Induction of α-Catenin, Integrin α3, Integrin β6, and PDGF-B by 2,8-Dihydroxyadenine Crystals in Cultured Kidney Epithelial Cells

Abstract

Background: Homozygous adenine phosphoribosyltransferase (APRT) deficiency is associated with 2,8-dihydroxyadenine (DHA) nephrolithiasis. Using whole kidney RNA from Aprt knockout mice, we previously showed that the renal deposition of DHA leads to changes in the expression of genes involved in tissue injury. To determine the cellular basis for these changes, we investigated gene expression in cultured human kidney (NHK-C) and African green monkey (BSC-1) epithelial cells exposed to DHA or calcium oxalate monohydrate (COM) crystals. Methods: First-strand cDNAs, synthesized from mRNA isolated from treated and untreated cells, were hybridized to membrane-bound cDNA arrays containing 588 genes associated with various physiological and pathological processes. Changes in gene expression were confirmed by reverse transcription PCR. Results: Twenty-seven percent of the array cDNAs were expressed in untreated NHK-C cells at varying levels relative to a housekeeping gene. The expression of three adhesion molecules (α-catenin, integrin α3, and integrin β6) and platelet-derived growth factor B (PDGF-B) was elevated following exposure of NHK-C cells to DHA. Increased expression of the adhesion molecules was also observed in BSC-1 cells, but PDGF-B expression could not be detected. COM crystals also stimulated the expression of these four genes in NHK-C cells, but the expression profile was quantitatively different compared with DHA. Conclusions: These findings suggest that DHA crystals stimulate the expression of specific genes in kidney epithelial cells and that the pathways for DHA-induced cell injury may be similar to those for COM crystals. The induction of adhesion molecules and PDGF-B may affect cell-cell or cell-matrix interactions and/or alter the actin cytoskeleton. These alterations may ultimately contribute to crystal-induced renal injury.