Transferrin but not albumin mediates stimulation of complement C3 biosynthesis in human proximal tubular epithelial cells

The high-affinity receptor for interleukin (IL)-2, IL-2R, is composed of three chains, i.e., the alpha, beta, and gamma chains. Previous studies have shown that human proximal tubular epithelial cells (PTEC) express IL-2R alpha during inflammation, such as in the kidneys after renal transplantation or in crescentic glomerulonephritis. Furthermore, in this study it is shown that PTEC in culture produce more complement C3 after stimulation with IL-2, suggesting the presence of a functional IL-2R on PTEC. In these experiments, the binding of IL-2 to PTEC was analyzed. PTEC stimulated with IL-2 exhibited very low binding of digoxigenin-labeled IL-2; however, stimulation of PTEC with IL-2, in combination with interferon (IFN)-gamma, resulted in increased binding of the digoxigenin-labeled IL-2. In addition, it was found that IL-2, together with IFN-gamma, enhanced the production of C3 by PTEC from baseline levels of 69.6 +/- 3.4 to 198.6 +/- 3.3 ng of C3 per 10(6) cells. The surface expression of IL-2R alpha and IL-2Rbeta was analyzed using monoclonal antibodies. Although unstimulated PTEC hardly showed detectable expression of these chains, stimulation of PTEC with the combination of IL-2 and IFN-gamma resulted in increases of the index of mean fluorescence for the alpha- and beta-chains of 5.5 +/- 0.5 and 9.7 +/- 0.7, respectively. Reverse transcription-PCR analysis revealed mRNA expression not only for the alpha- and beta-chains, but also for the gamma-chain, after stimulation with the combination of IL-2 and IFN-gamma. This study demonstrates that PTEC express the high-affinity IL-2R and that the IL-2R might be involved in the regulation of production of complement component C3 found during renal inflammation.

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Apical Proteins Stimulate Complement Synthesis by Cultured Human Proximal Tubular Epithelial Cells

Journal of the American Society of Nephrology ◽

10.1681/asn.v10169 ◽

1999 ◽

Vol 10 (1) ◽

pp. 69-76 ◽

Cited By ~ 2

Author(s):

SYDNEY TANG ◽

NEIL S. SHEERIN ◽

WUDING ZHOU ◽

ZARIN BROWN ◽

STEVEN H. SACKS

Keyword(s):

Renal Failure ◽

Chronic Renal Failure ◽

Epithelial Cells ◽

Serum Proteins ◽

Fold Increase ◽

Complement C3 ◽

Enzyme Linked Immunosorbent Assay ◽

Tubular Epithelial Cells ◽

Proximal Tubular Epithelial Cells ◽

Proximal Tubular

Abstract. There is increasing evidence to suggest that the renal tubular epithelium is important in the pathogenesis of progressive renal failure resulting from persistent proteinuria. The role of complement in the progression of chronic renal failure is not well defined. The purpose of this study was to characterize the production of complement by human proximal tubular epithelial cells exposed to serum proteins at the apical surface. Complement C3 gene expression was analyzed by reverse transcription and PCR. C3 protein biosynthesis was confirmed by metabolic labeling followed by immunoprecipitation and quantified by enzyme-linked immunosorbent assay. In the quiescent state, proximal tubular epithelial cells grown on permeable membrane supports secreted C3 predominantly into the apical medium. The addition of 5 mg/ml serum proteins led to an 8.9-fold increase in basolateral C3 secretion and a 2.1-fold increase in apical C3 secretion, altering the ratio of basolateral: apical C3 secretion from 0.44 ± 0.16 to 1.87 ± 0.52. C3 mRNA expression was also upregulated in a time- and dose-dependent manner. Serum fractionation demonstrated that the stimulant responsible for these effects was in the molecular weight range 30 to 100 kD. The observed phenomenon was not reproduced when purified human albumin alone was used as the stimulant. These findings could provide a possible mechanism for the link between proteinuria and interstitial fibrosis. This may have potential implications for strategies directed against complement in retarding the progression of chronic renal failure.

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Defective D1-like receptor-mediated inhibition of the Cl−/HCO3− exchanger in immortalized SHR proximal tubular epithelial cells

AJP Renal Physiology ◽

10.1152/ajprenal.00433.2003 ◽

2004 ◽

Vol 286 (6) ◽

pp. F1120-F1126 ◽

Cited By ~ 43

Author(s):

Rui Pedrosa ◽

Pedro A. Jose ◽

P. Soares-da-Silva

Keyword(s):

Epithelial Cells ◽

Apical Cell ◽

Skf 38393 ◽

Tubular Epithelial Cells ◽

Receptor Stimulation ◽

Anion Transporter ◽

Proximal Tubular Epithelial Cells ◽

Proximal Tubular ◽

Wistar Kyoto ◽

Stimulation Of

The sensitivity of the Cl−/HCO3− exchanger to dopamine D1- and D2-like receptor stimulation in immortalized renal proximal tubular epithelial cells from the spontaneous hypertensive rat (SHR) and Wistar-Kyoto rat (WKY) was examined. The activity of the Cl−/HCO3− exchanger (in pH U/s) in SHR cells (0.00191) was greater than in WKY cells (0.00126). The activity of Cl−/HCO3− exchanger was exclusively observed at the apical cell side and probably occurs through the SLC26A6 anion transporter that is expressed in both WKY and SHR cells. Stimulation of D1-like receptors with SKF-38393 markedly attenuated the HCO3−-dependent intracellular pH recovery in WKY cells but not in SHR cells. Stimulation of D2-like receptors with quinerolane did not alter Cl−/HCO3− exchanger activity in both WKY and SHR cells. The selective D1-like receptor antagonist SKF-83566 prevented the effect of SKF-38393. Both WKY and SHR cells responded to dibutyryl-cAMP (DBcAMP) with inhibition of the Cl−/HCO3− exchanger, and downregulation of PKA (overnight exposure to DBcAMP) abolished the inhibitory effect of both DBcAMP and SKF-38393 in WKY cells. Both SHR and WKY cells responded to forskolin with increases in the formation of cAMP. However, only WKY responded to SKF-38393 with increases in the formation of cAMP that was prevented by SKF-83566. It is concluded that WKY cells respond to D1-like dopamine receptor stimulation with inhibition of the apical Cl−/HCO3− (SLC26A6) exchanger and SHR cells have a defective D1-like dopamine response.

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