposure toEscherichia coli

Abstract

More than 80% of urinary tract infections in adults are caused by Escherichia coli (31). For E. coli, different factors of virulence, e.g., lipopolysaccharides (LPS), hemolysins, or various types of fimbriae, have been characterized (8). Multiple lines of evidence have emerged concerning the involvement of proximal tubular epithelial cells (TEC) in the renal immune response. These cells have been shown to express major histocompatibility complex (MHC) class II antigens, which are essential for antigen presentation to CD4 ϩ lymphocytes (32) and cellular adhesion molecules crucial for leukocyte migration, e.g., intercellular adhesion molecule-1 (16, 18) and VCAM-1 (6). They are capable of processing and presenting foreign antigen (27) and, besides other cytokines, produce different chemokines, a group of low-molecular-weight cytokines with chemotactic functions. So far, the secretion of RANTES (14), MCP-1 (10), ENA-78 (28), and interleukin-8 (IL-8) (29) has been studied in TEC. Secretion of IL-8 is supposed to be of major relevance for the influx of neutrophils after bacterial contact. In earlier studies we showed that, in contrast to renal carcinoma cells (3), the expression of MHC class II molecules and intercellular adhesion molecule-1 by TEC could not be significantly enhanced by S fimbriae, LPS, or E. coli (21, 23). Furthermore, the secretion of IL-6, tumor necrosis factor alpha, and IL-8 by TEC grown as monolayers could be stimulated by cytokines, but not by S fimbriae, LPS, or E. coli (23). Concerning signalling of TEC directed to the basolateral environment, the in vitro model of monolayer cultures grown on a continuous surface has its limitations. Therefore, we tested whether basolaterally directed IL-8 secretion by TEC differs from luminal secretion and, if so, whether basolaterally directed IL-8 secretion can be stimulated by virulence factors of E. coli. MATERIALS AND METHODSPrimary cell culture of TEC and electron microscopy. Normal renal tissue was obtained in the local Department of Urology from nephrectomies due to tumors (23). Cells were grown from 1-mm 3 pieces of renal cortex in Dulbecco's modified Eagle medium-Ham's F-12 medium (BioWhittaker, Heidelberg, Germany) supplemented with epidermal growth factor (10 ng/ml), insulin-transferrin-sodiumselenite medium supplement (5 mg/liter), hydrocortisone (37.4 g/liter), 3,3-5-triiodo-L-thyronine (40 mg/liter), penicillin (100 U/ml), streptomycin (100 g/ ml), and 1 M HEPES buffer (15 ml/liter of medium). All supplements were obtained from Sigma, Deisenhofen, Germany, except for penicillin and streptomycin (BioWhittaker). The purity and proximal tubular origin of each cell culture were determined by immunohistochemistry by using anti-cytokeratin (Dianova, Hamburg, Germany), anti-APM (kindly provided by J. E. Scherberich, Frankfurt, Germany), anti-CD68, and anti-factor VIII antibodies (both from Dako, Hamburg, Germany) (21) and by electron microscopy. The ultrastructure of TEC with a microvillus surface is presented in Fig. 1. For electron microscopy, sma...

Polarized Expression of Tamm-Horsfall Protein by Renal Tubular Epithelial Cells Activates Human Granulocytes

“…These studies have focused on effects of THP isolated and purified from human urine (22,25). In the urine, however, THP forms large aggregates with a molecular mass of 7 ϫ 10 6 kDa, while the monomeric molecular mass of THP is 90 to 95 kDa (10). In addition, intrarenal in vivo stimulation of granulocytes by THP presumably requires that the expression of that protein not be restricted to the apical (luminal) tubular surface; basolateral expression adjacent to the peritubullary vessels should also occur.…”

“…Tissue samples of kidney cortex were obtained from the uninvolved poles of kidneys removed during surgery for renal carcinoma (9). Serial 6-m-thick cryostat sections of that renal tissue were prepared for alkaline phosphatase and monoclonal anti-alkaline phosphatase complex staining as described earlier (10). A polyclonal rabbit anti-human THP antibody was used as the primary antibody (diluted 1:1,000; Tebu).…”

Effect of Polarized Release of CXC-Chemokines from Wild-Type and Cystic Fibrosis Murine Airway Epithelial Cells

“…We observed similar responses in respiratory epithelial cells. Moreover, IL-8 is preferentially released at the basolateral surface of human colonic epithelial cells after treatment with enterotoxin (16), and in polarized renal tubular epithelial cells after stimulation with IL-1a (39). Although the chemokines we examined (MIP-2, KC, LIX, and IP-10) are released basolaterally, higher concentrations of chemokines were measured at the apical surface.…”

15-Deoxy-Δ^12,14-Prostaglandin J₂ Modulates Lipopolysaccharide-Induced Chemokine Expression by Blocking Nuclear Factor-κB Activation via Peroxisome Proliferator Activated Receptor-γ-Independent Mechanism in Renal Tubular Epithelial Cells

“…In both experimental diabetic and nondiabetic kidney disease, chemokines are overexpressed [1,2]. Recent studies have suggested that renal tubular epithelial cells are the key cells which secreted such chemokines [3,4]. These findings suggest that intervention strategies to prevent renal tubular epithelial cells secreting chemokines facilitate a reduction in tubulointerstitial inflammation lesion.…”